US1933389A - Carburetor - Google Patents

Description

@ct. 31, 19330 A. M. PRENTESS CARBURETOR Filed May 11, 1931 IN VENTOR. 41/605 77/\/ M PREN775 A TTORNE Y.

Patented @ct. 31, 1933 PATENT @FF LEDES EW CAREUEETQDHE Augustin M. Prentiss, San Antonio, Tern, assignor to Bendix Stromberg (Carburetor Company,

South Bend, l[nd., a corporation of llllinois Application May llll, 1931.. Serial No. 536,398

7 Claims.

This invention pertains to carburetors and more particularly has reference to temperature controlled acceleration pumps therefor.

It has long been known in the carburetor art that the amount of additional fuel supplied to the mixture for accelerating the engine varies with the temperature of the engine and liquid fuel (gasoline). Thus, for a cold engine a relatively large accelerating charge of liquid fuel is required, and as the engine warms up, a gradually decreasing amount of accelerating fuel is needed until a certain temperature is reached when no accelerating fuel is necessary, and if any is supplied, it not only does not assist acceleration, but actually retards it.

Another problem of long standing in the carburetor art has been to eliminate flat spots in passing from idle, or slow speed operation, to main jet, or high speed operation. Flat spots 39 are particularly difficult to eliminate under quick acceleration for the reason that heretofore ac-= celerating devices have always injected a supplementary charge of liquid fuel into the mixing chamber in the region of relatively low suction below the throttle, and have never fed additional fuel into the mixture outlet in the region of high suction above the throttle during the period of transition from idle to main jet operation. I

have found that when the throttle is suddenly opened for quick and powerful acceleration, there is not time enough (with the relatively weak suction then in the mixing chamber) to transmit sufficient additional fuel from the mixing chamber to the intake manifold to compensate for the condensation due to drop in vacuum therein, and

a flat spot results regardless of how vigorous a charge is delivered by the accelerating pump. The time and space factors are the controlling elements in this problem and I have found that these can only be overcome by delivering a portion of the accelerating charge above the throttle in the region of high suction. In this way, the time and length of travel of a portion of the accelerating charge is considerably reduced and 5 the consequent fiat spot is eliminated.

Moreover, as stated above, when the temperature of the engine and liquid fuel approaches normal summer operating temperatures, which often exceed the boiling point of the lightest fraction of the liquid fuel, no extra fuel is needed for ac- (Cll. 261-341) celeration, and hence it is necessary that'a temperature control be placed upon that portion of the accelerating charge fed into the mixture out-= let above the throttle, as well as for the remain der of the charge that is fed into the mixing chamber below the throttle.

An object of this invention is to overcome the above difficulties by providing an acceleration pump that delivers a portion of the accelerating charge into the mixture outlet in the region of relatively high vacuum above the throttle.

Another object of my invention is to provide a temperature control for an acceleration pump which depends primarily upon the temperature of the liquid fuel rather than upon the temperature of the air or body of the carburetor.

Still another object of this invention is to pro vide a temperature control for an acceleration pump that not only regulates the output of the pump into the mixing chamber below the throttle, but also regulates that portion of the output that is discharged into the mixture outlet above the throttle.

With these and other objects in view, which may be incident to my improvements, my inven tion consists in the combination and arrangement of elements hereinafter described and illustrated in the accompanying drawing in which Figure 1 shows in central longitudinal section a carburetor embodying my improvements; and Figure 2 shows a similar view, on an enlarged scale, of the idle discharge outlet and valve.

