Abstrict An "exit" sign lighting system comprising, in combination
a housing having the word EXIT formed in an opening wall thereof,
a translucent member in said opening, a gas discharge device, such
as a fluorescent tube is driven from a source of a low-voltage,
high-frequency square wave voltage having a pair of output terminals
and an LC free circuit connecting the low-voltage, high-frequency
square wave voltage to the gas discharge device to non-thermionically
excite and illuminate the gas discharge device, and thereby illuminate
the translucent member and the word EXIT. The low voltage is from
about 2 volts to about 90 volts and the frequency is from about
75 kHz to about 3.5 MHz.
Claims I claim:
1. A sign lighting system comprising, in combination a housing
having an information indicia formed in one or more walls thereof,
a fluorescent gas discharge lamp means, a source of a low-voltage,
high-frequency square wave voltage having a pair of output terminals
and substantially LC free circuit connecting said low-voltage, high-frequency
square wave voltage to said fluorescent gas discharge means to non-thermionically
excite and illuminate said fluorescent gas discharge lamp means,
and thereby illuminate said information indicia.
2. The sign lighting system defined in claim 1 wherein said low
voltage is from about 2 volts to about 90 volts and the frequency
is from about 75 kHz to about 3.5 MHz.
3. A sign having a housing with information indicia thereon, the
sign having a lighting system including a fluorescent gas discharge
lamp device mounted in said housing, a source of low-voltage, high-frequency,
square wave AC voltage having output terminals and a substantially
LC-free circuit connecting said gas discharge lamp device to said
output terminals to excite and illuminate said fluorescent gas discharge
lamp device to thereby illuminate said information indicia.
4. A sign as defined in claim 3 including a source of AC line current,
a stepdown transformer connected to said source and having a low
AC voltage output, a rectifier connected to said low AC voltage
output, a rechargeable storage battery connected to said rectifier
and means connecting said low voltage output to said circuit and
said rechargeable battery.
5. A sign having a housing with information indicia thereon, the
sign having a lighting system for illuminating said information
indicia including a fluorescent gas discharge lamp device mounted
in said housing, a circuit including a source of low-voltage, high-frequency,
square wave alternating current voltage and means connecting said
gas discharge lamp device to said circuit to excite and illuminate
said fluorescent gas discharge lamp device and thereby illuminate
said information indicia.
6. A sign as defined in claim 5 including a source of AC line current,
a stepdown transformer connected to said source and having a low
AC voltage output, a rectifier connected to said low AC voltage
output, a rechargeable storage battery connected to said rectifier
and means connecting said low voltage output to said circuit and
said rechargeable battery.
7. A low-voltage, high-efficiency, fluorescent signage comprising
a housing having walls, sign in at least one of said walls and indicia
adapted to be illuminated from the rear, a fluorescent gas discharge
lamp device mounted in said housing, a source of low-voltage, high-frequency,
square wave AC voltage having output terminals and an LC-FREE CIRCUIT
connecting said low gas discharge lamp device to said output terminals
to excite said fluorescent gas discharge lamp device and illuminate
said sign indicia.
Description BACKGROUND AND BRIEF DESCRIPTION OF THE INVENTION
Exit signs are located in theaters, public buildings, high-rise
apartment buildings, and the like for purposes of guiding people
safely to exit stairways and exit doorways and the like from these
such structures in times of emergency. Normally, they use incandescent
lamps which generate large amounts of heat thereby shortening the
life of the light source and requiring considerable maintenance
and expense. Moreover, since these exit signs are located in buildings
which require that they be on in times of emergency and highly visible,
possibly through smoke and haze, they require a backup electrical
power source in the event of failure of the main power line, such
as a conventional 110 volt main. Such prior art systems also may
require the alternative lamps or low-voltage lamps which turn on
in the event of failure of the main power supply. See FIG. 1 and
U.S. Pat. Nos. 5611163 and 5526251. There have been efforts
to incorporate fluorescent lamps into exit signs. See U.S. Pat.
Nos. 4587600 and 4650265 as examples.
The object of the invention is to provide a new and improved ballastless,
non-thermionic and starterless fluorescent exit sign which works
on inducing oscillation on the gas contained in the tube at a frequency
which is related to the type of gas to obtain maximum luminosity
without the presence of a carrier, consumes little electrical energy
(2.6 watts) and which is dimmable without flickering regardless
of the level of luminosity and in which the light spectrum is constant.
