US2109260A

US2109260A - Carburetor

Info

Publication number: US2109260A
Application number: US700537A
Authority: US
Inventors: Milton E Chandler; Emil O Wirth
Original assignee: Bendix Aviation Corp
Current assignee: Bendix Aviation Corp
Priority date: 1933-12-01
Filing date: 1933-12-01
Publication date: 1938-02-22
Anticipated expiration: 1955-02-22

Description

v 1938. M. E. CHANDLER ET Al. 2,109,260

' CARBURETO'R Filed Dec. 1, 1933 2 Sheets-Sheet 2 INVENTOBJ. MILTON 2 CHQ/VOLEE EM/L. 0. W/erh' BY fifpM ATTORNEY.

Patented Feb. 22, 1938 UNITED STATES PATENT OFFICE caamma'roa Delaware Application December 1', 1933, Serial No. 700,537

Claims.

This invention relates to carburetors, and more particularly to acceleration pumps used in association with carburetors.

In designing a carburetor, it is desirable to so locate the acceleration pump that it will quickly inject a charge of liquid fuel when the throttle is opened rapidly. It is desirable to have the charge of fuel which is injected for acceleration purposes distributed over a period of several seconds, so graduated that a greater quantity is inlected at first and a decreasing quantity over the remaining portion of said period.

An object of the present invention is to produce a carburetor having an acceleration pump of the type above mentioned, which will be of simplified and improved design and economical to manufacture.

A further object of this invention is to provide an improved carburetor in which the fuel pump is cast integral with the body of the carburetor, and equipped with a yielding means such that the aforesaid desirable control of the charge of liquid fuel injected for acceleration purposes may be obtained.

A further object of this invention is to eliminate all possibility of leaks of air or fuel from the acceleration pump.

The above and other desirable novel features of this invention will appear more fully hereinafter from the following detailed description, when taken inconnection with the accompany-g ing drawings. It is expressly understood, however, that the drawings are employed for purposes of illustration only. and are not designed as a definition of the limits of the invention, reference being had for that purpose to the appended claims.

In the drawings: Figure 1 is an elevation of a carburetor unit embodying the invention, showing the operating a modification of the pump and the manner of venting the float chamber and acceleration pump to the air horn.

Referring more particularly to Figure 1, there is shown, for purposes of illustrating this invention, a downdraft carburetor comprising an up-' per body section l0 and a lower body section I2. A choke valve l4 operated by an actuating mechanism I 6 controls the amount of air admitted through the air horn IS. A throttle valve 20 manually controlled in the usual -=manne'r*by means of an actuating mechanism 22, governs the amount of combustible mixture admitted to the intake manifold of the enginethrough the carburetor outlet 24.

The acceleration pump unit is cast integral with the float chamber 26 and upper section III of the carburetor. It consists of a hollow cylinder 28 in which is mounted a piston 30, comprising a disk 32, a leather washer 34, and a'coiled helical spring 38 to expand said washer 34 into contact with the walls of cylinder 28. The piston is mounted on a rod 38 which is circumferentially wound by two coil springs 40 and 42, being separated by a washer 44 slidable on rod 38. These springs are held in compression by 'a nut 45 screwed to the end of rod 38. Rod 38 is actuated by a plunger actuating rod 48 having at its upper end an arm 50 apertured to encircle rod 38 in slidable relation, so that it will compress springs 40 and 42 when rod 48 is drawn downwardly. The means for drawing rod 48 downwardly comprises an arm 52 fixed to the throttle shaft 54 on the opposite side of the main carburetor passage to the throttle actuating mechanism 22, and

a link 56 connecting arm 52 with rod 48.

The acceleration pump discharges through an outlet passage 58, controlled by a valvefiil which is yieldingly held closed by a spring 52. Passage 58 connects with passages 64 and 68 which lead to the acceleration pump nozzle 68, discharging into a primary venturi 10 in the main carbureting passage. *Since arm 52 is fixed to throttle shaft 54, it will rotate therewith and impart movement to link 56, which will in turn actuate rod 48, compressing springs 40 and 42. The pressure exerted by the springs will urge piston 38 downwardly, and the resulting pressure on the fuel in cylinder 28 will compress spring 62, unseat valve 80 and allow fuel to flow to the acceleration fuel nozzle 68.

Since spring 42 is weaker than spring 40, the initial movement of arm 48 will compress it to the limit of its movement, and the force then exerted by piston 30 upon the fuel will then depend upon the reaction of the stiffer spring 40, which will cause a greater quantity of fuel to fiow during the early stages of the action. Spring 40 will expand first, giving a sustained flow during the middle portion of the period, and spring 42 will expand last, giving a decreased rate of flow during the latter stages of the action. At

full open throttle a retaining member 12' on piston 88 holds valve 88 open by contacting the end of its stem 14, allowing the fuel to continue to flow through the above-enumerated passages to nozzle 88, giving a richer mixture for. full power operation.

