Patent Description:
There are two different types of expansion anchor currently known. A first type of expansion anchor consists of anchors made entirely of plastic, some of which are designed for anchoring to walls made of bricks with internal partitions defining internal cavities which are hollow or filled with low-density material, and/or walls made of a relatively friable or non-homogeneous materials, such as multi-layer walls, wall made of loose (i.e. not very compact) granular-concrete, and/or walls made of compact material and therefore having a high density, such as concrete walls or walls made of natural stone or solid bricks, or another high-density material.

These plastic expansion anchors are used in a wide range of applications, but their use is limited to the anchoring of loads having a relatively low weight. Plastic expansion anchors are unable to anchor loads having medium duty weight. A plastic expansion anchor is disclosed in earlier patent application <CIT>, specifically a so-called straddling dowel for securing a threadable element, such as a bolt or a screw, comprising a substantially cylindrical body of a plastic material. Also, earlier patent application <CIT> discloses an expansion dowel for a screw, the expansion dowel comprising a split socket body and a wedge-shaped expansion element which can move axially under the action of the screw, like a nut, so as to expand the socket body.

The second type of anchor differs from the plastic expansion anchor essentially in that it includes a tubular body made of metal. The tubular body typically comprises a metal conduit with an anchoring tab. The anchor having the metal tubular body further comprises a conical body and a tightening screw. The conical body is attached at the end of the tightening screw. When in use, the screw is tightened which causes the conical body to move axially inside of the conduit. Wedges of the conical body are gradually urged or otherwise driven radially outwards between the anchoring tabs, moving them apart towards the inside wall of the hole in which the anchor is placed. The anchoring tabs are moved apart until they are positioned into abutment against the inside surface (i.e. hole) of the wall, securing the anchor into the hole in the wall using friction and using mechanical locking.

Metal anchors of this type are able to anchor loads to a greater extent compared to the plastic anchors. However, where there is a requirement to anchor even larger loads, even these types of anchors may not provide sufficient retention, capable of anchoring increased loads. Therefore, an anchor that is unable to provide the required retention may loosen or detach from the desired surface during use. Another problem associated with existing anchors is the lack of confirmation to a user that the anchor is completely, correctly, and securely fitted. Without such confirmation or indication to the user, a user may continue to tighten the anchor, causing overtightening of the anchor and/or damage to the surface in which the anchor is set. Yet, another problem associated with expansion anchors is the generation of pressure points from the expanding legs of the anchor that directly engage with the anchor screw thread. If the legs of the anchor expand in an uncontrolled manner, the contact between the legs of the anchor and the screw thread of the anchor causes damage to the anchor. In some instances, the damage is detrimental to the functioning of the anchor.

Therefore, it would be desirable to provide an expansion anchor that can alleviate or mitigate one or more of the aforementioned problems. Particularly, it is an object of the invention to provide an expansion anchor with a higher retention force, or at least which can be used for a greater range of applications. It is also an object of the invention to provide an expansion anchor which is capable of anchoring loads having an even higher weight. It is a further object of the invention to provide an anchor with an improved user experience, indicating the complete, correct and secure fitting of an expansion anchor.

The present invention provides at least an alternative to expansion anchors of the prior art.

In accordance with the present invention there is provided an expansion anchor according to the appended claims.

According to an aspect of the present invention, there is provided an expansion anchor comprising: a tubular sleeve having a longitudinal axis and comprising an expansion portion at a distal end and a body portion at a proximal end and expansion tabs attached to the body portion and extending towards the distal end; a tightening screw configured to move the expansion portion along the longitudinal axis inside the expansion tabs so as to expand the tabs radially outwardly relative to the longitudinal axis; at least one deformable leg extending between and attached to the body portion and to the expansion portion of the tubular sleeve, the deformable leg comprising at least two coupled segments, a distal segment, having a first attachment portion linking the distal segment to the expansion portion and a proximal segment, having a second attachment portion linking the proximal segment to the body portion, wherein the width of the proximal segment increases towards the proximal end of the tubular sleeve.

Thus, the deformable leg is reinforced near the proximal end. This provides a wider surface area at the proximal end of the deformable leg, allowing an increased surface area to be in contact with the wall, which improves the mechanical performance of the expansion anchor and increases the load capacity of the expansion anchor. Moreover, this allows the deformation of the deformable legs to be controlled, so as to prevent a pressure point onto the tightening screw to be generated.

