Screw type vacuum pump

Pumps – Successive stages – With interstage discharge or additional discharge from...

Reexamination Certificate

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Details

C417S310000, C417S308000, C418S201100, C418S201300

Reexamination Certificate

active

10490956

ABSTRACT:
A screw vacuum pump which allows reduced power, lower inside gas temperature, and reduced discharging time. The pump has a pair of screw rotors rotatively engaged with each other in a pump casing to discharge a gas along a longitudinal direction of the pump. Each rotor has three types of helical teeth serially located in a longitudinal direction of the rotor and different from each other in theoretical displacement volume. A bypass conduit communicating with a delivery side of the pump is connected via a first check valve to a first intermediate space defined between the first helical teeth and the second helical teeth and via a second check valve to a second intermediate space defined between the second helical teeth and the third helical teeth. The gas is compressed at the third stage to half the first stage volume before a discharge port opens.

REFERENCES:
patent: 3947163 (1976-03-01), Olofsson
patent: 4983107 (1991-01-01), Steffens et al.
patent: 5549463 (1996-08-01), Ozawa
patent: 5667370 (1997-09-01), Im
patent: 6375443 (2002-04-01), Yoshimura
patent: 7140846 (2006-11-01), Yamamoto et al.
patent: 3-111690 (1991-05-01), None
patent: 2000-136787 (2000-05-01), None

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