Device for sealing a rotatable component of a wind turbine power system

Abstract

An apparatus comprising: a first shaft and a second shaft, the first shaft and the second shaft being supported in a substantially concentric relationship so that they can rotate relative to each other about an axis of rotation (R); wherein one of the first shaft and the second shaft passes through a hole defined in the other of the first shaft and the second shaft; a sealing device located between the first shaft and the second shaft, the sealing device being locked to prevent rotation relative to the first shaft; wherein the sealing device comprises a first part and a second part, the first part being rotatably mounted on the second shaft by means of a bearing, and the second part being configured to seal against a running surface defined by the second shaft. Advantageously, since the sealing device is rotatably mounted on the same shaft with which it forms a seal, the sealing device can accommodate alignment errors between the first shaft and the second shaft.

Description

Technical Field

[0001] The present invention relates to a solution or arrangement for sealing a rotatable component in a wind turbine drive train. Background Art

[0002] In a typical 'horizontal axis' wind turbine, a nacelle mounted on a tower supports a rotor comprising a plurality of blades. The nacelle houses a main bearing arrangement which supports the rotor so that it can rotate as the blades are driven by the wind. The rotor is supported on the input of the power system of the wind turbine, which typically comprises a gearbox and a generator, but direct drive wind turbines which do not include a gearbox are also known. In a known configuration, the main rotor of the wind turbine is coupled to a so-called 'low speed' shaft which in turn is coupled to the input of the gearbox. The gearbox also comprises a high speed output shaft which is coupled to the generator.

[0003] In some wind turbine power systems, the power system includes a conduit extending along its axis of rotation and used to carry electrical and / or hydraulic services to the rotating hub. Those skilled in the art often refer to this conduit as a "pitch tube". One of the challenges of this approach is that the pitch tube must be precisely positioned in order to safely pass through the generator and gearbox. Moreover, the pitch tube passes through different environments, such as an air-filled cavity and an oil-filled cavity, so the pitch tube must be sealed to prevent contamination and leakage.

[0004] Known methods for sealing the running surface of a rotating shaft include annular lip seals and labyrinth seals. These are two examples, but others are also known. In both methods, it is important that the rotating shaft is supported in a precise concentric orientation relative to the ring seal. Too large tolerances can lead to increased wear and a less effective sealing function. In the case of a pitch tube, it may be the case that the seal position on the shaft is displaced a considerable distance along the axis of the shaft from the position where the shaft is rotationally supported, and this can lead to concentricity problems.

[0005] The present invention has been designed against this background. Summary of the invention

[0006] According to a first aspect of the invention, there is provided an apparatus comprising: a first shaft and a second shaft, the first shaft and the second shaft being supported in a substantially concentric relationship so that the first shaft and the second shaft can rotate relative to each other about a rotation axis; wherein one of the first shaft and the second shaft passes through a hole defined in the other of the first shaft and the second shaft. A sealing device is located between the first shaft and the second shaft and is locked to prevent rotational movement relative to the first shaft and comprises a first part and a second part, the first part being rotatably mounted on the second shaft by means of a bearing, and the second part being configured to seal against a running surface defined by the second shaft.

[0007] Advantageously, since the seal is rotatably mounted on the same shaft with which it forms a seal, the seal can accommodate misalignment between the first and second shafts. This may be the case in particular where both shafts are rotatable. But it may also be the case where the outer shaft is stationary and in effect forms a housing for the inner shaft. In either case, lateral movement of the inner shaft transverse to the axis of rotation may be significant, particularly where the shaft is supported by a bearing remote from the sealing point.

[0008] The invention has particular use in wind turbine applications where the first shaft is a gearbox output shaft and the second shaft is a pitch tube passing through the gearbox output shaft.

[0009] In one embodiment, the sealing device includes a radial surface opposite to the first shaft, thereby defining an annular gap. The annular gap actually provides a buffer that can accommodate alignment errors between the first shaft and the second shaft. In order to close this gap, the sealing device may include a flexible ring seal. The ring seal can take different forms suitable for closing the gap and preventing fluid leakage therethrough. However, in one embodiment, the ring seal takes the form of a sealing ring that is flat so as to resemble an annular diaphragm.

