US2361228A - Charge forming device - Google Patents

Description

Oct. 24, 1944. F. c. MOCK CHARGE FORMING DEVICE Filed Dec. 15, 1941 ZSheets-Sheet 1 /N l/f/VTOE FQA/VK C Mac/e 2 Sheets-Sheet 2 F. C. MOCK CHARGE FORMING DEVICE Filed Dec. 15, 1941 /NVA/ 7'0? FPAA/KC/VOCK a e. 927% A TTOE'NEY FIG. 2

Patented Oct. 24, 1944 UNITED STATES PATENT CHARGE FORMING DEVICE Frank C. Mock, South Bend, Ind., assignor to Bendix Products Corporation,

South Bend,

7 Ind., a corporation of Indiana Application December 15, 1941, Serial No. 422,945

15 Claims.

stand that many variations may be made without departing from the principles disclosed; and l continuation-in-part of my copending application, Serial No. 202,206, filed April 15, 1938.

One of the principal objects of the present invention is to supply the liquid fuel under positive pressure, the fuel supply being regulated to maintain a proper fuel to air ratio both at idle and through the open-throttle range. This arrangement causes the fuel to be atomized under pressure to produce a better'mixture and keeps the fuel under superatmospheric pressure at all times thereby eliminating boiling of the fuel and insuring accurate metering.

Another object of the invention is to prevent the formation of ice in the fuel mixture passage. This is accomplished by injecting the fuel into a warm or hot part of the manifold system or the like posterior to the throttle.

Another object of the invention is to provide an idling system having no tendency to form ice, which would interfere with idling operation. This is accomplished by utilizing ports adjacent the throttle which transmit suction but do not discharge fuel. 4

Another object of the invention is to provide an idling system in a pressure typecarburetor which is simple and inexpensive, but capable of producing any desired richness characteristic through the idling and low-speed range.

Another object is to provide a fuel feeding device or system which will operate properly in any position so that when it is installed on aircraft the engine will be properly supplied with fuel both at idle and open-throttle operation regardless of the position of flight. This is highly important during maneuvers of different kinds, at

contemplate the employment of any structures, arrangements, or modes of operation that are properly within the scope of the appended claims.

Figure 1 is a diagrammatic sectional view of a charge forming device embodying the invention;

Figure 2 is a partial view in section of the air passage of the device of Figure l, in which a modified idling arrangement is provided; and

Figure 3 is a view similar to Figure 2 of a further modification of the invention.

which time an adequate fuel supply is indispen- 3 I Referring first to Figure l, a main air lntalre conduit Ill leads to a rotary blower or super charger of an internal combustion engine which may be of any desirable type. The con duit I0 is controlled by a throttle it which is up erated by a rod l8 extending from the pilots cockpit. The pilot thu controls directly the air charge of the engine while the fuel charge is automatically controlled by the apparatus hereinafter described in detail. Anterior to the throt tie is a venturi it of any suitable contour. In some cases a second supercharger may be employed to supply air at higher than atmospheric pressure to the entrance it of passage lb, and

in such cases the supercharger l2 serves both to step up the pressure and as a fuel mixer and distributor. In other cases the entrance 2% is merely flared and opens in the direction of travel of the craft, so that the inertia of the entering air will 'build up a pressure above atmospheric at the entrance, which is in such cases usually referred to as a scoop.

An instrumentality such as the blower it is not essential to the invention, but is here shown as representing approved practice in aircraft engines, and serves to or assists in atcmizing and properly distributing fuel introduced into the air line in the manner presently referred to. The blower discharges into a generally annular chamber l5 from which pipes lead to the intake ports of the various cylinders, as usual in this type of engine.

It is to be understood that the entire air passage between the throttle and the engine intake ports represents broadly an intake manifold, and the term is to be so construed in this specification. Any known or suitable fuel pump, capable of delivering fuel. under positive pressure. is provided, that shown being of the sliding vane type and com-prising a rotor 22 slidably carrying a. set of vanes 23 and rotatably mounted in a casing it.

