Firing Circuits Inc.

John P Salva

Shashi B Dewan

John A Mills

Gregory M Mudzinski

A control circuit for use with a shuttle car used in mining operations and circuitry associated therewith. The control circuit generally comprises a chopper circuit in series with a reversing circuit and a traction motor which drives the shuttle car. The chopper circuit essentially comprises two separate current paths each through a separate set of silicon controlled rectifiers or SCRs and a common capacitor. A logic circuit controlled by the operator alternately gates the sets of SCRs thereby placing voltage across the traction motor. The magnitude of this voltage and hence the speed of the motor are directly proportional to the frequency of the gating pulses. The reversing section also employs two sets of SCRs and a common field inductance. The operator, through the logic circuit, triggers one set of SCRs and current flows through the field inductance in a forward direction causing the traction motor to operate in a forward mode. When the second set of SCRs are triggered, the current through the field inductance is reversed, and accordingly, the current through the motor will also be reversed causing it to reverse direction. Consequently, the chopper circuit controls the car's speed while the reversing circuit controls its direction. The control circuit is also provided with a power circuit which creates the voltage for the logic circuit as well as a pump motor circuit which controls the car's hydraulics and a conveyor motor circuit which controls the loading and unloading functions.

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Shelton, CT, United States of America

John P Salva