US Patent 7913574 Universal spherical tension adapter

A tension adapter is disclosed for a materials testing machine. The tension adapter includes a shank and a sleeve. The shank includes an enlarged head with a machined convex spherical bearing surface which forms a ring around the periphery adjacent to one end of the shaft. The opening of the sleeve includes a machine concave spherical bearing surface around the periphery thereof to form a seat for the convex spherical bearing surface. The sleeve further includes inner walls which are conical in order to allow the shank to rotate or pivot from the vertical orientation about the pivot point formed by the spherical bearing surfaces. The rotation or pivoting of the shank allows the tension adapter to align so that only tension forces are applied during materials testing.