US2004003A - Carburetor - Google Patents

Description

, June 4, 1935. G. L. KENNEDY- CARBURETOR Original Filed Jan. 5; 1925 2 Sheets-Sheet 1 INVENTOR Guy L KENNEDY ATTORNEY June 4, 1935. I '6. L. KE NNEDY 2,004,003

FARBURETOR I Original Filed Jan. 5, 1925 '2 Sheets-Sheet 2 INVENTOR ATTORNEY Patented June 4, 1935 oAaBUa roa Guy L. Kennedy, New York, N..Y., assignorto Ken-Grip Corporation, a corporation of New. York I Application January 5, 1925, Serial No. 687

Renewed ctober 14, 1931 1 Claims. (01. 261-44) w This invention relates to improvements in gastatably supported in bearings in the sides of the ifying devices or carburetors; particularly car.- casing, so that thisvalve can be turned to be buretors to supply the inflammable motive agent disposed transversely of .the bore '2, and thus close required in the operation of internal combustion the bore, or with its plane more or less in line 5 engines, with the bore, so as to open it. I also mount the 5 An object of the invention is to provide a simple, valve 3 so that it can turn about an axis transverse efficient and inexpensive carburetor that will, so with respect to the bore 2 to open or closing posivaporize a combustible liquid as to yield a homo: tion, this valve being supported upon a rotatable geneous practically dry product; and that is deshaft or spindle 6, turning in bearings in the side signed to maintain a substantially constant vacof the casing I, and being preferably parallel to 10 uum during vaporization, regardless of the fiucthe shaft 5. The valve 3 is hollow and closes an tuating vacuum in the intake manifold of the interior chamber 1, and this valve is also proengine. vided with an outlet 8 in the form of a slot, as

These and other objects and advantages of the indicated particularly in Figures 1, 5 and 6. On

invention will bemade clear in the following dethe inside of the valve 3, the spindle 6 is bored to 15 scription and the novel features of my improved provide a pair of ports; 9 which communicate carburetor will be defined in the appended claims. with a duct I0 through which gasoline and air But this disclosure is, of course, illustrative only, pass by way of the ports or nozzles 9, to the chamand I may alter the details of construction actuher "I, and the gasoline thus admitted to the chamally shown herein to a considerable extent, as inber 1 intermingles with the air in this chamber 20 dicated by the broad meanings of the terms in and flows out through the slot 8 into the bore 2.

h h th claimsgare expressed, Therefore, the valve 3 serves as an air regulat- On the drawings, I ing valve and spray nozzle combined. Figure 1 is a view of acarburetor according to This valve 3 should preferably have the shape my invention, presented in longitudinal section, of an oblate sphere consisting of two halves II, 25 on an enlarged scale; each half being hemispherical in shape, but not Figure 2 is a side iew thereof; truly hemispherical; and being somewhat flat- Figure 3 is an opposite side view; tened, and also held together rim to rim by a Figure 4 is a bottom plan of the carburetor; screw I2 which passes directly through the spin- Figure 5 is a section on line 5-5 of Figure 1, dle 6, the ,rims of each half H being recessed 30 looking downward, some of the outside members to enable them to be clamped upon the shaft or of the carburetor being omitted, the air valve spindle 6 with their edges in contact, except over and spray nozzle being illustrated as fully open; the portions where the opposed edges of the two Figure 6 is a similar section, the air valve and halves are cut away to provide the slot 8. This spray nozzle in this view being in shut-off or slot is entirely at one side of the valve and is 35 throttle position; this view being in section on somewhat less thana semicircle in length. As both line 5-5 and line 6-6 onFigure 1; shown clearly in the drawings, the diameter of Figures '7, 8, 9, l0 and 11 are views showing the this valve measured in the plane of the contactconstruction and function of the means for ading edges or rims of the substantially hemispheri- 40 mitting and regulating the admission of gasoline cal halves H, is greater than the diameter coin- 40 to the carburetor; and V ciding with the axis of the screw 12, the valve Figure 12 is a sectional view showing a modl- 3 thus being oblate in form or in the form of a fication of the carburetor in one detail. sphere flattened at the poles and bulging at the The samenumerals identify the same parts equator; The equatorial diameter is indicated 5 throughout. by the dotted line E in Figures 1 and 6, and the In the pa c description of t e draw polar diameter by the line indicated by the letter I use the numeral l to indicate atubular casing P in Figure 5. which has a bore 2 extending long tu When thevalve is turned on its shaft 6 so as through it, and is open at both ends. The bore 2 to carry it into the position shown in Figure 5,

