U.S. patent application number 10/520487 was filed with the patent office on 2005-11-03 for arrangement for guiding a web and for doctoring a calender roll in a calender.
Invention is credited to Koivukunnas, Pekka, Pullinen, Hannu, Viljanmaa, Mika.
Application Number | 20050242229 10/520487 |
Document ID | / |
Family ID | 8564328 |
Filed Date | 2005-11-03 |
United States Patent
Application |
20050242229 |
Kind Code |
A1 |
Koivukunnas, Pekka ; et
al. |
November 3, 2005 |
Arrangement for guiding a web and for doctoring a calender roll in
a calender
Abstract
An arrangement in a calender for guiding a paper web (W) from
one nip (N) to another nip and for doctoring a calender roll (1, 2)
has a doctor (4) supported by a web (W) guide means (5). The doctor
(4) includes at least one stationary and convex guide surface (51)
which receives the web from one nip (N) of the calender and over
and on which the web is guided towards the other nip of the
calender, so that between the guide surface and the web there is a
medium layer which carries the web.
Inventors: |
Koivukunnas, Pekka;
(Jarvenpaa, FI) ; Viljanmaa, Mika; (Helsinki,
FI) ; Pullinen, Hannu; (Riihimaki, FI) |
Correspondence
Address: |
STIENNON & STIENNON
612 W. MAIN ST., SUITE 201
P.O. BOX 1667
MADISON
WI
53701-1667
US
|
Family ID: |
8564328 |
Appl. No.: |
10/520487 |
Filed: |
July 1, 2005 |
PCT Filed: |
July 8, 2003 |
PCT NO: |
PCT/FI03/00551 |
Current U.S.
Class: |
242/615.12 ;
162/193; 226/97.1 |
Current CPC
Class: |
D21G 1/0086
20130101 |
Class at
Publication: |
242/615.12 ;
162/193; 226/097.1 |
International
Class: |
B65H 023/24 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 9, 2002 |
FI |
20021349 |
Claims
1-18. (canceled)
19. An apparatus forming part of a calender for guiding a web in
the calender from one nip to another nip and for doctoring a
calender roll, the apparatus comprising: a guide having least one
stationary and convex web guide surface extending in a cross
direction which receives the web from a first nip of the calender
and is arranged to guide the web toward a subsequent nip of the
calender; a doctor attached to and supported on the guide; and a
gas medium layer, between the guide surface and the web, which
carries the web.
20. The apparatus of claim 19, wherein the guide further comprises
a first part which serves as the at least partly convex web guide
surface, and a second part opposite to that of the first part;
wherein the doctor comprises a doctor blade which is attached to
the guide second part by a support arm.
21. The apparatus of claim 20, wherein the first part of the guide
is formed of a cylindrical surface.
22. The apparatus of claim 19, wherein the guide further comprises:
a first part comprised of an at least partly convex guide plate, an
outer surface of the at least partly convex guide plate defining
the guide surface with edge zones where the web engages and leaves
the guide surface; and a second part of the guide which extends
between the edge zones of the guide plate in the cross direction,
which second part supports and stiffens the guide.
23. The apparatus of claim 22, wherein the doctor blade is attached
to the second part of the guide and faces a calender roll so that
the doctor blade is directed, while supported by the second part,
towards the calender roll.
24. The apparatus of claim 19, wherein the radius of curvature of
the guide surface is invariable.
25. The apparatus of claim 19, wherein the radius of curvature of
the guide surface varies.
26. The apparatus of claim 19, wherein the gas medium layer is
supplied by a gas film between the web and the guide surface
brought about by the movement of the web from the nip towards the
guide.
27. The apparatus of claim 19, wherein the web guide surface has a
plurality of gas flow passages connected to a source of suction
through which gas is taken from the gas medium layer between the
web and the guide surface.
28. The apparatus of claim 19, wherein the web guide surface has a
plurality of gas flow passages connected to a source of pressurized
gas through which gas is supplied to the gas medium layer between
the web and the guide surface.
29. The apparatus of claim 28, wherein the gas flow passages are
bounded by edges in the shape of a closed periphery.
