EP0983416B1 - Fixing an anti-theft label on an object using a heat-shrinkable envelope - Google Patents

Description

The present invention relates to the field of the packaging of objects and that of the protection of these objects against theft, and more particularly a connection with anti-theft protection between two objects.

Stores are daily victims of theft shoplifting or markdown unknown, and thereby suffer a shortfall which amounts to considerable sums. The fight against this scourge pushes designers to imagine more and more protection systems sophisticated.

The technological background of the invention can be illustrated by document FR-A-2.605.747 describing a process consisting in permanently integrating into an object a flat resonant circuit used inside a gantry emitting a radio frequency electromagnetic wave, by document FR-A-2,358,713 describing an anti-theft marker in ferromagnetic material attached to the object to be protected, and by document WO-A-85 02285 describing an alarm system using a ribbon in two overlapping strips taken in sandwich between a face of the object and a label protective.

We can also refer to documents EP-A-0 698 561 and EP-A-0 698 562 describing an envelope packaging made of heat shrinkable plastic which is equipped with a metallic filament constituting an antenna for a functioning electronic monitoring system on a magnetic detection principle, said filament being arranged on the inner wall of the envelope in the first document or being integrated in a tear strip in the second document. The techniques described in these documents are interesting, but sometimes difficult to be implemented in the case of objects or parts objects with a small cross section (the branch of a pair of glasses, or the barrette of a pen for example).

There are also anti-theft systems using a link surrounding part of the object concerned. The document EP-A-0 615 041 thus describes an anti-theft device reusable for glasses, with a link reinforced by two steel cables, associated with a hooking plate provided with disarmable locking means only at using a specific tool.

We also know various systems of anti-theft protection of case type or rigid label, which are fixed by stapling or adhesive bonding to the object concerned. In recent years, we have in particular developed an advanced technology called magneto-acoustic technology, that the anti-theft protection system consists of two metal lamellas joined (separated by an insulating wall) capable of being put vibrating at a relatively predetermined frequency low (around 60 kHz for example). The interest of this type of protection system is that one can inhibit and uninhibit the system at will, as many times as we wants. Most of the time, such a protection system is disposed in a housing, one side of which is adhesive, of so as to be applied directly against the wall of the object to be protected. As is easy to understand, in the case of weak objects or parts of objects dimensions in section, it becomes difficult, even impossible, to fix such a case equipped with a magneto-acoustic system, and this for purely mechanical reasons.

The invention aims precisely to solve the problem of the anti-theft protection link between two objects, and to design a technique not presenting the aforementioned drawbacks.

The subject of the invention is therefore a device for anti-theft protection link between two objects which is both simple in structure and capable of providing protection optimal in terms of inviolability, while being easy installation.

• une enveloppe en matière plastique thermorétractable, réalisée sous la forme d'un manchon dont les parois sont localement rapprochées le long d'une génératrice commune pour former un compartiment principal ouvert à ses deux extrémités et destiné à envelopper un premier des deux objets à relier et un compartiment annexe dans lequel est disposé un barreau allongé s'étendant parallèlement à ladite génératrice commune ;
• une paroi prévue sur l'autre objet, paroi dans laquelle est ménagée une fente longitudinale étroite débouchant à l'une de ses extrémités, ladite fente étant dimensionnée pour permettre d'une part l'insertion de l'enveloppe précitée au niveau de la génératrice commune de celle-ci de façon que le barreau allongé associé soit disposé en arrière de la paroi et coopère avec celle-ci pour assurer la liaison entre ledit autre objet et l'enveloppe thermorétractée sur le premier objet, et d'autre part le blocage de l'enveloppe insérée dans la fente grâce à un moyen de blocage associé agencé pour barrer l'extrémité débouchante de ladite fente ;
• un moyen de protection anti-vol intégré à l'enveloppe et/ou à l'un au moins des deux objets.

It is more particularly a connection device with anti-theft protection between two objects, characterized in that it comprises:

• an envelope made of heat-shrinkable plastic, produced in the form of a sleeve whose walls are locally brought together along a common generator to form a main compartment open at its two ends and intended to wrap a first of the two objects to be connected and an annex compartment in which is disposed an elongated bar extending parallel to said common generator;
• a wall provided on the other object, wall in which is formed a narrow longitudinal slot opening at one of its ends, said slot being dimensioned to allow on the one hand the insertion of the aforementioned envelope at the level of the generator joint thereof so that the associated elongated bar is disposed behind the wall and cooperates with it to ensure the connection between said other object and the shrink-wrapped envelope on the first object, and secondly the blocking of the envelope inserted into the slot thanks to an associated locking means arranged to bar the through end of said slot;
• an anti-theft protection means integrated into the envelope and / or at least one of the two objects.

