WO2014008930A1

WO2014008930A1 - Apparatus for treating an exhaust gas stream with removable module

Info

Publication number: WO2014008930A1
Application number: PCT/EP2012/063509
Authority: WO
Inventors: Stilian VELINOV
Original assignee: Swenox Ab
Priority date: 2012-07-10
Filing date: 2012-07-10
Publication date: 2014-01-16

Abstract

An apparatus (1) for treating a diesel engine exhaust gas stream is disclosed. The apparatus (1) comprises a filter unit (2) including a diesel particulate filter (21), a metallic tubular enclosure (22) enclosing the diesel particulate filter, and a tubular extension (23) extending past the diesel particulate filter and being provided with at least one lateral opening (24). The apparatus further comprises a housing (10), having a tubular compartment (12) for accommodating the filter unit and an access opening (11) provided at one end of the tubular compartment for enabling mounting and dismounting of the filter unit in an axial direction of the tubular compartment, wherein the access opening is provided with an outwardly protruding first flange. A lid (3) is further provided to cover an axial end opening of the tubular extension of the filter unit, the lid being provided with a second flange protruding out from the tubular extension. An annular gasket (25) is arranged around and in contact with the tubular extension, the gasket in the mounted position being arranged between the first and second flanges, and a releasable clamping means (5) is arranged for clamping the first flange and the second flange towards each other, thereby exerting a compression force on said annular gasket to secure the filter unit both axially and radially within said housing.

Description

APPARATUS FOR TREATING AN EXHAUST GAS STREAM WITH

REMOVABLE MODULE

Field of the invention

The present invention relates to an apparatus for treating a diesel exhaust gas stream from internal combustion engines for motor vehicles and other applications, said apparatus comprising at least one removable section. It also relates to a method for mounting a removable section of an apparatus for treating an exhaust gas stream.

Background of the invention

Exhaust from diesel engines may contain a number of unwanted noxious gases, such as nitrogen oxides (NO_x), carbon monoxide and un-burnt hydrocarbons; the exhaust may also contain particulate matters. The amount of those gases emitted from the engines is regulated by legal requirements. To be able to remove them, they can be treated so as to render them less obnoxious. This is made in an after treatment system, i.e. an apparatus for treating an exhaust gas stream.

It is therefore common practice to pass the exhaust gases through one or more treatment chambers of such an apparatus, containing e.g. a catalytic converter in which the unwanted noxious gases are converted to less harmful emissions. In the case of diesel engines the particulate matters are removed from the exhaust gas stream by a metal gauze or mesh or a ceramic filter element. The NO_x and oxygen in the gas stream can react with the particulates trapped in the filter element to form for example carbon dioxide, which is then mixed with the other exhaust gases. The filtered gases can then be subjected to reduction of remaining nitrogen oxides to nitrogen gas by injecting a reducing agent such as a solution of urea into the gas stream after it leaves the filter element but before it leaves the silencer unit. The treated gas stream is then passed over a further catalyst to convert residual ammonia from the urea to nitrogen and water, which are acceptable exhaust emissions. The net result is a typical reduction in noxious components of the exhaust gases of over 90%.

In many applications, filtration treatment element needs to be removed from the apparatus, cleaned from residual ash stored in the filter and refitted. Other treatment elements may require replacement or servicing and different treatment elements may have different service intervals. It is therefore desirable to be able to remove at least some of the individual treatment elements such that they may be individually serviced without the need to substantially dismantle the gas treatment apparatus.

To this end, it is known to provide apparatuses for treating a diesel exhaust gas stream comprising a housing with at least one removable filter. Such removable filters may be mounted/dismounted either axially or radially. Such or similar apparatuses are e.g. disclosed in WO 2006/029201 and EP 1 235 976. How often the filter, catalytic converter etc need to be removed for replacement or service depends on a number of parameters, such as the type of combustion engine used, how frequently the engine is operated, etc, but for normal heavy duty vehicles at least some of the treatment sections would need to be removed once or twice a year, or even more frequently.

