| 摘要 |
Formation of tubular objects by spirally winding and seaming a relatively rigid strip of plastics material. In the prior form of this rigid plastic strip, it was difficult to control and change the diameter of the resulting tube due to the forces required to overcome the extreme frictional engagement between the interlocking portions of that prior art strip. This invention provides a sealing flap (15, 215) along one longitudinal edge (5, 25) of the strip, and an engaging surface (16, 216) along the other edge (11, 211) positioned close to but separate from the interlocking portions (8 and 12, 28, 212) of these longitudinal edges. The provision of these sealing flaps and engaging surfaces permit the interlocking portions at the edges to be designed independent of the ability of the these interlocking portions to create a fluid seal. This results in optimum operation of these interlocking portions to, for example, permit relatively rapid changes in the diameter of the tube as it is formed, as well as subsequent to its formation. |
