Patent Grant
7546807
1. Field of Invention
The present invention related to an improved side bearing design for mounting on a railroad car truck bolster that allows long travel, substantial weight reduction, improved hunting and curving characteristics, and various ease of installation features.
2. Description of Related Art
In a typical railway freight train, such as that shown in
As better shown in
Constant contact side bearings are commonly used on railroad car trucks. They are typically located on the truck bolster, such as on side bearing pads 60, but may be located elsewhere. Some prior designs have used a single helical spring mounted between a base and a cap. Others use multiple helical springs or elastomer elements. Exemplary known side bearing arrangements include U.S. Pat. No. 3,748,001 to Neumann et al and U.S. Pat. No. 4,130,066 to Mulcahy.
Typical side bearing arrangements are designed to control hunting of the railroad car. That is, as the semi-conical wheels of the railcar truck ride along a railroad track, a yaw axis motion is induced in the railroad car truck. As the truck yaws, part of the side bearing is made to slide across the underside the wear plate bolted to the railroad car body bolster. The resulting friction produces an opposing torque that acts to prevent this yaw motion. Another purpose of railroad car truck side bearings is to control or limit the roll motion of the car body. Most prior side bearing designs limited travel of the bearings to about 5/16″. The maximum travel of side bearings is specified by the Association of American Railroads (AAR) standards. Previous standards, such as M-948-77, limited travel to 5/16″ for many applications.
New standards have evolved requiring side bearings that have improved hunting, curving and other properties to further increase the safety and design of railcars. The most recent AAR standard is M-976 that now allows for longer travel side bearings and has several new requirements, such as new specifications for bearing preloads. Preload is defined as the force applied by the spring element when the Constant Contact Side Bearing is set at the prescribed height.
There is a need for improved side bearings for railroad cars that can meet or exceed these new AAR standards, such as M-976 or Rule 88 of the AAR Office Manual.
There also is a need for side bearings with better wear characteristics to increase service life, as a wear test has been added to AAR Standard M-948.
There further is a need for side bearings that can be designed for a particular application by incorporating design features that prevent interchangeability of incorrect components for that application.
There also is a need for a side bearing which maintains the preload force within 10% of the new condition for a long time. Preferably, this condition should be a minimum of 10 years or one million miles.
There also is a need for redesigned spring rates to improve handling characteristics of the truck and railroad car.
There also is a need for a standardized set of springs that can reduce parts inventories of various custom spring sizes.
The above and other advantages are achieved by various embodiments of the invention.
In exemplary embodiments, long travel can be achieved in a side bearing arrangement for railroad car trucks by a combination of features, including reduction of base and/or cap heights and/or reduction of the spring solid height to accommodate ⅝″ travel or more before the spring is fully compressed (solid) and before the base and cap bottom out.
In exemplary embodiments, substantial weight reduction is achieved by reducing sides and thicknesses of the base and cap in areas not needed for structural rigidity.
In exemplary embodiments, improved inspection capabilities are achieved by addition of an inspection slot to the base and increasing a corresponding side cutout in the cap to provide a viewing window of considerable size that allows inspection of the spring and other internal components of the side bearing during use. This feature also is able to achieve weight saving advantages over prior designs.
In exemplary embodiments, various design features are incorporated to the base and/or cap to prevent interchangeability with improper components. This may include features that allow mating of only matching base and cap components. Such mating may further include features that prevent improper orientation of the base relative to the cap. Such interchangeability prevention features may further include features that prevent use of improper spring(s) with universal base and cap. Also, the springs can be wound in the opposite direction of the adjacent spring to preclude one spring interfering with the travel of this adjacent spring.
In exemplary embodiments, improved, longer fatigue life is achieved by increasing the hardness of the components from Grade C to Grade E, or by using cast iron components.
In exemplary embodiments, improved operation of the side bearing, including improved control and hunting characteristics, is achieved by careful control of longitudinal clearances between the cap and base. This has been found to be important to prevent excessive movement between the cap and base, as well as reduce associated impact forces, stresses and wear.
In exemplary embodiments, improved characteristics of the side bearing and service life are achieved by strategic placement of hardened wear surfaces. In exemplary embodiments, improved tracking, curving and load leveling characteristics are achieved without adversely affecting hunting characteristics by changing the spring constant to be within a predetermined range, preferably between 2500-4000 lb/in.
In exemplary embodiments, a standardized set of three different springs are provided that can be mixed and matched in various combinations to achieve different preload values for use in a multitude of applications, while reducing the need for special, custom-designed springs for each application.
In exemplary embodiments, a better contact surface arrangement with a car body wear plate is achieved by coping the cap corners and increasing the flatness of the cap top contact surface to improve wear characteristics, such as reduced gouging.
The invention will be described with reference to the following drawings, wherein:
A first embodiment of a side bearing according to the invention will be described with reference to
Base 110 is fixed to bolster 38 by suitable means. As shown, base 110 is bolted to bolster 38 by way of mounting bolts (not shown) passing through mounting holes 146 provided on base flanges 112.
