Process for providing a filter insert

A process for producing a filter insert for a fluid filter, the insert comprised of filter material having a number of fold walls arranged in a zigzag-shaped continuous fold, adjacent fold walls being connected to one another and resting on one another at least in part by means of an adhesive spacer, the process comprising the steps of:

• providing a strip of the filter material with indentations which determine positions of fold edges;
• applying the adhesive spacers to at least corresponding areas of those parts of the strip of filter material which will become adjacent fold walls when the filter insert is complete;
• and
• folding the strip of filter material at the indentations in partial steps, including a first partial step of folding the filter material into folds at a small spacing such that the adjacent fold wall edges are at a small spacing from each other and the adhesive spacers contact each other, and a second partial step of pulling the folds apart again by a predetermined amount to extend the adhesive spacers so that at least some of the adhesive spacers have a height which is not constant in a direction at right angles to the fold edges, then curing the adhesive spacers.