Referring to the drawing, the reference numeral 1 denotes the body of the carburetor which consists of the usual air intake 2, mixing chamber 3, and mixture outlet 4 controlled by a throttle valve 5. Cast integrally with the body 1 is a liquid fuel float chamber 6, which is closed with a cover 32 and supplied with fuel by a pipe 2' leading to a main supply tank (not shown). Within the chamber 6 is a float 8 which acts on valve 9 to maintain the level of the liquid fuel in said cham ber at the normal static level indicated by the line Positioned within the mixing chamber 3 is a main fuel nozzle 10 which communicates with float chamber 6, through passageways 11 and 12 which latter is controlled by a needle valve 13 serving to regulate the main jet discharge and thus control the normal operating mixture. The

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idle or slow speed feed is delivered through a passageway 14; and a plurality of ports 15 and 163 which bestride the throttle when in closed position, in a well known manner. Adjacent port on the opposite side of passageway 14! is an air bleed port 17, controlled by a manually adjustable valve 18, which regulates the normal idle feed by admitting atmospheric air to modify the suction in passageway l l.

Cast integrally with the body 1 and positioned within floatchamber 6, is an acceleration pump cylinder 19 which is separated from the float chamber 6 by a double wall partition 20 through which are two passageways 21 and 22 leading from cylinder 19 to float chamber 6. The bottom passageway 22' through which liquid fuel is supplied from float chamber 6 to cylinder 19 is provided with aball check valve 23 which prevents the return of fuel from cylinder 19 to chamber d. Up-= per passageway 21 permits air to pass freely between chamber 6 and cylinder 19 so that the air pressures in the upper parts thereof may be equal at all times.

Slidably mounted in cylinder 19 is a stem 2% which passes through guide holes in cover 32 and bottom of cylinder 19 and extends both above and below cylinder 19 as shown in the drawing. The top of stem 24 is provided with a flat head 25 upon which bears a roller 26 carried on the free end of a lever 27 which is pivotally attached at 28 to the body 1 of the carburetor. Throttle 5 is mounted upon a shaft 29 to one end of which is fixedly attached an operating arm 30 and a cam 31 which latter bears against lever 27 and depresses it whenever arm 30 is rotated in a downward direction to open the throttle 5.

Surrounding stem 24.- between head 25 and the cover 32 of float chamber 6 is a helical spring 33 which normally tends to keep stem 2%- in its up permost position as determined by contact of collar 34 (fixed on stem 24) with cover 32.

Slidably mounted upon stem 24 and adapted for reciprocation in cylinder 19 is a piston 35 which is normally held in contact with a flange 36 on stem 24. by a helical spring 37. The lower part of stem 24 is provided with a central passageway 39 which extends from the bottom of stem 24.- to a point just above flange 36 and there makes a right angle bend and terminates in a port dill which is adapted to be covered and uncovered by the movement of piston 35 on stem 2% as will be hereinafter more fully explained.

In axial alignment below cylinder 19 is an aux-- iliary chamber ll into which liquid fuel is fed. from cylinder 19 through passageway 39 when port 40 is uncovered by piston 35. From chamber d1 fuel is discharged through a metering orifice d2 in passageway 11, said orifice forming the seat of a valve 4.3 which is actuated by a semi-circular thermostatic element id, attached to the wall of chamber 41 by a screw 45 and arranged to move valve 43 against seat l2 with a rise in fuel temper ature and to withdraw said valve from his seat with a fall in fuel temperature, thus regulating the flow of accelerating fuel inversely in accord ance with its temperature. A plug 461 in the bot== tom of chamber 4:1 permits draining and clearing said chamber.

The wall oi cylinder 1o, adjacent passage and at a point just below the highest point of travel of piston 35, is provided with a passageway 47 establishing communicating between cylinder 19 and passageway 14: of the idle feed system. Passageway 47 is controlled by a valve 48 held to its seat by a helical so which surrounds nesaseo a stem to which is attached to and actuated by a thermostatic element 51 secured to the wall of body 1 by screws 52. Spring s9 is of such strengththat it holds ball valve 48 on its seat against the maximum suction existing at any time in passage,

way is, but whenever appreciable pressure is exerted on the liquid fuel in cylinder 19 by piston 35, spring 49 is overcome, and valve'dfi opens passageway d7.

