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[ EN ]
Illuminated sign with emergency lighting function
Field of the Invention
The present invention relates to the provision of emergency lighting and signage in buildings and in particular the invention provides an improvement to the construction of illuminated emergency signs which incorporate an emergency lighting function.
Background to the Invention
Prior art illuminated emergency signs take a number of forms. These include streamlined designs centering on thin, edge lit, sign carrying blades, incorporating a light transmitting core extending from a lamp housing containing a fluorescent tube adjacent an edge of the blade as well as batteries, inverter and control circuits. At the other end of the scale, less expensive but bulkier rear illuminated signs are commonly found to be in use, in which the sign housing includes space behind a single sign panel or between bi-directional signs in which one or more fluorescent lamps are located. In each of these known sign types only limited illumination if any is available for emergency lighting.
In the known configurations emergency illumination is at best a secondary feature of the design with light radiated through the lower extremity of the sign housing or blade having travelled through the sign body first and therefore being limited both in intensity and angle of projection.
The location of lamp and electronic components in close proximity in prior art emergency sign configurations also tends to give rise to undesirable levels of heating which often requires mechanisms to carry heat away from components such as lamps and electronic components that suffer serious lifetime degradation when operated at elevated temperatures.
Embodiments of the present invention, by comparison provide improved illumination in emergency lighting conditions while providing relatively even illumination (with reference to requirements of appropriate national and international product standards) through sign carrying surfaces. Further, the spaced location of heat generating components can result in a reduction of thermal stress on sensitive electrical and electronic components.
Within the context of this specification, references to even distribution of light are intended to be read as meaning sufficiently even distribution to meet the relevant standard applicable to the device or the particular feature of the device (eg, standards relating to even illumination of emergency signs or even distribution of light emitted from an emergency light).
Summary of the Invention
According to a first aspect the present invention consists in a sign carrying element for an illuminated sign, the sign carrying element arranged to extend from a base and including a first edge adjacent to the base, a second edge parallel to the first edge and an internal light source located towards the second edge, the sign carrying element including light transmission means to distribute light emitted from the light source evenly through sign carrying surfaces of the sign carrying element and a light emitting region in the vicinity of the second edge through which light from the light source is emitted to provide emergency illumination of an area in the vicinity of the sign carrying element.
Preferably, the light source will be in the lower, one third of the sign carrying element and in the most preferred embodiment the light source is adjacent to the second edge of the sign carrying element.
The sign carrying element can take a number of forms including elements having opaque external structures, with a light transmitting region, in the second edge, or alternatively, the body of the element can be transparent with masking and/or diffusing material applied in appropriate regions.
Preferably, the sign carrying element is formed as a pair of half shells, moulded in translucent, high impact, plastics material, such as acrylic or poly-carbonate, surrounding a pair of lamps located at the upper and lower extremities.
In the case of an opaque body, the light transmitting region can be simply an opening or may incorporate a lens or diffuser.
The light source or sources, will preferably be a fluorescent tube (eg, 8 watt fluorescent tube), or a cold cathode lamp, but could also include other light sources such as LEDs, incandescent lamps, neon lamps or any other suitable light source.
In the preferred embodiment, the sign carrying element is removable from a base in which the power supply and control electronics is housed, however, embodiments in which the sign carrying element is integrated with the power and electronics housing are also possible.

Brief Description of the Drawings
An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which:
Figure 1 is a sectional front view of a sign assembly according to the present invention;
Figure 2 is a sectional end view of the sign assembly of Figure 1;
Figure 3 is a front view and half sectional side view of a sign cartridge from the assembly of Figures 1 and 2;
Figure 4 is a detailed sectional side view of the cartridge of Figure 3; and
Figure 5 is a detailed sectional side view of a cartridge with a different internal configuration to that of Figure 4.
Detailed description of the Preferred Embodiment
Referring to Figures 1 to 4 of the accompanying drawings, an emergency sign assembly is illustrated in sectional elevation view. In this embodiment a base unit 11 is arranged to be mounted to a ceiling and is provided with stand-offs 13 which project slightly above the upper surface for stable seating of the unit against the sealing surface. The base unit 11, houses batteries 14, transformers 15 and an electronics module 16 carrying the communications control, battery charging, device monitoring and electronic ballast circuits required to perform emergency lighting and illuminated sign functions.
In the preferred embodiment, the base unit 11 comprises a mounting and wiring unit 17 and an electronics unit 18, which connect together to form the base unit assembly 11 with the two components 17, 18 being latched together by cooperating latch elements 19, 20. This arrangement allows the mounting and wiring unit to be wired into the building power network and a building safety services monitoring network with the electronics unit 18 removed, allowing easy access to mounting fasteners and wiring connectors. Subsequent connection of the electronics unit 18 provides an assembly in which dangerous voltages are shielded from probing fingers and access to internal electronics, or connection points is restricted by the need of a tool to disassemble the unit.
Extending below the base unit 11 is a sign carrier element 12 which in the preferred embodiment is removable from the base unit 11. The sign carrier 12 fits into a cooperatively shaped opening in the bottom of the base unit 11 and is retained by depressions or detents 22 and cooperating projections 23. Electrical connection between the removable sign carrier 12 and the electronic module 16 of the base unit 11 is via a pair of cooperating electrical connectors 24, 25.
While the preferred embodiment is shown having a removable sign carrier 12, the primary concept of the invention is equally applicable to an assembly in which the sign element is either not removable or is semipermanently mounted to the base 11.
