| 摘要 |
The present invention relates to a hydraulically powered arm system with a hydraulic circuit, which hydraulic circuit (L) comprises a pressure source ( 6 ) and a lifting cylinder ( 1 ) arranged to an arm which is intended for handling a tool, said hydraulic circuit (L) comprising a partial circuit ( 45 A, 45 B), which can be connected into communication with said pressure cource ( 6 ) by means of a first valve element ( 44 ) and said lifting cyliner ( 1 ) by means of a second valve element ( 43 ), characterised in that said partial circuit ( 45 A, 45 B) comprises a pressure reducing/relieving unit ( 4 ) whichis arranged between said valve elements ( 43, 44 ), and that said pressure reducing/relieving unit ( 4 ) is controlled by a pressure controlling unit ( 62 A) in order to facilitate float control of the tool attached to the arm system, whereby a controlled ground pressure is obtained during the a floating motion.
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