Title of Invention	A POURING METHOD IN A VACUUM SEALED PROCESS
Abstract	A method and a device for pouring a molten metal in a vacuum molding for casting a thin-walled casting by using a V-process casting mold (molding frame body) and a casting cast by the method. The method comprises a shielding member fitting step for fitting a shielding member onto the surface of a prototype plate, a step for placing the molding frame body on the fitted shielding member and filling a filler not containing, a bond in the molding frame body, a step for sucking the shielding member to the filler side by bringing the inside of the molding frame body into a negative pressure by closing the upper surface of the filler to form the shielding member, a step for molding a semi-split casing mold with a molding surface by releasing the prototype plate from the shielding member, a step for defining a casting cavity and forming a completed casting mold by matching the semi-split casting mold with another semi-split casting mold molded in the same manner as in the case of the semi-split casting mold, a step for pouring the molten metal in the casting cavity, and a step for taking out the casting by releasing the state of negative pressure in the molding frame body. The method also comprises a step for depressurizing the inside of the casting cavity through the molding frame body before starting to pour the molten metal in the completed casting mold.

Title of Invention

A POURING METHOD IN A VACUUM SEALED PROCESS

Abstract

A method and a device for pouring a molten metal in a vacuum molding for casting a thin-walled casting by using a V-process casting mold (molding frame body) and a casting cast by the method. The method comprises a shielding member fitting step for fitting a shielding member onto the surface of a prototype plate, a step for placing the molding frame body on the fitted shielding member and filling a filler not containing, a bond in the molding frame body, a step for sucking the shielding member to the filler side by bringing the inside of the molding frame body into a negative pressure by closing the upper surface of the filler to form the shielding member, a step for molding a semi-split casing mold with a molding surface by releasing the prototype plate from the shielding member, a step for defining a casting cavity and forming a completed casting mold by matching the semi-split casting mold with another semi-split casting mold molded in the same manner as in the case of the semi-split casting mold, a step for pouring the molten metal in the casting cavity, and a step for taking out the casting by releasing the state of negative pressure in the molding frame body. The method also comprises a step for depressurizing the inside of the casting cavity through the molding frame body before starting to pour the molten metal in the completed casting mold.

