US2048535A - Venturi stack - Google Patents

Description

July 21, 1936. s. M. BICKNELL VENTURI STACK 3 Sheets-Sheet l Original Filed Nov. 18, 1930 IN VENTOR r- I L B 11 ATTORNEY y 1936- e. M. BICKNELL I 2,048,535

VENTURI STACK Original Filed Nov. 18, 1930 3 Sheets-Sheet 2 @5026: M fi/ae/vzu.

1N VEN TOR A TTORNE Y J ly 21, 19 e. M. BICKNEIL'L VENTURI STACK Original Filed Nov. 18, 1930 3 Sheets-Sheet 3 Gama: M fi/c/z/yzu INVENTOR ATTORNEY ,Venturi construction used in the carburetor or "gas mixer which is shown in the preceding para- .graphs.

Patented July 21, 1936 UNITED STATES PATENT OFFICE VENTURI STACK George M. Blcknell, St. Louis, Mo., asslgnor to Carter Carburetor Corporation, St. Louis, Mo., a corporation of Delaware Original application November 18, 1930, Serial No. 496,396. Divided and this application April 22, 1932, Serial'No. 606,803

10 Claims.

means to form said passageways, so that the carburetor or gas mixer may be manufactured in large quantities without substantial variations in the flow capacities thereof.

\ It is a further object of this invention to produce anew and generally improved air horn and Venturi construction for plain tube carburetors or gas mixers.

Other objects of the invention will appear from the following description and accompanying drawings, referring to which:

Figure 1 shows a plan view of a carburetor or gas mixer constructed according to my invention. Figure 2 shows a vertical sectional view of the carburetor or gas mixer shown in Figure 1, the section being taken along the line 22 of Figure'l.

Figure 3 is a vertical sectional view of a car buretor or gas mixer shown in Figure l, the section being taken along the line 3-3 of Figurel. Figure 4 is a vertical sectional view of the Figure 5 is a plan view of the Venturi construction shown in Figure 4.

Figure 6 is a fragmentary, vertical, sectional view taken along the line 6-6 of Figure 4 looking in the direction of the arrows.

The main body member of the carburetor or gas mixer is formed as a casting l which has a flange 2 formed on its lower end for attachment to the intake manifold of an internal combustion engine, not shown. An' upper body member 3 is attached to the member I by any suitable means,

such as screws 4. An air inlet 5 is formed in the .upper body member and registers with an air chamber 6 which forms the upper end of the main air passageway through the lower body member I.

' A venturi l is fitted into the air chamber and extends downwardly into a bore 8 which forms the mixing chamber of the carburetor or gas mixer. It will be understood that the bore 6 is larger'in diameter than the bore 8, and that the two portions are joined by a shoulder or tapered portion 9 to provide means for locating the venturi I with respect to the length of the carburetor or gas mixer.

The lower end or the bore 8 is controlled by a throttle valve 60 mounted on a shaft 10 which is journaled in the casting I as shown. Any suitable operating lever (not shown) may be attached to the shaft-l0 for operation by any suitable means.

An air inlet valve I2 is mounted on a shaft" in the upper body member 3, and any suitable operating lever (not shown) may be attached. A stop I5 is formed integral with the casting 3 and may be provided with an adjustment, if desired.

One or more openings l6 are formed in the upper body member 3 to communicate with the atmosphere, and these openings are controlled by a spring or valve member I! which is attached to the inner wall of the air inlet 5 by any suitable means, such as a screw or rivet Hi. It will be understood that the member I! acts as a valve which may be opened by suction to permit the admission of air through the port IS.

The tension of the spring I! is calibrated with respect to the size of the port I6 and the leakage which may occur past the valve l2, in such a way that the valve I! will remain in closedposition when the valve I2 is closed during cranking speeds of the engine, but when the suction of the engine is increased by its beginning to run under its own power, the valve I! will be unseated and air may flow in through the port' it. Obviously, thetension required in the spring ll will vary with difierent installations, but, as an illustration, the valve I! should ordinarily remain closed at speeds below one hundred revolutions per minute of the motor, and it should begin to open at speeds in excess of that figure.

