Valve devices for use in sorting apparatus ejectors

A pneumatic ejector for sorting apparatus in which material to be sorted is directed in a stream following an aerial path, and rejected material is removed from the stream by air pulses from such ejectors, which ejector has a housing comprising a central section and two side sections, each side section having a respective output port formed therein, and being attached to the central section by an adjustable mounting mechanism, the housing defining a pressure chamber;

• a diaphragm mounted in the housing and comprising a piezoelectric element;
• an input for connection to a source of pressurised gas, which input communicates with the chamber on both sides of the diaphragm;
• and an output port connecting the chamber on one side of the diaphragm to a delivery duct terminating in an ejector nozzle, an area of the diaphragm being disposed in juxtaposition with the output port and the diaphragm being elastically deformable by differential input gas pressure over said area thereof such that said area closes the output port, whereby the closure pressure between an output port and a respective diaphragm is altered by adjustment of said mounting mechanism, the valve device including an electric circuit selectively operable to activate the piezoelectric element to withdraw said area of the diaphragm from the output port to the admit gas from the pressure chamber to the output port, and thence to the ejector nozzle.