Abstract: A device for delivering a controlled dose of a fluid to an outlet from a fluid supply at an operating pressure which includes an actively operable check valve and pressure exerting means to selectively exert first and second pressures on the check valve. When one of the first and second pressures is exerted on the check valve, the valve prevents the passage of fluid at operating pressure through the outlet. When the other pressure is exerted on the check valve, the valve permits the passage of spray fluid at operating pressure. Signal generating means to generate a control signal characteristic of the fluid operating pressure, and control means derive at least one of the said first and second pressures from the control signal.

Abstract: In a rotary metering valve, a metering block is located in a chamber having a plurality of outlets. The metering block is connectable to a fluid supply and has an outlet selector rotatable to select one of several different outlets from the block to the chamber. A barrier extends between the wall of the chamber and the metering block to prevent fluid flowing in a 360 degree rotary motion around the block. A sprayer check valve is also disclosed. The valve has a diaphragm acted on by control fluid whose pressure is set to just below the spray fluid pressure and which is varied according to variations in the spray fluid pressure.