| 摘要 |
This invention relates to a slack adjuster mechanism for a tread brake apparatus used for braking a railway car wheel. A fluid pressure operated piston transmits a braking force to a brake shoe through an actuating lever and a brake rod which comprises a screw and a nut about which is disposed a slack adjuster mechanism that embodies a ratchet secured to the nut and a pawl that is operated by a linkage that includes a bell-crank lever that is pivotally mounted at the junction of its arcuate-shaped arm and bifurcated arm on a slack adjuster stem driver carried by an operating stem that constitutes one member of this linkage. The arcuate-shaped arm of the bell-crank lever abuts a roller carried by a stationary bracket, and one end of the bifurcated arm carries a roller that abuts a stop formed on a slack adjuster ring disposed in surrounding relation to the brake rod and anchored to the brake actuating lever to be movable therewith so that this movable stop constitutes a fulcrum about which the bell-crank lever is rocked as the bracket roller rolls along the arcuate surface of the arcuate-shaped arm when a brake application is effected to cause downward movement of the junction of the lever arms thereby, via the stem driver, the operating stem, which extends through the bifurcated arm, and other members of the linkage actuating the pawl and ratchet to take up slack upon effecting a brake release if the shoe clearance is excessive.
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