SELF-TAPPING UNDERCUT ANCHOR

Description

[0001] The invention relates to a self-tapping undercut anchor having the features of the preamble of claim 1.

[0002] Undercut anchors are expansion anchors that are anchored in an anchor hole by expanding into an undercut. This expansion ensures that the expansion anchors are held in the undercut by a positive locking mechanism, preventing them from being pulled out of the anchor hole. In addition to the positive locking mechanism, a force or frictional locking mechanism can also be present in the anchor hole. "Self-tapping" means that the expansion or undercut anchor creates the undercut in the anchor hole itself.

[0003] Patent EP 0 217 053 B1 discloses an undercut anchor with a rod-shaped anchor shaft having a truncated cone-shaped expansion body at a front end. An expansion sleeve is arranged on the anchor shaft. At its front end, facing the expansion body, this expansion sleeve is divided by longitudinal slots into cylindrical, curved, strip-shaped expansion elements. These elements are pivoted radially outward when pushed onto the expansion body, which can be understood as "spreading open" the expansion elements, the expansion sleeve, and the expansion anchor. At the front ends of two opposing expansion elements, cylindrical hard metal pins are inserted into bores in the expansion elements. These pins act as cutting elements, projecting obliquely forward and outward from the front ends of the two opposing expansion elements.By rotating the expansion sleeve as it is pushed onto the expansion body, the two carbide pins create a circumferential, frustoconical expansion in an otherwise cylindrical anchor hole. This expansion forms an undercut that positively engages the expansion elements, which are pivoted outward, i.e., expanded, as they are pushed onto the expansion body.

[0004] The object of the invention is to improve the expansion of the expansion elements of an undercut anchor of the type described above. In particular, the ratio of a radially outward expansion force exerted by an expansion body on the expansion elements to an axial force exerted on the expansion body for pushing the expansion elements open is to be improved, i.e., the expansion force is to be increased and / or the axial force is to be reduced.

[0005] This object is achieved according to the invention by the features of claim 1. The undercut anchor according to the invention extends along a centrally running longitudinal axis and has an expansion body and an expansion sleeve with at least one expansion element at a front end facing the expansion body. The expansion sleeve preferably has a plurality of expansion elements arranged evenly or unevenly distributed over a circumference. The expansion body is in particular frustoconical, although it can also be spherical or concave in the longitudinal direction. In general, the expansion body is arranged and designed such that when the expansion sleeve is displaced in the direction of the expansion body, it pivots the at least one expansion element at the front end of the expansion sleeve radially outwards away from the longitudinal axis, which can also be understood as spreading.

[0006] At a rear end facing away from the at least one expansion element, the expansion sleeve has a positive-lock coupling for the rotationally fixed attachment of a rotary drive tool to rotate the expansion sleeve about its longitudinal axis. The positive-lock coupling can, for example, be designed as a claw coupling with rectangular recesses similar to crenellations in the rear end of the expansion sleeve. Other positive-lock couplings are also possible.

[0007] The at least one expansion element of the expansion sleeve of the undercut anchor according to the invention has a base body and a cutting element having a cutting edge on an outer circumference, i.e., on a side or edge of the base body facing away from the longitudinal axis of the undercut anchor, for creating an undercut in an anchor hole. The cutting element creates the undercut when the expansion sleeve is driven in rotation as it is pushed onto the expansion body. By pushing the at least one expansion element onto the expansion body, the expansion element is pivoted radially outward, whereby the cutting element is also radially removed from the longitudinal axis of the undercut anchor. Due to the rotational drive of the expansion sleeve, the cutting element moves circumferentially around the longitudinal axis and in doing so creates the undercut in the anchor hole.

[0008] According to the invention, a cantilever element protrudes from the base body of the expansion element, the inner surface of which faces the expansion body, such that the inner surface of the cantilever element is supported on the expansion body during outward pivoting. The cantilever element protrudes, in particular, forward from the base body. It forms, in particular, the front end of the expansion element.

