阅读说明：本技术 轴承保持架 (Bearing retainer ) 是由 E·卢切塔 于 2019-07-09 设计创作，主要内容包括：本发明提供了一种用于涡轮分子泵的转子轴承的轴承保持架(13)。该轴承保持架包括多个轴承兜孔(14),其中每一个在使用中收容轴承滚珠(15),使得该轴承滚珠可操作地接合该转子轴承的内座圈和外座圈。该轴承保持架的每个轴承兜孔都具有用于收容该轴承滚珠的主腔室(17),并且每个轴承兜孔还包括贮槽(20)。(The invention provides a bearing cage (13) for a rotor bearing of a turbomolecular pump. The bearing cage includes a plurality of bearing pockets (14), each of which receives a bearing ball (15) in use such that the bearing balls operatively engage inner and outer races of the rotor bearing. Each bearing pocket of the bearing cage has a main chamber (17) for receiving the bearing ball and each bearing pocket further comprises a sump (20).)

1. A bearing cage for an oil-lubricated rotor bearing of a turbomolecular pump, wherein the bearing cage comprises a plurality of bearing pockets, each of which receives a bearing ball in use such that the bearing ball can operatively engage an inner race and an outer race of the rotor bearing, each bearing pocket having a main chamber for receiving the bearing ball, wherein each bearing pocket further comprises an oil sump.

2. The bearing cage of claim 1, wherein the primary chamber is defined at least in part by a substantially arcuate surface for surrounding a portion of a bearing ball received in the primary chamber, and wherein the sump is in the form of a secondary chamber extending radially outwardly from the substantially arcuate surface.

3. The bearing cage of claim 1 or 2, wherein the sump is located at a second end of the pocket opposite the first end, wherein the first end is a rotor-side end, and wherein the second end is a pump outlet-side end.

4. The bearing cage of claim 3, wherein each pocket comprises an opening at the first end defined in a substantially annular surface of the bearing cage, wherein the first end is a rotor-side end, and wherein the second end is a pump outlet-side end.

5. The bearing cage of any preceding claim, wherein the sump extends to an outer race side surface of the bearing cage.

6. The bearing cage of any preceding claim, wherein the sump extends to an inner race side surface of the bearing cage.

7. A bearing cage according to any preceding claim wherein the sump is open only on the inner or outer race side.

8. The bearing cage of any of claims 1-7, wherein the sump is defined on an inner race side or an outer race side by a wall extending longitudinally from a base of the sump, and wherein the longitudinally extending wall includes a bearing ball side surface that forms a portion of a substantially arcuate surface that defines the primary cavity.

9. The bearing cage of any of claims 1-8, wherein the sump is open.

10. A bearing cage according to any preceding claim wherein the sump is defined by a substantially arcuate surface.

11. The bearing cage according to claim 10 when dependent on claim 2, wherein the substantially arcuate surfaces defining the sump and the substantially arcuate surfaces defining the primary chamber are contiguous.

12. The bearing cage of claim 10 when dependent on claim 2 or 11, wherein the substantially arcuate surfaces defining the sump have radii such that: the radius is less than a radius of the substantially arcuate surface defining the primary chamber.

13. The bearing cage according to any of claims 1 to 9, wherein the sump comprises a surface substantially tangential to the axis of rotation of the bearing cage, preferably a planar surface substantially tangential to the axis of rotation of the bearing cage.

14. A bearing cage according to any preceding claim wherein, in use, a portion of bearing balls may extend through an opening of the bearing pocket and/or into the sump.

15. An oil-lubricated rolling bearing for a turbomolecular pump comprising an inner race, an outer race, a plurality of bearing balls and a bearing cage according to any of claims 1 to 14.

16. A turbomolecular pump comprising the oil-lubricated rolling bearing according to claim 15.

17. A method for retrofitting a turbomolecular pump comprising oil-lubricated roller bearings for use in a vertically inverted orientation or a non-vertical orientation, comprising the steps of:

a. removing the rolling bearing; and

b. replacing the rolling bearing with a ball bearing comprising a bearing cage, wherein the bearing cage comprises a plurality of bearing pockets each containing a bearing ball,

characterized in that each bearing pocket of the replacement bearing comprises an oil sump.

18. Use of an oil rolling bearing in a turbomolecular pump, the oil rolling bearing comprising a rolling bearing for a turbomolecular pump, the rolling bearing comprising an inner race, an outer race, a plurality of bearing balls, and a bearing cage according to any of claims 1 to 14.

