Abstract: A U-type clamp has two arms and a base and tightens around cylindrical stock. The surface of the clamp that makes contact with the cylindrical stock is not itself entirely cylindrical in its loosened state. The preferred embodiment involves a first cylindrical profile extending around about ¾ of the contact surface which is intended to match the curvature of the post. The final ¼ or so of contact surface has a larger radius of curvature than the first cylindrical profile. The second cylindrical profile may also be offset relative to the first cylindrical profile.

Abstract: A clamp is used to attach generally rectangular bar stock, such as existing Bookwalter/Codman rings, to a post in a surgical retractor system. The clamp interacts with corners of the ring at any of a wide range of widths and thicknesses, while still retaining a simple and intuitive tightening action such as through a rotational collar which absorbs some of the clamping force as a hoop stress. In the preferred arrangement, the clamp makes a tripod top/planar bottom contact with the generally rectangular bar stock of the ring. An articulating joint permits best fold up of the clamp, with a ball shaft which is constrained within the bisecting plane of the joint clamp. A spherical nut is used on the clamp bolt in one of the clamps, which permits some change in orientation of the clamp bolt when the clamp bolt is tightened using a cammed handle.