Abstract:
A pocket-casting is provided for a railcar slackless coupler having a draft gear subassembly for preloading the coupler assembly in the buff and draft directions, which pocket-casting and cooperating positive stops in a center-sill of a railcar limit the longitudinal travel and consequent loading of the slackless coupler in both the buff and draft directions for transfer of the forces to the plate-reinforced center sill to ease the shock loading on the coupler assembly.

Description:
BACKGROUND OF THE INVENTION 
     The present invention provides a railway car coupler or connector with a buff/draft gear assembly. More particularly, the invention relates to a slackless drawbar connector with an integral assembly to cushion the dynamic loading of the slackless connector in the buff and draft directions of the coupled railcars. 
     The rail industry developed with the steam locomotive, which is a lower torque drive means than the modern diesel locomotive. The steam locomotive did not have the torque capacity to initiate drive on the full length of a train of tightly coupled cars, therefore, a degree of free-travel or free-play between-cars was required to allow sequential initiation of car travel of loaded trains. The coupling apparatus between the cars had to accommodate the longitudinal travel in both directions, and also handled the vertical and horizontal travel at the coupling as the train progressed along the rails. In addition, couplers are generally assembled from as-cast components, which do not have the dimensional tolerances associated with machined elements. Therefore, all the free play and relatively loose connections associated with earlier couplers were acceptable conditions, and as noted above, they were necessary conditions. 
     The diesel locomotive brought changes in the load-bearing capacity of trains, their physical parameters and their operating characteristics. The physical and mechanical properties of the couplers joining the individual cars of the train also changed to accommodate the train improvements. The greater loads carried by modern railway trains have changed the perception of the coupler engineer and designer with regard to train operating characteristics. Indicative of this change in perception is that heavier loads are carried on rail cars and the industry has moved to maintain close-butted relationships between coupler draft components to lessen the impact forces on cars, couplers and lading. 
     Since most coupler drawbar connection parts are as-cast pieces with little or no finish machining to provide dimensional control, it is desirable to provide a self-adjusting coupling device to accommodate component wear and to lessen the slack in the coupler connections. One type of self-adjusting articulated coupler is shown in U.S. Pat. No. 3,716,146. 
     In an exemplary slackless drawbar coupling structure, the drawbar extends between the car sill sides and nests in a pocket casting. The butt end of the drawbar may be convexly arcuate and abut a complementary front concave surface of a follower block. The back surface of the follower abuts the front surface of a wedge, which has a rear surface abutting the rear wall of the pocket casting within the car sill. Either or both of the front and rear surfaces of the wedge member diverge upwardly to yield a gravity-assisted wedging force, which provides the slackless coupling arrangement. When the abutting surfaces become worn, the wedge member drops slightly to maintain the essentially slackless connection. 
     The top, bottom and vertically disposed side walls in the pocket casting of the drawbar coupling arrangement provide a cavity for the follower and the wedge. Upon horizontal angling of the drawbar, the side walls limit the lateral translation and, therefore, the rotation of the follower about the vertical axis of the arcuate butt end of the drawbar. Rotation of the follower may potentially cause the wedge to rotate about the car longitudinal axis and possibly hang up between the vertical walls, especially when the wedge is small in height relative to its width. A method of controlling rotation of the follower, and the relative orientation with the wedge, provides for a very close tolerance between the vertical side walls of the cavity and the follower side edges. As these are cast components, the procedure providing close tolerances between components requires an uneconomical amount of tolerance design and machining of finished parts. 
     The term slackless means that the drawbar, or coupler, is received within the center sill in a manner to minimize longitudinal play or movement. As successive railway cars in a train must accommodate relative movement between cars when curves and inclines are negotiated, there must be a provision for each car to move in pitch, yaw and roll modes with respect to the coupler member. Moreover, there must also be a provision to remove the draft components for repair and replacement of parts and, to disconnect coupled cars. 
     In a slackless system, the coupler member is held in a manner to eliminate, or minimize, longitudinal movement with respect to the car body. As noted above, this may be done by providing a tapered wedge between a rear wall of a pocket casting secured in the center sill and a follower block, which rests against the butt end of the coupler member shank. The wedge tends to force the follower block away from the pocket casting end wall and firmly against the butt end of the coupler member shank. In railway cars being pushed, the longitudinal forces cause compression of the coupler member against the follower, wedge and pocket end wall of the slackless arrangement. 
     When railcars are being pulled, a draft key or connecting pin acts against the longitudinal forces tending to separate the drawbar from the pocket casting. The pin or draft key is a metal bar extending laterally or vertically through the center sill and a slot or pin bore in the shank of the coupler member. In a slackless drawbar system, the drawbar is held tightly against the connecting pin or draft key by the action of the wedge separating the pocket casting from the follower block. The wedge compresses the follower block against the butt end of the drawbar, which biases the drawbar at the pin bore or slot against the pin or key. However, the mating faces of the follower block and drawbar are preferably curved to allow the drawbar to pivot, both vertically and laterally, and to permit the car to roll with respect to the drawbar. The drawbar may also pivot at the draft key or pin connection on an arcuate pin or key bearing-block interposed between the parts. 
     In U.S. Pat. No. 4,593,827 to Altherr, a slackless coupler is shown with the drawbar extending into the car center sill. The front surface of a follower block in the center sill has an arcuate concave section abutting the convex arcuate end of the drawbar. The follower block rear surface has a convex shape of two generally planar surfaces joined at a vertex substantially in the vertical center plane of the railcar. The wedge shim is provided with a generally concave surface, which complementarily abuts the convex surface of the follower block. The interrelationship of the shim and block surfaces maintains the orientation of the assembly and inhibits lateral translation between the shim, the follower and the side casting. 
     U.S. Pat. No. 4,700,853 to Altherr et al. also provides a slackless coupler with the placement of contoured spacer means within the center sill on either side of the coupler member, both above and below the draft key slots, to prevent lateral movement of the drawbar on the draft key. A preferred embodiment also includes access means or ports in the pocket casting for engagement or withdrawal of the wedge from contact with the follower blocks. 
     Draft gear assemblies have been known and utilized for coupler systems in the prior art, however, they frequently utilized large spring assemblies, which added to the weight of the undercarriage assembly and detracted from the freight carrying capacity of the railway car. Illustrative examples of draft gear assemblies operable to absorb buff and draft forces applied to the draft gear are shown in CAR AND LOCOMOTIVE CYCLOPEDIA, CENTENNIAL EDITION (1974), at page S9-S32. Force diagrams, which illustrate the effect of impact forces on a cushioning device from both directions along the longitudinal axis of the assembly, are noted in some of the figures. The intent of most known draft gear assemblies is generally to protect the freight car structure. Lading protection, however, requires varying degrees of energy dissipation. Sliding sill arrangements to accommodate lading protection are generally complicated assemblies with attendant higher assembly costs. Therefore, end-of-car cushioning devices evolved, which units could be installed outboard of the car bolsters but they do not fit within the standard draft gear pockets. These cushioning units have both greater travel and greater energy absorbing ability than conventional draft gears. The American Association of Railroads, A.A.R., specifications for Special Cushioning Devices for Freight Cars are delineated at A.A.R. specification number M-921-65, and include impact testing, as well as appraisal under actual service conditions and service experience. 
     Buff gears or buff gear assemblies are also known and utilized in railroad car couplers to form a compression spring assembly. These buff or draft gear assemblies are typically used between railway cars to buffer the impact of adjacent cars, and to compensate for the impact loads on the car couplers during operation of the train. A buff gear arrangement is illustrated in U.S. Pat. No. 4,556,678 to D. G. Anderson and includes a mounting assembly for positioning the cushioning apparatus in the coupler assembly. The buffer operates to absorb the force load from the impact between adjacent cars in a freight train, which impacts may occur during humping of freight cars. However, the utilization of these buff-draft gear assemblies has not been feasible with slackless couplers, as these couplers had to be operable in both the draft and buff directions with little or no longitudinal free play in the coupler assembly. 
     SUMMARY OF THE INVENTION 
     The present invention provides a shock-absorbing, dynamically-loaded, buff/draft gear apparatus to absorb the load on a slackless railroad car coupler in both the buff and draft directions of travel. The buff/draft gear structure avoids the shock-loading of the coupler assembly from sudden acceleration in the draft direction and retains the shock-absorbing capability of the assembly in the buff direction, especially for freight cars being humped. This buff/draft gear apparatus is operable with slackfree couplers, which are not the articulated type of connectors, without dramatic changes in the center sill or other mechanical structure of the coupler and drawbar assemblies. The buff/draft gear structure is not prohibitively large, which minimizes its space requirements, and it is also adaptable to existing railroad car center sills with draft gear assemblies. The buff/draft gear structure makes the utilization of extant slackless subassemblies adaptable for incorporation into the shock-absorbing apparatus, and provides a variable load-absorbing apparatus for each particular railroad car and coupler, which load-absorbing apparatus is based upon design criteria. This latter variation in shock-absorbing capacity is accommodated by the addition of more or fewer of the axially arranged friction pads in the load-absorbing elements. 
     The slackless coupler and the buff/draft gear assembly have individually been provided in couplers. However, slackless couplers have less free travel to accommodate the draft-direction coupler loading. Short-travel shock-loads in the draft direction can generate knuckle or coupler wear and damage in a slackless coupler. This concern is alleviated by the present invention as the load is transferred from the connecting pin and pocket-casting to front-stops and eventually to the sidewalls of the side sill. The pocket-casting and front-stops also permit the buff/draft gear to absorb the compressive load in the buff direction over a cushioned-load range and thereafter, the additional buff loading is accommodated through the front stops, and the side sill. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the figures of the drawing like reference numerals identify like components, and in the drawings 
     FIG. 1 is a plan view of the slackfree coupler and buff/draft gear assembly in partial cross-section; 
     FIG. 2 is an elevational view in cross-section of the slackfree coupler and buff/draft gear assembly of FIG. 1; 
     FIG. 2A is a cross-sectional end view taken along the line  2 A— 2 A in FIG. 2; 
     FIG. 3 is a plan view of an integral pocket casting in partial cross-section; 
     FIG. 4 is an elevational view of the pocket casting of FIG. 3 in cross-section taken along the line  4 — 4 ; 
     FIG. 5 is an elevational view of the front-stop and buff lug of FIG. 1; 
     FIG. 5A is a cross-sectional plan view of the front-stop in FIG. 5 taken along the line  5 — 5 ; 
     FIG. 6 is an elevational view of the front-stops in FIG. 5; 
     FIG. 6A is an elevational view of a front-stop mounting slot in the side sill; 
     FIG. 7 is a plan view of an annular-shaped elastomer body or pad for use as a load-absorbing element in a buff gear assembly; 
     FIG. 8 is an elevational cross-section of the elastomer body in FIG. 7, which has been compressed under a load; and, 
     FIG. 9 is a plan view in partial cross-section of a plurality of elastomer members axially aligned for a chamber. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Railway car standard coupler assembly  10  in FIGS. 1 and 2 has slackfree apparatus  12  with wedge  100  and follower  92  to minimize free play in coupler assembly  10 , and buff/draft gear apparatus  14  to accommodate dynamic shock loading of coupler  16  in both the buff and draft directions of travel along coupler-arm longitudinal axis  18 . Coupler shank  22  extends along axis  18  connecting coupler head  20  into pocket  26  of center sill  24 . Coupler head  20  is matable with a similar or mating member protruding from a second railway car or locomotive to connect the cars for travel along railway tracks, which railway cars and tracks are not shown, but are known in the art. 
     Slackfree coupler apparatus  12  minimizes the free travel of coupler  16  in the draft direction of railway travel through automatic adjustment of apparatus  12 . More specifically, coupler shank  22  has forward end  28  connected to coupler head  20 , and a rear or butt end  30 , which has an arcuate shape in the horizontal direction. Upper surface  32  and lower surface  34  of shank  22  are generally planar, however, their shape is not a limitation to the present invention. Coupler shank  22 , and particularly butt end  30 , extend into pocket casting  36  mounted in center sill pocket  26 . 
     Center sill  24  has first sidewall  38 , second sidewall  40  and top wall  42  in FIG. 2, which cooperate to provide center-sill pocket  26 . Supports  44  extend across lower edges  46  and  48  of first and second sidewalls  38  and  40  to provide an essentially closed pocket  26  in center sill  24  to receive draft/buff gear apparatus  14  and coupler shank  22 . 
     In FIGS. 1 and 2, coupler shank  22  in proximity to butt end  30  has a vertical connecting-pin bore  50 , which is transverse to axis  18  in the figures and about normal to upper surface  32  and lower surface  34 . Pocket casting  36  is connected to buff/draft gear apparatus  14  and shank  22  to provide a moving or sliding connection between these components. In FIGS. 1 to  4 , pocket casting  36  includes chamber  37  and, it has upper wall  52  with first passage  54  and lower wall  56  with second passage  58 , which passages  54  and  58  are aligned. Rear wall  60  of pocket-casting  36  has an aperture  62  generally centrally aligned with axis  18 . Pocket casting  36  is positioned and can slide in center-sill pocket  26  to receive the rear portion  30  of shank  22  in pocket-casting chamber  37 . Passages  54  and  58  are alignable with pin bore  50  for receipt of vertical connecting pin  64 , and connection of coupler  16  with center sill  24  for rotation or pivoting of shank  22  about pin  64 . Further, upper wall  52  and lower wall  56  have inner wall surfaces  66 ,  68 , respectively, which surfaces slope or are essentially outwardly tapered from passages  54 ,  58  toward open end  70  of center sill  24 . 
     Pocket casting  36  in the illustrated reference position of FIGS. 1 and 2 can slide in cavity  26  along axis  18 . However, travel of casting  36  in the draft direction is limited by contact between front surfaces  72  and  74  of pocket-casting front-plates  76  and  78 , respectively, with stop-surfaces  80 ,  82  of respective front-stops  84 ,  86 . Front-stops  84 ,  86  with stop-surfaces  80 ,  82 , respectively, limit the forward or draft motion of casting  36  and they simultaneously act as parallel sliding guides for pocket casting  36 . 
     Front-stops  84 ,  86  are secured in position relative to walls  38  and  40  within center-sill cavity  26 . More specifically, side sills  38  and  40  each have a mounting slot  81 , which slots  81  are shown in FIGS. 2A and 6A. Slot  81  is noted in FIG. 1 in side sill  38 , and at assembly receives buff lug  88  of FIGS. 1,  2 A,  5  and  5 A to secure front-stop  84 . It is recognized that a similar subassembly exists in side sill  40  for front-stop  86 . In FIGS. 5,  5 A and  6 , buff lug  88  and front stop  84  are noted as a single assembly or unit, which may be a single forging, welded elements or unitary cast structure for example. As noted, front-stop  84  generally extends across the height of pocket-casting chamber  37  to provide maximum load distribution from encounters between front stop surface  80  and pocket-casting front surface  72 . Front-stops  84  and  86  are contoured and shaped to minimize their weight, while maintaining operability and adequate mechanical strength for the application. Sill reinforcement plates  85  and  87 , each with an opening formed to receive lug  88 , are connected to sill sidewalls  38  and  40 , respectively, to increase the draft/buff gear load bearing area. Plates  85  and  87  may be secured to sidewalls  38 ,  40  by means known in the art, such as welding. 
     Pocket-casting rear wall  60  in FIGS. 3 and 4 has forward surface  90  tapered from upper wall  52  to lower wall  56  to accommodate a preferred embodiment of slackless adjustment apparatus  12 . The slope of the illustrated taper implies a more narrow section of wall  60  at upper wall  52 , and a wider section of wall  60  at lower wall  56 . The particular style of slackless adjustment apparatus is not a limitation to the present invention. 
     An enlarged illustration of cast front-stop  84  is provided in FIGS. 5,  5 A and  6 , and it is appreciated that casting  86  is a similar structure, thus only front-stop casting  84  will be described. As noted in FIGS. 5,  5 A and  6 , casting  84  has stop surface  80  to provide a draft stop surface for pocket casting surface  72 . A second stop surface  150  is provided as a buff stop surface for pocket-casting surface  152 . Front-stop surface  80  and front-stop second surface  150  are separated by valley  154  in FIGS. 1 and 5A for receipt of pocket-casting front plate  76 , which allows sliding contact of front plate  76  between first and second front-stop surfaces  80  and  150 . Valley  154  is within or coextensive with pocket-casting chamber  37 . 
     Slackfree or slackless coupler apparatus  12  has follower  92  and wedge  100 , and it is operable to minimize the free slack of coupler  16  along longitudinal axis  18 . In the illustrated embodiment of FIGS. 1 and 2, follower  92  has a downwardly tapered rear surface  94  and a concave, spherically curved, forward surface  96  for mating engagement with convex, spherical butt surface  98  of coupler rear end  30 . Tapered surface  94  provides a wider cross-section at its lower portion than at the upper cross-section of follower  92  in the figures. 
     Wedge  100  of slackless apparatus  12  has a generally wedge-shaped, vertical cross-section with a wider upper, cross-sectional area than its lower cross-sectional area. Wedge  100  is interposed between follower  92  and rear wall  60  in chamber  37 . Tapered forward face  102  of wedge  100  slidingly contacts rear face  94  of follower  92 . Rear face  93  of wedge  100  slidingly contact forward face  90  of pocket-casting rear wall  60 . In this configuration, wedge  100  is operable to move downward, as the coupler components wear, to accommodate any change in their dimensions and maintain the relative slackless condition, that is minimal longitudinal motion, of coupler assembly  10 . This general structure and operation of slackless apparatus  12  is a rather generic description of a slackless apparatus. However, the specific arrangement or component slackless structure is not a limitation to the operation and assembly of the present invention. 
     In FIG. 2, draft/buff gear apparatus  14  and pocket-casting  36  are slidably positioned in center-sill passage  26 . Front gear plate  110  of buff/draft gear apparatus  14  with generally central throughport  112  is slidably positioned in center-sill passage  26  contacting rear draft-stop faces  165  of front stops  84  and  86 . Rear gear plate  114  with central throughport  116  is positioned and secured in center-sill passage  26  contacting rear positive stop  115 , which front and rear gear plates  110  and  114 , and center sill  24  provide draft gear enclosure  118  within chamber  26 . Rear positive stop  115  is secured to center sill sidewalls  38  and  40  by means known in the art, and includes a generally centrally positioned throughbore  117  in FIG.  1 . 
     Buff/draft apparatus  14  has draft gear  120  in FIGS. 1,  2  and  9 , which draft-gear assembly  120  is composed of a plurality of elastomeric segments  122  each separated from an adjacent segment  122  by a divider plate  124 . Draft gear  120  is positioned and operable in draft-gear enclosure  118  to provide a shock-absorbing or dynamically loaded arrangement of coupler assembly  10 . 
     Each of elastomeric segments  122  and dividers  124  has a generally centrally positioned passage or aperture  130 ,  132 , respectively, to receive connecting rod or element  134  extending through pocket-casting port  62 , forward plate passage  112 , rear plate passage  116  as well as the noted passages  130 ,  132 . Rod  134  is illustrated as a bolt with its head  142  nested in a counterbore  61  at the forward surface  90  of pocket-casting rear wall  60 . Bolt  134  is secured against the rear wall of rear gear plate  114  by nut  138  on threaded bolt end  140 , which nut  138  is sized to pass through throughbore  117  of rear positive stop  115 . 
     Bolt end  140  of rod  134  has a passage  159  in FIG. 2, and nut  138  has at least one trough  161  in its top end. A retaining screw  163  with retaining nut  165  extends through the bolt-end passage  159  and is situated in trough  161  to secure nut  138  on bolt end  140 . Alternative securing means, such as a cotter pin, may also be utilized to secure nut  138  on bolt end  140 . 
     Nesting of bolt head  142  in counterbore  61  provides a smooth surface along front face  90  of pocket casting rear wall  60 , which smooth surface allows freedom of movement for wedge  100  of slackless apparatus  12 . The effect of a compressive load on elastomeric elements  122  is illustrated in FIGS. 8 and 9, where the deformation of passages  130  is demonstrated. The structure of FIG. 9 is a known embodiment of a draft gear assembly for absorbing buff forces in a coupler assembly, such as coupler assembly  10 . 
     Draft gear assembly  14  and slackfree apparatus  12  are both operable in standard operating modes as individual components. In these modes, slackfree apparatus  12  is operable to continuously adjust coupler  10  and arm  22  to maintain a cushioning slack or no slack condition. As noted above, the term slackless or slackfree is indicative of a very limited amount of free play between the several components of a railway car coupling connection. At assembly of coupler  10 , elastomeric elements  122  are slightly compressed to provide a dynamic load to coupler assembly  10  at the reference position, which dynamic load allows the draft gear  14  to assist in absorbing the shock load at initiation of railcar motion in the draft direction. There is a small separation distance, ‘x’, which is illustrated in FIG. 1, between front-stop surface  82  and,pocket-casting tongue front surface  74 , and a similar separation is noted at opposed front-stop  84 . This separation accounts for the cushioned draft slack provided by the precompressed draft/buff gear  120 . In the illustrated reference position of the coupler components noted in FIGS. 1 and 2, connecting pin  64  is provided in contact with the walls of passages  54  and  58 , which is the usual position of a coupler assembly during draft direction of travel of a railcar. 
     In the buff direction, that is coupler movement to the left in FIGS. 1 and 2, coupler assembly  10  moves pocket-casting  36  with slackless apparatus  12 , as well as front gear plate to compress elastomeric elements  122  for absorption of the buff forces from the railcar or locomotive, especially those forces experienced during humping of railcars in a classification yard. The limit of travel of draft gear  12  and pocket casting  36  in the buff direction is fixed by the separation distance ‘y’ between second stop surface  150  and pocket-casting stop surface  152 . This also limits the energy absorbed by draft gear  14 , as no further compression of elastomeric elements  122  may occur. 
     The limits of travel of the slackfree/draft-gear structure in coupler assembly  10  are thus fixed in the draft direction by separation distance ‘x’, which couples pocket casting  36  with stop castings  84 ,  86  and thereby connects center sill  24  with coupler assembly  10  and the coupled railcars. All the mechanical forces are, therefore, almost immediately transferred to front-stop castings  84 ,  86  and, thus, center sill  24 , as separation distance ‘x’ is about three-quarter (0.75) inch, which is generally related to the “slackless” condition in railway car couplers. The draft gear apparatus is also operable to absorb the shock load associated with railcar travel in the buff direction. In the illustration of FIGS. 1 and 2, the separation distance ‘y’ is about two and three-eights (2.375) inches. The travel distance of pocket casting  36  in the buff direction is limited by front-stop castings  84 ,  86 , as casting  36  slides parallel to the walls of front-stop castings  84  and  86  during inboard travel in center-sill cavity  26 . 
     While only specific embodiments of the invention have been described and shown, it is apparent that various alterations and modifications can be made therein. It is, therefore, the intention in therefore the appended claims to cover all such modifications and alterations as may fall within the true scope and spirit of the invention.