AU601683B2 - Improved type e coupler yoke - Google Patents

Description

i~wW el 60683 SPRUSON FERGUSON COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Class Int. Class Complete Specification Lodged: Accepted: Published: Priority: Related Art: 4 *1 t~t 4 4 t 4 Name of Applicant: McCONWAY TORLEY CORPORATION Address of Applicant: 109 48th Street, Pittsburgh, Pennsylvania 15201, United States of America Actual Inventor(s): WILLIAM OWEN ELLIOTT and BEATRICE SCHULTE Address for Service: Spruson Ferguson, Patent Attorneys, Level 33 St Martins Tower, 31 Market Street, Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: "IMPROVED TYPE E COUPLER YOKE" The following statement is a full description of this invention, including the best method of performing it known to us SBR:eah 195T 4 4

ABSTRACT

A coupler yoke including a butt end portion having a rear draft gear seat at a generally right angle relation with each of top and bottom straps extending in a generally parallel and spaced apart relation to a yoke head portion having outwardly diverging keyslot walls extending from front draft gear pocket walls which face towards said rear draft seat, a draft gear pocket being defined within the area surrounded by the rear draft gear seat, the front draft gear pocket walls and the top and bottom straps, each of said keyslot walls having an elongated keyslot opening with a semicircular front end from which a nose portion extends forwardly therefrom, each nose portion having a blunt contour to the contour of a standard yoke by a foreshortened length from a standard length of 3 1/2-inches measured from a point at the forward most surface of said semicircular front end inside said keyslot to the forward most end of the nose portion, each of said keyslot walls including a wall section with a generally trapezoid, cross-sectional configuration extending rearwardly of the semi-circular front end of the keyslot opening between each of opposite longitudinal sides of the keyslot opening and the outer boundary of the keyslot wall, said trapezoid cross-section configuration of the keyslot walls reducing stresses therein due to the trapezoidal configuration thereof, the stresses being generated by contact with a key member during angling of the key member against a longitudinal side of the keyslot opening.

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0P0r 00 al: to pt 04 0 O0 9040 0 *0 .0069 a so *0*O'a pr 40000 40 4 0 00 This invention relates to a yoke for an E-Type coupler for a railway vehicle and, more particularly, to such a yoke having a blunt nose portion by a foreshortened length of less than 3 1/2-inches to facilitate removal of the yoke together with the draft gear from a railway vehicle as well as if desired forming the nose portion of the yoke with uniformly thick walls having smooth convex outer surfaces to strengthen and improve the service life of the yoke by avoiding deformations at the keyslot areas immediately adjacent the nose portion of the yoke.

Couplers used to connect together two railway vehicles are joined to the vehicles by way of coupler yokes. A draft gear pocket Is formed in a coupler yoke to receive a draft gear assembly for dampening the pull and buff forces hlich must be V I transferred between the coupler head and the railway vehicle. A standard AAR E-Type coupler yoke is a unitary casting with a symmetrical configuration about longitudinal center planes. The yoke casting includes top and bottom straps extending between a rear end portion forming a rear draft seat and a yoke head where walls form the front of the draft gear pocket facing toward the rear draft gear seat. The area surrounded by the front draft gear walls, the rear t t 10 draft gear seat and the top and bottom straps form a draft gear pocket in which a draft gear can operate to rt C cushion the buff and pull forces occurring in train service. The keyslot walls in the yoke head diverge outwardly at each of opposite sides of the yoke. Each keyslot wall is provided with key slots extending generally parallel with the straps, Semicircular ends of the keyslots avoid a localization of forces on the casting by a horizontally arranged key used to interconnect the yoke with the shank portion of a railway coupler. Forwardly of the keyslot walls there is a nose portion which projects into a central cavity of a striker casting above a striker carrier which is an integral part of the striker casting and used to engage and support the shank of the coupler. The striker casting is secured to a center sill of the railway vehicle. Front draft lugs on the rear portion Sof the striker casting engage a front follower, which 2

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e t I. I is a rectangular block of metal, interposed between the draft gear and the front draft lugs of the striker for transferring forces from the draft gear.

The Y40 and Y41 standard yokes for type E couplers can offer significant improvements to their operation in a railway vehicle through an improved construction of the nose portion of the yokes to overcome two problems which have been found to exist.

