US3222039A

US3222039A - Carburetor

Info

Publication number: US3222039A
Application number: US258870A
Authority: US
Inventors: Vernon D Newman; Charles E Barry
Original assignee: ACF Industries Inc
Current assignee: ACF Industries Inc
Priority date: 1963-02-15
Filing date: 1963-02-15
Publication date: 1965-12-07
Anticipated expiration: 1982-12-07

Description

Dec. 7, 1965 Filed Feb. 15, 1965 2 Sheets-Sheet 1 II HI A W 47 44 /4 7.6% 25 i? 3% an 0 43 I 1 /a I 42 i 75 k E F G. 2 M

INVENTORJ VERNON D. NEWMAN AGENT United States Patent 3,222,039 CARBURETOR Vernon D. Newman, Normandy, and Charles E. Barry,

St. Louis, Mo., assignors to ACF Industries, Incorporated, New York, N.Y., a corporation of New Jersey Fiied Feb. 15, 1963, Ser. No. 258,870 2 Claims. (Cl. 261-69) This invention is directed to the fuel system for automotive vehicles and specifically is directed to an improvement in a carburetor for such a fuel system.

A type of carburetor for supplying an air and fuel mixture to an automotive vehicle engine is one in which fuel is delivered to a mixture conduit from a fuel reservoir in the carburetor. The fuel is forced by atmospheric pressure on the surface of fuel within the fuel reservoir through a main fuel passage to the mixture conduit where it flows into an air stream and mixes with the air in passing to the engine. To provide the optimum fuel air mixture ratio over the range of engine operation, one type of carburetor utilizes in the main fuel system a fuel jet or restriction of a predetermined size. A metering rod has a free graduated end positioned within this fuel jet. The graduations on the metering rod vary from a large diameter to one of small diameter. These graduated portions of the metering rod are moved into the jet in response to engine requirements. Generally, when the engine is operating at low speeds or at times where a minimum amount of fuel is required, the large diameter portion of the metering rod extends within the jet to minimize the flow of fuel to the main fuel passage. At other times when the maximum amount of fuel is required for proper engine operation, the smallest portion of the metering rod extends through the jet to maximize fuel flow into the engine. In the type of carburetor, with which the inven tion is associated, a vacuum motor consisting of a diaphragm is attached to the metering rod to move the several graduated portions of the rod through the jet as required for engine operation. It has been recognized that it is necessary to maintain the free graduated end of the metering rod at a constant position within the jet. If this is not done and during high speed operation of the engine when the flow of fuel through the jet is at a maximum, the free metering portion of the rod will tend to whip around the jet from side to side and cause considerable turbulence and disruption of the fuel flow through the jet. This has resulted in an inconsistent flow of fuel during engine operation so that the metering rod does not properly proportion the fuel to the engine. It has been found in the past that, if the metering rod is retained against one side of the jet in a fixed position, the flow of fuel will remain more consistent at all speeds of engine operation. It is known that the metering rod can be biased by a spring to one side of the jet to provide the optimum results. However, in the type of carburetor to be described the metering rod is suspended from a vacuum motor diaphragm through the main nozzle and through a fuel tube in such a manner that it has been ditficult to position and support a spring in the known way to bias the rod end against the side of the jet. For these reasons a well known type of spring, mounted at the upper end of the metering rod, has been ineffective for biasing the lower end of the metering rod against the jet wall.

Therefore, it is an object of this invention to provide a simplified yet effective spring bias for a metering rod.

Another object of the invention is to provide a simple spring biasing means which is easily accessible for servic ing to bias the metering rod against the edge of the metering jet.

The particular invention is one in which the graduated end of the metering rod extends through a jet into a fuel bowl of the carburetor in such a manner that when the 3,222,039 Patented Dec. 7, 1965 fuel bowl is removed, the metering rod end is easily accessible for servicing. A hairpin spring is mounted with one end on the metering rod and another end on a fixed stud extending from the carburetor body for biasing the metering rod end against the jet wall and to provide consistent flow of fuel through the jet.

FIGURE 1 is a plan view of a carburetor embodying the novel features of this invention.

FIGURE 2 is substantially a longitudinal sectional view of the carburetor of FIGURE 1, which is shown mounted on an engine manifold and with an air filter partially in section.

FIGURE 3 is a partial sectional view of the carburetor of FIGURE 1 and showing a portion of the main fuel passage.

FIGURE 4 is an enlarged sectional view of a portion of FIGURE 3 illustrating features of the invention.

FIGURE 5 is an enlarged plan view from below of the metering rod assembly of FIGURE 2, with the fuel bowl removed.

FIGURE 6 is a plan view of a metering rod spring, in accordance with the invention.

