Patent Application
20150252850
The present disclosure relates generally to rotary components and, more particularly, to a system and method for lubricating rolling bearing elements in oscillatory motion.
Mechanical bearings are used to support rotating equipment across a wide variety of industries, including amusement parks, manufacturing, automotive, computer hardware, industrial automation, and so forth. Bearing systems typically employ one or more rotating components that are lubricated to minimize friction between a rotating component (e.g., shaft) and a stationary component (a component that is generally stationary relative to the rotating component). For example, rolling bearing element assemblies often include multiple rolling bearing elements seated between rotating and stationary components.
Bearing systems operate more efficiently when they are adequately lubricated. Oil or grease is applied to the bearings to help prevent dents or other deformations from forming on the bearings, stationary components, and rotating components. Such deformations can lead to inefficient operation of the bearing systems and the larger mechanical systems that they support. In bearing systems with continuously rotating bearings, once the lubricant is applied to the bearing system, the bearings within the system mechanically apply and distribute the lubricant throughout the system. However, in bearing systems where the rotating components undergo oscillatory and/or very small rotations, it is now recognized that the bearings might not be able to adequately distribute the lubricant. Thus, it is now recognized that there exists a need for improved methods for lubricating bearing systems that facilitate oscillatory motion.
In accordance with one aspect of the present disclosure, a system includes a rolling bearing element assembly configured to enable rotation of a rotary element relative to a stationary element, the rotation being about a bearing system axis of the rolling bearing element assembly. The rolling bearing element assembly includes an inner race, an outer race, a plurality of rolling bearing elements disposed between the inner and outer races, and a rolling bearing element cage for maintaining rolling bearing element spacing. The rolling bearing element assembly is configured to facilitate oscillatory motion of the rotary element relative to the stationary element such that, when the rotary element rotates in a first direction about the bearing system axis, the rolling bearing elements revolve about the bearing system axis in the first direction, and when the rotary element rotates in a second direction opposite the first direction about the bearing system axis, revolution of the rolling bearing elements about the bearing system axis in the second direction is resisted or prevented.
In accordance with another aspect of the present disclosure, a bearing system includes an outer race disposed in alignment with a bearing system axis and an inner race concentric with the outer race and having an outer diameter less than an inner diameter of the outer race. The inner race is configured to rotate relative to the outer race about the bearing system axis. The bearing system also includes a plurality of rolling bearing elements disposed between and in rolling contact with the inner race and the outer race and a bearing cage coupled to the plurality of rolling bearing elements. The bearing cage is configured to keep the plurality of rolling bearing elements circumferentially spaced about the bearing system axis. The bearing system further includes a spring loaded indexing element (e.g., sprag) with a first end rotatably coupled to the bearing cage and a second end in contact with a contact surface of the inner race. The indexing element is a friction or interlocking mechanism configured to engage the inner race via the second end to enable rotation of the bearing cage in a first direction about the bearing system axis when the inner race is rotating in the first direction. The indexing element is configured to slide relative to the contact surface of the inner race to prevent or resist rotation of the bearing cage in a second direction about the bearing system axis when the inner race is rotating in the second direction opposite the first direction.
Present embodiments also provide a method for lubricating the plain bearing assembly. The method includes facilitating oscillatory rotation of a rotary element about a bearing system axis and relative to a stationary element via a rolling bearing element assembly. The rolling bearing element assembly includes an inner race coupled to the rotary element, an outer race coupled to the stationary element, and a plurality of rolling bearing elements disposed between the inner and outer races. The method includes allowing the inherent motion of the roller-element bearings to revolve about the bearing system axis in a first direction when the rotary element rotates in the first direction about the bearing system axis. In addition, the method includes preventing or resisting revolution of the roller-element bearings about the bearing system axis in a second direction when the rotary element rotates in the second direction about the bearing system axis.
