Patent Application
20110103728
This invention relates to a seal for a bearing having inner and outer rings and which undergoes large movements between the inner and outer rings.
Four- and eight-point contact ball bearings are used when moving parts are expected to be subject to a variety of loads such as radial, thrust, and moment loads. In wind turbines, large four or eight point contact ball bearings are used for yaw bearings and pitch bearings. The yaw bearings allow the nacelle, rotor, and blades to rotate in order to face into the wind. The pitch bearings serve two purposes: connection of each blade to the rotor and also to allow the blade to change its pitch depending on wind speed and conditions. The pitch bearings experience large relative deformations between their inner and outer rings due to large and random loads due to rotor rotation and variable winds. The bearings have inner and outer rings with a seal between the rings to help retain grease therein.
Pitch bearings and seals are seen in U.S. Pat. No. 7,331,761 and U.S. Patent Application Publication Nos. 20040026867; 20080104821; 20080246224.
The present invention resides in one aspect in a seal having a first circumference and a second circumference. The seal has an anchor portion proximate to the first circumference, a span portion extending in a span direction from the anchor portion towards the second circumference, the span portion including a hinge region. There is also a lip extending from the span portion to the second circumference. The lip is configured to protrude from the span portion in a direction that is transverse to the span direction.
According to another aspect of the invention, a bearing and seal assembly is provided which includes a first ring and a second ring in rotatable engagement with the first ring. The first ring defines a groove and the second ring defines a contact surface. The assembly includes a seal having an anchor portion mounted in the groove, a span portion extending from the anchor portion towards the second ring, and a lip extending from the span portion to the second ring and making engagement with the contact surface. The second ring comprises a groove in which the lip is disposed.
According to another aspect of the invention, a wind turbine having a pitch bearing and a yaw bearing includes a bearing and seal assembly as described herein.
A seal indicated at 10 in
The seal 10 has a span portion 16 which extends in a direction indicted by arrow S from the anchor portion 12 toward the second circumference B, where the seal 10 is configured to have a lip 18. In one embodiment, the lip 18, which is generally annular in shape, has a split configuration and includes a first lip member 20 and a second lip member 22 which are both joined to the span portion 16, and which are separated by a gap 24. The seal 10 is made of an elastomeric material so that when first lip member 20 and second lip member 22 are compressed towards each other (causing the gap 24 to diminish), the seal generates a responsive force tending to separate the first lip member 20 from the second lip member 22. Suitable elastomeric materials include, but are not limited to, VITON® fluoroelastomer (VITON® is a registered trademark of E. I. Du Pont De Nemours & Company, 1007 Market St., Wilmington Del.), acrylon nitrile, nitrile rubber, or rubber compounds blended for resistance to UV rays and moist salt air. The lip 18 is configured for sliding engagement with a second ring bearing. In particular, the lip 18 is configured to protrude from the span portion 16 obliquely from the span portion 16 to provide first and second seal surfaces 26a, 26b on the first lip member 20 and on the second lip member 22, respectively, for sliding contact with a bearing ring. Thus, in one embodiment, the lip 18 has a generally toroidal configuration.
The span portion 16 includes a hinge region 28 around which the lip 18 can rotate relative to the anchor portion 12 as described hereinbelow. In one embodiment, the hinge region 28 is a region of reduced thickness relative to the rest of the span portion 16 and/or relative to the anchor portion 12.
A bearing shown in partial cross-section at 30 in
The second ring 34 has a second groove 38 which is annular in configuration and which provides first and second groove surfaces 40 and 42. The second groove 38 has a depth in the second ring 34 indicated at Dg, and a width indicated at W. The bearing 30 is shown with the first ring 32 and a second ring 34 in their nominal positions relative to each other. The first ring 32 and the second ring 34 are expected to experience movement from the nominal relative positions in directions indicated in
The seal 10 is combined into the bearing 30 as shown in
For purposes of inserting the lip 18 into the seal groove 42, the first lip member 20 and second lip member 22 are compressed towards each other. Optionally, the seal surfaces 26a, 26b may be configured so that the lip 18 can be positioned against the mouth of the second groove 38 and, with the application of insertion force, the first lip member 20 and second lip member 22 are compressed together as the lip 18 enters the second groove and engages in sliding, sealing contact with the two groove surfaces 40 and 42. For example, the circumferential surface of the lip 18 may be generally rounded, tapered, chamfered or the like. The width W of the second groove 38 is dimensioned such that an interference is maintained between the first lip member 20 and second lip member 22 and the groove surfaces 40 and 42, respectively, while the lip 18 is in the second groove 38. As a result of this configuration, when the first lip member 20 and the second lip member 22 are in sealing contact with the groove surfaces 40 and 42 respectively, an annular sealed compartment 38a is formed in the second groove 38.
