GB2059196A - Testing emergency lighting units - Google Patents

Abstract

An emergency lighting unit and installation has a receiver 5 which is actuable by signals which can be transmitted through space, e.g. light, the receiver being connected to a control circuit of the emergency lighting unit. Upon receipt of signals transmitted through space and the resultant operation of the control circuit, the effect of a mains failure is simulated. The control circuit contains a switching device 5c switchable to on mode (in which the effect of a mains failure is simulated) by the said signals, the switching device being adapted to hold in the on mode after removal of the signals until a unit which is adapted to receive a switch off command, receives such a command. <IMAGE>

Description

SPECIFICATION Emergency lighting units and installations This invention relates to emergency lighting units and installations.

Emergency lighting is now used widely in buildings such as cinemas, discotheques, hotels, hospitals and the like wherein, at times, there are large numbers of members of the public. The requirement for emergency lighting furthermore is expected to be applied in due course to an even widerfield of public buildings such as public houses, offices, shops and so on.

As the name indicates, emergency lighting is a means whereby an area or position willl be illuminated in the event of an emergency occurring, in particular the failure of the mains power supply. The emergency lighting may be arranged to indicate a position such as an exit or fire hose or the like, or it may serve simply as space lighting, for example in locations such as hospitals, where absence of lighting could be dangerous to life, even where the lighting may be lost for only a short period.

Basically, emergency lighting can be of two types, "maintained" and "sustained". In the "maintained" type, a light source is normally illuminated from the mains supply, and in the event of failure of the supply, the same light source is illuminated from an emergency or standby supply. In the "sustained" type there are separate light sources, one of which is supplied from the mains supply, and the other of which is supplied by standby power and only illuminated by the standby power when the mains power supply fails.

In either case, when there is a mains failure, the emergency lighting is connected to a separate power source, for example one or more d.c. batteries, for the illumination of the lighting. There are three principal types of emergency lighting, these being "Single Point" where the emergency or standby power source is one or more d.c. batteries within each individual standby unit; "Central Battery" where a central battery and control service a number of lighting sources; and a "Standby Generator".

It will be understood that the maintenance and functioning of emergency lighting is very important and indeed fire officers make periodic checks on all emergency lighting installations to ensure that they are in good working order. Conventionally, each lighting unit of a non-maintained emergency lighting installation is provided at least with one indicator lamp, usually green, through which a small current is passed; this current is also passed through the emergency lamp in the unit and anyone inspecting the unit and seeing the small green monitor lamp on, will know that the filament of the emergency lamp is in order. It is also usual to provide a red monitor lamp which, when illuminated, indicates that the charging circuit for the battery or batteries is operating. In a maintained system it is of course not necessary to provide the green monitor lamp.

These monitor lamps, although useful, do not guarantee that the emergency lighting will however work in the event of a mains failure. The only method at present available for checking this is to simulate a mains failure by switching the power off at the mains. Apart from the fact that this testing procedure is inconvenient, it is not something which the fire authorities recommend and it could interfere with the sub-circuits of the emergency lighting units and could impair their performance.

In co-pending application No. 10300/77 (Serial No.

1567506) we provide an emergency lighting unit or installation, the testing of the operative condition of which can be effected easily and conclusively, without recourse to shutting off the mains supply.

According to the invention and in said co-pending application there is provided an emergency lighting unit provided with a receiver which is actuable by signals which can be transmitted through space, said receiver being connected to a control circuit of the emergency lighting unit so that upon receipt of signals transmitted through space and the resultant operation of the control circuit, the effect of a mains failure is simulated.

It will be appreciated that the person wishing to test the unit will have an appropriate transmitter for supplying the signals to the receiver. In practice, the transmitter and receiver will be selected so that the control circuit will not be operated spuriously.

The present invention is concerned with an improvement of the invention the subject of said co-pending application and in accordance with the present invention the control circuit contains a switching device switchable to on mode (in which the effect of a mains failure is simulated), by the said signals which can betransmitted through space, said switching device being adapted to hold in the on mode after removal of said signals until the unit which is adapted to receive a switch off command, receives such a command.

The control circuit is preferably such that the same type of signals switches the unit to the on mode and to the off mode.

By such means, the fitness of the emergency lighting unit to perform its function can be tested for long periods as required by British Standards which require that emergency lighting units should be operated in simulated emergency condition for one hour every six months and for three hours every three years where the unit is of such a type that it should operate for three hours duration in the case of mains supply failure.

The time of commencing the simulation of a mains failure and the time of terminating such simulated condition is under the control of the person testing the unit.

