Patent Publication Number: US-6708624-B2

Title: Side bearing with multi-purpose mounting points

Description:
BACKGROUND 
     This invention pertains to side bearings for a railway truck such as the well known three piece truck as commonly used in freight service. 
     Typically, a rail car body is rotatably supported at its opposite ends on the center bowls of respective truck bolsters. Each such bolster extends transversely of the track and is supported at its opposed longitudinal ends by springs carried by the respective truck side frames. 
     A railway truck bolster commonly carries a pair of side bearings which are spaced from the bolster center bowl toward the respective longitudinal ends of the bolster, and are secured thereto by mechanical fasteners such as bolts. Each side bearing engages a wear plate mounted on the car body to support the car body laterally outward of the bolster center bowl and thereby limit lateral car body rocking. 
     Certain types of side bearings, known as constant contact side bearings, are installed in a preloaded state to maintain continuous forceful engagement with the car body wear plate. A constant contact side bearing slides on the car body wear plate in operation to thereby provide frictional energy dissipation and assist in controlling the destructive, cyclic truck motion known as hunting. As the hunting phenomenon is well known and is discussed at length in the prior art, detailed description thereof is unnecessary here. Suffice it to note that in many known side bearings, the normal force for frictional energy dissipation is provided by resilient deformation of coil springs or other compliant elements such as elastomeric columns. The prior art of side bearings with resiliently deformable bearing elements includes those disclosed in, for example, U.S. Pat. Nos. 3,295,463, 3,957,318, 4,080,016, 4,712,487, 4,998,997, 5,207,161, 5,386,783, and 5,601,031. 
     SUMMARY 
     The present invention contemplates a side bearing wherein a side bearing cage is provided with through openings in the cage base to accommodate fasteners, for securing the cage to a railway truck bolster. One such opening can be provided in a cavity in the cage which houses an upstanding elastomeric column, or similar resiliently deformable bearing element. Such opening can be generally coaxial the center of the bearing cavity. Additionally, such opening can extend through an upwardly projecting boss located centrally in the base of the side bearing cage such that the boss can serve to locate and/or retain a lower end of the upstanding elastomeric column. Alternatively, the head of a fastener used to secure the bearing cage to the bolster via the opening can locate and/or retain the end of the bearing column. 
     The elastomeric bearing element can similarly be located and retained at its upper end by a cap member which engages the side bearing cage so that transverse loadings generally pass to the bolster from the cap member through the side bearing cage and are generally not carried by the elastomeric bearing element. 
     The structural configuration of the side bearing cage also permits mounting on a bolster such that a solid or rigid bearing element housed in the bearing cage, a roller for example, can be located near the midpoint of the bearing cage mounting points on the bolster, and thus typically the bolster centerline, which can be a useful feature in view of benefits related to symmetrical bearing loading. 
    
    
     These and other advantages of the invention will be more readily appreciated upon consideration of the following detailed description, and the accompanying drawings which are briefly described immediately below. 
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     FIG. 1 is an exploded perspective view of a side bearing according to one presently preferred embodiment of the invention; 
     FIG. 2 is a top plan view of the side bearing of FIG. 1 installed on a railway truck bolster, shown in fragmentary part; and 
     FIG. 3 is an enlarged sectional view taken on line III—III of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS 
     There is generally indicated at  10  in FIG. 1 a railway truck side bearing according to one presently preferred embodiment of the instant invention. Side bearing  10  includes a rigid base or cage  12 , for example a rigid metal casting or an assembly of cast and/or fabricated components, a rigid bearing element  14  such as a roller that is disposed in a first bearing cavity portion  16  of cage  12 , and a compliant bearing assembly  18  that is disposed in a second bearing cavity portion  20  of cage  12 . For the side bearing shown, the compliant bearing assembly  18  is comprised of an elongated, generally cylindrical, resiliently deformable element  22  having an axial through opening  24 , and a rigid cap  26 . Element  22  may be formed from any suitable elastomer, polyurethane for example. 
