Abstract:
Apparatus and methods are provided for locking retaining elements in place. One embodiment is a bearing having an outer race. The race has a first end and a second end. The race includes a flange on the first end that is able to mate with a housing, and the race also includes an annular threaded portion on the second end. The threaded portion receives an annular threaded retaining element that mates with the housing. The race additionally includes an annular protrusion on the second end, concentric with the threaded portion, that is able to be swaged, thereby increasing a diameter of the protrusion to overlap the threaded portion.

Description:
FIELD 
       [0001]    The disclosure relates to the field of mechanical engineering, and in particular, to bearings. 
       BACKGROUND 
       [0002]    Aircraft utilize a variety of systems to adjust how air flows over a wing. For example, an aircraft may change the position of one or more flaps on the wing in order to adjust flight dynamics. The flaps themselves may be driven along tracks that are mounted to the wing. Many tracks utilize bearings at joints that connect the track to the wing. The bearings ensure that the tracks do not unduly apply torque or other stresses to the wing, even if there is a misalignment in the tracks. However, the bearings for tracks of aircraft wings operate under substantial load, and are also subject to high vibration. Because of these load characteristics, it is not uncommon for a bearing to rotate or even migrate within its housing over time. Thus, after a period of use, the bearing may be in need of replacement. 
         [0003]    Existing solutions to hold a bearing in place utilize retainer nuts that are threaded onto a race of the bearing to hold the bearing within its housing. However, threaded retainer nuts themselves are subject to loosening over time. To address this issue, nylon pellets (or other friction devices) may be used within the threading for a retainer nut to hold the retainer nut in place. However, the nylon pellets themselves are subject to wear due to the high levels of vibration in aircraft. This means that the nylon pellets degrade over time, which in turn means that the retainer nut loosens and the bearing migrates as flight hours accumulate on the aircraft. The maintenance and replacement of the bearings therefore undesirably increases the expense of maintaining the aircraft, particularly because many days of labor may be required to access the bearings of the tracks. 
         [0004]    For at least these reasons, users of bearings continue to desire mechanical systems that effectively retain a bearing within its housing, even after sustained periods of use at high load or vibration. 
       SUMMARY 
       [0005]    Embodiments described herein utilize swagable protrusions on a race of a bearing. The protrusions may be swaged onto a retaining element, such as a retainer nut, in order to fixedly attach the retaining element to the race. Because the swaged protrusion locks the retaining element to the bearing, the retaining element is not subject to loosening over time. This in turn increases the operational lifetime of the bearing. 
         [0006]    One embodiment is an apparatus that includes a bearing having a swagable race. The bearing includes an outer race. The race has a first end and a second end. The race also includes a flange on the first end that is able to mate with a housing for the bearing, and the race further includes an annular threaded portion on the second end. The annular threaded portion is able to receive an annular threaded retaining element that mates with the housing. Furthermore, the race includes an annular protrusion on the second end, concentric with the threaded portion, that is able to be swaged, thereby increasing a diameter of the protrusion to overlap the threaded portion. 
         [0007]    Another embodiment is an apparatus that includes a race that has been swaged. The bearing includes an outer race that has a first end and a second end. The bearing also includes an annular threaded retaining element mated with a housing for the bearing. The race includes a flange on the first end that is mated with the housing for the bearing. The race also includes an annular threaded portion on the second end. The annular threaded portion has received the retaining element. Additionally, the race includes an annular protrusion on the second end, concentric with the threaded portion, that is swaged, where a diameter of the protrusion overlaps the threaded portion. 
         [0008]    Another embodiment is a method. The method includes inserting a bearing, including an outer race, into a housing. The method further includes threading a retaining element onto the race of the bearing, wherein the retaining element is adapted to mate with the housing. The method also includes swaging an annular protrusion of the race onto the retaining element, thereby fixedly attaching the retaining element to the bearing. 
         [0009]    Other exemplary embodiments may be described below. The features, functions, and advantages that have been discussed can be achieved independently in various embodiments or may be combined in yet other embodiments further details of which can be seen with reference to the following description and drawings. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0010]    Some embodiments of the present disclosure are now described, by way of example only, and with reference to the accompanying drawings. The same reference number represents the same element or the same type of element on all drawings. 
