Railway truck side bearing

Abstract

 A railway truck side bearing employing bearing elements (22,24) which are vertically deformable in shear to provide extended vertical travel of the side bearing.

Description

BACKGROUND OF THE INVENTION

[0001] In modern railway freight cars, conical wheels of the railway truck engage cylindrical rail heads of the railway track. The rolling engagement of the wheels on the track produces a steering action that can become unstable and cause the railway truck to oscillate laterally about the track centerline and yaw cyclically about a vertical axis as it continually seeks a centered position on the track. This phenomenon is commonly referred to as truck hunting. Hunting can cause or exacerbate lateral roll movement of the car body about its longitudinal axis. Reference is made hereby to prior U.S. patent No. 3,957,318 for further detailed explanation of railway vehicle truck hunting phenomena, and such explanation is hereby incorporated herein and made a part hereof by reference.

[0002] Railway truck side bearings have long been utilized to support rail car bodies with respect to their trucks laterally outward of the truck centerplates. Side bearings are necessary not only because of the tendency of the car body to roll about its longitudinal axis, but in addition to support the car body during negotiation of track curves.

[0003] Among many examples of railway truck side bearings are those which employ elastomeric elements to provide some or all of the load bearing capacity afforded by the bearing as well as hunting response restraint. Included among known side bearings are those disclosed in U.S. patents 4,715,290, 3,707,927, 3,670,661, 4,434,720, 3,045,998, 3,895,206, 4,355,583, 4,030,424 and 5,386,783. The above-mentioned U.S. patent 3,957,318 is another example of a side bearing utilizing elastomeric bearing elements.

[0004] One type of modern side bearing in particular is characterized as a constant contact side bearing, because the bearing assembly becomes engaged in load bearing engagement between the railway truck and the car body during the setup process when the car body is mounted on the truck. A constant contact side bearing remains in load bearing engagement, and preferably uniform load bearing engagement, between the truck and the car body throughout the entire range of car body motion relative to the truck. This includes, most notably, the entire range of car body roll motion.

BRIEF SUMMARY OF THE INVENTION

[0005] The present invention contemplates a novel and improved constant contact side bearing having improved vertical travel characteristics whereby improved bearing load response in the normal bearing operating range is achieved.

[0006] The bearing of this invention preferably employs compliant bearing assemblies of elastomeric elements bonded to rigid substrates. The bearing assemblies are configured in a novel way to provide an extended vertical travel or movement characteristic through reliance primarily on shear deformation of the elastomeric bearing elements as the vertical height of the bearing varies in response to changes in the vertical spacing between the truck and the car body at the bearing location. The increased vertical travel available with this side bearing allows for greater setup height tolerance or variation and a controlled spring rate in the operating range.

[0007] By relying primarily on shear loading in the elastomeric bearing elements, larger material strain can be tolerated with less permanent set or damage to the elastomeric material. The force deflection characteristic of the novel bearing can be customized by varying any of a variety of geometric, structural or dimensional specifications. These may include the deformation characteristics of the elastomeric elements, their section thicknesses, the number of elastomer sections employed, the shape or geometry of unbonded elastomeric surfaces, employment of multiple elastomeric materials of differing deformation characteristics, and so forth.

[0008] The invention also contemplates use of elastomeric bearing elements such as above characterized in conjunction with appropriate solid stops to limit the maximum elastomer deformation which can occur in operation of the bearing.

[0009] The novel side bearing includes modular assemblies of elastomeric elements bonded to rigid substrates such as steel in configurations to provide a relatively lower stiffness or spring rate in response to vertical deformation of the elastomeric elements in shear, while providing a relatively greater stiffness or spring rate in the longitudinal direction as a response to compressive deformation of the elastomeric elements. The longer vertical travel for the bearing thus is achieved without compromising longitudinal stiffness which is desirable for assisting in control of hunting.

[0010] Other variations to the novel side bearing can include employment of tapered or other shapes for unbonded elastomer surfaces, and variation in the shape of the substrates to which elastomeric elements are bonded.

[0011] It is, therefore, one object of the invention to provide a novel and improved constant contact side bearing for a railway vehicle.

[0012] A further object of the invention is to provide a railway vehicle side bearing with extended vertical travel achieved through use of elastomeric bearing assemblies.

[0013] Another object of the invention is to provide a constant contact side bearing with a force-deflection characteristic achieved primarily through deformation of elastomeric elements in vertical shear.

