US3065957A

US3065957A - Charge forming method and apparatus

Info

Publication number: US3065957A
Application number: US38534A
Authority: US
Inventors: Bernard C Phillips
Original assignee: Tillotson Manufacturing Co
Current assignee: Tillotson Manufacturing Co
Priority date: 1960-06-24
Filing date: 1960-06-24
Publication date: 1962-11-27
Anticipated expiration: 1979-11-27

Description

Nov. 27, 1962 B. c. PHILLIPS 3,065,957

CHARGE FORMING METHOD AND APPARATUS Filed June 24, 1960 5 Sheets-SheetI l 1n 44 4l E. 46 46 34 4 f/q I I I a 47 if s/ I f .5 26 z 32 455/50'1-1 @(24. T-

ATTY.

Nov. 27, 1962 B. c. PHILLIPS 3,065,957-

CHARGE FORMING METHOD AND APPARATUS Filed June 24, 1960 l 5 Sheets-Sheet A2.

BERNARD E PHILLIPS.

BY Agip?? NOV. 27, 1962 B, C, PHlLLlPs 3,065,957

v CHARGE FORMING METHOD AND APPARATUS Filed June 24, 1960 5 Sheets-Sheet 3 lNVENTOR: .BEHNAHU DPHILLIPS Way @e5/JW ATTORNEY.

United States YPatent O M' 3,065,957 CHARGE FORMING METHOD AND APPARATUS Bernard C. Phillips, Toledo, Ohio, assigner to The Tillotson Manufacturing Company, Toledo, Ohio, a corporan tion of Ohio Filed June 24, 1960, Ser. No. 38,534 Claims. (Cl. 261-35) This invention relates to a method of forming a combustible fuel and air mixture or charge for an internal combustion engine and charge forming apparatus and more particularly to a charge forming apparatus embodying a diaphragm controlled fuel metering means for regulating delivery of fuel from a supply into a diaphragm chamber and wherein fuel is delivered from the diaphragm chamber into an air and fuel mixing passage solely by aspiration or differential pressure established by air flow through the mixing passage.

Diaphragm type carburetors have been used for supplying combustible mixture particularly for engines of the two cycle type utilized for powering chain saws, lawnmowers, outboard motors and the like where fuel economy under comparatively light load conditions is not of primary importance and where large capacity carburetors have not been required.

In carburetors of the diaphragm type wherein the fuel delivery into the mixing passage is effected solely by aspiration or reduced pressure in a mixing passage acting upon an unvented fuel chamber of Variable volume through the provision of a diaphragm forming a wall of the chamber or reservoir, there is a marked tendency for the delivery into the mixing passage under comparatively light load conditions of more fuel than is required to maintain a normal fuel and air mixture ratio supplied to the engine. In engines, particularly those of larger size, it is desirable to supply a lean mixture at light loads for improved economy, and to supply a richer full-power mixture near full power loads. Furthermore it is desirable to provide for the momentary delivery of additional fuel to the mixing passage for engine accelerating purposes where the carburetor or charge forming device is utilized with engines adapted to operate under varying load conditions.

The present invention embraces a method of forming fuel and air mixture charges for an internal combustion engine providing for a reduction of fuel delivered into the mixing passage when the engine is operating under partial open throttle or light load conditions so as to render engine operation more economical without impairing the power of the engine under such operating conditions.

An object of the invention is the provision of a charge forming apparatus of the diaphragm type embodying a pressure responsive means for effecting the reduction in the amount of fuel delivered into an air and fuel mixing passage when the engine with which the charge forming apparatus is used is operating under light loads above the normal idling speed of the engine.

Another object of the invention is the provision of a method of and charge forming apparatus for leaning out of the fuel constituent of the combustible mixture under engine operating conditions where maximum power is not required.

Another object of the invention is the provision of a charge forming apparatus of the Idiaphragm type which may be fashioned for use with both two cycle and four 1,

cycle engines of various sizes and improve the efficiency and economy of operation of the engines.

Another object of the invention resides in a carburetor of the diaphragm type wherein fuel is delivered into the mixing passage solely by aspiration from an unvented 3,065,957 Patented Nov. 27, 1952 fuel chamber embodying primary and secondary fuel delivery systems, the arrangement providing means for the momentary delivery of fuel into the mixing passage for engine accelerating purposes and embodying a pressure controlled means for admitting air into the fuel prior to its delivery through the primary system into the mixing passage under certain operating conditions.

Another object of the invention resides in a diaphragm type carburetor wherein fuel delivery into the mixing passage is solely under the influence of aspiration or reduced pressure in the mixing passage, the carburetor embodying a secondary diaphragm as an assist in fostering or accelerating the momentary delivery of additional fuel into the mixing passage for engine accelerating purposes when an enriched mixture is required for rapid increase in engine speed.

Another object of the invention resides in a diaphragm type carburetor embodying a manually operable choke or air control valve mounted for automatic opening, the extent of opening of the choke valve being dependent upon and responsive to the velocity of air ow through the mixing passage.

Further objects and advantages are within the scope of this invention such as relate to the arrangement, operation and function of the related elements of the structure, to various details of construction and to combinations of parts, elements per se, and to economies of manufacture and numerous other features as will be apparent from a consideration of the specification and drawing of a form of the invention, which may be preferred, in which:

FIGURE l is a side elevational view of a charge forming apparatus or carburetor of the invention;

FIGURE 2 is a top plan view of the carburetor or charge forming apparatus illustrated in FIGURE 1;

FIGURE 3 is a view from the end of the carburetor which is adapted to be lattached to an engine crankcase or intake manifold;

FIGURE 4 is a view of the opposite end of the carburetor;

FIGURE 5 is an enlarged longitudinal sectional View through the carburetor, the View being taken substantially on the line 5-5 of FIGURE 2;

FIGURE 6 is an enlarged transverse sectional view taken substantially on the line 6 6 of FIGURE 2;

FIGURE 7 is a detail sectional view taken substantially on the line 7--7 of FIGURE l;

FIGURE 8 is a detail sectional view taken substantially on the line 8--8 of FIGURE 1;

FIGURE 9 is a detail sectional view taken substantially on the line 9 9 of FIGURE 2;

FIGURE l0 is a sectional view taken substantially on the line lil-lll of FIGURE 2;

FIGURE l1 is a detail sectional view taken substantially on the line 11-11 of FIGURE l0, and

FIGURE l2 is a semi-diagrammatic view illustrating the association `and operation of components of the carburetor of the invention.

