Patent GB-738103-A (GB)
Title: Improvements in carburettors
IPC: F02D9/00
Filed: 1953-05-15
Abstract: 738,103. Carburetters. GENERAL MOTORS CORPORATION. May 15, 1953 [June 26, 1952], No. 13605/53. Class 7(3). A carburetter has a throttle valve and a choke valve the limit of closing movement of the throttle valve being dependent during engine operation on the position of the choke valve and has a device by which the throttle valve can be opened sufficiently when the engine is inoperative to allow the throttle valve to take up an optimum position for starting the engine independently of the position of the choke valve and the throttle is carried by a shaft on which are mounted two resiliently connected arms one fixed on the shaft and the other rotatable thereon and arranged for connection to the throttle pedal one of the arms carrying an adjustable throttle stop member arranged to abut a fast idle cam member connected by a link to the choke valve the device being adapted to engage the arm fixed on the shaft and thereby effect momentary disengagement of the throttle stop member from the fast idle cam so that the choke valve can close and move the cam to its fast idle position. In Fig. 1 a solenoid 62 which is energised when the engine starter circuit is closed co-operates with an arm 68 fixed to the shaft 16 of the throttle valve 14 and opens the valve to a predetermined position. At the same time a fast idle cam 60 operated by the unbalanced choke valve 10 may be released a spring 72 connecting the arm 68 to an arm 18 rotatable on the shaft 16, the arm 18 carrying a " fast idle " stop screw 54 which co-operates with the cam 60. The arm 18 also carries a " hot idle " stop screw 26 which co-operates with a stop 32 on the carburetter housing. The choke is held closed at low temperatures by an automatic mechanism not shown. The cam 60 is operated by the choke valve through the medium of a weighted member 40 and co-operating lugs 36, 38. Figs. 3 and 6 show a modification in which the throttle valve is opened by a suction operated device when the engine is stopped. As shown a diaphragm 122 carries a rod 132 and nut 140. When the engine is inoperative the diaphragm is moved to the right and the nut 140 cooperates with a projection 142 on an arm 94 fixed to the throttle valve shaft 90 and opens the valve. When the suction is sufficient however the diaphragm and nut 140 are drawn to the left. The " fast idle " and " hot idle " stop screws 104 and 102 are carried by the arm 94. The throttle valve is operated by an arm 18 which has an offset portion 98 which engages a toe 96 on the lever 94. The suction is transmitted from the downstream side of the throttle valve by means of a member 130 which comprises a ball valve 148 for delaying the effect of the suction when the suction is increased. Thus on an increase of suction the valve 148 closes and the increase is transmitted to the diaphragm through a small passage 152. If the engine should slow down unduly on a sudden closing of the throttle valve the drop in suction permits the diaphragm to move to the right and open the throttle to prevent stalling but when the engine speeds up again 'the closing of the throttle is delayed by closing of the valve 148.