Patent GB-400538-A (GB)
Title: Improvements in carburettors for internal combustion engines
IPC: F02M9/127
Filed: 1933-05-01
Abstract: 400,538. Spray carburetters. WEIERTZ, A. H. and WEIERTZ, P. A. R., Svedala, Sweden. May 1, 1933, No. 12662. [Class 7 (iii).] In a carburetter, in which fuel from a conical sprayer disposed coaxially in the carburetter casing emerges through a circumferential nozzle slot &c. into a mixing chamber formed by an annular channel of variable cross section between an air inlet and mixture outlet and of greater internal diameter than the induction pipe, the flow of air is controlled solely by a member which varies the area of the annular channel in the neighbourhood of the nozzle slot between that slot and the mixture outlet, suction of fuel being effected solely by the suction of the air stream at the nozzle slot, and a needle valve &c. regulates the fuel supply between the float chamber and the nozzle slot in dependence on the setting of the control member or on suction in the induction pipe, or on both. An annular air passage 4 of narrow section is formed between a tapered portion 1 of the carburetter casing and the lower portion 3 of a fuel sprayer, the upper portion 2 of which is connected to the casing by screw threads and may be rotated by an arm 24 to vary the size of the passage 4 and control the engine speed thereby. The upper portion 2 carries a float chamber 6 disposed within the lower portion 3 and adapted to supply fuel through a needle valve 10 in its lower end to channels 11 between the float chamber and the lower portion 3 of the sprayer. The channels 11 deliver to a preliminary mixing chamber 12 to which air is admitted through ports 14 to mix with fuel drawn from a circumferential nozzle 5 between the parts 2, 3 of the sprayer. An adjustable rod 17 prevents the needle valve 10 from rising as the sprayer and float chamber 6 are lifted and carries a plate piston 21 formed with apertures 22 adapted to be closed by a disc 23 slidable on the rod 17, when the piston 21 is displaced downwardly in the float chamber by the raising of the sprayer ; the piston then forces fuel past the needle valve 10 to meet acceleration requirements. In a modification, the fuel sprayer is fixed in the casing 1 and the air passage is controlled by a tapered sleeve valve threaded in the casing. The functions of the piston 21 are performed by a diaphragm influenced by engine suction and secured to the needle valve, which opens upwards, the diaphragm closing a fuel chamber, at the bottom of the sprayer, in communication with the channels 11. In another form, the air valve 26, Fig. 3, is threaded in a projection 36 on the casing 1 and as it is raised to reduce the air opening, it lifts a rod 42 in contact with one end of a lever 45, the other end of which is connected, with a lost motion connection, to the spindle of the needle valve, to move the valve towards its seat. The lever 45 is supported by a spring 44 and its fulcrum 46 is eccentrically disposed on a shaft 47, rotatable by hand or a thermsotat to adjust the relative depression of the needle. The float 6 operates a lever 41 to press the ball 8 of a fuel inlet valve on to its seat and the pivot of the lever 41 is carried by a lever linked at its other end to the lever 45, the arrangement resulting in depression of the float when the air valve is opened. On closing the valve, the float is raised and a spring 43 is tensioned to assist this. The preliminary mixing chamber 12 is heated electrically. This construction may be modified to permit the needle valve to open downwardly; the diaphragm 27 is replaced by a piston connected to the needle valve and working in a chamber in the cover of the casing 1, the upper side of the piston being in communication with the mixture passage at the lower end of the casing. This form is provided in the mixing chamber 12 with an annular pipe through which exhaust gases or engine cooling liquid flows and the inlet and outlet tubes to this pipe constitute the means for securing the casing 1 to the sprayer 2, 3. The continuous fuel nozzle 5 may be replaced by a series of circularly arranged separate nozzle orifices.