Abstract:
Lightweight yokes are provided. According to some embodiments, the basic overall appearance of the yoke may be maintained, but the actual material of which it is constructed is changed. According to other embodiments, the yoke is provided with an improved lightweight construction, and, yet other embodiments the yoke may be provided with an improved construction and formed from a preferred material. Yokes may be constructed from cast austempered ductile iron; whereas cast iron has a density, 0.26 lbs/in̂3, which is approximately 8% less than steel, 0.283 lbs/in̂3, thereby allowing for a reduction in weight over steel. A suitable austempering process is used to produce the austempered metal yoke. Yokes have improved configurations which may require less metal to produce the yoke. Both, the lightweight material and improvements in configuration of the yoke structure may combine to provide a lighter weight yoke.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates in general to railcars and, more particularly, to railcar yokes for a coupler system. 
         [0003]    2. Brief Description of the Related Art 
         [0004]    Railcar couplers are disposed at each end of a railway car to enable joining one end of such railway car to an adjacently disposed end of another railway car. The engageable portion of each of these couplers is known in the railway art as a knuckle. For example, railway freight car coupler knuckles are taught in U.S. Pat. Nos. 4,024,958; 4,206,849; 4,605,133; and 5,582,307. 
         [0005]    Typically, adjacent railway cars are joined by heavy shafts extending from each car, known as couplers, and, generally, each coupler is engaged with a yoke housing a shock-absorbing element referred to as the draft gear. The type-E coupler is the standard coupler for railway freight cars. The type-E coupler has standard specifications such that producers making a type-E coupler adhere to a standard specification, so that the standard railway car couplers are completely interchangeable, regardless of the manufacturer. In addition, adherence to a standard also enables couplers from any one manufacturer to be able to be readily joined to couplers from any other domestic manufacturer. The Association of American Railroads (“AAR”) has adopted standards for railway couplers. The coupler must include specific geometry and dimensions that allow it to receive a knuckle, and the geometry must be such that the knuckle is allowed to freely operate when coupling and uncoupling railway cars. These dimensions and features of the coupler may be checked for compliance with AAR standards by using gauges, which are applied to the coupler to verify the coupler dimensions or parameters are within an allowable variation or tolerance range. 
         [0006]    Couplers have a particular life, and in instances may fail. In many cases when a railcar coupler fails, a replacement coupler must be carried from the locomotive at least some of the length of the train, which may be up to 25, 50 or even 100 railroad cars in length. The repair of a failed coupler can be labor intensive, can sometimes take place in very inclement weather and can cause train delays. 
         [0007]    The yoke is a generally elongated structure having two side sections that extend from and join with a tail portion. The side sections are also known and referred to as “straps”. The side sections or straps are joined at the opposite end by a head portion where the yoke is joined to the coupler with a securing component, such as a key or pin. The yoke generally has a pocket formed by the straps and a rear wall, and a draft gear is positioned between the straps of the yoke, and between the tail portion and the head portion. The best-known yokes are the E-type and F-type. The E-type yoke is governed by AAR standards that include the AAR S-143 Standard, SY 40AE, Y40 or YS93AE, for a 24⅝ inch gear pocket, although there are some tolerances that the pocket may have, as permitted by the standards. A typical E-type yoke has straps that are 5 inches. The F-type yoke is governed by the S-149 standard and the Y45 standard. Although there are other differences between E-type and F-type yokes, a primary difference is the design and orientation of the pin or key used to join the coupler to the yoke. 
         [0008]    Typical yokes contain apertures in the yoke head portion, which also may be known as the key slots or pin bores by which a coupler is joined to the yoke with the installation of a key or pin through the slot or bore to connect the yoke and coupler. Adjacent railcars, when coupled together and in motion, place tension on the yoke and compressive forces are transferred to bearing surfaces at opposed ends of the yoke where the draft gear is housed. 
         [0009]    Adjacent freight cars are separated in accordance with standard specifications which includes an allowance for a specified yoke length. In accordance with applicable AAR standards, typically, E-type and F-type yokes, respectively, may have a length of 41⅛″ or 37½″. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention provides a railcar yoke for use in a coupler system. 
         [0011]    A railcar coupler typically includes a coupler head portion extending from a shank portion. A yoke is designed to mount onto the sill of a railway vehicle and connect to the coupler shank portion. The coupler head portion is configured to couple to a first coupler knuckle for coupling the railcar coupler to a second railcar coupler of an adjacent railcar. The coupler head portion comprises a nose portion and a gathering face extending from the nose portion for engaging a second coupler knuckle coupled to the second railcar coupler. 
         [0012]    Another object of the invention is to provide a lightweight yoke for use with railway couplers. 
         [0013]    According to a preferred embodiment, a lightweight yoke is provided and is constructed from a material that is stronger than grade E cast steel. Is a further object to accomplish the above objects by providing a yoke that is constructed from a material that is at least as strong, or even stronger, than grade E cast steel but which is lighter in weight than grade E cast steel. 
         [0014]    According to embodiments of the present invention, the yoke is stronger and more fatigue resistant than prior yokes of the same weight. According to one preferred embodiment, the yoke is lighter in weight than prior yokes (such as those constructed from grade E cast steel) and is both stronger and more fatigue resistant. According to a second preferred embodiment, the yoke possesses or exceeds the strength and fatigue resistance of prior yokes (such as those constructed from grade E cast steel) but is lighter in weight. According to a third preferred embodiment, the yoke is constructed having the same weight as prior yokes (such as those constructed from grade E cast steel), but with improved strength and fatigue resistance. 
