GB2551494A - Alarm bell box with hinged cover - Google Patents

Abstract

A back plate 2 for an alarm bell box 1 comprising a first portion 5, a second portion 16 and a recess 18 between the first and second portions. The second portion 16 can be a resilient deformable hinge member which operates as a cantilever. The second portion 16 has a tab portion 26 which is used to change the configuration of the second portion between two states to affect the width of the recess 18. Pressing the tab portion 26 down in direction A (figure 2) configures the second portion 16 into a first state and causes the recess 18 to widen for receiving a cover member which can be a wing 23 disposed on the cover 3. In a second state, the tab portion 26 is pushed upwards in direction B (figure 3) which narrows the recess such that the wing 23 is engaged and locked in place. At least one of the first or second portions has a feature to releasably engage the other to retain the second portion in the first state.

Description

Alarm Bell Box with Hinged Cover

The present invention relates to a back plate for an alarm bell box and in particular to a back plate comprising a releasable engagement mechanism for a cover member.

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 typically comprise a back plate configured for mounting to the wall, and a cover member configured to fit over the back plate which may define an enclosed volume between the back plate and the cover member. The enclosed volume may house various components of the alarm system, such as for example, alarm bells or strobe lights, which are typically mounted to the back plate of the bell box. 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.

It is known to provide connection means to secure the cover member to the bell box. Such connection means may be for example a conventional screw which may pass through an aperture in the cover member and may be connected to the back plate via the use of a screwdriver.

It may be desirable to provide an alternative back plate for a security alarm bell box 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 provided a back plate for an alarm bell box, the back plate comprising: a first portion; a second portion; and at least one recess defined between the first portion and the second portion; wherein the second portion is configurable between a first state in which the or each recess is configured to receive a cover member and a second state in which the second portion is configured to engage the cover member; wherein at least one of the first or second portions comprises at least one feature configured to releasably engage the other of the first or second portions so as to retain the second portion in the first state.

The back plate of the first aspect of the invention provides the advantage that it allows for a convenient installation process. For example, where a cover member is desired to be connected to the back plate, during use a user may initially configure the second portion so that it is disposed in the first state. Whilst the second portion is disposed in the first state, the at least one feature of the first or second portion retains the second portion in the first state such that it is temporarily prevented from moving to the first state. As such, the user does not need to act upon the second portion to maintain the second portion in the first state, and therefore both of the user’s hands are free to deal with other tasks associated with the installation process. The user can then align the cover member with the recess of the back plate and then place at least a portion of the cover member within the recess. The user can then configure the second portion so that it is disposed in the second state, and in doing so secure the cover member to the back plate. It will be appreciated that in order to reconfigure the second portion from the first state to the second state, the at least one feature of the first or second portions is released by the user from the position in which the at least one feature retains the second portion in the first state.

It will be appreciated that the back plate of the first aspect of the invention is configured to maintain engagement between the cover member and the back plate without the need for tools. It will further be appreciated that because the at least one feature of the first or second portion retains the second portion in the second state; the user is not required to hold the second portion in the second state, and therefore the user may use both hands to align the cover member relative to the recess. This is advantageous because a user may be required to install the bell box at height, such as when stood at the top of a ladder. The present invention makes the installation process simpler, and therefore the amount of time required and the number of actions that must be completed whilst the user is working at height is reduced.

It will be appreciated that the term “configured to receive the cover member” is intended to mean that, in the first configuration of the second portion, a portion of the cover member may be freely moved into or out of the recess. For example, the second portion may deflect away from the first portion so as to make the recess large enough to receive a portion of the cover member.

The term “configured to engage the cover member” is intended to mean that, when the cover member has been received by the recess and the second portion is disposed in the second configuration, either the first portion or the second portion acts to retain the cover member in engagement with the back plate. As such, in the second configuration of the second portion, separation of the cover member and the back plate is substantially prevented.

It will further be appreciated that the term “releasably engage” is intended to mean that the at least one feature of the first or second portion can hold the second portion in the first configuration in response to a first user input, and may permit the second portion to be disposed in the second configuration in response to a second user input. That is to say, when the second portion is disposed in the first configuration the at least one feature will prevent the second portion from being disposed in the second configuration until acted upon by the user.