Preferably, the elongated bar is glued in the associated annex compartment of the envelope. We may of course provide, as a variant, for sealing the walls facing the envelope at the generator common.

Advantageously, the elongated bar is unitary and extends over the entire length of the annex compartment associated with the envelope. In particular, we can plan an elongated bar produced in the form of a bar or of a plastic tube.

According to another advantageous characteristic of the device, the envelope is further equipped with a anti-theft protection in the form of a filament metallic constituting an electromagnetic antenna, said filament extending along a generator of the compartment main. Preferably, the metallic filament is disposed at an inner flap of the constituent sleeve of the envelope, and the outer wall of said sleeve has a local cutout or notch at a end of the filament to allow gripping thereof with a view to tearing said wall. The antenna filament then also performs a tear strip function. We can also, in the presence or not of a filament metal forming antenna, provide that the envelope is equipped with a tear strip extending along a generator of the main compartment.

In accordance with an interesting mode of execution, one of the objects to be linked is an elongated plate identification and / or anti-theft protection. In particular, the elongated insert can be arranged in the form a housing used to house an anti-theft protection means such as a magneto-acoustic detection antenna, and one of the walls of the elongated plate is the wall above with narrow longitudinal slot.

Advantageously, the blocking means associated with the narrow longitudinal slot consists of a cleat blocking which is either clip on the wall or connected to the wall by a ligament forming a hinge, so that said cleat can then pivot between a position of release in which the entrance to the slot is cleared, and a blocking position in which the entry of the slot is crossed out. In this case, the ligament is designed to authorize a limited number of uses, by breaking naturally then. We can also foresee that the the aforementioned cleat is lockable in its position blocking, for example by clipping a solid lug said cleat in the slot.

Advantageously also, the blocking means associated with the narrow longitudinal slot consists of a double entry notch arranged to allow a passage in the direction of insertion only.

The invention also relates to an envelope heat shrink specially designed for the constitution a connection device having at least one of the aforementioned characteristics, said envelope being produced in the form of a heat-shrinkable plastic sleeve whose walls are locally close together on along a common generator to form on the one hand a main compartment open at both ends and on the other hand an annex compartment in which is blocked an elongated bar extending parallel to said common generator.

Preferably, this envelope is equipped with a anti-theft protection in the form of a filament metallic constituting an electromagnetic antenna, said filament extending along a generator of the compartment main.

• la figure 1 illustre en perspective un dispositif conforme à l'invention, avec son enveloppe prête à recevoir un objet, l'autre objet étant ici une plaquette allongée équipée d'un moyen de protection anti-vol;
• la figure 2 est une coupe selon II-II de la. figure 1, permettant de mieux distinguer la liaison entre l'enveloppe et la plaquette grâce à un barreau allongé qui est prisonnier dans la plaquette ;
• les figures 3A et 3B illustrent la mise en place du dispositif précité sur un objet ou une partie d'objet, en l'espèce respectivement sur une branche de lunettes ou sur une barrette de stylo, après rétraction de la paroi concernée de l'enveloppe autour de l'objet ou de la partie d'objet ;
• la figure 4 est une coupe selon IV-IV des figures 3A ou 3B, permettant de mieux distinguer la liaison mécanique ainsi réalisée après rétraction de la paroi de l'enveloppe extérieure à la plaquette ;
• la figure 5 est une vue éclatée en perspective illustrant le montage du dispositif précité, avant l'insertion d'une enveloppe équipée de son barreau allongé par la fente de la plaquette, le taquet de blocage de celle-ci étant en position de libération pour dégager l'entrée de ladite fente, la position de blocage dudit taquet étant illustrée en traits mixtes;
• les figures 6A, 6B, 6C illustrent d'autres variantes du dispositif de liaison selon l'invention.

