DE7534704U - HIGH PERFORMANCE HOT GAS FILTERS FOR SOLID GAS GENERATORS - Google Patents

Description

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Ottobrunn, October 28th

Dr «-Ing. Arthur Prochazka

8ol2 - Ottobrunn, Röntgenstr. 24

Siegfried Wolf

8o21 - Taufkirchen, Ahornring 2o

Hot gas filter for solid gas generator

The invention relates to a filter for solid gas generators, in particular for use in Impact protection devices, which through its special construction and the use of suitable materials Use of such gas generators allows.

Safety devices in vehicles, in which to reduce or prevent the impact of vehicle occupants a gas cushion is provided on hard objects in the vehicle cabin, which in the event of an impact by means of a gas generator whose gas is generated chemically is inflated have the disadvantage, among other things, that a very hot gas permeated with solid particles is conveyed into the airbag during gas generation will.

These are mainly gas generators whose propellants are based on alkali metal and which when burned produce a large amount of metal oxides, silicates, carbon monoxide, etc. These reaction products, Depending on the fuel mixture, a solid fraction of up to 6o% arises during combustion, which is extraordinary harmful to health and would affect the to and for

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Use of azide fuels with many advantages (e.g. _a mixture of NaN + KNO,. + SiO)

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prevent, it would not be possible to filter the reaction components mentioned.

In a registration dated July 13, 1973 g ..) (^ 2S. HQV. ig; P 23 5o Iö2.2) an attempt was made to solve this problem with the arrangement of quartz wool between metal sieves. Since the mechanical loads on the relatively small filter surface due to the high gas throughput and the vibration and shock loads that are added over the years due to environmental influences, as well as the thermal loads during the action phase, the resilience of the very fragile and difficult to process | By far exceeding quartz wool, such a filter is not possible for use in a security device for years to come.

The object of the invention is now to create an arrangement or device that, according to the strict specifications a filter performance is achieved with which nuisance or damage to the vehicle occupants is avoided will.

In general, it is to be said here that such filter arrangements as are described below always then used when the highest level of cleanliness is produced chemically, i.e. in solid gas generators Gas is required, as is the case with gas generators, for example

for steering gear, centrifugal engines, control elements, etc. must be assumed.

According to the invention, the object is achieved in that one or more in the path of the gas Filter units are introduced which are constructed so that coarse and fine filter stages alternate, the desired Result.

The decisive factor here is that expansion spaces are arranged between the individual filter stages, and indeed also in ^ s individual filter stages themselves, which is achieved through the use of a specially woven material, the braid will. Another intended effect is to create dirt accumulation spaces in the filters, what by the so-called Carnot's vision dead space is reached, which are formed when the air flows through the weave. Furthermore, the fine filter part, which here is made of a stainless steel fleece exists and its mechanical strength is limited by the application of pressure, supported in this way

that its excellent filter properties come into play.

Show it

1 shows the cross section through a basic filter unit,

which shows the basic structure,

2 shows the arrangement of a filter level in a gas generator, if the filter is flown directly,

Fig. 3 the arrangement of several filter levels in a gas generator, with expansion spaces in between

are in order and the filter is not exposed to direct flow.

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The basic arrangement of the filter consists according to Fig. 1 of a level double-body weave (1) in the pre-filter space, which can have different permeability and in the cavities of which dirt is already deposited. Furthermore, the fine filter part arranged afterwards is used (2), which consists of a high-temperature-resistant stainless steel fleece that is sintered onto a carrier fabric (3) is before being applied by too large an amount Solid particles protected »This is followed by another .1 * 3 level of double-bodied weave (4), which acts as a filter unit at the same time absorbs the high mechanical load and prevents the fleece from breaking or tearing. If the fleece were to lie on a coarse fabric (5) or even on the actual outflow cross-section, the is represented by a perforated diaphragm (6), it would tear at the loads of more than 50 bar that occur. Since the weft (4) is not a fabric that can be flowed through directly, but rather the flow can only be done by deflecting the gas several times, a good support of the fine filter part is ensured. On the other hand, a large part of the flow area would be due to the direct contact of the braid on the perforated diaphragm get lost, which is caused by the ridges between the holes. Hence it is necessary to have a suitable expansion space to create what is best is achieved by using a fabric with a large mesh size (5).

In Pig = 2, the arrangement of a complete filter unit C7), as previously described, becomes in one pyrotechnic gas generator shown, e.g. for the Inflation of an air cushion system is used »In the given case, however, the arrangement can only be one Filter unit may not be sufficient, so that two or more filter units behind one another must be switched, whereby special emphasis is placed on the formation of suitable expansion spaces must so that the desired efficiency is achieved. The direction of flow of the gas on the filter also plays a role the filter performance a role, so that the pre-filter chamber must be designed to be suitable in terms of flow »

In Fig. 3 is a summary of the described Points of view shown. In the pre-filter chamber (Io) the gas is passed through a perforated ring (8) after it has previously been deflected on a baffle plate (9). This avoids direct flow. This pre-filter chamber (Io) is assigned to the filter system, as their training is essential to overall efficiency. The gas flow is now parallel to the first filter level (11), which consists of one of the previously described Basic filter units of positions (1) - (4). This is followed by the second after an expansion chamber (12) Filter level (13), which is now flown against vertically and in turn a basic unit of positions (1) - (4) represents.

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Is the second filter stage, the final filter stage, As shown in Fig. 3, the arrangement of the wide-meshed fabric (5) again takes place in front of the perforated diaphragm (6) Formation of suitable expansion spaces and enlargement of the filter surface that can be flown through.

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Claims (6)

Dr ο-Ing »Arthur * Prochazica *" '* "28.1ο. 75 8ol2 - Ottobrunn, Röntgenstr. 24 Siegfried Wolf - Taufkirchen, Ahornring 2o jsjnsprüche High-performance hot gas filter, especially for solid gas generators, from at least one basic filter unit consisting of support layers and filter layers as well as a filter antechamber and expansion chamber is composed, or several basic filter units with correspondingly arranged Expansion chambers, characterized in that the support layer or support layers contained in the base unit made of knitted fabrics with defined permeabilities, on which fine filter layers are arranged are, and in which, due to the weave, cavities suitable for filtering, like Carnot's see dead spaces be formed. 2. High-performance hot gas filter according to claim 1, characterized characterized in that the fine filter units arranged between the supporting fabrics are made of stainless steel fleece exist, which is sintered onto a carrier fabric and has a defined permeability. - 2 - »T M» t 3. Cooking performance hot gas filter according to claim 1 and 2, I characterized in that in front of the filter unit a O appropriately designed filter antechamber arranged 1 is a vertical outflow of the filter If 5 prevented. I. 4. High-performance hot gas filter according to claim 1 to 3, I- - ■ I characterized in that dctS filter system I consists of several similar basic filter units, ι are arranged between which expansion chimneys, the ^ Io a vertical and parallel flow onto the filter plane enable., 5. High-performance hot gas filter η ch claims 1-4, I characterized in that after the final stage in each * - Case a wide-meshed net or fabric for support 1 15 creating an expansion space towards the housing, j is attached, creating a maximum flow area - the filter is guaranteed. 6. High-performance hot gas filter according to claim 1 to 5, characterized in that all materials used 2o are made of low-carbon and high-alloy steels and therefore do not react with the gas flowing through them is produced.