GB2551492A

GB2551492A - Box for a security alarm

Info

Publication number: GB2551492A
Application number: GB1610460.6A
Authority: GB
Inventors: Roberts Simon
Original assignee: Orisec Ltd
Current assignee: Orisec Ltd
Priority date: 2016-06-15
Filing date: 2016-06-15
Publication date: 2017-12-27
Anticipated expiration: 2036-06-15
Also published as: GB201610460D0; GB2551492B

Abstract

A box for a security alarm such as a bell box 1, comprising: a back plate 2 and a cover 3 held together by a fixing member 7. The bell box 1 can be attached to a surface such as wall 4 using screws 5. The fixing member 7 is elongate and can be a bolt or fastener (15, figure 4). The fixing member 7 has a first portion (17, figure 4) for receipt through a fixing aperture (18, figure 7) in the cover 3 which releasably engages with an attachment feature, such as an aperture (39, figure 10) in the back plate 2. The fixing member has a second portion (19, figure 4) for contacting an area around the fixing aperture in the cover 3. The back plate 2 and cover 3 are releasably attached together depending on the rotation of the fixing member 7 from a first orientation to a second orientation. The orientation of the fixing member 7 is monitored by a detector, which can be a switch (13, figure 9), for outputting a signal indicative of the orientation of the fixing member.

Description

Box For A Security Alarm

The present invention relates to a box for a security alarm. In particular, it relates to a box for a security alarm that is provided with anti-tamper detection.

Security alarm systems typically comprise a range of different devices that are interconnected (either by a physical link or wireless connections). A typical security alarm system may include any or all of the following devices: bell boxes, detectors, control panels, keypads, expanders and communicators. Each of these devices comprises a box which houses internal components of the device. These boxes are often provided with anti-tamper detection. The present invention may relate to a box for any device that forms part of a security alarm system.

Many intruder alarm systems comprise at least one bell box (also known as “external sounders” or “warning devices”), which are typically disposed on an external wall of a property that comprises the alarm system. Such bell boxes may contain audio and visual signalling devices, such as an alarm sounder or bell and a strobe light, which may be activated if there is an attempted break in at the property. Bell boxes can play an important role in an intruder alarm installation because they indicate to the outside world, and therefore any potential intruders, that the property is protected by an alarm system. The bell box can therefore act as a deterrent to potential intruders. A bell box is typically formed from two parts: a back plate and a front cover. The back plate is secured to a surface, for example an external wall of a building, using screws or the like. The front cover is secured to the back plate, typically by way of conventional threaded metal screws.

Bell boxes typically contain a tamper detection device to signal a warning if unauthorised access to the inside of the bell box is attempted. Typically such devices consist of a tamper detection switch positioned such that a switch actuator is forced closed when the front cover of the bell box is in place but springs open when the front cover is removed. The switch opening causes the bell box to alarm (this is known as “self activation”) and also to send a signal to a control panel to indicate that a tamper attempt had been detected. Such a signal may in turn be signalled or broadcast via network (for example the internet or a telecoms network) to warn remote users of the potential break in.

It may be desirable to provide an alternative box for a security alarm which at least partially addresses one or more of the problems of the prior art, whether identified herein or elsewhere.

According to a first aspect of the invention there is a provided a box for a security alarm, the box comprising: a first member for attachment to a surface, the first member comprising an attachment feature; a detector attached to the first member; a second member for releasable cooperation with the first member, the second member defining a fixing aperture; and a fixing member being generally elongate so as to define an axis and comprising a first portion for receipt through the fixing aperture and a second portion for contacting at least a portion of the second member surrounding the fixing aperture; wherein the fixing member is arranged to cooperate with the attachment feature of the first member so as to releasably attach the first member to the second member, said releasable attachment being achieved by rotation of the fixing member about the axis from a first orientation to a second orientation; and wherein the detector is operable to output a signal indicative of the orientation of the fixing member relative to the first member.

The box may be a bell box of an alarm system (also known as “external sounders” or “warning devices”). For example, the first member may be a back plate of a bell box and the second member may be a cover of a bell box. The first and second members may cooperate so as to generally contain internal components of known bell boxes such as, for example, a sounder (commonly referred to as a “bell”) and a strobe light.

The first aspect provides a particularly advantageous arrangement since it provides an arrangement wherein the first and second members of the box can be connected by way of the fixing member but wherein information relating to the orientation of the fixing member may be monitored (via the detector). Since connection of the first and second members is achieved by rotating the fixing member, by monitoring the orientation of the fixing member relative to the first member, the detector allows for tamper detection. That is, in the event that an attempt is made to remove the second member from the first member (by rotating the fixing device) this information can be transmitted by the signal from the detector.

In known bell boxes, a front cover is secured to a back plate by way of conventional threaded metal screws. Such bell boxes may contain a tamper detection switch positioned such that the switch actuator is forced closed when the front cover of the bell box is in place but springs open when the front cover is removed. Therefore, known bell boxes often have an anti-tamper detection that is operable to determine when the second member (i.e. a cover) is removed from the first member (i.e. a back plate). With such existing arrangements the tamper attempt is only detected after the screws have been unscrewed and the cover is being opened. In contrast to such known arrangements, the first aspect of the invention provides an arrangement that is operable to detect when the fixing members themselves are being undone. This allows a tamper warning signal to be generated before access to the inside of the bell box has been achieved.

The cooperation of the first member and the second member may define an internal volume.

The fixing member may comprise a detection protrusion and wherein rotation of the fixing member about the axis causes the detection protrusion to move around the axis. As the fixing member rotates about the axis from the first orientation to the second orientation so that the fixing member releasably engages with the attachment feature of the first member, the fixing member may remain at substantially the same axial position relative to the first member. Alternatively, the fixing member and the attachment feature may produce a camming action such that as the fixing member rotates, it also moves axially (for example by moving up a ramp on the attachment feature).

The signal output by the detector may be indicative of a position of the detection protrusion around the axis relative to the first member.

The detector may comprise any arrangement that is operable to determine the orientation of the fixing member. For example, the detector may be operable to determine the position of a detection protrusion. The signal output by the detector may be a binary signal. For example, it may indicate whether the box is either: (a) closed; or (b) at least partially open. Alternatively, the signal output by the detector may be contain more information indicative of the orientation of the fixing member.

The detector may comprise a switch. For example the detector may comprise a microswitch. Rotation of the fixing member may cause the detection protrusion to actuate (i.e. open or close) the switch.

The fixing member may be arranged to releasably engage with the attachment feature. Said releasable engagement of the fixing member and the attachment feature may result in the releasable attachment of the first member to the second member. For such embodiments, the attachment feature may be fixed relative to the first member.

The fixing member may comprise an engagement protrusion. Rotation of the fixing member about the axis from the first orientation to the second orientation may cause the engagement protrusion to engage with the attachment feature on the first member.

The engagement protrusion and the detection protrusion may be separate or integrally formed (i.e. may be provided by a single protrusion). The detection protrusion and/or the engagement protrusion may extend generally linearly away from a generally cylindrical body of the first portion along a direction which is offset from the axis. The detection protrusion may be axially spaced apart from the engagement protrusion.

The transition from the first orientation to the second orientation may be achieved by rotation of the fixing member through less than 360°. For example, transition from the first orientation to the second orientation may be achieved by rotation of the fixing member through approximately 180°.

The fixing member may engage with the second member. This means that the fixing members cannot fall out of the fixing aperture, which is particularly advantageous for installers of the bell box. It should be borne in mind that typically bell boxes are installed high up on the external wall of a building and the installer will typically use a ladder or the like to access the location. In prior art arrangements, wherein conventional screws are used to attach a cover to a back plate, it is common for the screws to be dropped by the installer once up the ladder during installation of the bell box. In such situations, the installer may have to descend the ladder and if possible retrieve the dropped screws or, if the screws are lost and cannot be located, to find replacement screws. Furthermore, bell boxes are typically transported from manufacturer to installer with the cover unfastened. This means that with prior art arrangements that use conventional screws, the screws can easily be lost prior to the installation. The retention of the fixing members on the second member overcomes these problems associated with prior art bell boxes. Additionally, there is significant reduction in installation time for the installer as the fixing members are retained by the second member rather than being provided as separate loose components.

