US3235236A - Carburetor - Google Patents

Description

Feb. 15, 1966 R. E. KALERT, JR 3,235,236

CARBURETOR Filed Feb. 25. 1963 INVENTGR. RALPH El. KALERT JR.

United States Patent 3,235,236 CARBURETOR Ralph E. Kalert, Jr., Granite City, Ill., assrgnor to ACF Industries, Incorporated, New York, N.Y., a corporation of New Jersey Filed Feb. 25, 1963, Ser. No. 260,414 4 Claims. (Cl. 261-41) This invention relates to carburetors, and particularly to carburetors of the class having a diaphragm for control of fuel admission thereto.

The invention is especially concerned with carburetors of the class described for small internal combustion engines, such as are used on power saws, for example, where ability to operate in any position, even upside down, is important. For such applications, float-type carburetors are generally unsuitable, and a diaphragm-type carburetor is preferred. A typical diaphragm-type carburetor has a fuel chamber closed by a diaphragm which is subject on the outside to atmospheric pressure. The diaphragm actuates a valve controlling admission of fuel to the fuel chamber from a fuel supply. Fuel is supplied from the fuel chamber to the mixture conduit of the carburetor through a so-called high-speed fuel system.

In the operation of such a carburetor, it is important that, when the throttle of the carburetor is opened for acceleration of the engine and particularly when the throttle is opened from idle position, fuel is immediately delivered by the high speed fuel system into the mixture conduit. Otherwise, there may be an undesirable lag in acceleration, and the engine may even stall. Lag in delivery of fuel to the mixture conduit may occur due to what may be referred to as excessive fuel lift, meaning excessively high pressure head to be overcome by the diaphragm before fuel is adequately delivered from the main nozzle of the high-speed fuel system of the carburetor. Lag in delivery of fuel may also occur due to What may be referred to as back bleeding, meaning diminution of fuel in the high-speed fuel system due to loss of fuel from the high-speed system, during idle operation of the engine. Thus, when the throttle is opened for acceleration, there is a lag in delivery of fuel through the main fuel system.

Accordingly, an object of this invention is the provision of a carburetor of the diaphragm type having a novel construction as to minimize fuel lift and back bleeding.

Another object of the invention is to provide novel carburetor structure for rapid engine acceleration.

In general, the stated minimizing of fuel lift and back bleeding is accomplished by a novel carburetor design in which the high-speed fuel system of the carburetor is taken directly from the fuel inlet of the carburetor instead of from the diaphragm fuel chamber. This results in a shorter flow path of fuel to the nozzle and results in less lift in drawing fuel to the mixture conduit. Also, during idle or low speed operation of the engine the novel design places all of the main fuel system at substantially atmospheric pressure so that there is no tendency to back bleed.

The invention accordingly comprises the constructions hereinafter described, the scope of the invention being indicated in the following claims.

In the accompanying drawings, in which several of various possible embodiments of the invention are illustrated,

FIG. 1 is a longitudinal section of a conductor constructed in accordance with this invention and connected to the intake manifold of an engine.

FIG. 2 is a central transverse section of the carburetor of FIG. 1 taken on line 2-2, showing the high-speed fuel system of the carburetor.

ice

FIG. 3 is a transverse section taken on line 3-3 of FIG. 1, showing the idle fuel system of the carburetor.

FIG. 4 is a partial sectional view of the throttle and idle port of the carburetor of FIGS. 1-3.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Referring to the figures of the drawings, a carburetor constructed in accordance with this invention and generally designated C comprises a body assembly 1 and a cylindrical metal tube assembly 3 forming the mixture conduit of the carburetor. Tube 3 has an integral flange 5 at its outlet 6. Flange 5 is backed by a plate 7. Flange 5 and plate 7 are provided with bolt holes for the reception of bolts for attaching the carburetor to intake manifold 13 of an internal combustion engine E in the usual manner. Tube 3 has at its other end a sleeve 14. with an integral flange 15 backed by a plate 17 forming an inlet 18 to the carburetor.

A throttle shaft 23 extends across the mixture conduit tube 3 adjacent its outlet 6 and carries a throttle valve 25 shown in a closed position in FIGS. 1 and 4. Secured on one end of shaft 23 is a throttle operating lever 27 engageable with a stop formed by an extension 31 on plate 7 to determine the wide-open position of the throttle valve. A choke shaft 33 extends across the mixture conduit tube 3 parallel to the throttle shaft and adjacent to the inlet 18 of the mixture conduit. Shaft 33 has a choke valve 35 fixed to it. Secured on one end of the choke shaft is a choke operating lever 37 having a portion 39 engageable with a stop formed by a tongue 41 on plate 17 to determine the wide-open position of the choke valve.

