US2718387A - Multi-stage carburetor - Google Patents

Description

H. A. CARLSON ET AL 2,718,387

MULTI-STAGE CARBURETOR Sept. 20, 1955 Filed March 27, 1955 5 Sheets-Sheet 1 6 m g a l U i I L( Ill Inn INVENTORS HAROLD A.CARLSON OLIN J. EICKMANN ATTORNEY Sept. 20, 1955 H. A. CARLSON ET AL 2,718,387

mumpsmcs CARBURETOR Filed March 27, 1953 5 Sheets-Sheet 2 Q m z\ m N N M w HAROLD A. CARLSON OLIN J. EICKMANN ATTORNEY Sept. 20, 1955 H. A. CARLSON ET AL 2,718,387

MULTI-STAGE CARBURETOR Filed March 27, 1955 5 Sheets-Sheet 3 FIG.3.

FIG.5.

INVENTORS HAROLD A. CARLSON OLIN J. EICKMANN ATTORNEY Sept. 20, 1955 Filed March 27, 1953 H. A. CARLSON ET AL 2,718,387

MULTL-STAGEZ CARBURETOR 5 Sheets-Sheet 4 INVENTORS HAROLD A. CARLSON OLIN J. EICKMANN BY W ATTORNEY Sept. 20, 1955 H. A. CARLSON ET AL 2,718,387

MULTI-STAGE CARBURETOR Filed March 2'7, 1953 5 Sheets-Sheet 5 FIG.6Q

ATTORNEY United States Patent MULTI-STAGE CAREURETOR Harold A. Carlson, Brentwood, and Olin I. lEickmann,

Normandy, Mo, assignors to Carter Carburetor Corporation, St. Louis, Mo., a corporation of Delaware Application March 27, 1953, erial No. 345,048

18 Claims. (Cl. 261-23) This invention relates to multi-barrel or inulti-stage carburetor systems for internal combustion engines. .fore particularly, the invention relates to a novel combination of a fuel supply and a new fuel nozzle system for such carburetors which eliminates the necessity .of two separate fuel bowls and of four separate nozzle systems.

The invention is shown applied to the type of carburetor disclosed in the application of Carlson and Moseley, Ser. No. 263,291, filed December 26, 1951. Briefly, this prior application shows a multi-barrel, multi-stage carburetor with four barrels and four separate float charnbars, which chambers are connected in pairs to form two fuel bowls, each supplying fuel to two individual fuel nozzle systems.

The performance of carburetors with multiple fuel bowls and nozzle systems is not wholly satisfactory be cause they cannot be readily calibrated for changes in acceleration, cornering, braking, or inclination of the vehicle. Such changes can produce an uneven distribution of fuel with its accompanying disadvantages in engine performance. Furthermore, the transition point which occurs when the secondary stages go into action is very pronounced, and is regarded, for that reason, as undesirable.

in the present invention, two fioat chambers are interconnected by a restricted passage to form a single fuel bowl. This bowl supplies fuel to two separate fuel nozzle systems of novel design-one for each pair of primary and secondary stages of the multi-barrel, multi-stage carburetor. The location of the point of supply for each nozzle system is adjacent one sideof the fuel bowl, preferably from a zone located in the restricted passage connecting the float chambers. Each fuel system has a conventionally arranged low-speed nozzle or idling ports supplied with fuel through passages connecting with a main inclined fuel passage from the point of supply within the fuel bowl. The main or high-speed primary and secondary nozzles are in a tube extending transversely of the primary and secondary stage barrels. connects with the inclined main fuel passage from the fuel bowl. The junction between the tube and the passage forms a single control point for both primary and secondary stage fuel nozzles, and this control point is pun posely located adjacent the volumetric center of the fuel bowl above the liquid level. Each fuel nozzle has one or more air bleeds at a point in a zone pressure-sensitive to throttle positions.

The combination of a single fuel bowl with twofuel nozzle systems has been found to avoid unequal distribution of fuel, and its disadvantages. This is due to the proximity of the fuel supply for each fuel nozzle system, and to the feature of having a single control point for each pair of main or high-speed nozzles. Because of the single control point, the amount of lift from the fuel bowl to each primary and secondary stage main nozzle is identical under the conditions above mentioned which occur due to accelerations or inclination of the vehicle. Furthermore, the interconnecting air bleeds provide a smooth transition from primary to secondary stage by enriching This tube, in turn,

'1 263,291, filed December 26,

the mixture in the primary stage to compensate for the additional air admitted through the secondary stage before the secondary stage fuel nozzle begins to function.

