GB2537478A

GB2537478A - Duct arrangement for high-temperature applications

Info

Publication number: GB2537478A
Application number: GB1603678.2A
Authority: GB
Inventors: Pluschke Michael; Balmer Bert
Original assignee: Witzenmann GmbH
Current assignee: Witzenmann GmbH
Priority date: 2015-03-03
Filing date: 2016-03-03
Publication date: 2016-10-19
Also published as: DE102015103035A1; GB201603678D0

Abstract

A duct arrangement 1 for high-temperature applications, having a duct element 2 including flexible sections, and having a rigid pipe element 3 extending into the duct element, at least in some sections being spaced apart from the duct element. At the connection end 2a the duct element 2 and the pipe element 3 have a flange portion bent outwards from the axis L of the duct arrangement. The ridged pipe element 3 having at least one slot 4, which slot 4 extending from the flange at the connection end into the duct element 2. The slot allows for thermal expansion and reduces deformation causes by repeated thermal expansion and contraction.

Description

Duct arrangement for high-temperature applications Description The invention relates to a duct arrangement in accordance with the preamble of claim 1 for high-temperature applications, having a duct element, at least some sections of which are flexible, with a rigid pipe element, which pipe element, starting from a connection end of the duct element, extends into the duct element where, at least in some sections, it runs spaced apart from the duct element in the manner of a flame tube or inner sleeve, wherein at the connection end the duct element and the pipe element have in common a portion that is bent outwards transversely with respect to a longitudinal axis of the duct arrangement.

Such duct arrangements are known and are routinely used in exhaust gas systems for motor vehicles having an internal combustion engine, especially in the field of construction machinery and heavy-duty engines.

It has been found to be a disadvantage that, as a result of the temperatures arising during operation, on the one hand the pipe element, which routinely acts as a kind of flame tube for protecting the flexible duct element, and on the other hand further components of an exhaust gas system, such as, for example, a manifold or a clamp connection, become hot and cold at different times. The temperature gradients that develop have the result that, especially on cooling, the pipe element becomes constricted and deformed in its (clamped) attachment region. This can result in leakage of the connection, which routinely relates only to the pipe element. The flexible duct element itself is sufficiently flexible not to be adversely affected by the described temperature gradients.

The invention is based on the problem of developing a duct arrangement of the kind mentioned at the beginning in such a way that the pipe element does not become constricted on cooling, in order thus to avoid the said constriction problems. -1 -

That problem is solved according to the invention by a duct arrangement having the features of claim 1.

Claim 12 relates to a preferred use of a duct arrangement according to the invention.

According to the invention, a duct arrangement for high-temperature applications, having a duct element, at least some sections of which are flexible, and having a rigid pipe element, which pipe element, starting from a connection end of the duct element, extends into the duct element where, at least in some sections, it runs spaced apart from the duct element, wherein at the connection end the duct element and the pipe element have in common a portion that is bent outwards transversely with respect to a longitudinal axis of the duct arrangement, is characterised in that the pipe element has at least one slot, which slot extends from the region of the bent portion into the duct element.

By virtue of the fact that the pipe element or inner sleeve has at least one slot of the said kind, the circumferential stress of the pipe element, especially on cooling, can be reduced, so that constriction and deformation no longer occur. The service life of the duct arrangement is increased and no leakages occur in the connection region.

In a preferred development of the duct arrangement according to the invention the pipe element has a plurality of such slots. Those slots can be distributed uniformly around a circumference of the pipe element in order to enhance their action. It has been found especially advantageous for the pipe element to have four such slots each displaced by 90° relative to the pipe element.

In order that the slots do not tear further during operation of the duct arrange-ment, an extremely preferred development of the duct arrangement according to the invention provides that at an end of a such a slot in the region of the duct element there is provided a terminal enlargement of a slot width. The slot can be substantially circular in the region of the terminal enlargement of the slot -2 -width. It has been found especially advantageous for the terminal enlargement to be in the form of a bore. A radius or diameter of the enlargement is preferably greater than the width of the rest of the slot.

In yet another development of the duct arrangement according to the invention, 5 the at least one slot opens towards the connection end of the duct arrangement. That connection end is arranged opposite the region of the said terminal enlargement of the slot.

It has proved especially advantageous for the at least one slot, measured from the bent portion in the direction into the duct element, to have a length of 10 approximately from 5 to 20 mm, preferably of approximately from 10 to 15 mm, without the invention being limited to such a dimension of the slot.

