GB2436883A

GB2436883A - Hinged cover for wall mounted alarm unit

Info

Publication number: GB2436883A
Application number: GB0606792A
Authority: GB
Inventors: Nigel Mills; Ben Edmonds; George Hines
Original assignee: ELMDENE INTERNAT Ltd
Current assignee: ELMDENE INTERNAT Ltd
Priority date: 2006-04-03
Filing date: 2006-04-03
Publication date: 2007-10-10
Anticipated expiration: 2026-04-03
Also published as: GB0606792D0; GB2436883B

Abstract

An alarm unit is provided for attachment to a wall surface. The alarm unit includes a back plate and a plastic outer cover. The cover is attached to the back plate by a hinge. The hinge has an orientation such that when the alarm unit is attached to a wall surface, hinged movement of the cover away from the back plate is assisted by gravity. The cover may be retained in position against the back plate by one or more screws which may be provided with a sliding cover.

Description

2436883

ALARM UNIT

5 Field of the Invention

The present invention relates to alarm systems, such as intruder and security alarms for buildings and fire alarms.

10 Background of the Invention

Security and intruder alarms for buildings and other premises are often placed for security reasons in locations that are visible but comparatively inaccessible, typically relatively high up a wall in an exposed location. The height of the alarm 15 usually requires a ladder for access, and the exposed location ensures that anyone attempting to gain such access may be readily seen. However, locating an alarm in such a position also makes it more difficult for legitimate operations to be performed on the alarm, for example, installation, maintenance, and servicing. In addition, the exposed location of an alarm means that both the visual appearance and weather-20 proofing of the alarm may be important concerns.

Summary of the Invention

One embodiment of the invention provides an alarm unit for attachment to a 25 wall surface or other similar structure (e.g. a fence, a post, etc). The alarm unit includes a back plate and an outer cover. The cover is attached to the back plate by a hinge. The hinge has an orientation such that when the alarm unit is attached to a wall surface, hinged movement of the cover away from the back plate is assisted by gravity.

30 Conventional alarm units generally retain their outer cover against the back plate using screws, clips, or other such mechanical fixings. Using a hinge instead has

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the advantage that when an engineer is working on the alarm unit, often up a ladder, they can gain access to the alarm unit without having to fully detach the cover from the back plate. This then avoids the engineer having to decide what to do with the cover while working on the alarm (such as balancing it on the ladder, dropping it to the 5 ground etc).

The centre of mass of the cover is lower when the cover is open than when the cover is closed. Consequently, opening the cover away from the back plate is assisted by gravity, which also tends to hold the cover in the open position. This is helpful 10 compared to having the cover open sideways (for example), in which case the cover is more vulnerable to being blown shut by wind.

In one embodiment, rotation of the cover away from the back plate is limited to a maximum angle. This avoids the cover rotating open too far and banging into the 15 wall, which might cause damage to the cover itself and/or the wall. The maximum angle may be determined by balancing various factors. Thus the cover must open far enough to give good access to the alarm unit. In general this implies opening at least 90 degrees or more. In addition, it can also be helpful to have the cover approximately horizontal, i.e. an opening of roughly 90 degrees, since this then allows the cover to be 20 used as a tray for holding tools or other parts of the alarm (see below). On the other hand, the open cover must not protrude so far that it makes it difficult for an engineer to access the alarm unit. This generally implies opening somewhat more than 90 degrees, thereby bringing the cover back towards the wall and so out of the way of an engineer. The significance of this factor depends on the absolute size of the cover; for 25 example, a cover which is only 20cm across will be much easier to work around than a cover which is 60cm across (say). (Note that both the height and width of the cover are important in this respect). On balance, the maximum angle of rotation may be in the range 100 to 180 degrees, or more preferably in the range 100 to 140 degrees.

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In one particular embodiment, the maximum angle of rotation of the cover away from the back plate is determined by the cover abutting the back plate on the opposite side of the hinge from the main portion of the cover and back plate. In particular, the back plate includes a recess for receiving the cover on the opposite side 5 of the hinge, and further rotation of the cover is prevented when the cover reaches the end of this recess. The skilled person will be aware of various other potential mechanisms for limiting rotation of the cover, for example by using a flexible cord that links the cover to the back plate. Such cord (or cords) would be loose when the cover is closed, and extend taut when the cover is rotated open to its maximum angle.

