By way of example only, the following is a list of dimensions and materials preferably employed in the above-described embodiment: the arcuate portions are given a radius of 15 mm; the cylindrical portions are given a radius of 12 mm and a height of 17 mm; the band-shaped winding components are made of stainless steel and have a thickness of 0.06 mm and a width of 5 mm; and the arms are given a he