The casing has a fuel inlet 25, an outlet 26, and a return by-pass l0 controlled by a pressure re sponsive valve 2, so as to maintain a substantially constant outlet fuel pressure, in the known manner. The pump thus delivers fuel to passage 20 and thence into annular chamber I, through ports 58 past a tapered poppet or lift type of valve I03 which seats at II I, into pressure chamber 20, through fixed metering orifice 23, an adjustable metering orifice 80, into chamber I21 and through passage 32 to a discharge Jet 34 positioned in the conduit l posterior to the throttle.

The discharge jet as is provided with a valve 36 opening away from the manifold and connected to a flexible diaphragm 39. Fuel pressure entering through the pipe 32 acts on one face of the diaphragm 39 tending to open the valve 36, and is opposed by a spring 38. Since manifold vacuum is effective on valve stem 30 merely to the extent of its application on an area equivalent to that of the valve orifice whereas the fuel pressure is efiective to the extent of its application on the relatively large area of the diaphragm 39, the fuel discharge pressure is practically unaffected even by large changes in manifold vacuum. The relatively large diaphragm area also enables the valve to change from a relatively closed position to a wide open one (to give low and high rates of fuel discharge) with but a slight change in discharge pressure. This relatively constant pressure feature aids in obtaining accurate metering under variable operating conditions. A fixed stop 31 is preferably pro-. vided to limit opening of valve 36 to prevent damage in case of back fire or the like.

A second pressure chamber 44 is positioned adjacent chamber 28 and is separated therefrom by a flexible diaphragm 46 which is preferably of the type having no elastic reaction to stress, comprising a fabric sheet secured at its outer flange ofcollsr I03 moves away from and is substantially free of any eflect of the spring at any substantial valve opening. The spring II. is carried by a gasket which engages the outer edge of the diaphragm 40 and when the shell surrounding the valve mechanism I00 is removed I 'which merely serves the purpose of a leakless stuiflng box. A second large diaphragm Cl separates chamber '0 from another chamber 01, and

rod 50 is connected to the disks 04 of this diaphragm in the same manner as to those of diaphragm 40. A second stuffing box" diaphragm 06 is secured to the end of rod 50 and separates the chamber 02 from a chamber 00 positioned adjacent thereto.

The sealing diaphragms 50 and 00 are preferably made of duprene, synthetic rubber or other suitable material and are formed with annular grooves as clearly shown to give a rolling action against the confining walls. It will be observed that the effective area of the diaphragm is unchanged regardless of the position to which it is moved. Fluctuations of pressures which might edges and having its central portion secured between a pair of disks 40. The disks are in turn secured to a rod which terminates at its extreme right end in a ball IOI slidable within a socket I03 which also receives a ball I 05 carried by the extreme left end of a valve stem I01 of inlet valve I00. A universal connection is thus provided between the valve and the rod 50 of the diaphragm assembly hereinafter described. The parts are thus free to float to align themselves, thereby decreasing side pressure on the rod or valve which might cause binding.

Valve I09 is carried by a plug 3 threaded on the valve stem I01. The valve assembly is held in place by means of an outer nut 5 which may be removed to take the assembly apart without disturbing the adjustment of the poppet valve on the valve stem relative to the diaphragms. A diaphragm II1 serves to seal the outer end of the valve member to prevent fuel from escaping. A passage II'IA communicates the fuel chamber 28 with the space to the right of the diaphragm Ill. The diaphragm III is equal in effective area to the effective area of the valve seat III and is thereby effective to balance the unbalance which would otherwise result from the differential in pressure across the valve I09.

A leaf spring Ill engages the socket I03 to urge the valve assembly towgard the open posi-- tion to provide an enrichment at idling speeds as will be described hereinafter. The force of the spring urging the valve toward open position may be varied by means of an'adiusting screw Hi. The spring is preferably of such design that it acts on rod 50 and valve I09 only when the said valve is in a nearly closed position. The

interfere with the proper operation of the parts to which the diaphragm is attached are thereby.

avoided. To facilitate assembly of the parts, the diaphragms may be formed with thickened sttaching flanges while the working sections remain thin.

In order to balance out the unavoidable pressure effects of diaphragms 50 and 00, chambers 33 and are interconnected by a pressure equalizing passage 10 formed in the rod '0.

