Double acting hydraulic jack control for drilling machine - has spool valve operating in three pressure stages, and non-return pilot valve controlling flow from piston rod chamber

摘要

The double acting hydraulic cylinder control has pressure lines connected to each end of the cylinder, a third line extending from an hydraulic motor circuit to the pilot inlet of a spool valve. The latter has outlets coupled to the cylinder pressure lines, the system operating in three pressure stages. A non-return pilot valve, operated by the pressure line to the piston chamber, to position in a line from the rod chamber pressure line to exhaust or atmos. This pilot valve is closed when no pilot pressure exists.