Self-tapping undercut anchor

Abstract

The invention proposes manufacturing a undercut anchor (1) of the self-tapping type by laser cladding a plurality of welding rods (17, 18) onto an expansion element (14) of an expansion sleeve (9) of the undercut anchor (1).

Description

TECHNICAL FIELD

[0001] The invention relates to a self-tapping undercut anchor and to a method for producing an undercut anchor. BACKGROUND

[0002] An undercut anchor is an expansion anchor which is anchored by opening an expansion sleeve in an undercut in the anchor hole. By opening, the expansion anchor is held against being pulled out of the anchor hole by means of a form-locking portion in the undercut, that is to say is anchored by means of the form-locking portion. "Self-tapping" means that the undercut anchor creates the undercut in the anchor hole itself.

[0003] The publication DE 10 2020 105 259 A1 discloses an undercut anchor having a rod-shaped anchor rod which has a truncated conical expansion body at the front end. On the anchor rod is arranged an expansion sleeve which is divided at its front end facing the expansion body by a longitudinal slot into column-shell-like curved expansion elements which are pivoted radially outwards by pushing onto the expansion body, which can be understood as an "opening" of the expansion elements, the expansion sleeve and the undercut anchor. By means of laser powder build-up welding, a functional layer is applied to the expansion elements in two layers one after the other on the outside at the front end of the expansion elements, wherein the powder has hard material particles of tungsten carbide embedded in steel. After the build-up welding, the functional layer is cold-formed by pressing into cutting elements which cut out the undercut in the anchor hole when the anchor rod is turned and simultaneously fed and the expansion elements of the expansion sleeve are opened in the anchor hole. SUMMARY

[0004] It is an object of the invention to propose a self-tapping undercut anchor of the type set forth at the outset and a method for producing an undercut anchor which has more stable cutting elements.

[0005] The object is achieved according to the features described below: The cutting element has at least two welds which transition into one another, which follow one another in the direction of the longitudinal axis of the undercut anchor. Advantageous embodiments and refinements of the invention include: The cutting element has at least two welds which lie radially to one another on the outside of the expansion element of the expansion sleeve, stacked one above the other in the direction of the longitudinal axis; a radially inner weld which is welded directly to the expansion element is thinner than a radially outer weld which is welded radially to the longitudinal axis to the inside of the radially outer weld; at least one weld is thinned in the circumferential direction of the expansion sleeve; the radially stacked welds differ in length in the circumferential direction of the expansion sleeve; a radially outer weld projects in the direction of the longitudinal axis further forward than a radially inner weld and / or further forward than the front end of at least one expansion element of the expansion sleeve; four welds for forming the cutting element are applied on the outside of at least one expansion element of the expansion sleeve, wherein two radially inner welds are arranged one after the other in the longitudinal direction of the undercut anchor and two radially outer welds are applied radially on the outside of the two radially inner welds; the ends of the cutting element are arranged in the middle on the at least one expansion element in the circumferential direction of the expansion sleeve.

[0006] The undercut anchor according to the invention extends along a longitudinal axis and has an expansion body and an expansion sleeve which has at least one expansion element at a front end of the expansion sleeve. The expansion body is in particular frustoconical and can in particular have one or more steps. The expansion body is determined according to its function of opening the at least one expansion element. The front end of the expansion sleeve and of the at least one expansion element is the end of the expansion sleeve or of the at least one expansion element which faces the expansion body. For opening, the expansion sleeve is thus displaced in the direction of the longitudinal axis in the direction of the expansion body, so that the at least one expansion element reaches the expansion body and is pivoted outwards away from the longitudinal axis of the undercut anchor. The pivoting outwards of the 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 in which the expansion sleeve is displaced relative to the expansion body in order to open the at least one expansion element is the expansion direction. By opening in the undercut in the anchor hole, the at least one expansion element enters into a back engagement behind the undercut, whereby the undercut anchor is held by the at least one pivoted-out expansion element of the expansion sleeve in the shape-locking manner in the undercut in the anchor hole, that is to say opened, which can be understood as the undercut anchor being anchored in the anchor hole by the shape-locking manner. By opening, the undercut anchor can be held in the anchor hole not only by the shape-locking manner but also by a force-locking or frictional-locking manner.

