US2397520A - Carburetor - Google Patents

Description

CARBURETOR :5 Sheets-Sheet 1 Filed April 16, 1943 INVENTOR JAMES E ARMSTRONG BY aamwadnzw ATTORNEYS April 2, 1946. J MS G 2,397,520

CARBURETOR Filed April 16, 1945 A 3 Shgets-Sheet 2 o INVENTOR FIG. 2

BY JAMES F. ARMSTRONG 4. exam View ATTORNEYS April 1946- J. F. ARMSTRONG 2,397,520

GARBURETOR 4 Filed April 16, 1943 3 Sheets-Sheet s n 9' IL INVENTOR JAIES E ARMSTRONG ATTORNEYS Patented Apr. 2, 1.946-

CARBURETOR James F. Armstrong, Plainfleld, N. J. Application April 16, 1943, Serial No. 483,239

(Granted under the act of March '3, 1883, as amended April 30, 1928: 370 0. G. 757) 4 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

The present invention pertains to a novel carburetor which is especially useful for aviation engines although not particularly limited thereto.

One of the objects of the invention is to provide a carburetor whose operation is not materially affected by its angular position, whether the carburetor be displaced 90 degrees or even completely inverted. This object is realized by providing a bowl with opposed diaphragms acting upon a fuel supply valve to control the fuel level therein and by positioning th discharge orifice in the volumetric center of the fuel bowl. In positions other than upright, the weights of the individual diaphragm operating mechanisms are equal and opposite so that they do not affect the valve when the carburetor is tilted.

The invention also includes a novel accelerating system which, when required, draws a proper charge of fuel from the lin but independently of the bowl inlet and forces it under pressure into the manifold pipe. .This charge is sufllcient until the motorpicks up speed and draws the required amount of fuel from the bowl.

Another characteristic of the invention is that all of the air that enters the fuel bowl passes into the main fuel passage and to the intake manifold pipe, thereby contributing to the improved operation of the device as described more fully hereinafter.

The invention is fully disclosed by way of example in the following description and in the accompanying drawings in which:

Figure l is a cross section of the carburetor on the line l-l of Figure 2;

Figure 2 is a side elevation; p Figure 3 is a section on the line 33 of Figure 1;

Figure 4 is a plan view, partly in section and Figures 5 and 6 are sections on the lines 5-5 and 8-4 of Figure 2.

Reference to these views will now be made by use of like characters which are employed to designate corresponding parts throughout.

The body of the carburetor includes the-usual manifold pipe I and a receptacle 2 constituting the bowl or liquid chamber. This chamber and the parts associated therewith also perform the function of the usual float chamber, as will presently appear, so that no separate float chamber ;is used. The sides 3 of the body are enlarged and substantiallycircular for the attachment of bolted plates 4 and I to hold a pair of diaphragms,

mediate sides 8 of the body 2 is integral with the main casting, and the opposite side I is an inserted sheet metal member.

Within the pipe i is inserted a Venturi member 8 with a hollow cross bar or tube 0 across the narrowest portion of the throat. .A member It extends from the pipe 8 to the plate I and is suitably channeled to provide a vent passage ll for the bowl. The member It is extended to the center of the bowl by means of an inserted tube ii. A second tube It is also inserted in the member i0 concentrically within the tube I! to constitute the main fuel passage. A ring M is inserted in the free end of the tube It and is formed with an apertured flange l6 bridging the space between the tubes l2 and it. The member it constitutes the main fuel orifice and the apertures It in the flange are the fuel bowl .vent holes.

The top of the bowl receives a fuel inlet 1- fitting formed at its lower end with a valve seat H. A valve stem or rod ll passes through the seat and carries a valve pits or head It held on the seat by a spring 20 which bears against a perforated retainer plate It secured in the fitting l8.

