US2271114A - Method of and means for supplying combustible mixtures to internal combustion engines - Google Patents

Description

Jan. 27, 194.2; R. F. BRACKET 2,271,114

METHOD OF AND MEANS FOR SUPPLYING COMBUSTIBLE MIXTURES TO INTERNAL COMBUSTION ENGINES Filed July 27, 1938 4 Sheets-Sheet l Ira/670501". Z0Zerf15r02 jheflflw zew z/m Jan. 27, 1942. R. F. BRACKE 2,271,114

METHOD OF AND MEANS FOR SUPPLiYING COMBUSTIBLE MIXTURES T0 INTERNAL COMBUSTION ENGINES Filed July 27, 1938 4 Sheets-Sheet 2 F. BRACKE 4 Sheets-Sheet 4 1000 1 soo 2000 2500 Engine RPMai Tull Huofl'le Engim 12PM at Full Uuoflle 0H 0 w m. w. m o m m w w 0 A l momuv P0 3.3.: Lfua u 33 6 tac 5 3 Q &5 S 1E 2 33 a E Jan. 27, 1942.

' of the engine to knock at low speed full throttle Patented Jan. 27, 1942 v UNITED STATES PATENT OFFICE METHOD OF AND MEANS FOR SUPPLYING COMBUSTIBLE MIXTURES TO INTERNAL COMBUSTION ENGINES Robert F. Bracke, Chicago, Ill.

Application July 27, 1938, Serial No. 221,485

1 Claim. (01. 123-119) y v tion pertains to a method and means the fuel feeding system is of the non-fuel lift for supp y n combustible mixtures t internal type, the float bowl of the carburetor is'maincombustion engines and is particularly adapted tained under atmospheric pressure and a diafor modern automobiles. phragm pump, separate vacuum tank, or other In general, it may be stated that it is desirpumping means is provided t pump t gasoable to use as igh a Compression ratio in the line from the main supply tank at the rear of automobile en as is possible Without PF the automobile to the float bowl of the carburetor in n ing of the engine W operetlng n attached to the engine manifold. Where the the usual Co e gasoline e p e on fuel feeding system includes a fuel lift carburetor,

ratio which can be used Without knocking of 10 no diaphragm pump, vacuum tank, or other indethe automobile engine depends somewhat upon pendent pumping means i necessary,

the materials used in the automobile engine and Th fuel feeding ystem incorporating th fuel p c y in the cylinder head, and it is not lift carburetor is. cheaper to manufacture and uncommon to P d different Cylinder heads has other advantages over a fuel feeding system made Of different materials and having different 15 comprising a non fue1 lift carburetor and gap. COmDI'GSSlOD. ratios for use on the same engine ara te pumpingmeang' Heretofore however the b1ock. With a y v n material, however, the fuel feeding system incorporating the fuel lift en ine has the test te y o knock when. carburetor has had the disadvantage that it reis operating at low speed and under full throtn ,duced the power f the engine at high speed full throttle and thus reduced th maximum s eed Today most automobiles are operated over wellwhich could be obtained by f automobn: iltfitiffififiitftfit anguished? of my to i t i isadvan age of the prior art fuel feeding mobll'es P$ E m fig gg 3 m systems incorporating fuel lift carburetors. figi'gimi f giif g 5 3 2 g p fi Anotherobjection to the prior art fuel feeding at d at low s eed and under iull throttle and systems embodying fuel 11ft carburetors lay in z when embed the eriod of Such the difficulty of calibrating these fuel feeding emtion is brief Hovever with present systems accurately under conditions of quantity methods and means fr sup lyin combustible 3O manufacture due to the delicacy of calibration p g of such prior art fuel feeding systems.

mixtures to automobile engines, this relatively rare condition of engine operation limits the compression ratio which can be used in the automobile engine even though a higher compression ratio would be much more desirable for most conditions of engine operation.

An object of my invention is to provide a method of supplying a combustible mixture to an internal combustion engine and a means for carrying out such method whereby the tendency Another object of my invention is to overcome this disadvantage of the prior art fuel feeding systems incorporating fuel lift carburetors.

Another object of my invention is to provide a novel method of supplying fuel to internal combustion engines whereby the efficiency of such engines is increased under normal operating conditions. u Another-object of my invention is to provide a fuel feeding system having a novel correlation to the internal combustion engine for the purpose of carrying out the-foregoing method.

Another object of my invention is to provide a simpler, less expensive, and more efficient fuel feeding system for modern automobiles.

is overcome, thereby permitting the use of higher compression ratio than is now possible and thus increasing the efficiency and power of the engine under normal driving conditions.

