| 摘要 |
A method for producing a multi-channel transparent jacket to accommodate microfilm strips having a given thickness, the jacket being constituted by top and bottom rectangular panels of flexible synthetic plastic material and plastic ribs formed in situ along parellel lines between the panels and integrally bonded thereto to maintain the panels in spaced relation and to define open-ended channels whose width is substantially equal to the width of the strips. In the method, extruded molten streams of polyester material compatible with the material of the panels are directed onto the surface of a first web of panel material in parallel paths thereon, the first web being advanced concurrently with a second web of panel material into combining rolls which act to compress and flatten the streams to produce the in situ ribs, the combined web then being sectioned into individual jackets. |
