Resin molding device and resin molding method

Abstract

To provide a resin molding device capable of preventing misalignment of a thermoplastic resin sheet set on an upper surface of a lower mold, improving a shape accuracy by press molding, and suppressing occurrence of distortion caused by air bubbles in the thermoplastic resin sheet.SOLUTION: There is provided a resin molding device for molding a heated thermoplastic resin sheet, comprises: a lower mold; an upper mold that presses the thermoplastic resin sheet between itself and the lower mold; and a cloth holding mechanism that is provided around the lower mold to hold a cloth stretched between the lower mold and the upper mold. The cloth is spaced apart from the lower mold and the upper mold in between the lower mold and the upper mold, and is stretched perpendicular to a pressing direction of the lower mold and the upper mold. The lower mold and the upper mold are provided so as to press the thermoplastic resin sheet in a state of placing apart from the lower mold and the upper mold on the cloth.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a resin molding apparatus and a resin molding method. [Background technology]

[0002] Various techniques have been proposed for resin molding devices that mold heated thermoplastic resin sheets. For example, in the method for conveying a heat-softened resin sheet described in the following patent document, a thermoplastic resin sheet is placed on a rotating belt and heated together with the rotating belt to soften the thermoplastic resin sheet. The rotating belt is then positioned directly above a lower mold, and a clamp is positioned so that it faces one end of the rotating belt.

[0003] Next, the belt member of the rotating belt is rotated in the feed direction, and one end of the thermoplastic resin sheet is held by the clamp, and the rotating belt is moved in a direction away from the lower mold while continuing to rotate in the feed direction. After that, at the same time that the other end of the thermoplastic resin sheet leaves the rotating belt, the clamp releases the hold of one end of the thermoplastic resin sheet, and the thermoplastic resin sheet rests on the upper surface of the lower mold. Then, the clamp leaves the lower mold, and the upper mold descends relative to the lower mold, molding the thermoplastic resin sheet into a predetermined shape. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-326328 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the thermoplastic resin sheet is released from its holding position at both ends above the lower mold and then dropped onto the upper surface of the lower mold, there is a risk that the thermoplastic resin sheet will encounter air resistance as it falls, or that the timing of releasing the clamps will be off. As a result, the thermoplastic resin sheet may be placed on the upper surface of the lower mold out of position relative to the reference position where it is intended to be set, which could result in a decrease in the shape accuracy achieved by press molding. Furthermore, when the thermoplastic resin sheet is placed on the upper surface of the lower mold, air bubbles may be trapped between the thermoplastic resin sheet and the upper surface of the lower mold, which could cause distortion in the thermoplastic resin sheet when pressed by the lower and upper molds.

[0006] Therefore, the present invention was devised in consideration of these points, and aims to provide a resin molding device and a resin molding method that can prevent the thermoplastic resin sheet set on the upper surface of the lower mold from shifting in position, improve the shape accuracy of press molding, and suppress the occurrence of distortion due to air bubbles in the thermoplastic resin sheet. [Means for solving the problem]

[0007] In order to solve the above problems, the first invention of the present invention is a resin molding apparatus for molding a heated thermoplastic resin sheet, comprising a lower mold, an upper mold that presses the thermoplastic resin sheet between the lower mold, and a cloth holding mechanism that is provided around the lower mold and holds a cloth stretched between the lower mold and the upper mold, wherein the cloth is stretched between the lower mold and the upper mold, spaced apart from the lower mold and the upper mold, and perpendicular to the pressing direction between the lower mold and the upper mold, and the lower mold and the upper mold are configured to be able to press the thermoplastic resin sheet placed on the cloth at a distance from the lower mold and the upper mold. The resin molding device may include a gripping unit that grips the thermoplastic resin sheet and places it on the cloth. In this case, the lower mold and the upper mold may be configured to press the thermoplastic resin sheet, which is released from the gripping unit and placed on the cloth at a distance from the lower mold and the upper mold, in a state in which the cloth is bent by the weight of the thermoplastic resin sheet.

[0008] Next, the second invention of the present invention is a resin molding apparatus according to the first invention, wherein the cloth holding mechanism holds the cloth stretched between the lower mold and the upper mold so that the center of the cloth faces a reference position on the upper surface of the lower mold on which the center of the thermoplastic resin sheet is placed.

[0009] Next, the third invention of the present invention is a resin molding apparatus according to the first or second invention, wherein the cloth holding mechanism is integrally formed with the lower mold, and the height of the cloth stretched between the lower mold and the upper mold from the top surface of the lower mold is fixed.

[0010] Next, the fourth invention of the present invention is a resin molding apparatus according to the first or second invention, wherein the cloth holding mechanism is provided separately from the lower mold and is set so that the vertical position of the cloth stretched between the lower mold and the upper mold does not change.

[0011] Next, the fifth invention of the present invention is a resin molding apparatus relating to any one of the first to fourth inventions above, wherein the cloth holding mechanism has a frame body portion that clamps and holds the cloth from above and below, and the frame body portion has a lower frame on which the cloth is placed and an upper frame that is attached to the lower frame and clamps the cloth.

[0012] Next, the sixth invention of the present invention is a resin molding apparatus according to any one of the first to fifth inventions, wherein the cloth has a brushed surface on which the thermoplastic resin sheet is placed.

[0013] Next, the seventh invention of the present invention is a resin molding method for molding the thermoplastic resin sheet using the resin molding apparatus according to the first invention, comprising a sheet placing step of placing the heated thermoplastic resin sheet in the center of the cloth, and a molding step of pressing the thermoplastic resin sheet, which has been placed on the cloth at a distance from the lower mold and the upper mold in the sheet placing step, using the lower mold and the upper mold. When the resin molding apparatus is equipped with the above-mentioned gripping unit, the resin molding method may include a sheet placing process in which the heated thermoplastic resin sheet is placed on the center of the cloth using the gripping unit, and a molding process in which the thermoplastic resin sheet, which has been placed on the cloth at a distance from the lower mold and the upper mold in the sheet placing process, is pressed by the lower mold and the upper mold in a state in which the gripping by the gripping unit is released and the cloth is bent due to the weight of the thermoplastic resin sheet. [Effects of the Invention]

[0014] According to the first and seventh inventions, the heated thermoplastic resin sheet is placed on the cloth stretched between the lower and upper molds, so that the weight of the thermoplastic resin sheet causes the cloth to bend, and the center (center of gravity) of the thermoplastic resin sheet moves to the center of the cloth. In this way, by positioning the thermoplastic resin sheet set on the upper surface of the lower mold at the center of the cloth, misalignment can be corrected, and the shape accuracy of press molding can be improved.

