Abstract
A fastening element is provided, in particular an expansion anchor, having a bolt and a retainer arranged on the bolt for introducing tensile forces into the bolt, the bolt having a first metal friction surface and the retaining element having a second metal friction surface, which is associated with the first friction surface. A coating in which particles, preferably hard particles, are embedded is arranged on at least one of the two friction surfaces.
Claims
1-10. (canceled)
11. A fastening element comprising a bolt; a retainer arranged on the bolt for introducing tensile forces into the bolt; the bolt having a metal first friction surface and the retainer having a metal second friction surface associated with the first friction surface; and a coating having embedded particles and arranged on at least one of the first or second friction surfaces.
12. The fastening element as recited in claim 11 wherein the retainer is an expansion body and the bolt has an expansion region for the expansion body.
13. The fastening element as recited in claim 11 wherein the retainer is a nut screwed to the bolt.
14. The fastening element as recited in claim 11 wherein the coating is arranged on the first friction surface.
15. The fastening element as recited in claim 11 wherein the coating has a lower hardness than the particles.
16. The fastening element as recited in claim 11 wherein the coating has a polymer.
17. The fastening element as recited in claim 11 wherein the Mohs hardness of the particles is greater than or equal to 6.
18. The fastening element as recited in claim 11 wherein at least a portion of all of the embedded particles is completely enclosed by the coating.
19. The fastening element as recited in claim 11 wherein the particles have a particle size D50 of between 0.1 m and 10 m.
20. The fastening element as recited in claim 11 wherein the particles have a particle size D50 between 0.7 m and 3.0 m.
21. The fastening element as recited in claim 11 wherein the particles have a particle size D50 of 1.5 m.
22. The fastening element as recited in claim 11 wherein the particles have a particle size D97 of between 0.6 m and 60 m.
23. The fastening element as recited in claim 11 wherein the particles have a particle size D97 of between of between 3.0 m and 12 m.
24. The fastening element as recited in claim 11 wherein the particles have a particle size D97 of 6.0 m.
25. The fastening element as recited in claim 11 wherein the coating has a layer thickness of between 0.5 m and 25 m
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The invention is explained in greater detail in the following with reference to preferred embodiments which are shown schematically in the accompanying drawings, it being possible to implement individual features of the embodiments shown in the following in principle individually or in any desired combination within the context of the invention. In the drawings, shown schematically:
[0023] FIG. 1 is a view, partially in longitudinal section, of a fastening element according to a first embodiment, which fastening element is set in a concrete substrate and is designed as an expansion anchor;
[0024] FIG. 2 is a detailed view of the fastening element from FIG. 1 at the point marked by a circle in FIG. 1, at the contact region between the expansion body and the bolt;
[0025] FIG. 3 is a side view of the bolt of the fastening element from FIG. 1;
[0026] FIG. 4 is a view, partially in longitudinal section, of a fastening element according to a further embodiment, which fastening element is set in a concrete substrate and is designed as an expansion anchor;
[0027] FIG. 5 is a detailed view of the fastening element from FIG. 4 at the point marked by a circle in FIG. 4, at the contact region between the expansion body and the bolt;
[0028] FIG. 6 is a view, partially in longitudinal section, of a fastening element according to a third embodiment, which fastening element is set in a concrete substrate and designed as an expansion anchor;
[0029] FIG. 7 is a detailed view of the fastening element from FIG. 6 at the point marked by a circle in FIG. 6, at the contact region between the expansion body and the bolt; and
[0030] FIGS. 8 and 9 are schematic views of the gap between the two friction surfaces of the aforementioned embodiments, before the friction process in FIG. 8 and during the friction process in FIG. 9.
DETAILED DESCRIPTION
[0031] FIGS. 1 to 3 show a first embodiment of a fastening element according to the invention. As shown in particular in FIG. 1, the fastening element is designed as an expansion anchor and comprises a bolt 10 and an expansion body 20 which is designed as an expansion sleeve and encloses the bolt 10. The bolt 10 has a neck region 11 having a constant cross section and an expansion region 12 for the expansion body 20 following the neck region 11 in the front end region of the bolt 10, at which expansion region the surface of the bolt converges toward the rear, preferably conically. The expansion region 12 forms a wedge, which can push the expansion body 20 radially outward in the event of axial tension in the bolt. On the side of the neck region 11 facing away from the expansion region 12, the bolt 10 has a stop 17, which is designed for example as an annular shoulder, for the expansion body 20. The bolt 10, at the rear end region thereof opposite the expansion region 12, is provided with an external thread 18, to which the bolt 10 is screwed by means of a nut 70.
[0032] During installation of the fastening element, the bolt 10 is pushed, with the expansion region 12 at the front, into a borehole in the substrate 5 from FIG. 1, against the pull-out direction 101 parallel to the longitudinal axis 100 of the bolt 10. Due to the stop 17, the expansion body 20 which is designed as an expansion sleeve is also inserted into the borehole. The bolt 10 is then pulled out slightly more from the borehole in the pull-out direction 101 extending parallel to the longitudinal axis 100, for example by tightening the nut 70. The expansion body 20 which is designed as an expansion sleeve remains behind due to the friction thereof against the borehole wall, and the bolt 10 is displaced relative to the expansion body 20. During said displacement, the expansion region 12 of the bolt 10 penetrates ever deeper into the expansion body 20 such that the expansion body 20 is radially expanded by the expansion region 12 and is pressed against the wall of the borehole, as a result of which the fastening element is anchored in the substrate 5. Tensile forces can then be introduced into the bolt 10 by means of the expansion body 20, which tensile forces, as constraining forces, axially retain the bolt 10 in the borehole. The expansion body 20 thus forms a retaining element. The installed state of the fastening element in which said element is anchored in the substrate 5 is shown in FIG. 1. An attachment 6 can be fixed to the substrate 5 by means of the nut 70.
