US2482401A - Carburetor - Google Patents

Description

P 1949- M. CHANDLER 2,482,401

CARBURETOR Filed'July l, 1943 2 Sheds-Sheet l I N V EN TOR. MLToAr 6'. GEWDLER.

Patented Sept. 20, 1949 Milton E. Chandler, New Britain,

by mesne assignments,

Company, West Hartfor of New Jersey Conn., assignor, to Niles-Bement-lond d, Conn.,- a corporation Application July 1, 1943, Serial n uaoii 9 Claims. (Cl. 261-69) The present invention relates to carburetors,

of fuel flowing thru the carburetor is propor tioned to the quantity of air flowing thru the carburetor. 1

It is an object of the present invention to provide improved means for controlling the flow of fuel thru a carburetor in accordance with the quantity of air flowing thru it.

Another object of the present invention is to provide an improved carburetor of the type in which the fuel flow is controlled by a main pressure operated valve, and'in which the operating pressure for the main valve is controlled by a pilot valve operated in accordance with the flow of air thru the carburetor.

A further object is to provide a curburetor of the type described, in which the fuel, after passing thru the main valve, flows thru a metering restriction, and in which the pilot valve is operated not only in accordance with the air flow thru the carburetor, but in accordance with the fuel pressure on the downstream side of the metering restriction. t

Another object of the present invention is to provide an improved pilot valve for a carburetor of the type described.

A further object is to provide improved mech anism for operating a valve in accordance with the resultant of a plurality of variable pressures, in which each of the variable pressures is transmitted to one of a plurality of expansible cham-. bers which are separated by flexible diaphragms.

A still further object is to provide, in such a device, improved means for transmitting the forces on the flexible diaphragms to the valve.

Other objects and advantages of my invention will become apparent from a, consideration of the appended specification, claims, and drawing, in which Figure 1 is a somewhat diagrammatic illustration of a carburetor and fuel supply system for an internal combustion engine embodying the principles of my invention,

Figure 2 illustrates a modified form of pilot valve which may be used in the carburetor of Figure 1, and 7 Figures 3 and 4 illustratebther modified forms of pilot valves which-may be used in the carburetor of Figure 1..

Referring now to Figure 1, there is shown a carburetor having a main body l0, through which extends a main air passage I l,- between an inlet l2 and an outlet l3; Although any suitable typ of carburetor may be used, I prefer to use one of the rectangular type shown and claimed in my copending application, Serial No. 406,776, filed August 14, 1941, now Patent No. 2,36 ,993, issued Nov. 7, 1944.

Air flowing through the passage H flows from the inlet l2 pasta plurality of parallel ,Venturi members 14, and past a pair of throttles l5 and a discharge nozzle I6 to the outlet I3; The flow of air through the passage- H is controlled by the throttles I5, and the flow of air is measured by a Venturi metering. arrangement including the Venturi members 1 f A plurality'of impact tubes I! extend into the inlet portion 12 of thepassage H, with their open ends exposed to the flowing air. The impact tubes l'l 'communicate'with a passage l8, commonly termed a'vent ring.

Each of the hollow Venturi members I4 is provided with a plurality of lateral openings 20, which openings connect the hollow interiors of the Venturi members I4 with the air passage H at or near its narrowest portion. It will be rec'- ognized that, in accordance with the known principles of Venturi meters, the difference between the pressure existing at theimpact tubes l1 and that existing at the openings 20 in the throat of the venturi, is a measure of the velocity of air flowing through passage I I.

In order to secure proper combustion of the fluel flowing through the carburetor, the mass of fuel flowing per unit time should be proportioned to the mass of air flowing (per unit time), rather than to the velocity of the flowing air. If the air were of constant density, its velocity could be taken as a measure of the mass of air flowing per unit time through passage I l. 'I-Iowever, since the density of the air varies with atmospheric pressure and temperature, the pressure differential produced by the Venturi structure must be corrected to obtain a pressure differential which is a true indication of the mass of air flowing through the carburetor.

