Railway truck bolster friction assembly

Abstract

A railway freight truck bolster friction assembly and more particularly improved friction assemblies of elastomeric material which are adapted to be captively retained intermediate an axial end portion of a bolster member and an adjacent side frame.

Description

A railway freight truck bolster friction assembly and more particularly improved friction assemblies of elastomeric material which are adapted to be captively retained intermediate an axial end portion of a bolster member and an adjacent side frame.

Modern three-piece railway freight car trucks use rigid wedge shaped friction members intermediate an axial end portion of the bolster member and an adjacent side frame. These friction members provided the fit-up between the bolster and the side frame columns and serve to snub or damp the freight car suspension.

In the normal travel of railway cars over a railbed, various differences in the surface profile of the laterally spaced tracks resulting from rail joints and superelevation of the outside track on curves, gives rise to a tendency of resonant swaying and bouncing of the car body. In modern cars with heavy load capacity and a relatively high center of gravity, the forces and weight shift of the car resulting from track surface variations becomes so large at times that a variety of effects may develop such as:

(1) Complete unloading of the wheels on one side of the truck to the extent of lifting the unloaded wheels off the rail with a high potential of derailments;

(2) The imposition of extreme stresses on the car body and truck members; and

(3) Cumulative damage and misalignment of track, ties and roadbeds through pounding action.

The need for adequate damping of railway vehicle suspensions has been recognized and to a certain extent alleviated by independent means. Specifically, as mentioned hereinabove, rigid friction members, for example as illustrated in U.S. Pat. No. 3,461,815 are generally utilized to dampen or snub the rocking motion by frictional resistance developed between the rigid friction members and the side frame column guides. In addition to the friction members highly successful hydraulic snubbers, such as shown in U.S. Pat. Nos. 4,004,525 and 3,868,912, which are vertically disposed in a spring group, have been developed and provide an even more effective means of snubbing the freight car swaying and bounce.

The utilization of rigid friction members for swaying has been shown to be defective in several areas. For example: the steel on steel frictional engagement between the rigid friction member and the side frame column guide wear plate results in a "stick-slip" friction action which produces poor ride quality. Furthermore, with an empty car the transmissability of the "stick-slip" friction can result in an excitation or coupling with any or all of the natural frequencies of the railway car components; and the "stick-slip" friction action results in an impacting type start and stop movement of the bolster with respect to the side frames thus leading to potential deleterious structural effect. Furthermore, the friction forces on the mating faces of the rigid friction member with respect to the side frame column guide and the bolster pockets may result in a requirement for frequent replacement of components and/or a renewal of wear surfaces. Still further, with the higher friction forces of some rigid friction members the railway trucks occasionally have a tendency to seize in a random lozenged angle (i.e., truck going out of square and the wheel flanges take an acute angle with respect to the guiding rail) thereby increasing unsymmetrical wheel flange and/or tread wear.

The above-mentioned problems have been recognized by the Applicant and overcome, or in the least, greatly alleviated in his invention described in co-pending U.S. patent application Ser. No. 953,012 which was filed on Oct. 20, 1978, now U.S. Pat. No. 4,230,047, and is assigned to the same assignee as is this invention. In this with reference to the axial extent of bolster 16, inner or inwardly and outer or outwardly shall refer respectively to towards and away from the centerplate 12 along the longitudinal axis of bolster 16 and upper and lower or upwardly and downwardly shall refer respectively to towards and away from the top of bolster 16 as viewed in FIGS. 2 and 3.

Friction wedge 28 comprises: a pair of identical laterally adjacent elastomeric friction members 32 and a spring follower member 34 which is biased into engagement with members 32 by means of a coil unit 36 which extends vertically between an upwardly facing lower surface 28 of side frame 22 and a downwardly facing lower surface 40 of follower member 34. Follower member 34 has a generally upwardly extending triangular configuration and includes a downwardly open keeper pocket 42 formed within surface 40 for the captive retention of the uppermost end of coil unit 36. As viewed in FIGS. 3 and 4, each friction member 32 comprises an outer generally rectangularly shaped portion 44 and in inwardly projecting formed triangular portion 46.

