Note: Descriptions are shown in the official language in which they were submitted.
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November 15, 2006
Texmag GmbH Vertriebsgesellschaft GmbH E 106563 CA Pts/Sjm/bar
Method and system for position control of webs and corrugated board with a
natural edge
Field of the Invention
The invention relates to a method and system for position control of one or
more
webs, especially of paper-like or board-like webs, which are preferably used
for
the manufacture of corrugated board and corrugated board which has a natural
edge.
Background
The principle construction of prior art installations for manufacturing
corrugated
board is shown in Fig. 1. Such an installation comprises one or more single-
face
groups, each of which joins together a flat and a corrugated web. Webs which
are
joined in such a way are called single-face webs. In the combination and
lamina-
tion, the single-face webs and a cover web are joined together and laminated
to a
single web. After lamination, the web passes through the heat and pull area.
Here,
the web is dried by introducing heat. In the final processing, the web of
corrugated
board is trimmed at the edges and is, depending on the needs, further cut into
de-
sired formats and is transported into a store.
Manufacturing with known installations causes that the used material is not ex-
ploited in an optimal way because of inaccuracies of the manufacturing
process.
Summary of the invention
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Accordingly, the present invention has the object to improve the manufacturing
accuracy.
According to the invention, this object is achieved by a method, a system and
a
corrugated board according to the independent claims of the invention. Advanta-
geous embodiments are described in the dependent claims.
According to the invention, a method for position control of one or more webs
is
provided, especially for paper-like or board-like webs. Here, the term web
relates
especially to paper or board webs, bit it can also relate among others to
fabric
webs, webs of plastic and webs of metal. A web can consist of one or more
layers
of one or of different materials. The method and the system of the invention
can
especially be adapted to such types of webs, which are used in the
manufacturing
of corrugated board. In this context, the term single-face web describes a
web,
which consists of two material layers, wherein one is flat and the other one
is cor-
rugated.
According to one aspect, the invention deals with optimizing the control of
webs.
Both for manufacturing a single-face web and for combining several single-face
webs with a cover web, the most optimal position control is desirable. The
better
the positioning is when joining the webs together, especially relative to each
other, the less scrap will be produced. For this purpose, the invention
detects first
position information for one or more webs downstream of one or more position
manipulation apparatuses by first position detection means. Then, a control of
the
web position(s) is conducted by the position manipulation apparatus, using the
first position information detected downstream.
Preferably, the position of one web is taken as a reference parameter for the
con-
trol of the other webs, and a predetermined parameter gives the desired
relative
position of the other webs relative to the one web, respectively. The center
of the
web and/or one or both edges of the web can serve to determine the position of
the
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web. In many installations, the center of the web serves to determine the
position
of the web, and the web position is aligned relatively to the center of the ma-
chines.
Furthermore, second position information for one or more webs can be detected
in
the region of the position manipulation apparatuses by second position
detection
means. This enables an even more accurate position control, because
information
is available for the location, where the control is acting, and for the
location,
which is to be manipulated by the control. Thus, the dynamics of the web can
be
taken into account for its position control.
Moreover, the second position information, especially its changes, can be used
for
controlling the position manipulation apparatuses of one or more of the other
webs, especially to reduce the position displacement of the webs with respect
to
each other. This allows that not only one web is controlled to a desired
position
without taking the other webs into account, but that the webs are aligned to
each
other. This results in a number of advantages. This way, e.g. for one web,
namely
the reference web, the data acquired downstream does not need to be taken into
account, a cheaper, even though most likely somehow more inaccurate control of
the reference web can be realized. Furthermore, e.g. for lamination of several
webs, the position of the webs relative to each other is of outstanding
importance.
In case that all webs are laminated in such a way that they are flush with
each
other on one side, this side does not need to be cut or trimmed later on, and
mate-
rial can be spared. Such a production, which can for the first time be
implemented
by the present invention, is called natural edge. For production, a manageable
po-
sition fluctuation of all webs can be tolerated, as long as the webs do not
fluctuate
with respect to each other. In absence of a noteworthy relative fluctuation,
it can
be processed further with natural edge. Preferably, the second position
informa-
tion relates to the cover web, to which the positions of the one or more other
webs
are controlled.