While the method of forming combustible mixture for use with an internal combustion engine and the charge forming apparatus of the invention are usable with both two cycle and four cycle engines, the invention has particular utility in use with engines where rapid engine acceleration is imperative yet economical operation desired under light load conditions of the engine.

Referring to the drawings in detail, the charge forming apparatus or carburetor for carrying out the method of the invention is inclusive of a carburetor body or body member lil preferably formed of die cast metal or of molded plastic or resin which is resistant to deterioration by hydrocarbon fuels. The body member 10 is formed with a fuel and air mixing passage 12 in which liquid fuel and air are mixed or commingled to provide a combustible mixture for delivery to an internal combustion engine with which the carburetor may be used.

The mixing passage includes an air inlet or inlet region 14, a venturi having a choke band or restricted portion or region 16 and a mixture outlet 17. The outlet end of the mixing passage is adapted to register with an inlet port inthe crankcase of a two cycle engine or, where the carburetor is employedy with a four cycle engine, the outlet end is in registration with an intake manifold arrangedto convey combustible mixture to the cylinders of the engine. The body 10, adjacent the outlet end of the mixing passage is provided with a mounting flange 18 formed with openings 19 adapted to receive bolts (not shown) for securing the vmounting flange to an engine crankcase or to an intake manifold.

A choke valve arrangement of novel construction is provided at the air inlet region 14 of the carburetor mixing passage for regulating or controlling the admission of air into thetmixing passage which is adaptable for semiautomatic operation in that its relative position is iniluenced by the magnitude of velocity of air entering the air inlet region 14. With particular reference to FIGURE 10, it will be seen 'that the carburetor body 10 is fashioned with transversely aligned boss portions .21 and-22, the boss Vportion 21 having a bore accommodating a bearing or sleeve 23, the outer end of the bore accommodating the sleeve-23 being closed by a plug or cap 24.

The boss 22 is provided with a bore adapted to receive a'bearing or bearing sleeve 25, the

bearings

23 and 25 being pressed into the aligned bores. Rotatably mounted in the

bearings

23 and 25 is a shaft 26 provided with a slot accommodating a thin disc-like choke valve 28 for the air inlet region 14, the valve disk 28 being secured to the shaft by a screw 29.

As shown in FIGURE l0, the axis of the shaft 26 is disposed above or eccentric with respect to the axis of the mixing passage inlet region 14 whereby a major area of the valve disk 28 is at one side of the axis of the shaft 26.

The bearing 25 in the boss 22 is provided with an extension or sleeve portion 32 of slightly larger diameter than that of the bearing portion'25. Mounted for rotation upon the sleeve portion 32 is a generally cylindrically shaped member 34 fashioned witha radially extending arm 35 having an opening at its distal end in which is journaled a cylindrically shaped connector 37 as shown in FIGURE 2. The fitting 37 is formed with an opening 3S to receive the extremity of a manipulating rod or bowden wire (not shown) which is secured in the opening 38 by a setscrew 40.

By manipulation of the wire or cable connected with the fitting 37, the member 34 may be rotated about the bearing provided by the sleeve extension 32. As particularly shown in FIGURE l0, the member 34 is formed with a cylindrical chamber 41. The shaft 26 is provided with a transverse opening in which is snugly fitted a pin 43. The member 34 is provided with an abutment in the form of a pin 44 whereby rotation of the member 34 in one direction engages the abutment 44 with the `pin 43 so as to elect positive manual rotation of the choke valve shaft 26 in said one direction. The sleeve extension 32 is provided at its outer end with a flange 45 disposed in a counterbore in the member 34 to prevent endwise movement of the member 34.

VThe outer end region ofthe member 34 is provided with a circular recess accommodating a circular disk-like plate or closure member 47 having an opening to receive a tenon portion 48 of a pin 49 which projects into the chamber 41. Surrounding the portion of the shaft 26 within the chamber 41 is a coilspring 50, one end 51 of the spring being hooked on the pin 43, the other end of the spring being engaged with the pin 49 as shown in FIGURE l0.

Through the resilient connection provided by the spring 4 50 between the pin 49 mounted by the member 34 and the choke valve shaft 26, the choke valve is resiliently biased against movement in the opposite direction by means of the spring 50. As the choke valve 28 is off center or eccentric with respect to the axis of the air inlet region 14 of the mixing passage, air flowing past the choke valve 28 tends to open the valve against the resilient bias of the spring 50.

Thus when the choke valve is manually moved to a closed position by rotating the cylindrical member 34 and the engine is started, the unbalanced condition of the choke valve 28 will admit air flow past the choke valve against the resilient bias of the spring 50 even though the member 34 has not been fully rotated to a position to permit full opening of the choke valve viz. the position of the choke valve illustrated in FIGURES 4 and 10.

However through the abutting connection of the pin 44 with the pin 43, movement or rotation of the member 34 in a direction to open the choke valve 28 will eifect a positive opening movement of the choke valve to the position shown in FIGURES 4 and l0.

The plate 47 supporting the pin 48 is secured in position by means of screws 46 threaded into suitable bosses formed on the substantially cylindrically shaped portion 34 the heads of the screws overlapping the peripheral region of plate 47. By loosening the screws the circular plate'47 may be adjusted to vary the biasing force of the .spring 50.

The mixture outlet region 17 of the mixing passage is provided with a disk-type throttle valve 54 which -is mounted in a slot formed in a throttle shaft 56 and held in place by a screw 57 threaded into a bore in the shaft 56. The shaft 56 is journaled in suitable bores formed in the body of the carburetor and in a boss 5S. A portion of the throttle shaft extends exteriorly of the boss 58 and is provided with an arm 60 equipped with a fitting 61 adapted to receive a Bowden wire control means (not shown) or other suitable means for manipulating the throttle valve shaft 56.

