Abstrict In a lighting fixture such as an exit sign, a light emitting diode
lighting device is provided for mating engagement with an electrical
socket of the lighting fixture. The light emitting diode device
has a plurality of light emitting diodes recessed in a U-shaped
channel for directing light through a diffuser into a desired illumination
pattern.
Claims What is claimed is:
1. A lighting device for illuminating indicia of an exit sign having
an enclosure, comprising:
(a) a lighting device housing having a light directing channel
in one side thereof;
(b) an illumination source in said housing, said illumination source
including a plurality of light emitting diodes recessed in said
light directing channel;
(c) a diffuser mounted to said housing adjacent said channel whereby
light from said light emitting diodes is directed by said light
directing channel through said diffuser into the enclosure to illuminate
the indicia of the exit sign; and
(c) a mounting base assembly on said housing for electrically connecting
said illumination source to the exit sign, said mounting base assembly
permitting orientation of said housing relative to said mounting
base assembly.
2. The lighting device in accordance with claim 1 wherein said
light directing channel is U-shaped.
3. The lighting device in accordance with claim 1 wherein said
light directing channel has sloping side walls.
4. The lighting device in accordance with claim 3 wherein said
light directing channel is U-shaped.
5. The lighting device in accordance with claim 1 wherein said
housing has a groove therein in which said diffuser is slidably
positioned.
6. The lighting device in accordance with claim 1 wherein said
diffuser has a light distributing surface thereon which distributes
light from said illumination source.
7. The lighting device in accordance with claim 1 wherein said
plurality of light emitting diodes are mounted on a printed circuit
board.
8. The lighting device in accordance with claim 7 wherein said
printed circuit board has electrical components thereon electrically
connected to said illumination source, said electrical components
also being electrically connected to a source of electrical power
for providing power to said illumination source.
9. The lighting device in accordance with claim 1 wherein said
mounting base assembly is matingly received in the exit sign through
relative rotational and axial movement therebetween.
10. The lighting device in accordance with claim 1 wherein said
mounting base assembly is adapted to connect to a primary electric
power circuit of the exit sign, and wherein an emergency electric
power circuit in said housing is operationally connected to the
primary electric power circuit through said mounting base assembly
to detect failure of the primary electric power circuit and thereafter
provide auxiliary power to said illumination source.
11. The exit sign in accordance with claim 10 wherein said emergency
electric power circuit includes at least one rechargeable battery.
12. The exit sign in accordance with claim 11 wherein said emergency
electric power circuit includes a charging device for keeping said
at least one rechargeable battery fully charged during periods of
nonuse.
13. An exit sign, comprising:
(a) a sign housing defining an enclosure therein and having indicia
to be illuminated; and
(b) at least one lighting device within said enclosure for illuminating
said indicia, each lighting device comprising:
(i) a lighting device housing having a light directing channel
in one side thereof;
(ii) an illumination source in said lighting device housing, said
illumination source including a plurality of light emitting diodes
recessed in said light directing channel;
(iii) a diffuser mounted to said lighting device housing adjacent
said channel whereby light from said light emitting diodes is directed
by said light directing channel through said diffuser into said
enclosure to illuminate said indicia; and
(iv) a mounting base assembly on said lighting device housing for
electrically connecting said illumination source to a primary electric
power circuit, said mounting base assembly permitting orientation
of said housing relative to said mounting base assembly.
14. The exit sign in accordance with claim 13 wherein said light
directing channel is U-shaped.
15. The exit sign in accordance with claim 13 wherein said light
directing channel has sloping side walls.
16. The exit sign in accordance with claim 15 wherein said light
directing channel is U-shaped.
17. The exit sign in accordance with claim 13 wherein said lighting
device housing has a groove therein in which said diffuser is slidably
positioned.
18. The exit sign in accordance with claim 13 wherein said diffuser
has a light distributing surface thereon which distributes light
from said illumination source.
19. The exit sign in accordance with claim 13 wherein said plurality
of light emitting diodes are mounted on a printed circuit board.
20. The exit sign in accordance with claim 19 wherein said printed
circuit board has electrical components thereon electrically connected
to said illumination source, said electrical components also being
electrically connected to a primary electric power circuit for providing
power to said illumination source.
21. The exit sign in accordance with claim 13 wherein said mounting
base assembly is matingly received in said sign housing through
relative rotational and axial movement therebetween.
22. The exit sign in accordance with claim 13 wherein an emergency
electric power circuit in said lighting device housing is operationally
connected to the primary electric power circuit through said mounting
base assembly to detect failure of the primary electric power circuit
and thereafter provide auxiliary power to said illumination source.
