GB2359649A

GB2359649A - Alarm unit

Info

Publication number: GB2359649A
Application number: GB0004368A
Authority: GB
Inventors: Pedro Francisco Marrero
Original assignee: DELAWARE ELECTRONIC TECHNOLOGY
Current assignee: DELAWARE ELECTRONIC TECHNOLOGY
Priority date: 2000-02-25
Filing date: 2000-02-25
Publication date: 2001-08-29
Anticipated expiration: 2020-02-25
Also published as: GB0004368D0; GB2359649B

Abstract

An alarm unit (12) comprises a substantially closed container (13) including a back plate (14) to be secured to an external wall (15) of a building or the like and a front plate (18), the container housing an alarm indicator (32, 33) and an electronic circuit (35) for operating the alarm indicator in response to initiation of an alarm condition within the building, in which the operative parts including the alarm indicator (32, 33) and circuit board (35) are housed in an integral module (20) which is detachably connectable within the container during installation. Preferably the module (20) is pivotally mounted on projections (22) on the back plate so that it can pivot and cause initiation of the alarm indicator if the unit is tampered with.

Description

2359649 1 ALARM UNIT This invention relates tG an alarm unit of the type

comprising a substantially closed container including a back plate intended to be secured to an external wall of a building or the like and a front plate, the container housing an alarm indicator, such as a sounder and/or a strobe light, and an electronic circuit for operating the alarm indicator in response to initiation of an alarm condition within the building.

It is conventional for such ' a unit to also include means for initiating the alarm indicator if the unit is itself tampered with in an attempt to disable it.

The present invention includes several novel features in this type of alarm unit, which features may be claimed independently or together.

It is conventional for all the operative parts of the alarm unit such as the sounder, the light source, the circuit board including all the electronics and switches and a backup battery to be fixedly mounted at separate positions on the back plate. In order to install the unit, the back plate already carrying all these elements has to be mounted on the wall and a cable extending through the wall then connected to the circuit, after which the front plate is secured over the back plate. This makes the back plate relatively heavy and cAfficult to install and if anything goes wrong with one element of the unit the whole unit must be taken down in order to examine the working parts. If the back plate is dropped the working parts may be damaged.

According to one feature of the present invention the operative parts such as the alarm indicator, circuit board and switches are housed in an integral module which is detachably connectable to the back plate. The back plate can be installed first, and then the module detachably connected on the back plate and the cover added. If anything goes wrong, the module is easily detached and replaced. If a customer requires merely a dummy container, the module can be omitted without the stockist needing to keep separate dummy containers.

2 According to another feature, the circuit includes a switch biassed in the working position of the unit to an off position in which the alarm indicator is not operated and is movable to an on position in which the alarm indicator will be "set ofF if the unit is tampered with. The switch is movably mounted in the container, normally on the circuit board so that the board can move between positions in which the switch will be respectively in the on and off conditions.

The board is subjected to at least one biassing means, such as a spring, urging it in one direction. Preferably there are two biassing means or a biassing means and an engagement means acting in opposite directions. The switch itself may be normally sprung to a "on" condition and held in the off condition by one of the biassing or engagement means.

Preferably the movement is a pivotal movement.

In a preferred form the whole module containing the circuit board and switch is movably mounted in the container, rather than just the circuit board and switch being movable. With advantage the module is suspended from one or more projections on the back plate so that it can pivot through a small angle.

If a drill is inserted through the container in an attempt to disable the alarm unit, it is likely to move the module or circuit board and thereby initiate the alarm indicator. Equally a heavy blow on the front cover is likely to cause such initiation. Preferably an element, which may be a spring, is arranged between the switch and the front plate to urge the switch to the off condition. If the front plate is removed this initiates the alarm because the switch can now move to the on condition. Preferably a biassing element acts between the movable part carrying the switch (either the mounting plate or the whole module) and the wall on which the alarm unit is mounted. This biassing element urges the movable part forwardly so that if the whole unit is dismounted from the wall, then the movable element will move rearwardly and again initiate the alarm indicator.

3 One embodiment of alarm unit, in accordance with the invention, will now be described, by way of example only, with reference to the accompanying drawings of which:- Figure 1 is a diagrammatic sectional elevation of an alarm unit fixed to the wall of a building.

Figures 2 to 5 show similar views, on a smaller scale, of various conditions under which the alarm unit is "set off" Figure 6 shows a view of the back plate with the operative module mounted with the container in one orientation, and Figure 7 is similar to figure 6 and shows the container mounted in another orientation.

The alarm unit 12 comprises a container 13, completely closed apart from openings in its back plate 14, which is secured to the external wall 15 of a building so that it is slightly spaced therefrom by feet 16. The back plate is integral with side walls 17 and the container is closed by a front plate or lid 18. The front plate could c include the side walls connectable to the back plate.

As seen in figures 6 and 7, the back plate is provided with wall fixing screws 20, lid fixing holes 21, forwardly projecting locating pins 22, retaining members 23 and locating clips 24. A hole 25 is provided for a cable extension through the wall from the alarm unit within the building. Openings 26 are provided to be explained later. The container is preferably moulded from plastics material and may be transparent or translucent so that a strobe light can be seen through the container.

