DE8535523U1 - Connection of two parts of a line by a bellows or a corrugated pipe - Google Patents

Description

Witzenmann GmbH Metal Hose Factory Pforzheim

Eastern Kärl-Friedrich-Straße 134

7530 Pforzheim ,

Connection of two parts of a line by a bellows or a corrugated pipe

The invention relates to a connection of the coaxially directed ends of two parts of a line for hot media, in particular exhaust pipes of motor vehicles, by means of a bellows or a corrugated pipe with essentially cylindrical connection ends connected to the line parts in one piece, in a form-fitting and/or force-fitting manner, and an inner protective pipe which, starting from the fixed connection of one end to one of the connection ends, extends over the entire length of the bellows and with its other end runs freely within the bellows.

In such designs, especially when it comes to exhaust pipes for motor vehicles, bellows or corrugated pipes as well as the adjacent pipe parts

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made of metal. However, since the invention is also suitable for numerous other applications, it is not intended to be limited to this, even if a design made of metal is envisaged below for the sake of simplicity.

A connection of the type described is installed in the line in order to absorb mutual relative movements of the connected parts in the form of axial, lateral and angular movements. The inner protective tube serves to guide the media flow as smoothly as possible and thus as favourably as possible, to shield the bellows from the sometimes very high temperature of the medium and finally to shield the bellows from excitation from periodic or pulsating vibrations of the flowing medium. However, in order for the bellows to be able to move freely, the free-running end of the inner protective tube must have a significant radial distance from the linear contour of the bellows, as it cannot follow the curved shape of the bellows, which it can assume as intended.

However, this radial distance between the free end of the inner protective tube and the inner contour of the bellows leads to a number of problems that are only reluctantly accepted. The inner diameter of the inner protective tube must be adapted to the cross-section required for the media flow, which, with regard to the radial distance mentioned,

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This means that the cross-sectional dimensions of the bellows must be chosen to be considerably larger than would be necessary for the cross-section required for the media flow itself. This also has an impact, for example, on the accessibility of the screw holes of the bellows' connecting flanges, which must also be placed further outwards. If the latter is not possible due to space constraints, a longer cylindrical section of the bellows must be provided between the corrugated part of the bellows and the connecting flange so that the holes in the connecting flange are accessible without being obstructed by the bellows corrugations. This increases the overall length and may require measures to mechanically reinforce these areas.

A further consequence of the known inner protective tube with the above-mentioned freely extending end is that the inside of the bellows is only incompletely shielded against temperature and pressure fluctuations from the medium, which in turn requires a more stable and thus more expensive design of the bellows , since it must be designed with a view to correspondingly high temperature and vibration loads.

The well-known inner protective tube ultimately limits the mobility of the bellows if one does not want to limit the radial

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Choose an excessively large distance between the inner protective tube and the bellows.

Overall, the known design requires an excessively large bellows shape in both the axial and radial directions, with the associated material and space requirements, in view of the required mobility between the two pipe sections to be connected and the size of the required flow cross-section.

The object of the invention is therefore to modify or further develop a bellows connection of the type mentioned at the beginning in such a way that, in relation to a certain flow cross-section and a certain required mobility, a smaller bellows design can be used in both the axial and radial directions between the two pipe parts to be connected, whereby the temperature and vibration load on the bellows can be reduced comparatively without any significant additional material and cost expenditure, and damping of the bellows should be possible in a completely new way compared to the known method.

The object is achieved according to the invention in that the inner protective tube consists of several pipe sections arranged one behind the other in its longitudinal direction, that adjacent pipe sections are connected to one another in an articulated manner and that the freely extending end of at least one pipe section is indirectly supported axially on the inner wall of the bellows.

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As a result of these measures according to the invention, the inner protective tube is designed as an articulated sectional tube that can adapt its course to an arcuate course of the bellows. This eliminates the need for a significant radial distance between the outer contour of the inner protective tube and the inner contour of the bellows, which means that, in relation to a certain flow cross-section and the resulting size of the inner protective tube, the bellows can be made smaller in the radial direction, which not only applies to the radial distance that is no longer required, but also has an impact on the corrugation height and wall thickness of the bellows. In relation to existing installation cases, this smaller bellows design in the radial direction also means that the screw holes of connection flanges can now be reached without having to provide cylindrical bellows sections between the connection flanges and the bellows corrugation, which results in a considerable axial reduction in the length of the bellows.

