Abstract:
A self-lubricating bearing assembly for supporting a load on a guide rail which includes a carriage having first and second ends, a guide surface adapter for translation atop the guide rail and an end cap assembly which mounts adjacent one of the ends of the carriage. The end cap assembly includes a seal and a lubricating assembly having a lubricating block made from a lubricant composition and a compression housing for enclosing a periphery of the lubricating block and for biasing the lubricating block against the guide rail to cause the lubricant to contact the rail.

Description:
This Application is A 371 of PCT/US99/09320 Apr. 29, 1999 which claims Benefit of Ser. No. 06/083555 Apr. 29, 1998. 
    
    
     BACKGROUND 
     The present disclosure relates to linear motion bearing assemblies which include components that are integrally attached to provide performance enhancing characteristics. More particularly, the present disclosure relates to linear motion bearing assemblies which include components designed to minimize the routine maintenance and enhance the performance characteristics of linear motion bearing assemblies. 
     TECHNICAL FIELD 
     Linear motion bearing assemblies or rolling element bearing assemblies of the type discussed herein are well known in the art and are typically utilized for the movement of machine parts, tools and masses. These assemblies typically include a bearing carriage mounted for movement along a shaft or along a modified Y-beam, I-beam or T-beam cross section rail. As used herein the terms rail and shaft are used interchangeably. Load bearing and return tracks are provided in association with the bearing carriage for re-circulating a plurality of rolling elements such as, for example, balls or rollers. These rolling elements travel alternately through the load bearing tracks and return tracks to facilitate movement of the bearing carriage along the rail with minimum friction. 
     The use of roller element bearings is especially conspicuous in the machine tool industry where requirements of accuracy, stiffness, reliability and repeatability are stringent. This type of bearing, e.g., U.S. Pat. No. 4,932,067, is typically constructed from monolithic components of both rail and carriage, with rolling elements (usually balls or rollers) disposed between the two bodies. See also U.S. Pat. No. 5,558,442. Provisions are commonly made for the circulation of the rolling elements via retainers, end caps, turnarounds or the like. Typically, provisions are also made for seals or devices intended to retain lubricant and prohibit the ingress of debris. 
     End caps are usually located on the ends of the bearing carriage and may have turnarounds formed therein for transferring the rolling elements from the load bearing tracks to the return tracks. The turnarounds typically comprise a semi-toroidal shaped track dimensioned and configured for the particular rolling element being employed. At the center of the semi-toroid, an internal guide may be provided to smooth the movement of the rolling elements in the turnarounds. 
     As can be appreciated, the operation and efficiency of a linear motion bearing is heavily influenced by the type of lubricant, the frequency the lubricant is introduced into the bearing and the amount of lubricant introduced. As a result, the performance of the bearing can be detrimentally influenced by the ingress of contaminants, such as machining chips, weld spatter, etc. 
     Linear motion bearing lubrication has typically been provided by  1 ) manual application by use of a grease gun or the like (See, for example, U.S. Pat. No. 4,932,067); 2) automatic lubrication via a centralized lubricant dispenser; or  3 ) through the use of rubber or synthetic resin impregnated with a lubricant and typically mounted on a carriage in position to contact a rail. (See, for example, U.S. Pat. Nos. 5,492,413, 5,494,354, 5,590,965 and 5,769,543.) Manual lubrication is very effective when the operator has access to the lubrication points. When access is limited, it is not unusual for that bearing to suffer a lubrication failure. Centralized lubrication is highly effective, but requires great expense and complication in the realization of the pump system,. the delivery lines and the attendant fittings. The lubricant impregnated rubber or synthetic resin blocks of the prior art typically require integral stiffeners or integral tensioners to facilitate uniform application of lubricant over time. The blocks are exposed to environmental conditions and contaminants. 
     Attempts have been made to address to these concerns and to provide self-lubricating properties to the bearing. U.S. Pat. No. 5,570,958 teaches a drawer slide type of bearing that contains a strip of lubricant-filled polymer. This strip of lubricating material contacts the rolling elements by incidental contact during re-circulation. Thus the rolling elements are intended to have sufficient lubricant on the surface as they enter the loaded region. 