[0009] Preferably, a rear end of the cantilever element, facing the claw coupling at the rear end of the expansion sleeve, is connected to the base body of at least one expansion element, and a front end of the cantilever element is free, such that it is movable radially relative to the cutting element of the expansion element. This allows the cantilever element to adapt to a "pitch" of the expansion body, for example, to a cone angle of a truncated cone-shaped expansion body, through elastic and / or plastic bending. As a result, the cantilever element rests against the expansion body with a front inner edge in a flat, non-linear, circumferential manner, which could lead to scraping or rubbing of this edge on the expansion body. Because the cantilever element rests against the expansion body in a non-linear, non-scraping manner, the expansion body is not damaged during expansion.In addition, the invention enables the cantilever element to be placed on the expansion body in front of the cutting edge of the cutting element, resulting in a lever arm of the cantilever element being placed on the expansion body with respect to the cutting edge, which increases a radially outwardly directed force on the cutting edge for a given spreading force between the cantilever element and the expansion body.

[0010] Preferably, a front outer edge of the cantilever element, i.e., the edge remote from the longitudinal axis of the undercut anchor, is offset radially inward relative to the cutting edge, i.e., the front outer edge of the cantilever element has a smaller radial distance from the longitudinal axis of the undercut anchor than the cutting edge. Generally, the cantilever element can be located between the cutting edge and the longitudinal axis of the undercut anchor—i.e., between the cutting edge and the expansion body when pushed onto the expansion body—or can have a smaller radial distance from the longitudinal axis of the undercut anchor than the cutting edge. Preferably, the cutting edge projects forward beyond the base body.

[0011] In particular, the cantilever element has a reduced thickness compared to the base body, which is in particular less than 50% of the thickness of the base body, in particular less than 30% of the thickness of the base body, whereby the "thickness" is measured radially to the longitudinal axis. Due to the reduced thickness, the cantilever element is easily deformable compared to the base body and can therefore adapt well to the geometry of the expansion body, thereby achieving a flat contact.

[0012] Toward the front end, the inner side of the cantilever element facing the expansion body preferably extends to at least one radial plane of the undercut anchor, in which the cutting edge is located. In particular, the cantilever element projects axially forward beyond the cutting edge. As a result, the cantilever element is supported during expansion in the radial plane of the cutting edge and preferably axially further forward on the expansion body, which improves the leverage ratio during expansion. This embodiment of the invention also includes, in particular, the inner side of the cantilever element beginning axially behind the cutting edge.

[0013] In embodiments of the invention, a free space between the cutting edge and the cantilever element enables radial movement between the cutting edge and the cantilever element. In particular, the cantilever element can radially approach the cutting edge with the cutting edge when the expansion element is spread and pivoted outward. The free space is located, in particular, radially between the cutting edge and the cantilever element, relative to the longitudinal axis.

[0014] The clearance can be formed by a slot extending in the longitudinal direction of the expansion sleeve between the cutting edge and the inner surface of the cantilever element, which is open at a front end of the expansion element. The slot can, in particular, have a rectangular or triangular cross-section with respect to an axial section.

[0015] Preferably, the slot is designed and arranged such that a connecting line connecting the cutting edge to the longitudinal axis runs through the base body of the expansion element and does not intersect the free space. In particular, the connecting line forms an angle of at least 35°, in particular at least 45°, with the longitudinal axis.

[0016] Furthermore, it is preferred that an annular step is arranged on an outer side of the base body of the expansion sleeve, forming a reduced-thickness region of the base body on which the cutting element is arranged. The annular step can extend radially or at an angle to the longitudinal axis, wherein the angle enclosed with the longitudinal axis is in particular greater than 45°.

[0017] Preferably, the cutting element is made of a material of greater hardness than the expansion sleeve, the expansion element, its base body, or the cantilever element. The expansion element can, for example, have a hard metal body as the cutting element, or the cutting element can be produced by overlay welding with a welding material whose hardness is greater than that of the expansion sleeve, the expansion element, its base body, or the cantilever element. Overlay welding has the advantage that no hole, recess, or the like is required to accommodate, for example, a hard metal body as the cutting element in the expansion element. This list is exemplary and not exhaustive.

[0018] 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.

[0019] The invention is explained in more detail below using an exemplary embodiment illustrated in the drawing. In the drawings: Figure 1 shows a self-tapping undercut anchor according to the invention, with an expansion sleeve of the undercut anchor shown in a half-section; Figure 2 shows an enlargement of a detail II from Figure 1 ; Figure 3an anchoring of the undercut anchor made of Figure 1 in an anchor hole; Figure 4, detail II from Figure 1 a modified embodiment of the invention; Figure 5 shows detail II from Figure 1 a further modified embodiment of the invention; and Figure 6 shows detail II from Figure 1 a further embodiment of the invention.