Body assembly 1 comprises a molded plastic body 53 formed with shallow circular cup-shaped portion 61 forming a shallow circular fuel chamber 55. A diaphragm 57 closes the fuel chamber. The peripheral wall of the cup-shaped portion 61 has an outwardly projecting fiared rim 63. The margin of diaphragm 57 is clamped against the face of this rim by a shallow cup-shaped plastic cap 59 having an annular groove 65 in the inside of its pe ripheral wall receiving the rim 63. In assembling the parts, the diaphragm is positioned over the recess or cham ber 55 with its periphery on the face of rim 63, then cap 59 is snapped into place over rim 63. The diaphragm consists of a circular piece of suitable flexible material such as, for example, a piece of thin fuel resistant synthetic rubber. Cap 59 has a central aperture 711 exposing diaphragm 57 to the atmosphere. Around aperture 71, the cap 59 has bosses 73 for limiting the outward movement of the diaphragm 57.

The circular fuel chamber 55 has a recess 77 within body 53. Depending from the bottom of recess 77 is a rib 79 of rounded contour molded integrally with the body 53. A stamped sheet metal lever 81 has a loop portion 83 receiving the rib 79. Lever 81 has one end portion 85 extending into contact with the center of a circular sheet metal plate 67 in contact with the adjacent surface of diaphragm 57. End portion 85 of the lever is apertured to receive tongue 69 struck out of the plate 67. At its other end, lever 31 is forked as indicated at 87 to fit into an annular groove 39 in one end of a needle valve 91.

Body 53 includes a cylindrical boss 93 on one side of the body. Extending up into this boss from recess 77 of chamber 55 is a cavity 95 of circular cross section accornmodating the needle valve 91. Boss 93 has a reduceddiameter tubular end extension 97 with a passage 99 of smaller diameter than cavity 95 extending from cavity 95 through extension 97. A ported resilient valve seat member 10]., made of fuel resistant synthetic rubber, is seated against a shoulder 103 at the upper end of cavity 95 around the lower end of passage 99. The needle valve 91 has a pointed end engageable with this seat member. It also has a collar 195 adjacent to this pointed end. A coil compression spring 107 reacts from a spring retainer and valve guide member 1119, pressed in the lower end of cavity 95, against collar 105 to bias the needle valve 91 toward its closed position illustrated in FIG. 2. Valve guide 109 is a thick washer and guides the needle valve 91 in axial sliding movement. It also provides restricted communication between cavity 95 and fuel chamber 55.

A molded plastic fitting 111 has a snap fit on extension 97. This fitting has a lateral nipple 113 for connection of a fuel line L through which fuel can flow by gravity from a fuel tank T. Fitting 111 holds in place and closes one end of a cylindrical filter screen 115. The other end of screen 115 extends into passage 99. Fuel flowing through screen 115 passes into chamber 55 when the needle valve is open. As will be described in greater detail, when the diaphragm 57 is moved into chamber 55, lever 81 is rocked counterclockwise, as viewed in FIG. 2, about rib 79, and acts to pull the needle valve 91 to open position for the flow of fuel from the tank T to the fuel chamber 55.

At the top of body 53, as viewed in FIGS. 13, there is an elongated concave arcuate surface 117 seating the mixture conduit tube 3. Tube 3 extends across the top of the body 53 to one side of boss 93. Extending upwardly from the bottom of surface 117 is a stem or post 119 molded with body 53 as an integral part thereof. This stem 119 is generally of circular cross section and somewhat tapered from its root in body 53 toward its upper end. It extends through an aperture 121 in the bottom of tube 3 and its upper end engages the inside of the top of the tube 3. A screw 12 is threaded into the stem 119 through a hole 123 in the upper surface of tube 3. An arcuate metal washer 127 and an annular sealing washer 129 are interposed between the head of the screw 125 and the top of tube 3 to hold the tube 3 and body 53 in assembly. A gasket 131 is interposed between the tube 3 and body 53 within the arcuate surface 117 and has an opening registering with aperture 121 through which the post extends. Post 119 is located approximately midway between the throttle shaft 23 and the choke shaft 33, and is clear of the path of rotation of the throttle and choke valves 25 and 35. The post 119 restricts the passage of air through tube 3 with a resulting venturi effect.

