US2138591A - Carburetor - Google Patents

Description

Nov. 29, 1938. R F. BRACKE 2,138,591

' CARBURETOR Filed Feb. 14, 1955 3 sheets-sheet 2 Zi-gig Y Il 60 El 62 '33 56 53 l Ill 80 l jfl 17d" .uffa/263021 ,hay M y s. I

NOV- 29 1938- R. F. BRACKE 2,138,591

CARBURETOR F ivled Feb. 14, 1935 3 Sheets-,Sheet 3 Patented Nov. l29, 1938 come .PTENT Fries amasar i Robert F.

Bracke, Chicago, Ill.

Application February 14, 1935, Serial No. 6,421

' 13 claims. (cl. act-s4)V My invention pertains to carburetors and is particularly concerned with the provision of a fuel lift carburetor for internal combustion eny gines which gives better engine operation and which is economical to manufacture and reliable in operation.

Another object is to provide a carburetor having an improved oat and guiding means therefor.

Another object is to provide a-carburetor having provided as an integral part thereof an improved filter for the fuel supplied tothe car-v buretor.

Another object is to provide a carburetor affor limiting opening of the secondary air valve while the choke is in use.

Another object is'to provide acarburetor of the fuel lift type havingv improved means for reducing the degree of suction in the fuel chamber while the choke is being used.

Another object is to .provide a carburetor of the fuel lift type having an improved booster Venturi tube.

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

In the drawings,l

Figure 1 is an elevational View, partly in section, showing one embodiment of my invention;

Figure 2 is a sectional elevation taken on the line 2-2 of Figurel; Y

Figure 3 is a horizontal section taken on the line 3-3 of Figure 1;

Figure 4 is a partial vertical section taken on the line 4--4 of Figure 3;

Figure 5 is an enlarged view pump mechanism;

Figure 6 is an enlarged partial vertical section taken on the line 6-6 of Figure 3;

Figure 7 is a vertical section taken on the line 'I-'I of Figure 2; and l' Figure 8 is a diagrammatic representation of my improved carburetor.

In the drawings, I have shown a downdraft 55 type of fuel lift carburetor wherein the upper of the accelerator Another object is to provide improved means casting A and the lower castingB are secured together by any suitable means and together composed the main body of the carburetor. The particular means for securing the castings A and B together are illustrated as bolts I0, and a suitable washer or gasket I2 is shown as clamped between the castings A and B to form an airtight seal therebetween. y

The upper castingA has an air horn I4 which is shown as communicating directly with atmosphere but which may be connected to a suitable air filter and silencer of the type -now commonly used in connection with internal combustion engines, particularly where such engines are used in automotive vehicles. In the air horn I4 is a hub I6 supported by spokes I 8. The hub I6 has a vertical opening therethrough in which a Venturi tubel or nozzle is suitably ailixed. The nozzle 20 hasa primary air inlet 22 converging toward a throat 2t terminating-at a step 26, which in the carburetor shown has a width of Aapproximately-ifteenthousandths of an inch onv a side so that-the diameter of the throat 24 is thirty thousandths of an inch less than the diameter of the nozzle 20 immediately below the step 26. The width of this step 25' will vary with diierent sizes of carburetors but will never be less than approximately ten thousandths of an inch on a side. l

Immediately beneath the step 26 are the inner 1 ends of diagonal fuel feed passages 28 Iwhich establish communication between the interior of the nozzle and an annular chamber 30 surrounding the adjacent portion of the nozzle. The manner in which fuel is supplied to the annular chamber 30 is an important part of my invention vand will be hereinafter described.

The fuel entering through the diagonal passages 28 mixes with the primary air and decreases the`temperature of the incompletely vaporized 4 mixture formed thereby. Surrounding the lower end of the nozzle 20 `is a secondary air valve 32 comprising a casting having an upper portion or sleeve 34 which telescopes with the lowerend tion 48 closes the restricted passageway formed by a throat member 50 so that no secondary air can enter the mixing chamber 38. The upper part of the air valve 34 is surrounded by a layer of cork 52 or other suitable insulating material which is held in place by a sheet metal cover54. The mixture of fuel and air passing downwardly through the nozzle 20 is at a temperature considerably lower than that of atmosphere. The lower end of the nozzle 20 directs this mixture against the upper end of cup`42 which causes this f mixture to be directed radially in the space prounder certain conditions of atmospheric temperature this moisture might freeze and render the air valve inoperative.

