Today in 1935, US Patent 2016926 A was issued, an invention of Rees Damon, assigned to Rahr Malting Co., for his “Apparatus For Emptying and Cleaning Beer and Other Pipes.” There’s no Abstract, although in the description it includes this summary:

My invention relates to methods of and apparatus for cleaning pipes, and other liquid containers and connections.

It is particularly applicable to the pipes, tanks, containers, and connections between the beer kegs and drawing faucets of beer dispensing apparatus, which are usually cleaned at the present time by discharging through the pipes and connections a cleaning fluid, such as water containing a cleaning material, and sometimes also air under pressure.

Before cleaning such pipes and connections, it has been necessary heretofore to draw 01f a considerable amount of beer in the pipes, which ‘was thus wasted. Furthermore, after the dispensing apparatus has been out of use overnight or during holidays, it has been necessary when dispensing was resumed, first to draw off all the beer in the pipes, etc., down to the supply kegs, because the beer becomes stale and otherwise deteriorates when it has been left standing in the pipes for a considerable period of time. All this beer was thus wasted causing considerable loss every day.

My invention comprises first a simple, convenient and effective method of and apparatus for forcing and restraining the beer in the pipes and. connections back into the supply kegs and thus saving all the beer, before cleaning the pipes and also before closing the bar for the night or holidays.

My invention also comprises a simple, convenient and effective method of and apparatus for cleaning the pipes and connections.

My invention also comprises various novel features of construction and combinations of parts hereinafter fully described and particularly pointed out in the claims.