US2445389A

US2445389A - Carburetor

Info

Publication number: US2445389A
Application number: US498471A
Authority: US
Inventors: Milton E Chandler
Original assignee: Niles Bement Pond Co
Current assignee: Niles Bement Pond Co
Priority date: 1943-08-13
Filing date: 1943-08-13
Publication date: 1948-07-20
Anticipated expiration: 1965-07-20

Description

I July 20, 1948.

M. E. CHANDLER CARBUREI'OR Filed Aug. 15, 1943 mzazm 2. #52:

2 Sheets-Sheet 1 I INVENTOR- V MLTmEZL'anmnd y M. E. CHANDLER 2,445,389

CARBURETOR Filed Aug. 15, 1943 2 Shee'ts-S heet 2 INVENTR SE ES me How MLTU/V E EHHNQLER AGENT Patented July 20, 1948 by mesnenassignments, to Niles-Bement-Pond Company, West Hartford, Conn, a corporation 'Newq r er Amman August 13, 1943, Serial No. 498,471

The present invention relates to carburetors for internal combustion-enginesior use on aircraft, and particularly to means for controlling the fuel to-air ratioin-such carburetors: Internal combustion engines-such as those used in aircraft, operate most efficiently ona lean mix.- tureiotiuel .andair. WI t istdesirable however, in order to secure the maximum power output of the engine to operateon a: somewhat richer mixture. v.Also, the engine runscooler on, a richer mixture and henceflit. isvidesirable, when operating with .adverse cooling conditions ,such as are encountered at high altitudes-or during a climb, to operate the engineonaa rich mixture.

Aircraft engines ;of conventional construction are usually provided with manual minturetcon trols whereby thepilot may shift from aleanto a rich mixture or vioe-ve-rsa. It sometimes occurs claims (01. 123-119) that thepilot iorgets to change themixturecon-l trol to correspond with the changing flight com ditions he encounters. .This mayresult in excessive. fuel consumption, if the mixture control is left in a rich position, orit mayeresult in dan gerous overheating of the engine iitthe mixture control is left in its lean positions It is; therefore-tan object ofithe present invention to provide .meansresponsive, to-.the flight conditions encountered byvv anaircraft ,for', controlling the fuel to air, ratio. -.Another object of theapresent invention is tolprovidemeans respon: sivepto-the, rate of change .oialtitudeof an aircraft for controlling? the :fuel to .air ratio.- Another object is to'Iprov-ide means responsive to the quantity of airentering thacarburetor to enrich the mixture of fuel and airwhenthequantity of air exceeds a'predeterminedamount i A further object is toLprov-ide mixturelcontrol means which is=or erable,inv atplu-rality of stages. A further. wobjectis to provide a multiple stage mixture control which. operates to increasethe fuel to air ratio in responseto a {flight condition of the aircraft, and which operates to additionally increase thefuel toair ratioinresponseto the quantity .oftairentering the, engine; V Other objects. andnadvantages oftthe presen invention will'become apparent .from a consideration of the appended specification,=.c1aims,;-and drawing inwhich t Figure '1 is a somewhat diagrammatic illustration of a carburetor adapted for use with an aircraft engine and provided with a mixture control arrangement embodying my invention, r 4 Figure 2 is a graphical illustration of the relationship between the fuel and air ratio and ai flow in the carburetor of Figure 1, and p Figure 3 illustrates an alternative form of control device which may be used in the carburetor of Figure 1. ,c

In Figure 1, there is shown a carburetor body portion Ill. thru which air flows from an inletgi I, thrua passage 12 to an outlet l3. In flowing thru thepassage 12 the air passes thru a Venturi restriction I4, pasta throttle I5, and a fuel .discharge nozzle I6. 4

