US2426741A

US2426741A - Charge forming device

Info

Publication number: US2426741A
Application number: US350518A
Authority: US
Inventors: Frank C Mock
Original assignee: BENDIX PROD CORP
Current assignee: BENDIX PROD CORP; BENDIX PRODUCTS Corp
Priority date: 1940-08-03
Filing date: 1940-08-03
Publication date: 1947-09-02
Anticipated expiration: 1964-09-02

Description

SPt- 2, 1947- F. c. MocK CHARGE FORMING DEVICE Filed Aug. 3, 1940 4 Sheets-Sheet l lilladall.. V

FRANK C. MOCK Y E a 4Q (9:1 M

' AHORNEY Sept. 2, 1947. F, C, MOCK CHARGE FORMING DEVICE Filed Aug. 5, 1940 4 Sheets-Sheet 2 N hmm INVENTOH FRANK QMOCK BY g Q 9;; M

ATTORNEY Sept. 2, 1947.

F. c. MocK CHARGE FORMING DEVICE Filed Aug. 3, 1940 4 Sheets-Sheet 3 T0 AIR INLET OR ATMOSPHERE INVENTOR T-'RANK C. MOCK c? Q 92;

A ITORNE Y Sept. 2, 1947. F, C, MOCK 2,426,741

CHARGE FORMING DEVICE Filed Aug. 3, 1940 4 Sheets-Sheet 4 F167 BY C Q 92 A TI'ORNFY Patented Sept. 2, 1947 alzava omas Foanrma nevica Frank C. Mook, South Bend, Ind., assigner to Bendix Products Corporation,

South Bend.

Ind., a corporation of Indiana Application August 3, 1940. Serial No. 850.518

(Cl. 12S-119) 15 Claims.

This invention relates to charge forming devices for internal combustion engines and more particularly to a control means for the supplementary fuel supply, or economiser system, for enriching the mixture supplied to the engine under certain conditions of operation. The invention is particularly adapted for use with an aircraft engine of the supercharged type but may be used on internal combustion engines of other types. The instant application is a continuationin-part of my copending applications Serial Numbers 120,654, led January 15, 1937 (now abandoned), and 202,208, iiled April 15, 1938, now Patent No. 2,390,658, granted December 4, 1945, which in turn is a continuation of my copending, but now abandoned. application Serial No. 118,- 718. filed January 2, 1937.

It has long been recognized that an enriched mixture is required to produce maximum power, as compared to that required for maximum economy; however, the particular operating conditions at which the mixture should be enriched, or the particular engine variables which should be used to effect the control of the enriching device. have not been entirely understood. In addition. an enriched mixture has a cooling eect tending to reduce the engine operating temperatures and therefore has a beneficial effect, quite apart from its effect on the power output, which finds particular usefulness in cooling the engine at high altitudes. In many cases this cooling eifect is depended upon at high power outputs to keep the operating temperatures at a safe level and a failure to supply a rich mixture under these conditions might result in overheating and serious damage to the engine or failure thereof in flight. Breakage or failure of the control mechanism should therefore result in enrichment of the mixture under all conditions rather than in no enrichment at any time; or as it is generally expressed. the device should fail rich'l rather than "fail lean." Since the absolute pressure of the charge in the intake manifold posterior to both the throttle and the supercharger largely determines the power developed per stroke of the engine it affords a convenient index of the richness required and is a satisfactory variable for operating the supplementary fuel supply control mechanism. At high altitude, however, the power produced at a given charge pressure is somewhat greater than at sea level, the decreased exhaust back pressure resulting in more complete scavenging of the exhaust gases and consequently a high altitude the air now over the engine has a somewhat decreased cooling eect due to its decreased density. The increased power and decreased cooling accompanying a decrease in barometric pressure both tend to require that the economizer enrichment be provided at a lesser charge pressure at altitude than at ground level. In some cases these elects are of rather small amount and may be neglected.

Increased atmospheric temperature also has a double eect in the determination of the charge pressure at which an enrichment of the mixture should be provided. An increase in air temperature decreases-the cooling effect of the air now over the engine and therefore tends to require that the mixture be enriched at a lower charge pressure than at low temperatures. In addition, an increase in atmospheric temperature increases the charge temperature and consequently reduces the weight of charge per stroke at a given charge pressure thus decreasing the power output and tending to require that the mixture be enriched at a greater charge pressure. The two temperature eil'ects are thus in opposite directions and in some cases the one may completely odset the other so that the desired economizer control should operate at a predetermined charge pressure independently of atmospheric temperature. In other cases. however. the decreased power effect more than oifsets the loss in cooling and the desired economiser should then enrich the mixture at a somewhat increased charge pressure upon increase in atmospheric temperature.

