WO2022248875A1

WO2022248875A1 - Attachment device for a cellular tracker

Info

Publication number: WO2022248875A1
Application number: PCT/GB2022/051353
Authority: WO
Inventors: James Alexander George Blyth; Matthew Leigh Plested; Rebecca Jane Lake; John William Gutch; Thomas Duncan Guy
Original assignee: Vodafone Group Services Limited
Priority date: 2021-05-28
Filing date: 2022-05-27
Publication date: 2022-12-01
Also published as: GB2607096B; GB2607096A; GB202107659D0

Abstract

An attachment device for attaching a cellular tracker to a strap such as a pet collar. The attachment device comprises a first unitary element comprising an envelope configured to provide an elastic circumferential grip and a second unitary element joined to the first unitary element. The second unitary element comprises a first elongate portion having a proximal end and a distal end, a second elongate portion having a proximal end and a distal end, a hinge portion between the proximal end of the first elongate portion and the proximal end of the second elongate portion, and a releasable clasp having an engaged configuration in which the clasp is configured to retain the distal end of the first elongate portion relative to the distal end of the second elongate portion. In a neutral position, the first and second elongate portions diverge from the proximal ends towards the distal ends so as to provide an opening between the distal end of the first elongate portion and the distal end of the second elongate portion. In a closed position, the first and second mutually cooperating clasp portions engage so as to retain the distal end of the first elongate portion and the distal end of the second elongate portion in mutual contact and thereby prevent return to the neutral position. The second unitary element has a coefficient of stiffness that causes the secondary unitary element to be biased towards the neutral position.

Description

Attachment device for a cellular tracker

Background

Tracking devices that make use of wireless communication technology, such as a cellular network, are becoming increasingly popular. Tracking devices may be fastened to articles such as key rings, handbags, wallets, etc. to enable the location of such articles to be determined.

It may be that a tracking device is generic rather than being bespoke for a particular purpose. As such, it may be useful to provide a range of different attachment devices such that the same tracking device may be attachable to a range of different articles. The attachment device may be chosen dependent upon the article to which the tracking devices is to be attached.

One known attachment device consists of a unitary element comprising an envelope configured to provide an elastic circumferential grip around the cellular tracker. The unitary element comprises an aperture by which the attachment device may be connected to, for example, a split ring such as a key ring. In this way, the cellular tracker may be attached to a bunch of keys, for example. This attachment device is not rigidly attached to the split ring and is movable around the split ring in the same way as a key is movable around the split ring.

Another article to which it may be desirable to attach a tracking device is a strap such as a pet collar or a belt.

Summary

Against this background, there may be provided an attachment device for attaching a cellular tracker to a strap such as a pet collar, the attachment device comprising: a first unitary element comprising an envelope configured to provide an elastic circumferential grip; a second unitary element joined to the first unitary element, the second unitary element comprising: a first elongate portion having a proximal end and a distal end; a second elongate portion having a proximal end and a distal end; a hinge portion between the proximal end of the first elongate portion and the proximal end of the second elongate portion; a releasable clasp having an engaged configuration in which the clasp is configured to retain the distal end of the first elongate portion relative to the distal end of the second elongate portion; wherein: in a neutral position, the first and second elongate portions diverge from the proximal ends towards the distal ends so as to provide an opening between the distal end of the first elongate portion and the distal end of the second elongate portion; in a closed position, the first and second mutually cooperating clasp portions engage so as to retain the distal end of the first elongate portion and the distal end of the second elongate portion in mutual contact and thereby prevent return to the neutral position; and wherein: the second unitary element has a coefficient of stiffness that causes the secondary unitary element to be biased towards the neutral position.

In this way, a tracking device may be fastened to a strap, such as a pet collar or a belt, in a manner that means the tracking device is secure and such that it does not swing or otherwise move relative to the strap.

In particular, in the closed position, the first elongate portion of the attachment device and the second elongate portion of the attachment device may clamp a strap between front and rear faces of the strap.