[0020] In principle, identical parts in the figures are provided with identical reference numbers.

[0021] The Figure 1The self-tapping undercut anchor 1 according to the invention shown is intended for anchoring in a particularly cylindrical anchor hole 2, wherein the undercut anchor 1 creates an undercut 3 in the anchor hole 2, which the undercut anchor 1 engages behind in a form-fitting manner. The anchor hole 3 is drilled, for example, into an anchor base 4 made of, for example, concrete, stone, or masonry.

[0022] The undercut anchor 1 has an anchor shaft 5 with a thread 6 and a frustoconical expansion body 7 at a front end 8 of the undercut anchor 1, as well as an expansion sleeve 9 arranged on the anchor shaft 5. The expansion body 7 widens in diameter toward the front. The anchor shaft 5, the expansion body 7, and the expansion sleeve 9 are coaxial with a longitudinal axis 10 of the undercut anchor 1.

[0023] The expansion sleeve 9 has longitudinal slots 11 that extend from a front end 8a of the expansion sleeve 9 facing the expansion body 7 over a (fracture) part of an axial length of the expansion sleeve 9. The longitudinal slots 11 do not have to extend straight in axial planes of the expansion sleeve 9 - as in the exemplary embodiment - but can also run, for example, helically at an angle to the axial planes, in a wave-like or zigzag shape. The list is exemplary and not exhaustive. The longitudinal slots 11 divide the expansion sleeve 9 into expansion elements 13 in an expansion section 12 that begins at the front end of the expansion sleeve 9 facing the expansion body 7 and extends over the (fracture) part of the expansion sleeve 9.In the exemplary embodiment, the expansion elements 13 can be understood as tabs or tongues that are curved in a cylindrical shell shape in a circumferential direction of the expansion sleeve 9 and that extend in the direction of the frustoconical expansion body 7, where the expansion elements 13 have free ends. By axially displacing the expansion sleeve 9 in the direction of the longitudinal axis 10 on the anchor shaft 5 towards the expansion body 7, the expansion elements 13 of the expansion sleeve 9 are pushed onto the expansion body 7. During pushing, the expansion body 7, which expands in the described direction of displacement of the expansion sleeve 9, presses the expansion elements 13 of the expansion sleeve 9 radially apart, whereby the front ends of the expansion elements 13 are pivoted outwards away from the longitudinal axis 10 of the undercut anchor 1. The pivoting apart of the expansion elements 13 can also be understood as spreading of the expansion sleeve 9 or the undercut anchor 1.

[0024] At a rear end facing away from the expansion body 7, the expansion sleeve 9 has rectangular recesses 14, whereby the rear end of the expansion sleeve 9 is designed as a positive-lock coupling 15 in the manner of a claw coupling. The positive-lock coupling 15 serves to rotary drive the expansion sleeve 9 with a tubular rotary drive tool 16, the end of which facing the expansion sleeve 9 is designed to be opposite to the positive-lock coupling 15 of the expansion sleeve 9. The rotary drive tool 16 can be pushed onto the anchor shaft 5 and brought into rotationally fixed engagement with the positive-lock coupling 15 of the expansion sleeve 9 by means of a positive lock, whereby the expansion sleeve 9 can be driven in rotation by a rotary drive of the rotary drive tool 16.By axially advancing the rotary drive tool 16 in the direction of the longitudinal axis 10 of the undercut anchor 1 on the anchor shaft 5 toward the expansion body 7, the expansion sleeve 9 can be displaced toward the expansion body 7 and the expansion elements 13 can be pushed onto the expansion body 7, whereby they are pivoted outward away from the longitudinal axis 10 in the manner described above, i.e., spread apart. The positive coupling 15 of the expansion sleeve 9 can be designed differently; a rotary drive and an advance of the expansion sleeve 9 are required.

