Expansion anchors with anti-twist properties

Abstract

Expansion anchor (T) for fixing panels (PT) to a wall (M) by means of a screw (V) having a screw head (V1) and a threaded shaft (V2), the expansion anchor (T) comprising: - a head (1) having a central hole (1a), an outer surface (1c) intended to face outwards and an inner surface (1b) intended to bear against the plate (PT) attached to the wall (M); - a stem (2) protruding from the inner surface (1b) of the head and intended to be inserted into a through hole (F1) obtained in the plate (PT) and into a hole (F2) obtained in the wall (M); the stem (2) having a proximal portion (2a) with a channel (25) communicating with the central hole (1a) of the head, and a distal portion (2b) with a channel (26) communicating with the channel (25) of the proximal portion; the distal portion (2b) having notches (2c) defining deformable ribs (20);wherein the channel (25) of the proximal portion has a larger diameter than the channel (26) of the distal portion, so that the screw head (V1) of the screw is suitable for being inserted into the channel (25) of the proximal portion of the shaft, and the threaded shaft (V2) of the screw is suitable for being screwed into the channel (26) of the distal portion of the shaft to cause spreading and expansion of the deformable ribs (20) of the expansion plug, which engage in the hole (F2) of the wall, and ; - at least one anti-rotation rib (3) projecting outwards from the proximal portion (2a) of the shaft (2) to tighten the plate (PT) in the hole (F1) of the brush and to prevent rotation of the expansion plug (T) with respect to the plate (PT) during screwing in of the screw (V).

Description

[0001] The present invention relates to an expansion dowel or anchor, preferably for building insulation, with anti-twist properties.

[0002] Thermal insulation is increasingly being applied to building facades, consisting of prefabricated panels with thermally insulating materials, which have the ability to significantly reduce the heat loss to which buildings are normally exposed through external walls.

[0003] The thermal insulation panels are attached to a masonry building wall, and then holes are drilled into these panels, passing through the panel and reaching the wall. Expansion anchors are used to attach the thermal insulation panels to the wall.

[0004] Such an expansion anchor consists of a head and a shaft protruding from the head. The shaft has an axial channel and longitudinal ribs of the expandable type. A screw is screwed into the channel of the shaft to cause the longitudinal ribs to expand, which then lock into the hole in the wall.

[0005] Such an expansion anchor has the disadvantage that it tends to rotate uncontrollably in relation to the thermal insulation board when the screw is screwed in.

[0006] This tendency toward uncontrolled rotation of the expansion anchor occurs particularly during the final phase of screwing, when the static friction between the thermally insulating plate and the head of the expansion anchor is insufficient due to the brittleness of the plate's thermally insulating material. Such uncontrolled rotation of the expansion anchor relative to the plate compromises the stability and correct positioning of the expansion anchor.

[0007] The object of the present invention is to overcome the disadvantages of the prior art by providing an expansion anchor having an anti-twist feature so that it is not subjected to uncontrolled rotation with respect to the heat-insulating plate during screwing of the screw into the expansion anchor.

[0008] Another purpose is to provide such an expansion anchor that has a simpler and more functionally practical structure.

[0009] These objects have been achieved according to the features set out in the appended independent claim 1.

[0010] Advantageous embodiments of the present invention are set out in the dependent claims.

[0011] For the sake of clarity, the description refers to the accompanying drawings, which are for illustrative and non-limiting purposes only, in which the following is shown schematically: Fig. 1 is an axonometric view of the expansion anchor according to the invention; Fig. 1A is a side view of the expansion anchor of Fig. 1; Fig. 2 and Fig. 3 are plan views of the inner surface and the outer surface of the head of the expansion anchor of Fig. 1; Fig. 4 - 7 are schematic sectional drawings illustrating two different ways of using the expansion anchor according to the invention.

[0012] With reference to Fig. 1 describes an expansion anchor according to the invention, which is designated overall by the reference symbol T.

[0013] The expansion anchor T has a monolithic structure made by molding plastic materials. The expansion anchor T includes: - a head 1; and - a shaft 2 protruding from the head.

[0014] The head 1 of the expansion anchor is in the shape of a circular disc or plate with a central hole 1a located in the middle. The head 1 has an outer surface 1c facing outwards and an inner surface 1b facing a heat-insulating plate PT, which must be attached to a wall M.

[0015] The shaft 2 of the expansion anchor has a cylindrical, tubular shape. The shaft 2 protrudes from the inner surface 1b of the head 1 in line with the hole 1a of the head. The shaft 2 has a proximal (i.e., centrally located) section 2a with a channel 25 communicating with the central hole 1a of the head, and a distal (i.e., remotely located) section 2b with a channel 26 communicating with the channel 25 of the proximal section of the shaft. The channel 25 of the proximal section of the shaft has a larger diameter than the channel 26 of the distal section of the shaft.

