Bending and hemming method and apparatus

Abstract: A bending and hemming apparatus configured to both bend and hem a sheet metal panel to form a body closure member at a single station. The apparatus includes a hemming machine movable between a retracted position spaced from a bending machine and advanced positions adjacent the bending machine to assist in the bending operation and to hem the body panel into a finished product. The apparatus also includes an anvil assembly pivotably supported on the hemming machine. The anvil assembly is movable between a lowered position where it engages the workpiece when the hemming machine is advanced to a bending position adjacent the bending machine. In the lowered position, the anvil assembly provides a fulcrum around which the workpiece is bent. The anvil assembly is pivotable to a raised position to allow the hemming machine to be advanced to a hemming position adjacent the bending machine from which the hemming machine can engage the bent workpiece to hem the workpiece.

Description: This invention relates to an apparatus for bending and hemming a metal panel into an automotive body closure member such as a tailgate. Background of the Invention An automotive body panel closure member such as a tailgate generally comprises both an inner panel and an outer panel that may be formed from a single sheet of material such as sheet metal. To form such a body panel, the sheet must be folded upon itself, i.e., "doubled-over" and the mating edges joined to provide a finished and structurally sound component for use on a vehicle. One well-known process for joining the edges of such a panel is known in the art as hemming and is accomplished using a hemming machine that folds the edge of one panel over the edge of the other panel to mechanically lock the panel edges together. US 4,928,388 discloses a single station hemming apparatus in which the hemming flanges of a workpiece are pre-hemmed and hemmed in the same station and using a single tool. The tool is moved first in a direction that is perpendicular to the flange of the workpiece and second in a direction that is parallel to the original orientation of the flange in order to pre-hem and final hem the flange. A plurality of similarly actuated hemming tools may be positioned around the workpiece in order to pre-hem and final hem the periphery of the workpiece. Summary of the Invention The invention is a bending and hemming apparatus comprising a bending machine configured to support a metal panel workpiece at a bending station and to bend the edge of the metal panel workpiece in preparation for hemming. The apparatus includes a hemming machine configured to hem the bent edge of the metal panel workpiece. The hemming machine is configured to hem metal panel workpieces while the workpieces are still supported on the bending machine at the bending station to obviate the need to transport the workpiece from the bending station to a separate hemming station following bending. According to another aspect of the invention, a method is provided for both bending and hemming a metal panel workpiece. The method includes loading a metal panel workpiece onto a bending machine and moving an anvil assembly into a position to act as a fulcrum for subsequent bending of the workpiece. The workpiece is then bent a predetermined number of degrees around an anvil tool portion of the anvil assembly by rotating a movable die element of the bending machine the predetermined number of degrees. A finally hemmed part is then formed from the workpiece by actuating the hemming machine to hem at least a portion of a bent edge of the workpiece. The bending machine and hemming machine are then actuated to release the finally hemmed part. Objects, features and advantages of this invention include the ability to bend and hem the edge of a sheet metal workpiece at a single work station, and to pre-hem the edge of a sheet metal workpiece at the same work station where initial bending and hemming occur. Description of the Drawings These and other objects, features and advantages of this invention will be apparent from the following detailed description of the preferred embodiment and best mode, appended claims, and accompanying drawings in which: FIG. 1 is a diagrammatic front view of a bending and hemming apparatus constructed according to the invention showing a bottom end hemming machine of the apparatus in a retracted position, an anvil assembly of the apparatus in a lowered position, the anvil assembly shown in a raised position in phantom, and with two side edge hemming machines and comer units of the apparatus omitted for clarity; FIG. 2 is a diagrammatic front view of the apparatus of Figure 1 showing the anvil assembly in a lowered position, the hemming machine advanced to a bending position, a movable die portion of the bending machine in an open position and with the side edge hemming machines and corner units omitted for clarity; FIG. 3 is a diagrammatic top view of the apparatus of Figure 2 and also showing the side and comer hemming units omitted from Figures 1 and 2; FIG. 4 is a diagrammatic front view of the apparatus of Figure 1 with the movable die portion of the bending machine in a partially closed position, the anvil assembly in the lowered position, the bottom end hemming machine advanced to a hemming position and with the side edge hemming machines and comer units omitted for clarity; FIG. 5 is a diagrammatic front view of the apparatus of Figure 1 showing the bottom end hemming machine and anvil assembly in the retracted position and with the side edge hemming machines and comer units omitted for clarity; FIG. 6 is a diagrammatic front view of the apparatus of Figure 1 showing the anvil assembly in the raised position, the movable die post portion of the bending machine in a fully closed position, and with the side edge