         [0015]    It is another object of the invention to accomplish the above objects by providing a yoke with an interior and/or exterior geometry that has one or more of coring (i.e., cavities) and ribs, or combinations thereof. Another object of the invention is to construct the yoke so that the maximum wall thickness preferably is about 1.25″ or less, and more preferably about 1.15″ or less, and with the yoke being constructed from a material that is lighter and of similar or greater strength than grade E cast steel. Preferred thicknesses for the yoke walls, according to some embodiments, are from about 0.25 inch to about 1.25 inches. According to preferred embodiments, the maximum wall thickness is defined as the maximum diameter of a sphere that can fit within the thickness of the part, such as, a wall of the yoke. 
         [0016]    It is an object of the invention to provide a yoke that is constructed from an austempered metal. In a preferred embodiment, the austempered metal is austempered ductile iron (ADI). In another preferred embodiment the austempered metal is austempered steel, such as austempered alloy steel, and, according to other embodiments the coupler and yoke may be constructed from an austempered metal alloy. 
         [0017]    The austempered ductile iron (ADI) yoke is produced by a suitable austempering process. For example, austempering of ductile iron may be accomplished by heat-treating cast ductile iron to which specific amounts of nickel, molybdenum, manganese or copper, or combinations thereof have been added to improve hardenability; the quantities of the elements needed to produce the ADI from ductile iron are related to the coupler configurations and, for example, may depend on the thickest cross-sectional area of the coupler or the yoke. Austempered steel and other austempered metals and austempered metal alloys, may be produced by any suitable austempering process. The yoke may be produced by casting, including sand casting or investment casting, or other suitable method. The casting of the yoke or formed yoke is austenitized by applying an austempering process on the yoke. For example, the yoke may be formed from a casting of ductile iron, and the ductile iron yoke casting austempered. 
         [0018]    According to one embodiment, it is another object of the invention to provide an improved lightweight yoke that is lighter in weight than existing current yokes, but without additional coring or modifications to the interior of the yoke geometry, by constructing a yoke from an ADI having a density of about 0.26 lbs/in̂3, which is less than that of grade E cast steel, 0.283 lbs/in̂3. According to one embodiment, a casting of the same shape will be lighter and stronger when constructed from ADI versus grade E cast steel. According to a preferred embodiment, there is a weight reduction of about 8% using the ADI as the preferred material for the yoke versus using grade E cast steel. 
         [0019]    Another benefit of the present invention is to provide a yoke, and process for producing the yoke that provides economic benefits of conservation of materials, without sacrificing strength. For example, the utilization of a preferred ADI material improves handling efficiencies (as iron is easier to pour than steel), and improves material usage, as the ADI material increases in volume, slightly, as the metal yoke casting cools compared to steel which shrinks Accordingly, embodiments of the present invention provide a more efficient use of the materials, meaning less metal may be used to make the same final shape (for a yoke having substantially the same or greater strength as if a greater amount of metal were used), as a way of reducing the yoke weight. 
         [0020]    In another preferred embodiment, the austempered metal is austempered steel. 
         [0021]    Austempered steel is produced by a suitable austempering process. For example, austempering of steel may be accomplished by heat-treating cast steel to which specific amounts of chromium, magnesium, manganese, nickel, molybdenum, or copper, or combinations thereof have been added to improve hardenability; the quantities of the elements needed to produce the austempered steel from the cast alloy steel are related to the yoke configurations and, for example, may depend on the thickest cross-sectional area of the yoke. 
         [0022]    According to another embodiment, a lighter weight yoke is constructed by selectively coring out material in thick load bearing areas (or alternatively otherwise reducing material in these areas when cores are not used) to provide an alternate interior and/or exterior geometry for the yoke so maximum wall thickness for the yoke is preferably about 1.15″ or less, and more preferably about 0.75″ or less. 
         [0023]    According to preferred embodiments, the yoke may be reduced in thickness in a given zone or area, such as a wall and the strength to weight ratio may remain the same as or greater than prior yokes having thicker walls, and even being heavier in weight. According to some preferred embodiments, the maximum wall thickness of the yoke may be about 1.15 inches, and, according to some embodiments, the yoke may have walls with thicknesses about 0.75″ or less. According to some preferred embodiments, the yoke wall thickness may be in a range from about 0.25 inches to about 1.25 inches. The present yoke, when used in a coupling assembly, also may improve payload to weight ratios, as a lightweight yoke may allow for more weight to be cargo or other payload, especially where a locomotive is pulling a great number of cars that have lightweight yokes. 
         [0024]    According to some preferred embodiments, the weight reduction may be made at the back, nose end sections or straps of the yoke, and may be accomplished with coring, such as, for example, exterior coring. Embodiments may be produced with reduced weight by providing exterior coring on the side and back sections of the keyslot walls, straps or rear or nose sections. 
         [0025]    According to embodiments, the yoke may have one or more zones of coring and ribs, or apertures, bores and/or divots, where the coupler or yoke has areas or walls of a maximum cross-sectional thickness and other areas that are less than the maximum cross-sectional thickness. 
         [0026]    The arrangement of coring (or cavities), ribs and wall thickness, may be provided to produce a yoke that is lighter in weight, but possesses sufficient strength, including meeting or exceeding railroad standards, such as AAR standards for yokes. In addition, the embodiments of the yoke may be produced from an austempered metal, such as, for example, austempered ductile iron, which is lighter in weight than grade E cast steel, but provides equal or greater strength, to provide a lightweight yoke that preferably is constructed from ADI and has an arrangement of ribs and/or coring (i.e., cavities). 
         [0027]    According to another embodiment, a yoke may be provided having one or more zones of residual compressive stresses. According to one embodiment, a zone, or zones, of residual compressive stresses may be created on the entire inside and outside surface of any of the above embodiments of the lightweight yoke, while according to alternate embodiments, zones of residual compressive stresses may be created only in areas that show high tensile stress when the part is used, or combinations thereof in the areas that show high tensile stresses. For example, according to a preferred embodiment, a yoke is provided with zones of residual compressive stresses in the main areas that exhibit high tensile stress during use. According to some preferred embodiments, the yoke is configured having zones of residual compressive stresses which, according to preferred embodiments, may be in the location of the key slot, the side walls transitions in the front and back and the back tail section, or combinations of these locations. 
