US2626137A

US2626137A - Carburetor

Info

Publication number: US2626137A
Application number: US196372A
Authority: US
Inventors: Gordon P Tapley
Original assignee: Niles Bement Pond Co
Current assignee: Niles Bement Pond Co
Priority date: 1950-11-18
Filing date: 1950-11-18
Publication date: 1953-01-20
Anticipated expiration: 1970-01-20

Description

G. P. TAPLEY Jan. 20, 1953 CARBURETOR 1 Original Filed Jun 7, 1946 2 SHEETS SHEET 1 INVENTOR. I THPLE'y AGENT Patented Jan. 20, 1953 UNITED STATES PATENT OFFICE CARBURETOR of New Jersey Continuation of application Serial No. 675,242, June 7, 1946. This application November 18, 1950, Serial No. 196,372

17 Claims.

This invention relates to carburetors for internal combustion engines, and particularly to carburetors of a type now used extensively on aircraft, such as disclosed in U. S. Patents to Twyman, 2,391,755, December 25, 1945, and Chandler, 2,394,664, February 12, 1946.

This application is a continuation of my application, Serial No. 675,242, filed June '7, 1946, and later abandoned.

In such carburetors, it is customary to provide means whereby the pilot, or other person in charge of the engine, can manually select either a rich fuel-air mixture or a lean fuel-air mixture. The rich mixture is generally used under high power output conditions, such as takeoff, climbing and high speed. The lean mixture is used under cruising conditions for purposes of economy. Engines tend to run hotter with lean mixtures than with rich mixtures. The carburetor is usually so designed that the lean mixture obtained by manual selection is about as lean as can be 'used under cruising conditions without overheating. The mixture so supplied is too lean for safe use under high power output conditions. It sometimes happens that the pilot forgets that he has set his mixture control in the lean position and attempts to operate the engine at high power output. This may result in overheating of the engine. Enrichment valves are therefore customarily provided to increase the fuel-air ratio at the higher power outputs.

In. carburetors of the type described herein, the mixture control takes the form of a pair of parallel passages, each having a metering restriction in it, and a selector valve movable between a lean position wherein only one passage is open to the flow of fuel and a rich position wherein both passages are open. The enrichment valve takes the form of a valve connected in parallel with the restriction in the one lean passage and movable in an opening direction by the fuel pressure differential across the restriction. The fuel pressure differential is varied by suitable mechanism as a function of the engine power output. The enrichment valve is spring biased to closed position. The strength of the biasing spring determines the value of fuel pressure difierential, and hence of power output, at which the enrichment valve starts to open, and the rate at which its opening increases with increasing power output.

Since the range of useful fuel-air ratios has a definite upper or rich limit as well as a lean limit, some means must be provided for limiting the flow thru the enrichment valve. ,Since this upper limit of useful fuel-air ratios is not ailected by the position of the manual mixture control, it is usually desired to have the same upper limit of fuel-air ratio regardless of the mixture control position. It has been the practice in the past .to achieve this limiting effect by providing an additional metering restriction to receive both the discharge from the enrichment valve and the discharge from the rich metering restriction. Such a limiting restriction effectively established a'n'upper limit to the fuel-air ratio and the upper limit was the same at both positions of the mixture control valve. .See patents to Twyman and Chandler, cited.

The series limiting restriction had one undesirable feature. When the mixture control was in its lean position, there was no flow thru the limiting restriction until the enrichment valve opened. Hence there was no pressure drop thru the limiting restriction and the total fuel pressure differential across the fuel metering system was available to open the enrichment valve against the biasing action of its spring. However, when the mixture control was in its rich position, there was a flow thru the limiting restriction at all times. The resulting pressure drop thru the limiting restriction reduced the fuel pressure differential available to open the enrichment valve. Hence the enrichment valve did not open until the total fuel pressure differential across the fuel metering system was somewhat higher than the fuel pressure. differential required to open the enrichment valve when the mixture control was in its lean position. In other words, when the mixture control was in its rich position, a higher power output was required to begin opening of the enrichment valve than when the mixture control was in the lean position. Since it is necessary that the enrichment valve open after a certain power output is exceeded, regardless of the position of the manual mixture control, it was customary to design the enrichment valve spring so that the enrichment valve opened at the required value of power output with the mixture control in its rich position. The result was that when the mixture control was in its lean position, the enrichment valve opened at a lower value of power output, where it was actually not needed. This resulted in a waste of fuel. It was especially undesirable because the high fuel consumption occurred under conditions (mixture control set lean and engine running at highest cruising power output) where the best efficiency should be expected.

