Negative angular forming dies and pressing apparatus thereof

Abstract: In a negative angular forming in which a lowering locus of an upper die (4) enters into a lower die (1), it is an object of the present invention to prevent a wrinkle from being generated in the entering portion of a work by pressing and clamping the entering portion of the work. A negative angular forming dies of the invention comprises: a lower die (1) having a supporting portion on which a metal thin plate work (w) is placed, an upper die which is lowered in the straight direction with respect to the lower die (1) to collide against the work for forming the work, a groove formed in the axial direction such as to open at an outer peripheral surface, an entering forming portion formed on an edge of the groove closer to the supporting portion such as to enter from the locus of the upper die, a columnar body rotatably provided on the lower die, an entering forming portion, a slide cam slidably provided on the upper die such as to be opposed to the columnar body, and an automatic returning tool provided on the lower die for rotating and retreating the columnar body to a state where the work can be taken out from the lower die (1) after the forming, the work being placed on the supporting portion of the lower die (1), the columnar body being turned and the slide cam sliding to form the work by the entering forming portion of the columnar body and the entering forming portion of the slide cam (9), the columnar body being turned and retreated by the automatic returning tool after forming so that the formed work can be taken out from the lower die, wherein a clamping member of a negative angular forming portion of the work is slidably provided on the columnar body, the work is clamped by the pressed clamping member and the slide cam (9) and formed.

Description: BACKGROUND OF THE INVENTION The present invention relates to a negative angular forming die for forming a metal thin plate and a pressing apparatus thereof. The term of negative angular forming die means forming dies whose upper die enters into its lower die from the lowering locus. The negative angular forming in which a metal thin plate work enters into the lower die from the lowering locus is generally carried out using a slide cam. In a conventional entering forming of a metal thin plate work, the work is placed on a lower die, an upper die is vertically lowered, a follower cam of the lower die is driven by an operation cam of the upper die, the work is worked from the lateral direction, and when the working is completed and the upper die rises, the operation cam is retreated by a spring. In this case, a forming portion of the follower cam which slides from the outer and lateral direction of the work to form the work is integrally formed into the same shape as that of a forming portion of the work. However, since the forming portion of the lower die on which the work is placed must be taken out from the lower die after the working is completed, the entering portion of the lower die must be divided and retreated, or a rear portion of the entering portion must be cut out so that the work can be moved forward and the work can be taken out. When the entering degree is slight, there is no serious problem. However, when the entering degree is great, or when the work is a part such as a metal thin plate front pillar outer of an automobile having a narrow and long frame-like cross section which is groove-like shaped, since the groove width of the work is narrow, if a portion of the entering lower die is divided or cut out, the shape of the work is not clearly formed by the forming portion of the follower cam and further, the strength of the lower die is insufficient, and it is impossible to carry out the entering forming. Further, in the case of the entering forming by the slide cam, since the follower cam is allowed to slide for quite a long distance, it is not always easy to repeatedly slide the follower cam accurately at the specified position, and it is difficult to produce products having stable quality. Further, twist or distortion occurs in the product and the adjustment of the product is required in some cases. However, in the case of a part constituting outer plate portions of an automobile such as a side panel, a fender, a roof, a bonnet, a trunk lid, a door panel and a front pillar outer, such a part has three-dimensional curved surfaces and curved lines and thus, it is almost impossible to fix or adjust the product. In the case of assembling of metal thin plates of the automobile, if twist or distortion occurs in the product, it is difficult to joint such product to another part, and it is not possible to provide the metal thin plate structure of the automobile of high quality, and it is not possible to maintain a predetermined precision of the product of the metal thin plate moulding. If the slide cam is used, it is necessary to provide a large follower cam or heel on a side on which the work of the lower die is placed and thus, the area of the lower die is increased, and the weight and the cost of the pressing dies are increased correspondingly. To solve the above problems, the following structure is proposed in order that the lowering straight motion of the upper die is converted into rotational motion to rotate a columnar body, thereby forming a forming portion which enters into the