Title of Invention

"AN APPARATUS FOR THE PRODUCTION OF PIPES HAVING A ROTARY STAND WHICH ROTARY STAND HAS A HORIZONTAL AXIS"

Abstract

The present invention relates to an apparatus for the production of pipes having a rotary stand which rotary stand has a horizontal axis and comprising several motor-drivable centrifugal moulds mounted rotatable about a horizontal axis, wherein said moulds are uniformly distributed at the same axial distance from the axis of the rotary stand characterized in that the rotary stand has six to eight centrifugal moulds each of which is provided with a drive motor, a drive and fixing device heating elements, partly surrounding the said rotary stand a gas extraction device a material feed device displaceable only parallel to the axis a device for ejecting pipes, cured by said heating elements and control device for controlling the respective position of the moulds .

Full Text

The present invention relates to all installation for the production of plastic pipes by the centritugal. casting method from the following starting materials: filler-containing synthetic resin, glass fibres and, if desired, further additives, such as, for example, sand. Such installations are disclosed, inter alia, in Swiss Patent 684,326 and PCT WO 93/08009. These known installations are used for producing pipes having a large length, i.e. for example of 6 metres or more, and a diameter of at least 30 cm. It has now been found that the production of pipes having a smaller diameter, i.e. a diameter of, for example, 10-20 cm, by means of such installations is possible but that there is a desire to have, for the production of such pipes, installations which possess a greater capacity but without the required space increasing in proportion to the output. German Patent 2,911,369 discloses an installation for the production of polyamide pipes. In this installation, caprolactam or laurolactam is introduced into a rotating mould at a certain initial temperature. For the formation of a pipe, the material introduced is then spun onto the wall of the mould by rapid rotation of the rotating mould. After the centrifugal process, the rotating mould is allowed to cool for a time which is a multiple of the centrifuging time so that the diameter of the resulting pipe is slightly reduced and the pipe can be readily removed from the rotating mould. One of the installations described has a drum magazine with five cylindrical chambers arranged therein and displaceable and heatable on both sides, a rotating mould removable axially from said chambers being housed in each of these chambers. A single drive motor serves for generating the centrifugal motion of the rotating mould. By stepwise rotation of the drum magazine, one chamber after the other can be brought to the position in which the rotating mould housed therein can be caused to rotate by the drive motor. After several rotary steps of the drum magazine, during which the temperature of the product decreases, the rotating mould with the finished product is removed axially from the chamber and the resulting pipe is then drawn out of the rotating mould. The disadvantage of this installation is that it can be used for producing only those pipes which consist of homogeneous material, i.e. neither pipes whose wall has incorporated components nor those whose wall is formed from different layers firmly connected to one another. The present invention achieves the object of providing a machine or installation with which relatively thin pipes, i.e. pipes having a diameter of 10 - 50 cm, and having a freely selectable layer structure of the wall, can be produced at a cost which corresponds to the cost of the pipes having a larger diameter, based on the weight. This is achieved if the installation is designed so that it can be used to produce several pipes simultaneously in a relatively small space in such a way that the production of at least 5 further pipes is begun at various times during the production of a pipe. Such a machine or installation according to the precharacterizing clause of Claim 1 is characterized in that the rotary stand has six to eight centrifugal moulds, each of which is provided with a drive motor, that a drive and fixing device is present for stepwise rotation^£ the rotary stand, ttiat heating elements are present for heating each mould in at least one of its positions, that an extraction device is present for extracting from the individual moulds gases liberated during curing, that a feed device displaceable only parallel to the axis during operation is present for introducing materials of which the pipe is composed into one mould or simultaneously into two moulds, that a demoulding device is present for drawing a finished pipe out of each mould at a fixed point and that a control device is present for controlling the following: = the stepwise rotation of the rotary stand, = the rotation of each mould at a speed