Abstract: An improved pump shell for a multistage metal working pump includes a plurality of pump shell units housed in series within a hollow cylindrical casing and has the impellers driven by a shaft. Each pump shell unit has a inner shell which forms a holding end at one side and a sealing flange at another side. The holding end of one pump shell may align and engage precisely and easily with the sealing flange of an adjacent pump shell unit to form a smooth fluid passage from the inlet of the impeller through the inner shell so that pumping efficiency may be enhanced with less turbulence. The sealing flange, holding end and the casing also form a close annular compartment for holding a seal ring inside to provide effective sealing function. The pump shell may be produced by stamping at low cost.

Abstract: A floatable impeller for multistage metal working pump includes an impeller hub which has an impeller metal working member supporting a rear wall of the impeller and an impeller plastic member integrally formed with the impeller working member. The impeller plastic member is engaged with and driven by the pump shaft. The impeller has a front wall attached with an impeller thrust ring which has a thrust metal working member integrally formed with a thrust plastic member located in front of the impeller front wall. The thrust plastic member serves as a bearing when rotating against a metallic pump shell of an adjacent pump unit for reducing friction loss. The impeller hub has axial grooves formed in the inside wall. The thrust plastic member has radial slots formed in the sidewall. The grooves and slots may collect and discharge grits and sands carried by fluid and generated by friction for reducing friction, improving pumping efficiency and enhancing pump durability.

Abstract: A sheet metal casing for multistage pump and its manufacturing method, the casing includes an outer shell and an inner shell. The outer shell is integrally formed and includes a front end ring, a step positioning ring, an outer shell surface and a positioning end. The inner shell is fixed to the inner side of the outer shell and includes an inner end, an inner shell surface and a step positioning rim. The step positioning rim forms a closed holding space with the outer shell surface for holding and squeezing a seal ring therein. When a plurality of casings being serially mounted on a spindle, the positioning end of a front casing may make contact with the step positioning ring of a rear casing, and the positioning rim of the front inner shell may make contact with the front end ring of the rear outer shell for axially positioning the casings on the spindle.

Abstract: A centrifugal pump impeller for easy positioning and avoid producing turbulence, includes a hub, a rear cover plate engaged with the hub, a front cover plate having an inlet at a front end thereof, and a plurality of vanes. Each vane has a front blade engaged with the front cover plate, a rear blade engaged with the rear cover plate and a blade to bridge the front and rear blade. The front blade has an indent section adjacent the inlet so that the front end of the front blade wont extend outside the front cover plate when the vane engages with the front cover plate. The rear blade has a curved front edge adjacent the spindle to make closed contact with the hub. The indent section and the curved front edge enable the impeller has smooth surface at the inlet without producing turbulence. The front and rear ends of the rear blade have respectively a vane balance hole and a positioning hole for the vane to be positioned between the front and rear cover plates precisely and easily.