Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS FOR'DETACHING A WEB THREADING TAIL FROM A MOVING
SURFACE
The present invention relates to an apparatus for detaching a
web-threading tail from a moving surface, in which the web-
threading tail is arranged to be cut in.connection with the
moving surface, in such a way that a point part, which is
essentially narrower than that actual threading width of the
web-threading tail, is created and is then arranged to be
spread out to the actual threading width of the web-threading
tail, and in which the apparatus arranged in connection with
the moving surface includes a belt loop permeable by air, which
is arranged to rotate, supported by turnover rolls, in the
direction of travel of the web-threading tail and to move the
detached web-threading tail forward.
Generally carrier rope systems are used for tail threading in
the finishing-section totalities after the dryer section of
paper and board machine, for instance, in connection with the
dryer groups located before and after coating stations, or,
instance, in connection with the calender. Nowadays,. however,
the trend is to not use them, on account of their uncertain
operation and even dangerousness. This has led to the develop-
ment of ropeless apparatuses, in which various kinds of guide
plates combined with air blasts. are used for threading the
tail. Particularly in the dryer section, doctors have also been
used to transfer the web-threading tail from the dryer cylin-
ders to the guide plates. In a doctor, a blade or a blast can
be used. The doctors, guide plates, and blasts can also be
separate.
The doctoring result achieved with an air blast is, however,
generally poor, which leads to breaks in tail threading.
Attempts are often made to improve the doctoring result by
increasing the power of the blast, but then the blast often
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interferes with the movement of the web-threading tail. As
blasts have nearly only a guiding effect, they cannot be used
to tension the web-threading tail. In addition, the nozzles
used to create the blasts are sensitive to changes in condi-
tions and their control is also imprecise. Doctor blades in
contact with the surface of a drying cylinder wear in use and
their construction is complex. In practice, web threading must
be assisted with manually operated blast pipes, or even
manually, which substantially reduces work safety.
Further, apparatuses based on belt loops have also been
developed. In these, the web-threading tail, which has been
guided onto a belt loop is propelled forwards by the rotation
of the belt loop and by a vacuum arranged inside it. One such
apparatus is disclosed in EP publication 1 205 415 A2. Even in
such an apparatus, special means are still required for
detaching the web-threading tail from the moving surface and
guiding it onto the belt loop.
Because the known apparatus solutions have not provided a
satisfactory way of taking hold of the web-threading tail,
attempts. have been made to shape the actual point part. of the
web-threading tail in such a way as to achieve the smoothest
possible catching of the tail and guiding of it forwards.
Publication US-6,379,502 Bl discloses a manner of cutting the
web-threading tail, in which, during the cutting of the tail,
its point part is arranged to be substantially narrower than
the threading width of the rest of the tail. After cutting, the
cutted sharp shape point part of the tail is spread to its
actual threading width, for example, using precisely the web-
threading tail cutting device. This publication discloses a
special moveable doctor device, which is used to detach the
cutted point part of the web-threading tail from the moving
surface and then to guide it onto a closed belt-loop conveyor,
to be carried forward. This makes the apparatus quite complex,
precisely in the case of the special detaching devices.
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However, it is really difficult to take hold, in a
controlled manner, this kind of a widening point part with a
sharp shape, for example, precisely when using known web-
threading devices based on blasts and/or doctoring. It is
well known that the point of the tail, which is sharp or at
least cut to be substantially narrower than the threading
width of the web-threading tail, will continue to travel
adhering tightly on the surface of the roll. Despite the new
kind of shaping of the point of the tail, the known types of
web-threading device described above cannot be used to
achieve satisfactory detaching, taking hold, or sending
forward of the web-threading tail, because the blast effect
directed at the narrow point part must be aimed very
precisely and otherwise too the very narrowness of the point
part of the tail makes it difficult to control with blasts.
The present invention is intended to create a new type of
apparatus for detaching a web-threading tail from a moving
surface, which is smaller and more reliable in operation
than previously and by means of which the drawbacks of the
prior art can be eliminated.
The apparatus according to the invention is simple and small
in size, so that it can be easily placed between structures.
By means of the apparatus, the point part of a web-threading
tail, which is arranged to be substantially narrower than
the conventional threading width of the tail, can be both
dependably detached from a moving surface and moved forward
in a controlled manner to the next web-threading device, or
component totality. In addition, the apparatus's power
requirement is small and its operation is easily controlled.
The apparatus also permits a certain degree of freedom in
locating web-threading devices relative to the cross-
direction of the web.
