PROBLEM TO BE SOLVED: To make wind noise during rotation as low as possible in a resin-made cutting blade extending in a plate shape for use in a bush cutter, and prevent a load of a driving source for rotating the cutting blade from being enlarged due to a cut material such as grass being caught more than required.SOLUTION: A cutting blade 22 is detachably attached to a rotating body 21 and extends in a plate shape in the centrifugal direction of the rotating body 21, and has a shape curved in backward of the rotating direction as proceeding outwardly in the centrifugal direction. The cutting blade 22 is made into a spindle shape having a cross-sectional shape in the rotating direction where a central part of the rotating direction is swelled out. In a blade part 22b formed in the front side of the rotating direction of the cutting blade 22, protrusions 22b1 and recesses 22b2 are alternatingly formed in a consecutive waveform in the centrifugal direction, and the width W1 of the protrusion 22b1 is formed more narrowly than the width W2 of the recess 22b2. In the surface being perpendicular to the rotating direction and the centrifugal direction of the cutting blade 22, small protrusions 22c are formed which reduce air vortexes passing therethrough.SELECTED DRAWING: Figure 3COPYRIGHT: (C)2018,JPO&INPIT【課題】刈払機に使用する板状に延びる樹脂製の切断刃において、回転時の風切り音をできるだけ低くするとともに、草等の被切断物が必要以上に引っかかることで切断刃を回転させる駆動源の負荷を大きくしないようにする。【解決手段】切断刃２２は、回転体２１に着脱可能に取り付けられて、回転体２１の遠心方向に板状に延び、遠心方向外向きに進むにつれて回転方向の後向きに湾曲した形状をしている。切断刃２２は回転方向の断面形状を回転方向の中央部が膨らむようにした紡錘形とした。切断刃２２の回転方向の前側に形成された刃部２２ｂには遠心方向に突部２２ｂ１と凹部２２ｂ２が交互に連続する波形に形成され、突部２２ｂ１の幅Ｗ１を凹部２２ｂ２の幅Ｗ２よりも狭く形成した。切断刃２２の回転方向及び遠心方向と直交する面には通過する空気の渦を小さくする小突起２２ｃを形成した。【選択図】図３
