US2595720A

US2595720A - Carburetor

Info

Publication number: US2595720A
Application number: US710388A
Authority: US
Inventors: Charles R Snyder
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-11-16
Filing date: 1946-11-16
Publication date: 1952-05-06
Anticipated expiration: 1969-05-06

Description

C. R. SNYDER May 6, 1952 CARBURETOR 3 Sheets-Sheet l Filed NOV. 16, 1946 May 6, 1952 3 Sheets-Sheet 2 May 6, 1952 Filed NOV. 16, 1946 C. R. SNYDER CARBURETOR 5 sheets-sheet 5 ('zarZeSR Snyder Patented May 6, 1952 UNITED STATES'PATENT OFFICE CARBURETOR Charles R. Snyder,Miam Beach, Fla.

Application November 16, 1946, Serial No. 710,388

6 Claims. (Cl. 261-50) This invention relates to improvements in carburetors for internal combustion engines, it being a general object of the invention to provide a carburetor so constructed as to produce in its operation properly proportioned combustible mixtures of volatized liquid fuel and air, and wherein such mixtures are delivered in regulated quantities to the cylinders of an associated engine in a manner best suitable to obtain high efciencies in the operation of the engine.

In conventional carburetor construction, liquid motor fuel is supplied to one or more vertical jets, or liquid fuel-receiving wells, under control of a float valve in a fuel reservoir. The fuel is withdrawn from these jets or wells by the air stream' passing through the mixing chamber ofthe carburetor under the action of the piston of an associated engine. Normally, there is provided a manually operated throttle valve in the outlet of the carburetor mixing chamber to govern the flow of fuel mixture to the engine cylinders. .In such conventional carburetors,

face of the air throttle valve, the latter functioning as a baie or turbulence-promoting element. The unvaporized fuel is removed from the surfaces and peripheral edges of the throttle valve by the sweep of air thereover and in particle sizes too large for instantaneous and complete vaporization. For this reason, intake manifolds and passages have been developed having physical designs for increasing turbulence in the mixture flowing to the engine cylinders, together with various types of heaters for asssting inthe vaporization of the liquid fuel before final delivery thereof to such cylinders.

In addition to incomplete fuel vaporization, and its resultant fuel wastage and other disadvantages, conventional carburetors are provided usually with a manually operated air valve control which admits of mixed fuel delivery to engine cylinders in a manner inconsistent with the fuel demands required in various stages of engine operation. For instance, whenV an engine is laboring under heavy load conditions, or when the accelerator control of the carburetor is substantially fully depressed, as in passing vehicles proceeding in the same direction, or in other attemps to produce rapid increase in the speed of a motor vehicle, the substantially fully open position of the air throttle valve of a standard carburetor, under these conditions, cause the carburetor to supply the engine cylinders with fuel mixtures in which the fuel-air ratio and volume of the mixture are disproportionate to the proper working requirements of the engine.

Accordingly, the present inventionhas for certain of its objects, among others, to provide: a carburetor in which the volumes'of the mixed fuel delivered thereby to the engine cylinders, and the fuel-air ratio of the mixtures, are governed automatically by working loads on the engine in addition to the control provided through the operation of manually regulated valves; a carburetor in which float-actuated valve controls are eliminated; a carburetor in which the air throttle valve is located in the entrance to the fuel-mixing chamber of the carburetor; a carburetor having a movable control valve for regulating the metered inflow of liquid fuel into a passage leading into the mixing chamber, and wherein provision is made for advancing a conned and independent stream of air through the passage to produce a primary fuel-air mixture which is forced through spray ports and delivered in an atomized state into the main air stream of the carburetor, producing the final fuel mixture; a carburetor in which a fuelmetering valve and air-throttle valve are linked together for movement in unison for maintaining proper proportions in the fuel-air mixture; a carburetor having a check mechanism responsive to varying degrees of vacuum in the mixing chamber thereof for restraining automatically the fuel-metering and air-throttle valves against operational movement under abnormal conditions of operation, and for releasing said valves upon restoration of normal operating conditions; and in the provision of a carburetor which will function in any position of operation so that the same may be adapted for use in conjunction with airplane engines.

Another object of the invention is to provide a carburetor which is characterized by its mechanical simplicity, manufacturing economy and the elimination of delicate controls and parts readily susceptible tocmechanical disorders.

