Patent Description:
A wind turbine usually comprises a tower with a nacelle at its top. A rotor is arranged at the nacelle, which rotor comprises a hub, to which one or more rotor blades, usually three rotor blades, are fixed interacting with the wind. The rotation of the hub respectively the rotor runs an electric generator. The rotor is arranged in at least one main bearing, which comprises an inner ring, which is usually stationary, and an outer ring, which is connected to the rotor and which rotates relative to the inner ring. It is though also known, especially in relation to geared wind turbines, to have the rotor connected to the inner ring of the main bearing and where the outer ring is stationary. Traditionally wind turbines use a roller bearing as a main bearing but new and large multi Megawatt wind turbines may find it beneficial to use a slide bearing as a main bearing. A slide bearing needs a liquid lubrication and a good sealing to avoid leakage, which nevertheless still occurs. A similar main bearing suitable for a wind turbine is known from <CIT> according to the preamble of claim <NUM>.

It is an object of the invention to provide a main bearing for a wind turbine with an improved lubrication.

For solving the problem the invention proposes a main bearing comprising a nacelle wherein said at least one main bearing is tilted with its rotation axis towards the horizontal axis and comprising an inner ring and an outer ring, whereby the main bearing is a slide bearing and the inner ring is stationary while the outer ring rotates around the inner ring, with the main bearing being lubricated with a lubrication fluid, and with the outer ring comprising a first and a second sealing means arranged at both sides of the outer ring for sealing to the inner ring and extending around the outer ring, whereby the first sealing means is due to the tilt of the main bearing lower than the second sealing means, whereby a stationary leakage lubrication fluid collection means is provided adjacent to the first sealing means adapted for collecting lubrication fluid leaking from the first and the second sealing means, whereby the outer ring is provided with one or more axial bores connecting a leakage lubrication fluid collection area adjacent to the second sealing means to the leakage lubrication fluid collection means and wherein each sealing means comprises a groove accommodating a sealing element and a sealing element carrier ring having a fold and a clamp ring attached to the carrier ring closing the fold to build the groove and clamping the sealing means in the groove.

The invention proposes a main bearing with a lubrication system using a lubrication fluid, preferably oil, for lubricating said main bearing, which is a slide bearing, and with the possibility to collect any leakage and to return the leakage back to the lubrication circuit. This is possible, as the rotating outer ring, which is preferably a one-piece-ring made of one single part, is provided with a first and a second sealing means, which are arranged on both sides of the outer rotating ring extending around the whole circumference of the outer ring. The sealing means are arranged to provide a good sealing towards the stationary inner ring. Nevertheless some leakage may occur. This leakage is collected. For collecting the leakage a stationary leakage lubrication fluid collection means is provided adjacent to the first sealing means. This stationary lubrication fluid collection means is adapted to collect the lubrication fluid leaking through both sealings. As the first sealing means is adjacent to the stationary lubrication fluid collection means, this leakage amount can easily be collected. As mentioned, a second sealing means is arranged on the other side of the outer ring. For collecting any leakage a leakage lubrication fluid collection area is provided adjacent to this second sealing means, which leakage lubrication collection area is preferably provided as rotating with the outer ring respectively the second sealing means. So any lubrication fluid leaking through the second sealing means will be collected in this leakage lubrication fluid collection area.

For transferring the collected leakage fluid the outer ring is provided with one or preferably more axial bores acting as rotating channels, which bores connect the leakage lubrication fluid collection area to the leakage lubrication fluid collection means arranged at the other bearing side, so that the leakage fluid can flow from one side of the bearing to the other side of the bearing. This flow is promoted by the fact that the main bearing and thus the rotor etc. is slightly tilted towards the horizontal axis. The tilt angle usually is about <NUM> - <NUM>°. Due to the slight tilt of the main bearing one side of the bearing is lower than the other side of the bearing. According to the invention the first bearing side, to which the first sealing means is arranged, is the lower bearing side, while the opposite second bearing side, to which the second sealing means is arranged, is the higher bearing side. As also the rings are tilted, and as the bore or the bores provided in the rotating outer ring connecting the leakage lubrication fluid collecting area with the leakage fluid lubrication fluid collecting means are parallel to the axis of rotation of the bearing, also the one or the several axial bores are tilted, so that there is a permanent incline from the leakage lubrication fluid collection area to the leakage lubrication fluid collection means, which incline promotes the flow of the leakage fluid from the collection area to the collection means.