Technical Field

The present invention relates to a bearing cage and in particular to a bearing cage for use in an oil lubricated rotor bearing in a vacuum pump, in particular a turbomolecular pump.

Background

Vacuum pumps typically include an impeller in the form of a rotor mounted on a shaft for rotation relative to a surrounding stator. The shaft is typically supported by a bearing arrangement comprising two bearings located at or intermediate respective ends of the shaft. Alternatively, the shaft may be a cantilever supported by two bearings located at one end or in the middle of the shaft. In both arrangements, one or both bearings may be in the form of rolling bearings. For example, the upper bearing may be a passive magnetic bearing and the lower bearing may be a rolling bearing.

Referring to fig. 1, a typical rolling bearing (1) includes an inner race (2) fixed with respect to a shaft (3) of a vacuum pump (4), an outer race (5), and a plurality of rolling elements (6), the plurality of rolling elements (6) being supported by a bearing cage (7) so as to allow relative rotation of the inner race (2) and the outer race (5). Typically, the outer race (5) is fixedly attached to a bearing support damper (8), which bearing support damper (8) is in turn fixedly attached to the housing (9) of the vacuum pump. The bearing support damper (8) is typically held in place by a bearing support nut (10).

The rolling bearing (1) typically comprises a plurality of bearing balls (6) which may be greased or oil lubricated to establish a bearing film separating the bearing parts in rolling and sliding contact in order to minimize friction and wear.

As discussed, the rolling bearing (1) will typically comprise a bearing cage (7). As better illustrated by referring to fig. 2 and 3, the bearing cage (7) may include a plurality of evenly spaced bearing pockets (30), with the bearing balls (6) positioned within the bearing pockets (30). Thus, the bearing cage (7) ensures uniform spacing of the bearing balls (6) around the passage between the inner race (2) and the outer race (5) and facilitates oil lubricant distribution within the bearing.

The rolling bearing (1) is typically lubricated by an oil lubricant which forms a film between each bearing ball (6), its corresponding bearing pocket (30) and the inner (2) and outer (5) races. The lubricating film formed between the bearing ball (6) and the bearing cage (7) ensures that the bearing ball (6) can rotate and spin with minimal wear and reduced losses due to friction. Ball movement is complex and may include a combination of rolling about the bearing axis and rotation about other axes due to the internal geometry of the bearing and the forces to which the balls are subjected during high speed operation.

Fig. 1 shows an external guide cage design, where an oil delivery nut (31) from the oil supply system extends between the inner race (2) and the bearing cage (7). Oil lubricant is supplied to the bearing balls (6) through a passage (32) between the inner race (2) and the bearing cage (7).

Fig. 1 shows the turbomolecular pump in a vertical upright position, with the axis of rotation (a) of the impeller shaft (3) in a substantially vertical orientation. When in the vertical upright position, the rotor chamber is positioned with the rotor chamber inlet above the rotor chamber outlet.

Fig. 2 shows the bearing cage (7) and the bearing balls (6) as seen in the lower rolling bearing of the turbomolecular pump in a vertical upright position. As shown, the axis of rotation (X) of the bearing cage (7) is oriented vertically, and the bearing cage (7) is positioned such that the opening (11) at the first end of each bearing pocket (30) faces upward. Under the influence of gravity, the bearing cage (7) will tend to be in place so that each bearing ball (6) is positioned more towards the first end of its bearing pocket (30), so that an oil lubrication film can form there. When in this orientation, the interaction between each bearing ball (6) and the opening (11) of its bearing pocket (30) interrupts the oil lubricant film and, thereby, reduces frictional losses when the vacuum pump is in operation. The openings (11) are typically characteristic of "clip-on" cages, wherein there is an open side to allow the cage to be clipped onto the balls in the event that the balls have been pre-assembled between the races. Openings may be provided in deep groove ball bearings because the balls may be unevenly spaced during assembly. In alternative designs, such as riveted ball bearings or angular contact ball bearings, there may be no open side.

