When valve spool 1 is shifted manually to the right, fluid is delivered by gear pump 2 to the right end of power cylinder 3, moving piston 4 to the left. Fluid from the left end of cylinder 3 is discharged through the valve body to the tank. If the stem of spool 1 is not held by force, then spring 5, compressed when the spool is shifted to the right, returns the spool to its neutral position (as shown). At this, pump 2 is connected to the tank through axial passage a in spool 1, and the fluid is blocked off inside cylinder 3. Spring 5 returns spool 1 in a similar way from its extreme left-hand position. Relief valve 6 protects the system against overloads.
$4217$CHP,Dr$