Thermoforming device

Abstract

A thermoforming device (100) for forming a resinous sheet (S) using a die (150) is provided. The thermoforming device (100) comprises: a sheet holder (50) which has a shape conforming to the die (150) and has the function of positioning and holding the resinous sheet (S); and a clamp (65) which presses the resinous sheet (S) against the surface of the die (150) when the resinous sheet (S) is placed along the surface of the die (150) by bringing the sheet holder 50 close to the die (150). The die (150) has a first jig receiving part (150b) for positioning the sheet holder (50). Due to the configuration, the resinous sheet (S), even in deep drawing, is less likely to have unevenness in thickness.

Description

thermoforming equipment

[0001] The present invention relates to molding using a thermoforming device, and more particularly to a technique for improving molding accuracy by utilizing positioning that is effective when deep drawing large parts.

[0002] Thermoforming machines are a technology used to manufacture a variety of products by heating and shaping plastic sheets. However, while misalignment is not a problem when making relatively small, single-color molded products such as food trays, misalignment can become a problem when making large parts such as automobile front and rear bumpers due to the relationship with holes and patterns in the parts. Furthermore, misalignment tends to worsen during deep drawing, so thermoforming machines have not been widely used for deep drawing.

[0003] Patent Document 1 discloses a technique for manufacturing a decorated molded product, which claims to improve molding position accuracy for molded products with deep molding surfaces. This technique involves using a mold with a cavity and a core. A film, consisting of a base film and a decorative pattern layer formed thereon, is positioned relative to the cavity in a half-open mold. The end face of the cavity mold facing the core mold is held in close contact around the molding surface, and the film is then adhered to the molding surface by vacuum suction. Molten resin is then injected into the cavity formed between the film and the core surface of the core mold in a closed mold to form the molded product body. At the same time, at least the decorative pattern layer of the film is attached to the design surface of the molded product body, thereby producing a decorated molded product whose design surface is decorated with the decorative pattern layer.

[0004] In this case, the decorative pattern layer is coated with a heat-melting protective layer at least at the portion pressed by the core mold, and when the mold is closed, the protective layer is pressed toward the cavity mold by the core mold, bringing the film held by the cavity mold close to the molding surface.The film is then brought into close contact with the molding surface by vacuum suction, and when the molded product main body is formed, the protective layer is melted by the heat of the molten resin injected into the cavity.

[0005] Patent Document 2 discloses a technology related to a heating device in which radiant heaters are arranged in a matrix, and a support member is connected to a frame body so that the distance from the sheet member to the radiant heaters can be adjusted, making it possible to adjust the distance between the sheet member and the radiant heaters. This makes it possible to heat the sheet member uniformly regardless of the shape of the sheet member.

[0006] Patent No. 5790513 Patent No. 7305177

[0007] However, in the technology described in Patent Document 1, when producing a molded product with a deep forming surface, the film is formed by vacuum suction into a cavity mold, which makes it inevitable that the thickness of the film or sheet will change during the forming process. When deep drawing is performed, tension is applied to the film or sheet, causing it to stretch, and the stretched portion will lose thickness. This can lead to a decrease in strength due to thickness changes, making it difficult to apply to the manufacture of parts that require deep drawing and strength, such as car bumpers.

[0008] Furthermore, in the case of a method using the technology described in Patent Document 2 in which the position of the radiant heater is adjusted to match the mold while the sheet member is in contact with the mold, it is thought that tension is applied when the hot plate is heated to align the sheet member, and so although this method can accommodate gradual shape changes such as curved shapes, it is not enough to accommodate deep drawing of the sheet member.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a thermoforming device that is less likely to cause variations in the thickness of a resin sheet even when deep drawing is performed.

[0010] In order to achieve the above object, a thermoforming apparatus according to one aspect of the present invention has the following features.

[0011] (1) A thermoforming device that uses a mold to mold a resin sheet heated by a heating means, comprising: a sheet holder that has a shape that conforms to the mold or a function that imitates the mold and has a function of positioning and holding the resin sheet; a pressing means that presses the resin sheet against an abutment surface provided on the mold when the resin sheet is aligned with the surface of the mold by bringing the sheet holder close to the mold; and a suction means that vacuum-sucks air between the mold and the resin sheet at the bottom of the mold, wherein the mold has a positioning portion that positions the sheet holder and the abutment surface that abuts against the outer periphery of the resin sheet; and after the resin sheet is aligned with the surface of the mold by the sheet holder, the resin sheet is heated by the heating means and thermoformed.

[0012] According to the aspect described in (1) above, the resin sheet is held in a shape that conforms to the mold using a sheet holder, and thermoforming is initiated while the resin sheet is deformed and held in place, thereby achieving a uniform thickness for the molded product. This is because, when thermoforming a resin molded sheet, if the resin sheet is deformed by heating it to around the glass transition point, the effect of thinning is likely to be significant when performing deep drawing, as described in the problem. Therefore, the sheet holder is used to deform and hold the resin sheet in a shape that conforms to the mold before heating. Then, by thermoforming, the risk of unintended thinning due to tension during thermoforming can be reduced.

[0013] Furthermore, by providing a contact surface on the mold side and pressing the resin sheet against the mold with a pressing means, it is possible to effectively suction air between the mold and the resin sheet. Furthermore, even when a transparent portion is desired in a molded product, the resin sheet undergoes minimal deformation during thermoforming, making it possible to obtain a molded product that maintains its transparency. When thermoforming a transparent resin sheet, problems such as cloudiness can be caused by gas escape, but by pressing the resin sheet with a pressing means, air is effectively released, which is expected to improve yield.

[0014] (2) In the thermoforming device described in (1), it is preferable that the pressing means comprises a propulsion mechanism that moves the sheet holder toward the mold, and a link mechanism that moves the sheet holder closer to the mold, and that the propulsion mechanism and the link mechanism operate in conjunction with each other.

[0015] According to the aspect described in (2) above, a propulsion mechanism is provided that moves the sheet holding fittings so as to press them against the mold side, and by providing a link mechanism, it is possible to press the resin sheet against the mold side from the side of the mold as well.

[0016] (3) In the thermoforming device described in (1) or (2), it is preferable that the suction means is provided with a first suction circuit and a second suction circuit that exert different suction forces, and the resin sheet is sucked toward the mold by switching between the first suction circuit and the second suction circuit.

[0017] According to the aspect described in (3) above, the flow rate can be changed by switching between the first and second suction circuits, thereby enabling the suction force to be switched. Depending on the shape of the mold, the resin sheet may first come into contact with the molding surface that will become the product. In this case, heat is lost from the resin sheet at the area below the mold's molding surface, causing the resin sheet to partially harden only where it comes into contact with the molding surface. This provides a positioning effect for the resin sheet, so by switching the suction circuit at this point to increase the flow rate, it is possible to suppress the effects of misalignment.

