US2327592A - Carburetor - Google Patents

Description

Aug- 24, 1943 l A. E. cHlsHoLM 2,327,592

lCARBUREJTO'R Filed April s, 1940 f5 sheets-sheet 1 (v.) i l` k y/l Y..

Afform'y.

Aug. 24, 1943. A. E. cHlsHoLM 2,327,592

CARBURETOR l Filed April 8, 1940 6 Sheets-Sheet 2 Aug 24, 1943 A. E. cHlsHoLM 2,327,592

CARBURETOR Filed April 8, 1940 6 Sheets-Sheet 3 Aug. 24, 1943. A. E. CHISHOLM cARUREToR Filed April 8, 1940 6 Sheets-Sheet 4 A//en E Chisholm ATTORNEY Patented Aug. 24, 1943 UNITED STATES y PATENT asusta 7 i oARBuREzron Allen E.vChsholm, Portland, Greg. Y Application April: s, 1940,! serial. No@ 32e-,449,

9 Claims. (Cs aaraar My inventionrelates to carburetors for internal combustion engines, and ith sparticularly adapted for use with engines whose operating speeds and loads vary frequently thereby imposing upon said carburetors vvarying demands as to the quantity of fuel'lmix'ture required, and alsou aste the qualityof saidmixture.` For con- Veni-ence, Il will describe my invention connection with automobile engines adaptedto burn gasoline, this. being a typical use for said invenf tion.

Automobile carburetors of the down draft type have heretofore beenA used wherein` a cylindrical conduit leading to the4 intake manifold Yof' the engine has been provided With a so-called venturi,v or constrictionIr adapted to produce a `fuel has been sumolied when the engine load was light and when it was heavy,t whe-reas the requirement has been fora. larger amount of additional fuel for accelerating under heavyl load as .comparedto the amount, required under light .loam

The principal object of my invention is to pro.- vide a carburetor that will automatically supply anengine with theproper'cluantity and quality of ain-fuel. mixture `under all operating conditions or said engne'as, to speedxand load. I achieve said-result,l broadly speaking, by providing a vcarburetor. comprising four more or lessseparate air-fuel passageways, each. adapted to perform a special. function, and by providing means for `correlating the operation of said air-.fuel pashigh velocity and low pressureof the air pass.- v

ing therethrough.' Said highY air velocity is` desirable for reasons hereinafter discussed. Audifculty immediately arose, however, in` that a venturiv of' suitable size to give the desired high velocity at low engine speeds would unduly re-l strict the flow of air to the 4engine at higher jengine speeds. [it has Vbeen;proposed to provide two cylindrical To meet the aforesaid difficulty,

conduits' leading to the intake manifold ofthe engine, each provided with a venturi, one to function alone at 710W "engine speeds` and the other to become also 'operative at higher engine speeds. 1

Thisv arrangement has not been Wholly'fsatisfactory, however, becausethe control means vby which the aforesaid lsupplen'iental venturiv has been made operative has not functioned to supplyv the required quantity and' quality of fuel mixture to thev engine at'the variousspeeds and loads thereof, Generally speaking, the requirements of an automobile' engine are for anienrichedfuel mixture for starting'l for accelerating, for pulling heavy loads, and for attaining themaximum speedfof which said engine is capable under load. Otherwise, a lean mixturel is preferable to save fuel and to minimize the dep-` osition of carbon-within the engine.

furthervdiiiculty that has been encountered with carburetors heretofore known is due tothe requirementsof an engine of an enriched fuel mixture for accelerating; An attempt has been made to meet said diculty by providing means for introducingv a small 'quantity of liquid fuel intothe. air stream entering the carburetor each time. the manually operated acceleratorl is actuated.. This expedient has beenobjectionable in that said. liquid fuel vhas riotbeen readily vaporized, and. alsoin that the samequantity of liquid "sagevvauzs-4 toi bring about. the desired over-all result..

More speecally, I provide a primary carburetingl chamber havingv a' manually controllable 'throttle valve vof. the ordinary type.A I so. proportion said primary carbureting chamber and `the .venturi therein. according to well known Ldesign data, that it will supply the proper amount v4lof' airif'uel mixture to. the"`engine when the latter is operating, at amoderate speed of, say, 35 miles per hour. Y At higl'nerV speeds, said primary carloureting chamber 'would supply an in- ,isufficientquantityofpairefuel mixture to said -enginel `t'o assure efficient and effective opera- "ti'on' thereof;- so provid'e a secondary carburetingohamber tobecome operative. at speeds'above "35' miles lper hour `as hereinafter described.

At' speeds below `35 miles per hour, the aforesaid primary carbureting chamber willv supply the engine with anair-fuel mixture that is too lean; forj effective operation thereof under cerstain conditions, such, for example, as rapid acjceleration or pulling heavy loads; so I provide anauxiliary' air-fuel passageway for enriching said air-fuel mixture automatically the proper 'amount' `when the manualV throttle valve is "openedt TheL required enrichment of said airfuel mixture `for accelerating differs at different engine speeds, more enrichment being required at slow speeds and little or nene at the assumed optimum speed of 35 miles per hour, this be- --ing thespeed at vwhich the primary carburet- 'ing chamber is assumed lto-v be designed to function properly bylitself.V `Lastly, I provide an idling airefuel passageway 4ofi a well1 known type,

"differ-ing fromy other idling devices, however, in

`tlfiai'lin' theform whichl'l prefer, saididling airlfuelfpassagewayis adapted :tosupply all of the `air-fuel mixture `for'the `engine Vduring idling,

A the automobile.

whereas it is necessary to open the main throttle of other carbureto-rs a slight amount during idling.

From the foregoing statements, it should not be inferred that the sole function of the socalled auxiliary air-fuel passageway which forms a part of my invention, is to provide an enriched air-fuel mixture for accelerating; it also provides an enriched mixture for starting, for pulling heavy loads at any speeds, and for attaining maximum speed. On the other hand, the action of said auxiliary air-fuel passageway is enhanced by the action of a choke engaging the'.

venturi of the primary carbureting chamber, said choke and the control valve of said auxiliary air-fuel passageway being mechanically inter,-`

locked so that, whenever said control valve opens to admit a rich mixture from the auxiliary airfuel passageway to the intake manifold of the engine, said choke will also operate to enrich the mixture passing from the primary carbureting chamber to said manifold by a choking action hereinafter described.