It is, therefore, an object of this invention to 3 provide an improved carburetor for an internal combustion engine.

Another object is to provide, in a carburetor having ainanual mixture control movable between lean and rich positions, improved1 enrichment valve mechanism responsive to fuel pressure difierential and opening at the same value v of fuel pressure differential regardless of the mixture control position.

Another object is to provide, in a carburetor of the type described, improved enrichment valve mechanism, whereby the same rich mixture is obtained at high power outputs, regardless of the position of the manual mixture control.

Other objects and advantages of thepresent invention will become apparent from thecon v sideration of the appended specification, claims mixture outlet 20. The mixture passes from the outlet 20 to the engine. In most, cases, a supercharger. is used between the outlet 28 and the engine. In some cases a second supercharger is used upstream from the entrance I2.

Air flowing thru the venturi I4 creates an air pressure differential between the entrance and throat of the ,venturi, which differential varies with the velocity of the air flowing. This air pressure differential is utilized to create a flow of air thru a secondary air conduit connecting the entrance and throat of the venturi. A plurality of impact tubes 22 are provided in the en,- trance 1 2, with their ends open to receive the impact: f. the ent ringair. Air flow n thru. th secondary conduit iustmention d. ent rs. these impact tubes a d, pas st a comm n passa e 2. u ual y ermed a vent, rin Fr m th ent ring24, the, air flows thru a conduit 26, a chamber 28 in a fuel meter generally indicated, at. 3.0, a fixedrestriction 32, an expansible chamber 34- in the fuel meter a conduit 36, past a valve 38 into a, chamber 40, and thence thru aconduit 42 to the throat of venturi l4.

Valve 38 ispositioned by a bellows 4.4, located the-chamber 48. The bellows 44. is. sealed so as to. expand and contract, with variations in pressure in chamber 46,, The bellows 44 is preferably partially filled with nitrogen or other suitable fluid having an appreciable coefiicient of thermal expansion, so that it also expands and contracts with variations in the air temperature. Since the bellows 44 responds to both temperature and pressure, it may besaid to respond to air density. The valve 36 is contoured with relation to the response characteristics of the bellows 44 so that the pressure differential appearing across the fixed restriction 32 in the fuel meter 30 is an accurate measure of the mass rate of air flow passing thru the venturi. In other words, the bellows operated valve 38 compensates for changes in density of the air passing thru the venturi.

Fuel enters the carburetor from a pump (not shown) and flows thru a conduit 50, past a valve 52 in the fuel meter 30, thru aconduit 54, toa mixture control 56 including ,adisc, valve 58 fixed on a shaft 60. From the mixture control 56, the fuel flows thru one or both of a pair of parallel conduits 62 and 64 into a jet system 66. From the jet system 66, the fuel flows thru an idle valve 68, a conduit 10, .a pressure regulator 12 and a conduit 14 to the fuel discharge nozzle I8.

I The fuel meter 30 includes a chamber 16 in addition to the

expansible chambers

26, 34 and 53 previously described. Chambers 16 and 28 are separated by a flexible diaphragm 18.

Chambers

28, and 34 are separated by a flexible diaphragm 80, and, chambers 34 and 53 are separated by a flexible diaphragm 82. The three

diaphragms

18, 86 and 82 are attached at their centers to the stem of the valve 52, which is balanced against-inlet pressure. Chamber 16 is connected thru a conduit 84 to the conduit 18 in the fuel line on the downstream side of the jet system 66. Chamber 53 is, of course, supplied with fuel at the pressure existing on the upstream side of the jet system. It may, therefore, be seen that the valve 52 is, positioned in accordance with the balance between, a downwardly acting force which is a measure of the rate of flow of air to the engine, and an upwardly acting force which is a measure of the rate of flow of fuel to the engine. The downwardly acting force is the difference between the pressures in