This application constitutes a continuationin-part of my prior application, Serial No. 670,814, filed May 18, 1946.

For a further understanding of the invention, reference is to be had to the following description and the accompanying drawings, wherein:

Fig. 1 is a vertical transverse sectional view taken through a carburetor constructed in accordance with' the present invention;

Fig. 2 is a top plan view thereof;

Fig. 3 is a vertical sectional view on the plane indicated by the line 3--3 of Fig. 1;

Fig. 4 is a fragmentary enlarged vertical sectional view taken through the fuel metering valve assembly of my improved carburetor;

Fig. 5 is a detail horizontal sectional view on the plane indicated by the line 5-5 of Fig. 4;

Fig. 6 is a vertical transverse sectional View on the line 6-6 of Fig. 4;

Fig. 7 is a front elevational view of the carburetor and disclosing the air-admitting valve shaft of the carburetor and its associated pneumatic check mechanism;

Fig. 8 is a rear elevational view of the carburetor disclosing the linkage uniting the operating shafts of the fuel-metering valve and the air-admitting Valve;

Fig. 9 is a detail vertical sectional view taken through the pneumatic check mechanism for regulating the operation of the air-admitting valve shaft;

Fig. 10 is a detail elevational view of a portion of the air and fuel valve uniting linkage, as indicated by the line |I0 of Fig. 8;

Fig. 11 is a horizontal sectional view on the line II-II of Fig. 10.

Referring more particularly to the drawings, wherein is illustrated a single preferred embodiment of my improved carburetor, the numeral I designates the lower section. of the casing C of the carburetor and the numeral I6, the upper section thereof. The upper part of the lower section is f-ormed with an outturned flange I1 upon the upper surface of which is seated a laterally directed annular flange IB formed with the lower end of the upper section I6. 'These flanges are formed with registering openings I9, the openings in the flange I1 being threaded for the reception of the threaded Shanks of cap screws 20, whereby to unite the two sections of the casing in assembled order. If desired, the lower part of the upper section may be formed with a depending web 2|, which protects the joints formed between the meeting surfaces of the casing sections I5 and I6 against undesired fluid passage or seepage.

Clamped between the casing sections I5 and I6, when the same are in assembled order, is a transversely and horizontally extending bar or cross member 22, the ends of the latter being formed with longitudinally projecting flanges 23 which are adapted to be received in recesses 24 provided in the upper surface of the lower section I5. In transverse cross section, as in Fig. 3, the bar 22 is semi-round, as at 25, the same being formed with a flat under surface 26, the outer surfaces of the bar being spaced from the inner surfaces of the casing section, as at 21, to'provide for the free flow of air through the casing Afrom the air inlet end 28 thereof in the top of the casing to the carburetor fuel mixture outlet 29 in the bottom thereof.

The bar 22 is formed with a longitudinally extending bore 30 in which is stationarily posi- -tioned a tube 3|. At one end, the tube 3| terminates in an externally threaded extension 32 projecting stationarily from the outer periphery -of the flange I1 of the base section I5. The outer end of the extension 32 is formed with a seat Iwith which engages the conically tapering end of a head 33 formed on a conducting pipe 34 through which liquid fuel, obtained from any suitable source of supply, is advanced positively, a-s under gravity or pump-pressure flow, to the carburetor. The head 33 is held in engagement vwith the seat of the extension 32 by means of an -internally threaded nut 35, one end of the latter being flanged to engage with the shoulder formed at the back of the head 33, whereby to retain the head in its seated position in connection with the extension 32.

The tube 3|, centrally lof its length, is formed with vertical ports 35 which register with a corresponding vertical opening 36 formed in the bar 22. The upper end of this opening is enlarged to receive the lower end of an air-conducting tube 31, the upper portion of this tube being received in and retained by openings formed in the wall of the upper casing section I6. The tube 31, as shown particularly in Fig. 3, is shaped and positioned so that it does not interfere mechanically with the operation of a diskshaped air-admitting or throttle valve 38, employed in regulating the flow of atmospheric air into the carburetor through its air inlet 28. The open upper end of the tube 31 is positioned so that air will pass through said tube at all times independently of the operating positions of the valve 38. The lower end of the vertical opening 36, which passes centrally through the bar 22, is enlarged and threaded for the reception of an injector plug 39, the latter being provided with a plurality of ports 49 of relatively restricted diameter as compared with that of the opening 35 and -through which ports liquid fuel under metered flow control and admixed with air is delivered to the maxing chamber M of the carburetor.

