SPREADING ANCHOR

Description

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

[0002] A generic expansion anchor is known from published patent application DE 10 2004 053 255 A1. The expansion anchor is a so-called bolt anchor, which is inserted into a borehole in the anchoring base for fastening an attachment to an anchoring base. The bolt anchor has a one-piece anchor shaft with an external thread at its rear end and a conical expansion body at its front end. An expansion sleeve of the expansion anchor is arranged in a neck section of the anchor shaft with a reduced diameter. To anchor the expansion anchor in the borehole, the front part of the expansion anchor, on which the expansion sleeve is arranged, is driven into the borehole, so that the expansion sleeve is clamped in the borehole. By moving the anchor shaft backward, the expansion body is drawn into the expansion sleeve, causing the expansion sleeve to expand and be pressed with its front end against the wall of the borehole.To ensure the expansion sleeve has the best possible hold in the borehole, the expansion sleeve features expansion segments separated by slots, the wall thickness of which is reduced by stamping at their front end in a ring-shaped, stepped section. This stamping creates two edges located in two parallel radial planes spaced apart from each other along the longitudinal axis. During expansion, the edges are pressed against the borehole wall and cut into the borehole wall in a linear fashion, improving the hold of the expansion sleeve in the borehole.

[0003] The object of the invention is to propose an expansion anchor in which the hold of the expansion sleeve in the borehole is further improved.

[0004] This object is achieved according to the invention by an expansion anchor having the features of claim 1. The expansion anchor according to the invention has an anchor shaft and an expansion sleeve. The anchor shaft extends along a longitudinal axis from a rear end forward in the insertion direction. The insertion direction is the direction in which the expansion anchor is intended to be inserted into a borehole. "Front" and "rear" refer here and below to the insertion direction. A front end of the expansion anchor is therefore the part of the expansion anchor that first enters the borehole when the expansion anchor is driven into the borehole. The anchor shaft has an expansion body that expands in diameter, particularly forward in the insertion direction and / or away from the expansion sleeve. "Diameter" refers to the diameter of a circle circumscribing the cross-section of the expansion body, the center of which lies on the longitudinal axis.The expansion body forms, in particular, the front end of the anchor shaft. The expansion sleeve can be expanded by pulling the expansion body into the expansion sleeve or by sliding the expansion sleeve onto the expansion body. The expansion sleeve is therefore expanded by a relative movement of the expansion body to the expansion sleeve, through which the expansion body penetrates the expansion sleeve and pushes it radially toward the longitudinal axis and outward away from it. For this purpose, the expansion body is particularly shaped like an expansion cone.

[0005] To ensure that the expansion sleeve can be easily expanded when the expansion body is retracted, the expansion sleeve has several expansion segments separated from each other by slots in the circumferential direction. Thus, the expansion sleeve does not have a closed circumference in the area of ​​the expansion segments. The slots can, in particular, run parallel to the longitudinal axis. They extend only over part of the axial length of the expansion sleeve, so that the expansion segments are integrally connected to one another via an annular connecting section.

[0006] At least one, in particular each, of the expansion segments has an end section with a reduced wall thickness, which, in a non-expanded state, faces the expansion body and / or rests against it. The end section is bounded on the outer side of the expansion sleeve in the longitudinal direction by two of the slots and in the circumferential direction by a first edge and a second edge. This means that the two slots are oriented in the longitudinal direction and the two edges in the circumferential direction. However, this does not preclude the slots from being entirely or partially inclined or extending transversely to the longitudinal direction and / or the edges from being entirely or partially inclined or extending transversely to the circumferential direction. "Outer side" refers to the surface of the expansion sleeve facing away from the longitudinal axis and extending in the circumferential and longitudinal directions.The first edge and the second edge are spaced apart from one another in the longitudinal direction and extend in the circumferential direction from a first of the slots to another of the slots. In particular, the second edge forms the free end of an expansion segment that faces the expansion body. In contrast, the first edge marks the transition from a rear part of the expansion sleeve to the end section, which occurs in a type of step at which the wall thickness of the expansion sleeve decreases to the wall thickness of the reduced end section. The step is thus part of the end section. The step can transition into the end section continuously or discontinuously, as a surface inclined to the longitudinal axis or as an abrupt right-angled transition. In the case of a continuous transition, the edge between the step and the end section and / or between the step and the rear part can be rounded. For example, it can be designed as a step-like annular step surrounding the expansion sleeve.

