Patent Application
20200231191
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 of a railway car. 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 buff and draft forces. The basic draft gear apparatus has been used for decades. However, in many cases, unacceptably large forces are transmitted to the railway car and it is now desired to provide a cushioning apparatus that dissipates more force during impact than the conventional draft gear.
A solution has recently been proposed in U.S. Pat. No. 10,086,852 (which is incorporated by reference) to add a second draft gear in a railway car sill behind a standard yoke to absorb buff loads. However, the dual draft gear solution may not provide sufficient energy absorption. Merely doubling the 3¼ inches of travel provided by a single draft gear may not provide sufficient travel.
A hydraulic cushioning unit comprises a piston received in a cylinder filled with fluid. Such devices may dissipate more energy than a conventional draft gear, but they are known to be prone to leakage. Also, the fluid in a conventional hydraulic unit does not cushion draft forces on the coupler.
U.S. Pat. No. 5,487,480 is incorporated by reference herein for its description of a hydraulic end-of-car cushioning (EOCC) unit.
Selective cushioning apparatuses using elastomeric pads arranged on plates to absorb buff and draft loads on a coupler are described in co-pending application Ser. No. 15/814,853, filed Nov. 16, 2017 and Ser. No. 16/133,085, filed Sep. 17, 2018, which are incorporated by reference.
It is now desired to increase the applications for such selective cushioning apparatus. Particularly, it is desired to develop a selective cushioning apparatus which can fit into a sill having forward, intermediate and rear lugs or “stops” to accommodate a hydraulic cushioning unit without having to reconfigure the sill.
Thus, in one aspect, the invention is an end-of-car cushioning apparatus for a railway car adapted to be received in a sill, said sill having longitudinal, lateral and vertical dimensions, the cushioning apparatus comprising: a yoke adapted to be received in the sill having a nose at one end, a tail comprising a transverse tail wall at an end opposite the nose, straps extending from the tail wall to the nose, and an inside area between the straps; 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 transverse tail wall of the yoke, each elastomeric unit in the first stack of elastomeric units comprising a first size rigid metal plate and at least one elastomeric pad positioned on said first size rigid metal plate; wherein said first stack of elastomeric units is compressed in response to buff and draft loads on the coupler; a second stack of elastomeric units positioned behind the vertical wall of the yoke, each elastomeric unit in the second stack of elastomeric units comprising a second size rigid metal plate and at least one elastomeric pad positioned on said second size rigid metal plate; wherein said second stack of elastomeric units is compressed in response to buff loads on the coupler; wherein, the transverse tail wall of the yoke is dimensioned to allow clearance between the yoke and a pair of intermediate stops on opposed inside surfaces of the sill. In embodiments, the second size rigid metal plates are larger (viewed as a vertical cross section in the sill) than the first size rigid metal plates, but they may also have the same size.
The modified yoke having a reduced-width transverse tail wall allows the yoke to be positioned between intermediate stops in a sill configured to house a hydraulic cushioning unit without reconfiguring the sill. In embodiments, the second stack of elastomeric units, absorbing only buff loads, abuts the assembly of the modified yoke and the first stack of elastomeric units at the intermediate stops.
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:
The drawings are schematic and may not be 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 clearly requires otherwise, the “front” of an element is in a direction away from the body of the car and “rear” is in the opposite direction, from the front end of the coupler toward the car body. 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 perpendicular to the longitudinal axis and parallel to the rail. A “transverse plane” or “vertical cross section” is a plane perpendicular to the longitudinal axis of the sill. 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 surface the train travels on.
“Buff force” on the coupler means force applied when the coupler is urged in the inboard direction of the railway car, as when two railway cars impact one another. “Buff travel” refers to displacement of any element of the cushioning unit in response to buff force. “Draft” is opposite to buff force and is applied to a coupler when a locomotive pulls on a railway car train, for example. “Neutral” refers to the position of components before buff or draft forces are applied. Some elements and components of the invention, including the elastomeric pads, may be pre-stressed and pre-biased in the neutral condition.
“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. Thermoplastic copolyesters used in some conventional draft gear may be used in the stacks of elastomeric units according to the invention.
As used herein, the term “about” associated with a numerical value is understood to indicate the numerical value as closely as possible, allowing for a margin of +/−20% of the value. With reference to specific standards, given dimensions vary at least within tolerances accepted in the railroad industry.
“Travel” refers to a distance traveled by the coupler follower upon impact and may also be referred to as “displacement”. In some instances, clear from the context, “travel” refers to the full possible extent of movement, i.e., when the pads are fully compressed.
