Bell + Howell Company

Rashmikant P Shah

Theodore E Dahlen

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.

Variable speed AC motor control circuit

The disclosure relates to an ultrafiche carriage assembly for use in an ultrafiche apparatus of the type which projects a magnified image of a selected one of a plurality of film frames on an ultrafiche onto a reference surface. Such ultrafiche readers include a light system and projection system and the present invention herein disclosed provides a carriage assembly allowing vernier control of the position of the film frames between the light and projection systems so that a particular film frame of a known location on the ultrafiche may be selected.

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Hartford, WI, United States of America

Rashmikant P Shah