From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Page 2 of a document describing the detailed mechanism of a carburettor, including its coned spring, bell, and tubes for automatic air-fuel mixture control.
| Identifier | ExFiles\Box 1\7\ B001_X15 20 46 50 59-page282 | |
| Date | 1st May 1916 guessed | |
| 2 102,043 pose is to act as a capillary evaporating surface to supply the petrol evenly into the inner tube 1. There is a coned helical spring 12 preferably made from spring steel wire, the convolutions of which are closely wound. The internal diameter of the small end 12A of the cone is made to fit the adjustable nozzle 9 and is adapted 5 to be fixed thereon near its upper end, and the external diameter of the larger end 12C of the cone is made equal to the internal diameter 1A of the inner tube 1 and forms a sliding fit therein. This coned spring is of a kind pre- viously proposed to control the admission of air to carburetters and its function is to throttle the air supply, the cone being adjusted automatically by the 10 variation in the vacuum created within the tubes by the varying speed of the engine under different loads. The coned spring may be inverted and the external diameter of the large end secured to the internal diameter of the inner tube, and the internal diameter of the small end of the spring made a sliding fit over the upper end 15 of the adjustable nozzle. As before mentioned, the inner tube 1 and the chamber 3 are secured to the base member 6, the inner tube being approximately 1½" shorter than the chamber and not supported at its upper end 1B, while the chamber at its upper end 3A is connected with the induction pipe 5. A gauze disc 13 is placed at 20 the upper end of the chamber to prevent back firing. The bell 2 is not fixed, but its lateral movement is limited by wire distance pieces 14 or the like attached to the upper end and the lower end of the bell. The bell with its crown 15 is preferably spun from some light material and the crown is in the form of an inverted cone, the point 15A of which projects 25 downwards to a short distance within the inner tube 1. If desired the bell may be supported at the upper end 1B of the inner tube. The bell rises more or less thus increasing or reducing the space 17 and admitting or choking the mixture passing from within the bell to the annular space 2D, when the engine develops a greater or lesser power according to its 30 load or speed. The tube 1 and the bell 2 are lined internally and externally with fine gauze indicated at 16, and the chamber 3 is lined internally only. A spring may be introduced to normally hold the bell against the base member, thereby demand- ing a greater vacuum in the outer tube before the bell will lift. 35 The carburetting starts within the inner tube. The induction stroke of the engine causes a vacuum in the tubular chamber which raises the bell and pulls apart the convolutions of the coned spring 12 thereby admitting air to the tubular chamber. The air passing through the coned spring plays on to the 40 gauze roll 10 secured to the top of the adjustable nozzle 9, and in its upward passage draws the petrol from the gauze roll. According to the amount of vacuum produced, more or less air passes between the convolutions of the coned spring and takes its charge with it. The mixture passes through the tubular chamber in the direction indicated by the arrows in Figure 2, the bell 45 crown 15 suspended over the inner tube 1 directing the mixture down to the base of the bell. Descending thence the mixture passes through the space 17 under the lower edge 2C of the bell, into the annular space 2D formed between the bell and the outside tube and is carried upwards in the said annular space under the influence of the vacuum and through the wire disc 13 50 at the top into the combustion chamber of the engine. It will be seen that the fuel mixture during its passage from the inlet for the mixture at the upper end 1B of the tube 1 to the induction pipe 5, passes through an expansion chamber of increasing size. It is well known that petrol comprises numerous particles having different 55 degrees of volatility and when fed to apparatus of the class hereinbefore described, the lighter and more volatile hydro-carbons will be immediately absorbed by the air introduced at the inlet end and induced to travel through | ||