An important feature of my invention is the manner in which the various parts thereof cooperate to achieve uniformoperation of thev engine at all speeds and loads. For example, an

lautomobile engine employing my invention may be started in the ordinary way, ther accelerating air-fuel passageway co-operating with vthe idling air-fuel passageway to give an enriched starting mixture. Then, after the engine has started, the accelerating air-fuel passageway will gradually become wholly inoperative, if the engine is warm, and the idling air-fuel passageway alone will supply said engine. However, if the engine is cold, or if for any other reason it tends tostop, said accelerating air-fuel passageway will be brought into use lto give an enrichedl mixture whenever the engine slows down. Furthermore, the aforesaid enrichment of the fuel mixture of the accelgiratingv air-fuel passageway when lthe 'engine slows down will take place so quickly that therer is little danger of the engine stopping due to a too lean mixture. Therefore, the idling air- Yfuel passageway may be adjusted to givea vlean mixture and low idling speed.

` `When it is desired to put the automobile in motion, it is, of course, necessary to supplymore fuel mixture to thegenginarand it is desirable that said fuel mixture should be enriched, as compared to the idling fuel mixture. In my invention, by means hereinafter described, the auxiliary air-fuel passageway is automatically brought into use when the manual throttle is opened, thereby enriching the fuel mixture for starting Thereafter, as the automobile gains speed, said auxiliary air-fuel passageway gradually becomes inoperative .and the primary vcarbureting chamber supplies the engine A with lthe proper fuel mixture, the idling air-fuel vpassageway supplying a small amount of said mixture,gof course, whenever the engine runs.

As mentioned, when the. manual throttle is opened to accelerate, or when a heavier load is encountered by the engine tending to slow it down, the auxiliary vair-fuel passageway is brought into use, byk means hereinafter described, to enrich the fuel mixture supplied to the engine. However, ask the speed of said engine increases and approaches the speed at which the secondary carbureting chamber is to be brought into use, there is less need for enriching the fuel mixture for accelerating so the auxiliary air-fuel passage- Way then becomes operative less readily, at certain I speeds functioning only when the engine is pulling a heavy load that requires the manually con-` trolled throttle to be open a substantial amount.

Then, when the secondary carbureting chamber However, to achieve extremely high engine speeds,

it is necessary that the fuel mixture be enriched, compared to the mixture desired at lower speeds, and therefore special means are provided for making the auxiliary air-fuel passageway readily Kthrough said venturi. .the auxiliarythrottle valve is slightly opened, the airvelocity through'the venturi will be low, where,- .as I'prefer to have a reasonably high velocity therethroughat all times; jI, therefore, provide -operative at extremely high speeds when the manual throttle is open.

A further object of my invention is to provide a carburetor that will, first,v thoroughly atomize the liquid fuel supplied to anr internal combustion engine and mix the same uniformlywith the air supply, land,vsecond, assure Vaporization of vsaid atomized liquid fuel.` I-achieve said object, in one respect, `by 4providing ,ja uniformly y high air velocity through the Venturi tubes lof my invention at all voperating speeds' and loads, whereby liquid fuel entering' said air streamiseffectively broken up. I achieve said result, in another respect,rby'

Iproviding a uniformly high vacuum at said Venturi tubes, thereby facilitating the vaporization of .saidl atomized 'liquid fuel according to the well 'said uniform air velocity and vacuum, an air bleed opening thereto. j'Iny other words,'instead of applying atmospheric pressure to the air fbleeds in'V the conventional way, 'If applyA thereto the air lpressureexisting in-a, portion Offmy carburetor wherein said air pressure varies with' differentl operating'conditions' of 'the'engina LA further Object of my invention is to provide l asecondary carbureting chamber having an auxfiliaryY throttle v'alve'ilthat will automatically be opened'when the capacity of the associated pri- 'Xmary carburetirigV chamba-1" isf'exceeded at high engine speedsy under load.' Iachieve said object f `by'providing.actuating'means for said auxiliary throttle valve' operativefrom the vacuum attire primary carburetirg" chamber' venturi. When said vacuum exceeds apredetermined value, cor'- resp'onding to a certain air velocity through said venturi, said primary Carbur'eting'chamber becomes inadequate "to, 'supply' said 4engine `with a proper. air-fuel mixture. Q therefore, lcause said auxiliary throttle to be opened progressively-when said vacuum increases above4 said predetermined 7 value. Y y y f j A further object of `my invention istoprovide ,a Venturi choke adapted. tov be operated synchronously-Awitrh the auxiliary throttle valve, thereby tending to maintain `a constant air vel ocity Withoutl said choke,k when an chcketorestrictlthe arearofsaidgventurig After said throttle has; been opened slightly, thereby increasing; said aifr'velocity,rlr.cause sardi choketo b'elifted mechanically as sai-dr throttleis. further opened; thus'. mairrtain'ing aruniform airl velocity. A. further objectief invention. is` to Iprovide a.carburetor` having an; auxiliary. air-fuelhpassageway whose control valve is controlledlby'the vacuum 'existing atfA various. placesv in. said carhuretor whereby an enriched fuel'mixtu-re. will be supplied to an. engine when the ioperating condi.- tions` thereoflmake `an;enri'chedmixt`11re desirable. Afurther object ofi. m5rinvention1 isl toprovide an auxiliary airsfuellfpass'agewayf'whose 'control valve will open abruptly, when the engine manifold vacuum decreases due either to-the slowingr downV of said engine dueto "an increased load thereon, or tol the-opening `of` lthe-manually opratedthrottle tof accelerate said engine; and close gradually assaid vacuum returns to armedL erately high value, asit normally will-when the load on the engine 4i's reduced'allowing itt'o gain speed; orr when the manually operatedI throttle is partially closed; upon Vthe completion kof said period of acce-lerationl i j u n Other' objects and-advantages of my invention will be describedi witlr reference to the accom'- panying drawings, in`whi'ch` i Fig. l'is aplan View of'a carburetor embodying my invention, the: parts thereof beingshown. in their usual operating positions, that 4is with the auxiliary air-fuelpassageway closed off from "the fuel' of `the carburetor;