Other characteristics and advantages of the invention will appear more clearly in the light of the description which follows and of the appended drawings, relating to a particular embodiment, with reference to the figures in which:

• Figure 1 illustrates in perspective a device according to the invention, with its envelope ready to receive an object, the other object here being an elongated plate equipped with anti-theft protection means;
• Figure 2 is a section on II-II of the. Figure 1, to better distinguish the connection between the envelope and the wafer through an elongated bar which is trapped in the wafer;
• FIGS. 3A and 3B illustrate the positioning of the aforementioned device on an object or part of an object, in this case respectively on a branch of glasses or on a bar of pen, after retraction of the wall concerned of the envelope around the object or part of an object;
• Figure 4 is a section on IV-IV of Figures 3A or 3B, to better distinguish the mechanical connection thus produced after retraction of the wall of the outer shell to the wafer;
• FIG. 5 is an exploded perspective view illustrating the mounting of the aforementioned device, before the insertion of an envelope fitted with its rod extended by the slot of the wafer, the blocking tab thereof being in the release position for clear the entrance to said slot, the blocking position of said cleat being illustrated in phantom;
• Figures 6A, 6B, 6C illustrate other variants of the connecting device according to the invention.

Figures 1 and 2 illustrate a device 10 of connection between two objects according to the invention, in accordance to a first variant in which the object carrying the wall with a longitudinal slot is an elongated plate, here equipped with anti-theft protection.

The device 10 essentially consists of two main components which are arranged to be associated with each other inseparably.

The first of these components is an envelope rated 20, made of heat-shrinkable plastic, made in the form of a sleeve. Plastic tape is closed on itself, and presents a line of seal marked 21 at a generator of the sleeve, in forming an end flap 22, which is here arranged on the side inside the sleeve. The walls of the sleeve are locally close together along a common generator, noted 23, to form a main compartment noted 24 which is open at both ends and intended to wrap a first (not shown in Figures 1 and 2) of the two objects to be linked (the other object here being constituted by the aforementioned brochure), and an annex compartment noted 25, here much smaller in section than the compartment main, in which is placed an elongated bar 26 (not visible in Figure 1) extending parallel to the aforementioned common generator 23.

The elongated bar 26 can be glued in the annex compartment 25 of envelope 20, as well as that is best seen in the section in Figure 2, where we distinguishes a thickness of glue 27 surrounding here the bar 26. One can imagine in a variant a rapprochement located with a seal made according to the generator common, at the contact between the internal walls in look. However, bonding has the advantage of good holding the elongated bar in place, a bar whose function will be explained later. This elongated bar 26 is preferably unitary, and extends over the entire length of associated annex compartment 25 of envelope 20, the advantage of a unitary bar being that one obtains optimal mechanical resistance evenly distributed over the entire length of the sleeve. We will see that this is particularly important since the bar lying down should serve as a liaison in a process mechanical attachment. The elongated bar 26 may be produced in the form of a bar or a tube of material plastic, the important material little as soon as the mechanical resistance against crushing (due to forces directed towards its axis) is sufficient.

It can also be seen in FIG. 1 that the envelope 20 is further here equipped with a metallic filament denoted 28 forming an electromagnetic antenna, said filament extending along a generator of the main compartment 24. Preferably, this generator will be chosen close to the common generator 23, in order to promote discretion the presence of the antenna once the device has been place on an object or part of an object. In this case the metallic filament 28 is arranged at the flap inside 22 of the sleeve constituting the envelope, and the outer wall of this sleeve also has a cutout or local notch 29 at one end of the filament 28 to allow gripping thereof by pliers suitable for tearing said wall (the filament-antenna then also providing a function of tear strip), as will be explained below, when it is desired to separate the device 10 from the object with which it is associated. It should be noted that this type of metallic filament constitutes an antenna operating by resonance and not by radiofrequency electromagnetic waves, and that this means cannot be deactivated. For this technology, reference may be made to document EP-A-0 698,561 already mentioned.

Regardless of the presence of a filament metal forming antenna, we can alternatively provide that the envelope is equipped with a tear-off strip of the type conventional (not shown here) extending in a main compartment generator 24.

The other fundamental component of device 10 is made up of part of the other object, namely for the variant of FIGS. 1 to 5 an elongated plate identification and / or anti-theft protection. We distinguish thus an elongated plate 30, which is arranged in the form of a case. This plate 30 has a wall 31 in which is formed a narrow longitudinal slot noted 32. This longitudinal slot 32 has one end 33 not opening, which is close to one end (rear in FIG. 1) of the plate, and one end 34 which meanwhile opens out at the front end of said wafer.

The slot 32 has a particular dimensioning, both for its width and for its length.

