US2346711A - Carburetor - Google Patents

Description

Api-il 18, 1944. L', F, STUPECKY 2,346,711

CARBURETOR Filed Dec. 15, 1941 Patented Apr. 18, 1944 AUNITED STATES egTENT OFFICE CARBURETOR Ladimir F. Stupecky, Manitowoc, Wis.

Application December 15, 1941, Serial No. 422,965

` 12 claims. (o1. zei-.41)

This invention relates to new and useful improvements in carburetors more particularly adapted for use in connection with internal combustion engines and consists in the matters hereinafter described and particularly pointed out i the appended claims.

One of the objects 0f my invention resides in the provision of a carburetor for internal cornbustion engines which is ecient in operation in a comparatively long range of varying altitudes without the aid of a fuel pump, or the well known vacuum fuel-supply tank, irrespective of the posi tion of the main fuel supply tank relatively tof` the carburetor.

Other novel features or objects of my invention may generally be stated as follows:

(a) During the operation of the carburetor, its sealed fuel chamber maintains a constantlevel supply of fuel below atmospheric pressure and insures quicker engine acceleration because of the control of the pressure in the fuel chamber directly by the vacuum within the engine cylinder manifold;

(ZJ) Proper proportions of combustible fuel mixtures are supplied to the engine at all engine speeds. During the increase in speed or power' of the engine, the proportionate flow of the fuel to the air is relatively slightly decreased so that the combustible mixture is automatically made leaner progressively with the increased speed of the engine with the result that not only fuel economy is attained but also increased power and smooth engine operation;

(c) The automatic control of the proper fuel mixtures for varying engine speeds and the advantages resulting therefrom, as set forth --in above paragraph (b), are attained through the interposition of a buoyant fuel-metering receptacle between the fuel supply jets and the fuel supply in the fuel reservoir;

(d) The buoyant fuel-metering receptacle, due to its limited fuel capacity, functions also to prevent 'flooding of the engine cylinders inV quick starting with a closed choke valve; and

A 4 (e) A novel means for adJustably varying the cross-sectional area of. the venturi is provided. through a plurality of telescopically mounted or concentrically disposed plurality of tubes which extend through the carburetor air inlet passage 50 into the'zone of the venturi below the main `orA high speed fuel jet. Through the arrangement Y of such concentrically nested and removably supported tubes, a standard size of carburetor may engines of varying piston displacement and varying crank shaft speeds.

With the above and other objects in view, my invention consists in the novel combination, construction and arrangement of the parts and members shown in preferred embodiment in the attached drawing, described in the following specification, and particularly pointed out in the appended claims.

In the drawing:

Fig. 1 is a vertical section through a carburetor embodying my invention;

Fig. 2 is a cross-section taken on line 2-2 of Fig. 1; and

Fig. 3 is a partial vertical section showing the use of shorter restrictor tubes whereby the carburetor shown in Fig. 1 may be adapted for proper air supply in an operation with an engine having an increased piston capacity.

The carburetor, as illustrated in the attached drawing, is provided with an air intake passage EEI, which may preferably be provided with an auxiliary or choke valve II, and a suction or outlet fuel passage I2 provided with a control throttle valve I3.

The valves II and I3 are centrally supported on rock shafts and operated by suitable means in the well known usual manner.

The throttle valve I3 and the fuel passage I2 are disposed in the upper member I4 which is cast with a suitable flange I5 for connection to an engine manifold, and the integral ears Iii are adapted to receive suitable cap screws I'I for securement of the upper member to the lower member I3 in which the air inlet passage IIJ and choke valve II are disposed.

I have preferred to show three screws I1 for securing the member I d to the member I8 and the proper alignment of these members is insured by preferably providing an annular extension I9 on the lower face of the upper member I4 which is adapted to be positioned in an annular recess 20 formed in the upper face of the lower member I8.

The upper member I4 is so formed that the fuel passage I2 is restricted in diameter near its lower end to form a Venturi throat 2 I.

The lower member I8 is formed with an integral inverted cup-like extension 22 which is closed at its open lower face with the closure wall 23 and which extension 22 and closure wall 23 enclose the constant-level fuel chamber 24.

