Patent Application
20080035012
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
