GB2568900A

GB2568900A - Exhaust gas treatment assembly comprising a gas permeable block and a housing, and method of assembly

Info

Publication number: GB2568900A
Application number: GB1719866.4A
Authority: GB
Inventors: A Niaz Naseer
Original assignee: Perkins Engines Co Ltd
Current assignee: Perkins Engines Co Ltd
Priority date: 2017-11-29
Filing date: 2017-11-29
Publication date: 2019-06-05
Anticipated expiration: 2037-11-29
Also published as: CN109838292A; GB201719866D0; GB2568900B; CN109838292B

Abstract

An exhaust gas treatment assembly 15 comprises a unitary outer housing body 60 having inlet 61 and outlet 62 regions to which an inlet 20 and outlet 30 are fluidly connected. An inner housing body 50 is arranged sealingly inside the outer housing body, and a gas permeable block 2 is arranged sealingly within a sealing region (51, fig 18) of the inner housing body so that a flowpath F extends from the inlet, though the gas permeable block to the outlet. There may be two sealing regions, each with a gas permeable block. The inner housing body may be connected to the inlet end region by a continuous annular welded joint (53, fig 18), and to the outlet end region by a discontinuously welded joint (55, fig 18). The outer housing can therefore be made to tight dimensional tolerances while the assembly compensates for dimensional variations in the blocks and provides a gas tight seal between the block and the inner housing.

Description

Exhaust gas treatment assembly comprising a gas permeable block and a housing, and method of assembly

Technical field

This invention relates to exhaust gas treatment assemblies of the type comprising a gas permeable block arranged in a housing.

Background

An exhaust gas treatment assembly typically comprises one or more gas permeable blocks of ceramic or mineral material which are arranged sealingly in a housing, typically cylindrical and often referred to as a can. The housing defines a flowpath with inlet and outlet connections via which exhaust gas is directed to flow through the block or blocks. Each block may act as a filter, for example, if the assembly is to function as a diesel particulate filter (DPF), or may comprise a catalyst, for example, if the assembly is to function as a diesel oxidation catalyst (DOC) or selective catalytic reductor (SCR). The blocks may be formed with numerous parallel channels separated by thin walls and opening alternately at either end of the block or otherwise as known in the art to allow gas to flow through the block from one axial end to the other.

In order to form a gas tight seal with the wall of the housing to prevent exhaust gas from bypassing the block, and in order to retain the block inside the housing against movement due to vibration or inertial forces, for example when mounted on an engine or in other mobile applications, the wall of the housing may be compressed radially inwardly, e.g. crimped or swaged, to form a sealing region of the housing which bears radially inwardly against the block to retain it in compression and so hold it in a fixed position within the housing. Since the blocks are typically hard and brittle and may reach a high temperature in use due to the exhaust gas temperature or additional heating means, a compressible material such as a needle mat is typically arranged around the block to cushion the block and accommodate differential expansion between the block and the housing. The block and mat may be arranged in the housing before compression of the housing, or alternatively may be installed in the housing after compression, for example, through a gradually tapering guide which compresses the mat as the block slides into the housing.

In practice, relatively large dimensional variations (for example, +/- 2mm or more in diameter) are known to occur in otherwise identical gas permeable blocks for use in such assemblies, even when manufactured under identical conditions in the same production facility and even in the same batch. It is therefore common to manufacture the housings as standard units with the same, predetermined dimensions, and then to 10 radially inwardly compress the sealing region of each housing which retains the block, by a different radial distance to correspond to the measured dimensions of the individual block which is (or will be) inserted into the housing.

Figs. 1-4 show a prior art exhaust gas treatment assembly 1 comprising a gas permeable block 2 arranged sealingly in a central housing 3 formed as a generally cylindrical metal tube, with a needle mat 4 arranged in compression between the block and the central housing. The central housing is closed at its opposite axial ends by a pair of pressed metal end caps 5, 6 which are fitted respectively with an inlet 20 and an outlet 30.