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The control can take the web speed and the distance into account, which the
web
to be controlled has to cover between the position manipulation apparatus and
the
position detection means. Thus, the dead time can be considered for the
control,
whereby the control can substantially be improved in its accuracy.
The detection of the first position information by first position detection
means
can be conducted in the region of the lamination, but after a bridge, and
especially
in the region of the pre-heater or the glue unit, or directly in front of the
lamina-
tion. Namely, the position detection is conducted behind the bridge, on which
the
position manipulation means are arranged. Position information is detected
only
for one or more webs, depending on the needs. The same holds for the control
of
the one or more position manipulation apparatuses. A web can either or alterna-
tively be controlled by the information extracted downstream about itself or
the
information extracted from one or more other webs.
Alternatively, the detection can be conducted for the first position
information by
first position detection means in the region of the pre-heater, and the
detection can
be conducted for the third position information by third position detection
means
in the region of the glue unit. Hereby, information is available about at
least two
positions of one or more webs, so that the dynamics of the system can better
be
taken into account. Accordingly, the first position information as well as the
third
position information can be used for controlling the position manipulation
appara-
tuses.
The position manipulation apparatuses are arranged upstream of the region of
the
pre-heater, particularly they are arranged on the bridge.
Alternatively or additionally, the first position detection means are arranged
in the
region of the combination of two material layers, particularly in the region
of a
corrugated roller. The one or more position manipulation means are then
prefera-
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bly arranged upstream of a material layer heater and/or a material layer
humidi-
fier.
By controlling a material layer depending on the first position information,
the
position of both material layers with respect to each other can be optimized,
par-
ticularly that they are centered on top of each other or that the edges of one
side
are on top of each other. This is in turn of importance for working with the
natural
edge.
Preferably, the control of the web positions controls the position
manipulation
apparatuses such that the web positions are flush with each other on one side,
par-
ticularly so that this side does not need to be trimmed anymore.
Optical sensors, cameras, CCD cameras, ultrasonic devices or piezoelectric ele-
ments working with ultrasound can be used for the position detection means.
Par-
ticularly, the invention is used for installations for corrugated board
production,
e.g. for corrugated board installations with one to five single-face groups.
According to a second aspect of the invention, the web width of at least one
web
is measured at a plurality of positions in the course of the corrugated board
manu-
facturing. Depending on the respective measurement arrangement for measuring
the web width, a position detection means or a separate width measurement appa-
ratus can be used. Alternatively or additionally to measuring the width, the
mois-
ture of the web can be measured. The acquired information concerning width and
moisture serves e.g. to determine a shrink factor, i.e. the relationship
between one
width and another, for a certain manufacturing segment or for the whole
process.
This information can be used for controlling the humidification to achieve a
better
process stability. Furthermore, the acquired shrink factors can serve for
judging
the quality of the used raw materials.
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A first web width and/or a first web moisture is preferably measured after un-
winding of a supply roller. At this point, the material still has its original
width
and moisture, it has not yet been humidified or joined with another web. There-
fore, the value determined here is used as a reference value for determining
an
overall shrink factor. Since it can be measured at such a position for each
supply
roller, it is advantageous to use the average value of the widths and
moistures
measured this way.
Furthermore, after producing a single-face corrugated board, a second web
width
and/or a second web moisture can be measured, and particularly the first web
widths and the second web widths can be used to judge the accuracy of the
join.
Additionally, before of lamination and/or directly after lamination in front
of the
heat and pull area and/or in front of the first trimming of the web, a web
width
and/or web moisture can be measured. Such attained sector-wise factors can be
used for controlling the respective single processes, such as humidification,
drying
or heating. Measurements in front of the first trimming in combination with
measurements after unwinding can be used to calculate factors for the whole
process, e.g. the shrink factor of the whole installation.
Moreover, the web widths in front of lamination and the web width in front of
the
first trimming of the web are used to judge the accuracy of the combination
and/or
the overlap.
A further aspect of the invention relates to a combination and lamination of a
cor-
rugated board installation, which comprises a system according to the
invention as
described above. The installation for producing corrugated board can
additionally
comprise one or more single-face groups and/or a heat and pull area and/or a
final
processing.