Firstly, it is frequently a difficult and tremendous task to remove a yoke with draft gear of E-Type coupler as a unit from a railway vehicle because yoke resides at a position that is too far forwardly of the vehicle whereby the nose portion and the coupler carrier of the striker interfere during the removal process even though such interference should not occur by reason of the design of the standard parts.

Secondly, deformations of the yoke casting at the yoke keyslot area are caused by loading on the keyslot peripheral rib by the key. Sometimes cracks occur in the yoke casting at the forward end of the keyslot.

It is necessary from time to time to remove the draft gear from a railway vehicle for servicing and/or replacement. It is necessary to remove the yoke with the draft gear and follower block located within the draft gear pocket thereof from the vehicle after which the draft gear can be removed from the yoke at a site remote to the railway vehicle. As is 3 1 W 1 well known in the art, tremendous loads are encountered by draft gear when transmitting pull and buff forces in train service. These loads are so great that dimensional clearances established by the design not withstanding manufacturing tolerances actually change because the yoke casting stretches to such an extent that intended clearances necessary to the removal of the yoke with the draft gear in tact are reduced to a point where yoke removal is S, 10 impossible.

In order to remove the yoke and draft gear from the railway vehicle, it is always necessary to H: compress the draft gear in the draft gear pocket approximately 1/8-inch or greater in order to provide a clearance at the front and rear draft lugs so that the draft gear and yoke assembly is free to slip out of the pocket formed in the center sill. The draft gear is usually compressed by placing a compression jack in the opening between the keyslot walls such that one part of the compression jack can push against the front follower block and thereby also an Jextendable member of the draft gear. The compression jack is supported by the yoke through the use of a cross member that extends through the keyslot openings in. the keyslot walls. The yoke must be shifted rearwardly of the railway vehicle when an interference i 1 occurs between the nose of the yoke and the coupler 4 E' IM

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carrier which prevents the lowering of the draft gear and yoke assembly passed the coupler carrier.

Attempts in the past to alleviate the interference problem required the placement of a shim having a suitable thickness usually 3/8-inch or greater between the rear of the draft gear and the rear draft gear seat. This gap must be created by forcing the yoke rearwardly in a manner simulating a buff condition.

The precompression force of the draft gear is resisted 10 by rear lugs on the center sill and front draft lugs on the striker that are in a forced transmitting relation with the draft gear via the draft gear follower. The purpose of the spacer between the rear of the yoke and the draft gear is to limit forward 15 movement of the yoke when the compression jack is operated to compress the draft gear. The draft gear is then compressed through the use of the compression jack while the spacer holds the yoke at a rearward position to relieve the front and rear draft lugs of the precompression forces developed by the draft gear.

However, this procedure may not be successful because there may still be insufficient clearance between the nose portion of the yoke and the striker carrier due to, for example, stretching of the yoke during use.

In order to move the yoke still further rearwardly to gain adequate clearance between the nose portion of the yoke and the striker carrier, the draft gear must 5 i 1.

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t it C 4 CC *t t 4 C *itt~ *1 i be first compressed to an extent sufficient to place spacers between the front stops and the front follower. The compression jack must then be released locking the draft gear between rear stops and the front spacers and thereby slide the yoke rearwardly with respect to the striker casting. A spacer must then be placed between the rear of the draft gear and yoke rear draft gear seat which has a thickness sufficiently great to provide the necessary clearance 10 between the nose portion of the yoke and the striker carrier. Thereafter the draft gear is then compressed so that the draft gear is out of compressive engagement between the front and rear draft lugs and the shims can be removed. This procedure is costly, time consuming and must be carried out under difficult working conditions since the yoke must be retained in the downwardly facing pocket of the center sill while ensuring access to various sites for the placement and removal of spacers and shims.

The present invention provides an improved construction for the nose portion of a yoke to alleviate the problem encountered incident to the removal thereof from a railway vehicle and, at the same time, the present invention prevents deformations in the yoke keyslot area particularly at the nose portion of a yoke which distorts and even fracture sometimes after a relatively short period of time.

6i9~ 1 The service life of a yoke can be very limited particularly where a yoke is provided in a unit train coal car. The deformation to the keyslot at the nose portion can be so severe that the yoke must be replaced. The type of deformation which has been found to occur is, it is believed, only caused by loading of the keyslot peripheral rib located in the keyslot walls and used to form a connection with the horizontal key with the shank portion of the coupler.

t S St 10 As a railway car is subject to varying track Or conditions, factors such as rocking and superrelevations cause the mating couplers to angle with respect to the car applying a torsional force to the coupler draft assembly as well as buff or draft forces. The torsional force produces a certain magnitude of a twisting angle between the interconnected components. The components will angle freely until clearances prohibit further twisting.