Advantageously, in some embodiments, the first and second attachment portions may be circumferentially offset from each other about the longitudinal axis, so as to deform the deformable leg torsionally and radially outwardly relative to the longitudinal axis when moving the expansion portion from the distal end towards the proximal end. This is particularly beneficial because the proximal segment and the distal segment of the leg both engage with the surface to be engaged, in order to increase the surface area of engagement between the anchor and the surface.

Thus, deformable leg(s) expand radially outwardly and torsionally to engage with the surface in which the anchor is set. The proximal segment and the distal segment of the leg both engage with the surface to increase the surface area of engagement between the anchor and the surface. This improves mechanical stability of the anchor in the wall, which increases the load capacity of the expansion anchor. Moreover, there is provided an indication to the user of a complete and secure setting in comparison with an anchor having legs that deform only radially outward, not least because the user will experience more friction when the legs deform and engage with the surface.

Advantageously, in some embodiments, the width of the proximal segment may increase uniformly towards the proximal end.

Advantageously, in some embodiments, the width of the distal segment may increase towards the distal end of the tubular sleeve.

Advantageously, in some embodiments, the width of the distal segment may increase uniformly towards the distal end.

Advantageously, in some embodiments, the expansion tabs may have a first rigidity, and the deformable legs may have a second rigidity greater than the first rigidity. By providing deformable legs that have a rigidity greater than that of the expansion tabs, the deformable of the deformable legs can be controlled to avoid the generation of pressure points on the tightening screw.

Advantageously, in some embodiments, the at least one deformable leg may comprise a first line of weakening between the distal segment and the proximal segment, having a width less than the distal and proximal segments. This provides a predetermined point of deformable at which the distal and proximal segments move relative to one another.

Advantageously, said first line of weakening may have a width less than said distal and proximal segments.

According to the invention, said at least one deformable leg comprises an outwardly facing second line of weakening provided between said first attachment portion and said distal segment. Preferably, said second line of weakening may be positioned proximal to said expansion portion. According to the invention, said first attachment portion further comprises a recess, arranged so as to continue from said second line of weakening and separating a portion of said distal segment from said expansion portion, and a ramped surface, configured to guidingly move said portion of said distal segment away from said longitudinal axis, during use.

Advantageously, said expansion anchor may comprise at least two deformable legs arranged adjacent to one another, each one adapted to stoppingly engage at a predetermined deformation, so as to prevent additional torsional and radial deformation, during use. Preferably, said at least two deformable legs may be circumferentially equidistantly spaced about said longitudinal axis.

Advantageously, said expansion anchor may further comprise a sleeve member coaxially arranged between said body portion and said tightening screw. Preferably, a distal end of said sleeve member may be adapted to operably engage with said expansion portion, so as to prevent contact between said tightening screw and said expansion portion moving from said distal end to said proximal end. Even more preferably, said sleeve member may be provided at said proximal end of said tubular sleeve.

Embodiments of the invention are now described, by way of example only, hereinafter with reference to the accompanying drawings, in which:.

The described example embodiment relates to an expansion anchor and particularly to an expansion anchor for use in the construction sector. However, the invention is not necessarily restricted expansion anchors for use in the construction sector altogether but may also be used to secure a plurality of components together.

Certain terminology is used in the following description for convenience only and is not limiting. The words 'right', 'left', 'lower', 'upper', 'front', 'rear', 'upward', 'down' and 'downward' designate directions in the drawings to which reference is made and are with respect to the described component when assembled and mounted. The words 'inner', 'inwardly' and 'outer', 'outwardly' refer to directions toward and away from, respectively, a designated centreline or a geometric centre of an element being described (e.g. central axis), the particular meaning being readily apparent from the context of the description.

Further, unless otherwise specified, the use of ordinal adjectives, such as, "first", "second", "third" etc. merely indicate that different instances of like objects are being referred to and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking or in any other manner.

Like reference numerals are used to depict like features throughout.

