There are known in the prior art linear ball bearings which receive shafts for rectilinear movement in the direction of the shaft axis. Generally such bearings include a plurality of circumferentially spaced closed ball paths, each of which includes a loaded ball path portion in which balls are disposed along a line parallel to the shaft axis and are in load-bearing relationship with the shaft and a member which transmits the load to the bore in which the shaft is mounted.
Each of the raceways also includes an unloaded ball path portion in which balls are disposed along a line parallel to the shaft axis, which balls are unloaded. Transition path portions are provided between the ends of the loaded ball path portion and the unloaded ball path portion.
Owing to the construction described above, linear ball bearings of the prior art must be constructed with a high degree of accuracy. Most of the linear ball bearing assemblies of the prior art do not readily accommodate either axial or radial misalignment of the shaft relative to the bore in which it is to be mounted by the bearing assembly.
Attempts have been made in the prior art to provide linear ball bearings which have the capability of accepting some misalignment of the shaft relative to the bore in which it is to be mounted. For example, Magee et al U.S. Pat. No. 3,545,826 discloses a linear ball bearing assembly including a cage of synthetic resin formed with unloaded ball path portions and with openings into which load-carrying plates are adapted to be snapped to complete the loaded ball path portions. The assembly of the cage, the load-carrying plates, and the balls is adapted to be inserted into the working bore.
In the arrangement disclosed in Magee et al, each of the load-carrying plates which are snapped into the synthetic resin cage, has a central thicker portion. These thickened central portions permit the load carrying plates to rock slightly by displacement of the resilient mass of the cage to accommodate angular displacement of the shaft relative to the bearing axis. In Magee et al the load plates are so constructed as to be biaxially resilient to distribute load. If the mounting bore is only roughly finished or is of soft material, an intermediate sleeve may be used.
While the Magee et al construction accommodates some shaft misalignment, it incorporates a number of disadvantageous features. First, in most installations it must react against the mounting bore in accommodating shaft misalignment. The relatively resilient load-bearing plates do not provide as good a bearing track as do relatively rigid plates.