Governing the flow of liquid fuel from the pipe 34 and the tube 3|, through port 35, opening 36 yand plug 39, is a sliding valve stem 4I, the latter being mounted for longitudinal sliding movement in the tube 3| of the bar 22. The inner end of the stem 4I is of tapered or needle-like form, as indicated at 42, and normally is disposed in registration with the ports 35. However, through means to be hereinafter described, the position of the tapered end of the valve stem may be varied, under manual control, to regulate the amountof fuel adapted for delivery to the mixing chamber, or to arrest such flow altogether. By reference to Fig. 5, it will be noted that the walls of the port or ports 35 are, in horizontal section, deepened or enlarged in the horizontal plane thereof registering with the stem 4I, so that the body of the stem, when in registration with said ports, will not interfere with the flow of air into the mixing chamber from the air-supplying tube 31. By maintaining this flow of air in a manner independent of the operating positions ofthe Valve 38, a carefully metered flow of motor fuel into the tube 31 is obtainable in all stages of engine operation, irrespective of the varying degrees of vacuum in the instrument below the airadmitting valve 38.

To operate the fuel-admitting valve stem 4I, the outer end of the latter is diametrically enlarged and threaded as at 43, the same being received in the internally threaded bore 44 of a sleeve 45. This sleeve, as shown in Fig. 6, is formed with laterally and outwardly projecting ribs 46 which are slidably but non-rotatably received in elongated s1ots'41' provided in the outer end of a stationary valve cage 48, the inner end 49 of said cage being received in a socket 50 formed in the flange I1 of the lower casing section I5. AInwardly the cage 48 is formed to provide a transverse web for the slidable reception of the valve stem 4I, and engaging with one surface of this web is one end of a coil spring 52, the latter surrounding the stern 4I for a limited part of its length. The end of the spring 52 opposite to that engaged with the web 5| bears on a collar 53 fixed to or forming a part of the stein, the tendency of the spring being to force the stem forwardly together with its sleeve 45. This movement is controlled by the engagement of the end surfaces of the ribs 46 of the sleeve 45 with cam surfaces 54 formed on the outer face of the hub 55 of a lever arm 56, the lever arm being freely rockable on the circular outer portion of the cage 48.

The lower end of the lever arm 56 carries a d block 51 having horizontal trunnions 58, the latter being received in openings formed in the lower end of the arm 56. The block 51 is formed with a bore for the slidable reception of a manually operated control rod 59 which, conveniently, may be operated through the usual manual controls of a motor vehicle, such, for example, as the accelerator pedal or a hand throttle control, not shown. Fixed to the rod 59 is a pair of spaced collars 60, and surrounding the rod 58 and in engagement with the outermost of these collars is one end of a coiled expansion spring 6 I, the other end of this spring being in contact with the block 51. The extent of oscillating movement of the arm 56 may be controlled by contact with one or the other of a pair of stop screws 62, the latter being adjustably mounted in brackets 63 stationarily carried in connection with the casing section I5.

Substantially midway of its length, the arm 56 is provided with an outwardly projecting stud 64 around which is adjustably clamped the bifurcated head 65 of a pair of crank rods 68. These rods, towardtheir outer ends, engage the under side of a block 61 provided upon the lower end of a substantially vertically disposed link rod 68, the rods 66 at their outer ends being provided with pivot blocks 69 between which the'lower end portions of the link rod 58 are pivotally confined. It will be understood that, in efiect, the lever arm 56 and the crank rods 66 move as a rigid unit. In Fig. 8 of the drawings, the lever arm is shown as occupying a position providing for full opening of the fuel valve 4I and the air throttle valve 38, as occurs. when the foot accelerator pedal of a motor vehicle is fully depressed. When the accelerator pedal is released, the lever arm 56 engages with the stop screw 62 at the right of Fig 8. When the lever arm is so positioned, the crank rods 66 and the Alink rod 68 occupy relatively elevated positions.