23. The exit sign in accordance with claim 22 wherein said emergency
electric power circuit includes at least one rechargeable battery.
24. The exit sign in accordance with claim 23 wherein said emergency
electric power circuit includes a charging device for keeping said
at least one rechargeable battery fully charged during periods of
nonuse.
Description BACKGROUND OF THE INVENTION
The present invention relates generally to electrical lighting
sources and, more particularly, to electrical lighting sources in
illuminated exit signs.
Under current local fire and building codes, buildings to which
the public has access are required to have signage therein identifying
the exits. Most of these signs are required to exhibit a specific
amount of illumination and, oftentimes, must have an emergency backup
power source to provide emergency illumination to the light for
a specified period of time during periods when utility power to
the building is discontinued, thereby facilitating egress of persons
from the building.
Traditionally, two 15-watt incandescent lamps driven by 120 volt
alternating current (120 VAC) have been employed to provide normal
illumination while two 3.6-watt incandescent lamps driven by a self
contained emergency battery power supply are used for illumination
during power failure situations. A switching or transfer device
will automatically operate the emergency backup illumination system
when a power failure is detected.
While these traditional exit sign lighting arrangements perform
adequately, they do have a few drawbacks. A major drawback is that
the incandescent bulbs use large amounts of electric power thus
requiring a relatively large emergency battery power supply for
use during emergency lighting situations. Furthermore, while the
incandescent bulbs provide adequate illumination, such bulbs do
not have a long life in service and require frequent replacement.
To alleviate the drawbacks associated with incandescent bulbs,
many manufacturers are beginning to utilize light emitting diodes
(LEDs) rather than incandescent bulbs in exit signs. Each light
emitting diode provides a relatively small amount of light as compared
to the traditional incandescent bulbs whereby a large number of
light emitting diodes must be used to provide the same amount of
illumination offered by the traditional incandescent bulbs.
It is an object of the present invention to provide a novel lighting
device for an exit sign using a plurality of light emitting diodes.
It is also an object to provide such a lighting device which allows
the light emitting diodes to be powered by both the normal utility
electrical power (120 VAC) and, during emergency power situations,
an emergency battery power supply and associated charging and transfer
circuitry.
Still another object is to provide such a lighting device in which
the light emitting diodes are arranged in the exit sign to provide
the amount of illumination required by building codes.
A further object is to provide such a lighting device which may
be readily and economically fabricated and will enjoy a long life
in operation.
SUMMARY OF THE INVENTION
It has now been found that the foregoing and related objects can
be readily attained in an exit sign having a sign housing defining
an enclosure therein and having indicia to be illuminated as well
as at least one lighting device within the enclosure for illuminating
the indicia. Each lighting device comprises a lighting device housing
having a light directing channel in one side thereof, an illumination
source in the lighting device housing and a diffuser mounted to
the lighting device housing adjacent the channel. The illumination
source includes a plurality of light emitting diodes recessed in
the light directing channel whereby light from the light emitting
diodes is directed by the light directing channel through the diffuser
into the enclosure to illuminate the indicia.
According to the invention, the light directing channel has sloping
side walls and is U-shaped. The lighting device housing has a groove
therein in which the diffuser is slideable positioned. The diffuser
has a light distributing surface thereon which distributes light
from the illumination source.
Ideally, the plurality of light emitting diodes are mounted on
a printed circuit board positioned in the lighting device housing.
The printed circuit board is electrically connected to the mounting
base assembly for electrically connecting the illumination source
to a primary electric power source. The printed circuit board also
has electrical components thereon for the light emitting diodes.
In accordance with the present invention, the mounting base assembly
is matingly received in the exit sign housing through relative rotational
and axial movement therebetween. Once it is full inserted, the mounting
base assembly permits orientation of the lighting device housing
relative to the mounting base assembly.
Desirably, an emergency electric power circuit in the lighting
device housing is operationally connected to the primary electric
power circuit through the mounting base assembly to detect failure
of the primary electric power circuit and thereafter provided auxiliary
power to the illumination source. The emergency electric power circuit
includes at least one rechargeable battery and a charging device
for keeping the at least one rechargeable battery fully charged
during periods of nonuse.
