Patent Description:
<CIT> describes an expansion anchor with expansion sleeve abutment walls provided on the expansion body. The expansion sleeve abutment walls can engage with the expansion sleeve to provide an interlock when the anchoring process has reached an advanced state. The expansion sleeve abutment walls can be provided at the ends of recesses provided in the expansion body. On this basis, <CIT> further teaches to provide said recesses with nonaxisymmetric cross-section. According to <CIT>, the expansion sleeve has non-uniform wall thickness. Both the expansions sleeves of <CIT> and of <CIT> are provided with expansion slits that define forwardly facing expansion fingers.

From <CIT> there is known an expansion anchor having an expansion sleeve with an expansion slit.

Expansion slits in an expansion sleeve can for example be formed by shape cutting. Alternatively (or additionally), the slits can be formed in a blanking process in which an essentially flat sleeve blank is locally ruptured by shearing in order to form the slits, before the blank is bent around the anchor bolt to give the expansion sleeve. This allows to obtain particularly narrow expansion slits, which can in term provide a particularly large remaining surface area of the expansion sleeve, which can in term be advantageous in view of anchor performance.

An inventive anchor is characterized in that the first flank and the second flank are both non-planar throughout, so as to form at least one widening and at least one narrowing along the stem.

Accordingly, the flanks of the expansion slit are not straight, and preferably not plan parallel. In particular, the flanks can form a free form surface. This can improve versatility and performance. In addition, it may facilitate manufacturing: Wave shaped expansion slits can counteract undesired clamping-together of expansion sleeve blanks, e.g. during coating or feeding, and therefore facilitate anchor assembly.

Preferably, the non-planar flanks are shaped by coining a generally flat blank, in which the expansions slits have been pre-formed, preferably by blanking. Besides forming of the expansion slits, the coining process also allows to provide non-uniform wall thickness within the expansion sleeve, which can further improve functionality. In the coining process, the material forming the flanks is widened, and the expansion slits are narrowed. Compared to a blanking-only process, the combination of blanking and subsequent coining can allow to obtain particularly narrow expansion slits (i.e. particularly small slit widths), which can in term increase contact surface of the expansion sleeve and thus improve anchor performance: In a blanking-only process, there is a technical limit of the slit width due to a technical limit of the blanking die used due to breakage by bending. In contrast, if blanking is followed by coining, the slit width can be further reduced, since the blanked slit width will be closed due to widening of the material that is located adjacent to expansion slit during coining operation.

The expansion slits define forwardly facing expansion fingers of the expansion sleeve, which expansion fingers are wedged radially outwardly by the wedge body during installation of the anchor. Since the head of the expansion slit is, in the circumferential direction, wider than the stem of the expansion slit, the head forms a constriction, i.e. a weakening, in the adjacent expansion fingers, which facilitates outward wedging of these expansion fingers. On the other hand, due to its rearward arrangement and due to its width, the head tends to define a bending point when the expansion sleeve is manufactured in a bending process.

The anchor bolt is an elongate body. The wedge body and the anchor bolt are, in particular, connected to transfer tensile forces. The wedge body can for example be threaded to the anchor bolt, in particular if the expansion anchor is a so-called sleeve-type expansion anchor.

The wedge body can also be tightly fixed to the anchor bolt, in particular if the expansion anchor is a so-called stud-type expansion anchor. It is particularly preferred in case of a stud-type expansion anchor that the wedge body and the anchor bolt are monolithic, i.e. that they form one piece. If the expansion anchor is a so-called stud-type expansion anchor, the anchor bolt is preferably provided with a forwardly facing shoulder for expansion sleeve abutment and for advancing the expansion sleeve into the borehole. The wedge body is a part of the expansion anchor.

The expansion sleeve surrounds the anchor bolt, in particular around the longitudinal axis of the anchor bolt. In particular, the expansion sleeve can be a single piece.

Preferably, the anchor bolt, the expansion sleeve and/or the wedge body are each steel parts. They can for example comprise carbon steel or stainless steel.

