Patent GB-567239-A (GB)
Title: Improvements in regulating devices for controlling the supply of fuel to internal combustion engines
IPC: F02D9/00
Filed: 1943-04-08
Abstract: 567,239. Spray carburetters. HOBSON (AIRCRAFT & MOTOR) COMPONENTS, Ltd., H. M., SIMPSON, T., GREENLAND, L. S., and RAMSAY, D. April 8, 1943, No. 5617. [Class 7 (iii)] In a fuel supply system for aircraft engines, in which the fuel is fed to the engine through a valve having a metering orifice, the effective area of which is varied as a function of boost pressure and across which the pressure difference, or a fraction thereof, developed by an enginedriven centrifugal impeller is maintained, a supplementary valve mechanically connected to the pilot's throttle lever effects a change in the mixture strength on movement of the lever to the slow running position. If the device enriches the mixture during slow running, it may be associated with means for weakening the mixture during cruising speeds. A pump 10 having a pressure relief valve 28 supplies valve fuel along a conduit 11 to a fuel metering valve comprising a hollow cylinder 30 formed with a triangular metering orifice 31 and movable in a divided cylinder, the lower half 32 of which is fixed while the upper half 33 is displaceable axially under control of a Bourdon tube 40 susceptible to temperature variations in the induction manifold. The fuel leaves the orifice 31 by a conduit 21 leading to a chamber 18 separated from a chamber 16 by a diaphragm 19 carrying a fuel valve 20, the valve 20 controlling the fuel flow to the nozzle 23. The diaphragm 19 and valve 20 ensure that the pressure in the chamber 18 is the same as that in the chamber 16 which is connected on the one hand by a pipe 14 to the inlet of the impeller 13, and on the other hand through a passage 26 and restricted orifice 27 to the delivery passage 25 of the impeller and the inlet side of the fuel metering valve 30, the pressure difference across the valve 30 being thus determined by the orifice 27. The valve 30 is connected by a rod 38 to a pile of evacuated capsules 35 in a chamber 36 maintained at boost pressure and the capsules actuate the piston 39 of a servomotor as described in Specification 567,106, [Group XXIX], to adjust the setting of the throttle which is connected by a link 52 to one end of a lever 51 pivoted centrally to the rod 53 of the piston 48 of the servomotor and having its other end engaged by a cam 50 on the pilot's control lever 42 ; the arrangement gives a limited mechanical control of the throttle valve. The control lever 42, through a cam 43, lever 44, link 45, lever 46, link 47 and lever 37 pivoted centrally to the rod 38 carrying the fuel valve 30, can exert pressure on the capsules 35 to raise the servomotor piston 48 as the throttle lever moves to the slow-running position. The piston reaches the limit of its lift as the slow-running position is approached and the lever 46 then rocks about its connection with the link 47 depressing a rod 57 which opens a valve 56 permitting fuel to bleed from the conduit 21 to the inlet side of the pump and so weaken the mixture. Alternatively, the valve 56 may be in a byepass for the restricted orifice 27 and so increase the pressure in the chamber 16. In another form, the valve 56, Fig. 3, opens a byepass 58, 59 for the fuel valve 30 and enriches the mixture during slow-running, an additional port on the valve being adapted during cruising speeds to open a byepass 58, 158 for the restricted orifice 27 to weaken the mixture. Specification 419,113 also is referred to.