Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DEVICE FOR TRANSFERRING A WEB-LIKE MATERIAL IN A FIBER WEB
MACHINE AND A FIBER WEB MACHINE
The invention relates to a device for transferring a web-like
material in a fiber web machine, which device includes:
- an air connection,
- openings arranged on a wall defining the air connection
for forming air blows that are parallel to the travel
direction of the web-like material, and
- a transfer surface for creating a vacuum effect with air
blows and thereby transferring the web-like material.
The invention also relates to a fiber web machine.
In a fiber web machine, various devices based on air blows are
used for transferring and guiding a web-like material. The
web-like material can be a full-width web or a narrow tail cut
from the web. At its simplest, the device is a pipe constitut-
ing an air connection with openings arranged on its wall for
forming air blows. So called blow plates also exist, the opera-
tion of which is also based on air blows.
Blow pipes alone are mainly used only for guiding the web-like
material approximately. Instead, a blow plate is provided with
a transfer surface on which a vacuum effect is created by air
blows by means of a so called Coanda effect. In other words,
the web-like material tends to follow the transfer surface
while the air blows parallel to the travel direction of the
web-like material simultaneously transfer the material forward.
In a known blow plate, openings open up to a shoulder which is
arranged between an air connection and a blow plate. In addi-
tion, air blows are oriented substantially parallel to the blow
plate. In operation, air blows create a vacuum effect but, at
the same time, significant friction is generated as the
web-like material passes the shoulder. Then a major part of the
transfer force of air blows is lost.
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In FI patent No. 78528, the blow plate is additionally combined
with a cut-off blow which first cuts the tail and thereafter
the tail is moved forward with the blow plate. Initially, this
system also involves the friction problem mentioned above.
An object of the invention is to provide a novel device in a
fiber web machine for transferring a web-like material, the
device providing a higher transfer efficiency than before with
a lower air volume and/or pressure level compared to hereto-
fore. Another object of the invention is to provide a novel
fiber web machine in which transferring a web-like material is
smoother and more reliable compared to heretofore. The charac-
teristic features of the device and fiber web machine according
to this invention are that openings are formed on a transfer
surface and the angle a between the blow direction of the
openings and the transfer surface is 15 - 300. As the openings
open up to a transfer surface instead of a shoulder, the fric-
tion phenomenon that has caused problems earlier is avoided.
Now the transfer surface remains smooth whereby, firstly, a
vacuum effect more uniform than before is created. Secondly,
due to the absence of a linear friction point, an air blow
transfers a web-like material forward faster than heretofore.
In operation, a forwarding force greater than before is achiev-
ed with the present air volume. On the other hand, the present
force can be achieved with an air volume smaller than before or
at a pressure level lower than before.
The invention is described below in detail by making reference
to the enclosed drawings which illustrate some of the embodi-
ments of the invention, in which
Figure la is a lateral view of a part of a fiber web ma-
chine position at which a device for transfer-
ring a web-like material is used,
Figure lb is a cross-sectional lateral view of a device
according to prior art,
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Figure 2a is a cross-sectional axonometric view of a first
embodiment of the device according to the inven-
tion,
Figure 2b shows a second embodiment of the device accord-
ing to the invention as in Figure 2a,
Figure 3a is a cross-sectional view of a third embodiment
of the invention,
Figure 3b is a cross-sectional view of a fourth embodiment
of the invention,
Figure 4 is a lateral view of a fifth embodiment of the
device according to the invention,
Figure 5 is a top view of the device of Figure 4 with the
main components disassembled,
Figure 6a is a cross-sectional axonometric view of a sixth
embodiment of the device according to the inven-
tion,
Figure 6b is a cross-sectional axonometric view of a
seventh embodiment of the device according to
the invention.
