1. Field of the Invention
The present invention relates to a railway car underframe having a fishbelly type center sill and in particular to a reinforcing structure for the transition sections of the center sill.
2. Description of the Prior Art
A fishbelly type center sill for a railway car underframe typically includes a pair of longitudinally extending transversely spaced parallel webs and a top plate and a bottom cover plate secured thereto and conforming to the shape of the webs. The center sill includes a center section, end sections, and transition sections connecting the end sections to the center section. Since the center section is of a considerably deeper and wider design than the end sections, each transition section includes a downward and outward taper which facilitates connecting the sections together as substantially a unitary construction; however, this results in the development of deleteriously high stress concentrations in the bottom coverplate and the vertical webs where it is bent or formed to conform to the cross-section of the center and end sections.
The prior art is exemplified by U.S. Pat. Nos. 3,145,666 and 3,577,934 assigned to Pullman Incorporated and incorporated by reference herein. U.S. Pat. No. 3,145,666 discloses a structure providing for reduced stress concentrations in the transition section by incorporating a plurality of smaller bends in the bottom cover plate of the center sill instead of a single larger bend; and, U.S. Pat. No. 3,577,934 shows a transition section structure having local stiffeners or reinforcing plates which reduce the stresses in the bottom cover plate by locally increasing the cross-sectional area of the load carrying member. Attention is also directed to U.S. Pat. Nos. 998,697 and 1,097,800 which show related fishbelly center sill constructions.