FASTENING ELEMENT

Abstract

Fastening element (100) for a porous material, in particular for balsa wood, comprising a fastening head (1) configured to receive a torque in both rotational directions around a main axis (10) and a shank (2) that extends from the fastening head (1) and ends in a tip (3) at the end facing away from the fastening head. The shank (2) has an outer thread (4) along at least a section of its extension in a direction of the main axis (10), for screwing the fastening element (100) into the material.

Claims

1.-17. (canceled)

18. Fastening element for a porous material, in particular for balsa wood, comprising a fastening head configured to receive a torque in both rotational directions around a main axis, a shank extending from the fastening head and ending in a tip at the end facing away from the fastening head, wherein the shank has an outer thread along at least a section of its extension in a direction of the main axis, for screwing the fastening element into the material, wherein the ratio of the outer diameter (D) of the outer thread along at least a section of its extension in a direction of the main axis and the core diameter (d) of the outer thread is D/d>2.5, wherein the outer thread has a first thread flank facing the fastening head and a second thread flank facing away from the fastening head, wherein the outer thread extends until the tip and wherein in particular the outer diameter (D) of the outer thread decreases towards the tip, wherein the thread profile of the second thread flank has a kink such that a first angle (a1) between the first thread flank and a first section of the second thread flank is larger between the kink and a thread base than a second angle (a2) between the first thread flank and a second section of the second thread flank between the kink and a thread tip.

19. Fastening element according to claim 18, wherein the outer thread is a self-tapping thread, for forming the material when screwing the fastening element into the material.

20. Fastening element according to claim 18, wherein the core diameter (d) of the outer thread remains the same along the total length of the outer thread.

21. Fastening element according to claim 18, wherein an angle between the first thread flank and the thread base is constant along the whole thread profile of the first thread flank.

22. Fastening element according to claim 18, wherein the first angle (a1) is between 45° and 65°, in particular between 55° and 60° and/or wherein the second angle (a2) is between 20° and 40°, in particular between 30° and 35°.

23. Fastening element according to claim 18, with D/d>2.8.

24. Fastening element according to claim 18, wherein the outer diameter (D) of the outer thread is between 4 mm and 5 mm and/or wherein the core diameter (d) of the outer thread is between 1 mm and 2 mm.

25. Fastening element according to claim 18, wherein the thread pitch is between 1.5 mm and 2 mm.

26. Fastening element according to claim 18, wherein a length of the shank from an end facing the fastening head to the tip is between 10 mm and 25 mm.

27. Fastening element according to claim 18, comprising steel, aluminium, fiber-reinforced plastic, or a combination thereof.

28. Fastening element according to claim 18, wherein the reception of the torque of the fastening head is formed as a hexalobular socket.

29. Fastening element according to claim 18, wherein a diameter of the fastening head is larger than the outer diameter (D) of the outer thread.

30. Fastening element according to claim 18, wherein the ratio of the outer diameter D and the thread pitch s is 2<D/s<3, in particular is D/s=2.5.

31. Use of the fastening element according to claim 18 for screwing into the porous material.

32. Use according to claim 31 wherein the porous material is balsa wood, foamed plastic, or aluminium foam.

33. Use according to claim 31, wherein the porous material has a density p of ρ<1 g/cm.sup.3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Further embodiments, advantageous and applications of the invention result from the dependent claims and the following description with reference to the drawings. Wherein:

[0042] FIG. 1 is a front view of the fastening element according to an embodiment of the invention;

[0043] FIG. 2 is a side view of the fastening element from FIG. 1 according to an embodiment of the invention; and

[0044] FIG. 3 is a section view of a detail view of detail A of FIG. 1 according to an embodiment of the invention.

MODES FOR CARRYING OUT THE INVENTION

[0045] FIG. 1 shows an embodiment of the inventive fastening element 100 comprising a fastening head 1 and a shank 2 that extends from the fastening head 1 towards a main axis 10 and ends in a tip 3 at an end facing away from the fastening head 1.

[0046] A length of the shank 2 from one end of the shank 2 that extends from the fastening head 2 until the tip 3 is preferably about 22 mm or about 25 mm.

