CA2093743A1 - Spiral wrapped gas generator filter - Google Patents

Spiral wrapped gas generator filter

Info

Publication number
CA2093743A1
CA2093743A1 CA002093743A CA2093743A CA2093743A1 CA 2093743 A1 CA2093743 A1 CA 2093743A1 CA 002093743 A CA002093743 A CA 002093743A CA 2093743 A CA2093743 A CA 2093743A CA 2093743 A1 CA2093743 A1 CA 2093743A1
Authority
CA
Canada
Prior art keywords
gas permeable
permeable support
filter
support material
layer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA002093743A
Other languages
French (fr)
Inventor
Bradley W. Smith
Linda M. Rink
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Morton International LLC
Original Assignee
Morton International LLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Morton International LLC filed Critical Morton International LLC
Publication of CA2093743A1 publication Critical patent/CA2093743A1/en
Abandoned legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/20—Other self-supporting filtering material ; Other filtering material of inorganic material, e.g. asbestos paper, metallic filtering material of non-woven wires
    • B01D39/2027—Metallic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
    • B60R21/02—Occupant safety arrangements or fittings, e.g. crash pads
    • B60R21/16—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags
    • B60R21/26—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags characterised by the inflation fluid source or means to control inflation fluid flow
    • B60R21/264—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags characterised by the inflation fluid source or means to control inflation fluid flow using instantaneous generation of gas, e.g. pyrotechnic
    • B60R21/2644—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags characterised by the inflation fluid source or means to control inflation fluid flow using instantaneous generation of gas, e.g. pyrotechnic using only solid reacting substances, e.g. pellets, powder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/20—Other self-supporting filtering material ; Other filtering material of inorganic material, e.g. asbestos paper, metallic filtering material of non-woven wires
    • B01D39/2068—Other inorganic materials, e.g. ceramics
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/0001—Making filtering elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
    • B60R21/02—Occupant safety arrangements or fittings, e.g. crash pads
    • B60R21/16—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/06—Filter cloth, e.g. knitted, woven non-woven; self-supported material
    • B01D2239/065—More than one layer present in the filtering material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/06—Filter cloth, e.g. knitted, woven non-woven; self-supported material
    • B01D2239/065—More than one layer present in the filtering material
    • B01D2239/0654—Support layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/06—Filter cloth, e.g. knitted, woven non-woven; self-supported material
    • B01D2239/069—Special geometry of layers
    • B01D2239/0695—Wound layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/12—Special parameters characterising the filtering material
    • B01D2239/1258—Permeability
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2275/00—Filter media structures for filters specially adapted for separating dispersed particles from gases or vapours
    • B01D2275/20—Shape of filtering material
    • B01D2275/206—Special forms, e.g. adapted to a certain housing
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S493/00—Manufacturing container or tube from paper; or other manufacturing from a sheet or web
    • Y10S493/941—Filter
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S55/00—Gas separation
    • Y10S55/05—Methods of making filter

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Ceramic Engineering (AREA)
  • Geometry (AREA)
  • Fluid Mechanics (AREA)
  • Air Bags (AREA)
  • Filtering Materials (AREA)

Abstract

PATENT 2125-21-00 ABSTRACT An improved method for the continuous fabrication of filter units for use in automotive air bag inflators by spirally winding a hollows cylindrical core, at least one filter layer, and an outer layer to form a continuous spirally wound filter unit. The continuous spirally wound filter unit is then cut into individual filter unit of desired length by the use of conventional cutting means.

Description

20937~3 ,. .

Field of the Inven~ion This inveQ~ion relates generally to inflatable type mo~ular occupant restraint systems fo~ passenger vehicles or, as they are ~ore commonly known, air bag restraint systems. Such a system may S be installed in an automobile or other vehicle, at least in part on the steering wheel for the protection of the driver and also in the dashhoard or passenger side nstrumen~ panel for passenger protection in the event of a collision. More particularly, this invention relates to an improved filter unit for use in passenyer side air bag restraint systems and a method for manu~acturing the filter unit.

