Patent GB-1302891-A (GB)
IPC: F02M69/04
Filed: 1968-12-04
Abstract: 1302891 Spray carburetters; diaphragm pumps J D FARLEY 4 March 1970 [4 Dec 1968] 57569/68 Headings F1B and F1A In an I.C. engine carburetion system having one or more orifices Y discharging fuel into the manifold passage or passages C downstream of the throttle valve H, a choke member J controlling a fuel metering device is movable in the induction passage G by a piston L, a pair of pistons or a diaphragm, subjected to a force proportional to the air-flow past the choke member and an opposing force proportional to the pressure drop across the throttle valve. The chamber P, above the piston L, is connected to the choke through a passage R and the chamber Q is connected to the passage G downstream of the valve H through an orifice U and to the atmosphere or the passage G upstream of the piston J through an orifice S. The orifices U and S are controlled by respective profiled needles KK and T and the needle KK, which is linked to the valve H, may close the orifice S when the valve H is fully open. The fuel metering device may be a valve W mechanically or electrically positioned by the piston J. The valve W may be supplied with fuel by a fuel pump Z having a pressure relief valve AA to provide a substantially constant fuel pressure. The valve W, valve AA or pump Z, if self regulating, may be modulated in operation in accordance with the pressure downstream of the valve H. The fuel metering may be effected by a variable displacement pump Z. Secondary air may be supplied to the nozzle forming the orifice Y through a passage JJ or CC. The air-flow through passage CC is controlled by a valve EE operated in accordance with the pressure downstream of the valve H. The nozzle forming the orifice Y may be provided with a pintle valve opening under a small pressure or a valve opening at a predetermined higher pressure. To provide for transient conditions a pressure relay GG having a differentiating function may be provided in the passage BB leading to the relief valve AA from downstream of the valve H. A relay GG controlling the output pressure of a diaphragm pump Z, Fig.2, may comprise a a diaphragm 32 subject in chamber 36 to the pressure in passage BB and controlling the pressure in a chamber 8 having an atmosphere pressure vent 40 which may contain a ball restrictor valve providing more restricted airflow to or from the chamber. The changes in pressure in chamber 8 act on the diaphragms 10 of the pump Z, which are operated in antiphase by the rods 18 hooked on a drive lever 20, so that the pump output pressure is varied. A small heated secondary manifold may be connected in parallel with the main manifold B, by-passing the valve H, and contain a secondary throttle valve linked to the valve H to open prior to the valve H. The secondary manifold may be provided with a fuel discharge orifice formed by a nozzle with a pintle valve more lightly loaded than the valves of the main nozzles and supplied through a separate fuel metering valve controlled by the piston J. The orifice Y may be supplied by a float chamber with the valve W therewithin or in the orifice. A float chamber with the valve W therewithin may provide the supply to the pump Z, the float chamber collecting leakage from the valve which is of needle or spool type without seals. A fuel stop valve operated mechanically from a moving part of the engine, by engine oil pressure or from the engine ignition circuit may be provided downstream of the pump Z. The valve W may close completely in the absence of air-flow through the passage G. The throttle valve shaft may have its axis extending in the direction of movement of the piston J.