lower die from the lowering locus in the straight direction of the upper die and then, the columnar body is rotated and retreated to a state in which the formed work can be taken out from the lower die. That is, as shown in Figs. 11 to 14 and as disclosed in EP-A-0 699 489 on which the preamble portion of claim 1 is based, a negative angular forming die comprises a lower die 102 having a supporting portion 101 on which a metal thin plate work W is place, and an upper die 103 which is lowered in the straight direction with respect to the lower die 102 to collide against the work W for forming the work W, a groove 104 is opened at an outer peripheral surface in the axial direction, an entering forming portion 107 which enters from the locus of the upper die 103 is formed on an edge of the groove 104 near the supporting portion 101, the lower die 102 is rotatably provided with a columnar body 106 and an entering forming portion 105, the upper die 103 is slidably provided with a slide cam 108 such as to be opposed to the columnar body 106, the lower die 102 is provided an automatic return tool 109 for rotating and retreating the columnar body 106 to a state in which the work W can be taken out from the lower die 102 after the forming, the work W is placed on the supporting portion 101 of the lower die 102, and with the entering forming portion 105 of the columnar body 106 and the entering forming portion 107 of the slide cam 108, the columnar body 106 is rotated, and the slide cam 108 slides, thereby forming the work W, and after the forming, the columnar body 106 is rotated and retreated by the automatic returning tool 109 so that the formed work W can be taken out from the lower die 102. The operation of this negative angular forming dies will be described below. First, as shown in Fig. 11, the upper die 103 is located at the top dead center. At that time, the work W is placed on the supporting portion 101 of the lower die 102. At that time, the columnar body 106 is rotated and retreated by the automatic returning tool 109. Next, the upper die 103 starts lowering and as shown in Fig. 12, a pad 110 first pushes the work W against the supporting portion 101 and then, a lower surface of the slide cam 108 abuts against a rotation plate 111 such that the slide cam 108 does not interfere with the entering forming portion 105 of the columnar body 106, thereby rotating the columnar body 106 rightward as viewed in Fig. 12. When the upper die 103 keeps lowering further, the slide cam 108 biased outward from the dies is moved leftward in the lateral direction by the operation of the cam against the biasing force of a coil spring 112 to assume a state shown in Fig. 13, and the entering forming of the work W is carried out by the entering forming portion 105 of the rotated columnar body 106 and the entering forming portion 107 of the slide cam 108. After the entering forming, the upper die 103 starts rising. The slide cam 108 is biased outward from the die by the coil spring 112, and the slide cam 108 moves rightward in Fig. 14 and rises without interfering with the entering formed work W. On the other hand, since the slide cam 108 which restricts the columnar body 106 rises, the columnar body 106 is rotated leftward by the automatic returning tool 109 as viewed in Fig. 14, and when the entering formed work W is taken out from the lower die 102, the work W can be taken out without interfering with the entering forming portion 105 of the columnar body 106. Even when the work is changed straightly in the axial direction (perpendicular direction with respect to the paper surface of Fig. 11) or is changed curvilinearly, if the amount of change is small (radius of curvature is great), a wrinkle is not generated in the entering forming portion of the work. However, when the work is changed curvilinearly in the axial direction and the amount of change is great (radius of curvature is small), a wrinkle is generated in the entering forming portion of the work. Fig. 12 shows a state before the entering forming. As can be seen from Fig. 12, the entering forming portion 107 of the slide cam 108 merely pushes the work W without pressing and clamping the work W, thereby generating the wrinkle between the entering forming portion 105 of the columnar body 106 (when the work is largely changed curvilinearly in the axial direction). Although it seems to be effective to incorporate various mechanism into the rotating element for preventing the wrinkle from being generated, since the rotating element is extremely small in general, it is difficult to incorporate the various mechanism. A wrinkle is generated in the entering forming portion in the case of a so-called shrink flange forming in which a formed portion shrinks after forming, but in the case of a so-called extending flange forming in which the formed portion extends after forming, the wrinkle is not generated. Thereupon, in view of the above circumstances, according to the present invention, in order to prevent a wrinkle from being generated in the entering portion of a work by pressing and clamping the entering portion of the work, there is provided a negative angular forming die, comprising the features of claim 1. Further, according to the present invention, in a negative angular forming in which a lowering locus of an upper die enters into a lower die, in order to prevent a wrinkle from being