Descri~tion of Related Art The air bag restraint system is located forward of the occupants and normally is in a deflated condition. In the event of a crash, however, the air bag is inflated in a matter of 20 to 40 millis~conds by a gas produced by the burning of a gas generant material in an inflator. Common features of such inflators that are used for the inf~ation of air bag cushion restraint system~ are the inclusion in a housing of a gas generant composition containin~
a pelletized alkali metal azide contained in a basket and a filker unit external to the basket to cool the gas positioned between the basket and gas discharge orifices, as defined by the housing. The gas generant is ignited by an igniter. The gas generant burns Lapidly usually with a temperature of about i20G C., and deveiop pressure in the housing in excess of 2000 psia. Furlher, the gas that is generated contains combustion residue including fine molten .

20937!1~

PATENT

particles of metal and/or reactant oxides. The pressure of combustion gases resulting from the rapid burning of the gas generant material causes gas to rush into the bag to effect a rapid rate of inflation thereof. The cooling and filtration of the gas to remove the fine particles for the safety and comfort o~ the passengers is of great importance.

Filter units typically available in the art include alternating layers of screen and ceramic paper. For example, Paxton et al., U.S. Patent No. 4,998,751, which patent is assigned to the assignee of the present invention, disclose a filter which includes two wraps of nickel coated carbon or stainless steel 30 mesh screen, then metal filter such as 80 x 700 or S0 x 250 mesh stainless steel or 40 x 180 mesh nickel coated carbon steel, then a single wrap of ceramic filter paper 0.080 inches thick, followed by two wraps of 30 mesh stainless steel or nic~el coated carbon steel. A wrap of 5 mesh stainl~ss steel or nickel coated carbon may be provided adjacent the wall of tubular portion to allow space around apertures therein for the free passage of generated gases.
The filter units are, typically, manufactured by rolling the different filter materials circumferentially around a mandrel similar to rolling wrapping paper circumferentially around a core.
For example, Cunningham, U.S. Patent No. 4,878,690, which patent is assigned to the assignee of the present invention, disclose a filter unit of this type of manufac~ure. The f~lter units are manufactured as single units by hand and with the aid of machine.
The geometry of the filter unit is determined by the vehicle into which the filter unit will be installed.

The individual filter elements for each filter unit are cut to 2~937~3 PATENT

size and are placed by hand on the mandrel of a automatic wrapping machine which wraps the filter and spot welds the outer layer. The - filter unit then is removed from the wrapping machine by hand and the cycle is repeated for the next filter unit. The cutting of each piece of filter material and the hand placement of each piece of filter material on the wrapping machine significantly increases the time of manufacture, cycle time, for each filter unit. This manufacturing system is incompatible with the high volume production requirements necessary to meet the demands of the automotive industry.

The consistent and economical manufacture of filter elements for passenger side gas generators which will efficiently cool and clean gas from the gas generant is of great concern. This m~st be done in light of the fact that the size of the passenger side generator, and therefore the filter element, is strongly depend~nt on the geometry of the automobile's interior and therefore varies significantly from automobile to automobile.

The use of spiral wrapping is disclosed in Merrill et al., U.S. Patent 4,101,423 for microporous layer over a porous inner layer for filtering bacteria from fluids. Shevlin, U.S. Pate~t No. 4,39B,931, discloses spiral wrapping a ~oven ceramic filter material over a rigid tubular cage for radially-inward filtration of hot industrial gases. The SAevlin invention is designed for a pressure drop of from 2 to 6 inches of water at a flow rate of 3.2 to 29.2 per minute per dm2 of filter area.

SUMMARY OF THE INVENTION
An object of this invention is to provide an improved method of manufacturing air bag inflator filter units which reduces the time required to manufacture a filter unit for a passenger side , '"~

2~93~13 PATENT

automotive air bag inflator. Further, an object of this inven~ion is to provide an improved method of manuracturing air bag inflator - filter units which reduces the set-up time require for the manufacture of such a filter unit. Another object of this S invention is to provide an improved method of manufacturing air bag inflator filter units which provides for the rapid change i~ the length of the filter unit.