The fixing member may define a groove at the intersection between the first portion and the second portion for receipt of part of the cover.

The fixing aperture may comprise a generally circular portion for receipt of a generally cylindrical body of first portion and a generally elongate slot portion for receipt of the detection protrusion and the engagement protrusion. An internal diameter of the circular portion of fixing aperture may be slightly smaller than an external diameter of a generally cylindrical portion of first portion and the fixing aperture may further comprise at least one slot arranged to allow the portion of the second member surrounding the fixing aperture to flex sufficiently to receive the first portion.

The fixing member may be provided with one or more resiliently deformable features that can deform to allow the fixing member to be inserted into the fixing aperture and can snap back to retain the fixing member on the second member once a portion of the fixing member has been inserted into the fixing aperture. Said resiliently deformable features may be of the form of wings or barbs. In such embodiments, the fixing aperture may be generally rigid.

The fixing aperture may be formed within a recess in the second member and, in use, the second portion of the fixing member may be at least partially received within this recess.

The recess may be provided on an inclined surface of the second member. A surface of the second portion of the fixing member may be inclined such that a shape of the second portion of the fixing member generally matches the shape of the recess. With such an arrangement: (a) the surface of the second portion can be generally aligned with and flush with a surface of the second member when the fixing member is disposed in the second orientation; and (b) the second portion of the fixing member can partially extend out of the recess when the fixing member is disposed in the first orientation. Advantageously, this can provide a visual indication to an installer that the fixing member has not yet been rotated into the second orientation.

The fixing member may be formed from a plastics material. For example, the fixing member may be formed from polycarbonate. Advantageously, such materials are durable and, unlike metal screws that many prior art arrangements use, such plastics materials do not corrode or rust and therefore do not need to be replaced.

The fixing members may be formed from the same material as the second member. The attachment feature may further comprise a bearing surface for a detection protrusion of the fixing member.

The first member may comprise at least one attachment aperture, the at least one attachment aperture being provided on an insert which is connected to a main body of the first member such that it can rotate relative to the first member. Rotation of the inserts (relative to the first member) can aid an installer since it allows a greater tolerance for the placement of holes for fixing screws.

The attachment feature may be movable relative to the back plate. Rotation of the fixing member may cause the attachment feature to move relative to the back plate. For example, the attachment feature may be slidably connected to the back plate such that it can move, for example linearly, relative to the back plate between at least a first end position and a second end position. The fixing member and the attachment feature may form any suitable cam mechanism or the like that converts rotation of the fixing member into linear movement of the attachment feature.

The movement of the attachment feature relative to the back plate may cause the attachment feature to releasably engage with the second member so as to releasably attach the first member to the second member. It will be appreciated that the releasable engagement between the attachment feature and the cover may be achieved in a variety of ways. In general, the attachment feature and the cover may be provided with complementary engagement features to allow this releasable engagement.

The signal output by the detector may be indicative of a position of the attachment feature, which in turn may be indicative of the orientation of the fixing member relative to the first member.

Various aspects and features of the invention set out above or below may be combined with various other aspects and features of the invention as will be readily apparent to the skilled person.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

Figure 1 is a schematic depiction of a cross section of a bell box which may form part of a security alarm system;

Figure 2 shows a back plate for a bell box according to an embodiment of the present invention.

Figure 3a shows a cover for releasable cooperation with the back plate of Figure 2, with two novel fixing members according to an embodiment of the present invention, the fixing members being disposed in a first orientation;

Figure 3b shows a cover for releasable cooperation with the back plate of Figure 2, with two novel fixing members according to an embodiment of the present invention, the fixing members being disposed in a second orientation;

Figure 4 shows a first view of the fixing member shown in Figures 3a and 3b; Figure 5 shows a second view of the fixing member shown in Figures 3a and 3b;

Figure 6 shows a third view of the fixing member shown in Figures 3a and 3b;

Figure 7 shows a portion of the cover shown in Figures 3a and 3b with the fixing member removed;

Figure 8 shows an enlarged portion of the back plate of Figure 2 provided with an attachment feature and a micro-switch, and a fixing member engaged with the attachment feature (the cover of Figures 3a and 3b not being shown for illustrative purposes);

Figure 9 shows the micro-switch and the fixing member as shown in Figure 8 but with the back plate removed for illustrative purposes;

Figure 10 shows an enlarged portion of the back plate of Figure 2 in plan view with no fixing member engaged with the attachment feature;

Figure 11 is a perspective view of an expander box according to another embodiment of the present invention;

Figure 12a is a partial cross sectional view of the expander box of Figure 11, with a fixing member of the expander box being disposed in a first orientation;

Figure 12b is a partial cross sectional view of the expander box of Figure 11, with the fixing member of the expander box being disposed in a second orientation;

Figure 13a is a perspective view of the expander box of Figure 11 with a cover of expander box not shown for illustrative purposes wherein the fixing member of the expander box is disposed in the first orientation;

Figure 13b is a perspective view of the expander box of Figure 11 with the cover of expander box not shown for illustrative purposes wherein the fixing member of the expander box is disposed in the second orientation;

Figure 14 is a first view of an attachment feature that forms part of the expander box of Figure 11;

Figure 15 is a second view of the attachment feature that forms part of the expander box of Figure 11 engaged with a compression spring that forms part of the expander box of Figure 11;

Figure 16 is a plan view of a back plate and spring that form part of the expander box of Figure 11, with other parts of expander box not being shown for illustrative purposes;

Figure 17 shows the attachment feature of Figures 14 and 15 engaged with the back plate of Figure 16 and a guide bush member, with other parts of expander box not being shown for illustrative purposes;

Figure 18 is a partial cross sectional view of the arrangement shown in Figure 17 through the line X-X;

Figure 19 shows a side view of a fixing member that forms part of the expander box of Figure 11;

Figure 20 shows a perspective view of the fixing member of Figure 19 that forms part of the expander box of Figure 11;

Figure 21 is a partial cross sectional view of the fixing member of Figures 19 and 20 engaged with a cover that forms part of the expander box of Figure 11, with other parts of expander box not being shown for illustrative purposes; and

Figure 22 is a perspective view of the fixing member of Figures 19 and 20 engaged with the cover of the expander box of Figure 11, with other parts of expander box not being shown for illustrative purposes.

Figure 1 shows, schematically, a bell box 1 which may form part of a security alarm system. Bell box 1 comprises a back plate 2 and a cover 3. The back plate 2 is for attachment to a surface 4. In use, the bell box 1 is typically provided on an external wall of a building that is protected by the security alarm system. To achieve this, the back plate 2 is typically attached to a surface 4 of the exterior wall using screws 5 or the like, in a conventional manner. The cover 3 cooperates with the back plate 2 so as to define an internal volume 6. The internal volume 6 may house internal components of main bell boxes such as, for example, an audio signalling device (for example a piezo sounder), a visual signalling device (for example a strobe light), internal circuitry and a battery. Connection of the cover 3 to the back plate 2 is achieved by way of one or more fixing members 7.

An embodiment of the present invention relates to a novel bell box, which is generally of the form of bell box 1 as shown in Figure 1, and which is now described with reference to the Figures 2 to 10.

Figure 2 shows a back plate 10 for a bell box according to an embodiment of the present invention.