hemming machines and comer units omitted for clarity; FIG. 7 is a diagrammatic front view of the apparatus of Figure 1 showing the position of one of the side hemming machines relative to the bending machine, showing the bottom end hemming machine being advanced from the retracted position by a harmonic drive, and with the comer units omitted for clarity; FIG. 8 is a diagrammatic top view of the apparatus of Figure 1 showing the bottom end hemming machine advanced to the bending position, showing the relative position of the bending machine and the side hemming machines, and with the comer units removed for clarity; FIG. 9 is a diagrammatic front view of the apparatus of Figure 8 with one of the side edge hemming machines and the comer units removed for clarity; FIG. 10 is a diagrammatic top view of the apparatus as shown in Figure 6 with the anvil assembly in the lowered position and comer units removed for clarity; FIG. 11 is a diagrammatic front view of apparatus of Figure 1 showing movable die portion of the bending machine in the opened position for removal of the part, and with the side edge hemming machines and comer units omitted for clarity; FIG. 12 is a diagrammatic front view of the apparatus of Figure 1 with the workpiece, side edge hemming machines and corner units omitted for clarity; FIG. 13 is a diagrammatic top view of the apparatus of Figure 12 as also shown in Figure 10 with the comer units omitted for clarity; FIG. 14 is a diagrammatic front view of the apparatus as also shown in Figure 2 with the side edge hemming machines and comer units omitted for clarity; FIG. 15 is a diagrammatic top view of the apparatus of Figure 14 as also shown in Figure 3; FIG. 16 is a diagrammatic front view of the apparatus of Figure 1 as also shown in Figure 7 but including the ball screw drive rather than a harmonic drive operatively connected to the bottom end hemming machine; FIG. 17 is a diagrammatic top view of the apparatus of Figure 1 as also shown in Figure 8 with the comer units removed for clarity; FIG. 18 is a flow chart depicting the sequence of bending and hemming operations for the apparatus of Figure 1; and FIG. 19 is a diagrammatic front view of an alternative bending and hemming apparatus constructed according to the invention. Detailed Description FIGS. 1-17 illustrate a combination body panel bender and hemmer apparatus 20 constructed according to the invention. The apparatus 20 has a turnover station or bending machine 22 with a fixed lower die 24 supported on a bending machine frame 26 and an upper die 28 pivotably mounted adjacent the fixed lower die 24 on the bending machine frame 26. The bending machine 22 also includes a bender drive mechanism 30 operatively connected to the upper die 28 and configured to rotate the upper die 28 between an open position, a partially closed position and a fully closed position. The bending machine 22 also includes a plurality of suction cups 32 or outlets disposed in the upper and lower die portions 28, 24 and configured to secure a metal panel workpiece 34 in position for bending on the die portions 24, 28. The bending machine 22 also includes a vacuum source (not shown) which may be of known construction in fluid communication with each suction cup of the plurality of suction cups 32. The apparatus 20 also has a lower end hemming machine 38 configured to hem an edge of the workpiece 34 that will become a lower end of a finished body panel following the bending and hemming operations. As shown in Figures 7, 9 and 16 the lower end hemming machine 38 includes a pre-hem steel 40 and a final hem steel 42 that are individually extendable and retractable by a hem steel drive mechanism 44 as is well known in the art. The lower end hemming machine 38 is supported on a linear slide 46 for reciprocal movement between a retracted position remote from the bending machine 22 and advanced bending and hemming positions adjacent the bending machine 22. The apparatus 20 also includes a hemming machine drive 48 operatively connected to the lower end hemming machine 38 and configured to move the lower end hemming machine 38 translationally on the linear slide 46 between the advanced and retracted positions. The hemming machine drive 48 may be a harmonic drive as shown in Figure 7, a ball screw drive as shown in Figure 16, or an air cylinder drive as shown in Figure 19. The apparatus 20 also has a hold-down anvil assembly 50 that is pivotably supported on the lower end hemming machine 38 for pivotal movement between a raised position best shown in Figure 11 and a lowered position best shown in Figures 2, 4, 5 and 14. An anvil assembly drive 52 is operatively connected to the anvil assembly 50 to move the anvil assembly 50 between the raised and lowered positions. The anvil assembly drive 52 may be either an air cylinder, an electric motor or any other suitable drive mechanism known in the art. An anvil tool 54 of the anvil assembly 50 is removably attached to an arm portion 51 of the anvil assembly 50 that is pivotally supported on the lower end hemming machine 38. The anvil tool 54 is configured to act as a fulcrum to control the bending of the panel. The anvil tool 54 includes a leading edge 56 and an adjacent bottom surface 58. The leading edge 56 of the anvil tool 54 acts as the fulcrum around which the panel is bent and the adj acent bottom surface 58 holds the workpiece down against the lower die 24 during the bending operation. The anvil tool 54 is an interchangeable part and can be exchanged for anvil tools of other configurations to accommodate body panels of varying configurations. The apparatus 20 has a vertical positioning mechanism 60 comprising apertured lower die tabs 62 fixed to the lower die part 24 of the bending machine 22 and apertured anvil arm tabs 64 fixed to the arm 51 of the anvil assembly 50. Apertures formed in the lower die