Injection-molding machine with reciprocating plasticizing screw

Abstract

A plasticizing screw of an injection-molding machine, axially movable in an extruder barrel, is driven by a tubular input shaft via a splined quill partly retractable into the shaft with which the quill is coupled through an internally and externally splined bushing. Another such bushing is removably seated, for possible replacement by a similar bushing of different inner diameter, in an internally splined cup-shaped head of the quill and engages the splined rear end of the screw. The quill head rests via a thrust bearing against the front end of a nonrotatable tubular piston coaxially surrounding the quill and entering by its rear end an annular cylinder which is hydraulically connected with a pressure accumulator including a gas cushion. The accumulator creates a back pressure by which molding material, plasticized by the screw during the preceding phase in which the screw was repressed into a rear position, is introduced via a check valve into a shooting pot alongside the extruder barrel. Another tubular injection piston extends rearwardly into an annular injection cylinder, which is pressurized only briefly upon closure of the mold, and bears at its front end upon a plunger penetrating into the shooting pot whose effective capacity is determined by a manually adjustable backstop for the injection piston. Lubricating oil from a sump in a gearbox surrounding the input shaft is pumped by the reciprocation of the quill, through passages provided for this purpose, to spaces inside the input and inside the extruder piston communicating with each other through the splines of the quill.

Dependencies are inferred from the claim text.