Full Text	SPECIFICATION Title of the i nvent i on : Pouring Method, Device, and Cast in Vacuum Molding Process Technical Field . This invention relates to a pouring method, a device, and a cast in a vacuum molding process to produce a cast, especially, a thin-wall cast. Here, the vacuum molding process (hereafter, referred to "the vacuum sealed process") denotes a molding and pour ing process that includes the steps of seal ingly covering the surface of a pattern plate by a shielding member; placing a mold framing on the shielding member and then putting a fi II that does not include any binder in the mold framing; sealingly covering the upper surface of the fill and then evacuating the inside of the mold framing to suck the shielding member to the fill to shape the shielding member; removing the pattern plate from the shielding member, thereby forming a mold half that has a molding surface; forming another mold half in a s imilar way and mating the mold halves to define a molding cavity; pour ing molten metal in the molding cavi:ty; and then releasing the negative pressure in the mold framing to take out a as-cast product. Background Art Conventionally, the vacuum sealed process is widely used (for instance, see JP, S54-118216, A). However, the process were mainly used to produce thick-wall casts such as piano frames, counterweights, etc. and it was not used to produce casts that have thin walls of the thickness about 3mm or less for instance. Moreover, conventionally there was no device that cools the mold framing in the vacuum sealed process. The rise in temperature of the mold framing is confined after the pour i ng by conti nuing to evacuate the inside of the mo Id framing. However,; i n a step, the evacuation is stopped over a certain period of time, and the as-cast product, the mold framing, etc., are naturally cooled. When a product that has a large heat capacity such as a counter weight is cast, during the natural cool ing the i metal mold framing, the surface plate, etc., receive heat from the as-cast product, and hence their temperatures rise, thereby causing the fi I ms used to melt and adhere to the metal mold framing, the surface plate, etc. The present invention has been conceived in view of the problems discussed above. A main purpose of this invention is to provide a pouring method and a device by using the vacuum sealed process, which are suitable for producing a cast, especially a thin-wall cast, and to provide a cast produced by using the pouriing method. Another purpose of this invention is to provide a device for cooling the mold 2 framing. Summary of the Invention To that.end, in one aspect of the present invention the pour ing method in the vacuum sealed process is character i zed in that the molding cavity is evacuated through the mold framing. That is, although in the usual vacuum sealed process the inside of the mold framing is intercepted by a shield member from the molding cavity that communicates with the atmosphere, and the inside of the mold framing is evacuated to suck the shielding member to the fill to shape the shielding member and to maintain the molding cavity, in the vacuum sealed process of the present invention such a shielding member used in the usual vacuum sealed process is removed to a I low the inside of the mold framing and the molding cavity, which communicates with the atmosphere, to communicates with each other (although this communication may be considered to collapse the sand mold). With the comrnunication being kept, the mold half and the molding cavity are maintained to produce a cast. Further, in the above-mentioned aspect a step of evacuating the molding cavity is performed through the mold framing. It is characterized in that this step is carried out through vent plugs after the steps of placing the shielding member, disposing the vent plugs in the model part of pattern plate, placing the mold framing on the shielding member and the vent plugs, and fi11 ing the fi 11 in the mold framing. Inaddition, it i s character ized that the step of evacuating the molding cavity through the mold framing in the one aspect is performed through a plural ity of vent holes formed in the shielding member after the mold half is produced. Moreover, it is characterized that the pouring method of the vacuum sealed process in the one aspect further comprises the steps of measuring the degree of a pressure reduction for at least one of the mated mold halves between the start and the completion of pour ing: transferr ing the measured degree of the pressure reduction to a controller; and adjusting the degree of pressure reduction in the mold half and molding cavity. In addition, it is characterized in the one aspect that the mold half is not provided with an open top riser. An open top riser functions to discharge air and slag of the molten metal, and hence it has been used to stably produce a cast that is not deformed. It was found that when the molding cavity is evacuated appropriately without using an open top riser inthis invention, theflowofmoltenmetal is improved and the molten metal can be effectively filled in the molding cavity before the deformation of the sand mold occurs. According to the one aspect of the present invention, since the molding cavity is evacuated in the vacuum sealed process (this is performed through at least one of the mo Id framing and the open top riser), a thi n-wa II cast can be produced by t he-vacuum mo I ding process. Moreover, sincetheinsideofthemoldandthemoldingcavity 3 " are simultaneously evacuated due to the vent holes, an additional device is not requiredforevacuatingthemoldingcavity, provinganadvantage in that the.structure of the molding machine can be s imple. When the open top riser is not provided, a- feeder head or throwing-away part for the molten metal can be assumed to be a minimum requirement. As a result, there is an advantage that the product yield improves. In addition, since this invention keeps the feature of the usual vacuum sealed process, it has an advantage in that the mold framing can be easily removed and that an as-cast thin-wall product can easily taken out. According to another aspect of the present invention, to achieve the above-mentioned purpose, the pouring method of the vacuum sealed process is characterized in that the lower mold half (drag) of the mated mold is formed with a gate, while the upper moid half (cope) is not formed with any gate. Moreover, the method is characterized in that the cope of the mated mold, which is positioned above a hold furnace, is adjusted so as to be kept horizontally. In addition, the method is characterized in that the pouring is carried out by using cushion means disposed between the mated mold and the holding furnace for keeping the cope of the mated mold horizontally. Moreover, to achieve the above-mentioned purpose, the pouring method of vacuum sealed process of this invention is characterized in that the pouring is carried out with a heat insulating material.being disposed between the mated mold and the holding furnace when the mated mold is disposed above the holding furnace. In addition, it is characterized in that a sand layer that functions as the heat insulating material communicates with a stoke at a lower part and is connected with a plurality of gates at an upper part. Moreover, to achieve the purpose, the pour ing method of the vacuum sealed process of this invention is" characterized in that it is the low pressure die casting or the. differential pressure die casting. In addition, the pouring method is characterized in that when molten metal i,s poured in the molding cavity, the pouring rate is controlled. According to the another aspect of the invention, since a gate.is formed only in the lower mold half of the mated mold (it is not formed in the upper mold half), this a I lows molten metal to be poured from below, where the flow of the molten metal becomes a laminar flow, entraining less air and slag to the molten metal compared with the gravity die casting and the die casting. Moreover, since a riser and a feeder head need not be provided, the throwing-away part for the molten metal can be assumed to be a minimum requirement. As a result, there is an advantage that the product yield improves. In addition, since this invention keeps the feature of the usual vacuum sealed process, it has an advantage in that the mold framing can be easily removed and that an as-cast thin-wall product can easily taken out. 4 . ' This invention is suitable for producing large thin-wall casts such as framings for large household electrical appliances, large televisions, cars, and machinery. Any material of metal may be used. In the two aspects of the invention discussed above, cooling means by spraying compressed air on the mold framing for cooling it can be used. These and other purposes, features, and advantages will be clear from the following descriptions about the embodiments referred to with reference to the accompanying drawings. Brief description of the Drawings Figure 1 is a schematic cross-sectional view of the first embodiment of this invention. Figure 2 shows the outline of the method of the first embodiment. Figure 3 is a schematic cross-sectional view of the second embodiment of this invention. Figure 4 shows the outline of one stage of the second embodiment. Figure 5 shows a pressure diagram of the second embodiment. Figure 6 is a.schematic cross-sectional view of the third embodiment of this invention (an example of evacuating the molding cavity through an open top riser). Figure 7 is a schematic cross-sectional view showing another pouring method (of a prior art) for comparison. Figure 8 shows the result by the second embodiment of this invention Figure 9 shows the result by the third embodiment of this invention. Figure 10 shows the result of pouring by the prior-art method for comparison. Figure 11 is a schematic cross-sectional view of the fourth embodiment of this invention. Figure 12 shows the pressure condition of the pouring test in the fourth embodiment. Figure 13 shows a result of the flow length of the pouring test in the fourth embodiment. Figure 14 shows another result of the flow length of the pouring test in the fourth embodiment. Figure 15 shows the result of the surface roughness of the pouring test in the. fourth embodiment. Figure 16 shows an example of the pressure control of the pouring test in the fourth embodiment. Figure 17 is a schematic cross-sectional view of the fifth embodiment of this invention. Figure 18 shows an alternative embodiment of a pour ing tool of thi s invention. 5. Figure 19 is a sectional plan view of a device (the sixth embodiment) of this invention for cooling a mold framing (a sectional view of a chamber part). Figure 20 is a sectional front view of figure 19. Figure 21 a sectional front view of a conventional mold framing structure. Preferred Embodiments of the Invention The preferred embodiment of this invention is now described. In some embodiments, the same or similar numbers are used for the same or similar elements. This invention of the vacuum sealed process is character ized in that vent holes are used to at low the molding cavity to communicate with the inside of the mold, a,nd in that the molding cavity is evacuated through the mold framing. That is,the invention is a pouring process in the vacuum sealed process, the process including the steps of seal ingly covering the surface of a pattern plate by a shielding member; placing a mold framing on the shielding.member and then putting a fi 11 that does not include any binder in the mold framing; seal ingly covering the upper surface of the fi 11 and then evacuating the inside of the mold framing to suck the shielding member to the fill to shape the shielding member; removing the pattern plate from the shielding member, thereby forming a mold half that has a molding surface; forming another mold half in a similar way and mating the mold halves to define a molding cavity; pouring molten metal in the molding cavity; and then releasing the negative pressure in the mold framing to take out a as-cast product. The process includes the step of evacuating the molding cavity through the mold framing before pouring the molten metal in the molding cavity and it is characterized in that Pm=1-75kPa, Pc=1-95kPa, and Pc~Pm=3-94kPa when the internal pressure of the mold and the pressure in the molding cavity are assumed to be Pm and Pc, respectively, when the molten metal is poured in the molding cavity. Here, the purpose of assuming mold internal pressure Pm to be 1-75 KPa is that if is less than 1 KPa, a huge vacuum pump is required, and that if it is more than 75 KPa, it is not possible to suck the gas generated at the pouring. Further, the purpose of assuming the molding cavity internal pressure Pc to be 1-95 KPa is that if it is more than 95 KPa. a smooth inflow of the molten metal cannot be assured since the differential pressure with atmospheric pressure (101.3 KPa) is not enough, and that if it is less than 1 KPa, the mold may col lapse toward the molding cavity. In addition, it is necessary to assure Pc>Pm, because making the mold internal pressure Pm to be a degree of pressure reduction lower than molding cavity internal pressure Pc prevents the molten metal from penetrating the mold. Moreover, the value of Pc-Pm, which is defined by Pc and Pm, must be 3-94 KPa. Here, the mold framing denotes a flask, or flask assembly, provided with a suction pipe used in the vacuum sealed process. 6 Moreover, in this invention the vent holes may be formed by distr ibutingj the vent plugs in the pattern part after the film is shaped, and then by molding,[and then by cutting the film along the slits of the vent plugs from the molding cavity I ¦ side after remolding. Alternatively, the vent holes may be formed by making hojes,. by a needle from the molding cavity side, which holes reach the inside of the mol-d. In addition, in this invention the open top riser may be eliminated by moderately decompressing the molding cavity as mentioned above. The open top riser is a tubular void that passes through the cope to connect the molding cavity tojthe atmosphere. Accordingly, if no open top riser is provided, there will bej no communication hole in the upper part of the cope connecting the molding cavity to the atmosphere. The First Embodiment Here, the first embodiment is explained in relation to Figures 1 and 2i. Figure 1 is a schematic sectional view of a device for the vacuum molding process used for the embodiment. Upper and lower mold halves 1a and 1b, which wiere produced by using the vacuum sealed process, are mated to define a molding cavity 2. ¦ ¦ . . ¦ Here, the method of producing the mold halves 1a and 1b is described in detjai I on the basis of Figure 2. In Figure 2, the surface of the pattern plate 12 is seal in'g.ly covered by a film 13 (a shielding member) by applying negative pressure to the surf ape. A flask 3 (a moid framing) is then placed on the film 13,¦and vent plugs 6 (as vpnt holes) are appropriately disposed at an upper mold half side according to the pattern configuration. Afterwards, molding sand is fi1 led in the flask, to produce the upper j mold half la. Next, the upper mold half 1a is separated from the pattern plate 12, and the film 13 is cut at the si its of the vent plugs 6. Thus the mold half 1a\| is produced with the vent holes being formed with the cuts in the f i Im and the associated vent plugs 6. A lower mold half 1b, which has been produced in a manner simi lar to the up^er mold half 1a, is mated with it to form a mated mold having a molding cavity (Figure 1). At this time, the molding cavity 2 communicates with the inside of the mol,d framing (flasks 3) and with the atmosphere through runners and a gate. Although! i,n this embodiment no vent plug, or vent hole, is provided in the lower mold half 1b, some vent plugs 6 may be provided when appropriate. Thus a device of the vacuum molding process is formed as shown in Figure 1. Next, the operation of that device of the vacuum mo I di ng process is described. In Figure 1 the inside of upper and lower mold halves 1a and 1b has been decompressed by a decompression pump 11 through the flasks 3, suction pipes 4 and 4, a piping\|5, and a reservoir tank 10. 7 Moreover, the molding cavity 2, together with the mold halves 1a and 1b, is decompressed through the vent plugs 6 (vent holes). The pressure in the.inside of-themoldhalvesiaandib is detected by a pressure sensor 7, and the detect ion pressure is sent to a controller 8. A control signal corresponding to the detected pressure is sent by this controller 8 to a proportional control valve 9 to adjust its degree of opening as required to change the sucking pressure in the mold halves 1a, 1b a'nd the molding cavity 2. Under this state, an aluminum alloy molten metal is poured in the molding cavity 2. Over a period of time, the negative state in the inside of the mold framing is released, and an as-cast product is taken out. This product was not defective in the thin wall of 3mm or less. Clearly from the above explanation, this invention can produce a cast under decompressed state by applying the vent plugs 6 (vent holes) that allow the molding cavity 2 to communicate with the inside of the mold halves la and 1b to the conventional vacuum sealed process mold. Second Embodiment Next, another embodiment (the second embodiment) that uses this invention is described with reference to Figures 3-5. Figure 3 shows an example to form vent holes by needles, which holes pass the inside of the upper mold half. Upper and lower mold halves 21a and 21b have been produced by the vacuum sealed process. Next, needles pass through the film from a molding cavity 22 side into the upper mold half 21a to form vent holes 23. This is carried out as shown in Figure 4. That is, a tool having needles 24 are moved by a drive 25, to form the vent holes in the mold half at one time. The position of needles 24 have been previously set under the control by a computer for the.places where the flow of molten metal is assumed to be bad and where-a casting configuration part is far from the gate. Moreover, vent holes 23 may be manual ly formed for simpl ifying the device o,r when the number of vent holes is less. Although no vent hoi e is formed in the lower mold half 21b in this embodiment/some may be formed according to circumstances. Afterwards, the mold halves 21a and 21b are mated to form a mated mold having a molding cavity 22 (Figure 3). By adjusting pressure conditions so that the internal pressure Pm in the mold halves 21a and 21b is kept as Pm=1-75 KPa and the internal pressure Pc of the molding cavity 22 as Pc=1-95 Kpa, the pouring was carried out. Figure 5 shows the example of pressures in the mold halves la, 1b and the molding cavity 2 in this embodiment. To assure a smooth inflow of the molten metal, the inner pressure Pc in the molding cavity 2 needs an enough pressure differential with the atmospher ic pressure. Further, if Pc-Pm is too small, the mold may collapse, and if Pc-Pm is too large, the vacuum equipment must be large since Pm becomes smal I, yielding a high cost. From the above-mentioned reasons and the experimental result, it has been 8 found that the conditions of Pm=1-75 KPa, Pc=1-95 KPa, and Pc-Pm=3-94 KPa are effective. In addition, the change in pressure is described in detail. The internal pressure Pm in the mold halves 1a and 1b is kept as a high degree of pressure reduction ¦ between the start and the end of the pouring for causing a good flow of the molten metal by the pressure reduction and for sucking gas generated by the burning of the shaping film. After the pouring, where the molding cavity 2 is fi I led with the molten metal, the pressure sensor 7 detects the internal pressure Pm in the mold halves 1a and,1b and sends it to the controller 8. The.controller 8 adjusts the opening of the proportional control valve 9 to adjust the internal pressure Pm in the mold halves 1a and 1b to a low degree of pressure reduction, to prevent the molten metal from penetrating the mold. 9 The Third Embodiment Figure 6 shows one example of the method of decompressing the molding cavity by using an open top riser R. The upper and lower mold halves 31a and 31b, which have been produced by using the vacuum sealed process, are mated todefinethemolding cavity 32. The inside of the mold halves 31a and 31b is decompressed by a decompression pump 37 through the flasks 33 and 33, suction pipes 34 and 34, a piping 35, and a reservoir tank 36. Moreover, the upper mold half 31a is provided with the open top riser R, which communicates with the molding cavity 32 and is opened to the upper surface of the upper mold half 31a. The riser R also acts as a feeder head. Further, the lower mold half 31b is provided with a flat gage (not shown) that connects the molding cavity 32 and the open top riser R. The molding cavity 32 is decompressed by a decompress ion pump 3.7 through a tool 38 connected to the opening of the open top riser R, which opening is located in the upper surface of the upper mold half 31a; a reservoir tank 39 for decompressing the molding cavity; a pressure regulating valve 40; and a reservoir tank 36. By adjusting the pressure conditions so that the internal pressure Pm in the . mold halves 31a and 31b and the internal pressure Pc of the molding cavity 32 are maintained as Pm=1-75 KPa and Pc=l -95 Kpa, respectively, the pour ing was carried-out.' An Example for Comparison Figure 7 shows one example of the mold provided with the open top riser R, where the molding cavity is not decompressed. The upper and lower mold halves 31a and 31b, which have been produced by the vacuum sealed process, are mated to define the molding cavity 32. The inside of the mold hal ves 31a and 31b has been decompressed by a decompression pump 37 through the flasks 33 and 33, suction pipes 34 and 34, a piping 35, and a reservoir tank 36. Moreover, the upper mold half 31a is provided with the open top riser R, which communicates with the molding cavity 32 and is opened to the upper surface of the upper mold half 31a. The riser R also acts as a feeder head. Further, the lower mold half 31b is provided with a flat gage (not shown) that connects the molding cavity 32 and the open top riser R. In the mold framing configured as mentioned above, pouring was carried out with the molding cavity not been decompressed. Figures 8-10 are schematic diagrams showing the results of pouring. These schematic diagrams show the photograph of the results of pouring in the imitative manner. Figure 8 shows the result of the pouring carried out by the method of the second embodiment. Figure 9 shows the result of the pouring carried out by the method of 10 the third embodiment. Figure 10 shows the result of the pouring carried out by the method of the reference example for comparison. As shown in Figure 10, it is understood that when the molding cavity is not decompressed as in the example for comparison, the molten metal is filled only partially in the molding cavity near -the flat gate. In the result shown in Fi gure 9 for the third embodiment of the pouring method of the present invention, the molten metal has reached the area where the open top riser R is located, thus the effect of decompressing the molding cavity is seen in comparison with the reference example. However, the area at which no open top riser is located is not f i I led with the molten metal, and thus the as-cast product is not good. In Figure 8 for the pouring method of the second embodiment of the present invention, the enti re molding cavity is fi I led with the molten metal. Thus a greater effect of decompressing the molding cavity is seen than the result of the third embodiment. Clearly from this result, the advantage of the use of this invention can be confirmed. Table 1 Degree of FiI I ing Casting Cost OperabiIity Hole by needle very good very good good Vent hole good average average Open top riser average average good In Table 1 three methods are shown to al low the molding cavity to communicate with the mold framing for decompressing the molding cavity. One is making holes by needles, one is to use vent holes, and the other is to use the open top riser. The degree of fi 11 ing of the molten metal, the casting cost, and the operabi I ity of molding of these methods are compared in Table 1. The method using the needles shows better result than two other methods. The Fourth Embodiment Next, the fourth embodiment of this invention is described with reference to Figures 11-16. This invention is characterized in that the pouring is carried out with the mated mold produced using the vacuum sealed process being disposed above a holding furnace. That is, in the pour ing method of the vacuum sealed process, a gate is formed at the lower mold half, and no gate is formed at the upper mold half. Further, the poring method is also character ized in that heat insulation means are disposed betwee'n the mated mo Id and the holding furnace. Further, the lower surface of the lower mo Id 11 half is made flat. Here, providing no gate at the upper mold half means that the pouring is carried out from below, since the gravity die cast, which is used for the vacuum sealed process, is not used, but the low pressure die cast or the pressure differential die cast is used for pouring. Thus the mated mold is located above the holding furnace. , The heat insulating means acts for preventing the film (the shielding member) from being melt due to the heat from the holding furnace. The heat insulating means includes heat insulating material disposed between the lower mold half and a lower die plate on which the lower mold half is placed. Alternatively, the heat insulating material may be partly inserted in the lower die plate. The material of the heat insulation may be any one that can resist the temperature of the molten metal such as earthenware, ceramics, gypsum, a sand mold, and a of se\|f hardening sand mold, etc. To adjust the lower mold