[0010] The flexible ring seal may extend between the surface of the first shaft and the surface of the sealing device to close the annular gap. In this way, the flexible ring seal actually locks the rotational movement of the sealing device to the rotational movement of the first shaft. This may be particularly advantageous in the case where the first shaft has a relatively high rotational speed relative to the second shaft, because the high rotational speed imparted to the sealing device can improve the operation of the seal.

[0011] In order not to affect the rotation of either of the two shafts, the bearings on which the first part of the sealing device is mounted to the first and second shafts preferably provide a very low friction interface. In one embodiment, the bearings may be roller bearings, but friction bearings and ball bearings are other options.

[0012] It is worth noting that in some embodiments, the bearing supporting the sealing device on the corresponding shaft is different from the bearing device that rotatably supports the shaft relative to another shaft, that is, the bearing supporting the sealing device on the corresponding shaft is not the same as the bearing device that rotatably supports the shaft relative to another shaft.

[0013] The sealing means may be selected so as to provide an effective seal for the specific application for which the apparatus is intended. In some cases, it may be preferred to use a type of labyrinth seal. This may be the case where the speed difference between the two shafts is high, for example a speed difference between 300 rpm and 400 rpm, and therefore a low friction seal is particularly desirable. In other cases, other rotary seals may be suitable, such as lip seals.

[0014] In the above apparatus, the first and second parts of the sealing means may be defined by a sealing member. Suitably, the sealing member may be defined by a single component and may be shaped to accommodate the bearing therein, thereby providing a particularly compact and elegant configuration.

[0015] Notably, the sealing device is compact and thus does not occupy excessive space between the shafts. For example: in one embodiment, the second portion of the sealing device is separated from the bearing by an axial distance along the axis of rotation that is less than the radial distance of the annular space defined between the first shaft and the second shaft; in one embodiment, the axial length of the sealing device along the axis of rotation is substantially the same as the radial distance of the annular space defined between the first shaft and the second shaft.

[0016] In another aspect, the present invention provides an apparatus comprising: a housing defining an inner hole; a shaft extending through the inner hole and rotatably mounted relative to the housing so as to rotate about an axis of rotation (R); a sealing device located between the inner hole of the housing and the shaft, the sealing device being locked to prevent rotational movement relative to the housing; wherein the sealing device comprises a sealing member spaced apart from the inner hole of the housing and comprising a first part and a second part, the first part being rotatably supported on the shaft by means of a bearing, and the second part being configured to seal against a running surface defined by the shaft.

[0017] It is worth noting that in this embodiment, the bearing supporting the sealing device on the corresponding shaft is different from the bearing device that rotatably supports the shaft relative to the housing, that is, the bearing supporting the sealing device on the corresponding shaft is not the same as the bearing device that rotatably supports the shaft relative to the housing.

[0018] It will be appreciated that preferred and / or optional features of the first aspect of the invention may be combined with other aspects of the invention.The invention in its various aspects is defined in the appended independent claims and advantageous features are defined in the appended dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0020] Figure 1 is a front view of a wind turbine in which embodiments of the present invention may be implemented;

[0021] Figure 2 can be accommodated in Figure 1 A perspective view of an example of a wind turbine power system within a wind turbine and to which embodiments of the present invention may be applied;

[0022] Figure 3 yes Figure 2 A schematic side view of the power system shown in ;

[0023] Figure 4 yes Figure 3 A schematic diagram of a portion of a power system in FIG. 1 , showing an apparatus for sealing a component of a power system according to an embodiment of the present invention;

[0024] Figure 5 is a perspective cross-sectional view of a sealing member according to an embodiment of the present invention;

[0025] Figure 6 is a perspective view of an annular ring seal according to an embodiment of the present invention;

[0026] Figure 7 yes Figure 6 A schematic diagram of an annular ring seal being stretched asymmetrically; and

[0027] Figure 8 is similar to Figure 4 , but showing an alternative embodiment of the invention.

