Method for manufacturing a press-formed product, conveying device for heating a workpiece and hot-press production line

Abstract

The method for manufacturing pressed and molded articles includes a heating process, a conveying process, and a pressing process. The conveying process includes the following steps: supporting and lifting the lower surfaces of both ends of a first heated workpiece using a pair of first arm claws; supporting and lifting the lower surfaces of both ends of a second heated workpiece using a pair of second arm claws; conveying the first heated workpiece, whose lower surfaces at both ends are supported by the pair of first arm claws, and the second heated workpiece, whose lower surfaces at both ends are supported by the pair of second arm claws, in a state of overlapping each other in the normal direction of the plate surface; driving the pair of first arms to lower the first heated workpiece to the pressing position of the press; and driving the pair of second arms to lower the second heated workpiece to the pressing position of the press.

Description

Technical Field

[0001] This invention relates to a method for manufacturing pressed and shaped articles, a conveying device for heating workpieces, and a hot pressing production line. Background Technology

[0002] Traditionally, a technique has been used to press raw materials heated to a predetermined temperature using a press. For example, in hot pressing, a hot-pressing steel sheet is heated to the austenitic region (approximately 900°C or higher) and hot-pressed. Following forming and quenching, pressed products with strengths of, for example, 1500 MPa or higher can be obtained. In typical hot pressing, quenching is performed by rapid cooling through heat transfer in contact with the die during pressing. Therefore, to achieve a sufficient quenching effect, the temperature of the raw material at the start of pressing, approximately equivalent to the quenching start temperature, needs to be maintained above a predetermined temperature. In this case, the predetermined temperature at the start of pressing varies depending on the raw material, but is, for example, 700°C or higher.

[0003] Japanese Patent Nos. 5910305 and 5910306 disclose a hot pressing forming method comprising the following steps: heating multiple overlapping conductive plate-shaped workpieces by mounting electrodes on them and energizing them; placing the heated plate-shaped workpieces in predetermined pressing positions different from the energized positions; and pressing the plate-shaped workpieces in the pressing positions into shape. By simultaneously heating multiple plate-shaped workpieces by energizing them, productivity is improved.

[0004] In the hot pressing method disclosed in Japanese Patent Application Publication No. 2019-177394, a first workpiece and a second workpiece are heated separately without overlapping, and then moved between an upper die and a lower die to form a position where the second workpiece overlaps the first workpiece. The upper die is then lowered for pressing. Before and after the pressing process, the die is lowered independently of the upper die, causing plastic deformation of the first and second workpieces. This results in a state where the overlapping portions of the first and second workpieces are interlocked and do not shift. A conveying device comprising an arm for conveying the first workpiece and a holder for conveying the second workpiece is also disclosed.

[0005] In the aforementioned prior art, heat dissipation occurs during workpiece transport, causing the workpiece temperature to drop. As a result, there is a concern that the required workpiece temperature cannot be maintained when it is fed into the die of the press, making it impossible to adequately quench the pressed product.

[0006] Therefore, Japanese Patent No. 5814669 discloses a hot pressing conveying device that holds and conveys a heated plate-shaped workpiece between different processes in a hot pressing production line. The hot pressing conveying device conveys the heated workpiece while covering it with an insulation cover. This maintains the workpiece at the temperature required for quenching during conveying.

[0007] Furthermore, the hot pressing apparatus disclosed in Japanese Patent No. 4673656, as a heating device for the workpiece, i.e., a metal sheet, includes a primary heating mechanism based on induction heating or electrostatic heating and a secondary heating mechanism based on radiative heat transfer. The secondary heating mechanism based on radiative heat transfer is arranged in the conveying device from the primary heating mechanism to the hot pressing die. Through secondary heating based on radiative heat transfer, the metal sheet can be heated uniformly, reducing temperature deviations in the metal sheet.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent No. 5910305

[0011] Patent Document 2: Japanese Patent No. 5910306

[0012] Patent Document 3: Japanese Patent Application Publication No. 2019-177394

[0013] Patent Document 4: Japanese Patent No. 5814669

[0014] Patent Document 5: Japanese Patent No. 4673656 Summary of the Invention

[0015] The problem the invention aims to solve

[0016] The inventors noted that when hot-pressing raw materials to a thinner thickness, the temperature drop during transport to the press after heating the raw materials can affect the quality of the pressed product. Therefore, methods to suppress the temperature drop of the raw materials during transport were investigated. The research revealed that, as with the prior art, simply covering the raw materials with an insulation cover during transport is insufficient to adequately suppress the temperature drop. Furthermore, a secondary heating mechanism for heating the raw materials during transport was considered. However, this would require adding equipment along the transport path, including a heat source for the secondary heating mechanism. This could lead to increased equipment size and higher equipment and operating costs.

[0017] Therefore, this application discloses a method for manufacturing pressed articles and a conveying device for heating workpieces, which can easily mitigate the temperature drop of raw materials during the conveying time from the heating of raw materials to the start of pressing in hot pressing.

[0018] Solution for solving the problem

[0019] The manufacturing method of the pressed molded article in the technical solution of the present invention includes: a heating step, in which at least two plate-shaped workpieces are simultaneously heated using a heating device; a conveying step, in which at least two heated workpieces heated in the heating step are conveyed to a press using a conveying device; and a pressing step, in which at least two heated workpieces conveyed to the press in the conveying step are processed using the press. The conveying step includes the following steps: driving a pair of first arms rotatably mounted on a base of the conveying device, using the claws of the pair of first arms to support and lift the lower surfaces of both ends of the first heated workpiece among the at least two heated workpieces; driving a pair of second arms rotatably mounted on the base of the conveying device using a system different from the pair of first arms, using the claws of the pair of second arms to support and lift the lower surfaces of both ends of the second heated workpiece among the at least two heated workpieces; and pressing the two ends of the... The first heated workpiece, whose lower surface is supported by the claws of the pair of first arms of the conveying device, and the second heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of second arms, are conveyed in a state of overlapping each other in the normal direction of the plate surface of the first heated workpiece; the pair of first arms are driven to lower the first heated workpiece supported by the pair of first arms to the pressing position of the press; and the pair of second arms are driven using a system different from that of the pair of first arms to lower the second heated workpiece supported by the pair of second arms to the pressing position of the press.

[0020] The effects of the invention

[0021] According to this disclosure, during the conveying time from the heating of the raw material to the start of pressing in hot pressing, the temperature drop of the raw material can be easily mitigated. Attached Figure Description

[0022] Figure 1 This is a top view showing a general outline of the hot pressing production line of this embodiment.

[0023] Figure 2A It means Figure 1 A side view of a structural example of a conveying device as seen from the y-direction.

[0024] Figure 2B It means Figure 2AThe diagram shows the second arm 72 of the conveyor device in the state of being opened outwards.

[0025] Figure 3 It means Figure 1 A side view of a structural example of a conveying device as seen from the x-direction.

[0026] Figure 4 This is a diagram used to explain an example of the control system for the first to fourth drive units.

[0027] Figure 5 This is a diagram illustrating an example of a heating process.

[0028] Figure 6 This diagram illustrates an example of a process in which a conveyor lifts the first heated workpiece.

[0029] Figure 7 This diagram illustrates an example of a process in which a conveyor lifts up the second heated workpiece.

[0030] Figure 8 This diagram illustrates an example of a process involving the transport of a workpiece and its placement in a pressing position.

[0031] Figure 9 This diagram illustrates an example where the first heated workpiece and the second heated workpiece are intermediate molded products.

[0032] Figure 10 This is a diagram illustrating an example where the dimensions of the first and second heated workpieces are different.

[0033] Figure 11 This diagram illustrates an example where the shapes of the first and second heated workpieces are different.

[0034] Figure 12 This diagram shows an example of a conveyor system equipped with a shielding plate.

[0035] Figure 13 This is another example of a conveyor system equipped with a shielding plate.

[0036] Figure 14 This is a diagram showing a variation of the shape of the shielding plate.

[0037] Figure 15 This is another example of a conveyor system equipped with a shielding plate.

[0038] Figure 16 This is a diagram illustrating an example of a conveying device for conveying plates of varying thicknesses.

[0039] Figure 17 This is a diagram showing a variation of the first and second arms.

[0040] Figure 18 This is a diagram showing another variation of the first and second arms.

[0041] Figure 19 This is a diagram showing a variation of the support structure for the conveying device supporting the heated workpiece.

[0042] Figure 20 It means Figure 19 The first and second heated workpieces are shown in a perspective view.

[0043] Figure 21 This is a diagram showing a variation of the support structure for the conveying device supporting the heated workpiece.

[0044] Figure 22 It means Figure 21 The first and second heated workpieces are shown in a perspective view.

[0045] Figure 23 It means Figure 21 The figure shows a modified example of the first heated workpiece and the second heated workpiece.

[0046] Figure 24 This is a diagram showing a variation of the support structure for the conveying device supporting the heated workpiece.

[0047] Figure 25 It means Figure 24 The first and second heated workpieces are shown in a perspective view.

[0048] Figure 26 It means Figure 24 The figure shows a modified example of the first heated workpiece and the second heated workpiece.

[0049] Figure 27 It means Figure 1 A diagram showing a modified example of the hot pressing production line 10.

[0050] Figure 28 Viewed from above Figure 27 The top view obtained from the tray 1 shown.

[0051] Figure 29 Observing from the direction of arrow F Figure 28 The side view obtained from the tray shown.

[0052] Figure 30 It means Figure 1 A diagram showing a modified example of the hot pressing production line 10.

[0053] Figure 31 Viewed from above Figure 30 The top view obtained from the tray 1 shown.

[0054] Figure 32 Observing from the direction of arrow F Figure 31 The side view obtained from the tray shown.

[0055] Figure 33 This indicates the temperature measurement location in Experiment Example 1.

[0056] Figure 34 It is a graph showing the average cooling rate as a result of the measurement.

[0057] Figure 35 It is a graph representing the range of objects derived as the average cooling rate.

[0058] Figure 36 This is a diagram showing the structure of the shielding plate used in Experiment Example 2.

[0059] Figure 37 It is a graph showing the average cooling rate as a result of the measurement.

[0060] Figure 38 It is a graph representing the range of objects derived as the average cooling rate. Detailed Implementation

[0061] In hot pressing, the initial temperature at the start of pressing depends on the heating temperature of the raw material and the temperature drop during the time it takes for the raw material to be conveyed to the pressing die after heating. The heating temperature of the raw material depends on the metallurgical conditions. Furthermore, the conveying time from heating to delivery to the die depends on the equipment structure and specifications. The amount of temperature drop during this conveying period depends on the heat capacity of the raw material. For example, in the case of steel plates, heat is mainly dissipated through heat transfer from the surface and back to the atmosphere and through thermal radiation. The inventors have found that the amount of temperature drop is highly dependent on the thickness of the raw material. That is, as mentioned above, when the thickness of the raw material decreases, even with the same conveying time, the temperature drop is greater, making it sometimes difficult to ensure the forming start temperature required for quenching. As a result, it is possible that the required part strength for the pressed product cannot be obtained.

[0062] The inventors researched a method to suppress temperature drop during transport without using a separate heat source. The research resulted in a structure in which multiple simultaneously heated plate-shaped raw materials (workpieces) are arranged and transported simultaneously in a direction perpendicular to the surface of the plates. According to this structure, the heated workpieces facing each other receive mutual radiant heat, thus compensating for each other's heat. Furthermore, the space between the facing heated workpieces provides a heat-insulating effect due to the retention of air heated by heat transfer from the two workpieces. As a result, temperature drop during transport can be mitigated.

[0063] The inventors have studied a method and apparatus for arranging and conveying multiple heated plate-shaped workpieces in a plane-vertical direction. A conveying device approaches each of the multiple workpieces heated by the heating device from a plane-vertical direction and lifts them, holding the multiple workpieces overlapping in the plane-vertical direction. Furthermore, to suppress temperature drop, it is preferable that the distance between the multiple workpieces during conveying is relatively close and that there is a large overlap in the plane-vertical direction. It is also known that temperature drop near the ends of the multiple workpieces during conveying is easily affected by the distance between the workpieces. Based on the above, in-depth research was conducted, and it was found that suction cups are unsuitable for simple and efficient conveying while suppressing temperature drop. That is, when holding and conveying multiple workpieces with a large overlap in the plane-vertical direction while keeping the distance between the workpieces relatively close, the suction cup can only hold the uppermost workpiece. Furthermore, since heat dissipation caused by the suction cup occurs at the contact area between the suction cup and the workpiece, a temperature drop area equivalent to the contact area of ​​the suction cup is generated. There are limits to the miniaturization of the suction cup for holding and conveying the workpieces. Therefore, when dealing with thinner workpieces, the temperature drop area and amount caused by contact between the discs cannot be ignored in terms of the quality of the quenching of the formed product. The inventors conceived of a structure in which a conveying device has a pair of arms supporting the lower surfaces of the two ends of multiple workpieces can be stably kept close together during transport. Based on this structure, it was found that multiple workpieces can be held under the same conditions regardless of their arrangement, and from the viewpoint of suppressing temperature drop, multiple workpieces can be transported while maintaining them in appropriate positions. Furthermore, according to this structure, lifting and lowering multiple workpieces can be performed efficiently. The following embodiments are based on this insight.

[0064] (Manufacturing Method 1)

[0065] The method for manufacturing a pressed molded article according to an embodiment of the present invention includes: a heating step in which at least two plate-shaped workpieces are simultaneously heated using a heating device; a conveying step in which the at least two heated workpieces, heated in the heating step, are conveyed to a press using a conveying device; and a pressing step in which the at least two heated workpieces conveyed to the press in the conveying step are processed using the press. The conveying step includes the following steps:

[0066] A pair of first arms, which are rotatably mounted on the base of the conveying device, are driven to support and lift the lower surfaces of both ends of the first heated workpiece, one of the at least two heated workpieces, using the claws of the pair of first arms.

[0067] A pair of second arms, which are rotatably mounted on the base of the conveying device, are driven using a system different from that of the pair of first arms. The claws of the pair of second arms are used to support and lift the lower surfaces of both ends of the second heated workpiece, one of the at least two heated workpieces.

[0068] The first heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of first arms of the conveying device, and the second heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of second arms, are conveyed in a state in which they overlap each other in the normal direction of the plate surface of the first heated workpiece.

[0069] Drive the pair of first arms to lower the first heated workpiece supported by the pair of first arms to the pressing position (first pressing position) of the press; and

[0070] The pair of second arms are driven using a system different from that of the pair of first arms, causing the second heated workpiece supported by the pair of second arms to descend to the pressing position (second pressing position) of the press. The first pressing position may also be a position different from the second pressing position.

[0071] In the manufacturing method 1 described above, the first and second heated workpieces are transported while the lower surfaces of both ends are supported by a pair of first-arm claws and the lower surfaces of both ends of the second heated workpiece are supported by a pair of second-arm claws. This allows for the efficient transport of the first and second heated workpieces with mutually efficient heat radiation through a simple device structure. Since the first and second heated workpieces are supported by the first and second claws respectively, the distance between the ends of the two workpieces can be stably maintained. That is, the first and second claws hold the first and second heated workpieces by supporting them from below, allowing their front ends to be formed into a simpler and thinner shape. Furthermore, compared to suction cup-based holding methods, it is easier to hold the workpieces in a closer distance. Moreover, multiple workpieces can be held under the same conditions regardless of their arrangement. Therefore, for example, the area where the first and second heated workpieces overlap in the vertical direction of the surface can be larger, and the gap between the first and second heated workpieces can be stably maintained at a small size. Furthermore, since the first and second arms are driven by different systems, the first and second heated workpieces can be lifted sequentially, and they can also be lowered sequentially to different pressing positions. Thus, in the above manufacturing method, the temperature drop of the first and second heated workpieces can be suppressed, and the conveying process can be simple and efficient. That is, during the conveying time from the heating of the raw material to the start of pressing in hot pressing, the temperature drop of the workpiece (raw material) can be easily mitigated.