           [0011]      FIG. 1  is a diagram illustrating an aircraft in an exemplary embodiment. 
           [0012]      FIG. 2  is a diagram illustrating a track for an aircraft in an exemplary embodiment. 
           [0013]      FIG. 3  is a diagram illustrating a side view of a forward fitting assembly of a track for an aircraft in an exemplary embodiment. 
           [0014]      FIG. 4  is a diagram illustrating a cut-away front view through a forward fitting assembly of a track showing the housing and bearing together with the attaching bolt for an aircraft in an exemplary embodiment. 
           [0015]      FIG. 5  is a perspective view of a housing of a forward fitting assembly together with a retained bearing in an exemplary embodiment. 
           [0016]      FIG. 6  is an exploded perspective view of a bearing and a housing in an exemplary embodiment. 
           [0017]      FIGS. 7-9  illustrate views of a bearing with a race that includes a swagable annular protrusion in an exemplary embodiment. 
           [0018]      FIGS. 10-12  illustrate views of a bearing with a race that has been swaged to retain a retaining element in an exemplary embodiment. 
           [0019]      FIG. 13  is a flowchart illustrating a method for installing a bearing in an exemplary embodiment. 
       
    
    
     DESCRIPTION 
       [0020]    The figures and the following description illustrate specific exemplary embodiments of the disclosure. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the disclosure and are included within the scope of the disclosure. Furthermore, any examples described herein are intended to aid in understanding the principles of the disclosure, and are to be construed as being without limitation to such specifically recited examples and conditions. As a result, the disclosure is not limited to the specific embodiments or examples described below, but by the claims and their equivalents. 
         [0021]      FIGS. 1-5  generally illustrate an exemplary system in which an enhanced bearing may be used.  FIG. 1  is a diagram of aircraft  100  in an exemplary embodiment. Aircraft  100  (e.g., a Boeing  747 - 8  series aircraft) includes wing  110 , onto which one or more flaps  112  are movably attached.  FIG. 2  illustrates track  200 , which supports flaps  112  and programs flap position and kinematic motion. Track  200  may be referred to as a “flap track.” Track  200  is attached to wing  110  via one or more fittings, such as forward fitting assembly  210 . Forward fitting assembly  210  may experience forces during flight as wing  110  flexes, particularly if there is any form of misalignment in how track  200  is installed onto wing  110 . To prevent these forces from transferring to wing  110  (which may unduly stress wing  110 ), forward fitting assembly  210  includes a bearing that allows components of track  200  to deflect/rotate as forces are applied to track  200 .  FIG. 3  is a diagram illustrating a side view of deflection with respect to forward fitting assembly  210  in an exemplary embodiment. In  FIG. 3 , the arrows indicate exemplary directions along which components of track  200  may deflect with respect to forward fitting assembly  210 . 
         [0022]      FIG. 4  is a diagram illustrating a cut-away front view through the forward fitting assembly  210  showing the housing and bearing together with the attaching bolt in an exemplary embodiment.  FIG. 4  shows that forward fitting assembly  210  includes housing  410 , and bearing  420 . Bearing  420  allows components of track  200  to misalign without transferring the resulting load to wing  110  of aircraft  100 . For example, in  FIG. 4 , the arrows indicate additional exemplary directions along which components of track  200  may deflect with respect to forward fitting assembly  210 .  FIG. 5  further illustrates both housing  410  and bearing  420 . 
         [0023]    Because flight operations may impart both heavy load and high vibration to bearing  420 , it is desirable to mount bearing  420  into housing  410  in a manner that ensures bearing  420  will not unexpectedly rotate or migrate with respect to housing  410 . Bearing  420  has been enhanced with swaging features that ensure that retaining elements used to hold bearing  420  in position (e.g., retainer nuts, jam nuts, washers, retainer clips, etc.) will not move under load. 
         [0024]      FIG. 6  is an exploded perspective view of bearing  420  and housing  410  in an exemplary embodiment.  FIG. 6  illustrates that bearing  420  comprises what is commonly referred to as a spherical bearing. Spherical bearings are a family of bearings that incorporate a ball with a substantially spherical outer diameter. Spherical bearings may be sliding surface bearings or rolling-element bearings (e.g., bearings that utilize tapered rolling elements). The inner diameter of a ball of a spherical bearing is typically cylindrical. In spherical bearings that utilize one-piece balls, the outer race of the bearing is typically formed around the ball. For multiple-piece balls, the outer race is typically machined and the bearing may be assembled and separated as desired. 
