Guiding apparatus for a work head

Claim 1

A SELVAGE TRIMMING APPARATUS FOR A PILE FABRIC COMPRISING MEANS FOR FEEDING THE PILE FABRIC IN A LONGITUDINAL DIRECTION, A CARRIAGE, MEANS FOR MOUNTING SAID CARRIAGE FOR RECTILINEAR MOVEMENT ALONG A LINE NORMAL TO A LONGITUDINAL EDGE OF THE PILE FABRIC AND MEANS INCLUDING A REVERSIBLE ELECTRIC MOTOR FOR MOVING SAID CARRIAGE IN BOTH DIRECTIONS ALONG SAID LINE, A CUTTER BLADE MOUNTED ON SAID CARRIAGE AND ADAPTED TO TRIM THE SELVAGE ALONG A LINE LONGITUDINALLY OF THE PILE FRABIC, MEANS ON SAID CARRIAGE FOR ACTUATING SAID CUTTER BLADE, AND MEANS FOR CONTROLLING THE ACTUATION OF SAID MOTOR TO MAINTAIN SAID CUTTER BLADE CLOSELY ADJACENT TO THE PILE EDGE COMPRISING A GUIDE ARM, MEANS FOR PIVOTALLY MOUNTING SAID GUIDE ARM ON SAID CARRIAGE FOR MOVEMENT ABOUT A PIVOT AXIS IN A PLANE NORMAL TO A PLANE DEFINED BY THE PILE FABRIC, FIRST AND SECOND ELECTRICAL SWITCHES MOUNTED ON SAID CARRIAGE, MEANS ON SAID GUIDE ARM FOR SELECTIVELY CLOSING SAID SWITCHES UPON PIVOTAL MOVEMENT OF SAID GUIDE ARM IN OPPOSITE DIRECTIONS FROM A NEUTRAL POSITION IN WHICH BOTH OF SAID SWITCHES ARE OPEN, MEANS ELECTRICALLY CONNECTING SAID SWITCHES WITH SAID MOTOR FOR ENERGIZING THE SAME TO DRIVE SAID CARRIAGE TOWARD THE PILE FABRIC UPON CLOSING SAID FIRST SWITCH AND TO DRIVE SAID CARRIAGE AWAY FROM THE PILE FABRIC UPON CLOSING SAID SECOND SWITCH, A GUIDE FINGER ON SAID GUIDE ARM FOR OVERLYING THE SELVAGE IN FRONT OF SAID CUTTER BLADE AND FOR FRICTIONALLY ENGAGING SAID PILE EDGE AS THE PILE IS MOVED PAST SAID GUIDE FINGER, SAID FRICTIONAL ENGAGEMENT BETWEEN SAID PILE EDGE AND SAID GUIDE FINGER PRODUCING A FORCE COMPONENT IN THE DIRECTION DEFINED BY THE FABRIC FEED AND ACTING UPON THE GUIDE FINGER TO BIAS SAID GUIDE ARM PIVOTALLY IN THE DIRECTION TO CLOSE SAID SECOND SWITCH, AND MEANS FOR PIVOTALLY BIASING SAID GUIDE ARM IN THE DIRECTION TO CLOSE SAID FIRST SWITCH, WHEREBY SAID BIASES ARE OPPOSED AND, WHEN BALANCED, SAID GUIDE ARM IS DISPOSED IN THE NEUTRAL POSITION AND, WHEN UNBALANCED, SAID GUIDE IS PIVOTALLY MOVED TO CLOSE THE RESPECTIVE ONE OF SAID SWITCHES.