US3330545A

US3330545A - Carburetor with fuel enrichment means

Info

Publication number: US3330545A
Application number: US495537A
Authority: US
Inventors: Daniel L Donovan
Original assignee: Tillotson Manufacturing Co
Current assignee: Tillotson Manufacturing Co
Priority date: 1965-10-13
Filing date: 1965-10-13
Publication date: 1967-07-11
Anticipated expiration: 1984-07-11
Also published as: DE1526754A1

Description

y 1967 D. L. DONOVAN 3,330,545

CARBURETOR WITH FUEL ENRICHMENT MEANS 2 Sheets-Sheet 1 Filed Oct. 13, 1965 1.9 56 v INVENTOR.

flA/wa A DOA/0 VAN Arrow/5y July 11, 1967 D. 1.. DONOVAN 3,330,545

CARBURETOR WITH FUEL ENRICHMENT MEANS Filed Oct. 13, 1965 2 Sheets-Sheet 2 l N VEN TOR. 04mm 1. flo/vom/v ATTORNEY United States Patent 3,330,545 CARBURETOR WITH FUEL ENRICHMENT MEANS Daniel L. Donovan, Toledo, Ohio, assignor to The Tillotson Manufacturing Company, Toledo, Ohio, a corporation of Ohio Filed Oct. 13, 1965, Ser. No. 495,537 4 Claims. (Cl. 261-41) This invention relates to carburetors of a character wherein varying pressures in the fuel and air mixing passage effect delivery of fuel from a fuel chamber into the mixing passage and control a fuel inlet valve to regulate fuel delivery from a supply into the fuel chamber, the fuel being mixed with air in the mixing passage and the mixture conveyed to an internal combustion engine. The invention has particular utility in a carburetor of the diaphragm type and is adapted for use in other types of carbuertor, carburetors embodying the invention being usable with either two cycle or four cycle internal combustion engines and especially those for powering vehicles, marine engines, industrial engines and the like. In a diaphragmtype carburetor wherein varying pressures in the mixing passage influence a diaphragm to control a fuel inlet valve a well as in other types of carburetors, the delivery of fuel from the main nozzle into the mixing pas-sage tends to decrease rapidly as air flow through the mixing passage decreases. This operational characteristic tends to impair the delivery of suflicient fuel for a proper fuel and air mixture at low speeds when the throttle is moved to wide open position, and to retard delivery of fuel from the main nozzle during acceleration.

The invention embraces apparatus for promoting the automatic delivery into the mixing passage of a carburetor of an increased amount of fuel during periods of engine acceleration and at low engine speeds when the throttle valve of the carburetor is in full open or near open position.

Another object of the invention resides in the provision in a carburetor of a valved passage between a main :fuel delivery orifice and a .fuel chamber for admitting additional fuel to the main orifice under low speed conditions at open throttle and to promote improved acceleration and additionally to interrupt flow of liquid fuel through the passage when the engine is operating at comparatively high speeds or whenever the reduced pressure in the mixing passage is suflicient to cause the valve to close the bypass.

Another object of the invention :is the provision in a diaphragm carburetor of a valved bypass between the fuel chamber and the main delivery orifice into the mixing passage wherein the valve is responsive to reduced pressure in the mixing passage to effect a closing of the valve under certain operating conditions.

Another object of the invention resides in the provision in a diaphragm type carburetor of a fuel bypass and pressure responsive valve construction arranged between the fuel chamber and the main fuel delivery orifice whereby slight reduced pressure established in the mixing passage is ineffective to close the valve whereby additional fuel is delivered through the main orifice for enriching the mixture at open throttle low engine speeds under load and to improve acceleration of the engine.

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 1 is a top plan view of a charge forming device or carburetor embodying the invention;

FIGURE 2 is a longitudinal sectional view through the carburetor, the view being taken substantially on the line 22 of FIGURE 1;

FIGURE 3 is a transverse sectional view taken substantially on the line 33 of FIGURE 1;

FIGURE 4 is an end elevational view of the carburetor illustrated in FIGURE 1;

FIGURE 5 is a bottom plan view taken substantially on the line 55 of FIGURE 4;

FIGURE 6 is a detail sectional view taken substantially on the line 6-6 of FIGURE 5;

FIGURE 7 is a detail sectional view taken substantially on the line 77 of FIGURE 4;

.FIGURE 8 is a fragmentary sectional view taken substantially on the line 8-8 of FIGURE 5;

FIGURE 9 is a sectional view taken substantially on the line 99 of FIGURE 5;

FIGURE 10 is a fragmentary sectional view taken substantially on the line 10-40 of FIGURE 5, and

FIGURE 11 is a detail sectional view illustrating a modified form of the invention.

