GB2208289A - A tamper detection device - Google Patents

Abstract

A tamper detection device is described in which a plurality of ferro-magnetic elements (29) are initially magnetically held in selected ones of a plurality of recesses (23) in predetermined permutation, in a two part device. On separation of the two parts (11, 13) the magnetic influence on the elements is removed therefrom permitting the elements to fall from their respective recesses with no way of determining the originally selected permutation. <IMAGE>

Description

A TAMPER DETECTION DEVICE.

This invention relates to a tamper detection device of simple yet secure construction which permits the determination of whether a container or other closed apparatus in which the device is incorporated has been opened in a manner such as to disturb the device. The advantage of the device is the difficulty of resetting the device after it has been disturbed.

It is an object of the present invention to provide a tamper detection device of simple construction.

According to the present invention, there is provided a tamper detection device of box-like form comprising a lid and a base arranged, when closed, to interfit, and adapted for mounting to respective parts of a closable container in such manner that, on opening of the container, the lid and the base of the box are separated, the base presenting a plurality of recesses into selected ones of which, ferro-magnetic elements may be inserted, and a magnetic means for initially magnetically retaining the elements in the selected recesses, the lid providing holding means for holding the elements in the selected recesses when the lid and the base are brought together and whilst the device is closed, contact means for establishing electrical paths indicative of which of the recesses contain the elements, and means for engaging the magnetic means so that, when the device is opened, the magnetic means attaches to the lid and the then unrestrained elements fall from the recesses.

The invention will be described further, by way of example with reference to the accompanying drawings, in which: Figures 1 and 2 are plan views of a base and a lid of a tamper detection device in accordance with the present invention; Figures 3 to 6 are diagrammatic cross-sectional views of the construction and manner of operation of a first embodiment of the device of- Figure 1; and Figures 7 to 10 are similar views of a second embodiment of the device of Figure 1.

Referring to Figures 1 to 6, there is shown a tamper detection device in accordance with a first embodiment of the present invention. The device comprises a base 11 and a lid 13 arranged to interfit together to form a closed, box-like receptacle.

The terms "box-like", "base" and "lid" are used herein for the sake of convenience. Shapes other than box-like and components which fit together to define a closed receptacle but not in the manner of a box lid and base are within the scope of this disclosure. The only requirement is that the two components should separate in a manner equivalent to that in which component parts of a container or similar apparatus to be protected are moved apart to open the container.

The base 11 comprises a body 15 defining a peripheral upstanding wall 17 surrounding a central member 19 comprising at least one and preferably (as shown) a pair of parallel spaced flanges 21. The flanges 21 provide, in their upper part, a plurality of equally spaced recesses in the form of apertures 23 extending through the respective flange 21. Removably located between the flanges 21 is a magnetic means comprising a strip 25 of transversely magnetized magnetic rubber and, therebelow, a spacer 27 of a non-magnetic material serving to locate the strip 25 in alignment with the apertures 23. A plurality of ferro-magnetic elements in the form of steel balls 29 are provided. The balls may be placed in selected apertures 23 in any desired combination.The balls 29 are held in the respective apertures 23 by the magnetic influence of the strip 25 but it will be appreciated that, in the absence of the strip 25, the balls would fall from the apertures.

The lid 13 comprises a top 31 having a depending peripheral wall 33 terminating in a reduced thickness peripheral lip 35 arranged, when the lid 13 is closed to the base 11, to interfit closely within the peripheral wall 17 of the base 11. Interiorly of the lid 13, spacer members 37 present inwardly directed spring contacts 39.

Alternate ones of the contact 39 are brought out at Ll to L33 and R1 to R33 for accessibility.

The spring contacts 39 are located in the lid 13 so that, when the lid is closed to the base 10, a respective one of the contacts 39 is presented between each of the apertures 23 in the flanges 21 of the box. A ball 29 in an aperture 23 will thus contact one commonly connected contact 39 and are intervening contact 39.

The lid 13 also provides a soft iron or similar strip 41 secured thereto an alignment (when the lid is closed to the base 11) with the magnetic strip 25.

As shown in Figures 3 to 6, in operation, balls 29 are placed in selected apertures 23 to provide a desired permutation. The lid 13 is then closed to the base 11. In so doing, the spacer members 37 and the spring contacts 39 contact the balls 29 in the recesses 23 and hold the balls in place (Figure 4). Simultaneously the strip 41 contacts the magnetic strip 25.

Assuming that the device is opened, the soft iron strip 41 holds the magnetic strip 25 thereto as the lid 13 moves away from the base (Figure 5). The strip 25 and its spacer 27 are withdrawn from between the flanges 21. The contacts 39 and spacer members 37 no longer hold the balls 29 in the recesses 23 and the balls fall therefrom (Figure 6). By the time the lid has been removed from the the base, permitting visual inspection, there is no way of determining what the original selection of apertures 23 containing balls 29 had been. Re-closing of the lid 13 to the base 11 is, of course, possible but selecting the correct permutation of ball-containing apertures 23 is very difficult. The device can be electrically checked, without opening, to see if the correct permutation exists and hence the device has not been opened.

