Title of Invention

METHOD AND DEVICE FOR NON-INDIVIDUAL CONTROLLING OF THE UV RADIATION SOURCES AND A WEATHERING APPARATUS INCORPORATING SAID DEVICE

Abstract Control of the UV radiation sources for a weathering apparatus on the basis of the averaged UV radiation intensity The radiation power emitted from the UV radiation sources (2) in a weathering apparatus is controlled such that the radiation power of each of the radiation sources (2) is measured in a predetermined spectral range of the radiation emitted from the radiation sources, with the spectral range being chosen such that the measured radiation power is representative of the radiation power in the UV, an averaged radiation power is calculated from the measured radiation powers, and the averaged radiation power is used for controlling the electrical power to be supplied to the radiation sources (2) . In particular, the control process can be carried out in such a way that the same electrical power, within a predetermined tolerance bandwidth, is supplied to each of the radiation sources (2) , and the averaged radiation power is kept constant over time at a desired nominal value.
Full Text The present invention relates to a method and a device
for non-individual controlling of the UV radiation
sources in a weathering apparatus.
In a weathering apparatus, the weather-dependent ageing
behaviour of a sample, in particular of a flat material
sample, is assessed, with the sample being subjected to
artificial weathering. The weathering apparatus for this
purpose normally has a weathering chamber, in which
holding means are arranged for holding samples to be
weathered, and in which one or more radiation sources are
arranged in order to apply radiation, in particular UV
radiation, to the samples.
Apparatuses for artificial weathering of material samples
are generally used to estimate the life of materials
which are continuously subjected to natural weather
conditions during their use, and which thus deteriorate
under climatic influences such as sunlight, solar heat,
humidity and the like. In order to obtain a good
simulation of the natural weathering characteristics, it
is advantageous for the spectral energy distribution of
the light produced in the apparatus to correspond as far
as possible to that of the natural solar radiation, for
which reason appliances such as these use xenon emitters
as their radiation source. An accelerated ageing test of
the materials is achieved essentially by illuminating the
samples much more intensively than the natural
conditions, thus speeding up the ageing of the samples. A
statement about the long-term ageing behaviour of a
material sample can thus be made after a relatively short
time.
The majority of the material samples which are
investigated in artificial weathering appliances are
composed of polymer materials. The weather-dependent
deterioration of polymer materials is caused
substantially by the UV component of the solar
radiation. The primary photochemical processes which
take place in this case, that is to say the absorption
of photons and the production of stimulated states or
free radicals, are not dependent on the temperature. In
contrast, the subsequent reaction steps with the
polymers or additives may be dependent on the
temperature, so that the observed ageing of the
materials is likewise dependent on the temperature.
The already known weathering apparatuses normally use a
number of UV radiation sources such as xenon radiation
sources. As is known, these can be used to simulate the
solar spectrum quite well, but the emitted radiation
has a relatively high spectral component in the
infrared spectral range. Within the life of a
commercially available xenon radiation source of about
1500 hours, the emitted UV radiation power, relative to
the electrical power that is supplied, decreases
continuously. In order nevertheless to keep the UV
radiation power constant over the entire life, in
particular within a weathering process, however, a
control system is used in conventional weathering
apparatuses. This provides for the radiation power
emitted from each UV radiation source to be measured
individually by means of a UV sensor, and for its
output signal to be used as a controlled variable for
the electrical power to be supplied to the UV radiation
source. Each of the control loops reacts to a reduction
in the radiation power by increasing the electrical
power that is supplied, so as to achieve the original
radiation power again.
This individual control of the radiation sources has
the advantage that the UV radiation power of all of the
radiation sources can be kept constant at one and the
same level over time. However, the disadvantage is that
the normally used radiation sources, in particular
xenon radiation sources, do not degrade in the infrared
range, or do not degrade as severely as in the UV
range. The application of a different electrical power
to the radiation sources in order to compensate for the
differences in the UV radiation power thus leads to the
radiation sources emitting different radiation powers
in the infrared. However, this means that the samples
to be weathered are heated to different extents, and
different temperatures occur on them. The results of
the weathering process are thus reliable only to a
limited extent owing to the ageing temperature
dependencies mentioned above.
A further disadvantage of applying different electrical
powers to the radiation sources is that the radiation
sources which are loaded to a greater extent age more
quickly because they are more highly loaded, so that
even more electrical power must be applied to them in a
self-reinforcing process, owing to the faster ageing.
This can lead to a considerable shortening of their
lives.
One object of the present invention is therefore to
specify a method and an arrangement for controlling the
radiation sources in a weathering apparatus, which
provide satisfactory control of the radiation sources
without temperature imbalances being produced on the
samples and/or without excessively shortening the life
of the radiation sources. One particular aim is to
