Thin sheet forming dies

Abstract: It is an object of this invention to use only one die for forming an excessively bent negative angle forming portion when negative angle forming is carried out on formed thin sheets (W) using rotating cams (2,3). This is a forming die with a forming portion to achieve a negative angle when the second die (21) is moved in the straight line to abut the first die (4) for forming thin sheets, and in the thin sheet forming dies in which a cylindrical ratating cam (2,3) with a groove (14,44) formed in the axial direction is rotatably mounted to the first die, a negative angle forming portion is formed in the groove edge portion of the rotating cam, a slide cam (27) with the negative angle forming portion is mounted to the second die in such a manner to be opposite to the said rotating cam, an automatic return device (12) for rotating and retracting the rotating cam to enable the removal of the work from the first die after forming is mounted to the first die, it is a thin sheet forming die designed to process an exessively bent negative angle forming portion with a plurality of rotating cams, the rotation axis positions of which differ and are parallel to one another.

Description: FIELD OF THE INVENTION The invention relates to thin sheet forming dies as defined in the preamble of claim 1 and as such disclosed in US-A-5 347 838. DESCRIPTION OF THE PRIOR ART The negative angle of thin sheets such as sheet metal or plastics is generally formed by the use of a slide cam. Now, the negative angle forming referred to here means forming with a forming portion which comes inwards towards the lower die from the working locus of the upper die when the work loaded on the lower die is formed by descending the upper die in the vertical direction for abutting. In the conventional negative angle forming of thin sheet products, the work is loaded on the lower die and the upper die descends downwards in the vertical direction to drive the driven cam of the lower die by the driving cam of the upper die, and the work is processed from the lateral direction, and when processing completes and the upper die ascends, the driven cam is retracted by springs. In this event, the forming portion of the driven cam which slides and forms the work from the outward lateral direction of the work is formed in the integrated profile identical to that of the forming portion of the work, but the forming portion of the lower die with the work loaded must be designed to divided and retract the portion forming a negative angle of the lower die, or the rear portion forming the negative angle is deleted and the work is moved forwards to enable the removal of the work. When the degree of negative angle is small, no serious problems occur but when the degree of negative angle is great or the work has a slender frame-like cross section with grooves, for example, parts such as front pillar outer of automobile sheet metal parts, due to the narrow groove width of the work, not only the profile is unable to be clearly formed at the forming portion of the driven cam when the portion of the lower die serving as an negative angle is divided or deleted, but also the strength of the lower die lacks and it is impossible to carry out negative angle forming. In negative angle forming using the slide cam, the driven cam is slid in a considerably long straight distance for forming, it is not always easy to repeatedly slide the driven cam exactly to a specified position and it is difficult to produce products with stable quality. In addition, there are cases in which distortion or bend is generated in products and the products must be touched up, but it is practically impossible to touch up products for parts composing the automobile outer plate portions such as side panels, front fenders, roofs, bonnets, trunk lids, door panels, or front pillar outers, because they have three-dimensional curved surfaces and profiles. In the case of automobile sheet metal assembly, if any distortion or bend is generated in products, it is difficult to combine such products with other parts and it is unable to provide high-quality automobile sheet metal structure and to maintain a specified product accuracy of thin-plate formed products. When the slide cam is used, a large driven cam and heel must be mounted on the side portion with the work of the lower die loaded, requiring a large lower-die area, increasing the die weight as much, and resulting in expensive dies. Therefore, in order to solve the above problems, a forming method of thin sheets and the forming dies in which the linear upward and downward motion of a press is converted into rotary motion has already been proposed by the present applicant under Japanese Patent Publication No. Sho 63-41652. Referring now to Figs. 6-10, the forming dies will be described in further detail. FIG. 6 shows right and left schematic perspective views of a complete front pillar outer, an automobile sheet metal part formed by the forming dies. In the figure, the bottom shows the front pillar outer for the right side and the top for the left side. This front pillar outer constitutes part of the front door frame, also part of the front wind shield frame, and in addition part of the frame supporting the roof panel, and comprises the joint part with other many parts, and is a product for which severe product accuracy is required, and if the required accuracy is not satisfied, it is unable to provide a sheet