The lower portion of the air valve is telescopically related to a cup-shaped guide 56 which is secured in place by a spring 58 confined between the inturned flange of the guide 56 and a Washer 60 secured to the upstanding sleeve 62. The inturned flange of the guide 56 is provided with a small orifice 64 registering with a passage 56 leading to the throttle bore 68. By means of passage 66 and orifice 64, the suction existing in the upper part of throttle bore 6B is communicated to the interior of the air valve 32 and draws this valve downwardly against the resistance ofthe spring 44 an amount proportional to the degree of suction existing in the upper part of the throttle bore.

A pin l0 is slidably guided in the sleeve 62 and has an enlarged head 12 conned between'the base of cup 42 and a plate 'Z4 which rests upon the upper end of the spring 44. The lower end of the pin 'i0 is tapered, as indicated at 16, and lies within a metered opening l0 controlling communication between the upper end of the throttle bore 60 and the discharge end of a booster Venturil tube 80 which draws fuel from a mainfuel tank, not shown. The position of the tapered end 'I6 of the pin 'l0 varies with the degree of suction existing in the upper end of the throttle bore 68, with the result that a substantially constant degree of suction is maintained in the discharge end of the booster 80.

In the throttle bore 58 is the usual throttle valve 82 supported on a rotatable shaft 84 attached at one end to a lever B6 yadapted to be connected by way of a knob 0B with thev usual accelerator pedal or other suitable control means. The lever 36 is provided with the usual adjustable stop 90. The other end of shaft 84 is provided with a collar 'a2 heid in piace by a pin 94 which projects from the collar and establishes a one-way connection with the U-shaped end of a second lever 96 having a knob 98 whereby this lever can be connected to the usual manual hand control of an automobile.

Part of the air entering the horn I4 .enters an opening |00 at one side of the horn and from thence passes into a vertical passage |02 communicating with a horizontal passage |04. The

opening |00 is slightly inclined in a reverse di-A rection relative to the direction of the air ,in the horn i4, and this opening |00 is located beneath duce wide variations in an overhanging shelf |06. `This construction prevents .the formation of a Pitot tube action at this point and also prevents dirt and moisture from entering the passage |02.

The horizontal passage |04 communicates with a metered orifice |08 in a plate ||0 oscillably mounted on a bolt H2. The orifice |08 restricts the amount of air admitted to the chamber ||4 formed by a sheet-metal cup I6 clamped against plate ||0 by star-shaped spring H6. The plate ||0 is provided with a second opening |20 having the peculiar conformation shown in Figure '7. This opening |20Anormal1y establishes free communication between the chamber M4 and the inlet end of the booster 80.

Opening |20 also normallyv establishes comgine side of the throttle valve is communicated to chamber ||4 by way of passages |22 and |24 and opening |20. A needle valve |26 is located at the juncture of passages |24l and |22 and constitutes the idling adjustment for the carburetor.

The manner in which this idling adjustment controls the operation ofthe carburetor is fully v described in my prior application, Serial No. 4,479, filed February 1, 1935. The carburetor disclosed and claimed in this present application is an improvement on that disclosed and claimedin this earlier application.`

The booster Venturi tube has a throat |28 terminating at a shallow step of from two to four thousandths of an inch on a side. Just tothe right of this step are passages '|30 leading to an annular chamber |32 communicating with a passage |34 leading to theupper end of the fuel chamber or iioat chamber |36.-

The booster Venturi tubes heretofore used have'been provided with a smooth throat which did not include any step. These prior art boosters were extremely difficult to manufacture .on a commercial scale because extremely riations in the drilling of the throat would prothe degree of suction which such boosters would produce for any given flow of air through them. ,By providing a slight step of the order soV slight val more, the. provision of this step renders the boosterless susceptible to disturbances resulting from the deposit of small particles of dirt in the throat of the booster. The step is so narrow that it does not appreciably detract from the eiiiciency .of the booster.