chambers

28 and 34, which difference" is applied to the diaphragm 86.. The upwardly acting force is the difference between the pressures in chambers 53 and I6, which is the fuel pressure differential across the jet system. Whenever the fuel flow is disproportionate with respect to the air flow, the valve 52 is moved to correct the fuel flow and maintain the same fuel-to-air ratio as before. The foregoing statement, with respect to the constant fuel-air ratio, assumes that the crosssectional area in the jet system open to the flow of fuel therethru is a constant. This, however, is not strictly constant, but is varied manually and. automat cally under a n o Fuel entering the jet system 66 thru conduit 62 may pass thru a restriction 86 directly to the outlet of the jet system. It may also pass thru a passage 88 controlled by an enrichment valve 90 biased to closed position by a spring 92. Fuel passing thru the conduit 64 flows thru a fixed restriction93. The opening movement of valve 90 is limited by a stop 94. A branch conduit 96 is provided, which connects the conduits 62 and 64 at pointsupstream from the restrictions therein. Flow thru the conduit 96 is controlled by a checl; valve 98, biased to closed position by a spring I80.

When the disc valve 58 of the mixture control 56 is in the position shown in full lines in the drawing, which is termed the lean position, fuel may enter the jet system only thru the conduit 62. With the valve 58 in its rich position, as shown in dotted lines on the drawinafuel may nter he i t t m t ru both conduits 62 and 64.

When the valve 58 is in its lean position, a first predetermined relationship is established between the fuel pressure differential across the jet system and the rate of flow of fuel. When the valve 58 is in its rich position, a second such relationship is established, such that a greater fuel flow is obtained for each value of fuel pressure differential. Since the fuel meter 36 establishes a fixed relationship between the mass air flow and the fuel pressure differential,

itmay be seen that movement of valve 58 between its "lean and rich positions selects respectively smaller and greater fuel-air ratios. The enrichment valve 99 opens under high fuel pressure differential conditions, which cor-v respond generally to conditions of high power output, to increase the fuel-air ratio. It should be noted that the operation of valve 99 is the across the jet system acts on the valve 98, tend- I ing to open it. When this fuel pressure differential exceeds a value determined by the strength of spring I99, the valve 98 opens. If the fuel pressure differential continues to increase, the valve 98 opens wider. After it reaches its wide open position, the relationships between the fuel pressure differential across the jet system and the total fuel flow thru the jet system are substantially the same as when the mixture control is in its rich position, even though the manual mixture control may actually be in its lean position. It is usually desirable 'to establish the rates of springs 92 and I99 so that valve 98 opens at a somewhat higher fuel pressure differential than valve 99.

When the mixture control is in its rich position, the fuel pressures on the opposite sides of valve 98 are the same, and the valve therefore remains closed under the influence of its biasing spring I99.

In the chart of Figure 2, the ordinates denote fuel/air ratios of the fuel/air mixture delivered to the engine, and the abscissas denote percentages of maximum air flow to the engine throughout its range of operation from minimum to maximum speed and power output. The curve ABCDEF represents the fuel/air ratios that obtain at various rates of air flow from minimum to maximum speed and. power output, when the manual mixture control 58 is in its rich position, while curve AGHIEF denotes the corresponding fuel/air ratios that obtain when the manual mixture control is in its lean position.

From these curves, it will be noted that the horizontal portion BC of the rich curve, and GH of the lean curve, show the respective constant mixture ratios that are obtained when the manual mixture control is in its rich and lean positions, before the enrichment valve 99 commences to open (i. e., between approximately 30 and 60 per cent of maximum air flow). At point C on the rich curve and point H on the lean curve, the fuel pressure differential reaches a value sufficient to commence the opening of enrichment valve 99. As valve 99 continues to open wider with increasing air flow (and corresponding fuel pressure differential), and the manual mixture control is in its rich position, the fuel/air ratio is progressively increased, as shown by the portion CDE of the rich curve. At point E (at approximately 90 per centof maximum air flow), the stop 94 limits the further opening of valve 99, whereupon .the fuel/air ratio reaches its maximum valve and remains constant at that value when the air flow further increases from 90' to 100 per cent of maximum air flow, as shown by the horizontal portion EF of the rich curve.

