Patent GB-1422633-A (GB)
Title: Automatic cold start devices for internal comnbustion engines
IPC: F02M1/04
Filed: 1972-03-16
Abstract: 1422633 Spray carburetters facilitating starting ZENITH CARBURETTER CO Ltd 13 March 1973 [16 March 1972] 12457/72 Heading F I B Cold starting device for an I.C. engine, comprises an auxiliary air supply passage 11, two throttle valve members 30 and 42, one of the valves, 30, being arranged so as to tend to be moved, by air flowing past it to the engine, into a position in which it restricts or prevents the flow of air and the other valve, 42, being arranged so as to tend to be moved to the open position by the air flow, at least one fuel supply orifice 23, 24, which opens into the portion of the auxiliary air supply passage which extends between the closed positions of the two valve members so that fuel can be drawn therethrough into the passage by engine suction when the valve 30 is in the open position and thermostatically operable means which are responsive to engine temperature and which allow limited movement of the valve 30 in the closing direction, for all conditions of engine temperature, the arrangement being such that the valve 30 is in the open position and the valve 42 is in the closed position during the cranking period, and the valve 30 begins to close progressively and the valve 42 begins to open progressively when the engine commences to run under its own power, the progressive movements of the valves continuing until the engine is running normally, whereupon the supply of fuel from the or each orifice 23, 24, ceases. The orifices 23 and 24 communicate with a bore 21 which is open to atmosphere through a restriction 22, and to the float chamber 12 through a passage 25 and a jet 26. At the bottom of the bore 21 is a further orifice 250 opening into the auxiliary air passage 11 and controlled by a volume screw 251. A fourth orifice 27 opens into the passage 11 at a point adjacent the periphery of the valve 42 when in its closed position, and is connected to the float chamber through a passage 28 and a jet 29. The closed position of the valve 30 is determined by a stop screw 350. A lever 32 is pivotally mounted on the spindle 31 to which the valve 30 is fixed, and one end 33 of the lever is connected to a temperature sensitive device which controls the position of the lever. At the other end of the lever is a notch 35 which receives a post 37 projecting from one end of a cranked lever 36 fixed to the spindle 31. The other end of the lever 36 is connected by a link to the free end 39 of a lever 40 which is fixed to the spindle 41 of the valve 42. Operation when the engine is cold, the lever 32 is held in a position so that the valve 30 moves to its fully open position under the influence of a spring tending to turn it in the opening direction. The connecting link causes the valve 40 to move to the closed position. As the engine is cranked, petrol is drawn through the orifice 27 and an air/ fuel mixture is drawn from the orifices 23 and 24. When the engine starts to run, the increased airflow causes the valve 42 to open and the valve 30 to close to an extent determined by the engine temperature. The increase in pressure in the passage 11 stops the supply of petrol from the orifice 27, and as the engine temperature increases the valve 30 closes and no mixture is drawn from the orifices 23 and 24. Mixture is still available from the orifice 250 and this may form part or all of the engine idling mixture. Fig. 3 (not shown) illustrates an embodiment in which the auxiliary air passage is L-shaped, each arm of the passage containing one of the throttle valves. Fig. 4 illustrates the arrangement of a temperature sensitive capsule 89 which has an operating rod 88 terminating in a flange 87 which it waves against a spring 90. The flange engages a post 86 projecting from a cam 84 which is pivotally mounted at 85. The cam determines the position of a lever 76 mounted on a throttle valve corresponding to the valve 30 in Fig. 1. A second lever 77 free to rotate on the spindle of this valve, has a notch 79 which engages an upstanding projection on the lever 76, so that these is a lost motion connection between the levers.  An extension 83 of the lever 77 engages a pin 94 on a lever 93 attached to a spindle 92 which carries a throttle valve corresponding to the valve 42 in Fig. 1, and ensures that the valve is held closed when the other valve is fully open. A resilient finger 95 urges the valve on the spindle 92 to the open position as the other valve closes.