| 摘要 |
The present invention relates to a safety device for an air balancing hoist for braking and finally stopping a reel drum in such a manner that upon fast rotation of the reel drum during a lifting-up operation, a braking pawl attached to the reel drum is locked into a ratchet wheel secured on an end cap due to centrifugal force. The air balancing hoist includes a housing 102 with a chamber 101, which compressed air is introduced into and discharged from, formed therein and with end caps 104, 111 mounted on both ends of the housing, a piston 105 reciprocating along an inner periphery of the housing 102, a ball screw 106 installed in the housing 102 so that it penetrates the piston 105 and is secured to the end caps 104, 111 so as not to rotate, and a reel drum 110 with one end thereof rotatably supported by the piston 105 through a bearing 107 and with the other end thereof secured on a ball nut 108 rotatably engaged with the ball screw 106 so that the reel drum is rotated when moving along the ball screw 106. The safety device includes a braking wheel 114 secured on an inner surface of the end cap 111 and with ratchet 113 longitudinally formed on an outer surface of the wheel over the length corresponding to a range of movable distance of the reel drum 110; and a braking pawl 115 radially pivotably mounted on a side of the reel drum 110 to be releasably locked into the ratchet 113 for braking the reel drum 110 upon fast rotation of the reel drum 110 during the lifting-up operation.
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