Note: Descriptions are shown in the official language in which they were submitted.
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Fl~
Description iL l~ ,
Lighting device for signalling on as well as designating
and marking traffic areas in airports
The invention relates to a lighting device for
signalling on as well as designating and marking traffic
areas in airports, for example runways, taxiways and the
like, by means of light sources for the direct emission
of visible light.
Such lighting devices, which serve as components
of airport lighting systems, generally have tungsten-arc
lamps or incandescent lamps as light sources. Such light
sources usually have a lifetime of approximately 1000 to
1500 hours. Since lighting devices used for airport
lighting systems must emit light in different colours,
there is a comparatively high consumption of electrical
power in the case of the operation of known lighting
devices equipped with tungsten-arc lamps and incandescent
lamps, since such light sources emit light in a wide
range of light waves, of which only a small proportion
can be used to generate light of a specific colour.
The object of the invention is to provide a
lighting device of the type mentioned at the beginning
which, on the one hand, permits a longer service life
and, on the other hand, by means of which the outlay on
power for operating the airport lighting system can be
substantially reduced.
This object is achieved according to the inven-
tion by virtue of the fact that the light sources of the
lighting device are designed as semiconductor elements.
It is possible by means of such semiconductor elements
for light to be emitted in a prescribed colour,
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without there being a need for any sort of optical
radiation filtering. Even in the case of controlling such
a semiconductor element, the range of wavelengths within
which the semiconductor element emits light is very
narrow and constant. Accordingly, such a semiconductor
element scarcely generates radiation outside the visible
range, in particular scarcely generates heat producing
infrared radiation or ultraviolet radiation. The outlay
on power for operating such a semiconductor element or a
lighting device having such semiconductor elements is
thus substantially reduced by comparison with
conventional lighting devices, and this is to be
ascribed, inter alia, to the fact that there is no need
to use any sort of colour filter. Moreover, such
semiconductor elements can be controlled within
microseconds, by comparison with a range of seconds in
the case of conventional incandescent lamps or tungsten-
arc lamps; as a result, there are substantial practical
advantages in traffic control in the field of airports.
The service life of such semiconductor elements is an
average of approximately 70,000 hours, compared with 1000
to 1500 hours for the incandescent lamps and tungsten-arc
lamps used in the lighting devices which are presently
customary. Lighting devices of such a configuration
render it possible for the first time for the driving of
an aircraft in the area of a runway or a taxiway to be
followed in real time. Using the lighting devices
configured in accordance with the invention, it is
possible given the appropriate selection of the
semiconductor elements assembled for the lighting device
to meet at once the standards in accordance with ICAO,
FAA, DOT, CIE, MIL-C-25050. A further advantage of the
lighting device according to the invention consists in
that it already provides the luminance required to detect
signals at a comparatively great distance from the
lighting device, it being the case, moreover, that the
risk of a dazzle effect is avoided in the case when an
aircraft driver or vehicle
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driver is located at only a short distance from the
lighting device.
The semiconductor elements of the lighting device
according to the invention can advantageously be designed
as light-emitting diodes (LEDs) or as light-emitting
polymers.
It is possible for a plurality of semiconductor
elements of the lighting device to form a cluster, it
being possible for 2 to 200, preferably 2 to 30, semi-
conductor elements to belong to a cluster. The failure ofsemiconductor elements can be compensated thereby, since
a cluster having a plurality of semiconductor elements
remains operable even when one or more semiconductor
elements fail.
In an advantageous embodiment, the lighting
device according to the invention can be designed as a
cluster arrangement of a plurality of individual clus-
ters, for example, of 1 to 30, preferably 1 to 16. The
spatial light distribution of the lighting device can
thereby be optimized in accordance with the abovemen-
tioned standard requirements or other requirements. The
global photometric properties of the lighting device are
determined by the cluster arrangement.
In an advantageous embodiment of the lighting
device according to the invention, the semiconductor
elements of a cluster, which are preferably designed
without a mounting, are arranged on a common substrate.
When the substrate holding the semiconductor
elements is provided on its side facing the semiconductor
elements with a layer made from a reflecting material, it
is ensured that the radiation components of the semicon-
ductor elements which are not directed towards the
radiation-emitting surface of the
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cluster or of the lighting device are deflected there as
far as possible.
In accordance with one embodiment of the lighting
device according to the invention, in which there is
arranged on the output side of the semiconductor elements
a mirror surface by means of which the direction of
emission of the semiconductor elements is deflected, the
direction of emission of the lighting device can be
provided virtually as desired, depending on the posi-
tioning of the mirror surface.
When the dimensions of the radiation-emitting
surface of the lighting device correspond approximately
to the area of the substrate holding the semiconductor
elements, the result is an emission of light from the
lighting device which is uniform and thus perceived as
pleasant.
