[0001] The invention relates to a runnability component and a method for drying a paper
web according to the preambles of the enclosed independent claims.
[0002] In a drying section of a paper or board machine the web to be dried is conveyed supported
by one or two wires in contact with a plurality of heated drying cylinders. In single-felting
draw the paper web runs supported by a drying wire through a drying cylinder group
so that the drying wire presses the web against the heated cylinder surfaces of the
drying cylinders. Thus, in single-felting draw the drying cylinders are arranged outside
the wire loop, and turn rolls are arranged inside the loop. A pocket space is formed,
which is defined by the wire and two adjacent drying cylinders and the turn roll situated
between the drying cylinders at a different level. An opening nip, or opening gap,
is formed on the entry side of the pocket space on an area where the drying wire separates
from the first drying cylinder and, correspondingly, a closing nip, or a closing gap,
is formed on the entry side of the pocket space when the wire runs to the turn roll.
In a similar manner, when the wire leaves the turn roll, an opening nip, i.e. an opening
gap, is formed on the exit side of the pocket space and, correspondingly, when the
wire runs to the adjacent, second drying cylinder, a closing nip, i.e. a closing gap,
is formed on the exit side between the wire and the second drying cylinder.
[0003] Runnability problems occur, when the paper web has a tendency to detach, at certain
points, from the contact with the drying wire. Problematic points are especially the
above described opening nips, i.e. points where the web and the wire disengage from
the drying cylinder surface. Up to that point, the web has been travelling between
the wire and the cylinder, and when the wire detaches from the cylinder, the web tends
to follow the cylinder surface and thereby to disengage itself from the wire. Similar
problems occur at closing nips, where the web and the wire are brought into contact
with the cylinder surface. At that point, the web tends to disengage from the wire
due to an overpressure formed in the nip.
[0004] Different kinds of runnability components, such as blow boxes or suction boxes, are
arranged in the pocket space between the succeeding drying cylinders and the turn
roll. Runnability components are used to create suitable underpressure in the pocket
space, which promotes the keeping of the web in contact with the wire and improves
the runnability of the dryer section of a paper machine. Blow boxes are typically
used in connection with grooved and drilled vacuum turn rolls, where the air is sucked
into the roll through holes in the roll shell. The suction is created by using a vacuum
forming device, such as a fan or the like, which is arranged in connection with the
interior of the roll. The underpressure inside the vacuum turn roll is typically about
2000 - 2500 Pa. On the other hand, suction boxes are typically used with so-called
passive turn rolls, which have cut-outs in the roll shell. Suction box, which is arranged
in the pocket space at the portion of the turn roll free from the wire, is arranged
to suck air through the cut-outs of the turn roll. The open area of the passive roll
is relatively large, typically around 4 - 10, more typically 6 - 8 %. The interior
of the passive roll has normally no direct connection with the vacuum forming devices.
[0005] Sometimes, especially when paper machines are renewed and rebuilt, there is a need
to change the runnability components in the pocket space without changing the turn
rolls. However, turn rolls that has been designed to operate with suction boxes are
not optimal for operation with blow boxes. There has been a need to find a simple
and economical solution that would enable the change of runnability components in
the pocket space without any other extensive modifications of the existing turn rolls,
drying cylinders, other machinery and/or apparatuses. Furthermore, there is a need
for runnability components with which the underpressure in the pocket space can be
more accurately and easily controlled.
[0006] An object of this invention is to minimise or even totally eliminate the disadvantages
existing in the prior art.
[0007] An object is also to provide a runnability component with which a good underpressure
can be created to the pocket space and which can be used together with different types
of turn rolls.
[0008] A further object of the invention is to provide a runnability component enabling
good control of the different underpressure zones in the pocket space.
[0009] Another object of the invention is to provide an alternative method for creating
the required underpressure in the pocket space, especially suitable for rebuild applications.
[0010] These objects are attained with the invention having the characteristics presented
below in the characterising parts of the independent claims.
[0011] Typical runnability component according to the present invention for a drying section
of a paper machine or the like comprises
- an entry side surface and an exit side surface, which are connected to each other
at least by a lower surface, whereby the entry side surface, exit side surface and
lower surface delimit the inner volume of the box-like elongated runnability component,
- a first end and a second end, between which the runnability component extends in its
length direction,
- a first blowing element, which is arranged in connection with the entry side surface
to blow air upwards,
- a first sealing element, which is arranged in connection with the entry side surface,
beneath the first blowing element, the first sealing element dividing the entry side
surface into a first region and a second region, whereby
the lower surface of the runnability component is provided with a first suction element,
which is formed by at least one suction gap or by at least one row of suction holes,
extending from the first end of the runnability component towards the second end of
the runnability component,
the runnability component comprising means for adjusting the size of the suction holes
or the width of the suction gap.
[0012] Typical arrangement for a paper machine or the like comprises
- a turn roll, which has cut-outs, such as perforations, and
- a runnability component according to the present invention, arranged at least partially
around the surface of the turn roll.
