Rotary positive displacement pump - has annular working space formed by fixed outer wall and annular diaphragm inner wall

摘要

The pump has an annular diaphragm (8) with a fixed radial portion (20). A rotary annular piston (10) is driven by planetary roller (17) so as to progressively urge the diaphragm against the peripheral wall (7) of a cylindrical chamber and draw working fluid through an inlet (3) and discharge it through an outlet. The piston has freedom to rock in directions perpendicular to its rotation axis relative to both the roller and the peripheral wall so as to ensure adequate radial clearance and reduce diaphragm wear. The area of contact of the diaphragm with the wall lags behind the area of contact of the roller with the inner surface (18) of the piston by an angle (A).