US1329308A

US1329308A - prentiss

Info

Publication number: US1329308A
Authority: US
Publication date: 1920-01-27
Anticipated expiration: 1937-01-27

Description

A. M. PRENTISS.

CARBURETER. APPLICATION FILED E s. Is. me.

Patented Jan. 27 1920.

2 sains-snaar I.

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A. M. PRENTISS.

CARBURETER.

APPLICATION FILED FEB. I9. Isls.

Patented Jan. 27,1920.-

2 sHEETs-sHEEI 2.v

vIINIIED STATES PATENT OFFICE.

AUGUSTIN M. PRENTISS, OF FORT CASNELL, NORTH CAROLINA, .ASSIGNOR 0F ONE-HALF TO DOUGLASS E. BULLOCH, 0F WASEINGTON, DISTRICT OF COLUMBIA.

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Specification of Letters Patent.

Patented Jan. 27, 1920.

Application iled February 19, 1916. Serial No. 79,379.

To all whom it may concern:

Be it known that I, AUGUSTIN M. PREN- 'riss, a citizen of the United States, residing at Fort Caswell, in the county of Brunswick and State of North Carolina, have invented certain new and useful Improvements in Carbureters, of which the following is a specification, reference being had therein to the accompanying drawing.

This invention relates to improvements in carburetcrs and has for its object:

First: To provide an improved system of this nature wherein the liquid fuel is fed into the mixing chamber' by a positive pressure which varies with the demands of the engine.

Second: To provide an improvedv system of this character wherein the liquid fuel feed is virtually independent of the aspirating `or induction cilects of the air column passing the fuel nozzles.

Third: To provide an improved system of this kind wherein the pressure on the liquid fuel is gradually diminished as the speed of the engine increases so as to neutralize the common tendency of devices now on the market to increase the feed of liquid fuel faster than the volume of air taken in as the lspeed of the engine increases.

Fourth: To provide an improved device that is self-priming` when starting; that is a device which will automatically and positively furnish a charge of highly enriched mixture euthe first suction stroke of the motor without the usual manual operation of flooding' or priming.

Fifth: To provide an improved system which will furnish a relatively rich mixture at low speeds either on nearly Open or nearly closed throttle to prevent stalling, and which will gradually reduce the richness of the mixture as the speed of the engine increases.

Sixth: To provide an improved system of this nature having means for supplying air under pressure to the liquid fuel column within the nozzleto break up the liquid column before it issues from the mouth of the nozzle, thereby forming` a spray independently of any condition of airl currents in the mixing chamber'.

Seventh: To provide an improved device of this nature having means of supplying mixture of air and liquid fuel which shall accompanying drawings forming a part hereof and wherein I have illustrated one embodiment of the invention.

In the drawings:

Figure l is a central vertical section of a device constructed in accordance with the present invention;

Fig. 2 is a section on the line 2-2 of Fig. l; Y l

Fig. 3 1s a section on the line 3-3 of Fig.

l, on an enlarged scale;

- F ig. 4 is a side elevation;

Fig. 5 is a Isection on the line 5--5 of Fig. l;

Fig. 6 is a. detailed sectional view, on an enhfrged s l,ale of one of thel nozzle structures;

Fig. 7 is a diagrammatic view to indicate the relative areas of one of the air inlet and mixture outlet ports, and of the cross section of the throat of the mixing chamber. The area of the air inlet port is marked B, and the area of the mixture outlet port is marked A, and the area of the cross-section of the mixing chamber is marked D.

rlhe invention broadly comprehends means 'for applying pressure upon the top of the liquid fuel in- Y the reservoir whereby the liquid fuel is fed into the mixing chamber by a positive pressure greater than atmospheric which varies with the demands of the engine, the pressure being Acontinuous and gradually diminishing as the speed of the engine increases. Morev particularly the invention contemplates means for this purpose incluchngl valve mechanism for varying the cross sectional areas of the air inlet and mixture outlet simultaneously with a prof gressively diminishing difference, ya member adapted to be moved through the influence of the difference in internal and external air pressures, and a piston or the like arranged to apply pressure upon the top of the liquid fuel in the reservoir and operatively connected with said member. Thev invention further contemplates a valve acting in conjunction with the first mentions valve mechanism, and operating automatically tliroujgli the difference in internal and external air pressures to increase the cross sectional area of the air inlet as the Speed of the engine increases. As will be appreciated the amount of pressure applied upon the topo the' liquid' fuel in* the reservoir by the piston depends upon the degree of vacuum in the mixing chamber or the differeneein internal and enternalair pressures and this: isi regulatedand gradually diminished thwugh the valve mechanism as the ofhheengine increases, so that at low speedsA either on nearly open or nearly closed throttle the pressure on the liquid fuel in the reservoir-.will be greatest and thc pressure gladmtlly diminished-as the speed of the en glnehcreaes, a relatively rich mixture'benag;furrnislli'edV oh low speeds, and the richness of the mixture being reduced as the speed of the engine increases.