Back plate 10 comprises six apertures 11 that allow back plate 10 to be attached to the external surface of a building (for example a wall), in a conventional manner. Each of the six apertures 11 is provided as an elongate slot on a generally circular insert 11a which is connected to a main body of the back plate 10 such that it can rotate relative thereto. This rotation of the circular inserts 11a (relative to the back plate 10) can aid an installer since it allows a greater tolerance for the placement of holes for fixing screws (which holes may be drilled in a brick wall or the like).

The back plate 10 further comprises two attachment features 12 for releasable engagement with fixing members, as will be described further below. A micro-switch 13 is attached to the back plate 10 adjacent to one of the attachment features 12.

The back plate 10 further comprises two piezo sounders 34, a second micro-switch switch 34 and a compartment 36 for housing control electronics (not shown). The control electronics are connected to the micro-switch 13, the two piezo sounders 34 and the second micro-switch 35. The control electronics are also connected to one or more other components of the security alarm, for example a control panel, which is typically internal to a building to which the bell box is attached. A cover 14 for releasable cooperation with the back plate 10 is shown in Figures 3a and 3b. Attachment of the cover 14 to the back plate 10 is achieved by way of two novel fixing members 15. The fixing members 15 are shown in a first orientation in Figure 3b and are shown in a second orientation in Figure 3b. In order to attach the cover 14 to the bake plate 10 the cover 14 is offered up to the back plate 10 when the fixing members 15 are disposed in the first orientation (see Figure 3a). An external profile of the back plate 10 generally matches an internal profile of the cover 14 so that the back plate 10 and the cover 14 cooperate and form a close fit with each other. The fixing members 15 are then rotated through approximately 180° until they are disposed in the second orientation (see Figure 3b). The rotation of the fixing members from the first orientation to the second orientation causes the fixing members 15 to releasably engage with the attachment features 12 of the back plate 10. This releasably attaches the cover 14 to the back plate 10.

The cover 14 may be further attached to the back plate 10 in such a way that the cover 14 can be hinged away from the back plate 10 when the fixing members 15 are disposed in the first orientation. Alternatively, when the fixing members 15 are disposed in the first orientation the cover 14 may detach from the back plate 10 so that it can be removed.

The second micro-switch switch 35 comprises an actuator lever 35a which is forced closed when a cover 14 of the bell box is in place but which springs open when the cover 14 is removed.

The fixing members 15 are now described in greater detail with reference to Figures 4, 5 and 6. The fixing member 15 is generally elongate and defines an axis 16. In the following, in relation to the fixing member, a direction generally parallel to the axis 16 may be referred to as an axial direction and a direction generally perpendicular to and passing through the axis 16 may be referred to as a radial direction.

The fixing member 15 comprises a first portion 17 and a second portion 19. The fixing member 15 is generally of the form of a bolt with the first portion 17 being generally of the form of a bolt shank and the second portion 19 being generally of the form of a bolt head. The first portion 17 is for receipt through a fixing aperture 18 in the cover 14 (see Figure 7). The second portion 19 is for contacting at least a portion of the cover 14 surrounding fixing aperture 18.

The first portion 17 of the fixing member 15 comprises a generally cylindrical body 25 which extends axially from the second portion 19 of the fixing member 15. The first portion 17 further comprises a detection protrusion 20 and an engagement protrusion 21.

The detection protrusion 20 extends generally radially outwards from the generally cylindrical body 25 of the first portion 17. It will be appreciated that in this context a protrusion extends generally radially if it extends from a first radial position to a second, different radial position and does not necessarily extend in a direction that passes through the axis 16. As can be seen from Figure 6 the detection protrusion 20 extends generally linearly away from the generally cylindrical body 25 of the first portion 17 along a direction 22 which is offset from the axis 16. The engagement protrusion 21 also extends away from the generally cylindrical body of the first portion 17 along direction 22. The detection protrusion 20 is axially spaced apart from the engagement protrusion 21.

The second portion 19 of the fixing member 15 defines a recess 23 for receiving and engaging with a tool (not shown). In use, a tool such as, for example, a screwdriver, a hex key or the like, may be inserted into recess 23 such that the tool engages with the fixing member 15. In this way, a torque may be applied to the fixing member 15 to rotate it (for example between the first and second orientations) in a conventional manner.

The fixing members 15 engage with the cover 14. In order to achieve this, the fixing member 15 defines a groove at the intersection between the first portion 17 and the second portion 19 for receipt of part of the cover 14. In particular, a generally annular groove 24 is defined around the circumference of the fixing member 15 at the intersection between the first portion 17 and the second portion 19. It will be appreciated that in alternative embodiments, the groove may not extend around the entire circumference of the fixing member 15.

As can be seen from Figure 7, the cover 14 comprises a fixing aperture 18 for receipt of part of the fixing member 15. The aperture has a profile which generally matches that of the first portion 17 of the fixing member 15. In particular, the aperture 18 comprises a generally circular portion 26 for receipt of the generally cylindrical body 25 of first portion 17. The fixing aperture 18 further comprises a generally elongate slot portion 27 for receipt of the detection protrusion 20 and the engagement protrusion 21. An internal diameter of the circular portion 26 of fixing aperture 18 is slightly smaller than an external diameter of the generally cylindrical portion 25 of first portion 17.

As can be seen from Figure 6, the profile of the fixing aperture 18 generally matches that of the fixing member 15 (in a plane perpendicular to the axis 16).

The fixing aperture 18 further comprises two slots 28, which extend radially outward from the circular portion 26. In order to engage the fixing member 15 with the cover 14, the fixing member 15 is offered up to fixing aperture 18 with the fixing member 15 being orientated such that the detection protrusion 20 and the engagement protrusion 21 are aligned with the elongate slot portion 27 of fixing aperture 18. The first portion 17 of the fixing member 15 is then inserted into fixing aperture 18. Although the internal diameter of the circular portion 26 of fixing aperture 18 is slightly smaller than the external diameter of the generally cylindrical portion 25 of first portion 17, the two slots 28 allow the portion of the cover 14 surrounding fixing aperture 18 to flex sufficiently to receive the first portion 17. When the first portion 17 has been fully inserted into fixing aperture 18 the portion of the cover 14 that surrounds the fixing aperture 18 snaps back and is received within the generally annular groove 24.

The fixing member 15 is therefore connected to and retained by the cover 14. When the portion of the cover 14 that surrounds the fixing aperture 18 is received within the generally annular groove 24, there is sufficient clearance to allow the fixing member 15 to rotate (about its axis 16) relative to the cover 14.

The portion of the cover 14 surrounding the fixing aperture 18 may comprise a reinforcing flange 29 which extends around a portion of the perimeter of fixing aperture 18. This reinforcing flange 18 is received within the generally annular groove 24 on the fixing member 15. The flange 29 may be arranged to allow the portion of the cover 14 surrounding the fixing aperture 18 to flex so as to allow the fixing member 15 to engage with the cover 14 but such that the portion of the cover 14 surrounding fixing aperture 18 cannot easily flex in the opposite direction.

In this embodiment of the invention, the fixing members 15 are retained by the bell box front cover 14, as explained above. This means that the fixing members 15 cannot fall out of the fixing aperture, which is particularly advantageous for installers of the bell box. It should be borne in mind that typically bell boxes are installed high up on the external wall of a building and the installer will typically use a ladder or the like to access the location. In prior art arrangements, wherein conventional screws are used to attach the cover the back plate, it is common for the screws to be dropped by the installer once up the ladder during installation of the bell box. In such situations, the installer may have to descend the ladder and if possible retrieve the dropped screws or, if the screws are lost and cannot be located, to find replacement screws. Furthermore, bell boxes are typically transported from manufacturer to installer with the cover unfastened. This means that with prior art arrangements that use conventional screws, the screws can easily be lost prior to the installation. The retention of the fixing members 15 on the cover 14 overcomes these problems associated with prior art bell boxes. Additionally, there is significant reduction in installation time for the installer as the fixing members are retained by the cover 14 rather than being provided as separate loose components.