When the lighting device according to the inven-
tion can be assembled in a modular fashion from possibly
different clusters and/or cluster arrangements, it is
possible to fit such a lighting device together without
great outlay for virtually any conceivable use and any
conceivable requirements.
Thus, for example, a lighting device, which is of
bidirectional design and has two cluster arrangements of
which each emits in a direction opposite to that of the
other, can be used to indicate the centre line of a
straight taxiway, and also as a stop light; if the
lighting device has two cluster arrangements which emit
light in directions inclined to one another, they can be
used on curved sections of taxiways to indicate the
centre line thereof, or as a stop light.
When the cluster arrangements of this lighting
device have a plurality of, for example three or five,
clusters arranged next to one another, mutually juxta-
posed clusters respectively enclosing an angle
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of less than 180 degrees, it is possible to optimize the
spatial distribution of the light emitted from the
lighting device.
If the lighting device is intended to be of
omnidirectional design, it is advantageous when its
cluster arrangements are of curved design and form a
circle or the lateral surface of a cylinder.
If the lighting device is to emit light in two
directions, it is advantageous when the semiconductor
elements are arranged in rows or in columns. If the
lighting device is to emit light omnidirectionally, an
arrangement of the semiconductor elements in circles or
cylinders is advantageous. However, other arrangements of
the semiconductor elements are also possible.
Owing to the reflecting configuration of the side
of the substrate facing the semiconductor elements, it is
possible to provide an elementary optical system in
cooperation with the radiation-emitting sections of the
semiconductor elements themselves, if the emitting
sections of the semiconductor elements have the form of
an aspherical lens. The use and the distribution of the
generated light can hereby be of optimum configuration.
The semiconductor elements of the lighting device
according to the invention can be constructed from an
inorganic or organic material, in particular from plas-
tic. This yields substantial advantages with regard to
weight and to the possibilities of production.
Moreover, the individual clusters can be cast or
injected from a plastic, it being possible to use a
recyclable plastic as plastic. It is
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possible to select a material which is a good conductor
of heat for the individual clusters, it also being
possible to use a pressure-resistant plastic.
If the clusters form a compact unit with a
housing of the lighting device, this dispenses with any
sort of hollow convection space such as was necessary
with the conventional tungsten-arc lamps and incandescent
lamps, and also with the attendant use of metallic
housings. As a result, the loads which are caused by an
aircraft or another vehicle can be more effectively
passed on to the roadway.
When there is arranged in front of the semicon-
ductor elements of the lighting device according to the
invention a cover plate by means of which the beams
emitted from the semiconductor elements can be influenced
optically, it is possible to improve the emission of
light from the lighting device, for example by focusing
and aligning the beams.
The semiconductor elements can be assigned an
optical device for beam refraction and/or total reflec-
tion, it being possible to provide a high-performance
optical system by means of which the light emission can
be optimally formed so that it satisfies in any case the
requirements, already mentioned at the beginning, occur-
ring in airport operation.
If the outside of the cover plate is easy toclean and is hardened, the outlay on maintenance for the
lighting device can be reduced. The outside of the cover
plate should expediently be of self-cleaning design, it
being possible for the cover plate to be coated in a
suitable way.
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A compact configuration of the lighting device
can be achieved when the semiconductor elements are
arranged embedded in a filler member.
If the filler member embedding the semiconductor
elements has a cutout on the active surface or the light-
emitting opening of the semiconductor elements, it is
possible to maintain the use of the previously explained
elementary optical system, to which the reflecting
configuration of the side of the substrate facing the
semiconductor elements and the aspherical lens on the
emitting section of the semiconductor elements belong.
In accordance with an advantageous embodiment of
the lighting device according to the invention, the
filler member is constructed from a transparent material,
for example a transparent resin, in particular epoxy
resin, whose refractive index preferably corresponds to
that of the cover plate. Optical losses on the transition
surface between the filler body and the cover plate are
hereby eliminated.
The individual semiconductor elements are expedi-
ently constructed such that they can be manipulated in a
fully or partly automatic fashion.
The clusters of the lighting device according to
the invention are expediently components of a redundantly
operating system, with the result that it is possible in
any case reliably to prevent a total failure of the
lighting device according to the invention. Since,
because of the redundant configuration of the system
formed by the clusters, not every failure of an in-
dividual semiconductor element need necessarily lead to
the exchange of a cluster, the outlay on maintaining the
lighting device according to the invention can be further
reduced.
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In order further to simplify the assembly, the
modification or the repair of the lighting device accor-
ding to the invention, it is advantageous when one or
more clusters of the lighting device is or are designed
as an exchangeable subunit, in particular as a cassette.
It is then possible for a cassette belonging to the
lighting device to be exchanged in situ.