These objectives have been achieved by a novel ~ilter element and a means for manufacturing the same. The filter element includes, a hollow cylindxical core open at both ends, at least one filtering layer, and an outer layer of gas permeable material which holds the filter layer in a cylindrical form about the hollow cylindrical core without the application of any external force The hollow cylindrical core is made by spirally winding a first gas permeable support material which has a first edge and a second edge. The material from which the first gas permeable support-material is made is bendable such that the material will conform to and retain the shape of the form over which it is pressed. The second edge of the first gas permeable support material is joined to the first edge of the adjacent wrap such that the hollow cylindrical core retains a cylindrical form without need for additional clamping. The second edge may overlap the adjacent first edge or the second edge may abut the first edge.

The filtering layer is spirally wound radially outward of the hollow cylindrical core. The filtering layer further comprise~ at least one layer of spirally wound filter media, such as a ceramic paper, and at least one layer of spirally ~ound second gas permeable support material such as a metal screen radlalll outward of the filter media. The second gas permeable support material 2~37~3 PATENT

having an inner surface and outer surface. The layers of filter media and gas permeable support material may contain one or more ~ layers of the respective materials. Optionally, at least one layer of a third gas permeable material, such as a coarse mesh metal S screen can be spirally wrapped radially outward o~ the hollow cylindrical core and radially inward of the filter media.

The outer layer is spirally wound radially outward of th~
filter layer and contains at least one layer of spirally wou~d fourth gas permeable support material, such as metal screen having inner and outer surfaces, a third edge and a fourth edge, and an end portion. The inner surface of the most radially outward third edge and fourth edge are joined to the outer surface of the next most radially inward layer of the fourth gas permeable support material or to the outer surface of the radially most outward second gas permeable material of the filter layer by bonding means, such that the outer layer retains the outer layer and the filter layer in a cylindrical relation about the hollow cylindrical core without further stxuctural support.
The respective layers of filter material; filter media, fir~t gas permeable support material, se~ond gas permeable support material, third gas permeable support material, and fourth gas permeable support material are spirally wound in such a way that the seam of one layer does not coincide with the seams of the other layers of filter material. The overlap of individual filter materials at the seams of adjacent wraps should be kept to a minimum such that thickness of the filter is not increased withou~
increasing the filtering capacity of the filter unit. A slight overlap is necessar~ so that no gaps are formed which permit the unfiltered flow of generated gas.

' , 20~374~

PATENT

The invention also comprises a method for continuous fabrication of filter units for use ln automotive air bag infla~or~
- comprising spirally winding a first gas permeable support material, which material is flexible, around a rotating mandrel to form a hollow cylindrical core having internal and external surface~, spirally winding at least a filter layer radially outward o~ the hollow cylindrical core, and finally spirally winding at least an outer layer radially outward of the filter layer.

The first gas permeable support material has a first edge and a second edge. The first gas permeable sheet is spirally wound such that the first edge of each wrap is a~uts the second edge of the adjacent wrap or the wrap linearly downstream of the spiral wrapping process. The first edge of the first gas permeable material is joined to th~ second edge of the first gas permeable material of the adjacent spiral wrap by means such that the hollow cylindrical core retains a cylindrical form without the application of external forces.

Next, at least one fil~er layer is spirally wound radially outward of the cylindrical core. Each filter layer compxiseg spirally winding at least one layer of filter media ha~ing a ~irst edge and a second edge and inner and outer surfaces radially outward of the cylindrical core, and spirally winding at lea~t one layer of a second gas permeable support material radially outward of the filter media. The second gas permeable support material has an inner and an outer surface and third and fourth edges.
Optionally, at least one layer of a third gas permeable support material is spirally wound radially outward of the cylindrical core and radially inwarcl of the first filter layer.

Following the last filter layer an outer layer is spirally 2~37~3 PATENT
~ 2125-21-00 wound radially outward or the filter layer. The outer layer comprises at least one layer of a fourth gas permeable support material. The fourth gas permeabLe support material having inner and outer surfaces, fifth edges and sixth edges, and an end portion. The inner surface of the fifth edge and sixth edge are joined to the next most radially inward layer of the fourth ga permeable support material or to the outer surface of the radially most outward second gas permeable support material of the filter layer by joining means such that the outer layer retains the outer layer and the filter layer in a cylindrical relation about the coxe without further structural support. Thus, a continuous spiral wound filter unlt.

