Patent Application
20210253143
The present description relates generally to systems for a rocker assembly for a side frame pedestal of a rail vehicle truck.
Rail vehicles (e.g., freight railroad cars) may include a car body and two spaced apart trucks. The car body or car body under frame may include two spaced apart center plates that respectively rest on and are rotatably or swivelly received by bolster bowls of the two trucks. The trucks rollingly support the car body along railroad tracks or rails. Each truck may include a three piece truck configuration that includes two spaced apart parallel side frames and a bolster. The side frames extend in the same direction as the tracks or rails, and the bolster extends transversely or laterally (such as perpendicularly) to the tracks or rails. The bolster extends laterally through and between and is supported by the two spaced apart side frames.
Each side frame may define a center opening and pedestal jaw openings on each side of the center opening. Each truck also includes two axles that support the side frames, four wheels, and four roller bearing assemblies respectively mounted on the ends of the axles. The truck further may include four bearing adapters respectively positioned on each roller bearing assembly in the respective pedestal jaw opening below the downwardly facing wall of the side frame that defines the top of the pedestal jaw opening. The wheelsets of the truck are thus received in bearing adapters placed in leading and trailing pedestal jaws in the side frames, so that axles of the wheelsets are generally parallel.
The interface between the wheelset bearings adapters and the roof of the pedestal jaw (also referred herein as pedestal) may impact railcar stability in terms of wheel load equalization, wheelset dynamic stability, steering, vibrating isolation, etc. As one example, there may be unacceptable trade-offs between steering performance (rolling resistance during curving) and hunting stability above a threshold speed (such as 65 mph).
In an embodiment, the issues described above may be at least partially addressed by a system for a rail vehicle truck that includes a pedestal rocker laterally movable about an axis perpendicular to an axle of a wheelset. The pedestal is positioned between a roof of a pedestal jaw of a side frame and a bearing adapter with a convex lower surface of the pedestal rocker in face sharing contact with a concave upper surface of the bearing adapter. In this way, by incorporating a rocker assembly in the adapter-pedestal interface, the warp stiffness or the resistance to un-squaring truck movement may be increased, and a certain degree of rolling motion between the adapter and the pedestal may be facilitated.
In another embodiment, a pedestal rocker may be sandwiched between a top surface of the bearing adapter and a roof of the pedestal jaw of the side frame. The pedestal rocker may have a curved, convex lower surface in face sharing contact with a curved, concave mating surface of the adapter. A recess (also referred herein as pocket) may be cast on the roof of the pedestal to receive the upper surface of the rocker. The rocker arrangement allows for a lateral movement of the pedestal rocker is a direction perpendicular to each of a direction of railway tracks on which the truck is positioned and another direction of an axle of a wheelset housed within the bearing adapter. Due to friction between the pedestal rocker and the mating valley of the adapter, metal dust may accumulate on the mating valley.
In this way, according to aspects of the invention, by incorporating a rocker assembly in the interface of the bearing adapter and the pedestal roof, un-squaring movement between the wheelsets and side frames may be resisted while allowing rolling motion of the side frames (roll, twist, and yaw) relative to the wheelsets. The rolling pendulum action provides a sink of kinetic energy that absorbs undesired lateral movements (such as due to track irregularities) instead of transmitting that energy into the dynamic response of the truck or the cargo itself. The technical effect of the convex shape of the lower surface of the rocker and the corresponding concave shape of the mating valley is that the metallic dust originating from friction may accumulate on the mating valley, thereby providing dry lubrication to the rocker arrangement.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
The FIGS are drawn to scale, although other relative dimensions may be used.