In use, the base 11 of the device is secured to one part of a container to be protected whilst the lid 13 is secured to another relatively movable part of the container to be protected. The container cannot therefore be opened without activating the tamper detection device.

In order to confuse a tamperer further, spare balls 29a may be provided initially in a recess 43 of the spacer 27.

In a second embodiment, shown in Figures 7 to 10, like reference numerals have been used to indicate similar parts to those described in relation to Figures 3 to 6.

In this embodiment, instead of a spacer 27 beneath the magnetic strip 25, a second magnetic strip 45 is provided.

The strip 45 is commensurate with the strip 25 secured in overlying relationship thereto and has its magnetic axis aligned with the magnetic axis of the strip 25 and its poles similarly located. As the material of the strip 45 cannot effectively be made to provide a recess 43 (as shown in Figure 3), a recess 43a is provided in the body 15 of the base 11. The additional magnetic strip 45 serves positively to withdraw the balls 29 from their selected recesses 23 when the lid 13 and the base 11 are subsequently separated. The magnetic strength of the strip 45 may be arranged to be sufficient to ensure that the balls 29 are withdrawn from their selected apertures 23 but are not held thereto (as is shown in Figure 6) as careful manipulation of the lid may permit the original permutation to be re-effected.

The base and the lid are susceptible to manufacture of a plastics material by moulding. Alternatively, they may be machined from a harder non-ferro-magnetic material.

Other variations are possible within the scope of the present invention For example, dummy balls (not shown) of a ferromagnetic but electrically insulating material may be provided for insertion into all non-selected apertures 23. Tell-tale traces of the recent presence of a ball 29 (indentations in the strip 25 or nontarnished areas of the contacts 39) would then be present in alignment with all the recesses.

The contacts 39 may be shuffled within the thickness of the lid before being brought out to prevent straightforward electrical determination of the location of the balls 29 in the recesses.

Other variations are possible within the scope of the present invention.

Claims (12)

CLAIMS:

1. A tamper detection device of box-like form comprising a lid and a base arranged, when closed, to interfit, and adapted for mounting to respective parts of a closable container in such manner that, on opening of the container, the lid and the base of the box are separated, the base presenting a plurality of recesses into selected ones of which, ferro-magnetic elements may be inserted, and a magnetic means for initially magnetically retaining the elements in the selected recesses, the lid providing holding means for holding the elements in the selected recesses when the lid and the base are brought together and whilst the device is closed, contact means for establishing electrical paths indicative of which of the recesses contain the elements, and means for engaging the magnetic means so that, when the device is opened, the magnetic means attaches to the lid and the then unrestrained elements fall from the recesses.

2. A device as claimed in claim 1 wherein the base comprises an upstanding wall, the recesses comprising through apertures in the wall, the magnetic means being initially locatable in abutting relationship to one side of the wall.

3. A device as claimed in claim 1 or 2 wherein the base comprises a pair of spaced upstanding walls defining a trough therebetween wherein the magnetic means may be initially located, each of the walls having a pluality of through apertures defining the recesses.

4. A device as claimed in any preceding claim wherein the magnetic means comprises a strip transversely magnetised magnetic rubber.

5. A device as claimed in claim 4 further including a nonmagnetic spacer strip secured to and underlying the magnetic means to align the magnetic means with the recesses.

6. A device as claimed in any preceding claim wherein the ferromagnetic elements comprise steel balls.

7. A device as claimed in any preceding claim further including a plurality of ferro-magnetic insulating elements for insertion into some or all of the unselected recesses.

8. A device as claimed in any preceding claim wherein the lid includes a peripheral lip extending into the base when the device is closed.

9. A device as claimed in claim 8 wherein the lip is arranged to prevent visual inspection of the recesses, as the box is opened, until after the holding means and the magnetic means permit the ferromagnetic elements to fall from the recesses.

10. A device as claimed in any preceding claim wherein the means for engaging the magnetic means comprises a ferro-magnetic member substantially commensurate with the magnetic means, secured to the lid, and arranged to lie in contact with the magnetic means when the box is closed.

11. A device as claimed in any preceding claim wherein the contact means comprises a pluality of spaced spring contacts, alternate ones of which are commonly connected and the others of which are brought out to an accessible location, the contacts being arranged, when the box is closed so that adjacent contacts contact a ferromagnetic element therebetween and form therewith an electrical path between the common contact and the respective brought out contact.

12. A tamper detection device substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 6 or Figure 1 and Figures 7 to 10 of the accompanying drawins.