GB990979A - Improvements in temperature controls - Google Patents

Abstract

990,979. Automatic temperature control. TILTMAN LANGLEY Ltd. Sept. 28,1962 [Sept. 1, 1961], No.31543/61. Heading G3R. A heating control system comprises a mercury thermometer 1 having contacts controlling the admission of both hot and cold air to an aircraft cabin and having an auxiliary heater 1C progressively controlled in accordance with the position of the air control valves. The bulb of the thermometer is in the mixed air duct and the auxiliary heater has a second part controlled, through a control box 3, by temperature sensitive resistors 4, 5 in the cabin and a manually adjusted set temperature resistance 6. The cabin temperature thus influences the height of the mercury column which, by contracts 1G, controls reversible servomotor or stepping solenoid 8B operating valve 8A in the cold air supply. A similar motor operated valve 9A in the hot air supply is controlled in unison with, but in the opposite sense to, valve 8A by a self balancing bridge circuit comprising potentiometers 8E, 9E coupled to the respective motors. Dince the bulb 1B of the thermometer is in the mixed air duct the mercury responds rapidly to stop the valve motors, and the response time is further shortened by the first half of auxiliary heater 1C, which is controlled by a rheostat 8C also coupled to motor 8B. Thus the valves are positioned in anticipation of correct cabin temperature, and by selection of suitable constants the system can be made almost deadbeat. Provision is also made for cooling an equipment space, using the balance of available cold air. This is regulated by a third valve 10A, again operated oppositely to valve 8A by further self balancing bridge potentiometers 8D, 10D so that the available cold air is divided between cabin and equipment space in accordance with the needs of the former. The temperature of the cold air in the equipment space duct is monitered by a second mercury thermometer 2 having contacts 2G which, when excessively high or low temperatures are detected, operate warning lights or override the control exerted by thermometer 1. It is mentioned that the system may be combined with an unspecified pressure control system.