公开(公告)号：ES2038222T3

公开(公告)日：1993-07-16

申请号：ES88102688

申请日：1988-02-24

Applicant: THE COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANISATION

Inventor： BEZ, ECKHARD ,  FARRANT, JOHN L.

IPC: F04B37/16 ,  F04B25/00 ,  F04B37/14

Abstract: The vacuum pump (10) includes two pairs of piston and cylinder assemblies (21, 22, 23, 24) mounted on opposite sides of a crankshaft (13) in a common plane with the gas inlets for the first and second cylinders of a first pair of piston and cylinder assemblies (21, 22) being connected to the device to be evacuated and the gas outlets thereof being connected to a common outlet (17) having a spring biased one-way valve controlling the outlet and to a passage connected to the inlet of a third cylinder in said second pair of piston and cylinder assemblies (23, 24). The gas outlet of the third cylinder (23) is connected to the inlet of the fourth cylinder (24) and the gas outlet of the fourth cylinder is connected to the common outlet through spring biased one-way valves. Each cylinder is provided with a cylinder head having a pair of one-way valves controlling inlet and outlet ports wherein the one-way valve controlling the gas inlet port acts as a torque reduction valve to reduce the amount of torque necessary to move the piston away from the cylinder head on the initial stroke of the piston. Each cylinder is provided with a liner in the form of a sleeve having an hard wear resistant oxide coating thereon and each piston is provided with a coating of filled polytetrafluorethylene for the purpose of reducing friction.