While the invention is illustrated and described herein as embodied in a charge forming apparatus or carburetor of the diaphragm type for supplying combustible mixture to internal combustion engines of either the two cycle or four cycle type, it is to be understood that the invention may be embodied in other types of carburetors.

Referring to the drawings in detail and initially to FIGURES 1 through 4, the charge forming apparatus or diaphragm carburetor comprises a body or body member 10 formed of cast metal or other suitable material of a nonporous character which is resistant to deterioration by hydrocarbon fuels. The body 10 is formed with a mixing passage 12 which includes an air inlet region 14, a Venturi 16, having a choke band or restriction 18, and a mixture outlet region 20.

The body 10 adjacent the air inlet region is formed with bosses 22 and 23 bored to journally support a shaft 24 equipped with a disc valve 26 providing a choke valve arrangement for starting the engine. An arm 28 is secured to the shaft 24 for manipulating the choke valve. The body 10 is provided with bosses 30 bored to journally support a shaft 32 on which is mounted a disc type throttle valve 34 for regulating the flow of fuel and air mixture to an engine with which the carburetor may be used. An exterior portion of the throttle shaft 32 is equipped with means 36 for connecting an operating member 37 with the throttle shaft.

The throttle shaft 32 is provided with an arm 38, an adjustable abutment screw 40 supported by the body 10 being engageable with the arm 38 for adjusting the engine idling or near closed position of the throttle valve 34.

The carburetor body has a mounting flange 42 at the outlet end 20 of the mixing passage, the flange having openings accommodating bolts 44 for securing the carburetor to the crankcase 46 of a two cycle engine, or for securing the carburetor to the manifold of an engine of the four cycle type. The body 10 adjacent the air inlet region 14 has threaded openings 48 to receive bolts for securing an air cleaner (not shown) to the body.

The carburetor body 10 is fashioned with a comparatively shallow circular recess providing a fuel chamber 50 adapted to contain liquid fuel. Extending across the fuel chamber 50 and forming a flexible wall thereof is a diaphragm 52 of impervious material, a circular gasket 53 being associated with the diaphragm. A generally circular member or closure plate 54 embraces the exterior major surface of the diaphragm 52, the member 54 having a recess or clearance space 56 to accommodate flexing movements of the diaphragm 52.

A fuel pump body 60 is disposed beneath the member 54 with a pumping diaphragm 62 positioned between the 3 member 54 and pump body providing a pumping or pulse chamber 64 and a fuel chamber 66, an arrangement hereinafter described. The carburetor body 10 at a region adjacent the periphery of the diaphragm 52 is provided with threaded openings and the

members

54, 60, the diaphragm 52 and gasket 53 fashioned with aligned openings to receive securing screws 68 for holding these components in assembled relation illustrated in FIGURES 2, 3 and 4.

The diaphragm clearance space or dry chamber 56 in member 54 is vented into the air inlet region 14 of the mixing passage in the manner illustrated in FIGURES 4 and 7. A bore in member 54 is in registration with a bore 71, the latter being equipped with a vent tube 72 opening into the air inlet region 14. The space 56 is in communication with the bore 70 by a passage 74. Thus the air chamber 56 is vented through passage 74, communicating bores 70 and 71 and vent tube 72 to the air inlet region of the carburetor. The chamber 56 may be vented direct to the atmosphere, if desired.

The diaphragm 52 is reinforced at its central region with disc-like members 73 and 75 disposed at opposite sides of the diaphragm, the discs being held in assembled relation with the diaphragm by a rivet 76 having a head portion 77. The diaphragm 52 is arranged to regulate or control flow of liquid fuel from the fuel pump or other fuel supply into the shallow fuel chamber 50. In the arrangement illustrated, connecting

fuel flow passages

78, 79 are provided from the fuel pump construction to an inlet 80 of the carburetor body. Where the fuel pump, or a fuel tank supplying fuel by gravity, is remote from the carburetor, the fuel inlet 80 is connected by a tube with the fuel supply.