As relative motion between the first ring 32 and the second ring 34 occurs, the position of the lip 18 in the second groove 38 can change accordingly without causing a gap between the seal 10 and the second ring 34, because one or both of the first lip member 20 and second lip member 22 remains in sealing contact with the groove surfaces 40 and/or 42 by sliding upon them.
The bearing 30 has two groove surfaces 40 and 42 and the seal 10 has two seal surfaces 26a, 26b, but the invention is not limited in this regard, and in other embodiments a seal need only have one contact surface for sliding contact with a bearing contact surface, or a seal may have more than two seal surfaces for sliding contact with one or more groove surfaces on a bearing ring.
When the seal 10 is oriented horizontally, as seen in
In one embodiment, the seal 10 and the bearing 30 are sized and configured such that in their respective nominal positions, the contact points of the first lip member 20 and second lip member 22 against the groove surfaces 40 and 42 are central relative to the depth of the second groove 38. In this way, sealing contact can be maintained between the lip 18 and the second ring 34 through a wide range of relative motion between the first ring 32 and a second ring 34 towards each other or away from each other caused by distortion of the bearing 30. The depth Dg of the second groove 38 can be made deep enough to allow for the largest anticipated relative motion between bearing rings 32, 34 in a direction parallel to the depth Dg, i.e., in direction D1.
The hinge region 28 of the seal 10 allows flexibility and control of the seal movement when relative ring movement occurs in direction D2. If the rings move relative to each other in direction D2, the first lip member 20 and second lip member 22 will tend to rotate about a circumferential axis through the hinge region 28. The toroidal shape of the lip 18, i.e., of the two lip members 20 and 22 together, allows for positive contact of the lip members with the groove surfaces 40 and 42 throughout such movement.
During the operation of the bearing 30, the seal 10 is able to move back and forth (in direction D1) in the second groove 38 in response to distortion in the bearing. Lubricant (e.g., grease) in the interior space 30a which makes its way past seal surface 26a and groove surface 40 will be contained in the second groove 38 by the sealing contact between the seal surface 26b and the second groove surface 42.
In one embodiment, the first lip member 20 (seen as the lower lip in the orientation of
The seal 10 and bearing 30 described herein are useful in various applications to prevent gaps between the seal and the bearing when the bearing experiences large radial and axial relative movements between the first ring 32 and the second ring 34, by maintaining sealing contact between the lip 18 and the second ring 34 despite substantial relative movement between them. Such motion may occur, for example, in bearings in wind turbines, which experience radial and axial relative movements as large as 0.5 inches (12.7 mm). If gaps occur between bearing ring and seal during operation, lubricant could escape the bearing and water, dust, and other contaminates can get in.
An escape of lubricant from the interior of a bearing, especially from pitch bearings, and the entrapment of contaminants within the lubricant from outside the bearing, are both detrimental to the operation of the bearing in a wind turbine or other device. Another feature of wind turbine pitch bearings is that the orientation of the bearings changes as the rotor of the wind turbine rotates. Gravity cannot be used to determine the dominant motion of lubricant or oil within the bearing. The seal 10 and bearing 30 described herein address these problems by maintaining the function of the seal in the bearing despite large radial and axial relative movements between the first ring 32 and the second ring 34 of the bearing. Not only is the function of the seal 10 maintained during such movements but the shape of the seal is such that a pumping action of the lubricant back into the bearing occurs.
A wind turbine, indicated generally at 50 in
The terms “first,” “second,” and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.
Although the invention has been described with reference to particular embodiments thereof, it will be understood by one of ordinary skill in the art, upon a reading and understanding of the foregoing disclosure, that numerous variations and alterations to the disclosed embodiments will fall within the scope of this invention and of the appended claims.
This application claims the benefit of U.S. provisional application No. 61/251,766, filed Oct. 15, 2009, the contents of which are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61251766 | Oct 2009 | US |
