Emergency door opening system

Claim 1

Emergency door opening system in combination with an automatically electrically operated door which moves generally within its own plane during opening and closing, comprising pneumatic actuating means for opening said door when pressurized including a pneumatic cylinder, a piston rod movable in said cylinder with its free end engageable with said door, said cylinder being supported against movement with said rod with its axis generally parallel to the plane of the door And being of a length corresponding to the distance of movement of the door, a stop fixed on said door for engagement by the free end of said piston to constitute a one-way connection between said door and piston rod which is disengaged from the door during its normal operation, a pressure tank, a connecting line between said tank and said pneumatic cylinder, an electrically operated control valve in said connecting line, said valve being open in rest position and displaced to closed position when electrically engaged, and means connecting said valve to the electrical power source for said door, whereby upon a power failure, said valve assumes its open rest position, pressurizing said pneumatic cylinder to open the door.