Hydraulic control unit for ramming or extraction device has valve arrangement for opening clamping device, imbalance setting adjustment device to zero-amplitude before switching on vibrator by moving operating lever from null position

摘要

The hydraulic control unit has a vibrator with an imbalance adjustment device and a clamping device, a valve arrangement with which the clamping device is opened and the imbalance adjustment device is set to a zero-amplitude before switching on the vibrator by actuating an operating lever out of its null position. The clamping device is then closed by moving the lever in the opposite direction and the flow of hydraulic medium to the hydraulic motor and imbalance device is enabled on reaching a maximum closing pressure.