[0072] (Manufacturing Method 2)

[0073] In the conveying process of manufacturing method 1 described above, it is preferable that the first heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of first arms, and the second heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of second arms, are conveyed in a state of overlapping each other at an interval of 50 mm or less in the normal direction of the plate surface of the first heated workpiece. This effectively suppresses the temperature drop of the heated workpieces during conveying. If the distance between the heated workpieces is too wide, the proportion of heat radiation emitted from one heated workpiece in the direction inclined relative to the normal of the plate surface at the ends of the first and second heated workpieces that does not reach the other heated workpiece becomes larger. As a result, there is a possibility that the effect of mitigating temperature drop cannot be sufficiently obtained. Furthermore, if the distance between the heated workpieces is too wide, the air heated by heat transfer from the two heated workpieces becomes difficult to retain between them, which may result in insufficient heat preservation.

[0074] In the conveying process of manufacturing method 1 or manufacturing method 2 described above, it is preferable that the first heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of first arms, and the second heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of second arms, are conveyed in a state where they overlap each other at intervals in the normal direction of the plate surface of the first heated workpiece. Thus, during conveying, the upper and lower surfaces of the first and second heated workpieces respectively come into contact with air. Therefore, compared to the case where the first and second heated workpieces are in contact with each other, the difference in conditions between the upper and lower surfaces during conveying is reduced. As a result, the quality difference between the upper and lower surfaces of the first and second heated workpieces can be suppressed.

[0075] Preferably, in the first and second heated workpieces that are conveyed overlapping each other, the support portion of the upper heated workpiece supported by the claws of the arms has a spacing of, for example, 3 mm or more in the normal direction of the plate surface of the first heated workpiece. For example, when the first and second heated workpieces have the same shape when viewed from above and overlap in the normal direction of the plate surface of the first heated workpiece, the claws of the pair of arms supporting the upper heated workpiece are inserted between the upper and lower heated workpieces. Therefore, if the spacing between the heated workpieces is too narrow, the thickness of the portion of the arm supporting the lower surface of the upper heated workpiece needs to be correspondingly thinned. As a result, it may be impossible to maintain the strength of the heated workpiece support. Therefore, the spacing between the first and second heated workpieces can be set to 3 mm to 50 mm, at least in the portion of the upper heated workpiece supported by the claws.

[0076] (Manufacturing Method 3)

[0077] In the conveying process of manufacturing method 1 described above, it is preferable that the maximum distance D (mm) in the normal direction of the plate surface between the first heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of first arms, and the second heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of second arms, and the minimum plate thickness t (mm) of the thinnest portion of the first heated workpiece and the second heated workpiece are in a relationship as follows. This effectively suppresses the temperature drop of the heated workpiece during conveying.

[0078] D≤60t

[0079] (Manufacturing Method 4)

[0080] In any of the manufacturing methods 1 to 3 described above, it is preferable that one of the first heated workpiece and the second heated workpiece, which are conveyed by the conveying device in an overlapping state in the normal direction of the plate surface, has a thicker plate than the other, and a larger area than the other. This allows for efficient suppression of temperature drop in the thinner workpiece.

[0081] (Manufacturing Method 5)

[0082] In the conveying process of any of the manufacturing methods 1 to 4 described above, it is preferable that the first heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of first arms, and the second heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of second arms, are conveyed with their front sides covered by side shielding plates in the conveying direction. The shielding plates prevent air from blowing onto the front surface of the heated workpiece in the conveying direction, thus mitigating the temperature drop starting from the front end of the heated workpiece in the conveying direction and suppressing the movement of stagnant air between the two heated workpieces heated by heat transfer from the two workpieces to the outside, maintaining a heat preservation effect. Therefore, the temperature drop of the heated workpieces during conveying can be further suppressed.

[0083] (Manufacturing Method 6)

[0084] In the manufacturing method 5 described above, it is preferable that the side shielding plate has an inclined surface that is inclined toward the first heated workpiece and the second heated workpiece as it approaches from the center toward the ends. As a result, air encountering the shielding plate flows along the inclined surface in a direction away from the first heated workpiece and the second heated workpiece. Therefore, the effect of suppressing temperature drop of the heated workpiece during transport is improved.

[0085] (Manufacturing Method 7)

[0086] In the conveying process of any of the manufacturing methods 1 to 6 described above, it is preferable that the first heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of first arms, and the second heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of second arms, are conveyed with their upper surfaces covered by an upper shielding plate. Heated air tends to move upwards, therefore, below the lower heated workpiece, the air heated by heat transfer from the lower heated workpiece tends to stagnate, thus achieving a heat-insulating effect on the lower surface of the lower heated workpiece even without the shielding plate. On the other hand, above the upper heated workpiece, the air heated by heat transfer from the upper heated workpiece moves upwards, making it almost impossible to achieve the resulting heat-insulating effect. By providing a shielding plate above the upper heated workpiece, the air heated by heat transfer from the upper heated workpiece can be stagnated between the upper heated workpiece and the upper shielding plate. This stagnant heated air can achieve a heat-insulating effect on the upper surface of the upper heated workpiece. This further improves the effect of suppressing the temperature drop of the heated workpiece on the upper side during conveying.

[0087] The distance between the upper shielding plate covering the top of the first heated workpiece and the top of the second heated workpiece and the heated workpiece supported on the upper side of the first and second heated workpieces in the normal direction of the plate surface is preferably within 200 mm, more preferably within 100 mm. This further improves the temperature drop suppression effect based on the upper shielding plate.

[0088] An upper shielding plate covering the top of both the first and second heated workpieces can also be disposed between the base frame and the upper heated workpiece among the first and second heated workpieces. This allows the upper shielding plate to be positioned near the top of the heated workpiece. Consequently, the temperature drop suppression effect based on the upper shielding plate can be further improved.

[0089] (Manufacturing Method 8)

[0090] In any of the manufacturing methods 5 to 7 described above, at least one of the first heated workpiece and the second heated workpiece may have a long side direction and a short side direction while being conveyed by the conveying device. In this case, the side shielding plate can cover the long side direction of both the first and second heated workpieces during the conveying process. By covering the long side direction with the side shielding plate, the effect of suppressing temperature drop of the heated workpieces during conveying can be further improved.

[0091] (Manufacturing Method 9)

[0092] In any of the manufacturing methods 1 to 8 described above, the first heated workpiece and the second heated workpiece may be differentially thick plates comprising thick-walled and thin-walled portions. In this case, it is preferable that, during the conveying process, the thick-walled portion of the first heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of first arms, and the thin-walled portion of the second heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of second arms, are conveyed in a state where they overlap in the normal direction of the plate surface. Thus, the thick-walled and thin-walled portions compensate for each other's heat, and as a whole, temperature drop can be efficiently suppressed.

[0093] (Manufacturing Method 10)

[0094] In any of the manufacturing methods 1 to 9 described above, the heating process may also involve heating the first heating workpiece in a state where it is placed above the plate-shaped heat storage material and overlaps with the heat storage material in the normal direction of the plate surface of the first heating workpiece, and the second heating workpiece is placed above the heat storage material and overlaps with the heat storage material in the normal direction of the plate surface of the second heating workpiece. The conveying process may also include the following step: conveying the first heating workpiece and the second heating workpiece, which are placed above the heat storage material, together with the heat storage material, from the heating device to a lifting position where they are lifted using the conveying device.

[0095] In the manufacturing method 10 described above, in the heating device, the first and second heated workpieces are heated while overlapping vertically with a plate-shaped heat storage material. After heating, the first and second heated workpieces, together with the heat storage material, are conveyed from the heating device to a lifting position. Therefore, from the time of heating until they are lifted by the conveying device, the first and second heated workpieces are in a state of overlapping vertically with the heat storage material. That is, the first and second heated workpieces overlap with the heat storage material in a direction perpendicular to the plate surface (normal direction) of each heated workpiece. For example, the lower surface of the first heated workpiece and the upper surface of the heat storage material face each other, and the lower surface of the second heated workpiece and the upper surface of the heat storage material face each other. Thus, from the end of heating until they are placed in the lifting position, the first heated workpiece and the heat storage material, and the second heated workpiece and the heat storage material, compensate for each other's heat. From the time they are lifted by the conveying device in the lifting position until they are placed in the pressing position, the first and second heated workpieces can compensate for each other's heat. Furthermore, the first and second heated workpieces are placed above the heat storage material. This allows for a simple and rapid lifting action. As a result, during the hot pressing process, the temperature drop of the raw material can be easily mitigated from the time it is heated until pressing begins. Additionally, the first and second heated workpieces can be conveyed above the heat storage material without overlapping each other in the vertical direction.

[0096] Plate-shaped heat storage materials are not limited to flat plates. For example, plate-shaped heat storage materials can also be plates with protrusions protruding in the direction normal to the plate surface, plates with hollow sections that penetrate the plate, or curved plates, etc.

[0097] In the heating process, the heat storage material may be placed on the tray body, and the first and second heated workpieces may be placed on a first support group of at least three supports extending upwards from the tray body or the heat storage material to a position higher than the upper surface of the heat storage material, and heating may be performed under these conditions. Alternatively, in the conveying process, the heat storage material placed on the tray body, along with the first and second heated workpieces, may be conveyed together with the tray body from the heating device to the lifting position. In this case, when the conveying device lifts the first and second heated workpieces placed on the first support group upwards, the first support group will not become an obstacle. Therefore, the lifting action can be performed simply and quickly.

[0098] The heat storage material may also have upwardly protruding convex portions. In the heating process, the first and second heated workpieces may be heated while respectively placed on the convex portions of the heat storage material. In the conveying process, the first and second heated workpieces may be conveyed from the heating device to the lifting position while still placed on the convex portions of the heat storage material. Thus, the conveying device can easily and quickly perform the action of lifting the workpieces upwards.

[0099] Preferably, the maximum vertical spacing Dc (mm) between the heat storage material and the first heated workpiece, and the maximum vertical spacing between the heat storage material and the second heated workpiece, and the minimum plate thickness t1 (mm) of the thinnest portion of the first and second heated workpieces are related by the following formula. This effectively suppresses temperature drop in the first and second heated workpieces during transport.

[0100] Dc≤120t1

[0101] The minimum plate thickness t1 (mm) of the thinnest portion of the first heated workpiece and the second heated workpiece, and the minimum plate thickness t2 (mm) of the thinnest portion of the heat storage material can also be expressed by the following formula. This effectively suppresses the temperature drop of the workpiece.

[0102] 0.8≤t2 / t1≤20

[0103] (Manufacturing Method 11)

[0104] In any of the manufacturing methods 1 to 9 described above, in the heating process, the first heated workpiece is placed on a first support group of at least three supports extending upward from a tray body having a hollow portion that runs vertically through when viewed from above; the second heated workpiece is placed on a second support group of at least three supports extending upward from the tray body; and the second heated workpiece is positioned above the first heated workpiece, overlapping the first heated workpiece in the normal direction of the surface of the first heated workpiece. In this state, heating is performed using the heating device. In the conveying process, the following steps may also be included: the first heated workpiece is placed on the first support group; the second heated workpiece is placed on the second support group; and the second heated workpiece is positioned above the first heated workpiece, overlapping the first heated workpiece in the normal direction of the surface of the first heated workpiece. In this state, the workpiece, together with the tray body, is conveyed from the heating device to a lifting position where it is lifted using the conveying device.

[0105] In the manufacturing method 11 described above, the first and second heated workpieces are heated in a state of vertical overlap using the support assembly of the tray in the heating device. After heating, the first and second heated workpieces, together with the tray, are conveyed from the heating device to the lifting position. Therefore, from the time they leave the heating device until they are lifted by the conveying device, the first and second heated workpieces are in a state of vertical overlap. That is, the first and second heated workpieces overlap in a direction perpendicular to the surface of the first heated workpiece (normal direction). For example, the upper surface of the first heated workpiece and the lower surface of the second heated workpiece are facing each other. Thus, from the time heating ends until the conveying device lifts them, and further from the time the conveying device lifts them until they are placed in the pressing position, the first and second heated workpieces are subjected to radiant heat from each other, thereby compensating for each other's heat. In addition, the first heated workpiece is placed in the first support assembly, and the second heated workpiece is placed on top of it in the second support assembly. The support assembly is formed extending upward from the tray body. Therefore, when the second and first heated workpieces placed on the support assembly are lifted sequentially or simultaneously using the conveyor, the support assembly will not become an obstacle. The lifting action can be performed simply and quickly. As a result, during the conveying time in hot pressing from the time the raw material is heated until the pressing begins, the temperature drop of the raw material can be easily mitigated.

[0106] Preferably, in the heating process and the conveying process, the maximum vertical distance Dt (mm) between the first heated workpiece placed in the first support group and the second heated workpiece placed in the second support group, and the minimum plate thickness t (mm) of the thinnest portion of the first heated workpiece and the second heated workpiece are related by the following formula. This effectively suppresses temperature drops in both the first and second heated workpieces during conveying.

[0107] Dt≤120t

[0108] From the same point of view, it is more preferable that Dt ≤ 100t, and even more preferably that Dt ≤ 60t. In addition, the distance between the first heated workpiece placed in the first support group and the second heated workpiece placed in the second support group is preferably 100mm or less, and more preferably 50mm or less.

[0109] (Structure 1)

[0110] The heated workpiece conveying device in an embodiment of the present invention comprises: a base frame capable of lateral movement perpendicular to the vertical direction; a pair of first arms rotatably mounted on the base frame; a pair of second arms rotatably mounted on the base frame; a first drive unit for driving the first arms; and a second drive unit for driving the second arms.

[0111] The pair of first arms have: a pair of first bases arranged laterally on the base frame and extending from the base frame in a vertical direction; and a first claw extending laterally curved from the pair of first bases respectively.

[0112] The pair of second arms have: a pair of second bases arranged laterally on the base frame and extending from the base frame in a vertical direction; and second claws extending laterally curved from the pair of second bases respectively.

[0113] The first drive unit changes the lateral distance of the pair of first claws by rotating the pair of first arms relative to the base frame.

[0114] The second drive unit changes the lateral distance of the pair of second claws by rotating the pair of second arms relative to the base frame.

[0115] The first drive unit and the second drive unit are configured to independently control the rotation of the first arm and the rotation of the second arm, respectively.

[0116] The pair of first claws are configured to support the lower surfaces of the lateral ends of the first heated workpiece in a state in which they are brought close to each other in the lateral direction.

[0117] The pair of second claws are configured to support the lower surfaces of the two lateral ends of the second heated workpiece in a state in which they are close to each other in the lateral direction.

[0118] The positions of the first pair of claws in the vertical direction and the positions of the second pair of claws in the vertical direction are different from each other.

