Abstract:
A rotary bending tool having a series of graphite plugs mounted in a saddle recess engaging a rocker surface to lubricate the same. The rocker is machined in an unhardened state and thereafter heat treated to be hardened, with reverse bending of the rocker thereafter carried out to correct any warpage.

Description:
BACKGROUND OF THE INVENTION 
   This invention concerns rotary bending tools of the type including a rocker rotationally mounted in a partially cylindrical seat in a saddle, tools used to form bends along an edge of a sheet metal workpiece by wrapping around an edge of an anvil die. The rocker has a lengthwise V-shaped recess which wraps the edge of sheet metal blank around an anvil die edge as the saddle is driven down in a press, the rotation of the rocker as it descend wrapping the sheet material around the lower die edge. 
   Such devices are used in high volume production of formed steel panels and thus are subject to considerable wear. Rockers for long length rotary bending tools have heretofore been constructed of very high strength alloys which are hardened prior machining, necessitating costly post hardening machining to very close tolerances as described in U.S. Pat. No. 5,913,931. 
   Also, sophisticated lubricating systems have been developed due to the demanding nature of this process to reduce tool wear in high volume production applications. 
   It is the object of the present invention to provide a lower cost simpler rotary bender which can be constructed in long lengths and used in high production volume applications. 
   SUMMARY OF THE INVENTION 
   The above objects or others which will be understood upon a reading of the following specification and claims are achieved by a rotary bender which incorporates graphite plugs in the saddle recess, contoured to conform to the rocker. The graphite plugs retain and dispense lubricant to provide an effective but simple lubrication of the rocker as it is oscillated in the saddle recess. 
   In manufacturing these components, the rocker is machined prior to being hardened, and thereafter heat treated, with any warpage eliminated by straightening the rocker in a press by reverse bending thereof. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a rotary bending tool according to the present invention. 
       FIG. 2  is an exploded perspective inverted view of the rocker and saddle components included in the tool shown in FIG.  1 . 
       FIG. 3  is a transverse sectional view taken through the tool shown in FIG.  1 . 
   

   DETAILED DESCRIPTION 
   In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims. 
   Referring to the drawings, a rotary bending tool  10  according to the present invention is shown in  FIG. 1 , which includes a rocker  12  and a saddle  14 . The rocker  12  is comprised of a generally cylindrical elongated shaft with a V-shaped lengthwise recess  16  machined therein. A suitable high strength steel allow is used to make the rocker  12 . The remaining cylindrical portions of the rocker  12  are nested into an arcuate recess  18  extending lengthwise along the saddle  14 . The rocker  12  is supported for oscillation in the saddle recess  18  by reason of the complementary cylindrical shape of the mating portions of the rocker  12  and saddle recess  18 . 
   The rotary bending tool  10  is installed in a die press by means of cap screws (not shown) and mates with a lower die D having an elongated forming contour C around which a sheet metal workpiece is wrapped, as described in the above referenced patent, which process is well known in the art, and will not be further described here. 
   As seen in  FIG. 3 , the rocker  12  is partially encircled by the saddle recess  18  to an extent sufficient to capture the rocker  12  and so as to be rotatable therein with the recess  18  facing down, as it would when the rotary bending tool  10  is affixed to the upper platen in a press (not shown). The rocker  12  is assembled therein by being slid endwise into the recess. 
   The rocker  12  is retained in this position by a series of tapered end pins  20  inserted through respective holes  22  in one side of the saddle  14  and received in respective pockets  24  in the rocker  12 . 
   The tapered end pins  20  are urged towards the rocker  12  by compression springs  26  compressed by set screws  28  installed in threaded sections of holes  22 . 
   The compressed springs  26  allow the pins  20  to be forced back as the rocker  12  is rotated counter clockwise by contact of one recess edge  32  with the sheet metal part P. 
   In order to lubricate the bearing surface of the rocker  12 , two linear series of lubricant impregnated graphite plugs  34  are inserted in pockets in the saddle recess  18  in the region above the rocker  12 . The ends of the graphite plugs  34  are machined to an arcuate shape matching the curvature of the rocker  12  and saddle recess  18 . This arrangement has been found to adequately lubricate the rocker  12  even when the forming operations are continued over many cycles. 
   The rocker  12  is machined while in the unhardened state by conventional machining methods. After machining, the rocker  12  is inspected and any warpage is corrected by bending of the rocker  12  in a reverse direction to the warpage in a press able to exert sufficient force to carry out such bending. This technique has been found to produce sufficient accuracy of the finished rocker  12  for use with long length rotary bending tools (24 inches) while greatly reducing the manufacturing costs.