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The hinge may be formed using any appropriate structure to provide a rotational opening for the cover. For example, the hinge may comprise a pair of moulded pins located in respective moulded pivot holes. In one particular implementation, the moulded pins are located on the cover, and these engage a pair of

15 corresponding moulded holes on the back plate (or alternatively, the pins may be located on the back plate and the holes on the cover). Such an arrangement provides for a rapid and convenient assembly without requiring any additional parts (such as a separate hinge unit, as used for conventional doors).

20 In one implementation, the alarm unit further includes one or more retaining clips that engage when the cover is rotated shut onto the back plate and that disengage when the cover is rotated away from the back plate. Such clips do not prevent rotation to open or close the cover, but they do protect the cover against any attempt to prise or pull the cover directly away from the back plate.

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In one embodiment, the alarm unit further comprises an inner cover inside the outer cover. The inner and outer covers may be made of metal and plastic respectively (or any other suitable materials). The outer cover includes one or more parking locators for holding the inner cover when the inner cover is separated from the back

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plate. This is convenient for an engineer, who would otherwise have to hold the inner cover (or find some other convenient location for it).

In one embodiment, the cover is retained against the back plate by one or more 5 screws, and a sliding cover is provided for at least one of the screws. The sliding cover helps to protect the screw from weathering (e.g. rusting) and dirt, and also enhances the visual appearance of the alarm. (It may also make it slightly more difficult for an adversary to gain access to the alarm, especially in the dark). In either position (whether covering the screw or not), the sliding cover is held in the alarm unit, 10 thereby ensuing that the sliding cover is not dropped or otherwise lost.

In one implementation, the back plate includes one or more channels that run parallel to the sliding direction of the sliding cover, and the sliding cover includes one or more fins. Each fin extends into a corresponding channel to guide the motion of the 15 sliding cover. At least one of the fins may be provided with a retaining foot that engages the back plate to prevent removal of the sliding cover in a direction perpendicular to the sliding direction. In addition, at least one of the channels may be provided with open ends to prevent a build-up of dirt or other material in the channel (which might then inhibit easy opening of the sliding cover).

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Another embodiment of the invention provides a method of opening an alarm unit attached to a wall surface. The alarm unit includes a back plate and a cover. The cover is attached to the back plate by a hinge. The method comprises rotating the cover away from the back plate. The hinge has an orientation such that hinged 25 movement of the cover away from the back plate is assisted by gravity.

Another embodiment of the invention provides an alarm unit for attachment to a wall surface. The alarm unit includes a back plate and an outer cover. The outer cover is attached to the back plate by at least one screw. The alarm unit further 30 includes a cover for at least one of the screws. The screw cover is operable to slide

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between a first position that covers a screw and a second position that exposes the screw. The sliding cover is attached to the alarm unit in both the first and second positions.

5 Brief Description of the Drawings

Various embodiments of the invention will now be described in detail by way of example only with reference to the following drawings:

Figure 1 is a front view of an alarm unit in accordance with one embodiment of 10 the invention with the cover open;

Figure 2 is a side view of an alarm unit in accordance with one embodiment of the invention with the cover open;

Figure 3 is an isometric view of an alarm unit in accordance with one embodiment of the invention with the cover open;

15 Figure 4 is a rear view of an alarm unit in accordance with one embodiment of the invention with the cover closed; and

Figure 5 is an isometric view of an alarm unit in accordance with one embodiment of the invention with the main cover closed but the screw cover open.

20 Detailed Description

Figures 1-5 illustrate an alarm unit 10 in accordance with one embodiment of the invention. Alarm unit 10 may represent a security or intruder alarm, a fire alarm, or any other such device. Alarm unit 10 is generally installed on the internal or 25 external wall of a building, but may also be installed on any other suitable,

substantially vertical, structure, such as a wall, a fence, a post, and so on.

The alarm unit 10 comprises two main components, a back plate 15 and a cover 20. The back plate 15 and cover 20 may be made of moulded plastic or any other 30 suitable material. The back plate 15 supports various components that allow the alarm

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to perform its function, such as a power unit and a siren. Although these components are shown in the Figures, they are conventional and will not be described further, since they are not directly relevant for an understanding of the present invention. In addition, it will be appreciated that these components may vary from one embodiment 5 to another.

The back plate 15 is attached in a substantially vertical orientation to a wall or other appropriate structure (not shown in the Figures). The cover 20 is attached to the base plate 15 by a hinge 30. Figures 4 and 5 show the alarm unit 10 with the cover 20 10 closed, while Figures 1, 2 and 3 show the alarm unit 10 with the cover 20 open, in other words rotated about the hinge 30 away from the back plate 15. It will be appreciated that the open configuration of Figures 1, 2 and 3 allows access to the back plate 15, for example for installation or maintenance of the alarm unit. However, in general the cover 20 is located in its closed position to provide the back plate with 15 protection against the weather, tampering, and so on.

