US1970026A - Charge forming device - Google Patents

Description

Aug. 14, 1934., w TEETER 1,970,026

CHARGE FORMING DEVICE 1 Filed May 51, 1930 IQ IaA firm... Illll s51, qgm oulm x 1M.

Patented Aug. 14, 1%34 UNITED res FATE 1,979,025 F FICE CHARGE FDR/MING DEVICE ration, Detroit, Mich.

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, a corporation of Dela- Application May 31, 1930, Serial No. 457,821

17 Claims.

This invention relates to carburetors for internal combustion engines, and more particularly to carburetors which comprise a plurality of primary mixture passages which are adapted to deliver a primary mixture of fuel and air to a plurality of secondary mixing chambers in which the primary mixture is adapted to be mixed with additional air under certain operating conditions.

A carburetor of this character is described in the copending application of Wilford H. Teeter, Serial No. 288,685, filed June 2'1, 1928, which has resulted in Patent No. 1,904,634, granted April 18, 1933, and the present invention is illustrated as embodied in a carburetor of the general construction disclosed in such application.

It is the principal object of this invention to provide improved means for automatically controlling the mixture proportions during operation under varying conditions and at varying speeds. More particularly, it is an object of this invention to provide means for automatically forming a mixture of substantially constant proportions and for preventing the leaning of the mixture subsequent to the opening of the secondary air valve.

It is a further object of the invention to provide means for securing the above results, which is simple in construction and free from moving parts.

In some carburetors of this type it has been observed that subsequent to the opening of the secondary air valve there is a tendency for the mixture to become too lean and various means have been provided to correct this tendency, generally a secondary fuel inlet which is controlled by a fuel valve normally closed and adapted to be opened either substantially simultaneously with the opening of the secondary air valve, or subsequent to the opening of such valve. Difficulty been experienced in synchronizing the operation of the various moving parts so that it has proved difficult to provide a mixture of the desired proportions.

According to this invention, the additional fuel inlet has been eliminated and means are provided to increase the suction effective on a single "ael inlet, as the quantity of air is increased, after the opening of the secondary air valve as well as before, so that the increase in fuel and air is at substantially the same rate throughout the operating range. Up to a predetermined throttle position, the suction at the fuel inlet is the static suction of the main air chamber, but when the throttle is opened further, the suction at the fuel inlet is modified by communicating the eifect of the velocity head thereto, the suction thus being increased to some extent in the higher speed range.

Further objects and advantages of the present invention will be apparent from the following dscription, reference being had to the accompanying drawing wherein a preferred embodiment of one form of the present invention is clearly shown.

In the drawing:

Fig. 1 is a vertical section through a carburetor unit forming a part of the charge forming device in which the present invention is embodied.

Figs. 2, 3 and 4 are sections on the lines 2-2, 33 and l4 respectively.

Fig. 5 is a detail view of a suitable operating connection between the throttle and an associated valve.

Referring to the drawing and particularly to Fig. l, the reference numeral 20 indicates the main housing of the carburetor which is provided with a flange 22 adapted to be secured to an intake manifold of the type shown in the above mentioned application and which is not disclosed herein for the purpose of simplifying the disclosure. A casting 24 is positioned just below the main housing and is secured thereto in any desirable manner. Various fuel supply passages and other chambers are formed in this casting. An air inlet coupling 26 is adapted to be secured in position in an opening in the upper wall of the main housing by screws 28 and a float bowl 30 is held tight against an annular shoulder 32 on the casting 24 by a screw 34, screwed into said casting, suitable gaskets being provided to prevent leakage of the fuel. Fuel is supplied to the float bowl from the main source of supply through a passage which is not shown and the flow is controlled by a float 36 which operates in the usual manner to maintain a constant level of fuel in the bowl.

