FALLING PREVENTIVE DEVICE FOR HUNG LOAD OF CHAIN BLOCK

PURPOSE: To prevent the drop of a cargo by retaining a chain in a fixed part through an upper fixed sheave and a lower movable sheave provided on a main body constituted by a pair of upper and lower parts and braking it when a tachometer provided on the sheave detects a speed exceeding a predetermined value. CONSTITUTION: An upper main body 11 is provided with at least two fixed sheaves 13a, 13b and a chain drive part 12, and both ends of a chain 3 are retained in a chain bucket 4. Moreover, a lower main body 21 is provided with three movable sheaves 22 and a hook 2 for hoisting a cargo. The chain 3 is driven by the drive part 12 so that it is wound into a chain bucket 4 and is pulled out of it through the fixed sheaves 13 and the movable sheaves 22 to lift and lower the hook 2. A tachometer 13a is provided in one of the fixed sheaves, for example, in 13, the fixed sheave 13a is braked by an electromagnetic brake not shown when it detects the rotation exceeding a predetermined value so as to prevent lowering of the lower main body. Consequently, abnormal lowering and drop of a cargo are prevented, and the safety is improved.