[0015] The lower and upper dies are also arranged so as to be able to press the thermoplastic resin sheet placed on the fabric at a distance from the lower and upper dies. As a result, the thermoplastic resin sheet placed on the fabric is spaced from the lower die, which prevents heat from escaping from the thermoplastic resin sheet to the lower die before it is pressed, thereby preventing a decrease in the temperature of the thermoplastic resin sheet. This prevents deterioration in the formability of the thermoplastic resin sheet.

[0016] Furthermore, when a thermoplastic resin sheet placed on a cloth is pressed with the lower and upper dies, even if air bubbles are trapped between the upper surface of the lower die and the thermoplastic resin sheet, the air bubbles are expelled from the gaps in the cloth arranged between the upper surface of the lower die and the thermoplastic resin sheet. Therefore, when a thermoplastic resin sheet placed on a cloth is pressed with the lower and upper dies, distortion of the thermoplastic resin sheet due to air bubbles can be suppressed.

[0017] According to the second invention, the center of the cloth stretched between the lower mold and the upper mold faces the reference position on the upper surface of the lower mold on which the center of the thermoplastic resin sheet is placed, so that when the cloth is bent by the weight of the thermoplastic resin sheet and the center (center of gravity) of the thermoplastic resin sheet moves to the center of the cloth, the center of the thermoplastic resin sheet is positioned so as to face the reference position on the upper surface of the lower mold to which the center of the thermoplastic resin sheet is to be aligned. This makes it possible to press the center (center of gravity) of the thermoplastic resin sheet by setting it to the reference position on the upper surface of the lower mold to which the center of the thermoplastic resin sheet is to be aligned, thereby further improving the shape accuracy of press molding.

[0018] According to the third aspect of the present invention, the cloth holding mechanism is provided integrally with the lower mold, and the height of the cloth stretched between the lower and upper molds from the upper surface of the lower mold is fixed. This eliminates the need for a drive mechanism to raise and lower the cloth, reducing the number of parts in the resin molding device and simplifying the structure.

[0019] According to the fourth aspect of the present invention, the cloth holding mechanism is provided separately from the lower mold and is set so that the vertical position of the cloth stretched between the lower mold and the upper mold does not change. This allows the vertical height of the cloth to be adjusted independently, making it easy to adjust the vertical height of the cloth.

[0020] According to the fifth aspect of the present invention, the fabric is sandwiched and held from above and below by a frame body consisting of an upper frame and a lower frame, so that when a thermoplastic resin sheet is placed on the fabric, the fabric bends due to the weight of the thermoplastic resin sheet, and the center (center of gravity) of the thermoplastic resin sheet can be reliably moved to the center of the fabric held by the frame body.

[0021] According to the sixth invention, the surface of the cloth on which the thermoplastic resin sheet is placed is brushed, so that when pressed with the lower and upper molds, the weave of the cloth can be prevented from being transferred to the surface of the thermoplastic resin sheet, thereby improving quality. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a perspective view showing an example of a schematic configuration of a resin molding apparatus according to a first embodiment. [Figure 2] FIG. 2 is an exploded perspective view showing a frame portion of the cloth holding mechanism that holds the periphery of the cloth. [Figure 3] 10 is a cross-sectional view illustrating a state in which the cloth is held by the frame body portion. FIG. [Figure 4] FIG. 10 is a perspective view illustrating a clamped state of a heated thermoplastic resin sheet. [Figure 5] 10A and 10B are diagrams for explaining a state in which a heated thermoplastic resin sheet is placed on a cloth and positioned; [Figure 6] 2 is a diagram for schematically explaining an example of a procedure for pressing a heated thermoplastic resin sheet by the resin molding apparatus shown in FIG. 1. FIG. [Figure 7] FIG. 10 is a perspective view showing an example of a schematic configuration of a resin molding apparatus according to a second embodiment. [Figure 8] 8A to 8C are diagrams illustrating an example of a procedure for pressing a heated thermoplastic resin sheet by the resin molding apparatus shown in FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, a first and second embodiment of a resin molding apparatus and a resin molding method according to the present invention will be described in detail with reference to the drawings. First, the schematic configuration of a resin molding apparatus 1 according to the first embodiment will be described with reference to Figs. 1 to 3. Fig. 1 shows an example of the schematic configuration of a resin molding apparatus 1 according to the first embodiment. The resin molding apparatus 1 is used, for example, when molding a resin rear window of a vehicle.

[0024] [First embodiment] As shown in FIG. 1, the resin molding apparatus 1 is an apparatus that molds a heated thermoplastic resin sheet 3. Specifically, the resin molding apparatus 1 presses the heated thermoplastic resin sheet 3 with a mold, thereby molding the thermoplastic resin sheet 3 into a desired shape that corresponds to the shape of the mold. The thermoplastic resin sheet 3 is heated in advance by a heating device such as a heating furnace, for example, to a temperature at which the thermoplastic resin softens and becomes moldable by pressing. The thermoplastic resin sheet 3 is a thermoplastic resin molded into a sheet shape. Examples of thermoplastic resins include PA6, PA66, ABS, PP, PPS, and PC.

