Internally illuminated sign

An internally illuminated sign in which a luminaire mounted on the border or periphery of the sign uniformly illuminates the face and/or faces of the sign thereby eliminating any necessity for providing human access to the interior of the sign for maintenance and relamping.

FIELD OF THE INVENTION 
This invention relates generally to illuminated signs and more specifically 
to an illuminated sign having internal illumination. 
BACKGROUND OF THE INVENTION 
Internally illuminated signs have one or more translucent faces or message 
areas which are illuminated by lamps mounted inside the sign. While 
internally illuminated signs are often preferred over externally lighted 
signs, internally lighted signs of the prior art have been much more 
expensive to construct than externally lighted signs, especially when the 
sign is large. Internally illuminated signs are usually lighted with 
fluorescent lamps, although in some instances the light in internally 
illuminated signs is provided by mercury vapor or metal halide lamps. The 
translucent faces of the sign can be either rigid or flexible. Small rigid 
translucent faced internally illuminated signs often have hinged faces in 
order to provide access to the lamps for maintenance and relamping, 
whereas, large internally illuminated signs normally utilize flex faces 
and are built up to thirty-six inches deep to allow a person to enter the 
sign through the side and thereby provide access to the lamps for 
maintenance and relamping. In order to provide a sign having sufficient 
depth to allow human access, it is necessary for sign manufacturers to 
build a framework structure for the sign which adds significantly to the 
cost of the sign. In externally lighted signs, aluminum extrusions which 
are relatively inexpensive are often used as the outer framing. However, 
since aluminum extrusions have a practical cross-section limit of about 
fifteen inches, the depth of the large internally illuminated signs 
precludes sign manufacturers from using aluminum extrusions for the 
outside structure of the signs which require human access, thereby greatly 
increasing construction costs of internally illuminated signs of the prior 
art. In addition, in internally illuminated signs of the prior art, there 
has been difficulty in achieving the desired uniformity of luminance 
across the full area of the sign face, since there is a tendency for the 
portion of the face of the sign adjacent the lamp to be much brighter than 
the rest of the sign face. 
BRIEF SUMMARY OF THE INVENTION 
This invention relates to an internally illuminated sign in which the need 
for human access into the interior of the sign for maintenance and 
relamping is eliminated thereby eliminating the need for a deep sign and 
the higher costs associated with such sign construction. The present 
invention provides an internally illuminated sign in which a luminaire 
mounted on the border or periphery of the sign uniformly illuminates the 
faces of the sign. A significant feature of the present invention is 
uniformly illuminating the face or faces of the sign. As noted above, in 
internally illuminated signs of the prior art, there was a tendency for 
the portions of the sign face adjacent the lamps to be brighter than the 
rest of the sign face resulting in an uneven and undesirable distribution 
of light across the sign face. 
The luminaire mounted on the border and internally illuminating the faces 
of the internally illuminated sign includes an aluminum reflector for 
distributing light in a fan-shaped pattern laterally along the sign and 
parallel to the sign faces, and a refractor which intercepts the light and 
directs the light to provide a uniform luminance on the sign faces while 
at the same time blocking direct source light from penetrating the sides 
of the refractor and producing a bright spot on a portion of the sign face 
adjacent the luminaire. 
These and other features and aspects of the invention, as well as its 
various benefits, will be made more clear in the detailed description of 
the invention which follows.

