Abstract:
A lubrication seal such as an oil seal is described for providing a lubrication barrier to confine lubrication in a bearing with a first bearing ring and second bearing ring, comprising a support ring that rotates with one of the bearing rings, mounted in the support ring are a first seal ring and a second seal ring which seal rings are suitable for forming the lubrication barrier with a sealing surface that rotates with the other bearing ring and which support ring is displaceable from a first sealing position in which the first seal ring forms the lubrication barrier with a first sealing area and the second seal ring does not engage the sealing surface to a second sealing position in which the second seal ring forms the lubrication barrier. The sealing surface comprises a second sealing area that only cooperates with the second seal ring after the support ring is displaced into the second sealing position.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation application and claims priority under 35 U.S.C. 120 of international application PCT/EP2007/062970, filed Nov. 28, 2007 and published in English as WO/2008/065153, the content of which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. 
     Aspects of the invention concern a lubrication seal. Such a seal is known from FR 2742837. The disadvantage of the known seal is that the second seal ring has to seal on the same sealing area as the first seal ring. The lubrication barrier is meant to have a long life expectancy and over a long operation period there might develop damage to the first sealing area. This means that if the lubrication barrier is leaking and the cause of leaking is damage to the first sealing area replacing the first seal ring by the second seal ring does not stop the leaking and does not bring the desired improvement. 
     SUMMARY 
     This Summary and Abstract are provided to introduce some concepts in a simplified form that are further described below in the Detailed Description. This Summary and Abstract are not intended to identify key features or essential features of the claimed subject matter, nor are they intended to be used as an aid in determining the scope of the claimed subject matter. In addition, the description herein provided and the claimed subject matter should not be interpreted as being directed to addressing any of the short-comings discussed in the Background. 
     A lubrication seal assembly such as an oil seal is described for providing a lubrication barrier to confine lubrication in a bearing with a first bearing ring and second bearing ring, comprising a support ring that rotates with one of the bearing rings, mounted in the support ring are a first seal ring and a second seal ring which seal rings are suitable for forming the lubrication barrier with a sealing surface that rotates with the other bearing ring and which support ring is displaceable from a first sealing position in which the first seal ring forms the lubrication barrier with a first sealing area and the second seal ring does not engage the sealing surface to a second sealing position in which the second seal ring forms the lubrication barrier. The sealing surface comprises a second sealing area that only cooperates with the second seal ring after the support ring is displaced into the second sealing position. By creating a new lubrication barrier with a new seal ring that seals on a new sealing area the lubrication barrier will function as completely new. 
     In accordance with an embodiment the second sealing area is at the side of the lubrication barrier nearest to the bearing when the support ring is in the first sealing position. In this way the second sealing area is protected from outside influences by the lubrication barrier so that damage to the second sealing area is prevented. 
     In accordance with an embodiment the first sealing area and the second sealing area have the same diameter and whereby the sealing surface has between the first sealing area and the second sealing area a groove with a width that is at least equal to the width of the second seal ring. In this way the first seal ring and the second seal ring can have the same dimensions which makes the support ring more compact and reduces costs. 
     In accordance with an embodiment the first sealing area and the second sealing area have different diameters. In this way it is avoided to make a groove m the sealing surface and the first seal ring can remain sealing against the sealing surface. 
     In accordance with an embodiment the material of the seal rings is polytetrafluoroethylene or a similar material. This material reduces friction between the sealing surface and the seal ring and so obtains an increased service life of the seal ring. In accordance with an embodiment the sealing areas are from tempered steel. This lengthens the service life of the sealing surface. 
     In accordance with an embodiment the sealing areas are part of a bearing ring. This makes it possible to make a compact bearing with a lubrication seal whereby the sealing areas can be made to the same quality as the surfaces of the bearing or if applicable the ball or roller track (s) of the bearing. 