The rod 50 carries enlarged cylindrical hub members 5| adjacent the diaphragms II and 00 of substantially the same diameter as the fist central portions of the diaphragms on the low pressure sides thereof. The diaphragms are formed with deep annular grooves as shown, the sides of which lie respectively against the members SI and outer circular confining walls. Due to this construction and the differential in fluid pressure which exists on the two sides of the diaphragms, the grooves in the diaphragms maintain a substantially constant effective radius as the rod 50 moves, so that the eflective areas thereof remain constant regardless of movement of the rod 50. The same construction is preferably followed in connection with the diaphragms l6 and 60 by providing circular flanges 40 and 05 on the plates 43 and 84 respectively. This is an important feature since it enables the diaphragms always to exert the same force in response to equal pressures regardless of the deflection of the diaphragms. It will be observed that the end of the rod so is rounded to minimize friction and to permit it to seek a non-binding position.

A small venturi 14 is positioned in the intake conduit I0 concentrically with the venturi II and is formed with an annular opening 10 substantially at its throat which is connected through a passage II with chamber 56. A small by-pass 33 interconnects the passage 10 with the induction passage posterior to the throttle It. A cali- 'brated reltrictlonl 1 limay be provided lnthepasuse It between the passaae fland the Venturi annulus 18. A similar passage: 88 leads irom chamber lite-an: annular: chamber Il -formed in the venturi I hand: communicatinrwith the inlet 'end oithezconduit' I 8 throughivza series o! 7 tubes 8| so'asto be sublected -to thelpressure of t the incoming air; Thewtubes :8l :project out a tionethus tar described areohere introduced in order toaid inxiclarifyingathe functions of parts of the invention hereinafter v described. Chamber 82 is subjected to air scoop pressureychamber' l8lto Venturi suction, modified by the pressure in the induction passage posteriorto the throttle at idling-speeds, chamber towhatis generally reierredto asmetered+fuel" pressure and chambers 28=-and 68 to *unmetered-iuel" pressure.

- When the: enginewis inn-operation, it draws air 'throughtheuair condult: l8, and a diflerential pressure isrthus created between the airscoop and the venturi,.the amount of which is a function of the rate oi -air now. This diilerential in pressuresactingin chambers 56: and 82 creates a net force tending to move rod 58'to the right in a directionto open valve I88. If this forceis equivalent tovthe pressure drop across orifice 28 and passage fl andt-is afunction of the rate 01 fuelilow therethrougln Since the-pressure in chamber is maintained within I relatively narrow limits 'by the actions of- 'Jet: 88'; opening or' valved 88' will increase the pressure in chamber 28 (due'todecreasedythrottllng lossacross said valve) thereby,"increasing the differentialpressure across the metering: orifices and. in-' creasing the: rate of. fueluflowt Thel diflerential in pressure between chamberM'andvchambers '28 and 88 will exert'a force 'onrod ntending to moveit to: thesleftorinna directionwto close valvel88, .thuswopposingm the force'onwrod 58 created by -thevdepressionaat venturi 145-,

neglecting thesprlngzl lawman has substantially no efle'ct except'latfvery 1' small flows correspond ing"tor-ldllnrranser wlll show 'that the rod 58 will adjust' itself 'tova point oi-Yequilibrium such that l the diflerential. across the fuel metering r orifices is equal- 1120- the differential pressure beto movetoward closed position thereby restoring the fuel meteringdifferential pressure'to its originalmvalue. If theengine speed is decreased, by

a changein the propeller pitch o'rfrom any'other cause, the rate-10f. air fiowthrough venturi H decreases; decreasing the: differential pressureacting on diaphragm 88," causing ,valve I89 to move toward closed position and thus decreasing. the fuel flow to compensate for the decreasedrate or air flow which initiated the adjustment.

Therateoi tuelilow is directly controlled therefore bytherate oi airflow, and a constant mixture ratio can be attained.

At lowair flowacorresponding to idle operationrthe spring H8 acts on rod 88, thus adding an increment of force 'tothe normal Venturi action tending to open the valve I89 and thereby requiring an increased-pressure differential across diaphragm 88 to balance the forces on rod 58. This results in increased fuel flow and a richer mixture for idle operation.