     As is known, a standard truck bolster may include two pairs of side bearing mounting holes, each pair being located generally symmetrically with respect to the bolster centerline and spaced 8½ inches apart on centers. Thus, the side bearing cage  12  can have a pair of corresponding mounting points for attachment thereof to the bolster. In FIG. 1, only one such mounting point is shown. Thus, a lug  28  extends from one end of cage  12  adjacent its lower extremity, and a hole  30  extends vertically through lug  28  to receive a bolt or other suitable fastener. Cage  12  includes a second such mounting hole  58  (FIG. 3) which is, in a typical application, spaced about 8½ inches from hole  30  to receive a second mounting bolt or other suitable fastener. 
     As shown in FIGS. 2 and 3, the upper surface  32  of a railway truck bolster  34  carries the side bearing  10  at a location spaced longitudinally of the bolster from the center bowl  36 . Thus, bolster surface  32  is provided with a two pairs of side bearing mounting holes, each pair being located generally symmetrically with respect to the bolster centerline, and commonly about 25 inches from the center of the bolster center bowl  36 . However, it is known that some bolsters can be provided with mounting pads (not shown), to which the side bearing cages  12  are attached, wherein the mounting pads are offset from the centerline of the bolster. In any case, each side bearing  10  is secured to upper surface  32  of the bolster, via the described mounting holes, by fastener assemblies  38  and  40  (FIG.  3 ), each comprising, for example, a nut and a bolt, although other fasteners, including non-threaded fasteners could be used. When thus secured to bolster  34 , side bearing  10  can engage a wear plate  42 , or other surface, of a car body  44  in frictional sliding engagement (FIG. 3) to thereby dissipate energy and assist in the control of hunting responses. 
     Fastener assembly  38  typically comprises a bolt  46  which passes through hole  30  in side bearing lug  28 , thence through a mutually aligned mounting hole  48  in bolster  34 , and can be secured by a nut  50 . As noted above, in accord with standard railway truck construction, bolster  34  includes a second through hole  52  for securing side bearing  10 , and the side bearing  10  includes a corresponding hole  58  located centrally in the bearing element cavity portion  20  of cage  12 . Hence, holes  52  and  58  are aligned to receive the fastener assembly  40  identified hereinabove, which may comprise a bolt  54  and a nut  56 , for securing side bearing  10  to bolster surface  32 . 
     Bearing element cavity portion  20  can include a generally cylindrical, upstanding sidewall portion  60  which confines elastomeric element  22  and cap  26 . In one presently preferred embodiment, a generally cylindrical, upstanding boss  62  projects upwardly from the base or floor  64  of cavity  20  and generally coaxially with respect to cylindrical sidewall  60 . Hole  58  extends coaxially within boss  62  and thus is coaxially disposed with respect to both sidewall  60  and boss  62 . When bolt  54  is installed in hole  58 , the head  66  of bolt  54  is retained atop boss  62  as shown. 
     As noted, elastomeric element  22  is comprised of a generally cylindrical, upstanding column having a coaxial through opening  24  whereby the lower end of elastomeric bearing element  22  fits over and surrounds boss  62  and bolt head  66 , and rests upon cavity floor  64 . It should be understood that the elastomeric element can also have a shape other than cylindrical. To accommodate such assembly, the bolt head  66  may be of any suitable geometry, although a conventional hex bolt certainly may be suitable, consistent with the requirements of convenient installation, retention, and removal of the side bearing on bolster  34 . 
     It will be further noted that although the cylindrical through opening  24  may be preferred in elastomeric element  22 , a suitable alternative not shown herein may be a blind opening extending coaxially from the lower end of elastomeric element  22  only so far as necessary to accommodate boss  62  and bolt head  66  in all anticipated modes of elastomeric element deformation. Also, the through opening  24  or blind hole may have a shape other than cylindrical. The geometric variation in the elastomeric column  22  may be limited by the resilient deformation requirements and properties necessary for proper functioning of the side bearing. 