The carburetor body 10 is provided with a threaded bore accommodating a fitting or valve cage 82 having a central passage in which is slidably disposed an inlet valve 84 having a cone-shaped valve portion 85, the valve portion 85 cooperating with a port provided by an annular valve seat 86 disposed in the bore accommodating the valve cage 82 for regulating or controlling fuel flow from the inlet 80 into the fuel chamber 50.

Pivotally supported or fulcrumed upon a pin 88 is a lever member 90, the pin being held in place by a threaded member 92 as shown in FIGURES 5 and 10.

The long arm 94 of the lever is adapted to be engaged by the head 77 of the rivet 76 carried by the diaphragm, the short arm 96 of the lever engaging the lower end of the valve body 84, as shown in FIGURE 3. An expansive coil spring 98 bottomed in a bore provided in the upper wall of the fuel chamber 50 is disposed close to the fulcrum pin 88 and engages the long arm 94 of the lever biasing the lever in a clockwise direction about its fulcrum, as viewed in FIGURE 3, normally urging the inlet valve 85 into seating position with the annular valve seat 86. The fuel chamber 50 is unvented and the diaphragm is flexed solely by aspiration or reduced pressure in the mixing passage 12.

By placing the spring 98 close to the fulcrum pin 88, a comparatively stiff spring 98 may be used and yet retain a high degree of sensitivity of control of the fuel inlet valve 85. The fuel chamber 50 is made as shallow as practicable and is disposed close to the mixing passage 12 to secure response of the diaphragm to low aspiration for delivering fuel into the mixing passage, and to reduce to a minimum the hydrostatic head of liquid fuel on the diaphragm. The upper wall of the fuel chamber 50 is fashioned with a recess 100 to accommodate swinging movement of the lever 90.

The carburetor is inclusive of a main nozzle or orifice construction for intermediate and high speed engine operation, the construction being preferably fashioned as a removable unit 102, shown in FIGURES 2, 6 and 8, and a secondary or supplementary fuel delivery system including engine idling and low speed orifices, shown in FIGURE 2, to facilitate idling of the engine and low speed operation. The main or primary nozzle arrange- A. ment or unit 102 includes a check valve construction for preventing back bleeding of air into the secondary fuel delivery system when the latter is delivering fuel into the mixing passage.

The main nozzle unit 102 is inclusive of a cylindricallyshaped fitting or cage 104 formed of brass or other suitable material snugly fitted or press fitted into a bore 106, as shown in FIGURE 6. The fitting 104 is provided with an axial bore 108 extending partially through the fitting. Arranged axially with the bore 108 is a counterbore 110 which accommodates a ball check valve 112. The bore 108, being of lesser diameter than the counterbore 110, provides an annular ledge or seat 114 for the ball valve 112.

Disposed in the upper or fuel delivery end of the fitting 104 is a grid 118 through which fuel is delivered into the mixing passage from the passages or bores in the fitting for normal and high speed engine operation.

As shown in FIGURE 2, the outlet or orifice 116 of the fitting 104 opens into the choke band region 18 of the Venturi 16 in the mixing passage. In assembly, the ball valve 112 is disposed in the counterbore 110, the grid member 118 disposed in position and the upper peripheral region of the fitting swaged to hold the grid 118 in place.

The grid 118 is spaced above the ball valve 112, a sufficent distance to facilitate movement of the valve from the seat 114 to provide for fuel flow around the valve. The ball check valve 112 is preferably fashioned of light weight material, such as nylon (polyamide resin) or polyoxymethylene (Delrin) so that the check ball will be lifted off of its seat under the influence of minimum lift or differential pressure. The fitting 104 is provided with a circumferential or peripheral recess 120 and transversely extending bores 122 establishing communication between the central bore 108 and the recess 120.

When the secondary orifice system is delivering fuel into the mixing passage, the check ball 112 seats on the ledge 114 and thereby prevents air bleeding through the main nozzle 116 into the secondary orifice system.

FIGURE 8 illustrates channel means and manually adjustable valve means for conveying and regulating fuel flow to the main fuel delivery unit 102. The body 10 is fashioned with a boss 126 having a bore 128 threaded to receive the threaded portion of a manually adjustable valve or valve body 130.

The bore 128 is in communication with a fuel chamber 50 by a passage or channel 132 and a restricted passage 134 connects the bore 128 with the peripheral recess 120 in the fitting 104. The valve body is provided with a needle valve portion 136 which cooperates with the restriction 134 to meter or regulate flow of liquid fuel to the interior of fitting 104 for delivery into the mixmg passage.

