摘要 |
<p>The method comprises of forming a first continuous sheet of material (12) having a first surface (16) and a second 45 surface (l8). Then forming a second continuous sheet of material (14) having a third surface (20) and a fourth surface (22). Then forming a first set of apertures (24) in the 50 first continuous sheet of material (12), forming a second set of apertures (26) in the first continuous sheet of material (12), adjacent apertures (24) in the first set of apertures (24) being spaced apart longitudinally of the first continuous sheet of material (12). adjacent apertures (26) in the second set of apertures. Then forming a third set of apertures (28) in the second continuous sheet of material (14),forming a fourth set of apertures (30) in the second continuous sheet of material (14), with adjacent apertures (28) in the third set of apertures (28) being spaced apart longitudinally of the second continuous sheet of material (14). Then winding the first and second continuous sheets of material (12,14) together into a spiral such that the apertures of the first set of apertures (24) in the first continuous sheet of material (12) are aligned with the apertures in the third set of apertures (28) in the second continuous sheet of material (14). Then sealing the edges (32.34) of the first surface (16) of the first continuous sheet of material (12) to the edges (36.38) of the third surface (20) of the second continuous sheet of material (14). Then sealing the apertures of the first set of apertures (24) in the first continuous sheet of material (12) to the apertures in the third set of apertures (28) in the second continuous sheet of material (14) and sealing the apertures of the second set of apertures .</p> |