Pull-down device for motion picture cameras

Claim 1

A PULL-DOWN MECHANISM FOR INTERMITTENTLY ADVANCING A PERFORATED FILM STRIP THROUGH A GATE LOCATED IN A SELECTED FILM PATH, WHICH COMPRISES: (1) A STATIONARY ARCUATE GUIDE MEMBER SPACED TO ONE SIDE OF SAID GATE MEMBER AND EXTENDING SUBANSTANTIALLY PARALLEL TO SAID FILM PATH; (2) A RECIPROCATABLE SHUTTLE HAVING A BEARING SURFACE OF SUBSTANTIALLY SEMI-TUBULAR CONFIGURATION ARRANGED CONCENTRICALLY OF SAID GUIDE MEMBER; (3) A FILM CLAW ON SAID SHUTTLE AND SPACED LATERALLY OF SAID BEARING PORTION TO ENGAGE THE PERFORATIONS OF FILM IN SAID PATH; (4) MEANS FOR MOUNTING SAID SHUTTLE ON SAID GUIDE MEMBER TO RECIPROCATE AXIALLY THEREOF TO INTERMITTENTLY ADVANCE FILM THROUGH SAID GATE AND TO OSCILLATE COAXIALLY THEREOF TO MOVE SAID GATE AND TO OSCILLATE ENGAGEMENT WITH PERFORATIONS OF FILM LYING IN FILM PATH, AND INCLUDING: (A) AT LEAST TWO PAIRS OF BALL MEMBERS SPEED LONGITUDINALLY OF SAID GUIDE MEMBER AND IN ROLLING CONTACT WITH SAID SEMI-TUBULAR BEARING SURFACE AND WITH SAID ARCUATE GUIDE MEMBER, AND (B) RESILIENT MEANS FOR HOLDING CONTACT WITH SAID BALL BEARING SURFACE IN ROLLING CONTACT WITH SAID BALL MEMBERS AND URGING IT IN A DIRECTION ARCUATELY OF SAID GUIDE MEMBER TO MOVE SAID CLAW INTO ENGAGEMENT WITH SAID FILM; (5) ADVANCE CAM MEANS FOR RECIPROCATING SAID SHUTTLE AXIALLY OF SAID GUIDE MEMBER OVER A DISTANCE COMMEASURATE WITH THE PERFORATION PITCH OF SAID FILM; AND (6) IN-AND-OUT CAM MEANS CONNECTED TO ROTATE SAID SHUTTLE COAXIALLY OF SAID GUIDE MEMBER AGAINST THE FORCE OF SAID RESILIENT MEANS TO REMOVE SAID CLAW FROM ENGAGEMENT WITH THE FILM AND MAINTAIN IT IN SAID POSITION DURING THE TIME SAID SHUTTLE IS MOVING IN. A DIRECTION COUNTER TO THE DIRECTION OF FILM ADVANCE.