[0007] By means of the build-up welding, a cutting element is mounted externally at the outer side of the at least one expansion element. The cutting element is in particular welded at or near the front end of the at least one expansion element facing the expansion body. The cutting element is in particular obtained by the build-up welding directly, so that in an advantageous manner no subsequent machining is required. Alternatively, the cutting element obtains its final shape after the build-up welding, for example by deforming or machining the build-up welding. According to the application, the cutting element is externally welded on the outer side of the at least one expansion element in the manner of at least two weld beads, wherein the two weld beads are arranged next to one another in the longitudinal direction of the undercut anchor, that is to say parallel to the longitudinal axis, and transition into one another. The weld beads are for example linear or strip-shaped welds, seams or the like. By welding at least two weld beads externally on the outer side of the at least one expansion element, it is possible to mount a cutting element which is wider in the direction of the longitudinal axis of the undercut anchor externally at the at least one expansion element of the expansion sleeve of the undercut anchor according to the application. Furthermore, the build-up welding of two weld beads next to one another in the longitudinal direction of the undercut anchor according to the application makes it possible to achieve a cutting element which projects forward beyond the front end of the at least one expansion element, or, if the cutting element projects forward beyond the front end of the at least one expansion element, in any case improves the stability of the cutting element.

[0008] An improvement provides that, in order to form the cutting element externally on the expansion element, the weld beads are not only arranged next to one another in the longitudinal direction of the undercut anchor, but the weld beads are also applied externally on the at least one expansion element one above another in the radial direction, so that the cutting element has a greater thickness or height in the radial direction of the expansion sleeve.

[0009] Preferably, the weld beads which are applied externally on the at least one expansion element of the expansion sleeve of the undercut anchor according to the application radially inward have a smaller thickness or height in the radial direction of the expansion sleeve than the weld beads which are applied externally on the weld beads radially outward. The weld beads which are applied radially inward on the at least one expansion element input less heat into the at least one expansion element when the build-up welding is carried out, as a result of which the strength loss due to the heat input is reduced.

[0010] An improvement of the application provides that the at least one weld bead is thinned in the circumferential direction of the expansion sleeve. This enables a wedge-shaped or serrated shape or generally a varying thickness or height of the cutting element in the circumferential direction of the expansion sleeve.

[0011] A wedge-shaped or serrated shape of the cutting element or in any case a stepped or varying height of the cutting element radially of the expansion sleeve also enables weld beads which are applied one above another radially in the circumferential direction of the expansion sleeve to be of different length.

[0012] One design variant of the application provides a welding rod which projects forwards, that is to say, which projects beyond the front end of the at least one expansion element. Alternatively, the radially outer welding rod can also project forwards beyond the radially inner welding rod, wherein the radially outer welding rod can also project 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] One preferred design variant of the application provides four welding rods which are applied externally to the outside of the at least one expansion element by means of build-up welding. Two radially inner welding rods are applied externally to the expansion element in succession with one another in the longitudinal direction of the undercut anchor and two radially outer welding rods are applied externally to the radially inner welding rods in the radial direction. The radially outer welding rods are likewise applied externally to the at least one expansion element or to the radially inner welding rods in succession with one 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 rods with or without longitudinal offset relative to the radially inner welding rods.

[0014] In one design variant of the application, the end of the cutting element is arranged in the middle of the 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 in the circumferential direction of the at least one expansion element. This design variant of the application enables a cut in the circumferential middle or in a middle section of the expansion element.

[0015] The method according to the application provides that a welding rod, for example in the form of a bead or a weld, is applied externally to the outside of the at least one expansion element of the expansion sleeve of the undercut anchor according to the application by means of build-up welding. In particular, the welding rod forms the cutting element without further processing of the welding rod. Alternatively, the welding rod is shaped into a cutting element, for example by deforming and / or machining the build-up welding. In particular, the welding rod is applied externally to the at least one expansion element at or near the front end.

[0016] In order 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 the at least one expansion element in the circumferential direction of the expansion sleeve and the welding speed is reduced. In order to reduce the thickness of the welding rod, the welding speed is increased.

[0017] A further possibility for changing the thickness or height of the build-up welding is to change the heat input during the build-up welding.

[0018] Preferably, the welding strips forming the expansion elements are applied to the at least one expansion element externally by laser deposition welding.

