Pump 1 delivers fluid through pipeline a and a valve with spool 2 to the bottom end of cylinder 3. Piston 5 moves upward and after it reaches its upper position, as shown, piston 6 begins to move upward in cylinder 4. For the return strokes, knob b of spool 2 is pulled out to the position shown by dash lines. At this, fluid is delivered by the pump through pipeline c to the top end of cylinder 3. First piston 5 moves downward and then piston 6.
$4175$CHP,Dr$