Pipes and tubular conduits – Flexible – Corrugated
Reexamination Certificate
2000-09-06
2001-05-15
Brinson, Patrick (Department: 3753)
Pipes and tubular conduits
Flexible
Corrugated
C138S114000, C138S148000, C138S118000, C138S123000
Reexamination Certificate
active
06230748
ABSTRACT:
This application claims the priority of German Patent Application No. 297 07 908.5, filed May 2, 1997, the subject matter of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
This invention was made for the purpose of constructing a flexible conduit element, especially for the exhaust systems of combustion engines in vehicles, and in particular, the invention is directed to helically or annularly corrugated metal bellows equipped with cylindrical end fittings and a metal hose which is located coaxially inside the bellows, where the outside diameter of the metal hose is smaller than the free (smallest) inside diameter of the bellows and the ends of the metal hose are lying inside the end fittings of the bellows, are flush with those fittings, and are fixed to them, with at least one hollow cylindrical element made of metal wire being arranged between the bellows and the metal hose. In this well-known type of conduit element, a braided hose is used as the metal wire element arranged between the bellows and the metal hose in order to improve the damping of vibrations. At least one of the ends of the braided hose is fixed inside an end fitting of the corresponding bellows. The damping effect of this design, however, was found to be quite low since the braided hose lies loosely in the cavity between the bellows and the metal hose and is in contact only with the bellows in order to have a damping effect. The damping effect is therefore subject to accidental conditions in the operation of the conduit element. Furthermore, the braided hose requires the fixing of at least one of its ends. In addition thereto, the braided hose causes a comparably high material consumption due to its design. Finally, the braided hose is particularly incapable of keeping the metal hose in a radially constant position inside the bellows. Under unfavorable operating conditions the metal hose may collide with the interior walls of the bellows. Conventionally, additional elements are to be packed into the cavity between the metal hose and the bellows to avoid such effects. As a consequence, the manufacturing costs of such a conventional conduit element are high and its installation is difficult.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an improved conduit element of the above-described type in which only one element made of metal wire is used for the purpose of vibration damping in the conduit element, and filling the cavity between the bellows and the metal hose at least locally without gaps. It is a further object to reduce considerably the quantity of material required for the element.
These objects are achieved according to the invention by using a metal wire knit as a damping insert which totally fills the cavity between the bellows and metal hose in a radial direction.
As a consequence of these measures, the metal hose is prevented from colliding with the interior wall of the bellows, since the cavity between these two parts is filled by the knit element flexibly, elastically and without gaps. In this design, the element is always in direct contact with both the bellows and the metal hose which will ensure a permanent damping of vibrations. Further, the use of a metal wire knit allows a considerable reduction of material consumption, compared with the conventional design, and the structure of the knit will avoid the contact between the bellows and the metal hose on one hand, and the element on the other hand, with the exception of a few small contact spots, which will reduce the wear between the components respectively. Nevertheless, the knit will, altogether, not have any negative effect on the flexibility of the bellows and the metal hose as it is a characteristic feature of a wire knit that its length may change in an axial direction without changing its radial dimensions. Thus, the characteristic of wire knit allows a considerable increase in the inherent damping of the metal wire element.
The installation of the knit will also not cause any problems, since the knit, due to its hose-like shape, can be pushed onto the metal hose. Another possibility, however, is the simultaneous manufacturing and installation of the knit which allows the immediate availability of an assembly, consisting of metal hose and metal wire knit, for further installation.
In this context, radial pre-setting of the element or its installation into the cavity is in pre-set relation to the bellows and/or the metal hose. As a consequence, there will be an additional mutual support between the bellows and the metal hose and also a desired damping effect, depending on the selected value of pre-setting adjustment.
As a principle, the structure of the knit, either narrow-meshed or wide-meshed, will have an influence on the damping effect and the elastic supporting properties of the knit element.
There are numerous possible versions of this element. In one version, the element may include a wire knit hose or wire knit ring covering at least a part of the axial length of the cavity. Depending on individual requirements, it is possible to fill the cavity in its total axial length with a wire knit hose. In another embodiment, several shorter hose sections with axial distances between them may be installed which may finally lead to the application of one or several wire knit rings, if very short hose sections are selected.
In yet another embodiment, the element may include at least one wire knit strip formed by helical windings and installed in the cavity, perhaps with axial distances between the neighboring windings. Depending on the design of the element, at least one of the element's ends can be fixed between the corresponding end fitting of the bellows and the end of the metal hose. Another possibility of fixing the element in an axial direction is to clamp an end of the knit element between the bellows and the metal hose by suitably profiling the bellows and/or the metal hose. Such a profiling may be a protuberance which is provided on the metal hose and which projects toward the knit element.
For the purpose of an appropriate adaptation of the damping and spring characteristics of the wire knit to individual requirements, the wire knit, of which the element consists, can be at least partly compressed, i.e. the basic wire knit is subject to compression before installation, in order to ensure high radial supporting and spring characteristics and also to increase both the internal friction of the element and the friction between the element on one hand, and the bellows and the metal hose on the other hand. Such compression can also be provided to the wire knit hose locally, for example to one or several sections of its overall length.
Another possibility of a sensitive setting of the wire knit element can be obtained by means of a profiled cross section in this element or of the wire knit from which it is made. This profiling of the wire knit can be formed by helical windings in radial direction in the cavity between the bellows and the metal hose, so that the element comes in alternating contact with either the bellows or the metal hose. There will always be an axial distance between individual contact spots. The profiled cross-section can also be the result of the corrugated geometric form of the wire from which the knit is made, which will have an interlocking effect on the neighboring individual meshes, and will also have a corresponding influence on the spring characteristics of the wire knit element.
In the wire knit itself, the metal wire which forms the knit may include several wire threads. On the one hand, this fact allows the use of especially thin threads, and on the other hand, threads of different materials or with different properties can be applied. Further, additional materials may be included with the wire of the knit, for example ceramic fibers or plastic fibers of high temperature resistance.
There is, however, also the possibility of applying a coating of another metal, a plastic material with high thermal resistance or graphite to the wire which form
Elsasser Fabian
Krawietz Tom
Brinson Patrick
Kelemen Gabor J.
Venable
Witzenmann GmbH Metallschlauch-Fabrik Pforzheim
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