[0013] Typical method according to the present invention for drying a paper web or the like
in a drying section of a paper machine or the like comprises
- supporting a paper web with a drying wire,
- guiding the paper web over a part of a heated surface of a first drying cylinder,
turning travel direction of the paper web by using a turn roll, and guiding the paper
web over a part of a heated surface of a succeeding second drying cylinder, whereby
a pocket space is defined by the first and second drying cylinders, arranged parallel
at a distance from each other, and the turn roll arranged between the first and second
drying cylinders, parallel with them and having its axis of rotation on a different
level from the axis of the first and second drying cylinder,
- arranging, at least partly, a box-like elongated runnability component to the pocket
space, the runnability component having an entry side surface, which faces the first
drying cylinder, and an exit side surface, which faces the second drying cylinder,
the surfaces being connected to each other at least by a lower surface, which faces
the turn roll, whereby the entry side surface, exit side surface and lower surface
delimit the inner volume of the box-like elongated runnability component, runnability
component extending from a first end to a second end in its length direction over
the width of the paper web,
- blowing air against the travel direction of the paper web, which is guided from the
first drying cylinder to the turn roll, by a first blowing element, which is arranged
in connection with entry side surface of the runnability component to create a negative
pressure space on the entry side surface, and
- increasing underpressure in the pocket space by removing air by suction from a space
between the turn roll and the lower surface of the runnability component into the
runnability component with a first suction element, which is formed by at least one
suction gap or by at least one row of suction holes, extending from the first end
of the runnability component towards the second end of the runnability component,
and
- adjusting the size of the suction holes or the width of the suction gap of the first
suction element for controlling the suction through the lower surface of the runnability
component.
[0014] The embodiments mentioned in this text relate, where applicable, to the runnability
component, the arrangement as well as to the method according to the invention, even
if this is not always separately mentioned.
[0015] Now it has been surprisingly found out that the underpressure in the pocket space
can be enhanced by sucking air from the area between the lower surface of the runnability
component and the turn roll by first suction means arranged to the lower surface of
the runnability component, which also comprises a blowing element on the entry side
for creating the underpressure. Furthermore, it has been found out that the underpressure
in the pocket space can be more accurately, efficiently and easily controlled for
each operational situation by adjusting the size of the suction holes or width of
the suction gap, which forms the first suction element. The air is sucked from the
interior of the turn roll through the cut-outs on the roll shell, thus creating at
least a part of the necessary underpressure in the turn roll to stabilise the turning
path of the wire and the web over the turn roll surface. In this manner part of the
air is removed through the turn roll and the underpressure in the pocket is improved.
The invention enables use of runnability components with blowing elements also in
connection with turn rolls with high open shell area without extensive increase in
used air volumes and energy consumption. The present invention combines the good runnability
and sealing of the pocket space towards the wire on the entry side of the runnability
component that are traditionally achieved with a blow-box with a use of a passive
turn roll, while providing good control of the underpressure in the pocket space due
to the adjustable first suction element.
[0016] In context of the present application the runnability component is arranged in a
pocket space, which is defined by the first and second drying cylinder and a turn
roll between them. The drying cylinders are parallel, i.e. their longitudinal axes
are parallel with each other, and they are arranged at a distance from each other.
[0017] Typically the adjacent drying cylinders are arranged horizontally on the same level
and the turn roll is arranged between the two adjacent drying cylinders so that the
longitudinal axis of the turn roll is substantially parallel with the longitudinal
axes of the drying cylinders, but located on a different level in the vertical direction
than the axes of the drying cylinders. Turn roll is thus arranged on a higher or lower
level than the drying cylinders, typically on a lower level. Furthermore, the turn
roll is placed between the drying cylinders so that its surface does not touch the
surfaces of the drying cylinders, i.e. is free from contact with the drying cylinder
surfaces. In a typical paper machine the box-like runnability component, the drying
cylinders and the turn rolls are elongated in the cross direction of the paper machine
or the like, and extend substantially over the entire width of the web run. Therefore
the pocket space defined by them is also elongated in the cross direction of the paper
machine. The ends of the pocket space are typically sealed, for example by means of
end plates according to prior art, such as gap plates. The vertical end plates are
arranged in machine direction, on both ends of the pocket space.
[0018] In this application, the entry side and the exit side of the pocket space have the
following meaning: The pocket space may be divided, in machine cross direction at
its centre point, by an imaginary vertical level having the width of the web run into
an entry side and an exit side. On the entry side, i.e. between the first drying cylinder
and the turn roll, and on the exit side, i.e. between the turn roll and the second
drying cylinder, the pocket space is delimited by the wire, and therefore, during
the operation of the paper machine, also by the web path formed by the wire and the
web. The lower surface of the runnability component means the surface of the runnability
component, which is located nearest to the turn roll, and which is arranged substantially
towards the turn roll.
[0019] In this application, a higher underpressure means a lower absolute pressure. Respectively,
a lower underpressure means a higher absolute pressure. An underpressure means a pressure,
which is lower than the normal atmospheric pressure ca. 1 bar, i.e. 100 kPa.
[0020] The runnability component comprises a first blowing element, which is arranged in
connection with the entry side surface of the runnability component to blow air upwards.
The first blowing element on the entry side is arranged at the opening nip between
the wire and the cylinder, for blowing air away from the gap between the wire and
the runnability component. The air jet discharging from the first blowing element
maintains a negative pressure in the space between the runnability component and the
web, and creates a negative pressure space at the opening nip on the entry side. The
first blowing element may be a blow nozzle or a blowing gap, extending from the first
end towards the second end of the runnability component, preferably to the second
end of the runnability component. The blow nozzle diameter or gap width of the first
blowing element is typically 1 - 3 mm, preferably 1.5 - 2.5 mm. In case the blowing
element is a blowing element using compressed air, the nozzle diameter or gap width
may be 0.1 mm - 0.5 mm.
[0021] The runnability component comprises also a first sealing element, which is arranged
in connection with the entry side surface of the runnability component, beneath the
first blowing element. The first sealing element is arranged at a short distance from
the opening nip between the wire and the cylinder, to project from the surface of
the runnability component towards the wire and dividing the entry side surface into
a first region and a second region. The first sealing element divides thus the negative
pressure space on the entry side into a first region of an intensified negative pressure
confined to the location of the opening nip and into a second region of a lower negative
pressure, i.e. lower underpressure, at the lower part of the pocket space on the entry
side, near the closing nip of the entry side. The first sealing element may be a mechanical
sealing element, such as a sealing strip or a labyrinth sealing, such as single-chambered
labyrinth sealing or multi-chambered labyrinth sealing. The material of the mechanical
sealing element may be, for example, Teflon, plastic, rubber, composite or metal,
such as steel or aluminium. A requirement for the material is a sufficient rigidity,
with which the free flow of air may be prevented. Preferably the first sealing element
is a mechanical sealing element, which is made of Teflon or of material comprising
carbon fibres.
