Patent Application
20110138963
The subject-matter disclosed herein relates generally to a sealing device and more particularly, to a sealing device for actively draining a fluid, a gearbox with a sealing device, and a wind turbine equipped with a sealing device.
Sealing for preventing fluid leakage or avoiding pollution of rotating equipment is an important issue in different technical applications such as pumps, compressors, or lubricated equipment. Preventing leakage of fluid from the equipment can be difficult, in particular in equipment where the area to be sealed includes rotating shafts, or the like. In the particular case of drive systems, such as those including gearboxes, the rotating shafts typically require sealing against oil loss in the area where the shaft end passes through the stationary housing. For these kinds of applications, sealing devices based on radial shaft seal rings are a known solution for sealing. However, due to material wear, such seal devices are not reliable over extended periods of times. For applications where reliability over time is required, labyrinth seals or glide ring seals represent further known options.
Labyrinth seals generally include a variety of chambers formed between the sealing surfaces of a stationary part and a rotating part. Passage of fluid through the chambers is controlled by centrifugal motion, as well as by the formation of controlled fluid vortices. In this manner, fluid leakage is avoided. In some known labyrinth seals used for gearboxes, the stationary part of the seal is adapted for fluid from the shaft area back to the gearbox interior by the effect of gravity.
However, in some equipment that includes two coaxial cylindrical shafts rotating relative to each other, such as some known gearboxes for wind turbines, draining the seal area by gravity is difficult, in particular when the exit of the inner shaft does not have access to the stationary housing. Further, the sealing effect of at least some known labyrinth seals is not efficient when the shafts do not rotate.
Accordingly, it is desirable to provide a sealing device capable of efficiently sealing the space formed between two cylindrical shafts rotatable relative to each other. Furthermore, it is desirable to provide a sealing device resistant to wear so that it is capable of efficiently and reliably sealing over an extended period.
The embodiments described herein include a sealing device which enables efficient sealing of a space formed by an inner shaft and an outer shaft by actively draining a fluid when the shafts rotate relative to a stationary housing. Furthermore, such a sealing device enables reducing wear of the sealing device by the circulation of fluid. In addition thereto, a sealing device according to embodiments described herein enables actively defining a preferential flow of liquid within the space or spaces to be sealed when the shafts rotate.
In one aspect, a sealing device is provided. The sealing device is for sealing a space formed by an inner shaft and an outer shaft and for directing a flow of fluid, the inner shaft and the outer shaft being rotatable about a common coaxial axis. The sealing device includes an inner seal element adapted for being coupled to the inner shaft so that the inner seal element is locked against rotation relative to the inner shaft, the inner seal element including a first inner sealing surface. The sealing device further includes an outer seal element adapted for being coupled to the outer shaft so that the outer seal element is locked against rotation relative to the outer shaft, the outer seal element including a first outer sealing surface. The first inner sealing surface and the first outer sealing surface are adapted to form, by contact with each other, a first seal area including a first channel arrangement including at least one channel configured to actively drain a fluid from the first seal area when the seal elements rotate with respect to each other.
In another aspect, another sealing device is provided. The sealing device is for sealing a space formed by an inner shaft and an outer shaft and for directing a flow of fluid, the inner shaft and the outer shaft being rotatable about a common coaxial axis. The sealing device includes an inner seal element adapted for being coupled to the inner shaft so that the inner seal element is locked against rotation relative to the inner shaft, the inner seal element including a first inner sealing surface. The sealing device further includes an outer seal element adapted for being coupled to the outer shaft so that the outer seal element is locked against rotation relative to the outer shaft, the outer seal element including a first outer sealing surface. The first inner sealing surface and the first outer sealing surface are adapted to form, by contact with each other, a first seal area. The sealing device further includes a drain conduit for draining a fluid out of the sealing device, the drain conduit being formed in at least one of the inner seal element or the outer seal element and ending with a conduit end forming an opening adjacent to the respective the first inner sealing surface or the first outer sealing surface so that the drain conduit is in fluid communication with the first seal area. The sealing device further includes an impeller rigidly coupled to the inner seal element or the outer seal element. The sealing device is configured to direct the fluid from the first seal area into the drain conduit by rotation of the impeller.
