Expansion anchor

0001The present innovation relates to an expansion anchor.

0002Specifically, the present innovation relates to an screw anchor adapted to be used for fastening or anchoring onto walls or articles, to which explicit reference will be made in the following description without therefore loosing in generality.

0003Screw anchors are known, comprising a tubular element having a deformable end portion in which longitudinal slits or cuts are obtained, which divide the end portion itself, at the zones concerned by the cuts, into a series of longitudinal anchoring fins; a cone-shaped expansion nut or body engaged onto the end of the end portion; and a screw, which is accommodated inside the tubular element and is adapted to be screwed onto the expansion nut or cone so as to be able to progressively displace it into the end portion of the anchor, so as to cause the radial deformation of the longitudinal fins which, by spreading outwards, determine the anchoring of the anchor to the wall.

0004Despite their efficiency, the screw anchors of the aforesaid type do not ensure a sufficiently high degree of fastening in some cases.

0005For this purpose, many efforts have been made during the past years to increase the degree of fastening of the anchors by means of a continuous search of solutions which allow to make the anchoring of the screw anchor to the wall more effective, but many more remain to be done.

0006It is the object of the present innovation to make a screw anchor structured so as to ensure a better anchoring/fixing to the wall than the expansion anchors of known type.

0007According to the present innovation, a screw anchor is provided as claimed in claim 1 and preferably, but not necessarily, in anyone of the claims which either directly or indirectly depend on claim 1.

0008The present innovation will now be described with reference to the accompanying drawings illustrating a non-limitative embodiment thereof, in which: <ul id="ul0001" list-style="dash" compact="compact"><li><figref idref="f0001">figure 1</figref> shows a perspective, enlarged view of an screw anchor made according to the dictates of the present innovation;</li><li><figref idref="f0002">figure 2</figref> is a first side view of the screw anchor shown in <figref idref="f0001">figure 1</figref>;</li><li><figref idref="f0002">figure 3</figref> shows the screw anchor taken along a section I-I in <figref idref="f0002">figure 2</figref> on an enlarged scale; while</li><li><figref idref="f0003">figure 4</figref> shows a diagrammatic side view of the screw anchor in an operative condition of expansion of the end part thereof.</li></ul>

0009With reference to <figref idref="f0001">figures 1</figref>, <figref idref="f0002">2</figref>, <figref idref="f0002">3</figref> and <figref idref="f0003">4</figref>, numeral 1 indicates as a whole an screw anchor, which is adapted to be engaged into a hole 25 obtained in a wall 26, or in any body or anchoring element, with the longitudinal axis A thereof coaxial to the axis of the hole 25 itself, and is capable of coupling with a fastening screw 2 of known type which, when actuated, is adapted to cause a deformation of the screw anchor 1 inside the hole 25 so as to determine the anchoring to the wall 26.

0010The screw anchor 1 essentially consists of a tubular element 3 preferably, but not necessarily, made of metal or plastic material, or of any other similar material, on which the following parts may be identified: a central truck 4; preferably, but not necessarily, a collar 5, and a deformable end portion 6, connected at the opposite ends of the central trunk 4, respectively.

0011On the end portion 6, longitudinal cuts or slots 7 are obtained which divide the end portion 6 itself, at the zone concerned by the longitudinal slots 7 themselves, into a series of anchoring sectors or fins 8.

0012The screw anchor 1 further comprises an expansion nut or body 9, which is engaged onto the end portion 6 of the screw anchor 1, on the part opposite to the collar 5, and is adapted to be screwed onto the threaded part of the shank 2a of the screw 2 to be axially displaced inside the end portion 6 of the screw 2 itself, so as to cause the outward radial deformation of the anchoring fins 8.

0013With reference to <figref idref="f0001">figure 1</figref>, each anchoring fin 8 has an essentially rectangular shape and at its end facing the expansion body 9, displays a ridge 10 defining the external side edge of the anchoring fin 8 and having an essentially triangular cross section.

0014At the two opposite ends of the ridge 10, along its external side edge, each anchoring fin 8 further presents two protruding side teeth 11 having a pointed shape, each of which is coplanar with the anchoring fin 8 and extends towards the protruding tooth 11 of an adjacent anchoring fin 8, so as to delimit, with the latter, the end of the longitudinal slot 7 present between the two facing side edges of the anchoring fins 8 themselves.

0015In detail, each protruding side tooth 11 has an essentially triangular shape and extends from the body of the anchoring fin 8 so as to be arranged, with its pointed portion, at least partially in abutment with the pointed portion of the protruding side tooth 11 of the adjacent anchoring fin 8.

