Thermoforming apparatus

Abstract

The objective is to provide a thermoforming apparatus that minimizes variations in the thickness of resin sheets even during deep drawing. [Solution] In a thermoforming apparatus 100 that forms a resin sheet S using a mold 150, a sheet holder 50 has a shape that conforms to the mold 150 and has the function of positioning and holding the resin sheet S, a clamp 65 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 a suction means is provided at the bottom of the mold 150 to vacuum-suction the air between the mold 150 and the resin sheet S, and the mold 150 has a positioning part (jig first receiving side part 150b) for positioning the sheet holder 50.

Description

Technical Field

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

Background Art

[0002] A thermoforming apparatus is a technique for manufacturing various products by heating and molding a resin sheet. However, misalignment that does not pose a problem when producing relatively small and single-color molded products such as food trays becomes a problem when producing large parts such as automobile front bumpers and rear bumpers. Due to the relationship with holes and patterns on the parts, misalignment is likely to occur, and when performing deep drawing molding, positional misalignment tends to increase. Therefore, it has not been widely used for deep drawing molding and the like.

[0003] Patent Document 1 discloses a technique related to a method for manufacturing a decorated molded product, stating that the molding position accuracy can be improved for a molded product with a deep molding surface. This involves using a mold equipped with a cavity mold and a core mold, positioning a film having a decorative pattern layer formed on a base material film with respect to the cavity mold in a half-open mold, and holding the film in a close contact state around the molding surface at the end face on the core mold side of the cavity mold, and then bringing the film into close contact with the molding surface by vacuum suction. Thereafter, molten resin is injected into the cavity formed between the film and the core surface of the core mold in the closed mold to mold the formed product body. At the same time, by attaching at least the decorative pattern layer of the film to the design surface of the formed product body, a decorated molded product in which the design surface of the formed product body is decorated with the decorative pattern layer is manufactured.

[0004] In this process, a film is used in which at least the portion of the decorative pattern layer pressed by the core mold is covered with a heat-melting protective layer. When the mold is clamped, the protective layer is pushed towards the cavity mold by the core mold, bringing the film held in the cavity mold closer to the molding surface. The film is then pressed tightly against the molding surface by vacuum suction, and during the molding of the molded product, the protective layer is melted by the heat of the molten resin injected into the cavity.

[0005] Patent Document 2 discloses a heating device in which radiant heaters are arranged in a matrix, and support members are coupled to a frame body in a way that allows adjustment of the distance to the sheet member, thereby allowing adjustment of the distance between the sheet member and the radiant heaters. This makes it possible to heat the sheet member uniformly regardless of its shape. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 5790513 [Patent Document 2] Patent No. 7305177 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, in the technology described in Patent Document 1, when creating molded products with deep molded surfaces, the film is formed by vacuum suction against a cavity mold, so changes in the thickness of the film or sheet are unavoidable during the molding process. When deep drawing is performed, tension is applied to the film or sheet, causing it to stretch, while the stretched portion becomes thinner. 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 high 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, tension is thought to be applied when the heating plate is heated to conform the sheet member to it. Therefore, although it can accommodate gentle shape changes such as curved shapes, it cannot handle deep drawing of the sheet member by itself.

[0009] Therefore, the present invention aims to provide a thermoforming apparatus that is less prone to variations in the thickness of resin sheets when deep drawing is performed. [Means for solving the problem]

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

[0011] (1) In a thermoforming apparatus that uses a mold to form a resin sheet heated by a heating means, A sheet holder having a shape that conforms to the mold or a function that mimics the mold, and having the function of positioning and holding a resin sheet, A pressing means for pressing the resin sheet against a contact surface provided on the mold when the sheet holder is brought close to the mold and the resin sheet is aligned with the surface of the mold, The mold is provided with a suction means at the bottom for vacuum-suctioning the air between the mold and the resin sheet, The mold has a positioning portion for positioning the sheet holder and a contact surface that contacts the outer periphery of the resin sheet. After the resin sheet is positioned along the surface of the mold using the sheet holder, the resin sheet is heated by the heating means and thermoforming is performed. It is characterized by the following.

[0012] As described in (1) above, by holding the resin sheet in a shape conforming to the mold beforehand using a sheet holder, and starting heat molding while the resin sheet is deformed and held, the thickness of the molded product can be made uniform. 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 of the wall material is likely to be significant when performing deep drawing molding as described in the problem. Therefore, by using a sheet holder to deform and hold the sheet in a shape conforming to the mold before heating, and then performing heat molding, the risk of unintended thinning of the wall material due to stretching during thermoforming can be reduced.

[0013] Furthermore, by providing a contact surface on the mold side and pressing the resin sheet against the mold using a pressing mechanism, it becomes possible to effectively draw air between the mold and the resin sheet. Also, for example, when it is desired to create a transparent portion in the molded product, the deformation of the resin sheet during thermoforming is minimized, making it possible to obtain a molded product that maintains transparency. This is because when thermoforming a transparent resin sheet, gas leakage can be a cause of defects such as clouding, but by using a pressing mechanism to hold the resin sheet in place, air can be effectively released, which is expected to improve yield.

[0014] (2) In the thermoforming apparatus described in (1), The pressing means, A propulsion mechanism for moving the sheet holder toward the mold, The sheet holder is provided with a link mechanism that brings it closer to the mold side, The propulsion mechanism and the link mechanism operate in conjunction with each other. It is preferable.

[0015] In the embodiment described in (2) above, by providing a propulsion mechanism that moves the sheet holding fitting so as to press it against the mold side, and by providing a link mechanism, it becomes possible to press the resin sheet against the mold side from the side of the mold as well.