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The principles of the present invention can not only be used for position
control,
but they can be used for web tension control in an analogous way. All aspects
which are disclosed for position control in this description or in the claims
can be
transferred and used for web tension control.
For web tension control the position detection means are replaced,
particularly by
tension sensing rollers, or adapted so that they are able to detect a web
tension.
The position manipulation apparatuses are replaced or adapted so that they are
able to manipulate a web tension.
Both for manufacturing a single-face web and for combining several single-face
webs with a cover web, the most optimal web tension control is desirable. For
this
purpose, the invention detects first web tension information for one or more
webs
downstream of one or more web tension manipulation apparatuses by first web
tension detection means. Then, a control of the web tension(s) is conducted by
the
web tension manipulation apparatus, using the first web tension information de-
tected downstream.
Short description of the drawings
Further aspects and advantages of the present invention will become clear from
the detailed description of the attached drawings.
Fig. 1 is a schematic overview of an installation for producing corrugated
board.
Fig. 2 is a schematic view of a single-face group of an installation for
producing
corrugated board according to the present invention;
Fig. 3 is a schematic view of a combination, lamination and a heat and pull
area
according to the present invention; and
Fig. 4 is a schematic view of a final processing according to the present
inven-
tion.
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Detailed description
Figure 2 is a schematic view of a single-face group. There can be one or more
of
such single-face groups in an installation for producing corrugated board.
In terms of their function and their principle construction, they are all the
alike.
The paper or paper-like raw material is on a supply roller 1. The supply
rollers 1
are always arranged in pairs, wherein the material is unwound from one roller,
whereas the other roller is kept ready for replacement. If the material of one
roller
is exhausted, it will be spliced at position 2 to the other roller, so that
the material
supply does not break away. From here, the paper is passed to a first material
storage 3. Paper is stored here to compensate for the delay of paper supply,
when
splicing from one roll to another. To regulate the storage content of storage
3, the
pulleys on the right and left side of the storage can be moved towards each
other
or separated from each other.
From the first storage 3, the paper is guided to a position manipulation
apparatus 4
and passes on it's way a width and/or moisture detection means 10. The width
and/or moisture detection means 10 detects the values of the paper web in its
original state. Behind the position manipulation means 4, the paper is guided
via
rollers, where it is heated particularly with rollers, which are supplied with
hot
steam from the inside. Additionally, the paper is humidified on its way to
improve
its ductility and to facilitate a joining of two paper layers later on.
The web coming from one side is then guided over a corrugated roller 5, where
it
is forced into a corrugated form. A glue apparatus 6 applies glue to this web.
From the other side comes a second web, which is then glued together with the
corrugated web with a single-face web. In the region of gluing both webs to-
gether, a position detection means 7 as well as a width and/or moisture
detection
means 11 is arranged. The position detection means 7 detects the position of
both
webs and/or their relative position to each other. This information can be
used in
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different ways for controlling the position manipulation apparatuses 4. It
can, for
example, be used to control one or both webs to an accurate position at the
com-
bination or to control one web such that it is accurately aligned to the other
web.
Preferably, one web is controlled to a predetermined position, wherein the
other
web is aligned with respect to the first web. For working with the natural
edge, i.e.
one side does not need to be cut or trimmed, the webs are controlled such that
the
edges of both webs lie accurately on top of each other on one side.
For moisture control, the width and/or moisture detection means 11 is arranged
in
the region of the corrugated roller 5. Thereby, the humidification of the
respective
webs can be controlled, so that there are constant and controlled conditions
for
lamination.
The produced single-face web is transported onto the bridge 8. Here, a second
storage, the so-called bridge storage 9, is arranged. It serves as a provision
for the
further processing. Normally, the production of the single-face web is slowed
down when splicing from one supply roller 1 to another supply roller to allow
for
a save and therefore slower splicing. For this time interval, the bridge
storage 9
serves as a provision to allow that the manufacturing process can continue
with a
speed of about 100 to 400 meters per minute. After having changed to a new sup-
ply roller 1, the production speed of the single-face web is raised to a value
above
average in order to refill the bridge storage 9.
A position detection means and/or a width and/or moisture detection means 12
is
arranged at the end of the bridge storage 9. Further data for process control
and
optimization is attained here. Particularly, information about the bridge
storage
can be attained here at the same time.
