US2408726A - Carburetor - Google Patents

Description

Oct 8, 1946. G M. BlCKNELL 2,403,726

' CARBURETOR Original Filed May 7, 1940 2 Sheets-Sheet 2- Patented Oct. 8, 1946 Carter Carburetor Corporation,

St. Louis, Mo.,

a corporation of Delaware Application November 5, 1942, Serial No. 464,643, which is a division of application Serial No. 333,759, May 7, 1940. Divided and this application September 6, 1943, Serial No.

6 Claims. (01.261-69) This invention relates to carburetors for internal combustion engines and more particularly to improvements in downdraft carburetors of the plain tube type. v

This application is a division of my application, Serial No. 464,643, filed November 5, 1942, which is a division of my application, Serial No. 333,759, filed May '7, 1940 which has now issued as Patent No. 2,328,504.

In devices, such as automotive carburetors, which utilize a diaphragm for actuating or sealing'a metering valve or other movable part, it has been necessary to completely dismantle the diaphragm in order to inspect or replace the valve or part carried'thereby.

It is the main object-of the present invention to facilitate applying and removing a valve or other diaphragm operated device which is located behind. the diaphragm.

. A more detailed'object is to provide means for sealingly attaching a metering valve to its actuating diaphragm in a manner to permit insertion and withdrawal of the valve through the diaphragm and without the necessity of disassembling the diaphragm.

Further objects and advantages of the present invention will be hereinafter set forth in the following specification and accompanying drawings, in which like numerals indicate identical parts.

Figrl is a vertical center section of an automotiv'e carburetor embodying the invention.

Fi.'2is a horizontal section taken on line 2-2 of Fi 3.

Fig. 3 is a vertical section taken on line 3-3 of Fig. 1.

Fig. 4 is a vertical ofrig. 1.

5 is a detailed view of the metering rod and attaching screw.

'In'the drawings, numeral l indicates a main carburetor body casting having a suitable flange 2 formed at the lower end thereof for attaching a carburetor to the intake manifold of an internal combustion engine.

section taken on line 4--4 A mixing conduit 3 is formed in the main body casting, and an adjacent constant level fuel chamber 4 is cast integral therewith, Aportionof the mixing conduit 3 has a ventunrorm as indicated at 3a which converges tothe constriction or: throat 5. The upper end of body casting l is provided with a smooth flange surface to whichis attached an air inlet casting or air horn G and a fuel bqwl cover 1 by means of attachingscrews 8. Depending from the air horn casting 1 and projecting into the upper end of the mixing conduitare two concentric Venturi tubes 9 and I0,Venturi tube 9 b'eingarranged todischarge near the throat of .venturi l3) and venturiin being arranged to discharge near the constriction 5. a

The outlet I l of the mixing conduitiscontrolled by a plate-type throttle valve l2 which is rigidly attachedto a throttle'shaft 13 by means of screws I' l; Throttle shaft I3 is journalled in the bosses l5 and 15a. For operation of the throttle valve, a stamped throttle operating .lever i6 is rigidly attached to one end of the throttle shaft 13. The throttle lever. I6 is fabricated from sheet stock by stamping and forming, and is provided at one end with a perforation I'l toreceive a remote control rod (not shown). The throttle lever is normally urged toward a throttle closing position by the usual throttle pull back spring (not shown), whichgenerally forms a part of the remote control linkage. Lever I6 is also provided with a pairof parallel bent-up portions [8 and i9 (Fig.2), which are perforated and internally screw threaded .to receive a throttle lever adjusting screw. 20. Provision of adjusting screw 2!! permits a fine adjustment of the throttle valve when in anear closed or idling position. An upper wing lug 2| on body casting l provides a throttle closing limit abutment, and a lower wing lug 2m provides a throttle opening limit abutment A- narrow tank 22 formed as part of lever I6 abuts lug 21a as the throttle valve reaches its open limit..

