Abstract: A method is disclosed for selective alteration and control of door movement modes utilizing an apparatus that is primarily non-hydraulic and incorporated with a known mechanism which is functional independently from the apparatus in one mode of operation and which includes a piston for controlling door closing characteristics by selected fluid flow within the mechanism. The apparatus includes a motor driven lead screw having a linearly movable shuttle unit mounted thereon, the shuttle unit being positioned relative to the piston of the mechanism to accommodate nonattached contact with the piston to urge the piston, when the shuttle unit is moved, in a direction that will at least provide selective assistance with door opening in another mode of operation. Operation of the apparatus is controlled by programming of a related controller including non-volatile memory.

Abstract: Apparatus is are disclosed for selective alteration and control of door movement modes, the apparatus being primarily non-hydraulic and incorporated with a known mechanism which is functional independently from the apparatus in one mode of operation and which includes a piston for controlling door closing characteristics by selected fluid flow within the mechanism. The apparatus includes a motor driven lead screw having a linearly movable shuttle unit mounted thereon, the shuttle unit being positioned relative to the piston of the mechanism to accommodate nonattached contact with the piston to urge the piston, when the shuttle unit is moved, in a direction that will at least provide selective assistance with door opening in another mode of operation.

Abstract: A control linkage for use with a door closer, wherein the linkage is provided with a spring which resiliently biases against relative rotation of a pair of arms as the arms approach a door-open limit position, and which aids the door closer in moving the door from the door-open limit position.

Abstract: A hydraulic door closer is provided with a fluid seal for its output shaft, the seal comprising multiple O-rings disposed side-by-side in an elongated annular chamber.

Abstract: An air lock has a chamber and a pair of doors in respective walls of the chamber. Operators associated with the doors include closers normally biasing the doors to closed positions and fluid powered openers associated with the closers capable of overriding the bias of the closers. A control system, operation of which may be initiated by initial opening displacement of one of the doors or (in one embodiment of the invention) by manually operable remote switch means, provides for opening of one of the doors and latching of the other to prevent simultaneous opening of both doors. The latch means for the doors may be overriden by direct displacement of the doors for safety purposes. The control system also triggers air handling apparatus associated with the chamber.