US2373224A - Carburetor - Google Patents

Description

April 10, 1945. J. F. BUTLER E-rm.l

cARBUREToR Filed July 10, 1942 Patented Apr. 10, 1945 'l a cARBUaEToR f A VJaim *Francis Butler, Hoiywood; and Wiuiimif Bruce -McCausland Kllen,`

Ireland Belfast, Northern 'Application July io, 1942,'s`ria1N `i.450,4j5}zY f t In Great Britain July 29,1940 l `"Ciaims- (ci. 2614-48) This invention fentes to carbureting devices'for internal combustion engines using liquid fuel of the type in which a jet or jetsv for fuel enter an air inlet pipe at a point Where reduction of the area of the pipe causes alocal 4increase of air velocity through the pipe'and the consequent reduction of air pressure in the pipe is used to draw fuel into the air stream and thence into the engine.

In known devices of this kind all or the' greater portion of the air used for combustion is drawn l through the restricted pipe into which the fuel iiows and control of engine power and `speed is effected by'means of a throttle valve between the fuel jet or jets andthe engine.

-An object of the invention is to provide a carbureting device wherein an emulsion of fuel and air is introduced into the air stream at a position or positions where the air is flowing at high speed through a `relatively small passage of Venturi shape of which the outerend is `open to the atmosphere or to a point inthe engine air supply system upstream of the throttle valve and the inner end opens into the engine main air inlet pipe preferably on or near the central faxis of the said pipe at a point 'where the air velocity and consequent reduction of air pressure'is suflicient to promote the required airflow through the said venturi but is not necessarily greater thanthe general velocity and reduction of pressure through the inlet pipe. lControl of engine powerl and speed is effected by means of a throttling device controllable bythe operator of the engine in the engine mainair inlet pipe at aV position between the end of the venturi vwhere it enters the engine main air inlet pipe arid theend of the engine air inlet pipe wherei't is open to the atmosphere, working in conjunction with'ine'ans for varying the amount of fuel in the emulsion entering the Venturi passage consisting ofvalves varying the effective area of passagesconnecting a chamber int-ol which a fueljet discharges withthe'said venturi and with a position at `which vthe air f pressure is higher than at'the' saidpositionin the venturi.

` There mayals'o be a jety or jets admitting fuel to other positions in the carbureting device and the 'flow of fuel through these jets may or lmay not be controlled by means Vconnected with Vthe throttling device.'V I The carbureting device according Vto this invention may be used in conjunction with an engine supercharger placed ,either between `the carburetor andthe atmosphere orbetween the carburetor and the engine. f i i H i 1 i In the accompanying drawing a constructional example of the invention isl illustrated.'

Figure 1 shows an' axial section through a car-- bureting device according to 'the invention.

Figure 2 `shows another axial section takenv at right'angles to that shown in Figure 1.

Fig. 3 is a section detail viewof a modified form of control valve for use in the arrangement shown in Fig. 1 instead of that shown at the left haffld f .Sad gurel 'Fig'. 4 is a vsectional detail view showing a further form which may be taken by the valve plunger4 at the left hand 'side of Fig. l.

Fig. 5 is a sectionaltdetail view of a further form-of the'valve plunger at the left hand side offFial. l

' Figfdis a sectional detail View of a modification "of 'the "fuel jet Vat theright hand side of Fig.1.4

Referring to Figs. 1 and l2 of the drawing:

The carburetor comprises a Venturi passage l connected at its upper end to the U-shaped passage Z'Which is open to atmosphere and at its lowerv end to the engine airsupply pipe 3f connected'to the engine. Theengineair supply pipe 3 is directly connected Iat its upperend to the atmosphere andY contains a throttle valve 4 which is controllable by the engine operator, by means l not shown, for varying the .power output of the engine. f f

- There-is `provided a oatrchaimber 1 in which the fuel is kept at a constant level in known manner by a float 8, bell crankl'ever 8fand needle valve 9. From the oatchamber 1 the fuel flows through the passage I0`to` jetsI Il and I2.

The` liquid fuel jet IIis provided in a sleeve I6 screwed into the bore 16a` and is controlled by a taper needle I3 on a plunger I4 which has fuel passages or Vfiutes I Iaregistering with the holes I5 in the sleeve, Whicnholescornmunicate with an annular space' l's'urrounding the sleeve IS and connected by thepassa'geI 6 to the downstream end of venturi I. The holes' I5 are locatedabove the level of the fuel in the float chamber so vthat they do not come into operation and supply fuel until the engine speed has increased the depression in the 'main air inlet'pipe 3 to a, predetermined arno'un't. The plungerliasA a `head 16 urged upwardly'by a compression spring IIC` into contact with an arm of a rocking lever 21.

