GB796527A - Improvements in or relating to control apparatus for air conditioning means - Google Patents

Abstract

796,527. Air-conditioning means. GARRETT CORPORATION. April 23,1956 [June 17, 1955], No. 12337/56. Class 137 [Also in Group XXIX] Compressed air, at a temperature and pressure somewhat higher than are required for an enclosure e.g., an aircraft cabin, is delivered to a conduit 11 connected to the conduit 12 leading to the enclosure 10 either directly via 24, or through a heat exchanger 17 using rammed air from conduit 26 as coolant, the coolant air being admissible to the conduit 12 via 31. The compressed air is further cooled by driving a turbine 18 coupled to a fan which aids in drawing the rammed air through the heat exchanger. The conduits 11. 24, 31 are controlled by pivoted valves 60, 80, 38 respectively all operated by pressure responsive means 36, 83, 35 each comprising a diaphragm coupled to the valve. By closing the valve 60, and opening the valve 38, the cabin is supplied with rammed air only, this being effected by turning a control knob 247 to a position in which a lever 212, pivoted at 214 is moved to open a ball valve 200 which functions as described below. The pressure for operating the diaphragms of the means 35, 36 is obtained through a restricted passage 74 from the compressed air pipe 11, and when the ball valve 200 is opened, the pipe 132 is in communication with the ambient atmosphere pipe 199 and the pressure above the diaphragms is low, the valves 38, 60 being in their normal open and closed positions respectively. When the knob 247 is turned to close the ball valve 200, pressure builds up behind the dia-. phragms and the valve 60 is opened and the valve 38 is closed. The valve 80 meanwhile remains closed so that the rammed air is directed through the heat exchanger 17 and the whole of the compressed air passes in heat exchange relation therewith en route to the cabin. The ball valve 200 and lever means 212 are incorporated in a unit 135 which automatically controls the means 83 for regulating the position of valve 80 so that the quantity of hot pressure air from the conduit 11 by-passed to the cabin supply duct 12 is determined by thermostatic means in the duct, as described below. When the ball valve 200 and a thermostatically controlled vent 261 to ambient atmosphere are closed, pressure, transmitted through a port 195, builds un under the diaphragm 190 and to a substantially equal extent above the diaphragm 190 because of the communicating port 253 which is regulably throttled by a pre-set needle valve 254. Pressure also builds up, via pipe 193, under the diaphragm 102 thereby raising a piston valve 112 to open a passage between a pipe 137 connected to the pressure air conduit 11 and a pipe 138 leading to a chamber 98 above the diaphragm 86 which thus opens the valve 80. Hot pressure air is thus by-passed into the cabin supply pipe 12 and raises the temperature thereof until a differential expansion device 263-270 allows the valve 269 to open to connect the space above diaphragm 190 to ambient air. The diaphragm 190 rises and moves a piston valve 222 to connect the space below the diaphragm to ambient air via the pipe 199, thus lowering the pressure below the diaphragm 102 with consequent closing of the piston valve 112. This allows the pressure in the chamber 98 to drop, via bleed 120, and the valve 80 to close somewhat to reduce the quantity of by-passed hot compressed air until the valve 269 again closes The temperature thus maintained in the duct 12 depends upon the amount of turning of the knob 247 and the consequent degree of compression of the spring 228, and upon the adjustment of the needle valve 254. The quantity of by-passed hot air is further regulated by a differential expansion device 162, 167 which unseats a ball valve 156 as the temperature rises and vents a chamber 146 to atmosphere, the chamber being normally kept at substantially the same pressure as the chamber 145 by a bleed 150 in which condition a valve 152 is closed. When the valve 156 is opened the chamber 98 is vented through the pipe 139 and the valve 80 is closed. The control knob 247 may be rotated, for manual controls, between "hot" and "cold" positions in which the consequent movement of the lever 212 presses a valve plate carried by a diaphragm 189' against a ball valve 207 with a variable intensity. The diaphragm 189 is raised away from the valve 207 to lower the pressure in the system which results in a closing motion of the valves 80, 60 to reduce the amount of hot air entering the cabin duct 12. At the "cold" position, the spring pressure on the diaphragm 189 has been so reduced that the valve 80 will be closed, all the hot air then passing through the heat exchanger and turbine 18.