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:
Dec. 25, 1990
Filed:
Oct. 10, 1989
Applicant:
Inventor:
Youichi Hayashi, Kanagawa, JP;
Assignee:
Fuji Photo Film Co., Ltd., Kanagawa, JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
B25B / ;
U.S. Cl.
CPC ...
81477 ; 173 12 ;
Abstract
A screw tightening device has a DC motor and a bit which is set to a screw. The DC motor is energized by a driving signal and rotates the bit. A torsion spring coupling is connected between the DC motor and the bit and absorbs an excessive torque produced therebetween. When the driving signal is cut, the motor is reversed under the returning force of the torsion spring coupling. A brake circuit causes a brake current which reduces the speed of the reverse rotation of the motor through the motor.