GB2255242A

GB2255242A - Emergency lighting system

Info

Publication number: GB2255242A
Application number: GB9109148A
Authority: GB
Inventors: Graham Wild
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-04-27
Filing date: 1991-04-27
Publication date: 1992-10-28
Also published as: GB9109148D0

Abstract

The system may be in the form of a plug or adaptor removably engageable with a mains socket, or formed as a face plate unit to fit a standard wall box, the unit incorporating a mains socket 4, a rechargeable battery, a mains powered battery charger and a switching device acting in response to mains failure to connect the battery to a lamp which is then visible through a translucent or transparent front wall 5. A timer or ambient light sensor may support any switching on of the light during daytime, or switch on the light at night irrespective of mains failure. An alternative embodiment, (Figs 4, 5), has a light operable to illuminate the glass panel (22) of a fire alarm switch, the light being energised from the battery of the alarm system when mains failure is sensed either by detecting absence of mains ripple on the battery charging voltage or by detecting a drop from charging voltage to battery voltage on the alarm system supply. The light may be activated, e.g. to flash, in response to breakage of the glass panel. <IMAGE>

Description

EMERGENCY LIGHTING SYSTEM This invention relates to emergency lighting systems.

It is known to provide emergency lighting systems comprising lights connected by specially provided wiring to a remote emergency power source. In the event that a main power circuit fails, the lights can be powered by the emergency source. Systems of this kind are widely used in commercial and industrial premises and other large buildings.

However, the cost and inconvenience of installation may not be justified in a domestic environment.

An object of the present invention is to provide an effective emergency lighting system which can be easily and conveniently installed.

According to one aspect of the present invention therefore there is provided an emergency lighting system comprising a unit incorporating terminals for connection to mains power supply, a chargeable battery, a charging circuit connected between the battery and the said terminals for charging the battery from the mains power supply, a light, and a detector device operable to connect the light to the battery to be powered thereby when said device detects a failure of said mains power supply.

With this arrangement the emergency lighting system can be installed in a particularly simple and convenient manner and is especially suitable for use in a domestic environment. It is however to be understood that the invention is not restricted to domestic use and can be used in any suitable context.

In a particularly preferred embodiment the unit of the lighting system is adapted to fit in the standard flush, or surface, mounting box of a mains socket in substitution for the usual socket. In this case the unit may incorporate a socket. Thus, for example, the unit may be adapted to replace a double socket and may incorporate a single socket in one part or half of the unit, the said light being in a remaining part or half thereof.

The invention is not however restricted to the incorporation of a socket in the unit. The unit may be adapted to fit in a socket mounting box without providing a substitute socket. Moreover, the unit may be in the form of a plug or adaptor removably engageable with an existing socket. If desired it is of course even possible to install the unit within a specially provided mounting box or other connecting and mounting arrangement, rather than using existing structures and circuitry.

With regard to the unit, this preferably comprises a housing of shape and construction appropriate to its intended means of installation.

Thus, for example, where the unit is to be installed in a socket-box, the housing may be in the form of a square or rectangular front plate supporting on its rear face, within an enclosure or in fully or partially exposed state, components of the lighting system.

Most preferably at least part of the unit housing, and particularly the above mentioned front plate, is formed from a transparent or translucent material whereby illumination from the light can be seen through such material. Suitably, translucent polycarbonate plastics material may be used.

With regard to the said light this may be a low voltage filament lamp, although any other suitable device may be used.

The said detector device may comprise circuitry which monitors the presence of mains voltage across the said terminals whereby in the absence of such voltage a switch is actuated to connect the light to the battery to be powered thereby. The switch may be non-latching so that the light is switched off when mains voltage reappears across the terminals.

The arrangement may be such that the light switches on and off irrespective of ambient conditions. Alternatively, the system may incorporate an additional device or devices to control the switching of the light in dependence on ambient conditions. That is, the system may incorporate an ambient light level detector (and/or a timing device) which operates to supress any switching on of the light during daytime (or high light level) conditions and/or which acts to switch on the light, irrespective of any failure of the mains power supply, during nighttime (or low light level) conditions. In the latter respect, the system can operate as a 'comfort' light or night light as well as an emergency light.

The lighting system may incorporate auxiliary features as desired.

Thus, for example, the system may include a manual switch for operating the light and/or for operating any socket incorporated in the unit.

Also, the system may be provided with an indicator, such as a printed arrow, e.g. to indicate the location of an emergency exit.

In accordance with a second aspect of the present invention there is provided an emergency lighting system, for use with an electrical device powered by a low voltage d.c. source comprising a chargeable battery connected to a charging circuit for charging the battery from mains power supply, said system having a light mounted relative to said electrical device, and a detector device operable to connect the light to the low voltage d.c. source to be powered thereby when said detector device detects a failure of said mains power supply by monitoring the low voltage d.c. source.

In this way a battery-backed low voltage electrical device, for example, a fire alarm emergency switch, can be provided with an emergency lighting system in a particularly simple and convenient manner. The system can be incorporated in or mounted on the electrical device and does not require its own power source since it derives power from the source used for the electrical device.