However, several problems with these known apparatuses with removable filters still exist. For example, in many of these known devices it is still relatively complicated and cumbersome to mount and dismount the removable sections. For example, a relatively large force and special tools are often required for

mounting/dismounting. Further, it is also often necessary to use complicated and expensive telescopically sliding arrangements or the like, or to allow only very small tolerances, which also makes the apparatus expensive and difficult to manufacture and assemble and reassemble. Further, these known apparatuses are often subject to very high temperatures, leading to significant heat elongation. Still further, it is often difficult to obtain adequate sealing in the connection between the removable section and other parts. Still further, many of the existing after treatment systems are relatively large and bulky, which is a disadvantage, since the present trend is to make all components of heavy vehicles as compact as possible. There is therefore a need for an improved apparatus for treating an exhaust gas stream, which addresses at least some of the above-discussed drawbacks of the prior art. Summary of the invention

It is therefore an object of the present invention to provide an apparatus for treating a diesel exhaust gas stream, and having at least one removable filter unit, which alleviates at least some of the above-discussed drawbacks of the prior art.

This object is achieved with an apparatus according to the appended claims. In particular it is an object of the present invention to provide an improved diesel exhaust gas treatment apparatus which has at least one, and preferably several, and most preferably all, of the following advantages:

It is relatively cost-efficient to manufacture;

It permits relatively large tolerances in the filter dimensions;

- It is relatively easy to mount/dismount; and/or

It provides good sealing and fixation of the filter.

This object is achievable by means of different features and aspects of the present invention, which may be used one by one, or in various combinations.

According to a first aspect of the present invention, there is provided an apparatus for treating a diesel engine exhaust gas stream, the apparatus comprising: a filter unit including a diesel particulate filter, a metallic tubular enclosure enclosing the diesel particulate filter, and a tubular extension extending past said diesel particulate filter and being provided with at least one lateral opening;

a housing, having a tubular compartment for accommodating said filter unit and an access opening provided at one end of said tubular compartment for enabling mounting and dismounting of said filter unit in an axial direction of the tubular compartment, wherein said access opening is provided with an outwardly protruding first flange;

a lid to cover an axial end opening of said tubular extension of the filter unit, said lid being provided with a second flange protruding out from said tubular extension;

an annular gasket being arranged around and in contact with the tubular extension, said gasket in the mounted position being arranged between said first and second flanges; and

a releasable clamping means for clamping the first flange and the second flange towards each other, thereby exerting a compression force on said annular gasket to secure the filter unit both axially and radially within said housing.

Hereby, a very cost-efficient and easy-to-use apparatus is obtained. The securing of the filter in place is here made very simple: the filter is simply inserted into the receiving tubular compartment, a lid is placed over the top, and the releasable clamp conveniently connects the parts together. In particular, the arrangement of an annular gasket between the flange of the housing, the flange of the lid, and the side wall of the tubular extension, provides simultaneous fixation/securing and sealing of the filter unit. Thus, mounting/dismounting hereby becomes very simple. Further, this fixation/securing is relatively uncomplicated, and cost-efficient to produce. Still further, this fixing/securing is relatively insensitive, and accepts large dimensional tolerances.

Further, since larger tolerances can be accepted by means of the present invention, the precision in the manufacture of the filter unit is less crucial, making the manufacturing easier and less costly.

The removable filter typically contains a cylindrical core of the filter element, such as a through- flow porous or apertured ceramic support or a filter core having a plurality of axial bores closed at alternate ends so as to provide a tortuous path for gas through the filter element. Such cores, their design and manufacture can be of conventional nature, and are per se well-known in the art. The cores are typically surrounded by a shock absorbing material, and by a cylindrical steel tubular wall or the like. The removable section is preferably reusable after removal, but disposable sections are also feasible.

Preferably, the lid is arranged to be at least partly inserted into the end opening of the tubular extensions. Hereby, the lid may have a lowered central portion, to be inserted into the opening of the tubular extension, an uprising rim, and continuing in an radially outwardly protruding flange.

The gasket may be tapering in an outward direction. For example, the gasket may have a trapetzoidal cross-sectional shape. Hereby, a good pressure distribution from the releasable clamping means towards the filter unit is obtained, which ensures a good fixation/securing both radially and axially, and a good sealing at the same time.

