Vacuum cleaner filter bags are predominantly made of nonwovens today. Due to their excellent dust-holding capacity, vacuum cleaner filter bags made of nonwovens have practically replaced filter bags made of paper. The manufacture of filter bags made of nonwovens fundamentally differs from the manufacture of paper bags. Rectangular flat bags that are formed from an upper and a lower layer that are welded on the edge around the periphery are common. Filter bags of that kind are known, for example, from DE 201 01 466, EP 0 161 790, EP 0 639 061, EP 1 059 056 or EP 1 661 500.
The positive characteristics of vacuum cleaner filter bags made of nonwovens can to some extent not be used because of an inadequate fit. For this reason, complex bag geometric shapes were developed in order to optimally use the installation space in the vacuum cleaner.
To obtain a greater filling volume than that of a purely flat bag, for instance, flat bags with a weld seam around the periphery and unfoldable side folds are used. Such filter bags are known, for example, from DE 20 2005 000 918, DE 10 2008 006769, DE 20 2009 012 839 or DE 10 2006 023 707.
In addition to flat bags, occasionally block bottom bags are also used. Block bottom bags made of a nonwoven are complex to manufacture. Block bottom bags are known, for example, from DE 20 2005 016309, DE 20 2007 000 198, DE 20 2007 017 064, DE 20 2009 004 433 or EP 1 677 660.
Various solutions have been proposed to increase the dust-holding capacity of vacuum cleaner filter bags.
A pre-filtration by means of loose fibres is disclosed, for example, in DE 10 2007 060 747, DE 20 2007 010 692 and WO 2005/060807. A pre-filtration by means of a filter bag in the filter bag was disclosed by WO 2010/000453, DE 20 2009 002 970 and DE 20 2006 016 303. Flow deflections or flow distributions in the filter bag are proposed, for example, by EP 1 915 938, DE 20 2008 016 300, DE 20 2008 007 717, DE 20 2006 019 108, DE 20 2006 016 304, EP 1 787 560 and EP 1 804 635.
DE 10 2007 060 748 discloses a filter bag in which the fleece material is stretched to form a three-dimensionally shaped bag wall.
EP 1 982 625 discloses a filter bag, whereby the filter material is embossed at least in areas and the effective filter area is enlarged by means of a profiling of the filter material. The profiling can be executed in the form of elongated ribs arranged parallel to one another. By means of the embossing with a pattern, however, the material characteristics and/or the filtration characteristics of the embossed nonwoven layer are modified
DE 20 2005 010 357 discloses a dust filter bag, whereby the bag wall has at least one layer of filter material, whereby at least one layer consists of creped fibre material. A coarse filter layer, a fine filter layer or all layers of the bag can thereby be creped. As a result of the creping, the at least one layer is irregularly creased, whereby the volume per unit area of the corresponding filter layer is enlarged. As a result of the creping, the mass per unit area of the filter layer and consequently its filtration characteristics are modified.
Filter materials are known that are used in a folded manner in order to enlarge the effective surface, whereby the folds are fixed/stabilized. For example, EP 1 080 770 discloses a zigzag-shaped folded fold pack made of a nonwoven that can be thermoplastically welded. Prefabricated strips for stabilizing the folds are known from DE 42 27 744, whereby these strips are connected to the fold edges by melting the strip and/or filter web material. Such filter materials have been used until now for air filtration, but not for vacuum cleaner filter bags.