Such a cassette is advantageously type coded, so
that it can be installed in the lighting device
exclusively in accordance with its arrangement prescribed
in the lighting device; as a result, it is virtually
impossible to make errors when replacing such cassettes
in situ.
In an advantageous embodiment, it is possible for
the purpose of realizing this type coding for there to be
constructed on the outside of the cassette projections or
depressions which are assigned to depressions or pro-
jections, respectively, on the holder of the lighting
device which holds the cassette. In the case of the
cassette and in the case of the holder on the side of the
lighting device, such projections or depressions can
contribute to their reinforcement and capacity to resist
shear stresses. Loads and stresses introduced onto the
cassette can be transferred by means of the holder onto
the roadway, it being possible for these to be both
mechanical, specifically static and dynamic loads, and
thermal loads resulting from the requirement for thermal
dissipation. For the purpose of connecting the cassette,
a mounting for electrical contacts which is sealed off
against the environment is provided on the holder; in
order to connect the cassette in the desired way to a
power supply, the holder can also have a part for power
supply and control.
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When the basic body or the housing of the cas-
sette is filled entirely or partly with an electrically
non-conducting material, for example resin or plastic,
electrical corrosion can be avoided.
If a non-conducting filler, for example glass, is
added to the electrically non-conducting material, the
thermal capacity for dissipation and load carrying of the
cassette can be increased. The thermal resistance between
the clusters present in the cassette is lowered, with the
result that the transfer of heat between the clusters and
the basic body or the housing of the cassette is based on
thermal conduction instead of convection. Since there are
no cavities inside the cassette, the cassette is
inherently watertight and gastight.
If the walls, in particular a bottom wall of the
basic body or of the housing of the cassette, are or is
designed as thermal conductors, for example, made from
stainless steel or aluminium, the temperature gradient
inside the cassette can be reduced.
The outside of the cassette is advantageously
provided with a hardening, at least on the main stress
regions; as a result, damage owing to abrasion, scratches
or point loads can be avoided to a very great extent.
Moreover, such a reinforcement, in particular at the
fastening points of the cassette, can have the effect
that the load stresses and shear stresses can be better
distributed on the holding part of the lighting device.
Externally exposed surfaces of the cassette or of the
entire lighting device can be hardened by means of
sapphire or appropriate glass, so as to avoid a degra-
dation of the efficiency of the lighting device owing to
abrasion, or physical or chemical damage.
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In one configuration of the lighting device as a
flush-marker light, the absence of cavities ensures that
the lighting device or the cassettes forming it are not
exposed to bending stresses, but exclusively to
compressive stresses. Since in the case of a lighting
device configured in this way as a flush-marker light the
rise in temperature owing to the operation of the light
sources is less than 20~ of the rise in temperature in
the case of conventional lighting devices, the stresses
from the aircraft tyres crossing the flush-marker light
can be substantially reduced. Moreover, the risk of burns
can be substantially excluded for operating personnel.
In accordance with an advantageous configuration
of the invention, the basic body or the housing of the
lighting device is constructed from a metallic and
electrically non-conducting material. The use of such
materials for lighting devices in airports has not so far
been practicable, since the tungsten-arc lamps and
incandescent lamps used as light sources have generated
excessively high temperatures. Since the non-metallic and
electrically non-conducting materials which can be used
in the case of the invention are electrically isolating,
no electrical corrosion occurs in the case of the light-
ing device according to the invention. By comparison with
the materials which can be used for conventional lighting
devices, the material provided in the case of the light-
ing device according to the invention can be formed into
virtually any shape with a low outlay. The material which
can be used in the case of a lighting device according to
the invention can, moreover, serve as a thermal conduc-
tor, in order to dissipate the heat generated by the
lighting device to the mounting part holding the lighting
device, or to the roadway. Since the entire basic body or
the entire housing of the lighting device according to
the invention can be designed as an insulator by select-
ing the material which can now be used, no costly sepa-
rate insulator is required. A recyclable plastic can be
used for the
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basic body or the housing of the lighting device, the
outcome being the ecological advantages resulting
therefrom. Since the materials which can now be used to
configure the lighting device according to the invention
have a substantially longer lifetime by comparison with
the prior art, the use cycles of the lighting device
according to the invention are correspondingly
lengthened.
The semiconductor elements of the lighting device
according to the invention can be controlled electrically
between very low and very high potentials, the range of
wavelengths of the emitted radiation being very narrow
over the entire control range and entirely constant with
regard to position and width, with the result that light
of one and the same colour can be emitted over the entire
control range.
If the lighting device according to the invention
has different semiconductor elements for emitting light
in different colours, it being possible for the emitted
light of different semiconductor elements to be mixed
arbitrarily, the light emitted from the lighting device
can be set arbitrarily with regard to colour and/or
intensity. It is therefore possible to use one and the
same lighting device to emit light of different colour.