The air inlet passage25 is controlled by a platetype choke valv 26 which is eccentrically mounted for rotation with the choker shaft 21 which, in turn, is journalled in the bosses 28 and 29. A pair of abutments 26a within the air inlet passageway. and castv as an horn casting ii provide a wide open stop for the choke valve. Referring to'Fig. 3, the left end of choker shaft 21' projects into a casing 30 which is cast as anintegral part ofthe airhorn casting 6. The casing 30, together with the cup-shaped cover 3|. form a housing which completely encloses'mechanism for the automatic control of the choker valve 26. y

Cast as'an integral part .of the fuel bowl cover l is a combination fuel inletand vent'boss. 82. Boss 82 is provided with a comparatively large,

horizontal bore 83in which is retained a cylindrically formed wire screen retainer 84. Fuel. entering through" bore 83 passes through screen 84 and through a horizontal passage 89 to a verticalpassage 90, see Fig.4. The lower end of passageway. is screwthreaded to receive a integral part of the air 7 3 needle seat member 9I, through which is provided a bore 92 to admit fuel to the fuel chamber 4. A conventional float 93 pivoted at 94 acts upon the needle valve 95 in a well known manner to maintain a constant level of fuel in chamber 4 substantially as indicated by the line :r-x. Fuel is supplied to the carburetor mixing conduit for normal and full speed and load operation of the engine through a metering jet 96, through passages 91 and 98 and is discharged through nozzle 99 into the primary Venturi tube 9. Fuel for low speeds or idling operation is also metered by jet 96 and passes into passage 9! from whence it passes through the idling jet tube I and suitable passages to the usual idling ports adjacent the edge of the throttle when closed.

The amount of fuel available for aspiration from the main nozzle 99 and the idling ports is varied in accordance with engine intake manifold vacuum and throttle position by a stepped and/or tapered metering rod I09 extending axially into metering jet 96. As the metering rod I09, Fig. 3, is moved toward the left, the net opening of jet 96 is decreased. To position the rod I09 in accordance with manifold vacuum, a flexible diaphragm member II 0 is rigidly attached to rod I69 at its center by means of the plunger member III. Referring to Fig. 3, the left hand side of diaphragm III) is subjected to intake manifold suction by reason of passages H2, H3, H4 and H5 which open as a port H5 in the wall of the mixing conduit below the throttle valve. The recess II I in the carburetor body casting and the generally cup-shaped cover plate I I8 form a working chamber for the dia hragm. The recess I I! communicates with the fuel chamber 4 through a large passage II'I'a, see Figure 2, so that the pocket of fuel therein and the diaphragm are in substantially unrestricted communication with the remainder of the bowl. The cover plate II 8 firmly clamps the periphery of the diaphragm and is attached to the body casting by means of screws H9. The central perforation of cover plate II8. wherein is fitted for reciprocation the plunger III, is provided with a packing gland I; The plunger, I II passes through a central perforation in diaphragm H0 and is firmly attached thereto by riveting or spinning over the reduc d end of the plunger as indicated at I -2 I.

Plunger I I I is further provided with a through axial bore of sufficient size to permit the passing of the entire metering rod and is provided with internal screw threads I22a at its outer end. An externally threaded sleeve I22, staked to the rod, as at I23, Fig. 5, is secured in the plunger. It will be seen from the foregoing that the metering rod I09 may be removed or assembled without the necessity of removing the cover plate II 8 and diaphragm IHJ. Metering .rod I09 is normally urged to the right, Fig. 3, by the lever I24 which is acted upon by a spring I25. The lever I24 is carried on pivot I26 which also forms a pivot for asecond lever I21 which is, in turn, connected to a lever I 28 by means of a link I29. Lever I26 is rigidly attached to the throttle shaft I3.

' Relative motion of levers I24 and I 27 is prevented in one direction by the finger vI3I carried by lever I24. It will be understood that spring I is so proportioned and calibrated with relation to the efiective area of diaphragm I09 thatthe desired position of the metering rod for a given manifold vacuum is attained. From the foregoing, it will be seen that sufficient vacuum applied to the left side of the diaphragm IIO will move metering rod I09 to the left; that, normally, the metering rod is urged to the right by spring I25 and that a clockwise rotation of the throttle shaft !3 (which is a throttle opening movement) will forcibly. move the metering rod to the right in a less restricting position in jet 96.

It will also be noted that a movement to the right of diaphragm I I0 caused by a drop in manifold vacuum or throttle opening movement will displace the fuel in chamber 1, causing an increased pressureon jet 96 and also momentarily raising the fuel level in the constant level chamber. This enriching effect is highly desirable.

