WO2001054102A1

WO2001054102A1 - Tamper resistant seal

Info

Publication number: WO2001054102A1
Application number: PCT/HU2001/000004
Authority: WO
Inventors: Tibor Neumann
Original assignee: Tibor Neumann
Priority date: 2000-01-17
Filing date: 2001-01-17
Publication date: 2001-07-26
Also published as: HU222262B1; HU0000142D0; AU2001226973A1; DE10194945T1; HUP0000142A2

Abstract

The invention relates to a tamper resistant security seal (10). The seal (10) comprises a flexible strap (12) provided with a dentation (24), and a head part (18) with an inner cavity (14) receiving the strap (12). A locking insert (16) is provided in the cavity (14) for preventing the withdrawal of the strap (12). The locking insert (16) comprises an orifice (36) for receiving the strap (12), and at least one retention catch (38) for engaging the dentation (24) of the strap (12) inserted into the orifice (36). The cavity (14) of the head part (18) further comprises a thermally resistant metal insert (40) with a flexible catching element (39) for engaging the dentation of the strap (12).

Description

TAMPER RESISTANT SEAL

Technical Field

The object of the invention is a seal, of the type which is used widespread as an official seal, or in cases where the unopened state of a locked door, building, box, sack or other type of storage means should be reliably verified. Such seals are commonly referred to as tamper resistant seals. The seal according to the invention comprises a flexible strap provided with a dentation, and a head part with an inner cavity receiving the strap. There is a locking insert provided in the cavity for preventing the withdrawal of the strap. The locking insert comprises an orifice for receiving the strap, and at least one retention catch for engaging the dentation of the strap inserted into the orifice.

Background Art

The most important requirement of such seals is that it should not be possible to open the device locked with the seal, without leaving a visible sign on the seal. With other words, the opening of the locked device or other tampering with the seal should necessarily cause some irreversible change on the seal, which can not be hidden and leaves visible marks. This is normally achieved by constructing the locking mechanism of the seal so that it allows a one-way locking only, as a result of which the locked seal can only be cut off or opened with some other destructive method.

Such types of tamper resistant seals described above are known in the art. With these seals the dentation of the strap engages the retention catches of the locking insert in the head part. The retention catches tighten flexibly around the strap, and the strap may only be displaced in the locking direction in the opening of the head part. The retention catches of the locking insert are inaccessible, because they are completely surrounded by the. head part. However, since these seals are made of plastic, it has been discovered that the retention catches of the locking insert may be temporarily fixed in their open position by freezing, and in this manner the seal may be opened without visible or otherwise noticeable sign. Also, it has turned out that in some instances, such seals may be opened by heating the seal to a certain temperature. Criminals also succeeded to widen the locking insert by winding tape on the strap of the seal, and opened it without leaving signs. It has been attempted earlier to overcome these problems.

As an example, US Patent No. 5,568,952 discloses a shackle seal with two locking inserts in series in the head part. The dentation of the strap and the locking inserts are dimensioned so that the two locking inserts are never in an open, i. e. the widened position simultaneously when the strap is pushed into the head part. Therefore, the seal can not be heated or cooled so that both locking inserts are opened, and at least one of the locking inserts will prevent the withdrawal of the strap. This known solution provided only a partial relief to the problems mentioned above.

Accordingly, it is the object of the present invention to provide an improved tamper resistant seal, which can not be opened with the above methods, or at least its unauthorised opening is made even more difficult. It is a further object of the invention to provide the improved locking in a simple and cost-effective manner with components that are easy to manufacture and require little or no modification of the existing manufacturing equipment.

Summary of the Invention

According to the invention the above objects are achieved with a seal of the type described in the introduction, where The cavity of the head part further comprises a thermally resistant metal insert, with a flexible catching element for engaging the dentation of the strap. The term „thermally resistant" is used to indicate that the resilient or flexible properties of the metal insert are substantially unaffected by heating or cooling in a temperature range where the material of the other parts of the seal remains mechanically stable. This is the temperature range, for example, in which the seal does not melt and/or does not break under normal bending. The invention is based on the recognition that the known plastic locking insert should be supplemented with a locking element, which does not loose its flexible properties neither on higher nor on lower temperatures.