For this purpose, it can be advantageous for the clusters
forming the lighting device to comprise semiconductor
elements of different types. The efficiency of such a
lighting device can be increased by virtue of the fact
that the semiconductor elements emit their light with a
very narrow colour bandwidth and at a very high satura-
tion. Since the colour of the emitted light does not
change perceptibly with control of the intensity, the
colour setting can be selected with respect to the
efficiency. Using a lighting device according to the
invention configured in such a way, light can be emitted
virtually in the entire
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visible colour range, all colours which can be used
sensibly in a technical way being possible. This does not
require any mechanical movement of lamps, filters or
other parts to be moved physically; the corresponding
properties of the lighting device according to the
invention follow from static, controlled components. The
addition of colours which are generated by individual
semiconductor elements means that the light visible to
the human eye can be of any colour, since resolution of
the light of different semiconductor elements after two
arc minutes corresponding to a distance of 0.5 m from the
lighting device can no longer be resolved.
The lighting device expediently has a control
device for controlling the power supply, by means of
which the lighting device can be dimmed and/or switched.
When this control device has an electronic light
controller, the sensitivity of the semiconductor elements
can be adapted to the customary sensitivity of incan-
descent lamps and tungsten-arc lamps, so that the light-
ing device according to the invention can be combined inthe same system with conventional lighting devices having
tungsten-arc lamps and incandescent lamps.
The control device can be connected for sig-
nalling purposes to a central unit by a power supply line
and/or a separate electric or optical data line. The
control device can serve to control the intensity of
emission of the semiconductor elements. Moreover, it can
be prescribed by means of the control device in which of
several possible directions light is emitted, if the
lighting device is designed as a bidirectional or omni-
directional lighting device.
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By means of this control device the intensity of
emission and the number of the semiconductor elements
emitting light of different colour can be set so that the
lighting device can be used to emit light of any desired
colour at any desired intensity.
Moreover, the control device can set a specific
succession of OFF and, if appropriate different, ON
operating states.
Of course, it is possible in accordance with an
advantageous embodiment of the lighting device according
to the invention to use the control device to monitor the
operating state and the operability of the semiconductor
elements functioning as light source.
When one or more clusters of the lighting device
according to the invention has or have semiconductor
elements which emit red, green or blue light and are
arranged alternately, it is possible for the variable
white light which is particularly important in operating
an airport to be emitted in any desired form. As a
result, the lighting device can be adapted in an optimum
way to different climatic conditions, it naturally being
possible, in addition, to take account of different
lighting conditions as well. Since red, blue and green
are arranged at the outer corners of a colour triangle,
and the lighting device can have a desired number of
corresponding semiconductor elements, this lighting
device can be used to generate all the colours provided
according to the standards already named at the begin-
ning. Moreover, the lighting device according to the
invention can be used immediately to fulfil the require-
ments with regard to light propagation.
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If the aim is to use the lighting device accor-
ding to the invention to emit only red, yellow, orange
and green light, it is sufficient if one or more clusters
has or have semiconductor elements which emit red or
green light and are arranged alternately. Semiconductor
elements emitting blue light are not required in this
case, since they are not important for the emission of
light in the abovementioned colours. If light is to be
generated only in the said four colours, specifically
red, yellow, orange and green, the result of dispensing
with semiconductor elements emitting blue light is that
the lighting device according to the invention can be
configured with smaller dimensions in conjunction with
the same possible light intensity.
It is possible to arrange mutually juxtaposed
rows of semiconductor elements of a cluster offset
relative to one another, resulting in some circumstances
in a denser population of a substrate with semiconductor
elements.
If the control device of the lighting device
according to the invention has a pulse-width modulation
device by means of which the electrical power fed to the
semiconductor elements can be controlled, the result is
a high efficiency for operating the lighting device
according to the invention, it being possible for the
power rendered available to be adapted in an optimum way
to the requirements of the lighting device or the
requirements of the semiconductor elements by means of
the pulse-width modulation device. There is no need for
a thyristor-controlled power supply which, in its turn,
would typically cause harmonization and reactive losses
in the main source. Moreover, the operation of the
lighting device according to the invention produces no
stroboscopic effect which could impair the correct
perception of the lighting device.
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The invention is explained in more detail below
with the aid of exemplary embodiments and with reference
to the drawing, the application of the invention in the
field of airports, in particular, being described.