The fixing aperture 18 is formed within a counter bore or recess 30 in the cover. When the fixing member 15 is engaged with cover 14 the second portion 19 of the fixing member 15 is at least partially received within this recess 30.

The recess 30 is formed from a generally cylindrical blind counter bore provided on a surface of the cover 14. A base of the recess 30 provides a generally flat surface 31. A shoulder 32 defined on the fixing member 15 seats against said surface 31. As can be seen from Figures 3a and 3b the recess 30 is provided on an inclined surface of the cover 14 such that the recess 30 is generally of the form of a cylindric section.

An upper surface 33 of the second portion 19 of the fixing member 15 is inclined such that a shape of the second portion 19 of the fixing member 15 generally matches the shape of the recess 30. The surface of the cover 14 on which the recess 30 is provided and the upper surface 33 of the second portion 19 are both inclined in such a way that the upper surface 33 is generally aligned with and flush with the surface of the cover 14 when the fixing member 15 is disposed in the second orientation (see Figure 3b). In contrast, when the fixing member 15 is disposed in the first orientation (see Figure 3a) the second portion of the fixing member 19 partially extends out of the recess 30. Advantageously, this can provide a visual indication to an installer that the fixing member 15 has not yet been rotated into the second (or fixed) orientation. Furthermore, having the upper surface 33 of the second portion 19 of the fixing member 15 being generally aligned with and flush with the surface of the cover 14, renders the fixing members 15 significantly less obtrusive than metal screws thus improving the aesthetic appearance of the bell box when installed.

The fixing members 15 may be formed from a plastics material such as, for example polycarbonate. Advantageously, such materials are durable and, unlike metal screws that many prior art arrangements use, such plastics materials do not corrode or rust and therefore do not need to be replaced. Bell boxes are typically installed externally and are therefore are exposed to the elements such that, over time, metal screws may corrode. The fixing members 15 may be formed in any conventional manner, for example by injection moulding.

The back plate 10 and cover 14 may also be formed from a plastics material such as, for example polycarbonate. The back plate 10 and cover 14 may be formed in any conventional manner, for example by injection moulding.

In some embodiments, the fixing members 15 are moulded from the same plastics material as the cover 14. This can further improve the aesthetic appearance of the bell box and allow the fixing members 15 to blend seamlessly into the housing cover 14 of the bell box. Although some prior art arrangements use plastic covers installed over the tops of the fixing screw heads to achieve this result, these plastic covers are an additional component which add to the overall cost of the installation and are easily lost.

As explained above, releasable engagement between the fixing members 15 and the attachment features 12 of the back plate 10 is achieved by rotation of the fixing members 15 about their axes 16 through approximately 180° (from the first orientation to the second orientation). This releasable engagement is now described in greater detail with reference to Figures 8, 9 and 10.

Figure 8 shows an enlarged portion of the back plate 10 showing the micro-switch 13 and the attachment feature 12 that is adjacent to it. Also shown in Figure 8 is a fixing member 15 which is engaged with the attachment feature 12. For illustrative purposes the cover 14 is not shown in Figure 8. Figure 9 shows the micro-switch 13 and the fixing member 15 as shown in Figure 8 (i.e. with the fixing member 15 disposed in the second orientation) but with the back plate 10 removed for illustrative purposes. Figure 10 shows an enlarged portion of the back plate 10 in plan view with no fixing member 15 engaged with the attachment feature 12.

The attachment feature 12 comprises a generally cylindrical protrusion 37 which extends outwards from the back plate 10. An upper surface 38 of the generally cylindrical protrusion is provided with an aperture 39 (see Figure 10) for receipt of the engagement protrusion 21 and a distal portion of the generally cylindrical body of first portion 17.

Similarly to fixing aperture 18, aperture 39 has a profile which generally matches that of the first portion 17 of the fixing member 15. In particular, the aperture 18 comprises a generally circular portion 40 for receipt of the generally cylindrical body 25 of first portion 17 and a generally elongate slot portion 41 for receipt of the engagement protrusion 21. An inner dimension of the generally circular portion 40 of aperture 39 is slightly larger than an external diameter of the generally cylindrical portion 25 of first portion 17 to allow the distal end of the first portion 17 to be inserted easily into aperture 39.

Aperture 39 forms a keyway that allows the fixing member to move axially relative to the back plate 10 when disposed in the first orientation, i.e. when the engagement protrusion 21 is aligned with the generally elongate slot portion 41 of aperture 39. Rotation of the fixing member about its axis 16 causes the engagement protrusion 21 to move around the axis 16. An upper surface 42 of the engagement protrusion 21 seats against an internal surface of the generally cylindrical protrusion 37 so as to axially constrain the fixing member 15. Note that the engagement protrusion 21 extends away from the generally cylindrical body 25 of the first portion 17 in two opposite directions, which may provide better axial constraint of the fixing member 15 than arrangements wherein the engagement protrusion 21 extends away from the generally cylindrical body 25 of the first portion 17 in one direction only.

As the fixing member 15 rotates about the axis 16 from the first orientation to the second orientation so that the fixing member 15 releasably engages with the attachment feature 12 of the back plate 10, the fixing member 15 may remain at substantially the same axial position relative to the back plate 10. Alternatively, the fixing member 15 and the attachment feature 12 may be shaped so as to produce a camming action such that as the fixing member 15 rotates, it also moves axially (for example by moving up a ramp on an internal surface of the generally cylindrical protrusion 37).

Around a portion of the circumference of the generally cylindrical protrusion 37 is provided a curved wall 43. The curved wall 43 forms an extension of the generally cylindrical protrusion 37 around a portion of its circumference. When the fixing member 15 engages with the attachment feature 12, as the fixing member 15 rotates around its axis 16 from the first orientation to the second orientation, the curved wall may act as a bearing surface for the detection protrusion 20.

The micro-switch 13 comprises an actuator lever 44. The back cover 10 comprises an outwardly extending post 45 and the actuator lever 44 is spring loaded so as to contact the post 45 in the absence of the fixing member 15 (see Figure 10). In this position, the switch is open. During engagement of the fixing member 15 with the attachment feature 12, as the fixing member 15 rotates about its axis 16 the detection protrusion 21 moves around the axis 16. As the fixing member 15 rotates through 180°, it contacts the actuation lever 44 and closes the micro-switch 13.

The micro-switch 13 may be considered to be a detector which is attached to the back plate 10 and which is operable to output a signal indicative of the orientation of the fixing member 15 relative to the back plate 10.

The bell box as described above provides an arrangement wherein the back plate 10 and the cover 14 can be connected by way of the fixing members 15 but wherein information relating to the orientation of the fixing member 15 may be monitored (via the micro-switch 13). Since connection of the back plate 10 and the cover 14 is achieved by rotating the fixing member 15, by monitoring the orientation of the fixing member 15 relative to the back plate 10, the micro-switch 13 allows for tamper detection. That is, in the event that an attempt is made to remove the cover 14 from the back plate 10 (by rotating the fixing member 15) this information can be transmitted by the signal from the micro-switch 13.

In known bell boxes, a front cover is secured to a back plate by way of conventional threaded metal screws. Such bell boxes may contain a tamper detection switch positioned such that the switch actuator is forced closed when the front cover of the bell box is in place but springs open when the front cover is removed (i.e. of the form provided by the second micro-switch 35). Therefore, known bell boxes often have an anti-tamper detection that is operable to determine when the cover is removed from the back plate. With such existing arrangements the tamper attempt is only detected after the screws have been unscrewed and the cover is being opened. In contrast to such known arrangements, the bell box described above provides an arrangement that is operable to detect when the fixing members 15 themselves are being undone. This allows a tamper warning signal to be generated before access to the inside of the bell box has been achieved.

