GB305338A - Improvements in and relating to mixture supply systems of internal combustion engines - Google Patents

Abstract

305,338. Beatson, F. H. P. Dec. 23, 1927. Spray-carburettors.-Temporary enrichment of the normal mixture is produced during opening of the throttle from or to any position, the enrichment being maintained during a period of acceleration; temporary weakening is produced during closure of the throttle from or to any position, the weakening being maintained during a period of retardation, and complete cessation of fuel flow occurs during a period of extreme retardation. A nozzle c fed from a float chamber b discharges fuel at the throat e of the suction passage a provided with a throttle valve d. The fuel flow is controlled by a valve f the spindle l of which is connected to a diaphragm or piston m forming a partition between chambers i, k. These chambers are connected by branch conduits h<1>, h<2> respectively and a conduit h to the throat e of the suction passage and a constricted orifice x is placed in the branch h'. The diaphragm is under the control of opposed springs n, o; its upward movement is limited by a resilient stop p, and its downward movement by a stop g<4> below the fuel valve. With any condition of running the diaphragm m will assume a position of equilibrium with a certain suction valve at the throat e. If, now, the throttle valve d be opened to accelerate, the suction at c increases. This increased suction is transmitted instantly to chamber k but only after a time lag, depending on the constriction x, to chamber i. The result is that the diaphragm is moved to open the fuel valve f and enrich the mixture, and this increased opening persists until equal pressures are established in the chambers i, k. Conversely a closing of the fuel valve takes place when the throttle valve is moved in the closing direction, but the stop p provides for a minimum flow which may vanish entirely if the retardation be extreme. At very large throttle openings air may be admitted to the chamber i to force the fuel valve against the stop g<4>. To .effect this the spindle q of the throttle valve has a cross passage r which, when the throttle is fully open, connects apertures s, t in the spindle bearing to form an air inlet to a conduit u which delivers to chamber i. In a modification, the valve f is replaced by a valve which controls the inlet to an air tube which surrounds and terminates approximately at the outlet of the fuel nozzle. The stem l may actuate a valve for controlling air direct to the nozzle c or to the float chamber.