GB1600424A

GB1600424A - Horizontal draught carburettor for internal combustion engines

Info

Publication number: GB1600424A
Application number: GB346278A
Authority: GB
Original assignee: IND NAZIONALE CARBUATORI DELL
Current assignee: IND NAZIONALE CARBUATORI DELL
Priority date: 1977-01-27
Filing date: 1978-01-27
Publication date: 1981-10-14
Also published as: ES466349A1; FR2378952A1; DE2803360A1; IT1076321B; FR2378952B1

Description

(54) HORIZONTAL DRAUGHT CARBURETTOR FOR INTERNAL COMBUSTION ENGINES (71) We, INDUSTRIA NAZIONALE CA RB UATORI DELL'ORTO S.p.A., a Societe Per Azioni organised under the laws of Italy, of Via S. Rocco, 5-20038 Seregno (Milano), Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in any by the following statement:- The invention relates to a horizontal draught carburettor for internal combustion engines and particularly, but not exclusively, for motor vehicle engines.

It is well known to experts of the art, and also to users such as motor cyclists and motorists, that vehicle running conditions exist in which the inclination of the liquid level in the carburettor float chamber and the structure of the carburettor itself give rise, for all or some engine speeds, to an undesirably irregular fuel feed to the outlet of the emulsifying tube, which in the most frequent cases results in power gaps, which can have even serious repercussions on the conduct of the vehicle (such as where motor cars or motor cycles are used in competitions) and in any case are damaging and annoying (even for the normal motorist).

The object of this invention is to obviate this drawback and to provide improvements in the construction and arrangement of such a horizontal draught carburettor as a result of which, when the carburettor is in use on an internal combustion engine serving as the power unit of a vehicle, the fuel-air mixture delivered by the carburettor to the engine will always be ready and substantially correctly proportioned for practically any engine speed condition and for practically any running condition and position of the vehicle.

According to one aspect of this invention there is provided a horizontal draught carburettor for internal combustion engines, wherein a constant level float chamber extends around the bottom and at least part of each side of a horizontal main intake duct and is so arranged that, in use, the fuel level therein is above the level of the lowest part of the interior of said duct; a main emulsifying tube, which is arranged within an emulsion block has a lower portion which extends substantially vertically downward through the centre of the float chamber; and two floats are arranged within the float chamber on the two opposite sides respectively of the lower portion of the emulsion block.

According to another aspect of this invention, there is provided a horizontal draught carburettor for internal combustion engines, comprising a horizontal main intake duct incorporating a main venturi; a constant level float chamber extending around the bottom and at least part of each side of the main intake duct; a substantially vertical emulsion block having a lower portion projecting downwardly into the float chamber from the middle bottom part of the main intake duct and an upper portion extending upwardly into the interior of the main intake duct from said middle bottom part, said emulsion block having a main emulsifying tube arranged in a vertical bore therein; a secondary venturi on the upper end of the upper portion of the emulsion block, the secondary venturi being axially aligned with the main venturi and having its downstream end located in uniformly spaced relationship within the throat of the latter and two floats arranged within the float chamber on the two opposite sides respectively of the lower portion of the emulsion block and of the main intake duct of the carburettor.

The invention is described hereinafter in detail by way of example with reference to the accompanying drawings showing a preferred embodiment thereof, and in which: Figure 1 is a cross-section through the carburettor according to this embodiment of the invention in a plane perpendicular to the axis of the main intake duct of the carburettor and containing the central axis of a main emulsifying tube; and Figure 2 is a longidutinal section in a plane containing the axis of the main intake duct and normal to the plane of the crosssection of Figure 1.

Referring to the drawings, a horizontal draught single carburettor comprises in known manner a carburettor body C through which a main horizontal intake duct CP extends and of which a constant level float chamber 8 forms a part.

In Figures 1 and 2, the reference number 1 indicates the fuel level in the float chamber 8, the reference number 2 indicates the outlet of a main emulsifying tube 32 and the reference number 3 indicates a secondary venturi into the centre of which the outlet 2 of the emulsifying tube 32 opens.