When disposed in the second state the second portion may be configured to engage the cover member such that the cover member is pivotable relative to the back plate. That is to say, when the cover member has been placed in the recess and the second portion has been engaged with the cover member, the cover member remains pivotally movable relative to the back plate. As such, the second portion and the cover member may be considered to define a hinge.

The second portion may be deformable and transition between the first state and the second state of the second portion may be achieved by deformation of the second portion. That is to say, at least a portion of the second portion is movable relative to the first portion so as to define the first and second states. For example, the second portion may be made from a resiliently deformable material such that the entire second portion can be bent or deflected so as to change the configuration of the second portion between the first and second states. Alternatively, the second portion may be made from a rigid material that is pivotable or slidable relative to the first portion.

The second portion may be biased towards the second state when the at least one feature of at least one of the first or second portions is not engaged with the other of the first or second portions. That is to say, the second portion will automatically move to the second state when it is not under the action of an input force and when the at least one feature of the first or second portions is not engaged with the other of the first or second portions. For example, the second portion may store elastic potential energy when it is disposed in the first state, and this elastic potential energy may be released when the second portion is no longer engaged in the first state by the at least one feature of the first or second portion.

The second portion may comprise at least one elongate member that extends from the first portion, the or each elongate member at least partially defining one of the at least one recesses and the or each elongate member may be arranged to pivot relative to the second portion about a pivot point. That is to say the or each elongate member may be a part of the second portion that is cantilevered relative to the first portion. It will be appreciated that or each elongate member may formed as a separate piece to the first portion or, alternatively, the or each elongate member may be integral with the first portion. The or each elongate member may be referred to as a leg. Since each elongate member at least partially defines one of the recesses, as the elongate member pivots relative to the second portion, the dimensions of the recess vary.

The second portion may comprise two elongate members that extends from the first portion. The second portion may further comprise a central portion that extends between the two elongate members. It will be appreciated that because both of the elongate members are connected via the central portion, a user can apply an actuating or input force to both elongate members by application of a single input force on the central portion. Advantageously, this may allow a user to apply a single input force, for example using a single finger.

The second portion may comprise a tab portion configured to be acted on by an input force. It will be appreciated that the tab portion may be any portion of the second portion of the back plate that to which an input force capable of changing the configuration of the second portion between the first and second states can be applied.

The tab portion may be configured to be received in a recess defined by the first portion of the back plate.

The tab portion may be configured to receive a finger of a user. For example, the tab portion may define a width that is large enough for a user to exert an input force on the tab using a finger.

The tab portion may be generally u-shaped.

The tab portion may be connected to the or each elongate member and a distance between a centre of the tab portion and the or each elongate member may be larger than a length of the or each elongate member. With such an arrangement, sufficient torque to cause the or each elongate member to pivot about its pivot point may be achieved by application of an input force to the tab portion that is lower than a force that would be required achieve the same torque when applied to a distal end (from the first member) of the or each elongate member.

The tab portion may be provided on the central portion. With such an arrangement, the tab portion is provided between the two elongate members, and two recesses at least partially defined by said two elongate members. It will be appreciated that the tab portion may therefore be used to cause deflection of both elongate members of the second portion.

The second portion may comprise a bore configured to receive a boss of the cover member when the second portion is configured in the second state. It will be appreciated that when the boss of the cover member is received within the aperture, the cover member is permitted to rotate relative to the back plate, whilst simultaneously preventing disengagement of the cover member from the back plate. Additionally or alternatively, the cover member may comprise a bore configured to receive a boss of the second portion when the second portion is configured in the second state.

The second portion may be integrally formed with the first portion. That is to say, the first and second portions of the back plate may be formed as a single piece. For example, the first and second portions may be formed of the same piece of moulded plastics material. The first and second portions may, for example, be formed by injection moulding.

The second portion may comprise at least one feature configured to releasably engage the first portion so as to retain the second portion in the first state. It will be appreciated that the first portion may additionally comprise at least one further feature configured to engage the at least one feature of the second portion so as to retain the second portion in the second state.

