| 摘要 |
<p>The invention relates to a method at the cross-cutting of tree stems to pre-determined timber lengths. According to the invention, an impulse is triggered when the nominal timber length has been attained, which impulse stops the advance movement and braking is effected while the braking energy is accumulated all the way to the stop of the stem after the stem has moved through a certain distance beyond the nominal length. The accumulated braking energy then is released for moving the stem back to substantially the nominal length, whereafter the cross-cutting is carried out. At an apparatus for carrying out the method according to the invention, the feeding wheels (2) of the stem (1) are driven by hydraulic motors (7) having a pressure conduit (5) and a return conduit (6) in common. The return conduit is connected to a pressure accumulator (9). A stop valve (8) is laid-in in each conduit (5,6). A measuring wheel (4) abutting the stem is provided with an impulse device, which is capable at attained nominal length (L) to emit an impulse to the valves (8 ) for closing the conduits (5,6) and thereby braking the stem. The braking pressure arising in the closed return conduit (6) builds up the pressure in the accumulator all the way to the stop of the stem. The accumulated braking energy there is released for returning the stem to the nominal position (N), where cross-cutting is effected by a cutting tool (3).</p> |
