US2801645A

US2801645A - Carburetor fuel inlet valve

Info

Publication number: US2801645A
Authority: US
Inventors: Jack M White
Original assignee: ACF Industries Inc
Current assignee: ACF Industries Inc
Priority date: 1954-12-30
Filing date: 1954-12-30
Publication date: 1957-08-06
Anticipated expiration: 1974-08-06

Description

Aug. 6, 1957 J. M. WHITE 2,801,645

CARBURETOR FUEL INLET VALVE Filed D90. 30, 1954 35 H]; J 2),? 623 F G. 3. k

22 58 t 1 G 21 v I; I! 39 26 25 '2! 20 7 1 l3 j F G. 2.

F 4 INVENTOR.

' JACK M. WHITE QwyA 441 ATTORNEY United States l atent assi o by mm a This srsat ss at s. s an imrrqrsrns i fu s sm r me veh le ar d he like, an m re spec fically, to a el fuel level control mechanism for a car buretor fuel bowl,

Where the fuel level control mechanism comprises a fls f nt l ed i sd val sj ciin a a ns a r u e head, ithas foii id t at the maximum size of the needle valve and itss'eat, svhich will give precise control of the fuelleyel, is dictated by the relative size of the floatwhich operatesaj givensize of needle valve. By this'itis meant'tliat the fioatsize determines the amount r e (tamp r) avai a le ho the v e n its seat against'fpu" p pressures. In. other words, where the approximatebucyanfil" force at the desired fuel level, the leyerage,aiid he exposedarea of the needle valve are known, it is p d ermi the safe pres sure agains twhic this lfloat valve A work. A certain safemrgin mustbe allowed infthedesign because at high ambient temperatures excessive pressures can build up in the'discharge lirie fr dmthdprimia, due" to boilingof the V These pressuresaet directly orithe exposed areas offthe valve,a1d"u ess the valve remains effectively closed by the buoy y force ofthe float,press irefwill forceany gasolih 'n the su ply lihe past the needle valve tojflood thecarburetor and engi airifold'with excess f 1 'f In order to avoid this di fliculty and others, present designs use a float'as largeas possible to obtain themaximum force from bueyancy, but it is obvious that thereare i Ii iQ iQ -J b th me ani a and. j ic. whi limit the float size} Once this choice is made, then theexposed needlejvalvearea and operating linka ge, may be varied with respect to one another so asto make possible the useof the largest size of needle valve, together with appropriate linkage, providir g full opehing for that valve anj nsfe ce ade ua e s vths a e m r n of force above mentioned.

U a l ll o es equ rem nt sed. y hese extreme pressures can be met, and a' carburetor float system can be designed which will function entirely satisfactorily under ordinaryconditions. Fuel pumps novv in generaluse are of the mechanically operated diaphragm type, and generally have a spring powered discharge stroke. Their maximum output pressuge is limited to about four to six pounds. Temperaturefconditions may raise this pressure to ten or twelve poi'mds when the en gin e is at rest. Even so, it is generally the case that the float valve system is capable ofrsupplying the maximum demands of the carburetor and still. effectively close at these maximum pressures,

The pump itselfnecessarily has several times the capacity of the maximum demand by the carburetor. Consequently, the float valve system under. normal conditions will continually act against a pressure approximately equal to the maximum discharge pressure ofthe pump. Under these conditions, the pump is never called upon to operate at its maximum capacity, and it is only desirable that it operate at, full capacity when heat has caused the formation of vapor in the discharge line, or in the suction line, or in both.

To attain maximum output from the pump, it is desirable to eliminate any back pressure in the discharge line 1C Fatented Aug. 6, '1957 2 from the pump, since this .will impede pump action by l m th .d ss'hsrg t k of t e P a It has"been discovered that the usual needle valve, when properly designed to fulfill the requirements imposed by the above discussed conditions, forms a restriction in the pump discharge line sufficient to restrict pump lq On h char e 51m 03 3? p r t at m x mum capacity is impossible. At higher temperatures, the vapors formed in the pump line sometimes cannot be expelledsoon enough, unless the pump is allowed to function at its maximum capacity. The carburetor then becomes starved for fuel, and a condition of complete vapor lock occurs. Once this happens, the fuel is soon exhausted fromthe float bowl the engine stalls, and restarting is impossible until the system cools,

According to the present invention, the fuel inlet between the pump and fuel bowl of the carburetor is controlled. by a pair of valves, one of which is closed by a float and tends to open by pump pressure, and the other of which is opened the float and is seated by pump pressure. Stated in another way, the flow capacity of the usual float valve issupplemented by the addition of a second valve held closed by pump pressure and arranged for successive operation by the weight of the float.

