Thermoforming apparatus

Abstract

To provide a thermoforming apparatus hard to generate the irregularity of the thickness of a resin sheet even at the time of deep drawing.SOLUTION: This is because the thermal forming device 100 for forming the plastic sheet S using the mold 150 includes the sheet holder 50 having a shape along the mold 150 and having functions of positioning and holding the plastic sheet S, and the clamps 65 for pressing the plastic sheet S against the surfaces of the mold 150 when the plastic sheet S is placed along the surfaces of the mold 150 by bringing the sheet holder 50 close to the mold 150, and the mold 150 has the positioning portion (the jig first receiving side portion 150b) for positioning the sheet holder 50.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to deep drawing, and more particularly to a technique for improving forming accuracy by utilizing positioning when deep drawing large parts. [Background technology]

[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 when deep drawing is performed, so thermoforming machines have not been widely used.

[0003] Patent Document 1 discloses a technique for manufacturing a decorated molded product, which claims to improve molding positioning accuracy for molded products with deep molding surfaces. This involves using a mold equipped with a cavity and a core. A film, consisting of a base film with a decorative pattern layer formed on it, 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 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. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5790513 [Patent Document 2] Patent No. 7305177 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the technology described in Patent Document 1, when creating 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 the change in thickness, 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 fit the mold while the sheet material is in contact with the mold, it is thought that tension is applied when the hot plate is heated to align the sheet material, 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 material.

[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 during deep drawing. [Means for solving the problem]

[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 for forming a resin sheet using a mold, a sheet holder having a shape that conforms to the mold or a function that follows the mold and has a function of positioning and holding a resin sheet; a clamp that presses the resin sheet against the surface of the mold when the sheet holder is brought close to the mold so that the resin sheet is aligned with the surface of the mold; a suction means disposed below the mold for vacuum-suctioning air between the mold and the resin sheet; the mold has a positioning portion for positioning the sheet holder; It is characterized by:

[0012] According to the aspect described in (1) above, by starting molding after holding the resin sheet in a shape that conforms to the mold using a sheet holder, it is possible to make the thickness of the molded product uniform. This is because, when thermoforming a resin molded sheet, if the resin molded sheet is deformed by heating it to around its glass transition point, problems such as thickness reduction can occur when performing deep drawing, as described in the problem. Therefore, by using a sheet holder to deform and hold the resin molded sheet in a shape that conforms to the mold before heating, the risk of unintended thickness reduction due to pulling during thermoforming can be reduced.

[0013] 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 occur due to gas leakage, but by performing vacuum suction using a suction means, the air between the mold and the resin sheet is sucked out, and by holding the resin sheet down with a clamp during this process, the air is effectively removed, which is expected to improve yield.

[0014] (2) In the thermoforming device according to (1), The clamp is fixed to the sheet holder, The rotation mechanism of the clamp is provided near the fixed portion with the sheet holder; is preferred.

[0015] According to the aspect (2) 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.

[0016] (3) In the thermoforming apparatus according to (1) or (2), the sheet holder is made of a frame that supports the entire periphery of the sheet, the function of the sheet holder to conform to the mold is realized by providing a plurality of joint portions on the frame; is preferred.

[0017] According to the aspect described in (3) above, the function of the sheet holder to imitate the mold is realized by providing multiple joint parts, so there is no need to maintain the sheet holder in a three-dimensional shape, improving workability and storability.

[0018] (4) In the thermoforming device according to any one of (1) to (3), the clamp uses a lever principle or air pressure as a biasing means for pressing the resin sheet against the surface of the mold; is preferred.

[0019] According to the aspect described in (4) above, the biasing means provided on the clamp firmly presses the resin sheet against the mold, making it easier to 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 will be easy to suck out any remaining air, but gaps are particularly likely to form if the resin sheet is thick, and sealing these with the clamp will enable effective vacuum forming.

[0020] (5) In the thermoforming device according to any one of (1) to (4), the heating means for heating the resin sheet has radiant heaters arranged in a matrix facing the mold; is preferred.