30. The apparatus of claim 28, wherein the plurality of gas flow
passages are arranged to extend substantially in the cross
direction across the guide surface, and each gas flow passage has
edges bounding each gas flow passage, and said edges are
substantially parallel to and spaced from one another.
31. The apparatus of claim 19, wherein the guide has a shape
selected from the group consisting of a straight tubular roll, a
sectional roll, a bowed one-part take-out or spreader roll, or a
bowed multiple-part take-out or spreader roll.
32. The apparatus of claim 19, wherein the guide surface for the
web is part of a doctor beam to which a doctor blade is attached by
a doctor support arm.
33. The apparatus of claim 19, wherein the convex guide surface has
at least two outwards curved guide surface parts placed one after
the other in a direction defined by web travel.
34. The apparatus of claim 19, further comprising at least one
cross-direction extending air guide member which is attached to the
guide and the air guide member is arranged to converge with the web
as the web moves on to the guide surface to guide gas to the gas
medium layer between the guide surface and the web.
35. A method for guiding a web in a calender from a first nip to a
second nip, comprising the steps of: causing the web to pass from
the first nip defined between a first and a second calender roll to
the second nip over a stationary guide which has a convex web guide
surface which extends in a cross machine direction, the web being
guided such that a gas medium layer is disposed between the web and
the stationary guide, the gas medium layer carrying the web; and
doctoring the second calender roll with a doctor which is attached
to and supported on the stationary guide.
36. The method of claim 35 wherein the stationary guide has a
plurality of passages formed therein, and wherein the gas medium
layer is in communication with the passages.
37. The method of claim 36 wherein the guide has a central cavity
with which the plurality of passages communicate, and further
comprising the step of maintaining a constant pressure on the
central cavity to maintain a to-and-fro flow in the passages into
which gas medium can be conducted to pass a flow through the
passages to a space between the web and the guide surface.
38. The method of claim 36 wherein the guide has a central cavity
with which the plurality of passages communicate, and further
comprising the step of sucking gas medium from the central cavity
to produce a flow through the passages away from a space between
the web and the guide surface.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This application is a U.S. national stage application of
International App. No. PCT/FI2003/000551, filed Jul. 8, 2003, the
disclosure of which is incorporated by reference herein, and claims
priority on Finnish Application No. 20021349, Filed Jul. 9,
2002.
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED
RESEARCH AND DEVELOPMENT
[0002] Not applicable.
BACKGROUND OF THE INVENTION
[0003] The invention relates to paper and equivalent fibrous web
machines and, more specifically, the present invention relates to
an arrangement in a calender for guiding a web, advantageously a
paper web or an equivalent fibrous web, in the calender from one
nip to another nip and for doctoring a calender roll.
[0004] Today, the general aim is to achieve higher running speeds
for the web. As a result of this, the risks of roll vibration
increase in fibrous web machines. Another problem caused by higher
web speeds and partly by roll vibration is the separation of the
web from the roll surface, which is accentuated at the dry end of
the fibrous web machine when the web dries. Thus, in multi-roll
calenders in which the web is guided from one nip between a pair of
calender rolls to another nip between a pair of calender rolls a
guide roll which does not have its own rotation drive, it becomes a
problem, when the web separates from the surface of the guide roll,
that the rotary movement of the guide roll, which is maintained by
the movement of the web in contact with the guide roll, slows down
and may even stop. When the web comes again into contact with the
surface of the guide roll because of the tension caused by the draw
of the web, a moment rotating the guide roll is generated but,
because of the slowness of the guide roll, a speed difference is
produced between the running speed of the web and the
circumferential speed of the guide roll, and friction that
decelerates the movement of the web is caused. In that connection,
there is a considerable risk of a web break.
[0005] Traditionally, the calender roll is kept clean by means of a
doctor, which comprises a doctor blade support means, by means of
which a doctor blade is attached to a doctor beam which extends in
the axial direction of the calender blade, i.e. in the cross
direction, and which is in turn attached by means of support arms
to a calender frame or to a bearing pedestal of a calender roll.
Because of this kind of structural arrangement and in particular
since other devices are also associated with the calender, such as
web guide or reversing rolls and their support structures, the
tending platform of the calender must be placed at a considerable
distance, even too far from the calender. If the doctor is again
placed on the other side of the calender with respect to the
tending platform, maintenance and visual control of the doctor will
become a problem.