Finally, the continuous spiral wound filter unit is cut transversely at intervals to form individual spiral wound filter units of the desired length.

BRIEF DESCRIPTION OF THE DRA~INGS
With this description of the invention, a detailed description follows with reference being made to the accompanying figures o~
drawing which form part of the specification, in which like parts are designated by the same reference numbers, and of which:
Fig. 1 is a front plan view illustrating the manufacturing of a spiral wrapped filter unit;

Fig. 2 is a series of view showing the individual filter elements broken out of the filter unit; and Fig. 3 is an fragmented view illustrating the placement of the ' ~, '; ~ ' 20937~

PATENT
~ 2125-21-00 filter unit in a passenger side automotive air bag inflator.

DETAILED DESCRI}?TION OF T~E INVENTION

As best seen in Fig 9 1, a method for the continuous fabrication of a passenger side air bag inflator filter is shown generally at 10. A first gas permeahle support material 12 having a first edge 14 and a second edge 16, is placed on a rotating center mandrel 13. The first edge 14 of the first gas permeable support material is joi.ned to the second edge 16 o~ the adjacent wra~. The first gas permeable support material 12 forms a hollow cylindrical core 20, as shown in Fig 2., which maintains its cylindrical shape without external clamping. Next, a layer of first filter media 22 is spirally wound radially outward o~ the first gas permeable support material 12. Next, a layer o~ second gas permeable support material 24 is spirally wound radially outward of the first filter media 22. Additional layers of filter media (not shown) and gas permeable support sheets (not shown) are added to build sufficient layers of and filter media and second gas permeable support material to produce a filter with the appropriate cooling and filtering capacity. Optionally, a third gas permeable support material 26 can be spirally wound radially outward of the first gas permeable support sheet 12 prior to the application o~
the first filter media 22. An outer layer 28 of a fourth gas permeable support material is spirally wound around the filter media and gas permeable suppoxt ma~erial and is joined by spot welds 30 or the like, so as to retain t~e shape of the continuously fabricated filter unit 32 which is manufactured. The continuous fabricated filter unit 32 is advanced along the length of the mandrel by conventional means as the several wraps are wrapped about the mandrel.

, .:

:

2~37~3 ~ATENT
- 2125-21~00 Each layer of filter material; first gas permeable support ma~erial, first filter media, second gas permeable support - material, third gas permeable support material, and fourth gas permeable support materlal, are held on to the center mandrel 18 by individual compression rollers (not shown). These compression rollers can be mounted such that the axis of the compres~ion rollers are perpendicular to the paths of the individual filter materials which they hoLd to the center mandrel 18. The compression rollers are located at the point where the respective filter materials start to wind about the center mandrel 18. The continuously fabrlcated filter is then cut to size by a rotary cutting blade 34 or the like to form individual filter units 36 of the desired length which maintain their shape without the application of external forces. The respective filtering materials are fed on to the center mandrel in such a way that the overlap of adjacent wraps is maintained at a minimum. Sufficient overlap is required such that no gaps for in the respective filter layers which would permit the unfiltered flow of generated gas.

A preferred filter unit as manufactured by the method of this invention is shown in a series of views in Fig. 2. The hollow cylindrical core 20 is shown with spot welded seams 38 which join first edge 14 and second edge 16 of adjacent wraps of first gas permeable sheet 12. The first gas permeable sheat can be made from coarse screening. More preferably the material from which the first gas permeable sheet is made is perforated sheet carbon st~el.
Stainless steel can be used, however, it is not required for good performance of the resulting filter unit. The perforations should be such that at least 25 per cent by area of the sheet is permeable to gas. More preferably the perforations should be such that from about 25 per cent to about 65 per cent of the sheet is permeable to gas in order to allow for the rapid dispersion of gas through the .
:: . ' `:

2~7~3 ~ATENT
~ 2125-21 00 filter unit.