It is accordingly an object of the invention to enrich the mixture supplied to an internal combustion engine when the absolute pressure of the charge entering the engine exceeds a predetermined lvalue.

It isa further object of the invention to supply supplementary fuel to an engine when the absolute pressure of the charge entering the engine exceeds a value determined by the atmosphric pressure.

It is a further obiect of the invention to provide a supplementary fuel supply which is rendered operative when the absolute pressure of the charge in the intake manifold posterior to the throttle and the supercharger exceeds a value determined by atmospheric pressure and temperature.

It is a further object of the invention to provide a supplementary fuel control mechanism in which a failure of the mechanism will produce an greater charge weight per stroke. In addition, at enriched mixture.

A still further object of the invention is to provide an improved supplementary fuel control mechanism.

Other obiects and advantages oi' the invention will be readily apparent from the following description taken in connection with the appended drawings in which:

Figure l is a diagrammatic view partially in section of a carburetor embodying the invention;

Figure 2 is a vertical sectional view of a slightly modined form of the invention shown in Figure l:

Figure 3 is an enlarged sectional view of the economizer valve oi' Figure l:

Figure 4 is a diagrammatic sectional view of a charge forming device of the pressure feed type utilizing another modification of the invention for controlling a supplementary fuel valve;

Figure 5 is an enlarged sectional view of the economizer control mechanism of Figure 4;

Figure 6 is a diagrammatic sectional view of a portion of the charge forming device of Figure 4 in which the invention controls an air bleed passage to efi'ect a supplementary fuel supply; and

Figure is a view similar to Figure 6 of a modified arrangement in which the invention controls another of the air passages of the charge forming device to eiiect a supplementary fuel supply.

Figures 1 and 2 disclose very similar modifications of the invention. differing from each other only as pointed out hereinafter. and may be described together. There is disclosed a carburetor having an induction passage comprising an air inlet or scoop I0, a venturi il, and a mixture outlet adapted to deliver into the intake of a supercharger Il. A throttle IB controls the induction passage. A main fuel nozzle I8 receives fuel from the fuel reservoir 2li through passage 22 and metering orice Il and discharges it into the induction passage adjacent the constrlcted portion of venturi I2. A fuel passage 26 bypasses the metering orifice Il and is controlled by an economizer valve indicated generally at 28. It is readily apparent thatthe passage 2B could discharge directly into the induction passage rather than into the main nozzle posterior to the metering orifice 24 as shown.

The economizer valve, as best shown in Figure 3, comprises a stem 30 having a shoulder I2. 'I'he lower portion of stem III is fluted as indicated at Il and slldabiy receives a tapered valve member 3B which is normally urged against the shoulder 32 by a compression spring 38. The flutes ll normally have an effective aggregate cross-sectional area equivalent to the effective fuel metering area of thev economlzer valve 28 when in open position. A spring retaining washer 39 and nut 40 retain the parts in assembled relation, the valve 2l acting merely as a solid type of fuel valve during normal periods of operation. Valve stem I0 is pivotally connected, preferably through a universal connection l2 as shown in Figure 2, to a lever I4 having a fixed pivot 4G at opposite sides of which are connected bellows l! and 48. The bellows are fixed to a base member 50 and are pivotally connected to lever u by rods B2 and 53. In Figure 1 the bellows are of equal effective diameters and are connected to the lever M at equal distances from the fixed pivot 46; whereas in Figure 2 the bellows are at unequal distances from the pivot, the bellows Il being preferably connected at a lesser distance from the pivot I6 than bellows 4l. Instead of decreasing the lever arm of bellows IB the bellows could be of somewhat smaller effective diameter than bellows 48 and accomplish an equivalent result as will be pointed out hereinafter.