Another object is to increase the efficiency of the engine when operating under conditions other Another Qbject is to Provide an p ed fuel than low speed run throttle. 11ft cerburetoij- In practically all automobiles now manufac- Another ob-lect 15 to Provide an p ed artured the engine is located at the forward end 50 buretor 0f the non-fuel lift p of the automobile and the main gasoline tank is Another Object is to provide an i proved fuel located t t rear of t automobi1e The fuel feeding system having a non-fuel lift carburetor. feeding systems for such automobiles may inot er object is to provide an p oved fuel corporate either a fuel lift carburetor or a nonfeeding sy rporating a fuel lift carbufuel lift carburetor. Where the carburetor of 55 r'etor.

Other objects and advantages will become apparent as the description proceeds.

In the drawings,

Figure 1 is a side view of a typical modern automobile, parts being cut away to show the internal combustion engin and the fuel feeding system therefor;

Figure 2 is a sectional view showing part of a fuel feeding system of a type embodying a nonfuel lift carburetor;

Figure 3 is a sectional View of a part of a second type of fuel feeding system embodying a non-fuel lift carburetor;

Figure 4 is a sectional view of part of a fuel feeding system incorporating a fuel lift carburetor;

Figure 5 is an enlarged View of the booster Venturi tube shown in Figure 4 Figure 6 is a fragmentary view illustrating a modified form of a part of the structure shown in Figure 4; and

Figures '7 and 8 are charts illustrating theoperating' characteristics of diiferent fuel feeding systems.

Referring to Figure 1 ofthe drawings, I have illustrated therein a typical modern automobile having aninternal combustion engine I2, located in a suitable enclosed compartment at the forward end of the automobile. The particular engine shown is indicated as being an engine of the type in which the cylinders are located in a straight line, but'it is to be understood that my invention isequally' applicable to automobiles having engines of the V type or of any other desired arrangement of cylinders.

The automobile engine is illustrated as comprising a cylinder block l4 and cylinder head 16, both of which may be made of any usual or suitable material. The cylinder block contains a plurality of cylinders I3, each having a piston 20 connected by means of a connecting rod 22 to the usual engine crank shaft which is not shown. Above each cylinder the cylinder head 16 is provided with a suitable cavity 24 whose volume with respect to the stroke of the piston a 20 determines the extent to which the combustible mixture is compressed in the engine cylinder prior to ignition under any condition of operation. In general, it maybe stated that an increase in the compression ratio of the engine results in greater power and operating efficiency and, generally speaking, it is desirable to make the compression ratio as high as possible without producing knocking in the engine under any conditions of operation with the fuels now commercially available.

The main gasoline tank from which the engine is supplied with fuel is indicated at 26 and is located at the extreme rear of the automobile. The fuel feeding system for supplying the engine l2 with a combustible mixture of gasoline and air comprises an intake manifold 28 to which a carburetor 39 is shown as being attached. This carburetor 30 isconnected with the fuel tank 26 by means of a pipe line consisting of a flexible section 32 which accommodates the rocking movement of the engine on its-support on the automobile frame and a relatively rigid portion 34' connecting the flexible portion-32 with the main fuel tank 26. I

Figure l discloses-my preferred type of fuel feeding system: wherein the carburetor 30 is of the fuel lift type and requires nofseparate pumping. means. Portionsofthefuel feeding system shown in Figure l are shown in greater detail.

in Figures 4 and 5 and the particular embodiment of my invention shown in Figure 1 will be described in greater detail in a later part of this application.

My novel method of supplying a combustible mixture to an internal combustion engine is not limited to automobile engines, but may be applied to any internal combustion engine operating upon any fuel. This novel method comprises the step of providing a free flow of suitable combustible mixture to the automobile engine, except when the engine is operating at low speed full throttle, and the further step of restricting the flow of combustible mixture to the engine when it is operating at low speed full throttle. By this method the engine operates most efiiciently under all conditions of operation. When the engineis operating at high speed full throttle, it receives the maximum quantity of combustible mixture and this is compressed to the maximum degree, thereby producing maximum efficiency and power.

When the engine is operating at low speedfull throttle, it receives a smaller charge of combustible mixture than it would receive if the combustible mixture were supplied by the prior art method, that is, without substantial restriction under this condition of operation. The smaller charge received by the engine when my novel method is used would normally tend to reduce the power which it produces. In actual practice, however, I have found that no appreciable reduction in power occurs and in fact an actual increase in power at low speed full throttle is often apparent. This increase in power is due in part to the increased compression ratio whereby the smaller charge taken in is compressed to the same pressure as the larger charge taken in by the prior art engines and in part to the improved atomization of the combustible mixture and improved distribution of this mixture among the several cylinders of the engine which results from. the increased vacuum in the intake: manifold.

In Figure 2 I have shown one form of fuel feeding system capable of carrying out this novel method. In this figure I have indicated a typical plain tube carburetor Ml having a float bowl 42 supplied with fuel through a pipe 44-. The float bowl communicates with atmosphere through an opening 46 and it will be understood that the pipe 44 leadsto a diaphragm pump or other suitable means for lifting fuel into the float bowl 42 from the main fuel tank 26 located at the rear of the automobile.