[0119] The aforementioned conveying device transports the first heated workpiece in a configuration where the lower surfaces of both ends of the first heated workpiece are supported by the claws of a pair of first arms, and the lower surfaces of both ends of the second heated workpiece are supported by the claws of a pair of second arms. This ensures a stable interval between the two heated workpieces during transport. Furthermore, by rotating the first and second arms, the first and second claws are positioned on the lower surfaces of both ends of the heated workpieces, allowing for simple and reliable lifting and lowering of the heated workpieces. In other words, with this simple device structure, the first and second heated workpieces can be transported in a manner where they are efficiently subjected to heat radiation from each other. Additionally, the first drive unit drives the first arm, and the second drive unit drives the second arm independently, i.e., through another system. Therefore, the first and second heated workpieces can be lifted sequentially, and they can also be lowered sequentially to different pressing positions. Thus, in this conveying device, temperature drops in both the first and second heated workpieces can be suppressed, and transport can be performed simply and efficiently. Therefore, during the conveying time from the heating of the raw material to the start of pressing in hot pressing, the temperature drop of the workpiece (raw material) can be easily mitigated.

[0120] The lateral direction of the base frame is a direction in a plane perpendicular to the vertical direction. The lateral directions of a pair of first arms and a pair of second arms can be the same or different in a plane perpendicular to the vertical direction. Alternatively, the base frame can move in both the vertical and lateral directions.

[0121] (Structure 2)

[0122] In the above structure 1, it is preferable that, in the vertical direction, the pair of first claws and the pair of second claws are separated by a distance of 0mm to 50mm beyond the maximum thickness of the heated workpiece supported by the lower claw of the first and second claws. This effectively suppresses temperature drop of the heated workpiece during transport. For example, assuming the thickness of the heated workpiece varies by 1mm to 3mm within a single heated workpiece, and the maximum thickness of the heated workpiece is 3mm, it is preferable that the pair of first claws and the pair of second claws are separated by a distance of 3mm to 53mm in the vertical direction.

[0123] (Structure 3)

[0124] In structure 1 or 2 described above, the conveying device for the heated workpiece may also include a side shielding plate that laterally covers both the pair of first claws and the pair of second claws. The side shielding plate can suppress the movement of heated, stagnant air between the two heated workpieces to the outside and maintain a heat-insulating effect, thus further suppressing the temperature drop of the heated workpieces during conveying.

[0125] (Structure 4)

[0126] In structure 3 described above, the side shielding plate may have a surface that is inclined toward the pair of first claws and the pair of second claws as it approaches from the center toward the ends. Therefore, during the transport of the heated workpiece, the air encountering the side shielding plate flows away from the heated workpiece along the inclined surface. Consequently, the effect of suppressing temperature drop of the heated workpiece during transport is improved.

[0127] (Structure 5)

[0128] In structures 1 to 4 described above, the conveying device for the heated workpiece may also include an upper shielding plate that covers the space between the pair of first arms and the space between the pair of second arms from above. This allows air heated by heat transfer from the upper heated workpiece to be trapped between the upper heated workpiece and the upper shielding plate. As a result, the temperature drop suppression effect of the upper heated workpiece during conveying can be further improved. Preferably, the upper shielding plate, when viewed from above, at least partially overlaps with each of the pair of first claws and the pair of second claws. Thus, the upper surface of the first and second heated workpieces supported by the first and second claws is covered by the upper shielding plate. Therefore, the temperature drop suppression effect based on the upper shielding plate can be further improved. More preferably, when viewed from above, the upper shielding plate extends to a range wider than the pair of first arms and the pair of second arms. In this case, the upper shielding plate extends beyond the range observed from above when the pair of first arms and the pair of second arms are in a closed state. Alternatively, the upper shielding plate can be connected to the side shielding plates. Furthermore, the upper shielding plate is not limited to a flat plate; for example, it can also have a shape that matches the shape of the heated workpiece being conveyed (e.g., an intermediate formed product).

[0129] Preferably, the vertical distance between the upper shielding plate covering both the pair of first and second claws and the upper claw of the first and second claws is, for example, within 200 mm of the maximum thickness of the heated workpiece supported by the upper claw of the first and second claws. More preferably, this distance is within 100 mm of the maximum thickness. This further improves the temperature drop suppression effect based on the upper shielding plate. For example, assuming the thickness of the heated workpiece varies by 1 mm to 3 mm within a single heated workpiece, the maximum thickness of the heated workpiece is 3 mm. Therefore, it is preferable that the vertical distance between the upper shielding plate covering both the pair of first and second claws and the upper claw of the first and second claws is within 203 mm, and more preferably, within 103 mm.

[0130] An upper shielding plate covering the top of the first claw and the top of the second claw can also be disposed between the base frame and the upper claw of the first and second claws. This allows the upper shielding plate to be positioned near the top of the heated workpiece supported by the claws. As a result, the temperature drop suppression effect based on the upper shielding plate can be further improved.

[0131] (Structure 6)

[0132] In any of the structures 1 to 5 described above, the base frame can also be configured to rotate 180 degrees about the vertical axis. This allows, for example, the orientation of the first heated workpiece supported by the claw of the first arm and the second heated workpiece supported by the claw of the second arm to be changed by 180 degrees. This allows, for example, in the case where the heated workpiece is a plate of varying thickness, the first and second heated workpieces to be held with their orientation changed by 180 degrees. This allows, for example, the workpieces to be held such that the thin-walled portion of one of the first and second heated workpieces overlaps with the thick-walled portion of the other.

[0133] (Structure 7)

[0134] In any of the structures 1 to 6 described above, the distance between the pair of first claws and the pair of second claws in the vertical direction can be adjusted. This allows the interval between the first and second heated workpieces during transport to be adjusted according to the workpiece's thickness, material, and other conditions.

[0135] (Structure 8)

[0136] In any of the structures 1 to 7 described above, the conveying device for the heated workpiece may also include: a pair of third arms rotatably mounted on the base frame; a pair of fourth arms rotatably mounted on the base frame; a third drive unit for driving the third arms; and a fourth drive unit for driving the fourth arms.

[0137] The pair of third arms have: a pair of third bases arranged in the transverse direction of the base frame and in a direction perpendicular to the arrangement direction of the pair of first bases, and extending from the base frame in a vertical direction; and third claws extending laterally curved from the pair of third bases respectively.

[0138] The pair of fourth arms have: a pair of fourth bases arranged in the transverse direction of the base frame and in a direction perpendicular to the arrangement direction of the pair of second bases, and extending from the base frame in a vertical direction; and fourth claws extending laterally curved from the pair of fourth bases respectively.

[0139] The third drive unit changes the lateral distance of the pair of third claws by rotating the pair of third arms relative to the base frame.

[0140] The fourth drive unit changes the lateral distance of the pair of fourth claws by rotating the pair of fourth arms relative to the base frame.

[0141] The positions of the first pair of claws in the vertical direction are the same as those of the third pair of claws in the vertical direction.

[0142] The positions of the pair of second claws in the vertical direction are the same as those of the pair of fourth claws in the vertical direction.

[0143] According to the above structure, the first heated workpiece and the second heated workpiece can be supported at four locations.

[0144] (Structure 9)

[0145] The hot pressing production line in embodiments of the present invention includes: a conveying device for heated workpieces of any of structures 1 to 8 described above; a heating device for heating the first heated workpiece and the second heated workpiece; a platform for placing the first heated workpiece and the second heated workpiece heated by the heating device; at least one press having at least two pairs of molds; and a moving device for moving the conveying device between a position above the platform and a pressing position between the at least two pairs of molds. The heated workpiece is pressed and formed using a pair of molds. The pair of molds are brought close together with the heated workpiece positioned between them, thereby pressing and forming the heated workpiece. It is possible that one press has at least two pairs of molds, or that at least two presses each have one pair of molds.

[0146] (Structure 10)

[0147] Alternatively, the hot pressing production line of structure 9 described above may also include a tray that supports the first and second heated workpieces when they are heated by the heating device. The tray comprises: a tray body; a plate-shaped heat storage material placed on the tray body; and a first support group of at least three supports extending upward from the tray body or the heat storage material. The first support group is configured such that, when viewed from above, the virtual straight lines connecting the supports form at least one triangle. Alternatively, the tray may have a protrusion in the heat storage material that projects upward from the heat storage material and is capable of supporting the first and second heated workpieces, instead of the first support group. The first support group may also be fixed relative to the tray body or the heat storage material.

[0148] (Structure 11)

[0149] Alternatively, the hot pressing production line of structure 9 described above may also include a tray that supports the first and second heated workpieces when they are heated by the heating device. Alternatively, the tray may include: a tray body having a shape extending along a surface perpendicular to the vertical direction, including a hollow portion extending vertically; and a support assembly extending upward from the tray body. Alternatively, the support assembly may include: a first support assembly of at least three supports configured to support the lower surface of the plate-shaped first heated workpiece; and a second support assembly of at least three supports configured to support the lower surface of the second heated workpiece located above the first heated workpiece supported by the first support assembly. The first support assembly is configured such that, when viewed from above, the virtual straight lines connecting the supports form at least one triangle. The second support group is positioned differently from the first support group when viewed from above, and is configured such that, when viewed from above, the virtual straight lines connecting the supports form at least one triangle, and each support in the second group is taller than the lowest support in the first support group. The first and second support groups may also be fixed relative to the tray body.

[0150] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same or equivalent parts in the drawings will be labeled with the same reference numerals, and their descriptions will not be repeated. The dimensional ratios between the constituent components shown in the figures do not necessarily represent actual dimensional ratios.

[0151] (Implementation Method 1)

[0152] [Example of device structure]

[0153] Figure 1 This is a schematic top view showing the hot pressing production line 10 of this embodiment. The hot pressing production line 10 includes a material table 12, a heating device 14, conveyor tables 16 and 17, a press 20, operators 41, 42, and 44, a conveying device 46, a forming table 18, and a controller 22. The end of the conveyor table 16 is connected to the outlet 14A of the heating device 14. The end of the conveyor table 17 is connected to the inlet 14B of the heating device 14. The material table 12 is arranged on the side of the conveyor table 17 opposite to the heating device 14. The forming table 18 is arranged on the side of the press 20 opposite to the conveyor table 16.

[0154] (Materials table, molded parts table)

[0155] Material table 12 is a table for holding materials before pressing. For example, a blank 24 obtained by cutting a flat steel plate into a predetermined shape is placed on material table 12. Forming table 18 is a table for holding pressed and formed articles. For example, a pressed and formed article formed by press 20 is placed on forming table 18.

[0156] (Heating device)

[0157] The heating device 14 is a device for heating an object (workpiece). Examples of heating devices 14 include resistance heating furnaces, gas heating furnaces, far-infrared heating furnaces, and near-infrared heating furnaces. The heating device 14 is not limited to a heating furnace; for example, it may be a high-frequency induction heating device, a low-frequency induction heating device, or an electrically powered heating device that directly heats the object by energizing it. The heating device 14 may also have a heating chamber. In the heating device 14, multiple indoor rollers driven to rotate by a drive mechanism (not shown) may be provided inside the heating chamber. By rotating the indoor rollers, the object to be heated on the indoor rollers is conveyed.

[0158] (Conveyor Platform)

[0159] Conveyor tables 16 and 17 are equipped with multiple conveyor rollers 26 that are driven to rotate by a drive mechanism (not shown). Each conveyor roller 26 rotates synchronously with the inner roller, thereby enabling the conveying of the object (heated workpiece) between the conveyor tables 16 and 17 and the heating chamber of the heating device 14. The multiple conveyor rollers 26 are arranged at intervals. The conveyor table 16 is an example of a table for placing a heated workpiece heated by the heating device. In addition, the conveyor table 16 is also an example of a conveying path for conveying the heated workpiece from the heating device to a lifting position. In this example, the conveyor table 16 becomes the lifting position where the heated workpiece is lifted by the conveying device 46. Furthermore, the structure of the conveying path is not limited to... Figure 1 The conveyor platform 16 is shown. For example, the conveying path could also be a conveyor belt or track, etc. Additionally, in Figure 1 In the example shown, the lifting position is located on the conveyor path, but the lifting position may not be located on the conveyor path. The platform can also be set as the lifting position independently of the conveyor path.

[0160] (Press machine)

[0161] The press 20 includes a lower die and an upper die for pressing and forming an object. The lower die, for example, is composed of a punch, and the upper die, for example, is composed of a die. Refrigerant flow paths can also be provided in the upper and lower dies. This allows the heat taken from the object during pressing to be released via the refrigerant. Two heated workpieces can be positioned between the upper and lower dies. The upper and lower dies can move relative to each other. In the press 20, the upper and lower dies are brought close together with two heated workpieces positioned between them, thereby pressing and forming the two heated workpieces. The movement of the upper and lower dies can be controlled, for example, by a controller 22. In this example, the lower and upper dies of the press 20 are configured to simultaneously produce multiple pressed and formed articles. This is an example of a single press equipped with two sets of paired dies. In this example, multiple workpieces are positioned between the lower and upper dies of the press 20, and these workpieces are pressed simultaneously. Alternatively, multiple presses can be installed. For example, two presses equipped with a set of paired dies can also be used.

[0162] (Manipulator)

[0163] The manipulator 44 uses a conveying device 46 to transport the workpiece between the conveyor table 16 and the press 20. The conveying device 46 performs actions such as lifting, holding, and placing the workpiece as the transport object. The manipulator 44 controls the position and orientation of the conveying device 46. The conveying device 46 can also be the end effector of the manipulator 44. The manipulator 44 moves the conveying device 46 between a position above the conveyor table 16 and a position between two pairs of molds (upper mold and lower mold) of the press 20. The manipulator 44 includes: a base that can rotate about at least one axis; and an arm that extends from the base and has at least one joint. The conveying device 46 is rotatably mounted at the end of the arm. Furthermore, the moving device that moves the conveying device 46 is not limited to the manipulator. For example, the moving device can also be a structure including a track connecting the conveyor table 16 and the press 20, and a suspension device that movably suspends the conveying device 46 vertically along the track. Figure 1 In the example shown, there is a manipulator 41 that moves the workpiece from the material table 12 to the conveyor table 17, and a manipulator 42 that removes the workpiece from the press 20 and places it on the forming table 18.

[0164] (Controller)

[0165] The controller 22 controls the heating device 14, conveyor tables 16 and 17, press 20, and manipulators 41, 42, and 44. The controller 22 may be configured as a control system including at least one computer. As an example, the controller 22 may also include control units (e.g., composed of circuitry or a processor) located at the heating device 14, conveyor tables 16 and 17, manipulators 41, 42, and 44, and press 20, respectively, to control each device. In this case, the controller 22 may also include an overall control computer that supplies control information to the control units of each device, controlling the overall operation of the hot pressing production line 10. The movement of the arm of the conveyor 46 (described later) may also be controlled by a part of the controller 22, such as the control unit of the manipulator 44.

[0166] (Conveying device)

[0167] Figure 2A It means Figure 1 A side view of the structure of the conveying device 46 as seen from the transverse (y direction). Figure 2B It means Figure 2A The diagram shows the second arm 72 of the conveyor 46 in the state of being opened outwards. Figure 3 It means Figure 1 A side view of the structure of the conveying device 46 as seen from the transverse (x direction).

[0168] (Framework)

[0169] exist Figure 2A and Figure 2B In the example shown, the conveying device 46 includes a base 48, a pair of first arms 71 and a pair of second arms 72 rotatably mounted on the base 48. When viewed from above, the base 48 is rectangular in shape (see reference). Figure 1 In this example, the vertical direction is defined as the z-direction. The direction within the plane perpendicular to the vertical direction is defined as the horizontal direction. Within the horizontal direction, the long side direction of the base frame 48 is defined as the y-direction, and the short side direction of the base frame 48 is defined as the x-direction.

