Servo motor control system for magnetic tape unit

Claim 1

A CONTROL SYSTEM FOR CONTROLLING THE TORQUE TAPE REEL DRIVE MOTOR IN A CERTAIN DIRECTION TO MAINTAIN A DESIRED LENGTH OF TAPE IN AN ADJACENT LOOP BOX COMPRISING (A) A MAGNETIC AMPLIFIER HAVING A CORE, (B) A FIRST CONTROL WINDING ON SAID CORE, (C) MEANS FOR PRODUCING A CURRENT FLOW IN SAID FIRST CONTROL WINDING OF MAGNITUDE RELATED TO THE ACTUAL LENGTH OF THE TAPE LOOP IN SAID LOOP BOX, (D) A SECOND CONTROL WINDING ON SAID CORE, (E) MEANS FOR PRODUCING IN SAID SECOND CONTROL WINDING A CURRENT FLOW OF MAGNITUDE RELATED TO THE DESIRED LENGTH OF SAID LOOP, (F) A POWER WINDING ON SAID CORE, (G) MEANS FOR PRODUCING A POTENTIAL HAVING A SQUARE WAVE SHAPE, SAID POTENTIAL PRODUCING MEANS CONNECTED THROUGH DIODE MEANS TO PRODUCE A UNIDIRECTIONAL CURRENT IN SAID POWER WINDIG DURING ONE HALF OF THE CYCLE OF SAID SQUARE TO DRIVE SAID CORE INTO SATURATION IN ONE DIRECTION DURING THAT HALF CYCLE OF SAID SQUARE WAVE, (H) SAID FIRST AND SECOND CONTROL WINDINGS BEING CONNECTED THEIR RESPECTIVE CURRENTS PRODUCE OPPOSING MAGNETOMOTIVE FORCES IN SAID CORE, (I) BIAS WINDING MEANS CARRYING A FIXED CURRENT TENDING TO DRIVE SAID CORE IN A DIRECTION OPPOSITE SAID ONE DIRECTION, (J) SAID CURRENTS IN SAID CONTROL WINDINGS AND SAID BIAS WINDINGS BEING SUCH THAT SAID CORE IS DRIVEN TO ITS SATURATED REGION BY CURRENT IN SAID POWER WINDING DURING A PORTION OF SAID HALF CYCLE OF SAID SQUARE WAVE WHEN THE CURRENTS IN SAID FIRST AND SECOND CONTROL WINDINGS DIFFER IN A CERTAIN SENSE, (K) SAID PORTION OF EACH HALF CYCLE HAVING A DURATION DIRECTLY RELATED TO THE DEVIATION OF SAID LOOP FROM ITS DESIRED SIZE, AND SAID SENSE REPRESENTING A SENSE OF SAID DEVIATION WHICH IS CORRECTABLE BY SAID MOTOR ROTATING ITS REEL IN SAID CERTAIN DIRECTION, (L) A SILICON CONTROLLED RECTIFIER COUPLED IN CIRCUIT WITH SAID MAGNETIC AMPLIFIER SO THAT IT FIRES WHEN SAID CORE IS IN ITS SATURATED REGION, (7) A TRANSFORMER HAVING ONE WINDING CONNECTED BETWEEN THE CATHODE AND ANODE OF SAID SILICON CONTROLLED RECTIFIER AND ANOTHER WINDING SERIALLY CONNECTED IN THE POWER CIRCUIT PRODUCES A TORQUE (N) WHEREBY SAID POWER CIRCUIT PRODUCES A TORQUE FORM SAID MOTOR IN SAID CERTAIN DIRECTION OF MAGNITUDE RELATED TO THE PORTION OF TIME SAID CORE IS IN ITS SATURATED CONDITION.