| 摘要 |
<p>Bookbinding cover is mfd. by bonding together two sheets one rigid and one flexible, then forming >=1 hinge line between the flat covers and spine of the binding in the form of a weld between the sheets. The thickness of the rigid sheet is greatly reduced in the weld, while that of the flexible sheet is maintained. Pref. the sheets are made of synthetic plastic materials, and the weld is formed by localised application of electric currents, both to join the edges of the sheets together and to form the hinge line. This method economically combines the rigidity of the sheet forming the flat covers and spine, with optimum flexibility for the hinges between the flat covers and the spine.</p> |
