EXPANSION DOWEL

Description

[0001] The invention relates to an expansible anchor having the features of claim 1. Expansible anchors that are not made entirely of plastic or metal are known. For example, European patent EP 3 477 126 B1 describes an expansible anchor made of both plastic and metal. The expansible anchor according to the patent specification consists of an outer sleeve and an inner core. The sleeve has expansion tongues separated from one another by slots extending in the longitudinal direction of the expansible anchor. The core is arranged inside the sleeve. Parts of the core are arranged in the slots of the sleeve and extend through them. An expansion cone is arranged at a front end of the expansible anchor. By screwing a screw into the core, the expansion cone is pulled towards a rear end of the expansible anchor.The sleeve expands outward, securing the expansion anchor in a drilled hole in the anchoring base. The core is compressed in such a way that, depending on the design of the drilled hole, the parts of the core located in the slots protrude from them in a bulge-like manner. Using the expansion anchor in hollow bricks, for example, ensures that the core is pressed, or rather "flows," into the recesses of the hollow brick, thereby forming a positive connection. Such an expansion anchor is also used, for example, for anchoring in a drilled hole in plasterboard, whereby in this case the core protrudes from the drilled hole on one side of the plasterboard and overlaps the drilled hole.

[0002] The object of the invention is to propose an alternative expansion anchor which ensures stable and reliable anchoring, particularly in plasterboard.

[0003] This object is achieved according to the invention by the features of claim 1. The invention proposes an expansion anchor which extends along a longitudinal axis between a front and a rear end of the expansion anchor. The expansion anchor has a core which is axially compressible in the longitudinal direction. The core is produced in particular from a plastic by injection molding, in particular from polyamide (PA), preferably from polycaprolactam (PA6) or polypropylene (PP). Other plastics and generally other materials suitable for the intended use are also possible. The core comprises a screw channel for inserting a screw, in particular a metric screw. The screw channel extends along the longitudinal axis. At the rear end of the expansion anchor, the core has an opening through which the screw can be inserted into the screw channel, or more precisely, inserted or screwed in. In other words, the screw channel is open at the rear end.Due to the screw channel, the core has at least a partially hollow cylindrical shape. In particular, the screw channel penetrates the core completely in the longitudinal direction.

[0004] An outer sleeve is arranged around the core. The sleeve is made of metal, in particular, and is preferably a sheet metal part, particularly preferably a bent sheet metal part. However, the sleeve can also be made of a plastic, for example, by injection molding. If both the core and the sleeve are made of a plastic, the plastic of the sleeve, in particular, has greater strength than the plastic of the core. The term "sleeve" does not refer to an idealized, completely closed sleeve. "Sleeve" simply means a substantially hollow, round shape that extends along the longitudinal axis and is, in particular, rotationally symmetrical with respect to the longitudinal axis. In particular, the sleeve encloses the core. This means that an inner circumference of the sleeve bears flatly against an outer circumference of the core, in the manner of a fit.The core and the sleeve are particularly matched to each other in such a way that the sleeve can be placed on the core in the direction of the longitudinal axis.

[0005] In a bending region, the sleeve has articulated arms, which extend in particular in the longitudinal direction and are separated by openings in the sleeve, which extend in particular in the longitudinal direction. In particular, the sleeve has a plurality of articulated arms and openings. In particular, the number of articulated arms and openings is identical. In particular, the articulated arms and the openings have identical lengths, in particular in the longitudinal direction, wherein the articulated arms and the openings begin in particular at a common position on the sleeve, extend an identical distance in the longitudinal direction along the sleeve, and end at a further common position. An extension of the articulated arms and the openings in the longitudinal direction is preferred, but not mandatory. The extension of both the openings and the articulated arms can also be at an angle to the longitudinal axis, i.e., "obliquely" to it.The length of the articulated arms and the openings define the bending area.