<FIG> show an anchoring member, namely a medium duty expansion anchor <NUM> that is suitable for insertion in an anchoring hole of a support or a wall. The meaning of light duty, medium duty and high duty are all common terms in the art and would be understood within the common general knowledge of the person skilled in the art. The expansion anchor <NUM> has a proximal end <NUM> and a distal end <NUM> and is structured such that it may be anchored or otherwise secured to a support or wall. It is preferable, though not essential, that the anchor <NUM> comprises a metal structure. It shall be understood that the anchor <NUM> may be secured to any wall structure. For example, the wall may be a solid structure or a non-solid structure. That is, the wall may be made from bricks, or the wall may be hollow, having defining spaces and/or a wall that is filled with a low-density material, or a non-compact wall such as a multi-layered wall or a wall made from a relatively friable material. The wall or structure may also be made from or filled with a material having a low compactness, or the wall may be made from a material of high density, such as, for example, concrete or natural stone or solid bricks.

The expansion anchor <NUM> comprises a sleeve <NUM> which, in this example, is tubular in shape and has a longitudinal axis <NUM>. The anchor <NUM> also comprises an expansion portion <NUM> at the distal end <NUM> which, in this example, is an expansion nut <NUM>. The anchor <NUM> has a tightening screw <NUM> having a drive head and a threaded shank <NUM> projecting from the bottom of the drive head in the direction of the longitudinal axis <NUM> towards the distal end <NUM> of the anchor <NUM>. The threaded shank <NUM> extends through an internal hole (not shown) of the sleeve <NUM>. That is, the threaded shank <NUM> extends from the bottom of the drive head of the tightening screw <NUM>, through to the distal end <NUM> of the anchor. The expansion portion <NUM> has an internal thread which is designed to engage with the threaded shank <NUM>, such that the expansion portion <NUM> is moved axially along the longitudinal axis <NUM> when rotated with a screwdriver or longitudinally expanded with an expansion tool. The expansion portion <NUM> is screwed onto the distal end <NUM> of the shank <NUM>. It is preferable that the expansion portion <NUM> is frustoconical in shape, having a taper towards the proximal end <NUM> of the anchor <NUM>. Alternatively, the expansion portion <NUM> may be cylindrical in shape (e.g. having rounded edges).

The sleeve <NUM> further comprises a body portion <NUM> at its proximal end. Expansion tabs <NUM> are attached to the body portion <NUM> and extend in a direction away from the body portion <NUM> towards the distal end <NUM>. In this particular example, the expansion tabs <NUM> form an angle of <NUM> degrees with the longitudinal axis <NUM>. However, it is envisaged that the expansion tabs <NUM> may form a different angle with the longitudinal axis <NUM> such as for example, <NUM> degrees to <NUM> degrees. It is preferred that the expansion tabs <NUM> have a free distal end portion (i.e. not connected to the expansion portion <NUM>).

During use, the tightening screw <NUM> is tightened and the expansion portion <NUM> moves axially towards the proximal end <NUM> of the anchor <NUM>. This axial movement of the threaded expansion portion <NUM> urges the ends of the expansion tabs <NUM> radially outward from the longitudinal axis <NUM>. In this example, each expansion tab <NUM> is provided with a number of gripping portions, namely teeth <NUM> which, as will be explained, are capable of gripping a surface on which the expansion tabs <NUM> engage. A suitable flange <NUM> may be provided below the drive head of the tightening screw <NUM>. The flange <NUM> may be made from metal in this example and prevents the tightening screw <NUM> from sinking into the wall or surface that the anchor <NUM> is to be attached to. This will be made clearer with reference to the subsequent drawings.

The anchor <NUM> is further provided with deformable legs <NUM>, circumferentially arranged about the sleeve <NUM>. Each one of the legs <NUM> extend between the body portion <NUM> and the expansion portion <NUM> of the sleeve <NUM> and are attached thereto. Thus, when the expansion portion <NUM> moves axially along the longitudinal axis <NUM> towards the body portion <NUM> (i.e. towards the proximal end <NUM>), a pushing force is exerted onto the legs <NUM> from the distal end <NUM>.

