US20190144015A1 - Cushioning apparatus for a railway car - Google Patents
Cushioning apparatus for a railway car Download PDFInfo
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- US20190144015A1 US20190144015A1 US15/814,853 US201715814853A US2019144015A1 US 20190144015 A1 US20190144015 A1 US 20190144015A1 US 201715814853 A US201715814853 A US 201715814853A US 2019144015 A1 US2019144015 A1 US 2019144015A1
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- Prior art keywords
- elastomeric
- stack
- plate
- yoke
- buff
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B61—RAILWAYS
- B61G—COUPLINGS; DRAUGHT AND BUFFING APPLIANCES
- B61G9/00—Draw-gear
- B61G9/04—Draw-gear combined with buffing appliances
- B61G9/10—Draw-gear combined with buffing appliances with separate mechanical friction shock-absorbers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B61—RAILWAYS
- B61G—COUPLINGS; DRAUGHT AND BUFFING APPLIANCES
- B61G9/00—Draw-gear
- B61G9/20—Details; Accessories
- B61G9/22—Supporting framework, e.g. cradles; Spring housings
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B61—RAILWAYS
- B61G—COUPLINGS; DRAUGHT AND BUFFING APPLIANCES
- B61G9/00—Draw-gear
- B61G9/04—Draw-gear combined with buffing appliances
- B61G9/06—Draw-gear combined with buffing appliances with rubber springs
Definitions
- the invention is directed to a cushioning apparatus for a railway car, and more particularly to a selective travel apparatus that absorbs draft and buff loads applied to a coupler of a railway car.
- railway cars are connected to an adjacent car by a coupler.
- the coupler is joined to a yoke, for example an “E-type” or “F-type” yoke, by a draft key or pin, and the assembly is mounted in a railway car center sill.
- one or more elastic elements such as a coil spring or a set of elastomeric pads, is enclosed in a housing mounted in the yoke behind the coupler.
- a piston-like element frictionally received in the housing absorbs buff loads transmitted via a coupler follower which moves inside the yoke in response to buff impact force applied on the coupler, and the draft gear is compressed in the yoke in response to draft loads.
- the basic draft gear apparatus has been used for decades. However, in many cases unacceptably large forces are transmitted to the railway car.
- a hydraulic cushioning unit comprises a piston received in a cylinder filled with fluid.
- Such devices may dissipate more force than a conventional draft gear, but they are known to be prone to leakage.
- U.S. Pat. No. 2,766,894 describes a selective travel draft gear with separate cushioning elements for buff and draft loads on the coupler. In this design, both of the cushioning elements are located forward of the back wall of the yoke.
- U.S. Pat. No. 2,825,472 describes a selective travel draft gear which comprises separate cushioning elements for buff and draft loads on the coupler, but both stacks of cushioning elements are attached to the yoke.
- U.S. Pat. No. 6,446,820 discloses a selective travel draft gear of more recent vintage where the separate draft and buff cushioning elements are coupled and adapted to fit into the draft gear pocket. These apparatuses have not been very well received, and may be prone to buckling, wherein a stack of elastomeric elements is pushed out of alignment and fails to operate according to specifications.
- one object of the invention is to provide an alternative cushioning device that provides cushioning over a range of impact speeds.
- Another object of the invention is to provide a cushioning apparatus for a railway car that provides cushioning for both draft and buff loads applied to the coupler, limiting force transmitted to the railway car over a range of impact speeds, such as may be encountered during train build, where impact speeds may be in the neighborhood of 4-14 mph or higher, and during start-up and stopping.
- Embodiments according to the invention may exhibit low displacement per unit of force applied over a range of relevant force levels.
- Yet another object of the invention is to provide improved alignment and positioning of elastomeric pads in a cushioning device, to prevent over-compression, permanent deformation, and buckling during use.
- Yet another object of the invention is to provide a cushioning apparatus that absorbs both draft and buff loads in a compact format, more easily installed in a standard pocket such as for an AAR standard EOC-9 or EOC-10 configuration.
- an end-of-car cushioning device for a railway car, comprising: a yoke having aligned apertures at a front end adapted to receive a pin or key for attaching the yoke to a railway car coupler, and having a vertical wall at a second end of the yoke opposite the front end; a coupler-receiving member adapted to receive buff force from the coupler and adapted to move inside the yoke; a first stack of elastomeric units positioned between the coupler-receiving member and the vertical wall of the yoke, said first stack being compressed by draft and buff loads on the coupler; a front buff plate positioned adjacent to and rearward of the yoke and connected to a rear buff plate by a center rod; a second stack of elastomeric units positioned between the front buff plate and the rear buff plate, said second stack being compressed in response to buff loads on the coupler; wherein, the yoke
- the invention resides in the arrangement of the plurality of elastomeric units, each comprising a plate and an elastomeric pad positioned in the middle of the plate.
