Abstract:
A railway truck side bearing with multi-purpose mounting points for securing the bearing cage with respect to a railway truck bolster.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention pertains to side bearings for a railway truck such as the well known three piece truck as commonly used in freight service.  
           [0002]    Typically, a rail car body is rotatably supported at its opposite ends on the center plates 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.  
           [0003]    A railway truck bolster commonly carries a pair of side bearings which are spaced from the bolster center plate 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 plate and thereby limit lateral car body rocking.  
           [0004]    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 U.S. Pat. Nos. 3,295,463, 3,957,318, 4,080,016, 4,712,487, 4,998,997, 5,207,161 and 5,386,783, among others.  
         BRIEF SUMMARY OF THE INVENTION  
         [0005]    The present invention contemplates a novel and improved side bearing wherein a side bearing cage is provided with through openings in the cage base to accommodate fasteners such as bolts, whereby the cage can be secured to a railway truck bolster. At least one such opening extends through an upwardly projecting boss located in the base of the side bearing cage such that the boss, together with the head of a bolt or other suitable fastener received in the through opening, serves to locate and retain the lower end of an upstanding elastomeric column or similar resiliently deformable bearing element.  
           [0006]    The elastomeric bearing element is similarly located and retained at its upper end by a cap member, and the cap, in turn, engages the side bearing cage in a manner that all transverse loading passes between them without being carried by the elastomeric bearing element.  
           [0007]    The novel structural configuration of the side bearing permits its mounting on a bolster with a solid or rigid bearing element, a roller for example, to be located substantially at the bolster centerline. This is a useful feature in view of the benefits of symmetrical bearing loading.  
         OBJECTS OF THE INVENTION  
         [0008]    It is therefore an object of the invention to provide a novel and improved railway truck side bearing.  
           [0009]    Another object of the invention is to provide a novel and improved railway truck side bearing cage.  
           [0010]    A specific object of the invention is to provide a railway truck side bearing cage wherein a structural portion thereof provides the dual function of a mounting point for mounting the bearing cage to a railway truck bolster, and a structure that is cooperable with a resiliently deformable bearing element for location and retention thereof in the bearing cage.  
           [0011]    Another object of the invention is to provide a railway truck side bearing wherein an elastomeric bearing element is isolated from transverse loadings evolved in operation by frictional sliding engagement between the side bearing and the car body wear plate.  
           [0012]    Yet another object of the invention is to provide a railway truck side bearing wherein a rigid bearing element which acts as a solid stop is located adjacent to the bolster centerline and closer thereto than other bearing elements.  
           [0013]    These and other objects and 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  
       [0014]    [0014]FIG. 1 is an exploded perspective view of a side bearing according to one presently preferred embodiment of the invention;  
         [0015]    [0015]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  
         [0016]    [0016]FIG. 3 is an enlarged sectional view taken on line  111 - 111  of FIG. 2. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]    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  
         [0018]    As is known, a standard truck bolster may include two pairs of side bearing mounting holes, each pair being located symmetrically with respect to the bolster centerline and spaced 8½ inches apart on centers. Thus, side bearing cage  12  includes a pair of corresponding mounting points for attachment thereof to the bolster of a railway truck. 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 bore  30  extends vertically through lug  28  to receive a bolt or other suitable fastener. Cage  12  includes a second such mounting point (not shown in FIG. 1 but shown in other figures and described in greater detail hereinbelow) which is spaced 8½ inches from bore  30  to receive a second mounting bolt or other suitable fastener.  
         [0019]    Referring now to 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 plate  36 . Thus, bolster surface  32  is provided with a two pairs of side bearing mounting holes, each pair being located symmetrically with respect to the bolster centerline, and commonly 25 inches from the center of the bolster centerplate. The side bearing  10  is secured to upper surface  32 , via the described mounting holes, by fastener assemblies  38  and  40  (FIG. 3), each comprising, for example, a nut and a bolt. When thus secured to bolster  34 , side bearing  10  engages a wear plate  42  of a car body  44  in frictional sliding engagement, as shown in FIG. 3, to thereby dissipate energy and assist in the control of hunting responses.  
         [0020]    Fastener assembly  38  comprises a bolt  46  which passes through bore  30  in side bearing lug  28 , thence through a mutually aligned mounting bore  48  in bolster  34 , and is secured by a nut  50 . As noted above, in accord with standard railway truck construction, bolster  34  includes a second through bore  52  for securing side bearing  10 , and the side bearing  10  includes a corresponding bore  58  located centrally of bearing element cavity portion  20  of cage  12 . Hence, bores  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 .  
         [0021]    Bearing element cavity portion  20  includes a generally cylindrical, upstanding sidewall portion  60  which confines elastomeric element  22  and cap  26 . 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 . Bore  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 bore  58 , the head  66  of bolt  54  is retained atop boss  62  as shown.  
         [0022]    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 . 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 and removal of the side bearing on bolster  34 .  
         [0023]    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. 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. It is also preferred that a close transverse fit be maintained in the assembly of elastomeric element  22  over boss  62  and bolt head  66 .  
         [0024]    The described structure serves to locate and retain the lower end of elastomeric element  22  in spaced relationship with respect to the surrounding sidewall portion  60  of bearing cavity  20 . 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 generally circular top portion  68  with an elongated, generally cylindrical peripheral skirt portion  70  depending axially therefrom. A cylindrical boss portion  72  of top portion  68  extends 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 bore of suitable length) to thereby locate and retain the upper end of elastomeric element in a centered position with respect to cap  26 .  
         [0025]    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 all transverse loading evolved by the frictional sliding engagement between the side bearing  10  and the wear plate  42  in operation.  
         [0026]    More specifically, with skirt  70  in close sliding fit within sidewall portion  60 , all 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.  
         [0027]    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 point  17  located generally centrally intermediate the opposed ends of surface  15 .  
         [0028]    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.  
         [0029]    Roller  14  rolls freely on surface  15 , and when not otherwise restrained, gravity causes it to come to rest at low point  17 . Due to the mechanical configuration of bearing cage  12 , and the scheme for attachment thereof to bolster  34  as described, the low point  17  may be located very closely adjacent to the bolster centerline, and in any event closer thereto than other bearing elements in the assembly. This is a preferred location for roller  14  in view of the benefits of bearing load symmetry.  
         [0030]    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.