[0018] (4) In the thermoforming device described in any one of (1) to (3), it is preferable that the suction means includes a first position suction circuit and a second position suction circuit for sucking different positions of the mold.

[0019] The aspect described in (4) above makes it possible to suppress the effects of misalignment by switching the suction position, which, like the effect described in (3), makes it possible to suppress misalignment of the resin sheet by selecting a configuration in which the portion corresponding to the molding surface of the mold is first suctioned and the other portions are not suctioned.

[0020] (5) In the thermoforming device described in (1), it is preferable that the clamp provided as the pressing means is fixed to the sheet holder, and the clamp has a rotation mechanism, which is provided near the fixed part with the sheet holder.

[0021] According to the aspect described in (5) above, by using a clamp to hold down the resin sheet, the gap with the mold is reduced, and it becomes possible to accurately transfer the shape of the mold surface when thermoforming using vacuum suction. This clamp is equipped with a rotation mechanism and is fixedly attached to the sheet holder, so there is no fluctuation in the positions of the clamp and the sheet holder, and the positions of the sheet holder and the mold are determined by the positioning means, so it is possible to obtain a molded product with high shape precision using this thermoforming device.

[0022] (6) In the thermoforming device described in (1), it is preferable that the sheet holder comprises a frame body that supports at least two opposing sides of the entire circumference of the resin sheet, and the function of the sheet holder to imitate the mold is realized by providing multiple joint parts on the frame body.

[0023] According to the aspect (6) above, the sheet holder has a function of conforming to the mold by providing a plurality of joints. Since the resin sheet conforms to the mold by using a frame that supports at least two opposing sides of the entire periphery, there is no need to maintain the sheet holder in a three-dimensional shape, which improves workability and storability.

[0024] (7) In the thermoforming device described in (5), it is preferable that the clamp uses the principle of leverage or air pressure as a biasing means for pressing the resin sheet against the surface of the mold.

[0025] According to the aspect described in (7) above, by firmly pressing the resin sheet against the mold using the biasing means provided on the clamp, it becomes possible to easily remove air trapped between the resin sheet and the surface of the mold during vacuum forming. If the resin sheet is softened and firmly conforms to the surface of the mold during vacuum forming, it becomes easy to suck out the remaining air, but if the resin sheet is thick, gaps are particularly likely to form, and by sealing these with the clamp, effective vacuum forming can be achieved.

[0026] (8) In the thermoforming device described in any one of (1) to (7), it is preferable that the heating means for heating the resin sheet has radiant heaters arranged in a matrix facing the mold.

[0027] According to the aspect (8) above, by using radiant heaters arranged in a matrix, it is possible to heat the areas that are to undergo a large degree of shape change more intensively. Since the output of each of the radiant heaters arranged in a matrix can be set, it is possible to heat the areas that do not need to be heated and the areas that do need to be heated separately. This improves molding accuracy.

[0028] FIG. 1 is a schematic diagram of a thermoforming device according to a first embodiment. FIG. 2 is a perspective view of a lower jig of a sheet holder according to the first embodiment. FIG. 3 is a side view showing a state in which a resin sheet is sandwiched between sheet holders according to the first embodiment. FIG. 4 is a perspective view of a mold according to the first embodiment. FIG. 5 is a schematic front view of a resin sheet held by sheet holders according to the first embodiment. FIG. 6 is a schematic front view of a resin sheet brought close to a mold according to the first embodiment. FIG. 7 is a schematic front view of a resin sheet being suctioned from the mold side according to the first embodiment. FIG. 8 is a schematic front view of an upper container being brought close to a mold according to the first embodiment. FIG. 9 is a schematic front view of a resin sheet being heated according to the first embodiment. FIG. 10 is a schematic front view of a resin sheet being pressure-molded according to the first embodiment. FIG. 11 is a schematic front view of a resin sheet held by sheet holders according to the first embodiment. FIG. 12 is a schematic front view of a resin sheet brought close to a mold according to the first embodiment. 1 is a schematic front view of the first embodiment, showing the state in which an upper container is brought close to a mold; FIG. 2 is a schematic front view of the first embodiment, showing the state in which a resin sheet is being heated; FIG. 3 is a perspective view of an example of a molded product of the first embodiment; FIG. 4 is a perspective view of a sheet holder of the second embodiment; FIG. 5 is a side view of the sheet holder of the second embodiment; FIG. 6 is a side view showing the sheet holder of the second embodiment, shown along the mold; FIG. 7 is a front view of the third embodiment, showing the sheet holder in an open state; FIG. 8 is a front view of the third embodiment, showing the sheet holder in a lowered state, where (a) shows the intermediate position of the cylinder, and (b) shows the position of the lower end of the cylinder; FIG. 9 is a cross-sectional view of a part of the mold of the third embodiment; (a) shows the state in which the cylinder is at the upper end, (b) shows the state in which it is at the intermediate position, and (c) shows the state in which it is at the lower end; FIG. 10 is a cross-sectional view of the mold of the third embodiment; and FIG. 11 is a cross-sectional view of the fourth embodiment, showing (a) the state in which the cylinder is at the upper end, (b) the state in which it is at the intermediate position, and (c) the state in which it is at the lower end. 10 is a conceptual diagram showing a molding process using a thermoforming device according to a fourth embodiment; FIG. 11 is a timing chart according to the fourth embodiment; FIG. 12 is a conceptual diagram showing a molding process using a thermoforming device according to a fifth embodiment; FIG. 13 is a timing chart according to the fifth embodiment.

[0029] First Embodiment First, a schematic configuration of a thermoforming apparatus 100 according to a first embodiment of the present invention will be described. FIG. 1 shows a schematic diagram of the thermoforming apparatus 100 according to the first embodiment. The thermoforming apparatus 100 includes an upper container 101 and a lower container 102. The thermoforming apparatus 100 is configured to heat an input resin sheet S using a heating means 110 and then perform compressed air / vacuum forming using a mold 150. While valves installed in the piping paths are omitted in FIG. 1 , the pressure in the upper container 101 and the lower container 102 can be adjusted by switching between appropriate circuits, and these vacuum circuits function as a vacuum suction means and a compressed air means. While two pumps and tanks are shown in FIG. 1 , this number can be increased or decreased as needed.

[0030] The resin sheet S is a sheet material made of thermoplastic resin. The resin sheet S is a rectangular sheet approximately 2 m long and approximately 0.2 mm to 1.0 mm thick. It has been confirmed that the first embodiment can also be applied to thicker or thinner sheets, so thickness and length can be changed as needed. This resin sheet S is molded into a molded product M, which is a car bumper part. Positioning holes (not shown) are provided around the periphery in relation to the sheet holder 50, which will be described later. The surface of the resin sheet S may also be decorated by printing.