     An aspect of the invention also concerns a wind turbine with a lubrication seal assembly. The maintenance costs of a wind turbine with a main bearing for supporting the blades are strongly influenced by the service costs of the main bearing. In the known wind turbines replacing the main bearings or the lubrication seals there of is very expensive. By using in the main bearing lubrication seals with increased life expectancy the service costs of the wind turbine are considerably improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Hereafter the invention is explained by describing various embodiments of the invention with the aid of a drawing. In the drawing 
         FIG. 1  shows a side view of a wind turbine, 
         FIG. 2  shows a detailed section of a main bearing of the wind turbine of  FIG. 1  with a first embodiment of an oil seal device, 
         FIG. 3  shows a detail of a second embodiment of an oil seal device in a first position, and 
         FIG. 4  shows a detail of the second embodiment of an oil seal device in a second position. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a wind turbine that is placed on a tower  1  and that has a housing  2 . The housing  2  is ro-tatable around a vertical axis. A housing ring  4  is with one side attached to the housing  2  and at the other side to a main bearing  9 . A rotor R, comprising a hub  11  with blades  10  is attached to the main bearing  9  and can rotate around a centreline  3 . At the front side the hub  11  is covered by a cap  12 . A generator rotor  6  with permanent magnets  5  is attached via a generator flange  8  to the main bearing  9  and rotates with the rotor R. A generator stator  7  is mounted on the housing ring  4 . The permanent magnets  5  move along the windings of the generator stator  7  to generate electrical power. The housing  2  can rotate around the vertical axis so that the rotor R can be directed towards the wind. 
     The wind turbine is designed with a direct drive generator and the generator rotor  6  is directly driven by the rotor R. The main bearing is located between the housing ring  4  and the rotor R and is designed to absorb the gravitational and aerodynamic loads on the rotor R. The service life of the main bearing  9  determines to a large extend the service life of the wind turbine as replacing the main bearing  9  leads to high costs. In circumstances whereby the wind turbine is placed m difficult accessible locations, for instance at sea, replacing the main bearing  9  during service life must be avoided. The service life of the main bearing  9  depends to a large extend on the service life of the oil seals between the rotating parts and the stationary parts of the main bearing  9 . These oil seals are required to ensure that sufficient lubrication means such as oil remains in the main bearing  9 . For this application, only oil seals that are mounted as a full ring between a rotating part and a stationary part have a service life that is long enough. Oils seals that are assembled and welded to a full ring around a part always have the weld as a weak spot. This weld reduces the service life to an unacceptable low level and this design is therefore not suitable. The assembly and disassembly of oil seals as full rings generally requires extensive dismantling of the equipment so that extension of the service life of the oil seal device is strongly desired. 
       FIG. 2  shows the main bearing  9 , which is a ball bearing with balls  18 , whereby an oil seal device is mounted between a stationary inner ring  17  and a rotating outer ring  16  on both sides of the balls  18 . The inner ring  17  is mounted on a flange  26  of the housing ring  4 . The generator flange  8  and the hub  11  are mounted on the outer ring  16 . A support ring  14  is coupled to the outer ring  16  by bolts  13 . A cylindrical part  27  of the support ring  14  is located between the inner ring  17  and the outer ring  16 . A static seal  19  is mounted on the outer circumference of the cylindrical part  27  and seals the opening between the outer ring  16  and the support ring  14 . 
     On the inner circumference of the support ring  14  an interior seal  20  and an exterior seal  21  are mounted, whereby the interior seal  20  is nearest to the parts to be lubricated such as the balls  18  and the exterior seal  21  is nearest to the surroundings. The outer circumference of the inner ring  17  near the support ring  14  has an exterior sealing surface  28  and an interior sealing surface  29  which is nearest to the parts to be lubricated and between the exterior sealing surface  28  and the interior sealing surface  29  a groove  22 . The groove  22  has a depth that ensures that the interior seal  20  or the exterior seal  21  are free when located above the groove  22  and do not have any contact with the inner ring  17 . 
     In the position shown in  FIG. 2  there is a spacer  15  between the support ring  14  and the outer ring  16  (via the generator flange  8  and the hub  11 ) and the support ring  14  is m a first position. In this first position of the support ring  14  the exterior seal  21  seals with a flexible sealing lip against the exterior sealing surface  28 . The interior seal  20  is above the groove  22  so that there is no contact between the stationary inner ring  17  and the flexible sealing lip of the rotating interior seal  20 . As the interior seal  20  is behind the exterior seal  21  it has no influence from any contamination or light and there is no wear on the lip of the interior seal  21 . This way the interior seal  20  remains ready for use and as long as it is m this first position, there is no diminishing of its service life. Also the interior sealing surface  29  is protected by the exterior seal  21  and remains ready for use. 
