GB393765A - Improvements in or relating to carburettors - Google Patents

Abstract

393,765. Spray carburetters. JENNINGS, J. T., 35, Wharf Road, King's Norton, Birmingham. June 30, 1932, No. 18464. [Class 7 (iii).] A suction-actuated air valve 21, Fig. 1, actuates through a pin 40, a valve 37 which controls the flow of mixture from a choke tube 12 to a space between the valve 21 and a fixed member 18, the adjacent surfaces of the valve and fixed member forming a relatively long and narrow variable passage or choke 20 having substantially parallel walls. The carburetter casing is in two parts 1, 2, the lower portion of part 2 having a facing 8, and a primary mixture port 10 restricted by a part 11 of crescent or other shape in plan. Fuel is supplied by a nozzle 13,and primary air enters at 14. The port 10 leads to a crescent-shaped chamber 15, Fig. 3, formed between the casing 2 and the member 18 which surrounds a secondary air inlet 17, Fig. 1. The part 2 has a lip 16 which, with the liner 18 forms an annular passage 19 leading to the variable passage 20. The air control valve 21 is recessed at 25 to slide over a fixed cap portion 29 carried by a bolt 27, preferably of rustless steel, supported by a bridge-piece 28. The valve 21 is loaded either by a single spring 31 or by two springs one of which is shorter than the other and adapted to come into action after a predetermined movement of the valve. The recess and cap form a dashpot, escape of air from which can occur between the sliding surfaces of the valve and cap, through which space also the suction is transmitted to actuate the valve. The surfaces of the valve 21 and the casing and parts surrounding it are made as far as possible of streamline form and the primary mixture is admitted through the annular port 19. The control valve 37 slides between the casing 2 and liner 18, the latter being provided for this purpose with a facing 38, Fig. 3. The passage 10 has diverging walls 39 leading to the valve 37. At the lower part of the casing 2 and coaxial with the passage 10 is a rotatable member 43 having an operating arm 44, Fig. 4, and provided with a circular aperture 46, Fig. 5, and diametrically opposite grooves or recesses 47, 48, the latter having an arcuate extension 49. The recesses are adapted, in certain positions of the member 43, to register with by-passages 50, 51, Figs. 1 and 4. The valve 37 has outlet orifices 53, Fig. 4, and one end is recessed at 52, the recess registering with the wall of passage 10 when valves 21, 37 are fully open. Three subsidiary air inlets to chamber 15 are provided at 54, Figs. 1, 2 and 4, and these are controlled by a slidable shutter 55 which carries a projection 57 which may be interposed between the casing 2 and a cover plate 56, Figs. 1 and 4, to prevent the valve 21 from opening. The plate 56 serves normally to control the inlets 54 is dependence on the movement of valve 21. A further by-passage 58, controlled by a screw 59, communicates at all times with the arcuate extension 49, Fig. 5, and with one of the air inlets 54. One or more holes 60, Fig. 1, in the lowest part of the casing allow of the entrance of air to pick up deposited fuel. Alternatively a small passage may be provided from the lowest part of the casing to the engine side of the throttle valve. In a modification, Fig. 6 (not shown), the cap 29 is mounted on a spider between the part 1, 2 and carries a hard metal valve guide. The bridge 28 is dispensed with and the valve carries an axial pin around which the loading springs are located. An outer chamber in the valve communicates through a number of peripheral apertures with the passage 20. In a further modification, Fig. 9 (not shown), the cap is carried by a bolt such as 27, Fig. 1, and the valve is similar to that described with reference to Fig. 6. In a further modification, Fig. 7, the valve 21 is adapted to work in a vertical direction, the bridge 28 carrying a hard metal tubular guide 72 closed at its upper end by a plug 74. The valve 21 slides over the guide, the chamber 75 serving as a dashpot chamber. Holes 76 are provided in the guide. A bolt 77 passes through the valve 21 and carries a collar 79 for two loading springs 32, 67. In a still further modification, Fig. 8, the valve 21 is adapted to move outwardly as it opens. The bridge 28 carries a stepped valve guide having parts 80, 81, 82 of different diameters over which slide corresponding bores in the valve. Dashpot chambers 83, 84 are formed, and the chamber 85 communicates by a duct 86 with the annular choke passage 20. The sliding surfaces are a free fit so as to establish communication between the chambers 83, 84, 85 and the valve is loaded by springs 32, 67 positioned by projections 86a, 87. The subsidiary air passages may be annularly arranged around the casing of the carburetter. The walls of the passage 20 in all the forms are shown straight, but they may deviate slightly from this form. They may be slightly concave or convex along their length and the passage may be slightly convergent or divergent in the direction of flow. To ensure a turbulent flow, small grooves or other surface irregularities may be formed on the valve or the inner surface of the surrounding member. The byepassages 50, 51 are used for starting from cold, and, in closing them as the engine warms up, the bye-passage 50 remains open longer than 51. The function of the bye-passage 58 is to supply, when required, extra primary mixture throughout the whole range of running when the valve 37 closes the bye-passage 51 before closing 50. Specification 387,230 is referred to.