[0014] These and other objects and further advantages of the invention will be more readily appreciated upon consideration of the following detailed description, and the accompanying drawings, in which:

Fig. 1 is a sectioned side elevation of a side bearing of the present invention taken on line I-I of Fig. 2;

Fig. 2 is a sectioned top plan view taken on line II-II of Fig. 1;

Fig. 3 is a sectioned side elevation of an alternative embodiment of the invention;

Fig. 4 is a sectioned side elevation of a presently preferred embodiment of the invention taken on line IV-IV of Fig. 5;

Fig. 5 is a sectioned top plan view taken on line V-V of Fig. 4;

Fig. 6 is a sectioned side elevation of another presently preferred embodiment of the invention taken on line VI-VI of Fig. 7;

Fig. 7 is a sectioned top plan view taken on line VII-VII of Fig. 6;

Fig. 8 is a sectional side elevation of another embodiment of the invention; and

Fig. 9 is a representation of a hypothetical force-deflection curve for a side bearing of the present invention.

[0015] There is generally indicated at 10 in Figs. 1 and 2 a railway truck side bearing according to one embodiment of the instant invention and comprising a rigid, unitary bearing housing 12 having a base portion 14 with mounting flanges 16, and an upstanding, generally cylindrical perimeteral wall portion 18. Flanges 16 include through openings 20 to receive suitable fasteners such as rivets or nut and bolt assemblies (not shown) for securing the side bearing 10 to a railway truck bolster (not shown) or comparable structure.

[0016] A bearing assembly 22 is received within the confines of perimeteral wall 18, the assembly 22 being comprised of plural, concentric elastomeric rings 24 and 26 having confronting cylindrical surfaces 28 and 30 thereof suitably bonded to a rigid, cylindrical substrate 32 of steel, for example. The inner cylindrical wall 34 of elastomeric element 26 is similarly bonded to a rigid cylindrical substrate 36, and the radially outermost cylindrical wall 38 of elastomeric element 24 is similarly bonded to the cylindrical inner surface 40 of bearing carrier wall portion 18.

[0017] As shown in Figs. 1 and 2, the plural elastomeric elements 24 and 26, as well as the cylindrical substrate elements 32 and 36, are arranged in mutually concentric relationship about axis X-X with respect to wall 18. Further, the radially inner elastomeric element 26 is positioned to extend vertically above the radially outer elastomeric element 24, and similarly substrate element 36 is positioned to extend vertically above substrate element 32. Additionally, both of the substrate elements 32 and 36 extend above the uppermost extent of either elastomeric element 24 or 26.

[0018] A vertical clearance 42 (Fig. 1) is provided between all elements of bearing assembly 22 and the upper surface 44 of base 14 to permit a range of vertical motion for elements of bearing assembly 22 upon application of downwardly directed loads L thereto.

[0019] From the above description it will be appreciated that when load L is applied to the side bearing, rigid substrate element 36 will move downwardly thereby deforming elastomeric element 26 in shear, rather than in compression, as indicated by S in Fig. 1. In turn, the downward impetus exerted by this shear deformation moves substrate element 32 vertically downward, thereby also deforming elastomeric element 24 in shear as indicated by S' in Fig. 1.

[0020] The bonding of the elastomeric elements to the metal substrates, together with reliance on shear deformation, allows a side bearing with lower stiffness or spring rate in a vertical direction, while providing much greater stiffness in the horizontal direction. In particular, with shear loading as described, much larger strains in the elastomeric material can be sustained with less permanent set or damage to the material. The shape of the force-deflection curve for a side bearing such as disclosed in Figs. 1 and 2 may be readily tailored to a specific application.

[0021] The overall force-deflection characteristic for the side bearing of Fig. 1 and 2 embodiments can be customized by such variations as the elastomeric material selected, the geometry of the elastomeric elements, the number of elastomeric elements used, and the shape of both the bonded and unbonded elastomer surfaces.

[0022] Other variations to achieve different modes of bearing response may include preloading the side bearing in various ways. For example, preloading the elastomer in shear, tension, compression or torsion can assist in generating the initial stiffness of the bearing so that the shear loading which the elastomer undergoes during setup will not have to generate as high a force response in order to provide adequate performance. It is to be appreciated that torsion is merely a special case of shear loading. The loading conventionally referred to as shear is developed by applying equal and opposite forces in planes parallel to the bonded interfaces between the substrates and the elastomeric element, whereas torsion is developed by applying equal and opposite torques to the substrate elements in planes parallel to the bonded faces.

