1. Field of the Invention
The present invention relates to formed metal end plates for end-plating railway crossties, scaffolding planks, and other wood products, and methods of using the end plates.
2. The Prior Art
Wood products such as railway crossties are cut from green wood and, as such wood products season or cure, they frequently develop large cracks or splits at their ends as a result of the relatively large differential between end-grain and side-grain moisture movement. Wood products may be treated to retard deterioration; but the treatment only penetrates the wood products to a limited depth. Thus, the deep interiors of the wood products remain untreated. As large cracks and splits enlarge, they reach into the untreated portions of the wood products, allowing these untreated portions to be exposed to the elements. This causes deterioration deep in the wood products. In the case of railway crossties, this interior damage may result in weakened crossties and rail dislocation, thereby requiring repair or even replacement.
Early in the development of this art, S-shaped and C-shaped irons (described in more detail below in connection with FIGS. 2 and 3) were used to prevent or retard cracks and splits in wood products, especially railway crossties. These devices suffered from the disadvantage that they could only reinforce the wood products to a limited extent as a result of their shape and location in the wood product end.
In addition to the irons mentioned above, end plates have been provided for preventing or reducing cracking or splitting of wood products. U.S. Pat. No. 5,116,179 (Matlock) discloses an end plate having teeth or prongs punched from the intermediate portion of the plate. These teeth are bent to an angle slightly less than 90 degrees and are pressed into the end of a wood product, thereby retarding large cracks and splits from forming in the wood product. The angle of the teeth helps prevent inadvertent withdrawal of the end plate teeth from the wood product. As with most prior art end plates, the plate of the Matlock patent is made from a thin steel plate, which is galvanized to reduce rusting.
Almost all of the prior art end plates provide prongs or teeth punched from the intermediate portion of the plates. While these teeth grip the interior end grain of the wood product, they do not effectively grip the wood fibers near the edges or perimeter of the end of the wood product. Therefore, large cracks and splits are allowed to develop near these edges. The cracking and splitting forces are greater at the edges of the wood product than at the interior of the wood product. Generally, these forces increase with increased distance from the cross-sectional center of the crosstie. Further, the edges of the prior art end plates are exposed, causing safety concerns.