As can be seen from Figure 1, the emulsifying tube 32 is arranged coaxially within a bore in an emulsion block 39 which is formed integrally with the wall of the main horizontal duct CP. An upper portion of the emulsion block 39 extends upwardly from the bottom middle part of the wall of the main horizontal duct CP into the interior of the said duct and has the secondary venturi 3 formed integrally on its upper end. The secondary venturi being axially aligned with the main venturi and having its downstream end located in uniformly spaced relationship within the throat of the latter. A lower portion of the emulsion block 39 extends downwardly from the said bottom middle wall part into the float chamber 8 to a position near the bottom of the latter.The float chamber 8 extends around the bottom and part of each side of the horizontal duct CP and contains at its centre the emulsifying tube 32. The fuel level 1 in the float chamber 8 is in the same horizontal plane as a point 4 on the emulsifying tube 32. The float chamber 8 contains two floats 5 and 6 which are located on two opposite sides of the emulsion block 39 and are interconnected in the region of their lower ends by a yoke member 7.

The fuel level in the float chamber 8 is a few mm., preferably not more than 10 mm., below the outlet 2 of the main emulsifying tube 32. Furthermore, if the carburettor is tilted in either direction through an angle , (Figure 1), which can even be of substantial extent, about the central axis of the main duct CP, it can be seen from Figure 1 that the fuel level in the vicinity of the point 4 on the main emulsifying tube 32 will not vary and the same result will be obtained if the carburettor is tilted in either direction through an angle A (Figure 2) about an axis perpendicular to the axis (r and extending through the point 4 on the main emulsifying tube 32.

Thus, not only is there a difference of a few mm. between the fuel level 1 in the constant level float chamber V and the outlet 2 of the main emulsifying tube 32, this being an important requirement for the proper and immediate operation of the carburettor in the horizontal position, but also this difference remains constant for any ordinary inclination which the carburettor can assume during the running of the vehicle in which the carburettor is installed.

In addition, even when the vehicle in which the carburettor is installed accelerates round a bend or is braked, the fuel level in the vicinity of the above-mentioned point 4 will not vary appreciably and consequently optimum or nearly optimum conditions for proper running of the engine will be maintained.

Figure 1 shows how the two floats 5 and 6, which are rigidly interconnected by the yoke member 7, determine the required fuel level 1 in the float chamber 8 by operating a needle valve 9 (Figure 2) so as to shut off the fuel feed, the float chamber 8 being connected to the atmosphere via two channels 10 and a bore 11 (Figure 1).

The fuel path in the idling circuit will now be examined with reference to Figure 2.

With the engine idling, fuel is drawn from the float chamber 8 via a main jet 12 and an idling jet 13 (derived idling) and flows up through a duct 14 to a level which is the same as the fuel level 1 in the float chamber.

At the same time, air drawn from the atmosphere through a metering duct 15 is conveyed from the latter through a further duct (not shown) to an opening in the wall of the duct 14, which opening is located above the fuel level 1.

Thus, it is apparent that, the engine idling or running at a low speed, an air-fuel mixture is formed in the duct 14 and reaches progression bores 17 and a mixtureproportioning screw 18 through a duct 16.

At least part of the duct system comprising the ducts 14 and 16 must reach a level higher than the fuel level 1 in the float chamber in order to prevent the discharge of fuel from the said duct when the engine is not running. In addition, as the idling emulsion air emerges above level at the highest point of the duct 14, there is no danger of a syphon effect being created in the idling system.

In order to reduce the emission of CO from l.C. engines fitted with carburettor illustrated, the latter is provided with means, indicated in broken lines in Figure 2.

whereby during idling and deceleration additional quantities of a lean air-fuel mixture are admitted to the duct CP at a position downstream of the mixture proportioning screw 18. The said means include an idling fuel mixture withdrawal orifice 19 in the wall of the duct 16, an extra air orifice 20 and a duct 21 leading from these orifices 19, 20 to an orifice formed in the wall of the duct CP and controlled by an idling revolutions adjustment screw 22. A small quantity of idling air-fuel mixture is withdrawn from the duct 14 through the duct 16 into the duct 21 where it is admixed with extra air drawn in through the orifice 20 and the resulting lean mixture is then delivered by the said duct 21 to the orifice controlled by the screw 22, through which last-mentioned orifice it is drawn into the main horizontal duct CP.