- The hollow cylindrical core 22 is spirally wrapped with an optional third gas permeabLe support material 26. Preferably at least two layer of third gas permeable material are used~ This gas permeable support sheets can be rnade of any suitable hlgh temperature conductive material such as metal screen made from carbon steel, nickel-plated carbon steel, stainless steel, or compressed non-woven material. Stainless steels which can be used with this invention include, but are not limited to the 300 serie~
stainless steels, i.e., 301, 304, 316, and 330. The third gas permeable support material 26 should preferably be of coarse me~h such as from about 18 to about 30 mesh (per Fed. Std. RR-W-360).
The first filter media 22 is spirally wound about the hollow cylindrical core 20 and the optional third gas permeable support sheet 26.

The first filter media and all subsequent layer~ of filter media can be any high temperature ceramic filter papers available for use in air bag inflator filters. Preferably this ceramic filter paper should be able to withstand temperatures up to about 1500 C. and a volumetric flow rate of between from about 250 to about 1870 cfm~ft2, with a permeability of between about 40 to about 200 cfm/ft2 at a pressure drop of 1/2 inches of water. Such filter medias are manufactured by Lydall of New Hampshire and Carborundum of New York.

A second gas permeable support screen 24 is spiraLly wound radially outward of the first filter media 22. The second screen 22 like the optional third gas permeable support screen 26 can be made of carbon steel or stainless steel with a mesh size from about 18 to about 30 mesh. A coarser or finer mesh screen can be used . .

- , ' 2~93~743 PATENT

depending on the amount o~ cooling and filtration required from the filter element being manufactured. ~referably, in ord~r to - support the ceramic filter media which normally is of low ten~ile strength the ceramic filter material and a layer of gas permeable support material can be combined after feeding from their respective roller and spirally wound around the center mandrel 18 simultaneously.

The preferred filter unit is further constructed using second filter media 40 and fourth gas permeable support screen 42. The second filter media 40 and fourth gas permeable support material 42 are as described herein above. Multiple layers of ceramic filt~r media and screen may be used as needed by the ultimate requirement of the filter element. A third filter media 44 and a fifth gas permeable support material 46 are included in the pre~erred embodiment of this invention as shown in Fig. 2. Also, each layer of screen and ceramic filter media may contain more than one wrap of the respective filter material. The last layer of filter screen, prior to the outer wrap should be of finer mesh, such as 24 x 110 to 45 x 170 mesh, commonly known as Dutch woven, in order to more completely cool and filter the gas. A non-woven metallic or metallic~ceramic filtex media may also be used. This is similar in nature to compressed steel wool.

2S Finally, the outer layer 28 is formed by spirally winding at least one layer of fourth gas permeable support material, the outer layer the edges of which are spot welded 30 or fused to the underlying layer of gas permaable support so as to hold the continuously fabricated filter unit 32 in cylindrical form. To spot weld the outer layer 28 third edge 48 and fourth edge 50, as shown in Fig. 1, of adjacent spiral may be overlapped sl~gh~ly~
approximately one half the length of the mesh opening, and the , . . . , , ~
' ~ .

, 20~37~3 ~ATENT

radiaLly most outward layer of third screen can then be spot welded 30. The overlapping of adjacent wraps is not preferred as this adds to the overall thickness of the filter unit 36 without adding to the filtering efficiency of the f:ilter unit 36.

The inflator 52 as shown in Fig~ 3 can be any of a number o~
known constructions, including the construction illustrated in U.S.
Patent No. 4,296,084 to Schneiter, which patent is assigned to the assignee of the present invention. The inflator 52 includes generally an outer housing 54 into which is inserted the spiral wound filter unit 36 of this invention. An inner basket 56 can than be inserted radially inward of the filter unit 36, howe~er, with this inventian such a basket may not be needed. An igniter 58 containing igniter granules and the appropriate ignition system is then inserted in to the center of the inflator 50. Gas generant 60 is then loaded in to the inflator 50 which is then sealed in a conventional manner known to those in the art.

Thus, in accordance with the invention, there has been provided an improved method for the continuous fabrication of a filter unit for use with automotive air bag inflators. There has also been provided an improve method for the fabrication of filter units for use in automotive air bags which reduces the time need to manufacture individual filter units. Additionally, there has been provided an improved method for the fabrication of filter units for use in automotive which reduces the cycle time in the manufacture of the filter units.

