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:
Mar. 21, 1995
Filed:
Mar. 26, 1993
Tadao Kitamura, Kawasaki, JP;
Toshio Kobayashi, Kawasaki, JP;
Yukio Osawa, Kawasaki, JP;
Noboru Usui, Kawasaki, JP;
Mamoru Yamada, Kawasaki, JP;
Fuji Electric Co., Ltd., Kanagawa, JP;
Abstract
An improved vacuum valve including an insulating container and an arc shield held in the insulating container, wherein a protrusion is formed on either the outer cylindrical surface of the arc shield or on the inner surface of the container. A detecting electrode is set confronted with the outer surface of the insulating container with an air gap therebetween, and is grounded through a current sensor. The current sensor detects a discharge current which is induced through the protrusion when the degree of vacuum of the vacuum valve is reduced, to output a detection signal. In response to the detection signal, a signal processing unit outputs an alarm signal indicating the reduction in the degree of vacuum of the vacuum valve. Thus, while the vacuum valve is in operation, its vacuum reduction can be positively detected with the vacuum valve maintained unchanged in reliability.