metal car body with good quality. Because the front pillar outer composes the outer plate portion of the automobile, it has three-dimensional curved surfaces and profiles. The portion with the negative angle formed by this forming dies is shown with letter F, whose cross section is shown as work W in Fig. 10. That is, after the negative angle is formed, the work W achieves the condition shown in Fig. 10 from the condition shown in Fig. 7. By the way, this press-working process includes drawing which takes place first, then, peripheral trimming to the condition shown in Fig. 7, and this forming process as the succeeding third process. With respect to the lower die 100, a cylindrical rotating cam 102 formed with an axial groove 101 is rotatably mounted to the lower die proper 103. The lower die proper 103 is securely fixed to the lower substrate 121 with a bolt 122. The top surface of the lower die proper 103 is formed in a shape that can receive the work W, and a negative angle forming portion 104 is formed at the edge portion of the groove 101 of the rotating cam 102 nearest to the top surface of the lower die 103. An automatic return device 105 which rotates and retracts the rotating cam 102 is embedded in the lower die proper 103 so that the work W can be removed from the lower die proper 103 after forming. In this example, the automatic return device 105 brings a push pin 107 energized by coil spring 106 in contact with the bottom surface of the tip end of the rolling plate 108 securely fixed to the surface opposite to the negative angle forming portion 104 of the groove 101 of the rotating cam 102 with a bolt 151. For the automatic return device, pneumatic devices, hydraulic devices, link mechanisms, cams, or other similar mechanisms may be used, and may be mounted not only to the lower die but also between the upper and the lower dies. On the other hand, to the upper die 109, a slide cam 110 is mounted to the position opposite to the said rotating cam 102. This slide cam 110 has the negative angle forming portion 112 formed at the bottom end, the slide cam 110 is guided by the guide (not illustrated), and the slide cam 110 is energized in the outward direction of the die by a coil spring 117 compressedly mounted between the slide cam 110 top surface and the inclined guide 154 bottom surface securely fixed to the top substrate 152 with a bolt 153. The slide cam 110 is stopped by a stopping plate 156 securely affixed to the inclined guide 154 with a bolt 155. The pad 157 is energized downwards by a coil spring 158, is hung from the top substrate 152 with the hang bolt 119, and strongly presses the work W against the lower die proper 103 to prevent the work W from moving before the negative angle is formed on the work W. Next description will be made on the operation of this forming die. First of all, as shown in Fig. 7, the upper die 109 is located at the top dead center, and then, the work W is loaded on the lower die proper 103 of the lower die 100. In this event, the rotating cam 102 is rolled and retracted by the automatic return device 105. Then, the upper die 109 begins descending and as shown in Fig. 8, first of all, the bottom surface of the slide cam 110 comes in contact with the rolling plate 108 to rotate the rotating cam 102 clockwise in Fig. 8 without causing the slide cam 110 to interfere with the negative angle forming portion 104 of the rotating cam 102. As the upper die 109 continues to descend further, the slide cam 110 energized in the outward direction of the die resists against the energizing force of the coil spring 117, moves to the left in the lateral direction by the operation of the cam, enters the state shown in Fig. 9, and the negative-angle forming portion 104 of the rolled rotating cam 102 cooperates with the negative-angle forming portion 112 of the slide cam 110 to negative-angle form the work W. After negative angle is formed, the upper die 109 begins rising. The slide cam 110 is energized in the outward direction of the die by the coil spring 117, moves to the right in Fig. 10, and ascends without interfering with the work W with the negative angle formed. On the other hand, the rotating cam 102 rotates to the left in Fig. 10 by the automatic return device 105 because the slide cam 110 being restrained ascends, enabling the work W to be removed without interfering with the negative angle forming portion 104 of the rotating cam 102 when the negative-angle formed work W is removed from the lower die 103. The formed thin sheet products had the negative angle formed using the rotating cam as described above, but because the rotating cam rotates around the rotation axis to process the work, if the work is nearly linear and is not greatly bent, the negative angle forming portion can enter one of the rotating cams and is able to be processed, but if the work is greatly bent, the negative angle forming portion is unable to completely enter one of the rotating cams and is unable to be processed. In particular, automobile sheet metal parts including door panels have many bent portions, and in recent years, there are many negative angle forming portions from the viewpoint of designs in addition to conventional bent portions, and it is demanded to form these negative angle forming portions in one process without undergoing many processes and to improve production efficiency. SUMMARY OF THE INVENTION The invention is defined by the features of claim 1. Because a plurality of