Patent GB-561663-A (GB)
Title: Improvements in or relating to fire-preventing means for power plants particularly on aircraft
IPC: A62C3/08
Filed: 1942-12-18
Abstract: 561,663. Fire-extinguishing devices. GRAVINER MANUFACTURING CO., Ltd., and MATHISEN, A. Dec. 18, 1942, No. 18016. [Class 47 (ii)] A fire fighting system for power units particularly for aircraft comprises fire extinguishing fluid containers; a control device for stopping the power plant, a delay action device adapted to effect discharge of one or more of the containers, and actuating means adapted to effect operation of the control device and of the delay action device when a fire occurs and in addition in the case of aircraft power units, air-screw feathering mechanism and actuating means for causing feathering of the air-screw, stopping of the power plant and discharge of the containers after predetermined delay when a fire occurs in flight and other means for discharging the containers on crashing, which controls may be automatic or semi-automatic. As shown in Figs. 1, 1A, on the occurrence of fire in the engine nacelles b of an aircraft, flame and temperature responsive switches i connected to three-way terminal blocks 2 will cause warning lamps j to be lighted in the fuselage a; the blocks 2 have three terminals 3, 4, 5 connected up 3, 4 to the switches i, 4, 5 to the current supply and 3, 5 to the lamps j. Visible warning being thus given in the case of semi-automatic operation hand switches k are closed to effect operation of air-screw feathering controls d, fire extinguishing fluid containers e connected to the air and fuel intake, fire extinguishing fluid containers g connected to spray piping over the engine and operated through delay action switches f and fluid shut-off valves h all connected to three-way terminal blocks 6, or, for automatic operation, the leads from flame &c. switches i may be connected by twin cables 10 to the blocks 6. Pairs of contacts from the impact switch n are connected to other three-way terminal blocks 14, 15 connected up with the current supply and containers e, g so that upon closure of the contacts in switch n the fluid containers will both be operated instantaneously in the case of a crash. A retractable undercarriage switch p disconnects a gravity operated switch o from the battery c when the undercarriage is up and the battery is cut out by a switch m connected to a terminal block 22 and comprising a delay action fuse device. In another automatic arrangement shown in Fig. 2, operation of any of the flame &c. switches I energizes the operating head of a device q effecting closure of a number of switch contacts, one closing a switch to cables 26 for the airscrew feathering motor control, another earthing the ignition system r, another lighting lamps j, another energizing the fuse in the delay action switch f and another closing the fuel valve device H and a normally closed switch s is provided in the fuselage to cut off the current to the control device q at any time it is desired to interrupt the automatic operation of the system. The flame &c. switches close the circuit of an electromagnet 118 of the control unit q, Fig. 14, the armature of which releases a torque spring-biassed shaft 123 carrying a cam 122 which closes the switch contacts above referred to ; shaft 123 also rotates the plug 133 of the fuel supply body 121. In another arrangement, Figs. 3, 3A, additional fire extinguishing fluid containers are provided for the fuel-tanks and brought into operation by flame &c. switches disposed adjacent the fuel tanks and impact switches N are provided in the fuselage and in the wings each with a single pair of contacts connected to a multi-point contact device v mounted centrally of the fuselage by which all the fire extinguishers are discharged on a crash, the device v incorporating an electrically operated cartridge head W, Fig. 18, effecting closure of contacts z. The air-screw feathering mechanism comprises a rod 45, Figs. 4 and 6, connected to-an arm 42 pivoted on a rod 40 and normally held locked against the bias of a spring 59 to a normally fixed arm 41 by a transverse pin 46 secured in a cartridge fitting 47 by a narrow frangible -rim 46A adapted to be broken by' explosive substance 50 fired by an electrically ignited fuse supplied with energizing current by a cable 55, arm 42 on being released moving rod 45 to the right which operates valve 47<1> causing fluid to be admitted to operate piston 48<1> carrying the feathering rod 49<1>; the fluid is pumped by a pump 52<1> operated by a motor 51<1> energized by closing switch 50<1> and at the end of its movement the feathering rod 49<1> closes a switch 531 and stops the pump. The delay action switch f comprises a cartridge 62, Fig. 8, with a frangible member fired by a longer fuse in a holder 63 causing delay of 12' to 15 seconds, a flanged pin 64 being blown out to cause rotation of a contact actuator 66 and close contacts 12, 13 which may be tested at any time by rotating a cam 74. Fig. 10 shows a fuel cut-off valve H, the plug 77 of which is projected by a spring 87 on breakage of the frangible flange 81 by means of an electrically fired cartridge 79. The delay action switch m, Fig. 12, for cutting out the battery comprises a cartridge with long fuse 101 which fires a charge adapted to break off a pin 46 and release the strut 99 moving with the contact carrying member.