US2275541A - Fuel lift carburetor - Google Patents

Description

Patented Mar. 10, 1942 FUEL um' canauaa'ron `Harold W. Meade, Covington, Ind, applic-uan september 11, 193s, serai No. 101,214

(ci. s-sei) 11 Claims.

My invention relates primarily to fuel-feed systems for internal combustion engines usmg liquid fuel and has for its object the provision of a fuel-feed system which will elevate fuel from a supply tank to the point of delivery anu which will be simple in construction and positive in operation. Another object of my invention is to produce a fuel-feed system which can readily be embodied in association with a carburetor of any desired type. A further object ofv my invention is to provide a suction-operated fuel-feed system of an automobile with means forpreventing flooding should the automobile ever asume a position in which fuel would tend to ow by gravity from the supply tank.

Still another object of my invention is to provide for a suction-operated fuel-feed system, or for any other suction-operated device, means which will insure the existence of a minimum pressure-differential under varying conditions of engine operation.

The accompanying drawingsv illustrate my in-A closed when the fuel-level in the chamber I3 is at or above a predetermined point. Y

Fuel is supplied to the chamber I3 through a port 2| communicating with the fuel-supply line 22 leading from a supply tank 20 which normally is at a lower level than the chamber I3. The

bottom of the chamber I3 is provided with a fuel-discharge opening 23 by means of which the fuel in the chamber may flow into the reservoir lll; and associated with the opening 23 is ava-Ive member 24 connected to move with the diaphragm I4.

Also movable with the diaphragm I4, and conveniently mounted directly upon it, is an upwardly opening cup-shaped member 25 which receives a stationary piston 26 and a spring 21, the latter acting between the piston 26 and the bottom of the cup to exert a downward force on the diaphragmV I4. A' small port 28 'extending through the bottom of the cup provides communication between the interior thereof and that portion of the chamber I3 lying beneath vention: Fig. 1 isalsomewhat diagrammatic view of a carburetor and associated fuel-feeding sys-V and Fig.- 3 is a fragmental view similar to Fig. 1 f

but showing the movable parts of the device in different positions.

The carburetor shown in the drawings embodies a fuel reservoir .I0 which, in that fuel supplied at regulated rate from it passes through a jet II to the mixture intake conduit I2 of the engine, is the equivalent of the float-bowl in the conventional carburetor; .but the reservoir I0 diii'ers from the conventional float-bowl in that it embodies no float. Associated with the reservoir l0, and conveniently disposed therein, is a fuel-feeding chamber I3 divided horizontally by a exible diaphragm I4. That part of the chamber `I3 lying above the diaphragm I4 communicates through a port I5 with a conduit I6 by means of which it is subjected to subatmospieric 'pressure as the result, either directly or indirectly, of the partial vacuum existing Within the intake manifold of the engine when it is operated.

That portion of the chamber I3 lying below the diaphragm I4 also communicates, through a port I1, with the conduit I6; but associated with the port I'I there is a valve IIi controlled 'by a float I9 -in the chamber and sc arranged as to be the diaphragm. vIn the annular wall of the cup 25 there of are one or more .ports 29 which provide communication between the interior of the cup and that portionof the chamber I3 lying above the diaphragm, the ports 29 being so located that in upward and downward movement of the cup and diaphragm they are alternately covered and uncovered by the lpiston 26.v

Conveniently, the upper end of the chamber I3 is so formed as to receive the .upper end of the cup 25 and to serve as a guide therefor. The valve 24 may be connected to the diaphragm by a valve stem 30, the upper end of which is screw-threaded into the bottom of the cup 25. 'Ihis valve stem 30 may conveniently serve as a guide for the float I9.

Except for the air-discharge ports I5 and I'I, and the fuel inlet and discharge openings 2| and 23, the chamber I3 is sealed. The fuel-reservoir IIL, however, is open to atmosphere as through a port 32 near the top thereof.

