EXPANDED METAL FILTERS

• US 20090184504A1
• Filed: 03/19/2009
• Published: 07/23/2009
• Est. Priority Date: 09/21/2006
• Status: Active Grant

• Current Assignee: ACS Industries Incorporated
• Original Assignee: ACS Industries Incorporated
• Inventors: McCarthy, Michael, Pfefferle, Richard, Greenwood, George
• Granted Patent: US 10,717,032 B2
• Time in Patent Office: Days
• US Class Current: 280/741
• CPC Class Codes: B01D 2279/10 for air bags, e.g. inflators therefor
• CPC Class Codes: B01D 46/24 Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
• CPC Class Codes: B21D 31/04 Expanding other than provided for in groups B21D1/00 - B21D28/00, e.g. for making expanded metal B21D47/00 takes precedence; enlarging tube ends B21D41/02
• CPC Class Codes: B60R 2021/26011 using a filter through which the inflation gas passes
• CPC Class Codes: Y10T 29/49604 Filter
• CPC Class Codes: Y10T 428/13 Hollow or container type article [e.g., tube, vase, etc.]

Abstract

Expanded metal sheets are used to produce tubular filters. The expanded metal sheet has a multiplicity of rows of openings arranged to reduce nesting when the sheet is rolled on itself. In particular, the pitch between the rows of openings, the sizes of the openings, or both the pitch between the rows of openings and the sizes of the openings are varied to reduce nesting when the expanded metal sheet is rolled on itself. The filters can include external circumferential grooves, rounded corners produced by a point loading process, textured surfaces between openings, and/or torturous internal paths produced by non-perforated areas of an expanded metal sheet. The expanded metal sheet can be composed of carbon steel coated with a material having a higher heat conductivity, e.g., tin. Among other things, the filters can be used in automobile airbag inflators to capture slag and absorb heat produced by the inflator'"'"'s explosive charge.

Claims

1. A tubular filter comprising an expanded metal sheet having a multiplicity of rows of openings arranged to reduce nesting when the sheet is rolled on itself, the sheet rolled into a tube, and welded to fix the tubular orientation, wherein:

(a) the expanded metal sheet is formed from a larger sheet of metal having a width and an axis;

(b) the expanded metal sheet has long edges formed by the larger sheet of metal and short edges where it has been cut as a portion of the larger sheet;

(c) the openings are formed by forming slits in the larger sheet of metal and stretching the slits in the direction of the axis; and

(d) the pitch between the rows of openings, the sizes of the openings, or both the pitch between the rows of openings and the sizes of the openings are varied to reduce nesting when the expanded metal sheet is rolled on itself.

2. The filter of claim 1 wherein the pitch between rows of openings is varied as a function of the circumference defined by a given portion of the expanded metal sheet in the rolled up filter so that radially adjacent openings do not nest.

3. The filter of claim 1 wherein the expanded metal sheet includes areas that do not include openings.

4. The filter of claim 1 wherein the filter is an automotive airbag filter.

5. A method of making a filter comprising:

(a) providing a sheet of metal having a width and an axis;

(b) forming slits in the sheet and stretching the slits in the direction of the sheet'"'"'s axis to form a multiplicity of rows of openings;

(c) cutting a smaller sheet from the sheet produced in step (b);

(d) rolling the smaller sheet of step (c) on itself to form a tube; and

(e) securing the tube of step (d) with a weld;

wherein in step (b), the multiplicity of rows of openings are arranged to reduce nesting when the smaller sheet is rolled on itself to form the tube.

6. The method of claim 5 wherein the pitch between the rows of openings, the sizes of the openings, or both the pitch between the rows of openings and the sizes of the openings are varied to reduce nesting when the smaller sheet is rolled on itself to form the tube.

7. The method of claim 6 wherein the pitch between rows of openings is varied as a function of the circumference defined by a given portion of the rolled up smaller sheet so that radially adjacent openings do not nest.

8. The method of claim 6 wherein in step (b) the sheet is fed at a rate which varies so as to vary the pitch between the rows of openings.