As shown in Fig. 5, the central housing 3 is compressed radially inwardly to define an axially central, sealing region 7 which retains the block and needle mat in compression. The cylindrical, axial end regions 8 of the central housing are not compressed and serve to connect the central housing to the end caps.

During assembly, the central housing 3 and end caps 5, 6 are arranged in alignment as shown in Fig. 7 before inserting the axial end regions 8 of the central housing 3 into the end caps and welding them together to form an enclosed flowpath F through the block 2 from the inlet 20 to the outlet 30.

Fig. 6 illustrates another prior art housing assembly which includes an inner housing 9 arranged concentrically inside a cylindrical outer heat shield 10, with a needle mat 4 being arranged between the gas permeable block and the inner housing 9, and a layer of thermal insulation material 11 between the inner housing and the outer heat shield.

KR 101683843 Bl teaches a similar arrangement comprising several gas permeable blocks, each in a separate housing, with the housings being arranged in series relation inside a tubular heat shield.

Fig. 9 illustrates how the prior art housing assembly of Fig. 6 may be arranged in a similar way to that of Fig. 5 between a pair of end caps 5, 6 to form an exhaust gas treatment assembly.

During assembly it is usual to support the sealing region of the central housing and the end caps in a jig while the axial end regions of the central housing are introduced into the end caps and the three parts are welded together. The jig may be adjustable to compensate for the variable external diameter of the sealing region of the central housing, in order to maintain a fixed geometric relationship between the inlet and the outlet in the finished assembly. Despite the use of an adjustable jig however, it is difficult to maintain tight tolerances between the inlet and outlet positions, and so the fluid connections on the engine and exhaust system in which the assembly is to be used must be designed to accommodate the resulting variations in axial and rotational position between the inlet and the outlet of the assembly.

In use, the assembly will typically be mounted on an engine or ancillary equipment by means of straps which must also be designed to accommodate the geometric variations in the assembly, particularly where they are arranged around the central housing. This can make it difficult to achieve a connection sufficiently firm to withstand the vibration of the engine in use.

Summary of the Disclosure

In a first aspect the present disclosure provides an exhaust gas treatment assembly as defined in the claims.

The assembly includes at least one gas permeable block and a housing, the housing including an inlet region, an outlet region, a sealing region arranged between the inlet region and the outlet region, an inlet fluidly connected to the inlet region, and an outlet fluidly connected to the outlet region. The housing defines a flowpath extending through the housing from the inlet to the outlet, with the gas permeable block being arranged sea Iingly within the sealing region of the housing so that the flowpath extends through the block. The housing further includes a unitary, outer housing body, and an inner housing body which is arranged sealingly within the outer housing body. The inlet and outlet regions of the housing comprise respective end regions of the outer housing body, while the sealing region comprising a sealing region of the inner housing body.

In a second aspect the present disclosure provides a method of assembling an exhaust gas treatment assembly, as defined in the claims.

The method includes providing at least one gas permeable block, an inner housing body, an inlet, and an outlet, and arranging the gas permeable block sealingly within a sealing region of the inner housing body. The method further includes providing a unitary, outer housing body, fluidly connecting the inlet to an inlet end region of the outer housing body, and fluidly connecting the outlet to an outlet end region of the outer housing body. After arranging the gas permeable block sealingly within the sealing region of the inner housing body, the inner housing body is arranged sealingly within the outer housing body between the inlet end region and the outlet end region, so that the inner and outer housing bodies together define a flowpath extending through the block from the inlet to the outlet.

