2. Background of the Related Art Linear motion ball spline bearings are known in the art. Typically, a ball spline bearing includes an outer housing, a holding apparatus, a support shaft and a series of balls. The outer housing includes internal projections and track grooves. The holding apparatus is fixed to the internal surface of the outer housing and includes windows positioned adjacent the track grooves. The support shaft is also formed with track grooves which contact the balls. The housing, the holding apparatus and shaft together define a track, about which the balls circulate. Such a ball spline bearing assembly is disclosed in U. S. Patent No. 4,634,296 to Watanabe.

One disadvantage associated with such a bearing is that the entire housing must be constructed from a hardened material which is not only expensive but also a difficult procedure. Also, because of the internal geometries associated with the various components of the prior art ball spline bearing assembly, the steps involved in manufacturing the ball spline bearing assembly are overly complex and time consuming.

Accordingly, a need exists for an improved linear motion ball spline bearing assembly which is easier and less costly to manufacture and still provides for the near frictionless movement of masses.

SUMMARY In accordance with the present disclosure, a linear motion anti- rotational ball spline bearing assembly is provided that can be manufactured more easily and less expensively than the prior art bearing assemblies. The bearing assembly includes a support rail having a plurality of contoured bearing races, a housing having a through bore configured to receive the support rail, a retainer cage, a lid, and a plurality of load bearing members, each having a pair of contoured bearing races. The lid defines an opening dimensioned to receive a load bearing member. The housing through bore includes a plurality of recesses, each being configured and dimensioned to receive a load bearing member/lid assembly. The retainer cage can be of one-piece construction or of multi-segmented construction.

In one embodiment, the retainer cage includes three retainer segments. Each retainer segment has two bearing tracks and a plurality of rolling elements positioned to circulate about the track. During assembly, the retainer cage and the load bearing members are positioned in the through bore of the housing. An end cap is secured to each end of the housing to prevent the internal components of the bearing assembly from sliding out of the through bore.

BRIEF DESCRIPTION OF THE DRA'VINGS Various preferred embodiments are described herein with reference to the drawings wherein: FIG. 1 is a perspective view of one embodiment of the linear motion anti-rotational bearing assembly with the end caps removed; FIG. 1A is a perspective view of an alternate embodiment of the linear motion anti-rotational bearing assembly with the end caps removed;

FIG. 2 is a perspective view of the linear motion bearing assembly shown in FIG. 1 with parts separated; FIG. 3 is a cross-sectional view of the linear motion bearing assembly shown in FIG. 1; FIG. 4 is a cross-sectional view of the retainer cage and load bearing member of the linear motion bearing assembly shown in FIG. 1; FIG. 4A is a perspective view of an alternate embodiment of the load bearing member of the linear motion anti-rotational bearing assembly; FIG. 5 is a top view of the retainer cage of the linear motion bearing assembly shown in FIG. 1; FIG. 6 is a cross-sectional view of an alterrate embodiment of the linear motion anti-rotation bearing assembly; FIG. 7 is a cross-sectional view of another alternate embodiment of the linear motion anti-rotation bearing assembly; and FIG. 8 is a cross-sectional view of yet another alternate embodiment of the linear motion anti-rotation bearing assembly.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Preferred embodiments of the presently disclosed linear motion anti- rotational bearing assembly will now be described in detail with reference to the drawings, wherein like reference numerals designate identical or corresponding elements in each of the several views.

One embodiment of the presently disclosed linear motion anti- rotational bearing assembly is illustrated in FIGS. 1-5. FIG. 1 illustrates the linear motion anti-rotational bearing assembly shown generally as 10 including a support rail 20. Briefly, bearing assembly 10 includes a housing 12 having a through bore

14 configured to receive a rolling element retainer cage 16, a plurality of lids 17, and a plurality of load bearing members 18, each being positioned within an opening 21 defined by a respective lid 17 (FIG. 2). End plates 19 (FIG. 2) are secured to each end of housing 12 to prevent the internal components of the bearing assembly 10 from sliding out of the through bore 14. Preferably, retainer cage 16 is of a multi-segment construction having first, second and third retainer segments 16a, 16b and 16c, respectively. Alternately, rolling element retainer cage 16 can be of one- piece construction as illustrated in FIG. 1A.