[0025] As in the enlargement of the Figure 2 As can be seen, the expansion elements 13 of the expansion sleeve 9 have on their outer sides 27 cutting elements 17 with cutting edges 18 on the front ends 8a facing the expansion body 7 on an outer circumference. Figures 1 and 2The cutting elements 17 are hard metal plates that are arranged in complementary recesses in the outer circumference of the expansion elements 13 and are fixed, for example, by brazing. It is not necessary for each of the expansion elements 13 to have a cutting element 17; rather, it is sufficient if at least one expansion element 13 has a cutting element 17. Preferably, several or all of the expansion elements 13 each have one or possibly even several cutting elements 17. The cutting edges 18 run in the circumferential direction and can be located at axially front ends 8a of the expansion elements 13 or—as in the exemplary embodiment—be set back from the expansion body 7 relative to the front ends of the expansion elements 13. At their longitudinal edges, the cutting elements 17 have secondary cutting edges 19 that run in the longitudinal direction or obliquely to the longitudinal direction of the undercut anchor 1.

[0026] For anchoring in the anchor base 4, the undercut anchor 1 is inserted with its expansion body 7 leading into the anchor hole 2 until the expansion body 7 or the front end 8 of the anchor shaft 5 sits on a hole bottom of the anchor hole 2. The expansion sleeve 9 is driven in rotation on the anchor shaft 5 with the rotary drive tool 16 or in another way and advanced in the direction of the longitudinal axis 10 towards the expansion body 7, whereby the expansion elements 13 are pushed onto the expansion body 7 and pivoted outwards by the expansion body 7 away from the longitudinal axis 10 of the undercut anchor 1. The cutting edges 18 and, if applicable, the secondary cutting edges 19 of the cutting elements 17 penetrate into a hole wall of the anchor hole 2 and, through the rotation and axial advance, create a circumferential, frustoconical widening which forms the undercut 3.After the undercut 3 has been created, the rotary drive tool 16 is removed from the anchor shaft 5. The expansion elements 13, which are pivoted into the undercut 3, i.e., expanded, engage behind the undercut 3, thereby holding the undercut anchor 1 in the anchor hole 2 by positive locking in the undercut 3; the self-tapping undercut anchor 1 according to the invention is anchored in the anchor hole 2 by positive locking.

[0027] On an inner side, the expansion elements 13 each have a cantilever element 20, the rear end of which, facing away from the expansion body 7, merges integrally into the expansion element 13 and which protrude forward from the expansion elements 13 in the direction of the expansion body 7. An area of the expansion elements 13 outside the cantilever elements 20 is referred to here as the base body 21 of the expansion elements 13. The base body 21 of the expansion elements 13 has the recesses with the cutting elements 17, which are arranged on the outer side 27 of the base body 21. The cantilever elements 20 are formed by slots 23 in the expansion elements 13 of the expansion sleeve 9, which extend a short distance in the longitudinal direction into the expansion elements 13 from the ends of the expansion elements 13 facing the expansion body 7. The slots 23 form free spaces 24 between the base bodies 21 radially outward and the cantilever elements 20 radially inward at the slots 23 or free spaces 24.The slots 23 forming the free spaces 24 enable a radial movement between the base bodies 21 of the spreading elements 13 with the cutting edges 18 and secondary cutting edges 19 of the cutting elements 17 on the one hand and the cantilever elements 20 on the other hand.

[0028] Front, radially outer edges of the cantilever elements 20 have a smaller radial distance from the longitudinal axis 10 of the undercut anchor 1 than the cutting edges 18 and secondary cutting edges 19 of the cutting elements 17. The front ends of the cantilever elements 20 form the front end of the expansion sleeve 9.

[0029] Inner surfaces 22 of the cantilever elements 20 face the expansion body 7 such that when the expansion elements 13 are pushed on, the inner surfaces 22 of the cantilever elements 20 slide along a conical circumferential surface of the expansion body 7. The cantilever elements 20 rest with their inner surfaces 22 against the expansion body 7. Due to the free space 24 between the cantilever elements 20 and the base bodies 21 of the expansion elements 13, the cantilever elements 20 can pivot or bend outward relative to the base bodies 21. When pushed onto the expansion body 7, the cantilever elements 20 pivot or bend outward, thereby adapting to a "slope" of the expansion body 7 and resting flatly against the expansion body 7 with their inner surface 22 instead of just their front inner edge. The "slope" is an oblique course of the circumferential surface of the expansion body 7 at an angle to the longitudinal axis 10 of the undercut anchor 1 due to its truncated cone shape.