[0023] Fig. 9 illustrates a force-deflection characteristic for a non-preloaded bearing with the values at the origin 0 of zero force and zero deflection being the starting point for bearing installation and setup. By contrast, the initial point for the force-deflection curve of a preloaded bearing would be shifted upward along the vertical (force) axis.

[0024] Additional possible variations to influence bearing performance may include the following, by way of example. In the Fig. 1 and 2 embodiment, more elastomeric rings of smaller radial cross section would be expected to provide a stiffer bearing than fewer rings of larger radial cross section. To equalize shear strength among the elastomeric rings, the radial section of the rings may be reduced and/or its vertical dimension increased as radius increases. The vertical clearance of the individual rigid substrate elements from the base or from the cap member may be individually varied to customize the bottoming behavior of the bearing assembly. This can permit equalization of the strain energy stored in each elastomeric element.

[0025] Further, by changing the shape of the circular elastomeric elements in plan view to an elongated or oval configuration, the bearing may exhibit different stiffness characteristics in the lateral and longitudinal directions. There also may be circumstances in which it would be desirable to leave part of the volume between pairs of inner and outer substrate elements empty, for such purposes as to avoid areas of stress concentration.

[0026] Other modes of preloading and other bearing assembly configurations such as those described hereinbelow may also be employed for purposes of this invention, so long as the bearing response to the generally vertical loading evolved between the truck bolster and the car body at the bearing location is primarily a response of shear deformation.

[0027] Still further variations and additional structural features of the invention are illustrated by Fig. 3 in a side bearing generally indicated at 46 and having an elongated bearing carrier 48 similar to a conventional side bearing housing or carrier. An assembly of plural elastomeric bearing elements 50 bonded to intervening rigid substrate elements 52 provide load bearing capacity which affords a range of vertical movement under loading L, with bearing response principally occurring as shear deformation S of the elastomeric elements 50. In these respects, bearing 46 is similar to the bearing described above with reference to Figs 1 and 2; however, because it can utilize a conventional bearing carrier 48, the bearing assembly of Fig. 3 can be retrofitted to existing side bearing hardware on freight car trucks.

[0028] Since the option of retrofitting the Fig. 3 bearing assembly requires that they fit within the confines of a conventional bearing carrier 48, the bearing assembly must be configured accordingly. Hence, the elastomeric elements 50 are located only at opposed longitudinal ends of the bearing assembly. One or more of the substrate elements 52 may include side portions 53 extending longitudinally of the bearing assembly, but having no elastomeric material bonded thereto. The side portions 53 on opposed lateral sides of the bearing assembly therefore lie closely adjacent one another and move vertically with respect to one another in response to loading L, but the bearing response afforded by shearing S of the elastomeric elements 50 is confined to the longitudinal end portions of the bearing assembly where the elastomeric elements 50 are located.

[0029] Conventional side bearings also have commonly employed a solid stop arrangement such as a roller 54 and a cap member 56. For purposes of the present invention, cap member 56 is carried atop the bonded elastomer and rigid substrate bearing assemblies to impart vertical loading thereto from a car body (not shown). The maximum vertical deflection of the Fig. 3 side bearing is limited to that deflection where a depending stop portion 58 of cap member 56 engages roller 54. Of course, either the roller or a corresponding solid bearing element, and/or cap member 56, may be incorporated in the Fig. 1 and 2 embodiment.

[0030] One presently preferred embodiment of the invention is shown in Figs. 4 and 5 as a bearing assembly 60 carried by a conventional side bearing cage or housing 62 and including a longitudinally spaced pair of bonded elastomeric bearing assemblies 64, and an intervening rigid bearing element such as roller 66. Each of assemblies 64 includes outer and inner rigid substrate elements 68 and 70, respectively, each being preferably of a generally rectangular form as shown in Fig. 5, but having rounded or radiused corners as shown at 72 and 74, for example. An intervening elastomeric element 76 is bonded to the confronting surfaces 78 and 80 of substrate elements 68 and 70, respectively. As shown in Fig. 4, one of the options mentioned hereinabove for customizing bearing response is illustrated in Fig. 4 by the selected shaping or forming of free (i.e. unbonded) surfaces of elastomeric element 76, for example as indicated at 82 and 84.