A 'portionof the air sage enters the impact tubes I'L. From there it passes through; a secondair passage, paralleling a portion of the main air passage I l, and including ventring 18, a conduit 2l ,a conduit 22 having a restriction 23 therein, a'conduit 24, a valve chamber 25, and a conduit 26 to the interior of the two central hollowVenturimembers [4,; and out through the openings 20 in those members 'to the main air passage ll. Y

A valve 21, located in the valve chamber 25, controls the flow of air through this second pasflowing through the passage. The valve 27 is biased by a spring 3| into engagement with a flexible bellows 28, which is exposed on one side to the pressure in the chamber 25, and on its other side to the pressure in a chamber 32 formed between the bellows 28 and a rigid casing 30. The chamber 32- is filled with nitrogen or other suitable' fluid, so that the volume of the chamber 32 varies with the temperature and pressure of the fluid surrounding it. If the density of the flowing air decreases, due either to a decrease in atmospheric pressure such as might be occasioned by an increase in altitude of an aircraft or due to an increase in temperature, the chamber 32 expands, thereby moving the valve member 21 to the right and decreasing the air flow through the second passage previously described. The valve 21 may be so designed'and proportioned with respect to restriction 23; in conduit 22, that the pressure difierential across the restriction 23 is always an accurate measurement of the mass of air flowing through the main air passage regardless of the variations in. the density in the air.

The exterior of the casing 38 is exposed to the air within a chamber 33 formed in the carburetor body [8. In order to maintain the temperature of the air in the chamber 33 at the same temperature ast'he air passing thru the passage H, the chamber 83 is connected through a conduit 34 to the 'interiors'of two outer Venturi members 54, which are not used for air flow measurement purposes. Another portion of the chamber '33. is open to, the passage H, as at 35, somewhat downstream from the Venturi members l4. A pressure differential is thereby created which causes a continuous flow of air around the outside of casing 38, thereby insuring that the fluid within the casing is maintained at thesame temperature as'the airflowing. through the careburetor. This condition is further aided by a projection 35 on the casing 38, which extends through the opening 35 a substantial, distance into the air pas' sage The fuel flowing through the carburetor is re; ceived from a fuel pump or other source of fuel unde superatmospheric pressure (not shown), and'pas'ses through a' vapor trap 40, a conduit 4|, amain fuel regulator valve unit 42, a conduit. 43, a mixture control valve 44, a jet system 45, a conduit 46, a pressureregulator valve 4], anda conduit 48 to thedisoharge nozzle l6.

The vapor trap 40 includes a screen 68, which prevents'the passage of foreign materials therethrough. A valve 6| .is located at the top of the vapor trap casing and is operated by'float 82, so that when the levelof the fuel in the vapor trap falls because of; the formation of vapor therein, the valve 6| is opened, allowingthe vapor to escape through aconduit 63 which may be con nected to, the fuel tank or to another suitable place for the disposition of the vapor. A ring 64 surrounds a ported sleeve 65, through which the valve 6| moves. The ring 65 isprovided so that if the aircraft is flown upside down, it slides down over the ports in the sleeve 65, preventing the drainage of fuel from the vapor trap through the valve 6|.

The mainlfuel regulator valve unit 42 includes a valve member 66 carried by a stem 61, which is attached by any suitable means to the central portion of a flexiblediaphragm 68, which is attached at its edges to the oasingof the'regulator unit 42, so as to divide the easing: into a pair of expansiblechambers '|0 and 5|. The valve member 68 cooperates with a seat formed in the 4 casing of the regulator unit 42. A spring 12, located within the chamber 5| biases the valve member 65 toward open position. The position of valve member 66 is determined by the difierence between the pressure in the chamber I0, which acts to close the valve, and the pressure in the chamber 5|, aided bythe spring 12, both of which act to open the valve. The pressure in the chamber 5| is regulated by the pilot valve unit 54 in a manner more completely described below.

The mixture control valve 44 includes a manually operable. shaft 13, carrying a disc valve 14. The disc valve 14 controls the flow of fuel thru a pair of conduits 15 and 16 extending from the mixture control unit 44 to the jet system 45. The disc valve 14 is usually positioned so that either conduit 76 alone is open, both conduits are open, or both are closed. When the conduit 76 alone is open, the carburetor is said to be operating with an automatic lean mixture, and when both conduits l5 and 18 are open, the carburetor is said to be operating with an automatic rich mixture. 1

When the conduit 'Hiis open, fuel flows to the carburetor through a fixed jet H, and upon the occurrence of a predetermined high pressure differential across the jet system 45, a spring loaded valve opens another jet 18, When the conduit 15 is also opened, a third jet 8| is opened. The maximum flow of fuel through the jets l8 and 8| is restricted by another jet 82. The jet system 45 is quite conventional on carburetors of the type described It will be understood that the quantity of fuel flowing thtQ lgh the jet system 45 for a give n position of the mixture control valve 44, is a function of the pressure differential across the jet system.