Another object of the invention is to provide an improved exit
sign which is low in cost and low in energy consumption.
The exit sign of the present invention incorporates a ballast-free,
starter-free, non-thermionic conventional fluorescent lamp or tube
driven by a high-frequency square wave driver circuit.
Another object of the invention is to provide a low voltage (under
85-90 volts), non-thermionic, ballast-free, fluorescent lighting
system for exit signs.
According to the invention at least one gas discharge lighting
lamp or tube (which may be constituted by UV-responsive phosphor-coated
envelope confining a gaseous discharge medium at a predetermined
pressure between a pair of electrodes) is mounted in an "exit"
sign housing and non-thermionically driven by a low-voltage square
wave power supply. The square wave power supply may incorporate
a solid state switch which is operated to generate a substantially
square wave alternating current wave at the lamp or tube electrodes
such that the voltage supplied to the electrodes reverses polarity
more rapidly than the pattern of electron and ion density in the
tube can shift so that electrons throughout the length of the tube
are continually accelerated and will, through several cycles of
said square wave, create free electrons and ions throughout the
tube's volume, in steady state operation and illuminate the fluorescent
lighting lamp. The frequency of oscillation is preferably related
to the type of gas to obtain maximum luminosity without the presence
of a carrier. The current in the tube is minimal and no noticeable
level of RFs are present, that is, there is substantially no radio
interference.
The oscillating transformer in the present invention provides a
level of luminosity which is a function of the voltage thereby making
dimming of the fluorescent lamp possible without flickering (90%
dimming) regardless of the level of luminosity. The band on the
spectrum is constant and reflects the initial reaction to the oscillation.
The system works in any type of gas filled envelope.
Thus, there is disclosed a sign lighting system comprising a housing
having signage indicia in a wall thereof. A fluorescent gas discharge
lamp is mounted inside the housing and a source of low-voltage high-frequency
square wave voltage having a pair of output terminals and an LC-free
circuit connecting the low-voltage, high-frequency, square wave
voltage to the fluorescent gas discharge lamp to non-thermionically
excite the fluorescent member and the indicia formed on the wall
of the housing.
In a preferred exit sign system, a 7.2 volt DC rechargeable battery
is used. The battery backup has a battery charging circuit and uses
a 7.2 volt nicad rechargeable battery. The fluorescent tube is an
FT6 fluorescent tube with no starter or ballast and the filaments
are not connected to a source of heater current. The light output
in such a lamp is bright and the battery good for three hours (when
only ninety minutes are required by federal regulations). The exit
sign uses 2.6 watts of energy (in comparison to the standard sign
on the market uses 50 watts). The display is green which corresponds
to the new spec for LED equipped signs in the market which are only
red. The cost of manufacturing is much lower than the standard sign
on the market.
In one preferred embodiment, the driver circuit of the present
invention includes an oscillating transformer having a primary and
secondary winding with the primary winding center tapped and coupled
to the toggle or gate electrode of a switching diode. A supply of
direct current such as a low-voltage battery is applied through
a electrolytic filter capacitor and a 1500 ohm resistor bypassed
by a capacitor. A third capacitor shunts the switching diode. The
circuit operates to provide 3.9 megahertz square waves output on
the secondary at 1.4 volts to a fluorescent tube such as FT6. An
AC supply is rectified and used to supply the driver circuit. A
charging circuit for a battery is connected to the AC supply. Upon
failure of the AC supply, the battery automatically supplies DC
voltage to the driver circuit.
DESCRIPTION OF THE DRAWINGS
The above and other objects, advantages and features of the invention
will become more apparent when considered with the following specification
and accompanying drawings wherein:
FIG. 1 is a block diagram of prior art incandescent exit signs,
FIG. 2 is a block diagram having a driver circuit incorporating
the present invention,
FIG. 3 is a detailed circuit diagram of the driver circuit of the
present invention,
FIG. 4 is a diagrammatic illustration of a transformerless square
wave inverter circuit of the present invention, and
FIG. 5 is a schematic isometric view of an exit sign and housing
incorporating the invention.
