The regulation of flow through residual spray nozzles. 2. Flow control orifices in soft rubber discs.

A sharp-edged orifice in a disc of rubber with a durometer tolerance of 35 to 40, properly mounted near the nozzle tip, is capable of regulating the discharge from a compression sprayer with an accuracy at least comparable to that of mechanical pressure regulator valves. The orifice can act as a flow control device under varying hydraulic pressures because of reduction of the diameter and change of the shape of the orifice under the fluid pressure on the upstream face of the disc. This is possible since, to maintain a constant rate of discharge, the diameter of the orifice need only be changed inversely as the fourth root of the pressure and the square root of the coefficient of discharge. Erosion of the orifice and "set" of the rubber, two potential causes of inaccurate flow, tend to cancel each other out.The device is best used in combination with an 8003 nozzle tip. The rubber discs can be produced commercially at a reasonable cost. Field trials of the combination are recommended.