The invention advantageously allows to use a lubrication fluid for lubricating a slide bearing. As it is a fluid, it allows for lubrication of all contact points during operation, all surfaces are wetted by the lubrication fluid and are therefore corrosion protected during operation and even during standstill, even a long standstill. Due to its fluid character it is possible to circulate the lubrication fluid in a lubrication circuit by means of at least one pump allowing to transport the lubrication fluid to any points of need, so that it is easily possible to supply the lubrication fluid to distinct points of the main bearing, where a good lubrication is necessary, from where the lubrication fluid then distributes within the whole main bearing.

While the wind turbine, which may be a direct drive wind turbine with a single bearing or a gear wind turbine, may comprise only one single main bearing, the wind turbine may also comprise a two-bearing system with the outer ring rotating around the stationary inner ring. The inventive leakage fluid collection and distribution system also allows for an excellent lubrication of the two-bearing system, which is a double slide bearing system.

As mentioned, a rotating leakage lubrication fluid collection area is provided at the rotating outer ring respectively the outer ring system. This leakage lubrication fluid collection area is preferably a collection groove extending around the outer ring, so that any leakage fluid leaking at any point at the circumference of the outer ring respectively the second sealing means can be collected in the circular groove. The leakage fluid usually collects at the low side of the rotating groove respectively at the lowest point, as it is fluid and as the rotational speed is not very high. Even if only one axial bore or channel with a certain diameter is provided, this rotating bore passes through the leakage fluid sump and takes some leakage fluid which flows to the other bearing side. Preferably certainly several bores connecting the leakage lubrication fluid collection area with the leakage fluid connection means are provided, which bores are preferably equally distributed around the circumference of the outer ring. This ensures that the leakage fluid is transported from one bearing side to the other side almost all the time, as there is a number of connection bores rotating through the leakage fluid sump, into which bores the fluid can flow. As these several bores are preferably equally distributed, there is almost a constant fluid flow.

As mentioned, the collected lubrication fluid leaking from both the first and the second sealing means is collected in a collection means arranged stationary adjacent to the first sealing means. This leakage lubrication fluid collection means is preferably arranged at the stationary inner ring, which is very close to the outer ring respectively the first sealing means, so that any fluid leaking from the first sealing means can almost directly be collected in the collection means. This collection means is preferably a collector ring extending around the main bearing, which ring as mentioned is preferably arranged at the stationary inner ring. In an alternative it may certainly also be fixed to any other stationary support means, as long it is adjacent respectively very close to the first sealing means. The collector ring allows the collection of the leakage fluid not only at the lowest point of the circumference but also along the whole <NUM>° rotation of the outer ring during which some leakage fluid max exit especially the bores.

A drip edge ring may be arranged at the outer ring extending to or into the leakage lubrication fluid collection means, especially the collector ring. This drip edge ring bridges any axial distance between the first sealing means and the collection means respectively the collector ring, so that no leakage fluid can flow anywhere else than into the collector ring. It drips from the drip edge of the drip edge ring into the collection means respectively the collector ring, which may have a certain collection groove or the like.

Each sealing means is adapted to provide a proper sealing between the rotating outer ring, to which it is fixed, and the stationary inner ring. Each sealing means preferably comprises a groove accommodating a sealing element, which is for example a lip seal element having one or more lips extending from a sealing element basis towards the inner ring, along which the sealing element respectively the sealing lip(s) slide. This sealing element is accommodated in a groove of the sealing means, so that it is easy to be arranged at the sealing means respectively installed.

Each sealing means comprises a sealing element carrier ring having a fold and a clamp ring attached to the carrier ring closing the fold to build the groove and clamping the sealing means in the groove. Each sealing means therefore consists of two parts, i.e. the sealing element carrier with the fold and a clamp ring closing the fold to build the groove. The width of the sealing element is a little bit larger than the width of the groove, so that the sealing means is clamped when the groove is closed.

As already mentioned, the leakage lubrication fluid area is preferably as close as possible to the second sealing means and preferably realised as a collection groove extending around the circumference of the outer ring. In a preferred embodiment the clamp ring of the second sealing means comprises the leakage lubrication fluid area, especially the collection groove. The collection area respectively the collection groove is integrated in the second sealing means comprising the sealing element carrier and the clamp ring. It is directly integrated in the clamp ring, so that any leakage fluid leaking from the very close sealing element can directly be collected in the collection groove.

