Patent GB-391711-A (GB)
Title: Improvements in and relating to bi-fuel carburettors for internal combustion engines
IPC: D04B23/00
Filed: 1932-11-11
Abstract: 391,711. Spray carburetters. HARRIS, T. M., 3, Burlington Gardens, London. Nov. 11, 1932, No. 31986. [Class 7 (iii).] In a bi-fuel carburetter having orifices which open into the choke tube and are continuously supplied with fuel, obturator means are moved axially in the orifices progressively to diminish the outflow of light fuel and to increase the outflow of heavy fuel as the throttle is opened and vice versa. The obturators may be so arranged that the outflow of light fuel increases for a time after the outflow of heavy fuel has commenced and thereafter diminishes. A choke tube 6 between a main air inlet 1 and an induction pipe 2 is closed by a throttle 5 movable transversely of the tube into a chamber 4. The choke tube 6 is supported by a carrier 7 secured in the side wall 10 of the carburetter and formed with two vertically spaced bores 13, 14. The bore 13 houses a distributer 15 and a control tube 16 for the heavy fuel and the lower bore 14 a control tube 20 for light fuel. Heavy fuel flows into the tube 16 through an inclined passage 72 supplied by an horizontal passage 71, Fig. 3, between which and a passage 70, leading from a float chamber outlet 52, are opposed ports 66, 67 in a hollow valve member 61. Light fuel flows through the outlet 51 of a separate float chamber along a passage 54 to a well 55. A constricted passage 57 leads to an annular recess 21 in the light fuel control tube 20 and thence through ports 23 to the inside of the tube. A further annular space 22 between the carrier 7 and a shoulder on the control tube 20 communicates with the induction tube 2 through a passage 29. The orifice of the heavy fuel control tube 16 is closed by a tapered needle 19 and that of the control tube 20 by a needle 30 terminating in a part 31 of triform section, on the end of which is secured a sleeve 32 having a sharply tapered front edge. When the throttle 5 is closed, as at starting, a limited amount of air is drawn through a port 36 into the sleeve 32 and mixes with light fuel drawn through the ports 23, the mixture traversing the passage 29 to the induction tube 2. The needles 19, 30 are adjustably mounted in apertures in a baseplate 5<1> of the throttle and a cam plate 74, and a pin 82 on the cam plate 74 engage horizontal slots 83 in the wall of the chamber 4 and cam slots 84 in a cam member 85 rotatable in the chamber 4 by a lever 86. A cap 89 screwed on to the base of the chamber 4 prevents axial movement of the cam member 85, rotation of which displaces the needles 19, 30 in their orifices. A small movement of the throttle 5 allows some air to be drawn along the air inlet 1, a very small amount of heavy fuel to enter the choke tube 6 together with light-fuel mixture in addition to what is being drawn through the passage 29. At wider openings more heavy fuel is admitted and the sleeve 32 cuts off the supply of light fuel. Simple tapered needles moving in opposite directions may replace the needles 19, 30 and a rotatable barrel throttle may be substituted for the axially movable throttle 5.