dependent * on the position in which it is located, = the displacement movement of the feed device relative to the rotary stand, and the instantaneous and the total amount of the materials to be introduced, and = the mode of operation of the demoulding device. Accordingly the present invention relates an apparatus for the production of pipes having a rotary stand which rotary stand has a horizontal axis and comprising several motor-drivable centrifugal moulds mounted rotatable about a horizontal axis, wherein said moulds are uniformly distributed at the same axial distance from the axis of the rotary stand characterized in that the rotary stand has six to eight centrifugal moulds each of which is provided with a drive motor, arrive/and fixing device heating elements, partly surrounding the said rotary'stand a gas extraction device a material feed device dispiaceable only parallel to the axis a device for ejecting pipes, cured by said heating elements and control device for controlling the respective position of the moulds . An embodiment of the invention is described below with reference to the attached, rather highly schematic drawing. In the drawing, in which the individual Figures are shown on different scales. The invention will now be described more in detail with reference to the accompanying drawings, in which; Fig. 1 shows a general view of the entire installation, but without heating elements, without extraction device, without demoulding device and without the control device, Fig. 2 shows details of the drive device for the rotary stand, Fig. 3 shows the drive and fixing device of the rotary stand, Fig. 4 shows an end view of the rotary stand, Fig. 5 shows a perspective view of an individual centrifugal mould, Fig. 6 and 7 each show a perspective view of the annular end disc, Fig. 8 shows a section through one end of a centrifugal mould and Fig. 9 and 10 show the essential part of the demoulding device in two different operation states. The general view of the entire installation shown very schematically in Fig. 1 reveals that it consists essentially of two parts, a rotary stand having a horizontal axis and denoted here as a whole by 1 and a feed device denoted as a whole by 2. The rotary stand 1 has, at the end facing the feed device 2, a circular disc 11 which is connected via several rods 12 and spokes 13 to a shaft stub 14 coaxial with the circular disc 11. The circular disc itself, which is provided with a tyre Hi, is mounted on two freely rotatable rollers 15 and 16, as can be seen in Fig. 3, which rollers in turn are held in a freely rotatable manner on a crossarm 17. Eight regularly distributed fixing tabs Ha, lib, 11c, l1d, 11e, llf, llg and llh are fastened to the circular disc 11, each of which tabs is provided with a hole. A fixing pin 21 which can be actuated by a solenoid 19 is accommodated in a housing 18 fastened to the crossarm 17, which fixing pin can be inserted into the hole of the fixing tab located at the bottom relative to the disc axis 1lk, which is also the axis of the rotary stand, i.e. into the hole of fixing tab Ha in the drawing, in order to prevent the circular disc 11 from rotating. At the other end of the rotary stand 1, the shaft stub 14 coaxial with the circular disc 11 is freely rotatably mounted in a bearing 22, which in turn is held fixed in a stand 23. The driver sleeve 27 provided with a driver pin 26 actuatable by a solenoid 25 is mounted at the free end of this shaft stub. In the region of this driver pin 26, the shaft stub 14 has eight regularly distributed holes, channels or grooves to enable the driver pin 26 to engage the shaft. The driver sleeve 27 in turn is provided with two arms 27a and 27b, the free ends of which are connected by a hinge joint to the piston 28a of a pneumatic or hydraulic cylinder 28. The dimensions of the arms 27 a, 27b and the displacement distance of the piston 28a are such that the driver sleeve 27 is rotated through 45° during one piston movement. This results in the rotary stand once again assuming its original position after eight rotational steps. The positions or points at which the individual centrifugal moulds are present when rotary stand 1 is stationary are therefore denoted by A, B, C, D, E, F, G and H, the position denoted by A being the lowermost position and the other positions following one another in the counterclockwise direction when viewed in a direction from the feed device 2 towards the rotary stand. Sixteen bearings 30, each pair of which serves for supporting one of the eight centrifugal moulds 31, 32, 33, 34, 35, 36, 37 and 38, are fastened to the rods 12 of the rotary stand 1 in such a way that they hold these moulds so that their axis is parallel to the axis Ilk of the rotary stand. Each of these eight moulds is connected by means of a belt drive 39 to a drive motor 40 assigned to it. Although in the drawing all eight centrifugal moulds have the same