The whole of the operative portion of the alarm unit is housed in a separate integral module 30 detachably mountable in the container 13. The module 30 includes a plastics material moulded housing 31 incorporating the alarm indicating 4 means in the form of both a sounder 32 and a strobe light 33, a backup battery 34, an electronic circuit board 35 including all the circuits and controls and having a plurality of serial connectors 36 for connection to a cable 38 entering from the building through the cable entry 25. The circuit on the circuit board includes a switch 37 which in its relaxed condition assumes an open position in which the alarm indicators will be set off.

In the embodiment illustrated the housing 3 1 includes two spaced apertures 40 and the module 30 is detachably mounted in the container 13 by suspending it from one pair of locating pins 22 engaging in the apertures 40. The module is arranged to be initially engaged with the pins 22 at an angle of about 45' to the back plate so that its edge is inserted behind the retaining members 23 before pivoting to the position shown in figure 1 at a slight angle to the back plate. The module is easily detached by the reverse movement. In this attached position the module is pivotable about an axis extending between the pins 22. The module is located in the working position of the alarm unit, between two opposing engaging elements 41, 42, at least one of which is a biassing means such as a coil spring. In this case, one biassing means comprise a coil spring 41 attached to the back of die module so that it extends through an aperture 26 and engages the wall 15 of the building. This spring urges the module forwardly with the movement limited by the locating clips 24. The second biassing elemedt.in the form of a spring 42 acts in the opposite direction on the module, being positioned between the front plate 18 and the movable member of the switch 37. The biassing means 42, which could be a fixed element, serves to close the switch 37 to its off position in which the alarm indicator is not set off. The switch is effectively compressed between the springs 41, 42 so that if either spring is relaxed the switch will open.

Various conditions in which the alarm indicator will be set off, if the unit is tampered with are shown in figures 2 to 5. In figure 2 the container has been opened by forcing up the front plate. This decompresses the spring 42 so that the switch 37 opens and the alarm is initiated. In figure 3 an object such as a drill 44 has been pushed through the front plate in an attempt to disable the alarm unit.

The drill has contacted the module and pushed it downwardly. This again releases the pressure on the spring 42 allowing the switch unit 37 to open and set off the indicator. In figure 4 the front plate has been depressed by a blow from a hammer or the like 45. This again has depressed the module, released the spring 42 and allowed the switch 37 to open. In figure 5 the whole alarm unit 12 has been partially detached from the wall so that the spring 41 no longer urges the module forwardly. The module moves backwardly releasing the pressure on spring 42 so that again the switch 37 opens.

Although the whole module is preferably movable, as an altemativej- the module could be fixed with the mounting plate carrying the switch 37 movable within the module.

As a further alternative a circuit board carrying a switch, corresponding to the switch 37 could be movably mounted within an alarm unit without being part of a separate detachable module.

The movement in any of these possibilities need not be a pivotal movement but could be a translational movement provided the movement activates the switch setting off the alarm system.

As seen in figures 6 and 7 the module can be suspended from different pairs of pivot pins 22 with the orientation of the major dimension of the container either vertical as in figure 6 or horizontal as in figure 7.

6

Claims

An alarm unit comprising a substantially closed container including a back plate intended to be secured to an external wall of a building or the like and a front plate, the container housing an alarm indicator and an electronic circuit for operating the alarm indicator in response to initiation of an alarm condition within the building, in which the operative parts including the alarm indicator and circuit board are housed in an integral module which is detachably connectable within the container during installation.
2. An alarm unit according to claim 1 in which the module is detachably connectable to the back plate after installation of the back plate on the wall of a building.
3. A unit according to claim 1 or claim 2 in which the module includes a back-up battery.
4. A unit according to any of claims 1-3 in which the module includes as a alarm c indicators both a sounder and a strobe light.
5. A unit according to any of claims 1-4 in which the module includes means for initiating the alarm indicator if the unit is tampered with after installation.
6. A unit according to any of claims 1-5 in which the module is suspended from projections on the back plate.
7. A unit according to any of claims 1-6 in which the module can only be engaged with and detached from the container at an angle to the back plate of the container.
8. A unit according to any of claims 1-7 in which the module after installation is 7 mounted to be movable within the container.
9. A unit according to claim 8 in which the module is pivotable within the container.
10. A unit according to any of claims 1-9 in which the electronic circuit includes switch means arranged to be switched from an off to an on condition in which it initiates the alarm indicator if the part on which the switch is mounted moves within the container after installation of the alarm unit.
11. A unit according to claim 10 in which the switch means is sprung to an on condition and is held in the off condition by biassing and/or engagement means acting in opposite directions.
12. An alarm unit comprising a substantially closed container including a back plate intended to be secured to an external wall of a building or the like and a front plate, the container housing an alarm indicator and an electronic circuit for operating the alarm indicator in response to initiation of an alarm condition within the building, the circuit including a switch bias5ed in the working position of the unit to an off position in which the alarm indicator is not operated and the switch being mounted on a part movable in the container such that movement of the part moves the switch to an on position in which the alarm indicator will be initiated.
13. An alarm unit according to claim 12 in which the switch is mounted on a circuit board which is movably mounted within the container.
14. An alarm unit according to claim 13 in which the circuit board is pivotally mounted in the container.
15. An alarm unit substantially as described herein with reference to or as illustrated in the accompanying drawings.