Abstract: An improved form of archimedean screw pump is disclosed comprising a pump cylinder having an internal helicoidal vane portion affixed to the said pump cylinder by its circumferential helical edge and a partial core portion affixed to and extending from the said vane portion, the length of a section of said partial core portion on a plane through the axis of the pump cylinder, being greater than or equal to the longitudinal distance, in the said plane, between adjacent longitudinally spaced vane portions. The provision of a ribbon core substantially avoids the "choking" problems of known pumps of this type and the particular form of ribbon core enables the throughput of the pump further to be improved.

Abstract: An archimedean screw pump is described comprising a cylindrical wall having at least one internal helicoidal vane fixed within it. The pump is built up from a plurality of like modules having helical and helicoidal portions which when assembled form the wall, the vanes, and other pump surfaces such as a ribbon core.