Allis-chalmers Corporation

Michael H Grace

Howard G Murphy

Harvey E Schmidt

Arvin Karazija

Thomas J Finlayson

George H Smith

A forced commutation chopper control for regulating speed of a DC series tractive motor limits peak motor current by sensing the voltage across the commutation capacitor during the on-time of the current pulses and gating the commutation SCR on in response to a predetermined magnitude of sensed voltage to thereby terminate current pulses to the motor.

Forced commutation chopper having current limit

A vehicle is driven by a traction motor energized by pulses of current from a battery conducted by a power switch and has forward and reverse contactors to control motor direction and a variable time-ratio control for regulating motor speed including an RC timing circuit in series with a bidirectional speed potentiometer whose resistance element is provided with a midtap for selectively varying time duration of the pulses. The speed potentiometer wiper is coupled to a manual speed and direction selecting lever having a neutral position wherein the speed potentiometer wiper engages the midtap so that duty cycle of the pulses is minimum and neither contactor is energized, and actuation of the lever in either direction from neutral increases the time duration of the pulses and also energizes the forward or the reverse contactors to thereby control direction of vehicle travel.

Time-ratio control having bidirectional speed potentiometer

The operator's station of a lift truck is optionally elevatable with the carriage and the electric control interconnection between the operator's station, and the truck main frame includes a novel reel mechanism for the multiple lead electric conduit which does not use slip rings. The reel mechanism includes two drums which rotate together on a stationary shaft secured to the main frame. One drum is for coiling a flexible multi-lead round conduit which has its free end connected to the electric control console at the operator's station. The other drum contains a multiple lead flexible ribbon having its outer end connected to the inner end of the round conduit. The ribbon is coiled about the stationary shaft with its radially inner end passing through a hollowed portion of the stationary shaft and thence to a point of connection to a terminal block on the main frame. As the operator's station is raised with the carriage the round conduit is reeled out from the primary drum thereby rotating it against the bias of a windup spring. As the round conduit is reeled out from the primary drum the secondary drum is coiling the loosely wound ribbon about the shaft thus increasing the number of turns of its coil. The use of ribbon type electric conduit in the loosely wound secondary drum obviates the binding and jamming incurred when round conduit is used.

Reel arrangement for electric wiring

A lift truck energized from a battery to supply pressurized fluid to elevate a load-supporting carriage has an energy recovery system for converting kinetic energy of the elevated carriage into battery charging current including a fluid motor through which fluid from the lift ram is exhausted when the carriage is descending, an alternator driven by the fluid motor, a rectifier between alternator and battery, a transistor having its emitter-collector circuit in series with the field winding of the alternator, and a rate-of-descent adjusting potentiometer for selectively varying base drive to the transistor to thereby regulate field excitation of the alternator and the regenerative braking of the fluid motor.

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Griffith, IN, United States of America

Michael H Grace