The accompanying drawings illustrate two forms of the instant invention.

Fig. l is a top plan view of a carburetor according to the present invention.

Fig. 2 is a vertical front elevational view of the carburetor with parts broken away to show the adjacent points of fuel supply to the fuel nozzle systems within the fuel bowl.

Fig. 3 is a side elevational view of the carburetor with parts broken away to illustrate a float chamber and its float control mechanism.

Fig. 4 is a vertical longitudinal section through the carburetor.

Fig. 5 is a detail view of the choke valve-operated mechanism for locking out the action of the throttles for the secondary stages.

Fig. 6 is a longitudinal section illustrating a modification of the present invention.

Fig. 7 is a diagrammatic view illustrating the lack of effect of changes in inclination of the vehicle on the relation between the fuel level in the fuel bowl and the control point for the fuel nozzle.

The drawings illustrate a four-barrel downdraft carburetor with a body it). As shown in Fig. 1, this body includes two forward or primary stage mixture conduits ill and 12, and two rear or secondary stage mixture conduits l3 and 14. These conduits are arranged in symmetrical relation in a compact group, and are supplied with air through a rectangular-shaped air horn structure 15 provided with a transverse partition 16. At the forward side of the partition is journaled a chokeshaft l7 mounting an unbalanced choke valve 18 (see Fig. 4-). The chokeshaft is controlled by any suitable automatic choke control mechanism within the housing 19 in Fig. 2. Extending across both primary and secondary mixture conduits are throttle shafts 20 and 21 mounting throttle valves 22 and 23. Each pair of primary throttles 22 moves as a unit. Likewise, each pair of secondary throttles 23 moves as a unit. The primary conduits may be connected by pressure-equalizing passages, and the secondary conduits may be likewise connected, if desired. A flange 26 surrounding the lower end of the conduits is provided for attaching the carburetor to the usual engine intake manifold.

Referring to Figs. 2 andS, the primary throttle shaft 2 9 has a projection onwhich is rigidly mounted a throttle-operating arm 27 having a hole 23 for attachment to the usual accelerator linkage. The throttle arm carries an adjusting screw 29 for engaging a fast idle cam 34 pivoted as at 31 to the carburetor body. The cam is connected by a torsion spring 32 to a concentrically pivoted loose lever 33, which, in turn, is connected by means of a link 34 to an arm 35 rigid with the projecting extremity of choke valve shaft 17, which is located opposite said housing 19. A small disk 36 is rigid with the adjacent projecting extremity of a secondary throttle shaft 21, and has a radial lug 36a. Also loosely mounted with respect to the pivot element Tall is an eccentrically weighted stop lever 37 provided with a finger 33 which is normally maintained by its own weight in position to interfere and engage with lug Sea on the secondary throttle shaft 21 when the choke valve is closed. This lock mechanism is the same as that shown in ctr-pending application Ser. No. 1951, by Carlson and Moseley. It is explained therein that lug 39, which is integral with lever 33, will engage eccentrically weighted lever 37 as the choke valve moves toward opening position, thereby shifting the lever 37 to unlock the secondary throttles 23 by its disengagement with the lug 36a.

The mechanism for operating the primary and secondary throttles in a sequential manner is shown in Fig. 3, and this mechanism comprises a small lever 100 fixed with primary throttle shaft 20, which lever is formed with radial and angularly extending lugs 101 and 102. A lever 103 is rotatably mounted on throttle shaft inward of lever 100, and has a finger 104 connected by a coil tension spring 105 to the finger 101 of the operating lever 100. Spring 105 normally maintains a second integral finger 102 in engagement with lug 106. Lever 103 has a second angular lug 107 mounted thereon for a purpose to be later described. Also rotatably mounted on the throttle shaft is a third lever 108 inwardly of fixed lever 100 and lever 103. This lever is connected by a link 109 toan arm 110 rigidly secured with the adjacent projecting extremity of secondary throttle shaft 21. Arm 110 may be biased in a counter-clockwise direction by a suitable torsion spring 120 or the like. In operation, counterclockwise movement of the shaft 20 to open the primary throttles 22 moves lever 100, and lever 103 is likewise rotated through spring connection 105 until radial lug 107 engages a shoulder 113 on third lever 108, whereupon the three levers rotate as a unit, causing opening of the secondary throttles 23 by link 109 and arm 110. Because of the lost motion connection between lug 107 and shoulder 113, primary throttles 22 are in a partially opened position before engagement between lug 107 and shoulder 113 causes initial movement of the secondary throttles. The linkage is such, however, that movement of the primary throttles from this partially-open position to wide-open causes full opening of the secondary throttles. Upon closing of the primary throttles, the aforementioned spring which may be used on the secondary throttles causes the secondary throttles to follow the movement of the primary throttles. Full closing of the primary throttles engages shoulder 114 with lug 115 to lock the secondary throttles in a closed position.