half so that it is kept horizontal denotes proving cushi on member or f i 11 i ng mater i a I between the I ower mo Id half or the heat insulating material and the lower die plate to prevent the molten metal from being escaped due to a gap caused when the bottom of the lower mold half or it is not horizontal, or it denotes operating any machinery (a scraper, vibrator, etc.) to flatten the fi I I ing material. The material for this cushion member may be soft material to fit the bottom shape of the lower mold half and that is durable to the temperature of the molten metal, such as glass wool and sand. Composite materials are acceptable. Figure 11 is referred first. Figure 11 is a schematic view of the embodiment of the vacuum molding process device of this invention. As sown in Figure 11 this device comprises a holding furnace 44 for holding molten metal; a lower die plate 42 placed on the holding furnace 44; a heat insulation 83 as heat insulating means placed on the lower die plate 42; flasks 53a, 53b placed on the heat insulation 83; an upper and lower mold halves 51a, 51b, which have been produced using vacuum seal process, and which are placed in the flasks 53a, 53b; an upper die plate 56 placed on the upper mold half 51a; and four rods 57 uprightly disposed on the upper surface of the holding furnace at it four corners. A compressed air introduction tube 58 to introduce compressed air into the holding furnace 44 is attached to the holding furnace. Moreover, the mated upper and lower mold halves 51a and 51b define a molding cavity 52. In addition, a stoke 60 is attached to the die plate 42 for introducing the molten metal from the holding furnace 44 into the molding cavity 52. Moreover, the heat insulation 83 is formed with an aperture at a position under the lower mold half 51b, corresponding to the gate, through which aperture the molten metal passes. Now, the operation of the vacuum molding process device of this embodiment is described. In Figure 11 the inside of the upper and lower mold hales 51a and 12 51b is decompressed, and the inside of the flasks 53a and 53b has been decompressed by the decompressing device 62 through the flasks 53a, 53b and the suction pipes 63 and 63. The upper and lower mold halves 51a and 51b are placed on the heat insulating materials 83, and the upper die plate 56 is placed on the upper mold half 51a. Next, the heat insulating materials 83 and the upper and lower mold halves 51a and 51b are sandwiched and clamped between the upper die plate 56 and the lower die plate 42. Afterwards, compressed air is introduced from a compressed air source (not shown) into the holding furnace"44 through the compressed air introduction tube 58, to apply a pressure on the surface of the molten metal, to raise the molten metal in the stoke 60 to f i 11 the molding cavity 52 with the molten metal. After the molten metal in the molding cavity 52 hardened, the introduction of compressed air was stopped, and the pressure in the holding furnace 44 was returned to the atmospheric one. Thus extra molten metal in gate and stoke 60 returned in the holding furnace 44, and thus the pouring was ended. Since in the vacuum molding process device of this embodiment the holding furnace is disposed just under the mold, the instal I at ion space for the device can be minimized. Although in this embodiment neither a feeder head nor a riser is used, they may be used when desired. Further, although the molten metal is supplied by introducing compressed air in this embodiment, it may be suppl ied using an electromagnetic pump etc. or using any other methods. Next, the pouring test carried on the vacuum molding process device of this embodiment is described. In the pouring test a molten aluminum is poured into the molding cavity 52, and the total length that is the length of the molten metal fi I led in the molding cavity 52 and the length of the good part that had been fi I led we 11 were measured. Figure 12 shows the pressure condition in the pouring test of the compressed air for pressurizing the inside of the holding furnace 44. The final target setting pressures are 0.03 and 0.06 MPa, and the pressure raising rates are 0.01 and 0.02 MPa/s. Figure 13 shows the result of the measured lengths of the total length that is a length of the molten metal filled in the molding cavity 52 and the length of a good part that is we I -I fi I led, where the thickness of the molding cavity 52 is 3mm. The pressure raising rate in the holding furnace 44 was 0.01 MPa/s, and the final target setting pressure was 0. 03 MPa. Figure 13 also shows the result of an exampl.e for comparison, where the gravity die cast was performed using a mold produced by the conventional vacuum sealed process. It is clear from Figure 13, both the total Iength and the length of the good part in the embodiment of the vacuum moIding process device are longer than those in the comparison example. Figure 14 shows the result of the measured lengths of the total length that is a length of the molten metal filled in the molding cavity 52 and the length of 13 a good part that is we 11 fi I led, where the thickness of the molding cavity 52 is 3 mm. The final target setting pressure was 0.03 Mpa, and the pressure raising rates in the holding furnace 44 were 0.005, 0.01, and 0.02 MPa/s. It is seen from Figure 14 that there is a tendency that both the total'length and the length of the good part become longer as the pressure raising rate become greater, and that the changes in these Iengths become smaI I when the pressure" raising rate exceeds 0.01 MPa/s. Thus, from the result of this test, the pressure raising rate is preferably 0.01 MPa/s. Next, Figure 15 shows the result of the measured surface roughness of the . produced casts. Figures 15 also shows the result of an example for comparison, where the gravity die cast was performed using a mold produced by the conventional vacuum sealed process. The part where the surface roughness was measured is a part where the molten metal flows from the runner into the molding cavity 52 in Figure 11. As understood from Figure 15, there was no difference between the comparison example using the gravity die cast and the vacuum sealed process device of this embodiment when the final target setting pressure of the compressed air that pressurizes the inside of the holding furnace 44 was 0.03 MPa. However, when the final target setting pressure of the compressed air for pressurizing the inside of the holding furnace 44 was 0.06 MPa, the numerical value of the surface roughness became greater, showing that the surface roughness became rough. It is considered that this is caused by the pressure of the molten metal, which became greater and allowed the molten metal to penetrate the mold. Next, Figure 16 shows the example of the pressure control during the pouring of the molten metal in this embodiment. As shown in Figure 16, the upper and lower mold halves 55a and 55b are mated to define the molding cavity 52. By pressurizing the upper surface of the molten metal in the holding furnace 44, the molten metal. rises in stoke 60 and is poured in the molding cavity 52. In the graph in the right of Figure 16 the point to start pressurizing with compressed air the surface of the molten metal in holding furnace 44 is assumed to be 0. The setting pressure P of the Compressed air for pressurizing the surface of the molten metal in the holding furnace 44 and the height h that the molten metal can attain to are expressed as an equation, P=pbh. Therefore, since the height of the molten metal changes rapidiy until the molten metal reaches the position hi at which the molten metal flows from the gate into the molding cavity 52 as shown in Figure 16, it is necessary to make great the pressure raising rate of the setting pressure P of the compressed air for pressurizing the inside of the holding furnace 44. Next, when the flat part of the molding cavity 52, i.e., the part from level hi to level h2, is filled with the molten metal, it is necessary to make less the pressure raising rate of the setting pressure P of the 14 compressed air for pressurizing the inside of the holding furnace 44. Because, the part from level hi to level h2 is a product part, and the flow of the molten metal becomes a turbulent one if the rate is great, therefore the molten metal concentrates at a part of the film (the shielding member) and contacts with that part, thereby causing its falI due to a partial burning and hence a partial fall of the mold. The less rates also prevents the generation of the slag entrainment in the flow, which would be caused by such a turbulent flow. • Moreover, since at the part from level h2 to h3 the height of the molten metal changes rapidly the same as in the part up to the level hi.- the pressure raising rate of the setting pressure P of the compressed air for pressurizing the inside of the holding furnace 44 should be made great. The Fifth* Embodiment Next, the fifth embodiment of this invention is described on the basis of Figure 17. Figure 17 is a schematic view of another embodiment of the vacuum sealed process device. As shown in the drawing, this vacuum sea led process device comprises a holding furnace 44 for holding molten metal, four upright props 72 disposed at the . side of the holding furnace 44, a lower die plate 42 mounted on the tops of the props 72 and 72, flasks 53a and 53b placed on the lower die plate 42, an upper and lower mo Id halves 51a, 51b,. which have been produced using the vacuum seal process and placed in the flasks 53a and 53b, respectively, an upper die plate 56 placed on the upper surface of the upper mold half 51a, and a pipe 79 for allowing the holding furnace 44 to communicate with an inlet 58 formed at the bottom of the lower die plate 56 for the i ntroduct ion of the molten met a.I. The four up r ight props 72 support the I ower die plate 42 at its four corner. The holding furnace 44 is provided with a compressed air introduction tube 80 to introduce compressed air into the holding furnace. Moreover, the upper and lower mold halves 51a and 51b are mated to define a molding cavity 52. In addition, stoke 60A that communicates with the pipe 79 to introduce the molten metal in the holding furnace 44 into molding cavity 52 is attached to the die plate 42. Moreover, the lower die plate 42 is formed with an aperture at a position corresponding to the gate of the lower mold half 51b for communicating with the pipe 79. Further, a heat insulation 83A is disposed around the aperture. Next, the operation of the vacuum molding process device of this embodiment is described. In Figure 17 the inside of the upper and lower mold halves 51a and 51b has been decompressed by pressure decompressing device 62 through the flasks 53a, 53b and suction pipes 63 and 63. The upper and lower mold halves 51a and 51b were placed on the lower die plate 42, and the upper die plate 56 was placed on the upper 15 mold half 51a. Next, the upper and lower mold halves 51a and 51b were sandwiched . clamped between the upper and lower die plate 56 and 42. Afterwards, compressed a.i r was introduced from an compressed air source (not show) into the holding furnace 44 through the compressed air introduction tube 80 to apply pressure on the surface of the molten metal. Thus the molten metal rose in the stoke 60A and the pipe 79, and . the molding cavity 52 was filled with it. The introduction of compressed air. was stopped after the molten metal in the molding cavity 52 hardened, and thus an extra molten metal in the gate, pipe 79, and stoke 60A returned into the holding furnace. 44 as the pressure in the holding furnace 44 returned to the atmospheric pressure. Thus the pouring was completed. Since in the vacuum molding process device of this embodiment the mold is not disposed above the hoIding furnace, suppl y i ng mol ten meta I in the furnace and removing detritus such as slag and oxides existing in the surface of the molten metal from the furnace can be performed easi ly. Although in this invention no feeder head or riser is use, they may be used if desired. Moreover, although in this embodiment the molten metal is fed by using compressed air, it may be done using an electromagnetic pump, etc. or by any other methods. . As shown in Figure .18, the molten metal may be suppl ied to a level under the die plate 42 by a pipe 79A, and a sand layer or block 84, which has passage therein for the molten metal, is attached to one end of the pipe 79A, which end faces the lower mold half 51b. Using this sand block 84 can feed the molten metal to the plurality of gates simultaneously. Therefore, it gives easy applications to a cast having a complicated shape and to a cast having a plurality of casting pieces. When the position of gates is chained due to the change of the casting plan, a sand block 84 may be formed that has passages for molten metal corresponding to the position of the gates. Using such a sand block 84 gives easy application to such a change of the position of gates. Although in the embodiment shown in Figure 18 the sand block 84 is connected to the pipe 79A, it may be connected to the stoke directly. The Sixth Embodiment A cooling system shown in Figure 19 and 20 for cooling a mold framing can be used for this invention. The system sprays compressed air to the bottom and side surfaces of the mold framing in order to suppress the rise of temperature of the mold framing and to prevent the film from being welded to it. By using this cool ing system, compressed air is supplied into a chamber of the mold framing, which has one side, or. surface, at which the metal mold framing and the film contact, to cool the mold framing to suppress the rise of it temperature and to prevent the film from being welded to it. Further, the compressed air may be sprayed to the bottom of a surface plate to cool it to prevent the film from being welded to it. 16 In the conventional metal mold framing as in Figure 21, the side walIs of both cope and drag are in the form of chambers 101, 101 (i.e., hollow). Since these chambers are evacuated by a vacuum pump (not shown), this negative pressure in the chambers shapes a cope 61a and a drag 61b. That is, the cope 61a and the drag 6tb are covered by an upper flask 93a, a lower flask 93b, an upper film 97, mold surface films 98, 98, and a bottom film 99 and sucked by the vacuum, so that the shapes o'f the cope and the drag are kept. ¦ During the pouring, the parts of the films that contact with the as-cast product are burned out, though the parts of the films between the upper and lower flasks remain and are then removed during the demolding. The upper and lower fi Ims remain and are removed before the demolding. After the pouring and when the as-cast product 96 hardens to some degree, the suction is stopped, and the as-cast product is natural ly cooled in the mold. If the as-cast product is one that has a great heat capacity, the heat are transferred from the ¦ product 96 to the upper and lower flasks 93a, 93b and the surface plate 95 through the cope 61a and the drag 61b, and the parts of the product surface films that are I ocated between the upper and lower f I asks 93a, 93b and the lower fi Im are undes i rably welded to the flask and the surface plate (Figure 21). To overcome this undesirable problem, the cooling device of the present invention includes air nozzles 91, 91 for the metal side walls and an air nozzle 92 for spraying compressed air to the metal mod framing to cool it. For a side air bIow, annuIar cool ing chambers 102, 102 are formed in the s ide wal Is at the matching plane (the plane at which the upper and lower flask mate). The air nozzles 91, 91, which are detachably attached to, or inserted in, the annular chambers. The annular cooling chambers 102, 102 has some apertures, which may be used as insertion holes for the nozzles 91, 91 and/or gateways for the compressed air (Figure 19). The side ai r blow is activated and deactivated by manual ly operating a valve 104 (Figures 19 and 20). For a bottom ai r blow, the air nozzle 92 for the surface plate is located below it at the central part. The air nozzle is activated or deactivated by manually operating the valve 104. Steps The metal mold framing is continuously sucked for a certain period of time after the pouring (to keep the shape of the sand mold). The suction is then stopped, and the as-cast product is naturally cooled in the metal mold framing. During this cooling, compressed air is sprayed to the metal mold framing to aggressively cool it. Although the cooling system of this embodiment is configured as a 11 semi-automated equipment, it may be fully automated by using actuators such as air cylinders to automatically attach and detach the nozzle, and electromagnetic valves to automatically carry out the air blow. Although some preferable embodiments of this invent ion are described, these embodiments are only for explanation purpose to faci I itate the understanding of the invention, and the invention is not I imited to these embodiments. Therefore, it is clear to one ski I led in the art that the embodiments may be changed and modified within the spirit and scope of the invention, and that the present invention includes such changes and modifications and is defined by the attached claims and the equivalents. 18 Claims 1. A pouring method in a vacuum sealed process comprising the steps of: sealingly covering the surface of a pattern plate by a shielding member; placing a mold framing on the shielding member and then putting afill that does not include any binder in the mold framing; sealingly covering an upper surface of.the. fi 11 and then evacuating an inside of the mold framing to suck the shielding member to the fi 11 to shape the shielding member; removing the pattern plate from trie shielding member, thereby forming a mold half that has a molding surface; forming another mold half in a simi lar way and mating the mold haives to define a molding cavity; pouring molten metal in the molding cavity; and releasing the negative pressure in the mold framing to take out a as-cast product, wherein the method further comprises the step of decompressing the molding cavity before pouring molten metal in the mated mold. 2. The pouring method of claim 1, including the step of. forming a plural ity of holes in the inner side of the fill in the mold framing, wherein the step of decompressing the molding cavity is performed by decompressing means that communicates with the holes through an inner chamber of the mold framing, through the holes and the fill. 3. The pouring method of claim ?., wherein the mold halves do not have any open top riser. 4. The pouring method of claim 1, including a step of disposing an open top r iser in the upper mold half, the open top riser being opened to the molding cavity, wherein the step of decompressing the molding cavity is performed by decompressing means that communicates with the open top riser through the holes and the fill. 5. The pouring method of claim 2, including a step of forming a plural ity of apertures in the shielding member that contacts the molding cavity, wherein the step of decompressing the molding cavity is performed by the decompressing means through the apertures formed in the shielding member, the fill, and a plural ity of apertures formed in an inner side of the mold framing, the inner side contact ing the fill. 19 6. The pouring method of claim 4, including a step of disposing vent plugs in the apertures formed in the shielding member, wherein the step of decompressing the molding cavity is performed through the vent plugs, the fill, and a plurality of apertures formed in an inner side of the mold framing, the inner side contacting the f i 11. ¦ ... . 7. The pouring method of any one of claims 1-6, further comprising the steps of: measuring a degree of pressure reduction for at least one of the upper and lower mold halves during a period between the start and end of the pouring; sending the detected degree of pressure reduction to a controller; and adjusting degrees of . pressure reduction in the inside of the at least one mold half and in the molding cavity. 8. The pouring method of any one of claims 1-7, wherein the molding cavity is decompressed so that Pm=1-75 KPa, Pc=1-95 KPa, and Pc-Pm=3-94 Kpa, where Pm and Pc are a pressure within the mated mold and a pressure in the molding cavity. 9. An as-cast product produced by the pouring method of any one of claims 1-8. 10. A molding device used in a vacuum sealed process, comprising a mold framing for receiving a fill that is a mold that defines a molding cavity, an inner surface of the mold framing is formed with a plural ity of apertures, the inner surface contact ing the fill, the mold framing having an inner chamber for communi cati ng with the plurality of apertures, the inner chamber being connectable to decompressing means positioned outside the mold framing for decompressing the molding cavity. 11. A molding device of claim 10, further comprising means for measuring'a degree of pressure reduction for at least one of the upper and lower mold halves during a period between the start and end of the pouring; and a controller for receiving the detected degree of pressure reduction and for adjusting degrees of pressure reduction in the inside of the at least one mold half and in the molding cavity. 12. A molding device of claim 10 or 11, further including cool ing means for cooling the mold framing by spraying compressed air to side walls and a bottom of the mold framing. 13. A molding device of claim 12, wherein the mold framing includes a lower 20 flask and an upper flask placed on the lower flask, the lower flask having at an inner upper part an annular cooling chamber in which the compressed air flows, the upper flask having at an inner lower part an annular cool ing chamber in which the compressed air flows. 14. A pouring method in a vacuum sealed process comprising the steps of: seafingl.y covering the surface of a pattern plate by a shielding member; placing a mold framing on the shielding member and then putting a fill that does not include any binder in the mold framing; seali ngly cover ing an upper surface of the fill and then evacuating an inside of the mold framing to suck the shielding member to the fill to shape the shielding member; removing the pattern plate from the shielding member, thereby forming a mold half 'that has a molding surface; forming another mo Id half in a simi lar way and mat i ng the mo Id ha I ves to def i ne a molding cavity; pouring molten metal in the molding cavity; and releasing the negative pressure in the mold framing to take out a as-cast product, wherein the method further compr ises the step of forming a gate in the lower mold half of the mated mold, and wherein no gate is provided in the upper mold half. 15. The pouring method of claim 14, further comprising a step of adjusting the lower mold half, which is disposed above a hold furnace, so that the lower mol,d half is kept horizontally. 16. The pour ing method of claim 14, further compr ising the steps of disposing the holding furnace below the mold framing; and providing cushion material between the lower mold half and the holding furnace to keep the lower mold half hor izontal ly. 17. The pouring method of claim 16, wherein the cushion material includes a heat insuI at ion. 18. The pour ing method of claim 17, further compr ising the step of disposing a lower die plate for supporting the flask, under the heat insulation. 19. The pouring method of claim 18, further compr ising the step of disposing cooling means at the lower die plate. 20. The pouring method of claim 18, wherein the heat insulation includes a 21 sand block. 21. The pouring method of claim 18, wherein the heat insulation includes a block of self-hardening sand. . 22. The pouring method of claim 20, wherein the sand block includes one gate for communicating with a stoke of the holding furnace and a plural ity of runners for communicating with the gate and the molding cavity. 23. The pouring method of any one of claims 14-22, wherein the pouring method is a low pressure casting. 24. The pouring method of any one of claims 14-22, wherein the pouring method is a differential pressure casting. 25. The pouring method of any one of claims 14-24, wherein a pouring rate is controlled when molten metal is poured in the molding cavity. 26. An as-cast product produced by using the pouring method of any one o claims 14-25. 27. The pouring method of any one of claims 1-8 and 14-25, further including the step of cooling the mold framing by spraying compressed air to side walls and a bottom of the mold framing. A method and a device for pouring a molten metal in a vacuum molding for casting a thin-walled casting by using a Vrprocess casting mold (molding frame body) and a casting cast by the method. The method comprises a shielding member fitting step for fitting a shielding member onto the surface of a prototype plate, a step for placing the molding frame body on the fitted shielding member and filling a filler not containing, a bond in the molding frame body, a step for .'. sucking the shielding member to the filler side by bringing the inside of the molding frame body into a negative pressure by closing the upper surface of the filler to form the shielding member, a step for molding a semi-split casing mold with a molding surface by releasing the prototype plate from the shielding member, a step for defining a casting cavity and forming a completed casting mold by matching the semi-split casting mold with another semi-split casting mold molded in the same manner as in the case of the semi-split casting mold, a step for pouring the molten metal in the casting cavity, and a step for taking out the casting by releasing the state of negative pressure in the molding frame body. The method also comprises a step for depressurizing the inside of the casting cavity through the molding frame body before starting to pour the molten metal in the completed casting mold.

