Thermoforming device

Abstract

The present invention is a thermoforming apparatus (100) that heats a sheet (S) using a hot plate to form a mold. The hot plate consists of an upper hot plate (110) and a lower hot plate (150). The upper hot plate (110) heats the sheet (S) from above, and the lower hot plate (150) heats the sheet (S) from below. The thermoforming apparatus (100) includes a holding device (120) disposed around the upper hot plate (110) for clamping and holding the outer periphery of the sheet (S). Furthermore, the holding device (120) has an upper support surface (121b) and a lower support surface (124a) for the sheet member. The upper support surface (121b) faces the upper end surface of the sheet member (S) to suppress the upward tilting of at least the periphery of the sheet member (S). The lower support surface (124a) supports the lower end surface of the sheet member (S) at the outer periphery of the sheet member (S). The distance between the upper support surface (121b) and the lower support surface (124a) is set to a predetermined distance, which is obtained by adding a distance to the thickness of the sheet member (S). This distance is such that the sheet member (S) can be adsorbed in a manner that contacts the upper support surface (121b).

Description

Technical Field

[0001] This invention relates to a technique used in the thermoforming of thick plate raw materials, and more specifically to a technique for suppressing the formation of wrinkles when the thick plate raw material is heated by a hot plate while being subjected to vacuum adsorption. Background Technology

[0002] Thermoforming machines are used to mold softened thermoplastic resin sheets into food containers or blister packs. They are also used to manufacture various plastic products such as automotive parts, home appliances, and industrial pallets. In recent years, thermoforming machines have also been used for transferring patterns, bonding to the outer surface of molded substrates, and in molding processes requiring precise positioning.

[0003] Patent Document 1 discloses a thermoforming apparatus and related technology. It demonstrates a thermoforming apparatus for bonding a sheet to the outer surface of a molding substrate, using upper and lower heating plates positioned vertically to heat the sheet. The apparatus employs a continuous sheet unwound from a roll and cut after forming, attracting and holding the sheet towards the first heating surface of the upper heating plate. The structure involves pressing the sheet held on the upper heating plate against the upper surface of a chamber and applying pressure to the chamber, thereby achieving a tight bond that covers the surface of the molding substrate, thus bonding the sheet by covering the molding substrate.

[0004] Patent document 2 discloses a coloring device and a coloring method. A flange is provided around the periphery of the opening end of the chamber member used in the forming device. The film is held by clamping it with the upper and lower flanges. The pressure inside the chamber is changed to make the film adhere closely to the surface of the object to be transferred, so as to transfer the picture printed on the film to the object.

[0005] [Existing Technical Documents]

[0006] [Patent Literature]

[0007] [Patent Document 1] Japanese Patent No. 6674227

[0008] [Patent Document 2] Japanese Patent No. 6550267 Summary of the Invention

[0009] [The problem the invention aims to solve]

[0010] However, when thermoforming is performed using the techniques described in Patent Documents 1 and 2, the processed sheet or film is relatively thin, making it difficult to apply to the purpose of heating and forming sheet parts with thickness. This is because when heating sheet parts with thickness, the sheet parts are heated from the top and bottom while the ends are firmly held. This process easily leads to deformation due to temperature differences. Furthermore, if the sheet part with thickness softens due to heating, its own weight can cause it to sag near the center.

[0011] The deformation of the sheet metal during heating can easily lead to misalignment during the forming stage, causing problems. This is especially true when printing has been applied to the sheet metal, as the elongation of the sheet metal caused by heating can result in misalignment of the shape and printed patterns. On the other hand, when using a method of holding the sheet metal with an adhesive, there is a risk that the deformation of the sheet metal during heating may prevent it from being held in place.

[0012] Therefore, the object of the present invention is to provide a thermoforming apparatus that is less prone to misalignment when using sheet metal parts with a thickness for thermoforming.

[0013] [Technical means to solve the problem]

[0014] To achieve the aforementioned objective, one aspect of the thermoforming apparatus of the present invention has the following features.