The anchor bolt can have, in particular in a rear region of the anchor bolt, a tension-introducing structure. The tension-introducing structure is for introducing tensile forces into the anchor bolt. The tension-introducing structure can for example be a thread, in particular an external thread, provided on the anchor bolt. The tension-introducing structure can for example also be a head, that forms a maximum cross-section, or a bayonet-type lock.

The wedge zone of the wedge body is intended to expand the expansion sleeve when the wedge body is moved rearwards with respect to the expansion sleeve, in particular to expand the expansion sleeve radially with respect to the longitudinal axis. The wedge body converges, on its lateral surface, towards the rear of the anchor bolt and/or towards the tension-introducing structure, wherein the focus of convergence can preferably be the longitudinal axis. This in particular implies that the radial distance of the lateral surface of the wedge body from the longitudinal axis becomes smaller towards the rear of the wedge body. In particular, the wedge zone forms a wedge for the expansion sleeve.

The at least one expansion slit cuts the expansion sleeve and subdivides the expansion sleeve into expansion fingers. In particular, the at least one expansion slit cuts all the way through the wall thickness of the expansion sleeve, i.e. the expansion slit forms a radial perforation of the expansion sleeve. The expansion slit originates from the front face and extends rearwardly into the expansion sleeve. Preferably, the expansion slit extends generally parallel to the longitudinal axis, but it could also be angled with respect to the longitudinal axis. The stem of the expansion slit is located between the head of the expansion slit and the mouth of the expansion slit, i.e. the head is located at the rear of the stem and the mouth at the front of the stem. In particular, the head can define a rear end of the expansion slit. The head is preferentially wider than the stem, in particular in the circumferential direction. The mouth of the slit opens at the front face of the expansion sleeve. In particular, it forms a delta structure that converges into the stem, for example to provide a rounding. In particular, the mouth can be wider than the stem (in particular in the circumferential direction), at least in some regions of the mouth.

The first flank and the second flank face each other and delimit the stem in the circumferential direction. The flanks are side walls of the expansion sleeve. The flanks can also extend into the mouth and/or into the head of the expansion slit.

Preferably, the expansion sleeve has a plurality of expansion slits originating at the front face of the expansion sleeve. If there is a plurality of expansion slits provided, at least some of them, preferably all of them, are preferably configured in analogy to the at least one expansion slit described herein.

The expansion sleeve might also have one or more additional slits.

Where the term "longitudinal axis" is used, this should, in particular, refer to the longitudinal axis of the anchor bolt, which is often also the longitudinal axis of the anchor. In accordance with the usual definition, the "longitudinal axis" can in particular be the axis that runs in the longitudinal direction, i.e. in the long direction of the elongate anchor bolt. Where the terms "radially", "axially" or "circumferentially" are used, this is should in particular be understood with respect to the longitudinal axis of the anchor bolt.

Preferentially, the first flank and the second flank are non-plan-parallel with respect to one another throughout.

In particular, the invention can be used with expansion anchors in which the expansion sleeve has non-constant wall thickness, i.e. in which the wall of the expansion sleeve varies in dependence of the position on the expansion sleeve. As explained in further detail in e.g. <CIT>, non-constant wall thickness can be provided in order to improve anchor performance.

The invention is explained in greater detail below with reference to preferred exemplary embodiments, which are depicted schematically in the accompanying drawings, wherein individual features of the exemplary embodiments presented below can be implemented either individually or in any combination within the scope of the present invention.

The figures show an embodiment of an inventive expansion anchor. The expansion anchor comprises an elongate anchor bolt <NUM> defining a longitudinal axis <NUM>, an expansion sleeve <NUM>, which surrounds the anchor bolt <NUM>, and a wedge body <NUM> provided on the anchor bolt <NUM>, namely in the vicinity of the front end of the anchor bolt <NUM>. The wedge body <NUM> is designed for wedging the expansion sleeve <NUM> radially outwardly when the wedge body <NUM> is drawn into the expansion sleeve <NUM> in the rearwards direction, i.e. in the pull-out direction. For this purpose, the lateral surface of the wedge body <NUM> converges rearwardly, at least regionally. The longitudinal axis <NUM> extends through the front end and through the rear end of the anchor bolt <NUM>.

