US3281132A

US3281132A - Carburetor

Info

Publication number: US3281132A
Application number: US481617A
Authority: US
Inventors: Llewellyn T Barnes
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-08-23
Filing date: 1965-08-23
Publication date: 1966-10-25
Anticipated expiration: 1983-10-25

Description

Oct. 25, 1966 T. BARNES 3,281,132

CARBURETOR Filed Aug. 23, 1965 5 Sheets-Sheet l t N mi" go l `r Milz', Q* Q ,.\\\\m\\\\\\\. Wx

LE WELLY/V 7." BAR/VES Oct. 25, 1966` L. T. BARNES CARBURETOR Filed Aug. 23, 1965 5 Sheets-Sheet 2 INVENTOR. LEM/ELL Y/V T BAR/VFS Oct. 25, 1966 A T. BARNES CARBURETOR Filed Aug. 23, 1965 5 Sheets-Sheet '5 INVENTOR. ZLEWEL YA/ 7T BR/V615' United States Patent O 3,281,132 CARBURETOR Llewellyn T. Barnes, 165 Meister Blvd., Freeport, Long Island, N.Y. Filed Aug. 23, 1965, Ser. No. 481,617 13 Claims. (Cl. 261-50) This application contains subject matter identical to that disclosed in my co-pending application Serial No. 127,170 tiled July 27, 1961 and constitutes a continuationin-part thereof.

This invention relates to a carburetor for an internal combustion engine and more particularly to a down draft carburetor of a variable vacuum design.

The primary object of the present invention resides in the provision of a carburetor for an internal combustion engine such as used on passenger cars and the like wherein the carburetor is so designed as to permit a motor car or other automotive vehicle to operate smoothly under varying conditions such as cornering at considerable speeds, driving at various atmospheric conditions such as at low and high elevations, accelerating out of a curve, and with the vehicle in a tilted position.

A further object of the present invention is to provide, in a carburetor, high jet friction for fuel so that when the throttle is closed suddenly the fuel will not continue to iiow because of jet friction thereby eliminating overrunning.

In accordance with an illustrative embodiment of the invention there is provided a down draft carburetor comprising a body having an air valve movably mounted therein. The air valve has a fuel passage therein and a metering needle is disposed in the fuel passageway for controlling the amount of fuel flow from a fuel chamber surrounding the air valve to the manifold. One of the principal features embodied in the invention is means for affording a variably progressive lift of the fuel needle with respect to the lift of the air valve, so as to achieve a jet orifice whose coefficient of discharge under all ordinary conditions is approximately constant with a ne atomizing of the fuel near the orifice. In order to achieve the variable progressive lift of the fuel needle in comparison to the lift of the air valve there is provided a linkage means including a cam ymounted on the air valve which is engaged by a link pivoted to the body of the carburetor, which link engages the cam and the needle. An adjusting screw having another cam mounted thereon is threadedly engaged in the body and is adapted to adjustably engage the link on the rst cam to control the relative rate of motion of the needle and the air valve.

Another feature of the invention resides in the employment of a float concentric with the air valve disposed in the fuel chamber. This concentric oat permits a motor car such as is used in racing to corner at considerable speed and to accelerate out of the curve without starving off the fuel supply. The concentric oat controls suitable fuel flow means for feeding fuel to the fuel chamber.

The construction of this invention -features an additional novel arrangement in parts lwherein the fuel passageway in the air valve is provided with a venturi therein with the fuel needle extending into the venturi and being tapered upwardly so that the further the needle extends downwardly into the venturi, the greater the amount of fuel will be able to iiow between the needle and the venturi. Because of the use of the venturi there is a tine atomizing of the fuel near the orice and more complete combustion is achieved.

A further object of the invention resides in the provision of a down-draft carburetor which is constructed and arranged so as to permit a jacket for heated water to warm the fuel air mixture to be provided.

3,Z.i,l32 Patented Get. 25, 1966 ICC The construction of the carburetor according to the present invention is such that the carburetor operates under a variable depression. When a constant suction carburetor is called upon to perform high duty such as in racing, it will no longer work under its normal or designed depression. However, a higher depression than is usually suitable for a constant suction design is also ydesirable in order to eect atomization of the fuel when discharge rate is high. The present invention is designed to provide fine atomization of the fuel under special conditions and is designed to work at a depression as high as 25 of water at its maximum limit while the low limit of working before `the air valve lift is 7" to 8 of water. By keeping the lower limit of working pressure low, the weight of the moving part, that is the air valve, and hence its inertia can be kept down. The air valve is counterbalanced as it is inverted and balanced by -metered springs. Further, under slow running and like conditions the depression in the mixing chamber is 4 of Water, but owing to the great restriction caused by the venturi tube about the orifice, the air velocity at this point is extremely high and in the order of 200 per second.