Of course, if the choke valve-operated lock-out mechanism previously described is in operation, the secondary throttle cannot be opened, and spring 105 will allow for movement of the primary throttles in'an opening direction after engagement of lug 107 with shoulder 113.

As shown in Figs. 2 and 3, the carburetor is provided with a fuel bowl having two identical float chambers 40 and 41. (A description of one will sufiice for both.) These chambers are interconnected by a restricted passage in which is located the supply point for two fuel nozzle systems.

Float chamber 40 contains a float 42 mounted on a float control arm 43 pivoted on a'shaft '44 supported by structure depending from float bowl cover 46 Finger on arm 43 engages and actuates a needle valve 47, which, in turn, controls the supply of fuel past valve seat 48 from a common inlet 49 for both chambers 40 and 41 shown in Fig. 1. Float 42 and needle valve 47 maintain a substantially constant fuel level within the fuel bowl 40-41.

The passage between the float chambers 40 and 41 has two metering orifices 50 and 50' located in the lower portion thereof. Each is, in turn, controlled by metering pins 51 and 51 carried at the upper end by a cross-bar 52 shown clearly in Figs. 1 and 2. This cross-bar is formed as an integral part of a stem 53 projecting upwardly from a piston 54, Which works in a cylinder 55 connected by means of a passage 56 to the primary mixture conduit posterior of the throttle 22. A coil spring 57 constantly urges the piston and metering pins upwardly against the force of suction acting downwardly on the piston.

Journaled in the fuel bowl cover 46 is a countershaft 58 which mounts an actuating lever 59 having a finger 60 underlying the cross-bar 52 so as to lift the cross-bar and metering pins when the countershaft is rotated. The countershaft, in turn, is connected to the primary throttle valves by an actuating arm 61 rigid with the projecting end of the countershaft 58 and a link 63 connected to throttle lever actuating arm 27.

Also attached to the countershaft is a lever 65 which is connected by a small link 66 to an accelerating pump piston not shown. This piston works in the usual cylinder and draws fuel into that cylinder on upward movement of the piston. Upon opening movement of the accelerator, the fuel is discharged from the cylinder of the pump past suitable check valves and into the primary mixture conduit through pump jets 76, all in a well known manne'r, as shown in the co-pending application to Otto Henning, Ser. No. 268,811, filed January 29, 1952. The mechanism just described is mounted under a dust cap 62 as shown in Figs. 1 and 2.

The main fuel supply from each fuel bowl to adjacent primary and secondary mixture conduits is through individual fuel nozzle systems which are identical. Consequently, only one fuel nozzle system will be described. In Fig. 2, fuel through the metering orifice 50 is supplied to a main fuel passage 77 through a connecting passageway. Passage 77 is inclined upwardly as shown in Fig. 4, and conencts with a fuel tube 78 extending across and between inner venturi tube 79P and 79S in the primary and secondary conduits. Tube 78 has fuel ports 80 and 81 in these venturi tubes, respectively, and air bleed openings 82 and 83 more or less in alignment therewith. A vertical passage 84 connects between a port 85 adjacent the secondary throttle and a restriction 86 in the fuel tube 78. The main fuel system also includes a combination air bleed and vapor vent orifice 87 connecting with the inclined fuel passage 77.

Idling fuel nozzles are provided for each primary mixture conduit. These are identical, and a description of one will suflice for both. This idling system has a vertical well 90 containing an idling tube 91 which connects through a series of passages 92 with idling ports 93 and 94 adjacent the primary throttle 22.

