Electric motor speed and braking control systems

Claim 1

AN ELECTRIC SPEED CONTROL SYSTEM FOR AN ELECTRIC MOTOR INCLUDING MEANS FOR PRODUCING A SPEED REFERENCE SIGNAL WHICH IS ADJUSTABLE IN STEPS WHEREBY TO CHANGE THE REFERENCE SPEED OF THE MOTOR IN STEPS, MEANS FOR PRODUCING A FEEDBACK SIGNAL DEPENDENT ON THE SPEED OF THE MOTOR, MEANS RESPONSIVE DIFFERENTIALLY TO THE SPEED REFERENCE AND FEEDBACK SIGNALS FOR ENERGISING THE MOTOR IN DEPENDENCE UPON THE EXCESS ONLY OF THE REFERENCE SPEED OVER THE MOTOR SPEED IN A MANNER TENDING TO MAINTAIN THE MOTOR SPEED NEAR THE SELECTED REFERENCE SPEED, ELECTRIC BRAKING MEANS FOR EXERTING WHEN ENERGISED A BRAKING TORQUE ON THE MOTOR WHEREBY TO REDUCE ITS SPEED, AND BRAKING CONTROL MEANS RESPONSIVE TO THE SPEED REFERENCE SIGNAL ONLY AND EFFECTIVE ONLY ON THE OCCURRENCE OF A STEP REDUCTION IN THE SPEED REFERENCE SIGNAL TO ENERGISE THE BRAKING MEANS FOR A PREDETERMINED TIME INTERVAL WHEREBY TO CAUSE THE MOTOR SPEED TO FALL TO A PREDETERMINED VALUE CLOSE TO THAT CORRESPONDING TO THE NEWLY SELECTED REFERENCE SPEED, THE BRAKING CONTROL MEANS INCLUDING TIMING MEANS FOR DETERMINING THE SAID TIME INTERVAL AND A SECOND TIMING MEANS FOR RE-ENERGISING TEMPORARILY THE BRAKING MEANS AFTER A PREDETERMINED TIME DELAY AND FOR MAINTAINING THE BRAKING MEANS SO ENERGISED FOR A SECOND PREDETERMINED INTERVAL OF TIME SO AS TO ENABLE THE MOTOR SPEED TO FALL A SECOND TIME TO THE PREDETERMINED VALUE.