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:
May. 16, 1995
Filed:
Jun. 18, 1993
Masahiko Sakoh, Anjo, JP;
Makita Corporation, Anjo, JP;
Abstract
A speed control device for a DC motor controls the rotational speed of the DC motor through adjustment of a duty cycle of a semiconductor switching element. The rotational speed to be obtained is determined by an amount of operation of an operation member. A second contact switch is arranged to bypass the semiconductor switching element and is turned on to eliminate influence of the internal resistance of the semiconductor switching element. A power source contact switch is provided between a power source and the DC motor and is turned on and off through operation of the operation member. A switch-on forcing signal generation circuit and a switch-off forcing signal generation circuit are provided to forcibly switching on and off the second contact switch and the power source contact switch immediately before turning on and off thereof, respectively, so that the second contact switch may not be turned on and off when the semiconductor switching element is off and that the power source contact switch may not be turned off when the semiconductor switching element is on.