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. 14, 1978
Filed:
Jun. 28, 1976
Theodore E Dahlen, West Bend, WI (US);
Rashmikant P Shah, Hartford, WI (US);
Bell & Howell Company, Chicago, IL (US);
Abstract
A microfilm reader has a film transport mechanism driven by separate forward and reverse motors. During operation, the driven one of the motors receives full AC power for driving it at high speed. During low speed operation, the driven motor receives partial power during half-cycles of one polarity, but only minimal power during half-cycles of opposite polarity. The undriven motor is pulled by its associated reel as the film is unwound therefrom. A large capacitor, which is part of a series circuit including both the forward and reverse motors, charges while either motor runs. When a driven motor is stopped, the capacitor is discharged into both of the motors to provide a unipolar field which produces a braking torque. Thus, the capacitor discharge not only stops the driven motor quickly and efficiently, but also stops the undriven motor to maintain film tension.