In yet another aspect, a gearbox including a sealing device is provided. The gearbox includes an inner shaft and an outer shaft, the shafts being rotatable about a common coaxial axis. The sealing device includes an inner seal element attached to the inner shaft, the inner seal element including an inner sealing surface; and, an outer seal element attached to the outer shaft, the outer seal element including an outer sealing surface. A seal area is formed by contact of the inner sealing surface and the outer sealing surface, the seal area including a first channel arrangement configured to actively drain a fluid from the seal area when the seal elements rotate with respect to each other.
The embodiments described herein include a sealing device for sealing a space formed by an inner shaft and an outer shaft, the shafts being rotatable with respect to a stationary housing, and for directing a flow of fluid. Typically, the inner and the outer shafts are disposed coaxially to each other. The terms inner and outer should be understood with respect to the common coaxial axis shared by the shafts. Typically, the inner shaft is configured to rotate within the outer shaft. The embodiments described herein further include a sealing device which is applicable to a system where the inner shaft axially extends outside of the outer shaft.
The embodiments described herein further include a sealing device for avoiding leakage of a fluid, typically a lubricant, included in a space enclosed by two rotatable coaxial shafts, which are themselves typically enclosed by a stationary housing.
In typical embodiments, the sealing device includes an inner seal element adapted for being coupled to an inner shaft and an outer seal element adapted for being coupled to an outer shaft. Thereby, the seal elements of the sealing device are disposed such that the seal elements rotate jointly with the respective shaft about a common coaxial axis. That is, in typical embodiments, the seal elements are adapted for being coupled to their respective shafts such that the seal elements are locked against rotation relative to the respective shaft. In some embodiments, the coupling of the inner and/or outer seal element to the inner and/or outer sealing shaft is realized by integrally forming the respective seal element on the respective shaft.
As used herein, the term integrally formed is intended to be representative of as being formed in a single piece. In alternative embodiments, the coupling of the inner and/or seal element to the inner and/or outer shaft is realized by providing fastening means, such as bolted, screw, or stud joints, in the respective seal element and the respective shaft so that the respective seal element can be mounted on the respective shaft in a releasable manner.
In embodiments of the present disclosure, the inner seal element includes an inner sealing surface, and the outer seal element includes an outer sealing surface. Typically, when the seal elements are disposed in the shafts, both first sealing surfaces confront each other forming a seal area by contact.
In embodiments of the present disclosure, the seal elements are configured for sealing and defining a preferential flow of fluid within the space or spaces to be sealed. Thereby, a sealing device according to the present disclosure not only facilitates a better sealing efficiency, but also enables active draining of fluid from one area of a sealed machine, such as a shaft exit area in a gearbox, into a different area in the sealed machine, such as the interior of the gearbox. Such fluid transfer from one specific area of the machine to be sealed to another area within the machine is implemented in some embodiments of the present disclosure by defining a preferential flow of fluid through the seal area and/or out of the sealing device. Thereby, wear of the sealing device, in particular of the sealing surfaces, is reduced by the lubricating effect of the fluid flowing through the seal area. Thus, a sealing device according to embodiments described herein extends the operating lifetime of the sealing device.
At least some of the embodiments described herein provide a sealing device having a seal area that includes a channel arrangement. The channel arrangement is typically configured for actively draining a fluid through the seal area when seal elements of the sealing device rotate with respect to each other. Thereby, a fluid in the inner space formed by the shafts and close to the area to be sealed is typically actively drained out when the shafts, and consequently the seal elements, rotate relative to each other. When the shafts are stationary, the contact between the inner sealing surface and the outer sealing surface has the effect of sealing the inner space of the shafts. In this manner, the seal area forms a barrier for avoiding fluid leakage. Typically, the channel arrangement is disposed in at least one of the inner sealing surface or the outer sealing surface.
In some embodiments, the sealing area includes a channel arrangement extending along the whole sealing area such that the fluid space and the external space are in fluid communication through the channel arrangement. In such embodiments, the channel arrangement is typically configured so that the sealing device effectively seals the fluid space, even when the shafts do not rotate (i.e., by appropriately selecting the structure, width and length of the channel or channels in the arrangement).
In at least some of the embodiments described herein, the channel arrangement in the seal area is provided in at least one of the inner or outer sealing surfaces. Typically, the channel arrangement is provided in the sealing surface of the seal element corresponding to the fast rotating shaft. As used herein, the term fast rotating shaft is intended to be representative of the shaft configured to rotate at a higher absolute velocity relative to a referential frame stationary to both shafts.