In the drawings, I have illustrated a pre ferned embodiment ofthe invention and the particular construction shown comprises a casing having a central longitudinally extending chamber 1 constituting the mixing chamber and upper and lower annular chambe's 2;.axid3 surrcundmgv the mixing chamber, the lower chamber 3 serving as the liquid fuel reservoir, and the upper has an wtl'et chamber from which the mixture is discharged into the engine manifold. The easing remade up of anv outer shell 4, an inner cylindrical shell 5 spaced from and arranged cement-ric with the outer shell, a bottom-welll 6 connecting the shells at one end .and a top wall 7 closing the shells at their upper ends. 8 is a dia hragm separating the

chambers

2 and 3. n the present instance the outer and

inner shells

4 and 5, and the bottem Wall -6 are shown as integral, and the top 7 is a separate part and detailhalbly secured in place, the top being provided with a threaded portion 9 engaging aj threaded portion 10 at the upper end of the outer-shell 4. The diaphragm 8 is also detwchably secured in position. the diaphragm having a threaded Vcollar 11 engagixg a threaded portion 12 on the upper end o the inner shell 5. The diaphragm has a dependirgangel tofit within the outer ell, the outer marginal portion of the diaagm fitting against the. upper end oi the outer` shell and being engaged at its upper side by aange 14 on the top 7, this particnlararrangement rding convenient access the interierof the casing. Theinner A l provided with'an enlarged por- "at `.ngper end,.and the walls of te" er fell .at the lower end thereof a .ldlwn ivergng to'provide `an enlarged valve mechanism for varying the cross sectional areas of the air inlet and mixture outlet simultaneously with a progressively diminishing difference, in the particular embodiment of the invention illustrated in the drawings, compri-ses the following construction and arrangement of parts.

Rotatably tting the interior of the inner shell is a hollow cylindrical valve member having an enlarged portion 16- at one end fitting Within the part 5 of the inner shell, an enlarged part 22 extending below the bottom Wall 6 of the shell, and intermediate portions and 22', the valve member being shown as made up of three sections, the intermediate portion 22. and the enlarged portion of the valve member being formed as separateV parts, the former being detachably connected by a thread connection 23 with the intermediate portion 15, and the enlarged portion 22 connected with the intermediate portion 22 by a. detachable thread connection 23. The enlarged portion 116 of the valve member has a closed upper end 17 from which projects a stern 18, One end of the valve member fits against the under face of the top 7, the stem 18 extending through an opening 19 in the top. A nut 19x11 engages a threaded portion 20 or the stem, and' a Washer 21 interposed between the nut and the upper face of the top is provided to support the valve member in place.

The enlarged portion 5 of the inner shell 5 is rovided with a series of ports 24, leading om the mixing 'chamber into the upper chamber 2, said chamber 2 being adapted to be in ioimnunfication through an opening 2 with the manifold of an internal combustion engine. The upper part 16 of the valve member is provided with a series of ports adapted to register with ports 24 to regulate the mixture outlet.

