Anvil assembly

Claim 1

An anvil against which generally straight parallel leg portions of a staple of a predetermined diameter and projecting at generally a right angle from opposite ends of a back portion of the staple can be pressed to bend the leg portions into arcuate shapes and form a generally B shaped closed staple, said anvil having walls defining a generally planar clamping surface, and staple leg shaping surfaces recessed from said clamping surface and defining a pair of elongate sockets aligned end to end, said leg shaping surfaces for each socket comprising a continuous bottom surface which is concave about axes transverse of the socket and comprises an initial contact portion adjacent its end opposite the other of said sockets and a final guide portion adjacent the other of said sockets, and longitudinally extending side surfaces extending between said clamping surface and said bottom surface, said initial contact portions having widths between said side surfaces at their ends opposite said final guide portions that are substantially larger than the the diameter of said leg portions and converge smoothly in width between said side surfaces toward the adjacent parts of said final guide portions so that legs of staples that contact said initial contact portions at positions spaced from the longitudinal center line of said sockets will be guided by said initial contact portions and side surfaces into said final guide portions, charcterized by the feature that said bottom surfaces (16) have generally uniform widths only slightly wider than the diameter of the leg portions (56,58) of said staple (50) between said side surfaces (28) along all of said final guide portions (24) so that the leg portions (56,58) of the staple (50) will be bent in alignment with each other for any initial contact position of the staple leg portions (56,58) against the initial contact portions (20) of said bottom surfaces (16) as the staple (50) is pressed against the anvil (10).