[0019] In order to vary the thickness of the deposited weld, it is possible according to the application to vary the laser power and / or the distance of the focal point of the laser beam from the outside of the expansion element of the expansion sleeve during laser deposition welding.

[0020] The features and combinations of features mentioned in the above description and the embodiments and designations of the application mentioned in the above description and / or shown in the attached drawings can be used not only in the respectively stated combinations, but also in other combinations, either individually or in sub-combinations. Embodiments of the application that do not have all the features of the independent claim are possible. The individual features of the claims can also be replaced by other disclosed features or feature combinations. Embodiments of the application are possible which do not have all the features of the examples, but have only a principle arbitrary part of the features of the examples. BRIEF DESCRIPTION OF DRAWINGS

[0021] The application is explained in more detail below on the basis of the embodiments shown in the drawings. Therein:

[0022] Figure 1 A half-section of an undercut anchor according to the application is shown;

[0023] Figure 2 An enlarged detail according to arrow II in Figure 1 is shown;

[0024] Figure 3 The anchoring of an undercut anchor from Figure 1 in an anchor hole is shown; DETAILED DESCRIPTION

[0025] The undercut anchor 1 shown in the drawings, according to the application, is provided for anchoring in an anchor hole 2, in particular a columnar anchor hole. The undercut anchor 1 is self-tapping, that is to say the undercut anchor 1 creates an undercut 3 in the anchor hole 2, which the undercut anchor engages form-fittingly behind when it is expanded in the undercut 3. The anchor hole 2 is drilled beforehand into an anchor base 4, for example of concrete, stone or wall, as a columnar blind hole.

[0026] The undercut anchor 1 has an anchoring shank 5 which has a thread 6 at the rear end and a conically expanding body 7 at the front end 8, and a dilatation sleeve 9 arranged on the anchoring shank 5. The expanding body 7 widens out towards the front. The anchoring shank 5, the expanding body 7 and the dilatation sleeve 9 are coaxial with a longitudinal axis 10 of the undercut anchor 1. In the present embodiment, the expanding body 7 is integral with the anchoring shank 5, however this is not mandatory for the invention.

[0027] The dilatation sleeve 9 has a longitudinal slot 11 which extends from a front end 12 of the dilatation sleeve 9 facing the expanding body 7 over a portion of the axial length of the dilatation sleeve 9. The longitudinal slot 11 does not necessarily extend straight in the axial plane of the dilatation sleeve 9, as in the embodiment, but can also extend, for example, helically at an angle to the axial plane, undulatingly or zigzag. The list is exemplary and not exhaustive. The dilatation sleeve 9 is divided by the longitudinal slot 11 into a dilatation section 13 which begins at the front end 12 of the dilatation sleeve 9 facing the expanding body 7 towards the front and extends over a portion of the axial length of the dilatation sleeve 9, and a dilatation element 14. In the present embodiment, the dilatation element 14 can be understood as a web or tongue which is vaulted in the peripheral direction of the dilatation sleeve 9 and which extends towards the conically expanding body 7, where the dilatation element 14 has a free front end 12 which is at the same time the front end 12 of the dilatation sleeve 9.

[0028] By axially displacing the dilatation sleeve 9 on the anchoring shank 5 in the direction of the longitudinal axis 10 towards the expanding body 7, the dilatation element 14 of the dilatation sleeve 9 is pushed onto the expanding body 7. In the displacement, the expanding body 7, which widens out in the described displacement direction of the dilatation sleeve 9, presses the dilatation element 14 of the dilatation sleeve 9 apart from one another in the radial direction, whereby the front end 12 of the dilatation element 14 pivots outwards away from the longitudinal axis 10 of the undercut anchor 1. The pivoting apart of the dilatation element 14 can also be understood as the opening of the dilatation element 14, the dilatation sleeve 9 and the undercut anchor 1.

[0029] As can be seen in particular in the enlarged view of Figure 2 A cutting element 16 is arranged at the outer side 15 of the dilatation element 14 of the dilatation sleeve 9. The outer side 15 is the side of the dilatation element 14 which faces away from the anchoring shank 5 and the expanding body 7.

