Sign construction for photographic transparencies

A sealed backlit sign frame having a photographic transparency as the viewing face of the frame is provided. Lights are provided behind the transparency for illumination. A partial vacuum or negative pressure is created in the frame and bows the transparency inwardly. This bowing action stabilizes the transparency and prevents wind induced undulations. Exhaust blowers and air vent dampers are provided to maintain the negative pressure in the frame. The blowers, dampers and lights are preferably controlled by a suitable control system.

BACKGROUND OF THE INVENTION 
This invention relates generally to outdoor sign constructions and, in 
particular, to a sign construction for outdoor photographic transparencies 
or other thin-walled rear-illuminated murals. 
Large photographic transparencies for indoor use are known in the art. Such 
photographic transparencies are constructed by splicing large processed 
strips of film together to form a transparency of the desired size having 
a unitary oversized picture thereon. One exemplary large indoor color 
photographic transparency of this type is displayed above the main waiting 
room of Grand Central Station in New York City. The tranparency forms a 
large display surface which is illuminated from the rear to provide a 
beautiful picture. 
However, use of a similar sign construction outdoors with a thin-walled 
transparency has so far proven impractical. Specifically, large 
transparencies undulate due to wind currents when displayed outdoors. The 
undulations become stronger and more frequent as wind velocity increases. 
Eventually, the undulations produced by high winds create stresses in the 
film and splices, stretch or otherwise deform the transparency and 
eventually destroy the integrity of the transparency. Supporting 
structures to prevent film undulation in outdoor installations have to 
date been impractical, costly and detrimental to the visual impact of a 
large backlit transparency. 
Accordingly, it is desired to provide a sign construction that is practical 
for outdoor display of large rear-illuminated photographic transparencies 
or other thin-walled murals. 
SUMMARY OF THE INVENTION 
Generally speaking, in accordance with the present invention, a sign 
construction for supporting a thin-walled mural such as a photographic 
transparency is provided. The sign construction includes a frame having an 
open front which supports the mural around the periphery thereof to cover 
the open front of the frame. A pressure system creates a negative pressure 
behind the mural in the frame to protect the mural from damage caused by 
wind or the like. 
In a preferred embodiment, a sealed backlit sign box or frame which 
supports a photographic transparency around the periphery thereof is 
provided. Appropriate lights are provided in the box behind the 
transparency for illuminating same. A partial vacuum or negative pressure 
is created in the box which tends to bow the transparency inward toward 
the rear of the frame. This bowing action stabilizes the transparency and 
substantially prevents wind-induced undulations. Exhaust blowers and air 
vent dampers are provided to assist in maintaining the negative pressure 
in the frame. The blowers, dampers and lights are controlled by a suitable 
control system. 
It is, therefore, an object of the invention to provide a sign construction 
suitable for outdoor display of large backlit transparencies. 
It is another object of the invention to provide a sign construction using 
a sign box or frame in which the transparency to be displayed forms the 
viewing face of the box. 
It is a further object of the invention to provide means for displaying 
large outdoor photographic transparencies or other thin-walled murals 
which prevent damage to the transparency caused by wind or other 
environmental factors. 
Still other objects and advantages of the invention will in part be obvious 
and will in part be apparent from the specification. 
The invention accordingly comprises the features of construction, 
combination of elements, and arrangement of parts which will be 
exemplified in the construction hereinafter set forth, and the scope of 
the invention will be indicated in the claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Reference is first made to FIG. 1 which depicts an outdoor sign, generally 
indicated at 10, constructed in accordance with a preferred embodiment of 
the present invention. Sign 10 is shown mounted on the roof of a building 
11. Sign 10 includes a sign box or frame 50 which supports a thin-walled 
photographic transparency 12. 
Referring now to FIGS. 2 through 5 in addition to FIG. 1, it is seen that 
sign frame 50 includes sides 52 and 54, a top 56, a bottom 58 and a back 
wall 59. Appropriate sign supporting members 60 anchor frame 50 to 
building 11. Front 62 of frame 50 is open to permit mounting of 
transparency 12 thereacross. 