As best shown in Figure 6, the upper end of passage |34 does not communicate directly with fuel chamber |36 but instead communicates with a space |30 located above the fuel chamber |36 and separated therefrom by a sheet metal cup |40. The air and vapor withdrawn from the fuel chamber |36 by booster a port down onto strainer and into the bottom of the cup |40 from whence it is returned to the fuel chamber through openings |46 adjacent the bottom of the cup |40. The purpose of this structure is to prevent liquid from being sucked or splashed into the upper end of passage H34.'

80 first passes through |42 into space |36 where any liquid falls |44 and passes therethrough The suction created. in the fuel chamber |36 75 castings A and B. A tubular wire screen |54,

having its bottom closed by a sheet metal cap |56, is supported in the rchamber |52 `by a head |58 threaded into the upperv end of the chamber. 'I'he head |58 also supports a shell |60 which -encloses the lower end of the screen |56 and is spaced therefrom. Fuel entering through conduit |48 and duct |50 ows through openings |62 into the space between the shell |60 land the screen |54. Any water-which may be in the fuel co1- lects in the bottom of the shell, whereas the fuel 4 being lighter; passes through the. screen |54 and lspace |66.

After the carburetor has been in use for an appreciable length of time, the head |58, screen |56 and shell |60 can be removed as a unit. The shellr |60 can then be 'separated from the head |68 with which it has a frictional engagement, and y any water collected in the shell |60 can then be disposed of. At the same time the screen |58 can be cleaned of dirt and other obstructing material. The unit is then reassembled and replaced` in the chamber |52.

Annular space |66 connects with one end of a passage |68 (Figure 3) leading to a port |10 (Figure 4) controlled by a valve |12. The lower end of the valve rests on a bifurcated lever |14' pivoted on a pin I 16 and having separated ends resting on a float |18 and disposed on opposite sides of a cylinder |80 located in the fuel chamber of the carburetor. The float |18 is annular and surrounds the cylinder |80 which forms a guide for it. The float |18 controls the valve |12 in the usual manner.

The diagonal passages 28 in the nozzle 20 are supplied withA fuel from the fuel chamber |36-by way of the interior'of cylinder |80 and bore |82. Betweencylinder |80 and bore l|82 is a knifeedged orifice |84 in which is located an economizer pin |86. 'I'he extreme upper end ofthe economizer pin is cylindrical for a space of approximately three thirty-seconds of an inch. Be-

low this the upper end of the economizer pin is tapered to the shoulder .|88 which connects the tapered portion of the pin with a cylindrical stem of smaller diameter. The pin |86 is carried by a piston |80 of an accelerator pump which I shall now describe.

As best shown in Figure 5, the piston has a circular inner series of ports |82 leading to the annular space provided by upstanding ribs |88 and |86. A disk, valve |88 is supported on these ribs and is providedv with a small orice 200 which provides for thepassage of suilclent fuel for the engine when it is idling. When the engine is operating at part and full throttle, disk-|88'is lifted away from the ribs |84 and |86 and moved into engagement with the `spring clip 202 so that additional fuel .can pass through the ports |82' and around the edge of .the disk |88 to provide for the increased fuel consumption of the engine. The piston |80 is urged downwardly by a spring 204 and is moved upwardly against the tension of this spring by piston rod 208 which rests on 'one end of a lever 208 pivoted at` 2|0.

An intermediate portion of. thelever 208 rests on a cam 2|2 on one end-of the throttle valve shaft so that as the throttle valve is opened the piston |80 is moved upwardly in its cylinder |80. This upward movement of the piston |80 results in the closing `of the ports '|82 by the disk |88 and pumps a .chargeof fuel to the nozzle 20.

When the throttle is suddenly opened through its full movement, this pumping action of the ypiston, |90 would force vtoo much fuelV to the nozzle 20, and to avoid this I have provided relief means comprising an outer series of ports 2H in ithel piston |80. These ports `are normally closed this piston in turn changes the `position vof, that` part of the pin |86 in the vknife-edged orice |84. The relationship between the pin |86 and the throttle valve can be varied by adjusting the nut 224 which engages the lower end of the piston rod 206. The short cylindrical upper end of the pin |86 provides the proper idling position of the pin |86 for al1 positions of the adjusting nut 226. Similarly, when the throttle iswide open, the reduced cylindrical stem portion of the pin |86 is always within the knife-edged orifice |86.

