US3565104A

US3565104A - Choke valve

Info

Publication number: US3565104A
Application number: US757576A
Authority: US
Inventors: Paul H Mcfadden
Original assignee: Bendix Corp
Current assignee: Bendix Corp
Priority date: 1968-09-05
Filing date: 1968-09-05
Publication date: 1971-02-23
Anticipated expiration: 1988-02-23
Also published as: GB1237806A; BR6912013D0

Abstract

A pressure sensitive, semiautomatic choke valve with spring mounting means to give the choke plate an axis of rotation that moves as it opens and closes in response to pressure fluctuations.

Description

United States Patent [56] References Cited UNITED STATES PATENTS 1,811,011 6/1931 Hettger 137/484X 2,051,881 8/1936 Mock 251/305X 2,486,639 11/1949 Ferguson... 251/228X FOREIGN PATENTS 16,483 7/1907 Great Britain 137/5253 Primary ExaminerM. Cary Nelson Assistant Examiner-R. B. Rothman Attorney- Piante, Hartz, Smith & Thompson choke valve with spring mounting means to give the choke plate an axis of rotation that moves as it opens and closes in response to pres- 7 sure fluctuations.

PATENTEUFEBNIHYI 3565,10 4

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INVENTOR.

CHOKEVALVE BACKGROUND OF THE INVENTION 1. Field of the Invention Choke valves for carburetors 2. Description of the Prior Art It is well known that a richer mixture, a mixture having a higher fuel to air ratio, is required for starting an internal combustion, spark ignition engine, than is required to run the engine immediately after it starts. Considerable difficulty has been had with hand operated choke plates designed to provide an engine with the proper air fuel mixture. The uninstructed operator is often prone to over-choke, and as a result, floods the engine, thus delaying starting and wasting fuel. One method of solving this problem has been to insert a poppet valve in the carburetor choke plate. With the carburetor choke plate in a closed position, a suction develops in the air passage leading to the engine as the engine is cranked. The springed poppet valve opens in response to this pressure and allows enough air flow to start the engine. Another well known choke plate mounting for allowing an air flow in response to pressure fluctuations across the plate in the air intake passage comprises a choke plate mounted on a shaft displaced slightly from the center of the intake passageway. The choke plate will be spring mounted to this shaft so that it rotates about the shaft. As a pressure differential builds ,across choke plate, there will be a net force tending to openthe plate. This net force occurs because there is more plate area on one side the shaft than the other, and the force causing rotation is dependent on both air pressure and the area over which the pressure acts. a

A second problem with hand operated choke plates is that the operator is apt to leave the plate in a closed position too long after the engine has started. In such a case, the engine does not receive enough air to burn all of the fuel being supplied to it. The continued supply of excess fuel not only wastes fuel, but contaminates the lubricating supply of the engine, eventually working past the pistons into the crank case. The poppet valve will not pass enough air to alleviate this problem.

SUMMARY OF THE INVENTION The purpose of the present invention is to provide an inexpensive choke plate with increased sensitivity to the proper amount of air that should be passed to an engine. A total force acting on an object such as a choke plate'will be determined by magnitude of air pressure and the amount of surface area over which that pressure acts. The choke plate herein described shows a more sensitive reaction to changes in the pressure differential across the plate than prior choke valves because the valve comprises a rigid plate mounted in an air intake passageway by means of resilient support fastened to the choke plate near one edge rather than substantially across the center of the plate. Thus, a given pressure differential across the choke plate will produce a larger and quicker response than in prior choke plates because a larger force tending to open the plate will be produced by the air pressure acting on substantially the entire choke plate. In prior choke plates mounted near their center, an air pressure differential will produce a large force to counteract the rotational opening of the plate since there is substantial choke plate area on each side of the axis of rotation. The present invention will also produce a larger opening in response to air pressure than is possible with choke plates in which only a small portion of the plate, such as a poppet valve, moves in response to air pressure.

It is highly desirable to build carburetors having cylindrical air passages. Such a tube will be cheaper and more efficient than any other shaped passageway because cross-sectional area is maximized and surface area is minimized in a cylinder. The choke plate mounting herein described finds particular application in such a cylindrical air passageway. A substantially circular choke plate is mounted within the air intake passage. Since this plate is designed to completely close the passageway, it can only rotate about an axis substantially along a diameter of the cylindrical passageway. If the axis of rotation is displaced toward the side of the cylinder, the choke plate will bind when opening. The center of the choke plate cannot be forced into the smaller area toward the sides of the cylinder. While the choke plate of the present invention rotates about a diameter of the choke plate which stays essen' tially parallel to the choke shaft during opening and closing, the plate is not supported along that diameter. Spring mountings are connected to the choke plate at points displaced from the axis of rotation. It is desirable for these points of support to be displaced from the axis of rotation as far as possible, that is, near the edge of the choke plate. When a pressure differential develops across the closed plate, the entire plate will act as a lever trying to rotate about this point of attachment. Pure rotation about this point will be impossible, the center of the choke plate will have to remain substantially in the center ofthe bore of the tube. However, since the plate is mounted resiliently rather than fixedly, translational motion along the tube will occur in response to fluctuations in air pressure. The plate will be resiliently restrained at the points where it is attached to the spring mounting, though. This restraint will cause the plate to rotate and thus open as it moves further into the air intake passage.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects, features and advantages of this invention will become apparent from a consideration of the following description, the appended claims and the accompanying drawings in which:

FIG. 1 is an illustration of a three-dimensional view showing the choke valve ofthis invention;

FIG. 2 is a diagrammative view of a carburetor containing the choke valve apparatus of this invention hand rotated to an open position;

FIG. 3 is an illustration of the choke plate in a closed position; 1

FIG. 4 is an illustration of the initial response of a choke plate to a variation of air pressure in the intake passage;

FIG. 5 is an illustration of an opening choke plate having been rotated and laterally displaced from its closed position in response to a variation in air pressure;

FIG. 6 is an illustration of further opening in response to air pressure; and

FIGS. 7, 8 and 9 are illustrations of particular leaf spring mountings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 1. Description of the Apparatus The invention will be more clearly understood if the elements of apparatus are recited prior to a description of the relative positions of these elements during the operation of the choke valve. Description is with reference to the drawings, with similar reference characters in the various illustrations designating corresponding parts. The construction of the carburetor choke valve. 10, herein disclosed, is most clearly illustrated by the three-dimensional-view of FIG. 1. Choke valve 10 is mounted in the cylindrical air passageway 12 and com prises a substantially circular choke plate 16 for closing the intake passageway 12. Plate 16 is resiliently mounted to a rotatable shaft 18 disposed substantially along a diameter of tube 12 by leaf spring 20. Leaf spring 20 is attached to plate 16 along Line BB, which is also more readily seen in FIGS. 7, 8 and 9. Line BB will be parallel toshaft 18, and as will hereinafter be seen, it is desirable to have Line BB displaced a substantial distance from that shaft. Line CC. as shown in FIGS. 7, 8 and 9, is also parallel to shaft 18, and represents the axis about which initial rotation occurs. The position of this axis will depend on .the design of leaf spring 20 and will be positioned proximate the area of greatest flexibility of a given leaf. In FIGS. 8 and 9 axis CC will be generally across the thinnest point of spring 20. Since spring 20 is of uniform construction in FIG. 7, axis CC will be midway between support line BB and shaft 18. As will hereinafter be shown, CC should also be substantially displaced from the center of the shaft 18.

2. Operation of the Preferred Embodiment The invention herein disclosed will be more clearly understood by illustration of the relative positions of the apparatus of the preferred embodiment during operation. With reference to the drawings, FIG. 2 is an illustration of a side view of choke valve mounted in a standard tubular, updraft carburetor 14. The choke valve 10 would be described as semiautomatic, that is, it is designed to rotate in response to hand operation, yet its position may vary in response to pressure fluctuations in the intake passage and independent of hand operated control. Choke plate 16, shaft 18, and leaf spring rotate as a single unit in response to manual manipulation. Leaf spring 20 is of stiff enough construction so that the plate rotates as if it were fixedly attached to shaft 18. FIG. 3 is an illustration of choke valve 10 manually rotated from the open position of FIG. 2 to completely closed position for starting of an engine (not shown). Spring 20 holds plate 16 against shaft 18.

If the engine (not shown) is cranked, a pressure differential develops in passageway 12 across plate 16. The choke plate will act as a lever supported along axis BB with a pressure acting on its entire area. The force tending to open plate 16 will be a product of this pressure and the area on which it acts. Constructing a support line BB near one end of the plate will increase the area across which the pressure tending to open the plate will act. Thus the net force tending to open the plate produced by a given air pressure will be maximized if Line BB is placed as far as possible from the center of the shaft 18. The plate 16 will not rotate about axis BB however, but about Line CC, the line of greatest flexibility of support spring 20. This line should also be substantially displaced from the center of the shaft 18 for maximum response to a given air pressure. Since rotation, initially, at least, occurs about Line CC, its positioning will determine the effective length of the lever arm represented by plate 16.