Slidably tittin the interior of the lower part 22 of the va ve member is a cylindrical cup-shaped piston valve 26, which is provided with a series of ports 27. and the part of the valve member has a series of ports 28 adapted to register with the ports 27 to permit air to enter the mixing chamber. The relative size. shape, and arrange ment of thc` respective sets of outlet ports 24.-25 and inlet ports 27--28. are such, that upon rotation of the valve member, the ports of each set Will be simultaneously brought into register and the cross sectional areas of the air inlet and mixture outlet. through the respectivo sets of ports will be varied simultaneously with a progressively diminishing di'erenoe, the cross sectional area of the mixture outlet being always greater than that of the free air inlet. Referring particularly to Fig. 7 of the drawings, the outlet ports 24-25 are shown rectangular in shape. the area of the outlet ports being designated by A. The combined portage of Ll l) these mixture outlet ports is equal to the area of the cross section of the throat of the mixing chamber, the latter being indicated and designated D in the ligure referred to, there being, in the present instance, tour o'i such ports 2%*25- The inlet ports QYHQS are elliptical in shape and are 'equal in number to the-outlet ports 24-25 The cross sectional area of the inlet ports is greater than that of the outlet ports, and the combined areas o1" the inlet ports is in excess oit the area ol the cross section of the throat oli' the mixing chamber. The Width oit the inlet and outlet ports is the same, but the area B t indicated by dotted lines in Fig. 7) equals the area of one of the outlet ports, the added strips at top and bottom designated C indicating the diierence in area of the inlet ports and out-let ports. rthe rotary adjustment of the valve member is adapted to be manually controlled, the stein 18 ot the valve having a crank arm 29 for connection with any suitable operating means. As will be understood the enlarged part of the inner shell 5 provided with the ports 2a, and the enlarged portion 16 ot the valve member provided with the series of ports constitute a valve for regulating the mixture outlet, and the throttling valve for the engine.

The valve 26 is adapted to slide longitudinally within the part 22 to bring the ports 27-28 into register to vary the cross sectional area of the air inlet in a direction at right angles to the direction in which the cross sectional area of the air inlet is varied by the rotary adjustment of the valve member. The valve 26, which is exposed at its upper side to the engine suction and at its under lace through the opening 30 in the bottom of the part 22 to atmospheric pressure, acts automatirally through the difterenee in the internal and external air pressures. The exi-Cess area oit the inlet ports 27-28 over the mixture outlet ports 25 aiforded by the added areas C at the top ant bottom et the inlet ports 24 2f, provides for a lowering of the valve 526 about two thirds ol its total litt, when the inlet and outlet ports have been opened as far as pos-- .sible by the rotaryY adjustment oft the valve member,` and when this relation exists, at open throttle, the areas `t the air inlet and mixture outlet through the respective ports are nearly7 equal. l

3l designates the annular piston arranged to Work in the liquid 'fuel reservoir to apply pressure upon the tcp ot the body ot liquid tuel. The piston 3l may be provided with any suitable form of packing, not shown, and also with

annular depending flanges

32 and 33 entering the body ot liquid. ituel in the reservoir and torming a seal against the escape oli' air from the under side of the piston. il. suitable vent opening 34 is provided in the Wall of the outer shell l above the piston. The piston 3l is operatively connected with the piston valve 26 so that upon the movement of the valve 26 in one direction, a corresponding movement will be transmitted to the piston 31 in the opposite direction. The connection between the piston 31. and the piston valve 26 comprises a stem 35 secured to the piston valve, levers 36 and links 37. rlhe levers 36, which extend through small openings 38 in the inn r shell 5 and slots 39 in the valve l5 are pivoted intermediate their ends to ears 40 on the inner shell, connected at their outer ends by links 37 with the piston 31 and at their inner ends to a head 29a of the stem 35, said head being provided with pin 4l engaging slots 4t2 in the inner ends ot the levers. -The links 37 Work through openings i3 in the diaphragm 8, and any suitable form o' packing, not shown, may be provided torthe openings. rllhe head 29a has a detachable screw thread connection with the upper end of the stem and is provided With cross arms 4A extending through slots in the valve l5 and engaging grooves L6 formed in the inner shell 5, the valve 26 being thus held liXed 'from rotation While permitted to move longitudinally.