[0025] The resin molding apparatus 1 includes a lower mold 5, an upper mold 6, and a cloth holding mechanism 7. The lower mold 5 is supported from below by, for example, a lower mold support portion 11 that is rectangular in plan view. The upper mold 6 is supported from above by, for example, an upper mold support portion 12 that is rectangular in plan view. The lower mold 5 and the upper mold 6 are a pair of molds that are arranged to face each other. When at least one of the lower mold 5 and the upper mold 6 moves in the pressing direction (the direction in which the molds close), the lower mold 5 and the upper mold 6 close.

[0026] For example, the upper die 6 is disposed vertically above the lower die 5, and the "pressing direction" is the vertical direction. Here, the upper die 6 moves vertically downward, causing the lower die 5 and the upper die 6 to close. The resin molding device 1 is equipped with actuators (not shown) that move each of the lower die 5 and the upper die 6 in the pressing direction.

[0027] The lower mold 5 is one of a pair of molds for pressing the thermoplastic resin sheet 3. The lower mold 5 has a lower mold base 5A and a lower mold protrusion 5B. The lower mold base 5A is formed, for example, in the shape of a rectangular plate in a plan view. The lower mold protrusion 5B is a thick plate-like portion formed to protrude from the upper surface of the lower mold base 5A (i.e., the surface facing the upper mold 6). The lower mold protrusion 5B is located approximately in the center of the lower mold base 5A and is formed in a rectangular shape in a plan view that is slightly smaller than the lower mold base 5A. The upper surface of the lower mold protrusion 5B is formed so that the upper edge of the side cross section in a direction perpendicular to the longitudinal direction protrudes upward in a curved shape with a predetermined radius of curvature. The lower mold base 5A and the lower mold protrusion 5B are integrally formed as a single member.

[0028] The upper mold 6 is the other of a pair of molds for pressing the thermoplastic resin sheet 3. The upper mold 6 presses the thermoplastic resin sheet 3 between the upper mold 6 and the lower mold 5. The upper mold 6 is formed in the shape of a thick rectangular plate in a plan view, and its longitudinal direction is arranged along the longitudinal direction of the lower mold convex portion 5B. The lower surface of the upper mold 6 (i.e., the surface facing the lower mold 5) is formed with an upper mold concave portion 6A that is recessed upward in a curved shape with a predetermined radius of curvature at the lower edge of the side cross section in a direction perpendicular to the longitudinal direction.

[0029] When the lower mold 5 and the upper mold 6 are closed, the upper surface of the lower mold convex portion 5B and the lower surface of the upper mold concave portion 6A are arranged to face each other. At this time, a gap is formed between the upper surface of the lower mold convex portion 5B and the lower surface of the upper mold concave portion 6A to form the thermoplastic resin sheet 3 into a curved shape with a predetermined curvature radius.

[0030] The cloth holding mechanism 7 is provided around the lower mold 5 and the upper mold 6, and holds the periphery of the cloth 9 stretched between the lower mold 5 and the upper mold 6. For example, the cloth holding mechanism 7 has a frame body 15 that is generally rectangular in plan view, and a first frame support 16A, a second frame support 16B, a third frame support 16C, and a fourth frame support 16D that support the four corners of the lower surface of the frame body 15. The first frame support 16A, the second frame support 16B, the third frame support 16C, and the fourth frame support 16D are pillars that are respectively arranged on the four corners of the lower mold support 11 so that their relative positions with respect to the lower mold 5 do not change, and are each provided to stand upright in the vertical direction.

[0031] Furthermore, the first frame support portion 16A, the second frame support portion 16B, the third frame support portion 16C, and the fourth frame support portion 16D are formed so that the height from the lower mold support portion 11 to the upper end surface is equal, and are attached to the four corners of the lower surface of the frame body portion 15. As a result, the frame body portion 15 is disposed between the lower mold 5 and the upper mold 6, spaced apart from the lower mold 5 and the upper mold 6, and perpendicular to the pressing direction (the mold closing direction) of the lower mold 5 and the upper mold 6.

[0032] 2 and 3, the frame body 15 includes a lower frame 15A, an upper frame 15B, and a cloth 9. The lower frame 15A includes a frame 17 formed as a rectangular frame in a plan view that opens vertically, and a cloth receiving portion 19 in a square frame shape that extends perpendicularly inward from the lower vertical end of the frame 17 around the entire periphery and has a rectangular opening 18 in the center in a plan view. As shown in FIG. 1, the opening 18 is formed in a rectangular shape that is larger than the lower mold protrusion 5B and the upper mold 6. The lower frame 15A is supported by the first to fourth frame support portions 16A to 16D so that the center of the opening 18 faces a reference position on the upper surface of the lower mold protrusion 5B where the center (center of gravity) of the thermoplastic resin sheet 3 is to be aligned, for example, opposite the center of the upper surface of the lower mold protrusion 5B.

[0033] As shown in Fig. 3, upper frame 15B is fitted inside lower frame 15A with fabric 9 sandwiched therebetween and is fixed by bolts or the like to hold the periphery of the stretched fabric 9. As shown in Figs. 2 and 3, upper frame 15B has a frame portion 21 that can be fitted inside lower frame 15A, and a square-frame-shaped fabric pressing portion 23 that extends a predetermined length (e.g., approximately 4 cm to 8 cm) inward at right angles around the entire periphery from the vertical lower end of frame portion 21 and forms in the center an opening 22 that is rectangular in plan view.

[0034] 1 and 3, the opening 22 is formed in the same shape as the opening 18, and is formed in a rectangular shape larger than the lower mold protrusion 5B and the upper mold 6. Similarly to the lower frame 15A, the upper frame 15B is arranged so that the center of the opening 22 faces the reference position on the upper surface of the lower mold protrusion 5B to which the center (center of gravity) of the thermoplastic resin sheet 3 is to be aligned, for example, opposite the center of the upper surface of the lower mold protrusion 5B.

