Process for casting thermoplastic materials

Claim 1

THE METHOD OF PRODUCING MASSIVE CASTINGS, SUCH AS GEARS, BUSHINGS, BEARINGS, PULLEYS AND PROPELLERS, OF SUBSTANTIALLY UNIFORM DENSITY, FROM THERMOPLASTIC RESINOUS MATERIAL WHICH IS SUBJECT TO SHRINKAGE UPON PHASE CHANGE DUE TO COOLING THE MOLTEN THERMOPLASTIC MATERIAL, WHICH METHOD COMPRISES: (A) EMPLOYING A MOLD HAVING A MOLD CAVITY CONFORMING TO THE SHAPE OF THE CASTING, WHICH MOLD HAS A RESERVOIR CHAMBER AT ITS VERTICAL AXIS, WITH THE VERTICAL AXIS OF THE RESERVOIR CHAMBER COINCIDENT WITH THE BERTICAL AXIS OF THE MOLD CAVITY AND WITH THE MOLD CAVITY EXTENDING IN A GENERALLY HORIZONTAL DIRECTION RADIALLY AWAY FROM THE BASE OF SAID RESERVOIR CHAMBER IN OPEN COMMUNICATION WITH THE MOLD CAVITY; (B) HEATING SAID MOLD TO A TEMPERATURE ABOVE THE MELT ING POINT OF THE THERMOPLSTIC MATERIAL; (C) FEEDING MOLTEN THERMOPLASTIC MATERIAL INTO THE MOLD CAVITY THROUGH SAID RESERVOIR CHAMBER WHILE ROTATING SAID MOLD ABOUT ITS VERTICAL AXIS; (D) CONTINUING SAID FEEDING UNTIL SAID MOLD AND AT LEAST A PORTION OF SAID RESERVOIR ARE FILLED WITH SAID MOLTEN MATERIAL TO LEVEL IN SAID RESERVOIR SUCH AS TO SUPPLY THE MOLD WITH ENOUGH OF THE MOLTEN MATERIAL TO TAKE CARE OF ALL SHRINKAGE WITHIN THE MOLD DUE TO PHASE CHANGE UPON COOLING OF THE THERMOPLASTIC MATERIAL; (E) CONTINUING SAID ROTATION ABOUT SAID VERTICAL AXIS TO EFFECT CENTRIFUGAL COMPACTION OF SAID MOLTEN MATERIAL IN A RADIAL DIRECTION TOWARD THE PERIPHERY OF SAID MOLD CAVITY WHILE COOLING THE MOLD AND ITS CONTENTS, THE MOLD CAVITY BEING MAINTAINED FULL OF THERMOPLASTIC MATERIAL FED THERETO FROM SAID RESERVOIR CHAMBER AS SHRINKAGE OCCURS DUE TO PHASE CHANGE WITHIN THE MOLD CAVITY THROUGHOUT SAID COOLING; (F) MAINTAINING THE THERMOPLASTIC MATERIAL IN THE RESERVOIR CHAMBER IN MOLTEN CONDITION AT LEAST UNTIL (1) SUBSTANTIAL SOLIDIFICATION OF THE MOLTEN THERMOPLASTIC MATERIAL IN THE MOLD CAVITY HAS TAKEN PLACE AND (2) SUBSTANTIALLY NO FURTHER SHRINKAGE OF THE THERMOPLASTIC MATERIAL IN THE MOLD CAVITY CAN OCCUR DUE TO PHASE CHANGE UPON COOLING; AND (G) ROTATING SAID MOLD AND ITS CONTENTS ABOUT A SECOND AXIS AT RIGHT ANGLES TO SAID VERTICAL AXIS, WITH THE DISTANCE BETWEEN SAID SECOND AXIS AND THE PORTION OF THE MOLD CAVITY NEAREST THERETO GREATER THAN THE DISTANCE BETWEEN SAID SECOND AXIS AND THE INLET TO THE RESERVOIR CHAMBER, AND WITH THE INLET TO THE RESERVOIR CHAMBER SPACED A SUBSTANTIAL DISTANCE FROM SAID SECOND AXIS SO THAT ROTATION OF SAID MOLD ABOUT SAID SECOND AXIS EFFECTS FEED OF MOLTEN THERMOPLASTIC MATERIAL INTO SAID MOLD CAVITY FROM SAID RESERVOIR CHAMBER THROUGH THE OPEN BASE OF SAID RESERVOIR CHAMBER TO MAINTAIN SAID MOLD CAVITY FULL NOTWITHSTANDING PHASE CHANGE WITHIN SAID MOLD CAVITY DURING THE COOLING AND EFFECT COMPACTION OF THE CONTENTS OF THE MOLD CAVITY IN A DIRECTION AT RIGHT ANGLES TO SAID RADIAL DIRECTION AND IN A DIRECTION TOWARD THE BASE OF SAID MOLD CAVITY AND AWAY FROM SAID RESERVOIR CHAMBER, THE SAID MOLD BEING SO DIMENSIONED THAT SUBSTANTIALLY THE ENTIRE CONTENTS THEREOF IN A DIRECTION AWAY FROM SAID RESERVOIR IS COMPACTED TO FORM A CASTING OF UNIFORM DENSITY.