[0031] The heating means 110 comprises a plurality of heaters 111 arranged in a matrix, each of which performs radiant heating. The heaters 111 are mid-infrared quick-response heaters, which can quickly heat the resin sheet S to be heated. As will be described later, the height and angle can be adjusted to match the shape of the mold 150, and in the first embodiment, the heaters 111 are arranged in an arc shape. While FIG. 1 shows a schematic representation of a small number of divisions, the number of heaters 111 can be increased or decreased to match the size of the resin sheet S to be molded. A similar configuration is also described by the applicant in Patent Document 2.

[0032] Figure 2 shows a perspective view of the lower jig of the sheet holder. Figure 3 shows a side view of the sheet holder clamping a resin sheet. The sheet holder 50 is composed of an upper jig 60 and a lower jig 70, and is structured so that the resin sheet S is clamped between the upper jig 60 and the lower jig 70. The lower jig 70 is a frame formed by combining a side member 70a and an end member 70b. The side member 70a of this frame is a plate material cut into a substantially arc shape, and the end member 70b is a flat plate material, and each is joined at its end. A plurality of positioning pins 71 are provided on the upper surface of the lower jig 70.

[0033] The positioning pins 71 function to position the resin sheet S. In the first embodiment, the central position of the resin sheet S is used as the reference, and therefore positioning is performed around the first pin 71a, which is located in the center of the positioning pins 71. The second pins 71b are located on both sides of the first pin 71a, and the third pin 71c is located on the outside. As described above, positioning holes corresponding to the positioning pins 71 are provided on the outer periphery of the resin sheet S, and the resin sheet S is positioned relative to the lower jig 70. Note that the number of positioning pins 71 is determined by the size of the resin sheet S, etc., and therefore it is not prohibited to increase or decrease the number as necessary.

[0034] The upper jig 60 is a plate material in the shape of a substantially square frame, and is configured to be able to be placed along the upper surface of the lower jig 70, and is fixed to the lower jig 70 to hold the resin sheet S. The upper jig 60 is configured to be able to fix a clamp 65, and with the resin sheet S sandwiched between the upper jig 60 and the lower jig 70, the clamp 65 is fixed to the upper jig 60. Although not shown, the upper jig 60 may be provided with holes to avoid interference with the positioning pins 71.

[0035] The clamp 65 is provided with a rotation mechanism 66 on the side where it is fixed to the upper jig 60, i.e., at the base of the clamp 65, and is configured so that by rotating the rotation mechanism 66, the tip side of the clamp 65 falls toward the inside of the sheet holder 50. The tip side of the clamp 65 is provided with a pressing part 67 that comes into contact with the resin sheet S and presses the resin sheet S against the mold 150. It is preferable that the rotation mechanism 66 has a function that can bias the pressing part 67 toward the resin sheet S when the clamp 65 is fallen toward the mold.

[0036] The provided clamp 65 can be used to press the resin sheet S held by the sheet holder 50 on the inside of the sheet holder 50. The clamp 65 is preferably provided with a biasing means, and it is desirable that the biasing force can be adjusted. For example, a biasing means using the principle of leverage, such as a toggle clamp, or a biasing means using air pressure, such as a toggle cylinder, may be provided, and the biasing force may be adjusted by changing the position of the fulcrum or the distance from the viewpoint, or by changing the air pressure.

[0037] 4 shows a perspective view of the mold. The mold 150 is shaped so that it can mold the shape of the bumper that will become the molded product M. Therefore, it consists of a convex portion 150a that forms the recess in the molded product M, a first jig receiving side portion 150b that is provided on both sides of the convex portion 150a and forms a gentle arc, and a second jig receiving side portion 150c that is linear. Since the mold 150 actually molds molded products M with more complex shapes, the mold 150 is shown in a schematic shape with only the characteristic parts extracted for the sake of explanation.

[0038] In the first embodiment, the mold 150 uses the locating pin 151 embedded in the jig first receiving side portion 150b as a positioning means, but as long as the sheet holder 50 can be positioned relative to the mold 150, it is not prevented from using other positioning means, such as providing a step in the mold 150. The back surface of the lower jig 70 is provided with a conical hole 72 in which the locating pin 151 is positioned.

[0039] The procedure for molding a resin sheet S using the thermoforming apparatus 100 configured as described above will now be described. Fig. 5 is a schematic front view showing a resin sheet held by a sheet holder. Fig. 6 is a schematic front view showing a resin sheet brought close to a mold. Fig. 7 is a schematic front view showing a resin sheet being sucked from the mold side. Fig. 8 is a schematic front view showing a state in which an upper container is brought close to a mold. Fig. 9 is a schematic front view showing a state in which a resin sheet is being heated. Fig. 10 is a schematic front view showing a state in which a resin sheet is being pressure-molded.

[0040] Figure 11 is a schematic side view showing the resin sheet being held by the sheet holder. It corresponds to the side view of Figure 5. Figure 12 is a schematic side view showing the resin sheet being brought close to the mold. It corresponds to the side view of Figure 6. Figure 13 is a schematic side view showing the resin sheet being sucked from the mold side. It corresponds to the side view of Figure 7. Figure 14 is a schematic side view showing the upper container being brought close to the mold. It corresponds to the side view of Figure 8. Figure 15 is a schematic side view showing the resin sheet being heated. It corresponds to the side view of Figure 9.

[0041] The resin sheet S is sandwiched between the sheet holders 50, and with the clamps 65 of the sheet holders 50 in place, the sheet holders 50 are brought close to the mold 150. This state is shown in FIGS. 5 and 11. The resin sheet S is cut into a flat plate, and although not shown, multiple positioning holes are provided around the periphery. The sheet holders 50 hold the rectangular cut resin sheet S in a bent state. As a result, the resin sheet S is held by the sheet holders 50 in a shape that is close to the general shape of the mold 150. Then, as shown in FIGS. 5 and 11, the resin sheet S positioned by the sheet holders 50 is brought close to the mold 150. At this point, the clamps 65 are released.

[0042] 6 and 12, the sheet holder 50 is lowered to bring the resin sheet S into contact with the mold 150. The mold 150 is provided with a locating pin 151 as shown in Fig. 4, and is therefore positioned relative to the conical hole 72 provided in the lower jig 70 of the sheet holder 50 as shown in Fig. 3. In other words, since the mold 150 and the sheet holder 50 are positioned, the resin sheet S positioned and held by the sheet holder 50 is also positioned relative to the mold 150.

[0043] Next, as shown in FIGS. 7 and 13 , the clamp 65 is rotated to press the resin sheet S against the mold 150. As a result, the resin sheet S held by the sheet holder 50 is pressed against the surface of the mold 150 by the clamp 65 at its outer periphery (the inner periphery of the sheet holder 50). Then, air is drawn (vacuum suction) from the bottom of the mold 150, bringing the resin sheet S into close contact with the surface of the mold 150. The mold 150 has multiple air holes (not shown) that allow air to be drawn into the bottom of the mold 150. Although not shown in FIGS. 7 and 13 , the lower container 102 is in close contact with the bottom surface of the mold 150, and vacuum suction begins from the connected air circuit. Then, air between the resin sheet S and the surface of the mold 150 begins to escape.