[0035] 2 and 3, the fabric 9 is formed, for example, in a rectangular shape larger than the lower frame 15A and upper frame 15B that constitute the frame body 15. The peripheral edge of the fabric 9 is placed on the fabric receiving portion 19 of the lower frame 15A, and is stretched with an appropriate tension while being pressed down by the fabric pressing portion 23 of the upper frame 15B inserted into the frame portion 17 of the lower frame 15A. Next, with the fabric 9 stretched with the appropriate tension, the upper frame 15B is pressed and fixed to the lower frame 15A by bolts or the like to sandwich the peripheral edge of the fabric 9, thereby holding the entire peripheral edge of the fabric 9 within the frame body 15.

[0036] Therefore, the center of the surface of the cloth 9 held by the frame 15 that faces the lower mold protrusion 5B is positioned at a reference position on the upper surface of the lower mold protrusion 5B where the center (center of gravity) of the thermoplastic resin sheet 3 is to be aligned, for example, so as to face the center of the upper surface of the lower mold protrusion 5B. Furthermore, the frame 15 is supported by the first frame support 16A to the fourth frame support 16D, so that the cloth holding mechanism 7 is provided integrally with the lower mold 5. As a result, the height from the cloth 9, which is stretched with appropriate tension between the lower mold 5 and the upper mold 6, to the upper surface of the lower mold protrusion 5B is fixed. In other words, the lower mold 5 and the upper mold 6 are provided so that the thermoplastic resin sheet 3, which is placed on the cloth 9 at a distance from the lower mold 5 and the upper mold 6, can be pressed.

[0037] The fabric 9 can be selected appropriately from among a polyester fabric woven from polyester fibers, a nylon fabric woven from heat-resistant nylon fibers, a cotton fabric woven from cotton fibers, etc., depending on the temperature to which the thermoplastic resin sheet 3 is heated. It is also desirable that at least the surface of the fabric 9 facing the upper mold 6 is brushed. This can prevent a textured pattern from appearing on the surface of the heated thermoplastic resin sheet 3.

[0038] As shown in Fig. 4, before the thermoplastic resin sheet 3 is pressed by the lower mold 5 and the upper mold 6, both opposing edge portions of the sheet 3 are clamped by a pair of gripping parts 25, and the sheet 3 is transported between the cloth holding mechanism 7 and the upper mold 6 and placed at the center of the cloth 9 (see Fig. 6). The pair of gripping parts 25 are arranged opposite each other on both sides in the horizontal direction perpendicular to the pressing direction, and are configured to selectively move the thermoplastic resin sheet 3 toward each other and move away from each other and retract outside the molds (see Fig. 6).

[0039] The pair of gripping sections 25 are configured to selectively grip both opposing edge portions of the thermoplastic resin sheet 3 over the entire length (shown by solid lines in FIG. 4 ) and release the grip of both opposing edge portions of the thermoplastic resin sheet 3 (shown by two-dot chain lines in FIG. 4 ). As will be described later, the pair of gripping sections 25 gripping both opposing edge portions of the heated thermoplastic resin sheet 3 are conveyed by a conveying mechanism (not shown) between the cloth 9 held by the cloth holding mechanism 7 and the upper mold 6 (see the left end of the upper row in FIG. 6 ). Next, as will be described later, after releasing their grip on the thermoplastic resin sheet 3, the pair of gripping sections 25 move horizontally outward and retreat to the outside of the mold, and place the thermoplastic resin sheet 3 on the cloth 9 (see the left end of the lower row in FIG. 6 ).

[0040] Next, the state in which the heated thermoplastic resin sheet 3 is placed and positioned on the cloth 9 will be described with reference to Fig. 5. As shown in Fig. 5, when the pair of gripping parts 25 release their grip on the thermoplastic resin sheet 3 and then move apart horizontally outward and retreat to the outside of the mold, the thermoplastic resin sheet 3 is placed in approximately the center of the cloth 9. Then, the weight of the thermoplastic resin sheet 3 causes the center of the cloth 9 to bend, and a force that stabilizes the center (center of gravity position) of the thermoplastic resin sheet 3 at the center of the cloth 9 acts on the thermoplastic resin sheet 3 from the cloth 9.

[0041] This allows the center (center of gravity) of the thermoplastic resin sheet 3 to be positioned at the center of the cloth 9. Furthermore, the center of the cloth 9 held by the cloth holding mechanism 7 faces the reference position of the upper surface of the lower mold convex portion 5B on which the center (center of gravity) of the thermoplastic resin sheet 3 is placed, for example, the center of the upper surface of the lower mold convex portion 5B, so the center (center of gravity) of the thermoplastic resin sheet 3 can be positioned so as to face the center of the upper surface of the lower mold convex portion 5B.

[0042] 5, the height of the cloth 9 held by the cloth holding mechanism 7 relative to the upper surface of the lower mold protrusion 5B is set so that a gap of a predetermined height (for example, about 1 cm to 3 cm) is formed between the lowermost end of the cloth 9, which has been bent downward by the weight of the thermoplastic resin sheet 3, and the upper surface of the lower mold protrusion 5B. This makes it possible to prevent heat from escaping from the thermoplastic resin sheet 3 to the lower mold 5 before it is pressed, and thus to prevent the temperature of the thermoplastic resin sheet 3 from decreasing.

[0043] Next, an example of a procedure (step) for pressing the heated thermoplastic resin sheet 3 by the resin molding apparatus 1 configured as described above will be described with reference to Fig. 6. First, in the step shown at the left end of the upper row of Fig. 6, the pair of gripping units 25 grip opposite end edge portions of the heated thermoplastic resin sheet 3, and the pair of gripping units 25 is conveyed by a conveying mechanism (not shown) between the cloth 9 held by the cloth holding mechanism 7 and the upper mold 6. The pair of gripping units 25 is also conveyed so that the center (center of gravity) of the thermoplastic resin sheet 3 faces approximately the center of the cloth 9 held by the cloth holding mechanism 7.

[0044] 6, the lower die support part 11 that supports the lower die 5 and the cloth holding mechanism 7 is moved upward in the pressing direction (vertical direction) by a predetermined height by an actuator (not shown) so that the bottom end of the thermoplastic resin sheet 3 comes into contact with the center of the cloth 9. Subsequently, in the step shown at the right end of the upper part of Fig. 6, the pair of gripping parts 25 release the opposing end edge parts of the thermoplastic resin sheet 3.