-A-second air passage connects the inlet H and the throat of venturi M. This second air passage may be traced from the inlet II thru a plurality o-fimpact tubes 11, Whose open ends project into the inlet H, a vent ring passage 18 interconnect; ing the impact tubes 11, a conduit 2|], anexpansible chamber 24 in a fuel regulator unit 25, arestriction 26, another'expansible chamber 2] in the-fuel regulator 25, a conduit 28, a chamber 33 and a conduit 34 to the throat of venturi i4; 1 I A A bellows 35 is mounted in the chamber 33, and operates-a valve 36 which controls the flow of air from therconduit 32 into the chamber 33. The bellows 35 is preferably filled with nitrogen or other temperature responsive fluid, so that the position of valve 36 is determined by the temperature andpressure of the air in the chamber 33,, and hence by the density of that air. I v V a -The,valve 36-restricts the flow of air to the second passage just described in such a manner that the pressure differential between chambers 24 and 21 is an accurate measure of the mass of air going thru the passage l2. Errors due to changes in the density, of the air with altitude and temperature, and also those errors due tothe inherent limitations of .a metering restriction of the Venturi type, are substantially eliminated by the operation of valve 36. This type oi altitude and metering error compensation is more com!- pletely-desc-ribed and claimed in my co-pending application ,Serial No. 490,281, filed June LU, 194 3, now Patent Number 2,383,144.

The fuel passing thru the carburetor comes froma'fuel pump .or other source of fuel under pressure (not shown) Frorn that source the iuel passes thru a conduit 31, the fuel regulator unit 25, a conduit 33, a jet system 40, an idle valve 49, a conduit 4!, a pressure regulator 42, and a conduit 43 to the discharge nozzle 15.

The fuel regulator unit 25 comprises a housing 44, which is divided by three flexible diaphragms 45, 46, and 41 into four

expansible chambers

48, 24, 2'! and 55. The diaphragms 45, 46 and 41 are all attached to a valve stem 5!, by any suitable means. The valve stem 5| carries a balanced valve 52 at its lower end. A compression spring 53 acting on the diaphragm 45 biases the stem 5! for movement of the valve 52 toward open position. a

The pressure in chamber 50 is the same as that existing on the upstream side of the jet system 40. Chamber 4-8 is connected thru a conduit 54 to the conduit 4! on the downstream side of the jet system 45. The diiferential between these pressures is a measure of the quantity of fuel flowing thru the jet system. This pressure differential is transmitted to the chambers 48 and 50, as described above, where it acts thru the diaphragms 45 and 47 in a direction tending to close.

the valve 52. As previously pointed out, the pressure differential between chambers 24 and 21 is a measure of the mass of air flowing thru the passage l2. This air pressure difierential acts on the valve 52 in an opening direction. It may be seen that the valve 52 is positioned in response to changes in the air pressure differential to produce a balancing change in the fuel pressure differential. Therefore, the valve 55 controls the quantity of fuel flowing thru the carburetor in accordance with the mass of air flowing thru the passage l2.

- The idle valve 49 is provided to control the flow of fuel when the air flow is small, as when idling the engine. The idle'valve 49 is connected to the throttle l5 for concurrent operation therewith, by means of a linkage generally indicated at 59. At low air flows, it has been found that the pressure differential between chambers 24 and 21 tends to be erratic. The spring 53 and idle valve 49 have been provided to control the fuel flow at such times. At low values of air flow, the force of spring 53, urging the valve 52 toward open position, overrides the force due to the pressure differential between chambers 24 and 21, thereby moving valve 52 in an opening direction. The connection between the throttle l5 and valve 49 is so designed that the valve 49 isretracted to a position where it does not appreciably restrict the fuel flow when the throttle is out of a range of positions near the closed position, sometimes termed the idling range. As the throttle moves into the idling range, the valve 49 is moved to restrict the fuel flow, and this restriction of the fuel flow becomes greater as the throttle moves toward closed position. In effect, the control of the fuel flow is transferred from the air flow responsive regulator 25 to the throttle-controlled idle valve 42 when the latter is in its closed or nearly closed positions.

Fuel entering the jet system 40 from the condlllt 38 passes into a chamber 55. The fuel may across the jet system 40 becomes large enough to overcome the spring. Therefore, the valve 58 operates to automatically enrich the fuel and air mixture supplied to the engine when the load on the engine is high.

The valve 6| has a main body portion of cylindrical form whose end cooperates with an annular seat 64 surrounding the entrance to restriction 60. The valve 6| is also provided with an elongated projection 65 of somewhat smaller cross-section than the restriction 60'. This projection extends completely thru the jet or restriction ,6!) when the valve 6| is'plojsed against the seat 5 shown in the drawing.