         [0025]    Bearing  420  includes spherical ball  610  and race  620 , which retains spherical ball  610 . As used herein, the term “spherical ball” is used to refer to ball  610 , even though ball  610  includes a cylindrically hollow passage/cylindrical cavity, because the phrase “spherical ball” is widely appreciated by those familiar with bearings to refer to components that are similar in shape and function to ball  610 . Ball  610  may, for example, be constructed as one piece or multiple pieces. When bearing  420  is inserted/slid into housing  410  from the left, retainer nut  630  is threaded onto race  620  and torque is applied in order to ensure that bearing  420  is not slid/driven back out of housing  410 . 
         [0026]      FIGS. 7-9  illustrate views of a bearing with a race that includes a swagable annular protrusion in an exemplary embodiment.  FIG. 7  illustrates a perspective cut-away view, while  FIG. 8  illustrates a side cut-away view and  FIG. 9  illustrates a front view. According to  FIG. 7 , bearing  420  includes ball  610 , which moves within race  620 . Race  620  defines a circular opening on each of its ends (i.e., race  620  includes a cylindrical passage), through which an axial rod may be inserted through ball  610 . When mounted in housing  410 , race  620  resists axial loads applied by such an axial rod to ball  610 . 
         [0027]    Race  620  includes mating feature  626  (e.g., a circumferential flange defined by a chamfer or bevel, a series of radial flanges, square lip, etc.) which mates with a corresponding feature on housing  410 , preventing race  620  from exiting housing  410  when race  620  is pushed towards the right within housing  410 . However, race  620  does not include a similar feature on the opposite side, which means that race  620  may be inserted/slid into housing  410 . To secure race  620  (and therefore bearing  420 ) on the right hand side, retainer nut  630  is threaded onto annular threaded portion  624  of race  620 . Retainer nut  630  includes a locking feature  632  (e.g., a chamfer, bevel, square lip, etc.) that mates with a corresponding feature of housing  410 , resisting forces that are applied when bearing  420  is pushed towards the left within housing  410 . Retainer nut  630  also includes tool features  636  (e.g., slots, lugs, holes, etc.) to accept torque from an installation tool (e.g., a special wrench) while being installed/threaded onto race  620 . 
         [0028]    Race  620  also includes an annular protrusion  622  (e.g., a ridge, lip, etc.) that is concentric with annular threaded portion  624 . Annular protrusion  622  may be swaged to overlap/cover/deflect/flare out onto circumferential feature  634  (e.g., a chamfer, bevel, etc.) of retainer nut  630 . This means that once annular protrusion  622  has been swaged, retainer nut  630  becomes fixedly attached to race  620 , and therefore to housing  410  Annular protrusion  622  may comprise any suitable protrusion capable of being swaged onto retainer nut  630 . As such, it may be desirable for annular protrusion  622  to be made from a material having sufficient ductility (e.g., capable of withstanding approximately 11% or more elongation) and also strength (e.g., an alloy of aluminum, steel or bronze, etc.) to withstand the swaging process. 
         [0029]    In one embodiment, annular protrusion  622  may comprise a machined “V-groove” on race  620 , annular protrusion  622  may comprise a cast ridge or lip on race  620 , or annular protrusion  622  may comprise a 3D-printed feature on race  620 . The race  620  and annular protrusion  622  may be swaged over retainer nut  630  using any desired swaging tooling as a matter of design choice. For example, when annular protrusion  622  comprises a V-groove, an outer wall of the V-groove may be swaged outward. 
         [0030]    In a further embodiment, annular protrusion  622  may comprise a series of concentric swagable arcs that are separated by gaps. The swagable arcs, together with the gaps, form an annulus, similar in nature to a ring defined by a dashed line. For example, in this embodiment protrusion  622  may comprise a series of semi-circumferential (e.g., interrupted) swaging grooves. Such a protrusion  622  may still be effectively swaged with a single application of a swaging tool, because the swagable arcs share a common center point and radius. 