A further object of the present invention is to provide a carburetor which has means for adjustment of the spring action on the fuel needle with respect to the air valve so that the carburetor can be adjusted for use at both low and high altitudes.

Still further objects and features of this invention reside in the provision of a down-draft carburetor that is simple in construction, eiicient in operation, capable of being utilized in conjunction with various existing internal combustion engines, and which is eflicient in use.

These, together with the various ancillary objects and features of the invention which will become apparent as the following description proceeds, are attained by this down-draft carburetor, a preferred embodiment of which has been illustrated in the accompanying drawings, by way of example only, wherein:

FIG. l is a vertical sectional view of a down-draft carburetor constructed in accordance with the concepts of the present invention;

FIG. 2 is -another vertical sectional view of the carburetor, taken on a plane normal to the plane of FIG. l, and illustrating in particular the coaction between the float and the means for feeding fuel into the fuel chamber;

FIG. 3 is a horizont-al sectional view taken along the plane of line 3-3 in FIG. 2 illustrating particularly the construction of the air valve and relative arrangement of the needle valve and fuel passageway in the air valve communicating with the fuel chamber;

FIG. 4 is a horizontal sectional view taken along the plane of line 4 4 in FIG. 2, illustrating details of the float and fuel feeding mechanisms;

FIG. 5 is a horizontal sectional view taken along the 4plane of line 5--5 in FIG. 2 and showing the air valve in a bottom plan view;

FIG. 6 is a partial elevationa-l view showing the control assembly for the fuel metering needle at a setting for a lean fuel mixture, with the engine in starting or idling condition;

FIG. 7 is a partial elevation view similar to FIG. 6 with the assembly set for a lean fuel mixture, but with the engine in accelerated condition;

FIGS. 8 and 9 are partial elevational views, similar to FIGS. 6 and 7, but showing the con-trol assembly for the fuel metering needle at a setting for medium fuel mixture, with the engine respectively at starting and accelerated conditions; and

FIGS. l0 and ll are partial elevation view-s similar to FIGS. `8 and 9, but showing the control assembly for the fuel metering needle at a setting for rich mixture.

With continuing reference =to the accompanying drawings wherein like reference numerals designate Similar parts throughout the various views, reference numeral generally designates a down-draft carburetor constructed in accordance with the present invention. The carburetor is provided with a body 12 formed of several sections including a base section 14, a central section 1o, and a -cover section 18. The base -section is designed to be connected to the intake manifold by mea-ns of suitable fasteners and includes a bowl 20 for receiving an atomized fuel-air mixture for feeding past a butterfly valve 22 into the manifold. Surrounding the bowl is a jacket 24 adapted to be -illed with hot water for heating the fuel air mixture so that better vaporization can be obtained and so as to aid in the starting operation of the internal combustion engine when it is cold.

The middle -section 16 of xthe carburetor is provided with ta liange 26 and bolts 28 or other suitable fasteners extend through the fiange 26 into the -ba-se 14 for attaching the middle section 16 of the carburetor in a detachable manner to the base. The cover 18 is likewise provided with a `flange 30 and bolts 32 or other suitable fasteners are threadedly engaged in the middle section 16 of the carburetor for detachably 4securing the cover thereto.

It is to be noted that each of the sections of the body 12 a-re preferably cast from bronze or aluminum. The centra-i section 16 of the body is provided with an inner wall 34 defining a fuel chamber 38 in conjunction with the outer wall 36 of the middle section 1-6. The fuel chamber 38 is closed off at the top by a downwardly extending projection 40 of the cover 18 and by a ring 42 and a `housing 4d. The housing 44 is provided with a iiange 46 which extends between the projection 40 and a ring 42.