Referring now to <FIG> and <FIG>, a close-up of the distal end <NUM> of an embodiment of the expansion anchor <NUM> is shown. Here, the expansion anchor <NUM> shown has a deformable leg in between the body portion and the expansion portion <NUM>. The deformable leg is formed from a distal segment 126a on the distal side of the expansion anchor <NUM>, and a proximal segment 126b on the proximal side of the expansion anchor <NUM>. The distal segment 126a and the proximal segment 126b are coupled together. A first attachment portion 127a links the distal segment 126a to the expansion portion <NUM>. A second attachment portion 127b links the proximal segment 126b to the body portion. The first attachment portion 127a and the second attachment portion 127b are circumferentially offset from one another about the longitudinal axis of the expansion anchor <NUM>. The first attachment portion 127a and the second attachment portion 127b are circumferentially offset from one another about the longitudinal axis of the expansion anchor <NUM>. In this example, a first line of weakening 136b is provided between the distal segment 126a and the proximal segment 126b, having a smaller cross-sectional area in comparison to the segments 126a,126b. The first line of weakening 136b is provided inwardly facing (i.e. radially inwardly facing). A second line of weakening 136a is provided on the first attachment portion 127a,. The second line of weakening 136a is provided outwardly facing (i.e. radially outwardly facing). The first line of weakening 136b and the second line of weakening 136a are opposingly facing. The lines of weakening 136a,136b facilitate a predetermined deformation of the deformable legs <NUM>, along selected areas of the legs <NUM>. The first line of weakening 136b acts as a living hinge, integrally formed with and linking the distal segment 126a and the proximal segment 126b. The first line of weakening 136b, in this way, allows the distal segment 126a and the proximal segment 126b to bend relative to one another about the first line of weakening 136b. Since the first line of weakening 136b is inwardly facing, the axial movement of the threaded expansion portion <NUM> exerts a pushing force onto the distal end of the deformable leg <NUM>, and urges the deformable leg <NUM> radially outward (i.e. in a direction opposite the inwardly facing first line of weakening 136b), such that the first line of weakening 136b folds outward to bend the distal segment 126a and the proximal segment 126b relative to one another. In substantially the same way, the second line of weakening 136a acts as a living hinge, integrally formed with and linking the first attachment portion 127a and the distal segment 126a. When the first line of weakening 136b folds outward, the outwardly facing second line of weakening 136a folds inwards (i.e. in a direction opposite the outwardly facing second line of weakening 136a), since the first line of weakening 136b and the second line of weakening 136a face opposite directions. The first line of weakening 136b has a width (i.e. size measurement of the deformable leg in a direction perpendicular to the longitudinal direction) that is small relative to the width of the distal segment 126a and the proximal segment 126b. The smaller width of the first line of weakening 136b relative to the distal segment 126a and proximal segment 126b provides a reduced cross-sectional area.

<FIG> shows a cross-section of the deformable leg <NUM> in more detail. The section view of the deformable leg <NUM> shows the arrangement of the distal segment 126a and the proximal segment 126b, linked by the first line of weakening 136b. In this example, the distal segment 126a and the proximal segment 126b are displaced apart by an angle of <NUM> degrees, but other ranges are envisaged such as <NUM> to <NUM> degrees, for example. The angle formed between the proximal segment 126b and the body portion (i.e. the second attachment portion 127b) is <NUM> degrees, but other ranges are envisaged such as <NUM> to <NUM> degrees, for example. The angle formed at the second line of weakening 136a is <NUM> degrees but other angles are envisaged such as <NUM> to <NUM> degrees, for example. The deformable leg <NUM> illustrated in <FIG> has a uniform thickness throughout. It is envisaged that certain parts of the deformable leg <NUM> may have a width or a thickness that is less than others so as to promote more deformation in those areas. For example, the first line of weakening 136b may have a smaller width and therefore a smaller cross-sectional area relative to the distal segment 126a and the proximal segment 126b. The second line of weakening 136a may have a smaller width or thickness and therefore a smaller cross-sectional area relative to the distal segment 126a. In some examples, the length of the distal segment 126a and/or the proximal segment 126b may be a different length. For example, the distal segment 126a and the proximal segment 126b may have a greater length, such as <NUM> and <NUM> respectively. Alternatively, the distal segment 126a and the proximal segment 126b may have a lesser length. The length of the distal segment 126a and the proximal segment 126b may be selected based on the desired deformation thereof. That is, the distance between the body portion and the expansion portion of the anchor <NUM> may be selected based on the desired extent of deformation of the expansion anchor <NUM> when it is expanded during use.