The arm is held to the shaft by swaging a portion-62 of the shaft into snug engagement with the arm 60. As shown in FIGURE 3, the carburetor body 10 is provided with a projection 64 accommodating an adjusting screw 65 adapted for engagement with a projection 67 fashioned on the arm 60 to limit the movement of the valve toward closed position, the valve being adjusted slightly open to accommodate the ow of a small amount of air through the mixing passage for admixing with the fuel supplied to the mixing passage for engine idling purposes.

As particularly shown in FIGURES 5 through 8, the carburetor body 10 is formed with a generally circular recess close to the mixing passage providing a relatively shallow fuel chamber 68 defined by an annular flange portion 69 of the carburetor body. A highly exible membrane or diaphragm 70 formed of impervious material which is resistant to deterioration by hydrocarbon fuels extends across the shallow fuel chamber 68 and forms a flexible wall-of the chamber.

Disposed between the circular peripheral region of the diaphragm 70 and the annular portion 69 is an annular sealing gasket 71 providing a Huid tight seal between the periphery of the diaphragm and the annular portion 69. A circular disk-like member 73 engages the opposite peripheral edge region of the diaphragm 70. The central region of the member 73 adjacent the diaphragm '70 is formed with a cone shaped recesss or chamber 75 defined by the surface 76 and the opposite central region of the member 73 is formed with a conically shaped surface 76 which denesva chamber or recess 77.

Extending across the recess or chamber 77 is a second diaphragm ormembrane 80 formed of highly flexible impervious material, which in cooperation with the diaphragm 70, provides an impulse arrangement under cerl tain operating conditions for engine accelerating purposes as hereinafter described. Disposed at the opposite side of the second diaphragm 80 is a circular closure plate 82 having a peripheral boss or ange portion S3 which engages the peripheral region of the second diaphragm Si? as shown in FIGURES 5 and 6.

The circular boss portion 83 is provided with a plurality of circumferentially spaced openings and the disklike member 73 formed with openings aligned therewith to accommodate securing screws 85 threaded into openings formed in the circular boss portion 60 of the carburetor body for securing the diaphragms 74?,l Si?, the disk-like member 73 and the closure plate S2 in assembled relation, as shown in FIGURES 5 and 6. The boss portion 83 of the closure member 82 defines a circular chamber 87 formed with a depen-ding centrally disposed boss portion 88.

The boss portion 88 is formed With a socket or recess 89, the bottom of the recess being defined by a partition 90 beneath which is a bore 91 and a counterbore, a fine mesh screen or filter 93 being disposed in the counterbore in the boss portion 80 as shown in FIGURE 6. The partition 90 is provided with a minute or very small vent passage 95. An expansive coil spring 97 is arranged in the socket 89, the spring being arranged to exert an upward bias or force upon the diaphragm 86.

The diaphragm 80 is provided with a circular reinforcing disk 99 preferably formed of sheet metal which is engaged by the spring 97, the spring being centered with respect to the diaphragm S0 by means of a pin 169, the upper end of which is swaged into engagement with a washer 101 for securing the reinforcing disk 99 to the diaphragm Si). As shown in FIGURE 5, an orifice 1114 is formed in a wall of the outlet region 17 of the .mixing passage, the orifice being the outlet of a channel 1116 which extends through a portion of the carburetor body 111, the sealing gasket 71, diaphragm 70, member '73, diaphragm 80 and partially into the closure member 82.

The closure member 82 is provided wtih a boss portion 108 in which is formed an angularly disposed passage 110 in communication with the channel 166 whereby under certain operating conditions of the engine the aspiration in the mixing passage is communicated to the chamber S7. The first diaphragm 70- provides a component of means for controlling or regulating the iiow of liquid fuel into the chamber 68 from a fuel supply in accordance with the rate of delivery of fuel into the mixing passage 12. The fuel chamber 63 is unvented to the atmosphere and is actuated or flexed solely by aspiration or reduced pressure Set up in the mixing passage 12.

The aspiration, suction or reduced pressure in the chamber 68 is effective to cause delivery of fuel through fuel delivery passages and nozzles or outlets hereinafter described opening into the mixing passage 12. The diaphragm 80 is actuated by impulse pressure set up or established in the chamber 87 under certain operating conditions as hereinafter explained.

The chamber '7S between the diaphragms 711 and 8th in the member 73 is preferably vented to the inlet region 14 of the carburetor body as the air inlet region is preferably provided with a filter (not shown) secured to a fiange or boss portion 112 having threaded openings 114 to accommodate securing bolts (not shown) for retaining an air filter in position. As shown in FIGURE 5, an air entrance tube 118 pressed into a bore in the wall of the body 10 defining the air inlet region 14 and is in communication with the passage 121i which extends partially into the member 73.

'Ihe interior portion of member 73 is provided with a notch or recess 122 which is in communication with the passage 120 by a restricted channel or duct 124 which is of small size to restrict or retard air flow out of the chamber 75 when the diaphragm S41 is rapidly moved upward under the inuence of the spring 97.

As shown in FIGURES 5 and 6, an elongated recess 128 formed in the wall region of the carburetor body de-A iining the shallow fuel chamber 68 accommodates a lever 130 formed of sheet metal, the lever 131) being provided intermediate its ends with a loop portion accommodating a pin 132 forming the fulcrum for the lever 130. The pin 132 is provided with a threaded portion 133, shown in FIGURE 4, threaded into a bore in the carburetor body facilitating assembly of the pin 132 and lever 13th in the body.

Disposed at opposite sides of the first diaphragm 70 are metal disks or reinforcing members 135 and 136, a member or rivet 137 extending through openings in the disks and diaphragm. The head portion of the rivet 137 is engaged by the long arm of the lever 130 at the right side of the lever fulcrum 132 as viewed in FIGURE 6. An expansive coil spring 139 is disposed in a recess formed in the carburetor body and engages the arm of the lever at the right side of the fulcrum 132 as viewed in FIGURE 6, normally biasing the lever 130 into engagement With the rivet 137 so that movement of the diaphragm 70 effects pivotal movement of the lever 130 about its fulcrum.

The short arm 14@ of the lever is adapted to engage an end of a fuel inlet valve member or valve body 142. The carburetor body 1t) is formed with a threaded bore to receive a valve cage or valve guide fitting 144, the fitting being fashioned with a central bore in which a valve member 142 is slidably accommodated. The valve body or member 142 is preferably of polygonal cross-section, for example, rectangular cross-section, to facilitate flow of liquid fuel along the facets provided by the polygonal cr0sssection.