In this context, a strap may be any elongate band of material having a thickness between its front face and its rear face that is less than a width of the front face and the rear face. The front face and the rear face of the strap may be substantially parallel. In a cross section through the strap in a direction orthogonal to the elongate direction, the front and rear faces of the strap may be flat. The cross sectional shape in the direction orthogonal to the elongate direction of the strap may be rectangular. The second element being biased towards the neutral position may mean that the attachment device is fastenable to a strap and unfastenable from a strap by a user using only one hand. The releasable clasp may reduce the likelihood of the attachment device being inadvertently released from the closed position.

The second unitary element may have a coefficient of stiffness of between and 0.1 N/mm and 5 N/mm.

The force required to close the second unitary element may be between approximately 5 Newtons and approximately 50 Newtons.

The second unitary element may have a flexural modulus of between 2,000 MPa and 3,000 MPa, for example approximately 2,400 MPa.

The hinge portion may have a thickness of between 0.5 mm and 2.0 mm. One or both of the first elongate portion and the second elongate portion may have a thickness of between 1.0 mm and 3.0 mm. One or both of the first elongate portion and the second elongate portion may have a thickness of between 2.2 mm and 2.3 mm.

The first elongate portion may have a thickness of 2.29 mm and the second elongate portion may have a thickness of 2.25 mm and the hinge portion may have a thickness of approximately 1.0 mm.

The first unitary element may have a shore A hardness of between 50 A and 80 A. The first unitary element may have a shore A hardness of between 60 A and 70 A. The first unitary element may have a shore A hardness of approximately 70 A.

The first unitary element may be joined to the first elongate portion of the second unitary element.

The first unitary element may comprise or consist essentially of a material having an appropriate degree of elasticity to retain the cellular tracker in situ. The first unitary element may comprise or consist essentially of thermoplastic polyurethane (TPU).

The second unitary element may comprise or consist essentially of a material having an appropriate degree of stiffness to be biased towards the neutral position.

The second unitary element may comprise or consist essentially of polycarbonate.

The second unitary element may be joined to the first unitary element by the second unitary element being interlocked with the first unitary element.

In this way, a risk of detachment of the first unitary element from the second unitary element may be reduced.

For example, the first and second unitary elements may be co-moulded, whereby one is moulded in situ onto the other. In this way, an intimacy of connection may be achieved which reduces a likelihood of detachment.

The second unitary element may be joined to the first unitary element at an interface region, wherein the interface region comprises a stepped configuration.

In this way, the extent of contact between the first and second unitary elements may be increased relative to a flat interface region which may reduce a risk of detachment of the first unitary element from the second unitary element.

The stepped configuration may comprise a cylindrical surface and a first annular surface.

In this way, there may be multiple directions of forces between the first and second unitary elements which may reduce a risk of detachment of the first unitary element from the second unitary element.

The stepped configuration may further comprise a second annular surface. The cylindrical surface may be between the first annular surface and the second annular surface. The interface region may comprise a plurality of protrusions that project radially from the cylindrical interface surface.

In this way, the extent of contact between the first and second unitary elements may be increased.

The plurality of protrusions may project radially inwardly from the cylindrical interface surface.

The first unitary element may comprise the plurality of protrusions and the second unitary element may comprise a plurality of corresponding cavities that accommodate the plurality of protrusions.

The releasable clasp may comprise first and second mutually cooperating clasp portions, wherein a first one of the first and second mutually cooperating clasp portions is located towards the distal end of the first elongate portion and a second one of the first and second mutually cooperating clasp portions is located towards the distal end of the second elongate portion.

The releasable clasp may comprise a hook and an aperture. Additional force may be required to push the distal ends of the first and second elongate portions together in order to release the clasp. In this way, single-handed operation is facilitated. Other clasp arrangements are contemplated.

One of the first elongate portion and the second elongate portion may comprise a plurality of apertures configured to receive a corresponding plurality of pins of a shim configured to occupy part of a gap between the first elongate portion and the second elongate portion.

In this way, the attachment device may accommodate different thicknesses of strap by using different thicknesses of shim.

