Patent Application
20080290058
The present disclosure generally relates to railroad cars and, more specifically, to a railroad car draft gear utilizing an elastomeric spring assembly for storing and dissipating energy during operation of the draft gear.
Railroad car draft gears have been used for many years at opposite ends of a railcar to absorb and cushion impact forces. Most railcar draft gears include a cast housing having an inwardly tapered bore at an open end, a spring disposed within the housing, a series of metal friction shoes or members arranged in the tapered bore of the housing and movable against the spring upon compression of the draft gear, and a wedge disposed in operable combination with the friction members such that impact blows directed against the wedge are transferred axially to the spring and radially to the housing. In most railcar draft gears, a spring seat or follower is arranged between an end portion of each friction member and the spring.
Recently, elastomeric materials have been used and accepted as replacements for steel springs. While offering advantageous results, unless the load applied to the elastomeric spring is perfectly aligned with the longitudinal axis of the spring, elongated elastomeric springs tend to snake or buckle under load. One elastomeric spring assembly offering beneficial results is disclosed in U.S. Pat. No. 5,351,844 to R. A. Carlstedt and includes multiple elastomeric springs stacked in axial relation relative to each other. A metal plate is bonded or otherwise secured to opposed faces of each elastomeric spring. The metal plate bonded to each face of each elastomeric spring offers numerous advantageous results. The metal plates act to limit snaking and/or buckling problems. Moreover, the metal plates bonded to opposed faces of each elastomeric spring yields increased work capacity from each spring. Such a spring assembly has been successfully used for years in combination with railcar draft gears.
Railcar manufacturers and suppliers for such railcar manufacturers are continually seeking methods and ways of reducing the manufacturing costs of railcars and the components used to build such railcars without having to sacrifice performance and quality. When considering costs savings in connection with draft gears, however, the options are few. First, the size of the draft gear housing cannot be changed without adversely effecting the relationship with a fixed size pocket provided in a railcar centersill in which the draft gear is accommodated. Second, and with the size of the draft gear housing being fixed, the amount of steel used to form the draft gear housing has already been minimized as with openings and voids wherever possible. Moreover, the size of the elastomeric spring assembly used in the draft gear to absorb impacts, as defined by the number of the elastomeric springs comprising the spring assembly, cannot be reduced without adversely effecting draft gear performance and operation.
Thus, there remains a continuing need and desire to provide a railcar draft gear capable of offering the same operating characteristics as known railcar draft gears but which is more economical to manufacture.
In view of the above, and in accordance with one aspect, there is provided a railroad car draft gear including a hollow housing having an open end with a series of friction members arranged in operable combination therewith. A wedge is arranged for axial movement relative to the open end of the housing and in operable combination with the friction members. An elastomeric spring assembly is axially arranged within the hollow housing for storing energy applied to said wedge during operation of the draft gear. One end of the spring assembly is arranged in contacting relation with a closed end of the housing. A spring seat is arranged within said housing between the spring assembly and an end portion of each friction member.
According to this aspect, and unlike other known spring assemblies, the metal plate at the end of the spring assembly arranged adjacent to the spring seat has been removed and eliminated, thus, resulting in costs savings. The spring seat defines a surface, arranged in contacting relation with an end of the spring assembly, and defining an incongruity for allowing the elastomer of the spring assembly to combine therewith so as to establish a mechanical bond between the end of the spring assembly and the spring seat.
In one embodiment, the incongruity on the spring contacting surface of the spring seat is defined by an annular groove concentrically arranged about a longitudinal axis of the draft gear housing. In another form, the incongruity on the spring contacting surface of the spring seat is defined by a series of equi-angularly disposed recesses concentrically arranged about a longitudinal axis of the housing. In still another form, the incongruity on the spring contacting surface of the spring seat can be configured as an annular projection or a series of equi-angularly spaced and shaped projections for gripping and resisting easy outward radial movement of the adjacent elastomer spring.
