BACKGROUND TO THE INVENTION AND PRIOR ART The present invention relates to a connection between two pipes in a pipeline according to the preamble of claim 1.

Exhaust lines which lead exhaust gases out from combustion engines in vehicles comprise usually a plurality of pipes and tubular components. A known practice for preventing leakage at a connection between two adjoining pipes in an exhaust line is to provide one of the pipes with an annular seal which abuts against a sealing surface of the other pipe. During operation of the engine, pipes in the exhaust line are subject to thermal stresses. To prevent their being deformed by these stresses, the pipes are usually provided with wearing surfaces to ensure that it is possible for the pipes to undergo mutual movements in an axial direction at the connection. After a certain period of use, however, the pipes' wearing surfaces which are initially quite smooth usually suffer wear and tear and therefore become uneven.

On occasions when pipes in the exhaust line are disassembled, their wearing surfaces are moved out of mutual engagement, causing the wearing surface of the first pipe to move past the seal on the second pipe. If the wearing surface is uneven and rough, there is risk of damage to the seal. If the seal sustains tears or similar damage, the result will be exhaust leakage at the connection between the pipes. On occasions when the pipes are reassembled, the wearing surface moves in an opposite direction past the seal, with risk of further damage to the seal. It is therefore not sufficient to change the seal, as the pipe with the wearing surface also needs changing, otherwise the wearing surface might damage the new seal when the pipes are being reassembled. The second pipe is usually also changed. Changing both of the pipes and the seal at a connection each time pipes are disassembled results in large consumption of pipes and seals. The cost of disassembling pipes with wearing surfaces in an exhaust line thus becomes relative high. SUMMARY OF THE INVENTION

The object of the present invention is to propose a connection of the kind mentioned in the introduction whereby it is possible to disassemble and reassemble the respective components without causing any obvious risk of leakage at the reassembled connection.

These objects are achieved with the device of the kind mentioned in the introduction which is characterised by the features indicated in the characterising part of claim 1. The connection is provided with a wearing region which allows mutual movements between the connecting portions of the pipes. This mobility substantially prevents the occurrence of thermal stresses at the connection between the adjoining pipes when they undergo temperature variations. Over time, the surfaces of the wearing region become more or less rough. To achieve a tight connection between the pipes, the connection is provided with a sealing region. For a good seal between the surfaces of the sealing region it is very important that the sealing surfaces be undamaged.

According to the invention, the wearing region is at a radial distance from a centreline through the connection which differs from the radial distance from the sealing region to the centreline. When pipes of the kind mentioned in the introduction are being disassembled, they are moved in a substantially axial direction relative to one another. As the wearing region and the sealing region are at different radial distances from the centreline, they do not come into mutual contact during disassembly. The risk of the surfaces of the sealing region being damaged by the wearing region's rough surfaces during disassembly and subsequent reassembly is thus substantially completely eliminated. It is therefore possible to disassemble and reassemble the respective components at the connection without causing any obvious risk of leakage at the reassembled connection. The pipes have with advantage a circular cross-sectional shape but may have substantially any desired functional shape. The term "pipe" is here to be construed in a broad sense. The connection may be made between two components each provided with a tubular portion at the region where the connection is effected. According to the present invention, the sealing region comprises a sealing surface of the first connecting portion and a seal means situated on the second connecting portion, which sealing surface and seal means are adapted to being in mutual contact when the connecting portions are in the connected state. The seal means abuts with advantage with a resilient force against the sealing surface of the first connecting portion. For the sealing region to be able to create a tight connection between the pipes, neither the seal means nor the sealing surface may have tears or other kinds of surface damage. The sealing surface faces inwards and the seal means has a surface facing radially outwards and adapted to being in contact with the sealing surface when the connecting portions are in the connected state. The radially external surfaces of the seal means abut here with advantage with a resilient force against the sealing surfaces of the first connecting portion.

According to an embodiment of the present invention, the wearing region is at a greater radial distance from the centreline than the radial distance from the sealing region to the centreline. Alternatively, the wearing region is at a smaller radial distance from the centreline than the radial distance from the sealing region to the centreline. Either of these alternatives may be adopted, depending on the mutual positions of the wearing region and the sealing region at the connection.

