Differential pressure gate

Claim 1

A DIFFERENTIAL PRESSURE GATE FOR USE WITH A MOTION PICTURE PROJECTOR HAVING A HIGH INTENSITY LIGHT SOURCE, A GATE HAVING FRONT AND BACK PLATES, EACH OF SAID FRONT AND BACK PLATES HAVING AN APERTURE THEREIN, SAID PLATES BEING POSITIONED WITH SAID APERTURES IN ALIGNMENT, TRANSPORT MEANS ASSOCIATED WITH SAID GATE FOR ADVANCING A FRAME OF A FILM INTO SAID GATE AND HOLDING SAID FRAME STATIONARY THEREIN WHEN ALIGNED WITH SAID APERTURES FOR THE SHORT TIME OF FRAME PROJECTION AND THEN ADVANCING THE NEXT FRAME INTO SAID GATE, A SHUTTER TO CONTROLLABLY PERMIT LIGHT TO PASS FROM SAID HIGH INTENSITY SOURCE THROUGH SAID APERTURES AND THROUGH THE FRAME ALIGNED WITH SAID APERTURES, AND A PROJECTION LENS TO PROJECT THE IMAGE ON SAID FRAME, SAID DIFFERENTIAL PRESSURE GATE COMPRISING A PLENUM CHAMBER POSITIONED ADJACENT ONE OF SAID PLATES, SAID PLENUM CHAMBER COMPRISING A WALLED CHAMBER COMMUNICATING WITH THE APERTURE IN SAID ONE OF SAID PLATES, SAID PLENUM CHAMBER HAVING AT LEAST ONE TRANSPARENT WALL PORTION TO PERMIT PASSAGE OF SAID CONTROLLED LIGHT THROUGH SAID PLENUM CHAMBER, AND MEANS COUPLED TO SAID PLENUM CHAMBER TO GENERATE A SUBSTANTIALLY UNIFORM GASEOUS PRESSURE THEREIN, SAID PRESSURE GENERATING MEANS COMPRISING A CHANNEL EXTENDING AROUND AT LEAST A PORTION OF THE PERIPHERY OF SAID PLENUM CHAMBER AND WHICH INCLUDES A PLURALITY OF DUCTS EXTENDING FROM SAID CHANNEL AND INTO SAID PLENUM CHAMBER, SAID DUCTS BEING SUBSTANTIALLY PARALLEL WITH SAID FRAME HELD WITHIN SAID GATE TO PREVENT NONUNIFORM DISTRIBUTION OF PRESSURE ON SAID FRAME AS GAS UNDER PRESSURE IS INTRODUCED THROUGH SAID CHANNEL AND SAID DUCTS INTO SAID CHAMBER, WHICH PRESSURE IS MAINTAINED BY THE WALLS OF THE PLENUM CHAMBER AND THE FRAME OF SAID FILM HELD WITHIN SAID GATE, AND IS THUS APPLIED SUBSTANTIALLY UNIFORMLY ACROSS THE ENTIRE SURFACE OF ONE FACE OF THE FRAME OF THE FILM HELD WITHIN SAID GATE, SAID GASEOUS PRESSURE BEING DIFFERENT FROM THE AMBIENT PRESSURE APPLIED TO THE OTHERWISE UNSUPPORTED OPPOSITE FACE OF SAID FRAME THROUGH THE APERTURE IN THE OTHER OF SAID PLATES.