9. The method of claim 5 wherein the smaller sheet includes areas that do not include openings.

10. The method of claim 5 wherein the filter is an automotive airbag filter.

11. A tubular filter comprising expanded metal that has been rolled on itself to form a multi-layered tube wherein the expanded metal comprises a multiplicity of openings and includes at least one section that is free of openings, said section producing circumferential flow of gas within the filter.

12. The tubular filter of claim 11 wherein the filter has an inner diameter and an outer diameter and substantially all possible flow paths from the inner diameter to the outer diameter include both radial and at least some circumferential flow over a distance greater than the average distance between openings.

13. A tubular filter comprising expanded metal that has been rolled on itself to form a multi-layered tube having a substantially cylindrical outer surface wherein the expanded metal comprises a multiplicity of openings and the substantially cylindrical outer surface comprises a circumferential groove.

14. The tubular filter of claim 13 wherein the outer surface comprises two circumferential grooves.

15. The tubular filter of claim 13 wherein the groove has an arcuate cross section.

16. The tubular filter of claim 13 wherein the groove is formed in the expanded metal before the expanded metal is rolled on itself.

17. An assembly comprising:

(a) a housing for an airbag inflator, said housing having a chamber for receiving a tubular filter and a circumferential ring of apertures for allowing gas to exit the chamber; and

(b) a tubular filter according to claim 13 within the chamber;

wherein the circumferential groove of the tubular filter is aligned with the circumferential ring of apertures of the housing.

18. An assembly comprising:

(a) a housing for an airbag inflator, said housing having a chamber for receiving a tubular filter and a circumferential ring of apertures for allowing gas to exit the chamber, said circumferential ring of apertures being offset from the midplane of the chamber; and

(b) a tubular filter according to claim 14 within the chamber;

wherein only one of the circumferential grooves of the tubular filter is aligned with the circumferential ring of apertures of the housing.

19. A tubular filter comprising expanded metal that has been rolled on itself to form a multi-layered tube having a central bore, a substantially cylindrical outer surface, and substantially flat end sections which extend between the central bore and the substantially cylindrical outer surface, wherein the expanded metal comprises a multiplicity of openings and the corners formed by the intersections between the substantially cylindrical outer surface and the substantially flat end sections have been rounded by a point loading process.

20. An assembly comprising:

(a) a housing for an airbag inflator, said housing comprising a chamber which has an inner wall which comprises a substantially cylindrical side wall section and end wall sections, wherein the corners formed by the intersections between the substantially cylindrical side wall section and the end wall sections are rounded; and

(b) a tubular filter according to claim 19 within the chamber;

wherein the rounded corners of the tubular filter mate with the rounded corners of the chamber so that maximum length of flame released from the housing when an inflator charge is ignited within the central bore of the filter is reduced by at least 25 percent compared to a filter whose corners have not been rounded.

21. The assembly of claim 20 wherein the maximum length of flame released from the housing when an inflator charge is ignited within the central bore of the filter is reduced by at least 50 percent compared to a filter whose corners have not been rounded.

22. The assembly of claim 20 wherein the mean radius of the rounded corners of the filter is within ±

10 percent of the mean radius of the rounded corners of the housing'"'"'s chamber.

23. A tubular filter comprising expanded metal that has been rolled on itself to form a multi-layered tube wherein the expanded metal comprises a multiplicity of openings and the surface of the expanded metal between at least some of the openings is texturized so as to reduce laminar flow of gas over the surface.

24. The tubular filter of claim 23 wherein the texturization has a linear feature density D in the range of 15 features/inch to 500 features per inch.

25. The tubular filter of claim 24 wherein the feature amplitude is less than or equal to 0.5/D.

26. A tubular filter comprising expanded metal that has been rolled on itself to form a multi-layered tube wherein the expanded metal comprises a multiplicity of openings and the expanded metal comprises a first metal at least one surface of which is coated with a second metal whose thermal conductivity is at least 25% greater than that of the first metal.

27. The tubular filter of claim 26 wherein the first metal is carbon steel and the second metal is tin.

28. The tubular filter of claim 27 wherein the tin is plated on the carbon steel.