Self-tapping undercut anchor

Abstract

According to the invention, a cutting element (16) of a self-tapping undercut anchor (1) is produced by laser surfacing a plurality of welding rods (17, 18) on an expansion element (14) of an expansion sleeve (9) of the undercut anchor (1).

Description

Technical Field

[0001] The invention relates to an undercut anchor of the self-drilling type having the features of the preamble of claim 1 and to a method for producing an undercut anchor having the features of the preamble of claim 9 . Background Art

[0002] Undercut anchors are expansion anchors that are anchored by expanding an expansion sleeve in an undercut in the anchoring hole. By expanding, the expansion anchor is held against being pulled out of the anchoring hole by means of a positive fit in the undercut, i.e. anchored by a positive fit. "Self-tapping" means that the undercut anchor creates an undercut in the anchoring hole itself.

[0003] Publication DE 102020105259 A1 discloses an undercut anchor with a rod-shaped anchor rod, which has a truncated cone-shaped expansion body at the front end. An expansion sleeve is arranged on the anchor rod, which is divided into cylindrical shell-shaped expansion elements by longitudinal grooves at its front end facing the expansion body. These expansion elements are pivoted radially outward by being pushed onto the expansion body, which can be understood as "opening" of the expansion element, the expansion sleeve and the undercut anchor. By laser powder cladding, a functional layer is applied to the expansion element in two layers at the front end of the expansion element, wherein the powder has hard material particles composed of tungsten carbide embedded in steel. After cladding, the functional layer is cold-formed into cutting elements by pressing, and these cutting elements cut an undercut in the anchor hole when the expansion sleeve rotates and is fed at the same time and the expansion element of the expansion sleeve is opened in the anchor hole. Summary of the invention

[0004] The object of the present invention is to provide a self-drilling undercut anchor of the type explained above having a more stable cutting element and a method for producing the undercut anchor.

[0005] This object is achieved according to the invention by the features of claims 1 and 9. Advantageous embodiments and developments of the invention are the subject matter of the dependent claims.

[0006] The undercut anchor according to the present invention extends along the longitudinal axis and has an expansion body and an expansion sleeve, which has at least one expansion element at the front end of the expansion sleeve. The expansion body is in particular truncated cone-shaped and can in particular have one or more steps. The expansion body is determined according to its function of opening at least one expansion element. The front end of the expansion sleeve and at least one expansion element is the end of the expansion sleeve or at least one expansion element facing the expansion body. In order to open, the expansion sleeve is pushed in the direction of the longitudinal axis in the direction of the expansion body so that at least one expansion element reaches the expansion body and is pivoted outward from the expansion body away from the longitudinal axis of the undercut anchor. The outward pivoting of at least one expansion element can also be understood as the opening of the expansion element, the expansion sleeve and the undercut anchor. The direction along which the expansion sleeve is pushed relative to the expansion body to open at least one expansion element is the expansion direction. By opening in the undercut in the anchoring hole, at least one expansion element enters into a rear engagement at or in the undercut, whereby the undercut anchor is held at or in the undercut in the anchoring hole by a positive locking portion of at least one expansion element of its expansion sleeve pivoted outward into the undercut, that is to say opened, which can be understood as the undercut anchor being anchored in the anchoring hole by the positive locking portion. By opening, the undercut anchor can be held in the anchoring hole by a non-positive locking portion or a friction locking portion in addition to the positive locking portion.

