GB2296388A - Fire smoke safety system - Google Patents

Abstract

A fire smoke safety system uses an ionizer unit to produce negative ions at a rate sufficient to precipitate smoke particles caused by a fire. The unit may be stored in the ceiling of an escape route (fig 3a) and be extended (fig 3b) in response to a signal from a smoke detector 3. In one form the unit comprises a screen 11 of metal meshing or carbon or graphite textiles which provide a large number of corona discharge points, the screen having a pulsed electrical supply. In another form the unit comprises strips of material joined by plastic separator strips. Alternative materials for the ionizer unit are carbon composite material on a non-earthing backing, and hessian type weave wall coverings that incorporate carbon fibres or gels impregnated with carbon filaments. <IMAGE>

Description

SNORE PRECIPITATION This invention relates to ionization apparatus for smoke precipitation.

Room ionizers which release streams of negatively charged ions into the atmosphere in order to provide air conditioning by removal of positively charged particles of dust and cigarette smoke are known. Such room ionizers use a sharp point or other elements coupled to a high voltage source, for example 7000 volts, to produce negative ions as a result of corona discharge. This technique has been applied successfully for example for home and aircraft air conditioning. Use has essentially been for comfort purposes in an environment where the concentration of particles to be removed has been low, such as only a fraction of one percent.

The present invention is directed towards using ionization for safety purposes, and especially to enable smoke reduction or elimination along escape routes in buildings.

Smoke and exhaust gases comprise small particles of burnt material which move through the air under the influence of draughts, convection and Brownian motion. These small particles are generally positively charged.

It has been shown from air conditioning ionizers that positively charged dust, cigarette smoke and dirt particles can be removed by negative ions. The present invention is based on the realization that it is possible to increase the quantity of negative ions produced very substantially to a level necessary to counteract the rapid production of positively charged ions generated for example in a fire. In such circumstances the concentration of particles may rise to greater than ten percent relatively rapidly. In particular the invention is directed towards providing structures that may be released and activated to clean smoke from escape routes such as corridors and stairways of buildings. For this purpose of ion generation many orders of magnitude greater than in the prior art becomes necessary.

Accordingly the present invention provides a fire smoke safety system comprising a large scale ionizer unit producing negative ions at a rate sufficient to precipitate smoke particles present in substantial concentrations.

The invention is now described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of ionizer components of an embodiment of the present invention; Figure 2 is a schematic circuit and layout diagram of an embodiment of an ionizer and smoke detector unit in accordance with an embodiment of the invention; Figures 3a and 3b are schematic diagrams of a drop screen embodiment of the invention; Figure 4a, 4b and 4c are schematic diagrams of a further embodiment of the invention having a dropping ionization member; Figure 5 is a schematic diagram of an embodiment of the invention illustrating a control sequence; and Figure 6 is a schematic diagram illustrating an embodiment of the invention servicing dual sites.

Referring to Figure 1, the basic elements of a smoke precipitation unit comprise an ion generating member, herein after called the ionizer element, shown generally as occupying area 1, with a fan 2 directing air from an inlet, over the ion generating circuit to an outlet. Such a unit is not intended to run continuously, but to be triggered to start in the event of a fire. Hence a smoke detector 3 is mounted externally of the unit and is provided with a warning light 4, and/or an audible alarm, which indicates when the unit has been activated and provides an alarm indication to personnel.

Figure 2 illustrates a suitable circuit for operating the unit. This embodiment uses the mains supply, indicated as 5. A transformer 6 converts the mains supply to 9000 volts, which in turn is fed to a pulsing unit 7 and DC conversion unit 8. The pulses of DC current of around 0.5 mA are supplied to ionizer element 1 which may have various structural forms described later. In the embodiment of Figure 1 the ionizer element 1 may be an array of points or a coil of fibrous material that provides points from which corona discharge can occur. A high rate of ion production is achieved by virtue of the far and large quantity of discharge points.

The mains supply is also applied through a second transformer 9 with zener diode circuit 10, 11 converting to DC to supply a relay in a smoke detector circuit. When the smoke alarm responds the relay is energized and the ionizer circuit is switched on.

The large size of the ion generating members increases the risk of arcing which would lead to breadkdown in ion production and also potential hazard. To present this the ionizer circuit is arranged to supply pulses via pulsating unit 7. The output pulses are of fixed duration, with the negative voltage being supplied to the ionizer 1 which constitutes a series of points at which corona discharge occurs to release the stream of negative ions.

Figure 3 illustrates a structure for the ionizer element 1.

