GB2421620A

GB2421620A - Fire alarm sounder

Info

Publication number: GB2421620A
Application number: GB0428143A
Authority: GB
Inventors: Kieron T N Chapman
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-12-23
Filing date: 2004-12-23
Publication date: 2006-06-28
Also published as: GB0428143D0

Abstract

A fire alarm has an acoustic cavity 7 located immediately behind the surface which is most remote from the mounting surface 2. The former surface is provided with apertures 8 which allow the sound from sounder 6 to be emitted. The sounder 6 is preferably a piezo disc.

Description

Detector sounder This invention relates to a method of combining detectors

used for detecting fires and a sound signalling device for signalling a fire condition.

it is common practice for fire alarm systems to use detection devices on detection circuits and sounding devices on sounder circuits This has been a standard practice for many years but results in two cabled circuits being installed which is more expensive that a single cable.

In an attempt to reduce system costs, addressable and analogue addressable system types have been developed which now enable low power sounding devices to be connected on the same electrical circuit to reduce costs.

As a result of these developments, sounding devices have been developed to fit between the detection device and the mounting surface to further simplify the installation and reduce costs.

A further development of this approach has been to integrate a sound4g device to a detection device so that the product is installed as one product instead of two or1more.

One of the problems with each of the current methods described above is that the sounding devices used are usually transducer modules. These could be piezo based or electromagnetic type devices. Both types of transducer module can be quite large when designed to produce the sounds required for fire alarm signalling applications and achieve the sound pressure levels required to signal an alarm.

The problem with current solutions for integrating a sounding device is that the main area available is reserved for the detection chamber and can not easily be changed with out affecting the detection characteristics of the detector. This leaves a small space behind the chamber which is normally used for housing the electronic assembly. Presently, some products use some of this space available but it is limited and only provides space for small sounding devices which have limited frequency and sound pressure level capabilities and are therefore limited in their performance. Alternatively, a larger device can be fitted but at the expense of significant aesthetic impact and sometimes poor acoustic performance as the devices are fitted into very small spaces leaving little or no space for a reasonable acoustic enclosure design.

The present invention provides means of integrating a sounding device into a detection device with minimal space requirements. This minimises any effects on the detection characteristics and eliminates the problems encountered when fitting transducer modules in to detection devices due to the limited space available. These problems include compromising acoustic performance due to using very small transducers and having restricted acoustic properties that reduce the performance of larger transducers.

Accordingly, this invention provides apparatus for integrating a sounding device into a detection device in such a way that minimal space is required whilst providing adequate acoustic performance. The apparatus comprises a housing having a base for mounting the apparatus in use to a surthce, the housing contains a detector unit, a suitable acoustic device and means for fixing the acoustic device into the housing where the acoustic device is located substantially displaced axially of the base.

Preferably the acoustic device may be located substantially axially displaced from the base and beyond a slot or slots provided in the housing.

Also, preferably the acoustic device may be fitted into the detector housing such that the housing provides some or all of the acoustic enclosure for the acoustic device to perform adequately.

A preferred embodiment of the invention will now be described with reference to the accompanying drawings in which: Fig I shows a simplified cross section of a typical smoke detector; Fig 2. shows a cross section view of how this invention could be integrated into a detector; As shown in fig I., all detectors have a surface that is the furthest most surface (1) from the mounting surface (2). This surface is normally centrally positioned and is of a diameter or size that is sufficient to house a detection chamber for smoke. Electronic components could be placed either side of the printed circuit board (3) and some form of electncal termination would be provided to connect from the printed circuit board to terminals in the base (4) of the detector. The base (4) of the detector needs to provide adequate space for the termination of cables used to connect the device to a detection circuit so this space is restricted for housing a transducer module for sound generation.

A transducer module suitable for generating an appropriate acoustic performance would be too large to place inside the housing of the detector shown in figi with out having a significant impact on the size and shape of the detector.

Now with reference to fig 2, the space required for a transducer module has been eliminated by integrating an acoustic housing in the detector behind the surface that is the furthest most surface from the mounting surface To achieve this, the invention provides a ledge (5) on which to fix a piezo disc (6) or other suitable acoustic device with an acoustic cavity (7) all built into the part that provides the furthest most surface from the detector body. This surface is then perforated with holes (8) to enable the sound to be emitted. The acoustic cavity (7) and the perforations (8) and the piezo disc (6) are all designed to provide a suitable acoustic performance.

The detector part that forms the furthest most surface from the mounting surface now also provides the acoustic enclosure and properties that would normally be provided by separate parts that create an acoustic module. This reduces the height substantially and with the size, particularly the height of the acoustic assembly much reduced, it becomes viable to position the acoustic assembly behind surface I of the detection device

Claims

I. Apparatus providing means for integrating a transducer greater than 30mm in diameter with an acoustic cavity in the top part of a moulding of a detector used for detecting fires, where an acoustic cavity is formed by the same part that forms the surface of the detector furthest away from the mounting surface.
2. A claim as in claim 1 where the fire detector uses optical technology, heat sensing technology, chemical sensing technology or any combination of these technologies for the purpose of detecting a fire or smoke particles.
3. A claim as in any of the previous claims where the apertures for sound emission are on the surface of the detector furthest away from the mounting surface.
4. A claim as in any of the previous claims where the apertures for sound emission are at the rear of the acoustic device facing towards the detection chamber.
5. A claim as in any of the previous claims where the part that forms the furthest most surface from the detector is a separate piece to that which forms the main body of the detector.