WO2011161441A1

WO2011161441A1 - Improvements in and related to electrical devices having anti-ligature properties

Info

Publication number: WO2011161441A1
Application number: PCT/GB2011/051152
Authority: WO
Inventors: David Michael Firth; Robert Patrick Oldland
Original assignee: Protec Fire Detection Plc
Priority date: 2010-06-21
Filing date: 2011-06-21
Publication date: 2011-12-29
Also published as: EP2583065A1; GB2481386A; GB201010360D0

Abstract

Disclosed is an electrical device comprising a base unit and an operational unit, each comprising a pair of electrical connectors, arranged to mutually electrically interconnect, the operational unit being retained on the base by means of a magnetic force. The device is intended to have anti-ligature properties for use in prisons, hospitals or other secure environments.

Description

Improvements in and related to electrical devices

having anti-ligature properties

The present invention is concerned with electrical devices which are required to be used in circumstances where they are required to offer some form of anti-ligature property. Such devices can include smoke detectors, fire detectors, alarm sounders, carbon monoxide detectors, speakers, CCTV cameras or any similar electrical device.

Circumstances where some form of anti-ligature property can be required include use in prisons, hospitals - particularly psychiatric and high-security hospitals, and other locations where inhabitants are at potential risk of harming themselves, particularly by attempting to hang themselves from fixtures and fittings provided in their rooms or cells.

The description which follows will focus on the installation of smoke detectors in prison cells, but the skilled person will appreciate that other situations and devices, not limited to those set out above, can also benefit from the present invention.

Presently, prisons in the UK and many other countries are required to provide smoke detectors in individual cells. However, some prisoners are susceptible to attempting self-harm and, in extreme circumstances, some will attempt suicide by use of a ligature fastened to a fitting in the cell which is then placed around their neck. Prison authorities are keen to avoid or mitigate this risk and presently, fixtures and fittings provided in cells are carefully designed to minimise the opportunity for self harm. However, there is a mandatory requirement to provide smoke detectors and these can be abused by those prisoners determined to harm themselves.

There exists a requirement to provide smoke detectors in prison cells which operate according to the required smoke-detection standards, but which deny prisoners the opportunity to successfully attach a ligature thereto. Indeed, the UK Ministry of Justice has recently announced a requirement for such a detector having an anti-ligature property.

According to the present invention there is provided an apparatus and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

In a first aspect, there is provided an electrical device comprising a base unit and an operational unit, each comprising a pair of electrical connectors, arranged to mutually electrically interconnect, the operational unit being retained on the base by means of a magnetic force, wherein at least one of the electric connectors is provided in the form of an arc.

Preferably, at least one of the electrical connectors is provided in the form of a plurality of arcs, each arc forming part of the circumference of the same circle.

Preferably, the arc is in the form of a complete annulus.

Preferably the base unit is permanently fixed to a surface (normally a wall or ceiling) and is then further connected to other electrical equipment.

Preferably, the operation unit is arranged to perform a particular task such as smoke or fire detection, sound transmission, image capture or the like. For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which:

Figures 1a and 1 b show a schematic representation of the principle of operation of embodiments of the present invention;

Figure 2 shows an external perspective view common to embodiments of the present invention in their normal, operational, state; Figure 3 shows the mating surfaces of a detector head and base according to a first embodiment of the present invention;

Figure 4 shows the mating surfaces of a detector head and base according to a second embodiment of the present invention;

Figure 5 shows a perspective view of a detector head and base according to a third embodiment of the present invention; and

Figure 6 shows a perspective view of a detector head and base according to a fourth embodiment of the present invention.

Figure 1 shows a diagrammatic representation of the operation of embodiments of the present invention. Each detector assembly 1 comprises a connector base 20 and a detector head 10. In normal use the detector head is detachably attached to the base 20. Under normal conditions, the head 10 remains attached and electrically connected to the base 20. However, if a certain force is applied to the detector head 10, then it comes away from the base 20, denying the prisoner the opportunity to use it as a fixing for a ligature. The removal of the detector 10 from the base 20 generates an alarm condition, alerting the guards to a potential problem in a particular cell.