[0031] Each of substrate elements 70 includes an opening 86 which receives a downwardly projecting interlock portion 88 of a rigid cap 90. the cap 90 spans the longitudinally spaced bearing assemblies 64 and includes an intervening depending portion 92 which is engageable with roller 66. This provides a solid stop to limit vertically downward travel of cap 90 under loadings L, thus also limiting deformation of elastomeric elements 76 in shear.

[0032] Figs. 6 and 7 show another presently preferred embodiment of the invention wherein an assembly of bearing elements 93 is carried by a conventional side bearing housing or carrier 94. Assembly 93 comprises a bonded elastomer and metal substrate bearing assembly 96 that is similar in many salient respects to that described with reference to Figs. 4 and 5. As shown in Fig. 7, however, bearing assembly 96 may be of a generally rectangular section form, rather than generally square as in the Fig. 4 and 5 embodiment. In addition, the cap or wear member 90 of the Fig. 4 and 5 embodiment is substituted in the Fig. 6 and 7 embodiment by an integral wear member portion 98 of the bearing assembly 96.

[0033] The assembly 96 resides in bearing carrier 94 longitudinally adjacent to a saddle member 100 having an upwardly projecting abutment 102 which confines bearing assembly 96 between itself and the opposed end 104 of housing 94. Between abutment 102 and the opposite end 106 of housing 94 there is confined a roller element 108, which may roll freely within a range of longitudinal movement between carrier end 106 and abutment 102.

[0034] Fig. 8 shows yet another embodiment of the invention in generally schematic form as a bearing assembly 110 comprising a base portion 112 having either a plurality of elastomeric elements, or a unitary ring-shaped elastomeric element 114 as shown. A substrate element 116 includes a peripheral side portion 118 and a top portion 120. A radially inwardly facing wall portion 122 of the peripheral side portion 118 confronts the radially outwardly facing wall 124 of base element 112, and elastomeric element 114 is bonded to these surfaces.

[0035] The confronting wall portions 122 and 124 are angled outward from the vertical by an angle A such that loading L produces shear deformations that are not parallel to the confining walls 122 and 124. The result is a degree of elastomeric compression in addition to the shear deformation under loading L. The limit on angle A for practical purposes has not been determined, although it will be clear that as angle A increases the deformation of the elastomeric elements 114 in response to loading L is increasingly greater compression and decreasing shear deformation. Since the novel bearing as described operates primarily in reliance on the response from shear deformation of the elastomeric elements, the magnitude of angle A is to be limited accordingly so that the bearing response is indeed primarily shear response.

[0036] Bearings according to the present invention may be configured in accordance with any described embodiment, and others not described. In addition, any embodiment of the invention may be modified in accordance with any of the alternative structures or modifications mentioned herein, as well as others which would have the function of altering in some preferred way the force-deflection response of the bearing upon deformation of the elastomeric materials in shear under vertical loading.

[0037] A force-deflection curve for a hypothetical side bearing of the present invention is illustrated in Fig. 9 as curve C representing the vertical bearing deflection D under force F.

[0038] Origin 0 represents the free or unloaded state of the bearing extending to its full free height. (As noted hereinabove, for a preloaded bearing, the initial point 0 of curve C would be shifted upwardly along the vertical axis.) Upon application of a force F directed vertically downward, the bearing response is observed as a deflection D over an initial range of loading I representing bearing installation and setup. The range of deflection R represents the variation which occurs due to normal error or variation in setup of the bearing. The functional characteristics of the bearing are such that, in this region the slope of curve C flattens significantly. Consequently, the variation V in force F over the entire setup range R of the bearing is relatively small. This provides for greater uniformity of the bearing setup.

[0039] Beyond setup range R, the slope of the force-deflection characteristic increases with each additional increment of deflection D. At a point S representing the solid stop, which is the limit of vertical travel, force increases with no additional vertical deflection.

[0040] The significance of flattening of the force-deflection characteristic in setup range R may be appreciated by extrapolating that portion of the curve C backward toward 0 deflection as indicated by extrapolation E. The deformation behavior of the elastomeric bearing assemblies in the setup range R corresponds to a hypothetical linear force-deflection characteristic which has undergone a very large deflection D before reaching the setup force range V.

