Crowell & Moring LLP
Hydraulic drive of operating machine
To rapidly stop an upperstructure even though relief pressure is lowered due to an abnormality in a hydraulic device included in a swing motor driving circuit while intending to stop the upperstructure when a predetermined delay time has passed since a swing operation tool is brought back to a neutral position, provided are: a first choke for controlling a parking brake to apply a braking force to a swing motor when a predetermined delay time has passed since the tool is brought back to a neutral position in a state where the tool is connected to a pilot pump; and an on-off valve and a second choke for controlling the parking brake to apply a braking force to the motor when a delay time shorter than the predetermined delay time has passed since the tool is brought back to the neutral position and disconnected from the pilot pump.
Hitachi Construction Machinery Co., Ltd.
F E E E E E
F16H E02F E02F E02F E02F E02F
inventional inventional inventional inventional inventional inventional
Shinji Hidetoshi Kouji Takatoshi
Nishikawa Satake Ishikawa Ooki