In addition, the inner protective tube, which is practically sealed along its length, is now in a media-sealing connection with the bellows from start to finish, so that the shielding of the bellows against temperature influences from the medium is practically reduced to the radiation that acts on it from the inner protective tube. On the other hand, for the same reasons, pressure fluctuations within the medium can no longer reach the inside of the bellows directly. For these two reasons, this means that there is the possibility of additional

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Reduction of the bellows material in terms of quantity and/or quality, whereby the bellows can be designed in particular with thinner walls, which in turn increases its flexibility and thus in itself provides the possibility of an additional shortening of the bellows with regard to a certain required mobility.

Finally, the design of the inner protective tube according to the invention also brings about additional damping (') of the bellows, in that the bellows can rest on parts of the inner protective tube from the outside and there, in particular with regard to building up natural vibrations, a detuning and damping by friction occurs.

Overall, this results in unrestricted mobility of the bellows and the possibility of internal support, which, in conjunction with the shielding of the bellows against temperature and vibrations, enables the bellows to withstand greater mechanical stress and/or a reduction in its wall thickness, although, as mentioned above, the bellows could also be made smaller in the longitudinal and radial directions.

As far as the articulated connection of adjacent pipe sections is concerned, this can be formed by axially interlocking their ends directed towards each other via a spherical layer-shaped ring surface that is essentially coaxial with the pipe axis. Such an articulated connection allows pivoting in all directions, but on the other hand holds the pipe sections that form it

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in the axial direction, while at the same time ensuring a seal of the quality required in this case. In addition, if desired, the mutual pivoting of the pipe sections can be limited by appropriate design of the ring surface.

Another possibility is that adjacent pipe sections are axially aligned with their

) ends interlock without play, so that the outer end is smooth-cylindrical and rests against the inner wall of the bellows and the inner end has a spherical layer-shaped ring surface on the outside that is essentially coaxial with the line axis. Here, on the one hand, there is a mutual articulated connection of the two pipe sections, but on the other hand, their mutual axial displacement is possible, so that at least one of these articulated connections in the course of the inner protective pipe is particularly suitable for cases in which the inner protective pipe is to be fixed at both ends of the bellows with its pipe sections there, so that

r\ the axial length changeability of the inner protective tube must be ensured at least at one point along its course.

The bellows can rest on the smooth cylindrical end of one pipe section with the inner edges of its bellows corrugations in a dampening manner. However, it is advisable here for the smooth cylindrical end of one

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The pipe section is located in contact with a smooth cylindrical intermediate section of the bellows, i.e. it is axially displaceable within this intermediate section, but is guided in the radial direction, which results in an improved damping effect between the bellows and the inner protective pipe and a better system in terms of the distribution of mutual friction.

Furthermore, it may be expedient for the front edge of the smooth cylindrical end to have at least one cross - sectional taper on the circumference to limit the radial movement of the inner end of the other pipe section if such an axial movement limitation is desired, for example to limit the possibility of changing the length of the bellows.

In the event that the inner protective pipe is only fixed at one of its ends to the connecting end of the bellows, it is advantageous that the freely extending end of the inner protective pipe has a spherical layer-shaped ring surface on the outside that is essentially coaxial with the line axis and that this is in contact with the other connecting end of the bellows. In this case, this design ensures the axial freedom of the inner protective pipe with respect to changes in the length of the bellows. However, there is no obstacle to providing additional axially movable joint connections between two adjacent pipe sections in the course of the inner protective pipe.

In the corresponding cases mentioned above, it may be expedient for the spherical layer-shaped annular surface of either the inner pipe end or the freely extending pipe end to be formed by the pipe end itself.

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However, it is also possible that the spherical layer-shaped ring surface is formed by a sealing ring, for example made of wire, possibly pressed with lubricants and/or fillers, and that the sealing ring is arranged in a circumferential groove of the pipe end.

Finally, it is expedient for all the designs described that in the direction of flow of the medium at the respective articulated connection between two adjacent pipe sections, the preceding pipe section is arranged within the following pipe section in order to keep the flow resistance within the inner protective pipe as low as possible. In the design according to the invention, however, in contrast to the known design discussed at the beginning, in which only a flow in the direction of the free end of the inner protective pipe is sensible and technically usable, this aspect is no longer so important, so that it can even be neglected if other advantages, for example a standardization of the type of pipe sections, can be achieved.

Further features and details of the invention will become _apparent from the following description of an embodiment shown in the drawing. In the drawing:

Fig. 1 a bellows with inner protective tube half in radial section;

Fig. 2 the middle section of the inner protective tube according to Fig. 1 with a modification in the overall view and

Fig. J5 is a sectional view along the section line HIHI in Fig. 2.

