| 摘要 |
<p>Provided is a tree shear head of a type including a main frame to which a pair of blade support arms are attached for pivotal movement about an axis orientated so as to extend generally perpendicular to a tree being cut. A pair of arcuate platelike blades are respectively fixed to the arms, the respective curvatures of the blades being such that the blades lie along the respective paths that they trace about the pivot axis of the arms during operation. The blades have respective cutting edges extending parallel to the pivot axis of the arms and are movable with the arms between an open position, wherein the cutting edges are spaced apart for receiving a tree to be sheared therebetween and a closed position, wherein the blades are slightly overlapped. Relative to the pivot axis of the blade support arms, the cutting edge of each of the blades is formed by inner and outer converging planar surfaces which respectively extend outwardly and inwardly from inner and outer parallel arcuate surfaces of the blade. The inner and outer plananr surfaces of each blade are dimensioned such that the area of the inner planar surface is less than the area of the outer planar surface, the planar surfaces being so angled relative to a radius line emanating from the center of curvature of the blades that as the cutting edge advances to a position between the open and closed positions thereof during shearing of a standing tree, the vertical reacting forces exerted on the blade will be balanced.</p> |