Similarly, when the manual mixture control is in its lean position, the opening of valve 99 with increasing air flow progressively increases the fuel/air ratio, as shown by the portion HI of the lean curve. When the manual mixture control 58 remains in its lean position and the air flow increases beyond point I (at about per cent of maximum air flow), valve 98 commences to open, and the fuel/air ratio is progressively increased by the further opening of both 99 and 98, as shown by the portion IE of the lean curve. At point E, both valves 99 and 98 are at their maximum opening and the fuel/air ratio is at its maximum value, and remains constant at such value when the air flow further increases from to per cent of maximum air flow, as shown by the horizontal portion EF of the lean curve.

It will further be noted, from Fig. 2, that the curved portions CD and HI of the rich and lean curves are parallel which indicates that the rate of enrichment from 60 to 80 per cent of maximum air flow is the same, regardless of whether the manual mixture control 58 is in its rich or lean position. When the air fio-w increases from 80 to 99 per cent of maximum air fiow, and mixture control 58 is in its rich position, valve 99 does not open, hence the fuel air ratio is increased only by the further opening of valve 99. However, if mixture control 58 is in its lean position, the increase of air fiow from 80 to 90 per cent causes valve 98 to open, and the fuel/air ratio increases from point I to point E at a greater rate than between points D and E on the rich curve (when 98 is closed). Since the lean curve coincides with the rich curve from points -D to E, it will be seen that the maximum fuel/air ratio is the same, regardless of whether the mixture control 58 is in its lean or rich position. It is also to be noted that the portion EF of both rich and lean curves is horizontal, denoting a constant fuel/air ratio, during a substantial portion (e. g., 10 per cent) of the operating range of the engine.

From the foregoing, it may be seen that the valve 98 insures that if the engine is operated at high power output with the manual mixture control in the lean position, then the actual mixture delivered to the engine will be just as rich as if the manual control had been moved to its rich position. It may also be seen that the enrichment flow thru valve 99 is limited by stop 94, and that the'flow thru valve 98 is limited by restriction 93.

The idle valve mechanism 68 includes a valve member I92 movable by means of an arm I94 connected thru a link I 96 to an arm I98 on the shaft H9 of the throttle I6. It will be noted that a spring H2 is provided, biasing the valve 52 toward open position; The spring H2 and the valve I92 cooperate to control the fuel flow to the engine under conditions of light load. When the engine is producing substantial power, the throttle I6 is fairly wide open, and the valve I92 is retracted to a position where it does not appreciably restrict the fuel flow. As throttle I6 approaches its closed position, the valve I92 is moved concurrently with the throttle to increasingly restrict the fuel flow. At the same time, the air flow thru the venturi I 4 is becoming less due to the restricted position of the throttle, so that the air pressure difierential actin on diaphragm an isbecoming: verrasmalh Under such; conditions, the spring; H2 becomes the predominating downward force acting on valve 52. 'The action of spring II2 may be described by saying that it sets a minimum fuel pressure, differential; across the jet system. If thedownward force, dueto, the. air pressure differential on diaphragm 80, be neglected, which is permissible under engine idling conditions, then it may be said that the spring H2 establishes a constant fuel pressure differential across the jet system, and that the valve I02 controls thev fuel flow obtained with that constant fuel, pressure differential in accordance with; thecontourof valve I02 and the throttle P ion, such an; .:arrangem n is, necess ry because of: theinaccuracy of the air. flow measurin system a v ry low flows.

The pressure regulator 12 is providedto prevent variations'in pressure at the fuel nozzle I8 from aifecting the now thru the jet system. The regulator i2 includes a valve H4 biased to closed position by a spring H6. A diaphragm IIB separates a pair of expansible chambers I20 and I22. The chamber I20 receives fuel atthe pressure on, the downstream side of the jet system, while chamber I22 is vented to vent ring 24 thru conduit I24 and conduit 26. The efiect of this arrangement is to maintain a substantially constant pressure on the downstreamside of the jet system. Y

The terms and expressions which I have employed are used as terms of description and not of limitation, and I have no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but recognize that various modifications are possible within the scope of the invention claimed.