In the most advantageous embodiment of the invention the metal insert is an essentially C-shaped spring, preferably a wire spring, and the catching element is constituted by the end of the spring. In this manner there is practically no need for any further component in the seal, beside the already known and used components of such seals. Practically, no other modification need to be made to the other components of the seal. The C-shaped spring may be manufactured in itself with a minimal material requirement and cost.

Preferably, the distance between the ends of the C substantially equals the width of the strap. Advantageously, the locking insert comprises multiple retention catches, with a slot between the retention catches, and the ends of the spring extend into the slots. Since the locking insert had a similar structure earlier, there is no need to change it substantially. Care should be taken only to provide an even number of retention catches. In this case there will be slots on the locking insert which are symmetrically positioned relative to the axis of the locking insert. It appeared to be optimal when each ends of the spring were located in the slots of the locking insert diametrically opposite each other relative to the strap. During manufacture of the seal" the assembly is greatly facilitated if the retention catches comprise a protrusion on the external side of the catches for positioning the spring.

It has proved to be most practical to make the strap with a substantially circular cross-section, and accordingly for the dentation to comprise conical portions and/or cylindrical portions. In this configuration the seal may be manufactured with a relatively thin strap. Firstly, such a thin strap is easy to bend, secondly, it facilitates the inserting of the strap through small holes (e. g. when closing money transport bags). In this case the orifice receiving the strap is practically a bore with a circular cross-section, completely surrounding the strap, which makes the retention catches in the cavity of the head part inaccessible.

It is an advantage of the seal according to the invention that it may be manufactured easily and in large quantities from a suitable flexibly (resilient) plastic material, and its manufacturing cost practically does not differ from the cost of earlier known seals with a simpler construction.

Brief Description of Drawings By way of example only, the invention is now described in more detail with reference to the exemplary embodiments shown in the enclosed drawings, where

Fig. la-b is a top and side view of the seal according to the invention, in the open state, Fig. 2 shows the head part of the seal shown Figs. 1 a-b, in cross-section in a different scale, where the strap is inserted into the locking insert, in the closed state of the seal, Fig. 3a is a top view of the locking insert and the supplementary metal insert,

Fig. 3b is a top view of a modified locking insert and a metal insert, Fig. 4 is a side cross^sectional view of the locking insert and the supplementary metal insert of Fig. 3, along the line IV-IV of Fig. 3a,

Fig. 5 illustrates a proposed embodiment of the metal insert according to the invention, and

Fig. 6 illustrates the functioning of the metal insert of the invention, in a view similar to Fig. 2.

Best Mode for Carrying out the Invention

Referring now to Figs, la, lb and 2, the seal 10 according to the invention comprises a flexible strap 12 provided with a dentation, and a head part 18 with an inner cavity 14 receiving the strap 12. Such seals are also called shackle seals. There is a locking insert 16 provided in the cavity 14 for preventing the withdrawal of the strap 12 from the head part 18. In the shown embodiment, the strap 12 has a generally circular cross-section, and the dentation is constituted by multiple successive tooth portions 24, the latter made up of adjacent cylindrical portions 20 and conical portions 22. The tooth portions 24 form a dented (serrated) section 26, approximately 15-25 cm long, having on one end an approx. 5-6 cm long pull-in section 28, which is smooth. The head part 18 of the seal 10 connects to the other end of the dented section 26 through a 3-4 cm long intermediate section 30. On the other side of the head part 18, opposite to the intermediate section 30, there is a marking ear 32 with a surface of a few cm , where various identification markings 34 may be provided. Generally, the seal 10 is made of a resilient or flexible plastic material, with a melting temperature preferably above 200 °C. The material of the locking insert 16 is also plastic, with a melting temperature preferably higher than the melting temperature of the head part 18.