The carburetor shown in FIGURES l and 2 consists essentially of a casting 10, which is formed with a fuel and air mixture conduit 12 and a fuel bowl cover portion 14, from which is integrally formed a depending accelerating pump cylinder 16, an accelerating fuel passage 18 and a fuel well structure 20. As shown, the mixture conduit 12 is arranged and aligned vertically during operation and is connected by a flange 13 to the intake manifold M of an internal combustion engine E. In the lower part of the conduit 12 there is rotatably mounted a throttle valve 22 fixed to a throttle shaft 24 journaled in appropriately aligned apertures of the body casting 10. A manually operable throttle lever 23 is fixed to throttle shaft 24 to move the throttle 22 between open and closed positions. In the upper portion of the fuel-air mixture conduit 12 there is similarly mounted for rotational movement an unbalanced choke valve 26 fixed to a choke valve shaft 28, which is also journaled in aligned apertures through the body casting 10. To the top of the mixture conduit 12 is connected an air filter 29, partially shown in section in FIGURE 2. Between the upper and lower portions of the mixture conduit 12 is formed a venturi or air flow restricting surface portion 30. A small booster venturi 32 is formed integrally with the body casting 10 and has an inner venturi surface 34 coaxially aligned with the mixture conduit 12 and the primary venturi surface 30.

A fuel bowl 36 is fixed beneath the fuel bowl cover 14 and is held with its rim tightly against a gasket fitted between the rim of the fuel bowl 36 and matching portions of the fuel bowl cover 14. A float 4t) fixed to a float lever 43 is pivotally mounted from pin 42 journaled in a depending portion of fuel bowl cover 14. A lever arm 41 of the float lever 43 abuts the lower end of a needle valve 44 having a tapered end extending into a valve seat of the inlet fitting 47 leading to the fuel bowl 36. The fitting 47 connects the carburetor to a fuel line .8. Fuel is forced under pressure by a pump 50 from a fuel tank 52, both schematically shown, through the fuel line 48 and into the carburetor inlet fitting 47. With the fuel level in bowl 36 low, the float 40 is lower and lever arm 43 allows valve 44 to be pressed by fuel pressure in line 48 to an open position. Fuel flows into the bowl 36 and when it reaches a predetermined level, the float lever arm 41 presses upwardly against the needle valve 4 to close the inlet to the fuel bowl.

The lower end of the fuel well 20 is closed by a fitting 56 having a central orifice 59 (FIGURE 4), which is carefully for-med to provide a metering jet for the flow of fuel from the fuel bowl 36 to the mixture conduit 12. The upper end of the fuel well 20 intercepts a cross fuel passage 58 directed downwardly into the secondary venturi structure 32. A nozzle fitting 60 is press-fitted into the end of passage 58 and has one end thereof extending into the center of the secondary venturi surface 34. Press-fitted within the well 20 is a fuel emulsion tube 62 having apertures 63 therethrough along its length, as shown in FIGURE 4.

A metering pin 66 is suspended within the fuel well 20. Pin 66 has, at its lower end 71, an intermediate reduced portion 68 positioned within the main fuel jet orifice 69 for operation in response to engine requirements. Flow of fuelthrough the main jet 56 is controlled by' the metering rod 66 and in accordance with the rod portion 68 011 71 within the jet 56, as described below. The metering rod 66 is supported from a retainer 70 in which the upper end of rod 66 is frictionally engaged.

As shown in FIGURES 2 and 4, the metering rod 66 extends upwardly across the main fuel passage 58 and into a recess 72 formed in the upper portion of the carburetor body casting 10. A diaphragm 76 is held on the retainer 70 by a cup washer 80 pressed tightly down over the upper end of retainer 70. A cylindrical bore 88 is formed in the upper surface of the carburetor casting and forms a continuation of the cavity 72. There is formed between bore 88 and cavity 72 an annular shoulder 90 having a conical surface. One end of a coil spring 85 is fitted into the cup washer 80. A sheet metal thimbleshaped retainer 92 is placed within the bore 88 in a position shown in FIGURE 4 with the upper end of spring 85 against the top of the retainer 92. A sheet metal eyelet-cup 89 is press-fitted into the top of bore 88 and has a central re-entrant portion 87 which telescopes over the end of retainer 92 to tightly press the retainer 92 downwardly into the bore 88 so that a flanged rim 91 of the retainer 92 will force the periphery of diaphragm 76 onto the surface of shoulder 90 with sufficient pressure to form a fuel-tight fit. Spring 85 is slightly compressed and will press the diaphragm and metering rod retainer assembly downwardly into its lowest position, as shown in FIGURE 4.

An aperture 93 through the wall of thimble retainer 92 provides access form bore 88 to the inside of retainer 92. As shown in FIGURE 3, a passage 94 is formed through the body casting 10 to the flange portion 13 of the carburetor and opens at 25 into the mixing con duit and manifold M below or downstream of the throttle 22. In this manner, passage 94 connects the space above the diaphram 76 to the manifold pressure of the engine.

