| 摘要 |
An air shaft comprises a hollow cylinder, an inflatable airtight bladder in the hollow cylinder and a number of movable members provided externally of the bladder, each of the movable members having a portion radially passed through the hollow cylinder. A number of curved members are also provided on an outer surface of the hollow cylinder and between both ends thereof, the portion of the movable member radially passed through the hollow cylinder being secured to an outer surface of the curved member. Each of the curved members comprises a first projection formed on one side, a first slot between any two adjacent ones of the first projections, and a second slot formed on the other side and lined up with the first projection. A second projection, formed on the other side and lined up with the first slots, is disposed axially and overlaid the hollow cylinder. The first projections are adapted to fit into the second slots, the second projections are adapted to fit into the first slots and, prior to inflating the bladder, tops of the first and second projections are substantially flush with tops of the first and second slots. The curved members are pushed outwardly by the movable members after inflating the bladder, such that the tops of the first and second projections are substantially flush with the tops of the first and second slots.
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