[0044] Next, the upper container 101 is lowered as shown in Figures 8 and 14. Next, as shown in Figures 9 and 15, the upper container 101 is lowered so that its edge abuts against the upper surface of the mold 150. At the same time, the resin sheet S is heated by the heating means 110, and the temperature of the resin sheet S is raised to the softening point of the material, thereby softening it. Vacuum suction is performed during this process, so that the resin sheet S adheres more firmly to the surface of the mold 150. Next, as shown in Figure 10, air is sent into the upper chamber formed by the end surface of the upper container 101 and the top surface of the mold 150 to apply pressure, and pressure molding is performed. The resin sheet S is sufficiently softened at this point, making it possible to form a precision molded product along the surface of the mold 150.

[0045] The thermoforming device 100 of the first embodiment has the above-described configuration, and therefore provides the following functions and effects.

[0046] First, it becomes possible to perform molding with high precision when producing a large molded product M with the thermoforming device 100. This is because the thermoforming device 100, which molds a resin sheet S using a mold 150, is characterized by including a sheet holder 50 that has a shape that conforms to the mold 150 and has the function of positioning and holding the resin sheet S, a clamp 65 that presses the resin sheet S against the surface of the mold 150 when the resin sheet S is aligned with the surface of the mold 150 by bringing the sheet holder 50 close to the mold 150, and suction means that vacuum-sucks air between the mold 150 and the resin sheet S at the bottom of the mold 150, and the mold 150 has a positioning portion (locate pin 151) that positions the sheet holder 50.

[0047] This is because the resin sheet S is deformed in advance by the sheet holder 50 and held in a shape that conforms to the mold 150, and is then heated and molded in that state, so there is little stretching of the resin sheet S during molding, and as a result, it is possible to achieve a uniform thickness distribution in the molded product M. As mentioned in the problem section, the resin sheet S becomes thinner when pulled during molding. This behavior is difficult to control, and problems such as thickness thinning in unintended areas can occur.

[0048] To prevent this, the resin sheet S is deformed with the sheet holder 50 before heating, which makes it possible to suppress changes in thickness and obtain a molded product M with high precision. Specifically, the sheet holder 50 is shaped to fit the general shape of the mold 150, and the sheet holder 50 deforms and holds the resin sheet S. Therefore, the resin sheet S is heated by the heating means 110 in a state in which it has been elastically deformed to fit the general shape of the mold 150. In this case, since the heating means 110 is arranged to fit the general shape of the mold 150, efficient heating is possible, and a predetermined position can be quickly heated to a predetermined temperature.

[0049] Furthermore, by pressing the resin sheet S with the clamps 65 and performing compressed air / vacuum forming, a highly accurate molded product M can be obtained. This is achieved by positioning and holding the resin sheet S in the sheet holder 50, and by positioning and abutting the sheet holder 50 against the mold 150. By using such a thermoforming device 100, a relatively thick resin sheet S can be thermoformed to obtain a molded product M with minimal variation in thickness. This makes it applicable to products that require strength, such as car bumpers.

[0050] Furthermore, by providing the clamp 65, the resin sheet S can be pressed against the surface of the mold 150, which makes it easier to remove air that is between the resin sheet S and the surface of the mold 150 during vacuum forming, thereby improving adhesion. The pressing portion 67 of the clamp 65 is structured to press the resin sheet S against the mold 150, and presses the outer periphery of the resin sheet S. It is desirable to press the entire periphery of the resin sheet S, but even pinpoint pressing on areas where spaces are particularly likely to form can be effective. It is desirable to press on areas where the resin sheet S may lift up from the mold 150.

[0051] At this time, it is desirable to be able to adjust the force with which the clamp 65 presses the resin sheet S, and it is also desirable to widen the contact area so that the force is dispersed across the resin sheet S. Furthermore, it is desirable that the position and range of contact be such that the clamp 65 contacts the portion that will be trimmed later, rather than the portion that will become the molded product M. However, since it is important to allow air to easily escape between the mold 150 and the resin sheet S, it is desirable to press the mold 150 at a portion that experiences a large change in shape, for example, the portions near the short side 150d and long side 150e of the mold 150 shown in FIG.

[0052] The heating means 110 uses radiant heaters 111 arranged in a matrix, and the output of each heater can be adjusted individually. Figure 15 shows an example of a perspective view of a molded product. The molded product M has a transparent portion M1 in the center for the purpose of transmitting light, taking design into consideration. This transparent portion M1 is created by providing a printed layer on the back side of a transparent resin sheet S, creating a non-transmitting portion and a transmitting portion (i.e., the transparent portion M1 is not printed), and is provided as a device to enhance design.

[0053] When obtaining such a molded product M, the portions of the mold 150 that undergo significant shape changes, i.e., the portions around the short side 150d and long side 150e of the mold 150 shown in Figure 4, are heated to a high temperature, while the portions that do not change are set to a relatively low temperature. In the case of the molded product M shown in Figure 15, the transparent portion M1 and its surroundings are set to a constant temperature. As a result, it is possible to suppress changes in the thickness of the molded product M without causing defects such as clouding in the transparent portion M1 of the molded product M.

[0054] Furthermore, by using this method, it is possible to avoid the effects of partial thinning of the molded product M, and therefore functionality is not impaired even when used for strength parts. Furthermore, the resin sheet S used in the first embodiment is intended for thermoforming large molded products M, but for large resin sheets S, increasing the output of the heater 111 in areas that are subject to large deformation can contribute to energy conservation. The molded product M shown in FIG. 15 is merely an example, and is not limited to this shape.

[0055] Furthermore, Patent Document 2 also shows a technique of arranging heaters 111 in a matrix as the heating means 110, suggesting that the temperature is adjusted so that the resin sheet S to be molded is uniform, but the first embodiment differs in that a temperature difference is actively created in the output of the heaters 111 to improve the quality of the molded product M. For this purpose, it is desirable that the heaters 111 be connected to a control device (not shown) so that the output can be adjusted individually.

[0056] Second Embodiment The second embodiment has substantially the same device configuration as the first embodiment, but differs in the configuration of the sheet holder 50, and therefore the following description will focus on the differences. FIG. 17 shows a perspective view of the sheet holder of the second embodiment. FIG. 18 shows a side view of the sheet holder. The sheet holder 50 of the second embodiment comprises an upper jig 160 and a lower jig 170, and is configured to sandwich the resin sheet S between the upper jig 160 and the lower jig 170. The lower jig 170 is a frame formed by combining side members 170a and end members 170b. The side members 170a of this frame are plates equipped with multiple lower joints 175, which have a pin-support structure. Multiple positioning pins 71 are provided on the upper surface of the side members 70a.