[0170] A connector 56 is provided on the upper surface of the base frame 48 and is connected to the actuator 44. The connector 56 is connected so that the base frame 48 can rotate relative to the actuator 44 about the vertical axis.

[0171] (Arm 1 and Arm 2)

[0172] A pair of first arms 71 are separately arranged laterally (x-direction). Each pair of first arms 71 has a first base 71a extending vertically from the base 48 and a first claw 71b extending laterally from the first base 71a. Each first arm 71 is rotatably mounted on the base 48 about a rotation axis 60 in the y-direction. One end of the first base 71a is rotatably connected to the base 48 relative to the base 48, and the first claw 71b extends from the other end of the first base 71a.

[0173] A pair of second arms 72 are separately arranged laterally (x-direction). Each pair of second arms 72 has a second base 72a extending vertically from the base 48, and a second claw 72b extending laterally from the second base 72a. Each second arm 72 is rotatably mounted on the base 48 about a rotation axis 60 in the y-direction. One end of the second base 72a is rotatably connected to the base 48 relative to the base 48, and the second claw 72b extends from the other end of the second base 72a.

[0174] The vertical positions of the first claw 71b and the second claw 72b are different from each other. Figure 2A and Figure 2B In the example shown, the first base 71a is shorter than the second base 72a in the vertical direction. The first claw 71b is located closer to the base 48 than the second claw 72b.

[0175] Preferably, in the vertical direction, the pair of first claws 71b and the pair of second claws 72b are separated by a distance of 0 mm to 50 mm based on the maximum thickness of the second heated workpiece W2 supported by the lower second claw 72b. That is, preferably, the interval D between the first heated workpiece W1 supported by the first claw 71b and the second heated workpiece W2 supported by the second claw 72b is 0 mm to 50 mm. For example, when the thickness of the second heated workpiece W2 varies within the second heated workpiece W2 by 1 mm to 3 mm, it is preferable that the distance H between the pair of first claws 71b and the pair of second claws 72b in the vertical direction is 3 mm to 53 mm (the range of interval D plus the maximum thickness of the second heated workpiece W2, 3 mm). Furthermore, the distance H is the distance between the first claw 71b and the second claw 72b when the pair of first claws 71b supports the lower surface of the first heated workpiece and the pair of second claws 72b supports the lower surface of the second heated workpiece. The distance H is set as the vertical distance between the upper ends of the first claw 71b and the upper ends of the second claw 72b.

[0176] From the viewpoint that the first heated workpiece W1, supported by a pair of first jaws 71b, and the second heated workpiece W2, supported by a pair of second jaws 72b, are subject to mutual thermal radiation to suppress temperature drop, a closer interval D (distance H) is preferable. An interval D is more preferably 30 mm or less, further preferably 20 mm or less, and even more preferably 10 mm or less.

[0177] It is also possible for a portion to have a gap D of 0. That is, at least a portion of the first heated workpiece W1 supported by the first claw 71b and at least a portion of the second heated workpiece W2 supported by the second claw 72b can also be in contact (specific examples described later). Additionally, as... Figure 2A In one example, a situation exists where the first claw 71b supporting the first heated workpiece W1 is inserted between the first heated workpiece W1 and the second heated workpiece W2 supported by the second claw 72b. In such a case, for example, the lower limit of the claw thickness can be set as the lower limit of the interval D. The lower limit of the claw thickness depends on the required claw strength. From this point of view, the lower limit of the interval D is preferably, for example, 3 mm, and more preferably 5 mm.

[0178] exist Figure 2A and Figure 2B In the example shown, the rotation axis 60 of the first arm 71 and the rotation axis 60 of the second arm 72 are coaxial. This allows the first arm 71 and the second arm 72 to be efficiently configured on the base 48. Alternatively, the rotation axis 60 of the first arm 71 and the rotation axis 60 of the second arm 72 can also be non-coaxial.

[0179] (Drive Department)

[0180] A pair of second arms 72 are driven by a second drive unit. The second drive unit rotates the pair of second arms 72 relative to the base frame 48, thereby changing the lateral (x-direction) distance of the pair of second claws 72b. Figure 2A and Figure 2B In the example shown, the second drive unit is composed of actuators 82 disposed relative to each of the second arms 72.

[0181] The actuator 82 is, for example, a cylinder. The actuator 82 adjusts the extension of the axially moving working shaft 82A. A pin 82B is provided at the end of the working shaft 82A. The pin 82B is freely movable and rotatable into the elongated hole of the connecting rod 90 fixed in the second arm 72.

[0182] like Figure 2A As shown, when each actuator 82 extends the working shaft 82A, the corresponding second arm 72 extends downward, and the pair of second claws 72b of the pair of second arms 72 become closed by bringing them close together. Additionally, as... Figure 2BAs shown, when each actuator 82 retracts the working shaft 82A, the pair of second claws 72b of the pair of second arms 72 move away from each other and become open.

[0183] A pair of first arms 71 are driven by a first drive unit. The first drive unit rotates the pair of first arms 71 relative to the base frame 48, thereby changing the lateral (x-direction) distance of the pair of first claws 71b. The first drive unit driving the first arms 71 can also be configured, for example, to have... Figure 2A and Figure 2B The actuator 82 shown has the same structure as the actuator shown. The pair of first arms 71 are also controlled by the first drive unit to: the pair of first claws 71b are brought close together in a closed state (see reference). Figure 2A Alternatively, the pair of first claws 71b may be in an open state, moving away from each other from a closed state. Furthermore, the actuators for the first and second drive units are not limited to cylinders; for example, they may be electric motors or hydraulic cylinders.

[0184] A pair of first jaws 71b can support the lower surfaces of the two lateral ends of the first heated workpiece W1 in a closed state, where they are close to each other in the lateral direction. A pair of second jaws 72b can support the lower surfaces of the two lateral ends of the second heated workpiece W2 in a closed state, where they are close to each other in the lateral direction.

[0185] (The 3rd and 4th arms)

[0186] exist Figure 2A , Figure 2B and Figure 3 In the example shown, a pair of third arms 73 and a pair of fourth arms 74 are rotatably mounted on the base frame 48. Additionally, although not shown, a third drive unit for driving the pair of third arms 73 and a fourth drive unit for driving the pair of fourth arms 74 are provided on the base frame 48. Furthermore, in Figure 3 The illustrations of the first to fourth drive units are omitted in the text.

[0187] A pair of third arms 73 are arranged in a direction perpendicular to the arrangement direction (x-direction) of a pair of first arms 71 (see reference). Figure 3 Each third arm 73 is rotatably mounted on the base 48 about a rotation axis 62 in a direction perpendicular to the rotation axis 60 of the first arm (x-direction). Each third arm 73 can be constructed in the same manner as each first arm 71. Each third arm 73 has a third base 73a and a third claw 73b. The lower surface of the first heated workpiece W1 is supported by a pair of third claws 73b and a pair of first claws 71b. In this example, the distance of the third claw 73b from the base 48 is approximately the same as the distance of the first claw 71b from the base 48. This is an example when the first heated workpiece W1 is a flat plate.

[0188] A pair of fourth arms 74 are arranged in a direction perpendicular to the arrangement direction (x-direction) of a pair of second arms 72 (see reference). Figure 3 Each fourth arm 74 is rotatably mounted on the base 48 about a rotation axis 62 in a direction perpendicular to the rotation axis 60 of the second arm (x-direction). Each fourth arm 74 can be constructed in the same manner as each second arm 72. Each fourth arm 74 has a fourth base 74a and a fourth claw 74b. The lower surface of the second heated workpiece W2 is supported by a pair of fourth claws 74b and a pair of second claws 72b. In this example, the distance of the fourth claw 74b from the base 48 is approximately the same as the distance of the second claw 72b from the base 48. This is an example when the second heated workpiece W2 is a flat plate.

[0189] (Control system)

[0190] Figure 4 This is a diagram used to explain an example of the control system for the first to fourth drive units. Figure 4 This illustrates an example of the configuration of the first to fourth drive units at base frame 48. Figure 4 In the example shown, four actuators 81 of the first drive unit, four actuators 82 of the second drive unit, two actuators 83 of the third drive unit, and two actuators 84 of the fourth drive unit are disposed on the upper surface of the base frame. The actuators 81 of the first drive unit and the actuators 83 of the third drive unit are controlled by a first control system. The actuators 82 of the second drive unit and the actuators 84 of the fourth drive unit are controlled by a second control system.

[0191] For example, actuators 81 and 83 are controlled by the same control signal, and actuators 82 and 84 are controlled by the same control signal. When actuators 81 to 84 are cylinders, for example, the control valves of actuators 81 and 83 may be shared, and the control valves of actuators 82 and 84 may also be shared.

[0192] According to the above structure, the first arm 71 and the second arm 72 are driven by different systems. That is, the rotation of the first arm 71 and the rotation of the second arm 72 are controlled independently of each other. Furthermore, the third arm 73 and the fourth arm 74 are also driven by different systems. The first arm 71 and the third arm 73 are driven by the same system. The second arm 72 and the fourth arm 74 are driven by the same system. Alternatively, the first arm 71 and the third arm 73 can also be driven by different systems. The second arm 72 and the fourth arm 74 can also be driven by different systems.

[0193] [Example of manufacturing process for pressed molded products]

[0194] An example of a process for manufacturing a pressed product using the hot pressing production line 10 described above will be explained. The manufacturing process of the pressed product in this embodiment includes: a heating process for heating the workpiece, a conveying process for conveying the heated workpiece, and a pressing process for pressing the heated workpiece.

[0195] (Heating process)

[0196] Figure 5 This diagram illustrates an example of a heating process. In this process, at least two plate-shaped workpieces W1 and W2 are simultaneously heated using heating device 14. Here, for the simultaneous heating of multiple workpieces, it is sufficient that the heating of all workpieces ends simultaneously; the start of heating does not necessarily have to be simultaneous. Furthermore, besides the case where the heating of multiple workpieces ends strictly simultaneously, cases where the ending times are slightly different are also included in the simultaneous heating of multiple workpieces. For example, even if there is a slight difference in the time required for the conveyor 46 to lift the heated workpiece, from the viewpoint of the temperature drop of the workpiece during conveying, it can be considered approximately simultaneous. After heating, the heated workpiece is conveyed out of heating device 14 by the rotation of roller 13 of heating device 14 and the rotation of conveyor roller 26 of conveyor table 16.

[0197] (Conveying process)

[0198] The conveying process includes: a process in which the conveying device 46 lifts the first heated workpiece W1, a process in which the conveying device 46 lifts the second heated workpiece W2, a process in which the first heated workpiece W1 and the second heated workpiece W2 are conveyed, a process in which the first heated workpiece W1 is lowered to the pressing position, and a process in which the second heated workpiece W2 is lowered to the pressing position.

[0199] Figure 6 This diagram illustrates an example of the process by which the conveyor 46 lifts the first heated workpiece W1. A pair of first arms 71, rotatably mounted on the base of the conveyor 46, are driven, using the claws of the first arms 71 to support and lift the lower surfaces of both ends of the first heated workpiece W1. At this time, the first arms 71 and the second arms 72 are opened, and the conveyor 46 is lowered, approaching the first heated workpiece W1 on the conveyor roller 26 of the conveyor table 16. The first arms 71 are rotated to a closed state, thereby causing the first claws of the first arms 71 to penetrate below the lower surfaces of both ends of the first heated workpiece W1. In this state, by raising the conveyor 46, the lower surfaces of both ends of the first heated workpiece W1 are supported and lifted using the first claws of the first arms 71.

[0200] Figure 7This diagram illustrates an example of the process by which the conveying device 46 lifts the second heated workpiece W2. In the conveying device 46, with the lower surface of the first heated workpiece W1 supported and held by a pair of first arms 71, a pair of second arms 72 are driven to lift the second heated workpiece W2. Similarly to the lifting action of the first heated workpiece W1, the lower surfaces at both ends of the second heated workpiece W2 are supported and lifted using the grippers of the pair of second arms 72.

[0201] Figure 8 The left side shows an example of the state in which the conveying device 46 conveys the first heated workpiece W1 and the second heated workpiece W2. In the conveying device 46, the first heated workpiece W1, whose lower surface is supported by a pair of claws of the first arm 71, and the second heated workpiece W2, whose lower surface is supported by a pair of claws of the second arm 72, are conveyed in a state in which they overlap each other in the normal direction of the plate surface of the first heated workpiece W1.

[0202] In the conveying process, it is preferable that the distance D between the first heated workpiece W1 supported by a pair of first arms 71 and the second heated workpiece W2 supported by a pair of second arms 72 in the normal direction of the plate surface of the first heated workpiece W1 is 0 mm to 50 mm. From the viewpoint that the first heated workpiece W1 supported by a pair of first claws 71b and the second heated workpiece W2 supported by a pair of second claws 72b are subject to mutual heat radiation to suppress temperature drop, and from the viewpoint that the air heated by heat transfer from the two heated workpieces and retained between the first heated workpiece W1 and the second heated workpiece W2 provides a heat preservation effect, a smaller distance D is preferable. The distance D is more preferably 30 mm or less, more preferably 20 mm or less, and even more preferably 10 mm or less. A portion where the distance D is 0 is also possible. In addition, for example, the lower limit of the thickness of the claws can be set as the lower limit of the distance D. From this viewpoint, the lower limit of the distance D is preferably 3 mm, more preferably 5 mm.

[0203] Furthermore, the interval D is equivalent to the value obtained by subtracting the thickness of the second heated workpiece W2 from the vertical distance H between the first claw 71b of the first arm 71 and the second claw 72b of the second arm 72. In the case where the thickness of at least one of the first heated workpiece W1 and the second heated workpiece W2 is uneven, the interval D is defined as the largest interval in the normal direction in the overlapping area when viewed from above. Preferably, the interval D (mm) and the minimum thickness t (mm) of the thinnest portion of both the first heated workpiece W1 and the second heated workpiece W2 are in a relationship of D ≤ 60t, more preferably D ≤ 40t.

[0204] Figure 8The right side illustrates an example where the conveyor 46 lowers the second heated workpiece W2 to the pressing position. The conveyor 46 moves to the pressing position of the second heated workpiece W2. In the conveyor 46, with the lower surface of the first heated workpiece W1 supported and held by a pair of first arms 71, the pair of second arms 72 are driven to open, causing the second heated workpiece W2 to descend to the pressing position of the press 20. Afterward, the conveyor 46 moves to the pressing position of the first heated workpiece W1, and the pair of first arms 71 are driven to open, causing the first heated workpiece W1 to descend to the pressing position of the press.

[0205] exist Figure 8 The example shown illustrates two workpieces positioned on the upper die 21 and lower die 23 of a single press, with both workpieces being pressed simultaneously. In this case, the first heated workpiece W1 and the second heated workpiece W2 are lowered to different pressing positions between the upper die 21 and the lower die 23, respectively. The manner in which the conveying device 46 lowers the two held heated workpieces to their respective pressing positions is not limited to this. For example, it could also be that the first heated workpiece W1 and the second heated workpiece W2 are lowered to their respective pressing positions on two separate presses.