Within the following description of the drawings, the same reference numbers refer to the same components. Generally, only the differences with respect to the individual embodiments are described.
The exemplary sealing device 100 in
In the exemplary embodiment, entry conduit 290 communicates fluid space 230 with seal area 40. Alternatively, inner seal element 120 includes a plurality of entry conduits 290 formed in inner seal element 120. In the exemplary embodiment, entry conduit 290 fluidly communicates seal area 40 with fluid space 230. During operation of the exemplary seal device 100, it is typical that fluid is actively suctioned from fluid space 230 into seal area 40 through entry conduit 290 in the direction of arrow 262 when the seal elements rotate.
In the exemplary embodiment of
In the exemplary embodiment of
In the exemplary embodiment shown in
In typical embodiments of the present disclosure, at least one of the seal elements is typically provided as a single integrally built part. Alternatively, at least one of the seal elements is typically modularly built, for example, constituted by multiple attached parts. In particular, the channel arrangement is typically provided as a part modularly built in a seal element. Thereby, the channel arrangement is typically easily exchanged, if required.
According to some embodiments of the present disclosure, a drain conduit is formed in at least one of the seal elements, the drain conduit ending with an opening on the sealing surface. In particular embodiments, the sealing device might include a plurality of such drain conduits. Typically, the drain conduit communicates with a draining area in the space formed between both shafts through another opening in the corresponding seal element. In some embodiments, the drain conduit is formed in the outer seal element. In alternative embodiments, the drain conduit is formed in the inner seal element.
In some embodiments of the present disclosure, the channel arrangement is adapted for actively draining a fluid from the seal area towards the drain conduit when the seal elements rotate with respect to each other. In these embodiments, draining is effected by an active displacement of fluid trapped in the channel or channels in the arrangement. This active displacement is typically combined, depending on the configuration of the sealing device, with the effect of the centrifugal force acting on the fluid. It is noted that, even in the case where both shafts rotate at the same speed, the sealing device is typically configured so that the fluid is actively drained towards the drain conduit through the channel arrangement by the effect of the centrifugal forces acting on the fluid.
In the exemplary embodiment of
In the exemplary sealing device 100 shown in
Typically, a small portion of fluid also circulates between non-patterned contacting sealing surfaces, thereby enhancing lubrication of the seal areas. In a typical application of the sealing device 100, fluid reaching the drain conduit 200 through the first seal area 240 is evacuated towards the fluid space 230, flowing in the direction marked by arrow 270 depicted in the figure so that fluid is actively drained back into fluid space 230 and away from the seal. In this manner, the active flow of fluid in a sealing device according to at least some of the embodiments described herein facilitates draining of fluid into particular regions of fluid space 230 when the shafts are rotating. In typical embodiments, an increase in the rotating speed of the shafts results in an increase in the draining efficiency of the sealing device.
In the exemplary embodiment of
According to at least some of the embodiments described herein, the sealing device includes a second channel arrangement disposed in a second seal area, or a portion thereof. The exemplary sealing device 100 of
Analogously as the first channel arrangement according to some of embodiments described above, the second channel arrangement in the second seal area is typically arranged on the second sealing surface of the seal element to be coupled to the fast rotating shaft. A second channel arrangement according to some of the embodiments described herein facilitates actively draining of a fluid from the second seal area.
As set forth above, a seal device according to some of the described embodiments includes a first seal area and a second seal area which communicate with a drain conduit. Thereby, fluid in both seal areas is typically drained from the sealing device through drain conduit back into a fluid space. It is noted that the second seal area is not essential for the functioning of the sealing device. Such a configuration of the sealing device with a second seal area is typically advantageous for applications of the sealing device where a higher sealing and/or draining efficiency is favored.
As set forth above, in at least some of the embodiments described herein, the drain conduit, the seal areas, and the channel arrangements are arranged such that fluid in the seal areas is drained in collaboration with the centrifugal forces (i.e., fluid in the seal areas is drained in the outward radial direction). The exemplary embodiments in
The configuration of the exemplary sealing device 100 shown in
In alternative embodiments where outer shaft 220 is configured to rotate at an absolute higher rotational speed than inner shaft 210, it is typical to provide the first and second channel arrangements in the first and second outer sealing surfaces, respectively. In this manner, these embodiments typically take advantage of the relative rotation of the channel arrangements with respect to inner shaft 210 when the shafts rotate. In alternative embodiments, sealing device 100 includes a combination of channel arrangements provided on sealing surfaces of both seal elements. Such embodiments are typically advantageous when the rotational speed of the shafts is not preconfigured.