Diaphragms 22 and 23 are held against the portions! by the bolted cover plates 4 and 5 respectively. The intermediate portion of each diaphragm is held between two rigid disks 24 in the usual manner. The stem 25 is threaded through washers 28 at the center of each diaphragm ,and is secured by a cap nut 21. Theplate I is bulged outwardly at 2. to accommodate the nut 21. Opposite the cap nut on the diaphragm adjacent to the plate 8, the plate is formed with a tapped nipple 2-! into which is inserted a fuel level adjusting screw ll. A-sprlng Si is positioned between the screw and adjacent washers 26. Adjustment of the screw regulates the spring tension on the adjacent diaphragm and on the valve "through the connecting linkage which will now be described.

From an intermediate point of each stem 25 a link 32 extends to the bottom of the bowl and is pivotaily attached to both parts at 33 and II. From the inner end of each stem a link 35 extends to the top of the bowl and is pivotally attached to both parts at 3! and II, the pivot points 31 being disposed at opposite sides of the valve is as shown in Figure 1. The upper end of each link it is formed with aninwa'rdly extending finger 38 'slidably' received in a socket member ll carried on the lower end of the valve stem ll. This mechanism transmits movement of the diaphragms to the valve stem ii. The tube 9 is .formed with ports (I for discharge of fuel.

thus provide a vent therefor.

In the operation of the device as thus far described, it may be assumed that the screw 30 has been adjusted to maintain the fuel level in the bowl at the line A with the engine stopped. The level may vary slightly with the density of the fuel and with the fuel pressure on the valve l9, the latter being maintained substantially constant by such means as,'for example, a die.- phragm-controlled relief valve in the fuel pump. The passage of air through the venturi 8 will cause depression at the ports 40 and in the member |4'.

position of the carburetor, even if it be rotated -The depression pressure communicated to the bowl from the orifice 40 in the Venturi system and, acting on the diaphragms 22, 23, draws them towards each other and lifts the'valve head Hi from its seat to permit fuel to enter thebowl. In the construction shown, the fuel lift need not exceed 95 of an inch to bring the level to the orifice at the member l4. The cylinder suction and the Venturi action will draw fuel through the tube l3, bar 9 and ports or jets 40 which discharge into the air steam.

v The small apertures l5 in the member |4 per- Obviously, in order to utilize fully the availablemetering 'depression, the apertures l5 in member l5 must be of a small area in relation to the main orifice in member M. The suction through the main orifice in the member- |4 results in opening the valve l9 and the fuel level will rise from its level at-A until it reaches the orifice and is'drawn therethrough into the tube l3 and discharged through the ports 40 into the air stream in the venturi 8. As long as a portion of the orifice in the member M is open to the fuel bowl the valve I9 will remain open and fuel will be admitted to the bowl. If fuel is admitted through the valve l9 faster than it is discharged through-the orifice, the fuel level will rise until the orifice is completely covered, at which time the valve l9 will close since the fuel bowl is no longer in communication with the suction. Inasmuch as there are a plurality of small apertures I5 spaced from each other near the periphery of the flange l5, it will be apparent that one or more of the apertures will be above the fuel level even when it completely covers the main orifice, and the fuel bowl will be vented through the passage Since both the air vent and the fuel orifice are located in the volumetric center of the fuel bowl, the carburetor will function as described above regardless of the position of the carburetor. is lost for venting the fuel bowl at the apertured member l5. ceed to to provide the fuel bowl with a suitable vent. A constant mixture. ratio curve at open throttle with a manifold depression from one-half to two inches of mercury is readily obtainable.

The location of the orifice 4 and the construction of the diaphragm mechanisms are of primary importance. The orifice, it will be seen. is in the volumetric center of the bowl. The construction of the diaphragm mechanisms is such that the individual mechanisms operate oppo sitely on the fuel valve if the carburetor is tilted A portion of the depression In practice this loss need not ex- I 90 or entirely inverted. Similarly, the delivery of fuel to the member I4 is not affected because of the location of the latter in the volumetric center of the bowl. is no egress of fuel from the bowl, in any position, without Venturi depression in passage la. The importance of these properties in aviation will readily be appreciated.