Piston rod 206 is guided by a member 226 'which is threadedly secured in the lower casting B. The upper end of member 226 extends above the normal level of the fuel in thevl fiiel :chamber |36 so that thereis no tendency for the fuel to leak out around the piston rod 206. 'It is equally important that no air 'leak into this `fuel chamber alongthe piston rod, and to prevent this I providernember 206 with radial ducts 228 communi# eating with a passage. 230 leading to the passage |28 which empties into the throttlebore '68 on the engine side of the throttle 82 so that any air which may tend to leak in along the piston rod 206 is disposed of before it can reach the fuel chamber |36.` The vfuel chamber |36 is provided with a drain plug 232.

-In Figure 'Z the choke plate H0 is shown in Vthe position which this plate assumes when the choke is not in use and the engine is operating under normal conditions. This plate ||0 is provided wlth an arm 238 having a ball connection .286 whereby. this plate can be attached to the usual manual. choke control. As the choke is applied by rotating the plate H0 counterclockwise, as 'viewed -in Figure 7, the large part of 4opening |20 moves away from the entrance to fuel chamber |36.. The degree to which the admission of air to the booster 80 is restriced `varies .with the extent to which the choke is applied.

When the choke is fully applied so that shoulder 288 of `the choke plate abuts the stop pin 240, the opening |20 is moved entirely away from. the entrance to the booster 80 and the very small orifice 262 registers with vthe booster and forms throttle :bore 68 so that when the choke-'is fully applied,l .opening |20vin the choke plate'and duct 264, admit Aair to the interior `ci' the `secondary air valve faster than this air can kbe sucked out y:ses

through the restricted orice 64, with the result that the secondary air valve remains substantially vin the closed position shown in the drawings when the engine is being started with full choke.

When the choke is inthe off position, as shown in Figures 1 and 7 of the drawings, one end of a finger 246, pivoted on pin 2|0, is held in engagement with the flat edge portion 248 of choke plate |I0 by a spring 250. The other end of the lever 246 abuts an arm 252 secured to throttle shaft 84. When plate I|0 is moved to produce a choking effect, the cam-shaped edge of this plate swings lever 246 about its pivot and cracks or slightly opens throttle valve 82 so that the engine will not stall so easily when operating under part or full choke.

The air horn I4 is shown as being provided with a shoulder 254 whereby an air cleaner and silencer of the usual type may readily be applied to the carburetor. The operation of the carburetor is the same, whether orvnot it be used with such an air cleaner and silencer.

In the operation of my invention, the air passing into the horn I4 through'opening |00, pas-l sages |02 and |04, and chamber I4, flows through the booster Venturi tube and discharges into the manifold bore 68. As this air passes through the throat of the booster 80, it creates a suction in passage |34 which communicates with the up` per end of fuel chamber |36 so that a vacuum is created in this fuel chamber which sucks fuel r and passage |82, to the annular space surrounding the throat of nozzle 20. From this space the fuel flows through diagonal passages 28 into the primary air stream passing through the nozzle 20. The mixture of air and fuel delivered by the nozzle -0 strikes the upper end of the cup 42 of the secondary air valve and has its direction changed from an axial to a radial ow.

In the normal part throttle and full throttle operation of the'engine, Ithe suction created in the interior ofthe secondary air valve 32 moves this air valvev downwardly from the position shown so that secondary air can enter around this valve. The mixture of air and fuel delivered by the nozzle 20 lforms a combustible mixture with the secondary air admitted around the air -valve 48, and this combustible mixture passes into the throttle bore 68 and from thence through the manifold to the engine cylinders.l

It is to be noted that as the secondary air valve 32 moves downwardly, its upper end forms in effect a continuation of the discharge end of the nozzle 20.- The air valve and throat member 50 are so designed that they constitute in effect a large Venturi tube for all positions of the air valve, this Venturi tube automatically varying in capacity in accordance with the volume of secondary air drawn in around the air valve. The particular structure of the secondary air valve and throat 50 is designed to provide quick opening of the air valve yand to prevent uttering thereof, particularly at low engine speeds when such fluttering is most likely to occur in the air valves of the prior art.