Whilst working to arrive at the present invention, alternative schemes were considered to achieve the controlled detachment of the detector head from the base. Various techniques for semi-permanently coupling the two parts of the device were considered, including the use of an adhesive substance or the use of hook-and-eye material (e.g. the material known as VELCRO ®). However, all such schemes were rejected as being impractical, since it is difficult, if not impossible, to accurately specify the separation force required. Furthermore, the separation force can change over time. The detector 10 is attached to the base 20 by the provision of one or more magnets, with electrical connection being maintained by a pair (or more) of electrical connectors 22. Similar, and mating, connectors (not shown in Figure 1 ) are provided on the detector head 10. One or more of the electrical connections themselves can also comprise one or more magnets or corresponding ferromagnetic material to attach to the magnet or magnets. If the connectors 1 1 do not comprise one or more magnets, then a separate magnet is provided on the base or the head, whose sole purpose is couple the detector to the base.

The magnets referred to throughout the description of embodiments of the present invention can be permanent magnets or electromagnets, powered as necessary to provide the necessary attractive force.

Generally, magnets can be classified in various ways, including ones that specify the force required to separate a given magnet from a ferromagnetic material. Embodiments of the present invention are arranged such that a force greater than a predefined minimum force will cause the detector 10 to separate from the base. The force which is selected should be sufficient to ensure that the detector remains in position in normal use, but low enough that it will separate easily under the weight of an average person. A suitable minimum force is in the range 50 to 200 Newtons (equivalent to a mass of 5-20Kg), although any suitable force may be specified as needed.

In some installations, the base 20 is mounted to a wall and, in others, to a ceiling. The operation of embodiments of the invention in these different arrangements is identical. The base 20 is connected to the smoke alarm detector system by wires and connectors which are concealed inside the base and inaccessible, in normal use, from the exterior. The base 10 may be assembled and fixed in place using security fastenings, such as those provided by Torx ®, which require special tools to disassemble the casing.

Provided inside the base may be a loop isolator, which ensures that the remainder of the smoke detector system continues to operate normally in the event that one or more detector heads is removed. Figure 2 shows a perspective view of a detector assembly 1 in normal use. The detector head 10 is clearly visible, mounted to mounting plate 21 of the base 20. The mounting plate 21 may be flush or substantially flush with the exposed surface of the base 20. Different connection schemes are possible and several are now described in relation to the following figures. In the following descriptions, the detector head is referred to commonly by the reference numeral 10. Its operation is identical in each case, with only the connector configuration changing between different embodiments.

Figure 3 shows the mating surfaces of a detector 10 and mounting plate 21 of a first embodiment of the present invention. The detector 10 comprises a pair of electrical connectors 1 1 , positioned to contact corresponding connectors 22 on the mounting plate 21 of base 20. In all the embodiments described herein, there is a common requirement that any exposed or possibly exposed surfaces should not have any prominent projections or recesses. This includes the mating surfaces shown in Figure 3. The reason is that even the smallest projection can be used to fix a ligature and the smallest recesses can be used to hide contraband, such as mobile telephone SIM cards or drugs.

To address this need, the connectors 1 1 , 22 take the form of slightly domed steel elements. When brought into contact, the electrical circuit is completed and the detector 10 is retained in position on the mounting plate 21 by the cooperation of magnet 23 and ferromagnetic material 12. Preferably, the magnet 23 is provided as part of the base 20 to cooperate with a ferromagnetic material 12 on the detector head, although they could, of course, be swapped to achieve an identical effect.

Whilst this solution works well in practice, a certain amount of care is required to ensure that the connectors 1 1 , 22 are aligned correctly and, of course, they are not visible once the detector head has been retained in position.

To address this potential shortcoming, the embodiment of Figure 4 may be utilised. In this second embodiment, a pair of modified connectors 24, each comprising a magnet, is provided as part of each on the base 20. In this way, once the detector 10 is offered up to the mounting plate 21 , then the attraction between the connectors 24 and the ferromagnetic connectors 1 1 on the detector head ensures the correct alignment of the detector head 10 in relation to the mounting plate 21. Again, as with the previous embodiment, the location of the magnets may be swapped between the detector head and the base.

Whilst this solution addresses the possible shortcoming with the first embodiment, a still better solution is provided in the third and fourth embodiments now described in relation to Figure 5 and 6.

The third embodiment, shown in Figure 5, shows a separated base 20 and detector head 10. The base 20 comprises a magnet 23 located centrally with respect to the circular configuration of the mounting plate 21. The magnet 23 attracts ferromagnetic part 12 located on the detector head and therefore acts to retain the detector head to the base. To ease the alignment of the detector head 10 and the base 20, the mounting plate 21 is provided with a pair of electrical connectors 25 in the form of concentric annular elements having different diameters. Each of these connectors 25 is arranged to connect one of a pair of connectors 1 1 provided on the detector head. Each of the connectors 1 1 on the detector head is offset by a different distance from the centre of the ferromagnetic portion 12, the distance being set to correspond to the positions of the concentric annular connectors 25.