Figure 3 shows a schematic view of a combination, a lamination and a heat and
pull area. The one or more single-face webs are guided hither. The position ma-
nipulation apparatuses 15, 16 control a position of the single face webs as
well as
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the needed web tensions. From a cover layer supply roller 13, the cover layer
is
guided via a storage to position manipulation apparatus 14. A width and/or
mois-
ture detection means can in turn be arranged in front of the position
manipulating
apparatus 14 in order to also detect the width of the cover web or its
moisture.
Behind the position manipulation apparatuses 14, 15, 16, the webs are guided
via
a pre-heater 17 and a glue unit 19 to the lamination 21, where the webs are
joined
together. Here, a positioning of the webs with respect to each other as
accurate as
possible is desirable. Only if the webs are glued together being flush on one
side,
it can be operated with the natural edge. Alternatively, all webs can be
aligned
centered to each other. However, it is decisive that the position of the webs
at the
point of lamination is of highest importance, whereby the last position
manipula-
tion apparatuses 14, 15, 16 are even placed in front of the pre-heater 17.
Those
cannot be placed closer to the lamination because of constructional reasons.
Thus,
the last position control possibility is quite a bit away from the lamination
21. For
this reason, the invention provides position detection means 18, 20, by which
in-
formation concerning the web positions can be attained at places, which are
sub-
stantially closer to the decisive lamination. Only single position detection
means
18, 20 can be assembled depending on the needs. For example, it can only be
measured after the glue unit 19, and also not all webs need to be measured.
The
information attained by the position detection means 18, 20 are used for
control-
ling the position manipulation apparatuses 14, 15, 16.
Here, again different types of information usage are possible. Each web can be
viewed separately and controlled to a certain position, whereby the deviation
from
this value, which is measured by the position detection means 18, 20 is used
as a
reference value for controlling the position manipulation apparatuses 14, 15,
16.
Alternatively, a web, particularly the cover web, can serve as a reference.
Then,
the positions of the other webs are controlled with respect to this one.
Addition-
ally, the information attained for the reference web can be used to control
the
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other webs for tracking them or to compensate for the dynamics of the
reference
web.
Taking the dynamics into account is particularly possible, when measuring in
the
region of the pre-heater 17 and in the region of the glue unit 19 at the same
time.
Furthermore, the position manipulation apparatuses 4, 14, 15, 16 themselves
can
be equipped with position detection means.
When using the information attained from the position detection apparatuses
18,
20, the distance, which has to be covered by the web between the position ma-
nipulation apparatuses 4, 14, 15, 16 and the measurement location as well as
the
web speed are taken into account. Additionally to the dead time, attenuations
can
be set.
Width and/or moisture detection means can be used additionally or
alternatively
to the position detection apparatuses 18, 20. Thereby, the desired moisture of
the
webs at the lamination 21 can be guaranteed. Additionally, all widths can be
measured in front of the lamination 21.
After the lamination 21, the web is dried within the heat and pull area.
Circulating
strips pull the web through this area, whereby the web is guided next to
heating
elements. The board is dehumidified and dried by introducing heat.
Figure 4 is a schematic view of a final processing. After the heat and pull
area 22,
another width and/or moisture detection means 23 is arranged. The measured
moisture serves to control the amount of heat to be introduced within the heat
and
pull area 22. The width measured is used together with the width value
measured
after unwinding to calculate a shrink factor of the whole manufacturing
process. It
gives a picture of the quality of the used raw materials. Additionally, the
value
measured here can be used to judge the positioning at the lamination 21 and to
improve it if needed. That way, the board web should not be much broader at
the
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measurement position after the heat and pull area 22 than the single webs in
front
of the lamination 21. Furthermore, the shrink factor of the heat and pull area
22
can be attained.
The web is forwarded to the first trimming 24. Usually, the edges of the web
are
cut or trimmed here. The invention makes operation with the natural edge possi-
ble. In this case, the corrugated board needs only to be trimmed on one side.
However, the inventive system does not need to be operated with the natural
edge.
In the further course, the web is cut in two desired dimensions in
longitudinal and
transversal directions, and it is transported into a storage, which is
schematically
shown on the right side of Fig. 4.