Arranged in a counterbore at the upper end of the fitting 144 is an annular valve seat 146 preferably formed of yieldable or semi-hard material such as neoprene or other suitable material which is resistant to deterioration by hydrocarbon fuels. The annular valve seat 146 provides a fuel inlet port 147. A sealing gasket 148 is disposed between the upper end of the fitting 96 and the ledge formed at the end ofthe bore in the body accommodating the fitting 144.

The valve member 142 is formed with a cone-shaped valve portion 150 extending into the port 147 and cooperating with the valve seat 146 to meter, regulate or control the flow of fluid fuel from a supply into the diaphragm chamber or a fuel reservoir 63. The carburetor body 10 is formed with a boss portion 152 provided with a threaded bore 153 accommodating a threaded fitting (not shown) adapted to be connected with a fuel tank, a fuel pump or other source or supply of liquid hydrocarbon fuel. A fuel strainer or screen 154 is preferably disposed in the threaded bore 153.

The port 147 in the Valve seat is in communication with the threaded bore 153 through connecting

passageways

155 and 156. The fuel supply for the carburetor may be by gravity flow directly from a tank or receptacle positioned or located above the carburetor, or the fuel supply may be from a fuel pump connected with a fuel tank. The port 147 provided in the annular valve seat 146 is preferably of comparatively small diameter in orderto present a minimum area of the coneashaped valve portion 150 to the pressure of the incoming fuel in order to render the fuel control means responsive to minute pressure variations in the chamber 68.

The carburetor body is fashioned With ducts, channels or passages formed or drilled therein for conveying fuel from the fuel chamber 68 into the mixing passage 12. As shown in FIGURES 5 and 7, the region of the carburetor body adjacent the choke band 16 of the venturi 15 is bored to accommodate a tubular fitting providing a main orifice or primary fuel discharge opening 162 at the choke band 16 of the venturi. Disposed Within the uppe portion of the tubular member 160 is a valve means in the form of a ball valve or check ball 164.

The lower portion of the tubular member 160 is provided with a tenon portion 165 of reduced diameter provided with a passage or bore 166 of lesser diameter than that of the check ball 164 and which is adapted to be closed by the check ball under certain conditions of operation as hereinafter explained.

A perforated member 168 preferably of sheet metal is disposed in the tubular fitting 160 above the ball check valve 164 to prevent dislodgment of the valve member 164 from the chamber in the tubular member 160. The member 168 permits the delivery of fuel through the main nozzle 162 into the mixing passage.

The hollow tenori portion 165 of fitting 160 extends into a well or duct 170, the lower end of which is closed by a Welsh plug 172. The Well 170 is of a size to accommodate a small amount of reservoir of fuel for accelerating purposes. Formed in a boss portion 174, shown in FIGURE 7, is a bore 175 which terminates adjacent the well 170 in a threaded counterbore of lesser diameter, the outer end of the bore 175 being closed by a threaded plug 176. Disposed in the bore 175 is a fitting 177 having a threaded portion 178 extending into the threaded counterbore.

The fitting 177 is provided with a restricted fuel metering passage 180 for metering or restricting fuel liow into the well 170. The bore 175 is in communication with the diaphragm fuel chamber 68 by a passage or duct 182, shown in FIGURE 7, whereby fuel from the diaphragm chamber 170 flows through passage 182, bore 175 and restricted metering passage 180 into the well 170 for delivery through the passage 166 past the check ball 164 into the mixing passage through the main orifice 162.

The embodiment of the invention illustrated embodies a secondary fuel delivery system for delivering fuel into the mixing passage for engine idling and low speed purposes. As shown in FIGURE 5, the carburetor body is formed with a bore 184, the end of the bore adjacent the fuel chamber 68 being closed by a plug 185. The bore 184 is in communication with the well 170 by means of a duct or channel 186. It should be noted that the point of entrance of channel 186 into the well 170 is at the upper end of the.well, the channel 186 supplying fuel from the well to the secondary fuel delivery or orifice system.

As shown in FIGURE 8, the carburetor body is formed with a supplemental chamber or bore 187, the exterior region of which is closed by a Welsh plug 188. The secondary orifice system includes an orifice 190 for engine idling purposes and a second orifice 192 for supplying fuel for low engine speeds. These orifices are illustrated in FIGURE l2 and in broken lines in FIGURE l and are in communication with a supplemental chamber 187 from which fuel is delivered through the orifices into the mixing passage under certain engine operating conditions.

The engine idling orifice 196 is disposed slightly forwardly of a nearly closed position of the throttle valve at the engine side of the throttle, while the low speed orifice 192 is at the opposite side of the throttle valve when the latter is in substantially closed position. As shown in FIGURE 8, the body 18 of the carburetor is provided with a boss portion 194 provided with a threaded bore to receive the threaded portion 196 of a manually adjustable valve body 198.

The threaded portion 196 is provided with a tenori 206 of reduced diameter which is of lesser diameter than the bore 262 which accommodates the tenon 200, the tenori terminating in a tapered needle valve portion 284 which extends into a restricted passage 206 which is in cornmunication with the bores 184and 202. A sealing gasket 288 is disposed in a counterbore formed in the boss 194 and an expansive coil spring 210 is disposed between the sealing gasket 288 and a knurled head 212 formed on the valve `body 198 providing a finger grip means for adjusting or manipulating the valve body 198.

The bore 262 is in communication with the supplemental chamber 187 by means of an angularly arranged channel or duct 214, It will be apparent from the forea going that the fuel for delivery through the secondary orifice system viz. the

orifices

190 and 192, fiows through the duct 186, bore 184 through the restricted passage 286, bore 282, channel 214 and secondary or supplemental chamber 187 thence through one or both of the orifices 199 and 192 into the mixing passage 12 depending upon the relative position of the throttle valve 54.

By rotating the valve body 198, the needle valve portion 264 may be adjusted to regulate or meter fuel flow to the secondary orifice system from the bore 184. The arrangement is inclusive of means for admitting a small amount of air into the upper end of the accelerating well 179 for bleeding air into the fuel for delivery from the main or primary orifice 162 when the engine is operating at intermediate or high speeds. As shown in Figure 5, a cup-like `fitting 218 is provided in a bore arranged between the air inlet region 14 and the accelerating well or chamber 17) as shown in FIGURE 5.

