US 4,102,608 AGranted

Reciprocatory piston and cylinder machines

AssigneeCommonwealth Scientific and Industrial Research Organization

InventorsGuenter Karl Willi Balkau, Eckhard Bez, John Lascelles Farrant

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Abstract

Vacuum pump of reciprocating piston and cylinder type. Cylinder is stepped to have front large diameter portion and rear small diameter portion. Piston has enlarged head portion sliding in front portion of cylinder and rear portion sliding in rear portion of cylinder. Front end of cylinder is closed to form high vacuum pumping chamber swept by front face of piston head. Gas enters the high vacuum pumping chamber through side wall of cylinder and can be exhausted through exhaust valve in closed front end of cylinder. Rear annular face of piston head sweeps lower vacuum chamber in cylinder behind the piston head. A gas transfer passage extends through cylinder wall from front end of high vacuum pumping chamber to port in cylinder wall so as to transfer gas from high vacuum chamber to lower vacuum chamber when piston approaches end of forward stroke. Gas is transferred through transfer duct at pressures lower than required to open the exhaust valve. Also claimed are specific forms of piston ring permitting lubrication-free operation of piston in the cylinder.

Claims23

Dependent claims

A vacuum pump comprising:

a cylinder having a first portion closed at one end and a second portion contiguous with, but of smaller diameter than, the first portion;
a piston having a head portion slidable in the first cylinder portion and a second piston portion of smaller diameter than the head portion and slidable in the second cylinder portion, said piston head portion having a front face facing the closed cylinder end and an annular back face;
a gas inlet for inlet of gas to the interior of the first cylinder portion between the front face of the piston head portion and the closed cylinder end on reciprocation of the piston;
a first exhaust duct for exhaustion of gas from the interior of the first cylinder portion ahead of the piston head portion by pumping action of the front face of the piston head portion;
a one-way valve in said first exhaust duct operable by gas pressure thereon to permit exhaustion of gas from the interior of the first cylinder portion ahead of the piston head portion but closable against reverse gas flow;
an exhaust means for exhaustion of gas from the interior of the first cylinder portion behind the piston head portion by pumping action of the back face of the piston head portion;
and
a gas transfer passage for transfer of gas from said interior of the first cylinder portion ahead of the piston head portion to the interior of the first cylinder portion behind the piston head portion by pumping action of the front face of the piston head which gas transfer passage is capable of said transfer of gas at gas pressures lower than required to open said one way valve.

5 more elements

Dependencies are inferred from the claim text.