Patent GB-689265-A (GB)
Title: Aircraft refrigeration control
IPC: B64D13/06
Filed: 1950-10-18
Abstract: 689,265. Automatic temperature control systems. VAPOR HEATING CORPORATION. Oct. 18, 1950 [Oct. 28, 1949], No. 25400/50. Class 38 (iv). A pressurized aircraft cabin is supplied with air compressed, cooled, refrigerated and dehumidified in turn, electrical means responsive to the temperature in the cabin control a valve in an air conduit by-passing the refrigerator and means responsive to temperature of the air entering the de-humidifier also control the valve to maintain the temperature in the dehumidifier above freezing. In Fig. 1 external air is delivered to a pressurized aircraft cabin 29 through primary compressors 10, a primary cooler 11, a secondary compressor turbine 12, a refrigerator 13, an expansion turbine 14, and a moisture extractor 15. The primary cooler is of the type in which cooling air is forced through ducts 19 by the movement of the aircraft through the atmosphere and in which the discharge of cooled air is controlled manually by a valve 20. The temperature of the air in the cabin and in moisture extractor 15 is controlled by by-passing heated air from primary cooler 11 to moisture extractor 15 through a conduit 30 having a valve 31 which is adjustable by an electric motor 32. Mercury thermostats A (not shown), in the cabin B, in the outlet from moisture extractor 15, C and D in the duct supplying the moisture extractor, are interconnected with a three-position manually operated switch, as in Fig. 2 (not shown), to produce the following operating conditions : (a) when the manual switch is in its " close " or " open " position, motor 32 runs until valve 31 is fully closed or opened respectively and a limit switch 36 or 37 opens to stop the motor; (b) when the manual switch is in its " automatic control " position the closing of upper contacts of cabin thermostat A at 75‹ F. or the opening of lower contacts at 70‹ F. operates a separate electromagnetic relay to run motor 32 in the appropriate direction to close or open valve 31 and thereby correct cabin temperature. When the upper contacts close, auxiliary electric heating of the thermostat is switched off and when the lower contacts open the auxiliary heating is increased to produce intermittent operation of motor 32; (c) if the temperature at the outlet of the moisture extractor falls below 65‹ F., thermostat B operates a relay to reduce the auxiliary heating of thermostat A, when the latter is between its limits, so as to shift the datum of thermostat A in anticipation of a fall in cabin temperature. An auxiliary electric heater produces intermittent operation of thermostat B; (d) to prevent the temperature at the moisture extractor falling beow 40‹ F., which is sufficiently above normal freezing point to allow for high altitudes, thermostat C operates a relay at 40‹ F. and thermostat D operates another relay at 42‹ F. Thermostat D ensures that below 42‹ F. manual or automatic control of motor 32 to close valve 31 is prevented if the cabin requires cooling. When the temperature is below 40 ‹ C. the relays associated with thermostats C and D co-operate to cause motor 32 to open valve 31. Intermittent operation is produced by an auxiliary electric heater associated with thermostat C.