Figure la shows the press section of a fiber web machine in a
lateral view. Fiber web machines include paper and board
machines, for example. At present, the tendency is to use a
closed transfer in the press section in which case, in addition
to the web, the tail cut therefrom is supported substantially
through the entire press section. However, in the application
example, the closed transfer breaks at the center roll 10 from
which the tail is run down to the broke treatment. When contin-
uing tail threading from this point, the tail must be first cut
and guided to the following tail threading device. In the
position shown, the tail is guided to the nip formed by a press
fabric 11 and a guide roll 12. In addition to this position,
the device according to the invention can be located in connec-
tion with the top roll 13 of a separate press, for example. In
Figure la, the positions of the device are represented by a
circled cross. The positions of the equipment can vary in
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different press sections. The device can be used in other
positions of a fiber web machine as well, such as in the dryer
section. In addition to the tail, the device can be used for
transferring a full-width web for tensioning the web, for
example, while running it down to the pulper.
A fiber web machine thus includes one of more devices for
transferring a web-like material. Based on the above, the
web-like material can be a tail or a full-width web or some-
thing between these. Figure lb shows a device according to
prior art wherein the device includes an air connection 14 and
openings 16 arranged on a wall 15 defining the air connection
for forming air blows that are parallel to the travel direction
of the web-like material. In addition, the device includes a
transfer surface 17 for creating a vacuum effect with air blows
and thereby transferring the web-like material. Air blows
together with the transfer surface create a vacuum effect
whereby the web-like material tends to follow the transfer
surface. At the same time, the air blows push the web-like
material forward.
Figures 2a - 3b show various embodiments of the device accord-
ing to the invention. According to the invention, openings 16
are formed on a transfer surface 17 and the angle a between the
blow direction of these openings 16 and the transfer surface 17
is 15 - 30 . Thus, according to the invention, the openings
open up to the transfer surface in which case harmful shoulders
are avoided. In other words, the transfer surface is smooth
without any shoulders or other protrusions which would generate
friction. On the other hand, air blows set at a suitable angle
firstly create a sufficient vacuum effect and secondly effi-
ciently forward the web-like material. In some embodiments the
angle may be smaller than that mentioned above, for example 10
150.
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In Figures 2a and 2b the transfer surface 17 is planar. In this
case the device is suitable for a linear transfer. The transfer
surface can also be convex in which case it is also possible to
change the travel direction of the web-like material. Specifi-
5 cally with the design of the air connection, new features,
which are described in more detail below, can be achieved.
Openings that open up to the transfer surface can be located in
different points, which increases adjustment possibilities of
the device features. However, the distance of the openings 16
from the front edge of the transfer surface 17 is 10 - 50 mm,
more advantageously 10 - 25 mm. Then, as the web-like material
arrives at the device, it is provided with a support surface
before the transfer effect of the air blows. At the same time,
a vacuum effect starts to generate immediately in the initial
part of the device, which, for its part, minimizes friction
forces and reduces the dimensions of the device. By freer
positioning of the openings, even the air connection alone
could function as a transfer surface. However, the transfer
surface 17 is advantageously composed of an air connection 14
and a transfer plate 18 connected thereto and located in a
stepless position relative to the air connection 14. Thus the
design of the device remains simple and the dimensioning and
shape of the transfer surface can be easily varied by changing
and/or shaping the transfer plate.
The novel design and the placement of openings enable to manu-
facture, on one hand, very short, and on the other hand, also
very long devices. According to the invention, the dimension of
the transfer surface 17 in the travel direction of the web-like
material is in the range of 20 - 300 mm, more advantageously in
the range of 40 - 200 mm. This dimension refers to the effec-
tive dimension obtainable with one air connection. By adapting
several successive air connections in the device, the effective
dimension of the device can be increased. Another alternative
is to adapt several devices successively, which is advantageous
particularly in the tail transfer.