- a first set of the plates is arranged in a rear or “buff” stack and the plates are each sized to fill the sill area to ensure alignment of the elastomeric pads.
- a second set of plates is arranged in a front or “draft” stack, sized to fit inside a yoke.
- the edges of the plates extending around the elastomeric pads are configured so that the plates can nest with each other, and at full compression the edges of the plates contact one another to prevent overcompression of the individual elastomeric pads.
- FIG. 1 is top view of a cushioning device assembly according to the invention assembled in a railway car sill;
- FIG. 2 is an isometric view of a front portion of a cushioning device according to the invention.
- FIG. 3 is an isometric view of a rear portion of a cushioning device according to the invention.
- FIG. 4 is an isometric view of an improved selective travel cushioning device according to the invention attached to an “F” Type coupler;
- FIG. 5 is a cross sectional view of the improved selective travel cushioning device assembly of FIG. 1 , taken along view lines 5 - 5 of FIG. 1 ;
- FIG. 6 depicts the response of a cushioning unit to static buff and draft loads.
- Directions and orientations herein refer to the normal orientation of a railway car in use.
- the “front” of a coupler is in a direction away from the body of the car and “rear” is in a direction toward the center of the car.
- the “longitudinal” axis or direction is parallel to the rails and in the direction of movement of the railway car on the track in either direction.
- the “transverse” or “lateral” axis or direction is in a horizontal plane perpendicular to the longitudinal axis and the rail.
- the term “inboard” means toward the center of the car, and may mean inboard in a longitudinal direction, a lateral direction, or both.
- “outboard” means away from the center of the car.
- “Vertical” is the up-and-down direction
- “horizontal” is a plane parallel to the rails including the transverse and longitudinal axes.
- Elastomer and “elastomeric” refer to polymeric materials having elastic properties so that they exert a restoring force when compressed. Examples of such materials include, without limitation, thermoplastic elastomer (TPE), natural and synthetic rubbers such as: neoprene, isoprene, butadiene, styrene-butadiene rubber (SBR), polyurethanes, and derivatives.
- TPE thermoplastic elastomer
- SBR styrene-butadiene rubber
- polyurethanes and derivatives.
- the term “about” associated with a numerical value is understood to encompass a margin of +/ ⁇ 10% of the value.
- An object is said to “substantially fill” a space (such as a railway car sill) when just enough space is provided to allow the object to move in the space without interference. This may mean a clearance of up to about 1 ⁇ 4 inch laterally and up to about 3 ⁇ 4 inch vertically.
- a cushioning device is adapted to fit into an Association of American Railroads (“AAR”) standard pocket.
- AAR Association of American Railroads
- the dimensions of a standard pocket and permitted tolerances may be set by the AAR. from time to time, and reference herein to AAR standards refers to standards in the AAR Manual of Standards and Recommended Practices in effect at the filing date of this application, including performance standards, such as M-921-B, for hydraulic cushioning units.
- performance standards such as M-921-B
- FIG. 1 depicts a cushioning assembly 10 according to one embodiment of the invention, including a sill 13 , coupler 14 , and front and rear units 20 , 30 of the cushioning device installed in the cushion unit pocket.
- FIG. 1 depicts center sill 13 with bell shaped opening 15 adapted to accommodate long shank coupler 14 for a greater range of coupler mobility, although the invention is not limited to a long shank coupler configuration.
- cushioning device assembly 10 may be characterized by a pocket length of about 383 ⁇ 4 inches described in AAR standard S-183 for an “EOC-9” pocket, or a pocket length of about 483 ⁇ 4 inches described in AAR standard S-184 for an “EOC-10” pocket. In other embodiments, the cushioning device may be adapted to fit other pocket dimensions.
- the “cushioning unit pocket”, or simply the “pocket”, is defined by front lugs 11 and rear draft lugs 12 mounted on the interior of center sill 13 .
- the cushioning elements are adapted to be inside the center sill without significantly reconfiguring the sill geometry.
- the cushioning apparatus comprises a first stack 17 of elastomeric units positioned forward of vertical wall 21 of the yoke, and a second stack 16 of elastomeric units positioned behind the first stack 17 , between a front buff plate and the rear buff plate (as shown in FIG. 3 ).
- the cushioning unit comprises a front portion 20 and a rear portion 30 , which are not fixed to one another.
- FIG. 2 is a view of a front “draft” portion 20 of a cushioning apparatus according to an embodiment of the invention.
