GB515040A - Improvements in and relating to carburettors for internal combustion engines - Google Patents

Abstract

515,040. Spray carburetters. SELFPRIMING PUMP & ENGINEERING CO., Ltd., and BERCOVITZ, B. Feb. 23, 1938, No. 5787. [Class 7 (iii)] In a downdraft carburetter the primary air supply is controlled by a valve subject to the engine suction and connected to means for controlling the main fuel supply and to means for .regulating a supply of air to the fuel stream before delivery. As shown in Fig. 1, a valve 3 is carried by a piston 10 the combination being opened by suction against the action of a spring 7, the suction also being transmitted through a passage 13 to the space above the piston 10. Atmospheric pressure acts on the opposite sides of the combination 3, 10. The valve 3 has a cylindrical portion normally disposed in a restricted portion 2 of the air inlet and as the valve opens slightly a steeply pitched conical part 61 admits air gradually. As the valve 3 opens a shoulder 14 engages a pivoted lever 16 to raise a spring-loaded piston 22 carrying a needle valve 28 which admits fuel from an inlet 29 to a mixing chamber 30 where it is mixed with air before being delivered to the nozzle 4 through a slot 25 controlled by the piston 22. When the engine stops the piston 22 cuts off admission of fuel to the chamber 30. The air admitted at 31 may be heated around the exhaust pipe. An operating lever 100 carrying a nose 21 limits the opening movement of the fuel and air valves and enables the valves to be closed when desired. If the air pressure falls, as at high altitudes, the spring 7 closes the air valve 3 and the lever 16 then reduces the fuel supply. In modified constructions (a) the lever 100 is omitted and a throttle valve is positioned between the differential piston valve 3, 10 and the fuel nozzle, whilst during idling the conduit leading to the fuel nozzle 4 is closed by the piston valve and the fuel and air admitted to the chamber 30 are discharged into the pipe 1 adjacent the edge of the throttle valve, (b) the piston valve 22 shuts off the air inlet to the chamber 30 when the valve 3 is fully open, (c) air is admitted to the chamber 30 through a permanently open inlet 31, Fig. 6, and through an opening 35 and channel 37 at intermediate speeds, this additional supply being cut off by the piston 22 at high and low speeds, (d) air is only admitted to the chamber 30 at intermediate speeds, the piston valve 22 cutting off a series of orifices which admit air from a channel 37 at low speeds, and at high speeds cutting off a second series of orifices supplying air from an inlet to the channel 37. When applied to an inlet pipe square in cross-section the valve 3 is replaced by a valve 46, 47 as shown in Fig. 13.