Today in 1995, US Patent EP 0645342 A1 was issued, an invention of Robert Bernard Harwood Cook, for his “Safety Dispensing Valve.” Here’s the Abstract:

A spear valve assembly (5) has a valve body (14) for engagement with a keg neck (3) and a skirt (17) on the valve body (14) including openings (18) for the throughflow of beer during filling. A downtube assembly (12) is movable relative to the valve body (14) and the skirt (17) and includes a downtube (12) for projecting into beer in a keg. A locking member (7) is carried by the downtube assembly (12) and is arranged to project through at least one further opening (19) in the skirt. In use, the locking member (7) normally prevents the spear valve assembly (5) from being ejected from a beer keg by engagement behind the keg neck. However, for removal of the spear valve assembly (5) the downtube assembly (12) is tilted relative to the skirt (17) to retract the locking element (7).