As shown, fluid from pump 1 is being discharged through directional valve 2 to the tank and piston 7 is stationary. When spool 6 is shifted to the left, fluid is delivered by pump 1 to the left end of cylinder 3, moving piston 7 to the right. At the end of the stroke, the pressure in the system increases and fluid passes through relief valve 4 to the left end of valve 2, shifting spool 6 to its initial position and connecting the pump to the tank through pipeline 8. When spool 5 is shifted to the left, piston 7 moves to the left. Spools 5 and 6 are locked by balls a, held by springs 9 in recesses b in the stems of the spools.
$4166$CHP,Dr$