The anchor bolt <NUM> has a neck, which is located adjacent to and rearwards of the wedge body <NUM>. The expansion sleeve <NUM> at least partly surrounds this neck, at least before installation of the anchor. At the neck, the diameter of the anchor bolt <NUM> can be minimal.

In the present embodiment, the expansion anchor is a stud type anchor. Hence, the anchor bolt <NUM> has, at the rearward end of the neck, a shoulder <NUM> facing forwards for axially engaging the expansion sleeve <NUM> and for advancing the expansion sleeve <NUM> forwards. In the present case, the wedge body <NUM> is, by way of example, integral with the remainder of the anchor bolt <NUM>, but in alternative embodiments, the anchor bolt <NUM> can consist of several separate parts.

In a rear region of the anchor bolt <NUM>, the anchor bolt <NUM> is provided with a tension-introducing structure <NUM>, which is here, by way of example, an external thread provided on the anchor bolt <NUM>. However, this is an example only, and other structures such as internal threads, bayonet mechanisms or heads can also be envisaged.

The expansion sleeve <NUM> is a C-shaped clip and is provided with a plurality of expansion slits <NUM>', <NUM>", <NUM>‴, 36ʺʺ. Each of these expansion slits <NUM>', <NUM>", <NUM>‴, 36ʺʺ originates at the front face <NUM> of the expansion sleeve <NUM> (i.e. at that face of the expansion sleeve <NUM> that faces the wedge body <NUM>) and extends towards the rear end of the expansion sleeve <NUM> (and thus towards the rear end of the anchor bolt <NUM>). Each of the expansion slits <NUM>', <NUM>", <NUM>‴, 36ʺʺ radially cuts through the expansion sleeve <NUM>, i.e. each of the expansion slits <NUM>', <NUM>", <NUM>‴, 36ʺʺ divides the expansion sleeve <NUM>.

The expansion slit <NUM>' comprises a mouth <NUM>', a stem <NUM>' that adjoins the mouth <NUM>' and a head <NUM>' that adjoins the stem <NUM>'. The mouth <NUM>' is arranged at the front face <NUM> of the expansion sleeve <NUM> and forwardly with respect to the stem <NUM>', whereas the head <NUM>' is arranged rearwardly with respect to the stem <NUM>'. Accordingly, the stem <NUM>' is arranged between the head <NUM>' and the mouth <NUM>'. The mouth <NUM>' forms the forward end of the expansion slit <NUM>' and the head <NUM>' forms the rearward end of the expansion slit <NUM>'. The stem <NUM>' is a narrow, generally linear trench. Compared to the stem <NUM>', the head <NUM>' has greater width in the circumferential direction, i.e. around the longitudinal axis <NUM>. Due to its width, the head <NUM>' forms a local weakening of the adjacent expansion sleeve <NUM>, which facilitates expansion of the expansion sleeve <NUM>. The mouth <NUM>' forms a delta structure that converges into the stem <NUM>'. The delta structure provides a rounding of the front face <NUM>.

In the shown embodiment, the stem <NUM>' extends, generally, in the axial direction, i.e. generally parallel to the longitudinal axis <NUM>. However, angled configurations could also be envisaged.

In the shown embodiment, the head <NUM>' is generally circular. This, however, is only an example, and other, non-circular outlines can also be envisaged. In particular, an elongate, for example approximately elliptical, outline, wherein the elongate direction generally follows the circumferential direction of the anchor bolt <NUM> can be provided.

