Phonograph record pressing machines

Claim 1

IN A COMPRESSION PHONOGRAPH RECORD PRESS, THE COMBINATION COMPRISING, A PAIR OF MOLD HALVES EACH HAVING RECOORD STAMPER MEANS ATTACHED THERETO FOR PRESSING GROOVES INTO PLASTIC RECORDS, A DISC MOUNTED OVER THE CENTRAL PORTION OF EACH STAMPER, SAID DISCS BEING IN OPPOSED CONFRONTING RELATIONSHIP, EACH DISC HAVING A SURFACE SUBSTANTIALLY FLUSH WITH THE GROOVE-FORMING SURFACE OF ITS CORRELATED STAMPER, A CENTERING PIN RECIPROCALLY MOVEABLE WITHIN A SAID FIRST IF DISCS, HYDRAULIC MEANS FOR BIAS SAID CENTERING PIN TOWARD AND INTO FLUSH ABUTTING CONTACT WITH THE SECOND DISC, WHEREBY SAID PIN PROTRUDES BETWEEN SAID DISCS TO PREVENT DEFORMATION OF THE PLASTIC MATERIAL IN THE REGION OF SAID PIN WHEN THE PRESS IS FORMING THE RECORD CENTER HOLE, MEANS FOR DETACHABLY SECURING SAID FIRST DISC TO SAID MOLD HALF, SAID PIN HAVING MEANS FOR CAPTIVE-KEYED REGISTER WITH COMPLEMENTARY SHAPED MEANS IN SAID FIRST DISC FOR EFFECTING ROTATING TURNING OF SAID FIRST DISC BY TURNING SAID PIN FOR DETACHING SAID SECURING SAID FIRST DISC WITH RESPECT TO ITS MOLD HALF TO ALLOW REPLACEMENT OF A CENTERING PIN AND ALSO TO PERMIT RELEASE OF THE STAMPER FROM SAID LAST-MENTIONED MOLD HALF.