' Fig.2 is avertical section talensubstantially on the line 2-2 "in Fig; l', the' upperbody"v section being shown in place Yin this, view, but omitted from the'other'vi'ews for "clartyf y l i, Fig. 3 isa foresh'ortenedJarg'e scale View taken substantially on the line in Fig.. 1, the parts thereof Vbeingfshown in a position with the auxiliary air-fuelpassagewayopen tothe throat to produce an enriched air-fuel mixture. Y

' Fig, l 1s a fragmentaryfsectional detail View of a portion' ofthe 'structure illustrated in Fig.. 35

`Fig. '5. isfa fragmentary horizontal sectional View taken'substantiall'y on theline -Bin Fig. 6i

EigLfGis Ia fragmentary Aside View of said Y carburetor, portions Athereof.being. shownbroken away, to various depths to disclose, the underlying structure; l l ,V n* Fig? is alfragmentary plan view -ofsaid car-k buretor, portions lthereof being shown broken away to various depths; y Fig. 8 is a foreshortened verticalsection taken along the line 8.-8 inFig. 7, the parts thereof be;- ingshown in their usual operatingzpositons,,that is, withthe auxiliary air-fuel passageway cut off from the throat ofthe carburetor;

Fig. 9 is a vertical section taken along the line @faint-n.5; i

Fig. l10 Vis a large scale vertical section taken on the line `Iii-ill yin Fig. 1, and l Fig. il, is a more or less ,diagrammatic illustration of all of the operating parts .of thecarburetor shown joined together. i i

Referring first to Figs. 1 and 2; a carburetor embodying. my invention-comprises a float-'valve controlled fuel reservoir, lphavingz a iioat 2t and fuel"` inlet tube 3 adapted toconduct fuelfrom suitable supply to said reservoir. Flange@v at they lower end of said Ycarburetor. is adapte'd to be connected:V to the intakeemanifoldoigan-ine ternalj combustion` .engi'ne. structure: 'thus far described is yoldin .theartif t 3 i I under! luel` from reservoir' l isasupplied' tol said. en gine. through. said; conduitby: fourseparate, but not' independent; carbureting' devices. First, an idling air-fuel` passageway is provided-for sup'-` plyingiairffuel: mixture: at the'slow rate necessary for ordinary idling'. Said idlingl air-fuel passageway is, in general, similar to those forming part of carburetorsheretofore: used'. It differs functionally therefrom,` however, in one respect in that it is adapted to:v supply all ofthe air-fuel mixturel required by the engine during idling. Whereas the manually operated throttle of .most carburetors heretofore used has been partially opened during idling. Myudling. airfuel passagewaydiifers functionally from those heretofore.v known in ano-ther and more impor'- tant respect in thatv it. is.A automatically supple:- mented by a richenair-fuel mixture from an auxiliary air-fuel passageway hereinafter described in case said engine slowsd'own approach'- ing its stopping point. yIt' follows` that saidJi'dling air-fuel passageway'may be adjusted. tof supply a rather lean mixturey suitable fior: idiing' with a warm engine, said mixturebeing automatically enriched if saidengine tends to stop while cold;

Said idling air-fuel passageway comprises a conduit 5, shown more clearly in' Fig; 3; leading from chamber 'vvhich is'conne'cted to the intake manifold of an engine by holes la. Said conduit leads to theatmosphere at its upper end S, but `the flow of airfthereinto is restricted by the constriction 9. Constricted air.l passage-ways of this kind will be called. air bleeds herein for convenience. Said air vbleeds do not reduire1 an extremely small hole in order torrestrict suflif cientlytheflow of air therethrough because.A of their "substantiallength.. They are ordinarily removable` in order that they mayy be: replaced by others having a different bore `therein( toad.- just ther flow ofv air therethrough. Due to;` the aforesaid restriction of thefiovv` of asubstanf, tial vacuum willY exist immediately below air bleed' 9, and saidvacuumisutilizedtoldraw `fuel from reservo-ir ixthrough: conduit iil. The-*censt'ricted"portion i-l of said conduit controls-the flow cf fuel therethrough, constrictions of this type being called"ffuel metering orifices herein, in the sense that they restrict the flow of fuel therethruaV They may be' removable for being replaced with others having-v different bores@ when adjustment is required' of the flow of. fuel. `Passageways 'i5-'connect said' fuel metering oricesl to reservoirl. Interposed` in conduit 5 is a manually: adjustable valve i 21. adapted.l to control the flow of aire-fuel' mixture to the engine thereby vto control the idlingY speed ofthe latter. Said valve functions in vtheordinary way as a flow controlvalve; butit is intended. to be more or `less permanently set. It will be' apparent that a mixtureofair from end'. of conduit 5' and gasoline through` fuel metering` orifice il` from reservoirl iwillthus'beA supplied to said engine, and4 that' thexflowfoff'said" mixturetmay readily be adjusted' tossecurea a desirable.`idling speed of said'engi'ne:

Referring to FigLB", Lwiil': now describe; another of the carlouretingi devices forming: part of my invention, namely, the primary: carbureting chamber. Barrel iii leads directly to the intake manifold of `the engine at `its lower` end, and to the atmosphere at its upper end either through draft tube Hi? orvthrough-Y the annular opening i5 .therea-round; Said annularropening'isadapt" ed to. be partly or whollyA closed by member IE. conditions hereinafter. described.` The outer boundary of opening |5J'is formed by venturi Il, in which area series of holes lleading to-annular chamber I9. Saidfholes IB'and chamber I9 are used for control purposes hereinafter described, so that, although small quantities of air may ilo-W therethrough under certain conditions, ordinarily nok air willflow therethrough and all of the air for said primary carbureting chamber may be deemed to'flowthrough either draft tube i4 or annular opening I5.

Referring now to Fig. 2, Afuel for said carburetor is drawn by the vacuum formed in bevelled end ISa of tube 28 bythe passage of air through draft tube I4. Said vacuum draws said fuel through fuel metering orifice 2| at a rate determined by the bore of said fuel metering orifice and by the bore of air bleed 22. Said air bleed and said fuel metering orice function like those hereinbefore described diering therefrom The flow of air-fuel mixture flow therethrough at a high velocity even at moderate engine speeds.

Principally for supplying an enriched air-fuel mixture for accelerating the engine, I provide an auxiliary air-fuel passageway adapted to draw fuel from reservoir I through fuel metering orice 24 and air through air bleed 25 when vacuum exists in tube 25, auxiliary air being supplied through holes 2l, if desired. The resultant mixture is drawn into the engine byway of chamber and holes The manner in `which I control the application of vacuum to tube\26 under various conditions of motor speed and load formsV an important part of my invention.

