GB2140874A - Carburettor - Google Patents

Abstract

To provide a sufficient fuel supply at full load of the associated engine, the carburettor is provided with a direct fuel passage 7, 13 from a tank (not shown) to a space 9 upstream of the main nozzle 16 or to a float chamber 4. This passage 7,13 is controlled by a control valve 10 connected to a movable pin 11 the head of which protrudes into a slide valve chamber 1 and is actuated by an air slide valve 2 when this is moved to its open position. Alternatively the valve 10 actuated by the air slide valve 2 may be replaced by a valve or flap controlled directly by a handle. <IMAGE>

Description

SPECIFICATION Carburettors The invention relates to carburettors. More particularly but not exclusively the invention relates to a carburettor for a motorcycle or other vehicle especially for alcohol fuels, which comprise a Venturi tube controlled by the sliding movement of an air slide valve movable together with a control needle controlling a fuel passage, and a float chamber with a float and valve controlling the height of the fuel level in the carburettor.

There are known carburettors for petrol, alcohol fuel and other liquid fuel, having a Venturi tube, in which an air passage is controlled by means of a slide valve and a fuel supply by means of a needle, and a float chamber, the purpose of which resides in keeping up a constant height of fuel level in the carburettor. In the case of carburettors for alcohol fuel designed especially for engines with a shorttime very high output, there are often employed float chambers having an extremely large capacity and sometimes even two float chambers for one carburettor. The fuel supply into the float chambers is carried out either by an inclined flow or by a fuel pump. A control valve for the float chambers is situated either in their cover, closing the float chamber from above, or it is formed in the lower part of the chamber.The control valve is controlled by a needle either carried directly by the valve or by a lever mechanism connected to the float. It is also known to provide float chambers, especially for alcohol fuel, with two inlets into the float chamber, which are controlled by means of one or two floats.

A drawback of hitherto known float chambers resides in their insufficient supply of fuel for a higher output engine for alcohol fuel having an extraordinarily high rate of consumption. In the case of one float chamber with an extremely large capacity, fuel in the float chamber provides some reserve for a short-time full loading of the engine, but during that time the height of the fuel level in the float chamber drops, and the fuel becomes poor, which causes an output drop of the engine or even a seizing-up of the engine. Carburettors with more fuel inlets and with more float chambers solve this problem, but such designs cause an increase in the weight and complicity of the whole carburettor.

According to the invention a carburettor for a motorcycle or other vehicle, preferably for use with alcohol fuel, comprises a Venturi tube controlled by a movable air slide valve being movable together with a control needle controlling the fuel passage, and a float chamber with a float and valve controlling the height of the fuel level in the carburettor, wherein there is provided a slide valve chamber into which a head of a movable pin protrudes and the movable pin is connected to a control valve of a direct fuel passage from a fuel supply into the space of a main nozzle.

Some of the above-mentioned drawbacks may be obviated by a carburettor for a motorcycle according to the invention, the principle of which resides in the fact that a head of a movable pin protrudes into a slide valve chamber. The movable pin is connected to a control valve of a direct passage of fuel from a tank into a float chamber. A carburettor according to the invention may be provided with an extremely small float chamber, as an auxiliary direct fuel inlet directed either into the float chamber or advantageously directed into the space of the main nozzle, which by-passes a control valve, thereby securing a constant level height in the carburettor. The rate of flow of a direct supply of fuel into the float chamber must always be lower than the rate of fuel consumption on opening of the direct inlet. That is why a limiting nozzle is arranged in the direct inlet.A control of the level height depends upon the float being connected to the control valve. An auxiliary passage controlled by a pin according to the movements of the slide valve may be replaced also by an auxiliary supply with a valve or flap controlled directly in dependence upon movements of a gas handle.

The carburettor according to the invention may be applied to single-cylinder engines and multi-cylinder ones, and to carburettors with one float chamber and more than one, and it answers for situating a control valve in the cover or in the lower part of the float chamber. The opening of the direct inlet of fuel into the float chamber may be instantaneous at a determined opening of the slide valve, or the control may be continuous by a special adaptation of the entering surface of the slide valve. The mechanism for a direct supply is usually connected to one main fuel inlet from the tank, which is branched to a branch to the control valve or it may be arranged so that there is a separate supply to both systems, eventually from two separate tanks with two fuels having different characteristics. The apparatus is simple, production costs are low and the function is absolutely reliable.As to the design, it may be arranged even inside the embodiment of the carburettor.

In order that the invention may be clearly understood and readily carried into effect, a preferred embodiment thereof is, by way of example, hereinafter described and illustrated in the accompanying diagrammatic drawings in which: Figure 1 shows a carburettor in section with a partially opened air slide valve; Figure 2 is a similar view as Figure 1 with the air slide valve fully opened.

Referring to the drawings, a carburettor comprises a Venturi tube 1, which is controlled by a movable air slide valve 2, to which a control needle 3 is connected. Another part of the carburettor is represented by a float chamber 4, in which a float 5 is situated, which controls a float valve 6 controlling the fuel supply. A direct fuel passage from the supply piping 7 from a tank (not shown) into the float chamber 4 is performed by means of a hose 8. Afuel supply into the space of the main nozzle 9 is controlled by a control valve 10, which is represented by a movable pin 11, the head 12 of which protrudes into the space of a slide valve chamber.

The rate of flow of the fuel passage through a hose 13 is limited by a nozzle 14. Figure 1 shows the stage of the carburettor when the direct passage of fuel through the hose 13 is closed by means ofthe control valve 10 being held down by a spring 15. Fuel flows to the float valve 6, which keeps a constant level in the carburettor by means of a float floating on the fuel. Figure 2 shows the carburettor fully opened, when the air slide valve 2 disengages the head 12 of the movable pin 11. Fuel flows into the space of the main nozzle 9 both through the hose 13 and nozzle 14 and then again through thefloatvalve 6; the float 5 keeps a constant fuel level height. To allow this condition, the fuel supply through the nozzle 14 must be at a lower rate than the fuel discharge through the main nozzle 16.

The carburettor described above is especially suitable for a motorcycle and alcohol fuel, but it is also applicable to other engines and petrol or other liquid fuels.

Claims (4)

1. A carburettor for a motorcycle or other vehicle, preferably for use with alcohol fuel, comprising a Venturi tube controlled by a movable air slide valve being movable together with a control needle controlling the fuel passage, and a float chamber with a float and valve controlling the height of the fuel level in the carburettor, wherein there is provided a slide valve chamber into which a head of a movable pin protrudes and the movable pin is connected to a control valve of a direct fuel passage from a fuel supply into the space of a main nozzle.

2. A carburettor as claimed in Claim 1, wherein the control valve is the head of the movable pin.

3. A carburettor as claimed in Claim 1 or Claim 2, wherein the control valve is closed by spring means acting on the head of the movable pin, and is opened by the air slide valve causing movement of the pin to disengage the head of the pin.

4. A carburettorfor a motorcycle or other vehicle substantially as herein before described with reference to and as shown in the accompanying drawings.