[0015] (1) A thermoforming apparatus that uses a hot plate to heat sheet parts for mold shaping, characterized in that...

[0016] The hot plate consists of an upper hot plate and a lower hot plate.

[0017] The upper hot plate heats the sheet from above.

[0018] The lower heating plate heats the sheet from below.

[0019] The thermoforming apparatus includes a holding device disposed around the upper hot plate for clamping and holding the outer periphery of the sheet material.

[0020] The retaining device has an upper support surface and a lower support surface.

[0021] The upper support surface faces the upper surface of the end of the plate to suppress the upward warping of at least the periphery of the plate.

[0022] The lower support surface supports the lower end surface of the plate member at its outer periphery, forming a frame structure.

[0023] The distance between the upper support surface and the lower support surface at the position where the plate is clamped is set to the following set distance, which is obtained by adding a distance to the thickness of the plate. This distance is the distance at which the plate can be attracted to the upper support surface when it leaves the upper support surface, and it is a distance that at least takes into account the increase in thickness caused by the thermal expansion of the plate.

[0024] With the form described in (1) above, when molding a thick sheet metal part, it is possible to achieve molding that is less prone to misalignment of the sheet metal part relative to the mold and suppresses the generation of wrinkles, etc. When heating the sheet metal part using an upper hot plate and a lower hot plate, the sheet metal part is held by adsorbing it towards the upper support surface and heated by the upper hot plate. At this time, even if the sheet metal part deforms under the influence of heat and the adsorbed part falls off, the sheet metal part will be caught by the lower support surface. The gap between the upper support surface and the lower support surface is designed to have a margin of, for example, 0.1 mm relative to the thickness of the sheet metal part. It is set to include the distance that can adsorb the sheet metal part. As a result, the end of the sheet metal part can be supported on the lower support surface and will not sag further. Therefore, it can be adsorbed again and held before misalignment occurs.

[0025] (2) In the thermoforming apparatus described in (1),

[0026] Preferably, a locating pin is provided protruding from the lower support surface.

[0027] The outer periphery of the plate is provided with a positioning hole with an elongated hole structure extending along the outer periphery and the extension direction of the plate. The positioning pin passes through the positioning hole to guide the plate, thereby restricting the movement of the plate in the planar direction.

[0028] By configuring elongated holes extending along the extension direction of the sheet metal as described in (2) above, the extension direction of the sheet metal can be restricted, thus contributing to preventing misalignment. In cases where misalignment is desired, such as when there is a printed portion on the sheet metal, this elongated hole structure can minimize misalignment and contribute to providing a high-precision molded product. For example, by providing an elongated hole extending along the extension direction of the sheet metal on the short side of the outer periphery of the sheet metal, misalignment can be avoided by guiding the material through the elongated hole. Furthermore, by configuring a second elongated hole in a direction orthogonal to the first elongated hole (configured such that the center lines of the first and second elongated holes are orthogonal), the extension direction of the sheet metal can be restricted, resulting in a more precise anti-misalignment effect. As a result, it contributes to improving the precision of the molded product.

[0029] (3) In the thermoforming apparatus described in (1) or (2),

[0030] Preferably, the adsorption distance is 0.1 mm.

[0031] With the configuration described in (3) above, when the sheet metal detaches from the upper support surface, it is supported from the lower side by the lower support surface. At this time, since the adsorption distance is set to 0.1 mm, the sheet metal can be reliably adsorbed when adsorption is performed using the air extraction hole provided on the upper support member. As a result, misalignment or wrinkling of the sheet metal can be prevented.

[0032] (4) In any of the thermoforming apparatuses described in (1) to (3),

[0033] Preferably, the opening end of the chamber facing downward abuts against the upper surface of the upper support of the retaining device, and the plate is adsorbed to the upper support surface by drawing air from the chamber.

