EXPANSION DOWEL

Description

[0001] The invention relates to an expansion anchor having the features of the preamble of claim 1.

[0002] Expansion anchors are well-known. They are expanded by screwing in an expansion screw or inserting another, usually pin-shaped, expansion element, and can then be anchored in an anchor hole.

[0003] Utility model DE 1 944 573 U discloses an expansion anchor which, beginning at a front end in the direction of insertion into an anchor hole, is divided by a longitudinal slot penetrating the expansion anchor in an axial plane into two expansion tabs extending over approximately two-thirds of the length of the expansion anchor. By screwing an expansion screw into the expansion anchor and between the two expansion tabs, the expansion tabs can be pushed apart, which can be interpreted as spreading the expansion anchor, allowing the expansion anchor to be anchored in an anchor hole. Beginning at a rear end of the expansion tabs, the known expansion anchor has two oppositely arranged cantilever fingers which end in front of a rear end of the expansion anchor which is remote in the direction of insertion into an anchor hole. Front ends of the cantilever fingers merge integrally into the expansion anchor and free rear ends of the cantilever fingers project radially outwards over a surface of the expansion anchor.Rib-shaped projections extend radially inward from the inside of the cantilever fingers, extending over approximately the rear half of the cantilever fingers, into a screw channel of the expansion anchor, so that the cantilever fingers can be pushed apart radially, i.e., expanded, by screwing in the expansion screw. The cantilever fingers of the known expansion anchor expand in the same direction as its expansion tabs.

[0004] The object of the invention is to propose an expansion anchor that can be expanded near a rear end and is suitable for expansion screws with different thread diameters and thread core diameters. Preferably, the expansion anchor should also be expandable in other segments of the expansion anchor, in particular in a front segment.

[0005] This object is achieved according to the invention by the features of claim 1. The expansion anchor according to the invention has: a front dowel end, a rear dowel end, a dowel axis, and a sleeve-like dowel body that is coaxial with the dowel axis and encloses a screw channel coaxial with the dowel axis. Furthermore, the expansion anchor according to the invention has one and preferably several cantilever spring elements that are arranged evenly or irregularly over a circumference of the expansion anchor, for example, in each case in an opening in a peripheral wall of the dowel body. The cantilever spring element is, for example, pin-shaped with a square or round cross-section, or strip-shaped. A front end of the cantilever spring element facing the front dowel end is rigid with the expansion anchor; in particular, the front end of the cantilever spring element merges integrally into the expansion anchor or the sleeve-like dowel body.A rear end of the cantilever spring element, facing the rear dowel end, is free and movable radially to the dowel axis by bending the cantilever spring element. The invention does not preclude mobility of the cantilever spring element in other directions. From front to back, i.e. from the direction of the front dowel end towards the rear dowel end, the cantilever spring element extends diagonally outwards at an acute angle to the dowel axis. This applies in any case to an outer side of the cantilever spring element facing away from the dowel axis. As a result, the rear end of the cantilever spring element is located further outwards than the front end, i.e. the outer side of the cantilever spring element facing away from the dowel axis has a greater radial distance from the dowel axis at the rear end of the cantilever spring element than at the front end of the cantilever spring element.If the cantilever spring element is undeformed and, in particular, not expanded, it projects radially outward beyond a surface of the anchor body that surrounds the cantilever spring element. If the expansion anchor is inserted into an anchor hole that has the same diameter as the anchor body, a wall of the anchor hole pushes the cantilever spring element radially inward.