[0206] exist Figure 8In the example shown, the second heated workpiece W2 is lowered to the pressing position of the lower mold 23 and positioned in contact with the upper part of the lower mold 23. The arrangement of the first heated workpiece W1 and the second heated workpiece W2 on the lower mold 23 is not limited to this. For example, although not shown, a plunger pin or similar device can be provided at the position where the heated workpiece is positioned on the lower mold 23, and the heated workpiece can be positioned on the plunger pin. That is, the heated workpiece can be supported at a position slightly higher than the upper surface of the pressure surface of the lower mold 23, maintaining it in a floating state from the pressure surface. This prevents the heated workpiece from continuously contacting the lower mold 23 from the time it is positioned on the lower mold until the forming of the heated workpiece begins from the upper mold 21 and the lower mold 23. This also prevents the temperature of the heated workpiece from unexpectedly and locally dropping significantly before forming begins. Typically, the contact area between the plunger pin and the heated workpiece is small, so even when the plunger pin is in contact with the heated workpiece, the temperature of the heated workpiece will not drop significantly. Furthermore, when force is applied to the plunger pin via the heated workpiece from the upper die 21, the plunger pin is immediately retracted into the lower die 23, thus not obstructing the pressing and forming of the heated workpiece. The plunger pin is a movable protrusion configured to protrude upward from the upper surface of the pressure surface of the lower die 23 when the heated workpiece is positioned, and to be retracted into the lower die 23 at the lower stop point. The structure for positioning the heated workpiece at intervals relative to the pressure surface of the lower die 23 is not limited to the structure using the movable protrusion. For example, a buffer member may be provided in the press 20 to hold the heated workpiece in a position that does not contact the lower die 23 or the upper die 21 before forming.

[0207] [Materials for the heated workpiece]

[0208] The material of the workpiece to be heated can be any formable metal. However, the material is not limited to this; examples include Fe-based carbon steel, stainless steel, Al-based materials, and Ti-based materials. Furthermore, the workpiece may also have a coating. For example, the workpiece may be a coated steel sheet. Examples of coatings include aluminum alloys, aluminum alloys, zinc alloys, or zinc alloys.

[0209] When the heated workpiece is a coated steel sheet, it is preferable to minimize the formation of oxide scale during transport. If oxide scale forms on the lower surface of the upper heated workpiece W1 while it is being transported overlapping each other using the conveyor 46, the oxide scale may detach and fall onto the upper surface of the lower heated workpiece W2. Similarly, oxide scale formed on the lower surface of the lower heated workpiece W2 may also detach. In such cases, there is a possibility that the difference in the amount of oxide scale adhering to the upper and lower surfaces of the lower heated workpiece W2 becomes greater than the difference in the amount of oxide scale adhering to the upper and lower surfaces of the upper heated workpiece W1. This difference in oxide scale adhering can lead to differences in the frictional characteristics of the die and the workpiece surfaces during pressing. As a result, it may be necessary to individually adjust the die and set the forming conditions for each heated workpiece. Therefore, by using coated steel sheets for the heated workpiece, the formation of oxide scale during transport can be suppressed, and deviations in the characteristics of the heated workpiece can be prevented.

[0210] [The effect of conveying multiple heated workpieces at intervals]

[0211] In the example above, the first heated workpiece W1 and the second heated workpiece W2 are conveyed by the conveying device 46 in a state of overlapping at intervals along the vertical direction. As a result, deviations in the characteristics of the upper and lower surfaces of each heated workpiece, as well as deviations in the characteristics of the upper and lower surfaces between the upper and lower heated workpieces, can be suppressed.

[0212] When the first heated workpiece W1 and the second heated workpiece W2 are conveyed overlapping without gaps, the contact time between the overlapping surface and the opposite surface of each heated workpiece with air differs. In this case, if the first heated workpiece W1 and the second heated workpiece W2 are uncoated plates, the amount of oxide scale generated on the upper and lower surfaces will also differ. If the amount of oxide scale differs on the upper and lower surfaces, differences in the frictional characteristics of the upper and lower surfaces may occur. Furthermore, the orientation of the overlapping surface and the opposite surface of the first heated workpiece W1 and the second heated workpiece W2 is reversed, which may also cause differences in frictional characteristics between the first heated workpiece W1 and the second heated workpiece W2. As a result, the time required for die adjustment and forming condition setting during pressing may increase. Therefore, by conveying the first heated workpiece W1 and the second heated workpiece W2 at intervals, the deviation in frictional characteristics between the upper and lower surfaces of the heated workpieces can be reduced.

[0213] [Variation Example]

[0214] (The shape of the heated workpiece)

[0215] The shape of the heated workpiece is not limited to a flat plate as in the example above. The heated workpiece can also be an intermediate molded product formed by pressing. In addition, the shapes or dimensions of the first heated workpiece W1 and the second heated workpiece W2 can be different.

[0216] Figure 9 This diagram illustrates an example where the first heated workpiece W1 and the second heated workpiece W2 are intermediate formed products. Figure 9 In the example shown, the first claw 71b of the first arm 71 and the third claw 73b of the third arm 73 are positioned differently in the vertical direction. The positional relationship between the first claw 71b and the third claw 73b is determined according to the shape of the intermediate molded product. Thus, the lower surface of the first heated workpiece W1 is supported by the first claw 71b and the third claw 73b. Similarly, the second claw 72b of the second arm 72 and the fourth claw 74b of the fourth arm 74 are also positioned differently in the vertical direction. The positional relationship between the second claw 72b and the fourth claw 74b is determined according to the shape of the intermediate molded product. Thus, the lower surface of the second heated workpiece W2 is supported by the second claw 72b and the fourth claw 74b.

[0217] Figure 10 This diagram illustrates an example where the dimensions of the first heated workpiece W1 and the second heated workpiece W2 are different. Figure 10 In the example shown, the amount of the first claw 71b protruding laterally inward when the pair of first arms 71 support the first heated workpiece W1 is different from the amount of the second claw 72b protruding laterally inward when the pair of second arms 72 support the second heated workpiece W2. This allows the amount of protrusion of the first claw 71b and the second claw 72b to be determined based on the size of the heated workpiece (the area of ​​the plate surface). Furthermore, Figure 10 The left figure shows a structural example of the conveying device 46 for conveying heated workpieces on a conveying plate. Figure 10 The right figure shows a structural example of a conveying device 46 for conveying intermediate molded articles of non-flat shape.

[0218] Figure 11 This diagram illustrates an example where the shapes of the first heated workpiece W1 and the second heated workpiece W2 are different. Figure 11 In the example shown, the positions of the first claw 71b of the first arm 71 and the third claw 73b of the third arm 73 are configured to match the shape of the first heated workpiece W1. The positions of the second claw 72b of the second arm 72 and the fourth claw 74b of the fourth arm 74 are configured to match the shape of the second heated workpiece W2.

[0219] (Shielding panel)

[0220] Alternatively, the conveying device 46 may also include a side shield that laterally covers both sides of a pair of first claws 71b and a pair of second claws 72b. Figure 12This diagram illustrates an example where a side shielding plate is provided on the conveyor device 46. Figure 12 In the example shown, side shielding plate 92 is mounted on the outer side of the second arm 72 in the lateral direction. Side shielding plate 94 is mounted on the outer side of the fourth arm 74 in the lateral direction. In this example, the claw of the multiple arms has a side shielding plate mounted on the outer side of the lowest arm in the lateral direction.

[0221] Figure 13 This is another example showing a conveyor 46 equipped with a side shielding plate. Figure 13 In the example shown, side shielding plate 91 is mounted on the inner side of the first arm 71 in the lateral direction. Side shielding plate 93 is mounted on the inner side of the third arm 73 in the lateral direction. In this example, the claw of the multiple arms has a side shielding plate mounted on the inner side of the uppermost arm in the lateral direction.

[0222] Side shielding plates 91-94 are positioned to laterally cover the first heated workpiece W1, the second heated workpiece W2, and the space between them, while the first arm 71 and the second arm 72 support the first heated workpiece W1 and the second heated workpiece W2. Thus, during transport, the side shielding plates prevent air from flowing into the space between the first heated workpiece W1 and the second heated workpiece W2, and prevent air that was originally present between the two heated workpieces and heated by heat transfer from the two workpieces from flowing out of the space between them. Therefore, the heat preservation effect provided by the heated, stagnant air between the first heated workpiece W1 and the second heated workpiece W2 is maintained, further suppressing the temperature drop of the heated workpieces during transport.

[0223] Figure 14 This is a diagram showing a variation of the shape of a side shielding plate. Figure 14 In the example shown, the side shielding plate 92 has a surface that is inclined laterally toward the pair of first claws 71b and the pair of second claws 72b as it approaches the ends from the center. That is, the side shielding plate 92 has a shape that protrudes laterally outward from the center and is curved at the ends in a position laterally inward than the center. This allows air encountering the side shielding plate to flow in a direction away from the heated workpiece in the vertical direction. Furthermore, in Figure 14 In this configuration, when viewed from the side of the conveying device, the side shielding plate has a structure in which the surface slopes inward laterally from the center to the end. Alternatively, when viewed from above the conveying device, the side shielding plate may have a structure in which the surface slopes inward laterally from the center to the end.

[0224] In addition, Figure 14In the example shown, the side shielding plate 92 covers the long side direction of the base frame 48. Therefore, during the conveying process, the side shielding plate 92 covers the long side direction of the first heated workpiece W1 and the long side direction of the second heated workpiece W2. Thus, during conveying, the side shielding plate prevents air from flowing into the space between the first heated workpiece W1 and the second heated workpiece W2 from the long side direction. Furthermore, in Figure 12 and Figure 13 In the example, side shielding plates are provided in both the long and short sides. Alternatively, side shielding plates can be provided in either the long or short side.

[0225] Figure 15 This diagram shows another example where the conveyor 46 is equipped with an upper shielding plate. Figure 15 In the example shown, an upper shielding plate 95 is provided to cover the top of the heated workpiece. The upper shielding plate 95 is positioned to overlap with both the first claw 71b and the second claw 72b when viewed from above. The upper shielding plate 95 is supported by a plurality of support members 96 extending vertically from the base frame 48. The upper shielding plate 95 is positioned between the base frame 48 and the first claw 71b of the pair of first arms 71. Therefore, the upper shielding plate 95 can be positioned near the first heated workpiece W1 supported by the first claw 71b. As a result, the air above the first heated workpiece W1, which is heated by heat transfer from the first heated workpiece W1, becomes easier to be trapped between the first heated workpiece W1 and the upper shielding plate 95. By trapping the heated air above the first heated workpiece W1, a heat preservation effect on the first heated workpiece W1 can be obtained. From the viewpoint of further improving the heat preservation effect, the distance J1 between the first heated workpiece W1 and the upper shielding plate 95 above it in the normal direction of the surface of the first heated workpiece W1 is preferably 200 mm or less, more preferably 100 mm or less. From the same viewpoint, it is preferable that the vertical distance J2 between the upper shielding plate 95 and the first claw 71b is less than or equal to the maximum thickness of the first heated workpiece W1 plus 200 mm. More preferably, the aforementioned distance J2 is less than or equal to the maximum thickness of the first heated workpiece W1 plus 100 mm. For example, if the thickness of the first heated workpiece W1 varies within the first heated workpiece W1 by 1 mm to 3 mm, and the maximum thickness of the first heated workpiece W1 is 3 mm, then the vertical distance J2 between the upper shielding plate 95 and the first claw 71b is preferably 203 mm or less, more preferably 103 mm or less.

[0226] Figure 15 The left figure shows a structural example of a conveying device 46 for conveying heated workpieces on a flat plate. In this case, the upper shielding plate 95 has the shape of a flat plate. Figure 15The right figure shows a structural example of a conveying device 46 for conveying an intermediate molded article with a non-flat shape. In this case, the upper shielding plate 95 has a shape that extends along the intermediate molded article. Thus, the shape of the upper shielding plate 95 is not limited to a specific shape. Alternatively, when viewed from above, the upper shielding plate 95 may extend outwards from the first arm 71 and the second arm 72. Furthermore, the conveying device 46 may also include... Figure 12 , Figure 13 or Figure 14 The side shielding panels shown (92, 94 or 91, 93) and Figure 15 The upper shielding panel 95 shown is one of these two. In this case, for example, the upper shielding panel 95 can also be connected to the side shielding panels (92, 94 or 91, 93).

[0227] (Conveying plates with varying thicknesses)

[0228] Figure 16 This is a diagram illustrating an example of a conveying device 46 for conveying plates of varying thicknesses. Figure 16 In the example shown, the first heated workpiece W1 and the second heated workpiece W2 are differentially thick plates including thick-walled and thin-walled portions. During the conveying process, the thick-walled portion of the first heated workpiece W1, supported by the first claw 71b of a pair of first arms 71, and the thin-walled portion of the second heated workpiece W2, supported by the second claw 72b of a pair of second arms 72, are conveyed in a state where they overlap in the normal direction of the surface of the first heated workpiece W1. Thus, the thick-walled portion, with its larger heat capacity, is conveyed in a state where it is relatively thin and its temperature is prone to drop. Therefore, the temperature drop of the thin-walled portion can be further suppressed. Overall, the temperature drop of the heated workpieces can be effectively suppressed.

[0229] In the conveying device 46, for example, after the first heated workpiece W1 is lifted by driving the first arm 71, the base frame 48 is rotated 180 degrees about the vertical axis. Then, the second arm 72 can be driven to lift the second heated workpiece W2. Thus, even if the first heated workpiece W1 and the second heated workpiece W2 on the conveying table 16 are facing the same direction and the thin-walled portion is in the same position after heating, since the conveying device 46 rotates 180 degrees to hold the second heated workpiece W2, it is possible to hold the first heated workpiece W1 and the second heated workpiece W2 overlappingly with the thin-walled portion in a state where the positions of the thin-walled portions are reversed.

[0230] Furthermore, differential thickness plates can also be welded plates obtained by butt-joining the ends of steel plates with different thicknesses. Alternatively, differential thickness plates can also be patch welded plates obtained by overlapping and joining steel plates of different sizes. Alternatively, differential thickness plates can also be differential thickness rolled plates obtained by locally changing the thickness of a single steel plate through processes such as rolling.

[0231] (Example of arm deformation)

[0232] Figure 17 This is a diagram showing a modified example of the first arm 71 and the second arm 72. Figure 17 In the example shown, the connection between the first base 71a and the first claw 71b of the first arm 71 is rotatable. That is, the first claw 71b is rotatably connected to the first base 71a about a transverse (y-direction) axis. The first base 71a is fixed relative to the base frame 48. Similarly, for the second arm 72, the second claw 72b is rotatably connected to the second base 72a about a transverse (y-direction) axis. In this way, the claws of the arm can rotate, and the rotation of the claws can be controlled, thereby controlling the transverse position of the claws and realizing the lifting and lowering of the heated workpiece.

[0233] exist Figure 17 In the example shown, the first arm 71 also has claws 71c supporting the upper surface of the first heated workpiece W1. The second arm 72 also has claws 72c supporting the upper surface of the second heated workpiece W2. Claws supporting the upper surface of the heated workpieces can also be provided on the arms in this manner. By using a pair of claws 71b, 71c of the first arm 71 and a pair of claws 72b, 72c of the second arm 72 to hold the ends of the first heated workpiece W1 and the second heated workpiece W2, the heated workpieces can be stably held even when the plate thickness of the heated workpiece is thin and the rigidity is low, and the distance D between the first heated workpiece W1 and the second heated workpiece W2 in the normal direction of the plate surface can be stably maintained.

[0234] Figure 18 This is a diagram showing another variation of the first arm 71 and the second arm 72. In Figure 18 In the example shown, the first arm 71 can be rotatably mounted on the base 48 with the vertical direction (z-direction) as the axis. The second arm 72 can also be rotatably mounted on the base 48 with the vertical direction (z-direction) as the axis. It is also possible to configure it such that the amount of extension of the claw to the lateral inward can be controlled by rotating the arm with the vertical direction as the axis.

