A NEW CARBURETTER.
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Adapted for Use with the Heavier Grades of Spirit and With Paraffin.
A new carburetter with many excellent features, and with which the makers, the Birmingham arid Midland Counties Transport Co. Ltd., and the inventor, Mr. G. E. D. Rails, of Bradford Street, Birmingham, have been experimenting for some time, has recently been patented. The object of the esigners has been the provision of a carburetter suitable, without addition or alteration, for working with paraffin as mit as with petrol. The line followed has evidently been that of eliminating from the essential carburetter part of the component all complications and particularly any impediments to the quick passage of the mixture of vaporized fuel and air to the engine. This object is attained mainly by the unusual design of the throttle valve, of which a detailed description follows, Not a little interest, however, attaches to the design of jet, which is of the type which is controllable by hand, either independently or in conjunction with throttle variations. A central standard communicates at its lower end with the float chamber. It is suitably bored from the bottom for about two-thirds of its length to receive a plunger, past which the fuel is permitted to flew along a helical groove. To the top of the plunger is secured a taper needle Which-protrudes through a hole in a diaphragm situated in the in-, terior of the standard. The plunger is movable vertically, and in
its topmost positidn closes the. jet orifice and cuts off the fuel sup
ply absolutely. As this procedure may he effected independently of the throttle, clearly it is possible. to arrange for, the engine to draw in supplies of pure air
only—a useful procedure, for example, when descending -a long hill. Above the diaphragm—which is fitted with a renewable disc, by changing which adjustments may be effected, as when, in the usual type of carburetter, a new. jet is fitted—the fuel emerges from the interior of the standard through horizontal jets, as shown in the illustration. The exterior of the top of the standard is enlarged, and forms a seat for the interior of the throttle valve. Other details of the design of the jet may be noted hy reference to the drawings
frieotin
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which we reproduce. They are Mainly constructional, and do not affect' the principle of its working.
Now to discuss the most important feature of the carburetter—its throttle valve. The inlet passage from the atmosphere leads to the inside of a hollow piston-like part which, in its closed position, beds as to its inner surface on the exterior of the standard which suerounds -the jet. The interior is a modified Venturi form of passage, the "throat being so disposed that, when the valve is closed, it is opposite the lateral fuel 'on
flees. Outwardly, this throttle valve is shaped like a trunk piston: with a bevelled top. The lower part, or skirt: bears in a bored• portion of the 'carburetter casting, and it has a helical slot cut in it, by means of which, through the medium of a lever working in a horizontal slob in' the carburetter body, the valve is operated by being elevated or depressed. The upper cylindrical portion of the valve fits in an obturation of the main body of the chamber, and the too coned -part, when the valve is closed, beds against a corresponding shaped seat. It will be clear, from a consideration
of this construction that the first movement of the'valve, although it causes the bevelled top iof the outside to leave its seat, does not immediately open a passage at this point. ,It•does in only in the interior of the valve at its junction with the outside of the central ,standard. Th-Ore is, in consecpence' -a fairly strong suction past the horizontal jets, and this is rendered the more effective owing to the particular shape of the interior of the valve. As the, throttle if further opened, the interior opening increases,
and so also does the area of the space round the jets, up to a cer tain point, when the latter ceases to increase. The turnedeouter portion of the valve thensleaves its guide, and air is allowed to enter through the annular opening thus formed. The object aimed at is the maintenance of a constant Velocity of air past the jets ; further, by the elimination, of a separate throttle valve above the mixing"' chamber, and disturbance of the mixture front this cause—which is well known to he a principal source of .initial recondensation—is avoided.
The float chamber, as well as the body of the carburetter, and the induction pipe, are suitably jacketed, and may , be heated -either by exhaust gases or hot water. Anlactual carburetter which we recently examined has been in use for some time on an " Allday's " tractor, on which, we understand, it was given good service, 'using paraffin as a fuel.
• Although designed and . intended for use as a paraffin carburetter, this component plainly does-not follow the 'usual plan of
fittings intended for use with the heavier and less volatile fuel. The exhaust-heated vaporizer, as a separate -entity, is absent, its'place being largely taken by the thorough jacketing which forms a feature. If it be found, and experience gained with the,Alldays tractor goes to confirm this, that the jacketing is an efficient alternative, then the design is commendable if from no other. standpoint than that of simplicity of design. The idea of removing all obstacles from the path of the mixture, from induction to cylinder, although not novel, is undoubtedly sound.