Today in 2013, US Patent EP 2583934 A1 was issued, an invention of Thomas W. Bates, Dan Morgan, and Leslie W. Ross, for their “Reusable Beer Keg.” Here’s the Abstract:

A reusable beer keg (1) is disclosed comprising a hollow beer keg body (2) with a dispenser tube assembly (10) having a dispenser valve (11), dispenser tube (12), and a disposable bladder (13). The dispenser valve (11) is releasably attached to a top portion of the keg body (2) and the dispenser tube (12) and bladder (13) extend into the interior of the keg body (2). When beer flows through the open dispenser valve (11) and into the bladder (13), the beer causes the bladder (13) to expand until it contacts the inside surface of the keg body (2). When the beer keg (1) has been emptied it can be returned to the brewery for reuse by cleaning the dispenser valve (11), dispenser tube (12) and disposing of the used bladder (13). The beer keg body (2) does not need to be cleaned, however, because the beer only comes in contact with the disposable bladder (13) and not the keg body (2). The beer keg parts can then be reassembled, using a new bladder in place of the used bladder.