Patent Application
20080202629
The invention concerns a process for filling a high pressure gas container and a device for filling a high pressure gas container, in particular a gas container for airbag systems.
For cold filling pressure containers, according to DE 101 07 895 a gas is cooled before its introduction into a pressure container, wherein on completion of the filling process the pressure container is sealed in a pressure-tight manner. As the gas warms up the pressure in the pressure container rises rapidly.
According to DE 198 17 324 a fuel gas is filled into a light weight tank made with a liner of chrome nickel steel inside of a fibre reinforced shell, wherein the fuel is introduced in deep cooled liquid form and is stored at a pressure above 300 bar.
According to WO 2005/043033 a pressure vessel, for example of an airbag system, is filled with a gas or a gas mixture at a temperature which is higher than the boiling point thereof, closing the cold vessel and a pressure is produced in the filled and closed vessel by heating it to ambient temperatures.
According to WO 2005/059431 a pressure container is filled with a gas mixture, wherein a gas mixture is introduced in its gaseous state or in its liquefied state or at least one gas component of a gas mixture is introduced in its gaseous state or in its liquefied state in a cooled pressure gas container.
U.S. Pat. No. 1,414,359 discloses a process for filling compressed gas containers, wherein a given quantity of liquefied gas is placed in a vessel of low specific heat capacity that is suspended within the container, the container is closed, and the walls of the container are maintained at a temperature above 0° C. until the enclosed substance has been converted into gaseous form.
DE 101 19 115 discloses a pressure container particularly suited for filling with low boiling permanent gases or gas mixtures at low temperatures which is provided on its inner surface with a material having a low heat conducting coefficient.
EP 0 033 3 86 discloses a process for transporting and storing permanent gases, in particular hydrogen, under pressure in pressure containers, wherein the gases are cooled to low temperatures above their boiling point and are transported and stored in isolated pressure containers.
It is known, that airbags in vehicles are increasingly using new types of gas generators, which in the event of an accident inflate the airbag within a few milliseconds. High pressure gas storage systems are used as gas generators.
Three different types of gas generators are currently in use:
The gas generators, which are filled with various gases at ambient temperatures, provide for considerable technical problems, both in terms of their production and their filling with pressures of up to 700 bar or above. The heat of compression in particular during a rapid filling leads to undefined temperature conditions which usually considerably affect the metering precision with which the amount of gas is introduced into the gas containers. To meet a high metering standard is important with respect to the subsequent inflation characteristics of the airbag. Very expensive and complex piston or diaphragm compressors are required to generate the very high pressures. This entails high investment and high maintenance costs. In addition, a correspondingly complex and expensive downstream gas supply is required for these pressures.
The known cold filling techniques avoid the problem originating from the filling of high pressures, however, these techniques usually work at extremely low temperatures which makes multiple adaptations of conventional process steps, such as the sealing of the gas container, to the low temperature conditions necessary, which is not desirable with respect investment and maintenance costs.
An object of the present invention is to provide for a process respectively a device for filling a high pressure gas container with pressures up to 1000 bar or above which is efficient, reliable and reproducible yet economical and quick and allows for a precise metering of the amount of gas that is introduced into the container.
This and other problems are solved according to the invention by the process respectively device for filling a high pressure gas container as defined in the claims below. Further advantageous embodiments and developments which can be employed individually or in any suitable combination are also provided.
According to the invention a process for filling a high pressure gas container comprises the following steps:
The first gas may be liquefied cryogenically or may be solidified cryogenically meaning that the phase transition from the gaseous state to the liquefied respectively solidified state is performed through cooling of the first gas.
The determination and the control of the amount of gas that is filled into the gas container may be performed manometrically, volumetrically gravimetrically, and/or by opening time of a valve.
The high pressure gas container is in particular for airbag systems.
The first gas and/or the second gas may be an inert gas, in particular a noble gas. Gases used in connection with airbag systems may be argon, oxygen, nitrogen, hydrogen, helium, dinitrogen monoxide (N2O) as pure gases or mixtures thereof. Advantageously, the first gas may be argon, the second gas may be helium.
The high pressure gas container may also be used in connection with fuel cells for storing fuel gases such as hydrogen.
The boiling temperature of the first gas is in particular lower than the boiling temperature of the second gas.
The ratio of the gas particles density of the first gas to the gas particles density of the second gas in the filled gas container may range from 1:1 to 100:1, in particular from 5:1 to 10:1.
The first gas may be a pure gas or a mixture of gases. The second gas may be a pure gas or a mixture of gases.