Friction wedge assembly 28 additionally includes a wear plate 48 having the outer generally vertically extending planar surface 50 thereof abutting an adjacent column guide 52 of a respective side frame 22. Wear plate 48 is secured to the column guide 52 in any suitable manner such as by welding or by a rivet (not shown) extending through an aligned countersunk bore 54. As is best illustrated in FIG. 4, the inner generally vertically extending surface 56 of wear plate 48 consists of a pair of transversely adjacent sloped surface portions 58 which slope transversely outwardly from the transverse mid-point of the wear plate 48. The vertically extending outermost surface 60 of each portion 44 of the friction members 32 also slopes transversely outwardly at an angle such that when wedge assembly 28 is in the assembled position thereof as illustrated in FIG. 3, surface 60 will fully engage the adjacent surface portion 58 of the wear plate 48. It is to be additionally noted that the transverse dimension of the friction members 32 is such that, as is best illustrated in FIG. 4, when wedge assembly 28 is operatively positioned within a railway freight truck 10, a space 72 exists between the adjacent transversely facing surfaces of the members 32.

With a general configuration as described above, when friction assembly 28 is biased into the operational position thereof by coil unit 36, the outer vertically extending transversely sloped surface 60 of each friction member 32 will be in biased engagement with the adjacent vertically extending transversely sloped surface portion 58 of the column guide wear plate 48 and the lower surfaces 62 of the triangular portions 46 will be in engagement with a complementary sloping surface 64 of follower member 34. Furthermore, the upper sloping surfaces 66 of the triangular portions 46 will be aligned in a common sloping plane with the inner sloping surface 68 of follower member 34 and the aligned surfaces 66 and 68 will be in continuous engagement with an adjacent inclined surface 70 of the bolster pocket 30. Thus, the elastomeric friction members 32 will be generally confined within the adjacent portions of the boundary surfaces 58, 70 and 64; however, the areas of portion 44 adjacent the upper and lower ends thereof will not be confined thereby allowing spaces for the members 32 to deform in response to vertical shear forces. Furthermore, the space 72 between the friction members 32 as well as the relief afforded by the outer end of the bolster pocket 30 will allow space for the members 32 to also deform in response to transversely directed shearing forces.

The confined fit of the elastomeric friction members 32 within the bolster pocket 30 provides the fit-up of the side frame 22 to bolster 16 relationship. The vertical pre-load provided by the upwardly directed biasing force of coil unit 36 imputes the vertical frictional force between the members 32 and the wear plate 48 interface which is necessary for vertical damping by the friction wedge assembly 28. This pre-load force developed by the coil unit 28 additionally dictates at least a portion of the transverse frictional force at members 32; however, in this latter regard, the wedging effect developed by compressing of the friction members 32 as they move or resile inwardly towards the longitudinal center line of the bolster 16 must also be considered.

The pre-load force yields a longitudinally extending component reflected to and generating friction at the wear plate surfaces 56. This friction force may be varied by varying the spring constant of the coil unit 32 or by varying the self-actuation angle. As the spring constant increases or the self-actuation angle decreases or becomes more acute the longitudinally extending force at the wear plate surfaces 56 increases.

The longitudinally extending force at the wear plate surfaces 56, in conjunction with the coefficient of friction between the surfaces 56 and 60, determines the amount of external vertical and/or transverse force necessary to break friction between the wear plate 48 and the elastomeric friction members 32. Inasmuch as the damping from the vertical friction force to aid in the prevention of excessive rocking or bouncing of the railway freight car is dependent upon the biasing force of the friction assembly 28, it is important that the predetermined force necessary to break friction not be so great as to prevent substantially all vertical movement of the bolster 16. Similarily, such predetermined force must not be so small as to provide an insignificant vertical damping effect. Furthermore, such predetermined frictional force must not be so great as to prevent substantially all transverse movement of the bolster 16 with respect to the side frame 22 or to be so insignificant as to provide no substantial transverse damping force.