Further features and advantages will become apparent from the following illustrative embodiments which will now be described, purely by way of example and without limitation to the scope of the claims, and with reference to the accompanying drawings, in which:

Brief Description of the Drawings

Figs. 1 and 2 are respectively a side view and end view of a prior art exhaust gas treatment assembly comprising a central housing arranged between a pair of end caps; Fig. 3 is a longitudinal section through the prior art assembly taken at III - III of Fig. 2; Fig. 4 is an enlarged detail view of part of Fig. 3;

Fig. 5 is an enlarged view of the central housing as shown in Fig. 3 and in the exploded view of Fig. 7;

Fig. 6 is a corresponding view of another prior art housing assembly comprising an outer heat shield;

Fig. 7 is an exploded view of the prior art assembly in the section of Fig. 3;

Fig. 8 is an enlarged detail view of part of Fig. 7;

Fig. 9 shows a second assembly including the prior art housing of Fig. 6 in an exploded view, corresponding to the view of Fig. 7;

Fig. 10 is an enlarged detail view of part of Fig. 9;

Figs. 11 and 12 are respectively a side view and end view of a third assembly in accordance with an embodiment of the present disclosure;

Fig. 13 is a longitudinal section through the third assembly taken at XIII - XIII of Fig. 12; Figs. 14 and 15 are enlarged detail views of respective parts of Fig. 13;

Fig. 16 shows a variant of the third assembly in longitudinal section, in a view corresponding to that of Fig. 13;

Fig. 17 is an enlarged detail view of part of Fig. 16;

Fig. 18 shows a stage in the assembly of the third assembly in a longitudinal section corresponding to that of Fig. 13;

Fig. 19 is an enlarged detail view of part of Fig. 18;

Figs. 20 and 21 are respectively a side view and end view of the outer housing body of the third assembly;

Figs. 22, 23 and 24 show the inlet of the third assembly, respectively in side view, outer end view, and longitudinal section taken at XIII - XIII of Fig. 12;

Figs. 25, 26 and 27 show the outlet of the third assembly, respectively in side view, outer end view, and longitudinal section taken at XXVII - XXVII of Fig. 26:

Figs. 28 shows an end cap of the third assembly in the view of Fig. 12;

Fig. 29 is a section through the end cap of Fig. 28 taken at XIII - XIII of Fig. 12;

Figs. 30 and 31 are respectively a side view and end view of the inner housing body of the third assembly;

Fig. 32 is a side view of the inner housing body of the variant assembly shown in Fig. 16, of which the end view is the same as Fig. 31;

Figs. 33 and 34 are respectively a side view and end view of one gas permeable block of the third assembly;

Fig. 35 shows the two gas permeable blocks of the variant assembly of Fig. 16 in side view;

Fig. 36 is a longitudinal section in the plane of Fig. 13, showing the gas permeable block of Figs. 33 and 34 assembled inside the inner housing body of Figs. 30 and 31;

Fig. 37 is a longitudinal section in the plane of Fig. 16, showing the twin gas permeable blocks of Fig. 35 assembled inside the inner housing body of Fig. 32; and

Fig. 38 is an end view of the assembly of Fig. 36, wherein the end view of the assembly of Fig. 37 is identical.

Reference numerals or letters appearing in more than one of the figures indicate the same or corresponding parts in each of them.

Detailed Description

Referring to Figs.11 -15, an exhaust gas treatment assembly 15 includes a gas permeable block 2 and a housing 40. The housing 40 comprises an inner housing body and an outer housing body 60. The housing 40 defines a flowpath F which extends through the housing from an inlet 20 to an outlet 30.

The outer housing body 60 is a unitary body, which is to say, it is made from one piece of material rather than as an assembly. Conveniently, the outer housing body 60 may be a cylindrical wall 65 made from one piece of metal, for example as a seamed or seamless tube as known in the art. For example, the outer housing body may be made from a single sheet of metal bent into a cylindrical shape and closed by welding together its abutting edges.

The outer housing body 60 defines an inlet region or inlet end region 61 and an outlet region or outlet end region 62 between two axial end apertures 68, one or both of which may have an internal section area and diameter (normal to length axis X) not smaller than, optionally equal to (as shown), the internal section area and diameter of the rest of the outer housing body 60, which conveniently may consist of a simple cylinder with apertures for the inlet and outlet. The housing 40 further includes the inlet 20 which is fluidly connected to the inlet end region 61, and the outlet 30 which is fluidly connected to the outlet end region 62, optionally to extend radially outwardly from the length axis X as shown, optionally at different radial angles about the axis X as shown, which radial angles are selected to suit the intended installation position of the finished assembly.

