GB2553290A

GB2553290A - Box for a security alarm

Info

Publication number: GB2553290A
Application number: GB1614472.7A
Authority: GB
Inventors: Roberts Simon
Original assignee: Orisec Ltd
Current assignee: Orisec Ltd
Priority date: 2016-08-24
Filing date: 2016-08-24
Publication date: 2018-03-07
Also published as: GB201614472D0

Abstract

A housing for an alarm device comprises a back plate (2, fig 1) and a cover (3, fig 1). The housing may contain a motion sensor such as a PIR detector. An intermediate member 13 is located between the back plate (2, fig 1) and cover (3, fig 1) and is movably connected to the back plate (2, fig 1). The intermediate member 13 has a spring 15, a screw 4 and a detection portion 26. The detection portion 26 has a detection protrusion 65.Shown in figure 18A, the detection protrusion 65 protrudes from a slot 67 with a micro switch 68 at one end. Undoing the screw causes the detection protrusion to move and trigger the micro switch 68 initiating a tamper alert. The alarm device may be a bell box, a detector, a control panel, a keypad, an expander or a communicator.

Description

(54) Title of the Invention: Box for a security alarm

Abstract Title: Anti-tamper mechanism for a motion detector (57) A housing for an alarm device comprises a back plate (2, fig 1) and a cover (3, fig 1). The housing may contain a motion sensor such as a PIR detector. An intermediate member 13 is located between the back plate (2, fig 1) and cover (3, fig 1) and is movably connected to the back plate (2, fig 1). The intermediate member 13 has a spring 15, a screw 4 and a detection portion 26. The detection portion 26 has a detection protrusion 65.Shown in figure 18A, the detection protrusion 65 protrudes from a slot 67 with a micro switch 68 at one end. Undoing the screw causes the detection protrusion to move and trigger the micro switch 68 initiating a tamper alert. The alarm device may be a bell box, a detector, a control panel, a keypad, an expander or a communicator.

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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 motion detector, which are typically disposed on a wall of a property that comprises the alarm system. Such detectors may use passive motion detection such as Passive Infrared Detectors (“PIRs”), active motion detection such as microwave or ultrasound detection, or a combination of both. These detectors typically comprise a casing or box which is 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. The functional components of the detector are housed within an enclosed volume formed by the back plate and the front cover. The front cover may comprise a lens behind which is disposed a sensor.

Motion detectors often contain a tamper detection device to signal a warning if unauthorised access to the inside of the casing or 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 box is in place but springs open when the front cover is removed. The switch opening causes the detector 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; a sensor connected to the first member; a second member for releasable cooperation with the first member, cooperation of the first member and the second member defining an internal volume and a first aperture; and an intermediate member, the intermediate member being movably connected to the first member such that it can move relative to the first member in an axial direction between at least a first end position and a second end position; wherein the intermediate member defines a second aperture aligned with the first aperture, wherein a line joining the first aperture and the second aperture is generally parallel to the axial direction; and wherein the sensor is operable to monitor a position of the intermediate member relative to the first member.

Since the second aperture is aligned with the first aperture, in use, a shank of a securing screw can pass through the first aperture and engage with the second aperture. Furthermore, since the line joining the first aperture and the second aperture is generally parallel to the axial direction, such engagement causes the intermediate member to move axially relative to the first member between the first end position and the second end position. In this way, the first member may be releasably secured to the second member by rotating the securing screw. The sensor is operable to monitor a position of the intermediate member relative to the first member. Therefore, the box according to the first aspect of the present invention provides a convenient anti-tamper arrangement whereby, using the sensor, it is possible to determine when the securing screw is being unscrewed, for example by a would-be intruder.

The first end position may correspond to an unsecured state of the box and the second end position may correspond to a secured state of the box.

The box may be a housing or casing for a detector, for example a passive infrared detector. The first member may be referred to as back plate. The second member may be referred to as a cover.

It will be appreciated that unless otherwise stated, the term axial direction is intended to refer to a direction along, or parallel, the direction along which the intermediate member can move relative to the first member.

The first member may comprise a first portion and a second portion. The first portion may be for attachment to a surface. The first portion may be connected to the second portion such that if the second portion is forced away from the first portion when the first member is attached to a mounting surface then the first and second portions of the first member separate. Movement of the intermediate member from the first end position to the second end position may cause the intermediate member to engage with the first portion of the first member.

For such embodiments the sensor may be connected to the second portion of the first member (either directly or indirectly). Therefore, the sensor may be operable to monitor a position of the intermediate member relative to the second portion of the first member.

Additionally, for such embodiments the intermediate member may be movably connected to the second portion of the first member.

Such an arrangement is particularly advantageous since the box provides an improved anti-tamper arrangement whereby, using the sensor, it is also possible to determine when the box is forcibly removed from a mounting surface. In use, the first portion is attached to the mounting surface using conventional screws or the like. If an attempt is made to detach the box from the mounting surface, for example by pulling the second member or the second portion of the first member away from the surface, the second portion of the first member will be forced away from the first portion of the first member. Since the first portion is attached to the mounting surface, this will force the second portion of the first member away from the first portion of the first member. In turn, this will cause the first and second portions of the first member to separate. Since movement of the intermediate member from the first end position to the second end position causes the intermediate member to engage with the first portion of the first member, if an attempt is made to detach the box from the mounting surface when the intermediate portion is in the second end position, at least a portion of the intermediate potion will be forced away from the second portion of the first member. This can be determined by the sensor. The box is therefore provided with a means for detecting when the detector is forcibly removed from such a mounting surface.

