Plural motor drive control apparatus

Claim 1

A DRIVE SYSTEM FOR A ROTATING LOAD, COMPRISING: A MAIN DRIVE MOTOR HAVING A PREDETERMINED OPERATING SPEED AND DELIVERING A PREDETERMINED TORQUE AT SAID OPERATING SPEED; A VARIABLE-SPEED SECONDARY MOTOR HAVING A PREDETERMINED OPERATING SPEED RANGE WHEREIN SAID SECONDARY MOTOR DELIVERS A SUBSTANTIALLY LOWER TORQUE AND HAS A LOWER POWER CONSUMPTION THAN SAID MAIN DRIVE MOTOR; A SPEED-REDUCING GEAR TRAIN HAVING A TORQUE-MULTIPLYING CHARACTERISTIC OF A PREDETERMINED VALUE SUITABLE FOR MULTIPLYING SAID TORQUE OF SAID SECONDARY MOTOR TO THE ORDER OF SAID MAIN DRIVE MOTOR TORQUE, SAID GEAR TRAIN BEING MOUNTED ENTIRELY ON SAID SECONDARY MOTOR AND FORMING AN ASSEMBLY THEREWITH INCLUDING AN OUTPUT ELEMENT DELIVERING TORQUE MATCHING SAID MAIN DRIVE MOTOR TORQUE AT LOW OUTPUT SPEED AND LOW POWER CONSUMPTION; SAID ASSEMBLY BEING COUPLED TO SAID MAIN DRIVE MOTOR SO AS TO BE BODILY DRIVEN THEREBY, AND SAID OUTPUT ELEMENT OF SAID ASSEMBLY BEING COUPLED TO SAID LOAD TO DRIVE THE SAME AT A SPEED THAT IS THE SUM OF SAID MAIN DRIVE MOTOR SPEED AND SAID LOW OUTPUT SPEED OF SAID ASSEMBLY; AND MEANS FOR SENSING THE DIFFERENCE BETWEEN THE ROTATIONAL FREQUENCY OF SAID LOAD AND A PREDETERMINED FREQUENCY, SAID MEANS BEING COUPLED TO SAID SECONDARY MOTOR FOR VARYING THE SPEED OF SAID SECONDARY MOTOR IN ACCORDANCE WITH SAID SENSED FREQUENCY DIFFERENCE AND FOR MAINTAINING SAID LOAD AT SAID PREDETERMINED ROTATIONAL FRQUENCY, WITHOUT ALTERING THE SPEED OF SAID MAIN DRIVE MOTOR.