Fluid under pressure is delivered through port 4 to the annular groove of piston 1 from where it passes through radial hole a to the annular groove of valve spool 2. This spool is shifted by stem 3 inside piston 1. When the spool is shifted to the right, the fluid passes from the annular groove of spool 2 through channel b to the left end of the cylinder, moving the piston to the right as well. From the right end of the operating cylinder, the fluid passes through channel c in the piston to the left annular groove of spool 2 and through its radial and axial passages to the tank, passing through radial hole d in the rod of piston 1. When the spool is shifted to the left, the piston moves in the same direction.
$3752$SHP,Dr$