The fitting 218 is provided with a small aperture or passage 229 to admit a restricted amount of air from the air inlet region 14 into the well 170 for admixing with the fuel for delivery through the main orifice 162 when the fuel in the accelerating well is exhausted or substantially exhausted through the main orifice 162.

The embodiment of the present invention is inclusive of a method and arrangement for admitting or introducing additional air for admixing with the fuel in the well for delivery from the main orifice when the engine is operating under light load or constant speed conditions where full power is not required. The arrangement includes means for automatically modifying or varying the fuel and air ratio by pressure differentials in the mixing passage. Such means comes into operation automatically to lean the mixture by bleeding additional air into the fuel when the engine is operating under light loads above the normal idling speed of the engine whereby a substantial increase in the economy of operation is effected.

With reference to FIGURE 9, the carburetor body 10 is formed with a cylindrically shaped boss portion 224 provided with a bore, cylinder or chamber 226 terminating in a counterbore 228 of lesser diameter. Slidably mounted in the cylinder 226 is a piston-type valve 238 formed with a recess accommodating an expansive coil spring 232, one end of the spring extending into the counterbore 228, the bottom of the counterbore forming an abutment for the spring. The end of the bore or cylinder 226 adjacent the piston valve is closed by a threaded plug 234.

The wall region of the cylinder 226 adjacent the inner end of the threaded plug 232 is in communication with the air inlet region 14 of the mixing passage by means of a channel or passage 236. The body 10 is formed with a boss portion 238, as shown in FIGURES l and 9, within which is a drilled channel 240 opening into the cylinder 226, the outer end of the channel 240 being closed by a cap or plug 241.

The lower end of the channel 240 is in communication with a passage or channel 242 shown in FIGURES 6 and 9, the outer end of the drilled channel 242 being closed by means of a cap 243 the channel 4or bore 242 is in communication with the channel 186, which supplies fuel to the secondary orifices, through a restricted passage or air metering channel 245 shown in FIGURE 6. The small diameter counterbore 228 formed at the end of the cylinder or bore 226, shown in FIGURE 9, is connected with a passage 248 in the carburetor body by means of a channel or passage 250.

A passage 252, shown in broken lines in FIGURES 1 and 9, connects the passage 248 with the mixing passage, the outlet or orifice 254 into the mixing passage being illustrated in broken lines in FIGURES l and 9. In this manner the bore or cylinder 226 at the left end of the slidable piston 230, as viewed in FIGURE 9, is under the inluence of pressure differentials existent in the outlet region of the mixing passage adjacent the throttle valve.

When the suction or aspiration in the outlet region 117 of the mixing passage is sufficient to move the slidable piston valve 230 in a left-hand direction as viewed in FIGURE 9, the movement of the valve 23) uncovers the ports of the passages 236 and 4241) in the bore or cylinder 226 so that air from the air inlet region 14 flows through the passage 236 into the bore 226 at the right-hand end of the piston valve 230, thence through the passages or channels 246, 242, the restricted air metering channel 245 and passage 186 to admit air into the accelerating Well 176, shown in FIGURE 5, for admixing with the fuel discharged through the main orifice 162.

This operating condition obtains when the engine with which the carburetor may be used is operating under light loads where full power is not required and thus the fuel and air ratio in the mixing passage is leaned out, viz. the amount of fuel to the volume of air moving through the mixing passage is reduced, effecting substantial economy in operation of the carburetor.

The operation of the charge forming apparatus or carburetor of the invention may be best understood by additional reference to the semi-diagrammatic view of FIG- URE 12. The engine is started by a conventional cranking method with the throttle valve 54 in partial or full open position and the choke valve 28 moved to closed position through the manipulation of the arm 35. When the `manipulating arm 35 is rotated in a direction to close the choke valve 28, the spring in the chamber' 41 of the cylindrical member 34 resiliently urges or biases the choke valve to closed position.

When the engine has started, air velocity through the mixing passage is increased and if the operator has not fully returned the arm 35 and member 34 toward full open position of the choke valve, the air velocity acting against the choke valve 28, which is eccentrically mounted with respect to the air inlet 14, is opened by the air pressure against the tension of the spring S so that continued engine operation is assured even though the manipulating arm 35 and member 34 have not been returned to fully open the choke valve 28.

Various engine operating conditions and speeds infiuence the action of various components of the carburetor construction and fuel flow through various channels for delivery into the mixing passage 12. Considering the operation of the carburetor when the internal cornbustion engine with which it is used is operating at idling speed, fuel flow to the mixing passage is as follows: Under engine idling conditions the throttle valve 54 is in near closed position, the idling orifice 1911 being at the mixture outlet side of the throttle valve, delivers fuel for engine idling purposes. With the throttle 54 in near closed position, the pressure in the venturi 15 is substantially atmospheric and hence the check ball Valve 164 is in a position closing the passage or duct 166 in the tubular fitting 160 shown in FIGURE 5.

This action prevents back bleeding of air from the mixing passage through the main orifice 162 into the fuel system. The metering diaphragm 70 is under the influence of the reduced pressure in the mixture outlet 17 through the idling orifice 19t) and the passages communieating therewith through the accelerating well 170.

The aspiration or reduced pressure in the outlet region of the mixing passage elevates the diaphragm 70 as viewed in vFIGURES and 6, swinging the lever 245 in a counterclockwise direction about its pivot 132, which movement effects a lowering of the valve body 142 whereby the valve portion 150 moves away from the annular valve seat' 146 so that fuel fiows from the supply through the port 148 along the facets of the valve body 142 into the fuel chamber 68. The aspiration effective in the channel 136 is communicated to the well 170 shown in FIGURE 7 1@ t'o cause fuel iiow into the well 170 through the passage 182, bore 17S and metering restriction 180.

It should be noted from FIGURE 5 that the channel 186 which conveys fuel away from the well 170 to the idling and low speed orifices is in communication with the upper region of the well 170 so that the latter is filled with fuel during engine idling and low speed operation.