In addition to reducing the mentioned circumferential stress, in order also to reduce a bending stress of the duct arrangement generated by temperature gradients in the region of the bent portion, a different, extremely preferred development of the duct arrangement provides that in the region of the bent portion a bending radius of the pipe element is selected to be greater than approximately 1.5 mm. Preferably the bending radius is in the range of approximately from 2 to 3 mm.

Furthermore, provision can also be made for the said bending radius of the pipe element to be different from a bending radius of the duct element. Preferably the bending radius of the pipe element is selected to be greater than the bending radius of the duct element.

In this connection, in a development of the duct arrangement according to the invention it is possible for the profile of the pipe element to make a smooth transition from the region of the bent portion to a smallest diameter of the pipe element inside the duct element. In that way the duct arrangement differs from previously known duct arrangements in which the pipe element had a stepped diameter profile. -3 -

The duct arrangement according to the invention is preferably used inside an exhaust gas system of a motor vehicle having an internal combustion engine, there being used, in addition to the duct arrangement, also a clamp arrangement, preferably a V-clamp, and at least one intermediate piece.

In the context of the present invention, the connection of the duct arrangement to other components in the exhaust gas system of a motor vehicle and the pipe element present in the duct arrangement can be relieved of stress in such a way that the pipe element is no longer subject to deformation and accordingly remains in its original, intended position.

Further characteristics and advantages of the invention will be evident from the following description of exemplary embodiments with reference to the drawing.

Figure 1 shows in detail views a) to c) a configuration of a duct arrange-ment according to the invention; Figure 2 shows in cross-section a preferred use of the duct arrangement according to the invention; and Figure 3 shows a diagrammatic view of an alternative configuration of the duct arrangement according to the invention.

In Figure 1, as in the other Figures, a duct arrangement according to the invention is denoted by the reference symbol 1. It comprises an outer, flexible duct element 2 (see Figure lb)) at least some sections of which are preferably in the form of a bellows or annularly corrugated hose. The duct arrangement 1 further comprises a rigid pipe element or inner sleeve 3 which can be constructed in the manner of a flame tube, as can be seen especially clearly in Figure lb). The duct element 3 extends into and radially inside the flexible duct element 2 and, in some sections in the region of its free end, runs spaced apart from the duct element 2. In this connection the further duct element 3 has a smaller diameter D1 at its free end than at its other end (diameter 02). Between those two diameter regions the pipe element 3 has a sloping portion 3a in order -4 -to effect the said reduction in diameter towards its free end. The pipe element 3 serves for guiding the flow of a medium flowing through the duct arrangement 1, preferably a hot exhaust gas of the internal combustion engine of a motor vehicle. This is known per se to the person skilled in the art.

The pipe element 3 has -without limitation -four slots 4 distributed uniformly around the circumference, which slots extend from the region of a terminal radially bent portion 3b of the pipe element 3 into the region of the pipe element 3 that is arranged inside the duct element 2. Such a slot can be seen especially clearly in Figure 1c) which shows a detail in accordance with circle X in Figure 1b). The slot 4 has a width b and is widened terminally by a bore 4a, the slot having a larger width (diameter) B in the region of the bore.

As can also be seen particularly in Figure lb), at its connection end 2a the flexible duct element 2 is bent radially outwards in common with the pipe element 3. The slots 4, however, are provided preferably only on the (rigid) pipe element 3. They reduce a circumferential stress of the pipe element 3 in the region in question, so that on cooling of the pipe element 3 the constriction known from the prior art can no longer occur.

The mentioned terminal bore or widened portion 4a of the slot 4 prevents the slot 4 from tearing.

Figure 2 shows a preferred use of the duct arrangement 1 according to Figure 1; here and hereinbelow elements that are the same or have the same effect are denoted by the same reference symbols. The slots 4 cannot be seen in the view according to Figure 2.

In the region of its bent portion the duct arrangement 1 co-operates with a connection piece 5 of a further pipe, which connection piece 5 has a sloping outer contour in some regions. A sealing element 6 is inserted between the duct arrangement 1 and the connection piece 5. On a side of the duct arrangement 1 remote from the connection piece 5 there is arranged an intermediate piece 7 which likewise has a sloping outer contour in some regions, as shown in the -5 -drawing. The duct arrangement 1 is held clamped in the region of the bent portion between the connection piece 5 and the intermediate piece 7, which clamping is effected by a V-clamp 8 or a circumferential V-band 9. This is known per se to the person skilled in the art.