[0006] An abutment element for screwing in a screw is arranged at the front end of the expansion anchor. The abutment element is, in particular, a hollow cylindrical bushing, wherein the bushing in particular has an insertion area by means of which the bushing is at least partially inserted longitudinally into the sleeve. An outer circumference of the bushing in the insertion area is, in particular, identical to the outer circumference of the core. In particular, when the core and the abutment element are arranged in the sleeve, a front end of the core rests against a rear end of the abutment element. The abutment element in particular has a longitudinally extending through-opening whose radial diameter is less than or equal to the diameter of the screw channel. The abutment element is, in particular, injection-molded from a durable plastic, in particular from the special polyamide PA6 GF50, also known as "Akromid."The use of the plastic polyoxymethylene (POM) is also possible. This list is exemplary and not exhaustive. However, the abutment element can also be made of metal. For example, a nut can be welded to the front end of the sheet metal sleeve. The abutment element can also be formed integrally with the sheet metal sleeve, for example, by bending the sheet metal.

[0007] By screwing a screw inserted into the screw channel into the abutment element, the abutment element can be moved axially toward the rear end of the expansion anchor. The screw can be designed such that, when screwed into the abutment element, the screw "grooves" an opening and thus a thread. This would be possible, for example, with wood screws. However, as already mentioned, it is preferred that the abutment element has at least one through-hole into which the screw can be screwed. The screw would then groove the thread into the pre-fabricated through-hole. However, it is particularly preferred that a thread, in particular a longitudinally extending internal thread, is already pre-fabricated in the abutment element, into which the screw engages.This is, in particular, a metric internal thread, and the screw to be screwed in is a corresponding metric screw. Due to the preferred use of the special polyamide, the internal thread has a sufficiently high strength.

[0008] The movement of the abutment element toward the rear end of the expansion anchor compresses the core in such a way that the core presses radially against the inside of the articulated arms at least at one or more points in the buckling area, initiating a defined toggle-like buckling of the articulated arms. "Toggle-like buckling" refers to the buckling arms forming inflection points when buckling. In other words, the articulated arms form toggle levers after buckling. The metal sleeve can buckle in the entire buckling area or only in a partial area.Thus, the expansion anchor according to the invention adapts its buckling behavior to the thickness of the fastening base used, for example, to the thickness of the plasterboard used, as explained below by way of example: If the plasterboard were so thick that the entire buckling area were located within the hole in the plasterboard, buckling would be completely prevented. The core would only press the buckling arms against the inner wall of the drill hole at specific points, resulting in a uniform radial expansion of the sleeve and a frictional connection in the drill hole.However, the intended use of the expansion anchor according to the invention is such that after the anchor has been inserted into the mounting base, i.e., in particular into the plasterboard, at least a portion of the bending area, which extends from the front end toward the rear end of the expansion anchor, remains "free," i.e., is not located in the drilled hole but protrudes rearward beyond the plasterboard. Due to the point-like pressure of the core against the sleeve in the free area of ​​the bending area, the bending arms are thus able to bend outward. In other words, the bending arms "bulge" more and more with increasing movement of the abutment element, and the respective bending points of the bending arms consequently move further and further radially away from the longitudinal axis. The formation of the individual bending points depends on the position at which the core presses against the bending arms at specific points.At the beginning of the toggle-like buckling, the core is in point-to-point contact with the articulated arms, and the inflection points form in the individual articulated arms. As the articulated arms continue to buckle, the point-to-point contact between the inflection points and the core is lost, and the radial distance between the inflection points and the core increases relative to the longitudinal axis.

[0009] This process is complete when the extended articulated arms rest against one side of the plasterboard. The core always remains within the sleeve and therefore does not protrude from it.

[0010] Preferably, the articulated arms do not have any "predetermined bending points", i.e. no points where a weakening of the articulated arms would promote the formation of bending points and thus a toggle-like buckling of the articulated arms.