Figure 4 illustrates a modified acceleration pump piston which may be used instead of the piston illustrated in Figure 3. It incorporates a relief valve, and consists essentially of a piston rod 88 to which is fixed a plunger 82 having a "bore 84 drilled longitudinally from the top to accommodate a check valve comprising a ball 88 held on its seat by a spring 88. An upper passage 88 and a lower passage 82 are drilled transversely through plunger 82 and communicate with bore 84 respectively above and below the check valve. An annular groove 84 cut around the circumference of plunger 82 accommodates a coil spring 98 which urges facing material 98 against the wall of the cylinder I88.

As the piston slides down cylinder I 88 under action of the actuating mechanism, which may be of any suitable type, pressure will be exerted through groove 84 and passage 82 upon said check valve and when the pressure rises sufflciently to overcome the resistance of spring 88, fuel will flow past ball 88 and through passages 84 and 88.

Therefore, when the pressure rises above a cer-.

tain value, dependent upon the stiffness of spring 88, a portion of the fuel will be by-passed through the piston and back to the supply chamber to prevent choking the engine with an excessive charge of raw fuel. When the engine is accelerated slowly no fuel will be bypassed, however, as the pressure will not be sufiicient to operate the check valve, and a prolonged discharge suitable for acceleration purposes will thereby be obtained.

Figure 5 illustrates a modification of an accel eration pump, embodying an internal pressure responsive mechanism, consisting essentially of a cylinder II8 having a compound piston II2 slidable therein. Piston I I2 comprises a body portion I I4, drilled to accommodate a small internal piston II8 slidable therein and yieldingly urged to the lower extremity of said body portion by spring I I8. Piston head I28 is provided with an annular groove I22 which receives a coil spring I24 to urge the facing I28 of said piston "against the walls of cylind r III, said facing being made of any suitable m terial such as leather, and held in place by compression between the piston head I28 and body portion II4 which are screwed'together.

' Piston H2 is provided with an actuating rod I28 connected thereto through pivotal joint I88.

I The pump outlet is provided with a check valve I82 which is similar in construction and operation to that disclosed in connection with Figure 3:

lowermost position, to hold said valve open and permit a continuous fiow of fuel through said valve to the fuel discharge nozzle, supplying a rich mixture for full power operation of the engine.

The operation of the device shown in Figure 5 is as follows. The actuating rod I28 is connected .by means of any suitable mechanism to the throttle shaft, or to a piston operated by the varying suction posterior to the throttle, so that as the throttle is opened, piston 2 slides downwardly in cylinder 8 compressing the entrained fuel and forcing check valve I82 open. Since the quantity of fuel which can pass through check valve I82 is limited by the area of the opening and size of ducts leading therefrom a method of relieving excessive pressure is provided so that the throttle will not be restricted in its operation. When thepressure builds up in the cylinder II8 below the piston II2 suiliciently to overcome the resistance offered by spring II8, piston 1H8 will slide upward in bore I84'and permit fuel to fill the chamber I85 below the piston II8. *When sufficient fuel has passed through check valve I82 to relieve the pressure suificiently, piston II8 will be forced downwardly by spring I I8 and when it reaches the end of cylindrical bore I34, if the throttle is held in open position, stud I 38 will engage valve stem I88 and hold valve I82 open, permitting a continuous flow of fuel through said valve to the acceleration fuel discharge nozzle.

As the throttle valve is closed, piston II2 will be drawn upwardly'in cylinder II8 by rod I28, permitting check valve I82 to close to prepare the acceleration pump for the next operation.

Figure 6 illustrates a vacuum operated acceleration pump, and a vent from the air horn to the partial vacuum existing at that point during certain conditions of operation of the engine.

The lower cylinder I52 also houses a piston I88 which is yieldingly urged to the lower extremity of cylinder I52 by spring I88 operating between a facing I18 fixed to rod I12 and washer I54 separating the two cylinders. Rod I12 is pivotaliy connected at its upper end with piston I58 of upper cylinder I58 by a universal joint I14 of known construction.

by means of a helical coiled spring I18.

A check valve is incorporated in the piston 88, consisting of a horizontal fuel passage 282 J nnecting with a vertical passage 284 whicli discharges into a circular bore 288 drilled piston I88, and closed by a. flat plate I88 having holes 288 drilled therein to permit fuel to flowi A disc 2I8 is free to move in circular bore 288 and rests upon fiat plate I88 by gravity except when the pump is in operation, at which time the pressure of the -entrained fuel will force disc 2I8 up, closing vertical passage 284 to prevent fuel from escaping. This'construction permits the acceleration pump to be filled through 'a port 2I2 communicating with the fioat chamber 288 below the fuel level XX, since said flat disc 2 I8 permits fuel to flow through piston I88 at all times except when said piston is actuated downwardly. Plate I88 is designed to engage valvestem I88 of an economizer valve I82 fitted in the bottom of cylinder I52, which valve is of a construction similar to that disclosed in connection with Figure 3. A fuel duct I84 leads from economizer valve I82 to the fuel discharge nozzle I88 in the main carbureting passage I88 of the carburetor.