As the fuel chamber |36v ,when the throttle 821s partly or fully open, an i increased suction is produced in the upper end of the'throttle bore 68. In thesev positions of the throttle 82 the secondary air valve 32 is lowered in proportion to the increase in vacuum in the throttle bore. The air valve inturn controls the position of the tapered end 16 of the pin 10 so that the suction obtaining at the discharge end cf booster 80 is maintained constant.

yWhen the throttle is opened suddenly, the piston forces an additional charge of fluid to the nozzle 20 to provide for rapid acceleration. However, where the throttle is suddenly opened over a wide range of throttle movement, the valve 2|6 in the piston |90 opens to prevent the piston |90 from supplying an excess of fuel to the nozzle 20. In idling position and in all intermediate throttle positions, the enlarged upper end of pin |86 is located in the knife-edged orifice |84 and correctly apportions the amount 20 of fuel supplied to the nozzle 20, whereas in full throttle position vthe reduced stem of pin |86 islocated in the knife-edged orice |84 and free iiow of fuel to the nozzle 20 is then permitted.

When the choke is applied the choke plate ||0 isso moved that the supply of air to the booster 80 is restricted to a degree corresponding to the degree ofA choking desired. This correspondingly reduces the suction created in the fuel chamber by this booster and provides a greater difference in pressure between the throttle of the nozzle 20 and the fuel chamber so that the nozzle 20 supplies a correspondingly richer mixture to the engine. Application of the choke also opens vor cracks the'throttle valve 82 slightly. The choke is seldom used except when the engine is cold, and

when an engine is operating below its normal operating temperature it stalls easily. By thus cracking the throttle, .this tendency to stall is offset.

While I have disclosed only one embodiment of l my invention, it is to be understood that my in'.

tion between said nozzle and the lower end of said fuel chamber, said Acylinder having smoothinternal and external surfaces, an accelerator pump piston reciprocable in said cylinder, a float in said fuel chamber closely fitting said cylinder and guided thereby, and valve means operated by said float, said valve means permitting straight line movement of said float lengthwise ofsaid cylinder. i

2. In a fuel lift carburetor of the class described, a nozzle, a fuel chamber, means connecting said nozzle with said chamber, a booster Venturi tube for maintaining the interior of said fuel chamber below atmospheric pressure, said booster Venturi tube being adapted to discharge into the intake manifold of an engine, valve y charge end, an' ai'r valve having a portion telescoping with said discharge end, a layer of insula-v tion surrounding said portion, and means for opening and closing said air'valve to provide controlled admission of air therepast. 4. In a fuel lift carburetor vof the class described, the combination of a nozzle Venturi tube providing a rich mixture of fuel and air, an air valve for admitting additional air for reducing the tion in'said fuel chamber, said booster Venturitube discharging through a metered oriilce lying in a plane normal to the movement of said air valve, said metered orifice being in alignment with said air valve, and a pin movable directly with said airvalve and having a tapered portion extending into said metered orifice to regulate flow through said booster.

5. In a fuel lift carburetor of the class described, the combination of a nozzle, a fuel chamber from which said nozzle is supplied, a booster for creating a suction in said fuel chamber, a compartment provided in the top wall of said fuel chamber, a port connecting one side of said compartment with the upper part of said fuel chamber, a passage connecting the other side of said compartment with said booster, and a sheet metal cup closing the bottom of said compartment to prevent fuel from splashing thereinto,

said cup having drain passages whereby liquid drawn into said compartment may return to said fuel chamber. 6. In a fuelllft carburetor of the class described, the combination of a nozzle, a fuel chamber from which said nozzle is supplied, a booster for creating a. suction in said fuel chamber, a compartment provided in the top wall of said fuel chamber, a port connecting one side of said compartment with the upper part of said fuel chamber, a passage. connecting the other side of said compartment with said booster, a sheet metal cup closing the bottom of said compartment to prevent fuel from splashing thereinto, said cup having drain passages whereby liquid drawn into said compartment may return to said fuel cham- A ber, and a strainer carried by said cup. 1