is indicated as a cylinder in cross-section, but may that is, with the polar diameter P transverse to have any other desired shape, and mounted in the axis of the bore 2, it will open the bore 2 the casing I, so as to control the bore 2, are two and permit air to flow through same as fully valves 3 and 4. The valve 4 may be regarded as as the shape of this valve will permit; but when a throttle or vacuum regulating valve, and is it is revolved into such a position that the polar mounted upon a transverse shaft 5 which is rodiameter is brought into line with the axis of the bore 2, thus placing the equatorial plane of the valve across the bore, the valve 3 will then close or nearly close the bore, and reduce the flow of air through the carburetor to a minimum. As indicated by the numeral I3, the valve 3 even when it occupies the position shown in Figure 6, will be separated from the inside surface of the bore 2 around its periphery by a small annular space, I3, and this space will be considerably larger when the valve is turned to its fullest open position as shown in Figures 1 and 5. At one side of the casing the spindle 6 is engaged by an external bearing I4 and at the opposite side of the spindle, it turns in another, outside. bearing I5. As I shall describe more fully below, the shape of the combined air regulating valve and spray nozzle 3 is such that the bore 2 can be opened to permit more and more air to flow therethrough in direct proportion to the degree of angular displacement of this valve from the position shown in Figure 6 to that of Figure 1; that is,.when the valve is turned from the position shown in Figure 6 through 45 degrees towards full open position, it will permit twice as much air to flow past it, as when it is turned through only 22 degrees, and when it is turned through 90 degrees to full open position, it allows twice as much air to flow past it, as when it is turned through only 45 degrees;

I thus the quantity of air which flows through the casing I is increased or decreased in the same ratio as the angular distance of the valve towards or from the position shown in Figure 6 is increased or decreased.

The extremity of the shaft 6 which is supported in thebearing I4 may be solid and integral, but the opposite extremity which turns in the hollow external projection or bearing I5, is hollow and comprises at least two parts or members for the convenient admission and regulation of gasolineand air to the carburetor. Thus the portion of the shaft 6 which contains the axial duct I delivering through the two ports or nozzles 9 to the chamber I, is expanded on the outside of the casing I to provide a disc or head I6, provided with a rim I1; making in effect a cup-shaped member which forms one section of the valve for regulating'thegasoline supplied to the carburetor. Thisvalve for supplying and regulating the gasoline is shown fully in Figures 1, 7, 8, 9, 10 and 11 inclusive. The rim I! of the disc I6 above mentioned, consists of two portions I8 and I9, the portion I8 being of less height than the portion I9, to provide a pair of shoulders 20, each portion being substantially half of a circumference. is provided by a similar disc I6, rigid with a journal 6A to be in axial alinement with the main portion of the shaft 6, and this section also has the form of a cylinder cup with a rim II comprising as before, two portions I8 and I9 of unequal depths, measured in the direction of the axis of the cup, to provide two similar shoulders 29.

Therefore, when the two sections of this valve are assembled by bringing them together as indicated in Figures -1, 8, 9, 10 and ll, rim to rim, with the shoulders of one engaging the shoulders 20 of the other, they must obviously rotate in unison when the valve 3 is rotated. In the portion I9 of the rim ll, of greater depth, on the disc I6, attached to the journal 6A, is cut a notch or recess 2I, this notch beginning at the point a, Figure '7, and extending along astraight diagonal line b, to a shoulder c, the recess being about 90 degrees in extent, andwith its extremi- The other section of this valve ties, namely the point a and the shoulder c equidistant from the two shoulders 20. Hence, when the two sections of this valve are assembled rim to rim, the recess will permit communication with the interior of the valve, so that gasoline can flow through this recess which will serve as an inlet for the gasoline to pass into the rotary valve to the duct I0. At its outer extremity, the projection I5 has internal threads 22, to engage external threads upon a perforated element or nut 23, between which and the extremity of the bearing I5, is clamped a washer or backing 24. This nut is perforated and serves as a bearing for the journal 6A.

