Patent Application
20060042498
Certain aspects of an embodiment of the present invention relate generally to railway car trucks and, more particularly, to a side bearing to yieldably resist hunting motion of the truck with respect to the car body.
A railroad car typically includes a car body supported at each end by a wheelset truck that is confined to roll on rails. A standard railroad truck is usually configured in a three-piece arrangement consisting of a pair of laterally spaced sideframes, a bolster extending between the sideframes, and a pair of wheelsets located at opposite ends of the sideframes.
During normal operation, when the railway car is rolling along a straight section of track, the longitudinal axis of each truck bolster is perpendicular to the longitudinal axis of the car body. Each end of the car body is pivotally supported by a truck bolster so that it can rock and swivel relative thereto on a substantially vertical axis. This pivotal connection is typically made by center bearing plates and bowls transversely centered on the car body underframe and the truck bolster, respectively. Accordingly, the truck may turn or pivot on the center plate under the car body and, under certain dynamic conditions and car speeds during operation, the truck may tend to adversely oscillate in a yaw-like manner beneath the car body. This adverse oscillation is commonly referred to in the art as “hunting,” and it typically occurs when the rail car is lightly loaded and operating at speeds greater than 50 mph.
In order to increase the train speed at which such hunting begins, railway freight cars often incorporate devices referred to as side bearings. The side bearings are positioned on the truck bolster, outwardly of the center bowl. A side bearing typically includes a base that is fastened to the top of the bolster and a cap or top that is biased upwardly from the base by a coil spring or elastomer so as to contact bearing wear plates (or wedges) on the car body underframe. The side bearing provides a force between the car body and the truck to frictionally retard the adverse hunting conditions.
The side bearing is designed to exert a predetermined force at a specified “set-up” height. The set-up height measured by the vertical space between the top surface of the bolster and the car body side wearing plate (or wedge). At this height, the side bearing is designed to exert a predetermined force between the truck bolster and the car body underframe. As the cap is compressed towards the base, e.g. due to side to side movement of the car body relative to the truck, the force exerted by the spring increases.
In freight cars the set-up height is typically either 5 1/16 (5.0625) inches or 5 7/16 (5.4375) inches. As a result, side bearings are typically designed to have a set-up height which matches one of these common freight car set-up heights. Railway tank cars have a much smaller set-up height than do railway freight cars. A conventional tank freight car has a set-up height on but may vary the order of 2¾ (2.75) inches from 2½ to 3⅛ or less. As a result, conventional contact side bearings, which have set-up that exceed the set-up heights in conventional railway tank cars, cannot be used in railway tank cars. Hence, there are thousands of railway tank cars in use in the United States and elsewhere that are not equipped with side bearings that provide such a predetermined force between the truck bolster and the car body. As a result, any train with a tank car must generally travel at reduced speeds to prevent hunting from occurring. Hence, there is a need for a side bearing that has a reduced height.
According to certain aspects of an embodiment of the present invention, a side bearing provides a predetermined force between a truck bolster and a railway car body. The side bearing includes a cage member mounted on top of the bolster. The cage member includes an upwardly facing opening. An insert member is received within the opening and includes upwardly facing pocket sections. A top member is positioned above the insert member for vertical movement relative thereto. The top member has downwardly facing pocket sections. The insert member and top member pocket sections combine to form at least one pocket. Pockets of the insert and top members are sized in one embodiment so that the side bearing has a set-up height on the order of 2⅜ (2.375) inches. Resilient devices are positioned in each of the pockets for urging the top member upwardly relative to the insert member. The resilient devices may comprise at least one unitary elastomeric device positioned in each of the pockets. The side bearing components are preferably configured to provide up to ⅝ (0.625) inches of vertical displacement of the top member relative to the insert member, although more or less vertical travel can be provided depending on the application and embodiment.
As is shown in
The bolster 18 further includes a center bowl 22, which is connected with the body (not shown) of the railroad car (not shown) via a body bolster and center plate. During normal operation, when the railway car is rolling along a straight section of track, the longitudinal axis 24 of each truck bolster 12 is generally perpendicular to the longitudinal axis 25 of the car body. The car body is supported by each bolster 12 so that it can rock and swivel relative thereto on a substantially vertical axis.