A coupler can imposing a turning movement on the key while restrained in the yoke keyslot. The coupler upon continued turning movement after metal to metal contact between the key and walls of the keyslot in the yoke, will turn the yoke until interference exists between the follower block and the yoke straps.

With data giving steady state train action loads normally o£ 200,000 pounds, restraints on further yoke twisting show, with a coefficient of friction equal to 7 0.2, a 40,000 pound frictional force. This forces is distributed over the follower-striker lug contact which prevents the follower from twisting. In an AAR E-Type coupler shank and yoke arrangement, the maximum angle which the key can attain under these conditions is about 5.25 degrees maximum, and a minimum of about 0.75 degrees. When the maximum and minimum angling of the key is compared with possible angling of the bolster and side frames on uneven or poor quality track, it is found that the maximum bolster rock relative to the track is 7.393 degrees peak-to-peak.

Side frame rock relative to bearing adapters is degrees peak-to-peak when two adjacent cars rock in opposite directions. This gives rise to a possible 22.39 degree angling between coupled cars. Since the torsional angling of couplers is limited relative to each other, then the remaining torsional displacement of 22.39 degrees must be absorbed by the system. When the torsional angling is compounded with the vertical angling the draft key binds on the key-slot rib Screating a point load on the rib periphery.

0 .It is an object of the present invention to provide an improved construction for the nose portion of a standard AAR type E coupler yoke which will avoid the problems and shortcomings innumerated hereinbefore.

-8- -9- It is a further object of the present invention to provide an improved construction for an AAR type yoke for an E-Type coupler shank in which the nose portion is foreshortened and embodies a blunted and robust configuration to prevent deformation of a forward portion of a keyslot at the nose portion of the yoke which heretofore brought about failure and a need to replace the entire yoke in a railway vehicle.

More particularly, according to the present invention, there is provided a coupler yoke including a butt end portion having a rear draft gear seat at a generally right angle relation with each of top and bottom straps extending in a generally parallel and spaced apart relation to a yoke head portion having outwardly diverging keyslot walls extending from front draft gear pocket walls which face towards said rear draft seat, a draft gear pocket being defined within the area surrounded by the rear draft gear seat, the front draft gear pocket walls and the top and bottom straps, each of said keyslot walls having an elongated keyslot opening with a semi- circular front end from which a nose portion extends forwardly therefrom, each nose portion having a blunt contour to the contour of a standard yoke by a foreshortened length from a standard length of 3 1/2-inches measured from a point at the forward most surface of said .o0 semicircular front end inside said keyslot to the forward most end of the nose portion, each of said keyslot walls including a wall section with a generally trapezoid, cross-sectional configuration extending rearwardly of the semi-circular front end of the keyslot opening between each of opposite longitudinal sides of the keyslot opening and the outer boundary of the S2'. keyslot wall, said trapezoid cross-section configuration of the keyslot walls reducing stresses therein due to the trapezoidal configuration thereof, the stresses being generated by contact with a key member during angling of the key member against a longitudinal side of the keyslot o opening.

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I 4 The present invention also preferably provides that the nose portions of the coupler yoke which extends beyond the keyslot openings are defined by solid substantially trapezoidal walls with smooth convex outer front nose surface and smooth inner surfaces. The outer convex surface of each nose portion extends rearwardly preferably beyond the semicircular front end of the keyslot openings through a short distance which is sufficient to withstand lU opposed torsional forces by a key on the forward end of the keyslot opening. The convex outer surface of each nose portion merges with ribs that extend rearwardly along the keyslot opening in keyslot walls and form a step like depression at opposite sides of 15 the keyslot opening for merging with conventional keyslot walls.

The foreshortened configuration of the nose portion produces a blunted contour of the nose portion of the yoke to facilitate removal from a center sill 20 of a railway vehicle without the need for longitudinally shifting the yoke in the center sill rearwardly away from the striker to avoid interference between the striker carrier and the nose portion of the yoke.

These features and advantages of the present invention as well as others will be more fully 10 ~hi4~' s art o .*r a 4 4 a a.

