US2485430A - Carburetor - Google Patents

Description

M. E. CHANDLER Oct. 18, 1949.

CARBURETOR 2 Sheets-Sheet 1 Filed Nov. 17, 1944 uzazu O. Mme-x5 INVENTOR. MLT N E ZZ IANULER AGENT Oct. 18, 1949. M. E. CHANDLER 2,435,430

' CARBURETOR Filed Nov. 17, 1944 I 2 Sheets-Sheet 2 v INVENTOR. JM TUNE QJANULE'R Patented Oct. 18, 1949 CARBURE'I'OR Milton E. Chandler, New Britain, Conn., assignor, by mesne assignments, to Niles-Bement-Pond Company, West Hartford, Conn., a corporation of New Jersey Application November 17, 1944, serial No. 568,884

15 Claims. (01. 261-39) The present invention relates to carburetors for internal combustion engines, and particularly to apparatus for correcting the operation of carburetors and other fluid flow measuring devices for variations in the pressure and temperature of the fluid being measured.

A carburetor for an internal combustion englue is required to maintain a controlled proportional relationship between the rate of flow of air to theengine and the rate of flow of fuel to the engine. In other words, the carburetor must control the fuel-to-air ratio. Since the fuels commonly used are of relatively constant density, while the density of the air varies with its pressure and temperature, it is necessary that the carburetor include a device which compensates its action for variations in air temperature and pressure. lows fllled with a fluid having an appreciable temperature coefllcient of expansion for that purpose. Since it is required that the bellows should not obstruct and thereby reduce the capacity of the air induction system, such bellows are commonly mounted in a chamber spaced from the air passage, and maintained in communication with the air passage by a branch air conduit of-relatively small cross-sectional area.

It has been found that when such a bellows is mounted in a chamber so constructed and connected to the main air passage, that the temperature of the air in the chamber tends to become heated to a higher temperature than the air in the intake-passage. The reason for this is that the carburetor body and the housing enclosing the bellows are usually formed of metal, and are so placed that they are exposed to heat from the engine. The air in the chamber takes up heat from the carburetor body and the walls of the chamber, and its temperature therefore increases. This causes the temperature responsive bellows to give a false indication of the temperature of the air entering the carburetor. This false indication is in a sense to indicate that the entering air is hotter and therefore less dense than is actually the case. The false indication given by the bellows causes the carburetor to cut down the fuel supply in proportion to the smaller mass of air flowing per unit time as indicated by the bellows, thereby causing the fuel-to-air ratio to be decreased. Because'of the undesired It is common to use a flexible belleanness of the mixture supplied to the engine under those conditions, the engine tends to heat up and to detonate.

It is, therefore, an object of the present invention to provide a device responsive to the pressure and temperature of the air entering an internal combustion engine, which does not obstruct the air induction passage and which is not adz'iersely affected by ambient temperature condions.

Another object of this invention is to provide a device which responds to the pressure at a first location and to the temperature at a second location spaced from said first location.

A further object of the present invention is to provide improved apparatus for measuring the rate of flow of a fluid of variable density. A still further object is to provide such a device including improved means for correcting the operation of the device for variations in the pressure and temperature of the fluid whose flow is being measured.

Other objects and advantages of the present 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 for an internal combustion engine embodying the pri'nciplesof my invention, Figure 2 is a cross-sectional view of a portion of a carburetor showing a pressure and tempera- Figure 1 Referring to the drawing, there is shown a body In of a carburetor for an aircraft type internal combustion engine. Air enters the carburetor body It at an inlet l2 and flows thru a Venturi restriction I4 and a passage I5, past a throttle I6 and a fuel discharge nozzle It to an outlet 20. A supercharger may be provided between the outlet 20 and the intake manifold of the engine. In certain cases the supercharger may be upstream from the inlet I2, or two superchargers may be used, one in each place.

The Venturi restriction It produces a pressure differential between the inlet I2 and the throat of the restriction which varies substantially in accordance with the square of the velocity of the air passing thru the restriction. Since the cross-sectional area of the venturi is constant, this pressure differential may be takenas a measure of the volume of air flowing thru the passage per unit time.

