Patent GB-530321-A (GB)
Title: Improvements in and relating to heating systems, more particularly for aircraft
IPC: E04B2/30
Filed: 1939-06-08
Abstract: 530,321. Cooking-apparatus. PRICE, N. C., and BOEING AIRCRAFT CO. June 8, 1939, No 16846. [Class 28 (i)] Cooking-apparatus on aircraft is heated by a circulating liquid heatec by exhaust gases from the engines, the liquid, which is preferably ethylene glycol, being heated in a boiler which is swept, in automatically regulated proportions by exhaust gases anc cool air, so that the heat absorbed by the boiler is determined by the heat withdrawn a the point of use, and overheating is avoided. The boiler 1 has heat-conducting fins 11 and is connected by feed and return pipes 10, 30 to the cooker. The return pipe 30 is connected to a liquid-supply tank 40, and the circulating system includes a pump 4 the discharge side of which is connected by a pipe 45 to the cylinder 52 of a servo-motor relaying the movements of a heatsensitive bi-metallic strip 2 to the means, described below, for adjusting the proportions of exhaust gas and air impinging on the boiler 1. If excessive pressure builds up in the boiler, a relief valve 42 allows the pump discharge to be effected into the tank 40 which has a vent 44 to maintain substantially atmospheric pressure. The boiler is placed in the muff or terminus 7 of the exhaust stack 70, at its forward side, the terminus 7 being so shaped that the air stream C flowing over it will produce a suction outwards through the end 72. The muff is provided with a forwardly directed air admission opening 73 which is regulated by a vane 60, pivoted at 66 and connected by a link 61 with a vane 6 pivoted at 65. The vane 6 is curved so that when it is swung away from the boiler it deflects exhaust gases, from the path A, into contact with the boiler. The vane 60 moves oppositely to the vane 6, so that as the impingement of exhaust gases on the boiler is increased, the impingement of cool air is decreased. A spring 62, associated with the link 61 tends to position the vanes 6, 60 in the positions of maximum heating of the boiler, this tendency being resisted by the admission of pressure fluid from the pump 4 to the top of the piston 5 in the cylinder 52, the piston rod 50 being connected by a cable 63 with the arm 64. Leakage past the piston 5 maintains in the space 53 a pressure which renders the piston non-operative and allows the spring 62 to function. The withdrawal of a plunger 55 from a bore 54 in the rod 50 vents the pressure in the space 53 and frees the piston to produce an adjustment of the vanes 6, 60 contrary to that effected by the spring 62. The plunger 55 is connected to the bi-metallic strip 2, so that as the temperature of the circulating fluid drops, the plunger 55 is raised and allows the spring 62 to produce greater heat absorption by the boiler, the piston 5 rising in the cylinder. When the fluid temperature rises, the plunger 55 is withdrawn from the bore and allows the balancing pressure in the space 53 to be vented by the pipe 46 to the tank 40. The piston 5 then descends under the pump pressure and produces a movement of the vanes 6, 60 to lessen the heat absorption by the boiler. A cam 58 on a handle 56 may be used to depress the piston and maintain the boiler inoperative. The heated fluid may be used to heat the expansion bulb of a refrigerator operating upon the absorption principle.