The pilot valve unit 54 includes a casing 83 whose interior, is divided by three flexible diaphragms 84, 8 5 and 86 into four expansible chambers 81, 88, 90 and55. The chamber 81 is connected througha conduit 9| to the conduit 58, andhence the pressure in the chamber 81 is the same as, or at least indicative of, the pressure on the discharge sideof. the jet system 45. Thechamber 881s connectedthrough a conduit 92 and the conduit 2| to the vent ring I8, so that thepr essure in cham ber 88 is indicative of the pressurein the inlet |2- of the air passage Thechamber 98 is connected through the conduit 83 to the downstream side of the restriction 23 in conduitZZ. Therefore, the. pressure differential betweenchambers 88 and QO is a measure of the. mass'of air flowing to the carburetor.

A valve member $14 is carriedcentrally of the diaphragm 86, and cooperates with a seat 95 attachedto the casing 83 by any suitable means. The chamber 55 in which the valve member 54 is located, is connected through the conduit 52 with the chamber 5| in the main regulator valve 42. The chamber 53, which receives the fluid discharged through the valve 84, empties into the conduit 58 through a 0017111111556: having a restriction 51 therein.

A force transmitting member 96, having a convex. upper surface, is attached to the, central part of diaphragm by any suitable means. Another force transmitting member 91; having 7 a fiat lower surface is attached to the central portion of the diaphragm 85. By reason. of the convex surface in the member 98' andthe flat surface on the member illi the two members may engage each otherjfor the transmission of forces from onej'member tothe other, without any lateral binding action between them, regardless of relative lateral displacement of the diaphragms i 85 and 86. The upper surface of the member 91 is provided with a central recess adapted to receive a projection 98 on the lower surface of a force transmitting member 99 attached to the central portion of diaphragm 81. The force transmitting member 99 is likewise provided with a recess in the central portion of its upper. surface, which recess is adapted to receive a guiding projection I90 on a plug IOI which is threadedly mounted in an aperture in the casing 83. The projections 98 and I 08, and the recesses with which they cooperate maintain the force'transmitting members 91 and 99 in a central position in the casing 83. It will be noticed that the projection 98 is slightly smaller in diameter than the recess in which it moves so as to permit relative lateral movement between the diaphragms 84 and 85. M

A tension spring I02 extends between the valve member 94 and a nut I03 threadedly mounted on a bolt I84 extending through the bottom of the casing 83. The bolt I04 is provided with a hexagonal head I05 by which it may be adjusted to vary the tension of the spring I02. A lock nut I99 is provided to fix the bolt I04 so as to maintain any adjustment established for the tension of spring I92.

The pressure in the chamber 81 is maintained at a value greater than atmospheric pressure, by the fuel pump or other similar means. The pressure in chamber 88 is always equal to atmospheric pressure, since that chamber is connected to the vent ring I8. Therefore, the differential pressure acting on the diaphragm 84 tends to move that diaphragm downwardly, and maintains the force transmitting member 99 in engagement with the member 91 attached to'diaphragm 85.

In a similar manner, it will be seen that the pressure in chamber 90 is always less than that in chamber 88, since it is established by the suction at the throat of the venturi. The force acting on diaphragm 85 is, therefore, downward.

The pressure in the chamber 55 is larger than the pressures in any of the other three chambers, since it is connected to the upstream side of jet system through the conduit 52 and restriction 50. Therefore, the pressure below the diaphragm 88 is higher than the pressure above it, and-the force actin on diaphragm 86 is upward, tending to maintain the member 96 in engagement with member 91.

The force acting on diaphragm 86, therefore, tends to open the valve 94, while the forces acting on diaphragms 84 and 85 tend toclose the valve 94. These latter two forces are aided bythe tension of spring I82. As the valve 94 moves towards its open position, the pressure in chamber'55 is released, thereby decreasing the force tending to move the valve toward open position. Likewise as the valve 94 moves towards its closed position the pressure in chamber is increased thereby building up an opposing force tending to stop the motion of the valve. It may, therefore, be seen that the valve 94 is positioned so as to regulate the pressure in the chamber 55 in accordance with the resultant of the pressures in the chambers 81, 88, and 90.

