GB2449678A

GB2449678A - Security fog system

Info

Publication number: GB2449678A
Application number: GB0710390A
Authority: GB
Inventors: Lee Dalby
Original assignee: Air Tube Conveyors Ltd
Current assignee: Air Tube Conveyors Ltd
Priority date: 2007-05-31
Filing date: 2007-05-31
Publication date: 2008-12-03
Also published as: GB0710390D0

Abstract

A security fog system comprises a fog generator 14 having an opening from which a fog-forming stream is expressed when the fog generator is activated via an alarm system 12, and control 16. A ducting has an inlet 22a aligned with an opening 15 of generator 14. A blower 18 blows air into the plastic ducting / tubing 20 so that the fog-forming stream is drawn into the ducting and conveyed to one or more duct outlets 28, 30, 32. Control means 16 and fog generator 14 may be synchronized in operation. The intention of the arrangement is so as to impair the visibility of an intruder once the associated alarm is activated.

Description

* . 2449678 Security Fog System The present invention relates to a

security fog system of a type suitable for use in protecting premises from intrusion, e.g. by burglars.

A security fog generating device is one that, when triggered by an alarm system, generates a fog with the aim of filling a space (room or other enclosed area) to impair the visibility of an intruder. These devices generate fog by expressing a heated moisture-containing stream through an opening so that the fog forms as the moisture meets colder air. One problem with this is that the fog is introduced at a single location in the room, and its effect can be overcome if the intruder quickly identifies the location and takes measures to prevent the fog from being delivered or adequately distributed in the room. For example, it has been known for intruders who have prior knowledge of the existence of a security fog generator, to come prepared with means for blocking the fog outlet orifice or directing the fog away through a window.

To make it harder for intruders, it has been known for security fog systems to include means for delivering the fog to multiple outlets in a room. However, such systems have a number of problems. Firstly, the pressure of the fog generated by the generators is only sufficient for the fog to be transported over a short distance. This also means that, where multiple outlets are employed, it is very difficult to arrange for the fog to be delivered uniformly to each outlet. Secondly, where the outlets are situated at ceiling level, the velocity of the fog is insufficient for it to penetrate down to floor level. Thirdly, because the ducting used to transport the fog is normally lower than room temperature, the heated fog stream condenses on the surfaces of the ducting, which may then drip out of the ducting during or after use.

The present invention has been conceived with the foregoing in mind.

According to the present invention there is provided a security fog system comprising: a fog generator having an opening from which a fog forming stream is expressed when the fog generator is activated; a ducting having an inlet aligned with the opening; and a blower for blowing air into the ducting so that the fog forming stream is drawn into the ducting and conveyed to one or more duct outlets.

It is an advantage that the use of a blower or fan and duct arrangement increases the velocity with which the fog can be expressed from the duct outlets. This means that multiple outlets can be used. In addition, the increased velocity of the fog stream prevents condensation forming on the duct surfaces.

In embodiments of the invention, the duct is comprised of an arrangement of tubes.

The tubes may be of a plastics material.

The ducting may be configured to provide air from the blower into branch piece from which the fog-forming stream is drawn into the ducting. The branch piece may comprise a curved portion for providing a substantially tangential conjunction between air from the blower and the fog-forming stream.

In embodiments of the invention, the ducting is configured to convey the fog-forming stream to a plurality of outlets. ft is an advantage that the use of the blower enables the fog to be dispersed from multiple outlets. The increased velocity of the fog expressed from the outlets provides for more rapid filling of a space with fog. Also, the use of multiple outlets makes it much more difficult for intruders to divert or block the fog. Another advantage is that the velocity with which the fog is expressed from the outlets allows the outlets to be positioned at ceiling level, but to still penetrate down to ground level.

In a preferred embodiment, the inlet of the ducting is spaced from the opening of the fog generator such that air is drawn into the inlet at the same time as the fog-forming stream. It is an advantage that drawing in air (e.g. from the surroundings) into the inlet at the same time that the fog-forming stream from the fog generator is drawn in, ensures immediate mixing of the air and fog stream and improves the effectiveness of fog formation.

Embodiments of the security fog system of the invention may ftnther comprise control means for controlling operation of the blower. Preferably, the control means comprises an electronic controller. The control means may be configured to start operation of the blower in synchronisation with operation of the fog generator. The control means may be configured to permit operation of the blower without operation of the fog generator, for example after operation of the fog generator has ceased. It is an advantage that continuing operation of the blower after operation of the fog generator has ceased ensures that the ducting is cleared of fog. This helps to ensure that condensation does not form inside the ducting.

The invention will now be described by way of example, with reference to Figure 1, which shows a schematic arrangement of a security fog system.