With this system of float and valves, when the fuel level withinthe floatboyvlis lowered, the first valve, which closes against the pressure in the fuel line, is allowed to open'. Becausethis is necessarily a small valve, it gives a fine control of the fuel lev el within the fuel chamber. When the level in the fuel chamber drops still further, the weight of the. floaflifts the second valve from its seat and"allows full pump capacity by removing the restrictioii to flow imposed by the size of the first valve.

fuel supply system provides all the advantages of previous systems plus. the added advantage of an unrestricted discharge opening, which may be necessary to permit thepurrip to operate at its maximum capacity. The size of the first valve is so chosen as to handle any pump discharge pressures, or any. pressures which might develop in the "discharge line from the pump when the fuel boils. Of course, the second valve will merely seat tighter under such pressures. On the other hand, as the fuel level drops the fuel bowl of the carburetor, the first valve will opei partiallyjrelieving the pressure on the second valvejso that the. weight of the float is capable of opening the second valve in case the level drops that far.

The present invention provides a float valve system which accomplishes similar results to that disclosed in my prior application with Alfred C. Korte, Ser. No. 465,206 and now abarrdoned filed October 28, 1 954, for Carburetor l uel Inlet with Pressure Relief.

In the accompanying drawings I have illustrated one form of the present invention, inwhich Fig. 1 is a. diagrammatic view of a motor vehicle fuel system.

Fig. 2 is an elevation of a carburetor with parts in section to showthe interior of the fuel bowl.

Fig. 3 is a fragmentary view of the structure in Fig. 2, partly in section, showing the operation of the valves as the float beginsto drop.

4 is a View similar to; Fig. 3 illustrating the position of the valves at the limit of downward movement of the float.

In Fig. 1, an engine 1 is shown having an exhaust manifold 2 and. arr intake manifold 3. A carburetor 4 is mounted on the. vertical riser 5 of the intake manifold. 3 and provided, with the usual heated jacket connected tothe, exhaustinanifold 2.. A combined fuel pump and suction booster 6-. is mounted on the side of the engine to be operated from the engine camshaft. The fuel pump has a suction line 8 extending to the fuel tank of the vehicle, and a discharge line 9 extending to the carburetor 4. The suction booster part of the pump 6 is connected by a line 10 with the intake manifold, and by a line 11 with the suction-operated accessory devices of the motor vehicle. In the pumps now in general use, the suction stroke is powered by the engine, and the exhaust stroke is spring powered.

Fig. 2 shows a fuel valve system according to the present invention, and its control by the float mechanism in the carburetor. The carburetor itself forms no part of the present invention, and is of the more or less conventional downdraft type, having an air horn 12, a float bowl 13, and a throttle body 14, interconnected in assembled relation.

Within the float bowl 13 is a float 17 secured to a float control arm 18 pivotally supported on pin 21 from a bracket integral with the float bowl cover 22. A series of screws 23, one of which is shown, secures the float bowl cover to the carburetor body.

Formed integral with the arm 18 is a finger 25 which bears directly against one end of a needle valve 26 slidably supported within the cage 27. The cage 27 provides a suitable guide for vertical movement of the needle valve 26 to and from its seat 28. The upper end of the cage 27 is secured by the threads 29 in a passage in the float bowl cover 22 between the fuel chamber 30 in the cap 31 and the fuel bowl 13. A boss on the cap 31 is threaded at 32 to receive the fuel line 9, as shown in Fig. 1. Means are provided (not'shown) for securing the cap 31 to the fuel bowl cover 22, and a sealing gasket 33 prevents any leakage at this joint.

Valve cage 35 is positioned adjacent valve cage 27, and has screw threads 36 at one end, by which it is secured in a passage between the float bowl 13 and the fuel chamber 30. Within the cage 36 is a large check valve 37 guided for movement vertically by the cage to and from a suitable valve seat 38 formed therein. Valve 37 has a depending stem 39 positioned to be operated by a finger 40 integral with arm 18 and positioned on the opposite side of pivot 21 from the finger 25.