The upper portions of the link rod 68 have xed thereto a pair of spaced but adjustable clamps and 1I, and slidably mounted on the link rod between these clamps is a collar 12. This collar is formed, as shown in Fig. 10, with a pair of outwardly directed horizontal studs 13 which pivotally support spaced sets of clamping links 14, these links being frictionally united with the outer end portions of a pair of crank rods by means of clamping screws shown at 16. The inner ends of the rods 15 project from a split type hub 11 which is adjustably fixed on the outer end of the operating shaft 18 of the air valve 38. y

Through this arrangement, and under normal conditions of operation, the air-admitting and fuel valves 38 and 4I operate ln unison to admit of proportioned inflow of air and fuel into the mixing chamber of the carburetor. However, provision is made under special conditions for admitting of limited relative movement, as will be presently described, between said valves to satisfy emergency or abnormal fuel demand conditions on the part of the carburetor.

For example, as my improved carburetor is constructed, its operation is responsive to variable suction, vacuum or pressure conditions existing in the mixing chamber of the carburetor. These conditions, in turn, are governed by (a) the operating positions of the air throttle valve 38 in the air inlet of thev carburetor, and (b) the load conditions on the associated engine, or (c) any combination of conditions (a) and (b). Thus, if the associated engine should be laboring under highload conditions, as when a motor vehicle is ascending a steep grade, the usual tendency of the vehicle operator is to press on manual controls opening the throttle and fuel valves to a maximum extent. Such action in an ordinary carburetor normally results in the feeding of an excess and too rich a fuel mixture to the engine cylinders, but in the present invention, this is avoided by the provision of a mechanism for checking or restraining the opening of the throttle and fuel valves until the engine attains higher operating speeds and the air valve comes into control instead of motor load.

To this end, the throttle valve shaft 'I8 is journaled for rocking movement in bearings shown at 'I9 and 88, which are formed in the upper casing section I6. One end of the shaft 18 projects beyond the bearing and has fixed thereon a U- shaped bracket 8| carrying adjustable stop screws 82. The inner ends of these screws are appropriately spaced for coaction with a stationary vertical web 83 formed exteriorly on the outer wall of the bearing 88, as in Fig. 2, whereby to positively but adjustably limit the extent of oscillation of the throttle valve shaft. Also, fixed on the same outer end of the throttle valve shaft as the bracket 8| is the split clamping hub 84 of a crank arm 85. Loosely mounted on the outer end of the shaft 18 around the hub 84 is the bifurcated end 86 of another crank arm 81. The crank arm 81 has xed thereto a pin 88 which projects through an opening A89 provided in the crank arm 85. The lower end of the pin 88 carries a stop nut 90 with which is engaged the lower end of a coil spring 9|, the upper end of the spring being engaged with the crank arm 85. crank arms and 81 move in unison during turning movement of the throttle valve shaft. However, under special conditions, the spring 9| will permit of limited turning movement -of the throttle valve shaft and the arm 85 relative to the arm 81 when the latter is held against movement by la uid actuated check mechanism 92 hereinafter defined.

This check mechanism has been best illustrated in Figs, 7 and 9 of the drawings. Conveniently, the same may consist of a cylinder 93 stationarily. supported in a substantially vertical position byl the lower section I5 of the casing. Arranged for reciprocation within the cylinder is a piston 94A Normally, the.

this link being `pivotally `connected as at I I 4with the outer end of the crankarm 81.

Thelower end of the cylinder 93 has threaded therein a tting IGZ in which is arranged a spring pressed check valve |33 which, when seated, prevents the passage of air, or other iuid, from within the cylinder to .the exterior thereof throughthe air inlet port Idil, thusholdingfthe piston 94, for example, yagainst.cS-.ovvnward 'movement.

` To render the operation of the check mechanism responsive automatically to variable ,vacuum conditions present in the carburetor, the upper section I6 of the casing immediately below Ythe valve 38 and in vertical registration with its shaft, is formed with an opening for thereception of ra threaded pipe fitting, or union H35. As shown in Fig. v'1, the pipe IE6 extends from this -fitting or union to avalve cylinder |31, which is threaded, as at IIl8, into the lower end of the main cylinder 93. A'One end of the cylinder |01 is formed with arestricted passage |63 which is adapted to be closed by a needle-Valve IIO. This valve is carried vby Aa'hollow piston III` slidably mounted in the cylinder LIQ?, and the-latter piston is forced forwardly to seat the valve lI I6 by a spring shown at II2. At one side of the tapered end of the needle valve I I0, the cylinder I1 is providedwith a fluid-exhausting port IIS. Internally, near its lower end, the cylinder 93 is slotted, as at I I1, to render the check mechanism ineffectivewhen the engine is operating in a given high speed range.