The first gas is supplied into the gas container at low temperatures, in particular below 200° K, in particular below 100° K. As the first gas is liquefied or solidified, only small amounts of compression heat is generated during the introducing step of the first gas into the gas container such that the degree of efficiency of the filling process is increased. As much less compression heat is generated, the temperature conditions of the filling process are much better defined. Consequently, the amount of the gases supplied respectively introduced into the gas container may be metered much more precisely.
The liquefied first gas may be introduced into the gas container by completely immersing the gas container into a bath of liquefied first gas such that the first gas enters the gas container. For this purpose, prior to immersing the gas container, the gas container may be precooled in a separate cooling bath, such as a cooling bath of liquid nitrogen.
Due to the cooling of the gas container the temperature of the gas container as well as the temperature of the gas content inside of the gas container is well-defined. A tight control of the temperature allows for precise controlling the amount of gas supplied into the gas container.
After supplying the first gas into the gas container and before introducing the second gas into the gas container, the cooling of the gas container may be stopped or at least interrupted. Between the supplying step and the introducing step the gas container may be transported from a supplying unit for supplying the first gas to an introducing unit for introducing the second gas. The heat capacity of the gas container as well as of the first gas supplied into the gas containers helps to stabilize the temperature of and in the gas container and the second gas may be introduced at comparatively low pressures, in particular below 200 bars, advantageously below 100 bars, eventhough it may be introduced at a ambient temperatures. A precise metering of the amount of gases filled into the gas container is facilitated.
By this provision it is possible to use conventional introducing units that are designed for comparatively low pressures in particular below 200 bar, advantageously below 100 bars, without them being adapted to operate at extremely low temperatures such as below 100° K.
In a specific embodiment the second gas may be precooled before being introduced into the gas container. The temperature of the second gas may be about the temperature of the first gas, in particular may be below 200° K, in particular below 100° K.
After the introducing step of the second gas into the gas container, the gas container is closed. The closing may be performed using a membrane valve and/or may be performed by welding.
After closing the gas container, it may be warmed up to ambient temperature, such that a high pressure builds up within the gas container. The pressure within the gas container at 15° C. may be in the range from 250 bar to 1300 bar, in particular in the range from 500 bar to 800 bar.
The cooling of the gas container may be performed in a cooling bath, in particular a cooling bath of liquid nitrogen, and a cooling may be stopped by disconnecting the gas container from the cooling bath. The gas container may be completely immersed in a cooling bath containing the first gas. The gas container may also be precooled prior to the supplying step of the first gas. With help of the cooling bath the temperature of the gas container is tightly controlled.
The process allows for tight metering control also in cases of batching the filling processes for a multitude of gas containers. This is important as the final pressure strongly influences the operating characteristics of the filled gas container in its use.
The cooling bath may be kept under a pressure other than ambient pressure, in particular above ambient pressure, such as in the range from 1.4 bar to 50 bar, in particular from 2 bar to 10 bar, in order to provide for a desired temperature in the cooling bath. For this purpose a third gas which is liquefied may be used as cooling medium in the cooling bath.
After the supplying step of the first gas and before the introducing step of the second gas the gas container may be temporarily closed. A temporal closing of the gas container may facilitate the transport of the gas container from the supplying unit, which supplies the first gas into the gas container, to the introducing unit, which introduces the second gas into the gas container. The temporal closing of the gas container helps to avoid or at least reduce evaporation losses and helps to increase the metering precision.
The gas container may be temporarily closed using an auxiliary valve. The auxiliary valve may be a ball cock, a ball valve, a bibcock, a butterfly valve, a gate valve, a globe valve, check valve, a rotary valve, a piston valve or any other valve that is able to temporarily close the gas container suitably.
The final respectively permanent closing of the gas container may be performed by welding.
The first gas and/or the second gas may be a mixture of pure gases. The gas containers may be adapted and destined for use in airbag systems. The gas container may also be adapted and destined for use in fuel cells.
The supplying of the first gas may be performed at a pressure in the range from 0.2 bar to 15 bar, in particular in the range from 0.5 bar to 4 bar.
The supplying of the second gas is performed at a pressure in the range from 2 bar to 100 bar, in particular in the range from 5 bar to 50 bar for example in the range from 10 bar to 20 bar.
The pressure values are meant to be absolute and not with respect to ambient pressure.
In a special embodiment of the invention the first gas may be supplied in a liquid state into the gas container and solidifies in the gas container. For this purpose the gas container respectively the first gas needs to be colder than the freezing temperature of the second gas.
The first gas may be supplied at a temperature lower than its boiling temperature, in particular at least 1° K, preferably at least 2° K, lower than its boiling temperature, and at a temperature higher than its freezing temperature, in particular at least 1° K, preferably at least 2° K, higher than its freezing temperature.