Vacuum from the intake manifold of the engine is applied through holes I to chamber 6 at all times ywhile said engine is operating, said vacuum varying, however, under various operating conditions. Whatever vacuum exists in chamber 5 will be applied to tube 26 whenever valve 23 is wide open. However, if valve 28 is partially closed, the vacuum applied to tube E5 will be reduced from that existing in chamber '6 and the .ILO

lcreased force on piston 3|' will move it to the left, opening valve 28. Asimlar resultv would ensue Vif theI throttle were opened suddenly. `But once valve 28 opens even slightly, the manifold vacuum is further'reduced due to the admission off air thru 'ports 29, the vforce tending. to move piston 3| to the left increases and valve 28 opens abruptly.

' yMotive power is supplied to valve 28 by the kdifference in air pressure on opposite sides of three pistons, 38, 3| and 32.` v In addition to valve 28, two of said pistons, namely, 30 and 3|, are rig` idly connected tofvalve stem 33, moving therewith at all times. On the other hand, piston 32,l sldably mounted in guide member 32a, merely abuts against piston 3| and may remain stationary While said valve stem moves. The position of piston 32 may be adjusted by' means of screw 32h. The aforesaid motive power for actuating valve 28 is derived from-the force of atmospheric air on one side of said pistons, the opposite side thereof being subjected to vacuum from the intake manifold` of the engine. Piston 3| is always subject to substantially the full vacuum of said manifold, applied through holes 1 and chamber 6. Full atmospheric air pressure is vapplied to the opposite side of said piston through aperture 34 at all times. Thus, insofar as piston 3| is concerned, the actuating force for valve 28 is proportional to the manifold vacuum'.

However, the pressures on both sides of pis.- tons 3|] and 32 are variable by means hereinafter described. The force exerted byk pistons 30, 3|, and 32 on valve stem 33 is opposed by the compression of spring '35, adjustable by screw 3B. I contemplate that,'under certain conditionsthe force of said pistons will be balanced by thatof said spring when the latter has been compressed somewhat, While under other conditions the force of said ,pistons will predominate to force valve 28 rmly against its seat 31. Of course, when the engine is notrotating, there will b e no vacuum in f its manifold; henceno force will be exerted by 'rich air-fuel mixture thereby drawn through said tube will be leaned by the admission of air i through ports 29. Ports 29 are arranged in spiral pattern extending through the walls of cylinder 39a as is shown in Fig. 4. Thussaid ports are consecutively uncovered by piston 3|! which is joined to valve 28 by rod 33 and moves with valve 28. Thus, when valve 28 is wide open, as it is shown in Fig. 3, the full manifold vacuum will be applied to tube v26 to draw a rich air-fuel mixture therethrough, When valve 23 is gradually closed, said mixture coming through tube 25 will be progressively leaned `by air admitted through ports 29 as they are uncovered, andthen shut off by the closing of said valve 28.

Under most operating conditions valve 28 will be closed. However, when the manifold pressure is increased the increased force against piston 3| moves it to the left (Fig. 3) and opens valve 23. This increased manifold pressure, or decreased manifold vacuum, will occur under various operating conditions, all of which require the richness of the air-fuel mixture to be quickly increased, and that is the result achieved by the opening of valve 28. For example, if the engine load is suddenly increased, slowing it down,

` the manifold vacuum will decrease' and the inleading to chamber `I, substantially full manifoldl lvacuum is always applied to the right-hand fac e Y of piston 30, asviewed in Fig. 3. However, .when

valve 28 is wide open, said ,vacuum 0n the right-` hand face of piston 30 is ineffective because a similar vacuum is then applied-to its left-hand face. When Valve 28 rst begins to open, ports 29are all open and the inrush of air...therethrough suddenly reduces the vacuum in chamber and the force on piston 3|. Spring 35 then moves stem 33 to the left (Fig. 3) quickly, and I deem this quick movement of stem 33 an impor. tant feature of my invention.

Whenever the engine is running and develop` ing a substantial vacuum in its manifold, stem 33 will be moved to the right (Fig. 3), Aseating valve 28a-nd raising choke rod 49 (hereinafter described). However, when said manifold vacuum is decreased due to the slowing down of the n movement" .with which. valve: ZBistarts. to z open. is thatcarries stem chan gedlto an'. Vabrupt movement 33 alsub'stantialfdistance.

vacuum may'beappned to the nemmeno end of piston 32;. as viewed inxFigB; from eitherof' First', it may befapplied through.

a's'i's shown more clearly in Fig. 2; Saidtubese are provided with check valvesA 42 anda to pre-v vent drawing air from one' when the otheris'at lO i higherpressure. That is, ifa higher vacuum eX.- ists i'nv either tube 39- or tubeft'l, saidrvacuum-` will? bel eiective on piston 32: without interference-,

bythe other ci said tubes. vSaidvacuumwillbel e-iective against piston SZ because atmospheric air is?` applied' tothel left-hand' ehd thereofl through orifice 43'. However, said atmospheric air pressure is applied somewhat slowlyto saidl left-hand end because of the constrictionI of said orice', andl vacuum supplied through tubelllmay se reduce the pressurein the left-hand end of cylinder @5i as to retardand delay the action of piston 3% I' supply sufficient vacuum through tube W to delay'the action of piston 32 only at high engine speeds, bymeans hereinafter de-V scribed.

