WO2005098210A1

WO2005098210A1 - A separator for a catalytic converter

Info

Publication number: WO2005098210A1
Application number: PCT/GB2005/001341
Authority: WO
Inventors: Adrian Mark Wood; Stephen Mark Forber
Original assignee: Catalytic Support Systems Limited
Priority date: 2004-04-06
Filing date: 2005-04-06
Publication date: 2005-10-20
Also published as: GB0407806D0; ZA200609231B

Abstract

A separator (11) for a catalytic converter (19). The separator (11) comprises an outer wire mesh sleeve (12) and a wire mesh insert (13) located within the outer sleeve (12). Opposite ends of the sleeve (12) are joined to each other to form an annulus. The outer sleeve (12) is flattened around the insert (13) to form a separator portion (14) on the internal side wall of the annulus with the insert (13) located wholly within the separator portion (14). The separator portion (14) defines the separation provided by the separator (11).

Description

A Separator for a Catalytic Converter

This invention relates to a separator for catalytic converters and in particular, a separator for separating two refractory bricks within a catalytic converter.

Typically, catalytic converters for vehicles comprise a tubular housing through which exhaust gases flow. The housing normally contains at least one ceramic refractory brick having through pores that are aligned axially with the housing to permit the exhaust gases to flow through the pores. The insides of the pores are coated with a catalyst, such as platinum or rhodium, to promote a catalytic reaction as the gases flow through the pores.

The housing is lined with a suitable expandable material, such as an intumescent material, within which the brick is located. The ceramic material is brittle and some designs require two, or perhaps in future, more short bricks used in tandem. The intumescent material lines the housing only in the region of each brick and may not necessarily extend between the bricks.

Conventionally, in catalytic converters requiring two bricks, the bricks are separated, usually by a separation of about 6mm to 10mm, by a pressed metal (usually Inconel) clip. Such clips have a tendency to creep with thermal expansion and lift away from their seating positions on the edges of the bricks. This allows hot, turbulent gas to pass beneath the clips, which causes corrosion and degradation of the intumescent material, as well as local heating of the housing, which can be a fire risk, and vibration of the bricks against the clip, which can cause chipping of the edges of the bricks.

The use of a knitted wire mesh separator, instead of the pressed metal clip, is also known. The mesh separator is a straight replacement for the clip, and is so proportioned. It comprises an annulus which has a separator portion adapted to fit between the bricks, at the normal spacing of about 6mm to 10mm, with flanges either side to locate over the ends of the bricks. The annulus is formed from two knitted concentric tubular structures, which are flattened, cut to length and the free ends welded together. The flattened and welded annulus is then compressed in a press tool to create a profiled section that forms the separator portion.

This conventional mesh separator is an improvement over the pressed metal clip, inasmuch as it is compressible, and so absorbs thermal expansion by consolidation, hence did not leak and damage the bricks and the housing. However, it does have a number of disadvantages. In particular, the pressing operation to create the profiled section can result in a large amount of creased mesh in the profiled section that forms the separator between the bricks. During use, this creased mesh can work itself loose and sag into the gap between the bricks and this can cause problems during vehicle operation.

In accordance with a first aspect of the present invention, there is provided a separator for a catalytic converter, the separator comprising an outer wire mesh sleeve and an insert located within the outer sleeve, opposite ends of the sleeve being joined to each other to form an annulus, wherein the outer sleeve is flattened around the insert to form a separator portion on the internal side wall of the annulus with the insert located wholly within the separator portion, and the separator portion defining the separation provided by the separator.

In accordance with a second aspect of the present invention, there is provided a method of manufacturing a separator for a catalytic converter, the method comprising forming an outer wire mesh sleeve around an insert, flattening the outer sleeve around the insert to form an separator portion on one side of the outer sleeve with the insert wholly located within the separator portion, and joining opposite ends of the sleeve together to form an annulus with the separator portion on the inside of the annulus and the separator portion defining the separation provided by the separator.

The invention has the advantage that by providing an insert wholly within an separator portion of the separator, it is possible to manufacture a separator of mesh material in which creasing of the mesh within the separator portion is minimised and therefore, the risk of sag of the mesh into the separation between the bricks in a catalytic converter, in use, is also minimised. It also has the advantage of enabling separators to be manufactured with a wider separator portion to provide a wider gap between bricks in the catalytic converter, in use.

Typically, the insert is formed from a wire mesh. Preferably, the wire mesh insert may be formed by knitting and may be in the form of a knitted sleeve. Typically, the insert is formed from a wire mesh sleeve that is flattened and folded, preferably, along a longitudinal axis. The insert may be flattened and folded and inserted into the outer sleeve during the forming of the outer sleeve.