Operation With the primary throttle 22 in idle position and the secondary throttles 23 closed, fuel is supplied to the separate idle nozzles in the separate primary mixture conduits from the fuel bowl 40, 41 through the metering orifices 50, 50', inclined passages 77, and idle tubes 91, to the idle ports 93 and 94. As the primary throttles are opened, suction gradually increases in the inner venturi tubes 79P which produce a flow of fuel through the fuel tubes 78, and thence to and through discharge nozzles 80. Simultaneously, suction decreases at the idle ports and a gradual transition takes place until nozzles 80 supply all of the fuel. The action of suction on the fuel nozzles 80 is somewhat modulated by the leakage of air at atmospheric pressure through the ports 81, 82, 83 and 85 into the fuel tubes 78 when the throttles in the secondary mixture conduits are closed. This modulating eifect of the air bleeds reduces the discharge from nozzles 80 to give a proper mixture for part-throttle operation.

When the primary throttles are opened far enough to begin opening the secondary throttles 23, then suction will exist in both the primary and secondary inner venturis 79P and 795, which will reduce the amount of air bleed through ports 81 and 83 and thereby increase the rate of fuel flow into the fuel tubes 78 in order to initially increase the amount of fuel to the fuel nozzles 80. Further opening of the secondary throttles increases the suction at ports 81 and 83 to further increase the flow through tubes 78 to supply suflicient fuel for both the primary and secondary nozzles. During the initial opening of the secondary throttles 23, ports 85, initially wholly anterior thereto, will be gradually exposed to manifold suction which, in turn, will decrease the effectiveness of these air bleeds and increase the amount of fuel delivered to enrich the mixture in the primary stages. But this invention contemplates the use of the device with or without the ports 85. The function would be the same regardless of their presence or absence.

Another advantage besides those-which are obvious and flow directly from the simplification of the mechanism, resides primarily in the feature of providing a carburetor of this type wherein the fuel is lifted a constant amount regardless of tip angle. In Fig. 7, for example, if the carburetor is tipped backwards due to a steep ascent, the amount of lift necessary to get the fuel to both the primary and secondary nozzles remains the same, as illustrated by intersection of lines xx and nn, the latter being the normal fuel level. This is fixed by the fact that the distance from the fuel levels nn and x-x to the intersection of passage 77 with the fuel tube 78 remains substantially constant because the control point at the intersection is located vertically above and substantially centrally of the fuel chamber 40. Consequently, the amount of lift due to tip angle is unchanged. Because of this, the carburetor will operate as satisfactorily at an inclination as at a level position. If the carburetor is tilted the other way (or forward, as illustrated by line y-y), the lift also remains unchanged. The secondary fuel nozzle will be above the primary, but this would only be in descending a steep grade, when it is very unlikely that the secondary throttle would be held wide open and when a leaner mixture in the secondary stages is desirable anyway.

Fig. 6 shows a modification of the invention described above in which metering rods are provided in each of the mixture conduits for operation with the fuel ports in the fuel tubes. In this modification, four metering rods 151 are received in the fuel ports 80, 81, respectively. The rods are pivotally connected at 152 with arms 153 mounted on the throttles 22 and 23, respectively. Metering rods 151 are provided with stepped ends 154 received in the fuel ports 80, 81, and air bleed orifices 82, 83.

In this modification, with only the primary throttles open, flow from the ports 80, 81 is controlled by the metering rods received therein. Because suction will exist only at the primary nozzle, the mixture is also controlled by the amount of air admitted by the metering rods 151 in the secondary nozzles through the ports 81, 83, 85. After the secondary throttles open, suction will exist in both the primary and secondary nozzles, and port 85 will aid in lifting the fuel from the bowl. This will increase flow sufiiciently to provide adequate fuel in both the primary and secondary nozzles. However, this invention contemplates the omission of port 85.

The invention may be modified as will occur to those skilled in the art and the exclusive use of all modifications as come within the scope of the appended claims is contemplated.