[0007] By surfacing, a cutting element is mounted externally on the outside of at least one expansion element. The cutting element is particularly welded at or near the front end of at least one expansion element facing the expansion body. The cutting element is particularly obtained directly by surfacing, so that subsequent processing is not required in an advantageous manner. Alternatively, the cutting element obtains its final shape after surfacing, for example, by deforming or cutting the surfacing portion. According to the present invention, the cutting element is welded externally on the outside of at least one expansion element in the form of at least two welding rods, wherein the two welding rods are arranged one after another in the longitudinal direction of the undercut anchor, that is, parallel to the longitudinal axis and transition into each other. The welding rods are, for example, linear or strip-shaped weld beads, weld seams, etc. By welding at least two welding rods externally on the outside of at least one expansion element, a wider cutting element in the direction of the longitudinal axis of the undercut anchor can be mounted externally on at least one expansion element of the expansion sleeve of the undercut anchor according to the present invention. Furthermore, the build-up welding of two welding rods according to the invention one after the other in the longitudinal direction of the undercut anchor enables a cutting element that projects forward beyond the front end of at least one expansion element or, if the cutting element projects forward beyond the front end of at least one expansion element, improves the stability of the cutting element in any case.

[0008] An improved solution provides that, in order to form the cutting element on the outside of the expansion element, welding rods are applied to the outside of at least one expansion element not only one after another in the longitudinal direction of the undercut anchor but also radially one above the other in such a way that the cutting element has a greater thickness or height in the radial direction of the expansion sleeve.

[0009] Preferably, the radially inner welding rod applied directly to at least one expansion element of the expansion sleeve of the undercut anchor according to the invention has a smaller thickness or height in the radial direction of the expansion sleeve than the radially outer welding rod applied radially on the outside to the radially inner welding rod. The radially inner welding rod applied directly to the at least one expansion element inputs less heat into the at least one expansion element during build-up welding due to its smaller thickness or height, thereby reducing strength losses due to heat input.

[0010] A development of the invention provides that at least one welding rod tapers in the circumferential direction of the expansion sleeve. This enables a wedge-shaped or sawtooth-shaped or generally a varying thickness or height of the cutting element in the circumferential direction of the expansion sleeve.

[0011] The wedge-shaped or sawtooth shape of the cutting element or in any case a stepped or varying height of the cutting element radially relative to the expansion sleeve also enables welding electrodes of different lengths in the circumferential direction of the expansion sleeve, which are applied radially one above the other.

[0012] One embodiment of the invention provides for welding rods that protrude forward, that is, that protrude beyond the front end of the at least one expansion element. Optionally, the radially outer welding rod can also protrude forward beyond the radially inner welding rod, wherein the radially outer welding rod can also protrude beyond the front end of the at least one expansion element, but does not necessarily have to do so in every case. The axially forward radially outer welding rod can also be axially retracted relative to the front end of the at least one expansion element.

[0013] A preferred embodiment of the invention provides four welding rods, which are applied externally to the outer side of at least one expansion element by build-up welding. Two radially inner welding rods are applied externally to the expansion element in the longitudinal direction of the undercut anchor one after another, and two radially outer welding rods are applied radially externally to the radially inner welding rod. The radially outer welding rods are also applied externally to at least one expansion element or to the radially inner welding rod one after another in the longitudinal direction of the undercut anchor and transition into one another. In the longitudinal direction of the undercut anchor, the radially outer welding rods can be applied to the radially inner welding rod without or with an offset in the longitudinal direction relative to the radially inner welding rod.

[0014] In one embodiment of the invention, the end of the cutting element is arranged in the middle of at least one expansion element in the circumferential direction. The end of the cutting element can also be arranged in a middle section, which extends over approximately one quarter or approximately one third of the circumferential direction of the at least one expansion element. This embodiment of the invention makes it possible to realize a cutting portion in the circumferential middle or in the middle section of the expansion element.

[0015] The method according to the invention with the features of claim 9 provides that a welding rod, for example in the form of a weld bead or weld seam, is placed or applied externally on the outer side of at least one expansion element of the expansion sleeve of the undercut anchor according to the invention by build-up welding. In particular, the welding rod forms a cutting element without further machining of the welding rod being required. Alternatively, the welding rod is formed into a cutting element, for example by deformation and / or cutting machining of the build-up weld. In particular, the welding rod is applied externally to the at least one expansion element at or near the front end.

