| 摘要 |
A multilegged portal crane is disclosed in which a plurality of legs including first, second and third spaced apart legs are affixed to a frame with each leg extending between the frame and a different one of a plurality of rails. Each leg has a pair of wheels at a base end, spaced apart in the direction in the length of the rails and rotatable along the rails. A first leg of the plurality of legs has a higher level of rigidity than the other legs which are more flexible relative to the first leg. Means for sensing skew of the crane is mounted on the first leg and the first leg is positioned between the second and third legs such that, for a predetermined amount of skew of the crane determined by the sensing means on the first leg, the skew movement of the second and third legs relative to the first leg is less than the skew movement of the second and third legs relative to each other. Only one of the legs is rigid and the other two are flexible. The rigid leg and the frame will follow irregularities and the rail upon which the rigid leg is mounted and the frame will move with the rigid leg and the wheels due to the irregularities. The flexible legs will flex to permit their wheels to also follow irregularities on their tracks and not become derailed and permit the rigid leg and the frame to move along with the irregularities of the rail on which the first leg is mounted.
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