Bellows 4B is partially filled with a body of oil 54. Bellows I0 is entirely lled with oil and communicates freely with a chamber Il which is closed by a flexible diaphragm 5B, the other face of which is connected through a conduit l1 with the induction passage posterior to both the throttle and the supercharger. As shown, the conduit 51 leads to the outlet ring of the supercharger and is thus subjected to supercharger discharge pressure. The pressure transmitted through conduit 51 may be either above or below atmospheric because of the action of the supercharger. Both bellows I8 and 4I are enclosed in a casing 68 which is connected by a passage 58 to the air scoop I0. A compression spring Il having an adjusting screw B2' for varying the spring force urges lever Il in a direction to close the economlzer valve 2l.

Referring more particularly to Figure 2 in which the details of construction are best shown it will be seen that the top closure plate '64 of bellows I8 is fixed to or formed integral with rod |52 and is provided with a cylindrical sleeve Il extending downwardly within the bellows adjacent the inner edges of the corrugations of the bellows so as to restrict the flow of oil into and out of the corrugations for purpose of damping. The other end of the bellows is closed by a base plate 6B having a tubular member 68 extending upwardly within the bellows and slldabiy receiving the rounded end of a plunger 10 depending from the closure plate B4 to form a guide and dashpot. A restricted port 1I may be provided in the lower end of member 69 to permit equalization of the oil level in the bellows and in member B8. It will be noted that this construction permits of misalinement between the parts and damps vibration as is more particularly described and claimed ln my copending application Serial No. 120,654, i'lled January 15, 1937. The bore of member B8 communicates with a filling aperture 12 which is closed by a set screw 13. The top of member 69 forms a stop to limit the extent to which the bellows may be collapsed. The lower portion of member B8 extends through the base member $0 and receives a nut 14 which secures the bellows to the base member.

Ii' it is desired that the control be not affected by variations in temperature of the air entering the engine the bellows I8 is evacuated by collapsing the bellows to a predetermined point, filling the collapsed bellows with oil or other liquid having a relatively constant temperatureviscosity relation. sealing the bellows with set screw 13, and then forcing the bellows to a partially extended position by the spring 6I). If, however, it is desired to modify the operation of the economizer in accordance with variations in entering air temperature, a predetermined quantity of gas, preferably an inert gas, is used in the space within the bellows above the oil level. By controlling the quantity of gas used in the space above the oil, that is the temperature, pressure and volume of the gas at the time of sealing, the sensitivity of the bellows to changes in temperature may readily be controlled, the bellows being non-responsive to temperature changes if the space is entirely evacuated, and becoming increasingly responsive as the degree of evacuation is decreased.

Bellows Il is closed at its upper end by a plate 1l which is :Iixed to or formed integral with rod Il. Plate 1l also has a depending portion extending downwardly within the bellows which terminates in a ball 18 forming a universal connection with a piston Il. The lower end of the bellows is closed by a base plate I2 having a hollow stem Il formed integral therewith extending through a bore in the base member It. A nut It closes the vertical passageway Il in the stem Il and also secures the bellows to the base member.

Passageway Il communicates at its lower end with the chamber ll through a passage 88 and at its upper end with the free space 'within the bellows through a plurality ot radial passages l0. A sleeve i2 ilxed to plate I2 and extending upwardly within the bellows slidably receives the piston 80, so as to form therewith a dashpot for damping vibrations. 'Ihe outer surface of the sleeve may be closely adiacent the inner edges of the corrugations to restrict the flow of oil into and out ot the corrugations for purpose of further damping vibrations of the bellows. A passageway il communicates the interior or sleeve $2. below the piston lll, with one of the, radial passages 90 and is partially restricted by an adjustable needle valve 05. The eiectiveness of the dashpot action oi piston 80 may thus be readily adjusted or varied.

A spring retaining cup $6 receives the spring lill and is urged upwardly thereby. A hardened rounded insert 01 in the head oi cup 98 engages the end of adjusting screw I2 to urge lever Il in a clockwise direction about the pivot I6 and thereby hold the economiser valve member 26 on its seat with a predetermined force. 'Ihe cup $6 has a downwardly extending rod l! formed integral therewith having a ball end D! which is slidably received by a tubular member INI extending upwardly irom the base member 50. A guide is thus provided to maintain the spring retaining cup 96 in proper alinement.