Preferably as shown, the inlet 20 may comprise an elongate inlet duct 21, and the outlet 30 may comprise an elongate outlet duct 31. The inlet duct 21 and outlet duct 31 may be inserted as shown, respectively into a first inlet aperture 63 and a first outlet aperture 64 formed in the wall 65 of the outer housing body 60 and connected to the wall 65 by welding.

Further preferably as shown, the wall 65 may include a second inlet aperture 66 and a second outlet aperture 67. Referring also to Figs. 20 - 27, either or both of the inlet and outlet ducts may comprise perforated tubes. The inlet duct 21 may be closed at a second end 23 opposite its open, first end 22, and the outlet duct may be closed at a second end 33 opposite its open, first end 32. In use, the exhaust gas flows via the flowpath F from the open, first end 22 of the inlet 20 via the perforations 24 along flowpath F through the block 2 along the length axis X of the housing 40, and then out via perforations 34 to the open, first end 32 of the outlet duct, with the perforations serving to distribute the flow inside the housing.

The closed, second end 23, 33 of each inlet and outlet duct extends for a small distance out through the respective second inlet or outlet aperture 66, 67 and is welded to the wall 65 all around the aperture. In this way, the first and second inlet and outlet apertures which are formed in the unitary outer housing body 60 accurately position the inlet and outlet ducts so that the open, first ends 22, 32 of the inlet and outlet ducts are assembled in accurately predetermined positions both axially and rotationally with respect to the central length axis X of the housing 40.

In the assembled position as shown in Figs. 11 -13 it can be seen that both the inlet duct 21 and the outlet duct 31 extend into the flowpath F within the outer housing body 60. For this reason, during assembly as further explained below, at least one of the inlet 20 and the outlet 30 is fluidly connected to the respective inlet end region 61 or outlet end region 62 of the unitary, outer housing body 60 after arranging the inner housing body 50 sealingly within the outer housing body 60.

Referring to Figs. 30 - 31 and 33 - 34, the inner housing body 50 is generally of conventional design, conveniently a generally cylindrical metal body with a radially inwardly compressed sealing region 51 arranged axially in-between its axially outward end regions 52. The end regions 52 are not compressed and have an outer diameter close to the inner diameter of the outer housing body 60 so as to be a sliding or interference fit inside the outer housing body 60.

The block 2 may be a solid cylinder made for example from a hard ceramic or mineral material, either with or without channels to distribute the flow through the block, to function for example as a filter or catalyst for aftertreatment of the exhaust gas from an internal combustion engine connected to the inlet 20.

Each block 2 is measured after manufacture, and the wall of the inner housing body 50 pressed radially inwardly (e.g. in a crimping or swaging machine as known in the art) to form the sealing region 51 which will retain the block in position. The sealing region 51 may be formed with the block in situ or before inserting the block axially into the housing via a tapered guide (not shown).

Referring to Figs. 36 and 38, the gas permeable block 2 is arranged sealingly within the sealing region 51 of the inner housing body 50 so that in the finished assembly the flowpath F extends through the block 2; which is to say, the block 2 is arranged in the sealing region 51 so that the exhaust gas flowing along the flowpath F can flow through the block 2 but not between the block 2 and its inner housing body 50.

The cylindrical outer surface of the block 2 may be surrounded as shown by a body or mat 4 of compressible material, e.g. a needle mat, which cushions the block against the inner surface of the inner housing body which exerts a radially inward force against the mat 4 and block 2, holding the block in compression to retain it in a fixed position inside the sealing region 51 of the inner housing body 50.

Referring also to Figs. 18 and 19, after arranging the gas permeable block 2 sealingly within the sealing region of the inner housing body, the inner housing body 50 is inserted axially into the outer housing body 60 via one of its axial end apertures 58 and arranged sealingly within the outer housing body 60 between the inlet end region 61 and the outlet end region 62. In the fully assembled position as shown in Fig. 13, the sealing region 51 containing the block 2 is arranged between the inlet end region 61 and the outlet end region 62, and the inner and outer housing bodies 50, 60 together define a flowpath F extending through the block 2 from the inlet 20 to the outlet 30.