In Figure 1 an alarm system 12 is provided with means for detecting an intrusion into a room, building or premises in a known manner. The alarm system 12 is configured to trigger a fog generator, or fog cannon 14 to introduce a fog into a certain protected area. In accordance with established standards for the operation of such systems, the alarm system 12 is placed in an active mode when personnel leave the building or premises. The system is configured to detect a break-in by any of a variety of known means. At this point, the fog cannon 14 is placed in an alert condition but is not triggered until the alarm system detects, for example by means of a positional infra-red (PIR) detector, that a person has entered the protected area.

When triggered, the fog cannon 14 produces a stream of fog-forming heated water vapour from an orifice 15. The fog-forming stream may contain other components, such as glycol to aid in the fog formation, but any such components are preferably water soluble, and not harmful in contact with persons or animals. The fog-forming stream generates a fog as it comes into contact with air at room temperature. As shown by arrows in Figure 1, the fog-forming stream enters an inlet 22a of a first branch tube 22, which forms part of a tubular ducting system 20, which in the preferred embodiment is formed from tubes of a plastics material.

An electronic controller 16 receives signals from the alarm system 12 and the fog cannon 14 and responds to triggering of the fog cannon 14 by starting operation of a fan 18. The fan 18 is typically situated at a suitable concealed location nearby, but outside the protected area. The fan 18 blows air into one end of a tube 21, forming part of the tubular ducting system 20. The tube 21 joins the first branch tube 22 at a junction 24, in which the first branch tube 22 has a curved portion 26 for providing a substantially tangential conjunction between air in the ducting 20 blown from the fan 18 and the fog-forming stream from the fog cannon 14. This arrangement of the tubular ducting 20 acts as an inductor that draws in the fog-forming stream. In addition, the inlet 22a to the branch tube 22 is spaced a short distance from the orifice of the fog cannon 24. This has the effect of drawing surrounding air in through the inlet 22a (as shown by arrows in Figure 1), which mixes with the fog-forming stream to start forming the fog.

The fog is carried by the air from the fan IS along the tube 21 in the direction of the arrows in Figure 1 towards three outlets 28, 30, 32. The first two outlets 28, 30, are at the end of short branch tubes that lead off the tube 21, and have curved portions at the respective junctions with the tube 21 to ensure a division of the flow.

As a consequence of the use of the fan 18 to blow air through the ducting arrangement 20, as shown in Figure I, fog is expressed through multiple (in this example 3) outlets 28, 30, 32, at a velocity substantially higher than the velocity of the fog-forming stream that emerges from the fog cannon 14. This means that multiple outlets can be positioned at, for example, a ceiling level and that the outlets are able to express a fog that can penetrate a room down to floor level. It would be extremely difficult for an intruder to block off all of the multiple outlets, or to divert fog from all of the outlets away from the protected area. Thus the intruder will very quickly be subjected to a loss of visibility in the protected area.

The controller 16 is configured to allow operation of the fan 18 without operation of the fog cannon 14. When the fog cannon 14 is operating, the velocity at which the blown air carries the fog is sufficient to prevent droplets of condensation forming on the walls of the ducting 20. The controller 16 is configured to start up the fan 18 as soon as the fog cannon 14 is triggered. However, after the fog cannon ceases operation, the controller 16 keeps the fan 18 running to blow air through the ducting 20. This ensures that there is no residual fog left inside the ducting 20 after operation has ceased, and leaves the ducting 20 free of condensation.

Claims

Claims: 1. A security fog system comprising: a fog generator having an

opening from which a fog-forming stream is expressed when the fog generator is activated; a ducting having an inlet aligned with the opening; and a blower for blowing air into the ducting so that the fog-forming stream is drawn into the ducting and conveyed to one or more duct outlets.
2. A security fog system according to claim I wherein the ducting is comprised of an arrangement of tubes.
3. A security fog system according to claim 2, wherein the tubes are of a plastics material.
4. A security fog system according to claim 2 or claim 3, wherein the ducting is configured to provide air from the blower into branch piece from which the fog-forming stream is drawn into the ducting.
5. A security fog system according to claim 4, wherein the branch piece comprises a curved portion for providing a substantially tangential conjunction between air from the blower and the fog-forming stream.
6. A security fog system according to any preceding claim, wherein the ducting is configured to convey the fog-forming stream to a plurality of outlets.
7. A security fog system according to any preceding claim wherein the inlet of the ducting is spaced from the opening of the fog generator such that air is drawn into the inlet at the same time as the fog-forming stream.
8. A security fog system according to any preceding claim, further comprising control means for controlling operation of the blower.
9. A security fog system according to claim 8, wherein the control means is configured to start operation of the blower in synchronisation with operation of the fog generator.
10. A security fog system according to claim 8 or claim 9, wherein the control means is configured to permit operation of the blower without operation of the fog generator.
Ii. A security fog system according to claim 10, wherein the control means is configured to continue operation of the blower after operation of the fog generator has ceased.
12. A security fog system according to any of claims 8 to 11 wherein the control means comprises an electronic controller.