[0033] It should be noted that the stop 17 is optional and that, for example, a longer expansion body 20 can be provided which extends up to the borehole mouth and is driven from there into the borehole, for example by means of the nut 70.
[0034] The bolt 10 has, in the expansion region 12 thereof, a first friction surface 19 and the expansion body 20 has a second friction surface 29, the expansion body 20 and the bolt 10 rubbing against one another on the two friction surfaces 19 and 29 during installation of the fastening element, in particular when the expansion body 12 is retracted into the expansion body 20.
[0035] As can be seen in particular in FIGS. 2 and 3, the first friction surface 19, i.e. the friction surface 19 associated with the bolt 10, comprises a coating 60 in which particles 61 are embedded, and the effect of said coating will be explained in detail below in connection with FIGS. 8 and 9. As FIG. 3 shows, the coating 60 (shown schematically enlarged in FIG. 3 with dashed lines) can also extend beyond the first friction surface 19 into the neck region 11, or otherwise (not shown) extend onto the entire bolt 10, which can simplify production.
[0036] Another embodiment of a fastening element is shown in FIGS. 4 and 5. In contrast to the fastening element of FIGS. 1 to 3, in which the bolt is made in one piece and in particular the expansion region 12 of said bolt is fixedly connected to the rest of the bolt 10, the bolt 10 of the embodiment of FIGS. 4 and 5 comprises an anchor rod 15 and a wedge body 16 that is separate from the anchor rod 15, the expansion region 12 for the expansion body 20 being formed on the wedge body 16. The wedge body 16 having the expansion region 12 comprises an internal thread which corresponds to an external thread on the anchor rod 15 of the bolt 10. In addition, in the fastening element of FIGS. 4 and 5, the expansion body 20, which is designed as an expansion sleeve and may also be made of multiple parts, extends up to the borehole mouth, and at the rear end region of the bolt 10 a widened head 88 having an external polygonal structure is preferably non-rotatably mounted on the anchor rod 15.
[0037] In order to set the fastening element of FIGS. 4 and 5, the anchor rod 15 is rotated, preferably by means of the head 88, about the longitudinal axis 100. The corresponding threads convert said rotational movement of the anchor rod 15 into an axial movement of the wedge body 16 having the expansion region 12 relative to the anchor rod 15 and thus relative to the expansion body 20, resulting in the retraction of the expansion region 12 into the expansion body 20 and in the anchoring of the fastening element. Once again, the expansion body therefore forms a retaining element by means of which constraining forces in the form of tensile forces can be introduced into the bolt.
[0038] Also in the fastening element of FIGS. 4 and 5, the bolt 10, at a first friction surface 19 arranged in the expansion region 12 of said bolt, comprises a coating 60 having particles 61, which coating is opposite a second friction surface 29 formed on the expansion body 20, the expansion body 20 and the bolt 10 rubbing against one another on the two friction surfaces 19 and 29 during installation of the fastening element, in particular when the expansion region 12 is retracted into the expansion body 20. The effect of the coating is explained below in connection with FIGS. 8 and 9.
[0039] FIGS. 6 and 7 show a further embodiment of a fastening element. The fastening element of FIGS. 6 and 7 substantially corresponds to the fastening element of FIGS. 1 to 3, such that reference may be made to the associated description. In contrast to the embodiment of FIGS. 1 to 3, in the embodiment of FIGS. 6 and 7 the second friction surface 79 is on the nut 70 and the first friction surface 19 which corresponds to the second friction surface 79 is on the external thread 18 of the bolt associated with the nut 70. Accordingly, the coating 60 according to the invention having the particles 61 is arranged on the nut 70 or/and on the external thread 18 of the bolt 10. The nut 70 can therefore form a retaining element for introducing tensile force into the bolt 10. The effect of the coating 60 in which particles 61 are embedded is again explained in detail below, in connection with FIGS. 8 and 9.
[0040] Embodiments are also conceivable in which a coating according to the invention having particles is located both between the nut and the bolt and between the expansion element and, i.e. in particular a combination of the embodiment in FIGS. 1 to 3 with the embodiment of FIGS. 6 and 7.
[0041] FIGS. 8 and 9 illustrate schematically the mechanism acting on the friction surfaces 19 and 29 or 79 of the aforementioned embodiments. By way of example, the coating 60 here is a relatively soft polymer matrix having a low coefficient of friction, and the particles 61, in contrast, have a significantly higher hardness. At low contact pressures between the friction surfaces 19 and 29, which pressures are present at the beginning of the installation of the fastening element, the friction is determined by thecomparatively lowfriction of the polymeric coating 60. At high pressures and/or longer friction distances, which may be present during progressive installation or under particular loads of the fastening element, in particular cyclic loads, the relatively poorly load-bearing coating 60 is removed, destroyed or/and delaminated. However, the comparatively hard and abrasion-resistant particles 61 remain between the friction surfaces 19 on one side and 29 or 79 on the other side, and can henceforth determine the frictional properties. In particular, the particles 61 can effectively counteract seizure and/or cold-welding of the friction surfaces 19 on one side and 29 or 79 on the other side and/or effect a targeted increase in friction under high load, in particular if the particles 61 are relatively hard.
[0042] In particular, a colloidal dispersion film can be provided by the introduction according to the invention of hard particles 61 into the coating 60. As the stress increases, the matrix-forming polymeric coating 60 may collapse, the hard particles 61 remaining between the metal friction surfaces 19 on one side and 29 or 79 on the other side, forming a hard separation layer between said friction surfaces.
