An emergency exit sign utilizes an EL lamp in combination with
a pilot light which is connected to the EL lamp via a photoelectric
link. The photoelectric link monitors the brightness of the EL lamp
and keeps the pilot light on so long as the EL lamp is lit. The
pilot light is necessary because the illumination provided by the
EL lamp may be less than the illumination of background brightness
making it difficult to tell by looking at the EL lamp whether or
not the EL lamp is energized. Since the pilot light provides a "point"
of illumination, it is easy to see when it is on so that one can
tell whether or not the sign is lighted by simply looking at the
pilot light. In order to see the exit sign even if power to the
EL lamp is interrupted and the room is dark, a translucent sheet
of phosphorescent material is placed over the EL lamp to transmit
light from the EL lamp while at the same time storing energy so
as to "glow in the dark" should the EL lamp be extinguished.
In order to increase utilization of this exit sign, structure is
provided for easily retrofitting the sign to existing emergency
exit housings. The structure includes spring-closed, U-shaped clips
which are frictionally attached to the housing and which each have
an exposable adhesive surface against which the exit sign is pressed
for permanently installing the sign on the housing. In addition,
an adapter is provided which allows the exit sign to be readily
plugged into the existing lightbulb socket prior to adhering the
exit sign to the housing.
What is claimed is:
1. An emergency exit sign comprising:
an EL light source; wherein the DL light source inclddes a layer
of phosphorous encapsulated between a layer of glass and a steel
means for energizing the EL light source;
means for configuring the light emitted by the EL light source
into a message meaning "exit";
photoelectric cell means disposed adjacent the EL light source
for monitoring the intensity of the illumination emitted by the
EL light source;
a pilot ligh for indicating that the EL light source is illuminating,
means for connecting the photoelectric cell means to the pilot
light for allowing current to flow to the pilot light only when
the photoelectric cell means detects illumination of the EL light
source, whereby the pilot light will indicate that the EL light
source is energized and working even when background illumination
is greater than the illumination from the EL light source.
2. The emergency exit bign of claim 1 further including retrofit
means for mounting the exit sign on an existing exit sign housing
which includes upper and lower flanges behind which an existing
emergency exit sign is held, and wherein the retrofit means includes
U-shaped clips having legs which are spring-biased toward one another,
wherein the U-shaped clips are slipped over the flanges with the
flanges between the legs of the clips so that the clips are frictionally
secured to the flanges;
an outwardly-facing adhesive surface on at least one of the legs
of each clip, and
a casing enclosing the retrofit sign with the casing having a rigid
back portion wherein when the sign is pressed against the adhesive,
a rigid structure results locking the retrofit sign to the housing.
3. The retrofit device of claim 2 further including a plug electrically
connected by a flexible line to the EL light source, and
an adapter having a socket at one end for receiving the plug and
screw threads at the other end for screwing into an existing light
bulb socket once the light bulb has been removed.
4. The emergency exit sign of claim 1 wherein the photoelectric
cell means is connected in series with the pilot light and in parallel
with the lines which energize the EL light source.
5. The emergency exit sign of claim 4 wherein the pilot light is
a neon lamp.
6. The emergency exit sign of claim 5 wherein resistance means
is placed between the photoelectric cell means and pilot light to
set a predetermined level at which the photocell switches off the
7. The emergency exit sign of claim 1 4 5 or 6 further including
means for retrofitting the sign to existing emergency exit sign
RELATED PATENT APPLICATION
U.S. patent application Ser. No. 353390 U.S. Pat. No. 4420878
filed Mar. 1 1982 titled "Flat Emergency Exit Sign Utilizing
An Electro-Luminescent Lamp."
BACKGROUND OF THE INVENTION
Almost all public buildings are required to have signs identifying
emergency exits. These signs are generally rectangles and are perhaps
twelve inches long and eight inches high. The dimensions may vary
depending on the code or standard governing the size of the signs.
Most of these signs are illuminated by incandescent lamps. In order
to illuminate the entire sign, two twenty-watt lamps are usually
required. Most fire codes require that the signs be lit continuously
while the building is occupied. Since many public buildings have
numerous exits, a single building may have hundreds of signs, consuming
thousands of kilowatts of electricity per year. In addition, the
signs generate heat which must be removed during the air conditioning
season. Since the signs are located near ceilings, the heat input
during the heating season is minimized because much of the heat
is conducted and convected along the floors to the exterior walls
of the building. Moreover, at least one of the emergency exit light
bulbs can be expected to burn out during the course of the year.
When a building has hundreds of emergency exit signs, the cost of
replacing these bulbs can be quite high. It has been estimated that
each emergency exit sign costs between $70 and $120 per year to
operate and maintain.
