GB1295774A - - Google Patents

Abstract

1295774 Throttle by-pass passages ZENITH CARBURETTER CO Ltd 19 April 1971 [31 March 1970] 15079/70 Heading F1B Constant-depression type carburetter having a butterfly throttle valve has a further passage for supplying air directly to the induction passage at a position downstream of the throttle valve, when the valve is in the idling position, and is controlled by the operation of the valve so that the supply of air through the further passage ceases when the valve has moved a small amount in the opening direction from the idling position. Air enters the carburetter body at 12 and flows past an air-valve slide 17 and fuel supply orifice 21, the amount of air being controlled by a valve 14. A profiled needle 22 controls the fuel supply. A passage 23 formed along the body, is connected to the induction passage by an opening 25, which is adjacent the edge of the valve 14 when in the idling position. The opening may be either a circumferential slot or a row of separate holes preferably subtending an angle of not more than 6 degrees at the axis of the induction passage. The other end of the passage 23 turns through a right-angle and opens into an external flat surface 29 on the body 10. A passage 31 leading from the air inlet passage 12 also opens into the surface 29. A flow restricting unit 32 secured to the surface 29 has a first passage 33 which connects with the passage 31, a second passage 37 which connects with the passage 23 and a third passage 34 which is joined to the first passage 33 by a cross-passage 35. A further cross-passage 36 connects the first, second and third passages. Flow from the passage 33 to cross-passage 35 is controlled by a plug 38 having bores 41, 42 and this is augmented by the flow pasta tapered section 45 of an adjustable screwed plug 43. The flow through the bores 41, 42 is further controlled by the tapered portion 46 of the plug 43 which cooperates with the passage 36. In a modification Fig.4 (not shown) the outlet opening 25 is moved to a position downstream of the throttle valve and a rotary valve is provided in the passage 23. This valve is linked to the throttle valve, so that as the throttle valve moves away from the idling position, the rotary valve moves to the closed position. Alternatively, a solenoid-operated valve may be provided in the passage 23, the valve being controlled by an electrical switch operated by the throttle linkage to move the valve to the closed position as the throttle moves away from the idling position. The air flow is shut off during a movement of the throttle valve such that the total air flow through the carburetter does not change by more than 1 lb/min.