Transparency 12 forms the view face of frame 50. A damper system 14 at the 
bottom 58 of frame 50 regulates airflow through vents 16 in the direction 
of arrows A. Exhaust blowers 18 supported on the top 56 of frame 50 
operate in conjunction with dampers 14 and are provided for the purpose of 
creating a negative pressure inside frame 50 to cause transparency 12 to 
bow inwardly as best depicted in FIGS. 2 and 4. Lights 20 are positioned 
on the back wall 59 of frame 50 in order to illuminate transparency 12 
from the rear thereof. 
Vents 16 are openings adapted to provide for the flow of air. Dampers 14 
are provided on each vent opening 16 for the purpose of regulating the 
size of the opening and controlling the quantity of airflow. In a 
preferred embodiment of the invention, filters 24 are also provided below 
each vent opening 16 to remove particulate matter from the air entering 
frame 50. The number of vent openings 16 is not critical but the number 
and size must be such as will allow for sufficient and uniform flow of air 
through frame 50 for the purpose of creating negative pressure inside 
frame 50. 
In a preferred embodiment, each damper 14 is provided on hinge arrangement 
28 such that vent 16 can be selectively opened and closed. Each hinge 
arrangement 28 is operated in turn by damper motor 26. Damper motor 26 may 
be any suitable type of motor that is conventional and well known in the 
art. It is noted that the type of damper and damper motor construction is 
not limited to the arrangement shown. It is to be understood that any 
suitable arrangement for providing controlled airflow through vents 16 
into frame 50 can suitably be used and is within the scope of the 
invention. 
Dampers 14 are operated in conjunction with exhaust blowers 18 for the 
purpose of regulating airflow within frame 50. Although a plurality of 
exhaust blowers 18 are shown in FIG. 1, the type and number of exhaust 
blowers 18 may be selected depending on the size of the frame and, as with 
dampers 14, any suitable construction for providing controlled airflow 
through frame 50 can suitably be used and is within the scope of the 
invention. Exhaust blowers such as those known as Peerless Electric Air 
Moving Equipment manufactured by Porter Electrical Division, H. K. Porter 
Company, Inc. are an exemplary type. 
A plurality of lights or lamps 20 are secured to back wall 59 of frame 50 
for the purpose of providing illumination to transparency 12. It is 
preferred that the transparency be as brightly illuminated as possible in 
order to provide a brilliant display in daylight hours. In a preferred 
embodiment of the invention, fluorescent lamps are used. Such lamps 
provide good color rendition and have a low envelope temperature. As is 
discussed in greater detail hereinbelow, the temperature of operation of 
the sign construction of the invention must be controlled. 
Lamps 20 can be secured to back wall 59 of frame 50 by any suitable 
securing means. In a preferred embodiment, multiple rows of fluorescent 
lamps are used and the lamps are staggered to break up continuous dark 
areas between the rows of lamps. 
The sign construction of the invention is especially suitable for use with 
a photograph provided on a film support 30 of the type shown in FIG. 6. In 
a preferred embodiment, film support 30 is polyester and can be of the 
type marketed by Kodak of Rochester, N.Y. under the tradename ESTAR.RTM.. 
Such a support is tough and has good properties for use in accordance with 
the invention. A photographic emulsion layer 32, a glossy polyester layer 
34 and a matte acrylic layer 36 are provided in order on support 30. The 
polyester/acrylic laminate, layers 34 and 36, on the face of transparency 
12 serves to protect emulsion layer 32 from environmental factors, 
increases the strength of transparency 12, provides protection from 
ultraviolet light and reduces undesirable reflection. Each section of 
transparency 12 can be up to a maximum of about 6 feet wide. Accordingly, 
multiple strips of a photograph or other mural are spliced together to 
form transparency 12. 
A glossy polyester tape 40 followed by matte acrylic tape 42 are provided 
on the outside of transparency 12 adjacent matte acrylic layer 36. 
Finally, narrow double sided polyester tape 44 and acetate splicing tape 
46 are provided along the back of transparency 12 adjacent film support 
30. It is preferable for the splice to be of a cemented type as opposed to 
a pressure sensitive type in order to withstand the effect of cross-wise 
forces. 