[0016] (3) In the thermoforming apparatus described in (1) or (2), The suction means includes a first suction circuit and a second suction circuit that exhibit different suction forces. It is preferable to switch between the first suction circuit and the second suction circuit to suck the resin sheet toward the mold side. is preferred.

[0017] According to the aspect described in (3) above, it is possible to change the flow rate and switch the suction force by switching between the first suction circuit and the second suction circuit. Depending on the shape of the mold, the resin sheet may first contact the molding surface that becomes the product part. Then, the resin sheet will be deprived of heat at the part where it contacts the molding surface of the mold, so the resin sheet will partially cure only at the location where it contacts the molding surface. And since the positioning effect of the resin sheet can be obtained, it becomes possible to suppress the influence of misalignment by switching the suction circuit and increasing the flow rate at this point.

[0018] (4) In the thermoforming apparatus according to any one of (1) to (3), the suction means includes a first position suction circuit and a second position suction circuit that suck different positions of the mold. is preferred.

[0019] According to the aspect described in (4) above, it is possible to suppress the influence of misalignment by switching the suction position. This makes it possible to suppress misalignment of the resin sheet by choosing a configuration such that the portion corresponding to the molding surface of the mold is sucked first and other portions are not sucked, similar to the effect described in (3).

[0020] (5) In the thermoforming apparatus according to (1), The clamp provided as the pressing means is fixedly provided to the sheet holder. The clamp has a rotation mechanism, and the rotation mechanism is provided near the fixed portion with the sheet holder. is preferred.

[0021] As described in (5) above, by using a clamp to hold down the resin sheet, the gap between the sheet and the mold is reduced, making it possible to accurately transfer the shape of the mold surface during thermoforming using vacuum suction. The clamp is equipped with a rotation mechanism and is fixedly attached to the sheet holder, so there is no movement 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 molded products with high shape accuracy using this thermoforming apparatus.

[0022] (6) In the thermoforming apparatus described in (1), The sheet holder consists of a frame that supports at least two opposing sides of the entire circumference of the resin sheet. The function of the sheet holder that mimics the mold is achieved by providing the frame with multiple joint parts. It is preferable.

[0023] In the embodiment described in (6) above, the function of the sheet holder to conform to the mold is realized by providing multiple joint parts. Since the sheet holder conforms to the mold by using a frame that supports at least two opposing sides of the entire circumference of the resin sheet, there is no need to maintain the sheet holder in a three-dimensional shape, improving workability and storage.

[0024] In the thermoforming apparatus described in (7)(5), The clamp uses the principle of leverage or pneumatics as a biasing means for pressing the resin sheet against the surface of the mold. It is preferable.

[0025] As described in (7) 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 mold surface during vacuum forming. When performing vacuum forming, if the resin sheet softens and conforms firmly to the mold surface, it is easy to suck out any remaining air. However, gaps tend to form, especially when the resin sheet is thick, so sealing these gaps with a clamp enables effective vacuum forming.

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

[0027] As described in (8) above, by using radiant heaters arranged in a matrix, it becomes possible to heat more intensively the parts that require a larger change in shape. Since the output of each radiant heater arranged in a matrix can be set, it is possible to heat parts that should not be heated and parts that should be heated separately. In this way, molding accuracy can be improved. [Brief explanation of the drawing]

[0028] [Figure 1] This is a schematic diagram of a thermoforming apparatus according to the first embodiment. [Figure 2] This is a perspective view relating to the lower jig of the sheet holder according to the first embodiment. [Figure 3] This is a side view showing how a resin sheet is held in place by the sheet holder in the first embodiment. [Figure 4] This is a perspective view of the mold according to the first embodiment. [Figure 5] This is a schematic front view of the first embodiment, showing how a resin sheet is held by a sheet holder. [Figure 6]This is a schematic front view of the first embodiment, showing the resin sheet in close proximity to the mold. [Figure 7] This is a schematic front view showing the resin sheet being sucked from the mold side in the first embodiment. [Figure 8] This is a schematic front view of the first embodiment, showing the upper container being brought close to the mold. [Figure 9] This is a schematic front view showing the heating of a resin sheet in the first embodiment. [Figure 10] This is a schematic front view showing the process of pressure molding a resin sheet according to the first embodiment. [Figure 11] This is a schematic front view of the first embodiment, showing how a resin sheet is held by a sheet holder. [Figure 12] This is a schematic front view of the first embodiment, showing the resin sheet in close proximity to the mold. [Figure 13] This is a schematic front view showing the resin sheet being sucked from the mold side in the first embodiment. [Figure 14] This is a schematic front view of the first embodiment, showing the upper container being brought close to the mold. [Figure 15] This is a schematic front view showing the heating of a resin sheet in the first embodiment. [Figure 16] This is a perspective view of an example of a molded product according to the first embodiment. [Figure 17] This is a perspective view relating to the seat holder of the second embodiment. [Figure 18] This is a side view relating to the sheet holder of the second embodiment. [Figure 19] This is a side view showing the sheet holder of the second embodiment in a state where it is aligned with the mold. [Figure 20] This is a front view showing the sheet holder in the open state of the third embodiment. [Figure 21] In the front view of the third embodiment with the seat holder in a lowered state, (a) shows the intermediate position of the cylinder, and (b) shows the lowered end position of the cylinder. [Figure 22]This is a cross-sectional view showing a part of the mold of the third embodiment. (a) shows the cylinder at its upper end, (b) shows it in an intermediate position, and (c) shows the cylinder at its lower end. [Figure 23] This is a cross-sectional view of the mold according to the third embodiment. [Figure 24] This is a cross-sectional view of the fourth embodiment, showing (a) the cylinder at its upper end, (b) an intermediate position, and (c) the cylinder at its lower end. [Figure 25] This is a conceptual diagram showing the molding process using a thermoforming apparatus according to the fourth embodiment. [Figure 26] This is a timing chart for the fourth embodiment. [Figure 27] This is a conceptual diagram showing the molding process using a thermoforming apparatus according to the fifth embodiment. [Figure 28] This is a timing chart for the fifth embodiment. [Modes for carrying out the invention]