SUMMARY OF THE INVENTION
[0006] One object of the invention is to eliminate or at least
substantially reduce the above-mentioned problems and drawbacks
associated with multi-roll calenders of conventional fibrous web
machines. In particular, it is an object of the invention to
provide a novel, more compact structural arrangement for the
calender for doctoring a calender roll and for guiding the web
between nips between calender rolls. In addition, it is an object
of the invention to prevent the web and its guide means from being
only intermittently in contact with each other, which intermittent
contact causes varying friction and increases the risk of a web
break. It is also an object of the invention to reduce the space
needed by the web guide means and the doctor and to assure easier
serviceability of them. Further, an object of the invention is to
create a guide means and doctor arrangement that is substantially
less expensive than the conventional guide means and doctor
arrangements, thus bringing about cost savings.
[0007] These objects are achieved by means of the arrangement
mentioned at the beginning, the new and inventive basic idea of
which arrangement is generally characterized in that the doctor is
supported by a web guide means to which the support means of the
doctor and the doctor blade have been attached and which includes
at least one stationary, outwards curved, i.e. convex, guide
surface which is not in contact with the web and which receives the
web from one nip of the calender and over and on which the web is
guided towards another nip of the calender, so that between the
guide surface and the web there is a medium layer carrying the web,
which layer is advantageously an air film.
[0008] In that connection, it is particularly advantageous in
accordance with the invention that the guide means includes a first
part, which serves as a convex web guide surface which receives the
web from one nip and guides the web in its running direction to a
subsequent nip, that the support means of the doctor blade are
connected with a second part of the guide means, which second part
is in the guide means on the side opposite to that of the first
part, and that the air film covers substantially the entire area of
the first part between the guide surface and the web.
[0009] The guide means is formed of an at least partly convex guide
plate, the outer surface of which forms a guide surface having a
radius of curvature which is selectably variable or invariable. To
stiffen the guide plate, it is recommended that a support or
stiffening element be arranged between the edges or edge zones of
the guide plate, which edges or edge zones extend in the axial
direction of the calender roll, i.e. in the cross direction. In
that case, the support means of the doctor are most appropriately
attached to the support or stiffening element on the side of the
calender roll, so that the doctor blade is directed towards the
calender roll while supported by the support means.
[0010] The guide means forms a convex guide surface, which is
advantageously a cylindrical surface, which is particularly
advantageously a cylindrical surface of a non-rotating web guide or
take-out roll, which cylindrical surface faces away from the
calender roll. In that connection, the support means of the doctor
have been attached to said guide or take-out roll, from which the
doctor projects towards the calender roll. More generally, it may
be noted that, in accordance with the invention, the non-rotating
cylindrical guide means can be a straight tubular roll, a sectional
roll, a bowed one-part take-out or spreader roll, a bowed
multiple-part take-out or spreader roll. In accordance with the
invention, the guide means having a convex web guide surface may
also be a doctor beam of the doctor to which the support arm of the
doctor blade is attached for supporting the doctor towards the
calender roll.
[0011] When the web runs on the guide surface, there is an air
and/or gas film between the web and the guide surface. The movement
of the web from the nip towards the guide means can alone cause
between the web and the guide surface an air and/or gas flow
producing a film.
[0012] To enhance the flow of air to the space between the web and
the guide surface, the arrangement in accordance with the invention
is provided with at least one cross-direction air and/or gas guide
member, which, when attached to the arrangement, is located before
the web guide means in the running direction of the web and guides
the air and/or gas flow to the space between the web and the guide
surface.
[0013] When the running or circumferential speed of the web is low
and the web is porous, a condition may arise in which the movement
of the web does not alone produce such an air and/or gas film
between the guide surface and the web that carries the web to a
sufficient extent. In that case, in addition to the flow coming
with the web, it is possible to conduct air and/or gas between the
web and the guide surface through air and/or gas flow openings
extending through the convex first part of the guide means and
bounded within an edge in the shape of a closed periphery, the
outer surface of which convex first part forms the guide surface of
the web, or through flow passages extending as open to the guide
surface, advantageously in a direction transverse to the running
direction of the web, i.e. in the cross-direction.