Vv'henthefcarburetor is functioning normally without excessive load conditions on the engine, sufficient vacuum is created in the air passage formed in the upper section IG of the carburetor to move the piston II I against theopposition of the spring II2 so that'the needle valve IIi occupies a position opening the passage |39. rhis permits the piston 911 to move freely in the cylinder 93, particularly in a downward direction, as the air or other fluid beneath the piston gli readily passes through the passage |33 and the exhaust port IIS. However, if the engine is laboring under heavy load conditions, with resulting decrease in value of the vacuum in the upper part of the carburetor casing, the spring i I?. be'- comes effective to move the piston III and the needle valve III) to a position obstructing the passage |09, thus'acting in conjunction with the checlcvalve |03 to arrest descent of the piston 94 inthe cylinder "93, thereby locking the throttle and fuel valves against undue acti-lation so :that an overly rich fuel mixture will not enter the engine cylinders.

With the fuel-metering valve I and the air throttle valve 38 thus held against movement, if the vehicle operator actuates the Vcarburetor manual control to its fullest extent in a direction to yopen the carburetor for maximum engine speed, the movement of the control rod 59 is yabsorbed by the spring EI, so that the latter becomes compressed and applies its load to the lever arm .55. As the engine gains speed, as a result of decreased loadconditions thereon, the suction forcesor vacuum in the carburetor casing increase, thereby moving the check mechanism piston Sli against the action of its springto cause the needle valve Ii to open the passage IUS, allowing the descent of the piston 34 under the `forces exercised'by the loading of the spring 5I, thus restoring the carburetor and its controls to normalv operation.

` 'When 'the fcheck mechanism is ,operative to f resist rotation Yof the tnrettle-valxeshaft '18, the controls ofthe carburetor aresuchthatA-limited oscillation of the lever arm-5 6 may-be provided to open the fuel metering -valve to a limited degree. `'Ihus'in Fig-8, it will be Yobserved that the clamps 10 and 1I may be -adjusted-onthe vertical link -68in slightlyaspacedrelation from the collar v1,2so that the lever armgimey swing a distance ina direction toppen,thefuelfadmitting valve-,4I governed by thespacingbetweenthe clamp 1I) and the collar 12. This adjustment provides foraslight increase in Vtherichness of the mixture whenthe air throttle ivalveisheld in substantially its position o f closure by the operation of the check mechanism. Similarly, the spring 9| may be-adjusted toadmit ofl a limited amount of opening movement of the throttle valve 38 vwhen the check mechanism is locked against movement of its piston 94, so that both the throttle valve and fuel valve may be. opened to a limited extent with'the piston 94 maintained against movement. The bearing 19in-the upper part of the carburetor casing is surroundedI by a coil spring, shown at I It. One end-of this spring is fastened to a collar II5 whichis fixed on the throttle valveshaft 13, while the other end ofthe spring is fastened tothe carburetor casing. `".IEhis torsion spring tends to turn the shaft 1-8 vin a direction-maintaining contactl betweenthe collar 'I2 and the lower of the stop clamps1l.

By the provision of the airitube 131, a positive flow of air takes place therethrough to maintain the flow of primary lfuel mixture'into'thecarburetor mixing chamber at all engine speeds and vacuum or suction conditions existingJ in the carburetor casing. jWhen the .air throlttle-valveis substantially closed, causing static .vacuum conditions around the injector plug 39,barometric pressures force atmospheric air through the tube 31 and around the valve stem SI. yWith the throttle valve open and motorfloadilimiting the speeding up of the motor, dynamicvacuum still maintains suction at the injector toicause air flow through the tube.