Referring to FIGS. 2 and 3, housing 12 may be formed from a low strength material such as aluminum. Alternately, other materials may be used to form the housing, e. g., polymers. Through bore 14 has a triangular configuration and includes a plurality of recesses 22. Each recess 22 is dimensioned and configured to receive a respective lid 17 and load bearing member 18. Each of the corners of the triangular through bore 14 includes a stepped portion 24 positioned to abut adjacent edges 26 of a lid 17. Stepped portions 24 and edges 26 assist in preventing rotation of rolling element retainer cage 16 within through bore 14.

Referring to FIGS. 2-5, each retainer cage segment 16a-c is preferably constructed from a polymeric material, although other materials such as metal may also be used. Each segment includes a pair of elliptical bearing tracks 28.

Alternately, each segment may include only one bearing track or more than two bearing tracks. Each bearing track 28 includes a load bearing track portion 30, a return track portion 32 and a pair of turnaround track portions 34. A plurality of rolling elements 36 are positioned to circulate about each bearing track 28. Rolling elements 36 are constructed from a high strength metal such as high carbon steel, high strength polymers and ceramics. Rolling elements 36 are preferably

spherically-shaped, although other rolling element configurations are envisioned, e. g., barrel-shaped or cylindrically-shaped.

Referring to FIGS. 2-4, each lid 17 includes a pair of longitudinally extending legs 23 and a pair of transverse members 25 which define opening 21.

Each load bearing member 18 is configured to be positioned within a respective opening 21 to form an assembly. Each lid/load bearing member assembly is dimensioned to b positioned in one of the recesses 22 formed in housing 12. Each load bearing member includes a pair of contoured load bearing races 38 configured to receive rolling elements 36. The load bearing races 38 are positioned adjacent to bearing tracks 28 to retain rolling elements 36 at a location between load bearing members 18 and support rail 20. Any or all of the retainer cage segments 16 a-c, the load bearing members 18 and the lids 17 may be secured together, such as by brazing or crimping, to form a two/three-piece unit. Alternately each component can be loosely positioned within housing 12.

As illustrated in FIG. 4A, each load bearing member 18 may include a self-aligning crown 40,41 which extends parallel to and transversely to the longitudinal axis of the load bearing member. Self aligning crown 40 can be formed monolithically with load bearing member 18 or as a separate element (s). Self- aligning crown 40 will tolerate shaft flexure and misalignment to provide increased smoothness of operation.

Support rail 20 is preferably constructed from a high strength material such as high carbon steel, ceramics, and high strength polymers. Support rail 20 includes a plurality of elongated races 42 monolithically formed with rail 20 and configured to receive rolling elements 36. Alternately, as illustrated in FIG. 8, race inserts 42'can be provided which can be formed separately from rail 20 and attached thereto using known techniques, e. g., brazing. Although dual race inserts

42'are preferred, single race inserts may also be provided. During use, rolling elements 36 are positioned between contoured races 38 of load bearing member 18 and contoured races 42 of support rail 20 to allow the bearing assembly to move freely along support rail 20. Legs 23 of lid 17 enclose return track portions 32 of retainer cage segments 16 and transverse members 25 enclose turnaround track portions 34. By positioning rolling elements 36 between contoured races 38 and 42, rotation of the bearing assembly about rail 20 is prevented.

FIG. 6 illustrates an alternate embodiment of the linear motion anti- rotation bearing assembly shown generally as 100. Bearing assembly 100 is similar to bearing assembly 10 and includes a housing 112 having a through bore 114, a rolling element retainer cage 116 formed from a plurality of cage sections 116a-d, a plurality of lids 117, and a plurality of load bearing members 118. Housing through bore 114 has a rectangular configuration and includes a plurality of recesses 122.

Each recess is dimensioned to receive a respective load bearing member/lid assembly. Each of the corners of through bore 114 includes a stepped portion 124 positioned to abut adjacent edges 126 of cage segments 116a-d. Retainer cage segments 116a-d are similar in construction to cage segments 16a-c and will not be discussed in further detail herein.

FIG. 7 illustrates another alternate embodiment of the linear motion anti-rotation bearing assembly shown generally as 200. The internal components of bearing assembly 200 are substantially identical to the internal components of bearing assembly 10. Bearing assembly 200 includes a housing 212 having a substantially cylindrical exterior geometry. A keyway 248 is formed in the exterior surface of housing 212. Housing 212 is dimensioned to be received within a cylindrical bore having a key formed therein (not shown), such that the key is positioned in keyway 248 to lock bearing assembly 200 within a cylindrical bore.

It will be understood that various modifications may be made to the embodiments disclosed herein. For example, the retainer cage may be constructed from a different number of segments than that disclosed such as two or five segments. Moreover a variety of different materials may be used to construct the various components of the bearing assembly. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.