The invention will be fully understood when reference is made to
the following detailed description taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view of an exit sign housing with
portions removed and broken away to illustrate internal structure
including two light emitting diode lighting devices made in accordance
with the present invention;
FIG. 2 is a side elevational view of the light emitting diode lighting
device of the present invention with a portion of the diffuser broken
away to illustrate internal structure;
FIG. 3 is a cross-sectional view of the light emitting diode lighting
device taken along the 3--3 line of FIG. 2;
FIG. 4 is a cross-sectional view of the light emitting diode lighting
device taken along the 4--4 line of FIG. 2;
FIG. 5 is an exploded perspective view of the light emitting diode
device of the present invention; and
FIGS. 6 and 6A show an electrical schematic for the exit sign of
FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
Referring first to FIG. 1 of the drawings, therein illustrated
is an exit sign generally designated by the numeral 10. The exit
sign 10 is mountable to both a canopy bracket (not shown) and a
standard electrical junction box (not shown) in a manner explained
in U.S. Pat. No. 5272605 entitled CANOPY MOUNTING DEVICE FOR
EXIT SIGNS AND THE LIKE. With this arrangement, the exit sign construction
of this invention can be mounted directly to a standard electrical
junction box found in a ceiling or wall of a building in any desired
location.
The exit sign 10 comprises a central rectangularly shaped frame
12 with front and back cover members 14 and 16 at least one of
which incorporates a large stencil 18 having the letters "EXIT"
in the major surface thereof and a colored plastic diffuser 20 therebehind.
The central rectangularly shaped frame 12 and the front and back
cover members 14 and 16 are snap-fit together and cooperate to form
a sign housing having an enclosure 22 containing the necessary internal
electrical lighting components. The front and back covers 14 16
can use a plurality of finger clips (not shown) to hold them in
assembly with the central rectangularly shaped frame 12. The exit
sign 10 is preferably molded from a plastic resin such as an engineering
type thermoplastic such as ABS, polycarbonate or polyphenylene oxide
but it should be apparent to those skilled in the art that they
may be manufactured from other suitable materials.
The enclosure 22 of the exit sign 10 is divided into a wiring compartment
24 and a lighting compartment 26 by a retaining wall 28 which extends
around the interior sides and top of the central rectangularly shaped
frame 12. In a manner explained further hereinafter, the wiring
compartment 24 contains an appropriate wiring harness 30 for powering
two 1-watt direct current light emitting diode lighting devices
34 held by standard screw type lamp sockets 36 extending downwardly
into the lighting compartment 26 from an upper part of the retaining
wall 28.
Referring to FIGS. 2-5 taken in conjunction with FIG. 1 each of
the light emitting diode lighting devices 34 has an elongated generally
rectangular plastic lighting device housing 38 having front and
rear halves 40A,40B forming an enclosure 42. Inside the enclosure
42 in the elongated rectangular plastic housing 38 is a printed
circuit board 44 with a plurality of light emitting diodes 46 in
a U-shaped pattern on one side thereof with a plurality of electrical
components 47 (FIG. 4) positioned between the light emitting diodes.
The light emitting diodes 46 extend parallel to one another and
are positioned to extend through apertures 48 in a U-shaped channel
50 in the front half 40A. The U-shaped channel 50 has sloping side
walls 51 designed to direct light rays from the light emitting diodes
46 in an appropriate illumination pattern. As shown in FIG. 4 the
electrical components 47 whose function and operation will be explained
further hereinafter, extend into a cavity formed by the sloping
side walls 51 in the center of the elongated rectangular plastic
housing 38.
The plastic housing 38 can be made of an opaque material such as
polyphenylene oxide (NORYL N-190 made by General Electric) and polycarbonate
(XANTAR G4F-23R made by DSM Polymers & Hydrocarbons BV). Desirably,
to achieve a satisfactory dispersion of the light emanating from
the light emitting diodes 46 the lighting device housing 38 is
provided with a translucent or clear plastic diffuser 52. The diffuser
52 has a lip portion 53 slideably received in a groove 54 on the
lighting device housing 38 and has longitudinally extending ribbed
surfaces 55 to scatter the light rays as they pass through the diffuser
52.
As illustrated in FIG. 1 in order for light rays from the light
emitting diode lighting devices 34 to evenly illuminate the stencil
18 when they pass through the diffuser 20 the position of the light
emitting diode lighting devices 34 can be adjusted to obtain the
desired illumination. To obtain this type of adjustment, the light
emitting diode lighting devices 34 are provided with mounting base
assemblies 56 which permit adjustment of the elongated rectangular
plastic housings 38 relative to the mounting base assemblies 56
once the assemblies 56 are fully inserted and tightened into their
respective screw-type lamp sockets 36. The adjustment of the elongated
rectangular plastic housings 38 relative to the mounting base assemblies
56 is described in a copending U.S. Patent application Ser. No.
08/160423 filed Dec. 1 1993 entitled MOUNTING BASE ASSEMBLY FOR
A LIGHTING DEVICE USED IN AN EXIT SIGN by inventors Charles R. Ruskouski
and James J. Burnes, which is hereby incorporated by reference,
with particular reference to FIGS. 5 and 6 and the description thereof.
