Note: Descriptions are shown in the official language in which they were submitted.
~11394`~
93-555
8~Z2 PR~BB AND ~T~OD FOR COATIN~ ~ W~ TH~R~IN
BA~ROUND OF ~a~ INV~NTION
The present invention relates to a size press, comprising a
first roll which is mounted ~igidly on the frame of the size press,
and a second roll which forms a size-press nip with the fir~t roll.
The second roll is mounted at a level higher than the level of the
first roll and on a pivotable loading arm that is supported on a
transverse shaft of the frame of the size press. The rolls that
form the size-press nip are provided with coating devices, e.g., of
the short-dwell type, for spreading films of coating agent onto
faces of the rolls. The coating agent is transferred from the roll
faces in the nip, and adheres to the paper web or equivalent that
passes through the nip. The loading arm is pivoted by means of
loading cylinders so as to produce the desired pressure level in
the nip and to open the nip for threading the web and for
replacement of the rolls, when needed. The paper web or equivalent
is guided by a guide roll and passed into the nip and is passed out
of the nip over a spreader roll or an air-turning device. A method
for coating a paper web using the size-press is also described.
An important objective of the surface sizing of paper is, in
view of improving the printing qualities of the paper, to increase
- the bonds between the fibers by using binding agents soluble in
water, most commonly starch. The surface-treatment device most
commonly used in s~rface sizing is a size press. A typical prior
art size press comprises size press rolls mounted in a conventional
way on the frame of the press and which form a nip with one another
21~3~
such that the paper web is passed through the nip. In a
conventional mode of adding size to the paper face, a size pond is
arranged in a gap placed before the nip and formed by the rolls
such that the paper web runs through the pond. The web is guided
by a guide roll and introduced into the nip so that the web is
guided into the nip in the direction of the tangent of each press
roll as precisely as possible.
A further development of the prior art size presses that make
use of the size pond principle consists of film-size presses in
which each roll in the size press is provided with a coating
device, preferably of the short-dwell type. This type of devics
spreads and smoothes a size film, or equivalent, onto the roll
faces. The films on the roll faces are then transferred in the
roll nip to the paper web to be treated. In addition to surface
sizing, such film-size presses may also be used for the pigmenting
of paper.
It is a conventional construction in size presses that a lower
one of the size press rolls that form the size-press nip is mounted
on the size-press frame in a stationary position, whereas the other
roll, i.e., the upper size-press roll, is mounted on a particular
pivotable loading arm which is linXed on the frame of the size
press. Between the size-press frame and the loading arm, loading
cylinders are arranged, by whose means the desired nip pressure can
be produced in the size-press nip. Also, by means of the
cylinders, the nip can be opened for tail threading of the web and
further, for replacement of the rolls. In the size presses
operating with the size-pond principle, the size-press rolls are
usually arranged so that the plane that passes through the axes of
the rolls, i.e., the nip plane, is substantially horizontal or only
slightly inclined from the horizontal plane. By means of such an
arrangement in which the nip plane is substantially horizontal, it
is possible to form a suitable size pond in the gap placed before
- 2~394~
the roll nip.
The film size presses that have been developed further from
these size presses operating with the size-pond principle, and in
which the size-press rolls are provided with particular coating
devices, have a substantially similar, basic construction in the
conventional technology. Thus, also in these prior art film-size
presses, the size-press rolls are arranged so that the angle
between the rolls, i.e., the angle of the nip plane in relation to
the horizontal plane, is very small, generally of an order of only
from about 15 to about 30O. One such device is described, e.g.,
in the assignee's Finnish Patent No. 87,475 of earlier date. In
the device shown in FI 87,475, the paper guide roll, over which the
web is passed into the nip, is arranged above the lower size-press
roll. The lower size-press roll is attached to a pivot arm which
is linked pivotally on the frame of the size press by ~eans of a
transverse pivot shaft so that, for replacement of the roll, the
paper guide roll can be pivoted into a position that has been
shifted aside from the running position. One particular drawback
of such a device is the complicated construction, and, as a result
of this, a comparatively high cost.
Ordinarily, the paper guide roll is attached to a frame of its
own, which is separate from the frame of the size-press rolls.