Full Text

SPECIFICATION Title of the i nvent i on :
Pouring Method, Device, and Cast in Vacuum Molding Process
Technical Field .
This invention relates to a pouring method, a device, and a cast in a vacuum molding process to produce a cast, especially, a thin-wall cast. Here, the vacuum molding process (hereafter, referred to "the vacuum sealed process") denotes a molding and pour ing process that includes the steps of seal ingly covering the surface of a pattern plate by a shielding member; placing a mold framing on the shielding member and then putting a fi II that does not include any binder in the mold framing; sealingly covering the upper surface of the fill and then evacuating the inside of the mold framing to suck the shielding member to the fill to shape the shielding member; removing the pattern plate from the shielding member, thereby forming a mold half that has a molding surface; forming another mold half in a s imilar way and mating the mold halves to define a molding cavity; pour ing molten metal in the molding cavi:ty; and then releasing the negative pressure in the mold framing to take out a as-cast product.
Background Art
Conventionally, the vacuum sealed process is widely used (for instance, see JP, S54-118216, A). However, the process were mainly used to produce thick-wall casts such as piano frames, counterweights, etc. and it was not used to produce casts that have thin walls of the thickness about 3mm or less for instance.
Moreover, conventionally there was no device that cools the mold framing in the vacuum sealed process. The rise in temperature of the mold framing is confined after the pour i ng by conti nuing to evacuate the inside of the mo Id framing. However,; i n a step, the evacuation is stopped over a certain period of time, and the as-cast product, the mold framing, etc., are naturally cooled. When a product that has a large heat capacity such as a counter weight is cast, during the natural cool ing the
i
metal mold framing, the surface plate, etc., receive heat from the as-cast product, and hence their temperatures rise, thereby causing the fi I ms used to melt and adhere to the metal mold framing, the surface plate, etc.
The present invention has been conceived in view of the problems discussed above. A main purpose of this invention is to provide a pouring method and a device by using the vacuum sealed process, which are suitable for producing a cast, especially a thin-wall cast, and to provide a cast produced by using the pouriing method.
Another purpose of this invention is to provide a device for cooling the mold