The following description relates to systems for a rocker assembly for a side frame pedestal of a rail vehicle truck. The railcar truck may be included in a freight railroad car as shown in
Each side frame may include two pedestal jaws at each end, a leading pedestal jaw (in the direction of motion of the railroad car) and a trailing pedestal jaw. The wheelsets of the truck are received in bearing adapters placed in openings framed by each of the leading and trailing pedestal jaws in the side frames. Each of the wheelsets has roller bearings and the side frames are seated upon the roller bearings including bearing adapters. In order to improve railcar stability, the interface between the wheelset bearings adapters and the roof of the pedestal jaw may include a rocker assembly as elaborated with reference to
Attempts for mechanical management of the adapter-pedestal interface may be categorized as one of frictional, electric, and swing motion. In examples, an adapter-pedestal interface relies on metal on metal friction and rolling contact (such as a pendulum action). The Association of American Railroads (“AAR”) specifies a flat pedestal roof surface and the adapters having a large radius convex crown to interface with the pedestal. Stress from the Hertzian contact between the flat roof and the adapter crown may be lowered in this approach. Resistance to swinging action of the side frame may also be higher and any deviation of the side frame from its equilibrium vertical position may be heavily biased back. Stick-slip friction within the pedestal-adapter interface may not always facilitate desired hunting and/or curving performance of the truck. A hunting oscillation may be characterized as a swaying motion of a railway vehicle caused by interaction of adhesion forces and inertial forces.
Further attempts for mechanical management of the adapter-pedestal interface may include use of various elastic components to provide an interface between the wheelset bearings adapters and the roof of the pedestal that provides resistance against an inherent instability of the conical wheelset, thereby elevating a “critical speed” of truck hunting while allowing desired axle-steering on curved track. An alternate truck system that does not rely on use of elastics may be a swing motion truck which may however be a cost ineffective system.
The pedestal rocker 212 may include a flat top surface 224 and a curved, convex, lower surface 222. The pedestal rocker 212 may extend along the L-L′ axis throughout the length of the opening 207 enclosed by the pedestal jaw 204 of the side frame. The longitudinal L-L′ axis of the pedestal rocker may be parallel to the A-A′ axis. Said another way, the longitudinal axis of the pedestal rocker 212 may be parallel to the direction of straight railway tracks on which the railroad car truck is positioned. The top surface 210 of the bearing adapter 206 may be a curved, concave surface providing a mating valley for lower surface 222 of the rocker 212. The radius of curvature of the top surface 210 may be higher than the radius of curvature of the lower surface 222 of the rocker 212 such that upon face sharing contact of the rocker 212 with the top surface 210 of the adapter, a rocking motion of the pedestal rocker 212 may be facilitated in a lateral direction (perpendicular to A-A′). In one example, the radius of curvature of the lower surface 222 of the rocker 212 may be in the range of 2-3 inches while the radius of curvature of the top surface 210 of the adapter may be 3-4 inches. The rocking or swinging motion of the pedestal rocker 212 may be about the L-L′ axis of the rocker 212. Further, the rocking motion of the pedestal rocker 212 may be in a direction perpendicular to a B-B′ axis of an axle of a wheelset received in the opening 218 framed by the bearing adapter 206. By allowing the swinging motion of the rocker, high performance trucks may maintain stability and reduce drag while travelling through curves. Steering displacements during entrance into, and exit from, curved track sections may manifest as longitudinal sliding along the line of contact between the pedestal rockers and the adapter surfaces (concavities) at each end of both wheelsets (all four such interfaces at the corners of a given truck set).
The roof 205 of the pedestal 204 may include a recess 214 or pocket cast in a flat surface 216 of the roof wherein the flat top surface 224 may rest. The recess 214 may be sized and shaped complementary to the top surface 224 of the rocker such that the entire top surface 224 of the rocker 212 may rest within the recess 214. By providing a designated recess 214 for aligning the rocker 212 with the pedestal roof 205, shear between the rocker and the roof may be reduced.
