CA2000370A1

CA2000370A1 - Gas generator especially for inflating a safety bag

Info

Publication number: CA2000370A1
Application number: CA002000370A
Authority: CA
Inventors: Bernd Werner; Harald Voggenreiter
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-10-13
Filing date: 1989-10-10
Publication date: 1990-04-13
Also published as: KR900006181A; DE3834892C1; EP0363560A3; US4998750A; EP0363560A2; JPH02169346A

Abstract

TITLE OF THE INVENTION GAS GENERATOR ESPECIALLY FOR INFLATING A SAFETY BAG A gas generator has a gas generating combustion chamber with an igniter or fuse for igniting an ignitable charge needed for the gas generation. At least one filter housing is attached to the gas generating chamber. The generated pressurized gases enter into the filter housing in one direction, for example an axial direction, and pass out of the filter in another direction, for example in a radial direction, under the influence of a gas flow distribution member which makes sure that the filter volume is efficiently used by uniformly distributing the gas volume throughout the filter volume. The gas exiting from the filter housing inflates a safety bag for the protection of persons in a vehicle.

Description

The invention relates to a gas generator for inflating a safety bag, for example, in a motor vehicle for protecting persons in the vehicle against injury resulting from impacts.

BACKGROUND INFORMATION

Gas generators of the above type are known in the art.
These generators have a gas generating chamber including `~ an igniter for a combustion charge and at least one filter housing. The generated compressed gases must pass through the filter volume before they pass through an exit for use in a safety device for the protection of persons in a vehicle, such as inflating a safety bag. U. S. Patent 3,868,125 describes a gas generator which includes deflection , sheet metal elements to permit air to flow radially into the gas generator for mixing with the generated compressed gas for filling and inflating a safety bag, whereby the mixed gas flows axially out of the gas generator. However, the filtering of the generated gas and of the mixed gas poses a problem in that the entire filtering volume is not uniform-ly exposed to the gas flow to be filtered.
.

OBJECTS OF THE INVENTION

, In view of the foregoing it is the aim of the invention to achieve the following objects singly or in combination:
..

:', ~
, .

: : . . :

'` :, ' ~ ' ' '` .' ' '' 1 to construct a gas genexator with its filtering device in such a way that the gas to be filtered is distri-buted as uniformly as possible so that the entire filter volume is uniformly and homogeneously used for the filtering to thereby efficiently use the available filter volume;

to use a flow distribution member which assures the ~- homogeneous distribution of the gas stream throughout the filter volume for a more efficient filtering and filter utilization;
and ., ''~.:
to combine an efficient filtering with a still suf-ficiently rapid inflation of the safety bag.
; ,. . .
, SUMMARY OF THE INVENTION

The above objects have been achieved by the combination of i~ the following features according to the invention. A ring filter body or cartridge is arranged in a filter housing to receive gas to be filtered in one direction and to discharge ~' filtered gas in another direction. For this purpose a gas discharge surface of the ring filter body or cartridge faces respective openings in the filter housing. A gas flow distri-bution member is arranged centrally in the ring filter body or cartridge and diverts an initial gas in-flow into a filtered - gas out-flow directed approximately perpendicularly to an in-~, flow direction. The gas flow distribution member causes a turbulence in the gas in-flow thereby uniformly distributing the gas in-flow onto the entire ring filter cartridge volume. -., : . ...

P~70 1 For example, an axial gas in-flow is converted into a turbulent radial flow. The gas flow distribution member comprises a plurality of flow throttling and deflecting elements extending radially and substantially across the axial initial flow direc-tion of the in-flowing gas. The flow throttling and deflecting elements are axially spaced from each other and have a diameter which preferably increases in the axial gas flow direction.
Thus, the deflecting element closest to an axial gas inlet has the smallest diameter or surface area while the deflection element furthest away from the axial gas inlet has the largest diameter or cross-sectional area.

, :.' The most important advantage of the features set forth above `~ is seen in the homogeneous distribution of the gas flow to be :
; flltered over the available filter cartridge volume, thereby achieving an efficient filter utilization.
. . :
, BRIEF DESCRIPTION OF THE DRAWINGS

' In order that the invention may be clearly understood, it will .
now be described, by way of example, with reference to the ac-companying drawings, wherein:
"~ .
Fig. 1 shows a perspective view of a gas generator according to the invention, for example, made ` of sheet metal;

-~ Fig. 2 illustra*es one embodiment of a filter con-struction according to the invention; and .. ~ . :, ~ 4 ~

.:. . : , - . ~ . :

- . , :: . . .: .:. : .
~: , : . . . :, : : :
::
,~ . ~ ~ ' : . , :

~ 7 ~
1 Fig. 3 illustrates another embodiment of a filter construction according to the invention.