[0057] The positioning pins 71 function to position the resin sheet S. In the second embodiment, the center position of the resin sheet S is also used as a reference, so positioning is performed around the first pin 71a, which is located in the center of the positioning pins 71. The second pins 71b are located on both sides of the first pin 71a, and the third pin 71c is located on the outside.

[0058] As described above, positioning holes corresponding to the positioning pins 71 are provided on the outer periphery of the resin sheet S, and the resin sheet S is positioned relative to the lower jig 70. The number of positioning pins 71 is determined by the size of the resin sheet S, and therefore may be increased or decreased as necessary. Although not shown, the lower jig 170 has a conical hole 72 on the back surface thereof for positioning the locating pin 151.

[0059] The upper jig 160 is a plate material in the shape of a substantially square frame, and is configured to be able to be placed along the upper surface of the lower jig 170, and is fixed to the lower jig 170 to hold the resin sheet S. The upper jig 160 also has an upper joint 165 at a position corresponding to the lower joint 175 of the lower jig 170. Here, as will be described later, the upper joint 165 needs to be bent in accordance with the lower joint 175, and therefore it is desirable for the upper joint 165 to have a loose structure that stretches as a whole when bent.

[0060] Although not shown, the upper jig 160 has a structure that allows a clamp 65 to be fixed thereto, and the clamp 65 is fixed to the upper jig 160 in a state in which the resin sheet S is sandwiched between the upper jig 160 and the lower jig 170. Although not shown, the upper jig 160 has a hole formed therein to avoid interference with the positioning pin 71.

[0061] The procedure for thermoforming using the sheet holder 50 configured as described above is as follows. Figure 19 is a side view showing the sheet holder aligned with the mold. First, the resin sheet S is held by the sheet holder 50, and the sheet holder 50 is positioned along the mold 150. At this time, as shown in Figure 19, the upper joint 165 and the lower joint 175 of the sheet holder 50 are bent, thereby pressing and holding the resin sheet S against the surface of the mold 150. The clamps 65 then act to press the outer periphery of the resin sheet S, vacuum suction begins, and thermoforming begins.

[0062] The thermoforming apparatus 100 of the second embodiment performs thermoforming using the sheet holder 50 described above, and therefore provides the same effects as the thermoforming apparatus 100 of the first embodiment. Specifically, the sheet holder 50 can be deformed to a shape that follows the general shape of the mold 150, eliminating the need for a three-dimensional shape like the sheet holder 50 of the first embodiment, resulting in benefits such as improved workability and storability. Furthermore, the sheet holder 50 of the second embodiment is more versatile than the sheet holder 50 of the first embodiment due to the deformable structure employed. In other words, it can be adapted to multiple types of molds 150.

[0063] (Third Embodiment) The third embodiment is similar to the device configuration of the second embodiment, but differs in the configuration of the sheet holder 50 and the mold 150, so the following description will focus on the differences. Figure 20 shows a front view of the sheet holder of the third embodiment in an open state. Figure 21 shows a front view of the sheet holder in a lowered state. Figure 21(a) shows the intermediate position of the cylinder, and Figure 21(b) shows the lowered end of the cylinder. The sheet holder 250 of the third embodiment is similar to the first and second embodiments in that it has an upper jig 260 and a lower jig 270, but differs in that a double-rod type clamp cylinder 280 is used and connected, and the upper jig 260 and the lower jig 270 are connected by a link mechanism 290.

[0064] The structure of the sheet holders 250 will be described next. Of the sheet holders 250 held on both sides of the mold 240, the upper jig 260 has a pair of upper first sections 261, each of which has an upper second section 262 connected to both ends by a first fulcrum 263, and the ends of the upper second sections 262 are connected to each other by a connecting member 265. In other words, the two upper first sections 261, the four upper second sections 262, and the two connecting members 265 are connected to form a substantially rectangular frame. The clamp cylinders 280 are held by cylinder brackets 285 fixed to both side surfaces of the mold 240. The sheet holders 250 are opened, closed, and raised and lowered by synchronously driving the clamp cylinders 280 provided on both sides.

[0065] The upper first section 261 is formed in an arc shape that convex outward (upward), and a lifting bracket 266 is fixed to its center. One end of a cylinder rod 281 provided in a clamp cylinder 280 is fixed to the lifting bracket 266. The upper second sections 262 are connected to both ends of the upper first section 261 by first fulcrums 263. The upper second sections 262 are also formed in an arc shape that convex outward, and on both the left and right sides, one end is supported by the first fulcrum 263 and the other end is provided with a second fulcrum 264.

[0066] The second fulcrum 264 is held by a slide bracket 282 fixed to the other end of the cylinder rod 281 via a link rod 291 and an L-shaped arm 292. That is, on both the left and right sides, one end of the link rod 291 is rotatably connected to the other end of the upper second section 262 at the second fulcrum 264, and the other end is rotatably connected to one end of the L-shaped arm 292 at a third fulcrum 298. The other end of the L-shaped arm 292 is slidably and rotatably connected to an elongated hole 283 provided in the slide bracket 282 at a fifth fulcrum 284. A bent portion 292a of the L-shaped arm 292 is rotatably supported by a lifting fulcrum bracket 296 at a fourth fulcrum 299. The lifting fulcrum bracket 296 is held so as to be able to move up and down relative to the base 210.

[0067] The lower jig 270 is formed in a generally arc-shaped convex shape, and is configured to sandwich the resin sheet S between the lower surface of the upper jig 260 (the inner surface of the arc that contacts the sheet) and the upper surface of the lower jig 270 (the outer surface of the arc that contacts the sheet). A plurality of positioning pins 271 are embedded in the outer surface of the lower jig 270 to position the resin sheet S. A spring 273 is provided below the lower jig 270 to support the elevation of the lower jig 270. Although not shown, the lower jig 270 is supported so as to be vertically elevated and lowered by a guide provided on the side of the mold 240. Although not shown, a recess is provided on the lower surface 260 a of the upper jig 260 in a portion corresponding to the positioning pin 271 provided on the outer surface 270 a of the lower jig 270.

[0068] The upper jig 260 and the lower jig 270 connected to the link mechanism 290 are configured to open and close and rise and fall in conjunction with the operation of the clamp cylinder 280 fixed to the side of the mold 240 by means of the cylinder bracket 285. Here, if a state in which one end of the cylinder rod 281 of the clamp cylinder 280 has moved upward is defined as the upper end, and a state in which the other end has moved downward is defined as the lower end, when the clamp cylinder 280 is at the upper end, the upper jig 260 is separated from the lower jig 270 as shown in Figure 20, allowing the resin sheet S to be inserted, and when the clamp cylinder 280 is at the lower end, as shown in Figure 21(b), the resin sheet S is sandwiched between the upper jig 260 and the lower jig 270 and pressed against the mold 240.