[0029] (First Embodiment) First, the general configuration of the thermoforming apparatus 100 of the first embodiment according to the present invention will be described. Figure 1 shows a schematic diagram of the thermoforming apparatus 100 of the first embodiment. The thermoforming apparatus 100 has an upper container 101 and a lower container 102, and is configured to heat the resin sheet S that is introduced by a heating means 110, and then perform compressed air / vacuum forming using a mold 150. In Figure 1, the valves provided in the piping are omitted, but the configuration allows the pressure in the upper container 101 and the lower container 102 to be adjusted by switching the circuits as appropriate, and these vacuum circuits function as a vacuum suction means and a compressed air means. Also, although Figure 1 shows two pumps and tanks, this does not prevent increasing or decreasing them as needed.

[0030] The resin sheet S is made of a thermoplastic resin. The resin sheet S is a rectangular sheet with a length of approximately 2m and a thickness of approximately 0.2mm to 1.0mm. It has been confirmed that the application of the first embodiment can also be applied to thicker or thinner sheets, so there is no prerequisite for changing the thickness or length as needed. This resin sheet S is molded to form a molded product M, which is then thermoformed to form a car bumper part. Positioning holes (not shown) are provided around the perimeter 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 consists of a matrix arrangement of multiple heaters 111, each performing radiant heating. The heaters 111 employ mid-infrared quick-response heaters, which can quickly heat the resin sheet S, which is the object 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. In Figure 1, the number of divisions is schematically reduced, but this does not prevent increasing or decreasing the number of heaters 111 according to 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 how the resin sheet is held in place by the sheet holder. The sheet holder 50 consists of an upper jig 60 and a lower jig 70, and is structured to hold the resin sheet S between the upper jig 60 and the lower jig 70. The lower jig 70 is a frame made by combining a side member 70a and an end member 70b. The side member 70a of this frame is a plate cut in a roughly arc shape, and the end member 70b is a flat plate, and they are joined at the ends. Multiple positioning pins 71 are erected on the upper surface of the lower jig 70.

[0033] The positioning pins 71 have the function of positioning the resin sheet S. In the first embodiment, since the center position of the resin sheet S is used as a reference, the positioning is centered on the first pin 71a, which is located in the center of the positioning pins 71. The second pin 71b is 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 circumference 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, etc., and does not prevent increasing or decreasing the number as needed.

[0034] The upper jig 60 is a roughly rectangular frame-shaped plate that can be positioned along the upper surface of the lower jig 70 and holds the resin sheet S by being fixed to the lower jig 70. The upper jig 60 has a structure to which a clamp 65 can be fixed, and the clamp 65 is fixed to the upper jig 60 with the resin sheet S sandwiched between the upper jig 60 and the lower jig 70. Although not shown in the figure, the upper jig 60 may be provided with a hole to avoid interference with the positioning pin 71.

[0035] The clamp 65 is equipped with a rotating mechanism 66 at the base of the clamp 65, which is the part that is fixed to the upper jig 60. By rotating the rotating mechanism 66, the tip of the clamp 65 tilts inward into the sheet holder 50. The tip of the clamp 65 is equipped with a pressing part 67 that contacts the resin sheet S and presses the resin sheet S against the mold 150. Preferably, the rotating mechanism 66 has a function that biases the pressing part 67 toward the resin sheet S when the clamp 65 is tilted toward the mold.

[0036] Furthermore, by using the provided clamp 65, it is possible to press down on the resin sheet S held by the sheet holder 50 from the inside of the sheet holder 50. It is desirable that the clamp 65 be equipped with a biasing mechanism, and that the biasing force be adjustable. For example, a biasing mechanism using the lever principle, such as a toggle clamp, or a biasing mechanism using air pressure, such as a toggle cylinder, may be provided so that the biasing force can be adjusted by changing the position of the fulcrum or the distance from the viewpoint, or by changing the air pressure.

[0037] Figure 4 shows a perspective view of the mold. The mold 150 is shaped to allow for the molding of the bumper shape that will become the molded product M. Therefore, it consists of a convex portion 150a that forms the recess of the molded product M, and two jig receiving sides 150b that form a gentle arc and a linearly constructed jig receiving side 150c on either side of it. In reality, the mold 150 molds a molded product M with a much more complex shape, so for the sake of explanation, only characteristic parts are shown in this schematic representation.

[0038] In the first embodiment, a locating pin 151 embedded in the first receiving side portion 150b of the jig is used as a positioning means for the mold 150. However, as long as the sheet holder 50 is positioned relative to the mold 150, it is sufficient to use other positioning means, such as providing a step in the mold 150. A conical hole 72 is provided on the back surface of the lower jig 70 in which the locating pin 151 is positioned.

[0039] The procedure for molding a resin sheet S using the thermoforming apparatus 100 with the above configuration will now be described. Figure 5 shows a schematic front view of the resin sheet being held by the sheet holder. Figure 6 shows a schematic front view of the resin sheet being brought close to the mold. Figure 7 shows a schematic front view of the resin sheet being sucked from the mold side. Figure 8 shows a schematic front view of the upper container being brought close to the mold. Figure 9 shows a schematic front view of the resin sheet being heated. Figure 10 shows a schematic front view of the resin sheet being compressed.