DETAILED DESCRIPTION OF PREFERRED EXA~PLE EMBODIMENTS AND OF
THE BEST MODE OF THE INVENTION

Fig. 1 shows a gas generator 1 having a substantially cylin-drical configuration including a sheet metal combustion cham-ber 10 with a closure section 10a and an ignition device 14.
These components are conventional, and hence not described in further detail. A filter housing 3 with gas outlet slots 4 and an integrated closure cover 15, is sff~d to each end of the co~s-;' tion chamber 10, 10a. The invention is not limited to secur-ing the filter housings 3 to the facing ends of the combus-tion chamber. It is possible to connect the filter housings 3 to the combustion chamber in any conventional way as long as the gas generated in the combustion chamber can enter into the filter housings 3~ The filter housings 3 are connected via a reaction . , .
can conventionally to a safety bag so that the latter can be inflated by the gas generated in the combustion chamber 10 ~; and filtered in the filter housings 3.
.. . . .
~ 20 Fig. 2 shows an axial sectional view through the left-hand end of the combustion chamber 10 and the respective filter housings 3. The sheet metal wall of the combustion chamber 10 may simultaneously form the filter housing 3 and the end cover 15 may be formed as an integrated or a removable and securable cover 15 for closing and opening the filter cavity 2 for the insertion of a filter cartridge 5 with the gas flow distribution mem-- ber 6 extending coaxially with the longitudinal axis 11 of''' "

, .:. :,.. : .. , , , , . . .. : .: .. ..... . :. ,: . .... ,: .. ,.. ,.:, .. , :. . . ., ::,.. .. . : . ., n~
1 he gas genera~or. The longitudinal slots 4 of the filter housings 3 extend in parallel to the longitudinal axis 11. The slots 4 through which the filtered gas exits into the safety bag as indicated by arrows 13, are cut into the sheet metal housings 3.

Gas generated in the chamber 10 passes through openings or nozzles lOa in an end wall 8' of the combustion chamber 10.
The generated gas indicated by the arrows 12 is caused to first flow radially inwardly in a chamber lOb formed between the end wall 8' of the combustion chamber 10 and a separation wall 8" between the filter and the combustion chamber. The separa-tion wall 8" has exit openings or nozzles 8a which are located radially inwardly relative to the nozzles or openings lOa to cause the above mentioned initial radially inwardly directed flow of the gas 12. The gas exits through the nozzles 8a sub-stantially in a direction parallel to the longitudinal axis ;~ 11 for distribution by the gas flow distribution member 6 ..
~,-` in such a way that the gas flow becomes turbulent and is caused to exit radially outwardly through the volume of the filter `` 20 cartridge 5.
, , . ~, . . .
The gas flow distribution member 6 has preferably a ~onical shape so that its tip 9 faces in the direction opposite to :~
the in-flowmg gas indicated by the anxws 12a. The gas flcw distribution m3~r cQuld be designed with the shcwn tip 9, which is received in a respective recess in a centering m~r 9a secured, for e~le, to the partition wall 8". This tip is rather a device for better positioning of the m ~ er in the filter unit and is not really necessary for the gas flow distribution contrQl. The flow distribution m~r 6 has a central shaft 6a to which there are se~lxd a plurality of flow distribution disks 7a, 7b, 7c, an~d 7d, . . .

~s~r~r~7~
.
1 for example. These disks have a diameter which preferably diminishes in the direction opposite to the gas inflow direc-tion. Further, each disk has a tapered edge to provide for an improved turbulence of the gas which is then diverted to flow through the filter cartridge volume 5 as indicated by the arrows in Fig. 2. Further, the spacing between the indi-vidual filter disks 7a, 7b, 7c, and 7d also diminishes in the axial direction. Thus, the spacing between the largest diameter disk 7a and the next smaller diameter disk 7b is the largest spacing. The next spacing between disks 7b an~ 7c is smaller and so on.
.' ..
An improved turbulence may be achieved by surrounding the space between tw~ neighboring disks with a perforated or nonperfora ring memker as sh~wn at 7~, 7n, and so forth. mese ring m~
bers are optional and hence shown by dashed lines in Fig. 2. mese m3~x~s 7', 7" and 7n~ are cylindrical and would surround the space etween tw~
neighboring disks which are arranged in the m~nner of poppet valve disks in steps.

