Multistage vacuum pump

摘要

A multistage vacuum pump is achieved by utilizing a single piston and cylinder assembly having opposite end portions with substantially equal diameters and an enlarged diameter central portion. One end of the cylinder is closed by a valve and a first stage pumping chamber is defined between the valve and the piston. The enlarged diameter portion of the piston has an axial extent less than the axial extent of the enlarged diameter portion of the cylinder to define second and third stage pumping chambers on opposite sides of the enlarged diameter portion of the piston. The three pumping chambers are interconnected by passage means to an inlet and outlet to provide a sequential reduction in pressure. A single drive unit may be connected to a plurality of pumping units for reciprocating the piston in each pumping unit.