DE8717998U1 - Flexible exhaust pipe for motor vehicles - Google Patents

Description

PATENT ATTORNEYS ' J- I ''"-.'_{&aacgr;&EEgr;}

DIPL.-ING. R. LEMCKE -5- j^?"'

DR.-ING. HJ BROMMER
Bismarckstrasse 16

KARUSRU HE 1
TELEPHONE (0721) 28778-9 FAX (07 21) 21105

Witzenmann GmbH Metal Hose Factory Pforzheim Eastern Karl-Friedrich-Straße 134

7530 Pforzheim

Flexible exhaust pipe for motor vehicles

The invention relates to a flexible exhaust pipe for motor vehicles, consisting of an inner and outer metal hose arranged between pipe connectors and fixed thereto, optionally wound together with a sealant and adjustable in length, as well as an insulating layer made of heat-insulating and sound-absorbing, heat-resistant material arranged between them.

Such flexible exhaust pipes are usually installed as intermediate pieces in the otherwise rigid exhaust pipe in order to absorb movements and vibrations and to prevent them from being passed on to

to decouple adjacent components, such as those caused by the elastic mounting of the drive engine, vibrations of the vehicle, changes in length due to temperature changes, etc. In addition to the property of flexibility, the question of thermal insulation, sound absorption and tightness against the escape of exhaust gases is becoming increasingly important, especially in connection with catalytic converter vehicles and stricter regulations regarding noise and exhaust emissions.

In the exhaust pipes mentioned above, the insulation layer is loosely inserted between the inner and outer metal hose, which means that it cannot accommodate operational changes in the length of these metal hoses and thus of the exhaust pipe. Rather, during operation it adjusts to the shortest length of the exhaust pipe or is compressed onto it, so that under all other operating conditions at least at one end the space between the two metal hoses is not filled with the insulation layer, which causes an interruption in the thermal insulation and also a passage for leaking exhaust gases, with the associated whistling noises etc., so that in this respect the requirements mentioned with regard to thermal insulation and emission protection are not met by the

known exhaust pipe can no longer be met.

The object of the invention is therefore to design an exhaust pipe of the type mentioned at the outset in such a way that the desired functionality of the insulating layer is always fully guaranteed over the entire length of the exhaust pipe, regardless of the length state of the exhaust pipe during operation.

This object is achieved according to the invention in that the insulating layer is designed to be variable in length and is fixed at the end together with the metal hoses to the connecting pieces.

These measures according to the invention have the effect that the insulation layer necessarily follows all length changes in the exhaust pipe, or can do so, since it is able to do so due to its variable-length structure and, on the other hand, due to its terminal attachment to the pipe socket, it is not able to escape length changes. This means that the function of the insulation layer, depending on the choice of material, in terms of thermal insulation, sound absorption and tightness, is always guaranteed to a constant extent over the entire length of the exhaust pipe, without the need for a

particularly significant technical effort or even additional space would be required.

It may be useful for the insulation layer to be designed as a possibly multi-layered braided or fabric stocking made of glass fibers, silicate fibers or similar insulating material. Such a braided or fabric stocking can be changed in length to the extent necessary without losing its tightness, heat insulation capacity and sound absorption capacity, which may be created by the multi-layered design.

However, it is also possible for the insulation layer to be wound in a spiral shape from a band of glass fiber, silicate fiber or similar braid, fabric, knitted fabric or fleece, which can result in considerable simplification and adaptability to different lengths and diameters of exhaust pipes with regard to the provision of the suitable insulation material and its processing.

Another possibility is that the insulating layer consists of ceramic paper or cardboard, whereby the insulating layer can also be made from a strip of the material mentioned by winding it in a helical manner.

This material ensures particularly high tightness and temperature resistance of the insulation layer.

In a further development of the inventive concept, it is particularly expedient that the insulating layer is profiled in a wave-like or accordion-like manner over its longitudinal extension with a corresponding radial distance between the metal hoses, whereby in the case of an insulating layer wound from a strip, the strip can be profiled to form a hooking profile and then wound as a hose.

