Breathing System for a Carburetor for an Internal Combustion Engine

Field of the Invention

The present invention relates to "Breathing System for a Carburetor for an
Internal Combustion Engine". More particularly this invention relates to prevention of dust and related particles entry through the air breather tube of the carburetor and thus to the combustion chamber of the internal combustion engine.

Background of the Invention

In a typical float bowl type carburetor, fuel flows from the reservoir to the float bowl through a fuel metering wherein the fuel is drawn up and mixed with air due to the pressure differential caused by the venturi region in the carburetor bore or throat. A proper fuel flow rate is facilitated by venting the excess pressure from the top of the float bowl to maintain a constant pressure region. This venting is done to the atmosphere through an air breather arrangement provided in the carburetor.

The air breather arrangement provided in the conventional carburetors has provision such that, air that is passing through the breather tube is opened to atmosphere, so that the likelihood of introducing additional contaminants such as dust into the carburetor is greatly possible. The introduction of the contaminants into the air breather tube of the carburetor contaminates the fuel in fuel bowl of the carburetor, and thus affecting the engine performance as well as the life of the engine components.

In addition as the dust particles enter into the carburetor bowl unit, the airflow in breathing path gets clogged and the pressure within the carburetor decreases, the pressure in the float bowl also decreases due to the passageway connecting the carburetor throat and the bowl, thereby causing unwanted engine operation conditions.

The entry of dust into the breathing system of carburetor results in reduction of carburetion and thus the engine performance. Hence there is a need for a
carburetor breathing system which prevents the entry of contaminants such as dust and related components into the carburetor unit.

Further, the provision of the independent air filter for the breathing system of the carburetor increases the manufacturing cost as well as increases the size of the carburetor system; hence there is a need for a carburetor breathing system which will prevent the entry of contaminants and does not result in increase of the size as well as the cost of the carburetor system.

Summary of the Invention

The main object of the present invention is to provide a carburetor for an internal combustion engine provided with an air breathing arrangement which prevents the contaminants entry through the air breathing tube into fuel in the carburetor float bowl and thus to the engine combustion chamber.

Another object of the present invention is to provide a breather system capable of preventing the dust entry into carburetor bowl through the air breather tube which does not result in increase in the size of the carburetor.

Yet another object of the present invention is to provide a breather system
capable of preventing the dust entry into carburetor bowl through the air breather tube which makes the carburetor system cost effective.

Yet another object of the present invention is to make the carburetor system work efficiently without affecting engine performance.

Further scope of applicability of the present Invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Brief Description of the Drawing

The present invention will become more fully understood from the detailed
description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein

Figure. 1 illustrates a conventional motorcycle.

Figure. 2 is front view of a conventional carburetor.

Figure. 3 is cross sectional view of a conventional float bowl.

Figure. 4 is a cross sectional view of float bowl with air breather inlet tube open as per first embodiment of the present invention.

Figure. 5 is a cross sectional view of float bowl with air breather inlet tube closed as per first embodiment of the present invention.

Detailed Description of the Drawings

Embodiments of the present invention now be described with reference to the accompanying drawings. In the following description, 'front, "rear", "upper", "lower", "right", "left" and "bottom" represent directions viewed from the perspective of the vehicle rider.

The present invention relates to the breathing system of a carburetor for an internal combustion engine, for the purpose of illustration only it will illustrated with the help of a two wheeler motorcycle.

First the whole structure of the vehicle will be roughly described. With reference to
Figure. 1, a motorcycle comprises of a frame (101), front fork (102) attached to a pivot tube (103) of the vehicle frame, a front wheel (104) attached to these front forks (102), a handle bar (105) connected to the front forks (102), a fuel tank (106) attached so as to straddle an upper part of the vehicle frame, a seat (107) attached to the upper rear portion of the vehicle frame, an engine unit (108) attached to the lower front section of the vehicle frame, a swing arm (109) attached to a lower rear section of the vehicle frame, suspended by a rear shock absorber (not shown in the drawing) from the vehicle frame and a rear wheel (110) attached to a rear end of swing arm (109). The intake system of the engine comprises of a carburettor (117), intake duct and an air cleaner. The exhaust system of the engine comprises of exhaust pipe and a muffler. The motorcycle is also provided with a side cover (111) for covering a side section of the vehicle frame, a seat cover for covering a rear section of the vehicle frame below the seat, a front fender (112) for covering an upper part of the front wheel (104), and a rear fender (113) for covering an upper part of the rear wheel (110). The drive from the engine (108) is transmitted from the engine to the driven wheel sprocket mounted on the rear wheel hub mounted on the rear wheel assembly. With reference to Figure.2 which represents a carburetor comprising a main body (201) including an intake (202) and outlet (203) passageways.