[0011] Advantageously, the diameter of the core increases by less than 40% when the core has reached a maximally compressed state, starting from the uncompressed state—i.e., when the core is not yet compressed by the abutment element. Preferably, the diameter increases by less than 30%, and particularly preferably by less than 25%. This promotes the toggle-like buckling of the articulated arms. When the articulated arms are sufficiently bent, the core forms an axially rigid body, and the user receives feedback about the completion of the setting process through the increase in torque.

[0012] In particular, the core is designed in such a way that the resulting bending points of the individual articulated arms are at least approximately at the same position in the longitudinal direction. This optimally results in identical buckling of each individual articulated arm.

[0013] The core therefore merely acts as an initiator for buckling and contributes little or nothing to the actual fastening, or rather, the strength of the fastening, i.e., the load that the expansion anchor can bear. As mentioned above, the improved, "intelligent" buckling behavior of the expansion anchor eliminates the need for prefabricated "predetermined buckling points" in the sleeve and core, as described, for example, in European patent EP 3 477 126 B1. If the sleeve is made of metal, the expansion anchor according to the invention can retain its functionality even in the event of a fire, at least for a short time, since the load is essentially entirely transferred via the bent metal articulated arms and not, as in the aforementioned patent, via the formed plastic bead.However, a prerequisite for at least conditional suitability in the event of fire is an abutment element made of a fireproof or at least fire-resistant material, such as metal.

[0014] In an advantageous embodiment of the invention, the core, the sleeve, and the abutment element are rotationally fixed to one another. In particular, the core has a collar at the rear end of the expansion anchor, to which the sleeve is connected. At the front end of the expansion anchor, the sleeve is connected to the abutment element. The sleeve is thus arranged between the core, or rather the collar of the core, and the abutment element. The core and the abutment element are held rotationally fixed to one another via the sleeve. The rotational stability of the individual parts relative to one another ensures that during buckling of the articulated arms, they twist only slightly or not at all. This ensures symmetrical buckling behavior of the articulated arms.

[0015] In a further advantageous embodiment of the invention, the sleeve has a collar at the front and / or rear end of the expansion anchor, which collar connects the articulated arms to each other at the front and / or rear end. Preferably, a circumferential collar is arranged at the front and rear ends of the sleeve, wherein the collars in particular have an identical extension in the direction of the longitudinal axis and the articulated arms and the openings are arranged in particular symmetrically between the metal collars. The collar, or the collars, ensure a sufficiently stable connection of the articulated arms to the sleeve.

[0016] It has proven particularly advantageous that the articulated arms each have an identical width. "Width" refers to the width, or rather the extension, of the respective articulated arm in the circumferential direction of the sleeve. This ensures or at least supports identical buckling behavior of the individual articulated arms in the buckling area. It has also proven advantageous that the openings each have an identical width. Here, too, "width" refers to the extension of each interruption in the circumferential direction. In particular, the widths of the articulated arms and the widths of the openings are identical. This further optimizes the buckling behavior of the individual articulated arms.

[0017] In a further advantageous embodiment of the invention, the width of the articulated arm(s) in the circumferential direction corresponds to 2 to 4 times the thickness of the articulated arm(s) in the radial direction. Because the thickness of the articulated arm(s) is significantly smaller than their width, the buckling behavior of the articulated arms is further optimized in that the articulated arms buckle slightly while still forming a large contact surface. The thicknesses of the articulated arms according to the invention resulted in the best buckling behavior in terms of homogeneous "initial buckling" and torsion-free behavior during buckling. Furthermore, the force required to move the abutment element toward the rear end is low for these thicknesses.

[0018] The core has one or more expansion elements which are deformed by the axial compression of the core in such a way that they press radially outwards with respect to the longitudinal axis against the articulated arms at one or more points in the bending region. In particular, the plurality of expansion elements are arranged equidistant from one another along the longitudinal axis. For example, the core can have the shape of a bellows. It is also possible for the core to have one or more rings arranged along the longitudinal axis which are also compressed and thus pushed outwards when the core is compressed. The ring or rings can be made of the same material as the core, but can also be different from the material of the core. In particular, the rings are made of the same plastic if the core and the rings are injection-molded as a single piece.However, it is also possible to manufacture the rings or the expansion elements in general from a different plastic than the core using a two-component injection molding process, or to mold them onto the core. This list of expansion elements is exemplary and not exhaustive. The use of additional expansion elements capable of radial expansion upon axial compression of the core is possible.