[0034] (5) In any of the thermoforming apparatuses described in (1) to (3),

[0035] Preferably, the lower surface of the upper hot plate functions as the upper support surface.

[0036] The molding process can suppress misalignment by means of the form described in (4) or (5) above, just like the form described in (1). Attached Figure Description

[0037] Figure 1 Explanatory diagrams related to the thermoforming apparatus of the first embodiment.

[0038] Figure 2 This is an enlarged view of the holding device portion of the first embodiment.

[0039] Figure 3 This is an enlarged cross-sectional view used to illustrate the holding device of the first embodiment.

[0040] Figure 4 This is a plan view of the lower support portion according to the first embodiment.

[0041] Figure 5A An explanatory diagram illustrating the molding sequence A of the first embodiment.

[0042] Figure 5B An explanatory diagram illustrating the molding sequence B of the first embodiment.

[0043] Figure 5C An explanatory diagram illustrating the molding sequence C of the first embodiment.

[0044] Figure 5D An explanatory diagram illustrating the molding sequence D of the first embodiment.

[0045] Figure 6 This is an enlarged cross-sectional view used to illustrate the holding device of the second embodiment.

[0046] Figure 7 This is an explanatory diagram for illustrating the holding device of the third embodiment.

[0047] Figure 8A An explanatory diagram illustrating the molding sequence A of the third embodiment.

[0048] Figure 8B An explanatory diagram illustrating the molding sequence B of the third embodiment.

[0049] Figure 8C An explanatory diagram illustrating the molding sequence C of the third embodiment.

[0050] Figure 8D An explanatory diagram illustrating the molding sequence D of the third embodiment.

[0051] Figure 9 This is a plan view of the lower support portion according to the fourth embodiment. Detailed Implementation

[0052] (First Embodiment)

[0053] First, a general description of the structure of the thermoforming apparatus 100 according to the first embodiment of the present invention will be given. Figure 1 This is an explanatory diagram illustrating the thermoforming apparatus 100 of the first embodiment. The thermoforming apparatus 100 includes a first chamber 101, a second chamber 102, an upper hot plate 110, a lower hot plate 150, a mold 200, and a holding device 120. It employs a hot plate heating method, that is, the sheet material S held on the holding device 120 is heated using the upper hot plate 110 and the lower hot plate 150, and then formed using the mold 200.

[0054] Vacuum pumps (not shown) are connected to the first chamber 101 and the second chamber 102 of the thermoforming apparatus 100, respectively, to depressurize the contents of the first chamber 101 and the second chamber 102. The apparatus has the following structure: the first chamber 101 opens downwards, the second chamber 102 opens upwards, the first chamber 101 abuts against the upper surface of the holding device 120, and the second chamber 102 abuts against the lower surface of the holding device 120. Furthermore, a pressure vessel (not shown) is provided, allowing compressed air to be introduced into the first chamber 101, which is already abutting against the upper surface of the holding device 120, to pressurize the first chamber 101. The second chamber 102 is designed to be raised and lowered as needed.

[0055] Sheet S is made of thermoplastic resin polycarbonate and is cut into rectangular sheets with a thickness of 5mm. Furthermore, the material and thickness are merely examples, and the material and thickness of sheet S are not limited to these. Additionally, the term "sheet" used here is defined in JIS as a thin sheet-like object with a thickness of 250μm or more, while the sheet S referred to here as the workpiece is envisioned as a relatively thick object with a thickness of a few millimeters. Around the standard-sized sheet S, there are a total of four elongated holes in the form of positioning holes: two short-side elongated holes S1 and two long-side elongated holes S2, described later.

[0056] The upper hot plate 110 is positioned above the holding device 120 of the retaining plate S and is used to heat the retaining plate S from its upper surface. The upper hot plate 110 has an internal heater (not shown) for heating, and a shielding plate 111 is provided on its lower surface, allowing it to be heated to the softening point of the resin (approximately 160°C in this embodiment) while in contact with the upper surface of the retaining plate S. Furthermore, a lifting device (not shown) is provided, configured to allow the upper hot plate 110 to be raised and lowered relative to the mold 200.

