US Patent 7367740 Mechanically lockable universal joint and structures employing such joint

An adjustable support stand for an article such as a camera employs a plurality of elongated links connected to one another at their ends by lockable universal joints. Each joint consists of a pair of complementary knuckles, each joined to a link end by a splined connection, which connections provide two axes of rotation to the joint. The knuckles are joined to one another about a third axis of rotation, perpendicular to the first two axes by means of a splined pin which passes through splined holes in the two knuckles. The splined connections employ splines of different count to achieve a high resolution of possible positions.