The ports 40 in theinjector plug39 collectively possess less area than that afforded by-the'internal diameter of the tube 31 or the openings 36, with the .result that the primary fuel mixture, upon being forcibly discharged from the nozzle plug into the mixing chamber of thecarburetor, is in a finely divided or mist-like form, being propelled atihigh velocity Vinto the .air stream passing through the carburetor; vand-witlrwhich the primary mixture is combined to .form vthe final combustible mixture for engine operation, thus overcoming variable vacuumconditions in the mixing chamber land preventing ysuch conditions from interfering with the vmetering of fuel into the mixing passage '36. As the Yair throttle valve is opened to a greater extent, providing for increased air flow through the carburetor, dynamic vacuum conditionsexist aroundftheinjector plug 39 to produce positively'the AVdesired force Vflow of rair through the tube-31.

Conveniently, 'the 'upper end of @the tube 31 may be associated with-'a conventional air lfilter, not shown, nowcommonly used on engine carburetors, so that air passing through the tube 31 will be filtered andsolids-aptto clog Alhefports 40 removed therefrom. By the positionand formation of the bar 22and thelocation of` the-plug 39 on thevunder sidethereofpfa conical'vacuum region,as indicated by thearrows V,jis believed to be .maintained around vthe injector plug, so

.that 4the finely divided vprimary mixture issuing mingling of the volatilized fuel particles with the air stream. l

In view of-the foregoing, it will be evident that the present invention provides a carburetor which is responsive automatically to the load on an associated engine to regulate the amount of the combustible fuel mixture supplied by the carburetor tothe engine cylinders. lByl providing the cylinders at all vtimes with a properly balanced fuel mixture, improved engine operating conditions vunder all stages of operation are made possible and, in addition, substantial savings are obtained, with respect to conventional carburetors, in fuel consumption. The mechanical construction of my improved carburetor is essentially simple, so that the same is reliable in operation, economical to manufacture, and is capable of giving long and satisfactoryr service without requiring frequent repairs or adjustments. While 4I have set forth above in considerable detail my beliefs as to the operating principles and theories which I consider to be inherent in my improvedcarburetor, nevertheless, Ido not wish to be understood as beine' limited thereto, as the same are offered by Way of explanationy and to facilitate description and, of course, do not affect the mechanical performance of the carburetor as disclosed.

'Ihe construction of my improved carburetor is such that it may be used in virtually any cperating position and, therefore, adapts itself readily to employment in airplanes. Also, .the fact that the fuel is substantially fully vaporized in the mixing chamber, and the air throttle valve is located in the air inlet to the mixing chamber, internal icing conditions in the carburetor under low temperature operation is avoided. In the conventional carburetor, a large part of the fuel is vaporized from the surfaces of the throttle valve disposed on the engine side of the mixing chamber, that is, in or near the outlet of such a chamber. When so disposed, fuel evaporation from the surfaces of such a conventionally located throttle valve very often results in ice developing within the carburetor of a nature which interferes with proper operation of the throttle valve. These difficulties are eliminated by my present design.

Also, it will be understood that various changes may be made in the mechanical design of the carburetor without departing necessarily from the spirit and scope of the following claims.

I claim:

1. In a carburetor of the type having a casing formed with an induction conduit in which a movable air-control valve is positioned, there being an operating shaft for said valve mounted for rocking movement in the walls of said casing, together with means for imparting rocking movement to the shaft, the improvement comprising: a cylinder carried by said casing, a piston slidable in said cylinder, motion-transmitting means linking said piston with said rock shaft and providing normally movement of said piston in unison with said rock shaft, passage means formed in said cylinder on one side of said piston, said passage means including an atmospheric vent, automatic valve means responsive to normal engine-created pressures existing in said conduit to maintain said vent open to the atmosphere and upon predetermined pressures in said conduit caused by the associated engine operating under a heavy load to close said vent and thereby retain said piston against movement in said cylinder.

2. A carburetor as specified in claim 1 comprising: air inlet and outlet port means of restricted cross-sectional area formed in the opposite ends of said cylinder, and a check valve positioned in the port means at the end of said cylinder carrying the automatic valve means.