The light may be a low voltage filament lamp or any other suitable device.

The detector device may be arranged to monitor mains failure in any suitable manner. In one embodiment the device is arranged to monitor residual a.c. ripple on the d.c. power source, the absence of such ripple being taken as indicative of a mains failure.

As with the first embodiment of the invention, provision may be made for controlling the switching of the light in dependence on ambient conditions.

The invention will now be described further by way of example only and with reference to the accompanying drawings in which: Fig. 1 is a front perspective view of one form of an emergency lighting system according to the invention; Fig. 2 is a rear perspective view of the system of Fig. 1; Fig. 3 is a circuit diagram of the system of Fig. 1; Fig. 4 is a front view of an electrical device provided with an emergency lighting system in accordance with the second embodiment of the invention; and Fig. 5 is a circuit diagram of the system of Fig. 4.

With reference to Figs. 1-3, these show an emergency lighting system unit which is adapted to fit in a standard back mounting box of a double-gang domestic mains power socket (of the 13a 240V 50Hz a.c.

mains kind).

The unit comprises a plastics housing 1 having a rectangular front plate 2 with a peripheral rearwardly directed rim 3. The housing 1 is formed from translucent (milky-white) polycarbonate and has, on its front surface: slots 4 for the standard 3-pin socket configuration in one half of the front plate 2; a raised or domed portion 5 in the other half of the front plate 2, and two holes 6 for fixing screws.

At the rear of the front plate 1 there is fixed a standard socket arrangement 7 behind the slots 4, such arrangement 7 having exposed earth, live and neutral terminals 8-10; and a box structure 11 behind the raised portion 5. Within the box structure 11 there is mounted a low voltage (4.5v 60ma) filament bulb 12 facing the rear side of the raised portion 5, a rechargeable Ni-Cad battery 13 (8.4v 110ma), and circuitry 14 on a printed circuit board. The battery 13 and bulb 12 are connected to the circuit 14 as also are the live and neutral terminals 9, 10 of the socket arrangement 7. As shown, the back of the box-structure 11 is open in the region of the battery 13 and bulb 12 to provide ready access thereto. The back of the box-structure 11 is closed with a panel 15 in the vicinity of the circuitry 14.

As can be seen in Fig. 3 the circuitry 14 on the printed circuit board comprises a full wave rectifier 16 with associated components 17 arranged to provide a suitable charging circuit for the battery 13 (with a maximum current of 3.9 ma) when the terminals 9, 10 are connected to mains power supply. The circuitry 14 further includes a transistor switch circuit 18 interposed between the battery 13 and the bulb 12 and connected at its control gate 19 to the output of the charging circuit 16, 17.

In use, the unit is fitted into the standard back-mounting box in substitution for the usual double socket. The terminals 8-10 are connected to mains supply leads and the unit is fixed in position with screws through the fixing holes 6. The various components on the rear side of the front plate 2 fit within the back-mounting box.

The socket arrangement 7 can now be used in conventional manner.

The battery 13 is constantly charged while mains supply is present on the terminals 8-10, and the battery 13 is isolated from the bulb 12 because the switch circuit 18 is held off by the presence of voltage on the control gate 19 from the output of the charging circuit 16, 17.

In the event of mains supply failure the voltage is removed from the control gate 19, the switch circuit 18 is switched on and the bulb 12 is powered by the battery 13. The bulb illumination can be seen through the translucent material of the front plate 2 which acts as a diffuser. As shown, an exit indicator may be provided on the raised portion 5 for illumination by the bulb 12.

With this arrangement an emergency lighting system can be installed in a particularly simple and convenient manner, especially in a domestic environment.

Figs. 4 & 5 show diagrammatically an emergency lighting system applied to a fire alarm switch of the kind comprising a press button 20 within a wall-mounted box-structure 21 having a front glass panel 22.

The button 20 is connected to an alarm system powered by 24v d.c.

whereby in the event of a fire the glass panel 22 is broken to expose the button 20 and the button 20 is pressed to actuate the alarm system.

The 24v d.c. power source is obtained from a battery which is constantly charged by a mains powered charging circuit. The 24v d.c. supply is across the terminals of the press button 20.

Within the box structure 21 there is provided an emergency lighting system comprising a bulb 23 arranged when powered to illuminate the glass panel 22 (either directly or via a suitable light guide). The bulb is connected via a transistor switch circuit 24 to the 24v d.c.

supply across the terminals 25, 26 of the press button 20 and the switch 24 is normally biased to an off state. The switch 24 has a control circuit input 27 which is connected to a detector circuit 28 which is corrected to the d.c. supply across the press-button terminals 25, 26. The detector circuit 28 monitors the presence of residual a.c.

ripple derived from the battery charging circuit. In the event of a mains failure the ripple disappears and the detector circuit 28 produces an output which is applied to the control input 27 of the switch circuit 24. The switch circuit 24 operates to connect the bulb 23 to the d.c.

supply so that the glass panel 22 is illuminated.

