Direct supply control device for a traction motor of vehicles, particularly for electric lifting trucks

Claim 1

An electronic control device for traction motors and the like comprising: a power source; a traction motor; a manually depressable operating pedal; adjustable means coupled between said power source and said motor and controlled by said operating pedal for adjustably coupling power to said motor from said power source in accordance with the amount of depression of said pedal; an electromagnet including first switch means for directly connecting said power source to said motor when said electromagnet is energized; second normally open switch means operable by said pedal for coupling said power source to said electromagnet when said pedal is fully depressed; first normally non-conductive electronic switch means coupled between said electromagnet and said power source and completing a current path including said power source, said electromagnet, said second switch means and said electronic switch means when said second switch means is closed and said electronic switch means is rendered conductive whereby said first switch means directly connects said power source to said motor bypassing said adjustable means; capacitor means coupled across said motor means for developing a voltage representing the value of the voltage supplied to said motor by said adjustable means; means further coupling said capacitor to said second switch means to couple said power source directly to said capacitor when said second switch means is closed; second normally non-conductive electronic switch means having first and second control inputs and an output, said first control input being coupled to said capacitor; means for coupling a constant proportional amount of the output level of said power source to said second control input to serve as a reference level; said second electronic switch means developing a signal at its output when the signal level at said first control input exceeds the reference lvel at said second control input; said first electronic switch means having a control input coupled to the output of said second electronic switch means for energizing said electromagnet to supply full power to said motor after a variable time delay interval said time delay interval being inversely proportional to difference between the value of the voltage level developed by said capacitor just prior to the time when said pedal is fully depressed and said reference level.