         [0028]    According to one embodiment, a preferred method for creating residual compressive stresses is by shot peening. Shot peening involves impacting the surface with small media projected at high speeds at the desired surfaces. According to embodiments of the invention, an engineered surface is provided, such as, for example, by subjecting the surface to a treatment process, such as, for example, shot peening, in order to provide the yoke with an improved ability to counteract tensile stresses that are applied during use that may otherwise tend to cause crack initiation. The provisioning of the residual compressive stresses on the yoke, such as, for example, using the shot peening procedure to impart impacts on the surfaces of the yoke at one or more desired locations, increases fatigue life and performance without the need to increase the overall strength of materials or of the part. 
         [0029]    The lightweight yokes according to the invention may be used with standard knuckles or lightweight knuckles, including, such as, for example, the lightweight knuckles disclosed in our co-pending U.S. patent application Ser. Nos. 13/378,021 and 13/842,229, for a lightweight fatigue resistant knuckle, the complete contents of which are herein incorporated by reference. 
         [0030]    According to some implementations, the lightweight yokes may be used together with lightweight couplers, such as, for example, lightweight couplers disclosed in our co-pending U.S. patent application Ser. No. 13/678,203, the complete contents of which are herein incorporated by reference. Further a lightweight coupler knuckle may be used with one or more of the lightweight yoke and lightweight coupler to provide a lightweight coupling system. 
         [0031]    Moreover, while specific advantages have been enumerated above, various embodiments may include all, some or none of the enumerated advantages. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]      FIG. 1  is a top plan view of a yoke for a railway coupling system, showing a yoke having a prior type Type F configuration shape, but being constructed according to the invention as a lightweight yoke. 
           [0033]      FIG. 2  is a side elevation view of the yoke of  FIG. 1 . 
           [0034]      FIG. 3  is a top plan view of an alternate yoke for a railway coupling system, showing a yoke having a prior type Type E configuration shape, but being constructed according to the invention as a lightweight yoke. 
           [0035]      FIG. 4  is a side elevation view of the yoke of  FIG. 3 . 
           [0036]      FIG. 5  is a top plan view of an alternate yoke for a railway coupling system, showing a yoke constructed according to the invention as a lightweight yoke and having an alternate configuration. 
           [0037]      FIG. 6  is a side elevation view of the yoke of  FIG. 5 . 
           [0038]      FIG. 7  is a perspective view of an alternate embodiment of an E-type yoke according to the invention. 
           [0039]      FIG. 8  is a side elevation view of the E-type yoke of  FIG. 7 , depicted in an orientation in which the yoke is used in operation. 
           [0040]      FIG. 9  is view looking from the bottom toward the top of a section of the yoke of  FIG. 14 , taken along the section line  9 - 9  of  FIG. 8 . 
           [0041]      FIG. 10  is top plan view of the E-type yoke of  FIG. 7 , looking overhead at the yoke. 
           [0042]      FIG. 11  is a rear elevation view of the yoke of  FIG. 7 , shown with the yoke resting on a side. 
           [0043]      FIG. 12  is a perspective view of an F-Type yoke according to the invention. 
           [0044]      FIG. 13  is a top plan view of the yoke of  FIG. 12 . 
           [0045]      FIG. 14  is a right side elevation view of the yoke of  FIG. 12 . 
           [0046]      FIG. 15  is a sectional view of the butt end portion of the yoke of  FIG. 12 , broken away from the other portions of the yoke, and taken along the section line  15 - 15  of  FIG. 14 . 
           [0047]      FIG. 16  is a front elevation view of the yoke of  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0048]    The present invention provides improved yokes which have improved strength and fatigue life. One way in which embodiments of the invention accomplish this is by providing coring (i.e., cavities) that may include interior coring, external coring, or both. The coring referred to may be cavities formed by traditional methods (where cores are used and placed in a mold) or cavities formed using other methods for producing the yoke or coupler). Another way in which embodiments of the invention accomplish this is by constructing the yoke from a material that is stronger than the grade E cast steel currently used. A further way in which embodiments of the invention accomplish this is by utilizing a material to construct the yoke that is stronger and lighter than the grade E cast steel currently used, while other embodiments provide a lightweight yoke by providing a unique geometry and using a material that is lighter than the current cast steel and/or stronger than the current cast steel. The embodiments also may include ribs provided for strengthening areas or zones of the yoke, which, according to preferred embodiments, may be done in conjunction with coring (e.g., forming of cavities). 
         [0049]    Referring to  FIGS. 1-4 , exemplary embodiments of a lightweight yoke  210 ,  310  are shown. The yokes  210 ,  310  are configured to resemble the prior yokes, and preferably are therefore, compatible with existing standards type couplers and knuckles to allow for use of the yokes  210 ,  310  in current railway coupling applications. The yokes  210 ,  310  are constructed from austempered metal, as discussed herein, and preferably may be constructed having suitable wall thicknesses to provide suitable strength to withstand force loads that a yoke would encounter during operations, including when in use on a railway vehicle, and including suitable strength properties to meet AAR standards. The yokes  210 ,  310 , may be configured as a casting, and they may be installed on a center sill of a railway vehicle along with a coupler and a draft gear (not shown).  FIGS. 5-6  illustrate preferred embodiments of a yoke  410  having alternate configurations with arrangements of ribs and dimples. 