These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Presently disclosed embodiments are directed to systems and methods for lubricating rolling bearing elements within a rolling bearing element assembly configured to support a rotary element (e.g., shaft) in oscillatory motion. The rolling bearing element assembly includes an inner race, an outer race, and a plurality of rolling bearing elements disposed therebetween. The inner race and outer race may be annular disks concentrically aligned with each other and with the rotary equipment being supported. The rolling bearing elements are circumferentially spaced (e.g., positioned at equally spaced angles) about the bearing system axis via a bearing cage disposed in the annular volume between the inner and outer races. The rolling bearing element assembly is generally configured such that, when the rotary equipment is rotated in a first direction about the bearing system axis, the rolling bearing elements in their circumferential spacing also revolve around the bearing system axis in the first direction. However, when the rotary equipment is rotated in a second direction opposite the first direction, the rolling bearing element assembly prevents or resists revolution of the rolling bearing elements about the bearing system axis in the second direction. Specifically, the rolling bearing elements may rotate about their own axes and even slip such that they revolve slightly in the second direction about the bearing system axis when the rotary equipment rotates in the second direction. However, the distance of this revolution may be negligible in comparison with the revolution of the rolling bearing elements in the first direction. Accordingly, when the rotary equipment oscillates, the rolling bearing elements disposed between the inner and outer races generally move about the bearing system axis in a single direction.
The presently disclosed embodiments may provide relatively increased distribution and reapplication of lubricant (e.g., oil, grease, etc.) between the inner and outer races and the rolling bearing elements, as compared to systems that allow the rolling bearing elements themselves to oscillate about the bearing system axis to accommodate the oscillatory motion. It is now recognized that traditional rolling bearing element systems that allow the rolling bearing elements to oscillate back and forth between the inner and outer races may encounter certain difficulties leading to inefficient bearing operation. For example, if the angular rotation of the rotary equipment about the bearing system axis is small, the rolling bearing elements may not move far enough about the bearing assembly to pick up and redistribute the lubricant left over from adjacent rolling bearing elements. This could lead to inadequate lubrication of the rolling bearing elements and inefficient operation of the rolling bearing element assembly. Presently disclosed embodiments include entirely mechanical components that facilitate motion of the bearings in just a single direction revolving about the bearing system axis, instead of the oscillatory motion described above, thereby increasing the mechanical application of lubricant throughout the bearing system.
In some embodiments, the inner race 14 is coupled to rotary equipment, such as a rotating shaft, during operation of the rolling bearing element assembly 10, and the outer race 16 is coupled to stationary equipment used to support the rotary equipment. Although the following discussion generally focuses on the bearing assembly 10 being driven by rotary equipment coupled to the inner race 14, it should be noted that, in other embodiments, the rolling bearing element assembly 10 may be driven by rotary equipment coupled to the outer race 16.
The rolling bearing elements 12 disposed between the races 14 and 16 may include ball bearings (arranged in a single row or double rows), cylindrical bearings (e.g., pins), tapered roller bearings, needle roller bearings, spherical roller bearings, and any other type of rolling bearing element 12 configured to be disposed between inner and outer races of a rolling bearing element assembly 10. The type of rolling bearing elements 12 used may be decided based on the expected loads on the rolling bearing element assembly 10. There may be any desirable number of rolling bearing elements 12 positioned in the rolling bearing element assembly 10.
Different configurations of the rolling bearing element assembly 10 may be used in different embodiments as well. For example, the disclosed rolling bearing element assembly 10 may be used in a radial loading configuration (e.g., supporting a rotating axle) or in a thrust loading configuration (e.g., vertically aligned rotary equipment). The rolling bearing element assembly 10 may promote one directional revolution of the rolling bearing elements 12 between the races 14 and 16 during oscillatory motion as well as during pre-loading of the rolling bearing element assembly 10.
The bearing cage 18, illustrated as a line in
The term “sprag” may refer to an asymmetrically shaped indexing element that is spring-loaded and shaped to contact at least one contact surface of another component of the bearing assembly 10. The illustrated embodiment includes several asymmetric (e.g., teardrop) shaped sprags 20, each with a rounded leading edge at the first end 24 and a tapered trailing edge at the second end 26. The trailing edge may be specifically shaped to interlock with teeth or to increase a frictional force between the sprag 20 and the sprag contact surface. Although illustrated as using one or more sprags 20 to index components of the rolling bearing element assembly 10, it should be noted that any other desirable spring-loaded indexing element may be used in other embodiments.