The at least one feature of the second portion may be a protrusion configured to engage a surface of the first portion of the back plate. For example, the first portion of the back plate may define a recess and the protrusion may be configured to engage a surface of the recess.

The configuration of the second portion may be maintained in either the first state or the second state until the second portion is acted upon by an input force. For example, the second portion may require an input force to move the second portion into the first state and may require another input force to move into the second state. During use, the input force may be provided by the user. To move the second portion from the first state to the second state may require an input force to release engagement between the at least one feature and the other of the first or second portions. To move the second portion from the second state to the first state may require an input force to act against a resilient bias (for example to elastically deform the second portion).

The first portion may be configured for attachment to a surface. For example the first portion may be connected to an outer surface a building.

According to a second aspect of the invention there is provided a bell box for an alarm system, the bell box comprising: a cover member; and a back plate according to the first aspect of the invention.

It will be appreciated that the cover member of the second aspect of the invention may comprise any of the optional features of the cover member set out with respect to the first aspect of the invention.

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 perspective view of an alarm bell box according to the present invention in an unassembled state;

Figure 2 is an enlarged front view of a portion of the alarm bell box comprising a hinge member in a first operational state;

Figure 3 is an enlarged front view of a portion of the alarm bell box in which the hinge member is in a second operational state; and

Figure 4 is an enlarged perspective view of a portion of the alarm bell box.

Figure 1 shows a bell box 1 of a security alarm system. The bell box 1 comprises a back plate 2 configured for attachment to a surface and a cover member 3. For clarity, the cover member 3 is shown in an unattached position relative to the back plate 2. However, as will be described below, during use the cover member 3 can be attached to the back plate 2 in a pivotable manner so as to permit the cover member 3 to rotate relative to the back plate 2.

In use, the bell box 1 is typically provided on an external wall of a building that is protected by the security alarm system. The back plate 2 is typically attached to a surface of the external wall using screws or the like, in a conventional manner. To achieve this, the back plate 2 comprises a number of apertures 4 that allow the back plate 2 to be attached to the external surface of a building (for example a wall), in a conventional manner. Each of the apertures 4 is provided as an elongate slot on a generally circular insert 6 which is connected to a main body of the back plate 2 such that it can rotate relative thereto. This rotation of the circular inserts 6 (relative to the back plate 2) can aid a user during the installation of the back plate 2 since the circular inserts 6 and apertures 4 allow 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 2 and the cover member 3 cooperate to define an internal volume which houses a number of internal components of the bell box 1. In the example embodiment the internal components are attached to the back plate 2 and comprise two piezo sounders 8, a micro-switch 10 and a compartment 14 for housing control electronics and/or a battery (not shown), however it will be appreciated that any number of internal components of the alarm system may be housed within the internal volume and/or mounted to the back plate 2. The control electronics are connected to the micro-switch 10 and the two piezo sounders 8. The control electronics are 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 1 is attached. The compartment 14 may also house a visual signalling device (for example a strobe light), which may be connected to the control electronics.

The back plate 2 comprises a main portion 5 and a hinge member 16 extending generally along an edge of the back plate 2. In the example embodiment, the hinge member 16 is positioned along an edge 7 of the back plate 2 which, in use, forms a top edge of the back plate 2. However, it will be appreciated that in alternative embodiments of the invention the hinge member 16 may be positioned along any suitable edge of the back plate 2, such as for example a side edge or a bottom edge of the back plate 2.

The hinge member 16 is a generally m-shaped elongate member comprising a central portion 17 and a pair of legs 20. The legs 20 extend from the main portion 5 of the back plate 2 and are connected at their distal ends by the central portion 17. The central portion 17 comprises a tab portion 26 centrally located between the legs 20. The hinge member 16 is made from a resiliently deformable material configured to deform in response to the application of an actuation force by a user. The hinge member 16 may be composed of any such resiliently deformable material, such as for example a plastics material (e.g. polyethylene, polycarbonate, acrylonitrile butadiene styrene, acrylic, polypropylene) or a metal (e.g. spring steel). In the example embodiment shown, the hinge member 16 is integrally formed with the back plate 2 such that the hinge member 16 and the back plate 2 may be manufactured as one piece, for example by injection moulding. However, it will be appreciated that in alternative embodiments of the invention the hinge member 16 may be formed separately to the back plate 2. For example, the back plate 2 may be formed from plastic, and the hinge member 16 may be formed from metal.