0016As far as the expansion nut or body 8 is concerned, it is preferably, but not necessarily, made of metal or plastic material, or of other similar material, is shaped so as to be essentially cone-shaped, and comprises a threaded through hole 14 which extends coaxially to the axis A and is adapted to accommodate the threaded shank 2a of the screw 2.

0017More in detail, in the example shown in <figref idref="f0001">figures 1</figref> and <figref idref="f0002">3</figref>, at its smaller base, the expansion nut or body 8 displays a portion 15 having an essentially square shape, in which the vertexes of the square define anti-rotation protrusions 16 each of which is engaged inside a corresponding longitudinal slot 7 and is adapted to prevent the expansion nut or body 9 from rotating about the longitudinal axis A.

0018In this case, in the example shown in <figref idref="f0002">figure 3</figref>, the smaller base of the conical portion of the expansion nut or body 9 is essentially inscribed in the square defining the portion 15, while the vertexes of the portion 15 which define the protrusions 16 of the expansion nut or body 9 are essentially pyramid-shaped so as to be inserted and displaced into the corresponding longitudinal slots 7 when screwing the screw 2 onto the expansion nut or body 9.

0019Each anchoring fin 8 of the anchor 1 further displays an external surface 8a comprising a plurality of annular notches 18, which are arranged coaxially to the axis A, and essentially equally spaced from each other so as to advantageously increase the degree of friction and grip of the anchoring fins 8 on the internal wall of the hole 25 which accommodates the screw anchor 1.

0020According to a variant (not shown), each anchoring fin 8 of the anchor 1 has an external knurled or milled surface 8a so as to increase the degree of friction and grip of the anchoring fins 8 on the internal wall of the hole which accommodates the screw anchor 1.

0021In the example shown in <figref idref="f0001">figures 1</figref>, <figref idref="f0002">2 and 3</figref>, in order to increase the degree of friction of the anchor 1, a segment of the central trunk 4 also displays an external surface 4a having a plurality of annular notches or cavities 4b which are coaxial to the longitudinal axis A and essentially equally spaced from each other along the longitudinal axis A itself.

0022According to a variant (not shown), the segment of the central trunk 4 of the anchor 1 comprises an external knurled or milled surface 8a so as to increase the degree of friction of the screw anchor 1 on the internal wall of the hole 25.

0023Anti-rotation ridges 20 are further present on the central trunk 4 of the screw anchor 1, which are arranged in pairs on two reciprocally orthogonal planes laying on the longitudinal axis A, and which overhangingly extend outwards from the central truck 4.

0024In rest conditions (<figref idref="f0002">Figures 2 and 3</figref>), the expansion nut or body 9 is partially engaged onto the end portion 6 of the screw anchor 1 so that the protrusions 16 of the square portion 15 are inside the corresponding longitudinal slots 7 in a contact position with the base of the protruding teeth 11 of the anchoring fins 8. In other words, the protruding side teeth 11 keep the longitudinal slots 7 closed.

0025With reference to <figref idref="f0003">figure 4</figref>, screwing the screw 2 on the expansion nut or body 9 causes the displacement of the expansion body 9 itself inside the end portion 6, which by radially pushing the anchoring fins 8 outwards determines the expansion of the end portion 6 itself into the hole 25 of the wall 26.

0026During the expansion caused by the expansion nut or body 9, the ridge 10 of each anchoring fin 8 is brought in abutment with the internal wall of the hole 25, while the protruding teeth 11 of the anchoring fin 8 are partially driven into the internal wall of the hole 25 itself, thus creating a pawl anchoring system which then counters the axial displacement of the screw anchor 1 in the direction for extracting the screw anchor 1 from the hole 25.

0027In this step, the external surface 8a of the anchoring fins 8 is brought in contact with the internal wall of the hole, thus generating, in virtue of the notches or cavities 18 thereof, a friction force which counters the axial displacement of the screw anchor 1 in the direction for extracting the anchor from the hole 25.

0028The above-described screw anchor 1 has the advantage of ensuring a particularly high degree of anchoring; indeed, the combined action of the anchoring performed by the protruding side teeth and the friction obtained by the notches of the external surface of the anchoring fins 8 ensures an excellent fixing of the anchor to the wall.

0029It is finally apparent that changes and variations may be made to the expansion anchor 1 described and shown herein without therefore departing from the scope of the present innovation.