As previously described, the differential between the pressures in the chambers 88 and 90 of the pilot valve unit 54 is a measure of the mass of air flowing per unit time thru the passage II. This pressure differential produces a force acting downwardly on diaphragm 85 which is likewise a measure ofthe mass of air flowing per unit time.

The pressure in chamber 55 is indicative ofthe: pressure in the fuelline on the upstream side of the jet system. The pressure in chamber 81 is indicative of the pressure in the fuel line on the downstream-side ofv the jet system. The differential between these two fuel pressures provides a force acting upwardly on the valve 94. The air pressure differential acting on diaphragm acts in a direction to close valve 94 and the fuel pressure differential acts to open valve 94. Closure of valve 94 results in an increase in pressure in chamber 55 which is transmitted thru conduit 52 to chamber 5| and acts on diaphragm 68 to move valve 85 in an opening direction. It may, there-- fore, be stated that the air pressure differential acts on the pilot valve94 in 'a fuel flow increasing direction, the fuel flow referred to being the flow thru the main fuel line. Conversely, the fuel pres-- sure differential acts on the pilot valve 94 in a fuel flow decreasingdirection. The pilot valve unit balances the air pressure differential against the fuel pressure differential and corrects the fuel flow to regain a condition of balance in case the two pressure differentials become unbalanced.

A pilot valve unit 54 is formed from an upper casting 89 and a lower casting 83. In assembling thisunit, the diaphragm 86 has its edges attached to casting 83 by the bolts between upper and lower plates as shown in the drawing, so that the chamber 55 is formed under the diaphragm 86 between the diaphragm and the lower plate. In a similar manner the diaphragm 84 is clamped to the upper casting 89, forming with the central recess in that casting the chamber 81. The two castings are then placed together, clamping the edges of the diaphragm 85 between them and are then fastened in that position. This completes the structure of the four chambers of the pilot valve unit. It should be noted that the diaphragms carry the force-transmitting members 96, 91 and 99 at their centers, so that the mechanism for transmittin the forces to the valve is completed by the act of assembling the diaphragms and the two castings of the housing.

The regulator valve 41 is attached to adiaphragm I II], which is exposed on one side to the inlet pressure of the fuel flowing thru the valve 41 and on its opposite side to the pressure in a chamber I connected through a conduit H2 to the vent ring I8. A spring II3 aids the pressure in the chamber I I I in balancing the force due to the pressure on the opposite side of diaphragm H0. The function of the regulator valve 41 is to maintain a substantially constant pressure inside the discharge nozzle I6, so that the fuel flow through the discharge nozzle will not be affected by variations in the pressure in the air passage I I downstream from the throttles I5.

An idling valve I I4 is located in the conduit 48 between the jet system 45 and the regulator valve' 41. The idling valve H4 is connected by a linkage, (not shown), to the throttles l5, so that when the throttles are moved toward their closed positions the idling valve H4 is moved towards its closed position to decrease the fuel flow therethrough. In a carburetor of the type described, the differential pressure in the chambers 88 and 99 is so small at low air flows that it exerts no appreciable controlling effect on the fuel flow.

The spring I02 acts on the valve 94 in a closing.

direction. As previously pointed out, movement of valve 94 towards closed position tends to cause an opening movement of valve 86 and a consequent increase in fuel'flowr The spring 12 directly biases the valve 68 in a fuel flow increasing art and I therefore intend that my invention shall be limited only by the appended claims.