If the throttle 54 is opened sufficiently to bring into operation the delivery of fuel through the low speed orilice 192, fuel flow is substantially thesame as with idling speed fuel discharge except that the fuel is delivered through the secondary system viz. both orifices 19t! and 192 with increased fuel flow through the carburetor due to the aspiration effective on both

orifices

190 and 192.

As the engine speed is increased by further gradual opening of the throttle S4, the pressure in the mixing passage rises adjacent the

orifices

190 and 192 and decreases in the choke band region 16 of the venturi so that the engine aspiration acts through the main orifice 162 to elevate the ball check valve 164 which is formed of nylon or other light material and discharge fuel from the well 170 through the passage 166 and the main orifice 162 into the mixing passage.

There may be some overlapping of fuel delivery through the secondary orifices with that of the main orifice 162, but as engine speed increases the delivery of fuel through the secondary orifices nearly ceases by reason of the high aspiration or reduced pressure in the venturi acting upon the main fuel delivery orifice 162. If the throttle 54 is moved toward open position, the fuel in the accelerating well 17@ is delivered through the main orifice 162 for engine accelerating purposes.

When the engine is operating under idling or low speed conditions, the reduced pressure at the engine side of the throttle 54 is effective through the orifice 104 and

passages

106 and 110 to establish reduced pressure in the chamber 87 beneath the second diaphragm S0 to cause the latter to move or be liexed downwardly as viewed in FIGURE 5, compressing the spring 97.

When the throttle 54 is suddenly moved toward full open or near open position rapid acceleration is attained in the following manner: The potential energy set up in the compressed spring 97 is effective to rapidly move the diaphragm S0 upwardly, imparting a momentary pressure impulse to the metering diaphragm 7i) to cause further opening of the valve 15@ through the movement of the lever 245 so fuel enters the fuel chamber 68 at an increased rate for delivery into the mixing passage through the well 170 and the main orifice 162.

The rapid release of the compression of spring 97 occurs for the reason that the reduced pressure which had been effective on the orifice 164 and passages 1116 and 116 is rapidly increased when the throttle valve S4 is opened rapidly so that the pressure in the chamber S7 shown in FIGURE 5 is rapidly increased and the second diaphragm moved upwardly rapidly by the rapid expansion of the spring 97.

It should be noted that the vent opening is of comparatively small size in cross-sectional area and serves to prevent fuel from the mixing passage accumulating in the chamber 87.

The metering diaphragm 71) is under the normal influence of aspiration in the mixing passage, the fuel chamber 66 being unvented except through the fuel discharge orifices. The pressure in the

chambers

75 and 77 between the diaphragms is equalized through the restricted passage 12eI and the passage 120 opening into the air inlet region 14 through the medium of the tube 118.

When the engine is operating at intermediate speeds and` under comparatively light loads Where full power is not required, the fuel and air mixture is leaned out by operation of the automatic means for admitting additional air to the fuel prior to its discharge through the main nozzle or outlet 162. When the throttle valve is lt in closed or near closed position, there is insufiicient reduction in pressure effective on the orifice 254 and associated passages to cause movement of the piston valve 230 from its normal port-closing position shown in FIG- URE 9.

However, when the engine is operating at intermediate speeds under light loads with the throttle in partial open or intermediate position, the pressure in the'mixing passage at the region of the throttle is reduced and is effective in the bore or cylinder 226 to cause longitudinal movement of the piston valve 236 in a left-hand direction, as viewed in FIGURES 9 and l2, compressing the spring 232 and establishing communication between the passages 236 and 24d through the bore 226 so as to admit air from the air inlet region 1d through passage 236, bore 226,

V passages

240, 242, the restricted air metering passage 245 and the fuel channel ld into the well E76.

The additional air is mixed with the fue! discharged through the main orifice 162 so that the ratio of fuel to the air is reduced, thus effecting economy of operation of the carburetor under such engine operating conditions.

Under all conditions of operation, a small amount of air is bled into the fuel from the air inlet region 14 through the minute air bleed passage 22) in the cuplike fitting 218, shown in FIGURES and l2, so that an emulsion of fuel and air is delivered through the main orifice 262 and some air bled into the fuel delivered through the secondary system comprising the

orifices

190 and 192 for engine idling and low speed operation.

Whenever the load on the engine increases and the throttle 5d opened fully or to near open position to take care of increased load on the engine or to rapidly increase the speed of the engine, the pressure in the mixing passage adjacent the orifice 254, shown in FIGURE 9 is increased, and the potential energy of the compressed spring 232 is released to move the piston valve 230 to its port-closing position, as shown in FIGURES 9 and l2 to interrupt or cut olic the supply of additional air to the channel 186 so that the fuel flow through the main orice 162 is increased and a richer mixture or a greater amount of fuel per unit of air is established in the mixing passage to take care of the added power requirements.

The fuel flow to the idling and low speed orifices 199 and 92 is controlled or metered by manual adjustment' of the metering valve 26d shown in FlGURE 8.

The carburetor of the invention is adaptable for both small and large engines of both two and four cycle types and is especially adaptable for four cycle engines where effective accelerating characteristics are required and yet economies in fuel consumption effected under light load conditions through the automatic control of fuel and' air ratio Iby the admission of additional air bled into the fuel prior to its discharge from the main orifice 162.

While a fixed fuel metering restriction 180, as shown in FIGURE 7, is utilized for controlling or metering fuel flow to the fuel delivery system, it is to be understoodv that an adjustable needle valve of the character illustrated at 2.36 in FIGURE 8 may lbe employed in lieu of the fixed fuel metering passage ist! shown in FIG- URE 7.

It is apparent that, within the scope of the invention, modifications and different arrangements may be made other than as herein disclosed, and the present disclosure is illustrative merely, the invention comprehending all variations thereof.

I claim:

lQCharge forming apparatus including, in combination, a body member formed with a fuel and air mixing passage and a recess, a diaphragmvforming with said recess a fuel chamber, a throttle valve for the mixing passage, means controlled by said diaphragm for admitting liquid fuel from a supply into the chamber, orifice means for delivering fuel into the mixing passage, fuel conveying duct means in communication with the chamber and the orifice means wherebyV fuel is delivered into the mixing passage by differential pressures in the mixing passage, passage means arranged to admit air into the duct means for adrnixing with the liquid fuel delivered through the orifice means, and valve means cooperating with said air passage means and movable by differential pressure in the mixing passage for controlling the admission of air through said passage means into said duct means.

