| 摘要 |
<p>There is provided an apparatus for topping trees, in which a carriage is movable along an elongated rail. The carriage defines an upper longitudinal recess capable of receiving a trunk of a tree, and a pair of topping blades are mounted to either side of the central recess longitudinally offset therefrom, with each blade pivoting about an axis substantially normal to the direction of carriage movement, between a first position in which the blade is out of interfering relationship with a tree or trees located in the central recess, and a second position in which the blade extends at right angles to the direction of carriage movement. The two blades in the second positions are aligned and have their cutting edges juxtaposed at about the mid-plane of the recess. The carriage is arranged to top trees held stationary with respect to the rail, while the carriage moves in one of the forward or rearward directions. The blades pivot from the first or second position as the carriage is travelling in one direction, and bite into the trees which are located in the recess. The tree motion with respect to the carriage urges the blades further toward the second positions thereof, thereby causing the blades the cut through the tree. The means which pivot the blades toward the second position causes the blades to move at a rate such that the component of motion of the cutting edges parallel with the rail is smaller than the speed of the carriage with respect to the rail, such that the biting of the blades into a tree causes the tree itself to continue the closing movement of the blades toward their second positions, thus relieving the closing means from having to exert the force necessary to cut through the tree.</p> |