In order to obtain a pressure differential varying as a function of the mass of air per unit time flowing thru the venturi 14, the pressure differential between entrance i2 and the throat of venturi i4 is utilized to create an air flow thru a secondary air passage extending from entrance l2 to the throat of venturi 14. A plurality of impact tubes 22 are provided, whose open ends project into the entrance I2 to receive the impact of the entering air. The secondary air passage may be traced from entrance l2, thru tubes 22, a passage 24 interconnecting the impact tubes, a conduit 28, a chamber 28 in a pressure meter generally indicated at 38, a restriction 32, a chamber 34 in the pressure meter 38, a conduit 38, past a valve 38 into a chamber 48, and thru a conduit 42 tothe throat of venturi l4. The valve 38 is operated by an expansible bellows 44.

The bellows 44 is filled witha fluid having a substantially zero coefficient of thermal expansion. For example, I may use a hydraulic fluid corresponding to Army Air Forces Specification 3580-D, Grade M. Alternatively, normal methyl aniline may be used. The interior of the bellows 44 is connected thru a conduit 43 to the interior of a rigid tube or bulb 41, which is mounted to extend transversely'of the entrance to the air passage thru the carburetor. The liquid in the bellows 44 extends upwardly in the tube 43 to a point substantially above the level of the highest point in bellows 44. The bulb 41 is filled with a fluid, preferably a gas, having a substantially lower specific gravity than the liquid filling the bellows 44. The fluid in bulb 41 should have a relatively high coefficient of thermal expansion. By way of example, I prefer to use nitrogen in the bulb 41.

It may be seen that a change in the pressure adjacent bellows 44 causes an expansion or contraction of the bellows 44, resulting in a raising or lowering of the level of the liquid in the tube 43. Since the liquid in bellows 44 is insensitive to temperature changes. the position of valve 38 is not affected by changes in the temperature in chamber 48. However, variations in temperature at the air entrance l2 produces changes in the volume of the fluid in the bulb 41, which changes are transmitted thru the tube 43 to the interior of bellows 44, where they cause expansion and contraction of the bellows.

Since the air in the chamber 48 enters that chamber after passing thru an elongated and somewhat tortuous passage of relatively small cross-sectional area, the air picks up heat from the engine through the surrounding walls during its flow to the chamber 48 and enters the chamber 48 at a temperature substantially higher than that existing at the entrance l2. It is, therefore, essential that the valve 38 should respond to variations in the temperature at the air entrance l2 and not to variations in the temperature in the chamber 48, if accurate metering of the air flow is to be obtained.

In the secondary air passage, the pressure differential between the entrance l2 and the throat of venturi I4 is divided into two component pressure drops, one across the restriction 32 and the ,other across the valve 38. The valve 38 is positioned in accordance with the density of the air flowing thru the passage. 15. Valve 38 is moved toward open position as the air pressure increases and toward closed position as the air pressure decreases. If the volumeoi air flowing per unit time thru passage l5 remains constant while its density decreases, then the mass of air flowin is decreased, but the pressure differential set up by the venturi l4 remains constant. However, the movement of valve 38 toward closed position causes the component pressure drop acros valve 38 to increase, and the component pressure drop across restriction 32 to decrease proportionately, reflecting the decrease in the mass of air flowing per unit time. By proper design of valve 38, the pressure drop across restriction 32 may be made to vary substantially in accordance with the mass of air flowing thru passage l5. This pressure differential across restriction 32 acts on a diaphragm 48 which separates the chambers 28 and 34. The force applied to diaphragm 46 is transmitted to a valve 48, on which it acts in a closing direction.

The fuel enters the carburetor from a fuel pump or other source of fuel under superatmospheric pressure. It flows thru a conduit 58, a valve 52 in a pressure regulator generally indicated at 54, a conduit 56, a mixture control unit generally indicated at 58, a jet system 88, past an idle valve I25, thru a conduit 82, a valve 64 in a second pressure regulator 88, and a conduit 68 to the fuel discharge nozzle I8.

The pressure regulator 54 includes a diaphragm 18 separating a pair of expansible chambers 12 and 14 and connected at its center to the valve 52. A spring 18 biases the valve 52 toward open position. A restriction 18 connects the chambers 12 and 14.

A portion of the fuel entering pressure regulator 54 flows thru chamber 14, restriction 18, chamber 12, a conduit 88, a chamber 82 in the pressure meter 38, past the valve 48, and thru a conduit 84 to the main air passage l5.

