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:
Jan. 10, 1989
Filed:
Jun. 05, 1987
Tadashi Hayakawa, Ebina, JP;
Kazuaki Shiinoki, Ebina, JP;
Sinji Mitsuhashi, Yokohama, JP;
Kotaro Naya, Ebina, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A vacuum evacuation system comprising a non-positive displacement type vacuum pump called molecular pump which obtains high pumping speed in a high vacuum range, and an oil-free, positive displacement type vacuum pump called screw vacuum pump. The non-positive displacement type vacuum pump and the positive displacement type vacuum pump are connected to each other such that the non-positive displacement type vacuum pump is located on a high vacuum side and the positive displacement type vacuum pump is located on a low pressure or atmospheric side, to thereby prevent oil from being penetrated into a system to be evacuated.