The disclosure also includes an attachment device kit comprising an attachment device and a plurality of differently dimensioned shims in order to allow selection of an appropriately dimensioned shim to allow a residual gap between the first elongate portion and the shim to be provided for suitability with a thickness of strap to be accommodated within the residual gap.

In a further aspect of the disclosure there is provided a method of forming an attachment device, the method comprising: moulding the second unitary element; moulding the first unitary element in situ on the second unitary element.

In this way, the first and second unitary elements may be conjoined by virtue of the two- stage moulding process. This may increase the intimacy of the contact between the first and second unitary elements and may in turn reduce a risk of detachment of the first unitary element from the second unitary element.

The method may involve using a mould tool having first deployable elements and second deployable elements, the method comprising: providing a first cavity defined by the mould tool and the first deployable elements in order to form the second unitary element; removing the first deployable elements and deploying the second deployable elements to form a second cavity defined by the mould tool, the second deployable elements and the second unitary element in order to form the first unitary element in situ on the first unitary element.

In this way, manufacturing of the attachment device may be simple and effective for ensuring a lasting intimate connection between the first and second unitary elements.

Brief description of the figures

An embodiment of the disclosure is now described with reference to the following Figures in which:

Figure 1 shows an outline view of an attachment device in accordance with the present disclosure and shown in its neutral position;

Figure 2 shows an outline view of the attachment device of Figure 1 in its closed position; Figure 3 shows a plan view and a cross sectional view of the attachment device in its closed position;

Figure 4 shows a plan view and a cross sectional view of the attachment device in its neutral position;

Figure 5 shows a plan view and a cross sectional view of the attachment device in its neutral position;

Figure 6 shows a plan view and a cross sectional view of the attachment device in its neutral position;

Figure 7 shows a tracking device for use with the attachment device of the present disclosure;

Figure 8 shows the tracking device of Figure 7 installed in the attachment device of Figure 1 ;

Figure 9 shows various views of a specific embodiment of the attachment device showing various dimensions and angles.

Detailed description

Figure 1 shows an outline view of an attachment device 100 in accordance with the present disclosure and shown in its neutral position.

The attachment device 100 comprises a first unitary element 160 and a second unitary element 120. The attachment device 100 may also comprise a shim 180 fastenable to the second unitary element 120.

The first unitary element 160 is generally annular and provides a circular opening into which a cellular tracker 10 (an example of which is shown in Figure 7) may be received (as shown in Figure 8). In the illustrated embodiment, the cellular tracker 10 takes a substantially cylindrical form, wherein the cylinder extends further in the radial direction than in the axial direction. When the cellular tracker 10 is placed in the circular opening of the first unitary element 160, a top face 20 and a circumferential lip 22 at the top face 20 of the cellular tracker 10 protrude from the first unitary element 160.

The second unitary element 120 comprises a first elongate portion 130 (more clearly visible in Figure 5), a second elongate portion 150 and a hinge portion 140 between the first elongate portion 130 and the second elongate portion 150.

The second unitary element 120 also comprises an annular portion 122 that projects from the first elongate portion 130 and that conforms substantially intimately with the first unitary element 160, as shown more clearly in Figures 3 and 5.

The first unitary element 160 surrounds and protrudes upwardly from the annular portion 122 of the second unitary element. As such, a lower part of the first unitary element 160 is radially outside the annular portion 122 of the second unitary element 120. The lower part of the first unitary element 160 is concentric with the annular portion 122 of the second unitary element 120. An upper part of the first unitary element 160 projects upwardly from both the lower part of the first unitary element 160 and the annular portion 122 of the second unitary element 120.

The first elongate portion 130 of the second unitary element 120 comprises a proximal end 131 and a distal end 133 (more clearly visible in Figure 3). The second elongate portion 150 comprises a proximal end 151 and a distal end 153. The hinge portion 140 is at the proximal end 131 of the first elongate portion 130 and the proximal end 151 of the second elongate portion 150.