[0006] According to the invention, in a front section adjoining the front end of the cantilever spring element, the cantilever spring element has a greater flexural rigidity radially to the dowel axis than in a rear section adjoining the front section of the cantilever spring element toward the rear end of the cantilever spring element. "Greater flexural rigidity" means that a given bending moment about an axis tangential to the dowel axis bends the cantilever spring element less in the radial direction toward the dowel axis in its front section than in its rear section. Bending rigidity refers to an axial area moment of inertia with respect to the bending of the cantilever spring element in the radial direction toward the dowel axis or with respect to the axis of the cantilever spring element tangential to the dowel axis.The cantilever spring element of the expansion anchor according to the invention is stiffer in its front section and is expanded more by an expansion screw screwed into the expansion anchor than in the rear section of the cantilever spring element. The less rigid rear section of the cantilever spring element conforms better to the wall of the anchor hole, thereby improving the hold of the expansion anchor in the anchor hole caused by the expanded cantilever spring element.

[0007] The cantilever spring element is arranged in particular in an opening in a peripheral wall of the sleeve-like dowel body, which extends through the peripheral wall of the dowel body from an outer side facing away from the dowel axis to an inner side facing the dowel axis and thus to the screw channel. In this embodiment of the invention, the front end of the cantilever spring element merges into the dowel body at a front edge of the opening facing the front end of the dowel.

[0008] The cantilever spring element is particularly intended for expanding the expansion anchor in a rear segment of the expansion anchor. The cantilever spring element is therefore located in particular in a rear segment of the expansion anchor, i.e., in a rear half and in particular in a rear third of a length of the expansion anchor, wherein the length is an extension of the expansion anchor in the direction of the anchor axis. Preferably, the expansion anchor can also be expanded outside the rear segment.

[0009] A distance of the rear end of the cantilever spring element from the rear end of the dowel is preferably shorter than an extension of the cantilever spring element in the direction of the dowel axis, or shorter than an outer diameter or half of the outer diameter of the dowel body at the rear end of the cantilever spring element.

[0010] One embodiment of the invention provides a threaded engagement element for engaging a screw thread of the expansion screw, which is or is screwed into the screw channel, which projects from an inner side of the cantilever spring element facing the dowel axis in the direction of the dowel axis. The threaded engagement element projects into the screw thread between two adjacent threads and holds the expansion screw against falling out of the expansion anchor, for example in the case of overhead installation, once the expansion screw has only been inserted a short distance into the expansion anchor. The cantilever spring element can also have several threaded engagement elements that are offset from one another in the direction of the dowel axis. It is possible to insert the expansion anchor into a drilled hole without the expansion screw to be screwed in and only then to bring the expansion screw into engagement with the threaded engagement element, thereby securing it against falling out.This is possible because the threaded engagement element has a certain degree of elasticity. It is also possible to bring the expansion screw and expansion anchor together before inserting them into the drilled hole. Only when the expansion anchor is subsequently inserted into the drilled hole does the threaded engagement element come into contact with the thread of the expansion screw, securing it from falling out.

[0011] One embodiment of the invention provides for a thickness of the cantilever spring element that decreases radially to the dowel axis in the direction from the front end toward the rear end, in the rear section of the cantilever spring element, which has a lower flexural rigidity radially to the dowel axis than the front section of the cantilever spring element. Due to the decreasing thickness in the rear section of the cantilever spring element, the flexural rigidity in the rear section of the cantilever spring element decreases from the direction of the front end toward the rear end of the cantilever spring element.

[0012] One embodiment of the invention provides a support on the inner side of the cantilever spring element facing the dowel axis, which protrudes inwards in the direction of the dowel axis from the inner side of the cantilever spring element. Viewed in a longitudinal direction of the cantilever spring element, the support is located in a section adjoining the front end of the cantilever spring element towards the rear end. The support is supported radially on the expansion screw when the expansion screw is screwed into the screw channel of the expansion dowel. When the expansion screw is or is screwed into the screw channel of the expansion dowel, the expansion screw presses the cantilever spring element radially outwards via the support in the section adjoining the front end of the cantilever spring element towards the rear end, thereby achieving a firm contact of the cantilever spring element with the wall of the anchor hole.The support can act, at least slightly, as a kind of "bending point" or "bending area" for the cantilever spring element, which is formed "close" to the front end of the cantilever spring element. The expansion screw pushes the support radially outward and presses the cantilever spring element firmly against the anchor hole at this point. The area where the cantilever spring element is connected to the anchor body can also be slightly forced or bent outward toward the wall. The support ensures that the cantilever spring element is pressed firmly against the wall of the anchor hole at the height of the support by screwing an expansion screw into the expansion anchor. This provides significantly improved holding values ​​compared to the expansion anchor disclosed in utility model DE 1 944 573 U, which does not have such a support, since the cantilever spring element is pressed against the wall by the expansion screw essentially over its entire length.In the case of the expansion anchor of the state of the art, the pressing is essentially concentrated only on the area in which the rib-shaped projections mentioned above are formed.