During periods ci operation at idle or low power outputs the valve 2B is held in a closed position under the combined forces of the spring 60 and bellows 48 and 49. The valve spring 38 under these conditions is sulciently strong to maintain the valve member 28 against the shoulder 22. As the power increases the pressure posterior to the supercharger and consequently the pressures in conduit I1, chamber 55 and bellows 49 will also increase thereby tending to open valve 2l. When the supercharger outlet pressure reaches a predetermined value the torce of bellows I9 will overcome the other forces holding the valve closed and the valve will open to supply supplementary fuel. In Figure 1 the bellows ll and l! are of equal size and have equal lever arms relative to the xed pivot 48. Variations in barometric or scoop pressure will act equally on the bellows 4l and Il thus creating equal but opposite forces on lever 44 and entirely canceling the effect of these variations. In addition, ii the bellows 4l has been completely evacuated leaving but a vacant space above the oil therein the bellows will be unaected by changes in temperature. It should furthermore be noted that bellows 49 is also not aiected by temperature changes since the change in the volume of oil resulting therefrom merely changes the position oi' the diaphragm I0 without changing the forces acting on the bellows. The arrangement of Figure l. utilizing an evacuated bellows ll therefore produces an economizer con- 0 trol which is independent of barometric pressure or temperature and solely dependent upon the absolute pressure at the outlet oi the supercharger.

As is generally known, an evacuated bellows is under rather severe stress and will therefore tend to iracture more readily than' a gas-lilled bellows. It will be readily apparent that the evacuation oi bellows Il creates an appreciable force tending to collapse the bellows and open the valve 2l which is normally counteracted by the force of spring Il. Ii the bellows Il iractures during service the loss o! this high collapsing torce will result in the valve beingheld on its seat with a greatly increased force. Under these conditions, however. the iorce tending to seat the valve is so high that the spring I8 permits stem Ill to move upwardly relative to member lt thereby uncovering the flutes Il and permitting Iuel to iiow past the valve. The device therefore iails rich, as was previously pointed out to be desirable.

I! bellows IB is but partially evacuated lt will respond t0 changes in temperature ci the entering air. an increase in temperature resulting in an increase in the expansive force oi bellows ll tending to seat valve 28 and therefore increasing the absolute supercharger outlet pressure required to open the valve 28. The eiiectiveness of changes in temperature on the required supercharger out let pressure may be readily controlled by varying the volume and absolute pressure oi the gas within bellows la, as previously pointed out.

By utilizing unequal lever arms for bellows Il and I9 (as shown in Figure 2), or bellows of unequal diameters, the forces created by the bellows on lever u by a change in entering air pressure will not balance each other and will vary the absolute pressure required at the supercharger outlet to open valve 28. 'Ihe amount the required supercharger outlet pressure will change for a given change in air inlet pressure will depend upon the relative lever arms ci the two bellows and/or the eective size of the bellows.

The economizer control unit is therefore capable of enriching the mixture when the absolute pressure posterior to the throttle and supercharger reaches a predetermined value, a value which may be independent of both the temperature and pressure of the entering air, or dependent to any desired degree upon the temperature. or pressure, or upon both the temperature and pressure of the entering air.

In Figures 4, 6 and 'l the invention has been applied to a charge forming device of the pressure feed type such as is particularly described in my copending application Serial No. 202,206, illed April l5, 1938. With particular reference to Figure 4, the main air passage includes an air intake llll, smal-l venturi and large venturi H2. The passage leads to the entrance oi' a supercharger IH o1' an internal combustion engine and is controlled by throttle IIB which is operated by a rod extending from. the pilots cockpit. The pilot thus controls directly the air charge of the engine while the fuel charge is automatically con` trolled by a metering unit hereinafter described.

The metering unit comprises chambers |20, i2 I, |22, |23 and |24 separated from each other by diaphragms |26, |21, |28 and |29 which are connected to a control rod.- I32 having a sleeve valve |34 connected thereto at its right end (as shown) and controlling fuel inlet ports |28. Fuel is delivered to ports |36 through conduit |31 by an engine driven constant pressure type fuel pump essere:

at |22 which receivesl fuel from a source. suon as a fuel tank. through conduit |22. The pump thus delivers fuel through ports |24. which are varied in edective area of opening by the axial positioning of sleeve valve |24. into the unmetered fuel chamber |22, through nxed metering orifice |42. an adjustable metering orifice |44, into metered fuel chamber |2i, and through passage |42 to a pressure responsive fuel discharge Jet indicated at |42 which discharges in the induction passage posterior to the throttle H2. A passage lll in the control rod |22 interconnects the chamber |24 and the metered fuel chamber I2|. The effect on control rod |22 of metered fuel pressure acting on sealing diaphragm |21 is thus balanced out by its equal and opposite effect on sealing diaphragm |22. A tapered needle lli is connected to pivoted lever |22 and has a disc |22 secured thereto to close orifice |44. by movement of lever |22 to the left, during periods of inoperation. During normal periods of operation the needle lli is positioned approximately as shown: however, if it is desired to manually enrich the mixture the needle may be further withdrawn from the orifice by movement of lever |22. An economiser bypass |22 is provided around the adjustable metering orice |44 and includes a metering restriction |l1 controlled by an econominer valve |22. Diaphragme |22 and |22 are connected to the stem of valve |22, the former forming a portion of the wall of the metered fuel chamber |2| and the latter forming a chamber |24 with acap |42. A passage |44 in the valve |42 connects the chamber |24 with the metered fuel chamber to balance out the effect of the metered fuel pressure on diaphragm |22. A lever |22 is pivoted at one end at |22 and engages the stem of valve |24 intermediate the diaphragme |22 and |22 at its other end. A guided control rod |12 of an economiser control unit indicated generally at |14 is pivotally connected to the lever |22 at |12 for actuating' the valve |22 to enrich the mixture, a slot being provided in the lever to permit pivotal movement thereof.

During operation. air iiow through the main air passage creates a differential pressure between the air scoop and the venturi throat which varies as the square root of the rate of air flow. The air scoop and venturi pressures are transmitted to air chambers |22 and |22 and create a force to the right on diaphragm |22 and control rod |22 tending to open the fuel inlet valve |24. Fuel ilow through the metering unit creates a dinerential force across the metering orices and therefore a differential in the fue] pressures in the unmetered fuel chamber |22 and metered fuel chamber |2| which is proportional to the square root of the rate of fuel flow. The dierentlal in fuel pressures acting on diaphragm |26 creates a force to the left on control rod |22 tending to close the fuel valve |24. The control rod |22 and valve |24 thus regulate the fuel flow so as to maintain the fuel force on rod |22 equal to the sir force. Bince the air force and fuel force on the rod |22 are respectively proportional to the quantities of air and fuel being delivered tothe engine a constant ratio is maintained between these quantities thus providing a constant mixturc richness. Spring ill engages control rod |22 creating an additional force tending to open the valve |24 which is of appreciable amount compared 'to the air force at idle but of negligible amount at higher air flows. This increases the fuel flow at idle to provide a rich mixture as is desired.

As the density of the entering air decreases from increase in altitude or increase in temperature. the air differential created by the venturis increases for a given weight of air and tends to increase the mixture richness. At such times the bellows |22 expands and valve |22 restricts passage |22. The bleed |22 which previoiuly had but a negligible effect in disturbing the pressures in chambers |22 and |22 now becomes effective to decrease the pressure in chamber |22 thus reducing the pressure which would otherwise be present in chamber |22 and maintaininl the diiferential pressure across diaphragm |22 at a constant value for a given weight of air ow. The mixture is thus maintained at a constant richness at all altitudes unless varied by a change in the fuel metering area, as for example by withdrawing needle III from orifice |44. The orifice |42 is relatively large compared to the normal metering area of orice |44 and therefore has 4very little metering effect. If. however. the valve III is entirely withdrawn the orince |42 becomes effective to meter the fuel and thus limits the maximum richness which is obtainable at the will of the pilot. The orifice |42 could be omitted if desired.

The economiser control unit |14. shown in detail in Figure 5, is quite similar to that of Figure 2 and consequently corresponding parts are given corresponding reference numerals with the addition of 222. Control rod |12 is connected through universal connection 242 to a lever 244 having a fixed pivot 242.

Bellows

242 and 242 are pivotally connected at one end to lever 244 by rods 222 and 222 and are fixed at their other ends to

base members

252 and 22|. Bellows 242 is preferably partially filled with a body of oil 224. Bellows 242 is entirely lled with oil and communicates freely with a chamber 222 which is closed by a exible diaphragm 222. the other face of which is connected by conduit 251 to the supercharger outlet. The bellows are enclosed in a casing 224 which may be opento itmosphere or be connected through conduit l2 to the air inlet ill. 'I'he bellows 242 and 249 have internal structure comparable to that oi' the

bellows

42 and 42 of Figure 2.