Figure 1 shows a representation of the principle
of a semiconductor element designed as a light-emitting
diode;
Figures 2 to 4 show, in front, side and top
views, the principle of a first embodiment of a cluster
of a lighting device according to the invention;
Figures 5 to 7 show, in front, side and top
views, the principle of a second embodiment of a cluster
of the lighting device according to the invention;
Figure 8 shows a top view of a first exemplary
embodiment of the lighting device according to the
nvent lon;
Figure 9 shows a top view of a second exemplary
embodiment of the lighting device according to the
invention;
Figure 10 shows a top view of a third exemplary
embodiment of the lighting device according to the
invention;
Figure 11 shows a sectional representation of the
exemplary embodiment, represented in Figure 8 for
example, of the lighting device according to the inven-
tion;
Figure 12 shows a representation corresponding to
Figure 11, the lighting device being constructed from
clusters in accordance with Figures 5 to 7;
Figure 13 shows a further embodiment of the
lighting device according to the invention;
Figures 14 to 17 show representations of the
principle of clusters having different semiconductor
elements;
Figure 18 shows a representation of the fixed
colours provided for airport lighting systems;
Figure 19 shows a representation of the principle
of the control, regulation and monitoring of airport
lighting systemsi
.
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Figure 20 shows a representation of the principle
of the output side of a pulse-width modulation device of
the lighting device according to the invention;
Figure 21 shows a control device of the lighting
device according to the invention; and
Figure 22 shows a modified control device of the
lighting device according to the invention.
A lighting device according to the invention has
a multiplicity of semiconductor elements which are
designed in the case of the embodiments described below
as light-emitting diodes 1. The light-emitting diode 1
represented in principle in Figure 1 has, in that region
in which the light generated emerges from the diode 1, a
configuration as an aspherical lens 2, as is represented,
in particular, in Figure 1.
Owing to the aspherical configuration of the
light-refracting lens 2, the distribution of the light
emitted by the diode 1 can be optimized.
The light-emitting diode 1 is, in particular, a
bright or superbright LED.
The lighting device according to the invention is
assembled from a multiplicity of previously described
light-emitting diodes 1. A plurality of such light-
emitting diodes 1 can be combined to form a cluster 3
represented in Figures 2 to 4. In the exemplary embodi-
ment represented in Figures 2 to 4, the cluster 3 has ten
light-emitting diodes 1, which are arranged in two rows,
of five light-emitting diodes 1 each, arranged one above
another.
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It is possible for the centre lines of the diodes
1 of a row to be arranged inclined with respect to the
centre lines of the diodes 1 of a neighbouring row.
A11 the light-emitting diodes 1 of this cluster
3 are arranged without a mounting on a substrate 4 which
serves as a holder for the light-emitting diodes 1. The
cluster 3 has an elementary optical system, to which
there belongs a reflecting layer 5 which is applied to
the side of the substrate 4 facing the light-emitting
diodes 1. The aspherical lenses 2 of the light-emitting
diodes 1, which optimize the use and distribution of the
light generated by the light-emitting diodes 1, belong to
this elementary optical system. The aspherical lens 2
respectively forms the actual active surface or the
light-emitting opening of the light-emitting diodes 1.
The cluster 3 represented in Figures 2 to 4 is
configured as a module part which can be assembled with
other identical or similar clusters 3. On the light-
emitting surface 6, the cluster 3 is closed by means of
a cover plate 7 which, in the case of the cluster 3
represented in Figures 2 to 4, is arranged parallel to
the substrate 4. With regard to its dimensions, the
radiation-emitting surface 6 of the cluster 3 corresponds
essentially to the surface of the substrate 4, which is
virtually completely covered by the light-emitting diodes
.
The light-emitting diodes 1 of the cluster 3 are
surrounded by a filler member 8 which fills up the space
between the substrate 4 and the cover plate 7 and is
produced from a transparent material, for example from a
resin. The filler member 8 has a cutout 9 which is
assigned directly to the emitting section of the cluster
3 formed by the aspherical lenses 2 of the light-emitting
diodes 1 of the cluster 3;
. . .
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the cutout 9 is constructed between the active surface of
the light-emitting diodes 1 of the cluster 3 and the
filler member 8, in order not to lose use of the
elementary optical system formed by the reflecting layer
5 of the substrate 4 and the aspherical lenses 2 of the
light-emitting diodes 1.
The refractive index of the material forming the
filler member 8 expediently corresponds to that of the
material forming the cover plate 7. As a result, optical
losses at the contact surface between the filler member
8 and the cover plate 7 can be prevented.
The outside of the cover plate 7 of the cluster
3 is of hardened and smooth configuration; it can,
moreover, be self-cleaning.
In the embodiment of the cluster 3, as it is
represented in Figures 2 to 4, the direction of emission,
represented by the arrow in Figure 3, of the cluster 3 is
arranged perpendicular to the plane of the substrate 4.