The movement of 'valve stein under the force exertedby pistons 3e, 3ll, and 3.2 in one direction and the Vforce oi' spring 35 the other servesth-reepurposes. First, it opens or closes valve 28. Second, it opens or closes ports 29'- in" ythewall of cylinder 1W. Third; vcone i3' affixed to valve stem 33- engages rod il@ to raise or lowery member i6 by means of yoke 7F41, spring'ill appoging said raising to cause said member: to assume a position determined by the positionof saidvalve stem. I call the mechanism actuated by stem 33 the accelerating valve mechani'sr-n. `i I will now describe the operation of `that porlti'on of my invention thus far described, assuming that high enough engine speeds are not attained to apply sufficient Vacuum through' tube-tit toy impairl the operation oi' piston 32. engine is started, there is no vacuum in the mani;A fold, and spring 35 forces valve'stem 3Std/the left Vto the position shown in Fig.` 3. This position of said valve stern `may befregulated by screw dil, being determined largely byfthe position of' cone 48 with respect to rod dit, it being desired' to have member i6 start to raise slightly after stem 33-starts to'move to the right. v

New, when the engine i's rotated by some extornai means, a small amount of a moderately rich air-fuel mixture will be drawn through the idling air-fuel passagewayhereinbefore described, said amount being regulable by'valve i2." In' additionthereto, a richer airafuel mixture will be drawn through the auxiliary air-fuel Apassageway hereinbefore described. I `do Vnot contemplate any lother airor fuel being supplied to saiden-V gine for starting, although throttle 23 may be opened todraw an airfuel mixture through the primary carbureting chamber' if desired." Supposing throttle 23 to be closed,`lwhenthe engine starts and attains a slow speedwell below normal idling' speed, the vacuum applied to pistons Sii, 3 i and 32 moves saidpistons' toV the right, as viewed in Fig. V3. I prefer to make'piston 32 large in diameter in order that said movement may start at very low engine speeds, when the ymanifold vacuum is rather low.

The' iirst result of said movement is tostartto raise member H3, but this is of no importance since `throttle .23 is closed. At the-same time;

passageway only.

two; important results.` First, itv admits air to dilutetherich' starting mixture supplied by they auxiliary` air-fuel passageway; Second, it` re` duces-thewa-cuumdn both of chambers iii and 55,. thereby'reducing'the force tending Vto movefsaid pistons to the right since piston 32 is-larger than piston 30:. l

However when the speed of the engine increases slightly, as it normally will due to the dilution or the rich'st'arting mixture, thereby in-y creasing the vacuum applied to said pistonsthe latterr will'V move further to the right notwithstanding the-reduotion oi` the Vacuumapplied to` piston du'el to th'e uncovering off more o Thus, as the engine speed increases,

ports 2d; ports Ztl are gradually opened and liinallyvalve Zit' is.closed, whereupon the engineis supplied withian, air-fuel mixture by the idling air-fuel If, however,V the engine" is cold, orior` some other reason the fuel` mixturer sup,- plied bysaid idling airfuelpassageway-is tempo-rarilyrinadeduate to maintain the idling speed" or said'engineand' the latter begins to slouT down,Y

thevacuumapplied'to pistons 3i! and Sti to hold" valve.l ed closed will be reduceduntil spring willcausefvalve 28 toopen slightly whereupon the previously described quick opening ci said valve will take-place;l Said quick opening-is'highlydeu sirable, in this case, because an enriched mixture is thereby/#supplied to the engine in time toprevent stopping thereof, whereas if valve 28 opened toc` sluggishly, the engine would stop. f

It shouidrbe understood that I do not conn template the functioning oi the auxiliary air-fuell gine'whenever the latter slows down to the point' Y If 'a loa'd'should be applied to the enginewhile the'latter is ruiming at idling speed thereby causing it to slow down, the iuel mixture would be enriched in the way just described. This is a desirable result inasmuch as a richer mixture is requiredI bysaid engine under load. If throttle' 23fbe slightly opened with the engine running at idling speed,` the manifold vacuum will be thereby suddenly reduced by the admission of air through saidthrottle, and itis desirable that the fuel mixture for said engine be then quickly enriched in order that it may quickly accelerate. This will be achieved by the opening of valve 28 as described, the reduction of the manifold vacuum having the same effect whether caused by the opening of throttle 23 o-r by the slowing down of the engine: However, the enrichment of the fuel `mixturesupplied to the engine with throttle 23 piston til-.uncovers one of ports 2S, thusachieving for rapid acceleration at all engine speeds. Thus, in addition to the auxiliary air-fuel passageway contr-olled by valve 28, member I6 is also effective to enrich the fuel mixture during acceleration,

whereas said auxiliary airfuel passagewayuby it;

self has an important function during the idling of the engine.

As mentioned, I desire to enrich the fuel mix-A ture suppliedv to the engine quickly for acceleratingA the same. However, when vsaid engine is operating at moderately high speeds, lI do not` wish said fuel mixture to be enriched when throttle 23 is slowly opened; the requirement ofi duction of the vacuum applied to pistons'30 and 3 l, but said slight reduction does notpermit spring 35 to open valve 28 because ofthe vacuum applied to piston 32 from venturi l1. Furthermore, if throttle 23 is opened suddenly so that valve 28 is opened by spring 35, member I6 will be thereby loweredthus increasing the .vacuum at venturi I1, and thisincreased vVacuum acting on piston 32 quickly moves said piston and valve 28 to the right, whereas otherwise an unduly high engine speed would be required to close said valve 28.

Thus, in the structure thusfar described, I provide means foraut-omatically enriching the fuel ymixture supplied to an engine at idling speeds by means of an auxiliary air-fuel passageway. Said mixture is further enriched, when the manually controlled throttle is open, bya member actuated by the controlmechanism of. said auxiliary air-fuel passagewayboth enriching' means are actuated simultaneously., The aforesaid enriching means are actuated by a spring opposed in Ypart by a piston operated directly by the 4manifold vacuum, and in part by a larger piston .to which vacuum is applied only at moderately high motor speeds or when said` enriching means are active. The result is that an enriched mixture is supplied promptly for accelerating,

and said enriched.v mixture is maintained until said acceleration is accomplished whereupon the normal, lean mixture is promptly restored.

The structure hereinbefore described Yconstitutes a satisfactory carbureting device exceptat high speeds wherein it is defective in two respects. First, "its capacityl for supplying a V sufficient amount of fuel mixture is not great enough; the powerdeveloped by an internal combustion engine is reduced by restricting itsv fuel supply. Sec-ond, further means` for enrichingsaid fuel mixture at extremely high speeds arerequired an enriched mixture being. essential 'in order that the enginey may. reachthe highest speed of which it is capable .under load-. I am aware .that the dimensions of the means heretofore, disclosed mightbe enlarged suiilciently to supply an engine with enough fuel mixture. But such enlarge,- ment would result in low velocity of the air, at and immediately above venturi l1 at low engine speeds. I desire to maintain a highvelocity of said air, so I.make.thel structurethus far described only of suflicient sizeY top supply the engine at` moderatelyv low speedsv thereby achieving said high air-velocity even at low engine speeds. I kthen provide a secondary carbureting chamber for supplying additional fuel mixture .at high en@ gine speeds.' Furthermore; vI increase .theralrg velocity. `at the venturis. underp certain: conditions by providing air restricting members therefor.` if