[0069] Figure 22 shows a partial cross-sectional view of the mold. (a) shows a cross-section when the cylinder is at the uppermost position, (b) shows a cross-section when it is at an intermediate position, and (c) shows a cross-section when the cylinder is at the lowermost position. That is, Figure 22(a) shows the uppermost position of the clamp cylinder 280 corresponding to Figure 20, Figure 22(b) shows the intermediate position of the clamp cylinder 280 corresponding to Figure 21(a), and Figure 22(c) shows the lowermost position of the clamp cylinder 280 corresponding to Figure 21(b).

[0070] As shown in Fig. 20, the mold 240 is formed into an overall shape that is convex upward, and is fixed to a base 210. During thermoforming, the resin sheet S comes into contact with the product forming surface 240a. A sealing surface 240b is formed at the end of the cross section taken at the center of Fig. 20 (a portion of which is shown as an enlarged cross section in Fig. 22). The sealing surface 240b comes into surface contact with the resin sheet S, and a sealing material 241 is provided around the sealing surface 240b to prevent air leakage.

[0071] FIG. 23 shows a cross-sectional view of the mold. The cross-section is perpendicular to the cross-section shown in FIG. 22. The cross-section of FIG. 23 also shows that the mold 240 has a product molding surface 240a that contacts the resin sheet S and a sealing surface 240b formed around the product molding surface 240a. A sealing material 241 is provided on the sealing surface 240b. Furthermore, multiple suction paths 240c are provided at key locations on the product molding surface 240a, penetrating into an internal space 242 provided within the mold, as shown in FIG. 23. While the suction paths 240c and internal space 242 are enlarged in FIG. 23 for illustrative purposes, they are actually small holes that do not affect the molding of the resin sheet S. The internal space 242 is also shown only diagrammatically, and is not limited to this shape.

[0072] Next, the procedure for thermoforming the resin sheet S using the sheet holder 250 will be described.

[0073] First, as shown in Figure 20, with the sheet holder 250 in the open position, the resin sheet S is attached to the lower jig 270. To open the sheet holder 250, the cylinder rod 281 of the clamp cylinder 280 is moved to the raised end, and the upper jig 260, which is lifted by the lift bracket 266, is held in an open position by the link mechanism 290 with the upper second section 262 in the open position. The resin sheet S is then inserted between the upper jig 260 and the lower jig 270, and the outer peripheral surface 270a of the lower jig 270 is provided with a plurality of positioning pins 271, and the resin sheet S is held by these pins. This state is the same as the state shown in Figure 22(a).

[0074] Next, the clamp cylinder 280 is driven to lower the cylinder rod 281. The state during this process is shown in FIG. 21(a). As the lifting bracket 266 is lowered, the upper first section 261 descends, and the upper second section 262 begins to close due to the action of the link mechanism 290. The lower jig 270 reaches the state shown in FIG. 22(b), in which the resin sheet S is sandwiched between the lower surface 260a and the outer peripheral surface 270a of the upper jig 260. Further lowering the cylinder rod 281 to its lower end pushes down the lower jig 270 together with the upper jig 260, as shown in FIG. 21(b), and the upper second section 262 also closes as shown in FIG. 21(b). This allows the resin sheet S to be maintained pressed against the sealing surface 240b of the mold 240, as shown in FIG. 22(c).

[0075] 23, while the resin sheet S is heated by the heating means 220, the internal space 242 is suctioned by vacuum as shown in FIG. 23, and air is sucked through the suction path 240c, causing the resin sheet S to begin to deform. In this state, the sealing material 241 is crushed to exert a sealing effect, creating a negative pressure state that suppresses leakage and enables the resin sheet S to be thermoformed (vacuum formed).

[0076] The thermoforming device 100 of the third embodiment has the above-described configuration, and therefore provides the following functions and effects.

[0077] First, it becomes possible to perform molding with high precision when producing large molded products M using the thermoforming apparatus 100. The mold 240 and sheet holder 250 used in the thermoforming apparatus 100 of the third embodiment achieve an effect similar to that of the clamp 65 used in the first embodiment, by means of the sheet holder 250 and mold 240. This is because, since the structure that prevents leaks using the clamp 65 as in the first embodiment can be difficult depending on the shape of the mold, in the third embodiment a sealing surface 240b is formed like in the mold 240, and the sheet holder 250 itself is required to perform the same function as the clamp 65.

[0078] That is, by closing and lowering the sheet holders 250 using the clamp cylinders 280, the resin sheet S sandwiched between the sheet holders 250 is pressed against the mold 240, and the resin sheet S comes into contact with the sealing material 241 on the sealing surface 240b of the mold 240, thereby preventing air leakage. In this state, air is drawn in from the mold 240 side and the resin sheet S is heated by the heating means 220, so that the resin sheet S comes into contact with the product molding surface 240a of the mold 240 and is thermoformed into any desired shape. By this procedure, a molded product M as shown in FIG. 16 is obtained.

[0079] When the resin sheet S is thermoformed by such means, it is possible to thermoform the resin sheet S more practically than in the first embodiment. This is because, when the clamp 65 of the first embodiment is configured to press the outer periphery of the resin sheet S, it is thought that it may be difficult to prevent leakage depending on the material and thickness of the resin sheet S. However, by providing the mold 240 with the sealing surface 240b, it is possible to improve airtightness, which can contribute to thermoforming a molded product M with higher precision.

[0080] (Fourth Embodiment) The fourth embodiment has almost the same device configuration as the third embodiment, but differs in the configuration of the mold 340 and in the absence of the upper container 101, so the following description will focus on the differences. Figure 24 shows a front view of the sheet holder in a lowered state. Figure 24 shows a partial cross-sectional view of the mold in the fourth embodiment. (a) shows the cross-section when the cylinder is at the upper end, (b) shows the cross-section when it is at an intermediate position, and (c) shows the cross-section when the cylinder is at the lower end. The mold 340 used in the fourth embodiment differs from the mold 240 in the third embodiment in that the seal material 241 is not provided on the sealing surface 240b, but similar functionality can be expected.

[0081] In other words, the sealing surface 340b provided on the mold 340 has a surface formed as shown in Figure 24 (c), so by pressing the sheet holder 50 in a direction that brings the resin sheet S closer to the mold 340, it is possible to increase airtightness as in the third embodiment, and this can contribute to thermoforming a molded product M with higher precision.