2. Charge forming apparatus including, in combination, a body member formed with a fuel and air mixing passage and a shallow recess, a diaphragm extending across the recess and forming therewith a fuel chamber, a fuel inlet in said body member, a valve for said inlet controlled by said diaphragm for admitting liquid fuel from a supply into the chamber, a throttle valve for the mixing passa e, an orifice for delivering fuel into the mixing passage, lfuel conveying duct means in communication with the chamber and the orifice whereby fuel is delivered into the mixing passage by aspiration in said mixing passage, air passage means arranged to admit air into the duct means for admixing with the liquid fuel delivered through the orifice, relatively movable valve means disposed in said air passage means, said valve means being arranged to be moved by pressure differentials in the mixing passage for controlling the admission of air into said duct means.

3. Charge forming apparatus including, in combination, a body member formed with a fuel and air mixing passage and a shallow recess, a diaphragm forming with said recess a fuel chamber, a throttle valve for the mixing passage, a fuel inlet in said'body member, a valve for said inlet controlled by said diaphragm for admitting fuel from a supply into the chamber, orifice means for delivering fuel from the chamber into the mixing passage, fuel conveying duct means in communication with the chamber and the orifice means where'oy fuel is delivered into the mixing passage by aspiration in said mixing passage, air channel means arranged to admit air into the duct means for admixing with the liquid fuel delivered through the orifice means, an air chamber in Communication with said air channel means, valve means movable in said air chamber, resiiient means normally biasing the valve means to a position interrupting air fiow through the air channel means, said valve means being arranged to be moved by reduced pressure in the mixing passage to a position admitting air through the air channel means into said duct means.

4. Charge forming apparatus including, in combination, a body member formed with a fuel and air mixing passage and a shallow recess, a diaphragm forming with said recess a fuel chamber, a throttle valve for the mixing passage, means controlled by said diaphragm for admitting fuel from a supply into the chamber, orifice means for delivering fuel into the mixing passage, fuel conveying duct means in communication with the chamber and the orifice means whereby fuel is delivered into the mixing passage by differential pressures in said mixing passage, air channel means arranged to admit air into the duct meansV for admixing with the liquid fuel delivered through the orifice, an air chamber in communication with said air channel means and the mixing passage, and valve means in said air chamber reciprocable under the infiuence of varying pressures in the mixing passage for controlling air fiow through said air channel means, and a restriction in said air channel means for metering air fiow therethrough.

5. Charge forming apparatus including, in combination, a body member formed with a fuel and air mixing passage and a recess, a diaphragm forming with said recess a fuel chamber, a throttle valve for the mixing passage, means controlled by said diaphragm for admitting fuel from a supply into the chamber, orifice means for delivering fuel into the mixing passage, fuel conveying'duct means in communication with the chamber and 13 the orifice means whereby fuel is delivered into the mixing passage by dierential pressures in said mixing passage, air passage means formed in said body including a port in communication with said fuel duct means, and movable valve means cooperating with said port actuated by variation in pressure in the mixing passage for controlling air tlow through said air passage means.

6. Charge forming apparatus including, in combination, a body member formed with a fuel and air mixing passage and a shallow recess, a diaphragm forming with said recess a fuel chamber, a throttle valve for the mixing passage, said body member being formed with a fuel inlet, means cooperating With the inlet controlled by said diaphragm for admitting liquid fuel from a supply into the chamber, orifice means for delivering fuel into the mixing passage, fuel conveying duct means in communication with the chamber and the orifice means whereby fuel is delivered into the mixing passage by differential pressures in said mixing passage, an air chamber formed in said body, valve means movable in said chamber, an air inlet for the air chamber, air passage means between said air chamber and said fuel duct means, a channel establishing communication between the air chamber and the mixing passage, and means normally biasing the valve means to a position interrupting air ow through said air passage means, said valve means being adapted to be moved under the iniiuence of reduced pressure in said mixing passage communicated to the air chamber through said channel.

` 7. Charge forming apparatus including, in combination, a body member formed with a fuel and air mixing passage and a recess, a diaphragm forming with said recess a fuel chamber, a throttle valve for the inlet passage, inlet valve means controlled by said diaphragm for admitting liquid fuel from a supply in the chamber, primary and secondary orifices for delivering fuel into the mixing passage, fuel conveying duct means in communication with the chamber and the orices whereby fuel is delivered into the mixing passage by differential pressures in said mixing passage, air passage means in communication with said fuel duct means, and valve means movable under the influence of reduced pressure in said mixing passage for controlling air flow through said air passage means to the duct means for admixing with liquid fuel delivered through the primary oriice into the mixing passage.

8. Charge forming apparatus including, in combination, a body member formed with a fuel and air mixing passage and a shallow recess, a diaphragm forming with said recess a fuel chamber, a throttle valve for the mixing passage, means controlled by said diaphragm for admitting liquid fuel from a supply into the chamber, an orifice for delivering fuel into the mixing passage, fuel conveying duct means in communication with the chamber and the orifice whereby fuel is delivered into the mixing passage by differential pressures in said mixing passage, an air chamber formed in said body, valve means movable in said chamber,an air inlet for the air chamber, air passage means between said air chamber and said fuel duct means, a channel establishing communication between the air chamber and the mixing passage, resilient means normally biasing the valve means to a position interrupting air ow through said air passage means, said valve means being adapted to be moved under the influence of reduced pressure in said mixing passage communicated to the air chamber through said channel, and a restriction in said air passage for metering air admitted to the fuel duct means.

9. Charge forming apparatus including, in combination, a body member formedwith a fuel and air mixing passage and a recess, a diaphragm forming with said recess an unvented fuel chamber, a throttle Valve in the mixing passage, a fuel inlet formed in said body in communication with the chamber, means in said inlet actuated by said diaphragm for controlling ow of liquid fuel from a supply into said chamber, a main fuel delivery system including a fuel well formed in said member for delivering fuel from the chamber into the mixing passage, a secondary fuel delivery system for delivering fuel to the mixing passage, said secondary fuel delivery system being in communication with the well by a fuel conveying duct whereby fuel iiow through the secondary system effects delivery of fuel from the chamber into the Well, said body member being formed with air channel means in communication with the fuel duct for admitting air into the well for admixing with fuel delivered by the main fuel delivery system into the mixing passage, and valve means actuated by varying pressures in the mixing passage for controlling air flow through said air channel means.