In this installation, three venturis are provided, the largest venturi 1 fitting the outer wall of the carburetor or gas mixer as shown. The second venturi l9 terminates at the throat or at the most restricted portion of the venturi 1, and the third venturi 20 terminates at the throat of the most restricted portion of the venturi l9.

To prevent eddy currents being formed in the venturis, I provide one or more vanes or straighteners 2| which extend parallelto the lines of flow and which are preferably made thicker at the inlet end then at the end adjacent the outlet of the carburetor or gas mixer. The shape 01' the longitudinal section of the vane is indicated in Figure 6. These vanes are mainly for the purpose of preventing the rotation oi. the aircurrents in the carburetor or gas mixer, or checking it any rotation which may have been set up in the inlet, but they are also highly useful as devices for locating the venturis 'with respect to each other. It will be understood that where many thousands of carburetors or gas mixers are to be produced, it is essential that the air flow characteristics in each be substantially the same. By forming the venturis and the vanes as a single die casting, I am able to secure absolute uniformity so that there is no' need of separately adjusting the venturis in each carburetor or gas mixer.

A liquid fuel bowl 22 is cast integrally with the lower body member i and conventional mechanism, not shown, is located in this bowl for maintaining the fuel at a constant level substantially as indicated by the line AA. The fuel is supplied to the bowl by any suitable means which, being entirely conventional, is not shown.

The fuel is supplied from the bowl to a nozzle 2'! by means of a passageway 36 in the usual manner, and the passage 36 is also connected to the idling conduit by means of a cross bore 39 and other connecting passages which, being unrelated to the present invention and covered in the divisional application and patent above referred to, are not shown. It may be noted, however, that the idling conduit 40 terminates in the usual idling port 4i adjacent the edge of the throttle when it is in closed position, as indicated in Figure 3.

The Venturi stack shown in Figures4 and 5 is formed as a die casting with the vanes 2i cast integral with the venturis. This integral construction provides for extremely accurate dimensioning of the venturis with respect to each other. Accuracy in this is highly important on account of the multiplying effect of the venturis on the suction. If the venturis were made separate, what is known as the limit stack in manufacturing tolerances would cause such variations in the relation of the venturis with respect to each other in large quantity production as to make the use of multiple venturis very undesirable. It may be noted that the advantages of two and three Venturi constructions have been known for over twenty years, but the three-Venturi construction has been entirely impractical on account of difficulties in maintaining the relative sizes and relations of the parts which, in previous constructions, were made separately. This new construction has resulted in a practical construction which has been used in approximately a million installations within less than two years after it was put on the market and its success is chiefly due to the fact that the venturis were made in an integral die'casting, so that the shapes and sizes of the parts in large quantity prcduction did not vary to any great extent.

The operation of the device is as follows:

The carburetor or gas mixer is attached to the intake manifold of an engine, and fuel is supplied to the float. chamber 22 by any suitable means.

Assuming that the engine is to be started cold,

mitted.

the engine begins to fire. and run \mder is own power, its speed will substantially increase, and the increased suction will cause the opening of the valve H to permit the admission of suihcient air through the port l8 to supply the require- Assuming that the throttle 69 is in open position, air flows through the venturis 20, I9, and I, and the most. rapidly moving part of the air stream flows" through the venturi 20. The speed of this rapidily moving air being increased by the restriction at the throat of the venturi 20, a strong suction on the end of the nozzle 21 is caused, servingto draw fuel out of that nozzle in proportion to the speed of the air stream at low speeds, and at high speeds the normal tendency of the fuel nozzle to over-richness is overcome in two ways. -First, the increasing impact of the air against the fuel issuing from the nozzle and the partial reversal of the flow of fuel which is caused to occur in the venturi 20 partially cor- In modern carburetors or gas mixers, the high capacity which is so greatly desired necessarily involves comparatively large venturis and air passageways and correspondingly low suctions available to draw fuel from the nozzle during low speed operation with wide open throttle. With this construction, the dimculty of getting enough fuel at low speeds when the throttle is open is overcome, to a great extent, by the. fact that the impact of air against the outlet of the nozzle 21 at low speeds is very much less than at high speeds and, accordingly, I am able'to use a comparatively large metering Jet which permits the free flow of fuel at the low speeds and yet does not give too much fuel at high speeds on account of the economizing action of the impact of the airstream against the fuel which is discharged from the from coming into operation until the port ll begins to go out of operation by reason of the fact that the suction from the port 4| is communicated to the nozzle 21 through passages 30, 39, etc. By this arrangement, the nozzle 21 is permitted to out gradually.