<FIG> show the distal end of an expansion anchor <NUM> after expansion, where the expansion portion <NUM> is moved axially along the threaded shank towards the body portion of the anchor <NUM>, to exert a force onto the deformable leg <NUM>. The first attachment portion 127a and the second attachment portion 127b of the deformable leg <NUM> are circumferentially offset from one another. As the deformable legs <NUM> are urged outward, the proximal segment 126b and the distal segment 126a of the deformable leg <NUM> deform torsionally apart from one another and are urged radially outwards relative to the longitudinal axis of the expansion anchor <NUM>. More specifically, as the expansion portion <NUM> moves towards the body portion of the anchor <NUM>, the distal segment 126a is urged towards the proximal side of the anchor <NUM>. Since the first attachment portion 127a and the second attach portion 127b of the deformable leg <NUM> are circumferentially offset from one another, the distal segment 126a moves towards the proximal segment 126b at an angle offset from one another. The first line of weakening 136b urges outward which allows the deformable leg <NUM> to be radially offset and torsionally offset about the longitudinal axis of the expansion anchor <NUM>. The proximal segment 126b and the distal segment 126a torsionally deform relative to one another about the first line of weakening 136b. The first line of weakening 136b provides a predetermined point of bending at which the deformable leg <NUM> deforms. In this example, three deformable legs <NUM> are provided circumferentially equidistantly spaced from one another. The body of the expansion anchor <NUM> has three expansion tabs <NUM> circumferentially equidistantly spaced from one another interjacent of the three deformable legs <NUM>. In other examples, however, it is also envisaged that any other suitable number of deformable legs <NUM> may be provided, such as two, or four, or five or six, for example. The number of deformable legs <NUM> may be selected based on the desired surface area or extent of engagement between the expansion anchor <NUM> and the surface in which the anchor <NUM> is fixed.

In this particular example, the distal segment 126a and the proximal segment 126b torsionally deform such that the angle between them may be <NUM> degrees after expansion. Other angular offsets are also envisaged, such as <NUM> degrees, <NUM> degrees or <NUM> degrees, for example. Other smaller angular offsets are also envisaged, such as <NUM> degrees, <NUM> degrees, <NUM> degrees, <NUM> degrees, <NUM> degrees or <NUM> degrees, for example. At a predetermined angular offset, adjacent deformable legs <NUM> may be placed such that adjacent legs <NUM> engage with one another to prevent further torsional deformation and/or further radial deformation about the longitudinal axis of the expansion anchor <NUM>. As the segments 126a,126b of the deformable leg <NUM> deform torsionally and radially outward, the expansion tabs <NUM> are urged outward relative to the longitudinal axis of the expansion anchor <NUM>. After expansion, the proximal segment 126b is flush against the board in which the expansion anchor <NUM> is retained. In some examples, the distal segment 126a is torsionally offset from the proximal segment 126b and also engages with the board. This increases the area of engagement between the deformable legs <NUM> and the surface in which the expansion anchor <NUM> is retained which increases the structural rigidity of the anchor into the wall.

<FIG> illustrates an alternative design that prevents the engagement of the deformable leg <NUM> with the tightening screw <NUM>. In this example, a sleeve member in the form of a cylindrical sleeve <NUM> is provided towards the proximal end of the expansion anchor <NUM>. When the expansion portion <NUM> moves from the distal end of the expansion anchor <NUM> towards the proximal end, the deformable leg <NUM> deforms in the way previously described. The second line of the weakening 236a of the deformable leg <NUM> projects inward towards the tightening screw <NUM>. However, the second line of weakening 236a of the deformable leg <NUM> engages directly with the sleeve member <NUM> to prevent it from engaging with the tightening screw <NUM>. The sleeve member <NUM> is provided between the tightening screw <NUM> and the deformable leg <NUM> to protect the deformable leg <NUM> from engaging with the tightening screw <NUM>, and thus damaging the screw thread.

<FIG> illustrate an alternative embodiment for an expansion anchor <NUM> in which the first attachment portion 327a of the expansion anchor <NUM> comprises a recess <NUM> between a portion of the distal segment 326a and the expansion portion <NUM>. The recess <NUM> or cut line may join up with the line of weakening 336a. The expansion portion <NUM> is provided with a ramping portion <NUM> (ramp surface) that, during expansion, engages with a disjointed part (i.e. separating the expansion portion and the distal segment 326a) of the first attachment portion 327a such that a direct engagement between the deformable leg <NUM> with the tightening screw is prevented. The engagement directly with the tightening screw is prevented by moving the end portion of the distal segment 326a away from the tightening screw, preventing a pressure point from being formed. Referring particularly to Figure <NUM> (B), each deformable leg <NUM> is provided with a recess <NUM>, and a portion of the expansion portion <NUM> is provided with a corresponding ramping portion <NUM> that receives a second line of weakening 336b, such that engagement of the deformable leg <NUM> onto the tightening screw is prevented. The ramping portions <NUM> move an end portion of the distal segment 326a away from the tightening screw during expansion.