Turning now to FIGS. 6 and 6A taken in conjunction with FIG. 1
to power the light emitting diode lighting devices 34 the utility
power (120 VAC) is provided to the wiring harness 30 through electrical
leads (not shown) which extend into an electrical junction box (not
shown) found in the ceiling or wall of the building. Each light
emitting diode lighting device 34 incorporates a battery charger
and converter circuit 60 on the printed circuit board 44. The circuit
60 is designed in a manner well known to those skilled in the art
to rectify the utility power into direct current and charge an auxiliary
rechargeable battery pack 62 located in the lighting device housing
38 between two electrical contacts 63 (FIGS. 3 and 5) extending
from the printed circuit board 44. The circuit 60 also is designed
to switch between the primary alternating current power supply and
the emergency direct power supply provided by the rechargeable battery
pack 62 if the alternating current power supply fails as would be
the case during a utility power outage.
During normal operation, utility power on the wiring harness 30
energizes the light emitting diodes 44 and maintains a charge on
the battery pack 62 and, during emergency operation when the utility
power fails, the battery pack 62 energizes the light emitting diodes
44 until utility power resumes on the wiring harness 30.
When the utility power is supplied on the wiring harness 30 the
alternating current is first passed through a current limiting resistor
R1 and capacitor C1 and is then passed through a bridge circuit
BR1 which rectifies the alternating current into direct current.
If the utility power fails, the current in the capacitor C1 discharges
through the resistor R1 to prevent electrical shocks. The direct
current from the bridge circuit BR1 initially flows through a Zener
diode D1 and energizes a coil K1 for closing contacts Ca and Cb
and opening contacts Cc and Cd so that the battery pack 62 is connected
in series with the coil K1 and the light emitting diodes 44 which
are electrically connected in series, parallel or series parallel
to one another. This maintains the closure of the contacts Ca and
Cb, charges the battery pack 62 and energizes the light emitting
diodes 44. At this point, no current flows through the Zener diode
D1.
When the utility power is not supplied on the wiring harness 30
the coil K1 is deenergized, which opens the contacts Ca and Cb and
closes the contacts Cc and Cd. This causes the battery pack 62 to
discharge through a boost regulator circuit 64 (shown in detail
in FIG. 9A) which boosts the battery voltage to a level sufficient
to operate the light emitting diodes 44. For example, when the utility
power is off, the direct current flows from the positive side of
the battery pack 62 through the contact Cc, into point a and out
point b of the boost regulator circuit 64 where the output voltage
Vb is greater than the input voltage Va. The direct current then
flows through the light emitting diodes 44 which are electrically
connected across points b and c as shown, into point c and out point
d of the boost regulator circuit 64 through the contact Cd and
back to the negative side of the battery pack 62.
The boost regulator circuit 64 is well known in the art and one
example is shown in FIG. 6A. It has an input voltage Va coupled
to pin 1 of a DC-to-DC converter IC1 and to one side of an inductor
L1. The other side of the inductor L1 is coupled to a drain of a
FET transistor Q1 having its gate coupled to pin 6 and its source
coupled to ground. A Schottky diode D3 is connected between the
drain of the FET transistor Q1 and an output voltage Vb. In operation,
the direct current passes into the boost regulator circuit 64 at
point a, discharges through the inductor L1 and the diodes D2 and
D3and passes from the boost regulator circuit 64 at point b to
the light emitting diodes 44. The inductor L1 the DC-to-DC converter
IC1 the FET transistor Q1 the diodes D2 and D3 combined to boost
the output voltage Vb so it is greater than the input voltage Va
needed to provide the direct current to the light emitting diodes
44. Upon return from the light emitting diodes 44 the direct current
passes into the boost regulator circuit 64 at point c, through a
resistor R2 and passes from the boost regulator circuit 64 at point
d. From there, the direct current passes through the contact Cd
and back to the negative side of the battery pack 62 to complete
the circuit. The Zener diode D4 fixes the voltage at pin 5 of the
DC-to-DC converter IC1. A capacitor C4 filters out undesirable voltage
surges at point c of the boost regulator circuit 64 pin 3 is a
ground connection for the convertor IC1 and pin 8 is grounded since
it is not being used.
It will therefore be seen from the above that the present invention
provides an effective light emitting diode lighting device within
an exit sign. The exit sign using the light emitting diode lighting
devices has the same amount of illumination as found in exit signs
using traditional incandescent lamps while at the same time greatly
reducing power consumption.
It will thus be seen that the objects set forth above, among those
made apparent from the preceding description, are efficiently attained
and, since certain changes may be made in the above product without
departing from the 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 invention which, as
a matter of language, might be the to fall therebetween. |