As will be recognized, a railroad car generally has two such trucks 10, with each truck supporting one end of the car body. A pair of the side bearings 26 according to the present invention are mounted on opposite sides of the center plate 22 of a given truck 10. Hence, a given railroad car has four of the side bearings 26.
As is shown in
Cage member 28 is usually comprised of cast steel and includes a base portion 35 supported on the top surface side bearing pad of bolster 18. Cage member 28 also includes a raised section 37 that is of a generally rectangular shape and extends upwardly from base section 35. Raised section 37 has an opening 39 formed therein. Opening 39 is generally rectangular in shape and is upwardly facing.
Insert member 29 is usually comprised of cast steel and includes a base section 41, raised end section 43 and 45, and a raised center section 47. Insert member 29 is of a generally rectangular shape. Raised end section 43 and center section 47 combine to form pocket section 53. Raised end section 45 and center section 47 combine to form pocket section 55. Pocket section 53 and 55 are generally circular in shape, but could be square or rectangular based on design choice and the shape of resilient members 31.
Projection 49 is of a generally cylindrical shape and extends upwardly from a central position in pocket section 53. The outer edge of projection 49 is of a diameter greater than the diameter of the main cylindrical section of projection 49.
Projection 51 is of a generally cylindrical shape and extends upwardly from a central position in pocket section 55. The outer edge of projection 51 is of a diameter greater than the diameter of the main cylindrical section of projection 51.
Insert member 29 is of a longitudinal dimension such that a space is left at each end between raised end sections 43 and 45 and the internal surface 61 of raised section 37 forming opening 39.
Referring now also to
Projection 71 is of a generally cylindrical shape and extends downwardly from a central position in pocket section 81. The outer edge 77 of projection 71 is of a diameter greater than the diameter of the main cylindrical section of projection 71.
Projection 73 is of a generally cylindrical shape and extends downwardly from a central position in pocket section 79. The outer edge 75 of projection 73 is of a diameter greater than the diameter of the main cylindrical section of projection 73.
Resilient member 31 is of a generally cylindrical shape, with a centrally axially located base 32 extending therethough. Alternately, base 32 could extend only partially inwardly from the top and bottom surfaces. Also, resilient member 31 could be of a rectangular or square cross section.
Resilient member base 32 receives projection 71 from top member 30. Resilient member base 32 also receives projection 49 from insert member 29. Resilient member 34 is identical to resilient member 31 and is therefore not described with regard to its positioning in its pocket.
Resilient member 31 is received in pocket section 53 of insert member 29 and in pocket section 81 of top member 30.
End section 63 of top member 30 extends downwardly into the opening between raised end section 43 of insert member 29 and internal surface 61 of raised section 37 of cage member 28. Similarly, end section 65 of top member 30 extends downwardly into the opening between raised end section 45 of insert member 29 and internal surface 91 of raised section 37 of cage member 28.
Using a resilient elastomeric spring in each pocket is advantageous because it allows the desired forces to be achieved with a relatively short set-up height, e.g., on the order of 2¾ (2.75) inches or less. The set-up height is measured between the bottom face of the car body wear plate and the top surface of the side bearing pad of the truck bolster 18.
When the side bearing 26 is installed on the railway car, the springs 31,34 support the top member 30 for vertical movement relative to the cage member 28 between an upper position, corresponding to the set-up height and a lower solid position. According to one embodiment, the components of the side bearing 26 are configured to provide up to ⅝ (0.625) inches of vertical travel of the top member 30 relative to the cage member 28, with a set-up height of 2⅜ (2.375) inches.
Means are provided for aligning the cage and top members 28, 30, limiting downward travel of the top member relative to the base member, and for restricting relative horizontal movement, e.g. rotation, lateral displacement and longitudinal displacement, between these components when the side bearing is installed on the rail car. The means may include a post formed on the central portion either the top member 30 or the cage member 28. In the illustrated embodiment, a downwardly extending post 60 is formed on the central portion 50 of the top member 30. The post 60 is positioned to mate with a reciprocal aperture 62 in the central portion 35 of the cage member 28.
Resilient members 31, 34 are preferably comprised of a unitary elastomeric element. Such an element can be comprised of an elastomeric polymer.