[0028] Note that identical or similar features in different drawings are indicated by the same reference numerals. DETAILED DESCRIPTION

[0029] The present invention relates to an apparatus in which a shaft rotates in a housing and is provided with a dynamic seal. The housing may be stationary, but the invention has particular use in embodiments where the housing itself is a rotating shaft, such that the apparatus comprises a pair of coaxial and nested shafts rotating at different speeds with a seal therebetween. In such an apparatus, providing adequate sealing between the shafts may be challenging, particularly if one or other of the shafts has tolerance errors that compromise the mutual concentricity of the shafts.

[0030] Such sealing arrangements may be applied in many different industries, but in order to give the invention a context in which it will be better understood, the technology will now be described in more detail with reference to a wind turbine in which a so-called pitch tube extends axially through a hollow rotating shaft. As known to those skilled in the art, a pitch tube is a hollow shaft that passes through one or more sections of a wind turbine powertrain to provide a protected conduit for hydraulic and electrical services between the fixed reference frame of the nacelle and the rotating reference frame of the hub. However, reliably sealing the pitch tube within the interior of a powertrain component when required is challenging.

[0031] In order to place the embodiments of the present invention into proper context, reference is first made to Figure 1 , which shows a typical horizontal axis wind turbine (HAWT) 2, the HAWT comprising Figure 2 Although this particular image depicts an offshore wind turbine, it will be appreciated that equivalent features will also be found on offshore wind turbines. Furthermore, although such wind turbines refer to a 'horizontal axis', those skilled in the art will appreciate that for practical purposes the axis is typically slightly tilted to prevent contact between the rotor blades and the wind turbine tower in the event of strong winds.

[0032] The wind turbine 2 includes a tower 4, a nacelle 6 rotatably coupled to the top of the tower 4 by a yaw system (not shown), a rotating hub or 'rotor' 8 mounted to the nacelle 4, and a plurality of wind turbine rotor blades 10 coupled to the hub 8. The nacelle 4 and the rotor blades 10 are rotated and pointed into the wind direction by the yaw system.

[0033] As mentioned above, the nacelle 6 houses a power generation device 20, which includes a power system or a drive train. Both terms are used in the art, and for consistency, "power system" will be used from now on. As will be understood by those skilled in the art, a wind turbine power system includes a gearbox 22 and a generator 24 driven by a main shaft 26.

[0034] The main shaft 26 is supported by the main bearing housing 28 and is connected to and driven by the rotor 8, thereby providing input drive to the gearbox 22. The gearbox 22 steps up the speed of the low speed main shaft 26 via an internal gear (not shown) and drives the gearbox output shaft (at Figure 2 The gearbox output shaft in turn drives a generator 24, which converts the rotation of the gearbox output shaft into electricity. The electricity generated by the generator 24 may then be converted by other components (not shown) as needed before being supplied to appropriate consumers (e.g., a distribution system).

[0035] Referring generally to the gearbox 22, its housing 30 is generally cylindrical in form, due to the particular type of gearbox used in this particular powertrain arrangement. As is known to those skilled in the art, an epicyclic gearbox includes a series of planetary gears arranged around a central sun gear and collectively arranged within a surrounding ring gear. Such a gearbox may include more than one stage of planetary gears. The gear ratios between the ring gear, the planetary gears, and the sun gear may be used to determine the gear ratio of the gearbox. For the sake of clarity, the fine details of the gearbox will not be described in further detail herein, as the gearbox is not the primary subject of the present invention. It is sufficient to say that other gearbox configurations may also be used.

[0036] Reference will now also be made to the schematic diagram which more clearly illustrates some of the components. Figure 3 To describe the further details of the power system. It should be noted that Figure 3 It is schematic in form, and thus for the sake of brevity and clarity, some components of the generator are not shown or described so as not to detract from the focus of the present discussion.

[0037] As can be seen, the main shaft 26 is supported in the main bearing housing 28 by front and rear bearings 32, 34. The axially spaced bearings 32, 34 ensure that the main shaft 26 is securely supported for rotation about a main axis of rotation, shown here as R, despite the high loads applied to the main shaft. Since the gearbox 22 is an epicyclic gearbox, the main shaft 26, the gearbox 22 and the generator 24 are all centered on and share the same axis of rotation R.

[0038] Main shaft 26 is coupled to gearbox 22 at gearbox input shaft 36. Similarly, gearbox 22 is coupled to generator 24 via gearbox output shaft 38. More specifically, gearbox output shaft 38 is coupled to a rotor 40 of generator 24, hereinafter, "generator rotor."

