| 摘要 |
PROBLEM TO BE SOLVED: To resolve problems of a wheel of two-wheeled caster that it cannot clear such an obstacle as a slight step gap, etc., due to its small diameter and that restrictions in appearance and design prevent enlarging of its diameter though the larger diameter may solve the problem. SOLUTION: This wheel is provided with an additional leg member having its pivot within the same support frame as that of the wheel and its diameter larger than that of the used wheel, so as not to change the wheel diameter nor enlarge its mounting space. This will temporarily produce a condition as if an external wheel form appears to be rotating since such a leg member first touches the step gap. Subsequently both wheels rise to the surface simultaneously to clear the step gap, and then loaded weight speedily shifts to the original wheel, the leg member is returned to its former position by a coil spring.
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