[0082] 25 is a conceptual diagram showing a molding process using a thermoforming apparatus. In the first to third embodiments, an upper container 101 and a lower container 102 are used in the thermoforming apparatus 100, but the thermoforming apparatus 100 of the fourth embodiment is configured to perform thermoforming without using the upper container 101. Therefore, a suction circuit 310 is connected to the mold 340 as suction means, and the resin sheet S can be vacuum-formed from below the mold 340 using the suction circuit 310.

[0083] The suction circuit 310 has a first path 315 and a second path 316 connected in parallel to each other and connected to the internal space 345 of the mold 340, and the circuits can be switched arbitrarily by a three-way valve 311 connected to the control device 105. A flow rate adjustment valve 312 is provided in the first path 315, and the flow rate of the first path 315 can be reduced below the flow rate of the second path 316. Note that a device capable of generating negative pressure, such as a vacuum pump or a ring blower, is connected to the end of the suction circuit 310 (not shown).

[0084] A timing chart is shown in Figure 26. In the figure, "heater lift" indicates the lifting and lowering operation of heating means 110. "Heater heating" indicates the ON / OFF of heating by heater 111 provided in heating means 110. "First suction circuit" indicates suction by suction circuit 310 using first path 315, and "second suction circuit" indicates suction by suction circuit 310 using second path 316. "Clamp cylinder" indicates the opening and closing of clamp cylinder 280. "Trigger" indicates the start timing of the operation of each device.

[0085] The period from T11 to T16 constitutes one cycle for molding the molded product M, and is controlled by the control device 105. At T11, suction (first suction circuit) is started through the first path 315. This causes the set resin sheet S to be pulled toward the mold 340. Heating by the heater is started at T12, and the heating means 110 starts to descend at T13. At this stage, the resin sheet S has begun to soften due to heating, so at T14, suction through the first path 315 is ended and suction (second suction circuit) through the second path 316 is started. At T15, heating by the heater 111 of the heating means 110 is ended and the heating means 110 is raised. At the same time, suction through the second path 316 is also ended. The entire process is completed by T16.

[0086] The thermoforming device 100 of the fourth embodiment has the above-described configuration, and therefore provides the following functions and effects.

[0087] The thermoforming apparatus 100 of the fourth embodiment makes it possible to precisely form a large molded product M, as in the first to third embodiments. Unlike the first to third embodiments, the upper container 101 is not used, thereby increasing the degree of freedom in designing the mold 340. To form a large, deep-drawn molded product M, the use of a convex mold 240 as shown in FIG. 20 of the third embodiment and a jig equipped with a drive mechanism such as the sheet holder 250 imposes significant constraints if the upper container 101 is present. Therefore, a configuration is adopted in which the resin sheet S is formed by vacuum suction from the underside of the mold 340 without using the upper container 101.

[0088] Furthermore, by configuring the suction circuit 310 to be switchable between the first path 315 and the second path 316, it is possible to make it less likely for the resin sheet S to become misaligned. As shown in Fig. 25, the flow rate is restricted by a flow rate adjustment valve 312 provided in the first path 315, and as shown in Fig. 26, suction begins using a circuit passing through the first path 315 at the timing of T11 of the "trigger," and is switched to suction using a circuit passing through the second path 316 at the timing of T14. Because the flow rate of the first path 315 is restricted by the flow rate adjustment valve 312, control is exercised so that the flow rate of vacuum suction is restricted from T11 to T14 and increased from T14 to T15.

[0089] As a result, the resin sheet S is heated by the heating means 110, and is sucked by the first suction circuit until the resin sheet S abuts against the product molding surface 340a of the mold 340. At this point, the portion of the resin sheet S that abuts against the product molding surface 340a of the mold 340 is hardened by heat absorbed by the mold 340, which has a large heat capacity. As a result, the resin sheet S is positioned, and this timing corresponds to the timing for switching the circuit at T14. In other words, after the positioning of the resin sheet S is completed, the suction circuit is switched to the second suction circuit to increase the flow rate when sucking the product outside 340c (corresponding to the portion to be trimmed after molding), and this configuration achieves the effect of suppressing positional displacement of the resin sheet S.

[0090] In the fourth embodiment, the "first suction circuit" is the suction circuit 310 using the first path 315, and the "second suction circuit" is the suction circuit 310 using the second path 316. However, the "first suction circuit" may be the suction circuit 310 using the first path 315, and the "second suction circuit" may be the suction circuit 310 using both the first path 315 and the second path 316. In other words, the gist of the invention of the fourth embodiment is that the suction force can be changed in multiple stages by providing suction means that switches between suction circuits that exert different suction forces. Switching between the first suction circuit and the second suction circuit is shown as an example, and the number of suction circuits can be increased as needed.

[0091] Fifth Embodiment The fifth embodiment has almost the same device configuration as the fourth embodiment, but differs in the configuration of the mold 440 and the vacuum circuit, so the following description will focus on the differences. Figure 27 shows a conceptual diagram illustrating the molding process using a thermoforming device according to the fifth embodiment. The mold 440 used in the thermoforming device 100 of the fifth embodiment is similar in configuration to the mold 340 of the fourth embodiment, but the mold 440 is provided with a central space 445 and outer peripheral spaces 441 and 442.

[0092] A first position suction circuit 430 is connected to the central space 445, and a second position suction circuit 420 is connected to the outer peripheral spaces 441 and 442. The outer peripheral spaces 441 and 442 may be connected to each other inside the mold 440. The first position suction circuit 430 and the second position suction circuit 420 are each connected to a device capable of generating negative pressure, such as a vacuum pump or a ring blower (not shown).

[0093] The first position suction circuit 430 has a first path 435 and a second path 436 arranged in parallel, and the circuit can be arbitrarily switched by a first three-way valve 431 connected to the control device 105. A flow rate adjustment valve 432 is provided in the first path 435, and the flow rate of the first path 435 can be made smaller than the flow rate of the second path 436. The second position suction circuit 420 has a third path 425 and a fourth suction path 426 arranged in parallel, and the circuit can be arbitrarily switched by a second three-way valve 421 connected to the control device 105. A flow rate adjustment valve 422 is provided in the third path 425, and the flow rate of the third path 425 can be made smaller than the flow rate of the fourth path 426.

[0094] A timing chart is shown in Figure 28. In the figure, "heater lift / lower," "heater heating," "clamp cylinder," and "trigger" are the same as in Figure 26, and "first suction circuit" refers to suction by the first position suction circuit 430 using the first path 435, while "second suction circuit" refers to suction by the first position suction circuit 430 using the second path 436. "third suction circuit" refers to suction by the second position suction circuit 420 using the third path 425, and "fourth suction circuit" refers to suction by the second position suction circuit 420 using the fourth path 426.

[0095] The period from T21 to T27 constitutes one cycle for molding the molded product M, and is controlled by the control device 105. At T21, suction (first suction circuit) is started through the first path 435. As a result, the set resin sheet S is pulled toward the mold 440. Heating by the heater is started at T22, and the heating means 110 starts to descend at T23. At this stage, the resin sheet S has begun to soften due to heating, so suction (second suction circuit) is started using the second path 436 switched from the first path 435.