Stem 50 is so arranged as to be moved by thermostat 51 toward. ball 48 with a rise in temperature and thus restrict the passageway 47 by limiting the opening movement of theball. The opposite action takes place with a fall in temperature of the liquid fuel, and thus the flow of ac-= celeratingiuel to the idle portsld and it is regulated inversely in accordance with said temperat ture.

Passageway 14, below valve 5a is provided with a ball check valve 53 to prevent accelerating fuel discharged through passageway d7 from escaping back through main nozzle 1c. The seat 5% of valve 53 is a calibrated restriction to meter the flow of liquid fuel when this valve is open.

The operation of my device is as follows: When the. throttle 5 is closed cam 31 just contacts with lever 27 but exerts no pressure thereon. Under these conditions spring 33 keeps stem 2d in its uppermost position, that is, with collar as contacting with cover 32, and spring 37 keeps piston 35 iri contact with collar 36, thus closing port so. Liquid fuel flows from float chamber 6 through passage 22 into cylinder 19 and thence through port so, passage 39, chamber ill, and passage ii to main jet l0 and idle feed passageway id where it rises to the line X-X whenever the engine is at rest.

It now the throttle is opened cam 31 bears upon lever 27 which in turn depresses stem 24. The downward thrust of stem 2%, transmitted through collar 34'.- and spring 37, to piston 35, causes piston 35 to exert a downward pressure on the column of liquid fuel in cylinder 19 below the piston. The reaction of the liquid against piston 35 retards its downward travel while the downward travel of stem 24.- is not so retarded, with the result that stem 24 travels faster than piston 35, and spring 37 is thereby compressed and port so uncovered. The liquid fuel in cylinder 19, being under in creased pressure from piston 35, escapes rapidly through passageway 39, chamber 41, and pas= sageway 11 to main jet 10 where it is discharged as a supplement to the normal how of liquid fuel from chamber 6 through passageway 12 to nozzle id. A portion of the liquid fuel escaping through passageway 39 also reaches passageway 14 and rises above the line Ill-X. However, due to the relative resistance to flow and the short length of mainnozzle 10, as compared to passage 14, and to the metering restriction in valve seat as. the rise of liquid fuel in passage 14 is not suiidcient to discharge through ports 15 and 16.

When piston 35 first starts on its downward stroke, and before port so is uncovered, a small portion of liquid fuel in cylinder ll-B escapes through passageway 4? into passage 14.. Here check valve 53, prevents its esca main nozzle it), so that it rises in passage 14 and discharges through idle ports 15 and it a supplementary iced to the fuel that is normally fed through these ports by suction when the throttle is in re stricted position.

as soon as the lower edge of piston to over passageway at, this supplementary accelera tion feed through idle ports 15 and it is cut oil,

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nesasea so that it is only for a brief interval of time during the first part of the stroke of the acceleration pump that this additional acceleration feed through the idle system is supplied. But it is just at this interval that flat spots have occurred in the prior art devices because of the length of time required for the additional accelerating fuel to reach the intake manifold when fed through the longer and more circuitous channel through the mixing chamber. This delay of the acceleration fuel in reaching the intake manifold, when the throttle is suddenly opened, is caused by the in= herent inertia of the liquid mass, its friction in passing through various chambers and passageways, and the fact that it is discharged into the mixing chamber in the region of relatively low suction below the throttle from which it still has a considerable distance to travel before it reaches the intake manifold.

By my provision of a supplementary passage= way direct from the acceleration pump cylinder through the idle feed system into the mixture out let above the throttle, I greatly reduce the time required for the first portion of the accelerating charge to reach the intake manifold and thus eliminate the flat spots which have proven so troublesome in the prior art.