The bell box as described above has a number of advantages over prior art arrangements, as now discussed. The fixing members 15 incorporate an actuator (in the form of detection protrusion 20) that provides tamper detection while the fixing member 15 is being unfastened. Furthermore, transition between a fully fastened state to a fully unfastened state is achieved by rotation of the fixing member 15 by half a turn (for example using a screwdriver or the like). This is in contrast to prior art arrangements wherein attachment is achieved using standard metal screws which typically require many multiple turns to transition between a fully fastened state and a fully unfastened state. This can be difficult or inconvenient when working at height. Particularly bearing in mind that installation is often carried out at height with the installer using a ladder or the like, only needing to perform half a turn of the fixing members 15 makes installation significantly easier.

The fixing member 15 is retained on the cover 14 by virtue of a portion of the cover 14 being received in a groove on the fixing member 15. In the above-described embodiment this is achieved by having a fixing aperture with a profile that substantially matches that of the first portion 17 of the fixing member 15, the fixing aperture being dimensioned such that it is slightly smaller than the first portion 17 of the fixing member 15 and the cover 14 having sufficient flexibility to allow the first portion 17 of the fixing member 15 to be inserted into the fixing aperture 18. It will of course be appreciated that in alternative embodiments the fixing member 15 may be retained on the cover 14 by one of a number of different alternative arrangements. For example, in one alternative embodiment the first and second portions 17, 19 may be formed separately and may be connected together (for example by a snap-fit or otherwise) such that each of the first and second portions 17, 19 is disposed on an opposite side of a fixing aperture in the cover 14 and such that a portion of the cover 14 surrounding said aperture is retained in a groove formed between the first and second portions 17, 19.

In the above described embodiment of a bell box 1, an internal diameter of the circular portion 26 of the fixing aperture 18 on the cover 14 is slightly smaller than an external diameter of the generally cylindrical portion 25 of first portion 17 of the fixing member 15. However, the fixing aperture 18 on the cover 14 has sufficient freedom of movement so as to flex sufficiently to receive the first portion 17 of the fixing member 15. When the first portion 17 has been fully inserted into fixing aperture 18 the portion of the cover 14 that surrounds the fixing aperture 18 snaps back and is received within the generally annular groove 24 of the fixing member. In an alternative embodiment, the fixing member 15 may be provided with one or more resiliently deformable features that can deform to allow the fixing member 15 to be inserted into the fixing aperture 18 and can snap back to retain the fixing member 15 on the cover once the first portion 17 has been fully inserted into fixing aperture 18. Said resiliently deformable features may be of the form of wings or barbs. In such embodiments, the fixing aperture 18 may be generally rigid.

As described above, in some embodiments, the fixing member 15 is retained on the cover 14. A further advantage of such a feature is that in the event that the cover 14 is forcibly removed from the back plate 10, the fixing member 15 may also be removed from the back plate 10. In turn, this will cause the micro-switch 13 to open, which can indicate that the bell box 1 has been tampered with.

Although the above-described embodiment uses a micro-switch 13 to determine an orientation of the fixing member 15, it will be appreciated that any detector for determine an orientation of the fixing member 15 may be used. The signal output by the detector may be a binary signal (as in the case of a micro-switch). For example, it may indicate whether the box is either: (a) closed; or (b) at least partially open. Alternatively, the signal output by the detector may contain more detailed information indicative of the orientation of the fixing member. For example, the signal output by the detector may indicate that the orientation of the fixing member is one of more than two different orientations (either discrete or continuous).

Although the fixing members 15 of the above-described embodiment use two separate protrusions for engagement with attachment feature 12 (i.e. the engagement protrusion 21) and for detection of the orientation of the fixing member 15 (i.e. the detection protrusion 20) it will be appreciated that in alternative embodiments a single protrusion may serve both of these functions.

Although the above described embodiment of a bell box 1 comprises two fixing members, it will be appreciated that in alternative embodiments the box may be provided with one or more than two fixing members.

In the above described embodiment, the rotation of each fixing member 15 from the first orientation to the second orientation causes the fixing member 15 to releasably engage with a substantially fixed attachment feature 12 of the back plate 10. In this way, the cover 14 is releasably attached to the back plate 10.

Another embodiment of the present invention relates to an expander box 100, which is now described with reference to the Figures 11 to 22.

The expander box 100 comprises: a back plate 101, an attachment feature 102, a printed circuit board 103, a cover 104 and a fixing member 105.

As best shown in Figure 16, the back plate 101 comprises apertures 106, 107 that allow the back plate 101 to be attached to a surface (for example a wall), in a conventional manner using screws or the like. Some of the apertures 106 are provided as an elongate slots. Optionally, some of the apertures 107 may be generally keyhole-shape, having a slot portion and a larger circular portion for receipt of a screw head. This allows the back plate to be hung on a screw that is already fixed to the surface. Once hung on the surface using apertures 107, additional screws can be used to fix the back plate 101 to the surface via apertures 106. The back plate 101 is also provided with a plurality of slits 108.

The attachment feature 102 engages with the back plate 101 such that the attachment feature 102 is movable relative to the back plate 101, as is now described with reference to Figures 14 to 18.

The back plate 101 is provided with a first guide member 110 and a second guide member 111. The first guide member 110 comprises an elongate ridge 112 on an interior surface of the rear wall 113 of the back plate 101 and three tabs 114 which extend away from the elongate ridge 112 towards the second guide member 111. Similarly, the second guide member 111 comprises an elongate ridge 115 on the interior surface of the rear wall 113 of the back plate 101 and three tabs 116 which extend away from the elongate ridge 115 towards the first guide member 110. The elongate ridges 112, 115 of the first and second guide members 110, 111 are generally mutually parallel.

The back plate 101 further comprises first and second spring retaining features 117, 118. The first and second spring retaining features 117, 118 extend away from the rear wall 113 of the back plate 101 and are disposed between the first and second guide members 110, 111. A compression spring 119 is retained between the first and second spring retaining features 117, 118. The compression spring 119 extends in a direction that is generally parallel to the elongate ridges 112, 115 of the first and second guide members 110, 111.

The first spring retaining feature 117 is generally U-shaped in plan view (see Figure 16) and is dimensioned such that a first end 119a of the compression spring 119 is received within the first spring retaining feature 117. The first spring retaining feature 117 is provided with a recess 120 on a central portion of the U-shape. The cross section of Figure 18 passes through the recess 120 such that in Figure 18 only a small part of the first spring retaining feature 117 can be seen.

The second spring retaining feature 118 is generally rectangular in plan view (see Figure 16) and a second end 119b of the compression spring 119 contacts the second spring retaining feature 118. As can be best seen in Figure 16, the dimensions of the second spring retaining feature 118 in plan view are smaller than those of the compression spring 119 such that the compression spring 119 extends beyond the second spring retaining feature 118 in both directions.

The first guide member 110 defines a first channel, the first channel being formed between the rear wall 113 of the back plate 101 and the three tabs 114 of the first guide member 110. Similarly, the second guide member 111 defines a second channel, the second channel being formed between the rear wall 113 of the back plate 101 and the three tabs 116 of the second guide member 111. The first and second channels face each other.

Optionally, a generally rectangular aperture 109 may be provided in the rear wall 113 of the back plate 101 below each of the three tabs 114 of the first guide member 110 and each of the three tabs 116 of the second guide member 111. This may aid in the forming of the back plate 101 by injection moulding.

In plan view, the attachment feature 102 comprises an elongate, generally rectangular body with first and second opposed longer sides 121, 122 and first and second opposed shorter sides 123, 124 (see Figures 14 and 15).

In use, a portion of the attachment feature 102 proximate to the first longer side 121 of the attachment feature 102 is received in the channel defined by the first guide member 110 and a portion of the attachment feature 102 proximate to the second longer side 122 of the attachment feature 102 is received in the channel defined by the second guide member 111.