The legs 20 of the hinge member extend from the main portion 5 of the back plate 2 at locations denoted by the points X. The legs 20 are integrally formed with the remainder of the back plate 2 such that the legs 20 define a cantilever relative to the main portion 5 of the back plate 2. Each leg 20 is disposed opposite a different surface 21 of the back plate 2 to define a recess 18 therebetween. The legs 20 and surfaces 21 are generally parallel to one another and extend in a direction generally normal to the edge 7 of the back plate 2 along which the hinge member 16 extends. The central portion 17 of the hinge member 16 extends between the two legs 20 in a direction generally perpendicular to the two legs 20. For example, in the present embodiment, during use the hinge member 16 extends along the top edge of the back plate 2 in a generally horizontal direction, and the legs 20 and surfaces 21 extend in a generally vertical direction.

Each leg 20 further comprises a generally circular bore 22. Each bore 22 is located towards a distal end of its respective leg 20 relative to the point X at which the leg 20 joins the main portion of the back plate 2. In the example embodiment the bores 22 are through holes positioned on a side of each leg 20 which faces the recesses 18. However it will be appreciated that in alternative embodiments of the invention the bores 22 may be blind holes.

The cover member 3 comprises a pair of wings 23 configured for receipt in the recesses 18. Each wing 23 comprises a generally flat portion and a generally cylindrical boss 24 which extends perpendicular to the generally flat portion of its associated wing 23. In the example embodiment, each of the bosses 24 extends towards the other of the bosses 24. The bosses 24 are generally collinear and together define a pivot axis of the cover member 3. Each of the wings 23 may be considered to be cover member that can be received in one of the recesses 18 and which can engage the hinge member 16.

The tab portion 26 of the hinge member 16 is generally u-shaped and comprises a pair of side arms 27 which extend from the central portion 17 of the hinge member 16 towards the main portion 5 of the back plate 2. The tab portion 26 is sized so as to be able to receive a user’s finger between the side arms 27. The tab portion 26 further comprises a pair of protrusions 28 which face outwardly from the side arms 27 towards the legs 20. The back plate 2 comprises a pair of surfaces 30 which define a central recess 32 configured to receive the tab portion 26, side arms 27 and protrusions 28.

With reference to Figures 2 and 3, the tab portion 26 is configurable between a first state in which the recess is configured to receive a cover member (as shown in Figure 2) and a second state in which the recess is configured to engage the cover member (as shown in Figure 3), as is now described.

As is shown in Figure 2, during use (e.g. during installation of the bell box 1), a user can pull the tab portion 26 into the central recess 32 by exerting a force on the tab portion 26 in the direction shown by the arrow A in order to downwardly deform the hinge member 16 into the central recess 32. The resulting movement of the hinge portion 16 causes the protrusions 28 of the tab portion 26 to engage the surfaces 30 of the central recess 32. As the tab portion 26 is inserted into the central recess 32, the tab portion 32 is deformed, with the side arms 27 being forced closer together by the surfaces 30 of the central recess 32. As the hinge member 16 attempts to return to its undeformed position, the side arms 27 push outwardly from the tab portion 26 in a direction normal to the surfaces 30 of the central recess 32. Frictional contact between the protrusions 28 and the surfaces 30 thereby holds the tab portion 26 within the central recess 32 in the deformed position shown. This may be considered to correspond to a first operating state of the hinge member 16.