The fuel chamber 2d is supplied with fuel through the usual fuel connection 26 controlled be adjustably adapted for operation'with s'everalfffby the valve 2l. A valve seat clean-out plug 28 is preferably provided in the connection 25 which is a part of the closure wall 23.

The fuel supply is maintained at a constant level by a suitable float 29 in the fuel chamber 24 which is operatively connected to the Valve El' by the forked lever 33, pivoted at 3l between the ears 32, and having its forked end in engagement with the collar 33 on the lower end of the float tubular extension 34 and its opposite balllike end 35 positioned in a recessof the valve 2'I.

The oat 29 isfreely movable .up and. down upon the pin 33 which extends through the float and its tubular extension 34 and through the closure wall 23 into threaded engagement with top wall of the extension 22.

A nut 3l on the lower threadedl end v 38,01? thepin 38 is adapted to secure the removable closure wall 23 to the extension 22.

The lower member I 8 is formed with a fuel well 39 and, as illustrated in the drawing, this fuel well 39 is preferably disposed between theair inlet; Ill and the fue1 chamber 24.,

The fuel-well 3S is provided-with. a vertical elongatedv opening., 43 to permit yfree passage; of fuel therethrough from thefuel lchamber 24, and this fuelv well 39,-is alsoproyidedwith an opening` lll to provide communication withtheair inlet passage I3. Itr will be. noted that the vertical opening 43 extends above the nQrmaLconstant fuel level X of the fuel chamber; 2.4:; that likewise thel transverse opening 4I. is disposed well above the fuel level X, andi;. thatthe yopening 4I is positioned slightly-below the-,Venturi throat 2I wherein the flow of air through the inlet Igpast the opening 4I will create a partial vacuum, in the well 39 and in the -otherwise sealed fuel chamber 24. Since a partial vacuum is maintained in the fuel chamber 24 Vduring theoperaf tion of the carburetor-an adequate fuel supply in chamber 24 is assured.

A buoyant fuel-metering receptacle 42 is positioned in thewell 39. The fuel-metering receptacley 42 is `formed from comparatively thin. metal in the shape of a vertically disposed elongated cup-like body of circular crosssectionopen, at its upper end, and formed at its lower end with a Wall 42Ahaving-,a fuel inlet opening 43 therein. The fuel is suppliedY from the fuel chamber-'24 through the vertically disposed opening. 4t into the well' 39 and through theopening 43 into the receptacle 42. When the carburetor is in anl inoperative state, thereceptacle is lled with fuel to a level aligned with the fuel level X ofjthe fuel chamber 24 and the bottom of the receptacle l2 rests on the plurality of small opstanding lugs or projections 44, formed integrally with the upperface of the bottom of the well 39, to insure a free flow of fuel under the bottom of the receptacle42 and through the-inlet opening 43 into the receptacle 42.

The main nozzle, generally indicated by numeral 45, consists of a horizontal tubular jet 46 having a discharge end 4l extended into the center of the Venturi throat 2I and formed *withportv 50A extending vertically downwardly and;

this port A is disposed substantially centrally relatively to the well 39 and metering receptacle 42.

The high speed horizontal jet 46 includes a vertical tubular extension 48A which extends from the port 53, through the port 53A, into the metering receptacle 42 to a point below the fuel level X of the fuel chamber 24.

The carburetor is provided with a low or idling speed fuel outlet port 52 controlled by a fuelregulating screw-mounted adjustable pin valve 53. The outlet port 52 is supplied by fuel through thek vertical port 54 which is connected, at its lower end, with the vertical idling jet extension 55;

If desirable, the port 54 may be provided with a check valve, as for example a metal ball, to positiveiy; preventl the flow of the fuel into and through the idling speed outlet port 52 during the operation of the engine when the fuel is being discharged from the nozzle 45.

Theidlingjet extension-55 4is smaller indiameter. than the main or high speed tubular jet extension 46A, extends throughthecenter of the extension` 43A, and isV provided with avhorizontal, jet extension 55A extending withinand centrally of the enlarged passage 490i thehorizontal high speed .iet 43.

