GB160925A - Improvements in carburetters for internal combustion engines - Google Patents

Abstract

160,925. Prestiss, A. M. Dec. 30, 1919. Spray carburettors. -Means are provided for automatically maintaining a pressure greater than atmospheric uron the surface of the fuel in the float chamber, the pressure being gradually diminished as the speed of the engine increases. In the form shown, the mixing-chamber 1 is surrounded by a float-chamber 4 to which fuel is supplied by a pump (not shown) through a pipe 57 controlled by a needle valve 56 connected to the float 55. The mixing-chamber 1 is constituted by a tube 15 carrying fuel-nozzles 49, Fig. 3, and extending upwardly to a mixture-outlet valve box 16 and downwardly to an air-inlet va.lve box 22. The rotation of the combined members 16, 15, 22 effected through a handle 29 causes the rectangular ports 25 to register more or less with mixture outlet apertures 24, the fuel-nozzles 49 to register successively with fuel-ports a, b, c, d, Fig. 3, and the elliptical air-inlet ports 28 to register in part with corresponding ports in a non- rotatable but vertically-sliding piston member 26. The fuel leaving the nozzles 49 is atomized by air supplied by a pump (not shown) to a tube 47 round each nozzle by way of passages 54, 52. Situated over the surface of the fuel in the float chamber is a piston 31 connected by links 37, 36 to the rod 35 of the vertically-sliding member 26, the piston exerting its maximum pressure on the fuel at low speeds. As the speed is increased by opening the throttle, the pressure exerted by the piston on the fuel is gradually diminished to keep the ratio of petrol to air constant. In order to control the degree of vacuum in the chamber 1, the areas of the mixture outlet ports and the airinlet ports are so arranged that when starting there is a big excess of outlet area, thus causing the member 26 to rise and depress the piston 31. On further opening of the throttle, the inlet area progressively increases in relation to the outlet area, and the member 26 tends to fall to relieve gradually the pressure on the surface of the fuel in the float chamber.