A passage 96 (FIGURE 2) is formed between the mixing conduit 12 from a region between the choke valve 26 and the throttle valve 22 to extend downwardly into the upper portion of well 20. Within the passage 96 is press-fitted a restriction element 98 for controlling air flow through passage 96 into the well 20.

The operation of the main fuel circuits of the carburetor is as follows: Fuel from the fuel bowl 36 flows into the well structure 20, to fill it to the level of the fuel in the bowl. Upon the turning over of the engine, air is sucked through the air filter 29 into the mixture conduit 12 and the intake manifold M. The flow of air through the booster venturi 32 provides a sub-atmospheric pressure within the venturi surface 34 which extends back through the fuel passage 58 to the upper end of fuel well 20. The atmospheric pressure on the surface of the fuel within bowl 36 raises the fuel within the well and simultaneously air is sucked through the restriction 98 and the bleed passage 96 into the upper portion of the fuel well. This air passes around and through the apertures 63 in the emulsion tube 62 to mix with the fuel and its vapor and to form an air-fuel emulsion. The emulsion is carried upwardly from the fuel well into the main fuel passage 58 and out the nozzle 60 to form a fuel and air mixture with the air passing through the mixture conduit 12. When the engine is operating at low or idling speed such that the manifold vacuum is high, in the order of 18 inches of mercury, the diaphragm is forced by atmospheric pressure to its uppermost position. This places the larger portion 71 of the rod 66 in the central metering portion of jet 56. A drop in manifold vacuum reduces the force of atmospheric pressure on diaphragm 76 and spring presses rod 66 downwardly a corresponding amount until the reduced rod portion 68 is positoned within the jet to" permit an increase of fuel flow. As the shoulder between the

rod portions

68 and 71 falls below the central metering portion of the jet passage 59, a maximum amount of fuel can flow through the jet. Manifold vacuum tends to drop as the throttle is opened from a closed position and thus the movement of the reduced portion 68 of rod 66 into the jet coincides with greater need for fuel as the throttle opens. The particular metering rod 66 substantially operates as an off and on construction. That is, the fuel flow is either restricted by the large portion 71 of the rod or is less restricted by the reduced portion 68 of the rod and with little or no effect produced by the shoulder between rod portion 68 and rod portion 71. However, other types of metering rods may be used with a graduated thickness between

rod portions

68 and 71.

It has been found that during engine operation the fuel flow through the metering jet 56 will tend to move the metering rod end around and from side to side within the jet opening. This effect is particular-1y extreme at high engine speeds when fuel flow is at a maximum. Then the free end of rod 66 whips around the jet opening 59. Any change in position of the metering rod during fuel flow through the jet provides an uneven flow of fuel so that the engine performance is not uniform. It has been found in the past that it is advantageous to bias the metering rod 66 to one side of the jet so that it is retained always in one position during engine operation. In prior art structures, the biasing spring has been mounted at the upper portion of the metering rod to force the lower end against the side of the jet. However, with the construction of the particular carburetor structure shown in FIGURE 4, it is diflicult to arrange a spring along the length of the metering rod 66 to appropriately bias the end of the rod against the side of the jet 56.

Accordingly, then, in accordance with this invention, a light spring is used for biasing the lower end of metering rod 66 against the metering jet 56. Spring 95 consists of a light, thin, single strand hairpin spring fixed between the end of rod portion 71 and a fixed stud 97 extending from the portion of casting 10. Spring 95 is formed with a separate loop at each end. One loop 101 is fitted within a groove in the rod end 71 and the other end loop 103 is fixed into a groove in the end of the stud 97. The bias of spring 95 is such as to move the end 71 of the rod 66 away from the stud 97 and against one side of the metering jet 56, as shown in FIGURE 4. This spring bias eliminates any movement of the metering rod 66 freely from side to side in the pass-age 59. Thus, the flow of fuel through the jet 56 is maintained consistent.

The shape of the spring 95 is substantially that shown in FIGURE 6. The spring itself may be made of 0.012" gauge music wire having a precoating of zinc or cadmium to prevent corrosion. This particular material is notlimiting and any appropriate material may be used for this spring.

Spring 95 has the advantage of maintaining the friction of the rod 66 against the jet 56 to a minimum so as not to interfere with the action of the diaphragm 76. The support of spring 95 is such that as the rod 66 moves vertically, spring 95 will pivot around the stud 97. This arrangement minimizes friction between the spring 95 and rod 66 which would be greater if rod ,66 had to slide through the loop 101. Thus spring 95, being attached as described to the end 71 of the metering rod, moves directly with the metering rod and is not forced to slide over a surface of the rod with a greater friction of movement.