The projection I5 has an extension receiving in its outer extremity a gland 26 to secure therein a gasoline supply conduit 21 having a bore 28. See Figure 2. This bore 28 leads to an inlet opening 29 in the side of the projection I5 and when the port formed by the triangular recess 2I in the hollow rotary valve disposed within the bearing I5, uncovers this inlet 29, gasoline can, of course, flow freely into the valve for regulating the gasoline in the projection i5, and thence by way of the duct I0, through the nozzles 9 to the chamber I in the valve 3. In practice, the rims of the two sections of this valve do not quite make contact with each other, but are separated to a slight extent, as indicated in Figures 1, 8, 9 and 11; and for this purpose, I place inside of the valve a compression spring 39, which seats against the two opposing discs I6 and normally tends to move the two sections of the rotary gasoline valve apart.

Figure 7 shows the two sections of the valve for regulating the gasoline, in perspective, before assembling; while Figure 8 shows these two sections brought together rim to rim with the triangular recess forming the inlet port which leads to the interior of this valve, on top. The axis of the extension 25 is at right angles to the axis of the bore 2, so that when the casing I is vertical, both the projection I5 and extension 25 will lie in a horizontal plane, and, therefore, the conduit 21 will communicate with the interior of the valve for controlling the gasoline through the inlet 29, through the side of the projection I5. The location of the conduit 21 is indicated in Figure 8 with reference to the axis of the spindle 6 only; but when the valve 3 is in such position that it closes as much as possible, the bore 2, the valve forcontrolling the entrance of gasoline to the carburetor, will be in such position that the point a .of the notch or port 2| will be sub-; stantially in line with the bore 28 through the conduit 21, as indicated in Figure 9. No gasoline at all will now be enabled to flow into the carburetor. As, however, the valve 3 is turned to bring its polar axis more and more transverse to the axis of the bore 2, the diagonal edge b of the port or recess 2I, will pass across the inlet 29 and expose a larger and larger portion of the area of the bore 28, and thus admit more and more gasoline to the inside of the valve and the duct I0. When the valve 3 has come to such position that it opens the bore 2 as much as possible, the sections of the valve for controlling the gasoline will occupy the position shown in Figures 1 and'll with the shoulder c adjacent the inlet 29 and with the area of the bore 28 in the conduit 29 uncoveredto the maximum extent. By tuming the nut 23, the position of the diagonal edge of the notch or port 2| can be so adjusted that the extent to which the inlet 29 will be uncovered, as the valve for admitting the gasoline is rotated,

oblate spherical valve 3.

can be adjusted and increased or decreased at will.

As the edge b of the notch H is diagonal with reference to the spindle 6, it is clear that more and more gasoline will be admitted in direct proportion to the angular degree of rotation of the valve for controlling the gasoline in the same manner as the supply of air is regulated by the That is, in the positions of theparts shown in Figure l, twice as much air and twice as much gasoline will be admitted to the carburetor, as when the parts occupy positions 45 degrees distant, and so for all other positions, so that while the quantities of air and gasoline may be varied, the amounts of the two ingredients are always present in the same ratio, and the composition of the fuel which results from the action of the air upon the gasoline, is rendered constant. At the same time, precise and complete regulation as to the amount of air and gasoline admitted can always be secured, and the quantity of each will be increased in exact proportion to the extent of angular movement of the valve 3, and the valve for controlling the gasoline supply which must always move with the air valve.

With the parts in the positions occupied in Figure 1, the direction of rotation of the shaft 6 to move the valves towards closing position is indicated by the arrow A; while the arrow in Figures 3 and 6 indicate the direction of rotation to open position. The end of the shaft 3 adjacent the bearing M has afiixed thereto an arm 3!, and on the corresponding end of the shaft 5 is a similar arm 32. These two arms 3i and 32 are united by a link 33, to be operated together.

On the interior of the casing l, between the valves 3 and 4 is a tubular member 34, presenting a relatively large end to the valve 3, and secured around its periphery at this end to the inside surface of the bore 2. The opposite end of this member is smaller, and separated from the inside of the bore 2 by an annular space 35. Between its ends the member 34 is contracted, as shown at 31, somewhat like a Venturi tube. Opposite the contraction 31, the casing l has an air inlet port 38, controlled by an arc-shaped strip or shutter plate 39, with a curved slot 46 therein. To the convex edge of the plate 39 at the middle is afiixed an arm 4|, bent to extend towards the lever 3|, with an opening 42 to give passage to the end of the spindle 6; and having a transverse slot 43, to receive a screw 44, entering a threaded opening in the arm 3|. By means of this screw and slot, the arm 4! and plate 39 can be adjusted within the necessary limits. The member 34 is imperforate between its open ends, that is to say, the walls thereof are continuous from end to end and have no lateral openings therein.