[0045] 6, the pair of gripping parts 25 that have released their grip on the thermoplastic resin sheet 3 are moved horizontally outward and retracted to the outside of the mold, i.e., horizontally outward of the cloth holding mechanism 7. As a result, the center of the cloth 9 is bent by the weight of the thermoplastic resin sheet 3, and the center (center of gravity) of the thermoplastic resin sheet 3 can be positioned at the center of the cloth 9 (see FIG. 5). That is, the center (center of gravity) of the thermoplastic resin sheet 3 can be positioned at a reference position on the upper surface of the lower mold protrusion 5B on which the center (center of gravity) of the thermoplastic resin sheet 3 is placed, for example, so as to face the center of the upper surface of the lower mold protrusion 5B. Furthermore, a gap of a predetermined height (for example, a height of approximately 1 cm to 3 cm) is formed between the lowermost end of the cloth 9 that has been bent downward by the weight of the thermoplastic resin sheet 3 and the upper surface of the lower mold protrusion 5B.

[0046] 6, the lower die support part 11 supporting the lower die 5 and the cloth holding mechanism 7 is moved downward in the pressing direction (vertical direction) by a predetermined height by an actuator (not shown) to position it at the origin. Then, the upper die support part 12 supporting the upper die 6 is moved downward in the pressing direction (mold closing direction) by an actuator (not shown), and the thermoplastic resin sheet 3 placed at the center of the cloth 9, separated from the lower die 5 and the upper die 6, is pressed together with the cloth 9. The cloth 9 is made of a polyester fabric, a nylon fabric, a cotton fabric, or the like, and is set to stretch appropriately within its elastic range when the lower die 5 and the upper die 6 are closed.

[0047] As a result, the thermoplastic resin sheet 3 is pressed by the lower mold 5 and the upper mold 6 with the cloth 9 sandwiched between it and the upper surface of the lower mold convex portion 5B, and is molded into a desired shape corresponding to the shapes of the lower mold convex portion 5B and the upper mold concave portion 6A. If the lower mold 5 and the upper mold 6 are resin molds, the pressed state is maintained for, for example, about 5 minutes. If the lower mold 5 and the upper mold 6 are metal molds such as aluminum alloy molds, the pressed state is maintained for, for example, about 40 to 60 seconds.

[0048] 6, the upper die support part 12 supporting the upper die 6 is moved upward in the pressing direction (die opening direction) by an actuator (not shown) to the origin position. As a result, the press-molded thermoplastic resin sheet 3 is placed on the elastically restored cloth 9 and can be removed by an operator or a robot hand, etc.

[0049] Here, the process shown at the left end of the upper row of Fig. 6 to the process shown at the left end of the lower row of Fig. 6 constitutes an example of a sheet placing process. Also, the process shown at the center of the lower row of Fig. 6 to the process shown at the right end of the lower row of Fig. 6 constitutes an example of a forming process.

[0050] As explained in detail above, in the resin molding apparatus 1 according to the first embodiment, the heated thermoplastic resin sheet 3 is once placed on the cloth 9 stretched between the lower mold 5 and the upper mold 6, so that the cloth 9 is bent by the weight of the thermoplastic resin sheet 3, and the center (center of gravity) of the thermoplastic resin sheet 3 moves to the center of the cloth 9. This makes it possible to correct any misalignment of the thermoplastic resin sheet 3 set on the upper surface of the lower mold convex portion 5B of the lower mold 5, thereby improving the shape accuracy achieved by press molding.

[0051] Furthermore, since the thermoplastic resin sheet 3 placed on the cloth 9 is separated from the upper surface of the lower die protrusion 5B of the lower die 5, it is possible to prevent heat from escaping from the thermoplastic resin sheet 3 to the lower die 5 and a decrease in the temperature of the thermoplastic resin sheet 3 before it is pressed. Therefore, it is possible to prevent deterioration in the formability of the thermoplastic resin sheet 3.

[0052] Furthermore, when the thermoplastic resin sheet 3 placed on the cloth 9 is pressed by the lower mold 5 and the upper mold 6, even if air bubbles are trapped between the upper surface of the lower mold convex portion 5B of the lower mold 5 and the thermoplastic resin sheet 3, the air bubbles are expelled from the gap in the cloth 9 arranged between the upper surface of the lower mold convex portion 5B and the thermoplastic resin sheet 3. Therefore, when the thermoplastic resin sheet 3 placed on the cloth 9 is pressed by the lower mold 5 and the upper mold 6, distortion of the thermoplastic resin sheet 3 due to the air bubbles can be suppressed.

[0053] Furthermore, the center of the cloth 9 stretched between the lower mold 5 and the upper mold 6 faces the reference position on the upper surface of the lower mold convex portion 5B on which the center (center of gravity) of the thermoplastic resin sheet 3 is placed, for example, the center of the upper surface of the lower mold convex portion 5B of the lower mold 5. Therefore, when the cloth 9 is bent by the weight of the thermoplastic resin sheet 3 and the center (center of gravity) of the thermoplastic resin sheet 3 moves to the center of the cloth 9, the center of the thermoplastic resin sheet 3 is positioned so as to face the center of the upper surface of the lower mold convex portion 5B. This allows the center of the thermoplastic resin sheet 3 to be set at the reference position on the upper surface of the lower mold convex portion 5B, for example, the center of the upper surface of the lower mold convex portion 5B, and pressed, thereby further improving the shape accuracy by press molding.

[0054] Furthermore, the cloth holding mechanism 7 is provided integrally with the lower mold 5 via the lower mold support part 11, and the height from the cloth 9 stretched between the lower mold 5 and the upper mold 6 to the upper surface of the lower mold convex part 5B of the lower mold 5 is fixed. This eliminates the need to provide a drive mechanism for raising and lowering the cloth 9, thereby reducing the number of parts in the resin molding apparatus 1 and simplifying the structure.

