Bearing mount and preload assembly

An assembly includes a first structure, a first bearing assembly, and a second structure. The first structure has a first predetermined stiffness, and the first bearing assembly is mounted on the first structure. The second structure, which has a second predetermined stiffness, is mounted on the first bearing assembly, whereby relative motion about a first rotational axis is allowed between the first and second structure. At least one of the first structure and the second structure distort when a force is supplied thereto along the first rotational axis, and the distortion of at least one of the first structure and the second structure imparts a first preload force on the first bearing assembly.

TECHNICAL FIELD

The present invention generally relates to bearing assemblies, and more particularly relates to a bearing mount and preload assembly.

BACKGROUND

Most mechanical systems that rely on relative rotational motion between system components include one or more bearing assemblies. The bearing assemblies, which may include, for example, inner and outer races, provide for the relative rotational motion between the system components with minimal friction. To avoid play or “slop” in the bearing assemblies, individual bearing preload assemblies may be preloaded with some sort of spring or flexure.

A typical preload assembly includes multiple components. For example, one particular type of preload assembly, which is depicted inFIG. 5, includes a spring502, a cap504, and a housing506. The spring502and bearing assembly (or assemblies)508(only one depicted) are disposed within the housing506. The spring502, which supplies the preload force to the bearing assembly (or assemblies)508, is retained within the housing via the cap504. As may be appreciated, such preload assemblies add size, weight, and complexity to the overall mechanical system. This can become increasingly problematic as the system becomes smaller and/or more integrated.

Hence, there is a need for a bearing preload assembly that does not add size, weight, and/or complexity to a mechanical system. Most notably relatively small and/or integrated systems. The present invention addresses at least these needs.

BRIEF SUMMARY

In one embodiment, an assembly includes a first structure, a first bearing assembly, and a second structure. The first structure has a first predetermined stiffness, and the first bearing assembly is mounted on the first structure. The second structure, which has a second predetermined stiffness, is mounted on the first bearing assembly, whereby relative motion about a first rotational axis is allowed between the first and second structure. At least one of the first structure and the second structure distort when a force is supplied thereto along the first rotational axis, and the distortion of at least one of the first structure and the second structure imparts a first preload force on the first bearing assembly.

In another embodiment, an assembly includes a first structure, a first bearing assembly, a second bearing assembly, and a second structure. The first structure, which has a first predetermined stiffness, includes a first bearing mount portion and a second bearing mount portion spaced apart from the first bearing mount portion. The first bearing assembly is mounted on the first bearing mount portion, and the second bearing assembly is mounted on the second bearing mount portion. The second structure is mounted on and interconnects the first and second bearing assemblies, whereby relative motion between the first and second structures is allowed along a first rotational axis. The second structure has a second predetermined stiffness that is less than the first predetermined stiffness to thereby distort at least when a force is supplied thereto. The second structure, via its distortion, imparts preload forces on the first and second bearing assemblies.

In yet another embodiment, a gimbal mounting assembly includes an inner gimbal ring, a shaft, a first bearing assembly, a second bearing assembly, a third bearing assembly, a fourth bearing assembly, and an outer gimbal ring. The inner gimbal ring, which has a first predetermined stiffness, includes a first bearing mount portion and a second bearing mount portion spaced apart from the first bearing mount portion. The shaft includes a first end and a second end, and has a second predetermined stiffness. The first bearing assembly is mounted on the first bearing mount portion, the second bearing assembly is mounted on the second bearing mount portion, the third bearing assembly is mounted on the shaft at least adjacent to the first end, and the fourth bearing assembly is mounted on the shaft at least adjacent to the second end. The outer gimbal ring is mounted on and interconnects the first, second, third, and fourth bearing assemblies, whereby relative motion between the inner and outer gimbal rings is allowed along a first rotational axis, and whereby relative motion between the shaft and outer gimbal ring is allowed along a second rotational axis that is perpendicular to the first rotational axis. The outer gimbal ring has a third predetermined stiffness that is less than the first predetermined stiffness and the second predetermined stiffness to thereby distort at least when a force is supplied thereto along the first and second rotational axes. The outer gimbal ring, via its distortion, imparts equal magnitude first and second preload forces on the first and second bearing assemblies, respectively, and imparts equal magnitude third and fourth preload forces on the third and fourth bearing assemblies, respectively.

DETAILED DESCRIPTION

Referring first toFIG. 1, a simplified cross section view of a portion of a structural assembly100that incorporates a bearing mount and preload assembly is depicted, and includes at least a first structure102, a first bearing assembly104, and a second structure106. The first structure102includes a bearing mount portion103. As is seen, the first bearing assembly104is mounted on the bearing mount portion103, and the second structure106is mounted on the first bearing assembly104. Thus, relative motion about a first rotational axis108is allowed between the first and second structures102,106.

The bearing assembly104includes, as is generally known, an inner race112and an outer race114. In the depicted embodiment, the inner race112engages the bearing mount portion103, the outer race114engages the second structure106, and the bearing assembly104is held in place, against the second structure106, via suitable fastener hardware. Although the fastener hardware may vary, in the depicted embodiment it includes a simple threaded fastener116, such as a screw, and a washer118.