The parts of the device are illustrated in Fig. 1 `of the drawings in the positions they respectively occupy when the fuel contained in the chamber I3 is being discharged into the reservoir I0 and is not being augmented by any fuel supplied through the port 2|. Under such conditions, the valve I8 is closed by the float I9 and the diaphragm I I, under the inuence of intakemanifold vacuum available through the conduit I6, is elevated to maintain the valve 24 open and the ports 29 closed. Under these circumstances,

the fuel-level in the reservoir II) remains approximately constant at an elevation just sufficient to prevent air flow from the reservoir ID to the chamber I3, for fuel can not escape from the chamber I3 except as air enters the opening 23 to permit its displacement. As fuel is used from 5 the reservoir I0, the opening 23 is uncovered, and air enters the chamberV I3 through the opening 23 to permit fuel to run'into the reservoir I0,

When the fuel level in the chamber i3 drops to the point where the valve 'I 8 opens, as .indicated l0 in Fig. 3, vthe sub-atmospheric pressure ofthe intake-manifold is applied through the tube IE to the chamber I3 below the diaphragm I4 to counteract the effect on the diaphragm I4 of the subatmospheric pressure existing thereabove.

prevent any further discharge of fuel through the opening 23. Because of the sub-atmospheric pressure now existing in the chamber I3 as the result of the opening of the valve I8 fuel from the tank 20 is drawn thereinto through the pipe 22 and port 2 I. The tank 20, of course, is vented.

As fuel enters the chamber I3' the fuel-level 25 differential pressure tending to elevate the diaphragm is created. Two factors contribute to the creation of such a differential pressure. In the first place, the liquid fuel cannot enter the port 28 with the same facility as did air; and, in

the second place, any liquid fuel which does enter the port and the vcup 25 builds up a liquid column rising above the level ofthe fuel below the diaphragm and creating a hydrostatic pressure which, transmitted to the lower surface of the diaphragm, tends to move it upwardly. As the result of these factors, the diaphragm I4` is raised to open the valve 24 and closethe ports 29, as shown in Fig. 1. The closing of the ports 29 preventsy the imposition of sub-atmospheric pressure upon the fuel in the chamber 83 even 50 .when the fuel-level therein drops; and fuel is therefore free to escape from vthe chamber I3 into the reservoir Illas air enters the opening 23. I have found it desirable to associate with the opening. 23 a" downwardly extending tube Q0, the 55 lower end of which is cut off obliquely at a relatively sharp angle. In the absence of such or an equivalent arrangement I find that the opening 23 must be made inordinately large; as otherwise the surface tension of the liquid fuel may .pre- 60 vent it from running out of the chamber I3 even when the level in the reservoir I9 drops below the bottom of the chamber.

During the interval in which lthe valve 24 is closed, the fuel level in the reservoir I0 will drop 5 as fuel is discharged into the mixture conduit, and will continue to drop until the chamber I3 becomes filled with fuel. In practice, I have found no vdifficulty in so proportioning the device that the chamber la will remi before the fue1 .m

level in the reservoir I0 has dropped vsufdciently to effect any material change in the mixture proportions.

Y In the ordinary operation of an automobile As l5 the result of this counteracting effect and of the force exerted by the spring 21, the diaphragm is forced downwardly to close the valve 24 and to pressure applied 30 low speed and open throttle, when the intake manifold vacuum is insufficient to be depended upon to elevate the fuel into the chamber I3. I therefore prefer to employsome type of booster arrangement by which the effect of intake-manifold vacuum in creating sub-atmospheric pres sure in the chamber I3 may be augmented. To this end, I may dispose between the carburetorthrottle 45 and the engine a venturi 46 the throat of which communicates through ports 4l with an air-inlet passage 48 supplied with air through the venturi 49 of an aspirator 50. The throat i of this aspirator communicates with the tube I6;

and, as the static pressure at the throat of the aspirator venturi 49 will be lower than that at the throat of the venturi 46, which latter pressure will in turn be lower than that existing' in the intake manifold beyond the venturi 45, the pressure applied through the tube I6 to either the upper or both compartments of the chamber I3 will be; materially lower than that existing in the intake manifold. With this arrangement, fuel can be elevated through a considerably lgreater distance than if the unaided intake-manifold vacuum were employed.

