| 摘要 |
PURPOSE:To prevent a failure in operating a brake shoe gap adjusting mechanism in a structure without a ling mechanism or a wire coupling mechanism by using a shape memory alloy, an electric heater, a switch and the like. CONSTITUTION:When brake shoes 11, 12 are worn away, and a gap therebetween is over a fixed value, the turning angle of a cam lever 22 exceeds a fixed value, and the turning angle of a lever 41 exceeds a fixed value, which results in that a switch 42 is closed and an electric heater is turned on electricity to generate heat so as to deform an operation lever 43 formed on a shape memory alloy. As a result, a driving lever 33 is moved clockwise against a spring 34 to go over one tooth portion of a ratchet wheel 25. When the brake is released, a switch 42 is opened to gradually cool the operation lever 43 to be softened, and the ratchet wheel 35 is rotated for one tooth by the lever 33 so as to adjust the gap to a reguired gap. |