In this way, the length of the insulation layer can be changed to a particularly large extent without the material of the insulation layer being stretched or compressed, so that in this respect too, any influence on the properties of the insulation material in terms of tightness, sound absorption capacity, etc. is avoided. In addition, the profiling of the insulation layer creates an air volume between it and the metal hoses on both sides, which can significantly support or supplement the heat-insulating and sound-absorbing effects of the insulation layer.

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As far as the metal hoses mentioned at the beginning are concerned, these can be designed as agraff hoses, the great length changeability of which, while maintaining their specified tightness in particular, creates an exhaust pipe that meets high requirements for large freedom of movement. Of course, however, depending on the individual requirements, it is also possible to design only one of the two metal hoses as an agraff hose, while the other metal hose can, for example, be wound from a step-shaped pre-profiled band into a hose with scale-like interlocking connections or can be designed as a braided hose.

As far as the terminal assembly of the exhaust pipe is concerned, it is advisable that the respective end of the metal hoses is pressed together with the associated end of the insulation layer by means of a diameter reduction of a metal sleeve placed at the end onto the associated pipe connection piece, thus creating a permanent, tight connection that holds the insulation layer captive. If the insulation layer is profiled in a wave-like or similar manner, it is of course compressed in the area of the metal sleeve, which, however, has a functional effect.

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impairment, since in this area the outer and inner metal hose also loses its ability to change its length.

However, in particular for corrugated or similar profiled insulating layers, it can be provided that an additional metal intermediate sleeve is inserted between the outer metal hose or inner metal hose and the insulating layer and pressed in with a reduced diameter. This intermediate sleeve creates a certain radial distance between the inner and outer metal hose, also in the area of the respective pipe connection piece, so that the metal hoses maintain the mutual radial distance over their entire length, including the end fastening, which is provided for the corrugated or similar profiled insulating layer.

In addition, it can be provided that the pipe connection piece is subjected to a radial expansion at the same time as the pressing, so that the entire radial change required for the connection does not have to be carried out via the metal sleeve and, if necessary, the intermediate sleeve, but rather the pipe connection piece accommodates this from the inside, which simplifies the production of the connection, particularly with regard to the forces to be applied, and thus

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the production of a consistently good quality connection is also ensured.

Finally, it can be provided that the free ends of the metal sleeve and the intermediate sleeve are connected to each other and to the pipe connection piece by welding or soldering in order to counteract any loosening of the connection even for long operating times and thus to give the exhaust pipe according to the invention a long service life.

Further features and advantages of the invention emerge from the following description of embodiments shown in the drawing. In the drawing:

Fig. 1 a connection end of an exhaust pipe in axial half section;

Fig. 2 shows a modified design in the representation according to Fig. 1;

Fig. 3 a further modification of an exhaust pipe in the representation according to Fig. and

Fig. 4 to 8 various other designs of the exhaust pipe in axial half-section without connection ends.

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Fig. 1 shows a piece of pipe 1 made of metal with a diameter that is reduced towards the right by being stepped twice. An inner metal hose 2 is pushed onto the right end of the piece of pipe 1 and is surrounded by an insulating layer 3, which is made by winding a zigzag-shaped or accordion-like profiled edge made of ceramic paper in a helical manner, with adjacent edges overlapping over a certain area, as can be seen at 4.

The insulating layer 3 is itself surrounded by an outer metal hose 5 in the form of a wound agraff hose, whose inner diameter is so much larger than the outer diameter of the agraff hose 2 that the insulating layer 3 can move unhindered in the axial direction between the two metal hoses.

In the area of the right-hand end of the pipe connection piece 1, the insulating layer 3 is surrounded by an intermediate sleeve &ogr; and the agraff hose 5 is surrounded by a metal sleeve 7, whereby these parts and the end of the pipe piece 1 together with the ends of the agraff hoses 2 and 3 lying between them as well as the insulating layer 3 are pressed radially into a solid composite. The profiling of both the insulating layer 3 and the agraff hoses

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and 5 are pressed together. In order to give this connection fastening additional durability, the intermediate sleeve 6 and the metal sleeve 7 are also connected to the pipe connection piece 1 by a weld 8, whereby the first step 9 of the pipe connection piece 1 accommodates the weld connection to reduce its mass.