The head part 18 of the seal 10 is shown enlarged in cross section in Fig. 2. It may be seen that there is a 14 cavity in the head part 18, formed as a cylindrical bore, and the 16 locking insert is placed in the T4 cavity. The 16 locking insert has an opening or orifice 36, which tightly, butrdisplaceably receives the strap 12. The 36 orifice is a bore matching the cylindrical form of the strap 12. A tooth portion 24 of the dented section 26 of the strap 12 inserted into the orifice 36 of the locking insert 16 co-operates with the retention catches 38 formed on the locking insert 16. With other words, when someone tries to withdraw the dented section 26 of the strap 12 from the head part 18 in a direction opposite to the inserting direction (the latter indicated with the arrow F), the tooth portion 24 engages the retention catch 38.

It is noted that the locking insert 16 is shown as a separate piece in the presented embodiments. It is also possible to manufacture a seal according to the invention where the locking insert is integral with the head part 18. However, from a manufacturing point of view, it is easier to make the locking insert separately from the head and strap part of the seal, and enclosing the insert within the head in a following assembling step.

According to the invention, beside the locking insert 16 there is a further retention element in the cavity 14 of the head part 18, namely, a thermally resistant metal insert 40 with a flexible catching element 39 for engaging the dentation of the strap 12. In the presented most advantageous embodiment the metal insert 40 is constituted by an essentially C-shaped spring 42, preferably realised as a wire spring. The catching element 39 is constituted by the ends 44 of the spring 42. The spring 42 is made of a thin hardened steel wire with a diameter of approx. 0,5 millimetres. Several types of spring steel is available commercially, which preserve its flexible properties substantially unchanged on the practically achievable low or high temperatures, at least in the temperature range where the plastic material of the seal does not yet show irreversible change. Outside this temperature range the seal can not be opened without leaving signs, due to the properties of the plastic, e. g. the melting thereof. As best seen in Figs. 4 and 5, the distance d between the ends 44 of the C-shape substantially equals the width v of the strap 12, where the width v of the strap 12 (actually, the diameter of the strap 12) is considered to be the width of the portions 46 between the tooth portions 24.

Referring now to Fig. 3a, the locking insert 16 comprises multiple retention catches 38, preferably an even number thereof. There are slots 48 between the retention catches 38, and the ends 44 of the spring 42 extend into the slots 48. It is practical to have an even number of retention catches 38 on the locking insert 16, e. g. two, four or six (four with the embodiment shown in the figures), because in this case the ends 44 of the spring 42 may be positioned in slots 48 of the locking insert 16, diametrically opposite each other relative to the strap 12, symmetrically to the tooth portion 24 of the strap 12, more precisely, symmetrically to the shoulder or flange constituted by the rim 50 of the tooth portion 24 (shown with broken line in Figs. 3a and 3b).

It is also foreseen to provide a protrusion 54 on the external side 52 of the retention catches 38 for positioning the spring 42. This is illustrated by an alternative embodiment of the locking insert, shown in Fig. 3b. These protrusions are important for the assembly of the head part 18 and the locking insert 16, because the protrusions 54 hold the spring 42 onto the locking insert 16, until the locking insert 16 is placed in the cavity 14 formed in the head part 18. After the assembly, the spring 42 is held in place by the annular shoulder 58 extending from the wall 56 of the cavity 14 (see also Figs. 2 and 6). However, the head part 18 and the locking insert 16 may also have other form, where the protrusions 54 also play a role in the positioning of the spring 42 during the intended operation of the seal.

The seal 10 according to the invention operates as follows (see Figs. 2 and 6 in particular): The user threads the strap! 2 of the seal through the appropriate holes of the device to be closed or lacked (not shown), and thereafter inserts the pull-in section 28 of the strap 12 into the orifice 36 of the locking insert 16 in the head part 18. Since the pull-in section 28 is without dentation, the pull-in section 28 may be easily passed through the head part 18 and the locking insert 16. Thereafter the user pulls in the dented section 26 of the strap 16 into the head part 18, and also into the orifice 36 of the locking insert 16, in the direction indicated by the arrow F, holding the strap 12 by the pull-in section 28. The dented section 26 is pulled until at least one, but normally several tooth portions 24 pass beyond the rim 60 of the 38 retention catches of the locking insert 16. Since the retention catches 38 are resilient, the conical portions 22 of the tooth portions 24 press the retention catches 38 apart while the tooth portions 24 pass between the retention catches 38. After the tooth portions 24 went through, the retention catches 38 again close at their upper rim 60, in practice to such extent that the rim 60 presses against the strap 12, more precisely, against the portion 46 between the tooth portions 24 of the strap 12.