The second unitary element 120 further comprises a clasp comprising first and second mutually cooperating clasp portions 135, 155. A first clasp portion 135 of the first and second mutually cooperating clasp portions 135, 155 is located towards the distal end 133 of the first elongate portion 130. A second clasp portion 155 of the first and second mutually cooperating clasp portions 135, 155 is located towards the distal end 153 of the second elongate portion 150. The second unitary element 120 is of a material, shape and geometry that results in a coefficient of stiffness that is: (a) sufficiently low so as to facilitate movement of the second elongate portion relative to the first elongate portion about the hinge portion 140 on application of a force; and (b) sufficiently high such that the second unitary element 120 is biased towards a neutral (open) position in which the distal end 133 of the first elongate portion 130 is at a distance from the distal end 153 of the second elongate portion 150, as shown in Figure 1. In this way, when starting in the neutral position (Figure 1), application of a force on the distal end 153 of the second elongate portion 150 towards the distal end 133 of the first elongate portion 130 enables the first elongate portion 130 and the second elongate portion 150 to move into the position shown in Figure 2 in which the first elongate portion 130 is parallel to the second elongate portion 150. Flowever, the stiffness of the second unitary element 120 is such that, on release of any force (including in the absence of any force provided by the mutually cooperating clasp portions 135, 155), the second unitary element 120 will immediately transition back to the neutral position of Figure 1 .

It should be understood that the second unitary element 120 being biased towards the neutral position means that the effect of the bias is relatively immediate. In other words, on removal of a closing force, the second unitary element 120 returns to its neutral position within less than 1 second. For example, it may return to the neutral position within 0.1 seconds.

In the illustrated embodiment, the first and second mutually cooperating clasp portions 135,

155 comprise a hook portion 136 and an opening 156. By applying a force to move the distal ends 133, 153 together, such that the opening 156 slides past and over the hook portion 136, and then by releasing the force, the hook portion 136 catches in the opening

156 and prevents the second elongate portion 150 moving back to the neutral position.

The attachment device 100 is thereby retained in the closed position, as shown in Figure 2 and Figure 3. It should be noted that, in order for the clasp to engage or be released, the distal ends 133, 153 are closer to each other than the proximal ends 131 , 151 are to each other. Once the clasp is engaged, the first elongate portion 130 and the second elongate portion 150 are parallel such that the distance between the distal ends 133, 153 is substantially the same as the distance between the proximal ends 131 , 151.

In order to release the clasp and allow the second unitary element 120 to return to its neutral position, a first force is applied to move the distal ends 133, 153 together. This results in the distal ends 133, 153 moving closer to one another, which results in the first and second mutually cooperating clasp portions 135, 155 moving apart with respect to each other. This in turn enables the opening 156 to be moved in a distal direction past the hook portion 136 by application of a second force in a direction away from the hinge portion 140. Then, when the first and second forces are released, the second unitary element 120 returns to the neutral position of Figure 1.

Referring to Figure 3, when the attachment device 100 is in the closed position, an aperture 190 is formed between the first elongate portion 130 and the shim 180. By choosing a shim 180 of appropriate thickness, the width of the aperture 190 may be selected such that it is just sufficient to accommodate a strap (such as the pet collar or belt) with which the attachment device 100 is to be used. Furthermore, if the width of the aperture 190 is only just sufficient to accommodate the strap then lateral movement of the attachment device 100 relative to the strap may be prevented when the attachment device 100 is in the closed position. By restricting movement, the likelihood of the attachment device becoming detached unintentionally from the strap (for example by becoming caught by another object) is reduced.

The attachment device 100 may be provided as part of a kit. The kit may comprise the attachment device 100 and a plurality of shims 180. Each shim 180 of the plurality of shims 180 may have a different thickness, to allow a user to select a shim 180 of most appropriate thickness to accommodate the strap (e.g. of the pet collar) in the aperture 190 (that is a residual gap between the shim and the first elongate portion 130).