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In the following, the invention is examined in greater detail
with reference to the accompanying drawings showing some
embodiments of the invention, in which
Figure 1 shows a side view of an end of a dryer sec-
tion equipped with an apparatus according to
the invention,
Figure 2 shows a perspective view of the location of
the apparatus according to the invention at
the end of a dryer section,
Figures 3a, 3b show a schematic example of the formation of
the point part of a web-threading tail,
Figure 4 shows a partial cross-section of the appara-
tus shown in Figures 1 and 2,
Figure 5a shows a schematic drawing of a top view of
the apparatus of Figure, 4,
Figures 5b-5d show partial cross-sections of variations of
the apparatus of Figure 4,
Figure 6 shows a side view of a second embodiment of
the apparatus of Figure 4, and
Figure 7 shows a top view of the embodiment of Figure
6.
Figure 1 shows the point of application of an apparatus 10
according to the invention on a paper machine. Besides paper
machines, the apparatus 10 can also advantageously be used in
board machines. The figure shows a side view of the dryer
section, and particularly the end of it. In this embodiment,
the dryer section is formed of rotating cylindrical pieces
arranged on two levels. These form dryer groups 60, of which
Figure 1 shows the latter half of the last group. In this
single-wire dryer section, the heated drying cylinders 11.1 are
on the upper level and the vacuumed suction rolls 11.2 are on
the lower level.
In such a single-wire dryer section, the paper web. 62 is
CA 02447191 2003-10-28
supported on a single drying wire 13. Lead rolls 12 are
arranged above the dryer section for the drying wire 13 and the
wire 13 is arranged to travel in such a way that, in connection
with the drying cylinders 11.1, the paper web 62 travels
5 between the drying wire 13 and the drying cylinder 11.1, while,
in connection with the suction rolls 11.2, the paper web 62
travels outside the drying wire 13, so that the wire 13 travels
between the suction roll 11.2 and the web 62. In the area
between the drying cylinders 11.1 and the suction rolls 11.2,
the web 62 travels supported on the drying wire 13. Inverted
dryer groups are also possible, in which case the operational
components formed by the dryer group 60 are arranged in an
opposite manner to that shown, as are also twin-wire-draw dryer
sections, in which case there are also drying cylinders in
place of the suction rolls 11.2 and there are guide rolls for
both the upper and the lower wire, in the pockets formed by the
cylinders (not shown).
Before the end of the dryer section, in this application
example for instance, three drying cylinders 11.1 before the
end, there is, in the pocket formed by the cylinder 11.1 and
rolls 11.2, a water-cutting device according to the prior art,
such as a double water cutter 61, the basic technique of which
is referred to in publication WO-98/33974. Other types of
apparatus based on liquid cutting can also be used, there being
also no restrictions on their positioning in a dryer section.
At the end of the dryer section, after the final drying
cylinder 11.1, there is a web-threading device 10 according to
the invention, which will be examined in greater detail later..
Figure 2 shows a schematic perspective view of the end of the
dryer section shown in Figure 1. Using the water cutting device
61 shown in Figure 1, it is possible to cut the web-threading
tail in. the machine direction, i.e. not only to form a web-
threading tail 16, but also to cut it in the transverse
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direction of the web 62. In cutting transversely, a point part
16', which is substantially narrower than the conventional
width of a web-threading tail 16, is cut in the web-threading
tail 16. The point part 16' can be preferably have a sharp
shape, which reach on a slant the uniform threading width of
the web-threading tail 16, as shown in Figure 2.
Figure 2 shows the situation immediately after the web-thread-
ing tail 16 has been detached from the drying cylinder 11.1.
For reasons of simplicity, the drying wire is not shown at all
in the figure. The actual detaching from the moving surface,
which is in no way restricted by this example of a drying
cylinder, but can be understood very broadly, takes place using
a vacuum, which is formed inside the drum 18 of the device 10.
The blasts used in the prior art to detach the web-threading
tail 16 are then unnecessary. Generally, the apparatus 10 also
includes means 22, arranged after the drum 18 in the direction
of travel of the web-threading tail 16, for guiding the web-
threading tail 16 detached from the drying cylinder 11.1, and
transferring it to the next web-threading point (not shown).
The rest of the web 62 continues to travel on the surface of
the cylinder 11.1, until it is detached from the cylinder 11.1
by a doctor 63 and led to broke processing or similar.
Figures 3a and 3b show an example of one way of cutting the
point part 16' of the web-threading tail 16 and, in this
connection, also of cutting it off completely. In both figures,
.an arrow shows the, direction of travel of the moving web 62.
