Patent ID: 7080935

Claim:
A multi-screw extruder for the continuous processing and/or working of a bulk material, in particular a powder, grain or flaked product, with several screws arranged as a rim in a hollow space of an extruder casing, which run parallel to the axial direction of the extruder and form an inner process space inside the rim along with an outer process space outside the rim, wherein the intersecting points formed by the axis lines of the respective screws with an imagined plane perpendicular to the axial direction lie on a rim line, and wherein each of the screws carries a plurality of axially consecutive processing elements, of which at least a portion are conveying elements, and with which adjacent screws tightly intermesh at least in partial areas, wherein the extruder casing is provided at the radially inner and radially outer surface of the hollow space with axially parallel concave circular segments that serve as a guide for the axially parallel screws with their processing elements on the inside or outside of the screw rim, and wherein the extruder has a feed hole at its first axial end leading to the hollow space as well as an outlet hole for the product to be processed at its second axial end, wherein at least one conveying screw element with at least one conveying screw web is used in the area of the feed hole in the extruder casing, which is not tightly meshing in at least one partial area along the axial direction; wherein at least one conveying screw element forms a gap toward the adjacent screw element whose radial dimension ΔR ranges between about 1/30 and ½ of the screw shank outer diameter Da, and has an axial dimension ΔL alongside the screw elements that is derived from dimension ΔR and the pitch of the screw elements and measures about 2ΔR.