Transistorized speed control for industrial truck

Claim 1

A MOTOR CONTROL SYSTEM FOR AN INDUSTRIAL TRUCK HAVING A BATTERY AND A D.C. TRACTION MOTOR, COMPRISING: (A) A PLURALITY OF PARALLEL CONNECTED POWER TRANSISTORS FOR CONTROLLING THE FLOW OF CURRENT BETWEEN THE BATTERY AND THE TRACTION MOTOR (B) MEANS FOR EQUALIZING THE FLOW OF CURRENT FROM SAID BATTERY THROUGH EACH OF SAID POWER TRANSISTORS (C)MEANS FOR SUPPLYING A PULSATING CURRENT TO SAID POWER TRANSISTORS TO CAUSE SAID POWER TRANSISTORS TO INTERMITTENTLY CONDUCT CURRENT FROM SAID BATTERY TO SAID MOTOR TO DRIVE SAID TRACTION MOTOR (D) MEANS FOR VARYING SAID PULSATING CURRENT TO VARY THE AVERAGE CONDUCTION TIME OF SAID POWER TRANSISTORS TO THEREBY VARY THE SPACED OF THE TRUCK (E) MEANS RESPONSIVE TO A PREDETERMINED RATE OF CURRENT THROUGH SAID MOTOR FOR VARYING SAID PULSATING CURRENT TO DECREASE THE AVERAGE CONDUCTION TIME OF SAID POWER TRANSISTORS SO AS TO PREVENT THE RATE OF CURRENT THROUGH SAID MOTOR FROM EXCEEDING SAID PREDETERMINED RATE, AND (F) A UNIDIRECTIONAL CONDUCTOR CONNECTING OPPOSITE SIDES OF SAID TRACTION MOTOR TO PROVIDE FOR FLOW OF CURRENT DURING PERIODS OF NON-CONDUCTION OF SAID POWER TRANSISTORS.