Claim 2

THE METHOD OF PRODUCING MASSIVE CASTINGS, SUCH AS GEARS, BUSHINGS, BEARINGS, PULLEYS AND PROPELLERS, OF SUBSTANTIALLY UNIFORM DENSITY, FROM THERMOPLASTIC RESINOUS MATERIAL WHICH IS SUBJECT TO SHRINKAGE UPON PHASE CHANGE DUE TO COOLING THE MOLTEN THERMOPLASTIC MATERIAL, WHICH METHOD COMPRISES: (A) EMPLOYING A MOLD HAVING A MOLD CAVITY CONFORMING TO THE SHAPE OF THE CASTING, WHICH MOLD HAS A RESERVOIR CHAMBER AT ITS VERTICAL AXIS, WITH THE VERTICAL AXIS OF THE RESERVOIR CHAMBER COINCIDENT WITH THE BERTICAL AXIS OF THE MOLD CAVITY AND WITH THE MOLD CAVITY EXTENDING IN A GENERALLY HORIZONTAL DIRECTION RADIALLY AWAY FROM THE BASE OF SAID RESERVOIR CHAMBER IN OPEN COMMUNICATION WITH THE MOLD CAVITY; (B) HEATING SAID MOLD TO A TEMPERATURE ABOVE THE MELT ING POINT OF THE THERMOPLSTIC MATERIAL; (C) FEEDING MOLTEN THERMOPLASTIC MATERIAL INTO THE MOLD CAVITY THROUGH SAID RESERVOIR CHAMBER WHILE ROTATING SAID MOLD ABOUT ITS VERTICAL AXIS; (D) CONTINUING SAID FEEDING UNTIL SAID MOLD AND AT LEAST A PORTION OF SAID RESERVOIR ARE FILLED WITH SAID MOLTEN MATERIAL TO LEVEL IN SAID RESERVOIR SUCH AS TO SUPPLY THE MOLD WITH ENOUGH OF THE MOLTEN MATERIAL TO TAKE CARE OF ALL SHRINKAGE WITHIN THE MOLD DUE TO PHASE CHANGE UPON COOLING OF THE THERMOPLASTIC MATERIAL; (E) CONTINUING SAID ROTATION ABOUT SAID VERTICAL AXIS TO EFFECT CENTRIFUGAL COMPACTION OF SAID MOLTEN MATERIAL IN A RADIAL DIRECTION TOWARD THE PERIPHERY OF SAID MOLD CAVITY WHILE COOLING THE MOLD AND ITS CONTENTS, THE MOLD CAVITY BEING MAINTAINED FULL OF THERMOPLASTIC MATERIAL FED THERETO FROM SAID RESERVOIR CHAMBER AS SHRINKAGE OCCURS DUE TO PHASE CHANGE WITHIN THE MOLD CAVITY THROUGHOUT SAID COOLING; (F) MAINTAINING THE THERMOPLASTIC MATERIAL IN THE RESERVOIR CHAMBER IN MOLTEN CONDITION AT LEAST UNTIL (1) SUBSTANTIAL SOLIDIFICATION OF THE MOLTEN THERMOPLASTIC MATERIAL IN THE MOLD CAVITY HAS TAKEN PLACE AND (2) SUBSTANTIALLY NO FURTHER SHRINKAGE OF THE THERMOPLASTIC MATERIAL IN THE MOLD CAVITY CAN OCCUR DUE TO PHASE CHANGE UPON COOLING; AND (G) ROTATING SAID MOLD AND ITS CONTENTS ABOUT A SECOND AXIS AT RIGHT ANGLES TO SAID VERTICAL AXIS, WITH THE DISTANCE BETWEEN SAID SECOND AXIS AND THE PORTION OF THE MOLD CAVITY NEAREST THERETO GREATER THAN THE DISTANCE BETWEEN SAID SECOND AXIS AND THE INLET TO THE RESERVOIR CHAMBER, AND WITH THE INLET TO THE RESERVOIR CHAMBER SPACED A SUBSTANTIAL DISTANCE FROM SAID SECOND AXIS SO THAT ROTATION OF SAID MOLD ABOUT SAID SECOND AXIS EFFECTS FEED OF MOLTEN THERMOPLASTIC MATERIAL INTO SAID MOLD CAVITY FROM SAID RESERVOIR CHAMBER THROUGH THE OPEN BASE OF SAID RESERVOIR CHAMBER TO MAINTAIN SAID MOLD CAVITY FULL NOTWITHSTANDING PHASE CHANGE WITHIN SAID MOLD CAVITY DURING THE COOLING AND EFFECT COMPACTION OF THE CONTENTS OF THE MOLD CAVITY IN A DIRECTION AT RIGHT ANGLES TO SAID RADIAL DIRECTION AND IN A DIRECTION TOWARD THE BASE OF SAID MOLD CAVITY AND AWAY FROM SAID RESERVOIR CHAMBER, THE SAID MOLD BEING SO DIMENSIONED THAT SUBSTANTIALLY THE ENTIRE CONTENTS THEREOF IN A DIRECTION AWAY FROM SAID RESERVOIR IS COMPACTED TO FORM A CASTING OF UNIFORM DENSITY.