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

[0041] The resin sheet S is placed in the sheet holder 50, and with the clamp 65 of the sheet holder 50 in place, it is brought close to the mold 150. This is shown in Figures 5 and 11. The resin sheet S is cut into a flat shape, and although not shown, several positioning holes are provided around its circumference. The sheet holder 50 holds this rectangularly cut resin sheet S in a bent state. As a result, the resin sheet S is held by the sheet holder 50 in a shape close to the general shape of the mold 150. Then, as shown in Figures 5 and 11, the resin sheet S, positioned by the sheet holder 50, is brought close to the mold 150. At this point, the clamp 65 is released.

[0042] Next, as shown in Figures 6 and 12, the sheet holder 50 is lowered to bring the resin sheet S into contact with the mold 150. As shown in Figure 4, the mold 150 is provided with locating pins 151, so the sheet holder 50 is positioned relative to the conical hole 72 provided in the lower jig 70, as shown in Figure 3. In other words, since the mold 150 and the sheet holder 50 are positioned, the resin sheet S, which is positioned and held by the sheet holder 50, is also positioned relative to the mold 150.

[0043] Next, as shown in Figures 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, which is held by the sheet holder 50, is pressed against the surface of the mold 150 by the clamp 65, which presses its outer circumference (the inner circumference side of the sheet holder 50). Then, by drawing air from the bottom of the mold 150 (vacuum suction), the resin sheet S is made to adhere tightly to the surface of the mold 150. The mold 150 is provided with several air holes (not shown) that allow air to be drawn into the bottom of the mold 150. Although not shown in Figures 7 and 13, the lower container 102 is in close contact with the bottom surface of the mold 150, and vacuum suction is started from the connected air circuit. Then, the air between the resin sheet S and the surface of the mold 150 begins to escape.

[0044] Next, as shown in Figures 8 and 14, the upper container 101 is lowered. Then, as shown in Figures 9 and 15, the upper container 101 is lowered so that its end contacts the upper surface of the mold 150. At the same time, the resin sheet S is heated by the heating means 110, raising the temperature of the resin sheet S to the material's softening point and softening it. Since vacuum suction is performed at this time, 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 face of the upper container 101 and the upper surface of the mold 150 to pressurize it and perform pressure molding. At this point, the resin sheet S is sufficiently softened, making it possible to form a precise molded product along the surface of the mold 150.

[0045] Since the thermoforming apparatus 100 of the first embodiment has the above configuration, it provides the following functions and effects.

[0046] First, when producing large molded products M with the thermoforming apparatus 100, it becomes possible to perform molding with high precision. This is because the thermoforming apparatus 100, which molds a resin sheet S using a mold 150, is characterized by having a sheet holder 50 that has a shape conforming 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 a suction means at the bottom of the mold 150 that vacuums the air between the mold 150 and the resin sheet S, and the mold 150 has a positioning part (locate pin 151) for positioning the sheet holder 50.

[0047] This method involves pre-deforming the resin sheet S with a sheet holder 50 and holding it in a shape that conforms to the mold 150. Since it is then heated and molded in this state, there is less stretching of the resin sheet S during molding, and as a result, it is possible to make the thickness distribution of the molded product M uniform. As mentioned in the problems section, the resin sheet S becomes thinner when stretched during molding. Because this behavior is difficult to control, problems such as the thickness becoming thinner in unintended areas may occur.

[0048] To prevent this, the resin sheet S is deformed by the sheet holder 50 before heating, which helps to suppress changes in thickness and allows for the production of a highly accurate molded product M. Specifically, the sheet holder 50 is shaped to conform to the general shape of the mold 150, and the sheet holder 50 deforms and holds the resin sheet S. As a result, the resin sheet S is heated by the heating means 110 from a state in which it has been elastically deformed to conform to the general shape of the mold 150. In this case as well, because the heating means 110 is positioned to conform to 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 clamp 65 and performing compressed air / vacuum forming, a highly accurate molded product M can be obtained. This is achieved because the resin sheet S is positioned and held by the sheet holder 50, and the sheet holder 50 is positioned and in contact with the mold 150. By using such a thermoforming apparatus 100, a relatively thick resin sheet S can be thermoformed to produce a molded product M with minimal variation in thickness. For this reason, it can be applied to products that require strength, such as car bumpers.

[0050] Furthermore, the presence of the clamp 65 allows the resin sheet S to be pressed against the surface of the mold 150, making it easier to remove air between the resin sheet S and the surface of the mold 150 during vacuum forming and improving adhesion. The pressing portion 67 of the clamp 65 is structured to press the resin sheet S towards the mold 150, and holds down the outer circumference of the resin sheet S. It is desirable to hold down the entire circumference of the resin sheet S, but even just pinpointing and holding down areas where gaps tend to form can be effective. It is desirable to hold down any parts of the resin sheet S that tend to lift away from the mold 150.

[0051] At this time, it is desirable that the clamping force on the resin sheet S by the clamp 65 can be adjusted, and that the contact area be widened so that the force is distributed across the resin sheet S. Furthermore, it is preferable that the contact position and range be the part that will be trimmed later, rather than the part that will become the molded product M, but it is important to allow air to escape easily between the mold 150 and the resin sheet S. For this reason, it is desirable to press on the part of the mold 150 that has a large change in shape, for example, the part close to the short side 150d and the long side 150e of the mold 150 shown in Figure 4.

[0052] Furthermore, the heating means 110 uses radiant heaters 111 arranged in a matrix, and the output of each can be adjusted individually. Figure 15 shows an example of a perspective view of the molded product. The molded product M has a transparent portion M1 in the center, which is intended to transmit light for aesthetic purposes. This transparent portion M1 is created by providing a printing layer on the back side of a transparent resin sheet S, creating a non-transparent and a translucent portion (i.e., the transparent portion M1 is not printed on), and is provided as a way to enhance the aesthetic appeal.