The width of the slot 32 is chosen so as to allow the double thickness of the envelope 20 to pass level of the common generator 23 thereof, without however pass the elongated bar 26 which is then disposed behind the wall 31 of the plate 30. Thanks to this arrangement, the elongated bar 26 cooperates with the wall 31 to ensure the connection between the envelope 20 heat shrunk on the first object and the other object constituted by the elongated plate 30. The device 10 is indeed intended to be associated with an object or with a part of the object (the "first object"), being intimately attached to that object or part of it as a result of shrinkage of the wall of the envelope corresponding to the main compartment thereof, as illustrated in FIG. 3A for a branch of glasses, or FIG. 3B for a pen bar, and on the associated cut of Figure 4, the object or the associated object part being referenced 100.

It is furthermore necessary to arrange the plate 30 of such that the elongated bar 26 inserted through the entrance 34 of slot 32 can be locked in place in this slot, in order to avoid any risk of detachment, this which would ruin the effectiveness of the anti-theft protection means which can be associated with the elongated plate 30, in particularly when this plate is produced under the shape of a housing receiving an anti-theft protection means denoted 50 such as a magneto-acoustic detection antenna.

A locking means is provided for this purpose, here constituted by a cleat noted 36 which is integral with the plate 30, which is arranged to bar the end opening 34 of the slot 32.

Cleat 36 can be an independent part of the plate 30 and be able to clip, in its position blocking, so as to block the inserted envelope. According to one such variant (not illustrated here), the blocking cleat 36 may be produced in the form of a bar having on one side two male nipples that can snap into two associated holes provided for this purpose in the plate 30. However, it is interesting to plan for a cleat mechanically associated with the plate 30, which facilitates the handling of this cleat, and avoids any risk loss of it. As it is better visible on Figures 1 and 5, the locking tab 36 is here connected to the housing 30 by a ligament forming a hinge 37, so that said cleat can pivot between a position of release (illustrated in Figure 5), in which the entry 34 of the slot 32 is cleared, and a position of blocking (illustrated in Figures 1 to 4) in which entry 34 of slot 32 is blocked.

The housing 30 carrying a detection antenna magneto-acoustic 50 can thus be reused once that it has been detached from the shrink-wrapped envelope 20 on the object. However, it is advisable to ensure that the number of uses remains de facto limited, which may be readily obtained by providing that ligament 37 is designed to allow a limited number of uses in se then naturally breaking, for example five to ten manipulations to the maximum. In order to avoid any risk of inadvertent release of the envelope 20 out of the slot. insertion 32, it is advantageous to provide that the cleat 36 is lockable in its locked position. This can be achieved by any mechanical means such as clipping. In the present case, as is best seen on the Figure 5, we can provide a lug 38 on the inner face of the pivoting cleat 36, which lug is arranged and dimensioned so that it can snap into slot 32 when the cleat 36 is folded against the wall 31 of the box 30. In Figure 5, we noted L the length of the envelope 20 and its associated elongated bar 26, and we find this length L on the main portion of the slot 32 located between the end 33 thereof and the limit point of recovery by the cleat 36 when it is folded down. The envelope 20 is then perfectly maintained between two end stops, in the part associated with slot 32.

As mentioned above, the brochure elongated could be made in a monolithic form with simply its longitudinal slot 32. Such a variant is illustrated in section in FIG. 6A, the elongated plate being referenced 30 '. In this case rear face 39 opposite to face 31 essentially serves to support identification means marked 39.1, 39.2, by example a weight-price label or a code carrier to bars, or a digital label, or a battery solar. It is however interesting to arrange the brochure elongated 30 in the form of a box, as is illustrated in the variant shown, in particular for receive a sophisticated means of anti-theft protection 50 such than a magneto-acoustic detection antenna. In this case, it is advisable to provide a notch 35 at the level of the end facets of the housing 30, these notches having a profile suitable for letting the portion of the envelope corresponding to annex compartment 25 in which is arranged the elongated bar 26. Depending on the case, these notches 35 will be limited to the end walls of the box 30, or may constitute the through ends a longitudinal housing arranged inside said housing.

The establishment of a system such as the previously described device is carried out in accordance with a method of threading the object or part of an object concerned 100 in compartment 24 of envelope 20, then heat shrink the wall of the main compartment 24 to secure the device 10 to the object 100. We then arrives at the representation given in FIGS. 3A, 3B, and 4. The object 100 may be of a very diverse type, in particular chosen in the field of perfumery, cosmetics or stationery. However, it is interesting to predict, as illustrated in the two applications Figures 3A and 3B, that the object or the part object 100 threaded into main compartment 24 of the envelope 20 extends opposite the blocking cleat 36 and thus constitutes a natural locking of said cleat a once the heat shrinkage has been performed.