         [0050]    According to one embodiment, a type F coupler yoke  210  is provided having a top strap  220  and bottom strap  221 . The top strap  220  is shown having a head portion  222 , and the bottom strap  221  also has a head portion  223 . A rear portion  225  connects the top strap  220  and bottom strap  221  to form a central pocket  226  within the yoke  210 . The pocket  226  is shown open at the two sides between the top and bottom straps  220 ,  221 . A first pin hole  230  is provided extending through the head portion  222  of the top strap  220  and a second pin hole  231  is provided extending through the head portion  223  of the bottom strap  221 . The pin holes  230 ,  231  are configured to receive a pin (not shown), and a draft gear (not shown) is provided and seated within the pocket  226 . The yoke  210  may be installed by securing a coupler shank (not shown) to the yoke  210  with a pin (not shown) that is installed in the pin holes  230 ,  231 . The yoke  210  preferably has lightener pockets  214 ,  215  at the rear portion  225 . The yoke  210  has a draft gear seat  216  with a planar surface  217 . 
         [0051]    According to another preferred embodiment, an alternate configuration of yoke  310  is shown configured as a type E yoke. The yoke  310  has a butt end portion  313 , and also preferably has lightener pockets  314 ,  315 . A draft gear seat  316  is shown having a substantially planar face  317 . Connected to the butt end portion  313  are top and bottom straps  320 ,  321 , which span to the yoke head  322 . The yoke  310  illustrated in  FIG. 3  is shown rotated ninety degrees from the position of the yoke when it is operatively installed in the center sill of a railway vehicle. Keyslot walls  350 ,  351  are provided in the yoke head  322 , and, in the embodiment illustrated, the keyslot walls  350 ,  351  are outwardly divergent from one another. The keyslot walls  350 ,  351  span from the front draft gear walls  352 ,  353  from which they extend forwardly, to the nose portion  354 ,  355 . The draft gear pocket  359  is shown defined between the rear draft gear wall face  317 , the top and bottom straps  320 ,  321 , and the front draft gear walls  352 . The keyslot walls  350 ,  351  are provided with keyslots  356 ,  357 , respectively, which oppose each other, as shown in  FIGS. 3 and 4 . The keyslots  356 ,  357 , each preferably has a radiused configuration at each end thereof. According to a preferred embodiment the yoke  310  may have ribs  361 ,  362  running along the length of the keyslot  356  (and along the keyslot  357 ). 
         [0052]    The yoke  310  may be configured with standard yoke contour dimensions for E-Type couplers (such as Y40 and Y41). According to preferred configurations, a yoke configured with the Y40 yoke dimension preferably has a draft gear pocket length of 25⅝ inches, and for a Y41 yoke configuration, the draft gear pocket length is 36⅜ inches long. 
         [0053]    Alternate configurations may be made to the yoke  310  and yoke  210 , including providing wall thicknesses that are reduced compared to current existing yokes, providing ribs or combinations of reduced wall thicknesses and ribs. The yokes  210  and  310  are shown as examples, and other configurations, preferably, yoke constructions meeting the standard geometries of AAR coupler yoke standards may be provided and produced in accordance with the present invention, including constructing the yoke to be lighter in weight and/or have thinner walls or wall portions, and more preferably, constructing the yokes from austempered metal. 
         [0054]    Referring to  FIG. 5 , an alternate embodiment of a lightweight yoke  410  is shown having a butt end portion  413 , lightener pockets  414 ,  415  and a draft gear seat  416  with a substantially planar face  417 . Top and bottom straps  420 ,  421  connect to the butt end portion  413  and span to the yoke head  422  and are located on opposite sides of the draft gear pocket  459 . A draft gear pocket  459  is shown defined by the front draft gear walls  452 , rear draft gear wall face  417  and top and bottom straps  420 , 421 . 
         [0055]    In  FIG. 5 , the yoke  410  is shown rotated ninety degrees from the position of the yoke  410  when it is operatively installed in the center sill of a railway vehicle. The yoke head  422  preferably is constructed with a plurality of weight reduction areas. The yoke head  422  has outwardly diverging keyslot walls  450 ,  451  which span from the front draft gear walls  452 ,  453  from which they extend forwardly, to the nose portion  454 ,  455 . 
         [0056]    Referring to  FIG. 6 , a pair of broken lines is shown defining a cross-sectional thickness “a” of the keyslot wall  450  and nose portion  454 . According to a preferred embodiment, the yoke is constructed having a maximum thickness at the location of the yoke  410  defined by the arrows “a”. According to preferred embodiments, the maximum thickness dimension is measured by the maximum diameter of a sphere that can be within the part, and more preferably, is the maximum diameter of a sphere that can be within the yoke keyslot wall  450  and nose portion  454  shown in  FIG. 6 . According to preferred embodiments, the maximum thickness, as measured corresponding with the spherical dimension, is a maximum spherical diameter of about 1.25 inches, and more preferably about 1.2 to 1.15 inches. According to some preferred embodiments, the wall thickness may be a maximum of 0.75 inches, as measured in connection with the spherical diameter fitting with the wall of the yoke  410 .  FIG. 5  illustrates a preferred embodiment having a zone of weight reduction “z 1 ” provided in the nose portion  454  of the yoke  410 . The weight reduction zone z 1  is illustrated schematically with a boxed area of the yoke  410  drawn to represent a preferred area of the yoke  410  for weight reduction. Preferably, there is a corresponding zone of weight reduction “z 2 ” provided in the second nose portion  455  of the yoke  410 . The weight reduction zone z 1  preferably may comprise an arrangement of ribs, such as, for example, the ribs  471 ,  472 ,  473  shown in  FIG. 5 . Between the ribs  471 , 472 , 473  are spaces  475 ,  476 , and there is a space  474  on the side of the first rib  471 , and a space  477  on the side of the third rib  473 . The keyslot  456  is shown with ribs  461 , 462  running along the length of the keyslot  456 . According to a preferred embodiment, the keyslot ribs  461 , 462  preferably extend to join ribs on the nose portion  454  of the yoke  410 . According to a preferred embodiment, ribs  471 , 473  join with the ribs  462 , 461 , respectively, that are disposed on each side of the keyslot  456 , and the ribs  471 , 473  preferably extend beyond the keyslot  456  to the nose portion  454  diverging toward an edge of the yoke  410 . As shown in the yoke  410  of  FIG. 5 , the keyslot ribs  461 , 462  join, respectively, with the third rib  473  and the first rib  471 . The force load distribution from loads received at the keyslot  456  preferably is distributed through the arrangement of ribs. The lightweight austempered metal construction and rib arrangement provide a lightweight yoke  410  that is both suitably strong for railway vehicle coupling operations and lightweight. Preferably, the opposite nose portion  455  also is configured with ribs and spaces similar to the arrangement shown and described in connection with the nose portion  454 . Although not shown, the keyslot  457  also has keyslot ribs alongside the keyslot (one rib  461   a  being shown in  FIG. 6 ) that preferably join with ribs on the nose portion  455  (the nose ribs  473   a  and  472   a  being shown in  FIG. 6  separated by the spaces  477   a  and  476   a,  respectively). Although the zone of weight reduction z 1  is illustrated with an arrangement of ribs joining the keyslot ribs, alternatively, in alternate embodiments, the zone of weight reduction z 1  may comprise a dimpled surface, wherein dimples having a coring depth are distributed on the surface portions of the nose  454  or head  422  of the yoke  410 . Alternate embodiments may include both an arrangement of ribs as well as dimples disposed in the yoke wall surfaces. 
