Abstract:
An improved side bearing for railway cars is provided that achieves improved tracking and curving by the limitation of rock of the railway car. The side bearing comprises a base with a generally upwardly extending wall portion. A cap comprising a top section with generally downwardly extending wall portion is provided. The cap extends into or around the wall section of the base. Two coil springs are provided within the base that extend to the underside and support the cap. An elastomer spring is also provided that is located within an least of one of the coil springs.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an improved side bearing for mounting on a railway car truck bolster that provides improved control to limit rock and roll characteristics of the railway car in service. 
     In a typical railway freight train, such as shown in  FIG. 1 , railway cars  212 ,  214  are connected end to end by couplers  216 ,  218 . Couplers  216 ,  218  are each received in draft sills  220 ,  222  of each respective car along with cushioning or draft gear assemblies not shown. Draft sills  220 ,  222  are provided at the end of the railway car center sill, and include center plates that rest in center plate bowls of railway car trucks  226 ,  228 . 
     As is better shown in  FIG. 2 , each typical car truck  226  includes a pair of side frames  230 ,  232  supported on axle-wheel sets  234 ,  236 . Bolster  238  extends between and is supported on springs  240  mounted on side frames  230 ,  232 . Bolster center plate  224  includes a central opening  242 . Side bearing pads  260  are provided laterally to each side of the center plate  224  on bolster  238 . Side frames  230 ,  232  comprise a top member  244 , compression member  246 , tension member  248 , column  250 , pedestal  254 , pedestal roof  256 , wheel axle bearings  258 , and bearing adapter  262 . Side bearings are commonly used on railroad car trucks. Such side bearings are typically located on the truck bolster such as on side bearing pads  260 , but may be located elsewhere on the bolster. 
     Typical side bearing arrangements are designed to control hunting of the railroad car. As a railroad car travels along the railroad track, a yaw excess motion can be induced in the railroad car truck. As the truck yaws, part of the side bearing is made to slide across the underside of a wear plate bolted to the railroad car body bolster. The resulting friction produces an opposing torque that acts to prevent such yaw motion. Another purpose of railroad car truck side bearings is control or limit the rock or roll motion of the car body. Most prior side bearing designs limited vertical travel of the side bearings. The maximum vertical travel of side bearings is specified in the Association of American Railroad Standards. 
     Accordingly, it is an object of the present invention to provide an improved side bearing which will limit the vertical rock or roll motion of the railway freight car. 
     It is another object of the present invention to provide an improved side bearing which will provide improved control over the rock or roll motion of an empty railway freight car. 
     SUMMARY OF THE INVENTION 
     A side bearing is provided with improved characteristics to enhance the performance of rail cars, especially in unloaded conditions. 
     One embodiment of a side bearing in accordance with the present invention includes a base having a bottom portion and a base wall structure extending generally upwards therefrom. The base wall structure forms a base receiving structure with a generally open centrally located top. The dual rate spring assembly is positioned in the base receiving structure. A first coil spring is positioned within a second coil spring and an elastomer spring. The second coil spring has a larger diameter and is located adjacent the inner surface the base wall structure. The first and second coil springs each have a preselected non-compressed height. 
     An elastomer spring of a generally cylindrical rod shape is positioned within the first coil spring. The elastomer spring has a non-compressed height that is less than the non-compressed height of the second coil spring, and in certain embodiments of the present invention, of a lesser height than the first coil spring. 
     A cap that is of a generally inverted cup structure has a top portion and a cap wall structure extending generally downward from the top portion. The cap wall structure forms the cap receiving structure having an open bottom. 
     The top portions of the first coil spring and the second coil spring extend into the cap receiving structure open bottom to support the cap. 
     The base is usually a unitary cast steel or cast iron structure, but could be fabricated. The cap structure is also usually a generally cast steel or cast iron unitary structure, but also in certain embodiments could be fabricated. 
     The first and second coil springs are typical steel coil springs. The elastomer spring is usually formed of a urethane polymer, or other suitable elastomer. 
     In another embodiment, a side bearing for use in a railway car truck is provided comprising a base having a bottom portion and a base wall structure extending generally upward therefrom. The base wall structure forms a receiving structure having an open top. 
     A first coil spring having a preselected non-compressed height is positioned in the base receiving structure. An elastomer spring of a generally cylindrical shape having a preselected non-compressed height less than the height of the first coil spring, is positioned within the first coil spring. A second coil spring having a preselected non-compressed height is positioned within the central opening of the cylindrical elastomer spring. 
