Self luminous characters and signs incorporating same

A self luminous character comprises a transparent light carrier having a plan shape defining the desired shape of the character and includes a longitudinally extending recess housing one or more self luminous light sources. Light from the or each light source diffuses through the transparent light carrier and is reflected by reflector means to be emitted through a front surface of the carrier and illuminate the plan shape of the character.

This invention relates to self luminous characters and signs incorporating 
same. 
More particularly the invention is concerned with such characters which 
employ self luminous light sources of the type where a phosphor coating 
within a translucent envelope is excited to luminescence by a gaseous 
radionucleide such as tritium. Such light sources are manufactured by the 
applicants under the Trademark "Betalight". 
In this specification the term character is intended to mean any letter, 
numeral, symbol or pattern which may be used either individually or, in 
combination, to construct self powered illuminated signs, for example 
emergency EXIT signs. 
A wide range of such signs currently manufactured by applicants utilize a 
reflector assembly located in a housing, the reflector being formed with 
depressions having a parabolic cross sectional shape outlining the shape 
of all of the characters of the sign. Self luminous light sources are 
supported at the optical centre along the reflector depressions. 
The form of characters used in emergency signs is defined by British 
Standards and in one case requires a character width of 19 mm. In order to 
obtain efficient "flashing" of the surfaces of the parabolic reflector in 
the above referenced signs, this requirement dictates the use of self 
luminous light sources having a minimum diameter of 5 mm. It will be 
apparent that the larger the diameter of light source the greater is the 
quantity of costly radioactive gas required to provide the desired light 
intensity and, for example, a typical EXIT sign having a 10 year life 
requires eight Curie. 
A diffuser is located above the reflector assembly and the use of a 
parabolic cross section reflector means that the width at the lip of the 
section is greater than the required width of the character (e.g. 19 mm), 
and a stencilled mask is used above the diffuser to define the character 
width and mask the dark areas along the lip regions of the parabolic cross 
section reflectors. 
The diffuser and stencilled mask are retained by a bezel which is bonded to 
the housing, and the assembly may be considered rather complex and 
consequently costly. 
It is therefore an object of this invention to provide a self luminous 
character as hereinbefore defined in which the quantity of radioactive gas 
is substantially reduced and which can be used to construct self luminous 
displays simply and economically. 
Accordingly, in one aspect this invention provides a self luminous 
character comprising a transparent light carrier having a plan shape 
defining substantially the desired shape of the character, at least one 
longitudinally light source located in the recess, and reflector means, 
whereby light emitted by the light source diffuses through the transparent 
carrier and is reflected by the reflector means to be emitted through the 
front surface of the carrier to illuminate the plan shape of the 
character. 
The or each recess may be formed in the front surface of the carrier and in 
one embodiment may be located at the bottom of a channel formed in the 
front surface of the light carrier. 
Diffuser means may be attached over the front surface of the light carrier. 
The reflector means may comprise a coating of reflective paint. 
In one embodiment of the invention the light carrier may be generally 
rectangular in cross section and said reflector means may be provided on 
side and rear surfaces of the light carrier. The reflector means may 
comprise a reflector housing having reflective interal surfaces for 
location around the side and rear surfaces of the light carrier. In such 
an embodiment attachment means may be provided for attaching the light 
carrier to the reflector and may comprise at least one headed stud 
protruding from the rear surface of the light carrier for location through 
a mating hole in an internal web of the reflector. 
Further attachment means may be provided for attaching the reflector to a 
support structure and may comprise screw holes in said internal web, 
In another aspect the invention provides an illuminated sign comprising at 
least one self luminous character constructed as hereinbefore set forth.

An illuminated character 11 illustrated in the form of a capital letter E 
suitable for use in a self luminous EXIT sign includes an injection 
moulded transparent acrylic light carrier 12 having a plan shape defining 
the shape of a capital letter E. 
The carrier is generally rectangular in cross section and a channel 13 
formed in a front surface provides a continuous upstanding boundary edge 
14. The width `A` of carrier 12 corresponds to the required illuminated 
width of the character 11. 
Two longitudinally extending recesses 15 are formed in the front surface of 
the carrier 12 which, in the illustrated embodiment, comprises the surface 
at the bottom of the channel 13. Each recess 15 contains a plurality of 
straight miniature self luminous light sources 16 arranged end to end. 
An injection moulded white acrylic reflector housing 17 locates around side 
and rear surfaces of the light carrier 12 and is retained by three 
integral headed studs 18 (FIG. 2) protruding from the rear surface of the 
carrier 12 and located through mating apertures 19 in an internal web 20 
of the reflector 17. A rearwardly extending continuous wall portion 21 is 
formed integral with the reflector 17 and is slightly longer than the 
protruding length of the studs 18. 
Referring now to FIG. 3, an integral boss 22 protrudes rearwardly from the 
internal web 20 of reflector body 17 and is the same length as the wall 
21. A central aperture 23 through boss 22 facilitates attachment of the 
reflector body 17 as hereinafter described. 
A combined cover and diffuser device 24 is attached over the entire front 
surface of the character 11 and is located against an outwardly protruding 
flange 25 formed integral with carrier 12. 
Light from the plurality of light sources 16 diffuses through the 
transparent light carrier 12 and is reflected by the reflector 17 to be 
emitted through the front surface of the carrier 12 and the cover/diffuser 
20 so as to illuminate the plan shape of the character 11. The arrangement 
provides an even light output and the width of the visible light defining 
the character 11 is defined by the width `A` of the light carrier 12 which 
can be selected to meet the requirements of any specification. 
The use of the miniature light sources 16 which can have a diameter of 
about 2 mm and a length of 22 mm substantially reduces the amount of 
radioactive gas required to effectively illuminate the character 11 and, 
consequently, an illuminated sign using such characters. For example, an 
EXIT sign with a 10 year life and constructed using characters according 
to this invention contains a total of about 4.8 Curie of radioactive gas 
compared to the eight Curie of the existing sign. 
In the illustrated embodiment it is envisaged that the light reflecting 
body 17 of each character 11 in a sign would first be secured such as by a 
screw through each attachment boss 22 (one only being shown) to a support 
structure which may be a wall or other surface on which the sign is to be 
sited, or on to a baseplate or boxtype frame which in turn is secured to 
the support structure. In either case the assembled light carriers 12 for 
the individual characters 11 are then located and retained in the 
reflector body 17 by insertion of the headed studs 18 through the 
apertures in the internal wall of the body 17. 
Thus, the individually illuminated characters 11 of this invention use a 
very small quantity of radioactive gas and represent a very versatile 
method of constructing any desired self luminous sign that is very simple 
to construct and therefore economical. 
Whilst one embodiment of the invention has been described and illustrated 
it will be understood that many modifications may be made without 
departing from the scope of the invention. For example the channel 13 
could be dispensed with and the light sources 16 located at the bottom of 
deeper recesses 15. The reflector device 17 may be of any suitable 
material such as aluminum which is provided with a reflective internal 
surface or, alternatively, may comprise simply a coat of reflective e.g. 
white, paint, on the side and rear surfaces of the light carrier 12. The 
light carrier 12 may be of any suitable cross sectional shape having a 
generally planar front surface, for example semi-circular, and any 
suitable means may be used to attach the light carrier 12 to the reflector 
17 and to attach the reflector 17 to a support structure. The use of the 
short, straight small diameter light sources 16 means that similar light 
sources can be used in characters having a curved outline shape such as 
the letter `S` however, alternatively, curved small diameter light sources 
could be used.