主权项 |
1. A vented brake drum consisting essentially of:
an annular hub portion and drum portion having a cylindrical shape, a circumferential outer surface, and a cylindrical internal braking surface against which a brake lining of a semicircular brake shoe can be frictionally engaged for braking; and a series of spaced-apart ventilation openings extending depthwise through the drum portion from the outer surface to the internal braking surface, the series of ventilation openings being distributed in a pattern that is repeated circumferentially in a plurality of said patterns spaced around the drum portion; in which each pattern of ventilation openings is in the form of a helical line oriented diagonally across the internal braking surface, each of said patterns positioned in a different circumferential section of the drum such that a single one of each of the ventilation openings occupies a unique circumferential position on the drum. |