Patent GB-892034-A (GB)
Title: Improvements in or relating to diaphragm carburettors
IPC: F02M17/04
Filed: 1960-01-14
Abstract: 892,034. Spray carburetters. TILLOTSON MANUFACTURING CO. Jan. 14, 1960 [July 20, 1959], No. 1360/60. Class 7(3). A carburetter comprises means formed with a fuel and air mixing passage 12, Fig. 3, and a recess, a throttle valve 30 in the mixing passage, a diaphragm 44 forming with the recess a fuel chamber 40, an orifice 112 opening into the mixing passage for delivering fuel from the chamber 40 into the mixing passage, a fuel inlet 108, Fig. 4, in communication with the chamber 40, the diaphragm being responsive to differential pressure in the mixing passage, means actuated by the diaphragm for controlling flow of fuel from a supply e.g. a pump into the fuel chamber, and means responsive to movement of the throttle valve towards open position to impart a fluid pressure impulse to the diaphragm for admitting additional fuel through the inlet 108 into the chamber 40 to accelerate the rate of delivery through the orifice 112 into the mixing passage. As shown in Fig. 4, the fuel flows into chamber 40 from the inlet 108 via the valve 94 controlled by the diaphragm 44 through the spring loaded lever 80 pivoted at 82, the end 88 of which rests on the rivet 86. The valve proper consists of a valve head 104 resting on a valve seat 98 made of neoprene or similar substance. The fuel flows from chamber 40 to the orifice 112, according to the subpressure in the Venturi 18, via a port 130, Fig. 2, a metering device 127, a passage 128, and chamber 118. Two secondary orifices 114, 116 are provided adjacent the throttle valve for idling and low speeds respectively. These are connected to the main orifice duct system via a passage 148, a metering device 145, and chamber 134. An air bleed duct 152 is provided to admix air with the fuel before delivery through the secondary orifices. At low engine speeds a spring loaded flexible member 50 is in the position shown in Fig. 3, but on sudden opening of the throttle 30 the pressure rises in the passage 12 and chamber 62 via passages 64, 66 allowing the spring 72 to force the flexible member 50 upwards giving the diaphragm 44 a fluid pressure impulse and allowing more fuel to flow into the chamber 40 and thus to orifice 112. The pressure in chamber 52 between the diaphragm 44 and member 50 gradually decreases by means of a vent 68 to the atmosphere. A modification is described wherein the orifice 116 is the main orifice and the fuel flows from chamber 40 direct to passage 140 and via the metering device 145 to chamber 134. Another modification is shown in Figs. 9 and 10, wherein a shaft, riding on cam 388 on the throttle shaft 232, controls the spring loaded flexible member 250 via lever 378, pivoted at 380, the end of which rests on pivot 382. A fluid pressure impulse is given to diaphragm 244 on sudden opening of the throttle 230. The pressure decreases in the chambers 252, 252<SP>1</SP>, connected by opening 372, via the vent system 390, 389. 389<SP>1</SP>. The fuel flow to the fuel chamber 240 is as above described and a secondary orifice system 345, 347 is also provided. A fuel well 320 is provided at the main orifice 315 to give an immediate supply of fuel on sudden acceleration. A ball valve 317 allows the fuel to flow out of orifice 315 but prevents air entering. An air bleed port is provided at 342.