JPH09109262A - Method and apparatus for fusion-bonding non-contact heating plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to heat the fusion-bonding part of a molding without contact, to increase the life of a heating plate and to eliminate the necessity of replacement by heating the plate to a high temperature. SOLUTION: A heating plate 1 made of stainless steel is heated by a heating coil 2 to a predetermined temperature (e.g. 600 deg.C). Resin moldings 5, 6 are respectively mounted at lower and upper holding members 3, 4. The plate 1 is moved from a heating stage to a fusion-bonding stage, and the fusion-bonding part of the molding is heated. After it is waited until the fusion-bonding part of the molding is sufficiently melted, the plate is reset to the original heating stage, the upper member 4 is lowered, the molding 6 is pressed to the molding 5 to be fusion-bonded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for welding a resin molded product using a hot plate.

[0002]

2. Description of the Related Art Resin molded products having various shapes are used in a wide variety of fields. These resin molded products are mainly formed by the injection molding method. However, when a desired shape cannot be obtained by one molding step,
A plurality of molded products will be welded to produce one product. Known methods for welding resin molded products include a hot plate heating method, an electromagnetic induction heating method, and an ultrasonic method.

FIGS. 7A to 7F are sectional views in order of steps showing the welding process by the conventional hot plate method. in this way,
First, a resin molded product 15 is mounted on the lower holding member 13 and a resin molded product 16 is mounted on the upper holding member 14, and an electric heater is embedded between the two resin molded products 15 and 16 to heat them. The hot plate 11 is arranged [Fig. 7
(A)]. At this time, the hot plate 11 is heated to a temperature equal to or higher than the softening point of the material of the resin molded product, for example, 300 ° C.

Next, the upper holding member 14 is lowered and the hot plate 1 is pressed by the resin molded product 16. The welding surface of the resin molded product 15 also comes into contact with the hot plate 11 due to the pressing force. As a result, the welded portions of the two resin molded products are melted and a part of the resin is extruded to form the molten metal balls 17 (FIG. 7B). When the resin is sufficiently melted, the upper holding member 14 is once raised [FIG. 7 (c)] to retract the hot plate 11 [FIG.
(D)]. The upper holding member 14 is lowered and both resin molded products are pressed. At this time, the burr 18 is formed [FIG.
(E)]. This state is maintained until the molten resin in the welded portion is completely solidified. After that, the upper holding member 14 is raised [Fig. 7 (f)] and the finished product is taken out.

8 (a) and 8 (b) are sectional views showing the actual structure of the heat plate 1. FIG. 8 (a) shows a case where the welding surface exists on a plane. (B) shows the structure when the welded surface is three-dimensional. As shown in FIG. 8, the hot plate 1 is formed by fixing a template 22 on a heater block 21, and the heater block 21 is manufactured by sandwiching a heater 21b made of nichrome wire or the like between metal plates 21a. It is a thing. Further, a resin coat 23 made of polytetrafluoroethylene or the like is applied to the surface of the template 22 in order to prevent adhesion of the resin to be welded.

9A to 9C are sectional views in order of steps showing a conventional welding method using an induction heating method. FIG. 9A shows a case where a wire is used as a heating body, and FIG. 9B shows a heating method. The case where a magnetic adhesive is used for the body is shown. In the case of FIG. 9A, the wire 34 is sandwiched between the two resin molded products 32 and 33, and the heating coil 31 is energized to heat the wire. After the resin around the wire 34 is melted, the energization of the coil is stopped and pressure is applied to weld both resin molded products. The wire 34 is embedded in the product. In the case of FIG. 9B, one resin molded product, for example, a welded portion of the molded product 32 is coated with a magnetic adhesive 35 formed by mixing magnetic material powder with resin to form two resin molded products 32. , 33 on top of each other. The heating coil 31 is energized to sufficiently heat and melt the magnetic adhesive, and then the heating coil 3
Stop energizing 1 and apply pressure to bond both resin molded products.