Also provided on the central section 16 is a fuel inlet member 48 which has an internally threaded portion S0 for reception of a cap 52. A fuel supply line 54 is connected to the full inlet member 48 and is designed to feed fuel upward through the fuel inlet member and into the fuel chamber 38. ln order -to cont-rol ow of fluid there is provided a needle valve 56 having a rod 58 attached thereto and having a pair of colla-rs 60 and 62 on the rod. The collars are Iadapted to be engaged by a follower 64 which, as can be best seen in FIG. 4 is in the form of a bifurcated end portion of a float bracket 66 pivoted as at 68 to the central section 16. The bracket 6'6 is in the form of a yoke of semi-circular shape and has stub axles 70 and 72 -on the ends thereof which stub axles engage the

bearing blocks

74 and 76 fixed to a fioat 78 which is Isubstantially of a doughnut or torus shape and is concentrically disposed about the cylindrical inner wall 34 of the central portion 16.

The cap contains a plate 80 provided with an aperture 82 therethrough, through which the upper end 84 of the pin 58 extends. The pin 58 is provided with a threaded portion 86 and threadedly engaged on the threaded portion is a washer 88. A spring 90 is positioned so as to bias the plate 80 4and the washer 88 whereby the needle valve `56 is normally urged lto a closed position and is held out of the closed position by action `of the yoke 66. As can lbe readily seen, `the float is in a lowered position due to Ia low Ilevel of fiuid in the fuel ychamber 36. Further, when the level of fuel in the fuel chamber 38 achieves that to which the assembly is set for optimum performance of the carburetor, by adjustment of the position of Athe threaded washer 88, the pin S8 will be pushed downwardly until the needle 56 cuts off the flow of fluid to the fuel chamber 38. As fuel leaves the fuel chamber 38, the needle valve 56 will open permitting the fiuid chamber 38 to be always filled to the proper level.

The center section 16 of the body 12 is provided with a portion 100 of reduced cross sectional dimension which has a plurality of apertures 102 therethrough communicaring with -the atmosphere. Further, the ange portion 26 of the central section 16 is provided with a valve seat 104 in the form of a bevelled surface which is adapted to cooperate with the bevelled surface 106 of an air valve member 108 which is slidably movably closely iitted with the inner cylindrical wall 34 of the center section 12. The air valve 108 has its lower portion provided with a plurality of diverging passages or -outlets 110 which communicate with the mixing chamber 20. The bottom end 112 of the air valve member 108 is concave. The air valve member is provided with a fuel vapor passage 114 therein which communicates with the outlet 110. Further, the air valve is provided with an enlarged area 118 and a cylindrical wall 120 which closely engages the inner surface 122 of the cover portion 18. A coil spring 124 engages the flange 46 of the housing 44 and the shoulder 126 formed by the enlargement 118, so that the spring 124 normally urges the air valve 1018 into a closed position preventing tflow of air from entering the mixing cham-ber 20. However, when -the air valve member moves downwardly due to suction induced in the mixing chamber 20 and applied against the bottom surface of the air valve member, the air valve member will be sucked downwardly against the action lof the spring 124 permitting fiow of air into the mixing chamber 20 and thence into the manifold.

A metering needle 130 is slidably, movably disposed and extends upwardly and out of the air valve member through a -bore 132 in the upper portions of the air valve member. The metering needle 130 is provided with a bushing or fitting 134 having a collar 136 at the upper end thereof 4and is provided with an upwardly tapering portion 138 which controls ow of fluid through an orifice 140. The orifice 140 is formed in an orifice block 150 (FIG. 2) which is fixedly held in place in .association with the housing 44 and which has a tortuous passageway 152 therein communicating at one end with the tube 154, which extends into the fuel chamber 38, and at the other end with the orifice 140. The orifice block extends through a slot in the valve lmember 108, thereby permitting downward sliding movement of said valve member relative to the orifice block 150, which is always stationary.

Fixed in place `and held thereto by the lower portion 111 of the air valve 108, which is threadedly detachably secured to the upper member 119 of the air valve member 108, is a venturi 160. The venturi is adapted to move with the air valve 108 and the orifice yblock 150 extends almost all the way through to the constriction when the air valve is in a closed position such as during idling operation of the engine.

It will be observed that the orifice block 150, having the fuel orifice 140, is a fixed portion of housing 44 and is, therefore, stationary at all times. The metering needle 130, -on the other hand, is mounted on -and carried by the 'air valve 108 such that when the air valve 108 is drawn downwardly, the needle 130 is drawn with it, so that its narrower upper tapered portion 138 moves into registry with the orifice 140 and permits fuel to feed therethrough. If the metering valve 130 were rigidly secured to the air Avalve 108, the amount of fuel fed through orifice 140 would be dependent solely on the degree of travel of said air valve. In accordance with the invention herein, however, there is provided an Iarrangement whereby the metering needle 130 can move at 'a controlled rate relative to the movement of the air valve 108; that is to say, the rate of movement of needle 130 can be adjusted so that its movement is selectively faster than the rate of 'movement' of the air valve 108.