Bellows

242 and 242 are connected to lever 244 on the same side of fixed pivot 242. in contrast to the modification of Figure 2; however. in either case the bellows actin opposition to each other and produce an equivalent result.

Since bellows 24B is normally evacuated, it creates a force tending to move lever 244 in a counterclockwise direction which is much greater than that exerted by the bellows 242 tending to move the lever in the opposite direction. A resilient means is therefore provided to overcome this unbalance and to urge the valve ill onto its seat with a predetermined force such that the supercharger outlet pressure acting on bellows 242 must reach a predetermined value before the valve |22 will open. As shown. such resilient amarsi means comprises a sleeve 888 carried by a cup member 882 which is slidably mounted in a cylindrical member 884. The member 884 carries an adjusting screw 884 bearing on the end of the cup 882 for adjusting its position and conseduently the force of spring 288. A cap 888 encloses the adiusting screw. A rod 288 has a ball end 288 slidably mounted in the sleeve 888 and terminates in a head 281 bearing against a knife edge lill carried by lever 244. A sleeve 288 is secured to head 281 and serves as a partial housing for the spring 284 which bears at one end against head 281 and at its other end on the cup member 882.

By making

bellows

248 and 248 of the same size and evacuating bellows 248 an economiser control is obtained, as was described in connection with Figure 1. which will enrich the mixture when the absolute pressure of the supercharger outlet exceeds a predetermined value independently of the entering air temperature or pressure. Also, if bellows 248 is made smaller than bellows 248, as in the modification oi Figure 7, the absolute supercharger outlet pressure required to open fuel valve |58 will decrease with decrease in barometric or air inlet pressure. Also. by using a gas filled bellows 248 rather than an evacuated bellows the device will be temperature responsive and the absolute supercharger outlet pressure required i'or operating valve |58 will change with change in air temperature an amount dependent uponthe volume and pressure of the gas within the bellows.

It will be apparent that by reversal of fixed pivot |88 and pivot |18 the valve |88 could be arranged to open in the opposite direction such that the spring type valve of Figure 3 could be utilized with the arrangement of Figure 4.

The economiser control units of Figures 6 and 7 are substantial duplicates o f Figure 4 but operate air bleed valves, rather than fuel valves. to` accomplish an economiser enrichment.

In Figure 6 a valve 482 controls a passage 4|I4 connecting the passages |88 and |82 and is pivotally connected to one end of a lever 484 which has a fixed pivot at 488 and is connected at its other end to the economiser control rod |12. A stop screw 4 I is provided in the economiser control unit |14 and engages the lever arm 244 when the valve 402 is open the proper amount for normal operation. Under these conditions the lever 244 is urged against the stop 4I|| by spring 288 with a predetermined force which must be overcome by the supercharger outlet pressure acting on bellows 248 before the valve 482 can move toward closed position.

The bleed passage |88 is preferably placed to the left of passage 484 and a restriction 4|2 lnserted in the passage |88 between the passages |88 and 484. The passage |88 to the left of the restriction 4|2 is relatively large such that the bleed |88 has no substantial effect on the pressure in chamber |22 but reduces the pressure in chamber |28 when the altitude control valve |88 restricts the passage |88. On the other hand. the bleed 484 is relatively small compared with the passages |82 and |88 such that the bleeding action therethrough has substantially no effect on the pressure in chamber |22, but due to the restriction 4|2 has an appreciable effect on the pressure in chamber |22. Altitude control is thus obtained by modifying the pressure in chamber |28 whereas the economiser control is obtained by modifying the pressure in chamber |22. When so arranged, each control operates independently of the other. It will be apparent that passages |88 and 484 could be reversed in position in which case each control would operate on the other of the chambers |22 and |28 from that described above. Furthermore by varying the relative sizes of passages |88 and 484 and restriction 4|2. either or both controls could be made to have an effect on the other control.