[0007]

In the conventional welding method using a hot plate, since the hot plate has a complicated structure as shown in FIG. 8, it is expensive and has a relatively short life. After a certain period of time, there was a trouble that the replacement was necessary. The reason for the limited life is mainly due to the following two points.
First, since a heater such as a nichrome wire is used, this deteriorates. Secondly, when the hot plate comes into contact with the product to be welded, the resin coating of the hot plate is soft, whereas the surface of the resin molded product is in a cold and hard state. Therefore, the resin coat is damaged by the impact at the time of contact, and the surface of the template is exposed during repeated use. The use of such finite life equipment has serious consequences in current production systems, which are premised on unattended work at night. That is, the line is stopped at night or a large number of defective products are produced, so that the product cannot be supplied in time, which affects other lines (assembly line, etc.).

Further, the conventional hot plate has a drawback that it becomes heavy because of its complicated structure as described above. For example, it is not rare that the weight exceeds 100 kg. 3
The one of nearly 100 kg has been put into practical use. Since such a heavy-weight hot plate has a large heat capacity, it takes a long time to start up (time after the switch is turned on and before work can be started), for example, about 2 hours for a 100 kg one. It was Further, in such a heavy-weight hot plate, it takes a long time to replace the hot plate when the model is changed. To replace the hot plate,
It is necessary to wait for the hot plate that was used to be cooled and then replace it, and then to start up the replaced hot plate, but it takes 2 to 4 hours each to cool and start up, so it takes more than half a day to replace it. Will be lost. As described above, it takes a long time to switch the model, and as a result, productivity is remarkably reduced when a large number of products are manufactured in small quantities. Further, since a heavy heat plate is used, the driving mechanism becomes large in scale, and as a result, it is inevitable that the welding apparatus becomes large. Further, since the hot plate is heavy, it cannot be driven at high speed, which is an obstacle to improving productivity.

Further, the conventional hot plate has a problem in that it has a low thermal efficiency and the temperature distribution is hardly constant because the template is fixed to the heater block. In particular, when the welded portion has a three-dimensional shape, as shown in FIG.
Since the protrusions are formed on the template as shown in (b), the temperature tends to be low here, it is difficult to completely melt the resin, and reliable welding cannot be performed. Moreover, the conventional hot plate has a very low thermal efficiency because the heater heats the metal plate and the metal plate heats the template, and the surface of the template must be coated with a resin.

Further, since the conventional hot plate method is a method of contacting a resin molded product of the hot plate, the shape of the contact portion of the molded product with the hot plate is liable to be broken, and the burr generated on the product tends to be large, There is a drawback that the variation in shape becomes large.
Further, the hot plate is easily soiled, and the soil contaminates the surface of the next welded molded product, so that a defective product is likely to occur and it is difficult to improve the yield. The drawbacks of adopting such a contact method can be solved by adopting a non-contact method. However, when the non-contact method is adopted, the temperature of the hot plate must be raised. That is, the contact method is 30
Although it may be about 0 ° C., in the non-contact method, the resin of the molded product cannot be melted unless the hot plate is heated to about 600 ° C. However, in the conventional heater type hot plate,
If such high temperature heating is adopted, the life of the heater will be extremely shortened, so it is unrealistic to adopt the non-contact method.

On the other hand, in the conventional induction heating method shown in FIG. 9, since wires or magnetic powders are left in the product, an extra material must be used, leading to an increase in cost. Further, there are drawbacks such as pollution prevention problems when used, and resource recycling processing becomes difficult. Therefore, the user has requested improvement.
The present invention has been made in view of the problems of the conventional example, and the first object thereof is to realize uniform and highly reliable welding in which defects due to deformation and dirt hardly occur. Secondly, it is possible to
An object of the present invention is to provide a hot plate welding apparatus which is lightweight, has high productivity, and has high thermal efficiency.

[0012]

A non-contact hot plate welding method according to the present invention for achieving the above object is to place hot plates heated by an induction heating method between resin molded products to be welded. And heating the welded portion of the resin molded product in a non-contact manner, and moving the hot plate and the resin molded product relative to each other so that the hot plate does not interfere with the welding of the resin molded product. It is characterized by having a process and a process of pressing the resin molded products together to perform welding.

