A device for controlling the fuel supply comprises a valve regulating the admission of fuel to a chamber having in its wall two diaphragms, the first connected to the valve to cause it to close upon an increase in pressure in the chamber and the second actuated by engine suction to cause the valve to close when the engine depression falls below a predetermined valve. An anterior throttle 3, Fig. 1, regulates a fuel valve 6 controlling a passage 4 leading from a chamber 11 into which fuel is admitted from a headed tank or a pump past a valve 14. A diaphragm 20 in the wall of the chamber 11 separates the chamber from a suction chamber 21 communicating with the mixing chamber 1 of the carburetter through a passage 22 opening at the throat of the Venturi 5 adjacent the fuel outlet passage 4. When the engine is running, the diaphragm 20 is held against a stop 27, but when the engine stops, a spring 26 moves the diaphragm downwards bringing a stud 24 into contact with a lever 16 which engages the fuel valve 14 with its other end to close it. On starting the engine, the stud 24 is withdrawn and the spring 11 opens the fuel valve to an extent determined by the engagement of the end 36 of the lever 16 with a hook 35 on a second diaphragm 19 separating the chamber 11 from a chamber 28 at atmospheric pressure or that pressure as modified by a controlled passage 30 leading to the outlet 23 of the suction passage 22. As the pressure in the chamber 11 increases with the inlet of fuel thereto the pressure‐regulating diaphragm 19 is depressed and the hook 35 engages the lever 16 to close the fuel valve 14. In a modification, the shut‐off diaphragm 20 operates the stud 24 through a lever. In the form shown in Fig. 4, the pressure‐regulating diaphragm 19 is connected to one end 49 of a floating lever 50 engaging at its other end 59 with the stem CO of an outwardly opening fuel valve 61. The centre of the lever 50 is joined through rods 52, 54 to a lever 55 actuated by a diaphragm 58 forming one wall of a suction chamber 37. When the engine stops, a spring 39 depresses the diaphragm 58, raising the centre of the floating lever 50 to lift the end 59 off the stud 61 and permit a spring 64 to close the valve 61, the end 49 of the lever engaging a stop 67. When the engine is running, suction holds the diaphragm 58 against a stop 65 and the diaphragm 19 and it spring 33 regulate the fuel pressure in the chamber 11. Equal diaphragms 19, 73, Fig. 6, may be used, the fuel valve 61 being closed by the fuel pressure, a spring 64 and a slight difference in strength between the springs 74, 33 co‐operating with the diaphragms, this form avoiding closure of the valve during sudden acceleration. The suction and air chambers 21, 28 may be disposed side by side and the diaphragms be connected by a two‐armed lever of which the arms may be proportioned to compensate for inequality in the sizes of the diaphragms. As shown in Fig. 9, the air and suction chambers 28, 21 are between intercommunicating fuel chambers 98, 99 and a single spring 108 urges the diaphragms 19, 73 apart, a one‐way connexion 107, 106 between cylinders 103, 105 secured to the diaphragms ensuring lifting of the lower diaphragm to permit a spring 64 to close the fuel valve 61 when the engine stops. Specifications 378,025, 378,038, 382,948, 454,782 and 464,327 are referred to.
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