Preferably, the outer sleeve is formed by knitting. The insert may be inserted into the outer during knitting of the outer sleeve.

Preferably, the insert is located substantially centrally within the outer sleeve, and the separator portion is formed substantially centrally within the outer sleeve so that it is equidistant from the edges of the annulus.

Typically, both the outer sleeve and the insert are formed from a metal wire mesh.

Typically, the separator may be welded circumferentially around the section of the annulus corresponding to the insert. This has the advantage of helping to prevent sagging of the separator portion. The welding may be by welding in a number of locations around the circumference. Preferably the locations are equidistant around the circumference. The welding may be spot welding.

Typically, the opposite ends of the sleeves are joined by welding them together.

In one example of the invention a through aperture may be formed in the annulus through the separator portion. This has the advantage of permitting a probe to be inserted into the gap between the bricks, in use.

The edges of the aperture may be finished using a number of different methods. One method is to apply an eyelet to the aperture, which can be punched in the same manner as eyelets for paper or of laces in shoes. The eyelet also helps retain the insulating fibres within the mesh structure. The eyelet is typically metal and may be solid or a mesh structure. The cut edges, however, may be spot welded or sewn together, after the fashion of buttonholes in garments.

Alternatively, the aperture may be finished by compressing the material around the aperture so that the wire mesh around the aperture is compressed. Typically, the aperture may be formed by piercing the side-wall of the mesh annulus with a spike and then compressing the material drawn up by the spike down onto the side-wall of the spike.

An example of a separator for a catalytic converter in accordance with the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a cross-sectional view through a two-brick catalytic converter incorporating a separator: Figure 2 is an axial cross-sectional view through the separator shown in Figure 1 ; Figure 3 is a cross-sectional view along the line AA in Figure 2; Figure 4 is an enlarged view of region B in Figure 3; Figure 5 is a cross-sectional view showing an inner mesh sleeve being fed into an outer mesh sleeve during manufacturing of the separator; Figure 6 is a cross-sectional view showing flattening of the outer mesh sleeve to form a central separator region with the inner sleeve located within the central separator region; Figure 7 is a view of a first stage in a process for forming an aperture; and Figure 8 is a view of a second example of a finished aperture.

Figures 1 to 4 show a separator 11 for a catalytic converter 19 comprising an outer wire mesh sleeve 12 incorporating an insert 13. The separator 11 is annular and has a central separator region 14, which is in the form of a thickened portion within which the insert 13 is located. The central separator region extends on only inner side 41 of the separator so that outer side 42 is substantially flat, in that there are no outwardly extending sections on the outer side 42. The insert 13 is formed from a mesh sleeve that is flattened and then folded and inserted into the outer mesh sleeve 12. The separator is formed such that the insert

13 is located wholly within the central thickened region 14. Outer regions of the separator 11 between the central region 14 and edges 7 of the separator 11 form flanges 8 which are outside the central region 14.

Both the outer sleeve and the sleeve from which the insert 13 is formed are manufactured by being knitted. Typically, they are knitted from metal wire, such as stainless steel wire. However, any suitable metal or metal alloy wire could be used, the requirement being that the wire retains integrity and resilience at the operating temperature of the converter and does not degrade over time due to the high temperatures encountered and the thermal cycling that occurs in vehicle catalytic converters. In this example, the outer sleeve 12 is knitted from four wires of 310 grade stainless steel wire of 0.25mm diameter and the sleeve from which the insert 13 is formed is knitted from two wires of 309 grade stainless steel wire of 0.35mm diameter.

As shown in Figure 1 , in use, the separator 11 is located centrally within a housing 21 of a catalytic converter 19 and the flanges 8 fit over edges 6 of bricks 15, so that the end faces 6 butt against edges 9 of the central region 14 of the separator 11. Therefore, the central region 14, and the distance between the edges 9 defines the separation S between the bricks 15. The bricks 15 are separated from the housing 21 by intumescent sleeves 22 that locate between the bricks 15 and the inside wall of the housing 21. Wire mesh seals 25 help to isolate the ends of the intumescent sleeves 15 from exhaust gases passing through the converter 19.

The sleeves 22 are compressed during manufacturing assembly and expand with heat to maintain sufficient holding pressure through changes in thermal expansion. The conventional pressed metal clip or ring may be welded to the outer shell of the converter. During service the welds tend to break causing the metal ring to rattle against the ceramic substrate of the bricks 15 causing fatal damage to the converter. The resilience of the wire mesh separator 11 mitigates this problem. By providing a separator 11 with an insert 13 wholly within the central region 14, it is possible to reduce the problems of the mesh sagging into the gap between the bricks

15 that is present in conventional mesh separators. This enables larger separations to be used and a separation S of up to and even greater than 30mm can be readily accommodated, giving catalytic converter designers more freedom to select optimum spacing.