Owing to the relative location of the size-press rolls, it has been
necessary to construct the frame of the paper guide roll to be
quite massive, because it is necessary to support the paper guide
roll above the size press. It has also been necessary to support
the paper guide roll above the size press in order that it should
be possible to make the web pass into the nip parallel to the
tangent of each press roll as precisely as possible. In such an
embodiment, it has not been possible to attach the paper guide roll
to its frame directly, but generally, it has been attached by means
of an articulated pivot arm linked to the frame construction in
--3--
-
2113~4 3
order to facilitate the lifting of the guide roll out of the way
when replacing the press rolls. Thus, in these prior art devices,
it is a problem that they require a considerable amount of space
both in the machine direction and in the vertical direction, in
view of the pivoting of the quide roll. ~uring pivoting or lifting
of the guide roll, the paper guide roll and its pivot arm rise to
a very high level, which is, in connection the prior art devices,
a factor determining the height of the paper mill hall.
Owing to the fact that the angle of the nip plane of the size-
press rolls in relation to the horizontal plane has been verylittle in prior art devices, i.e., of an order of only from about
15~ to about 30, it has been necessary to pass the web out of the
nip so that the web follows the face of the upper roll over some
distance. This has resulted in a significant drawback in that the
web is separated from the upper roll indefinitely, and often causes
so-called "web-stealing", i.e., a tendency of the web to follow the
lower roll. This produces a fluttering movement in the web as the
web is alternatingl~ separated from, and adheres to, the lower
roll. This has had the consequence, especially in pigmenting
processes, that the quality of the coating applied to the web has
deteriorated, and a fully even coating is not produced.
In view of improving the web separation properties, in some
cases, air-blow boxes have been used underneath the size press
rolls in an attempt to separate the web from the faces of the size-
press rolls by means of the air jets being directed from the air-
blow boxes. Since the air-blow boxes are placed underneath the
size-press rolls, contamination of the air-blow boxes has, however,
constituted quite an significant drawback. The eame drawback al~o
applies to the web guide roll placed underneath the nip. In
particular in the case of pigmenting processes, for reasons of
guality, it would be optimal if the web could be taken out of the
nip at an angle of about 90 in relation to the nip plane. In such
~. : . , , : :
:, ...;
.,,., . ~ ~ .
;..'::
2~ 3~4~
a case, the quality of the coating would become as good as
possible.
Further, it is a drawback of the prior art devices tha* the
size-press rolls have a different hardness, i.e., the lower size-
press roll and the upper size-press roll are provided with coatings
of different hardness. This emanates from the fact tha*, after ~he
nip, the web initially follows the upper roll and, nevertheless,
a*tempts to adhere to the lower roll. In the prior art, the upper
size-press roll has generally been harder than the lower roll.
Thus, for the size press, it has been necessary to keep spare rolls
of two types in stock, i.e., some for replacement of the upper roll
and others for the replacement of the lower roll. This drawback
has constituted quite an important cost factor, and in some cases
also results in a problem of the space needed to store a sufficient
supply of both types of rolls.
O~JBCT~ AND B~NARY OF T~B INY~NTION
Accordingly, it is an object of the present invention to
provide a new and improved size press by whose means the drawbacks
associated with the prior art devices are substantially eliminated.
It is another object of the present invention to provide a new
and improved size press by whose means the coating result can be
improved over that obtained by the prior art devices.
It is yet another object of the present invention to provide
a new and improved size press in which two size-press rolls having
a substantially equal hardness can be utilized.
In view of achieving the objects stated above, and others, in
the present invention, the pair of rolls that form the size-press
nip are arranged in such a way in relation to one another that the
nip plane passing through the rolls ~orms an angle o from about
35 to about 120, preferably from about 50 to about 60, in
relation to the horizontal plane. The web is arranged to be passed
.. : .
'.: ~: .
' , ~ ` .
:, : ' ,
:.:
2~13~'~ u~
into the nip at an angle of substantially about 9o in relation to
the nip plane and to be passed out of the nip at an angle of
substantially about 90 in relation to the nip plane.
By means of the present invention, compared with the prior art
device, a number of advantages are obtained, of which, e.g., the
following should be mentioned in this connection. In the present
invention, the running line of the web can be made very smooth,
which results in easy tail threading and good runnability of the
web. The web can be separated from the nip at an angle of about
90 without any extra support members, such as air-blow boxes or
equivalent. In connection with the present invention, it is,
however, possible to use such support members if they are
considered necessary, or desired.
AB the web is passed out of the nip substantially at an angle
of about gOc, the quality of the coating is very good, in
comparison to the coating results of the prior art arrangements. ~ ;~
In a size press in accordance with the present invention, it
is possible to use rolls of equal hardness, unlike the prior art
devices in which the one-sided separation of the web required rolls
of different hardness. Thus, for the size press of the present
invention, a lower number of spare rolls are needed than in the -
prior art devices. The present invention enables the paper guide
roll that precedes the nip to be mounted on a separate, stationary
frame so that it does not hamper the replacement of the nip rolls
in any way. In the size-press in accordance with the present
invention, the nip is constructed to be opened in two stages so
that the first open position is a normal tail threading position,
whereas the second open position is a roll replacement position.
