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Multi-stage vacuum pump

  • US 4,854,825 A
  • Filed: 02/27/1987
  • Issued: 08/08/1989
  • Est. Priority Date: 02/27/1987
  • Status: Expired due to Term
First Claim
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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.

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