The first and second portions of the first member may be separate members which may be arranged to mutually engage, for example via an interference or friction fit. Alternatively, the first and second portions of the first member may be formed from a single member. For such embodiments the first and second portions may be connected via one or more frangible portions (for example one or more tabs of reduced thickness) that form the weakest portion of the first member.

The first member may be arranged such that separation of the first and second portions of the first member is achieved by movement of the first portion of the first member relative to the second portion of the first member in direction that is generally perpendicular to the axial direction.

With such an arrangement, if an attempt is made to detach the box from the mounting surface then at least a portion of the intermediate potion will be forced away from the second portion of the first member in a direction that is generally perpendicular to the axial direction.

Sensor may be connected to the second portion of the first member either directly or indirectly. Additionally or alternatively, the intermediate member may be movably connected to the second portion of the first member either directly or indirectly.

The box may further comprise a second intermediate member engagable with the second portion of the first member. The sensor may be connected to the second intermediate member. Additionally or alternatively, the intermediate member may be movably connected to the second intermediate member.

The second intermediate member may be of the form of a housing or casing and may define an internal volume. The sensor may be disposed within the internal volume. The intermediate member may be movably connected to an exterior surface of the second intermediate member. One of more other components of the detector may be disposed within the internal volume of the second intermediate member.

It will be appreciated that the movable connection of the intermediate member to the second portion of the first member, or another member attached thereto (for example the second intermediate member), may be achieved in any suitable way. For example, the intermediate member may be retained in a groove, channel or the like on the second portion of the first member or another member attached thereto. Alternatively, the second portion of the back plate, or another member attached thereto, may be retained in a groove, channel or the like on the intermediate member. The groove or channel may be defined by two rails or the like. 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.

The sensor may be operable to determine whether the intermediate member is in the second end position.

Additionally or alternatively the sensor may be operable to determine whether the intermediate member is in the first end position.

As explained above, the second end position may correspond to a secured state of the box. Therefore, determining whether the intermediate member is in the first end position or not may be equivalent to determining whether or not the intermediate member is in the secured state.

The sensor may, for example, be operable to output a binary output signal. For example, the sensor may indicate whether the intermediate is either in the second end position or not. Alternatively, the sensor may be operable to output a signal that contains more information indicative of the position of the intermediate member.

It will be appreciated that determining whether the intermediate member is in the second end position may involve determining whether the intermediate member is in or close to the second end position, for example to within a measuring tolerance.

The box may further comprise a biasing mechanism arranged to bias the intermediate member towards the first end position.

As explained above, the second end position may correspond to a secured state of the box. Therefore, such an arrangement may bias the intermediate member towards the unsecured position.

The biasing mechanism may comprise: a first spring retaining feature provided on the intermediate member; a second spring retaining feature provided on the first member, or another member attached thereto; and a resilient member arranged between the first spring retaining feature and the second spring retaining feature.

The resilient member may be a spring, for example a compression spring. Alternatively the resilient member may comprise a resiliently deformable material such as, for example, rubber.

The first and second spring retaining features may be arranged to contact opposed ends of the resilient member such that when the intermediate member is engaged with the second portion of the back plate, or the other member attached thereto, the resilient member is retained between the first and second spring retaining features. The resilient member may extend in the axial direction.

The intermediate member may comprise a detection protrusion and the sensor is arranged to monitor a position of the detection protrusion relative to the first member.

The detection protrusion may extend in a direction that is generally perpendicular to the axial direction.

The first member, or another member attached thereto, may define an elongate slot arranged such that when the intermediate member is engaged with the first member, or another member attached thereto, the detection protrusion extends through the slot.

As the intermediate member moves relative to the first member the detection protrusion moves along the elongate slot.

The sensor may comprise a switch. For example, the switch may be a microswitch. The microswitch may be mounted on a printed circuit board. The elongate slot may be at least partially defined by the printed circuit board. The microswitch may be mounted adjacent to the elongate slot.

The intermediate member may comprise a main portion and a detection portion. The main portion may be connected to the detection portion by a connecting portion of a reduced thickness relative to the main portion and the detection portion.

The connection portion forms a relatively weak part of the intermediate member. Under application of external forces, the intermediate may therefore bend or fold at or around the connection portion.

The main portion may be arranged to engage with the second portion of the first member, or another member connected thereto, such that it can move relative to the second portion of the first member in the axial direction. The second aperture may be provided on the main portion.

The detection protrusion may be provided on the detection portion of the intermediate member.

For embodiments wherein movement of the intermediate member from the first end position to the second end position causes the intermediate member to engage with the first portion of the first member this engagement may be between the detection portion of the intermediate member and the first portion of the first member. The detection portion may therefore be arranged to cooperate with the first portion of the first member. To achieve this, the detection portion and the first portion of the first member may be provided with complementary engagement features.

According to a second aspect of the invention there is provided a box for a security alarm, the box comprising: a first member comprising a first portion and a second portion, the first portion for attachment to a surface, the first portion being connected to the second portion such that if the second portion is forced away from the first portion when the first member is attached to a mounting surface, the first and second portions of the first member separate; a second member for releasable cooperation with the first member, cooperation of the first member and the second member defining an internal volume and a first aperture for receipt of a securing member; an intermediate member, the intermediate member being movably connected to the second portion of the first member such that it can move relative to the first member between at least a secured position and an unsecured position; and a sensor connected to the second portion of the first member, the sensor being operable to monitor a position of the intermediate member relative to the second portion of the first member; wherein the intermediate member is arranged such that a securing member can extend through the first aperture and engage with the intermediate member so as to cause the intermediate member to move from relative to the first member between the secured position and the unsecured position; and wherein movement of the intermediate member from the unsecured position to the secured position causes the intermediate member to engage with the first portion of the first member.