It will be appreciated that in the undeformed position of the hinge member 16 (best shown in Figure 3) the protrusions 28 of the tab portion 26 are spaced apart by a distance that is greater than a corresponding width of the central recess 32. As such, when the hinge member 16 is deformed in response to an input force by a user, the protrusions 28 of the tab portion 26 contact the surfaces 30 of the channel and the side arms 27 deflect inwardly (i.e. towards a centre of the tab portion 26) so as to permit the protrusions 28 to pass over a vertex of each surface 30 where the surface 30 joins the top edge 7 of the main portion 5 of the back panel 2. It will be appreciated that this helps to provide a normal contact force between the surfaces 30 and the side arms 27 that results in a frictional force between the surfaces 30 and the side arms 27 that is sufficient to prevent the hinge member 16 from returning to its undeformed position.

In response to the movement of the tab portion 26, the side arms 27 are elastically deflected towards one another and, in turn, the legs 20 are elastically deflected towards one another so that they are no longer parallel. This causes the recesses 18 to widen.

The hinge member 16 is maintained in the first operating state until it is acted upon by the user. In the example embodiment, the hinge member 16 is retained in the first operating state by engagement between the surfaces 30 of the central recess 32 and the protrusions 28 of the tab portion 26. However, in alternative embodiments the hinge member 16 may be retained in the first operating state by the engagement of any suitable feature or group of features formed by the back plate 2 and/or the hinge member 16. For example, the central recess 32 may comprise a protrusion configured for receipt by a recess formed in the tab portion 26. Alternatively, the surfaces 30 of the central recess 32 may comprise additional protrusions or formations that are configured to engage with the tab portion 26 so as to maintain the hinge member 16 in the first operating state.

Another alternative is that the central recess 32 may define a lip extending outwards from a plane defined by the main portion 5 of the back plate 2 (i.e. in a direction perpendicular to the plane of Figures 2 and 3). The tab portion 26 may be configured to engage and/or disengage the lip by lifting the tab portion 26 away from the plane defined by the main portion 5 of the back plate 2 and over the lip.

It will be appreciated that when the hinge member 16 is in the first operating state, the recesses 18 have been widened enough such that the recesses 18 are able to receive the wings 23 and bosses 24 of the cover member 3. As such, the user can insert the cover member 3 into the recesses 18 such that the bosses 24 are approximately aligned with the bores 22 of the legs 20. It will be appreciated that the point of maximum deflection of the legs 20 will be at the distal ends of the legs 22 relative to the point X, and therefore in the present embodiment the bores 22 are located towards the distal ends of the legs 20. It will be appreciated that this allows the bores 22 to receive bosses 24 of greater depth than if the bores 22 were positioned closer to the point X.

It will be appreciated that because the tab portion 26 of the hinge member 16 is connected to both legs 20 via the central portion 17, a user need only apply a single input force to the tab portion 26 to cause deflection of both legs 20. That is to say, by connected to both legs 20, the tab portion 26 provides the advantage that only one input force need be applied by the user rather than two. As such, the user can apply the input force required using a single finger.

It will further be appreciated that by pulling on the tab portion 26 (i.e. by exerting a force on the tab portion 26 in the direction of arrow A), the user exerts a torque about each point X at which the legs 20 are connected to the main portion 5 of the back plate 2. In general, the torque about a given point is equal to the product of an input force and the shortest distance between the given point and a longitudinal axis of the input force. As such, by increasing the distance between the longitudinal axis of the input force and the given point, the torque applied to the given point may be increased. In the example embodiment, the tab portion 26 of the hinge member 16 is centrally positioned between the legs 20, and as such is optimally positioned to provide an equal amount of torque about both points X. Furthermore, the distance between the centre of the tab portion 26 and the points X parallel to the top edge 7 of the main portion 5 is larger than the distance between the points X and the distal ends of the legs 20. As such, the input force required to provide sufficient torque to cause deflection of the legs 20 when applied to the tab portion 26 is lower than the force that would be required if the user attempted to exert a normal force directly against the distal ends of the legs 20. That is to say, the spacing of the tab portion from the points X by an amount greater than the spacing of the distal ends of the legs 20 from the points X provides a mechanical advantage and therefore the required input force to cause deformation of the legs 20 is reduced.