[0055] Furthermore, rectangular cloth 9 is sandwiched at its four sides from above and below by frame 15, which is rectangular in plan view and is composed of upper frame 15B and lower frame 15A, both of which are rectangular in plan view, and the entire periphery of the cloth 9 is held. As a result, when thermoplastic resin sheet 3 is placed on cloth 9, cloth 9 is bent by the weight of thermoplastic resin sheet 3, and the center (center of gravity) of thermoplastic resin sheet 3 can be reliably moved to the center of cloth 9 held by frame 15.

[0056] In addition, since the surface of the cloth 9 on which the thermoplastic resin sheet 3 is placed is brushed, when pressed with the lower mold 5 and the upper mold 6, the weave of the cloth 9 can be prevented from being transferred to the surface of the thermoplastic resin sheet 3, thereby improving quality.

[0057] [Second embodiment] Next, a second embodiment of a resin molding apparatus and a resin molding method according to the present invention will be described with reference to Figures 7 and 8. In the following description, the same reference numerals as those in the configuration of the resin molding apparatus 1 according to the first embodiment indicate the same or equivalent parts as those in the configuration of the resin molding apparatus 1 according to the first embodiment.

[0058] The configuration of the resin molding apparatus 31 according to the second embodiment is substantially the same as the configuration of the resin molding apparatus 1 according to the first embodiment. However, as shown in Fig. 7, a frame mount 32 formed in a substantially rectangular frame shape in plan view is arranged to surround the periphery of a lower mold support portion 11 that is rectangular in plan view and supports the lower mold 5 from below. In addition, the center of the inner side of the frame mount 32 in plan view is arranged to overlap the center of the upper surface of the lower mold protrusion 5B at the same position in plan view.

[0059] The first, second, third, and fourth frame support parts 16A, 16B, 16C, and 16D of the cloth holding mechanism 7 are pillars arranged at the four corners of the frame mount 32 so that their relative positions with respect to the frame mount 32 do not change, and are different in that they are arranged to stand vertically. Therefore, the center of the surface of the cloth 9 held by the frame 15 that faces the lower mold protrusion 5B is arranged so that the center (center of gravity) of the thermoplastic resin sheet 3 faces the reference position of the upper surface of the lower mold protrusion 5B on which it is placed, for example, the center of the upper surface of the lower mold protrusion 5B.

[0060] Furthermore, by supporting the frame body portion 15 by the first frame support portion 16A to the fourth frame support portion 16D, the cloth holding mechanism 7 is provided separately from the lower mold 5, and is set so that the vertical (up-down) position of the cloth 9 stretched with an appropriate tension between the lower mold 5 and the upper mold 6 does not change. In other words, the lower mold 5 and the upper mold 6 are provided so that the thermoplastic resin sheet 3 placed on the cloth 9 at a distance from the lower mold 5 and the upper mold 6 can be pressed.

[0061] Next, an example of a procedure (step) for pressing the heated thermoplastic resin sheet 3 by the resin molding device 31 configured as described above will be described with reference to Fig. 8. First, in the step shown at the left end of the upper row of Fig. 8, the pair of gripping units 25 grip opposite end edge portions of the heated thermoplastic resin sheet 3, and the pair of gripping units 25 is conveyed by a conveying mechanism (not shown) between the cloth 9 held by the cloth holding mechanism 7 and the upper mold 6. The pair of gripping units 25 is also conveyed so that the center (center of gravity) of the thermoplastic resin sheet 3 faces approximately the center of the cloth 9 held by the cloth holding mechanism 7.

[0062] 8, the pair of gripping parts 25 gripping opposite end edge parts of the heated thermoplastic resin sheet 3 is lowered by a conveying mechanism (not shown) so that the bottom end part of the thermoplastic resin sheet 3 comes into contact with the center part of the fabric 9. Subsequently, in the step shown at the right end of the upper part of Fig. 8, the gripping of the opposite end edge parts of the thermoplastic resin sheet 3 by the pair of gripping parts 25 is released.

[0063] 8, the pair of gripping parts 25 that have released their grip on the thermoplastic resin sheet 3 are moved horizontally outward and retracted to the outside of the mold, i.e., horizontally outward of the cloth holding mechanism 7. As a result, the center of the cloth 9 is bent by the weight of the thermoplastic resin sheet 3, and the center (center of gravity) of the thermoplastic resin sheet 3 can be positioned at the center of the cloth 9 (see FIG. 5). That is, the center (center of gravity) of the thermoplastic resin sheet 3 can be positioned at a reference position on the upper surface of the lower mold protrusion 5B on which the center (center of gravity) of the thermoplastic resin sheet 3 is placed, for example, so as to face the center of the upper surface of the lower mold protrusion 5B. Furthermore, a gap of a predetermined height (for example, a height of approximately 1 cm to 3 cm) is formed between the lowermost end of the cloth 9 that has been bent downward by the weight of the thermoplastic resin sheet 3 and the upper surface of the lower mold protrusion 5B.

[0064] 8, the lower die support part 11 supporting the lower die 5 is moved upward in the pressing direction (mold closing direction) by an actuator (not shown), so that the entire upper surface of the lower die protrusion 5B comes into contact with the fabric 9. At the same time, the upper die support part 12 supporting the upper die 6 is moved downward in the pressing direction (mold closing direction) by an actuator (not shown), so that the thermoplastic resin sheet 3 placed in the center of the fabric 9 is pressed together with the fabric 9. The fabric 9 is made of a polyester fabric, a nylon fabric, a cotton fabric, or the like, and is set so as to stretch appropriately within its elastic range when the lower die 5 and the upper die 6 are closed.

