US1705282A - Carburetor - Google Patents

Description

CARBURETOR R. F. B RACKE Filed Nob. 21, 1921 O fr f Q March 12,1929.

' 25 vide a carburetor with a 35 the smallest engine vPatented Mar. `12, 19,29. l y I' STATES iATEuT. o'FFics'.

noBEn'rr; Buscar, or CHICAGO, ILLINOIS, Assuntore., BY'MESNE AssIeNMENrsgr y oUnrIs n. CAMP, rnusriin, or oai: ramt, rumors. y

, AppIication tiled November 21, 1921. Serial No. 516,582.

My invention relatesto carburetors, and has for itsgeneral object the provision of means for feeding fuel .from a supply reservoir to a carburetor located above the reservoir. My inventionis illustrated in the form for application to a stationary engine, the

speed of which is controlled by a governorv driven from the engine.

One object of the invention is to provide a 1o carburetor in which an extremely rich mixture is delivered through a' small Venturi tube into the main stream of air flowingv through the carburetor casing, the structure being` such as lto substantially compensate for the over-richness at high engine demand which is ordinarily characteristic of a fixed orifice carburetor. v i

Another object of the inveiitionis to so locate the governor controlled throttle that it assists in bringing about the compensation by constituting agreater restriction to the maininduction passage `than to the Venturi tube discharge for low engine demands.

A further object of my invention'is to pro fixed main air intake for all engine demands, and in which the fuel is fed to the intake passage througha very small Venturi tube leading from atmosphere into said passage.

'A further object of the invention is to provide a nozzle Venturi tube constituting a primary air' intake in combination With a fixed ksecondary intake both together constituting such 'a restriction to the flow of air-that, for demand, the suction at the throat of the nozzle Venturi tube will be at least sufficient to lift fuel a distance equal to the height ofthe nozzle above the base of the fuel supply tank plus seven times the depth 4o of the main supply tank so that the difference in height of fuel lift will under no conditionsv be more than fourteen and one-half per cent of the fuel lifting differential;

Still other'objects of the invention will appear from the following detailed description.

" My invention is illustrated inthe accompanying drawing kwhich re resents a section through a carburetor, the rawing also illusti'ating an engine'driven governor connected with lthe carburetor" anda low level supply y tank.

A main casing .1` provides the induction passage located, operatedlby a rod 4 connected with a u governor mechanism 5 driven by the engine,

2 in which a butterfly throttle 3 is not shown, which is being lsupplied with fuel from the carburetor. The entrance to the in-l duction passage 2 is restricted at 6, the size of-this opening being fixed as to size, depending upon the cylinder displacement of the enine.A

For starting purposes, a choke 7 controlled by lever 8 is provided, which in its illustrated position entirely closes. the entrance to the induction passage,butwhen moved to its a1- ternate position affords alfreespassage for'air into. the induction passagefrom the air tube 9, which in practice may connect with the` engine crank casing or with soine other suitable source of warm air, such as a so-called exhaust stove. In practice this choke may be set to constitute a slightly greater or less restriction to compensate for differences in fuel quality and to that extent is manually fixed for ruiming conditions at a certain posiion.

' Fuel is supplied to the induction passage through a small Venturi tube 10, entering the induction passage at an angle to the flow of air therethrough. This Venturi tube is provided with fuel openings 11 which are in communication With the main sup ly of fuel in the low level tank 12 by means cfa pipe 13, this pipe being preferablyv provided with a check valve 14, permitting the fiow of fuel in one direction only. The external end of the Venturi tube 10 is'provided with a cap 15 having a baffle 16 therein to prevent the discharge of fuel from the externalv end of the Venturi tube by the suction strokes of the en ine. i

n operation the clioke 7 is closed and the engine rotated. At this time, the speed of the engine being far below normal, the throttle 3 is in substantially its wide open position, All of the air drawn into the'carburetor in starting the engine passes through the Venl turi tube 10, creating `a high suction at its throat, drawing the fuel from thelow level sup ly tank to the nozzle openings 11, and disc arging it in a fine spray into the induction passage 2, engine cylinders through the intake manifold, notshown. As soon as the first explosionsare obtained, the choke 7 is opened, preferably first to a position somewhat less than full open, but'as the engine warms u the choke is opened to its final position. s the speed of the engine increases, the governor balls cause the rod 4 to be pushed up- Aso whence it is vcarried to the duction passage 2, and Will be crease in suction of l0 Wardly partially closing the throttle 3 to hold the engme to a substantially constant predetermined speed.