Preferably, the control circuit comprises a flip flop connected to shift between on and off conditions alternatively upon receipt of signals from said receiver. There may be a monostable multivibrator connected between the receiver and the flip flop in order to shape electrical pulses which are received by the multivibrator from the receiver.

Conveniently, the transmitter may be a light source such as a battery torch which emits a narrow and higher than average power beam of light, and the receiver may be a photo-cell or photo-transistor device, and the control circuit may include a transistor driven from the flip flop which is made to cut off thereby causing a relay to drop out when the photo-cell device receives transmitted light signals.

The invention can be applied to maintained and sustained units and to units embodying the auxiliary power souce or not; normally the receiver will be embodied in a casing of the unit. It is not necessary that this be so, however, and in an emergency lighting installation involving a number of units, the receivers for the units may be located remote from the units.

In another form of the invention the receiver is for receiving and being operated by magnetic signals; thus, the receiver may be a reed switch which is operable for example by means of an electro magnet or permanent magnet carried by the person who tests the equipment.

In all cases, when the condition of mains failure is simulated, the appropriate emergency lighting unit will operate, indicating that it is functioning correct ly, and the emergency lighting can be switched off by subsequent sending of signals to the receiver.

Emergency lighting units invariably are arranged at a high level, and the present invention like the invention the subject of said co-pending application provides a means whereby a person with an approp riate transmitter e.g. a torch or electro-magnet can test the units without having to shut down the mains supply and without, in the case of the preferred embodiments, having to climb up ladders to the units to inspect them.

Embodiments of the present invention will now be described by way of example, with reference to the accompanying drawings, wherein:- Figure 1 is a circuit diagram of a non-maintained emergency lighting unit, and Figure 2 is a diagrammatic side view showing the receiver of the circuit of Figure 1.

Referring to the drawings, in Figure 1 there is shown the circuit for a non-maintained emergency lighting unit having a lighting tube Toftheflourescent type. The circuit is supplied from AC mains through a transformer and the AC voltage is rectified by a full wave rectifier Dl-D4to provide DC at rails R1 and R2. The tube T has conventional control gear G. The circuit includes relay contacts RL I which are operated by relay RL. In the normal operation of the unit, the casing of which is indicated in dotted line, the relay RL is maintained energised which keeps contacts RL 1 in the dotted line position shown in which supply of power to tube T is cut off, and the tube Tis off.In the event that relay RL is de energised and drops out, for example in an emergency when there is a mains failure, contacts RL 1 move to the full line position shown and an auxiliary power supply in the form of battery D either in the unit or at a remote location is connected to the tube Tthrough now closed contacts RL land tube T is switched on.

In accordance with the embodiments of the invention illustrated in Figure 1, a circuit comprising Zener diode 1 and resistor 3 connected in series, and capacitor 2 in parallel with resistor 3, is connected between rails R1 and R2. A transistor 6 is connected between relay RL and rail R2 as shown, whilst a diode 8 is connected across RL in order to suppress reverse voltage spike caused by the energy in the relay coil collapsing so that no damage can be caused to the active components by such a spike.

The base voltage of transistor 6 is set by a resistor 4 connected between the base of transistor 6 and the junction between diode 1 and resistor 3.

A receiver in the form of a light energy photo transistor 5 is connected to the trigger input of a monostable multivibrator 5A, the output of which is connected to the input of a flip-flop 5B which is connected to provide output at half the frequency of the input. The flip-flop output is buffered by a single transistor 5C to provide the necessary current source to actuate the transistor 6. The elements 5A, 5B and 5Cform a switching means biased from a line 7 which is maintained at a reduced voltage by being connected to line R1 through resistor 9. Line 7 is connected to line R2 (earth) through Zener diode 11.

When appropriate signals are received by detector 5, in particular signals in the form of a continuous white light spectrum, the detector 5 triggers the multivibrator 5A from its stable state to its transient state and an output pulse, such as a square pulse of predetermined shape, is supplied to the flip flop 5B which changes state from one of two possible states to the other of said two states. When the next pulse from the multivibrator 5A is received by the flip flop SB,the flip flop returns to the said first state.

The utility of this arrangement is as follows.

