The present invention relates to a method for filling a pressurized gas reservoir.
The invention relates more particularly to a method for filling a pressurized gas reservoir, in particular a pressurized reservoir for a protection system of the airbag type, with a gas or a gas mixture, comprising a first step of introduction of a first fixed quantity of gas or gas mixture in the liquid state into the reservoir.
According to this filling method, one or more gases are introduced into the reservoir in the cryogenic liquid state. After the introduction of the gas in the liquid state followed possibly by the introduction of an additional gas in the gas state, the reservoir is then closed and heated (the heating can be carried out by an active heating or by stopping its cooling and allowing it to stand at ambient temperature). In this way, the gas or gas mixture is vaporized in the reservoir and thereby generates a high pressure, for example 500 bar, 700 bar or more.
Such a method is described in particular in document WO 2005/59431.
In such a method, it is very important to control the precise batching of the quantity of gas in the liquid state introduced into the reservoir. In fact, this batching conditions the operating characteristics of the filled reservoir and particularly the pressure of the gas it contains when it is at ambient temperature.
A known solution for carrying out this batching consists in accurately measuring the quantity of gas introduced into the reservoir, for example by pressure gauge or flow detection means. Another solution consists in accurately measuring the volume of liquid introduced by using a buffer tank between the liquid source and the reservoir to be filled. The buffer tank has volume characteristics that serve to control the volume of gas delivered to the reservoir to be filled.
However, these methods are relatively complex, costly and difficult to implement industrially on a large scale, particularly at high production rates.
Furthermore, in the case in which the reservoir is not closed immediately after the introduction of the gas in the liquid state and must undergo an additional operation (for example, the introduction of an additional gas or gas mixture), there is a risk that a part of the liquefied gas will evaporate and escape from the reservoir. These potential leaks may also occur when the reservoir is conveyed to a welding machine for hermetically sealing it. The dispersions thus created alter the characteristics of the final reservoir.
It is an object of the present invention to overcome all or part of the drawbacks of the prior art described above.
For this purpose, the method for filling a pressurized gas reservoir according to the invention, which also conforms to the generic definition given in the above introduction, is essentially characterized in that the first introduction step comprises a step of intermediate introduction of an intermediate quantity of gas or gas mixture in the liquid state in the reservoir, the intermediate quantity being higher than the first quantity, and a step of withdrawal of a part of the gas in the liquid state from the reservoir in excess of the first quantity, in order to batch the first quantity of gas in the liquid state in the reservoir.
Moreover, the invention may comprise one or more of the following features:
Other features and advantages will appear on a reading of the description below, provided with reference to the figures appended hereto in which:
An example of the filling of the reservoir 1 with an argon/helium gas mixture will now be described with reference to
To introduce a first fixed quantity Q1 of liquid argon into the reservoir 1, a first step A (
The first step A may consist in immersing the reservoir 1, for example completely, in a bath 3 of liquefied cryogenic argon (LAr, temperature of −186° C. or lower). This means that the empty reservoir 1 is open at the level of at least one orifice 4 and is immersed in the bath 3 of liquid argon so that the argon penetrates into its internal volume. Preferably, the reservoir 1 may be completely filled with liquid argon.
Advantageously, the reservoir 1 may be precooled before being immersed into the bath 3 of liquid argon. For example, and as described in greater detail below with reference to
As a variant or in combination, it is possible for the bath 3 of liquid argon to be maintained at a temperature lower than the boiling point of liquid argon (lower than −186° C.). For example, the bath 3 of liquid argon may be cooled by a second colder external bath (liquid nitrogen for example).
After its filling in the argon bath 3 (quantity Q3), the reservoir 1 is withdrawn from the argon bath 3 and may be the subject of other handlings/operations or may be allowed to stand at ambient temperature (or at least at warmer temperatures than those of the bath 3). Thus, between the times to just after the withdrawal from the bath 3 and a later time t1, a quantity of liquid argon may evaporate from the internal volume of the reservoir 1 (
After the handlings and/or a waiting period (between to and t1,
The withdrawal of excess liquid argon can be carried out, for example, by sucking liquid argon from the reservoir 1. For example, and as shown in
After suction (time t3,
Preferably, the quantities Q1 of liquid argon and helium Q2 filled in the reservoir 1 are selected in order to form a gas mixture in the reservoir 1 at ambient temperature (for example 15° C.) with the following proportions by volume: argon 97% and helium 3%.
Obviously, the invention may apply to any other type of gas or gas mixture (argon, helium, CO2, N2, N2O, H2, O2 . . . ) with all possible relative proportions.
To carry out the filling of reservoirs on an industrial scale, all or part of the steps described above are preferably carried out simultaneously and/or in succession on a plurality of reservoirs 1. For example, a set of eight to twelve reservoirs 1 is placed on a common support 9 (cf.
By referring now to
In such a non-limiting configuration, the reservoirs 1 may thus reside in the bath 10 for a duration five times longer than the duration of a loading/unloading of a support 9.
According to an advantageous feature, the means for handling the reservoirs 1 are arranged so that their components which are sensitive to low temperatures (motors, lubricated hinges, moving mechanical parts in friction, electrical parts . . . ) are relatively distant from the reservoirs 1 and from the cryogenic baths 3, 10. For example, the handling and/or treatment means for the reservoirs 1 are arranged at two distance levels relative to the low temperature portions (cold reservoirs, cryogenic baths). Thus, the handling/treatment components are arranged close to and/or in contact with the cold portions. These handling/treatment components, such as manipulator arms 12, are preferably made from stainless steel and/or low-thermal-conductivity materials (
The components 13 sensitive to low temperatures are arranged at a greater distance from the cold elements, for example by about 1.5 to 2 m. In
In this way, only the parts capable of withstanding cryogenic temperatures are exposed to these low temperatures. The parts 13 sensitive to low temperatures are beyond the limits of the risks of direct or indirect cooling caused by the cold portions.
The handling/treatment components 12 are liable to accumulate frost or ice in contact with the low temperature portions. Advantageously, defrosting zones may be provided between the immersion stations and the cryogenic baths. These defrosting zones (not shown) may, for example, comprise means for heating the handling/treatment components 12, for example by blowing.
It is therefore easy to conceive that the method according to the invention, while having a simple structure, permits an effective filling of reservoirs suitable for large scale production, particularly at high production rates.
The invention applies particularly advantageously to the filling of pressurized gas reservoirs or cylinders for airbags. Obviously, the method according to the invention may apply to any other equivalent application.
Furthermore, the invention is not limited to the embodiment described. Thus, the reservoir precooling step may be carried out by any other equivalent means (jet or flow of cryogenic liquid against the outer walls of the reservoir, for example).
Similarly, it is possible to omit this precooling step. In this case, the cooling of the reservoir 1 is carried out exclusively by the gas in the liquid state of the bath 3 (external and internal cooling by liquid argon).
Furthermore, the first quantity Q1 of gas introduced may comprise gas in the solid state (liquid/solid mixture). Similarly, the second quantity Q2 of gas in the gas state may be cooled prior to its introduction into the reservoir 1. As a variant, this second quantity Q2 of gas (optional) may consist of or comprise gas in the liquid and/or solid state. Moreover, the step A of intermediate introduction of a quantity Q3 of gas in the liquid state into the reservoir 1 may be carried out by any other equivalent known means. For example, it is possible to transfer the liquid argon to the reservoir 1 via a line supplied by a liquid argon source.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/FR06/50735 | 7/20/2006 | WO | 00 | 9/13/2010 |