The box according to the second aspect of the present invention is advantageous since it provides an arrangement with a means for detecting both: if a securing member of the box is being undone; and if the box is forcibly removed from a mounting surface, as now discussed.

The first member is secured to the second member by way of an engagement between a securing member (for example a screw) and the intermediate member. The sensor is operable to monitor a position of the intermediate member relative to the second portion of the first member. Any attempt is made to use the securing member to move the intermediate member to the unsecured position can be determined by the sensor. Therefore, the box according to the second invention provides a convenient antitamper arrangement whereby, using the sensor, it is possible to determine when the securing screw is being unscrewed, for example by a would-be intruder. Furthermore, if an attempt is made to detach the box from a mounting surface, for example by pulling the second member or the second portion of the first member away from the mounting surface, then the second portion of the first member will be forced away from the first portion of the first member. If the first portion is attached to the mounting surface, this will force the second portion of the first member away from the first portion of the first member. In turn, this will cause the first and second portions of the first member to separate. If an attempt is made to detach the box from a mounting surface when the intermediate portion is in the secured position then at least a portion of the intermediate potion will be forced away from the second portion of the first member. This can be determined by the sensor and, therefore, the box is provided with a means for detecting when the detector is forcibly removed from such a mounting surface.

The unsecured position may be referred to as a first end position. The secured position may be referred to as a second end position.

The movable connection of the intermediate member to the second portion of the first member may be such that it can move linearly relative to the first member. Additionally or alternatively, the movable connection of the intermediate member to the second portion of the first member may be such that it can rotate relative to the first member.

The movable connection of the intermediate member to the second portion of the first member may be such that it can move relative to the first member in an axial direction between at least the secured position and the unsecured position. The intermediate member may define a second aperture aligned with the first aperture. A line joining the first aperture and the second aperture may be generally parallel to the axial direction.

For such embodiments, the securing member can extend through the first aperture and engage with the intermediate member via the second aperture, so as to cause the intermediate member to move from relative to the first member along the axial direction. For example, since the second aperture is aligned with the first aperture, in use, a shank of a securing screw can pass through the first aperture and engage with the second aperture. Furthermore, since the line joining the first aperture and the second aperture is generally parallel to the axial direction, such engagement causes the intermediate member to move axially relative to the first member between the first end position and the second end position. In this way, the first member may be releasably secured to the second member by rotating the securing screw.

The sensor may be operable to determine whether the intermediate member is in the secured position.

Additionally or alternatively the sensor may be operable to determine whether the intermediate member is in the unsecured position.

The sensor may, for example, be operable to output a binary output signal. For example, the sensor may indicate whether the intermediate is either in the secured position or not. Alternatively, the sensor may be operable to output a signal that contains more information indicative of the position of the intermediate member.

It will be appreciated that determining whether the intermediate member is in the secured position may involve determining whether the intermediate member is in or close to the secured position, for example to within a measuring tolerance.

The box may further comprise a biasing mechanism arranged to bias the intermediate member towards the unsecured position.

The biasing mechanism may comprise: a first spring retaining feature provided on the intermediate member; a second spring retaining feature provided on the second portion of the first member, or another member attached thereto; and a resilient member arranged between the first spring retaining feature and the second spring retaining feature.

The intermediate member may comprise a detection protrusion and the sensor may be arranged to monitor a position of the detection protrusion relative to the second portion of the first member.

The second portion of the back plate, or another member attached thereto, may define an elongate slot arranged such that when the intermediate member is engaged with the second portion of the back plate, or another member attached thereto, the detection protrusion extends through the slot.

As the intermediate member moves relative to the second portion of the back plate the detection protrusion moves along the elongate slot.

The engagement between the intermediate member and the first portion of the first member may be achieved by engagement between the detection portion of the intermediate member and the first portion of the first member. The detection portion may therefore be arranged to cooperate with the first portion of the first member. To achieve this, the detection portion and the first portion of the first member may be provided with complementary engagement features.

According to a third aspect of the invention there is provided a detector comprising the box of first aspect of the invention or the box of the second aspect of the invention.

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

Figure 2 Figure 3 Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9 Figure 10

Figure 11

Figure 12A

Figure 12B

Figure 13A is a first perspective view of a detector according to an embodiment of the present invention which may form part of a security alarm system; is a second perspective view of the detector shown in Figure 1; is a third perspective view of the detector shown in Figures 1 and 2; is a perspective view of the detector shown in Figure 1 with the front cover removed;

is an exploded view of the detector shown in Figure 4 (with the front cover removed);

is an exploded view of an inner detector assembly that forms part of the detector shown in Figures 1 to 5;

is a first perspective view of an intermediate member that forms part of the inner detector assembly shown in Figures 5 and 6; is a second perspective view of the intermediate member shown in Figure 7;

is a side view of the intermediate member shown in Figures 7 and 8; is perspective view of the intermediate member shown in Figure 7 engaged with a securing screw and biasing spring;

is an exploded view of a back plate of the detector shown in Figures 1 to 3 and the intermediate member shown in Figures 7 to 9; is a first assembled perspective view of the back plate and the intermediate member shown in Figure 11 disposed in a first configuration;

is a second assembled perspective view of the back plate and the intermediate member shown in Figure 11 disposed in a first configuration;

is a first assembled perspective view of the back plate and the intermediate member shown in Figure 11 disposed in a second configuration;

