| 摘要 |
<p>A gear mechanism (34) has a first gear (38) which is coaxially connected to a drive shaft (20) of a rotary driving source (16), a second gear (44) which is meshed with the first gear (38), and a third gear (45) which is meshed with the second gear (44) and which is integrally interlocked with a ball screw nut (48). Diameters of the first to third gears (38, 44, 45) are set to be smaller than a dimension (C) of an upper body (12a) in a widthwise direction and a dimension (B) of a lower body (12b) in the widthwise direction. <IMAGE></p> |
