GB1375419A - - Google Patents

Abstract

1375419 Spray carburetters H MORGENROTH 30 Nov 1971 55635/71 Heading F1B A carburetter comprises a fuel-air mixture outlet 6, Fig. 1 discharging into a fuel mixing region 7 which has upstream thereof a throttle valve 8, a contoured metering rod 1 extending into a fuel metering orifice 2 fed by a fuel level holding device, the rod and valve being coupled so that the rod is displaced axially when the valve is rotated. The coupling means comprises a lever 10 with three linkage points, the third linkage point 15 being adjustable so that changing its position also changes the axial position of the metering rod and the flow area of the metering orifice. The linkage point between the lever (10), Fig. 3 (not shown) and spring plate (19) is offset so that the resulting couple tends to tilt the rod 1 towards the orifice wall. Fuel from duct 25 passes through an emulsion chamber 3 to orifice 6. The rod section 34 reduces the flow area of orifice 6 at idle and low engine load. In modifications the air bleed 4 spans into a small auxiliary Venturi (4a), Fig. 5 (not shown) and the orifices are spaced farther apart to co-operate with a rod having a cylindrical section (52) Fig. 4 (not shown) which maintains a constant flow area at the emulsion orifice 6 in the idle range. The straight taper on the rod may be replaced by a profiled taper to achieve a desired fuel/air ratio at each throttle position. The carburetter is arranged to maintain the correct fuel/air ratio at full throttle low speed conditions by use of a variable spring-bias load on diaphragm 22A. At full throttle the second spring 31 is inactive and only a constant bias spring 30 keeps the inlet valve 26 open until a fuel column (representing fuel pressure 'c') overcomes the spring 30 and pushes down the diaphragm to close the valve. In the part-load position of Fig. 1 an extension 32 of rod 1 activates spring 31 to cancel part of the pressure of spring 30 to lower the fuel level (pressure 'b'). In a modification the spring 31 is replaced by a spring (41), Fig. 6 (not shown) attached to the side of the chamber.