     A cap having a top portion and a cap wall structure extending generally downward from the top portion is provided, with the cap wall structure forming a cap receiving structure having an open bottom. The top portions of the first coil spring and the second coil spring extend into the cap receiving structure open bottom to support the cap. 
     The base is usually a cast steel or cast iron unitary component, but could be a fabricated structure. The cap is also usually a cast steel or cast iron unitary component, but also could be fabricated. The coil springs are typical steel coil springs. The elastomer spring is usually formed of a urethane polymer. 
     In both embodiments, at the standard set-up height of 5 1/16 inches, the cap will not contact the elastomer spring under normal operating conditions for an empty or loaded railway car. The coil springs accordingly will support the cap and thusly the railway freight car bolster which extends across and above the railway truck bolster and has a lower structural portion that contacts the top of the side bearing cap. In a rock condition due to curving or other forces that the freight car is being subjected to, the appropriate side bearing coil springs will be compressed until the cap contacts the elastomer spring. Such elastomer spring will limit the rock of the railway freight car as the elastomer will have a selected load rating to increase the spring stiffness during further travel downward into or over the base of the side bearing. By limiting such downward travel of the cap, the rock of the railway freight car, especially in an unloaded condition, is kept within preselected design parameters. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, 
         FIG. 1  is a partial schematic of coupled ends of typical railway freight cars; 
         FIG. 2  is a perspective view of a typical railway car truck; 
         FIG. 3  is an exploded perspective view of one embodiment of a side bearing according to the present invention; 
         FIG. 4  is a cross sectional view of the first embodiment of the side bearing; 
         FIG. 4A  is a cross sectional view of a second embodiment of the side bearing; 
         FIG. 5  is an exploded view of a third embodiment of a side bearing; and 
         FIG. 6  is a side cross sectional view of the third embodiment of a side bearing; 
         FIG. 6A  is a side cross sectional view of a fourth embodiment of a side bearing. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIGS. 3 and 4 , a first embodiment of the side bearing according to the present invention is shown. Side bearing  10  includes a base structure  12 , which is comprised of a bottom portion  22  and a base wall  24  extending generally vertically upward therefrom. Base  12  is usually cast steel or cast iron unitary structure, but can be fabricated or machined as well. The shape of base  22  can be circular, somewhat rectangular, or somewhat oval or diamond shaped as the use dictates. 
     Cap  14  is seen to be comprised of a top portion  26  with a wall structure  28  extending generally downward from the outer edge of cap  14 . Again, cap  14  is usually a cast steel or cast iron unitary structure, but can be fabricated or machined as well. 
     Base  12  is seen to also include a base wall top stop surface  38  which is located at the top of base wall  24 . Similarly, cap  14  is seen to include a cap inner stop surface  30  which is formed by an inner surface within cap  14  and is adjacent and complementary to base wall top stop surface  38 . An elastomer spring  20  is seen to be formed in a generally cylindrical rod structure, with a bottom supported on side bearing pad  260  of bolster  238 . A first coil spring  16  is located outwardly from elastomer spring  20 . A second coil spring  18  is located radially outward from first coil spring  16 . Second coil spring  18  accordingly is adjacent the inner surface of base wall  24 . Cap inner center projection  32  is adjacent a top portion  21  of elastomer spring  20  as depicted in  FIG. 4 . First coil spring  16  and second coil spring  18  would be compressed by the downward travel of cap  14  to the point that cap inner center projection  32  would contact elastomer spring  20 . Such contact could occur in an unloaded car condition under a rock condition of railway freight cars  212  or  214 . Such contact with cap inner center projection  32  and top  21  of elastomer spring  20  would limit the rock of the railway freight car  212  or  214 . 
     It should be understood that under normal operation of railway freight cars  212  and  214  in an unloaded condition, cap inner center projection  32  will not contact top  21  of elastomer spring  20 . Accordingly, under normal operation of railway  212  and  214 , cap  14  would be supported by first coil spring  16  and second coil spring  18 . 
     First coil spring  16  would be of a typical length of about 5.63 inches with a load rating of about 1500 lb/in. Second coil spring  18  would be of a typical length of about 5.78 inches and a load rating of about 2500 lb/in. Such coil springs are typically steel coil springs that are readily available from suppliers such as ASF-Keystone, Inc. 