I claim as my invention:

1. A carburetor for an internal combustion engine, comprising in combination, a first conduit for conveying air for combustion purposes to said engine, metering means in said first conduit for producing two unequal pressures therein whose difference is a measure of thequantity of air flowing therethru, a, source of fluid fuel under superatmospheric pressure, a second conduit for conveying fuel from said source to said engine, a metering restriction in said second conduit, means for regulating the fuel pressure in said second conduit at the discharge side of said restriction, first valve means for controlling the fuel pressure on the intake side of said restriction and thereby controlling the flow of fuel therethru, means for operating said first valve means including a third conduit for by-passing fuel from said source around said restriction to said fuel pressure regulating means, said third conduit including a restriction, an expansible chamber having a movable wall attached to said first valve means for positioning the same, and second valve means for controlling the flow of fluid thru said third conduit and thereby the pressure in said chamber and the position of said first valve means, said second valve means comprising a seat member having a port therein, a valve member movable with respect to said seat member to open and close said port, a housing, at least three flexible partitions extending transversely of said housing to provide four expansible chambers in said housing, sleeve means attached to all said partitions and carrying one of said members so that said one member is positioned in accordance with the resultant of the forces acting on said partitions, means for supplying to two of said chambers fluid under said two unequal pressures so that an increase in the difference between said two pressures tends to cause a closing movement of said valve member, means connecting a third of said chambersto said second conduit at the discharge side of said restriction, means connecting the fourth of said chambers to said third conduit so that the difference between the pressures in said third and fourth chambers tends to cause an opening movement of said valve member, and a passage thru said sleeve means connecting said third and fourth chambers and controlled by said valve and seat members, said passage, said third and fourth chambers and their associatedconnecting means forming a portion of said third conduit.

' 2. A carburetor for an internal combustion engine, comprising in combination, a first conduit for conveying air for combustion purposes to said engine, metering means in said first conduit for producing two unequal pressures therein whose difference is a measure of the quantity of air flowing therethru, a source of fluid fuel under superatmospheric pressure, a second conduit for conveying fuel from said source'to said engine, a metering restriction in said second conduit, means for regulating the fuel pressure in said second conduit at the discharge side of said restriction, first valve means for controlling the fuel pressure on the intake side of said restriction and thereby controlling the flow of fuel therethru, means for operating said first valve means including a third conduit for by-passing fuel from said source around said restriction to said fuel pressure regulating means, said thirdiconduit including a restriction, an expansible chamber having a movable wall attached to said first valve means for positioning the same, and second valve means for controlling the flow of fluid thru said third conduit and thereby the pressure in said chamber and the position of said first valve means, said second valve means comprising a seat member, a valve member movable with respect to said seat member, a housing for said members, at least three flexible partitions extending transversely of said housing to provide four eXpansible chambers in said housing, means for transmitting the forces acting on said flexible partitions to at least one of said members to control the relative positions of said members, means for supplying to two of said four chambers fluid under said two unequal pressures so that an increase in the difference between said two pressures tends to cause a closing movement of said valve member, means connecting a third of said four chambers to said pressure regulating means, and means connecting the fourth of said four chambers to said third conduit so that'the difference between the pressures in said third and'fourth chambers tends to cause an opening movement of said valve member, said third and fourth chambers being adjacent each other and interconnected by said valve and seat members, and forming therewith a portion of said third conduit.

3. A carburetor for an internal combustion engine, comprising in combination, a first conduit for-conveying air for combustion purposes to said engine, metering means in said first conduit for producing two ,unequal pressures therein whose dliference is a measure of the quantity of air flowing therethru, a source of fluid fuel under superatmospheric pressure, a second conduit for conveying fuel from said source to said engine, a metering restriction insaid second conduit, means for regulating, the fuel pressure in said second conduit at the discharge side of said restriction, first valve means for controlling the fuel pressure on the intake side of said restriction and thereby controlling the flow of fuel therethru, means for operating said first valve means including a third conduit for toy-passing fuel from said source around said restriction to said fuel pressure regulating means, said third conduit including a restriction, an expansible chamber having a movable wall attached to said first valve means for positioning the same, and second valve means for controlling the flow of fluid thru said .third conduit and thereby the pressure in said chamber and the position of said first valve means, said second valve means comprising a seat member, a valvemember movable with respect to said seat member, a housing for said members, at least three flexible partitions extending transversely of said housing to provide four expansi-ble chambers in said housing, means for transmitting the forces acting on said flexible partitions to at least one of said members to control the relative positions of said members, means for supplying to two of said four chambers fluid under saidtwo pressures so that an increase in the difference between said two pressures tends to cause a closing movement of said valve member, means connecting a third of said four chambers to said pressure regulating means, and means connecting the fourthof said four chambers to said third conduit so that an increase in the difference between the pressures in said third and fourth chambers tends to cause an opening movement-of said valve member, said members '11 controlling a passage interconnecting said third and fourth chambers, and forming with said third and fourth chambers a portion of said third conduit.