A counterbore in the boss 126 accommodates a sealing ring 140 surrounding the valve body 130. The valve body 130 is provided with a manipulating head 142, and an expansive coil spring 144 is disposed between the head and the sealing gasket 140 to exert pressure on the seal to prevent fuel seepage or leakage of air along the valve body. By reason of aspiration or reduced pressure in the mixing passage 12 under normal operating conditions fuel flows from the fuel chamber 50 through passage 132, the bore 128, restriction 134, recess 120, transverse bores 122 into the central bore 108 in the fitting for delivery past the check valve 112 into the mixing passage and mixed with air providing a combustible mixture.

The supplemental or secondary fuel delivery system is inclusive of a supplemental chamber 150, shown in FIG- URES 2 and 9, an engine idling orifice 152 and a low speed orifice 154 being in communication with the supplemental chamber 150.

The engine idling orifice 152 delivers fuel into the mixing passage on the downstream or engine side of the throttle valve 34 for engine idling purposes, and the low speed orifice 154 delivers fuel into the mixing passage when the throttle valve 34 is opened a slight amount for low speed engine operation. The lower end of the chamber 150 is closed by a Welsh plug 156.

FIGURE 9 illustrates the fuel channels and manually adjustable valve means for conveying and metering fuel flow to the engine idling and low speed orifices. The boss 126 is provided with a bore 162 threaded to receive the threaded portion of a valve body 164 having a manipulating head 165. A channel 166 establishes communication between the fuel chamber 50 and the bore 162. A restricted passage 168 connects the bore 162 with the supplemental or auxiliary chamber 150.

The valve body 164 is provided with a needle valve portion 169 which cooperates with the restriction 168 for metering or regulating fuel flow to the supplemental chamber 150. A sealing ring 163 is biased into sealing engagement with the valve body 164 by a coil spring 167. Thus, for engine idling and low speed engine operation, fuel flows through channel 166, bore 162, past the needle valve 169 through restriction 168 into the supplemental chamber 150 for delivery through the

orifices

152 and 154.

As shown in FIGURES 2, 3 and 4, the fuel pump is of the diaphragm type and is of the character shown in Phillips Patent 2,796,838. The pump includes the pump body 60 which has an annular recess providing a fuel receiving chamber 170, a cap 171 being secured to the pump body.

The cap 171 is provided with a nipple portion 172 to accommodate a tube (not shown) connected with a fuel tank or fuel supply. A screen 173 extends across the chamber 170 for filtering the incoming fuel.

The pumping diaphragm 62 is connected by channel means 181 through the mounting flange 42 with an opening in the engine crankcase 46 wherebythe pumping diaphragm 62 is pulsated or vibrated by varying fluid pressures in the engine crankcase for pumping fuel through the chamber 66. The pumping diaphragm 62 is provided with an integral inlet valve 174 which controls a port in communication with the fuel chamber 170, and an integral outlet valve 175 controlling an outlet port in the pump body 60 whereby fuel is pumped from the pumping chamber 66 past the outlet valve 175 and through the connecting

passages

78, 79 and 80 to the region of the inlet valve 85, shown in FIGURE 3.

The carburetor is inclusive of a valved passage or bypass between the main orifice 116 and the fuel chamber 50 for supplying additional fuel for delivery through the main orifice to provide for increased fuel delivery into the mixing passage and enrichment of the fuel and air mixture under wide open throttle conditions at low engine speed under load and for purpose of engine acceleration. The arrangement for supplying additional fuel is shown in FIGURES 5 and 6. The upper wall of the fuel chamber 50 is fashioned with a partial cylindrically-shaped recess 176 which is in communication with a counterbore 178 The counterbore 178 is adjacent a smaller counterbore 180, the counterbore 180 being in communication with the peripheral recess 120 in the fitting 104 through a restricted passage 182. Disposed at the entrance of the first counterbore 178 is a screen or grid 184. Loosely disposed in the counterbore 178 is a check valve or ball valve 186. It will be seen in FIGURE 6 that the recess 176, the connecting counterbores and the restriction 182 are axially aligned on the axis AA which is disposed at an angle relative to a horizonal plane substantially parallel with the diaphragm 52.