generated in the entering portion of a work by pressing and clamping the entering portion of the work, there is provided a pressing apparatus, comprising the features of claim 4. BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1a and 1b are sectional views respectively showing a fender before and after being formed which is a metal thin plate part of an automobile to be formed by a negative angular forming die of the present invention; Fig. 2 is a vertical sectional view of a state in which an upper die of the negative angular forming die of the present invention for entering forming the fender shown in Figs. 1a and 1b is lowered from top dead center and a pressing apparatus starts advancing; Fig. 3 is a plan view of transmit bars, a pad and a coil spring for biasing the pad as viewed from the above; Fig. 4 is a plan view of a state in which the coil spring in Fig. 3 extends; Fig. 5 is a front view of a state in which a lock piece engages the transmit bar; Fig. 6 is a sectional view of a state in which a lock piece engages the transmit bar; Fig. 7 is a vertical sectional view of a state in which the upper die of the negative angular forming die of the present invention shown in Fig. 2 is lowered and abutted against the lower die; Fig. 8 is a vertical sectional view of a state in which the upper die of the negative angular forming die of the present invention shown in Fig. 2 is at its bottom dead center; Fig. 9 is a vertical sectional view of a state in which the negative angular forming die of the present invention shown in Fig. 2 carries out the entering forming and the upper die rises; Fig. 10 is a vertical sectional view of a state in which the negative angular forming die of the present invention shown in Fig. 2 carries out the entering forming, the upper die rises, and the columnar body is rotated and retreated; Fig. 11 is a vertical sectional view of a state in which an upper die of a conventional negative angular forming die for entering forming is at its top dead center; Fig. 12 is a vertical sectional view of a state in which the upper die of the conventional negative angular forming die shown in Fig. 11 is lowered and a slide cam which abuts against a lower die starts contacting with a work; Fig. 13 is a vertical sectional view of a state in which the upper die of the conventional negative angular forming die shown in Fig. 11 is at its bottom dead center; and Fig. 14 is a vertical sectional view of a state in which the conventional negative angular forming die shown in Fig. 11 carries out the entering forming, and the upper die rises and assumes the top dead center. EMBODIMENT The present invention will be explained in detail based on one concrete embodiment shown in the accompanying drawings below. Figs. 1a and 1b are sectional views respectively showing a fender before and after being formed which is a metal thin plate part of an automobile to be formed by a negative angular forming die of the present invention. A lower portion of the fender is an entering forming portion 5. The entering forming portion 5 of the fender relatively largely varies curvilinearly in its axial direction, and the working is of a so-called shrink flange forming in which the formed portion shrinks after forming. The fender has three-dimensional curved surfaces and curved lines for constituting an outer plate portion of an automobile. In Fig. 2, a lower die 1 is formed at its upper portion with a supporting portion 2 for a work W, and is provided with a groove 3 which is opened at its outer peripheral surface and formed in the axial direction. The lower die 1 is rotatably provided with a columnar body 6 formed with an entering forming portion which enters from the locus of an upper die 4 on an edge at the side of the supporting portion 2 of the groove 3. The lower die 1 is provided with an air cylinder 61 as an automatic returning tool for rotating and retreating the columnar body 6 so that the work W can be taken out from the lower die 1 after the work W is formed. A tip end of a piston rod 62 of the air cylinder 61 connected to the lower die 1 through a pin 65 is connected, through a pin, to a link 63 fixed to an outer periphery of the columnar body 6 through a bolt 66. As the automatic returning tool, a push pin biased outward of an air pressure apparatus by a coil spring, a hydraulic apparatus, a link mechanism, a cam or a similar mechanism can be used. The upper die 4 is provided with a slide cam 9 which slides to a position opposed to the columnar body 6. The slide cam 9 is formed at an upper portion of its tip end with an entering forming portion 10, the slide cam 9 is guided by a guide (not shown), and the slide cam 9 is biased outward of the dies by a coil spring 11 compressed between an upper surface of the slide cam 9 and an inclined guide portion 7. The slide cam 9 is stopped by a stopping portion 12 rising from the inclined guide portion 7. A pad 13 is biased downward by a coil spring 14 and is hung from the upper die 4 by a hanger bolt 15, and the work W is strongly pushed so that the work W is not moved before the entering forming. In order to make it possible to press and clamp a portion of the work W which becomes the entering portion between the entering forming portion 10 of the slide cam 9 so that a wrinkle is not generated in the entering portion of the work W, the dies comprise a work pressing and clamping