The high-speed fuel metering system of the carburetor is indicated generally in FIGS. 1 and 2. Post 119 is formed with a circular passage 135 extending through the post substantially parallel to the axis of tube 3 and adjacent to the bottom of tube 3. From this passage 135 there is a second passage 137 along the axis of the post down to a cross passage 139 in body 53 which extends transversely in respect to tube 3 through body 53 to the cavity 95. The end of cross passage 139, which opens into cavity 95, is tapered at 141 converging toward cavity 95. A high-speed fuel metering screw 14-3 has its outer end threaded into the other end of cross passage 139 and has a reduced diameter elongated shank 145 extending through the cross passage 139. The fuel threaded metering screw 143 has a tapered end 147 which is thus adjustable relative to the tapered end 141 of passage 139. A main fuel nozzle 149 is pressed in passage 137 and projects upward into passage 135. Fuel nozzle 149 has a restricted outlet 151 opening into passage 135.

The idle fuel system of the carburetor is indicated generally at 153. Body 53 is formed with a passage 155 extending down from the arcuate surface 117 and terminating short of chamber 55. This passage 155 is downstream from post 119 and is closed at the top by gasket 131. Body 53 has a groove 157 in the arcuate surface 117 extending laterally from the upper end of passage 155. Gasket 131 and tube 3 are formed with registering holes forming an idle port 159 for flow of idle fuel from groove 157 into the tube. A passage 161 extends from the one side of body 53 (FIG. 3) to the passage 155, the inner end of passage 151 which opens into passage 155 is tapered, as indicated at 163 and converges toward passage 155. Extending up from fuel chamber 55 to passage 161 adjacent the inner end of passage 161 is a channel 165. An idle adjusting screw 1137 has its outer end threaded into the outer end of passage 161 and has a reduceddiameter shank 169 extending through the passage 161 with a tapered end 171 adjustable relative to the tapered end 153 of passage 151 for idle fuel material purposes.

Under engine idling conditions, throttle is in the FIG. 1 idle or closed position, and choke in the FIG. 1 open position. Manifold vacuum in conduit 3 downstream from the closed throttle 25 induces flow of fuel from fuel chamber to the mixture conduit through fuel passages 165, 163, 155, 157 and port 159. The tapered portion 163 of passage 161 with portion 169 of idle adjustiing screw 157 meters the flow of idle fuel into conduit 3. Some air will bleed past the throttle for mixing with this idle fuel, or an idle air bleed port may be provided for bleeding air from upstream of the throttle into the assage 157 in a known manner.

When the throttle 25 is opened for acceleration, air will flow through conduit 3. Post 119 provides a restriction to this air flow and the air passing through passage 135 of the post flows at an accelerated rate and provides a sub-atmospheric pressure in the region of the main nozzle 151. Fuel flows through passage 141 where the flow is metered by tapered portion 14-7 of the adjustment screw 143 and through passage 139 and nozzle 149 into the air passage 135.

As fuel flows from cavity 95, fuel pressure in the cavity drops. Diaphragm 57, subject on its outer side to atmospheric pressure, moves inwardly against the bias of spring 197, which is connected to diaphragm 57 through lever 21 and needle valve 91. This inward movement of the diaphragm 57 moves needle valve 91 off of its seat 1111 and permits the flow of fuel into cavity to replace fuel flowing to chamber 55 or to passage 139. Normally, valve 91 is in an open position during operation of the engine for the flow of fuel from tank T at a rate necessary to make up for the flow of fuel from cavity 95.

As explained above, the opening of the inlet valve 91 is due to the lowering of fuel pressure within the cavity 95 and the sensing chamber 55. This drop in pressure results from the flow of fuel out through the main fuel system or the idle fuel system of the carburetor during engine operation and the fuel pressure within chamber 55 falls to a level below atmospheric at which the diaphragm under atmospheric pressure will move inwardly against the bias of spring 197 to open the valve 105.

A chronic defect of carburetors of this type utilizing a fuel chamber, in which the pressure of the fuel is controlled by a diaphragm exposed to ambient air pressure, is the insensitiveness of the inlet valve opening mechanism. There is considerable loss in friction between the diaphragm plate 67 and lever 81 as well as between lever 81 and the end 89 of the inlet valve 91 when valve 91 is operated. Furthermore, the valve closing spring 107 must of necessity be of a certain strength to retain the needle valve 91 closed against the fuel pressure within the inlet line L. This fuel pressure in line L is due to gravity or the pressure of a fuel pump in the line L between the tank and carburetor.

