Pneumatic door-operating arrangement

Abstract

A pneumatic door control equipped with a door control valve for operating a door drive to an open or a closed position. The door control valve has an opening and a closing solenoid-operated pilot valve and an opening and closing spool valve, each operable to a passage or a vent position. A shuttle valve is part of the control valve and works in conjunction with an operator-controlled emergency valve to vent both spool valves simultaneously. A differential pressure switch is connected to the door drive to sense abnormal pressure expended in a door-opening or closing movement. Such an occurrence will output a signal to an electronic switching device which also monitors, via limit switches, whether a door is fully opened or fully closed. If excess pressure occurs during a door-closing movement, the switching device will trigger the control valve to reverse to the opening position. If excess pressure occurs during an opening movement, the switching device triggers both solenoid-operated pilot valves simultaneously. The control valve has a non-return valve which recognizes the dual triggering condition and outputs to the shuttle valve so that the two spool valves can be vented simultaneously. A throttle valve is disposed between the emergency valve and control valve for restricting the flow of pressurized air following an emergency condition.