Once the bosses 24 of the cover member 3 and the bores 22 of the hinge member 16 have been aligned, the user can push the tab portion 26 of the hinge member 16 away from the central recess 32 of the back plate 2 in the direction shown by arrow B such that the protrusions 28 disengage from the surfaces 30. Because the hinge member 16 is resiliently deformable, in response to the protrusions 28 being disengaged from the surfaces 30, the legs 20 automatically return to their elastically undeformed position. That is to say, in the first state the hinge member 16 is deformed such that it stores elastic potential energy and when the hinge member 16 is moved from the first state to the second state the elastic potential energy is released. When the legs 20 return to their undeformed positions, the bosses 24 of the cover member 3 are captured within the bores 22 of the legs 20 so as to secure the cover member 3 to the back plate 2. This configuration is shown in Figure 3.

In the example embodiment, the legs 20 are parallel to one another when the legs 20 are in their elastically undeformed position. In this operating state of the hinge portion 16, the bores 22 circumferentially enclose the bosses 24 so as to substantially prevent the disengagement of the cover member 3 from the back plate 2. This may be considered to correspond to a second operating state of the hinge portion.

It will be appreciated that the portion of the back plate 2 which does not define the hinge member 16 may be considered to correspond to a first portion of the back plate 2, whilst the hinge member 16 may be considered to correspond to a second portion of the back plate 2. That is to say, the second portion of the back plate 2 may be considered to be the part of the back plate which is configurable between a first operating state and a second operating state as described above.

It will be appreciated that because the bores 22 of the hinge member 16 and the bosses 24 of the cover member 3 are generally circular, the cover member 3 is permitted to pivot relative to the back plate 2. In particular, the cover member 3 is pivotable between an open position in which the back plate is accessible to the user (shown in Figure 3), and a closed position in which the cover member 3 substantially encloses or covers the back plate 2. In the closed position, the cover member 3 prevents access to the internal components of the alarm system which are mounted to the back plate (e.g. the piezo sounders 8, micro-switch 10, control electronics or battery). In addition, the bell box 1 may comprise a locking means configured to retain the cover member 3 in the closed position so as to prevent access to the internal components of the alarm system. The bell box 1 may further comprise one or more anti-tamper features to prevent unauthorised access to the internal components of the alarm system. The micro-switch 10 may form part of such an anti-tamper feature.

It will be appreciated that the hinge member 16 and cover member 3 may comprise features configured to hold the cover member 3 in a number of positions relative to the back plate 2. Figure 4 shows an enlarged view of a portion of the bell box 1 before the cover member 3 has been attached to the back plate 2. The generally flat portion of each wing 23 of the cover member 3 comprises a widened portion 34, and each leg 20 comprises a protrusion 36 positioned on a side of the leg 20 facing into the recess 18. The widened portion 34 and protrusion 36 are spaced apart from the boss 24 and bore 22 respectively such that when the cover member 3 is attached to the back plate 2 the widened portion 34 and protrusion 36 may engage with one another.

The widened portions 34 of the cover member 3 and the protrusions 36 of the back plate 2 are arranged such that they engage one another when the cover member 3 is disposed in an open position relative to the back plate 2. In the open position the cover member 3 is generally oriented along a plane perpendicular to the plane defined by the back plate 2. Engagement between the widened portions 34 and the protrusions 36 prevents cover member 3 from rotating towards the back plate 2 in the absence of a closing force applied by a user. When it is desired for the cover member 3 to be placed in the closed position the widened portions 34 and the protrusions 36 can be disengaged by application of a closing force. For example, a user can simply pull down on the cover member 3. This may cause the wings 23 and legs 20 to deflect by a small amount so that the widened portions 34 may pass over the protrusions 36. In order to aid the deflection of the wings 23 and legs 20, the widened portions 34 and protrusions 36 are provided with ramped surfaces.

It will be appreciated that in alternative embodiments of the invention the features configured to hold the cover member 3 in an open or closed position may be formed by any suitable part of the cover member or back plate 2. For example, the protrusion 36 may be formed on another surface of the recesses 18 (for example the surface 21 of the back plate 2). Furthermore, the cover member 3 may comprise a plurality of features formed on the wings 23 configured to engage with the protrusions 36 of the hinge member 16 or surface 21 so as to define a plurality of positions of the cover member 3.