According to another preferred embodiment of the present invention, the wearing region comprises a first wearing surface of the first connecting portion and a second wearing surface of the second connecting portion which are adapted to being in mutual contact when the connecting portions are in the connected state. The shape of the wearing surfaces is such as to allow mobility between the connecting portions when they undergo thermal stresses. The first wearing surface and the second wearing surface are with advantage so configured as to allow a certain mutual mobility between the pipes in an axial direction when the connecting portions are in a connected state, making it possible for changes in the lengths of the pipes to be absorbed at the connection. According to another preferred embodiment of the present invention, the first wearing surface faces radially inwards and the second wearing surface radially outwards. The first connecting portion serves here as a radially external element of the connection which encloses the second connecting portion. The wearing surfaces here take the form of cylindrical surfaces with an axial extent which defines a maximum linear movement between the pipes at the connection.

According to another preferred embodiment of the present invention, the seal means is a sealing ring made of metal material. Where the pipes convey a gaseous or liquid medium at a high temperature, the seal means has to be made of heat-tolerant material. This makes it appropriate for the seal means to be made of metal material with suitable characteristics. The connection is with advantage between two pipes in an exhaust line. Pipes in exhaust lines are subject to great thermal stresses. These pipes are usually provided with wearing surfaces to allow mutual movements between the pipes. Such pipes typically form part of exhaust manifolds and turbo manifolds.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below by way of examples with reference to the attached drawings, in which

Fig. 1 depicts a connection in an exhaust line according to a first embodiment of the invention,

Fig. 2 depicts the connection in Fig. 1 in more detail,

Fig. 3 depicts a connection in an exhaust line according to a second embodiment of the invention and

Fig. 4 depicts the connection in Fig. 3 in more detail. DETAILED DESCRIPTION OF PREFERRED EMB ODEVIENT S OF THE

INVENTION

Figs. 1 and 2 depict a connection between a first pipe 1 and a second pipe 2 in an exhaust line which leads exhaust gases out from a combustion engine. The first pipe 1 may be an exhaust manifold and the second pipe 2 a turbo manifold. The first pipe 1 usually has an external connecting portion la which is pushed onto an internal connecting portion 2a of the second pipe 2 to achieve a connected state. The first pipe 1 has stationary fastening by means of a number of fastening means 3 which may be bolts. The second pipe 2 has stationary fastening by means of a number of fastening means 4 which may likewise be bolts. During operation of the engine, the pipes 1, 2 in the exhaust line for exhaust gases are subject to varying temperatures. The exhaust gases in a diesel engine may be at a temperature of up to about 600-700°C. To prevent the pipes from being deformed by the thermal load from the exhaust gases, the connecting portion la of the first pipe is provided with an internal wearing surface 5. The connecting portion 2a of the second pipe is provided with an external wearing surface 6 adapted to being in contact with the first pipe's wearing surface 5 when the pipes 1, 2 are in a connected state. The two wearing surfaces 5, 6 provide assurance that the first pipe 1 and the second pipe 2 can undergo changes in length and move in an axial direction relative to one another in response to variation in the temperature of the exhaust gases in the exhaust line. The pipes' wearing surfaces 5, 6 are initially smooth but over a period of use they inevitably suffer wear and tear such that they may become uneven and rough. The second pipe's connecting portion 2a has an end surface 2b and a bearing surface 7 which faces radially outwards and is adapted to accommodating and supporting an annular seal means 8. In this embodiment the second pipe's wearing surface 6 is at a greater distance from the end surface 2a than the distance which the bearing surface 7 is from the end surface 2a. The second pipe's connecting portion 2a comprises also a radial stop surface 9 which defines an intended fitting position for the seal means 8 on the bearing surface 7. The seal means 8 is made of material which tolerates the high temperatures which occur in the exhaust line. The seal means 8 may be made of suitable metal material. The first pipe's connecting portion la has an end surface lb and a sealing surface 10 which faces radially inwards and which is adapted to coming into contact with the seal means 8 when the pipes 1, 2 are in a connected state. The first pipe's sealing surface 10 is at a greater distance from the first pipe's end surface lb than the wearing surface 5 is from the end surface lb. The first pipe's wearing surface 5 and the second pipe's wearing surface 6 form a wearing region A between the pipes 1, 2 when they are in a connected state. The first pipe's wearing surface 5, the second pipe's wearing surface 6 and the wearing region A are at a radial distance ΓΑ from a centreline 11 of the connection. The first pipe's sealing surface 10 and the seal means 8 form a sealing region B between the pipes 1, 2. The first pipe's sealing surface 10, the seal means 8 and the wearing region B are at a radial distance r _B from the centreline 11 of the connection. In this embodiment, the wearing region A is at a greater radial distance ΓΑ from the centreline 11 than the radial distance r _B from the sealing region B to the centreline 11.

