| 摘要 |
<p>A relief valve assembly is disclosed which comprises a main valve (6) and a pilot valve (13). The pilot valve is acted upon by biassing means (15) which tends to close the pilot valve, the arrangment being such that the state of the pilot valve determines whether or not the main valve is opened to modify the fluid flowpath within the valve. The biassing means associated with the pilot valve is seated, at its end remote from the valve head of the pilot valve, against a plunger (17) or similar device whose position is adjusted by a pilot motor (22). The pilot motor is under the command of a microprocessor or other operating means for varying the operation of the motor according to a predetermined sequence, program or signal. Conveniently, the pilot motor is under servo control. A position transducer (23) is preferably provided on the output shah of the motor, and the output of the transducer is fed into a servo amplifier where it is compared with the command signal from the microprocessor to derive an error signal which is used to control the pilot motor.</p> |