The re leasable clamping means may be a band clamp. In particular it is preferred that the band of the band clamp is substantially V-shaped. The term "V- shaped" is here used as a common denominator for essentially all circumferential clamp straps having a concave inner shape, i.e. forming an annular groove in the side facing inwardly, thereby providing both a radial force and an axial force compressing the parts enclosed by the strap when the strap is tightened.

The lid may be provided with two metallic walls, which are separated to form a cavity there between. An isolating material is preferably arranged between the walls, i.e. enclose in said cavity. However, alternatively the cavity may be filled with a gas, such as air, be provided with a vacuum, or the like.

The tubular extension preferably has a plurality of lateral openings being distributed around the circumference. The plurality of lateral openings may be uniformly distributed around the circumference, i.e. arranged equidistant ly. However, other configurations are equally possible, such as having the openings provided around only part of the circumference, having openings of different sizes, etc. By having a plurality of openings, exhaust gas coming out from the filter may be distributed among said several openings for a good gas flow through the apparatus. However, alternatively only one lateral opening may suffice in many applications.

A second annular gasket may further be arranged around and in contact with the metallic tubular enclosure, wherein the second annular gasket is arranged to form a seal between the metallic tubular enclosure and the tubular compartment.

Preferably, the annular gasket is arranged to be in the vicinity of the opening of the tubular compartment in a mounted disposition. Hereby, annular gasket and the seal between the tubular compartment and the filter unit is not arranged close to the inlet of the filter unit, but instead arranged close to the outlet. However, it has been found that the seal works just as well at this position. Further, by arrangement of the annular gasket close to the trailing end of the filter unit, at a distance from the first to be inserted forward end, mounting is greatly facilitated, since the annular gasket needs only to be inserted for a short distance into the tubular compartment.

The tubular compartment further preferably comprises, at an area opposite said opening, a plurality of inward protrusions arranged to engage with the filter unit in a mounted disposition for radial stabilization of the filter unit. Due to this arrangement, the inward protrusions become slightly flexible, which allows for a radial securing and stabilization of the filter unit. At the same time,

mounting/dismounting is easy. Further, dimensional width tolerances for the filter may hereby easily be accepted, by provision of a calibrated outer surface at the lower end of the metallic tubular enclosure being arranged over the inward protrusions in the mounted position.

The tubular compartment, the filter unit and the lid preferably all have a rounded cross-section, and preferably a circular, elliptical, super-elliptical or oval cross-section. This makes e.g. strap connections more effective and easier to tighten properly.

The gaskets may be made from rubber, a ceramic string or braid, and possibly impregnated with graphite, or other deformable thermally stable materials.

The tubular extension may be arranged as a telescopic slip joint around the tubular enclosure, allowing the tubular extension to be fixed at a desired height. Hereby, the height of the filter unit can easily be adjusted prior to assembly, and calibrated to a desired height. Hereby, relatively large variations in height dimensions for the filters can be accepted, since this may be compensated by the telescopic slip joint. This telescopic slip joint arrangement may be used, and is of great advantage, also in relation to other types of gas treatment apparatuses.

Thus, in accordance with another aspect of the present invention, there is provided an apparatus for treating an diesel engine exhaust gas stream, the apparatus comprising:

a filter unit including a diesel particulate filter, a metallic tubular enclosure enclosing the diesel particulate filter, and a tubular extension extending past said diesel particulate filter, and being provided with at least one lateral opening;

a housing, having a tubular compartment for accommodating said filter unit and an opening provided at one end of said tubular compartment for enabling mounting and dismounting of said filter unit in an axial direction of the tubular compartment;

a lid to cover an axial end opening of said tubular extension of the filter unit; wherein said tubular extension is arranged as a telescopic slip joint around said tubular enclosure, allowing the tubular extension to be fixed at a desired height. In accordance with this aspect of the invention, similar advantages and specific preferred features as discussed above with reference to the first aspect of the invention are obtainable and useable.