During periods of normal operation the pressure in chamber |22 of the metering unit is modified due to the bleeding action of passage 484. The dierential pressure acting across diaphragm |28 is reduced as compared to that existing between the Venturi throat and the air scoop: however, it will always bear a ilxed relation to the Venturitoairscoop diiferential pressure. unless modied by the action of the bellows controlled valve |88. The device therefore meters the fuel in accordance with air ilow as in Figure 4, a slightly larger metering orifice being required for a given mixture richness due to the reduced effective Venturi-to-scoop differential pressure acting on diaphragm |28 at any given air now. When the supercharger discharge pressure exceeds a predetermined value the lever 244 moves upwardly oil of stop 4|8 and closes the valve 482, decreasing or eliminating the air bleed action through passage 4M. The increased differential pressure across diaphragm |28 resulting from the closing of valve 482 increases the fuel flow for a given weight of air thus providing an enriched mixture as is desired.

The modification of Figure 'l is very similar to that of Figure 6. In Figure 'I the economiser valve 428 and bellows controlled valve |88 operate in series to control the effective area of passage |82 and consequently together control the effectiveness of the ilxed bleed |88 between passages |88 and |82. Closing movement of valve |88 with increase in altitude further restricts passage |82 rendering bleed |88 more effective. producing an altitude mixture control as before. When the supercharger outlet pressure exceeds a predetermined value lever 244 moves of! of stop 4|8 and opens the valve 428, thus decreasing the effectiveness of the bleed 88 and increasing the richness of the mixture as is desired. The bellows 248 is. as shown, smaller than bellows 248 therefore making the device responsive to variations in air inlet pressure transmitted to the economiser control unit through conduit 288.

Although the invention has been described with particular reference to several modications it is to be understood that the invention is not limited thereto nor otherwise than by the appended claims, it being apparent that the invention could be used to accomplish an economiser control in other ways, or to position a control element in response to variations in the absolute pressure of any desired iluid or in response to the absolute pressure of one duid source and the pressure and/or temperature of a second fluid source.

I claim:

l. In a device for supplying fuel to an engine having a fuel pump and regulating means for controlling the rate of fuel supply. a control device comprlsing an evacuated bellows responsive to changes in barometric pressure, a second bellows connected to the engine intake manifold to be responsive to pressure changes therein, and means jointly controlled by said bellows to automatically modify the control eifected by said regulating means.

2. In a device for supplying fuel to an engine having a fuel pump and regulating means for controlling the rate oi' fuel supply, a control device comprising an evacuated bellows responsive to changes in barometric pressure. a second bellows connected to the engine intake manifold to be responsive to pressure changes therein, a lever connected to both of said bellows to be jointly controlled thereby, a spring urging said lever to a. normally balanced position, and control means operated by said lever to modify the control effected by said regulating means.

3. A sensitive control element for an engine carburetor having a throttle controlled induction passage comprising a bellows, means connecting the interior of said bellows to the carburetor induction pipe posterior to the throttle to be responsive to pressure variations therein, a second bellows sealed with a predetermined interior pressure, a control member connected to both of said bellows to be actuated jointly thereby, and means including a body of liquid in each of said bellows to damp vibrations thereof.

4. In a charge forming device for an engine having a supercharger on the downstream side of said device, a source of fuel, a source of air, means for controlling the normal fuel supply to the engine, a device rendered operative for enriching the mixture of air and fuel when the pressureiosterior to the supercharger exceeds a predetermined value, and means responsive to temperature for modifying said predetermined value.

5. In a charge forming device for an internal combustion engine having a supercharger. an induction passage having a throttle. an air supply, a main fuel supply, a supplementary fuel supply, a valve controlling said supplementary fuel supply, means responsive to the pressure posterior to the supercharger and throttle for actuating said valve to enrich the mixture, and means responsive to temperature for varying the value of said pressure necessary to actuate said valve.

6. In a. charge forming device for an internal combustion engine provided with a supercharger, and an induction passage having a throttle and a main fuel supply; means for supplying supplementary fuel to the engine, means responsive to the pressure posterior to the throttle and supercharger controlling said supplying means, and means responsive to variations in barometric pressure and temperature for modifying said control.

7. In a charge forming device for an internal combustion engine provided with a supercharger and an induction passage having a throttle and a main fuel supply; a supplementary fuel supply, a valve for normally rendering the supplementary fuel supply inoperative, and means responsive to variations in the pressure posterior to the throttle and supercharger and to variations in the pressure and temperature of the air supplied to the device for actuating said valve to supply supplementary fuel to the engine.

8. In a charge forming device having an induction passage including a throttle, an air supply, a normal fuel supply, a supplementary fuel supply, means for controlling said supplementary fuel supply including a valve, means responsive to the differential between the pressure of the air supplied to the device and the pressure in the induction passage posterior to the throttle connected to said controlling means, and means responsive to the pressure of the air supplied to the device connected t Said $011- trolling means for at least partially neutralizing the effect thereon of variations in said air pressure.