[0039] Turning now to the generator 24, in the arrangement shown, it is an IPM (internal permanent magnet) machine having an external stator 50 surrounding the generator rotor 40. "External" means that the generator stator 50 is in a radially outer position relative to and surrounds the generator rotor 40, compared to a generator design where the rotor is external to the stator. The magnetically active components of the generator 24 are housed within a generator housing 53, which in this arrangement is of cubic form, as shown in FIG. Figure 2 shown.

[0040] A cylindrical magnet group 55 is supported on the generator rotor 40 and is arranged to rotate about an axis of rotation R. The magnet group 55 is supported by a generator rotor hub 56 and a support flange 58. The exact structural configuration of the generator rotor hub 56 and the support flange 58 is not critical. However, functionally, these components serve to transmit drive from the generator rotor hub 56 (such as transmitted from the gearbox) through the support flange 58 to the magnet group 55, thereby ensuring that the magnetically active components of the generator rotor 40 are coupled to the gearbox output shaft 38.

[0041] As is common in many designs of wind turbine power systems, an elongated hollow conduit or shaft in the form of a "pitch tube" 60 is provided to transfer hydraulic and electrical services from the stationary frame of the nacelle to the rotating frame of the main rotor hub. As shown in the figure, the pitch tube 60 extends along the rotation axis R and passes through the generator 24, the gearbox 22 and extends into the main shaft 26. The precise form of the pitch tube is not critical to the present invention, so further explanation is omitted.

[0042] Although the pitch tube 60 passes through powertrain components that rotate at relatively high rotational frequencies, such as the gearbox output shaft 38 and the generator rotor 40, the pitch tube 60 rotates at the same frequency as the main shaft 26. Therefore, the pitch tube 60 must be rotationally supported relative to the generator rotor 40 and the gearbox output shaft 38. To this end, the pitch tube 60 is rotationally supported at various points along its axial length by suitable bearings. The exact configuration of the bearings is not critical, but as shown in FIG. Figure 3 As shown, in this arrangement, the pitch tube 60 is supported at a first (rear) bearing 62 and a second (front) bearing 64. The rear bearing 62 is located at a central hole provided in the rear face 54 of the generator housing 53, and the front bearing 64 is defined within the gearbox 24 and is Figure 3 The two bearings 62, 64 together function to support the pitch tube 60 about the axis of rotation R in a concentric relationship relative to the gearbox 24 and the generator 22. Those skilled in the art will appreciate that other configurations are acceptable.

[0043] Because the pitch tube 60 extends through different components of the power system, suitable seals are required to ensure that the surrounding environment of the power system is not contaminated by the oil-filled environment. For example, the internal environment of the generator needs to be protected from the oil and grease inside the gearbox. However, because it may be difficult to ensure that the pitch tube is truly concentric with the gearbox output shaft, meeting the sealing requirements can be challenging. In the event that the pitch tube is slightly misaligned, the effectiveness of conventional rotating seals may be compromised, which may cause oil mist to enter the generator and increase wear on the running surfaces of the pitch tube.

[0044] To this end, embodiments of the present invention provide a sealing device 70 for sealing the pitch tube 60 against the high speed output shaft 38 of the gearbox. Figure 3 However, due to the scale of the drawings, Figure 4 It is schematically shown in Figure 3 A more detailed view of area A circled in FIG.

[0045] At this point, it should be noted that Figure 4 This may be considered a simplified view in order to focus on the main features of the inventive concept without obscuring them with unnecessary detail. Here, it can be seen that the gearbox output shaft 38 is in a radially outer position relative to the pitch tube 60. It should be noted that for the sake of clarity, details on how the gearbox output shaft 38 is rotationally supported are not shown in this view. However, those skilled in the art will understand that the gearbox 22 will be provided with suitable bearing arrangements to ensure that the output shaft is adequately supported.