When the throttle i6 is in the idling position, the suction existing posterior to the throttle is transmitted through passage 83 and .tends to ,increase'the suction in passage 18 and chamber 58. The increased force'operating on rod 58 tends to openvalve I88 and a richer mixture is consequently produced at idle. It will be apparent that restriction 18 may be omitted if desired; however, its use'increases the sensitivity [of the passage 83. It will be observed that the port 83 opens into the induction passage adjacent the-trailing edge of the throttle, so as to change fromposterior to anteriorto the throttle as the throttle opens. The enrichmen created by port 83may thus be eliminated at any desired throttle position.

Spring H8 and bypass 83' have similar effects at idle, namely to increase the richness of the mixture. The port 83, however, is effective to enrich the mixture at low air flows corresponding to idling operation but not at low air flows with the throttle open, as at heavy load and low engine speed, whereas spring H8 enriches the mixture at low air flow regardless of whether the throttle is open or closed. The idle. spring I I8 and port 83 may be used together or either ricpressuresias at-ground or sealevel) andto maybe used without the other as desired. Use of the port 83 either alone or in combination with spring H9 makes possible a leaner mixture at low speed wide open throttle than is used at partthrottle, a. feature which is very desirable for many engines.

The passage 88- is controlled by a capsule or aneroidi8l, shown in Figure-1 as-a sealed, corrugated bellows which carries a valve member 88 which tendsto .open passage at high barometclose the same at low pressures (as at high altitudes). A calibrated passage 88 connects the lower portion of chamber 62 to the passage 18.

Passage 88 is sufliciently small in comparison with passages 18 and 88 that when valve 88 is open, air flow through passage 88 is not effective A summation of forces actingon the rod 88,

in materially altering the pressures existing in chambers Hand 58, As altitude is gained, valve 88 movestoward closed position under action of the'bellows 88, flow of airfrom chamber 82 into passage 881s thereby restrlctedand the air flow from passage 88 through passage 88 becomes more effective in reducing the pressure existing inchamber 62, thus decreasing the differential pressure :acting on diaphragm 88' and tending tovclose' valve I88 and'lean out the mixture as desiredwith increase in altitude. Passage 88=also serves as a drain for any moisture collecting in chamber '82.

To guard against the building up of a differential of fluid pressures between chambers 58 and It willsures between the chambers 56 and 52; however,

these two passages may be made sufficiently small that they will accomplish their desired functions without interfering with the operation of the device.

The bellows 84 is preferably only partially evacuated so that it will be responsive to changes in temperature as well as pressure, the amount of temperature response being controlled by the degree of evacuation. As the temperature of the air entering the air scoop 20 increases, bellows 84 will elongate slightly, moving. valve 85 to a position to restrict the passage 90, reducing the pressure in chamber 62, and thereby reducing the pressure differential across the diaphragm 60. Consequently the fuel flow will be slightly reduced to provide a leaner mixture as the inlet air temperature rises.

In some cases it is desirable to design spring H9 and by-pass 83 to give an excessively rich idling mixture and then use valve 90, which is throttle connected through bell crank 92 and link 94 and arranged to move into passage 30 at closed throttle, to restrict the flow of fuel through passage 30 so as to obtain the desired idle richness, The valve 90 can be given any desired configuration to provide the desired rate of fuel flow at closed as well as substantially closed throttle. Valve 90 is drawn clear of passage 30 as the throttle valve I6 is opened so that during normal operation the valve 90 occupies substantially the position shown and does not affect the fuel flow. The use of valve 90 represents a preferred embodiment but may be omitted if desired, in which case the idle spring IIS and/or port 83 are designed to produce the necessary enrichment for idling operation.

The port 30 may further be controlled by a plunger I04 controlled manually from the pilots seat through a linkage I05 to provide either a rich or lean mixture. When the end of the plunger I04 is projecting into the port 30, as

shown, the flow of fuel is restricted and a lean mixture results. To obtain a richer mixture the pilot may operate linkage I05 to withdraw the plunger I04 completely from the port 30 to leave it unrestricted. Preferably the plunger I04 carries a disc I09 adapted to close the port 30 completely so that the pilot can cut off the fuel supply at will in case of emergency or when the engine is to be stopped.