[0235] (Mechanism for adjusting the position of the claw)

[0236] The distance between the pair of first jaws 71b and the pair of second jaws 72b in the vertical direction can also be adjusted. For example, at least one of the first base 71a of the first arm 71 and the second base 72a of the second arm 72 can be configured to extend and retract in the vertical direction. For example, at least one of the first base 71a and the second base 72a can be provided with a telescopic mechanism that extends and retracts in the vertical direction. Thus, the position of the jaws can be adjusted to match the heated workpiece to be conveyed. Furthermore, the distance between the pair of third jaws 73b and the pair of fourth jaws 74b in the vertical direction can also be adjusted in the same way.

[0237] (A variation of the support structure for a heated workpiece)

[0238] Figure 19 This is a diagram showing a modified example of the support structure of the conveying device 46 supporting the first heated workpiece W1 and the second heated workpiece W2. Figure 20 It only indicates that by Figure 19 A perspective view of the first heated workpiece W1 and the second heated workpiece W2, supported by the conveyor device 46. Figure 19 and Figure 20 In the example shown, the first heated workpiece W1 and the second heated workpiece W2 are supported on the conveying device 46 in a state of overlapping and contacting each other in the vertical direction (the normal direction of the first heated workpiece W1). Specifically, the lower surface of the first heated workpiece W1, supported by a pair of first claws 71b of the first arm 71, and the upper surface of the second heated workpiece W2, supported by a pair of second claws 72b of the second arm 72, are in contact with each other. In this example, the entire upper surface of the second heated workpiece W2 supported on the lower side is in partial contact with the lower surface of the first heated workpiece W1 supported on the upper side. In this case, the distance D between the first heated workpiece W1 and the second heated workpiece W2 is 0 mm. The width B1 of the plate surface of the first heated workpiece W1 supported on the upper side is larger than the width B2 of the second heated workpiece W2 supported on the lower side. In addition, the distance between the pair of second claws 72b supporting the second heated workpiece W2 is smaller than the distance between the pair of first claws 71b supporting the first heated workpiece W1. That is, the second claw 72b protrudes inward compared to the first claw 71b. The distance H between the pair of first claws 71b and the pair of second claws 72b in the vertical direction is set to be approximately the same as the thickness of the second heated workpiece W2.

[0239] Figure 21 This is a diagram showing another variation of the support structure of the conveying device 46 supporting the first heated workpiece W1 and the second heated workpiece W2. Figure 22 It only indicates that by Figure 21 A perspective view of the first heated workpiece W1 and the second heated workpiece W2, supported by the conveyor device 46. Figure 21 and Figure 22In the example shown, the first heated workpiece W1 and the second heated workpiece W2 are supported on the conveyor 46 in a state of overlapping and contacting each other in the vertical direction (the normal direction of the first heated workpiece W1). Specifically, the lower surface of the first heated workpiece W1, supported by a pair of first claws 71b of the first arm 71, and the upper surface of the second heated workpiece W2, supported by a pair of second claws 72b of the second arm 72, are separated at both ends in the width direction, and are in contact with each other in the portion between the two ends. In this case, the distance D between the two ends of the first heated workpiece W1 and the second heated workpiece W2 is 0 mm. The shapes of the first heated workpiece W1 supported on the upper side and the second heated workpiece W2 supported on the lower side are the same when viewed from above. The first claws 71b are inserted into the separated portions at both ends of the first heated workpiece W1 and the second heated workpiece W2. The distance D between the separated portions at both ends is larger than the thickness (vertical dimension) of the first claws 71b. Figure 21 , Figure 22 In the example shown, the two ends of the first heated workpiece W1, supported on the upper side, are bent at a position higher than the portion between the two ends. The two ends of the second heated workpiece W2, supported on the lower side, are bent at a position lower than the portion between the two ends. The manner in which the two ends separate is not limited to this. For example, as... Figure 23 As shown, it can also be done in such a way that the two ends of either the first heated workpiece W1 or the second heated workpiece W2 are bent, while the two ends of the other are not bent. Furthermore, it is preferable that... Figure 2A Similarly, the distance H between the pair of first claws 71b and the pair of second claws 72b in the vertical direction is set to the thickness of the second heated workpiece W2 plus 0mm to 50mm. Since the first claw 71b is inserted into the separated portions at both ends of the first heated workpiece W1 and the second heated workpiece W2, the lower limit of the distance H can also be the value obtained by adding the lower limit of the thickness of the first claw 71b to the thickness of the second heated workpiece W2. The lower limit of the distance H is preferably, for example, the thickness of the second heated workpiece W2 + 3mm, and more preferably, the thickness of the second heated workpiece W2 + 5mm. Furthermore, in Figure 21 , Figure 22 In the example shown, the separating portions of the ends of the first heated workpiece W1 and the second heated workpiece W2 are located on a pair of long sides, but the method of end separation is not limited to this. For example, the separating portions of the ends of the first heated workpiece W1 and the second heated workpiece W2 may also be located on a pair of short sides. Furthermore, the separating portions of the ends of the first heated workpiece W1 and the second heated workpiece W2 may also be located on both a pair of long sides and a pair of short sides.

[0240] exist Figures 21-23In the example shown, the two ends of the first heated workpiece W1 in the width direction and the two ends of the second heated workpiece W2 in the width direction are separated along the entire length direction perpendicular to the width direction. In contrast, the two ends in the width direction can also be partially separated. Figure 24 This is a diagram illustrating an example of the support structure of the conveying device 46 supporting the first heated workpiece W1 and the second heated workpiece W2 in this case. Figure 25 It only indicates that by Figure 24 A perspective view of the first heated workpiece W1 and the second heated workpiece W2, supported by the conveyor device 46. Figure 24 and Figure 25 In the example shown, the portions at both ends of the first heated workpiece W1 in the width direction and the portions at both ends of the second heated workpiece W2 in the width direction corresponding to the pair of first claws 71b of the first arm 71 are separated, while the remaining portions other than the ends in the width direction are in contact with each other. Furthermore, the portions at both ends of the first heated workpiece W1 in the length direction and the portions at both ends of the second heated workpiece W2 in the length direction corresponding to the pair of third claws 73b of the third arm 73 are separated, while the remaining portions other than the ends in the length direction are in contact with each other. This reduces the amount of separation between the ends of the first heated workpiece W1 and the ends of the second heated workpiece W2. Figure 24 and Figure 25 In the example, it is the way the ends of both the first heated workpiece W1 and the second heated workpiece W2 are bent. In contrast, for example, as... Figure 26 As shown, it can also be that the two ends of either the first heated workpiece W1 or the second heated workpiece W2 are bent while the two ends of the other are not bent.

[0241] (Implementation Method 2)

[0242] (Example of a transport system using pallets and heat storage materials)

[0243] Figure 27 This is a diagram illustrating a structural example of a hot pressing production line 10 in which a tray and heat storage material are used to transport the first heated workpiece W1 and the second heated workpiece W2. Figure 27 The hot pressing production line 10 shown also includes a tray 1. The tray 1 is a tray that carries the first heated workpiece W1 and the second heated workpiece W2 on the heating device 14 and the conveyor table 16. The tray 1 has a tray body 2, a heat storage material 5 placed on the tray body 2, and a first support assembly 3. The first support assembly 3 includes at least three supports that extend upwards from the tray body 2 or the heat storage material 5 to a position higher than the upper surface of the heat storage material 5. The first support assembly 3 is configured such that, when viewed from above, the virtual straight lines connecting the supports form at least one triangle. Furthermore, in Figure 27The example shown depicts a first heated workpiece W1 and a second heated workpiece W2 being heated by a heating device 14 while mounted on a tray 1, and then conveyed by a conveyor table 16. As a variation, the first heated workpiece W1 and the second heated workpiece W2 can be heated and conveyed with one piece of either the first heated workpiece W1 or the second heated workpiece W2 mounted on each tray. Alternatively, heating and conveying can be performed with three or more heated workpieces mounted on a single tray.

[0244] In the heating device 14, the first heating workpiece W1 and the second heating workpiece W2 are heated while supported by the first support column group 3. Thus, the first heating workpiece W1 and the second heating workpiece W2 are supported above the heat storage material 5 at different positions when viewed from above, and are supported at positions overlapping with the heat storage material 5. The first heating workpiece W1 and the second heating workpiece W2 are conveyed from the heating device 14 to a lifting position on the conveyor table 16 using the conveyor device 46, while being carried on the tray 1. Thus, the first heating workpiece W1 and the second heating workpiece W2 remain overlapping with the heat storage material 5 from the time of heating until they are lifted by the conveyor device 46. Therefore, the temperature drop is mitigated. Furthermore, when the conveyor device 46 lifts the first heating workpiece and the second heating workpiece W2 placed on the first support column group 3 upwards, the first support column group 3 does not become an obstacle.

[0245] exist Figure 27 In the example shown, the heat storage material 5 is in contact with the tray body 2. The configuration of the heat storage material 5 is not limited to this. For example, although not shown, the heat storage material 5 can also be placed on a second support group separately provided relative to the first support group 3, and positioned vertically and vertically overlapping the tray body 2 at intervals. The second support group includes at least three supports extending upwards from the tray body 2, and positioned differently from the first support group 3 when viewed from above. This allows for the suppression of heat-induced deformation of the tray body 2.

[0246] The tray body 2 has a shape that extends vertically in the vertical direction, and may also include a hollow portion that runs through the vertical direction. Thus, during the heating process, heat from below the tray body 2 can be easily transferred to the heat storage material 5, the first heated workpiece W1, and the second heated workpiece W2.

[0247] The area of ​​the upper surface of the heat storage material 5 can also be wider than the area of ​​the upper surface of the first heated workpiece W1 and the upper surface of the second heated workpiece W2. In this case, during the heating process and the conveying process in which the first heated workpiece W1 and the second heated workpiece W2 are conveyed to the lifting position by the conveying device 46 while supported on the tray 1, it is preferable that, when viewed from above, the outer edge of the heat storage material 5 placed on the tray body 2 is located outside the outer edge of the first heated workpiece W1 and the second heated workpiece W2 placed on the first support group 3. As a result, the first heated workpiece W1 and the second heated workpiece W2 as a whole receive radiant heat from the heat storage material 5. Therefore, it is easy to maintain the temperature of the heated workpiece as a whole uniformly.

[0248] For example, the thickness of the heat storage material 5 can be greater than the maximum thickness of the first heated workpiece W1 and the second heated workpiece W2. In this case, the temperature drop of the first heated workpiece W1 and the temperature drop of the second heated workpiece W2 are suppressed by radiant heat from the heat storage material 5, which has a larger heat capacity. Therefore, the temperature drop of the heated workpieces can be effectively suppressed.

[0249] (tray)

[0250] Figure 28 This is a top view of tray 1 taken from above. Figure 29 Observing from the direction of arrow F Figure 28 The side view obtained from tray 1 shown. Figure 28 In the example shown, the tray body 2 has a shape extending along a surface perpendicular to the vertical direction and includes a hollow portion 2G extending vertically through it. When viewed from above, the area of ​​the hollow portion 2G is wider than the area of ​​the constituent components of the tray body 2. The tray 1 has heat storage material 5 placed on the tray body 2. The tray 1 has a plurality of supports 3 extending upward toward the heat storage material 5.

[0251] (Pallet body)

[0252] exist Figure 28 In the example shown, the pallet body 2 has a frame 2c and rod members 2f mounted inside the frame 2c. The frame 2c includes a pair of longitudinal frames 2b and a pair of transverse frames 2a. The pair of longitudinal frames 2b are separated laterally and arranged parallel to each other. The pair of transverse frames 2a are separated longitudinally and arranged parallel to each other between the pair of longitudinal frames 2b. The pair of longitudinal frames 2b and the pair of transverse frames 2a form a rectangular frame 2c when viewed from above. The rod members 2f include longitudinal rod members 2d and transverse rod members 2e. The longitudinal rod members 2d are mounted between the pair of transverse frames 2a. The transverse rod members 2e are mounted between the pair of longitudinal frames 2b. In the frame 2c, the rod members 2f are arranged in a grid pattern.

[0253] It can also be configured to allow adjustment of the position of the rod member 2f (at least one of the longitudinal rod member 2d and the transverse rod member 2e) within the frame 2c. For example, multiple positioning holes or locking pieces can be provided in the frame 2c. In this case, the rod member 2f is fixed to the holes or locking pieces in the frame 2c using fasteners or the like as needed. By changing the position of the holes or locking pieces for fixing the rod member 2f, the position of the rod member 2f within the frame 2c can be adjusted.

[0254] Furthermore, the structure of the pallet body 2 is not limited to Figure 28 The example shown. For instance, the pallet body can also be formed in a ladder shape, having: a pair of longitudinal members that are separated and arranged substantially parallel to each other; and a plurality of transverse members that are positioned between the pair of longitudinal members in a direction intersecting the pair of longitudinal members. Alternatively, the pallet body can also be formed from a plate-like member having a plurality of through holes running vertically as a hollow portion.

[0255] The constituent components of the pallet body 2 (in) Figure 28 In the example, frame 2c and rod member 2f can be either tubular or solid material. Furthermore, the constituent components of the pallet body 2 can be either angle members with an L-shaped cross-section or channel members with a U-shaped cross-section. The material of the constituent components of the pallet body 2 is not particularly limited and can be formed from heat-resistant materials such as heat-resistant steel or ceramics. Preferably, the maximum operating temperature of the constituent components is set to, for example, a range of 900°C or higher, commonly used in heating devices, and 1050°C or lower, which is the upper limit set temperature of the heating device. Examples of heat-resistant steels (heat-resistant alloy steels) that can be used as constituent components include SCH22 (0.4C-25Cr-20Ni) and SCH24 (0.4C-25Cr-35Ni-Mo, Si). Using heat-resistant alloy steel to form the constituent components of the pallet body 2 simplifies processing and manufacturing. Furthermore, the materials that can be used as the constituent components of the pallet body 2 can also be used as the materials for the support column 3.

[0256] (Heat storage material)

[0257] The heat storage material 5 is supported on the tray body 2. The heat storage material 5 is a plate-shaped component. The heat storage material 5 has a rectangular shape when viewed from above. The heat storage material 5 has through holes for the support column 3 to pass through. The support column 3 extends upward through the through holes of the heat storage material 5 placed on the tray body 2.

[0258] The material of the heat storage material 5 is not particularly limited and can be formed from heat-resistant materials such as heat-resistant metals or ceramics. Examples of heat-resistant metals suitable for use as heat storage material 5 include heat-resistant steel, stainless steel, Ni-based alloys, and other alloys. Furthermore, it is preferable that the heat storage material 5 has a low thermal conductivity. A low thermal conductivity makes it less likely for the temperature to drop, allowing the heat compensation effect on the first heated workpiece W1 and the second heated workpiece W2 based on radiant heat to last longer. For example, the heat storage material 5 can also be formed from a material having a thermal conductivity equal to or less than that of the workpiece being heated. The thermal conductivity of the heat storage material 5 is not limited to this; for example, it is preferably 200 W / mK or less, more preferably 100 W / mK or less, and even more preferably 70 W / mK or less. Furthermore, the heat storage material 5 and the tray 1 can also be used for heating and conveying processes of other workpieces after the first heated workpiece W1 and the second heated workpiece W2 are lifted by the conveying device 46 and conveyed to the pressing position.

