A small yet critical component of railroads is a railroad spike. It is a relatively simple metal fastener numerous of which are used to secure the thousands of miles of railroad tracks to wooden crossties. FIG. 1A shows well known railroad spikes, which typically have a crude, asymmetrical shape. FIG. 1B shows how railroad spikes help fasten tracks (rail bases) to crossties, sometimes via tie plates. The prior art railroad spikes shown here are of the strike-in type as opposed to the threaded type that is screwed through a tie plate to fasten to a crosstie. The present invention is primarily concerned with the strike-in type of railroad spikes.
Once it is hammered through a tie plate and into a crosstie, a railroad spike will be subject to cyclic stresses as trains pass by and apply loads on the track rails, causing fatigue to its metal material. The spike will reach its fatigue life and break sooner or later. Apart from cyclic stresses, fungi and insects, known as “spike kill,” can erode railroad spikes, thereby further shortening their useful life. As a result, railroad spikes have to be removed and replaced from time to time, which process costs railway companies a significant amount of time and resources.
Railroad spikes typically have been manufactured in hot forging processes which involve heating up raw metal parts above their recrystallization temperature before deforming them into desired shapes. However, hot forged spikes have shown an unsatisfactorily short fatigue life, usually failing approximately one to two inches from the bottom of the head. Current hot forging processes for manufacturing spikes are inefficient in a number of aspects, such as manual placement of discrete metal blanks into a forming die, the need to significantly heat up the raw material, the need to cool down the spikes after forging, and the use of bulky and heavy metal containers for the spikes.
Furthermore, the current asymmetrical designs of strike-in railroad spikes make it inefficient or difficult to load them into automatic spiker machines.
Previous railroad spikes also lack adequate surface treatment (e.g., protective coating). As a result, they suffer from corrosion and/or cause deterioration to crossties.
In view of the foregoing, it may be understood that there are significant problems and shortcomings associated with current designs and manufacturing methods of railroad spikes. As railway companies consume large quantities of railroad spikes, even a small incremental improvement in spike design and/or spike manufacturing process could translate into tremendous savings in terms of time, materials, and other resources.