         [0057]    A weight reduction zone “z 3 ” preferably is provided in the rear of the yoke  410 . The boxed area z 3  illustrates a preferred location or zone of the yoke  410  where one or more weight reduction features are provided. The weight reduction zone z 3  preferably is provided in the tail section of the yoke  410 . According to one preferred embodiment, the wall thickness of the yoke  410  in the zone of weight reduction z 3 , and preferably in one or more, any or all, of the rear wall  419 , draft gear seat  416 , and strap portions  420 , 421  connecting with the rear wall  419 , is preferably configured having a maximum thickness, measured corresponding with the spherical dimension, of a maximum spherical diameter of less than about 1.25 inches, more preferably, less than about 1.2 to 1.15 inches, and most preferred about or less than 0.75 inches. According to one embodiment, the weight reduction zone z 3  includes a plurality of dimples, such as those dimples  481 , 482  shown in the top of the yoke  410 , and the dimples  483 , 484 ,  485 , 486  shown in the wall  490  of the rib  413 . Although the exemplary embodiment illustrated in  FIGS. 5 and 6  shows a preferred arrangement of dimples, other arrangements of dimples may be provided, including providing dimples on the opposite sides of the surfaces, and, more preferably, staggering the dimples on opposite surface sides to provide an increased continuous thickness across the part. Although six dimples are shown in the exemplary embodiment, a plurality of dimples, which may number greater than the six shown, may be provided in the surfaces of the yoke  410  at locations of the yoke  410 , including, preferably, one of the preferred weight reduction zones z 1 , z 2 , z 3 , or other surfaces of the yoke  410 . 
         [0058]    According to an alternate embodiment, ribs may be provided in the rear section of the yoke  410 . For example, the weight reduction zone z 3  may include a plurality of ribs in the locations at the top or bottom surfaces of the walls, such as, for example, the rear wall  419 , the draft gear seat  416 , or both. According to one embodiment, U-shaped ribs are provided running in the direction of the yoke, which in some embodiments may include crossing ribs that cross each other. A plurality of ribs may be provided in the tail section of the yoke  410 . 
         [0059]    Referring to  FIGS. 7-11 , an alternate embodiment configured as an E-type yoke  510  is shown. The yoke  510  includes a head  511  at one end thereof and a butt portion  512  at the other end thereof. Connected to the butt end portion  512  are top and bottom straps  520 , 521 , respectively, which span to extend to the yoke head  511 . A draft gear seat  513  is shown having a substantially planar surface  513   a.  The yoke head  511  includes keyslot walls  515 , 516  which, in the embodiment illustrated, are outwardly divergent from one another. The keyslot walls  515 , 516  span from the front draft gear walls  522 , 523  from which they extend forwardly, to the nose portion  524 , 525 . The draft gear pocket  526  is shown defined between the rear draft gear wall face  513   a,  the top and bottom straps  520 , 521 , respectively, and the front draft gear walls  522 , 523 . The keyslot walls  515 , 516  are provided with keyslots  527 , 528 , respectively, which oppose each other, as shown in  FIGS. 7 ,  9 ,  10  and  11 . Each keyslot  527 , 528  preferably has a radiused configuration at each end thereof. In addition to the keyslot walls  515 , 516 , the head  511  also is shown having a first wall and a second wall, which may be referred to as a top wall  531  and a bottom wall  532 . 
         [0060]    The yoke  510  may be configured with standard yoke contour dimensions for E-Type couplers (such as Y40 and Y41). According to preferred configurations, according to one exemplary embodiment, a yoke configured with the Y40 yoke dimension preferably has a draft gear pocket length of 24⅝ inches, and for a Y41 yoke configuration, the draft gear pocket length is 36 inches long. According to preferred embodiments, the draft gear pocket  526  preferably is sized and dimensioned in accordance with AAR specifications and standards to accommodate a draft gear and/or other components that may be installed for the coupling assembly. According to a preferred embodiment, the E-type yoke may have a preferred length of 41⅛″. 
         [0061]    According to a preferred embodiment illustrated, openings  535 , 536  are provided in the respective straps  520 , 521 . The openings  535 , 536  in the straps  520 , 521  preferably oppose each other. According to a preferred embodiment, the openings  535 , 536  are elongated to span across the straps  520 , 521 . The openings  535 , 536  are shown having radiused ends and a straight elongated portion. The straps  520 , 521  may be constructed in accordance with an AAR standard, which in some preferred embodiments is 5 inches in height. The openings  535 , 536  are preferably provided within the 5 inches of strap height. According to a preferred embodiment, the height H 1  of the openings  535 , 536  preferably are up to about one half of the strap height H 2 , as depicted according to a preferred embodiment shown in  FIG. 9 . According to one preferred embodiment, the strap height H 2  is 5 inches and the opening height H 1  is 2½ inches. 