The pressure meter 38 includes a diaphragm =86 separating the chambers 34 and 82 and a diaphragm 88 separating the chamber 28 from a fourth expansible chamber 88. The valve 48 is biased toward closed position by a spring 32.

The chamber 88 is connected thru a conduit 94 to the fuel conduit 82 downstream from the jet system 88. The pressure in chamber 98 is therefore the same as that in the fuel line downstream from the jet system. The pressure in chamber 82 is the same as that in chamber 12 of pressure regulator 54.

The position of diaphragm 18 and valve 52 is determined by the balance between the pressure in chamber 14 acting in a valve closing direction and the spring 16 plus the pressure in chamber 12 acting in a valve opening direction. If the balance between theseforces is upset, the diaphragm 18 and valve 52 move until the balance is restored.- Therefore the pressure in chamber 12 is a measure of the pressure in chamber 14, which is substantially the same as the pressure on the upstream side of the jet system 88. For any given constant cross-sectional area of the fuel passages thru the jet system 88, the pressure differential across it is a measure of the fuel flow thru it. This pressure differential, or rather a ber 82 is transmitted to chamber 12 of pressure regulator 54 where it controls the. position of valve '52, and hence the pressure on the upstream 1 side of the jet'system 60.

The pressure regulator 66 operates to maintain a substantially constant pressureon the downstream side of the jet system 60 and thereby to prevent variations in pressure at the fuel discharge nozzle I8, which may be due to operation of the throttle or to variations in engine speed, from reaching the downstream side of the jet system and affecting the fuel flow.

.The pressure regulator 68 includes a pair of expansible chambers 96 and 98 separated by a flexible diaphragm I00, which is attached at its center to the valve 84. A spring I02 biases the valve 64 toward closed position. The chamber 96 is connected thru a conduit I04 to the conduit 26 and thence thru the passage 24 and impact tubes 22 to the air entrance I2. The chamber 98 is connected to the conduit 62.

The mixture control 58 includes a disc valve I06 fixed on a shaft I08. The disc valve I06 controls the flow of fuel thru ports opening into conduits H and 2 which lead into the jet system 60. When the disc I08 is in the position illustrated in full lines in the drawing, fuel can flow to the jet system only thru the conduit I I0. This full line position of the disc valve I06 is known as 6. sure regulator 54 biases valve 52 in an opening or fuel flow increasing direction.

The idle valve I25 is pivotally attached to a lever I28, whose opposite end is connected by a link I30 to an arm I82-fixed on the shaft I34 of throttle I6. The idle valve is normally wide open when the throttle is beyond the range of posithe lean position of the mixture control 58.

when the disc valve I08 is in the dotted line 'position shown in the drawing, the fuel can flow thru both the conduits III) and H2. The dotted line position of disc valve I06 is termed the rich" position of the mixture control. .The disc valve I06 can also be moved to a cut-off positionwherein it cuts off the flow thru both conduits I I0 and H2.

The conduit IIO conducts fuel either thru a' fixed restriction or jet H4, or thru a restriction I I6 controlled by an enrichment valve I I8biased to closed position by a spring I20. The conduit I I2 conducts fuel to a fixed restriction I22. Fuel flowing thru the restrictions H6 and I22 alsoflows thru another restriction I24 which limits the total flow thru restrictions H6 and I22.

The valve II 8 is normally closed, but opens at high pressure differentials across the jet system to increase the fuel-to-air ratio under heavy load conditions.

At low air flows, such as are encountered under idling conditions, the pressure diflerential set up by the venturi I4 tends to be erratic, and is not a reliable indication of the volume of air entering the engine. Provision is made to control the fuel flow directly in accordance with the throttle position at such times. The spring 92 in the pressure meter 30 acts on valve 48 in a closing direction. When the differential pressure acting on diaphragm 48 is small, as under low air flow conditions, the spring 92 becomes the predominating force acting on valve 48. A closing movement of valve 48 causes an increase in the fuel flow thru the main fuel line, since the closure of valve 48 increases the pressure in chamber 82 of pressure meter 30 and hence in chamber 12 of pressure tions nearv its closed position, usually termed the idling range. As the throttle moves into the idling range, thereby decreasing the air flow, the idle valve I25 moves toward closed position; At the same time, the springs 92 and 18 cause operation of valve 52 in an opening direction. The valve 52 is thereby opened sufilciently so that its restrictive effect on the fuel flow is less than that of the idle valve I25. Therefore the fuel flow under idling conditions is controlled primarily by the valve I25 in accordance with the position of the throttle, and not by the pressur meter 30 in accordance with the mass of air entering the engine.

