Abstract:
A caster includes a yoke for retaining a wheel, a bearing housing connected to the yoke and a replaceable shielded bearing occupying the bearing housing. The inner wall of the bearing housing is provided with a groove into which a retaining ring may be inserted to prevent the shielded bearing from escaping. A caster mounting assembly having a connecting member which passes through a central opening of the shielded bearing is configured to connect the yoke and the bearing housing to a rollable article, such as chair or table. In the event that the shielded bearing needs to be replaced, the caster may be disassembled, the retaining ring removed from the groove, a new shielded bearing substituted for the old shield bearing, the retaining ring replaced in the groove, and the caster reassembled.

Description:
RELATED APPLICATIONS 
     The present invention claims priority to U.S. Provisional patent application No. 61/355,135, filed Jun. 15, 2010, and also to U.S. Provisional patent application No. 61/380,543, filed Sep. 7, 2010. 
    
    
     BACKGROUND 
     The present invention is directed to a caster for a rollable article such as a chair, the caster having a replaceable shielded bearing. 
     SUMMARY 
     In one aspect, the invention is directed to a caster for a rollable article such as a chair. The caster includes a yoke having a wheel mounted thereto and a bearing housing fixed to an upper portion of the yoke. The bearing housing comprises an outer wall, an upper rim and an inner wall. A circumferential groove is formed in the inner wall proximate the upper rim. A replacement shielded bearing having a central opening formed therein is located in the bearing housing, and a retaining ring occupies the groove to prevent the shielded bearing from escaping the bearing housing. The caster further include a mounting assembly configured to connect the yoke and the bearing housing to the rollable article, the mounting assembly including a connecting member having a portion that passes through the central opening of the shielded bearing. 
     In another aspect, the invention is directed to a method of repairing a caster having a worn or damaged shielded bearing. The method comprises: disassembling a caster mounting assembly of a caster; removing a retaining ring from a groove of a bearing housing; replacing the worn or damaged shielded bearing with a new shielded bearing; inserting the retaining ring back into the groove; and reassembling the caster mounting assembly. 
     In yet another aspect, the invention is directed to a caster fork assembly comprising: a yoke having a wheel mounted thereto and a bearing housing fixed to an upper portion of the yoke. The baring housing comprises an outer wall, an upper rim and an inner wall; and a circumferential groove formed in the inner wall proximate the upper rim. The bearing housing also has a lower rim and the bearing housing has a lower rim; and the yoke comprises a pair of yoke sides connected to one another by the lower rim of the bearing housing. 
     In still another aspect, the invention is directed to a first kit comprising some of the aforementioned components. A second kit comprising the remaining aforementioned components may be manufactured and combined with the first kit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exploded view of one embodiment of a caster in accordance with a first embodiment of the present invention. 
         FIG. 2  shows an exploded view of one embodiment of a caster in accordance with a second embodiment of the present invention. 
         FIG. 3  shows an exploded view of one embodiment of a caster in accordance with a third embodiment of the present invention. 
         FIG. 4A  shows a perspective view of the bearing housing. 
         FIG. 4B  shows a side view of the bearing housing. 
         FIG. 4C  shows a top view of the bearing housing. 
         FIG. 4D  shows a bottom view of the bearing housing. 
         FIG. 4E  shows a cross-sectional view of the  FIG. 4C  taken along line  4 E- 4 E. 
         FIG. 5  shows a bottom perspective view of the yoke in combination with the bearing housing. 
         FIG. 6A  shows a bottom perspective view of the base plate seen in  FIG. 3   
         FIG. 6B  shows a side view of the base plate seen in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an exploded view of a caster  100  in accordance with one embodiment of the present invention. Caster  100  includes a caster yoke  102  having a pair of yoke sides  104   a ,  104   b . A wheel  110  is retained by the caster yoke  102  at the latter&#39;s spaced apart lower side portions  106   a ,  106   b , by means of wheel bolt  112 , washers  114  and wheel retaining nut  116  engaged to the wheel bolt  112 . In some embodiments, the wheel is a “crown-point” wheel (i.e., has a ground contact surface comprising a rounded cross-section, rather than a flat cross-section). 
     In some embodiments, and as seen in  FIG. 5 , the yoke sides  104   a ,  104   b  may be connected to one another at a top portion thereof by a lower rim  404  of a bearing housing  400 . In such case, the yoke sides  104   a ,  104   b  may be welded, brazed or otherwise permanently fixed to the lower rim  404  to the bearing housing  400 . 