As best seen in Figs. 14,18 and 19, after inserting the inner housing body 50 into the outer housing body 60, an upstream end region 52 of the inner housing body 50 may be connected to the inlet end region 61 of the outer housing body by a substantially continuous, annular welded joint 53 which extends around an inner surface of the outer housing body, conveniently by introducing a welding head 80 through one of the end apertures 68 into the outer housing body.

An air filled annular gap 54 may be defined between the sealing region 51 of the inner housing body and the outer housing body 60, the gap 54 extending in an axial direction of the inner housing body substantially for an axial length of the sealing region 51.

As best seen in Figs. 15,18 and 19, a downstream axial end region 52 of the inner housing body 50 may be connected to the outlet end region 62 of the outer housing body by a discontinuously welded joint 55 which extends around an inner surface of the outer housing body 60. The discontinuously welded joint may comprise spot welds 56 as shown, formed by a spot welder 81 which conveniently may be introduced via the other axial end aperture 68 into the outer housing body as shown. Alternatively for example the discontinuously welded joint may comprise stitch or tack welds, which is to say, short weld beads spaced apart along the length of the joint, formed for example by a welding head 80 also introduced via the respective end aperture 68 into the outer housing body 60.

Referring to Figs. 28 and 29, the end apertures 68 of the outer housing body may be closed by two end plates 70, made for example as metal pressings. After inserting the inner housing body 50 containing the block 2 into the outer housing body 60 via one of its axial end apertures 68 and welding the inner housing body 50 to the outer housing body 60, the respective inlet or outlet 20, 30 may be inserted and welded into the respective apertures 63 and 66 or 64 and 67 of the outer housing body before the end plate 70 is welded to the outer housing body 60 to close the aperture 68.

Referring to Figs. 32, 35 and 37, the inner housing body 150 may include two or more sealing regions 151, with two or more gas permeable blocks 2 being arranged, each in a respective one of the sealing regions 151 with a body 4 of needle mat or the like as described above. The two blocks 2 may have different functions, for example, one block functioning as a diesel oxidation catalyst and the other as a diesel particulate filter. An axially central region 160 of the inner housing body 150 may be left uncompressed to help support the inner housing body 150 inside the outer housing body 60 and to help support compressive loads applied by fixing straps or the like to the outer housing body in use.

Referring to Figs. 16 and 17, the axial end regions 52 of the inner housing body are left uncompressed. The inner housing body 151 is inserted and installed in the outer housing body 60 and its axial end regions 52 connected to the outer housing body 60, preferably by welding as described above, so that the two or more sealing regions 151 are arranged in series relation in the flowpath F in the finished assembly as shown. The inlet and outlet and end plates are connected as described above to finish the assembly (15').

Industrial Applicability

The novel assembly and method may be used in place of a conventional exhaust gas treatment assembly, particularly where tight dimensional tolerances are required between the inlet and outlet connections.

Since the outer housing body is formed from a single piece of material, it can be made to tight dimensional tolerances, while the tolerance for the position of the inlet and outlet apertures is limited only by the tooling used to form them. Thus, after connecting the inlet and outlet (preferably by welding) to the outer housing body, the inlet and outlet positions are found to be highly repeatable. The improved tolerances of the outer housing body and inlet and outlet positions reduce the need for adjustable or flexible fixings and fluid connections, so that the assembly may be easier to install and more reliable in service.

Optionally, an annular air filled gap (i.e. not filled with a solid thermal insulation material) may be provided between the inner and outer housing bodies; this obviates the need to compress a thermal insulation material into the annulus and so makes it easier to assemble the inner housing body inside the outer housing body.

