Title of Invention

METHOD OF DRYING PAINT COATING AND PAINT COATING DRYING OVEN

Abstract

The present invention relates to a method of drying paint coating on workpieces of different types which is to be baked at different temperatures in a paint coating drying oven, comprising the steps of: baking a first batch of workpieces whose paint coating is to be baked at a lower temperature with a hot- air circulating mechanism in the paint coating drying oven: and baking a second batch of workpieces whose paint coating is to be baked at a higher temperature with the hot-air circulating mechanism and a far-infrared heating mechanism in the paint coating drying oven.

Full Text

Heretofore, it has been known in the art to apply a paint coating to a workpiece such as a vehicle component and then dry the paint coating by baking. Available paint coating drying processes include a proc¬ess of applying hot air directly or indirectly to a paint coating on a workpiece and a process of applying far-infrared rays or near-infrared rays to a paint coating on a workpiece. In another baking process, workpieces of dif¬ferent types which are coated with paint coating that is to be baked at different respective temperatures are de¬livered through one drying oven. According to this bak¬ing process, it is the general practice to send the work-pieces of different types through the drying oven while the drying oven is heated successively to different tem¬peratures that match the workpieces of different types, respectively. The above baking process which needs to change oven temperatures for the workpieces of different types is usually performed by the circulation of hot air in the drying oven. However, the hot-air circulation oven sys¬tem is time-consuming in setting the drying oven to de¬sired temperatures. For example, it is assumed that a first batch of workpieces is to be baked in a temperature range from 75°C to 80"C and a second batch of workpieces is to be baked in a temperature range from 140"C to 150°C, with the temperature difference in the range from 65"C to 70"C. When these batches of workpieces are suc¬cessively dried in the hot-air circulation oven, it re¬quires a relatively long loss time of about 60 minutes until the oven temperature is increased to a desired tem¬perature setting after the final workpiece of the first batch has left the oven, and it also requires a loss time of about 60 minutes until the oven temperature is lowered to a desired temperature setting after the final workpie¬ce of the second batch has left the oven. The hot-air circulation oven controls its In¬side temperature by controlling the temperature of the atmosphere in the oven. Therefore, when the temperature in the hot-air circulation oven is controlled, it is also necessary to increase or reduce the temperatures of a workpiece delivery conveyor, ducts, and inner wall sot-faces of the oven to a desired temperature setting. As a result, a large amount of heat needs to be generated or dissipated for changing oven temperatures. It is therefore an object of the present in¬vention to provide a method of drying paint coating on workplaces of different types which is to be baked at different respective temperatures, with a reduced period of time required to change oven temperatures for in¬creased oven availability and with a reduced amount of heat energy needed to change oven temperatures. Another object of the present invention is to provide a paint baking drying oven which allows oven tem¬peratures to be changed within a reduced period of time for increased oven availability and with a reduced amount of heat energy. According to the present Invention, there is provided a method of drying paint coating on workpleces of different types which is to be baked at different tem¬peratures in a paint coating drying oven, comprising the steps of baking a first batch of workpleces whose paint coating is to be baked at a lower temperature with a hot-air circulating mechanism in the paint coating drying oven, and baking a second batch of workpleces whose paint coating is to be baked at a higher temperature with the hot-air circulating mechanism and a far-infrared heating mechanism in the paint coating drying oven. The workpieces whose paint coating is to be baked at the lower temperature are baked by a heated at¬mosphere created by the hot-air circulating mechanism, and the workpieces whose paint coating Is to be baked at the higher temperature are baked by both the heated at¬mosphere created by the hot-air circulating mechanism and far-infrared rays applied by the far-infrared heating mechanism. Thus, the higher temperature can quickly be achieved by both the hot-air circulating mechanism and the far-infrared heating mechanism, with a reduced loss time. For increasing the temperature in the paint coating drying oven from the lower temperature to the higher temperature, it ts not necessary to heat a work-piece conveyor, ducts, and inner wall surfaces because the higher temperature can be reached by energizing the far-infrared heating mechanism in addition to the hot-air circulating mechanism. The amount of heat energy re¬quired to achieve the higher temperature can be reduced. The method may further comprise the step of introducing the second batch of workpieces into the paint coating drying oven after the higher temperature is achieved In the paint coating drying oven by the hot-air circulating mechanism and the far-infrared heating mecha¬nism. According to the present invention, there is also provided a paint coating drying oven for drying paint coating on workpleces of different types which is to be baked at different temperatures, comprising a hot-air circulating mechanism for generating an atmosphere to bake a first batch of workpleces whose paint coating Is to be baked at a lower temperature, and a far-infrared heating mechanism for