7. In a carburetor of the class described, the

combination of a fuel feeding nozzle, a pump for supplying fuel thereto, said pump comprising a vertical cylinder,` a piston reciprocable therein,-

said piston including a body having two series of ports therethrough, a disk above said piston urged by gravity to close one of said series-of ports except for a small idling orice through said disk, an annulus vbelow said piston, a spring urging said annulus against said piston to close said second series of ports, a throttle valve for said nozzle, common means for. opening said throttle valve and raising said piston, and a spring for returny ing said piston.

8. In a fuel lift carburetor of the class de- I admitting a restricted volume of air to said chamber, an accelerator pump for supplying fuel from said fuel chamber to said nozzle,an operating rod for said pump extending through a wall of said fuel chamber, a guide for said rod, saidguide having radial passages communicating with said rod intermediate the ends of said guide, a throttle valve for said nozzle, and a duct connecting the engine side of said throttle valve with said radial passages and the chamber communicating with the inlet to said booster. Y

9. In a. fuel lift carburetor of the class described, the combination of a nozzle, a fuel chamber'from which said nozzle is supplied, a booster Venturi tube for creating a suction in said fuel chamber, a plate having a port controlling the inlet to said booster, a sheet metal cup forming an inlet chamber for said booster, a second port in said plate forming a restricted air inlet for said last-named chamber, and meansforshifting said plate to vary the `amount of air admitted charges, a fuel supply chamber, a booster nozzle i for creating a sub-atmospheric pressure in said cylinder, a rod for movingsaid piston in one direction, an interconnection between said rod and lsaid throttle whereby upon opening said throttle said piston advances in a direction tending to supply an accelerating charge to said fuelfeeding nozzle, and a valve coacting with said piston to regulate return ow of fuel therethrough whereby the accelerating charge is prevented from becoming excessive.y

11. In a self-feeding carburetor of the class described, the combination of a mixing chamber, a fuel supply chamber, means for creating a subatmospheric pressure in said fuel supply c ham- Aas ber, an automatic air valve for maintaining minimum depression in said fuel chamber and in said mixing chamber, va fuel-feeding nozzle discharging into said mixing chamber and supplying the normal operating requirements of an engine to which said carburetor is attached. a throttle valve l on the engine side of said air valve, an accelerating pump interposed between said nozzle and said fuel chamber whereby all fuel supplied to said nozzle passes through said pump, said pump comy prising a cylinder, a perforate piston therein, means for advancing said piston upon opening of said throttle valve, said piston being in communication with said fuel chamber whereby fuel from said chamber is admitted through said piston to said cylinder, a member for regulating return flow of fuel through said piston to prevent oversupply of fuel to said nozzle during acceleration, and a fuel `discharge passage leading from" said cylinder to said nozzle.

12. In a carburetor of the class described, the

combination of a fuel-feeding nozzle supplying .-65

the normal operating requirements of an engine to which said carburetor is attached, an accelerator pump `for supplying fuel thereto, said pump comprising a cylinder, a perforate piston through which fuel is normally supplied to said nozzle, a conduitconnecting said cylinder with said nozzle, means for advancing said piston to supply an ac celerating` charge of fuel to said nozzle, and a valve-controlled opening permitting back flow of fuel through said piston to prevent oversupply of fuel to said nozzle during acceleration.

13. In a fuel lift carburetor of the class described, a. nozzle, a fuel chamber, means connecting said nozzle with said chamber, a. booster Venturi tube for maintaining the interior oi said fuel chamber below atmospheric pressure, said booster Venturi tube being adapted to discharge into the intake manifold of kan engine, a. choke plate movable to restrict the inlet of the booster Venturi tube for reducing the suction produced by said booster Venturi tube, a. throttle valve, and means comprising a cam on said choke plate and a lever operated thereby to partially open said throttle valve when said choke plate is in position to restrict the inlet of said booster Venturi tube. A

ROBERT F. BRACKE.

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