A substantially continuous, annular welded joint may be provided at the upstream end of the inner housing body so as to prevent exhaust gases from travelling through the air filled gap to bypass the block.

A discontinuously welded joint may be provided at the downstream end of the inner housing body. The discontinuously welded joint ensures minimal welding distortion of the housing and so can be applied closer to the block without damaging the block; thus, the axial length of the inner housing body may be slightly reduced, providing a slightly more compact assembly overall. In addition, the discontinuously welded joint may allow the air inside the annular gap to escape into the flowpath, relieving pressure from the volume of the gap and so avoiding distortion of the housing as the temperature changes in service.

In summary, a preferred exhaust gas treatment assembly comprises a unitary outer housing body 60 to which the inlet and outlet fittings 20, 30 are directly connected, preferably by welding. An inner housing body 50, 150 containing a gas permeable block is arranged inside the outer housing body before inserting the inlet or outlet and closing the outer housing body with an end cap 70.

Many further possible adaptations within the scope of the claims will be evident to those skilled in the art.

In the claims, reference numerals and characters are provided in parentheses for ease 5 of reference and should not be construed as limiting features.

Claims

1. An exhaust gas treatment assembly (15,15') including:

at least one gas permeable block (2), and a housing (40), the housing including:

an inlet region(61), an outlet region (62), a sealing region (51,151) arranged between the inlet region and the outlet region, an inlet (20) fluidly connected to the inlet region, and an outlet (30) fluidly connected to the outlet region;

the housing defining a flowpath (F) extending through the housing from the inlet to the outlet, the gas permeable block (2) being arranged sealingly within the sealing region of the housing so that the flowpath extends through the block; wherein the housing further includes:

a unitary, outer housing body (60), and an inner housing body (50,150), the inner housing body being arranged sealingly within the outer housing body;

the inlet and outlet regions of the housing comprising respective end regions of the outer housing body (60), the sealing region (51,151) comprising a sealing region of the inner housing body (50, 150).

2. An exhaust gas treatment assembly according to claim 1, wherein the inner housing body (150) includes two sealing regions (151), the two sealing regions being arranged in series relation in the flowpath, and two gas permeable blocks (2) are arranged respectively in the two sealing regions.

3. An exhaust gas treatment assembly according to claim 1, wherein the inner housing body (50,150) is connected to the inlet end region (61) of the outer housing body by a substantially continuous, annular welded joint (53) which extends around an inner surface of the outer housing body (60).

4. An exhaust gas treatment assembly according to claim 3, wherein an air filled annular gap (54) is defined between the sealing region (51,151) of the inner housing body (50, 150) and the outer housing body (60), the gap (54) extending in an axial direction of the inner housing body substantially for an axial length of the sealing region of the inner housing body, and the inner housing body is connected to the outlet end region (62) of the outer housing body by a discontinuously welded joint (55) which extends around an inner surface of the outer housing body (60).

5. An exhaust gas treatment assembly according to claim 1, wherein the inlet (20) comprises an inlet duct (21) and the outlet (30) comprises an outlet duct (31), and both the inlet duct and the outlet duct extend into the flowpath (F) within the outer housing body (60).

6. A method of assembling an exhaust gas treatment assembly (15,15'), including: providing:

at least one gas permeable block (2), an inner housing body (50,150), an inlet (20), and an outlet (30), and arranging the gas permeable block sealingly within a sealing region (51,151) of the inner housing body; and further including:

providing a unitary, outer housing body (60);

fluidly connecting the inlet (20) to an inlet end region (61) of the outer housing body, and fluidly connecting the outlet (30) to an outlet end region (62) of the outer housing body; and, after arranging the gas permeable block sea I ingly within the sealing region of the inner housing body, arranging the inner housing body (50,150) sealingly within the outer housing body (60) between the inlet end region and the outlet end region so that the inner and outer housing bodies together define a flowpath (F) extending through the block (2) from the inlet to the outlet.

7. A method according to claim 6, wherein at least one of the inlet (20) and the outlet (30) is fluidly connected to the respective inlet end region (61) or outlet end region (62) of the outer housing body (60) after arranging the inner housing body (50, 150) sealingly within the outer housing body (60).