During the pull-in of the strap 12, the conical portions 22 also push the ends 44 of the spring 42 apart from each other, while the spring 42 sitting loosely in the cavity 14 slightly turns under the effect of the pulling force, so that the ends 44 of the C- shape move towards the direction of the pulling, i. e. upwards as seen in Fig. 2. In this position the spring 42 slightly spreads under the pressure of the conical portion 22, and lets through the tooth portion 24 of the strap 12 between its ends 44. After the cylindrical portion 20 of the tooth portion 24 passed through, the stems of the spring 42 close again, and the ends 44 normally press against the strap 12. At least, the 44 ends approach each other so much so that the cylindrical portion 20 of the tooth portion 24 is unable to pass between them.

In case the retention catches 38 of the locking insert 16 remain in the opened state, e. g. due to heating or cooling, the strap 12 may be withdrawn between them. However, in this case, as it is shown in Fig. 6, the stems of the spring 42 remain closed, because the 44 ends will still remain so close to each other that the tooth portions 24 can hot pass through between them. In an attempt to withdraw the strap 12, the ends 44 of the spring 42 will turn downwards in the cavity 14, and the 44 ends abut the bottom 62 of the slot 48 between the retention catches 38. In this situation the ends 44 of the spring 42 engage the rim 50 of the tooth portion 24, and prevent the further movement of the tooth portion 24 in the direction opposite to the arrow F. Thus it may be realised that the metal insert according to the invention - in the shown embodiment the spring 42 - effectively prevents the withdrawal of the strap 12 from the head part 18, even if the retention catches 38 of the locking insert 16 should remain ineffective for some reason.

The invention is not limited to the shown embodiments, and may be realised in other ways as well. As an example, the metal insert need not be made as a wire spring, but could be a ring with flexible inwardly extending tongues, made of a flexible metal sheet material. This ring may be put around the locking insert, so that the tongues extend into the dentation of the strap through the slots between the retention catches of the locking insert. Also, the cross-section of the strap part need not be circular, but may be flattened as well. Of course, in this case the tooth portions will have different configuration. As an example, there may be tooth portions on both sides of the flat strap, and the thermally resistant metal insert may engage the tooth portions on the two sides of the strap.

Claims

Claims:

1. Tamper resistant seal, comprising a flexible strap (12) provided with a dentation, and further comprising a head part (18) with an inner cavity (14) receiving the strap (12), with a locking insert (16) provided in the cavity (14) for preventing the withdrawal of the strap (12), the locking insert (16) comprising an orifice (36) for receiving the strap (12), and at least one retention catch (38) for engaging the dentation of the strap (12) inserted into the orifice (36), characterised in that the cavity (14) of the head part (18) further comprises a thermally resistant metal insert (40) with a flexible catching element (39) for engaging the dentation of the strap (12).

2. The seal of claim 1 , wherein the metal insert (40) is an essentially C-shaped spring (42), preferably a wire spring, and the catching element (39) is constituted by the end (44) of the spring (42).

3. The seal of claim 2, wherein the distance (d) between the ends (44) of the C substantially equals the width (v) of the strap (12).

4. The seal of claim 2 or 3, wherein the locking insert (16) comprises multiple retention catches (38), with slots (48) between the retention catches (38), and the ends (44) of the spring (42) extend into the slots (48).

5. The seal of claim 4, wherein each end (44) of the spring (42) is located in the slots (48) of the locking insert (16) diametrically opposite each other relative to the strap (12).

6. The seal of any one of claims 2 to 5, wherein the retention catches (38) comprise a protrusion (54) on the external side (52) of the catches (38) for positioning the spring (42).

7. The seal of any one of claims 1 to 6, wherein the strap (12) has a substantially circular cross-section, and the dentation comprises conical portions (22) and/or cylindrical portions (20).

8. The seal of any one of claims 1 to 7, wherein the orifice (36) receiving the strap (12) is a bore with a circular cross-section.

9. The seal of any one of claims 1 to 8, made of a flexible plastic material.