[0007] The expansion anchor can, in particular, be a bolt anchor with a one-piece anchor shaft, at the front end of which the expansion body is arranged. In a bolt anchor, the anchor shaft is, in particular, one-piece and has a load application means at the rear with which a force can be transferred from an attachment to the expansion anchor. The load application means is, in particular, a thread onto which a nut can be screwed to fasten the attachment or, in the case of an internal thread, a screw can be screwed. Alternatively, the expansion anchor can also be designed as a sleeve anchor, in which the expansion body of the anchor shaft is usually a conical nut, which is screwed onto a screw thread to expand the expansion sleeve backwards, i.e., opposite the direction of insertion. The screw also forms part of the anchor shaft of a sleeve anchor.Regardless of whether the expansion anchor is designed as a bolt or sleeve anchor, the expansion sleeve is located in an expansion area at the front of the expansion anchor. It is, in particular, made of a single piece of sheet metal, bent circumferentially around the anchor shaft, as is typical for bolt anchors. Alternatively, the expansion sleeve can be made of a tube, as is common with sleeve anchors.

[0008] According to the invention, the first edge extends in the shape of an arc between the two slots, and the second edge extends in the shape of an arc between the two slots. "Arc" here generally refers to a curved curve that, when the expansion sleeve is unfolded in a plane, does not form a straight line. Due to the arc-shaped shape, the points of an edge, i.e., all points that geometrically form the edge, are no longer located together in a radial plane relative to the longitudinal axis. Instead, a vertex of the arc is axially offset from at least one of the endpoints. An "endpoint" is the point at which the edge begins or ends at one of the slots. In particular, the vertex is axially offset from both endpoints, so that it forms the front or rear end of the arc.As a result, for example, the apex of the second edge is closer to the expansion body than the two end points of the second edge during expansion in the insertion direction, so that the apex is pressed against the wall of a borehole earlier and, as a result, more strongly than the end points, which is preferred. In general, the curved shape presses individual points, particularly the apex and / or the end points, more strongly against the borehole wall, resulting in stress peaks at specific points, which improves the incision or indentation of the edge into the borehole wall.

[0009] Preferably, the edges are produced by a stamping process. During stamping, the material of a starting body for the production of the expansion sleeve is displaced and reshaped by the application of force, which increases the strength of the metal of the expansion sleeve in the end section, particularly in the area of ​​the edges. Stamping also enables cost-effective production of the expansion sleeve of the expansion anchor according to the invention.

[0010] In particular, the edge extends in an arc from one of the endpoints at least to a center point of the edge. The "center point," however, lies circumferentially in an axial plane in which the longitudinal axis of the expansion anchor lies and which is equidistant from the two endpoints.

[0011] In particular, the edge runs from a first end point of the edge to the center point of the edge in a first arc section which, with respect to an axial plane in which the center point lies, is symmetrical to a second arc section running from the second end point of the edge to the center point. In this case, the center point forms the apex of the arc. This facilitates production, particularly production by embossing, since during embossing the material is displaced more towards the center or more material is moved than towards the end points. In particular, the two arc sections merge continuously into one another at the apex. Alternatively, they can form a tapered apex.

[0012] In a preferred embodiment of the expansion anchor according to the invention, the first and second edges are curved in the same direction longitudinally. This means that for both edges, the apex of the curve is offset in the same direction relative to the longitudinal axis relative to the respective endpoints. In this embodiment, the edges can be arranged so closely together that they support each other when pressed into the borehole wall, and the stresses in the borehole wall generated by one edge overlap with the stresses induced by the second edge, which is particularly advantageous for hard building materials such as high-strength concrete.

[0013] Alternatively, the two edges are curved longitudinally in opposite directions, whereby the two vertices of the edges are further apart than the end points of the edges. This increases the surface area of ​​the end section, which can lie flat against the borehole wall. This is advantageous for softer building materials such as normal concrete, low-strength concrete, or sand-lime brick, as it counteracts localized damage to the borehole wall. Furthermore, the edges engage the borehole wall at spatially separated locations without interaction, which compensates for inhomogeneities in the surface of the borehole wall.