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understood when the following description is read in light of the accompanying drawings in which: Figure 1 is an elevational view, partly in section, of an E-Type coupler assembly which includes a coupler yoke embodying the features of the present invention; Figure 2 is an isometric view of a Z-sill for a railway vehicle together with a rtriker which form part of the coupler assembly shown in Figure 1; 10 Figure 3 is a view in perspective of an E- Type coupler yoke embodying the features of the present invention; Figure 4 is a view illustrating the keyslot which is provided in the head portion of the yoke 15 shown in Figure 3 and embodying the features of the present invention; Figure 5 is a view taken along lines V-V of Figure 4; Figure 6 is a view similar to Figure 4 but 20 illustrating the head portion of a standard AAR E-Type coupler yoke; Figure 7 is an enlarged fragmentary view of the keyslot opening in the keyslot walls shown in Fig.

6 and illustrating, in an exaggerated manner, distortion of the wall of the keyslot opening; and In Fig. 1 of the drawings, the E-Type railway coupler assembly includes a coupler head 11 i i

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9C 99 4: 69 9-9 9C 9 constructed in a manner, per se, well known in the art. Extending rearwardly of the coupler head is a coupler shank 11 which conforms to AAR standards for an E-Type coupler shank and is characterized by a butt end 12 forwardly of which there is a horizontal keyslot 13 in the coupler shank. A draft key 14 extends through the keyslot and projects from opposite sides of the coupler shank outwardly through keyslot openings, as will be described in greater detail 10 hereinafter, in the nose portion of a yoke Opposite ends of the draft key also extend through keyslot openings 16 in a striker casting 17. The striker casting, as best shown in Fig. 2, is secured by welded metal, preferably in the manner described in U.S. Patent No. 4,445,617 to a center sill 18. The sill shown in Fig. 2 of the drawings is a Z-sill made up of two Z-shaped sections having flange portions 19, upstanding side sill walls 21 in which horizontal slots 22 are formed to receive horizontal ribs of the striker casting. The striker casting is welded to the sill about the periphery of the ribs which are provided on opposite sides of the striker casting.

The side walls 21 of the sill extend to top walls 23 which are welded together along their longitudinal edges so that a pocket is formed for receiving the striker casting and, rearwardly of the striker ~~49 12 a ii r: o i~I :i 1: ai

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r 0 0 o 0 0 0I 4 04 0* 4 0040 j casting, the yoke and draft gear are located in the pocket of the Z-sill.

A yoke strap carrier 25 maintains the yoke in the pocket of the Z-sill. The rearward most end of the draft gear engages rear draft lugs 26 that extend from the inride face surfaces of walls 21. The forward end of the draft gear presses against a follower 27 which is in turn supported by front draft lugs 28 formed on the rear portion of the striker casting. A generally rectangular, continuous striker face 29 protrudes from the forward end of the Z-sill.

The striker face is part of spaced apart side walls which are joined together along their top edge portion by a top wall 31 and a bottom wall 32, which is 15 commonly referred to in the art as a striker carrier.

As shown in Fig. 1, the striker carrier engages the bottom surface of the coupler shank to support the coupler during lateral, side-to-side movement as well as longitudinal movement of the coupler shank in buff and pull conditions.

In Figs. 3-5, there is illustrated the details of the construction of a coupler yoke according to the present invention. The coupler yoke includes a butt end portion 35 having lightener pockets 36 at opposite sides of a rear draft gear seat 37 comprised f a generally planar face surface.

Extending forwardly from the butt end portion are top 13

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and bottom straps 38 and 39 which extend to a yoke head 40. It will be understood by those skilled in the art that the yoke in the illustration of Fig. 3 is shown in a position which is rotated 90 degrees from the position of the yoke when operatively arranged in the center sill of a railway vehicle as shown in Fig.

1. Returning to the illustration of Fig. 3, the yoke head portion includes outwardly diverging keyslot walls 41 which commence at front draft fear walls 42 10 and extend forwardly to a nose portion 43. A draft gear pocket is defined in the yoke by the area surrounded by the rear draft gear seat 37, the front draft gear walls 42 and the top and bottom straps 38 and 39. The keyslot walls 41 're each provided with keyslot openings that extend lengthwise of the yoke, generally parallel with the top and bottom straps 38 and 39. The keyslot walls are provided with upstanding ribs 44. The end of each keyslot which is closely spaced from the front draft gear walls 42 has a semicircular rear portion and the end of the keyslot which is at the front nose portion 43 has a semicircular front end. The length of the nose portion 43 which is defined in Figs. 3-5 as distance X is foreshortened to a length less than 3 1/2-inches from a point at the forward most surface of the semicircular front end inside the keyslot to the forward most end of the nose portion. Preferably, the 14 i -n fW S, rt r 4 *4 I 4 4