4. A carburetor for an internal combustion engine, comprising in combination, a first conduit for conveying air for combustion purposes to said engine, metering means T'm said first conduit for producing two unequal pressures therein whose difference is a measure of the quantity of air flowing therethru, a source of fluid fuel under superatmospheric pressure, a second conduit for conveying fuel from said source to said engine, a metering restriction in said second conduit, means for regulating the fuel pressure in said second conduit at the discharge side of said restriction, first valve means for controlling the fuel pressure on the intake side of said restriction and thereby controlling the flow of fuel therethru, means for operating said first valve means including a third conduit for by-passing fuel from said source around said restriction to said fuel pressure regulating means, said third conduit including a restriction, an expansible chamber having a movable wall attached to said first valve means for positioning the same, and second valve means for controlling the flow of fluid thru said third conduit and thereby the pressure in said chamber and the position of said first valve said second valve means comprising a seat member, a valve member movable with respect to said seat member, a housing, at least three flexible par-titions extending transversely of said housing to provide four expansible chambers in said housing, means for transmitting the forces acting on said flexible partitions to at least one of said members to control the relative positions of said members, stop means for limiting the opening movement of said valve member with respect to said seat member, means for supplying to two of said four chambers fluid under said two unequal pressures so that an increase in the difference between said two pressures tends to cause a closing movement of said valve member, means con necting a third of said "four chambers to said pressure regulating means, and means connecting the fourth of said four chambers to said third conduit so that an increase in the d iiference between the pressures in said third and fourth chambers tends to cause an opening movement of said valve member, said members controlling a passage interconnecting said third and fourth chambers, and forming with said third and fourth chambers a portion of said third conduit.

'5. A carburetor for an internal combustion engine, comprising in combination, a first conduit for conveying air for combustion purposes to said engine, metering means in said first conduit for producing two unequal pressin s therein whose diiference is a measure of the quantity of air flowing therethru, a source of fluid fuel under superatmospheric pressure, a second conduit for conveying fuel from said source to said engine, a metering restriction in said second conduit, means for regulating the fuel pressure in said second conduit at the discharge side of said restriction, first valve means for cmitrolling the fuel pressure on the intake side of said restriction and thereby controlling the how of fuel therethru, means for operating said first valve means including a third conduit for by-passing fuel from said source around said restriction to said fuel pressure regulating means, said third conduit including a restriction, an expansible chamber hav- 'ing a movable wall attached to said first valve means for positioning the same, and second valve means for controlling the flow of fluid thru said third conduit and thereby the pressure in said chamber and the position of said first valve means, said second valve means comprising a housing, at least three flexible partitions extending transversely of said housing to provide four expansible chambers therein, sleeve means attached to all said partitions and having a passage therethru interconnecting the chambers at the opposite ends of said housing, a valve member carried by said sleeve means'at one end thereof, a seat member attached to said housing for cooperation with said valve member to control the flow of fluid thru said passage, mounting means for said seat member comprising a post extending thru said passage for guiding the movements of said sleeve means, means for supplying to two of said chambers fluid under said two unequal pressures so that an increase in the difierenoe between said two pressures tends to cause a closing movement of said valve member, means connecting a third of said chambers to said second conduit at the discharge side of said restriction, and means connecting the fourth of said chambers to said third conduit so that the difference between the pressures in said third and fourth chambers tends to cause opening movement of said valve memher, said passage connecting said third and fourth chambers and forming therewith .a portion of said third conduit.

