Patent GB-577134-A (GB)
Title: Improvements in or relating to mechanism for regulating the supply of fuel to internal combustion engines
IPC: F02M69/00
Filed: 1940-06-14
Abstract: 577,134. Fluid-pressure servomotor-control systems. BRAME, E. June 14, 1940, No. 10339. [Class 135] A mechanism for controlling the supply to fuel to supercharged aeroplane engines of the kind in which a throttle is operated by a fluid - pressure servomotor controlled by a pilot's lever and a capsule stack subject to boost pressure is provided with means actuated by excessive pressure generated in the servomotor at full throttle openings with falling boost pressure to reset the mixture strength and reset the control valve of the servomotor. As shown in Fig. 1, the throttle valve is actuated by a piston 2 controlled by. a valve 6 connected at 10 to a capsule stack 11 responsive to boost pressure. The other end of the stack is connected to a rod 101 coupled to a mixture control mechanism for example a fuel metering valve and to a lever 13 connected at 13<1> to a pilot's throttle control lever. A piston 16 centralized by pre-compressed springs 20, 21 and subject to the pressures on each side of the piston is coupled by a rod 15 to the lever 13. If the aeroplane rises above its rated altitude with the throttle fully open, excessive pressure generated on the left-hand side of the piston moves the piston 16 against the action of the spring 21, lowering the pivot 14 and so lowering the rod 10<1>, resetting the valve 6 and preventing further supply of fluid to the lefthand side of the piston 2 and at the same time resetting the mixture control to reduce the mixture strength. The throttle is directly operated at small throttle openings moving the piston to the right and the pressure generated raises the piston 16, to increase the mixture strength. The main throttle may be servo-operated throughout its range, and a small auxiliary throttle valve provided for direct manual operation. In this case the piston 16 is made singleacting and the top spring omitted. In the form shown in Fig. 2 the throttle valve is actuated by a double-acting power cylinder controlled by a valve 32 connected to a capsule stack 30 while the fuel-injection pumps are adjusted by a rod 50, actuated by a cam 46 in the tubular boss 42 of an oscillating vane motor 41. The control valve 40 of this motor is housed in the tubular boss and is actuated by a capsule stack 37 open to atmosphere through a passage 38 and vent 39. The stacks which are responsive to boost pressure are anchored to a beam 51 formed with a segmental chamber 52 housing an oscillating vane 53 having a tubular boss directly connected to the pilot's throttle lever. A torsion spring 55 is secured between vane and beam. Oil ducts opening into the chamber 53 on each side of the vane are connected to the two sides of the throttle valve power cylinder. When at small throttle openings the throttle is directly actuated the beam begins to move with the vane and resets both valves 32, 40 but excessive pressure on the throttle closing side of the throttle servomotor causes a further resetting movement of the valves. According to the Provisional Specification a byepass valve may be provided in the piston or other relatively moving part of the power device to relieve pressure set up during positive operation of the throttle at small throttle openings.