One of the reasons for designing a converter with a wide interbrick spacing is to accommodate temperature and other probes 26 for engine management. The separator 11 includes an aperture 16 through which the probe 26 extends into the gap between the bricks 15. The aperture 16 is "finished" by a metal eyelet 17 which can be punched into the aperture 16 with or without washers 18. Other ways of finishing the aperture can be used, such as sewing, as in buttonhole stitching, or spot welding around the periphery of the aperture. The aperture 16 may be oval, as shown in Figures 2 and 3, may be circular or any other suitable shape. In the particular example shown, the aperture is located in the separator at angle of 108° to joining weld 45. However, other positions for the aperture 16 could be used.

The separator 11 is manufactured by first forming the insert 13. As described above, the insert 13 is formed by knitting a metal wire mesh sleeve. The wire mesh sleeve is then flattened and folded in half along the longitudinal axis of the flattened sleeve to form the insert 13. The outer mesh sleeve 12 is then formed by knitting another metal wire mesh sleeve and during the knitting operation the insert 13 is fed into the outer sleeve 12 being knitted, as shown in Figure 5, so that as the outer sleeve 12 comes off the knitting machine, the insert 13 is located within it.

The outer sleeve 12 with insert is then fed to a positioning bar (or stretcher bar) 50, which feeds the outer sleeve 12 and insert 13 to a pair of press rollers 52, 53, as shown in Figure 6. The positioning bar has a central aperture 51 through which the insert 13 is fed to the rollers 52, 53 and the bar 50 locates within the outer sleeve 12 so that the outer sleeve is fed around the outside of the bar 50 to the rollers 52, 53. The positioning bar 50 positions the insert 13 centrally within the outer sleeve 12 and also stretches the outer sleeve 12 for feeding to the rollers 52, 53. The roller 52 has a recessed section 54 so that when the outer sleeve 12 and insert 13 are pressed by the rollers 52, 53, the insert locates in the recessed section 54 and the outer sleeve

12 is flattened and pressed around the insert 13 so that the recessed section 54 of the roller 52 forms the central section 14 of the separator.

After the outer sleeve 12 and the insert 13 have been pressed by the rollers 52, 53, the cross-sectional profile of the flattened outer sleeve 12 and insert 13 is similar to the cross-section shown in Figure 4, with the insert 13 located wholly within the central region 14.

The outer sleeve 12 and insert 13 have been pressed by the rollers 52, 53, the pressed outer sleeve 12 and insert 13 is cut to length. This may be done using a pneumatic guillotine or could be performed using rollers with a rotary blade using a combination of gear ratios to control the cut length. Each length is then spot welded a number of times along the length of the central section 14, preferably along longitudinal axis 43. This is shown in Figures 2 and 3 where spot welds 44 are indicated. The number of spot welds can vary depending on the circumference of the final separator 11. However, in this example eight spot welds are used with each spot weld being separated from adjacent spot welds by an angle of 36° in the finished separator 11.

The opposite ends of the cut outer sleeve 12 and the insert 13 are then joined by spot welding across the ends to form a continuous spot welded joint 45. The mesh annulus formed from the outer sleeve 12 and the insert 13 is then inserted into a press tool to perform the final forming operation to form the separator 11.

The aperture 16 can be formed by punching out a portion of the outer sleeve 12 and insert 13 in the region of the central region 14 and then finishing the aperture with the eyelet 17, as shown in Figure 1.

Alternatively, the aperture 16 can be formed by using a spike to pierce the outer sleeve 12 and the insert 13. This causes material 30 of the sleeve 12 and insert 13 to be drawn up by the spike, as shown in Figure 7. The material 30 that is drawn up by the spike is then compressed around the spike to form a finished aperture 31 (see Figure 8). In Figures 6 and 7 the aperture 31 is circular. However, the same process could be used form an oval or other shape of aperture.

Advantages of the separator 11 are that by having the insert 13 wholly within the separator portion, creasing and sagging of the mesh into the gap between the bricks 15 is reduced. This problem is also alleviated by flattening and/or pressing the mesh forming the insert 13 before inserting the insert 13 into the outer sleeve 12. This has the advantage that the insert 13 is relatively compressed and rigid before the outer sleeve 12 is compressed. This also minimises the risks of creasing of the mesh in the separator region 14.