The valve member carries a plurality ot nozzles l? arranged at separated points thereabout to feed inwardly into the mixing chamber. The nozzles 47 comprise an outer air jet pipe 48' and an oil tube a9 extending centrally Within the air pipe. The inner shell 5 is provided with a series ot oil outlets a, b, c, d, arranged at dierent points aboutJ the shell, the arrangement of the 'oil outlets and oil pipes 49 being such that as the valve l5 is turned to bring the air inlet ports 2l, 25 and the mixture outlet ports 27, 2S into register', the oil tubes will be simule taneously with the air yports brought into register in succession with the oil outlets 50 to suit the demand of the engine. The oil outlets a, Z), c, d, are preferably 'formed as shown extending tangentially through the Wall of the shell 5, andthe inner mouth. of each tube is made or such Width that the mouth of tube a is the smallest, that the tube b is substantially twice the width ot 0 that of c substantially three times the VWidth ot a, anc CZ is substantially leur times the Width olf a.. Thus in turning the valve meinbcr l5, in a counter clockwise direction, l is brought into register lirst, then cl and c; then d, c, and Y); and finally at full opening c, 7) and L are all in reg` er, one Wall of each oil outlet being curved as shown to obtain a very line outlet oriiie at lirst as the pipe is gradually brought into register with the outlet, the outlet being gradually increased in size as the iet pipes are brought in lull register with the outlets.

Means is provided for supplying air under pressure to the liquid fuel column Within the oil pipes 49 in the nozzles to break up the liquid column before it issues from the mouth of the nozzles thereby forming a spray independently of any condition of air currents in the mixing chamber. In the present instance, auxiliary air supply eonduits 52 are provided for supplying air to the nozzles, said conduits communicating with the outer air spray pipes 47 of the nozzles, and a motor operated pump 53 is provided to supply air under pressure to said auxiliary conduits, the pump being connected to the auxiliary air supply conduit by a connection 54.

Any suitable means may be provided for maintaining liquid fuel in the reservoir 3 at a substantially constant predetermined level. The means for this purpose illus trated in the drawings comprises a ioat 55 operatively connected with a cutoff valve 56 interposed in the oil supply conduit 57. 59 designates a pump connected with the oil supply conduit for supplying oil under pressure to the reservoir, said pump being adapted to force the oil through the conduit at a pressure at least equal to the maximum pressure that is applied to the top of the liquid in the reservoir by the piston 81. The pump 59 may be of any approved form, that illustrated being the conventional type of force pump having the

check valves

61, 62. 63 designates a by-pass connection for the pump. Any suitable form of motor maxv be provided to operate the air pump and oil pump, but preferably an electric motor. not shown, is provided for this purpose.

The operation of the device is as follows:

With the engine at rest, the valve 15 and the piston valve 26 are in the positions indicated in Fig. 1 of the drawings, the

ports

24 and 25 and the

ports

27 and 28 being completely out of register, said last mentioned ports being out of alinement longitudinally but slightly alining with each other transversely. In starting. the valve 15 is turned a slight distance to bring the ports 24-25 partially into register and the

ports

27 and 28 into register to a small extent. Now as the engine is turned over, on the out stroke of the engine piston, the piston valve 26 will be caused t0 move upward by the difference in the internal and external air pressures. the piston 31 being forced downwardly and pressure is applied upon the top of the liquid fuel in the reservoir, to force oil out through the oil outlet and oil tube of the nozzle, which at that time is in register'. It will be understood that at this time the air and oil pumps have been set in operation. and the air supplied to the fuel nozzle under pressure serves to break up the liquid column before it issues from the mouth of the nozzle, so that the liquid fuel is forced out in a very fine spray independently of any condition of air currents in the mixing chamber. As the valve 26 rises, the

