Stripper unit for a punch retainer

Abstract

A stripper unit incorporates a precision threaded plug that preloads a mechanical die spring that, in turn, preloads the movable or traveling stripper adjacent the punch tip. The precision threaded plug simultaneously accurately locates the stripper unit on a commercially available ball-lock punch retainer. The stripper unit is entirely self-contained on the face of the ball-lock punch retainer, thus minimizing the space required on the press platen.

1 - 4 . (canceled) 
   
   
       5 . A self-contained stripper unit for attachment to a punch retainer having a punch retention hole with a punch received therein, the punch extending from the punch retainer and having a predetermined outside diameter where it extends from the punch retainer, the stripper unit having an installed position wherein it is received on the punch, the stripper unit comprising:
 a hollow body having a hole in a flat bottom thereof and an upper bore in the top of the hollow body;   a stripper disposed at least partially within the hollow body and movable in the upper bore;   a die spring engaging the stripper within the hollow body, the die spring located within the hollow body; and   a precision plug received into the hole in the flat bottom of the hollow body so as to engage the die spring, the precision plug having a central passage defined therethrough, the passage having sides, the passage being sized such that the sides contact the predetermined outside diameter of the punch, whereby when the stripper unit is received on the punch, the sides of the passage locate and align the stripper unit on the punch;   the precision plug, the stripper, the die spring and the hollow body being attachable to the punch retainer as a single unit.   
   
   
       6 . The stripper unit of  claim 5 , wherein the upper bore and the stripper have a D-shape to prevent rotation of the stripper relative to the hollow body. 
   
   
       7 . The stripper unit of  claim 5 , wherein the hole in the bottom of the hollow body has a counterbored ledge, the precision plug being seated on the counterbored ledge. 
   
   
       8 . The stripper unit of  claim 7 , wherein the precision plug preloads the die spring. 
   
   
       9 . The stripper unit of  claim 5 , wherein the hole in the bottom of the hollow body is a threaded hole, the precision plug being threaded so as to engage the threaded hole. 
   
   
       10 . The stripper unit of  claim 5 , wherein the stripper has a hole shaped to match a shape of the punch. 
   
   
       11 . The stripper unit of  claim 5 , wherein the precision plug and the flat bottom of the hollow body cooperate to define a flush surface that fits flush against the punch retainer when attached thereto. 
   
   
       12 . The stripper unit of  claim 5 , wherein the passage is a multi-sided hole in the plug.