[0022] The lower surface of the runnability component is provided with a first suction element.
The first suction element removes air from the pocket space, from the space between
the lower surface of the runnability component and the turn roll. Indirectly the first
suction element is also used for creating a underpressure to the turn roll, as the
suction of the first suction element creates an air flow through the open areas of
the turn roll surface from the inside of the turn roll to the space between lower
surface of the runnability component and the turn roll. The first suction element
is connected to a suction channel, arranged inside the runnabilty component, as described
later in the application. The first suction element is formed by at least one suction
gap or by at least one row of suction holes, extending from the first end of the runnability
component towards the second end, preferably to the second end, of the runnability
component. The first suction element may also comprise a plurality of adjacent suction
gaps or rows of suction holes. For example, the first suction element may preferably
comprise 2 - 4 adjacent rows of suction holes or adjacent suction gaps. The suction
holes may have a diameter of 15 - 50 mm, preferably 20 - 40 mm, and the distance between
two adjacent holes in a row is typically 50 - 500 mm, preferably 150 - 350 mm. In
case the suction means comprise a uniform suction gap, the width of the gap is 2 -
10 mm, typically 2 - 4 mm, preferably 2 - 3 mm. The form of the suction holes may
be selected freely, for example they may be circular or oval-shaped.
[0023] The suction through the lower surface of the runnability component is controlled
by adjusting the suction of the first suction element according to the requirements
of one or several of the process parameters, such as web speed, web tension or weight
of the paper web which is produced. It is possible to adjust the suction of the first
suction element by adjusting the size of the suction holes or the width of the suction
gap with adjustment means. Thus the runnability component comprises means for adjusting
the size of the suction holes or the width of the suction gap of the first suction
element. The adjustment means may be, for example, a movable hole plate, which is
arranged on top of the suction hole row in the cross direction of the paper machine.
When the holes of the hole plate and the suction holes completely overlap, the suction
is as the strongest. When the hole plate is moved, the overlap of the holes of the
hole plate and the suction holes decrease, and the suction through the suction holes
is reduced.
[0024] According to one embodiment of the invention the runnability component further comprises
a second suction element, which is arranged on the entry side surface of the runnability
component, beneath the first sealing element, the second suction element being formed
by at least one suction gap or by at least one row of suction holes, extending from
the first end of the runnability component towards the second end of the runnability
component, preferably to the second end of the runnability component. The second suction
element is thus arranged to remove air by suction from the negative pressure space
on the entry side of the runnability component. The second suction element may be
connected to a suction channel, which is arranged inside the runnability component,
as described later in the application. The second suction element may also comprise
a plurality of adjacent suction gaps or rows of suction holes. For example, the second
suction element may preferably comprise 2 - 4 adjacent rows of suction holes or adjacent
suction gaps. The suction holes may have a diameter of 15 - 50 mm, preferably 20 -
40 mm, and the distance between two adjacent holes in a row is typically 50 - 500
mm, preferably 150 - 350 mm. In case the suction means comprise a uniform suction
gap, the width of the gap is 2 - 10 mm, typically 2 - 4 mm, preferably 2 - 3 mm. The
form of the suction holes may be selected freely, for example they may be circular
or oval-shaped.
[0025] Optionally the second suction element comprises means for adjusting suction through
the second suction element. In this manner the suction effect of the second suction
element is adjusted for controlling the suction from the negative pressure space through
the entry side surface of the runnability component according to the requirements
of the process parameters, such as web speed, web tension or weight of the paper web
which is produced. For example, the second suction element may be attached to a connection
provided with a damper with which the direct suction from the negative pressure space
between the entry side of the runnability component and the wire may be adjusted.
It is also possible to adjust the suction of the second suction element by adjusting
the size of the suction holes or the width of the suction gap with adjustment means.
Thus the runnability component comprises second means for adjusting the size of the
suction holes or the width of the suction gap of the second suction element. The second
adjustment means may be, for example, a movable hole plate, which is arranged on top
of the suction hole row in the cross direction of the paper machine. When the holes
of the hole plate and the suction holes completely overlap, the suction is as the
strongest. When the hole plate is moved, the overlap of the holes of the hole plate
and the suction holes decrease, and the suction through the suction holes is reduced.
[0026] The first and/or second suction element may be connected to an external suction device
or vacuum air system. It is possible to connect the suction element(s) to existing
suction air systems intended for creating an underpressure to the pocket space or
for the turn roll. This is advantageous when existing paper machine constructions
are rebuilt, as no new suction systems need to be built, which saves time, costs and
usually also space. The suction of the first and/or second suction means may be adjusted
according to the process parameters and/or process situation. The first and/or second
suction means may be connected to the external suction device or vacuum air system
with a connection, which is provided with a regulating means for regulating the air
flow, such as valve or a throttle. The regulating means may be automatically adjustable
or they may be adjustable manually.
[0027] According to one embodiment of the invention the runnability component comprises
at least one second sealing element, preferably a plurality of second sealing elements,
arranged in connection with the lower part of the runnability component, preferably
with the lower surface of the runnability component. The second sealing element(s)
may be arranged to extend outwards from the surface of the runnability component.
The second sealing element may be a mechanical sealing element or a sealing blow nozzle,
preferably a mechanical sealing element. The at least one second sealing element is
arranged to seal the gap between the runnability component and the turn roll, in order
to intensify the suction from the turn roll to the runnability component and from
the space between the lower surface of the runnability component and the turn roll.