[0021] According to the aspect (5) 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 radiant heater 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. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic diagram of a thermoforming device according to a first embodiment. [Figure 2] FIG. 3 is a perspective view of a lower jig of the sheet holder in the first embodiment. [Figure 3]3 is a side view showing a state in which a resin sheet is sandwiched between sheet holders in the first embodiment. FIG. [Figure 4] FIG. 2 is a perspective view of a mold according to the first embodiment. [Figure 5] 1 is a schematic front view of a resin sheet held by a sheet holder according to a first embodiment. FIG. [Figure 6] FIG. 2 is a schematic front view of the resin sheet brought close to a mold in the first embodiment. [Figure 7] FIG. 3 is a schematic front view of the first embodiment showing a state in which a resin sheet is being sucked from the mold side. [Figure 8] FIG. 3 is a schematic front view showing how an upper container is brought close to a mold in the first embodiment. [Figure 9] FIG. 2 is a schematic front view of the resin sheet being heated in the first embodiment. [Figure 10] FIG. 2 is a schematic front view showing a state in which a resin sheet is pressure-formed in the first embodiment. [Figure 11] 1 is a schematic front view of a resin sheet held by a sheet holder according to a first embodiment. FIG. [Figure 12] FIG. 2 is a schematic front view of the resin sheet brought close to a mold in the first embodiment. [Figure 13] FIG. 3 is a schematic front view of the first embodiment showing a state in which a resin sheet is being sucked from the mold side. [Figure 14] FIG. 3 is a schematic front view showing how an upper container is brought close to a mold in the first embodiment. [Figure 15] FIG. 2 is a schematic front view of the resin sheet being heated in the first embodiment. [Figure 16] FIG. 2 is a perspective view of an example of a molded product according to the first embodiment. [Figure 17] FIG. 10 is a perspective view of a sheet holder according to a second embodiment. [Figure 18] FIG. 10 is a side view of the sheet holder of the second embodiment. [Figure 19] FIG. 10 is a side view showing a state in which the sheet holder is placed along the mold in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] (First embodiment) First, the outline of the 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 has an upper container 101 and a lower container 102, and is configured to heat an inserted resin sheet S using a heating means 110 and then perform compressed air / vacuum forming using a mold 150. Although 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 appropriately switching the circuits, and these vacuum circuits function as a vacuum suction means and a compressed air means. Also, while two pumps and tanks are shown in FIG. 1, this number can be increased or decreased as needed.

[0024] The resin sheet S is a sheet material made of thermoplastic resin. The resin sheet S is a rectangular sheet about 2 m long and about 0.5 mm to 1.0 mm thick. It has been confirmed that the first embodiment can also be applied to thicker or thinner sheets, so there is no restriction on changing the thickness or length as needed. This resin sheet S is molded into a molded product M, which is a car bumper part, and is thermoformed. Furthermore, positioning holes (not shown) are provided around the periphery in relation to the sheet holder 50 described below. The surface of the resin sheet S may be decorated by printing.

[0025] The heating means 110 comprises a plurality of heaters 111 arranged in a matrix, each of which performs radiant heating. Mid-infrared quick-response heaters are used for the heaters 111, enabling them to 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 simplified 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.

[0026] FIG. 2 shows a perspective view of the lower jig of the sheet holder. FIG. 3 shows a side view of the sheet holder clamping a resin sheet. The sheet holder 50 consists 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 side members 70a and end members 70b. The side members 70a of this frame are plate members cut into a roughly arc shape, and the end members 70b are flat plate members, and they are joined at their ends. A plurality of positioning pins 71 are erected on the upper surface of the lower jig 70.

[0027] The positioning pins 71 have the function of positioning the resin sheet S. In the first embodiment, the central position of the resin sheet S is used as the 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. As described above, positioning holes corresponding to these 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., so it is not prohibited to increase or decrease the number as necessary.

[0028] 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 a hole to avoid interference with the positioning pin 71.

[0029] The clamp 65 is provided with a rotation mechanism 66 on the side where it is fixed to the upper jig 60, i.e., on the base of the clamp 65, and is structured 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, which 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.

[0030] 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. It is desirable that the clamp 65 is 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.

[0031] Fig. 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 protrusion 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 protrusion 150a and forms a gentle arc, and a second jig receiving side portion 150c that is linear. Note that the mold 150 actually molds molded products M with more complex shapes, so for convenience of explanation, the mold 150 has been shown in a schematic shape with only the characteristic parts extracted.

[0032] 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.

[0033] 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 the mold. FIG. 9 is a schematic front view showing a resin sheet being heated. FIG. 10 is a schematic front view showing a state in which a resin sheet is being pressure-molded.

[0034] Figure 11 is a schematic side view showing the resin sheet being held by the sheet holder. This 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. This 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. This 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. This corresponds to the side view of Figure 8. Figure 15 is a schematic side view showing the resin sheet being heated. This corresponds to the side view of Figure 9.

[0035] 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 in a released state.

[0036] 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.

[0037] 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 has its outer periphery (the inner periphery of the sheet holder 50) pressed against the surface of the mold 150 by the clamp 65. Then, air is drawn (vacuum suction) from the bottom of the mold 150, causing the resin sheet S to adhere tightly to the surface of the mold 150. The mold 150 has multiple air holes (not shown) that allow air to be sucked 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.