[0057] The lower hot plate 150 has a heater assembly capable of radiating heat to the plate S and is equipped with a lateral travel device. It is a structure that can heat the lower surface of the plate S held on the holding device 120 and move it to a retracted position outside the first chamber 101 and the second chamber 102.

[0058] The mold 200 is fixed to the lower frame 210 for forming the sheet metal part S. Four side walls 201 are erected around the mold 200 on the base plate 202. The base plate 202 is mounted on the frame base 203. The mold 200 is shown as a concave mold, but it can also be a convex mold. Furthermore, a flow path (not shown) is formed inside, and by evacuating air during the forming of the sheet metal part S, forming is facilitated. The frame base 203 is equipped with a liftable device (not shown) that can be raised or lowered at any time.

[0059] Figure 2 A side view of the retaining device 120 is shown. Figure 3 An enlarged cross-sectional view is shown to illustrate the holding device 120. Figure 4 The plan view of the lower support portion 122 is shown. The retaining device 120 consists of a rectangular frame-shaped lower support portion 122 and an upper cover 121 (corresponding to the upper support portion), wherein the upper cover 121 is configured to clamp the sheet piece S together with the lower support portion 122. The lower support portion 122 is like... Figure 2It has a stepped cross-section as shown and is equipped with a pad 124. The lower support portion 122 has a wall surface 122b that is vertically erected from the support surface 122a of the pad 124 and an abutting surface 122c that abuts against the upper cover material 121.

[0060] Wall 122b is formed as an image Figure 4 As shown, a gap d is formed between itself and the outer peripheral surface of the sheet S. A rectangular frame-shaped pad 124 is held removably on the support surface 122a. Locating pins 123 are provided at the center of each of the four sides of the pad 124, protruding from the side of the sheet S. Ideally, the locating pins 123 are positioned on a straight line passing through the center of the sheet S, assuming the linear expansion direction of the sheet S. Figure 4 As shown, the short-side elongated hole S1 and the long-side elongated hole S2 formed on the plate S are respectively configured such that their center lines overlap with the straight line passing through the center of the plate S. Ideally, the lengths of the short-side elongated hole S1 and the long-side elongated hole S2 are set to be relatively long, taking into account the linear expansion rate of the plate S.

[0061] The upper cover 121 is a rectangular plate in the shape of a "U". Four recesses 121a are provided on its upper support surface 121b (equivalent to the upper support surface) corresponding to the positioning pin 123 of the lower support portion 122. The positioning pin 123 is configured to penetrate the length of the plate S when the plate S is already positioned on the lower support portion 122; that is, in this case, it is configured to be 5mm or more. Therefore, the recesses 121a are formed to prevent the positioning pin 123 from interfering with the upper cover 121 when the upper cover 121 and the lower support portion 122 overlap.

[0062] Therefore, a retaining device 120 is formed by fixing the upper cover 121 against the contact surface 122c of the lower support 122, thereby clamping and supporting the end of the sheet S between the lower support 122 (the pad 124 directly abuts against the sheet S) and the upper cover 121. At this time, if the thickness x of the sheet S is 5mm, the gap y between the upper support surface 121b of the upper cover 121 and the upper surface of the pad 124, i.e., the lower support surface 124a of the sheet, is set to 5.1mm. Furthermore, although... Figure 3 The image depicts a gap between the upper support surface 121b of the sheet member and the sheet member S. However, by drawing air from the first chamber 101, the air flows as indicated by the arrow, thereby adsorbing the sheet member S onto the upper support surface 121b side of the sheet member. Furthermore, the gap y will be described later.

[0063] Figures 5A to 5D Explanatory diagrams illustrating the molding sequence A through D are displayed. Figure 5AThe state of the plate piece S after it has been placed is shown in the form of forming sequence A. The operator places the plate piece S on the lower support part 122 at the placement position by means of positioning pins 123 passing through the short side long hole S1 and the long side long hole S2 respectively, and then covers it with the upper cover material 121 from above and fixes it, thereby keeping the plate piece S on the holding device 120.