[0053] To obtain such a molded product M, the mold 150 is heated to a high temperature in the areas where the shape changes significantly, that is, the areas around the short side 150d and long side 150e of the mold 150 shown in Figure 4, while the areas 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 part 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 part 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, even when used in strength components, the function is not impaired. In addition, although the resin sheet S used in the first embodiment is intended for thermoforming large molded products M, it is possible to contribute to energy saving by increasing the output of the heater 111 in areas of large deformation for large resin sheets S. Note that the molded product M shown in Figure 15 is merely an example and is not limited to this shape.

[0055] Furthermore, while a method of arranging heaters 111 in a matrix as a heating means 110 is also shown in Patent Document 2, which suggests that the temperature is controlled so that the resin sheet S to be molded is uniform, the first embodiment differs in that it improves the quality of the molded product M by actively creating a temperature difference in the output of the heaters 111. 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 almost the same apparatus configuration as the first embodiment, but the configuration of the sheet holder 50 is different, so the explanation will focus on the differences. Figure 17 shows a perspective view of the sheet holder of the second embodiment. Figure 18 shows a side view of the sheet holder. The sheet holder 50 of the second embodiment consists of an upper jig 160 and a lower jig 170, and has a structure in which a resin sheet S is sandwiched between the upper jig 160 and the lower jig 170. The lower jig 170 is a frame made by combining a side member 170a and an end member 170b. The side member 170a of this frame is a plate material equipped with a plurality of lower joints 175, and the lower joints 175 have a pin support structure. A plurality of positioning pins 71 are erected on the upper surface of the side member 70a.

[0057] The positioning pins 71 have the function of positioning the resin sheet S. In the second embodiment as well, the center position of the resin sheet S is used as the reference, so the positioning is centered on 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 circumference 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 needed. Although not shown in the figure, a conical hole 72 for positioning the locating pins 151 is provided on the back surface of the lower jig 170.

[0059] The upper jig 160 is a roughly rectangular frame-shaped plate that can be positioned 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 to match the lower joint 175, so it is desirable to have a loose structure that stretches as a whole when bent.

[0060] Although not shown in the diagram, the upper jig 160 is structured to allow the clamp 65 to be fixed to it. With the resin sheet S sandwiched between the upper jig 160 and the lower jig 170, the clamp 65 is fixed to the upper jig 160. Although not shown in the diagram, the upper jig 160 is provided with a hole to avoid interference with the positioning pin 71.

[0061] The procedure for performing thermoforming using the sheet holder 50 configured as described above is as follows. Figure 19 shows a side view of 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 lower joint 175 of the sheet holder 50 are bent, pressing the resin sheet S against the surface of the mold 150 and holding it in place. In addition, the clamp 65 acts to press down on the outer circumference of the resin sheet S, vacuum suction is started, and thermoforming is performed.

[0062] The thermoforming apparatus 100 of the second embodiment performs thermoforming using the sheet holder 50 described above, and therefore obtains the same effects as the thermoforming apparatus 100 of the first embodiment. Specifically, since the sheet holder 50 can deform to conform to the general shape of the mold 150, it does not need to have a three-dimensional shape like the sheet holder 50 of the first embodiment, resulting in advantages such as improved workability and storage. In addition, the sheet holder 50 of the second embodiment is more versatile than the sheet holder 50 of the first embodiment because it employs a deformable structure. In other words, it can be used with multiple types of molds 150.

[0063] (Third embodiment) The third embodiment is similar in device configuration to the second embodiment, but differs in the configuration of the sheet holder 50 and the mold 150, so the explanation will focus on the differences. Figure 20 shows a front view of the third embodiment with the sheet holder in the open position. Figure 21 shows a front view of the sheet holder in the lowered position. Figure 21(a) shows the cylinder in an intermediate position, and (b) shows the cylinder at its lowered end. 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 configuration of the sheet holder 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, with upper second sections 262 connected to both ends at first support points 263, and the ends of the upper second sections 262 connected to each other by connecting members 265. In other words, two upper first sections 261, four upper second sections 262, and two connecting members 265 are connected and arranged as a roughly rectangular frame. The clamp cylinders 280 are held by cylinder brackets 285 fixed to both sides of the mold 240. By driving the clamp cylinders 280, each provided on both sides, in synchronous motion, the sheet holder 250 is opened and closed and raised and lowered.

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

[0066] This second pivot point 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. In other words, 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 pivot point 264, and the other end is rotatably connected to one end of the L-shaped arm 292 at the third pivot point 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 the fifth pivot point 284. The bent portion 292a of the L-shaped arm 292 is rotatably supported by the lifting pivot bracket 296 at the fourth pivot point 299. The lifting pivot 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 roughly arc shape, convex upwards, and has a structure that sandwiches the resin sheet S between the lower surface of the upper jig 260 (the inner circumferential surface of the arc that contacts the sheet) and the upper surface of the lower jig 270 (the outer circumferential surface of the arc that contacts the sheet). Multiple positioning pins 271 are embedded in the outer circumferential surface of the lower jig 270 to position the resin sheet S. A spring 273 is provided at the bottom of the lower jig 270 to support the up and down movement of the lower jig 270. Although not shown, the lower jig 270 is supported to move vertically up and down by a guide provided on the side of the mold 240. Also, although not shown, the lower surface 260a of the upper jig 260 has recesses in the portion corresponding to the positioning pins 271 provided on the outer circumferential surface 270a of the lower jig 270.

