Patent Publication Number: US-10328957-B2

Title: Railcar draft gear assembly

Description:
RELATED APPLICATION 
     This patent application is a continuation patent application of co-assigned U.S. patent application Ser. No. 14/468,033, filed Aug. 25, 2014, now U.S. Pat. No. 9,789,888; the entirety of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION DISCLOSURE 
     This invention disclosure generally relates to railcar draft gears and, more specifically, to a railcar draft gear assembly specifically designed to consistently and repeatedly withstand up to about 110,000 ft-lbs of energy imparted thereto while not exceeding a force level of 900,000 lbs. while having a wedge member of the draft gear assembly travel in an inward axial direction approximating 4.5 inches relative to an open end of the draft gear. 
     BACKGROUND 
     As railroads push to increase car capacity to handle the increasing demands on the transportation network, freight car designers/builders have been stepping up to the challenge. With the overall train lengths limited by system constraints such as passing siding lengths, the challenge has been how to achieve more railcar capacity in the same or shorter lengths of freight cars and trains. Freight car designers/builders have heretofore met this challenge by pushing the top and bottom of the defined clearance line envelopes to the limits allowed by the Association of American Railroads (the “AAR”). Additionally, car designers/builders have utilized modern design tools to make freight car designs lighter in weight, while still meeting the AAR standard design loads whereby allowing each freight car to carry more lading while maintaining maximum allowable gross rail loads. 
     During the process of assembling or “making-up” a freight train, railcars are run into and collide with each other to couple them together. Since time is money, the speed at which the railcars are coupled has significantly increased. Moreover, and because of their increased capacity, the railcars are heavier than before. These two factors and others have resulted in increased damages to the railcars when they collide and, frequently, to the lading carried within such railcars. 
     Providing an energy absorption/coupling system at opposed ends of each railcar has long been known. Such a system typically includes a coupler for releasably attaching two railcars to each other and a draft gear assembly arranged in operable combination with each coupler for absorbing, dissipating and returning energy imparted thereto during make-up of the train consist and during operation of the railcar. As railroad car designer/builders have reduced the weight of their designs, however, they have also identified a need to protect the integrity of the railcar due to excessive longitudinal loads being placed thereon, especially as the railcars are coupled to each other. Such longitudinal loads frequently exceed the design loads set by the AAR. 
     While conventional draft gears have high shock absorbing capacities and capabilities, they tend to transmit high magnitude of force to the railcar structure during a work cycle. Of course, transmitting a high magnitude of force to the railcar structure can result in damages to the goods being carried by the railcar and the railcar itself. 
     A conventional draft gear assembly is disposed within a pocket defined by a centersill on the railcar and has an operative length of travel in one direction of movement of about 3.5 inches before solid stops limit the travel and no more energy can be absorbed by the draft gear. Over this limited distance, the energy of the moving railcar must be absorbed so as to reduce the impact forces and resulting damage to the adjacent railcar to be coupled thereto. Largely because of their increased coupling speeds and the increased weights of the loads being carried thereby, heretofore known energy absorption/coupling systems have been shown to be inadequate. As such, railcars are experiencing severe end-impacts that can cause a complete collapse of the end of the car—resulting in large repair costs—coupled with damage to the lading—resulting in significantly higher insurance premiums. 
     Increasing the travel of the draft gear assembly may advantageously allow more energy to be absorbed. The challenge of increasing the travel of the draft gear assembly is, however, complicated. Passing sidings and loading facilitates often limit the number of railcars that can be joined to each other in one train. Lengthening the draft gear housing also means lengthening the size or length of the pocket wherein the draft gear assembly is accommodated which requires lengthening the centersill resulting in adding length to the railcar. The length of a railroad car, however, is critical. 
     By itself, adding to the length of the railcar does not appear problematical. When considering, however, that the railcars are not transported individually but rather as part of a much longer train consist, increasing the length of a single railcar is exponentially multiplied when considering the cumulative or overall length of a 100 railcar train consist. Increasing the length of an individual railcar can result in the last railcar in a 100 car consist no longer fitting on the siding and, thus, having to be left behind. As such, there would be at least a one percent (1%) loss in train efficiency. This is simply unacceptable. Accordingly, the concept of simply increasing the length of the draft gear assembly to solve the problem of energy absorption between railcars is unacceptable to the railroad industry. 
     Thus, there is a continuing need and desire for a draft gear assembly which not only allows for increased travel over which the high level of energy from impact loads of colliding railcars can be absorbed, dissipated and returned but the overall length of the draft gear assembly housing cannot be lengthened and the draft gear assembly must be capable of absorbing the increased impact loads being realized in today&#39;s railroad industry. 
     SUMMARY 
     In view of the above, and in accordance with one aspect of this invention disclosure, there is provided a draft gear assembly including a hollow metal housing open at a first end and closed toward the second end thereof. The housing is configured to fit within a standard sized pocket defined by the centersill on the railcar. The housing defines a series of tapered longitudinally extended inner surfaces opening to and extending from the first end of the housing. A series of friction members are equally spaced about a longitudinal axis of the draft gear assembly toward the first end of the housing, with each friction member having axially spaced first and second ends and an outer surface extending between the ends. The outer surface on each friction member is operably associated with one of the tapered longitudinally extended inner surfaces on the housing so as to define a first angled friction sliding surface therebetween. 
     A wedge member is arranged for axial movements relative to the first end of the housing and to which external forces are applied during operation of the railcar. The wedge member defines a series of outer tapered surfaces equally spaced about the longitudinal axis of the housing and equal in number to the number of friction members. In one form, each outer tapered surface on the wedge member is operably associated with an inner surface on each friction member so as to define a second angled friction sliding surface therebetween and such that the wedge member produces a radially directed force against the friction members upon movement of the wedge member inwardly of the housing. A spring seat is arranged within the housing. One surface of the spring seat is arranged in operable engagement with the second end of each friction member. 
     A spring assembly is disposed in the housing between the closed end of the housing and a second surface of the spring seat for storing, dissipating and returning energy imparted to the draft gear assembly. The spring assembly includes an axial stack of individual elastomeric springs. In one embodiment, the spring assembly, in operable combination with the disposition of the first and second angled sliding surfaces of the draft gear assembly relative to the longitudinal axis of the draft gear assembly, permits the draft gear assembly to consistently and repeatedly withstand about 70,000 ft-lbs. to about 85,000 ft-lbs. of energy imparted to the draft gear assembly while not exceeding a force level of 600,000 lbs. over a range of travel of the wedge member in an inward axial direction relative to the housing approximating 3.5 inches. 
     In accordance with this family of embodiments, the first angled friction sliding surface of the draft gear assembly is disposed at an angle ranging between about 1.5 degrees and about 5 degrees relative to the longitudinal axis of the draft gear assembly. Preferably, the second angled friction sliding surface of the draft gear assembly is disposed at an angle ranging between about 32 degrees and about 45 degrees relative to the longitudinal axis of the draft gear assembly. In one form, the elastomeric pad of each individual elastomeric spring is formed from a polyester material having a Shore D hardness ranging between about 40 and 60. 
     In one embodiment of the invention disclosure, the spring assembly of the draft gear assembly further includes a rigid separator plate disposed between two axially adjacent individual springs in the axial stack of elastomeric springs. The disposition of the separator plate creates different dynamic elastic absorption characteristics on opposite sides thereof whereby optimizing dynamic lost work opportunities during an impact event of the draft gear assembly. 
     According to another aspect of this invention disclosure there is provided a draft gear assembly including a hollow metal housing open at a first end and closed toward the second end thereof. The draft gear assembly housing is configured to fit within a standard sized pocket defined by the centersill on the railcar. The housing defines a series of tapered longitudinally extended inner surfaces opening to and extending from the first end of the housing. A series of friction members are equally spaced about a longitudinal axis of the housing toward the first end of the housing. Each friction member has axially spaced first and second ends and an outer surface extending between the ends. The outer surface on each friction member is operably associated with one of the tapered longitudinally extended inner surfaces on the housing so as to define a first angled friction sliding surface therebetween. 
     A wedge member is arranged for axial movements relative to the first end of the housing. External forces are applied to the wedge member during operation of the railcar. Toward an opposite end, the wedge member defines a series of equally spaced outer tapered surfaces. In one form, the outer tapered surfaces on the wedge members are operably associated with inner surfaces on the friction member so as to define a second angled friction sliding surface therebetween and such that the wedge member produces a radially directed force against the friction members upon movement of the wedge member inwardly of the housing. A spring seat is arranged within the housing. One surface of the spring seat is arranged in operable engagement with the second end of each friction member. 
     A spring assembly is disposed within and between the closed end of the housing and a second surface of the spring seat for storing, dissipating and returning energy imparted thereto. The spring assembly is configured to function in operable combination with the disposition of said first and second angled sliding surfaces of said draft gear assembly such that said draft gear assembly consistently and repeatedly withstands about 110,000 ft-lbs. of energy imparted to the draft gear assembly at a force level not to exceed 900,000 lbs. over a range of travel of the wedge member in an inward axial direction relative to the housing of at least 4.5 inches. 
     Preferably, the first angled friction sliding surface on the draft gear assembly is disposed at an angle ranging between about 1.5 degrees and about 5 degrees relative to the longitudinal axis of the draft gear assembly. In the preferred form, the second angled friction sliding surface is disposed at an angle ranging between about 32 degrees and about 45 degrees relative to the longitudinal axis of the draft gear assembly. 
     The spring assembly preferably includes an axial stack of individual elastomeric springs. Each spring includes an elastomeric pad having a generally rectangular shape, in plan, approximating the cross-sectional configuration of the hollow chamber defined by the housing whereby optimizing the capability of the spring assembly to store, dissipate and return energy imparted to the draft gear assembly by the coupler. The elastomeric pad of each individual elastomeric spring is preferably has a Shore D hardness ranging between about 40 and 60. In one embodiment, the spring assembly of the draft gear assembly further includes a rigid separator plate disposed between two axially adjacent individual springs in the axial stack of elastomeric springs to create different dynamic elastic absorption responses on opposite sides of the plate whereby optimizing dynamic lost work opportunities during an impact event of the draft gear assembly. 
     In another family of embodiments, there is provided a draft gear assembly including a hollow metal housing open at a first end and closed toward the second end thereof. The housing is configured to fit within a standard sized pocket defined by a centersill on a railcar. The housing defines a series of tapered longitudinally extended inner surfaces opening to and extending from the first end of the housing. A series of friction members are equally spaced about a longitudinal axis of the housing and are arranged toward the first end of the housing. Each friction member has axially spaced first and second ends and an outer surface extending between the ends. The outer surface on each friction member is operably associated with one of the tapered longitudinally extended inner surfaces on the housing so as to define a first angled friction sliding surface therebetween. 
     A wedge member is arranged for axial movements relative to the first end of the housing. External forces are applied to the wedge member during operation of the railcar. The wedge member defines a series of equally spaced outer tapered surfaces. In one form, each outer tapered surface on the wedge member operably associates with an inner surface on each friction member so as to define a second angled friction sliding surface therebetween. In operation, the wedge member produces a radially directed force against the friction members upon movement of the wedge member inwardly of the housing. A spring seat is arranged within the housing. One surface of the spring seat is arranged in operable engagement with the second end of each friction member. 
     A spring assembly is arranged between the closed end of the housing and a second surface of the spring seat for storing, dissipating and returning energy imparted to the draft gear assembly. The spring assembly of each draft gear assembly is configured and operates in operable combination with the first and second angled surfaces on the draft gear assembly such the draft gear assembly consistently and repeatedly withstands about 70,000 ft-lbs to about 110,000 ft-lbs. of energy imparted thereto while not exceeding a force level of 900,000 lbs. over a range of travel of wedge member in an inward axial direction relative to the housing of about 4.5 inches. 
     Preferably, the first angled friction sliding surface on the draft gear assembly is disposed at an angle ranging between about 1.5 degrees and about 5 degrees relative to the longitudinal axis of the draft gear assembly. In one form, the second angled friction sliding surface is disposed at an angle ranging between about 32 degrees and about 45 degrees relative to the longitudinal axis of the draft gear assembly. 
     In one embodiment, the housing of each draft assembly has two pairs of joined and generally parallel walls extending from the closed end toward the open end of the housing such that the walls define a hollow chamber having a generally rectangular cross-sectional configuration, in plan, for a major portion of the length thereof and which opens to the open end of the housing. Preferably, the spring assembly includes an axial stack of individual elastomeric springs, with each spring including an elastomeric pad having a generally rectangular shape, in plan, approximating the cross-sectional configuration of the hollow chamber defined by the housing whereby optimizing the capability of the spring assembly to store, dissipate and return energy imparted to the draft gear assembly. In a preferred embodiment, the elastomeric pad of each individual elastomeric spring has a Shore D hardness ranging between about 40 and 60. 
     In one embodiment, the spring assembly of the draft gear assembly further includes a rigid separator plate disposed between two axially adjacent individual springs in the axial stack of elastomeric springs so as to create different dynamic elastic absorption reaction on opposite sides of the separator plate whereby optimizing dynamic lost work opportunities during an impact event of the draft gear assembly. In one form, a first group of springs, disposed to one side of the separator plate, have a different cumulative spring rate than a group of springs disposed to an opposite side of the separator plate. In this later embodiment, the group of springs disposed between the separator plate and the spring seat offer less resistance to axial compression than the group of springs disposed between the opposite side of the separator plate and the closed end of the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevational view of a draft gear assembly of this invention disclosure; 
         FIG. 2  is a sectional view taken along line  2 - 2  of  FIG. 1 ; 
         FIG. 3  is a longitudinal sectional view of the draft gear assembly illustrated in  FIG. 1 ; 
         FIG. 4  is an axial plan view of the draft gear assembly illustrated in  FIG. 1 ; 
         FIG. 5  is an enlarged sectional view of one end of the draft gear assembly illustrated in  FIG. 1 ; 
         FIG. 6  is a is a schematic graphical representation of the forces realized by a conventional draft gear assembly; 
         FIG. 7  is a schematic graphical representation of the forces realized by a draft gear assembly having a spring assembly embodying some of the principals and teachings of this invention disclosure; 
         FIG. 8  is a schematic representation of the performance of one form of draft gear assembly embodying principals and teachings of this invention disclosure; and 
         FIG. 9  is a schematic representation of the performance of another form of draft gear assembly embodying principals and teachings of this invention disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     While this invention disclosure is susceptible of embodiment in multiple forms, there is shown in the drawings and will hereinafter be described preferred embodiments, with the understanding the present disclosure is to be considered as setting forth exemplifications of the disclosure which are not intended to limit the disclosure to the specific embodiments illustrated and described. 
     Referring now to the drawings, wherein like reference numerals indicate like parts throughout the several views, there is shown in  FIG. 1  a railroad car draft gear assembly, generally identified by reference numeral  10 , and embodying teachings and principals of this invention disclosure. One of the many advantages of the draft gear assembly  10  of this invention disclosure being that it can be relatively easily installed without incurring any changes or modifications to a standard sized pocket  12  defined by a centersill  14  on a railcar  16 . 
     The centersill  14  can be cast or fabricated and has many standard features. As shown in  FIG. 1 , the centersill  14  has longitudinally or axially spaced front and rear stops  15  and  17 , respectively, connected to and carried by sidewalls (not shown) on the centersill  14 . The longitudinal distance between the inboard face of the front stop  15  and the inboard face of the rear stop is 24.625 inches. 
     As shown in  FIG. 1 , draft gear assembly  10  includes an axially elongated hollow and metallic housing  20  defining a longitudinal axis  22 . Housing  20  is closed by an end wall  24  ( FIG. 4 ) at a first or closed end  26  and is open toward an axially aligned second or open end  28 . 
     In the embodiment illustrated in  FIG. 2 , housing  20  includes two pairs of joined and generally parallel walls  30 ,  30 ′ and  32 ,  32 ′, extending from the closed end  26  toward the open end  28  and defining a hollow chamber  34  within housing  20  ( FIGS. 2 and 3 ). As shown in  FIG. 2 , the housing walls  30 ,  30 ′ and  32 ,  32 ′ provide the housing chamber  34  with a generally rectangular or box-like cross-sectional configuration, in plan, for a major lengthwise portion thereof. 
     Moreover, and as shown in  FIG. 3 , toward the open end  28 , housing  20  is provided with a plurality (with only one being shown in  FIG. 5 ) of equi-angularly spaced and longitudinally extended tapered inner angled friction surfaces  36 . Each tapered inner angled friction surfaces  36  on housing  20  converges toward the longitudinal axis  22  and toward the closed end  26  of the draft gear housing  20 . Preferably, housing  20  is provided with three equally spaced longitudinally extended and tapered inner angled friction surfaces  36  but more tapered surfaces could be provided without detracting or departing from the spirit and novel concept of this invention disclosure. 
     In the embodiment shown in  FIG. 3 , draft gear assembly  10  is also provided with a friction clutch assembly  40  for dissipating forces or impacts axially directed against the draft gear assembly  10  as a result of a coupling operation or normal operation of the railcar  16  ( FIG. 1 ). In the embodiment shown in  FIGS. 3 and 4 , the friction clutch assembly  40  includes a plurality of friction members or shoes  42  radially arranged about axis  22  and in operable combination with the open end  28  of the draft gear housing  20 . As shown by way of example in  FIG. 3 , the friction clutch assembly  40  can be provided with three equi-angularly spaced friction members  42  but more friction members could be provided without detracting or departing from the spirit and novel concept of this invention disclosure. Suffice it to say, in the embodiment shown by way of example in  FIGS. 3 and 4 , the number of friction members  42  forming part of the friction clutch assembly  40  are equal in number to the number of tapered inner angled friction surfaces  36  on housing  20 . 
     In the embodiment shown by way of example in  FIG. 5 , each friction member  42  has axially or longitudinally spaced first and second end  44  and  44 ′, respectively. Moreover, each friction member  42  has an outer or external tapered sliding surface  46 . As will be appreciated by those skilled in the art, each inner angled friction surface  36  on housing  20  combines with each outer tapered sliding surface  46  on each friction member  42  to define a first angled friction sliding surface  48  therebetween. The first friction sliding surface  48  is disposed at an angle θ relative to the longitudinal axis  22  of the draft gear assembly  10 . Preferably, the angle θ of the first friction sliding surface  48  ranges between about 1.5 degrees and about 5 degrees relative to the longitudinal axis  22  of the draft gear assembly  10 . In a preferred embodiment, the angle θ of the first friction sliding surface  48  ranges between about 1.7 degrees and about 2 degrees relative to the longitudinal axis  22  of the draft gear assembly  10 . 
     In the illustrated embodiment, the friction clutch assembly  40  further includes a wedge member or actuator  50  arranged for axial movement relative to the open end  28  of housing  20 . As shown in  FIGS. 1, 4 and 5 , an outer end  52  of the wedge member  50  preferably has a generally flat face extending beyond the open end  28  of housing  20  for a distance measuring about 4.5 inches and is adapted to press or bear against a conventional follower  53  such that impact forces directed against to an against the actuator  50  are axially applied to the draft gear assembly  10  during operation of the railcar  16  ( FIG. 1 ). As known, wedge member  50  is arranged in operable combination with the friction members  42 . 
     In the embodiment illustrated by way of example in  FIG. 5 , wedge member or actuator  50  defines a plurality of outer tapered or angled friction surfaces  57  arranged in operable combination with the friction members  42  of the clutch assembly  40 . Although only one friction surface  57  illustrated in  FIG. 5 , the number of friction surfaces  57  on the wedge member  50  equals the number of friction surfaces on members  42  forming part of the clutch assembly  40 . 
     In the embodiment illustrated by way of example in  FIG. 5 , each outer angled friction surface  57  on wedge member  50  combines with an inner angled sliding surface  47  on each friction member  42  to define a second angled friction sliding surface  58  therebetween. The second friction sliding surface  58  is disposed at an angle β relative to the longitudinal axis  22  of the draft gear assembly  10 . Preferably, the angle β of the second friction sliding surface  58  of friction clutch assembly  40  ranges between about 32 degrees and about 45 degrees relative to the longitudinal axis  22  of the draft gear assembly  10 . 
     Wedge member  50  is formed from any suitable metallic material. In a preferred form, and as shown in  FIGS. 3, 4 and 5 , the wedge member or actuator  50  defines a generally centralized longitudinally extending bore  54 . 
     As shown in  FIGS. 3, 4 and 5 , toward the open end  28 , housing  20  is provided with a series of radially inturned stop lugs  23  which are equi-angularly spaced circumferentially relative to each other. Toward a read end thereof, wedge member  50  includes a series of radially outwardly projecting lugs  53  which are equi-angularly disposed relative to each other and extend between adjacent friction members  42  so as to operably engage in back of the lugs  23  on housing  20  and facilitate assembly of the draft gear assembly  10 . 
     As shown in  FIG. 5 , draft gear assmbly  10  furthermore includes a spring seat or follower  60  arranged within the hollow chamber  34  of housing  20  and disposed generally normal or generally perpendicular to the longitudinal axis  22  of the draft gear assembly  10 . Spring seat  60  is adapted for reciprocatory longitudinal or axial movements within the chamber  34  of housing  20  and has a first surface  62  in operable association with the second or rear end  44 ′ of each friction member  42 . As shown in  FIG. 4 , spring seat  60  also has a second or spring contacting surface  64 . 
     An axially elongated elastomeric spring assembly  70  is generally centered and slidable within chamber  34  of the draft gear housing  20  and forms a resilient column for storing, dissipating and returning energy imparted or applied to the free end  52  of wedge member  50  during axial compression of the draft gear assembly  10 . One end of spring assembly  70  is arranged in contacting relation with the end wall  24  of housing  20 . A second end of spring assembly  70  is pressed or urged against surface  64  of the spring seat  60  to oppose inward movements of the friction members  42  and wedge member  50  in response to impact forces being directed to and/or against the draft gear assembly  10 . 
     Spring assembly  70  is precompressed during assembly of the draft gear assembly  10  and serves to: 1) maintain the components of the friction clutch assembly  40 , including friction members  42  and wedge member  50  in operable combination relative to each other and within the draft gear housing  20  both during operation of the draft gear assembly  10  as well as during periods of non-operation of the draft gear assembly  10 ; 2) maintain the free end  52  of wedge member  50  pressed against the follower  53  ( FIG. 1 ); and, 3) maintain the follower  53  and the draft gear housing  20  pressed against stops  15  and  17  on the centersill  14  ( FIG. 1 ), respectively. In the illustrated embodiment, spring assembly  70 , in combination with the friction clutch assembly  40 , is capable of absorbing and dissipating impacts or energy directed axially thereto up to about 900,000 lbs. 
     In the form shown in  FIG. 4 , spring assembly  70  is configured with a plurality of individual units or springs  72  arranged in axially stacked adjacent relationship relative to each other. In the form shown in  FIG. 4 , the spring assembly  70  is comprised of five springs  72  with a rigid separator plate  73  being disposed between two axially adjacent springs  72  in the stack of the springs. It will be appreciated that more than five springs  72  can be arranged in axially stacked relationship relative to each other without seriously detracting or departing from the novel nature and true scope of this invention disclosure. 
     As described in further detail below, the purpose of the separator plate  73  between the springs  72  is to provide the springs  72  with different dynamic elastic absorption characteristics on opposite sides of the separator plate  73  so as to optimize dynamic lost work opportunities during an impact event of the draft gear assembly  10 . To effect such desirous ends, the separator plate  73  is extremely rigid and is preferably formed from steel or the like. 
     As shown in  FIG. 4 , plate  73  has upper and lower generally planar and generally parallel spring engaging surfaces  74  and  76 , respectively. In one form, a distance of about 0.375 inches to about 0.5 inches separates the spring engaging surfaces  74  and  76  on plate  73 . The separator plate  73  preferably has a generally rectangular configuration which allows it to freely move within the chamber  34  in the same direction as do the springs  72  in response to an axial load being placed on the spring assembly  70 . 
     In a preferred embodiment, the springs  72  disposed between the lower surface  76  of plate  73  and the end wall  24  of housing  20  combine with each other to offer a greater resistance to compression than do the combination of springs  72  disposed between the upper spring engaging surface  74  of plate  73  and the spring engaging surface  64  of spring seat  60 . 
     Each cushioning unit or spring  72  includes an elastomeric pad  78 . Preferably, each spring  72  has a configuration which complements the configuration, in plan, of the housing chamber  34 . In a preferred form, each spring  72  has a generally rectangular shape, in plan, and is sized to optimize the rectangular area of the hollow chamber  34  wherein spring assembly  70  is slidably centered for axial endwise movements in response to loads or impacts being exerted axially against the draft gear assembly  10 . Preferably, the pad  78  of each elastomeric spring  72  has two spaced and generally planar surfaces  74  and  77 . As shown in  FIG. 4 , the planar surface  74  of the pad  78  of the uppermost spring  72  in the stack of springs  72  is pressed against the spring contacting surface  64  of spring seat  70 . As further shown in  FIG. 4 , and with the exception of the pads  78  arranged adjacent to plate  73 , the lower planar surface  77  on the pad  78  of any two axially adjacent springs  72  abuts with and is pressed against the planar surface  74  of an axially adjacent spring  72 . Moreover, the planar surface  77  of the pad  78  on the lowermost spring in the stack of springs  72  is pressed against the end wall  24  of housing  20 . 
     Preferably, the elastomeric pad  78  and thereby each spring  72 , comprising spring assembly  70  is configured such that its radial expansion, in response to impacts or loads being placed thereon, is limited by the walls of housing  20  thereby enhancing the absorption capabilities of spring assembly  70 . Turning again to  FIG. 2 , each spring pad  78  is preferably configured such that the radial or outward expansion of the pad  78  will be limited by the housing walls  32 ,  32 ′ before the pad  78  expands to engage housing walls  30 ,  30 ′. In a preferred embodiment, and during operation of the draft gear assembly  10 , and especially those pads  78  of springs  72  disposed closer to the spring seat  60 , will radially expand in response to an impact load being placed thereon, to such an extend as they positively engage and/or contact against the inner surface of the housing walls  32  and  32 ′ whereby enhancing the absorption capabilities of those springs  72  of the spring assembly  70  disposed closest to the spring seat  60 . In one form of this invention disclosure, the springs  72  are maintained in general axial alignment with each other and relative to the longitudinal axis  22  during operation of the draft gear assembly  10  by an elongated guide rod  79  ( FIG. 2 ) which, in one form, preferably extends substantially the entire length of the spring assembly  70 . 
     Preferably, each elastomeric pad  78  is formed from a polyester material having a Shore D durometer hardness ranging between about 40 and 60 and an elastic strain to plastic strain ratio of about 1.5 to 1. The working process and methodology for creating the each spring unit  72  involves creating a preform block which is precompressed to greater than 30% of the preformed height of the preform thereby transmuting the preform into an elastomeric spring. 
     In one embodiment of the present invention disclosure, the durometer hardness of those elastomeric springs comprising spring assembly  70  may be different relative to each other. That is, the cumulative durometer hardness of the springs  72  disposed between spring seat  60  and plate  73  can be different from the cumulative durometer hardness of the springs  72  disposed between housing end wall  24  and plate  73 . As mentioned, however, it is preferable for the cumulative durometer hardness of the springs  72  between the housing end wall  24  and plate  73  to be greater or harder than the cumulative durometer hardness of the springs  72  between spring seat  60  and plate  73 . Such a design allows the functionality and performance characteristics of the of the draft gear assembly  10  to be “fine tuned” to the particular environment wherein the draft gear assembly  10  is to be used and function. 
     As shown in  FIGS. 1, 2 and 4 , a relatively large rectangular opening  80  is preferably formed in wall  30  of the draft gear housing  20 . Opening  80  is sized such that one or more of the spring units  72  and plate  73  can be inserted through the opening  80  in a direction extending generally normal to the longitudinal axis  22  of the draft gear assembly  10  and into the hollow chamber  34  of housing  20 . Housing wall  30 ′ may also be provided with an opening  82 . Preferably, the peripheral margin  84  of opening  82  defines a smaller area than the margin  83  of opening  80 . 
     As mentioned above, the purpose of the rigid separator plate  73  between the springs  72  is to provide the springs  72  with different dynamic elastic absorption characteristics on opposite sides of the separator plate  73  so as to optimize dynamic lost work opportunities during an impact event of the draft gear assembly  10 .  FIG. 6  is a schematic graphical representation of the forces realized by a conventional friction/elastomeric draft gear assembly. Whereas,  FIG. 7  is a schematic graphical representation of the forces realized by a draft gear assembly embodying a spring assembly  70  as described above and configured with a separator plate  73  between the opposed ends thereof. A comparison between  FIGS. 6 and 7  quickly and readily reveals how the spring assembly  70  configured with plate  73  disposed between opposed ends of the spring assembly  70  optimizes the dynamic lost work opportunities during an impact event of the draft gear assembly  10 . 
     As used herein and throughout, the phrase “lost work opportunity” means and refers to where the force levels imparted to the draft gear assembly drop-off or fall off dramatically over a given travel. The areas shown in dash lines in  FIG. 6  between points A-B and C-D represent lost work opportunities for a conventional draft gear assembly.  FIG. 7  schematically represents force levels for a given travel of a draft gear assembly embodying principals and teachings of the present invention disclosure. The points A, B, C, D and E in  FIG. 7  are similar to the force levels for a given travel schematically represented at points A, B, C, D and E in  FIG. 6 . The force levels for a given travel shown in  FIG. 6  as compared to the force levels for a given travel shown in  FIG. 7  shows how the a draft gear assembly embodying those features and teachings of the present invention disclosure optimizes the lost work opportunities during an impact event on the draft gear assembly  10 . In the embodiment shown by way of example in  FIG. 7 , the distance between points D and E schematically represent additional work opportunities provided by a draft gear assembly embodying the teachings and principals of this invention disclosure. 
       FIG. 8  schematically represents the performance of a draft gear assembly  10  embodying the principals and teachings of this invention disclosure, with the spring assembly  70  being configured to function in combination with the angles θ and β of the first and second friction sliding surfaces  48  and  58 , respectively, relative to the longitudinal axis  22  the draft gear assembly  10 . As shown in  FIG. 8 , such a draft gear  10  consistently and repeatedly withstands between about 70,000 ft-lbs. and about 85,000 ft-lbs. of energy imparted thereto at a force level not exceeding 600,000 lbs. over a range of travel of the wedge member  50  in an inward axial or longitudinal direction relative to the draft gear housing  20  approximating 3.9 inches. 
     Alternatively,  FIG. 9  schematically shows performance of a draft gear  10  with the spring assembly  70  of the draft gear assembly  10  being configured to function in operable combination with the angles θ and β of the first and second friction sliding surfaces  48  and  58 , respectively, relative to the longitudinal axis  22 . As shown, the draft gear assembly  10  consistently and repeatedly withstands about 110,000 ft-lbs. of energy of energy imparted thereto at a force level not exceeding 900,000 lbs. over a range of travel of the wedge member  50  in an inward axial direction relative to the draft gear housing  20  not exceeding 4.5 inches 
     Suffice it to say,  FIG. 9  also schematically shows performance of a draft gear  10  with the spring assembly  70  being configured to function in operable combination with the angles θ and β of the first and second friction sliding surfaces  48  and  58 , respectively, relative to the longitudinal axis  22  the draft gear assembly  10 . As shown, the draft gear assembly  10  consistently and repeatedly withstands between about 70,000 ft-lbs energy to about 110,000 ft-lbs of energy imparted thereto while not exceeding a force level of about 900,000 lbs. over a range of travel of the wedge member  50  in an inward axial direction relative to the draft gear housing  20  not exceeding 4.5 inches. 
     With the present invention disclosure, and with no design changes to the centersill  14  on railcar  16 , the draft gear assembly  10  is configured such that the wedge member  50  can achieve a range of longitudinal or horizontal movement in one axial direction of about 4.5 inches. That is, the draft gear assembly  10  of this invention disclosure permits 4.5 inches of travel in a “buff” direction and 4.5 inches of travel in a “draft” direction. This advantageous gain in longitudinal movement of the wedge member  50  allows the draft gear assembly  10  to consistently and repeatedly withstand between about 70,000 ft-lbs and about 110,000 ft-lbs of energy imparted thereto while not exceeding a force level of about 900,000 lbs. over a range of travel of the wedge member  50  in an inward axial direction relative to the draft gear housing  20  not exceeding 4.5 inches. 
     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 this invention disclosure. Moreover, it will be appreciated, the present disclosure is intended to set forth exemplifications which are not intended to limit the disclosure to the specific embodiments 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.