[0064] Figure 5B The image shows the state where the upper hot plate 110 is in contact with the sheet metal S, in the form of molding sequence B. The second chamber 102 and the holding device 120 are raised, and the upper hot plate 110 is lowered to contact the upper surface of the sheet metal S. At this time, the opening of the first chamber 101 abuts against the upper surface of the upper cover 121. By evacuating the air from the first chamber 101, the upper surface of the sheet metal S is brought into close contact with the lower surface (shielding plate 111) of the upper hot plate 110, thereby heating the sheet metal S using the upper hot plate 110. The upper hot plate 110 has been heated to approximately 160°C, further heating the sheet metal S.

[0065] Figure 5C The molding sequence C illustrates the heating of the sheet material S using the lower hot plate 150. With the second chamber 102 and mold 200 retracted to the lower side, the lower hot plate 150 is moved to the lower side of the holding device 120 by means of a lateral travel device, and heating is performed from the lower surface of the sheet material S. Radiant heating is performed to raise the temperature above the glass transition temperature of the sheet material S, i.e., polycarbonate. Specifically, it is heated to approximately 200°C. The sheet material S has a specified thickness x, so by using the upper hot plate 110 and the lower hot plate 150 for efficient heating, the temperature of the sheet material S can be raised in a short time.

[0066] Figure 5D The molding process of sheet metal part S is shown in the molding sequence D. The mold 200 is moved to the underside of sheet metal part S and compressed air is supplied to sheet metal part S through the first chamber 101, thereby molding under air pressure. Simultaneously, air is drawn from the second chamber 102, thus smoothly molding sheet metal part S. Afterwards, the molded part is removed from the mold 200. Through this sequence, the molding of part P can be achieved.

[0067] Since the thermoforming apparatus 100 of the first embodiment has the above-described structure, the following functions and effects are achieved.

[0068] First, a forming method can be provided that mitigates the effects of linear expansion of a thick sheet S due to heating during thermoforming, thus preventing misalignment. This is achieved through a thermoforming apparatus 100 that heats the sheet S using hot plates (an upper hot plate 110 and a lower hot plate 150) to shape it using a mold. The thermoforming apparatus 100 is characterized by the hot plates being composed of an upper hot plate 110 and a lower hot plate 150. The upper hot plate 110 heats the sheet S from above, and the lower hot plate 150 heats it from below. The thermoforming apparatus 100 also includes a holding device 120 disposed around the upper hot plate 110 to clamp and hold the outer periphery of the sheet S. Furthermore, the holding device 120 has an upper support surface 121b and a lower support surface 124a for the sheet plate. The upper support surface 121b faces the upper end surface of the sheet plate S to suppress the upward tilting of at least the periphery of the sheet plate S. The lower support surface 124a supports the lower end surface of the sheet plate S at the outer periphery of the sheet plate S. The distance between the upper support surface 121b and the lower support surface 124a is set to a predetermined distance, which is obtained by adding a distance to the thickness of the sheet plate S. This distance is such that the sheet plate S can be adsorbed in a manner that contacts the upper support surface 121b.

[0069] The sheet piece S is formed by holding its ends in a manner that is clamped by a holding device 120 (upper cover 121 and lower support 122). For example... Figure 3 As shown, the gap y used for holding is the distance from the upper support surface 121b of the upper cover 121 to the lower support surface 124a of the pad 124 provided on the lower support portion 122. It has a margin of 0.1 mm relative to the thickness of the sheet S. In the first embodiment, the thickness x of the sheet S is set to 5 mm. Therefore, the gap y is set to 5.1 mm. So even if the adsorption fails due to the deformation of the sheet S, it can be adsorbed again.