counteract the processes of the UV radiation powers of
the radiation sources drifting apart, without this
leading to differences in the infrared radiation power.
Accordingly, the invention provides a method for non-
individual controlling the UV radiation sources in a
weathering apparatus, comprising :
measuring the radiation power of each of the radiation
sources in a predetermined spectral range of the radiation
emitted from the radiation sources, the spectral range
being chosen such that the measured UV radiation power is
representative of the radiation power in the UV,
calculating an averaged radiation power from the
measured UV radiation powers, and
using the averaged radiation power for controlling the
electrical power to be supplied to the radiation sources.
Advantageous developments and refinements are described
hereinafter.
The invention also provides a device for non-individual
controlling the UV radiation sources in a weathering
apparatus, comprising :
sensors for measurement of the radiation powers of the
UV radiation sources in a spectral range of the radiation
emitted from the radiation sources, with the spectral range
being chosen such that the measured UV radiation power is
representative of the radiation power in the UV,
a monitoring device for calculating an averaged
radiation power from the measured radiation powers, and for
production of control signals for the electrical power to
be supplied to the radiation sources.
One major aspect of the invention is to determine the mean
radiation power of the UV radiation sources in the
weathering apparatus and to use this for control purposes.
The radiation sources are thus no longer controlled
individually, but their radiation powers are detected and
are averaged, and the radiation sources are controlled on
the basis of the averaged radiation power.
Thus, in the method according to the invention, the
radiation power of each of the radiation sources is
measured in a predetermined spectral range of the radiation
emitted from the radiation sources, with the spectral range
being chosen such that the measured radiation power is
representative of the radiation power in the UV. An
averaged radiation power is then calculated from the
measured radiation powers, and the averaged radiation power
is used for controlling the electrical power to be supplied
to the radiation sources.
The radiation power of the radiation sources is preferably
measured directly in the UV range. This can advantageously
be achieved by using UV broadband sensors with a
sensitivity range from 300 nm to 400 nm. Sensors for a
spectrally narrower sensitivity range, for example 330-350
nm, may however also be chosen. Since the radiation source
can be designed such that it emits not only in the UV but
at least in one sub-band of the adjacent visible spectral
range as well, the radiation power can also be measured
outside the UV, for example in the visible blue spectral
range by means of a sensor with a sensitivity range from
410 nm to 430 nm. This is dependent on the spectral
measurement
range being chosen such that the measured radiation
power is representative of the radiation power in the
UV, in particular of the radiation power integrated
over the entire UV range. In particular, a fixed ratio
may exist between two radiation powers, such that the
radiation power in the UV can be calculated at all
times by multiplication of the radiation power in the
visible by a constant.
The concept according to the invention thus includes a
control process in which the decrease in the UV
radiation power of an individual radiation source is
compensated for not just by this on its own and,
instead, the compensation power to be applied is
distributed uniformly between all of the radiation
sources. There is no longer any need for each
individual radiation source to supply a constant UV
radiation power. In fact, the critical factor is that
the mean UV radiation power behaves as specified, in
particular by remaining constant over time.
In consequence, fundamentally, there is now only one
common control loop rather than a number of independent
control loops, corresponding to the number of radiation
sources, as in the prior art, in which common control
loop the mean radiation power is the measured variable
and its error from a nominal value is used as the
controlled variable for controlling all of the
radiation sources. These radiation sources therefore
nominally always have the same electrical power applied
to each of them, and this electrical power can be
varied over time as appropriate for the control
requirement.
The electrical power to be supplied to the radiation
sources is thus preferably controlled in such a way
that the averaged radiation power remains constant over
time.
The control process should be carried out in such a way
that the same electrical power, within a predetermined
tolerance bandwidth, is supplied to each of the
radiation sources. This tolerance bandwidth may, for
example, be + 2%.
The radiation powers of the individual radiation
sources can be measured at regular time intervals, with
the mean radiation power being calculated from this.
The control process responds to an incremental
reduction in the mean radiation power by uniformly
increasing the electrical power to the radiation
sources, until the original mean radiation power level
is achieved again.
As already stated, the radiation power can be detected
by broadband measurement in the range from 300 to
400 nm, corresponding to the IS Standard, using UV
sensors designed appropriately for this purpose. As an
alternative to this, detection can also be carried out
by narrowband measurement, in the range from 330 nm to
350 nm, in accordance with the NB Standard. A further
measurement range which is specified in the NB Standard
and which can be used for the method according to the
invention is that from 410 nm to 430 nm, which is
outside the UV, in the visible spectral range.
An arrangement according to the invention for
controlling the radiation sources in a weathering
apparatus has sensors for measurement of the radiation