The vertical damping of the wedge assembly 28 of this invention is essentially identical to the vertical damping described in my hereinbefore mentioned copending U.S. Patent application Ser. No. 953,012 U.S. Pat. No. 4,230,047. More specifically, upon initial movement of the bolster 16 with respect to the side frames 22, the elastomeric friction members 32 deform vertically. After this initial vertical deformation, portions of the friction members 32 will continue deforming while other portions will slip with respect to the adjacent wear plate 48. Finally, friction will be entirely broken and the entire surfaces 60 of friction members 32 will slip vertically with respect to the mating surfaces 56 of wear plate 48. Thus, the transition of friction members 32 from stationary to vertical sliding is extremely smooth and not at all like the abrupt "stick-slip" action of prior art rigid friction wedges. Furthermore, during the entire transition from preliminary partial deformation, deformation and partial sliding and complete sliding, the vertical motion of the bolster 16 with respect to the side frames 22 is resisted influenced by vertical bolster spring forces, including the coil units 36, and the damping or friction forces that occur during rocking or vertical bouncing. Still further, the physical properties of the elastomeric material of friction members 32 are such that the members 32 will not cause excessive wear, abrading or gulling galling of the mating metallic surfaces.

Thus, for vertical restraint the invention herein will perform substantially identically to the elastomeric friction wedge assembly discussed in the hereinbefore mentioned U.S. Patent application Ser. No. 953,012. However, the configuration of the elastomeric friction wedge assembly 28 of the present invention provides superior controlled bolster to side frame lateral restraint from such aforesaid patent application. The invention herein increases the threshold hunting speed and reduces the lateral bolster gib impact for both rocking and hunting control. Insofar as hunting control, the operation of the friction assembly 28 and the lateral deformation characteristics of the elastomeric friction members 32 will be similar to the general operation and deformation characteristics described heretofore with respect to the elastomeric bearing blocks in the side bearings 14 as are discussed in U.S. Pat. Nos. 3,957,318 and 4,090,750. The primary distinction between such patents and the present invention is that in such patents the elastomeric side bearing blocks inhibit hunting by restraining the movement of the truck body with respect to the car body wherein whereas in the present invention, the elastomeric friction members 32 act to control hunting by adding more restraint to the transverse or horizontal movement of the bolster 16 with respect to the side frames 22.

Specifically, the transversely sloping surface portions 58 of the wear plate 48, in conjunction with the surfaces 64 and 70 which act to confine the adjacent inner surfaces of the friction members 32, provide a wedging effect as the friction members 32 are urged transversely towards the vertically extending transverse juncture 74 of the surface portions 58. Accordingly, as a transverse force is applied at the wedge assembly 28, the friction member 32 adjacent the applied force will provide an initial deformation constant to resist the transverse force. The other elastomeric friction member 32 does not participate in the lateral direction and, in fact, the transverse deformation constant thereof is actually relieved. Thus, the elastomeric friction members 32 aid in the prevention of hunting by individually providing a sufficiently rigid shearing constraint within a predetermined acceptable modulus of elasticity while still providing the ability of the members 32 to insure the desired side frame to bolster fit-up effect and the vertical damping as discussed hereinbefore. Furthermore, the transverse wedging effect provided by the inclined surface portions 58 permits transverse movement to occur between the active friction member 32 and the adjacent surface portion 58 without an appreciable "flattening out" effect insofar as the transverse force resisting characteristics of the active friction member 32. This latter characteristic is realized because, as the active member 32 moves transversely towards the juncture 74, the member 32 is further compressed because of the hereinabove mentioned transverse wedging effect between adjacent confining surfaces therefor. This further compression applies an even greater normal force to the surface portion 58 and results in an increase of friction at surface portion 58 and the active elastomeric friction member 32.

If the sloped surface 58 were not provided, the adjacent surfaces of portion 58 and friction member 32 would merely be in wiping contact during the transverse movement of the friction member 32 and, thus, the transverse force-deflection curve for the friction member 32 would not increase during such transverse movement. Hence, the inclusion of the sloping surface portion 58 provides a superior wider range hunting control over heretofore conceived elastomeric friction wedge arrangements while still allowing for the fit-up and translation requirements of three-piece railway freight trucks 10. Furthermore, because of the above discussed operating characteristics of the wedge assembly 28 of the present invention, a substantially wider range of materials is available for the composition of the friction members 32. Thus, in addition to wide range operating characteristics for the members 32 themselves, the invention herein may foretell, in certain instances, that elastomeric side bearing blocks such as illustrated in U.S. Pat. Nos. 3,957,318 and 4,090,750, may no longer be required for adequate hunting control or, in the least, the range of materials for such side bearing blocks will certainly be wider or, the operational requirements thereof may be substantially lessened.

