Automatic rail clamp

In an automatic rail clamp having a supporting frame and confronting rail gripping jaw assemblies, one of which is at one side of the frame and the other at the opposite side of the frame, both jaw assemblies being fulcrummed to rotate about a common fulcrum shaft supported on the frame in a vertical plane midway between the two jaw assemblies in a direction parallel with the length of the rail to be gripped between them, each jaw assembly having a plurality of lever elements rotatably mounted one after the other along the common fulcrum shaft with the lever elements providing jaw portions located below said common fulcrum shaft and lever arms extending laterally and upwardly from said common fulcrum shaft for connection with operating means carried by the frame, the jaw portions of said plurality of lever elements of each jaw assembly having a common railhead gripping insert fixed thereto in such manner that when the lever arms of said two jaw assemblies are spread apart by said operating means, said inserts move toward each other to grip opposite sides of a railhead and, when said lever arms of the two assemblies are moved toward each other, the respective inserts move away from the railhead to release the grip of the jaw assemblies, the invention comprising:

• (a) means mounting said common fulcrum shaft in the frame for rotation about its own axis,
• (b) means for permitting rotation of the common fulcrum shaft in one direction and holding it against rotation in the opposite direction,
• (c) means rotating said common fulcrum shaft through an arcuate increment of rotation when the amplitude of movement of the lever arms exceeds a predetermined amount as said gripping inserts wear thinner with repeated operations of the clamp;
• and
• (d) adjustment means responsive to each increment of rotation of said common fulcrum shaft for adjusting the relative position of said jaw assemblies to accommodate for the wear on said inserts and to reduce the amplitude of movement of the lever arms so that the common fulcrum shaft is not incrementally rotated again until the inserts have worn sufficiently to cause the amplitude of movement of the lever arms to again exceed said predetermined amount, said adjustment means including, two series of eccentrics on the common fulcrum shaft offset from the axis of rotation thereof, the eccentrics of one series being 180.degree. out of phase with those of the other series, said eccentrics being positioned one after the other along the common fulcrum shaft with the lever elements of one jaw assembly being fulcrummed about the eccentrics of one series and the lever elements of the other jaw assembly being fulcrummed about the eccentrics of the other series in such manner that with each increment of rotation of the common fulcrum shaft, the eccentrics shift the centers of rotation of the lever elements on their respective fulcrums in opposite directions with respect to the axis of rotation of the common fulcrum shaft.