[0065] As a result, the thermoplastic resin sheet 3 is pressed by the lower mold 5 and the upper mold 6 with the cloth 9 sandwiched between it and the upper surface of the lower mold convex portion 5B, and is molded into a desired shape corresponding to the shapes of the lower mold convex portion 5B and the upper mold concave portion 6A. If the lower mold 5 and the upper mold 6 are resin molds, the pressed state is maintained for, for example, about 5 minutes. If the lower mold 5 and the upper mold 6 are metal molds such as aluminum alloy molds, the pressed state is maintained for, for example, about 40 to 60 seconds.

[0066] 8, the upper die support part 12 supporting the upper die 6 is moved upward in the pressing direction (the mold opening direction) by an actuator (not shown) to be located at the origin position. Also, the lower die support part 11 supporting the lower die 5 is moved downward in the pressing direction (the mold opening direction) by an actuator (not shown) to be located at the origin position. As a result, the press-molded thermoplastic resin sheet 3 is placed on the elastically restored cloth 9, and can be removed by an operator or a robot hand, etc.

[0067] Here, the process shown at the left end of the upper row of Fig. 8 to the process shown at the left end of the lower row of Fig. 8 constitutes an example of a sheet placing process. Also, the process shown at the center of the lower row of Fig. 8 to the process shown at the right end of the lower row of Fig. 8 constitutes an example of a forming process.

[0068] As explained in detail above, in the resin molding apparatus 31 according to the second embodiment, the heated thermoplastic resin sheet 3 is once placed on the cloth 9 stretched between the lower mold 5 and the upper mold 6, so that the cloth 9 is bent by the weight of the thermoplastic resin sheet 3, and the center (center of gravity) of the thermoplastic resin sheet 3 moves to the center of the cloth 9. This makes it possible to correct any misalignment of the thermoplastic resin sheet 3 set on the upper surface of the lower mold convex portion 5B of the lower mold 5, thereby improving the shape accuracy achieved by press molding.

[0069] Furthermore, since the thermoplastic resin sheet 3 placed on the cloth 9 is separated from the upper surface of the lower die protrusion 5B of the lower die 5, it is possible to prevent heat from escaping from the thermoplastic resin sheet 3 to the lower die 5 and a decrease in the temperature of the thermoplastic resin sheet 3 before it is pressed. Therefore, it is possible to prevent deterioration in the formability of the thermoplastic resin sheet 3.

[0070] Furthermore, when the thermoplastic resin sheet 3 placed on the cloth 9 is pressed by the lower mold 5 and the upper mold 6, even if air bubbles are trapped between the upper surface of the lower mold convex portion 5B of the lower mold 5 and the thermoplastic resin sheet 3, the air bubbles are expelled from the gap in the cloth 9 arranged between the upper surface of the lower mold convex portion 5B and the thermoplastic resin sheet 3. Therefore, when the thermoplastic resin sheet 3 placed on the cloth 9 is pressed by the lower mold 5 and the upper mold 6, distortion of the thermoplastic resin sheet 3 due to the air bubbles can be suppressed.

[0071] Furthermore, the center of the cloth 9 stretched between the lower mold 5 and the upper mold 6 faces the reference position of the upper surface of the lower mold convex portion 5B on which the center (center of gravity) of the thermoplastic resin sheet 3 is placed, for example, the center of the upper surface of the lower mold convex portion 5B of the lower mold 5. Therefore, when the weight of the thermoplastic resin sheet 3 causes the cloth 9 to bend and the center (center of gravity) of the thermoplastic resin sheet 3 moves to the center of the cloth 9, the center of the thermoplastic resin sheet 3 is positioned so as to face the center of the upper surface of the lower mold convex portion 5B. This allows the center of the thermoplastic resin sheet 3 to be set at the reference position of the upper surface of the lower mold convex portion 5B, for example, the center of the upper surface of the lower mold convex portion 5B, and pressed, thereby further improving the shape accuracy by press molding.

[0072] The cloth holding mechanism 7 is supported on a frame mount 32 formed in the shape of a rectangular frame in plan view and arranged so as to surround the periphery of the lower mold support part 11, and is provided separately from the lower mold 5, so that the vertical position of the cloth 9 stretched between the lower mold 5 and the upper mold 6 does not change. This allows the vertical height of the cloth 9 to be adjusted independently, and the vertical height of the cloth 9 can be easily adjusted.

[0073] Furthermore, rectangular cloth 9 is sandwiched at its four sides from above and below by frame 15, which is rectangular in plan view and is composed of upper frame 15B and lower frame 15A, both of which are rectangular in plan view, and the entire periphery of the cloth 9 is held. As a result, when thermoplastic resin sheet 3 is placed on cloth 9, cloth 9 is bent by the weight of thermoplastic resin sheet 3, and the center (center of gravity) of thermoplastic resin sheet 3 can be reliably moved to the center of cloth 9 held by frame 15.

[0074] In addition, since the surface of the cloth 9 on which the thermoplastic resin sheet 3 is placed is brushed, when pressed with the lower mold 5 and the upper mold 6, the weave of the cloth 9 can be prevented from being transferred to the surface of the thermoplastic resin sheet 3, thereby improving quality.

[0075] The resin molding apparatus and resin molding method of the present invention are not limited to the configuration, structure, appearance, shape, processing procedures, etc. described in the first and second embodiments, and various changes, improvements, additions, and deletions are possible within the scope that does not change the gist of the present invention. In the following description, the same reference numerals as those of the resin molding apparatus 1, resin molding apparatus 31, etc. in Figures 1 to 8 above indicate the same or equivalent parts as those of the resin molding apparatus 1, resin molding apparatus 31, etc.

[0076] (A) For example, in the upper mold 6 of the resin molding apparatus 1 and the resin molding apparatus 31, the cloth 9 may be attached to the entire lower surface of the upper mold recess 6A as well. In this way, when the thermoplastic resin sheet 3 placed on the cloth 9 is pressed by the lower mold 5 and the upper mold 6, even if air bubbles are trapped between the thermoplastic resin sheet 3 and the lower surface of the upper mold recess 6A of the upper mold 6, the air bubbles are expelled from the gaps in the cloth 9 arranged between the lower surface of the upper mold recess 6A and the thermoplastic resin sheet 3. Therefore, when the thermoplastic resin sheet 3 placed on the cloth 9 held by the cloth holding mechanism 7 is pressed by the lower mold 5 and the upper mold 6, the occurrence of distortion of the thermoplastic resin sheet 3 due to air bubbles can be further suppressed.

