Abstract: A fluid medium pump includes a piston having a hollow interior for receiving a connecting rod adapted to open and close a passage through the piston selectively in accordance with the sense of movement of the rod. The connecting rod includes a groove that opens and closes the passage on the piston's compression stroke and opens the passage on the piston's return stroke. User apparatus includes the pump and various pump heads for effecting spraying, foaming and container pressurization. A control mechanism for pump operation renders the pump inoperative for transport, selectively operable upon triggering or continuously operable.

Abstract: A fluid medium pump includes a piston having a hollow interior for receiving a connecting rod adapted to open and close a passage through the piston selectively in accordance with the stroke of the rod. User apparatus includes the pump and various pump heads for effecting spraying, foaming and container pressurization. Control mechanism for pump operation renders the pump inoperative for transport, selectively operable upon triggering or continuously operable.