[0019] In a further advantageous embodiment of the invention, the core is formed, at least in the bending region, i.e., in the region of the longitudinal extension of the articulated arms and the openings, by individual, interconnected, particularly elliptical, ring segments whose main axes are inclined to the longitudinal axis. The ring segments form the expansion elements. Two interconnected ring segments intersect in such a way that, viewed orthogonally to the longitudinal axis, they have an X-shaped configuration. Two interconnected ring segments form a common X-shaped expansion unit. In a particularly elliptical configuration of the rings, they are arranged along the longitudinal axis in such a way that the main vertices of the elliptical rings each form the outer ends of the "X." In particular, a plurality of such expansion units extend along the longitudinal axis.In particular, so many expansion units extend along the longitudinal axis that the entire bending area is filled with these expansion units. Each of the ring segments has a ring opening, wherein the ring openings together form the screw channel of the core. At the points, in particular at the main vertices, where the individual X-shaped expansion units are connected to one another, in particular molded onto one another, two adjacent expansion units each form predefined, in particular point- or line-shaped expansion zones at the connection points. The expansion zones are in particular mirror-symmetrical with respect to the longitudinal axis and have in particular equidistant distances from adjacent expansion zones along the longitudinal axis.

[0020] The X-shaped expansion units fulfill a dual function: Firstly, the X-shaped expansion units act as a type of spring. When the abutment element is moved towards the rear end of the expansion anchor by screwing in a screw, the user of the expansion anchor according to the invention feels an increase in the torque required for screwing in the screw, as the X-shaped expansion units are compressed, particularly elastically, along the longitudinal axis. The increase in torque increases with the distance the abutment element travels towards the rear end of the expansion anchor. This gives the user a familiar haptic feedback while screwing in the screw. This essentially corresponds to, for example, screwing a wood screw into a wooden substrate, where the torque to be applied also continually increases. Secondly, the movement of the abutment element causes the expansion zones to expand radially.In other words, the joints move radially outward. At the points where the joints, or rather the expansion zones, move radially outward, buckling of the articulated arms is initiated or at least enabled, provided the expansion anchor can freely buckle at these points and is not surrounded by a drilled hole. Multiple expansion zones can also jointly contribute to buckling of the articulated arms in the buckling area.

[0021] In a further embodiment of the invention, the individual ring segments are designed identically. This optimizes the functions of the ring segments and the spreading units formed thereby.

[0022] In order to increase the compressive strength of the core along the longitudinal axis, or to adapt the force that the user must exert when moving the abutment element, in a further embodiment of the expansion anchor according to the invention, the individual ring segments are connected to one another by axially extending predetermined buckling struts. The predetermined buckling struts are arranged outside or adjacent to the screw channel. In particular, four predetermined buckling struts, each offset by 90° relative to the longitudinal axis, extend between the individual ring segments. In particular, each of the predetermined buckling struts extends parallel to the longitudinal axis. However, the individual predetermined buckling struts can also form an angle to the longitudinal axis. The predetermined buckling struts prevent the X-shaped expansion units from unintentionally "springing together."If the abutment element is moved toward the rear end, the predetermined buckling struts begin to break or at least bend. The predetermined buckling struts ensure that at least a predetermined force must be applied to compress the individual X-shaped expansion units along the longitudinal axis. The predetermined force can be adjusted by the design of the predetermined buckling struts, particularly by adjusting their thickness.