The engine idling revolutions are adjusted by the screw 22, as the screw 23 which adjusts the throttle opening and the screw 18 which adjusts the mixture composition are sealed.

The operation of the main jet will now be examined with reference to Figure 2.

When the engine is running at a speed at which the main emulsifying tube 32 is not active, the fuel in a main discharge tube 24, which is connected to the float chamber 8 via the main jet 12, reaches the fuel level 1 in the float chamber.

When the throttle opening and the engine revolutions provide a sufficient depression in the main venturi 25 and the secondary venturi 3, an air and fuel emulsion is drawn from the outlet 2 of the main emulsifying tube 32 into the secondary venturi 3.

This emulsion is formed inside the emulsifying tube 32 from the fuel coming from the main jet 12 and the air which is drawn in from the atmosphere through a calibrated duct 26 into an interspace 27 from which it penetrates through bores 28 into the tube 32. The calibrated air duct 26 must be positioned above the fuel level in the float chamber 8 in order to prevent fuel from being discharged through it even if the carbutettor should be inclined at a considerable angle while the engine is not running.

Figure 2 also shows diagrammatically a conventional accelerator pump with its suction valve 29, delivery valve 30 and an outlet 31, and mainly in broken lines a conventional starter unit with its jet 33, calibrated air duct 34, shut-off plunger 35, starter control lever 36 and outlet duct 37 for the supply of mixture downstream of the throttle valve 38.

Having thus described the construction and operation of preferred embodiment of the carburettor according to the invention, the advantages of the present invention can be better appreciated, in that in any position of inclination of the carburettor, within a wide range, the level difference h to be overcome by the mixture, for the latter to be able to emerge from the emulsifying tube 32, is just a few mm. (from the fuel level 1 in the float chamber 8 to the outlet 2 of the main emulsifying tube 32).

It also dispenses with the long ducts between the zone where the air-fuel mixture is formed and the outlet 2 of the main emulsifying tube 32 which is in the centre of the secondary ventruri 3, such as are provided in conventional horizontal draught carburettors with float chamber alongside or under the duct. As a result of these few mm. of difference h (approximately 6 to 8 mm.), carburation of considerable promptness and response is obtained.

The carburettor according to the invention is particularly suitable for use on motor cars and motor cycles or for special uses, where operation with considerable inclination any direction is demanded. This operation is excellent even with a weak mixture such as is necessary for reducing pollution.

WHAT WE CLAIM IS: 1. A horizontal draught carburettor for internal combustion engines, wherein a constant level float chamber extends around the bottom and at least part of each side of a horizontal main intake duct and is so arranged that, in use, the fuel level therein is above the level of the lowest part of the interior of said duct; a main emulsifying tube, which is arranged within an emulsion block, has a lower portion which extends substantially vertically downward through the centre of the float chamber; and two floats are arranged within the float chamber on the two opposite sides respectively of the lower portion of the emulsion block and of the main intake duct of the carburettor.

2. A horizontal draught carburettor for internal combustion engines, comprising a horizontal main intake duct incorporating a main venturi; a constant level float chamber extending around the bottom and at least part of each side of the main intake duct; a substantially vertical emulsion block having a lower portion projecting downwardly into the float chamber from the middle bottom part of the main intake duct and an upper portion extending upwardly into the interior of the main intake duct from said middle bottom part, said emulsion block having a main emulsifying tube arranged in a vertical bore therein; a secondary venturi on the upper end of the upper portion of the emulsion block, the secondary venturi being axially aligned with the main venturi and having its downstream end located in uniformly spaced relationship within the throat of the latter and two floats arranged within the float chamber on the two opposite sides respectively of the lower