I claim as my invention: 1

l. A fuel supply system for an internal combustion engine, comprising a main conduit for fuel flowing to said engine, a pair of parallel branch conduits connecting two spaced portions of said main conduit, a selector valve at one of the junctions of said branch conduits with said main conduit, said selector valve being movable between a first position wherein only one'of said branch conduits is open and a second position wherein both said branch conduits are open, metering restrictions in each of said branch conduits for determining the rate of fuel flow to the engine throughout its operating range, means for controlling the fuel pressure differential between said portions of said main conduit, said selector valve being effective upon movement to said first and second positions to establish respectively first and second relationships between said fuel pressure differential and the rate of flow of fuel to'said engine, a third branch conduit connecting said pair of branch conduits at points between said selector valve and said restrictions, a check valve-in said third branch conduit, spring means biasing said check valve closed, said check valve being inoperable when said selector valve is in said second position and being operable to open position by the fuel pressure differential when said selector valve is in said first position and said pressure differential exceeds a value determined by the characteristics of said spring means,. whereby, when said pressure difierential exceeds said value, the rate of flow of fuel to the engine is gradually increased, to the same, constant, maxi:

mum value whether the selector valve, is in its firstv or second position.v

2. Fluid flow control apparatus, comprising a main conduit, a pair of parallel branch conduits connecting two spaced portions of said main conduit, a selector valve at one of the junctions of said branch conduits with said main conduit, said selector valve being movable between a first position wherein only one of said branch conduitsis open and a second position wherein both of said branch conduits are open, metering restrictions ineach of said branch conduits for determining the rate of fuel flow to the engine throughout its operating range, said selector valve being effective upon-movement to said first and second positions to'establish respectively-first; and second relationships between: the fluid pressure differential between said portions of' said main conduit and therate offlowofi fluidtherethru, a third branch conduit connecting said pair of branch conduits at points between said selector valve and said restrictions, a check valve in said third branch conduit, and spring means biasing said check valve closed, said check valve being inoperable when said selector valve is insaid second position and being operable to open position by said fluid pressuredifierential when said selector valve is in said first position and said pressure differential exceeds a value determined by the characteristics of said spring means, whereby, when said pres,- sure differential exceeds said value, the rate of flow of fluid thru said main conduit is gradually increased to the same constant maximum value whether the selector valve is in its first or second position.

'3. A fuel supply system for. an internal combustion engine, comprising a main conduit for fuel flowing to said engine, a pair of parallel branch conduits connecting two spaced portions of said main conduit, a selector valve at one of the junctions of said branch conduits with said main conduit, said selector valve being movable between a first position wherein only one of aid branch conduits iso en and a second position wherein both said branch conduits are 'open,

meterin restrictions in each of said branch conduits for determining the rate of fuel fiow to the en ine throughout its operatin ran e. means for controlling the fuel pressure differential between said portions of said main conduit, said selector valve being effective upon movement to said first and second po itions to establish'respectively first and second relationships between said fuel pressure differential and the rate of flow of fuel to said engine, a third branch conduit connecting said pair of branch conduits at points between said selector valve and said restrictions, a check valve in said third branch conduit opening in the direction of flow from said one branch conduit to the other, spring means biasin said check valve closed in opposition to the difference between the fuel pressures acting on o posite sides thereof, said check valve being inoperable when said selector valve is in said second position and being operable to open position by said difference of fuel pressures when said selector valve is in said first position and said pressure differential exceeds a value determined by the characteristics of said spring means; whereby, when said pressure differential exceeds said value, the rate of flow of fuel to the engine is gradually increased to the same constant maximum value whether the selector valve is in its first or second position.