For operational reasons, vacuum pumps, including turbomolecular pumps, may need to be used in orientations other than the vertical upright position described above, for example with the axis of the impeller horizontal, vertically inverted (that is, with the rotor chamber outlet above the inlet), or at any angle therebetween. However, it has been observed that when the vacuum pump is oriented in a position other than the vertical upright position, then the operating temperature for a given rotor speed may increase, thereby reducing the operating range of the vacuum pump, and the power required to run the vacuum pump at the given rotor speed may increase, or vice versa, with increased power losses resulting in increased temperatures within the bearings. It has been found that these problems, known as parasitic losses, are particularly acute when the pump is arranged in a vertically inverted position. Power losses due to friction within the bearing have been measured to increase by as much as 100% in certain orientations.

Accordingly, there remains a need for vacuum pumps having reduced parasitic losses, and in particular, vacuum pumps comprising lubricated oil, wherein power losses are independent of the orientation of the device.

The inventors have found that the cause of these problems is viscous losses in the bearing cage of the lower oil-lubricated rolling bearing (i.e. the rolling bearing located at the outlet end of the rotor chamber of the turbomolecular pump).

Fig. 3 shows the bearing cage (7) and the bearing balls (6) as seen in the lower rolling bearing of the turbomolecular pump in a vertically inverted position. As shown, the axis of rotation (X) of the bearing cage (7) is vertical, however, the bearing cage (7) is inverted compared to the arrangement shown in fig. 1 and 2. In this position, the bearing cage (7) is positioned such that the opening (11) of the bearing pocket (30) faces downward.

It has been found that in this position, under the influence of gravity, the bearing cage (7) can tend to be in position so that each bearing ball (6) is positioned more towards the second closed end (12) of its bearing pocket (30). As a result, the surface of the closed end of the bearing pocket (12) is positioned significantly closer to the bearing ball (6) than when in the upright position. Thus, the oil lubrication thickness is reduced at the closed end (12) of the bearing pocket (30) and is not interrupted by the opening (11) of the bearing pocket, resulting in higher viscous losses.

Similar problems, although to a lesser extent, may occur in other non-vertical orientations.

The present invention addresses these and other problems of prior art oil-lubricated bearing systems.

Disclosure of Invention

Accordingly, in a first aspect, the present invention provides a bearing cage for an oil lubricated rotor bearing of a turbomolecular pump. The bearing cage includes a plurality of bearing pockets, each of which receives a bearing ball in use such that the bearing ball can operatively engage an inner race and an outer race of the rotor bearing. Each bearing pocket has a main chamber for receiving the bearing ball, wherein each bearing pocket further comprises an oil sump.

For the purposes of this invention, the sump has its normal meaning. Typically, oil is a lubricating liquid which can flow into the depression from the main chamber for use. Grease lubricated bearings having grease sumps configured for containing substantially solid grease are known, but the present invention is not intended for use with such grease lubricated bearings.

Typically, the sump is located at a second end of the pocket opposite the first end. Typically, the first end of each pocket includes an opening. The width of the opening is generally the same or wider than the width of the opening of the receptacle. Typically, the width of the opening is narrower than the diameter of the bearing ball.

Typically, the opening at the first end of each pocket is defined in a substantially annular surface of the bearing cage.

The inventors have found that providing an oil sump in each bearing pocket reduces viscous losses, particularly when the bearing cage is oriented such that the bearing pocket opening faces downward. Advantageously, when the bearing cage according to the invention is employed in an oil-lubricated lower rolling bearing in a turbomolecular pump, parasitic losses are significantly reduced when the pump is operated in a vertically inverted position compared to when a standard bearing cage is employed. Additionally, and advantageously, it has been found that the amplitude of cage vibrations is reduced during operation.

The main chamber may be at least partially defined by a substantially arcuate surface that surrounds a portion of the bearing balls housed in the main chamber. The primary chamber may include two or more arcuate surfaces. Typically, the arcuate surface has an arc defined by a perimeter imaginary circle. Where the primary chamber includes two or more arcuate surfaces, they are defined by the perimeters of the same imaginary circle.

In an embodiment, the substantially arcuate surface defining the primary chamber may be in the form of a portion of an outer surface of an imaginary cylinder having a central axis radially aligned with the rotational axis of the bearing cage. The radius of the substantially arcuate surface defining the primary chamber may be the radius of the bearing ball plus a small gap to allow the bearing ball to rotate and allow the formation of an oil lubrication layer. The radius of the substantially arcuate surface defining the primary chamber may be from about 0.25 mm to about 6mm, preferably from about 1mm to about 5 mm.

