Railways – Track layers – Tie platers
Reexamination Certificate
2002-11-07
2004-09-21
Morano, S. Joseph (Department: 3617)
Railways
Track layers
Tie platers
Reexamination Certificate
active
06792871
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a railroad car energy absorption apparatus and, more particularly, to a railroad car energy absorption apparatus including a spring assembly having an elastomer spring element arranged in operable combination with structure for inhibiting localized heat deterioration of the elastomer spring element.
BACKGROUND OF THE INVENTION
An energy absorption apparatus is known to be utilized on a railroad car in various applications and between two masses. For example, an energy absorption apparatus is typically arranged in operable combination with a railroad car draft gear for absorbing forces between adjacent ends of railroad cars. A railroad car energy absorption apparatus is also commonly configured as a side bearing. A railroad car side bearing is typically disposed to opposite sides of a car body between a centerpiece or bolster of a wheeled truck and an underside of the railroad car body. During movement of the railcar, each side bearing acts as an energy absorption apparatus and furthermore serves to control or restrict “hunting” movements of the railcar.
Hunting is a phenomenon created by the wheeled trucks during movement of the railway vehicle over tracks or rails. The coned wheels of each truck travel a sinuous path along a tangent or straight track as they continually seek a centered position under the steering influence of wheel conicity. In traveling such a sinuous path, a truck will yaw cyclically in an unstable fashion with respect to the car body about an axis defined by a vertical centerline of the truck bolster. Hunting, and the resulting side or lateral translation or oscillation of the railway car body is of particular significance when the car is traveling in an empty condition at relatively high speeds, e.g., in excess of 45 miles per hour. Of course, the truck also tends to yaw or rotate quasi-statically with respect to the car body in negotiating curved sections of track. Suffice it to say, excessive hunting can result in premature wear of the wheeled truck components including the wheels. Hunting can also cause damage to lading being transported in the railroad car body.
Known railroad car energy absorption devices typically use compressed resilient members such as spring loaded steel elements or elastomeric blocks or columns or both. The spring loaded steel elements, utilizing a steel on steel friction interface, proved ineffective in some applications because of seizing and galling problems. Recently different forms of thermoplastic elastomers have advantageously been used to develop the necessary force absorption characteristics required for such railroad car uses. One such elastomer is marketed and sold by the Assignee of the present invention under the tradename “TecsPak”.
Regardless of the application, the buildup of heat in proximity to the thermoplastic spring is a serious concern. During operation of the railroad car and use of such energy absorption apparatus, heat develops. Unless such heat buildup can be controlled, however, the thermoplastic spring will tend to soften and deform, thus, adversely affecting the operable performance of the railroad component with which it finds utility. For example, as a wheeled truck yaws back and forth, an undersurface of the railcar body slides across and relative to a metal top plate of the side bearing which is biased against the undersurface of the railcar body by the elastomeric spring. The resulting friction advantageously produces an opposite torque which acts to inhibit yaw motion. Such resulting friction also typically causes an excessive amount of heat at the interface between the top plate and the underside of the car body. Such heat buildup often exceeds the heat deflection temperature of the thermoplastic spring. As used herein and throughout, the term “heat deflection temperature” means and refers to a temperature level at which the related component, regardless of its composition, tends to soften and deform.
When such localized heat created by the friction between the side bearing and the car body exceeds its heat deflection temperature, the elastomeric spring will tend to deform and/or, when the temperature is high enough, cause melting of the elastomeric spring. Deformation and melting of the elastomeric spring significantly reduces the ability of the spring to apply a proper preload force and, thus, decreases vertical suspension characteristics of the side bearing which, in turn, results in enhanced hunting of the wheeled truck. Enhanced hunting and/or unstable cyclic yawing of the truck increases the resultant lateral translation/oscillation of the railcar leading to a further increase in the levels of heat buildup and further deterioration of the elastomeric spring.
Thus, there is a need and continuing desire for a railroad car energy absorption apparatus having a spring assembly including an elastomeric spring arranged in operable combination with structure for inhibiting deterioration of the elastomeric spring resulting from localized heat.
BRIEF SUMMARY OF THE INVENTION
In view of the above, there is provided a railroad car energy absorption apparatus which is specifically designed to limit the adverse affects local heat has on such apparatus. In accordance with one aspect of the invention, a railroad car side bearing assembly is adapted to be disposed intermediate an elongated bolster and a car body of a railway vehicle. The side bearing includes a housing and a cap or top plate which is movable toward and away from the housing. Both the housing and cap include wall structure which, when the cap is arranged in operable combination with the housing, combine to define a cavity or void in the side bearing. An elastomeric spring is accommodated within the cavity between the housing and cap for urging the surface on the cap against the bottom of the car body. According to one aspect of the present invention, the housing wall structure and the cap wall structure are each configured to promote dissipation of heat away from the elastomeric spring thereby prolonging effective usefulness of the side bearing assembly.
The elastomeric spring is preferably formed from a thermoplastic elastomer capable of imparting a predetermined preload or force to the cap or plate of the side bearing assembly to inhibit hunting movements of the wheeled truck as the railroad car moves along the tracks. In a preferred embodiment, the elastomeric spring defines a generally centralized throughbore which opens at opposite ends in the direction of spring compression.
Preferably, the housing wall structure and the cap wall structure are each configured to limit generally horizontal shifting movements of the cap relative to a longitudinal axis of the housing. Moreover, the housing and cap are each configured to allow movement of the cap relative the housing while inhibiting rotation therebetween.
In a preferred embodiment, the housing wall structure has a noncomplete configuration toward a free end thereof In one form, the housing wall structure comprises only between about 30% and about 70% of a free end boundary of the housing wall structure. More specifically, the housing wall structure preferably defines openings arranged to opposed lateral sides of a longitudinal axis of the side bearing and which generally align with openings in the cap wall structure to permit air to move into the side bearing, around the elastomeric spring, and, ultimately, from the cavity whereby venting heat away from the elastomeric spring thereby prolonging usefulness of the side bearing assembly.
Preferably, the openings defined by the cap wall structure extend away from a planar surface of the cap and toward a free end of the cap wall structure for a distance measuring between about 35% and about 60% of a distance measured between the planar surface of the cap and the free end wall structure of the cap. Moreover, in a preferred embodiment, the planar car body engaging surface of the cap is configured to promote both free and forced convection of heat from the cavity wherein the el
Dillon Michael S.
Jensen Erik D.
O'Donnell William P.
VanMaldegiam Michael D.
Wilt Donald E.
Harbst John W.
McCarry, Jr. Robert J.
Miner Enterprises Inc.
Morano S. Joseph
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