[0068] As shown in Figure 20, the upper jig 260 and the lower jig 270, which are connected to the link mechanism 290, are configured to open and close and move up and down in conjunction with the operation of the clamp cylinder 280, which is fixed to the side of the mold 240 using a cylinder bracket 285. Here, if we define the state in which one end of the cylinder rod 281 of the clamp cylinder 280 is moved upward as the raised end and the state in which the other end is moved downward as the lowered end, then when the clamp cylinder 280 is at the raised end, the upper jig 260 is separated from the lower jig 270, allowing the resin sheet S to be inserted. When it is at the lowered end, as shown in Figure 21(b), the upper jig 260 and the lower jig 270 sandwich the resin sheet S and press it against the mold 240.

[0069] Figure 22 shows partial cross-sectional views of the mold. (a) shows a cross-section with the cylinder at its upper end, (b) shows a cross-section with the cylinder at an intermediate position, and (c) shows a cross-section with the cylinder at its lower end. In other words, Figure 22(a) is the upper end position of the clamp cylinder 280 corresponding to Figure 20, Figure 22(b) is the intermediate position of the clamp cylinder 280 corresponding to Figure 21(a), and Figure 22(c) is the lower end position of the clamp cylinder 280 corresponding to Figure 21(b).

[0070] As shown in Figure 20, the mold 240 is formed in a shape that is generally convex upwards and is fixed to the base 210. During thermoforming, the resin sheet S comes into contact with the product molding surface 240a to form the mold. At the end of the cross-sectional view cut in the center of Figure 20 (a portion of which is shown as an enlarged cross-sectional view in Figure 22), a sealing surface 240b is formed. The sealing surface 240b is in surface contact with the resin sheet S, and a sealing material 241 is provided around the sealing surface 240b to prevent air leakage.

[0071] Figure 23 shows a cross-sectional view of the mold. It shows a cross-section perpendicular to the cut shown in Figure 22. It can be seen that the mold 240 has a product molding surface 240a that contacts the resin sheet S, and a sealing surface 240b formed around it, even in the cross-section of Figure 23. A sealing material 241 is provided on the sealing surface 240b. In addition, multiple suction passages 240c, which are provided to open at key points on the product molding surface 240a, penetrate into an internal space 242 provided inside the mold, as shown in Figure 23. Note that the suction passages 240c and internal space 242 depicted in Figure 23 are drawn large for illustrative purposes, but in reality they are small holes so as not to affect the molding of the resin sheet S, and the internal space 242 is also shown schematically, so it is not limited to this shape.

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

[0073] First, as shown in Figure 20, the resin sheet S is attached to the lower jig 270 with the sheet holder 250 in the open position. To open the sheet holder 250, the cylinder rod 281 of the clamp cylinder 280 is moved to its upper end, and the upper jig 260, which is lifted by the lifting bracket 266, is held in an open position by the link mechanism 290 with the upper second section 262 open. The resin sheet S is then inserted between the upper jig 260 and the lower jig 270, and the outer circumferential surface 270a of the lower jig 270 is provided with a number of positioning pins 271, and the resin sheet S is held in place by these pins. This 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. As shown in Figure 21(a), the lifting bracket 266 is lowered, causing the upper first section 261 to descend and the upper second section 262 to begin closing due to the action of the link mechanism 290. The lower jig 270 is in the state shown in Figure 22(b), with the resin sheet S sandwiched between the lower surface 260a and the outer surface 270a of the upper jig 260. Then, by further lowering the cylinder rod 281 to the lowered end, the lower jig 270 is pushed down together with the upper jig 260 as shown in Figure 21(b), and the upper second section 262 also closes as shown in Figure 21(b). In this way, the state in which the resin sheet S is pressed against the sealing surface 240b of the mold 240 can be maintained as shown in Figure 22(c).

[0075] Next, while the resin sheet S is heated by the heating means 220, the internal space 242 is vacuum-suctioned as shown in Figure 23, causing air to be drawn in through the suction passage 240c and the resin sheet S to begin to deform. In this state, the sealing material 241 is compressed and exerts a sealing effect, creating a negative pressure state that suppresses leakage and enables thermoforming (vacuum forming) of the resin sheet S.

[0076] Since the thermoforming apparatus 100 of the third embodiment has the above configuration, it provides the following functions and effects.

[0077] First, when producing large molded products M with the thermoforming apparatus 100, it becomes possible to perform molding with high precision. 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, but through the sheet holder 250 and the mold 240. This is because, as in the first embodiment, it is difficult to implement a structure that prevents leakage using the clamp 65 depending on the shape of the mold. Therefore, in the third embodiment, a sealing surface 240b is formed on the mold 240, and the sheet holder 250 itself is required to perform the same function as the clamp 65.

[0078] In other words, by using the clamp cylinder 280 to close and lower the sheet holder 250, the resin sheet S held by the sheet holder 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 provided on the mold 240, thereby suppressing 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 the desired shape. A molded product M as shown in Figure 16 is obtained by this procedure.

[0079] When thermoforming the resin sheet S by this method, it is possible to thermoform the resin sheet S more practically compared to the first embodiment. This is because, in the configuration of the first embodiment, where the outer circumference of the resin sheet S is held down by the clamp 65, it is considered difficult to suppress leakage depending on the material and thickness of the resin sheet S. By providing a sealing surface 240b on the mold 240, it is possible to improve airtightness, which contributes to thermoforming a more high-precision molded product M.