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

[0031] A plurality of welding beads 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 beads material-lockingly transition into one another and which form the cutting element 16. Figure 2 In the present embodiment, two radially inner welding beads 17 are applied directly to the expansion element 14, axially one after the other and thus sealingly one from the other, on the outside, so that the two radially inner welding beads material-lockingly transition into one another, the radially inner welding beads 17 likewise material-lockingly into the expansion element. In the present embodiment, radially on the outside, two radially outer welding beads 18 are applied to the radially inner welding beads 17 by means of build-up welding. The outer welding beads 18 are likewise arranged axially one after the other and thus sealingly one from the other, so that they material-lockingly transition into one another. Furthermore, the radially outer welding beads 18 material-lockingly transition into the radially inner welding beads 17 by means of build-up welding.

[0032] The outer welding beads 18 can be welded to the inner welding beads 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 beads 18 are welded to the inner welding beads on the inside, offset in the direction parallel to the longitudinal axis 10, that is to say towards the expansion body 7. In the present embodiment, the offset is approximately half the width of the inner welding beads 17, that is to say the rear outer welding bead 18 is located in the middle of the inner welding beads 17, seen in the longitudinal direction of the undercut anchor 1, and the front outer welding bead 18 projects forwards beyond the front inner welding bead 17. Also in the present embodiment, the front inner welding bead 17 projects beyond the front end 12 of the expansion element 14. It is thereby possible to configure the cutting portion 19 at the foremost portion of the expansion element 16.

[0033] The welding beads 17, 18 are strip-shaped or wire-like welds or seams which are applied to the expansion element 14 on the outside by means of build-up welding.

[0034] The inner welding beads 17 are thinner and in any case thinner than the outer welding beads 18, so that the heat input into the expansion element 14 by means of the build-up welding is less, which can impair the strength of the expansion element 14.

[0035] The welding beads 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 beads 17, 18 and thus also the cutting element 16 begin approximately in the middle of the expansion element 14, seen in the circumferential direction, and extend therefrom against the set direction of rotation of the expansion sleeve 9 when creating the undercut 3 in the anchor hole 2.

[0036] When the undercut 3 is created in the anchor hole 2, the radial thickness or height of the welding strips 17, 18 and thus also of the cutting elements 16 is reduced in the circumferential direction from the circumferential middle of the expansion element 14 against the set direction of rotation of the expansion sleeve 9 so much that the cutting elements 16 are radially thickest or highest at their front end in the set direction of rotation. Seen in the direction of the longitudinal axis 10, the cutting elements 16 are thus sawtooth-shaped or wedge-shaped. A varying thickness of the cutting elements 16 in the circumferential direction can also be achieved by the inner and outer welding strips 17, 18 being of different length in the circumferential direction and / or by varying the distance of the focal point of the laser beam from the outer side 15 of the expansion element 14 when laser cladding. After the welding of the welding strips 17, 18, the welding strips 17, 18 are not further processed or deformed. The welding strips 17, 18 form the cutting elements 16 of the undercut anchor 1.

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

[0038] Figure 3 The anchoring of the undercut anchor 1 in the anchor hole 2 is shown: In order to be anchored in the anchor bottom 4, the undercut anchor 1 with its expansion body 7 is previously placed into the anchor hole 2 until the front end 8 of the expansion body 7 or of the anchor rod 5 rests on the hole bottom of the anchor hole 2. The expansion sleeve 9 is driven rotationally on the anchor rod 5 with a tubular rotary drive tool 20 or else in another way and is displaced in the direction of the longitudinal axis 10 towards the expansion body 7, whereby the expansion elements 14 are pushed onto the expansion body 7 and are pivoted outwards away from the longitudinal axis 10 of the undercut anchor 1. The cutting portions 19 of the cutting elements 16 penetrate into the hole wall of the anchor hole 2 and a undercut 3 in the form of a circumferential frustoconical widening of the anchor hole 2 is created by rotation and axial feed. After the creation of the undercut 3, the rotary drive tool 20 is removed from the anchor rod 5. The outwardly pivoted expansion elements 14 behind the undercut 3, that is to say flared, engage the undercut 3, whereby the undercut anchor 1 is held in the anchor hole 2 by the form-locking in the undercut 3. The self-tapping undercut anchor 1 according to the application is anchored in the anchor hole 2 by the form-locking.