The first unitary element 160 projects from, and conforms substantially intimately with, the second unitary element 120. The material properties of the first unitary element 160 are different from those of the second unitary element 120. In particular, the first unitary element 160 is of a material that is both softer and has a higher coefficient of friction than the second unitary element 120. The annular aperture of the first unitary element 160 and the second unitary element 120 is dimensioned to receive a cellular tracker, such as that shown in Figure 7. Furthermore, the first unitary element 160 is of a material capable of being temporarily deformed in shape in order for the tracker to be received within the aperture as shown in Figure 8 (or for the tracker to be released from the aperture). The first unitary element 160 may have a shore A hardness of between 50 A and 80 A, preferably between 60 A and 70 A, more preferably approximately 70 A.

The second unitary element 120 may have a coefficient of stiffness of between and 0.1 N/mm and 5 N/mm. The coefficient of stiffness of the second unitary element 120 may be calculated as the force (in Newtons) required to close the clip over the distance (displacement in mm) between the clip being in the neutral position and being in the closed position. The force required to close the second unitary element may be between approximately 5 Newtons and approximately 50 Newtons. The second unitary element 120 may have a flexural modulus of between 2,000 MPa and 3,000 MPa, preferably approximately 2,400 MPa.

Note that all numerical values mentioned in this disclosure should be assumed as valid at room temperature (assumed to be approximately 20 ^“C) unless otherwise stated. Different numerical values may apply at higher temperatures. Indeed, the range of values for the coefficient of stiffness of the second unitary element 120 would not be applicable during the moulding process prior to the material setting in the mould.

In a preferred embodiment, the first unitary element 160 is be of thermoplastic polyurethane (TPU). Alternatively, the first unitary element 160 may be of silicone. Alternatively, the first unitary element 160 may be of a composite material. The first unitary element 160 may of any material having an appropriate degree of elasticity.

In a preferred embodiment, the second unitary element 120 may be of polycarbonate. Alternatively, the second unitary element 120 may be of acrylonitrile butadiene styrene (ABS). Alternatively, the second unitary element 120 may be of polypropylene (PP). Alternatively, the second unitary element 120 may be of a composite material, for example a composite of polycarbonate and ABS.

Referring to Figure 3 and Figure 6, the shim 180 may comprise a pair of pins 182, 184 configured to be received within a pair of apertures in the second elongate portion 150 of the second unitary element 120. The pins 182, 184 each have a head that has a head that has a larger diameter its stem such that they are configured to snap fit into the apertures and are thereby easier to insert than to remove. The first unitary element 160 and the second unitary element 120 may be moulded elements. What follows is an example method of manufacture. It should be noted that, in the context of this example method of manufacture, the second unitary element is moulded first and the first unitary element is moulded second.

Moulding provides a straightforward manufacturing approach. Moulding the second unitary element 120 and then moulding the first unitary element 160 in situ may facilitate intimate connectivity between the second unitary element 120 and the first unitary element 160.

A mould tool may be provided having one or more first deployable elements such that a first cavity is provided whose bounds are defined by a combination of (i) the mould tool and (ii) the first deployable elements. The first cavity has the three dimensional form of the second unitary element 120.

The second unitary element 120 is formed by injecting liquid material for the second unitary element 120 into the first cavity and allowing that material to harden.

Once the second unitary element 120 is formed, the first deployable elements may be retracted and instead second deployable elements may be deployed. In this way, a second cavity is provided whose bounds are defined by a combination of (i) the mould tool, (ii) the second deployable elements and (iii) the (already moulded) second unitary element 120. The second cavity has the three dimensional form of the first unitary element 160.

The first unitary element 160 is then formed by injecting liquid material for the first unitary element 160 into the second cavity and allowing that material to harden.

It will be noted that if the first unitary element 160 and the second unitary element 120 made contact with one another in only a single plane, the area of overlap between the two would be limited and the risk of detachment would be high.

