Flat air filter element and air filter

1. A flat air filter element comprising:

a filter medium of cellulose material having an inflow face, an opposite outflow face and having an outer contour formed by a plurality of lateral sides which extend from the inflow face to the outflow face, the plurality of lateral sides including a first lateral side and an opposite lateral side;

wherein the filter medium is zig-zag folded forming zig-zag folds, the zig-zag folds extending across the filter medium in a direction from the first lateral side to the opposite lateral side, the zig-zag folds having a first end edge at the first lateral side of the filter medium and a second end edge at the opposite lateral side of the filter medium;

at least one recess formed into a respective one of the first or the second lateral sides of the filter medium such that the end edges of the zig-zag folds at the at least one recess are indented inwardly into the filter medium;

a sealing element arranged at the filter medium and extending circumferentially about the filter medium on the plurality of lateral sides;

wherein the sealing element at the at least one recess is indented inwardly, following the respective lateral side into the recess;

wherein the sealing element comprises

a circumferentially extending holding groove configured to be engaged by a housing part of a filter housing.

2. The flat air filter element according to claim 1 , wherein

the at least one recess is formed at a corner region of the outer contour of the flat air filter element.

3. The flat air filter element according to claim 2 , wherein

the at least one recess is a bevel.

4. The flat air filter element according to claim 1 , wherein

the at least one recess is formed centrally on the respective lateral side.

5. The flat air filter element according to claim 1 , wherein

the at least one recess is a curved indentation into the respective lateral side of the filter medium.

6. The flat air filter element according to claim 1 , wherein

the at least one recess has a projecting depth of at least 10 mm.

7. The flat air filter element according to claim 1 , wherein

the flat air filter element comprises a plurality of said at least one recess.

8. The flat air filter element according to claim 1 , wherein

the filter medium is a zigzag-folded bellows.

9. The flat air filter element according to claim 1 , wherein

the end edges at the first lateral side are glued to each other and the end edges at the second lateral side are glued to each other.

10. The flat air filter element according to claim 9 , wherein

the filter medium comprises an end edge bond at the end edges.

11. The flat air filter element according to claim 10 , wherein

the end edge bond extends at least in a region of the at least one recess at a tangential angle of at most 45° relative to a main direction of the filter medium.

12. The flat air filter element according to claim 11 , wherein

the end edge bond extends along the entire end faces of the flat air filter element at the tangential angle of at most 45° relative to the main direction of the filter medium.

13. The flat air filter element according to claim 10 , wherein

a seal joining contour of the sealing element and the end edge bond extend parallel to each other in a region of the at least one recess.

14. The flat air filter element according to claim 13 , wherein

the seal joining contour of the sealing element and the end edge bond extend parallel to each other along the entire end faces of the flat air filter element.

15. The flat air filter element according to claim 9 , wherein

the sealing element and the end edges at the respective lateral side extend parallel to each other in a region of the at least one recess.

16. The flat air filter element according to claim 15 , wherein

the sealing element and the end edges extend parallel to each other along the first and the second lateral sides of the filter medium of the flat air filter element.

17. The flat air filter element according to claim 9 , wherein

the filter medium comprises an end edge bond,

wherein the sealing element and/or the end edges in a region of the at least one recess extend parallel to the end edge bond.

18. The flat air filter element according to claim 17 , wherein

the sealing element and/or the end edges extend parallel to the end edge bond along the entire end faces of the flat air filter element.

19. The flat air filter element according to claim 1 , wherein

the sealing element is manufactured of polyurethane.

20. The flat air filter element according to claim 19 , wherein

the sealing element is injection molded or foamed onto the filter medium.

21. An air filter comprising:

a filter housing comprising

a housing pot,

a housing cover to cover the housing pot, and

at least one closure element for closing the filter housing;

a flat air filter element arranged in the filter housing, the flat air filter element comprising:

a filter medium of cellulose material having an inflow face, an opposite outflow face and having an outer contour formed by a plurality of lateral sides which extend from the inflow face to the outflow face, the plurality of lateral sides including a first lateral side and an opposite lateral side;

wherein the filter medium is zig-zag folded forming zig-zag folds, the zig-zag folds extending across the filter medium in a direction from the first lateral side to the opposite lateral side, the zig-zag folds having a first end edge at the first lateral side of the filter medium and a second end edge at the opposite lateral side of the filter medium;

at least one recess formed into a respective one of the first or the second lateral sides of the filter medium such that the end edges of the zig-zag folds at the at least one recess are indented inwardly into the filter medium; and

a sealing element arranged at the filter medium and extending circumferentially about the filter medium on the plurality of lateral sides,

wherein the sealing element at the at least one recess is indented inwardly, following the respective lateral side into the recess;

wherein the flat air filter element is secured in the closed state of the filter housing by circumferentially clamping the sealing element between the housing pot and the housing cover;

wherein the sealing element comprises

a circumferentially extending holding groove,

wherein the housing pot or the housing cover engages the holding groove of the sealing element;

wherein the at least one closure element of the filter housing is arranged in a region of the at least one recess.

22. The air filter according to claim 21 , wherein

the closure element is arranged along or substantially along a linear continuation of the sealing element,

wherein the linear continuation bridges the at least one recess.

23. The air filter according to claim 21 , wherein

the closure element is a clamping spring or a screw or a clamping element.

24. The air filter according to claim 21 , wherein

the housing cover and the housing pot, at a housing side facing away from the at least one recess of the flat air filter element, are connected to each other by a hinge or a hook element.

25. The air filter according to claim 21 , wherein

the filter housing comprises

a plurality of said at least one closure element,

wherein the flat air filter element comprises

a plurality of said at least one recess,

wherein as many of said closure elements as of said recesses are provided.