-The-vertical idling jet extension 55. extends kdownwardly below the lower end of the4 verticalv high speed jetextension 46A, is preferably flanged atfits lower end, as indicated. by. numeral. 55,3', and is provided with` fuel inlet slots 25 extending; through the flange 55B and into thelower. part of the `extension 55.

As indicatedabo-ve, my inventionincludesnovel. means for adjustably varyingthe cross-section .of the, Venturi ythroat and same` consists improvldr ing anupstanding pinn56 having a flangel'jcon.- nectedby screws 58 to abottom portion ofthe.v carburetor lower member I 8.

Asshown in vthe illustrations,A the pin ex.HV tends into the air inlet passage I0 and its.upperend .is disposed. within the zone of theVenturi throatll and,`obviously, this pinv 56 itself acts as acentrally disposed restrictor for the Venturi.

`In order to further adjustably Variably restrict the Venturi throat 2| so that a standardsize of. carburetor maybe operatively adapted to anumber `of engines varying. in piston displacementyl, provide, andsupport about thepin 56, a plurality of 4ooncentrically arranged `removable tubular restrictors 59, 30, 6I, 62 and 63 in' telescopedanA rangement about the pin 56.

They upper ends of the tubular restrictors areground to form aconical face generallyindicated-f by numeral 54, and, as shown assembled insthe illustrations, clearly illustrate the maximum restricted venturiv for thev comparatively smallest.r engine adaptation. Forsenginesiof comparatively-- greater.pistondisplacements one or moreof'the tubular. restrictors may be. removed Yto .proporetionately increase the cross-sectional areaaof the venturi tosuit the piston displacement..

When any ofthe-restrictortubes are removed in .adapting the. carburetor. to engines of greater: piston displacement;` the removed'restrictorszfarei replaced by shorterv tubes 59A; 60A and,y 6I'e"hav. ingupper.; endsV groundi to fit the contour` of ther` curvedgwall IGAl of theairinlet Ill, asfillustratediv in Fig ..3. y

Anyfsuitable g means for securingv the; restrice` tors 59.ftof63'inclusive maybe provided.Vr Ihavee fpreferredfto `use .apap-screw 65rhavlnga pinelikea extension 66 extending through aligned openings v near the lower end of the restrietors. The pinlike extension 66 also functions as means for indexing the tubular restrictors for properly positioning the shorter filler restrictors 59A, .IIlA and SIA with respect to the curved face. II)A of the air inlet I0.

The func-tion of the choke valve II is well un. derstood in the carburetor art, however, it may be stated that in a quick engine starting operation, with the choke valve II in closed position,

the fuel will be forcibly rapidly withdrawn from the metering receptacle 42 through the idling jet In the acceleration of the speed of the engine,

as the throttle valve I3 is gradually progressively opened, the iiow of the fuel from thedischarge port 52 will cease, but fuel will immediately be discharged into the Venturi throat 2I through the high speed jet nozzle 45.

In the initial stages of such progressively increased speed of the engine, the fuel discharged from the high speed jet nozzle 45 will flow from the metering receptacle 42 through the high speed jet extension 46A and also through the idling jet extensions 55 and 55A. I

During such initial stages of progressively increased engine speed, the fuel will be withdrawn through the extensions 45A, 55 and 55A from the metering receptacle 42l slightly faster than it be supplied to the metering receptacle through the opening 43, hence the head pressure of the fuel in the metering receptacle will be gradually progressively decreased as the speed of the engine is progressively-increased and while the velocity of the air through the Venturi throat 2| is progressively increased with the result that the combustible mixture will be slightly progressively f made leaner. l

During these initial stages of operation the fuel level in the metering receptacle 42 will begradually lowered and the buoyant metering receptacle will be gradually raised inthe fuel well 39 and at further advanced stages of increased engine speed the fuel level in the metering receptacle 42 will move to a line below the bottom end of the high speedjet extension 46A where'- upon the supply-of fuel to the high speed jet nozzle 45 will be further decreased since the fuel will then be supplied only through the extensionsv 55 and 55A. Y

As the speed of the engine is still further gradually increased the fuel level in the metering receptacle 42 will continue to be gradually lowered .within the space between the bottomr end of the extension 46A. and the flanged bottom end 55B of the extension 55; but during such final lowering of the fuel level in the metering receptacle, the bottom 42A of the metering receptacle 42 will finally be raised into stopped position against the flange end 55B of the extension 55 before the fuel level in the metering receptacle can possibly pass below such anged endv 55B, and when lthe loottomlIZA of the fuel metering receptacle 42 is instoppedE engagement with the flanged end 55B the fuel will pass through the receptacle opening 43 into the open end of the extension 55 and through the slots 25 thereof.

