Method and apparatus for mixing and extruding visco-elastic materials

Claim 1

In an apparatus of the type known generally as an elastic melt extruder for extruding a visco-elastic material having first and second members with surfaces spaced from and facing each other in close proximity; means for rotating at least one of said members relative to the other to shear the visco-elastic material between said surfaces at a rate sufficient to produce a centripetal force in excess of the centrifugal force on the material and thereby cause a flow of said material toward the axis of rotation of the rotating member; means for feeding viscoelastic material into the gap between said surfaces; and a discharge opening formed through one of said members near said axis of rotation; the improvement of which comprises: recesses in said walls of said first and second members, said recesses defined by recessed portions extending inward from said spaced apart surfaces, said recessed portions forming surfaces of revolution about said axis of rotation, said recessed wall portions defining each recess comprising an upstream portion and a downstream portion, said upstream recess portion curving inward from said wall surface and said downstream recess portion gradually sloping from within said recess out to where it meets said wall at the downstream side of said recess, whereby the visco-elastic material in intimate contact with or adjacent said walls loses contact with said wall surfaces as it is accelerated centripetally past said recesses, and such material located in the area of said recess is also caused to move away from said recessed wall portions towards the center of the gap and be mixed with the mass of material.