The float bowl 42- supplies fuel to a nozzle 48 located betweena choke valve 50 and the usual throttle valve 52; The carburetor 40 is of the down-draft type and is attached to the riser 54 of an intake manifold 56 indicated asattached to a cylinder block 58.

In order to restrict the flow of combustible mixture to the enginecylinders when the engine is operating at low speed full throttle, I have provided the riser 54- with a special valve 50. This valve is pivotally mounted on a shaft 62 aid is urged toward closed position by a weight The valve is opened by the flow of combustible mixture fromthe carburetor to the engine cylinders. When the engine is operating at low speed full throttle, the flow of combustible mixture is relatively small so that the valve 60 is opened to only a slightextent." The lever arm ofthe weight-64' is a maximum sothat'va'lve 60 materially restricts the flow of combustible mixture to the engine cylinders. On the other hand, when the engine is operating at high speed full throttle, the flow of combustible mixture to the engine cylinders is great and the valve 60 is opened to its maximum opening. In this latter position of the valve 60, the lever arm of the weight 64 is a minimum so that the valve 60 has little restrictive effect onthe flow of combustible mixture to the engine cylinders.

In Figure 3 I have shown a part of another type of fuel feeding system capable of carrying out my improved method of supplying the fuel to the internal combustion engine. In this type of fuel feeding system there is illustrated a typical air valve carburetor of the non-fuel lift type. This carburetor has a float bowl I2 communicating with atmosphere through an opening I4 and supplied with fuel by means of a pipe 16. It is to be understood that the pipe I6, like the pipe 44 is connected to a diaphragm pump or other similar pumping means which lifts the fuel from the main fuel tank 26 to the carburetor float bowl 12.

The carburetor 10 has a fuel mixture nozzle 18 provided with a primary air inlet 80 and a manual adjustment 82 for regulating the richness of the mixture delivered by the nozzle I8.

. In addition to the main nozzle 18 this carburetor is provided with an idling jet 84.

The secondary air inlet 86 is provided with j the usual choke valve 88. In the normal operation of the engine the admission of secondary air is controlled by the secondary air valve 90 pivoted on a rod 92 and urged toward closed position by a spring 94 whose tension may be adjusted by rotating the sleeve 96.

In order to adapt an air valve carburetor to carry out my novel method, the sleeve 96 is adjusted to produce an unusually high tension on the spring 94 so that the air valve 90 mateconsequently the flow of combustible mixture to the engine when the engine is operating at low speed full throttle. I have provided the secondary air valve 90 with a vane 98 which is most effective to hold the secondary air valve in full open position when the engine demand for combustible mixture is great, as when the engine is operating at high speeds and under full throttle. Under these conditions the secondary air valve offers relatively little resistance to the inflow of secondary air, wherefore the engine receives a maximum charge of combustible mixture. The lower end of the carburetor I0 is provided with the usual throttle valve I00 and is adapted to be attached to the engine inlet manifold indicated at I02. It will be understood that while I have provided the secondary air valve with a vane 98' for rendering its resistance less when the engine is operating under full throttle and at high speeds,

means other than the vane 98 may be providedto accomplish this purpose.

In the fuel feeding systems which I have just described in some detail, the carburetors are of the non-fuel lift type and require a separate pumping means to supply them with fuel from the main fuel tank at the rear of the automobile. For use on modern automobiles I prefer a fuel feeding system wherein this separate means is dispensed with and wherein the carburetor is of the fuel lift type. I have illustrated such a fuel feeding system in Figures 1, 4 and 5 of the drawings.

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- rially restricts the inflow of secondary air and Referring particularly to Figures 4 and 5 I have illustrated the fuel feeding carburetor 30 as having an air inlet H0 of a form suitable for attachment of an air strainer if desired. Part of the air entering the inlet H0 flows through chamber H2 and through fuel feeding nozzle H4 into mixing chamber H6. The lower end of the mixing chamber H6 is provided with the usual throttle valve H8 and is attached to the engine manifold 28.

The nozzle H4 has a restricted throat provided with a step immediately below which are the discharge ends of inclined fuel feeding passages I20 communicating with an annular chamber I22. A duct I24 connects the annular chamber I22 with the upper end of a cylindrical passage I26 whose lower end is located'in the float chamber I28. The cylindrical passage I26 is divided by a partition I30 providing a metering orifice in which a metering pin I32 is movably mounted.