Figure 13B

Figure 14

Figure 15A

Figure 16A

Figure 16B

Figure 17A

Figure 17B

Figure 18A

Figure 18B

Figure 19A

Figure 19B is a second assembled perspective view of the back plate and the intermediate member shown in Figure 11 disposed in a second configuration;

is a perspective view of a rear plate of a cartridge that forms part of the the inner detector assembly shown in Figures 5 and 6; is a rear view of the inner detector assembly shown in Figures 5 and 6 disposed in a first configuration;

is a rear view of the inner detector assembly shown in Figures 5 and 6 disposed in a second configuration;

is a first perspective view of the rear plate shown in Figure 14 and the intermediate member, securing screw and biasing spring shown in Figure 9 disposed in a first configuration;

is a first perspective view of the rear plate shown in Figure 14 and the intermediate member, securing screw and biasing spring shown in Figure 9 disposed in a second configuration;

is a second perspective view of the rear plate shown in Figure 14 and the intermediate member, securing screw and biasing spring shown in Figure 9 disposed in a first configuration;

is a second perspective view of the rear plate shown in Figure 14 and the intermediate member, securing screw and biasing spring shown in Figure 9 disposed in a second configuration;

shows the detector with the front cover removed as shown in Figure 4 with a front plate of the cartridge removed and disposed in a first configuration;

shows the detector with the front cover removed as shown in Figure 4 with a front plate of the cartridge removed and disposed in a second configuration;

is a cross sectional view of the detector shown in the previous figures disposed in a first configuration; and is a cross sectional view of the detector shown in the previous figures disposed in a second configuration.

Figures 1 to 3 shows three different perspective views of a detector 1 comprising a box according to an embodiment of the present invention. The detector 1 is a motion detector and may form part of a security alarm system. That is, the detector 1 may be connected (by a physical or wireless link) to a control panel of a security alarm system. It will be appreciated that the detector 1 may be any type of motion detector. The detector 1 may be a passive motion detector, for example the detector 1 may be a Passive Infrared Detector (“PIR”). Additionally or alternatively, the detector 1 may be an active motion detector 1, for example using microwave detection or an ultrasound detection. In one embodiment the detector 1 uses a combination of passive and active detection methods.

The box of the detector 1 comprises a back plate 2 and a cover 3. The back plate 2 may be referred to as a first member and the cover 3 may be referred to as a second member. The back plate 2 is for attachment to a mounting surface (for example a wall or similar structure). The cover 3 is arranged to releasably cooperate with the back plate 2, so as to define an internal volume. In this way, the cover 3 and the back plate 2 can cooperate to form a closed box. The internal volume is generally enclosed by this box however the cooperation between the cover 3 and back plate 2 defines a first aperture in the box. As will be described further below, the cover 3 may be secured to back plate 2 by way of a securing screw 4 via the first aperture.

As can be best seen in Figures 3, 5 and 11 the back plate 2 comprises two separate portions: a first portion 5 and a second portion 6. The first portion 5 is for attachment to the mounting surface. For this purpose, the first portion 5 is provided with four generally circular thin portions 7 through which a conventional screw may be driven so as to attach the first portion 5 to the mounting surface.

The first and second portions 5, 6 of the back plate 2 are two separate members which are arranged to mutually engage via an interference or friction fit. In this way, the first portion 5 can be releasably connected to the second portion 6 such that if the second portion 6 is forced away from the first portion 5 when the back plate 2 is attached to a mounting surface then the first and second portions 5, 6 of the first member separate. In particular, the first portion 5 remains attached to the mounting surface while the second portion 6 separates and moves away from the mounting surface.

The connection between the first and second portions 5, 6 therefore forms a relatively weak part of the back plate 2. Therefore, under application of external forces, the back plate 2 is arranged to break apart in a controlled manner.

The second portion 6 of the back plate 2 is provided with a plurality of thin portions 8 through which a conventional screw may be driven so as to attach the second portion 6 to the mounting surface. The second portion 6 of the back plate 2 is also provided with two frangible tabs 9. The frangible tabs can be removed from the second portion 6, for example by an installer, so as to form cable apertures in the back plate 2. In this way, one or more wires can be connected between internal components of the detector 1 to another device (for example the control panel of a security alarm system).

The cover 3 comprises a lens 10 and three light transmitting windows 11. The lens 10 is arranged to focus infrared radiation onto a sensor for the purposes of detecting movement within a field of view, in a conventional manner. The light transmitting windows 11 allow light to be emitted, for example via one or more light-emitting diodes (LEDs), from within the detector box in a conventional manner. In this way, information, for example relating a status of the detector, can be visually communicated to third parties.

Figures 4 and 5 show a perspective view and an exploded view of the detector 1 with the cover 3 removed respectively. As can be seen from these two Figures, the detector 1 comprises an inner detector assembly 12 that engages with the back plate 2, as now described. Figure 6 is an exploded view of the inner detector assembly 12.

The inner detector assembly 12 comprises an intermediate member 13, a washer 14, a spring 15 and a cartridge 16. In turn, the cartridge 16 comprises a back plate 17, a front plate 18 and a printed circuit board 19. The back plate 17 and front plate 18 are arranged to mutually engage, for example via a snap fit, an interference or friction fit, so as to form a generally enclosed volume. The back plate 17 and front plate 18 may therefore be considered to form a housing 17, 18. The printed circuit board 19 is housed within the generally enclosed volume formed by the back plate 17 and front plate 18.

Various views of the intermediate member 13 are shown in Figures 7 to 10. The intermediate member 13 comprises a main portion 25 and a detection portion 26. The main portion 25 is connected to the detection portion 26 by a connecting portion 27 of a reduced thickness relative to the main portion 25 and the detection portion 26. The connection portion 26 forms a relatively weak part of the intermediate member 13. Under application of external forces, the intermediate 13 may therefore bend or fold at or around the connection portion 26, as described further below.