By providing connectors 1 1 , 25 in this form, the detector head can be offered up to the detector base in any radial configuration and once the magnet 23 attracts and captures ferromagnetic portion 12, each of the pair of connectors 1 1 is guaranteed to be correctly aligned with the respective one of the pair of concentric annular connectors 25. The detector head can rotate relatively freely about its central axis and remain physically and electrically in contact with the detector base. However, in the event that a greater than specified force is applied to the detector head, either in a direct pulling or shearing direction, then the attractive force of the magnet is overcome and the detector head separates from the base. This prevents the detector assembly from being used as a ligature point and if the detector head 10 is removed, then there is no suitable ligature connection point provided on the base 20. Furthermore, the detector head 10 can be simply re-attached and the detector system will continue operation as before.

In a further embodiment, at least one of the electrical connectors provided in the form of an annulus, can be provided as one or more arc sections. By providing a connector in this way, the amount of exposed connector can be reduced, but a degree of flexibility can be preserved when it comes to attaching the detector head. For instance, instead of providing a complete annulus of metallic connector material to connect to connector 1 1 , a number of arcs, each centred on the same spot can be provided so that the detector head can still be attache with minimal positioning. A suitable arrangement is four arc sections of 30° equispaced around the centre of a notional circle centred on the magnet 23. Of course, other arrangements making use of a discontinuous annulus may be used.

Figure 6 shows a fourth embodiment of the present invention, with some features in common with the second embodiment shown in Figure 4. In this embodiment, a modified connector 26 is provided at the centre of the mounting plate 21. The modified connector 26 comprises a magnet as well as an electrical connector and is arranged to contact a central connector 13 provided on the detector head 10. Surrounding the modified connector 26 is a single annular connector 25 which is provided to align and connect with a connector 1 1 on the detector head, offset appropriately from the central connector. As with the previous embodiment, the detector head 10 can be offered up to the detector base 20 in any radial configuration and correct connection is assured.

A further feature which may be added to any of the embodiments described thus far is a cage or mesh which is dimensioned and arranged to fit over the detector head and couple to the detector base 20. Such a cage can be arranged to be held in place magnetically and serves the purpose of preventing access to the apertures in the detector head 10 which are necessarily present to allow smoke to enter the device. Prisoners are known to use any available space, no matter how small, to conceal contraband, and provision of a mesh or cage, can prevent access to the apertures of the detector 10, whilst still allowing smoke to enter the detector to trigger an alarm.

The cage itself can be alarmed, such that if it is tampered with, a different alarm can be raised with prison guards. Although embodiments of the present invention have all concerned smoke detectors, the skilled person will appreciate that these are exemplary only and other uses may be envisaged which benefit from the inventive concept.

Furthermore, although a pair of electrical connections have been described, it is apparent that more than two connections can be provided by simply adding extra connectors on the detector head and base, as required.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. An electrical device comprising a base unit and an operational unit, each comprising a pair of electrical connectors, arranged to mutually electrically interconnect, the operational unit being retained on the base by means of a magnetic force, wherein at least one of the electric connectors is provided in the form of an arc.

2. The device of claim 1 wherein at least one of the electrical connectors is provided in the form of a plurality of arcs, each arc forming part of the circumference of the same circle.

3. The device of claim 1 or 2 wherein the arc is in the form of a complete annulus.

4. The device of any preceding claim wherein the magnetic force is provided either by a magnet which is a permanent magnet or an electromagnet.

5. The device of claim 4 wherein the magnet is arranged to cooperate with a ferromagnetic material.

6. The device of claim 4 or 5 wherein the magnet is provided as part of the base unit.

7. The device of any of claims 4-6 wherein the magnet is collocated with at least one of the electrical connectors.

8. The device of claim 7 wherein the magnet forms at least one of the electrical connectors.

9. The device of claim 8 wherein the base unit is provided with a pair of electrical connectors in the form of concentric annuli of different diameters.

10. The device of claim 9 wherein the operational unit is provided with a pair of electrical connectors, each of which is arranged to contact a respective one of the annuli provided on the base unit.

1 1. The device of any preceding claim wherein the operational unit is one of: a smoke detector, a fire detector, an alarm sounder, a carbon monoxide detector, a speaker and a CCTV camera.

12. The device of any preceding claim further comprising a cage arranged to couple to the base unit and to completely encapsulate the operational unit.

13. The device of claim 12 wherein the cage is retained by means of one or more further magnets.

14. An electrical device substantially as herein described, having particular reference to the accompanying figures.