The friction due to rotational movement of spring loop 103 in the grove of stud 97 is small in comparison to prior art arrangements.

We claim:

1. A carburetor comprising a body having an air and fuel mixture conduit therethrough, a main fuel passage within said carburetor body, means forming a restricted jet portion of said fuel passage, a metering rod movably mounted within said fuel passage and having a free end of varying thickness extending through said restricted jet passage portion, means attached to the other end of said rod for supporting said rod and for providing reciprocable motion of said rod along its longitudinal axis, and a spring biasing said free rod end against the Wall of said jet passage portion, said spring consisting of a single strand of wire forming a single loop and having spaced outwardly biased ends each being formed with an arcuate portion, a stud projecting from said carburetor body in a direction substantially parallel to the longitudinal axis of said metering rod and closed spaced therefrom on the downstream side of said restricted jet portion, one arcuate end portion of said spring loop being fixed to said free rod end and the other arcuate end portion thereof being fixed to said stud, the movement of said rod along its longitudinal axis moving the end portion of said spring fixed to the rod relative to said end portion fixed to said stud whereby friction from said spring upon movement of said metering rod is minimized.

2. A carburetor comprising a body having an air and fuel mixture conduit therethrough, a main fuel passage within said carburetor body, means forming a restricted jet portion of said fuel passage, a metering rod movably mounted within said fuel passage and having a free end of varying thickness extending through said restricted jet passage portion, diaphragm actuated means attached to the other end of said rod for supporting said rod and for providing reciprocable motion of said rod along its longitudinal axis, and a spring biasing said free rod end against the wall of said jet passage portion, said spring consisting of a single strand of wire forming a single loop and having spaced outwardly biased ends each being formed with an arcuate portion, a stud projecting from said carburetor body in a direction substantially parallel to the longitudinal axis of said metering rod and closely spaced therefrom on the downstream side of said restricted jet passage portion, a first groove formed in said free metering rod end, a second groove formed in said stud, one arcuate end portion of said spring loop being fitted within said first groove of said free rod end and said other arcuate end portion thereof being fitted within said second groove of said stud, the movement of said rod along its longitudinal axis moving said spring end portion on the rod relative to the spring end portion on the stud whereby friction from said spring upon movement of said metering rod is minimized.

References Cited by the Examiner UNITED STATES PATENTS 1,961,747 6/1934 Ewart 251122 2,394,663 2/1946 Carlson et a1. 261-69 2,969,965 1/1961 Braun 26169 3,025,877 3/1962 Buckay 25l61 3,084,865 4/1963 Fleer et a1. 251-122 3,089,684 5/1963 Smith 261-69 HARRY B. THORNTON, Primary Examiner.

RONALD R. WEAVER, Examiner.

Claims

1. A CARBURETOR COMPRISING A BODY HAVING AN AIR AND FUEL MIXTURE CONDUIT THERETHROUGH, A MAIN FUEL PASSAGE WITHIN SAID CARBURETOR BODY, MEANS FORMING A RESTRICTED JET PORTION OF SAID FUEL PASSAGE, A METERING ROD MOVABLY MOUNTED WITHIN SAID FUEL PASSAGE AND HAVING A FREE END OF VARYING THICKNESS EXTENDING THROUGH SAID RESTRICTED JET PASSAGE PORTION, MEANS ATTACHED TO THE OTHER END OF SAID ROD FOR SUPPORTING SAID ROD AND FOR PROVIDING RECIPROCABLE MOTION OF SAID ROD ALONG ITS LONGITUDINAL AXIS, AND A SPRING BIASING SAID FREE ROD END AGAINST THE WALL OF SAID JET PASSAGE PORTION, SAID SPRING CONSISTING OF A SINGLE STRAND OF WIRE FORMING SINGLE LOOP AND HAVING SPACED OUTWARDLY BIASED ENDS EACH BEING FORMED WITH AN ARCUATE PORTION, A STUD PROJECTING FROM SAID CARBURETOR BODY IN A DIRECTION SUBSTANTIALLY PARALLEL TO THE LONGITUDINAL AXIS OF SAID METERING ROD AND CLOSED SPACED THEREFROM ON THE DOWNSTREAM SIDE OF SAID RESTRICTED JET PORTION, ONE ARCUATE END PORTION OF SAID SPRING LOOP BEING FIXED TO SAID FREE ROD END AND THE OTHER ARCUATE END PORTION THEREOF BEING FIXED TO SAID STUD, THE MOVEMENT OF SAID ROD ALONG ITS LONGITUDINAL AXIS MOVING THE END PORTION OF SAID SPRING FIXED TO THE ROD RELATIVE TO SAID END PORTION FIXED TO SAID STUD WHEREBY FRICTION FROM SAID SPRING UPON MOVEMENT OF SAID METERING ROD IS MINIMIZED.