After the supplying step of the first gas and before the introducing step of the second gas, the gas container may be connected to a sealing device, in particular a welding apparatus, and after the introducing step of the second gas the gas container is sealed by the sealing device, in particular by welding.
The described two-step process provides for more freedom with respect to organizing the individual process steps. In particular comparatively simple devices, in particular conventional sealing devices or introducing units for introducing the second gas, that are not adapted to high pressure or low temperature appliances, may be used. In consequence complexity of the filling process as well as investments and development cost are considerably reduced. Due to the two-step structure the cold filling technique may still be combined with the conventional sealing technology known from high temperature filling without the need of complex adaptation of the conventional devices to the cold temperature environment. On the other hand the advantages of the cold filling process with respect to its metering precision and its high thermodynamic efficiency may still be enjoyed as eventhough the sealing device may operate at ambient temperature, the gas containers may remain at low temperatures. The pressures involved in the gas container during the filling process may thus be kept well below 250 bar, in particular well below 100 bar.
The cooling of the gas container may be performed using a liquefied third gas in particular liquid nitrogen, wherein in particular the temperature of the third gas is controlled by controlling the pressure in the third gas. The gas container may be cooled before the supplying step of the first gas. In particular the gas container may be precooled in the cooling bath prior to the supplying step of the first gas.
According to the invention, the device for filling high pressure gas containers comprises:
The device is in particular adapted for carrying out the process according to the invention. The device is in particular destined for carrying out the process according to the invention. The introducing unit may be at a separate location of the supplying unit and may be displaced therefrom. In particular the stopping unit transports the gas container from the supplying unit to the introducing unit. The stopping unit may disconnect the gas container from a cooling unit for cooling the gas container. The cooling unit may be a cooling bath in which the gas container is at least partially immersed. The unit for closing the gas container may comprise a welding apparatus.
The device may further comprise a transport mechanism for transporting the gas containers through the cooling bath. Advantageously the transport mechanism at least partially immerses the gas container before the gas containers are connected to the supplying unit, transports the gas container to the supplying unit where the gas container are filled with the first gas and transports the gas containers from the supplying unit to the introducing unit, where the gas container are connected with the introducing unit and are filled with the second gas. Advantageously the transport mechanism transports the gas containers from the introducing unit to the unit for closing the gas container. The unit for closing the gas container may be a welding apparatus. The stopping unit may be provided as being part of the transport mechanism.
The device may be for filling high pressure gas containers for airbag systems or for fuel cells.
The device may further comprise a gas supply station and at least one thermally isolated filling tube with a tube head that is in fluid connection with the gas supply station, wherein the filling tube is for supplying the first gas to the gas containers. The tube head is moveable and may be positioned by a positioning device. The filling tube is flexible and helps to establish the connection between the gas container and the gas supply station. The flexible filling tube is particularly advantageous when a multiplicity of gas containers need to be filled and a fast connecting of the gas container with the gas supply station is desired.
Further details and favourable aspects, which may be applied alone or may be combined in any suitable manner, will be explained with respect to the following drawings, which shall not restrict the scope of the present invention but shall schematically and exemplarily illustrate the invention.
In the following, further aspects, which are related to the present invention, are described. These individual aspects may be employed individually and separately or in any suitable combination with each other respectively one another:
An advantageous process for filling high pressure gas containers 1 comprises the steps: Supplying a liquefied or solidified first gas 2 from a gas supply station 13 through a thermally insulated filling tube 14 with a movable tube head 15 to the high pressure gas container 1. During the supplying step of the first gas 2, the gas container 1 may be cooled, in particular by a cooling bath 4. The filling tube 14 is in particular cooled at least partially along its length, in particular by the cooling bath 4. The filling tube 14 may be filled using a two step filling process, in which after the supplying step of the first gas 2, a gaseous second gas 3, in particular Helium, is introduced into the gas container 1, wherein in particular during the supplying step of the first gas 2, the gas container 1 is cooled, in particular by a cooling bath 4, and before or during the introducing step of the second gas 3 the cooling of the gas container 1 is stopped, in particular the gas container 1 is taken out of the cooling bath 4. Advantageously high pressure gas containers 1 for air bag systems or for fuel cells are filled. The first gas 2 and/or the second gas 3 may be a mixture of gases.
An advantageous process of batch filling of high pressure gas containers 1 with gas, comprises the step cooling multiple gas containers 1 in parallel, which are filled sequentially using the process according to the invention.