In the embodiment, represented by Figures 5 to 7,
of the cluster 3, the direction of emission, represented
by the arrow in Figure 6, of the cluster 3 is deflected
by 90 degrees, for which purpose a mirror surface 10 is
provided which is arranged between the light-emitting
diodes 1 and the radiation-emitting surface 6 of the
cluster 3. The mirror surface 10 resets the light beams
by 90 degrees in the exemplary embodiment represented,
with the result that they emerge parallel to the plane of
the substrate 4 from the cluster 3 through the light-
emitting surface 6 thereof or through the cover plate 7
thereof.
A taxiway centre and stop light for a straight
section of a taxiway is represented in Figure 8. What is
involved in this case
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is a so-called bidirectional lighting device, having a
first cluster arrangement 11, which emits in the
direction marked by the arrow 13, and a second cluster
arrangement 12, which emits in the direction opposite to
that of the cluster arrangement 11 and marked by the
arrow 14.
The lighting device represented in Figure 8 is a
compact device, the two cluster arrangements 11, 12 being
arranged in a common housing 15. That region of the
interior of the housing 15 which is arranged between the
two cluster arrangements 11, 12 as well as, in Figure 8,
to the side of the two cluster arrangements 11, 12 is
filled with a suitable material. The housing 15 can be of
metal construction.
Apart from the fact that they emit in different
directions, the cluster arrangements 11, 12 corresponding
to one another, and so only the cluster arrangement 11 on
the right in Figure 8 is described in detail below.
The cluster arrangement 11 has three clusters 3,
which are arranged in a row next to one another, it being
possible for each of these clusters 3 to have, for
example, the embodiment represented by Figures 2 to 4.
The middle cluster 3 is arranged at right angles to the
centre line 16 of the taxiway, intersecting this centre
line 16 in its middle region. The two outer clusters 3
respectively enclose with the middle cluster 3 an angle
which is slightly less than 180 degrees. An efficient
horizontal light distribution is achieved hereby. The
cover of the lighting device represented in Figure 8 has
a hardened, smooth outer surface which is thereby
configured such that it can be cleaned in a simple way.
. _
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The lighting device represented in Figure 9
likewise serves for marking the centre line of a taxiway,
but on a curved section thereof, and as a stop light
which can be used there. It differs from the lighting
device represented in Figure 8 by virtue of the fact that
the directions of emission of the two cluster arrange-
ments 11, 12 are inclined to one another, and that there
are provided per cluster arrangement 11, 12 five indi-
vidual clusters 3, which can likewise be such as the
embodiments represented in Figures 2 to 4. Since a curved
section of the taxiway is involved, the middle cluster 3
of the two cluster arrangements 11, 12 is offset and
inclined to the centre line CL of the lighting device.
The clusters 3 of the two cluster arrangements 11, 12
likewise enclose with the respectively adjacent cluster
3 an angle alpha which is less than 180 degrees.
Figure 10 shows a lighting device which acts in
all directions and can likewise be provided for marking
a taxiway. Six curved clusters 17, which form a closed
circle with one another and are separated from one
another by structural ribs 18, are provided in the
embodiment represented. Light can be emitted virtually in
all directions by means of the six curved clusters 17.
In the lighting devices described above with the
aid of Figures 8 to 10, the outer optical surface can be
of transparent and hard configuration, for example made
from sapphire or glass with a hardened surface, so that
a degradation of the efficiency of the lighting devices
because of abrasion and physical or chemical damage is
avoided. The outer optical surface can be hardened or
coated in such a way that any possible Fresnel losses are
reduced.
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Represented in Figures 11 and 12 are cross-
sections through lighting devices, which correspond, for
example, to the lighting devices represented in Figures
8 to 10, and are designed as flush-marker lights. They
differ from one another essentially in that, in Figure
11, the clusters 3 of the embodiment described with the
aid of Figures 2 to 4 are used, whereas in the case of
the flush-marker light in accordance with Figure 12 use
is made of clusters of the embodiment explained with the
aid of Figures 5 to 7.
The lighting device in accordance with Figures 11
and 12 is arranged with substantial parts below ground
level 19. The arrows represented in Figures 11 and 12
mark the directions of emission of the flush-marker
lights. As follows, in particular, from Figure 11, the
part of the flush-marker light having the cluster or
clusters 3 is configured in the form of a cassette 20
which, as such, forms a unit which can be exchanged
without a high outlay. Such a flush-marker light can have
one or more such cassettes 20. Depending on the configu-
ration of the lighting device, a plurality of identical
or, possibly, also different cassettes can be assembled
to form the lighting device.
In an advantageous embodiment, such a cassette 20
is type coded, the type coding corresponding to its
arrangement inside the lighting device. As a result of
this, errors are rendered virtually impossible during an
in situ replacement of the cassette 20. The type coding
can be implemented by projections or cutouts on the
cassette side, corresponding cutouts or projections then
being provided in a holding part 21 of the lighting
device. Such relief-type configurations of the cassette
20 and of the holding part 21, or configurations provided
with indentations can, moreover, contribute to the
capacity to withstand shear stresses.