4. ,A'fuel supply system for an internal C0111: bustion engine comprising, aconduit for combustion air flowing to said engine, means associated with said conduit for producing two unequal air pressures whose difference is a measure of the rate of flow of air thru said conduit, a main conduit for fuel flowing to said engine, a pair of parallel branch conduits connecting two spaced portions of said main conduit, a selector valve at the upstream junction of said branch conduits with said main conduit, said selector valve being movable between a first position wherein only one of said branch conduits is open and a second position wherein both said branch conduits are open, metering restrictions in each of said branch conduits for determining the rate of fuel flow to the engine throughout its operating range, means responsive to the difference between said two unequal air pressures for controlling the fuel pressure differential between said portions of said main conduit, said selector valve being effective upon movement to said first and second positions to establish respectively first and second relationships between said fuel pressure differential and the rate of flow of fuel to said engine, a third branch conduit connecting said pair of branch conduits at points upstream of the restrictions therein, a check valve in said third branch conduit opening in the direction of flow from said one branch conduit to the other, spring means biasing said check valve closed in opposition to the difference between the fuel pressures acting on opposite sides thereof, said check valve being inoperable when said selector valve is in said second position and being operable to open position by said. difference of fuel pressures when said selector valve is in said first position and said pressure differential exceeds a value determined by the characteristics of said spring means, whereby, when said pressure differential exceeds said value, the rate of flow of fuel to the engine is gradually increased to the same constant maximum value whether the selector valve is in its first or second position.

5. Fluid flow control apparatus, comprising a main conduit, a pair of parallel branch conduits connecting two spaced portions of said main conduit, a selector valve at one of the junctions of said branch conduits with said main conduit, said selector valve being movable between a first position wherein only one of said branch conduits is open and a second position wherein both of said branch conduits are open, metering restrictions in each of said branch conduits for determining the rate of fuel flow to the engine throughout its operating range, said selector valve being effective upon movement to said first and second positions to establish respectively first and second relationships between the fluid pressure differential between said portions of said main conduit and the rate of flow of fluid therethru, a third branch conduit connecting said pair of branch conduits at points between said selector valve and said restrictions, a check valve in said third branch conduit opening in the direction of flow from said one branch conduit to the other, spring means biasing said check valve closed in opposition to the difference between the fluid pressures,

acting on opposite sides thereof, said check valve being inoperable when said selector valve is in said second position and being operable to open position by said difference of fluid pressures when said selector valve is in said first position and said pressure difierential exceeds a value determined by the characteristics of said spring means, whereby, when said pressure differential exceeds said value, the rate of flow of fluid thru said main 10 conduit is gradually increased to the same constant maximum value whether the selector valve is in its first or second position.

6. Fluid flow control apparatus, comprising a main conduit, a pair of parallel branch conduits connecting two spaced portions of said main conduit, a selector valve at the upstream junction of said branch conduits with said main conduit, said selector valve being movable between a first position wherein only one of said branch conduits is open and a second position wherein both of said branch conduits are open, metering restrictions in each of said branch conduits for determining the rate of fuel flow to the engine throughout its operating range, said selector valve being effective upon movement to said first and second positions to establish respectively first and second relationships between the fluid pressure differential between said portions of said main conduit and the rate of flow of fluid therethru, a third branch conduit connecting said pair of branch conduits at points between said selector valve and said restrictions, a check valve in said third branch conduit opening in the direction of flow from said one branch conduit to the other, spring means biasing said check valve closed in opposition to the difference between the fluid pressures acting on opposite sides thereof, said check valve being inoperable when said selector valve is in said second position and being operable to open position by said difference of fiuid pressures when said selector valve is in said first position and said pressure differential exceeds a value determined by the characteristics of said spring means, whereby, when said pressure differential exceeds said value, the rate of flow of fluid thru said main conduit is gradually increased to the same constant maximum value whether the selector valve is in its first or second position.

7. A fuel supply system for an internal combustion engine, comprising a main conduit for fuel flowing to said engine, a pair of parallel branch conduits connecting two spaced portions of said main conduit, a selector valve at one of the junctions of said branch conduits with said main conduit, said selector valve being movable between a first position wherein only one of said branch conduits is open and a second position wherein both said branch conduits are open, metering restrictions in each of said branch conduits, means for controlling the fuel pressure differential between said portions of said main conduit, said selector valve being effective upon movement to said first and second positions to establish respectively first and second relationships between said fuel pressure difierential and the rate of flow of fuel to said engine. a passage connected in parallel with said meteringrestrictions, an enrichment valve in said passage movable in an opening direction by said fuel pressure differential, spring means biasing said enrichment valve closed, stop means for limiting the opening movement of said enrichment valve, a

