| 摘要 |
A differential lift hoist apparatus includes an endless roller-and-link chain and upper and lower rotatably mounted spaced sprockets. The chain includes a pair of vertically-extending side-by-side loop sections. Each loop section has outer and inner leg portions and a lower bight portion interconnecting them. The chain also includes an upper bight section which interconnects the outer leg portions and a lower bight section which interconnects the inner leg portions. A group of the upper sprockets entrain and support the upper bight section, whereas a single upper sprocket spaced below the group of upper sprockets entrains and supports the lower bight section. The lower sprockets entrain and are supported by the respective lower bight portions of the chain loop sections. The apparatus also includes a differential arrangement connecting the single upper sprocket with one of the group of upper sprockets to cause movement of the upper bight section at a speed faster than the lower bight section such that one loop section decreases in length as the other increases in length or vice versa depending upon the direction of chain movement. The chain can be driven at a shaft end extending from at least one of the upper and lower sprockets by using a tool to applying a rotary motion thereto to move the chain and rotate the spockets.
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