2 framing.
Summary of the Invention
To that.end, in one aspect of the present invention the pour ing method in the vacuum sealed process is character i zed in that the molding cavity is evacuated through the mold framing. That is, although in the usual vacuum sealed process the inside of the mold framing is intercepted by a shield member from the molding cavity that communicates with the atmosphere, and the inside of the mold framing is evacuated to suck the shielding member to the fill to shape the shielding member and to maintain the molding cavity, in the vacuum sealed process of the present invention such a shielding member used in the usual vacuum sealed process is removed to a I low the inside of the mold framing and the molding cavity, which communicates with the atmosphere, to communicates with each other (although this communication may be considered to collapse the sand mold). With the comrnunication being kept, the mold half and the molding cavity are maintained to produce a cast.
Further, in the above-mentioned aspect a step of evacuating the molding cavity is performed through the mold framing. It is characterized in that this step is carried out through vent plugs after the steps of placing the shielding member, disposing the vent plugs in the model part of pattern plate, placing the mold framing on the shielding member and the vent plugs, and fi11 ing the fi 11 in the mold framing.
Inaddition, it i s character ized that the step of evacuating the molding cavity through the mold framing in the one aspect is performed through a plural ity of vent holes formed in the shielding member after the mold half is produced.
Moreover, it is characterized that the pouring method of the vacuum sealed process in the one aspect further comprises the steps of measuring the degree of a pressure reduction for at least one of the mated mold halves between the start and the completion of pour ing: transferr ing the measured degree of the pressure reduction to a controller; and adjusting the degree of pressure reduction in the mold half and molding cavity.
In addition, it is characterized in the one aspect that the mold half is not provided with an open top riser. An open top riser functions to discharge air and slag of the molten metal, and hence it has been used to stably produce a cast that is not deformed. It was found that when the molding cavity is evacuated appropriately without using an open top riser inthis invention, theflowofmoltenmetal is improved and the molten metal can be effectively filled in the molding cavity before the deformation of the sand mold occurs.
According to the one aspect of the present invention, since the molding cavity is evacuated in the vacuum sealed process (this is performed through at least one of the mo Id framing and the open top riser), a thi n-wa II cast can be produced by t he-vacuum mo I ding process. Moreover, sincetheinsideofthemoldandthemoldingcavity

3 "
are simultaneously evacuated due to the vent holes, an additional device is not
requiredforevacuatingthemoldingcavity, provinganadvantage in that the.structure of the molding machine can be s imple. When the open top riser is not provided, a- feeder head or throwing-away part for the molten metal can be assumed to be a minimum requirement. As a result, there is an advantage that the product yield improves. In addition, since this invention keeps the feature of the usual vacuum sealed process, it has an advantage in that the mold framing can be easily removed and that an as-cast thin-wall product can easily taken out.
According to another aspect of the present invention, to achieve the above-mentioned purpose, the pouring method of the vacuum sealed process is characterized in that the lower mold half (drag) of the mated mold is formed with a gate, while the upper moid half (cope) is not formed with any gate.
Moreover, the method is characterized in that the cope of the mated mold, which is positioned above a hold furnace, is adjusted so as to be kept horizontally.
In addition, the method is characterized in that the pouring is carried out by using cushion means disposed between the mated mold and the holding furnace for keeping the cope of the mated mold horizontally.
Moreover, to achieve the above-mentioned purpose, the pouring method of vacuum sealed process of this invention is characterized in that the pouring is carried out with a heat insulating material.being disposed between the mated mold and the holding furnace when the mated mold is disposed above the holding furnace.
In addition, it is characterized in that a sand layer that functions as the heat insulating material communicates with a stoke at a lower part and is connected with a plurality of gates at an upper part.
Moreover, to achieve the purpose, the pour ing method of the vacuum sealed process of this invention is" characterized in that it is the low pressure die casting or the. differential pressure die casting.
In addition, the pouring method is characterized in that when molten metal i,s poured in the molding cavity, the pouring rate is controlled.
According to the another aspect of the invention, since a gate.is formed only in the lower mold half of the mated mold (it is not formed in the upper mold half), this a I lows molten metal to be poured from below, where the flow of the molten metal becomes a laminar flow, entraining less air and slag to the molten metal compared with the gravity die casting and the die casting. Moreover, since a riser and a feeder head need not be provided, the throwing-away part for the molten metal can be assumed to be a minimum requirement. As a result, there is an advantage that the product yield improves. In addition, since this invention keeps the feature of the usual vacuum sealed process, it has an advantage in that the mold framing can be easily removed and that an as-cast thin-wall product can easily taken out.

4 . '
This invention is suitable for producing large thin-wall casts such as framings
for large household electrical appliances, large televisions, cars, and machinery.
Any material of metal may be used.
In the two aspects of the invention discussed above, cooling means by spraying
compressed air on the mold framing for cooling it can be used.
These and other purposes, features, and advantages will be clear from the
following descriptions about the embodiments referred to with reference to the
accompanying drawings.
Brief description of the Drawings
Figure 1 is a schematic cross-sectional view of the first embodiment of this invention.
Figure 2 shows the outline of the method of the first embodiment.
Figure 3 is a schematic cross-sectional view of the second embodiment of this invention.
Figure 4 shows the outline of one stage of the second embodiment.
Figure 5 shows a pressure diagram of the second embodiment.
Figure 6 is a.schematic cross-sectional view of the third embodiment of this invention (an example of evacuating the molding cavity through an open top riser).
Figure 7 is a schematic cross-sectional view showing another pouring method (of a prior art) for comparison.
Figure 8 shows the result by the second embodiment of this invention
Figure 9 shows the result by the third embodiment of this invention.
Figure 10 shows the result of pouring by the prior-art method for comparison.
Figure 11 is a schematic cross-sectional view of the fourth embodiment of this invention.
Figure 12 shows the pressure condition of the pouring test in the fourth embodiment.
Figure 13 shows a result of the flow length of the pouring test in the fourth embodiment.
Figure 14 shows another result of the flow length of the pouring test in the fourth embodiment.
Figure 15 shows the result of the surface roughness of the pouring test in the. fourth embodiment.
Figure 16 shows an example of the pressure control of the pouring test in the fourth embodiment.
Figure 17 is a schematic cross-sectional view of the fifth embodiment of this invention.
Figure 18 shows an alternative embodiment of a pour ing tool of thi s invention.

5.
Figure 19 is a sectional plan view of a device (the sixth embodiment) of this invention for cooling a mold framing (a sectional view of a chamber part). Figure 20 is a sectional front view of figure 19. Figure 21 a sectional front view of a conventional mold framing structure.
Preferred Embodiments of the Invention
The preferred embodiment of this invention is now described. In some embodiments, the same or similar numbers are used for the same or similar elements.
This invention of the vacuum sealed process is character ized in that vent holes are used to at low the molding cavity to communicate with the inside of the mold, a,nd in that the molding cavity is evacuated through the mold framing.
That is,the invention is a pouring process in the vacuum sealed process, the process including the steps of seal ingly covering the surface of a pattern plate by a shielding member; placing a mold framing on the shielding.member and then putting a fi 11 that does not include any binder in the mold framing; seal ingly covering the upper surface of the fi 11 and then evacuating the inside of the mold framing to suck the shielding member to the fill to shape the shielding member; removing the pattern plate from the shielding member, thereby forming a mold half that has a molding surface; forming another mold half in a similar way and mating the mold halves to define a molding cavity; pouring molten metal in the molding cavity; and then releasing the negative pressure in the mold framing to take out a as-cast product. The process includes the step of evacuating the molding cavity through the mold framing before pouring the molten metal in the molding cavity and it is characterized in that Pm=1-75kPa, Pc=1-95kPa, and Pc~Pm=3-94kPa when the internal pressure of the mold and the pressure in the molding cavity are assumed to be Pm and Pc, respectively, when the molten metal is poured in the molding cavity.
Here, the purpose of assuming mold internal pressure Pm to be 1-75 KPa is that if is less than 1 KPa, a huge vacuum pump is required, and that if it is more than 75 KPa, it is not possible to suck the gas generated at the pouring. Further, the purpose of assuming the molding cavity internal pressure Pc to be 1-95 KPa is that if it is more than 95 KPa. a smooth inflow of the molten metal cannot be assured since the differential pressure with atmospheric pressure (101.3 KPa) is not enough, and that if it is less than 1 KPa, the mold may col lapse toward the molding cavity. In addition, it is necessary to assure Pc>Pm, because making the mold internal pressure Pm to be a degree of pressure reduction lower than molding cavity internal pressure Pc prevents the molten metal from penetrating the mold. Moreover, the value of Pc-Pm, which is defined by Pc and Pm, must be 3-94 KPa.
Here, the mold framing denotes a flask, or flask assembly, provided with a suction pipe used in the vacuum sealed process.

6
Moreover, in this invention the vent holes may be formed by distr ibutingj the vent plugs in the pattern part after the film is shaped, and then by molding,[and
then by cutting the film along the slits of the vent plugs from the molding cavity
I ¦
side after remolding. Alternatively, the vent holes may be formed by making hojes,. by a needle from the molding cavity side, which holes reach the inside of the mol-d. In addition, in this invention the open top riser may be eliminated by moderately decompressing the molding cavity as mentioned above. The open top riser is a tubular void that passes through the cope to connect the molding cavity tojthe atmosphere. Accordingly, if no open top riser is provided, there will bej no communication hole in the upper part of the cope connecting the molding cavity to the atmosphere.
The First Embodiment
Here, the first embodiment is explained in relation to Figures 1 and 2i.
Figure 1 is a schematic sectional view of a device for the vacuum molding
process used for the embodiment. Upper and lower mold halves 1a and 1b, which wiere
produced by using the vacuum sealed process, are mated to define a molding cavity
2. ¦ ¦ . . ¦
Here, the method of producing the mold halves 1a and 1b is described in detjai I on the basis of Figure 2. In Figure 2, the surface of the pattern plate 12 is seal in'g.ly covered by a film 13 (a shielding member) by applying negative pressure to the surf ape. A flask 3 (a moid framing) is then placed on the film 13,¦and vent plugs 6 (as vpnt holes) are appropriately disposed at an upper mold half side according to the pattern configuration. Afterwards, molding sand is fi1 led in the flask, to produce the upper
j
mold half la. Next, the upper mold half 1a is separated from the pattern plate 12, and the film 13 is cut at the si its of the vent plugs 6. Thus the mold half 1a| is produced with the vent holes being formed with the cuts in the f i Im and the associated vent plugs 6.
A lower mold half 1b, which has been produced in a manner simi lar to the up^er mold half 1a, is mated with it to form a mated mold having a molding cavity (Figure 1). At this time, the molding cavity 2 communicates with the inside of the mol,d framing (flasks 3) and with the atmosphere through runners and a gate. Although! i,n this embodiment no vent plug, or vent hole, is provided in the lower mold half 1b, some vent plugs 6 may be provided when appropriate. Thus a device of the vacuum molding process is formed as shown in Figure 1.
Next, the operation of that device of the vacuum mo I di ng process is described. In Figure 1 the inside of upper and lower mold halves 1a and 1b has been decompressed by a decompression pump 11 through the flasks 3, suction pipes 4 and 4, a piping|5, and a reservoir tank 10.