DETAILED DESCRIPTION OF THE INVENTION
The system of the present invention uses a square wave AC inverter
circuit to drive the electrodes of a fluorescent tube mounted in
an exit sign. The square wave alternating current wave at the tube
electrodes is such as to reverse polarity more rapidly than the
pattern of electron and ion density in the tube can shift so that
electrons throughout the tube are continuously accelerated and will,
through several cycles of the square wave create free electrons
and ions throughout the gas tube's volume, in steady state operation
and illuminate the exit sign's fluorescent lighting lamp. The frequency
of oscillation can be related to the type of gas to obtain maximum
luminosity without the presence of a carrier. The current on the
tube is minimal so when operating from the battery, there is low
drainage and long time of operation when there is a power outage,
and there is no noticeable level of RF present so there is little
or no radio interference. The present invention uses an oscillation
transformer, and the level of luminosity is a function of the voltage
making dimming of the fluorescent lamp possible without flickering
(90% dimming) regardless of the level of luminosity. The band on
the light spectrum is constant and reflects the initial reaction
to the oscillation. The system works in any type of gas-filled envelope.
Referring now to FIG. 2 a step-down transformer supplies AC voltage
(120V) 26 to an inverter 10 which charges battery 11 coupled to
an alternating square wave driver circuit 12 which in turn supplies
the high-frequency (3.9 megahertz at about 1.4 volts) alternating
current square wave to fluorescent tube 13 which emits light 14.
The driver circuit is shown in detail in FIG. 3. Switch 15 couples
DC voltage (7.2 volts) from battery 11 to the driver circuit 13.
The driver circuit includes an oscillation transformer T1 having
a center tapped primary having windings P1 P2 with the center tap
connected to the gate electrode of solid state switch or oscillating
diode D1. The opposing ends of oscillating diode D1 are connected
to the upper and lower ends of the primary windings P1 P2 of transformer
T1. A filter capacitor C1 is connected across the 7.2 volt direct
current input, and a filter capacitor C3 is connected to coupling
resistor R1. A shunt capacitor C2 shunts the oscillating diode D1.
The output to the fluorescent tube is about 1.4 volts at 3.9 megahertz
open circuit and 1.7 megahertz square wave at the tube. Thus, the
circuit has no ballast, no starter, no filament current source,
is non-thermionic and produces more light using the conventional
fluorescent lamps and because it is non-thermionic is significantly
more efficient.
FIG. 3 illustrates a low-voltage square wave inverter circuit requiring
a minimum of five components (the electrolytic filter capacitor
C1 is deemed to be a part of the DC power source or supply). Switch
15 couples DC voltage (7.2 volts for example) from a battery to
the low-voltage square wave inverter drive circuit resistor R1 can
be a dimmer (intensity control) resistor. This driver circuit includes
an oscillation transformer T1 having a center tapped CT primary
winding having primary windings P1 and P2 with the center top CT
connected to gate electrode G of solid state switch D1. The opposing
ends of switch D1 are connected to the upper and lower ends of the
primary windings P1 and P2. A capacitor C3 shunts the oscillating
transistor/diode D1.The output to the fluorescent tube is about
1.4 volts RMS at 3.9 MHz open circuit and 1.7 MHz, square wave at
the tube. Thus, the system has no ballast transformer, no thermionic
heating of filaments, no starter circuit, and produces light in
a more energy-efficient way.
FIG. 4 diagrammatically illustrates a transformerless square wave
inverter circuit. Here, the positive (+) and negative (-) terminals
of a direct current source are alternately connected to opposing
electrodes of the fluorescent lamp(s). In this case, when switches
S1 and S2 are closed simultaneously or at the same time (preferably
by the same signal from controller CONT, the positive terminal (+)
is connected to electrode 4-1 and the negative terminal (-) is connected
directly to electrode 4-2. When the switches S3 and S4 are simultaneously
closed (and switches S1 and S4 are open) by controller CONT, the
positive terminal (+) is connected directly to lamp electrode 4-2
and the negative terminal (-) is connected to fluorescent lamp electrode
4-1. Controller CONT can operate the switches in the range of about
75 kHz to about 3.9 MHz and preferably operates the switches to
cause the square wave applied to lamp electrodes 4-1 and 4-2 to
be at a frequency of about 100 kHz.
FIG. 5 illustrates an "exit" sign housing HO in which
the word "exit" is formed in openings OP in a wall WA
and a translucent panel member TPM, colored green or red, etc. so
that when illuminated from inside the closed housing HO by the fluorescent
lamp which has been excited by the square wave driver circuit disclosed
herein. The word "exit" or other signage is illuminated.
While preferred embodiments of the invention have been shown and
described, it will be appreciated that other embodiments, adaptations
and modifications to the invention will be readily apparent to those
skilled in the art. |