With this description of the invention in detail~ those skilled in the art will appreciate that modification may be made to the invention without departing from the spirit thereof.
Therefore, it is not intended that the scope of the invention be .. .

-: :;~:

~09~ 3 PP~TENT

limited to the specific embodiments that have been illustrated and describedO Rather, it is intended that the scope to the inventio~
be determined by the scope of the appended claims.
.

- . . :
. .
.

.. ..

Claims (22)

PATENT
1. A gas generator filter element comprising;

a hollow cylindrical core having first and second open ends and internal and external surfaces, comprising a spirally wound first gas permeable support material of bendable material having a first edge and a second edge, forming adjacent wraps of said first gas permeable support material, wherein said first edge of said first gas permeable support material is joined to said second edge of said first gas permeable support material of said adjacent wrap by joining means such that said hollow cylindrical core retains a cylindrical form without need for additional clamping;

at least one filter layer spirally wound radially outward of said core, wherein each filter layer comprises at least one layer of spirally wound first filter media, having an inner and outer surface, and at least one layer of spirally wound second gas permeable support material radially outward of said first filter media; and and an outer layer radially outward of said spirally wound filter layer comprising at least one layer of spirally wound third gas permeable support material forming adjacent wraps of said third gas permeable support material wherein said third gas permeable support material having inner and outer surfaces, a third edge and a fourth edge, and an end portion, wherein said third edge and said fourth edge of the most radially outward layer of said third gas permeable support material is joined to the next most radially outward gas permeable support material by joining means such that said outer PATENT

layer retains said outer layer and said filter layer in a cylindrical relation about said core without further structural support.
2. A gas generator filter element of claim 1 further comprising a fourth gas permeable support material radially outward of said hollow core and radially inward of said first filter media.
3. A gas generator filter element of claim 1 wherein said first gas permeable support material is in the form of a perforate sheet.
4. A gas generator filter element of claim 1 wherein said second gas permeable support material is screen.
5. A gas generator filter element of claim 1 wherein said third gas permeable support material is screen.
6. A gas generator filter element of claim 1 wherein said fourth gas permeable support material is screen.
7. A gas generator filter element of claim 1 wherein said core is made from a material selected from a group consisting of carbon steel and 300 series stainless steel.
8. A gas generator filter element of claim 1 wherein said second gas permeable support material is made from a material selected from a group consisting of carbon steel, nickel-plated carbon steel, and 300 series stainless steel.
9. A gas generator filter element of claim 1 wherein said second gas permeable support material is made from screen having a mesh size from about 18 to about 30 mesh.

PATENT
10. A gas generator filter element of claim 1 wherein said second gas permeable support material is made from screen having a mesh size of 45x170.
11. A gas generator filter element of claim 1 wherein said first filter media is made from a ceramic filter paper, wherein said filter paper is able to withstand temperatures up to about 1500 C.
and a volumetric flow rate of between from about 250 to about 1870 cfm/ft2, with a permeability of between about 40 to about 200 cfm/ft2 at a pressure drop of 1/2 inches of water.
12. A gas generator filter element of claim 2 comprising said hollow cylindrical core, a plurality of fourth gas permeable support materials spirally wound radially outward of said hollow cylindrical core, three filter layers spirally wound radially outward of said fourth gas permeable material, wherein each of said filter layers comprise a spirally wound first filter media and a spirally wound second gas permeable support material radially outward of said first filter media, and an outer layer radially outward of said spirally wound filter layers, comprising two spirally wound third gas permeable support materials forming adjacent wraps of said third gas permeable support materials, wherein said third gas permeable support material having inner and outer surfaces, third and fourth edges, and an end portion, wherein said third edge and said fourth edge of the most radially outward layer of said third gas permeable support material is joined to the next most radially outward gas permeable support material by bonding means such that said outer layer retains said outer layer and said filter layer in a cylindrical relation about said core without further structural support.
13. A method for continuous fabrication of filter units for use in PATENT

automotive air bag inflators comprising:

spirally winding a first gas permeable support material of bendable material around a rotating mandrel to form a hollow cylindrical core having internal and external surfaces, said first gas permeable support material having a first edge and a second edge, forming adjacent spiral wraps of said first gas permeable support material wherein said first edge of said first gas permeable support material is joined to said second edge of said first gas permeable support material of said adjacent spiral wrap by means such that said cylindrical core retains a cylindrical form without the application of external forces;