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In the embodiment of Figure 2a, the openings 16 are composed of
holes 19. In other words, air blows are formed without separate
nozzles. The holes are easy to process using a laser, for
example, particularly when the air connection is made of a
drawn aluminum profile. Plastic and plastic composite materials
are also possible. According to the invention, relatively small
holes are used, having a diameter of 1 - 3 mm, more advanta-
geously 1.5 - 2.5 mm. Thus the air consumption remains reason-
able. In addition, separate nozzles are unnecessary. Depending
on the basis weight of the web-like material to be transferred
and the transfer distance, the distance between the holes is
selected to suit each particular case. Generally, the distance
between the holes is in the range of 10 - 50 mm, more advanta-
geously in the range of 20 - 40 mm, such that the larger the
holes, the further away they are from each other. Instead of a
straight row, the holes can be arranged imbricately or slant-
wise, for example, for directing the vacuum effect in a desired
way.
According to one embodiment, the middle openings of the trans-
fer surface can be larger than the openings in the edge areas.
In this way, a boosted blow effect can be provided in the
center area which automatically centers the web-like material
to be transferred. In other words, a centering force is gener-
ated which keeps the material, such as a tail, substantially at
the center of the transfer surface in the longitudinal direc-
tion. At the same time, harmful effects of the openings exter-
nal to the web-like material reduce as the venturi air de-
creases. For example, the area of boosted air blows can range
from one third to two thirds of the blow width of the device,
advantageously about a half of the blow width, however, less
than the width of the web-like material. A device equipped with
a boosted air blow area is shown in Figure 6a in which the
web-like material is represented by a dot-and-dash line. A
boosted air blow area can also be formed with slits while the
holes are in the edge areas, or vice versa.
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In the embodiment of Figure 2b, the openings 16 are composed of
slits 20 which can also be processed with a laser. Slits create
extremely uniform air blows and, in addition, the noise of air
discharging from slits is lower compared to holes. According to
the invention, the width of the slits is 0.05 - 1 mm, more
advantageously 0.1 - 0.5 mm. Slits can also be located in a
straight line or suitably imbricately arranged whereby a com-
prehensive and uniform air blow is achieved (Figure 2b). The
length of the slits depends mainly on case-specific require-
1o ments and the slit width. Discontinuous slits are longer than
5 mm, advantageously longer than 10 mm. A slit can also be
continuous, having a width almost equal to the entire device.
In this case the slit width is approximately 200 - 300 mm, even
as wide as 400 mm in particularly wide applications.
Due to the simple design and small friction, highly variable
pressures can be applied in the device. According to the inven-
tion, the device, and particularly the openings 16, are so
dimensioned that a pressure of 0.25 - 7, more advantageously
0.5 - 2 bar, can be applied. Then significant forces transfer-
ring the web-like material can be achieved already at a low
pressure. On the other hand, a high pressure can also be used,
which can be utilized particularly for achieving a sufficient
flow speed. In other words, the device can be used in fast
fiber web machines as well.
Furthermore, the efficiency of the device, more precisely the
guiding vacuum effect on the web-like material, can be in-
creased by adapting the air blows to two different directions.
According to the invention, the device includes second openings
21 adapted, in the travel direction of the web-like material,
before the openings 16 and directed substantially to the oppo-
site direction relative to the openings 16. This is shown in
Figure 3a where the openings 16 and 21 are adapted on the
surface of a curved air connection 14. Another embodiment is
shown in Figure 3b where the surface of the air connection 14
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is mainly smooth but the openings 16 and 21 are arranged in the
slanting parts. Despite the small bend, the air blows function
as air cushions preventing the web-like material from chafing
against the edge. Other mainly convex surface profiles can also
be used. The slanting parts in Figure 3a can have another
profile besides straight, such as curved, convex or concave or
combinations of these; in any event, the blow angle is the most
critical feature. The elevation between the levels of the
transfer surface 17 and the transfer plate 18 is advantageously
small, less than 4 mm or equal to or smaller than 3 mm. In
addition, the slanting parts and the curved surfaces can be in
a slight angle relative to each other.