[0259] (pillar)

[0260] The support column 3 extends upward from the tray body 2 to a position higher than the upper surface of the heat storage material 5. Multiple supports 3 are configured such that, when viewed from above, the virtual straight lines connecting the supports 3 form at least one triangle. The multiple supports 3 are configured to support either the first heated workpiece W1 or the second heated workpiece W2 in a state of overlapping vertically with a distance between them and the heat storage material 5. Figure 28 In the example shown, the multiple supports 3 are located between the hollow portions 2G of the pallet body 2 when viewed from above. That is, the pallet body 2, which is sandwiched between the hollow portions 2G, has supports 3 in its structural components.

[0261] exist Figure 29 In the example shown, multiple supports 3 penetrate the heat storage material 5. The heat storage material 5 has through holes for the multiple supports 3 to pass through. Thus, as... Figure 28 As shown, when viewed from above, multiple support pillars 3 can be arranged inside the outer edge of the heat storage material 5. In this case, the first heating workpiece W1 can be arranged on the multiple support pillars 3 such that the entire first heating workpiece W1, whose area is smaller than the area of ​​the heat storage material 5 when viewed from above, overlaps with the heat storage material 5. Figure 29 In the example shown, the heat storage material 5 is a flat plate, but the shape of the heat storage material 5 can also be, for example, a shape corresponding to the first heated workpiece W1. In this case, the distance between the first heated workpiece W1 and the heat storage material 5 can be made approximately uniform across the entire surface. Furthermore, Figure 29 This example shows a configuration with a first heated workpiece W1, but a second heated workpiece W2 can also be configured in the same way as the first heated workpiece W1.

[0262] Preferably, the maximum vertical distance Dc (mm) between the heat storage material 5 placed on the pallet body 2 and the first heated workpiece W1 and the second heated workpiece W2 placed on the support column 3, and the minimum plate thickness t1 (mm) of the thinnest part of the first heated workpiece W1 and the second heated workpiece W2 are related by the following formula. This effectively suppresses the temperature drop of the first heated workpiece W1 on the pallet 1 during transport.

[0263] Dc≤120t1

[0264] Alternatively, the minimum plate thickness t1 (mm) and the minimum plate thickness t2 (mm) of the thinnest part of the heat storage material 5 can be related by the following formula. This effectively suppresses the temperature drop of the workpiece.

[0265] 0.8≤t2 / t1≤20

[0266] The structure of placing the first heating workpiece W1 and the second heating workpiece W2 above the heat storage material 5 is not limited to the example described above. For example, a support assembly 3 for placing the first heating workpiece W1 and the second heating workpiece W2 may be provided on the heat storage material 5. In this case, the support assembly 3 may also be part of the heat storage material 5. Alternatively, at least a portion of the first heating workpiece W1 and at least a portion of the second heating workpiece W2 may be in contact with the heat storage material 5. Alternatively, for example, the heat storage material 5 may have an upwardly protruding protrusion. The protrusion may be shaped to support the first heating workpiece W1 and the second heating workpiece W2. For example, the top surface of the protrusion may be made flat. In this case, the top surface becomes the mounting surface of the first heating workpiece W1 and the second heating workpiece W2. Alternatively, the protrusion may be at least one ridge. Additionally, the heat storage material 5 may have a shape that is curved in the vertical direction.

[0267] As another variation of the heat storage material 5, when viewed from above, a portion of the heat storage material 5 may extend upwards from the outer edges of the first heated workpiece W1 and the second heated workpiece W2. This allows for heat compensation through radiant heat between the lateral ends of the first heated workpiece W1 and the second heated workpiece W2 and the upwardly extending portion of the heat storage material 5. Alternatively, when viewed from above, a portion of the heat storage material 5 may extend upwards from the outer edges of the first heated workpiece W1 and the second heated workpiece W2, reaching at least the same height as both the first and second heated workpieces. This covers the sides of the workpieces with the heat storage material 5. Therefore, similar to the case with a side shielding plate, a heat preservation effect can be maintained.

[0268] (Implementation Method 3)

[0269] (Example of palletized transport)

[0270] Figure 30 This is a diagram illustrating a structural example of a hot press production line 10 in which the first heated workpiece W1 and the second heated workpiece W2 are heated and transported in an overlapping manner using a tray. Figure 30 The hot pressing production line 10 shown also includes a tray 1. The tray 1 is a tray that carries a first heated workpiece W1 and a second heated workpiece W2 on the heating device 14 and the conveyor table 16. The tray 1 has a tray body 2 and a support assembly 3 extending upward from the tray body 2. The support assembly 3 has a first support assembly for placing the first heated workpiece W1 and a second support assembly for placing the second heated workpiece W2. The first support assembly includes at least three supports configured to support the lower surface of the first heated workpiece W1. The second support assembly includes at least three supports configured to support the second heated workpiece W2 such that the second heated workpiece W2 is positioned above the first heated workpiece W1 supported by the first support assembly. The first support assembly is configured such that, when viewed from above, the virtual straight lines connecting the supports form at least one triangle. The second support assembly is positioned differently from the first support assembly when viewed from above, and the second support assembly is configured such that, when viewed from above, the virtual straight lines connecting the supports form at least one triangle. The second pillar group is taller than the lowest pillar in the first pillar group.

[0271] In the heating device 14, a first workpiece W1 is placed on a first support group, and a second workpiece W2 is placed on a second support group, with the second workpiece W2 being heated in a state of overlapping arrangement above the first workpiece W1. The first and second workpieces W1 and W2 are conveyed from the heating device 14 to a lifted position on the conveyor table 16 via a conveyor device 46, while supported on a tray 1. Thus, the first and second workpieces W1 and W2 are in an overlapping state from the time they are heated until they are lifted by the conveyor device 46. Therefore, the temperature drop is mitigated.

[0272] Alternatively, at the lifted position on the conveyor table 16, the first heated workpiece W1 placed on the first support group and the second heated workpiece W2 placed on the second support group are simultaneously lifted upwards, supported by the second claw 72b of the second arm 72 and the first claw 71b of the first arm 71 of the conveying device 46, respectively, and conveyed by the conveying device 46 to their respective pressing positions on the press 20. At this time, the actions of driving the first arm 71 to position the pair of first claws 71b on the lower surface of the second heated workpiece W2 and driving the second arm 72 to position the pair of second claws 72b on the lower surface of the first heated workpiece W1 can be performed simultaneously, or the two actions can be performed sequentially. By simultaneously lifting the first heated workpiece W1 and the second heated workpiece W2 carried on the tray 1 using the conveying device 46, the conveying time can be shortened, and temperature drop can be further reduced. Alternatively, the second heated workpiece W2, placed in the second support group, can be lifted upwards by the first claw 71b of the first arm 71 of the conveying device 46. Then, the first heated workpiece W1, placed in the first support group, can be lifted upwards by the second arm 72 of the conveying device 46, and both are conveyed by the conveying device 46 to the pressing position of the press 20. When the conveying device 46 simultaneously or sequentially lifts the first heated workpiece W1 placed on the first support group and the second heated workpiece W2 placed on the second support group in the support group 3, the support group 3 will not become an obstruction.

[0273] The tray body 2 has a shape that extends vertically in the vertical direction, and may also include a hollow portion that runs vertically through it. This allows heat from below the tray body 2 to be easily transferred to the first heated workpiece W1 and the second heated workpiece W2 during the heating process. Alternatively, when viewed from above, the first support group and the second support group are located between the hollow portions of the tray body 2. This allows heat from below the tray body 2 to be more easily transferred through the hollow portions surrounding the first and second support groups to the first heated workpiece W1 placed in the first support group and the second heated workpiece W2 placed in the second support group.

[0274] The second support group may also include at least three supports, each of which is higher than the at least three supports in the first support group by a certain height ΔH. In this case, the second heated workpiece supported by the second support group can be positioned at a height ΔH higher than the first heated workpiece supported by the first support group.

[0275] (tray)

[0276] Figure 31 This is a top view of tray 1 taken from above. Figure 32 Observing from the direction of arrow F Figure 31 The side view obtained from tray 1 shown. Figure 31In the example shown, the tray body 2 has a shape extending along a surface perpendicular to the vertical direction and includes a hollow portion 2G extending vertically through the tray body 2. When viewed from above, the area of ​​the hollow portion 2G is wider than the area of ​​the constituent components of the tray body 2. The tray 1 has a plurality of supports 3 (3a, 3b) extending upward from the tray body 2. The plurality of supports 3 includes a first support group 3a capable of supporting a first heated workpiece W1 and a second support group 3b capable of supporting a second heated workpiece W2 above the first heated workpiece W1. The first support group 3a and the second support group 3b are both located between the hollow portions 2G of the tray body 2 when viewed from above.

[0277] (Pallet body)

[0278] exist Figure 31 In the example shown, the pallet body 2 has a frame 2c and rod members 2f mounted inside the frame 2c. The frame 2c includes a pair of longitudinal frames 2b and a pair of transverse frames 2a. The pair of longitudinal frames 2b are separated laterally and arranged parallel to each other. The pair of transverse frames 2a are separated longitudinally and arranged parallel to each other between the pair of longitudinal frames 2b. The pair of longitudinal frames 2b and the pair of transverse frames 2a form a rectangular frame 2c when viewed from above. The rod members 2f include longitudinal rod members 2d and transverse rod members 2e. The longitudinal rod members 2d are mounted between the pair of transverse frames 2a. The transverse rod members 2e are mounted between the pair of longitudinal frames 2b. In the frame 2c, the rod members 2f are arranged in a grid pattern.

[0279] It can also be configured to allow adjustment of the position of the rod member 2f (at least one of the longitudinal rod member 2d and the transverse rod member 2e) within the frame 2c. For example, multiple positioning holes or locking pieces can be provided in the frame 2c. In this case, the rod member 2f is fixed to the holes or locking pieces in the frame 2c using fasteners or the like as needed. By changing the position of the holes or locking pieces for fixing the rod member 2f, the position of the rod member 2f within the frame 2c can be adjusted.

[0280] The constituent components of the pallet body 2 (in) Figure 31In the example, frame 2c and rod member 2f can be either tubular or solid material. Furthermore, the constituent components of the pallet body 2 can be either angle members with an L-shaped cross-section or channel members with a U-shaped cross-section. The material of the constituent components of the pallet body 2 is not particularly limited and can be formed from heat-resistant materials such as heat-resistant steel or ceramics. Preferably, the maximum operating temperature of the constituent components is set to a range of 900°C or higher, commonly used in heating devices, and 1050°C or lower, which is the upper limit set temperature of the heating device. Examples of heat-resistant steels (heat-resistant alloy steels) that can be used as constituent components include SCH22 (0.4C-25Cr-20Ni) and SCH24 (0.4C-25Cr-35Ni-Mo, Si). Using heat-resistant alloy steel to form the constituent components of the pallet body 2 simplifies processing and manufacturing. Furthermore, the materials that can be used as the constituent components of the pallet body 2 can also be used as the materials for the support column 3.

[0281] (pillar)

[0282] The first support group 3a includes at least three supports forming a triangle when viewed from above, with virtual straight lines connecting the supports to each other. The second support group 3b includes at least three supports forming a triangle when viewed from above, with virtual straight lines connecting the supports to each other. When viewed from above, each of the second support groups 3b is positioned differently from the first support group 3a. Each of the second support groups 3b is taller than the lowest support in the first support group 3a. Thus, the first support group 3a can support the first heated workpiece W1. Furthermore, the second support group 3b can support the second heated workpiece W2 above the first heated workpiece W1 supported by the first support group 3a.

[0283] Viewed from above, the second support group 3b is positioned in the area where the second heated workpiece W2 is placed, and in an area that does not overlap with the area where the first heated workpiece W1 is placed. Furthermore, viewed from above, the second support group 3b is configured not to overlap with the area where the first heated workpiece W1 is placed. That is, the second support group 3b is configured such that when the first heated workpiece W1 is lifted upwards by the conveyor 46, the first heated workpiece W1 will not snag on the second support group 3b.

[0284] There is no particular limitation on the number of supports in the first support group 3a and the second support group 3b. The number of supports in the first support group 3a and the second support group 3b can be the same or different. For example, if it is desirable to strengthen the support of the second heated workpiece W2 compared to the first heated workpiece W1, considering the characteristics and support positions of the first heated workpiece W1 and the second heated workpiece W2, the number of supports in the second support group 3b can be more than the number of supports in the first support group 3a.

[0285] exist Figure 31In the example shown, when viewed from above, the first heated workpiece W1 has a notch at its edge (end). A second support group 3b is disposed in the area corresponding to the notch of the first heated workpiece W1. Thus, by distributing the second support group 3b in the area corresponding to the notch or hole of the first heated workpiece W1, it is possible to distribute the second support group 3b in an area that does not overlap with the first heated workpiece W1 when viewed from above. Furthermore, the structure of the first support group, the second support group, and the heated workpiece is not limited to... Figure 31 The example shown. For instance, a first heating workpiece W1 and a second heating workpiece W2 of the same shape can be arranged in a staggered position when viewed from above. In this case, when viewed from above, the first heating workpiece W1 and the second heating workpiece W2 are arranged in such a way that a portion of the second heating workpiece W2 does not overlap with the first heating workpiece W1. The second support group 3b is arranged in the area where the second heating workpiece W2 is arranged, and in a position that does not overlap with the area where the first heating workpiece W1 is arranged. In this case, it is also possible that no notches, holes, etc. are provided in the first heating workpiece W1.

[0286] Reference Figure 32 Preferably, the maximum vertical distance Dt (mm) between the first heated workpiece W1 placed in the first support group 3a and the second heated workpiece W2 placed in the second support group 3b, and the minimum plate thickness t (mm) of the thinnest portion of the first heated workpiece W1 and the second heated workpiece W2 are related by the following formula. This effectively suppresses temperature drops in both the first heated workpiece W1 and the second heated workpiece W2 during transport.

[0287] Dt≤120t

[0288] From the same point of view, it is more preferable that Dt ≤ 100t, and even more preferable that Dt ≤ 60t. In addition, the interval Dt (mm) is preferably 100mm or less, and more preferably 50m or less.

[0289] exist Figure 32 In the example shown, ΔH is the height difference between the first support group 3a and the second support group 3b. The range of ΔH (mm) can be, for example, set as the range of the aforementioned interval Dt (mm) plus the maximum plate thickness of the first heated workpiece W1. As an example, when the plate thickness of the first heated workpiece W1 varies by about 1 mm to 3 mm within the first heated workpiece W1, ΔH is preferably 3 mm to 103 mm, more preferably 3 mm to 53 mm.

[0290] (Another variation)

[0291] This invention is not limited to the embodiments described above. For example, the third arm 73 and the fourth arm 74 may be omitted. Furthermore, in the above example, the lateral directions of the pair of first arms 71 and the pair of second arms 72 are both in the x-direction, which is the same. As a variation, for example, it could be a structure where the pair of first arms 71 are arranged in the x-direction and the pair of second arms 72 are arranged in the y-direction perpendicular to the x-direction. In the above example, the second arm 72 is longer than the first arm 71, but the first arm 71 may also be longer than the second arm 72. Similarly, the third arm 73 may be longer than the fourth arm 74.

[0292] In the above embodiment, multiple pairs of first arms 71 and multiple pairs of second arms 72 are provided. Conversely, a pair of first arms 71 and a pair of second arms 72 may also be provided.

[0293] The base frame 48 can also extend and retract freely in the lateral direction (at least one of the x and y directions).

