Rod mill loop control by imaging loop on differential detector system

Claim 1

AN INSTRUMENT FOR THE AUTOMATIC MAINTENANCE OF A LOOP OF PREDETERMINED ORIENTATION IN THE FABRICATION OF A CONTINUOUS LENGTH OF SELF-LUMINOUS FLEXIBLE MATERIAL COMPRISING IN COMBINATION, (A) AT LEAST TWO SETS OF DRIVE ROLLS BETWEEN WHICH THE LOOP IS TO BE MAINTAINED, MEANS FOR DRIVING SAID ROLLS, (B) SERVO MEANS FOR VARYIGN THE ROTATIONAL SPEED OF AT LEAST ONE PAIR OF ROLLS IN EACH SET, (C) A DIFFERENTIAL RADIATION DETECTING SYSTEM HAVING TWO SECTIONS CAPABLE OF TRANSFORMING RADIATIONS INTO ELECTRICAL OUTPUT SIGNALS, SAID SYSTEM BEING LOCATED ADJACENT TO THE LOOP AND HAVING A NARROW DIVIDING LINE BETWEEN THE TWO SECTIONS THEREOF, MEANS FOR IMAGING THE ROD IN THE LOOP AT A PREDETERMINED CENTRAL POSITION ONTO THE DIVIDING LINE, (D) MASKING MEANS IN THE DIFFERENTIAL DETECTING SYSTEM PROVIDING MINIMUM AREA AT THE DIVIDING LINE AND INCREASING IN EACH HALF OF THE DIFFERENTIAL DETECTOR SYSTEM AS THE IMAGE OF THE LOOP MOVES FROM THE DIVIDING LINE AND MEANS FOR ACTUATING THE SERVO MECHANISM BY THE OUTPUT SIGNAL OF THE DIFFERENTIAL DETECTOR SYSTEM TO OPERATE THE SERVO MECHANISM IN A DIRECTION TO RESTORE THE LOOP TO ITS PREDETERMINED POSITION.