- Yoke 206 includes rear vertical wall 21 and a front portion including two aligned apertures 23 adapted to receive a pin 42 (not shown in FIG. 2 ).
- a coupler-receiving member 22 conventionally termed a “coupler follower” is adapted to receive buff force from the coupler and adapted to move inside the yoke.
- coupler follower 22 includes a recess 24 adapted to receive the shank end of the railway car coupler 14 , such that follower 22 moves under buff force from the coupler.
- FIG. 1 The configuration shown in FIG.
- FIG. 2 is “F-type”, in that a pin is used to attach coupler 14 (shown in FIG. 4 ) to yoke 206 , and walls 26 are on the top and bottom of the yoke.
- An “E-type” configuration using a draft key to attach the coupler to the yoke using draft key, may also be used without departing from the scope of the invention, and indeed without changing the dimensions of elastomeric units 25 , or of the stacks 16 , 17 .
- each elastomeric unit 25 is shown in FIG. 2 in the space between vertical wall 21 and coupler follower 22 , each elastomeric unit comprising a metal plate 225 , and at least one elastomeric pad 27 .
- several elastomeric units 25 form stack 17 contained in this space (as shown in FIG. 4 and FIG. 5 ), which (in one non-limiting example) may be about 9-10 inches from the vertical wall to the follower, in a compressed state, comprising for example, 10-15 plates and a corresponding number of elastomeric pads, although other pad sizes and configurations may be employed to tune performance to a particular type of car or lading.
- the elastomeric unit 25 includes metal plate 225 and a single elastomeric pad 27 . In other embodiments, multiple elastomeric pads may be positioned on a plate.
- FIG. 4 depicts an installed position where coupler pin 42 engages the front side of aperture 23 .
- the first stack 17 of elastomeric elements is compressed between vertical wall 21 and coupler follower 22 which abuts stops 11 .
- the first or “draft” stack 17 is compressed when the coupler is subjected to buff loads and also when the coupler is subjected to draft loads.
- the coupler follower 22 may be held in place with a predetermined pressure on the elastomeric pads 27 , using a set of destructible shear pins fixing the coupler follower to the yoke.
- two c-shaped spacers may be provided on rear unit 30 between rear plate 32 and nut 54 to provide a pre-load on the rear stack for installation.
- each elastomeric unit 25 comprises elastomeric pad 27 mounted in a recessed area 29 of the metal plate 225 .
- the rigid plates may be adapted to prevent over-compression of the elastomeric pads 27 .
- the plates may be made of cast or fabricated metal such as steel, and a stop surface may be provided on the periphery of the plate around the recess.
- protrusions 28 permit a nesting arrangement of elastomeric units 25 in stack 17 , as shown in FIG. 4 and FIG. 5 , which also contributes to alignment of the elastomeric units 25 .
- Metal-to-metal contact on the stop surfaces occurs when an elastomeric pad 27 between two adjacent plates 225 is compressed a predetermined amount, such as 20-80%, and in embodiments 20-60%, of the uncompressed thickness of the pads.
- the pads in the front or draft stack compress about 0.5 inches (from their uncompressed thickness prior to installation) before metal to metal contact prevents further compression.
- the plates 225 forming front stack 17 extend to the walls and/or the straps of the yoke 206 .
- an uncompressed thickness of each pad 27 forming front stack 17 may be about 1.37 inches. Installed, under a static load of 32 klb, the thickness of the draft pads is 0.92.
- the elastomeric pads 37 in the draft stack may have a thickness of 0.68 inches. These dimensions are provided for guidance and should not be deemed to limit the invention. In practice many configurations are possible without departing from the scope of the invention.
- the elastomeric pads 27 may be provided with a through hole in the center, which aligns with a protrusion, which may be cast, stamped or fabricated on the plate, for example, and provided to keep the pads in alignment.
- the diameter of the through hole may be referred to as the “inner diameter”.
- the lateral edge of each elastomeric pad 27 may be curved in a toroidal manner, and the outside diameter of the pad is measured at the middle of the thickness dimension of the pad.
- FIG. 3 represents the rear “buff” portion 30 of the cushioning apparatus, positioned adjacent to and rearward of the yoke and comprising front plate 31 connected to rear plate 32 by a rod 34 which passes through a plurality of elastomeric units 35 .
- a single center rod 34 is shown, a plurality of rods may also be used.
- Each elastomeric unit 35 comprises a plate 226 and at least one elastomeric pad 37 , similar in construction to the elastomeric unit 25 . However, the plate 226 and the elastomeric pad 37 both have a hole to receive rod 34 . As in the description of FIG. 2 , only a single elastomeric unit 35 is shown in FIG.