<FIG> illustrates such a pressure point projected towards the tightening screw <NUM> in the absence of the aforementioned ramping portion. As the deformable legs <NUM> expand outward of the longitudinal axis, the first attachment portion 427a (i.e. the second line of weakening of the deformable leg <NUM>) projects inward towards the tightening screw <NUM> to counteract a radial and torsional movement of the first line of weakening of the deformable leg <NUM>. By provided a ramp on the expansion portion, the disjoined portion of the deformable leg <NUM> engages with the ramp instead of the tightening screw <NUM>.

<FIG> shows another example of a sleeve <NUM> of an expansion anchor <NUM> in an open arrangement, showing the sleeve <NUM> in an unfolded state (sheet metal stamping configuration). The body <NUM> of the expansion anchor <NUM> has three expansion tabs <NUM> spaced equidistantly from one another. Deformable legs <NUM> are positioned between the expansion tabs <NUM>. The design of the deformable legs <NUM> in this example limits torsion when the anchor <NUM> is expanded, as will be described below. A flange <NUM> is provided on a proximal side, having a first central aperture <NUM> configured to receive the shank of the tightening screw. On a distal end, there is provided a further flange <NUM>, having a second central aperture <NUM> (coaxial with the first central aperture <NUM>) and which is threaded and configured for receiving the shank of the tightening screw. A greater width (i.e. size measurement of the deformable leg <NUM> in a direction perpendicular to the longitudinal direction) is provided outward of the second line of weakening 536a in a tapered manner. That is, from the second line of weakening 536a towards the distal end, the distal segment 526a tapers outward such that the width of the distal segment 526a increases in the distal direction. From the second line of weakening 536a towards the proximal end, the proximal segment 526b tapers outward such that the width of the proximal segment 526b increases in the proximal direction. In this particular example, more material is provided on the deformable leg <NUM> relative to the expansion tab <NUM> in order to increase the rigidity of the expansion anchor <NUM>. Thus, when the expansion anchor <NUM> expands (i.e. when the expansion portion moves from the distal end towards the proximal end), the torsional deformation of the legs <NUM> are limited (minimised). Though not shown, the tightening screw may be provided with a tighter pitch to further limit torsional deformation. At the proximal end of the deformable leg <NUM>, the proximal segment 526b is provided with a wider surface to increase the engagement contact with the wall in which the expansion anchor <NUM> is to be set. This further increases mechanical stability of the anchor <NUM> once is it set, and improves the structural performance of the anchor <NUM>.

Through the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps.

The invention is not restricted to the details of any foregoing embodiments.

Claim 1:
An expansion anchor (<NUM>, <NUM>, <NUM>, <NUM>) comprising:
a tubular sleeve (<NUM>) having a longitudinal axis and comprising an expansion portion (<NUM>, <NUM>, <NUM>) at a distal end (<NUM>) and a body portion (<NUM>) at a proximal end (<NUM>) and expansion tabs (<NUM>, <NUM>) attached to said body portion and extending towards said distal end;
a tightening screw (<NUM>, <NUM>, <NUM>) configured to move said expansion portion along said longitudinal axis inside said expansion tabs so as to expand said tabs radially outwardly relative to said longitudinal axis; and
at least one deformable leg (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) extending between and attached to said body portion and to said expansion portion of said tubular sleeve, said deformable leg comprising at least two coupled segments, a distal segment (126a, 326a, 526a), having a first attachment portion (127a, 327a, 427a) linking said distal segment to said expansion portion and a proximal segment (126b, 526b), having a second attachment portion (127b) linking said proximal segment to said body portion the width of said proximal segment increasing towards said proximal end of said tubular sleeve,
characterised in that that said at least one deformable leg (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) comprises an outwardly facing line of weakening (136a, 236a, 336b, 536a) provided between said first attachment portion (127a, 327a, 427a) and said distal segment (126a, 326a, 526a),
and in that said first attachment portion (127a, 327a, 427a) further comprises a recess (<NUM>), arranged so as to continue from said line of weakening (136a, 236a, 336b, 536a) and separating a portion of said distal segment (126a, 326a, 526a) from said expansion portion (<NUM>, <NUM>, <NUM>), and a ramped surface (<NUM>), configured to guidingly move said portion of said distal segment (126a, 326a, 526a) away from said longitudinal axis, during use.