ports

27 and 28 are brought further into reglstra tion, and as the valve 15 is rotated to bring the ports 24-25 and :E7-28, into registration as fully as possible, the difference of cross sectional areas of the air inlet and mixture outlet is gradually diminished with a consequent lessening of the difference of internal and external air pressures and the pressure applied upon the top of the liquid by piston 31 until, at open throttle, the area of the air inlet and mixture outlet are nearly equal and the superposed pressure on the liquid fuel in the reservoir is reduced to nearly atmospheric pressure, there being, however, always some difference in pressure. Referring particularlyY to Fig. 7 of the drawings, it will be seen that the inlet ports are elliptical in cross section whereas the outlet ports are rectangular, the horizontal dimension of each being the same but the vertical dimension of the inlet being greater than that of the outlet. Therefore during the first stages of opening of the inlet and outlet valves, thc rectangular area of the outlet ports in register is greater than the corresponding segmental area of the inlet ports in register, and a condition of vacuum in the mixing chamber is established. A further opening of the valves, however, reduces the preponderance of the outlet portage over that of the inlet portage resulting in a decrease of vacuum in the mixing chamber. If now there were no vertical adjustment of the inlet valve 26, a point would be reached, near quarter turningwhere the area of the inlet port would exactly equal that of the outlet and a condition of steady flow would be set up and the vacuum would be greatly reduced, and if the area of the inlet and outlet ports happened to be each equal to that of the cross section of the mixing chamber at that point, the vacuum would practically vanish. But this reduction in the intensity of the vacuum results in a lowering of the inlet valve member which reduces the inlet portage, so that a point where the inlet and outlet are exactly equal can never be reached with the result that there is always some vacuum in the mixing chamber. It will thus be understood that the greatest degree of vacuum in the mixing chamber is when the preponderance of the outlet ports over the inlet ports is a maximum, that is, at the beginning of the opening of the valves, and that this vacuum is gradually reduced as the preponderance is reduced. namely, as the valves are opened. It therefore follows that the piston valve 26 will be in its uppermost position during the initial stages of the opening of the valves and will gradually descend as the vacuum is relieved, that is, as the valves are opened,

consequently the superimposed air pressure upon the oil in the float chamber will be a maximum during the initial stages of the openingl of the valves and will be gradually lessened as the valves are manually opened, reaching its minimum at full openinO'. At open throttle the piston valve has lowered about two thirds of its total lift, the pressure at the under side of the piston 31 serving to force the piston upwardly as the pressure is relieved from the upper side thereof. rihe valve Q6 acting through the difference in the internal and external air pressure serves to further regulate the degree of `facuum in the mixing chamber or the difference in internal and external air pressures, balancing the action of the mechanism to obtain the desired continuous gradually diminishing pressure upon the top of the liquid in the reservoir.

It will be remarked that the invention provides for a lessening of the superimposed air pressure upon the oil feed to counteract the common tendency of all suction operated carbureters to feed an excess of oil on the higher speeds or the engine speeds up, As is well known, the flow of air does not follow the law of efliux or influx of liquids due to a varying density in its more or less attenuated condition. This difference in the efliux of air and liquids causes a departure from any fixed ideal ratio of the two at any given speed, or degree of difference of internal and external pressures, and therefore any device 'in v-,hieh the feed of oil is made to depend directly upon the velocity of the current of air passing the fuel outlet must necessarily fail to maintain a fixed ideal ratio between the two as the suction and therefore the velocity of the air current is increased. The present invention acceuiplishes this maintenance of a fixed ideal ratio by first applying a superimposed pressure upon the liquid fuel in the fuel reservoir, thus making the conditions at the fuel outlet of the nozzle virtually independent of the air current in the mixing' chamber, and then gradually decreasing the superimposed pressure upon the fuel feed as the speed of the engine increases, until at open throttle this superimposed pressure is reduced to nearly atmospheric pressure, but never quite so.

It will also be observed that provision is made for increasing the volume of the mixture b r bringing a plurality of fuel ports progressively into action simultaneously with an opening of the air inlet ports, but the rat io of air flow to fuel flow is controlled by a system of balanced pressures whereby the volume of the mixture can be increased without altering the quality or departing from a fixed ideal ratio of air to oil.

It will be understood that the term positir@ pressure in the specification and claims is used to mean a pressure greater than atmospheric.

I desire it to be understood that changes anc modications in the particular form of the device illustrated in the drawings, as will appeal to those skilled in the art may be iii-ade without departing from the broad principles of the invention.

lllhat l claim is:

i. ln a carbureter, a mixing chamber, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level, means for maintaining a positive pressure always greater than atmospheric upon said liquid fuel and means for varying the pressure upon said liquid fuel inversely as the pressure in the mixing chamber.