- each elastomeric pad 37 may be circular when viewed in plan, having an outer diameter. An “inner diameter” defines a through hole in the middle adapted to receive the center rod.
- Pads 37 in the buff stack 16 may have the same general shape as pads 27 in the draft stack 17 but they are scaled larger.
- the maximum design force of the larger pads 37 is higher due to larger surface area, but the surface pressure on each pad is the same.
- the uncompressed thickness of a pad 37 may be about 1.70 inches and the outer diameter may be about 8.82. Compressed for installation with a force of about 32 klb, the installed thickness of the pads is about 1.24 inches. Under full compression, with metal-to-metal contact of plates 226 preventing further compression of pads 37 , the pad thickness may be about 0.91 inches and the outside diameter may reach 10.63 inches.
- the pads and plates are designed to allow compression of 20-80 percent, and in embodiments 40-60 percent, where the amount that the pad is compressed at full compression is expressed as a percentage of the uncompressed thickness of the pad, prior to installation.
- Bolt head 33 is flush mounted in front plate 31 so that the rear unit 30 may be mounted directly against front unit 20 .
- rear unit 30 is not attached to the front unit 20 , which facilitates installation.
- rod 34 is secured by nut 54 .
- the same elastomeric material may be used for the elastomeric pads in the draft stack as in the buff stack, such as a thermoplastic elastomer.
- the elastomeric units of the draft pack are adapted to slide between straps 26 of yoke 20 .
- the yoke is attached to the coupler using a draft key, but the performance considerations for the pads and plates are similar.
- draft stack 17 is provided in a pre-shortened installation configuration, which allows draft portion 20 and the buff portion 30 to slide into the pocket and allows the coupler to be installed without interference.
- a plurality of shear pins for example four shear pins pass through the yoke into the coupler follower 22 . The pins break on first impact, and in this fully-installed or post-installation position, the coupler is pre-stressed, applying buff force against the first and second stacks.
- FIG. 6 depicts performance modeling of a cushioning unit according to the invention using response to static buff and draft loads.
- the dynamic response of the material would be dependent on impact speed and could approach twice the static load values. Nevertheless, the response to static loads provides information to guide product design to achieve performance objectives.
- 11 pads are used in the buff stack, each having an uncompressed thickness of 1.7 inches and an uncompressed diameter of 8.82 inches.
- the draft stack comprises 14 pads, each having an uncompressed thickness of 1.37 inches and uncompressed diameter of 6.63 inches.
- a static compression test is performed to obtain the response to static load and subsequent recovery or “release”. Separation of compression and release curves represents hysteresis.
- the relatively large hysteresis depicted in the response curves is at least partly an advantage of using the plates to limit compression of the elastomeric pads within a predetermined range, resulting in a greater absorption and dissipation of impact energy.
- very little permanent deformation is expected during the lifetime of the cushioning unit, on the order of less than 10%, preferably less than 5%.
- the stiffening observed under buff loads greater than about 400 klb occurs after the draft stack is fully compressed, and the rear “buff” stack assumes the remainder of the force absorption.
- Hysteresis may be expressed as the ratio of energy absorbed by cushioning unit (W A ) to the energy input during impact (W E ) (modeled as a static load).
- Hysteresis for the cushioning unit may be extrapolated from the deflection of the buff and draft pads versus applied static force during compression and release from different starting points (i.e., pre-loaded, uncompressed and fully compressed).
- a cushioning unit according to the invention will have a W A /W E ratio derived in this manner of 0.3 to 0.65.
- the large distance between the compression and release curves in FIG. 6 indicates relatively high hysteresis for a cushioning unit according to the invention.
Abstract
Description
- The invention is directed to a cushioning apparatus for a railway car, and more particularly to a selective travel apparatus that absorbs draft and buff loads applied to a coupler of a railway car.
- As is generally known, railway cars are connected to an adjacent car by a coupler. The coupler is joined to a yoke, for example an “E-type” or “F-type” yoke, by a draft key or pin, and the assembly is mounted in a railway car center sill.
- To prevent damage to the railway cars and the laded goods during operation, and especially during assembly of the railway car train in the yard, various devices have been installed to absorb loads on the coupler so that impact forces are not transmitted to the railway car.
- In a conventional frictional draft gear, one or more elastic elements, such as a coil spring or a set of elastomeric pads, is enclosed in a housing mounted in the yoke behind the coupler. A piston-like element frictionally received in the housing absorbs buff loads transmitted via a coupler follower which moves inside the yoke in response to buff impact force applied on the coupler, and the draft gear is compressed in the yoke in response to draft loads. The basic draft gear apparatus has been used for decades. However, in many cases unacceptably large forces are transmitted to the railway car.