         [0062]    According to one embodiment, the draft gear pocket  526  may be 25 inches (measured from a plane of the rear surface  513   a  to a plane of the draft gear pocket front walls  522 , 523 ). According to one preferred embodiment, the openings  535 , 536  are provided at a central location of the straps  520 , 521 , relative to the strap height. According to one embodiment, the openings preferably are provided to be located within about 1.5 inches from the edge of a strap wall. 
         [0063]    Referring to  FIGS. 7 ,  9  and  10 , the top wall  531  and bottom wall  532  of the head portion or head  511  preferably have wall openings  537 , 538 , respectively, disposed therein. According to a preferred embodiment, the wall openings  537 , 538  are provided to oppose each other, and preferably, the openings  537 , 538  are centrally located in the top and bottom walls  531 , 532 , respectively. According to a preferred embodiment, the top wall  531  and bottom wall  532  have a curved or radiused edges  531   a,   532   a,  respectively, which are provided at the front wall end. According to a preferred embodiment, the openings  537 , 538  preferably are provided with a forward portion  537   a,   538   a,  which is radiused or curved. According to some preferred embodiments, the radiused or curved forward portion  537   a,   538   a  of the respective top and bottom wall openings  537 , 538  has a profile corresponding with the radius or curve of the top and bottom front wall edges  531   a,   532   a.  In a preferred embodiment, the wall openings  537 , 538  have radiused or curved corners. As illustrated the top and bottom walls  531 , 532 , respectively, support the yoke  510  and the keyslot walls  515 , 516  connecting to the respective top and bottom walls  531 , 532 . 
         [0064]    According to a preferred embodiment, the thickness of the yoke walls preferably may be constructed to be from about 1.25 inches to about 0.25 inch. For example, the thickness of the walls forming the straps  520 , 521  may be from about 1 inch to 1.25 inches, with a preferred thickness of about 1.125 inches. According to some embodiments, the top and bottom walls  531 , 532  of the head portion  511  may have a wall thickness that is similar to the walls of the straps  520 , 521 . Preferably the thickness of the keyslot walls  515 , 516  may be provided to be about 1.25 inches or less, and according to some preferred embodiments, the thickness of the keyslot walls  515 , 516  is about 1 inch. According to a preferred embodiment, the wall thicknesses of the key slot walls  515 , 516 , the straps  520 , 521  and top and bottom walls  531 , 532  may be from about 1 inch to 1.25 inches, wherein each wall or strap pair may have a thickness within this range, which may be a different thickness than the other wall pair or strap pair. According to a preferred embodiment, each strap  520 , 521  preferably may have a uniform thickness along its length between joining locations (which is shown joining with the butt end  512  at one end thereof, where a radiused fillet may be provided ( FIG. 9 ), and joining with the head  511  at the other end thereof, which also may have a radiused fillet at the head portion  511 . 
         [0065]    According to a preferred embodiment, as illustrated, the yoke  510  has a butt end portion  512  disposed opposite the head portion  511 . The butt end portion  512  is shown having radiused or curved edges  512   b,   512   c,  and a pair of pockets  550   a,   550   b  (see  FIG. 9 ) provided in the butt end portion  512 . Referring to  FIG. 11 , the butt end portion  512  is shown having tapered side wall portions  512   e,   512   f  which taper inwardly toward the center of the butt end portion  512 . The butt end portion  512  is shown with a rear wall portion  512   a  formed by the narrowing of the converging side wall portions  512   e,   512   f.  Referring to  FIG. 15 , the butt end portion  512  is shown having an inner wall portion  512   g  which preferably is connected with the rear wall portion  512   a.  According to a preferred embodiment, the inner wall portion  512   g  connects with the rear wall portion  512   a  by a connecting structure, which in the preferred embodiment illustrated, is shown as a rib or wall  512   h.  The connecting rib or wall  512   h  preferably is transversely disposed and is provided at the mid level of the height of the butt end portion  512 , such as, for example, the height of the inner wall  512   g.  The inner wall  512   g  according to some preferred embodiments may be formed from the wall that forms the draft gear seat  513  and may be coextensive with it, or formed such that the draft gear surface  513   a  is on one side of the wall and the rear surface of the draft gear seat wall faces into the cavities or pockets  550   a , 550   b.    
         [0066]    Referring to  FIGS. 12-16 , an alternate embodiment of a yoke  610  is shown configured as an F-type coupler yoke. The yoke  610  is generally oriented vertically when in use, as depicted in the view of  FIG. 12 , where the pin bores  615 , 616  are shown located vertically to receive a connecting member, such as a pin (not shown) to connect with a component of a coupling assembly (e.g., a coupler). The yoke  610  has a head or head portion  611  at one end thereof and a butt portion  612  at the other end thereof. The head portion  611  preferably includes an upper head portion  611   a  and lower head portion  611   b.  Connected to the butt end portion  612  are top and bottom straps  620 , 621 , respectively, which span to extend to the yoke head  611 . A draft gear seat  613  is shown having a substantially planar surface  613   a.  The yoke head  611  includes pin bores  615 , 616  which are provided in the respective top and bottom walls  617 , 618  of the head  611 . According to a preferred embodiment illustrated, the top and bottom walls  617 , 618  may be outwardly divergent from one another. Preferably, an upper window  622  and lower window  623  are formed in the respective top and bottom walls  617 , 618  through which observation of the draft gear (not shown) may be made when the yoke is installed in an assembly with other coupling components. A front supporting structure, shown including a pair of side walls  624 , 625  is provided, and connects the upper front wall portion or wall  617  with the lower front wall portion or wall  618 . A pocket  626  is shown provided between the draft wall surface  613   a  and the yoke head portion  611 . 