The term “substantially parallel” in the present disclosure should be generally understood as a deviation of plus/minus 15 degrees from the exact parallel orientation. The term “substantially perpendicular” in the present disclosure should be generally understood as “forming an angle between 75 degrees and 105 degrees” with respect to a given axis or plane.
In at least some embodiments of the sealing device, the first sealing surfaces and the second sealing surfaces are respectively disposed for forming a first seal area and a second seal area substantially parallel to each other. Typically, the seal surfaces are oriented perpendicular to the coaxial rotational axis of the seal elements.
At least some embodiments provide a sealing device including a plurality of seal areas disposed, e.g., along the axial direction of the sealing device. Typically, the plurality of seal areas is implemented by providing multiple parallel members in the inner seal element. These parallel members extend in a radial direction of the seal device and register portions of the outer seal element. Alternatively, the plurality of seal areas is implemented by sequentially disposing multiple inner and outer seal elements on the shafts and along their longitudinal axis.
In the exemplary embodiments shown in the figures, drain conduit 200 is oriented substantially perpendicular to the seal surfaces. In alternative embodiments, a sealing device provides a drain conduit so configured as to be tilted with respect to a common coaxial axis of the seal elements.
In the exemplary embodiment of
In some of embodiments, as set forth below, an outer seal element further includes an impeller. Within the present disclosure, an impeller should be understood as an element which, by rotation, is capable of increasing the pressure and flow of a fluid in a predetermined direction. Typically, the impeller is configured to direct a flow of fluid into the drain conduit and in the direction in which a drain conduit is oriented. In this manner, active draining of the fluid is further enhanced by combining an impeller and a particular orientation of the drain conduit which takes advantages of the rotational flow impinged on the fluid.
According to some embodiments, the half cross-section of inner seal element 120 is L-shaped, that is, inner seal element 120 has a portion 122 thereof extending in a radial direction of seal device 100 and another portion 124 thereof extending in an axial direction of seal device 100. Typically, radial portion 122 of inner seal element 120 is sandwiched by outer seal element 140. In at least some embodiments, radial portion 122 registers with outer seal element 140. In typical embodiments, axial portion 124 is secured (i.e. attached) to inner shaft 210 in a movable manner. For example, inner seal element 120 may be secured to inner shaft 210 by an anti-rotation lock.
In some embodiments, inner seal element 120 includes an axial portion 124 extending along common coaxial axis 250. Typically, axial portion 124 has the form of a central tubular extension or hub. In the exemplary embodiment, axial portion 124 is oriented substantially parallel to common coaxial axis 250. In the exemplary embodiment, radial portion 122 and axial portion 124 are oriented perpendicular to each other. Typically, inner seal element 120 is coupled to inner shaft 210 such that axial portion 124 faces external space 600 and radial portion 122 faces fluid space 230. Typically, outer seal element 140 is designed according to the shape of inner seal element 120 so that the outer sealing surfaces are oriented to register the inner sealing surfaces.
Typically, a channel arrangement of a sealing device according to at least some embodiments described herein includes a groove or grooves formed on the surface of the corresponding seal element. Typically, the groove or grooves are oriented such that fluid enclosed within the channel arrangement is forced to flow along the seal area where the channel arrangement is disposed. According to typical embodiments, the orientation of the groove or grooves in the channel arrangement is such that the fluid therein is forced towards, or directly into, a drain conduit formed in the seal device. Typically, the groove or grooves are designed to direct a flow of fluid in collaboration with the centrifugal force caused by the rotation of the seal elements. According to typical embodiments, the channel arrangement, the groove or grooves are arranged as a spiral. In alternative embodiments, the groove or grooves are arranged as a set of spirals that, typically, are arranged equally spaced from each other.
In typical embodiments, the channel arrangement includes at least one groove formed as a spiral oriented to match a predetermined rotational direction of the sealing surface on which it is formed (i.e., typically, the spiral increases radially in the direction of rotation of the sealing surface). The channel arrangement may include a groove formed such that it enables the sealing device to function as described herein, such as, but not limited to, as a curved groove or grooves radially extending towards a drain conduit, as a straight groove or grooves oriented perpendicular to a common coaxial axis of the seal, or as a set of grooves forming a plurality of crossing spirals.