     After a period the end of the service life of the exterior seal  21  is detected by observing oil leakage between the sealing lip of the exterior seal  21  and the exterior sealing surface  28 . After determining that the exterior seal  21  is at the end of its service life the spacer  15  is removed and the support ring  14  is pushed inwards and fastened to the outer ring  16  with the bolts  13  (via the generator flange  8  or the hub  11 ). The support ring  14  is now in its second position. 
     In this second position, the flexible sealing lip of the interior seal  20  seals on the interior seal surface  29  and the flexible lip of the exterior seal  21  is free of the inner ring  17  as it is above the groove  22 . (In other embodiments it might be possible that the exterior seal  21  remains in sealing contact with the exterior sealing surface  28 .) As the service life of the interior seal  20  and the interior sealing surface  29  only starts after the support ring  14  is placed in the second position and the flexible sealing lip of the interior seal  20  contacts the interior seal surface  29 , the service life of the oil seal device is twice as long. In order to extend service life of the oil seals as much as possible the exterior sealing surface  28  and the interior sealing surface  29  are preferably from tempered steel and have a ground surface. This way the wear on the flexible sealing lip is reduced as much as possible. The interior seal  20  and the exterior seal  21  are made from flexible material such as rubber or preferably Teflon or similar material m order to obtain a service life that is as long as possible. The service life of an oil seal device that can be obtained m this application with a single seal is approximately 15-20 years, which is slightly less than its expected service life. By using the oil seal device with two oil seals that are in service one after the other the oil seal device is no longer a limiting factor on the service life of the wind turbine. It will be clear that m order to make it possible to displace the support ring  14  m axial direction towards the balls  18  the exterior sealing surface  28  and the interior sealing surface  29  must be provided with a gradual transition such as sloped and/or rounded surfaces in order to avoid damage to the flexible sealing lips of the interior seal  20  or the exterior seal  21 . Also the outer ring  16  must be provided with a sloped surface in order to avoid damage to the static seal  19  when the support ring  14  is brought between the inner ring  17  and the outer ring  16 . In the embodiment shown m  FIG. 2  the main bearing  9  is shown as a double row ball bearing. It will be clear to the skilled man that the invention is applicable for other types of ball bearings and for roller bearings or for any other type of bearing. Also aspects of the invention is applicable for other applications such as an oil seal device between a rotating shaft and a housing, whereby the rotating shaft rotates in roller bearings or ball bearings or in any other type of bearing. 
       FIGS. 3 and 4  show a sealing between an inner ring  25  and an outer ring  23  which rotate relative one another. In this embodiment the support ring  14  is coupled to the outer ring  23  and the exterior sealing surface  28  and the interior sealing surface  29  are on the inner ring  25 . It will be clear that this situation is preferred, as grinding an outer surface is easier. However there might be embodiments whereby it is preferred to have the exterior sealing surface  28  and the interior sealing surface  29  on the inside surface of the outer ring  23 . In the embodiment shown in  FIGS. 3 and 4  the support ring  14  is movable in axial direction m a chamber  24  which is in open connection with space in which the parts to be lubricated such as one or more bearings, gears etc. are located. By using the support ring  14  with the interior seal  20  and exterior seal  21 , a doubling of the service of the oil seal device is obtained. 
     In situations whereby an even longer service life is desirable it is possible to use three or more seal rings with two or more grooves, so that seal rings can be used one after the other. The different grooves will then have an increasing width, seen from the exterior, in order to ensure that after moving the support ring over a small distance to a next position a next seal ring contacts a next sealing surface that has not been used by any other seal ring. 
     In the described embodiments the interior sealing surface  28  and the exterior sealing surface  29  have the same diameter and also the interior seal  20  and the exterior seal  21  have the same diameter. The same effect of using one oil seal after the other can be obtained without a groove  22  when the interior seal  20  and the interior sealing surface  29  have a slightly larger diameter than the exterior seal  21  and exterior sealing surface  28 . In this way the support ring  14  also has a first position in which the exterior ring  21  seals and a second position in which also the interior ring  20  seals. 
     Although the subject matter has been described in language specific to certain compositions, structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific compositions, features or acts described above as has been determined by the courts. Rather, the specific compositions, features and acts described above are disclosed as example forms of implementing the claims. Furthermore, the description herein is provided for purposes of understanding and that the components or functions performed described can be separated or grouped in other ways, if desired.