| 摘要 |
An elongate element in the form of a longitudinally split tube (2) is arranged to be progressively flattened and wound about an axis (6) extending transversely to the longitudinal extent of the tube to form a coil (4). To enable the tube (2) to be structurally rigid, but yet to enable it to be easy to wind and to remain coiled without being potentially explosive, a second layer (10, 12, 14 or 16) is affixed to the layer of spring steel (8) forming the tube (2). The second layer is arranged to be stressed to oppose the bias of the spring steel (8) which favours the formation of the tube.
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