Illumination – Light fiber – rod – or pipe – Illuminating or display apparatus
Reexamination Certificate
1999-12-30
2002-10-29
O'Shea, Sandra (Department: 2875)
Illumination
Light fiber, rod, or pipe
Illuminating or display apparatus
C362S217060, C362S225000, C362S260000, C362S396000, C362S812000, C362S035000, C313S318110, C040S570000
Reexamination Certificate
active
06471388
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to an illumination source for signs utilizing miniature fluorescent lamps. More particularly, the present invention is directed towards an illumination source for edge lit display signs, such as edge-lit emergency exit signs.
BACKGROUND OF THE INVENTION
An illuminated display sign generally comprises a light source to illuminate a display surface upon which words, symbols, or other indicia are imprinted. Illuminated display signs include a variety of advertising signs, household number display signs, information bearing signs, and a variety of emergency information signs.
One common type of display sign in an emergency exit sign. Emergency exit signs include several different light source configurations. Exit signs are almost universally required in various types of commercial establishments under modem building codes, which specify the size, shape, and required luminance of the sign.
FIG. 1
is a perspective view of an exit sign
100
in which the light source is configured to illuminate a display panel
130
. The configuration shown in
FIG. 1
is commonly known as an “edge lit” emergency exit sign
100
because light generated in a housing
120
is coupled to an “edge” (entrance surface)
112
of a transparent display panel
110
. Display panel
110
is shaped to form a light guide which couples light to an outer display surface
130
. Display panel
110
is typically made from a plastic material with colored indicia. The plastic display panel
110
acts as a light pipe or optical guide that transmits light to painted or printed opaque or translucent indicia within panel
110
. Light passing through and around the indicia illuminates the indicia, thus creating a contrast between the clear plastic and the colored indicia.
FIG. 2
is an exploded side view of prior art edge lit emergency exit sign
100
. As can be seen in
FIG. 2
, a lamp
150
occupies most of the volume of housing
120
. Lamp
150
is commonly a T-5 fluorescent lamp, which is a tube-shaped lamp with a diameter of at least about 16 millimeters. As shown in
FIG. 2
, commonly the diameter, D, of lamp
150
is greater than the width
170
of the plastic or glass panel sections
160
,
162
comprising light guide
110
. Depending upon the specific design geometry, typically less than 20-30% of the light emitted from lamp
150
enters guide
110
in a conventional emergency exit sign
100
.
While
FIGS. 1 and 2
show an emergency exit sign with only one display surface
130
, it will be understood that edge lit emergency exit signs commonly have two opposed display surfaces such that two T-5 lamps
150
are placed side-by-side to illuminate two opposed side-by-side optical guides
110
. The shape of optical guide
110
also has several different common shapes. Optical guide
110
may comprise planar or wedge-shaped pieces of glass or plastic. Thus while
FIGS. 1-2
illustrate one common style of edge-lit emergency exit sign
100
, it will be understood that there are several different commonly used styles of edge-lit emergency exit sign in use today.
Conventional edge-lit emergency exit signs have several drawbacks. One drawback is that an edge-lit emergency exit sign
100
has a substantial operating cost, consisting of electricity charges, replacement parts and related labor. Two T-5 lamps consume about 24 watts of input power. For many situations the exit sign must be illuminated at all times. The energy costs will depend upon local utility rates but can be significant in applications, such as office complexes, which have a large number of emergency exit signs. There are also significant maintenance costs. The lamps have a limited lifetime and must be frequently replaced. An edge lit sign with T-5 lamps typically has a useful lamp lifetime of about 12,000 hours. Since emergency exit signs are typically operated 24 hours a day, seven days a week, this corresponds to a useful lifetime of about 1.4 years. Conventional T-5 lamps are also hot cathode lamps which require the use of standard fluorescent lamp sockets to hold the lamps in place. In the confined space of an emergency exit sign the heat of the T-5 lamps tends to make the sockets brittle. This can necessitate replacement of the sockets as often as every three years, further increasing the maintenance costs.
Another drawback with using T-5 lamps to illuminate an edge lit sign is that it is difficult, given space constraints, to include a large enough battery in housing
120
to illuminate exit sign
100
during extended power outages. In addition to lamp
150
, the sign must include other equipment such as a step down transformer, ballast, lamp sockets and holder, and a mounting mechanism to permit the lamp and socket holders to be inserted and removed from housing
120
. There is not much room left over for an economical large capacity battery. Conventional edge lit emergency exit signs typically have a battery with sufficient energy for about 90 minutes of power to illuminate one T-5 lamp
150
. While this is sufficient to address present statutory regulations, there is a growing interest in emergency exit signs which have sufficient battery power to provide two-to-four hours or more of backup power when normal line power is unavailable.
Light emitting diode (LED) light sources are one alternative to the use of T-5 fluorescent lamps in edge lit emergency exit signs. LED illumination sources are energy efficient and have a longer operating lifetime compared to T-5 lamps. Additionally, LED illumination sources typically can be powered from AC line voltage using a comparatively compact AC-DC power converter.
FIG. 3
is an exploded perspective view of a prior art emergency exit sign
300
using an LED light source
330
including a plurality of LEDs
368
. Exit sign
300
is similar to one sold commercially by LITHONIA LIGHTING™ of Decatur, Ga. LED light source
330
is shaped to slide into a housing
352
and typically includes an electrical connector
362
to receive line power and an AC-DC voltage converter (not shown in
FIG. 3
) to convert AC line voltage into low-voltage DC suitable for driving the LEDs. Top and bottom surfaces
382
,
384
of LED light source
330
are shaped to fit into slots
380
in housing
352
. LED light source
330
typically includes about 60 LEDs for a dual faced sign in order to achieve a reasonable total light output. A diffuser panel
364
is disposed to diffuse the light from LEDs
368
prior to the light entering acrylic panels
354
. Panels
354
are shaped to form two tapered optical guides with graphic symbols
356
spelling out the word “EXIT.” One advantage of LED light source
330
is that LEDs have a long operating lifetime, resulting in a cost savings over T-5 fluorescent lamps. Additionally, an LED light source
330
typically uses two-to-three watts of power for an exit sign with two opposed display surfaces, resulting in about a factor of eight-to-twelve energy saving compared with two T-5 lamps
150
.
However, LED light source
330
has several drawbacks. One drawback is that the brightness of an edge lit sign
300
using LED light source
330
is typically only about ⅓ that of an edge lit sign
100
using two T-5 lamps
150
. The low brightness of an LED light source
330
is a significant disadvantage because it reduces the distance at which individuals can see edge lit sign
300
, particularly in large, darkened, or smoke-filled rooms. Another drawback is that LED sources tend to have less contrast than conventional white light sources. In exit signs illuminated by a conventional T-5 lamp, the panels are illuminated by a white light. The indicia, which are colored, convert the white light into colored light (e.g., red). There is a large contrast between the brightly light colored indicia and neighboring portions of the display surface, which are faintly lit by white light. Commonly available, low cost LEDs, however, are typically monochromatic, i.e., they produce light of a single color, such as red or green. Although the price and av
Alavi Ali
BJI Energy Solutions LLC
Kleinberg Marvin H.
Kleinberg & Lerner ,LLP
Lerner Marshall A.
LandOfFree
Illumination apparatus for edge lit signs and display does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Illumination apparatus for edge lit signs and display, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Illumination apparatus for edge lit signs and display will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2996281