Although I have illustrated a particular type of carburetor, it will be appreciated by those skilled in the art that my invention may be.appli'ed with equal facility to other types of carburetors. The carburetor illustrated may, for example, be modified by omitting the pressure regulator 54 and placing the valve 48 of the pressure meter 30 directly in the fuel line between the pump and the mixture control 58. If the carburetor is so modifled, the valve 48 should be modified so that it is balanced against inlet pressure rather than discharge pressure, and so that it opens in a downward direction. The structure of valve 48 would then be similarto that of valve 52.

Figures 2 and 3 There is shown in Figure 2 a portion of the main body I50 of a carburetor, which may be of the rectangular. type shown and described in my co-pending application Serial No. 406,776, filed August. 14, 1941, and matured into U. S. Patent 2,361,993, issued November'l, 1944. This body I50 carries an end plate I52 which supports a plurality of parallel Venturi' bars, one of which is shown at I54. A casing I56 is attached to the body I50 by any suitable means, such as bolts The casing I56 is provided with a cover A shell I62 is enclosed within the casfiig I56 and a recess in the body I50. Inside \the shell I62 is a flexible bellows I84. The space between the bellows m and the shell I62 is filled with a suitable fluid having a negligible thermal coeflicient of expansion. The inner end oi. the bellows I64 is closed by a pair of cylindrical members I68 and F68. A spring I10 is retained between the cyllndrical members I66 and I68 and the bottom of shell I82. The inner cylindrical member I 68 carries at its center a cup I12 which cooperates with a guide I14 attached to the bottom of shell I62. The bottom of cup I12 abuts against a valve I 16 which corresponds'functionally' to the valve 38 of Figure 1. The valve I16 cooperates with a port I18 formed in a seat member I80. The seat member I is provided with a threaded extension I82 at its left end, which cooperates with an adjusting nut I84 and a lock nut I86. The extension I82 is in threaded engagement with a cap I88, which'is in turn threaded into the cover I60. The seat member I80 is hollow and is provided with ports I aligned with ports I92 in the cap I88, which are in fluid communication with a passage I94, which may be the same as conduit 36 of Figure 1.

regulator 54. Furthermore, the spring 16 of pres- 75 The space between bellows I64 and shell I62 corresponds to the space inside bellows ll of Figure 1. This space is connected thru a tube I96 to an elongated bulb I98 which is suspended across the entrance to the air passage by means of a pair of brackets 266, which are attached by bolts 262 to the end plates I52 of the carburetor body. The bulb I98 corresponds to the bulb 41 of Figure 1.

Figures 4 and 5 There is shown .inFigures 4 and 5 a modified traction of the bulb without distorting the. connecting tube or the supporting structure.

The bulb 250 of Figure 4 is an elongated metal tube having its ends sealed by plugs 262 and 254. The plug 252 is apertured to receive the connecting tube 256 which corresponds to the tube 43 of Figure 1 and the tube I96 of Figure 2. The plug 252 is also slotted, as at 260, to receive a transversely extending bolt 256. The bolt 256 is carried by two brackets 262 attached by any suitable means to a plate 264, which is bolted to the end plate 266 by bolts 268.

The plug 254 at the opposite end of bulb 250 is recessed to receive a pin 210 whose opposite end extends into a socket 212 in the end wall 266 of the carburetor. The plug 252 to which the tube 256 is attached, may be fixed in position by tightening the nut on the bolt 258. The tube 250 may then expand and contract freely. The resulting movements of the plug 254 will merely cause the pin 210 to move in and out of the socket 212. Therefore, any expansion or contraction due to temperature cannot place any strain on the various parts.

Altho, in the arrangements illustrated, the liquids of different thermal coeiflcients of expansion are kept separate by using containers at different levels and liquids of different specific gravities, it should be apparent that other equivalentarrangements could be used. For example, the two containers could be placed on the same level and a pressure-transmitting diaphragm placed in the line connecting them.