[0046] The gearbox output shaft 38 is hollow and thus defines an axial inner bore 72. The pitch tube 60 passes through the inner bore 72 and in this way extends from the generator side through the gearbox 22 to the main shaft side. As already mentioned, the pitch tube 60 is supported independently of the gearbox output shaft 38 on respective bearings 62, 64, so that the pitch tube 60 can rotate relative to the gearbox output shaft 38 about the rotation axis R. Therefore, the gearbox output shaft 38 and the pitch tube 60 are supported in a mutually concentric orientation, so that the pitch tube 60 is nested within the gearbox output shaft 38.

[0047] The pitch tube 60 has an outer diameter that is smaller than the inner diameter of the gearbox output shaft 38, such that an annular space 74 is defined between the two components. The annular space 74 must be sealed to prevent contamination between the oil-carrying environment within the gearbox 22 and the surrounding environment of the generator 24. To this end, a sealing device 70 is located in the annular space 74 between the pitch tube 60 and the gearbox output shaft 38. More specifically, in this embodiment, the sealing device 70 is located in the annular space 74 near the opening 76 of the inner bore 72 of the gearbox output shaft 38.

[0048] In a typical rotating shaft seal, a sealing member, such as an annular lip seal, would be mounted on the gearbox output shaft 38 and seal against the running surface of the pitch tube 60. However, such a conventional arrangement would be susceptible to concentricity errors between the two shafts, which could result in excessive wear on the running surface of the pitch tube and / or increased leakage from the seal.

[0049] In contrast to conventional arrangements as described above, in particular, the sealing device 70 of the present invention is mounted, supported or otherwise fixed to the pitch tube 60. More specifically, the sealing device 70 is rotatably mounted to the pitch tube 60 so that the sealing device can rotate relative to the pitch tube. As can be seen in the figure, the sealing device 70 is directly mounted to the pitch tube 60 because there are no other shafts or housing components between them. The sealing device 70 is therefore fixed to the pitch tube 60 so that it can rotate while being fixed to the pitch tube. In other words, the pitch tube 60 carries the sealing device 70. In addition, as will be understood from the following discussion, it should be noted that the bearings that support the sealing device 70 on the pitch tube 60 are different from the bearing devices that rotatably support the pitch tube and the gearbox output shaft 38. For the avoidance of doubt, it should be noted that this distinction applies to each embodiment of the present invention discussed below.

[0050] In this embodiment, seal arrangement 70 includes two components: bearing 82 and seal member 84. Bearing 82 is shown here as a roller bearing because this is a convenient way to provide a low friction interface between pitch tube 60 and seal member 84. However, it is contemplated that other types of bearings are acceptable, such as different types of ball bearings, roller bearings, and friction bearings.

[0051] and Figure 4 A side view of the sealing member 84 is shown, Figure 5 A perspective view is shown from which the details can be better understood.

[0052] The sealing member 84 in this embodiment is an annular component that is generally cylindrical in external form. The internal form of the sealing member 84 is shaped to define two sections: the first section 86 serves as a connection function to connect or fix the sealing member 84 to the bearing 82; and the second section 88 performs a sealing function. The two sections 86, 88 each define approximately half of the axial length of the sealing member 84.

[0053] In the illustrated embodiment, the first section 86 of the sealing member 84 comprises a circular socket 90 defined by a cylindrical inner wall 92, the inner diameter of the circular socket being comparable to the outer diameter of the bearing 82 on which the sealing member is mounted. In the illustrated arrangement, the socket 90 has a frustoconical base or floor 94 at which the first section 86 merges into the second section 88. Thus, the second section 88 has a thicker wall section than the first section 86.

[0054] The sealing member 84 can be mounted on the bearing 82 by means of a press fit, since the inner diameter of the socket 90 is comparable to the outer diameter of the bearing 82. Additional or alternative measures may be taken to ensure secure fixation. For example, a suitable adhesive may be applied to the contacting surfaces of one or both of these components. In addition, a suitable open spring ring, set screw or pin arrangement may be integrated into the sealing device 70 to ensure that the sealing member 84 is securely connected to the bearing 82. It is also contemplated that heat shrinking may be a suitable option for fixing the sealing member to the bearing.