[0013] Tangentially to the dowel axis, the support is preferably narrower than the cantilever spring element in an area radially adjacent to the outside of the support; in particular, the cantilever spring element has a T-cross section in the area of ​​the support.

[0014] When the cantilever spring element is undeformed, i.e., not expanded, the inner side or support surface of the column facing the dowel axis runs parallel to the dowel axis. When the expansion screw is or will be screwed into the expansion anchor, the screw thread or the core of the screw thread of the expansion screw presses against the inner side or support surface of the column.

[0015] The expansion anchor according to the invention preferably has more than one cantilever spring element, which are distributed evenly or irregularly around the circumference of the expansion anchor or the sleeve-like anchor body. In particular, the expansion anchor has two identically designed cantilever spring elements arranged opposite each other with respect to the anchor axis.

[0016] The features and combinations of features, embodiments and configurations of the invention mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or drawn in a figure can be used not only in the respective combination specified or drawn, but also in principle any other combinations or individually. Embodiments of the invention are possible which do not have all the features of a dependent claim. Individual features of a claim can also be replaced by other disclosed features or combinations of features. Embodiments of the invention which do not have all the features of the exemplary embodiment, but basically any part of the identified features of the exemplary embodiment, are possible.

[0017] The invention is explained in more detail below with reference to an embodiment illustrated in the drawing. In the drawings: Figure 1 is a perspective view of an expansion anchor according to the invention; Figure 2 is a side view of the expansion anchor from Figure 1 ; Figure 3a opposite Figure 2 Side view of the expansion anchor rotated by 90° Figure 1 ; Figure 4 an axial section of the expansion anchor from Figure 1 with the same viewing direction as in Figure 2 ; Figure 5 an enlarged detail according to arrow V in Figure 2 ; and Figure 6 an enlarged view of a rear segment of the expansion anchor from Figure 1 in a Figure 4 corresponding axial cut when screwing in an expansion screw.

[0018] The expansion anchor 1 according to the invention shown in the drawing is—in the exemplary embodiment—made in one piece by injection molding from plastic. It has a front anchor end 2, a rear anchor end 3, a anchor axis 4, and a sleeve-like anchor body 5 coaxial with the anchor axis 4, which encloses a screw channel 6 coaxial with the anchor axis 4. The anchor body 5 and the screw channel 6 are provided for screwing an expansion screw 7 through the rear anchor end 3 to expand the expansion anchor 1. "Front anchor end 2" refers to the end with which the expansion anchor 1 is inserted into an anchor hole. "Rear anchor end 3" refers to the opposite end, remote from the anchor hole.

[0019] In its dowel body 5, the expansion anchor 1 has four longitudinal slots 8 running parallel to the dowel axis 4, which - in the exemplary embodiment - end at a distance from the front and rear dowel ends 2, 3, i.e., the longitudinal slots 8 are closed at both ends. The longitudinal slots 8 define an expansion range of the expansion anchor 1, in which the expansion anchor 1 or its dowel body 5 can be expanded by screwing the expansion screw 7 into the screw channel 6 in order to fasten it in an anchor hole (not shown). The expansion of the expansion anchor 1 by screwing the expansion screw 7 into the screw channel 6 can also be understood as expanding the expansion anchor 1, and the fastening of the expansion anchor 1 by expanding it in the anchor hole can be understood as anchoring the expansion anchor 1 in the anchor hole. A different number, arrangement and / or shape of slots instead of the described and illustrated longitudinal slots 8 is possible (not shown).