. The aforesaid high airvelocityatand above venturil'l is desired :for two reasons. First, it

preliminary to its vaporizaticn, and to thoroughly mix' the same with the air. j The great value of i Y this function willbe apparent whenjit is 'ccnl sidered that the time'available forV the vaporiza-v tion of Iliquid fuel, and its intermixture withair;`

in a carburetor is extremely brief.v Y

` Referring now to Fig.` 8: Barrel 52 isy similar to barrel I3, and the two join at their lowerv ends to be coupled to the intake manifold of ,theengine Venturi 53 at the upper end of pare-.j rel 52-issimilar to venturi l'l.u I prefer, however,`

by ange 4.

to make venturi 53 somewhat larger' than venturi IJ in order yto supply ample fuel-'mixture to said The flow of fuel mixtureA engine at high speeds. through barrel 52 is controlled by throttle vvalve 54 which in turn -is controlled by the Vacuum existing in chamber I9 surrounding venturi l1, means by which said throttle 54 is so controlled being hereinafter described.

f lAbove venturi 53-isa draft tube 55.4 Said draft tube is adapted to draw fuel from reservoir l through tube (see Fig: 6) and fuel metering orifice 5'!,a small amount Of'air being admitted through air bleed 58. The means by which fuel is drawn into draft tube 55 differin nov way from those by which fuel is drawn into draft tube-i4 except, of course, that different sizes of air bleeds and fuelmetering orices may be used in each.

Said venturi is provided with an air restricting member 59 resembling member I6, but differing therefrom, in the form which I prefer, 'in'that lit does not completely close the annular'spacebetween the venturi and the draft tube, whereas member I6 does completely closer the correspond` ing space when fully lowered. 1- Air Yrestricting member 59 is adapted to be raised by yoke 60' carried by rod 6| (see Fig. 8) which engages cam 62 afxed to shaft 63 which also. carries throttle 54. Thus, when said'throttle is opened, member 59 will be raised correspondingly. shape said cam so that said throttle f will be opened substantially before said choke is raised. I desire throttle 54 to be gradually opened, and member 59 to be gradually raised, when the speed of. the engine increasesV to the pointwhere the velocity of the air through venturi l1 reaches a predetermined value, said value being that at which the performance of said engine begins to be impaired by an inadequate supply of air-fuel mixture. creases with said velocity in venturi I1, I utilize said vacuum to open throttle 54, said velocity in venturi I1 thus indirectly causing said opening. Iapply the aforesaid vacuum in chamberv l 9 to piston 64 in cylinder 65 by means of tube 4| (see Fig. 2). Said vacuum is also applied by said tube to piston 32 in cylinder 45 for the purpose hereinbefore described. Passageway 66 connects the in cam 62 to rotate the latter when said piston-` I prefer vto Y Since the vacuum in chamber I9 inseamos moves. Movement of sa-id piston is restrained Lby spring 'flu whose com-pression is adjustable by screw Il-i. '-Ihus, when lvacuum -is 'applied 'to lcylinder piston 'li will r-meve to the left, -asviewed `in Figs. l and t6, under Iat'rnosp'lzeric air :pressure applied `to said lpiston 'through hole d'2. VAs 4said piston moves 4to the leit,r;pin d8 wil-1 -cause cam 52 to rotate thus opening throttle `=54 and lifting choke 59. i y

I deem -it vimportant that 'screw fH tbe so adjusted that s pring'fm nasa certain lbasic compression when no vacuum -eXists --in cyl-inder, that is, I prefer 4said spring to press vpiston^6il against the right-hand end `of Ycylinder 615 -as is lshown -inFig 5. Then, `when vacuum is appli-ed vto 'cylinder 155, piston 64 will not immediately Lbegin. to move; it wi-llremain stationary until tthe force due ito said vacuum -exceedsfsaid basic -compression whereupon -a ffur'ther increase ofi Torce due to -said vacuum will produce movement :of said piston. Thus, throttle it lwill be opened when -a 'predetermined -air Lvelocity in venturi lI?! iis reached, and said'i'predetermine force ymay be :regulated -by :means of screw 215|. AvByfway of example, -it'imay -ibe :found that the primary car'- bureting l'chamber her-einbefore described 1becomes inadequate to supply its engine with air-fuelimrrture yat automobile speeds above 35 miles `per Lhour. Screw "Till Imay then be adjusted -s0 that ithrottle 5ft twill'foagin `to open atfan automobile speed of Si) miles -perhoun :thus Pbringinginto use le secondary fcanbureting chamber when lit ris needed. Then, las the speed of said Lengine 1is increased 'furthe-r, throttle i515 will vJoe further "opened `and member T59 further-raised-unti-l, finally, fthe f'full :capacityoi barrel 552 ovillioe available.

"However, theioperiingofithrottle dllisfcontrolled iprimaiiily '-Ioy the vacuum Vsurzuiuniling Aventuri fifi, :which iis not :necessarily proportional Ito :en-- gine speed.l n'I1-nus, the engine 4may `operate `:at high speed .with th'e :automobile .going downhill without' thes econdaryfcarbureting :oh-amber "being rought into fuse, :because manually .operated itlirott-le 22 3 :will *theniordinarily ib eclosed, or :nearly closed, :so thatzlittlevacuum will 'eXistabove wit. 'lipreier ithesse'oondary `oarourstingchamber to :loe 'brought 'into use 101115' whenwthe engine fis ropera ng at high :speed :and :under 4suilio'ientload :to over `inthe :primary icarhuretinglcham'ber, Vand `the herein described twill achieve :said 1reult. `cura-.enum atsiliiscannccurateiindieator of fused for -fgreater iearburetor .capacity It will he understood that the idling air-:fuel :pasffsagoway herein :described lisalso e'iective atvhighrer speeds, v:but zits capacity fis vnecessarily dimited. y

Si describedfrneansf'or Asupplying lan: engine s.with the proper quantity l.of fuel frnxture atlow speedsand alsofa-thighfspeeds, but er1-extremely 'highfspeeds itis desirahleitoienrichftherusl-rnix ture-:so supplied. To 'achieve thiszresultjI-fcause the auxiliary fair-,fuel passageway fhereinbeiore describedn to :beibrought dnto :useat said extremely high fspeeds. "This trequires z-iuait Naive -stem .68, land parts assembled thereon, 'move .to 'the fle'ft -from A4the :pnsitionfinwhidh it dsishown in fFig.i2.