The opening 43 in the bottom of the metering receptacle 42 is large enough to supply all of the required fuel through both high and low speed jets for all engine speeds.

When the high speed jet extension 46A ceases to supply fuel to the nozzle 45, due to the fact that the fuel level in the metering receptacle has been lowered to a level below the inlet end of the high speed jet extension 46A, the flow of the fuel will then in such event continue to be supplied to the nozzle 45 through the low speed jet extension 55 but in such event the fuel level in the metering receptacle 42 will also gradually rise even though the speed of the engine is gradually increased and during such rise of the fuel level in the mel tering receptacle, the head pressure of the fuel vacuum in the fuel reservoir 22 and in the metering receptacle 42 is slightly increased. 'I'he gradual rise of the fuel level in the metering receptacle 42 will continue until the fuel demand of the low speed nozzle 55 is equal to the supply of the fuel passing through the inlet opening 43 in the bottom of the metering receptacle 42 and such balance between the maximum demand and supply of fuel being substantially Aat the point ,of maximum engine speed.

From the above description of the operation of my improved carburetor it will be readily understood that the operations of my carburetor are not effected by atmospheric pressure; that the fuel supply for the constant-level fuel chamber is readily maintained and insured by partial vacuum l induced therein; that properly proportioned combustible fuel mixtures are provided to meet varied increased engine speeds, through the novel buoyant fuel-metering receptacle in combination with the novel 4construction and arrangement of the.. high speed and idling jets; and that the novel re- While the drawing and above description Vis directed to a preferred embodiment of my inventlonoand are solely for the purpose of illustrating an operative embodiment of the invention, I do not Wish to be understood as limiting myself to the exact details of construction and 'arrangement of the parts and members shown and described therein. The invention is particularly pointed out in and defined by the appended claims.

" I claim:

y1. A carburetor for internal combustion engines including a mixing chamber having a valvecontrolled outlet, a restricted Venturi throat below said mixing chamber, an air inlet passage communicating with said Venturi throat, a constant-level fuel reservoir having a oat-controlled fuel inlet valve therein, a fuel well disposed adjacent to said fuel reservoir, an open passage providing air communication between said air inlet passage and the upper portion of said fuel well,

fuel communication betweensaid fuel reservoir' throughzsaid jrstenamedropen passage whent'he. carburetor 'is'. inoperative but subject' to. :the fin'- duction of. a` partial-1 vacuum therein bythe flow. of' airrpast said. first'fnarned-:ilopeningl during theoperation of the carburetor;` am buoyant fuelimetering ,receptacle mounted". in saidf fuel. .well having. an openvtop and ai. fuel-inletopeningtgin the-f bottom Wall thereof,v a .single fuelzdi'scharge nozzle, ai. pair` of' concentrically disposed' high speed .rand Vidling fuel jetr extensions. having dischargeendsrarranged 5to discharge fuel through.. said single#dischargevnozzle into said.' Venturi: throatand. opposite ends extending .f intosaid.

fuel-metering receptacle; ysaid .idlingi jet :extern sion, extendingbelow the,- lower end of.I said'high speed .jet extension, airidling fuel. outletport adaptedito discharge fuel' intosaid mixing cham'- ber,. andan: fuerpassage connecting. said idling fuel port withz saididling .jet-extension theiflowV` of the `fuel` from: said fuel-metering"y receptacle being. adapted to be. successively discharged through' said idling fuelsoutlet port', thence throughV said .pair of -concentrically .disposed-high' speedandaidling `iet extensions and said single discharge. nozzle and finally only through said idlingjet extension and saidldischarge nozzle responsively lto increased engine speeds and corresponding variations of the fuel. level in said fuelmetering receptacle.