[0020] In a rear segment, which extends over no more than one half and preferably no more than one third of the length of the expansion anchor 1 in the direction of the anchor axis 4, the expansion anchor 1 has two cantilever spring elements 9 arranged opposite one another. In the exemplary embodiment, the cantilever spring elements 9 are rod-shaped with a small bend 10 and have a rectangular cross-section with - in the exemplary embodiment - a constant width in the tangential direction to the anchor axis 4 and a thickness that varies radially to the anchor axis 4 over the length of the cantilever spring elements 9. A distance d of the rear ends 11 of the cantilever spring elements 9 facing the rear anchor end 3 from the rear anchor end 3 is, in the exemplary embodiment, no greater than one half of the outer diameter of the anchor body 5.

[0021] The cantilever spring elements 9 are arranged in openings 12 of the dowel body 5 of the expansion dowel 1 according to the invention, wherein front ends 13 of the cantilever spring elements 9 facing the front dowel end 2 merge integrally into the dowel body 5 at a front edge of the openings 12. Starting from their front ends 13 in the direction of the rear ends 11, the cantilever spring elements 9 extend obliquely outwards at an acute angle to the dowel axis 4, i.e. a radial distance of the cantilever spring elements 9 from the dowel axis 4 increases in the direction of the rear ends 11 of the cantilever spring elements 9, wherein the angle of the cantilever spring elements 9 to the dowel axis 4 decreases at the bend 10 of the cantilever spring elements 9. The rear ends 11 of the cantilever spring elements 9 are free, i.e. not connected to the dowel body 5, so that they can be moved inwards and outwards radially to the dowel axis 4 by elastic bending of the cantilever spring elements 9.Due to their course obliquely outwards in the direction of their rear ends 11 relative to the dowel axis 4, the cantilever spring elements 9 and their rear ends 11 project radially outwards over a lateral surface of the dowel body 5.

[0022] From the bend 10 to the rear end 11, the thickness D of the cantilever spring elements 9 decreases radially to the dowel axis 4, whereby the flexural rigidity of the cantilever spring elements 9 also decreases in a rear section 14 of the cantilever spring elements 9. The flexural rigidity is an axial area moment of inertia of the cantilever spring elements 9 with respect to a bend or a bending moment about an axis tangential to the dowel axis 4. In a front section 15, the flexural rigidity or the axial area moment of inertia of the cantilever spring elements 9 with respect to the bend or the bending moment about the axis tangential to the dowel axis 4 is greater.In the exemplary embodiment, the front section 15 with the greater flexural rigidity extends from the front end 13 to the bend 10 and the rear section 14 with the lower flexural rigidity or the flexural rigidity which decreases towards the rear end 11 of the cantilever spring elements 9 extends from the bend 10 to the rear end 11 of the cantilever spring elements 9. Other configurations are possible, wherein the flexural rigidity in a front section 15 of the cantilever spring elements 9 adjoining the front ends 13 of the cantilever spring elements 9 is greater than the flexural rigidity in a rear section 14 which adjoins the front section 15 or is in any case closer to the rear ends 11 of the cantilever spring elements 9.