[0016] To increase the radial thickness or height of the welding rod in the circumferential direction of the expansion sleeve, the welding rod is applied to at least one expansion element in the circumferential direction of the expansion sleeve and the welding speed is reduced. To reduce the thickness of the welding rod, the welding speed is increased.

[0017] Another possibility for varying the thickness or height of the weld overlay is to vary the heat input during the weld overlay.

[0018] Preferably, the welding rod forming the expansion element is applied externally to the at least one expansion element by laser build-up welding.

[0019] In order to vary the thickness of the build-up weld, according to the invention the laser power and / or the distance of the focal point of the laser beam from the outer side of the expansion element of the expansion sleeve can be varied during the laser build-up welding.

[0020] The features and feature combinations, embodiments and designs of the present invention mentioned above in the specification and the features and feature combinations mentioned below in the description of the drawings and / or shown in the drawings can be used not only in the respectively specified or shown combination, but also in any other combination in principle or individually. Embodiments of the present invention that do not have all the features of the dependent claims are feasible. The individual features of the claims can also be replaced by other disclosed features or feature combinations. The following embodiments of the present invention are feasible, which do not have all the features of the embodiments, but have any part of the features described in the embodiments in principle. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be explained in more detail below based on the embodiments shown in the accompanying drawings.

[0022] Figure 1 shows a half section of an undercut anchor according to the present invention;

[0023] Figure 2 Shows that according to Figure 1 Enlarged detail of arrow II in ;

[0024] Figure 3 Shown from Figure 1 Anchorage of the undercut anchor in the anchor hole. DETAILED DESCRIPTION

[0025] The undercut anchor 1 according to the invention shown in the figures is provided for anchoring in a particularly cylindrical anchor hole 2. The undercut anchor 1 is self-drilling, that is to say the undercut anchor 1 creates an undercut 3 in the anchor hole 2, which it engages behind in a form-fitting manner when the undercut anchor 1 is opened in the undercut 3. The anchor hole 2 is previously drilled into an anchoring base 4 consisting, for example, of concrete, stone or wall as a cylindrical blind hole.

[0026] The undercut anchor 1 has an anchor rod 5 and an expansion sleeve 9 arranged on the anchor rod 5, which has a thread 6 at the rear end and a truncated cone-shaped expansion body 7 at the front end 8. The expansion body 7 widens forward. The anchor rod 5, the expansion body 7 and the expansion sleeve 9 are coaxial with the longitudinal axis 10 of the undercut anchor 1. In the present embodiment, the expansion body 7 is integral with the anchor rod 5, but this is not mandatory for the present invention.

[0027] The expansion sleeve 9 has a longitudinal groove 11, which extends from a front end 12 of the expansion sleeve 9 facing the expansion body 7 over a portion of the axial length of the expansion sleeve 9. The longitudinal groove 11 does not have to extend straight in the axial plane of the expansion sleeve 9, as in the embodiment, but can also extend, for example, spirally at an angle to the axial plane, in a wavy or zigzag manner. The above list is exemplary and not exhaustive. The expansion sleeve 9 is divided into an expansion section 13 and an expansion element 14 by the longitudinal groove 11, which starts at the front end 12 of the expansion sleeve 9 facing the expansion body 7 and extends over a portion of the axial length of the expansion sleeve 9. In the present embodiment, the expansion element 14 can be understood as a connecting piece or a tongue-shaped part, which is arched in a cylindrical shell-like manner in the circumferential direction of the expansion sleeve 9 and extends in the direction of the truncated cone-shaped expansion body 7, where the expansion element 14 has a free front end 12, which is also the front end 12 of the expansion sleeve 9.

[0028] By axially displacing the expansion sleeve 9 on the anchor rod 5 in the direction of the longitudinal axis 10 in the direction of the expansion body 7, the expansion element 14 of the expansion sleeve 9 is displaced onto the expansion body 7. During the displacement, the expansion body 7, which widens in the described displacement direction of the expansion sleeve 9, presses the expansion elements 14 of the expansion sleeve 9 radially apart from one another, whereby the front end 12 of the expansion element 14 is pivoted outwardly away from the longitudinal axis 10 of the undercut anchor 1. The pivoting of the expansion element 14 apart from one another can also be understood as an expansion of the expansion element 14, the expansion sleeve 9 and the undercut anchor 1.