A particular problem results during the idle or low speed operation of a carburetor. During idle, fuel is utilized by the engine at a low rate and this fuel is removed from the sensing chamber 55. However, the drop in fuel pressure in chamber 55 may not be effective in opening valve 91 to replenish the idle fuel before air is first drawn into the main fuel nozzle 149 and through the fuel passages 139 into the cavity 95. The presence of this air prevents rapid acceleration of the engine when the throttle is suddenly opened, as there is no fuel in nozzle 149 and fuel passage 139 to be immediately available for acceleration upon the opening of the throttle. Thus, the engine may stumble and may stop before fuel can be drawn up through passage 139 and nozzle 149 into the mixture conduit 3. This is an unwanted operation of the carburetor as in some installations, such as with chain saws, for example, it is necessary and very desirable that instant acceleration of the engine take place upon the manual opening of throttle 25. Oftentimes, the sudden opening of the throttle is accompanied by application of a load to the engine and, with a complete lack of fuel in the main fuel passages of nozzles 149 and 139, acceleration is not obtained and the engine frequently stalls out. In some types of carburetors where the main fuel and the idle fuel passages are interconnected, air drawn into the main fuel passages during idle, as described above,

will also pass into the idle system and out the idle port.

Such air bleeding into the idle circuit causes an unduly lean idle mixture and the engine will stop because of lack of fuel.

In accordance with this invention, the main fuel passages are connected adjacent to the inlet valve seat 101. As shown in FIG. 2, the reduced passage 141 leading into the main fuel passage 139 of the carburetor is positioned as close to the inlet needle seat 101 as possible. Furthermore, the guide 109 is provided with a small clearance so that the area between the inner periphery of guide 109 and the surface of the needle valve 91 is minimized, and is only slightly larger in area than that of the smallest passage 163 in the idle circuit. For example, in a carburector of the type described, the minimum area of the tapered passage 163 is around 0.00085 square inch and the area of the space between the guide 109 and the peripheral surface of the valve 91 may be as large or slightly larger. For example, the outer surface of the needle valve 91 may have an outside diameter of 0.170 inch, while the inner diameter of the guide 109 would be in the order of 0.173 inch. This difference leaves a space between the guide 109 and the surface of valve 91, which is as large as that of the restriction 163 in the idle passage.

Fuel from tank T or from a fuel pump in line L may have several pounds of pressure above atmospheric at the valve seat opening 101. During normal operation of the carburetor, either at low speed or at high speed operation, fuel is caused to flow out of the main nozzle 149 or the idle port 159 by the low pressure in the mixture conduit 3. This results in a lowered pressure in the sensing chamber 55, which provides an opening of the needle valve 91 by atmospheric pressure against diaphragm 57. Thus during engine operation there is a pressure drop from several pounds above atmospheric upstream of valve seat 101 to a subatmospheric pressure in the sensing chamber 55 around /2 inch of water. The greatest drop in fuel pressure is across the valve seat 101. During idle operation with closed throttle, fuel flows through cavity 95 into the sensing chamber 55 and out the low speed fuel passages 165, 161, 155 and 157. At this time, because of the fuel restriction between guide 109 and the surface of valve 91, there is a drop in fuel pressure between that in cavity 95 and the fuel pressure in the sensing chamber 55. With fuel pressure upstream of valve seat 101 above atmospheric and fuel pressure in chamber 55 at subatmospheric, it is believed that during this low speed operation, fuel pressure within cavity 95 is very close to atmospheric and that fuel at atmospheric pressure exists in a region immediately downstream of valve seat 101 within the cavity 95.

Thus, in accordance with the invention, the inlet 141 of the main fuel passage is placed within the cavity region 95 and close to the downstream side of the valve seat 101. This places entrance passage 141 Within this region of fuel under atmospheric pressure. This arrangement eliminates air bleeding through nozzle 149, during idle or low speed operation of the engine, when the throttle 25 is closed, since fuel in the main fuel. nozzle will be under substantially atmospheric pressure equal for practical purposes to the pressure of the fuel at the entrance to the main fuel passage in the restricted region 141. Thus, with the nozzle 149 and region 141 at substantially the same pressure, there is no tendency for a flow of fuel between these points during low speed or idle operation of the engine.

