Engine speed control including frequency

Claim 1

AN ENGINE SPEED CONTROL SYSTEM FOR CONTROLLING THE SPEED OF A PRIME MOVER BY ADJUSTING VALVE MEANS THEREOF COMPRISING: A TACHOMETER GENERATOR DRIVEN BY SAID PRIME MOVER FOR PRODUCING A GENERATED SIGNAL HAVING AN OUTPUT FREQUENCY PROPORTIONAL TO ITS SPEED OF ROTATION, TRANSFORMER MEANS CONNECTED TO SAID TACHOMETER GENERATOR FOR PRODUCING A FIRST OUTPUT AND A SECOND OUTPUT EACH ISOLATED FROM EACH OTHER, RECTIFIER MEANS CONNECTED TO SAID FIRIST OUTPUT FOR PRODUCING A BIAS CONTROL SIGNAL INDEPENDENT OF FREQUENCY, A FREQUENCY SENSITIVE CIRCUIT FOR PRODUCING A D.C. SIGNAL OF MAGNITUDE AND DIRECTION CORRESPONDING TO THE DIFFERENCE BETWEEN THE FREQUENCY OF AN APPLIED SIGNAL AND A REFERENCE SIGNAL, MEANS CONNECTING SAID SECOND OUTPUT TO SAID FREQUENCY SENSITIVE CIRCUIT FOR PRODUCING A D.C. SIGNAL CORRESPONDING TO THE DIFFERENCE BETWEEN THE SPEED OF SAID PRIME MOVER AND A REFERENCE SPEED, OPERATING MEANS HAVING APPLIED THERETO SAID D.C. SIGNAL FOR OPERATING SAID VALVE MEANS OF A RESPECTIVE ENGINE IN A DIRECTION TO COUNTERACT AN INCREASE OR A DECREASE IN THE SPEED OF SAID ENGINE FROM SAID REFERENCE SPEED TO BRING THE ENGINE BACK TO ITS DESIRED SPEED, SAID OPERATING MEANS INCLUDING A FIRST AND A SECOND OPERATIONAL AMPLIFIER EACH HAVING A SUMMING JUNCTION AT SUBSTANTIALLY GROUND POTENTIAL AND AN OUTPUT TERMINAL, EACH OF SAID OPERATIONAL AMPLIFIERS INCLUDING A HIGHGAIN D.C. AMPLIFIER AND FEEDBACK RESISTOR EACH CONNECTED BETWEEN THE SUMMING JUNCTION AND SAID OUTPUT TERMINAL AND A FIRST AND A SECOND INPUT RESISTOR CONNECTED TO SAID SUMMING JUNCTION, MEANS FOR APPLYING SAID D.C. SIGNAL TO SAID FIRST RESISTOR OF SAID FIRST OPERATIONAL AMPLIFIER AND FOR APPLYING SAID BIAS CONTROL SIGNAL TO THE SECOND OF SAID INPUT RESISTORS, MEANS CONNECTING SAID OUTPUT TERMINAL OF SAID FIRST OPERATIONAL AMPLIFIER TO SAID FIRST INPUT RESISTOR OF SAID SECOND OPERATIONAL AMPLIFIER, A POSITION REFERENCE MONITOR CONNECTED TO SAID VALVE MEANS FOR PRODUCING A FEEDBACK SIGNAL, AND MEANS FOR APPLYING SAID FEEDBACK SIGNAL TO SAID SECOND INPUT RESISTOR OF SAID SECOND AMPLIFIER FOR BALANCING WITH SAID D.C. SIGNAL.