     In the case of the &#39;958 patent, the incidental contact of rolling elements with the lubricating strip is not sufficient, over extended periods, to deposit consistent amounts of lubricant. Thus, under any but the least stringent applications, a lubrication failure would be expected. 
     Thus, it would be highly desirable to provide a linear motion bearing that is simple to assemble and acts in a consistent, self-lubricating fashion reducing environmental contamination and extending bearing life. Additionally, it would be highly desirable to provide a bearing that will remove debris attached to the rail, prohibit the ingress of contaminants and/or provide a simple means of attaching an end cap or the like for the same purpose. Lastly, it would be highly desirable to provide a bearing where these and other features may be added and/or deleted in a simple manner depending upon the particular bearing application involved. 
     SUMMARY 
     Accordingly, the present disclosure is related to linear bearings which provide an enclosed self-lubrication system, scraping ability, enhanced sealing and other features arranged in a simple building-block manner. Further, each of the above-mentioned features may be added or omitted from the building-block arrangement depending upon the particular bearing application involved. 
     One embodiment of the present disclosure includes a self-lubricating bearing for supporting a load on a guide rail which includes a carriage having first and second ends, a guide surface adapted for translation atop the guide rail and an end assembly which mounts to one of the ends of the carriage. The end assembly includes a seal and a self contained lubricating assembly using a polymer block made from a synthetic lubricant composition. The lubricating assembly also includes a radially compressive housing enclosing the perimeter of the polymer block and biasing the polymer block against the guide rail to cause the synthetic lubricant to lubricate the bearing. 
     In one embodiment, the biasing force is accomplished by providing a mechanical interface, e.g., a T-shaped detent or a V-shaped wedge, which engages a complimentary mechanical interface, e.g., groove, formed within the polymer block. In another embodiment, the compressive housing is selectively adjustable. 
     Yet in another embodiment, the lubricating assembly is engaged with the end assembly in a press-fit manner and includes a plurality of radial slits to facilitate press-fit engagement within the end assembly. Still other embodiments of the present disclosure include end assemblies which include scrapers for removing excess debris from the rail during translation and positioning disks, spacers and/or alignment racks for positioning the various components of the end assembly. 
     One embodiment includes a self-lubricating bearing having a carriage with a guide surface adapted for translation along the guide rail and an enclosed ring-shaped end housing which mounts to at least one of the ends of the carriage. The ring-shaped end housing includes a plurality of flexible fingers arranged in spaced array about an inner periphery of the end assembly. Each of the flexible fingers biases the polymer block against a portion of the rail to consistently lubricate the rail. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded, isometric view of a self lubricating linear motion bearing having multiple stacked components according to the present disclosure, 
     FIG. 2 a  is an end view of a stand-off of FIG. 1; 
     FIG. 2 b  is a side, elevational view of the stand-off of FIG. 1; 
     FIG. 3 is a front, elevational view of the lubed polymer of FIG. 1; 
     FIG. 4 is a front, elevational view of the seal of FIG. 1; 
     FIG. 5 is a front, elevational view of the spacer of FIG. 1; 
     FIG. 6 is a front, elevational view of the scraper of FIG. 1; 
     FIG. 7 is a front, elevational view of the compressive housing of FIG. 1; 
     FIG. 8 is a front, elevational view of the bellows attachment clip of FIG. 1; 
     FIG. 9 is an isometric view of an alternate embodiment of the lubed polymer block; 
     FIG. 10 is an alternate embodiment of a self-contained sealed housing for the lubricating assembly according to the present disclosure showing coil springs for regulating the contact pressure of the polymer against the guide rail; 
     FIG. 11 is an alternate embodiment of the lubricating assembly according to the present disclosure showing an enclosed compression member which biases the polymer against the guide rail while inhibiting contamination of the polymer and/or bearing assemblies; 
     FIGS. 12A and 12B show an alternate embodiment of the linear motion bearing of the present disclosure which includes a housed lubricating assembly having an aperture for receiving the circular shaft and a lubed polymer ring which is disposed within the inner periphery of the aperture for lubricating the bearing as it slides along the shaft; 