tabs 62 are positioned to coaxially align with apertures formed in the anvil arm tabs 64 when the anvil assembly 50 is in the lowered position and the lower end hemming machine 38 is in the bending position. A tapered pin 74 of the vertical positioning mechanism 60 is automatically driven axially through the aligned apertures when the lower end hemming machine 38 is in the bending position to lock the anvil assembly 50 to the lower die 24 of the bending machine 22 as the bending machine 22 is bending the workpiece. The tapered pin 70 is automatically withdrawn before the lower end hemming machine 38 is withdrawn along the linear slide 46. In other embodiments of the combination body panel bender and hemmer apparatus such as the one shown at 20' in Figure 19, the vertical positioning mechanism may include a key 66 and keyway 68 arrangement instead of the pin lock mechanism described above. As shown in Figure 19, the key 66 is supported on the lower die part 24 of the bending machine 22 and the keyway 68 is supported under the arm 51 of the anvil assembly 50. When the lower end hemming machine 38 is advanced to the bending position, the key 66 is received into a complimentary shaped notch 69 in the keyway 68 to prevent any relative vertical motion between the anvil tool 54 and the bending machine 22. In Figure 19, reference numerals with the designation prime (') indicate alternative configurations of elements that appear in Figures 1-17. Side hemming machines 76 are positioned on either side of the lower die 24 of the bending machine 22 in respective positions to hem respective side edges of the workpiece 34 that will become side seams of the finished body panel. Each side hemming machine 76 includes a pre-hem steel 78 and a final hem steel 80 that are individually movable to a position engaging respective side edges of the workpiece 34 to hem those edges. Each side hemming machine 76 also includes a hem steel drive unit 82 that is operatively connected to the pre-hem and final hem steels 78, 80 of each side hemming machine 76, respectively, to individually advance and retract the steels 78, 80 for pre-hem and final hem operations. Comer hemming machines 84 may be positioned adjacent the side hemming machines 76 in respective positions to initiate hemming operations at comers of the body panel as is known in the art. In practice, a vehicle closure member such as tailgate can be formed according to the invention by loading a pre-stamped metal panel workpiece 34 onto the upper and lower die portions 24, 28 of the bending machine 22 as shown in Figure 1. The vacuum source is then actuated to provide suction at the suction cups 32 to hold the workpiece 34 securely in a position for bending and hemming as is also shown in Figure 1. The workpiece 34 may be loaded by a robot or any other means known in the art. The anvil assembly drive 52 is then actuated to rotate the anvil assembly 50 from the raised position to the lowered position. The hemming machine drive 48 is then actuated to advance the lower end hemming machine 38 and the anvil assembly 50 to a position where the anvil tool 54 engages the panel, i.e., the bending position as shown in Figures 2 and 3. Once the lower end hemming machine 38 has advanced to the bending position, the pin lock mechanism 60 is actuated to drive the tapered pin 74 through the coaxially aligned apertures, 70 of the lower die tabs 62 and the anvil arm tabs 64. The bender drive mechanism 30 of the bending machine 22 is then actuated to pivot the upper die portion 28 to the partially closed position as shown in Figure 4 which bends the panel workpiece 34 approximately 148° to the partially closed position. During the bending operation, the leading edge 56 of the anvil tool 54 acts as a fulcrum against which the panel workpiece 34 is bent. After the apparatus 20 completes the bending operation, the pin lock mechanism 60 is actuated to remove the tapered pin 74 from the lower die tabs 62 and the anvil arm tabs 64. The hemming machine drive 48 is then actuated to retract the lower end hemming machine 38 and anvil assembly 50 along the linear slide 46. To begin the hemming operation, the anvil assembly drive 52 is actuated to rotate the anvil assembly 50 to the raised position as shown in Figure 6. The hemming machine drive 48 is then actuated to advance the lower end hemming machine 38 to the hemming position shown in Figures 8 and 9. The bender drive mechanism 30 is then actuated to pivot the upper die portion 28 a final 12° to the closed position as shown in Figure 6. The pre-hem steels of the lower end hemming machine 38 and side hemming machines 76 are then extended to pre-hem the panel workpiece 34. If present, the comer hemming machines 84 may be then extended to initially hem respective comers of the panel workpiece 34. The comer hemming machines 84 may then be retracted from engagement with the panel workpiece 34 and the final hem steels of the lower end and side hemming machines 38, 76 are extended to accomplish a final hem of the side and bottom end edges of the panel workpiece 34. The final hem steels are then retracted from their respective positions in engagement with the panel workpiece 34. Following the completion of the hemming operation, the bender drive mechanism 30 is actuated to pivot the upper die 28 portion away from the lower die 24 portion to the fully open position. The hemming drive is actuated to retract the lower end hemming machine 38 along the linear slide 46. The hemmed body panel is then removed from the bending machine 22. This description is intended to illustrate certain embodiments of the invention rather than to limit the invention. Therefore, it uses descriptive rather than limiting words. Obviously, it's possible to modify this invention from what the description teaches and one may practice the invention other than as described.