With this arrangement, a fire alarm button or other electrical device can be provided with an emergency lighting system in a particularly simple and convenient manner.

It is of course to be understood the invention is not intended to be restricted to the details of the above embodiments which are described by way of example only.

Thus, for example, with the embodiment of Figs. 4 & 5, instead of monitoring a.c. ripple it is possible to monitor voltage level. In order to maintain the back-up battery in a charged state a charging voltage in excess of the nominal battery voltage is required. Thus, on mains failure the voltage will drop from the charging level to the battery level and this drop can be monitored and utilised to actuate the emergency lighting system.

Also, with the embodiment of Figs. 4 & 5, a sensor may be provided to detect breakage of the glass panel, such detection then being utilised to switch on the emergency lighting system for that fire device, possibly in a flashing mode, so that it can be readily seen which fire device has been activated.

Claims

1. An emergency lighting system comprising a unit incorporating terminals for connection to maIns power supply, a chargeable battery, a charging circuit connected between the battery and the said terminals for charging the battery from the mains power supply, a light, and a detector device operable to connect the light to the battery to be powered thereby when said device detects a failure of said mains power supply.

2. A system according to claim 1 which is adapted to fit in a standard flush, or surface, mounting box of a mains socket.

3. A system according to claim 2 wherein said unit incorporates a socket.

4. A system according to claim 2 or claim 3 wherein said unit is adapted to replace a double socket.

5. A system according to claim 4 wherein said unit incorporates a single socket in one part on half of the unlit, the said light being in a remaining part or half thereof

6. A system according to claim 1 or claim 2 wherein said unit is adapted to fit in a socket mounting box without providing a substitute socket.

7. A system according to any one of claims 1 to 6 wherein said unit is in the form of a plug or adaptor removably engageable with an existing socket.

8. A system according to any one of claims 1 to 3 wherein said unit is installed within a specially provided mounting and connecting arrangement.

9. A system according to claim 8 wherein said mounting and connecting arrangement comprises a mounting box.

10. A system according to any one of claims 1 to 9 wherein said unit comprises a housing of shape and construction appropriate to its intended means of installation.

11. A system according to claim 10 wherein, where the unit is to be installed in a socket-box, the housing comprises a square or rectangular front plate supporting on its near face, within an enclosure or in a fully or partially exposed state, components of the lighting system.

12. A system according to claim 10 or claim 11 wherein at least a part of the unit housing is formed from a transparent or translucent material whereby illumination from the light can be seen through such material.

13. A system according to claim 11 wherein said front plate is formed of a transparent or translucent material whereby illumination from the light can be seen through such material.

14. A system according to claim 12 or claim 13 wherein said transparent or translucent material comprises translucent polycarbonate plastics material.

15. A system according to any one of claims 1 to 14 wherein said light comprises a low voltage filament lamp.

16. A system according to any one of claims 1 to 15 wherein said detector device comprises circuitry which monitors the presence of mains voltage across the said terminals whereby in the absence of such voltage a switch is actuated to connect the light to the battery to be powered thereby.

17. A system according to claim 16 wherein said switch is non-latching so that the light is switched off when mains voltage reappears across the terminals.

18. A system according to any one of claims 1 to 17 wherein the system is arranged such that the light switches on and off irrespective of ambient conditions.

19. A system according to claims 1 to 17 wherein said system incorporates an additional device or devices to control the switching of the light in dependence on ambient conditions.

20. A system according to claim 19 wherein said system incorporates an ambient light level detector (and/or timing device) which operates to suppress any switching on of the light during day time (or high light level) conditions and/or which acts to switch on the light, irrespective of any failure of the mains power supply, during night time (or low light level) conditions.

21. A system according to any one of claims 1 to 20 further including a manual switch for operating the light and/or for operating any socket incorporated in the unit.

22. A system according to any one of claims 1 to 21 wherein the system is provided with an indicator to indicate the location of an emergency exit.

23. An emergency lighting system for use with an electrical device powered by a low voltage d.c. source comprising a chargeable battery connected to a charging circuit for charging the battery from mains power supply, said system having a light mounted relative to said electrical device, and a detector device operable to connect the light to the low voltage d.c. source to be powered thereby when said detector device detects a failure of said mains power supply by monitoring the low voltage d.c. source.

24. A system according to claim 23 which is mounted on or incorporated in said eletrical device and which drives power from a source used to power said device.

25. A system according to claim 23 or claim 24 wherein said light comprises a low voltage filament lamp,

26. A system according to any one of claims 1 to 25 wherein the detector device is arranged to monitor mains failure.

27. A system according to claim 26 wherein the detector device is arranged to monitor residual ripple on the d.c.

power source, the absence of such ripple being taken as indicative of a mains failure.

28. A system according to any one of claims 23 to 27 wherein said system includes provision for controlling the switching of the light in dependence on ambient conditions.

29. An electrical lighting system substantially as hereinbefore described with reference to and as illustrated in Figs. 1 to 3 or 4 and S.

30. An electrical device incorporating an emergency lighting system according to any preceding claim.