Digital control for shear

Claim 1

A CONTROL FOR A MOTOR DRIVING A SHEAR TO CUT A CONTINUOUSLY MOVING SUBJECT INTO PRESELECTED LENGTHS, COMPRISING, A PULSE GENERATOR FPR PRODUCING SUBJECT POSITION PULSES CORRESPONDING TO PREDETERMINED INCREMENTS OF SUBJECT ADVANCE WITH RESPECT TO A POINT WHERE THE SHEAR OPERATES TO CUT THE SUBJECT, MEANS INCLUDING A PRESET COUNTER CONNECTED TO RECEIVE SAID SUBJECT POSITION PULSES AND OPERABLE AFTER EACH SUCCESSION OF THE PRESET NUMBER OF SAID PULSES TO PRODUCE SAID PULSES AT ITS OUTPUT UNTIL A CUT IS MADE, A PULSE GENERATOR FOR PRODUCING FORWARD SHEAR POSITION PULSES WHEN THE SHEAR IS GOING FORWARD AND REVERSE SHEAR POSITION PULSES WHEN THE SHEAR IS GOING IN REVERSE, THE INCREMENT OF SHEAR BLADE TRAVEL REPRESENTED BY A SHEAR POSITION PULSE CORRESPONDING TO THE INCREMENT OF SUBJECT ADVANCE REPRESENTED BY A SUBJECT PULSE, A DIFFERENCE COUNTER CONNECTED TO COUNT IN ONE DIRECTION IN RESPONSE TO SAID SUBJECT PULSES AT SAID OUTPUT, TO COUNT IN SAID ONE DIRECTION IN RESPONSE TO SAID REVERSE SHEAR POSITION PULSES, AND TO COUNT IN THE OPPOSITE DIRECTION IN RESPONSE TO SAID FORWARD SHEAR PULSES, SAID DIFFERENCE COUNTER PRODUCING AT ITS OUTPUT A COUNT VALUE VARYING IN DIRECTION ACCORDING TO WHETHER THE SHEAR POSITION IS AHEAD OR BEHIND THE SUBJECT POSITION, A DIGITAL TO ANALOGUE CONVERTER RESPONSIVE TO SAID COUNT VALUE TO PRODUCE A MOTOR CONTROL SIGNAL VARIABLE TO CAUSE THE MOTOR TO PROPERLY TRACK THE SUBJECT, AND MEANS OPERABLE WHEN THE SHEAR MAKES A CUT TO GIVE SAID DIFFERENCE COUNTER A COUNT VALUE IN SAID ONE DIRECTION CORRESPONDING TO THE DISTANCE BETWEEN THE SHEAR CUT POSITION AND REFERENCE POSITION.