US Patent 7775075 Lock cylinder

A lock cylinder including a housing defining a cylindrical cavity, and a plug disposed in the cylindrical cavity and rotatable between a locked position and an unlocked position. The plug includes an inner pin chamber aligned with an outer pin chamber of the housing when the plug is in the locked position. An inner pin is housed in the inner pin chamber and is engageable with the outer pin when the plug is in the locked position, and includes an outer surface having a non-axial groove. The non-axial groove has a curved surface that defines a substantially semi-circular cross-section. An engagement member is supported by the plug and has a substantially semispherical end portion extending into the non-axial groove such that the semispherical end portion is substantially engaged with the curved surface.