Safety valve for a venting line in a liquid container

The present invention relates to a safety valve for the venting circuit of a liquid tank, particularly a fuel tank may be fitted to a motor vehicle.

liquid tanks, in particular fuel tanks for motor vehicles, are today generally have, among other things, an air-conditioning circuit. This circuit allows the introduction of air into the tank in case of depression (especially to compensate for the volume of liquid consumed) or evacuation of gas in the tank in case of overpressure (especially when heated). This circuit also allows the pipeline and possible filtering of gas to be released into the atmosphere in order to meet environmental requirements becoming more stringent in this regard.

The vent circuit comprises in known manner a safety valve preventing as much as possible the liquid outlet from the reservoir in case of overturning or excessive inclination of the tank. This safety valve must offer a quick and safe response when its intervention conditions occur but with minimal sensitivity to abnormal phenomena such as including very high data rates, excess pressure in the reservoir or the waves of low amplitude.

Many safety valves implement a float with an upper needle closing an access opening between the tank and the air conditioning circuit. These elements are not only possible to meet all the above requirements.

There is neck to add to them one or more resilient means of calibration, especially springs, but such units are not responding satisfactorily with requirements, especially as they fail to prevent a shutter adverse risk in conditions severe can cause the breakdown of the balance of power used, for example in case of significant pressure in the tank.

It is also known, in particular according to the patent US 3,765,435 to involve the float ball being movable on an inclined plane pierced with openings and allowing in principle to cause the float upwards and off by means a needle an upper opening of connection between the tank and the vent circuit if the tank tilt. Such a system is still very sensitive to abnormal phenomena as mentioned above.

The invention therefore aims to provide a safety valve for venting circuit of a liquid container preventing liquid from training and having a minimum sensitivity to abnormal phenomena as mentioned above.

Provided for this purpose a safety valve for the venting circuit of a liquid container preventing liquid training, comprising a chamber which opens out inside the tank under the upper wall of the -ci, and whose upper portion is connected via an orifice to the vent circuit, comprising:<ul><li>a) a needle can be closed, in the high position, the hole in the valve head;</li><li>b) a float associated with the needle and vertically slidable inside the enclosure;</li><li>c) float means for supporting and moving said float upwardly when the enclosure tilt;</li><li>d) a shaft extending the lower portion of the chamber inside the tank under the support means and float movement.</li></ul>

The safety valve is designed to vent circuit of a tank that can contain any liquid. In particular, the liquid may be a fuel, a brake fluid or a lubricant. More particularly, the liquid is a fuel. The container may be intended for any use, especially to equip a vehicle and still more particularly to equip a motor vehicle.

The enclosure may have any shape, often internally adapted to the sliding of the float. Most often, it is for the purpose of constant inner section, at least in the part where the float must be able to slide. It is in particular at least in this section, internally cylindrical.

The outer shape of the float is of course adapted to that of the interior of the enclosure where it must be movable. In particular, it is externally cylindrical.

The float is associated with the needle any conventional manner. Preferably, it is secured to the needle. The float and the needle can be produced in one piece or be produced separately and assembled. The needle can advantageously be equipped with a seal, for example an elastomeric gasket membrame, favoring the sealing of the valve in the closed position.

The orifice in the head of the valve makes it possible, when it is closed, the closing of the valve. This port may also or alternatively be equipped with a seal, for example of a type of flat sealing elastomeric membrane.

The barrel extends the lower part of the enclosure inside the tank under the support means and float movement. It allows to channel the flow of fuel and obtain the necessary sensitivity to the proper functioning of the valve. It protects the moving parts of the valve, in particular the float substantially lateral waves of large amplitude that could destabilize the delay the closure of the valve and thus causing liquid entrainment in the air conditioning circuit. The valve is thus rendered insensitive to this problem and its functioning improved significantly.

The height of the barrel can be adapted case by case according to the magnitude of abnormal phenomena to which we want to make the valve insensitive. course be taken into account also in view of this dimensioning of the precise position of the valve in the reservoir and the effects that can induce the possible proximity of other elements such as for example a wall of the tank.

The safety valve allows venting of a liquid tank as described above. He did not, as such, serves to prevent overfilling of the tank. This function must, where appropriate, be performed by an independent device or by additional means that would be associated with the valve. The characteristics of the valve, in particular the height of the drum are not dictated by the function of prohibiting overfilling.

