Patent attributes
A relationship of 0<α1<2θ1 is satisfied, where α1 is an angle formed between a first line which is vertical to a parallel line passing through a pivot center point and being parallel to a pivot extending direction, passes through a center point of a first portion from the center point of the first portion toward the parallel line, and a second line which is vertical, at the center point of the first portion, to a first portion extending direction, passes through the center point of the first portion toward a vertical line being vertical to the parallel line and passing through the pivot center point, and where θ1 is an angle formed between the first line and a third line connecting the pivot center point and the center point of the first portion from the center point of the first portion toward the pivot center point.