8. A method according to claim 6, including inserting the inner housing body (50, 150) into the outer housing body (60) via an axial end aperture (68) of the outer housing body, and then welding a plate (70) to the outer housing body (60) to close the axial end aperture (68) of the outer housing body.

9. A method according to claim 6, including connecting the inner housing body (50, 150) to the inlet end region (61) of the outer housing body (60) by a substantially continuous, annular welded joint (53) which extends around an inner surface of the outer housing body (60).

10. A method according to claim 9, including connecting the inner housing body (50, 150) to the outlet end region (62) of the outer housing body (60) by a discontinuously welded joint (55) which extends around an inner surface of the outer housing body (60).

Amendments to the claims have been filed as follows

26 03 19

1. An exhaust gas treatment assembly (15,15') including:

at least one gas permeable block (2), and

5 a housing (40), the housing including:

an inlet regional), an outlet region (62), a sealing region (51, 151) arranged between the inlet region and the outlet region,

10 an inlet (20) fluidly connected to the inlet region, and an outlet (30) fluidly connected to the outlet region;

the housing defining a flowpath (F) extending through the housing from the inlet to the outlet, the gas permeable block (2) being arranged sealingly within the sealing region of the

15 housing so that the flowpath extends through the block; wherein the housing further includes:

20 the outer housing body having opposite axial ends (68) and defining a central length axis (X) extending between its opposite axial ends (68), the inlet and outlet regions of the housing comprising respective end regions of the outer housing body (60) between its opposite axial ends, the outer housing body (60) further comprising inlet and outlet apertures (63, 64) formed respectively in the inlet 25 and outlet regions (61, 62);

the inlet (20) and outlet (30) extending radially outwardly, respectively from the inlet and outlet apertures (63, 64) with respect to the length axis (X);

the sealing region (51,151) comprising a sealing region of the inner housing body (50, 150).

26 03 19

4. An exhaust gas treatment assembly according to claim 3, wherein an air filled annular gap (54) is defined between the sealing region (51,151) of the inner housing body (50,150) and the outer housing body (60), the gap (54) extending in an axial direction of the inner housing body substantially for an axial length of the sealing region

15 of the inner housing body, and the inner housing body is connected to the outlet end region (62) of the outer housing body by a discontinuously welded joint (55) which extends around an inner surface of the outer housing body (60).

20 5. An exhaust gas treatment assembly according to claim 1, wherein the inlet (20) comprises an inlet duct (21) and the outlet (30) comprises an outlet duct (31), and both the inlet duct and the outlet duct extend into the flowpath (F) within the outer housing body (60).

25 6. A method of assembling an exhaust gas treatment assembly (15,15'), including:

providing:

at least one gas permeable block (2), an inner housing body (50,150), an inlet (20), and an outlet (30), and

26 03 19 arranging the gas permeable block sealingly within a sealing region (51,151) of the inner housing body; and further including:

providing a unitary, outer housing body (60), the outer housing body having opposite axial ends (68) and defining a central length axis (X) extending between its opposite

5 axial ends (68);

the outer housing body (60) further comprising inlet and outlet apertures (63, 64) formed respectively in an inlet end region (61) and an outlet end region (62) of the outer housing body between its opposite axial ends (68);

fluidly connecting the inlet (20) to the inlet end region (61) of the outer housing body to

26 03 19

10 extend radially outwardly from the inlet aperture (63) with respect to the central length axis (X), and fluidly connecting the outlet (30) to the outlet end region (62) of the outer housing body to extend radially outwardly from the outlet aperture (64) with respect to the central length axis (X); and,

15 after arranging the gas permeable block sealingly within the sealing region of the inner housing body, arranging the inner housing body (50,150) sealingly within the outer housing body (60) between the inlet end region and the outlet end region so that the inner and outer housing bodies together define a flowpath (F) extending through the block (2) from the inlet to the outlet.