The cover 20 includes a tab 50 that is provided with a screw hole 55. When the cover is rotated to its closed position, tab 50 abuts a corresponding tab 40 on the back plate 15. Tab 40 includes a hole 45 that is aligned with hole 55 when the cover is in 20 the closed position. The hole 45 receives a fixing screw (not shown) that passes through hole 55 in tab 50 to retain the cover in its closed position.

In one embodiment, the hole is provided with a thread in the plastic to receive the fixing screw, while in another embodiment, a self-tapping screw may be used. In 25 another embodiment, a nut for receiving the screw is moulded into the back plate 15 around hole 45. The nut is held in position, and this prevents any movement or rotation of the nut. In this way, a service engineer may open the cover 20 away from the back plate 15 without having to worry about holding or potential loss of the nut. In another embodiment, a cage (not shown in the Figures) for holding a retaining nut is

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located behind tab 40 - i.e. between tab 40 and the wall or other structure to which back plate 15 is attached.

In some embodiments, the fixing screw used to hold the cover 20 against the 5 back plate 15 can rotate within hole 55 but cannot completely pass through it. In this way, even when the cover is opened, the screw remains located within tab 50. This avoids the risk of the screw being lost by an engineer when opening the alarm unit. In one particular embodiment, this is achieved by having the fixing screw slightly larger than hole 55. Consequently, when the fixing screw is first engaged to hold the cover 10 20 against the back plate, it forms a thread in the plastic cover within hole 55. This thread then serves to retain the fixing screw within hole 55, even when the cover is opened away from the back plate.

Conventional alarm units generally have a cover that is completely detachable. 15 In contrast, alarm unit 10 has a hinge 30 to attach the cover 20 to the back plate 15. Accordingly, the cover may be opened to provide access to back plate 15 without having to detach the cover fully from the back plate. This has the advantage that an engineer, who may be working up a ladder, does not have to worry about where to place the cover while working on the back plate. For example, there is no temptation 20 to try balance the cover on the ladder or some portion of the building, or to throw the cover down to the ground from the ladder.

Hinge 30 has a horizontal orientation and is arranged so that the centre of gravity of the cover 20 is lower when the cover is in the open position than when the 25 cover is in the closed position. Consequently, when the cover is open, the force of gravity helps to retain the cover in the open position, and so helps to resist any movement of the cover that might otherwise occur. For example, if the hinge had a vertical orientation to allow the cover to move in a horizontal plane, the wind might blow the cover open or shut.

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In other embodiments, the rotation axis may have both horizontal and vertical components. For example, in one embodiment, the triangular shape of alarm unit 10 might be inverted (compared to that shown in the Figures), so that the point of the alarm unit triangle points upwards rather than downwards, with the hinge being 5 provided on one of the sides extending diagonally downwards. One advantage of such a diagonal orientation for the rotation axis is that when the cover opens, it moves sideways away from the back plate (in addition to the downwards movement). This may then allow easier access to the back plate 15, especially for an engineer working from a ladder. Such a diagonal rotation axis might also arise (for example) with 10 respect to a diamond, hexagonal, octagonal, or circular shape for alarm unit 10 (or for any other appropriate shape).

In one embodiment, hinge 30 is located within the alarm unit 10. (This is in contrast to an external type of hinge, which is frequently used for door fittings). In 15 addition to aesthetic considerations, having an internal hinge helps to protect hinge 30 against weathering and potential tampering.

In one embodiment, hinge 30 is formed from a pair of lugs 60 attached to cover 20. Each lug is provided with a hole, such that the alignment of the pair of holes 20 defines the axis rotation of the hinge. The back plate 15 is provided with a pair of pins 65, one for each lug 60. Each pin is received into the hole of a corresponding lug 60. The pins may have a circular cross-section or any other appropriate cross-section to occupy the holes in lugs 60. In one particular embodiment, the pins have a cross-shaped cross-section, whereby the arms of the cross extend across the diameter of the 25 hole. The lugs 60 are formed as part of the moulded plastic of the cover, while the pins 65 are formed as part of the moulded plastic of the back plate 15. Accordingly, hinge 30 does not require any additional parts beyond the cover 20 and back plate 15.

The skilled person will be aware of many other potential designs for hinge 30. 30 For example, the cover 20 may be provided with pins that are received into

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corresponding holes provided on the back plate 15. Another possibility would be to provide a separate axle, with both cover 20 and back plate 15 able to rotate about the axle. Thus hinge 30 may comprise any mechanism that permits the desired rotational movement between cover 20 and back plate 15.