Fig. 1 shows a metal bellows, designated as a whole by 1, with an inner protective tube, designated as a whole by 2. The bellows 1 has ring-corrugated bellows sections 3> 4, which are connected to one another via a smooth cylindrical intermediate section 5. The inner protective tube consists of tube sections 6, 7, 8 and 9.

The connecting ends of the bellows 1 are connected to further line parts or units (not shown) by means of ring flanges 10, 11 while simultaneously capturing and fixing the ends of the pipe sections 6 and 9 there, for which purpose the ring flanges 10, 11 have holes 12, 13 for the passage of screws or the like.

The ends 14 to 17 of adjacent pipe sections 6, 7 on the one hand and 8, 9 on the other hand, which are directed towards one another, are connected to one another in an articulated manner in that these ends axially interlock and touch one another along a spherical cap-shaped annular surface that is essentially coaxial with the line axis 18. This articulated connection allows for swiveling in all directions, but does not permit the adjacent pipe sections 6, 7 and 8, 9 to move axially relative to one another.

The ends 19, 20 of the pipe sections 7, 8, which are directed towards one another, also engage with one another in the axial direction. They also form a joint connection that can be moved in all directions, in that the end 20 has a spherical layer-shaped ring surface of the type described on the outside. However, in this joint connection, the pipe sections 7, 8 are axially

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&idigr; movable relative to one another in that the end 19 is designed as a smooth cylinder and, moreover, fits in the j smooth cylindrical intermediate section 5 of the bellows 1.

Instead of the spherical layer-shaped ring surface of the end 20, a sealing ring can also be inserted from the outside into a circumferential groove of the pipe 8 in a manner not shown, which rests against the pipe end 19 with an outer spherical ring surface. The sealing ring can, for example, be a wire press ring, which may additionally contain lubricants or fillers.

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From the design described with reference to Fig. 1, it is clear that, due to the link-shaped design of the inner protective tube 2 between it and the bellows 1, a special radial distance to enable the bellows 1 to bend is no longer necessary, so that the bellows 1 can be built directly around the inner protective tube in the radial direction with respect to a specific line cross-section guaranteed by the inner protective tube 2. In addition, the bellows 1 can be brought with its velcro up to the flanges 10, 11, since the small diameter of the bellows 1 now allows unhindered access to the holes 12, 13 in the flanges.

In addition, the bellows 1 is virtually completely decoupled from the media flow by the inner protective tube 2, both in terms of its temperature and its pressure fluctuations, so that it is no longer exposed to the resulting stresses and can be designed with thinner walls. This thinner-walled design leads to greater flexibility of the bellows 1, from which one can derive both a shorter design of the bellows 1 and a bellows design that has a lower radial height of the bellows waves in relation to a certain required mobility.

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The bellows 1 is located with its intermediate section 5

in frictional engagement at the end 19 of the pipe section \ te3 7, which not only provides an internal support of the

bellows 1, but also a damping with regard to

Vibrations occurring in the bellows, the same effect ':

can occur at joints 14, 15 or 16, 17. |

Fig. 2 shows the partial side view of the inner protection tube according to Fig. 1. Here, the possible joints 14, * 15 and 16j 17 are indicated by dashed lines.
Swivel angle, which can be adjusted by appropriate
Formation of the spherical ring surface there | can be adequately dimensioned, but can also be limited if this is desirable or necessary in the individual case. j

As regards the ends 20, 21 of the pipe sections 7, 8 directed towards each other, the end 21 essentially corresponding to the end 19 in Fig. 1, here a
Limitation of the mutual axial displacement of the | pipe sections 7, 8 is given by the fact that the free edge \ of the end 21 has cross-sectional tapering in the form of flanges 22, so that the end 20 has its axial movement limits on the one hand at these flanges 22 j and on the other hand at the tapering j given by the cross-section of the pipe section 7 beyond the end 21.

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As explained, in the design according to Fig. 1, the arrangement is such that the guide sections 6 and 9 are connected to I

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the ends of the bellows 1 are fixed to it, while the length-adjustable extension of the inner protective tube 2 required for a length change of the bellows "1 is laid out on its middle at the ends 19, 20.

However, the principle underlying the new design has already been implemented, for example, in an embodiment that is created by placing the flange 10 immediately to the left of the bellows section in Fig. 1 while simultaneously shortening the pipe section from the left in order to omit the left half of the illustration according to Fig. 1. This results in a bellows 4 with connecting flanges 10, 11 and two pipe sections 8, 9 that form the inner protective pipe, whereby the pipe section 9 is fixed together with the flange 11 and the right bellows end, while the pipe section with its left end 20 is guided axially displaceably but articulated approximately within the flange 10 that is then seated there in the bellows.

