| 摘要 |
A tree shear includes a pair of cutting blades which are respectively carried by a pair of blade support arms that are mounted for pivotal movement towards and away from each other about an axis which extends horizontally when the tree shear is level. Mounted for movement about respective axes which extend parallel to the axis of movement of the blade support arms are a pair of crankshafts that are located above and spaced equidistant from the pivotal axis of the blade support arms. A pair of force-transmitting links are respectively pivotally interconnected between the pair of crankshafts and the pair of blade support arms and a hydraulic actuator is located between and is pivotally interconnected with the pair of crankshafts and is selectively extensible and retractable to move the crankshafts about their respective pivot axes. The force-transmitting links are collapsible and are designed to transmit a cutting force to the cutting blades as long as the compressive forces therein are below a predetermined amount. If the forces rise above this predetermined amount, the link will collapse and permit the hydraulic actuator to finish its stroke without further transmittal of force to that blade associated with the link which collapsed. |