         [0067]    The yoke  610  is shown according to a preferred embodiment, with strap openings  635 , 636  provided in the respective straps  620 , 621 . The strap openings  635 , 636  preferably oppose each other. According to a preferred embodiment, the strap openings  635 , 636  are elongated to span across the straps  620 , 621 . The strap openings  635 , 636  are shown having radiused ends and a straight elongated portion. The straps  620 , 621  may be constructed in accordance with an AAR standard, which in some preferred embodiments is 5¾ inches in height (as viewed in  FIG. 13 , where a strap height H 4  is represented). The strap openings  635 , 636  are preferably provided within the 5¾ inches of strap height dimension H 4 . According to a preferred embodiment, the height H 3  of a strap opening  635 , 636  preferably is up to about one half of the strap height H 4 , as depicted according to a preferred embodiment shown in  FIG. 19 , showing the strap  635 . According to one embodiment, yoke  610  may have an overall length of 37½ inches, with the draft gear pocket  626  having a length of 24⅝ inches, (measured from the rear surface  613   a  to a point 4 17/32 inches behind the center point of the pin or pin bore  615 , 616 ). According to a preferred embodiment, the rear surface  613   a  to the center of a pin bore  615 , 616  is 29 5/32 inches. According to one preferred embodiment, the strap openings  635 , 636  are provided at a location between the butt end portion  612  and the head portion  611 . According to one embodiment, the openings preferably are provided to be located within about 1 inch to 1.5 inches, and preferably about 1.25 inches to 1.375 inches from the edge of a strap wall. According to a preferred embodiment, the straps  620 , 621  may increase in width at the locations near each of the ends of the respective straps  620 , 621 , including, for example, at the strap locations where the front and rear of the openings  635 , 636  begin or end. 
         [0068]    According to a preferred embodiment, the thickness of the walls of the yoke  610  preferably may be constructed to have thicknesses between about 1.25 inches to about 0.25 inch. For example, the thickness of the walls forming the straps  620 , 621  may be from about 1 inch to 1.25 inches, with a preferred thickness of about 1.125 inches. According to some embodiments, the top and bottom walls  617 , 618  of the head portion  611  may have a wall thickness that is similar to the walls of the straps  620 , 621 . The top and bottom walls  617 , 618  may comprise extensions of the respective straps  620 , 621  and have similar thicknesses or, alternatively, have different thicknesses than the respective straps  620 , 621 . Accordingly, the pin bores  615 , 616  preferably have a depth corresponding with the thickness of the respective top and bottom wall  615 , 616 , or respective top or bottom strap  620 , 621 . According to a preferred embodiment a positioning feature is provided at the yoke head portion  611 . Referring to  FIG. 16 , the positioning feature is shown in accordance with a preferred construction as a plurality of positioning tabs  661 , 662  provided on the inner surface  617   a  of the top wall portion  617 , and positioning tabs  663 , 664  provided on the inner surface  618   a  of the lower wall  618 . The positioning feature facilitates even loading to control and distribute loads, for example, from a coupler shank. The positioning tabs  661 , 662 , 663 , 664  preferably comprise wear surfaces and preferably are constructed from the same composition as the other portions of the yoke  610 . Preferably the positioning tabs, such as the upper tabs  661 , 662  and lower tabs  663 , 664 , are provided in opposing relation to each other so that the upper tabs  661 , 662  face the lower tabs  663 , 664 , with each upper tab  662 , 662 , facing a respective lower tab  663 , 664 . As shown in  FIG. 14 , the tab  662  has a generally flat or substantially flat inner surface portion  662   a  and has tapered sides  662   b,   662   c.  Preferably, the other tabs  661 , 663 , 664  also are constructed having a flat or substantially flat inner surface portion and tapered sides. The tabs  661 , 662 , 663 , 664  narrow the opening provided at the head  611  of the yoke  610 . According to one preferred embodiment, the tab pairs  661 , 662  and  663 , 664  are disposed proximate the respective pin bore openings  615 , 616 , with each tab of a pair being provided on an adjacent side of a respective pin bore opening  615 , 616 . 
         [0069]    According to a preferred embodiment, as illustrated, the yoke  610  has a butt end portion  612  disposed opposite the head portion  611 . The butt portion  612  is shown having radiused or curved edges  612   b,   612   c,  and pockets  650   a,   650   b  provided in the butt end portion  612 . According to preferred embodiments, the pocket arrangement includes a first pocket  650   a  and second pocket  650   b.  Referring to FIGS.  13 , 14  and  15 , the butt end portion  612  is shown having tapered side wall portions  612   e,   612   f  which taper inwardly toward the center of the butt end portion  612  (similar to the walls  512   e,   512   f  of the butt end portion  512  shown in  FIG. 11 , in connection with the yoke  510 ). The butt end portion  612  is shown with a rear wall portion  612   a  formed by the narrowing of the converging side wall portions  612   e,   612   f.  Referring to  FIG. 15 , the butt end portion  612  is shown having an inner wall portion  612   g  which preferably is connected with the rear wall portion  612   a.  According to a preferred embodiment, the inner wall portion  612   g  connects with the rear wall portion  612   a  by a connecting structure, which in the preferred embodiment illustrated, is shown as a rib or wall  612   h.  The connecting rib or wall  612   h  preferably is transversely disposed and is provided at the mid level of the height of the butt end portion  612 , such as, for example, the height of the inner wall  612   g.  The inner wall  612   g  according to some preferred embodiments may be formed from or be part of the wall that forms the draft gear seat  613  and may be coextensive with it, or formed such that the draft gear surface  613   a  is on one side of the wall and the rear surface thereof faces into the cavities or pockets  650   a,   650   b.    