By disposing the bore 178 containing the check ball 186 at an inclination to a horizontal plane with the carburetor in upright position, the ball valve 178 normally falls by gravity to an open position to provide a passage or bypass for fuel flow to the main nozzle direct from the fuel chamber 50 in addition to the fuel normally delivered to 6 the main nozzle through the channel and needle valve arrangement shown in FIGURE 8.

In the operation of the arrangement of valved fuel bypass construction with the engine operating at normai or high speeds, the aspiration, reduced pressure or suction developed in the mixing passage by air velocity therethrough is sufficient to lift and maintain the check ball 186 onto its seat at the entrance of the counterbore 181] to interrupt or block fuel flow through the bypass restriction 182 to the main nozzle.

When the engine is operating at comparatively low speeds under load and the throttle valve is opened rapidly there is insuificient aspiration or suction in the Venturi acting on the main nozzle to seat the ball check member 186, and fuel flows direct from the fuel chamber 50 past the ball check valve 186 through the restriction 182 for delivery from the main orifice construction through the main orfice outlet 116 to thereby enrichen the mixture in the mixing passage being delivered to the engine.

The fuel enriched mixture causes rapid acceleration of the engine. As the engine approaches the speed for which the throttle is adjusted, the aspiration or suction increases in the Venturi and the aspiration or reduced pressure, transmitted through the passages in the main orifice unit construction 102 and the restriction 182, is sufficient to maintain the ball valve 186 in its seat and thereby interrupt fuel flow through the bypass restriction 182.

Under another condition, viz. the throttle being substantially open and the engine operating under load at low speed, the aspiration or suction in the mixing passage is insufiicient to hold the ball valve 186 in its seat, and hence additional liquid fuel from the fuel chamber 51) flows through the open restriction or passage 182 and through the main nozzle 116 to provide a full power or enriched fuel and air mixture in the mixing passage at low air flow.

The ball check valve 186 is always in open position during engine idling because the aspiration or suction in the mixing passage at the region of the main orifice is of low amplitude when the throttle is in closed or near closed position. Under conditions where the speed of the engine increases generally in proportion to the position of opening of the throttle valve, fluel flow through the bypass or restriction 182 continues only until the pressure differential between the main nozzle 116 and the fuel chamber 511 is sufiicient to lift the ball check valve 186 onto its seat.

The differential pressure which will cause the ball valve 186 to be lifted onto its seat is, in a measure, dependent upon the weight of the ball valve and the size of the restriction 182. It is found desirable to fashion the restriction 182 of a size to provide sufiicient fuel to provide an enriched mixture for acceleration purposes. The check ball 186 may be made of a material such as nylon or Delrin as a check ball fashioned of these materials has been found to be influenced by comparatively low aspiration or suction in the mixing passage to interrupt the flow of liquid fuel through the bypass 182 without overenriching the mixture, a condition which would lower the efficiency of the engine in lieu of the intended purpose of securing increased acceleration through a properly enriched mixture.

If it is desired to maintain an enriched mixture until the engine reaches a higher speed with a consequent increase in air velocity through the mixing passage, the ball valve 186 may be made of metal so that higher aspiration or suction in the mixing passage is required to elevate the ball valve 186 onto its seat. The check ball 186 is made of a material of greater density than the liquid fuel so that the ball normally falls away from its seat by gravity.

FIGURE 11 illustrates a modified form of valved fuel passage or bypass for admitting additional fuel into the mixing passage under certain operating conditions. In the form shown in FIGURE 11, the valved bypass is em- '3 a bodied in the main orifice unit construction. In this form the carburetor body 10' is fashioned with a bore 106 and snugly fitted or pressed into the bore 106 is a fitting 190 similar in shape to the fitting 104, shown in FIGURE 6. The fitting 190 is fashioned with a central bore 192 and a peripheral recess 194, the bore being in communication with the recess through transverse passages 196.

The peripheral recess 194 receives fuel in the normal manner from the fuel chamber 50' through a fuel channel and metering valve arrangement of the character shown in FIGURE 8 and hereinbefore described. The upper portion of the fitting 190 is fashioned with a counterbore 198 of larger diameter in which is loosely disposed a ball valve 290 which seats on the ledge 201 between the bore 192 and the counterbore 198.

The ball valve 200 is adapted to prevent back bleeding of air through the main nozzle into the secondary fuel delivery system when the latter is delivering fuel into the mixing passage.

