1 a has the same configuration as that of the sowc 1 except for the position where an elastic body is provided the pocket plate 11 in the sowc 1 a is the same as that of the sowc 101 see fig6 as illustrated in fig3 the sowc 1 a is provided with an elastic body 161 made of rubber or the like on the side of the notch plate 12 a in the contact portion between strut 113 a and the notch plate 12 a the configuration of the elastic body 161 is the same as that of the first embodiment see fig2 the sowc 1 a is also provided with an elastic body 163 made of rubber or the like on the side of the strut 113 a in the contact portion between the strut 113 a and the pocket plate 11 the elastic body 163 is provided by cutting a part of the strut 113 a on the side of the pocket 112 and provided in the cut portion the elastic body 163 is provided in the cut portion so as to hold an original profile shape outline of the strut 113 a that is the strut 113 a provided with the elastic body 163 and the strut 113 not provided with the elastic body 163 see fig6 have the same profile therefore the engagement operation or the non engagement operation of the sowc 1 a is not interrupted due to the presence of the elastic body 163 for the sake of convenience of description the bottom surface of the pocket 112 is expressed by a flat surface in fig3 however in practice.