Press with a plurality of injection plungers

Claim 1

A press for simultaneously producing a plurality of moldings of plastics, particularly for producing packages of semiconductor circuits, comprising a plurality of injection plungers; at least one injection mold having a plurality of filling pots to be filled with a plastics material, a plurality of channels each connected to the associated pot and a plurality of cavities each connected to the associated channel, each of said injection plungers forcing a heated molding material in the associated pot and through the associated channel into the associated cavity; the injection plungers being provided with a common drive for simultaneously forcing said plungers into the associated pots; and a plurality of pressure-compensating pistons each adjoining a respective pot of said injection mold and each being associated with each of the injection plungers, said injection plungers and respective compensating pistons associated therewith being located opposite each other on a common axis and being laterally spaced from the mold cavities; hydraulic actuating means for actuating said compensating pistons; and means to cause a retreat of said compensation pistons in such a manner that, when a predetermined maximum pressure is reached in the respective pot each of the compensating pistons slightly retreats independently from the other compensating pistons to cause a pressure reduction in said pot.