Fluids mixing and proportioning device

A fluids proportioning and dispensing device of a piston-type has a first piston that operates in a piston chamber to draw one of the fluids into the chamber and to thereafter dispense a proportioned mixture of the one fluid with another fluid. The second fluid is fed to the chamber by a pumping mechanism that has a reciprocating pump element which extends into the chamber and also into a bore in the piston housed therein. The second fluid is discharged into this piston bore and the piston carries a toggle-type valve that controls the release of the pumped fluid from the piston bore to the free space in the chamber in a manner such that the piston is moved during its fluid intake stroke by a fluid coupling that is established between the pump element and piston. The pump element is driven through a clutch drive arrangement and the device has a locking mechanism that alternately locks the pumping element in an extended position while the clutch slips and the piston is driven by a spring during its fluid discharge stroke, and then locks a discharge valve in a closed position where it remains during reciprocating movement of the pump element. A bellow-type locking mechanism is also used to interlock the pump element and the piston when a pressure drops develops in the piston chamber for reasons of an exhausted fluid supply and other valving combinations are disclosed. The device is designed to cease dispensing the fluids mixture when the supply of either fluid becomes exhausted.