- A hydraulic cushioning unit comprises a piston received in a cylinder filled with fluid. Such devices may dissipate more force than a conventional draft gear, but they are known to be prone to leakage.
- U.S. Pat. No. 2,766,894 describes a selective travel draft gear with separate cushioning elements for buff and draft loads on the coupler. In this design, both of the cushioning elements are located forward of the back wall of the yoke.
- U.S. Pat. No. 2,825,472 describes a selective travel draft gear which comprises separate cushioning elements for buff and draft loads on the coupler, but both stacks of cushioning elements are attached to the yoke.
- U.S. Pat. No. 6,446,820 discloses a selective travel draft gear of more recent vintage where the separate draft and buff cushioning elements are coupled and adapted to fit into the draft gear pocket. These apparatuses have not been very well received, and may be prone to buckling, wherein a stack of elastomeric elements is pushed out of alignment and fails to operate according to specifications.
- All of the above-referenced U.S. Patents are incorporated by reference.
- In view of the prior art, one object of the invention is to provide an alternative cushioning device that provides cushioning over a range of impact speeds.
- Another object of the invention is to provide a cushioning apparatus for a railway car that provides cushioning for both draft and buff loads applied to the coupler, limiting force transmitted to the railway car over a range of impact speeds, such as may be encountered during train build, where impact speeds may be in the neighborhood of 4-14 mph or higher, and during start-up and stopping. Embodiments according to the invention may exhibit low displacement per unit of force applied over a range of relevant force levels.
- Yet another object of the invention is to provide improved alignment and positioning of elastomeric pads in a cushioning device, to prevent over-compression, permanent deformation, and buckling during use.
- Yet another object of the invention is to provide a cushioning apparatus that absorbs both draft and buff loads in a compact format, more easily installed in a standard pocket such as for an AAR standard EOC-9 or EOC-10 configuration.
- These and other objects of the invention are met in one aspect with an end-of-car cushioning device for a railway car, comprising: a yoke having aligned apertures at a front end adapted to receive a pin or key for attaching the yoke to a railway car coupler, and having a vertical wall at a second end of the yoke opposite the front end; a coupler-receiving member adapted to receive buff force from the coupler and adapted to move inside the yoke; a first stack of elastomeric units positioned between the coupler-receiving member and the vertical wall of the yoke, said first stack being compressed by draft and buff loads on the coupler; a front buff plate positioned adjacent to and rearward of the yoke and connected to a rear buff plate by a center rod; a second stack of elastomeric units positioned between the front buff plate and the rear buff plate, said second stack being compressed in response to buff loads on the coupler; wherein, the yoke, the front buff plate and the rear buff plate are positioned within a center sill of the railway car; and wherein, the yoke is not mechanically attached to the front buff plate or the rear buff plate.
- In another aspect, the invention resides in the arrangement of the plurality of elastomeric units, each comprising a plate and an elastomeric pad positioned in the middle of the plate. A first set of the plates is arranged in a rear or “buff” stack and the plates are each sized to fill the sill area to ensure alignment of the elastomeric pads. A second set of plates is arranged in a front or “draft” stack, sized to fit inside a yoke. The edges of the plates extending around the elastomeric pads are configured so that the plates can nest with each other, and at full compression the edges of the plates contact one another to prevent overcompression of the individual elastomeric pads.
- The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:
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FIG. 1 is top view of a cushioning device assembly according to the invention assembled in a railway car sill; -
FIG. 2 is an isometric view of a front portion of a cushioning device according to the invention; -
FIG. 3 is an isometric view of a rear portion of a cushioning device according to the invention; -
FIG. 4 is an isometric view of an improved selective travel cushioning device according to the invention attached to an “F” Type coupler; -
FIG. 5 is a cross sectional view of the improved selective travel cushioning device assembly ofFIG. 1 , taken along view lines 5-5 ofFIG. 1 ; and -
FIG. 6 depicts the response of a cushioning unit to static buff and draft loads. - The drawings are not to scale, and features not necessary for an understanding of the invention are not shown.
- Directions and orientations herein refer to the normal orientation of a railway car in use. Thus, unless the context dearly requires otherwise, the “front” of a coupler is in a direction away from the body of the car and “rear” is in a direction toward the center of the car. Likewise, the “longitudinal” axis or direction is parallel to the rails and in the direction of movement of the railway car on the track in either direction. The “transverse” or “lateral” axis or direction is in a horizontal plane perpendicular to the longitudinal axis and the rail. The term “inboard” means toward the center of the car, and may mean inboard in a longitudinal direction, a lateral direction, or both. Similarly, “outboard” means away from the center of the car. “Vertical” is the up-and-down direction, and “horizontal” is a plane parallel to the rails including the transverse and longitudinal axes.
