Today in 2012, US Patent 20120111874 A1 was issued, an invention of William P. Apps, for his “Plastic Beer Keg.” Here’s the Abstract:

A plastic keg includes a liner including a neck portion and a body portion. A lid having an opening is disposed at least partially over the liner. The liner is disposed in an outer container having a wall with at least one locking rib projecting therefrom. The locking rib angles downward and the lid secured to the outer container by the at least one locking rib. Optionally, a locking ring securing the neck portion of the liner to the lid may be configured to release the liner when the filled keg is dropped.