PROBLEM TO BE SOLVED: To reduce the force of lifting a rear cover by a rod member of a cover bouncing-down device for urging the rear cover of a rotary power tiller in the grounding direction, and to facilitate the recognition of the amount of expansion/contraction of the rod member when tilling is carried out in such a state that the rear cover is slightly lifted from a ground surface.SOLUTION: In this rotary power tiller, a lift is screwed into a screw shaft so that the lift can be moved in the longitudinal direction of a supporting rod by the rotation of the screw shaft around the axial center. The one side of a machine frame and the rear cover is connected to a holder so that the rear cover can be lifted or lowered by movement of the holder in the longitudinal direction of the supporting rod. In order to fluctuate a position to regulate the movement of the rear cover in the grounding direction, depending on the position of the movement of the lift in the longitudinal direction of the supporting rod, the movement of the holder to the other side of the machine frame or the rear cover is regulated by the lift. A spring for pressing the holder toward the other side of the machine frame or the rear cover is installed so as to urge the rear cover in the grounding direction. An assist spring for urging the lift to the one side of the machine frame or the rear cover is installed so as to assist the movement of the lift in the direction of lifting the rear cover.COPYRIGHT: (C)2008,JPO&INPIT【課題】 ロータリ耕耘機の後部カバーを接地方向に付勢するカバー弾下装置のロッド部材を、後部カバーの持ち上げ力の軽減を図ると共に、後部カバーを地面から少し浮かせた状態で耕耘する場合に、ロッド部材の伸縮量が容易にわかるようにする。【解決手段】 ねじ軸の軸心廻りの回転によりリフトが支持杆の長手方向に移動するようにリフトがねじ軸に螺合され、ホルダの支持杆長手方向への移動により後部カバーが昇降移動するように、ホルダに機枠又は後部カバーの他方が連結され、リフトの支持杆長手方向の移動位置に応じて後部カバーの接地方向への移動規制位置が変動するべく、リフトによりホルダの前記機枠又は後部カバーの他方側への移動を規制するように構成され、後部カバーを接地方向に付勢すべくホルダを前記機枠又は後部カバーの他方側に向けて押圧するバネが設けられ、リフトが後部カバーを上昇させる方向に移動するのをアシストすべくリフトを前記機枠又は後部カバーの一方側に付勢するアシストバネが設けられている。【選択図】図1