As can be seen, the line structure shown in Fig. 1 can be changed in length to a large extent within the scope of the axial mobility of the agraff hoses 2 and 5, whereby the insulating layer 3 can also carry out all length changes without having to detach itself from the connection ends, the other of which must be imagined in a manner comparable to the illustration at the right end of the line.

Fig. 2 basically shows the same structure of inner clamp hose 10, profiled insulation layer 11 and outer clamp hose 12, whereby here the pipe connection piece 13 is only stepped once, while the outer metal sleeve 14 has a radial taper 15 on the side facing the pipe connection piece, in order to close off the chamber 40 in which the ends of the metal hoses 10 and 12, the insulation layer 11 and the intermediate sleeve 16 are arranged. The chamber 40 can also be filled with insulating material or soldering powder in order to ensure a frontal seal of the parts caught between the pipe connection piece 13 and the metal sleeve 14.

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In the example according to Fig. 2, the parts are also pressed together radially in the area of the chamber 40 mentioned, whereby the radial deformation does not only have to be at the expense of the metal sleeve 14 and the intermediate sleeve 16, but can also be partially applied by radially expanding the end of the pipe connection piece 13. If the chamber 40 has been filled with soldering powder in the manner mentioned, this can then be liquefied by inductive heating.

The example according to Fig. 3 also shows an inner clamp hose 17, an insulating layer surrounding it with a zigzag profile and an outer clamp hose 19, which are pressed at the end to the right end of a pipe connection piece 22 by means of a metal sleeve 20 and an intermediate sleeve 21. Here, however, the metal sleeve 20 and the end of the clamp hose 19 are set back from the intermediate sleeve 21 and the end of the clamp hose 17 in such a way that the clamp hose 19 and the metal sleeve 20 can also be connected to the intermediate sleeve 21 by a weld seam 23, which in turn is then welded to the pipe connection piece 22 at 24.

Fig. 4 to 8 show variants of the structure of the exhaust pipe formed by the inner and outer metal hose on the one hand and the insulating layer on the other.

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Thus, Fig. 4 shows an inner agraff hose 25 and an outer agraff hose 26, while the insulating layer 27 is wound from a band of ceramic paper that is pre-profiled in a step-like manner so that the individual band turns interlock in a scale-like manner and thus the desired length changeability of the insulating layer 27 is provided without its closedness with regard to thermal insulation, tightness and sound absorption being lost.

In the embodiment according to Fig. 5, an insulating layer 30, for example made of ceramic paper, is arranged between an inner clamping tube 23 and an outer clamping tube 29, which is profiled in the manner of a ring-shaped or helical corrugated metal tube and thus has the desired length changeability.

In the embodiment shown in Fig. 6, an insulating layer 33 is arranged between the inner agraff hose 31 and the outer agraff hose 32, which is wound by helically winding an S-shaped pre-profiled strip, for example made of ceramic paper, in the manner of a hook hose, the individual turns of which can move relative to one another within the axial freedom provided by the hook profile.

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According to Fig. 7, an inner braided hose 34 is surrounded by an insulating layer 35, which can be, for example, a stocking, a fabric or a braid made of glass fibers or silicate fibers, but can also be a fleece made of this material, which can be made to the desired length by appropriate production. The outer metal hose 36 is here a hose made of metal wire braid.

Finally, Fig. 8 shows an insulating layer 37 of the type explained with reference to Fig. 7, which is surrounded on the outside by a clamping hose 33, while the metal hose 39 arranged inside the sealing layer 37 is made by winding a stepped profiled metal strip in a helical manner, the individual windings of which interlock in a scale-like manner and thereby ensure the desired ability to change the length of the metal hose 39.

With regard to all embodiments, it is important to emphasize once again that the radial distance between the inner metal hose and the outer metal hose must be selected in such a way that the insulating layer arranged between the two hoses is not hindered in its mobility, i.e. that it does not have any

is exposed to excessive frictional stress. In addition, the design features shown in Fig. 1 to 8 can of course be
Details, in particular regarding the
The arrangement of the hoses can vary.

