Plural motor tensioning system for rewinding tape cassettes

Claim 1

In a tape transport for a tape cassette having a supply reel and a take-up reel, a system for rewinding the tape on the supply reel while maintaining tension on the tape being rewound to provide a good wrap of the tape around the supply reel comprising a rewind motor having characteristic torque and speed outputs for different supply voltages applied thereto for driving said supply, a holdback motor having characteristic torque and speed outputs for different supply voltages applied thereto, said motor being driven in a plugging mode by said take-up reel, means for applying a substantially constant supply voltage to said rewind motor during the entire rewind duration for producing the desired speed and torque output from the motor, and control means connected to said supply voltage means and to said rewind motor for applying a current of predetermined value through said holdback motor to operate said motor in the plugging mode which predetermined value (1) is an inverse function of said rewind motor current and (2) independent of the holdback motor speed thereby forcing the holdback motor torque to maintain proper tension on said tape, said rewind motor current varying in value as a direct function of the value of said rewind motor torque and said supply voltage means including means responsive to said rewind motor current for producing at a junction a control voltage which varies in value as an inverse function of the value of said rewind motor current, said control means including a first transistor connected in its common base configuration, current ampilifier means connected between an emitter of said first transistor and said control voltage junction for producing said predetermined value holdback motor current which remains constant at any one value control voltage independent of said holdback motor speed and voltage, and, said current amplifier comprising a second transistor the emitter of which is connected to said emitter of said first transistor, and a Zener diode operating as a level converter connected between the base of said second transistor and said control voltage junction.