Claims: A bending and hemming apparatus (20) for forming a finished panel having an inner panel and an outer panel formed from a single sheet material that is folded over onto itself, the apparatus comprising: a bending machine (22) configured to support a metal panel workpiece (34) at a bending station and to bend the metal panel workpiece until the workpiece is doubled over such that opposite mating edges of the panel are brought together and generally aligned with one another in preparation for hemming; a hemming machine (38) configured to hem the bent edge of the metal panel workpiece; the hemming machine being configured to hem metal panel workpieces while the workpieces are still supported on the bending machine (22) at the bending station to obviate the need to transport the workpiece from the bending station to a separate hemming station following bending. The bending and hemming apparatus of claim 1 in which: the hemming machine (38) is moveable between a retracted position spaced from the bending machine and advanced bending and hemming positions adjacent the bending machine and; the apparatus includes an anvil assembly (50) pivotally supported on the hemming machine for motion between a lowered position and a raised position, the anvil assembly engaging and providing a fulcrum (56) for bending the workpiece when the hemming machine is in the bending position and the anvil assembly (50) is in the lowered position, the anvil assembly being moveable to the raised position to prevent the anvil assembly from interfering with the hemming of the bent workpiece when the hemming machine is advanced to the hemming position. The bending and hemming apparatus of claim 2 in which the bending machine includes; a fixed lower die part (24); an upper die part (28) mounted for pivotal motion relative to the lower die part; a workpiece retainer mechanism (32) that secures a metal panel workpiece on the upper and lower die parts; and a bender drive mechanism (30) operatively connected to the upper die part to rotate the upper die part relative to fixed lower die part to bend a workpiece secured on the die parts. A method of both bending and hemming a metal panel workpiece; the method including the steps of: loading a metal panel workpiece onto a bending machine (22); supporting an anvil assembly (50) on a moveable support (51) that is spaced from the bending machine; moving the anvil assembly into a position to act as a fulcrum for subsequent bending of the workpiece; bending the workpiece a predetermined number of degrees around an anvil tool portion (54) of the anvil assembly by rotating a moveable die element (28) of the bending machine a predetermined number of degrees; forming a finished part from the workpiece by actuating the hemming machine to hem at least a portion of a bend edge of the workpiece; and actuating the bending machine and hemming machine to release the finished part. The method of claim 4 in which the step of loading a metal panel workpiece onto a bending machine includes actuating a workpiece retainer mechanism (32) of the bending machine to hold the metal panel in position on the bending machine. The method of claim 4 in which the step of moving an anvil assembly into a position to act as a fulcrum includes: pivoting an anvil assembly (50) to a lowered position approximately level with a portion of the workpiece to be bent; and moving a hemming machine (38) that pivotably supports the anvil assembly to a bending position adjacent the bending machine. The method of claim 6 in which the step of forming a hemmed part includes: retracting the hemming machine (38) and anvil assembly (50) from engagement with the panel; pivoting the anvil assembly (50) to a raised position; and advancing the hemming machine (38) into a hemming position adjacent the panel. The method of claim 7 including the additional step of further bending the workpiece by actuating the bending machine to rotate the moveable die portion (28) of the bending machine to a closed position after the step of pivoting the anvil assembly (50) to a raised position and before the step of actuating the hemming machine to hem the workpiece.

Inventors: SCHLAFHAUSER JOSEPH K, WIENS PHILIP V, SCHLAFHAUSER, JOSEPH K., WIENS, PHILIP V.
Applicants: UNOVA IND AUTOMATION SYS INC, UNOVA IP CORP.
Application year: 2001
Main classification: B21D39
IPC codes: B21D39