[0023] In order to enable the simplest possible installation of the expansion anchor, in a further advantageous embodiment of the invention, the abutment element is connected to the sleeve at the front end of the expansion anchor and the core is connected to the sleeve at the rear end of the expansion anchor by a snap-in connection. In particular, two pins on the abutment element that are mirror-symmetrical with respect to the longitudinal axis and extend in the direction of the longitudinal axis engage in corresponding grooves in the sleeve. The pins can also be arranged on the sleeve and the grooves accordingly on the abutment element. In particular, the grooves are introduced into the collar that is arranged at the front end. In particular, the collar of the core at the rear end also has two pins that are mirror-symmetrical with respect to the longitudinal axis and extend in the direction of the longitudinal axis. These are in particular identical to the pins on the abutment element.The tenons on the collar engage in corresponding grooves in the collar at the rear end. In particular, the grooves and tenons are identically designed and oriented parallel to the longitudinal axis. The identical design of the grooves and tenons offers a certain degree of flexibility when installing the expansion anchor, since in this case, it doesn't matter which opening in the sleeve is connected to the abutment and which opening is connected to the core collar.

[0024] To further improve the anti-rotation locking of the core, the abutment element, and the sleeve relative to one another, a further advantageous embodiment of the invention provides an anti-rotation lock between a front end of the core and a rear end of the abutment element. The front end of the core is facing away from the opening of the screw channel. The rear end of the abutment element makes contact with the front end of the core, particularly in a form-fitting manner. A frictional connection is also possible.

[0025] The expansion anchor according to the invention is preferably intended for use with a metric screw. Therefore, in a further preferred embodiment, the abutment element has a longitudinally extending internal thread. The internal thread is adapted to the metric screw to be used.

[0026] To prevent the screw from directly hitting the abutment element during insertion, or more precisely, when inserting the screw into the screw channel, which could lead to the abutment element being pushed out of the sleeve, the core has an insertion lock for the screw at its front end. The insertion lock narrows the screw channel at the front end of the core such that the screw to be used cannot be inserted over the insertion lock into the abutment element. The screw must be turned to overcome the insertion lock and reach the abutment element. In particular, the insertion lock corresponds to a thread of the screw to be used.

[0027] At the rear end of the expansion anchor, or more precisely, at the rear end of the core, an anti-rotation device is arranged. This device prevents the expansion anchor from rotating with the screw during screwing into the screw channel or the abutment element after it has been inserted into the mounting base. Specifically, the anti-rotation device is designed by cutting edges extending in the direction of the longitudinal axis. Specifically, the cutting edges are arranged on the plastic collar, offset by 90° from each other.

[0028] The features and combinations of features, embodiments, and refinements 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 any other combinations or individually. Embodiments of the invention are possible that 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.

[0029] The invention is explained below using an embodiment.

[0030] They show: Figure 1 shows an expansion anchor according to the invention in a perspective view; Figure 2 shows the expansion anchor according to the invention of Figure 1 in a side view; Figure 3 a part of the Figure 2in side view of the expansion anchor; Figure 4 a sectional view of a front part IV of the Figure 3 in side view of the expansion anchor; and Figure 5 the expansion anchor according to the invention of Figures 1 and 2 in an installed state.

[0031] In the Figures 1 and 2 An expansion anchor 1 according to the invention is shown in perspective and in a side view. Figures 3 and 4 show parts of the expansion anchor 1 according to the invention, whereas in Figure 5 The expansion anchor 1 according to the invention is shown in an installed state in a plasterboard 33. For reasons of clarity, not all reference numerals are included in all figures. The reference numerals have been inserted where they are useful and necessary for understanding the function.

