Extruder screw for use in foam plastic extruder
AssigneeABC Group
InventorChangize Sadr
Life of this patent
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Abstract
In the production of foamed plastic articles using a screw extruder, it is known to introduce a gaseous foaming agent into the plastic while the latter is passing through the extruder. It has been found that a foamed thermoplastic with pores or cells of uniform size and distribution can be produced by passing a gaseous foaming agent, e.g. nitrogen gas through a central passage extending substantially the entire length of the extruder screw, discharging the agent into the thermoplastic proximate the discharge end of the extruder, and mixing the foaming agent with the plastic immediately prior to discharge of the mixture into a mold.
Claims4
An extruder screw for use in an extruder including an elongated barrel, an inlet for introducing solid plastic into the barrel near one end thereof, and an outlet at the other end of the barred for discharging molten plastic from the barrel, the screw comprising substantially continuous elongated cylindrical body means for rotation in the barrel;
- helical flight means on substantially the entire length of said body means for receiving material from said inlet and for feeding molten plastic through the barrel during rotation of said body means;
- first axial passage means in said body means extending from said one end to the other end of said body means for carrying gaseous foaming agent through said body means;
- thread means in said first axial passage means at said other end of the body means for receiving head means on said other end of said body means;
- bolt means on said head means at the upstream end thereof in the direction of foaming agent flow for engaging said thread means, permitting removable mounting of the head means on said body means;
- second axial passage means in said head means forming a continuation of said first axial passage means;
- third, generally radially extending passage means in said head means proximate the outlet end of the extruder barrel for discharging the gaseous foaming agent from the screw for intimate mixing with the molten plastic immediately prior to extrusion from the barrel.
Dependencies are inferred from the claim text.