The pin I32 is mounted on a guide member I34 reciprocable in the lower end of the cylindrical passage I26 and supported on'a bar I36 attached to the lower end of a rod I38 whose upper end is connected by suitable linkage to the throttle valve H8 so that as the throttle valve is opened and closed, the rod I38 and metering pin I32 rise and fall. The upper end of the metering pin I32 is tapered and variably restricts the flow of fuel from thefloat bowl to the fuel feeding nozzle when the throttle valve H8 is closed or only partly open. When the throttle valve H8 is fully open or nearly so, the smaller portion of the pin I32 below the tapered part thereof is in the metering orifice and permits free flow of fuel from the float bowl to the nozzle.

In addition to the fuel feeding nozzle H4, the carburetor 30 is provided with an idling jet I40 supplied with fuel from the float bowl by way of vertical passage I42, horizontal passage I44, vertical passage I46, and groove I48, in the lower end of rod I38. The groove I48 is so arranged with respect to the lower end of a guide sleeve I50 that when the throttle valve H8 is well opened, communication between the idling jet I40 and the float bowl I28 is cut off.

A small opening I52 connects the mixing chamber H6 with the vertical passage I42 and provides an air supply for the idling jet I40. A very fine hole I54 breaks any siph'oning action in the passages leading to the idling jet I40 without supplying any appreciable quantity of air to this idling jet. The idling jet may be adjusted by means of a needle valve I56.

The general arrangement of the idling jet and control therefor which I have just described is described and claimed in my prior application Serial No. 136,544 filed April 13, 1937. This prior application also discloses an accelerator pump which is connected up with and controlled by the throttle valve. Accelerator pumps are commonly used in the fuel feeding systems of modern automobiles and it is to be understood that the carburetor 30 may, if desired, be provided with an accelerator pump like that disclosed in my prior application.

The admission of secondary air to the mixing chamber I I6 is regulated by a secondary air valve I mounted on a pivoted shaft I62 and urged toward closed position by a weight I64. A pin I66 attached to weight I64 moves in a slot in the rod I68 attached at its upper end to the piston I10 of a dashpot I12. The lower end of the rod. IE8. is provided with, a'tapered portion I14 movableain an orifice: :1 $5 for regulating: the a tion ofi'abooster venturiltube I18.

The purpose 'of the-booster Venturi tube H8 is to 'maintain sufficient suction in the float bowl I28 to draw' fuel thereinto from the main fuel tank 26.: located at the rear of the automobile. The suction maintained in the float bowl I28 must always be sumcient to overcome the difference in head between the fuel inthe main tank 26 and the inlet I80 tolthe carburetor float bowl. This difference in head varies with the level of the. fuel in the fuel tank 2'6 and also with the grade of the road over. which the automobile is traveling. For practical purposes this difference in headmust be figured as the maximum difference in head between the inlet I80 and the surface of the fuel in the main-tank 26 when this tank is practically empty and When the automobile is traveling up the maximum grade for which it is designed to operate. In addition to overcoming this difference in head, the suction existing in the carburetor float bowl must at any time be suflicient to overcome the frictional and inertia losses in the pipe line between the float bowl and main tank under the conditions of flow then existing.

One of the principal difficulties with prior art fuel feedingsystems incorporating fuel lift carburetors has lain in the fact that the float bowl suction for high speed engine operation was necessarily so great that the differential in pressure between the float bowl and the throat of the main fuel feeding nozzle was too slight to permit pro-per regulation of the fuel supply to the nozzle for the purpose of proper carburetor calibration. The very small difference in pressure between the float bowl and the fuel supply nozzle made the regulation of fuel supplied to the nozzle so delicate that extreme accuracy was necessary in the manufacture and assembly of the carburetor, wherefore the carburetor was ill-adapted for manufacture by large production methods.

In the chart of Figure 8 I have graphically illustrated this difference in pressure. Curve l on this chart shows the difference in pressure between the float bowl and the fuel feeding nozzle of a plain tube carburetor for different engine speeds when the engine is operatingat full throttle. In such a carburetor the float bowl is usually maintained under approximately atmospheric pressure. From this curve it is apparent that when the engine is operating at low speed full throttle, there is only a small difference in pressure between the float bowl and the fuel feeding in pressure between the float bowl and the fuel feeding nozzle is on the order of two to three inches and that this difference in pressure never rises above eight or nine inches of gasoline even when the engine is operating at full speed. Since the difference in pressure between the nozzle and the float bowl must. be relied upon to draw fuel from-the-float bowl to the'nozzle; and must also be relied upon as. affordingthe' means for regulating the fuel delivery to the nozzle under different conditionsof engine operation, it will be apparent thatthe calibration of such a fuel feeding syste'm is extremely delicate and unsuited for large production. manufacture.

