| 摘要 |
A valve device is disclosed for controlling the delivery of gas from a pressurised source suitable for use in a pneumatic ejector in particle sorting apparatus. It uses a diaphragm (42) as a valve member disposed over an output port (52) from a chamber (61, 63) which is in substantially continuous communication with a source of gas or air under pressure. Both sides of the diaphragm are exposed to pressurised gas or air in the chamber. For this reason, and because the diaphragm itself engages the output port to close it, when the input pressure is applied, there is a differential pressure which elastically deforms the diaphragm to close the output port. The diaphragm has a piezoelectric element (44), and the valve device includes an electric circuit (56, 58) operable to selectively activate the piezoelectric element and withdraw the valve member from the output port to admit pressurised gas or air thereinto.
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