A further manual control is provided by a valve H0 in the passage 80 urged onto its seat by a spring H2 and connected to the linkage I06 by a link H4, The link H4 is pivoted to one end of a bell crank lever II6, the other end of whichis slidable on the stem of the valve H0 and is adapted to engage a nut II8 on the end thereof. This arrangement provides a lost motion connection so that the plunger I04 can be operated as described above without affecting the valve IIO. However, if the linkage I06 is pulled back to its extreme limit the valve IIO will be opened to admit air at intake pressure to the chamber 62 thereby opening the valve I09 further and increasing the richness of the mixture regardless of position of valve 85.

The control means thus far described provide a mixture of suitable richness for varying speeds, loads, and throttle openings, and provide a degree of compensation for changes in altitude. However, during periods of operation at high power output it is desirable to richen the mxture and for this purpose a iluel-metering-head economizer is employed. In; this device a calibrated by-pass I250 around metering orifice 30 connects the unmetered fuel in chamber 28 with the metered fuel in chamber I21 above the chamber 44. A valve I25 controls the by-pass and is urged toward the closed position by a spring I29. The valve may be urged toward the open position by a diaphragm assembly I3I, A spring I33 in the diaphragm chamber I35 urges the diaphragm in the direction to open the valve I25 against the spring I29. The spring I33 may be adjusted to seat the valve I25 at any predetermined value. The rate of valve opening is of course a function of the differential forces exerted by the springs I29 and I33 and the differential in the fuel pressures on opposite sides of the diaphragm I 3|.

The diaphragm I3I is subjected on the right side to the metered fuel pressure in the chamber I21 and on the left side to the pressure of the unmetered fuel in the diaphragm chamber I35, a conduit I31 being employed in the form shown to transmit the unmetered fuel from the chamber 29 to the diaphragm chamber I 35. A small vent I39 serves to permit the escape of any air from the chamber I35, which might be trapped in the unmetered fuel.

A dashpot I4 I may be provided on the end of the economizer valve I25 if it is desired to damp out sudden oscillations or movements of the valve.

As the power output of the engine increases, by opening the throttle or otherwise, the fuel delivered to the engine increases and consequentiv the fuel metering differential pressure increases. The fuel metering differential pressure, that is the differential in the pressures in chambers 23 and 44, acting on the economizer diaphragm I3I tends to open the economizer valve I25. When the fuel differential pressure equals or exceeds a predetermined value the force of spring I29 will be overcome and the valve I25 will open, thereby enriching the mixture as is desired.

It is to be noted that with this type of economizer control only one diaphragm is utilized in contrast to other arrangements in which balanced sealing diaphragms are required in addition to the main actuating diaphragm.

'A relatively small orifice I23 extends through the diaphragm 45 to permit both diaphragm chambers 29 and 44 to fill with fuel simultanetime shall be automatically regulated independently of the control of the pilot. Either of these conditions can be obtained as desired by incluslon or exclusion of the orifice 29 or by properly proportioning the size of this orifice. For example, if the area of passage I25a is greater than that of orifice 29, orifice 29 functions as the sole restriction to fuel flow when valve I 25 is open as at full power, and operation of plunger I04 has then no effect on the fuel flow On the other hand, if the restriction formed by the orifice 29 is omitted or the orifice is made larger than the combined areas of passages I250 and 30, fuel flow is metered by these two passages and the pilot, through operation of plunger I04, may control the mixture both during normal and emergency operation.

Figures 2 and 3 disclose modified forms of the suction idling arrangement of Figure 1. Corresponding parts have been given the same reference numerals but where the structure or arrangement differs from that of Figure 1 corresponding reference numerals with the addition of 200 in Figure 2 and 300 in Figure 3 have been used.

In Figure 2 the throttle 216, arranged to open in the opposite direction from that of Figure 1,

is actuated by the pilot through the link 2l8.