[0030] The cantilever elements 20 protrude longitudinally forward in the direction of the expansion body 7 beyond the base body 21 of the expansion elements 13 and beyond a radial plane in which the cutting edges 18 of the cutting elements 17 are located. As a result, the cantilever elements 20 support the expansion elements 13 in the axial direction in front of the cutting edges 18 on the expansion body 7. This results in a lever arm, whereby a spreading force with which the expansion body 7 presses the expansion elements 13 radially outwards is smaller than a spreading force with which the cutting edges 18 of the cutting elements 17 are pressed radially outwards against the hole wall of the anchor hole 2 when spreading open in the anchor hole 2. The cantilever elements 20 protruding forward in the direction of the expansion body 7 reinforce the spreading force with which the cutting edges 18 are pressed outwards against or into the hole wall of the anchor hole 2 when spreading open.

[0031] The cutting elements 17 made of hard metal have a greater hardness than the expansion elements 13, which, like the expansion sleeve 9, are made entirely of structural steel, for example.

[0032] At the Figure 4 In the modification of the undercut anchor 1 according to the invention shown, the cutting elements 17 are "standing", that is to say in axial planes of the undercut anchor 1, instead of as in Figure 3 "lying", i.e. tangential to the undercut anchor 1, on the outer circumference of the expansion elements 13 of the expansion sleeve 9 of the undercut anchor 1. The Figure 4 as well as in Figure 3 Cutting elements 17 designed as hard metal plates are in Figure 4arranged on a circumferential annular step 25 of the expansion elements 13, which supports the cutting elements 17 in the axial direction. Due to their "upright" arrangement, edges extending radially to the longitudinal axis 10 of the undercut anchor 1 and extending in the longitudinal direction of the undercut anchor 1 and remote from the longitudinal axis 10 of the undercut anchor 1 form the cutting edges 18 of the cutting elements 17.

[0033] With the formation of a further ring stage 26, Figure 4 In the illustrated embodiment of the undercut anchor 1 according to the invention, the cantilever elements 20 extend from the front ends of the base bodies 21 of the expansion elements 13 forward in the direction of the expansion body 7 from the base bodies 21. The inner surfaces 22 of the expansion elements 13 continue without a step from the base bodies 21 to the cantilever elements 20.

[0034] In Figure 4There is no slot or free space between the cantilever elements 20 and the base bodies 21 of the expansion elements 13 of the expansion sleeve 9. The cantilever elements 20 projecting forward in the direction of the expansion body 7 can be pivoted or bent outwards away from the longitudinal axis 10 of the undercut anchor 1 by bending when pushed onto the expansion body 7 in order to spread the expansion elements 13. In the longitudinal direction of the undercut anchor 1, the cantilever elements 20 are in Figure 4forward in the direction of the expansion body 7 over the cutting edges 18 of the cutting elements 17, i.e. the cantilever elements 20 protrude beyond an imaginary radial plane at the front ends of the cutting edges 18. During expansion, the expansion body 7 thereby supports the expansion elements 13 on the cantilever elements 20 axially in front of the cutting edges 18 of the cutting elements 17, thereby creating a lever which increases the radially outwardly directed expansion force, which acts on the cutting edges 18 outwards against the hole wall of the anchor hole 2, compared to the radially outwardly directed expansion force, which the expansion body 7 exerts on the cantilever elements 20 on the expansion elements 13.

[0035] At the Figure 5 illustrated embodiment of the invention as shown in Figure 3Slots 23 in the expansion elements 13 of the expansion sleeve 9, which extend from the front ends of the expansion elements 13 facing the expansion body 7 into the expansion elements 13 a short distance in the longitudinal direction of the undercut anchor 1. The slots 23 form free spaces 24 between the base bodies 21 and the cantilever elements 20 of the expansion elements 13, which delimit the cantilever elements 20 from the base bodies 21. Through the slots 23 or free spaces 24, the cantilever elements 20 can be pivoted or bent outwards relative to the base bodies 21 of the expansion elements 13 away from the longitudinal axis 10 of the undercut anchor 1.

[0036] In Figure 5 The cutting elements 17 are manufactured by deposition welding and subsequent grinding into a desired shape. The welding material, and thus the cutting elements 17, are harder than the expansion sleeve 9 and its expansion elements 13.

