Injection molding machine having a plasticizing plunger

Claim 1

An injection molding machine for processing plasticizable plastics, comprising an injection cylinder, an injection nozzle at one end of said cylinder and communicating therewith, a reciprocating filling plunger having a front end within said cylinder, a reciprocating plasticizing plunger positioned in said injection cylinder between said front end of said filling plunger and said injection nozzle having means to plasticize plastic within a dosing space between said filling plunger and said plasticizing plunger, means to feed plastic to said dosing space between said filling plunger and said plasticizing plunger, said plasticizing plunger comprising a plunger body having a front side and a back side and defining between its contour and the inside wall of said injection cylinder a restricted annular passage for plasticized plastic between the dosage space behind said back side and the space in front of said front side, said plasticizing plunger body being secured at its back side to a plunger rod of smaller outside diameter than the outside diameter of said contour of said plasticizing plunger, said plunger rod extending coaxially and displaceably through an axial bore in said filling plunger, means to move said plasticizing plunger so that said front end of saiD filling plunger having a front surface adapted to snugly fit the surface of said back side of said plasticizing plunger body abut after said plastic has been plasticized, and when said filling plunger abuts against said plunger body of said plasticizing plunger means to advance said plungers to inject said plasticized plastic through said injection nozzle.