     FIGS. 13A and 13B show an alternate embodiment of the linear motion bearing of the present disclosure which includes a housed lubricating assembly having a lubed polymer interposed between a retaining ring and a positioning disk; 
     FIGS. 14A and 14B show an alternate embodiment of the linear motion bearing of the present disclosure which includes a self-contained alignment system of positioning rings and retaining rings for staging the various internal components of the enclosed lubrication assembly; 
     FIGS. 15A and 15B show an alternate embodiment of a pillow block having the polymer internally housed in the pillow block between the bushing and the seal with a compression ring/clip disposed within the polymer for biasing the polymer against the guide rail; 
     FIGS. 16 shows an alternate embodiment of a polymer block with a compression ring formed in a peripheral groove; 
     FIGS. 17A-17C show alternate embodiments of a coil-like compression member disposed within the polymer designed to fit atop a shaft; 
     FIGS. 18A-18B show alternate press-fit designs of the lubricating assembly; 
     FIG. 19 shows an alternate embodiment of the polymer having a series of heating wires integrally formed therein; and 
     FIGS. 20A-20C show alternate embodiments of the end assembly which include a series of foldable tabs which releasable retain the polymer within the end cap. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The drawings in which like reference numerals identify similar or identical components throughout several views, there is illustrated a linear motion bearing assembly with integral performance enhancing features in accordance with the principles of the present disclosure. Turning now to FIG. 1 which is an exploded view of one embodiment of the linear motion bearing  10  according to the present disclosure which includes a pair of fasteners  75  which pass through and mount a bellows clip  70 , scraper  65  (See FIG.  6 ), a spacer  60  (See FIG.  5 ), a seal  55  (See FIG. 4) and a pair of standoffs  35  (See FIGS. 2A and 2B) against an end cap  30  of a bearing carriage  20 . The scraper  65  removes excess debris and/or contaminants from the guide rail  25  as the linear bearing  10  translates along the rail  25 . The standoffs  35  facilitate mounting of a lubricating polymer block  50  (See FIG. 3) and a compressive housing  40  (See FIG. 7) between the end cap  30  and the seal  55 . The compressive housing  40  substantially encloses the perimeter of the polymer block  50  to protect the assembly from contamination and to inhibit evaporative losses of lubricant from the polymer block  50 . Housing  40  also promotes contact between the polymer block  50  and the rail  25  (FIG.  10 ). 
     Typically, a bellows clip  70  (See FIG. 8) is mounted between the fasteners  75  and the scraper  65 . It is envisioned that the polymer block  50  is impregnated with a lubricant to lubricate the bearing  10  and the housing  40  ensures consistent and constant contact between the rail  25  and the polymer block  50  as the polymer block  50  shrinks due to the lubricant weeping therefrom. Preferably, the lubricating polymer block  50  is made from a synthetic lubricant composition. 
     The end cap assembly  15 , made up of clip  70 , scraper  60 , seal  65 , polymer block  50 , housing  40 , end cap  30  and standoffs  35 , is mounted in a sequential stacked configuration to carriage  20  as shown. It is envisioned that the amount of inward or contractile force exhibited by the compressive housing  40  (See FIG. 7) correlates to the amount of lubrication deposited on the guide rail  25  for self-lubricating the linear motion bearing  10 . It is also contemplated that compressive housing  40  can be manufactured with varying contractile forces depending upon the desired amount of lubricant needed for a particular linear motion bearing  10 . Also, various lubricating polymers  50  can be employed and/or easily substituted depending upon the particular purpose and/or load requirements of the bearing  10 . 
     It is also envisioned that by manufacturing the end assembly  15  to include an internal self-lubricating system and by designing the end assembly  15  to easily mount to the end of the carriage  20  will greatly simplify the assembly process. In addition, in the case of a lubrication failure, the end assembly  15  can be easily replaced and a new end assembly  15  containing a new polymer block  50  can be easily mounted to the carriage  20 . The various components or combinations of the various components of the end cap assembly  15  can be easily substituted and/or replaced with alternate embodiments without departing from the scope of the present disclosure. For example and as illustrated in FIGS. 9-28, the components can be specifically designed for different rail cross-sections, e.g., I-beam, T-beam, Y-beam and circular, and end cap configurations. 