rotating cams according to this invention are arranged in such a manner that the rotation axis becomes parallel to one another, the end faces do not interfere with each other at the joints of adjoining rotating cams, when rotated. Preferred embodiments of the invention are defined by the features of the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view of one specific embodiment of the invention; Fig. 2 shows two cross-sectional views of the work taken on line III-III of Fig. 1 before and after negative-angle forming; Fig. 3 is a longitudinal cross-sectional view taken on line III-III of Fig. 1; Fig. 4 is a longitudinal cross-sectional view taken on line IV-IV of Fig. 1; Fig. 5 shows two views showing a linkage mechanism according to this invention; Fig. 6 shows schematic right and left perspective views of the completed front pillar outer, a sheet metal part of automobiles; Fig. 7 is a longitudinal cross-sectional view when the upper die of the forming dies to form negative angles for the front pillar outer of Fig. 6 is in the top dead center condition; Fig. 8 is a longitudinal cross-sectional view of the upper die of the forming dies of Fig. 7 which descends to come in contact with the lower die; Fig. 9 is a longitudinal cross-sectional view of the upper die of the forming dies of Fig. 7 in the bottom dead center condition; and Fig. 10 is a longitudinal cross-sectional view of the upper die which ascends and is in the top dead center condition after the forming dies of Fig. 7 finish negative-angle forming. EMBODIMENTS Referring now to one specific embodiment shown in FIG. 1-5, this invention will be described in further detail. The work W formed by the forming dies according to this invention is an automobile trunk lid outer as shown in Fig. 1, and the recessed circulator arc curved portion of the front edge portion of the trunk lid outer as viewed from the plane is negative-angle formed, and as shown in Fig. 2, it is negative-angle formed to have a cross-section shown below from that shown above. Fig. 1 shows a plane view of the thin sheet forming dies, Fig. 2 the condition of a flange 1 before and after the work W, Fig. 3 a longitudinal cross-sectional view taken on the line - of Fig. 1, Fig. 4 a longitudinal cross-sectional view taken on the line - of Fig. 1, and Fig. 5 a linkage mechanism of the rotating cam. The processed portion of the work W of the thin sheet forming dies is the front edge portion of the trunk lid outer and as clear from Fig. 1, it is a recessed form as seen from the plane, and as clear from Fig. 4, both end portions are located considerably below the center portion and considerably displaced towards the right. If this is processed with one piece of rotating cam, an extremely large rotating cam is required. Excessively increasing the size is practically impossible in fabricating dies, and is about 320 mm in diameter at maximum. In addition, the flange angle differs at the center portion and both end portions, and there is a case in which the negative-angle forming portion of the rotating cam becomes too acute to maintain the strength. In this embodiment, the rotating cam is divided into three portions; namely, the center portion and both end portions, and a linkage mechanism is mounted to the rotating cam, so that all the rotating cams can be driven by one slide cam. On both end portions of the center rotating cam 2 of the rotating axis C A in Fig. 1, edge portion rotating cams 3 of the rotation axis C B are arranged, respectively. As is clear from Fig. 4, the edge-portion rotating cam 3 is displaced by H downwards and by L rightwards from the center rotating cam 2. The lower die 4 has a support block 7 fixed to the lower die base 5 with a bolt 6, and rotatably supports the cylindrical center rotating cam 2 with a groove 14 formed axially in a horizontal slot groove 8 at the top center of the support block 7. In this embodiment, an air cylinder 12 is equipped as an automatic return device of the rotating cam. Needless to say, the automatic return device is not limited to an air cylinder but a spring, hydraulic equipment, link mechanism, cam, or any mechanisms similar to these may be used, and can be mounted not only to the lower die but also to the upper die. In Fig. 3, a connecting member 9 is fixed to the bottom surface of the center rotating cam 2 with a bolt 10, and to the tip end of a piston rod 13 of the air cylinder 12 whose base end is pivotally mounted to the bracket 11 fixed to the support block 7 with a bolt 15, the said connecting member 9 is pivotally mounted, so that the piston rod 13 is contracted to return the center rotating cam 2. At the bottom portion of the slot groove 8 of the support block 7, a window slot 16 is provided for allowing the connecting member 9 to rotate. At the edge portion of the groove 14 of the center rotating cam 2, a negative angle forming portion 17 is formed, and a rolling plate 72 is fixed to the side opposite to the negative angle forming portion 17 of the groove 14 with a bolt 73. By the way, in Fig. 1, the rolling plate 72 is omitted. The negative angle forming portion 17 of the center rotating cam 2 is formed into a work loading portion 18 in the profile same as the bottom surface of the work W so that the work W is loaded, and a work support portion 19 in the profile same as the bottom surface of the work W is formed slightly outwards in the upper portion linked to the work loading portion 18 of the center rotating