LOW-EFFORT METERING VALVE SPOOL AND METHOD OF MANUFACTURE THEREOF

摘要

Axially directed fluid flow reaction forces on a valve spool (11) are reduced by a spool groove (61) and metering slot (71b) configuration which causes fluid to leave a groove on the spool at a predetermined inclination selected to reduce flow reaction force on the spool. Preferably the exit angle corresponds to the effective angle at which fluid is metered in at the entrance end (77) of the metering slot. Less effort is needed to shift the spool or to maintain the spool at a selected position and the valve is less sensitive to changes of pressure drop at the groove. Precise control of the fluid exit angle is provided for during manufacture by first turning a conical exit ramp at one wall (74) of the spool groove having the selected inclination.