[0014] In a preferred embodiment of the expansion anchor according to the invention, at least one of the edges is curved in a circular arc. This facilitates production, particularly production by stamping, since the material can be displaced in an approximately circular shape during stamping. In particular, the circular arc extends from a first end point of the edge to the second end point. The center of the circular arc lies, in particular, in an imaginary development on the outer surface of the expansion sleeve.

[0015] In a further preferred embodiment of the expansion anchor according to the invention, both edges are curved as circular arcs, with both circular arcs having different radii and, in particular, different center points. In particular, the radius of the edge forming the free end of the end section is smaller than the radius of the edge delimiting the end section in the region of the step.

[0016] It is further preferred that the slots are widened in the circumferential direction in the region of the end section. In particular, the width of an expansion segment measured in the circumferential direction in the region of the end section is smaller than the width at the widest point of the expansion segment. This makes it easier to bend the end section radially outward and press it against the borehole wall during expansion. Furthermore, a correspondingly shaped widening of the slots can create additional edges on the expansion segment, which come into active contact with the borehole wall during expansion, further increasing the friction and thus the hold of the expansion sleeve in the borehole.

[0017] Furthermore, it is preferred that the end section extends radially away from the longitudinal axis toward the front end. The end section is thus already bent radially outward before expansion, which facilitates retraction of the expansion body into the expansion sleeve.

[0018] 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, are not only usable in the respective specified or drawn combination. Embodiments of the invention are possible that do not have all the features of a dependent claim.

[0019] The invention is explained in more detail below with reference to the drawings. They show: Figure 1 shows an expansion anchor according to the invention with a first expansion sleeve in a side view; Figure 2 shows an enlarged view of the expansion section of the expansion anchor of the Figure 1 ; Figure 3 a plan view of the outside of a development of the first expansion sleeve; Figure 4 a section along the line IV-IV of the Figure 3; Figure 5 shows an enlarged view of the end section of an expansion sleeve of a second expansion anchor according to the invention; Figure 6 shows a plan view of the outside of a developed section of an expansion sleeve of an expansion anchor; and Figure 7 shows a plan view of the outside of a developed section of an expansion sleeve of a third expansion anchor according to the invention.

[0020] In the Figures 1 to 4a first expansion anchor 1 according to the invention is shown. The expansion anchor 1 is designed as a bolt anchor and has a one-piece anchor shaft 2 made of steel, which extends from a rear end 3 along a longitudinal axis L in the insertion direction E to a front end 4, which is formed by an expansion cone 5 acting as an expansion body 5. The expansion body 5 is an integral component of the anchor shaft 2 and widens in diameter in the insertion direction E. At the rear of the anchor shaft 2, an external thread 6 is arranged as a load application means, onto which a nut 7 is screwed and on which a washer 8 is arranged. At the front of the expansion anchor 1, an expansion region 9 is formed, on which an expansion sleeve 10 made of steel is arranged. The expansion sleeve 10 is supported on a stop collar 11 when driven into a borehole (not shown) against the insertion direction E.After insertion into a borehole, the expansion sleeve 10 is held in the borehole by wedge-shaped retaining projections 12, so that the expansion body 5 is retracted from the borehole into the expansion sleeve 10 by a movement of the anchor shaft 2 counter to the insertion direction E. This causes the expansion sleeve 10 to expand in its front area, expand in diameter, and be pressed against the borehole wall. More precisely, expansion segments 13 of the expansion sleeve 10 are pushed radially outward by the expansion body 5.

[0021] These expansion segments 13 are formed by slitting the expansion sleeve 10 from the front end at two points over two-thirds of its axial length parallel to the longitudinal axis L. Since the expansion sleeve 10 is made from a flat sheet and is bent in the circumferential direction around the anchor shaft 2 of the expansion anchor 1, the bent expansion sleeve 10 has three slits 14, 15, 16, of which a third slit 16 cuts through the expansion sleeve 13 over its entire length, while the first two slits 14, 15 cut through only two-thirds of the expansion sleeve 10 from the front end, so that an annular connecting section 17 is created which extends in the circumferential direction and from which the three expansion segments 13 protrude in the axial direction. As in Figure 3As can be seen, the first two slots 14, 15 each extend to a cylindrical through-opening 18, which represents the rear end of the first two slots 14, 15 and which is enlarged compared to the slots 14, 15. In the area of ​​the third, continuous slot 16, the expansion sleeve 10 has semicircular cutouts 19 ( Figure 3 ), which when bent form a circular passage ( Figure 1 ).