[0014] An excessive air and/or gas flow to the space between the
web and the guide surface can cause stagnation of air and thus
formation of a decelerated air and/or gas layer. To prevent this,
part of the air and/or gas film, advantageously the boundary layer
of the film near the guide surface, can be passed to the inside of
the guide means through the air and/or gas flow openings or
passages extending through the convex first part of the guide
means, the outer surface of said part forming the guide surface of
the web. It must be emphasized further that when the aim is to
maintain an uniform pressure distribution over the entire area of
the guide surface, air and/or gas flow(s) in part of the guide
surface through the openings or passages to the inside of the guide
means and in part of the guide surface through the openings or
passages to the space between the guide surface and the web.
[0015] Regarding the advantages of the invention, it may be
mentioned that
[0016] rotating guide rolls can be replaced with guide rolls, guide
beams or the like which are non-moving with respect to the web,
i.e. non-rotating, whereby the quantity of rotating masses is
reduced,
[0017] the web is guided between the nips on a carrying medium
layer, such as a film, over guide rolls, guide beams or the
like,
[0018] support of the web on the guide rolls, guide beams or the
like can be enhanced by additional air and/or gas fed through the
shell of a hollow guide roll, a wall of a hollow guide beam or the
like,
[0019] the shape of the guide rolls, guide beams or the like can be
optimized to provide an even pressure distribution between the
guide surface of the guide roll, guide beam or the like and the
web,
[0020] the doctor can be attached to the guide roll, guide beam or
the like to the side of the calender roll that is doctored, thereby
providing an integrated structure which is economical as to its
costs,
[0021] in the integrated structure the doctor beam can be shaped
into a guide means for guiding the web between nips,
[0022] the integrated structure can be disposed in a small space,
so that, for example, the tending platform of the calender can be
brought closer to the calender and the calender can always be
placed at a location that is easier from the point of view of
servicing and control,
[0023] in addition, devices for monitoring the temperature of the
rolls and/or the moisture content of the fibrous web can be
integrated with the guide roll, guide beam or the like without any
problems.
[0024] In the following, the invention will be described by way of
example through some of its embodiments and applications, yet not
being limited to them, with reference to the appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a schematic view of a first embodiment of the
invention.
[0026] FIG. 1A is an enlarged fragmentary view of the invention of
FIG. 1 taken at the region 1A.
[0027] FIG. 2 is a schematic view of a second embodiment of the
invention.
[0028] FIG. 2A is an enlarged fragmentary view of the invention of
FIG. 2 taken at the region 2 A.
[0029] FIG. 3 is a schematic view of an embodiment of the guide
means.
[0030] FIG. 4 is a schematic view of a second embodiment of the
guide means.
[0031] FIG. 5 is a schematic view of a third embodiment of the
guide means.
[0032] FIG. 6 is a schematic view of a fourth embodiment of the
guide means.
[0033] FIG. 7 is a schematic view of an embodiment of the invention
for guiding air to the space between the web and a guide surface or
vice versa in the web guide means.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] FIGS. 1-7 illustrate schematically the arrangement in
accordance with the present invention, which arrangement has been
arranged in connection with a pair of rolls 1, 2 of a calender for
doctoring one calender roll 2 of the pair of rolls and for guiding
a web W, which is advantageously a paper web or an equivalent
fibrous web, over and on a guide means 5 of the arrangement the
pair of rolls 1, 2, which guide means 5 comprises at least one
outwards curved, i.e. convex, guide surface 51 for the web W. Thus,
the guide surface 51 receives the web W from one nip N and guides
the web forward, most appropriately in the running direction of the
web to the next nip of the calender (not shown in the figures).
When the web runs on the guide surface 51, between the web and the
guide surface there is a medium layer which carries the web and
which is advantageously an air and/or gas film. Most appropriately,
the film extends over the entire area of the guide surface between
the guide surface 51 and the web W. In the following, such a medium
layer is referred to by the definition "air film".
