| 摘要 |
The present invention provides a ratchet block with a block body 10 having a pair of side cheeks 11,12 and a sheave assembly 15 therebetween, which comprises a hub 16 supporting an annular sheave 17 for rotation about a principal axis. The ratchet block also includes a ratchet mechanism comprising ratchet teeth 19 on the sheave and a pawl 20 mounted on the hub 16 or a side cheek 11,12 for movement between an engaged setting, where the ratchet mechanism is active, and a free setting where the ratchet mechanism allows free rotation of the sheave. An actuator 25 is also mounted on the hub 16 or said side cheek 11,12 and linked to the pawl 20 to effect movement thereof between its engaged and free settings. Means are provided for pivoting the hub between loaded and unloaded limiting positions about an axis parallel to but spaced from the hub's principal axis. Spring means 33 are provided for biasing the hub 16 to said unloaded limiting position. There are also included means 38 for interconnecting the actuator 25 and the other of the hub 16 and said side cheeks 11,12. Pivoting movement of the hub from its unloaded position against the action of the spring means 33 under an applied load on the sheave 17 causes the actuator to effect movement of the pawl 20 to its engaged setting.
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