Emergency sign

Abstract

 An illuminated emergency sign is provided which comprises a housing adapted to contain one or more light emitting diodes and an image defining panel covering a front portion of the housing, said housing having one or more openings through which light from the or each light emitting diode can pass, the or each opening defining the shape of a predetermined image. The use of LED's makes the sign easy to see in low visibility conditions, such as a smoke filled room. In one embodiment, a solid state relay is provided of the low voltage reed-type which causes the LED's to flash.

Description

[0001] This invention relates to an improved emergency sign especially but not exclusively for use in buildings accessible to the public.

[0002] It is known to provide signs which indicate the direction to the nearest emergency exit in a building. Indeed in many countries it is a legal requirement that such signs are provided in buildings to which the public have access.

[0003] It is also known to provide emergency exit signs which are illuminated using a fluorescent light source provided behind a screen printed with an image such as a running man or an image of the word "exit".

[0004] According to a first aspect the invention provides an illuminated emergency sign comprising a housing adapted to contain one or more light emitting diodes and an image defining panel covering a front portion of the housing, said housing having one or more openings through which light from the or each light emitting diode can pass, the or each opening defining the shape of a predetermined image.

[0005] Thus the invention provides an emergency sign in which light emitting diodes (LED's) are used to illuminate the sign. It has been found that the point source of light from an LED is easier to see in low visibility conditions, such as a smoke filled room, than a fluorescent light.

[0006] The emergency sign may further comprise a light diffusing means adapted to diffuse the light passing through one or more of the or each opening. It may be provided between the or each LED and the one or more openings. The diffusing means may be an optically transparent (clear) sheet having a substantially smooth flat surface on one side and a number of prismatic lenses formed on the surface of the other side. The diffuser can be secured across at least one of the openings. Best performance has been achieved with the prismatic surface facing away from the LED's, although it could be positioned with the prismatic surface facing the LED's.

[0007] The openings may be defined by cut-outs in the image defining panel which may be of an optically translucent, opaque or non-optically transmissive material. Thus light from the LED's only passes through the openings and is blocked by the remaining panel material. Alternatively the panel may be made from an optically transparent material and the openings may be defined by screen printing a pattern thereon or otherwise obscuring parts of the panel.

[0008] The emergency sign may include an electronic circuit adapted to drive the light emitting diodes. The circuit may be battery operated, for example from a two cell Ni-Cad battery pack having an open circuit voltage of approximately 2.8 volts maximum and 2.5 volts nominal. The light emitting diodes may be adapted to be illuminated for at least three hours on a single set of batteries without the need for recharging.

[0009] One or more of the or each of the light emitting diodes may be adapted to flash. They may flash continuously in use or only during an emergency. A switching means may be provided having a first state and a second state. The switch may be adapted to be in the first state during normal use and in the second state in the event of an emergency such as a fire. The flashing rate may have a cycle time of substantially 0.5 seconds or one, two or three seconds or any value therebetween.

[0010] The electronic circuit may include a low voltage reed-type relay adapted to open and close to cause one or more of the LED's to flash. The use of a relay is advantageous over the use of solid state switching devices because it does not present a significant voltage drop. Solid state devices typically provide voltage drops of 0.6-0.7 volts for silicon and around 0.2-0.3 volts for germanium devices.

[0011] The relay may be operated by an astable drive circuit. The relay may include a coil driven directly by an active element within the astable drive circuit to minimise power losses.

[0012] Three openings may be provided. Each may respectively define a predetermined image of the outline of a running man, a directional arrow and a door respectively. When illuminated by the LED's an observer will see these shapes illuminated by the LED's and quickly recognise the direction to the nearest emergency exit. Of course other predetermined images may be used by changing the shape and number of cut-out. For example four openings may be provided having outlines defining the letters E, X, I and T respectively.

[0013] There will now be described, by way of example only, one example of the present invention with reference to the accompanying drawings on which:

Figure 1 is a perspective view of an illuminated exit sign in accordance with the present invention;

Figure 2 is an exploded view of the sign of Figure 1; and

Figure 3 is a block diagram showing an electronic drive circuit for the light emitting diodes within the sign.