In order to facilitate engagement of the attachment feature 102 and the back plate 101, each of the first and second longer sides 121, 122 of the attachment feature 102 are provided with a plurality of recesses 125 formed between discrete sections 126 of the attachment feature 102. In order to engage the attachment feature 102 with the back plate 101, the attachment feature 102 is offered up to the back plate 101 such that the recesses 125 on the first longer side 121 are generally aligned with the three tabs 114 of the first guide member 110 and recesses 125 on the second longer side 122 are generally aligned with the three tabs 116 of the second guide member 111. Subsequently, the attachment feature 102 is pushed towards the rear wall 113 of the back plate 101.

As the attachment feature 102 is pushed towards the rear wall 113 of the back plate 101, a central portion 127 of the attachment feature 102 houses the first spring retaining feature 117 and the compression spring 119. As can be best seen in Figure 15, in order to achieve this a rear surface 128 of the attachment feature 102 (i.e. a surface of the attachment feature which in use is disposed adjacent to the rear wall 113 of the back plate 101) is provided with a recess 129 for receipt of the first spring retaining feature 117 and the compression spring 119. The compression spring 119 is also shown in Figure 15 for illustrative purposes. The recess 129 is partially open on one side, being provided with a shoulder 130 on either side of an opening 131. When the attachment feature 102 is pushed towards the rear wall 113 of the back plate 101, the second spring retaining feature 118 is disposed in the opening 131 and the portion of the second end 119b of the compression spring 119 that extends beyond the second spring retaining feature 118 in both directions is disposed adjacent to the shoulder 130.

When disposed in this engaged arrangement, the attachment feature 102 can move linearly in the direction indicated by arrow 132 from the position shown in Figure 17 so that the discrete sections 126 of the attachment feature 102 are received in the channels formed by the first and second guide members 110, 111. Such linear movement of the attachment feature is achieved by the application of an actuating force. In this way, the attachment feature 102 is slidably connected to the back plate 101 such that it can move linearly relative to the back plate between at least a first position (as shown in Figure 17) and a second position (wherein the discrete sections 126 of the attachment feature 102 are received in the channels formed by the first and second guide members 110, 111).

As the attachment feature 102 moves linearly in the direction indicated by arrow 132, the shoulder 130 in the recess 129 moves towards the first spring retaining feature 117 and the compression spring 119 is further compressed between the shoulder 130 and the first spring retaining feature 117. Once the actuating force is removed, the compression spring 119 will expand until it contacts the second spring retaining feature 118. This returns the attachment feature 102 to the first position, as shown in Figure 17. The compression spring 119 therefore acts as a biasing mechanism that biases the attachment feature 102 to the first positon.

Once the attachment feature 102 is in place, a guide bush member 133 and the printed circuit board 103 are both attached to the back plate 101. The guide bush member 133 is attached to the back plate 101 using screws 134 that cooperate with threaded bores 135 provided on the back plate 101. Similarly, the printed circuit board 103 is attached to the back plate 101 using screws 136 that cooperate with threaded bores 137 provided on the back plate 101. Since the guide bush member 133 and the printed circuit board 103 both partially cover the attachment feature 102, they each act to prevent disengagement of the attachment feature 102 from the back plate 101.

The attachment feature 102 is provided with a protrusion 138 on a front surface of the attachment feature 102 (i.e. a surface of the attachment feature 102 which in use is distal from the rear wall 113 of the back plate 101). As can be best seen in Figures 12a, 13a and 13b, the printed circuit board 103 is provided with an elongate slot 139. When the printed circuit board 103 is attached to the back plate 101, the protrusion 138 extends through the slot 139. As the attachment feature 102 moves relative to the back plate 101 (i.e. in the direction indicated by arrow 132) the protrusion 138 moves along the elongate slot 139. A micro-switch 140 is attached to the printed circuit board 103 adjacent to the elongate slot. The micro-switch 140 is provided with an actuator 141 which is arranged to close the switch as the protrusion 138 moves along the elongate slot 139 from the first position to the second position.

The printed circuit board 103 further comprises components that implement control electronics. It will be appreciated that a vast array of different combinations of components and control electronics may be provided as desired, dependent on the intended use of the expander box 100. The printed circuit board 103 further comprises connections 142 that allow the expander box 100 to be connected to one or more other components of the security alarm such as, for example, a control panel. Such connection may be via wires (not shown), which may exit the expander box 100 via cable cut out sections 143 on the back plate 101, in a conventional manner.

The cover 104 is arranged for releasable cooperation with the back plate 101. Attachment of the cover 104 to the back plate 101 is achieved by way of the fixing member 105. In order to attach the cover 104 to the bake plate 101 the cover 104 is offered up to the back plate 101 when the fixing member 105 is disposed in a first orientation (as shown in Figure 12a). An external profile of the back plate 101 generally matches an internal profile of the cover 104 so that the back plate 101 and the cover 104 cooperate and form a close fit with each other. The fixing members 105 are then rotated through approximately 180° until they are disposed in a second orientation (as shown in Figure 12b). The rotation of the fixing members 105 from the first orientation to the second orientation releasably attaches the cover 104 to the back plate 101, as described further below.

The cover 104 may be further attached to the back plate 101 in such a way that the cover 104 can be hinged away from the back plate 101 when the fixing members 105 are disposed in the first orientation. Alternatively, when the fixing members 105 are disposed in the first orientation the cover 104 may detach from the back plate 101 so that it can be removed.

The fixing member 105 is now described in greater detail with reference to Figures 19 and 20. The fixing member 105 is generally elongate and defines an axis 145. In the following, in relation to the fixing member 105, a direction generally parallel to the axis 145 may be referred to as an axial direction and a direction generally perpendicular to and passing through the axis 145 may be referred to as a radial direction.

The fixing member 105 comprises a first portion 146 and a second portion 147. The fixing member 105 is generally of the form of a bolt with the first portion 146 being generally of the form of a bolt shank and the second portion 147 being generally of the form of a bolt head. The first portion 146 is for receipt through a fixing aperture 148 in the cover 104 (see Figure 18). The second portion 147 is for contacting at least a portion of the cover 104 surrounding the fixing aperture 148.

The first portion 146 of the fixing member 105 comprises a generally cylindrical body 149 which extends axially from the second portion 147 of the fixing member 105. The first portion 146 further comprises an engagement protrusion 150. The engagement protrusion 150 extends axially from a distal end of the generally cylindrical body 149 of the first portion 146 and is radially offset from the axis 145.

The second portion 147 of the fixing member 105 defines a recess 151 for receiving and engaging with a tool (not shown). In use, a tool such as, for example, a screwdriver, a hex key or the like, may be inserted into recess 151 such that the tool engages with the fixing member 105. In this way, a torque may be applied to the fixing member 105 to rotate it (for example between the first and second orientations) in a conventional manner.

The fixing member 105 engages with the cover 104. In order to achieve this, the fixing member 105 defines a groove 152 at the intersection between the first portion 146 and the second portion 147 for receipt of part of the cover 104. The groove 152 is defined around the circumference of the fixing member 105 at the intersection between the first portion 146 and the second portion 147. It will be appreciated that in alternative embodiments, the groove may not extend around the entire circumference of the fixing member 105.

An outer dimension of the generally cylindrical body 149 is smaller than an inner dimension of the fixing aperture 148 in the cover 104 such that the generally cylindrical body 149 can be inserted through the fixing aperture 148. To facilitate engagement between the fixing member 105 and the cover 104, the fixing member 105 is provided with two resiliently deformable features 153 on opposed sides of the generally cylindrical body 149. The resiliently deformable features 153 are of the form of wings or barbs and extend radially outboard of the generally cylindrical body 149 such that, when the resiliently deformable features 153 are in their equilibrium state, an outer dimension of the first portion 146 of the fixing member 105 is larger than the inner dimension of the fixing aperture 148 in the cover 104. However, the resiliently deformable features 153 can deform to allow the first portion 146 of the fixing member 105 to be inserted into the fixing aperture 148 and, once they have passed through the fixing aperture 148, the resiliently deformable features 153 can snap back to retain the fixing member 105 on the cover 104 (as shown, for example, in Figure 21).