FIGS. 5 and 6 illustrate another embodiment of an elastomeric friction wedge assembly 28' which is constructed in accordance with the principles of the present invention. Assembly 28' is generally similar in construction and operation to the friction assembly 28 discussed hereinbefore with the primary distinctions therebetween being twofold. First, the friction assembly 28' comprises a single elastomeric friction member 80 and secondly the relative orientation of the slopes of the adjacent surfaces of friction member 80 and the wear plate 48' are generally reversed from the corresponding orientation of the adjacent surfaces of the friction members 32 and wear plate 48 of the hereinbefore discussed friction wedge assembly 28. In view of the similarity between assemblies 28 and 28', elements of assembly 28' which are essentially identical to like elements of assembly 28 will be identified with identical reference numerals and similar elements will be identified with identical reference numerals primed.

Wear plate 48' includes inner and outer generally vertically extending surfaces 82 and 84, respectively, each of which consists of a pair of transversely adjacent sloped surface portions 86 which slope transversely inwardly from the transverse midpoint of the wear plate 48'. Elastomeric friction member 80 additionally includes a pair of transversely adjacent outer surfaces 88 thereof which slope transversely inwardly from the transverse midpoint thereof such that when wedge assembly 28' is in the assembled position thereof as illustrated in FIG. 5, surfaces 88 of member 80 engage the adjacent surface portions 86 of wear plate 48'. In the embodiment illustrated, the column guide 52' of the respective side frame 22' therefor is formed to complement the configuration of the outer surface 84 of wear plate 48'.

With a configuration of wedge assembly 28' as discussed hereinabove, the assembly, structural cooperation and operation thereof is essentially identical to the assembly, structural cooperation and operation of wedge assembly 28 as discussed hereinbefore. However, because of the reversal of the slope of cooperating surfaces between wear plate 48' and friction member 80, the lateral restraint offered by the wedging effect of friction member 80 occurs at the transverse side of member 80 opposite from the direction of the transverse load imparted thereto. An additional factor to be considered with the utilization of wedge assembly 28' is that because assembly 28' does not include a space 72, the selection of the elastomeric material for member 80 may be somewhat limited in comparison with the available material range for the friction members 32. Such a limitation occurs because it is essential that the member 80 does not provide excessive lateral restraint or inhibition to transverse movement of the bolster 16 with respect to the side frame 22'.

The invention herein is primarily directed to a side frame to bolster friction assembly having elastomeric friction means which undergo compression during the transverse movement thereof. Accordingly, various changes can be made by those skilled in the art to the embodiment described hereinabove without departing from the scope of the invention herein, which is defined by the scope of the claims hereinafter. For example: the sloped orientations between the wear plate 48 and members 32 and also between the wear plate 48' and member 48 may be reversed from the specific orientations illustrated; the elastomeric friction members 32 and 80 may be formed with one or more differing layers of elastomer if conditions so dictate; the surfaces of wear plate 48 and 48' may be lubricated for initial break-in, if desired; hydraulic snubbers can be disposed in the spring groups 20 to aid in the control of rocking or swaying of the railway freight truck 10; and the like.

Claims

1. A railway truck bolster friction assembly adapted to be captively retained within a pocket of an elongated truck bolster member which extends between spaced elongated side frame members of a railway truck vehicle comprising: elastomeric friction means adapted to have a first portion thereof in communication engagement with adjacent surfaces of such a pocket and a second portion thereof in biased frictional engagement with adjacent portions of wearing wear surface means of a column guide of a respective one of said side frames, said second portion being spaced longitudinally outwardly, with respect to outwardly of such a pocket from the longitudinal axis of such a bolster member, from such a pocket and said first portion being spaced longitudinally inwardly from said second portion; bias means cooperable with said elastomeric friction means to maintain such frictional engagement; said elastomeric friction means being operative to deform and maintain said frictional engagement, without slipping between adjacent engaging surfaces, during at least initial vertical and transverse movements of such a bolster member with respect to such a respective one of said side frame members; during a subsequent transverse movement of such a bolster member with respect to such a side frame member, at least a section of said section second portion slips transversely with respect to the adjacent portion of said wearing wear surface means; and during such transverse slipping, said adjacent portion of said wearing wear surface means cooperates with such a pocket to continuously increase the friction between said section of said second portion and said adjacent portion of said wearing wear surface means in direct proportion to the amount of said subsequent transverse movement.