cam 2 of the support block 7. The upper die 21 has a support block 23 fixed to the lower surface of the upper die base 22 with a bolt 24, and a wear plate 25 fixed to the lower surface of the support block 23 with a bolt 26, and the slide cam 27 is held by a guide plate 28 and slid on the lower surface of the wear plate 25. At the portion opposite to the groove 14 of the center rotating cam 2 of the slide cam 27, a negative angle forming portion 34 is fixed with a bolt 35. On the top surface of the slide cam 27, a support plate 29 is fixed with a bolt 30, and between this support plate 29 and the longitudinal wall 24 of the support block 23, a coil spring 31 is compressedly mounted to energize the slide cam 27 to the outward direction of the die. The said coil spring 31 is mounted in the externally fitted form to the positioning pin 32 screwed into the longitudinal wall 24, and the tip end of the said positioning pin 32 allows a stopping plate 33 fixed to the side surface opposite to the longitudinal wall 24 to pass through. When the upper die 21 rises, the slide cam 27 moves outwards of the die until the support plate 29 comes in contact with the stopping plate 33 by the energizing force of the coil spring 31. Though it is not illustrated, in order to stably support the work W, the positioning member of the work W is mounted to the lower die 4, and to the upper die 21, as described in the conventional example, a pad for pressurizing the work W is mounted to the lower die, but as these would make the illustration complicated and essential points of this invention difficult to understand, the positioning member and the pad are omitted. Next, referring to Fig. 4, the construction of the dies on both edge portions of the work W will be described. To the lower die base 5, an edge supporting block 41 is fixed with a bolt 42, and a cylindrical edge portion rotating cam 3 with a groove 44 formed in the axial direction is rotatably supported in a horizontal slot groove 43 at the top surface center of the edge supporting block 41. At the peripheral portion of the groove 44 of the end portion rotating cam, a negative angle forming portion 45 is formed, and on the side opposite to the negative angle forming portion 45 of the groove 44, a rolling plate 40 is securely fixed with a bolt 47. In Fig. 1, a rolling plate 40 is omitted. The negative angle forming portion 45 of the edge portion cam 3 is formed into a work loading portion 48 in the profile same as the bottom surface of the work W so that the work W is loaded, and a work support portion 49 in the profile same as the bottom surface of the work W is formed slightly outwards from the top portion linked to the work loading portion 48 of the edge portion rotating cam 3 of the edge portion supporting block 41. In Fig. 4, like elements of the upper die 21 of Fig. 3 are given like reference characters and they fulfill like functions. To the position opposite to the groove 44 of the edge portion rotating cam 3 of the slide cam 27, a negative angle forming portion 50 is fixed with a bolt 51. In Fig. 4, same as in Fig. 3, to the lower die 4, a work W positioning member and to the upper die 21, a pad are mounted, respectively, but their illustrations are omitted. In Fig. 5, there is shown a linkage mechanism for transmitting the rolling force transmitted to the center rotating cam 2 by the air cylinder 12 to the adjoining edge portion rotating cams 3 on both sides. A latching plate 62 with a notched groove 61 formed is fixed to the end face of the center rotating cam 2 with a bolt 63, and a positioning pin 65 is fixed with a bolt 64 to the position of the end portion rotating cam 3 on the end face opposite to the notched groove 61 of the latching plate 62 on the end face of the said center rotating cam 2. When the center rotating cam 2 is driven with the air cylinder 12, the edge portion rotating cam 3 is simultaneously rotated in the same direction because the pin 65 is engaged with the latching plate 62. By the way, it is possible to drive the edge portion rotating cam with an air cylinder to drive the center rotating cam. In addition, there described is an example of three pieces of rotating cams, but it is possible to drive four or more rotating cams by one air cylinder with a linkage mechanism interposed. Next description will be made on the operation of the thin sheet forming dies. The condition shown in Figs. 3 and 4 is all the bottom dead center condition and corresponds to Fig. 9 of the conventional example. It is not illustrated but as shown in Fig. 7 of the conventional example, the upper die 21 is located at the top dead center, when the work W is loaded to the work support portions 19, 49 of the lower die 4. In this event, the center rotating cam 2 and the edge portion rotating cam 3 are rolled to retract by the air cylinder 12. Next, as shown in Fig. 8 of the conventional example, in the upper die 21, the inclined surface 71 of the slide cam 27 comes in contact with the rolling plates 18, 46 without allowing the slide cam 27 to interfere with the negative angle forming portions 17, 45 of the center rotating cam 2 and edge portion rotating cam 3, causing the center rotating cam 2 and the edge portion rotating cam 3 to rotate clockwise. As the upper die 21 further continues to descend, the slide cam 27 energized in the outward direction of the dies resist against the energizing force of the coil spring 31 and moves to the left in the lateral direction by