[0023] In the front section 15, the cantilever spring elements 9 have a support 16 which projects inwards from the inner sides 17 facing the dowel axis 4 in the direction of the dowel axis 4 from the cantilever spring elements 9. The supports 16 begin at the front ends 13 of the cantilever spring elements 9 and, in the exemplary embodiment, extend over approximately one-third to one-half the length of the front sections 15 of the cantilever spring elements 9. Longer or possibly shorter supports 16 are possible. Tangentially to the dowel axis 4, the supports 16 are narrower than the cantilever spring elements 9 outside the supports 16, so that the cantilever spring elements 9 have a T-cross section in the area of ​​the supports 16, which Figure 5into the cantilever spring element 9. The supports 16 further increase the flexural rigidity of the cantilever spring elements 9 in the front section 15 and ensure that the expansion screw 7 presses the respective cantilever spring element 9 firmly against the anchor hole at the height of the respective support 16. The area of ​​the respective front end 13, in which the cantilever spring elements 9 are connected to the dowel body 5, is also forced at least slightly towards the anchor hole, since the support 16 acts slightly as a "bending point," or more precisely, a "bending area" for the respective cantilever spring element 9. Support surfaces 18 of the supports 16 facing the dowel axis 4 run parallel or approximately parallel to the dowel axis 4 when the cantilever spring elements 9 are undeformed, i.e., not elastically bent inwards or outwards, or in any other direction.

[0024] In the rear section 14, the cantilever spring elements 9 have threaded engagement elements 19, which in the exemplary embodiment are tooth-like, projecting from their inner sides 17 in the direction of the dowel axis 4.

[0025] The invention is not limited to the described cantilever spring elements 9. At least theoretically, an expansion anchor with only one cantilever spring element or an expansion anchor with more than two cantilever spring elements, which can be distributed evenly or unevenly around the circumference of the expansion anchor (not shown), is possible. The shape and arrangement of the cantilever spring elements are also not limited to the illustrated and described embodiment of the invention.

[0026] For anchoring in a not shown, for example drilled, cylindrical anchor hole in an anchor base such as a building wall or a ceiling, the expansion anchor 1 is inserted into the anchor hole with its front anchor end 2 leading until it is completely located in the anchor hole or in the anchor base. A wall of the anchor hole presses the cantilever spring elements 9, which originally protrude radially outwards from the anchor body 5 of the expansion anchor 1, radially inwards in the direction of the anchor axis 4, as Figure 6 To spread it, as shown in Figure 6As shown, the expansion screw 7 is inserted from the rear end 3 of the expansion anchor 1 into the screw channel 6. The threaded engagement elements 19 projecting inwards from the cantilever spring elements 9 engage with a screw thread 20 of the expansion screw 7 in such a way that, for example, in the case of overhead installation, the expansion screw 7 is held against falling out of the expansion anchor 1.

[0027] When the expansion screw 7 is screwed into the screw channel 6 of the expansion anchor 1, the expansion screw 7 radially pushes the cantilever spring elements 9, which are supported by the threaded engagement elements 19 and the supports 16 on the expansion screw 7, apart, which can also be interpreted as spreading the cantilever elements 9. The expansion screw 7 pushes the cantilever elements 9 outwards against the hole wall of the anchor hole. In doing so, the supports 16, which rest against the expansion screw 7 with their support surfaces 18, cause the cantilever elements 9 to spread significantly. Due to the lower flexural rigidity in the rear sections 14 of the cantilever spring elements 9, the rear sections 14 of the cantilever spring elements 9 adapt to expansion screws 7 with different diameters and form themselves to the hole wall of the anchor hole.This, in conjunction with the strong expansion due to the greater bending stiffness in the front sections 15 of the cantilever spring elements 9, results in a good hold, i.e. a good anchoring of the expanded expansion dowel 1 in the anchor hole.

[0028] In a front segment of the expansion anchor 1 from the front end 2 of the expansion anchor to the front ends 13 of the cantilever spring elements 9, the expansion screw 7 widens or spreads the anchor body 5 of the expansion anchor 1, whereby the expansion anchor 1 is or becomes anchored in the anchor hole in this front segment as well. List of reference symbols Expansion dowel

[0029] dDistance DDickness Cantilever spring element 9 1Expansion dowel 2Front dowel end 3Rear dowel end 4Dowel axis 5Dowel body 6Screw channel 7Expansion screw 8Longitudinal slot 9Cantilever spring element 10Angled section 11Rear end of cantilever spring element 9 12Opening 13Front end of cantilever spring element 9 14Rear section 15Front section 16Support 17Inside 18Support surface 19Threaded engagement element 20Screw thread

