Railway draft appliances – Cushioned – Springs
Reexamination Certificate
2003-03-04
2004-09-28
Le, Mark T. (Department: 3617)
Railway draft appliances
Cushioned
Springs
C213S007000, C213S06700R, C213S050000, C213S009000
Reexamination Certificate
active
06796448
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to an energy management system subjected to extremely high impacts loads applied thereto, and more particularly, to a railcar draft gear housing configured to offer enhanced energy dampening capabilities to a railcar draft gear assembly while advantageously being both stronger and weighing significantly less than the same type prior art draft gear housing.
BACKGROUND OF THE INVENTION
Energy management systems are used in a variety of industrial applications wherein a vehicle is subjected to extremely high impact loads and forces during operation. For example, in the railroad industry, an energy management system in the form of draft gear assemblies have been in widespread use on rolling stock for many decades. A railcar draft gear assembly is used to cushion shocks and dissipate energy encountered by railway rolling stock during make-up and/or operation of a train consist on track structure. The draft gear assembly typically nests in a pocket of a railcar center sill. A typical draft gear assembly includes a housing having a closed end, which abuts a rear wall of the pocket within the car sill, and an open end.
It is recognized by persons skilled in the railcar draft gear art, these draft gear assemblies must maintain certain minimum shock absorbing capacity during in-track service. The railcar industry furthermore continues to express interest in new, higher capacity draft gear assemblies. Presently, minimum shock absorbing capacity is specified by the Association of American Railroads (AAR) Standards.
To accomplish and meet these standards, it is known to equip such railcar draft gear assemblies with a suitable spring biased mechanism arranged primarily within the confines of the draft gear housing. A portion of the spring biased mechanism extends axially beyond the housing to engage and operate in combination with a follower plate. During in-track service, it is inevitable that energy imparted to the railcar draft gear exceeds the reaction capacity of the spring biased mechanism. As such, the draft gear spring biased mechanism assumes an “over-solid” condition and all remaining energy is imparted to the draft gear housing. As will be appreciated by those skilled in the art, and while occurring on a frequent basis, the energy required for the spring biased mechanism to assume an “over-solid” condition is exceedingly substantial, i.e. in excess of 600,000 inch pounds. After the spring biased mechanism reaches its “over-solid” condition, any excessive energy is thereafter transferred through the draft gear housing into the car sill and car body and, ultimately, to the lading carried therewithin. Such energy imparted to the car frequently causes significant damage to the lading carried within the railcar.
The railcar draft gear housing has been heretofore designed from exceedingly massive ferrous metal, i.e., steel castings which can withstand repetitive high energy impacts after the spring biased mechanism has achieved an “over-solid” condition without stress break or fracture. Such castings, however, typically require further machining and/or other secondary operations prior to incorporation of the spring biased mechanism therewithin. As will be appreciated, such processes and/or operations require trained manual efforts adding to the draft gear assembly costs without contributing any appreciable benefit to its performance characteristics.
With ever increasing fuel costs, there are continuing and concerned efforts in the railroad industry to increase productivity. Historically, increases have been achieved by increasing the rolling stock comprising a train consist and additionally the capacity of the railcars. Of course, increasing the rolling stock comprising a train consist furthermore adds to the dynamic energy transferred between adjacent cars comprising the consist. AAR Standards regarding regulating the size of the railcars along with the practical load limit of today's railroad track system, however, has generally been reached. Accordingly, attention is now being directed to other areas. For example, lightening of the overall weight of the rolling stock without sacrificing or unreasonably increasing costs is an on-going goal and would improve railcars.
In the mid 1990's, the North American railroad industry transported approximately 1.2 trillion ton-miles of lading in a fleet consisting of about 1.5 million railroad cars with a revenue of about $31 billion. Since the mid 1990's, such statistics have only increased. Accordingly, and although minor improvements may seem trivial when viewed with a narrow perspective, the overall benefits to be achieved can be significant. Even when considering individual train consists, it will be apparent, in a train consist comprised of 100 cars, a mere five pound reduction in weight of duplicated railcar components translates to one-half ton weight reduction per train. As will, be appreciated, reducing the cumulative empty weight of the 100 car train consist by one-half ton allows that same train consist to transport an additional 1000 pounds of lading with no additional costs being added.
Thus, there is a need and continuing desire for a railcar draft housing which is even stronger than known draft gear housing of the same type and allow such draft gear housing to sustain excessive energy applied thereto but is also significantly less weight whereby contributing to fuel savings and increased train lading capacity and which can be manufactured to such close tolerances whereby substantially eliminating the need for subsequent and expensive machining and/or other secondary operations prior to actual use on the railcar.
SUMMARY OF THE INVENTION
In view of the above, and in accordance with the present invention, there is provided a new and improved housing for an apparatus or energy management system. In one form, there is provided a railroad draft gear housing having improved operating characteristics which can be manufactured at a lower cost than heretofore known draft gear housing of a similar type. Although the material of the railcar draft gear housing has been modified along with its cross-sectional dimensions, it advantageously remains and retains its interchangeability with draft gear housings serving the same purpose while offering an improved strength to weight ratio. The present railcar draft gear housing is especially advantageous in that it is not only stronger than prior railcar draft gear housings of the same type, it is also significantly lighter in weight thereby contributing to fuel savings and/or increased lading capacity for the associated railcar.
In accordance with a first aspect, there is provided a railcar draft gear housing which combines the strength, ductility, fracture toughness and wear resistence of steel with the castability and product economies of ductile iron. The draft gear housing of the present invention is produced from an austempered ductile iron casting having an open end, a closed end, and wall structure axially extending between the housing's ends. The wall structure of the housing defines an axial section between and spaced from the ends. In accordance with the present invention, the axial section of the wall structure is designed and configured to act as an elastic member which is capable of withstanding impact energy imparted to the casting in excess of 81,000 inch pounds while retaining and exhibiting substantially linear elasticity wherein the resultant ratio of stress to energy input remains substantially constant. That is, and unlike heretofore known steel draft gear housings, the wall structure of the draft gear housing is designed and configured to flexibly distort within a yield range of austempered ductile iron whereby advantageously serving to absorb, dissipate and return energy imparted thereto during operation of the railcar and thereby enhancing overall operation of a draft gear assembly, of which the housing forms an integral part, without increasing the cost of such assembly.
Research has revealed superior
Anderson David G.
Wilt Donald E.
Withall Andrew W.
Harbst John W.
Le Mark T.
Miner Enterprises Inc.
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