Fuel flows from the bowl 30 to a plurality of primary mixing chambers 38, the construction of which is described more fully hereinafter. The fuel conduit between the-fuel bowl and the primary mixing chambers comprises an angular fuel passage 40, which communicates at its upper end with a horizontal fuel canal .2 connecting with three horizontal passages 43, each of which connects with one of three vertical passages to, which are connected at their upper ends with horizontal passages 46. Passages 46, at their delivery ends, are restricted, as indicated at 48, and supply fuel to a horizontal passage 50, which communicates with three vertical passages 52, at the lower ends of which are provided three fuel feeding orifices 54, each of which supplies fuel to one of the primary mixing chambers 38. The static suction of the air chamber, as more fully described hereinafter, is maintained at the fuel inlet orifices 48 up to a predetermined throttle opening, so that no velocity head is present at these orifices under such operating conditions. As will be explained more fully hereinafter, the efiect of a velocity suction is communicated to the inlets 48 when the throttle is opening beyond the predetermined position referred to. A calibrated plug 56 is provided at the intake end of the fuel delivery passage 40 to regulate the flow of fuel therethrough, while the restrictions 54 regulate the flow from each fuel feeding orifice into the primary mixing chamber with which it is associated.

The primary mixing chambers 38 comprise the vertical intake ends of primary mixture passages 58, which are parallel to each other and relativ ly close together, as indicated in Fig. 5. When the carburetor is attached to the manifold, these passages are adapted to register with conduits which convey the primary mixture to secondary mixing chambers formed in the manifold and constructed in the manner fully disclosed in the application above referred to. A single throttle valve 60 controls the flow through the primary mixture passages and extends across all of said passages, being provided with grooves 62 which register with the mixture passages.

Air is admitted to the carburetor through the inlet coupling 26 and is controlled by a main air valve 64, normally held against the seat 66 by a spring 68, received between the valve and a flange '70, projecting from a sleeve 72, slidably mounted on a sleeve '74, fixed in the main housing and guiding the stem '76 on which the air valve is secured. To facilitate starting, the flange 70 is lifted by an arm 78, which extends thereunder and is operated at will by the operator of the vehicle, to hold the valve 64 closed, as fully disclosed in the above mentioned application. Sufiicient air to carry the starting fuel from the nozzles to the intake ports is admitted through an orifice in the housing as is also described in said above mentioned application.

The valve 64 admits air to a main air chamber 80, from which air flows directly into the primary mixing chambers 88 and to the secondary mixing chambers through a passage 82, which is adapted to connect with the inlet of the manifold when the carburetor unit is secured thereto. The fiow through this passage is controlled by manually and suction operated valves 84 and 86 secured to shafts 88 and 90, journalled in the main housing.

The operating connections for the throttle and the valve 84 form no part of this invention. It is regarded as sufficient for the purposes of this disclosure to state that the primary throttle is connected to the valve 84 by an adjustable lost motion connection, which permits a predetermined movement of the primary throttle indeendent of said valve 84 and is generally adjusted so that the primary throttle is movable without accompanying movement of the valve 84 until the former reaches a position corresponding to a vehicular speed of approximately 15 to 20 miles per hour on the level. On further opening of the primary throttle, the valve 84 is moved simultaneously therewith. Such a lost motion connection is illustrated in Fig. 5, which connection comprises a pin 108 secured to an arm 110 on shaft 90 of valve 84 and projecting through a slot 112 in a link 114 secured to an arm 116 on throttle 60. The valve 86 is opened by engine suction and opens only after the valve 84 is opened.

Any increase of suction in the main air chambar is accompanied by an opening movement of the valve 64, which movement is retarded to prevent iiuttering of the valve and to prevent leaning of the mixture by a dashpot comprising a cylinder 92 and a piston 94 slidable therein, and secured to the end of the valve stem '76. The details of construction of the dashpot are unimportant so far as the present invention is concerned and that disclosed is of the same form as described in detail in application Serial No. 288,685.

The passage 96 constitutes a fuel delivery passage from the cylinder, which forms a fuel pump, to the primary mixture passages 58, into which fuel is injected by the pump on every opening of the main air valve following an opening movement of the throttle. At the same time the pump is effective, the opening of the suction operated valve 86 is temporarily retarded to restrict the admission of air through the secondary air passage for reasons which are fully set forth in application Serial No. 288,685 in which the pump and the means for retarding the opening of the valve 86 are also fully described.