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The basic body or the housing of the cassette 20
is filled entirely or partially with an electrically non-
conducting material, for example a resin or plastic;
electrical corrosion is avoided hereby. A thermally
conducting material, for example glass, can be added to
the non-conducting material, in order thus to increase
the capacity of the cassette 20 for thermal dissipation
and its capacity for accepting loads.
The thermal transmission between the clusters 3
and the basic body or the housing of the cassette 20 is
then based on thermal conduction instead of air/gas
convection, with the result that the thermal resistance
of the cassette 20 is substantially reduced.
Since no convection gas is present, any possible
aircraft or vehicle loads which act on the cassette 20 do
not lead to bending stresses, but exclusively to
compressive stresses, which can be absorbed or dissipated
more easily.
The cassette 20 is inherently watertight and
gastight, because there are no cavities, and thus no
convection gas, inside the cassette 20.
The rise in temperature occurring in the cassette
20 is only less than 20~ of the rise in temperature in
the case of a lighting device with a conventional
tungsten-arc light source, with the result that aircraft
or vehicle tyres are by far less stressed, and burning of
operating and maintenance staff can be excluded.
The bottom wall of the cassette 20 can be con-
structed by a thermal conductor, for example stainless
steel or coated aluminium; the temperature gradient
inside the cassette 20 is reduced hereby.
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The outside of the cassette 20 can be constructed
in a hardened fashion, for example from a stainless
steel, thus avoiding damage owing to abrasion, scratches
or point loads.
Fastening points of the cassette 20 can be of
reinforced design, so that load and shear stresses on the
structure supporting the cassette 20 or on the holding
part 20 can be distributed more effectively.
The introduction of power or the transmission of
signals into the cassette 20 is accomplished by self-
cleaning and self-sealing contacts. Watertight and
vapourtight protection against the environment is
provided.
Because of the design of the lighting device with
light-emitting diodes 1, the transmission of electrical
power between the cassette 20 and the remaining parts of
the lighting device is performed at a very low voltage
level, with the result that it is possible to carry out
a "hot" cassette replacement without the danger of
damaging the electrical contacts and without the risk of
electric shock to the staff; in this case, the voltage
level is below a peak voltage of approximately 25 V.
The cassette 20 is arranged above a power supply
and control device 22 of the lighting device.
Since the cassette 20 is constructed as far as
possible without cavities, it resists mechanical stresses
of 100 G and vibrational stresses of up to 30 G, it being
unimportant whether the lighting device is energized or
not energized.
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Loads and stresses introduced onto the cassette
20 are transferred onto the roadway by means of the
holding part 21. These stresses are static and dynamic
mechanical loads as well as thermal loads which arise
from the need to dissipate the heat produced.
Figure 13 shows an embodiment of the lighting
device which is arranged in a conventional way above a
roadway. There, too, a cassette 20 configured to be
capable of exchange in a modular fashion is arranged
above a power supply and control device 22, the power
supply and control device 22 being arranged above the
ground level 19 with the aid of a detachable coupling 23.
Figure 14 shows a representation of the principle
of a cluster 3 which is assembled from red, yreen and
blue light-emitting diodes 1. In a way still to be
described, the intensity with which the light-emitting
diodes 1 emit light of each colour can be controlled.
Owing to the fact that the light-emitting diodes 1 of
each of the three colours can emit light at the respec-
tively desired intensity, light can be emitted virtuallyin all visible colours by means of the cluster 3 shown in
Figure 14, it being possible, moreover, for this light to
be emitted at different intensities. As follows, in par-
ticular, in conjunction with Figure 18, the colours of
red, green and blue provide the possibility of emitting
light of any intensity and in any colour conceivable for
possible signals.
Such a configuration of a cluster 3 can also be
used to emit white light at different intensities, some-
thing which is difficult with conventional lightingdevices. The reason for this is that red, green and blue
are arranged in the colour spectrum approximately at the
corners of a triangle
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which describes the visible colour range, as follows from
Figure 18.
The light emerging from the cluster 3 can no
longer be differentiated into individual light sources at
a distance of two arc minutes corresponding to an obser-
ving distance of 10 m, with the result that light can be
produced in the desired colour and intensity for all
purposes. This also holds, in particular, for the stan-
dards ICAO, FAA, DOT, CIE, MIL-C-25050 valid in aviation.
A cluster 3 which, as already mentioned, contains
light-emitting diodes 1 whose light is red, blue or green
is best suited for generating variable white light. As
already mentioned, these three colours are arranged at
the outer corners of a triangle which is to be seen in
Figure 18 and corresponds to the said standards.
