| 摘要 |
A hoisting device, in particular a block, comprises a case having a shorter side and a longer side. A rotatable sheave is rotatably mounted in the case on a shaft that extends between the two sides and projects beyond the shorter side. Two fixed sheaves are mounted on the projecting portion of the shaft. A brake shoe slidably mounted on the longer side of the case below the rotatable sheave is slidable between an upper portion in engagement with the sheave and a lower position disengaged from the sheave. In hoisting condition, a rope passes over the rotatable sheave. In lowering condition, the rope passes from the rotatable sheave, down under the brake shoe and then over the inner non-rotating sheave, thereby pulling the brake block up against the rotatable sheave. In locked position, the rope further passes from the inner non-rotatable sheave around the outer non-rotatable sheave. |
