Piston 1 has holes 2 and 3. Ball-type check valve 4 is mounted in hole 2. As the piston travels upward, ball 4, owing to the resistance of the viscous liquid in the cylinder, compresses spring 5 and opens hole 6. As piston 1 travels downward, ball 4 closes hole 6. This provides for different speeds of piston travel in the up and down strokes.
$3639$SHP,DC$