The second sealing element also helps to guide the air flow, which moves the exit
side surface of the turn roll, in the rotational direction of the roll, away from
the contact with the surface of the turn roll.
[0028] In case the second sealing element is a sealing blow nozzle, it is provided on the
exit side surface of the runnability component, i.e. on the side of the opening nip
from the turn roll. The control of the underpressure in the pocket space between the
drying cylinders and the turn roll may be improved with the second sealing element,
which is an exit side sealing blow nozzle with which air is ejected out of the pocket
space and/or the entry of the air into the pocket space via the gap between the exit
side surface of the runnability component and the second drying cylinder is prevented.
[0029] When the second sealing element is a mechanical sealing element, the second sealing
element extends outwards from the lower part, preferably lower surface, of the runnability
component, preferably towards the turn roll. According to one embodiment of the invention
the second sealing element is arranged to the lower surface of the runnability component
on the exit side. According one preferred embodiment, the mechanical second sealing
element is arranged at at least one, preferably at both lower corners of the runnability
component, extending towards the surface of the turn roll. The mechanical second sealing
element(s) serve(s) as a concrete physical obstacle(s) for the entry of air into the
space between the runnability component and the turn roll. Thus, only a minute amount
of air possibly enters into the said space.
[0030] The second mechanical sealing element may be a mechanical sealing element, such as
a sealing strip or a labyrinth sealing, such as single-chambered labyrinth sealing
or multi-chambered labyrinth sealing. The material of the mechanical sealing element
may be, for example, Teflon, plastic, rubber, composite or metal, such as steel or
aluminium. A requirement for the material is a sufficient rigidity, with which the
free flow of air may be prevented. Preferably the second sealing element is a mechanical
sealing element, which is made of Teflon or of material comprising carbon fibres.
[0031] The first and second sealing elements may be similar to each other or they may be
different from each other. According to one embodiment of the invention the first
and/or second sealing element is a mechanical sealing element, which is provided with
means for adjusting the distance of the sealing element(s) to the turn roll or the
drying cylinder. The length of the sealing element extending outwardly from the surface
of the runnability component may be adjusted with the adjusting means. For example,
the distance between the first drying cylinder surface and the first sealing element
may be adjusted according to the needs of the process situation, and air may be leaked
to the pocket space or to the intensified negative pressure space at the opening nip
on the entry side, if need be. Similarly the distance between the second sealing element(s)
and the turn roll may be adjusted and the air leaked to the area between the lower
surface of the runnability component and the turn roll. Sometimes the first and/or
second sealing element(s) create(s) such an effective sealing that the underpressure
in the pocket space or at the opening nip is significantly enhanced. The location
of the second sealing element may then be adjusted further away from the turn roll,
whereby a gap between the second sealing element and the turn roll is formed or increased.
From this gap air may be allowed to leak to the pocket space or to the space between
the lower surface of the runnability component and the turn roll from the opening
nip on the exit side.
[0032] The first and second mechanical sealing elements are preferably elongated in the
cross direction of the paper machine or the like and extend substantially over the
entire width of the web run. According to an embodiment of the invention, the first
and/or second sealing element are mechanical sealing elements which are formed of
at least two parts, preferably of several parts, in the lateral direction, i.e. cross
direction, of the machine. Thus their mounting, transportation and storage is easier.
[0033] The runnability component may comprise a by-pass channel leading from a first region
on the entry side to the second region on the entry side of the runnability component.
The by-pass channel enables a more precise control of the underpressure difference
between the first and second region in the negative pressure space at the opening
nip on the entry side. This improves also the overall pressure balance in the pocket
space, whereby the operation of the turn roll may be considerably intensified and
the control of the web may be enhanced with low energy consumption. The by-pass channel
allows air to be transferred between the first and second pressure region, which makes
it possible to control the underpressure by adjusting the flow, for example to balance
the pressure differences between the first and second pressure region in a desired
manner. According to an embodiment of the invention, a valve, a throttle or other
device or means adjusting the air flow in the by-pass channel is arranged in the by-pass
channel. The by-pass channel may therefore be considered as a controlled active leak
channel. The by-pass channel is preferably elongated in the cross direction of the
paper machine or the like and extends substantially over the entire width of the web
run.
[0034] According to another embodiment of the invention the runnability component may comprise
a by-pass channel leading from the entry side of the runnability component to the
exit side of the runnability component or to the upper surface of the runnability
component. Also in this case by-pass channel may be used for balancing the pressure
conditions in the first and/or second region on the negative pressure space on the
entry side. If the underpressure on the entry side is too high the by-pass channel
leading to the exit side or to surroundings may be opened, which leads reduced underpressure
on the entry side.
[0035] According to one embodiment of the invention a second blowing element is arranged
in connection with the entry side surface, beneath the first sealing element. The
second blowing element may be a blow nozzle or a blowing gap, arranged on the first
underpressure region. The second blowing element extends from the first end towards
the second end of the runnability component, preferably to the second end of the runnability
component. The second blowing element may be arranged to blow upwards, against the
moving direction of the wire. Typically the goal is to intensify the underpressure
level especially in the closing nip on the entry side and generally in the negative
pressure region on the entry side, which makes the prevention of the wire bending
more accurate and easy. The second blowing element creates an air cushion which prevents
the pumping/pulsating effect, otherwise typical for suction. The blow nozzle diameter
or gap width of the second blowing element is typically around 2 - 3 mm, and the blow
speed 10 - 50 m/s, preferably 20 - 40 m/s. The air which is ejected from the second
blowing element may be led to a second suction element, arranged above the second
blowing element. By means of the second suction element the air from the second blowing
element is led to the suction channel inside the runnability component.