A spring 56 biases the valve 6| to closed position. The valve 5| may be opened against the force of spring 66 by a pair of electro-magnetic coils GT and 68. When the coil 51 is energized, the valve 7 6| ismoved to a partly open position, wherein the main body portion of valve 6| is separated from the seat 64, but the projection 65 extends into and partially obstructs the restriction 60. When the coil 68 is also energized, the valve BI is moved farther to the left from the position shown, to a point where the projection 65 is completely withdrawn from the jet 60, which is then fully opened. In the system shown in Figure 1, the energization of coil 61 is controlled either by an altitude responsive switch unit 3! or by an attitude responsive switch 10. The energizationof coil 68 is controlled by an air flow'responsive switch 22'. The switch units 22 and 3| are both located in a casing II, in which they are separated by a, wall 59, apertured at 9|. I

The switch 3! is in the lower portion'of casing H, which is divided by a flexible diaphragm 72 into a pair' of

expansible chambers

30 and 13. The diaphragm 72 carries at its center a bridging contact 14, which cooperates with a pair of stationary contacts 15 and 16. A compression sprin 11 biases the diaphragm 12 in a direction to separate contact 14 from the stationary contacts 15 and 76. The chamber 30 is connected through aconduit 32 tothe chamber 21 of fuel regulator 25. The chamber 13 is connected thru aconduit 18 to the chamber 33. Therefore the pressure difference flow out of the chamber 55 either thru a fixed restriction 56, a restriction 5'! controlled by a poppet valve 58, or a restriction 6U oontrolledby a valve 61. Fuel flowing thru the restrictions 5'! and 60 must also pass thru another fixed restriction 62 before passing out of the jet system 4!] into the conduit 4 I.

The poppet valve 58 is biased to closed position by a spring 63, and is opened against the action of this spring only when the pressure differential between the chambers 30 and I3 is determine-d by the pressure differential across valve 3 3. This pressure differential varies with the altitude of the aircraft, since the va1ve36 is operated .by bellows 35 inaccordance with the density 'of'the air. As the altitude increases, the bellows 35 expands moving the valve 36 toward closed positi on,.and thereby'ino'reasing the pressure differential between

chambers

30 and 13. The diaphragm 12 then moves downwardly against spring 11. When the aircraft rises above a predetermined altitude, the bridging contactv 14 engages contacts 15 and IB. The pressure differential between

chambers

30 and 13 also varies with the quantity of air flowing thru the passage l2. Therefore, thealtitude at which the contacts of switch unit 3| are closed varies with the air flow. The altitude and air flow characteristics of the switch may be determined by the characteristics of spring 11. For example, the spring 11 may be chosen so that at sea level, even with maximum air flow, the switch contacts are not closed. 0n the other hand, the spring 11 may be chosen so that at sea level, the switch closes when a predetermined air flow, which may be that indicated by the ordinate passing thru the point I05 in Figure 2 is exceeded. Then at any other altitude, abov'e'sea 1evel., the switch closes at a lower value of air flow.

The attitude responsive switch 10 is illustrated ncnduluur. tie-warmers. a qtabiec ntact .41 which cooperates with a stationary contact 831, henen ulumfliis a ei o h t iisn th aimrait-t l sunwardim s c imbms he ontest .1. smqved to en a e. o ta t l Whenan aircraft is .in its normalwflyingposrics, thefittin ;forceum ucrdmrthemizement ai -th a t re t. the. nes. is: a maxmiu and e. frictio al resistanc of. e.- w ng. to. crement thru1 the. air. i a minimum, In other words, he. Iift-t u drag: ratio. of; the, aircraft is a maximum. the aircraft departs from. this. norm l fl in position, the, lifting force is decreased. and; the; a isiucreased. With a giyenhorscpowerout, out from the engine, the. Speed. ofitheaircr it will: be. a mammum when the lift tcrdragz ratio. is a. maximl'llm As; the lift-to-drag ratio. changes, due, to. climbing, of; the aircraft or from. other causes such as improperload distribution, the speed of. the aircraft for: a. giyerr power out-put is decreased; As theair speed: decreases, the, flowofi cooling air; over-- t e engine decreases.) Likewise, in. an. air.- craft having a liquid cooled engine. the flow of cooling air thru the radiatordecreases It may: thcreiore. be: stated that the attitude; oi the. aircrait, as; measured by the pendulum 8D: is an in.- icatiorr of the variation in the cooling. oi the. engine. I

pendulum as is also. affected by. acceleration and deceleration of. the airc-ratt. The;- action oithe pendulum. in response to acceleration is to increase the tuei-to-air ratio upon; acceleration,- ami to decreasethe f-uei-to-air ratio upon cteceleration. It therefore tends to increase the fueleto-air ratio as. the. power output at the engine I increases and tov decrease the tuei-to-air: ratio as. the poweroutput decreases. The; efiiect of; the response oi the: pendulum; 8.11 to. acceleration is. therefore beneficial, althoughit is incidental, t the: primary object oi the present invention.