2. A railway truck bolster friction assembly as specified in claim 1 additionally including biasing means to bias said elastomeric friction means into said communication and said frictional engagement.

3. A railway truck bolster friction assembly as specified in claim 2 wherein during a subsequent vertical movement of such a bolster member, said elastomeric friction means are operative such that at least sections of said second portion will slip with respect to adjacent portions of said wearing surface means.

4. A railway truck bolster friction assembly as specified in claim 2 wherein said adjacent portion of said wearing surface means slopes transversely outwardly from a generally vertically extending longitudinally innermost surface of said wearing surface means.

5. A railway truck bolster friction assembly as specified in claim 4 wherein said wearing surface means includes a pair of said adjacent portions, each of said adjacent portions slope transversely outwardly from said innermost surface and a respective section of said elastomeric friction means frictionally engages each of said adjacent portions.

6. A railway truck bolster friction assembly as specified in claim 5 wherein said adjacent portions are identical and said innermost portion is transversely equidistant from the transverse edges of said wearing surface means.

7. A railway truck bolster friction assembly as specified in claim 6 wherein during said second subsequent transverse movement in one direction only the friction between one of said sections of said second portions and said second adjacent portion of said wearing surface means adjacent thereto increases and during said second subsequent transverse movement in a direction opposite said one direction only the friction between the other of said sections of said second portion and the other of said adjacent portion of said wearing surface increases.

8. A railway truck bolster friction assembly as specified in claim 7 wherein said elastomeric friction means comprises a pair of transversely adjacent, identical elastomeric friction members.

9. A railway truck bolster friction assembly as specified in claim 8 wherein when said friction members are in operational position within such a pocket, the transversely adjacent surfaces thereof are transversely spaced from each other.

10. A railway truck bolster friction assembly as specified in claim 9 wherein said biasing means continuously biases each of said elastomeric friction members into said communication and said frictional engagement.

11. In a friction assembly adapted for use in a railway truck intermediate a longitudinal end portion of an elongated truck bolster and an adjacent column guide portion of a truck side frame to provide frictional damping of relative vertical and lateral motion between the bolster and the side frame, the combination comprising:

a friction element adapted to be retained with respect to such a longitudinal end portion of such a bolster;

a wear surface means adapted to be retained with respect to such an adjacent column guide portion of such a side frame;

bias means operable to maintain frictional engagement between said friction element and said wear surface means throughout such relative motion between such a bolster and such a side frame;

said friction element being relatively movable in opposite lateral directions with respect to said wear surface means while in frictional engagement therewith during such relative motion between such a bolster and such a side frame;

and said wear surface means and adjacent portions of said friction element being configured to continuously increase the magnitude of friction between said wear surface means and at least a portion of said friction element during relative lateral motion therebetween throughout a range of such lateral motion in either of such opposite lateral directions. 12. The combination as claimed in claim 11 wherein said increase in the magnitude of friction between said wear surface means and said at least a portion of said friction element is directly proportional to the magnitude of such relative lateral motion. 13. The combination as claimed in claim 12 wherein said friction element includes a resiliently deformable means which is initially deformed in response to the bias of said bias means. 14. The combination as claimed in claim 13 wherein said resiliently deformable means includes a surface portion thereof which is mantained in frictional engagement with said wear surface means. 15. The combination as claimed in claim 14 wherein said resiliently deformable means is further deformed beyond said initial deformation in response to such relative motion. 16. The combination as claimed in claim 15 wherein said friction element is retained with respect to an end portion of such a bolster in an outwardly open pocket. 17. The combination as claimed in claim 16 wherein said at least a portion of said friction element is a pair of portions thereof and the magnitude of friction between said wear surface means and said friction element is increased during such relative lateral motion by increasing the magnitude of friction with respect to a respective one of said pair of portions during such relative lateral motion in respective opposite lateral directions. 18. The combination as claimed in claim 11 wherein said wear surface means and said adjacent portions of said friction element are mutually engageable in frictional engagement along respective adjacent surface portions thereof to provide such frictional damping of such relative vertical and lateral motion and said respective surface portions are configured to continuously increase the magnitude of friction between said wear surface means and said at least a portion of said friction element during such relative lateral motion therebetween.