2. A carburetor forinternal combustion engines including a valve-controlled mixing chamber, an air inlet/passage, a .Venturi throat disposedf'between said air inlet passage and said mixing; chamber, a-constant-level fuel reservoir, a fuelwell having a= verticallyf disposed elongated opening^.provding=`for the passage of fuel into said well from saidfreservoir, said elongated opening providing'also for air. communication between y said well and said reservoir'above the reservoirv fuellevel, a secondopening providing communication of the-upper portions of said'fuel reservoirV and said well with said. air inlet passage, a semi-s buoyant fuel-meteringreceptacle mountedzin said Welland having a restricted fuel inlet in the lower portion thereof andan opening'in the upper end thereof above the fuel level, fuel supply means extended into saidv Venturi throat comprising apair of concentricallyl disposed high speed andi idling fuel jets extending-into saidfuelernetering.

receptacle, said idling iet extension extending. be. low the lower end of said high speed 'jet extension,. an idling fuel outlet port adapted to .dis-

charge fuel into saidmiidng chamber, and afuel, passage .connecting said idling fuel, port withfthe.y

idling jet, the flow of thefuel: from said fuel-. metering receptacle beingadapted to befsuccessively discharged through said idling fuel outlet port, thence. through said pair of .concentrically disposedhigh .speed'and idlingjets and nally only through said idling jet responsively to in; creased engine speeds and correspondingvariations of the-fuel level of saidfuel-metering. device.

3.' In acarburetor for internal combustion en'-v gines including avalve-controlled mixing -charnber,an airinlet passage, a lVenturi throat dis-- posed betweensaid mixingcharnber and-said air inlet passage,.and an enclosed constant-level fuel reservoir; an enclosed fuel well open toair and: fuel communication with said fuel reservoir, said fuel. well having an open passage disposed above the fuel level. in said fuel reservoir in open communication with said .air inlet passage. near said.

assegni and :saidlfu'elwell,v saidifuel:reservoirandasaidl'fuel:V welll beingfseal ed :toy atrnpspheric".pfressure'Y except:

tacle: rnountedf:A in; said Ifuel'` well,y an idling; fuelI jethaving' anl idling.:fuel-discharge'zport inlcom'- municationfwitnsaidtmixing chamberand having; a fuels inletfend disposedlwithin'.saidi'fuel-meterin'gxreceptacla: andia: high speed'ffuel. jet having. a L'discharge nozzle'; disposedclwithinf. said Venturi#r being.; subjected to apartial. vacuum induced.

thereinbythe.flowy of air-'past said open passage:- 4': Ina carburetor' having'a Venturi throatrdis .posedr'betweenz an air. inlet passage and the fuel.

mixture chamberl thereima"'closedconstantelevel.: fuel reservoir.,v a '.buoyant fuel-.metering recepx- I tacle operatively associated .with said l fuel7 reser'- l voir having.v an. open'. topf-anda' fuel 'inletxopening for admission: of.. fuel `thereinwfrom. said: fuel res-, I ervoir;an-xidling. :fuel jet, a high 'speed fuel jet,.

an.-idling speed fuelv port vin open communication withl said fuel mixture chamber, saidv idling, and high speed fuel jets extending: into said fuel:- metering receptacle andzhaving; fuel' inlet .openings."v disposed at.v relatively; different elevations with respect -to .the normal'fuelilevel in said reservoir;acombined fuel-discharge 'nozzle extend'.-

ingiintosaid Venturi throatadapted to discharges,

fuel from said high andidlingspeed j.ets,.any extendednpassage'from said idlingjspeed jetto said idling .;speed port, and means. whereby a partial` vacuum.I is maintained in said closed reservoir and' saidefuel-metering .receptacle during vthe .opera- .,tion; of the: carburetor, said4 difference in' relative:

elevations of said high speedfandlidlingispeedjetf inletsfunotioning to progressivelydecrease the discharge.: oftthe.v fuel from' both'of said jets'.

through. said nozzle Vduring a range. of progresa sively.- increased enginefspeeds responsively. toa:

progressively'.` lowering fuel .level inA said fuel-me-v teringhreceptaoleV whereby` the flow of thexfuelf,

throug-hr both of said; jets.. isprogressively. de'- creased simultaneously: Withi increased. engine. speedsswithin.-- said rangeuntil a-higher range.;

of'. increased engine-:speeds beyond. said: first=- recited.-.rangeof. speeds.y is attainedr whereupon, due..to..the.lowered'fuel level in said fuel-meter+- ing receptacle, only the fuel admittedthrought the lower one .of said. jet inlet openings i will .be dischargedfrom said nozzle..