In typical embodiments, the orientation of a channel arrangement is predetermined taking into account the rotational characteristics of the shafts. For example, in the embodiment shown in
In such embodiments, the rotation of the seal elements typically causes channel arrangement 280 to force a fluid within a seal area towards drain conduit 200. In this manner, a fluid is typically drained back into fluid space 230. Further, as long as fluid space 230 is not subject to a sufficiently high pressure, fluid in drain conduit 200 is prevented from re-entering a seal area by a rotation of channel arrangement 280. In typical embodiments, a flow of fluid effected by channel arrangement 280 is enhanced by the centrifugal forces acting on the fluid when a seal element rotates.
As set forth above, according to at least some of the embodiments described herein, sealing device 100 is typically provided with a closed sealing surface 330 adopted for fluid-tight sealing of a space formed by the shafts (e.g., fluid space 230) from an external space (e.g., external space 600). According to some embodiments, a closed sealing surface 330 is formed in a seal area contiguous to the external space. According to some embodiments, a closed sealing surface 330 is formed by a tight contact over a whole radial section of the sealing surfaces forming a seal area. According to typical embodiments, a closed sealing surface 330 is typically formed by contact of non-patterned (i.e., without a channel arrangement) areas of the sealing surfaces forming a seal area.
In at least some of the embodiment according to the present disclosure, a fluid circulates through at least one seal area of the sealing device when a seal element rotates. Such circulation of fluid typically has a lubricating effect on sealing surfaces forming the seal areas. Such lubricating effect is typically desirable in order to avoid or minimize wear of the sealing surfaces. Furthermore, the flow of fluid effected by the sealing device is typically desirable for cooling the sealing surfaces. Such a cooling effect further minimizes wear of the sealing surfaces. Accordingly, the operating lifetime of the sealing device is typically further improved.
In at least some of the embodiments according to the present disclosure, it is typically desirable to link in fluid communication a first and a second seal area through a lubrication hole. Thereby, it is typical that a portion of a fluid within the first seal area directly flows into the second seal area. In typical embodiments, the lubrication hole is disposed in an inner seal element. More specifically, the lubrication hole is typically disposed in a radially oriented portion of the inner seal element (e.g., radial portion 122).
Typical embodiments of the sealing device according to the present disclosure include an impeller configured to direct a fluid from a first seal area into a drain conduit or conduits. In this manner, the impeller and the drain conduit or conduits typically constitute a fluid pump for generating a directed flow of fluid. According to some embodiments, the impeller and the drain conduit or conduits are configured in a manner such that a flow of fluid is directed in an axial direction with respect to the sealing device (e.g., parallel to common coaxial axis 250).
According to some embodiments, the impeller consists of a notch array including notches or splines. In typical embodiments, the notch array is disposed in the outer part of a radially-extending portion of an inner seal element of the sealing device (e.g., radial portion 122). The notch array is typically designed for generating a directed flow of fluid. For example, according to some embodiments, a flow of fluid is directed parallel to common coaxial axis 250. In some embodiments, the flow of fluid is directed so that the flow of fluid into drain conduit 200 is further directed towards fluid space 230. In such embodiments, the impeller further enhances the draining efficiency through drain conduit 200. In this manner, the impeller typically increases the sealing efficiency of the sealing device when the seal elements rotate with respect to each other. Moreover, in contrast to at least some known labyrinth seals, evacuation of a fluid enclosed within the seal areas is further enabled through the enhanced draining effect (i.e., without requiring the action of gravitational forces).
As set forth above, in at least some embodiments, drain conduit 200 is oriented in a tilted manner with respect to common coaxial axis 250. That is, in these embodiments, drain conduit 200 is oriented to form a helix and/or an elevation angle. As set forth above, in at least some of these embodiments, sealing device 100 includes an impeller which is configured for directing a flow of fluid in the direction in which drain conduit 200 is oriented. That is, such an impeller is configured to direct a flow of fluid in the direction defined by the helix and the elevation angle in which the drain conduit is oriented. In at least some of these embodiments, sealing device 100 further takes advantage of the centrifugal and rotational forces acting on a fluid for enhancing an active draining of a fluid through drain conduit 200.