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

I claim as my invention:

passage connecting the interiors of said bulb and bellows so that the expansion of the fluid in said bulb tends to produce expansion of said bellows and thereby modifies the position of said valve and the air flow thru said secondary passage in accordance with the temperature in said main conduit, so that the pressure drop-established across one of said restrictions is a function of the mass air flow. in .said main conduit, and

form of bulb supporting structure, which is-desigsigned to permit longitudinal expansion and conl. A carburetor for an internal combustion engine, comprising a main conduit for air flowing to said engine, means associated with said conduit for producing two unequal pressures whose diiference is a measure of the velocity of air flowing thru said conduit, a secondary air conduit connecting two points in said main conduit subject to said two unequal pressures so that a flow of air is induced thru said secondary conduit by the difference of said pressures, a chamber forming a part of said secondary conduit and subject to heat from said engine, a pair of restrictions in series in said secondary conduit, valve means for varying the cross-sectional area of one of said restrictions, a flexible bellows in said chamber for operating said valve means, said bellows being expansible and contractible in accordance with pressure variations in said chamber and filled with a liquid having substantially zero coefiicient of thermal expansion, a bulb having rigid walls and placed in said main, air conduit above the uppermost part of said bellows, said bulb being filled with a fluid having a substantial coeflicient of thermal expansion, a

means "responsiveto said pressuredropfor controlling the flow of fuel'to 'said engine proportional to said mass air flow.

2. A carburetor for an internal combustion engine, comprising a main conduit for air flowing to said engine, means associated with said conduit for producing two unequal pressures whose difference is a measure of the velocity of the air flowing thru said conduit, a secondary air conduit connecting two points in said main conduit subject to said two unequal pressures so.

that a fiow of air is induced thru said secondary conduit by the difference of said pressures, said secondary conduit extending for a substantial portion of its length outside said main conduit pair of restrictions in series in said secondary conduit, where it is subject to heat from said engine, a chamber forming apart of said secondary conduit, a valve means for varying the cross-sectional area of one of said restrictions, a flexible bellows in said chamber for operating said valve means, said bellows being expansible and contractible in accordance with pressure variations in said chamber and filled with a liquid having substantially zero coefficient of thermal expansion so that its expansion and contraction are independent of the temperature in said secondary conduit, a bulb having rigid walls and placed in said main air conduit above the uppermost part of said bellows, said bulb being filled with a fluid having a substantial coeflicient of thermal expansion and substantially less dense than said liquid, a passage connecting the interiors of said bulb and bellows so that the expansion of the fluid in said bulb tendstoproduce expansion of saidbellows and thereby modifies the position of said valve and the air flow thru said secondary passage in accordance with the temperature in said main conduit, so that the pressure drop established across one of said restrictions is a function of the mass air flow in said main conduit, and means responsive to said pressure drop for controlling the flow of fuel to said engine proportional to said mass air flow.

3. In a carburetor for an internal combustion engine comprising, an air conduit, a. chamber spaced from said conduit and subject to heat from said engine, a passage connecting said chamber and said conduit, means for measuring the mass air flow in said conduit including a valve to be operated in accordance with the temperature of the air in said conduit and the pressure of the air in said chamber, a flexible bellows in said chamber for operating said valve, said bellows being expansible and contractible in accordance with variations of air pressure in said conduit and filled with a liquid having substantially zero coeflicient of thermal expansion, a bulb having rigid walls and placed in said main air conduit above the uppermost part of said bellows, said bulb being filled with a fluid having '9 thereby modifies the position of said valve in accordance with the temperature in said main conduit, and means responsive to said air flow measuring means for controllingjthe flow of fuel to said engine proportional to said mass air flow.

