Hydraulic circuit for crane

摘要

A hydraulic circuit for a crane having both lift and boom hoist pumps driven by the same engine with appropriate control valves to independently control the lift hooks and the boom angle. An unloading valve is interposed in the boom hoise circuit and dumps the boom hoise pump directly to reservoir when the pressure in the left pump circuit becomes excessive. A boom limit valve, actuated as the boom reaches both upper and lower limits, also causes the unloading valve to dump the boom hoise pump to reservoir.