FIGS. 4-6 are illustrations of a time sequence of an opening of the choke valve of this invention in response to an air pressure differential. A rigid plate 16 acts as a lever supported along BB. Its initial response to the force created by the air pressure differential would be a rotation about CC, the flexible area of spring 20. Plate 16 will initially be permitted only a very small rotation about axis CC before it will bind on cylinder 12. Plate 16 will move slightly away from shaft 18, however the center 17 of the plate 16 must remain substantially in the center of the bore of tube 12. It is not possible to force a diameter of the choke plate 16 into the smaller area toward the sides of tube 12. However, not'enough air will flow past the slightly opened plate shown in FIG. 4 to eliminate the pressure differential across plate 16. The pressure differential will push plate 16 toward the area of lower pressure or to the right as is shown in FIG. 5. But because the plate is resiliently restrained near one edge, or along Line BB, it will be further rotated as it is pushed along into passageway 12. The force of air pressure acting on plate 16 causes bending of leaf spring 20. Thus Lines BB and CC along plate 16 move toward the center of passageway 12 as indicated in FIGS. 5 and 6. Plate 16 moves to the right away from shaft 18, as the center 17 of the plate 16 moves along the center of the bore of tube 12. This displacement allows greater rotational opening of plate 16.

The illustration of FIG. 6 approximates a maximum intended response to an air pressure differential. Leaf spring 20 shows substantial bending so that Lines BB and CC have been substantially displaced from the closed position of FIG. 3 and center point 17 has been substantially displaced from shaft 18 in the rotational opening of plate 16. Note that shaft 18 has not been rotated in this process. The opening has been entirely in response to air pressure. Also note the position of plate 16 in FIG. 6 does not closely apdaroximate the fully opened positron of FIG. 2. Choke valve has been designed to be responsive to the pressure fluctuations in an air intake passage during the starting of an engine. It has not been designed so flexibly that the choke plate will rotate completely independently of manual control. The system is not a fully automatic one and will be responsive tomanual control at all times.

From the above description it is seen that this invention pro vides an economically constructed semiautomatic choke valve 10. A preferred embodiment of this invention shows a choke valve with only three different elements. The choke plate 16 is mounted resiliently by means of a leaf spring 20 to a rotatable shaft 18. The leaf spring is of sufficiently stiff construction so that the combination is completely responsive to manual operation of choke valve shaft 18. The plate may be fully opened or fully closed manually. Yet if the system is overchoked and insufficient air is being supplied to an engine during starting, air pressure caused by suction in the intake passage to that engine will produce a relatively large opening of the choke plate and the proper amount of air will be metered to the engine. A relatively large opening will occur because the resilient mounting allows almost the entire choke to function as a lever arm with all incoming air acting to rotate the lever toward an open position.

It will be understood that the method and apparatus which are herein disclosed and described are presented for purposes of explanation and illustration and are not intended to indicate limits of the invention, a scope of which is defined by the following claims.

lclaim:

1. A carburetor choke valve for regulating air flow to an engine comprising:

an intake passageway for providing air flow to the engine;

a choke plate for regulating air flow through said passageway;

means resiliently mounting said choke plate in said intake passageway;

said resilient mounting means being constructed to allow movement including rotation of said choke plate in response to pressure fluctuations in said passage; and

said choke plate and said passageway being shaped so that said passageway comprises a guide to said plate that causes said relative movement to include displacement of the axis of rotation of said choke plate as said plate opens and closes.

2. The device of claim I in which said choke valve comprises a substantially circular choke plate disposed within a substantially cylindrical air intake passageway, and said resilient mounting means comprise a rotatable shaft and leaf spring connecting said choke plate and said shaft.

3. The device ofclaim 2 in which said leaf spring constitutes the only connection between said choke plate and said rotatable shaft, and in which the shape of said leaf spring determines in part the magnitude of said movement caused by :ressure fluctuations within said air intake passage.

4. The device of claim 2 in which said resilient mounting means and the relative dimensions of said choke plate and intake passageway are constructed to allow rotation of said choke plate about substantially only one diameter of said plate, and in which said mounting means is also constructed so that all points of support for said choke plate provided by said mounting means are displaced from said diameter.

Claims

1. A carburetor choke valve for regulating air flow to an engine comprising: an intake passageway for providing air flow to the engine; a choke plate for regulating air flow through said passageway; means resiliently mounting said choke plate in said intake passageway; said resilient mounting means being constructed to allow movement including rotation of said choke plate in response to pressure fluctuations in said passage; and said choke plate and said passageway being shaped so that said passageway comprises a guide to said plate that causes said relative movement to include displacement of the axis of rotation of said choke plate as said plate opens and closes.

2. The device of claim 1 in which said choke valve comprises a substantially circular choke plate disposed within a substantially cylindrical air intake passageway, and said resilient mounting means comprise a rotatable shaft and leaf spring connecting said choke plate and said shaft.

3. The device of claim 2 in which said leaf spring constitutes the only connection between said choke plate and said rotatable shAft, and in which the shape of said leaf spring determines in part the magnitude of said movement caused by pressure fluctuations within said air intake passage.