| 摘要 |
<p>A control system for a hydraulic drive element such as a cylinder for a press includes a pilot valve having a plurality of fluid outlets controlled by a pilot valve spool unidirectionally biased by a resilient spring at one end thereof to a neutral position. A main valve having an elongated main valve spool resiliently biased to a center position. The opposite ends of the main valve spool are contiguous with individual pressure chambers separately connected to one of the plurality of outlets of the pilot valve. A link engaged with an end of the pilot valve spool which is opposite the end engaged by the resilient spring. A set value drive including stepping motor is coupled to the link for moving the pilot valve spool in either of opposite directions from the neutral position. The link is coupled for movement by the main valve spool to return the pilot valve spool to the neutral position.</p> |