In order to accomplish the aforementioned adjustment, an assembly generally indicated at is provided. This assembly includes a plate 172 mounted on the air valve to which a multiplying lever 174 is pivoted at 176. The multiplying lever 174 has a cam surface 178 which is adapted to be engaged by a roller cam follower 18,0

rotatably mounted by means of axle 182 and the bifurcated ends 184 of a link 186 pivotally mounted at 188 on the cover section 18 of the body and normally urged by torsion springs 190 upwardly clockwise as shown in FIG. 1. The link 186 is provided with a notch 194 therein. A further link 196 is pivoted as at 198 to the plate 172 and also pivoted -at 200 to a link 202 which is pivoted at 204 to a link 206 also pivoted to the plate 172 by pivot shaft 176 making a parallelogram linkage. The link 206 is thus mounted to turn in unison with multiplying lever 174. The link 196 is formed as a lever h-aving an angul'arly disposed integral arm 210 having a terminal cam surface which engages the collar 136 at the upper end of the metering needle 130 yso that as the link 196 rotates, it 4will translate such rotational motion to reciprocal motion of the -metering needle 130.

Threadedly secured in the cover 18 is an -adjusting cap 220 which has a recess 222 therein. Within the recess 222 there is provided a spring 224 which eng-ages the cap 220 and the collar 136 on the metering needle 130.

The spring 224 exerts a downward biasing force on collar 136, which in turn biases the lever arm 210 of link 196 in a downward or clockwise direction, and urges the multiplying lever 174 in an upward or clockwise direction through the

parallelogram linkage

172, 196, 202, 206. The -cam surface 178 of multiplying lever 174 is thus biased into engagement with the roller 180 on link 186. The lower end `of the cap 220 is shaped to extend at an oblique angle to form Ia cam 226 which engages within the notch 194 in the link 186 to vary the inclination `of said link 186 and selectively position the roller 180 along the cam surface 178.

It will be observed in FIGS. 6-l1 that the multiplying lever 174 has a main body portion 175 having the arcuate Cam surface 178, and a terminal body portion 177 having 4a planar cam 'surface 179 larranged at a substantial angle to the arcuate cam surface 178.

In the position shown in FIGS. l and 6, the cap 220 is adjusted so that the highest point on its cam surface 226 engages the notch 194 in link 186. This positions the link 186 at an angle of approximately 45 from the vertical, as shown in FIG. 1, and represents a setting for lean fuel feed.

The cap 220 may be turned to the position shown in FIG. 8, representing a medium fuel feed. When this occurs, a lower portion of cam surface 226 moves into engagement with notch 194, causing the link 186 to turn in a counter-clockwise direction toward the vertical. This movement permits the multiplying lever 174 to turn in an upward or counter-clockwise direction, in turn, permitting the metering needle 130 to move downwardly under the biasing force of spring 224. If the cap 220 is turned to the position of FIG. l0, in which the lowermost portion of cam surface 226 engages notch 194, the link 186 is turned to the substantially vertical position shown, and the multiplying lever 174 moves counterclockwise to the position shown, allowing the metering needle 130 to move further downwardly under the force of spring 224. The position of FIG. 10 represents a setting for rich fuel feed.

As can be readily seen, when the metering needle 130 is in a lowered position, the lower the position, the more iiid can flow past the tapered portion 138 of the metering needle. This tapered portion 138 has tapering and inverted slots for the purpose of metering the ow of the fluid with a high jet friction to prevent over-running of the jet upon decreasing engine speed. In other words, spillover is prevented. The grooves in this needle are V-cut and have rounded corners.

In the adjusted position of FIGS. l and 6, representing the setting for a lean mixture, the link 186 is disposed at such an angle that it maintains the multiplying lever 174 at the angle shown, with the terminal body portion 177 vertically upstanding. The roller 180 is located at the lower end of the planar cam surface 179 of the terminal body portion, and the parallelogram linkage is so disposed that the tapering end portion 138 of metering needle 130 blocks the orifice 140.