The spacing and disk diameters shown, for example, in Fig. 2, are not critical to the invention. Thus, it is possible to select different spacings which, for example, may be equal to one another and the distribution of the disk diameters may also differ in accordance with the desired gas flow and in accordance with the desired gas throughput. Further, the gas flow distribution member 6 does not necessarily have to have the shown conical configuration. Rather, all disks ,' ' , :

P~70 1 could have the same diameter to form a substantially cylindrical distribution member. A centering tip as shown at 9 could also be provided on the closure end near the cover 15.

In the embodiment shown, the disks 7a, 7b, 7c, and 7d form steps which contribute to causing a turbulent flow which is then diverted in the radial direction through the volume of the filter cartridge 5 which is arranged between the outer ; peripheral edges of the disks and the housings 3 so that the gas to be filtered must pass through the filter cartridge 5 and through the slots 4.

Referring to Pigs. 2 and 3, the filter body or cartridge 5 may be constructed in different ways. For example, filtering material may be formed into a package enclosed by perforated sheet material such as films, membranes, and the like. The -~ filtering material in the filter body or cartridge 5 may com-prise fiber material or steel wool type material or any other suitable material, such as large pore sponge material includ-ing foam-type sponge material having interconnected open pores or labyrinth type channels. The filtering material may also take the form of granular material, whereby the granules may ::
have aspherical configuration or tablet or pellet form. Further, the size and configuration may be uniform or random as long as the individual granules form filtering passages among one another to provide randomly distributed flow passages between the filter material packaged in an envelope or the like which is perforated to permit the gas inlet and exit.

:

" ' . ' Z'?i~g~7~

1 The gas distribution member S comprises at least one gas flow influencing element in the form of a central shaft 6a to which the above mentioned disks 7a, 7b, 7c, and 7d are attached to éxtend radially a~ shown in both Figs. 2 and 3. The per-forated gas flow influencing elements 7', 7" and 7"' may be u~d in ccmbination with the disks or these elements 7', 7" and 7"' may be used alone. The largest diameter disk 7a is so dimensioned that it fits into the cavity 2 inside the filter body or car-tridge 5. At least one, preferably two disks have a diameter fitting into the cavity 2. The length of the gas flow distri-bution member 6 is also dimensioned to properly fit into the ; cavity 2. -By providing thachcd~r lOb an ~l~nati~a or a~diti a con~l of tha gas flow from the combustion chamber 10 into the cavity 2 and - through the filter body or cartridge 5 is accomplished so that the gas flow passes more uniformly through the volume of the filter body 5 to exit through the slots 4 as indicated ; by the arrows 13.
";, :
Fig. 3 illustrates two embodiments. The upper half shows the disks 7a, 7b, 7c, and 7d as substantially the same as in Fig. 2, however, in the upper half of Fig. 3, the per-- forated ox nonperforate cylindrical gas flow influencing elements 7', 7"
and 7"' are not used. ~ ther, the disks 7a, 7b, 7c, and 7d have ~een :
., :
; replaced, as shown in the lower half of Fig. 3,by a stepped perforated or nonperforated element 17 i.e. having holes 18 therem which influ-ence the gas flow by making the gas flow turbulent and thereby .
i ~ _ 9 _ :, . . . . . . . . . .

~ 7 ~

1 uniformly distributing the gas flow for passing through the entire volume of the filter body or cartridge 5.

Fig. 3 also shows that the central shaft 6a is made of a mater-ial different from that of the disks 7a, 7b, 7c, and 7d. These disks may be made of sheet metal while the shaft 6a may be made of any other suitable material. Further, the shaft 6a in Fig. 3 rests centered between the end cover 15 and the com-bustion chamber end wall 8'. In Fig. 3 the combustion chamber end wall 8' is provided with radially outer perforations or nozzles 10a and additionally with radially inner perforations or nozzles 10c. On the other hand, the partition wall 8"
. ., which, together with the wall 8', forms the chamber 10b has only one central hole 8b through which the gas passes axially outwardly toward the gas flow distribution member 6 in the cavity 2.