third branch conduit connecting said pair of branch conduits at points between said selector valve and said restrictions, a check valve in said third branch conduit, spring means biasing said check valve closed, said check valve being inoperable when said selector valve is in said second position and being operable to open position by the fuel pressure differential whensaid selector valve is in said first position and said pressure differential exceeds a value determined by the characteristics of said spring means, said check valve being also so adapted that, when said presgates-st 11 7 sure differential exceeds said value, the rate of flow of fuel to the engine substantially the same whether the selector valve is in its first or second position.

8. A fuel supply system for an internal combustion engine, comprising a 'main conduit for fuel flowing to said engine, a pair of parallel branch conduits connecting two spaced portions of said main conduit, "a selector valve at one of the junctions of said"branch conduits with said main conduit, said selector valve being movable between a first position wherein only one of said branch conduits is open and a second position wherein both said branch conduits are open, metering restrictions in each'o'f saidbranch conduits, means for controlling the "ma pressure differential betweensaid portions 'o'f said main conduit, said s'ele'ctor'valvebeing effective upon movement to said first and second positions to establish respectively first and second'rela'tionships between said fuel'pressure differential and the rate of flow of fuel to said engine, a passage connected in parallel with said metering restrictions, an'enrichmen't valve in said passage movable in an opening direction 'by said fuel pressure differential, spring means biasing said enrichment valve closed, stop means for limiting the opening movement of said enrichment valve, a third branch conduit connecting said pair of branch conduitsa't points between said selector valve and said restrictions, a check valve in said third branch conduit opening in the direction of flow from said one branch conduit to the other, spring means biasing said check valve closed in opposition to the difference between the fuel pressures acting on opposite sides thereof, said check valve 7 being inoperable when said selector valve is in said'second position and being operable to open position by said difierence of fuel pressures when said selector valve is in said first position and said pressure difierent aliexceeds a value determined by' the characteristics of said spring means, said check 'valve being also'so adapted that, when said pressure differential'exceeds said value, the rate of flow of fuel 'to the engine is substantially the same whether'the selector valve is in its first or second position.

9'. 'Fluid new 'controlapparatus, comprising a main conduit, a pair of parallel branch conduits connecting two spaced portions of said main conduit, 'a' selector valve at one of the junctions of sa'id'branch conduits with said main conduit, said selector valve being movable between a first positionwherein only one of said branch conduits is open and a second position wherein 'both of said branch conduits are open, metering restrictions in each" of said branch conduits, said selector valve being 'efiective upon movement to said first and second positions to establish respectively first and second relationships between'thefluid pressure differential between said portions of said mainconduit and the rate of flow of fluid therethru, a passage connected in parallel with said metering restrictions, a, valve in said passage movable in ano ening direction by said fluid pressure differential, spring'means biasing said last-mentioned valve closed, stop means for limiting the opening movement "of said last-mentioned valve, a third branch conduit connecting said pair of branch'condu'i'ts at'poin'ts 'between said selector valve'andsa'id restrictions, va'chec'k valve in said third "branch conduit opening in the direction of flow from said one branch conduit to the other,

spring means biasing said check 'valve closed in pressures acting on opposite sides thereof, said check valve being inoperable when said selector valve is in said second position and being operable to open position by said diiference of fiuid pressures when said selector valve is in said first poi sition and said pressure differential exceeds a value determined by the characteristics of said spring means, said check valve also being so adapted that, when said pressure difierential'exceeds said value, the rate of flow of fluid thru said main conduit is substantially the same whether theselector valve is in its first or second position.

10. A fuel supply system for an internal combustion engine, comprising manual m xture control means for selectively supplying fuel to said engine at an automatically regulated lean mixture rate orrich mixture rate, means for automatically proportioning both mixture rates in response to the power output of said engine, means for progressively enriching both mixture rates commencing at the same value of said power output, first additional means for further enriching the lean mixture rate in the highpower output range of the engine and second additional means for making both mixture rates attain the said maximum value which remains constant throughout a substantial portion of the high power output range of said engine.