A person having ordinary skill in the art has a general knowledge of standards and procedures established by the Association of American Railroads (“AAR”) and the published AAR standards cited herein are incorporated by reference as background. Reference herein to AAR standards refers to standards in effect on the filing date of this application. Draft gears for freight cars are certified under either section M-901E or section M-901G of the Association of American Railroads (AAR) Manual. Hydraulic units are tested using dynamic impact tests set out in AAR standards M-921B or M-921D. An E-Type yoke has the dimensions specified in AAR Standard S-143, which allows for a draft gear pocket of 24⅝ inch. An F-Type yoke has the dimensions specified in Standard S-149. In embodiments, a cushioning apparatus according to the invention fits between front and rear stops of an “EOC-9” dimensions of about 38¾ inches described in AAR standard S-183 or EOC-10 pocket with a pocket length of about 48¾ inches described in AAR standard S-184. In other embodiments, the cushioning device may be adapted to fit other AAR standard or non-standard pocket dimensions depending on the application.
A selective cushioning unit according to the invention comprises two stacks of elastomeric units. The first stack is behind the coupler receiving member (the “coupler follower”) and in front of the tail wall of the yoke, where a draft gear is positioned in a conventional arrangement. The second stack is behind the yoke and absorbs only buff loads on the coupler. The dimensions of the first stack are determined by the geometry of the inside area of the yoke. The overall dimensions of the second stack are determined by the geometry of the sill behind the coupler. Although the size of the plates in each stack, viewed from a vertical cross section of the sill may vary, the stacks of elastomeric units according to the invention are substantially as described in co-pending application Ser. No. 15/814,853, filed Nov. 16, 2017 and Ser. No. 16/133,085, filed Sep. 17, 2018, which are incorporated by reference.
Oblong hole 17 receives pin 46 to attach modified yoke 11 to a coupler and to allow pin 46 to take different positions in hole 17 depending on the forces on the coupler and on the travel afforded by the first and second stacks of elastomeric units. As pin 46 is engaged only in draft, lengthening hole 17 allows for a shortened overall construction for the cushioning unit, with stack 59 of elastomeric units abutting end wall 16 shortened modified yoke. In embodiments, stacks 19 and 59 of elastomeric units absorb greater buff and draft loads than two conventional draft gear fitting in the same space, and may allow more travel than a combined pair of draft gears, each having a nominal 3.25 inches of travel. In a non-limiting embodiment, the length of oblong hole from end to end longitudinally is in a range of about 6 to 7 inches, for example 6.25 inches. When buff forces are applied, pin 46 is at the rear end of oblong hole 17, and in draft pin is at the forward end of the hole.
A second stack 59 of elastomeric units may be positioned behind the modified yoke to absorb buff loads on the coupler. The second stack is similar to first stack, comprising a set of rigid metal plates with pads between them, but the metal plates and pads of the second stack may be larger because they need not fit between the straps of the yoke. In embodiments, the plates of the second stack are identical and substantially fill a vertical cross section of the sill. Second stack may be held between front and rear plates by one or more connecting rods and compressed to a predetermined neutral condition by a suitable fastener.
In the embodiment shown, second stack 59 is held together with a single connecting rod 55 which passes through a front plate 44, through a set of nested metal plates and elastomeric pads, through rear plate 441, and fastened behind rear plate 441 with a nut 43. In embodiments, stack 59 is sized to fit in a pocket adapted to house a hydraulic cushioning unit, between rear stops 47 and intermediate stops 45. Thus, second stack 59 and yoke 11 abut one another and together fill the entire length between front stops 69 and rear stops 47, such as in one embodiment 48¾ inches and in another embodiment 38¾ inches.
According to the invention, the nose of the yoke may be wider than the tail. Transverse tail wall 16 has a reduced width to fit between intermediate stops 45. The sill may have a nominal width of about 12 to 13 inches, for example 12.875 inches. Stops 45 may protrude about 0.5 to 2.0 inches from opposed inside surfaces of the sill, for example 1.5 inches on either side of the sill. Thus, the tail is designed to have a width reduced by about 1.0 inch to about 4.0 inches to fit between stops 45. For example, the yoke 11 may have a transverse tail wall 16 with a width of about 9 to about 10 inches.
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 as described in the aforesaid co-pending applications incorporated by reference. In certain non-limiting embodiments, the pads may be made of thermoplastic polyester, such as Arnitel® thermoplastic copolyester elastomer from DSM and Hytrel® thermoplastic polyester from Dupont. Suitable materials will typically have a Shore D durometer hardness of 40-70 and must have reasonably consistent properties across a temperature range that would be encountered during use.
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.