[0055] The second section 88 of the sealing member 84 provides a sealing function. In this embodiment, the second section 88 defines a labyrinth seal 98. It should be understood at this point that the precise form of the seal is not critical. As shown, the labyrinth seal 98 is shown as a simple non-isolated radial labyrinth seal, characterized by a plurality of axially spaced ring sealing fins 100 defined by the second section 88 of the sealing member. In a conventional manner, the sealing member 84 is configured so that the sealing fins 100 define a very small gap with the lower running surface of the pitch tube 60 to provide a non-contact seal. The exhaust passage 101 is provided in the sealing member 84 so that the fluid trapped between the fins 100 can be discharged radially outward. Other types of labyrinth seals are also acceptable in this application, such as axial labyrinth seals and isolation labyrinth seals. For example, the pitch tube may be provided with a reverse fin that extends radially away from the pitch tube and intersects with the fins of the sealing member. In addition, other seal types, such as lip seals, may be used. Combinations of seal types may also be used. However, those skilled in the art will appreciate that different types of seals may increase the complexity of the device.

[0056] The sealing member 80 may be made of any suitable material. Different materials may be more suitable for different applications. For example, types of engineering plastics and rubbers (e.g., nylon, PEEK, FKM or EPDM) may be suitable for some applications, as may metal seals (e.g., steel).

[0057] Advantageously, because the seal 70 is rotatably mounted on the pitch tube 60, the sealing fins 100 of the seal member 84 are accurately positioned relative to the opposing running surface, regardless of the mounting accuracy of the pitch tube 60 relative to the gearbox output shaft 38. This ensures that an accurate seal is established.

[0058] Specific reference Figure 4 , it will be noted that the outer diameter of the sealing device 70 is smaller than the inner diameter of the gearbox output shaft 38. This ensures that the sealing device 70 can extend freely within the annular space 74 and also provides space to accommodate an eccentric mounting between the pitch tube 60 and the gearbox output shaft 38. Due to the difference in diameter, an annular gap 102 is defined between the radially outer surface 103 of the pitch tube 60 and the inner bore 72. In other words, the sealing member 84 is spaced apart from the inner bore 72. It should be noted that any eccentricity in how the pitch tube 60 is mounted relative to the gearbox output shaft 38 will cause the annular gap 102 to be non-uniform around its circumference. Therefore, in practice, it can be considered that any tolerance between the pitch tube 60 and the gearbox output shaft 38 is transmitted radially outward to the annular gap 102 between the sealing device 70 and the gearbox output shaft 38.

[0059] In order to seal the annular gap 102, the sealing device 70 comprises a cover in the form of a flexible ring seal 104 which closes the annular gap 102. The flexible ring seal 104 is also Figure 6 Shown in a stereogram.

[0060] In the illustrated embodiment, the flexible ring seal 104 is in the form of a ring or membrane seal. The ring seal 104 is shaped to be generally flat in cross section. When installed in the annular gap 102, the plane of the ring seal 104 is transverse to the axis of rotation R. The flat shape of the ring seal 104, together with the material from which it is made, provides radial elasticity to the ring seal, enabling the ring seal to stretch in the radial direction to accommodate unevenness in the annular gap 102. Although it is envisioned that a flat ring would be acceptable for the ring seal 104, the illustrated embodiment is shaped to provide a greater degree of flexibility.

[0061] To this end, the ring seal 104 includes a radially inner flange or lip 106 and an outer flange or lip 108 connected by an intermediate ridge, rib, or bridge 110. The curved shape of the bridge 110 links the inner and outer flanges 106, 108 out of the general plane of the ring seal 104 and thus provides a greater degree of flexibility to allow the inner and outer flanges 106, 108 to move toward and away from each other. Figure 7, which depicts a ring seal 104 adapted to a non-uniform annular gap 102 , wherein a lower portion of the ring seal 104 , in the orientation shown in the figure, is stretched relative to an upper portion, wherein a majority of this stretching is absorbed by the bridge 110 .

[0062] The two radial flanges 106, 108 of the ring seal may be secured to their respective mounting surfaces in any suitable manner. Although not shown here, it is contemplated that the flanges 106, 108 may be adhesively bonded or mechanically fastened to the surface to which they are to be attached. Figure 4 , it can be seen that the ring seal 104 is positioned so that it extends between the surface of the gearbox output shaft 38 and the surface of the sealing device 70, and therefore, closes the annular gap 102. More specifically, in the illustrated embodiment, the ring seal 104 extends between the gearbox output shaft 38 and the corresponding adjacent axially facing surfaces 112, 114 of the sealing device 102. These adjacent axially facing surfaces 112, 114 are aligned in the axial direction along the rotation axis R.