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

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

[0082] Figure 25 shows a conceptual diagram illustrating the molding process using a thermoforming apparatus. In the first to third embodiments, the thermoforming apparatus 100 was shown to have an upper container 101 and a lower container 102. However, in the fourth embodiment, the thermoforming apparatus 100 employs a configuration in which thermoforming is performed without using the upper container 101. Therefore, a suction circuit 310 is connected to the mold 340 as a suction means, and the resin sheet S can be vacuum-formed from the bottom of 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 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. The first path 315 is provided with a flow control valve 312, and is configured to reduce the flow rate of the first path 315 compared to the flow rate of the second path 316. 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] Figure 26 shows the timing chart. In the figure, "Heater Lifting / Lowering" indicates the lifting / lowering operation of the heating means 110. "Heater Heating" indicates the ON / OFF status of the heater 111 provided in the heating means 110. "First Suction Circuit" indicates suction by the suction circuit 310 using the first path 315, and "Second Suction Circuit" indicates suction by the suction circuit 310 using the second path 316. "Clamp Cylinder" indicates the opening and closing of the 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 through the first path 315 (first suction circuit) is started. This causes the set resin sheet S to be pulled towards the mold 340. At T12, heater heating is started, and at T13, the heating means 110 begins to descend. At this stage, the resin sheet S has begun to soften due to heating, so at T14, suction through the first path 315 is terminated and suction through the second path 316 (second suction circuit) is started. At T15, heating by the heater 111 of the heating means 110 is terminated, and the heating means 110 is raised. At the same time, suction through the second path 316 also terminates. The entire process is completed by T16.

[0086] Since the thermoforming apparatus 100 of the fourth embodiment has the above configuration, it provides the following functions and effects.

[0087] The thermoforming apparatus 100 of the fourth embodiment makes it possible to accurately mold large molded products M, similar to the first to third embodiments. Unlike the first to third embodiments, the absence of an upper container 101 allows for greater design freedom of the mold 340. To mold large, deep-drawn molded products M, a convex mold 240 is used as shown in Figure 20 of the third embodiment, and a jig equipped with a drive mechanism such as a sheet holder 250 is used. The presence of an upper container 101 imposes significant constraints. Therefore, instead of using an upper container 101, the resin sheet S is molded by vacuum suction from the bottom surface of the mold 340.

[0088] Furthermore, by making the suction circuit 310 switchable between a first path 315 and a second path 316, it is possible to reduce the likelihood of misalignment of the resin sheet S. As shown in Figure 25, the flow rate is restricted by a flow control valve 312 provided in the first path 315, and as shown in Figure 26, suction is started using the circuit passing through the first path 315 at the timing of the "trigger" T11, and then switched to using the circuit passing through the second path 316 at the timing of T14. Since the flow rate of the first path 315 is restricted by the flow control valve 312, the flow rate of the vacuum suction is restricted from T11 to T14, and the flow rate is increased from T14 to T15.

[0089] As a result, the resin sheet S is heated by the heating means 110, and the resin sheet S is sucked by the first suction circuit until it contacts the product molding surface 340a of the mold 340. At the point of contact, the portion of the resin sheet S in contact with the product molding surface 340a hardens as heat is absorbed by the mold 340, which has a large heat capacity. As a result, a positioning effect is obtained for the resin sheet S, and this timing coincides with the timing of the circuit switch at T14. In other words, after the positioning of the resin sheet S is complete, the suction circuit is switched to the second suction circuit to increase the flow rate when sucking the product exterior 340c (corresponding to the part that will be trimmed after molding), thus providing an effect of suppressing misalignment of the resin sheet S.

[0090] In the fourth embodiment, the "first suction circuit" is a suction circuit 310 using the first path 315, and the "second suction circuit" is a suction circuit 310 using the second path 316. However, the "first suction circuit" may be a suction circuit 310 using the first path 315, and the "second suction circuit" may be a suction circuit 310 using both the first path 315 and the second path 316. In other words, the gist of the invention in the fourth embodiment is to change the suction force in multiple stages by providing a suction means that switches between suction circuits that exhibit different suction forces. One example of this is the switching between the first and second suction circuits, and this does not prevent further addition of suction circuits as needed.

[0091] (Fifth embodiment) The fifth embodiment has almost the same apparatus configuration as the fourth embodiment, but the configuration of the mold 440 and the configuration of the vacuum circuit are different, so the explanation will focus on the differences. Figure 27 shows a conceptual diagram of the molding process using the thermoforming apparatus of the fifth embodiment. The mold 440 used in the thermoforming apparatus 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. Note that outer peripheral spaces 441 and 442 may be connected within the mold 440. Negative pressure generating devices, such as vacuum pumps or ring blowers (not shown), are connected to the first position suction circuit 430 and the second position suction circuit 420, respectively.

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

[0094] Figure 28 shows the timing chart. In the figure, "heater lifting / lowering," "heater heating," "clamp cylinder," and "trigger" are the same as in Figure 26. "First suction circuit" refers to suction by the first position suction circuit 430 using the first path 435, and "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 towards the mold 440. Heater heating is started at T22, and the heating means 110 is lowered 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, which has been switched from the first path 435.

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

[0097] Since the thermoforming apparatus 100 of the fifth embodiment has the above configuration, it provides the following functions and effects.

[0098] The thermoforming apparatus 100 of the fifth embodiment makes it possible to accurately mold large molded products M, similar to the first to third embodiments. In addition, because the vacuum suction is switched more precisely than in the fourth embodiment, it enables more precise molding with less positional deviation. The first and second suction circuits perform vacuum suction on the portion corresponding to the product molding surface 440a, and the third and fourth suction circuits perform vacuum suction on the outer part of the product 440c (corresponding to the portion that will be trimmed after molding). In the fourth embodiment, the internal space 345 of the mold 340 was not divided, but in the fifth embodiment, the mold 440 is divided into a central space 445 and outer peripheral spaces 441 and 442, and since separate suction circuits (first position suction circuit 430 and second position suction circuit 420) are connected to each, it is possible to perform suction at different timings.

