PROBLEM TO BE SOLVED: To prevent or allow swing of a main body leg to a front axle only by locking the pin locking hole to an operation pin or disengaging the operation pin from the pin locking hole by immersing the operation pin in the main body leg. SOLUTION: A front axle 24 is loosely inserted into a pair of long axle holes 12c of a pipe-shaped main body leg 12, and a first pin 21 holds the main body leg so as to swing laterally with respect to the front axle. A substantially U-shaped lever member 26 is rotatably attached to the main body leg, and an operation pin 27 urged in a direction of projecting upward by the elastic force of the first spring is attached to the main body leg so as to be able to appear and disappear. The hole edge of the pin locking hole 26a formed in the lever member is locked to the upper part of the operation pin, and the second spring 32 is urged so as to rotate the lever member upward. When the operation pin is immersed in the main body leg, the upper part of the operation pin comes off from the pin locking hole, and the lever member rotates upward due to the elastic force of the second spring, allowing the main body leg to swing with respect to the front axle. It is configured to be. [Selection diagram] Fig. 1【課題】ピン係止孔の操作ピンへの係止又は操作ピンの本体脚への没入によるピン係止孔からの離脱だけで、本体脚のフロント車軸への揺動を阻止又は許容する。【解決手段】パイプ状の本体脚１２の一対の車軸用長孔１２ｃにフロント車軸２４を遊挿し、本体脚をフロント車軸に対して横方向に揺動可能に第１ピン２１が保持する。本体脚に略コ字状のレバー部材２６を回動可能に取付け、第１ばねの弾性力により上方に突出する方向に付勢される操作ピン２７を本体脚に出没可能に取付ける。レバー部材に形成されたピン係止孔２６ａの孔縁が操作ピンの上部に係止し、レバー部材を上方に回転するように第２ばね３２が付勢する。操作ピンを本体脚に没入させたときに、操作ピンの上部がピン係止孔から外れ、レバー部材が第２ばねの弾性力により上方に回転して、本体脚のフロント車軸に対する揺動が許容されるように構成される。【選択図】図１
