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United States Patent 4112516
Douris , ê et al. September 5, 1978

Plasticizing device of an injection molding machine for plastics

Hotz September 5, 1978

Abstract

A plasticizing device for an injection molding machine for plastics comprises a screw housing having a cylindrical plastic material chamber at one end having a discharge opening. A cylindrical screw is rotatably and axially displaceably mounted in the housing and has a screw head portion adjacent the discharge with an intermediate body portion of reduced diameter adjacent the head portion and a uniform diameter portion on the opposite side of the intermediate portion from the head portion. The uniform diameter portion carries a spiral screw thread which projects radially outwardly from the surface of the screw. A seal ring having an outer periphery engaged with the interior of said screw housing and having an interior diameter greater than and spaced radially outwardly from the intermediate portion of the screw defines a plasticizing material passage with the intermediate portion which connects through a passage defined between a seal washer on the screw which cooperates with the seal ring. In addition a plurality of axially extending and circumferentially spaced passages are defined around the periphery of the screw adjacent the seal washer. These passages may be defined on a separate insert or on a plurality of axially arranged inserts and in this latter case the adjacent inserts are rotated relatively to each other so that the passages are not directly communicated but are offset.