PROBLEM TO BE SOLVED: To provide a rotary cultivator which has a gear box shape sufficiently ensuring a connection strength.SOLUTION: This rotary cultivator manufactured by disposing approximately circular openings on the right and left sides of a gear box receiving a transmission gear, connecting both the openings to the inside surfaces of a pair of right and left plate-like connection brackets, and connecting the outside surfaces of both the connection brackets to the inside end surfaces of a pair of right and left cylindrical main beams extended in the right and left directions, respectively, is characterized by forming radially expanded portions in the outer peripheral portions of the approximately circularly opened openings to increase the outer peripheral edge lengths of the openings surface-contacting with the inside surface portions of the connection brackets. Since the outer peripheral edge lengths of the openings are increased, connection strengths obtained by welding the outer peripheral end portions of the openings over the whole peripheries can be increased, and the connection strengths can sufficiently be ensured.COPYRIGHT: (C)2010,JPO&INPIT【課題】接続強度を十分に確保すること。【解決手段】伝動ギヤを収容したギヤボックスの左右側部に略円形に開口する開口部を設けて、両開口部に左右一対の板状の連結用ブラケットの内側面部を接続し、両連結用ブラケットの外側面部に、左右方向に伸延する左右一対の筒状のメインビームの内側端面を接続したロータリ耕耘装置であって、略円形に開口する前記開口部の外周縁部に、半径方向に膨出する膨出部を形成して、連結用ブラケットの内側面部と面接する開口部の外周縁長を増大させている。開口部の外周縁長を増大させているため、同開口部の外周端部の全周にわたって溶接することで得られる接続強度を増大させることができて、接続強度を十分に確保することができる。【選択図】図7