In at least some of the embodiments where an impeller is constituted by a notch array, the orientation and angle of the notches or splines in the notch array are chosen in view of the rotational characteristics of the shafts. In particular, in at least some embodiments, the notch array is designed to take into account which of the sealing elements are attached to the fast rotating shaft, the rotational speeds of the shafts, the direction of rotation of the shafts, and the characteristics of the fluid. The notches or splines may consist of any element that enables the impeller to confer a directed flow such that the sealing device functions as described herein. More specifically, the notch array may consist of a set of notches or splines configured as a helical toothing. Typically, the helical toothing is oriented to generate a directed flow towards a drain conduit. Alternatively, the impeller is formed by elements, such as blades, or the like, which are suitable for directing a flow of fluid into a drain conduit.
According to some embodiments of the present disclosure, the sealing device includes a housing unit adapted for being secured to any of the shafts, the housing unit being configured to generate a sealing force on at least one of the sealing surfaces of the sealing device. More specifically, in at least some embodiments, an outer seal element of the sealing device includes a housing unit adapted for being secured to the outer shaft. In some embodiments, the housing unit is secured to the outer shaft by integrally forming it on the shaft. Alternatively, the housing unit is secured to the outer shaft by providing fastening means, such as bolted, screw or stud joints, in the housing unit and the outer shaft so that the housing unit can be mounted on the shaft in a releasable manner. Typically, a thrust unit is coupled to the housing unit, the thrust unit being adapted for exerting a sealing force on at least one of the sealing surfaces. In this manner, the thrust unit presses the seal surfaces against each other, thus increasing the sealing efficiency of the device. The term sealing force should be understood as a force exerted on at least one of the sealing surfaces in order to enhance a contact between them. In typical embodiments, the sealing force is an elastic sealing force.
Typically, a contact area between inner seal element 120 and housing unit 410 forms first seal area 240. Thrust unit 400 may be placed in contact with the inner seal element 120, as in the exemplary embodiment. In the exemplary embodiment, a contact area between inner seal element 120 and thrust unit 400 forms a second seal area 300. In the exemplary embodiment, first seal area 240 is placed proximate to fluid space 230, and second seal area 300 is placed proximate to external space 600. Typically, thrust unit 400 generates a pressure on inner seal element 120 by actively exerting a sealing force thereon. In typical embodiments, such a sealing force is generated parallel to the common coaxial axis 250.
According to some embodiments of the present disclosure, thrust unit 400 may include a first thrust element. Typically, one of the surfaces of the first thrust element constitutes a second outer sealing surface 320. In some embodiments, thrust unit 400 includes a second thrust element secured to housing unit 410. In some embodiments, the second thrust element is secured to the housing unit 410 by being integrally formed thereon. Alternatively, the second thrust element is secured to housing unit 410 by providing fastening means, such as bolted, screw or stud joints, in the second thrust element and housing unit 410 such that the second thrust element can be mounted on housing unit 410 in a releasable manner. Typically, the first thrust element is movable relative to the second thrust element. In particular, the first thrust element may be mounted so as to be movable over a relatively small distance along a longitudinal axis of the sealing device. In this manner, a sealing force may be exerted on inner seal element 120 through the first thrust element. Alternatively, thrust unit 400 is secured to inner seal element 120.
Referring further to
A movable arrangement of first thrust element 420 typically facilitates that the sealing surfaces in sealing device 100 are in planar, eventually lubricated, contact over a significant area thereof. Such a movable arrangement typically achieves tight contact between sealing surfaces, even in the case that these sealing surfaces suffer unbalancing wear. Furthermore, such a movable arrangement typically compensates for manufacturing tolerances in the different elements of sealing device 100.
According to typical embodiments of the present disclosure, a load force element (or a plurality thereof) couples first thrust element 420 and second thrust element 440 to each other for generating a sealing force. Typically, this load force element includes a resilient member, such as a spring or the like, which generates the sealing force, typically, by compression thereof. Typically, this sealing force is generated by generating a load force by the load force element which is exerted onto first thrust element 420. Typically, the load force is transmitted to inner seal element 120 through first thrust element 420. The load force element may consist of any suitable structure that enables a generation of a sealing force. The load force element may include any suitable component such as, but not limited to, a spring, a plurality of springs, or the like. Typically, the load force is exerted in a direction substantially perpendicular to second outer sealing surface 320. Typically, the load force element is adapted to generate just the necessary elastic sealing force to achieve the sealing effect required by a particular application of a sealing device according to the present disclosure. Thereby, unnecessary friction and wearing of sealing surfaces of the sealing device is avoided. In at least some embodiments, first thrust element 420 is disposed adjacent to inner seal element 120 and second thrust element 440 is secured to outer shaft 220.
