Abstract:
A set of composite boss blocks for a rail car truck having equalizer arms and side frames uses a thermoset plastic resin system with a synthetic fiber reinforcement contained within the plastic matrix to handle severe loads under impact and vibration, in combination with set screw or pin extending through the mounting portion and well into the body of the boss block, a complementary wear pad also being usable.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     High capacity freight cars such as well car, depressed center, and straight flat cars, large tank cars and other types for transporting heavy special equipment, use trucks of suitable carrying capacity often arranged for equalized design. Typical trucks, include Buckeye Elasto-Cushion six wheel (three axle) trucks and use a combination of side frames and equalizer arms that extend from the location of the central axle. The equalizer arms and side frame portions bear on cast steel boss blocks having male and female sets mounted on the side frames and equalizer arms. The invention uses a combination of features to achieve a composite boss block set having improved performance and service life. 
     2. Description of Related Art 
     The existing steel boss blocks cause wear on the side frames and equalizers as well as wearing themselves. Other plastic wear parts performing functions of original equipment steel rail car parts are known, such as coupler carrier wear plates, (U.S. Pat. No. 4,344,541 entitled “Coupler carrier arrangement for railroad cars”) center bearing liners (U.S. Pat. No. 4,075,951 entitled “Self lubricating center bearing liner”) and brake beam guides (U.S. Pat. No. 4,480,721 entitled “Snap-on slide bearing for recessed type guide lugs of unit brake beams.”). These are cited as examples of the use of plastics, but do not contain the teachings of this specification for high load, mechanically fastened boss blocks. Their disclosures, however, are incorporated by reference as if fully set forth herein. 
     The AAR Manual of Standard and Recommended Practices Section D, Truck and Truck Details 8-300-95 at Page D-3, No. 23 covers these components and is incorporated by reference as if fully set forth herein. 
     SUMMARY OF THE INVENTION 
     The composite boss blocks of the invention may be made advantageously with a composite material that will prevent wear on faying surfaces as well as wear on themselves. The periodic build-up of contaminants and worn material and the need for replacement of the truck components causes mechanical inefficiency in the operation of the equipment and therefore a solution to this problem will prove very beneficial to the owners of cars using the three axle trucks. 
     The boss blocks of the invention are made from a new advanced bearing grade composite material sold under the trademark UltraComp. This material combines a proprietary thermoset plastic resin system with a synthetic fiber contained within the plastic matrix and is able to handle severe loads under impact and vibration. UltraComp remains self-lubricating throughout its bearing life. UltraComp is available from Tri-Star Plastics Corp. of 906 Boston Turnpike Shrewsbury Mass. 01545. A complementary wear pad can be used with, or in lieu of the composite boss block sets themselves. 
     The composite parts, formed and arranged as taught herein, and using the materials described, will reduce wear on interfacing surfaces of the truck at the location of the boss blocks. Relevant material properties of the preferred fiber reinforced resin are: Compressive Strength: 54,000 psi.; Coefficient of Friction on Steel:0.16, and Continuous Service Temperature: 260° F. 
     The static vertical load on each composite boss block pair is about 50,000 lbs. producing a pressure of about 2,941 psi. Using a vertical dynamic load of 2 g., this provides a factor of safety of 8.5. 
     Related to the composite boss blocks is an approach using the same materials in a different configuration. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of a six-wheel (three axle) truck. 
     FIG. 2 is a side elevational view of a six-wheel (three axle) truck. 
     FIG. 3 is a fragmentary elevational view of a typical boss block arrangement for a sixwheel (three axle) truck. 
     FIG. 4 is top plan view of the female boss block. 
     FIG. 5 is a side elevational view of the female boss block. 
     FIG. 6 is an end elevational view of the female boss block. 
     FIG. 7 is a side elevational view of the male boss block. 
     FIG. 8 is top plan view of the male boss block. 
     FIG. 9 is an end elevational view of the male boss block. 
     FIG. 10 is an end elevation showing a boss block wear pad. 
     FIG. 11 is a top plan view showing a boss block wear pad. 
     FIG. 12 is an end elevation showing a boss block wear pad in place with a boss block on a truck casting. 
     FIG. 13 is top plan view of the female boss block of the press fit pin embodiment. 
     FIG. 14 is a side elevational view of the female boss block of the press fit pin embodiment. 
     FIG. 15 is an end elevational view of the female boss block of the press fit pin embodiment. 
     FIG. 16 is a side elevational view of the male boss block of the press fit pin embodiment. 
     FIG. 17 is top plan view of the male boss block of the press fit pin embodiment. 
