GB420810A - Improvements in carburettors - Google Patents

Abstract

420,810. Spray carburetters. CARTER CARBURETOR CORPORATION, 2838, North Spring Avenue, St. Louis, Missouri, U.S.A. April 27, 1933, No. 12320. Convention date, May 7, 1932. [Class 7 (iii)] [See also Group XXIX] The initial opening movement of an eccentrically-mounted choke valve in the air inlet of a carburetter is resisted until a predetermined degree of suction is attained, whereupon the choke valve releases itself and moves freely towards its fully-open position. In the construction shown in Fig. 1, a bimetallic coil 30 is mounted on a shaft 31 which is adjustably carried by a housing 32 secured to the exhaust manifold. One end of the coil engages a pin 36 carried by a yoke 35, which is mounted on the shaft 31 and connected through a link 38 and arm 37 to a shaft 8 on which the choke valve 7 is mounted eccentrically. The arm 37 has a cam surface 381 provided with a notch 39, and a latch 40 is normally held in engagement with the cam surface 38 by a spring 42. When the engine is stopped and the temperature is low, the coil 30 closes the valve 7 and permits the latch 40 to drop into the notch 39. When the engine is cranked with the throttle valve 23 partly open, the valve 7 remains closed, but a slight opening can be obtained either by enlarging the notch 39 or by mounting a spring between the lever 37 and the shaft 8. When the engine fires, the increased suction overcomes the resistance of the latch 40 and of the coil 30 and allows the valve 7 to open. To prevent stalling of the engine through having too rich a mixture, if the throttle valve 23 is now closed or moved to a wide open position, the valve 7 is opened to admit more air by a lever 43 mounted on the throttle shaft 24 and connected by a spring 45 to a pin 44 on the arm 37, so that the lever 43 crosses the centre line between the shaft 24 and the pin 44 when the throttle valve is one-third open. Closing of the throttle at starting pulls the arm 37 downwards against the resistance of the coil 30, and maintains the valve 7 partly open. If the throttle is suddenly opened wide during starting, the valve 7 is also opened. To ensure that the valve 7 is opened rapidly at first, but is not fully opened until the engine is warm, the arm 37 extends at an angle of 45‹ from the shaft 8 when the valve 7 is closed, and in the corresponding position the yoke 35 is horizontal. The slow-running nozzle 25 discharges at the edge of the throttle valve, and is fed with air past an adjustable valve 28, and with fuel from a calibrated orifice, the area of which is controlled by a stepped needle valve actuated with the throttle valve, the same orifice supplying fuel for normal running to a nozzle 22. The throttle valve actuates an accelerating-pump, provided with non- return inlet and outlet valves, to deliver fuel into the mixing-chamber through a separate nozzle. In a modified construction, the latch 40 and the notch 39 on the lever 37 are omitted, and as shown in Fig. 8, the choke valve 70 is cut away to permit the insertion of a latch 72 which is pivoted at 73 and prevented from rotating on its pivot by a strong spring 74 attached to a bracket 75 on the valve. A catch member 77 pivoted at 78 is held by a weak spring 79 in the path of the latch 72. In operation, the spring 74 provides a strong but resilient resistance to the opening of the valve 70 by suction, and as suction is applied the member 72 is rotated to the position shown in Fig. 8, and then slides out from under the latch member 77 to allow the valve 70 to open. As the engine cools, the latch 72 forces the catch member 77 back, compressing the light spring 79. In the modified construction shown in Fig. 4, the position of the latch member 83 can be adjusted by a screw 80 mounted in a bracket 81.