| 摘要 |
A SHEATH(S) IS PROVIDED WITH NECESSARY CONDITIONS WHERE INNER AND OUTER SURFACES(1,2) THEREOF ARE BOTH FORMED IN AN UNEVEN HELICAL SHAPE, WHERE THE OUTER SURFACE OF A TROUGH(3) IS ALMOST FLAT, WHERE A WIDTH W OF THE TROUGH(3) BETWEEN INFLECTION POINTS OF A CURVE ALONG THE INNER SURFACE(1) OF THE TROUGH(3) AND A WIDTH W OF A TOP(4) BETWEEN INFLECTION POINTS OF A CURVE ALONG THE TOP(4) SATISFY THE RELATION OF W > W, WHERE A THICKNESS T OF THE TROUGH(3) AND A THICKNESS T OF THE TOP(4) SATISFY THE RELATION OF T > T, WHERE A PROJECTION(5) OF THE INNER SURFACE(1) OF THE TROUGH (3) IS FORMED IN A GENTLE ARC COMPARED TO A RECESS(6) OF THE INNER SURFACE(1) OF THE TOP(4), AND WHERE AN INNER PERIMETER OF THE RECESS(6) OF THE INNER SURFACE PROJECTS CIRCUMFERENTIALLY OUTWARD MORE THAN AN OUTER PERIMETER OF THE OUTER SURFACE(2) OF THE TROUGH(3). THE SHEATH(S) IS ENTIRELY FORMED OF POLYOLEFIN RESIN MATERIAL.FIGURE 1
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