The fixing member 105 is therefore connected to and retained by the cover 104. When the portion of the cover 104 that surrounds the fixing aperture 148 is received within the groove 152, there is sufficient clearance to allow the fixing member 105 to rotate (about its axis 145) relative to the cover 104.

As can be seen in Figure 21, the fixing aperture 148 is formed within a counter bore or recess in the cover 104 such that when the fixing member 105 is engaged with cover 104 the second portion 147 of the fixing member 105 is at least partially received within this recess.

Any or all of the following components may be formed from a plastics material such as, for example polycarbonate: the back plate 101, the attachment feature 102, the cover 104, the fixing member 105 and the guide bush member 133. Advantageously, such materials are durable and, unlike metals, such plastics materials do not corrode or rust and therefore do not need to be replaced. These components may be formed in any conventional manner, for example by injection moulding.

In some embodiments, the fixing members 105 are moulded from the same plastics material as the cover 104. This can further improve the aesthetic appearance of the bell box and allow the fixing members 105 to blend seamlessly into the housing cover 104 of the expander box 100. Although some prior art arrangements may use plastic covers installed over the tops of the fixing screw heads to achieve this result, these plastic covers are an additional component which add to the overall cost of the installation and are easily lost.

The rotation of the fixing members 105 from the first orientation to the second orientation releasably attaches the cover 104 to the back plate 101, as described further below.

As explained above, releasable attachment of the cover 104 to the 101 is achieved by rotation of the fixing member 105 about its axis 145 through approximately 180° (from the first orientation to the second orientation). This releasable engagement is now described in greater detail.

The guide bush member 133 defines a generally circular aperture 155 for receipt of at least part of the generally cylindrical body 149 of the first portion 146 of the fixing member 105. The guide bush member further comprises a wall 156, which extends around a portion of the circumference of the generally circular aperture 155. As the cover 104 (and the fixing member 105 attached thereto) is brought into cooperation with the back plate 101, the wall 156 of the guide bush member 133 guides the first portion 146 of the fixing member 105 towards the aperture 155. The wall 156 of the guide bush member 133 may also provide some support for the first portion 146 of the fixing member 105.

As can be seen best in Figure 14, the attachment feature 102 defines a recess 154 on its front surface (i.e. the surface of the attachment feature 102 which in use is distal from the rear wall 113 of the back plate 101). The recess 154 is of the form of a elongate slot, having a shorter dimension and a longer dimension. As can be seen in Figure 17, the recess 154 is disposed below the circular aperture 155 of the guide bush member 133. When the cover 104 (and the fixing member 105 attached thereto) is brought into cooperation with the back plate 101, the fixing member 105 being disposed in the first orientation, the engagement protrusion 150 of the fixing member 105 is received in the recess 154. An outer dimension of the fixing member 105 generally matches the shorter dimension of the recess 154.

As explained above, the engagement protrusion 150 of the fixing member 105 is radially offset from the axis 145 of the fixing member 105. Therefore, rotation of the fixing member 105 from the first orientation (as shown in Figures 12a and 12b) to the second orientation (as shown in Figures 13a and 13b) causes the engagement protrusion 150 of the fixing member 105 to rotate around the axis 105. As the engagement protrusion 150 moves around the axis of rotation 145 of the fixing member 105, it contacts an inner surface of the recess 154 causing the attachment feature 102 to move linearly. Rotation of the fixing member 105 from the first orientation (as shown in Figures 12a and 12b) to the second orientation (as shown in Figures 13a and 13b) causes the attachment feature 102 to move from the first positon to the second position.

This movement of the attachment feature 102 relative to the back plate 101 causes the attachment feature 102 to releasably engage with the cover 104 so as to releasably attach the back plate 101 to the cover 104, as now described. When the attachment feature 102 is disposed in a first position (and the fixing member 105 is disposed in the first orientation), the cover 104 may be brought into cooperation with the back plate 101 so as to define an internal volume. This may be referred to as a closed configuration of the expander box 100. When the cover 104 and back plate 101 are disposed in the closed configuration, the fixing member 105 may be rotated through 180° so as to move the attachment feature 102 relative to the back plate 101 from the first position (as shown in Figures 12a and 12b) to the second position (as shown in Figures 13a and 13b). When disposed in the second position, the attachment feature 102 engages a portion of the cover 104.

To achieve this, the cover 104 comprises a flange 157 that extends away from the cover 104 in a direction generally perpendicular to a plane of the cover 104. Therefore, when the cover 104 and back plate 101 are disposed in the closed configuration, this flange 157 extends towards the back plate 101. The flange 157 is provided with two holes 158, as shown in Figure 22.

The attachment feature 102 comprises two protrusions 159 (see Figure 14) that are received by the holes 158 in the flange 157 when the engagement feature 102 is moved towards the second position. In this way, the cover 104 is releasably attached to the back plate 101.

During this attachment of the cover 104 to the back plate 101, as the fixing member 105 rotates about its axis 145 the protrusion 138 on the front surface of the attachment feature 102 moves along the elongate slot 139 in the printed circuit board 103. When the attachment feature 102 is disposed in the first position, the protrusion 138 is separated from the actuator 141 of the micro-switch 140 and the micro-switch 140 is open. As the attachment feature 102 moves towards the second position, the protrusion 138 contacts the actuator 141 of the micro-switch 140 and closes the microswitch 140. The actuator 141 of the micro-switch 140 is biased towards an open state such that when the attachment feature 102 moves back towards the first position, and the protrusion 138 moves away from the actuator 141, the micro-switch 140 opens.

The micro-switch 141 may be considered to be a detector which is attached to the back plate 10a and which is operable to output a signal indicative of the orientation of the fixing member 105 relative to the back plate 101.

The cover 103 may comprise a window 160, which may be formed from a different material to a main portion of the cover. In particular, the window 160 may be formed from a transparent material whereas the main body of the cover 103 may be formed from an opaque material. The printed circuit board 103 may comprise a display unit 161 or the like, which may display information that can be viewed through the window 160.

The expander box 100 as described above provides an arrangement wherein the back plate 101 and the cover 104 can be connected by way of the fixing member 105 and attachment feature 102 and wherein information relating to the orientation of the fixing member 105 may be monitored (via the micro-switch 140). Since connection of the back plate 101 and the cover 104 is achieved by rotating the fixing member 105, by monitoring the orientation of the fixing member 105 relative to the back plate 101, the micro-switch 140 allows for tamper detection. That is, in the event that an attempt is made to remove the cover 104 from the back plate 101 (by rotating the fixing member 105) this information can be transmitted by the signal from the micro-switch 140.

In known boxes for alarm systems, a front cover is often secured to a back plate by way of conventional threaded metal screws. Such bell boxes may contain a tamper detection switch positioned such that the switch actuator is forced closed when the front cover of the bell box is in place but springs open when the front cover is removed. Therefore, such known alarm boxes often have an anti-tamper detection that is operable to determine when the cover is removed from the back plate. With such existing arrangements the tamper attempt is only detected after the screws have been unscrewed and the cover is being opened. In contrast to such known arrangements, the expander box 1 described above provides an arrangement that is operable to detect when the fixing members 105 themselves are being undone. This allows a tamper warning signal to be generated before access to the inside of the expander box 100 has been achieved.