Claims

1. Expansion dowel (1), with a front end of the dowel (2) and with a rear end of the dowel (3), with a dowel axis (4), with a sleeve-like dowel body (5) which is coaxial with the dowel axis (4) and which encloses a screw channel (6), coaxial with the dowel axis (4), for screwing in an expansion screw (7) for expanding the expansion dowel (1) and with a cantilever spring element (9) which is arranged obliquely outwards from the direction of the front end of the dowel (2) in the direction of the rear end of the dowel (3) at an acute angle to the dowel axis (4), the front end (13) of which, which is closer to the front end of the dowel (2), is rigidly connected to the dowel body (5) and the rear end (11) of which, which is closer to the rear end of the dowel (3), is connected to the dowel body (5) by means of free end (11) is movable radially to the dowel axis (4) by bending the cantilever spring element (9) and, when the cantilever spring element (9) is not deformed, projects radially outwards beyond a lateral surface of the dowel body (5) surrounding the cantilever spring element (9), characterised in that in that the cantilever spring element (9) has a greater bending stiffness radially to the dowel axis (4) in a front section (15) of the cantilever spring element (9) adjoining the front end (13) than in a rear section (14) of the cantilever spring element (9) adjoining the front section (15) of the cantilever spring element (9) in the direction of the rear end (11) of the cantilever spring element (9).

2. Expansion dowel (1) according to claim 1, characterised in that the cantilever spring element (9) is arranged in an opening (12) of the dowel body (5), wherein the front end (13) of the cantilever spring element (9) merges integrally into the dowel body (5) at one edge of the opening (12).

3. Expansion dowel (1) according to claim 1 or 2, characterised in that the cantilever spring element (9) is arranged in a rear half, in particular in a rear third, of the expansion dowel (1).

4. Expansion dowel (1) according to one or more of claims 1 to 3, characterised in that the cantilever spring element (9) is arranged on the dowel body (5) at a distance (d) from the rear end of the dowel (3) which is shorter than the length of the cantilever spring element (9) in the direction of the dowel axis (4).

5. Expansion dowel (1) according to one or more of the preceding claims, characterised in that the cantilever spring element (9) has a thread engagement element (19) projecting from its inner side (17) facing the dowel axis (4) in the direction of the dowel axis (4) for engagement in a screw thread (20) of the spreader screw (7) screwed into the screw channel (6) of the expansion dowel (1).

6. Expansion dowel (1) according to one or more of the preceding claims, characterised in that a thickness (D) of the cantilever spring element (9) decreases radially to the dowel axis (4) from the front end (13) to the rear end (11) of the cantilever spring element (9) in the rear section (14) of the cantilever spring element (9).

7. Expansion dowel (1) according to one or more of the preceding claims, characterised in that the cantilever spring element (9) has, in a section adjoining the front end (13) of the cantilever spring element (9) in the direction of the rear end (11) of the cantilever spring element (9), a support element (16) projecting inwards in the direction of the dowel axis (4) from the inner side (17) of the cantilever spring element (9) facing the dowel axis (4), at which the spreader screw (7) screwed into the screw channel (6) of the expansion dowel (1) acts on the cantilever spring element (9) radially outwards away from the dowel axis (4).

8. Expansion dowel (1) according to claim 7, characterised in that the support element (16) is narrower tangentially to the dowel axis (4) than the cantilever spring element (9) in an area radially adjacent to the outside of the support element (16).

9. Expansion dowel (1) according to claim 7 or 8, characterised in that a supporting surface (18) of the support (16) facing the dowel axis (4) runs parallel or approximately parallel to the dowel axis (4) when the cantilever element (9) is undeformed.

10. Expansion dowel (1) according to one or more of the preceding claims, characterised in that the expansion dowel (1) has two cantilever spring elements (9) which are arranged opposite one another with respect to the dowel axis (4) and which are arranged in particular symmetrically with respect to the dowel axis (4).