.ns mentioned, iat llow engine :speeds Vanyy considerable 'opening of :throttle :23 `Will -cause fsaid Ivalve 'stem to move to ithe ileit. ,Ii-Iou'ever, zat moderately high engine (speeds, .a substantial v:vacuum from venturi "irl fis lappliedftomisten i312 :throughtube :M thereby ionposi-ngfsaid movement of -`stem :313, permittingfit ,to ,move only when 4.throttle .12:3 iis suddenly 'opened Art extremely vrhigh speeds, :the device zassdescribed thus'rfa'r `-would :permit 'stern :Bil :to imove sto zthe left only upon -a .verysudden opening o'i .throttle 23; 4.with the .normal wide open v.position `of said .throttle 23 A.and o'fitl'irottle di .at-extremely high speeds, the auxiliary Yair-duel Jpassageway would not `be `5 brought Sinto puse, whereas .itis .desired that it 4function .at top engine speeds with Athe throttles open. As mentioned,-the reason for this diiier- `ence is :the application of vacuum to .piston 3,2y through itube 41. Therefore, to :permit said :aux- Al() iliary ain-:fuel :passageway .to `he :brought into use :readily at high engine .speeds with throttles '23 and 154 iope'n, I :compensate ifor the .aforesaid applicationrof vacuum :to piston 132 through tube 4-I by-applying vacuum Yalso to .ftheiotherside of .said :piston through 'tuhefilf f(seeFig.-6-).

llheivacuum applied to .piston r3.2 through ,tube M is produced by the oW of air-fuel mixture through venturi.53,rholes T3 'connecting` said tube fto lsaid '.venturi. Sincesaid venturi is yrendered '20 -operativeby the iopening Aoi throttle '5d only .at

Lhighispeeds, its wtaouum loan .be `applied to `piston `3-2onlya'tfsaidrspeeds.` iIIowever, `I do `not wishsaid'vaeuumto become .effective against pisiton 32 .itoienriohithe ifuelim'ixture supplied to the 2.5iengineiexceptat.extremelyhigh speeds; I do .not Wishfit ito Yiloeeorne 4effective .at' the lmoderately 'dow :speed at `which @throttle li'd starts to open. This -result isachieved :through aperture d3 having a :bore fsuf'ciently ,flarge fto `:permitatmos- -phericairto1heeifectiveagainst said .piston until ia 1ra-ther fhigh Vacuum is produced 'by venturi 53, that is, until entremely'high -engine speeds are;reacued. dtiwillibeiapparent .that the speed fat which .anreffective lvacuum 1is applied to the 35.1et-hand end ofepiston 3.2 .may be regulated by varying the bore of 4aperture 143.

IWitli misten 32 rendered,ineffective at .extreme- .flfyhigh engine speeds, 'spring' 3.5 will `move stem w35 to `.the lleit when throttle :23 is yopened, the

.40 vacuum than eecive :against pistons and im berlg .fsuioien't tooppose Vsaid .i spring. This re- :suits :in ;an renriched :mixture `for itheuengine vat extremelyshigh tengin'e :speeds only 'when throttle 'l2-3 isfopen, whichis'thedesired result. `Of course,

the movement of stem #83 to the left not lonly `@nous :valve 32.3 to make the auxiliary air-'fuel "hassagevayeiective :but it also lowers yi'nen'iber :L6 thus further enriching said .mixture .Although I yhave/described various pistons vand cylinders for utilizing Adifferentair pressures .to

Qontrol :the iautomatic :features -of my invention,

zit :.Wiil fhe iunderstood that .said pistons and cylin- .derszmightzhe replaced 'by any suitable form of diaphragmzorbellows adapted toiproduce a simsilarfresult Pwith-out .departing from the `principles @of .said iinvention.

Although I have :described members Iii andtig .asair ucstricting members, `.the principal funcwtinnmf these membersiistotincrease the velocity of air .1in :order tthat -zit may better'serve to break eupimechanically and iintermix withthe gasoline,

:and to sincrease fthe vacuum immediately below @fait '.tu'hes flil vfand .5.5 itfhereby` assuring `complete fvaporzation of said gasoline.

Llna carburetor, aeplurality of carbureting idovices fdischarging fin't'o a common outlet, one

offsad devicessconstituting a primary device vand :anotherroonstituting asecondary device, man- `-uatly ,ope-rated `'throttle 'valve arranged in `said 'fpriniary `device La yfncirrnall-y closed auxiliary throttle l:valve -arranged 'in ysaid secondary chainhel, meanszoperativelyactuated by pressure iiuctuations in said primary carburetingdevice operf'o ativelyzengaging :the throttle fvalve in said 'secondary ,carbureting device, Vsaid primary and secondary carbureting devices each including a Venturi tube,a duct leading from the throat of the Venturi tube in the primary device to said means, a choke ring resiliently seated in the mouth of the Venturi tube in the secondary device to decrease the cross-sectional area of the bore of said Venturi tube, said ring being operatively `ioined to the throttle valve in said secondary device to be unseated when saidauxil'- iary throttle valve is opened, whereby when the auxiliary throttle valve in the secondary device is initially opened said secondary carbureting device is choked and further opening thereof moves said choke ring progressively out of the thoat of the Venturi tube in said secondary carburetor.