During use a user may initially configure the hinge member 16 so that it is disposed in the first state by applying a force to the tab portion 26 in the direction of arrow A (i.e. as shown in Figure 2). Whilst the hinge member 16 is disposed in the first state, the protrusions 28 of the hinge member 16 act upon the surfaces 30 of the central recess 32 to retain the hinge member 16 in the first state such that it is temporarily prevented from moving to the second state. The user can then align the wings 23 of the cover member 3 with the recesses 28 of the back plate 2 and then place the wings 23 within the recesses such that the bosses 24 are generally aligned with the bores 22 of the hinge member 16. The user can then configure the hinge member 16 so that it is disposed in the second state by applying a force to the tab portion 26 in the direction of arrow B to cause the protrusions 28 of the hinge portion 16 to disengage from the surfaces 30 of the central recess 32. As such, the hinge member 16 is allowed to return to an undeformed position in which the bosses 24 of the cover member 3 are received within the bores 22 of the legs 20 to thereby secure the cover member 3 to the back plate 2.

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 (19)

CLAIMS:

1. A back plate for an alarm bell box, the back plate comprising: a first portion; a second portion; and at least one recess defined between the first portion and the second portion; wherein the second portion is configurable between a first state in which the or each recess is configured to receive a cover member and a second state in which the second portion is configured to engage the cover member; wherein at least one of the first or second portions comprises at least one feature configured to releasably engage the other of the first or second portions so as to retain the second portion in the first state.

2. A back plate according to claim 1, wherein when disposed in the second state the second portion is configured to engage the cover member such that the cover member is pivotable relative to the back plate.

3. A back plate according to any preceding claim, wherein the second portion is deformable and transition between the first state and the second state of the second portion is achieved by deformation of the second portion.

4. A back plate according to any preceding claim, wherein the second portion is biased towards the second state when the at least one feature of at least one of the first or second portions is not engaged with the other of the first or second portions.

5. A back plate according to any preceding claim, wherein the second portion comprises at least one elongate member that extends from the first portion, the or each elongate member at least partially defining one of the at least one recesses and wherein the or each elongate member is arranged to pivot relative to the second portion about a pivot point.

6. A back plate according to claim 5, wherein the second portion comprises two elongate members that extends from the first portion, and wherein the second portion further comprises a central portion that extends between the two elongate members.

7. A back plate according to any preceding claim, wherein the second portion comprises a tab portion configured to be acted on by an input force.

8. A back plate according to claim 7, wherein the tab portion is configured to be received in a recess defined by the first portion of the back plate.

9. A back plate according to claim 7 or claim 8, wherein the tab portion is configured to receive a finger of a user.

10. A back plate according to any of claims 7 to 9, wherein the tab portion is generally u-shaped.

11. A back plate according to any one of claims 7 to 10 when dependent either directly or indirectly on claim 6, wherein the tab portion is provided on the central portion.

12. A back plate according to according to any one of claims 7 to 10 when dependent either directly or indirectly on claim 5, wherein the tab portion is connected to the or each elongate member and wherein a distance between a centre of the tab portion and the or each elongate member is larger than a length of the or each elongate member.

13. A back plate according to any preceding claim wherein the second portion comprises a bore configured to receive a boss of the cover member when the second portion is configured in the second state.

14. A back plate according to any preceding claim, wherein the second portion is integrally formed with the first portion.

15. A back plate according to any preceding claim, wherein the second portion comprises at least one feature configured to releasably engage the first portion so as to retain the second portion in the first state.

16. A back plate according to claim 15, wherein the at least one feature of the second portion is a protrusion configured to engage a surface of the first portion of the back plate.

17. A back plate according to any preceding claim, wherein the configuration of the second portion is maintained in either the first state or the second state until the second portion is acted upon by an input force.

18. A back plate according to any preceding claim, wherein the first portion is configured for attachment to a surface.

19. A bell box for an alarm system, the bell box comprising: a cover member; and a back plate according to any preceding claim.