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

[0040] The cantilever element 21 projects in the longitudinal direction beyond the cutting element 16 in the direction of the expansion body 7. The cantilever element 21 thus supports the expansion element 14 in the axial direction in front of the cutting element 16 at the expansion body 7. A lever arm is thus obtained, whereby the expansion force with which the expansion body 7 presses the expansion element 14 radially outwards when being opened is smaller than the expansion force with which the cutting element 16 is pressed radially outwards against the hole wall of the anchoring hole 2 when being opened. The cantilever element 21, which projects in the direction of the expansion body 7, increases the expansion force with which the cutting element 16 is pressed outwards against or into the hole wall of the anchoring hole 2 when being opened.

[0041] List of reference signs:

[0042] 1 undercut anchor

[0043] 2 anchoring hole

[0044] 3 undercut

[0045] 4 anchoring base

[0046] 5 anchoring stem

[0047] 6 thread

[0048] 7 expansion body

[0049] 8 front end of the anchoring stem 5

[0050] 9 expansion sleeve

[0051] 10 longitudinal axis

[0052] 11 longitudinal slot

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

[0054] 13 expansion section

[0055] 14 expansion element

[0056] 15 outer side

[0057] 16 cutting element

[0058] 17 inner welding rod

[0059] 18 outer welding rod

[0060] 19 cutting portion

[0061] 20 rotary drive tool

[0062] 21 cantilever element

[0063] 22 V-shaped slot

Claims

1. A self-tapping undercut anchor (1) extending along a longitudinal axis (10), having an expansion body (7) and an expansion sleeve (9), the expansion sleeve having at least one expansion element (14) at its front end (12), the expansion element being pivotable outward in the expansion direction about the expansion body (7) away from the longitudinal axis (10) by pushing the expansion sleeve (9) along the longitudinal axis (10) of the undercut anchor (1), wherein, The cutting element (16) is applied to the outside (15) of the at least one expansion element (14) by overlay welding, characterized in that the cutting element (16) has at least two welding rods (17, 18) that transition into each other, which are sequentially connected to each other along 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 rods (17, 18) that are radially stacked on each other 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, The radially inner welding rod (17) directly welded to the expansion element (14) is thinner than the radially outer welding rod (18) welded to the inner welding rod (17) radially to the longitudinal axis (10).

4. The undercut anchor (1) according to any one of claims 1 to 3, characterized in that, At least one welding electrode (17, 18) is thinned along the circumferential direction of the expansion sleeve (9).

5. The undercut anchor (1) according to claim 2 or 3, characterized in that, The welding electrodes (17, 18) arranged radially stacked on top of each other have different lengths along the circumferential direction of the expansion sleeve (9).

6. The undercut anchor (1) according to claim 2 or 3, characterized in that, The outermost welding rod (18) extends forward along the longitudinal axis (10) beyond the innermost welding rod (17) and / or extends forward beyond the front end (12) of at least one expansion element (14) of the expansion sleeve (9).

7. The undercut anchor (1) according to claim 2 or 3, 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 (14) of the expansion sleeve (9), wherein two radially inward welding rods (17) are arranged successively to each other along the longitudinal direction of the undercut anchor (1), and two radially outward welding rods (18) are applied radially to the two radially inward welding rods (17).

8. The undercut anchor (1) according to any one of claims 1 to 3, characterized in that, The end of the cutting element (16) is arranged in the middle of the at least one expansion element (14) along the circumferential direction of the expansion sleeve (9).

9. A method for manufacturing a self-tapping undercut anchor according to any one of the preceding claims, characterized in that, The welding electrodes (17, 18) are manufactured by overlay welding.

10. The method according to claim 9, characterized in that, The welding can be performed at an increased welding speed to increase the radial thickness or height of the weld overlay relative to the longitudinal axis (10), or at a decreased welding speed to decrease the radial thickness or height of the weld overlay relative to the longitudinal axis (10).

11. The method according to claim 10, characterized in that, During the welding process, the heat input is changed to alter the thickness or height of the welded portion radially relative to the longitudinal axis (10).

12. The method according to any one of claims 9 to 11, characterized in that, The welding process is achieved through laser welding.

13. The method according to claim 10 or 11, characterized in that, During the welding process, the laser power is changed to alter the thickness or height of the welded portion radially relative to the longitudinal axis (10).

14. The method according to claim 10 or 11, characterized in that, During the welding process, 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 to change the radial thickness or height of the welded portion relative to the longitudinal axis (10).

Images