[0032] The expansion anchor 1 according to the invention extends along a longitudinal axis L between a front end 2 and a rear end 3. The expansion anchor 1 has a core 4 made of plastic, which Figure 3is shown in detail. The core 4 also extends along the longitudinal axis L between a front end 5 and a rear end 6. The front end 5 of the core 4 is oriented in the direction of the front end 2 of the expansion anchor 1 and the rear end 6 of the core 4 corresponds to the rear end 3 of the expansion anchor 1. The core 4 has a circular opening 7 at its rear end 6, or at the rear end 3 of the expansion anchor 1, through which opening a metric screw 8 can be inserted into a screw channel 9 of the core 4. The screw channel 9 penetrates the core 4 completely along the longitudinal axis L. The core 4 also has a circumferential collar 10 at the rear end 3 of the expansion anchor 1. Individual elliptical ring segments 11 are arranged along the longitudinal axis L. Two of the ring segments 11 together form a spreading unit 12 with an X-shaped configuration.The elliptical ring segments 11 are arranged along the longitudinal axis L such that the main vertices of the elliptical rings 11 each form the ends of the "X." The main axes of the elliptical rings 11 are each inclined to the longitudinal axis L. At the main vertices, the individual ring segments 11 are molded together and each have a connection point V there. Adjacent connection points V are equidistant from one another along the longitudinal axis L and are mirror-symmetrical with respect to the longitudinal axis L. Each of the connection points V additionally forms an expansion zone S. The function of the expansion zone S will be discussed in more detail below. Each of the ring segments 11 has an annular opening 13, which together form the screw channel 9 for the metric screw 8.Four predetermined buckling struts 14, which extend along the longitudinal axis L and are arranged offset by 90° relative to the longitudinal axis L in the circumferential direction, connect the individual ring segments 11 to one another. The predetermined buckling struts 14 border the screw channel 9 and connect the main vertices and the secondary vertices of the ring segments 11. An insertion lock 15 is arranged at the front end 5 of the core 4. The insertion lock 15 narrows the screw channel 9 at the front end 5 of the core 4 such that the screw 8 cannot be pushed over the insertion lock 15. To overcome the insertion lock 15, the screw 8 must be turned in the screw channel 9. The insertion lock 15 corresponds to the thread of the screw 8 to be screwed in.

[0033] A sleeve 16 made of sheet metal is arranged on the core 4 and encloses it. The sleeve 16 extends between a front end 18 and a rear end 19. The front end 18 of the sleeve 16 is oriented towards the front end 2 of the expansion anchor 1. The rear end 19 of the sleeve is oriented towards the rear end 3 of the expansion anchor 1. The sleeve 16 has a circumferential collar 17 at its front end 18, or at the front end 2 of the expansion anchor 1. Such a collar 17 is also arranged at the rear end 19. The two collars 17 are identical. The core 4 and the sleeve 16 are arranged coaxially with respect to the longitudinal axis L. An outer diameter of the core 4 is matched to an inner diameter of the sleeve 16 such that the sleeve 16 can be pushed onto the core 4 in the longitudinal direction until the sleeve 16 comes into contact with the collar 10 of the core 4.Between the two collars 17, longitudinally extending articulated arms 20 and openings 22 are formed. The articulated arms 20 and the openings 22 are arranged alternately with one another and each have identical widths in the circumferential direction of the expansion anchor 1. The length of the articulated arms 20 defines a buckling area K of the expansion anchor 1. In this buckling area K, the articulated arms 20 can form buckling points 21, the formation of which will be discussed below.

[0034] At the front end 2 of the expansion anchor 1, an abutment element 23 is arranged. The abutment element 23 extends between a front end 24 and a rear end 25. A through-hole 26 extends along the longitudinal axis L through the abutment element 23. The abutment element 23 is designed as a bushing 27 having an internal thread 28. The internal thread 28 is matched to the thread of the screw 8. The screw 8 can be screwed into the screw channel 9 and into the abutment element 23. In this case, the insertion lock 15 must be overcome by the screwing-in movement of the screw 8. The bushing 27 has an insertion area 29 at its rear end 25. This is in the Figure 3The insertion area 29 is inserted into the front end 18 of the sleeve 16. The rear end 25 of the abutment element 23, or rather the bushing 27, comes into contact with the front end 5 of the core 4. A positive-locking anti-twist device 30 is formed at the contact area, which contributes to the fact that, in the assembled state of the expansion anchor 1, as shown in Figure 1 shown, the core 4 is rotationally fixed to the abutment element 23. Two locking connections R fix the expansion anchor 1 in the Figure 1 shown state. A locking connection R is formed between the abutment element 23 and the front end 18 of the sleeve 16. The further locking connection R is formed between the rear end 19 of the sleeve 16 and the collar 10 of the core 4. The locking connections R are formed in that, as shown in the Figures 1 and 2As can be seen, pins engage in corresponding grooves in the sleeve 16. Both snap-in connections R are identical. The snap-in connections R allow the expansion anchor 1 to be assembled by plugging them together. The snap-in connections R ensure that the core 4, the sleeve 16 and the abutment element 23 are rotationally fixed to one another. At the rear end 3 of the expansion anchor 1, a co-rotation lock 31 in the form of cutting edges 32 is arranged, which ensure that the expansion anchor 1 does not rotate in the fastening base with the screw 8 (not shown).