[0029] If in particular Figure 2 As can be seen in the enlarged view of , a cutting element 16 is arranged on the outer side 15 of the expansion element 14 of the expansion sleeve 9. The outer side 15 is the side of the expansion element 14 facing away from the anchor rod 5 and the expansion body 7.

[0030] The cutting element 16 is applied to the outer side 15 of the expansion element 14 at the front end 12 of the expansion sleeve 9 by build-up welding in a material-locking manner. In the present exemplary embodiment, the cutting element 16 is applied to the cutting element 16 on the outside by laser build-up welding. The welding material is a metal powder, which can include hard material particles, for example hard metal particles or ceramic particles. Other welding materials are possible.

[0031] A plurality of welding rods 17, 18 are welded to the outer side 15 of the expansion element 14 at the front end 12 of the expansion sleeve 9 axially one after the other and radially one above the other, which welding rods merge into one another in a materially bonded manner and form the cutting element 16 ( Figure 2 ). In the present embodiment, two radially inner welding rods 17 are applied directly to the expansion element 14 externally in an axial direction one after another and in such a way that they are sealed to one another, so that the two radially inner welding rods merge into one another in a material-locking manner, and the radially inner welding rod 17 also merges into the expansion element in a material-locking manner. In the present embodiment, two radially outer welding rods 18 are applied to the radially inner welding rod 17 by build-up welding radially on the outside with respect to the longitudinal axis 10. The outer welding rods 18 are also arranged axially one after another and in such a way that they merge into one another in a material-locking manner. In addition, the radially outer welding rod 18 merges into the radially inner welding rod 17 in a material-locking manner by build-up welding.

[0032] The outer welding rod 18 can be welded to the inner welding rod 17 without an offset in the longitudinal direction of the undercut anchor 1 or of the expansion sleeve 9. In the present embodiment, they have an offset: the outer welding rod 18 is welded to the inner welding rod 17 parallel to the longitudinal axis 10, forwardly, in the direction of the expansion body 7, offset from the inner welding rod 17. In the present embodiment, the offset is approximately half the width of the inner welding rod 17, that is, the outer welding rod 18 at the rear is located in the middle of the inner welding rod 17 as viewed in the longitudinal direction of the undercut anchor 1, and the outer welding rod 18 at the front protrudes forwardly beyond the inner welding rod 17 at the front. In the present embodiment as well, the inner welding rod 17 at the front protrudes beyond the front end 12 of the expansion element 14. This makes it possible to form the cutout 19 at the frontmost point of the expansion element 16.

[0033] The welding rods 17 , 18 are strip-shaped or linear weld beads or weld seams which are applied externally to the expansion element 14 by build-up welding.

[0034] The inner welding rod 17 is thinner and in any case thinner than the outer welding rod 18 , so that the heat input into the expansion element 14 due to the build-up welding, which could impair the strength of the expansion element 14 , is smaller.

[0035] The welding rods 17, 18 are welded to the outer side 15 of the expansion element 14 at the front end 12 of the expansion sleeve 9, extending in the circumferential direction of the expansion sleeve 9. The welding rods 17, 18 and therefore also the cutting element 16 start approximately in the middle of the expansion element 14, viewed in the circumferential direction, and extend from there counter to the provided rotational direction of the expansion sleeve 9 when producing the undercut 3 in the anchoring hole 2.