[0099] In other words, by adopting a configuration in which the product molding surface 440a is sucked first and the product exterior 440c is sucked later, it is possible to further reduce the possibility of misalignment compared to the fourth embodiment. By sucking the product molding surface 440a first, the resin sheet S is brought into contact with the product molding surface 440a of the mold 440. At the stage of contact, the portion of the resin sheet S in contact with the product molding surface 440a hardens as heat is absorbed by the mold 440, which has a large heat capacity. As a result, a positioning effect of the resin sheet S is obtained.

[0100] The first position suction circuit 430 and the second position suction circuit 420 can be controlled separately, and as shown in Figure 28, the suction force is switched, making the resin sheet S less likely to shift. In other words, it becomes possible to manufacture a molded product M with high precision by thermoforming. In the fourth embodiment, the flow rate is switched using the first and second suction circuits. In the fifth embodiment, the first and second suction circuits, as well as the third and fourth suction circuits, are provided, and in addition to switching the flow rate, the suction position is also switched, making it even less likely 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 spaces 411 and 442 may be connected to separate position suction circuits for suction. Also, the first position suction circuit 430 has a first path 435 and a second path 436 in parallel, but there is no prerequisite for adding more paths in parallel. Similarly, there is no prerequisite for increasing the number of paths in the second position suction circuit 420. Of course, a configuration without path switching is also possible. Therefore, the gist of the invention in the fifth embodiment is to provide suction circuits that attract different positions and adjust the suction force for each location. As an example, a first position suction circuit and a second position suction circuit are provided, and there is no prerequisite for further increasing the number of suction circuits as needed.

[0102] The above describes the thermoforming apparatus 100 according to the present invention, but the present invention is not limited thereto, and various modifications are possible without departing from its spirit. For example, in the first embodiment, an example of the shape of the sheet holder 50 was shown, but since the shape of the sheet holder 50 is determined by the shape of the mold 150, there is no presumption that it may be changed as appropriate. Similarly, there is no presumption that the shape of the mold 150 may be changed as appropriate depending on the shape of the molded product. In addition, although a locating pin 151 is used to position the mold 150 and the sheet holder 50, there is no presumption that positioning may be performed by other means.

[0103] Furthermore, this does not prevent increasing or decreasing the number of upper joints 165 and lower joints 175 of the seat holder 50 in the second embodiment, or changing the length of the links (straight sections). In addition, although straight links are used in Figures 17 to 19, the number of links and joints may be increased, or curved shapes may be used for the links.

[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 to make it larger or to enable more complex movements by increasing the number of links in the upper jig 260 or increasing the number of clamp cylinders 280. Also, the thermoforming apparatus 100 of the fifth embodiment is not prevented to integrate the first suction circuit and the second suction circuit, and the third suction circuit and the fourth suction circuit, respectively, as needed, to switch only the suction position. [Explanation of Symbols]

[0105] S Resin sheet M Molded product 50 Sheet holders 65 Clamp 71 Positioning pins 100 Thermoforming equipment 150 molds

Claims

1. In a thermoforming apparatus that uses a mold to form a resin sheet heated by a heating means, A sheet holder having a shape that conforms to the mold or a function that mimics the mold, and having the function of positioning and holding a resin sheet, When the sheet holder is brought close to the mold, the resin sheet is brought along the surface of the mold, and a pressing means is provided to press the resin sheet against a contact surface provided on the outer circumference of the mold, The mold is provided with a suction means at the bottom for vacuum-suctioning the air between the mold and the resin sheet, The mold has a positioning portion for positioning the sheet holder and a contact surface that contacts the outer periphery of the resin sheet. After the resin sheet is held in a shape conforming to the surface of the mold by the sheet holder, the resin sheet is heated by the heating means and thermoforming is performed. A thermoforming apparatus characterized by the following.

2. In the thermoforming apparatus according to claim 1, The pressing means, A propulsion mechanism for moving the sheet holder toward the mold, The sheet holder is provided with a link mechanism that brings it closer to the mold side, The propulsion mechanism and the link mechanism operate in conjunction with each other. A thermoforming apparatus characterized by the following.

3. In the thermoforming apparatus according to claim 1 or claim 2, The suction means is equipped with a first suction circuit and a second suction circuit that exert different suction forces. Switching between the first suction circuit and the second suction circuit to suck the resin sheet towards the mold, A thermoforming apparatus characterized by the following.

4. In the thermoforming apparatus according to claim 1 or claim 2, The suction means includes a first position suction circuit and a second position suction circuit that suction different positions of the mold. A thermoforming apparatus characterized by the following.

5. In the thermoforming apparatus according to claim 1, The clamp provided as the pressing means is fixed to the sheet holder. The clamp has a rotating mechanism, and this rotating mechanism is provided near the fixing portion with the seat holder. A thermoforming apparatus characterized by the following.

6. In the thermoforming apparatus according to claim 1, The sheet holder consists of a frame that supports at least two opposing sides of the entire circumference of the resin sheet. The function of the sheet holder that mimics the mold is achieved by providing the frame with multiple joint parts. A thermoforming apparatus characterized by the following.

7. In the thermoforming apparatus according to claim 5, The clamp uses the principle of leverage or pneumatics as a biasing means for pressing the resin sheet against the surface of the mold. A thermoforming apparatus characterized by the following.

8. In the thermoforming apparatus according to claim 1, The heating means for heating the resin sheet has radiant heaters arranged in a matrix facing the mold. A thermoforming apparatus characterized by the following.

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