In this manner, the lower nip roll can be replaced even if the
upper roll remains in its position.
It is a further advantage of the present invention that it is
possible to minimize the entire space that is required by the size
,'.;;.,", ~ : ~; :
211394 ~
press in the longitudinal direction of the machine, i.e., in the
machine direction.
In the method for coating a paper web in a size press in
accordance with the present invention, a first roll is arranged on
a frame of the size press and a second roll is arranged to form a
size-press nip with the first roll ~uch that a nip plane between
the first and second rolls forms an angle of from about 35 to
about 120~ in relation to a horizontal plane. Coating devices are
arranged to spread a film of coating agent onto faces of the first
and second rolls. The paper web is passed through the nip such
that the coating agent is transferred in the nip from the faces of
the first and second rolls to the paper weh. The web is passed
into the nip at an angle of substantially about 90 in relation to
the nip plane, and guided out of the nip at an outlet angle of
lS substantially about goo in relation to the nip plane. The second
roll may be mounted on a loading arm which is supported on a
transverse shaft on the frame. Loading cylinders are then arranged
to pivot the loading arm to produce the deeired pressure level in
the nip, to open the nip for threading of the web and for
replacement of the rolls, when needed. The outlet angle is
adjusted by means of a spreader roll or an air-turning device.
Further advantages and characteristic features of the
invention will come out from the following detailed description of
the invention with reference to the accompanying drawings.
BRIEF DE8CRIPTION OF T~E DRA~ING8
The following drawings are illustrative of embodiments of the
present invention and are not meant to limit the scope of the
invention as encompassed by the claims.
Figure 1 is a fully schematic side view of a size press in
accordance with the present invention and used in a method in
accordance with the invention.
:, ~: :: -
2~ 1394~
Figure 2 is a schematic sectional view of a coating device of
the short-dwell type used in the size press and method in
accordance with the present invention.
Eigure 3 is a schematic illustration of the running of the web
line in the size press and method in accordance with the present
invention.
Figure 4 is an illustration corresponding to Fig. 1 of the
size press having contact free dryers are arranged in the path of
the web coming out of the dryer before the drying cylinder.
Figure 5 is a schematic illustration of a embodiment having
air-turning devices arranged to turn, spread and guide the weh
after the nip.
DETAILED DE~CRIPTION OF T~B INV~NTION
In Fig. 1, a size press in accordance with the present
invention is denoted generally with reference numeral 10. The size
press 10 compriseæ a size-press frame 11 which is mounted on a base
B. Size-press rolls 12,16 are mounted on base B in a conventional
way. A bearing housing 13 of the first size-press roll 12, i.e.,
the lower roll, is mounted directly on the frame 11 of the size
press and preferably attached to it rigidly. Bearing housing 17 of
the second size-press roll, i.e., the upper roll, is mounted on a
loading arm 19 which is linked pivotally to the size-press frame 11
- by means of a pivot shaft 20 arranged transverse to the machine
direction. Loading cylinders 22 are arranged between the loading
arm 19 and the size-press frame 11, by whose means the loading arm
19 is loaded so as to produce a nip pressure of the desired
magnitude in the nip N formed by the lower roll 12 and the upper
roll 16. Either one of the size-press rolls 12,16, preferably the
upper roll 16, or alternatively both of the size press rolls 12,16,
may be variable-crown rolls so that the pressure in the nip N can
be brought to a desired level in the transverse direction of the
~3~4~1
machine.
Each size-press roll 12,16 is provided with a coating device
15,21, e.g~, of the short-dwell type, by whose means size films, or
equivalent coating-agent films, are applied andismoothed onto faces
14,18 of the rolls 12,16, respectively. When the web W runs
through the nip N, the films of coating agent are transferred from
the faces 14,18 of the roll 12,16 to the web W', i.e., the coated
web. The uncoated web W is passed into the size-pre6s nip N over
a guide roll 23 which is mounted on a stationary frame 24 installed
on the base B. After the size-press nip N, the coated web ~' is
passed over a spreader roll 25 and further to the dryer section,
whose first drying cylinder is denoted with reference numeral 26.
The construction and the operation of the coating devices 15,21 of
the short-dwsll type are described in more detail in the
description related to Fig. 2. The means of support of the
spreader roll 25 are not described in more detail in this
application; however, any known roll support means can be utilized.