As described in more detail below, the main portion 25 is arranged to engage with the back plate 17 of the cartridge 16, such that it can move relative to the back plate 17 in an axial direction 28. The cartridge 16 is connected to the second portion 6 of back plate 2. In this way, the intermediate member 13 is movably connected to the back plate 6 such that it can move relative to the back plate 2 in the axial direction 28 between at least a first end position and a second end position. This connection is achieved indirectly, via the housing 17, 18 of the cartridge 16. The housing 17, 18 of the cartridge 16 may therefore be referred to as a second intermediate member.

The first end position corresponds to an unsecured state of the detector 1 and the second end position corresponds to a secured state of the detector 1. It will be appreciated that unless otherwise stated, the term axial direction is intended to refer to a direction along, or parallel, the direction along which the intermediate member 13 can move relative to the back plate 2 and/or the cartridge 16.

The detection portion 26 of the intermediate member 13 is arranged to engage with the first portion 5 of the back plate 2, as now described with reference to Figures 11 to 13B. To achieve this engagement, the detection portion 26 of the intermediate member 13 and the first portion 5 of the back plate 2 are provided with mutually engagable features. In particular, the first portion 5 of the back plate 2 comprises two protrusions 29 that extend from an interior surface of the first portion 5 into the interior of the detector 1. The protrusions 29 are shaped such that, together with the interior surface of the first portion 5, they each define a recess 30. The detection portion 26 of the intermediate member 13 comprises two side portions 31.

In use, each of the two side portions 31 detection portion 26 of the intermediate member 13 can be slid into a corresponding one or the two recesses 30 on the first portion 5 of the back plate 2. This is achieved by sliding the intermediate member 13 in the axial direction 28 relative to the back plate 2 (see Figures 12A-13B). Figures 12A and 12B show the intermediate member 13 disposed in a first position with the two side portions 31 of the detection portion 26 of the intermediate member 13 aligned with the corresponding recesses 30 on the first portion 5 of the back plate 2. Figures 13A and 13B show the intermediate member 13 disposed in a second position (once it has been moved in the axial direction 28 relative to the back plate 2) with the two side portions 31 of the detection portion 26 of the intermediate member 13 received within the corresponding recesses 30 on the first portion 5 of the back plate 2.

Therefore, in use, movement of the intermediate member 13 from the first end position to the second end position causes the intermediate member 13 to engage with the first portion 5 of the first member 2.

When the intermediate member 13 is disposed in the second position (see Figures 13A and 13B), the intermediate member 13 is engaged with the first portion 5 of the back plate 2. This engagement prevents the intermediate member 13 from moving away from the first portion 5 of the back plate 2 (i.e. movement in a direction 32 perpendicular to the axial direction 28). In order to disengage the intermediate member 13 from the first portion 5 of the back plate 2, the intermediate member 13 should be moved along the axial direction 28 back towards the first position.

It will be appreciated that the side portions 31 and protrusions 29 only form a single example of mutually engagable features that can facilitate engagement between the intermediate member 13 and the first portion 5 of the back plate 2. Other embodiments may comprise different forms of such mutually engagable features.

The main portion 25 of the intermediate member 13 is arranged to engage with the back plate 17 of the cartridge 16, such that it can move relative to the back plate 17 in an axial direction 28, as is now described with reference to Figures 14 to 17B.

An exterior surface of the back plate 17 is provided with a first guide 35 and a second guide 36.

The first guide 35 comprises three protrusions 37, 38, 39 that extend from the exterior surface of the back plate 17. Each of the three protrusions 37, 38, 39 is generally Lshaped in cross section. The three protrusions 37, 38, 39 are aligned so as to form a first channel, the first channel being formed between the exterior surface of the back plate 17 and the protrusions 37, 38, 39 of the first guide member 35.

Similarly, the second guide 36 comprises three protrusions 40, 41,42 that extend from the exterior surface of the back plate 17. Each of the three protrusions 40, 41, 42 is generally L-shaped in cross section. The three protrusions 40, 41,42 are aligned so as to form a second channel, the second channel being formed between the exterior surface of the back plate 17 and the protrusions 40, 41, 42 of the first guide member

36.

The first and second channels face each other.

Optionally, a generally rectangular aperture 45 may be provided in the back plate 17 below each of the three protrusions 37, 38, 39 of the first guide 35 and each of the three protrusions 40, 41,42 of the second guide 36. This may aid in the forming of the back plate 17 by injection moulding.

The back plate 17 further comprises a generally half cylinder first recess 46. A first spring retaining feature 47 is provided at one end of the first recess 46. Similarly, the main portion 25 of the intermediate member 13 comprises a generally half cylinder second recess 48. A second spring retaining feature 49 is provided at one end of the second recess 48. In use, the compression spring 15 is partially received within the first recess 46 and partially received within the second recess 48. Furthermore, the compression spring 15 is retained between the first retaining feature 47 and the second retaining feature 49.

The main portion 25 of the intermediate member 13 comprises an elongate, generally rectangular body with first and second opposed longer sides 50, 51 and first and second opposed shorter sides 52, 53. In use, a portion of the main portion 25 of the intermediate member 13 proximate to the first longer side 50 is received in the channel defined by the first guide 35 and a portion of the main portion 25 of the intermediate member 13 proximate to the second longer side 51 is received in the channel defined by the second guide 36.