Assume that in the first stage of the flip flop 5B the relay RL is energised and the contacts RL 1 are in the dotted line position shown in Figure 1 so that the tube Tis not illuminated. If an initiating signal is received by photo transistor 5, multivibrator 5A is triggered, a pulse is delivered to flip flop 5B which changes state causing transistor SCto conduct the transistor 6 to drop out, de-energising relay RL. The contacts RL 1 move to the full line position and the source B is applied across T, causing same to be illuminated, indicating that the emergency lighting unit is functioning satisfactorily. This condition is maintained because of the use of the flip flop 5B, despite the fact that the initiating light source may be removed and the fact that the monostable returns to its stable state.When a subsequent signal is applied to the photo transistor 5, the same procedure takes place except that the flip flop moves to the other state and the relay RL once more is energised causing contacts RL 1 to move to the dotted line position and the tube Tto be extinguished. The duration between initiating signals can be as desired by the person who is testing the unit and who directs the initiating signals at the unit Thus, for a general test, the person performing the test would shine his torch at the unit once to simulate a mains failure and as soon as the tube T illuminates, he would switch off the torch, and then immediately switch it on again to extinguish the tube T. Four a longer test, he would simply allow appropriate time, e.g. one hour or three hours between the initial shining of the torch at the unit to illuminate tube Tand the final shining of the torch to extinguish the tube T.

If tube Trails to illuminate when the unit is subjected to this testing, then this will indicate a fault in the unit requiring investigation. The production of continuous white light spectrum suitable for actuating the unit can be produced by a higher than average power torch.

The detector 5 is shown diagrammatically in Figure 2, and the photo transistor 10 thereof is housed in housing 12 having an insert 14 acting as a light guide, such that only when light energy is aimed directly at the insert 14 will the transistor 10 be activated. The housing 12 can be set such that incident light will not cause spurious activation of the circuit. The receiver can be mounted on or adjacent the emergency lighting unit (Luminaire) and in the example shown in Figure 2, the housing 12 is provided with a threaded sleeve 16 and a fixing nut 18 and washer 19 forthe connection of the receiver to an existing lighting unit casing. The electrical connection leads extending from transistor 10 are indicated by numeral 20.

In a modified form of the invention, the receiver switch is magnetically operated. It may be for example, a reed switch which is normally open, but which closes, with the effect of bringing on or extinguishing the tube T as above described, when a magnetic field is impressed thereon. The magnetic field can be impressed by means of a permanent or electro-magnet. In another arrangement there is a magnetically actuated device in addition to a light sensitive device and they are connected in the control circuit such that both must be actuated for the effect of a mains failure to be simulated.

Furthermore several types of receiver may be used in combination in orderto make it as difficult as possible for anyone other than authorised personnel to operate the testing of the equipment.

The invention provides the advantage that a person whose job it is to test emergency lighting units can test them quickly and effectively and over as long a period as desired simply by carrying a light transmitter as a means providing magnetic or other signals when the units are equipped in accordance with the present invention without having to remove the mains supply to each unit by manually operating a switch of each unit or by physically removing a fuse of each unit.

Claims (10)

1. An emergency lighting unit and installation having a receiver which is actuable by signals which can be transmitted through space, the receiver being connected to a control circuit of the emergency lighting unit so that upon receipt of signals transmitted through space and the resultant operation of the control circuit, the effect of a mains failure is simulated, the control circuit containing a switching device switchable to on mode (in which the effect of mains failure is simulated) by the said signals, the switching device being adapted to hold in the on mode after removal of the signals until a unit which is adapted to receive a switch off command, receives such a command.

2. An emergency lighting unit and installation according to Claim 1, wherein the same type of signals switches the unit to the on mode and to the off mode.

3. An emergency lighting unit and installation according to Claim 1 or Claim 2, wherein the control circuit comprises a flip flop connected to shift between on and off conditions alternatively upon receipt of signals from said receiver.

4. An emergency lighting unit and installation according to Claim 3, wherein there is a monostable multivibrator connected between the receiver and the flip flop in order to shape electrical pulses which are received by the multivibrator from the receiver.

5. An emergency lighting unit and installation according to any of Claims 1 to 4, wherein the signals are transmitted from a transmitter in the form of a light source which emits a narrow and higher than average power beam of light.

6. An emergency lighting unit and installation according to any of Claims 1 to 5, wherein the receiver is a photo-cell or photo-transistor device.

7. An emergency lighting unit and installation according to Claim 6, wherein the control circuit includes a transistor driven from the flip flop which is made to cut off thereby causing a relay to drop out when the photo-cell device receives transmitted light signals.

8. An emergency lighting unit and installation according to any of Claims 1 to 4, wherein the signals are transmitted from a magnetic signals source.

9. An emergency lighting unit and installation according to Claim 8, wherein the receiver is a reed switch operable by means of an electro magnet or a permanent magnet.

10. An emergency lighting unit and installation substantially as herein described with reference to and as illustrated in the accompanying drawings.