| 摘要 |
PROBLEM TO BE SOLVED: To suppress manufacturing cost by making main parts common when changing the length of a suppressing roller.SOLUTION: The right and left box step machines are divided into outside and inside, the box step machines B1 in the outside have a fixed length and ones having various lengths are prepared in the box step machines B2 in the inside closer to a body. The box step machine B2 of a proper length is selected and is coupled to the box step machine B1 by a coupling member 91 to match to the lateral width of a house in each agricultural field. |