member for pressing and clamping the work between the work pressing and clamping member and the slide cam and having an entering forming portion slidably provided on the columnar body, a transmit member projected from the work pressing and clamping member for transmitting the pressure, a pressing apparatus for transmitting the pressure to the transmit member, moving means for moving the pressure apparatus with the lowering movement of the upper die, and lock means for locking the movement of the transmit member. Work W is pressed and clamped by the entering forming portion 10 of the slide cam 9 and pads 22, the pads 22 are slidably provided in a guide hole 21 of the columnar body 6. In order to clearly form the shape of the work W at the bottom dead center, left end surfaces of the pads 22 as viewed in the drawing are formed such that the left end surfaces can collide against a bottom surface 23 of the guide hole 21. A left side of the guide hole 21 is continuously formed with through holes 24 whose diameter is slightly smaller than that of the guide hole 21. Round bar-like transmit bars 25 are threadedly connected to the left end portions of the pads 22, and the transmit bars 25 are passed through the through holes 24 and extended outward. Guide plates 26 are fixed to the ends of the through holes 24 of the columnar body 6 for guiding the transmit bars 25. Each of the transmit bars 25 is turned together with the columnar body 6 which turns by driving of the air cylinder 61. Fig. 3 is a plan view of the transmit bars 25, the pads 22 and a coil spring 34 for biasing the pads 22 as viewed from the above. The transmit bars 25 are disposed at an appropriate distance from each other at positions suitable for pressing the pads 22. The pads 22 comprise two long members fixed to each other by a bolt 32. The pads may be a single member. The coil spring 34 is mounted in a holding hole 33 formed in the columnar body 6, the coil spring 34 is abutted against a washer 30, and a supporting bolt 36 is passed through the washer 30 and the coil spring 34 and threaded to the hole bottom of the holding hole 33. S 1 shown in figure 3 is a stroke of pad 22 based on the coil spring 34. After the work W is formed at the bottom dead center, the coil spring 34 functions as a so-called knockout that floats the formed work W from the formed position. After the forming is completed, the columnar body 6 is turned and retreated by the air cylinder 61 and then, when a new work is formed, the columnar body 6 is again turned by the air cylinder 61, and functions to position the tip ends of the transmit bars 25 toward the columnar body 6 from lock pieces 35 which will be described later. Fig. 4 shows the transmit bars 25 whose tip ends are drawn toward the columnar body 6 in a state in which the force pressed by the transmit bars 25 is released. As shown in Fig. 5, two lock pieces 35 are disposed at positions opposed to the tip ends of the transmit bars 25 of the lower die 1. An annular groove 42 is formed in the tip end of each of the transmit bars 25 to form a head portion 43, and the head portion 43 is formed at its outer periphery with a tapered surface 44. When pressing force of gas springs 45 which will be described later is released and rods 46 thereof are retreated, and if the transmit bars 25 enter toward the lock pieces 35 and the tapered surface 44 passes through the lock pieces 35, the lock pieces 35 engage the annular grooves 42 as shown in Fig. 6 and then, the transmit bars 25 can not retreat toward the columnar body 6, and the transmit bars 25 are brought into locked states. Each of the lock pieces 35 is covered with a cover 58 and is slidably provided on a basement 55 toward the transmit bar 25, and is biased toward the transmit bar 25 by a compressed coil spring 56. The movement of the lock piece 35 toward the transmit bar 25 is restricted by a stopping pin 57 protruding from the lower die 2. The basement 55 is fixed to the lower die by bolts 59. The lock means should not be limited to the above-describe structure only if the lock means has the same function. On the other hand, each of the gas springs 45 is disposed such as to be opposed to the transmit bar 25 such that the gas spring 45 can advance and retreat in the axial direction of the transmit bar 25. The gas spring 45 is fixed to a moving base 47, and the moving base 47 is moved on a rail 49 fixed to the lower die 1. A follower cam 50 is fixed to the moving base 47. An operating member 51 is mounted to the upper die 4 opposed to this follower cam 50 through a bolt 67, the operating member 51 is rotatably provided with a roller 52, and the roller 52 is set such that it can abut against the follower cam 50. High pressure gas suitable for use, e.g., high pressure gas of 150 kg/cm 2 is accommodated in a cylinder 54 of the gas spring 45, and even if the rod 46 projecting from the cylinder 54 extends or retracts, substantially constant output, e.g., output of 150 kg/cm 2 can be obtained over the entire length of the stroke of the rod. That is, two tanks are built in the cylinder 54, and if the rod 46 retracts and pressure is applied to one of the tanks, high pressure gas flows out from the one tank and flows into the other tank so that substantially constant output can be obtained over the entire stroke of the rod 46. As described above, the gas spring 45 is different from the coil