     Elastomer spring  20  is a typical polymer elastomer available from companies such as the Pennsy Corporation, and is seen to be comprised of a circular rod structure. Of course other cross sectional structures of elastomer spring  20  would be operable in this embodiment such as squares or multiple edges such as octagons, but as elastomer spring  20  is located within first coil spring  16 , a cylindrical rod structure would be preferred. 
     Referring now to  FIG. 4A , a second embodiment of the side bearing according to the present invention is shown. Side bearing  310  includes a base structure  311 , which is comprised of a bottom portion  322  and a base wall  324  extending generally vertically upward therefrom. Base  311  is usually a cast steel or cast iron unitary structure, but can be fabricated or machined as well. The shape of base  322  can be circular, somewhat rectangular, or somewhat oval or diamond shaped as the use dictates. 
     Cap  314  is seen to be comprised of a top portion  326  with a wall structure  328  extending generally downward from the outer edge of cap  314 . Again, cap  314  is usually a cast steel or cast iron structure, but can be fabricated or machined as well. Cap includes a lower edge  330 . 
     Base bottom portion  322  is seen to also include a base inner surface  334  which is located inward of base wall  324 . 
     Cap  314  extends downwardly and inwardly inside base wall  324  until cap wall lower edge  330  contacts base inner surface  334 . An elastomer spring  320  is seen to be formed in a generally cylindrical rod structure, with a bottom portion supported on side bearing pad  260  of bolster  238 . Elastomer spring support  321  is typically a metal cup like structure that supports elastomer spring  320 . A first coil spring  316  is located outwardly from elastomer spring  320 . A second coil spring  318  is located radially outward from first coil spring  316 . Second coil spring  318  accordingly is adjacent the inner surface of cap wall  328 . Cap inner center projection  332  is adjacent a top portion  321  of elastomer spring  320  as depicted in  FIG. 4A . First coil spring  316  and second coil spring  318  would be compressed by the downward travel of cap  314  to the point that cap inner center projection  332  would contact elastomer spring  320 . Such contact could occur in an unloaded car condition under a rock condition or railway freight cars  212  or  214 . Such contact with cap inner center projection  332  and top  321  of elastomer spring  320  would limit the rock of the railway freight car  212  and  214 . 
     It should be understood that under normal operation of railway freight cars  212  and  214  in an unloaded condition, cap inner center projection  32  will not contact top  21  of elastomer spring  20 . Accordingly, under normal operation of railway cars  212  and  214 , cap  14  would be supported by first coil spring  216  and second coil spring  318 . 
     First coil spring  316  would be of a typical length of about 5.63 inches with a load rating of about 1500 lb/in. Second coil spring  318  would be of a typical length of about 5.78 inches and a load rating of about 2500 lb/in. Such coil springs are typically steel coil springs that are readily available from suppliers such as ASF-Keystone, Inc. 
     Elastomer spring  320  is a typical polymer elastomer available from companies such as Pennsy Corporation, and is seen to be comprised of a circular rod structure. Of course other cross sectional structures of elastomer spring  320  would be operable in this embodiment such as squares or multiple edges such as octagons, but as elastomer spring  320  is located within the first coil spring  316 , a cylindrical rod structure would be preferred. 
     Referring now to  FIGS. 5 and 6 , a third embodiment of the present invention is shown. Side bearing  110  is seen to be comprised of base  112 , which includes base bottom portion  122  and base wall structure  124  extending generally upward therefrom. Base  112  is usually a cast steel or cast iron unitary steel structure but could be fabricated or machined as well. Base  112  is seen to also comprise a base top stop surface  138  which is adjacent and inner surface of base wall  124 . 
     Cap  114  is seen to be comprised of a top portion  126 , which has a cap inner center projection  132  extending downwardly from a center portion thereof. Cap  114  also includes cap wall  128  extending generally downward from the outer edge of cap  114 . Cap  114  is usually cast steel or iron but could be fabricated or machined as well. 
     Cap  114  wall  128  is seen to extend inward into base  112 . Cap inner stop surface  130  is located at the lower edge of cap wall  128 . Cap inner stop surface  130  is seen to limit the downward travel of cap  114  by contacting base top stop surface  138 . Although cap  114  is seen to travel downwardly with cap wall  128  extending into an open structure formed by base wall  124 , it is conceivable that in another embodiment of the present invention cap wall  128  could extend outward of base wall  124 . 