The. altitude switch. if; is an: dication orthe iiectiveness 01..- the air flowin p st t e. ngine or radiator as a cooling agent. The thermal. conu ty o the ai vari s w th its densitm Asthe" d n y; decreases at high a titudes it becomes less: eifisi nt a med um,- for transfierri-n lreat o the enginethe e gine. here ore ends to hotter.

Whe eith he: alt tude or'th attitude or th a rc aft ssumes a value which indicates the P es nc of advers oo n c ndi ousrone at t e: ii h t o it is clcse s sie c ilisci s c-- tail h r i a te c osur o eit er o ih sssw t lies cause enrichmen I th m ture o inch and ai 's ipe ied o he. enem which qesrsthc en.- gine operating temperature.

r the a r f w sw h un t 32 i i thwPr -mries ea n h s'ssraia d by a d lh as #4 n o p si e ch mbers 4! nd The. diaphragm- 134 carries at ts center ahridg -g n a 86 which c s rei s with of $.97 ime o at s tl te 88- Mm es sta ce 0 mew time 5 qu l ties tessvar ate he Ctit 8 5- om t e sta ionary contacts 81 and 88".v "The chamhei 2!, is cor -necteg. t n- 111i. nd t Z; i am .4 in he Ri l r u ato it Chamber 8.5 i cpnrlected thr'u'the aperture- 9.! to chamber 3!). ans thehc'e thruconduit 32 to her. 2! in 11611 regulator The. pro sure ential between chambers 2! and. is the the same as. that existing. between haifihrs Z5 and Z1. {is preyiouslfif' desc'rihed',v this r n al a l es 'e Qfihs s J br h pas e s I- Wheri'the. fliq rsthm P ssa 4;? x e s j. I1.

valu contact. is. moved dow wardly and.

bridges. the. contacts fiandzll f he.pressurere ulatorfn.is;provided toma n.- tain. the. ressureom the. downstream. sidcjotthe jet system 40 at a value greaterjhainj'atmospheric. The pressure regulator 42 includes a ber' at a value greater than the atrriospheric pressur in chariibef In this way,"it is as: stired that thefuel' issues from nozzle [6 at a; pressure greater than that inthe passage [2, therebimininiizing any tendency of the'i'uel to vaporize iuthecoiiduit flor nozzle l3;

Operation of Figure 1- Witch tlot ircraft is 0 r it n. 6359 fli ht 4 w h. unit 39% not. lo e. its more t e. re?

muonsmp between the fuel and air r atio andthe air flow is. illustrated by the curve Figure 2- As a rflow incr ase om e o fu l? flows. ol lr hru the. Je until the. oi ".10 'o'itcutvs i re ei e u e a r s he "1s 5. b rp. suflicierit to open valve '58 against the tens u f. sp i .3.- The. uel and; air atio. then be omic r fs ing r ich. e lt s i ow. n r ses this enricheoir g' oi the miigture being limited y the. fixect restriction 52; The foregoin 0p n takes place. 01 1.55 WhQE the spri i 16 is 'chQSQfi so that sw t h all does not. clos its. contacts, even at maximum air. flow, at the particular attitude cohsi denedlf When. the air craft. is operating under altitude and air flow conditions such that switch 3i is: closed,- or it iscliinbi ng, the relation of fuel] and air ratio to the air flow is illustrated by the curve Bin rg 'gure 1. For exa ple; a su thatthe aircraft is. operating at an altitude and air flow such that'th'e switch 3|"moves cont-act M into: engagement with contacts 15 arid, 16, Au. energizing circuit for coil 6-! is then complted; which maybe traced from the upper terminalfof a. battery I01 thru. a conductor I02, contacts 15; 14" and l6, a conductor I03, a corid'uctor IM, coil: 61-, a conductor I05, to the lower terminal oi battery tilt. Energization of coil- 61 causes. yaliieffilto. move off. its seatIaugi the jet Bll' ilstheii partialli 'opened, beir grestricted; ily he iq iflow increases beyond the value. 'epoii it IE3 or! curVeB, the switchtsc 8 in o e em t i h co es and m l tes an: na tin TY iti s i 5%. which ma be tra edrom the upper terminal of battery I!!! thru conducor i12 c nt c s 1.4 an duc orsm3 and. Iii-I, contacts 81, 86 and 88, a conductor 't i d iq l fih 'lq sr rm-ina-l ofbattery lflL' Epergizatiou qt coil figtcauses projection 65 tolhe compietel-y moved out of jet. 6 thereby enriching the fuel andairflrriixture; as-