In a preferred embodiment, splices 38 are provided in the vertical 
direction of transparency 12. Once all the splices have been made and 
transparency 12 is ready for viewing, transparency 12 is rolled in such 
way that it can be secured along a side edge of frame 50 and unrolled in a 
horizontal direction to provide the viewing surface. It is necessary to 
seal transparency 12 against the front legs 70 of frame 50. As best 
depicted in FIGS. 3 and 5, the perimeter of transparency 12 is captured 
intermediate a beam 80 and an opposing gasket 82. 
It is, however, known that plastic film of this type will creep when 
maintained under tension for an extended period of time. Accordingly, the 
securing means of the type shown in FIGS. 3 and 5 are preferably used to 
secure transparency 12. The construction 90 shown in FIG. 3 fixes the top 
of transparency 12 in an unmoving position and is preferably used along 
the top of transparency 12 adjacent exhaust blowers 18. As depicted in 
FIG. 3, mounting bracket 92 is secured to top 12a of transparency 12 
through grommets 13. Mounting arm 94 is secured to top 56 of frame 50. 
Mounting bracket 92 includes mounting plate 92a which is secured to 
mounting arm 94 by means of bolt 96 and nut 97. A plurality of mounting 
devices 90 extend across top of transparency 12 to provide adequate 
support therefor. 
As depicted in FIG. 5, the sides and bottom of transparency 12 are 
supported by a plurality of adjustable mounting devices 100. Each device 
100 includes mounting bracket 92 with mounting plate 92a. Turnscrew device 
102 includes U-shaped arm 104 having rod 106 which extends through opening 
92b in plate 92a. Mounting arm 108 supports turnscrew device 102 on 
extension support 50a of frame 50. As screw 103 is rotated, the tension on 
transparency 12 can be selectively adjusted. 
Controller 120 of the type manufactured by Staefa Control System Inc, of 
Larchmont, N.Y. is used to regulate the pressure and temperature inside 
frame 50. Controller 120 is coupled to temperature probes 122, pressure 
probes 124 and damper motor 26. Although exhaust blowers 18 operate 
continuously, controller 120 is used to regulate the opening of dampers 14 
and, correspondingly, the size of vents 16, for the purpose of regulating 
airflow through frame 50. Airflow is regulated primarily to maintain the 
required negative pressure, but also to regulate the temperature inside 
frame 50. In experimental tests conducted by the inventor, it was found 
that pressures of less than about 2 inches of water can desirably be used. 
More preferably, the pressure should be between about 0.6 and 1.5 inches 
of water although the optimum pressure can only be determined when the 
material used to construct the transparency and the environmental 
conditions to which the sign will be subjected are known. 
It is important that the temperature inside frame 50 and of transparency 12 
not become too elevated or the structural integrity of transparency 12 
will be destroyed. The controller can be adjusted so as to turn off lights 
inside the box if the temperature becomes too elevated. In general, the 
temperature inside the box should not exceed 120.degree. F. although it 
may be desirable to regulate the temperature by turning off banks of 
lights when the temperature reaches 105.degree. F. or at selected 
intervals thereafter. In addition, an electronic programmable time clock 
is preferably provided for the purpose of sequencing the lighting in 
accordance with a preset schedule and making seasonal adjustments. 
As can be seen, by providing a sign construction in accordance with the 
invention, an outdoor backlighted transparency can be provided for 
viewing. The outdoor backlighted transparency forms the viewing face of a 
specially constructed sign frame having a negative pressure selectively 
created inside. Accordingly, the transparency is not affected by wind or 
other environmental factors. 
It will thus be seen that the objects set forth above, among those made 
apparent from the preceding description, are sufficiently attained and, 
since certain changes may be made in the above construction without 
departing from the spirit and scope of the invention, it is intended that 
all matter contained in the above description or shown in the accompanying 
drawings shall be interpreted as illustrative and not in a limiting sense. 
It is also to be understood that the following claims are intended to cover 
all of the generic and specific features of the invention herein described 
and all statements of the scope of the invention which, as a matter of 
language, might be said to fall therebetween.