The nozzles 61.1, 61.2 of the water cutting device 61 are
initially run on essentially the same machine-direction line,
as shown in Figure 3a. After this, the second nozzle 61.2 is
begun to be moved, in a manner that is as such known, in the
cross-direction of the machine, so that, after its movement,
the width of the web-threading tail 16 cut by the nozzles 61.1,
61.2 corresponds to the width.of the web-threading tail 16,
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which is, as such, conventional, being, for example, 300 - 500 mm
(Figure 3b) . The movement of the second nozzle 62.2 is shown in
Figure 3a by the arrow attached to it.
The nozzle 61.2 is preferably moved as rapidly as possible,
because already at the web-threading stage, the web 62 too is
running at nearly the production speed of the machine. The shape
of the point part 16' of the web-threading tail 16 that is thus
created is sharp and short, allowing the web-threading tail 16 to
reach its standard width as soon as possible and preventing
narrowly shaped point part area 16' from causing, for example,
control problems. It should be noted, that cutting can be
performed, and thus the point part 16' also shaped using
different kinds of movements of the nozzles 61.1, 61.2, and that
the manner described above is in no way restrictive. As a second
application example, the nozzles 61.1, 61.2 can first of all be
moved in such a way that, starting from the cutting width of the
web-threading tail 16, they first of all approach each other,
without, however, touching and then immediately separate back to
the cutting width of the web-threading tail (not shown). Further,
as a third application example, the nozzles 61.1, 61.2 are moved
in such a way that they now touch each other and move crosswise
relative to each other, thus changing places relative to the
initial situation.
As is known, the web-threading tail 16 moving between the drying
cylinder 11.1 and the wire 13 tends to adhere to the surface of
the hot drying cylinder 11.1, after the opening gap 14 (Figure
1). Thus, the web-threading tail 16 must first of all be detached
from the surface of the drying cylinder 11.1 and then guided
forward to its next location. According to the invention, after
the opening gap 14, a vacuum is used to detach the web-threading
tail 16 from the surface of the drying cylinder 11.1.
Figure 4 shows a first embodiment of the apparatus 10 according
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to the invention in greater detail as a partial cross-section.
The apparatus 10 includes a belt loop 28 permeable by air as the
guide means 22 for the detached web-threading tail 16. The belt
loop 28 is arranged to rotate, supported on turnover rolls 29 and
30, in the direction of travel of the web-threading tail 16.
Thus, the web-threading tail 16 cut narrower from a point part
16' can be guided over a sufficiently long distance and more
precisely than in the prior art. An essential feature of the
apparatus 10 according to the invention is that the first 29 of
the turnover rolls is the said vacuum drum 18.
A vacuum box 24 is fitted inside the drum 18, and generally
covers 20 - 70 preferably 30 - 60 % of the inner circumference
of the drum. In Figure 4, the vacuum box 24 covers about one half
of the inner circumference of the drum 18. For this distance, the
web threading tail 16 is arranged to travel on the surface of the
drum 18. The jacket 19 of the drum 18 is in cross section, so
that the holes 23 are clearly visible.
The drum 18 is thus arranged after the opening gap 14 and
separately from the surface of the drying cylinder 11.1, so that
it does not wear and it has no effect on the drying cylinder
11.1. Generally, the gap is 2 - 10 mm, preferably 3 - 6 mm. This
gives greater freedom and tolerances than previously in
positioning the drum 18. The web-threading tail 16, with a
narrower cutted point part 16' is thus detached using the
rotating drum 18, in connection with which a vacuum is arranged.
The smallness of the gap means that only a small vacuum is
required. The detaching of the web-threading tail 16 from the
drying cylinder 11.1 can, however, be ensured by using a greater
vacuum, without, however, disturbing the movement of the web-
threading tail 16.
The use of a vacuum avoids blasts that interfere with the
movement of the web-threading tail 16. In addition, the vacuum
can be easily regulated while the rotating drum 18 also guides
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the web-threading tail 16. The drum 18 can also be dimensioned
to be advantageously small, so that it is simple to place it in
different positions in the gap. In addition, the drum 18 is
unaffected by variations in conditions.
The apparatus 10 is used specifically to thread and guide the
web-threading tail. During the normal operation of the dryer
section, the apparatus 10 according to the invention can be
turned to the rest position. For this purpose, the apparatus 10
is. supported rotatably on an articulated arm in the structure
of the dryer section (not shown). By suitable dimensioning, the
apparatus 10 can be made to move simply a sufficient distance
from the drying cylinder 11.1 and the web 62., In addition, the
apparatus 10 can be easily and rapidly turned from the rest
position to the operating position and back again. In practice,
the drum 18 can be turned to a distance of up to 100 mm from
the drying cylinder 11.1. Correspondingly, the distance from
the web 62 is at least 40 mm.
