| 摘要 |
A control circuit for a tree harvester having a processing implement and a shear assembly for cutting standing trees with a drive mechanism for propelling the tree past the implement and grapples for maintaining the tree in engagement with the drive mechanism. A single control valve is operable into a first position for actuating the shear assembly and into a second position for retracting the shear assembly and operating the drive mechanism. A directional valve provides operating fluid for positioning the grapples and implement in engagement with the tree while the control valve is in either of its operating positions, the directional valve being selectively operable to retract the grapples and implement in order to release the tree from the harvester. A check valve for communicating fluid to the implement and grapples tends to maintain those components in engagement with the tree while also functioning to coordinate operating pressures for the grapples and drive mechanism and to permit floating operation of the implement in order to provide for effective and efficient operation of the tree harvester. |