4. A carburetor for an internal combustion engine, comprising a'main, conduit for air flowing to said engine, means associated with said conduit for producing two unequal pressures whose diflerence is a measure of the velocity of the air flowing thru said conduit, pressure differential responsive means for measuring air flow, a pair of branch conduits connecting said pressure differential responsive means to two points in said main conduit subject to said two unequal pressures, a chamber forming a part of one of said branch conduits, said. chamber being spaced from said main conduit and having walls subject to heat from said engine, valve means for compensating the action of said pressure differential responsive means for variations in the pressure in said chamber and the temperature in said main conduit thereby rendering said pressure difllerential responsive means effective to measure the mass air flow in said conduit, 9. flexible bellows in said chamber for operating said valve means, said bellows being expansible and contractlble in accordance with pressure variations in said chamber and filled with a liquid having substantially zero coefiicient of thermal expansion so that its expansion and contraction are independent of the temperature in said chamber, a bulb having rigid walls and placed in said main air conduit above the uppermost part of said bellows, said bulb being filled with a fluid having a substantial coefiicient of thermal expansion and substantially less than said liquid, a passage connecting the interiors of said bulb and bellows so that the expansion of the fluid in said bulb tends to produce expansion of-said bellows and thereby modifies the position of said valve in accordance with the temperature in said main conduit, and means responsive to said pressure differential responsive means for controlling the flow of fuel to said engine proportional to said mass air flow.

5. A carburetor for an internal combustion engine, comprising: a conduit for combustion air flowing to said engine, means for measuring the mass flow of air thru said conduit including a valve to be operated in accordance with the variations of pressure and temperature of the air in "said conduit, a flexible bellows for operating said valve, a chamber for containing said bellows spaced from said conduit so that said bellows will not restrict said conduit, said chamber being subject to heat from said engine, a passage ccnnecting said chamber and said conduit, said chamber having walls subject to ambient temperatures difierent from the temperatures in said main conduit-said bellows being expansiblev and contractiblein accordance with variations of air pressure in said conduit and filled with a first fluid having substantially zero coefficient of thermal expansion so that its expansion and contraction areindependent of the temperature in said chamber, a bulb in said main air conduit and spaced vertically from said bellows, said bulb being filled with .a second fluid having a substantial coeflicient of thermal expansion and of different density than said first fluid and nonmiscible therewith, a passage connecting the interiors of said bulb, and bellows so that the expansion of the second fluid in said bulb tends to produce expansion of said bellows and there-' 10 I 1 by modifies the position of said valve in accordance with the temperature in said main conduit,- and means responsive to said air flow measuring means for controlling the flow of fuel to said engine proportional tosaid mass air flow.

. 6. A carburetor for an internal combustion engine, comprising: a conduit for combustion air flowing to said engine, means for measuring the mass flow of air thru said conduit including a valve to be operated in accordance with the variations of pressure and temperature of the air in said conduit, a flexible bellows for operating said valve, a chamber for containing said bellows spaced from said conduit so that said bellows will not restrict said conduit, said chambers being subject to heat from said engine, a passage connecting said chamber and said conduit, said chamber having walls subject to ambient temperatures different from the temperatures in said main conduit, said bellows being expansibleand centractible in accordance with variations ofgair pressure in said conduit and filled with a first fluid having substantially zero coefficient of thermal expansion so that its expansion and contraction are independent of the temperature in said chamber, a bulb in said main air conduit filled with a second fluid having a substantial coeflicient, oi. thermal expansion, a pressure transmitting connection between the interiors of said bulb and bellows so that the expansion of the second fluid in said bulb tends to produce expansion of said bellows and thereby modifles the position of said valve in accordance with the temperature in said main conduit, and means responsive to said air flow measuring means for controlling the flow of, fuel to said engine proportional to said mass air flow.

7. Apparatus for regulating the flow of a liquid in proportion to the flow of a fluid of variable density, comprlsing a conduit for said fluid, means associated with said conduit for producing two unequal pressures whose difference is a function of the velocityof the fluid flowing thru said conduit, regulating means responsive to the difierence of said pressures, a control device for compensating the action of said regulating means in accordance with the variations of pressure and temperature of the fluid in said conduit, a flexible bellows for operating said control device, a chamber for containing said bellows spaced from said conduit so that said bellows will not restrict said conduit, a passage connecting said chamber and said conduit, said chamber having walls subject to ambient temperatures different from the temperatures in said conduit, said bellows being expansible and contractible in accordance with pressure variations in said chamberand filled with a flrstfluid having substantially zero coeflicient of thermal expansion so that its expansion and contraction are independent of the temperature in said chamber, a bulb in said conduit filled with a second fluid having a substantial coeflicient of thermal expansion, and a pressure-transmitting connection between the interiors of said bulb and bellows so that the expansion ofthe second fluid in said bulb tends to produce expansion of said bellowsand thereby modifles the position of said control device in accordance with the temperature in said conduit.