Fig. 2 is a more detailed schematic sectional view of the
construction of one specific coating device of the short-dwell type
used in a size press in accordance with the present invention.
Other short-dwell coating devices may also be applied in accordance
with the present invention. Fig. 2 shows the coating device lS of
the short-dwell type placed in connection with the first size-press
- roll 12 in the size press 10. It is obvious that the coating
device 21 placed in connection with the second size-pxess roll 16
may have a construction of a corresponding or related type. In the
coating device 15 in accordance with the invention, as is also the
case in coating devices of the short-dwell type in general, the
application of the coating-agent film onto the face 14 of the roll
12 is carried out so that, in the coating device 15, the coating
agent is supplied preferably under pressure, into a coating-agent
chamber 153. Coating agent chamber 153 is defined by a coating
2113940
member 151, a front edge 152 of the coating-agent chamber 153, the
face 14 of the size-press roll, and lateral seals (not shown).
The front edge 152 of the pressurized coating-agent chamber
153 may be similar to that shown in Fig. 2, so that the front edge
152 rests against the roll face 14. Alternatively, there may be a
gap between the front edge 152 of the coating-agent chamber and the
roll face 14, through which overflow of the coating agent passes
from the coating-agent chamber 153 into a collecting basin.
In the embodiment shown in Fig. 2, the coating member that is
used is a coating bar 151 which is mounted rotatably in a bar
cradle 154, made of, e.g., polyurethane or an equivalent material.
The bar cradle 154 is mounted in a holder 155 and is secured in its
position by a fastening device 156. A profile rib 158 is arranged
behind the bar cradle 154 of the coating member, which rests
against the rear face of the bar cradle 154 by the intermediate of
a loading hose 157, i.e., the loading hose 157 is interposed
between the profile rib 158 and the bar cradle 154. Adjusting
spindles 159 are fixed to the frame of the coating device 15, by
means o~ suitable fixing means (not shown). A number of such
spindles are arranged to be uniformly spaced in the transverse
direction of the machine. For each adjusting spindle 159,
preferably spindle motors (not shown) are mounted on the frame of
the coating device 15. By displacing the adjusting spindles 159,
- the profile bar 158 is pulled and/or pushed so that the pro~ile bar
158 can be deflected as desired to coat the face 14 of the roll 12
in the desired way.
The coating device 15 as shown in Fig. 2 is provided with a
coating-agent supply pipe 161 arranged transverse to the machine
direction. The coating agent is supplied into the pipe 161 from
one end or, preferably, from both ends of the supply pipe 161. The
supply pipe 161 is provided with a large number of holes or
equivalent nozzles 162 in the transverse direction of the machine.
--10--
2-1 ~3~
~he holes or nozzles 162 form a throttle for the flow of the
coating agent. Thus, the coating agent is passed out of the supply
pipe 161 through the nozzles 162 and into the coating-agent chamber
153. The front edge 152 of the coating-agent chamber 153 is
installed in its holder 160 in a conventional manner. Other means
to supply and apply coating agent onto the face 14 of the roll 12
may also be used in the present invention.
The embodiment æhown in Fig. 2 is one example of a coating
device 15 of the short-dwell type used in a size press 10 in
accordance with the present invention. Other constructions of the
coating device may show even considerable variation within the
scope of the invention. It is a common feature of the coating
devices 15 of the short-dwell type that the device comprises a
pressurized coating-agent chamber 153, which is defined by the
15coating member 151, the front edge 152 of the coating agent
chamber, the roll face 14, and lateral seals (not shown).
In the following, in addition to Figs. 1 and 2, reference is
also made to Fig. 3. As shown in Fig. 1 and especially in Fig. 3,
the size-press rolls 12,16 are mounted in the size press in a
20manner different from the conventional arrangement, so that the
angle a of the nip plane T-T, which runs through the central axes
of the size press rolls 12,16, in relation to the horizontal plane
S is substantially larger than in the prior art devices. In the
present invention, the angle ~ is in a range from about 35 to
25about 120, advantageously from about 50O to about 60~, preferably
about 55. In contrast to the present invention, in the prior art
devices, the angle of the nip plane in relation to the horizontal
plane is smaller, generally of an order of only from about 15 to
about 30.