10. Charge forming apparatus including, in combination, a body member formed with a fuel and air mixing passage and a shallow recess, a diaphragm forming with said recess an unvented fuel chamber, a throttle valve in the mixing passage, a fuel inlet formed in said body in communication with the chamber, means in said inlet actuated by said diaphragm for controlling liquid fuel from a supply into said chamber, a main fuel delivery system including a fuel well formed in said member for delivering fuel from the chamber into the mixing passage, a secondary fuel delivery system for delivering fuel to the mixing passage, said secondary fuel delivery system being in communication with the well and arranged whereby fuel iiow through the secondary system effects delivery of fuel from the fuel chamber into the well, said body member being formed with an air chamber, a valve for said air chamber, air passage means between the air chamber and the fuel well, a channel connecting the air chamber with the outlet region 0f the mixing passage, said valve being under the influence of pressure variations in the mixing passage for actuating the Valve to control the admission of air through said air passage means into the fuel well.

ll. Charge forming apparatus inclding, in combination, a body member formed with a fuel and air mixing passage and a recess, a diaphragm forming with said recess an unvented fuel chamber, a throttle valve in the mixing passage, a fuel inlet formed in said body in communication with the chamber, means in said inlet actuated by said diaphragm for controlling liquid fuel from a supply into said fuel chamber, a main fuel delivery system including a fuel well formed in said member for delivering fuel from the chamber into the mixing passage, a secondary fuel delivery system for delivering fuel to the mixing passage, said secondary fuel delivery system being in communication with the well and arranged whereby fuel flow through the secondary system effects delivery of fuel from the chamber into the well, said body member having a cylinder formed therein, a valve movable in said cylinder, a channel between the cylinder and an air inlet region of the mixing passage, a second channel between the cylinder and the main fuel delivery system, a third channel between the cylinder and the outlet region of the mixing passage, means normally biasing the valve toward a position cl-osing the second channel, said valve being under the iniiuence of pressure variations in the mixing passage for actuating the valve to control the admission of air through said first and second lchannels into the main fuel delivery system.

l2. Charge forming apparatus including, in combination, a body member formed with a fuel and air mixing passage and a recess, a diaphragm forming with said recess a fuel chamber, a throttle valve for the mixing passage, means controlled by said diaphragm for admitting liquid fuel from a supply into the fuel chamber, orifice means for delivering fuel into the mixing passage, fuel conveying duct means in communication with the fuel chamber and the orice means whereby fuel is aspirated into the mixing passage by differential pressures in said mixing passage, an air control valve in the inlet region of the mixing passage, a shaft journaled in the body memaccese? ber and supporting said air control valve, the axis of the shaft being transverse to and at one side of the axis of the mixing passage, an element journaled for rotation relative to said shaft, cooperating means on said shaft and element whereby movement of the element in one direction effects movement of the shaft and air control valve in the same direction, and resilient means engaging the shaft and element whereby differential pressure acting on said air control valve opens said valve.

13. Charge forming apparatus including, in combination, a body member formed with a fuel and air mixing passage and a recess, a diaphragm forming with said recess a fuel chamber, a throttle valve in the mixing passage, means controlled by said diaphragm for admitting liquid fuel from a supply into the chamber, orice means for delivering fuel into the mixing passage, fuel conveying duct means in communication with the chamber and orifice means whereby fuel is delivered into the mixing passage by differential pressures in said mixing passage, an air control valve in the inlet region of the mixing passage, a shaft journaled in the body member and supporting said air control valve, the axis of the shaft being transverse to and at one side of the axis of the mixing passage, an element journaled for rotation relative to said shaft, cooperating abutment means 4on said shaft and element whereby movement of the element in one direction eects movement of the shaft and air control valve in the same direction, a member mounted by said element, and resilient means connecting the shaft and member whereby differential pressure acting on Said air control valve opens said valve, said member being adjustable relative to said element for varying the effective force of said resilient means.

14. Charge forming apparatus including, in combination, a body member formed with a fuel and air mixing passage and a recess, a diaphragm forming with said recess a fuel chamber, a throttle valve in said mixing passage, means controlled by said diaphragm for admitting liquid fuel from a supply into the chamber, orifice means for delivering fuel into the mixing passage, fuel conveying duct means in communication with the chamber and `orifice means whereby fuel is delivered into the mixing passage by differential pressures in said mixing passage, air passage means arranged to admit air into the duct means for admixing with the liquid fuel delivered through the orifice means, means associated with said air passage means and influenced by pressure differentials in the mixing passage for controlling the admission of air into said duct means, an air control valve in the inlet region of the mixing passage, a shaft journaled in the body member and supporting said air control valve, the axis of the shaft being transverse to and at one side of the axis of the mixing passage, an element journaled for rotation relative to said shaft, cooperating abutment means on said shaft and element whereby movement of the element in one direction effects movement of the shaft and air control valve in the same direction, and resilient means arranged between the shaft and element whereby differential pressure acting on said air control valve opens said valve.

l5. Charge forming apparatus in combination, a body member formed with a mixing passage and a recess, a flexible diaphragm extending across said recess and forming therewith a fuel chamber, said body being formed with a fuel inlet, means actuated by movement of the diaphragm for controlling flow of liquid fuel from a supply into the fuel chamber, main and secondary fuel orifices for delivering fuel from the fuel chamber into the mixing passage, duct means connecting the main and secondary orifices with the fuel chamber, a throttle valve in the mixture outlet region of the mixing passage, an air control valve in the inlet region of the mixing passage, a shaft journaled in the body member and supporting said air control valve, the axis of the shaft being transverse to the axis of the mixing passage and at one side of the mixing passage axis, an element journaled for rotation relative to said shaft, cooperating abutment means of said shaft and element whereby movement of the element in one direction effects movement of the shaft and air control valve in the same direction, and resilient means having operative connection with the shaft and element whereby differential pressure acting on said air control valve opens said valve.

Phillips June 25, 1957 Brown Feb. 18, 1958