AsFIG. 1further depicts, the assembly100does not incorporate a conventional preload assembly. Instead, the preload is provided via the second structure106. More specifically, via the relative stiffness of the second structure106. That is, the first structure102is formed of a material having a first predetermined stiffness, and the second structure106is formed of a material having a second predetermined stiffness. In some embodiments the second predetermined stiffness is less than the first predetermined stiffness, in other embodiments it is equal to the first stiffness, and in still others it is greater than the first stiffness. Regardless of the relative values of the first and second predetermined stiffnesses, when a force is supplied to the second structure106along the first rotational axis108, at least one of the first structure102and the second structure106distorts, and this distortion imparts a preload force on the first bearing assembly104.

It will be appreciated that the materials of which the first and second structures102,106are formed may vary. It will additionally be appreciated that the first and second stiffnesses may vary, so long as the second structure106distorts, relative to the first structure102, when a load is applied thereto. Some example materials of the first and second structures102,106include various metals, metal alloys, plastics, and composites that exhibit elasticity when a force is applied thereto. It will additionally be appreciated that the second structure106may be variously shaped. For example, it may be any one of numerous known closed shapes, such as round, diamond, rectangular, or star-shaped, just to name a few, or it may be any one of numerous known open shapes, such as C-shaped or L-shaped, just to name a few.

Referring now toFIG. 2, a perspective view of one embodiment of an actual physical implementation of a device that incorporates the bearing mount and preload configuration ofFIG. 1is depicted. The depicted device is a gimbal mechanism200, and the first structure102is configured as an inner gimbal ring, and the second structure106is configured as an outer gimbal ring. The depicted gimbal mechanism200additionally includes a second bearing assembly202. The second bearing assembly202is mounted on a second bearing mount portion203, which is formed on the inner gimbal ring (e.g., the first structure102). Though not visible inFIG. 2, it will be appreciated that, similar to the first bearing assembly104, the second bearing assembly202is held in place, against the second structure106, via suitable fastener hardware.

The second bearing mount portion203is spaced apart from the first bearing mount portion103, and is disposed on the first rotational axis108. The outer gimbal ring (e.g., the second structure106) is also mounted on the second bearing assembly202and, via its distortion, imparts a second preload force on the second bearing assembly202. As may be appreciated, because the first and second bearing assemblies104,202are disposed coaxially along the first rotational axis108, the second preload force is equal in magnitude (but opposite in direction) to the first preload force.

AsFIG. 2also depicts, the gimbal mechanism200, at least in the depicted embodiment, additionally includes a third structure206. The third structure206, which is implemented as a shaft in the depicted embodiment, is rotationally coupled to the outer gimbal ring (e.g., the second structure106) to allow relative rotation between the shaft (e.g., the third structure206) and the outer gimbal ring106about a second rotational axis208that is perpendicular to the first rotational axis108.

As may be appreciated, the shaft206is rotationally coupled to the outer gimbal ring106via bearing assemblies. In particular, via a third bearing assembly212and a fourth bearing assembly214. The third bearing assembly212is disposed between the shaft206and the outer gimbal ring106. The fourth bearing assembly214is spaced apart from the third bearing assembly212, and is also disposed between the shaft206and the outer gimbal ring106. The outer gimbal ring106is configured such that it also distorts at least when a force is supplied thereto along the second rotational axis208and, via its distortion, imparts preload forces on the third and fourth bearing assemblies212,214. More specifically, it imparts a third preload force on the third bearing assembly212, and a fourth preload force on the fourth bearing assembly214. The third and fourth preload forces are equal in magnitude, but opposite in direction. It will be appreciated that in some embodiments the third and fourth bearing assemblies212,214may be allowed to slide along the second rotational axis. In such embodiments, while there would be no preload on the third and fourth bearing assemblies212,214, there would still be a preload force on the first and second bearing assemblies118,202

It may be appreciated from the above description that the outer gimbal ring (e.g., second structure106) implements at least two functions—mechanical support and preloading of all bearing assemblies104,202,212,214in the first and second rotational axes108,208. The outer gimbal ring (e.g., second structure106) may be configured such that the stiffnesses, and thus the preload force magnitudes, in the first and second axes108,208may be equal or unequal. Thus, the outer gimbal ring (e.g., second structure106) may be configured to have both a second predetermined stiffness in, for example, the first rotational axis108, and a third predetermined stiffness in, for example, the second rotational axis208that is unequal to the second predetermined stiffness.

The mechanism by which the outer gimbal ring (e.g., second structure106) implements the different stiffnesses may be vary. For example, asFIG. 3depicts, one or more dimensions (e.g., width, thickness, etc.) of the outer gimbal ring (e.g., second structure106) may be sized to provide the second and third predetermined stiffnesses. Alternatively, or additionally, and asFIG. 4depicts, the outer gimbal ring (e.g., second structure106) may have a plurality of features402, such as holes, notches, indentations, grooves or corrugations, formed therein that are dimensioned to provide the second and third predetermined stiffnesses.

In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Numerical ordinals such as “first,” “second,” “third,” etc. simply denote different singles of a plurality and do not imply any order or sequence unless specifically defined by the claim language.