[0096] At T24, suction (third suction circuit) is started via the third path 425. At T25, suction (fourth suction circuit) is started using the fourth path 426 switched from the third path 425. At T26, heating by the heater 111 of the heating means 110 is stopped, and the heating means 110 is raised. At the same time, suction via the fourth path 426 is also stopped. The series of processes is completed by T27.

[0097] The thermoforming device 100 of the fifth embodiment has the above-described configuration, and therefore provides the following functions and effects.

[0098] The thermoforming apparatus 100 of the fifth embodiment not only enables the molding of large molded products M with high precision, as in the first to third embodiments, but also allows for more frequent switching of vacuum suction than in the fourth embodiment, thereby enabling more precise molding with less misalignment. The first and second suction circuits perform vacuum suction on the portion corresponding to the product molding surface 440a, while the third and fourth suction circuits perform vacuum suction on the outer product surface 440c (corresponding to the portion to be trimmed after molding). While the internal space 345 of the mold 340 in the fourth embodiment was not divided, the mold 440 of the fifth embodiment is divided into a central space 445 and peripheral spaces 441 and 442, each connected to a separate suction circuit (first position suction circuit 430 and second position suction circuit 420), allowing for suction at different times.

[0099] In other words, by adopting a configuration in which the product molding surface 440a portion is sucked first and the product outer portion 440c is sucked later, it is possible to reduce the possibility of misalignment more than in the fourth embodiment. By sucking the product molding surface 440a portion first, the resin sheet S is brought into contact with the product molding surface 440a of the mold 440. When the resin sheet S comes into contact with the product molding surface 440a, the contacting portion of the resin sheet S with the product molding surface 440a is hardened by the heat absorbed by the mold 440, which has a large heat capacity. As a result, the resin sheet S is effectively positioned.

[0100] The first position suction circuit 430 and the second position suction circuit 420 can be controlled separately, and the suction force can be switched as shown in FIG. 28, which makes it more difficult for the resin sheet S to shift. In other words, it is possible to manufacture a molded product M with high precision by thermoforming. In the fourth embodiment, the flow rate is switched using the first suction circuit and the second suction circuit. In the fifth embodiment, the first suction circuit, the second suction circuit, the third suction circuit, and the fourth suction circuit are provided, and by switching the suction position in addition to switching the flow rate, it is possible to make it more difficult for the resin sheet S to shift.

[0101] In the fifth embodiment, the first position suction circuit 430 is connected to the central space 455, and the second position suction circuit 420 is connected to the outer peripheral spaces 411 and 442. However, for example, the outer peripheral space 411 and the outer peripheral space 442 may be connected to separate position suction circuits for suction. Furthermore, while the first position suction circuit 430 includes the first path 435 and the second path 436 in parallel, additional paths may be added in parallel. Similarly, the second position suction circuit 420 may also include additional paths. Of course, a configuration without path switching is also possible. Therefore, the gist of the fifth embodiment is to provide suction circuits for suctioning different positions and adjust the suction force for each location. As an example, the first position suction circuit and the second position suction circuit are provided, and it is not prevented from adding more suction circuits as needed.

[0102] The thermoforming apparatus 100 according to the present invention has been described above, but the present invention is not limited to this and various modifications are possible without departing from the spirit of the present invention. For example, in the first embodiment, one example of the shape of the sheet holder 50 is shown, but the shape of the sheet holder 50 is determined by the shape of the mold 150, so appropriate modifications are not prevented. Similarly, the shape of the mold 150 is also appropriately modified depending on the shape of the molded product. Furthermore, although the locating pin 151 is used to position the mold 150 and the sheet holder 50, other means of positioning are also acceptable.

[0103] In addition, the number of upper joints 165 and lower joints 175 of the seat holder 50 of the second embodiment may be increased or decreased, and the length of the links (straight portions) may be changed. Furthermore, although straight links are used in Figures 17 to 19, the number of links and joints may be increased, or curved links may be used.

[0104] Furthermore, although the sheet holder 250 of the third embodiment is configured such that the upper jig 260 and the lower jig 270 are connected by a link mechanism 290, it is not prevented from being made larger or from performing more complex movements by increasing the number of links in the upper jig 260 or by increasing the number of clamp cylinders 280. Furthermore, in the thermoforming apparatus 100 of the fifth embodiment, it is not prevented from being made only for switching the suction positions by integrating the first suction circuit and the second suction circuit, and the third suction circuit and the fourth suction circuit, as necessary.

[0105] S: Resin sheet M: Molded product 50: Sheet holder 65: Clamp 71: Positioning pin 100: Thermoforming device 150: Mold

Claims

1. A thermoforming device that uses a mold to mold a resin sheet heated by a heating means, comprising: a sheet holder that has a shape that follows the mold or a function that follows the mold and has a function of positioning and holding the resin sheet; a pressing means that presses the resin sheet against a contact surface provided on the mold when the resin sheet is aligned with the surface of the mold by bringing the sheet holder close to the mold; and a suction means that vacuum-sucks air between the mold and the resin sheet at the bottom of the mold, wherein the mold has a positioning part that positions the sheet holder and the contact surface that abuts against the outer periphery of the resin sheet; and after the resin sheet is aligned with the surface of the mold by the sheet holder, the resin sheet is heated by the heating means and thermoformed.

2. A thermoforming device as claimed in claim 1, wherein the pressing means comprises a propelling mechanism that moves the sheet holder towards the mold, and a link mechanism that moves the sheet holder closer to the mold, and the propelling mechanism and the link mechanism operate in conjunction with each other.

3. A thermoforming device as claimed in claim 1 or 2, characterized in that the suction means comprises a first suction circuit and a second suction circuit which exert different suction forces, and the resin sheet is sucked towards the mold by switching between the first suction circuit and the second suction circuit.

4. A thermoforming device according to claim 1 or 2, characterized in that the suction means comprises a first position suction circuit and a second position suction circuit for sucking different positions of the mold.

5. A thermoforming device as claimed in claim 1, characterized in that the clamp provided as the pressing means is fixed to the sheet holder, and the clamp has a rotation mechanism which is provided near the fixed part with the sheet holder.

6. A thermoforming device as claimed in claim 1, wherein the sheet holder comprises a frame that supports at least two opposing sides of the entire periphery of the resin sheet, and the function of the sheet holder to imitate the mold is achieved by providing the frame with multiple joints.

7. A thermoforming device according to claim 5, wherein the clamp uses the principle of leverage or air pressure as a biasing means for pressing the resin sheet against the surface of the mold.

8. A thermoforming device according to claim 1, characterized in that the heating means for heating the resin sheet has radiant heaters arranged in a matrix facing the mold.

Images