     In other embodiments, the top portions of the yoke sides  104   a ,  104   b  may be connected to one another by a connecting strip formed of the same material as the yoke sides. In such case, the yoke sides and connecting material may be formed by stamping a flat metal sheet to form a yoke blank and then bending the strip-connected yoke sides  104   a ,  104   b  using a mandrel in a known manner. An opening may then be formed in the connecting strip to accommodate a bolt, pin or other fastener, as described further below, either before or after a housing affixed to the yoke to accommodate the shielded bearing, also as discussed further below. 
       FIGS. 4A-4E  shows one embodiment of a bearing housing  400 . The bearing housing  400  may have a generally cylindrical outer wall  402 , a lower rim  404 , an upper rim  406  and an inner wall  408  defining a passage through the bearing housing  400 . Provided on the inner wall  408  of the bearing housing, proximate the upper rim  406 , is a circumferential groove  410  configure to accommodate a retaining ring  130 . 
     The inner wall  408  of the bearing housing  400  may be provided with a circumferentially extending step  412  proximate the lower rim  404 . The step  412  projects in a radially inward direction of the bearing housing  400 . The step  412  is configured to support a bottom periphery of a cylindrical shielded bearing  120  thereon. Thus, the inner wall  408  of the bearing housing  400  may be considered to be a stepped inner wall. Between the step  412  and the lower rim  404 , the inner wall  408  has a reduced diameter lower portion  414 , whose diameter is smaller than that of the upper portion  406  of the inner wall  408 . 
     The lower rim  404 , in a side view thereof, is stepped, having two spaced apart cutouts  420   a ,  420   b  formed therein, resulting in two spaced apart raised sections  422 ,  424 . Each raised section  422 ,  424  is defined between two parallel step portions  426   a ,  426   b . Meanwhile, cutout  420   a  is defined by two collinear step portions  420   a  while cutout  420   b  is defined between two other collinear step portions  420   b , the two collinear step portions  420   a  being generally parallel to the two collinear step portions  420   b . Each cutout  420   a ,  420   b  has a downwardly facing corresponding abutment surface  428   a ,  428   b.    
       FIG. 5  shows one embodiment of how the yoke  102  may be constructed from the yoke sides  104   a ,  104   b  and the bearing housing. As seen in  FIG. 5 , the upper surface  105  of each yoke side  104   a ,  104   b  is in abutment with a downwardly facing abutment surface  428   a ,  428   b  of a corresponding cutout  420   a ,  420   b  formed in the lower rim  404  of the bearing housing. As stated above, the upper surface  105  of each yoke side  104   a ,  104   b  may be welded, brazed or otherwise permanently attached to the lower rim  404  of the bearing housing  400 . 
     In the assembled caster, a shielded bearing  120  is located in the bearing housing  400 , and the retaining ring  130  occupies the circumferential groove  410  to keep the shielded bearing  120  in place. The shielded bearing  120  may be a commercially available bearing having a generally cylindrical outer surface  122 , a central opening  124 , a generally annular top surface  126  surrounding the central opening  124  and a similarly annular bottom surface also surrounding the central opening  124  (and hidden from view in the figures). The shielded bearing  120  is selected to have an appropriate size and ABEC designation in light of its intended use. In one embodiment, the shielded bearing  120  has an ABEC-5 designation, a 1.375 inch OD outer surface and a 0.437 inch ID central opening  124 . 
     In the embodiment seen in  FIG. 1 , the caster  100  is mounted to a horizontally extending leg  600  (shown in phantom in  FIG. 1 ) of a chair or other piece of furniture, via the former&#39;s caster mounting assembly. As seen in  FIG. 1 , the caster mounting assembly  190  includes a bottom bolt  140 , a lower nut  146  and a lower washer  146 . The bottom bolt  140  includes a threaded bolt shaft  142  connected to a bolt head  144 . In the assembled caster  100 , the bolt head  144  can abut the bottom surface of the shielded bearing  120  which, as stated above, is kept in position by the retaining ring  130 . The lower nut  146  and lower washer  148  are mounted on the threaded bolt shaft  142 . In some embodiments, the lower nut  146  may abut the top surface  126  of the shielded bearing  120 , thereby serving as a spacer  146 , while the lower washer  148  may abut an underside of the leg tube  600 . The far end of the threaded bolt shaft  142  may pass through the leg tube  600  and be affixed thereto via upper washer  150  and upper nut  152 . 