7
Moreover, the molding cavity 2, together with the mold halves 1a and 1b, is decompressed through the vent plugs 6 (vent holes). The pressure in the.inside of-themoldhalvesiaandib is detected by a pressure sensor 7, and the detect ion pressure is sent to a controller 8. A control signal corresponding to the detected pressure is sent by this controller 8 to a proportional control valve 9 to adjust its degree of opening as required to change the sucking pressure in the mold halves 1a, 1b a'nd the molding cavity 2. Under this state, an aluminum alloy molten metal is poured in the molding cavity 2. Over a period of time, the negative state in the inside of the mold framing is released, and an as-cast product is taken out. This product was not defective in the thin wall of 3mm or less.
Clearly from the above explanation, this invention can produce a cast under decompressed state by applying the vent plugs 6 (vent holes) that allow the molding cavity 2 to communicate with the inside of the mold halves la and 1b to the conventional vacuum sealed process mold.
Second Embodiment
Next, another embodiment (the second embodiment) that uses this invention is described with reference to Figures 3-5. Figure 3 shows an example to form vent holes by needles, which holes pass the inside of the upper mold half. Upper and lower mold halves 21a and 21b have been produced by the vacuum sealed process. Next, needles pass through the film from a molding cavity 22 side into the upper mold half 21a to form vent holes 23. This is carried out as shown in Figure 4. That is, a tool having needles 24 are moved by a drive 25, to form the vent holes in the mold half at one time. The position of needles 24 have been previously set under the control by a computer for the.places where the flow of molten metal is assumed to be bad and where-a casting configuration part is far from the gate.
Moreover, vent holes 23 may be manual ly formed for simpl ifying the device o,r when the number of vent holes is less. Although no vent hoi e is formed in the lower mold half 21b in this embodiment/some may be formed according to circumstances. Afterwards, the mold halves 21a and 21b are mated to form a mated mold having a molding cavity 22 (Figure 3). By adjusting pressure conditions so that the internal pressure Pm in the mold halves 21a and 21b is kept as Pm=1-75 KPa and the internal pressure Pc of the molding cavity 22 as Pc=1-95 Kpa, the pouring was carried out.
Figure 5 shows the example of pressures in the mold halves la, 1b and the molding cavity 2 in this embodiment.
To assure a smooth inflow of the molten metal, the inner pressure Pc in the molding cavity 2 needs an enough pressure differential with the atmospher ic pressure. Further, if Pc-Pm is too small, the mold may collapse, and if Pc-Pm is too large, the vacuum equipment must be large since Pm becomes smal I, yielding a high cost.
From the above-mentioned reasons and the experimental result, it has been

8
found that the conditions of Pm=1-75 KPa, Pc=1-95 KPa, and Pc-Pm=3-94 KPa are effective.
In addition, the change in pressure is described in detail. The internal pressure Pm in the mold halves 1a and 1b is kept as a high degree of pressure reduction ¦ between the start and the end of the pouring for causing a good flow of the molten metal by the pressure reduction and for sucking gas generated by the burning of the shaping film.
After the pouring, where the molding cavity 2 is fi I led with the molten metal, the pressure sensor 7 detects the internal pressure Pm in the mold halves 1a and,1b and sends it to the controller 8. The.controller 8 adjusts the opening of the proportional control valve 9 to adjust the internal pressure Pm in the mold halves 1a and 1b to a low degree of pressure reduction, to prevent the molten metal from penetrating the mold.

9
The Third Embodiment
Figure 6 shows one example of the method of decompressing the molding cavity by using an open top riser R. The upper and lower mold halves 31a and 31b, which have been produced by using the vacuum sealed process, are mated todefinethemolding cavity 32. The inside of the mold halves 31a and 31b is decompressed by a decompression pump 37 through the flasks 33 and 33, suction pipes 34 and 34, a piping 35, and a reservoir tank 36.
Moreover, the upper mold half 31a is provided with the open top riser R, which communicates with the molding cavity 32 and is opened to the upper surface of the upper mold half 31a. The riser R also acts as a feeder head. Further, the lower mold half 31b is provided with a flat gage (not shown) that connects the molding cavity 32 and the open top riser R.
The molding cavity 32 is decompressed by a decompress ion pump 3.7 through a tool 38 connected to the opening of the open top riser R, which opening is located in the upper surface of the upper mold half 31a; a reservoir tank 39 for decompressing the molding cavity; a pressure regulating valve 40; and a reservoir tank 36.
By adjusting the pressure conditions so that the internal pressure Pm in the
. mold halves 31a and 31b and the internal pressure Pc of the molding cavity 32 are
maintained as Pm=1-75 KPa and Pc=l -95 Kpa, respectively, the pour ing was carried-out.'
An Example for Comparison
Figure 7 shows one example of the mold provided with the open top riser R, where the molding cavity is not decompressed. The upper and lower mold halves 31a and 31b, which have been produced by the vacuum sealed process, are mated to define the molding cavity 32. The inside of the mold hal ves 31a and 31b has been decompressed by a decompression pump 37 through the flasks 33 and 33, suction pipes 34 and 34, a piping 35, and a reservoir tank 36.
Moreover, the upper mold half 31a is provided with the open top riser R, which communicates with the molding cavity 32 and is opened to the upper surface of the upper mold half 31a. The riser R also acts as a feeder head. Further, the lower mold half 31b is provided with a flat gage (not shown) that connects the molding cavity 32 and the open top riser R. In the mold framing configured as mentioned above, pouring was carried out with the molding cavity not been decompressed.
Figures 8-10 are schematic diagrams showing the results of pouring. These schematic diagrams show the photograph of the results of pouring in the imitative manner.
Figure 8 shows the result of the pouring carried out by the method of the second embodiment. Figure 9 shows the result of the pouring carried out by the method of

10
the third embodiment. Figure 10 shows the result of the pouring carried out by the method of the reference example for comparison.
As shown in Figure 10, it is understood that when the molding cavity is not decompressed as in the example for comparison, the molten metal is filled only partially in the molding cavity near -the flat gate. In the result shown in Fi gure 9 for the third embodiment of the pouring method of the present invention, the molten metal has reached the area where the open top riser R is located, thus the effect of decompressing the molding cavity is seen in comparison with the reference example. However, the area at which no open top riser is located is not f i I led with the molten metal, and thus the as-cast product is not good. In Figure 8 for the pouring method of the second embodiment of the present invention, the enti re molding cavity is fi I led with the molten metal. Thus a greater effect of decompressing the molding cavity is seen than the result of the third embodiment.
Clearly from this result, the advantage of the use of this invention can be confirmed.
Table 1 Degree of FiI I ing Casting Cost OperabiIity
Hole by needle very good very good good
Vent hole good average average
Open top riser average average good
In Table 1 three methods are shown to al low the molding cavity to communicate with the mold framing for decompressing the molding cavity. One is making holes by needles, one is to use vent holes, and the other is to use the open top riser. The degree of fi 11 ing of the molten metal, the casting cost, and the operabi I ity of molding of these methods are compared in Table 1. The method using the needles shows better result than two other methods.
The Fourth Embodiment
Next, the fourth embodiment of this invention is described with reference to Figures 11-16. This invention is characterized in that the pouring is carried out with the mated mold produced using the vacuum sealed process being disposed above a holding furnace. That is, in the pour ing method of the vacuum sealed process, a gate is formed at the lower mold half, and no gate is formed at the upper mold half. Further, the poring method is also character ized in that heat insulation means are disposed betwee'n the mated mo Id and the holding furnace. Further, the lower surface of the lower mo Id

11
half is made flat.
Here, providing no gate at the upper mold half means that the pouring is carried out from below, since the gravity die cast, which is used for the vacuum sealed process, is not used, but the low pressure die cast or the pressure differential die cast is used for pouring. Thus the mated mold is located above the holding furnace. ,
The heat insulating means acts for preventing the film (the shielding member) from being melt due to the heat from the holding furnace. The heat insulating means includes heat insulating material disposed between the lower mold half and a lower die plate on which the lower mold half is placed. Alternatively, the heat insulating material may be partly inserted in the lower die plate. The material of the heat insulation may be any one that can resist the temperature of the molten metal such as earthenware, ceramics, gypsum, a sand mold, and a of se|f hardening sand mold, etc.
To adjust the lower mold half so that it is kept horizontal denotes proving cushi on member or f i 11 i ng mater i a I between the I ower mo Id half or the heat insulating material and the lower die plate to prevent the molten metal from being escaped due to a gap caused when the bottom of the lower mold half or it is not horizontal, or it denotes operating any machinery (a scraper, vibrator, etc.) to flatten the fi I I ing material. The material for this cushion member may be soft material to fit the bottom shape of the lower mold half and that is durable to the temperature of the molten metal, such as glass wool and sand. Composite materials are acceptable.
Figure 11 is referred first. Figure 11 is a schematic view of the embodiment of the vacuum molding process device of this invention. As sown in Figure 11 this device comprises a holding furnace 44 for holding molten metal; a lower die plate 42 placed on the holding furnace 44; a heat insulation 83 as heat insulating means placed on the lower die plate 42; flasks 53a, 53b placed on the heat insulation 83; an upper and lower mold halves 51a, 51b, which have been produced using vacuum seal process, and which are placed in the flasks 53a, 53b; an upper die plate 56 placed on the upper mold half 51a; and four rods 57 uprightly disposed on the upper surface of the holding furnace at it four corners.
A compressed air introduction tube 58 to introduce compressed air into the holding furnace 44 is attached to the holding furnace. Moreover, the mated upper and lower mold halves 51a and 51b define a molding cavity 52. In addition, a stoke 60 is attached to the die plate 42 for introducing the molten metal from the holding furnace 44 into the molding cavity 52. Moreover, the heat insulation 83 is formed with an aperture at a position under the lower mold half 51b, corresponding to the gate, through which aperture the molten metal passes.
Now, the operation of the vacuum molding process device of this embodiment is described. In Figure 11 the inside of the upper and lower mold hales 51a and

