GB395414A - Improvements in or relating to carburettors - Google Patents

Abstract

395,414. Spray carburetters. GRACE, C. J., Cleveland House, City Road, London. Dec. 15, 1931, No. 11732/32. Divided application. [Class 7 (iii).] In a carburetter wherein the air valve serves as the throttle valve, the area of the fuel orifice is controlled in accordance with throttle movement, and the proportion of air to fuel is varied by independent means actuated by suction and adapted to control the supply of air through an auxiliary passage. A nozzle tube 8 is surrounded by a shroud 11, fuel flowing between the tube and shroud past filtering grooves 9 and through larger grooves 10 which correspond with air channels 11b, 11d formed respectively in the shroud and in a cap 11c screwed therein. Around the shroud is a sleeve 12 carrying at its lower end a piston 12a the under side of which is in communication through a controlled duct with the mixing chamber in the neighbourhood of the Venturi tube 30. The sleeve 12 is lifted by suction and by the air stream acting upon a flange PVR at the upper end of the sleeve which is ported at 12b, Fig. 7, to expose more or less of the fuel discharge ports. The closed upper end of sleeve 12 is splined at 14a to receive a splined portion of an axial rod 16, the lower end of which is also splined to engage a boss 18a of an arm 18 connected by a link 19, arm 20 and spring 23 to the actuating arm 22 of the air throttle 21. As the throttle is opened, the spring actuates the members 20, 19, 18 so as to rotate the sleeve 12 and open the fuel orifices for about the first third of throttle opening. After that, the sleeve remains stationary and, when the throttle is closed, is returned by engagement of stops 25, 26, Fig. 3, assisted by the spring. The sleeve 12, when raised by suction, serves firstly to uncover, by the port 14, the air channels 11d to admit air, which enters tube 8 at its lower end, over the fuel orifices and secondly, to cut off by its upper edge 12d the fuel outlets 11b. The extent to which the sleeve can be raised by suction is limited by a spring clip 17 on the rod 16 which can be moved by rod 27 and lever 28. The duct leading to the under side of the piston 12a has the effect of producing a time lag before pressure on both sides of the piston becomes equal and, in consequence, a sudden increase of throttle opening is accompanied by a fall of the sleeve 12, and an enrichment of the mixture.