The sump may be in the form of a secondary chamber extending radially outwardly from a substantially arcuate surface defining the primary chamber.

Typically, each pocket includes an opening at the first end defined in a substantially annular surface of the bearing cage. Typically, each pocket includes two pocket claws (pocket jaws) that define the opening at a first end of the pocket. The substantially arcuate surface and the annular surface may be contiguous. Typically, the pocket fingers include edges where the substantially arcuate surface and the annular surface intersect.

The bearing pockets may be substantially evenly spaced apart in the circumferential direction.

In use, each bearing pocket may receive a bearing ball therein such that the bearing ball is at least partially enclosed within the main chamber. An oil lubricant may be located between the outer surface of the bearing ball and the surface of the main chamber, and within the sump. By supporting the bearing balls and separating them from the bearing cage, inner and outer races, the oil lubricant acts to reduce friction and wear of the bearing components. In addition, the oil lubricant prevents oxidation and/or corrosion of the bearing balls, acts as a barrier to contaminants, and conducts heat away from the bearing. Typically, the oil lubricant may flow out of the sump to substantially prevent compression of the oil lubricant film between the balls and the sump surface.

In use, oil lubricant may be supplied to the bearing by the oil delivery nut. Oil lubricant may be delivered to the oil delivery nut from the felt oil reservoir via the wick.

Typically, the first end is a rotor-side end and the second end is a pump outlet-side end.

The sump may extend to an outer race side surface of the bearing cage. Additionally or alternatively, the sump may extend to an inner race side surface of the bearing cage.

In an embodiment, the receptacle is open-sided. "open" means a configuration that: wherein the sump extends uninterrupted the width of the bearing retainer wall. Advantageously, the open sump is easy to manufacture.

In embodiments, the sump may not extend the entire width of the bearing cage. For example, the sump may be open on only one of the inner race side or the outer race side. The sump may be defined on the inner race side and/or the outer race side by a wall extending longitudinally from the base of the sump. The thickness of the wall may be between about 1mm and about 6mm depending on the size and design of the bearing.

The longitudinally extending wall may include a bearing ball side surface forming a portion of the substantially arcuate surface defining the primary chamber.

Advantageously, sumps that do not extend the full width of the bearing retainer wall better retain oil lubricant during use. Without wishing to be bound by theory, it is believed that the use of the wall limits the outward movement of the oil lubricant from the sump due to centrifugal forces acting on the oil lubricant when in use.

In an embodiment, the sump may be defined by a substantially arcuate surface. Typically, a single substantially arcuate surface. The substantially arcuate surface may have a substantially uniform radius across the width of the sump. Thus, the substantially arcuate surface may be in the form of a portion of the outer surface of an imaginary cylinder having a central axis radially aligned with the axis of rotation of the bearing. Alternatively, the radius of the substantially arcuate surface of the sump may vary across the width of the sump. The arc will typically form part of an imaginary circle across the width of the sump, i.e. the radius of the arc may vary across the width of the sump, but may not vary around the perimeter of the sump.

The radius of the substantially arcuate surface of the sump is typically from about 0.5 mm to about 10 mm, preferably from about 0.75 mm to about 2 mm, with one example being 0.9 mm. As with the other specific dimensions defined herein, the skilled person will understand that the invention can be applied to many different bearing sizes and that although these dimensions are preferred, they are not limiting.

Typically, although not exclusively, the substantially arcuate surfaces defining the sump may have a radius, that is: the radius is less than the radius of the substantially arcuate surface defining the primary chamber.

The radius of the substantially arcuate surface defining the primary chamber may be from about 0.25 mm to about 6 mm.

Typically, the substantially arcuate surfaces defining the sump and the surfaces defining the main chamber, such as one or more substantially arcuate surfaces, are contiguous. The surfaces defining the main chamber and the sump may intersect at an edge. Alternatively, the intersection between the surface defining the main chamber and the surface defining the sump may be rounded.

In embodiments, the sump may comprise a surface, such as a base, that is substantially tangential to the axis of rotation of the bearing cage. The sump may, for example, have a planar base. The base of the sump may be joined to the main chamber by one or more side walls. Typically, the sidewall will intersect the base at an angle of 85 degrees or greater, typically 90 degrees or greater. 90 degrees is one example. Alternatively, the side walls may intersect one another at the base of the sump.