An advantageous arrangement for filling high pressure gas containers 1 with gas comprises a gas supply station 13 and multiple high pressure gas containers 1, wherein the gas supply station 13 comprises at least one thermally insulated filling tube 14 with a movable tube head 15 for gas filling of the gas containers 1, wherein the arrangement may comprise a positioning device 16 for moving the tube head 15 to the individual gas containers 1. Advantageously, a metering valve 17 for controlling a gas flow through the filling tube 14 may be provided in the tube head 15. The gas supply station 13 may comprise a cooling bath 4 for cooling the gas containers 1, wherein the filling tube 14 may be at least partially immersed in the cooling bath 4 and wherein the arrangement may further comprise a transport mechanism 12 for transporting the gas containers 1 through the cooling bath 4. In a useful embodiment, the filling tube 14 may be at least doubled walled and may comprise an insulation vacuum for thermal insulation. The filling tube 14 may be actively cooled by a cooling medium, in particular a liquefied third gas 6 and/or may comprise a gas channel 18 and a tubular heat shield 19 at least partially around the gas channel 18, wherein the heat shield 19 is cooled by the cooling medium. Tube head 15 may comprise an auxiliary valve 5 for temporarily closing the gas container 1. The gas filling tube 14 is in particular for filling a liquefied first gas 2 into the gas containers 1. The gas supply station 13 may comprise a first container 21 for a liquefied first gas 2. The gas supply station 13 may advantageously comprise an introducing unit 9 for introducing a gaseous second gas 3 into the gas container 1. The gas supply station 13 may comprise a second container 22 for a liquefied second gas 3, wherein the gas supply station 13 may comprise an evaporator 25 for converting the liquefied second gas 3 into its gaseous state. The gas supply station 13 may comprise a third container 23 for a liquefied third gas 6 as cooling medium.
An advantageous gas supply station 13 for filling high pressure gas containers 1 with gas is adapted and in particular destined for use in the arrangement according to the invention.
An advantageous high pressure gas container 1 with a container body 26 for storing gas and at least one first valve 27 for discharging the stored gas, is characterized by further comprising an auxiliary valve 5 for introducing the gas into the container body 26 and for temporarily closing the container body 26 until the container body 26 is sealed permanently, wherein the first valve 27 and the auxiliary valve 5 are in fluid connection with the container body 26, wherein in particular the first valve 27 and the auxiliary valve 5 may be connected to the container body 26 with separate fluid connection lines 28, 29, or, wherein in particular the first valve 27 and the auxiliary valve 5 may be connected to the container body 26 in a fluid series connection 30. The first valve 27 may be non-reversibly openable. Alternatively, the auxiliary valve 5 may be reversibly openable and closable. A sealing portion 31 may be provided at the auxiliary valve 5 for permanently closing the auxiliary valve 5, wherein in particular the sealing portion 31 may be provided in the fluid connection between the auxiliary valve 5 and the container body 26, or, wherein in particular the auxiliary valve 5 may be provided in the fluid interconnection between the sealing portion 31 and the container body 26. The auxiliary valve 5 may be one of the following valves: a ball cock, a ball valve, a bibcock, a butterfly valve, a gate valve, a globe valve, a check valve, a rotary valve, or a piston valve. The first valve 27 may in particular be a membrane valve. Advantageously, the high pressure gas container 1 may be adapted and/or destined for an air bag system, or, the high pressure gas container 1 may be adapted and/or destined for a fuel cell.
An advantageous process for filling a high pressure gas container 1 having a container body 26 for storing gas, at least one first valve 27 for discharging the stored gas and an auxiliary valve 5, wherein the first valve 27 and the auxiliary valve 5 are in fluid connection with the container body 26, comprises the following steps: The gas is introduced into the container body 26 through the auxiliary valve 5; the auxiliary valve 5 is at least temporarily closed; the auxiliary valve 5 is sealed permanently, wherein in particular the auxiliary valve 5 may be sealed by welding. The auxiliary valve 5 may also or instead be sealed by the first valve 27. Prior to filling the container body 26 with gas, the first valve 27 may be provided and may be configured at the gas container 1.
The invention concerns a process respectively a device for filling a high pressure gas container 1, comprising the following steps: Supplying a liquefied or solidified first gas 2 into a gas container 1 while the gas container 1 is being cooled; stopping the cooling of the gas container 1 after the supplying step of the first gas; then introducing a gaseous second gas 3 into the gas container 1 and closing the gas container 1. The invention allows for a efficient, reproducible, reliable and economical filling of high pressure gas containers 1, in particular for airbag systems or for fuel cells, and allows to use conventional devices for introducing gases respectively closing gas containers that are not particularly adapted for low temperature respectively high pressure applications.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 019 413.3 | Apr 2005 | DE | national |
| 0552500 | Aug 2005 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2006/000713 | 1/27/2006 | WO | 00 | 5/7/2008 |
