HYDRAULIC VALVES

摘要

A hydraulic valve (10) includes a spool (40) movable within a body (12) to regulate flow across the valve (10). Movement of the spool (40) is controlled by an electromagnetic actuator (78) that operates either directly or through a pilot stage upon the spool (40). When operating through a pilot stage, the actuator varies pilot pressure by an operating member co-operating with an orifice. A flapper valve (129) may be used to vary a pair of pilot flows in complementary manner. Feedback signals of pressure and spool position are provided to a controller which selectively combines the signals to monitor the operating parameters of the valve. The controller may modify the position signal with the pressure signal to obtain an indication of flow rate through the valve (10).