In order to facilitate engagement of the intermediate member 13 and the back plate 17, each of the first and second longer sides 50, 51 of the main portion 25 are provided with a plurality of recesses 55 formed between discrete sections 56 of the main portion

25. In order to engage the intermediate member 13 with the back plate 17, the intermediate member 13 is offered up to the back plate 17 such that the recesses 55 on the first longer side 50 are generally aligned with the three protrusions 37, 38, 39 of the first guide 35 and recesses 55 on the second longer side 51 are generally aligned with the three protrusions 40, 41, 42 of the second guide 36. Subsequently, the intermediate member 13 is pushed towards the back plate 17.

As the intermediate member 13 is pushed towards the back plate 17 the first spring retaining feature 47 is received in the second recess 48 and the second spring retaining feature 49 is received in the first recess 46.

The spring may be inserted into the first recess 46 or the second recess 48 before the intermediate member 13 and the back plate 17 are brought into engagement. In order to achieve this engagement, the spring 15 is compressed such that the intermediate member 13 can offered up to the back plate 17 with the recesses 55 on the first longer side 50 are generally aligned with the three protrusions 37, 38, 39 of the first guide 35 and the recesses 55 on the second longer side 51 generally aligned with the three protrusions 40, 41,42 of the second guide 36.

Alternatively, the spring 15 may be inserted into a cavity formed by the first recess 46 and the second recess 48 via a window 57 provided in a wall of the second recess 48 once the intermediate member 13 and the back plate 17 have been brought into engagement.

When disposed in this engaged arrangement, the intermediate member 13 can move linearly in the axial direction 28 so that the discrete sections 56 of the main portion 25 are received in the channels formed by the first and second guides 35, 36. Such linear movement of the intermediate member 13 is achieved by the application of an actuating force. In this way, the intermediate member 13 is slidably connected to the back plate 17 such that it can move linearly relative to the back 17 plate between at least the first position (as shown in Figures 15A, 16A and 17A) and the second position (as shown in Figures 15B, 16B and 17B).

As the intermediate member 13 moves linearly towards the second positon, the spring 15 is compressed between the first and second spring retaining features 47, 49. Once the actuating force is removed, the compression spring 15 will expand, which will return the intermediate member 13 to the first position. The compression spring 15, the first spring retaining feature 47 and the second spring retaining feature 49 may be considered to form a biasing mechanism that biases the intermediate member 13 to the first positon. The compression spring 15 may be referred to as a biasing member.

The main portion 25 of the intermediate member 13 is generally of the form of a rectangular plate. At the second shorter side 53 of the main portion 25 of the intermediate member 13, the main portion is provided with a flange 60 that extends away from the generally rectangular plate of the main portion 25 in the direction 32 that is perpendicular to the axial direction.

On the flange 60, the intermediate member 13 defines a second aperture 61. The flange 60 further defines a recess 62 for receipt of the washer 14. The washer 14 defines an aperture 63. When the washer 14 is received in the recess 62, the aperture 63 is aligned with the second aperture 61. The washer 14 may be considered to form part of the intermediate member 13. Therefore, the aperture 63 defined by the washer 14 may be considered to be part of a second aperture defined by the intermediate member 13.

In use, the securing screw 4 engages with the second aperture 61 and/or the aperture 63 defined by the washer 14. In order to allow this, the second aperture 61 and the aperture 63 defined by the washer 14 are aligned with the first aperture (as defined by the cooperation between the cover 3 and back plate 2). Furthermore, a line joining the first aperture and the second aperture 61 and the aperture 63 defined by the washer 14 is generally parallel to the axial direction 28.

The intermediate member 13 further comprises a detection protrusion 65, provided on the detection portion 26. The detection protrusion 65 extends in the direction 32 that is perpendicular to the axial direction 28.

The back plate 17 of the cartridge 16 defines an elongate slot 66. Similarly, the printed circuit board 19 defines an elongate slot 67. When the intermediate member 13 is engaged with the back plate 17, the detection protrusion 65 extends through the slot 66 in the back plate 17 and the slot 67 in the printed circuit board. As the intermediate member 13 moves relative to the back plate 17 along the axial direction 28 the detection protrusion 65 moves along the elongate slots 66, 67. A micro-switch 68 is attached to the printed circuit board 19 adjacent to the elongate slot 66. The microswitch 68 is provided with an actuator 69 which is arranged to close the switch as the detection protrusion 65 moves along the elongate slot 67 from the first position to the second position.

The micro-switch 68 is therefore arranged to monitor a position of the intermediate member 13 relative to cartridge 16. Since the cartridge 16 is connected to the back plate 2, the micro-switch 68 is therefore arranged to monitor a position of the intermediate member 13 relative to cartridge 16. Note that the micro-switch is therefore connected to the back plate 2 indirectly, via the housing 17, 18 of the cartridge 16. The micro-switch 68 is, in particular, arranged to determine whether the intermediate member 13 is in, or close to, the second (secured) position. The microswitch 68 may therefore be considered to be a sensor that is operable to monitor a position of the intermediate member 13 relative to the back plate 2.

The micro-switch 68 is a push-to-make switch with the actuator 69 being biased to the open state.

The printed circuit board 19 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 or type of detector 1.

The above-described detector 1 has a number of advantages, as now described.

The cover 3 can be releasably secured to the back plate 2 using the securing screw 4. In order to achieve this, the shank of the securing screw 4 is inserted into the first aperture (as defined by the cooperation between the cover 3 and back plate 2) and screwed into the box. As the securing screw 4 is screwed into the box the shank of the securing screw moves into the box along the axial direction 28 it engages with and paces through the second aperture 61 and/or the aperture 63 defined by the washer 14. The screw engages with the second aperture 61 and/or the aperture 63 defined by the washer 14. The detector 1 may be provided to an installer with the screw already engaged with, and held captive by, the washer 14.