In particular, the tubular extension may be arranged as a telescopic slip joint around the tubular enclosure, allowing the tubular extension to be fixed at a desired height. Hereby, the height of the filter unit can easily be adjusted prior to assembly, and calibrated to a desired height. Hereby, relatively large variations in height dimensions for the filters can be accepted, since this may be compensated by the telescopic slip joint.

The connection of the lid to the upper end, and the axial and radial

stabilization and fixation of the filter unit may be obtained in various ways, and preferably in the way discussed above. However, this telescopic slip joint

arrangement may be used, and is of great advantage, also in relation to other types of gas treatment apparatuses. For example, it may be used with alternative clamping means, such as bolt connections, threaded lids and the like.

The tubular extension is preferably permanently fixed to the tubular enclosure, and e.g. by means of welding. This allows the tubular extension to be adjusted to a suitable height once, which is normally sufficient, since the dimensions of the filter is normally essentially constant over time. However, it is alternatively feasible to releasably fix the tubular extension to the tubular enclosure, and e.g. by means of adhesion. Hereby, repeated adjustments are enabled.

The tubular extension preferably has an inner diameter being at least slightly larger than an outer diameter of said tubular enclosure.

mounting/dismounting is easy. Further, dimensional width tolerances for the filter may hereby easily be accepted, by provision of a calibrated outer surface at the lower end of the metallic tubular enclosure being arranged over the inward protrusions in the mounted position. A second annular gasket may further be arranged around and in contact with the metallic tubular enclosure, wherein the second annular gasket is arranged to form a seal between the metallic tubular enclosure and the tubular compartment.

This arrangement of the annular gasket may be used, and is of great advantage, also in relation to other types of gas treatment apparatuses.

Thus, in accordance with yet another aspect of the present invention, there is provided an apparatus for treating an diesel engine exhaust gas stream, the apparatus comprising:

a filter unit including a diesel particulate filter, a metallic tubular enclosure enclosing the diesel particulate filter;

an annular gasket arranged around and in contact with the metallic tubular enclosure, said annular gasket being arranged to form a seal between the filter unit and the tubular compartment;

wherein said annular gasket is arranged to be in the vicinity of said opening of the tubular compartment in a mounted disposition.

In accordance with this aspect of the invention, similar advantages and specific preferred features as discussed above with reference to the first two aspects of the invention are obtainable and useable.

In particular, the second annular gasket may be arranged to be in the vicinity of the opening of the tubular compartment in a mounted disposition. Hereby, annular gasket and the seal between the tubular compartment and the filter unit is not arranged close to the inlet of the filter unit, but instead arranged close to the outlet. However, it has been found that the seal works just as well at this position. Further, by arrangement of the annular gasket close to the trailing end of the filter unit, at a distance from the first to be inserted forward end, mounting is greatly facilitated, since the annular gasket needs only to be inserted for a short distance into the tubular compartment.

The tubular compartment may comprise, at an area opposite said opening, a plurality of inward protrusions arranged to engage with the filter unit in a mounted disposition for radial stabilization of the filter unit.

This arrangement of inward protrusions may be used, and is of great advantage, also in relation to other types of gas treatment apparatuses.

a filter unit including a diesel particulate filter, a metallic tubular enclosure enclosing the diesel particulate filter; and

wherein said tubular compartment comprises, at an area opposite said opening, a plurality of inward protrusions arranged to engage with the filter unit in a mounted disposition for radial stabilization of the filter unit.

In accordance with this aspect of the invention, similar advantages and specific preferred features as discussed above with reference to the first three aspects of the invention are obtainable and useable.

In particular, due to this arrangement, the inward protrusions become slightly flexible, which allows for a radial securing and stabilization of the filter unit. At the same time, mounting/dismounting is easy. Further, dimensional width tolerances for the filter may hereby easily be accepted, by provision of a calibrated outer surface at the lower end of the metallic tubular enclosure being arranged over the inward protrusions in the mounted position. The inward protrusions are preferably uniformly distributed around the circumference of the tubular compartment.

The inward protrusions are further preferably flexible.