     The provision of the hole  58 , and boss  62 , centrally within the elastomeric bearing cavity  20  and generally coaxial with the mounting hole  52  in the bolster can provide certain benefits. For example, it permits the bearing cage  12  to be mounted on the bolster  34  such that the rigid bearing member  14  is generally centered between the bearing cage  12  mounting holes  30  and  58 , which also typically corresponds to the centerline of the bolster—midway between the bolster  34  mounting holes  48  and  52 . This can be advantageous in view of the benefits related to symmetrical bearing loading. Additionally, the described structure serves to locate and/or retain the lower end of the elastomeric element  22  in spaced relationship with respect to the surrounding sidewall portion  60  of the elastomeric bearing cavity  20 . Alternatively, in this regard, it must also be understood that the boss  62  need not be provided, and the head of the bolt  54  can itself locate and/or retain the lower end of the elastomeric element  22 . Alternatively, it should be understood that neither a boss nor a protruding bolt head would necessarily be required, since the bottom of the elastomeric bearing cavity  20  could be configured, such as with a recessed portion or raised rib to locate and/or retain the lower end of the elastomeric element  22 . The recessed portion or raised rib could locate the lower end of the elastomeric  22  by cooperating either with the outer perimeter of the elastomeric element  22  or the blind/through hole. 
     Bearing cap  26  provides a corresponding locating and retaining function for the upper end of elastomeric element  22 . Accordingly, the cap  26  comprises a rigid, preferably unitary member having a top portion  68 , which may be generally circular, having an elongated peripheral skirt portion  70 , which also may be generally cylindrical, depending axially therefrom. A boss portion  72 , which may correspondingly be generally cylindrical, of the top portion  68  can extend coaxially with respect to skirt portion  70  sufficiently to provide a locating and retention element similar in function to boss  62  and bolt head  66 . Accordingly, boss  72  extends into the upper open end of through opening  24  in elastomeric element  22  (or alternatively, into an axial blind hole of suitable length) to thereby locate and retain the upper end of elastomeric element in a centered position with respect to cap  26 . 
     Skirt portion  70  is of an outside diameter to provide a close sliding fit with the adjacent, inner cylindrical surface  74  of cage sidewall portion  60 , and their mutually engaged cylindrical surfaces are suitably finished to accommodate such sliding. Moreover, the inside diameter of both sidewall portion  60  and skirt  70  is sufficiently larger than the outside diameter of elastomeric element  22  to maintain the element  22  in radially spaced relationship with respect to both, whereby elastomeric element  22  is isolated from transverse loading evolved by the frictional sliding engagement between the side bearing  10  and the wear plate  42  in operation. 
     More specifically, with skirt  70  in close sliding fit within sidewall portion  60 , transverse forces imposed on cap  26  during frictional sliding on wear plate  42  are carried via skirt  70  to sidewall  60 , and thence via bearing cage  12  and fastener sets  38  and  40  to bolster  34 . The elastomeric element  22  is thus isolated from such forces. 
     Bearing element cavity portion  16  is disposed adjacent to bearing cavity portion  20 , as shown in FIG. 3, and roller  14  is disposed therein. The cavity portion  16  includes a sloping surface  15  on which roller  14  is supported, and which slopes downwardly from its opposed ends to a low area  17  located generally centrally intermediate the opposed ends of surface  15 . 
     Roller  14  acts as a solid stop to limit vertically downward displacement of cap  26 , and hence to also limit vertical, compressive deformation of elastomeric column  22 . The resulting limitation on the normal force between cap  26  and wear plate  42  serves to establish a maximum frictional force that can be evolved therebetween, and hence ensures that the frictional restraint opposing truck rotation or yaw with respect to the car body will not exceed a predetermined maximum restraint. 
     Roller  14  rolls freely on surface  15 , and when not otherwise restrained, gravity causes it to come to rest at low area  17 . Due to the mechanical configuration of bearing cage  12 , and the scheme for attachment thereof to bolster  34  as described, the low area  17  may be located very close to the bolster centerline, and in any event closer thereto than other bearing elements in the assembly. This can be a preferred location for roller  14  in view of the benefits of bearing load symmetry. While the invention has been shown with a rigid bearing, such as a roller  14 , other embodiments without a rigid bearing may also be used. 
     According to the description hereinabove, we have invented a novel and improved side bearing for use on a railway truck. Of course, we have contemplated various modified and alternative embodiments of our invention, and certainly such would occur to others versed in the art once they were apprised of the invention. Accordingly, it is our intention that the invention should be construed broadly.