Freight car grain door

Claim 1

A GAIN DOOR ASSEMBLY COMPRISING A MOVABLE DOOR SUBASSEMBLY, A VERTICALLY EXTENDING TRACK SUBASSEMBLY FOR HOLDING SAID DOOR SUBASSEMBLY IN A VERTICAL LOWERED POSITION AND A TRANSVERSELY EXTENDING TRACK SUBASSEMBLY FOR HOLDING SAID DOOR SUBASSEMBLY IN AN ELEVATED HORIZONTAL POSITION; SAID MOVABLE DOOR SUBASSEMBLY COMPRISING A SERIES OF HINGEDLY CONNECTED TOGETHER HORIZONTALLY EXTENDING RIGID PANELS, A PAIR OF FRONT AND REAR OUTER ROLLERS SUPPORTED ON AND ROTATABLY ATTACHED TO THE FRONT AND REAR END OF EACH SAID PANELS, SAID ROLLERS EACH BEING ROTATABLE ABOUT THE SAME LONGITUDINALLY EXTENDING AXIS, EACH FRONT AND REAR OUTER ROLLER ROTATING IN A ZONE EXTERIOR TO THE EXTERIOR SURFACE OF THE PANEL TO WHICH ATTACHED AND EACH SAID FRONT AND REAR ROLLER BEING LONGITUDINALLY SPACED INWARD FROM THE FRONT AND REAR END RESPECTIVELY OF SAID PANEL, A PAIR OF FRONT AND REAR INNER ROLLERS ROTATABLE ABOUT A COMMON AXIS EXTENDING LONGITUDINALLY OF SAID PANEL AND ROTATABLY SUPPORTED ON EACH OF SAID PANELS, EACH OF SAID FRONT AND REAR INNER ROLLERS ROTATING IN A ZONE EXTENDING BEYOND THE FRONT AND REAR EDGES RESPECTIVELY OF SAID PANELS, SAID PANELS EACH RESPECTIVELY EXTENDING FORWARD OF THE FORWARD EDGE OF A FORWARD FRAME MEMBER OF A DOOR OPENING AND REARWARD OF A REAR FRAME MEMBER OF THAT DOOR OPENING AND FORMING A GRAIN TIGHT SEALING CONTACT BETWEEN THE OUTER SURFACE OF EACH SAID PANEL AND THE INNER SURFACE OF EACH SAID FRAME MEMBER; SAID VERTICALLY EXTENDING TRACK SUBASSEMBLY COMPRISING A VERTICALLY EXTENDING TRACK ATTACHED TO AND SUPPORTED BY THE FRONT