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:
Aug. 17, 1993
Filed:
Mar. 27, 1992
Shigeru Honma, Katsuta, JP;
Genji Hirata, Katsuta, JP;
Takahito Ishizuka, Katsuta, JP;
Toshio Mizoguchi, Katsuta, JP;
Hitachi Koki Co., Ltd., Tokyo, JP;
Abstract
A control circuit for use in an electrically powered tool, such as a screw driver, includes a double-pole double-throw (DPDT) relay switch having two wiper contacts movable between ON and OFF positions. A motor is connected to a power supply through the DPDT relay switch. To stop the rotations of the motor, the two wiper contacts trip from ON positions to OFF positions in ganged fashion. With the use of DPDT relay switch, even if one of the two wiper contacts undergoes chattering actions at its OFF position, the remaining wiper contact allows a large braking current to flow in a closed loop, whereby contacts of the DPDT relay switch are prevented from being melted caused by the braking current.