In Figure 5, there is also illustrated a box 30 produced by assembling two noted components 30.1 and 30.2, namely a plate 30.1 to which is attached the cleat 36 and which has the slot 32, and a housing proper 30.2, the joining edges of these two components here notched to achieve locking positive preventing, once the 30.1 plate clipped on the case 30.2, any slip relating to the way of a drawer in the direction of the slot.

The connection of the two objects made by the device 10 is both very safe and quick to set up artwork. As can be seen in Figure 5, it suffices put on the envelope part 20 equipped with its bar elongated 26 in the slot 32 until it comes into abutment against the end 33 of this slot 32. Then, it suffices to raise the blocking cleat 36, and snap said cleat in its locked position. We then arrive at device illustrated in FIGS. 1 and 2. The connection to the other object can then be easily produced, by example on a branch of glasses or on the bar of a pen, by subjecting the relevant wall to heating localized, for example by blowing hot air or by approaching the wall with a gas burner flame.

It will be appreciated that in this position the device 10 does not harm the examination of the object 100, nor the fitting of it in the case of a spectacle frame. In addition, the small size of the housing 30 (in the practical we will use a parallelepiped housing dimensions 5mm x 20 mm x 45 mm) is completely compatible with the use of displays traditionally used by opticians.

When the customer has decided to acquire an object equipped with such a connecting device, it is advisable to disconnect the device 10, and for this to cut the associated envelope. Different ways can be envisaged for this, and we could use for example a cutting blade (not shown here) inserted between the object 100 and the housing 30, so. to cut the envelope appreciably at the level of the common generator 23, or else a traditional tear-off strip (not shown here) extending along a generator of the compartment principal 24. Another particularly elegant way of to solve this problem is to provide a means of lifting of the wall which is none other than the metallic filament 28 provided to constitute an electromagnetic antenna. In this case, the antenna wire itself constitutes a strip tearing, thus ensuring a double function. To avoid too easy gripping of the end of the filament, which would significantly weaken performance in terms of protection, it may be appropriate to provide a small notch or cutout, such as the cutout 29 illustrated here, so that only a small terminal portion of the filament is accessible, and moreover by means of a special tool such as needle nose pliers.

Once the two components have been separated, is easy to remove the residual envelope wall from the object, and the residual envelope wall of the housing. Then just put another envelope in the box, and block this envelope by closing the swivel cleat.

In practice, depending on the dimensioning of the objects concerned, it will be preferable to use a film with a high shrinkage percentage (70 to 80% for example), the thickness of which will be of the order of forming the heat-shrinkable envelope. 50 to 60 µ m. It is easy to understand that with relatively thick films, the tearing of the heat-shrunk envelope becomes more difficult to implement, which makes the above-mentioned solution even more effective, consisting in using an antenna filament as a tape. 'uprooting.

Other applications of the linkage device the invention could naturally be envisaged. We have illustrated by way of nonlimiting examples two others variants in FIGS. 6B and 6C.

For these variants, the object having a wall with narrow longitudinal slit is no longer as before a elongated plate, forming a housing (Figures 1 to 5) or not (Figure 6A).

In FIG. 6B, there is an object 100 provided to be received in main compartment 24 of envelope 20. The other object, noted 30 ", is a protuberance having a slot 35 with slot 32 intended for receive the part of the envelope 20 surrounding the bar 26. The associated blocking means is here realized not in the form of a cleat which can be clipped onto the other object or pivoting, being connected to said other object, but under the shape of a double entry notch, denoted 36 ′, arranged for allow a passage in the direction of insertion only (at the way of a hook). This 30 "protrusion can make part of an object hanging support (objects such as object 100), or an object such as a container or container packaging (object 100 is then a promotion associated with the sold object).

In FIG. 6C, the object noted 100 'which is received in the main compartment 24 of the envelope 20 is a identification and / or anti-theft protection plate, for example a plate-type housing of the plate 30 previously described, equipped with a magneto-acoustic antenna 50. The other object, noted 30 '' ', is here a bottle having a localized recess with a slot 32 and a blocking cleat 36, so as to receive the part of the envelope 20 surrounding the bar 26. The object 30 '' ' may alternatively be a packaging or an object support, then equipped with a very effective inviolability system.

It will be noted that the envelope 20 illustrated in Figures 6B and 6C is as previously equipped with a means anti-theft protection in the form of a filament 28 constituting an electromagnetic antenna.

