Today in 1973, US Patent 3776260 A was issued, an invention of Maurice Ruddick, for his “Beer Kegs and Like Containers.” Here’s the Abstract:

A spear and closure assembly which is arranged to be fitted as a single unit in the neck of a beer keg or like container comprises a tubular housing having one end open and the spear fixed to the housing and projecting from its other end, and a valve seat which is fixed to the housing so that it is located adjacent the open end of the housing and projects radially inwards with respect to the open end. The housing, the spear, and the valve seat are connected to form a unitary structure, such as by welding or by a combination of welding and being formed integrally. A spring located within the housing acts on a disc like closure member so that a resilient valve ring is pressed by the closure member against the valve seat, hence closing the opening bounded by the valve seat. Assembly of the spring, the closure member, and the valve ring within the structure is made easy by arranging that the size and shape of the spring and closure member allow these to be passed through the opening bounded by the valve seat, and by providing the valve ring with sufficient resilience to allow it to be deformed and squeezed through this opening. In use, application of a filling or dispensing fitting moves the valve ring and the closure member axially inwards against the action of the spring, the valve ring being displaced axially relative to the closure member and forming a seal against a second valve seat formed on the housing so that two separate passages are formed through the fitting and into the container, one through the housing and the spear and the other outside the housing via an aperture between the two valve seats.