The said intake (202) is for the air to enter the passageway and the said outlet (203) is from which air fuel mixture goes to the engine. A throttle valve inside 204 is located at the bottom of the carburetor. The float bowl is used as a reservoir for holding fuel which is supplied from a fuel inlet line. The fuel is drawn from the float bowl (205) to the main body passageway to mix with the air coming from intake (202) which passes into the combustion chamber of an internal combustion engine through outlet (203). The carburetor provides a combustible fuel air mixture to an internal combustion engine. Air is supplied to the carburetor through the air inlet side (202) of the carburetor. The carburetor has a control in any of the required form for constituting the fuel metering orifice of the carburetor. The fuel flows from the reservoir through a fuel metering orifice into the float bowl (205) from which the fuel is drawn up and mixed with air due to the pressure difference caused by the venturi region in the carburetor.

With reference to Figure.3 which represents a conventional carburetor float bowl (205) with a drain tube (301). The said drain tube (301) has one end (303) open to the atmosphere and the other top end (302) opens inside the float bowl (205). Normally it is necessary to drain fuel from the carburetor of an internal combustion engine when the fuel level inside the said float bowl (205) exceeds the predetermined level and to accomplish this draining, the carburetor has a drainage outlet (303) at the lowermost point of the said float bowl and the top end (302) of the said drain tube (301) is opened for facilitating and providing a pressure balance in the drain passage of the carburetor.

An air breather tube (304) is provided in the carburetor float bowl (205) with one end opened to the atmosphere and the other end connected to the breather chamber of the carburetor, for balancing the excess pressure in the carburetor float bowl (205) to a constant required pressure. The fuel flow is facilitated by venting the excess pressure in the carburetor to atmosphere through the air breather tube (304) provided in the carburetor.

Fuel in the fuel supply chamber passes through certain openings and then upwardly through the annular insert into a float bowl (205) to thereafter be aspirated by way of nozzle tube into the venturi region (305) of the carburetor bore during normal engine operation. The float regulated chamber with nozzle tube constitutes a conduit for conveying fuel from the float bowl (205) to air passing through the carburetor and into the engine during normal engine operation.

With reference to Figure.4, which is a cross sectional view of the carburetor float bowl with breathing system according to the first embodiment of the present invention. The said carburetor is provided with a light weight ball means (401) made of polymer is provided in a valve like configuration placed at the air breather inlet path (402) of the carburetor. The valve is configured in such a way that, whenever there is excess pressure inside float bowl (403), the light weight ball (401) gets lifted up in the air breather inlet tube (404) thereby opening the passage to release excess pressure out to the atmosphere.

Further when there is no pressure available in the carburetor bowl or float bowl as shown in figure 5, the gravity makes the ball (401) in the valve to move down to close the airflow path and thereby restricting the air entry as well as dust entry into the carburetor float bowl (403), thus preventing the dust entry into carburetor float bowl (403) and the engine combustion chamber.

The said light weight ball (401) is preferably of a diameter which is greater than the diameter of air breather inlet tube part (405).

The effectiveness of the present invention in breathing operation allows the carburetor to prevent the entry of contaminants through the air breather tube, and thus enhancing carburetor and engine operation conditions, as well as the life of the engine components.

The restriction in the entry of dust and contaminants into the breathing system of carburetor results in increase in effectiveness of carburetion and thus enhancing the engine performance.

From the foregoing it is now apparent that a novel process for preventing the entry of dust and contaminants through the breather tube into the breathing system of carburetor of an internal combustion engine as well as a novel arrangement for venting the breather tube to atmosphere has been disclosed meeting the objects and advantageous features are presented by way of illustration only, and not by way of any limitation, and that various alternatives and modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention.

We claim:

1. A breathing system for a carburetor for an internal combustion engine
comprising in combination a main body (201) defining venturi throat extending therethrough for the movement of air from the atmosphere toward internal combustion engine;

a throttle valve located in the main body passageway for regulating the air fuel mixture flow; and

a float bowl (403) located at the bottom of the main body for holding fuel wherein the said float bowl comprises:

a air breather inlet tube (404) to balance excess pressure inside the float bowl; and

a light weight ball (401) disposed in the air breather inlet tube (404).

2. A breathing system for a carburetor for an internal combustion engine as claimed in claim 1, wherein the said light weight ball is preferably made up of polymer.

3. A breathing system for a carburetor for an internal combustion engine as claimed in claim 1, wherein the said light weight ball opens the air breather inlet tube when there is excess pressure inside the float bowl.

4. A breathing system for a carburetor for an internal combustion engine as claimed in claim 1, wherein the said light weight ball closes the air breather inlet tube when there is no excess pressure inside the float bowl.

5. A breathing system for a carburetor for an internal combustion engine as claimed in claim 1, wherein the said light weight ball diameter is preferably made larger than the diameter of air breather inlet tube part (405).