the action of the cam, and enters the condition shown in Fig. 9 of the conventional example, that is, the condition shown in Figs. 3 and 4, and the negative angle forming portions 17, 45 of the rolled center rotating cam 2 and edge portion rotating cam 3 cooperate with the negative angle forming portions 34 and 50 of the slide cam 27 to negative-angle form the work W. After negative-angle forming, the upper die 21 begins to ascend. The slide cam 27 is energized in the outward direction of the dies by the coil spring 31, moves to the right as shown in Fig. 10 of the conventional example, and ascends without interfering with the negative-angle formed work W. On the other hand, when the restrained slide cam 27 ascends and the air cylinder 12 contracts the piston rod 13, the center rotating cam 2 and the edge portion rotating cam 3 rotate in the right direction to enable the removal of the work W without interfering with the negative angle forming portions 17, 45 of the center rotating cam 2 and the edge portion rotating cam 3, when the negative-angle formed work W is removed from the lower die 41. In order to take out the work W without allowing the work W to interfere with the lower die, rolling the center rotating cam 2 by the air cylinder 12 rolls and retracts the separate edge portion rotating cam 3 positioned on both sides. It is possible to operate a plurality of rotating cams by one air cylinder with a linkage mechanism interposed. Described is a forming die with a forming portion to achieve a negative angle when the second die is moved in the straight line to abut the first die for forming, and in the thin sheet forming dies in which a cylindrical rotating cam with a groove formed in the axial direction is rotatably mounted to the first die, a negative angle forming portion is formed in the groove edge portion of the rotating cam, a slide cam with the negative angle forming portion is mounted to the second die in such a manner to be opposite to the said rotating cam, an automatic return device for rotating and retracting the rotating cam to enable the removal of the work from the first die after forming is mounted to the first die. Because it is a thin sheet forming die designed to process an excessively bent negative angle forming portion with a plurality of rotating cams, the rotation axis positions of which differ and are parallel to one another, it becomes possible to form an excessively bent negative angle forming portion with one forming die, to reduce the number of processes, and to improve the processing accuracy. Because an excessively bent negative forming section is divided into a plurality of portions, it is possible to give consideration to prevent the negative-angle forming portions of the rotating cams from being excessively acute, and the rotating cams are free of short strength. In addition, because in this invention, a plurality of rotating cams are arranged with their rotation axes to be parallel to one another, their end faces do not interfere with one another at the joints of adjoining rotating cams when the rotating cams rotate. In addition, a linkage mechanism is equipped to the adjoining rotating cams so that rotating cams can be driven by one automatic return device. Furthermore, a latching plate and a pin are engaged as a linkage mechanism, achieving an extremely simple construction.

Claims: A thin sheet forming die comprising a first die (4) and a second die (21), wherein said first die (4) comprises a plurality of rotatably mounted cylindrical rotating cams (2,3), said rotating cams (2,3) being respectively provided with a groove (14,44) formed in the axial direction and with a negative angle forming portion (17,45) formed at an edge portion of said groove (14,44), whereby said negative angle forming portions (17,45) of said rotating cams (2,3) constitute a continuous forming portion for a continuous, longitudinally bent negative angle section of a thin sheet work piece (W), and an automatic return device (12) for rotating said rotating cams (2,3) to a position in which the work piece (W) can be removed from the first die (4) after forming, and said second die (21) comprises a slide cam (27) arranged opposite to said rotating cams (2,3) of the first die (4) and having a negative angle forming portion (34,50) provided thereon in such a manner so as to cooperate with the negative angle forming portions (17,45) of the first die (4) to form the continuous, longitudinally bent negative angle section of the thin sheet work piece (W) when the slide cam (27) of the second die (21) is moved in a straight line direction and abutted to the rotating cams (2,3) of the first die (4), characterised in that the rotation axes of the rotating cams (2,3) are differing from and parallel to one another. The thin sheet forming die according to claim 1, wherein a linkage mechanism (61-65) is provided to allow said plurality of rotating cams (2,3) to be driven by one automatic return device (12). The thin sheet forming die according to claim 2, wherein said linkage mechanism comprises a latching plate (62) mounted on an end face of one of said rotating cams (2,3) facing an end face of an adjacent one of said rotating cams (2,3) and engaging with a pin (65) mounted on said end face of said adjacent one of said rotating cams (2,3).

Inventors: MATSUOKA MITSUO, MATSUOKA, MITSUO
Applicants: UMIX CO LTD, UMIX CO., LTD.
Application year: 1997
Main classification: B21D5
IPC codes: B21D19, B21D5