Control system

Claim 1

APPARATUS FOR CONTROLLING A PROCESSING ELEMENT ADAPTED TO EFFECT A CHANGE IN A PHYSICAL CHARACATERISTIC OF A CONTINUOUSLY MOVING MATERIAL STRIP COMPRISING, A FIRST TRANSDUCER LOCATED UPSTREAM OF SAID PROCESSING ELEMENT AND ADAPTED TO PROVIDE AS AN OUTPUT A SIGNAL INDICATIVE OF THE VALVE OF SAID PHYSICAL CHARACTERISTIC IN THE REGION ADJACENT TO SAID TRANSDUCER; A SECOND TRANSDUCER LOCATED DOWNSTREAM OF SAID PROCESSING ELEMENT AND ADAPTED TO PROVIDE AS AN OUTPUT A SIGNAL INDICATIVE OF THE VALVE OF SAID PHYSICAL CHARACTERISTIC IN THE REGION ADJACENT TO SAID SECOND TRANSDUCER; A FIRST DELAY UNIT HAVING ITS INPUT COUPLED TO THE OUTPUT OF SAID FIRST TRANSDUCER AND ADAPTED TO PROVIDE AS AN OUTPUT SAID FIRST TRANSDUCER OUTPUT SIGNALS AFTER A TIME DELAY EQUAL TO THE TIME REQUIRED FOR SAID MATERIAL STRIP TO TRAVEL FROM SAID FIRST TO SAID SECOND TRANSDUCER; A SIGNAL GENERATOR COUPLED TO SAID SECOND TRANSDUCER OUTPUT AND SAID DELAY UNIT OUTPUT AND ADAPTED TO PROVIDE AN OUTPUT SIGNAL RELATED TO THE DIFFERENCE BETWEEN SIGNALS FROM SAID SECOND TRANSDUCER OUTPUT AND SAID FIRST DELAY UNIT OUTPUT; MEANS COUPLING SAID SIGNAL GENERATOR OUTPUT TO SAID PROCESSING ELEMENT; FIRST DRIVE MEANS FOR SCANNING SAID FIRST TRANSDUCER TRANSVERSELY ACROSS SAID MATERIAL STRIP; SECOND DRIVE MEANS FOR SCANNING SAID SECOND TRANSDUCER TRANSVERSELY ACROSS SAID MATERIAL STRIP; FIRST POSITION INDICATING MEANS ASSOCIATED WITH SAID FIRST TRANSDUCER AND ADAPTED TO PROVIDE CONTINUOUSLY A SIGNAL INDICATIVE OF THE TRANSVERSE POSITION OF SAID FIRST TRANSDUCER; SECOND POSITION INDICATING MEANS ASSOCIATED WITH SAID SECOND TRANSDUCER AND ADAPTED TO PROVIDE CONTINUOUSLY A SIGNAL INDICATIVE OF THE TRANSVERSE POSITION OF SAID SECOND TRANSDUCER; A SECOND DELAY UNIT COUPLED TO SAID FIRST POSITION INDICATING MEANS AND ADAPTED TO PROVIDE AS AN PUTPUT SAID SIGNALS FROM SAID FIRST POSITION INDICATING MEANS AFTER A TIME DELAY EQUAL TO THE TIME REQUIRED FOR SAID MATERIAL STRIP TO TRAVEL FROM SAID FIRST TO SAID SECOND TRANSDUCER; A BALANCING AMPLIFIER COUPLED TO THE OUTPUT OF SAID SECOND DELAY UNIT AND SAID SECOND POSITION INDICATING MEANS AND ADAPTED TO PROVIDE AN OUTPUT WHENEVER SAID SECOND DELAY UNIT OUTPUT IS DIFFERENT FROM SAID SECOND POSITION INDICATING SIGNAL; SAID SECOND DRIVE MEANS BEING RESPONSIVE TO SAID BALANCING AMPLIFIER OUTPUT TO DRIVE SAID SECOND TRANSDUCER TO OCCUPY SUBSTANTIALLY THE SAME TRANSVERSE POSITION THAT SAID FIRST TRANSDUCER OCCUPIED ONE DELAY PERIOD PREVIOUSLY.