Patent ID: 7654725
Filing Date: 2010-02-02
Classification: B29B,B29C

Abstract:
1. A ring extruder comprising a housing; a core concentrically within said housing; and a plurality of screws disposed in parallel between said housing and said core and circumferentially about said core to define an outer annular process chamber for passage of a material between said housing and said screws and an inner annular process chamber for passage of a material between said core and said screws, each pair of adjacent screws having at least one thread thereon disposed in overlapping relation with a thread of the adjacent screw for mutual stripping of adhering material, said one thread of one of said screws having a circumferential portion of reduced radius ΔR to define a transverse passage for a material exchange between said outer process chamber and said inner process chamber, said one screw being a double-threaded screw, in which the radius of a first land is a smaller radius than the complete radius and the radius of a second land is the complete radius.