The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 16, 1996
Filed:
Aug. 29, 1994
Akira Nishiuchi, Ibaraki-ken, JP;
Masahiro Mase, Tochigi-ken, JP;
Noboru Matsumura, Ibaraki-ken, JP;
Katsuaki Kikuchi, Tsuchiura, JP;
Takashi Nagaoka, Tsukuba, JP;
Seiji Sakagami, Ibaraki-ken, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A turbo vacuum pump for compressing a low-pressure gas to discharge the compressed gas into atmosphere comprises pump stator having a gas flow passage comprising a plurality of annular flow passages on an inner surface thereof arranged stepwise diameters of which become smaller toward downstream and passages intercommunicating with adjacent annular flow passages and a gas discharge port communicated with one of the plurality of annular flow passages disposed at the most downstream. The pump stator includes a cylindrical spiral grooved pump impeller and a plurality of peripheral flow pump impellers facing the annular flow passages provided downstream of the cylindrical spiral grooved pump impeller and having stepwise diameters which become smaller toward downstream to form a peripheral flow pump stage. The suction casing has a spiral groove on a cylindrical inner surface thereof arranged with a predetermined clearance in relation to the spiral grooved pump impeller of the pump rotor so as to form a spiral grooved pump stage and a gas suction port communicated with the spiral grooved pump stage.