An important object of my present invention is toovercome this'difflculty with prior fuelfeeding; systems utilizing-fuel lift carburetors without decreasingthe' volumetric efficiency of. the engine when operating full .speed full throttle. I accomplish this new result by changing the connections between. the'fioat bowl of the carburetor and the main fuel. tank. 28.-. As a first step in this direction I have enlarged and redesigned the inlet valve I82 controlled by float I84 in such a manner as toiprovide a freer andless restrictedv flow offuel into the float bowl of. the carburetor. As a second step. I have enlarged and redesigned the strainer. I86 and its associated chamber [88. to offer less restriction to the flow of fuel therethrough. As a third step I utilize a larger diameter of flexible tubing 32 and.

relatively rigid conduit 34 and arrange this tubing and conduit to eliminate sharp bends in so far as this is possible. Ihave discovered that these changes make it possible materially to reduce the degree of suction in the carburetor float bowl when the engine is operating at full speed full throttle.

I may cite as a typical example the difference in operation between afuel feeding system incorporating a fuel lift carburetor of the type disclosed and claimed in my said prior application and an improved fuel feedingsystem incorporating an improved fuel lift carburetor embodying the invention disclosed in the instant application when both of these fuel feeding: systems were tested on a standard Fordv V-8 automobile. In such prior fuel feeding system it was necessary to maintain a suction. of 42 inches of gasoline in the carburetor float bowl when the engine was idlingto overcome the 24 inch. difference in static head between the carburetor and the fuel tank and allowing 18 inches of gasoline to overcome additional differencev in headdue to. a maximum road grade of 15%.

With this fuel feeding system it was necessary to increase the suction in the float bowl to sixtysix inches of gasoline when the engine was operating at full speed full. throttle in order to provide for the thirty-three inch head of gasoline which-was requiredto overcome the friction and inertia lossesin drawing fuel at the required rate from the main fuel tank to the carburetor float bowl. Evenby increasing the vacuum in the float bowl to sixty-six inchesof gasoline, only nine inches of gasoline was available to overcome additional differences in level between the float bowl and the gasoline in the main fuel tank re sulting from road grades. This nine inches of gasoline is equivalent to the additional difference in head resulting from a road grade of 7% The differences in pressure between the nozzle andv the float bowl of this fuel feeding system are best illustrated by curve No; 2 in Figure 8. Even when the engine wasoper'ating at-full speed full throttle, the differential in pressure between'the nozzle and the float bowl was only 7.8 inches of gasoline. In order to obtain even this small difference in head, it was necessary to unduly restrict the flow of air 'tothe engine manifold at iull speedfull throttle. The result of this undue restriction was a loss in engine power atfullspeed full throttle.

Referring to Figure '7, curve I of the chart represents the manifold vacuum in inches of gasoline when the engine is operating at different speeds and at full throttle where the engine is equipped with a typical plain tube carburetor. Curve 2 of Figure 7 shows the corresponding manifold vacuum when'the engine is equipped with a fuel feeding system having a fuel lift carburetor like that of my said prior application. By comparing curves I and 2, it will be seen that when the engine is operating at full speed full throttle, the manifold vacuum was approximately five inches of gasoline less when the engine was equipped with the plain tube carburetor. The additional five inches of manifold backing obtaining at full speed full throttle when the engine was equipped with my prior fuel lift carburetor resulted in a noticeable loss in power and maximum speed as compared with the power and maximum speed developed by the same engine when equipped with a plain tube carburetor. This fact reduced the commercial possibilities of my prior carburetor.

As a result of elaborate tests, I have discovered that in the fuel feeding system incorporating my prior fuel lift carburetor, the restrictions tothev flow of fuel from the main fuel sup-ply tank to the float bowl of the carburetor when the engine was operating at full speed full throttle, were as indicated in the following chart. By a drastic change in that part of the fuel feeding system connecting the carburetor float bowl with the main fuel tank, it was possible to reduce the total resistance to approximately one-third. These drastic changes included increasing the size of the copper tubing from one-fourth of an inch 0. D. to five-sixteenths of an inch 0. D., materially increasing the size of the flexible tube, redesigning the strainer to secure freer passage of gasoline, and redesigning the float valve to secure freer passage of gasoline. The corresponding resistances for this drastically changed fuel feeding system are also shown in this table:

, timproved fuel ee ing system Fuel tecdlng system of prior application of this appliea 7 tion The 34 copper tube leading from the rear tank to the flexible tube attached to the carburetor float bowl 20 of gasoline 6" of gasoline The flexlble tube which is inserted between the end of the copper tube and the carburetor of gasoline 2 of gasoline The strainer of the carburetor 3 of gasoline 2" of gasoline The float valve 5 of gasoline 2 of gasoline Total 33 of gasoline 12 of gasoline In the improved fuel feeding system of my present application, the suction in the float bowl of the carburetor can thus be reduced from sixtysix inches of gasoline at full speed full throttle to only forty-five inches of gasoline. This would give an increased differential between the nozzle and float bowl at full speed full throttle from 7.8 inches to 28.8 inches of gasoline. All of this additional difference in head between the float bowl and fuel feeding nozzle could be utilized for purposes of calibration. Because of the greatly increased difierence in head between the nozzle and the float bowl, it would be necessary to provide a small restricting orifice between the nozzle and the float bowl in order to prevent the nozzle from drawing too great a volume of fuel due to this increased difference in head.