applying far-Infrared rays directly to a second batch of workpleces whose paint coating is to be baked at a higher temperature to bake the second batch of workpleces in combination with the hot-air circulating mechanism. The hot-air circulating mechanism creates a heated atmosphere to bake the workpleces whose paint coating is to be baked at the lower temperature. The far-infrared heating mechanism applies far-infrared rays directly to the workpleces whose paint coating is to be baked at the higher temperature to bake these workpleces in combination with the heated atmosphere created by the hot-air circulating mechanism. The paint coating drying oven may further com¬prise means for energizing the far-infrared heating mechanism a predetermined period of time before the sec¬ond batch of workpleces is introduced into the far-infrared heating mechanism. The above and other objects, features, and ad¬vantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodi- ment of the present invention is shown by way of illustra¬tive example. BRIEF DECCnirTIOM OF TIIF PBAWIMGS FIG. 1 is a schematic side elevational view of a paint coating drying oven according to the present in¬vention; FIG. 2A is a diagram showing periods of time required to change oven temperatures in a conventional method of drying a paint coating; and FIG. 2B is a diagram showing periods of time required to change oven temperatures in a method of dry¬ing a paint coating according to the present invention. DETAILED DKCCnirTIOH OF THE PmSFEnnED EMDODIMENiT As shown in FIG. 1, a paint coating drying oven 1 according to the present invention serves to dry, by baking, workpieces such as vehicle components while they are moving along a workpiece delivery path H which comprises a conveyor. Specifically, the workpieces that are delivered along the workpiece delivery path H include a plurality of batches of workpieces Vfa, Wb which are coated with paint coating that is to be baked at differ¬ent respective temperatures, e.g., components of cold rolled steel sheet whose paint coating is to be baked in a temperature range from 140"C to 150"C, and components of synthetic resin whose paint coating is to be baked in a temperature range from 75"C to 80"C. in the illustrat¬ed embodiment, it is assumed that the batch of workpieces Wa comprises components whose paint coating is baked in a lower temperature range, e.g., components of synthetic resin whose paint coating is to be baked in a temperature range from 75°C to 80"C, and the batch of workpieces Wb comprises components whose paint coating Is baked In a higher temperature range, e.g., components of cold rolled steel sheet whose paint coating is to be baked in a tem¬perature range from 140"C to 150°C. Of course, these workpieces Wa, Wb and their baking temperature ranges are illustrated by way of example only, and other workpieces and baking temperatures can be employed in the present invention. The paint coating drying oven 1 has a pair of air sealing chambers 2 disposed respectively at inlet and outlet ends thereof for blocking ambient air against en¬try into the paint coating drying oven 1 for thereby pre¬venting impurities such as dust particles from being in¬troduced Into the paint coating drying oven 1. The paint coating drying oven 1 has a hot-air circulating mechanism 3 for circulating hot air in the paint coating drying oven 1 to develop a heated atmos¬phere for heating the workpieces Wa in the lower baking temperature range, and an far-infrared heating mechanism 4 for applying far-infrared rays directly to the work-pieces Wb in the higher baking temperature range. The hot-air circulating mechanism 3 has an air intake duct 5 for drawing air from within the paint coat- ing drying oven 1, an air heater 6 connected to the air intake duct 5 for heating the air introduced from the air intake duct 5, and an air discharge fan 7 connected to the air heater 6 for supplying heated air from the air heater 6- into the paint coating drying oven 1. The hot-air circulating mechanism 3 Is capable of keeping the in¬terior of the paint coating drying oven 1 in a tempera¬ture range from 75* C to 80"C. The far-infrared heating mechanism 4 comprises an array of far-infrared heaters 8 arranged in four blocks along the workplece delivery path H where each of the blocks represents a distance that is traversed by a workpiece along the workplece delivery path H in 10 min¬utes. The far-infrared heaters 8 can apply far-infrared rays directly to workpieces that are delivered along the workpiece delivery path H. The workpieces Wb in the higher baking tem¬perature range are heated by both the hot-air circulating mechanism 3 and the far-infrared heating mechanism 4. Specifically, while the workpieces Wb are heated by both the hot-air circulating mechanism 3, they are also heated directly by the far-infrared heating mechanism 4, so that the workpieces Wb can be heated to their higher baking temperature range, i.e., the temperature remge from 140"C to 150* C. The paint coating drying oven 1 also has a pair of upstream and downstream probes 9a, 9b spaced from each other along the workpiece delivery path H. The up¬stream probe 9a is positioned upstream of the far-infrared heating mechanism 4, and the downstream probe 9b is positioned in a downstream end portion of the far-infrared" heating mechanism 4. The probes 9a, 9b are as¬sociated with respective switches (not shown) for turning on and off the far-infrared heating mechanism 4, and can be actuated by leading and trailing ends of the batches of workpieces Wa, Wb. The probes 9a, 9b are spaced from each other by a distance corresponding to 1.5 blocks and the batches of workpieces Wa, Wb are spaced from each other by at least the distance between the probes 9a, 9b. Therefore, there is a 15-minute no-workpiece space be¬tween the batches of workpieces Wa, Wb, and the