[0016] The distal portion 2b of the shaft has longitudinal notches 2c that create deformable ribs 20 that can deform and expand outwardly.

[0017] In the Fig. Figures 4 to 7 show a thermal insulation panel PT attached to a wall in the form of a masonry structure M. A through hole F1 is provided in the thermal insulation panel PT, which extends into a hole F2 in the wall M.

[0018] The shaft 2 is inserted into the through hole F1 of the thermal insulation board and extends to the hole F2 in the wall M. Specifically, the expansion anchor T is pushed into the holes F1 and F2 of the board and the wall until the head 1 of the expansion anchor comes into contact with the thermal insulation board PT. The head 1 of the expansion anchor then acts as a stop flange.

[0019] At this point, a screw V is inserted into the hole 1a of the dowel head. The screw V has a screw head V1 with a diameter corresponding to the diameter of the channel 25 of the proximal section 2a of the shaft 2 of the expansion dowel T, and a threaded shaft V2 that can be screwed into the channel 26 of the distal section 2b of the shaft 2.

[0020] When screwing in the screw V, the screw head V1 of the screw rests on a lower part of the channel 25 of the proximal portion 2a of the shaft 2 of the expansion anchor T, while the threaded shaft V2 of the screw is screwed into the channel 26 of the distal portion 2b of the shaft 2 of the expansion anchor T, gradually causing bulging or twisting of the deformable ribs 20 of the distal portion 2b of the shaft within the hole F2 of the wall M.

[0021] As expected, with known expansion anchors, it can happen that the rotation of the screw is unfavorably transmitted to the expansion anchor, causing the expansion anchor itself to rotate relative to the plate. To prevent such rotation of the expansion anchor (anti-rotation), the expansion anchor T has at least one anti-rotation rib 3 protruding outward from the proximal portion 2a of the shaft 2 to tighten the plate PT within the hole F1 of the plate and prevent rotation of the expansion anchor relative to the plate PT during screwing in the screw V.

[0022] Advantageously, the at least one anti-rotation rib 3 is a radial rib that protrudes radially from the shaft 2. Advantageously, there are four anti-rotation ribs 3 arranged at the same angle of 90° to each other. Each anti-rotation rib 3 has an end section that tapers toward the distal section 2b of the shaft 2.

[0023] The anti-rotation ribs 3 are connected to the inner surface 1b of the head 1 of the expansion anchor T and extend in their length beyond a connection point 2d between the proximal section 2a and the distal section 2b of the tubular shaft 2.

[0024] When the expansion anchor T is forcibly inserted into the holes F1, F2 of the plate and the wall, the anti-rotation ribs 3 cut the heat-insulating plate PT and are firmly embedded in a thickness of the plate PT, taking advantage of the fragility of the plate structure.

[0025] The four anti-rotation ribs 3 are therefore able to provide a non-rotational (or anti-rotation) anchorage in the thermally insulating plate PT in order to prevent the expansion anchor T from being subjected to uncontrolled rotation in the hole F1 of the plate during screwing in of the screw V.

[0026] It should be noted that the expansion anchor T has a monolithic or one-piece structure in which the head 1, the shaft 2 and the at least one anti-rotation rib 3 are manufactured in a single piece by injection molding of plastic material.

[0027] The expansion anchor T also includes a cap 4 which can be inserted into the central hole 1a of the head 1 to close the central hole 1a and give the external surface 1c of the head 1 a perfect flatness.

[0028] In order to ensure that the expansion anchor T has a better grip in the hole F2 of the wall, the distal portion 2b of the shaft 2 has a grooved surface 2e which is suitable for generating strong friction and thus greater tensile strength in the hole F of the wall M.

[0029] In the preferred embodiment illustrated in the accompanying figures, the ribbed surface 2e of the distal portion 2b of the shaft comprises a grid of longitudinal and transverse ribs.

[0030] The outer surface 1c of the head 1 has a knurling FZ which serves to facilitate adhesion with a layer of plaster which normally covers the outer surface of the thermal insulation board PT.

[0031] In the Fig. Figures 4 to 7 show the possible installation and functional modes of the expansion anchor T.

[0032] In particular, the Fig. 4 and Fig. 5 the stages of installation of the expansion anchor T in the presence of a wall made of perforated bricks.