The idling system comprises a tube or jet 4| mounted within the bar 9, and extending to a passage 42 formed in the wall of the pipe I adjacent to the mixing chamber 43. In the chamber is rotatably mounted a throttle valve shaft 44' carrying a butterfly throttle valve 45. Ports 46 and 41 are drilled in the wall to connect the passage 42 with the chamber 43 and are preferably located respectively above and below the throttle valve in closed position. The intake end of the tube 4| is closed at 48 and the side walls are perforated at 49, thereby reducing the intake area to requirements and causing the tube to function as a metering jet. Also, a mass of liquid fuel in the tube 4| is not likely to cover all the perforations, so that the air cannot be completely choked off.

The upper end of the passage 42 communicates at 50 with the pipe i on the air intake side of the venturi, and the effective area of the port 50 is regulated by an adjusting screw 5|.

tem, to regulate the amount of fuel drawn into the mixing chamber 43 by the idling engine. The main discharge Jets 4!] also act as air bleeds on the idling system, while the Venturi depression is less than the main fuel passage depression.

At open throttle, some of the air entering the port 50 passes throughthe tube 4| and bleeds the main fuel discharge ports 40 to a very slight degree. In order to supply sufficient fuel to idle the engine properly at a slightly greater speed than as ,low idle, the port 46 is so positioned that it becomes effective when the throttle valve is opened slightly. In this manner the depression in the idle passage is increased sufficiently to furnish the desired fuel richness at small throttle openin 7 The economizer system comprises a diaphragm 52 clamped to the bottom of the bowl by a plate 53 and having one side exposed to the bowl through a port 54. The opposite side of the diaphragm is exposed to the mixing chamber 43 through a suitably shaped passage 55. A suitably supported bracket 56 pivotally supports a valve crank lever 51 provided on one arm with a pin 58 adapted under certain conditions to enter the member l4 and restrict the orifice. The other arm of the lever 51 is engaged by a rod 58 mounted on the diaphragm 52. A spring 59 between the diaphragm and the plate 53 tends to remove the pin 58 from the orifice against the action of a tension spring 60 joining the. lever 51 to an opposite point on the bracket 56.

When the pressure in the mixing chamber between the throttle valve 45 and the engine valves exceeds .the pressure in the bowl by four or five inches of mercury, the diaphragm 52 compresses the spring 59 and the tension spring 60 draws the pin 58 into the orifice 14 as shown in dotted lines in Figure 1. This obstruction in the main fuel orifice thins the fuel mixture to the desired degree for maximum economy in this condition of operation. When the mixing chamber pressure increases relatively to the bowl pressure, the

For the same reason, there This constitutes a 'bleeder or vent for the idling sysshown in Figure 4;

I spring 59 overcomes the spring til. and the pin so is withdrewnirom the orifice to enrich the mixture for the maximum power output from the engine under these conditions.

The acceleration system is supplied with fuel through a. fitting ti mounted in a. suitably iormed plete 62 attached to a, side the pipe i. The

fitting is intended to be connected directly to the fuel supply pump or line without interfering with the bowl suppl fitting i6. Between the plate es and the side of the pipe l is formed schemher he in which is clamped o. diephruum M. A passage connects the fitting 6!! with the inner side of the diaphragm. A check valve so to held useinst the outlet end of the fitting by e light spring (ll.

C utside the pipe 6, the throttle valve shell. t l curries on ectuotine' lever so adopted to he linked to the ecceleretion meal. The opposite end of the throttle shaft curries an arm till to which is pivotelly attached at link lt. To the link is pivotelly attached as lever ll terminating in s. fork l2 disposed udlscent to the piste G2.

The fort: curries a pin it pivoted in lugs it ere tending from the plate. A rod. lo secured to the center oil the diaphragm 65 is adopted to slide in the plate 32 and towards a. point on lever ll suecedsomewhnt from the pin it. A spring it hetween the diaphragm and the plate tends to withdrew the rod it from the lever.

