Tennant Company

Raymond C Hawkins

Donald J Haub

Howard N Seim

Keith N Krier

Neil T Brown

An improvement for electrically driven floor maintenance apparatus including means for varying the speed of the driving motors is disclosed. Two speed ranges are provided by switching means which change the interconnection of the drive motors from series for the low speed range, and parallel for the high speed range. Within each speed range, intermediate speeds are provided by placing resistors with shunt in series with the motors. Time delay circuitry is also included to prevent immediate operation of the vehicle in the high speed of each range until the vehicle has had some time to accelerate. Additionally, means are provided for detecting whether a vehicle is rolling in a forward or reverse direction and circuits are provided to prevent the operator from driving the vehicle in an opposite direction until the vehicle has slowed down to a near stop. A deadman control is provided to prevent the energizing of the drive motors when the operator is no longer seated on the driver's seat. ///

Multi-speed drive with forward/reverse lockout

A reversible electrically driven motor is disclosed together with circuitry for controlling the direction of the motor such that the current to the drive motor cannot be reversed to an opposite direction while the motor continues operation in a first direction. Once the motor slows to predetermined speed, which may approximate near-stop condition, the circuitry permits the voltage to operate in the opposite direction thereby reversing the motor. The control apparatus may include the portion of the electric motor which operates as a generator when the motor is not being electrically driven, a solid state sensor for sensing the voltage generated, and a lock-out circuit which responds to the sensed voltage to disable the operation of the driving circuit which reverses the motor.

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Minneapolis, MN, United States of America

Raymond C Hawkins