| 摘要 |
A hub brake apparatus for use on an axle fixed to a frame of a bicycle. The apparatus includes a hub rotatable in a first direction about the axle when the bicycle moves forward, a brake drum rotatable with the hub, brake shoes arranged around the axle and radially inwardly of the brake drum to be movable between a first position for frictionally engaging the brake drum and a second position retracted from the brake drum, a ring spring for biasing the brake shoes toward the second position, and a cam mechanism disposed radially inwardly of the brake shoes for moving the brake shoes from the second position to the first position. The cam mechanism includes intermediate members having radially outward portions for contacting the brake shoes, and a cam disposed radially inwardly of the intermediate members and having peripheral portions for contacting the intermediate members. The peripheral portions of the cam define inclined surfaces opposed to the intermediate members. Each of the inclined surfaces has a radius from the axle diminishing in the first direction. The inclined surfaces displace the intermediate members radially outwardly into pressure contact with the brake shoes when the cam is manually rotated in the first direction.
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