| 摘要 |
<P>PROBLEM TO BE SOLVED: To make a dust accumulating space relatively small and restrain limitation of forming efficiency and to easily revolve a rotating portion in a closing direction by sufficiently easily starting breakage of a second circumfer ential breaking means (14) or by revolving the rotating portion (34) at a predeter mined angle of α in spite that the rotating portion is sufficiently exactly held at the position in the angle of α. <P>SOLUTION: There is no stopping protrusion (56) in the area (58) of both the breakage starting portions where both the breakage starting edges of the second circumferential breakage means are located. A circular outer seal piece (52) has thickness locally decreased in at least the upstream portion of both the breakage starting angle areas of the second circumferential breakage means. A supporting protruding piece (38) and supporting recess (40) are arranged in a skirt wall (6). <P>COPYRIGHT: (C)2004,JPO |