[0037] At the Figure 6In the embodiment shown, the free space 24 is arranged such that a connecting line 29, which connects the cutting edge 18 to the longitudinal axis 10, runs through the base body 21 but does not intersect the free space 24, wherein the connecting line 29 forms an angle α of 50° with the longitudinal axis 10. The cutting edge 18 is arranged on an outer side 27 of a reduced-thickness region 28 of the base body 21 and projects forward beyond the base body 21. An annular step 25, which runs radially to the longitudinal axis 10, is formed on the outer side 27 of the base body 21 and marks the transition to the reduced-thickness region 28. List of reference symbols

[0038] 1Undercut anchor 2Anchor hole 3Undercut 4Anchor base 5Anchor shaft 6Thread 7Expansion body 8, 8Front end 9Expansion sleeve 10Longitudinal axis 11Longitudinal slot 12Expansion section 13Expansion element 14Recess 15Form-lock coupling 16Rotary drive tool 17Cutting element 18Cutting edge 19Secondary cutting edge 20Cantilever element 21Base body 22Inner surface 23Slot 24Free space 25Annular step 26Further annular step 27Outside of the base body 21 28Thickness-reduced area of the base body 21 29Connecting line αAngle

Claims

1. Self-cutting undercut anchor (1), which extends along a longitudinal axis (10), with an expansion body (7) and with an expansion sleeve (9), which has at least one expansion element (13) at a front end (8), which can be swivelled outwards away from the longitudinal axis (10) by pushing the expansion sleeve (9) forwards onto the expansion body (7) in the direction of the longitudinal axis (10) of the undercut anchor (1), wherein the expanding sleeve (9) has a positive-locking coupling (15) at the rear for a non-rotatable attachment of a rotary drive tool (16) by positive locking for a rotary drive of the expanding sleeve (9) about the longitudinal axis (10) and wherein the expanding element (13) has a base body (21) with a cutting element (17), which has a cutting edge (18, 19) on an outer circumference for producing an undercut (3) in an anchor hole (2) by rotating and simultaneously pushing the expanding sleeve (9) onto the expanding body (7), characterised in that in that a cantilever element (20) projects from the base body (21) of the expanding element (13), the inner surface (22) of which cantilever element faces the expanding body (7) in such a way that the inner surface (22) of the cantilever element (20) is supported on the expanding body (7) when the expanding element (13) is swivelled outwards.

2. Self-cutting undercut anchor (1) according to claim 1, characterised in that a front outer edge of the cantilever element (20) has a smaller radial distance from the longitudinal axis (10) than the cutting edge (18, 19) of the cutting element (17).

3. Self-cutting undercut anchor (1) according to claim 1 or 2, characterised in that a radially inner region of the cantilever element (20) extends in the direction of the longitudinal axis (10) of the undercut anchor (1) at least up to a radial plane of the undercut anchor (1), in which the cutting edge (18) is located, and preferably projects axially forwards beyond the cutting edge (18).

4. Self-cutting undercut anchor (1) according to one or more of claims 1 to 3, characterised in that the expansion element (13) has a free space (24) between the cutting edge (18) and the cantilever element (20), in particular radially between the cutting edge (18) and the cantilever element (20).

5. Self-cutting undercut anchor (1) according to claim 4, characterised in that the expanding element (13) has a slot (23) extending in a longitudinal direction of the expanding sleeve (9) between the cutting edge (18, 19) and the inner surface (22) of the cantilever element (20), which is open at a front end (8a) of the expanding element (13), as a free space (24) between the cutting edge (18, 19) and the inner surface (22) of the cantilever element (20).

6. Self-cutting undercut anchor (1) according to claim 4 or 5, characterised in that a connecting straight line (29), which connects the cutting edge (18) to the longitudinal axis (10), runs through the base body (21) and does not intersect the free space (24), encloses an angle (α) of at least 35°, in particular of at least 45°, with the longitudinal axis (10).

7. Self-cutting undercut anchor (1) according to one or more of the preceding claims, characterised in that the cutting edge (18) projects forwards beyond the base body (21).

8. Self-cutting undercut anchor (1) according to one or more of the preceding claims, characterised in that an annular step (25) is arranged on an outer side (27) of the base body (21) of the expanding sleeve (9), by means of which annular step a thickness-reduced region (28) of the base body (21) is formed, on which the cutting element (17) is arranged.

9. Self-cutting undercut anchor (1) according to one or more of the preceding claims, characterised in that the cutting element (17) has a greater hardness than the base body (21) of the expanding element (13).

10. Self-cutting undercut anchor (1) according to one or more of the preceding claims, characterised in that the cutting element (17) is welded onto the at least one expanding element (13), in particular is produced by build-up welding.