Today in 1999, US Patent EP 0949195 A1 was issued, an invention of Willem Terpstra and Jeroen Alexander Töpfer, assigned to Dispense Systems International B.V., for their “Spear Valve for a Keg.” Here’s the Abstract:

A valve for a keg of beer comprises a neck ring (2) to be secured to the container (1) and an inner part (3) formed with a valve member (4), which fits an opening of the neck ring (2). Locking means (7-9) function to lock the inner part (3) in the neck ring (2), and a sealing ring (16) forms a seal between the inner part (3) and the neck ring (2) at the location of opposite seat portions in the neck ring (2) and the inner part (3). The inner part (3) and the neck ring (2) are provided with mutually cooperating coupling means (12-15), which, after the locking means have been released, provide for the removal of the inner part (3) from the neck ring (2) in two steps, wherein pressure relief takes place in the first step via at least one pressure relief opening (20). The pressure relief opening (20) is formed through the wall of the neck ring (2), at a location a small distance above the seat portion in said neck ring, so as to effect a reliable pressure relief.