     FIG. 18 is an end elevational view of the male boss block of the press fit pin embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The male  10  and female  12  boss blocks as shown in the drawings, and described herein, are components in the Buckeye Elasto-Cushion six-wheel (three axle) truck  14 . These components (one male  10  and one female  12 ) comprise a set  16 , and are located at each of four locations  18  per truck—two locations  18  on each side—between the equalizer arms  20  and side frame assembly  22 . These components function together to provide a connection of the equalizer arms  20  and side frame assembly  22  in a manner which provides for vertical flexibility of the truck  14  to allow negotiation of vertical curves. The convex surface  30  of the male block  10  slides relative to the concave surface  32  of the female block  12  when an angle is produced between the two side frame halves  34 ,  36 . The original equipment boss blocks  38  are steel castings that experience rapid and costly wear in service on all interfacing surfaces. It will be understood that the steel boss block  38  illustrated in FIG. 12 is to emphasize the wear pad  50 . However, wear pads could also complement all-composite boss block sets, especially when wear on the side frame and equalizer have occurred as a result of the steel-on-steel contact of the prior art boss blocks  38 . 
     The design of the boss blocks  10 ,  12  of one embodiment of the invention incorporate a 1 in. diameter set screw  40  that provides additional shear strength to the retention feature of the parts. These screws  40  are rated such that it will require a shear load in excess of 40,000 lbs. to shear them off. That value is greater than that of the UltraComp material. Thus, should the boss assembly  42  see high shear forces one can expect some deformation of the composite material  44  before other failure modes occur. An improved embodiment uses a pin, as more fully described below, which maintains the pin in position should the composite material deform or work under load. 
     A complementary wear pad  50  can also be used advantageously. As shown in FIGS. 10-12, where an original equipment boss block  38  is used, or as an adjunct to the Ultra Comp formed material boss blocks  10 ,  12  such as for additional protection, as shims or the like. It will be noted that a serious drawback to the original equipment steel boss blocks  38  is that they not only wear the opposed boss blocks, but the base portions of the steel boss blocks  38  cause wear on the equalizer  20  and side frame  22  sections of the truck  14 . Thus, it has been discovered, instead of merely being a replaceable wear part, in fact the wear part itself causes wear on the parts it should be protecting. Accordingly, spacing wear pads  50  as shown in FIGS. 10-12 can serve to isolate the equalizer  20  and side frame  22  sections from the steel boss blocks  38 . As described above, wear pads  50  may also be used with the composite boss blocks  10 ,  12 . 
     The UltraComp material of the boss blocks and spacing wear pads has already proven itself in North American freight car applications such as hydraulic cushioning device guide rings and hand brake sleeve bearings. These applications have been in service for about four years with zero replacement and no significant wear. UltraComp is also being used as coupler pivot bearings in heavy rail transit. 
     The composite material  44  combines a thermoset plastic resin portion  52  with a thermoplastic synthetic fiber reinforcement  54 . In various rail car parts, numerous plastics with a variety of reinforcements have been attempted. 
     In operation boss block  10  and  12  each have a projecting cylindrical portion  60 ,  62  projecting from the side opposite their respective surfaces  30 ,  32 . Set screws  40  are threaded into the cylindrical portions  60 ,  62  to provide reinforcement against shear loads. Cylindrical portions mate with corresponding recesses in the side frames, as is know to one of ordinary skill as original equipment steel boss blocks  38  are installed in that manner. 
     During testing of the original set screw embodiment it has been determined that an alternative embodiment can provide improved durability and performance. In the improved embodiment, boss block  110  and boss block  112  have body portions  120 ,  122  formed in a counterbored shape to provide recesses  124 ,  126  to receive headed pins  128 . In order to maintain bearing surfaces  130 ,  132 , corresponding plugs  140 ,  142  are press fit in place. Thus, unlike the set screw  40 , that may be inserted into a threaded recess formed in the boss block, from the side opposite the surface, and relying on the threads to maintain it in position as the boss block material works, flexes or creeps under load, the headed pin  128  fits from the surface side. Thus the headed pin does not work free from the boss block  110 ,  112  in use as the plastic material works under load. Like the set screw, pings  128  are rated such that it will require a shear load in excess of 40,000 lbs. to shear them off. That value is greater than that of the UltraComp material. Thus, should the boss block  110 ,  112  have high shear forces imposed, deformation of the composite material will not diminish overall shear strength. 
     While the present invention has been disclosed and described with reference to a single embodiment thereof, it will be apparent, as noted above that variations and modifications may be made therein. It is also noted that the present invention is independent of the particular brand of rail car trucks being used, and is not limited to the a particular manufacturer&#39;s trucks. It is, thus, intended in the following claims to cover each variation and modification that falls within the true spirit and scope of the present invention.