In typical embodiments, the load force element, or elements, further accomplishes an anti-rotary lock function. More specifically, the load force element may be configured to avoid that first thrust element 420 rotates relative to second thrust element 440. Alternatively, any element that is suitable for avoiding that first thrust element 420 rotates relative to second thrust element 440 may be included in sealing device 100. For example, a screw, or the like, may couple, in an anti-rotary manner, first thrust element 420 and second thrust element 440. In one of these embodiments, second thrust element 420 is secured to housing unit 410, so that first thrust element 420 rotates together with housing unit 410.
The exemplary embodiment of
First thrust element 420 and second thrust element 440 in the exemplary embodiment are provided with mounting holes 540 for fixing of both thrust elements to each other through a fixing element, such as a screw (not shown). Typically, both units are fixed to each other for mounting or disassembling of the sealing device 100. Typically, mounting holes 540 are adapted for fixing of the thrust elements through a screw, bolt, or the like. Typically, mounting holes 540 are threaded to enable fixing of the thrust elements through a screw.
In a typical procedure for assembling the thrust units in sealing device 100, the thrust units, coupled to each other through load force element 560, are first fixed to each other by a screw (not shown), or the like, provided in mounting holes 540. Then, the thrust units are placed within housing unit 410 facing inner seal element 120. In a further step, first thrust element 420 is coupled to outer radial support 460. As a next step, outer fitting key 520 is mounted between housing unit 410 and second thrust element 440, so that thrust unit 400 is rotary locked to housing unit 410. Typically, an axial lock 522 is mounted between housing unit 410 and second thrust element 440, so that thrust unit 400 is locked against a displacement relative to housing unit 410 along a longitudinal axis of sealing device 100. Finally, the screw provided in mounting holes 540 is extracted in a manner such that load force element 560 applies a load force onto first thrust element 420 in an axial direction and away from the second thrust element 440. In the exemplary embodiment, the load force is coupled to inner seal element 120 for generating a sealing force.
In the exemplary embodiment shown in
In general, according to some embodiments of a sealing device as described above, movable seal components facilitate a closer tightening of seal areas of the sealing device. Close tightening of the seal areas is typically advantageous for compensating eventual wear of sealing surfaces in the seal areas by self-adjustment of the position of seal components. Eventual wear of the sealing surfaces may deteriorate the sealing performance of the seal areas over time when uncompensated. Further, self-adjustment of the position of seal components is typically useful for reduction of manufactured defects. Moreover, for some applications where manufacturing tolerances are above the requirements for correct functioning of the sealing device, seal components having self-adjustable positioning for compensation of such failures are typically desirable.
At least some embodiments of a sealing device according to the present disclosure are for sealing a space formed by an inner shaft and an outer shaft. Some of these sealing devices include an inner seal element adapted for being coupled to the inner shaft and an outer seal element adapted for being coupled to the outer shaft and a thrust unit for exerting a sealing force onto the inner seal element. According to these embodiments, formation of a first seal area is effected between the inner seal element and the outer seal element by the sealing force. Typically, the first seal area includes a first channel arrangement which includes at least one channel for actively draining a fluid from the first seal area when the seal elements rotate with respect to each other.
According to typical embodiments of a gearbox according to the present disclosure, an outer shaft of the gearbox may be provided with at least one auxiliary conduit for evacuation of a fluid. In the exemplary embodiment of
In typical embodiments, when the shafts of gearbox 750 remain stationary, fluid is evacuated into drain area 570 in collaboration with the gravitational force. To achieve this effect, outer shaft 220 remains stationary in a position such that fluid is evacuated through auxiliary shaft conduit 660 into drain area 570 by the effect of gravitational forces acting on the fluid. In some embodiments, a plurality of such auxiliary shaft conduits 660 is provided in the outer shaft 220.