     The caster  200  seen in  FIG. 2  is generally similar to the caster  100  of  FIG. 1  except for the caster mounting assembly. Therefore, the components in caster  200  which are identical to those in caster have not been labeled. 
     As seen in  FIG. 2 , the caster mounting assembly  290  includes a caster pin  240  having, at lower end thereof, a lower threaded portion  242  which passes through the central opening  124  of the shielded bearing  120  and threadingly engages a retaining nut  262  located below the shielded bearing  120 . 
     In addition to its lower threaded portion  242 , the caster pin  240  includes a lower shaft portion  244 , an upper shaft portion  246  and an enlarged spacer portion  248  between the lower shaft portion  244  and the upper shaft portion  246 . The enlarged spacer portion  248  has the largest diameter of any portion of the caster pin  240 . The caster pin  240  is provided with a narrowed neck portion  250  proximate its upper end  252 . The narrowed neck portion  250  is configured to receive a grip ring  272 . The caster  200  thus is mounted to a chair or other piece of furniture by insertion of the caster pin&#39;s upper end  252  into a suitable aperture configured to receive and retain the caster pin  240 . 
     In the assembled caster  200 , the retaining nut  262  may be in abutment with the bottom surface of the shielded bearing  120 . And in some embodiments, the spacer portion  248  may have a lower surface thereof abut the top surface  126  of the shielded bearing  120 . 
     The caster  300  seen in  FIG. 3  is generally similar to the caster  100  of  FIG. 1  and the caster  200  of  FIG. 2 , except for the caster mounting assembly. Therefore, the components in caster  300  which are identical to those in casters  100  and  300  have not been labeled. 
     As seen in  FIG. 3 , the caster mounting assembly  390  includes a bolt-on type base plate  340 . In some embodiments, the base plate  340  is made of steel. The base plate  340  includes a threaded shaft  342  projecting from its underside and a plate member  344  provided with a plurality of bolt holes  382 . 
     In the assembled caster  300 , the threaded shaft  342  passes through the central opening  124  of the shielded bearing  120  and threadingly engages a retaining nut  362  located below the shielded bearing  120 . In the assembled caster  300 , the retaining nut  362  can be in abutment with the bottom surface of the shielded bearing  120 . As best seen in  FIGS. 6A and 6B , the threaded shaft  342  may be provided near its base with a spacer  346 . The spacer  346  may be configured to abut the top surface  126  of the shielded bearing  120 . In some embodiments, the spacer  346  may have one-piece unitary construction with the threaded shaft  342  while in other embodiments the spacer  346  may be in the form of a nut threadingly engaged to, and located at the base of, the threaded shaft  342 . 
     From the foregoing, it should be evident that the fork assembly  107  comprising the yoke  102  having the housing  400  affixed thereto, the shielded bearing  120  and retaining ring  130  are common to all caster embodiments. Thus, a manufacturer, supplier or retailer may provide a first kit comprising: (a) a fork assembly  107  including the yoke  102  having the bearing housing  400  affixed thereto; (b) a retaining ring  130 ; and (c) the shielded bearing  120 , and may further provide a second kit comprising one of the caster mounting assemblies  190 ,  290  or  390 . A variation of this might be to provide a first kit comprising just the fork assembly  107  and the retaining ring, and a second kit comprising any one of the caster mounting assemblies  190 ,  290  or  390 , with the shielded bearing being sold separately. Thus, a manufacturer, supplier or retailer need not produce and/or carry all three embodiments of fully assembled casters  100 ,  200 ,  300 , but instead may only carry the aforementioned kits and/or individual components thereof. 
     Furthermore, a caster  100 ,  200 ,  300  in accordance with the present invention is amenable to repair in the event of damage to one or more of its components. For instance, if the shielded bearing  120  is worn or damaged, one may disassemble the caster mounting assembly, remove the retaining ring from the groove, replace the old shielded bearing with a new one, insert the retaining ring back into the groove, and reassemble the caster mounting assembly. Replacement of other components may also be performed, thereby obviating the need to toss out the entire caster in the event that a single component is worn or damaged. 
     The foregoing disclosure provides illustrative embodiments of the invention and is not intended to be limiting. It should be understood that modifications of the disclosed embodiments are possible within the spirit and scope of the invention, and the invention should be construed to encompass such modifications.