The electro-luminescent emergency exit sign disclosed in U.S. patent
application Ser. No. 353390 may have the disadvantage of not appearing
to be on or lit if background lighting is at a certain level. In
other words, the regular lighting in the room or hallway containing
the emergency exit sign may appear brighter than the light emitted
by the emergency exit sign itself. Consequently, the fact that the
sign is energized may not be apparent to an observer, even though
once the background lighting is extinguished or substantially diminished,
the electro-luminescent sign appears lit. Fire inspectors are used
to seeing emergency exit signs in which incandescent bulbs emit
illumination from a small area which illumination is bright enough
to be seen above the ambient or regular room illumination. When
the fire inspector does not see light being emitted from the sign,
he assumes that the sign is out and that it will not be visible
in the dark. Accordingly, if the concept set forth in U.S. patent
application Ser. No. 353390 is to be acceptable to many fire inspectors,
the fire inspectors need an indication that the exit signs utilizing
electro-luminescent lamps are energized so that they will be visible
in the dark. This is especially the case with exit signs utilizing
electro-luminescent panels having extremely low wattages. For example,
this is a problem with the electro-luminescent panels manufactured
by the Potter Electronics Company of Charlotte, N. C., which successfully
illuminate emergency exit signs in darkened rooms with a power consumption
of less than one watt.
The light output of electro-luminescent lamps tends to degrade
with time. After years of service, a lamp may become so dim that
the sign it lights is not readily visible in a darkened room. Consequently,
there is a need for a monitor which informs maintenance people that
the lamp needs replacement or servicing. With emergency exit signs
using incandescent lamps, it is readily apparent that a lamp is
on or off simply because one can readily see if a twenty-five watt
incandescent lamp is either lit or unlit above regular or ambient
If emergency exit signs utilizing the principles set forth in U.S.
patent application Ser. No. 353390 are to be widely adopted, it
is necessary that such signs be configured for convenient retrofitting
to existing exit sign housings so as to minimize the difficulties
for those who wish to take advantage of the energy and maintenance
savings inherent in such signs.
SUMMARY OF THE INVENTION
In view of the aforementioned considerations, it is a feature of
the instant invention to provide a new and improved emergency exit
sign which is inexpensive to purchase, operate and maintain, and
which has a relatively long life. In addition, it is a feature of
the instant invention to provide a new and improved emergency exit
sign which includes an indicator that tells whether the sign is
lit or extinguished when illumination from an EL lamp used with
the sign is not bright enough to surpass background illumination.
In view of the aforementioned feature, the instant invention contemplates
an emergency exit sign which includes a flat electro-luminescent
EL lamp and a stencil defining the word "EXIT" or a facsimile
of the word "EXIT" disposed over the lamp. The exit sign
further includes a phosphorescent material associated with the word
"EXIT" which remains lit even if the EL lamp is extinguished
whereby the sign is visible when power to the EL lamp is cut. Moreover,
the emergency exit sign includes a pilot light which remains lit
as long as the lamp is lit. When the lamp is not energized, the
pilot light, which is connected by a photo-electric link to the
lamp, is extinguished.
The instant invention further contemplates a photo-electric link
between the pilot light and EL lamp wherein the pilot light extinguishes
when the illumination from the lamp drops beneath a predetermined
The instant invention further contemplates an emergency exit lamp
wherein the lamp has mounting structure readily suitable for retrofit
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded, perspective view of an emergency exit sign
in accordance with the instant invention.
FIG. 2 is a front view of an emergency exit sign in accordance
with the instant invention.
FIG. 3 is a side view of an emergency exit sign in accordance with
the instant invention.
FIG. 4 is a side sectional view showing the emergency exit sign
mounted on an existing exit sign support housing.
FIG. 5 is an enlarged sectional view taken along lines 5--5 of
FIG. 2 showing various electrical components.
FIG. 6 is an enlarged sectional view taken along lines 6--6 of
FIG. 7 is a circuit diagram showing the configuration of a pilot
light circuit utilized with the instant invention.
FIG. 8 is a perspective view of a single mounting clip.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1 there is shown an emergency exit sign
assembly, designated generally by the numeral 10which includes
a housing, designated generally by the numeral 11 which has a front
face 12 that is cut out at locations 13 to make a stencil forming
the word "EXIT". The housing 11 is preferably made of
thermoformed plastic and includes side flanges 16. The side flanges
16 cooperate with a thermoformed back panel 17 to form an enclosure
which contains an EL light source panel or lamp 18; a translucent,
phosphorescent sheet 19 and a transparent protective plastic sheet
20. Mounted beside the EL panel 18 is a circuit board 21 which includes
a neon pilot lamp 22 and circuitry, designated generally by the
numeral 25 for driving the neon lamp. The neon lamp 22 is visible
through the front face 12 of the housing 11 via an opening 26 that
is aligned with openings 27 and 28 in the protective plastic sheet
20 and translucent phosphorescent sheet 19 respectively. A transparent
lens 29 is seated in the opening 26 to protect the bulb 22.
