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:
Oct. 06, 1998
Filed:
Sep. 02, 1997
Applicant:
Inventors:
Assignee:
Ebara Corporation, Tokyo, JP;
Primary Examiner:
Int. Cl.
CPC ...
F04B / ; F04C / ;
U.S. Cl.
CPC ...
4174104 ; 417420 ; 418-9 ;
Abstract
A multistage positive-displacement vacuum pump which is preferably used in the fabrication of semiconductor devices and can be operated from atmospheric pressure. The vacuum pump comprises a pump casing, a pump assembly housed in the pump casing and comprising a pair of pump rotors rotatable in synchronism with each other and arranged in multiple stages, and an intermediate pressure chamber provided between a preceding stage and a subsequent stage in the pump casing. The shaft portions of the pump rotors located between the preceding and subsequent stages are located in the intermediate pressure chamber.