Fig. 3 shows the position of the parts with the valve 27 open wide. In this position of the valve sufficient fuel will be supplied to the fuel bowl to accommodate engine requirements under ordinary conditions and with the elements of the system operating properly.

It sometimes occurs, however, that the discharge line 9 from the pump reaches such a temperature that the fuel therein will boil, causing excessive pressures in the line after the engine has stopped with the float leveled in the bowl sufficient to close both valves. With these conditions existing, if the engine 1 is restarted, fuel will gradually be consumed within the float bowl 13, opening the valve 26. This may not lower the pressure in the line 9 sufficiently, however, for the fuel pump 6 to operate, at least not at its full capacity.

It becomes quite apparent, then, that valve restriction imposes a limitation on the pump conducive to vapor lock, and all the fuel in the bowl is consumed before the pump rate of delivery will equal the rate of consumption by the engine. Before this can happen, however, float 17 will drop far enough to open the valve 37 by pressure of the finger 40 against the stem 39. The weight of the float 17 will be suflicient to perform this function, since the pressure in the chamber 30 and the fuel supply 9 is somewhat reduced by opening of the valve 27. When both valves are open, the restriction in the supply from the pump is substantially eliminated, and continued operation of the engine will drive the pump at full capacity to clear the vapor from the lines.

A structure has been described which will fulfill all the objects of the present invention, but it is contemplated that other embodiments will occur to those skilled in the art which come within the scope ofthe invention as defined by the appended claims.

I claim:

1. In a fuel system for a motor vehicle having an engine, a fuel source, a fuel pump of a type having maximum capacity at low discharge pressure driven by said engine and connected to said source, a carburetor for said engine including a constant level fuel chamber and a discharge line connecting between said pump and said chamber, the combination of a float in said constant level fuel chamber, first and second float controlled valves both controlling the flow of fuel from said discharge line into said chamber, said first float controlledvalve having a liquid capacity suflicient to meet fuel requirements of the carburetor during engine operation and arranged to open in the direction of fuel 'flow from the pump and closed by buoyant action of said float, saidsecond float controlled valve providing with said first valve a total flow capacity suflicient to completely relieve back pressure on said pump to allow a full stroke of the pump when said engine is operating and arranged to close in the direction of fuel flow from said pump, and means for opening said second valve by said float as the fuel level in said bowl lowers and after said first valve is fully opened to partially relieve excessive pressure on said second valve, whereby an effective vapor vent is provided to increase the volumetric efliciency of said pump and obtain rapid pump priming by decreasing the resistance to the action of the pump expelling vapors from the fuel system.

2. In a carburetor, the combination of a fuel reservoir, an inlet for said fuel reservoir, and a float valve system for controlling the supply from said inlet to said reservoir, comprising a float in said reservoir, first and second float controlled valves both controlling the flow of fuel through said inlet into said reservoir, said first float controlled valve having a liquid capacity sufficient to meet fuel requirements of the carburetor during engine operation and arranged to open in the direction of fuel flow and close by buoyant action of said float, said second float controlled valve providing with said first valve a total flow capacity suflicient to relieve any back pressure in said inlet when said first valve is open, said second valve being arranged to close in the direction of fuel flow, and means for opening said second valve by said float as the fuel level in said bowl lowers and after said first valve is fully opened to partially relieve pressure on said second valve.

3. In a carburetor, a fuel reservoir, a fuel discharge line to said reservoir, first and second valves both controlling the flow of fuel from said line into said reservoir, a float in said reservoir operable responsive to a predetermined drop in fuel level within said reservoir, and means carried by the'float and engaging said first and second valves to successively open said valves to progressively increase the rate of fuel flow into the reservoir.

4. In a carburetor, a fuel reservoir, a fuel discharge line to said reservoir, first and second valves both controlling the flow of fuel from said line into said reservoir, a float in said reservoir operable responsive to a predetermined drop in fuel level within said reservoir, means carried by the float and engaging said first and second valves to successively open said valves to progressively increase the rate of fuel flow into the reservoir, said first valve having a variable flow capacity normally suflicient to maintain the fuel in said reservoir above a predetermined level, and said second valve being opened only when the fuel in said reservoir drops below said predetermined level.

References Cited in the file of this patent UNITED STATES PATENTS