3. In a carburetor of the type having a casing formed with an induction conduit, an air-iiow control valve positioned in the conduit, an operating shaft for the valve mounted for rocking movement in the walls of the casing, and means for imparting rocking movement to the shaft to control the operating positions of the valve, the improvement comprising: a cylinder and piston assembly having a movable element, a crank arm fixed to one end of said valve shaft, a second crank arm loosely mounted on said shaft and disposed normally in side by side relationship with said xed arm, yieldable connecting means uniting said crank arms for movement in unison with each other, motion-,transmitting means linking the second or free crank arm with Ithe movable element of said assembly, and means responsive to predetermined enginedeveloped suction forces established in said carburetor to applyl motion-restraining forces to said piston, whereby to hold said air-flow control valve against operation except for limited movement on the part of said valve permitted by said yieldable connecting means for said arms.

`4:. In a carburetor for internal combustion engines, a casinar formed with an internal longitudinally extending open-ended induction conduit, an air-flow control valve positioned in the conduit, an operating shaft for the valve mounted for rocking movement in opposite Walls of the casing, the ends of said shaft projecting beyond said walls, a stationary cross member extending from one side to the other and disposed transversely of said conduit intermediately of its length, said member being formed with a passage which communicates at one end with a source of liquid fuel supply and at its other end with the interior of said conduit, a fuelmetering valve in said cross member controlling the flow of fuel through said passage, said fuelmetering valve at one end thereof extending exteriorly of said casing, crank arms carried by adjoining exterior ends of said rock shaft and said fuel-metering valve, manually operated means joined with the crank arm of said fuelmetering valve for imparting movement thereto,

metering valve against the restraint oiere'd thereon by said check mechanism.

5. An engine carburetor of the type having a casing formed with an induction conduit, there' being` an air-now control valve positioned' in saidrcondnuit having a manually controlled operating'shaft mounted for rocking movement in' the walls of' the-casing, the improvements comprising: automaticv check mechanism restraining said shaft against undue'- rocking movement upon' the presence of' predetermined negative pressurel conditions in' saidA induction' conduit, said meczli'anisinA including a' cylinder, a p'isto'n slidable in said cylinder, motionLtransmittin'g mea-nsf linking' saidl. piston'- Withl said rock* shaft to' produce' normally'movem'ent' of said piston' i'nlunis'on' vvithlsaidvr rook shaft; valve means' responsive to s'a'id predetermined negative' pressure'oonditio'ris ofi said-conduit to operatively' retain' saidpisto'n' and shaft against normal movement, yieldable elements coopera'- tiv'e"with said motion-transmitting means providin'g limited movement' o'f'sa'id' airf-low control valve when' saidpi'sto'nis' retained' against move'n ment Yby said check' mechanism, passage means for delivering a volatile' liquid fuel to said conduitY for adihixture with air passing there` through',l saidfuel-delive'ring' means including a` fuel-mete'iin'g-'valvei means linking' the air-flow' contr'lvalv'e' and s 'aid fuel-metering valve' for substantially' synchronous movement, a'. lost-A mo'tondevic'e in" said last-named linking' device prvidiii'g' fori limited' actuation of said' fuel-A metering-'valve befor'emotion 1is imparted to s'aid airo'wf' co'n'trolvalve",l and manually controlledspringm'ean'sforoperating saidivalves.

(vvI' al carburetor' for internalcombustion engines, a'ca'sn'g'formed With' an internal-1ong'itdinally extending' open-ended induction 'conduit', a'narflo'vv' control valve`positioned inthev air-flow control valve.

said conduitinterm'ediately of its'flength, sa'id' member being `formed vvith'I a pass'agelfcomrriuni-'J- eating at-one endwith a-s'ource` of"1iqui'd" fel supply and at itsiother' Witl'itheintei'ioroff said conduit on the' under 'side'- of f's'aid' cross member, a fuel-metering v alve disposed? for longitudinal movement in saidcro'ss' membercontrollin'g the' iiow of fuel throughlsa'idvpassage and into-saidl conduit, saidA` fuellmetering' v'al've'-A atone* end3 thereof extending exteriorliu o'f said casing, a

sleeve carried by theI e'xteriorly exten'ding'- en'd of said fuel-metering valve positioned f'rslidii'gl movement* in a casin'geformed socket"V having slotted Walls, saidz slee'v'e-v being' formed? with' wings'projecting laterally-:therefrom an'dslid'ably disposed in saidslotsa-crank a'r'i'nrotatably-f surfaces arrangedin engagement v'vithth'eyvi'n'gs'V of said sleeve, whereby upon"y oscillation' o'f s'aid