12
51b is decompressed, and the inside of the flasks 53a and 53b has been decompressed by the decompressing device 62 through the flasks 53a, 53b and the suction pipes 63 and 63. The upper and lower mold halves 51a and 51b are placed on the heat insulating materials 83, and the upper die plate 56 is placed on the upper mold half 51a. Next, the heat insulating materials 83 and the upper and lower mold halves 51a and 51b are sandwiched and clamped between the upper die plate 56 and the lower die plate 42.
Afterwards, compressed air is introduced from a compressed air source (not shown) into the holding furnace"44 through the compressed air introduction tube 58, to apply a pressure on the surface of the molten metal, to raise the molten metal in the stoke 60 to f i 11 the molding cavity 52 with the molten metal. After the molten metal in the molding cavity 52 hardened, the introduction of compressed air was stopped, and the pressure in the holding furnace 44 was returned to the atmospheric one. Thus extra molten metal in gate and stoke 60 returned in the holding furnace 44, and thus the pouring was ended.
Since in the vacuum molding process device of this embodiment the holding furnace is disposed just under the mold, the instal I at ion space for the device can be minimized. Although in this embodiment neither a feeder head nor a riser is used, they may be used when desired. Further, although the molten metal is supplied by introducing compressed air in this embodiment, it may be suppl ied using an electromagnetic pump etc. or using any other methods.
Next, the pouring test carried on the vacuum molding process device of this embodiment is described. In the pouring test a molten aluminum is poured into the molding cavity 52, and the total length that is the length of the molten metal fi I led in the molding cavity 52 and the length of the good part that had been fi I led we 11 were measured. Figure 12 shows the pressure condition in the pouring test of the compressed air for pressurizing the inside of the holding furnace 44. The final target setting pressures are 0.03 and 0.06 MPa, and the pressure raising rates are 0.01 and 0.02 MPa/s.
Figure 13 shows the result of the measured lengths of the total length that is a length of the molten metal filled in the molding cavity 52 and the length of a good part that is we I -I fi I led, where the thickness of the molding cavity 52 is 3mm. The pressure raising rate in the holding furnace 44 was 0.01 MPa/s, and the final target setting pressure was 0. 03 MPa. Figure 13 also shows the result of an exampl.e for comparison, where the gravity die cast was performed using a mold produced by the conventional vacuum sealed process. It is clear from Figure 13, both the total Iength and the length of the good part in the embodiment of the vacuum moIding process device are longer than those in the comparison example.
Figure 14 shows the result of the measured lengths of the total length that is a length of the molten metal filled in the molding cavity 52 and the length of

13
a good part that is we 11 fi I led, where the thickness of the molding cavity 52 is 3 mm. The final target setting pressure was 0.03 Mpa, and the pressure raising rates in the holding furnace 44 were 0.005, 0.01, and 0.02 MPa/s.
It is seen from Figure 14 that there is a tendency that both the total'length and the length of the good part become longer as the pressure raising rate become greater, and that the changes in these Iengths become smaI I when the pressure" raising rate exceeds 0.01 MPa/s. Thus, from the result of this test, the pressure raising rate is preferably 0.01 MPa/s.
Next, Figure 15 shows the result of the measured surface roughness of the . produced casts. Figures 15 also shows the result of an example for comparison, where the gravity die cast was performed using a mold produced by the conventional vacuum sealed process. The part where the surface roughness was measured is a part where the molten metal flows from the runner into the molding cavity 52 in Figure 11.
As understood from Figure 15, there was no difference between the comparison example using the gravity die cast and the vacuum sealed process device of this embodiment when the final target setting pressure of the compressed air that pressurizes the inside of the holding furnace 44 was 0.03 MPa. However, when the final target setting pressure of the compressed air for pressurizing the inside of the holding furnace 44 was 0.06 MPa, the numerical value of the surface roughness became greater, showing that the surface roughness became rough. It is considered that this is caused by the pressure of the molten metal, which became greater and allowed the molten metal to penetrate the mold.
Next, Figure 16 shows the example of the pressure control during the pouring of the molten metal in this embodiment. As shown in Figure 16, the upper and lower mold halves 55a and 55b are mated to define the molding cavity 52. By pressurizing the upper surface of the molten metal in the holding furnace 44, the molten metal. rises in stoke 60 and is poured in the molding cavity 52. In the graph in the right of Figure 16 the point to start pressurizing with compressed air the surface of the molten metal in holding furnace 44 is assumed to be 0. The setting pressure P of the Compressed air for pressurizing the surface of the molten metal in the holding furnace 44 and the height h that the molten metal can attain to are expressed as an equation, P=pbh.
Therefore, since the height of the molten metal changes rapidiy until the molten metal reaches the position hi at which the molten metal flows from the gate into the molding cavity 52 as shown in Figure 16, it is necessary to make great the pressure raising rate of the setting pressure P of the compressed air for pressurizing the inside of the holding furnace 44. Next, when the flat part of the molding cavity 52, i.e., the part from level hi to level h2, is filled with the molten metal, it is necessary to make less the pressure raising rate of the setting pressure P of the

14
compressed air for pressurizing the inside of the holding furnace 44. Because, the part from level hi to level h2 is a product part, and the flow of the molten metal becomes a turbulent one if the rate is great, therefore the molten metal concentrates at a part of the film (the shielding member) and contacts with that part, thereby causing its falI due to a partial burning and hence a partial fall of the mold. The less rates also prevents the generation of the slag entrainment in the flow, which would be caused by such a turbulent flow.
• Moreover, since at the part from level h2 to h3 the height of the molten metal changes rapidly the same as in the part up to the level hi.- the pressure raising rate of the setting pressure P of the compressed air for pressurizing the inside of the holding furnace 44 should be made great.
The Fifth* Embodiment
Next, the fifth embodiment of this invention is described on the basis of Figure 17.
Figure 17 is a schematic view of another embodiment of the vacuum sealed process device. As shown in the drawing, this vacuum sea led process device comprises a holding furnace 44 for holding molten metal, four upright props 72 disposed at the . side of the holding furnace 44, a lower die plate 42 mounted on the tops of the props 72 and 72, flasks 53a and 53b placed on the lower die plate 42, an upper and lower mo Id halves 51a, 51b,. which have been produced using the vacuum seal process and placed in the flasks 53a and 53b, respectively, an upper die plate 56 placed on the upper surface of the upper mold half 51a, and a pipe 79 for allowing the holding furnace 44 to communicate with an inlet 58 formed at the bottom of the lower die plate 56 for the i ntroduct ion of the molten met a.I. The four up r ight props 72 support the I ower die plate 42 at its four corner.
The holding furnace 44 is provided with a compressed air introduction tube 80 to introduce compressed air into the holding furnace. Moreover, the upper and lower mold halves 51a and 51b are mated to define a molding cavity 52.
In addition, stoke 60A that communicates with the pipe 79 to introduce the molten metal in the holding furnace 44 into molding cavity 52 is attached to the die plate 42. Moreover, the lower die plate 42 is formed with an aperture at a position corresponding to the gate of the lower mold half 51b for communicating with the pipe 79. Further, a heat insulation 83A is disposed around the aperture.
Next, the operation of the vacuum molding process device of this embodiment is described. In Figure 17 the inside of the upper and lower mold halves 51a and 51b has been decompressed by pressure decompressing device 62 through the flasks 53a, 53b and suction pipes 63 and 63. The upper and lower mold halves 51a and 51b were placed on the lower die plate 42, and the upper die plate 56 was placed on the upper

15
mold half 51a. Next, the upper and lower mold halves 51a and 51b were sandwiched . clamped between the upper and lower die plate 56 and 42. Afterwards, compressed a.i r was introduced from an compressed air source (not show) into the holding furnace 44 through the compressed air introduction tube 80 to apply pressure on the surface of the molten metal. Thus the molten metal rose in the stoke 60A and the pipe 79, and . the molding cavity 52 was filled with it. The introduction of compressed air. was stopped after the molten metal in the molding cavity 52 hardened, and thus an extra molten metal in the gate, pipe 79, and stoke 60A returned into the holding furnace. 44 as the pressure in the holding furnace 44 returned to the atmospheric pressure. Thus the pouring was completed.
Since in the vacuum molding process device of this embodiment the mold is not disposed above the hoIding furnace, suppl y i ng mol ten meta I in the furnace and removing detritus such as slag and oxides existing in the surface of the molten metal from the furnace can be performed easi ly. Although in this invention no feeder head or riser is use, they may be used if desired.
Moreover, although in this embodiment the molten metal is fed by using compressed air, it may be done using an electromagnetic pump, etc. or by any other methods. . As shown in Figure .18, the molten metal may be suppl ied to a level under the die plate 42 by a pipe 79A, and a sand layer or block 84, which has passage therein for the molten metal, is attached to one end of the pipe 79A, which end faces the lower mold half 51b. Using this sand block 84 can feed the molten metal to the plurality of gates simultaneously. Therefore, it gives easy applications to a cast having a complicated shape and to a cast having a plurality of casting pieces. When the position of gates is chained due to the change of the casting plan, a sand block 84 may be formed that has passages for molten metal corresponding to the position of the gates. Using such a sand block 84 gives easy application to such a change of the position of gates. Although in the embodiment shown in Figure 18 the sand block 84 is connected to the pipe 79A, it may be connected to the stoke directly.
The Sixth Embodiment
A cooling system shown in Figure 19 and 20 for cooling a mold framing can be used for this invention. The system sprays compressed air to the bottom and side surfaces of the mold framing in order to suppress the rise of temperature of the mold framing and to prevent the film from being welded to it. By using this cool ing system, compressed air is supplied into a chamber of the mold framing, which has one side, or. surface, at which the metal mold framing and the film contact, to cool the mold framing to suppress the rise of it temperature and to prevent the film from being welded to it. Further, the compressed air may be sprayed to the bottom of a surface plate to cool it to prevent the film from being welded to it.

16
In the conventional metal mold framing as in Figure 21, the side walIs of both
cope and drag are in the form of chambers 101, 101 (i.e., hollow). Since these
chambers are evacuated by a vacuum pump (not shown), this negative pressure in the
chambers shapes a cope 61a and a drag 61b. That is, the cope 61a and the drag 6tb
are covered by an upper flask 93a, a lower flask 93b, an upper film 97, mold surface
films 98, 98, and a bottom film 99 and sucked by the vacuum, so that the shapes o'f
the cope and the drag are kept. ¦
During the pouring, the parts of the films that contact with the as-cast product are burned out, though the parts of the films between the upper and lower flasks remain and are then removed during the demolding. The upper and lower fi Ims remain and are removed before the demolding.
After the pouring and when the as-cast product 96 hardens to some degree, the suction is stopped, and the as-cast product is natural ly cooled in the mold. If the as-cast product is one that has a great heat capacity, the heat are transferred from the ¦ product 96 to the upper and lower flasks 93a, 93b and the surface plate 95 through the cope 61a and the drag 61b, and the parts of the product surface films that are I ocated between the upper and lower f I asks 93a, 93b and the lower fi Im are undes i rably welded to the flask and the surface plate (Figure 21).
To overcome this undesirable problem, the cooling device of the present invention includes air nozzles 91, 91 for the metal side walls and an air nozzle 92 for spraying compressed air to the metal mod framing to cool it.
For a side air bIow, annuIar cool ing chambers 102, 102 are formed in the s ide wal Is at the matching plane (the plane at which the upper and lower flask mate). The air nozzles 91, 91, which are detachably attached to, or inserted in, the annular chambers. The annular cooling chambers 102, 102 has some apertures, which may be used as insertion holes for the nozzles 91, 91 and/or gateways for the compressed air (Figure 19). The side ai r blow is activated and deactivated by manual ly operating a valve 104 (Figures 19 and 20).
For a bottom ai r blow, the air nozzle 92 for the surface plate is located below it at the central part. The air nozzle is activated or deactivated by manually operating the valve 104.
Steps
The metal mold framing is continuously sucked for a certain period of time after the pouring (to keep the shape of the sand mold). The suction is then stopped, and the as-cast product is naturally cooled in the metal mold framing. During this cooling, compressed air is sprayed to the metal mold framing to aggressively cool it.
Although the cooling system of this embodiment is configured as a

11
semi-automated equipment, it may be fully automated by using actuators such as air cylinders to automatically attach and detach the nozzle, and electromagnetic valves to automatically carry out the air blow.
Although some preferable embodiments of this invent ion are described, these embodiments are only for explanation purpose to faci I itate the understanding of the invention, and the invention is not I imited to these embodiments. Therefore, it is clear to one ski I led in the art that the embodiments may be changed and modified within the spirit and scope of the invention, and that the present invention includes such changes and modifications and is defined by the attached claims and the equivalents.