In this embodiment the ion producing element comprises a screen 11 of fire metal meshing or carbon or graphite textiles such as felts or cloths, all of which provide a large surface area having a very high number of end points from which corona discharge exhibit low thermal inertia and low outgassing.

The screen is adapted to fold or be gathered in a concertina manner, as shown in Figure 3a, and this configuration is maintained while the unit is on standby. It will be appreciated that in the folded configuration the screen is unobtrusive or may even be concealed. When the associated smoke detector 3 senses smoke, or any other connected fire alarm is activated, the screen is released to drop into the open configuration shown in Figure 3b. Screens of this nature may be installed in workplaces and along escape routes. The current in the screen is at very low amperage, of the order of 0.5 mA. As with all embodiments, to reduce the possibility of arcing the current is pulsed.

In the standby mode the unit may be powered by a battery 20, and the screen held and released by electromagnetic catches 21. The system includes an audible alarm 22. It will be appreciated that all embodiments are housed in an insulating casing of plastics or other suitable material. The circuitry is housed in the area referenced 23.

Figures 4a, 4b and 4c show a further embodiment of folded ionizer element. In this embodiment strips 12 replace the screen 11 of the previous embodiment. Figure 4a shows the general appearance of the unit from below when concealed in a ceiling space. Figure 4b shows the strips held in folded configuration.

When the associated smoke alarm is activated, or other triggering occurs, electromagnetic switches holding the strips in the folded configuration are released and the strips fall under their own weight to the configuration shown in Figure 4c.

Plastic separator strips 13 keep the strips apart, assist the dropping action and stabilize the deployed configuration. The separators may also be used for holding and folding purposes. Use of thin strips 12 instead of a screen increases the surface area and hence the number of end points.

Figure 5 schematically illustrates a link between the smoke detector, a first relay 14 which closes to activate horn 22 and light 4, and a second relay 15 that activates an ionizer. The supply for the ionizer is preferably mains, transformed as described earlier, the supply for the smoke detector may be mains, battery or mains with a battery backup.

A further modification of the invention is shown in Figure 6. In this embodiment more than one ion generating site is activated by the sensor 3. As in other embodiments the unit comprises a horn 22 and light 4 in addition to smoke detecting apparatus.

The primary ion generating site 16 comprises an ionizer element in the form of a carbon composite material that both conveys current to the secondary site or site 17 and produces ions via electron emission from its surface.

Preferably or alternatively copper or other high conductivity wires running through the material also carry the current to the secondary site. This ionizer element may extend for some distance, or more than one such link may be provided.

One or more secondary sites 17 of ion generating material are provided of significantly larger surface area to produce hyper anionization levels that will effectively remove fire smoke particles from other locations, which may be remote from the detection apparatus. For example escape route ionizers may become activated irrespective of the location of fire detection as a precautionary measure. It will be appreciated that a modification of this system is for the link provided by the primary ion generating site to be replaced by a purely electrical or signalling link.

The secondary site ion generating material may be any of those previously described or, for example, a large area of carbon composite material on a non-earthing backing. Other possible structures include hessian type weave wall coverings that incorporate small electrically conducting carbon fibres or composite gel materials such as polysaccharide gels impregnated with loose carbon filaments that upon drying provide a conductive medium with ion generating end points. Such gels are presently made incorporating carbon and graphite powders and used in scanning election microscopy where the election beam generates an electric current access the gel compound.

Filament addition could be achieved by air blasting wet gels with carbon/graphite fibres that on drying provide a coating of fine ion generating filaments.

Supplementary highly electrically conductive elements or auxiliary units may also be incorporated to ensure dispersion of current throughout the structures.

Claims (7)

1. A fire smoke safety system comprising a large scale ionizer unit producing negative ions at a rate sufficient to precipitate smoke particles present in substantial concentrations.

2. A fire smoke safety system according to claim 1 in which the ionizer unit comprises an element that is stored in a contracted configuration while the unit is on a standby setting and is deployed in an extended configuration when the unit is switched to an ion generating state.

3. A fire smoke safety system according to claim 2 in which the contracted configuration is one in which the element is a flexible sheet or strip retained in folds or gathers and which, when released, drops to adopt the extended configuration.

4. A fire smoke safety system according to any preceding claim in which the ionizer unit is loaded along escape routes.

5. A fire smoke safety system according to any preceding claim in which the ionizer unit comprises an ionizer element that provides multiple points from which corona discharge occurs.

6. A fire smoke safety system according to claim 5 in which the points are provided by fibre ends.

7. A first smoke safety system according to claim 5 or claim 6 in which the ionizer element is in the form of specially adopted soft furnishings.