Forging die apparatus for steering racks

Abstract

A die apparatus for forging a steering rack from a bar. The die apparatus comprises a first and a second bolster movable towards each other, and at least one gripper adapted to grip the bar as the rack is forged. The gripper comprises first and second gripper halves carried by, and movable relative to, the first and second bolsters respectively. A gripper bias means biases the gripper halves towards each other. As the bolsters move towards each other to forge the rack, the first gripper half abuts against the first bolster, and the second gripper half abuts the second bolster.

1 . A die apparatus for forging a steering rack from a bar, the steering rack having a toothed portion, the die apparatus comprising a first bolster and a second bolster movable towards each other to forge the steering rack, a plurality of die elements carried by the bolsters, each die element having a forming surface shaped as the obverse of a region of the toothed portion, at least one gripper adapted to grip a portion of the bar as the steering rack is forged, the gripper comprising a first gripper half and a second gripper half, the first and second gripper halves being carried by, and movable relative to, the first and second bolsters respectively, and a gripper bias means adapted to bias the gripper halves towards each other as the steering rack is forged, characterised in that the die apparatus is arranged such that as the bolsters move towards each other to forge the steering rack, the first gripper half moves relative to the first bolster until it abuts against the first bolster, and the second gripper half moves relative to the second bolster until it abuts against the second bolster. 
     
     
         2 . A die apparatus as claimed in  claim 1 , wherein the first gripper half is supported by a first piston movable in a first bore in the first bolster, and the second gripper half is supported by a second piston movable in a second bore in the second bolster, the gripper bias means comprising restricting the flow of fluid from the bores as each piston moves in its respective bore. 
     
     
         3 . A die apparatus as claimed in  claim 2 , wherein at least one of the first and second gripper halves abuts its respective bolster by means of its respective piston abutting the bolster. 
     
     
         4 . A die apparatus as claimed in  claim 3 , wherein at least one of the first and second gripper halves abuts its respective bolster by means of the end face of its respective piston abutting the end of the respective bore that it moves in. 
     
     
         5 . A die apparatus as claimed in  claim 4 , wherein the end face of the piston is locally relieved to allow fluid to pass the end face of the piston when it is abutting the end of the bore. 
     
     
         6 . A die apparatus as claimed in  claim 5 , wherein the end face of the piston is locally relieved by means of at least one groove in the end face of the piston. 
     
     
         7 . A die apparatus as claimed in  claim 4 , wherein the end of the bore is locally relieved to allow fluid to pass the end face of the piston when it is abutting the end of the bore. 
     
     
         8 . A die apparatus as claimed in  claim 1 , wherein the at least one gripper comprises two grippers disposed either side of the die elements. 
     
     
         9 . A die apparatus as claimed in  claim 1 , wherein the steering rack is a Y-rack. 
     
     
         10 . A die apparatus as claimed in  claim 1 , wherein the steering rack is a Y-rack and the toothed portion comprises an array of gear teeth, two opposed guide faces angled to each other, and an end face opposite the teeth. 
     
     
         11 . A die apparatus as claimed in  claim 9 , wherein the die elements comprise a tooth die having a forming surface shaped as the obverse of the array of gear teeth, a centre punch having a forming surface shaped as the obverse of the end face of the toothed portion, and first and second side punches each having a forming surface shaped as the obverse of a guide face of the toothed portion, the tooth die being supported by the second bolster, the side punches being supported by the first bolster, and the centre punch being supported by a centre punch piston movable in a bore in the first bolster.