Even when the booster effect of such a device as the aspirator 50 is utilized, there still may be occasions when the intake-manifold vacuum is insufficient to elevate fuel into the chamber I3. To prevent this condition from interfering with the satisfactory operation of my device I may include therein mechanism which will in- 'sure that a. predetermined lminimum vacuum will exist in the intake-manifold. As indicated in the drawings, this mechanism takes the form of a pressure-responsive element which `controls the position of an auxiliary throttle valve 56 disposed in the intake yconduit ofthe engine between the throttle 45 and the venturi 46, the arrangement being such that a decreased vacuum -in the intake-manifold will result in a partial closing of the auxiliary throttle 56.

Preferably, the pressure-responsive element 55 is responsive, not directly to the pressure in the intake manifold, but instead to the pressure at the throat of the aspirator-venturi 49. As the s vacuum at the throatl of the aspirator 49 is usually several times as great asthe vacuum` in the intakemanifjold, I am thus enabled to use a less sensitive pressure-responsive mechanism in the element 55,., 1

As indicated in the drawings, the pressureresponsive element 55 includes a casing 5l within which is mounted a diaphragm 58 dividing the interior of the casing into two compartments, the upper one of which communicates with Athe throat of the venturi 49 and the lower of which communicates with the atmosphere. 59 tends to force downwardly the diaphragmy 58 and a slidable member 6 0 which is rigid therewith and which projects outwardly through the lower wall of the casing 51. The lower end of the sliding member 50 is connected, as by means of a link 5I, with an arm 62 on the shaft of the auxiliary throttle 56.

Any drop in intake-manifold vacuum will be reflected as an increased pressure at the throat of the venturi 49; and this increased pressure, aided bythe spring 59, will force downwardly the .diaphragm 58 and member 50 to move the auxiliary throttle Valve 56 toward closedl position.J This vmovement of the throttle valve will impose a Arestriction upon the gases flowing through the intake conduit and will thus create engine conditions frequently arise. especially at a pressure-drop (or an increase in vacuum) in A spring the intake-manifold. When the vacuum in the intake-manifold is above the predetermined minimum, the resultant reduced pressure at the throat of the venturi 49 will-be transmitted to the upper compartment on the casing 51 with the result that the diaphragm and slidable member 60 will be raised and the valve 56 moved toward open position so as to reduce the resistance it offers to the yflow of mixture through the intake conduit.

The auxiliary throttle '56 with its operating mechanism has Van advantage in addition to its function of maintaining a minimum intake-manifold vacuum as such. When an internal combustion engine is operating at low speeds and fully open throttle the velocity of flow at all points along the intake conduit is not infrequently so low that poor atomization of the liquid fuel is obtained. As a result, the engine may deliver less power than if the throttle were partially closed or the intake-conduit otherwise restricted` to produce a localized increase in the velocity of mixture-flow. My auxiliary throttle 56 operates automatically to produce such a lo. calized increase in mixture velocitypfor the drop in intake-manifold vacuum which occurs at low speedsand open throttle causes the .pressureresponsive element 55 to move the auxiliary throttle 56 toward closed position and increase the velocity of the mixture flowing past it.

With my invention embodied in an automobile conditions may arise, as when the automobile with its gasoline tank'i'n the rear and engine in front is headed down a steep slope, under which' the chamber I3 may be lower than the fuel tank. In these circumstances, `fuel would tend to flow by gravity from the fuel tank into thechamber I3. To prevent this, I may place in the fuel-supply line 22 a valve 65 controlled by a pressure-responsive element 66' responsive to the pressure in the chamber I3 and adapted to close the valve 65 whenever the pressure in the chamber I3 becomes substantially atmospheric. So long as the chamber I3 is not full, fuel can of course iiow thereinto without producing any harmful result; and as soon as the chamber I3 becomes full, its connection with the Athroat of the venturi 49,(or with the intakemanifold) is broken to destroy the partial vacuum which previously existed. When this occurs, the pressure-responsive element 66 closes the valve 65 and prevents fuel from running into the chamber I3 even if the fuel-supply tank is above the level of the chamber I3. Y I claim as my invention: 1. In a fuel feed apparatus, a fuel reservoir, a

fuel feed chamber disposed above said reservoir in said chamber and controlling the connection.