Claims (1)

PATENT ATTORNEYS DIPL.-ING. R. LEMCKE DR.-ING. HJ BROMMER
Bismarckstrasse 16 KARLSRUHE 1 TELEPHONE (07 21) 287 78-9
FAX (07 21) 211 05 Witzenmann GmbH Metal hose factory Pforzheim Eastern Karl-Friedrich-Straße 134 7530 Pforzheim PROTECTION CLAIMS 1. Flexible exhaust pipe for motor vehicles, consisting of an inner and outer metal hose arranged between pipe connectors and fixed to them, wound together with a sealant if necessary and adjustable in length, as well as an insulating layer made of heat-insulating and sound-absorbing, heat-resistant material arranged between them, characterized, that the insulating layer (3, 11, 18, 27, 30, 33, 35, 37) is designed to be variable in length and is fixed at the end together with the metal hoses (2, 5; 10, 12; 17, 19; 25, 26; 28, 29; 31, 32; 34, 36; 38, 39) to the pipe connectors (1, 13, 22). 2. Exhaust pipe according to claim 1, characterized in that the insulating layer (3, 11, 18, 27, 30, 33, 35, 37) is designed as a possibly multi-layered braided or fabric stocking made of glass fibers, silicate fibers or similar insulating material. 3. Exhaust pipe according to claim 1, characterized in that the insulating layer (3, 11, 18, 27, 30, 33, 35, 37) is wound in a helical manner from a band of a glass fiber, silicate fiber or similar braid, fabric, knitted fabric or fleece. 4. Exhaust pipe according to claim 1, characterized in that the insulating layer (3, 11, 18, 27, 30, 33, 35, 37) consists of ceramic paper or cardboard. 5. Exhaust pipe according to claim 4, characterized in that the insulating layer is wound in a helical manner from a strip of ceramic paper or cardboard. 6. Exhaust pipe according to one of the preceding claims, characterized in that the insulating layer (3, 11, 18, 30) is profiled in a wave-like or accordion-like manner over its longitudinal extent with a corresponding radial spacing of the metal hoses (2, 5; 10, 12; 17, 19; 23, 29). 7. Exhaust pipe according to claim 5, characterized in that the insulating layer (33) at corresponding with a suitable radial distance between the metal hoses (31, 32) and is profiled and wound as a hose with a hooking profile. 3. Exhaust pipe according to claim 1, characterized in that the metal hoses are designed as agraff hoses (2, 5; 10, 12; 17, 19; 25, 26; 28, 29; 31, 32; 34, 38). 9. Exhaust pipe according to one of the preceding claims, characterized in that the respective end of the metal hoses (2, 5; 10, 12; 17, 19) together with the associated end of the insulating layer (3, 11, 18) is pressed onto the associated pipe connection piece (1, 13, 22) by means of a diameter reduction of a metal sleeve (7, 14, 20) placed at the end. 10. Exhaust pipe according to claim 9, characterized in that an intermediate sleeve (21, 6, 16) made of metal is inserted between the outer metal hose (19) or inner metal hose (2, 10) and the insulating layer (18, 3, 11) and is pressed in with a reduction in diameter. 11. Exhaust pipe according to claim 9 or 10, characterized in that for pressing the pipe connection piece (1, 13, 22) is simultaneously subjected to a radial undergoes expansion. 12. Exhaust pipe according to one of claims 9 to 11, characterized in that the free ends of the metal sleeve (7, 20) and the intermediate sleeve (6, 21) are connected to one another and to the pipe connection piece (1, 22) by welding (3, 23, 24) or soldering. 13- Exhaust pipe according to one of claims 9 to 11, characterized in that a cavity (40) existing between the associated ends of metal hoses (10, 12), insulating layer (11) and optionally intermediate sleeve (16) on the one hand and adjacent wall of pipe connection piece (13) and metal sleeve (14) on the other hand is filled with insulating material or soldering material.