[0036] According to one embodiment of the invention second blowing element is arranged to
blow into the by-pass channel extending from the entry side of the runnability component,
especially into a by-pass channel leading from the entry side of the runnability component
to the exit side of the runnability component or to the upper surface of the runnability
component.
[0037] The runnability component preferably comprises a suction channel extending from the
first end to the second end of the runnability component, and a blow channel extending
from the second end to the first end of the runnability component. The suction channel
and blow channel are arranged inside the runnability component, inside the space,
which is defined by the outer walls, i.e. surfaces, of the runnability component.
Typically the blow channel is arranged at the upper part of the runnability component
and the suction channel is arranged at the lower part of the runnability component,
beneath the blow channel. Preferably the runnability component comprises a tapering
suction channel extending from the first end to the second end of the runnability
component and a tapering blow channel extending from the second end to the first end
of the runnability component. Tapering suction and blow channels are advantageous
as they enable the keeping of the pressure on even level along the length of the channels,
in cross direction of the paper machine, and they minimise the pressure losses in
the channels between the first and the second end of the runnability component. According
to one embodiment of the invention the runnability component comprises an inclined
division wall extending from the first end to the second end and dividing the inner
volume of the runnability component into tapering suction channel and tapering blow
channel.
[0038] The suction channel and the blow channel may be connected to adjustment means for
adjusting the air flows to and/or from the runnability components. The air flows are
preferably controlled independently from each other, i.e. the suction in the suction
channel and the blow in the blow channel of the runnability component are controlled
independently from each other.
[0039] According to one embodiment of the invention the runnability component comprises
a tail threading zone. The tail threading zone may be located, with respect to the
web run, on the tending side and/or on the driving side, in the area of the first
end and/or the second end of the runnability component. During tail threading the
suction force in the tail threading zone may be controlled into one value and after
the tail threading, i.e. in a normal running situation with a wide web run, to a second
value. The tail threading zone is defined by a dividing wall arranged inside the runnability
component, dividing the suction channel it a tail threading zone and normal operation
zone. The dividing wall is normally vertical and it is arranged perpendicular to the
length axis of the runnability component, i.e. the dividing wall is vertical and arranged
parallel with the machine direction and with direction of web movement. The adjustment
of suction force between the tail threading zone and the normal operation zone may
be achieved by appropriate control means. For example, the tail threading zone may
be connected to a separate and individual suction means, which are controlled independently
from the suction devices or the like that create the suction to the normal operation
zone of the suction channel.
[0040] According to one preferred embodiment of the present invention the control of the
suction force at the tail threading zone and at the normal operation zone is achieved
by using an integrated control means. The integrated control means comprise a first
and a second coaxial pipe with different diameter. The first pipe is in contact the
suction element of the tail threading zone and the second pipe is in contact with
the suction element of the normal operation zone. Both the first and the second pipe
of the integrated control means are in contact with the suction device or vacuum air
system. A damper is arranged to the second pipe, so that the air flow through it may
be restricted or totally terminated. When the damper is open, the suction is evenly
divided to both the first and the second pipe, and the suction through suction element
on the tail threading zone is equal to the suction through the suction element on
the normal operation zone. When the damper is partially or wholly closing the second
pipe, the suction is mainly or only occurring through the first pipe, i.e. mainly
or only through suction element on the tail threading zone. According to one preferred
element the cross section of the first pipe is circular and cross section of the second
pipe is angular, preferably rectangular.
[0041] The turn roll used in connection with the invention may be a perforated turn roll,
a grooved turn roll or a turn roll provided with both perforations and grooves, known
per se. According to one preferred embodiment of the present invention the turn roll
has an open area of at least 4 %, preferably 4 - 10 %, more preferably 6 - 8 %. This
means that the surface of the turn roll comprises a large amount of cut-outs, such
as perforations. The turn roll is typically so-called passive turn roll, which means
that the turn roll is free of internal suction devices. In other words, there are
no internal suction devices or suction connections to the turn roll but the air is
sucked from the turn roll, through the cut-outs on its surface, by external suction
means, elements or devices, arranged in the runnability component.
[0042] According to one embodiment of the invention the runnability component comprises
a distribution chamber, which is arranged on the entry side surface of the runnability
component. The distribution chamber comprises a front plate, and it extends from the
first end of the runnability component towards the second end of the runnability component,
preferably to the second end of the runnability component. The front plate may be
attached on the entry side surface of the runnability component by welding, or by
using attachment means, such as bolts, rivets, or the like. The distribution chamber
is preferably formed beneath the first sealing element, on the area between the opening
nip of the first drying cylinder and the closing nip of the turn roll. The front plate
comprises at least one row of leak holes, preferably a plurality of parallel rows
of leak holes. The diameter of a single leak hole may be 15 - 50 mm, preferably 20
- 40 mm and the distance between the adjacent leak holes in a row is typically 150
- 350 mm, preferably 200 - 300 mm.
[0043] The web bending at and after the first drying cylinder may be controlled by distributing
leak air by the distribution chamber arranged on the entry side surface of the runnability
component. The web bending at the opening nip of the first drying cylinder increases
the negative pressure in the space between the web and the runnability component.
The increased negative pressure in its turn increases the web bending, thus leading
to a vicious circle. This negative phenomenon may be counteracted by distributing
a small amount of leak air through the holes in the front plate of the distribution
chamber. The control of the web bending is clearly improved and the runnability of
the web increased.
[0044] A transversal flow may be arranged to the distribution chamber by bringing the leak
air into the distribution chamber from the ends of the chamber. Regulating means,
such as a damper or the like, may be arranged on the end(s) of the distribution chamber
to control the flow to the distribution chamber.