[0036] When the undercut 3 is produced in the anchoring hole 2, the radial thickness or height of the welding rods 17, 18 and therefore also of the cutting element 16 decreases from the circumferential center of the expansion element 14 in the circumferential direction opposite to the set rotation direction of the expansion sleeve 9 so that the cutting element 16 is the thickest or highest in the radial direction at its front end in the set rotation direction. The cutting element 16 is thus sawtooth-shaped or wedge-shaped, as seen in the direction of the longitudinal axis 10. A thickness of the cutting element 16 that varies in the circumferential direction can also be achieved by inner and outer welding rods 17, 18 of different lengths in the circumferential direction and / or by varying the distance between the focus of the laser beam and the outer side 15 of the expansion element 14 during laser cladding. After welding the welding rods 17, 18, they are not further processed or deformed. The welding rods 17, 18 form the cutting element 16 of the undercut anchor 1.

[0037] It is not necessary to arrange a cutting element 16 on each of the expansion elements 14, but it is sufficient if a cutting element 16 is arranged on at least one expansion element 14. Preferably, one or possibly also a plurality of cutting elements 16 are arranged on a plurality or all expansion elements 14 in each case.

[0038] Figure 3 The anchoring of an undercut anchor 1 according to the invention in an anchoring hole 2 is shown: for anchoring in an anchoring bottom 4, the undercut anchor 1 is inserted into the anchoring hole 2 with its expansion body 7 until the front end 8 of the expansion body 7 or the anchor rod 5 rests on the hole bottom of the anchoring hole 2. The expansion sleeve 9 is driven rotationally on the anchor rod 5 by means of a tubular rotary drive tool 20 or in another way and is pushed forward in the direction of the longitudinal axis 10 in the direction of the expansion body 7, whereby the expansion element 14 is pushed onto the expansion body 7 and pivoted outward from the expansion body 7 away from the longitudinal axis 10 of the undercut anchor 1. The cutting portion 19 of the cutting element 16 penetrates into the hole wall of the anchoring hole 2 and creates an undercut 3 in the form of a circumferential truncated cone-shaped widening of the anchoring hole 2 by rotation and axial feed. After the undercut 3 has been created, the rotary drive tool 20 is removed from the anchor rod 5. The expansion elements 14 pivoted outward into the undercut 3, i.e. opened, engage behind the undercut 3, whereby they hold the undercut anchor 1 in the anchoring hole 2 by means of a positive fit in the undercut 3. The self-drilling undercut anchor 1 according to the invention is anchored in the anchoring hole 2 by means of a positive fit.

[0039] The expansion elements 16 each have a cantilever element 21 on the inner side, which protrudes from the base body of the expansion element 14 forward in the direction of the expansion body 7. The cantilever elements 21 are formed by V-shaped grooves 22 in the front end face of the expansion element 14 extending in the circumferential direction.

[0040] The cantilever element 21 projects forward in the longitudinal direction in the direction of the expansion body 7 beyond the cutting element 16. As a result, the cantilever element 21 supports the expansion element 14 in the axial direction in front of the cutting element 16 on the expansion body 7. As a result, a lever arm is obtained, whereby the expansion force with which the expansion body 7 presses the expansion element 14 radially outward during expansion is smaller than the expansion force with which the cutting element 16 is pressed radially outward in the anchoring hole 2 against the hole wall of the anchoring hole 2 during expansion. The cantilever element 21 projecting forward in the direction of the expansion body 7 increases the expansion force with which the cutting element 16 is pressed outward against the hole wall of the anchoring hole 2 or into the hole wall during expansion.

[0041] List of reference numerals:

[0042] 1 Undercut Anchor

[0043] 2 anchor holes

[0044] 3 Undercut

[0045] 4 Anchor bottom

[0046] 5 Anchor rod

[0047] 6 Thread

[0048] 7 Expansion

[0049] 8 Front end of anchor rod 5

[0050] 9Expansion sleeve

[0051] 10 Vertical axis

[0052] 11 longitudinal grooves

[0053] 12 Front end of the expansion sleeve 9 or the expansion element 14

[0054] 13 Expansion section

[0055] 14 Expansion elements

[0056] 15 Outer side

[0057] 16 cutting elements

[0058] 17 Internal welding rod

[0059] 18 External welding rod

[0060] 19 Cutting Department

[0061] 20 turn drive tool

[0062] 21 Cantilever element

[0063] 22 V-grooves.