The suction reduced in the induction chamber 2 is su stantially the same as that on the engine side of the throt-tle 3 when the throttle is ,Wide open. Under these conditions, the discharge end of the Venturi tube 10 is subjected to this suction. As the throttle 3 approaches its closed position,vthe suction on the engine side of the throttle becomes proportionately-greater than that on the an terior side of the throttle, but since the discharge end of the venturi 10 communicates with the induction passage at a position Where it is subject part-ly to the suction on the engine side of the throttle 3 and partly to the suction anterior to that throttle, the suction acting upon it will, under all conditions excepting for Wide open throttle, be somewhat greater than the suction in the in- Vconsiderably greater for the substantially closed position of the throttle 3. This arrangement `com-` pensates for the tendency of the Venturi tube to deliver a greater proportion of fuel for high air velocities than for low air velocities. This tendency to richness at high velocities is also partially overcome Iin my structure by the fact that the Venturi tube 10 is made'so small that it does not, under any condition of` operation, deliver all of the air necessary for the operation of the engine. This results in the Venturi tube delivering at all times a mixture of fuel and air Which is over-rich of fuel, the mixture becoming correct only as that part `which is delivered through the Venturi tube is co-mingled with that air which comes through the induction passage 2. lt is characteristic of a Venturi tube which is feedingy a very over-rich mixture that the suction ef-` iciency of the Venturi tube isgreatly decreased by a comparatively small increase in fuel Hovving from the nozzle openings in the Venturi tube. To make this statement more specific, let it be assumed that a suction at the discharge end of the Venturi tube l0 equivalent to 30 of gasoline in a manometer tube under idling conditions produces asuc tion of 60 of gasoline in a manometer .tube at the nozzle openings 11 in the Venturi tube. It it `Were not for the rich mixture of fuel and air passing out of the Venturi tube, an inat the discharge end of the Venturi tube would result in an increase of substantially 20"l at the throat of that is, under a change' results in a partial compensation for the tendency to over-richness lat high engine demand. l

In the intake passage of four cycle, single cylinder engines, there is often a slight resurgence of air between the suction strokes. This resurgence may be caused by the intake valve ybeing opened slightly 'after the closure of the exhaust valve at the end of thescav'- enger stroke, or it may be caused by the intake valve failing to close until after the crank shaft has passed deadfcenter at the end of the intake stroke. In some engines, it may also be caused by the mere flexibility and inertia of the air in the intake passage; the liow of air being suddenly cut off by the Closure of the intake valve will be slightly compressed by the inertia ofthe column of air in the intake passage and Will again slightly expand. It may a so be caused by the fact that the air when taken into the intake passage is comparatively cool and has an opportunity to become heated during the non-suction period of the engine, the heat expanding the air and causing it to resurge. Any one of these conditions causes a putti of air in an outward direction through the Venturi tube l0 and carries a small amount of fuel out of the carburetor into the atmosphere unless provision is made to retain the fuel. For this purpose, a cap 15 and baille 16 are provided, the liquid fuel being collected within the cap and being drawn back into the `carburetor upon the neat inovv of air on the suction strokeo l .have found it to be tance that the 'throat of tube and the size of the restriction at the entrance to the induction passage be s`o small that 'for the lowest engine demand, the suction produced at the discharge openings in the Venturi tube will be far in excess of the suction necessary tor lifting fuel. T the suction at the throat oit the nozzle Venturi tube Were only great enough to lift fuel from the base of the supply tank, then the change in fuel Jfeeding dilerential it the tank were filled would be se great that the proportion alit of fuel to air would be so greatly distur ed that the mixture 'would be. very much of extreme impor-- the nozzle' Venturil ovr-rich. l have found by experimentation y tube is equal to the actual maximum. fuel lift i plus at least seven times the possible variation in tuel head in the main tank. Tn other Words, T have discovered by experimentation that the fuel `feeding' diiderential on each side et the nozzle restriction mu'st be at least seven times as great as the os'sible change in the litt on the tank side otp the nozzlerestriction. ll believe that l am therstto have discovered that a suction greatly in excessof the necessary suction forglitting :tuel to 'the nozzle ist . the supply tank,

Although I have shown and described my f invention with respect to certain details of construction, it should be understood thatV modifications ma be made without departing from the spirit or scope of my invention.

What I claim is:

1. In a carburetor, lthe lcombination with an induction passage having a -secondary air intake opening manually fixed as to size,I of a choke for said intake, a Venturi tube extending from atmosphere and .discharging into" said induction passage, a low level supply tank, a `pipe connecting the low level supply tank with discharge openings at the throat of said Venturi tube, the fixed openings into the induction passage and vatthe throat of the Venturi tube being so small that the suction produced at the fuel openings in the Venturi tube at the smallest engine demandwill be at least sufficient to lift fuel fromthe base of the low level supply tank plus a distance seven times as great as the possible variation in fuel level in the supply tank, whereby not more than fourteen and one-third percent change Ain fuel feeding differential will result from a change of fuel level from the substantiall empty to the substantially full condition o the supply tank.

2. In a carburetor provided with aimain ing admitting the greater portion of the air through said inlet opening,

air inductionv passage having an inlet openfI to the engineserved by the carburetor, a small Venturi tube having one end sub]ected to the depression within said induction passage between said inlet opening and the engine and having the other end exposed to atmospheric pressure, a fuel dischar e port at the throat of said small Venturi tu e, a low level source of fuel sup ly in which the level of fuel varies'throug 1 a wide range between the full and the empty eonditions'of the fuel tank, a conduit leadingfrom said fuel tank directly to the nozzle opening in said small Venturi tube, the size and proportions of the `air oritice through the Venturi tube and that being such that during the least fuel mixture demand of the engine to ,which the carburetor is attached, the suction at the throat of the Venturi tube and available for lifting the fuel from the low level source of suppl to the carburetor and discharging it into the air passing through the Venturi tube isequivalent to that necessary to actually liftthe fuel plus at least enough to lift fuel seven times the height of the variation in fuel level fromlowest to highest levels in the main fuel supply tank whereby A supply tank will not materially alter the power output of the engine to which the carburetor is attached.

In witness. whereof, I hereunto subscribe my name this 22nd day of October, 1921.

ROBERT F. BRACKF variations in fuel level in the mainv

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