Mold closing unit with separately acting rotary and fluid pressure piston drives

Claim 1

A mold closing unit for injection molding machines for plastics for processing duroplasts, thermoplasts and elastomers and which includes separate driving mechanism for the production of closing and opening movements and also for applying and eliminating a closing force to the mold, comprising a movable mold member movable in closing and opening directions for opening and closing the mold and being forced into a closing direction to apply a closing force to the mold comprising a housing connected to the movable part of the mold, a mechanical movement mechanism for moving the housing with the movable part of the mold in opening and closing direction including an operating piston guided within the housiNg and connected to the movable mold member, and a fluid pressure operated piston arranged coaxially with said operating piston and connected to said housing for shifting said housing for the production of the closing force and in a reverse direction for the elimination of the closing force, an electrical contact means connected to said operating piston and said fluid pressure piston, spring means biasing said housing to a neutral position after said fluid pressure piston is unloaded after the closing or opening movement, the stroke of said fluid pressure piston being equal to the sum of the clearance gap permitted between the movable mold member and the fixed mold member, the clearance gap being set for operating said electrical contact means for switching from the operating piston to said fluid pressure piston to effect the production of the closing force after the predetermined clearance gap is exceeded.