The arm 3| is perforated to be united to a link connected to an actuating lever, and the valves 3 and 4, of course, move together. As the valve 3 and the valve for the gasoline in the projection l5 are opened further, and further, more air and more gasoline are admitted to fiow through the casing in exact proportion to the degree of movement of these valves from fully closed to fully open position; but the ratio of the quantity of gasoline to the quantity of air is always the same and is, of course, selected according to the known capacity of air to absorb the gasoline as the latter is admitted to the carburetor.

The journal 6A may have a channel 6 open to the atmosphere to let air enter the inside of the gasoline valve. The vaporization begins in the chamber 1 of the valve 3 and the gasoline issues from the nozzles 9 in the form of bubbles; ecause as the gasoline flows into the duct !0, enough air will be entrained from the inside of the gasoline valve in the projection 15, to cause bubbles to appear. From the chamber 1 the air and the gasoline taken up by it are sprayed through the slot 8, and drawn into the member 34 by air flowing around the valve 3 through the bore 2, the slot. 8 being turned towards the member 34, as the valve 3 moves to fully open position. Upon passing the contraction 31, the air and vaporized gasoline meet and mix with air entering the port 38 and flowing through the annular space 36. ,Thus air coming in by way of the inlet 38 blows through the space 36 toward the axis of the bore 2, all around the member 34, forcing the spray to intermingle still further, the gasoline thus becoming more completely vaporized, so that when the intake manifold of the engine is reached, a practically dry combustible motive agent has been produced. Hence the member 34 facilitates vaporization with the annular air space 36 and inlet 38, through which air flows and escapes as a thin annular stream, to envelop and surround the spray of air and gasoline proceeding from the air regulating valve and'spray nozzle 3. annular stream of air surrounds the spray and drives any unvaporized particles of the mixture that mayreach this point, away from the surrounding wall of the casing to the axis of the bore 2, and greatly increases vaporizing action. As many of these annular air streams and members 34 may be employed as may be found necessary to secure a satisfactory degree'of vaporization.

The ratio between the quantity of air and the quantity of gasoline is kept constant, as above stated; though the amounts of air and gasoline may vary as the valves are opened or closed, to a greater or less extent. But a constant airgasoline ratio is impossible with any device wherein the vacuum or pull upon the gasoline is variable. It is essential that a steady, constant pressure be applied to the gasoline at all times and under all conditions, if we expect to produce a. steady, constant flow thereof; and

such flow can not be procured with any carburetor wherein the vacuum and consequently the unbalanced pressure on the gasoline is variable or fluctuating.

The normal vacuum in the intake manifold of e an internal combustion engine is known to vary in proportion to the opening or closing of the air inlet valve; for example, the throttle valve 4; and this variation may be such that the vacuum ranges from 20 inches of mercury displacement when the throttle valve is closed, to one-half an inch when the throttle is fully open. Clearly, a pressure equivalent to 20 inches of mercury displacement will force a greater quantity of gasoline through an orifice in a given time, than will a pressure equivalent to but one-half an inch of mercury displacement; therefore, the normal vacuum can not be relied upon to supply a steady and regular flow of gasoline to the carburetor.

If the gasoline were exposed to this fluctuating vacuum and the gasoline tank placed at a level lower than the carburetor, it will be found that in every case a surplus of gasoline will be in evidence when the throttle is closed; and, if the level of the gasoline is more than six inches below This the carburetor, no gasoline will be supplied at all when the throttle is full open. In view of this fact, the usual fluctuating vacuum of a gasoline engine cannot be depended upon as the force for supplying gasoline to a self feeding carburetor; but means for producing a constant not a variable pressure upon the gasoline must be found. It is imperative to decrease the maximum normal vacuum and increase the minimum normal vacuum until the two extremes meet on common ground which cannot be less than an equivalent of three inches of mercury displacement, or a fuel lift of 36 inches necessary when automobiles are on grades.

Reference to Figure 1 will show how I secure the end under consideration.