In addition to this example, other designs that use the basic idea of the new design are also conceivable. For example, further pipe sections can be connected to pipe section 8, which are connected to one another in an articulated manner, as in 14, 15 or 16, 17, and whose last pipe section is guided with its free end on the left inside flange 10 on the bellows in an articulated but axially displaceable manner. In this case, as well as in a pipe section with both ends on the

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Bellows fixed inner protection tube in the course of the
Inner protective tube several pairings in the manner of the ends 19, 20, in particular in the form developed according to Fig. 2 and 3, can be provided.

Finally, as can be seen from Fig. 1, with respect to
the flow direction 23 of a medium the pairing of the
Ends 16, 17 of the pipe sections 8, 9 are arranged so that the end 17 of the upstream pipe section 9 is on the inside. If only the flow resistance were taken into account, this arrangement would also be indicated for the pairing of the ends 14, 15 of the pipe sections 6 and 7,
dorc, however, is evidently not the case. The reason for this is that, due to the arrangement actually present there, the ear sections 6 and 9 can be manufactured as identical components, thus making it possible to achieve considerable savings in manufacturing costs, which are less important than the aerodynamic advantage given up, especially since they are hardly noticeable due to the spherical cap-shaped design of the ends 14, 15.

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Claims (5)

PATENT ATTORNEYS ■ .!..I.. '..·...* DJPL-&Igr;&Ngr;&THgr;. R. LEMCKE December 17, 1985 DR.-IN6. H. J. BROMMER (13980/81) L/Bz AMALIENSTRASSE29 KARLSRUHE 1 Witzenmann GmbH Metallschlauch-Fabrik Pforzheim Östliche Karl-Friedrich-Straße 134 7530 Pforzheim 1. Connection of the coaxially directed ends of two parts of a line for hot media, in particular exhaust lines of motor vehicles, by means of a bellows or a corrugated pipe with essentially cylindrical connection ends connected to the line parts in one piece, in a form-fitting and/or force-fitting manner and an inner protective pipe, which, starting from the fixed connection of one end with one of the connection ends, extends over the entire length of the bellows and runs freely with its other end within the bellows, characterized in that that the inner protective tube (2) consists of several tube sections (6, 7, 8, 9) arranged one behind the other in its longitudinal direction, that adjacent tube sections are connected to one another in an articulated manner and that the freely extending end (19, 20, 21) of at least one tube section (7, 8) is supported at least indirectly on the inner wall of the bellows (1) in an axially displaceable manner. IlI Il 2. Connection according to claim 1, characterized in dart the articulated connection of adjacent pipe sections (6, 7 or 8, 9) is formed by axial interlocking of their mutually directed ends (14, 15 or 1b, 17) via a spherical layer-shaped annular surface that is essentially coaxial with the line axis (18). 3. Connection according to claim 1, characterized in that adjacent pipe sections (7, 8) are axially aligned with their 1 ends directed towards each other (19 or 21 and 20) play I ( ) freely interlock so that the outer end (19 I or 21) smooth cylindrical and against the inner wall of the I bellows (1) is in place and that the internal I end (20) outside a spherical layer-shaped, for line I axis has an essentially coaxial ring surface. &rgr; 4. Connection according to claim 3> characterized in I that the smooth cylindrical end (19 or 21) is in I position on a smooth cylindrical intermediate section (5) I of the bellows (1). I 5. Connection according to claim 3, characterized in that the front edge of the smooth cylindrical end (k1) has at least one cross-sectional taper (22) on the circumference for limiting the axial movement of the inner end (20). 1. 6. Connection according to claim 5, characterized in that the cross-sectional taper is a flange (22). 7t Connection according to claim 1, characterized in that the freely extending end (20) of the inner protective tube (2 or 8) has a spherical layer-shaped annular surface on the outside, which is essentially coaxial with the line axis (18) and * I this is located at the other connection end of the bellows (1) ® . 8. Connection according to one of claims 3 to 7, characterized in that the spherical layer-shaped annular surface is formed by the pipe end (20) itself. 9. Connection according to one of claims 3 to 7, characterized in that the spherical layer-shaped ring surface is formed by a sealing ring, for example made of wire, possibly pressed with lubricants and/or fillers, and that the sealing ring is arranged in a circumferential groove of the pipe end (20). 10. Connection according to one of the preceding claims, characterized in that in the flow direction of the medium at the respective articulated connection, the preceding pipe section is arranged within the following pipe section.