Patent ID: 6113375
Filing Date: 2000-09-05
Classification: B29C

Abstract:
A foam extrusion assembly comprising:a) a melt region structured to receive and melt a plurality of material pellets;b) an agent addition assembly structured to add a foaming agent to said melted material pellets;c) a mixing assembly structured to substantially mix said melted material pellets and said foaming agent, said mixing assembly comprising:a generally elongate barrel having at least one inlet and at least one outlet;at least one mixing plug disposed in said barrel at a point generally between said inlet and said outlet of said barrel,said mixing plug defining at least two sequentially disposed flow passages along a length thereof, said flow passages being structured and disposed to receive said melted material pellets and said foaming agent therethrough so as to define a flow path past said mixing plug,a flow through area of each of said flow passages being substantially small so as to restrict amounts of said melted material pellets and said foaming agent which enter said flow passage at one time and to thereby substantially homogenize said melted material pellets and said foaming agent passing therethrough with one another, andsaid flow through area of an upstream one of said flow passages being larger than said flow through area of at least one downstream one of said flow passages disposed along said mixing plug;d) a die structured to receive a homogenized mixture of said melted material pellets and said foaming agent therethrough at an extrudable temperature; ande) said flow through area of at least two of said downstream ones of said flow passages being sequentially smaller than one another and said flow through area of said upstream one of said flow passages.