         [0070]    According to a preferred embodiment, the front portion of the straps  620 , 621  may be constructed to slightly taper inwardly at the head portion  611 . According to a preferred embodiment, the inwardly taper of the straps  620 , 621  preferably is after the front of the openings  635 , 636 , and the straps  620 , 621  and head walls  617 , 618  that join with straps  620 , 621 , respectively, also may have an inward taper. According to a preferred embodiment, a further inward taper of the front portions of the walls  617 , 618  may be provided, and the inward taper may include a portion of converging wall thickness in the front of each wall  617 , 618 , preferably at each front flange  617   b,   618   b.    
         [0071]    According to some embodiments, the yoke  610  may be configured with standard yoke contour dimensions for F-Type yokes. According to preferred configurations, a yoke configured with the S-149 yoke dimension preferably has a draft gear pocket length of 24⅝ inches and a length of 37½ inches. The spacing between the straps  620 , 621 , as depicted in  FIG. 20 , preferably, meets or exceeds the AAR standards (including any allowable tolerances) so the pocket  626  formed between the straps  620 , 621  may accommodate coupling components (e.g., a draft gear). According to some preferred embodiments, the yoke height, as shown by reference to the orientation in  FIG. 20 , may have a height of about 11½ inches. The yoke  610  preferably may be configured with dimensions that meet the AAR specifications for F-type yokes including with any permitted tolerances, and, may exceed the specifications. 
         [0072]    According to a preferred embodiment, the yokes  210 , 310 , 410 , 510 , 610  are constructed from an austempered metal, and more preferably, from austempered ductile iron (ADI). Although other austempered metals may be used, and other grades of ADI, according to a preferred embodiment, yokes may be constructed from Grade 3 ADI. According to a preferred embodiment, the ADI may be Grade 3 ADI in accordance with ASTM A897/A897M for ADI castings. According to some preferred embodiments, yokes  10 , 110  may have properties that meet or exceed the specifications for Grade 3 ADI. 
         [0073]    The yoke preferably joins with a coupler that carries a pivotally connected knuckle movable between open and closed positions. According to alternate embodiments, the yokes  210 ,  310 , 410 , 510 , 610  may be made from austempered steel, which may be an austempered alloy steel. Other austempered metals, such as, for example, austempered ductile iron, and austempered metal alloys, may be used to construct the yokes  210 , 310 , 410 , 510 , 610 . As discussed herein, the coupler, as well as the knuckle used in conjunction with the yoke  210 , 310 , 410 , 510 , 610  also may be constructed from austempered metal. As discussed above in connection with the couplers, preferred compositions, such as steel, as well as alloy steel compositions, e.g., alloyed preferably with magnesium, manganese, molybdenum, copper or mixtures thereof, or more preferably, with chromium, nickel or mixtures thereof, (or mixtures of the preferred and more preferred metals), may be used to form the yokes  210 , 310 , 410 , 510 , 610 . The steel or preferred/more preferred alloy steel composition is austempered to obtain tensile strength, yield, and elongation properties for the inventive yokes which are suitable to meet or exceed the AAR standards for yokes utilized in coupling systems, including the current standard set forth by the American Association of Railroads (AAR) in AAR Manual of Standards and Recommended Practices, such as current standard M-211, M-205, M-220 NDT and Rule 88 of the AAR Office Manual, the complete contents of which are herein incorporated by reference. Like the couplers discussed herein, the yokes  210 , 310 , 410 , 510 , 610 , according to preferred embodiments, may be constructed from ductile iron that is austempered. The ductile iron also may be used in alloy form, preferably, with nickel, molybdenum, manganese, copper, or mixtures thereof, to form the yokes  210 ,  310 , 410 . The yokes  210 . 310 . 410 . 510 , 610  may be produced using any suitable production method. According to one method, the yoke  210 , 310 , 410 , 510 , 610  may be formed from a casting. For example, where the casting of the yoke is made from ductile iron, the ductile iron casting may be subjected to an austempering process to produce an austempered ductile iron yoke. 
         [0074]    According to some embodiments, the yokes may be provided with one or more zones of reduced material, which, for example, where a casting process is used to form the yoke, may be accomplished by coring, and preferably, with specialized coring in designated zones of the yoke. Embodiments of the yoke may be provided with ribs for strengthening areas or zones of the yoke, and, according to some preferred embodiments, ribs may be provided in conjunction with coring. The ribs may be provided in configurations alternate to those preferred configurations shown and described herein. Although some embodiments of the present lightweight yoke may be constructed to resemble prior yoke geometries, including prior exterior yoke geometries, lightweight yokes according to the invention may be constructed to have geometries that are different than prior yokes but which also are compatible with coupling and usage of the prior yokes for connection with and use with prior and existing standard AAR couplers and other components of the coupling assembly. The lightweight yokes of the invention provide a lightweight alternative that may be used in place of prior yokes, wherever the prior yokes have been used or are called for. 
         [0075]    According to preferred embodiments, the yokes may be made from a casting, although any suitable process for forming the yokes may be employed, including, for example, investment casting. 
         [0076]    These and other advantages may be realized with the present invention. While the invention has been described with reference to specific embodiments, the description is illustrative and is not to be construed as limiting the scope of the invention. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some or none of the enumerated advantages. The yokes may be formed by any suitable process, including, for example, molding, casting, and forging. The dimensions and thicknesses of the yokes, according to some preferred embodiments, are such that the yokes according to the invention, such as the yokes,  210 , 310 , 410 , 510 , 610  shown and described herein, may be used in standard coupling assemblies with other standard coupling assembly components, such as, for example, couplers, knuckles, locks and lock lifts. The improved yokes preferably may be interchangeable with prior yokes, and yokes according to the invention may meet or exceed AAR standards for yokes. Various modifications and changes may occur to those skilled in the art without departing from the spirit and scope of the invention described herein and as defined by the appended claims. It is intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention. 
         [0077]    It is intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention. Numerous other changes, substitutions, variations, alterations and modifications may be ascertained by those skilled in the art and it is intended that the present invention encompass all such changes, substitutions, variations, alterations and modifications as falling within the spirit and scope of the appended claims.