[0070] Since the sheet piece S is clamped between the upper cover 121 and the pad 124 with a gap of 0.1 mm, even if the adsorption at the end of the sheet piece S fails, it can be easily re-adsorbed with a gap of about 0.1 mm. As a result, the adsorption and holding performed by the holding device 120 can continue, thereby enabling the sheet piece S to be transported without misalignment.

[0071] Furthermore, although the gap y is set to the thickness x + 0.1 mm of the plate S, ideally, the distance of the gap y should be increased or decreased according to the weight and material characteristics of the plate S and the adsorption capacity of the holding device 120 side, thereby setting it to an optimal distance. The gap y must be the following distance: taking into account the thermal expansion of the thickness of the plate S caused by the heating of the lower hot plate 150, and on this basis, it should be able to be adsorbed by evacuating the first chamber 101 when the plate S is separated from the upper support surface 121b of the upper cover 121. In addition, for example, in the case of the following structure, even if the distance from the upper support surface 121b of the plate to the lower support surface 124a of the plate is further increased, i.e., the gap y, the plate S can still be adsorbed: for example, the upper support surface 121b of the plate is sealed with a sealing material such as an O-ring, and when adsorbing the plate S, the plate S first abuts against the O-ring (not shown).

[0072] Furthermore, the heating of the sheet piece S is performed by the upper hot plate 110 and the lower hot plate 150. When heat is transferred from the outside to raise the temperature of the sheet piece S from room temperature to 200°C, the heat transfer is always from the outside to the inside, which can easily lead to deviations in heat transfer and deformation. In this case, as described in the problem to be solved by the invention, if the sheet piece S is clamped by the holding device 120, the sheet piece S will bulge and deform due to linear expansion in the center caused by heating. Moreover, if the clamping is released too quickly, the sheet piece S will deform. As a result, misalignment occurs during the molding stage. This problem is solved in the first embodiment by adopting a structure in which the upper surface of the sheet piece S is heated and transported by evacuating the first chamber 101 while the holding device 120 holds the sheet piece S, thus eliminating the effect of linear expansion of the sheet piece S.

[0073] At this time, since the plate S has a short-side elongated hole S1 and a long-side elongated hole S2, misalignment of the plate S can be suppressed. Thermal expansion of the plate S causes it to elongate in the outward peripheral direction. At this time, the short-side elongated hole S1 and the long-side elongated hole S2 are guided by the locating pin 123, thus suppressing misalignment. Therefore, the holding device 120 can also position the plate S during heating.

[0074] By employing such a holding device 120 to transport the sheet metal S, in addition to preventing misalignment of the sheet metal S after molding, the reproducibility of the sheet thickness distribution is also improved. Therefore, even when the surface of the sheet metal S is printed, the molded article P can be manufactured with high precision. Furthermore, it is expected that the yield of the molded article P can be improved. In order to reduce the influence of linear expansion during heating of the sheet metal S, the following method is also considered: spending time preheating the sheet metal S and placing the preheated sheet metal S into the molding apparatus. However, there is a concern that this will increase the unit time required for manufacturing the molded article P, and as a result, the cost of the molded article P is expected to increase. Therefore, the thermoforming apparatus 100 of the first embodiment can also contribute to the cost reduction of the molded article P.

[0075] (Second Implementation)

[0076] Next, a general description of the structure of the thermoforming apparatus 100 according to the second embodiment of the present invention will be given. The structure of the second embodiment is similar to that of the first embodiment, but the structure of the holding device 120 is slightly different, so it will be described with reference to the figures below. Furthermore, structures with the same functions as those in the first embodiment will be described using the same reference numerals.

[0077] Figure 6 An enlarged cross-section of the holding device 120 used to illustrate the second embodiment is shown. The holding device 120 used in the thermoforming apparatus 100 of the second embodiment is identical in that it consists of an upper cover 121 and a lower support portion 122, but differs in that an extraction groove 121c is formed on the upper support surface 121b of the upper cover 121 sheet. This extraction groove 121c is connected to multiple flow paths 121d in a communicating manner and is connected to an extraction device (not shown). Therefore, the structure is such that the sheet S can be adsorbed by means of the holding device 120 regardless of whether the first chamber 101 is being extracted. The forming sequence of the sheet S is the same as in the first embodiment.

