GB2282684A - Visual warning devices - Google Patents

Abstract

In a method of monitoring a plurality of remote visual warning devices (20) from a central monitoring station (26), (i) the central monitoring station (26) interrogates a visual warning device (20); and (ii) the interrogated visual warning device (20) sends a signal indicative of whether it is operating acceptably to the central monitoring station (26). The interrogation may be by addressing, or by applying or removing power to/from the communication channel (in which case the reply is by time-division or frequency-division multiplexing). <IMAGE>

Description

VISUAL WARNING DEVICES The present invention relates generally to the field of visual warning devices.

Visual warning devices in the industrial sector are generally in the form of steady-illumination, coloured status lights as used on platform helidecks or in conjunction with fire and gas warning systems; or, flashing warning devices which incorporate xenon or incandescent light sources and are often referred to as "beacons" or "status lights".

Visual warning systems are employed to supplement other safety systems such as public address systems and fire detection systems. They usually comprise a plurality of separate visual warning devices which are driven in parallel by a common supply and/or control signal. The operator of such a visual warning system is unable to ascertain whether all the visual warning devices are or will be operating correctly in the event of an emergency or potentially hazardous event.

Clearly, when the visual warning devices are deployed in a high-risk environment where, for example, dangerous chemical or gas releases, smoke or fire, or ionising radiation releases may be encountered, this is a serious drawback of the known systems. This problem is particularly acute in noisy areas where sounders or public address systems may be ineffective.

Chemical plants, material handling plants, ships, oil refineries, nuclear installations are all examples of environments, which are considered to be high risk.

At present, correct operation of the visual warning devices is confirmed by an individual visiting the point of installation of a visual warning device and visually verifying its operation - usually following a suitable announcement. This is time consuming and prone to human error when recording which units fail.

Accordingly, an aim of this invention, therefore, is to provide a quick and reliable system of identifying failed visual warning devices amongst a plurality of visual warning devices. It is a further aim to provide a visual warning device suitable for use within such a system.

A definition of the present invention is given in the appended claims.

Exemplary embodiments of the invention are hereinafter described with references to the accompanying drawings, in which: Figure 1 shows a first system in accordance with the present invention; Figure 2 shows a second system in accordance with the present invention; Figure 3 shows a physical lay-out for a visual warning device; Figure 4 shows a block diagram illustrating the electronic circuitry in a visual warning device; and Figure 5 shows a block diagram of a control monitoring station in accordance with the present invention.

A first system in accordance with the present invention is featured in Figure 1: it comprises a plurality of remote visual warning devices 20, each with its own local power supply 22, which are connected to one another by a communication channel 24, to form a network. In these figures, the dotted lines indicate the presence of further unillustrated visual warning devices. Also, in the network a central monitoring station 26 is provided. The station 26 has outputs 30,32,34 to a data highway, printer and diagnostics display, respectively; and its own power supply 28. The communication channel 24 may comprise address lines for addressing an individual device 20 and/or a control line for activation of the visual warning devices 20 and status lines for reporting on the operational status of the visual warning devices 20.The communication channel 24 may be in the form of either dedicated copper or fibre optic pathways or be part of a multipurpose data highway.

A second system in accordance with the present invention is featured in Figure 2. Its structure is similar to that of Figure 1 except that each visual warning device 20 is without a local power supply, and its communication channel 24' comprises a single pair of conductors, which also supply power to the visual warning devices 20.

A visual warning device 20 is shown in Figure 3: it comprises a light output element 10; a sensor 12, which is responsive to the light output from the element 10; and an electronic circuit means 14, which is operable to process the sensor output and generate a signal indicative of whether the light output element 10 is operating acceptably. The visual warning device 20 is housed within an enclosure 16, which may comprise either a unit certified for use in hazardous atmospheres, or an enclosure, designed for commercial or industrial environments and may contain multiple warning devices of different colours or characteristics.

The light output element 10 may be an incandescent light source, a single or multiple xenon light source, a light source with a mechanical rotating reflector, a fluorescent light source, or a neon light source.