2. In a carbureter, an outlet chamber, a liquid fuel reservoir, means for maintaining liquid fuel therein at 'a substantially constant predetermined level, means for maintaining a positive pressure always greater than atmospheric upon said liquid fuel and means to vary the pressure upon said liquid fuel directly as the vacuum in the outlet chamber..

ln a carbureter, a mixing chamber, a liquid fuel reservoir, means for maintainlng liquid fuel therein at a substantially constant predetermined level, means for maintaining a positive pressure always greater than atmospheric upon said liquid fuel and means to vary the pressure upon said liquid fuel inversely as the pressure in the mixing chamber, and in a constantly decreasing ratio as the pressure in said chamber increases. i

4:. A carbureter comprising an outlet chamber, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level, means for n'iaintaining a positive pressure always greater than atmospheric upon said liquid fuel, and means to vary this pressure directly as the vacuum in the outlet chamber and in a constantly decreasing .ratio as the vacuum in said chamber increases.

5. In a carbureter, an air inlet port of conie cross section, a pluraliy of fuel inlets, i

a mixture outlet, and means consisting of a single rotary valve member for varying the cross sectional area of said inlets and outlet simultaneously.

6. ln a. carbureter, an air inlet port of come cross section, a mixture outlet port, and means consisting of a single rotary valve member to vary the cross sectional areas of said inlet and outlet ports simultaneously with a progressively diminishing difference as said ports are opened. Y

7. In a carburetor. an air inlet, a liquid fuel reservoir, means to vary the cross sectional area of said inlet, and means associated with said first mentioned means for varying the pressure upon the fuel in said reservoir as the cross sectional area of said inlet is varied.

8. In a carbureter, a mixing chamber having an air inlet and a mixture outlet, a fuel feeding nozzle associated with the mixing chamber, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level, means for supplying pressure upon the liquid fuel in the reservoir directly as the vacuum in .the mixing chamber, and means for supplying air under pressure to the fuel feeding nozzle.

9. In a carbureter, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level, said means including a iioat and valve mechanism for the reservoir, and a pump for supplying liquid fuel under pressure to the reservoir, and means for supplying pressure upon the liquid fuel in the reservoir directly as the vacuum in the mixing chamber.

10. In a carbureter, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level including a motor operated pumpl for supplying liquid fuel under pressure to the reservoir, and lmeans for supplying pressure upon the liquid fuel in the reservoir directly as the vacuum in the mixing chamber.

11. In a carbureter, a mixing chamber having an air inlet and a mixture outlet, means for varying the cross sectional areas of said inlet and outlet simultaneously, a liquid fuel reservoir, means for maintainingr liquid fuel therein at a substantially constant redetermined level, and means for supplying pressure upon said liquid fuel irectly as the vacuum in the mixing cham- 12. In a carbureter, a mixing chamber having an air inlet and a mixture outlet, means for varying the cross sectional areas of the inlet and outlet simultaneously with a progressively diminishing difference, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level, and means for supplying pressure upon the liquid fuel in the` reservoir directly as the vacuum in the mixing chamber.

13. In a carbureter, a mixing chamber having an air inlet and a mixture outlet, a fuel feeding nozzle associated with the mixing chamber, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level. means providing pressure upon the liquid fuel in the reservoir directly as the vacuum in the mixing-chamber, means for varying the cross sectional areas of said inlet and outlet simultaneously, and means for supplying air under pressure to the fuel feeding nozzle.

14. In a carbureter, a mixing chamber having an air inlet and a mixture outlet, a fuel feeding .nozzle associated with the mix-l ing chamber, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level, means providing pressure upon the liquid fuel in the reservoir directly as the vacuum in the mixing chamber, means for varying the cross sectional areas of the air inlet and mixture outlet simultaneously with a proressively diminishin difference, and means for supplying air un( er pressure to the fuel feeding nozzle.

15. In a carbureter, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constantpredetermined level, means for maintaining a positive pressure always greater than atmospheric upon said liquid fuel, a mixing chamber and means actuated automatically by the difference of pressures interna] and external of said mixing chamber for varying the pressure upon the liquid fuel in the reservoir iiiversely as the pressure in the mixing chamber.

16. In a carbureter, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level, and means acting automatically to always maintain a pressure greater than atmospheric and for varying the pressure upon the liquid fuel in the reservoir inversely as the pressure in the mixing chamber, said means including a piston operated by the difference in the internal and external air pressures.

17. In a carbureter, a carbureter or mixing chamber, having an air inlet and a mixture outlet, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level, and means for varying the pressure upon the liquid fuel in the reservoir inversely as the pressure in the mixing chamber, said means including a piston operating automatically by the difference in internal and external air pressures, and a valve controlling the air inlet and operatively connected With said piston.