[0077] Furthermore, it is desirable that the surface of the cloth 9 attached over the entire lower surface of the upper mold recess 6A, facing the lower mold 5, be subjected to a nap-raising process, which makes it possible to prevent a textured pattern from appearing on the surface of the heated thermoplastic resin sheet 3 facing the upper mold 6.

[0078] (B) For example, in the procedure (step) shown in Fig. 6 for pressing the heated thermoplastic resin sheet 3 by the resin molding apparatus 1, the lower die support part 11 that supports the lower die 5 and the cloth holding mechanism 7 may be prevented from moving upward in the pressing direction (vertical direction) in the step shown in the center of the upper part of Fig. 6. Then, the pair of gripping parts 25 may be lowered by a conveying mechanism (not shown) while gripping both opposing edge parts of the heated thermoplastic resin sheet 3 so that the bottom end of the thermoplastic resin sheet 3 contacts the center of the cloth 9.

[0079] 6, the pair of gripping parts 25 may be released from gripping the opposing end edge parts of the thermoplastic resin sheet 3. Then, in the step shown at the left end of the lower part of Fig. 6, the pair of gripping parts 25 that have released their grip on the thermoplastic resin sheet 3 may be moved apart horizontally outward to retract to the outside of the mold, i.e., horizontally outward of the cloth holding mechanism 7.

[0080] As a result, the center of the fabric 9 bends due to the weight of the thermoplastic resin sheet 3, and the center (center of gravity) of the thermoplastic resin sheet 3 can be positioned at the center of the fabric 9 (see FIG. 5). In other words, the center (center of gravity) of the thermoplastic resin sheet 3 can be positioned so as to face the center of the upper surface of the lower mold convex portion 5B. Furthermore, a gap of a predetermined height (for example, a height of about 1 cm to 3 cm) is formed between the lowermost end of the fabric 9, which has bent downward due to the weight of the thermoplastic resin sheet 3, and the upper surface of the lower mold convex portion 5B.

[0081] 6, upper die support part 12 supporting upper die 6 may be moved downward in the pressing direction (die closing direction) by an actuator (not shown), so that thermoplastic resin sheet 3 placed in the center of fabric 9 away from lower die 5 and upper die 6 may be pressed together with fabric 9. Thereafter, in a step shown at the right end of the lower part of FIG. 6, upper die support part 12 supporting upper die 6 may be moved upward in the pressing direction (die opening direction) by an actuator (not shown), so as to be positioned at the origin position.

[0082] As a result, the lower die support part 11 that supports the lower die 5 and the cloth holding mechanism 7 can be located at the origin position in all steps from the step shown at the left end of the upper part of Fig. 6 to the step shown at the right end of the lower part of Fig. 6. Therefore, it is possible to eliminate the actuator that moves the lower die support part 11 that supports the lower die 5 and the cloth holding mechanism 7 upward and downward in the pressing direction, thereby reducing the number of parts of the resin molding apparatus 1 and further simplifying the structure. [Explanation of symbols]

[0083] 1, 31 Resin molding equipment 3 Thermoplastic resin sheet 5 Lower mold 6 Upper mold 7 Cloth retention mechanism 9 cloth 15 Frame body part 15A bottom frame 15B Upper frame

Claims

1. A resin molding device that molds a heated thermoplastic resin sheet, Lower mold and an upper mold that presses the thermoplastic resin sheet between itself and the lower mold; a cloth holding mechanism provided around the lower mold and holding a cloth stretched between the lower mold and the upper mold; a gripping portion that grips the thermoplastic resin sheet and places it on the cloth; Equipped with the fabric is stretched between the lower mold and the upper mold, spaced apart from the lower mold and the upper mold, and perpendicular to the pressing direction of the lower mold and the upper mold; the lower mold and the upper mold are arranged so as to be able to press the thermoplastic resin sheet, which is released from the gripping parts and placed on the cloth at a distance from the lower mold and the upper mold, in a state in which the cloth is bent by the weight of the thermoplastic resin sheet. Resin molding equipment.

2. 2. The resin molding apparatus according to claim 1, the cloth holding mechanism holds the cloth stretched between the lower mold and the upper mold so that the center of the cloth faces a reference position on the upper surface of the lower mold on which the center of the thermoplastic resin sheet is placed. Resin molding equipment.

3. 3. The resin molding apparatus according to claim 1, the cloth holding mechanism is provided integrally with the lower mold, and the height of the cloth stretched between the lower mold and the upper mold from the upper surface of the lower mold is fixed. Resin molding equipment.

4. 3. The resin molding apparatus according to claim 1, the cloth holding mechanism is provided separately from the lower mold and is set so that the position of the cloth stretched between the lower mold and the upper mold does not change in the up-down direction. Resin molding equipment.

5. The resin molding apparatus according to any one of claims 1 to 4, the cloth holding mechanism has a frame portion that holds the cloth by clamping it from above and below, The frame portion is a lower frame on which the cloth is placed; an upper frame attached to the lower frame with the cloth sandwiched therebetween; having Resin molding equipment.

6. The resin molding apparatus according to any one of claims 1 to 5, The fabric has a raised surface on which the thermoplastic resin sheet is placed. Resin molding equipment.

7. A resin molding method for molding the thermoplastic resin sheet using the resin molding apparatus according to claim 1, comprising: a sheet placing step of placing the heated thermoplastic resin sheet on the center of the fabric by the gripping portion; a molding process in which the thermoplastic resin sheet, which has been placed on the cloth at a distance from the lower mold and the upper mold in the sheet placing process, is pressed by the lower mold and the upper mold in a state in which the holding by the holding parts is released and the cloth is bent by the weight of the thermoplastic resin sheet; Equipped with Resin molding method.

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