     More particularly and by way of example, FIG. 9 shows one embodiment of the lubricating polymer block  150  which is designed for use with a linear bearing having an I-shaped rail  25  such as the ACCUGLIDE® manufactured by Thomson Industries, Inc. It is contemplated that the polymer block  150  of FIG. 9 can be mounted within compressive housing  40  of FIG. 1, however, it is not beyond the scope of the present disclosure to use a differently shaped compressive housing  40  which is specifically designed and shaped to further enhance the lubricating characteristics of polymer block  150 . 
     FIG. 10 shows an alternate embodiment of the FIG. 1 linear motion bearing  10  having a lubricating assembly  255  which includes a generally rectilinear housing  252  having a top  256 , two L-shaped sides  257  and a back plate  258  which together encapsulate and retain two blocks of lubed polymer material  250  in opposing relation relative to one another by way of a plurality of lower and upper flanges  253  and  254 , respectively. The two L-shaped sides  257  depend from top  256  and each have an aperture  259  formed therein for receiving a coil spring  240  which selectively adjusts the biasing pressure of the polymer blocks  250  against the guard rail  25  which, in turn, lubricates the linear bearing  10 . It is envisioned that other types of mechanically adjustable interfaces could be employed to apply consistent biasing pressure to the polymer block  250 , e.g., a screw or a camming mechanism. 
     FIG. 11 shows an alternate embodiment of a lubricating assembly  355  which includes a generally rectilinear housing  352  having a top  356 , two L-shaped sides  357  and a back plate  358 . The sides  357  and the back plate  358  depend from the top  356 . The top  356 , sides  357  and back plate  358  cooperate to encapsulate and retain a polymer block  350  within housing  352 . The lower portion of each L-shaped side  357  includes an upwardly projecting flange  343  which abuts the distal ends  341  of a compressive housing  340 . Preferably, the distal ends  341  flare outwardly at a projection  347  which biases the polymer block  350  against rail  225  (See FIG. 10) which, in turn, operates to prevent block  350  from collapsing inward, prohibiting the assembly to rail  225 . Polymer block  350  preferably includes apertures  351  disposed therein for receiving fastening elements  75  (See FIG. 1) for mounting the lubrication assembly  355  to the carriage  20  (or end cap  30 ). 
     FIGS. 12A and 12B show an alternate embodiment of an end cap assembly  415  which is designed to mount directly to carriage  420  configured for movement along a shaft  525  (See FIG.  13 B). The end cap assembly  415  includes a generally rectilinear housing  452  defining a central bore  463  configured to receive shaft  525 . The end cap assembly  415  also includes a ring-shaped lubed polymer  450  and a ring-shaped seal  462  which are both seated within the bore  463  with the seal  462  facing outward. It is contemplated that the polymer block  450  will lubricate the bearing as it translates along the rail  525 . Preferably, seal  462  retains lubricant inside the assembly  415  and prevents contaminants from entering the bearing. Housing  452  includes apertures  451  disposed therein for receiving fastening elements  75  (See FIG. 1) for mounting the end cap assembly  415  to the carriage  420 . 
     FIGS. 13A and 13B show an alternate embodiment of the end cap assembly  515  designed to mount directly to carriage  520  which is configured for movement along shaft  525 . End assembly  515  includes a ring-shaped lubed polymer  550  interposed between a positioning ring  560  and a housing  564 . The housing  564  preferably includes flanges  557  which project radially from the housing  564  which each have an aperture  559  located therethrough for receiving fastening element  75  (See FIG. 1) to mount the housing  564  to the carriage  520 . A ring-shaped seal  562  is enclosed by the housing  564  preferably in a press-fit or similar manner. 
