Direct gassing extruder with gas pockets

Claim 1

An improved single screw, direct gassing extruder assembly comprising: 1. a casing having an upstream end and a downstream end and, in said casing, 2. a worm screw having a. a spiral thread and, b. a fluid conduit inside the root of the screw communicating externally with a fluid reservoir and internally through at least one opening located between two adjacent worm flights with the space between the root of the screw and the casing, 3. a fluid contact means comprising: a. a solid flow barrier extending between and connecting said adjacent worm flights, said barrier having substantially the same clearance with regard to the casing as the worm screw and having a forward side and a rearward side and, b. a gap extending substantially from root to top of flight in the downstream worm flight of said adjacent worm flights adjacent to the forward side of said barrier at a point where said barrier connects to the downstream worm flight of said adjacent worm flights and, c. said opening located between said two adjacent worm flights, near the rearward side of said barrier, whereby when the extruder is in operation on a thermoplastic feed, plasticized feed being forwarded by said rotating worm screw is blocked by said flow barrier at its forward side and forced through said gap, and a space free of plasticized feed is maintained between said two adjacent worm flights adjacent the rearward side of said barrier in the vicinity of said opening.