The object of the present invention is to prevent the wearing surfaces 5, 6 from causing tears or other damage to the seal means 8 or the sealing surface 10 when the pipes are being disassembled and reassembled. On occasions when the first pipe 1 and the second pipe 2 are being disassembled, connecting means 3, 4 of at least one of the pipes 1, 2 are released. The first pipe 1 and the second pipe 2 are then moved in an axial direction away from one another. To prevent damage to the seal means 8, it must not come into contact with the first pipe's wearing surface 5 during disassembly. To prevent damage to the first pipe's sealing surface 10, it must not come into contact with the second pipe's wearing surface 6 during disassembly. As in this embodiment the first pipe's sealing surface 10 and the second pipe's wearing surface 6 are so arranged that they need not pass one another when the pipes 1, 2 are being

disassembled and reassembled, there is no risk of the sealing surface 10 being damaged by the second pipe's wearing surface 6. However, the first pipe's wearing surface 5 will pass the seal means 8 when the pipes 1, 2 are being disassembled and reassembled. To prevent its coming into contact with the seal means 8 in this situation, the first pipe's wearing surface 5 is at a greater radial distance ΓΑ from the centreline 11 than the radial distance r _B from the seal means 8 to the centreline 11. When the pipes 1, 2 are being disassembled and reassembled, the first pipe's wearing surface 5 thus passes at a distance from the seal means 8 which is defined by the difference between said radial distances ΓΑ, r _B . The risk of the first pipe's wearing surface 5 damaging or tearing the seal means 8 when the pipes are being disassembled or reassembled is thus substantially eliminated.

Figs. 3 and 4 depict an alternative connection between the first pipe 1 and the second pipe 2. Here again the first pipe 1 has a wearing surface 5 facing inwards and adapted to coming into contact with a wearing surface 6 facing outwards on the second pipe 2 when the pipes 1, 2 are in a connected state. The second pipe 2 has a bearing surface 7 facing radially outwards which accommodates and supports an annular seal means 8. The second pipe 2 has a radial stop surface 9 which defines an intended fitting position for the seal means 8 on the bearing surface 7. When the pipes 1, 2 are in the connected state, the first pipe's wearing surface 5 and the second pipe's wearing surface 6 form a wearing region A which is at a radial distance ΓΑ from a centreline 11 of the connection. The first pipe's sealing surface 10 and the seal means 8 form a sealing region B which is at a radial distance r _B from the centreline at the connection. In this embodiment the wearing region A is at a smaller radial distance ΓΑ from the centreline 11 than the radial distance r _B from the sealing region B to the centreline 11.

On occasions when the first pipe 1 and the second pipe 2 are being disassembled, connecting means 3, 4 of at least one of the pipes 1, 2 are released. The first pipe 1 and the second pipe 2 are then moved in an axial direction away from one another. The object of the invention is therefore to prevent the occurrence of tears or other types of damage to the seal means 8 or the sealing surface 10 when the pipes are being disassembled and reassembled. To achieve this, the first pipe's wearing surface 5 must not come into contact with the seal means 8 when the pipes are being disassembled. Nor may the second pipe's wearing surface 6 come into contact with the first pipe's sealing surface 10. As in this embodiment the seal means 8 and the first pipe's wearing surface 5 are so arranged that they need not pass one another when the pipes 1, 2 are being disassembled, there is no risk of the seal means 8 being damaged by the first pipe's wearing surface 5. However, the second pipe's wearing surface 6 will pass the first pipe's sealing surface 10 when the pipes 1, 2 are being disassembled. To prevent its coming into contact with the first pipe's sealing surface 10, the second pipe's wearing surface 6 is at a smaller radial distance ΓΑ from the centreline 11 than the radial distance r _B from the first pipe's sealing surface 10 to the centreline 11. In this case, when the pipes 1, 2 are being disassembled and reassembled, the first pipe's sealing surface 10 passes at a distance from the second pipe's wearing surface 6 which is defined by the difference between the radial distances ΓΑ, r _B . The risk of the second pipe's wearing surface 6 tearing or otherwise damaging the first pipe's sealing surface 10 is thus substantially eliminated.

The invention is in no way restricted to the embodiment described above but may be varied freely within the scopes of the claims. The invention may in alternative versions be used also in connection with other lines which form part of an exhaust system for a combustion engine, and in any pipelines where similar problems occur.