Claims

1. A self-drilling undercut anchor (1), which extends along a longitudinal axis (10), has an expansion body (7) and an expansion sleeve (9), which has at its front end (12) at least one expansion element (14), which can be pivoted outwardly in an expansion direction relative to the expansion body (7) away from the longitudinal axis (10) by pushing the expansion sleeve (9) in the direction of the longitudinal axis (10) of the undercut anchor (1), wherein: A cutting element (16) is applied to the outer side (15) of the at least one expansion element (14) by build-up welding, characterized in that the cutting element (16) has at least two welding strips (17, 18) which merge into one another and which follow one another in the direction of the longitudinal axis (10) of the undercut anchor (1).

2. The undercut anchor (1) according to claim 1, characterized in that The cutting element (16) has at least two welding electrodes (17, 18) which are arranged one above the other radially with respect to the longitudinal axis (10) on the outer side (15) of the expansion element (14) of the expansion sleeve (9).

3. The undercut anchor (1) according to claim 2, characterized in that A radially inner welding rod (17) welded directly to the expansion element (16) is thinner than a radially outer welding rod (18) welded radially to the longitudinal axis (10) on the outside to the inner welding rod (17).

4. Undercut anchor (1) according to any one or more of claims 1 to 3, characterized in that At least one welding electrode (17, 18) tapers in the circumferential direction of the expansion sleeve (9).

5. Undercut anchor (1) according to any one or more of claims 2 to 4, characterized in that The welding rods (17, 18) arranged radially one above the other have different lengths in the circumferential direction of the expansion sleeve (9).

6. Undercut anchor (1) according to any one or more of claims 2 to 5, characterized in that A radially outer welding rod (18) projects forward in the direction of the longitudinal axis (10) beyond a radially inner welding rod (17) and / or beyond a front end (12) of at least one expansion element (14) of the expansion sleeve (9).

7. Undercut anchor (1) according to any one or more of claims 2 to 6, characterized in that Four welding rods (17, 18) for forming the cutting element (16) are applied externally to the outer side (15) of at least one expansion element (16) of the expansion sleeve (9), wherein two radially inner welding rods (17) are arranged one behind the other in the longitudinal direction of the undercut anchor (1) and two radially outer welding rods (18) are applied radially externally to the two radially inner welding rods (17).

8. Undercut anchor (1) according to any one or more of the preceding claims, characterized in that The end of the cutting element (16) is arranged in the middle on the at least one expansion element (14) in the circumferential direction of the expansion sleeve (9).

9. A method for producing an undercut anchor of the self-drilling type according to any one or more of the preceding claims, characterized in that The welding rods (17, 18) are manufactured by build-up welding.

10. The method according to claim 9, characterized in that The overlay welding is performed at an increased welding speed to increase the thickness or height of the overlay weld radially relative to the longitudinal axis (10), or the overlay welding is performed at a reduced welding speed to reduce the thickness or height of the overlay weld radially relative to the longitudinal axis (10).

11. The method according to claim 9 or 10, characterized in that: The heat input is varied during the build-up welding to vary the thickness or height of the build-up weld radially to the longitudinal direction (10).

12. The method according to any one or more of claims 9 to 11, characterized in that The surfacing welding is implemented as laser surfacing welding.

13. The method according to any one or more of claims 9 to 12, characterized in that During the build-up welding, the laser power is changed to change the thickness or height of the build-up weld radially relative to the longitudinal axis (10).

14. The method according to any one or more of claims 9 to 13, characterized in that During the build-up welding, the distance between the focal point of the laser beam and the outer side (15) of the expansion element (14) of the expansion sleeve (9) is changed in order to change the thickness or height of the build-up weld radially with respect to the longitudinal axis (10).

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