18 Claims
1. A pouring method in a vacuum sealed process comprising the steps of:
sealingly covering the surface of a pattern plate by a shielding member;
placing a mold framing on the shielding member and then putting afill that does not include any binder in the mold framing;
sealingly covering an upper surface of.the. fi 11 and then evacuating an inside of the mold framing to suck the shielding member to the fi 11 to shape the shielding member;
removing the pattern plate from trie shielding member, thereby forming a mold half that has a molding surface;
forming another mold half in a simi lar way and mating the mold haives to define a molding cavity;
pouring molten metal in the molding cavity;
and releasing the negative pressure in the mold framing to take out a as-cast product,
wherein the method further comprises the step of decompressing the molding cavity before pouring molten metal in the mated mold.
2. The pouring method of claim 1, including the step of. forming a plural ity
of holes in the inner side of the fill in the mold framing, wherein the step of
decompressing the molding cavity is performed by decompressing means that
communicates with the holes through an inner chamber of the mold framing, through
the holes and the fill.
3. The pouring method of claim ?., wherein the mold halves do not have any
open top riser.
4. The pouring method of claim 1, including a step of disposing an open top
r iser in the upper mold half, the open top riser being opened to the molding cavity,
wherein the step of decompressing the molding cavity is performed by decompressing
means that communicates with the open top riser through the holes and the fill.
5. The pouring method of claim 2, including a step of forming a plural ity
of apertures in the shielding member that contacts the molding cavity, wherein the
step of decompressing the molding cavity is performed by the decompressing means
through the apertures formed in the shielding member, the fill, and a plural ity of
apertures formed in an inner side of the mold framing, the inner side contact ing the
fill.

19
6. The pouring method of claim 4, including a step of disposing vent plugs
in the apertures formed in the shielding member, wherein the step of decompressing
the molding cavity is performed through the vent plugs, the fill, and a plurality
of apertures formed in an inner side of the mold framing, the inner side contacting
the f i 11. ¦ ... .
7. The pouring method of any one of claims 1-6, further comprising the steps
of: measuring a degree of pressure reduction for at least one of the upper and lower
mold halves during a period between the start and end of the pouring; sending the
detected degree of pressure reduction to a controller; and adjusting degrees of .
pressure reduction in the inside of the at least one mold half and in the molding
cavity.
8. The pouring method of any one of claims 1-7, wherein the molding cavity
is decompressed so that Pm=1-75 KPa, Pc=1-95 KPa, and Pc-Pm=3-94 Kpa, where Pm and
Pc are a pressure within the mated mold and a pressure in the molding cavity.
9. An as-cast product produced by the pouring method of any one of claims
1-8.

10. A molding device used in a vacuum sealed process, comprising a mold
framing for receiving a fill that is a mold that defines a molding cavity, an inner
surface of the mold framing is formed with a plural ity of apertures, the inner surface
contact ing the fill, the mold framing having an inner chamber for communi cati ng with
the plurality of apertures, the inner chamber being connectable to decompressing
means positioned outside the mold framing for decompressing the molding cavity.
11. A molding device of claim 10, further comprising means for measuring'a
degree of pressure reduction for at least one of the upper and lower mold halves during
a period between the start and end of the pouring; and a controller for receiving
the detected degree of pressure reduction and for adjusting degrees of pressure
reduction in the inside of the at least one mold half and in the molding cavity.
12. A molding device of claim 10 or 11, further including cool ing means for
cooling the mold framing by spraying compressed air to side walls and a bottom of
the mold framing.
13. A molding device of claim 12, wherein the mold framing includes a lower

20
flask and an upper flask placed on the lower flask, the lower flask having at an inner upper part an annular cooling chamber in which the compressed air flows, the upper flask having at an inner lower part an annular cool ing chamber in which the compressed air flows.
14. A pouring method in a vacuum sealed process comprising the steps of:
seafingl.y covering the surface of a pattern plate by a shielding member;
placing a mold framing on the shielding member and then putting a fill that does not include any binder in the mold framing;
seali ngly cover ing an upper surface of the fill and then evacuating an inside of the mold framing to suck the shielding member to the fill to shape the shielding member;
removing the pattern plate from the shielding member, thereby forming a mold half 'that has a molding surface;
forming another mo Id half in a simi lar way and mat i ng the mo Id ha I ves to def i ne a molding cavity;
pouring molten metal in the molding cavity;
and releasing the negative pressure in the mold framing to take out a as-cast product,
wherein the method further compr ises the step of forming a gate in the lower mold half of the mated mold, and wherein no gate is provided in the upper mold half.
15. The pouring method of claim 14, further comprising a step of adjusting
the lower mold half, which is disposed above a hold furnace, so that the lower mol,d
half is kept horizontally.
16. The pour ing method of claim 14, further compr ising the steps of disposing
the holding furnace below the mold framing; and providing cushion material between
the lower mold half and the holding furnace to keep the lower mold half hor izontal ly.
17. The pouring method of claim 16, wherein the cushion material includes
a heat insuI at ion.
18. The pour ing method of claim 17, further compr ising the step of disposing
a lower die plate for supporting the flask, under the heat insulation.
19. The pouring method of claim 18, further compr ising the step of disposing
cooling means at the lower die plate.
20. The pouring method of claim 18, wherein the heat insulation includes a

21 sand block.
21. The pouring method of claim 18, wherein the heat insulation includes a
block of self-hardening sand. .
22. The pouring method of claim 20, wherein the sand block includes one gate
for communicating with a stoke of the holding furnace and a plural ity of runners for
communicating with the gate and the molding cavity.
23. The pouring method of any one of claims 14-22, wherein the pouring method
is a low pressure casting.
24. The pouring method of any one of claims 14-22, wherein the pouring method
is a differential pressure casting.
25. The pouring method of any one of claims 14-24, wherein a pouring rate
is controlled when molten metal is poured in the molding cavity.
26. An as-cast product produced by using the pouring method of any one o
claims 14-25.
27. The pouring method of any one of claims 1-8 and 14-25, further including
the step of cooling the mold framing by spraying compressed air to side walls and
a bottom of the mold framing.
A method and a device for pouring a molten metal in a vacuum molding for casting a thin-walled casting by using a Vrprocess casting mold (molding frame body) and a casting cast by the method. The method comprises a shielding member fitting step for fitting a shielding member onto the surface of a prototype plate, a step for placing the molding frame body on the fitted shielding member and filling a filler not containing, a bond in the molding frame body, a step for .'. sucking the shielding member to the filler side by bringing the inside of the molding frame body into a negative pressure by closing the upper surface of the filler to form the shielding member, a step for molding a semi-split casing mold with a molding surface by releasing the prototype plate from the shielding member, a step for defining a casting cavity and forming a completed casting mold by matching the semi-split casting mold with another semi-split casting mold molded in the same manner as in the case of the semi-split casting mold, a step for pouring the molten metal in the casting cavity, and a step for taking out the casting by releasing the state of negative pressure in the molding frame body. The method also comprises a step for depressurizing the inside of the casting cavity through the molding frame body before starting to pour the molten metal in the completed casting mold.

Documents:

02576-kolnp-2006 abstract.pdf

02576-kolnp-2006 claims.pdf

02576-kolnp-2006 correspondence others.pdf

02576-kolnp-2006 description(complete).pdf

02576-kolnp-2006 drawings.pdf

02576-kolnp-2006 form-1.pdf

02576-kolnp-2006 form-3.pdf

02576-kolnp-2006 form-5.pdf

02576-kolnp-2006 international publication.pdf

02576-kolnp-2006 international search authority report.pdf

02576-kolnp-2006 pct form.pdf

02576-kolnp-2006 priority document.pdf

02576-kolnp-2006-assignment.pdf

02576-kolnp-2006-correspondence-1.1.pdf

02576-kolnp-2006-form-3-1.1.pdf

02576-kolnp-2006-g.p.a.pdf

02576-kolnp-2006-priority document-1.1.pdf

2576-KOLNP-2006-CORRESPONDENCE 1.1.pdf

2576-KOLNP-2006-CORRESPONDENCE.pdf

2576-KOLNP-2006-FORM 27.pdf

2576-KOLNP-2006-FORM-27.pdf

2576-KOLNP-2006-REPLY TO EXAMINATION REPORT.pdf

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Patent Number

242085

Indian Patent Application Number

2576/KOLNP/2006

PG Journal Number

34/2010

Publication Date

20-Aug-2010

Grant Date

10-Aug-2010

Date of Filing

07-Sep-2006

Name of Patentee

SINTOKOGIO, LTD.

Applicant Address

28-12, MEIEKI 3-CHOME NAKAMURA-KU NOGOYA-SHI AICHI-KEN

Inventors:

#	Inventor's Name	Inventor's Address
1	MAKINO HIROYASU	C/O SINTOKOGIO, LTD. TOYOKAWA SEISAKUSHO 1, HONOHARA 3-CHOME TOYOKAWA-SHI AICHI-KEN 442-0061
2	TAKAFUMI OBA	C/O. SINTOKOGIO, LTD. TOYOKAWA SEISAKUSHO 1, HONOKAWA-SHI AICHI-KEN 442-0061
3	SUZUKI HIROAKI	C/O. SINTOKOGIO, LTD. TOYOKAWA SEISAKUSHO 1, HONOKAWA-SHI AICHI-KEN 442-0061
4	MIZUNO KENJI	C/O. SINTOKOGIO, LTD. TOYOKAWA SEISAKUSHO 1, HONOKAWA-SHI AICHI-KEN 442-0061
5	ANDO TOSHIAKI	C/O. SINTOKOGIO, LTD. TOYOKAWA SEISAKUSHO 1, HONOKAWA-SHI AICHI-KEN 442-0061
6	ENDOMOTO YOSHINOBU	C/O. SINTOKOGIO, LTD. TOYOKAWA SEISAKUSHO 1, HONOHARA 3-CHOME TOYOKAWA-SHI AICHI-KEN 442-0061
7	INQUE TAKAO	C/O. SINTOKOGIO, LTD. TOYOKAWA SEISAKUSHO 1, HONOKAWA-SHI AICHI-KEN 442-0061
8	TAKEDA SHIZUO	C/O. SINTOKOGIO, LTD. TOYOKAWA SEISAKUSHO 1, HONOKAWA-SHI AICHI-KEN 442-0061
9	TOMITA TAKETOSHI	C/O. SINTOKOGIO, LTD. TOYOKAWA SEISAKUSHO 1, HONOKAWA-SHI AICHI-KEN 442-0061

PCT International Classification Number

B22C 9/00

PCT International Application Number

PCT/JP2005/006481

PCT International Filing date

2005-04-01

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2005-028325	2005-02-04	Japan
2	2004-108911	2004-04-01	Japan
3	2004-132681	2004-04-28	Japan