[0047] The shank 2 has an outer thread 4 along a section of its extension in a direction of the main axis 10. The outer thread 4 shown in the figure is a right-handed thread, this means that a front view on the thread shows the ridges ascending towards the right side and therefore the thread is screwed into the material in clockwise direction. In another embodiment, the outer thread 4 might also be a left-handed thread, being screwed into a material in a counterclockwise direction.

[0048] A ratio of the diameter D of the outer thread, in particular the largest diameter D′ of the outer thread 4, also known as nominal diameter, and the core diameter d of the thread 4 is D/d>2.5 or D/d>2.8 or 3>D/d>2.5 over at least a portion of the extension of the thread 4 along the shank 2 in a direction of the main axis 10.

[0049] The largest outer diameter D′ of the thread is preferably around 4.2 mm. The core diameter d of the thread is preferably around 1.5 mm.

[0050] A ratio of the largest outer diameter D′ and the thread pitch s is preferably 2.5.

[0051] The outer thread 4 has a first thread flank 41 facing towards the fastening head 1 and a second thread flank 42 facing away from the fastening head 1 in a direction towards the tip 3.

[0052] The section of the shank 2 that is formed as an outer thread 4 extends until the tip 3. The outer diameter D of the outer thread 4 decreases towards the tip and is smaller than the largest outer diameter D′ of the outer thread. The outer diameter D″ of the last ridge 31 of the outer thread 4 before the tip 3 might be 50% smaller than the largest outer diameter D′ of the thread 4.

[0053] In addition, a distance between the tip 3 and the particular ridge 32 of the outer thread 4 that is arranged closest to the tip 3 and has an outer diameter D that corresponds to the largest outer diameter D′ of the thread 4, the so called thread runout, might be around 3 mm.

[0054] The core diameter d remains the same along the total length of the outer thread 4.

[0055] A thread-free section 21 of the shank 2 extends between the fastening head 1 and the outer thread 4 in a direction of the main axis 10.

[0056] In particular, the thread-free section 21 might have a length of around 6 mm. In particular, a diameter of the thread-free section 21 might correspond more or less to the largest outer diameter D′ of the outer thread 4. In another embodiment, a diameter of the thread-free section 21 can also be smaller than the largest outer diameter D′ of the outer thread 4.

[0057] In particular, a diameter of the thread-free section 21 of the shank 2 is smaller than the diameter of the fastening head 1.

[0058] The fastening element might be rotated in both directions around the main axis. For the embodiment of the screw shown in FIG. 1 having a right-handed thread, the element is screwed into a material by a rotation in a clockwise direction, wherein a rotation in a counterclockwise direction enables the loosening of the screw out of the material.

[0059] FIG. 2 shows a side view of the fastening element 100 from FIG. 1. The fastening head 1 is shown, wherein the main axis 10 is directed into the drawing plane.

[0060] The fastening head is configured to receive a torque or a turning load respectively, such that the fastening element can be rotated around the main axis. Therefore, the fastening head has a reception for a tool that can apply a torque. In particular, the reception is formed as a hexalobular socket 11 as shown in FIG. 2.

[0061] FIG. 3 shows a cross section of the outer thread 4 of detail A of FIG. 1. The thread profile of the second thread flank 42 has a kink 43 that separates the second thread flank 42 in a first section 421 between thread base 33 and kink 43 and a second section 422 between kink 43 and thread tip 45. A first angle a1 between the first thread flank 41 and the first section 421 of the second thread flank 42 is larger than a second angle a2 between the first thread flank 41 and the second section 422 of the second thread flank 42. The first angle a1 is preferably around 40%, 50%, or 60% larger than the second angle a2. In particular, the first angle a1 is around 60° and the second angle a2 is around 30°.

[0062] The cross section of the outer thread 4 shown in FIG. 3 is preferably formed along the whole extension of the usable thread length of the outer thread. In the thread runouts of the outer thread 4, close to the tip 3 and close to the fastening head 1, the cross section of the thread profile might distinguish from the one in FIG. 3.

[0063] While the present application describes preferred embodiments of the invention, it is clearly mentioned, that the invention is not limited to those and can also be enabled in a different manner falling within the scope of the following claims.