For avoiding any collected leakage fluid again leaking from the leakage lubrication fluid collection area respectively the collection groove, a sealing element like a sealing lip is arranged at the clamp ring sealing the collection groove to the inner ring. This sealing lip seals the collection groove on the other side of the groove, so that any leakage fluid collected in the groove remains in the groove until it is guided away via the axial bores to the leakage fluid collection means on the other side of the main bearing.

As mentioned above, the sealing means preferably comprises the sealing element carrier and the clamp ring, closed to which respectively integrated into which the leakage lubrication fluid collection area is realised, preferably in form of the groove. According to another embodiment of the invention the at least one axial bore respectively each axial bore communicates with the leakage lubrication fluid collection area, especially the groove, and extends from the clamp ring through the sealing element carrier ring of the second sealing means, the outer ring and through the sealing element carrier and the clamp ring of the first sealing means and is open to the leakage lubrication fluid collection means. Each axial bore which connects the leakage lubrication fluid collection area with the leakage lubrication fluid collection means comprises several bore sections, which together realise the complete axial bore connecting the collection area to the connection means. The bore sections are realised in the clamp ring and the carrier ring of the second sealing means, in the outer ring and in the element carrier and the clamp ring of the first sealing means. The or each axial bore is open on both ends. On the side of the second sealing means it is open to the collection area respectively the collection groove, and on the side of the first sealing means it is open to the collection means respectively the collector ring. As all respective bore sections are realised on the same radius of all ring components, it is only necessary to adjust the separate parts and to align the bore sections, so that the respective axial bore is realised. Especially when the axial bores are equally distanced around the circumference the alignment is simple.

The clamp ring and the element carrier ring are preferably fixed to the outer ring by means of several bolt connections, which are preferably equally distributed around the circumference of the outer ring. Also the fixation of the respective parts is realised with equally distanced bolt connections. For example a bolt connection follows each axial bore or the like. Nevertheless the spacing may also be different.

In this circumstance it is also possible to fix the sealing element carrier with first bolt connections to the side of the outer ring and the clamp ring with the second bolt connections either to the sealing element carrier or also to the outer ring side.

As each sealing means is a two-piece device sealing or collecting a fluid it is preferable when at least one sealing ring is arranged each between the clamp ring and the element carrier ring and the element carrier ring and the outer ring, which sealing rings are arranged in respective grooves. With these sealing rings a radial tight connection of the clamp ring to the element carrier ring and of the element carrier ring to the outer ring is realised. It is possible to provide the groove in only one of the adjacent pieces, or it is also possible that both are provided with respective parts which complement to the final groove.

As already mentioned the inventive main bearing is preferably automatically lubricated. For realising such an automatic lubrication the wind turbine preferably comprises an automatic lubrication arrangement with a lubrication circuit with a pump for circulating the lubrication fluid, to which lubrication circuit the leakage lubrication fluid collection means, especially the collector ring is connected. This lubrication arrangement allows for automatically providing the lubrication fluid to the points of need at or in the one or two main bearings, i.e. one or two slide bearings. As the leakage lubrication fluid collection means, especially the collector ring is connected to the lubrication circuit, also any leakage fluid is recirculated in the lubrication circuit and therefore not lost. So the amount of lubrication fluid in the circuit remains constant over a long time. Maintenance can be reduced regarding any refill of lubrication fluid or the like.

The main bearing for a wind turbine according to the above detailed disclosure, comprises an inner ring and an outer ring, whereby the main bearing is a slide bearing and the inner ring is adapted to be stationary when mounted, while the outer ring is adapted to rotate around the inner ring when mounted, with the main bearing being lubricated with a lubrication fluid, and with the outer ring comprising a first and a second sealing means arranged at both sides of the outer ring for sealing to the inner ring and extending around the outer ring, whereby an associated stationary leakage lubrication fluid collection means is provided to be arranged adjacent to the first sealing means, which leakage lubrication collection means is adapted to collect lubrication fluid leaking from the first and the second sealing means, whereby the outer ring is provided with one or more axial bores connecting a leakage lubrication fluid collection area adjacent to the second sealing means to the leakage lubrication fluid collection means and wherein each sealing means comprises a groove accommodating a sealing element and a sealing element carrier ring having a fold and a clamp ring attached to the carrier ring closing the fold to build the groove and clamping the sealing means in the groove.