It will be understood that the valve 86 may be in the position in which it is shown herein as indicated at 98 in Fig. 2 for a purpose to be later described, or the secondary air passage 82 may be somewhat lengthened and the valve 86 placed in a position posterior to the valve 84 as in certain earlier devices, for instance that shown in the copending application of Wilford H. Teeter et al., Serial No. 288,683, filed June 27, 1928.

Communicating with the middle one of vertical passages 52, as shown in Fig. 2, is a tube 100, extending upwardly into the air chamber where it is bent to project horizontally into the secondary air passage 82, the posterior end of the tube being received within a small Venturi tube 102, secured in position against the lower wall of the secondary air passage by a screw 104, screwed into the main housing. The tube 106 terminates adjacent the point of greatest restriction in the mixture tube and an inlet orifice 105 is provided in the tube intermediate its ends. The admission of air through the tube 100 and the communication of suction therethrough to the passage 52 controls the amount of fuel through the orifices 48, thus regulating the mixture proportions. Plugs 108 close the two outer vertical passages so that the tube 100 admits air to all of said passages 52.

The operation of this tube and its function in controlling the mixture proportions is substantially as follows: At all times and under all operating conditions when the valves in the secondary air passage 82 are closed, air is admitted to the passages 52 through the open end of the tube 100 and the orifice 106. The inside area of the tube is greater than the combin d areas of the outlets 54, therefore, the air must move through the passages 52 at so low a velocity that no velocity head is created at the orifices 48 prior to the opening of the valves 84 and 86, and the suction maintained at such orifices is substantially the static suction of the air chamber 80. Subsequent to the opening of the valves 84 and 86, the increase in the amount of air supplied to the intake ports on opening movement of the throttle is so rapid that there must be a corresponding increase in the amount of fuel supplied, and to effect such increase in fuel flow, the suction at the orifices 48 must be increased more rapidly on opening of the throttle than was necessary prior to the opening of the valves 84 and 86. This stepping up of the rate of increase in fuel flow is accomplished by the Venturi tube 162, which creates a velocity suction at the end of the tube 100 subsequent to the opening of the valves 84 and 86, which is communicated through the tube to the orifices 48.

The efiect of the velocity head is modified to some extent by the admission of air through the orifice 106, which may be made of whatever size is suitable to give exactly the increase desired, or the hole may be omitted altogether if it be desired to communicate the velocity head unmodified to the fuel feeding orifices 48.

In the embodiment shown in the drawing the suction which is actually maintained at the orifices 48 is greater than the static suction of the air chamber 80, but is less than the velocity suction created at the end of the tube 100, due to the modifying effect of the orifice 106 in the tube. Also, owing to the fact that the velocity suction within the Venturi tube 102 increases more rapidly than the static suction of chamber 80, it will be apparent that the increase in suction at orifice 48 on opening movement of the throttle is greater after the opening of valves 84 and 86 than before. The actual suction at the orifices 48 after the venturi has begun to function might be said to be the sum of the suction efi'ects of the static suction of chamber and the velocity suction of the venturi 102, being somewhere between these two suctions, the exact degree of suction depending on the relative sizes of the various parts.

While the form of embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A carburetor having in combination, a mixture passage, a fuel inlet supplying fuel to the mixture passage, an air inlet therefor, means for effecting a flow of fuel from said fuel inlet by a suction substantially equal to the static suction within the carburetor until the throttle has made a predetermined opening movement, means for communicating the effect of a velocity head to said fuel inlet when the throttle is opened to a greater degree, and means operated after said predetermined opening movement of the throttle to render the second-mentioned means operative.

2. A carburetor comprising a primary mixture passage adapted to deliver a primary mixture of air and fuel to a secondary mixing chamber, a secondary air passage adapted to supply air to be mixed with the primary mixture, a throttle, a fuel inlet for supplying fuel to said primary mixture passage, a main air chamber adapted to supply air to said primary mixture passage and secondary air passage, means for communicating substantially the static suction of the air chamber to the fuel inlet, normally ineffective means for communicating the velocity suction of the secondary air passage to the fuel inlet, and means for rendering said last mentioned means effective after the throttle has made a predetermined opening movement.