At least some embodiments of the present disclosure provide a gearbox including an additional seal for sealing a space between an outer shaft and a stationary housing. As an example, gearbox 750 shown in
Typically, each of the seal elements of a sealing device according to embodiments of the present disclosure is integrally formed of a material which is resistant to the conditions to which the seal elements are exposed. Typically, these conditions include high- and low-temperature ranges, chemical properties of a fluid enclosed in a space to be sealed, or wear between seal surfaces of the sealing devices. According to some embodiments, each surface of a sealing area in the sealing device is made of a different material for minimizing wear of the surfaces by friction. For example, one of the sealing surfaces may be made of hardened steel, and the other sealing surface may be made of a low friction material, such as bronze or brass. In some embodiments, antifriction materials, such as Teflon, are applied to the sealing surfaces of the sealing device to further minimize friction between the sealing surfaces.
As used herein, the term shaft should be understood as an element including a cylindrical bar (i.e. an element which is used to support rotating pieces or to transmit power or motion by rotation). Such shafts are typical in many different applications such as brakes, drives, pumps, generators, steering systems, or those found in automobiles gear-boxes or wind turbine gear-drives. A sealing device according to embodiments of the present disclosure is suitable for such applications, and others not explicitly mentioned herein.
More specifically, the embodiments of the sealing device, as set forth above, are particularly suitable for gearboxes including two coaxial shafts which are rotatable relative to a stationary housing. The embodiments set forth above provide a sealing device with low wear and effective sealing during the lifetime of the gearbox. Thereby, maintenance and inspection of the sealing device are significantly reduced.
In particular, a sealing device according to embodiments of the present disclosure is particularly suitable for a gearbox in wind turbines. Typically, a wind turbine gearbox is connected to a main shaft driven by a bladed rotor (i.e., a low speed shaft) and further connected to an electrical generator through another shaft (i.e., a high-speed shaft) to convert the rotational speed of the bladed rotor into a rotational speed suitable for the electrical generator. The terms low and high should be understood as relative to the speed of each shaft. Some types of gearboxes in wind turbines are equipped with coaxial shafts which are rotatable relative to a stationary housing. In some particular designs of gearboxes for wind turbines, an inner shaft thereof does not have access to a stationary housing. A sealing device according to embodiments described herein might be particularly advantageous for such gearboxes.
A gearbox including a sealing device, as described herein, may be adapted for implementation in a wind turbine having a bladed rotor and an electrical generator. Typically, such a gearbox couples a low speed shaft to a high speed shaft of the wind turbine. The low speed shaft is coupled to the bladed rotor and the high speed shaft is coupled to the electrical generator.
A sealing device and a gearbox according to embodiments of the present disclosure adapted for implementation in wind turbines are typically configured for a rotational speed of the outer shaft between 350 and 500 rpm, such as 400 to 440 rpm. A sealing device and a gearbox, according to embodiments of the present disclosure, adapted for implementation in a wind turbine are typically configured for a rotational speed of the inner shaft between 5 and 20 rpm, such as 12 to 16 rpm. A sealing device and a gearbox according to the present disclosure are suitable for different kinds of applications and for a wide range of rotational speeds of the shafts. For example, the inner shaft may be configured as the fast rotating shaft.
Typically, a sealing device according to at least some of the embodiments of the present disclosure is for avoiding leakage of lubricating fluid in a gearbox of a wind turbine and for active draining of a lubricating fluid, such as lubricating oil, into a drain area of the gearbox. As set forth above, a sealing device according to the present disclosure reduces wear of the sealing components. Such wear reduction typically implies a reduction of the maintenance requirements of a wind turbine. A reduction of maintenance requirements is particularly desirable for a wind turbine since, therein, a gearbox is typically placed in the wind turbine nacelle, which is difficult to access. Further, wind turbine systems are commonly placed in remote locations, such as off-shore, where servicing requirements should be kept at a minimum for economical reasons. Moreover, a sealing device according to the present disclosure has a robust design which avoids contaminants entering the gearbox components. In particular, such a robust design efficiently protects a gearbox from the harsh conditions to which the nacelle of the wind turbine is typically exposed.
Exemplary embodiments of systems for a sealing device, a gearbox, and, in particular, a gearbox adapted for use with a wind turbine, are described above in detail. The systems and methods are not limited to the specific embodiments described herein, but rather, components of the systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. For example, the thrust element is typically combined with an inner seal element including notches in an outer part thereof. Furthermore, as set forth above, one or both of the sealing elements is, or are, typically integrally built into the respective shaft.
Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the present disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.
This written description uses examples to disclose the invention, including the best mode, and to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
