PROBLEM TO BE SOLVED: To provide a pruning machine where the rotation of a motor 2 is transmitted to a final gear 7 via a first gear 5 and converted into reciprocating movement of an upper blade 10 and a lower blade 11 via an upper-side cum ring 8 and a lower-side cum ring 9 built in the eccentric axis of the final gear 7 to prune the branches of grass or trees, solving the following problem: engagement between the blade and a crank cum does not get off when a hard log, a small stone or the like is bitten in the machine in some pruning operation because the respective surfaces where the upper-side cum ring 8 and the upper blade 10 are engaged, are parallel to each other, and thereby the impact from the log or the like is directly applied to the teeth surface of the gear to be easy to break.SOLUTION: The pruning machine is designed as follows: a slanted surface narrowing downward is formed on the sliding surface of the upper-side cum ring which transmits the reciprocating movement converted from the rotational movement to the blade, and thereby the sliding surface of the blade moves to the slanted surface from the flat surface part of the ring when such strong force as to put the rotation of the ring or the blade under restraint acts if the steel wire or the small stone is bitten in, so that transmission is released and the breakage of the surfaces of the gear teeth is prevented.COPYRIGHT: (C)2010,JPO&INPIT【課題】【背景技術】モータ2の回転を、ファーストギヤ5を介しファイナルギヤ7に伝達し、ファイナルギヤ7の変心軸に組込まれた上側カムリング8と下側カムリング9によって、上ブレード10と下ブレード11が往復動に変換し、草や木の枝を刈込みを行う刈込み機において、上側カムリング8と上ブレード10が嵌合するそれぞれの面は平行になっているため、刈込み作業によっては硬い木や小石などを噛み込んだとき、ブレードとクランクカムの嵌合が外れないため、その衝撃が直にギヤの歯面に加わり、破損しやすい。【解決手段】回転運動から往復運動に変換してブレードに伝達する上側カムリングの摺動面に下側に向かって絞り込む斜面を形成することで、針金や小石を噛みこんだ際、リングやブレードの回転を拘束するような強い力が働いたとき、ブレードの摺動面がリングの平面部から傾斜面に移動するため、伝達が解除され、ギヤ歯面の破損を防止できる。【選択図】図1
