Reciprocating screw injection molding machine

Claim 1

AN INJECTION MOLDING MACHINE COMPRISING A CYLINDER HAVING FEED AND DISCHARGE OPENINGS; A FEED SCREW HAVING A HELICAL FLIGHT THEREAROUND; SAID FEED SCREW BEING ROTATABLE AND AXIALLY MOVABLE IN SAID CYLINDER RESPECTIVELY TO ADVANCE MATERIAL FROM SAID FEED OPENING TOWARD SAID DISCHARGE OPENING FOR MELTING OF THE MATERIAL DURING SUCH ADVANCE, AND TO PROVIDE A SPACE OF INCREASING AXIAL LENGTH ADJACENT, AND TO PROVIDE A SPACE OF INCREASING AXIAL LENGTH ADJACENT SAID DISCHARGE OPENING TO RECEIVE SUCH MELTED MATERIAL; SAID FEED SCREW HAVINGAT ITS DISCHARGE END A PISTON HEAD ROTATABLE THEREWITH AND INCLUDING A CHECK VALVE ASSEMBLY THEREIN; SAID CHECK VALVE ASSEMBLY BEING OPERATIVE TO BLOCK RETURN FLOW OF THE MATERIAL AS THE FEED SCREW IS MOVED AXIALLY TOWARD SAID DISCHARGE OPENING THUS TO DISPLACE THE MELTED MATERIAL IN SUCH SPACE THROUGH SAID DISCHARGE OPENING, SAID CHECK VALVE ASSEMBLY COMPRISING A PLURALITY OF CHECK VALVE MEMBERS OF CIRCULAR CROSS-SECTION AXIALLY MOVABLE CARRIED BY SAID FEED SCREW, SAID CHECK VALVE MEMBERS HAVING ROLLING CONTACT WITH SAID CYLINDER AND THUS CONSTITUTING AN ANTIFRICTION BEARING FOR SUPPORTING THAT END OF THE FEED SCREW CENTRALLY IN SAID CYLINDER WITH SAID PISTON HEAD AND THE HELICAL FLIGHT OF SAID FEED SCREW OUT OF RUBBING CONTACT WITH SAID CYLINDER.