Typically, in use, a portion of the bearing balls may extend through the opening of the bearing pockets and/or into the sump. Preferably, the sump is configured such that bearing balls are prevented from engaging surfaces defining the sump. This ensures that the layer of oil lubricant formed between the surface of the bearing ball and the surface of the main chamber remains interrupted.

Generally, the bearing cage may be configured to include from six to eleven bearing pockets, preferably six bearing pockets. Each bearing pocket typically receives a single bearing ball.

In another aspect, the present invention provides an oil-lubricated rolling bearing for a turbomolecular pump comprising an inner race, an outer race, a plurality of bearing balls, and a bearing cage as disclosed in the preceding aspect of the invention. Advantageously, such a rolling bearing can be retrofitted to a turbomolecular pump comprising a bearing oil lubrication system.

Typically, in use, the rolling bearing is oriented such that the rotational axis of the rolling bearing is substantially the same as the rotational axis of the rotor of the turbomolecular pump. Typically, the rolling bearing is a lower bearing of the turbomolecular pump.

In another aspect, the invention provides a turbomolecular pump comprising an oil-lubricated rolling bearing comprising a bearing cage according to the aforementioned aspect of the invention. Beneficially, such oil-lubricated turbomolecular pumps may be used in any orientation.

In another aspect, the present invention provides a method of retrofitting a turbomolecular pump comprising an oil lubricated bearing for a position other than vertical, preferably for a vertically inverted position, comprising the steps of: removing the rolling bearing; the rolling bearing is replaced with a ball bearing comprising a bearing cage comprising a plurality of bearing pockets each containing a bearing ball, wherein each bearing pocket comprises a sump.

In a further aspect, the present invention provides the use of an oil rolling bearing comprising a bearing cage according to the previous aspect of the invention in a turbomolecular pump.

Drawings

Preferred features of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

fig. 1 shows a prior art oil lubricated bearing in situ in a turbomolecular pump.

Fig. 2 shows a prior art oil lubricated bearing in a vertical upright orientation.

Fig. 3 shows a prior art oil lubricated bearing aligned in a vertically upside down orientation.

Fig. 4 and 5 show a bearing cage according to the invention.

Fig. 6 shows an alternative bearing cage according to the invention.

Fig. 7 and 8 show an alternative bearing cage according to the invention.

Detailed Description

The invention provides a bearing retainer for an oil-lubricated rotor bearing in a turbomolecular pump.

Referring to fig. 4, in one example, the bearing cage (13) includes a plurality of bearing pockets (14), each of which is configured to receive a bearing ball (15). The bearing pockets (14) are evenly circumferentially spaced and, in use, the bearing cage (13) maintains a circumferentially even spacing of the bearing balls (15).

The bearing cage (13) is a substantially cylindrical tube. Preferably, the bearing cage has an inner radius (r) of from about 2.5 mm to about 6.5 mm. 3.5 mm is an example. Typically, the bearing cage has a wall thickness (t) of from about 1mm to about 6 mm.

The bearing holder (13) has a guide flange (16) extending radially outward from the bearing holder (13). In use, the guide flange (16) slidably engages an outer race of a bearing (not shown) to maintain the radial position of the bearing cage (13) about the axis of rotation of the rotor shaft of the turbomolecular pump.

The bearing cage may be made of any suitable material, typically a high performance polymer selected from the list comprising phenolic resin, polyamide-imide, Polyetheretherketone (PEEK) and Polytetrafluoroethylene (PTFE). The bearing cage including pockets and sumps (sumps) may be manufactured by machining, injection molding, by additive manufacturing techniques, or by a combination thereof.

Each bearing pocket (14) comprises a main chamber (17). The main chamber has an open end (18) defined in an annular surface (32) of the bearing cage (13). The main chamber (17) is defined by a substantially arcuate surface (19), which surface (19) surrounds a portion of the bearing balls (15) housed therein. As shown, each bearing ball projects radially outward from the bearing cage such that it may operatively engage an outer race. Similarly, each bearing ball projects radially inward so that it may operatively engage an inner race. Each bearing ball also protrudes through the opening of its pocket and into the oil sump. The amount of protrusion of the bearing ball in any direction may vary in use, for example, depending on the orientation of the bearing.

Each bearing pocket (14) also includes an oil sump (20). The illustrated oil sump (20) is in the form of a secondary chamber extending radially outwardly from a substantially arcuate surface (19) defining the primary chamber (17) opposite the open end (18).