Piston I88 in the lower cylinder is fitted with a leather washer I18 which\ .is yieldingly urged into contact with cylinder I82 Cylinder I52 is provided with a vent I81 which communicates by means of duct I88 with an annular groove I60 formed between the body section I92 of the carburetor and the venturi I94. A passage I96 leads from groove I90 to the air horn anterior to the choke valve I98. Duct I88 has a branch I89 which terminates in the float chamher 200 above the fuel level X-X.

The operation of the device shown in Figure 6 is as follows. When the engine is idling a partial vacuumexists in the main carbureting passage I60 posterior to throttle valve I62. This suction is transmitted by means of duct I64 to cylinder I of the acceleration pump and will cause piston I56 to slide upward in said cylinder, compressing spring I58 and carrying with it piston I66 fixed to rod I12, by means of the joint I14, and compressing spring I 68.

When throttle valve I62 is opened, the partial vacuum is destroyed, and as the suction exerted on piston I56 drops below that required to keep springs I58 and I68 compressed, piston I56 will slide downwardly in cylinder I50, leaving piston I66 free to move downwardly in cylinder I52 under the influence of spring I68, exerting pressure on the entrained fuel, which will open the economizer valve I82 and pass through duct I84 to the fuel discharge nczzle I86.

If the throttle is moved from closed position to full open position quickly, piston I56 will be quickly forced to the bottom of cylinder I50 by spring I58, and piston I 66will slide downward in cylinder I52 less quic' y' under action of spring I68. Since the opening through the economizer valve is restricted, an interval of time will be required before the piston I66 reaches the end of its stroke, so thata sustained discharge will be obtained. When throttle valve I62 is closed again a partial vacuum will be created in the main carbureting passage posterior to the throttle valve which when transmitted to cylinder I50 through duct I64 will cause piston I56 to move upwardly. During this upward movement, plate 2 I0 permits fuel to flow through passage 204 to the space below piston I66 to prepare the pump for the next operation. An adjusting pin M4 is threaded through a plug 2I6 in the upperend of cylinder I50 and projects therefrom to form an adjustable stop for piston I56, to permit the stroke of the pump to be varied as desired.

As previously noted, cylinder with a vent I 81 which equalizes the pressure in the acceleration pump cylinder, float chamber and air horn, thus insuring uniform operation, and providing air which has passed through the air cleaner (not shown) commonly connected to the air horn.

We claim:

1. In a carburetor, an acceleration pump comprising a cylinder, a piston therein, a piston rod I52 is provided charge connected to said piston, an actuating member slidable on said piston rod, and a plurality of springs of different resiliency connected in series between the actuating member and piston.

2. In a carburetor having a body portion forming a main carbureting passage, a float chamber, an acceleration pump having a cylinder formed integral with said body portion and float chamber, mechanism for actuating said acceleration pump including a member fixed to one end of the throttle shaft, a rod connected to said member having an arm thereon, a piston rod associated with said pump and slidable within an aperture in said arm, and a plurality of coil springs of different stiffness wound around said piston rod and connected in seriesin such manner that the acceleration pump discharges a gradually decreasing sustained fiow of liquid fuel as the throttle valve is actuated.

3. In a carburetor, an acceleration pump com-- prising a cylinder, a piston slidable in said cylinder, a piston rod, an arm fixed to the throttle shaft, an actuating member between said arm and said piston rod and'slidable thereon, and a plurality of springs of ciated with said piston rod and forming an actuating connection between the actuating member and the piston.

4. In a carburetor, an induction passage, 21

throttle valve, means to actuate the throttle Valve, a fuel reservoir, a main fuel nozzle, an auxiliary fuel nozzle, acceleration means to disfuel from the reservoir into the induction passagethrough the auxiliary fuel nozzle upon opening movement of the throttle valve,

said acceleration means including a cylinder positioned in the fuel reservoir and communicating with the induction passage, a piston having a stem movable in the cylinder, and a yielding connection including a plurality of coaxially wound springs of varying resiliency surrounding the stem of the piston and connected with the throttle actuating means.

5. In a carburetor, an induction passage. a

throttle valve controlling the induction passage,

manual means to actuate the throttle valve, 2. fuel reservoir, means including a cylinder positioned in the fuel reservoir and communicating with the reservoir and the induction passage, a throttle controlled piston movable in the cylinder for supplying a quantity of fuel to the induction passage under certain operating conditions, and yielding means including a plurality of springs of different resiliency between the throttle controlled piston and the throttle to vary the rate offlow of fuel discharged from the cylinder.

MILTON E. CHANDLER. EMIL O. WIRTH.

different resiliency asso-