The expander box 100 as described above has a number of advantages over prior art arrangements, as now discussed. The fixing member 105 and attachment feature 102 incorporate an actuator (in the form of protrusion 138) that provides tamper detection while the fixing member 105 is being unfastened. Furthermore, transition between a fully fastened state to a fully unfastened state is achieved by rotation of the fixing member 105 by half a turn (for example using a screwdriver or the like). This is in contrast to prior art arrangements wherein attachment is achieved using standard metal screws which typically require many multiple turns to transition between a fully fastened state and a fully unfastened state. This can be difficult or inconvenient when working at height. Particularly bearing in mind that installation may be carried out at height, only needing to perform half a turn of the fixing member 105 makes installation significantly easier.

As described above, the fixing member 105 is retained on the cover 104. A further advantage of such a feature is that in the event that the cover 104 is forcibly removed from the back plate 101, the fixing member 105 may also be removed from the back plate 101. In turn, this will cause the micro-switch 140 to open, which can indicate that the expander box 100 has been tampered with.

Although the above-described embodiment uses a micro-switch 140 to determine an orientation of the fixing member 105, it will be appreciated that any detector for determining an orientation of the fixing member 105 may be used. The signal output by the detector may be a binary signal (as in the case of a micro-switch). For example, it may indicate whether the box is either: (a) closed; or (b) at least partially open. Alternatively, the signal output by the detector may contain more detailed information indicative of the orientation of the fixing member. For example, the signal output by the detector may indicate that the orientation of the fixing member is one of more than two different orientations (either discrete or continuous).

Although the above described embodiment of an expander box 100 comprises one fixing member 105, it will be appreciated that in alternative embodiments the box may be provided with more than one fixing members.

In the above-described embodiment of an expander box 100, the back plate 102 is provided with one attachment feature 102 that is movable relative to the back plate 101. It will be appreciated that in alternative embodiments, more than one such movable attachment feature may be provided. Furthermore, it will be appreciated that the attachment feature 102 may be slidably connected to the back plate in a variety of alternative ways such that it can move relative to the back plate 101 between at least a first position and a second position. For example, the attachment feature may be retained in a groove, channel or the like on the back plate. Alternatively, the back plate may be retained in a groove, channel or the like on the attachment feature. The groove or channel may be defined by two rails. The groove or channel may extend substantially along the length of the attachment feature or, alternatively, the groove or channel may comprise a plurality of discrete, aligned guide members.

It will be appreciated that a variety of alternative arrangements may allow for the rotation of the fixing member 105 from the first orientation to the second orientation to cause movable attachment feature 102 to move relative to the back plate 101. For example, the fixing member 105 and the attachment feature 102 may form any suitable cam mechanism or the like that converts rotation of the fixing member 105 into linear movement of the attachment feature 102.

In the above described embodiment, movement of the attachment feature 102 relative to the back plate 101 causes the attachment feature 102 to releasably engage with the cover 104 so as to releasably attach the back plate 101 to the cover 104. It will be appreciated that the releasable engagement between the attachment feature 102 and the cover 104 may be achieved in a variety of ways. In general, the attachment feature 102 and the cover 104 may be provided with any complementary engagement features to allow this releasable engagement.

In the above described embodiment of a bell box 1, rotation of the fixing member 15 directly actuates the actuator lever 44 of the micro-switch 13. In this way, the microswitch 13 is operable to output a signal indicative of the orientation of the fixing member 15 (relative to the back plate 10). Flowever, in alternative embodiments, the fixing member may indirectly actuate a detector (for example a micro-switch). For example, as the fixing member rotates, it may act on an intermediate mechanical linkage causing it to move so as to actuate a detector (for example by acting on an actuator of a micro-switch). This is the case with the above-described embodiment of an expander box 100, wherein the back plate 101 is provided with a slidable attachment feature 102 that is movable relative to the back plate 101 and the movable attachment feature 102 form such an intermediate mechanical linkage.

Although, the above-described embodiments of a box according to the invention are: a bell box 1 and an expander box 100, it will be appreciated that this is by way of example only and in alternative embodiments the box may be for any type of device for a security alarm systems. The box may, for example, be a box for any or all of the following: bell boxes, detectors, control panels, keypads, expanders and communicators.

It will be appreciated that any of the features of the above-described embodiment of a bell box 1 may be combined with any of the features of the above-described embodiment of an expander box 100 as desired.

While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

CLAIMS:

1. A box for a security alarm, the box comprising: a first member for attachment to a surface, the first member comprising an attachment feature; a detector attached to the first member; a second member for releasable cooperation with the first member, the second member defining a fixing aperture; and a fixing member being generally elongate so as to define an axis and comprising a first portion for receipt through the fixing aperture and a second portion for contacting at least a portion of the second member surrounding the fixing aperture; wherein the fixing member is arranged to cooperate with the attachment feature of the first member so as to releasably attach the first member to the second member, said releasable attachment being achieved by rotation of the fixing member about the axis from a first orientation to a second orientation; and wherein the detector is operable to output a signal indicative of the orientation of the fixing member relative to the first member.

2. The box of claim 1 wherein the fixing member comprises a detection protrusion and wherein rotation of the fixing member about the axis causes the detection protrusion to move around the axis.

3. The box of claim 2 wherein the signal output by the detector is indicative of a position of the detection protrusion around the axis relative to the first member.

4. The box of any preceding claim wherein the detector comprises a switch.

5. The box of any preceding claim wherein the fixing member is arranged to releasably engage with the attachment feature, said releasable engagement of the fixing member and the attachment feature resulting in the releasable attachment of the first member to the second member.

6. The box of any preceding claim wherein the fixing member comprises an engagement protrusion.

7. The box of any preceding claim wherein transition from the first orientation to the second orientation is achieved by rotation of the fixing member through less than 360°.

8. The box of any preceding claim wherein the fixing member engages with the second member.

9. The box of claim 8 wherein the fixing member defines a groove at the intersection between the first portion and the second portion for receipt of part of the cover.

10. The box of claim 8 or claim 9 wherein the fixing aperture comprises a generally circular portion for receipt of a generally cylindrical body of first portion and a generally elongate slot portion for receipt of a detection protrusion and a engagement protrusion.

11. The box of claim 10 wherein an internal diameter of the circular portion of fixing aperture is slightly smaller than an external diameter of a generally cylindrical portion of first portion and the fixing aperture further comprises at least one slot arranged to allow the portion of the second member surrounding the fixing aperture to flex sufficiently to receive the first portion.

12. The box of any preceding claim wherein the fixing member is provided with one or more resiliently deformable features that can deform to allow the fixing member to be inserted into the fixing aperture and can snap back to retain the fixing member on the second member once a portion of the fixing member has been inserted into the fixing aperture.

13. The box of any preceding claim wherein the fixing aperture is formed within a recess in the second member and wherein, in use, the second portion of the fixing member is at least partially received within this recess.

14. The box of claim 13 wherein the recess is provided on an inclined surface of the second member and wherein a surface of the second portion of the fixing member is inclined such that a shape of the second portion of the fixing member generally matches the shape of the recess.

15. The box of any preceding claim wherein the fixing member is formed from a plastics material.

16. The box of any preceding claim wherein the fixing members are formed from the same material as the second member.

17. The box of any preceding claim wherein the attachment feature further comprises a bearing surface for a detection protrusion of the fixing member.

18. The box of any preceding claim wherein the first member comprises at least one attachment aperture, the at least one attachment aperture being provided on an insert which is connected to a main body of the first member such that it can rotate relative to the first member.

19. The box of any preceding claim, wherein the attachment feature is movable relative to the back plate and wherein rotation of the fixing member causes the attachment feature to move relative to the back plate.

20. The box of claim 19 wherein the movement of the attachment feature relative to the back plate causes the attachment feature to releasably engage with the second member so as to releasably attach the first member to the second member.

21. The box of claim 19 or claim 20 wherein the signal output by the detector is indicative of a position of the attachment feature, which in turn is indicative of the orientation of the fixing member relative to the first member.