For practical purposes, however, it is not necessary to have all of this additional difference in head between the fuel feeding nozzle and the float bowl in order to reduce the sensitivity of the carburetor sufliciently so that it can be made by large production manufacture. Instead, therefore, of utilizing all of this gain for the purpose of increasing the pressure differential between the fuel feeding nozzle and the float bowl, I prefer touse only a part of the increased pressure differential for this purpose and to avail myself of the rest of the advantage thus gained to increase the power output of the automobile engine by reducing the restricting effect of the secondary air valve.

In Figures 4 and 5 of this application I have shown a fuel feeding system having the improved and less restrictive float valve I80, I82, the improved strainer and strainer chamber I86 and I88, the enlarged flexible tube 32 and the enlarged copper tube 34. The carburetor forming part of this fuel feeding system of Figures 4 and 5 is designed to make the most desirable use of the reduction in float bowl suction'made possible by the improved fuel feeding connections between the float bowl and the main fuel'tank 26.

In the carburetor of Figure 4 the nozzle I I4 is made of reduced size as compared with the nozzle shown in my said prior' application. While Figure 4 of the instant application shows only a single nozzle H4 and a single mixing chamber I I6, it is to be understood that the carburetor shown in this figure may be of the dual type like that shown in my said prior application and in'fact both carburetors used in the tests on the Ford V-8 automobile were of the dual type, the nozzles and mixing chambers being arranged generally as shown in my said prior application. The smaller nozzles of the carburetor shown in Figure 4 of the instant application are, made possible by the reduction in the float bowl suction which in this carburetor is only forty-five inches of gasoline at full speed full throttle, there being provided a maximum difference in pressure between the nozzles and the float bowl of approximately twenty-three inches at full speed full throttle as illustrated by curve 3'in Figure 8, which shows the difference in pressure between the nozzle and float bowl of my improved carburetor for all engine speeds at full throttle.

The use of the smaller nozzles II4 has several important advantages. In the first place it provides better idling operation of the automobile engine in that less air is drawn into the mixing chambers through the nozzles when the secondary air valve I is closed. These smaller nozzles are also less sensitive to manufacturing variations in the sizesof the various parts of the carburetor and thus made possible larger commercial tolerances in the manufacture of these parts.

The booster Venturi tube I18 is provided for the purpose of maintaining the proper degree of suction in the float bowl I28 under all condi-,

Y tions of operation. This booster is supplied with ing at full speed full throttle.

the stud 2E8 by a manual control accessible to the operator of the vehicle for temporarily reducing the effectiveness of the booster I78 and thereby increasing the richness of the mixture supplied by the nozzle I I4 to provide easier starting when the engine is cold.

The booster I78 is shown in greater detail in Figure 5. This booster has a restricted throat provided with a step 2M which is materially larger than the step of the booster in my said prior application. Just beyond the step 2M are radial passages 2H5 leading to an annular space 2H3 communicating with the float bowl of the carburetor through duct 220. The larger step 2 I4 renders the booster I'IB less eflicient to create suction in the carburetor float bowl under normal operating conditions, but this larger step materially increases the ability of the booster I78 to withdraw large quantities of vapor from the float bowl whenever the gas in the float bowl is heated to-such an extent as to give off large quantities of vapor.

The ability to use effectively a booster having a larger step in its throat is an important ad- Vantage of my present invention. It is only possible'to use such a booster because of the increased suction obtaining in themixing chambers IIfiunder idling conditions resulting from the sm'allernozzles 'I I4 which admit less air to the'mixing' chambers when the secondary air valve IGI'I is closed. The larger nozzles used in the carburetor of my said prior application admit'so. much airto the mixing chambers when the engine is idling that a booster having a smallerstep'and capable of creating a higher degree ofsuction in'the float bowl with less flow I ondary air valve [6%], whereby this air valve offers less restriction to the flow of air into the mixing'chamber HIS when the engine is operat- This in turn reduces the 'manifold vacuum :at high engine speeds and increasesthe'power. of the engine -underrsuch conditions .of "operation. In -the chart, Figure 7, the manifold vacuum of an engine having the improved fuel feeding system shown in Figure 4, is indicated'by curve 3. This curve shows that at full speed full throttle the manifold vacuum is slightly less than the manifold vacuum in a corresponding "engine equipped with an ordinary plain tube carburetor wherein the manifold vacuum is represented by curve I.

An-automobile equipped with my improved fuel feeding system of Figure 4 thus develops greater power and speed when the engine is operating at full speed full throttle than does a similar automobile having a conventional plain tube carburetor of the most improved type. My improvedfuel feeding system of Figure 4 thus overcomes one of the'greatestdisadvantages of prior fuel feeding 'systems'having fuel lift carburetors.