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distance X is about 3 inches. The foreshortened length of the nose portion produces a blunted contour defined by edge surface 45. These edge surfaces are preferably defined a radius struck from a point about 1/4-inch rearwardly from the forward most surface of the semicircular front end of the keyslot and can be joined with a standard yoke contour for E-Type couplers identified as Y40 and Y41. A Y40 yoke has a 5/8-inch long draft gear pocket whereas a Y41 yoke has a 36 3/8-inch long draft gear pocket. The foreshortened length of the yoke nose portion alleviates the problems innumerated hereinbefore as well as a practice of removing, as by use of a cutting torch, a part of the rear portion of the striker carrier 32 (Figs. 1 and 2) which was sometimes necessary to permit removal of the coupler yoke from the center sill. The degregation to the striker carrier could be overlooked in the rep'acement process for the yoke whereby inadequate support for the 20 coupler might result due to weakening of the coupler carrier.

As can also be seen from Figs. 3-5, the nose portion of the coupler which extends beyond the keyslot openings in the keyslot walls is defined by trapezoidally shaped, in cross section, (Fig. 5) walls 46 each with a smooth convex outer front nose surface and a smooth inner surface. The trapezoidal cross 15 i

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sectional shape of each wall 46 extends rearwardly, preferably beyond the semicircular front end of the keyslot opening through a short distance along the keyslot to a point where the wall thickness can smoothly merge with the ribs 44. The point of merger is sufficiently rearward to increase the strength of the forward portion of the keyslot wall against deformations of the type shown in Figs. 6 and 7. It will be observed that the extension of the uniformly thick wall at each nose portion of the yoke terminates at generally the formation of walls sections 46 which extend transversely to the length of the keyslot.

By way of contrast to the yoke of the present invention, in Fig. 6, a standard Y40 AAR E- Type coupler yoke is shown in which the nose portion is provided with a single upstanding rib 48 extending from the semicircular rib portion at the forward end of the keyslot to the end of the yoke. The wall thickness of the yoke nose end portion at the top and 20 bottom sides of the ribs 48 are of inadequate strength to prevent severe distortion to the forward portion of the keyslot opening which is illustrated by Fig. 7.

In Fig. 7, the keyslot at its forward lower surface can be deformed, as shown to an exaggerated extent, by torsional angling combined with vertical angling of the coupler which causes the draft key to bind in the keyslot rib creating a point loading condition at 16 point 49 in the periphery of the rib. This condition is exaggerated in Fig. 7 but nevertheless have been found to result in a failure in the yoke casting because of a crack which is typically illustrated and identified by reference numeral R0920 917

Claims (2)

1. A coupler yoke including a butt end portion having a rear draft gear seat at a generally right angle relation with each of top and bottom straps extending in a generally parallel and spaced apart relation to a yoke head portion having outwardly diverging keyslot walls extending from front draft gear pocket walls which face toward said rear draft seat, a draft gear pocket being defined within the area surrounded by the rear draft gear seat, the front draft gear pocket walls and the top and bottom straps, each of said keyslot walls having an elongated keyslot opening with a semi- circular front end from which a nose portion extends forwardly C Orn? therefrom, each nose portion having a blunt contour to the contour of a standard yoke by a foreshortened length from a standard length of 3 1/2-inches measured from a point at the forward most surface of said semicircular front end inside said keyslot to the forward most end of the nose portion, each of said keyslot walls including a wall section with a generally trapezoid, cross-sectional configuration extending rearwardly of the semi-circular front end of the keyslot opening between each of opposite longitudinal sides of the keyslot opening and the outer boundary of the keyslot wall, said trapezoid cross-section configuration of the keyslot walls reducing stresses therein due to the trapezoidal configuration thereof, the stresses being generated by contact with a key member during angling of the key member against a longitudinal side of the keyslot opening. 1 OT-- i-rri,,, I- WBWW,