30The web W is passed into the nip N guided by the guide roll
23, so that the web W is guided into the nip N substantially
parallel to the tangent of each press roll 12,16 as precisely as
-11- :'
: : ~ ' ,. ':
.! ' : : , .' . . ' '
:':"' : . ' ~ ~.: . `
''. " : " ,
- 2~13~4~
possible. Thus, the web W is passed into the nip N substantially
at an angle of about 90D in relation to the nip plane T-T. The
; inlet angle of the web running line in relation to the nip plane
is, in Fig. 3, denoted with reference character Bl.
In the embodiment of Fig. 3, the coated web W' is passed from
the nip N over the spreader roll 25 to further processing. As
0 stated in the description above, especially in pigmenting
proces es, it is preferable to pass the coated web W' out of the
nip N as precisely as possible at an angle of about 90 in relation
to the nip plane T-T. As shown clearly in the figures, in the
i present invention this objective is achieved so that the coated web
W' can be passed out of the nip N at an angle B2 which is about 90
+ 7, i.e., there is a small allowance on both sides of 90. The
variation in the outlet angle B2 of the web line is produced so
that the position of the spreader roll 25 is adjustable in the
vertical direction. This adjustability can be arranged in a simple
way by conventional means. By means of the adjustability of the
position of the spreader roll 25, it is possible to regulate the
outlet angle A2 of the web line in relation to the nip plane T-T in
the desired way. Such a need of adjustment may arise, for example,
when the properties of the upper face and the lower face of the web
W to be coated differ from one another, e.g., in respect of the
porosity or smoothness desired. These properties of the web W
affect the adhesion between the web W and the faces 14,18 of the
rolls 12,16, respectively.
The size press 10 shown in Fig. 4 is similar to that already
described with reference to Fig. l. The embodiment shown in Fig.
4 differs from that shown in Fig. 1 in that the web W' is passed
from the size-press nip N onto a first drying cylinder 26 in the
dryer section. Before the drying cylinder 26 and after a spreader
roll 35, the web W' is dried by means of contact-free dryers 36,37
arranged. Contact-free dryers suitable for this purpose are, for -~
' ~
-12-
. : . :
',: !'
~, 2~l3~4a
example, convection dryers, infrared dryers and/or air dryers, such
as hot-air blow dryers. Contact-free dryers 36,37 are advantageous
and necessary, especially when large coating quantities are applied
onto the web W' by means of the ~ize press 10. As shown in Fig. 4,
dryer 36 is arranged to operate in an opposite direction to that of
dryer 37, e.g., to thereby dry both ~ides of the web.
In Fig. 4, it is shown further that, in the guiding of the web
W' onto the drying cylinder 26, air blowing by means of an air-
turning device or an equivalent blow box 38 is used as an aid.
Blow box 38 is arranged after dryers 36,37.
The embodiment shown in Fig. 5 differs from that shown in Fig.
4 in that, in the embodiment of Fig. 5, the spreader roll 35 as
shown in Fig. 4 has been completely substituted for by air-turning
devices 38a,38b, by whose means the web W' is turned and guided
onto the first drying cylinder 26 in the dryer section. In the
embodiment of Fig. 5, it is shown further that air blows coming out
of blow boxes 3~c,38d, or equivalent air-turning devices which
provide a directed flow of air, are arranged to support the web W'
and are directed at an angle to the running direction of the web.
In the embodiment of Fig. 5, it is also possible to use contact-
free web W' dryers similar to those described in relation to Fig.
4. The air-turning devices 38a,38b,38c and 38d cooperate to turn
the web in desired directions. -
In a size press 10 constructed in the manner described above,
rolls of equal hardness can be used as the upper and lower rolls
12,16. The rolls 12,16 can be provided with identical coatings, in
which case a high number of spare rolls are not needed as were
needed in the prior art devices in which the upper and lower rolls
have different coatings.
Replacement of the rolls 12,16 can also be carried out in a
simple way in a size press 10 in accordance with the present
invention. As shown in particular in Figs. 1, 4 and 5, by pivoting
-13-
.: . .
,.. . ~
- 2~ 4~
the loading arm 19, the rolls 12,16 can be brought into a roll
replacement position in which the lower roll 12 can also be
replaced readily even if the upper roll 16 were in its position.
The nip N is prePerably constructed so that it is opened in two
stages, so that, by means of the loading arm 19 and the loading
cylinders 22, the upper roll 16 can be pivoted firet into a normal
tail threading position, in which the tail threading of the web W
can be carried out very easily and simply because of the
substantially straight web line. After the catches of the tail
threading position (not shown) have been opened, the nip N can be
opened to the roll replacement position.
The examples provided above are not meant to be exclusive.
Many other variations of the present invention would be obvious to
those skilled in the art, and are contemplated to be within the
scope of the appended claims.
-14-