Figure 6b shows an additional embodiment of the device. Here
the plane surface 17 is provided with a V-shaped incision 34
opening up to the blow direction with the openings 16 opening
up to the first wall thereof. Then the individual openings are
advantageously oriented and the blows discharging from the
openings even out in the incision providing an efficient for-
warding force. The dimensioning of the incision can also vary
in the width direction of the device, which can influence the
centering of the tail, for example. In Figure 6a, the openings
16 are holes 19, but it is also possible to use slits. Another
alternative is to leave a gently-sloping low elevation in the
plane surface arranging the openings in its trailing edge (not
shown). In addition, it has been noted that the embodiments of
Figures 2a-b and 3a-b also function crosswise. In other words,
the devices of Figures 3a-b function only with transfer blows
alone. Correspondingly, the devices of Figures 2a-b function
with parallel and counter blows (not shown).
The dimensioning principles of the second openings correspond
to the dimensioning of the openings intended for forming paral-
lel air blows. Thus the angle R between the blow directions of
the openings 16 and the second openings 21 is 120 - 150 . Then,
due to the combined effect of the air blows, a comprehensive
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vacuum effect which reliably seizes the web-like material is
created on the transfer surface. This affords reliability to
the device operation, which is essential particularly in the
tail transfer. In Figure 4 the angle R is approximately 130 .
Figures 4 and 5 show a fifth embodiment of the device according
to the invention which additionally includes a doctor blade 22.
The doctor blade is used, for example, to detach a tail from a
cylinder surface. Detaching is additionally aided by a
block-off blow which is formed by leading pressurized air from
the second openings 21. Advantageously the direction of the
blow-off blow is parallel to the doctor blade. After this, a
parallel transfer blow is created by leading pressurized air
from the openings 16. Here, in fact, two devices are combined
of which the latter has only a parallel transfer blow.
The device shown in Figures 4 and 5 is composed of three main
parts 23, 24 and 25, which are drawn aluminum profiles. The
middle main part 24 has a hollow construction for minimizing
the mass. However, the hollow cavities have a functional mean-
ing in supporting the device. The circular cavity 26 has an
overhanging shaft installed therein with which the device is
turnably supported. The mounting flange of the overhanging
shaft is screwed to one or more small cavities 27. The mass of
the proposed construction is so small that a spring-return
actuator cylinder can be used. In other words, the doctor blade
is loaded against the surface with a single-acting actuator
cylinder. After successful tail threading, when the actuator
cylinder is depressurized, the spring returns the device to the
3o rest position (not shown). The front main part 23 is fastened
to the middle main part 24 with bolts 28. The front main part
23 is also an aluminum profile in which two adjacent cavities
29 have been formed and the cavities are provided with machined
holes for forming the openings. Here the blow-off blows and the
transfer blows have cavities of their own forming the air
connections, which allows guiding the air blows independently
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of each other. In addition, the front and middle main parts are
steplessly positioned relative to each other whereby friction
problems are avoided. The smooth upper surface of the middle
main part forms a part of the functional transfer plate.
5
In some embodiments, a device composed of the front and middle
main parts would be sufficient for achieving the necessary
transfer distance. However, according to the invention, the
middle main part includes a counter clamp 30 to which the rear
1o main part 25 is fastened in Figure 4. Advantageously, a
form-fitting connection is used and its fastening is secured
with bolts 31. The rear main part 25 is also an aluminum pro-
file having additionally an air removal slit 32 machined
therein. Thus any extra air that has already lost its kinetic
energy can discharge from the air removal slit before the
second transfer blow. The rear-most device has a transfer plate
18 for which the length can be selected to suit each particular
case. Advantageously, a stainless steel plate is used, which is
connected with countersunk screws 33 to form a plane with the
rear main part 25. The surfaces of all main parts located on
the side of the tail form together a planar transfer surface to
which openings according to the invention open up. Figure 5
shows the mains parts disassembled from each other.
The design and dimensioning of the device according to the
invention can vary in different applications. However, openings
opening up to the transfer surface and with which earlier
friction problems are avoided, are essential. Also significant
are the air blows set at a certain angle by which a web-like
material can be both reliably seized and smoothly forwarded.