internal diameter, it is entirely possible to arrange on a rotary stand centrifugal moulds having different internal diameters. In such a case, it will be expedient to provide each centrifugal mould with two bearings 30 and to design the bearing housings 30a so that they can be fastened to the rotary stand 1 and detached from it again by simple means, the bearing housings 30a being dimensioned so that, regardless of the internal diameter of the individual moulds, the geometric axes 3la of all moulds mounted on the rotary stand 1 are the same distance from the axis Ilk of the rotary stand. In such a case, however, it is advantageous if the belt pulleys 31b of all moulds have the same external diameter. As is evident from Fig. 4, five stationary heaters 41, 42, 43, 44 and 45, which partly surround the stand 1, are arranged outside the rotary stand 1. Each heater extends over the entire length of the centrifugal moulds so that it can readily heat the centrifugal mould present in its immediate vicinity to a predetermined temperature or can keep the heated mould at a certain temperature. In the position of the rotary stand 1 which is shown, the centrifugal moulds 38, 31, 32, 33 and 34 can thus be heated, i.e. the moulds which are present in the positions H, A, B, C and D. Each heater contains one or more heating elements which can be heated electrically or with hot air or with hot water or with steam, the temperature required for pipe production being controlled by means of the control device described below. However, heating the moulds can also be carried out by another method: the mould 31 shown in Fig. 5 has an electrical heating element 31c which is wound onto it and whose lead is connected to a current source controllable by the control device, via a slip ring connection which is not shown. As is evident from Fig. 5 and 8, each centrifugal mould 31 has a conical end piece 31k at its end facing away from the feed orifice 31e, all end pieces, regardless of the internal diameter of the pipe, expediently having the same orifice diameter 31d. These orifices denoted by 31f are adjacent to the stationary annular end disc 50 which is shown in Fig. 6 and 7 and which is provided with eight extraction fans 50b, each of which is arranged behind an inlet orifice 50a and the outlet orifices 50c of which lead into a blow-out duct, which is not shown. As is particularly readily evident from Fig. 8, each centrifugal mould has, before the beginning of the conical surface of the conical end piece 31k, an annular insert 31r which, on the one hand, serves for giving the resulting centrifugally cast pipe 100 an exactly defined end face and, on the other hand, serves as a guide for the four ejection rods 31s. These four rods are each passed through a slot 31e in the conical end piece 31k to the outside, where they are fixed to a ring 31i. Mounted on the annular end disc 50 in the position G are two radial tabs 51, to each of which is fastened an ejection cylinder 46 whose piston rod serves for pushing the ring 31i away from the annular end disc 50 against the force of two restoring springs 48 and thus for displacing the finished centrifugally cast pipe 100 through the distance s, i.e. a few cm to the right, i.e. in the direction towards the feed orifice 31e, so that it no longer sticks to the inner wall of the centrifugal mould 31 and can be easily drawn out of it by means of a demoulding device. For this purpose, the demoulding device, whose essential components are shown in Fig. 9 and 10, is arranged on the other side of the centrifugal mould 31, in the same position G. Said demoulding device has a draw-out rod 52 displaceable in its longitudinal direction. A cylinder 53 having a connection 53b for the supply of compressed air and the extraction of air is mounted at the free forward end of said draw-out rod, which end faces the centrifugal mould 31. A closed rubber bellows 54 fits on said cylinder with several radial holes 53a and can be inflated by the compressed air flowing into it from the holes 53a so that said bellows can rest tightly and firmly, along its entire length, against the inner surface of a plastic pipe 100 produced in the centrifugal mould 31, when the cylinder 53 is present inside such a plastic pipe. The feed device denoted as a whole by 2 has two pedestals 55 and 56 which are connected to one another, are displaceably guided on a guide rail 59 parallel to the axis 1lk of the rotary stand and are displaceable from the position indicated to the left and back again to the position indicated by means of a motor accommodated in the housing 24, via cable lines which are not visible. Each of these two pedestals 55 and 56 contains, as disclosed in PCT WO 93/08009, storage containers provided with metering pumps and intended for the individual components of the liquid plastic, i.e. of the resin and of the curing agent, and for the sand and also the necessary storage space