Thus, the subatmospheric pressure in the sensing chamber is not effective in pulling fuel out of the main fuel passages of nozzle 149 and passage 139. Rather, instead, fuel is retained in these portions of the main fuel passage and, upon sudden opening of the throttle, fuel is readily available in both the nozzle 149 and the fuel passage 139. This fuel with flow quickly into the mixture conduit 3 and sustain a rapid acceleration of the engine and prevent it from stalling out under a sudden increase in load conditions.

In carburetors of the type described above, utilizing a diaphragm sensing chamber, it has been customary to connect the main fuel passage directly into the sensing chamber 55 so that fuel flowing to the main nozzle during wide open throttle operation passes not only through a cavity similar to 95 of applicants structure but also through the sensing chamber corresponding to 55 of the described invention. This results in an extensive path of fuel flow from the inlet valve seat to the main fuel nozzle.

A long fuel passage will provide a greater resistance to fuel flow than a correspondingly shorter passage. Greater resistance to fuel flow in the main fuel passage requires a greater suction or lift at nozzle entrance 151 to draw fuel into the air passage 135. Thus, small changes in the fuel requirements of the engine are not sensed as quickly as when a fuel path of less resistance to fuel flow is used.

Therefore, in accordance with this invention, an advantage is obtained by placing the entrance to the main fuel passage 14-1 as close to the inlet valve seat 101 as feasibly possible so that the fuel path from the inlet valve seat 101 to the main fuel nozzle 149 is minimized. As shown in FIG. 2, the flow of fuel from the valve seat 101 through passage 139 into the main fuel nozzle 149 is of considerably less distance than if the fuel passed through the cavity 95 and through the sensing chamber 55 before it flows into the restricted passage 141 as in some prior art carburetors. This results in a lowered resistance to fuel flow and provides greater sensitivity of the diaphragm to the requirements of the engine. Fuel will pass out of the nozzle 149 at lower vacuum or depression pressures within the air passage than would be possible if a longer flow path oifering greater resistance to fuel flow. Also, changes in pressure at the nozzle entrance are reflected more quickly back to the sensing chamber 55 and thus enable the diaphragm and lever as sembly to respond to smaller pressure differentials be tween the fuel in sensing chamber 55 and the atmosphere. The carburetor described will thus respond quicker and to a greater extent to rapid acceleration requirements of the engine.

In view of the above, it willbe seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A carburetor comprising a body formed with an air and fuel mixture conduit therethrough, a throttle valve within said mixture conduit mounted for movement between an open and closed position, a choke valve within said mixture conduit spaced from said throttle valve and mounted for movement between an open and a closed position, a fuel inlet, said body having a fuel sensing chamber, a flexible diaphragm forming a wall portion of said chamber, an elongated cavity forming an extension of said chamber and having means defining a restricted fuel inlet passage at one end connection with said fuel inlet, a valve member having a conical shape with the apex of the valve member extending into the restricted passage and movable axially of said cavity to open and close said restricted passage, means biasing said valve member toward closed position, said valve member being spaced from the side walls of said cavity to define the between a fuel passageway for the flow of fuel from said fuel inlet to said fuel sensing chamber, means forming an operative connection between said diaphragm and said valve member to move said valve member in an open direction against said biasing means, means forming a restricted outlet fuel passage at the other end of said cavity between said cavity and sand sensing chamber, air flow restricting means within said mixture conduit including a tubular post having an air passage therethrough and aligned with the direction of air flow through said mixture conduit, said post extending transversely across said mixture conduit, a main fuel nozzle extending into said air passage and having an outlet in said air passage, a main fuel passageway connecting said fuel passageway between the restricted fuel inlet opening and the restricted fuel outlet opening with said main fuel nozzle, said main fucl passageway including an inlet opening of tapered form and a high-speed fuel metering screw having a conical extremity which extends into the tapered inlet opening for regulating the flow of fuel therethrough, a port opening into said mixture conduit adjacent to said throttle in closed position, and an independent idle fuel passage extending only from said fuel sensing chamber directly to said port.

2. The invention of claim 1 wherein the elongated cavity is of circular cross-section and the valve member positioned therein is likewise of circular cross-section but of a smaller diameter and an annular member is fixed to the lower end of said cavity with its inner wall spaced from the valve member to provide a restricted passageway for the fluid from the cavity to the sensing chamber.

