Die center pad

Claim 1

IN APPARATUS FOR COLD DRAWING PLASTIC SHEET MATERIAL INTO ARTICLES HAVING SMOOTH EXTERIOR SURFACES AND INTERIOR SURFACES WHICH INCLUDE MINUTE RAISED AREAS, INCLUDING A MALE DIE CENTER PAD HAVING AN ELONGATED BODY, A FEMALE DIE HAVING A CAVITY FOR TELESCOPICALLY RECEIVING THE DIE CENTER PAD BODY DURING A DRAWING OPERATION, MEANS FOR NORMALLY POSITIONING THE PLASTIC SHEET MATERIAL BETWEEN THE DIE CENTER PAD AND THE FAMALE DIE PRIOR TO RELATIVE MOVEMENT THEREBETWEEN, AND MEANS FOR MOVING SAID DIE CENTER PAD AND FEMALE DIE RELATIVE TO EACH OTHER WHEREBY THE PLASTIC SHEET MATERIAL IS AT LEAST PARTIALLY DRAWN FROM THE NORMAL POSITION THEREOF TO A POSITION AT LEAST PARTIALLY SURROUNDING THE DIE CENTER PAD BODY BETWEEN AN EXTERIOR SURFACE OF SAID BODY AND THE CAVITY OF SAID FEMALE DIE, THE IMPROVEMENT COMPRISING A SURFACE DEFINING SAID CAVITY CONTOURED TO THE GENERAL CROSS-SECTIONAL CONFIGURATION OF SAID BODY, SAID CAVITY SURFACE BEING SMOOTH AND UNBROKEN WHEREBY THE EXTERIOR SURFACE OF A DRAWN ARTICLE IS SIMILARLY SMOOTH AND UNBROKEN, A PLURALITY OF ELONGATED GROOVES FORMED IN THE EXTERIOR SURFACE OF SAID BODY AND EACH OF SAID GROOVES RANGING IN DEPTH UPWARDLY FROM ABOUT .0005 INCH TO A DEPTH SUFFICIENT TO PREVENT NECKING-DOWN BUT INSUFFICIENT TO MATERIALLY DISFIGURE THE DRAWN ARTICLE WHEREBY THE INTERIOR SURFACE OF THE ARTICLE IS PROVIDED WITH MINUTE RAISED AREAS CORRESPONDING IN SHAPE AND CONFIGURATION TO THE DIE BODY GROOVES.