The illustrated bearing assembly 10 may enable the rolling bearing elements 12 to revolve about the bearing system axis 22 in one direction, regardless of the direction of rotation of the driven inner race 14. Specifically, when the inner race 14 rotates in a first direction indicated by arrow 28 (e.g., clockwise), the sprags 20 engage with a contact surface of the inner race 14. In presently disclosed embodiments, the sprag 20 may be spring-loaded. More specifically, a spring or other biasing feature biases each sprag 20 against the contact surface, and a frictional force locks the sprags 20, the attached bearing cage 18, and the rolling bearing elements 12 into rotation in the first direction 28 as well. When the inner race 14 rotates in a second direction 30 (e.g., counterclockwise) opposite the first direction 28 about the bearing system axis 22, the inner race 14 slides past the sprags 20. The sprags 20 may be specifically shaped to minimize friction between the sprag 20 and the inner race 14, thereby enabling this sliding motion between the inner race 14 and the sprag 20, in one direction and to increase friction between the sprag 20 and the inner race 14 in the opposite direction. In some embodiments, as described below, the sprag 20 and the contact surface engaged by the sprag 20 may include a positive interlock (e.g., ratcheting) mechanism to provide this one directional engagement.
In the illustrated embodiment, a groove 48 formed in the inner race 14 provides a contact surface 50 for the sprags 20. In some embodiments, the groove 48 is not included and the contact surface 50 is flush with an outer boundary of the inner race 14 (or the outer race 16 in other embodiments). The sprags 20 may be biased toward the contact surface 50 so that a frictional force between the sprags 20 and the contact surface 50 maintains the two components in engagement with one another as the inner race 14 rotates in the first direction 28. In some embodiments, the contact surface 50 may be textured to increase the frictional force between the contact surface 50 and the sprags 20. As discussed above, the sprags 20 are shaped to allow the inner race 14 to slip past the sprags 20 as the inner race 14 rotates in the opposite direction.
It should be noted that both the inner race 14 and the outer race 16 are collared in the illustrated embodiment. That is, each of the inner race 14 and the outer race 16 include collars that define grooves 48 on both sides of the rolling bearing elements 12. This may enable relatively flexible designs of the sprag 20/contact surface 50 interface to accommodate different configurations of the rolling bearing element assembly 10. For instance, in embodiments where the outer race 16 is driven instead of the inner race 14, the sprags 20 may be rotatably coupled to the bearing cage 18 in an opposite direction such that they extend into the groove 48 of the outer race 16 to engage a contact surface of the outer race 16. In either configuration (inner race 14 driven or outer race 16 driven), the sprags 20 may be disposed on both sides of the bearing cage 18 between the inner and outer races 14 and 16. This may provide redundancy and a balance of internal forces within the rolling bearing element assembly 10.
Other variations of the sprag 20 and contact surface 50 may be used in other embodiments. For example,
In still other embodiments, the rolling bearing element assembly 10 may be sealed, as illustrated in
As noted above, some embodiments of the rolling bearing element assembly 10 may utilize a positive interlock mechanism to revolve the rolling bearing elements 12 about the bearing system axis 22 in a single direction.
As discussed above, other arrangements of the rolling bearing element assembly 10 may be used in other embodiments. For example, in embodiments where the outer race 16 is driven by the rotary component, the teeth 70 may be disposed on a surface of the outer race 16 and the sprags 20 may be reversed so that the second end 26 of the sprags 20 interlock with the teeth 70. Still further, in other embodiments, the teeth 70 may be disposed on a surface of the bearing cage 18, while the sprags 20 may be coupled to the inner race 14, the outer race 16, or the seal 60 configured to rotate with the driven race.
The teeth 70 may be sized and spaced around the contact surface 50 of the inner race 14 appropriately for the desired rotary application. That is, the teeth 70 may be arranged about the inner race 14 at a certain number of degrees about the bearing system axis 22 relative to each other. The number of degrees may be scalable and related to the relative size of components in the rolling bearing element system 10, such as a radius of the inner race 14, a radius of the outer race 16, a radius of the rolling bearing element 12, and a shape of the sprag 20.
It should be noted that in the embodiments disclosed above, the rolling bearing elements 12 may revolve slightly in the second direction 30 in response to the rotary element rotating in the second direction 30. However, the distance of this revolution may be negligible in comparison with the revolution of the rolling bearing elements 12 in the first direction 28, as permitted by the sprags 20 and the contact surface 50. In addition, the rolling bearing elements 12 themselves are permitted to rotate about their own axes, regardless of whether or in what direction the bearing cage 18 and the rolling bearing elements 12 are revolving about the bearing system axis 22.