The removable sign element 12 of the preferred embodiment is preferably formed in a transparent, semi-transparent or translucent material and is moulded as a pair of shell halves which when assembled together, encapsulate one or more light sources. The half shells are clipped together by cooperating clip elements 38 around the periphery of each half shell. In the preferred embodiment, the shell of the sign element 11, encapsulates two light sources 26, 27, an upper one of which (light source 26) performs a normal sign illuminating function and the other of the two light sources 27, performs an emergency illumination function whereby the sign is
illuminated, as well as a surrounding area of the floor under emergency conditions when the main lighting supply is interrupted. Alternatively the lower light source 27 can perform both functions, such that it is maintained illuminated under normal supply conditions and is switched over to the emergency supply when the normal supply is interrupted. Wiring 28 to the light sources 26, 27 is run through channels 29 provided in the edges of the sign carrying element 12.
The light sources 26, 27 are located in the chambers 30, adjacent to the upper and lower edges of the sign carrying element 12 and transmit light into the body of the sign carrying element 12. Light from the upper light source 26 shines down through a cavity 31 in the centre of the sign carrying element 12 and is coupled into the transparent plastics material of the sign carrying element 12, through the corrugated surface 32 of the cavity 31. Light coupled into the material of the sign carrying element 12 back-illuminates a sign or signs located on one or both sign carrying surfaces 33. The sign itself may either be screen printed (not shown) onto one of the surfaces 33, or may be a sign formed in a translucent film (also not shown), extending over the surfaces 33 of the sign carrying element and retained by tabs 34.

The lower lamp 27 projects light into the wall 35 of the two halves of the body of the sign carrying element 11, which act as light pipes, having multiple internal reflection modes. In one of the possible reflection modes, light travels from the lower light source along each of the halves of the sign body and is subsequently refracted and reflected out of each of the body halves. The light emerging from the outer surfaces of the body halves back illuminates the signs carried on the sign carrying surfaces of the respective body halves, while the light emerging from the inner surfaces of the body halves travels across the cavity 31 and through the opposite walls 35 of the sign carrying element 12 to back illuminate the signs carried over the opposite outer surfaces of the sign carrying element. Again, light is refracted and/or reflected towards the respective sign carrying surfaces 33 by virtue of the corrugated surfaces 32 bounding the interface between the cavity 31 and the respective wall portions 35 of the sign carrying element 12.
Other possible internal reflection modes involve light undergoing multiple internal reflections within one of the body halves before emerging from one of the surfaces 32, 33.
It should be noted that while the light sources 26, 27 are illustrated located in cavities at the upper and lower extremities of the sign carrying element 12, it is possible to move one or other of the light sources to an intermediate cavity in the sign carrying element 12 such as the cavity 40 illustrated in Figure 5. The design of the corrugations 32 is designed to maximise coupling of light through the sign carrying surfaces of the sign carrier.
Referring to figure 5, an alternative embodiment of the sign carrier is illustrated in which the lower lamp cavity 40 is located approximately midway between the upper and lower edges of the sign body and the modes of distribution of light in the lower portions of the sign body by the lower light source are similar to those previously described for the upper light source with reference to figure 4. Similarly the modes of distribution of light in the upper portions of the sign body of figure 5, by the upper light source, are also similar to those previously described for the upper light source with reference to figure 4.
A portion of the light from the lower light source 27 also projects through lower surfaces 37 of the sign carrying element to illuminate an area below the sign under emergency conditions. In this regard, it should be noted that the two light sources are not generally simultaneously operated. The upper light source 26 providing a normal sign illuminating function during non-emergency conditions and the lower light source 27 operating under emergency conditions to illuminate the sign and to provide emergency lighting functions. The light sources 26, 27 will typically be a high efficiency tubes that provide efficient use of battery power in emergency conditions. The lamps will typically be 8w Fluorescent tubes, although other lamp types such as cold cathode tubes can also be employed. Switching between the operation of the upper light source 26 and the lower light source 27 will typically occur under control of the electronics module 16 which monitors mains voltage and switches over to a battery powered inverter circuit when failure of the mains supply is detected.
Referring to Figures 4 and 5, optional reflector elements 39 may either be formed as part of the sign body moulding or may be provided as an insert member. In either case the reflector elements 39 may inherently have reflective surface characteristics or may optionally be provided with a reflective material applied to their surfaces. The channel 36 formed behind the reflector elements 39 carries wiring running across the top of the sign carrying element, and the reflector elements 39 provide a secondary function of protecting the wiring from heat radiated from the upper lamp 26.
Location of the two lamps within the sign carrying element has the advantage that the lamps are separated from the electronics module, batteries etc. In particular, the lower light source 27 is located remotely from the electronics and this enables the lamp to be substantially in thermal isolation, which in turn enables this lamp to remain operational for a significantly greater period than might otherwise be the case if located in closer proximity to the various heat generating elements of the assembly.
The shell of the sign carrier element 12 of the preferred embodiment, is also openable once it has been removed from the base 11 such that tubes 26, 27 in the carrier 11 may be readily replaced. Removal of the sign carrier element 12 from the base 11 does not expose any dangerous surfaces and therefore may be performed by an unskilled person, as can the task of replacement of the tubes in the sign carrying element.
A further benefit of the removable sign carrier is that the sign carriers may be held in storage during building construction and the installation of the base units 11, to protect the sign carriers from damage. The sign carriers may then be installed after the more robust building activities have been completed. This also enables correct signage to be more easily located when installation takes place. Further, this operation can easily take place just prior to building hand over.
A further benefit of this arrangement is that lamp replacement can be performed at floor level, reducing the number of operations that need to be performed while the workman is standing on a ladder.
In some embodiments, the sign carrying element may also be a sealed unit which is not capable of being opened to replace the lamps. Such an arrangement has the advantage of high functional reliability by ensuring that inappropriate replacement lighting elements are not used.
It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.