2. In a carburetor, a carbureting chamber having air and fuel passageways discharging into said chamber,` an automatically actuated accelerating device having an auxiliary air-fuel `passageway adapted to discharge a fuel rich airfuel intermixture into said chamberya pressure responsive valve mechanism for restricting iiovv of both air and fuel from said auxiliary air-fuel passageway, and resilient means tending to hold said valve mechanism closed inthe presence of a predetermined air pressure within said chamber and to yield in the presence of a greater air pressure within said chamber to permit the dis-- charge from said auxiliary air-fuel passageway into said carbureting chamber. f f

3. In a carburetor, a carbureting chamber having air and fuel passageways discharging into said chamber, an automatically actuated accelerating device having an auxiliary air-fuel passageway adapted to discharge a fuel 'rich airfuel intermixture into said chamber, a pressure responsive valve mechanism for restricting flow of both air and fuel from said auxiliary air-fuel passageways, and resilient means tending to hold said valve mechanism closed in the presence of a predetermined air pressure within said chamber and to yield in the presence of a greater air pressure Within said chamber to permit the disf charge from said auxiliary air-fuel passageway into said carbureting chamber, and means for progressively increasing the ratio of fuel to air as said valve mechanism moves from seated position to fully opened position. f

4. In a carburetor, a carbureting chamber, air and fuel passageways leading to and discharging into said chamber, an automatically actuated accelerating device having an accelerating valve mechanism, an auxiliary air-fuel passageway discharging into said chamber, said accelerating valve mechanism controlling the flow'through said auxiliary air-fuel passageway, said accelerating valve mechanism comprising a reciprocally mounted Valve stem extending transversely of said chamber, a cylinder opening to ksaid chamber, a piston element operatively mounted in said cylinder, saidpiston element carried by one end of said valve stem, a plunger carried by the other end of said stem, a plunger cylinder, said plunger operatively mounted therein, a valve carried by said stem, a valve seat lying transversely of said auxiliary air-fuel passageway, said valve in one position being adapted to engage said seat, said valve seat lying intermediate said chamber and said plunger cylinder and elastic means engaging said plunger and being formed and arranged to tend to space said valve from said seat.

5. In a carburetor, a carbureting chamber, air

and fuel passageways leading to and discharging into said chamber, an automatically actuated accelerating device having an accelerating valve mechanism, an auxiliary air-fuel passageway discharging into said chamber, said accelerating valve mechanism controlling the iiowl through said auxiliary air-fuel passageway, said accelerating valve mechanism comprising a reciprocally mounted valve stem extending transversely of said chamber, a cylinder opening to said chamber, a piston element operatively mounted in said cylinder, said piston element carried by one end of said valve stem, a plunger carried by the other end of said stem, a plungerl cylinder, said plunger being operatively mounted therein, a valve carried by said stem, a valve seat lying transversely of said auxiliary air-fuel passageway-said valve in one position adapted to engage said seat,.said valve seat lying intermediate said chamber and said plunger cylinder, and a series of ports extending from the bore of said plunger cylinder to atmosphere, said ports being spaced longitudinally of that portion of said plunger cylinder traversed by l said plunger thereby to be covered and uncovered by said plunger as it moves back and forth in said cylinder.

6. In a carburetor, a carbureting chamber, air and fuel passageways leading' to and discharging into said chamber, an automatically actuated accelerating device having an accelerating valve mechanism, an auxiliary air-fuel passageway discharging into said chamber, said accelerating valve mechanism controlling the flow through said auxiliary air-fuel passageway, said accelerating valve mechanism comprising a reciprocally mounted valve stem extending transversely of said chamber, Aa cylinderv opening to said chamber, a piston elemen-t yoperatively mounted in said cylinder, said piston element carried by one end of said valve stem, a plunger carried by the other end of said stem, a plungercylinder, said plunger being operatively mounted therein, a valve carried by said stem, a valve seat lying transversely of said auxiliary air-fuel passageway, said valve in one position adapted to engage said seat, said valve seat lying intermediate said chamber and said plunger cylinder, an adjustable choke ring in said chamber, a tapered cam on said stem, and a follower operatively engaging said choke ring and said cam, whereby said choke ring is actuated by the reciprocal movement oi said stem.

7. In a carburetor, a carbureting chamber, air

, and fuel passageways leading to and discharging into said chamber, 4an automatically actuated accelerating device having an accelerating valve mechanism, an auxiliary air-fuel passageway discharging into said chamber, said accelerating valve vmechanism controlling the flow through said auxiliary air-fuel passageway, said accelerating valve mechanism comprising a reciprocally mounted hollow bored valve stem extending transversely of said chamber, a cylinder opening to said chamber, a piston element operatively mounted in said cylinder, Asaid-'piston element carried by one end of saidvalve stem, said stem being ported tothe bore thereof, said ported portion opening to said chamber, a plunger carried by the other end of said stem, a plunger cylinder, said plunger operatively mounted therein, the borein said stem opening Ythrough. the plunger and into the plunger cylinder, a valve carried by said stem, a valve seat lying transversely of said auxiliary air-fuel passageway, said valve in one position adapted to engage said seat, said valve seat lying intermediate said chamber and said plunger cylinder, and elastic means engaging said plunger and being formed and arranged to tend to space said valve from said seat.

8. In a carburetor, a carbureting chamber, air and fue] passageways leading to and discharging into said chamber, an automatically actuated accelerating device having an accelerating valve mechanism, an auxiliary air-fuel passageway discharging into said chamber, said accelerating valve mechanism controlling the flow through said auxiliary air-fuel passageway, said accelerating valve mechanism comprising a reciprocally mounted hollow bored valve stem extending transversely of said chamber, a cylinder opening to said chamber, a piston element operatively mounted in said cylinder, said piston element carried by one end of said valve stern, said stem being ported to the bore thereof, said ported portion opening to said chamber, a plunger carried by the other end of said stem, a plunger cylinder, said plunger being operatively mounted therein, the bore in said stem opening through the plunger and into the plunger cylinder, a valve carried by said stem, a valve seat lying transversely of said auxiliary air-fuel passageway, said valve in one position adapted to engage said seat, said valve seat lying intermediate said chamber and said plunger cylinder, elastic means engaging said plunger and being formed and arranged to tend to space said valve from said seat, a series of ports extending from the bore of said plunger cylinder to atmosphere, said ports being spaced longitudinally of that portion of said plunger cylinder traversed by said plunger thereby to be covered and uncovered by said plunger as it moves back and forth in said cylinder, an adjustable choke ring in said chamber, a tapered cam on said stem, and a follower operatively engaging said choke ring and said cam, whereby said choke ring is actuated by the reciprocal movement of said stem.

9. In a carburetor, a throat having a discharge outlet leading therefrom, an air inlet, a draft tube extending longitudinally of the latter, a fuel conduit discharging into said draft tube intermediate its ends a Venturi tube leading from said draft tube but spaced laterally therefrom, a movable annular choke ring slidably mounted upon said draft tube adapted in one position to seat in said Venturi tube and close the space between the latter and the draft tube, and in another position to be spaced substantially from said Venturi tube to uncover said space, and means actuated by the variance of the pressure of air in said throat for moving said choke from one position to another.

ALLEN E. CHISHOLM.

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