GB704195A - Improvements in carburettors for internal combustion engines - Google Patents

Abstract

704,195. Spray carburetters. HUNTER, A. R., HUNTER, G. F., and HUNTER, R. M. Oct. 2, 1952 [Oct. 2, 1951], No. 22904/51. Class 7(3) A carburetter of the type having a variable choke 19 carrying a fuel metering needle 14 and operated by a piston or bellows 12 responsive to the suction in the mixing chamber between the choke and mixture throttle valve 20, is provided with an auxiliary air valve 30, Fig. 3, for admitting air to the mixing chamber, which valve is opened as the throttle valve 20 is moved towards closing and vice versa, and with a valve 23, actuated by the piston or bellows 12 operating the choke 19, for metering the auxiliary air. As shown, Fig. 4, the choke 19 is integral with piston 12 operated by suction transmitted through a passage 18 and the valve 23 is carried by a bar 26 fixed to the choke 19 and comprises a conical member controlling an auxiliary inlet 28 leading into the mixing chamber from a chamber 22, the flow of air into which from a passage 40, Fig. 2, is controlled by the valve 30 actuated by a diaphragm in. a chamber 38 connected to the suction downstream of the throttle valve 20 through a pipe 35. At wide open throttle the suction is insufficient to hold the valve 30 open, so that a fairly rich mixture is obtained. If the throttle valve 20 is moved towards closing, the increased suction therebelow opens the valve 30 and the mixture is diluted with air to an extent determined by the position of the valve 23. On acceleration, the valve 30 closes in order to enrich the mixture. The end of the pipe 35 may be situated downstream of the throttle valve 20 or at the point where the edge of the valve disc contacts the mixture passage wall when closed; in the latter case, the pipe 35 will be closed when the throttle valve is closed and the suction-responsive device 38 will close the valve 30 to produce a rich idling mixture. The end of the auxiliary air inlet passage 40 is preferably arranged adjacent the carburetter air inlet and a common air filter may be arranged over both inlets. One or more valves such as the valve 30 may be provided in order to adjust the fuel-air ratios, the valves in operation being selected manually. In a modification the valve 30 is operated mechanically from the throttle valve or its operating mechanism. The valve 30 may be operated from the throttle valve spindle 47 through friction discs which allow lost motion to take place when the throttle valve has moved the valve 30 to either of its limit positions, and a lost-motion connection may be provided between the throttle valve operating mechanism and the spindle 47. Alternatively the friction clutch may connect the valve 30 to the throttle operating mechanism, the latter having a lost-motion connection to the spindle 47 which is provided with a friction check device to prevent the spindle from moving until the valve 30 completes its movement.