Patent Grant
7549379
The present invention related to an improved side bearing for mounting on a railroad car truck bolster that allows long travel, substantial weight reduction, improved hunting and curving characteristics, longer service life and various ease of installation features.
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.
Under certain conditions, undesirable wear is caused to the railroad car body bolster due to contact with the side bearings. Further, undesirable wear may occur within the side bearing itself when two metallic components are moving in contact with each other.
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, and M-948 for side bearings.
There also is a need for side bearings with better wear characteristics to increase service life.
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 having improved wear characteristics in contacting the freight car body bolster.
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, non-metallic inserts are provided in the flat top surface of the cap of the side bearing to reduce wear contact with the freight car body bolster.
In exemplary embodiments, non-metallic coatings are applied to the outer surface of the cap of the side bearing to reduce wear in the side bearing.
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.
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 about 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.
Further, in order to improve the wear of cap 120 top contact surface 128 against a freight car body bolster, top contact surface 128 includes a generally circular cut out section 119. Circular cut out section or well 119 is usually about 0.187 inch in depth. Further, a generally circular elastomer or other suitable non-metallic pad 122 is received in cut out section 119. Pad 122 is usually about 0.25 inch in thickness, so it typically protrudes from cut out section 119. Notches 129 can be provided around the edges of cut out section 119 to aid in the insertion of a tool to remove and replace elastomer pad 122. The actual depth of well 119 and the height of pad 122 are not critical; it is a part of the present invention that pad 122 protrudes above well 119.
Non-metallic elastomer pad 122 can be of several compositions. One such composition is a combination of carbon, rubber and strengthening fiber that is mold formed. Other non-metallic elastomeric compounds also would be operative.
Further, side walls 121 of cap 120 can be coated with a lubricant to reduce the wear of cap 120 within walls 116 of base 110. Such coating or sidewalls 121 can be a graphite lubricant impregnated into the metal surface or can be a hardening yet friction reducing coating such as titanium nitride. Similar coatings could be applied to the inside of walls 116 of base 110.
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 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 inside 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 116. 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.″
Further, base 110 is seen to have a generally cylindrical opening 147 that is centrally located between flange 112. As shown in
| Number | Name | Date | Kind |
|---|---|---|---|
| 7121212 | Schorr et al. | Oct 2006 | B2 |
| 20040187726 | Schorr et al. | Sep 2004 | A1 |
| 20050087092 | McKisic et al. | Apr 2005 | A1 |
| 20060042498 | Schorr et al. | Mar 2006 | A1 |
| 20080035012 | Monaco et al. | Feb 2008 | A1 |
| 20080035013 | Johnstone et al. | Feb 2008 | A1 |
| 20080115690 | Mitchell et al. | May 2008 | A1 |
| 20080173211 | Kennedy | Jul 2008 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20080035012 A1 | Feb 2008 | US |