We claim:

1. In a multi-stage carburetor, primary and secondary mixture conduits, primary and secondary throttles, respectively, controlling said conduits, a fuel bowl, a floatoperated valve for controlling the fuel supply to said bowl, a fuel metering orifice in the lower part of said bowl, a main fuel passage from said orifice to a control point above the fuel level and adjacent the middle of said fuel bowl, a fuel tube connecting with said passage at said control point and extending transversely through said primary and secondary mixture conduits, and primary and secondary fuel nozzles in said tube for the respective mixture conduits, whereby a substantially constant relationship is maintained between the fuel level and said control point to supply each said nozzle uniformly on inclination of said carburetor.

2. The combination defined in claim 1, with fuel metering means in said secondary nozzle controlled by said secondary throttle.

3. The combination defined in claim 1, with fuel metering means in said nozzles actuated by said throttles.

4. The combination defined in claim 1, with means in said secondary mixture conduit in communication with said tube to modulate the effect of suction in the primary nozzle during part-throttle operation of said carburetor.

' mospheric bleed.

- 5. The combination defined in claim 4, in which said means in said secondary mixture conduit includes an at- 6. The combination defined in claim 5, in which said atmospheric bleed includes a port adjacent the secondary throttle swept by opening movement of said throttle.

7. In a multi-stage carburetor, primary and secondary mixture conduits, primary and secondary throttles, respectively, controlling said conduits, a fuel bowl, a float-operated valve for controlling the fuel supply to said bowl, a fuel metering orifice adjacent one side of said bowl, a main fuel passage from said orifice to a control point above the fuel level and adjacent the center of said fuel bowl, a fuel tube connecting with said passage at said control point and extending transversely through said primary and secondary mixture conduits, and a fuel nozzle in said tube for each mixture conduit, whereby a substantially constant relation is maintained between the fuel level and said control point to supply each said nozzle uniformly on inclination of said carburetor.

8. The combination defined in claim 7, with fuel metering means in said secondary nozzle actuated by said secondary throttle.

9. The combination defined in claim 7, with fuel metering means in said nozzles actuated by said throttles.

10. The combination defined in claim 7, with means in said secondary mixture conduit in communication with said tube to modulate the effect of suction in the primary nozzle during part-throttle operation of said carburetor.

11. The combination defined in claim 10, in which said means in said secondary mixture conduit includes an atmospheric bleed.

12. The combination defined in claim 11, in which said atmospheric bleed includes a port adjacent the secondary throttle swept by opening movement of said throttle.

13. In a multi-stage carburetor, primary and secondary mixture conduits, sequentially operated primary and secondary throttles for said conduits, a constant level fuel bowl, and a fuel nozzle system for said mixture conduits comprising a plurality of fuel discharge passages connected with said fuel bowl and said primary mixture conduit, an idle port in said primary passage adjacent said primary throttle, a main fuel tube connected with said passages and extending to said primary and then to said secondary mixture conduits, a fuel nozzle for said primary mixture conduit communicating with said main fuel tube, and means to produce an enriching effect in the primary mixture conduit on initial opening of said secondary throttle, including an air bleed connecting said main fuel supply and said secondary mixture conduit at a point in a zone pressure-sensitive to throttle positions.

14. The combination of claim 13, wherein said air bleed is adjacent said secondary throttle.

15. The combination of claim 13, wherein said air bleed is adjacent said fuel nozzle in said secondary mixture conduit.

16. In a multi-stage, multi-barrel carburetor, a pair of primary and a pair of secondary mixture conduits, sequentially operated pairs of throttles for said pairs of conduits, a constant level fuel bowl, and a pair of fuel nozzle systems for each pair of said mixture conduits comprising a plurality of fuel discharge passages for each of said nozzle systems separately connected at adjacent points with said fuel bowl and with each said primary mixture conduit, idle ports communicating with said passages adjacent said throttles in said primary mixture conduits, a pair of main fuel tubes separately connected with said fuel bowl through said passages and extending to said primary and then to said secondary mixture conduits, a fuel nozzle for each said primary mixture conduit communicating with each of said main fuel tubes, and means to produce an enriching effect in said primary mixture conduits on initial opening of said throttles in said secondary mixture conduits, including an air bleed connec'ted with "said main fuel tubes and 'said sebondary mix- Rf'ern'es Cited in the fil'e bf't'hipateiit ture conduits at a "point in a zone pressure sen'sitive to UNITED STATEg p throttle positions. n I

18. The combination of claim 16-, wherein said air bleed is adjacent said fuel nozzle in said secondary mixture conduit.

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