' 4The jet I2` is provided Vat the foot of aslceve 33 screwed into a boreSIlv and the jety enters the chamber I1 zof which the uppersurfa'ce is formed v by the bottom of a 'plungerml slidable in the sleeve 33. The plunger I9 consists of' upper and upwardly into engagement with the rocking lever-vv 2`| by the spring lh. The chamber communicates with another chamber formed by the waist I9c and sleeve 33 throughholes 2 .I andv 22 and annular space 23 between, the sleeve 33 4and `bore 34.' Chamber '20 communicates with the atmosphere through holes 24 in the sleeveand with venturi I by means of holes 25 and annular passage 25a in the sleeve 33 and passage` 5.

The throttle 4 has attached to it a cam 2s engaging an arm of 4the rocking lever 21.

The rocking lever 2'I is mounted on an accentric bush 28 attached to thelever 29. l

In operation fuel passes. from the float chamber through: passage I0 to the jetlt through which it passes; and up tothe flutes-I4, through the holes I5 into thev space ISP and thence through passage 6 into the air stream near the outletgend of the venturi I.

Fuel also passes from the .float chamber I along the passage l0 and through the jet I2 into the chamber -Thischamber is in communication with the atmosphere through the passages |8. and |82. A mixturey of air and-fuelpasses from lthe, chamberl via holes 2|, space23 and holes 22 to the chamber 20. Here it mixes with more air which enters by thel holes 2,4 andY then passes,Y into the top of the venturi and so into the airstream by the holes 25, passage 25at and vpassage 5. VIt will bei seen. that vertical movement of the plunger will vary the effectivey area of the holes 2,2 and 2,4. As the throttle 4, is opened from the substantially closed position shown the lever 2 1 willl depress the plunger I9- and will decrease the effective area of holes 24,and increase that of the holes 22. Thus the supply of air through the holes 24 will be decreased-,and the supply of air-fuel mixture through the holes 22 vwill be increased. A t the same time the plunger I4 will rise under the spring action and progressively open the jet and commence or increasethe supply of fuel, through the passage 6. f Thus variation inthe amount of airflowing to the engine through the inlet .pipe 3 effected by movement of throttle 4 is accompanied by variation of the` amount of fuel flowing tothe engine through With the throttle 4 stationary, movement of the lever 29 and bush 2,8causes a movement of lever 21 and varies the relative positions of the plungers I4 and I9 and thusvaries the proportion of fuel to-airin the mixture supplied to the engine. It will be understood that the spring 19 will be stronger than the spring I6d so as always to keep the'lever 21 in engagement with the cam 26. l t

Fig. 3 indicates an arrangement similar to Fig. 1 except that the valve plunger |9,l has lthe lower part and the passages Ill-'omitted so that control-of the supply of fuel-.airemulsion is effected solely by control of the air ports 24. Otherwise the operation -is the same as inFig. l.

Fig. 4 shows a further modification ofthe are rangement Qf Fie. 1. in` which the upper part 0f the waist is cylindricalbelow the shoulder 3,0 and` thus control of the supply of fuel-air emulsion is effected solely by control of the ports 22 but other- Wise the operation is the same as in Fig. 1.

Fig. 5 shows a further modification in the form of the plunger I9, in which the Valve plunger waist I 9 is formed with a central cylindrical portion and two frusto-conical parts 3|, 32 so spaced as to act consecutively on the respective ports 22 and 24, 'the ports 22 being fully open while the ports 24 are being varied and vice versa. It is to be understood that the forms of the plunger 9 shown in Figs. l, 3, 4 and 5 are only by way of examples and that the shape of the waist |9c, may be varied in any desired manner to suit the fuel demands of the engine for varying throttle openings.

. Fig. 6 shows a modification of the jet Il of Fig. l in that the control needle valve is omitted to give a more or less constant supply of fuel. This constant jet form may beused in combination with the fuel-:air emulsion jet as shown in n Figs. l, 3, 4 or 5.

The carburetor as described offers several technical advantages over existing practice. The following areA some of these advantages:

(a) Provision of weak mixture at part throttle openings for economy. By arranging the small venturi sothat the` airA flow through it is controlled by the pressure drop across the throttle 4, a limiting air speed and depression is reached in the low pressure zone at a lower engine speed than the normal running speed for the throttle opening concerned. As the engine speed increases from that giving limiting air speed in the small 5 venturi to normal running speed the amount of fuel discharged from the main jet remains unaltered while the amount of air passing through the main air inlet continues to increase, so the mixture becomes, progressively weaker.

(b.) provision of correct mixture at full throttle at all speedsv byy controlling the flow from the main jet I2 bymeans of variable area, air bleed 24 and associated mixture passages.

(c) Provision of'correctmixture at full throttle at lowspeed by means of low air pressure in the small venturi I. If the main air passage 3 were reduced in area to give as great a reduction of pressure in itself, full speed performance would be. penalised by the consequent lreduction of air flow.