6. A carburetor for an internal combustion engins, comprising in combination, a first conduit for conveying air for combustion purposes to said engine, metering means in said first conduit for producing two unequal pressures therein whose difference is a measure of the quantity of air flowing therethru, a source of fluid fuel under superatmospheri-c pressure, a second conduit for'conveying fuel from said source to said engine, a metering restriction in said second confrom said source around said restriction to said fuel pressure regulating means, said third conduit including a restriction, an expansible chamber having a movable wall attached to said valve means for positioning the same, and second valve means for controlling the flow of fluid thru said third conduit and thereby the pressure .in said chamber and the position of said first valve means, said second valve means comprising a seat memher having a port therein, a valve member movable with respect to said seat member to open and close said port, a housing, at least three flexible partitions extending transversely of said housing to provide four 'expans-ible chambers in said housing, means for transmitting the forces acting on said flexible partitions to at least one of :said members to control the relative positions of said members, means for supplying to two of said four chambers fluid under said two unequal air pressures so that an increase in the difierence between said two pressures tends to cause a closing movement of said valve member, means connecting a third of said four "chambers to said pressure regulating means, and means connecting the fourth :of said vfour 'ol'rambers to said third conduit so that an increase in the difference between the pressures in said third and fourth chambers tends to cause an opening movement of said valve member.

7. Fuel and air proportioning apparatus for an internal combustion engine, comprising a conduit for combustion air flowing to said engine, 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 of fuel therethru in accordance with the fuel pressure differential established thereacross, means for maintaining a substantially constant pressure in said fuel conduit on the downstream side of said restriction, and means for controlling the pressure on the upstream side of said restriction including a valve, an expansible chamber having a movable wall subject on its external surface to the pressure controlled by said valve, a restricted inlet passage for admitting fuel to said chamber from the fuel conduit on the upstream side of said restriction, a restricted outlet passage for discharging fuel from said chamber to saidfuel conduit at the downstream side of said restriction, and pilot valve means responsive to the difference of said two unequal air pressures for varying the crosssectional area of one of said restricted passages.

8. Apparatus for positioning a valve to be operated in accordance with the resultant of four variable pressures, comprising a generally cylindrical housing, three parallel flexible diaphragms extending transversely of said housing and separating said housing into four expansible chambers, three separately movable, rigid force-transmitting members, one mounted substantially centrally of each of said diaphragms, first guide .means including cooperating guide elements on one end of said housing and on the force-trans- :mitting member on the diaphragm nearest said one end, second guide means including cooperating guide elements on the other end of said housing and on the force-transmitting member on the diaphragm nearest said other end, third guide means including cooperating guide elements on the force-transmitting member of the center one of said diaphragms and on the force-transmitting member of one of the adjacent diaphragms, cooperating surfaces on the force-transmitting member on said center diaphragm and on the force-transmitting member on the other adjacent diaphragm, one of said surfaces being rounded and the other flat to permit relative lateral movements of said center diaphragm and said other adjacent diaphragm and to transmit only forces acting normal to the point of contact of said surfaces, means directly connecting one of said diaphragms to said valve, and means for supplying each of said four chambers with a fluid under one of said four variable pressures, so as to apply to each of the diaphragms not directly connected to the valve a force acting toward said directly connected diaphragm and thereby to hold 14 said members in engagement with one another and to operate said valve in accordance with the resultant of said pressures.

9. Apparatus for positioning a valve to be operated in accordance with the resultant of four variable pressures, comprising a pair of complementary housing members, each housing member having a first generally cylindrical recess in one face thereof and a second generally cylindrical recess of smaller diameter at the bottom of said first recess, a valve seat in one of said second recesses, three diaphragm units, each unit comprising a. flexible diaphragm and a rigid forcetransmitting member mounted substantially at the'center thereof, means for clamping the periphery of the diaphragms of two of said units to the edges of said second recesses in said two housing members so that said two units with their associated recesses form expansible chambers, a valve carried by the one of said two units adjacent said valve seat for cooperation with said seat, the third of said units being adapted to have its periphery clamped between the edges of said first recesses when said housing members are fastened together, so that said third unit forms with said first recesses two more expansible chambers, each pair of adjacent force-transmitting members having cooperating surfaces which permit relative lateral movements of said members, said units including all the force-transmitting mechanism between said diaphragms, so that said members are assembled in force-transmitting relation by the assembling of said units and said housing members, means for supplying to each said chamber a fluid under one of said variable pressures, so that, for each of said units except the one carrying said valve, the pressure on the side farthest from said valve is greater than the pressure on the side nearest said valve, each said force-transmitting member being moved toward said valve by the pressure differential acting on its associated diaphragm, so that said force-transmitting members are stressed in compression and said cooperating surfaces are maintained in contact to position said valve in accordance with the resultant of the pressures in all said chambers. MILTON E. CHANDLER.

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

UNITED STATES PATENTS-

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