| 摘要 |
<p>A valve unit for modulating the delivery pressure of a gas comprises a main duct (2) for the delivery of a gas-flow between an inlet opening (3) and an outlet opening (4), a servo-valve (5) mounted in the duct (2) and having a first closure element (6) controlled by a diaphragm (8), the diaphragm being subjected to the gas-delivery pressure (Pu) on one side and, on the other side, to a control pressure (Pt) established in a corresponding control chamber (9) of the servo-valve (5), a tapping duct (12) for tapping off the gas delivered to the inlet of the unit, communicating at its opposite ends with the main duct (2), upstream of the servo-valve (5), and with the contro l chamber (9), respectively. The unit further comprises a pressure-regulation device (10) associated with the servo-valve and including a valve seat (15) mounted in the tapping duct (12) and a respective second closure element (16 ) associated with the seat, as well as an actuator means (17) associated with the second closure element (16) for the operative control thereof, and a control circuit for generating a control signal for the actuator. The actuat or means (17) is of the piezoelectric type and the movement of the second closu re element (16) relative to the corresponding valve seat (15) is correlated proportionally with the actuator-control signal so that, for a preselected signal value, a corresponding control-pressure value (Pt) is generated so as consequently to modulate the delivery pressure (Pu) in a proportionally correlated manner.</p> |