5.` In. acarburetor. forv internall combustion. en@l gines havingranz airrinlet 'passageprovided with, aVenturi throat and athrottle valve,.and in com# bination, aconstant-.level fuel. reservoir, a buoy.- ant ...fuel-metering; receptacle .'havin'g; .a i fuelriinlet opening. in vthe-lower .portion thereofY` for admitting fuel` therein .-solely through vsaid opening, a.:

Venturi .th'roat,..a-.bhoyant .fuel-metering., recepuv lnfliditig .saidconstant-level fuelA reservoirrand:

said fuel-metering receptacle enclosed in an airtight housing to thereby provide and maintain a partial vacuum within said housing during the l' operation of the engine, said vacuum being induced through an opening in said housing which is open only to communication with the flow of air passing through said air inlet passage.

7. In a carburetor for internal combustion engines having an air inlet passage provided with a Venturi throat and a throttle valve, and in combination, an enclosed constant-level fuel reservoir and an enclosed fuel well in open fuel and air communication therewith, said fuel well having an opening in open communication with said air inlet passage whereby a variable partial vacuum is maintained within said enclosed fuel reservoir and within said enclosed fuel well during the operation of the engine, the partial vacuum increasing progressively relatively to the progressively increased speeds of the engine, an open-kl top cup-like buoyant fuel-metering receptacle mounted in said well and having a fuel-inlet opening in the bottom thereof, and fuel jet means disposed within said Venturi throat and extending into said fuel-metering receptacle, said fuel jet means having a plurality of fuel-inlet openings disposed at different elevations relatively to and below the constant fuel-level of said reservoir whereby the fuel discharged through said fuel jet means is admitted through a progressively decreased number of said fuel-inlet openings responsively to the progressively decreasing level of the fuel in said fuel-metering receptacle during progressively increased engine speeds and in a progressively decreased volumetric flow relatively to the progressively increased volumetric flow of air through said air inlet passage.

8. In a carburetor having a valve-controlled air passage, and including a constant-level fuel reservoir closed to atmospheric pressure during the operation of the carburetor, said fuel reservoir having passage means communicating with the flow of the air through said air passage whereby a variable partial vacuum is maintained in said fuel reservoir responsively to varying engine speeds, a buoyant fuel metering receptacle within said fuel reservoir, a Venturi throat in said valve-controlled air passage, a high speed jet, a low speed jet, both of said jets being disposed to discharge fuel into said Venturi throat and both of said jets having fuel-feeding extensions extending into said fuel metering receptacle, the fuel inlet end of said low speed jet extension extending below the fuel inlet end of said high speed jet extension whereby at certain advanced engine speeds and after the fuel level within said metering receptacle has been lowered below the inlet end of said high speed jet extension, fuel will then be fed into the Venturi throat only through the inlet end of said low speed jet extension, and means for admitting fuel into said fuel metering receptacle.

9. A carburetor for internal combustion engines including a mixing chamber having a valve-controlled outlet, a restricted Venturi throat below said mixing chamber, an air inlet passage communicating with said Venturi throat, a constantlevel fuel reservoir having a float-controlled fuel inlet valve therein, an open passage providing air communication between said air inlet passage said fuel reservoir, said fuel reservoir being scaled to atmospheric pressure except through said open passage when the carburetor is inoperative but subject to the induction of a partial vacuum therein by the flow of air past said opening during the operation of the carburetor, a buoyant fuel-metering receptacle mounted for buoyant support in the fuel in said constant-level fuel reservoir and having an open top and a fuelinlet opening in the lower portion thereof, a single fuel discharge nozzle, a pair of concentrically disposed high speed and idling fuel jet extensions having discharge ends arranged to discharge fuel through said single discharge nozzle into said Venturi throat and opposite ends extending into said fuel-metering receptacla'said idling jet extension extending below the lower end of said high speed jet extension, an idling fuel outlet port adapted to discharge fuel into said mixing chamber, and a fuel passage connecting said idling fuel port with said idling jet extension, the flow of the fuel from said fuelmetering receptacle being adapted to be succese sively discharged through said idling fuel outlet port, thence through said pair of concentrically disposed high speed and idling jet extensions and said single discharge nozzle and finally only through said idling jet extension and said discharge nozzle responsively to increased engine speeds and corresponding variations of the fuel level in said fuel-metering receptacle.