tempera¬ture in the paint coating drying oven 1 is increased or lowered in an idle time that is provided by the 15-minute no-workpiece space. The idle time is selected to be 15 minutes be¬cause the paint coating drying oven 1 takes about 15 minutes until the temperature rises from the lower tem¬perature range from 75"C to 80"C to the higher tempera¬ture range from 140"C to 150"C and is then stabilized, or until the temperature falls from the higher temperature range from 140" C to 150"C to the lower temperature range from 75"C to 80"C and is then stabilized. When only the batch of workpieces Wa in the lower baking temperature range from 75° C to 80" C i." de- livered in the paint coating drying oven 1, the work-pieces Wa are baked by only the hot-air circulating mechanism 3. If the batch of workplece Wb in the higher baking temperature range from 140" C to 150" C is to be baked after the batch of workpieces Wa, then the down¬stream probe 9b is actuated by the trailing end of the batch of workpieces Wa, turning on the far-infrared heat¬ing mechanism 4. After about 15 minutes, the leading end of the batch of workpiece Wb begins to face the far-infrared heaters 8. The batch of workpiece Wb now starts being heated to the temperature range from 140" C to 150"C by both the hot-air circulating mechanism 3 and the far-infrared heating mechanism 4. As shown in FIG. 2A, it has heretofore taken about 60 minutes to increase the temperature in the paint coating drying oven from lower baking temperature range from 75° C to 80" C to the higher baking temperature range from 140"C to 150"C. According to the present invention, as shown in FIG. 2B, it takes about 15 minutes to in¬crease the temperature in the paint coating drying oven from lower baking temperature range from 75" C to 80"C to the higher baking temperature range from 140"C to 150"C. Consequently, the availability of the paint coating dry¬ing oven 1 according to the present invention is greatly Increased. Furthermore, since the workpieces Wb are heat¬ed by being directly irradiated with far-infrared rays from the far-infrared heaters 8, it is not necessary to heat the workpiece delivery path H, the ducts, and the inner wall surfaces of the paint coating drying oven 1. Consequently, the paint coating drying oven 1 consumes a much smaller amount of heat energy than the conventional hot-air circulation oven system. More specifically, the conventional hot-air circulation oven system requires an amount of heat energy including 83,676 Kcal/hr for heating the workpieces, 61,921 Kcal/hr for heating conveyor rails, 22,620 Kcal/hr for heating inner wall surfaces, 12,095 Kcal/hr for heat¬ing ducts, and 10,121 Kcal/hr for heating the air in the oven. However, the paint coating drying oven 1 incorpo¬rating both the hot-air circulating mechanism 3 and the far-infrared heating mechanism 4 requires an amount of heat energy including 60,010 Kcal/hr for heating the workpieces, 8,126 Kcal/hr for heating inner wall sur¬faces, and 5,060 Kcal/hr for heating ducts. Therefore, the amount of heat energy consumed by the paint coating drying oven 1 is reduced to less than one-half of the amount of heat energy consumed by the conventional hot-air circulation oven system. The probes 9a, 9b may be of any structures, and the workpieces Wa, Wb may be of any types. The num- ber of types of workpleces to be dried successively in the paint coating drying oven 1 is arbitrary. Although a certain preferred embodiment of the present invention has been shown and described In detail. It should be understood that various changes and modifi¬cations may be made therein without departing from the scope of the appended claims. WE CLAIM: }. A method of drying paint coating on world- pieces of different types which is to be baked at different temperatures in a paint coating drying oven, comprising the steps of: baking a first batch of workpieces whose paint coating is to be baked at a lower temperature with a hot- air circulating mechanism in the paint coating drying oven: and baking a second batch of workpieces whose paint coating is to be baked at a higher temperature with the hot-air circulating mechanism and a far-infrared heating mechanism in the paint coating drying oven. 2. The method as claimed in claim 1, wherein said second batch of workpieces is introduced into said paint coating drying oven after said higher temperature is achieved in said paint coating drying oven by said hot-air circulating mechanism and said far infrared heating mechanism. 3. A paint coating drying oven for drying paint coating on workpieces of different types which is to be baked at different temperatures, comprising a hot-air circulating mechanism for generating an atmosphere to bake a first batch of workpieces whose paint coating is to be baked at a lower temperature and a far-infrared heating mechanism for applying far-infrared rays directly to a second batch of work- pieces whose paint coating is to be baked at a higher temperature to bake said second batch of workpieces in combination with said hot-air circulating mechanism. 4. The paint coating drying oven as claimed in claim 3, wherein means for energizing comprises said far-infrared heating mechanism a predetermined period of time before said second batch of workpieces is introduced into said far-infrared heating mechanism.

Documents:

0876-mas-1999 abstract-duplicate.pdf

0876-mas-1999 abstract.pdf

0876-mas-1999 claims-duplicate.pdf

0876-mas-1999 claims.pdf

0876-mas-1999 correspondence-others.pdf

0876-mas-1999 correspondence-po.pdf

0876-mas-1999 description(complete)-duplicate.pdf

0876-mas-1999 description(complete).pdf

0876-mas-1999 drawings-duplicate.pdf

0876-mas-1999 drawings.pdf

0876-mas-1999 form-1.pdf

0876-mas-1999 form-19.pdf

0876-mas-1999 form-26.pdf

0876-mas-1999 form-3.pdf

0876-mas-1999 form-5.pdf

0876-mas-1999 petition.pdf