US Patent 7378013 Gooseneck trailer coupler

A coupler comprised of a coupler housing having a first opening formed therein. The opening has a concave cavity. A cylindrical socket is formed within the housing. A second opening in the housing communicates with the cylindrical socket. A lock ring is provided, the lock ring having a cylindrical portion and an arm portion extending therefrom. The cylindrical portion of the lock ring is disposed within the cylindrical socket in the housing with the arm portion extending from the housing through the second opening. An opening is formed through the cylindrical portion of the lock ring. The cylindrical portion of the lock ring is rotatable in the cylindrical socket wherein the lock ring is movable between a first position wherein the opening in the lock ring is aligned with the concave cavity to allow a tow ball to be inserted into the concave cavity through the opening in the lock ring and a second position wherein the opening is not in alignment with the concave cavity.