Fuel for acceleration is supplied to the mixing conduit under pressure by the diaphragm type accelerating device generally indicated at I32, Figs. 2, 3 and 4, and which comprises a circular chamber I 33 formed by a recess in the main body casting and by the recessed cover I34 which is attached thereto by means of attaching screws I35. A flexible diaphragm member I36 firmly clamped at its periphery between cover I34 and the carburetor body is provided and forms a partition in chamber I33. The diaphragm I36 is attached at its center to a horizontal plun r I 31 which passes through the cover I 34 and projects therefrom. A spring I38 hearing at one end against a retainer I39 and at its other end against cover I34 normally urges the diaphragm I36 and plunger I3! toward the right, Fig. 3. which is an intake stroke. A rocker arm I40 pivoted at one end at MI and having attached at its other end at I50 a spring I 42 which is connected to lever I28 moves the plunger and diaphragm to the left (discharge stroke) as the lever I28 is rotated clockwise (throttle opening direction). I

It will be understood that spring I 42 is substantially stronger than spring I38 and that its provision in lieu of a non-yielding, link results in a smooth yielding pressure being exerted upon the plunger and diaphragm I36 which is desirable.

The accelerating device further comprises inlet passageways I 5| and I52, Figs. 2 and 3, leading from the constant level fuel chamber 4 to the expansible chamber I 33. A cylindrically formed wire mesh strainer I53 is provided and is retained in passage I52 by the screw threaded inlet check plug I54. The inlet check plug I54 is provided with a valve seat I55, a disc checkvalve I56 and a valve retainer I51. The fuel is discharged from chamber I33 through passages I58, I59, diagonal passage I 60 and an accelerating jet (not shown) into the mixing conduit. A discharge valve seat is formed at the lower end of passage I59 at I62 by a reduction in diameter. and a gravity seating ball check valve I63 is provided and adapted to engage seat I 62. The upper end of passage I59 is screw threaded and re ceives a screw plug I64 which is provided with a downwardly extending stem I65 which limits the upward movement of ball check I63 When the same is acted on by discharge pressure.

A decided advantage gained by the present arrangement of the accelerating device is that, by extending the discharge passageway upwardly from the very top of the expansible chamber I 33 to a point above the fuel level, pressures..which frequently build up in chamber I33 clue to vaporization are-released without the forcing of fuel from the chamber as occurs in many constructions. This advantage has particular significance I due .to the importance of maintaining a full charge of fuel in the accelerating chamber.

Referring to Fig. l, acomparativelyllarge veritical passageway IE9 is provided,.extending. from the main fuel passage98 to apoint above the fuel level. The upper part of this passage communicates with the mixing conduit through a tube I10. This provision has the purpose of relieving vapor pressures at theba'se of nozzle 99,. and its operation is fully describedin my copending application, now PatentNo. 2,234,946,

The operation of'the carburetor is astfollow's:

Fuel is supplied to the .float chamberA through inlet passage83, screen 84, and passages 09,50 and 92 wherein a substantially constant level as indicatedby line a r-m is maintained by the action of the float 93 on needle valve 95.

Fuel for normal and high speed operation is supplied to the mixing conduit from fuel chamber 4 through metering jet 06, passages 91,.98and nozzle 99. During comparatively light load operation, the intake manifold suction will act on. diaphragm I I to move. metering rod I00 toward the left, Fig. 3, that is, toward a more restricting position. The position of the metering rod under these conditions will also be determined by the throttle position. When sufficient load is applied to the engine for any given throttle position to cause a sufiicient resulting drop in manifold vacuum, spring I will urge the metering rod toward the right to a less restricting position.

Fuel for idling operation is supplied to the mixing conduit from fuel chamber A through jet 06, passage 91, idling jet I03, idling tube I00, passages l0! and I02, and is discharged into the mixing conduit near the upward opening edge of throttle valve I2 through the usual idling ports (not shown) Fuel for acceleration is sure to the mixing conduit from the accelerating chamber I33 during the discharge stroke of diaphragm I35, through passages I58, I59, and I60. The diaphragm I36 is actuated through its discharge stroke by an opening movement of the throttle valve by means of linkage comprising the rocker arm I40, the spring I42, and lever I28.

When the throttle is suddenly opened from nearly closed position, pressure in the carburetor outlet and in diaphragm control passages H2 and H3 increases, causing rapid inward movement of diaphragm IIO by spring I25. This forces liquid fuel back through open bowl communication I Ila, momentarily raising the level in the bowl, and through main metering jet 90. Additional fuel is thus supplied to the mixture conduit through the main nozzle, both because of the raised level and consequent increased pressure in the bowl and because of the extra charge of fuel forced directly into the main nozzle passage. As the throttle is opened, the distance diaphragm I I0 can move because of a drop in suction to the carburetor becomes progressively less, since the diaphragm is impelled inwardly by lever I24 operated by the throttle. This is an advantage because less auxiliary pick-up fuel is needed for acceleration from a substantially open throttle position than from a nearly closed throttle position.