(d) Promotion of good mixing and distribution by concentration of rich mixture from the venturi in the centre of the main air passage'3. This advantage rwould be nullifled if the throttle were located downsteam of the Venturi outlet because the mixture would then have t0 go round the edges of the throttle valve.

(e) Fine 'pulverisation of fuel droplets by means of high air speed in the small venturi I. (At part throttle this air speed is controlled by the pressure drop acrossvmain throttle valve 4.

(f) Improvement of vconditions for starting. The upstream positionl of the main throttle valve 4 obviates the need for a separate strangler. Rich mixture is obtained by operation of the separate mixture control. The advantage of this is thatwith the mixture control set at rich" as the throttle is opened the mixture graduates to normal and vdangerof cylinder wear due to liquid fuel reaching cylinder walls is reduced.

What we claim is:

l. A carbureting device for internal combustion engines using liquid fuel comprising a body member, a main air supply conduit 4in the body -member in communication with an air supply, an

`operator controlled throttle valve in the conduit, a secondary air supply Venturi conduit having an inlet end in connection with an air supply independently of control by said valve, an in- I termediate zone of restricted cross sectional area and low pressure and a discharge end located downstream of said throttle valve in and sur-V rounded by and facing downstream `of the main air supply conduit, means for supplying an emulsion of fuel and air to said zone which com- ,prises a guide bore in said body, a valve plunger slidably guided in said bore and including end parts which area close sliding fit in said bore and an intermediate waist of reduced varying cross section, a first chamber formed by an end of said bore and one of said end parts, a liquid fuel jet of constant area discharging into said chamber, a second chamber formed by the wall of said bore and the surface of said waist, a'first and second port in the wall of said bore respectively inthe first and second chamber, passage means connecting said ports, a second and third passage means respectively from a source of air at higher pressure and from said restricted zone, a third port and fourth port in the wall of the bore forming part of the second chamber respectively being terminations of said second and third passage means and a fourth passage means independent of controls by the throttle between a source of air at a higher pressure and said first chamber, and connection means between said throttle valve and valve plunger to cause simultaneous operation thereof to maintain the supply of fuel and air in the relative desired proportions, the axial movement of the plunger causing the wall of the waist part to vary its proximityto and consequent control of said second and third ports.

2. A device as claimed in claim 1, in which said waist has oppositely tapering parts located to cause simultaneous and opposite control of thel second and third ports.

, 3. A device as claimedA in claim 1, in which said waist has two oppositely tapering parts located to cause opposite and consecutive control of said second and third ports.

4. A `device as claimed in claim 1, including a float chamber and having additional means for supplying `fuel comprising a further guide bore in said body member, a fuel jet communicating therewith, a slidable member in said bore having a needle valve controlling said jet and a body portion having grooves, an outer chamber communicating at a level above the fuel level in the float chamber through said grooves with said jet, and a conduit from said outer chamber to the downstream end of said Venturi conduit, and

wherein said connection means comprises a lever i having one end engaging said plunger valve and the other end engaging said slidable member, an eccentric pivot for said lever intermediate CTL lever and the throttle valve and means for adneous positions of said throttle valve with reference to those of said plunger and needle valve. v 5. A carbureting device for internal combustion engines using liquid fuel comprising a body member, a main air supply conduit in said body in communication with an air supply, an operator controlled throttlevvalve in said conduit, a secondary air supply Venturi conduit having an inlet end in connection with an air supply independently of control by said valve, an intermediate zone of restricted cross sectional area and lower pressure and a discharge end located downstream of said throttle valve in and surrounded by and facing downstream of the main air supply conduit, a float chamber for supplying fuel, means for supplying an emulsion of fuel and air to said zone which comprises a guide bore in said body, a valve plunger slidably guided in said bore and including a part which is a close sliding fit and a part having a reduced cross section which varies in the direction of movement of the plunger, chamber means formed by the bore and the end of said plunger, a fuel jet of constant area discharging into said chamber means, a passage between said zone and chamber means and a second passage independent of the throttle ing grooves, an outer chamber round said bore,

port means between said bore and outer chamber located above the level of the fuel in the float chamber and communicating with said jet by lmeans of said grooves, `and passage means between said outer chamber and the downstream end of said Venturi conduit, and a connection between lthe throttle valve, plunger and slidable member comprising a rocking lever respectively engaging said plunger and slidable member at opposite ends, an intermediate eccentric pivot for the lever, a connection between said throttle valve and lever to cause simultaneous operation of said throttle valve, plunger and slidable member and means for adjusting said pivot to adjust the relative simultaneous positions of said plunger and slidable member with reference to that of the throttle valve.

JOHN FRANCIS BUTLER. WILLIAM BRUCE McoAUsLAND KnLEN.

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