While
Due to the concave-up arrangement of the bearing adapter and pedestal rocker interface, particles produced by friction (wear) of the two surfaces in contact may be contained within the interface and may not fall away from the system, thereby providing a level of dry lubrication to the interface and facilitate adherence of the pedestal rocker and the bearing adapter. In contrast, if the bearing adapter had a convex (protruding) top surface in contact with a concave bottom surface of the pedestal rocker, the wear particles may not be retained in the interface and may no longer provide the desired lubrication.
The side frame of the truck and the bearing adapter may be manufactured by casting steel. The pedestal rocker 212 may be forged from steel. The curved top surface 210 of the bearing adapter and the recess 214 on the pedestal roof 205 may be manufactured by machine casting.
The cross-section of the pedestal rocker 212 show a curved, convex lower surface 222 and a flat upper surface 224 coupled by arcuate side walls on both sides. The curved, convex lower surface 222 of the rocker 212 rests on (in face sharing contact) on a curved, concave upper surface 210 of the bearing adapter 206. The radius of curvature of the curved, convex lower surface 222 of the rocker 212 is lower than the radius of curvature of the curved, concave upper surface 210 of the bearing adapter 206 causing the lower surface 222 to contact the upper surface 210 at the center of the upper surface 210 which serves as the mating valley. Due to the difference in curvature of the two surfaces in contact, there may be a gap (along the sides away from the center of the upper surface 210 where there is contact) between the curved, convex lower surface 222 of the rocker 212 and the curved, concave upper surface 210 of the bearing adapter 206. Metal particles produced from fraction between the contacting metal surfaces may be deposited in the said gap, thereby providing cushioning and lubrication for the pedestal rocker interface.
The pedestal jaw 204 of the side frame may be a hollow structure and the roof of the pedestal jaw may include a recess 214 or pocket in face sharing contact with the flat upper surface 224 of the rocker 212. The width of the recess 214 may be longer than the width of the rocker 212 causing the arcuate ends of the recess to overhang on both ends of the rocker 212.
The rocker 212 is adapted to swing or rock laterally about a longitudinal axis, shown by a dot 530, of the rocker 212. The direction of motion of the rocker 212 may be perpendicular to the direction of straight railway tracks (along axis A-A′) on which the railroad car truck is positioned. Further, the direction of motion of the rocker 212 may be perpendicular to an axle of a wheelset (along B-B′ axis) framed by the bearing adapter 206.
In this way, a rail vehicle truck may include two spaced apart parallel side frames coupled via a bolster, a side frame of the two side frames including two pedestal jaws at each end, a pedestal jaw of the two pedestal jaws interfaced with a wheel bearing adapter via a pedestal rocker adapted to swing laterally about an axis parallel to railway tracks on which the railroad car truck is positioned, the pedestal rocker including a flat upper surface in face sharing contact with a recess in a roof of the pedestal rocker, and a convex lower surface placed on a concave mating surface of the bearing adapter.
In alternate embodiments, when an elastic pedestal suspension component is used, the elastic component may store and return the energy of lateral car/truck movement with minimal damping, and have kinetic natural frequencies that approach the frequency range of Association of American Railroads (AAR) specified wheelset instability as higher speeds (such as in the range of 65-70 mph).
The oscillation frequency of the wheelsets coupled to a truck when a railcar approaches critical speed is in the range of 2-3 Hz. Computer based simulations have been carried out to determine natural/resonant frequency of pedestal-adapter system of different configurations. The simulations were carried out for each of a first configuration including a steel liner positioned between a flat pedestal roof and a 40-60 inch radius crown of a bearing adapter, a second configuration including elastic shear pads between nominally flat pedestal roof and a 40-60 inch radius adapter crown, and a third configuration including a pedestal rocker with a 5 inch radius set upon a 10 inch radius adapter cup.