When suction in the bowl 20 causes the valve member 108 to slide downwardly, the plate 172,

parallelogram linkage

196, 202 and 206, and metering needle are carried `downwardly with said valve member 108. The link 186, however, remains stationary and its end roller 180 rides along the vertically-disposed planar cam surface 179 .of multiplying lever 174, so that there is no pivoting movement of said lever 174, no movement of the parallelogram linkage, and no vertical movement of the metering needle 130 relative to the valve member 108. As shown in FIG. 7, the tapering portion 138 of metering needle 130 moves downwardly through the orifice 140 of the fixed iorice block so that a portion of lesser diameter is brought into registry with said lorifice to provide an annular fuel outlet opening. It will be understood, however, that in this lean adjustment of FIGS. 6 and 7, the metering needle 130 is carried downwardly with the air valve member 108 at the same rate of travel as the latter.

When the carburetor assembly is adjusted for a medium fuel mixture, as shown in FIG. 8, by turning the cap 220, as previously described, the link 186 is pivoted downwardly, :or in a Conner-clockwise direction by the cam surface 226 lof said ca As link 186 turns from the adjusted position of FIG. 6 to the adjusted position of FIG. 8, the roller rides downwardly along the arcuate cam surface 178 of multiplying lever 174. This arcuate cam surface 178 describes an arc whose center is at the axis of pivot 188, so that this adjusting movement does not affect the angular disposition lof the multiplying lever 174, and the metering needle 130 is maintained in the position in which its tapering end portion 138 blocks the orifice 140.

With the assembly set in this position of m-edium fuel feed, when the valve member 108 is drawn downwardly by suction, the multiplying lever 174 tends to move away from the roller 180. However, the spring 224, exerting a downward biasing force `on metering needle 130, thereby urges the arm 210 of lever 196 downwardly, causing the parallelogram linkage to shift in a direction to move the multiplying lever 174 in a clockwise direction. The multiplying lever is thus biased to remain in engagement with the roller 180, and as the valve member 108 moves downwardly, the multiplying lever 174 turns in a clockwise direction, lowering the lever arm l210 and permitting the metering needle 130 to be urged downwardly by spring 224. Thus, the metering needle moves downwardiy at'a faster rate than the valve member A108, and the tapering end portion 138 extends a further distance through orifice 140, presenting an annular opening of greater diameter, as can be seen b a com a' FIG.9with FIG. 7. y p uson of When the carburetor assembly is adjusted for a rich fuel mixture, as shown in FIG. l0, the cap 220 is turned until the lowest point of its cam surface 226 engages the notch 194, and the link 186 is thus disposed in a substantially vertical position. The multiplying lever 174 is biased further in a clockwise direction so that it is lmore vertically upstanding from the pivot 176, and the lower portion of its arcuate cam surface 178 is in en a em ent with roller 180. g g

At this setting,

when suction in the bowl 20 causes the valve member 10 the orifice 140, and its small diameter provides a large annular fuel outlet opening.

The venturi 160 terminates short of the outlets 110 and the venturi will change the rate of flow of the fuel to increase it to the extent that it flows at the rate of about 200 feet per second causing the fuel to atomize into a fine mist which is combined with air in the bowl 2) after the fuel has left the ,outlet 110. The air brought into the bowl 20 may of course be filtered by a filter or screen positioned concentrically about the portion 100 of reduced cross sectional area by means of the

complementary notches

260 and 262 formed in the center section 16 of the under surfaces :of the center section 16 of the body.

The oat 78 which is concentri-cally disposed about the air valve member 108 and about the fuel passage controls the operation of the fuel needle valve 56 whereby liow of fuel into the fuel chamber 38 is controlled. As the speed of the engine increases, a greater suction op the bowl 20 will be present and the air valve member 108 which is normally held ina raised position against gravity by the spring 124 will be sucked downwardly. Dependent on the position of the link 186, the metering needle 139 will move with respect to the air valve member. The farther the metering needle 130 is permitted to move downwardly, the greater the flow of fuel into the bowl 2t) there will be.

A latitude of modification, change and substitution is intended in the foregoing disclosure and in some instances some features `of the invention will be employed Without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.

