Plastic article or earthenware shaping or treating: apparatus – With separate and distinct upstream agitating or kneading means – Within pressurizing chamber
Patent
1988-07-18
1990-10-30
Chiesa, Richard L.
Plastic article or earthenware shaping or treating: apparatus
With separate and distinct upstream agitating or kneading means
Within pressurizing chamber
137854, 366 78, 4253761, 425559, 425563, 425587, B29C 4552
Patent
active
049665391
ABSTRACT:
An extruder screw of a plastic injection molding machine has a tip seal device at its forward end. The tip seal device has a body portion and a tapering tip portion, a circumferential sealing skirt is provided between the tip portion and the body portion. During extrusion, the pressure of molding material behind the skirt compresses it radially to allow for passage of the material through an extruder nozzle. When the screw is moved forwardly after extrusion, pressure of material forwardly of the skirt increases and expands the skirt radially into contact with the extruder barrel to form a seal.
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