The enlarged secondary air valve IE0 and freer flow of air permitted thereby reduces the suction created by the nozzles IE4. Whereas, in .the carburetor of my said prior application the nozzles developeda suction of 73.3 inches ofgasoline when the engine was operating at full speed-full throttle, the nozzles of my improved carburetor of Figure 4 develop only. a suction equivalent to 68 inches of gasoline under as indicated by curve 3 in Figure 8.

the same conditions. This leaves a pressure differential between the nozzles and float bowl 1 approximately 23 inches of gasoline when the engine is operating at full speed full throttle This pressure differential is ample for the calibration of carburetors made by large production methods.

Thus far I have illustrated and described an improved fuel feedingsystem using an improved fuel-lift carburetor which has many advantages over anything'known' to theprior art. The reduction in the float bowl suction which I have obtained by improving'the connection between this float bowl and the main fuel supply tank located at'the rear 'of the automobile, makes it possible to provide a fuel lift carburetor which operates on an entirely different principle'from the carburetor shown in Figures 4 and 5. In Figure 6 I have illustrated a modification of the carburetor shown'in Figures 4 and 5. I shall now describe the modified carburetor of Figure 6 and its new principle of operation.

In the carburetor of Figures 4 and 5 the booster Venturi tube I I8 is relied upon to produce a suction in the float bowl I28; I In the modified carburetor of Figure 6 the booster I18 no longer performs this function. The main fuel supply nozzles are relied uponto produce the suction in the float bowl and the booster I'I8 acts solely as ameans to limit the" degree of suction created in the float bowl by the fuel feeding nozzles.

It is to be understood that the modified'form of carburetorwhichiis partially shown in Figure 6 is identical with the carburetor of Figures 4 and 5, except in the respects which I shall now point out. In this carburetor of Figured it will be understood that the fuel feeding nozzles corresponding to the nozzles H4 of Figure 4 are large nozzles of a size like-that of the carburetor of my said prior applicationinstead of being-the smaller nozzles H4 of Figure 4. I have previously pointed out that where-such largernozzles are used with my improved fuel supply line and reduced float bowl suction, it is essential to provide an additional restriction between the float bowl and the nozzles and in Figure 6 I have illustrated such a restriction. In this figure the cylindrical passage I26 which projects downwardly into the float bowl I28 is provided with the usual metered orifice I3Ilin which there is located a metering vpin I32a. This metering pin is mounted on a guide I340, having a restricted passage 25!! communicating with the float bowl I28.

In the wall of the cylindrical passage I25 I have provided three small openings 252 for the purpose of removing vapor from the upper part of the float bowl I28. The upper one of these openings 252 is always above the fuel level in the float bowl as is clearly indicated in Figure 6, whereas the other two of these openings are sometimes above the fuel level in this float bowl and sometimes below this level, as the level of the fuel-varies, the lower level being indicated by the dotand-dash line of Figure 6.

Inthe operation of'thecarburetor of Figure 6, the-main fuel feeding nozzles create a suction in the cylindrical passage I26 sufficient to raise fuel from the float bowl I28 through the'restriction 250, the metering orifice I30 and passages I26 and I24 to the nozzle throats. The restriction 250 maintains a pressure differential between the float bowl I28 and .the passage I26 which is effective to draw vapor .thereinto through the openings 252. These openings are so small that when the lower openings are immersed in liquid, there is no appreciable liquid flow therethrough. The flow of vapor through the openings 252 removes vapor from the upper part of the float bowl I28.

The modified form of the invention shown in Fig. 6 is particularly desirable for hot weather operation, wherein the carburetor float bowl is heated sufliciently to create a considerable amount of vaporization of the fuel contained therein. Under this type of operation, all of the vapor created in the float bowl is drawn through the openings 252, orifice I30, and passages I26 and I24 to the nozzle Venturi tubes where it is mixed with air discharged into the mixing chamber. The capacity of the nozzle Venturi tube to withdraw vapor from the float bowl is, of course, much greater than the capacity of the ordinary booster Venturi tube to withdraw such vapor, so

that with the arrangement of Fig. 6 there is no possibility that in hot weather the vaporization of the fuel in the float bowl will interfere with the creation of suflicient suction in the float bowl to draw liquid fuel thereinto from the main fuel supply tank located at the rear of the automobile.

The modification of Fig. 6 has av further advantage, in that the vapor existing in the float bowl is drawn into the nozzle Venturi tubes where it is mixed with air and ultimately forms a combustible mixture which creates power in the engine cylinders. In prior carburetors, the vapor from the float bowl has been withdrawn by way of the booster Venturi tube, and while the vapor so withdrawn ultimately reaches the engine cylinders, it is supplied to the cylinders as excess fuel and is thus wasted from a power standpoint. In fact, with the prior arrangement, the vapor withdrawn from the float bowl is worse than wasted, in that it tends to over enrich the mixture supplied to the cylinders and thus contributes to the production of excess carbon in these cylinders.