     A first coil spring  116  is seen to extend upwardly from cup shaped spring support  121  which itself is generally a steel structure. A top portion of first coil spring  116  is seen to extend upwardly to support the bottom inner surface of cap top  126 . Cap inner center projection  132  is seen to extend into a top opening of first coil spring  116 . An elastomer spring  120  is seen to be comprised of generally cylindrical open structure that is located radially outward from first coil spring  116 . Another way of describing this arrangement is to state that first coil spring  116  is located within the central opening of cylindrical elastomer spring  120 . The top of elastomer spring  123  contacts the underside of the cap  131  under a rock condition of railway freight cars  212  or  2 A. 
     A second coil spring  118  is seen to be located outwardly of elastomer spring  120 . Another way of describing this arrangement is to say that second coil spring  118  is located radially within both base wall structure  124  and cap wall structure  128 . 
     First coil spring  116  and second coil spring  118  are typical steel coil springs available suppliers from such as ASF-Keystone, Inc. The typical length of first coil spring  116  is about 5.63 inches with a typical load rating of about 805 lb/in. A typical length of second coil spring  118  is about 5.65 inches with a typical load rating of about 2500 lb/in. 
     Elastomer spring  120  is typically comprised of an elastomer polymer and is available from the Pennsy Corporation. 
     It should be understood that under normal operation of railway freight cars  212  and  214  in an empty or loaded condition, cap inner surface  131  will not contact top  123  of elastomer spring  120 . Accordingly, under normal operation of railway  212  and  214 , cap  114  would be supported by first coil spring  116  and second coil spring  118 . 
     Referring now to  FIG. 6A , a fourth embodiment of the present invention is shown. Side bearing  410  is seen to be comprised of base  412 , which includes base bottom portion  422  and base wall structure  424  extending generally upward therefrom. Base  412  is usually a cast steel or cast iron unitary steel structure but could be fabricated or machined as well. Base wall  424  is seen to also comprise a base top stop surface  434 . 
     Cap  414  is seen to be comprised of a top portion  426 , which has a cap inner center projection  432  extending downwardly from a center portion thereof. Cap  414  also includes cap wall  428  extending generally downward from the outer edge of cap  414 . Cap  414  is usually cast steel or iron but could be fabricated or machined as well. 
     Cap  414  wall  428  is seen to extend outwardly over base wall structure  424 . Cap inner stop surface  429  is located at an inner upper edge of cap wall  428 . Cap inner stop surface  429  is seen to limit the downward travel of cap  414  by contacting base wall top stop surface  434 . Although cap  414  is seen to travel downwardly with cap wall  428  extending over base wall  424 , it is conceivable that in another embodiment of the present invention cap wall  428  could extend inward of base wall  424 . 
     A first coil spring  416  is seen to extend upwardly from support on bolster side bearing end  260 . A top portion of first coil spring  416  is seen to extend upwardly to support the bottom inner surface of cap top  426 . Cap inner center projection  432  is seen to extend between first coil spring  416  and second coil spring  418  and adjacent the top of elastomer spring  420 . 
     An elastomer spring  420  is seen to be comprised of generally cylindrical open structure that is located radially outward from first coil spring  416 . Another way of describing this arrangement is to state that first coil spring  416  is located within the central opening of cylindrical elastomer spring  420 . The top of elastomer spring  420  contacts cap inner projection  432  under a rock condition of railway freight cars  212  or  2 A. 
     A second coil spring  418  is seen to be located outwardly of elastomer spring  420 . Another way of describing this arrangement is to say that second coil spring  418  is located radially within both base wall structure  424  and cap wall structure  428 . 
     First coil spring  416  and second coil spring  418  are typical steel coil springs available suppliers from such as ASF-Keystone, Inc. The typical length of first coil spring  416  is about 5.63 inches with a typical load rating of about 805 lb/in. A typical length of second coil spring  418  is about 5.65 inches with a typical load rating of about 2500 lb/in. 
     Elastomer spring  420  is typically comprised of an elastomer polymer and is available from the Pennsy Corporation. 
     It should be understood that under normal operation of railway freight cars  212  and  214  in an empty or loaded condition, cap inner projection  433  will not contact the top of elastomer spring  421 . Accordingly, under normal operation of railway cars  212  and  214 , cap  414  would be supported by first coil spring  416  and second coil spring  418 .