[0063] The ring seal 104 may be attached to an associated mounting surface by any suitable means, including clamping rings and bolts, as appropriate and as will be apparent to the skilled artisan.

[0064] In addition to closing the annular gap 102, the ring seal 104 also acts as a radial linkage between the seal member 84 and the gearbox output shaft 38. Because the seal member 84 is mounted on the bearing 82, the ring seal 104 acts as a torque support and therefore allows the seal member 84 to rotate synchronously with the gearbox output shaft 38. Since the gearbox output shaft 38 rotates at a higher speed than the pitch tube 60, this helps to ensure that the labyrinth seal works optimally because such a seal tends to capture leaking fluid more effectively due to the higher radial forces.

[0065] From the above discussion, it will be noted that the sealing arrangement 70 is relatively compact in the axial direction along the axis of rotation R. This means that the sealing function of the sealing member 84 is predictable and reliable and does not occupy excessive space in the annular space 74 between the two shafts 38, 60. It is worth noting that the second portion 88 of the sealing member 84 is located close to the bearing, such as Figure 4 More specifically, dimension D1 is smaller than the radial distance of the annular space 74 between the gearbox output shaft 38 and the pitch tube 60, and the radial distance of the annular space 74 is Figure 4 Dimension D1 is also less than the diameter of pitch tube 60, which is indicated as dimension D3. It should also be noted that the depth of sealing member 84 (i.e., when Figure 4The axial length of the sealing member 84 when oriented as shown in FIG. 7 , as indicated by dimension D4, is substantially equal to dimension D2. Furthermore, since the socket 92 is provided, the bearing (82) is contained within the axial length of the sealing member 84 and does not extend from the socket 92 in this embodiment. This facilitates space-efficient packaging of the sealing device 70.

[0066] It will be appreciated by those skilled in the art that the illustrated embodiments are provided as an indication of one way in which the inventive concept may be implemented. Some variations have been described above, but other variations will be apparent. Therefore, the scope of the present invention should be determined by the terms of the appended claims rather than by the features of the illustrated embodiments.

[0067] In the embodiments discussed above, the sealing device 70 is configured to be mounted directly to the pitch tube 60 and also seal against the running surface on the pitch tube 60. Expressed in another way, the sealing device 70 provides a radially inward facing seal. However, it is contemplated that the principles of the present invention are also applicable to sealing devices that can be configured to provide a radially external seal between two rotating shafts. Figure 8 Such a configuration is depicted in , wherein it will be noted that the components are identical to the previous figures and therefore, for the sake of clarity, the same reference numerals will be used. A detailed description of this arrangement will not be provided and only the differences will be explained.

[0068] In this embodiment, the sealing device 70 is located at Figure 4 1 and 1 . The annular space 74 of the pitch tube 60 and the generator output shaft 38 is located in the same position as in the embodiment of the present invention, i.e., in the annular space 74 between the pitch tube 60 and the generator output shaft 38 at an axial position adjacent the open end of the gearbox output shaft 38. However, it will be apparent that the orientation of the sealing device 70 has been reversed so that the bearing 82 is fixed to the inner bore 72 of the gearbox output shaft 38 and the sealing member 84 is opposed to the running surface on the gearbox output shaft 38 and therefore seals against the running surface. Therefore, the annular gap 102 that is then closed by the ring seal 104 is now defined by the radially inward surface of the sealing device 70 and the outer surface of the pitch tube 60. It is worth noting that in this embodiment, a set of optional mating fins 116 mounted on the carrier 118 are provided. The mating fins 116 are opposed to the fins of the labyrinth seal member 84 and therefore provide additional isolation for the sealing device 70. More specifically, the mating fins 116 intersect with the fins of the sealing member 84, as will be understood by those skilled in the art. The mating fins 116 and associated carrier 118 may form an annular component that may be received over the seal member 84 and the bearing 82. The combined assembly of the mating fins 116 / carrier 118, the seal member 84, and the bearing 82 may thus be installed as a single component.

