Today in 1948, US Patent 2443550 A was issued, an invention of Michael J. Zwosta, for his “Beer Control and Pipe-Cleaning Apparatus.” There’s no Abstract, though it’s described this way in the application:

This invention relates to beverage dispensing apparatus in which pipe connections extend from the beverage containers to the dispensing faucets and :air or carbonic gas pipes extend from a pump or tank to the beverage containers for supplying the pressure needed to raise the beverage from the containers to the dispensing faucets. More especially, this invention relates to arrangements for cleaning the beverage piping.

The pipe cleaning operation in such dispensing apparatus in general use today, is performed with special portable apparatus which necessitates disconnecting the pipe system from the beverage containers for cleaning and flushing. The operation is usually performed when the beverage dispensing apparatus is not in use and when it is performed during service hours service is necessarily discontinued during the pendency of the operation. This method is poor at best; it does not encourage or permit of sufficiently frequent and sufficiently thorough cleaning operations to insure at all times the best sanitary and palatable conditions. It also causes a serious loss of beverage contained in the pipe lines extending from the containers to the dispensing faucets. In addition to these serious shortcomings, this method is inconvenient and costly.

To overcome these objections, methods and apparatus have been invented for cleaning the pipe lines without causing loss of beverage and without disconnecting the pipe lines from the beverage containers. Invariably, however, these new methods and apparatus are complicated and impractical. In most cases the beverage in the pipe lines is saved by driving it back into the containers before the cleaning operation is started. This is an undesirable practice for the reason, among others, that the beverage from the unclean pipes would have a deleterious effect upon the beverage in the containers. Thus, despite the great shortcomings of the first mentioned method, the last mentioned methods and apparatus have not been generally accepted.

The principal object of the present invention is to provide a practical method and means for encouraging and permitting the frequent cleaning of the pipe system at any time during as well as outside of service hours, without loss of beverage, without the necessity for returning the containers, without the necessity for disconnecting the pipe lines from the beverage containers and without the employment of special portable apparatus.

Another object is to provide apparatus of the character described, having easily accessible controls located in the immediate vicinity of the dispensing faucets.

A further object is the provision of safety control means which function automatically to prevent accidental fouling of the cleaning and flushing system, as for example, the passage of cleaning fluid into the beverage containers.