[0041] Thus, to achieve such a response in a purely linear elastomeric side bearing would be a practical impossibility because the required range of vertical deflection needed to reach setup force levels would be far greater than the deflection available in the vertical space envelope for standard side bearing applications. Due to other space limitations that must be observed in conventional side bearing applications, one could not reduce the required vertical space envelope by significantly increasing the number or size of elastomeric bearing elements, for example to increase the mass of elastomer undergoing shear.

[0042] Thus, by virtue of this invention, a side bearing force-deflection characteristic that would be thought unavailable, due to the space limitations that must be observed, is nevertheless achieved within those space limitations and without sacrificing any favorable aspect of bearing performance that is offered by the force-deflection characteristic C within the setup range R of the bearing.

[0043] It will be understood that the force-deflection characteristic of Fig. 9 is merely illustrative and not intended to limit the scope of the invention. There may be many circumstances where the invention provides a different but equally desirable force-deflection characteristic.

[0044] Notwithstanding the description hereinabove of certain presently preferred embodiments of the invention, it is to be understood that we have envisioned and anticipated various alternative and modified embodiments. All such alternative embodiments are intended to be included within the scope of the invention as described. Elastomeric materials for the invention may be chosen from a range of materials having suitable properties that they can be subjected to the necessary deflections with minimal permanent set or hysteresis, while generating the required load responses as described hereinabove within the side bearing space limitations. Similarly, metallic substrates may be selected from a variety of materials based on load bearing capacity and the wear to which the material may be subjected. The bonding techniques for producing the elastomer and metal substrate bearing assemblies may be standard bonding methods or heretofore unknown bonding techniques.

Claims

1. A side bearing for supporting a railway car body with respect to a railway truck, comprising:

first rigid means (12) adapted to be supported with respect to such a truck;

second rigid means (36) spaced from said first rigid means and adapted to engage such a car body; and

resiliently deformable elastomeric means (22,24) extending between and fixed to said first and second rigid means (12,36);

said first and second rigid means (12,36) being movable relative to each other along an axis (x-x) resiliently to deform said elastomeric means (22,24) in response to relative movement of such a car body with respect to such a truck;

   characterized in that said elastomeric means (22,24) is fixed to said first and second rigid means (12,36) in a manner that said elastomeric means (22,24) is deformed substantially only in shear, without significant compressive deformation thereof, in response to relative movement of said first and second rigid means (12,36) with respect to each other along said axis (x-x).

2. A side bearing according to claim 1, wherein said first rigid means (12) includes an upstanding means (18) adapted to extend upwardly with respect to such a truck to a given elevation.

3. A side bearing according to claim 2, wherein said second rigid means (36) is disposed with respect to said first rigid means to extend upwardly to an elevation higher than said given elevation for substantially all relative positions of said first and second rigid means (12,36) with respect to each other along said axis (x-x).

4. A side bearing according to any preceding claim, wherein said first rigid means (12) is spaced transversely from said second rigid means (36), and said elastomeric means (22,24) extends transversely between said first and second rigid means (12,36).

5. A side bearing according to any preceding claim, wherein said first rigid means (12) transversely encloses said second rigid means (36).

6. A side bearing according to claim 5, wherein said elastomeric means (22,24) encloses said second rigid means (36) transversely outwardly thereof.

7. A side bearing according to any preceding claim, wherein said second rigid means (36) includes a rigid cap means (90) for engaging such a car body in bearing engagement.

8. A side bearing according to any preceding claim, additionally including solid stop means (54,58) for limiting relative axial movement of said first and second rigid means (12,36) with respect to each other.

9. A side bearing according to any preceding claim, wherein said first and second rigid means (12,36) are generally cylindrical first and second rigid members, respectively, disposed coaxially with respect to said axis (x-x) and defining therebetween a generally annular space disposed in mutually coaxial relationship with said first and second rigid members (12,36).

10. A side bearing according to claim 9, wherein said elastomeric means (22,24) comprises a generally annular elastomeric member disposed at least partially within said annular space.

11. A side bearing according to claim 10, wherein said annular elastomeric member is bonded to said cylindrical first and second rigid members.

12. A side bearing according to any preceding claim, wherein said first and second rigid members (12,36) are axially offset with respect to each other such that any relative axial movement of said first and second cylindrical members (12,36) so as to reduce the axial offset therebetween will deform said elastomeric means (22,24) in axial shear.

13. One or more side bearings according to any preceding claim, received in a rigid carrier means (48).

Drawing