| 摘要 |
<p>The present invention relates to a method of producing a web of material (6) having a generally flat upper surface and a pattern of perforated recesses (13; 14) which project downwardly from the flat upper surface. According to the invention, a flat web (6) of plastically deformable material is provided with a pattern of mutually separated cuts with the aid of an ultrasonic welding arrangement (1), whereafter a recess (13; 14) is formed on one side of each cut in the web. The invention also relates to apparatus for carrying out the method. <IMAGE></p> |