Therefore, referring to the close-up cross-sectional image of Figure 4, it will be noted that the geometry of the first unitary element 160 and the second unitary element 120 at the interface between the two is such that the interface region comprises a first annular interface surface 191 , a cylindrical interface surface 192 and a second annular interface surface 193. The cylindrical interface surface 192 is located between the first (lower) annular interface surface 191 and the second (upper) annular interface surface 193. In this way, there is contact between the first unitary element 160 and second unitary element 120 in multiple directions, inwardly (and outwardly) and downwardly (and upwardly).

In addition, the interface region comprises, in the second unitary element 120, a number of radial cavities of circular cross section into which inwardly projecting cylindrical protrusions 165 of the first unitary element 160 are moulded.

In this way, the area of contact and the orientations of contact between the first unitary element 160 and second unitary element 120 increase the degree of connection between the first unitary element 160 and second unitary element 120 making it extremely difficult, if not impossible, to detach the first unitary element 160 from the second unitary element 120 without causing irreversible damage to at least one of the first unitary element 160 and second unitary element 120.

In the illustrated embodiment, the cellular tracker 10 takes a substantially cylindrical form and hence the attachment device 100 is configured to receive a cellular tracker having a substantially cylindrical form. The disclosure is not, however, limited to cellular trackers having a cylindrical form or cellular trackers having any particular form or geometry. For example, instead of a circular top face and a cylindrical outer face, the cellular tracker may have a top face taking the form of a polygon and an outer face that comprises a plurality of rectangular faces, one projecting downwardly from each side of the polygon. In another example, the cellular tracker may have an oval top face and arcuate outer face. In another example, the cellular tracker may have a top face whose perimeter is defined by a plurality of arcs and a plurality of arcuate outer faces. Whatever the shape of the top face, the outer face may project substantially perpendicular to the upper face or there may be an angle other than 90 ^“ between the top face and the side face.

As shown in the illustrated embodiment, the cellular tracker 10 may have a circumferential lip 22 at the top face 20 that extends radially outwardly relative to the circumferential outer face 30. It may be that a lower surface of the circumferential lip 22 is intended to rest on a top surface 162 of the first unitary element 160. It may also be that a profile of the exterior circumferential edge of the circumferential lip 22 is in continuation of the profile of the exterior surface of the first unitary element 160, as shown in Figure 8. It may also be that the cellular tracker 10 comprises one or more circumferential ridges 32 that may be intended to aid resistance to removal of the cellular tracker 10 from the attachment device 100.

It may be that the material properties of the cellular tracker 10, at least of the circumferential outer face 30, are intended such as to provide sufficient coefficient of friction relative to the material of the first unitary element 160 so as to resist removal of the cellular tracker 10 from the attachment device 100. An outer diameter of the cellular tracker 10 may be dimensioned to match an inner diameter of the circular opening in the first unitary element 160.

It should also be noted that the disclosure is not limited to the clasp arrangement of the illustrated embodiment. Other clasp arrangements than that illustrated are envisaged within the scope of the disclosure.

The disclosure uses the term “unitary element” (specifically “first unitary element” and “second unitary element”) to mean that the unitary element is not assembled from a plurality of pieces but rather is formed as a single monolith. In the described method, the unitary elements are moulded. However, the disclosure also envisages that the unitary elements may not be provided by moulding, or not exclusively by moulding. Other manufacturing techniques may be employed instead or in addition to moulding. Such manufacturing techniques may, for example, involve some element of machining.

While the described method of manufacture involves co-moulding the first unitary element 160 onto the second unitary element 120, the disclosure is not limited to co-moulding the second unitary element followed by the first unitary element. For example, the first unitary element may be co-moulded onto the second unitary element. In addition, techniques other than moulding may be employed. The disclosure includes the possibility of forming the first and second unitary elements independently and adhering the two by appropriate means.

