| 摘要 |
PROBLEM TO BE SOLVED: To make a noise hardly occur between transmission members of an operation connecting mechanism and to make contact sections hardly abrade. SOLUTION: A first rotary shaft 32 supporting a drive steering wheel 19 via a drive unit support 31 and a second rotary shaft 34 supporting a caster 20 via a caster arm 35 are operationally connected by a transmission arm 33 connected to the first rotary shaft 32 and the arm section 42 of the caster arm 35 connected to the second rotary shaft 34. Contact faces 41a and 42a brought into contact with each other to transmit rotation when an arm section 41 and the arm section 42 are rotated are formed into an involute shape on the cross sections perpendicular to the axes of both rotary shafts 32 and 34.
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