Thus, the web-threading tail 16 is detached from the moving
surface of the drying cylinder 11.2 and at the same time moved
by means of the belt loop 28 towards the next webrthreading
point. Further, at least one foil list 31 is arranged between
the turnover rolls 29 and 30, inside the belt loop 28, in order
to create a vacuum 'effect on the surface of the belt loop 28.
The web-threading tail 16 will then remain firmly on top of the
belt loop 28, making the operation of the apparatus 28 particu-
larly reliable.
The vacuum is thus created in the area of the. belt loop 28,
mainly with the aid of two foil strips 31. Generally there are
1 - 3 foil strips, preferably only one. In addition, the
distance between the turnover rolls 29 and 30 is, in practice,
200 - 600 mm, preferably 300 - 500 mm. Thus, the apparatus 10
according to the invention becomes especially short, compared
to known belt applications. In addition, thanks to the suction
CA 02447191 2003-10-28
turnover roll 29, little additional vacuum effect is required,
so that fewer foil strips 31 than before are needed. Corre-
spondingly, the apparatus 10 can be made sufficiently wide.
5-According to one embodiment of the invention, the suction
inside the belt loop 28 is created with the aid of a foil
effect, without actual devices creating suction. The foil
effect arises, when the point. of a foil strip 31 is in contact
with, or nearly in contact with the moving surface of the belt
10 28. The air from the intake side of the foil strip'31 is then
directed downwards guided by the leading edge of the foil strip
31 and a. vacuum is created at the downstream.edge of the foil
strip 31. The foil effect can be boosted using Coanda blasts,
which are usually optional and adjustable. Instead of, or in
addition to the foil effect, other ways of creating a vacuum
can naturally also be used.
The web-threading tail 16 can also be tensioned using the
apparatus according to the invention. Tension is' achieved by
rotating the belt 28 at a higher speed than the web 62. It is
then possible to use a small difference in speed, as the web-
threading tail 16 adheres to the belt 28. By using a .suitable
difference in speed, the web-threading tail 16 can be kept
tight, thus ens,a.ring the success of the web threading. In
practice, a speec 2 - 5 % higher than that of the web is used.
The vacuum effect will keep the web-threading tail 16 firmly on
the belt 28. The upper surface of the belt 28 may be roughened,
which will improve the ability of the apparatus to detach the
web-threading tail 16 from the drying cylinder 11.1.
In the disclosed apparatuses, the diameter of only the drum is
about 300 mm. In belt applications, the turnover. roll 29 is
considerably smaller. A belt application can even be narrower
than the web-threading tail 16, thanks to the covering suction
effect. A belt application can be dimensioned case-specifi-
cally.
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Figure 5a shows a schematic drawing of one belt application of
the apparatus 10 according to the invention. A belt loop 28,
which moves in the direction shown by the arrow, is supported
on turnover rolls 29 and 30. The web-threading tail 16, which
is now cut in such a way that the transverse transfer speed of
the second nozzle 61.2 increases when it approaches the point
corresponding to the standard width of the web-threading tail
16, is guided on top of the belt loop 28. Correspondingly,
Figures 5b - 5d show a surprising solution, by means of which
the belt loop 28 is made to remain firmly held on top of the
turnover rolls 29, 30. According to the invention, at least one
longitudinal guide element 35 is arranged in the belt loop 28,
a corresponding space 36 being arranged in connection with the
turnover rolls 29 and 30, in order to hold the belt loop 28 on
the turnover rolls 29 and 30. In practice, the guide element
can be a.protrusion 37 attached to the belt loop 28, or a fold
38 in the belt loop 28. The protrusion 37 can, for example,
easily be glued to the belt loop 28, which in practice is
usually a short and narrow wire.
The fold shown in Figure 5d can formed simply by weaving a
suitable crease into the wire 28. Figure 5b shows two different
applications at the opposite ends of the drum. The crease can
also be at the edges of the wire, in which case the machining
in the jacket 19 of the drum 18 will be unnecessary. Corre-
spondingly, the space 36 can be a corresponding recess 39
arranged in the jacket of the turnover rolls 29 and 30. In the
ways shown, the belt loop will remain in place without being
tensioned and despite the loosening caused by heat. In addi-
tion, it will be unnecessary to camber the turnover rolls 29,
30.