[0022] Each of the expansion segments 13 has a front end section 20 with a wall thickness d2 which is reduced compared to the wall thickness d1 of the rear part of the expansion sleeve 10 with the connecting section 17 and the rear parts of the expansion segments 13 adjoining the end sections 20 opposite to the insertion direction E ( Figure 4 ). The thickness d2 was reduced by a stamping process in which the starting material, a steel sheet, was compressed and cold formed. As in Figure 1As can be seen, the end sections 20 in a non-spread state face the expansion body 5. In addition, the end section 20 extends radially away from the longitudinal axis 20 towards the front end 4 of the anchor shaft 2 ( Figure 4 ), so that the end section 20 already in the non-expanded state rests flat against the expansion body 5 with its inner side 21 facing the anchor shaft 2.

[0023] The end sections 20 are delimited in the longitudinal direction by two of the slots 14, 15, 16 on their outer sides 22 facing away from the anchor shaft 2. In the circumferential direction, a first, rear edge 23 and a second, front edge 24 delimit the end section. The edges 23 and 24 are spaced apart from one another in the longitudinal direction. The two edges 23, 24 both extend in the circumferential direction from one of the two slots 14, 15, 16 delimiting the respective outer side 22 to the other slot 14, 15, 16. Thus, the first edge 23 of the middle expansion segment 13 of the Figure 3 between the first slot 14 and the second slot 15, as well as the second edge 24. Starting from the rear edge 23, the thickness of the end section 20 is reduced to the thickness d2 via a step 28 which runs orthogonal to the longitudinal axis L.

[0024] In the example of Figures 1 to 4the two edges 23, 24 each extend in the form of an arc between the two slots 14, 15, 16 which delimit the respective end section 20. The two edges 23, 24 are designed identically for all three end sections 20 and each extend as a circular arc from an end point 25, which marks the transition from one of the slots 14, 15, 16 to one of the edges 23, 24 or the beginning of one of the edges 23, 24, via a central vertex 26 of the respective circular arc to a further end point 25, which delimits the respective edge 23, 24 on the opposite side of the expansion segment 13 at the transition to the next slot 14, 15, 16, or marks the end of the edge 23, 24. The two edges 23, 24 form sharp-edged elements for engaging the wall of the borehole, wherein the apex 26 of the second edge 24, when spreading, comes into contact with the wall of the borehole as the first element of the second edge 24.In the case of the first embodiment according to the . Figures 1 to 4 The two circular edges 23, 24 are curved in opposite directions and have different radii. Thus, the radius of the first edge 23 is larger than the radius of the second edge 24, so that the vertex 26 of the second edge 24, which lies in front of the end points 25 of the second edge 24 in the insertion direction E, is further away from the end points 25 of the second edge 24 in the longitudinal direction than the end points 25 of the first edge 23 are from the vertex 26 of the first edge 23, which is located behind these end points 25.

[0025] In the Figures 5 and 7 Alternative expansion sleeves 110, 310 for an expansion anchor according to the invention are shown. To avoid repetition, only the differences from the expansion sleeve 10 described above will be discussed below.

[0026] The Figure 5The expansion sleeve 110 shown differs from the expansion sleeve of the Figures 1 to 4 solely because the slots 115, 116 (114 not shown) each have a widening 127 at their front ends in the direction of insertion E, by means of which the width of the end sections 120 of the expansion segments 113 is reduced in the circumferential direction, which facilitates the bending of the end section 120 during expansion and enables the apex 126 of the second edge 124 to be pressed against the wall of a borehole even with low expansion forces.

[0027] In contrast, Figure 6 an expansion sleeve 210 is shown which is not part of the invention, in which the front second edge 224 of the end section 220 runs straight in the circumferential direction, whereas the rear first edge 223 of the end section 220 runs between its end points 225 in the form of a pointed arch which consists of two straight sections which are connected by a rounded apex 226.