for the glass fibre bobbins. Each of the two pedestals 55 and 56 is provided with a loading arm 57 and 58, respectively, in which the transport devices and the delivery devices for these starting materials are housed, i.e. inter alia the tubes for the liquid plastic components, which tubes are provided with nozzles at their ends, a conveyor screw for sand transport and a pulling device and rotating cutter for the glass fibre strands. The geometric arrangement is such that the loading arm 57 is introduced into the feed orifice 31e of a centrifugal mould present at position A and the loading arm 58 is simultaneously introduced into the feed orifice of the adjacent mould 32 present at position B. The two loading arms 57 and 58 are so long that their free end on which the delivery orifices for the plastic resin, sand and the glass fibres are arranged is present at the end of the displacement, at a point inside a centrifugal mould at which the cylindrical section 31g is connected to the conical section 31k. The control devices, connected to computers, and the measuring and monitoring devices for the entire installation are housed in a box 29 which is connected by lines 29a to the rotary stand 1 and by lines 29b to the feed device 2, i.e. including, for the rotary stand 1, the controllers for the rotary stand drive device consisting of the parts 22, 25, 26, 27 and 28, for the fixing device consisting of the parts 19 and 21, for the drive motors 40, for the extraction fans 50b, for the compressed air-operated cylinders 46 of the ejection device, for the actuation of the demoulding device, namely for displacement of the draw-out rod 52, and for inflating and evacuating the rubber bellows 54 and for the switches for switching the mould heaters on and off, which switches are controlled by programs and by temperature sensors mounted on the moulds. A device not shown in the drawing may of course also be present, by means of which a mould release agent can be introduced into each centrifugal mould, after removal of a completely produced pipe but before the introduction of the materials used for the production of the next pipe, in order to prevent the material from sticking to the mould wall. The drive and control devices for the feed device include, inter alia, the control members for moving this device to and fro and of course the measuring and metering devices for delivery of the construction materials for the production of the pipes, i.e. the metering pumps for the resin components, the conveyor screw for the sand and the transport and comminution device for the glass fibres. The mode of operation of the installation described above is explained below. In the state shown, the rotary stand 1 is prevented from rotating by the fixing pin 21 inserted in the fixing tab lla. The mould 31 is present in position A, the mould 32 in position B, the mould 33 in position C, the mould 34 in position D, the mould 35 in position E, the mould 36 in position F, the mould 37 in position G and the mould 38 in position H. All moulds, with the exception of mould 37 in position G, are driven by their associated motor 40 by means of the belt drive 39, for example in such a way that the speed at position H is 200 min"1, that at position A is 455 min"1, that at position B is 655 min"1 and that at positions C, H, D and E is about 300 min-1 and at position F the speed decreases until the mould is stationary. The mould release agent which prevents the subsequently introduced construction materials used for constructing a pipe from sticking to the mould wall is sprayed into the mould 38 present in position H, by means of a nozzle not shown in the drawing. The mould rotates at a speed which ensures uniform distribution of the mould release agent over the entire inner surface. At positions A and B, loading arms 57 and 58 travel simultaneously at constant speed into the moulds 31 and 32, respectively, standing in front of them and rotating at high speed, and travel out of these again. This may take place once or several times. They deliver the construction materials required for the construction of a glass fibre-reinforced plastic pipe 100, i.e. resin enriched with fillers, and curing agent and sand and glass fibres in accordance with a program stored in the controller, the loading arm 57 producing the outer layers of the pipe and the loading arm 58 the inner layers. Since the mould heating is in operation, curing of the plastic resin begins simultaneously. At positions C, D and E, the introduced material from which a pipe has been formed by the centrifugal process cures completely at slightly reduced speed, and compaction may also take place at the beginning, i.e. position C, where the material is still fairly soft. Depending on the requirement, which is determined by heat sensors mounted on the moulds and which is dependent on the pipe diameter, the pipe wall thickness and of course also the prevailing