Patent ID: 7244115

Claim:
An extruder for extruding shaped bodies formed from a flowable slurry containing particulate material and liquid, the extruder comprising: an extruder body having (a) an inlet space where the flowable slurry containing particulate material and liquid is supplied under a high hydrostatic pressure, (b) first and second walls of which respective opposed first and second surfaces together define an elongate moulding space into which the flowable slurry from the inlet section is introduced under the high hydrostatic pressure, said moulding space having a longitudinal flow axis and a uniform cross section, and (c) an extrusion outlet located adjacent a terminal end of the moulding space whose cross-sectional shape is defined by the surfaces of said first and second walls, and whose cross-sectional shape defines a shaped body extruded from the moulding space which shaped body is derived from the flowable slurry containing particulate material and a liquid; and (d) a friction section over a length of the moulding space between the intermediate portion and the extrusion outlet, said friction section including a friction contact between the shaped body and each of the opposed walls of the moulding space which said friction contact exerts a reaction force, on the shaped body against the high hydrostatic pressure by which the flowable slurry is supplied into the moulding space from said inlet space, said reaction force of said friction contact being sufficient by itself to at least substantially prevent the shaped body from moving alone the opposed walls and out of said extrusion outlet due to the high pressure of said flowable slurry without assistance to the shaped body; a means for reducing said reaction force of said friction contact between the shaped body and each of the opposed walls in the friction section so that the shaped body exits from said extrusion outlet; and a plurality of passages at an intermediate portion of one of said first and second walls upstream from said extrusion outlet and in the molding space, which said passages open through the one of said first and second walls from the moulding space to define dewatering slots for the flowable slurry; whereby said reaction force forms in the friction section a non-flowable consolidated material which is extrudable through the outlet as the shaped body, which shaped body is formed when liquid is expelled from the moulding space through the dewatering slots at the intermediate portion.