[0069] Suitable drain passages 120 may be provided in the outer shaft 38 to drain leakage fluid from the seal 70 to a suitable drain or sump.

[0070] In the above discussion, seal 70 is located in the space between the nested rotating shafts so that radially outer shaft 38 is effectively a rotating housing for inner shaft / pitch tube 60. However, the present invention may also be advantageous in applications where the radially inner shaft extends through a stationary housing.

Claims

1. An apparatus for sealing a rotatable component of a wind turbine power system, the apparatus comprising: a first shaft (38) and a second shaft (60), the first shaft and the second shaft being supported in a substantially concentric relationship such that the first shaft and the second shaft are rotatable relative to each other about an axis of rotation (R); wherein one of the first shaft (38) and the second shaft (60) passes through a hole (72) defined in the other of the first shaft (38) and the second shaft (60); a sealing device (70) located between the first shaft (38) and the second shaft (60), the sealing device (70) comprising a sealing member (84) and a bearing (82), the sealing member (84) being locked against rotational movement relative to the first shaft (38); The sealing member (84) comprises a first portion (86) and a second portion (88), wherein the first portion is rotatably mounted on the second shaft (60) by means of the bearing (82), and the second portion is configured to seal against a running surface defined by the second shaft (60).

2. The device according to claim 1, wherein The sealing member (84) includes a radial surface (103) that opposes the first shaft (38) to define an annular gap (102).

3. The device according to claim 2, wherein: The sealing device (70) comprises a flexible ring seal (104) closing the annular gap (102).

4. The device according to claim 3, wherein: The flexible ring seal (104) extends between a surface (112) of the first shaft (38) and a surface (114) of the sealing member (84) to close the annular gap (102).

5. The device according to claim 3 or 4, wherein: The flexible ring seal (104) extends between the first shaft and respective adjacent axially facing surfaces of the sealing member.

6. The device according to claim 3 or 4, wherein: The flexible ring seal (104) is a membrane seal.

7. The device according to any one of claims 1 to 4, wherein: The bearing (82) on which the first portion (86) of the sealing member (84) is mounted to the second shaft (60) is a roller bearing.

8. The device according to any one of claims 1 to 4, wherein: The second portion of the sealing member (84) includes one or more lip seals.

9. The device according to any one of claims 1 to 4, wherein: The second portion of the sealing member (84) includes a labyrinth seal.

10. The apparatus according to any one of claims 1 to 4, wherein: The first shaft (38) is a radially outer shaft through which the second shaft (60) passes.

11. The apparatus according to any one of claims 1 to 4, wherein: The first portion (86) and the second portion (88) are defined by the sealing member (84).

12. The apparatus according to any one of claims 1 to 4, wherein: The first shaft (38) is rotatable, and wherein the second shaft (60) is rotatable.

13. The apparatus according to any one of claims 1 to 4, wherein: The second portion (88) of the sealing member (84) is spaced an axial distance (D1) from the bearing (82) along the rotational axis (R), the axial distance (D1) being less than a radial distance (D2) of an annular space (74) defined between the first shaft (38) and the second shaft (60).

14. The apparatus according to any one of claims 1 to 4, wherein: An axial length (D4) of the sealing device (70) along the axis of rotation (R) is substantially the same as a radial distance (D2) of an annular space (74) defined between the first shaft (38) and the second shaft (60).

15. An apparatus for sealing a rotatable component of a wind turbine power system, the apparatus comprising: a housing (38) defining an inner bore (72); a shaft (60) extending through the inner bore (72) and rotatably mounted relative to the housing (38) for rotation about an axis of rotation (R); A sealing device (70) is located between the inner bore (72) of the housing (38) and the shaft (60), the sealing device (70) comprising a sealing member (84) and a bearing (82), the sealing member (84) being locked to prevent rotational movement relative to the housing (38); wherein the sealing member (84) is spaced from the inner bore (72) of the housing (38), and the sealing member comprises a first portion (86) and a second portion (88), the first portion being rotatably supported on the shaft by means of the bearing (82), and the second portion being configured to seal against a running surface defined by the shaft (60).

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