A corresponding part of the metallic enclosure, arranged to be in contact with said inward protrusions in the mounted disposition, is preferably provided with a calibrated diameter.

In a preferred embodiment, at least three inward protrusions are provided, and most preferably at least five, such as six or eight.

According to still another aspect of the present invention, there is provided a vehicle comprising an apparatus for treating a diesel engine exhaust gas stream from an internal combustion engine, the gas treatment apparatus being as discussed above.

In accordance with this aspect of the invention, similar advantages as discussed above with reference to the first aspect of the invention are obtainable.

The present invention is of special application in the treatment of the exhaust gases from internal combustion engines, notably diesel or spark ignition engines. The engine may be a stationary engine, for example driving an electricity generator or an hydraulic fluid compression unit, or a marine engine. However, the invention is of especial application in the treatment of the exhaust gases from a diesel engine in a modular silencer assembly on a motor vehicle to attenuate the engine noise and to reduce the noxious emissions from the engine as described above. For convenience, the invention will primarily be described in terms of such a preferred use.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

For exemplifying purposes, the invention will be described in closer detail in the following with reference to embodiments thereof illustrated in the attached drawings, wherein:

Fig 1 is a schematic perspective view of a diesel exhaust treatment apparatus in accordance with one embodiment of the present invention;

Fig 2 is an exploded perspective view of the apparatus of Fig 1; Fig 3 is an exploded and cross-sectional perspective view of the apparatus of Figs. 1 and 2;

Fig 4 is an exploded and cross-sectional perspective view of a part of the apparatus of claim 3, shown in somewhat more detail; and

Fig 5 is a cross-sectional view of a part of the apparatus of the previous figures.

Description of preferred embodiments

With reference to Figs. 1-5, all illustrating the same embodiment of the present invention, the invention generally relates to an apparatus 1 for treating an exhaust gas stream, for use in e.g. heavy duty vehicles. The apparatus comprises a housing 10, forming a protective enclosure in which exhaust treatment elements are arranged.

The housing comprises an opening 11 for mounting and dismounting of a filter unit 2. Inside the opening 11, there is provided a tubular compartment 12, arranged to receive and accommodate the filter unit 2. A lid 3 may be provided for closing the opening 11.

A diesel exhaust gas stream enters the apparatus 1 through an inlet (not shown), and is conveyed along a predetermined path, leading inter alia through the filter unit 2, to an outlet (not shown). In the illustrative embodiment, the exhaust gas stream is conveyed through the filter unit from the bottom of the tubular compartment and up towards the opening 11. However, alternatively, the exhaust gas stream may also be conveyed in an opposite direction.

The filter unit comprises a diesel particulate filter 21 enclosed in a metallic tubular enclosure 22. The filter unit is also preferably provided with a tubular extension 23, connected to the metallic tubular enclosure and extending past the diesel particulate filter in a direction towards the opening 11 in the mounted position. The tubular extension, which will be discussed in more detail in the following, is preferably provided with at least one lateral opening 24. Diesel particulate filters are per se well known. A general problem with such filters is that the exact dimensions are difficult to control precisely. Accordingly, the dimensions in both diameter and length will typically vary between filter with a few, or up to several, millimetres. In the illustrated example the filter unit is arranged in the mounted position in a secured and sealed manner by means of a combination of fixation means arranged close to the bottom of the tubular compartment, an annular gasket arranged close to the upper part of the filter unit, i.e. close to the opening 11, and a lid connection arrangement. These parts will be discussed more thoroughly in the following.

However, it to be acknowledged by the skilled addressee that each of these may alternatively be used without the presence of the others, alone or in combination with other fastening and sealing arrangements.

Close to the bottom of the tubular compartment, a number of inward protrusions 13 are arranged and distributed around the circumference of the tubular compartment 12. Preferably, the inward protrusions are formed as narrow elongate ridges, extending primarily, and preferably solely, in the axial direction of the tubular compartment. Preferably at least three inward protrusions are provided, such as six or eight. The inward protrusions are preferably equidistantly arranged around the circumference of the tubular compartment. Due to the limited size of the inward protrusions, they become at least partly flexible, since a outward pressure applied on the ridges will cause a slight elastic deformation of the tubular compartment.