19- 2. The coupler yoke according to claim 1 wherein the foreshortened length of said nose portion is 3 inches. 3. The coupler yoke according to claim 1 whereir nose portion includes convex outer wall surfaces in a direction which is transverse to the extended length of the coupler yoke, said convex outer wall surfaces extending between opposite edge boundaries of the nose portion. 4. The coupler yoke according to claim 1 wherein said nose portion is defined by wall sections which have a generally trapezoid cross-sectional configuration in a direction transverse to the length of the nose portion. The coupler yoke according to claim 4 wherein said wall sections having a trapezoidal cross section extending rearwardly in a direction toward said rear draft h gear seat to points along said keyslot to merge with outwardly t" protruding ribs at opposite sides of the keyslot. :c 6. A coupler yoke including a butt end portion having a rear draft gear seat at a generally right angle relation with each of top and bottom straps extending in a generally parallel and spaced apart relation to a yoke head portion having outwardly diverging keyslot walls extending from front draft gear pocket walls facing toward said rear 6 t draft seat, a draft gear pocket being defined within the area s 'S surrounded by the rear draft gear seat, the front draft gear pocket walls and the top and bottom straps, said keyslot walls 'el each having an elongated keyslot opening with a semi-circular end at a point spaced forwardly from said front draft gear A A .5. 20 pocket walls and a semi-circular end at a forward end of said keyslot opening from which a nose portion extends forwardly therefrom, said nose portion having a circumferentially extending edge surface struck from a point inside said keyslot to foreshorten the nose portion from a standard length of 3 1/2 inches measured from a point at the forward most surface of said semi-circular key slot to the forward most end of the nose portion, said nose portion being defined by a convexly shaped outwardly facing surface which extends continuously along said nose portion and rearwardly along opposie sides of the keyslot opening on each keyslot wall, the convexly shaped outwardly facing surface merging with a rib protruding outwardly on the keyslot walls at each of opposite lateral sides of the keyslot therein to thereby define a trapezoidal configuration in section generally radiating from the slot of the wall of said nose portion with the forward sidewalls of the keyslot, and protecting against deformations and reduce stresses caused by repeated angular loading of a draft key against one of opposite lateral sides of said keyslot. 7. The coupler yoke according to claim 6 wherein the foreshortened length of said nose portion is 3 inches. o 8. The coupler yoke according to claim 6 wherein said nose portion is defined by wall sections which have a trapezoidal cross-sectional configuration in a direction transverse to the length of the nose portion. 9. The coupler yoke according to claim 8 wherein said wall sections having a trapezoidal cross section extend rearwardly In a direction toward said rear draft gear seat to points along said keyslot to merge with outwardly protruding ribs at opposite sides of the keyslot. 10. A coupler yoke including a butt end portion having a rear draft gear seat at a generally right angle relation with each of top and bottom straps extending in a generally parallel and spaced apart relation to a yoke head portion, said yoke head portion having outwardly diverging keyslot walls extending from front draft gear pocket walls facing toward said rear draft seat, a draft gear pocket being defined within the area surrounded by the rear draft gear seat, the front draft gear pocket walls and the top and bottom straps, said keyslot' walls each having an elongated keyslot opening with a semi-circular end at a point spaced forwardly from said front draft gear pocket walls and a semicircular end at a forward end of the keyslot opening from which a nose portion extends forwardly therefrom, said nose portion having a circumferentially extending edge S121u a i- i Si:- P I;' ~ti r g 21 surface spaced from the keyslot opening therein by a distance to foreshorten the nose portion to less than 3 1/2 inches, said nose portion being defined by a continuous convex outwardly facing surface and having a trapezoidal wall section in a plane generally radiating outwardly from the slot and which is extending rearwardly along the nose portion and rearwardly along part of opposite longitudinal sides of the keyslot in said keyslot walls, said continuous convex outer face surface merging with ribs protruding outwardly on the keyslot wall at opposite longitudinal sides of the keyslot opening therein, said trapezoidal wall section reducing stresses in said nose portion and the forward sidewall portions of the keyslot wall around opening, caused by repeated angular loading by a draft key against opposite lateral sides of the keyslot opening. t ttt S t t cI tI f It Itt t i tt{ TMS/1121U Lrua e ndl at- a forward and of said which a nose portion extends forwardly therefr, mfid nose portion having a generally radia. esaid nose portion being defined by continu sconvex outer face surfaces which form a tr zodal wall sections that extend rearwardly d merge with ribs protruding from T)A'PE i-hi c TNTH AY Mly JUE 18 McCONWAY TORLEY CORPORATION Patent Attorneys for the Applicant SPRUSON FERGUSON 4&L P21