I claim:

1. A carburetor comprising a body, an air valve movably disposed in said body, said air valve having a fuel passage therethrough, a metering needle disposed in said passage, first means mounting said air valve for movement in said body and second means connecting said needle to said air valve for movement with said air valve and for relative movement with respect thereto, adjusting means coacting with said second means for adjusting the relative movement of said needle with respect to said air valve in response to movement of said air valve between one extreme where said needle is carried by said air valve without movement relative thereto, and another extreme where said needle is carried by said air valve and has maximum movement relative thereto, said body including a chamber concentric with said air valve, said passage communicating with said chamber, a float concentric with said air valve disposed in said chamber, and fuel ow means connected to and controlled by said float for feeding fuel to said chamber.

2. A carburetor comprising a body, an air valve movably disposed in said body, said air valve having a fuel passage therethrough, a metering needle disposed in said passage, a stationary fuel orifice in said passage surrounding and controlled by said needle, means for adjusting said needle relative to said air valve to adjust the mixture of air and fuel, first means mounting said air valve in said body and second means mounting said needle in said body for adjusting the relative movement of said needle with respect to said air valve upon movement of said air Valve, said fuel passage having a venturi therein surrounding said orifice, said venturi being carried by said air valve for movement therewith, said needle extending beyond said orifice into said venturi, said needle being tapered upwardly so that the further said needle extends downwardly into said venturi, the greater the amount of fuel that can be discharged from said venturi.

3. A carburetor Comprising a body, an air valve movably disposed in said body, said body including a valve seat, spring means supporting said air valve and urging said air valve against said seat, said air valve having a fuel passageway therethrough, a metering needle disposed in said passage, linkage and cam means mounting said needle and said air valve in said body for progressively moving said needle in response to movement of said air valve, and said linkage and cam means including means adjusting said needle and air valve between one extreme where said needle is moved with said air valve without movement relative thereto and another extreme where said needle is moved with and has maXimum movement relative to said air valve.

4. A carburetor according to claim 3, in which said linkage and cam means includes a first cam mounted on said air valve, means operatively coupling said first cam with said needle, a link mounted on said body engaging said first cam, a second cam and means adjustably mounting saaid second cam on said body for engagement with said link to adjust the position of said link on said first cam.

5. A carburetor comprising a body having an air valve movably mounted therein, spring means connecting said air valve to said body and normally urging said air valve to a closed position during idling operation, means for urging said air valve to an open position by a vacuum condition in said body during operation at speeds higher than idling, said body having a fuel chamber therein, said air valve having a fuel passageway therein communieating with said fuel chamber, a metering needle disposed in the fuel passageway for controlling the amount of fuel ow from said chamber through said fuel passageway, linkage means connected to said air valve to engage said needle for adjusting the relative travel of said needle with respect to said air valve when said air valve moves in response to a vacuum condition in said body, and means for adjusting said linkage means between a first position in 4which said needle is moved with said air valve without movement relative thereto and a second position in which said needle is moved with and has a maximum movement relative to said air valve.

6. A carburetor according to claim 5, in which said carburetor is a downdraft carburetor and includes, a float concentric with said air valve disposed in said chamber, and fuel flow means on said body connected to and controlled by said float for feeding fuel to said chamber.

7. A carburetor according to claim 5, in which said carburetor is a downdraft carburetor and said linkage means includes a first cam mounted on said air valve and controlling the movement of said linkage, and said adjusting means includes a link mounted on said body for engaging said first cam, and a second cam adjustably mounted on said body engaging said link to adjust the position of said link on said rst cam to adjust the relative movement of said needle and said air valve.

S. A carburetor according to claim 5, in which said carburetor being a downdraft carburetor and, said fuel passageway has ra venturi therein, said needle extending into said venturi, said needle being tapered upwardly so that the further said needle extends downwardly into said venturi, the greater the amount of fuel that can be discharged from said venturi so that the rate of fuel flow increases at substantially the same ratio as the rate of air flow increases.

9. A carburetor according to claim S, in which said linkage means includes a rst cam mounted on said air valve, a link mounted on said body for engaging said first cam and means operatively coupling said first cam with said needle, and in which said adjusting means includes a second cam adjustably mounted on said body engaging said link for adjusting the position of said link on said first cam to adjust the relative movement of said needle and said air valve, said carburetor also including a float concentric with said air valve disposed in said chamber, and fuel fio-w means on said body connected to and controlled by said oat for feeding fuel to said chamber.