[0035] The function of the expansion anchor 1 according to the invention is explained below: In a first step, the expansion anchor 1 is inserted into a prefabricated drill hole in a fixing base, for example a plasterboard 33, shown in Figure 5, inserted. The drill hole is a through hole, it penetrates the plasterboard completely. The plasterboard 33 is significantly narrower than the length of the expansion anchor 1, more precisely than the extension of the bending area K in the longitudinal direction. The expansion anchor 1 is inserted into the drill hole until the cutting edges 32 cut into the drill hole wall and the rear end 3 of the expansion anchor 1 is flush with a surface of the front side of the plasterboard 33. This front side of the plasterboard 33 is a rear side of the plasterboard 33 made of Figure 5 turned away and consequently in Figure 5not visible. By screwing the screw 8 into the abutment element 23, the abutment element 23 is moved towards the rear end 3 of the expansion anchor 1. This movement compresses the core 4. The predetermined buckling struts 14 stabilizing the core 4 are broken in the process. The X-shaped ring segments 11, or rather the X-shaped expansion units 12 formed from the ring segments 11, are elastically compressed along the longitudinal axis L, whereby the core 4 is shortened and its diameter increases by approximately 20%. By compressing the expansion units 12, they expand it radially outwards at the connection points V (represented by the arrows of the expansion direction 34 in Figure 3). The expansion zones S formed at the connection points V press against the inner sides of the articulated arms 20. At the free points of the buckling area K, i.e. at the points where the buckling area K is not enclosed by the borehole wall, the articulated arms 20 are pushed radially outwards at the expansion zones S, which initiates the buckling of the articulated arms 20 at these points of the buckling area K. After the initiation of buckling, a distance between the articulated arms 20 and the core 4 increases. The articulated arms 20 consequently buckle and form buckling points 21, shown in Figure 5 . As a result, the articulated arms 20 assume the shape of a toggle lever after buckling. The buckling of the articulated arms 20 is completed when the articulated arms 20 return to the Figure 5visible side of the plasterboard 33 and no further shortening of the core 4 is possible. The expansion anchor 1 according to the invention thus forms the bending points 21 itself, at which the bending arms 20 bend, depending on the thickness of the plasterboard 33. Thus, pre-formed "predetermined bending points" in the sleeve 16 and / or in the core 4 are not necessary. List of reference symbols

[0036] 1Expansion anchor 2Front end of expansion anchor 1 3Rear end of expansion anchor 1 4Core 5Front end of core 4 6Rear end of core 4 7Opening 8Screw 9Screw channel 10Collar of core 4 11Ring segment 12Expansion unit 13Ring opening 14Predetermined buckling strut 15Insertion lock 16Sleeve 17Collar 18Front end of sleeve 16 19Rear end of sleeve 16 20Buckling arm 21Buckling points 22Aperture 23Abutment element 24Front end of abutment element 23 or bushing 27 25Rear end of abutment element 23 or bushing 27 26Through opening of abutment element 23 27Bushing 28Internal thread 29Insertion area of ​​the socket 27 30Anti-rotation device 31Anti-rotation device 32Cutting edge 33Gypsum board 34Expansion direction 35Expansion element LLongitudinal axis VConnection point SSpreading zone RRack connection KKinking area