<FIG> shows an inventive wind turbine <NUM>, comprising a rotor <NUM> rotatably arranged at a nacelle <NUM>, which is arranged on the top of a tower <NUM>. The rotor <NUM> comprises three rotor blades <NUM> attached to a hub <NUM> as is commonly known. The rotor blades <NUM> interact with the wind making the rotor rotate. The rotor drives an electric generator, preferably a direct drive generator.

<FIG> shows an arrangement with the central elements of the wind turbine <NUM>. It shows the hub <NUM> which is connected to a direct drive generator <NUM> comprising a rotor <NUM>, which here is directly coupled to the hub <NUM>, and further a stator <NUM>. The stator <NUM> is stationary fixed to a main shaft <NUM>.

The arrangement of hub <NUM> and rotor <NUM> is rotatable relative to the stationary shaft <NUM> respectively the stator <NUM>. For bearing the hub-rotor-arrangement a main bearing <NUM> is provided, which in the shown embodiment is a slide bearing <NUM> comprising an outer ring <NUM>, to which the hub-rotor-arrangement with the hub <NUM> and the rotor <NUM> is connected, so that, when the hub <NUM> rotates, also the outer ring <NUM> and the rotor <NUM> rotate. The main bearing <NUM> further comprises an inner ring <NUM> which is stationary and which is fixed to the main shaft <NUM>.

As the main bearing <NUM> is a slide bearing <NUM> the rotating outer ring <NUM> is slidingly guided by axial and radial guiding or sliding pads or alternatively by tapered guiding or sliding pads in a tapered sliding bearing. <FIG> shows front axial pads <NUM> and rear axial pads <NUM> for axially guiding the outer ring <NUM> and radial pads <NUM> for radially guiding the outer ring <NUM>. The pads <NUM>, <NUM> and <NUM> are stationary fixed to the stationary inner ring <NUM>. A sliding pad (<NUM>, <NUM>, <NUM>) may comprise several components (not shown) e.g. an outer sliding part, a support part for attachment to a structure by bolts or similar, a tilting support part to ensure that the sliding pad is able to tilt and/or a resilient means like e.g. a spring to ensure a preloading of the sliding pad and the tilting support.

The axis of rotation of the rotor <NUM> and therefore also the axis of rotation of the main bearing <NUM> is slightly tilted relative to the horizontal plane or axis. <FIG> shows the tilt angle α, which the axis of rotation <NUM> of the main bearing <NUM> shows relative to the horizontal plane or axis <NUM>. Therefore the main bearing <NUM> is slightly tilted, which is advantageous for a simple leakage lubrication fluid collection system, which will be explained in detail below.

As mentioned, the main bearing <NUM> is a slide bearing. This slide bearing needs to be lubricated by a lubrication fluid, which provides an extremely thin hydrodynamic fluid film between the sliding surfaces of the outer ring, which rotates, and the axial and radial pads <NUM>, <NUM> and <NUM>. It is therefore necessary to constantly provide enough lubrication fluid in this area, which can either be flooded or directly introduced respectively lubricated to respective bearing point or evacuated bearing cavities etc. The lubrication system needs to maintain a permanent and constant lubrication amount in this area.

For providing a constant lubrication, an automatic lubrication arrangement <NUM> is provided, which is shown in principle in <FIG>. This lubrication arrangement comprises a reservoir <NUM> with the lubrication fluid <NUM>, which is integrated in a lubrication circuit <NUM>. The lubrication fluid <NUM> circulates in the circuit <NUM> with a pump <NUM> integrated in the circuit <NUM>. The circuit <NUM> comprises one or more fluid pipes, which or at least some of which are guided to the main bearing <NUM> to emit the lubrication fluid <NUM> at one or several points to the main bearing <NUM> or to completely flood it. As <FIG> further shows, the lubrication arrangement <NUM> further comprises in the circuit <NUM> a redirection pipe which allows for redirecting any collected leakage lubrication fluid which leaks from the main bearing <NUM> and which is redirected in the circuit <NUM>, which collection system is explained below.

<FIG> shows an enlarged partial view of the main bearing <NUM> respectively the slide bearing <NUM>. The figure shows partly the outer ring <NUM> and the inner ring <NUM>, and also the hub <NUM> which is in this embodiment attached to the outer ring <NUM>. <FIG> shows a cross sectional view of the lower end of the main bearing <NUM>.