A grid 202 is mounted in the orifice 2114 of the fitting and prevents dislodgement of the back bleeding check valve 200. The lower portion of the fitting 190 is provided with a counterbore 208 of larger diameter than the bore 192 and is in communication therewith. An annular ledge or seat 210 is formed at the juncture of the

bores

192 and 208 and provides a seat for a ball check valve 212 of lesser diameter than the bore 208 to facilitate fuel flow around the ball valve 212 when it is out of engagement with its seat 210.

Disposed beneath the ball check valve 212 at the lower end of the fitting 190 is a Welsh plug 214 or other closure means provided with a fuel passage 216 opening into the fuel chamber 50 and preferably offset from the axis of the bore 268 so that when the ball valve 212 is engaged with the Welsh plug 212, such engagement will not impede or block flow of fuel through the passage 216. The ball valve 212 is loosely disposed in the counterbore 298 and is enabled to fall by gravity away from its seat into contact with the Welsh plug 214 so as to permit the admission of fuel through the passage 216 for delivery through the outlet or orifice 204 into the mixing passage.

The arrangement shown in FIGURE 11 functions substantially in the same manner as the arrangement shown in FIGURES and 6. Under normal engine operation the fuel is admitted into the recess 196 from a fuel channel system of the character shown in FIGURE 8. When the engine is idling, the ball valve 212 is in engagement with the Welsh plug 214 under the influence of gravity. If the throttle valve is suddenly opened, the air velocity through the mixing passage is low and does not establish sufficient suction or aspiration to elevate the ball valve 212 onto its seat 210.

Hence, during the period of acceleration of the engine, additional fuel flows from fuel chamber 50 through the passage 216, bores 208, 192 and 1% around the

ball valves

212 and 200 and is delivered through the main orifice 204 to enrich the mixture in the mixing passage. A similar condition obtains when the engine is operating under heavy load at low speed so that additional fuel flows through the bypass and past the

valves

212 and 200 into the mixing passage.

As the engine increases in speed, the aspiration or reduced pressure becomes greater in the mixing passage to an extent as to elevate the ball 212 into engagement with the valve seat 210 thereby interrupting or blocking further delivery of additional fuel by way of the bypass arrangement into the mixing passage.

During normal or high engine speeds, the ball valve 212 is maintained in fuel blocking position by high aspiration or suction existent in the mixing passage. The engine, during such periods receives the normal mixture of fuel delivered through the conventional channel system and past the manual metering and regulating valve shown in FIGURE 8.

It is to be understood that the enrichment valve arrangement is not limited to use in a diaphragm type carburetor but may be utilized in carburetors wherein float controlled valve means is employed for regulating fuel flow from a supply into the carburetor fuel chamber.

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:

1. In combination, charge forming apparatus including a body having a mixing passage, an unvented fuel chamber in said body, a flexible impervious diaphragm responsive to aspiration in the mixing passage and forming a wall of the fuel chamber, a fuel inlet for the fuel chamber, an inlet valve for the fuel inlet, means associated with the diaphragm engageable with the fuel inlet valve for regulating flow of liquid fuel from a supply into the fuel chamber, a fuel delivery orifice opening into the mixing passage, fuel channel means in said body arranged to deliver fuel from the fuel chamber into the mixing passage through said orifice, manually adjustable valve means for regulating fuel flow through said fuel channel means into the mixing passage, a fuel bypass in said body for conveying fuel from the fuel chamber into the mixing passage independently of fuel flow regulated by the manually adjustable valve means, the axis of the bypass being angularly arranged with respect to the diaphragm, said bypass including a counterbore providing a valve seat in said bypass, and a ball valve of lesser diameter than the counterbore disposed for free movement in the counterbore, said ball valve being loosely disposed below said valve seat and normally maintained by gravity out of engagement with the valve seat, said ball valve being responsive to increased aspiration in said mixing passage to engage the ball valve with the valve seat to interrupt fuel flow through the bypass.

