Electric heating – Metal heating – Rail bond
Reexamination Certificate
2000-09-29
2003-02-04
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
Rail bond
C104S015000, C228S112100
Reexamination Certificate
active
06515249
ABSTRACT:
BACKGROUND OF THE INVENTION
1 . Field of the Invention
This invention relates to a method of repairing a railroad rail which includes a defect, and more specifically, to a method of repairing a railroad rail having a defect which includes the step of removing the portion of the rail with the defect and welding the remaining rail ends together.
2. Background Information
Railroad rails may be manufactured with internal defects or, as a result of wear-and-tear, develop defects. Such defects include, but are not limited to, inclusions, pits, rust, welds, batter, and engine burns. Such defects need to be repaired in order to safely operate the railroad.
There are two common methods of railroad repair: thermite welds and flash-butt welding. Rails repaired by flash-butt welding are typically stronger and higher in quality than those repaired by a thermite weld. Additionally, rails may be temporarily repaired through the use of Joint Bar splices.
When repairing a rail with a thermite weld, a portion of the rail localized around the defect is removed. The thermite material is then poured in a mould. As the thermite material cures, it forms a plug which bonds to, and is contiguous with, the rail being repaired. The area of the rail having the thermite weld material is not as strong and is not of the same quality as a normal rail. As such, the thermite weld may require successive repairs in order to maintain the railroad rail in a safe condition. This method also requires the repair crew to transport the repair materials to the repair site.
Flash-butt welding is accomplished by bringing two ends of rail segments together and passing a current through the interface. As the current passes through the interface the rail becomes heated and malleable to the point where the two rail ends are forged together to provide a weld. When repairing railroad rail using flash-butt welding, a portion of the rail, typically five feet to nineteen feet, on both sides of the defect is removed. A new rail segment is then placed in the gap left by the removed rail. The two ends of the replacement segment are then flash-butt welded to the original rail. The rail segment is then shaped to match the existing rail. This repair method results in the removal of a considerable length of rail and requires two flash-butt welds in order to complete the repair. This process is time consuming and requires the repair crew to transport repair materials is addition to the repair equipment.
Joint Bar splices are, essentially, a reinforcing clamp applied to the rail adjacent to the repair. A Joint Bar splice is used when there is not enough time to perform a complete repair or when other repair materials are not available. A Joint Bar splice, by government regulation, is a temporary repair and must be replaced in about 90 days. The Joint Bar splice reduces the operational limit of the rail in the repair area.
Regardless of the repair method used, there is a need to track the Neutral Rail Temperature (“NRT”). The NRT is based on the temperature of the rail when the rail is installed. The rails are structured to contract and expand in response to environmental temperature changes. The amount of expansion and contraction is determined by the NRT. When a repair is made, the NRT of the rail is altered. For example, use of a thermite repair changes the material that comprises the rail. These different materials have different coefficients of thermal expansion. When a repair is accomplished using a flash-butt welding to insert a rail segment, the segment may, or may not, be made of the same material as the rail, however, it is unlikely that the segment will be installed at exactly the same temperature as the rail. As such, the segment will have a different NRT than the rail, thus, the NRT of the entire rail is changed. Management of the NRT could be simplified if only the original rail material was used and only a small portion of the rail was removed.
There is, therefore, a need for a rail repair method which results in a rail having the strength and quality of a flash-butt-welded rail, but without the wasted material.
There is a further need for a rail repair method which may be accomplished with existing equipment.
There is a further need for a rail repair method which reduces the number of flash-butt welds on the remaining rail.
There is a further need for a rail repair method which reduces the amount of materials and equipment that must be transported to the repair site.
There is a further need for a rail repair method which does not require the rail to be reshaped in order to complete the repair.
There is a further need for a rail repair method which may be completed in less time than prior art repair methods.
There is a further need to eliminate the use of temporary Joint Bar splices.
There is a further need to simplify the management of the NRT.
SUMMARY OF THE INVENTION
These needs, and others, are satisfied by the disclosed method which provides for repairing a rail having a defect using a single weld.
The repair method begins when a rail defect is identified by using an ultrasonic rail-testing car. The ultrasonic rail-testing car can precisely locate and mark the area of the rail containing the defect. Additionally, manual testing of the defect may further delineate the areas of the rail which contain the defect. The defect is then consumed by a welding procedure.
To accomplish the repair, the railroad rail having the defect, and extending a predetermined length on either side of the defect, is removed. The removed rail portion is to be minimized to maintain the Neutral Rail Temperature (NRT). Once the defect has been removed, the truncated ends of the railroad rail may be shaped to correspond to each other which will result in a stronger weld. Preferably, both truncated ends have a surface that is generally perpendicular to the rail. Flash-butt welding is, preferably, used to heat the rail ends. The truncated rail ends are drawn together and a current is passed through the interface. As the current passes through the interface between the truncated rail ends, the rail is heated, becomes malleable, and is welded together. Alternate means of heating the rail ends, such as friction welding, may also be used.
Because the repair is accomplished using only original rail material, there is no need to transport repair materials to the repair site. Additionally, the NRT of the original rail is maintained as no additional materials are being added to the rail. Because only a single weld needs to be made, the repair procedure is faster than prior repair procedures. Given that the repair method is faster and does not require additional materials, this method of repair can be performed instead of using a Joint Bar splice.
It is an object of this invention to provide a method of repairing a rail which results in a rail having the strength of a welded rail but without the necessity of inserting a rail segment and having two welds.
It is a further object of this invention to provide a method of repairing a rail which does not result in excessive wasted rail material.
It is a further object of this invention to provide a method of repairing a rail which will not require the rail repair crew to carry large amounts of rail in order to accomplish a repair.
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Rovnyak Mark Edward
Valley Greg A.
Eckert Seamans Cherin & Mellott , LLC
Harsco Technologies Corporation
Jenkins David C.
Shaw Clifford C.
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