DESCRIPTION OF THE INVENTION 
Referring to FIG. 1, there is shown in an embodiment of the present 
invention a sectional view of the interior of an internally illuminated 
sign generally identified by the reference numeral 10 in which a number of 
luminaires 12 mounted at a lower periphery or border 14 of the sign 10 are 
adapted to provide a light distribution pattern generally identified by 
the reference numeral 16 to uniformly illuminate the faces 18 of the sign 
10. Each of the luminaires 12 is mounted in such a manner that its lamp or 
light source 20 is positioned below the translucent faces 18 of the sign 
10 and has an easily openable housing 11 which extends down below the sign 
10. The housing 11 may be opened in any number of ways, for instance, it 
may be pivotally mounted about a hinge 13 and secured in a closed position 
by a latch 15, so that it may be opened to provide easy access to the 
interior of the luminaire for maintenance and relamping. 
With the luminaires 12 mounted at the lower border 14 of the sign 10, the 
luminaires can be opened for maintenance and relamping without the need 
for a deep sign to provide human access. Since the present invention 
eliminates the necessity of having a deep sign, the translucent faces 18 
of the sign 10 can be spaced less than 15 inches apart from one another 
and the outer structure of the sign can be made out of aluminum extrusion 
or other relatively inexpensive construction. While FIG. 1 illustrates the 
utilization of a number of luminaires, it should be apparent that the 
number of luminaires necessary is dependent on the size of the sign. Also, 
while in the embodiment of the invention illustrated in FIG. 1, the sign 
has two translucent faces the same principles of the present invention 
apply whether the sign has one or more translucent faces. Furthermore, 
while in the embodiment of the invention illustrated in the drawings, the 
luminaire is positioned at the bottom of the sign it is equally 
satisfactory to position the luminaires anywhere along the border of the 
sign such as at the top or the sides for instance. 
Referring to FIG. 2, there is shown a frontal sectional view of the 
interior of one of the luminaires 12 mounted on the border of the sign 10, 
having therein the lamp or light source 20, a reflector 22, made of 
aluminum or the like, positioned below the light source 20 and a refractor 
24. As illustrated in FIG. 2, the reflector 22 is designed to reflect the 
light from the light source 20 in a fan-shaped pattern, generally 
identified by the reference numeral 26, laterally across a segment of the 
sign 10. 
In FIG. 3 there is shown a side sectional view of the interior of the 
luminaire 12 of FIG. 2, illustrating the parabolic contoured bottom 28 of 
the reflector 22 reflecting light rays from the light source 20 up through 
the top 30 of the refractor 24 in a light distribution pattern generally 
identified by the reference numeral 32, parallel to the face 18 of the 
sign 10. 
With reference to FIG. 7, there is further shown an additional embodiment 
of reflector 22 having fluted sections 33 vertically disposed in housing 
11 to redirect light and reduce the brightness of "hot spots" or "bright 
spots" on the sign translucent faces 18 near luminaires 12. 
FIG. 4 is a frontal sectional view of the interior of the luminaire 12 in 
FIG. 2, illustrating the manner in which the refractor 24, by means of 
prisms as shown in FIG. 4, directs light from the light source 20 into a 
uniform pattern of light, generally identified by the reference numeral 
34, onto the inside surfaces of the sign faces 18. 
Referring now to FIG. 5, there is shown again the side sectional view of 
the interior of the luminaire 12 as pictured in FIG. 3, now illustrating a 
light pattern, generally identified by the reference numeral 36, formed by 
the action of horizontal reflecting prisms 37, as shown in FIGS. 3 and 5 
on the outside surfaces of the sides 38 of the luminaire refractor 24 
adjacent the translucent faces 18 of the sign 10 blocking and/or 
reflecting and redirecting most of the direct light from the light source 
20 and minimizing light penetration through the sides 38 of the refractor 
24 that would normally produce excessive luminance on the sign translucent 
faces 18. 
All or a portion of these reflecting prisms 37 may be coated to assist in 
blocking and redirecting the light rays. Reflecting prisms 37 may be 
selectively coated with ceramic paints or other known heat-tolerant paints 
which can provide similar blocking performance. In the preferred 
embodiment, as shown in FIGS. 3-5, prisms 37 are selectively rear surface 
metalized via spraying or other known deposition techniques to obtain the 
required light blocking and/or light redirection. The coating process is 
applied to prisms 37 at a selected angle depending on the prismatic 
structure in order to partially coat the prisms. The uncoated areas of the 
prismatic structure allow light to penetrate and be refracted. The coated 
parts of the prismatic structure allow light to be redirected back to the 
reflector 22, allow light to be directed toward some other useful part of 
the luminaire 12 or allow light to be blocked. 
In an alternative embodiment as shown in FIG. 8, layers of translucent 
material 39 such as white diffusing panels, for example, may be used to 
block light near the luminaire 12, thereby reducing the brightness of the 
sign. Layering the translucent material provides a means of adjusting the 
correct amount of light blockage. Those skilled in the art will thus 
recognize that multiple layers will block more light, where necessary. 
In yet another alternative embodiment as shown in FIG. 9, vertically 
disposed and spacially separated perforated metal plates 41 may also be 
used to reduce the brightness on the sign translucent faces 18 near the 
luminaire. Still further, in yet another alternative embodiment as shown 
in FIG. 10, vertically disposed and spacially separated louvers 43 may 
also be used to reduce "bright spots" on sign translucent faces 18. 
Louvers 43 may also be coated preferably with a heat resistant material to 
improve their efficiency in blocking light. 
Referring now to FIG. 6, which is a top sectional view of the side 
sectional view of the interior of the luminaire 12 pictured in FIG. 5, 
there is illustrated the action of vertical biasing prisms 33, as shown in 
FIG. 6, located on the inside surface of the sides 38 of the refractor 24 
to reduce penetration of light through the refractor sides 38 and redirect 
light from the light source 20 laterally along the translucent faces 18 of 
the sign 10. 
The action of the vertical biasing prisms located on the inside surface of 
the sides 38 of the refractor 24 cooperate with the horizontal reflecting 
prisms 37 on the outside surfaces of luminaire refractor 24 to effectively 
avoid the appearance of a bright spot on the portion of the sign 
translucent face 18 adjacent the light source 20. 
The horizontal reflecting prisms 37 on the outside of the sides 38 of the 
refractor 24 are positioned so their axes are coincident with the light 
rays inside the glass. Since there is normally some rounding on each peak 
and valley of the prisms 37, this rounding will allow light to go directly 
through and cause brightness on the face of the sign were it not for the 
action of the vertical biasing prisms 39. Since each peak and valley of 
the vertical biasing prisms 39 will also be rounded and to illustrate the 
point, assuming for example, the rounding of each prism to be 
approximately 10%, the inside vertical prisms coupled with the outside 
horizontal prisms will reduce the amount of the light going directly 
through the refractor to 10% times 10% or 1%. 
Another function of the internal biasing prisms 39 is to allow as much 
greater acceptance angle for the outside reflecting prisms 37. With light 
going directly into a reflecting prism, there is only a range of .+-.3 
degrees for total internal reflection. If the source is larger than this 
.+-.3 degrees, than the prism will start to "leak." Accordingly, with the 
action of the internal vertical biasing prisms 39 biasing the light in a 
direction parallel to the reflecting prism path 37, the angle of the light 
with respect to the normal of the reflecting surface becomes much greater 
and therefore total reflection occurs from a much larger source. 
From the foregoing, it can be seen that there has been provided by the 
subject invention a new and improved internally illuminated sign in which 
a luminaire mounted at the lower border or periphery of a sign utilizes a 
reflector to distribute light in a fan-shaped pattern laterally along the 
sign and parallel to the face of the sign, and a refractor to intercept 
light and redirect it to provide a uniform luminance on the sign face 
while at the same time blocking direct source light from penetrating the 
sides of the refractor and producing hot spots on the sign face. 
It should be obvious that although a preferred embodiment of the invention 
has been described, it is possible to make changes to certain specific 
details of the assembly without departing from the spirit and scope of the 
invention.