powers of the radiation sources, and has a monitoring
device for calculation of an averaged radiation power
from the measured radiation powers and for production
of control signals for the electrical power to be
supplied to the radiation sources.
The monitoring device has inputs which are connected to
the outputs of the sensors, and also has outputs which are
connected to control inputs of power supply devices for
the radiation sources.
The invention also relates to a weathering apparatus
comprising a weathering chamber, having UV radiation
sources and incorporating a device as described above for
non-individual controlling of the radiation sources.
One exemplary embodiment of an arrangement according to
the invention is illustrated schematically in the sole
figure of the accompanying drawing.
A weathering apparatus has a weathering chamber 1 in which
material samples to be investigated can be subjected to
artificial weathering conditions. For this purpose, a
number of UV radiation sources are fitted into openings in
an inner wall in the illustrated type of weathering
apparatuses. As in the illustrated case, the radiation
sources are preferably fitted to one of the two opposite
inner walls of the weathering chamber 1 with the largest
area. The material samples (not illustrated) to be
weathered can be fitted in the opposite inner wall, with
these material samples preferably having the normal
standard dimensions for this field and being placed in
cutouts of appropriate size in this inner wall. These
material samples are accordingly arranged opposite the UV
radiation sources 2. Each of the UV radiation sources 2
emits a divergent radiation beam. The radiation beams are
superimposed on one another on the sample plane. The inner
walls of the weathering chamber 1 are preferably provided
with a coating that is highly reflective for UV, such as
an aluminium coating, in order to make optimum use of the
emitted UV radiation. This results in an approximately
homogeneous, constant UV radiation power on the sample
plane.
The UV radiation sources 2 are formed in particular,
but not exclusively, by xenon radiation sources. Their
relatively high spectral component in the infrared
spectral range is - as mentioned in the introduction -
a part of the original problem on which the present
invention is based. If desired, an infrared filter can
additionally be arranged between the xenon radiation
sources and the samples.
However, other radiation sources may also be used, in
particular including those in which the initially
mentioned problems of unequal infrared radiation load
and thus unequal heat application to the samples do not
occur, or are not so important. The invention can also
advantageously be used with radiation sources such as
these to the extent that it solves the problem, which
was likewise mentioned in the introduction, of unequal
application of electrical power to the radiation
sources. By way of example, a halogen lamp, in
particular a metal-halogen lamp, may also be used as a
radiation source, although it is somewhat more
difficult to control radiation sources such as these
than xenon lamps. Fluorescent lamps may also be used as
radiation sources, although in general these have
shorter lives than the radiation sources mentioned
above. Furthermore, UV light-emitting diodes may also
be used as radiation sources, in particular those based
on GaN, in which case the infrared problem would be
entirely irrelevant. Recently, it has been possible to
use GaN LEDs to satisfactorily cover the entire UV
range of the solar spectrum. The achievable radiation
densities are already sufficiently high that the
radiation power of a conventional xenon lamp can be
achieved without any problems by the arrangement of a
number of UV LEDs. The radiation sources 2 illustrated
in the drawing figure may thus, by way of example, be
formed by in each case one individual UV LED or an
array of a number of UV LEDs.
Three radiation sources 2 are illustrated in the
exemplary embodiment illustrated in the drawing figure.
However, this number is irrelevant to the invention. It
is also possible to provide two radiation sources, or
more than three radiation sources. In addition, these
radiation sources need not necessarily be arranged on
one and the same inner wall of the weathering chamber.
They may also be distributed over different inner
walls. In particular, the invention can also be used
for different types of weathering apparatuses with a
different geometry. The samples to be weathered are
either inserted into suitable depressions on the
baseplate of the weathering chamber or are inserted in
the same way into a holding plate which is arranged
above the baseplate, parallel to it, and is mounted in
a suitable manner in the weathering chamber.
According to the invention, the radiation power of each
of the radiation sources is measured in a predetermined
spectral range. In the illustrated exemplary
embodiment, UV sensors 4 are used for this purpose, in
which case, in principle, one UV sensor 4 is associated
with each radiation source 2. These UV sensors 4 are
preferably, as illustrated, inserted into openings in a
side wall of the weathering chamber 1, in such a way
that they are aligned obliquely upwards with respect to
the respectively associated radiation source 2. They
are preferably designed for a broadband measurement in
the UV range from 300 to 400 nm, in accordance with the
IS Standard. As an alternative to this, however, they
may also be designed in accordance with the NB Standard
for narrowband measurements in the range of 340 nm
(+ 10 nm) or in the already visible region of 420 nm
(± 10 nm) . However, in the latter case, they would no
longer be referred to as UV sensors.
On the output side, the UV sensors 4 are connected to a
corresponding number of inputs of a monitoring device
5, to which they supply the measured values of the UV
radiation power. The monitoring device 5 calculates the
mean value of the radiation powers (as measured by and
supplied from the UV sensors 4) of the radiation
sources 2, that is to say in particular the arithmetic
mean value.