When the distal end of the securing screw 4 contacts the cartridge 16 its axial movement into the box stops. As the securing screw 4 is further rotated, the engagement between the securing screw 17 and intermediate member 13 (optionally via the washer 14) causes the intermediate member 13 to move axially relative to the back plate 2 from the first end position to the second end position.

As it does so, the detection protrusion 65 moves along the elongate slot 67 defined by the printed circuit board 19. As the intermediate member 13 approaches the second end position the detection protrusion contacts the actuator 69 of the micro-switch 68. This closes the micro-switch 68.

If an attempt is made to gain access to the interior of the detector 1 by unscrewing the securing screw 4, the engagement between the securing screw 17 and intermediate member 13 causes the intermediate member 13 to move axially relative to the back plate 2 from the second position to the first position. This causes the detection protrusion 65 to moves along the elongate slot 67 defined by the printed circuit board 19. As the intermediate member 13 moves away from the second position the detection protrusion 65 moves clear of the actuator 69 of the micro-switch 68 and the micro-switch 68 opens.

Therefore, the detector 1 provides a convenient anti-tamper arrangement whereby, using the micro-switch 68, it is possible to determine when the securing screw 4 is being unscrewed, for example by a would-be intruder.

Furthermore, the detector 1 also provides an improved anti-tamper arrangement whereby, using the micro-switch 68, it is also possible to determine when the detector is forcibly removed from a mounting surface, as now discussed.

If an attempt is made to detach the detector 1 from a mounting surface, for example by pulling the cover 3 or the second portion 6 of the back plate 2 away from the mounting surface, the second portion 6 of the back plate 2 will be forced away from the first portion 5 of the back plate 2. Note that the first portion 5 of the back plate 2 is, in use, generally inaccessible since it is disposed against the mounting surface. Since the first portion 5 is attached to the mounting surface, this will force the second portion 6 away from the first portion 5. In turn, this will cause the first and second portions 5, 6 of the back plate 2 to separate. Note that separation of the first and second portions 5, 6 of the back plate 2 is achieved by movement of the first portion 5 relative to the second portion in the direction 32 that is generally perpendicular to the axial direction 28.

Since the detection portion 26 of the intermediate member 13 is engaged with the first portion 5 of the back plate 2, the detection portion 26 of the intermediate member 13 is forced away from the main portion 25 of the intermediate member 13 in the direction 32 perpendicular to the axial direction. This causes the intermediate member 13 to bend or fold at or around the connection portion 27. As the detection portion 26 of the intermediate member 13 is forced away from the main portion 25 of the intermediate member 13, the detection protrusion 65 is pulled out of the slot 67 defined by the printed circuit board 19. As detection protrusion 65 is pulled out of the slot 67 the detection protrusion 65 moves clear of the actuator 69 of the micro-switch 68 and the micro-switch 68 opens.

Therefore, the detector 1 provides a convenient anti-tamper arrangement whereby, using the micro-switch 68, it is also possible to determine when the detector 1 is forcibly removed from a mounting surface, for example by a would-be intruder.

Any or all of the following components may be formed from a plastics material: the first and second portions 5, 6 of the back plate 2, the cover 3, the intermediate member 13 and the back plate 17 and the front plate 18 of the cartridge 16. The plastics material may comprise any of: such as, polycarbonate, acrylonitrile butadiene styrene (ABS), acrylic styrene acrylonitrile (ASA) or polyoxymethylene (acetal). Advantageously, such materials are durable and are not susceptible to corrosion or rusting and therefore do not need to be replaced. These components may be formed in any conventional manner, for example by injection moulding.

Although in the above described embodiment, the first and second portions 5, 6 of the back plate 2 are two separate members which are arranged to mutually engage via an interference or friction fit, in an alternative embodiment, the back plate may comprise first and second portions that are formed from a single member. For such embodiments the first and second portions may be connected via one or more frangible portions (for example one or more tabs of reduced thickness) that form the weakest portion of the first member. Such an arrangement may reduce the number of parts and therefore the manufacturing costs of the detector. However, with such embodiments, once separated the first and second portions 5, 6 cannot be reconnected (as they can be with the above described embodiment).

Although in the above described embodiment, a micro-switch 67 is used to monitor a position of the intermediate member 13 relative to the back plate 2, in alternative embodiments other sensors of detectors may alternatively be used. The micro-switch 67 provides a simple arrangement with a binary output (the position of the intermediate member 13 being determined to be either in a secured position or an unsecured position. Alternative embodiments may allow the position of the intermediate member 13 being determined to be in one of a greater number of discrete positions or, alternatively in a range of generally continuous positions.

When the intermediate member 13 is disposed in the first (unsecured) position the detector 1, inner detector assembly 12 and intermediate member 13 may each be considered to be disposed in a first configuration. When the intermediate member 13 is disposed in the second (secured) position the detector 1, inner detector assembly 12 and intermediate member 13 may each be considered to be disposed in a second configuration.

Although in the above described embodiment the back plate 2 comprises two separate portions (first portion 5 and second portion 6) that are arranged to separate upon application of a suitable force, in some alternative embodiments, the back plate 2 may be formed from a single portion. Such embodiments do not provide an anti-tamper arrangement whereby it is possible to determine when the detector 1 is forcibly removed from a mounting surface. However, they do still enjoy the benefit of the antitamper arrangement whereby it is possible to determine when the securing screw 4 is being unscrewed, for example by a would-be intruder. For such embodiments, the intermediate member 13 may or may not be arranged to engage with the back plate as it moves between the first and second positions.