[0294] (Experimental Example 1)

[0295] The steel plates were heated, and the temperature change after heating was measured under varying conditions. Specifically, the following experiments were conducted. 1.5 GPa grade hot-pressing steel plates with thicknesses of 0.8 mm and 1.6 mm were used as test materials, and thermocouples were installed on the surface of the steel plates to measure the temperature. The steel plates were heated to 950°C using a heating furnace, and the temperature drop during air cooling after removal from the furnace was measured. Comparative Example 1 used the condition of heating and naturally cooling a single 1.6 mm thick steel plate, Comparative Example 2 used the condition of heating and naturally cooling a single 0.8 mm thick steel plate, and Example 3 used the condition of overlapping two 0.8 mm thick steel plates in the normal direction of the plate surface and arranging them at a predetermined interval D and fixing them. Under the condition of overlapping two steel plates, the interval D was set to three standards: 10 mm, 30 mm, and 50 mm, which were respectively set as Example 1, Example 2, and Example 3. Figure 33 This indicates the temperature measurement locations. The temperatures of the upper and lower steel plates were measured at distances of 5mm, 20mm, 30mm, and 50mm from the ends of the steel plates, as well as at the center of the steel plates.

[0296] Figure 34 This is a graph representing the average cooling rate as a result of the measurements. The average cooling rate was derived from the measured temperature drop curve, from 800℃ to 750℃. Figure 35 This is a graph representing the range of the object derived as the average cooling rate. From Figure 34The results confirmed that, at all measurement locations, compared to the condition of a single 0.8mm thick steel plate (Comparative Example 1), the average cooling rate of two 0.8mm thick steel plates stacked vertically (Examples 1-3) could be reduced. It was also confirmed that, when two steel plates are stacked, a smaller interval D between the two plates reduces the average cooling rate near the ends of the plates, and the improvement in average cooling rate is significant at all measurement locations. In Example 3, where the interval D was set to 50mm, the cooling rate was improved to an intermediate level between the conditions of a single 0.8mm thick steel plate (Comparative Example 1) and a single 1.6mm thick steel plate (Comparative Example 2). In Example 1, where the interval D was set to 10mm, the cooling rate was improved to the same extent as in Comparative Example 2, where a single 1.6mm thick steel plate was used. By appropriately setting the interval D between two overlapping steel plates, it is possible to obtain the same cooling characteristics as a steel plate with twice the thickness, i.e. twice the heat capacity.

[0297] (Experimental Example 2)

[0298] Next, with two 0.8mm thick steel plates stacked vertically, the plates were heated to 950°C using a heating device, and the temperature drop during conveying by the conveyor after heating was measured. The maximum conveying speed was 1.6 m / s, and the travel distance was approximately 3.2 m. Furthermore, the temperature drop was also measured with shielding plates installed in front of and above the conveyor in the conveying direction. Figure 36 The structure of the shielding plate 97 used in the experiment is shown. The shielding plate 97 is configured such that both steel plates M1 and M2 are completely covered when viewed from the front during transport, and are also completely covered when viewed from above. The interval D between the two steel plates M1 and M2 is set to 30 mm. In the experiment, to accurately fix the interval D, the upper and lower steel plates M1 and M2 are fixed using connector 31, thereby implementing heating and transport. Example 4 describes the condition without the shielding plate, and Example 5 describes the condition with the shielding plate. The temperature measurement positions are set at 5 mm, 30 mm, and 50 mm from the ends of the steel plates M1 and M2. The temperature of the upper and lower steel plates M1 and M2 is measured using thermocouple NT.

[0299] Figure 37 This is a graph showing the average cooling rate as a result of the measurement. During the movement of the steel plate using the conveyor, the time after exiting the heating furnace is approximately 5 to 8 seconds. Therefore, the average cooling rate within the 5 to 8-second interval after exiting the heating furnace is derived from the measured temperature drop curve. Figure 38 This is a graph representing the range of the object derived as the average cooling rate. Figure 37 In the results shown, in Example 4 without the shielding plate, the cooling rate at the end of the steel plate became relatively large. Furthermore, the upper steel plate cooled faster than the lower steel plate. This is consistent with... Figure 34 The results of Example 2, in which the interval D was set to 30 mm and temperature measurements were taken in a static state, showed the same tendency, but the absolute value of the cooling rate increased due to the influence of the conveying process. On the other hand, in Example 5, where shielding plates were provided in front of and above the conveying device in the conveying direction, the cooling rate at the end of the steel plate and the cooling rate of the upper steel plate were greatly improved. In addition, the difference in cooling rate between the portion in the plate width direction and the upper and lower steel plates could also be significantly reduced.

[0300] As can be seen from the above results, when multiple heated workpieces are conveyed overlapping in the normal direction of the plate surface, it is important to maintain an appropriate distance between the multiple heated workpieces from the viewpoint of reducing the cooling rate. In the above embodiment, the two ends of the first heated workpiece and the two ends of the second heated workpiece are supported by the first claw and the second claw, respectively, thus stably maintaining the distance between the two workpieces. Therefore, the temperature drop of the first heated workpiece and the temperature drop of the second heated workpiece can be suppressed, and the conveying can be performed simply and efficiently.

[0301] Explanation of reference numerals in the attached figures

[0302] 46. ​​Conveying device; 48. Base frame; 71. First arm; 71b. First claw; 72. Second arm; 72b. Second claw; W1. First heated workpiece; W2. Second heated workpiece.

Claims

1. A method for manufacturing a pressed molded article, wherein, The method for manufacturing the compressed molded article includes: The heating process involves simultaneously heating at least two plate-shaped workpieces using a heating device. The conveying process involves using a conveying device to transport at least two heated workpieces, which have been heated in the heating process, to a press; and In the pressing process, the press is used to process the at least two heated workpieces that were conveyed to the press in the conveying process. The conveying process includes the following steps: A pair of first arms, which are rotatably mounted on the base of the conveying device, are driven to support and lift the lower surfaces of both ends of the first heated workpiece, one of the at least two heated workpieces, using the claws of the pair of first arms. A pair of second arms, which are rotatably mounted on the base of the conveying device, are driven using a system different from that of the pair of first arms. The claws of the pair of second arms are used to support and lift the lower surfaces of both ends of the second heated workpiece, one of the at least two heated workpieces. The first heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of first arms of the conveying device, and the second heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of second arms, are conveyed in a state in which they overlap each other in the normal direction of the plate surface of the first heated workpiece. Drive the pair of first arms to lower the first heated workpiece supported by the pair of first arms to the pressing position of the press. as well as The pair of second arms are driven using a different system than the pair of first arms, causing the second heated workpiece supported by the pair of second arms to descend to the pressing position of the press. In the conveying process, the first heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of first arms, and the second heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of second arms, are conveyed in a state where they overlap each other at an interval of 0 mm or more and 50 mm or less in the normal direction of the plate surface of the first heated workpiece.

2. The method for manufacturing a pressed molded article according to claim 1, wherein, In the conveying process, the maximum distance D in the normal direction of the plate surface between the first heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of first arms, and the second heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of second arms, and the minimum plate thickness t of the thinnest portion of the first heated workpiece and the second heated workpiece are related by the following formula: D≤60t, The units for the interval D and the minimum plate thickness t are mm.

3. The method for manufacturing a pressed molded article according to claim 1 or 2, wherein, The first heated workpiece and the second heated workpiece, which are conveyed by the conveying device in an overlapping state in the normal direction of the plate surface, have a plate thickness greater than that of the other and a larger area than that of the other.

4. The method for manufacturing a pressed molded article according to claim 1 or 2, wherein, In the conveying process, the first heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of first arms, and the second heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of second arms, are conveyed with their front ends covered by side shielding plates in the conveying direction.

5. The method for manufacturing a pressed molded article according to claim 4, wherein, The side shielding plate has an inclined surface that is inclined toward the first heated workpiece and the second heated workpiece as it moves from the center toward the end.

6. The method for manufacturing a pressed molded article according to claim 4, wherein, At least one of the first heated workpiece and the second heated workpiece has a long side direction and a short side direction when it is being conveyed by the conveying device. The side shielding plate covers the long side of the first heated workpiece and the long side of the second heated workpiece during the conveying process.

7. The method for manufacturing a pressed molded article according to claim 1 or 2, wherein, In the conveying process, the first heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of first arms, and the second heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of second arms, are conveyed with their upper surfaces covered by an upper shielding plate.

8. The method for manufacturing a pressed molded article according to claim 1 or 2, wherein, The first heated workpiece and the second heated workpiece are differential thickness plates comprising a thick-walled portion and a thin-walled portion. In the conveying process, the thick-walled portion of the first heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of first arms, and the thin-walled portion of the second heated workpiece, whose lower surfaces at both ends are supported by the claws of the pair of second arms, are conveyed in a state where they overlap in the normal direction of the plate surface.

9. The method for manufacturing a pressed molded article according to claim 1 or 2, wherein, In the heating process, In the heating device, heating is performed with the first heating workpiece placed above the plate-shaped heat storage material and overlapping the heat storage material in the normal direction of the plate surface of the first heating workpiece, and the second heating workpiece placed above the heat storage material and overlapping the heat storage material in the normal direction of the plate surface of the second heating workpiece. The conveying process includes the following steps: conveying the first heated workpiece and the second heated workpiece, which are placed above the heat storage material, together with the heat storage material, from the heating device to a lifting position where they are lifted using the conveying device.

10. The method for manufacturing a pressed molded article according to claim 1 or 2, wherein, In the heating process, The first heated workpiece is placed on a first set of at least three supports extending upward from a tray body having a hollow portion that runs vertically through when viewed from above. The second heated workpiece is placed on a second set of at least three supports extending upward from the tray body, and is positioned above the first heated workpiece. The second heated workpiece overlaps with the first heated workpiece in the normal direction of the surface of the first heated workpiece. In this configuration, heating is performed using the heating device. The conveying process includes the following steps: The first heated workpiece is placed on the first support group, and the second heated workpiece is placed on the second support group and above the first heated workpiece. The second heated workpiece is arranged overlapping the first heated workpiece in the normal direction of the plate surface of the first heated workpiece. In the above state, together with the tray body, it is conveyed from the heating device to the lifting position where it is lifted by the conveying device.

11. A conveying device for heating workpieces, wherein, The conveying device for the heated workpiece includes: The base frame is capable of lateral movement perpendicular to the vertical direction; A pair of first arms, which are rotatably mounted on the base frame; A pair of second arms, which are rotatably mounted on the base frame; A first driving unit, used to drive the first arm; and The second drive unit is used to drive the second arm. The pair of first arms have: a pair of first bases arranged laterally on the base frame and extending from the base frame in a vertical direction; And the first claw, which extends laterally curved from the pair of first base portions, The pair of second arms have: a pair of second bases arranged laterally on the base frame and extending from the base frame in a vertical direction; And a second claw, which extends laterally curved from the pair of second base portions, The first drive unit changes the lateral distance between the pair of first claws by rotating the pair of first arms relative to the base frame. The second drive unit changes the lateral distance between the pair of second claws by rotating the pair of second arms relative to the base frame. The first drive unit and the second drive unit are configured to independently control the rotation of the first arm and the rotation of the second arm, respectively. The pair of first claws are able to support the lower surfaces of the lateral ends of the first heated workpiece in a state where they are close to each other in the lateral direction. The pair of second claws are able to support the lower surfaces of the lateral ends of the second heated workpiece in a state where they are close to each other in the lateral direction. When the pair of first claws supports the first heated workpiece and the pair of second claws supports the second heated workpiece, the positions of the pair of first claws in the vertical direction and the positions of the pair of second claws in the vertical direction are different from each other, so that the first heated workpiece and the second heated workpiece overlap each other in the normal direction of the plate surface of the first heated workpiece.

12. The conveying device for heated workpieces according to claim 11, wherein, In the vertical direction, the pair of first claws and the pair of second claws are separated by a distance of 0mm to 50mm based on the maximum thickness of the heated workpiece supported by the lower claw of the first claw and the second claw.

13. The conveying device for heated workpieces according to claim 11 or 12, wherein, The conveying device for the heated workpiece also includes a side shielding plate that laterally covers both the pair of first claws and the pair of second claws.

14. The conveying device for heated workpieces according to claim 13, wherein, The side shielding plate has a surface that slopes toward the pair of first claws and the pair of second claws as it moves from the center toward the ends.

15. The conveying device for heated workpieces according to claim 11 or 12, wherein, The conveying device for the heated workpiece also includes an upper shielding plate that covers both the pair of first claws and the pair of second claws from above.

16. The conveying device for heated workpieces according to claim 11 or 12, wherein, The base frame can rotate 180 degrees about the vertical axis.

17. The conveying device for heated workpieces according to claim 11 or 12, wherein, The distance between the pair of first claws and the pair of second claws in the vertical direction can be adjusted.

18. The conveying device for heated workpieces according to claim 11 or 12, wherein, The conveying device for the heated workpiece includes: A pair of third arms, which are rotatably mounted on the base frame; A pair of fourth arms, which are rotatably mounted on the base frame; A third drive unit, used to drive the third arm; and The fourth drive unit is used to drive the fourth arm. The pair of third arms each has: a pair of third bases arranged laterally on the base frame and in a direction perpendicular to the arrangement direction of the pair of first bases, and extending vertically from the base frame; and third claws extending laterally curved from the pair of third bases. The pair of fourth arms each has: a pair of fourth bases arranged laterally on the base frame and in a direction perpendicular to the arrangement direction of the pair of second bases, and extending vertically from the base frame; and fourth claws extending laterally curved from the pair of fourth bases. The third drive unit changes the lateral distance between the pair of third claws by rotating the pair of third arms relative to the base frame. The fourth drive unit changes the lateral distance between the pair of fourth claws by rotating the pair of fourth arms relative to the base frame. The vertical positions of the pair of first claws and the pair of third claws are the same. The positions of the pair of second claws in the vertical direction are the same as those of the pair of fourth claws in the vertical direction.

19. A hot pressing production line, wherein, The hot pressing production line includes: The conveying device for the heated workpiece according to any one of claims 11 to 18; A heating device that heats the first workpiece and the second workpiece. A platform for placing the first heated workpiece and the second heated workpiece, which have been heated by the heating device; At least one press having at least two sets of paired dies; and A moving device that moves the conveying device between its position above the table and the pressing position between the at least two pairs of molds.

20. The hot pressing production line according to claim 19, wherein, The hot pressing production line also includes a tray that supports the first and second heated workpieces when the heating device heats them. The tray has: Pallet body; A plate-shaped heat storage material is placed on the tray body; and A first support group consisting of at least three supports extending upward from the tray body or the heat storage material, or a protrusion of the heat storage material protruding upward from the heat storage material and capable of supporting the first heated workpiece and the second heated workpiece. The first support group is configured such that, when viewed from above, the virtual straight lines connecting the supports to each other form at least one triangle.

21. The hot pressing production line according to claim 19, wherein, The hot pressing production line also includes a tray that supports the first and second heated workpieces when the heating device heats them. The tray has: The pallet body has a shape extending along a surface perpendicular to the vertical direction, including a hollow portion extending vertically; and The support assembly extends upward from the tray body. The support assembly includes: A first support group with at least three supports, the first support group with at least three supports configured to support the lower surface of the plate-shaped first heated workpiece; and A second support group with at least three supports, the second support group being configured to support the lower surface of the second heated workpiece located above the first heated workpiece supported by the first support group. The first support group is configured such that, when viewed from above, the virtual straight lines connecting the supports form at least one triangle. The second support group is positioned differently from the first support group when viewed from above, and the second support group is configured such that when viewed from above, the virtual straight lines connecting the supports form at least one triangle, and each of the second support groups is taller than the lowest support in the first support group.

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