where M is the number of radiation sources 2, In is the
radiation power of the N-th radiation source 2, and N
is the sequential index of the radiation sources 2.
The monitoring device 5 controls the electrical power
to be supplied to the radiation sources 2 on the basis
of the mean value of the radiation powers as calculated
by it. For this purpose, it is connected to the power
supply devices 3 for the radiation sources 2. Each
radiation source 2 has its own associated power supply
device 3, that is to say a voltage or current source.
Each power supply device 3 also has a control input,
and each of the control inputs of the power supply
devices 3 is connected to a corresponding output of the
monitoring device 5.
The control process to be carried out by the monitoring
device 5 may, for example, be carried out in such a way
that a mean value (which is calculated initially by it
during operation of the weathering apparatus) of the
radiation power is stored and is then from then
regarded as the nominal value for the mean radiation
power. The power supply devices 3 are then driven in
such a way that the mean radiation power is always
maintained at this nominal value, so that it is kept
constant for the duration of operation of the
weathering apparatus. If the UV radiation power of one
or more of the radiation sources 2 thus becomes
degraded, the monitoring device 5 thus detects a
decrease in the mean radiation power. In response to
this, the monitoring device 5 transmits control signals
to the power supply devices 3 in such a way that they
uniformly increase the electrical power to be supplied
to their respective radiation sources 2. By way of
example, the monitoring device 5 may be designed such
that it uses the decrease in the mean radiation power
as determined by it to calculate the amount by which
the electrical power supplied by each of the power
supply devices 3 must be increased in order to recreate
the nominal value of the mean radiation power. The
characteristics of the radiation sources 2 may be
stored in the monitoring device 5 for this purpose.
It is also possible to provide for the monitoring
device 5 to check the radiation powers measured by the
UV sensors 4 at regular time intervals, and to use this
to calculate an actual value of the mean radiation
power. If this actual value differs from the nominal
value of the mean radiation power, in particular
differing by more than a noise-dependent threshold
value, the control process is activated, resulting in
the power supply devices 3 increasing or, if
appropriate, also reducing, their emitted electrical
power.
The control process carried out by the monitoring
device 5 may be a simple proportional control process,
in which the electrical power is increased in
proportion to the magnitude of the decrease in the mean
radiation power. However, it is also possible in a
manner known per se to provide a more complex control
process, for example a proportional integral (PI)
control process or a proportional integral differential
(PID) control process in particular in order to avoid
the oscillations which frequently occur in control
processes such as these, in which previously determined
values are also taken into account in the determination
of the control signal to be supplied to the power
supply devices 3, rather than just a currently
determined discrepancy between the nominal value and
actual value of the mean radiation power.
We Claim :
1. Method for non-individual controlling the UV
radiation sources in a weathering apparatus, comprising :
providing a plurality of UV radiation sensors each
arranged for measuring the radiation power of one of the
radiation sources, wherein the number of the UV radiation
sensors is the same as the numeber of the UV radiation
sources;
measuring radiation power of each of the radiation
sources in a predetermined spectral range of the radiation
emitted from the radiation sources, the spectral range
being chosen such that the measured radiation power is
representative of the radiation power in the UV,
calculating an averaged radiation power from the
measured radiation powers by summing the radiation powers
of all radiation sources measured by the respective
radiation sensors and dividing the sum by the number of the
radiation sources, and
controlling the electrical power to be supplied to the
radiation sources in accordance with the averaged radiation
power.
2. Method as claimed in Claim 1, wherein
the electrical power is controlled such that the
averaged radiation power remains constant over time.
3. Method as claimed in Claim 1 or 2, wherein
the control process is carried out in such a way that
the same electrical power, within a predetermined
tolerance bandwidth, is supplied to each of the
radiation sources.
4. Method as claimed in Claim 1 or 2, wherein
an averaged radiation power is calculated from
measured radiation powers at regular time intervals.
5. A device for non-individual controlling the UV
radiation sources in a weathering apparatus, comprising :
sensors (4) for measurement of the radiation powers of
the UV radiation sources (2)in a spectral range of the
radiation emitted from the radiation sources, with the
spectral range being chosen such that the measured UV
radiation power is representative of the radiation power in
the UV,
a monitoring device (5) for calculating an averaged
radiation power from the measured radiation powers, and for
production of control signals for the electrical power to
be supplied to the radiation sources (2) .
6. Device as claimed in Claim 5,wherein
each radiation source (2) is connected to a power
supply device (3), and each power supply device (3)
has a control input which is connected to an output of
the monitoring device (5).
7. Weathering apparatus comprising a weathering chamber
(1), having UV radiation sources (2) and incorporating a
device for non-individual controlling the UV radiation
sources (2), as claimed in claims 5 or 6.
8. Weathering apparatus as claimed in Claim 7, having
a weathering chamber (1) in which the radiation
sources (2) and the sensors (4) are accommodated,
wherein
the radiation sources (2) are arranged along a first
wall of the weathering chamber (1), and the samples to
be weathered are arranged along a second wall, which
is opposite the first wall, and
the UV sensors (4) are fitted to a third inner wall,
which connects the first wall and the second wall, and
in particular are inserted into openings in the third
wall.
Weathering apparatus as claimed in Claim 8, wherein
the samples to be weathered are held by the second
wall or a holding plate.