Figure 9 provides views of a specific embodiment of the attachment device showing various dimensions and angles. The specific embodiment of Figure 9 is shown in the neutral position. In the specific embodiment, an angle that defines the extent of the opening between the first elongate portion 130 and the second elongate portion 150 is 39 ^“. Other angles are contemplated. For example, the angle may be between 20 ^“ and 50 ^“. It has been determined, for a second unitary element 120 of polycarbonate having a coefficient of stiffness of between 0.1 N/mm and 5 N/mm, that an angle of between 20 ^“ and 50 \ more preferably between 35 ^“ and 45 \ provides for a hinge portion that is easily operated with only one hand, is unlikely to become unintentionally unfastened, facilitates a long life of the hinge and has advantages over other angles for moulding of the second unitary element 120. The combination of angle, material and stiffness also reduces the flexing of the second elongate portion 150 when applying the force closing the attachment device.

Claims

CLAIMS:

1. An attachment device for attaching a cellular tracker to a strap such as a pet collar, the attachment device comprising: a first unitary element comprising an envelope configured to provide an elastic circumferential grip; a second unitary element joined to the first unitary element, the second unitary element comprising: a first elongate portion having a proximal end and a distal end; a second elongate portion having a proximal end and a distal end; a hinge portion between the proximal end of the first elongate portion and the proximal end of the second elongate portion; a releasable clasp having an engaged configuration in which the clasp is configured to retain the distal end of the first elongate portion relative to the distal end of the second elongate portion; wherein: in a neutral position, the first and second elongate portions diverge from the proximal ends towards the distal ends so as to provide an opening between the distal end of the first elongate portion and the distal end of the second elongate portion; in a closed position, the first and second mutually cooperating clasp portions engage so as to retain the distal end of the first elongate portion and the distal end of the second elongate portion in mutual contact and thereby prevent return to the neutral position; and wherein: the second unitary element has a coefficient of stiffness that causes the secondary unitary element to be biased towards the neutral position.

2. The attachment device of claim 1 wherein the second unitary element is joined to the first unitary element by the second unitary element being interlocked with the first unitary element.

3. The attachment device of any preceding claim wherein the second unitary element is joined to the first unitary element at an interface region, wherein the interface region comprises a stepped configuration.

4. The attachment device of claim 3 wherein the stepped configuration comprises a cylindrical surface and a first annular surface.

5. The attachment device of claim 4 wherein the stepped configuration further comprises a second annular surface.

6. The attachment device of claim 5 wherein the cylindrical surface is between the first annular surface and the second annular surface.

7. The attachment device of claim 4 or any claim dependent on claim 4 wherein the interface region comprises a plurality of protrusions that project radially from the cylindrical interface surface.

8. The attachment device of claim 7 wherein the plurality of protrusions project radially inwardly from the cylindrical interface surface.

9. The attachment device of claim 7 or claim 8 wherein the first unitary element comprises the plurality of protrusions and the second unitary element comprises a plurality of corresponding cavities that accommodate the plurality of protrusions.

10. The attachment device of any preceding claim wherein the releasable clasp comprises first and second mutually cooperating clasp portions, wherein a first one of the first and second mutually cooperating clasp portions is located towards the distal end of the first elongate portion and a second one of the first and second mutually cooperating clasp portions is located towards the distal end of the second elongate portion.

11 . The attachment device of any preceding claim wherein one of the first elongate portion and the second elongate portion comprises a plurality of apertures configured to receive a corresponding plurality of pins of a shim configured to occupy part of a gap between the first elongate portion and the second elongate portion.

12. The attachment device of claim 11 further comprising the shim.

13. An attachment device kit comprising an attachment device of claim 11 and a plurality of differently dimensioned shims in order to allow selection of an appropriately dimensioned shim to allow a residual gap between the first elongate portion and the shim to be provided for suitability with a thickness of strap to be accommodated within the residual gap.

14. A method of forming an attachment device of any preceding claim, the method comprising: moulding the second unitary element; moulding the first unitary element in situ on the second unitary element.

15. The method of claim 14 wherein the method involves using a mould tool having first deployable elements and second deployable elements, the method comprising: providing a first cavity defined by the mould tool and the first deployable elements in order to form the second unitary element; removing the first deployable elements and deploying the second deployable elements to form a second cavity defined by the mould tool, the second deployable elements and the second unitary element in order to form the first unitary element in situ on the first unitary element.