Referring now to FIGS. 3 and 4 in accordance with one embodiment
of the invention, the entire exit sign assembly 10 is configured
for retrofit installation on an existing emergency exit sign housing
30. In accordance with one approach, the exit sign assembly 10 is
mounted with upper and lower mounting clips, designated generally
by the numeral 31. The mounting clips 31 are U-shaped in cross section
and simply fit over upper and lower flanges 33 and 34 on the housing
30 in order to secure the exit sign assembly 10 to the housing.
Preferably, the clips 31 are similar to the clips shown in FIG.
8 and similar to clips manufactured by Richo Plastics, which clips
are normally used for holding flat cable in place. The clips 31
have legs 35 and 36 which are normally spring-shut so that they
will grip the flanges 33 and 34 on the housing 30. On each of the
legs 36 of the clips 31 there is an adhesive surface 37 which is
exposed by peeling a backing 38 off a double adhesive foam core.
The rear surface of the back panel 17 is simply pressed against
the exposed adhesive surface 37 in order to mount exit sign assembly
10 on the housing 30. The U-shaped clips 31 are preferably one inch
to three inches in length.
By utilizing clips such as the clips 31 which are initially separate
and apart from the housing 30 and the exit light assembly 10 the
assembly 10 can be conveniently retrofitted to an existing housing
30 regardless of the size of the opening defined by the flanges
33 and 34.
In order to energize the electro-luminescent lamp 18 when mounted
as a retrofit, the lamp is connected by line 50 to a plug 51 having
prongs 52 that are received in the female end 53 of an adapter 54.
The adapter 54 has a threaded end 55 which screws into an existing
lightbulb socket 56. Normally, the light-bulb socket 56 is of a
candelabra size, so that the adapter 54 needs a threaded end 55
In mounting the exit sign assembly 10 on a housing 30 the following
steps are taken. First, the existing lightbulbs are removed from
the sockets 56. (Normally there are two lightbulbs.) The adapter
54 is screwed into one of the sockets 56. The clips 31 are mounted
on the flanges 33 and 34. The plug 51 is plugged into the adapter
54. The protective tape 38 is peeled from the clips 31 to expose
the adhesive backing 37. The exit sign assembly 10 is aligned with
the housing 30 and pressed home against the exposed adhesive 37.
Referring now more specifically to FIGS. 5 and 7 a photocell 60
is mounted adjacent to the EL lamp 18 to sense the illumination
generated by the lamp. The photocell 60 is connected in series with
the neon lamp 22 and serves as a switch to maintain current flowing
to the lamp as long as the illumination from the panel 18 is above
a predetermined level. For example, a level of 1.6 foot lamberts
may be considered sufficient. When the illumination from the lamp
18 drops below the predetermined level, the photocell 60 turns off
and no longer transmits current to the neon pilot light 22. The
pilot light 22 receives current from leads 61 and 62 which are contained
within the power line 50 and which provide 60-cycle alternating
line current to the electro-luminescent panel 18 via lines 64 and
65. Resistors Rl and R2 control the amount of current flowing to
the neon light 22 from lines 61 and 62.
In accordance with one embodiment of the invention, the following
electrical components are utilized with 60 hz, 120 volt input current
on line 50:
EL lamp 18--phosphors encapsulated on steel substrate by glass-manufactured
by Potter Electronics, Yancyville, N.C.
Neon lamp 22 NE-2 neon lamp
Photocell 60--Clairex CL705L, cadium sulfide photocell
Resistor R1--15K.OMEGA., 1/4 watt
Resistor R2 68K.OMEGA., 1/4 watt.
The translucent phosphorescent sheet 19 stores light energy emitted
by the EL lamp 18 as well as ambient light energy while allowing
light from the EL lamp to pass therethrough and out of the stencil
opening 13. If there is a power failure in the building which cuts
off the electrical lights and also cuts power to the exit sign assembly
10 the phosphorescent panel 19 will still emit light through the
stencil 13 so that the word "EXIT" can be seen in the
In summary, the instant invention provides an energy-efficient
exit sign which utilizes an electro-luminescent (EL) light source
or lamp 18 as a primary light source for the exit sign assembly
10 and a phosphorescent light source 19 as a secondary light source
should power to the exit sign assembly be interrupted. The monitoring
circuit 25 indicates whether there is adequate luminescence of the
electro-luminescent lamp 18 and indicates the presence of electrical
power to illuminate the sign if the sign is not readily visible
in ambient light. Moreover, a technique for mounting the exit sign
assembly 10 is provided by the clips 31 which allow the assembly
10 to be retrofitted on existing housings of various configurations.
Since the electro-luminescent lamp 18 and the neon pilot light
22 together consume less than 1 watt of electricity and since the
lamps 18 have a life expectancy of ten years, there is approximately
a 99% reduction in operating costs compared to conventional incandescent
fixtures. Since the EL lamp 18 cannot be easily broken due to its
rugged construction, maintenance costs due to vandalism can be greatly
The foregoing embodiments and examples are merely illustrative
of the instant invention which is to be limited only by the following