         [0031]    Any suitable form of swaging may be used to deform protrusion  622 . For example, any of a Roller Swage, Anvil Swage, Ball Stake or Line Stake may be applied in order to accomplish permanent deformation of protrusion  622  into circumferential feature  634  (e.g., a circumferential lip). Roller swaging utilizes a rotating series of rollers to apply pressure to protrusion  622 , and may be used to ensure a substantially even application of pressure to protrusion  622 , even if there are physical inconsistencies in the dimensions of the swaging tool or protrusion  622 . In anvil swaging, pressure is applied to protrusion  622  by directly pressing a lip or die. Anvil swaging may utilize tools that are more durable and less expensive than those used in roller swaging. Ball staking and line staking are similar to anvil swaging, except they apply pressure to protrusion  622  in concentric local areas in embodiments where protrusion  622  comprises a semi-circumferential series of interrupted concentric grooves/holes. 
         [0032]      FIGS. 10-12  illustrate views of bearing  420  wherein race  620  has been swaged to retain a retainer nut  630  in an exemplary embodiment. Specifically,  FIG. 10  illustrates a perspective cut-away view, while  FIG. 11  illustrates a side cut-away view and  FIG. 12  illustrates a front view. In  FIGS. 10-12 , annular protrusion  622  has been swaged onto circumferential feature  634  on retainer nut  630 . Specifically, the outer diameter of annular protrusion  622  has been increased beyond a thread diameter (e.g., an outer or inner thread diameter) of annular threaded portion  624  (and therefore beyond a thread diameter of retainer nut  630 ). Thus, any attempt to unthread retainer nut  630  encounters substantial resistance. This means that the swaging process effectively locks retainer nut  630  in place, regardless of heavy load or vibration. Additionally, use of swaging ensures that mechanisms for holding retainer nut  630  in place are not overly bulky or heavy and use a reduced amount of design space, which imparts a benefit to the fuel economy of aircraft  100 . Heavy items have a direct impact on fuel efficiency of aircraft  100 , while bulky items may impact the overall aerodynamics of aircraft  100 . 
         [0033]    Illustrative details of the operation of bearing  420  will be discussed with regard to  FIG. 13 . Assume, for this embodiment, that bearing  420  is about to be installed into forward fitting assembly  210  of track  200  of aircraft  100 . 
         [0034]      FIG. 13  is a flowchart illustrating a method  1300  for installing a bearing in an exemplary embodiment. The steps of method  1300  are described with reference to bearing  420  of  FIG. 4 , but those skilled in the art will appreciate that method  1300  may be performed for other bearings. The steps of the flowcharts described herein are not all inclusive and may include other steps not shown. 
         [0035]    In step  1302 , race  620  is inserted into housing  410 . Since race  620  includes a mating feature  626  on one side, but not the other, race  620  may be slid or thrust from one direction into housing  410  (e.g., until mating feature  626  is seated or touching housing  410  and resists further forces). 
         [0036]    In step  1304 , retainer nut  630  is threaded onto annular threaded portion  624  of race  620 . When fully threaded, locking feature  632  of retainer nut  630  mates with housing  410 , meaning that bearing  420  resists axial loads to the left and right. Retainer nut  630  may, for example, be torqued into place according to a specific standard in order to ensure that bearing  420  is properly seated and retained. 
         [0037]    In step  1306 , annular protrusion  622  of race  620  is swaged over/onto retainer nut  630 , which in turn ensures that retainer nut  630  will not migrate or loosen. This means that retainer nut  630  will continue to effectively restrain axial loads applied to bearing  420  over its operational lifetime. 
         [0038]    Using swaging techniques in the manner described above, a bearing can be kept from migrating or rotating in an unexpected fashion. Fixedly attaching a retainer nut that is normally removable provides a substantial benefit in this case. Many bearings in aircraft cannot be visually inspected externally because the bearings are nested inside of other structures. Utilizing the swaging features described herein ensures that retainer nuts do not come loose between periodic inspections of those nested bearings. This is particularly important because it may take days of labor to access a retainer nut for a track. Thus, it is desirable to ensure that the retainer nut stays in position for a long period of time without requiring maintenance. 
         [0039]    Although specific embodiments are described herein, the scope of the disclosure is not limited to those specific embodiments. The scope of the disclosure is defined by the following claims and any equivalents thereof.