Motor speed control system

Claim 1

A CONTROL SYSTEM FOR APPLYING DIRECT CURRENT POWER TO A MOTOR TO CONTROL THE SPEED THEREOF, SAID SYSTEM INCLUDING IN COMBINATION, REFERENCE MEANS FOR PROVIDING A REFERENCE VOLTAGE, TACHOMETER MEANS COUPLED TO THE MOTOR FOR PRODUCING A VOLTAGE CORRESPONDING TO THE SPEED THEREOF, MEANS FOR COMPARING THE REFERENCE VOLTAGE AND THE TACHOMETER VOLTAGE TO PROVIDE AN ERROR VOLTAGE, RING MODULATOR MEANS FOR CONVERTING THE ERROR VOLTAGE INTO AN ALTERNATING CURRENT SIGNAL, AMPLIFIER MEANS FOR AMPLIFYING THE ALTERNATING CURRENT SIGNAL, POTENTIOMETER MEANS HAVING A MOVABLE ARM FOR PROVIDING A DIRECT CURRENT CONTROL POTENTIAL, SERVO MEANS CONNECTED TO SAID MOVABLE ARM FOR MOVING THE SAME, MEANS FOR APPLYING THE SIGNAL FROM SAID AMPLIFIER MEANS TO SAID SERVO MEANS TO VARY SAID CONTROL POTENTIAL IN ACCORDANCE WITH SAID ERROR VOLTAGE, RECTIFIER MEANS FOR SUPPLYING CURRENT TO THE MOTOR, CONTROL CIRCUIT MEANS INCLUDING BALANCED PHASE SHIF BRANCHES FOR APPLYING PULSES TO SAID RECTIFER MEANS TO CONTROL THE CURRENT SUPPLIED THEREBY TO THE MOTOR, EQUALIZER MEANS FOR APPLYING SAID THEREBY TO THE MOTOR, CONTROL CIRCUIT MEANS, AND MEANS APPLYING SAID CONTROL POTENTIAL TO SAID CONTROL CIRCUIT MEANS, WHEREBY THE PULSES APPLIED TO SAID RECTIFIER MEANS VARY WITH SAID ERROR VOLTAGE AND WITH SAID CONTROL POTENTIAL TO CONTROL THE MOTOR SPEED TO ELIMINATE THE ERROR SIGNAL.