[0014] The emergency exit sign 1 comprises a box-like body 2 having a lid 3 which forms an image defining panel. The lid 3 is made from metal sheet provided with three cut-outs or openings 4,5,6 in the shape of a running man, an arrow and a door respectively. An electronic circuit 7 is provided in the body 2 which provides control for a number of light emitting diodes 8 and a battery pack 9 is provided for supplying power to drive the electronic circuit.

[0015] It has been found that in low visibility conditions such as would arise in a smoke filled room, it is easier to identify high level "point light" sources than diffused sources, such as incandescent bulbs or fluorescent lighting. LED's represent such point light sources and are arranged in the housing behind each opening to illuminate the sign.

[0016] A diffuser panel 10 is provided between each opening and the light sources. The panel is fabricated from clear plastic and has a smooth side (which faces the light source) and a textured side provided with a large number of prismatic lenses which face the opening. This has been found to present a minimal disruption to the light source, whilst enabling the light emitted from the sign to be seen over a wide range of angles in low visibility conditions.

[0017] The electrical circuit is shown schematically in Figure 3. The circuit comprises a battery pack, an astable drive circuit, a low voltage reed-type relay and an LED array.

[0018] The battery pack comprises two Ni-Cad batteries having an open circuit voltage of 2.8 volts and a nominal voltage of 2.5 volts; other types and sizes of battery may be used. The battery powers an astable circuit which oscillates at a predetermined frequency of, say, 2Hz. The astable outputs a signal to a coil of a low voltage reed-type relay causing the relay to open and close a connection between the array of LED's and the battery at the oscillation frequency. Thus the LED's will flash under the control of the astable circuit. The use of the reed-relay provides a significant advantage over the use of solid state semiconductor switches such as transistors as it exhibits negligible voltage drop across its contacts whilst being capable of switching the current demanded by the array of LED's.

[0019] The reed-type relay is (optionally) arranged so that the moving contacts are totally enclosed. This makes the device suitable for use in hazardous environments and prevents degradation of the relay contacts.

[0020] The exit sign may therefore be fully self-contained, deriving all of its power from the battery pack. Switching means may be incorporated into the electronic circuit for activating the astable so that the lights only flash in an emergency.

Claims

1. An illuminated emergency sign (1) comprising a housing (2) adapted to contain one or more light emitting diodes (8) and an image defining panel (3) covering a front portion of the housing (2), said housing (2) having one or more openings (4, 5, 6) through which light from the or each light emitting diode (8) can pass, the or each opening (4, 5, 6) defining the shape of a predetermined image.

2. An illuminated emergency sign (1) according to Claim 1 which further comprises a light diffusing means (10) adapted to diffuse the light passing through one or more of the or each opening (4, 5, 6).

3. An illuminated emergency sign according to Claim 2 in which the light diffusing means (10) is provided between the or each LED (8) and the one or more openings (4, 5, 6).

4. An illuminated emergency sign according to Claim 2 or Claim 3 in which the diffusing means (10) comprises an optically transparent (clear) sheet having a substantially smooth flat surface on one side and a number of prismatic lenses formed on the surface of the other side.

5. An illuminated emergency sign according to any preceding claim in which the or each opening (4, 5, 6) is defined by a cut-out in the image defining panel (3) which is of an optically translucent material.

6. An illuminated emergency sign according to any preceding claim which further includes an electronic circuit (7) adapted to drive the or each of the light emitting diodes (48).

7. An illuminated emergency sign according to any preceding claim in which one or more of the or each light emitting diodes (8) is/are adapted to flash.

8. An illuminated emergency sign according to Claim 7 in which the electronic circuit (7) includes a low voltage reed-type relay adapted to open and close to cause one or more of the light emitting diodes (8) to flash.

9. An illuminated emergency sign according to Claim 7 in which the relay is operated by an astable drive circuit.

Drawing