Abstract
An expansion anchor, including at least one anchor body as a first element and at least one bolt as a second element, wherein the bolt has an expansion body, which pushes the anchor body radially outward when the expansion body is moved in an extraction direction in relation to the anchor body is provided. A double coating having an inner layer and an outer layer covering the inner layer is provided on one of the two elements in an area of contact with the other element, wherein the outer layer has a coefficient of friction with respect to the other element that is greater than a coefficient of friction of the inner layer with respect to the other element.
Claims
1. An expansion anchor comprising: at least one anchor body as a first element; and at least one bolt as a second element, the bolt including an expansion body pushing the anchor body radially outwardly when the expansion body is moved in an extraction direction relative to the anchor body; a double coating having an inner layer and an outer layer covering the inner layer is provided on one of the first and second elements in an area of contact with the other of the first and second elements, the outer layer having a coefficient of friction (.sub.2) with respect to the other element greater than a coefficient of friction (.sub.1) of the inner layer with respect to the other element.
2. The expansion anchor as recited in claim 1 wherein the coefficient of friction (.sub.2) of the outer layer with respect to the other element is at least 20%, 50%, or 100% greater than the coefficient of friction (.sub.1) of the inner layer with respect to the other element.
3. The expansion anchor as recited in claim 2 wherein the coefficient of friction (.sub.2) of the outer layer with respect to the other element is at least 50% greater than the coefficient of friction (.sub.1) of the inner layer with respect to the other element.
4. The expansion anchor as recited in claim 3 wherein the coefficient of friction (.sub.2) of the outer layer with respect to the other element is at least 100% greater than the coefficient of friction (.sub.1) of the inner layer (61) with respect to the other element.
5. The expansion anchor as recited in claim 1 wherein the double coating is provided at least on the expansion body.
6. The expansion anchor as recited in claim 1 wherein the anchor body is an expansion sleeve enclosing the bolt at least in areas, and the expansion body is an expansion cone.
7. The expansion anchor as recited in claim 1 wherein the expansion anchor is an expansion anchor of the bolt type.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The present invention is explained in greater detail below with reference to preferred exemplary embodiments that are schematically illustrated in the appended figures; within the scope of the present invention, individual features of the exemplary embodiments described below may in principle be implemented alone or in any arbitrary combination.
(2) FIG. 1 shows a partial longitudinal sectional view of an expansion anchor according to the present invention that is set in a concrete substrate, according to a first specific embodiment;
(3) FIG. 2 shows a detailed view of the expansion anchor from FIG. 1;
(4) FIG. 3 shows a partial longitudinal sectional view of the bolt of an expansion anchor in a modification of the specific embodiment in FIGS. 1 and 2;
(5) FIG. 4 shows a partial longitudinal sectional view of an expansion anchor according to the present invention that is set in a concrete substrate, according to another specific embodiment; and
(6) FIG. 5 shows a detailed view of the expansion anchor from FIG. 4.
(7) Identical or functionally equivalent elements are denoted by the same reference numerals in the figures.
DETAILED DESCRIPTION
(8) FIGS. 1 and 2 show a first exemplary embodiment of an expansion anchor according to the present invention. As shown in particular in FIG. 1, the expansion anchor includes a bolt 10 and a anchor body 20, designed as an expansion sleeve, which encloses bolt 10. Bolt 10 includes a neck area 11 having a constant cross section, and, adjoining neck area 11 in the front end area of bolt 10, includes an expansion body 12, designed as an expansion cone, for anchor body 20, at which the surface is designed as an inclined surface 13. Inclined surface 13 has a rotationally symmetrical design here. Due to inclined surface 13, bolt 10 widens at expansion body 12, starting from neck area 11 toward the front end of the bolt. On the side of neck area 11 facing away from expansion body 12, bolt 10 includes a stop 17, designed as a ring shoulder, for example, for anchor body 20, which is designed as an expansion sleeve. At its rear end area facing opposite from expansion body 12, bolt 10 is provided with an external thread 18 for a nut 8.
