Hydraulic control circuit in a hydraulic excavator

Abstract

Pilot change-over valves for operating actuators are connected in a center bypassing form and a cut-off valve is disposed downstream of each such pilot change-over valves. Commands which are in a proportional relation to each other are outputted from a controller to a pilot port of the cut-off valve and a pilot port of a pilot change-over valve for boom. Both valves are closed synchronously. Operation commands for both valves can be altered with a volume control for setting operation characteristics. Hydraulic pump oils for arm are joined together by a confluent valve. Consequently, highly responsive operations can be attained in operating the attachment of a hydraulic excavator. This is effective in the ground hardening work with a bucket, the work for removing mud from the machine body and the work for scattering soil.

Dependencies are inferred from the claim text.