Today in 1872, US Patent 129938 A was issued, an invention of Patrick Francis Donnelly, for his “Improvement in Beer Faucets.” There’s no Abstract, although in the description it includes these claims:

Referring to the drawing, A is a bush or socket-piece, which tapers slightly from the shoulder ato the end. From the shoulder a to the end a fine-threaded screw is cut. This piece accommodates the valve B, which controls the flow of the liquid, and is screwed into the head of the barrel. The valve B rests against a rubber seat, C, being held, when closed, against this seat by the spiral spring b wound round the stem of the valve. D is a plug having several holes through it to permit the liquid to pass through. This plug is screwed into the end of the bush-piece, which projects into the barrel. At the outer end of the bush-piece, which projects outside of the barrel, there is an internal screw cut, and into this the conduit-stem E of the faucet is screwed. F is the operating-rod, which terminates, after passing beyond the conduit stem, in a little wheel, G. This rod F has a double-threaded screw at f, which screws into a corresponding thread cut in the interior of the conduit-stem. H is a packing-box of usual form, supplied, where the rod F passes out of the conduit-stem, to prevent leakage. I is the exit-passage for the liquid.

The operation is as follows: The bushpiece is inserted in the barrel-head, and may remain there until the barrel is worn out. The stem’ part of the faucet is applied when the liquid is to be drawn off, the flow being regulated by screwing the rod F against the valve B.

Instead of the double-threaded screw being supplied on the rod F, this rod may be pushed forward and drawn back by other suitable mechanism not necessary to describe.