Today in 2003, US Patent WO 2003093163 A1 was issued, an invention of Christopher Wheaton and Courtenay Simon, for their “Dispensing Valve Assembly for a Beer Keg.” Here’s the Abstract:

A dispensing valve assembly for a beer keg comprises a body (11) having a pair of flexible legs (24) which form non-pivotal projection means when splayed outwardly by locking means (14) fixed on a valve stem (12) which is biased sealingly to engage a valve seat (32) of the body (11). The valve stem (12) has an internal valve seat against which is biased a plug (33). In a first position of the locking means (24), when the valve stem is off its valve seat (32), the legs (24) are unsplayed and can pass through an opening of the beer keg, whilst once the valve assembly is thereafter engaged in the beer keg the locking means are allowed to move under spring means (45) to splay the legs outwardly and prevent removal of the assembly from the keg. A special insertion tool is provided to hold the valve stem off its valve seat, and thus the locking means in its first position, prior to assembly of the valve in the beer keg, removal of the tool thereafter allowing the locking means automatically to move to its second position.