| 摘要 |
A first metal laminate sheet in a form of strip is rolled into a cylindrical shape to form a first impermeable layer. A first gap is defined between widthwise opposite edges of the first metal laminate sheet. Then, a second metal laminate sheet in a form of strip is rolled into a cylindrical shape on an outer periphery of the first metal laminate sheet, with intervening a rubber elastic layer therebetween, to form a second impermeable layer. A second gap is also defined between widthwise opposite edges of the second metal laminate sheet. The first gap and the second gap are staggered with respect to each other in a circumferential direction. |