(9) During setting of the expansion anchor, bolt 10 together with expansion body 12 is pushed forward into a borehole in substrate 5 from FIG. 1 in the direction opposite extraction direction 101, in parallel to longitudinal axis 100 of bolt 10. Due to stop 17, anchor body 20 which is designed as an expansion sleeve is also introduced into the borehole. Bolt 10 is then pulled slightly farther out of the borehole in extraction direction 101 in parallel to longitudinal axis 100, for example by tightening nut 8. Due to its friction with the borehole wall, anchor body 20 which is designed as an expansion sleeve remains behind, resulting in a displacement of bolt 10 relative to anchor body 20. During this displacement, expansion body 12 of bolt 10 penetrates increasingly more deeply into the anchor body 20 in such a way that anchor body 20 is radially widened by expansion body 12 and is pressed against the wall of the borehole. The expansion anchor is fixed in substrate 5 as a result of this mechanism. The set state of the expansion anchor, in which it is fixed in substrate 5, is shown in FIG. 1. A mounting part 6 may be fixed to the substrate 5 with the aid of nut 8.
(10) As is particularly apparent in FIG. 2, expansion body 12 has a double coating made up of an inner layer 61 and an outer layer 62 in an area of contact with anchor body 20 formed on its inclined surface 13, inner layer 61 being situated between outer layer 62 and expansion body 12 which has the two layers 61, 62, in particular in an integrally joined manner. The coefficient of friction, in particular static coefficient of friction, .sub.2 of outer layer 62 with respect to adjoining anchor body 20 is greater than the coefficient of friction, in particular static coefficient of friction, .sub.1 of inner layer 61 with respect to adjoining anchor body 20; i.e., .sub.2>.sub.1. In a simple static load situation, bolt 10 together with expansion body 12 rubs against outer layer 62 on anchor body 20, so that comparatively high coefficient of friction .sub.2 acts, and high static extraction loads may thus be achieved. In contrast, in a dynamic load situation, outer layer 62 of bolt 10 may be rubbed off. From this point on, expansion body 12 then rubs against inner layer 61 on anchor body 20, so that now, comparatively low coefficient of friction .sub.1 acts, and effective sliding of expansion body 12 back and forth in anchor body 20 is made possible.
(11) The double coating, made up of layers 61 and 62, on expansion body 12 has been described in the exemplary embodiment in FIGS. 1 and 2. As shown in FIG. 3, however, the double coating having layers 61 and 62, schematically illustrated with dashed lines in greatly enlarged form in FIG. 3, may additionally extend onto neck area 11.
(12) The expansion anchor in the exemplary embodiments in FIGS. 1 through 3 is a so-called bolt type. Another exemplary embodiment, in which the expansion anchor is designed as a so-called sleeve type, is shown in FIGS. 4 and 5. In contrast to the expansion anchors from FIGS. 1 through 3, in which expansion body 12 is axially fixedly fastened to the remainder of bolt 10 and in particular is designed in one piece with the remainder of bolt 10, bolt 10 in the exemplary embodiment in FIGS. 4 and 5 includes an anchor rod 15 that is separate from expansion body 12; i.e., anchor rod 15 and expansion body 12 are two separate parts. Expansion body 12 with inclined surface 13 has an internal thread that corresponds to an external thread on anchor rod 15 of bolt 10. In addition, in the expansion anchor in FIGS. 4 and 5, anchor body 20, which is designed as an expansion sleeve and which may also have a multipart design, extends to the mouth of the borehole, and a widened head 88 is rotatably fixedly situated on anchor rod 15 at the rear end area of bolt 10.
(13) For setting the expansion anchor in FIGS. 4 and 5, anchor rod 15 is set in rotation about longitudinal axis 100, preferably via head 88. The corresponding threads convert this rotational movement of anchor rod 15 into an axial movement of expansion body 12 relative to anchor rod 15 and thus relative to anchor body 20, resulting in retraction of expansion body 12 with inclined surface 13 into anchor body 20.
(14) Also in the expansion anchor in FIGS. 4 and 5, in an area of contact with anchor body 20 formed on inclined surface 13, expansion body 12 of bolt 10 has a double coating made up of an inner layer 61 and an outer layer 62, coefficient of friction .sub.2 of outer layer 62 with respect to adjoining anchor body 20 being greater than coefficient of friction .sub.1 of inner layer 61 with respect to adjoining anchor body 20; i.e., .sub.2>.sub.1, so that particularly good static and dynamic properties may also be achieved in this way.