- “Elastomer” and “elastomeric” refer to polymeric materials having elastic properties so that they exert a restoring force when compressed. Examples of such materials include, without limitation, thermoplastic elastomer (TPE), natural and synthetic rubbers such as: neoprene, isoprene, butadiene, styrene-butadiene rubber (SBR), polyurethanes, and derivatives.
- As used herein, the term “about” associated with a numerical value is understood to encompass a margin of +/−10% of the value. An object is said to “substantially fill” a space (such as a railway car sill) when just enough space is provided to allow the object to move in the space without interference. This may mean a clearance of up to about ¼ inch laterally and up to about ¾ inch vertically.
- In embodiments, a cushioning device according to the invention is adapted to fit into an Association of American Railroads (“AAR”) standard pocket. The dimensions of a standard pocket and permitted tolerances may be set by the AAR. from time to time, and reference herein to AAR standards refers to standards in the AAR Manual of Standards and Recommended Practices in effect at the filing date of this application, including performance standards, such as M-921-B, for hydraulic cushioning units. A person having ordinary skill in the art has a general knowledge of AAR standards and the published AAR standards cited herein are incorporated by reference as background.
-
FIG. 1 depicts acushioning assembly 10 according to one embodiment of the invention, including asill 13,coupler 14, and front andrear units FIG. 1 depictscenter sill 13 with bell shapedopening 15 adapted to accommodatelong shank coupler 14 for a greater range of coupler mobility, although the invention is not limited to a long shank coupler configuration. - In embodiments,
cushioning device assembly 10 may be characterized by a pocket length of about 38¾ inches described in AAR standard S-183 for an “EOC-9” pocket, or a pocket length of about 48¾ inches described in AAR standard S-184 for an “EOC-10” pocket. In other embodiments, the cushioning device may be adapted to fit other pocket dimensions. - In
FIG. 1 , and as used herein, the “cushioning unit pocket”, or simply the “pocket”, is defined byfront lugs 11 andrear draft lugs 12 mounted on the interior ofcenter sill 13. According to embodiments of the invention, the cushioning elements are adapted to be inside the center sill without significantly reconfiguring the sill geometry. - In
FIG. 1 , the cushioning apparatus comprises afirst stack 17 of elastomeric units positioned forward ofvertical wall 21 of the yoke, and asecond stack 16 of elastomeric units positioned behind thefirst stack 17, between a front buff plate and the rear buff plate (as shown inFIG. 3 ). The cushioning unit comprises afront portion 20 and arear portion 30, which are not fixed to one another. -
FIG. 2 is a view of a front “draft”portion 20 of a cushioning apparatus according to an embodiment of the invention.Yoke 206 includes rearvertical wall 21 and a front portion including two alignedapertures 23 adapted to receive a pin 42 (not shown inFIG. 2 ). A coupler-receivingmember 22, conventionally termed a “coupler follower” is adapted to receive buff force from the coupler and adapted to move inside the yoke. In the embodiment shown,coupler follower 22 includes arecess 24 adapted to receive the shank end of therailway car coupler 14, such thatfollower 22 moves under buff force from the coupler. The configuration shown inFIG. 2 is “F-type”, in that a pin is used to attach coupler 14 (shown inFIG. 4 ) toyoke 206, andwalls 26 are on the top and bottom of the yoke. An “E-type” configuration, using a draft key to attach the coupler to the yoke using draft key, may also be used without departing from the scope of the invention, and indeed without changing the dimensions ofelastomeric units 25, or of thestacks - For ease of understanding the invention, a single
elastomeric unit 25 is shown inFIG. 2 in the space betweenvertical wall 21 andcoupler follower 22, each elastomeric unit comprising ametal plate 225, and at least oneelastomeric pad 27. In actual usage, severalelastomeric units 25form stack 17 contained in this space (as shown inFIG. 4 andFIG. 5 ), which (in one non-limiting example) may be about 9-10 inches from the vertical wall to the follower, in a compressed state, comprising for example, 10-15 plates and a corresponding number of elastomeric pads, although other pad sizes and configurations may be employed to tune performance to a particular type of car or lading. In the embodiment shown, theelastomeric unit 25 includesmetal plate 225 and a singleelastomeric pad 27. In other embodiments, multiple elastomeric pads may be positioned on a plate.FIG. 4 depicts an installed position wherecoupler pin 42 engages the front side ofaperture 23. When a draft load is applied oncoupler 14 throughpin 42, thefirst stack 17 of elastomeric elements is compressed betweenvertical wall 21 andcoupler follower 22 which abuts stops 11. The first or “draft”stack 17 is compressed when the coupler is subjected to buff loads and also when the coupler is subjected to draft loads. To install theelastomeric units 25 in the front portion of the cushioning unit, thecoupler follower 22 may be held in place with a predetermined pressure on theelastomeric pads 27, using a set of destructible shear pins fixing the coupler follower to the yoke. In the rear stack, two c-shaped spacers (not shown) may be provided onrear unit 30 betweenrear plate 32 andnut 54 to provide a pre-load on the rear stack for installation. - Referring again to
