Screw vacuum pump with a reduced starting load
AssigneeEbara Corporation
InventorsNoburu Shimizu, Kiyoshi Yanagisawa
Life of this patent
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Abstract
A screw vacuum pump is designed so that it is possible to reduce the load on the pump at the time of starting and evacuation of a gas under atmospheric pressure. The screw vacuum pump has male and female rotors rotating in mesh with each other around two parallel axes, respectively, and a casing for accommodating the rotors, the casing having a suction port and a discharge port, wherein the discharge port is formed so that V.sub.1 /V.sub.2 is in the range of 1.5 to 0.51, where V.sub.1 is a groove volume defined by the casing and the male and female rotors immediately after a gas has been trapped, and V.sub.2 is a groove volume immediately before the gas is discharged.
Claims5
A screw vacuum pump, which comprises:
- a male and female rotor rotating in mesh with each other around two parallel axes, respectively,
- a casing for accommodating said rotors, said casing having a suction port and a discharge port, said casing and said rotors having a groove space formed therebetween
- wherein a rotor rotation angle at which said suction port closes said groove space formed by said casing and said rotors is set at an angle at which the volume of said groove space has not yet reached a maximum, and wherein said discharge port is formed so that V.sub.1 /V.sub.2 is about 1, where V.sub.1 is a groove volume defined by said casing and said rotors immediately after a gas has been trapped, and V.sub.2 is a groove volume immediately before the gas is discharged.
A pump apparatus comprising a plurality of screw vacuum pumps which are connected in series in a multi-stage structure, each of said screw vacuum pumps comprising:
- a male and female rotor rotating in mesh with each other around two parallel axes, respectively,
- a casing for accommodating said rotors, said casing having a suction port and a discharge port, said casing and said rotors having a groove space formed therebetween
- wherein a rotor rotation angle at which said suction port closes said groove space formed by said casing and said rotors is set at an angle at which the volume of said groove space has not yet reached a maximum, and wherein said discharge port is formed so that V.sub.1 /V.sub.2 is about 1, where V.sub.1 is a groove volume defined by said casing and said rotors immediately after a gas has been trapped, and V.sub.2 is a groove volume immediately before the gas is discharged.
Dependencies are inferred from the claim text.