In another form, the metal plate at the end of the spring assembly arranged adjacent to the draft gear housing has also been removed and eliminated. Preferably, a surface on the draft gear housing arranged in contacting relation relative to the adjacent end of the spring assembly defines an incongruity for limiting radial expansion of the end of the spring assembly when an axial compressive load is applied to the draft gear.
According to another aspect, there is provided a railroad car draft gear including a hollow housing having an open end and a series of friction members arranged in operable combination with the open end of the housing. A wedge is arranged for axial movement relative to the open end of the housing and in operable combination with the friction members. A multi-tiered spring assembly is arranged within the draft gear housing for storing and dissipating energy applied to the wedge during compression of the draft gear. One end of the spring assembly is arranged in contacting relation with a closed end of the housing. The multi-tiered spring assembly includes a series of stacked elastomeric springs with at least one plate between each pair of axially adjacent springs. A spring seat is arranged within the draft gear housing between the multi-tiered spring assembly and an end portion of each friction member.
According to this aspect, and to reduce the manufacturing cost of the railcar draft gear, the metal plate normally disposed between the end of the multi-tiered spring assembly and the spring seat has been removed and eliminated. A surface on the spring seat, arranged in contacting relationship with the multi-tiered spring assembly, preferably defines at least one incongruity for allowing the elastomer of the spring assembly, arranged adjacent to the spring seat, to deform and operably combine with the incongruity thereby limiting radial expansion of the spring arranged adjacent to the spring seat.
Preferably, the spring contacting surface of the spring seat defines a recess coaxially arranged relative to a longitudinal axis of the draft gear housing. In one form, the incongruity on the spring contacting surface of the spring seat is defined by an annular groove concentrically arranged about a longitudinal axis of the housing. In an alternative embodiment, the incongruity on the spring contacting surface of the spring seat is defined by a series of equi-angularly disposed recesses concentrically arranged about a longitudinal axis of the draft gear housing.
The metal plate at the opposite end of the multi-tiered spring assembly, arranged adjacent to the draft gear housing, has also preferably been removed and eliminated, thus, resulting in further costs savings. In one form, a surface on the draft gear housing arranged in contacting relation relative to the spring assembly preferably defines an incongruity for limiting radial expansion of the end of the elastomeric spring when an axial compressive load is applied to the wedge of the draft gear.
According to another aspect, there is provided a railroad car draft gear including an elongated hollow housing having an open first end and a closed second end along with a plurality of friction members arranged in operable combination with the open end of the draft gear housing. A wedge is arranged for axial movement relative to the open end of the draft gear housing and in combination with the series of friction members. A multi-tiered spring assembly is disposed within the hollow housing for storing and dissipating energy applied to the wedge during operation of the draft gear. One end of the spring assembly is arranged in contacting relation with the closed end of the draft gear housing. The spring assembly includes a series of stacked elastomeric springs with at least one plate between each pair of axially adjacent springs. The opposite end of the spring assembly defines a protrusion arranged generally coaxial with a longitudinal axis of the housing and axially extending from the spring disposed the furthest from the closed end of the draft gear housing. A spring seat is arranged in the housing between the second end of the spring assembly and an end portion of each friction member. The spring seat defines a surface arranged in contacting relation with the end of the spring assembly.
To aid in costs savings, the metal plate normally disposed between the multi-tiered spring and the spring seat has been removed and eliminated. The spring contacting surface on the spring seat preferably defines an incongruity for allowing the elastomer of the compression spring arranged adjacent to the spring seat to deform into operable combination with the incongruity thereby forming a mechanical bond between the end of the multi-tiered spring assembly and the spring seat. Preferably, the spring contacting surface on the spring seat further defines a central recess for accommodating the protrusion axially extending from the end of the spring assembly so as to advantageously affect and maintain axial alignment of the multi-tiered spring relative to a longitudinal axis of the draft gear housing.
In one form, the incongruity on the spring contacting surface of the spring seat is defined by an annular groove concentrically arranged about a longitudinal axis of the housing. In an alternative form, the incongruity on the spring contacting surface of the spring seat can be defined by a series of equi-angularly disposed recesses concentrically arranged about a longitudinal axis of the draft gear housing.
To further aid in reducing the manufacturing cost of the railroad car draft gear, the metal plate at the opposite end of the multi-tired spring is also eliminated. In this regard, a surface on the draft gear housing arranged in contacting relation relative to the end of the multi-tiered spring assembly defines an incongruity for limiting radial expansion of the adjacent spring when an axial compressive load is applied to the wedge of the draft gear.
While the present invention is susceptible of embodiment in multiple forms, there is shown in the drawings and will hereinafter be described preferred embodiments of the invention, with the understanding the present disclosure is to be considered as setting forth exemplifications of the invention which are not intended to limit the invention to the specific embodiments illustrated and described.
Referring now to the drawings, wherein like reference numeral indicate like parts throughout the several views, there is shown in
In the embodiment shown in
Spaced longitudinally or axially inward of shell section 24, draft gear housing 12 is provided with an internal cavity 28. As shown in
In the embodiment shown in
In the illustrated embodiment, friction clutch assembly 22 of draft gear 10 further includes a wedge 40 arranged for axial movement relative to the end 16 of housing 12. As shown in
An axially elongated spring assembly 50 is arranged within the cavity 28 of the draft gear housing 12 for storing and dissipating energy imparted or applied to the end 42 of wedge 40 during axial compression of the draft gear 10. One end of spring assembly 50 is arranged in contacting relation with the end wall 29 of housing 12. As is known, spring assembly 50 is precompressed during assembly of the draft gear 10 and also serves to maintain the components of the friction clutch assembly 22 including members 30 and wedge 40 in operable engagement with each other and within the draft gear housing 12 both during operation of the draft gear 10 as well as during periods of non-operation of the draft gear 10. Suffice it to say, the draft gear housing 12, the friction members 30, and wedge 40 are each suitably configured in a conventional and well known manner to coact with each other such that they are all positively retained in operable combination under the resilient compressive force of spring assembly 50.
In the form shown, spring assembly 50 has a multi-tiered construction including a series of longitudinally stacked elastomeric compression springs, generally identified by reference numeral 52. As shown in
To reduce manufacturing costs, the end springs 52′ and intermediary springs 52″ embody similar technology and parts. One element common to the end springs 52′ and intermediary springs 52″ is an elastomeric spring pad 54. The elastomeric spring pad 54 is formed using the process and methodology disclosed in U.S. Pat. No. 5,351,844 to R. A. Carlstedt; the applicable portions of which are incorporated herein by reference. Suffice it to say, the elastomeric spring pad 54 of each spring 52′ and 52″ is formed from a copolyester polymer elastomer such as that manufactured and sold by DuPont under the tradename “HYTREL” and the art known equivalents thereto.
The copolyester polymers previously referred to come in pellet form for use in casting or extruding. An initial step in the process of forming each spring 52′, 52″ involves creation of a preform block of material, generally identified in
The next step in the spring forming process involves working the preform 60 as through precompression of the preform 60. The process of working the preform 60 and thereby transmuting the preform into an elastomeric spring pad 54 is described in further detail in the above-mentioned U.S. Pat. No. 5,351,844 to R. A. Carlstedt. When forming any one of the intermediary springs 52″, the preform 60 is preferably precompressed between a pair of metal plates 66. Each plate 66 is arranged in operable combination with opposed ends or load faces 67′, 67″ (
As shown in
The intermediary spring 52″ resulting from the above-described process is illustrated in
To inhibit the elastomer from easily flowing along the inner surface 66′ of each plate 66 as the compressive force is applied to the preform, a relatively simple manufacturing procedure is used to obtain a mechanical bond between the plates 66 and the preform. One such procedure involves providing each plate 66 with a series or multiple holes or openings 69, as shown in
During working of the preform 60, the elastomer plastically deforms and flows into each opening 69 whereby establishing a mechanical bond between each plate 66 and the spring pad 54. It will be appreciated the plates 66 can be designed differently from that shown and described but yet offer a bonding relationship between each plate 66 and the spring pad 54 without detracting or departing from the true spirit and scope of the present disclosure.
The process of forming the end springs 52′ is substantially similar to that discussed above regarding the intermediary springs 52″ except the end spring 52′ has only a single metal plate 66 bonded or otherwise secured to only one of the load faces 67′, 67″ thereof. Suffice it to say, each end spring 52′ is formed from a preform 60 like that shown in
When forming either end spring 52′, the preform 60 is precompressed with a plate 66 provided in operable combination with only one load face 67″ as shown by way of example in
During working, a suitably configured plate or member 96 is arranged to operably engage with the opposite end or face 67 of preform 60. As shown in
The end spring 52′ resulting from the above-described process is illustrated in
Returning to
As shown in
As shown in
In the form shown by way of example in
In the illustrated embodiment, the annular groove or recess 82 has a generally constant radial width ranging between about 0.375 inches and about 0.562 inches. In a most preferred form, the annular groove or recess 82 has a generally constant radial width of about 0.503 inches. Moreover, recess 82 has a generally constant depth ranging between about 0.080 inches and about 0.188 inches. In a most preferred form, recess 82 has a generally constant depth of depth of about 0.094 inches.
As illustrated in
The spring seat 70 illustrated in
In the exemplary embodiment, the recesses 92 have a diameter ranging between about 0.437 inches and about 0.75 inches. In a preferred form, each recess 92 has a diameter of about 0.563 inches. Moreover, each recess 92 has a depth ranging between about 0.77 inches and about 0.125 inches. In a preferred embodiment, each recess has a depth of about 0.094 inches.
As illustrated in
Alternatively, the surface incongruity 80 can be defined by an annular projection or a series of equi-angularly and like shaped projections which depend from surface 74 on the spring seat 70. Suffice it to say, the annular projection or series of projections defining surface incongruity 80 on spring seat 70 extends away from the spring seat surface 74 and has a radial shoulder which serves to grip and resist radial movement of the elastomer of the adjacent end spring 52′ during compression of spring 50. Such annular projection or series of annular projections would preferably be arranged concentric to the longitudinal draft gear axis 14. In a preferred embodiment, the projection or series of equi-angularly spaced projections would be radially spaced from the longitudinal draft gear axis by a distance slightly greater than the radius of the predetermined diameter PD of the elastomeric preform 60 (
Returning
In a preferred form, the draft gear housing 12 is also configured to establish a bonding relationship between the end of spring assembly 50 and the draft gear housing 12. Preferably, and as shown in
The surface incongruity on the spring contacting surface 104 of draft gear housing 12 can take a myriad of different designs without detracting or departing from the true spirit and scope of the present disclosure. One form of surface incongruity, generally identified by reference numeral 120, is shown by way of example in
Preferably, the recesses 132, 132′ are equidistantly spaced from the longitudinal centerline 14 of the housing 12. In a most preferred form, the recesses 132, 132′ are spaced apart by a distance generally equal to the predetermined diameter PD of the elastomeric preform 60 (
Preferably, the recesses 132, 132′ are substantially identical relative to each other such that they apply an equal gripping force to the end spring 52′ upon compression of the spring assembly 50. In the exemplary embodiment, each recess 132, 132′ has a diameter ranging between about 0.437 inches and about 0.75 inches. In a preferred form, each recess 132, 132′ has a diameter of about 0.563 inches. Moreover, each recess 132, 132′ preferably has a depth ranging between about 0.77 inches and about 0.125 inches. In a preferred embodiment, each recess has a depth of about 0.094 inches.
As shown in
Alternatively, and while serving the same purpose and functioning substantially the same as the surface incongruity mentioned above, the surface incongruity 120 can include more than one recess arranged on opposite sides of recess 108; with each recess of the incongruity defining an open cavity arranged adjacent to the end of the spring assembly 50. The recesses forming this embodiment of surface incongruity are shaped substantially similar to recesses 132, 132′ discussed above. In this embodiment, at least one of the pairs of recesses arranged to opposite sides of the longitudinal axis 14 of the draft gear housing 10 are spaced apart by a distance generally equal to the predetermined diameter PD of the elastomeric preform 60 (
Another alternative surface incongruity, represented generally by reference numeral 220, is shown by way of example in
Each of the recesses 232 are configured substantially similar to the recesses 132, 132′ described above. As illustrated in
Still another form of surface incongruity, represented generally by reference numeral 320, is shown by way of example in
The annular groove or recess 322 is shaped substantially similar to the annular recess 82 discussed above regarding surface incongruity 80. In the exemplary embodiment illustrated in
As will be appreciated from an understanding of the present disclosure, the overall manufacturing cost of the draft gear 10 is reduced through elimination of multiple parts used to form spring assembly 50. This advantageous result has been accomplished with no reduction in draft gear performance, or interferences with tried and accepted production methods. Although multiple metal plates associated with the end springs 52′, arranged adjacent to the spring seat 70 and to the end wall 29 of the draft gear housing 12, have been eliminated, thus resulting in costs savings, positive alignment of the spring assembly 50 relative to the longitudinal axis 14 of the draft gear 10 has been maintained coupled with the ability to maintain force control of the end spring 52′ arranged adjacent to the spring seat 70 and end wall 29 of the draft gear housing 12.
In a preferred form, radial twisting and snaking of the elastomeric spring 50 is inhibited so as to advantageously affect performance of the spring assembly 50. Notably, the projection 62 axially extending from the end spring 52′ arranged adjacent to the spring seat 70 is received and accommodated within the recess 78 defined by the spring seat 70. As such, the end spring pad 52′ is maintained in axial alignment with the spring seat 70 thus effectively assuring transference of the forces applied to the spring seat 70 from the friction clutch assembly 22 in a direction axially aligned with the longitudinal axis 14 of the draft gear 10 thus optimizing performance of the spring assembly 50.
With regard to the other end of spring assembly 50, the projection 62 axially extending from the end spring 52′ arranged adjacent to the spring engaging surface 104 of the end wall 29 of housing 12 is received and accommodated within the recess 108 defined by the end wall 29 of housing 12. As such, the end of spring assembly 50 arranged adjacent to the end wall 29 of housing 12 is likewise maintained in axial alignment with the longitudinal axis 14 of the draft gear 10 thus optimizing performance of the spring assembly 50.
Moreover, the incongruities, in whatever form, provided on the spring seat 70, serve to grip the elastomer of and inhibit the end spring 52′ arranged in contact with the spring seat 70 from easily flowing along the spring contacting surface 74 of the spring seat 70. As will be a appreciated from an understanding of this disclosure, the surface incongruities provided on the spring seat 70 serve to operably control radial expansion of the end spring 52′ arranged adjacent to the spring seat 70 thus resulting in a spring assembly having greater compressive strength.
Similarly, the incongruities, in whatever form, on the spring contacting surface 104 of the draft gear housing rear wall 29 grip and inhibit the end spring 52′ arranged in contact with the draft gear housing rear wall 29 from easily flowing along the spring contacting surface of the housing 12. As such, the surface incongruities provided on the rear wall 29 of the draft gear housing 12 operably control radial expansion of the end spring 52′ arranged adjacent to draft gear housing end wall 29 thus resulting in a spring assembly with greater compressive strength.
From the foregoing, it will be observed that numerous modifications and variations can be made and effected without departing or detracting from the true spirit and novel concept of the present invention. Moreover, it will be appreciated, the present disclosure is intended to set forth an exemplification of the invention which is not intended to limit the invention to the specific embodiment illustrated. Rather, this disclosure is intended to cover by the appended claims all such modifications and variations as fall within the spirit and scope of the claims.