[0035] It must be emphasized that the calender type per se is not
essential from the point of view of the invention, but it is
advantageous that the roll stack of the calender comprises at least
three calender rolls which form at least two successive nips N, so
that the arrangement in accordance with the invention can be
arranged between two nips. It is particularly advantageous that the
arrangement is positioned so that it is at least partly aligned
with the calender roll 2 which is doctored.
[0036] In general, the guide means 5 of the arrangement in
accordance with the invention includes a first part 51, which
comprises at least one stationary, outwards curved, i.e. convex,
guide surface 51 which is not in contact with the web W and which
receives the web from one nip N of the calender and over and on
which the web is guided towards another nip of the calender. In
addition, the guide means 5 includes a second part 52 which
supports a doctor 4 and to which have been attached support means,
or a support arm, 42, 43, 44 of a doctor blade 41 such that the
doctor blade 41 is directed towards the calender roll 2 while the
doctor blade is supported by the support means 42, 43, 44. These
first part 51 and second part 52 of the guide means are typically
on the opposite sides of the guide means 5.
[0037] According to the embodiment shown in FIG. 1, the first part
51 of the guide means 5 is formed of a convex guide plate or guide
the outer surface of which forms a convex and non-rotating guide
surface 51 directed away from the calender. The shape of the guide
surface 51 can be selected freely, so the radius of curvature may
be selectably variable or invariable. It is recommended that the
radius of curvature of the convexity of the guide surface shall be
variable to provide a uniform pressure distribution between the
guide surface and the web. It is also recommended that the curved
guide plate is stiffened by means of a support or stiffening
element extending in the axial direction of the calender roll 2
which is doctored, i.e. in the cross direction, which element is
advantageously a plate, which is attached between the
cross-direction free edges or edge zones 53 of the curved guide
plate to form the second part 52 that makes the guide means
stronger. In such a guide means 5 provided with a support or
stiffening element it is advantageous to attach the support means
42, 43, 44 of the doctor blade 41 to the support or stiffening
element of the guide means 5 on the side of the calender roll 2
which is doctored, so that the doctor is directed, while supported
by the support means, towards the calender roll 2 to be
doctored.
[0038] In connection with the embodiment shown in FIG. 1 it may be
noted that the first part 51 and the second part 52 of the guide
means can form together a doctor beam for the doctor 4. In that
case, the web W runs over the doctor beam on an air film from a nip
N to a subsequent nip and the doctor 4 has been attached to the
wall portion of the doctor beam facing towards the calender. It
must be emphasized that the cross-sectional profile of the almost
semicircular hollow beam shown in FIG. 1 may be a full circle as
shown in FIGS. 2 and 6 or a quadrangular parallelepiped as shown in
FIG. 7. In addition, it is recommended that the radius of curvature
of the convexity of the guide surface 51 formed of the first part
shall be variable to provide a uniform pressure distribution
between the guide surface and the web.
[0039] In accordance with the embodiment shown in FIG. 2, a guide
means 5 is formed of a cylindrical piece, so that a first part 51
forms, in accordance with the basic idea of the invention, an
outwards curved, i.e. convex, and non-rotating guide surface 51,
which is a cylindrical surface facing away from the calender. In
accordance with one embodiment, the non-rotating cylindrical
surface is the cylindrical surface of a guide or take-out roll of
the web W, which cylindrical surface faces away from the calender
roll. In such a guide means formed of a cylindrical piece, the half
of the cylindrical piece facing towards the calender forms a second
part 52 of the guide means 5, support means 42, 43, 44 of a doctor
blade 41 being attached to the second part 52 such that a doctor 4
projects from the guide or take-out roll of the web W formed of a
cylindrical piece towards a calender roll 2 which is doctored.
[0040] In accordance with the basic idea of the invention, an air
or gas flow that produces an air film between the web W and the
guide surface 51 can be brought about by the movement of the web
alone from the nip N towards the guide means 5.