3. A carburetor comprising a primary mixture passage adapted to deliver a primary mixture of air and fuel to a secondary mixing chamber, a secondary air passage adapted to supply air to be mixed with the primary mixture, a fuel inlet for supplying fuel to said primary mixture passage, a main air chamber adapted to supply air to said primary mixture passage and secondary air passage, normally ineffective means for communicating the velocity suction of the secondary air passage to the fuel inlet, and a valve in said secondary air passage for controlling the effectiveness of said last mentioned means and regulating the flow of air through'said secondary air passage. i

4. A carburetor comprising a primary mixture passage adapted to deliver a primary mixture of air and fuel to a secondary mixing chamber, a secondary air passage adapted to supply air to be mixed with the primary mixture, a fuel inlet for supplying fuel to said primary mixture passage, a main air chamber adapted to supply air to said primary mixture passage and secondary air passage, normally ineffective means for communicating the velocity suction of the secondary air passage to the fuel inlet, a valve in said secondary air passage adapted to render said last mentioned means effective when said valve begins to open and adapted to be opened after a predetermined opening movement of the throt tle.

5. A carburetor comprising a mixture passage, a fuel inlet supplying fuel thereto, an air inlet therefor, a throttle, means, for creating a suction at said fuel inlet which increases as the throttle is opened, means for accelerating the rate of increase in suction at the fuel inlet during opening movements of the throttle under certain operating conditions, and means operated after a predetermined movement of the throttle to render the second-mentioned means operative.

6. A carburetor comprising, a primary mixture passage adapted to deliver a primary mixture of air and fuel to a secondary mixing chamber, a secondary air passage adapted to supply air to be mixed with the primary mixture, a fuel inlet for supplying fuel to said primary mixture passage, a main air chamber adapted to supply air to said primary mixture passage and secondary air passage, a throttle, a valve in the secondary air passage, means for maintaining a suction at the fuel inlet which increases as the throttle is opened, and means for accelerating the rate of increase of said suction after the valve in said secondary air passage is open.

7. A carburetor comprising, a primary mixture passage adapted to deliver a primary mixture of air and fuel to a secondary mixing chamber, a secondary air passage adapted to supply air to be mixed with the primary mixture, a fuel inlet for supplying fuel to said primary mixture passage, a main air chamber adapted to supply air to said primary mixture passage and secondary air passage, and a tube communicating with the fuel inlet, the main air chamber and the secondary air passage, whereby the suction of the air chamber is communicated to the fuel inlet under certain operating conditions and under other operating conditions the velocity suction of the secondary air passage becomes effeotive in controlling the fuel flow.

8, A carburetor comprising, a primary mixture passage adapted to deliver a primary mixture of air and fuel to a secondary mixing chamber, a secondary air passage adapted to supply air to be mixed with the primary mixture, a fuel inlet for supplying fuel to said primary mixture passage, a main air chamber adapted to supply air to said primary mixture passage and secondary air passage, and a tube communicating with the fuel inlet, the main air chamber and the secondary air passage, whereby the suction maintained at the fuel inlet is the composite suction effect of the static suction of the main air chamber and the velocity suction of the secondary air passage. V

9. A carburetor for internal combustion engines comprising a mixture passage, a throttle regulating the flow therethrough, fuel and air inlets therefor, a tube communicating with the fuel inlet and operative to control the suction effective on the fuel inlet, means for accelerating the flow of air past the end of the tube to create a velocity suction, to be communicated through the tube to said fuel inlet and a vent in said tube adapted to admit air to modify the effect of the velocity suction.

10. A carburetor comprising a primary mixture passage adapted to deliver a primary mixture of air and fuel to a secondary mixing chamber, a secondary air passage adapted to supply air to be mixed with the primary mixture, fuel and air inlets for supplying fuel and air to the primary mixture passage, a valve in said secondary air passage, a tube communicating with said fuel inlet and extending into said secondary means for accelerating the flow of air past the end of said tube when said valve is open, to create a velocity head at the end of the tube to be communicated thereby to the fuel inlet and a vent in said tube to modify the effect of the velocity suction on the fuel inlet.