10. A downdraft carburetor comprising a body having an air valve movably mounted therein, spring means mounting said air valve in said body and normally urging said air valve t a closed position during idling operation, means urging said air valve to an open position by a vacuum condition in said body during operation at speeds higher than idling, said body having a fuel chamber therein, said air valve having a fuel passageway therein communicating with said fuel chamber, a metering needle disposed in said fuel passageway for controlling the amount of fuel flow from said chamber through said fuel passageway, said fuel passageway having a venturi therein, said needle extending into said venturi, said needle being tapered upwardly so that the further said needle extends downwardly into said venturi, the greater the amount of fuel that can be discharged from said venturi, linkage means connected to said air valve and said needle for adjusting the relative travel of said needle with respect to said air valve when said air valve moves in response to a vacuum condition in said body, said linkage means including a rst cam mounted above said air valve, means operatively coupling said rst cam with said needle to vary the position of Said needle relative to said air valve in response to movement of said first cam a link pivoted to said body and having a roller cam follower engaging said cam, a second cam, and means adjustably mounting said second cam on said body with said second cam engaging said link for adjusting the position of said roller cam follower on said iirst cam to adjust the relative travel of said needle and said air valve to control the richness of the air fuel mixture.

11. A downdraft carburetor according to claim which also includes a oat concentric with said air valve disposed in said chamber, and fuel ow means on said body connected to and controlled by said iloat for feeding fuel to said chamber.

12. A carburetor comprising a body, an air valve movably disposed in said body, said air valve having a fuel passage therethrough, a metering needle disposed in said passage, iirst means mounting said air valve in said body and second means mounting said metering needle in said body for progressively moving said needle relative to said air valve in response to movement of said air valve such that the rate of fuel flow increases and decreases at substantially the same ratio as the rate of air flow increases and decreases, said second means including means mounting said metering needle for adjustable movement with respect to said air valve between a first position in which said needle moves with said air valve and without movement relative to said air valve and a second position in which said needle moves with said air valve and has a maximum movement with respect to said air valve.

13. A carburetor comprising a body having a stationary fuel outlet orice, an air valve movably mounted in said body, said air valve having a fuel passage therethrough, a metering needle carried by said air valve for movement therewith relative to said stationary fuel outlet orifice, means mounting said metering needle movably relative to said air valve, a linkage mounted on said air valve and engaging said metering needle for adjusting the position of said needle relative to said air valve, a cam member connected to said linkage for varying the position thereof, and manually adjustable means mounted on said body and engaging said cam for progressively adjusting the relative movement of said needle with respect to said air valve in response to movement of said air valve between one extreme in which said needle is moved with said air valve without movement relative to said air valve and another extreme in which said needle moves with said air valve and has a maximum movement to said air valve.

References Cited by the Examiner UNITED STATES PATENTS 1,010,185 11/1911 Schultz. 1,356,661 10/ 1920 Schultz. 1,737,184 11/ 1929 Bright. 2,868,522 1/1959 ONeil. 2,999,674 9/ 1961 McClain 261-50 FOREIGN PATENTS 435,768 9/ 1935 Great Britain.

HARRY B. THORNTON, Primary Examiner.

RONALD R. WEAVER, Examiner.

Claims

12. A CARBURETOR COMPRISING A BODY, AN AIR VALVE MOVABLY DISPOSED IN SAID BODY, SAID AIR VALVE HAVING A FUEL PASSAGE THERETHROUGH, A METERING NEEDLE DISPOSED IN SAID PASSAGE, FIRST MEANS MOUNTING SAID AIR VALVE IN SAID BODY AND SECOND MEANS MOUNTING SAID METERING NEEDLE IN SAID BODY FOR PROGRESSIVELY MOVING SAID NEEDLE RELATIVE TO SAID AIR VALVE IN RESPONSE TO MOVEMENT OF SAID AIR VALVE SUCH THAT THE RATE OF FUEL FLOW INCREASES AND DECREASES AT SUBSTANTIALLY THE SAME RATIO AS THE RATE OF AIR FLOW INCREASES AND DECREASES, SAID SECOND MEANS INCLUDING MEANS MOUNTING SAID METERING NEEDLE FOR ADJUSTABLE MOVEMENT WITH RESPECT TO SAID AIR VALVE BETWEEN A FIRST POSITION IN WHICH SAID NEEDLE MOVES WITH SAID AIR VALVE AND WITHOUT MOVEMENT RELATIVE TO SAID AIR VALVE AND A SECOND POSITION IN WHICH SAID NEEDLE MOVES WITH SAID AIR VALVE AND HAS A MAXIMUM MOVEMENT WITH RESPECT TO SAID AIR VALVE.