10. A carburetor for internal combustion `engines including a valve-controlled mixing chamber, an air inlet passage, a Venturi throat disposed between said air inlet passage and said mixing chamber, a constant-level fue1 reservoir, an opening -providing communication of the upper portions of said fuel reservoir with said air inlet passage, a buoyant fue1-metering receptacle mounted for buoyant support in the fuel in said constant-level fuel reservoir and having a restricted fuel inlet in the lower portion thereof and an opening in the upper end thereof above the fuel level, fuel supply means extended into said Venturi throat comprising a pair of high speed and idling fuel jets having extensions ex tending into said fuel-metering receptacle, said idling jet extension extending below the lower end of said high speed jet extension, the flow oi the fuel from said fuel-metering receptacle being adapted to be discharged through said pair of high speed and idling jets and finally only through said idling jet responsively to increased engine speeds and corresponding variations of the fuel level in said fuel-metering receptacle.

11. In a carburetor having a Venturi throat disposed between an air inlet passage and the fuel mixture chamber therein, a closed constantlevel fue1 reservoir, a buoyant fuel-metering receptacle operatively associated with said fuel reservoir having an open top and a fuel inlet opening for admission of fuel therein from said fuel reservoir, an idling fuel jet, a high speed fuel jet, said idling and high speed fuel jets extending into said fuel-metering receptacle and having fuel inlet openings disposed at relatively different elevations with respect to the normal fuel\level in said reservoir, a combined fuel-discharge nozzle extending into said Venturi throat adapted to discharge fuel from said high and idling speed jets, and means whereby a partial vacuum is maintained in said closed reservoir and said fuelmetering receptacle during the operation of the carburetor, said difference in relative elevations of said high speed and idling speed jet inlets functioning to progressively decrease the discharge of the fuel from both of said jets through said nozzle during a range of progressively increased engine speeds responsively to a progressively lowering fuel level in said fuel-metering 4receptacle 4whereby".the,silow'fof the f uelithrongh both fof i sai-d jets isvprogressivel'y decreased `simultaneouslyy withincreased enginel speeds within `said rangeluntila higherrrange of increased engine speedsbeyond said Yfirst-recited range of speeds is'attained whereupon, dueto the lowered 'fuel level in said vfuel-metering receptacle, only lthe fuel admitted through the lower oneof .said

open communication with said air inlet passage Wherebya variable partial `vacuum is maintained within said enclosed lfuel reservoir during the operation of the iengine, ythe .partial vacuumincreasing progressively relatively to theprogres- 20 ysively*increaseclspeeds.of vthe enginagan open-*top fcupf-:like buoyant fuel-metering receptacle mounted in Asaid reservoir and having'a fuel-inlet opening in the bottom thereof, and fuel jet'means -adisposed within said Venturi throat andextend- `ing into said'fuel--nrietering receptacle, said. fuel jet means havingf'a lplurality of fuel-inlet open ings disposed'atdiferent elevations relatively to :and belowthe fuel level of vsaid reservoir-whereby the fuel discharged through said fuel :jetmeans lis admitted through lavprogressively decreased number of said fuel-inletopenings responsivel-y to the progressively ldecreasing level of vthe fuel infsaidfuel-'metering receptacle during progressively'incr-eased engine speeds and in a progresf sively .decreased volumetric .flow relativelyto the progressively increased volumetric now of air ythrough said air'inlet passage.

LADIM'IR F. STUPECKY.

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