11. A carburetor for internal combustion engines comprising a plurality of primary mixture passages, fuel and air inlets for each of said mixture passages, a secondary air passage adapted to supply air to be mixed with the primary mixture formed in each of said primary mixture passages, an" air chamber for supplying air to all of said primary mixture passages and said secondary air passage and a passsge for communicating the suction of the air chamber and the secondary air passage to all of the fuel in lets.

12. A carburetor, comprising, a primary mixture passage adapted to deliver a primary mixture of fuel and air to a secondary mixing chamber, a throttle, a secondary air passage adapted to supply air to said secondary mixing chamber to be mixed with the primary mixture of fuel and air and operative only under certain conditions, a main air chamber adapted to supply air to the primary mixture passage, means operative under certain conditions for maintaining at the fuel inlet substantially the same suction as is maintained in the main air chamber, means for creating a flow of air at high velocity in said secondary air passage when the latter is effective, and means for communicating the suction of the high velocity air current to the fuel inlet to modify the air chamber suction maintained at said fuel inlet.

13. A carburetor, comprising, a primary mixture passage adapted to deliver a primary mixture of fuel and air to a secondary mixing chamber, a throttle, a secondary air passage adapted to supply air to said' secondary mixing chamber to be mixed with the primary mixture of fuel and air and operative only under certain conditions, a main air chamber adapted to supply air to the primary mixture passage, means operative under certain conditions for maintaining at'the fuel inlet substantially the same suction as is maintained in the main air-chamber, a Venturi tube in said secondary air passage through which air flows at high velocity when said secondary air passage is effective and means for communicating the suction maintained within the Venturi tube to the fuel inlet to modify the air chamber suction maintained at said fuel inlet.

14. A carburetor, comprising, a primary mixture passage adapted to deliver a primary mixture of fuel and air to a secondary mixing chamber, a throttle, a secondaryair passage adapted to supply air to said secondary mixing chamber to be mixed with the primary mixture of fuel and air and operative only under certain conditions, a main air chamber adapted to supply air to the primary mixture passage, means operative under certain conditions for maintaining at the fuel inlet substantially the same suction as is maintained in the main air chamber, means for creating a flow of air at high velocity in said secondary air passage when the latter is effective, and a conduit extending from the point of high velocity air flow to the fuel inlet to communicate the velocity suction created by said air flow to the fuel inlet to modify the effect of the air chamber suction.

15. A carburetor, comprising, a primary mixture passage adapted to deliver a primary mixture of fuel and air to a secondary mixing chamber, a throttle, a secondary air passage adapted to supply air to said secondary mixing chamber to be mixed with the primary mixture of fuel and air and operative only under certain conditions, a main air chamber adapted to supply air to the primary mixture passage, means operative under certain conditions for maintaining at the fuel inlet substantially the same suction as is maintained in the main air chamber, means for creating a flow of air at high velocity in said secondary air passage when the latter is effective, a conduit extending from the point of high velocity air flow to the fuel inlet to communicate the velocity suction created by said air flow to the fuel inlet to modify the effect of the air chamber suction and an orifice in the conduit to modify the eifect produced at the fuel inlet.

16.. Acarburetor comprising a primary mixture pamage adapted to deliver. a primary mixture of air and fuel to a secondary mixing chamber, a throttle, a secondary air passage adapted to supply air to be mixed with the primary mixture after a certain opening movement of the throttle, a fuel inlet for supplying fuel to said primary mixture passage, a main air chamber adapted to supply air to said primary mixture passage and secondary air passage, means for communicating substantially the static suction of said air chamber to the fuel inlet when the secondary air passage is ineffective and means for modifying this suction only after the secondary air passage has been rendered effective to supply additional air.

17. A carburetor comprising a primary mixture passage adapted to-deliver a primary mixture of air and fuel;to a secondary mixing chamber, a throttle, a secondary air passage adapted to supply air to be mixed with the primary mixture after a certain opening movement of the throttle, a fuel inlet for supplying fuel to said primary mixture passage, a main air chamber adapted to supply air to said primary mixture passage and secondary air passage, means for communicating substantially the static suction of the air chamber to said fuel inlet when the secondary air passage is ineffective and means for communicating the suction created by the air passing through the secondary air passage to the fuel inlet when this secondary air passage has been rendered effective to supply additional air.

WILFORD H. TEETER.

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