Importance

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Abstract

A ball joint is disclosed to couple together elements of an electric lamp fixture. Two semi-spherical ball joint members are pivotalbly mounted about a pin so as to form a sphere. An arm portion extends from each ball joint member along its equatorial plane. Each arm draws its ball joint member into a socket having a truncated spherical surface so that semi-spherical surfaces of both semi-spherical ball joint members are drawn into sliding contact with truncated spherical surfaces of the socket. In drawing both ball joint members into the socket, the two ball joint members are urged together. The forces with which the arm portion is drawn into the socket determines frictional forces required to rotate each socket relative to the ball joint members as well as one ball joint member relative to the other ball joint member. A continuous passageway passes internally through the ball joint through which electrical wires may pass. The noval construction utilizes semi-spherical ball joint members which are identical and may be manufactured by injection molding at low cost.

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First Claim