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As can be seen most easily in Figure 2, rotation of the cover 20 away from the back plate 15 about hinge 30 is limited to a maximum angle. In particular, the back plate is provided with a ledge 90 that defines a recess 92. The cover 20 includes a portion 95 on the opposite side of the hinge 30 to the main body of the cover. This 10 cover portion 95 rotates into recess 92 when the cover is opened, with the maximum angle of rotation being reached when the cover portion 95 abuts against the wall of recess 92 and ledge 90. Limiting rotation of the cover 20 in this manner avoids the risk of cover 20 swinging freely when opening, which might potentially cause damage if the cover then bangs into a wall or other support structure for back plate 15. The 15 skilled person will be aware of various other potential mechanisms for preventing rotation of the cover past the maximum opening angle, apart from the use of cover portion 95, recess 92 and ledge 90. For example, rotation of the cover may be limited by (flexible) ties or any other suitable mechanism.

20 There are various considerations for setting the maximum opening angle. Thus to provide good access to the components on the back plate 15, it is generally desirable for the cover to open at least 90°, while in order to avoid potential damage to the wall or cover, the maximum angle should be no more than approximately 180° (depending on the exact relationship between the alarm unit and the wall). In addition, when the 25 cover 20 is in its open position (such as shown in Figure 2), cover 20 may be used as a tray to assist the engineer. Thus in one embodiment, cover 20 is configured with parking locators to receive a metal inner cover for alarm 10 (this metal inner cover is not shown in the Figures). Cover 20 functions most easily as a tray when the cover is at an angle of approximately 90° (from the wall). On the other hand, at this angle the 30 cover is also at its maximum extension from the wall, which may cause problems for

an engineer working on the alarm unit 10 (especially if the physical size of the cover is relatively large, and the engineer is working up a ladder). Accordingly, an appropriate value for the maximum opening angle of any given alarm is dependent on various factors, such as the shape and size of the alarm, whether the alarm unit has an inner 5 cover, and so on. In the particular embodiment of Figure 2, the maximum opening angle is approximately 105°, but other embodiments may have a smaller or larger value for the maximum opening angle.

In one embodiment, cover 20 is provided with retaining clips 71, 72. In 10 particular, one retaining clip is provided for each lug 60 and corresponding pin 65 of hinge 30. The retaining clips 71, 72 help to prevent lateral motion (i.e. parallel to the rotation axis) of the cover 20 with respect to the back plate 15 when the cover is in the closed position. The retaining clips 71, 72 also serve to resist over-rotation of the cover onto the back-plate. Consequently, the retaining clips 71, 72 help to provide 15 protection against someone trying to lever or prise the cover 20 away from the back plate 15.

As previously indicated, a screw (not shown in the Figures) may be passed through hole 55 in the cover and hole 45 in the back plate to hold the cover shut 20 against the back plate. In one embodiment, a sliding cover 80 is used to cover and protect this screw. The sliding cover 80 opens in the direction indicated by arrow A in Figure 5. When the sliding cover is in the open position, as shown in Figure 5, the screw used to retain the cover in the closed position is exposed, thereby allowing an engineer to open the cover to obtain access to back plate 15. However, moving the 25 sliding cover 80 in the opposite direction to arrow A closes the sliding cover, thereby protecting the screw against weathering and corrosion. In addition, covering the screw in this manner may make it slower and more difficult for an intruder or other adversary to identify how to open the alarm unit 10 (for example, when trying to disable the alarm).

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The sliding cover 80 is provided with three parallel fins (not visible in the Figures) that extend out perpendicularly from the sliding cover towards the back plate. The back plate has three parallel channels for receiving respective fins. The two outer channels 81, 82 are visible in Figures 1 and 3, while the third channel is not visible in 5 the Figures, but is central and runs upwards from tab 40. Note that channels 81 and 82 are open at their ends to avoid the build-up of water or dirt that might otherwise hinder or prevent correct sliding movement of screw cover 80.

The three channels permit vertical movement of the sliding screw cover 80 in 10 the direction of arrow A, but prevent horizontal movement perpendicular to the direction of arrow A. In particular, horizontal movement of the sliding cover 80 towards the back plate 15 is constrained by the fins abutting the bottom of channels 81 and 82. Horizontal movement of the sliding cover 80 away from the back plate is constrained by the central channel, which is relatively narrow close to the cover 80, 15 and then wider further away from the cover 80. The central fin is provided with a retaining foot that is located in the wider portion of the central channel, and prevents removal of the sliding cover 80 from back plate 15 (since the retaining foot is too wide to fit through the narrow portion of the central channel).