between said air-exhausting means and said lower compartment, a fuel tank below said chamber and .connected to the lower compartment thereof, said fuel tank being open to atmosphere,A

means providing a passage between said upper vand lower compartments, said passage being restricted to Yan extent such that upward fuel-ow through it under the influence of said exhausting means cannot occur without the existence of valve in said passage and operatively associated a differential pressure sufficient to""`raise said diaphragm, and gl-provlsions for preventing flow through said passage when 'said diaphragm.A is

raised. i

2. In a fuel-feed system, a fuel-feed chamber,

a horizontal exible diaphragm dividing said chamber into upper land lower compartments and biased downwardly, a fuel-supply tank connected to said lower compartment, said fuel tank being open to atmosphere, means forG exhausting said upper compartment, means providing a passage between said upper and lower compartments, a

operatively Connected to said diaphragm to be opened when the diaphragm is raised.

3. In a fuel-feed system, a fuel-feed chamber, a Vfuel-supply tank open to atmosphere and connected to said fuel-feed chamber, an air chamber adapted' for connection to air-exhausting means, means providing a passage connecting said two chambers and -communicating with said fuel-feed chamber at a point slightly below the maximum fuel level therein whereby fuel will enter the passage as such maximum fuel level is approached, a valve in said passage, a pressureresponsive element responsive to the differential in fluid pressures at opposite ends of said passageand operatively associated with said valve, said yfuel-feed chamber being provided with an outlet port near itscbottom, an outlet valve controlling said outlet port and operatively connected to said pressure-responsive element to be closed thereby in response to the effect of differential pressures thereon, said passage being restricted to an extent suchthat fuel-flow through it cannot occur without the'creation of a pressure-differential sufficient to cause said pressureresponsive element to close said first named valve.

4. In a fuel-feed system, a fuel-feed chamber, a fuel-supply tank open to atmosphere and connected to said fuel-feed chamber, an air chamber adapted for connection to air-exhausting means, means providing a passage connecting said two chambers, a valve in said passage, said fuel-feed chamber being provided with an outlet port near its bottom, an outlet valve controlling said port, and means operative when the fuelle vel in said chamber reaches a predetermined maximum for closing saidfrst named valve and opening said outlet valve, said means including a pressure-responsive element responsive to the differential in fluidpressures at opposite ends of said passage and operating both said valves.

l5. In a fuel-feed system, a fuel-feed chamber, a Yhorizontal Iflexible, diaphragm dividing said chamber into upper and lower compartments, a fuel-supply tank below said chamber and connected 'to the lower compartment thereof, means for exhausting said upper compartment, means providing a restricted passage between said upper and lower compartments, said diaphragm being biased downwardly with a force greater than the resultant of the'total fluid pressures on opposite sides of said diaphragm when air is flowing upwardly through said passage under the influence of saidI exhausting means and less thansuch resultant when liquid fuel is flowing upwardly through said passage under the influence of said exhausting means, said lower compartment being provided with an outlet near its bottom, an outlet valve controlling said outlet, and a second valve controlling ow through said restricted passage, said diaphragm being operatively connected to said valves to close the latter and openthe former when the diaphragm moves upwardly as the result of the entry of'liquid fuel into said passage.

6. 'In a fuel-feed system for an internal combustion engine having an intake passage, a fuel- Asaid valve and thereby preventing egress of fuel through said outlet and means for intermittently connecting said fuel chamber to said intake passage to exhaust said chamber and induce fuelflow from said supply tank to said chamber, said means including a pressure-responsive element responsive at all times to uid pressure in said passage -and operative upon the conclusion of each period of chamber-exhaustion to open said valve. against the iniiuence of said yieldable means and to maintain it open until the chamber is substantially empty of fuel or until the pressure in said passage reaches a predetermined maximum.