[0038] 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 and its edge is brought into contact with 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, causing it to soften. Vacuum suction is performed during this process, so 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 between 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.

[0039] The thermoforming apparatus 100 of the first embodiment has the above-described configuration, and therefore provides the following functions and effects.

[0040] 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 at the bottom of the mold 150 that vacuum-sucks air between the mold 150 and the resin sheet S, and the mold 150 has a positioning portion (locate pin 151) that positions the sheet holder 50.

[0041] 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 the resin sheet S stretches less 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.

[0042] 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 has a shape that conforms to 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 conform to the general shape of the mold 150. In this case, since the heating means 110 is arranged to conform to the general shape of the mold 150, efficient heating is possible, and the temperature of a predetermined position can be quickly raised to a predetermined temperature.

[0043] Furthermore, by pressing the resin sheet S with 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 then positioning and abutting the sheet holder 50 against the mold 150. By using such a thermoforming device 100, a molded product M can be obtained by thermoforming a relatively thick resin sheet S with minimal variation in thickness. This makes it applicable to products that require strength, such as car bumpers.

[0044] 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 simply pinpointing and pressing the parts that are particularly prone to forming spaces can be effective. It is desirable to press the parts of the resin sheet S that may lift up from the mold 150.

[0045] At this time, it is desirable to be able to adjust the force with which the clamps 65 press the resin sheet S, and it is also desirable to widen the contact area so that the force is distributed across the resin sheet S. Furthermore, it is desirable that the position and area of ​​contact be with the portion that will be trimmed later, rather than with the portion that will become the molded product M, but since it is important to make it easy for air to 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.

[0046] 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.

[0047] 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 portion 150d and the long side portion 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.

[0048] 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, and by increasing the output of the heater 111 in areas of the large resin sheet S that are subject to large deformation, it is possible to contribute to energy conservation. Note that the molded product M shown in FIG. 15 is merely an example, and is not limited to this shape.

[0049] Furthermore, Patent Document 2 also shows a technique of arranging heaters 111 in a matrix as 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 are connected to a control device (not shown) so that the output can be adjusted individually.

[0050] (Second embodiment) The second embodiment has a device configuration that is substantially the same as the first embodiment, but differs in the configuration of the sheet holder 50, so only the differences will be described. 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.

[0051] The positioning pins 71 have the function of positioning 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.

[0052] 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 can 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.

[0053] 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 is also provided with 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.

[0054] 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 is provided with a hole that avoids interference with the positioning pin 71.

[0055] 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 so that it is aligned with the mold 150. At this time, as shown in Figure 19, the upper joints 165 and lower joints 175 of the sheet holder 50 are bent, thereby pressing and holding the resin sheet S against the surface of the mold 150. Then, the clamps 65 act to press the outer periphery of the resin sheet S, vacuum suction begins, and thermoforming begins.

[0056] 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, since the sheet holder 50 can be deformed to a shape that follows the general shape of the mold 150, it is no longer necessary for the sheet holder 50 of the first embodiment to have a three-dimensional shape, which provides 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 use of a deformable structure. In other words, it can be adapted to multiple types of molds 150.

[0057] 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 locating pins 151 are used to position the mold 150 and the sheet holder 50, other means of positioning are also acceptable.

[0058] 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. [Explanation of symbols]

[0059] S Resin seat M Molded product 50 Sheet holder 65 Clamp 71 Locating pin 100 Thermoforming equipment 150 molds

Claims

1. In a thermoforming device that forms a resin sheet using a mold, a sheet holder having a shape that conforms to the mold or a function that follows the mold, and having a function of positioning and holding a resin sheet; a clamp that presses the resin sheet against the surface of the mold when the sheet holder is brought close to the mold so that the resin sheet is aligned with the surface of the mold; a suction means disposed below the mold for vacuum-suctioning air between the mold and the resin sheet; the mold has a positioning portion for positioning the sheet holder; A thermoforming device characterized by:

2. 2. The thermoforming apparatus of claim 1, The clamp is fixed to the sheet holder, The rotation mechanism of the clamp is provided near the fixed portion with the sheet holder; A thermoforming device characterized by:

3. 2. The thermoforming apparatus of claim 1, the sheet holder is made of a frame that supports the entire periphery of the sheet, the function of the sheet holder to conform to the mold is realized by providing a plurality of joint portions on the frame; A thermoforming device characterized by:

4. The thermoforming apparatus according to claim 1 or 2, the clamp uses a lever principle or air pressure as a biasing means for pressing the resin sheet against the surface of the mold; A thermoforming device characterized by:

5. The thermoforming apparatus according to claim 1 or 2, the heating means for heating the resin sheet has radiant heaters arranged in a matrix facing the mold; A thermoforming device characterized by:

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