room temperature, heat can be supplied by the heating elements at positions H, A, B, C and D. The pipe produced in this manner now undergoes final curing in position F, the speed of the mould being decreased until the mould is stationary. At the same time, the ejection cylinder 46 is first actuated in the mould present in position G, in order to detach the plastic pipe 100 tightly fitting in the mould from said mould, as described further above. At the same time, the demoulding device travels from the other side into the plastic pipe 100 to such an extent that its rubber bellows 54 is located completely inside the pipe. As soon as this is pushed out slightly, the rubber bellows is inflated by inflowing compressed air to such an extent that it fits firmly in the pipe and is capable of drawing out the pipe towards the right during subsequent displacement of the draw-out rod 52. The appropriate fan 5Ob which blows the gases into the waste gas duct is switched on by the control device in all positions where vapours or gases are liberated during curing of the plastic. When all these movements described above and taking place simultaneously are complete, the solenoid 19 draws the fixing pin 21 out of the hole in the fixing tab lla, whereupon the piston 28a of the hydraulic cylinder 28 is pushed out and the shaft stub 14 and hence the entire rotary stand 1, whose circular disc 11 rotates on the two rollers 15 and 16, rotates through 45° so that the fixing tab lib is located in front of the fixing pin 21 which is pushed into the hole in this fixing tab by the solenoid 21, with the result that the stand is once again fixed in the new position. In this new position, the mould 31 is thus in position B, the mould 32 in position C, etc., i.e. a subsequent working process, as described above, takes place in each mould. Thus, a finished plastic pipe is drawn out after each one eighth rotation. If, as is quite possible, 2.5 s are required for releasing and locking a fixing tab and 7 s are required for rotating the stand 1 through 45°, 180 s are available, in a 192 second cycle, for repeatedly inserting and withdrawing each of the two loading arms 57 and 58, i.e. a total of 6 min for introducing the material required for the construction of a pipe, which experience shows is in general completely sufficient. In other words, a time of 25 min 36 s is required for the production of a pipe, the installation thus delivers a pipe every 192 seconds or 75 pipes of, for example, 6 m in 4 hours, i.e. 450 linear metres of pipe. With such a production rate, production costs of such high-quality, reinforced plastic pipes are no greater than the production costs of metal pipes. However, since such plastic pipes are substantially lighter, the transport and laying costs are lower than in the case of metal pipes. Since moreover the life is several times that of metal pipes, pipes produced in this manner constitute a substantial advance compared with all conventional pipes of comparable dimensions. WECLAIM: 1. An apparatus for the production of pipes having a rotary stand (1) which rotary stand (1) has a horizontal axis and comprising several motor-drivable centrifugal moulds (31-38) mounted rotatable about a horizontal axis, wherein said moulds (31-38) are uniformly distributed at the same axial distance from the axis (11k) of the rotary stand (1) characterized in that the rotary stand (1) has six to eight centrifugal moulds (31, 32, 33, 34, 35, 36, 37, 38), each of which is provided with a drive motor (40), a drive (25, 26, 27, 28) and fixing device (1 la, 1 1b, 1 1c, 1 1d, 1 le, 1 1f, 1 1g, 1 1h, 19, 20) heating elements (41, 42, 43, 44,,45; 31c), partly surrounding the said rotary stand (1); a gas extraction device (50b); a material feed device (2) displaceable only parallel to the axis (11k); a device (46) for ejecting pipes, cured by said heating elements ( 41, 42, 43, 44, 45, 31c) and control device (29) for controlling the respective position of the moulds (32). 2. The apparatus as claimed in claim 1, wherein said heating elements (41, 42, 43, 44, 45) are arranged in a stationary manner and in immediate vicinity to the centrifugal moulds (31, 32). 3. The apparatus as claimed in claims 1 or 2, wherein the said material feed device (2) has two loading arms (57, 58) arranged insertable into two adjacent moulds (31, 32). 4. An apparatus for the production of pipes substantially as herein described with reference to the accompanying drawings

Documents:

2903-del-1996-abstract.pdf

2903-del-1996-claims.pdf

2903-del-1996-correspondence-others.pdf

2903-del-1996-correspondence-po.pdf

2903-del-1996-description (complete).pdf

2903-del-1996-drawings.pdf

2903-del-1996-form-1.pdf

2903-del-1996-form-13.pdf

2903-del-1996-form-19.pdf

2903-del-1996-form-2.pdf

2903-del-1996-form-3.pdf

2903-del-1996-form-4.pdf

2903-del-1996-gpa.pdf

2903-del-1996-petition-137.pdf

2903-del-1996-petition-138.pdf