'llie side well oi the pipe i and the plots $2 form e lower diaphragm chemher ll in which is clamped e dieohregm it. A flitting ls mounted in the pipe well edjueent to the diaphragm it provides it velveseet till ensuing into the min ins chemher 68 below the throttle valve. To the diaphragm it is clumped e. channeled velve stern ill having at head it? normally seated on the valve seet to by a, spring 88st the oupoeite side of the clieohree'm. Channels t l end to connect the divisions of the chomloer 6% respectively to the divisions oi the chamber ll. In the onere= tion oi this portion or the apparatus, the fuel entering the fitting hi hes sumcient pressure to open the check velve so aseinst the spring or. The uiuphreem so isthus-xnoveol sumciently to bfillg the rod ll; against the lever ll. The fuel pressure is not normellv sumcient, however; to

overcome the s rine ill which holds the valve heed S2 on its seat 8%.

When the throttle volve is opened, the memhers lit end ill operate to swing the lever it end move the reel '65 end thus sense the dienhreum 66 to exert pressure on the fuel in the pressure side oi the chernher ill. "The check valve to closes under this pressure and the fuel is trumped. The increased pressure on the treppeti fuel moves the diaphragm it against the spring t3, whereby the velve 82 is opened. This operetion releases the necessery amount of fuel into the engine to cover the lee between-the. starting of Bill the air flow end the starting of the fuel flow when the air flow through the venturi is sudldenly increased.

The low pressure sides 0! the chambers 88 and 'l. in a carburetor having a. fuel bowl, on airpipe one u throttle valve in sold air pine, a fuel discharge tuhe extending from sold pipe into sold fuel howl and heving an entrance locutecl substuntlellv out the volumetric center thereof o, movable velve tor eo mlttlng iuel into soirl howl,

operetinu moons for said valve erreueed to meiotuin fuel in sulol' hovll suhetentiullv ut the level of the volumetric center thereof when sold. throttle valve is open regardless oi? the ensuler position of the curhuretor e sleeve surroimdine sold fuel disoherge tulle one forming therewith en annular chomher. end can at the outer enol of sold sleeve suhstentiellv et the volumetric center of seiol bowl, sold cuu hevluu u ulurelitv oi vent openings therein estshllshius communication be tween sold annular chernher end seicl loevvl to vent the letter.

2. in e curhuretor heviue on ulr plus one u. howl, o luel disoheree tulle communicetine with sold pipe until ext-outline into sold hotvl end ter urinating; suhsttmtiellv at the volumetric center of solo howl, u. sleeve conoentrlc with one our rounding suiel tulle enrl cooperetlnu therewith to form on ennuler eheinher thereleetvveen, sold choniher having one end eommuuioohnu with selol pine until u eeu covering the outer ends of soiol tuhe unol tutti sleeve, sold eon hnving e centrel; opening estuhlishlne eommunlcetion hetvveen solo tulle unol eeiol howl for the onssuue of fuel enol o, plurelitv oi" smell openings estnhlishing communication hetiveen solo ennuler chumher until sold howl to vent letter.

It in u eerhuretor or fuel howl, en eir nine one u tl'lrottle velve in solo eir nine, as tool dlseheree tulle extending from seicl pl es into sold fuel howl unol having on entruuoe loceteil suhstentlellv the volumetric center thereof, e movehle vulve lor ournittine fuel into seirl howl, operating for sold velve erroneetl to meiotoin fuel in sold. howlv suhetuntielly et the level of the volumetnc neuter thereof when soul throt= tle velve h ooen reserrllese oi the euelllorgooet tion of the ourhuretor. one o series of reletively smell vent nessoees erreneecl eoncentrlcullr with seiol fuel olischore'e tuhe end ouenine into eeiu howl et uoints suscerl redieilv outtverdlv from sold tube.

s. in o oeriiuretor huvlns e'tuel howl. on air pipe end u throttle valve in solo nlr else, u fuel discharge tuice extending from sold nine into sold fuel loovvl' one heviuu on entrence lcoeteu suhstoutieilv out the volumetric center thereof, e movehle t'ullflh tor admitting luel into sold howl, operutine menus iorseiol vulve errenuetl to st toin fuel in solo howl v at the level ll ore vented by .a passage 86 formed through each oi the diephragms 22, 23 and the adjacent cover plate is vented by a passage 81 extending of the volumetric center thereof when said throt tle valve in open regardless of the r pooltion of the carburetor, end u series of relatively from the space through said plate and the side I well of the pipe I to the interior of the pipe, as

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