During the simulation, all parameters used for the three configurations such as loaded car mass, ˜12 inch pendulum length from pedestal contact surface to spring seat, secondary suspension spring stiffness, damping from control wedges, etc. were identical. In the first configuration, the natural frequency was computed to be 3.0 Hz. In the second configuration, the natural frequency was computed to be 3.25 Hz and in the third configuration, the natural frequency was computed to be 1.25 Hz. The higher natural frequencies (relative to the third configuration) of the first two configurations are closer to the oscillation frequency of the wheelsets at critical speed. The first and second configurations may result in destructive resonance with the wheelset near the critical speed which may exacerbate lateral vibrations (also referred as hunting). The lower resonant frequency (almost half of the resonant frequency of the wheelset) of the rocker assembly (third configuration) may ensure that the lateral swing/roll of the side frame may not be prone to sympathetic vibrations as the wheelset nears its critical speed. Since the wheelset natural frequency near critical speed is completely outside a range of frequencies at which the rocker assembly may resonate, by including the rocker assembly in the interface of the pedestal jaw and the bearing adapter, a source of resonance of the railcar component may be removed.
Vertical damping/snubbing provided by secondary suspension in trucks of certain designs (such as Barber design) may be affected by vertical sliding of certain faces of sprung wedges against a pillar, vertically arranged columns with wear plates. With the rocker assembly, the intended swing motion of the side frames may produce lateral sliding relative to the said wedges and the friction therefrom may cause a degree of damping that may further discourage resonant behavior of the lateral/swinging/rolling side frame.
Contact stresses between the curved (cylindrical) surfaces of the pedestal rocker and the bearing adapter may be estimated using the Hertzian method. In order to reduce surface degradation, it is desirable that the contact stresses remain lower than one third of the final stress limit of the material. As an example, the lower the difference in the curvature of the two surfaces of the interface, the lower would be the contact stresses. Therefore, the difference between the radius of curvature of the top surface of the bearing adapter and the bottom surface of the rocker is not increased above one inch.
In the second rocker assembly 401, the pedestal rocker 412 may include a flat top surface 424 and a curved, convex, lower surface 422. The top surface 210 of the bearing adapter 206 may be a curved, concave surface providing a mating valley for lower surface 422 of the rocker 412. The radius of curvature of the top surface 210 may be higher than the radius of curvature of the lower surface 422 of the rocker 412.
Unlike the first embodiment, the roof 205 of the pedestal jaw 204 does not include a recess for housing the top surface 424 of the rocker 412. The rocker 412 may be fixed to a flat surface 404 of the roof 205 via a plurality of screws 406. The screws may pass through corresponding holes 408 in the rocker 412 and attach the rocker to the flat surface 404 of the roof 205. In other embodiments, the rocker may be fixed to the flat surface of the roof fasteners via fastening means other than screws, such as bolts, pins, welding, etc.
While
In this way, an improved mounting for the side frame may improve performance in stability and curving of fright railcars. The truck design including a pedestal rocker at an interface of the pedestal jaw and a bearing adapter may increase warp stiffness, interaxle shear stiffness, or the resistance to the unsquaring forces which are applied to the truck during higher speed operation and curving. The pedestal rocker may reduce the potential for longitudinal, lateral and yaw movement between the elements at the interface. The presence of the rolling motion, on an axis transverse to that of the wheelset, between the roller bearing adapter and the side frame may protect the side frame components from premature degradation due to constant eccentric loading.
