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:
Feb. 19, 1991
Filed:
Jul. 19, 1988
Riichi Uchida, Ibaraki, JP;
Kotaro Naya, Shimizu, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A vacuum pump apparatus comprises a male and female screw rotors meshing with each other, a casing for accommodating the male and female screw rotors and having a working space, a suction port and a discharge port both communicating with the working space, bearing portions for supporting shafts of the male and female screw rotors on the suction and discharge sides thereof. Shaft seal portions which are respectively disposed between the working space and each of the bearing portions and are adapted to seal the shafts of the male and female screw rotors on the suction and discharge sides thereof. Seal gas introducing device introduces seal gas into the shaft seal portions, and a controller controls the pressure of the seal gas introduced into the shaft seal portions.