Pump 1 delivers fluid through pipeline a, a valve with spool 6 and pipeline b to the bottom end of cylinder 2. When piston 4 reaches its upper position and pressure in the system increases, opening valve 7, fluid is delivered through pipeline c, a groove of spool 6 and pipeline d to the bottom end of cylinder 3. This moves piston 5 upward. For the return strokes, knob e of spool 6 is pulled out to the position shown by dash lines, after which pistons 4 and 5 move downward.
$4174$CHP,Dr$