1.1. vA fuel supply system for an internal combustion engine, comprising manual mixture control means for selectively supplying fuel to said engine at an automatically regulated lean mixture rate or rich mixture rate, means for automatically proportioning both mixture rates to the power output of said engine, means responsive to said power output for progressively enriching both mixture rates commencing at the same value of said power output, first additional means responsive to high power output of said engine for,

automatically further increasing the lean mixture rate when said manual control means is set to supply fuel at a lean mixture rate, and second additional means for making both mixture rates attain the same maximum value which remains constant throughout a substantial portion of the high power output range of said engine.

12. A fuel supply system for an internal combustion engine, comprising manual mixture controlmeans for selectively supplying fuel to said engine at an automatically regulated lean mixture rate or rich mixture rate, valve means for auto: matically enriching both mixture rates in proportion to the power output of said engine, means responsive to said power output for progressively enriching both mixture rates commencing at the same value of said power output, first additional valve means for further increasing the leanimixtureirate, and second additional means for making the maximum lean mixture rate the same as the maximum rich'mixture rate throughout a substantial portion of the high power output of said engine. 7

'13. 'A fuel supply system for an internal combustion engine,. comprising a manual m xture control, movable between lean and rich mixture positions, forselectively controlling the supply of fuelito said engine at an automaticallyregulated lean mixture rate or rich mixture rate, in accordance with the power output of the engine, and valve means adapted to commence opening at the same value of said power output and enrich both mixture rates at progressively-increasing rates,

and stop means to limit the opening of said valve -means soas'to obtain the same'constant mixture rate at high power outputs of said engine, regardless of the position of said manual mixture control.

14. A fuel supply system for an internal combustion engine comprising manual mixture control means for selectively supplying fuel to said engine at an automatically regulated lean mixture rate or rich mixture rate, means for coordinately enriching both mixture rates in response to the power output of the engine beginning at the same value of said power output, first additional means for further enriching the lean mixture rate at a higher rate than the enrichment rate of the rich mixture rate, and second additional means for maintaining both mixture rates at the same constant maximum value throughout a substantial portion of the high power output range of said engine.

15. A fuel supply system for an internal combustion engine comprising manual mixture control means for selectively supplying fuel to said engine at an automatically regulated lean mixture rate or rich mixture rate, means for coordinately enriching both mixture rates in response to the power output of the engine beginning at the same value of said power output, regardless of whether the manual control means is functioning to supply a lean or rich mixture rate, and stop means to limit the range of operation of said enriching means and maintain both mixture rates at the same constant maximum value throughout a substantial portion of the high power output range of said engine.

16. A fuel supply system for an internal combustion engine comprising manual mixture control means for selectively supplying fuel to said engine at an automatically regulated lean mixture rate or rich mixture rate, means for proportioning both mixture rates in response to the power output of the engine, valve means for enriching both mixture rates at the same increasing rate throughout a substantial portion of the power output range of the engine, additional valve means to further increase the enrichment rate of the lean mixture rate throughout a substantial portion of the higher power output range of the engine, and means for maintaining both mixture rates at the same constant maximum value throughout a substantial portion of the high power output range of the engine.

17. A fuel supply system for an internal combustion engine comprising manual mixture control means for selectively supplying fuel to said engine at an automatically regulated lean mixture rate or rich mixture rate, valve means for coordinately enriching both mixture rates in response to the power output of the engine, additional valve mechanism, responsive to the power output of the engine, for further enriching the lean mixture rate, and adapted to open at the same value of said power output, regardless of whether the manual control means is functioning to supply a lean or rich mixture rate, and stop means to limit the maximum opening of said valve mechanism and thereby limit the maximum enrichment of the mixture rates to a selected value.

GORDON P. TAPLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,224,472 Chandler Dec. 10, 1940 2,361,227 Mock Oct. 24, 1944 2,391,755 Twyman Dec. 25, 1945 2,394,664 Chandler Feb. 12, 1946 2,432,274 Barr Dec. 9, 1947 2,465,549 Orr Mar. 29, 1949 2,463,941 Orr May 3, 1949