     FIGS. 14A and 14B show an alternate embodiment of the end cap assembly  615  which is designed to mount directly to the carriage  620  configured for movement along a shaft  625 . It is contemplated that stacking the various internal components provides a simple “building block” approach to assembling end cap assembly  615 . More particularly, end cap assembly  615  includes a housing  652  defining a large internal volume for enclosing the various components, e.g., the lubed polymer block  650 , scraper  665 , end seal  662  and positioning ring  626 . The housing  652  also includes an alignment rack  646  (See FIG. 14B) which stages the various components within the housing  652  to allow certain components, e.g., scraper  665 , to float while maintaining other components, e.g., polymer block  650  and end seal  662 , in a fixed manner within the housing  652 . It is contemplated that as the bearing  10  translates along the shaft  625 , the polymer block  650  will lubricate the shaft  625  and reduce friction, the scraper  665  will float and scrape accordingly to eliminate excess lubricant and unwanted debris from the shaft and the seal  662  will retain the lubricant inside the end cap assembly  615  in contact with the shaft  665 . 
     FIGS. 15A and 15B show an alternate embodiment of the end assembly  1115  which is designed to seat within a cavity formed in the ends of a pillow block  1120 . More particularly, pillow block  1120  includes a central bore  1163  which is sufficiently dimensioned to slidingly receive shaft  1125  therethrough and an annular groove  1152  dimensioned to seat end assembly  1115  therein. End assembly  1115  includes a ring-shaped lubed polymer block  1150  having a compressive member  1140  engaged therein for biasing the polymer  1150  against the rail  1125  to ensure adequate contact pressure for consistently lubricating the rail  1125 . A seal  1155  is also seated within annular groove  1152  to retain the lubricant within the end assembly  1115 . 
     FIG. 16 shows a polymer block  1150  having an annular groove  1157  formed therein which receives compressive member  1140 . 
     FIGS. 17A-17C show other alternate embodiments of the lubricating assembly  1355 , i.e., lubed polymer block  1350  and compressive member  1340  combination. More particularly and with reference to FIGS. 17A and 17B, polymer block  1350  is molded having an annular groove  1351  formed therein which seats compressive member  1340 . It is contemplated that compressive member  1340  ensures adequate contact pressure of the polymer block  1350  against the shaft  1325  for lubricating the shaft  1325 . FIG. 17C shows an alternate embodiment wherein the polymer block  1350  and corresponding coil-like compressive member  1340  are semi-circular in shape which is contemplated to reduce the frictional drag between the polymer block  1350  and the shaft  1325 . 
     FIG. 18A shows another alternate embodiment of the compressive member  1440  which includes an annular flange  1443  which flexes inwardly to bias the polymer block  1450  against the shaft  1125  and FIG. 18B includes a similar annular flange  1443  having a plurality of fingers  1447  which also flex inwardly to bias the polymer block  1450  against the shaft  1125 . 
     FIG. 19 shows an alternate embodiment of the lubricating assembly  1555  designed to engage a shaft (not shown). More particularly, lubricating assembly  1555  includes a semi-annular polymer block  1550  having a plurality of semi-annular wires  1540  integrally formed therein. The wires  1540  may act as heating elements to thermally induce emission of lubricant from the block  1550 . 
     FIGS. 20A-20C show alternate embodiments of end cap assembly  1615  which are designed to mount directly to a carriage (not shown). More particularly, end cap assembly  1615  includes a semi-annular end cap  1630  having a pair of flanges  1631  which radially project therefrom each including an aperture  1633  located therein for receiving fastening element  75  (See FIG. 1) to mount the end cap  1630  to the carriage. As best shown in FIG. 20B, end cap  1630  also includes a semi-annular staged groove  1637  which is dimensioned to receive lubed polymer block  1650  therein. Tabs  1639  bend to secure the polymer block  1650  within the end cap  1630 . FIG. 20C shows an alternate embodiment wherein both the flanges  1631  and the tabs  1639  bend; the flanges  1631  bend outwardly to mount the end cap  1630  to the carriage and the tabs  1639  bend inwardly to secure the lubed polymer block  1650 . The FIG. 20C embodiment includes staging tabs  1641  which also bend inwardly to form a staging area for seating and securing the lubed polymer block  1650 . 
     From the foregoing and with reference to the various figure drawings, those skilled in the art will appreciate that certain modifications can be made to the present disclosure without departing from the scope of the present disclosure. While particular embodiments of the disclosure have been described, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplications of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.