If the throttle 5 is opened slowly, as when rapid acceleration is not desired, there is sufficient clearance between piston 35 and cylinder 19 to permit the liquid fuel in cylinder 19 to escape past piston 35 so that not enough liquid pressure is developed to compress spring 37 and uncover port l0 or to unseat valve l8. Under these circum-- stances no liquid fuel escapes from cylinder 19 but merely surges from below piston 35 to the space above it. Check valve 23 prevents any return of liquid fuel from cylinder 19 to float chamber 6.

The above described operation has been premised upon valves a3 and 48 being open to permit how of liquid therethrough, but these valves are only fully opened by their thermostatic controls at the lowest operating temperature of the carburetor when the maximum volume of accelerating charge is desired. As the temperature rises, valves 43 and 48 are gradually closed until the highest operating temperature of the carburetor is reached when they completely cut ofi fuel flow, and no accelerating charge is supplied when the throttle is suddenly opened, as none is desired at this temperature. When valves 43 and 48 are closed and the throttle is suddenly opened, stem 24 descends as before, but since no fuel escapes from cylinder 19, piston 35 is held in its original position and spring 37 is correspondingly compressed to take up the travel of stem 24. If now the throttle is held open, piston 35 gradually descends as the liquid fuel escapes past it to the space above it in cylinder 19. If now the throttle is suddenly closed, the volume of liquid fuel trapped above piston 35 is returned to float chamber 6 by way of passage 21.

The rate of opening and closing of valves 43 and 48 can be regulated by calibrating thermostatic elements 414 and 51 so that the amount of accelerating charge supplied at any time is in versely proportional to the temperature of the liquid fuel.

While I have shown and described the preferred embodiment of my invention, I desire it to be understood that I do not limit myself to the constructional details disclosed by way of illustra= tion, as it is apparent that these may be changed and modified by those skilled in the art without departing from the spirit of my invention or exceeding the scope of the appended claims.

I claim:

1. In a carburetor having a fuel nozzle and a mixture outlet controlled by a throttle, an acceleration device comprising means to deliver a portion of its accelerating fuel charge direct to the mixture outlet above the throttle and a portion to the fuel nozzle, and separate means for regulating each portion of the accelerating charge in accordance with the temperature of said fuel.

2. A carburetor comprising a main fuel nozzle, an idling fuel nozzle, and an accelerating device adapted to discharge a portion of its fuel charge through said main nozzle and a portion through said idling nozzle, and separate means for regulating each portion of the accelerating charge in accordance with the temperature of said fuel.

3. In a carburetor, a throttle, a mixture outlet above said throttle, a mixing chamber below said throttle, and an accelerating device comprising means to deliver a portion of its fuel charge to said outlet and a portion to said chamber, and separate means for regulating each portion of the accelerating charge in accordance with the liquid fuel temperature.

a. A carburetor comprising a mixture outlet, a throttle controlling said outlet, a float chamber,

an idling jet leading from said chamber and discharging above the throttle, and an accelerating pump positioned within said chamber, comprising means to deliver a portion of its fuel charge direct to said idling jet, and means to regulate said portion of the accelerating fuel charge in accordance with the temperature of said fuel] 5. A carburetor comprising a mixture outlet, a throttle controlling said outlet, a float chamber, an idling jet leading from said chamber and discharging above the throttle, and an accelerating pump comprising means to deliver a portion of its fuel charge direct to said idling jet, and means to regulate said portion of the accelerating fuel charge in accordance with the temperature of said fuel.

6. In a carburetor, a throttle, a mixture outlet above said throttle,'a mixing chamber below said throttle, and an accelerating device comprising means to successively deliver a portion of its output to said outlet and a portion of said chamber, and separate means to regulate the amount of each portion in accordance withthe liquid fuel temperature.

"I. A carburetor comprising a main fuel nozzle,

an idle fuel feed passageway, an accelerating device adapted to successively discharge a portion of its fuel charge through said nozzle and a portion through said passageway, and separate thermal-responsive means for regulating the amount of each portion of the accelerating charge in accordance with the temperature of the liquid fuel.

AUGUSTIN M. PRENTISS.

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