The invention also has the advantage that by minimising creasing and subsequent sagging in the separator region 14, it is also possible to construct catalytic converters with wider separator regions, thereby facilitating the possibility of inserting a probe 26 into the separator region 14.

Claims

1. A separator for a catalytic converter, the separator comprising an outer wire mesh sleeve and an insert located within the outer sleeve, opposite ends of the sleeve being joined to each other to form an annulus, wherein the outer sleeve is flattened around the insert to form a separator portion on the internal side wall of the annulus with the insert located wholly within the separator portion, and the separator portion defining the separation provided by the separator.

2. A separator according to claim 1 , wherein the insert is formed from a wire mesh.

3. A separator according to claim 2, wherein the wire mesh insert is knitted.

4. A separator according to claim 3, wherein the wire mesh insert is in the form of a knitted sleeve.

5. A separator according to any of claims 2 to 4, wherein the insert is formed from a metal wire mesh.

6. A separator according to any of the preceding claims, wherein the outer sleeve is knitted.

7. .A separator according to any of the preceding claims, wherein the outer sleeve is formed from a metal wire mesh.

8. A separator according to any of the preceding claims, wherein the insert is located substantially centrally within the outer sleeve.

9. A separator according to any of the preceding claims, wherein the separator portion is formed substantially centrally within the outer sleeve so that it is substantially equidistant from the edges of the annulus.

10. A separator according to any of the preceding claims, wherein the separator is welded circumferentially around the section of the annulus corresponding to the insert.

11. A separator according to claim 10, wherein the separator is welded at a number of discrete locations around the circumference.

12. A separator according to claim 11 , wherein the locations are equidistant around the circumference.

13. A separator according to any of the preceding claims, wherein the opposite ends of the outer sleeve are joined by a welding process.

14. A separator according to any of the preceding claims, wherein the opposite ends of the insert are joined together.

15. A separator according to any of the preceding claims, wherein the opposite ends of the insert are joined by a welding process.

16. A separator according to any of the preceding claims, wherein a through aperture is formed in the annulus through the separator portion.

17. A separator according to claim 16, wherein the edges of the aperture are finished by applying an eyelet to the aperture.

18. A separator according to claim 16, wherein the edges of the aperture are finished by compressing the material around the aperture so that the wire mesh around the aperture is compressed.

19. A method of manufacturing a separator for a catalytic converter, the method comprising forming an outer wire mesh sleeve around an insert, flattening the outer sleeve around the insert to form an separator portion on one side of the outer sleeve with the insert wholly located within the separator portion, and joining opposite ends of the sleeve together to form an annulus with the separator portion on the inside of the annulus and the separator portion defining the separation provided by the separator.

20. A method according to claim 19, the method further comprising forming the insert.

21. A method according to claim 20, wherein the insert is formed from a wire mesh sleeve.

22. A method according to claim 21 , wherein the wire mesh sleeve insert is flattened and folded along a longitudinal axis.

23. A method according to claim 22, wherein the insert is flattened and folded and inserted into the outer sleeve during the forming of the outer sleeve.

24. A method according to any of claims 19 to 23, wherein the outer sleeve is formed by knitting and the insert is inserted into the outer sleeve during knitting of the outer sleeve.

25. A method according to any of claims 19 to 24, further comprising locating the insert substantially centrally within the outer sleeve.

26. A method according to any of claims 19 to 25, further comprising forming the separator portion substantially centrally within the outer sleeve so that it is substantially equidistant from the edges of the annulus.

27. A method according to any of claims 19 to 26, further comprising welding the separator circumferentially around the section of the annulus corresponding to the insert.

28 A method according to claim 27, wherein the separator is welded at a number of discrete locations around the circumference.

29. A method according to claim 28, wherein the locations are equidistant around the circumference.

30. A method according to any of claims 19 to 29, wherein the opposite ends of the outer sleeve are joined by welding.

31. A method according to any of claim 19 to 30, wherein the opposite ends of the insert are joined together.

32. A method according to claim 31 , wherein the opposite ends of the insert are joined by welding.

33. A method according to any of claims 27 to 30 and 32, wherein the welding is spot welding.

34. A method according to any of claims 19 to 33, further comprising forming a through aperture in the annulus through the separator portion.

35. A method according to claim 34, wherein the edges of the aperture are finished by applying an eyelet to the aperture.

36. A method according to claim 34, wherein the edges of the aperture are finished by compressing the material around the aperture so that the wire mesh around the aperture is compressed.

37. A method according to claim 36, wherein the aperture is formed by piercing the side-wall of the annulus with a spike and then compressing the material drawn up by the spike down onto the side-wall of the spike.