| 摘要 |
An elastic cord having at least one tapered protruding portion along its length, wherein the extent of protrusion is reduced when the cord is axially stretched, and returns to its original size when the cord is relaxed, is described. One embodiment includes an elastic core about which a flexible sheath is fitted, wherein chosen axially spaced-apart portions of the sheath form tapered isolates or knots in accordance with selected patterns for protrusions therein when the elastic core is in its relaxed state. Such knots are formed when the sheath is cause to bunch up at these axial locations. Sheath patterns may be achieved by employing a woven structure for the sheath. The protruding portions or knots reversibly resist movement of the elastic cord through an opening having a chosen size, such as an eyelet of a shoe. When a unidirectional force is applied to the cord whereby the cord is stretched, the extent of the protruding portion or knot may be sufficiently reduced to enable the cord to be drawn through the opening.
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