US2252122A - Carburetor structure - Google Patents

Description

5 '10. GORDON E-rm.

/ CARBURETOR STRUCTURE Filed Aug. 29. 1936 INVENTOES DWIGHT GORDON HAROLD A.CARLSQN 5y 4L4 Patented Aug. 12, 1941 CARBURETOR STRUCTURE Dwight Gordon, St. Louis County, and Harold A.

Carlson, University City, Mo., assignors to Carter Carburetor Corporation, St. Louis, Mo., a

corporation of Delaware Application August 29, 1936, Serial No. 98,450

3 Claims.

This invention relates to carburetors, and particularly, to accelerating or pick-up systems therefor.

Modern automotive carburetors are uniformly provided with means for supplying additional fuel to the mixture conduit and intake manifold of the engine at times when the engine is being subjected to abnormal power demands, such as when the throttle is opened rapidly. In such cases, the suction in the carburetor drops substantially, and the fuel and air mixture supplied to the engine may be otherwise excessively leaned out.

The accelerating system performs its chief function only at predetermined intervals, and it is frequently desirable to prevent fuel from being drawn through the accelerating passages at other times due to suction within the carburetor. Various devices have been suggested for preventing the discharge of liquid fuel through the accelerating jet due to suction, but these have not been wholly satisfactory and practical, or have been too complicated or expensive.

An object of the present invention is to provide novel means for preventing the discharge of fuel from the accelerating system due to suction within the carburetor. A more detailed object is to provide means for breaking the suction supplied to the accelerating passage, such means communicating with the mixture conduit horn of the carburetor so as to be substantially protected from dirt and grease by the usual air tachment to the inlet manifold (not shown) of L Pivoted in the air hornan associated engine. is a butterfly type choke valve 5 and the usual throttle valve 6 is mounted adjacent the outlet portion on a shaft 1. A suitable crank or arm (not shown) is rigidly secured to shaft 1 for manual operation of the throttle valve. During normal operation, the choke is wide open, as shown, and the air inlet portion of the mixture conduit, being relatively large, forms a zone of low suction and low air velocity. Supported centrally in the mixture conduit is a venturi stack 24 constituting, in effect, elongated, annular restricting means. Between the venturis and the wall of the mixture conduit is a zone of relatively high suction and air velocities, due to the restricting effect of the venturis. Inside the smallest venturi is the zone of highest velocity and suction into which the main nozzle (not shown) discharges.

Located adjacent the mixture conduit is a bowl 8 within which fuel is maintained at a substantially constant level by the usual float and needle valve mechanism (not shown). A cylinder 9 within the bowl receives a pump piston Ill, having a piston rod ll connected to and controlled from the throttle by means of link l2 secured at one end to arm l3 rigid with throttle shaft 1 and at the other to lever I4 pivoted at l5 to project IS on projecting the bowl cover ll. A coiled spring I 8 rests on the bottom of cylinder 9 and constantly urges the piston upwardly.

The pumping cylinder communicates with the fuel bowl through a passage l9, having an inlet check 119a and with the mixture conduit through passage 20, controlled by outlet check ball 2|, and chamber, or passage 22 closed at its upper end by a plug 23 and opening at its lower end into the relatively high suction and velocity zone of the mixture conduit outside venturi stack 24. Threadedly mounted in chamber 22 is a nozzle 25 having a jet 29 and a portion 26 extending through passage 22 and spaced from the walls thereof and opening into the mixture conduit. Extending vertically from passage 22 is an air duct 21 having an inlet opening facing against the direction of flow in the air horn. Nozzle portion 26 of the accelerating jet has a number of holes as at 28 through which air, delivered through duct 21, may pass into the central bore or aperture of the jet.

Rotation of the throttle valve in a clockwise, or opening, direction depresses piston l0 against spring 18 causing fuel in the cylinder to be forced through passage 20 and restriction 29 from whence it is discharged in a compact, straight jet past holes 28 into the mixture conduit. counterclockwise or closing movement of the throttle raises piston [0 drawing fuel into the pump cylinder past inlet check l9a. During this time, and at other times when the accelerating system is inoperative, the discharge end of jet 25 is exposed to substantial suction within the mixture conduit. The air duct 21 is provided to break this suction and prevent discharge of fuel from the accelerating system except during the celerating jet so that suction on the nozzle por tion 26 of the jet will be readily satisfied through the air duct rather than through this restriction.

The form in Figure 2 is the same as that in the previous form except that accelerating jet 25a terminates within the enlarged chamber or passage 22a, communicating with the air horn, I

through a tube 30 opening in the air horn against the direction of flow therein. Passage 221: communicates with the accelerating pump through an opening 20a as in the previous form. The accelerating nozzle or jet discharges across air chamber 22a and through a restricted passage 3| into the mixture conduit. Passage 3| is made as small as possible without impeding the accelerating stream so as to provide a minimum communication between the accelerating system and the reduced pressure within the mixing conduit.

In Figure 3, the air chamber 32 communicating with the air horn through tube 33 is formed as a separate member and communicates with the mixture conduit through a relatively sharp edged orifice 34. Accelerating jet 251: extends partially through passage 32 past air duct 33 and discharges through orifice 34, into the mixture conduit. This form has the advantage that less air can pass through the orifice 34 at a given difl'erence of pressures on opposite sides thereof, than through an elongated or streamlined passage, as the nozzle portion 26 of the jet in Figure 1, and the passage 3| in Figure 2.

In each 01' the forms, the duct functions effectively to impede or prevent drawing over of liquid fuel from the accelerating system due to suction in the carburetor.

Various features of the carburetor are merely illustrative and these, as well as the form and arrangement of the accelerating system, may be modified in various 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.

We claim:

1. In a carburetor, a mixture conduit including a partially restricted portion forming a zone of substantial suction during operation, an accelerating pump, a discharge passage for said pump having a restricted orifice adjacent said suction zone for forming a jet of acceleration fuel, an air chamber between said orifice and the wall of said mixture conduit and having an enlarged intermediate portion and a partially restricted outlet opening substantially flush with said conduit wall and aligned with said orifice, and an air bleed duct for said air chamber, said chamber being proportioned as to length and cross section so that said acceleration jet will pass therethrough beyond said conduit wall without substantial difiusion or wall friction and said air bleed duct having effective cross sectional area and capacity substantially equal to or greater than said outlet opening whereby suction applied to said outlet opening will be substantially satisfied by air in said bleed.

2. A carburetor as specified in claim 1 in which the inlet opening of said air bleed duct is located in said mixture conduit and faces against the direction of air flow therein whereby said duct will be exposed to higher pressure during operation than said outlet opening to insure the bleeding of air from said duct through said opening.

3. In a carburetor, a mixture conduit including a partially restricted portion forming a zone of substantial suction during operation, an accelerating pump, a discharge passage for said pump having a restricted orifice adjacent said conduit for forming a jet of acceleration fuel, an air chamber between said orifice and the wall of said conduit, and an air bleed duct for said chamber, said conduit wall being provided with an outlet opening aligned with said orifice and of less effective cross sectional area and capacity than said duct whereby suction applied to said opening will be substantially satisfied by air in said bleed duct, said air chamber and outlet opening being relatively short and wide so that the jet of acceleration. fuel: will pass therethrough beyond said conduit wall without substantial retardation and diffusion due to air and wall resistance.

DWIGHT GORDON. HAROLD A. CARLSON.

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