3. The invention of claim 2 wherein said annular men.- ber has its upper wall forming a seat for a coil spring providing the means for biasing the valve towards closed position.

4. The invention of claim 1 wherein the idle fuel passage is provided with an adjustable metering means for regulating the flow of idle fuel through the idle fuel passage.

References Cited by the Examiner UNITED STATES PATENTS 2,680,605 6/1954 Bracke. 2,823,905 2/1958 Brown. 3,093,699 6/1963 Demitz 261-'72 3,118,009 1/1964 Phillips.

HARRY B. THORNTON, Primary Examiner.

RONALD R. WEAVER, Examiner.

Claims (1)

1. A CARBURETOR COMPRISING A BODY FORMED WITH AN AIR AND FUEL MIXTURE CONDUIT THERETHROUGH, A THROTTLE VALVE WITHIN SAID MIXTURE CONDUIT MOUNTED FOR MOVEMENT BETWEEN AN OPEN AND CLOSED POSITION, A CHOKE VALVE WITHIN SAID MIXTURE CONDUIT SPACED FROM SAID THROTTLE VALVE AND MOUNTED FOR MOVEMENT BETWEEN AN OPEN AND A CLOSED POSITION, A FUEL INLET, SAID BODY HAVING A FUEL SENSING CHAMBER, A FLEXIBLE DIAPHRAGM FORMING A WALL PORTION OF SAID CHAMBER, AN ELONGATED CAVITY FORMING AN EXTENSION OF SAID CHAMBER AND HAVING MEANS DEFINING A RESTRICTED FUEL INLET PASSAGE AT ONE END CONNECTION WITH SAID FUEL INLET, A VALVE MEMBER HAVING A CONICAL SHAPED WITH THE APEX OF THE VALVE MEMBER EXTENDING INTO THE RESTRICTED PASSAGE AND MOVABLY AXIALLY OF SAID CAVITY TO OPEN AND CLOSE SAID RESTRICTED PASSAGE, MEANS BIASING SAID VALVE MEMBER TOWARD CLOSED POSITION, SAID VALVE MEMBER BEING SPACED FROM THE SIDE WALLS OF SAID CAVITY TO DEFINE THEREBETWEEN A FUEL PASSAGEWAY FOR THE FLOW OF FUEL FROM SAID FUEL INLET TO SAID FUEL SENSING CHAMBER, MEANS FORMING AN OPERATIVE CONNECTION BETWEEN SAID DIAPHRAGM AND SAID VALVE MEMBER TO MOVE SAID VALVE MEMBER IN AN OPEN DIRECTION AGAINST SAID BIASING MEANS, MEANS FORMING A RESTRICTED OUTLET FUEL PASSAGE AT THE OTHER END OF SAID CAVITY BETWEEN SAID CAVITY AND SAND SENSING CHAMBER, AIR FLOW RESTRICTING MEANS WITHIN SAID MIXTURE CONDUIT INCLUDING A TUBULAR POST HAVING AN AIR PASSAGE THERETHROUGH AND ALINGED WITH THE DIRECTION OF AIR FLOW THROUGH SAID MIXTURE CONDUIT, SAID POST EXTENDING TRANSVERSELY ACROSS SAID MIXTURE CONDUIT, A MAIN FUEL NOZZLE EXTENDING INTO SAID AIR PASSAGE AND HAVING AN OUTLET IN SAID AIR PASSAGE, A MAIN FUEL PASSAGEWAY CONNECTING SAID FUEL PASSAGEWAY BETWEEN THE RESTRICTED FUEL INLET OPENING AND THE RESTRICTED FUEL OUTLET OPENING WITH SAID MAIN FUEL NOZZLE, SAID MAIN FUEL PASSAGEWAY INCLUDING AN INLET OPENING OF TAPERED FORM AND A HIGH-SPEED FUEL METERING SCREW HAVING A CONCIAL EXTREMITY WHICH EXTENDS INTO THE TAPERED INLET OPENING FOR REGULATING THE FLOW OF FUEL THERETHROUGH, A PORT OPENING INTO SAID MIXTURE CONDUIT ADJACENT TO SAID THROTTLE IN CLOSED POSITION, AND AN INDEPENDENT IDLE FUEL PASSAGE EXTENDING ONLY FROM SAID FUEL SENSING CHAMBER DIRECTLY TO SAID PORT.

Images