Similar techniques may be applied to bearing systems that include cylindrical plain bearings disposed directly over the shaft or other rotary element. As an example,
The collar 114 is disposed about and coupled to the shaft 112, and the collar 114 is configured to be disposed adjacent the intermediate bearing 116 disposed about the shaft 112. The intermediate bearing 116 is configured to freely rotate between the rotating shaft 112 and the stationary external bearing 118, in order to reduce the friction between the rotating shaft 112 and stationary equipment. Grease, or some other lubricant, may be pumped into a space between the intermediate bearing 116 and the external bearing 118, between the intermediate bearing 116 and the shaft 112, or both. As the shaft 112 rotates in an oscillating motion, the plain bearing assembly 110 encourages one directional rotation of the intermediate bearing 116 about the bearing system axis 22, in order to keep the lubricant evenly distributed between the bearing elements.
As discussed above with reference to the rolling bearing element assembly embodiments, a combination of the sprag 20 and the appropriate contact surface 50 may enable transfer of oscillatory rotation of a rotary component (e.g., shaft 112) to one-directional rotation of a bearing component (e.g., rolling bearing elements 12 or intermediate bearing 116). In the illustrated embodiment, the sprags 20 are disposed on and rotatably coupled to the collar 114 of the shaft 112. The sprags 20 are configured to engage the contact surface 50, which is part of the intermediate bearing 116. In the illustrated embodiment, the contact surface 50 includes teeth 70 for providing a ratcheting (e.g., interlock) engagement between the sprags 20 and the contact surface 50. In other embodiments, such as the embodiment illustrated in
In
To facilitate increased distribution and mechanical application of the lubricant in the plain bearing assembly 110, the intermediate bearing 116 may include distribution features configured to distribute the lubricant between the intermediate bearing 116 and the external bearing 118, between the intermediate bearing 116 and the shaft 112, or both. For example, in the illustrated embodiment, the intermediate bearing 116 includes directional flow grooves 120 formed therein, although other types of distribution features may be used in other embodiments. The grooves 120 may extend part of the way into the intermediate bearing 116 in some embodiments. Similar grooves 120 may also be present along a surface of the intermediate bearing 116 facing the shaft 112, in order to provide lubrication between the shaft 112, the intermediate bearing 116, and the external bearing 118. In embodiments with relatively lighter loads on the plain bearing assembly 110, the grooves 120 may extend entirely through the intermediate bearing 116, such that the intermediate bearing 116 has rungs arranged in a cylindrical shape.
The directional flow grooves 120 may be shaped specifically to aid application of the lubricant as the intermediate bearing 116 rotates in the first direction 28. In the illustrated embodiment, for example, the grooves 120 follow a curved profile, where a concave side of the curved profile faces the first direction 28 in which the intermediate bearing 116 is configured to rotate. In other embodiments, the grooves 120 may be formed in a “Chevron shape”, similar to a V-shaped pattern. Other shapes and profiles of the grooves 120 may be used in different embodiments to promote the distribution of lubricant in the plain bearing assembly 110.
In some embodiments, it may be desirable to provide redundancy to the main sprag 20 and contact surface 50 mechanism between the shaft-mounted collar 114 and the intermediate bearing 116.
The second set of sprags 20 and the contact surface 50 coupled between the intermediate and exterior bearings 116 and 118 may be positioned in a way that prevents or resists rotation of the intermediate bearing 116 in the second direction 30 about the bearing system axis 22. If the first set of sprags 20 do not slip past the teeth 70 of the first contact surface 50 as desired when the shaft 112 rotates in the second direction 30, then the second set of sprags 20 may engage the contact surface 50 of the external bearing 118 to prevent or resist rotation of the intermediate bearing 116 in the second direction 30 along with the shaft 112. When the shaft 112 and the intermediate bearing 116 rotate together in the first direction 28, the second set of sprags 20 may simply slip over the contact surface 50 of the exterior bearing 118. Thus, the second set of sprags 20 and the contact surface 50 may provide redundancy the primary set of sprags 20 and the corresponding contact surface 50 between the shaft 112 and the intermediate bearing 116.
Similar techniques may be applied to other types of plain bearing assemblies 110 in addition to plain cylindrical bearings. For example,
While only certain features of the present embodiments have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the present disclosure.