As best shown in
To increase the travel length of the side bearing, walls 116 are reduced in total height by 5/16″ from prior designs, such as that used in U.S. Pat. No. 3,748,001. This helps to achieve greater travel of the spring before cap 120 and base 110 mate and prevent further travel. In an exemplary embodiment, base 110 has a total height of 4.188 in. (+/−0.030), with walls 116 extending approximately 3.626 in. above flange 112.
Referring to
Cap 120 is further provided with a top contact surface 128, lower stop edge 123, and lower recessed spring support surface 127. Preferably, all peripheral edges 129 are coped or rounded with a scoped or flat transition area 129A extending from top contact surface 128 to edge 129. This serves several purposes. It reduces weight of the cap. Moreover, by coping the corners, there is a better contact surface is made that abuts against a car body wear plate (unshown but located on the underside of a car body immediately above cap 120 in use). In particular, by having coped corners, it has been found that less gouging occurs on the car body wear plate when the cap slides and rotates in frictional engagement with the car body wear plate during use. To further assist in a better contact surface, top contact surface 128 is formed substantially flat, preferably within 0.010″ concave or 0.030″ convex to further improve wear characteristics. In particular, this bias reduces the chance of the edge “binding” against the wear plate and is easier to manufacture.
To assist in providing long travel of the springs, cap 120 is shortened similar to that of base 110. In an exemplary embodiment, cap 120 is shortened in height by 5/16″ over previous designs to allow further travel of spring(s) 130 before cap 120 and base 110 mate and prevent further travel. Cap 120 preferably has a total cap height of 3.875 in., with side wall 121 extending downward approximately 3.375 in. below lower support surface 127. This allows the cap to insert farther onto base 110 before lower stop edge contacts the inside surface of base 110.
As mentioned, the inventive side bearing cap 120 and base 110 can be used with one or more urging members, such as springs 130. To achieve long travel of at least ⅝″, it is preferably to reduce the spring solid height from that used in prior designs. This is because prior spring designs would have gone solid before ⅝″ of travel was achieved. That is, the individual spring coils would have compressed against each other so that no further compression was possible.
Although two springs per side bearing are described in the embodiments, the invention is not limited to this and fewer, or even more, springs could be used. In fact, the number and size of springs may be tailored for a particular application. For example, lighter cars will use a softer spring rate and may use softer springs or fewer springs. Similarly, multi-unit articulated cars may use lighter or fewer springs because such cars use four side bearings instead of two per truck. As such, the load carrying capacity of each must be reduced. Also, it has been found that better performance can be achieved through use of substantially stiffer spring constants than previously used. This has been found to provide a suspension system with a slower reaction time, which has been found to achieve improved tracking and curving, without adversely affecting hunting. This also has been found to result in reduced sensitivity to set-up height variations or component tolerances so as to achieve a more consistent preload on the truck system. This tends to equalize the loading and allow a railcar to stay more level, with less lean or roll both statically and dynamically.
To obtain longer fatigue life, the material used for base 110 and cap 120 can be Grade E steel or cast iron. To assist in longer service life, hardened wear surfaces are provided on the outside surfaces of base wall 116.
Additionally, in an exemplary preferred embodiment, to prevent excessive movements and accelerated wear, reduced longitudinal clearances between cap 120 and base 110 are provided by reducing the tolerances from prior values. This can be achieved, for example, by more closely controlling the casting or other formation process of the cap 120 and base 110 side walls. In a preferred embodiment, base 100 has a longitudinal distance of 7.000″ (+0.005/−0.015) between inside surfaces of side wall 116 and outside surfaces of side wall 121 of cap 120 have a longitudinal distance of 7.031″ (+0.000/−0.020). This results in a closely controlled combined longitudinal spatial gap having a minimum of 0.006″ and maximum of 0.046″. The minimum is achieved when base side wall 116 is at the maximum tolerance of 7.005″ and cap side walls 121 are at the minimum tolerance of 7.011.″ The maximum is achieved when the base side wall 116 are at the minimum tolerance of 6.985″ and the cap side walls 121 are at the maximum tolerance of 7.031.″
Because of the possibility of various spring combinations, it is desirable to provide a safety feature that prevents interchangeability of improper components for a given application. To achieve this, exemplary embodiments provide keying features on both the cap 120 and base 110 to prevent mismatch of components. Also, cap 120 can be provided with spring lockout features that prevent improper combinations of springs to be used.
Further, base 110 is seen to have a generally cylindrical opening 147 that is centrally located between flange 112. As shown in
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| 20040187726 | Schorr et al. | Sep 2004 | A1 |
| 20050087092 | McKisic et al. | Apr 2005 | A1 |
| 20080035012 | Monaco et al. | Feb 2008 | A1 |
| 20080035013 | Johnstone et al. | Feb 2008 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20080035013 A1 | Feb 2008 | US |
