Patent ID: 8343177

Claim:
A trephine apparatus comprising an outer casing having structure with a lower end and defining a substantially cylindrical passage opening at a substantially circular lower end element; an inner, substantially cylindrical tube disposed within the substantially cylindrical passage of the outer casing and having a bore opening at a substantially circular lower end element, the lower end element of the inner tube being proximate to, but spaced upwardly from, the lower end element of the outer casing; means for mounting a substantially cylindrical trephine blade within the bore of the inner tube, said inner tube and said means for mounting being so constructed that the blade can be raised and lowered in said bore of said inner tube by said means for mounting, relative to the lower end elements of the outer casing and the inner tube; and a substantially cylindrical trephine blade mounted by said means for mounting and terminating in a hollow, cylindrical cutting edge downwardly disposed, said blade being disposed within said bore of said substantially cylindrical tube, with said cutting edge thereof disposed upwardly of said substantially circular lower end element of said substantially cylindrical tube in the course of normal operation of said apparatus, at least a basal element at the lower end of the outer casing being made of a non-opaque material so as to enable edge-on observation of the zero position of the trephine blade cutting edge in the course of normal operation of said apparatus.