The filter unit is preferably provided with at least a lower part having a calibrated circular outer wall, having a predetermined diameter. This may be provided by making the entire metallic tubular enclosure of a calibrated size. However, preferably this is obtained by increasing the size of a lower area to the calibrated size. Hereby, diameter variations in the filter may easily be accepted. The calibrated diameter is preferably chosen to be the same, or slightly larger than, the diameter of a circle extending around the inward edges of the inward protrusions 13.

When the filter unit is mounted, and inserted into the tubular compartment, the calibrated circular outer wall will come into contact with the inward protrusions 13, and thereby be fixed and secured in a radial direction. At the same time, mounting becomes easy, and does not require much force, since the contact between the filter unit and the tubular compartment is limited to the contact areas provided at the edges of the inward protrusions, and due to the flexibility provided by the tubular compartment due to this arrangement.

An annular gasket 25 is further preferably provided between the filter unit and the tubular compartment 12. The annular gasket 25 is arranged to provide a sealed closure between the outer wall of the metallic tubular enclosure 22 of the filter unit 2, and the inner wall of the tubular compartment 12. The annular gasket 25 may be arranged at any position the filter unit, such as close to the lower, first-to-be inserted end. However, in a preferred embodiment the annular gasket 25 is arranged on an upper part of the filter unit 2, as in the illustrated example. Hereby, the annular gasket 25 is arranged close to the upper end of the metallic tubular enclosure 22, i.e. close to the end facing the opening 11 in the mounted position, and also close to the upper end of the tubular compartment. By this arrangement, the annular gasket 25 only needs to be inserted a very limited distance into the tubular compartment during mounting. This makes the mounting and dismounting processes simpler, and with less force being required. In addition, it limits the wear on the filter during mounting and dismounting. The fact that exhaust gas may enter the space between the filter unit and the tubular compartment beneath the annular gasket is not a problem, since the exhaust gas will anyway be hindered to escape past the annular gasket, and thereby forced to take the path through the filter instead.

At an upper end of the filter unit, a tubular extension 23 is arranged, and being provided with lateral openings 24, to allow the exhaust gas to escape laterally when having passed the filter. The tubular extension 23 is preferably connected to the metallic tubular enclosure 22 by means of a telescopic slip joint, allowing the height of the tubular extension to be varied. This makes it possible to adjust the height of the filter unit in a very simple and convenient way, to compensate for variations in the height of the filter. The tubular extension 23 is then preferably fixed in the desired position by means of a non-releasable connection, such as by welding, or a releasable connection, such as by adhesion. However, other ways of obtaining a fixation are naturally feasible, such as by bolt connections, threaded connections, and the like.

Preferably, a plurality of lateral openings 24 are provided in the tubular extension 23, and being distributed around the circumference. Most preferably, the lateral openings are uniformly distributed around the circumference.

The opening 11 is in the illustrated example arranged at the end of a second compartment 14 being arranged between the opening 11 and the tubular compartment 12. The second compartment preferably extends past the tubular compartment in one or several lateral direction(s), in order to convey the exhaust gas laterally. However, alternatively, the opening 11 may be formed directly at the end of the tubular compartment 12.

As best seen in Fig. 5, The opening 11 is preferably provided with an outwardly protruding first fiange 15. The flange 15 may be directed solely in a lateral, outward direction. However, preferably, the flange is inclined, and extends both outwardly and upwardly, i.e. in a direction away from the tubular compartment and the filter unit.

The lid 3 is preferably provided with a second flange 31 , arranged to extend past the edge of the filter unit. The second flange 31 may be directed solely in a lateral, outward direction. However, preferably, the flange is inclined, and extends both outwardly and downwardly, i.e. in a direction towards the tubular compartment and the filter unit.

An annular gasket 4 may be arranged around and in contact with the filter unit, and here the tubular extension 23, so that, in the mounted position, the annular gasket 4 is provided between the first flange 15 and the second flange 31. The annular gasket 4 is preferably tapering in an outward direction, and preferably has a trapetzoidal cross-sectional shape.