spring, and when the gas spring 45 starts operating, high output can be obtained over the entire stroke, and it is possible to reliably transmit the pressure to the pad 22 through the transmit bar 25. The description has been made while taking the gas spring as an example of the pressure apparatus, the pressure apparatus should not be limited to the gas spring in the present invention only if the pressure apparatus has the same function as a resilient member or the gas spring. The transmit means of the pressure apparatus also should not to be limited to the above example. If a stroke of the moving base 47 is represented by S 2 , a stroke of the rod 46 of the gas spring 45 is also equal to S 2 . The stroke S 2 of the gas spring 45 is set to a stroke capable of sufficiently pressing the pad 22. Since the coil spring 34 may only draw the transmit bar 25 toward the work W, its stroke S 1 is generally set smaller than S 2 . The reference number 53 represents a stopper of the pad 22 pushed by the rod 46 of the gas spring 45 though the transmit bar 25. The stopper 53 is fixed to the columnar body 6 by a bolt 60. The pressing stroke of the moving base 47 is carried out by collision of the roller 52 of the operating member 51 against the follower cam 50 as the upper die 4 is lowered. If the upper die 4 rises, the operating member 51 which has restricted the moving base 47 rises so that the moving base 47 is not restricted by the operating member 51, and the moving base 47 returned by reaction force of the gas spring 45. In order to reliably return the moving base 47, the moving base 47 is biased toward the operating member 51 by a spring (not shown) in addition to the reaction force of the gas spring 45. The operation of this negative angular forming die will be described below. First, the upper die 4 is located at its top dead center, and at that time, the work W is placed on the supporting portion 2 of the lower die 1. At that time, the columnar body 6 is located at the forming position in a state in which the piston rod 62 of the air cylinder 61 is extended. Next, the upper die 4 starts lowering, the pad 13 first pushes the work W against the supporting portion 2 and then, as shown in Fig. 2, the lower surface of the slide cam 9 abuts against a rotating plate which is fixed to the columnar body 6 through the bolt 64 such that the slide cam 9 does not interfere with the entering forming portion of the columnar body 6. At that time, the roller 52 of the operating member 51 of the upper die 4 collides against the follower cam 50 of the moving base 47, and the moving base 47 starts advancing. As shown in Fig. 7, the pad 22 starts contacting with the work W. The moving base 47, i.e., the gas springs 45 advance toward the work W, the rods 46 push the transmit bars 25, the slide cam 9 also advances toward the work W, and the entering forming portion 10 and the pads 22 press and clamp the work W. Next, when the upper die 4 is lowered, as shown in Fig. 8, the entering forming portion 10 of the slide cam 9 enters toward the gas springs 45, the transmit bars 25 are also moved toward the gas springs 45, and the work W reaches the bottom dead center while being pressed. At that time, the head portion 43 of the rod 25 passes through the holding pieces 35 against the biasing force of the coil spring 56 as shown in Fig. 5, and the holding pieces 35 engage the annular groove 42 as shown in Fig. 6 and then, the transmit bars 25 can not retreat toward the columnar body 6 and are locked. After the entering forming, the upper die 4 starts rising. As shown in Fig. 9, the slide cam 9 is biased outward of the dies by the coil spring 11, and the slide cam 9 moves rightward. The slide cam 9 which has been restricted by the columnar body 6 rises, the piston rod 62 of the air cylinder 61 is retracted to turn the columnar body 6 leftward as shown in Fig. 10 so that when the formed work W is taken out from the lower die 1, the work W can be taken out without interfering with the entering forming portion of the columnar body 6. When the upper die 4 rises, the restriction of the moving base 47 by the operating member 51 is released, and the moving base 47 is retreated by the reaction force of the gas springs 45. At that time, if the transmit bars 25 are not locked, the transmit bars 25 move toward the work W by the rods 46 of the gas springs 45, and the formed work W is deformed. The transmit bars 25 are locked so that the work W is not deformed. The lock means plays important role for not deforming the formed work W. When the columnar body 6 is turned leftward by the air cylinder 61, the engagement between the transmit bars 25 and the holding pieces 35 is released (in Fig. 5, the holding pieces 35 are not disposed below and the transmit bars 25 are allowed to turn downward), the pad 22 biased by the coil spring 34 is moved rightward as viewed in the drawing, the work W is floated up, and the head portion 43 of the transmit bar 25 is drawn toward the columnar body 6. Next, if the columnar body 6 is turned to a state where the work W has not yet been placed by extending operation of the air cylinder 61, the transmit bars 25 are also turned together with the columnar body 6, and the head portions 43 of the transmit bars 25 are located closer to the columnar body 6 than the holding pieces 35. This state is the state where the work W has not yet been placed.

