Patent GB-608679-A (GB)
Title: Improvements relating to choke valves for internal combustion engine carburetters
IPC: F02M1/10
Filed: 1946-02-27
Abstract: 608,679. Spray carburetters. CARTER CARBURETOR CORPORATION. Feb. 27, 1946, No. 6082. Convention date, June 15, 1945. [Class 7 (iii)] An unbalanced choke valve in the air inlet is controlled by a device comprising thermo-sensitive means for moving the valve towards closed position to enrich the air fuel mixture when the temperature is low, an element for locking the valve, means adapted to urge the element into locking position with relation to the valve when the engine is at rest and an engine throttle valve partly open and means responsive to a force produced by the engine when the latter starts to run under its own power for withdrawing the element from locking position and the element is arranged to be capable of locking the valve in substantially any position of the valve. As shown, Fig. 2, a choke valve 20 urged closed at low temperatures by a bimetallic coil 24 is controlled by a locking device comprising a locking member 33 and a toothed sector 27. The locking member is carried by a piston 30 which is acted on by suction on the engine side of a mixture throttle valve 26 and by a spring 31. The sector is rigidly secured to the choke valve shaft. When the throttle valve is fully closed a cam 36 on the throttle valve shaft operates a rod 37 to hold the piston 30 in such a position that the locking member is out of engagement with the sector 27. Thus, when the engine is stationary the choke valve can take up a position according to the engine temperature by reason of the coil 24. When the throttle is slightly opened, rod 37 moves to a low portion of cam 36 and releases the piston 30 so that under the action of the spring it moves the locking member into engagement with the sector to lock the choke valve in the position in which it is held by the coil 24. When the engine starts, suction on the piston 30 removes the locking member and frees the choke valve. At high throttle valve openings a high portion 42 of the cam 36 positively removes the locking of the choke valve. In a modification, Fig. 3, a piston 30a carrying a locking point 33a engages a sector 27a fixed to an extension of the choke valve shaft and enclosed in a housing 50. A bimetallic coil 24a in the housing is used in place of the coil 24. The connection between the throttle valve and the locking member comprises a rod 56 lever 55 and sleeve 54, which operate a cam 36a which frees the choke from the locking point when the throttle is fully closed or fully open. An inwardly opening valve 23 may be provided in the choke valve and in addition the choke valve may carry a permanently open air inlet hole. A fuel needle valve 65 may be interconnected with the throttle valve. A slow running arrangement is shown at 64. In a modification of Fig. 3 the piston 30a has attached to it a slotted link the slot of which passes over a pin fixed to the sector 27a. When the throttle valve is substantially fully opened it depresses the piston and the upper edge of the slot engages the pin to move the choke valve slightly open. In this position, continued cranking of the engine will draw air through the carburetter and manifold and sweep out excess fuel which otherwise might prevent prompt starting. Heated air may be drawn into the housing 50 from a point near the exhaust pipe by suction acting through a small hole 63 in the piston 30a.