Patent GB-315504-A (GB)
Title: Improvements in or relating to carburetters
IPC: F02M17/16
Filed: 1928-05-01
Abstract: 315,504. Smith, F. H. May 1, 1928. Surface carburettors. - In a carburettor of the type in which the fuel is vaporized by being spread over a perforated or porous rotating disc through which air is drawn the disc, of gauze or perforated material, presents a complete and unobstructed annular area for the passage of air, and means are provided whereby the amount of vaporized fuel withdrawn from said annular area is varied bv the movement of a throttle valve. The carburettor body 4 has a float chamber 1 and recessed at one side to form. in conjunction with a cover 5, a chamber 2 in which the rotating disc 8 is located, said disc being mounted on a spindle 7 driven from the engine. The lower part of the disc dips into fuel supplied through a duct 3, and the upper part is located between an air-inlet aperture 20 and outlet apertures 9 leading to a mixing chamber 10. The number of these apertures exposed to engine suction is varied by a slot 14 in a tubular throttle valve 11 mounted on a spindle 12 rotatable by an arm 13. The wall 15 of the throttle has extra-air inlet apertures 15<a>, and at the end of the throttle spindle is fitted so as to slide thereon but be rotatable therewith, a ported disc 16 working over a fixed disc 17 also ported at 17<a>. The open end of the throttle is bevelled and is forced against a bevelled seating by a spring 19. The extra air may be admitted through apertures 22<a> in the end cover 22, such apertures being covered with gauze 23, and by a disc 24 located by a spring 25. The disc 24 covers the apertures until a predetermined suction exists and thus starting is facilitated. Fuel is admitted to the float chamber by a valve 30 actuated bv a float 26 the arm 27 of which is pivoted at 28. Additional feed ducts 3<a> may be provided, and holes such as 39 prevent the formation of a vacuum in the float chamber. Radial ribs 21 in chamber 2 prevent fuel from being thrown up within the chamber and ensure even distribution over the disc. In a modification, Figs. 7 and 8 (not shown), the ported disc members 16, 17 are dispensed with, and the extra air is controlled by a perforated disc mounted on the throttle spindle and rotating over apertures in the end cover. In the modification, Fig. 9, the throttle valve 11 has an axial movement imparted to it by a cam slot 51 in a lever 50 pivoted at its end, the cam slot engaging a roller on a pin 52 screwed into the valve. A triangular aperture 47, with base uppermost if desired, controls the apertures 9, and the extra air is controlled by an aperture in the end of the throttle moving over a fixed member 49 the axial cross-section of which is first parallel and then tapered. In a further modification, Figs. 11 and 12, the apertures 9 are replaced by a narrow slot 57 opposite which is a narrow slot in a block 58 in chamber 2, which slot communicates with the atmosphere through a row of holes 59 which replace the aperture 20. The fuel is positively fed by a tube 60 to the centre of the disc over which it is spread uniformly and the flow of fuel is controlled by a gravity needle valve 61 lifted by suction. The throttle comprises a domeshaped part 62 adjustably mounted on a screwed spindle 63 which can be moved axially by a coarse-pitch screw 63<a>, 65 rotated by an arm 13. The axial movement adjusts the part 62 relatively to its seat 64 and at the same time controls extra air, entering at 68, by a valve 67 cooperating with a seat 66<a>. The throttle spindle carries a tapered sleeve 69 which serves to limit the lift of the fuel valve which is raised by suction acting on a piston 70 the underside of which is open to atmosphere at 72. The valve may be raised to clear the passage of obstruction by a plunger 73 carried by a cap 74 containing a gauze filter 76. The perforations in the disc 8 are prederably countersunk. To produce a more effective bursting of the petrol film and to ensure that the fuel is not carried past the apertures 9 or slot 57, a hollow block 80, Fig. 15, is placed in front of the air-inlet aperture 59, said block having a row of perforations or a slot 81 which extends radially of the chamber 2 and is in advance of the apertures 9 or slot 57.