[0041] When the running or circumferential speed of the web W is
low and/or the web is porous, a condition may arise in which the
movement of the web does not alone produce such an air film between
the guide surface 51 and the web W that carries the web to a
sufficient extent. In that case, in addition to the air and/or gas
flow coming with the web, it is possible to conduct air, which is
illustrated with curved arrows in FIGS. 3-5, to the space between
the web W and the guide surface 51
[0042] through air flow openings 6 which are bounded, as shown in
FIGS. 3 and 5, as open to the guide surface 51, within an edge in
the shape of a closed periphery, or
[0043] through flow passages 6 which extend, as shown in FIG. 4, as
open to the guide surface 51, advantageously in a direction
transverse to the running direction of the web, i.e. in the
cross-direction, across the guide surface 51, so that the edges
defining the air flow passage 6 are most appropriately parallel to
and spaced from each other,
[0044] which air flow openings and passages extend through the
convex first part of the guide means 5, the outer surface of which
convex first part forms the guide surface 51 of the web.
[0045] Regarding the guide surface 51 provided with openings or
passages 6, it is noted further that in order to maintain a uniform
pressure distribution between the web W and the guide surface 51,
the flow of air or gas through the openings or passages can also
take place such that the flow is directed in part of the guide
surface from between the web W and the guide surface 51 to the
inside of the guide means 5 and in part of the guide surface from
inside the guide means 5 to the space between the web W and the
guide surface 51.
[0046] As illustrated in FIGS. 1, 2, 6 and 7, the flow of air to
the space between the guide surface 51 and the web W can be assured
and enhanced by providing the arrangement with at least one
cross-direction air guide member 54. Such an air guide member 54 is
attached to the arrangement, to achieve the desired effect, in the
running direction of the web W before the guide means of the web
such that it guides the air and/or gas coming with the movement of
the web W to the space between the web and the guide surface 51. In
the embodiments shown in FIGS. 1 and 2, the air and/or gas guide
member is on the same side of the guide means 5 as the doctor 4 and
it is situated between the doctor 4 and the web W, so that it forms
a wing-like air guide member.
[0047] Reference is made to FIG. 6 and it is noted that in
connection with FIGS. 1-5 above the invention has been described by
means of embodiments and applications in which the first part of
the guide means comprises only one convex guide surface 51. When
the height of the guide means 5 and, thus, the height of the guide
surface is not greater than the diameter of the calender roll 2
which is doctored and which is at least partly aligned with the
guide means, the angular deviation of the change of direction
experienced by the web W on the guide surface 51 is
.ltoreq.180.degree.. It shall be emphasized that the guide means 5
comprising one guide surface is, however, not a necessity from the
point of view of the operation of the invention but, in accordance
with the invention, the convex guide surface 51 may comprise two or
even more outwards curved, i.e. convex, guide surface parts 511,
512 placed one after the other. When the guide means 5 is
substantially in the shape of a parallelepiped as shown in FIG. 7
and has two guide surface parts 511, 512 and when the height of the
guide means 5 does not exceed the diameter of the calender roll 2
which is doctored and which is at least partly aligned with the
guide means, the angular deviation of the change of direction
experienced by the web W on both guide surface 51 is
.ltoreq.90.degree..
[0048] Reference is made to FIGS. 3-6, which show the guiding of
air and/or gas in the guide means 5 to the space between the web W
and the guide surface 51 and vice versa from between the web and
the guide surface to the inside of the guide means 5. An air and/or
gas excessive flow to the space between the web W and the guide
surface 51 can cause stagnation of air and/or gas and, thus,
formation of a decelerated air film. To prevent this, part of the
air film, advantageously the boundary layer near the guide surface
51 of the air film, can be passed to the inside of the guide means
5 through the air flow openings or passages 6 extending through the
convex first part of the guide means 5, the outer surface of which
first part forms the guide surface 51 of the web W. In the
embodiment of FIG. 7, the guide means has a central air cavity,
[0049] in which a constant pressure can be kept to maintain a
to-and-fro flow in the flow openings or passages 6,
[0050] into which air and/or gas can be conducted to pass a flow
through the flow openings or passages 6 to the space between the
web W and the guide surface 51, or
[0051] from which air can be sucked to produce an air flow through
the air flow openings or passages 6 away from the space between the
web W and the guide surface 51.
[0052] Above, the invention has been described only by way of
example by means of some of its embodiments and applications
considered to be advantageous. It shall be understood that the
invention is not meant to be limited to these only, but variations
and modifications are feasible within the scope of protection of
the inventive idea defined in the appended set of claims.
* * * * *