spiral winding at least one filter layer radially outward of said cylindrical core, wherein each filter layer comprises spirally winding at least one layer of first filter media radially outward of said hollow cylindrical core and spirally winding at least one layer of a first gas permeable support material layer radially outward of said first filter media;

spirally winding an outer layer radially outward of said filter layer comprising spirally winding at least one third gas permeable support material forming adjacent spiral wraps of said third gas permeable support material, wherein said third gas permeable support material having inner and outer surfaces, third and fourth edges, and an end portion, wherein said third edge and said fourth edge of the most radially outward spiral wrap of said third gas permeable support material is joined to the next most radially outward layer by means such that said outer layer retains said outer layer and said filter layer in a cylindrical relation about said cylindrical core without further structural support, thereby forming a continuous spiral wound filter unit; and PATENT

transversely cutting said continuous spiral wound filter unit at intervals to form individual spiral wound filter units of desired lengths.
14. A method for continuous fabrication of filter units for use in automotive air bag inflators of claim 13 further comprising a fourth gas permeable support material radially outward of said hollow core and radially inward of said first filter media.
15. A method for continuous fabrication of filter units for use in automotive air bag inflators of claim 13 wherein said first gas permeable support material is screen.
16. A method for continuous fabrication of filter units for use in automotive air bag inflators of claim 13 wherein said second gas permeable support material is screen.
17. A method for continuous fabrication of filter units for use in automotive air bag inflators of claim 13 wherein said third gas permeable support material is screen.
18. A method for continuous fabrication of filter units for use in automotive air bag inflators of claim 13 wherein said first gas permeable material made from a material selected from a group consisting of carbon steel, nickel-plated carbon steel, and series 300 stainless steel.
19. A method for continuous fabrication of filter units for use in automotive air bag inflators of claim 13 wherein said second gas permeable support material is made from a material selected from a group consisting of carbon steel, nickel-plated carbon steel, and series 300 stainless steel.

PATENT
20. A method for continuous fabrication of filter units for use in automotive air bag inflators of claim 13 wherein said second gas permeable support material is screen with a mesh size from about 18 to about 30 mesh.
21. A method for continuous fabrication of filter units for use in automotive air bag inflators of claim 13 wherein said first filter media is made from a ceramic filter paper, wherein said filter paper is able to withstand temperatures up to about 1500 C.
and a volumetric flow rate of between from about 250 to about 1870 cfm/ft2, with a permeability of between about 40 to about 200 cfm/ft2 at a pressure drop of 1/2 inches of water.
22. A method for continuous fabrication of filter units for use in automotive air bag inflators of claim 13 wherein said third gas permeable support material is screen with a mesh size from about 18 to about 30 mesh.
CA002093743A 1992-04-30 1993-04-08 Spiral wrapped gas generator filter Abandoned CA2093743A1 (en)

Applications Claiming Priority (2)

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US07/876,270 1992-04-30
US07/876,270 US5230726A (en) 1992-04-30 1992-04-30 Spiral wrapped gas generator filter

Publications (1)

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CA2093743A1 true CA2093743A1 (en) 1993-10-31

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EP (1) EP0568381B1 (en)
JP (1) JPH07114903B2 (en)
KR (1) KR960010370B1 (en)
AU (1) AU649368B2 (en)
CA (1) CA2093743A1 (en)
DE (1) DE69308065T2 (en)
MX (1) MX9302262A (en)

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AU649368B2 (en) 1994-05-19
EP0568381B1 (en) 1997-02-12
JPH0631120A (en) 1994-02-08
AU3314393A (en) 1993-11-11
US5230726A (en) 1993-07-27
KR960010370B1 (en) 1996-07-31
EP0568381A1 (en) 1993-11-03
DE69308065D1 (en) 1997-03-27
DE69308065T2 (en) 1997-05-28
MX9302262A (en) 1993-10-01
JPH07114903B2 (en) 1995-12-13
KR930021250A (en) 1993-11-22

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