Further, the non-contact hot plate welding apparatus according to the present invention for achieving the above object comprises first and second holding members capable of holding resin molded products so that they face each other. A drive mechanism for moving one or both of the first and second holding members so that the opposing resin molded products can be separated or brought into contact with each other, and a hot plate heated by an induction heating method. A heating coil for applying an alternating magnetic field to the hot plate; and moving the hot plate between a position for heating a welding portion of the resin molded product and a position where the welding of the resin molded product is not hindered. And a moving mechanism.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described. 1 and 2 are cross-sectional views in order of the processes, for illustrating an embodiment of the present invention. As shown in FIG. 1A, a resin molded product 5 is mounted on the lower holding member 3, and a resin molded product 6 is mounted on the upper holding member 4. At least the upper holding member 5 is provided with molded product fixing means by vacuum suction or other mechanical means for fixing the molded product. Further, at least one holding member,
It is possible to move up and down, as described later, it is possible to accommodate the hot plate between the molded products in a non-contact manner, and to press the two resin molded products 5, 6. ing. The resin molded product is preferably applied to a large molded product such as polyethylene or polypropylene, but if it is a thermoplastic resin, it can be welded, and its material is not particularly limited.

The heating stage of the heating plate 1 includes a heating coil 2
Is arranged. In the illustrated example, the heating coil is wound two turns above and below the heating plate, but the number of turns is not particularly limited. Further, although it can be arranged only on one surface side of the heat plate, it is desirable to arrange the heat plate divided into upper and lower parts in terms of efficiency. The heating coil is preferably hollow so that a cooling medium such as water flows in order to suppress heat generation due to a large current. As the material of the heat plate 1, stainless steel is preferably used because it can largely reduce both hysteresis loss and eddy current loss, but other materials can be adopted as long as they are metals or magnetic materials. Further, the surface of the hot plate may be provided with an oxide film or a ceramic coating in order to efficiently radiate infrared rays. Even if such a coating is applied, the structure is simple, so that it can be manufactured at an extremely low cost. Hot plate 1
The weight depends on the shape of the molded product, but even in the case of a large size, it is within 5 to 10 kg (the total weight of the heating coil and the high frequency oscillator that are stopped is 20 to 30 kg).
Degree).

The heating plate 1 has a temperature sensor embedded therein, and is controlled by, for example, on / off control to, for example, 60.
It is designed to be maintained at a constant temperature such as 0 ° C. By using a magnetic material as the material of the hot plate and setting the set temperature to the Curie point or higher, the deviation of the temperature in the hot plate can be reduced. The reason is as follows. In the induction heating method, the hot plate is heated by heat generation due to hysteresis loss and heat generation due to eddy current loss. Now, assuming that there is a difference in the heat distribution in the hot plate and there are coexisting points that exceed and do not exceed the Curie point, magnetism is lost at the points that exceed the Curie point, which causes hysteresis loss. The heat generation is eliminated, and only the heating due to the eddy current loss suppresses the temperature rise. On the other hand, at points below the Curie point, heat is generated due to hysteresis loss and eddy current loss, so that the temperature continues to rise. As a result, the temperature distribution in the hot plate can be made uniform.

From the state shown in FIG. 1A, the hot plate 1 is moved to the welding stage as shown in FIG. 1B to heat the resin molded product. It is known that it is desirable to heat not only the surface but also the inside of the molded product in order to perform uniform and reliable welding. In the present invention, since the hot plate has a high temperature of, for example, about 600 ° C., a large amount of infrared radiation is emitted to reach the inside of the molded product. Therefore, the inside of the molded article is heated to a high temperature because it is heated by both heat conduction from the surface portion heated by radiant heat and heating by infrared rays. On the other hand, the conventional hot plate having a low temperature of about 300 ° C. emits little infrared rays, and the inside is heated only by heat conduction from the surface, so that the inside cannot be sufficiently heated. In the present invention,
Since it is non-contact heating, it does not lose its shape or become dirty due to contact.