[0078] (Third Implementation)

[0079] Next, a general description of the structure of the thermoforming apparatus 100 according to the third embodiment of the present invention will be given. The structure of the third embodiment is similar to that of the first embodiment, but the structure of the holding device 120 is slightly different, so it will be described with reference to the figures below. Furthermore, structures with the same functions as those in the first embodiment will be described using the same reference numerals.

[0080] Figure 7An explanatory diagram illustrating the holding device 120 of the third embodiment is shown. The holding device 120 used in the thermoforming apparatus 100 of the third embodiment has the following structure: the lower support portion 122 supports the sheet piece S, while the function equivalent to the upper support surface is realized by the lower surface of the upper hot plate 310. Multiple airflow paths 311 are formed on the upper hot plate 310, and the adsorption of the sheet piece S is performed by the upper hot plate 310. The lower support portion 122, like in the first embodiment, has a stepped cross-section and is equipped with a pad 124. A positioning pin 123 is provided on the pad 124.

[0081] The distance between the upper surface of the lower support portion 122 and the lower surface of the upper hot plate 310 is set in the same manner as the gap y in the first embodiment. That is, it has a margin of +0.1mm relative to the thickness of the plate member S (5mm), and 5.1mm is the distance of the gap y. Furthermore, the distance of the gap y can be increased or decreased according to the weight and material characteristics of the plate member S and the adsorption capacity of the holding device 120 side.

[0082] Furthermore, the plate S, which is supported by the lower support portion 122, is conveyed by adsorption from the upper hot plate 310. Figure 8A ~D shows an explanatory diagram illustrating the molding sequence A~D. Figure 8A The image shows the placement of sheet metal piece S in the form of forming sequence A. The operator places sheet metal piece S onto the lower support part 122 at the placement position. Figure 8B The process is shown in the molding sequence B, where the upper hot plate 310 is used to adsorb and transport the sheet piece S. The upper hot plate 310 is brought close to the sheet piece S and air is drawn from the exhaust air passage 311 provided on the upper hot plate 310, thereby adsorbing the sheet piece S.

[0083] Figure 8C The image shows a molding sequence C where the sheet material S is being heated by the lower hot plate 150. The sheet material S is moved to the upper part of the lower hot plate 150 using the upper hot plate 310 and the lower support 122, and is heated from its lower surface. Radiant heating is performed until the material of the sheet material S, namely polycarbonate, reaches a temperature above its glass transition temperature. Figure 8D The molding process of sheet metal part S is shown in the form of molding sequence D. Sheet metal part S is moved above mold 200 by the upper hot plate 310 and the lower support 122. Air is supplied to sheet metal part S from the upper hot plate 310, and molding is performed under air pressure. Simultaneously, air is drawn from the second chamber 102 side, thereby smoothly molding sheet metal part S. Afterwards, the molded product is removed from mold 200. Through this sequence, molded product P can be formed.

[0084] When the sheet piece S is transported using the holding device 120 of the second or third embodiment, similar to the first embodiment, a molding method can be provided that mitigates the effects of linear expansion of the sheet piece S due to heating, thus preventing misalignment. The distance between the lower surface of the upper cover material 121 (corresponding to the upper support surface) or the upper hot plate 310 and the lower support surface 124a (corresponding to the lower support surface) of the sheet piece has a margin relative to the thickness of the sheet piece S. This margin is set as an adsorption distance, so that even if the sheet piece S falls off due to deformation caused by heating, it will be caught by the lower support surface 124a, making it easy to re-adsorb and preventing misalignment.