FIG. 2 , eachelastomeric unit 25 compriseselastomeric pad 27 mounted in a recessedarea 29 of themetal plate 225. The rigid plates may be adapted to prevent over-compression of theelastomeric pads 27. For example, the plates may be made of cast or fabricated metal such as steel, and a stop surface may be provided on the periphery of the plate around the recess. Additionally,protrusions 28 permit a nesting arrangement ofelastomeric units 25 instack 17, as shown inFIG. 4 andFIG. 5 , which also contributes to alignment of theelastomeric units 25. Metal-to-metal contact on the stop surfaces occurs when anelastomeric pad 27 between twoadjacent plates 225 is compressed a predetermined amount, such as 20-80%, and in embodiments 20-60%, of the uncompressed thickness of the pads. In embodiments, the pads in the front or draft stack compress about 0.5 inches (from their uncompressed thickness prior to installation) before metal to metal contact prevents further compression. Theplates 225 formingfront stack 17 extend to the walls and/or the straps of theyoke 206. By way of example and not limitation, an uncompressed thickness of eachpad 27 formingfront stack 17 may be about 1.37 inches. Installed, under a static load of 32 klb, the thickness of the draft pads is 0.92. Fully compressed, at the point when metal-on-metal contact of the plates prevents further compression of the pads, theelastomeric pads 37 in the draft stack may have a thickness of 0.68 inches. These dimensions are provided for guidance and should not be deemed to limit the invention. In practice many configurations are possible without departing from the scope of the invention. - The
elastomeric pads 27 may be provided with a through hole in the center, which aligns with a protrusion, which may be cast, stamped or fabricated on the plate, for example, and provided to keep the pads in alignment. The diameter of the through hole may be referred to as the “inner diameter”. The lateral edge of eachelastomeric pad 27 may be curved in a toroidal manner, and the outside diameter of the pad is measured at the middle of the thickness dimension of the pad. -
FIG. 3 represents the rear “buff”portion 30 of the cushioning apparatus, positioned adjacent to and rearward of the yoke and comprisingfront plate 31 connected torear plate 32 by arod 34 which passes through a plurality ofelastomeric units 35. Although asingle center rod 34 is shown, a plurality of rods may also be used. Eachelastomeric unit 35 comprises aplate 226 and at least oneelastomeric pad 37, similar in construction to theelastomeric unit 25. However, theplate 226 and theelastomeric pad 37 both have a hole to receiverod 34. As in the description ofFIG. 2 , only a singleelastomeric unit 35 is shown inFIG. 3 , whereas 10-20plates 226 and a corresponding number of elastomeric pads could be employed, depending on the design. The elastomeric unit(s) 35 substantially fill the sill area to help alignelastomeric units 35 andpads 37.Pads 37 may be shaped likepads 27. In the embodiment shown, eachelastomeric pad 37 may be circular when viewed in plan, having an outer diameter. An “inner diameter” defines a through hole in the middle adapted to receive the center rod. -
Pads 37 in thebuff stack 16 may have the same general shape aspads 27 in thedraft stack 17 but they are scaled larger. The maximum design force of thelarger pads 37 is higher due to larger surface area, but the surface pressure on each pad is the same. For example, and not by way of limitation, the uncompressed thickness of apad 37 may be about 1.70 inches and the outer diameter may be about 8.82. Compressed for installation with a force of about 32 klb, the installed thickness of the pads is about 1.24 inches. Under full compression, with metal-to-metal contact ofplates 226 preventing further compression ofpads 37, the pad thickness may be about 0.91 inches and the outside diameter may reach 10.63 inches. Thus, in embodiments, the pads and plates are designed to allow compression of 20-80 percent, and in embodiments 40-60 percent, where the amount that the pad is compressed at full compression is expressed as a percentage of the uncompressed thickness of the pad, prior to installation.Bolt head 33 is flush mounted infront plate 31 so that therear unit 30 may be mounted directly againstfront unit 20. In embodiments,rear unit 30 is not attached to thefront unit 20, which facilitates installation. As shown inFIG. 5 ,rod 34 is secured bynut 54. - The same elastomeric material may be used for the elastomeric pads in the draft stack as in the buff stack, such as a thermoplastic elastomer.