When the resin on the surface of the molded product is sufficiently melted, the hot plate 1 is moved to the heating stage, and as shown in FIG.
As shown in (a), for example, the upper holding member is lowered and the molded products are pressed together to perform welding. At this time, the shape of the surface of the molded product has not collapsed, and the occurrence of burrs and the like can be suppressed to a minimum, so that it is possible to finish the product into a regular shape with little variation. After the welded part has cooled, Fig. 2
As shown in (b), the upper holding member 5 is raised to take out the product. Then, the next molded article is supplied and the next welding cycle is started.

In the examples shown in FIGS. 1 and 2, one lower molded product and one upper molded product are welded together. However, for example, one lower molded product has a plurality of upper molded products. The present invention can also be applied to the case where a plurality of molded products are welded to one molded product, such as the case of welding individual molded products. In addition, a plurality of combinations of the lower holding member and the upper holding member may be arranged side by side and simultaneously heated by one heating plate so that a plurality of products can be manufactured at the same time. Alternatively, a plurality of molded products may be held by the lower and upper holding members, and a plurality of molded products may be welded at the same time.

[0020]

Next, embodiments of the present invention will be described with reference to the drawings. [First Embodiment] FIG. 3 is a sectional view for explaining the first embodiment of the present invention. In this embodiment, the hot plates 1 are provided only at the portions corresponding to the welded portions of the molded product, and the hot plates are joined by the hot plate connecting body 7. Further, the heating coil 2 is provided for each hot plate 1. The operation and effect are the same as in the case of the embodiment shown in FIGS. 1 and 2, but such a configuration enables more efficient heating.

[Second Embodiment] FIGS. 4 and 5 are sectional views in order of steps for explaining a second embodiment of the present invention. This embodiment relates to the case where the welding point has a three-dimensional shape. The upper and lower surfaces of the hot plate 1 are processed in parallel with the welding surfaces of the resin molded products 5 and 6. As shown in FIG. 4A, after the resin molded products 5 and 6 are mounted on the lower holding member 3 and the upper holding member 4, respectively, on condition that the temperature of the hot plate 1 is equal to or higher than a predetermined temperature, As shown in FIG. 4 (b),
The hot plate 1 is moved to the welding stage. When the hot plate reaches the predetermined position, the upper holding member is slightly lowered to bring the resin molded product 6 closer to the hot plate 1.

After the welded portion of the resin molded product is sufficiently melted, as shown in FIG. 4 (c), the upper holding member 4
After slightly raising, the heating plate 1 is moved to the heating stage. Immediately thereafter, the upper holding member is lowered to perform welding [FIG. 5 (a)]. After the welded portion is cooled, as shown in FIG. 5B, the upper holding member 5 is lifted to take out the product. Then, the next molded article is supplied and the next welding cycle is started. Since the hot plate in the present invention is heated by the heat generated by the hot plate itself, it does not have to be a flat shape, that is, a shape having irregularities,
The temperature difference in the hot plate can be reduced.

[Third Embodiment] FIGS. 6A to 6C show
It is a process order sectional view for explaining the 3rd example of the present invention. In this embodiment, the heating stage for the hot plate is provided at the same location as the welding stage. Here, the lower and upper holding members 3 and 4 are made of ceramics. Below the position shown in FIG. 6A, the lower holding member 3 receives the resin molded product 5 and the upper holding member 4 receives the resin molded product 6 above the illustrated position, and rises respectively. Alternatively, it descends and stands still at the position shown.

When the resin on the surface of the molded product is sufficiently melted, as shown in FIG. 6 (b), the heating plate 1 is moved to the left in the figure, and the upper holding member 4 is lowered or the lower holding member is lowered. 3 is raised and the molded products are pressed together to perform welding. After the welded portion has cooled, the lower holding member 3 is lowered and the upper holding member 4 is raised, as shown in FIG.
Returns to the original heating stage. Below the illustrated position, the product is taken out and the lower holding member is newly supplied with the resin molded product. Further, the upper holding member 4 is newly supplied with a resin molded product in the upper part of the drawing. The lower and upper holding members move up or down to return to the state of FIG.