The invention is not limited in details to the structure shown but may be modified in various respects as will occur to those skilled in the art and the exclusive use of all .such modifications that come within the scope of the appended claims is contemplated.

' come in only gradually as the idling supply goes venturi being substantially anterior to the inlet I claim:

1. In a device of the class described, means forming a mixing conduit, a plurality of co-axial venturis mounted in said conduit, and means for preventing the rotation of the air stream as it passes through said venturis, comprising one or more longitudinally extending vanes adjacent said venturis.

2. In a device of the class described, means forming a mixing conduit, a plurality of co-axial venturis mounted in said conduit, and means for preventing the rotation of the air stream as it passes through said venturis comprising one or more longitudinally extending vanes adjacent said venturis, said vane or vanes being formed integral with at least one of said venturis.

3. In a device of the class described, means forming a mixing conduit, a plurality of co-axial venturis mounted in said conduit, and means for preventing the rotation of the air stream as it passes through said venturis comprising one or more longitudinally extending vanes adjacent said venturis, said venturis being formed as an integral casting.

4. In a device of the class described, means forming a mixing conduit, a plurality of co-axial venturis mounted in said conduit, and means for preventing the rotation of the air stream as it passes through said venturis comprising one or more longitudinally extending vanes adjacent said venturis, said vane or vanes and said venturis being formed as an integral casting, and said vane or vanes being of substantially greater thickness at the end adjacent the inlet of the mixing conduit than at the opposite end.

5. A nest of venturis comprising a unitary die casting, the outlet end of one of said venturis terminating near the most restricted portion of the next venturi, and an air straightener comprising a vane extending longitudinally with respect to said venturis and integral therewith.

6; A fluid conduit having an inlet of comparatively large diameter and an outlet of compara tively smaller diameter, a plurality of co-axial venturis in said conduit, said venturis being connected by one or more vanes, said vane or vanes and venturis being formed integrally with each other.

7. A nest of venturis comprising a main venturi, a secondary venturi having an outlet extending to and terminating at a point near the throat of said main venturi, the inlet of said secondary of said main venturi, a plurality of vanes formed integrally with said venturis and holding them in fixed relation with respect to each other, said vanes being of great length and comparatively,

little thickness, the leading edge of said vanes extending from the inlet end of the secondary venturi to the inlet end of the primary venturi and the trailing edge of said vanes terminating substantially at the throat of the main venturi.

8. In a device of the class described, a primary venturi, a larger venturi, said venturis being coaxial with each other and said primary venturi being mounted anterior to the larger venturi so that the outlet of the primary venturi extends to and terminates in the throat of the larger :nturi, one side of the primary venturi having a nozzlereceiving opening therein, a plurality of vanes connecting said primary venturi with said larger venturi, said vanes being of comparatively great length in comparison with their thickness, the leading edge of said vanes connecting the entrances of said venturis,'and the trailing edge of said vanes extending from the outlet of the primary venturi to the throat of the larger venturi.

9. A device of the class described in claim 8 and further characterized by the provision of three vanes, said nozzle opening being located between two of said vanes and the third vane being substant ally diametrically opposed to the nozzle opening. I

10. A nest of venturis comprising a main venturi having a flange surrounding its inlet end, a secondary venturi extending into the inlet end of said main venturi and terminating substantally at the throat thereof, a primary venturi extending into sad secondary venturi and terminating substantially at the throat thereof, said venturis being co-axial, a plurality of vanes connecting said venturi and forming straightening devices to prevent the rotation of the stream of fluid flowing thru said venturis, said vanes being of great length compared with their thickness, the leading edges of said vanes connecting the inlet ends of said venturis, the trailing edges of said vanes connecting the outlet end of the primary venturi with the throat of the secondary venturi and connecting the outlet end of the secondary venturi with the throat of the main venturi, and a nozzle opening formed in said primary venturi.

GEORGE M. BICKNELL.

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