Patent GB-621490-A (GB)
Title: Improvements in or relating to de-icing means for aircraft
IPC: B64D15/16
Filed: 1944-09-21
Abstract: 621,490. Valves controlled by auxiliary valves. BENDIX AVIATION CORPORATION. Sept. 21, 1944, No. 18066. Convention date, Aug. 11, 1943. [Class 135] [Also in Group XXXIII] In aircraft de - icing apparatus in which a plurlity of flexible inflatable and deflatable units 5-8, 5A-8A, 9, 10 and 11 located externally on parts of the aircraft are connected in succession to a pressure conduit 15, to atmosphere and to a suction conduit 16 by means of a plurality of distributer valve units 31A-I operated by a central control, each valve unit comprises a casing having ports connected to the associated de-icer unit, the pressure conduit, atmosphere and the suction conduit, a primary valve member which is moved alternately to one or other of two positions, and a secondary valve member movable in one direction by a spring and in the other direction by fluid pressure, the primary valve member when moved to one position connecting the unit to the pressure port, and when moved to the other position connecting the unit to atmosphere through the secondary valve member and placing it in communication with the suction port, the secondary valve member then being unseated by pressure from the unit to open the atmospheric port, and when pressure in the unit has dropped to a sufficiently low value being seated by its spring to close the atmospheric port and thus allow the suction connection to become effective. In an alternative construction, the unit is not placed in communication with the suction port by movement of the primary valve member, the suction connection being effected by the return movement of the secondary valve member under the action of its spring. In the system shown in Figs. 1 and 2, each de-icer unit comprises tubes 12 and 14 which are inflated and deflated alternately with a third tube 13, the tubes being formed of elastic reinforced material and connected to the associated distributer valve unit by pipes 32 and 32A respectively. The atmospheric port of the distributer valve is connected to a pipe 33. The pressure conduit 15 is supplied by engine-driven pumps 21-24, and the suction conduit 16 is connected to the inlet of pump 23. The valve units 31A-H are connected directly in the pressure and suction conduits and are mounted on the aircraft by means of flanges 38, thus acting as supports for the conduits. The valve unit 31I is connected by a conduit 37 and relief valve 36 to the pressure conduit, and by a conduit 42 to the suction conduit. A second suction line 43 connects the unit 311 to a low-pressure area of the aircraft and contains a valve 44 which opens if the vacuum in conduit 42 drops below a predetermined minimum value. Unloading valves 34, 35 of the kind described in Specification 604,913 are provided at the ends of the conduits 15, 16. In one form, Fig. 6, each distributer valve unit comprises spring-loaded disc valves 59, 59A, one for tubes 12, 14 and the other for tube 13, controlling ports 65, 69 and 65A, 69A and connected to a. diaphragm 56. The valves are operated by air pressure and vacuum admitted to chambers 57, 58 and 57A, 58A on opposite sides of the diaphragm under control of spring - loaded electromagnetically-operated pilot valves 150, 150A. With valve 150A to the left, as shown, and magnet 156A energized, pressure air is admitted to chamber 57A and chamber 58A is evacuated to move the valve rapidly to close port 69A. In this position pressure air flows from the chamber 51, forming part of the conduit 15, into the chamber 64A connected to the de-icer tubes. On de-energization of the magnet, valve 150A is moved to the right to admit pressure air to chamber 58A and evacuate chamber 57A and thus cause movement of valve 59A to close port 65A and open port 69A. Pressure in chamber 64A then unseats a spring- loaded valve 71A and the tubes exhaust to atmosphere through pipe 77. After the pressure has dropped to a predetermined value, the valve 71A is re-seated by its spring, and the air remaining in the de-icer tubes is sucked out through chamber 64A and a passage 80A connected to the suction conduit 16. On reenergization of magnet 156A, the cycle is repeated. The magnets 156, 156A of each valve unit are energized through wires 173 by an electrical timing device 174, Fig. 21, comprising an arm 202 which is rotated over commutator segments 204 by an electric motor 203, the speed of which is controllable by a variable resistance 212. The segments 204 vary in size according to the capacity of the various de-icer tubes and are connected in circuit so that de-icer units similarly positioned on opposite sides of the aircraft are operated together. Alternatively, the magnets may be connected to a timing device of the kind described in Specification 621,464, [Group XXXIII]. In a second form, Figs..15 and 16, each valve unit comprises a plurality of piston valves 220, each mounted for movement in a sleeve 213 on an actuating rod 228 carrying a plunger 230. A sleeve 231 slidable on the rod 228 is maintained normally in engagement with the piston 220 by a spring 234. The valves are controlled by spring-loaded electromagnetically-operated pilot valves 300 similar to those shown in Fig. 6. With magnet 205 energized and valve 300 in its outer position, pressure air is admitted from chamber 211, forming part of the conduit 15, through duct 269, valve 300 and port 279 to the chamber above piston 220, and the chamber below plunger 230 is placed in communication with a chamber 212 forming part of the suction conduit through port 277, channel 276, annular groove 273, passage 272, valve 300 and passage 270. The piston 220 and sleeve 231 are then moved downwardly until the sleeve 231 closes the port 217 leading to the chamber 212, and ports 222, 223 in the piston are opposite ports 218, 214 in the sleeve 213, pressure air then being admitted to the de-icer tubes through passage 251. On deenergization of the magnet and inward movement of valve 300, pressure air is admitted through port 277, and the port 279 placed in communication with the chamber 212, to move piston 220 and sleeve 231 upwardly. Ports 222, 223 and 218 are then closed by sleeve 213 and piston 220 and as the port 221 in the piston is positioned so as to overlap the port 214 before the port 237 in the sleeve 231 overlaps the port 217, the pressure in passage 251 forces the sleeve 231 out of engagement with the piston 220 to open the port 215 in the sleeve 213 and allow the tubes to exhaust to atmosphere through passage 252. After the pressure has dropped to a predetermined value, spring 234 will re-engage the sleeve 231 with the piston, thus closing port 215 and spring port 217. Air remaining in the de-icer tubes will then be sucked out through ports 214, 221, 237, 217 and passage 253 connected to chamber 212. Specification 548,138 also is referred to.