,terior to the throttle regardless of throttle position. As a consequence the richness of the mixture does not decrease as rapidly as the throttle is opened as with the arrangement of Figure 1.

The modification of Figure 3 is similar to that of Figure 2 but differs therefrom in that a suction conduit 383 intercommunicating the Venturi passage 18 and the induction passage is provided with two outlets 381 and 389 adjacent the leading edge of the throttle and on opposite sides thereof when in a closed position.

With a single port, as disclosed in Figure 2, the mixture richness will tend to decrease quite rapidly as the throttle opens from idle because of the decreasing vacuum at the port and also because the increment increase in suction in passage 18 created thereby will produce a diminishing percentage enrichment as the air flow and resulting suction at venturi M increase. With the arrangement of Figure 3 the port 389 is gradually brought into the high suction range as the throttle opens, thus preventing'too rapid decrease in mixture richness as the throttle opens. By controlling the relative sizes of ports 381 and 389 and the position of the latter relative to the throttle when in closed position, any desired richness characteristic through the idle and near idle range may be obtained. If desired, the port 381 may be provided with an adjustable valve so that the richness at idle may be readily varied. Obviously, more than two ports could be used if desired or a narrow slot might also be used.

It will also be understood that many changes might be made in form and arrangement of parts and it is not intended that the scope of the invention shall be limited to the forms shown and described nor otherwise than by the terms of the appended claims.

I claim:

1. In a fuel supplying system for an internal combustion engine. an induction passage, a throttle therein. a venturi in the passage anterior to the throttle, a fuel conduit for supplying fuel to the engine. a metering element in the conduit. fuel valve means for controlling the flow of fuel to the engine, a casing. diaphragms within the casing forming four chambers therewith, said diaphragms being operatively connected to said valve means for operating the same, pressure transmitting means interccmmunicating two of the chambers with the fuel conduit anterior and posterior to the metering element and arranged so that an increase in the differential of said pressures tends to decrease the fuel flow to the engine, a pressure transmitting connection from the venturi to another of the chambers and arranged so that a decrease in pressure at the venturi tends to increase the fuel. flow to the engine, means for decreasing the pressure in said other chamber during idling including port means in the induction passage posterior to the throttle, and a passageway interconnecting the port means and the said other chamber.

2. The invention defined in claim 1 wherein the port means is adjacent the trailing edge of the throttle.

3. In a fuel supplying system for an internal combustion engine including an air passage, a throttle therein, air differential pressure creating means in the air passage anterior to the throttle, a fuel conduit, fuel valve means controlling the flow of fuel to the engine, a casing, pressure responsive diaphragm means in the casing forming movable walls of a plurality of chambers and being operably connected to the valve means, area restricting means in the fuel conduit for creating a differential in the fuel pressures at spaced points in the conduit, means for subjecting two chambers .to the fuel pressures in the fuel conduit at the said spaced points in such manner that an increase in the differential in the fuel pressures acting on the diaphragm means tends to decrease the fuel flow to the engine, and means for subjecting two chambers to air pressures derived from the air differential pressure creating means in such manner that an increase in the differential in the air pressures acting on the diaphragm means tends to increase the fuel flow to the engine: the combination therewith of means for increasing the flow of fuel to the engine during idling operation comprising means for increasing the differential between said air pressures during idling including a passage leading from the chamber subjected to the lower of the air pressures and having an opening into the induction passage posterior to the throttle when in the idling position.

4. The invention defined in claim 3 comprising in addition a throttle controlled valve for varying the effective area of the area restricting means.

5. The invention defined in claim 3 comprising in addition a spring for yieldingly urging the valve means in a direction tending to increase the fuel flow to the engine.

6. The invention defined in claim 3 comprising in addition a spring urging the valve means in a direction tending to increase the fuel flow to the engine during idling, and a throttle controlled valve for decreasing the effective area of the area restricting means as the throttle is moved toward closed position.