[0033] Fig. Figure 4 shows the initial installation methods of the expansion anchor T. The head 1 abuts the outer surface of the thermal insulation board PT. The proximal part 2a of the shaft 2 is inserted into the hole F1 of the thermal insulation board PT. The anti-rotation ribs 3 of the expansion anchor are driven into the thermal insulation board PT. The distal part 2a of the rod 2 is inserted into the hole F2 of the perforated brick wall M. The screw V is partially inserted into the shaft 2 of the expansion anchor T, but is not screwed in.

[0034] Fig.Figure 5 shows how the final installation of the expansion anchor T is performed. The screw head V1 of the screw rests on the bottom of the channel 25 of the proximal section 2a of the shaft 2. The threaded shank V2 of the screw V is screwed into the channel 26 of the distal section 2b of the shaft 2 to cause rotation of the ribs 20 of the distal section 2b of the shaft. Tightening the screw V creates a backward pull in the axial direction of the distal section 2b of the shaft 2, with a deformation of the ribs 20 of the distal section of the shaft, which creates a thickening C within the hole of the perforated brick of the wall. This thickening C ensures stable locking of the expansion anchor T through interference within the perforated brick. Finally, the closure cap 4 is inserted into the central hole 1a of the head 1.

[0035] In summary, an expansion anchor T for fastening thermal insulation panels PT to a wall M is disclosed, wherein the expansion anchor has anti-rotation ribs 3 which hold the thermal insulation panels PT in order to prevent a relative rotation of the expansion anchor T with respect to the thermal insulation panel PT.

Claims

[1] Expansion anchor (T) for fixing panels (PT) to a wall (M) by means of a screw (V) having a screw head (V1) and a threaded shank (V2), the expansion anchor (T) comprising: - a head (1) having a central hole (1a), an outer surface (1c) intended to face outwards and an inner surface (1b) intended to bear against the plate (PT) attached to the wall (M); - a stem (2) protruding from the inner surface (1b) of the head and intended to be inserted into a through hole (F1) obtained in the plate (PT) and into a hole (F2) obtained in the wall (M); the stem (2) having a proximal portion (2a) with a channel (25) communicating with the central hole (1a) of the head, and a distal portion (2b) with a channel (26) communicating with the channel (25) of the proximal portion; the distal portion (2b) having notches (2c) defining deformable ribs (20);wherein the channel (25) of the proximal portion has a larger diameter than the channel (26) of the distal portion, so that the screw head (V1) of the screw is suitable for being inserted into the channel (25) of the proximal portion of the shaft, and the threaded shaft (V2) of the screw is suitable for being screwed into the channel (26) of the distal portion of the shaft to cause spreading and expansion of the deformable ribs (20) of the expansion plug, which engage in the hole (F2) of the wall, and; - at least one anti-rotation rib (3) projecting outwards from the proximal portion (2a) of the shaft (2) to tighten the plate (PT) in the hole (F1) of the brush and to prevent rotation of the expansion plug (T) with respect to the plate (PT) during screwing in of the screw (V). [2] Expansion anchor (T) according to claim 1, wherein the at least one anti-rotation rib (3) is a radial rib which projects radially from the proximal part (2a) of the shaft. [3] Expansion anchor (T) according to claim 1 or 2, wherein the at least one anti-rotation rib (3) is connected to the inner surface (1b) of the head (1) and has a tapered end portion pointing in the direction of the distal portion (2b) of the shaft (2). [4] Expansion dowel (T) according to one of the preceding claims, wherein the at least one anti-rotation rib (3) extends in its length beyond a connecting section (2d) between the proximal section (2a) and the distal section (2b) of the shaft (2). [5] Expansion anchor (T) according to one of the preceding claims, wherein the distal portion (2b) of the shaft has a grooved outer surface (2e). [6] Expansion anchor (T) according to claim 5, wherein the corrugated outer surface (2e) of the distal portion (2b) of the shaft comprises a network of ribs. [7] Expansion anchor (T) according to one of the preceding claims, wherein the outer surface (1b) of the head has a knurling (FZ). [8] Expansion anchor (T) according to one of the preceding claims, wherein the expansion anchor (T) comprises a cylindrical expansion anchor (4) which can be inserted into the central hole (1a) of the head (1). [9] Expansion anchor (T) according to one of the preceding claims, wherein the expansion anchor (T) has at least one longitudinal rib (5) arranged on the outer surface of the distal part (2b) of the shaft (2) between the at least one longitudinal rib (3) and the grooved surface (2e) of the distal part (2b) of the shaft. [10] Expansion anchor (T) according to one of the preceding claims, wherein the expansion anchor (T) has a monolithic structure in which the head (1), the shaft (2) and the at least one anti-rotation rib (3) are manufactured in a single piece by injection molding of plastic material. [11] Expansion dowel (T) according to one of the preceding claims, which has four anti-rotation ribs (3) arranged equidistant from one another by 90°.

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