20 In conclusion, although a variety of embodiments have been described herein,

these are provided by way of example only, and many variations and modifications on such embodiments will be apparent to the skilled person and fall within the scope of the present invention, which is defined by the appended claims and their equivalents.

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Claims

Claims

1. An alarm unit for attachment to a wall, the alarm unit including a back plate 5 and an outer cover, wherein the cover is attached to the back plate by a hinge, said hinge having an orientation such that when the alarm unit is attached to the wall, hinged movement of the cover away from the back plate is assisted by gravity.

2. The alarm unit of claim 1, wherein rotation of the cover away from the back 10 plate is limited to a maximum angle.

3. The alarm unit of claim 2, wherein said maximum angle is in the range 100 to 180 degrees.

15 4. The alarm unit of claim 3, wherein said maximum angle is in the range 100 to 140 degrees.

5. The alarm unit of any of claims 2 to 4, wherein the maximum angle of rotation of the cover away from the back plate is determined by the cover abutting the back

20 plate on the opposite side of the hinge to the main portion of the cover and back plate.

6. The alarm unit of claim 5, wherein the back plate includes a recess for receiving the cover on said opposite side of the hinge, and wherein the size of the recess determines said maximum angle of rotation.

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7. The alarm unit of any preceding claim, wherein said hinge comprises at least one moulded pin located in a corresponding moulded pivot hole.

8. The alarm unit of claim 7, wherein the moulded pin or pins are located on the 30 back plate, and the corresponding moulded holes are located on the cover.

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9. The alarm unit of any preceding claim, further comprising one or more retaining clips that engage when the cover is rotated against the back plate and that disengage when the cover is rotated away from the back plate.

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10. The alarm unit of any preceding claim, further comprising an inner cover inside the outer cover, wherein said outer cover includes one or more parking locators for holding the inner cover when the outer cover is rotated away from back plate.

10 11. The alarm unit of any preceding claim, wherein said outer cover is retained against the back plate by one or more screws.

12. The alarm unit of claim 11, further comprising a sliding cover for at least one of said one or more screws.

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13. The alarm unit of claim 12, wherein said back plate includes one or more channels that run parallel to the sliding direction of said sliding cover, and said sliding cover includes one or more fins, whereby each fin extends into a respective channel to guide the motion of the sliding cover.

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14. The alarm unit of claim 13, wherein at least one of said one or more fins has a retaining foot that engages the back plate to prevent removal of the sliding cover in a direction perpendicular to the sliding direction.

25 15. The alarm unit of claim 13 or 14, wherein at least one of said channels has an open end.

16. The alarm unit of any of claims 12 to 15, wherein the sliding motion of the sliding cover does not detach the sliding cover from the back plate.

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17. A method of opening an alarm unit attached to a wall surface, the alarm unit including a back plate and a cover, wherein the cover is attached to the back plate by a hinge, and said method comprises rotating the cover away from the back plate,

wherein said hinge has an orientation such that hinged movement of the cover away

5 from the back plate is assisted by gravity.

18. The method of claim 17, further comprising undoing a mechanical fixing prior to rotating the cover away from the back plate.

10 19. The method of claim 18, wherein said mechanical fixing comprises one or more screws.

20. The method of claim 19, further comprising initially moving a sliding cover to expose at least one of said one or more screws.

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21. An alarm unit for attachment to a wall surface, the alarm unit including a back plate and an outer cover, the outer cover being attached to the back plate by at least one screw, said alarm unit further including a cover for at least one of said one or more screws, wherein the screw cover is operable to slide between a first position that

20 covers a screw and a second position that exposes said screw, wherein said sliding cover is attached to the alarm unit in both said first and second positions.

22. The alarm unit of claim 21, wherein said back plate includes one or more channels that run parallel to the sliding direction of said sliding cover, and said sliding

25 cover includes one or more fins, whereby each fin extends into a respective channel to guide the motion of the sliding cover.

23. The alarm unit of claim 22, wherein at least one of said one or more fins has a retaining foot that engages the back plate to prevent removal of the sliding cover in a

30 direction perpendicular to the sliding direction.

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24. The alarm unit of claim 22 or 23, wherein at least one of said channels has an open end.

25. The alarm unit of any of claims 21 to 24, wherein the sliding motion of the sliding cover does not detach the sliding cover from the back plate.

26. An alarm unit substantially as described herein with reference to the accompanying drawings.

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