8. Apparatus for regulating the flow of a liquid means associated with said conduit for producing two unequal pressures whose difierence is a function of the velocity of the fluid flowing thru said conduit, a secondary conduit connecting two points in said main conduit subject to said two unequal pressuresso that a flow of fluid is induced thru said secondary conduit by the difference of said pressures, a chamber connected to said secondary conduit,a pair of restrictions in series in said secondary conduit, valve means for varying the cross-sectional area of one of said restrictions a flexible' bellows in said chamber for operating said valve means, said bellows being expansible and, contractible inaccordance with pressure variations in said chamber and filled? with a liquid'having substantially zero'coeficient of thermal expansion, abulb having rigid walls and placed in said main conduit above the upper secondary passage, for supplying fuel to said main air passage in proportion to the velocityof air flow-therethrough, means for compensating the "fuel supply for variations in density of air flowing j bellows positionedi'n said secondary air passage most part of said bellows, said bulb being fill d 3-. with aiiuid having a; substantial coenicient of thermal -expansion and substantially-less dense than saidliquid, a passage connecting the in-' teriors of said bulb and bellowsso that the expansion of the fluid in said bulb tends to produce expansion of said bellows and to adjust the position of saidvalve means and the fluid flow thru said secondary conduit is thereby modified in ac-' cordance with the pressure in said chamber and the temperature in said main conduit, and liquid said Venturi restriction, means, including a fixedrestriction and a variable-restriction in said secondary passage, for supplying fuel to said main air'passage in proportion to the velocity'of air flow therethru, means for compensating the fuel supply for variations in density of air flowing thru said main air passage comprising a bellows positioned in said secondary air passage which is'insensitive to the temperatureof the air and adjacent walls of said secondary air passage flow regulating means responsive to the pressure through said main air passage comprising a and responsive to variations inair pressure therein and to the temperature of the air at the inlet of said main air passage, a sealed chamber located at the inlet of the main air passage, unaffected by the air pressure in said passage, and containing a temperature responsive fluid, a conduit connecting said chamber with said bellows,

and a valve actuated by said bellows for varying the size of saidvariable restriction.

13. A carburetor according to claim 10, wherein said bellows is .filled with a liquid having a zero coefficient of expansion and said chamber is filled with an expansible fluid having a relatively high coefiicient of thermal expansion; said liquid and fluid being nonmiscible.

14. Acarburetor according to claim 10, wherein said chamber is so located as to be completely surrounded and thermally insulated from the heat of the carburetor by the air passing through said main air passage.

15. A carburetor according to claim 10, wherein said chamber is filled with a gas and each end wall of said chamber is attached to the adjacent wall of said main air passage by a flexible connection, whereby said end walls are relatively movable with changes in temperature of said chamber.

but is responsive to variations inair pressure therein and which is operatively connected to an element responsive tothe temperature of the air at the inlet of said mainair passage,'and a valve actuated by'said bellows for varying the size of said variable restriction.

10. A carburetor comprising an air' passage with an air supply and a liquid fuel supply-thereto, means for regulating the fuel supply in accordance with variations in density of the air supply, comprising a temperature control, responsive to the temperature but insensitive to the pressure of said air supply, 'and including a rigid sealed chamber suspended across the entrance to said air passage so as, to be completely'surrounded by the total air supply passing therethrough, and thereby insulated from the heat of said carburetor.

11. A carburetor comprising an air passage with an air supply and a liquid fuel supply thereto, means for supplying fuel to said air passage in proportion to the velocity of air flow therethrough, and means for compensating said fuel supply for variations in density of said air supply, including MILTON E. CHANDLER.

REFERENCES CITED UNITED STATES PATENTS Name Date Connet Dec. 12, 1916 Thomson Dec. 31, 1918 v Brown Oct. 1, 1935 Shivers May 10, 1938 Seldon Sept. 10, 1940 Lippincott et a1. Jan. 27, 1942 Hunt May 2, 1944 Thompson et a1. Nov. 20, 1945 Twyman Dec. 25, 1945 Chandler Jan. 15, 1946 FOREIGN PATENTS Country Date Great Britain Aug. 6, 1925 Great Britain May 2, 1944 Number Number

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