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;

a sensor connected to the first member;

a second member for releasable cooperation with the first member, cooperation of the first member and the second member defining an internal volume and a first aperture; and an intermediate member, the intermediate member being movably connected to the first member such that it can move relative to the first member in an axial direction between at least a first end position and a second end position;

wherein the intermediate member defines a second aperture aligned with the first aperture, wherein a line joining the first aperture and the second aperture is generally parallel to the axial direction; and wherein the sensor is operable to monitor a position of the intermediate member relative to the first member.

2. The box of claim 1 wherein the first member comprises a first portion and a second portion, the first portion for attachment to a surface, the first portion being connected to the second portion such that if the second portion is forced away from the first portion when the first member is attached to a mounting surface then the first and second portions of the first member separate and wherein movement of the intermediate member from the first end position to the second end position causes the intermediate member to engage with the first portion of the first member.

3. The box of claim 2 wherein the first member is arranged such that separation of the first and second portions of the first member is achieved by movement of the first portion of the first member relative to the second portion of the first member in direction that is generally perpendicular to the axial direction.

4. The box of any preceding claim further comprising a second intermediate member engagable with the second portion of the first member.

5. The box of claim 4 wherein the sensor is connected to the second intermediate member.

6. The box of claim 4 or claim 5 wherein the intermediate member is movably connected to the second intermediate member.

7. The box of any preceding claim wherein the sensor is operable to determine whether the intermediate member is in the second end position.

8. The box of any preceding claim further comprising a biasing mechanism arranged to bias the intermediate member towards the first end position.

9. The box of claim 8 wherein the biasing mechanism comprises: a first spring retaining feature provided on the intermediate member; a second spring retaining feature provided on the first member, or another member attached thereto; and a resilient member arranged between the first spring retaining feature and the second spring retaining feature.

10. The box of any preceding claim wherein the intermediate member comprises a detection protrusion and the sensor is arranged to monitor a position of the detection protrusion relative to the first member.

11. The box of claim 10 wherein the detection protrusion extends in a direction that is generally perpendicular to the axial direction.

12. The box of claim 10 or claim 11 wherein the first member, or another member attached thereto, defines an elongate slot arranged such that when the intermediate member is engaged with the first member, or another member attached thereto, the detection protrusion extends through the slot.

13. The box of any preceding claim wherein the sensor comprises a switch.

14. The box or any preceding claim wherein the intermediate member comprises a main portion and a detection portion, the main portion being connected to the detection portion by a connecting portion of a reduced thickness relative to the main portion and the detection portion.

15. A box for a security alarm, the box comprising:

a first member comprising a first portion and a second portion, the first portion for attachment to a surface, the first portion being connected to the second portion such that if the second portion is forced away from the first portion when the first member is attached to a mounting surface, the first and second portions of the first member separate;

a second member for releasable cooperation with the first member, cooperation of the first member and the second member defining an internal volume and a first aperture for receipt of a securing member;

an intermediate member, the intermediate member being movably connected to the second portion of the first member such that it can move relative to the first member between at least a secured position and an unsecured position; and a sensor connected to the second portion of the first member, the sensor being operable to monitor a position of the intermediate member relative to the second portion of the first member;

wherein the intermediate member is arranged such that a securing member can extend through the first aperture and engage with the intermediate member so as to cause the intermediate member to move from relative to the first member between the secured position and the unsecured position; and wherein movement of the intermediate member from the unsecured position to the secured position causes the intermediate member to engage with the first portion of the first member.

16. The box of claim 15 wherein the movable connection of the intermediate member to the second portion of the first member is such that it can move relative to the first member in an axial direction between at least the secured position and the unsecured position, wherein the intermediate member defines a second aperture aligned with the first aperture, and wherein a line joining the first aperture and the second aperture is generally parallel to the axial direction.

17. The box of claim 16 wherein the first member is arranged such that separation of the first and second portions of the first member is achieved by movement of the first portion of the first member relative to the second portion of the first member in direction that is generally perpendicular to the axial direction.

18. The box of any one of claims 15 to 17 further comprising a second intermediate member engagable with the second portion of the first member.

19. The box of claim 18 wherein the sensor is connected to the second intermediate member.

20. The box of claim 18 or claim 19 wherein the intermediate member is movably connected to the second intermediate member.

21. The box of any one of claims 15 to 20 wherein the sensor is operable to determine whether the intermediate member is in the secured position.

22. The box of any one of claims 15 to 21 further comprising a biasing mechanism arranged to bias the intermediate member towards the unsecured position.

23. The box of claim 22 wherein the biasing mechanism comprises: a first spring retaining feature provided on the intermediate member; a second spring retaining feature provided on the second portion of the first member, or another member attached thereto; and a resilient member arranged between the first spring retaining feature and the second spring retaining feature.

24. The box of any one of claims 15 to 23 wherein the intermediate member comprises a detection protrusion and the sensor is arranged to monitor a position of the detection protrusion relative to the second portion of the first member.

25. The box of claim 24 when dependent either directly or indirectly on claim 16 wherein the detection protrusion extends in a direction that is generally perpendicular to the axial direction.

26. The box of claim 24 or claim 25 wherein the second portion of the back plate, or another member attached thereto, defines an elongate slot arranged such that when the intermediate member is engaged with the second portion of the back plate, or another member attached thereto, the detection protrusion extends through the slot.

27. The box of any one of claims 15 to 26 wherein the sensor comprises a switch.

28. The box of any one of claims 15 to 27 wherein the intermediate member comprises a main portion and a detection portion, the main portion being connected to the detection portion by a connecting portion of a reduced thickness relative to the

5 main portion and the detection portion.

29. A detector comprising the box of any preceding claim.

Intellectual

Property

Office

Application No: GB1614472.7