Plainly, if the valve 4 be closed, no vacuum or unbalanced pressure can act upon valve and nozzle 3, and if the valve 4 be turned to fully open position, the total vacuum or unbalanced pressure possible will take effect on the valve and nozzle 3.

Also, if a hole, say one-sixth of an inch in diameter, be drilled through valve 4, or a slight free air space such as the space i3, is provided between the inside wall of the casing and the periphery of the valve 4; and the engine is then started; there will result a relatively higher or major vacuum in the intake manifold, (which will be connected to the upper end of the carburetor), and a relatively low or minor vacuum between the valves 3 and 4. Increasing this opening in the valve 4 increases the vacuum on the valve 3; and decreasing this opening, decreases the vacuum acting on the valve 3, but as the valve 4 also governs idling conditions, the air passage through the valve 4 cannot be greater than that demanded for idling conditions. Instead of an opening through the valve 4, this valve may be arranged to be closed not entirely, but to leave a small space 43 between its edge and the inside of the casing I.

The relation of valves 4 and 3 and the respective volumes of air permitted to pass them when the valves are closed and in idling positions, is important in this discussion. If the volume of air passing the valve 4 were equal to the volume passing the valve 3, the vacuum in the manifold above the valve 4 would be equal to the vacuum between the valves 3 and 4. If the volume of air passing the valve 4 were less than the volume passing the valve 3, the vacuum in the manifold above the valve 6 would be greater than the vacuum between the valves 3 and 4; and if the volume of air passing the valve 4 is greater than the volume passing the valve 3, the vacuum between the valves 3 and 4 would increase in exact ratio to the increase in volume of air permitted to pass the valve 4.

From these easily demonstrated facts it is clear that if we set the valve i to allow air for idling to pass, we may make a free air space i3, around the periphery of the valve 3 and provide for a wide range of vacuum or unbalanced pressure or force on the valve and nozzle 3; and consequently upon the air and gasoline within it; while the parts are in idling and low speed positions. In practice it has been found that the free air space around the valve 3 should, in cross section or area, be five times the cross section or area of the required idling stream passing the valve 4. These proportions will reduce the maximum vacuum of about 18 inches of mercury displacement in the manifold to approximately 3 inches on the valve 3, and the gasoline entering it;

One must bear in mind that the arms 3| and 32 are joined by the link 33; and any movement of one arm thus imparts a corresponding movement to the other.

Having shown how the maximum vacuum is reduced to the desired point, it is necessary to explain how to increase the minimum normal vacuum on the gasoline, when the valves are in full open position as shown in Figure 1.

Reference to Figure I shows that if air control valve and nozzle 3 were a thin disc of metal like the valve 4, there would be, with both valves fully open, no resistance to the air passing through the device and consequently no vacuum to speak of. To obviate this condition and increase the vacuum or unbalanced pressure on the valve 3 and the gasoline when the valves are in fully open position, I employ the hollow oblate spherical air valve and spray nozzle 3 already described.

When the valve 4 is fully open, it offers no resistance to the air stream and, therefore, produces no vacuum. On the contrary the oblate valve 3 even when fully open greatly reduces the free air passage or bore 2, through the body of the device, and increases the vacuum on this valve 3, and the gasoline and air within it. Owing to its special shape, this valve 3 always, in any of its positions, will necessarily reduce the air passage between its circumference, and the inner wall of the casing l, to the size essential for maximum speed and efliciency; and though the vacuum above the valve 4 may tend to fluctuate widely, the vacuum at the valve and nozzle 3 remains substantially constant and or" the degree needed.

It has been amply demonstrated that if the bore 2 through the body I be 1 and inches in diameter, the polar diameter P of the valve 3 may be A; of an inch, thus leaving a free air passage around the valve 3 of an inch in width. This air passage has been found suflicient to supply air freely at maximum speed for all engines having from 192 to 250 cubic inches of piston displacement; and at the same time, it produces a vacuum sufiicient to draw the fuel from the tank at the rear of the car; even when on steep grades and under most trying conditions.