in sated 'byth e. curVe'B. between: the points More that ther i let 9.1 scutt eswitch on the operation of the system is the same as that of altitude switch 3| since the two Operation of Figure 3 There is shown in Figure 3 a switch mechanism which is operated in accordance with the rate of change of altitude of an aircraft. This switch mechanism may be substituted for the attitudeswitch E8 of Figure 1. Referring to Figure 3, there is shown a generally cylindrical casing 2B0 attached to a base 2m by any'suitable means such as the bolts 202. Inside the casing there is mounted on the base 2M a flexible bellows 203. A spring 204 is compressed between the bellows 253 and the base L .A pair of guide members 235 and 265 project from the base 20! and maintain the spring 204 in proper alignment. The exterior of bellows 203 is exposed to atmospheric pressure thru a suitable aperture I99 in the casing 200. A passage 20! extends horizontally from the space adjacent the exterior of bellows 283 to a vertical passage 20!! which extends upwardly thru the base 2M and is concentric with the bellows 203 and an elongated nozzle 2 I connecting the passage 293 with the interior of bellows 203. nozzle 2H] is of a very narrow cross-section, and restricts the flow of air between the exterior and interior of bellows 263.

As long as the aircraft is operating at a constant altitude the pressures inside and outside the bellows 233 are equal. When the aircraft changes its altitude, for example by climbing,

the pressure outside the bellows decreases due to the increase in altitude. This change in pressure is not immediately communicated to the interior of bellows 263 because of the restriction in nozzle 2 ll"... Since the pressure inside the bellows 203 is then greater than'the pressure outside, the bellows tends to expand. The force acting to expand the bellows is proportional to the rate of change of altitude of the aircraft.

A rod 2H is mounted on the free upper end of the bellows 203. The rod 2H extends thru a bushing 2| 2 in a portion of a casing 298, and near its upper end carries a movable switch contact 2 l3 which cooperateswith a stationary contact 2H,, The structure is such that when the aircraft is flying level the contact 2l3 is below and spaced from the contact 2M, as shown in the drawing. When the aircraft starts to rise, the contact 253 is moved upwardly by an'amount depending upon the rate of climb. When, the rate of climb exceeds a value determined by the characteristics of the bellows 203 and spring 204, contact 2J3 is moved into engagement with.

contact 2M. This completes a circuit between terminals H5 and H6, which correspond to the terminals having the same reference numerals in Figure 1.

Stationary contact 2M is in the form of a, disc mounted between two insulating plates 2l5, which are held on'the top of the casing 209 by bolts 2H6. The circuit between terminals I I5 and H5 may be traced from terminal II 5 thru a conductor 211, a connector 2H3, a conductor 220, binding post 22L casing 2B0, rod 2, contacts H3 and 2%, a conductor 222, connector H8 and a conductor 223 to terminal I [6.

The operation of the system when the switch unit shown in Figure 3 is used therein is similar tothe operation when the switch unit 10 is used,

The passage thru and it is believed no further description of this operation is necessary.

