| 摘要 |
<p>PROBLEM TO BE SOLVED: To impede any more rotation when it exceeds slightly in clockwise/ counterclockwise two turns. SOLUTION: Cam grooves 7, 8 are formed in each opposed surface of fixed/ movable case members, to provide a stopper ball simultaneously engaged with both the cam grooves 7, 8. The first cam groove 7 comprises a discontinued peripheral groove 7b of radius R1 , circular arc groove 7a of a radius R2 and a diametric direction linear groove 7c of connecting both the grooves 7a, 7b. The second cam groove 8 is a zigzag groove of meandering between virtual circles of radius R1 , R2 , to provide the number of mountains of the groove by about 21/4 in the right/left. When the movable case member is rotated relating to the fixed case member, the stopper ball is pressed to the linear groove 7c of the first cam groove 7, to be moved along the second cam groove 8. When exceeding two turns a little to reach end parts 15, 20 of the second cam groove 8, rotating is impeded by the stopper ball.</p> |