[0025]

As described above, the hot plate welding method and apparatus according to the present invention heats a molded article to be welded by using a hot plate heated by an electromagnetic induction method. Can be enjoyed. Since the hot plate has a simple structure, the weight can be extremely light, which is several tenths of that of the conventional hot plate. Therefore, the driving mechanism of the hot plate can be downsized and simplified, the operation speed can be increased, and the productivity can be improved. In addition, it is possible to significantly reduce the start-up time and the setup time for hot plate replacement accompanying model switching. Since the heat plate is heated by the heat generated by itself, it can be heated with high efficiency, and even if it has irregularities, it is possible to reduce the temperature difference inside the hot plate, and to finish the welding. It is possible to prevent "unevenness" from occurring. In particular, when the temperature of the hot plate is set slightly above the Curie point, the temperature deviation inside the hot plate can be further reduced. Since the hot plate can be heated to a high temperature, it is possible to heat the molded product in a non-contact manner and prevent the molded product from losing its shape or becoming dirty due to contact with the hot plate. it can. Therefore, it is possible to reduce the occurrence of burrs and the like and finish the product in a regular shape. Since it becomes possible to radiate a large amount of infrared rays from the hot plate, it becomes possible to heat the inside of the article to be welded and the welding quality can be improved. Here, this effect can be further enhanced when a coating that promotes infrared radiation is provided on the surface of the hot plate. Unlike the conventional hot plate, the hot plate does not cause the heater to burn out and has a semi-permanent life. Therefore, it is possible to reduce the man-hour and cost required for the hot plate replacement. Since it is not necessary to use extra parts and materials as in the case of the conventional induction heating method, welding can be performed at low cost. In addition, since no wire or the like remains in the product, no problem occurs in pollution control and resource recycling.

[Brief description of the drawings]

FIG. 1 is a part of a process sequence cross-sectional view for explaining an embodiment of the invention.

2A to 2C are cross-sectional views in order of the steps in a step that follows the step of FIG. 1 for explaining the embodiment of the present invention.

FIG. 3 is a sectional view of a welding device for explaining the first embodiment of the present invention.

FIG. 4 is a part of a process sequence cross-sectional view for explaining a second embodiment of the present invention.

FIG. 5 is a view for explaining the second embodiment of the present invention.
Sectional sectional view in a step following the step.

6A to 6C are sectional views in order of the processes, for illustrating a third embodiment of the present invention.

7A to 7C are sectional views in order of the processes, for illustrating a conventional hot plate welding method.

FIG. 8 is a sectional view of a conventional hot plate.

9A to 9C are cross-sectional views in order of the processes, for illustrating a conventional induction heating welding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11 Hot plate 2, 31 Heating coil 3, 13 Lower holding member 4, 14 Upper holding member 5, 6, 15, 16 Resin molded product 7 Hot plate connection body 17 Hot water ball 18 Burr 21 Heater block 21a Metal plate 21b Heater 22 Template 23 Resin coat 32, 33 Resin molded product 34 Wire 35 Magnetic adhesive

Claims (5)

[Claims] (1) A process of arranging a hot plate heated by an induction heating method between resin molded products to be welded and heating a welded portion of the resin molded products in a non-contact manner; ) A process of moving the hot plate and the resin molded product relative to each other so that the hot plate does not interfere with the welding of the resin molded product, and (3) welding by pressing the resin molded products together. A non-contact hot plate welding method comprising: 2. The non-contact hot plate welding method according to claim 1, wherein the heating of the hot plate is performed at a place different from a place where the resin molded product is welded. 3. The non-contact hot plate welding method according to claim 1, wherein the hot plate is made of a magnetic material, and the hot plate is heated to a temperature equal to or higher than the Curie point of the material. 4. A first holding member and a second holding member capable of holding resin molded products so that they face each other, and either one or both of the first and second holding members face each other. A drive mechanism for moving the resin molded product so as to be separated from or in contact with each other, a hot plate heated by an induction heating method, a heating coil for applying an alternating magnetic field to the hot plate, and the hot plate A non-contact hot plate welding apparatus comprising: a moving mechanism that moves between a position that heats a welding portion of the resin molded product and a position that does not hinder the welding of the resin molded product. 5. The non-contact hot plate welding apparatus according to claim 4, wherein the hot plate is covered with a metal oxide film or a ceramic coating.