Although the invention has been described with reference to specific example embodiments, it will be appreciated that it is intended to cover all modifications and equivalents , . . .

within the scope oi the appended claims.

. ' ~

.: ' .
:

; - 10 -

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A gas generator, especially for inflating a safety bag, comprising gas generating means including a combustion chamber for producing a gas for said inflating, a filter hous-ing connected to said combustion chamber, means for passing gas produced in said combustion chamber into said filter hous-ing in a first direction, ring filter means having a given filter volume and a central cavity, located in said filter housing, so that produced gas enters into said central cavity, said filter housing having a housing wall with gas exit means in said housing wall so that gas entering said cavity in said first direction must pass through said ring filter means and out through said gas exit means in a second direction, and gas flow distribution means in said cavity for substantially uniformly distributing in-flowing gas over a ring filter sur-face facing said cavity, said gas flow distribution means comprising at least one gas flow influencing element for caus-ing a turbulent gas flow which is substantially uniformly distributed onto said ring filter surface for efficiently using substantially all of said given filter volume of said ring filter means.

2. The gas generator of claim 1, wherein said gas flow influencing element comprises a plurality of disks for influenc-ing said gas flow and a central shaft, said disks being secured to said central shaft at axially spaced intervals, said shaft having a longitudinal axis coinciding with a longitudinal axis of said gas generator.

3. The gas generator of claim 2, wherein said spaced intervals have axial lengths that increase in the axial direc-tion from a gas inlet side of said filter housing toward an opposite end of said filter housing.

4. The gas generator of claim 2, wherein said disks have diameters that increase in the axial direction from a gas inlet side of said filter housing toward an opposite end of said filter housing so that all disks together form an approximately conical configuration facing with its tip in an axial direction opposite to a gas inflow direction.

5. The gas generator of claim 4, wherein said gas flow influencing element further comprises perforated rings surround-ing said intervals.

6. The gas generator of claim 1, wherein said gas flow influencing element comprises a perforated sheet material member.

7. The gas generator of claim 1, wherein said first direction extends substantially in parallel to a longitudinal central axis of said gas generator and of said filter housing, said second direction extending substantially radially to said first direction.

8. The gas generator of claim 1, wherein said gas flow distribution means have an approximately conical or stepped configuration.

9. The gas generator of claim 2, wherein said gas flow influencing disks are made of one material and said central shaft is made of another material, said disks extend-ing radially in the manner of a poppet valve disk, said disks being axially spaced from one another.

10. The gas generator of claim 9, wherein said flow influencing disks are spaced from one another at nonuniform spacings in an axial direction, and wherein said disks have diameters or cross-sections which also differ from disk to disk.

11. The gas generator of claim 10, wherein the spac-ing between the largest diameter disk and the next smaller diameter disk is the largest spacing so that the spacings and disk diameters diminish in a direction along the shaft opposite to an axial gas in-flow direction.

12. The gas generator of claim 10, wherein said flow influencing disks form steps in the axial direction, said gas flow distribution means further comprising gas throttling or flow delay means surrounding said gas flow distribution means around said spacings in accordance with said steps.

13. The gas generator of claim 12, wherein said throttling or flow delay means comprise sheet metal rings having perforations therein for causing a turbulent gas flow.

14. The gas generator of claim 1, wherein said gas flow distribution means have an approximately conical shape with a conical tip directed axially toward an axial gas in-flow.

15. The gas generator of claim 1, wherein said gas flow distribution means is received centrally in a filter cavity into which it fits with regard to its length and its diameter.

16. The gas generator of claim 15, wherein said filter cavity has a gas in-flow wall comprising gas in-flow nozzles positioned for directing in-flowing gas toward said gas flow distribution means.

17. The gas generator of claim 16, further comprising a gas exit wall as part of said combustion chamber, said gas exit wall being spaced from said gas in-flow wall to form a cooling and gas flow directing chamber between said combus-tion chamber and said filter cavity.

18. The gas generator of claim 1, wherein said ring filter means have a ring filter volume of filter material surrounding said gas flow distribution means, said volume surrounding a filter cavity with a bore sufficient to receive the largest diameter portion of said gas flow distribution means.