For closing of the opening and for fixation of the filter unit within the housing, a releasable clamping means 5 is arranged around the first and second flange, to clamp the first flange and second flange towards each other. Hereby, a compression force is also applied on the annular gasket 4, which thereby secures the filter unit both axially and radially to the opening and within the housing. Hereby, a combined securment of the filter unit and closing of the opening is obtained simultanesouly, and in a very easy and quick procedure.

The releasable clamping means is preferably a band/strap clamp, and most preferably a band clamp where the band 51 is substantially V-shaped in cross-section, with the concave surface facing the parts to be adjoined. In addition to the V-shaped band, an outer band 52 may be provided to provide increased stability. The outer band 52 may be fixedly connected to the inner band 51. Further, tensioning means, such as a bolt connection 53, connects the ends of the band, and are operable to increase and increase the tension of the band. However, any suitable tensioning means could be used, as would be apparent for someone of ordinary skill in the art. For example, tension may be applied by means of screws, nuts or bolts which secure the ends of straps; by twisting adjacent straps together; by applying a transverse force to the straps, for example by pulling them sideways to attach to hooks on the exposed wall of the sections in a manner similar to that used to tension a drum skin; by wedges or other means. Alternatively, the straps can be tensioned by an over-centre tensioning device, by the use of tension springs in the mounting and/or securing of the straps, or by applying the straps hot and allowing them to cool and contract once in situ.

However, alternative releasable clamping means are feasible, such as bolt connections arranged through the radially outwardly extending flanges.

The lid 3 is preferably shaped so that it may be at least partly inserted into the end opening of the tubular extension. The lid may further be provided with two metallic walls, an inner wall 32 and an outer wall 33, and an isolating material 34 arranged there between.

By means of this apparatus, it becomes easy to open and enter the housing, and very simple to mount and dismount the filter unit from the housing during maintenance services.

The apparatus may, in addition to the filter unit, comprise additional gas treatment elements, as is per se previously known, such as a catalyst and additional filters, and the like.

It is to be appreciated by someone skilled in the art, that the above-discussed features of the exemplary embodiment may be use in combination, or in combination with other types of sealing and fixation arrangements. For example, the radial fixation arrangement provided by the inward protrusions may be used with any type of opening closure, sealing and the like. Further, the opening closure arrangement, providing both closure and radial and axial fixation of the filter unit, may be used with any type of sealing and fixation between the filter unit and the tubular compartment. The slip joint arrangement of the tubular extension and the arrangement of an annular gasket at the upper part of the filter unit may also be used in any system, regardless of how it is mounted and secured.

Further, it is to be realized that many variations are feasible within these concepts. For example, other types of releasable clamping means are feasible, the cylindrical units need not have a circular cross-section, but oval cross-sections and the like are also feasible. Still further, the lid may have any shape feasible to cover the opening. Such and other obvious modifications must be considered to be within the scope of the present invention, as it is defined by the appended claims. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting to the claim. The word "comprising" does not exclude the presence of other elements or steps than those listed in the claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. Further, a single unit may perform the functions of several means recited in the claims.

Claims

1. An apparatus for treating a diesel engine exhaust gas stream, the apparatus comprising:

a filter unit including a diesel particulate filter, a metallic tubular enclosure enclosing the diesel particulate filter, and a tubular extension extending past said diesel particulate filter and being provided with at least one lateral opening;

2. The apparatus of claim 1, wherein said lid is arranged to be at least partly inserted into the end opening of the tubular extension.

3. The apparatus of claim 1 or 2, wherein the gasket is tapering in an outward direction.

4. The apparatus of claim 3, wherein the gasket has a trapetzoidal cross- sectional shape

5. The apparatus of any one of the preceding claims, wherein the releasable clamping means is a band clamp.

6. The apparatus of claim 5, wherein the band of said band clamp is substantially V-shaped.

7. The apparatus of any one of the preceding claims, wherein said lid is provided with two metallic walls, providing a cavity there between, and wherein an isolating material is preferably arranged in said cavity.