- The elastomeric units of the draft pack are adapted to slide between
straps 26 ofyoke 20. In an E-type arrangement, the yoke is attached to the coupler using a draft key, but the performance considerations for the pads and plates are similar. - In embodiments,
draft stack 17 is provided in a pre-shortened installation configuration, which allowsdraft portion 20 and thebuff portion 30 to slide into the pocket and allows the coupler to be installed without interference. A plurality of shear pins, for example four shear pins pass through the yoke into thecoupler follower 22. The pins break on first impact, and in this fully-installed or post-installation position, the coupler is pre-stressed, applying buff force against the first and second stacks. -
FIG. 6 depicts performance modeling of a cushioning unit according to the invention using response to static buff and draft loads. The dynamic response of the material would be dependent on impact speed and could approach twice the static load values. Nevertheless, the response to static loads provides information to guide product design to achieve performance objectives. In this example, 11 pads are used in the buff stack, each having an uncompressed thickness of 1.7 inches and an uncompressed diameter of 8.82 inches. The draft stack comprises 14 pads, each having an uncompressed thickness of 1.37 inches and uncompressed diameter of 6.63 inches. A static compression test is performed to obtain the response to static load and subsequent recovery or “release”. Separation of compression and release curves represents hysteresis. The relatively large hysteresis depicted in the response curves is at least partly an advantage of using the plates to limit compression of the elastomeric pads within a predetermined range, resulting in a greater absorption and dissipation of impact energy. At the same time, very little permanent deformation is expected during the lifetime of the cushioning unit, on the order of less than 10%, preferably less than 5%. The stiffening observed under buff loads greater than about 400 klb occurs after the draft stack is fully compressed, and the rear “buff” stack assumes the remainder of the force absorption. Hysteresis may be expressed as the ratio of energy absorbed by cushioning unit (WA) to the energy input during impact (WE) (modeled as a static load). Hysteresis for the cushioning unit may be extrapolated from the deflection of the buff and draft pads versus applied static force during compression and release from different starting points (i.e., pre-loaded, uncompressed and fully compressed). In embodiments a cushioning unit according to the invention will have a WA/WE ratio derived in this manner of 0.3 to 0.65. The large distance between the compression and release curves inFIG. 6 indicates relatively high hysteresis for a cushioning unit according to the invention. - The description of the foregoing preferred embodiments is not to be considered as limiting the invention, which is defined according to the appended claims. The person of ordinary skill in the art, relying on the foregoing disclosure, may practice variants of the embodiments described without departing from the scope of the invention claimed. A feature or dependent claim limitation described in connection with one embodiment or independent claim may be adapted for use with another embodiment or independent claim, without departing from the scope of the invention.
Claims (13)
Priority Applications (6)
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US15/814,853 US10308263B1 (en) | 2017-11-16 | 2017-11-16 | Cushioning apparatus for a railway car |
US16/133,085 US10513275B2 (en) | 2017-11-16 | 2018-09-17 | Selective cushioning apparatus assembly |
AU2018369996A AU2018369996A1 (en) | 2017-11-16 | 2018-11-15 | Selective cushioning apparatus for a railway car |
PCT/US2018/061286 WO2019099675A1 (en) | 2017-11-16 | 2018-11-15 | Selective cushioning apparatus for a railway car |
MX2020005139A MX2020005139A (en) | 2017-11-16 | 2018-11-15 | Selective cushioning apparatus for a railway car. |
CA3082374A CA3082374A1 (en) | 2017-11-16 | 2018-11-15 | Selective cushioning apparatus for a railway car |
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US15/814,853 US10308263B1 (en) | 2017-11-16 | 2017-11-16 | Cushioning apparatus for a railway car |
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WO2020113150A1 (en) * | 2018-11-30 | 2020-06-04 | Strato, Inc. | Hybrid cushioning apparatus with draft gear |
USD886674S1 (en) * | 2018-05-01 | 2020-06-09 | Strato, Inc. | F-type yoke for a railway car cushioning unit |
USD896701S1 (en) * | 2018-05-01 | 2020-09-22 | Strato, Inc. | Coupler follower for selective cushioning unit |
USD897238S1 (en) * | 2018-05-01 | 2020-09-29 | Strato, Inc. | Selective cushioning apparatus for a railway car |
US11142228B2 (en) | 2019-01-17 | 2021-10-12 | Strato, Inc. | Cushioning unit with reduced tail yoke |
US11584404B2 (en) | 2020-01-28 | 2023-02-21 | Strato, Inc. | Selective cushion unit yoke with integral draft gear housing |
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