Multi-stage vacuum pump
First Claim
1. A multi-stage recipricatory vacuum pump, comprising:
- first, second, third and fourth cylinders each having a first portion closed at one end and a second portion contiguous with, but of smaller diameter than the first portion;
each cylinder being provided with a piston having a cylindrical head portion relatively slideable in the first cylinder portion and a second cylindrical piston portion relatively slideable in the second cylinder portion, said piston head portion having a front face facing the closed cylinder end to define a main pumping chamber and an annular backface to define an annular pumping chamber;
a gas inlet port disposed in each first cylinder portion and adapted to be uncovered when said piston reaches a bottom dead center position of each piston stroke;
common drive means for reciprocating each piston in a respective cylinder;
a first exhaust port in each first cylinder portion for exhaustion of gas from the main pumping chamber by pumping action of the front face of the piston head portion;
a one way valve in said first exhaust port operable to permit exhaustion of gas from the main pumping chamber ahead of the piston head portion;
a second exhaust port in each cylinder for exhaustion of gas from the annular pumping chamber by pumping action of the annular backface of the piston head portion;
common inlet passage means connected to the gas inlet ports of said first and second cylinders;
first and second exhaust passages connected to the first and second exhaust ports of said first and second cylinders respectively;
a common passage interconnecting said first and second exhaust passages and communicating with a first outlet valve and a third exhaust passages connecting the first exhaust port of the third cylinder with the inlet port of the fourth cylinder;
a fourth exhaust passage connecting the second exhaust port of the third cylinder with the third exhaust passage; and
a final exhaust passage connecting the first exhaust valve of the fourth cylinder to a second outlet valve.
1 Assignment
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Accused Products
Abstract
A vacuum pump includes two pairs of piston and cylinder assemblies mounted on opposite sides of a crankshaft in a common plane with the gas inlets for the first and second cylinders of a first pair of piston and cylinder assemblies being connected to the device to be evacuated and the gas outlets thereof being connected to a common outlet 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. The gas outlet of the third cylinder is connected to the inlet of the fourth cylinder 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.
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Citations
6 Claims
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1. A multi-stage recipricatory vacuum pump, comprising:
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first, second, third and fourth cylinders each having a first portion closed at one end and a second portion contiguous with, but of smaller diameter than the first portion; each cylinder being provided with a piston having a cylindrical head portion relatively slideable in the first cylinder portion and a second cylindrical piston portion relatively slideable in the second cylinder portion, said piston head portion having a front face facing the closed cylinder end to define a main pumping chamber and an annular backface to define an annular pumping chamber; a gas inlet port disposed in each first cylinder portion and adapted to be uncovered when said piston reaches a bottom dead center position of each piston stroke; common drive means for reciprocating each piston in a respective cylinder; a first exhaust port in each first cylinder portion for exhaustion of gas from the main pumping chamber by pumping action of the front face of the piston head portion; a one way valve in said first exhaust port operable to permit exhaustion of gas from the main pumping chamber ahead of the piston head portion; a second exhaust port in each cylinder for exhaustion of gas from the annular pumping chamber by pumping action of the annular backface of the piston head portion; common inlet passage means connected to the gas inlet ports of said first and second cylinders; first and second exhaust passages connected to the first and second exhaust ports of said first and second cylinders respectively; a common passage interconnecting said first and second exhaust passages and communicating with a first outlet valve and a third exhaust passages connecting the first exhaust port of the third cylinder with the inlet port of the fourth cylinder; a fourth exhaust passage connecting the second exhaust port of the third cylinder with the third exhaust passage; and a final exhaust passage connecting the first exhaust valve of the fourth cylinder to a second outlet valve. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification