Patent Publication Number: US-7900785-B2

Title: Taper under tapered plate to increase side force on the movable plate

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation-in-part of a prior non-provisional application Ser. No. 11/071,004 filed Mar. 3, 2005, now abandoned, which claims the benefit of U.S. Provisional Application No. 60/561,050 filed Apr. 8, 2004. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates, in general, to draft gear assemblies for use in cushioning both buff and draft shocks normally encountered by railway rolling stock during make-up and operation of a train consist on a track structure and, more particularly, the present invention relates to a draft gear assembly having a tapered plate wherein a portion of the bottom surface which contacts a build-up portion on the third horizontal rib of the housing is angled to increase the side force on the movable plate thus increases the draft gear assembly&#39;s resistance to closure and increases the capacity of the draft gear assembly. 
     BACKGROUND OF THE INVENTION 
     Draft gear assemblies which utilize friction-type clutch mechanisms to absorb heat energy generated during service have been in widespread use in the railroad industry for many years to absorb both buff and draft shocks applied to the railway rolling stock. Many of such draft gear assemblies which were in use, prior to the present invention, are taught in U.S. Pat. Nos. 2,916,163; 3,178,036; 3,447,693; and 4,645,187. Each of the above-identified patents is owned by the assignee of the present invention. The teachings of each of these patents are all incorporated into the present application by reference thereto. 
     These draft gear assemblies are designed to receive coupler forces and dissipate them without damage to the car structure and lading. The assemblies are disposed within an elongated opening located in the center sill member of the railway car along the longitudinal axis thereof and behind the shank, or innermost end, of the railway car&#39;s coupling mechanism. In this position, these friction clutch type draft gear assemblies will absorb at least a relatively large portion of both the buff and draft forces generated during service. Such buff and draft forces encountered by such railway cars are usually being applied in an alternating manner to the center sill member during normal car operation on the track. 
     It is well recognized in the art that these draft gear assemblies must be provided with the capability of maintaining at least a certain minimum shock absorbing capacity both during making up a train consist and in-track service. Such minimum capacity has been specified by the Association of American Railroads (AAR) and is defined in the standards issued by the AAR. For example, friction clutch type draft gear assemblies have a specified absolute minimum capacity rating of at least 36,000 foot pounds. Any draft gear assembly with a capacity rating which is determined to be below 36,000 pounds will not receive approval from the AAR for service on any railroad car which may be used in interchange. 
     It is, likewise, important to note that the heat energy absorbing action of the friction clutch mechanism must enable this minimum capacity rating to be readily achieved without exceeding a specified maximum 500,000-pound reaction force, or pressure, being exerted on the center sill member of the railway car during both such make-up and operation of such train consist. It has been found that such maximum reaction pressure is required to enable these high energy shocks to be readily absorbed without upsetting the end of the coupling member shank and/or damaging other critical car components and/or lading that is being transported by such railway car. 
     In order for the manufacturers of such friction clutch type draft gear assemblies to meet the requirements of the railroad industry, with the ever-increasing load carrying capacity of their modern day railroad cars, it has become of extreme importance to enhance the overall rated capacity of the friction-type draft gear assemblies as much as possible. This higher capacity rating being found necessary in order to minimize any damage to such cars and/or the lading due to the increased forces being exerted on the center sill member of the cars by the heavier loads such cars are now carrying. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to produce a draft gear assembly having an increased capacity and resistance to closure. 
     It is a further object of the invention to provide a frictional cushioning means for a draft gear assembly wherein an additional side force is applied to the movable plates from the tapered plate. 
     It is yet a further object of the invention to provide a cushioning means for a draft gear assembly wherein an angle is provided on the portion of the bottom edge of the tapered plate which contacts the third horizontal rib of the housing and/or to the taper plates ear/lug which sits on the third horizontal rib so as to increase the side force on the movable plate, increasing the capacity of the draft gear and providing a greater resistance to closure. 
     It is an additional object of the invention to provide sufficient clearance between the angled edge surface of the tapered plate and the seat means of the draft gear assembly while accounting for wear of the compressible cushioning element. 
     Briefly, and in accordance with the forgoing objects, the invention comprises a draft gear assembly comprising a housing closed at one end and open at the opposed end and having a rear portion adjacent the closed end and a front portion adjacent the open end, a compressible cushioning element centrally disposed within the rear portion abutting the housing end and extending longitudinally there from, a seat means abutting the opposite end of the compressible cushioning element during application and release of a force on the draft gear assembly, and a friction cushioning means positioned at least partially within said front portion of said housing for absorbing energy during a compression of said draft gear assembly. The friction cushioning means includes a pair of laterally spaced outer stationary plates having an outer surface for engaging the housing and an opposed inner friction surface, a pair of laterally spaced movable plates having an outer friction surface for movably engaging the outer stationary plates, an inner friction surface and at least one substantially flat edge intermediate said outer friction and inner friction surfaces for engaging the seat means, a pair of laterally spaced tapered plates having an outer friction and an inner friction surface wherein the outer friction surface movably and frictionally engages the inner friction surface of the movable plate, a pair of laterally spaced wedge shoes having an outer friction surface for movably and frictionally engaging an inner friction surface of the tapered plate, and a center wedge having a pair of matching predetermined tapered portions for engaging the tapered portion of the wedge shoe to initiate frictional engagement of said friction cushioning means and thereby absorb energy. The housing includes three horizontal ribs for positioning and/or holding the components of the cushioning means. A spring release means is provided which engages and longitudinally extends between the seat means and the center wedge for continuously urging the friction cushioning means outwardly from the compressible cushioning means to release the friction cushioning element when an applied force compressing the draft gear is removed. 
     The present invention increases the capacity and resistance to closure of the draft gear assembly by providing an angled bottom surface on the tapered plates intermediate of the inner and outer friction surface in the area where the tapered plate contacts the third horizontal rib of the housing. Providing an angle on the bottom edge surface of the tapered plates and cooperating angled surfaces formed on the build-up portions of the third horizontal rib increases the side force on the movable plates during the application of a buffing shock to the draft gear assembly. 
     Although a number of objects and advantages of the present invention have been described in some detail above, various additional objects and advantages of the draft gear assembly of the present invention will become more readily apparent to those persons who are skilled in the art from the following more detailed description of the invention, particularly, when such detailed description of the invention is taken in conjunction with both the attached drawing figures and with the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal cross-sectional view of a draft gear assembly of the invention incorporating one form of a presently preferred embodiment of a cushioning element for the draft gear assembly; 
         FIG. 2  is a longitudinal cross-sectional view of a draft gear assembly of the invention incorporating an alternative embodiment of a cushioning element for the draft gear assembly; 
         FIG. 3  is a longitudinal cross-sectional view of a draft gear assembly of the invention incorporating an alternative embodiment of a hydraulic cushioning element for the draft gear assembly; 
         FIG. 4  is a perspective view of the draft gear housing illustrating the first, second, and third horizontal lugs; 
         FIG. 5  is a perspective view of a tapered plate which is employed within the draft gear and which is constructed according to one embodiment of the present invention; 
         FIG. 6  is a partial elevation view of the draft gear assembly along lines  6 - 6  of  FIG. 3 , particularly illustrating an angled surface of the tapered plate and a built-up area of the third horizontal rib of the draft gear housing; and 
         FIG. 7  is a cross-sectional view of the draft gear assembly along lines  7 - 7  of  FIG. 6   
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The draft gear assembly, according to the present invention, is installed in alignment with a railroad car center sill between a front and a rear draft gear lug. A vertical yoke is connected to a coupler shank by a draft key with a coupler horn spaced from a striking plate and with a front follower member within the yoke which is positioned adjacent to the front lugs, all substantially in accordance with the prior art conventional practice as illustrated in the aforementioned U.S. Pat. No. 2,916,163 whose teachings are incorporated into this document by reference thereto. 
     Prior to proceeding to the more detailed description of the various embodiments of the instant invention, it should be pointed out that, for the sake of clarity, identical components which have identical functions have been identified with identical reference numerals throughout the several views that have been illustrated in the drawings. 
     Now reference is made, more particularly, to drawing  FIGS. 1-4 . Illustrated therein are the essential components a draft gear assembly, generally designated  10 , used in a railway car (not shown). The assembly  10  includes a housing, generally designated as  12 . The housing  12  is open at one end and has a rear portion  14  adjacent a bottom wall  16  which closes the other end of housing  12 . Rear portion  14  is provided for receiving therein a compressible cushioning means, generally designated as  26 . Housing  12  includes a front portion  18  adjacent the open end. Front portion  18  is in open communication with the rear portion. Housing  12  additionally includes first, second, and third horizontal ribs  20 ,  22 , and  24  as shown in  FIG. 4 . 
     The compressible cushioning element  26  is centrally disposed within the rear portion  14  and has one end thereof abutting at least a portion of an inner surface  28  of the bottom wall  16  of housing  12 . The compressible cushioning element  26  extends longitudinally from bottom wall  16  where the opposite end is placed into abutting relationship with at least a portion of one surface  30  of a seat means  32 . Seat means  32  is positioned within the housing  12  for longitudinal movement therein for respectively compressing and releasing the compressible cushioning element  26  during application and release of a force on the draft gear assembly  10 . 
     As shown in  FIG. 1 , the compressible cushioning element  26 , according to one embodiment of the invention, comprises at least one and preferably at least two springs  34 ,  35 .  FIG. 2  shows an alternative embodiment for a compressible cushioning element  26  which comprises an outer coil spring  36  and an inner rubber spring  37 .  FIG. 3  shows another alternative embodiment of the invention in which the compressible cushioning element  26  is a hydraulic unit  38  such as taught in U.S. Pat. No. 3,447,693 whose teachings are incorporated into this document by reference thereto. 
     A friction cushioning means, generally designated as  40 , is positioned at least partially within the front portion  18  of the housing  12 . The friction cushioning means  40  absorbs energy during application of a force sufficient to cause a compression of the draft gear assembly  10 . 
     The friction cushioning means  40  includes a pair of laterally spaced outer stationary plates  42  having an outer surface  44  and an opposed inner friction surface  46 . The outer surface  44  engages the housing  12 . A pair of laterally spaced movable plates  48  of substantially uniform thickness is also provided. Movable plates  48  have an outer friction surface  50  and an inner friction surface  52  and at least one substantially flat edge  54  intermediate the outer friction surface  50  and the inner friction surface  52  which edge  54  engages the seat means  32 . At least a portion of the outer friction surface  50  movably and frictionally engages the inner friction surface  46  of the outer stationary plate  42 . A pair of laterally spaced tapered plates  56  is provided. The tapered plates  56  include an outer friction surface  58  and an inner friction surface  60 . The outer friction surface  58  movably and frictionally engages at least a portion of the inner friction surface  52  of the movable plate  48 . 
     Each of the tapered plate  56  includes at least one angled or tapered inner edge  62  intermediate the outer friction surface  58  and the inner friction surface  60 . Such at least one angled edge  62  is disposed vertically when such draft gear assembly  10  is installed to cushion shocks and is angled at a predetermined angle inwardly from the outer friction surface  58  in a direction toward inner friction surface  60 . The predetermined angle of the at least one angled edge  62  may range from approximately 10 to approximately 40 degrees. 
     Generally, the laterally spaced outer stationary plates  42  and the tapered plates  56  sit on the third horizontal rib  24  of the housing  12 . This angled or tapered edge  62  is in the area where the tapered plates  56  contact the third horizontal rib  24 , as best shown in  FIGS. 6-7 . Tapering the area of the tapered plate  56  where the tapered plate  56  sits in the housing  12  requires the area on the front surface  24   a  of the third rib  24  to be built up. Accordingly, pair of build-up areas  25  are disposed in a spaced apart relationship on the front surface  24   a  of such third horizontal rib  24 , each of the pair of build-up area  25  having an angled surface  25   a  which is cooperatively angled at an angle of the at least one angled edge  62 . 
     When the tapered plate  56  are constructed and positioned within the draft gear housing  12  so that the inner vertical edge is positioned over the third horizontal rib  24 , such tapered plate  56  may be provided with a build-up portion  62   a  disposed on the bottom edge thereof, as best shown in  FIG. 5 , and wherein such build-up portion  62   a  has a vertical angled surface  62   b  which is cooperatively positioned in abutting engagement with the angled surface  25   a  of the build-up area  25  of the third horizontal rib  24 . Preferably, the build-up portion  62   a  is formed integral with the tapered plate  56 , although it can be secured thereto by any conventional securing means, for example, such as by welding. 
     Friction cushioning means  40  further includes a pair of laterally spaced wedge shoes  64  which have at least a portion of an outer friction surface  66  movably and frictionally engaging at least a portion of the inner friction surface  60  of the tapered stationary plate  56 . Wedge shoes  64  have at least a portion of one edge  68  engaging seat means  32  and a predetermined tapered portion  70  on an opposed edge thereof. A center wedge  72  is provided which has a pair of matching tapered portions  74  for engaging the tapered portion  70  of the wedge shoe  64  to initiate frictional engagement of the friction cushioning means  40 . 
     It has been discovered that providing an angled surface  62 ,  62   b  on the tapered plates  56  in the area that frictionally contacts the angled surface  25   a  of the build-up portion  25  of the third horizontal rib  24  of the housing  12 , results in a greater side force being applied to movable plates  56 . Thus, the capacity of the draft gear and its resistance to closure is increased. A spring release means  76  engages and extends longitudinally between the seat means  32  and the center wedge  72  for continuously urging the friction cushioning means  40  outwardly from the compressible cushioning means  26  to release the friction cushioning means  40  when an applied force compressing the draft gear assembly  10  is removed. 
     A draft gear typically has approximately 0.125″ clearance between the bottom edges of the taper plates  56  and the seat means  32 . High loading from the taper plate requires that the housing&#39;s bearing area and the cross-sectional area on the taper plate&#39;s ear remain equal to the present design so shear failures do not occur. As the draft gear wears out, the assembled height of the spring type compressible cushioning elements  26  of  FIGS. 1 and 2  increases, resulting in a reduced clearance between the bottom edges of the taper plates  56  and the seat means  32 . A draft gear nearly worn out has near zero clearance between the bottom edges of the taper plates  56  and the seat means  32 . The present invention&#39;s new design criteria and assembly conditions are as follows: 
     For a 10 degree taper, approximately 0.176″ of clearance is provided. 
     For a 20 degree taper, approximately 0.364″ of clearance is provided. 
     For a 30 degree taper, approximately 0.5571″ of clearance is provided. 
     For a 40 degree taper, approximately 0.839″ of clearance is provided. 
     In operation, the buffing shock is transmitted from the coupler through the front follower to the central wedge  72 , causing it to act through the wedge shoes  64  and thereby compress all of the cushioning elements simultaneously. These parts will furnish sufficient cushioning for light buffing shocks. After suitable travel, however, the follower will come against the outer ends of the movable plates  48  introducing energy-absorbing friction between the movable plates  48  and the stationary plates  42  and  56  which have been pressed together by the action of the wedge shoes  64 . As this action continues, the pressure between the adjacent surfaces of the plates has been enormously increased due to the fact that the wedge shoes  64  are loaded against the cushioning mechanism  40 . 
     The energy absorption and dissipation through friction and compression of the cushioning mechanism continues until the gear is closed including compression of cushioning element  26 . 
     During release of the gear, the compressible cushioning element  26  is maintained in alignment by the seat means  32 . 
     Although, the present invention has been illustrated in terms of having a build-up area  25  on the third horizontal rib  24 , it would be apparent to one of ordinary skill in the art that such build-up area  25  may be formed on other horizontal ribs, for example a second horizontal rib  22 , particularly, when the draft gear assembly  10  uses the tapered plate  56  of  FIG. 5 . 
     Thus, the present invention has been described in such full, clear, concise and exact terms as to enable any person skilled in the art to which it pertains to make and use the same. It will be understood that variations, modifications, equivalents, and substitutions for components of the specifically described embodiments of the invention may be made by those skilled in the art without departing from the spirit and scope of the invention as set forth in the appended claims.