This means alone provides anti-theft protection for the variant of FIG. 6B, and completes the protection by magneto-acoustic antenna for the variant of the figure 6C.

We thus managed to achieve a system identification and / or anti-theft protection both simple structure and extremely efficient in terms of fight against shrinkage unknown.

The invention is not limited to the embodiment which has just been described, but on the contrary includes any variant using, with equivalent means, the essential characteristics set out in the revendications.

Claims (16)

1. A device for making an antitheft link between two objects, the device being characterized in that it comprises:

   an envelope (20) of heat-shrink plastics material, implemented in the form of a sleeve whose walls are brought together locally along a common generator line (23) to form a main compartment (24) and an auxiliary compartment (25), the main compartment being open at both ends and being designed to envelop a first one (100, 100') of the two objects to be connected together, and the auxiliary compartment (25) having an elongate pin (26) disposed therein, which pin extends parallel to said common generator line;

   a wall (31) provided on the other object (30, 30', 30", 30"'), which wall has formed therein a narrow longitudinal slot (32) opening out at one of its ends, said slot being dimensioned firstly to enable the common generator line (23) of the above-mentioned envelope (20) to be inserted therein so that the associated elongate pin (26) is disposed behind the wall (31) and co-operates therewith to provide the link between said other object and the envelope when heat-shrunk onto said first object, and secondly to lock the envelope (20) as inserted in the slot (32) by associated locking means (36, 36') organized to close the open end (34) of said slot; and

   antitheft means (28, 50) integrated in the envelope (20), and/or at least one of the two objects.
2. A device according to claim 1, characterized in that the elongate pin (26) is held in the associated auxiliary compartment (25) of the envelope (20) by adhesive.
3. A device according to claim 1 or claim 2, characterized in that the elongate pin (26) is a single piece extending over the full length of the associated auxiliary compartment (25) of the envelope (20).
4. A device according to any one of claims 1 to 3, characterized in that the elongate pin (26) is made in the form of a bar or a tube of plastics material.
5. A device according to any one of claims 1 to 4, characterized in that the envelope (20) is fitted with antitheft means in the form of a metal filament (28) constituting an electromagnetic antenna, said filament extending along a generator line of the main compartment (24).
6. A device according to claim 5, characterized in that the metal filament (28) is disposed level with an inside flap (22) of the sleeve constituting the envelope (20), and the outer wall of said sleeve has a local cutout or notch (29) level with one end of the filament (28) to enable it to be grasped for the purpose of tearing said wall.
7. A device according to any one of claims 1 to 4, characterized in that the envelope (20) is fitted with a tear strip extending along a generator line of the main compartment (24).
8. A device according to any one of claims 1 to 7, characterized in that one of the objects is an elongate identity and/or antitheft plate (30, 30', 100').
9. A device according to claim 8, characterized in that the elongate plate (30, 100') is implemented in the form of a box serving to house antitheft means such as an antenna for magnetoacoustic detection (50).
10. A device according to claim 8 or claim 9, characterized in that one of the walls of the elongate plate (30, 30') is the wall (31) having the narrow longitudinal slot (32).
11. A device according to any one of claims 1 to 10, characterized in that the locking means associated with the narrow longitudinal slot (32) is constituted by a locking catch (36) which is either snap-fastenable to the wall (31) or else is connected to the wall (31) by a hinge-forming ligament (37) such that said catch can pivot between a release position in which the entrance (34) of the slot (32) is disengaged, and a locking position in which the entrance (34) of the slot (32) is closed.
12. A device according to claim 11, characterized in that the ligament (37) is designed to allow use on a limited number of occasions, thereafter breaking naturally.
13. A device according to claim 11 or 12, characterized in that the catch (36) is lockable in its locking position e.g. by a stud (38) secured to said catch and snap-fastening in the slot (32).
14. A device according to any one of claims 1 to 10, characterized in that the locking means associated with the narrow longitudinal slot (32) is constituted by a pair of inlet barbs (36') organized to allow passage in the insertion direction only.
15. A heat-shrink envelope specially designed for constituting a link device according to any one of claims 1 to 14, characterized in that it is made in the form of a sleeve of heat-shrink plastics material whose walls are brought together locally along a common generator line (23) to form both a main compartment (24) open at both ends, and an auxiliary compartment (25) in which an elongate pin (26) extending parallel to said common generator line is held in place.
16. An envelope according to claim 15, characterized in that it is fitted with antitheft means in the form of a metal filament (28) constituting an electromagnetic antenna, said filament extending along a generator line of the main compartment (24).

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