The outer ring <NUM> is provided with a first sealing means <NUM> attached to the one respectively inner side of the outer ring <NUM> and with a second sealing means <NUM> attached to the other side of the outer ring <NUM>. Each sealing means <NUM>, <NUM> comprises a sealing element <NUM>, <NUM>, which slidingly contacts the adjacent stationary surface of the inner ring <NUM>. Each sealing element <NUM>, <NUM> may comprises lips slidingly contacting the inner ring surface, which lips respectively detailed setup is not shown in the figure.

Each sealing means <NUM>, <NUM> further comprises a sealing element carrier <NUM>, <NUM> having a fold <NUM>, <NUM>. Furthermore each sealing means <NUM>, <NUM> comprises a clamp ring <NUM>, <NUM> attached to the element carrier <NUM>, <NUM>, which closes the fold <NUM> for building a respective groove <NUM>, <NUM>, in which the sealing element <NUM>, <NUM> is arranged respectively clamped.

Both sealing means <NUM>, <NUM> provide a good and tight sealing, nevertheless some leakage of the lubrication fluid <NUM> may occur. As mentioned this leakage lubrication fluid is collected and redirected to the lubrication circuit <NUM>.

For collecting the leakage fluid leaking from the second sealing means <NUM> a leakage lubrication fluid collection area <NUM>, which is realised as a circular groove <NUM> is realised in the clamp ring <NUM>. This groove <NUM> is as close as possible to the sealing element <NUM>, so that any lubrication fluid leaking from this sealing element <NUM> is collected in the groove <NUM>.

This leakage lubrication fluid collection area <NUM> is connected to a leakage lubrication fluid collection means <NUM> realised as a collector ring <NUM> extending around the main bearing. This lubrication collecting means <NUM> respectively the collector ring <NUM> is stationary attached preferably to the inner ring <NUM>, so that it is close to the first sealing means <NUM>.

The collector ring <NUM> comprises a collection groove <NUM>, where any leaking lubrication fluid is collected, which collection groove <NUM> is connected to the lubrication circuit <NUM> for redirecting the collected leakage fluid.

For transferring leakage fluid collected in the groove <NUM> several axial bores <NUM> are provided, which connect the leakage lubrication fluid collection area <NUM> to the leakage lubrication fluid collection means <NUM>, therefore it connects the groove <NUM> to the collector ring <NUM>. A number of parallel axial bores <NUM> are provided and distributed equally around the circumference of the outer ring <NUM>. Each axial bore <NUM> is open to the groove <NUM> at the one end and open to the collector ring <NUM> at the other end. It comprises several bore sections, as each axial bore <NUM> extends through the clamp ring <NUM>, the sealing element carrier <NUM>, the outer ring <NUM>, the sealing element carrier <NUM> and the clamp ring <NUM> as <FIG> clearly shows. All respective bore sections are in alignment, so that a fluid channel is built.

As the main bearing <NUM> is slightly tilted towards the horizontal axis as shown by the axis of rotation <NUM> and the horizontal axis <NUM> and the tilt angle α in <FIG>, and as therefore the right side of the main bearing with the first sealing means <NUM> is, due to the tilt, somehow lower than the other side with the second sealing means <NUM>, each axial bore <NUM> is also slightly tilted with a tilt angle α towards the horizontal axis, so that a natural flow direction is realised and the lubrication fluid flows automatically from the groove <NUM> to the collector ring <NUM>.

When exiting the respective axial bore <NUM> the lubrication fluid flows on a drip edge ring <NUM> fixed to the first sealing means <NUM>, which drip edge ring <NUM> collects the fluid exiting the axial bore <NUM> and guides it to the collector ring <NUM>. It axially extends into the collector ring <NUM> as <FIG> clearly shows.

Not only the lubrication fluid leaking the second sealing means <NUM> is collected on the drip edge ring <NUM> and the carrier ring <NUM>, but also the lubrication fluid leaking from the first sealing means <NUM>. This leakage fluid directly flows on the drip edge ring <NUM> and from there directly to the collector ring <NUM>.

The respective leakage fluid flow is shown in <FIG> by the respective arrows.