In the example shown, the width (w) of the sump (20) is less than the width (v) of the opening. Preferably, the width (w) of the sump is less than the diameter of the bearing balls housed in the main chamber.

The sump (20) is shown to have a rectangular cross-section. The sump may have any cross-section, but is preferably rectangular, acute trapezoidal (e.g., circular or oval), triangular or arcuate (e.g., circular or oval) in cross-section.

The sump (20) in fig. 4 and 5 has a base defined by a surface (21), the surface (21) being substantially tangential (radial) to the axis of rotation (X). The sump (20) is further defined by a pair of side wall surfaces (22, 23), the pair of side wall surfaces (22, 23) being in a substantially face-to-face orientation substantially perpendicular to the surface (21) tangential to the axis of rotation. The side wall surfaces (22, 23) extend longitudinally between a surface (21) tangential to the axis of rotation and substantially arcuate surfaces (19, 33) defining the main chamber (17). In this embodiment, the intersection between the substantially arcuate surface (19, 33) and the sidewall surface (22, 23) is defined by an edge. These intersections may be rounded if preferred.

The sump (20) is shown extending to both the inner race side surface (24) and the outer race side surface (36) of the bearing cage (13). Thus, the sump (20) is open.

Fig. 4 shows the bearing cage (13) in a vertically inverted position: the axis of rotation (X) is vertical and the sump (20) is positioned vertically above the open end (18). In this configuration, the effect of gravity acting on the bearing cage (13) is to cause the bearing balls (15) to extend partially into the sump (20). The bearing balls do not engage with surfaces (21) or side walls (22, 23) substantially tangential to the axis of rotation. Advantageously, the presence of the sump (20) interrupts the lubricant layer formed between the bearing balls (15) and the main chamber (17). This makes the power loss attributable to the bearing cage (13) substantially independent of the bearing orientation. As such, any vacuum pump that includes a bearing cage (13) as shown is not limited to any particular orientation by the bearing cage.

Fig. 5 shows the bearing cage (13) of fig. 4 from a different perspective.

Fig. 6 shows an alternative bearing cage (13) to the bearing cage shown in fig. 4 and 5. In this case, the sump (20) also comprises and is defined by a wall (25) on the inner race side, the wall (25) extending longitudinally from the base of the sump (20). The wall (25) extends across the entire width of the sump (20).

In this embodiment, the longitudinally extending wall (25) has a bearing ball side surface (26) which forms part of a substantially arcuate surface (19) defining the main chamber (17). In this embodiment, the longitudinally extending wall (25) and the substantially arcuate surface (19) defining the primary chamber (17) are contiguous, having a substantially constant radius. The radius is constant across the width of the primary chamber.

Fig. 7 illustrates another alternative bearing cage (13). The sump (20) is similarly in the form of an auxiliary chamber which extends radially outwardly from a substantially arcuate surface (19) defining the main chamber (17) opposite the open end (18) of the bearing cage pocket (14). The sump (20) is open and defined by a substantially arcuate surface (26).

The substantially arcuate surface (26) defining the sump (20) typically has a radius, i.e.: the radius is smaller than the radius of the substantially arcuate surface (19) defining the primary chamber (17). In this example, the diameter (27) of an imaginary circle defining the substantially arcuate surface (26) of the sump (20) is 0.7 times the diameter of an imaginary circle defining the substantially arcuate surface of the primary chamber. Generally, a ratio of from about 0.5 to about 0.9 is preferred.

As shown, the substantially arcuate surface (19) defining the primary chamber (17) and the substantially arcuate surface (26) defining the sump (20) are contiguous and their intersection (28) is defined by an edge. The intersection may be rounded if desired.

Fig. 8 illustrates the bearing cage (13) of fig. 7 from an alternative perspective. The bearing cage (13) includes an inner guide flange (29) extending radially inward from an inner surface of the bearing cage (24) toward the axis of rotation. The inner guide flange (29) is configured to slidably engage with an inner race of the bearing, in use, to maintain a radial position of the bearing cage about the axis of rotation.

It is noted that the invention disclosed herein may be used equally well with bearing cages of either an externally guided design or an internally guided design.

It will be appreciated that various modifications may be made to the illustrated embodiments without departing from the spirit and scope of the invention as defined by the appended claims as interpreted according to the patent laws.