Abstract: A self-powered spraying device for dispensing a metered amount or a continuous amount of chemical. A valve is connected through conduits to a cavity in front of a piston, to a cavity in the rear of the piston, to a fluid pressure source and to a nozzle. In the open position of the valve the rear cavity is connected to the fluid pressure source, and the front cavity to the nozzle. In the closed position of the valve the front and rear cavities are connected so that a spring within the front cavity drives the piston to the rear, thereby transferring chemical from the rear cavity to the front cavity. A second valve is also provided which in an opened position permits the metered dispensing of chemical when the first valve is operated and when in a closed position permits the continuous release of chemical when the first valve is operated.

Abstract: A piston-operated spraying device dispenses a metered amount of liquid. A valve is connected through conduits to a cavity in front of the piston, to a cavity in the rear of the piston, to a pressure supply, to a supply of liquid to be sprayed, to a nozzle, and to a vent for releasing the pressure. In the open position the valve connects the rear cavity to the pressure supply, and the front cavity to a nozzle so that any liquid in the front cavity will be dispensed. In the closed position the valve connects the rear cavity to the vent for releasing the pressure, and the front cavity to the supply of liquid so that a spring can drive the piston to the rear, thereby allowing the front cavity to be filled by the liquid and preparing the device for another delivery.