By virtue of the slots 4 in the pipe element 3 shown in Figure 1, according to the invention the pipe element 3 now no longer becomes constricted in the clamped region on cooling, as was otherwise the case in the arrangement according to the prior art shown in Figure 2, that is to say without slots.

Figures 1 and 2 show a configuration of the duct arrangement 1 in which, in the region of the bent portion and thereafter, the flexible duct element 2 and the pipe element 3 in each case run in parallel, especially parallel to the longitudinal axis L of the arrangement shown by way of example in Figure 3. This is again shown correspondingly in Figure 3 at reference symbol 3 for the pipe element. Accordingly, the duct element 2 and the pipe element 3 have the relatively small bending radius shown only diagrammatically in the drawing at reference symbol R1. In Figure 3, dotted lines indicate an alternative configuration of the pipe element 3' in which the pipe element 3' has a smooth, that is to say stepless transition from its larger diameter D1 to its smallest diameter D2 (see Figure 1). This has an advantageous effect on the bending stress generated by a temperature gradient at the pipe element 3. The above-described smooth transition of what is known as the inner sleeve sloping flange of the pipe element 3' is associated with a correspondingly larger bending radius, which is indicated symbolically by reference symbol R2 in Figure 3.

In the context of the present invention, both the pipe element 3 and the pipe 25 element 3' according to Figure 3 have at least one of the slots 4 shown by way of example with reference to Figure 1, which is not visible in Figure 3.

As the person skilled in the art will readily recognise, the duct arrangement 1 according to Figure 3 with variant 3' of the pipe element can also be used in the application example according to Figure 2. -6 -

Claims

Claims 1. Duct arrangement (1) for high-temperature applications, having a duct element (2), at least some sections of which are flexible, and having a rigid pipe element (3, 3'), which pipe element (3, 3'), starting from a connection end (2a) of the duct element (2), extends into the duct element (2) where, at least in some sections, it runs spaced apart from the duct element (2), wherein at the connection end (2a) the duct element (2) and the pipe element (3, 3') have in common a portion that is bent outwards transversely with respect to a longitudinal axis (L) of the duct arrangement (1), characterised in that the pipe element (3, 3') has at least one slot (4), which slot (4) extends from the region of the bent portion into the duct element (2).
2. Duct arrangement (1) according to claim 1, characterised in that the pipe element (3, 3') has a plurality of such slots (4), preferably four slots (4).
3. Duct arrangement (1) according to claim 2, characterised in that the slots (4) are distributed uniformly around a circumference of the pipe element (3, 3').
4. Duct arrangement (1) according to any one of claims 1 to 3, characterised in that at an end of the at least one slot (4) in the region of the duct element (2) there is provided a terminal enlargement (B) of a slot width (b).
5. Duct arrangement (1) according to claim 4, characterised in that the slot (4) is substantially circular in the region of the terminal enlargement (B) of the slot width (b), preferably that the terminal enlargement is in the form of a bore (4a).
Duct arrangement (1) according to claim 4 or 5, characterised in that a radius or diameter of the enlargement (B) is greater than the slot width (b). -7 -
7. Duct arrangement (1) according to any one of claims 1 to 6, characterised in that the at least one slot (4) opens towards the connection end.
8. Duct arrangement according to any one of claims 1 to 7, characterised in that the at least one slot (4), measured from the bent portion in the direction into the duct element (2), has a length (I) of approximately from 5 to 20 mm, preferably approximately from 10 to 15 mm.
9. Duct arrangement (1) according to any one of claims 1 to 8, characterised in that in the region of the bent portion a bending radius (R2) of the pipe element (3') is greater than approximately 1.5 mm, preferably approximately from 2 to 3 mm.
10. Duct arrangement (1) according to claim 9, characterised in that the bending radius (R2) of the pipe element (3') is different from a bending radius of the duct element (2), preferably greater.
11. Duct arrangement (1) according to claim 9 or 10, characterised in that a transition of a profile of the pipe element (3') from the region of the bent portion to a smallest diameter (D1) of the pipe element (3') is a smooth transition.
12. Use of the duct arrangement (1) according to any one of the preceding claims together with a clamp arrangement (8, 9), preferably a V-clamp, and at least one intermediate piece (7) in an exhaust gas system of a motor vehicle having an internal combustion engine. -8 -