Control of the UV radiation sources for a weathering
apparatus on the basis of the averaged UV radiation
intensity
The radiation power emitted from the UV radiation sources
(2) in a weathering apparatus is controlled such that the
radiation power of each of the radiation sources (2) is
measured in a predetermined spectral range of the
radiation emitted from the radiation sources, with the
spectral range being chosen such that the measured
radiation power is representative of the radiation power
in the UV, an averaged radiation power is calculated from
the measured radiation powers, and the averaged radiation
power is used for controlling the electrical power to be
supplied to the radiation sources (2) . In particular, the
control process can be carried out in such a way that the
same electrical power, within a predetermined tolerance
bandwidth, is supplied to each of the radiation sources
(2) , and the averaged radiation power is kept constant
over time at a desired nominal value.

Documents:

672-kol-2005-assignment.pdf

672-kol-2005-correspondence 1.1.pdf

672-KOL-2005-CORRESPONDENCE.pdf

672-kol-2005-examination report.pdf

672-kol-2005-form 18.pdf

672-KOL-2005-FORM 27.pdf

672-kol-2005-form 3.pdf

672-kol-2005-form 5.pdf

672-KOL-2005-FORM-27.pdf

672-kol-2005-gpa.pdf

672-kol-2005-granted-abstract.pdf

672-kol-2005-granted-claims.pdf

672-kol-2005-granted-description (complete).pdf

672-kol-2005-granted-drawings.pdf

672-kol-2005-granted-form 1.pdf

672-kol-2005-granted-form 2.pdf

672-kol-2005-granted-specification.pdf

672-kol-2005-priority document.pdf

672-kol-2005-reply to examination report.pdf

672-kol-2005-translated copy of priority document.pdf


Patent Number 243342
Indian Patent Application Number 672/KOL/2005
PG Journal Number 41/2010
Publication Date 08-Oct-2010
Grant Date 06-Oct-2010
Date of Filing 26-Jul-2005
Name of Patentee ATLAS MATERIAL TESTING TECHNOLOGY GMBH
Applicant Address VOGELSBERGSTR. 22, D-63589 LINSENGERICHT-ALTENHASSLAU
Inventors:
# Inventor's Name Inventor's Address
1 SCHONLEIN ARTUR WEISENAUERSTR. 48, D-65428 RUSSELSHEIM
2 RUDOLPH BERND AM ELZEGRABEN 2, D-63755, ALZENAU
3 MARCH PETER SINDLINGER STR. 15/3,D-60326, FRANKFURT AM MAIN
4 BORNER BERNHARD ALTVATERSTR.22, D-63579,FREIGERICHT
PCT International Classification Number H05B 41/29
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10 2004 037 603.4 2004-08-03 Germany