2. In combination, a charge forming apparatus including a body having a mixing passage, an unvented fuel chamber in said body, a flexible impervious diaphragm responsive to aspiration in the mixing passage forming a wall of the fuel chamber, a fuel inlet for the fuel chamber, an inlet valve for the fuel inlet, means associated with the diaphragm engageable with the fuel inlet valve for controlling flow of liquid fuel from a supply into the fuel chamber, orifice means opening into the mixing passage, fuel channel means in said body arranged to deliver fuel from the fuel chamber into the mixing passage through the orifice means, means associated with said fuel channel means for metering fuel flow through the channel means, a fuel bypass independent of said fuel metering means in communication with the fuel chamber and the mixing passage, said fuel bypass including a valve chamber formed with a valve seat, a ball valve disposed for free movement in said valve chamber, said ball valve being loosely disposed below said valve seat and normally spaced from its seat by gravity to accommodate flow of additional fuel through the bypass into the mixing passage under low aspiration in the mixing passage, said ball valve being influenced by increased aspiration in the mixing passage for interrupting fuel flow through said fuel bypass.

3. In combination, charge forming apparatus including a body having a mixing passage, an unvented fuel chamber in said body, a flexible impervious diaphragm forming a wall of the fuel chamber, a fuel inlet for the fuel chamber, an inlet valve for the fuel inlet, means associated with the diaphragm engageable with the fuel inlet valve for regulating flow of liquid fuel from a supply into the fuel chamber, a fitting in an opening in said body having an outlet providing a main orifice for delivering fuel into the mixing passage, a secondary orifice in said body opening into the mixing passage, said fitting having a passage in communication with the outlet, fuel channel means in said body for conveying fuel from said fuel chamber to the passage in said fitting and to said secondary orifice, manually adjustable valve means associated with the fuel channel means for regulating fuel flow to the passage in said fitting, a fuel bypass for conveying fuel from the fuel chamber direct to the fuel passage in said fitting, said fitting being fashioned With counterbores providing two valve seats, a first valve means comprising a ball member in one counterbore in said fitting for preventing back bleeding of air through the main orifice when the secondary orifice is delivering fuel into the mixing passage, and a second valve means comprising a ball member in the second counterbore for said fuel bypass responsive to aspiration in the mixing passage for controlling fuel flow through the bypass.

4. The combination according to claim 3 including a closure for the end of the fitting adjacent the second counterbore, and a fuel passage in said closure offset from the axis of said second counterbore.

References Cited UNITED STATES PATENTS HARRY B. THORNTON, Primary Examiner. R. R. WEAVER, Assistant Examiner.

Claims

2. IN COMBINATION, A CHARGE FORMING APPARATUS INCLUDING A BODY HAVING A MIXING PASSAGE, AN UNVENTED FUEL CHAMBER IN SAID BODY, A FLEXIBLE IMPERVIOUS DIAPHRAGM RESPONSIVE TO ASPIRATION IN THE MIXING PASSAGE FORMING A WALL OF THE FUEL CHAMBER, A FUEL INLET FOR THE FUEL CHAMBER, AN INLET VALVE FOR THE FUEL INLET, MEANS ASSOCIATED WITH THE DIAPHRAGM ENGAGEABLE WITH THE FUEL INLET VALVE FOR CONTROLLING FLOW OF LIQUID FUEL FROM A SUPPLY INTO THE FUEL CHAMBER, ORIFICE MEANS OPENING INTO THE MIXING PASSAGE, FUEL CHANNEL MEANS IN SAID BODY ARRANGED TO DELIVER FUEL FROM THE FUEL CHAMBER IN TO THE MIXING PASSAGE THROUGH THE ORIFICE MEANS, MEANS ASSOCIATED WITH SAID FUEL CHANNEL MEANS FOR METERING FUEL FLOW THROUGH THE CHANNEL MEANS, A FUEL BYPASS INDEPENDENT OF SAID FUEL METERING MEANS IN COMMUNICATION WITH THE FUEL CHAMBER AND THE MIXING PASSAGE, SAID FUEL BYPASS INCLUDING A VALVE CHAMBER FORMED WITH A VALVE SEAT, A BALL VALVE DISPOSED FOR FREE MOVEMENT WITH A VALVE CHAMBER, SAID BALL VALVE BEING LOOSELY DISPOSED BELOW SAID VALVE SEAT AND NORMALLY SPACED FROM ITS SEAT BY GRAVITY TO ACCOMODATE FLOW OF ADDITIONAL FUEL THROUGH THE BYPASS INTO THE MIXING PASSAGE UNDER LOW ASPIRATION IN THE MIXING PASSAGE, SAID BALL VALVE BEING INFLUENCED BY INCREASED ASPIRATION IN THE MIXING PASSAGE FOR INTERRUPTING FUEL FLOW THROUGH SAID FUEL BYPASS.