GB246539A - Improvements in and connected with carburetters for internal combustion engines - Google Patents

Abstract

246,539. Drayton, T. J. B. Sept. 29, 1924. Spray carburettors.-The pressure in the float chamber is varied in such a manner as to ensure the correct proportion by weight of air and fuel at all engine speeds and loads. The top of the float chamber has a vent to the atmosphere and to the air intake, and is in communication with the induction passage at a point near the throttle valve and also with the choke tube through a passage concentric with the nozzle. The float chamber a is sealed and supplies the nozzle d through a calibrated nozzle h, Fig. 3, duct k, well g, and duct d<1>. A supply tube l for a slowrunning nozzle f depends to the level of the well g. A tube m concentric with the nozzle d puts the top of the float chamber in communication with the choke tube through passages o, o', Fig. 2. The space around the slow-running jet is also in communication with the top of the float chamber through a duct p. A sleeve r surrounds a tubular extension 2 of a valve s which is rotatable by a handle u and is held on its seating by a spring t. The valve s, Fig. 4, has a diametral passage v and right-angled passages 1, z and 1<a>, y, the diametral passage forming the float chamber vent. When passages v, ware in register, air can flow past a valve x to the slow-running nozzle by way of ducts w, w<1>, y, 1<a>, Fig. 4, and 2a, r, Fig. 2. the mixture passing by way of ducts 1, z, 3 and 4 to the port 5, Fig. 1, at the edge of the throttle valve. A port 7 on the engine side of the throttle valve 6, Fig. 1, is in communication with the top of the float chamber through passages 8, 9, w<2>, Figs. 1 and 3. The port 7 may be dispensed with and the port 5 need not be closed by the throttle valve. During slow-running the strong suction exerted through the ports 5, 7 is nullified by air entering the float chamber through the tube m. At high speeds the vent v is incapable of admitting sufficient air to satisfy the suction through tube m and ports 5, 7, with the result that a lowering of pressure occurs in the float chamber. With an increase of load the suction at these points decreases and the pressure in the float chamber rises. Calibrated or adjustable orifices may be fitted at 5, 7, v, and m. Once these orifice areas are known a master jet h may be found which gives the correct fuel flow. If this jet be too large the tube m may be increased in size and vice versa. The valve s may be turned to close the vent v and stop the supply of fuel. The vent to the float chamber may be controlled in accordance with atmospheric conditions. Where the carburettor is fed with air under pressure, such air may be supplied to the vent v.