Only four colours, specifically red (R), yellow
(Y), orange and green (G) are required to mark taxiway
markings and route information. It is simpler and less
expensive for such an application when a cluster 3
contains only two different types of light-emitting
diodes 1, specifically ones which emit red light, and
ones which emit green light. Such a cluster 3 is repre-
sented in principle in Figure 15. Diodes 1 emitting blue
light can be dispensed with in this case.
The clusters 3 in accordance with Figure 16 and
Figure 17 differ from the clusters 3 represented in
Figure 14 and Figure 15 only by virtue of the fact that
the individual light-emitting diodes 1 are not arranged
in rows offset relative to one another; in the case of
the clusters 3 in accordance with Figures 16 and 17, the
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light-emitting diodes 1 arranged below or above one
another are not offset relative to one another.
Light-emitting diodes 1 are available on the
market from different manufacturers and in different
colours. Thus, for example, the Toshiba company manufac-
tures LEDs for emitting light in red, orange and yellow
colours; the Hewlett-Packard company manufactures diodes
for emitting light in amber, orange, red-orange and red
colours; the Ledtronics company manufactures diodes for
emitting light in green, yellow, orange, red and blue
colours.
The supply of power to the light-emitting diodes
1 is controlled with minimum losses by a pulse-width
modulation device 24, the peak current being set in an
initialization method by means of which the type of the
light-emitting diode is identified in accordance with the
result of a comparison of the voltage drop across a chain
of light-emitting diodes with the voltage drop across a
reference LED.
The control or inclusion and integration of the
lighting devices according to the invention into a
control system of an airport will now be explained with
the aid of Figure l9.
An air traffic control centre 25, an emergency
control centre 26 and a maintenance control centre 27 are
connected in a suitable way to a controller 28 for routes
and gates. This controller 28 is connected, in turn, to
substations 29, 30, 31, of which only the substation 29
is represented in detail in Figure 19.
It may be pointed out that a star-shaped connec-
tion between the controller 28 and the substations 29,
30, 31 is represented in Figure 19, but that it is also
possible in principle
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to provide a loop connection or a bus connection.
The substation 29 has a subcontrol device 32 with
a panel 33. Via a CCR 34 and a master circuit 35 in each
case, the actual control devices 22 of the lighting
devices according to the invention are connected to the
subcontrol device 32.
The already mentioned pulse-width modulation
device 24 belongs to the control device 22, which is
represented in detail in Figures 21 and 22. The output
power of the said pulse-width modulation device 24 can
vary, as emerges from Figure 20, whose upper part rep-
resents an output power of the pulse-width modulation
device 24 with a low intensity, and whose lower part rep-
resents an output power of the pulse-width modulation
device 24 with a high intensity.
The control devices 22 represented in Figures 21
and 22 differ from one another only in that the control
device 22 represented in Figure 21 has no separate data
line 36, but has only a power supply line 37, which also
serves the purpose of data transmission.
The control device 22 includes a power adapting
and sensor unit 38 which is connected to the pulse-width
modulation device 24 and a controller 39.
The pulse-width modulation device 24 is likewise
connected to the controller 39 and an outlet sensor 40,
which is likewise connected to the controller 39 and via
which the light-emitting diodes 1 of the lighting device
are driven. The controller 39 is connected to the power
supply line 37 or the data line 36 via a modem 41 and a
connecting circuit 42.
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A unit of the Intel 8051 type can be used as the
controller 39. A PC can be used as the substation control
device 32, a SICOMP-PC being a possibility.
The control of the lighting device includes the
regulation of the intensity of emission of the diodes 1,
the selection of that direction or those directions in
which light is to be emitted from the lighting device,
the selection of the colour in which light is to be
emitted, the light flash coding or the time sequence of
light pulses, ON and/or OFF operation controlled as a
function of time, monitoring of the diodes 1, and auto-
matic "power on default start-up" selection and an
automatic "fallback default" selection in the event of
control failure. Further optional features are possible.
The input power incoming at the control device 22
is automatically detected and adapted to the requirements
of the lighting device.
In the case of a standard constant-current series
circuit input power, the output power of the pulse-width
modulation device 24 is adapted such that the exponential
response typical of tungsten-arc lamps or incandescent
lamps is produced, with the result that the lighting
device according to the invention can be combined with
conventional lighting devices in one and the same cir-
cuit.
The modem 42 codes the modulated control signalsfrom the power supply line 37 or the data line 36 and
assigns the control signals. The modem 41 alternately
modulates and codes monitoring signals which come from
the lighting device, in order to make these available to
a central control and monitoring system. The modem 41
operates
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in two directions, in order to be able to transmit the
control and monitoring signals in a suitable way.
A component of the control device 22 is a moni-
toring part by means of which the lighting device is
monitored for line interruption, earth fault, supply lead
faults and the like.
The clusters 3 can, for example, also be moni-
tored for operability by means of a selenium cell.