It should be noted that the switch mechanism of Fig. 3 and the switches 3| and 10 of Fig. 1 are responsive to conditions-which-affect the thermal capacity of the air passing the engine and therefore affect the rate at which heat can be dissipated from the engine. This is true of both air cooled and water cooled engines. Water cooled engines depend for their ultimate cooling on the ability of a radiator to dissipate heat to the outside atmosphere. As the density of the air decreases, its specific heat decreases and, therefore, the'thermal capacity of a given vol ume of it decreases. It is, therefore, not possible to dissipate as much heat from the engine. Similarly, when the aircraft is climbing, its forward speed is slower and the quantity of air passing the engine is decreased so that the thermal capacity of the air is decreased and it cannot be cooled as efficiently. Under such conditions, it is desirable to enrich the mixture of fuel-to-air supplied to the engine so that its temperature will not rise as high.

While I have shown and described certain preferred embodiments of my invention, other modifications thereof will readily occur to those skilled in the art, and I therefore intend that my invention shall be limited only by the appended claims.

' I claim as my invention:

1. In a fuel supply system for an internal combustion engine, a conduitfor air flowing to said engine for combustion purposes, means associated with said conduit fOlfpl'OdllCiIlE' two unequal pressures whose difference is a measure of the rate of flow of air thru said conduit; a conduit of said restriction when said differential exceeds a predetermined value to increase said fuel-to-air ratio, and additional means responsive to a condition affecting the thermal capacity of the air passing said engine for increasing the cross-sectional area of said restriction to increase said fuel-to-air ratio when said condition assumes a predetermined value indicative of insufiicient cooling of said engine.

2. In a fuel supply system for an internal com bustion engine, a conduit for air flowing to said engine for combustion purposes, means associated with said conduit for producing two unequal pressures whose difference is a measure of j the rate of flow of air thru said conduit, a conduit for fuel flowing to said engine, a metering restriction in said fuel conduit for regulating the'flow thru said fuel conduit as a function of, the fuel pressure differential across said restriction, means for controlling said fuel pressure differential as a function of the difierence of said two unequal pressures so as to maintain a substantially constant'fuel-to-air ratio as long as the cross-sectional area of said metering restriction remains fixed, and means responsive to a condition afiecting the thermal capacity .of the air passing said engine for suddenly and substantially increasing the cross-sectional area of said restriction to when said dd di-- increase-s id fuel-to-air as V I 7 are indicative or thin assumes apr'eueterm ed instrument coolingof'sai die I'nafiiel supplysvst'e'infor' 'iijintein'al cambustionenginefa'cond t' for flowing to'sa'id engine for combustion" pu poses, "a conduit for fuelflowing tosai'de'ngine nsior ceiitr'oumg the relationship of 'sa'id'air "l tain asdb'stantially constant fuel-to-air atio, andmeans responsive to "a condition affecting the thermal capacity-"of the air passing said engine for suddenly and substantially increasing said fuel5toair ratio when fsaidc'ondition assumes a predetermined value indicative of insuific'i-ent cooling ofsaid'engine. I

In a fuel suppiy system fo""a"n' intefriai'c'd'mbustion engine, a conduit for air flowing to said engine for combustion purposes, a conduit for fuel flowing to said engine, means for controlling the relationship of said air and fuel flows to maintain a substantially constant fuel-to-air ratio, means responsive to the load on said engine and effective when said load exceeds a predetermined value to increase saidfuel-to-air ratio, and additional means responsive to a condition affecting the thermal capacity of the air passin said engine for suddenly and substantially in creasing said fuel-to-air ratio when said condition assumes a value indicative of insufficient cooling of said engine.

5. In a fuel supply system for an aircraft internal combustion engine, a conduit for air flow-- ing to said engine for combustion purposes, means associated with said conduit for producing two unequal pressures whose difference is a measure of the rate of flow of air thru said conduit, a conduit for fuel flowing to said engine, a metering restriction in said fuel conduit for regulating the flow thru said fuel conduit as a function of the fuel pressure differential across said restriction, means for controlling said fuel pressure differential as a function of the difference of said two unequal pressures so as to maintain a substantially constant fuel-to-air ratio as long as the cross-sectional area of said metering restriction remains fixed, means responsive to said fuel pressure differential for increasing the cross-sectional area of said restriction whensaid differential exceeds a predetermined value to increase said fuel-to-air ratio, and additional means responsive to the rate of climb of said aircraft for suddenly and substantially increasing th crosssectional area of said restriction to increase said fuel-to-air ratio when said rate of climb assumes a value indicative of insuflicient cooling of said engine.