Both the first and second systems operate in generally the same manner.

The central monitoring station 26 selects the remote visual warning device 20 which is to be tested, either under automatic or manual control, and provides a signal to that effect on the communication channel 24 or 24'.

The selected visual warning device 20 then responding to that signal, tests itself, and reports on the communication channel 24 or 24' with a signal indicative of whether the visual warning 20, in general, and the light output element 10 in particular, is functioning correctly. The central monitoring station 26 then decodes the signal and compares the results with a preset memory of the number and location of devices in the network, and provides an output of the status of the device for use on either a diagnostics display, fault logging printer or to an equipment status data network provide for overall operation monitoring.

The first system employs a bus system which enables the central monitoring station 26 to address a selected visual warning device 20 individually via the address lines; instruct the selected visual warning device to test itself via the control lines; and report the results of the test via status lines.

Whereas the second system is instructed to test itself merely by the application or disconnection of power to the communication channel 24' and each reports its results by either time-division or frequency-division multiplexing the channel 24' after removal of power from the network.

The electronic circuit means 14 derives its power by either, a) utilising the residual energy in the visual warning devices energy storage reservoirs, or b) by utilising a small proportion of the power from the power supplied to the control relay provided for the purpose of initiating the visual warning device.

An exemplary central monitoring station is shown in more detail in Figure 5: it comprises a CPU and memory unit 110 having the outputs 30, 32, 34 defined above. The CPU 110 co-ordinates the monitoring of the visual warning devices 20. It selects a particular visual warning device 20 for testing via the control circuitry 108, polling encoder 104 and transmitter 100 by which means it places the label or address of the selected visual warning device 20 on the communication channel 24, and receives the return message from the selected visual warning device 20 on the communication channel via a receiver 102 and a decoder 106.

An electronic circuit means 14 suitable for use in the first system is shown in Figure 4. The circuit means 14 comprises a polling monitor 50; a polling decoder 52; an address set stage 54; control circuitry 56; a detector 58; a store 60; an encoder 62; a data transmitter 64; a power supply for monitor 66; and driver circuitry 68.

It is preferred that the visual warning device 20, as illustrated in Figure 4 is provided with a sensor 12 which is responsive to the actual light output of light output element 10. However, in other embodiments, the sensor 12 can monitor fluctuations in the current or voltage which is supplied to the element 10.

Claims (9)

1. A method of monitoring a plurality of remote visual warning devices from a central monitoring station, the method involving the steps of : (i) the central monitoring station interrogating a visual warning device; and (ii) the interrogated visual warning device sending a signal indicative of whether it is operating acceptably to the central monitoring station.

2. A method as in claim 1, wherein the interrogation is effected by the application or disconnection of power to the visual warning device.

3. A method as in claim 1, wherein the interrogation is effected by sending an initiation signal to the visual warning device.

4. A method as in any preceding claim, wherein each visual warning device comprises a light output element, and the interrogated visual warning device establishes whether the light output element is operating acceptably by monitoring the current or voltage which is supplied to the output element.

5. A method as in any of claims 1 to 3, wherein each visual warning device comprises a light output element and a sensor, and the sensor of the interrogated visual warning device establishes whether the light output element of the interrupted visual warning device is operating acceptably by monitoring the light which radiates from the output element.

6. A method as in any preceding claim, wherein steps (i) and (ii) are carried out for each of the visual warning devices.

7. A system of monitoring a plurality of remote visual warning devices comprising a plurality of remote visual warning devices and a central monitoring station arranged in a network, the central monitoring station being operable to interrogate the visual warning devices; and the visual warning devices being operable, when interrogated, to send a signal indicative of whether it is operating acceptably to the central monitoring station.

8. A system of monitoring a plurality of remote visual warning devices constructed, arranged and adapted to operate substantially as herein described with reference to the accompanying drawings.

9. A method of monitoring a plurality of remote visual warning devices from a central monitoring station substantially as herein described with reference to the accompanying drawings.