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. 15, 1991
Filed:
Dec. 15, 1988
Koutarou Naya, Shimizu, JP;
Kazuaki Shiinoki, Shimizu, JP;
Tadashi Hayakawa, Kamakura, JP;
Kiyoshi Masujima, Chigasaki, JP;
Riichi Uchida, Ibaraki, JP;
Katsumi Matsubara, Ushiku, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
The screw type vacuum pump comprises a pump casing having a suction inlet and a discharge outlet, and a pair of rotors incorporated within the pump casing and meshing with each other to rotate in synchronized manner. The vacuum pump evacuates a reaction vessel, to which process gas is applied, to obtain a negative pressure condition of a predetermined level. Upon operation of the pump, inert gas is introduced into a compression working chamber directly or through a sealing portion disposed adjacent the discharge outlet. The introduced inert gas is adiabatically compressed therein to generate heat to heat the rotors and a casing wall. Further the inert gas effects a reduction of partial pressure of the process gas in the pump. Accordingly, a side reaction product is prevented from accumulating on the rotors and the casing wall.