In the circumferential direction, the stem <NUM>' is delimited by a first flank <NUM>' of the expansion sleeve <NUM>, and by a second flank <NUM>' of the expansion sleeve <NUM>, wherein the first flank <NUM>' and the second flank <NUM>' face each other. Both the first flank <NUM>' and the second flank <NUM>' are generally free form shaped when in the axial direction. In particular, the first flank <NUM>' and the second flank <NUM>' extend non-parallel with respect to one another. Both the first flank <NUM>' and the second flank <NUM>' are non-planar each. Due to the non-planar shape of the first flank <NUM>' and the second flank <NUM>', the stem <NUM>' has a widening <NUM>' (at which the width of the expansion slit <NUM>' is a local maximum, in particular a strict local maximum) and a narrowing <NUM>' (at which the width of the expansion slit <NUM>' is a local minimum, in particular a strict local maximum, wherein in both cases, the width can in particular be measured in the circumferential direction).

Expansion slit <NUM>" also comprises a mouth, a stem and a head <NUM>", wherein these items are arranged and configured in analogy to expansion slit <NUM>', so that the description above is applicable mutatis mutandis. Expansion slit <NUM>‴ also comprises a mouth, a stem and a head <NUM>‴, wherein these items are arranged and configured in analogy to expansion slit <NUM>', so that the description above is applicable mutatis mutandis. Expansion slit 36ʺʺ also comprises a mouth 64ʺʺ, a stem 61ʺʺ and a head <NUM>"", wherein these items are arranged and configured in analogy to expansion slit <NUM>', so that the description above is applicable mutatis mutandis. The expansion slits <NUM>', <NUM>", <NUM>‴ are blind slits each, and accordingly, they do not reach the rear end of the expansion sleeve <NUM>. Accordingly, the head <NUM>' defines a rear end of expansion slit <NUM>', the head <NUM>" defines a rear end of expansion slit <NUM>" and the head <NUM>‴ defines a rear end of expansion slit <NUM>‴. The expansion slit <NUM>"", on the other hand, is a through slit which extends all the way through the expansion sleeve <NUM>, i.e. from the front face <NUM> of the expansion sleeve <NUM> to the rear end of the expansion sleeve <NUM>. Accordingly, the expansion slit 36ʺʺ has a tail 69ʺʺ, which extends from the head 63ʺʺ to the rear end of the expansion sleeve <NUM>. The head 63ʺʺ is thus located axially between the stem 61ʺʺ and the tail <NUM>"". The expansion slit 36ʺʺ being a through slit can be interrelated to a manufacturing process in which a flat blank is bent around the anchor bolt <NUM> to give the expansion sleeve <NUM>, so that the expansion slit 36ʺʺ gives the closure interface of the expansion sleeve <NUM>.

The expansion sleeve <NUM> has non-constant wall-thickness, i.e. the wall thickness is dependent on the position on the expansion sleeve <NUM>, in particular on the circumferential position.

Claim 1:
Expansion anchor having
- an anchor bolt (<NUM>),
- an expansion sleeve (<NUM>) that surrounds the anchor bolt (<NUM>), and
- a wedge body (<NUM>) located in a front region of the anchor bolt (<NUM>) for wedging the expansion sleeve (<NUM>), wherein the expansion sleeve (<NUM>) has a front face (<NUM>) facing the wedge body (<NUM>),
- wherein at least one expansion slit (<NUM>) is provided within the expansion sleeve (<NUM>), wherein the expansion slit (<NUM>) originates at the front face (<NUM>) of the expansion sleeve (<NUM>), wherein the expansion slit (<NUM>) has a mouth (<NUM>) that is located adjacent to the front face (<NUM>), a stem (<NUM>) that adjoins the mouth (<NUM>) and a head (<NUM>) that adjoins the stem (<NUM>), wherein the head (<NUM>) is wider than the stem (<NUM>), and wherein the stem (<NUM>) is located between the head (<NUM>) and the mouth (<NUM>),
- wherein the stem (<NUM>) of the expansion slit (<NUM>) is delimited by a first flank (<NUM>) of the expansion sleeve (<NUM>) and by a second flank (<NUM>) of the expansion sleeve (<NUM>),
characterized in that
- the first flank (<NUM>) and the second flank (<NUM>) are both non-planar throughout, so as to form at least one widening (<NUM>) and at least one narrowing (<NUM>) along the stem (<NUM>).