[0045] The invention is described in more detail below with reference to the enclosed schematic
drawings, in which
- Figure 1
- shows a schematic view of a pocket space between two drying cylinders and one turn
roll,
- Figure 2
- shows an arrangement according to a first embodiment of the present invention,
- Figure 3
- shows an arrangement according to a second embodiment of the present invention,
- Figure 4
- shows an arrangement according to a third embodiment of the present invention,
- Figure 5
- shows an arrangement according to a fourth embodiment of the present invention,
- Figure 6
- shows an arrangement according to a fifth embodiment of the present invention,
- Figure 7
- shows an arrangement according to a sixth embodiment of the present invention, and
- Figure 8
- shows an arrangement according to a seventh embodiment of the present invention.
[0046] Figure 1 shows a schematic general view of a pocket space 9 between two drying cylinders
1, 2 and one turn roll 3 in the drying section of a paper machine. The pocket space
9 is delimited by a first drying cylinder 1, a second drying cylinder 2, a turn roll
3 and a web run 5a, 5b. Described more in detail, the pocket space 9 is delimited,
on its entry side 9a, by a web run 5a between the first drying cylinder 1 and the
turn roll 3, and on the exit side 9b of the pocket space, by a web run 5b between
the turn roll 3 and the second drying cylinder 2. The location of the turn roll in
a horizontal direction x and in a longitudinal direction L of the paper machine is
between the drying cylinders 1, 2, but in a vertical direction y lower than said cylinders
1, 2. The directions of rotation of the cylinders 1, 2 are shown by arrows R. It is
to be understood, that the above-presented arrangement is repeated by its substantial
parts in the drying section of a paper or a board machine.
[0047] Figure 1 also shows
- an opening nip 7a of the first drying cylinder 1 on the entry side 9a, i.e. the point
where the wire and the web detach from the periphery of the first drying cylinder
1 towards the turn roll 3,
- a closing nip 8a of the turn roll 3 on the entry side 9a, i.e. the point where the
wire enters into connection with the turn roll 3 after the first drying cylinder 1,
- an opening nip 8b of the turn roll 3 on the exit side 9b, i.e. the point where the
wire detaches from the periphery of the turn roll 3 towards the second drying cylinder
2, and
- a closing nip 7b of the second drying cylinder 2 on the exit side 9b, i.e. the point
where the wire and the web enter into connection with the second drying cylinder 2
after the turn roll 3.
[0048] Figure 2 shows an arrangement according to a first embodiment of the present invention.
A runnability component 10 is arranged in connection with a pocket space between the
drying cylinders 1, 2 and the turn roll 3 of a paper machine. The entry side 10a of
the runnability component 10 is provided with a first blowing element 11, such as
a blow nozzle. The first blowing element 11 blows air upwards, as indicated with arrow
13, against the travel direction of the paper web, which is guided from the first
drying cylinder 1 to the turn roll 3, in order to create an intensified first negative
pressure space 91 on the entry side 10a. The first blowing element 11 ejects air away
from the pocket space and prevents the air entailed by the web from entering into
the pocket space via the gap between the first drying cylinder 1 and the entry side
10a of the runnability component. A blow channel 12, which communicates with the first
blowing element 11, is arranged inside the upper part of the runnability component
10.
[0049] A first sealing element 20, such as a labyrinth sealing, is arranged in connection
with the surface of the entry side 10a of the runnability component 10 and in connection
with the opening nip 7a between the runnability component 10 and the first drying
cylinder 1. The first sealing element 20 is arranged beneath the first blowing element
11 and it divides the surface of the entry side 10a into a first region and a second
region. At the same time the first sealing element 20 divides the negative pressure
space on the entry side of the pocket space into an intensified first negative pressure
space 91 and a second negative pressure space 92.
[0050] The lower surface of the runnability component 10 is provided with a first suction
element. The first suction element comprises three parallel rows 31, 31', 31" of suction
holes, through which the air is sucked from the space 93 between the turn roll 3 and
the lower surface of the runnability component 10. A suction channel 32 is arranged
inside the lower part of the runnability component 10. The suction created by the
suction channel 32 removes also air from the interior of the turn roll 3, through
cut-outs or perforations on the surface of the turn roll 3. The air flows are indicated
with arrows.
[0051] Second sealing elements 19, 19', such as sealing strips are arranged in connection
with the lower part of the runnability component 10. The purpose of the second sealing
elements 19, 19' is to intensify the suction from the suction space 93 between the
lower surface of the runnability component and the turn roll and prevent leakage of
air to the suction space 93. The second sealing element 19' guides also the air flow
16 so that it does not enter the suction space 93 but is guided after the opening
nip 8b of the turning suction roll 3 on the exit side away from the pocket space in
the direction of the web run 5b.
[0052] Figure 3 shows an arrangement according to a second embodiment of the present invention.
In a similar manner as in Figure 2 a runnability component 10 is arranged in connection
with a pocket space between the drying cylinders 1, 2 and the turn roll 3 of a paper
machine. The structure of the runnability component 10 corresponds generally to that
what is presented in Figure 2, except that the lower surface of the runnability component
10 is provided with a first suction element, which comprises two parallel suction
gaps 31, 31', through which the air is sucked from the suction space 93 between the
turn roll 3 and the lower surface of the runnability component 10. Furthermore, in
Figure 3 the runnability component 10 comprises one second sealing element 19, such
as sealing strip, which is arranged in connection with the lower part on the entry
side 10a of the runnability component 10. Another second sealing element, which is
an exit side blow nozzle 15, is arranged on the exit side 10b of the runnability component
10. The exit side blow nozzle 15 blows air in the travelling direction of the web
run 5b according to arrow 14, and thereby ejects air away from the pocket space and
prevents the air from entering into the pocket space via the gap between the exit
side 10b of the runnability component 10 and the second drying cylinder 2. The exit
side blow nozzle 15 is connected to the blow channel 12 arranged inside the runnability
component 10.