The lubrication fluid is present in the inner of the main bearing <NUM>, which is either flooded with the lubrication fluid respectively the oil, or the fluid is directly lubricated to certain points. The lubrication fluid is present in the areas <NUM>, <NUM> of the main bearing <NUM>, therefore on one side of each sealing means <NUM>, <NUM>, from where it leaks through the sealing means <NUM>, <NUM> and is collected as explained above.

<FIG> shows in an enlarged perspective view the second sealing means <NUM> with the sealing element carrier <NUM> and the clamp ring <NUM> with the groove <NUM>. Attached to the clamp ring <NUM> is a sealing element <NUM> in form of a sealing lip which extends to the inner ring <NUM>. This sealing element <NUM> provides a sealing on this side, so that any leakage lubrication fluid collected in the groove <NUM> remains in the groove <NUM> until it flows in the respective bore <NUM>.

For fixing the element carrier <NUM> tightly to the inner ring <NUM> and for fixing the clamp ring <NUM> tightly to the element carrier <NUM>, respective further sealing elements <NUM>, <NUM> are arranged in respective grooves <NUM>, <NUM> for example provided in the sealing element carrier <NUM> and the clamp ring <NUM> for example. This allows for an axial sealing of this element connection.

An enlarged view of the other bearing side showing the first sealing means <NUM> is shown in <FIG>. Also here respective sealing elements <NUM>, <NUM> are arranged in respective grooves <NUM>, <NUM>, preferably again provided in the surfaces of the sealing element carrier <NUM> and the clamp ring <NUM>.

<FIG> shows furthermore the attachment of the collector ring <NUM> to the stationary inner ring <NUM> and the overlap of the drip edge ring <NUM> over or into the collector ring <NUM> respectively the collection groove <NUM>, so that any leakage oil dripping from the drip edge of the drip edge ring <NUM> directly drips into this collection groove <NUM>.

<FIG> shows a cross section view showing the fixation of the first and second sealing means <NUM>, <NUM> to the outer ring <NUM>. Each sealing element carrier <NUM>, <NUM> is connected with first bolt connections <NUM>, <NUM> to the outer ring <NUM>. The outer ring <NUM> is provided with respective threaded bores, into which the bolt connections <NUM>, <NUM>, which are accommodated in respective through bores of the sealing element carrier <NUM>, <NUM>, are screwed.

The clamp rings <NUM>, <NUM> and in addition, as a second fixation means, also the whole sealing means <NUM>, <NUM> is fixed by respective further bolt connections <NUM>, <NUM>, which engage a respective through bore in the clamp ring <NUM>, <NUM> and the sealing element carrier <NUM>, <NUM> and extends into respective threaded bores in the outer ring, as shown in <FIG>.

Claim 1:
Main bearing for a wind turbine comprising an inner ring (<NUM>) and an outer ring (<NUM>), whereby the main bearing (<NUM>) is a slide bearing (<NUM>) and the inner ring (<NUM>) is adapted to be stationary while the outer ring (<NUM>) is adapted to rotate around the inner ring (<NUM>), with the main bearing being (<NUM>) lubricated with a lubrication fluid (<NUM>), and with the outer ring (<NUM>) comprising a first and a second sealing means (<NUM>, <NUM>) arranged at both sides of the outer ring (<NUM>) for sealing to the inner ring (<NUM>) and extending around the outer ring (<NUM>), whereby an associated stationary leakage lubrication fluid collection means (<NUM>) is provided to be arranged adjacent to the first sealing means (<NUM>), which leakage lubrication fluid collecting means (<NUM>) is adapted to collect lubrication fluid leaking from the first and the second sealing means (<NUM>, <NUM>), whereby the outer ring (<NUM>) is provided with one or more axial bores (<NUM>) connecting a leakage lubrication fluid collection area (<NUM>) adjacent to the second sealing means (<NUM>) to the leakage lubrication fluid collection means (<NUM>) and wherein each sealing means (<NUM>, <NUM>) comprises a groove (<NUM>, <NUM>) accommodating a sealing element (<NUM>, <NUM>) characterized in that each sealing means (<NUM>, <NUM>) comprises a sealing element carrier ring (<NUM>, <NUM>) having a fold (<NUM>, <NUM>) and a clamp ring (<NUM>, <NUM>) attached to the carrier ring (<NUM>, <NUM>) closing the fold (<NUM>, <NUM>) to build the groove (<NUM>, <NUM>) and clamping the sealing means (<NUM>, <NUM>) in the groove (<NUM>, <NUM>).