'7. In a charge forming device, an induction passage having an air entrance, a throttle valve in the passage, a venturi in the passage anterior to the throttle, a fuel conduit, fuel valve means controlling the flow of fuel through the conduit, area restricting means in the fuel conduit creating a pair of fuel pressures the differential of which varies with variation in fuel flow through the conduit, diaphragm means connected to the fuel valve means for controlling the latter to thereby regulate the fuel flow, the said diaphragm means forming movable walls of four chambers, means forsubjecting two of the chambers to the said pair of fuel pressures, a passageway connecting another of the chambers to a source of air at substantially air entrance pressure, and passageway means connecting the fourth chamber to the venturi and to the induction passage posterior to the throttle.

8. The invention definedin claim 7 comprising in addition a throttle controlled member for varying the effective area of the area restricting means.

9. The invention defined in claim '7 comprising in addition a spring for urging the fuel valve means in a direction tending to increase the fuel flow to the engine.

10. The invention defined in claim 7 comprising in addition a spring urging the fuel valve means in a direction tending to increase the fuel flow to the engine during idling, and a throttle controlled valve for decreasing the eifective area of the area restricting means as the throttle is moved toward closed position.

11. In a fuel feeding system, an air passage, a throttle therein, means in the air passage anterior to the throttle for creating an air differential pressure variable in accordance with variations in air flow, a fuel conduit leading from a source of fuel and discharging in the induction passage posterior to the throttle, means in the fuel conduit for creating a fuel differential pressure variable in accordance with variations in fuel flow, a fuel valve controlling the fiow through the conduit, diaphragms responsive to variations in said air and fuel differential pressures operably connected to the' fuel valve and so arranged that an increase in the air differential pressure tends to increase the fuel flow and an increase in the fuel differential pressure tends to decrease the fuel flow; whereby substantially constant fuel to air proportioning is obtained, and means for increasing the air differential pressure to which the diaphragms are subjected during idling to thereby increase the ratio of fuel to air during idling comprising a port opening into the air passage posterior to the throttle, and a pressure transmitting passageway leading from the port to the pressure responsive diaphragms and so constructed and arranged that an increase in suction at said port tends to move said fuel valve in a direction to increase the fuel flow.

12. The invention defined in claim 11 comprising in addition a throttle controlled element for modifying the fuel flow increasing effectiveness of the last recited means.

13. In a fuel supply system for an internal combustion engine, an air-induction passage provided with a throttle for controlling the flow of air to the engine, means in said passage anterior the throttle creating a differential air pressure varying in relation to the rate of air flow, a conduit for supplying liquid fuel under superatmospheric pressure to said passage to be mixed with air flowing to the engine, means in said conduit creating a fuel differential pressure varying in relation to fuel flow to the engine, a fuel valve movable to vary the flow of fuel through the conduit, a casing, flexible diaphragm means operatively connected to said valve, said diaphragm means in the casing being in opposed pressure communication with said air differential pressure creating means and said fuel differential pressure creating means, respectively, to produce fuel flow in proportion to air flow, and a pressure-transmitting passage forming a communication between said diaphragm means and the air-induction passage posterior the throttle to supplement the air differential pressure applied to said diaphragm means when the throttle is in near idling or idling position to thereby increase the richness of the mixture during idling.

14. In a charge forming device for an internal combustion engine, an induction passage having an air inlet, a throttle in the passage, a venturi in the passage anterior to the'throttle, a fuel regulating device having a depression air chamber and a pressure air chamber, valve means for controlling the flow of fuel to the engine, means responsive to the air pressure in said chambers controlling said valve means, an air passage leading from the venturi adjacent the throat thereof to the depression air chamber, an air passage connecting the air inlet to the pressure air cham.- ber, and a passage connecting the depression air chamber to the induction passage posterior to the throttle.

15. In a charge forming device for an internal combustion engine, an induction passage having an air inlet, a throttle in the passage, a venturi in the passage anterior to the throttle, valve means for controlling the flow of fuel to the engine, a depression air chamber, a pressure air chamber, means responsive to the pressures in said chambers for actuating the valve means, an air passage from the air inlet to the pressure air chamber, a calibrated passage interconnecting the pressure and depression air chambers, an air passage from the depression air chamber to the venturi adjacent the throat thereof, and a calibrated connection between the last-named passage and the induction passage posterior to the throttle.

FRANK C. MOCK.

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