[0053] Figure 4 shows an arrangement according to a third embodiment of the present invention.
In a similar manner as in Figure 2, a runnability component 10 is arranged in connection
with a pocket space between the drying cylinders 1, 2 and the turn roll 3 of a paper
machine. The structure of the runnability component 10 corresponds generally to that
what is presented in Figure 2, except that the lower surface of the runnability component
10 is provided with a first suction element, which comprises two parallel rows 31,
31' of suction holes, through which the air is sucked from the suction space 93 between
the turn roll 3 and the lower surface of the runnability component 10. Furthermore,
a second suction element 33 is arranged on the entry side 10a of the runnability component
10, beneath the first sealing element 20. The second suction element removes air from
the second negative pressure space 92, and thus intensifies the overall underpressure
in the pocket space. The second suction element 33 is connected to the suction channel
32 arranged inside the lower part of the runnability component 10.
[0054] Figure 5 shows an arrangement according to a fourth embodiment of the present invention.
In a similar manner as in Figure 2, a runnability component 10 is arranged in connection
with a pocket space between the drying cylinders 1, 2 and the turn roll 3 of a paper
machine. The structure of the runnability component 10 corresponds generally to that
what is presented in Figure 2. The entry side 10a of the runnability component 10
is provided with a by-pass channel 22, which is extending between the first negative
pressure space 91 and the second negative pressure space 92. The by-pass channel 22
may be used to regulate, for example, to balance, the underpressures of or the pressure
difference between the negative pressure spaces 91, 92 in a controlled and desired
manner.
[0055] Figure 6 shows an arrangement according to a fifth embodiment of the present invention.
In a similar manner as in Figure 2, a runnability component 10 is arranged in connection
with a pocket space between the drying cylinders 1, 2 and the turn roll 3 of a paper
machine. The runnability component 10 comprises a by-pass channel 25 leading from
the entry side 10a of the runnability component 10 to the exit side 10b of the runnability
component 10. The by-pass channel 25 may be used for balancing the pressure conditions
in the second negative pressure space 92 on the entry side 10a. Furthermore, a second
blowing element 24 is arranged to blow into the by-pass channel 25.
[0056] Figure 7 shows an arrangement according to a sixth embodiment of the present invention.
In principle, the runnability component 10 in Figure 7 corresponds to that presented
in Figure 2. A distribution chamber 4 is arranged on the entry side 10a of the runnability
component 10. The distribution chamber 4 has a front plate, which is attached on the
entry side surface of the runnability component 10 beneath the first sealing element
20. The front plate comprises parallel rows 16, 16' of leak holes. The web bending
at the second negative pressure space 92 is controlled by distributing leak air from
the distribution chamber 4 through the rows 16, 16' of the leak holes. The leak air
is supplied to the distribution chamber 4 from the ends of the chamber 4, whereby
a transversal flow is created. Regulating damper (not shown) can be arranged on the
end of the distribution chamber 4 to control the inflow to the distribution chamber.
[0057] Figure 8 shows an arrangement according to seventh embodiment of the present invention.
Runnability component 10 is presented without the entry side cover plate and without
tending side end plate. The interior of the runnability component comprises a tapering
suction channel 32 and a tapering blow channel 12. The suction channel inlet 17 extends
from the first end 10' of the runnability component 10 on tending side to the second
end 10" on the driving side, through the whole runnability component 10. Correspondingly,
the blow channel 12 extends from the second end 10" to the first end 10' of the runnability
component 10. An inclined division wall 21 is arranged inside of the runnability component
10 for dividing its inner volume into the tapering suction channel 32 and tapering
blow channel 12. The diameter of suction and blow channels 32, 12 are uniformly decreasing
from the channel inlets 17, 18 onwards. This counteracts the pressure decrease in
the channels 32, 12.
[0058] Figure 8 shows also a tail threading zone 42, which is arranged on the first end
10' of the runnability component 10. The tail threading zone 42 is defined by a dividing
wall 40 arranged inside the runnability component 10. The wall 40 divides the suction
channel 32 in a tail threading zone and a normal operation zone. The wall 40 is normally
arranged perpendicular to the length axis of the runnability component 10.
[0059] The suction between the tail threading zone 42 and the normal operation zone can
be changed by using control means integrated to the suction channel inlet 17. These
control means comprise a first circular pipe element 43 and a second rectangular pipe
element 44. The second pipe element 44 is arranged inside the first pipe element 43
and coaxially with it. The pipe elements 43, 44 have different diameter. When the
second pipe element 44 is open the suction is performed both through the first and
second pipe element 43, 44, which is the normal suction operation during paper making.
When the second pipe element 44 is closed the suction is performed only through the
first element 43, and the suction is concentrated only on the tail threading zone
42.
[0060] Even if the invention was described with reference to what at present seems to be
the most practical and preferred embodiments, it is appreciated that the invention
shall not be limited to the embodiments described above, but the invention is intended
to cover also different modifications and equivalent technical solutions within the
scope of the enclosed claims.
1. Runnability component (10) for a drying section of a paper machine or the like, comprising
- an entry side surface and an exit side surface, which are connected to each other
at least by a lower surface, whereby the entry side surface, exit side surface and
lower surface delimit the inner volume of the box-like elongated runnability component
(10),
- a first end (10') and a second end (10"), between which the runnability component
(10) extends in its length direction,
- a first blowing element (11), which is arranged in connection with the entry side
surface to blow air upwards,
- a first sealing element (20), which is arranged in connection with the the entry
side surface, beneath the first blowing element (11), the first sealing element (20)
dividing the entry side surface into a first region and a second region, whereby
the lower surface of the runnability component (10) is provided with a first suction
element, which is formed by at least one suction gap or by at least one row of suction
holes (31, 31', 31"), extending from the first end (10') of the runnability component
(10) towards the second end (10") of the runnability component (10),
characterised in that
the runnability component (10) comprises means for adjusting the size of the suction
holes (31, 31', 31 ") or the width of the suction gap.