[0085] Furthermore, a positioning pin 123 is provided on the pad 124. By having the positioning pin 123 pass through the short-side elongated hole S1 and the long-side elongated hole S2 provided on the plate member S, the plate member S is positioned relative to the holding device 120. Therefore, even if the plate member S undergoes thermal expansion, misalignment can be suppressed.

[0086] (Fourth implementation)

[0087] Next, a general description of the structure of the thermoforming apparatus 100 according to the fourth embodiment of the present invention will be given. The structure of the fourth embodiment is generally the same as that of the first embodiment, but the structure of the sheet S used for forming is different, so it will be described below with reference to figures. Furthermore, structures with the same functions as those in the first embodiment will be described using the same reference numerals.

[0088] Figure 9 A plan view of the lower support portion 122 according to the fourth embodiment is shown. The difference from the first embodiment lies in the following structure: the number of short-side elongated holes S1 provided on the sheet metal S is one, and a hole for the positioning pin 123 to pass through is provided on the extension line of the center line of the short-side elongated hole S1. On the other hand, the number of long-side elongated holes S2 is two. That is, it is a structure that absorbs the expansion of the sheet metal S based on a unilateral reference. This approach of absorbing the thermal expansion of the sheet metal S based on a unilateral reference is effective for printing portions requiring positional accuracy near the hole through which the positioning pin 123 passes.

[0089] Furthermore, Figure 9The design is based on a hole on the short side through which the positioning pin 123 passes, but it can also be based on a hole on the long side. In this case, it becomes a structure with two long holes S1 on the short side. Furthermore, although not shown, the positioning mechanism can also be structured as follows: one hole for the positioning pin 123 and one long hole S1 on the short side, using a single-sided reference to absorb the effects of thermal expansion of the sheet metal S. In this case, the center of the hole through which the positioning pin 123 passes and the center line of the long hole S1 do not necessarily have to overlap with the center of the sheet metal S.

[0090] The thermoforming apparatus 100 of the present invention has been described above in the first to fourth embodiments, but the present invention is not limited thereto, and various modifications can be made without departing from its spirit. For example, the embodiments describe the sheet material S as being made of thermoplastic resin polycarbonate, but this is not a limitation, and the present invention can be applied to thick sheets made of other materials. For example, it can also be applied to the molding of thick foamed materials. Furthermore, the temperature settings of the upper hot plate 110 and the lower hot plate 150 should also be adjusted according to the material of the sheet material S.

[0091] Symbol Explanation

[0092] S…sheet plate

[0093] 100…Thermoforming apparatus

[0094] 110… Upper Hot Plate

[0095] 120…holding device

[0096] 150…lower hot plate

[0097] 200… mold.

Claims

1. A thermoforming apparatus that performs mold shaping by heating a sheet member with a hot plate, characterized by comprising: the hot plate that is composed of an upper hot plate and a lower hot plate; the upper hot plate that performs heating from above the sheet member; the lower hot plate that performs heating from below the sheet member; and a holding device that is provided around the upper hot plate and holds the sheet member by sandwiching a peripheral portion of the sheet member.

2. The thermoforming apparatus according to claim 1, characterized in that: a positioning pin is provided protruding from the lower holding surface; and a positioning hole that is a long hole structure extending in a peripheral direction and in an extension direction of the sheet member is provided in the peripheral portion of the sheet member, and the positioning pin is inserted into the positioning hole to guide the sheet member, thereby restricting movement of the sheet member in a planar direction.

3. The thermoforming apparatus according to claim 1 or 2, characterized in that: the adsorbable distance is 0.1 mm.

4. The thermoforming apparatus according to claim 1 or 2, characterized in that: an opening end of a chamber that opens downward abuts against an upper surface of an upper supporting portion of the holding device, and the sheet member is adsorbed to the upper holding surface by suctioning air in the chamber, and a lower surface of the upper supporting portion is the upper holding surface.

5. The thermoforming apparatus according to claim 1 or 2, characterized in that: a lower surface of the upper hot plate functions as the upper holding surface. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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