Claims: A negative angular forming die comprising: a lower die (1) having a supporting portion (2) for supporting a workpiece (W); a columnar body (6) rotatably supported on said lower die (1), the columnar body (6) having a groove (3) therein for receiving a portion of said workpiece (W) therein during working of said workpiece (W); an upper die (4) which is adapted to be lowered in a straight direction with respect to said lower die (1); a slide cam (9) slidably provided on the upper die (4) such as to be opposed to the columnar body (6); an entering forming portion (10) provided on the slide cam (9), the forming portion (10) being engageable with the workpiece (W) when the upper die (4) is lowered; and a returning tool (61-63) provided on the lower die (1) for rotating the columnar body (6) to a position at which the workpiece (W) can be removed from the lower die (1) after forming; characterized in that a clamping member (22) is slidably provided on the columnar body (6), the clamping member (22) being engageable with a side of the workpiece (W) which is opposite to a side of the workpiece (W) which is engageable with the entering forming portion (10) of the slide cam (9) so that in use the workpiece (W) is clamped and deformed between the clamping member (22) and the entering forming portion (10) of the slide cam (9). The negative angular forming die of claim 1, further comprising a biasing member (34) for biasing the clamping member (22) towards the workpiece (W). The negative angular forming die of claim 1 or 2, further comprising a transmit member (25) for transmitting a force to the clamping member (22), the transmit member (25) being connected to the clamping member (22) and projecting therefrom through the columnar body (6). A pressing apparatus comprising: a negative angular forming die of any one of claims 1 to 3; a pressure apparatus (45) for transmitting a force to the clamping member (22) via a/the transmit member (25); a moving means (47,50,51) for moving the pressure apparatus (45) towards the transmit member (25) as the upper die (4) is lowered; and lock means (35,56,58) for locking the movement of the transmit member (25) at a predetermined position. The pressing apparatus of claim 4, wherein: the transmit member includes a rod (25) provided with a groove (42); the pressure apparatus includes a gas spring (45); the lock means includes a holding piece (35) which is engageable with the groove (42) of the transmit member (25); and a resilient element (34) is interposed between the clamping member (22) and the columnar body (6), the resilient element (34) biasing the clamping member (22) and the transmit member (25) towards the workpiece (W). The pressing apparatus of claim 4 or 5, wherein the moving means (47,50,51) comprises: an operating member (51) connected to the upper die (4); a moving base (47) movably provided on the lower die (1), the pressure apparatus (45) being mounted on the moving base (47); and a follower cam (50) operatively connected to the moving base (47) for moving the pressure apparatus (45) together with the moving base (47) towards the transmit member (25) as the upper die (4) is lowered.

Inventors: MATSUOKA MITSUO, MATSUOKA, MITSUO, Matsuoka, Mitsuo, c/o UMIX Co., Ltd.
Applicants: UMIX CO LTD, UMIX CO., LTD.
Application year: 1999
Main classification: B21D22
IPC codes: B21D37, B21D5, B21D22