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. proportioning screw 18. The said means include an idling fuel mixture withdrawal orifice 19 in the wall of the duct 16, an extra air orifice 20 and a duct 21 leading from these orifices 19, 20 to an orifice formed in the wall of the duct CP and controlled by an idling revolutions adjustment screw 22. A small quantity of idling air-fuel mixture is withdrawn from the duct 14 through the duct 16 into the duct 21 where it is admixed with extra air drawn in through the orifice 20 and the resulting lean mixture is then delivered by the said duct 21 to the orifice controlled by the screw 22, through which last-mentioned orifice it is drawn into the main horizontal duct CP. The engine idling revolutions are adjusted by the screw 22, as the screw 23 which adjusts the throttle opening and the screw 18 which adjusts the mixture composition are sealed. The operation of the main jet will now be examined with reference to Figure 2. When the engine is running at a speed at which the main emulsifying tube 32 is not active, the fuel in a main discharge tube 24, which is connected to the float chamber 8 via the main jet 12, reaches the fuel level 1 in the float chamber. When the throttle opening and the engine revolutions provide a sufficient depression in the main venturi 25 and the secondary venturi 3, an air and fuel emulsion is drawn from the outlet 2 of the main emulsifying tube 32 into the secondary venturi 3. This emulsion is formed inside the emulsifying tube 32 from the fuel coming from the main jet 12 and the air which is drawn in from the atmosphere through a calibrated duct 26 into an interspace 27 from which it penetrates through bores 28 into the tube 32. The calibrated air duct 26 must be positioned above the fuel level in the float chamber 8 in order to prevent fuel from being discharged through it even if the carbutettor should be inclined at a considerable angle while the engine is not running. Figure 2 also shows diagrammatically a conventional accelerator pump with its suction valve 29, delivery valve 30 and an outlet 31, and mainly in broken lines a conventional starter unit with its jet 33, calibrated air duct 34, shut-off plunger 35, starter control lever 36 and outlet duct 37 for the supply of mixture downstream of the throttle valve 38. Having thus described the construction and operation of preferred embodiment of the carburettor according to the invention, the advantages of the present invention can be better appreciated, in that in any position of inclination of the carburettor, within a wide range, the level difference h to be overcome by the mixture, for the latter to be able to emerge from the emulsifying tube 32, is just a few mm. (from the fuel level 1 in the float chamber 8 to the outlet 2 of the main emulsifying tube 32). It also dispenses with the long ducts between the zone where the air-fuel mixture is formed and the outlet 2 of the main emulsifying tube 32 which is in the centre of the secondary ventruri 3, such as are provided in conventional horizontal draught carburettors with float chamber alongside or under the duct. As a result of these few mm. of difference h (approximately 6 to 8 mm.), carburation of considerable promptness and response is obtained. The carburettor according to the invention is particularly suitable for use on motor cars and motor cycles or for special uses, where operation with considerable inclination any direction is demanded. This operation is excellent even with a weak mixture such as is necessary for reducing pollution. WHAT WE CLAIM IS:

1. A horizontal draught carburettor for internal combustion engines, wherein a constant level float chamber extends around the bottom and at least part of each side of a horizontal main intake duct and is so arranged that, in use, the fuel level therein is above the level of the lowest part of the interior of said duct; a main emulsifying tube, which is arranged within an emulsion block, has a lower portion which extends substantially vertically downward through the centre of the float chamber; and two floats are arranged within the float chamber on the two opposite sides respectively of the lower portion of the emulsion block and of the main intake duct of the carburettor.

portion of the emulsion block and of the main intake duct of the carburettor.

3. A carburettor as claimed in claim I or 2, wherein the two floats are interconnected, at a level below the bottom of the main intake duct, by a yoke arranged to control the operation of a needle valve which regulates the entry of fuel into the float chamber.

4. A carburettor as claimed in any of claims 1 to 3, wherein a metering and inlet duct is provided in the emulsion block, at a level above the fuel level in the float chamber when the carburettor is in use, for the admission of air to form in the main emulsifying tube an air-fuel emulsion with fuel from the float chamber.

5. A carburettor as claimed in any of claims 2 to 4, wherein the emulsion block contains a duct or system of ducts for conveying fuel from an idling jet to a position where it is admixed with air to form an idling air-fuel emulsion and part of the said duct or system of ducts extends above the fuel level in the float chamber when the carburettor is in use and a metering duct is provided in the upper portion of the emulsion block for the admission of the air forming said idling air-fuel mixture.

6. A carburettor as claimed in any of claims 1 to 5, wherein the constant level float chamber is so arranged that even when, in use, the carburettor is tilted through a substantial angle in any direction, the level of the fuel therein is lower than the outlet of the main emulsifying tube by only a few millimetres.

7. A horizontal draught carburettor substantially as hereinbefore described with reference to the accompanying drawings.