18. In a carbureter, an air inlet port of conic cross section, manually operable means for varying the cross sectional area of the inlet in one direction, and automatic means acting directly through the difference in internal and external air pressures for varying the cross sectional area of said inlet in another direction.

19. In a carbureter, an air inlet port of conic cross section, manually operable means for varying the cross sectional area of the inlet in one direction, and automatic means acting directly through the difference of internal and external air pressures for varying the cross sectional area of said inlet in a direction at right angles to the first mentioned direction.

20. In a carbureter, an air inlet, a mixture outlet, manually operable means for varying the cross sectional areas of the inlet and outlet simultaneously, and means acting automatically through the difference in internal and external air pressure for varying the cross sectional area of the air inlet.

Q1. In a carbureter, an air inlet, a mixture outlet, manually operable means for varying the cross sectional areas of the inlet and outlet simultaneously With a progressively diminishing difference, and means acting automatically through the difference in internal and external air pressures to vary the air inlet.

22. In a carbureter, a mixing chamber having an air inlet and a mixture outlet, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level, .and means for varying the pressure upon the liquid fuel in the reservoir inversely as the pressure in the mixing chamber, said means including a piston acting automatically through the difference in internal and external air pressures, a piston in. the liquid fuel reservoir, and an operative connection between said pistons.

23. In a carbureter, a mixing chamber having an air inlet and a mixture outlet, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level, and means for varying the pressure upon the liquid fuel directly asthe vacuum in the mixing chamber, said means including a piston operating automatically through the difference in internal and external air pressures, a rod connected With said piston, a second piston in the liquid fuel reservoir, and a lever pivoted intermediate its ends and connected at opposite ends with said rod and said first mentioned pistons respectively.

24. In a carbureter, a mixing chamber having an air inlet and a mixture outlet, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level, means for varying the cross sectional areas of said inlet and outlet simultaneously with a progressively diminishing difference, and means for varying the pressure upon the liquid fuel in the reservoir inversely as the pressure in the mixingr chamber.

25. In a carbureter, a mixing chambe having an air inlet and a mixture outlet, means for varying the cross sectional areas of the inlet and outlet simultaneously vvith a progressively diminishing difference. a valve operated automatically by the difference in internal and external air pressures, to increase the cross sectional areas of the inlet as the speed of the engine is increased,l

a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level, and means for supplying pressure. upon the liquid fuel in the reservoir directly as the vacuum in the mixing chamber.

26. In a carbureter, a mixing chamber having an air inlet and a mixture outlet, means for varying the cross sectional areas of the inlet and outlet simultaneously in one direction with a progressively diminishing difference, a valve operating automatically by the difference in internal and extern al air pressures to increase the cross sectional areas of the inlet in a direction at right angles to the first mentioned direction as the speed of the engine increases, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level, and means for supplying pressure upon the liquid fuel in the reservoir directly as the vacuum in the mixing chamber.

2'?. in a carbureter, a liquid fuel reservoir, aV mixing chamber having an air inlet and a mixture outlet, a fuel feeding nozzle comprisingan outer air jetpipe, and an oil tube extending Within the said air jet pipe and communicating with the oil reservoir, means for supplying air under pressure to the air pipe of the nozzle, means for maintaining liquid fuel in the reservoir at a substantially constant predetermined level, means for supplying pressure upon the liquid fuel in the reservoir directly as the vacuum in the mixing chamber.

28. In a carbureter, a mixing chamber having an air inlet, a fuel inlet, and a mixture outlet, means for varying the cross sectional areas ef said inlets and outlet simultaneously, and varying the cross sectional areas of the air inlet and the mixture outlet with a progressively diminishing difference, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level, and means for supplying pressure upon the liquid fuel in the reservoir directly as the vacuum in the mixing chamber.

29. In a carbureter, a mixing chamber having a rectangular shape mixture outlet port, and a tapering air inlet port, a valve provided with a rectangular shape port and with a tapering port, said last mentioned ports corresponding in size and shape and adapted to register respectively with the mixture outlet ports and the air inlet port of the mixing chamber, the valve being adapted to be adjusted to simultaneously bring the respective sets of ports into register for varying the cross sectional areas of the air inlet and mixture outlet simultaneously vvith a progressively diminishing difference, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constaat predetermined level, andineansfor varying the pressure upon the liquid fuel in the reservoir inversely as thepressure in the mixing chamber.

