Abstract: A filter insert (1A) for a fluid filter with an outer square or hollow cylindrical shape has a plurality of continuous zigzag folded walls (5) made of a fluid-permeable material (2) and provided in the plane of at least part of the folded walls with stiffening embossed depressions (3) and/or projections for keeping the walls folded. The depressions and/or projections of adjacent folded walls are interconnected at least in part and supported on each other. Stiff spacers are provided between the depressions or projections in at least part of their length for interconnecting them and supporting them on each other.

Abstract: A process for manufacturing a fluid filter and a device for carrying out the process in which a fluid-permeable material is pre-folded to form a first filter region including a number of fold walls arranged as substantially zig-zag shaped continuous folds having at least one folded edge portion including a plurality of folded edges. An adhesive is applied in a form of strips or threads to a substantially flat substrate material. The adhesive strips or threads on the substrate material are brought into contact with the folded edge portion in an orientation crossing the folded edges of the folded edge portion for interconnecting the fold walls and so that the substrate material essentially covers the entire folded edge portion. The adhesive is cured for bonding the strips or threads of adhesive to the folded edge portion.

Abstract: A process and apparatus is provided for producing a filter insert for a fluid filter. The insert is comprised of filter material having a number of fold walls arranged in a zigzag-shaped continuous fold. Adjacent fold walls are connected to one another and rest on one another at least in part by means of an adhesive spacer. A strip of the filter material is provided with indentations which determine positions of fold edges. The adhesive spacers are applied 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. The strip of filter material is folded at the indentations in partial steps, including a first partial step of folding the filter material into folds at a small spacing, and a second partial step of pulling the folds apart again by a predetermined amount 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.