[0028] The Figure 7 shows an expansion sleeve 310 in which the two edges 323, 324 of each end section 320 have the same radius and are curved in the same direction, namely backwards, opposite to the insertion direction E. In this case, the two front end points 325 of the second front edge 324 are the first to engage the borehole wall during expansion and ensure secure hold of the expansion anchor in the borehole.

[0029] The alternative expansion sleeves 10, 110, 310 for an expansion anchor according to the invention can all be produced cost-effectively by stamping, so that they can be used to produce high-performance, cost-effective expansion anchors that are tailored to the respective building material due to their different designs. List of reference symbols Expansion anchor

[0030] 1Expansion anchor 2Anchor shaft 3Rear end of anchor shaft 2 4Front end of anchor shaft 2 5Expansion body 6External thread 7Nut 8Washer 9Expansion area 10, 110, 210 310Expansion sleeve 11Stop collar 12Retaining projection 13, 113, 213, 313Expansion segment 14, 114, 214, 314First slot 15, 115, 215, 315Second slot 16, 116, 216, 316Third slot 17Connecting section 18Through opening 19Punch 20, 120, 220, 320End section 21Inside of end section 20, 22, 122, 222 322Outside of the end section 20, 120, 220, 320 23, 123, 223, 323First edge 24, 124, 224, 324Second edge 25, 125, 225, 325End point 26, 126, 226, 326Crest 127Widening 28, 128, 228, 328Step d1First wall thickness d2Second wall thickness EInsertion direction of the expansion anchor 1 into a drill hole LLongitudinal axis of the anchor shaft 2

Claims

1. An expansion bolt (1) that has a bolt shaft (2) with an expansion body (5) and an expansion sleeve (10, 110, 210, 310), wherein the bolt shaft (2) extends from a rear end (3) in the insertion direction (E) forward along a longitudinal axis (L), wherein the expansion sleeve (10, 110, 210, 310) is arranged in an expansion region (9) of the expansion bolt (1) at the front of the bolt shaft (2) and has a plurality of expansion segments (13, 113, 213, 313) which are separated from one another by slots in the circumferential direction, wherein at least one of the expansion segments (13, 113, 213, 313) has an end portion (20, 120, 220, 320) of reduced wall thickness, which in a non-expanded state faces the expansion body (5) and which is delimited on the outside in the longitudinal direction by two of the slots (14, 15, 16) and in the circumferential direction by a first edge (23, 123, 223, 323) and a second edge (24, 124, 224, 324), wherein the two edges (23, 123, 223, 323, 24, 124, 224, 324) extend in the circumferential direction from a first of the slots (14, 15, 16) to a second of the slots (14, 15, 16), characterized in that in an imaginary development of the expansion sleeve (10, 110, 210, 310), the first edge (23, 123, 223, 323) extends in the form of an arc between the first of the slots (14, 15, 16) and the second of the slots (14, 15, 16), and in that the second edge (24, 124, 224, 324) extends in the form of an arc between the first of the slots (14, 15, 16) and the second of the slots (14, 15, 16).

2. The expansion bolt according to claim 1, characterized in that the two edges (323, 324) are curved in the same direction in the longitudinal direction.

3. The expansion bolt according to claim 1, characterized in that the two edges (23, 123, 24, 124) are curved in the opposite direction in the longitudinal direction.

4. The expansion bolt according to any of the preceding claims, characterized in that at least one of the edges (23, 123, 323, 24, 124, 324) is curved as a circular arc.

5. The expansion bolt according to any of the preceding claims, characterized in that both edges (23, 123, 24, 124) are curved as circular arcs, and in that the two circular arcs of the two edges (23, 123, 24, 124) have different radii.

6. The expansion bolt according to any of the preceding claims, characterized in that the slots (114, 115, 116) are widened in the circumferential direction in the region of the end portion (120).

7. The expansion bolt according to any of the preceding claims, characterized in that the end portion (20, 120, 220, 320) extends radially away from the longitudinal axis (L) towards the front end (4).

8. The expansion bolt according to any of the preceding claims, characterized in that the edges (23, 123, 223, 323, 24, 124, 224, 324) are produced by an embossing process.