| 摘要 |
PROBLEM TO BE SOLVED: To improve the ease of assembly by forming guide sloped surface and positioning parts at either of the guide parts of an upper case and the guided parts of a brake lock and forming projections which are guided by these guide slopes and are positioned by the positioning parts at the other in such a manner that both are positioned by the intrusion of one under rotation into the other. SOLUTION: The projections 52 of the brake lock 5 are formed of three vanes. The guide member 11 formed at the upper case 1 is composed of three walls 11a constituting an arcuate shape. Clearances 11b are formed among the walls 11a. The three projections 52 of the brake lock 5 intrude into these clearances 11b. Both ends (the surfaces forming the clearances 11b) of the walls 11a are formed as approximately perpendicular surfaces to surely position the brake lock 5 so as not to rotate. The front surfaces of the walls 11a are formed as slopes 11c approximately flush with each other. As a result, even if the projections 52 do not align to the clearances 11b and abut on the front surfaces of the walls 11a, the projections 52 may be guided to the clearances 11b by the slopes 11c.
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