'1. In a. fuel-feed system`- a fuel reservoir, a fuel-feed chamber disposed above said reservoir and having near its bottom an outlet port through which fuel may pass to said reservoir, a fuel supply tank, a conduit interconnecting said supply tank and said fuel-feed chamber, means for intermittently exhausting said fuel-feed chamber to induce fuel flow thereinto through said conduit, an outlet valve controlling said outlet port, mechanism for automatically closing said valve during periods in which said fuel-feed chamber is maintaining said last named valve closed when the fluid pressure in said chamber is above a predetermined value and open when such pressure is below that predetermined value.

8. In a fuel-feed system, a fuel reservoir, a

of fuel from said chamber into said reservoir; a valve in said conduit, and means for automatically opening saidlast named Ivalve when said outlet valve is closed and for closing said last named valve when said'outlet valve is open.

9. In a fuel-feed system, a fuel-feed chamber,

- a fuel supply tank disposed below said fuel-feed chamber, a fuel-supply conduit interconnecting ,said fuel-feed chamber and supply tank, said fuel-feed chamber having an outlet port near its bottom, an outlet valve controllingfuel iiow through said port, an air chamber, means providing a passage between said two chambers, said passage communicating with said fuel-feed chamber at a point adjacent but below the maximum fuel level therein, a second valve in said passage, air-exhausting means connected to said two chambers, means responsive to the differen- .tial in fluid pressures at the respective ends of said passage and operatively connected to said outlet valve and said second valve, said passage being restricted to an extent such that fuel flow through it from said fuel-feed chamber into said air chamber cannot occur without the existence of a pressure-differential sufiicient to cause said pressure-responsive element to close said. second valve, a third valve controlling the connection of said air-exhausting means to said fuel chamber independently of said second valve, means responsive to fuel-level in said fuel-feed chamber for opening said third valve Whenever the fuel level in said fuel-feed chamber reaches a predetermined minimum, a fourth valve in said fuel-supply conduit, and means responsive to fluid-pressure in said fuel-feed chamber for maintaining said fourth valve closed except when the uid pressure in said fuel-feed chamber is at or below a vpredetermined maximum.

10. In a fuel-feed apparatus, a fuel-feed chamber, a fuel-supply tank below said chamber and outlet port near its bottom, an outlet valve controlling said port, an air chamber, an air-exhausting means connected to said air chamber, said two chambers being interconnected by a passage through which air may be exhausted from said fuel-feed chamber to induce fuel-flow thereinto from said supply tank, a second valve in fuel-feed chamber'disposed above said reservoir and having near its bottom an outlet port through which fuel may pass to said reservoir', a fuel supply tank, a conduit interconnecting said supply tank and said fuel-feed chamber, means for intermittently exhausting said fuel-feed `chamber to induce fuel' flow thereinto through said conduit, an outlet valve controlling said outlet port, mechanism for automatically closing said valve during periods in which said fuel-feed chamber is being exhausted and for opening said valve during the intervals between such exhaustion periods, said outlet' port constituting the sole passage for'the admission of air to said fuel-feed chamber whereby-to provide a barometric feed said passage, means responsive to the fuel-level in said fuel-feed chamber for automatically closing said second valve when such fuel-level rises to a predetermined maximum, said means including a pressure-responsive element jointly responsive to the respective fluid-pressures in said two chambers and operating to close said second valve whenever the fluid pressure in said air chamber is below that in vsaid fuel-feed chamber and to open said second valve when the fluid pressures in said two chambers are substantially the same, and a secondmeans responsive to fuellevel in said fuel-feed chamber and operating when such fuel-level reaches a predetermined minimum to equalize the pressures in said two chambers and thereby cause said pressure-responsive element to open said second valve.

' ll. The invention set forth in claim 10 with and to be closed thereby when said secondvalve is opened. Y y

HAROLD W. MEADE.

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