6. In a fuel supply system for an aircraft internal combustion engine, a conduit for air flowing to said engine for combustion purposes, a conduit for fuel flowing to said engine, means for controlling the relationship of said air and fuel flows to maintain a substantially constant fuelto-air ratio, and means responsive to the rate of climb of said aircraft for suddenly and substantially increasing said fuel-to-air ratio when said rate of climb assumes a value indicative of insufficient cooling of said engine.

7. In a fuel supply system for an aircraft internal combustion engine, a conduit for air flowing to said engine for combustion purposes, a conduit for fuel flowing to said engine, means for controlling the relationship of said air and fuel flows to maintain a substantially constant fuel-to-air ratio, means responsive to the load on said engine and effective when said load exceeds 10 a predeti'minedvalii to increase said fuel -to-air 'r'a i0, and addition ma: es'p'on'sive'to the rate of climb of said-airs" aft for increasing said fuelto air ratiowh'msaid'rate of climb assumesa value indicative "of insufficient cooling of said engine.

'BQI'n a fuel sites svstem'for an internal coir ensues engines conduit for air "flowing to said engine for combustion purposes, means associated with sweetnessiorsrtauein two unequal pressures whose difference is a measure of the rate of new of air thru said conduit, a conduit for fuel nowhere-said engine, a metering restriction in said fuel conduit for regulating the flow'thi'u said fuel conduit as a function of the fuel pressure differential across said restriction, means for controlli said fuel pressfiredifferefitiaf'as a funtioii'fif the difference said two' 'iiiiqiim pressures so as to maintain a substantially constant fuel-to-air ratio as long as the cross-sectional area of said metering restriction remains fixed, valve means for controlling the cross-sectional area of said restriction, electrical means for operating said valve means including a pair of electrical circuit-s, first motor means connected in one of said circuits and effective when said circuit is completed to move said valve means to a partly open position, second motor means connected in the other of said circuits and effective when said other circuit is completed to move said valve means to a fully open position, first switch means connected in both said circuits, means responsive to a condition affecting the thermal capacity of the air passing said engine for closing said first switch means and thereby completing said one circuit, second switch means connected in said other circuit in series with said first switch means, and means responsive to the rate of flow of combustion air to said engine for closing said second switch means and thereby completing said other circuit when said first switch means is also closed.

9. In a fuel supply system for an internal combustion engine for use on aircraft, in combination, a plurality of parallel conduits for conveying fuel to said engine, valve means for controlling the flow of fuel thru one of said conduits, means biasing said valve means to closed position, electrical means for operating said valve means selectively to an intermediate position or to its full open position against the action of said biasing means, first switch means for controlling the energization of said electrical means, said first switch means being effective when closed to cause energization of said electrical means so as to operate said valve means to said intermediate position, means responsive to a condition affecting the thermal capacity of the air passing said engine for operating said first switch means to closed position when said condition assumes a value indicative of insufficient cooling of said engine, second switch means for controlling the energization of said electrical means, said second switch means being effective when closed to cause energization of said electrical means so as to operate said valve means to said full open position, and means responsive to the quantity of air for combustion purposes flowing to said engine for operating said second switch means.

10. In a fuel supply system for an internal combustion engine for use on aircraft, in combination, means for controlling the flow of fuel to said engine in proportion to the quantity of air flowing'to said engine, first means for increasing the ratio of fuel to air, second means for addi- 11 tionally increasing the ratio of fuel to air, means responsive to a condition afiecting the thermal capacity of the air passing said engine for operating said first means when said condition assumes a value indicative of insufficient cooling of said engine, and means responsive to the quantity of air flowing to said engine for operating said second means when said quantity exceeds a predetermined value.

MILTON E. CHANDLER.

REFERENCES CITED UNITED STATES PATENTS Name Date Bourne Nov. 26, 1912 Number Number 12 I Iame --.Date Hicok et al., Aug, 25, 1925 Mabee et a1; May 17,1932 .King et'al. Aug. 2, 1932 Barker et a1. .......L.. May 29,1934 Loeifler Aug. 10, 1937 Mennesson Feb. 18, 1941 Campbell Apr, 28, 1942 Thompson Dec. 22, 1942 Weiche Sept. 28, 1943 FOREIGN PATENTS Country Date I Great Britain July 25, 1940 Great Britain Jan. 27, 1942 France Sept. 26, 1939