The float means for supporting and moving said float in an enclosure inclination can be of any known type. Advantageously, they include a material dense ball movable by gravity in a perforated frustoconical cup. By perforated it is meant that several openings are made in the cup which allow liquid passage through the cup. In particular, the cup includes a frustoconical central orifice.

In case of inclination of the tank, the ball moves in the truncated cup, causes the float upward and causes the shutter by the needle of the valve of the head port before the rising liquid level in the valve avoiding completely the liquid passage in the air conditioning circuit.

In case of overturning of the tank, the dense material of ball also pushes the float to the valve closing position and maintained by gravity in that position.

In case of rise of the liquid level in the tank, this liquid enters the valve through the lower part, through the openings of the frustoconical cup causes the float upwards and also causes the shutter by the needle of the orifice in the valve head.

In a preferred embodiment, the enclosure comprises in its upper part one or more lateral apertures allowing the passage of gases. More preferably, the enclosure comprises in its upper part several lateral openings allowing the passage of gas. Advantageously, the lateral apertures are sized small dimensions to prevent the passage of significant flows of liquid, in particular by rolling. These openings may for example be made of a circuit provided with one or more baffles or labyrinth. In particular, these openings are of elongated rectangular cross section. Advantageously, these openings are at least in number of two, even more preferably at least 4. Preferably, the number does not exceed 8. The assembly of these openings is preferably a total passage cross section of at least 35 mm²Even more preferably at least 45 mm². Good results were obtained when all of these apertures represents a total passage section not exceeding 100 mm².

By gas is particularly designate the outside air to be introduced into the reservoir or the gas mixtures contained in the reservoir and evacuation must be made possible. In the case of a fuel tank, these gas mixtures consist essentially of air and fuel vapor.

By positioning at the top of the enclosure openings for the passage of gas is significantly reduced potential impacts on these openings the level of liquid and its movements, allowing the venting even in some situations criticism.

Advantageously, the float sliding inside the chamber is formed by an adjusted guide. Thus, the float can hardly move in another direction than the vertical direction. This adjusted guide may in particular be performed by suitably radial dimensioning of the two parts in contact and / or by a set of longitudinal ribs on the float and / or on the enclosure.

This embodiment improves the functioning of the valve in that, by this adjusted guidance, it appears when the liquid level rises in the enclosure, a dynamic piston effect generated by the fluid pressure and promotes the movement of the float to the top. On the contrary, when the liquid comes down, a suction effect also helps drive the float to its low position.

Preferably, when the needle is in the high position and shuts off the orifice, it defines in the upper part of the enclosure an enclosed volume. In valve closing position, closed gas-filled volume provides the advantage of avoiding a buffer liquid to reach near the vent hole and a fortiori to leave the reservoir.

In a particular embodiment, the shaft may be beveled. In this way, one can optionally selectively protect the valve against the fluid movement from a particular direction.

The components of the valve may be made of any material. Preferably, they are made based on a thermoplastic material. In this case, it is obviously necessary to choose the material or materials so that they withstand the stresses of use. The materials chosen must of course be particularly inert vis-a-vis liquids with which they are caused to be in contact, in particular vis-a-vis fuel.

The mode and valve mounting location on the tank can be selected from any conventional manner adapted to the specific conditions. Preferably, the valve is assembled directly on the upper wall of the tank.

The invention also relates to a container comprising a valve as defined above.

The invention is illustrated in a nonlimiting way by the following figures:<ul><li>1 shows a safety valve according to the invention in open position;</li><li>2 shows the same valve in the closed position.</li></ul>

According to Figure 1, the safety valve (1) for the air conditioning circuit (2) is fixed on the upper wall of the tank (3). The safety valve (1) comprises an enclosure (4) which opens out inside the tank. In the enclosure (4), a float (5), shown in the lowered position, can slide vertically for closing via a needle (6) (produced in one piece with the float) in the high position, an orifice (7) located in the valve head. To improve the sealing of the closure, the orifice (7) is provided with an elastomeric seal (8). The float (5) can be moved by the rising liquid in the valve through the perforated frustoconical cup (9) or, in case of inclination of the tank, by movement of a ball (10) of dense material in the truncated cup (9). The enclosure (4) is extended in its lower part by a shaft (11). It comprises in its upper part four lateral openings (12) of small dimensions, allowing the passage of gas but prevent the passage of significant flows of liquid.

2 illustrates the float (5) in the upper position when the needle (6) closes the orifice (7). A closed volume (13) filled with gas is defined in the upper part of the enclosure.