8. The apparatus of any one of the preceding claims, wherein said tubular extension has a plurality of lateral openings being distributed around the

circumference.

9. The apparatus of claim 8, wherein the plurality of lateral openings are uniformly distributed around the circumference.

10. The apparatus of any one of the preceding claims, wherein the tubular extension is arranged as a telescopic slip joint around said tubular enclosure, allowing the tubular extension to be fixed at a desired height.

11. The apparatus of any one of the preceding claims, further comprising a second annular gasket arranged around and in contact with the metallic tubular enclosure, said annular gasket being arranged to form a seal between the filter unit and the tubular compartment, wherein said annular gasket is arranged to be in the vicinity of said opening of the tubular compartment in a mounted disposition.

12. The apparatus of any one of the preceding claims, wherein said tubular compartment comprises, at an area opposite said opening, a plurality of inward protrusions arranged to engage with the filter unit in a mounted disposition for radial stabilization of the filter unit.

13. A vehicle comprising an apparatus for treating a diesel engine exhaust gas stream from an internal combustion engine, the gas treatment apparatus being as claimed in any one of the preceding claims.

14. Apparatus for treating an diesel engine exhaust gas stream, the apparatus comprising:

a lid to cover an axial end opening of said tubular extension of the filter unit; wherein said tubular extension is arranged as a telescopic slip joint around said tubular enclosure, allowing the tubular extension to be fixed at a desired height.

15. The apparatus of claim 14, wherein the tubular extension is permanently fixed to the tubular enclosure, and preferably by means of welding.

16. The apparatus of claim 14, wherein the tubular extension is releasably fixed to the tubular enclosure, and preferably by means of adhesion.

17. The apparatus of claim 14, 15 or 16, wherein the tubular extension has an inner diameter being at least slightly larger than an outer diameter of said tubular enclosure.

18. The apparatus of any one of the claims 14-17, further comprising a second annular gasket arranged around and in contact with the metallic tubular enclosure, said annular gasket being arranged to form a seal between the filter unit and the tubular compartment, wherein said annular gasket is arranged to be in the vicinity of said opening of the tubular compartment in a mounted disposition.

19. The apparatus of any one of the claims 14-18, wherein said tubular compartment comprises, at an area opposite said opening, a plurality of inward protrusions arranged to engage with the filter unit in a mounted disposition for radial stabilization of the filter unit.

20. A vehicle comprising an apparatus for treating a diesel engine exhaust gas stream from an internal combustion engine, the gas treatment apparatus being as claimed in any one of the claims 14-19.

21. Apparatus for treating an diesel engine exhaust gas stream, the apparatus comprising: a filter unit including a diesel particulate filter, a metallic tubular enclosure enclosing the diesel particulate filter;

22. The apparatus of claim 21, wherein the annular gasket in the mounted disposition is arranged to provide a seal leaking less than 50 litre/minute at 0.3 bar internal pressure, and preferably less than 30 litre/minute, and most preferably less than 25 litre/minute.

23. The apparatus of claim 21 or 22, wherein said tubular compartment comprises, at an area opposite said opening, a plurality of inward protrusions arranged to engage with the filter unit in a mounted disposition for radial stabilization of the filter unit.

24. A vehicle comprising an apparatus for treating a diesel engine exhaust gas stream from an internal combustion engine, the gas treatment apparatus being as claimed in any one of the claims 21-23.

25. Apparatus for treating an diesel engine exhaust gas stream, the apparatus comprising:

26. The apparatus of claim 25, wherein the inward protrusions are uniformly distributed around the circumference of the tubular compartment.

27. The apparatus of claim 25 or 26, wherein the inward protrusions are flexible.

28. The apparatus of claim any one of the claims 25-27, wherein a

corresponding part of the metallic enclosure, arranged to be in contact with said inward protrusions in the mounted disposition, is provided with a calibrated diameter.

29. The apparatus of any one of the claims 25-28, wherein at least three inward protrusions are provided, and preferably at least five.

30. A vehicle comprising a gas treatment apparatus for the treatment of an exhaust gas stream from an internal combustion engine, the gas treatment apparatus being as claimed in any one of the claims 25-29.