Claims

1. Expansion anchor (1) which extends along a longitudinal axis (L) between a front end (2) and a rear end (3), comprising - a core (4) axially compressible in the direction of the longitudinal axis (L), wherein the core (4) comprises a screw channel (9) for inserting a screw (8), wherein the screw channel (9) has an opening (7) at the rear end (3) of the expansion anchor (1), - an outer sleeve (16) arranged around the core (4), the sleeve (16) having buckling arms (20) extending in particular in the longitudinal direction in a buckling region (K), which are separated from perforations (22) in the sleeve (16) extending in particular in the longitudinal direction - an abutment element (23) for screwing in a screw (8) at the front end (2) of the expansion anchor (1), wherein by screwing a screw (8) inserted into the screw channel (9) into the abutment element (23), the abutment element (23) is axially movable in the direction of the rear end (3) of the expansion anchor (1), - wherein the core (4) can be compressed by the movement of the abutment element (23) in the direction of the rear end (3) of the expansion anchor (1) in such a way that the core (4) is pressed at least selectively in the buckling region (K) at one or more points (V, S) radially with respect to the longitudinal axis (L) from the inside against the buckling arms (20), whereby a defined toggle lever-like buckling of the buckling arms (20) is initiated.

2. Expansion anchor (1) according to claim 1, characterised in that the core (4) has one or more spreading elements (35) which are deformed by the axial compression of the core (4) in such a way that they press radially outwards against the buckling arms (20) at one or more points (V, S) with respect to the longitudinal axis (L).

3. Expansion anchor (1) according to claim 1 or 2, characterised in that the core (4), the sleeve (16) and the abutment element (23) are rotationally fixed relative to one another.

4. Expansion anchor (1) according to one of claims 1 to 3, characterised in that at the front end (2) and / or at the rear end (3) of the expansion anchor (1), the sleeve (16) has a collar (17) in each case, which connects the buckling arms (20) at the front end (2) and / or at the rear end (3) of the expansion anchor (1) to one another.

5. Expansion anchor (1) according to one of claims 1 to 4, characterised in that the buckling arms (20) each have an identical width.

6. Expansion anchor (1) according to one of claims 1 to 5, characterised in that the perforations (22) each have an identical width.

7. Expansion anchor (1) according to one of the preceding claims, characterised in that a width of a buckling arm (20) in the circumferential direction corresponds to 2 to 4 times the thickness of the buckling arm (20) in the radial direction.

8. Expansion anchor (1) according to one of the preceding claims, characterised in that the core (4) is formed, at least in the buckling region (K), by individual interconnected, in particular elliptical, ring segments (11), two interconnected ring segments (11) in each case having an X-shaped configuration when viewed orthogonally to the longitudinal axis (L).

9. Expansion anchor (1) according to claim 8, characterised in that the individual ring segments (11) are of identical design.

10. Expansion anchor (1) according to claim 8 or 9, characterised in that the individual ring segments (11) are connected to one another by predetermined buckling struts (14) extending in the axial direction.

11. Expansion anchor (1) according to one of claims 3 to 10, characterised in that at the front end (2) of the expansion anchor (1) the abutment element (23) is connected to the sleeve (16) and at the rear end (3) of the expansion anchor (1) the core (4) is connected to the sleeve (16) by a snap-in connection.

12. Expansion anchor (1) according to one of the preceding claims, characterised in that an anti-rotation device (30) is formed between a front end (5) of the core (4) and a rear end (25) of the abutment element (23).

13. Expansion anchor (1) according to one of the preceding claims, characterised in that the abutment element (23) has an internal thread (28) extending in the longitudinal direction.

14. Expansion anchor (1) according to one of the preceding claims, characterised in that the core (4) has an insertion lock (15) for a screw (8) at its front end (5).

15. Expansion anchor (1) according to one of the preceding claims, characterised in that the core (4) has a locking device (31) at the rear end (3) of the expansion anchor (1).