Figures 6 and 7 .show a second embodiment of the apparatus
according to the invention. In this case, the belt loop 28 is
550-mm wide and it is described with a dashed line. In this
case too, two turnover rolls 29 and 30 are used, supported by
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which the belt loop 28, rotates. According to the aforemen-
tioned, a suction effect is arranged in connection with the
first turnover roll 29. Grooves 40 that essentially cover the
entire circumference of the drum are used in place of a
perforated jacket. Longitudinally arranged grooves 40 cover
substantially the entire circumference of the turnover roll 29,
the total surface area of the grooves 40 being 10 - 30 %,
preferably 15 - 25 % of the surface area of the turnover roll
29. In addition to this, a chamber 41, in which a vacuum is
arranged, is arranged inside the belt loop 28. The vacuum of
the chamber 41 extends through the grooves 40 to the belt loop
28, thus creating the force required to detach the web-thread-
ing tail 16. The, chamber 41 is bounded by a foil strip 31 and
by a blast plate 42 extending from it. The chamber 41 is also
bounded by a base plate 43 and by the feed pipe 44 of the blast
plate 42. This prevents the unnecessary spread of the vacuum
and disturbances in the operation of the foil strip .31. Air
discharging from the blast plate 42 exhausts from the side of
the apparatus 10 before the second turnover roll 30 and partly
through the belt loop 28. The use of the solution in question
achieves an extremely compact construction, which is, in
addition, powerful and operationally reliable.
The construction of the apparatus 10 is new in other ways too.
The vacuum is preferably created using compressed air, making
separate fans unnecessary. In the embodiment shown, a venturi
pipe 45 is used, with a ring nozzle 46 attached to it. The
compressed air blown from the small hole of the ring nozzle 46
creates a flow in the ' venturi pipe 45 and thus a sufficient
vacuum in the apparatus. The venturi pipe 45 is also connected
to an intermediate pipe 47, which is correspondingly connected
to the chamber 41 by a angle pipe 48. In addition, a drum motor
49 creates the force required to rotate the belt loop 28. In
other words, the motor 49 is inside the second turnover toll
30. In addition, the motor 49 is fitted to the side at the
attachment, point, so that the centre of gravity of the appara-
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tus is close to the attachment point. Further, the motor 49 is
connected to the intermediate pipe 47, so that the flow removes
the heated air from the motor 49.
Compressed air is also used in connection with the blast plate
42. For this purpose there is a transverse feed pipe 44 and
compensating pipes 50, which terminates in the actual blast
pipe 51 connected to it. In the blast pipe 51, the compressed
air is distributed evenly over the width of the belt loop 28
and then discharges through the holes in the blast pipe 51,
creating the aforesaid Coanda blast (not shown). The foil strip
31 and the Coanda blast create a powerful vacuum soon after the
first turnover roll 29. Closer to the second turnover roll 30,
the vacuum effect diminishes, allowing the web-threading tail
16 to detach naturally from the surface of the belt loop 28.
The detaching can be ensured by means of an air doctor 52,
arranged in connection with the second turnover roll 30 (Figure
7). Figure 6 shows only the direction of the blasts of the air
doctor. The first blast detaches the web-threading tail 16 from
the surface of the belt loop 28 while the second guides it
forward.
In addition to what is described above, the apparatus according
to the invention can also be used elsewhere in a paper machine.
One example is coating stations and the dryer groups arranged
in connection with them. Further, several applications for the
apparatus according to 'the invention can be found in the
calender.
Using the apparatus according to the invention will ensure the
detaching, from a 'moving surface, of a web-threading tail 16,
cut to an substantially narrower point part 16', and its
transfer to the next web-threading point. The use of a vacuum
avoids air blasts and the difficulty of directing them. The
vacuum required is also advantageously low, being well under
0,1 bar.
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The apparatus according to the invention is versatile and
easily adaptable. Using the apparatus 10, the web-threading
tail 16 can be detached reliably even at high speeds and with
different paper grades. In addition, it can be installed in
different positions. Retrofitting is also easy. The elements
can be rotated in a manner suitable at each time. Generally,
electric or pneumatic motors are used, which are preferably
arranged connected to, or even inside a turnover roll. Espe-
cially the exhaust air from 'a pneumatic motor can be. used to
form the vacuum inside the drum. Particularly in a drum
application, the upper limit of the speed of rotation is very
high, allowing a pneumatic motor to be used to rotate the drum
at a clear overspeed, relative to the surface.
It must be understood that the above description and the
related figures are only intended to illustrate the apparatus
according to the present invention. The invention is therefore
in no way intended to be restricted to the embodiment disclosed
above or defined in the Claims, instead many different varia-
tions and adaptations of the invention, which are possible
within the scope of the inventive idea defined in the accompa-
nying Claims, will be obvious to one versed in the art.