30. vIn a carbureter, a mixing chamber having a rectangular shape mixture outlet port, and -an elliptical shape air inlet ort, a valve provided with a rectangular s ape port and an elliptical shape port, said ports corresponding in size and shape and being adapted to register respectively with the mixture outletport and the air inlet port of the mixing chamber, the valve being adapted to be adjusted to simultaneously bring the respective sets of ;portsinto register to vary the cross sectional areas of said inlet and outlet simultaneously with a progressively diminishing diierence, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level, and means for varying the pressure upon the liquid fuel in the reservoir inversely as the pressure in the mixing chamber.

31. In a carbureter, a mixing chamber having a plurality of rectangular shape mixture outlet ports and a plurality of elliptical shape air inlet ports, a valve provided with a lurality of rectangular shape ports and Wit a plurality of elliptical ports, the

orts corresponding in shape and size and eing adapted to register respectively with the mixture outlet ports and inlet ports of the mixing chamber, the combined portage f of the mixture outlet ports being equal in area to cross section of the mixing chamber. said valve being adapted to be adjusted to simultaneously bring therespective sets of ports into reglster to vary the cross sectional areas of the inlet and outlet simultaneously with a progressively diminishing difference, a liquid fuel reservoir, meansfor maintaining liquid fuel therein at a substantially constant predetermined level, and means for varying the pressure upon the liquid fuel inversely as the pressure in the mixing chamber.

32. In a carbureter, a mixing chamber having a plurality of mixture outlet ports, a hollow cylindrical valve rotatably fitting the interior of the mixing chamber said valve being provided with a plurality of ports to register with the said outlet ports of the mixing chamber, and with a plurality of air inlet orts, a valve sl-idable longitudinally Within the hollow cylindrical valve and provided with a plurality of air inlet ports to register with the air inlet ports of said first mentioned valve, the outlet ports being rectangular in shape and the inlet ports being elliptical in shape, the relative size and arrangement of the ports being such that upon rotary adj ustmont of the hollow cylindrical valve the air inlet mixture outlet ports will be simultaneously brought into register to vary the cross sectional area of the air inlet and mixture outlet with a progressively diminishing difference. said second mentioned valve being adapted to be operated automatically through the difference in internal and external air pressure to vary the cross sectional area of the air inlet in a direction at right angles to the direction that it is varied by the rotary adjustment of the valve. a liquid fuel reservoir. means for maintaining liquid fuel therein at a suhstantially constant predetermined level. and means for varying the pressure upon the liquid fuel in the reservoir inversely as the pressure in the-mixing chamber.

33. In a carbureter. a mixing chamber having a plurality of mixture outlet ports. a hollow cylindrical valve rotatably fitting the interior of the mixing chamber said valve being provided with a plurality of ports to register with the said outlet ports of the mixing chamber, and with a plurality of air inlet ports. a valve slidable longitudinally within the hollow cylindrical valve and provided with a plurality of air inlet ports to register with the' air inlet ports of said first mentioned valve, the outlet ports being rectangular in shape and the inlet ports being elliptical in shape, the relative size and arrangement of the ports being such that upon rotary adjustment of the hollow cylindrical valve the air inlet and mixture outlet ports will be simultaneously brought into register to vary the cross sectional area of the air inlet and mixture outlet with a progressively diminishing diiference, said second mentioned valve being adapted to be operated automatically through the diiierence in internal and external air pressures to vary the cross sectional area of the air inlet in a direction at right angles to the direction that it is varied by the rotary adjustment of the valve, a liquid fuel reservoir, means for maintaining liquid fuel therein at a substantially constant predetermined level, a member mounted to slide longitudinally in the mixing chamber `and adapted to be operated through the difference in internal and external air pressures, a'pistonarranged to apply pressure upon the top of the liquid fuel in the reservoir and an operative connection between said member and the piston.

In testimony whereof I hereunto atlix my signature in the presence of two Witnesses.

AUGUSTIN M. PRENTISS,

Vitnesses:

ANNE H. PRENTIss: THEO. K. VOGEL, JR.