The slot 46 in the shutter-plate 39 is not as long as the plate, but leaves unperforated portions or the same area at the ends of the plate. When the air regulating valve 3 is closed as in Figure 6, one end of the plate 39 closes the port 38, and when the valve 3 is turned by the lever 3! to fully open position as in Figure l, the other end portion of the shutter-plate 39 also closes the port 38; but on passing from closed to fully open position of valve 3 or vice versa, the slot 43 in the plate 39 exposes the air inlet port 38, and admits air throughout a turn or" 93 degrees. When the valve 3 is closed, the air inlet 38 is closed to allow the engine to idle; and the inlet 33 is also closed when the valves 3 and 4 are opened fully for starting, but at intermediate positions of the valves 3 and 4, the air inlet is exposed through the slot 43.

At its lower end, the casing may have the usual air-choke valve 41, mounted on a shaft 48, rotating in bearings 4-3, and carrying an operating arm 53. The arm 3! has one or more openings to attach it to an operating lever.

In some cases, I may dispense with the arcshaped shutter-plate 39, and adopt the construction shown in Figure 12. The outer end of the boss surrounding the inlet 38 is internally threaded, and into this boss is screwed a bushing 52, bearing a poppet valve 53, seating on its inner extremity. This bushing has screw threads 54 on its outer end to receive a perforated cap 55, with a central bearing 5%, in which the valve stem 5? can slide. This stem has threads 58 at its outer end to be engaged by a nut 59, and between the nut 59 and the cap is a spring 65, holding the valve normally shut. The nut enables the tension of the spring to be adjusted as required. This modification operates as above to admit air during normal running of the engine.

At the top of the casing is a flange (ii to enable the carburetor to be bolted to the end of the conduit leading to the intake manifold of the engine.

While I have mentioned gasoline herein, I wish to be understood as asserting that I am not limited thereto, but any other volatile combustible liquid may also be employed.

No claim is made herein to the combined valve and spray nozzle 3 which is the subject of my copending application, Serial No. 49,963, filed August 13, 1925; or the rotary gasoline valve which is the subject or" my copending application, Serial No. 49,964 filed August 13, 1925.

Having described my invention, What I believe to be new and desire to secure and protect by Letters Patent oi the United States is:-

l. A carbureter having a casing with a bore therethrough, the opposite ends or" the bore serving as the main inlet and outlet of the casing, a hollow member open at both ends in the bore, said member presenting one end to said inlet and being secured around its periphery at said end to the inside of said bore, and being separated from the inside of said bore by a restricted space at its opposite end, which is the smaller, said member being contracted and imperforate between its ends, the casing having a port to admit air to said space adjacent the contracted part of said member, means for admitting hydrocarbon to said bore, a combined rotary valve and spray nozzle in said bore adjacent the end of said member secured to the inside thereof, and means connected to the rotary valve and nozzle to control said port.

2. A carbureter having a casing with a bore therethrough and an air port leading to said bore, a hollow member open at both ends in the casing adjacent said port, said member presenting one end to said inlet and being secured around its periphery at said end to the inside of the bore and being separated from the inside of the bore by a restricted space at its opposite end, which is the smaller, said member being contracted and imperforate between its ends, said port lying adjacent the contracted part of said member and between the ends of same, a combined rotary valve and spray nozzle in said bore adjacent the end of said member secured to the inside thereof, a fuel valve outside the casing and connected to the rotary valve and spray nozzle to be operated thereby, and a valve to control said port connected to the rotary valve and spray nozzle, said port leading to the space surrounding said member.

3. A carbureter having a casing with a bore therethrough, a hollow member in the bore, said member being secured around its periphery at one end to the inside of the bore, and being spaced from the inside of said bore at the opposite end, the casing having a port to admit air to the bore adjacent said member, means for admitting hydrocarbon to said bore, a valve in said casing, and means connected to the valve to control the port.

4. A carburetor comprising a casing with a bore therethrough, a spindle extending transversely of the bore supported by the casing, a valve having convex opposite faces mounted on the spindle, and a tubular member in the casing beyond the valve, secured to the inside surf-ace of said bore around its end adjacent to said valve, but spaced from the inside of the bore at its opposite end, the casing having an inlet through one sidebetween said two ends of said member.

5. A carburetor comprising a casing with a bore therethrough, a spindle extending transversely of the bore supported by the casing, a valve having a convex exterior mounted on a spindle and a tubular member in the casing having a restricted portion beyond the valve when the valve and member are in such relative positions that air can flow past the exterior of the valve, said member filling said bore and having a portion spaced from the'inside of the bore, the casing having an inlet through one side to admit air between the ends of said member.

GUY L. KENNEDY.

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