9. In combination with a supercharged internal combustion engine having a throttle controlled induction passage, a normal fuel supply, means for supplying supplementary fuel to the engine; and a valve controlling said supplying means, a sealed bellows and a second bellows connected to said valve for controlling the same, means for subjecting the outside of the sealed bellows and one side of the second bellows to a source of substantially atmospheric pressure, and means for subjecting the other side of said second bellows to the pressure in the induction passage posterior to the throttle and superclarger.

l0. In a charge forming device having an induction passage including a throttle and a supercharger, means for normally supplying fuel to the induction passage, means for supplying supplemental fuel to the induction passage, a valve controlling said last named supplying means, and a control unit for said valve comprising a bellows sealed with a predetermined interior pressure connected to said valve. a second bellows connected to said valve, a diaphragm chamber, means connecting one side of said diaphragm chamber to the interior of said second bellows, said second bellows, said connecting means and said one side of the diaphragm charnber being filled with liquid to damp vibrations of the second bellows, and means connecting the other side of said diaphragm chamber to the induction passage posterior to both the throttle and the supercharger.

l1. In a charge forming device for an engine having a normal fuel supply, a supplementary fuel supply, valve means including a stem and a spring loaded valve member thereon for controlling the supplementary fuel supply, a bypass uncovered by movement of the stem relative to the valve member when the valve means is closed with an abnormal force, and means for controlling said valve means comprising a flexible chamber responsive to variations in barometric pressure and a second flexible chamber responsive to pressure changes in the induction passage of the engine.

12. In a charge forming device having means for normally supplying fue] to an engine, a passage for supplementary fuel, a valve in said passage, means including an evacuated member for controlling said valve, and means becoming operative upon failure of said evacuated member to bypass supplementary fuel past said valve.

13. In a charge forming device, a uid passage, a valve controlling said passage, means including a sealed capsule responsive to changes in pressure controlling said valve, said capsule being at times subjected to an external pressure different than the internal pressure thereof, the capsule and valve being operatively interconnected in a manner such that upon failure of the capsule a closing force is exerted on said valve, and means becoming operative upon failure of the capsule to provide a by-pass for fluid past said valve.

14. In a charge forming device for an engine having an air induction system provided with a supercharger, fuel metering means for maintaining a predetermined normal ratio of fuel to air, means rendered operative by an increase in pressure beyond a predetermined value in the air induction system posterior the supercharger for enriching the charge, and means responsive 13 to temperature for modifying the action of said enriching means.

15. In a charge forming device for an engine having an air induction system provided with a supercharger, fuel metering means for maintaining a predetermined normal ratio of fuel to air, valve means adapted to meter supplementary fuel to the normal supply and enrich the fuel-air mixture under abnormal charge pressure and temperature conditions, means responsive to changes in pressure and temperature controlling said valve means, and means for subjecting said pressure and temperature responsive means to a measure of the pressure and temperature of the air comprised in the charge.

FRANK C. MOCK. REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Cloedy et al Feb. 27, 1940 Number Number Correction FRANK C. MOCK It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows' Column 12, line 6, claim 9, for a normal fuel supply, read and a. normal fuel supply; line 8, for engne; and read angina;

and that the said Letters Patent should be re 14 Name Date Wunsch et al. Sept. 6, 1938 Lockwood June 22, 1937 Della Chiesa et al. Dec. 26, 1939 Halford et al Oct. 8, 1940 Fulton Sept. 1, 1908 Fulton Dec. 31, 1918 Udale Feb. 18, 1941 Lozivit Dec. 31, 1940 Gregg Nov. l2, 1935 Berger Feb. 21, 1939 Dodson Apr. 16, 1935 Schimanek June 2, 1942 Goodman Feb. 9, 1937 Beardsley May 10, 1938 Gregg Aug. 3, 193'? FOREIGN PATENTS Country Date France 1938 England 1936 September 2, 1947.

ad with these corrections therein that case in the Patent Oce. Signed and sealed this 7th day of December, A. D. 1948.

THOMAS F. MURPHY,

13 to temperature for modifying the action of said enriching means.

THOMAS F. MURPHY,