2. Runnability component according to claim 1, characterised in that it comprises a second suction element (33), which is arranged
on the entry side surface of the runnability component (10), beneath the first sealing
element (20), the second suction element (33) being formed by at least one suction
gap or by at least one row of suction holes, extending from the first end (10') of
the runnability component (10) towards the second end (10") of the runnability component
(10), and optionally comprising means for adjusting the suction through the second
suction element.
3. Runnability component according to claim 1 or 2, characterised in that it comprises at least one second sealing element (19, 19'), preferably a plurality
of second sealing elements, arranged in connection with the lower part of the runnability
component (10).
4. Runnability component according to any of claims 1, 2 or 3, characterised in that the first and/or second sealing element (20, 19, 19') is a mechanical sealing element,
which is provided with means for adjusting the distance of the sealing element to
a turn roll (3) or a drying cylinder (1, 2).
5. Runnability component according to any of preceding claims 1 - 4, characterised in that it comprises a second blowing element (24) arranged in connection with the entry
side surface, beneath the first sealing element (20), the second blowing element (24)
being preferably arranged to blow into a by-pass channel (25) extending from the entry
side surface of the runnability component (10).
6. Runnability component according to any of preceding claims 1 - 5, characterised in that it comprises a tapering suction channel (32) extending from the first end (10') to
the second end (10") and a tapering blow channel (12) extending from the second end
(10") to the first end (10').
7. Runnability component according to claim 6, characterised in that it comprises a tail threading zone (42), which is defined by a dividing wall (40)
arranged inside the runnability component (10), dividing the suction channel (32)
in a tail threading zone (42) and a normal operation zone.
8. Runnability component according to claim 7, characterised in that it comprises integrated control means comprising a first and a second coaxial pipe
(43, 44) with different diameter, the first pipe (43) being in contact the suction
element of the tail threading zone (42) and the second pipe (44) is in contact with
the suction element of the normal operation zone.
9. Runnability component according to any of preceding claims 1 - 8, characterised in that a distribution chamber (4) extending from the first end (10') of the runnability
component (10) towards the second end (10") of the runnability component (10) and
comprising a front plate, is arranged on the entry side surface of the runnability
component (10).
10. Method for drying a paper web or the like in a drying section of a paper machine or
the like, comprising
- supporting a paper web with a drying wire,
- guiding the paper web over a part of a heated surface of a first drying cylinder
(1), turning travel direction of the paper web by using a turn roll (3), and guiding
the paper web over a part of a heated surface of a succeeding second drying cylinder
(2), whereby a pocket space (9) is defined by the first and second drying cylinders
(1, 2), arranged parallel at a distance from each other, and the turn roll (3) arranged
between the first and second drying cylinders (1, 2), parallel with them and having
its axis of rotation on a different level from the axis of the first and second drying
cylinder (1,2),
- arranging, at least partly, a box-like elongated runnability component (10), to
the pocket space, the runnability component (10) having an entry side surface, which
faces the first drying cylinder (1), and an exit side surface, which faces the second
drying cylinder (2), the surfaces (1, 2) being connected to each other at least by
a lower surface, which faces the turn roll (3), whereby the entry side surface, exit
side surface and lower surface delimit the inner volume of the box-like elongated
runnability component (10), runnability component (10) extending from a first end
(10') to a second end (10") in its length direction over the width of the paper web,
- blowing air against the travel direction of the paper web, which is guided from
the first drying cylinder (1) to the turn roll (3), by a first blowing element (11),
which is arranged in connection with the entry side surface of the runnability component
(10) to create a negative pressure space on the entry side surface,
- increasing underpressure in the pocket space (9) by removing air by suction from
a space between the turn roll (3) and the lower surface of the runnability component
(10) into the runnability component (10) with a first suction element, which is formed
by at least one suction gap or by at least one row of suction holes (31, 31', 31"),
extending from the first end (10') of the runnability component (10) towards the second
end (10") of the runnability component (10),
characterised in
- adjusting the size of the suction holes (31, 31', 31") or the width of the suction
gap of the first suction element for controlling the suction through the lower surface
of the runnability component (10).
11. Method according to claim 10, characterised in removing air by suction from the negative pressure space on the entry side surface
by arranging a second suction element (33) on the entry side surface of the runnability
component (10), beneath the first sealing element (20).
12. Method according to claim 11, characterised in adjusting the suction effect of the second suction element (33) for controlling the
suction from the negative pressure space through the entry side surface of the runnability
component (10).
13. Method according to claim 10, 11 or 12, characterised in sealing the gap between the runnability component (10) and the turn roll (3) with
at least one second sealing element (19, 19'), preferably a plurality of second sealing
elements, arranged in connection with the lower part of the runnability component
(10), and optionally adjusting the distance of the first and/or second sealing element
(20, 19, 19') to the turn roll (3) or the drying cylinder (1, 2).
14. Method according to any of preceding claims 10 to 13, characterised in arranging a tapering suction channel (32) in the runnability component (10) extending
from the first end (10') to the second end (10") of the runnability component (10)
and a tapering blow channel (12) extending from the second end (10") to the first
end (10') in order to minimise the pressure losses between the first and the second
end (10', 10") of the runnability component (10).
15. Method according to any of preceding claims 10 to 14, characterised in controlling the web bending at and after the first drying cylinder (1) by distributing
leak air by a distribution chamber (4) arranged on the entry side surface of the runnability
component (10).