Rails, like most structures changes dimensionally in response to heat; expanding when heated and contracting when cooled. For many years, rails were joined end to end by splice bars spanning the joint and bolts extending transversely through the splice bars and the rail. The presence of such joints allowed for thermally induced lengthening and shortening of the rail to be accommodated by corresponding narrowing or widening of a gap between the rail ends on opposite sides of the joint. The gap is what gives rise to the "clackety-clack" sound often associated with rail travel which occurs when the wheelsets of the train cross the gap.
More recently, it has become a common practice to weld the adjoining ends of adjacent rail sections together using electrical or thermite welding techniques. This produces a stronger joint and a quieter track than the prior splice bar and bolt joints. Welded rail however has significantly longer sections between expansion joints than bolted rail (often several miles) and accordingly is subject to significantly greater stresses arising from thermal expansion and contraction.
Thermal stresses generally cause more problems in cold weather than in hot weather. When longitudinal expansion occurs, it is generally accommodated by elastic deformation longitudinally and possibly some lateral flexion of the rails. In contrast, contraction can only be accommodated by elastic deformation which often causes failure at any weaker areas, such as weld joints or defects in the rail. Weld joints are particularly susceptible to failure because of metallurgical changes in what is sometimes referred to as the "heat affected zone", impurities in the filler material and incorrect weld temperatures.
If a rail separates because of stress induced failure, electrical conductivity along the rail is interrupted giving rise to a signal failure. Should this occur, the location of the break must be located and an assessment made as to whether a train can be safely permitted to cross the break. If the span of break exceeded 2 to 3 inches then, at least before the present invention, a rail repair crew had to be sent out to repair the rail. At a minimum, this caused a delay and traffic problems as it upset the rail scheduling for any trains that had to pass the broken area. It also caused crewing problems if the delay was enough for a crew to exceed the permitted time before re-crewing at a location remote from the scheduled replacement crew.
It is therefore an object of the present invention to provide a structure that can be readily installed to cap a break in the rail to permit trains to pass over the break at least at a reduced speed until a proper repair can be effected thereby minimizing staffing and crewing problems.
It is a further object of the present invention to provide such a structure which can be installed by one person.
It is another object of the present invention to provide such a structure with features that avoid its being displaced longitudinally relative to the break and from being caught by and damaged by a wheel flange.
It is also an object to provide such a structure which will restore a signal that has been interrupted by the break.