| 摘要 |
The felling unit is rotatably and tiltably fixed to the end of a crane arm, and incorporates hydraulically-operated grip jaws and a hydraulically driven chain saw. In a tilt cylinder (9) is a hydraulic piston which tilts the felling unit at the same time as a saw motor (19) is fed with pressure oil. It returns the felling unit to its normal position only after a further hydraulic piston has reached an end position corresp. to open jaws. This further piston is fitted in a grip cylinder (25) and controls grip jaws. A valve component (26) is connected to the tilt cylinder and actuates the tilting movement due to the torque effect of the falling tree after the sawing operation has been completed. This valve comprises two channels provided with check valves (32,35) for oil feed to each of the two connections of the tilt cylinder from the pressure feed to the hydraulic motor. It also feeds a chamber of the grip cylinder and two pilot pressure-controlled pressure limiting valves (27,28) for control of return flow from the tilt cylinder connection. |
