Patent GB-1466544-A (GB)
Title: Carburetor choke system
IPC: F02M1/10
Filed: 1975-03-13
Abstract: 1466544 Automatic choke valves FORD MOTOR CO Ltd 13 March 1975 [1 April 1974] 10465/75 Heading F1B Automatic choke carburetter has choke valve 28 spring-biased towards the closed position, temperature responsive means 40 operably connected with the choke valve for moving the valve in an opening direction upon increase in temperature and vice-versa, pressure responsive means 100 adapted for connection to an engine intake manifold to be responsive to intake manifold pressure and operably connected to the choke valve to open the valve to a predetermined position to lean the mixture when manifold pressure drops upon engine start-up and locking means 128, 130 to prevent the choke valve from moving towards the closed position from the predetermined position should the manifold vacuum subsequently decay below the level establishing the predetermined position of the choke valve, choke valve 28 is mounted on spindle 30 which is connected by lever 58, link 56 lever 48 and spindle 44 to a bi-metal spring unit 40, through which air, heated by passage over the exhaust manifold, is drawn when the engine is running. Freely rotatable on spindle 44 is a fast idle cam 60, having steps 70, 72, 74 which are engaged by a screw 78 carried by a lever 180 which is fixed on the spindle 38 of the throttle valve. Cam 60 has a projecting arm 62 which, by gravity, falls against a finger 50 projecting laterally from lever 48. At low temperatures, unit 40 tends to rotate spindle 44 anti-clockwise to move choke valve 28 to the closed position. A vacuum motor 100 comprises housing 102 divided by diaphragm 108 into an atmospheric chamber 104 and a vacuum chamber 106, which is connected by tube 110 to the inlet manifold, downstream of the throttle valve. Adjustable stop 116 limits the displacement of the diaphragm, which is spring-biased to move to the right in Fig. 2. Link 112 connects diaphragm 108 to lever 48 so that movement of the diaphragm in response to vacuum in chamber 106 causes clockwise rotation of lever 48. A locking mechanism, Fig. 3, limits closing movement of choke valve 28 during the period immediately after starting an engine to which the system is fitted. The mechanism comprises an angled extension 120 of lever 180, a locking lever 124 and a lug 130 on lever 48. Operation, assuming an engine being started from cold in cold weather. Before operating the starter motor the throttle valve control member is operated to move the throttle valve to the wide open position. Anti-clockwise rotation of lever 180 causes clockwise rotation of locking lever 124 and releases lug 130 so that lever 48 is turned anticlockwise by unit 40 to close choke valve 28. Finger 50 lifts arm 62 and turns cam 60 so that the highest step, 70, is under screw 78 when the throttle valve control member is released. When the engine starts to run, manifold vacuum acting on diaphragm 106 turns lever 48 clockwise to partially open choke valve 28, locking lever 124 runs up sloping surface 132 and drops into the path of lug 130. If the vehicle in which the engine is fitted is driven before the engine has warmed up, then if the engine falters under load so that the manifold vacuum decreases, the locking lever prevents rotation of the choke valve to the fullyclosed position. As the engine warms up, unit 40 moves the choke valve 28 to the open position and arm 62 is allowed to rotate clockwise so that the fast-idling steps of cam 60 are not engaged by screw 78.