An example system for a rail vehicle truck, comprises: a pedestal rocker laterally movable about an axis perpendicular to an axle of a wheelset, the pedestal rocker positioned between a roof of a pedestal jaw of a side frame and a bearing adapter with a convex lower surface of the pedestal rocker in face sharing contact with a concave upper surface of the bearing adapter. In the preceding example, additionally or optionally, the roof of the pedestal jaw includes a recess. In any or all of the preceding examples, additionally or optionally, an upper, flat surface of the pedestal rocker is in face sharing contact with the recess on the roof of the pedestal jaw. In any or all of the preceding examples, additionally or optionally, a length of the recess is longer than a corresponding length of the pedestal rocker and a width of the recess is greater than a corresponding width of the pedestal rocker. In any or all of the preceding examples, additionally or optionally, the convex lower surface includes a first radius of curvature and wherein the concave upper surface includes a second radius of curvature. In any or all of the preceding examples, additionally or optionally, the first radius of curvature is lower than the second radius of curvature. In any or all of the preceding examples, additionally or optionally, the first radius of curvature is in a range of 2-3 inches and the second radius of curvature is in a range of 3-4 inches. In any or all of the preceding examples, additionally or optionally, the axis of the pedestal rocker about which it is movable is parallel to a direction of railway tracks on which the rail vehicle truck is configured to be positioned. In any or all of the preceding examples, additionally or optionally, the pedestal rocker is movable in a direction perpendicular to the direction of railway tracks on which the rail vehicle truck is configured to be positioned. In any or all of the preceding examples, additionally or optionally, the axle of the wheelset is positioned within an opening framed by the bearing adapter, the axle perpendicular to the direction of the railway tracks. In any or all of the preceding examples, additionally or optionally, the rail vehicle truck includes two parallel side frames coupled via a bolster, each side frame including two pedestal jaws and two corresponding bearing adapters. In any or all of the preceding examples, additionally or optionally, the pedestal rocker is cast from steel. In any or all of the preceding examples, additionally or optionally, the pedestal rocker is coupled to the roof of the pedestal jaw via one or more screws.
Another system, comprises: a rail vehicle truck including two spaced apart parallel side frames coupled via a bolster, the two side frames including two pedestal jaws at each end, and a pedestal jaw of the two pedestal jaws interfaced with a wheel bearing adapter via a pedestal rocker adapted to swing laterally about an axis parallel to straight railway tracks on which the rail vehicle truck is configured to be positioned, the pedestal rocker including a flat upper surface in face sharing contact with a recess in a roof of the pedestal rocker, and a convex lower surface placed on a concave mating surface of the bearing adapter. In the preceding example, additionally or optionally, the bearing adapter frames a wheelset including an axle, and two or more wheels mounted on the axle, the axle perpendicular to the axis about which the pedestal rocker is adapted to swing. In any or all of the preceding examples, additionally or optionally, a radius of curvature of the convex lower surface of the pedestal rocker is lower than another radius of curvature of the concave mating surface of the bearing adapter. In any or all of the preceding examples, additionally or optionally, the pedestal rocker touches the mating surface at a center of the mating surface. In any or all of the preceding examples, additionally or optionally, the pedestal rocker extends along an entire length of an opening between two parallel walls of the pedestal jaw.
Yet another example system for a rail vehicle truck, comprises: a pedestal jaw including a recess on a first surface of the pedestal jaw facing a second surface of a bearing adapter, the second surface being concave, and a pedestal rocker in face sharing contact with each of the recess on the first surface of the pedestal jaw and the second surface of the bearing adapter, the pedestal rocker adapted to laterally swing about its longitudinal axis perpendicular to each of a direction of straight railway tracks on which the rail vehicle truck is configured to be positioned and another direction of an axle of a wheelset housed within the bearing adapter. In the preceding example, additionally or optionally, the pedestal rocker includes a convex lower surface contacting the second surface of the bearing adapter, a flat upper surface contacting the recess on the first surface of the pedestal jaw, and arcuate side walls coupling the upper surface and the lower surface.
Although embodiments have been described herein in regards to rail vehicle trucks, other embodiments may be applicable to trucks for other types of vehicles, e.g., on road trailers.
As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property. The terms “including” and “in which” are used as the plain-language equivalents of the respective terms “comprising” and “wherein.” Moreover, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements or a particular positional order on their objects.
This written description uses examples to disclose the invention, including the best mode, and also to enable a person of ordinary skill in the relevant art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.
The present application claims priority to U.S. Provisional Application No. 62/978,578 filed on Feb. 19, 2020. The entire contents of the above-listed application is hereby incorporated by reference for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 62978578 | Feb 2020 | US |