The invention is not limited in details to the structure shown, respects as will occur to those skilled in the art and the exclusive use of all such modifications as come within the scope of'the appended claims is contemplated.

I claim: I

1. In a carburetor, a mixture conduit, a main fuel passage, a constant level fuel chamber havsupplied under presmg, a. lateral extension below the fuel level and opening through the side .wall of said chamber, a diaphragm closin'g said opening and acting against the fluid in said chamber, a plate fixed over said diaphragm and forming a suction chamber therewith, said plate having an opening axial of the. center of said diaphragm, a. suction passage connecting said conduit and said cham- Ioe'r, a metering orifice in said main. fuel passage, a metering pin for regulating the fuel passing through said orifice, said metering pin extending axially through said orifice, diaphragm, and plate opening, andmeans removable through said plate opening and securing said metering pin to said diaphragm whereby movement of said diaphragm by suction regulates theflow of fuel through said jet.

2. The substanceof claim 1, further including guide structure .for said metering pin in a portion of the carburetor wallspaced from Isaid diaphragm.

but may be modified in various said common wall and forming formed 3. Ina carburetor, a mixture conduit,.,afuel bowl forming a constant level float chamber formed on one wall of said conduit, the common wall between said conduit and said chamber being thickened, a main fuel nozzle passage extending from the lower part of said bowl through said common wall and opening into said mixture conduit, a fuel nozzle arranged in said nozzle passage and extending into said mixing conduit, a pocket formed in the wall of the lower part of said float chamber and in open communication therewith, a suction responsive diaphragm one wall of said recess, a passageway in said thickened wall connecting said said recess, a metering orifice a metering valve secured to nozzle passage and in said passageway, said diaphragm and trolling said metering orifice, and guide means closely fitting a portion of said valve, said guide means being aligned with said passageway.

4. In a carburetor, a mixture conduit, a fuel bowl forming a constant level float chamber formed on one wall of said conduit, the common wall between said conduit and said chamber being thickened, a main fuel nozzle passage extending from the lower part of said bowl through said common wall and opening into said mixture conduit, a fuel nozzle arranged in said nozzle passage and extending into said mixing conduit, a pocket formed in the wall of the lower part of said float chamber and in open communication therewith, a suction responsive diaphragm forming one wall of said pocket, said thickened common wall terminating short of said pocket at one edge to provide open communication between said pocket and said bowl, a passageway formed in said thickened wall connecting said nozzle passage and said pocket, a metering orifice in said passageway, a metering valve secured to said diaphragm and extending through and controlling said metering orifice, and guide means closely fitting a portion of said valve said guide means being aligned with said passageway and being positioned inward of said metering orifice.

5. In a carburetor, a mixture conduit, a fuel bowl forming a constant level float chamber formed on one wall of said conduit, the common wall between said conduit and said chamber being thickened, a main fuel nozzle passage extending from the lower part of said bowl through opening into said mixture conduit, a fuel nozzle arranged in said nozzle passage and extending into said mixing conduit, an opening in an outer wall of said float chamextending through and conher, a suction responsive diaphragm secured over said opening, a passageway formed in said thickened wall and connecting said nozzle passage and said float chamber, a metering orifice in said passageway, a metering valve secured to said diaphragm and extending through and controlling said metering orifice, and guide means closely fitting a portion of said valve, said guide means being aligned with said passageway and being positioned inward of said metering orifice.

6. In a carburetor, a mixture conduit, a fuel bowl forming a constant level float chamber formed on one wall of said conduit, a portion of the wall of said conduit adjacent said float chamber being thickened, a main fuel nozzle passage extending from the lower part of said bowl through said thickened wall portion and opening into said mixture conduit, a fuel nozzle arranged in said nozzle passage and extending into said mixing conduit, an opening in an outerrwall of said float chamber, a suction responsive diaphragm secured over said wall opening and formed with a central opening, a suction chamber formed over the outer face of said diaphragm including a wall formed with an opening in alignment with the opening in said diaphragm, a tube secured at one end portion to the Wall defining the central opening in said diaphragm and movable with said diaphragm, the outer end of said tube extending through and closely fitting the wall defining the wall opening in said suction chamber, a passageway formed in said thickened wall and connecting said nozzle passage with said float chamber, a metering orifice in said passage- Way, a metering valve having one end portion extending into said tube and its other end portion extending through said metering orifice, means for adjustably securing said metering valve in said tube, and means engaging said valve to maintain its axis in constant predetermined relationship with the axis of said metering orifice.

GEORGE M. BICKNELL.

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