While the nozzle Venturi tubes are withdrawing relatively large 'quantities of vapor from the float bowl, these nozzle Venturi tubes are withdrawing a slightly decreased quantity of liquid fuel from the float bowl, so that under these conditions there is a slight decrease in the total quantity of fuel supplied to the engine cylinders. This in turn results in superior engine operation, since the slight decrease in fuel supplied compensates for the increase in engine temperature, as a hot engine requires less fuel than a cold engine.

While my novel fuel feeding systems are primarily intended to be incorporated at the factory in new automobiles and similar mechanisms, my invention may readily be applied to existing automobiles and other like mechanisms. If the existing automobile is provided with a plain tube carburetor similar to the carburetor 40 shown in Fig. 2, the efficiency and maximum power developed by the automobile engine can be increased by removing the regular cylinder head and substituting therefor a higher compression cylinder head. The high compression head should be so selected that it provides the maximum compression which can be used without knocking when the engine is operating at full speed, full throttle, with the desired fuel.

In order to make the automobile operate properly at low speed full throttle, it will be necessary to provide means such as the valve mechanism 60, 62, and 64 of Fig. 2 in order to raise 7 the manifold" vacuum sufficiently at low speed full throttle to prevent knocking under this condition of operation.

Referring to the chart, Fig. 7, it will be noted that this chart contains a series of short vertical lines indicating the area in which knocking will I occur when the engine is operated at low speed full throttle when used with a high compression head of the kind which I contemplate using. From this chart it will be noted that the curve numbered l which represents the manifold vacuum in the intake manifold of an engine equipped with a plain tube carburetor, passes through this area of knocking. The function of the valve means 60, 62, 64 is to increase the manifold vacuum at low speeds so that the corresponding curve would be raised above the area in which knocking occurs.

The curve numbered 3, which represents the manifold vacuum under different conditions of operation of an engine equipped with a fuel lift carburetor, like either Fig. 4 or Fig. 6, is an example of a curve which avoids this area of knocking and which makes possible the use of the high compression head which I contemplate. The fuel feeding system of Fig. 2 comprising the plain tube carburetor with the valve for maintaining high manifold suction at low engine speeds, would approximate the curve numbered 3 in the chart of Fig. 7.

In a somewhat similar manner, an existing automobile equipped with an air valve carburetor generally similar to that shown in Fig. 3, could be modified to give increased efliciency and power by using a higher compression head and modifying the operation of the valve mechanism of the air valve carburetor to increase the manifold vacuum at low engine speeds. In lieu of changing the valve mechanism of the air valve carburetor, the same result could be accomplished by using an additional valve similar to the valve 60, 62, 64 of Fig. 2..

In an existing automobile provided with a fuel lift carburetor, increased power and efficiency could be obtained by substituting a higher compression head and by removing the carburetor and fuel line supplied with the automobile and substituting therefor a carburetor and fuel line like that of Fig. 4 or Fig. 6.

It is to be understood that my invention is not limited to the details shown and described, but may assume numerous forms, and that the scope of my invention is limited solely by the following claim.

I claim:

An internal combustion engine comprising a cylinder, a high compression head therefor, a piston reciprocable in said cylinder, means driven by said piston, a manifold for supplying a combustible mixture to said cylinder, a throttle valve controlling the quantity of combustible mixture supplied to said cylinder, and fuel feeding means including said throttle valve for maintaining a suction of between 25 and 60 inches of gasoline in said manifold for all conditions of engine operation when said valve is fully opened, said lastnamed means comprising a mixing chamber in which said valve is located, a nozzle for supplying fuel to said mixing chamber, a float bowl constituting a source of fuel supply for said nozzle, a passage connecting said nozzle with said float bowl, means for reducing the weight of a column of fuel in said passage and consisting of a series of vertically spaced orifices connecting the upper part of said float bowl with said pasa restriction in said passageflbelow-tsaidmriflces, a booster Venturi tube discharging into :said mixing chamber, a passage connecting the throat of said Venturi tube with .said float how], an .air .valve for admitting air to said mixingchamber,

and. a Weight variably urging said valve toward Isage and including orifices located both. above and below the normal level of :fuel imsaidfloati bowl,

closed positiomsaid Weight exerting. greater; force on said valve; and .thereby;smaintaining :a "higher degree of suction: in said manifold when said engine is operating at lowcspeed full throttle'nthan when said engine is operating at :high speed full throttle whereby'the'tendencyt ofsaid engine to knock at low speeds isreduced.

ROBERT BRACKE.

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