U.S. patent application number 11/498470 was filed with the patent office on 2007-02-08 for machine for the production of tissue paper.
Invention is credited to Rogerio Berardi, Danilo Oyakawa, Thomas Scherb, Luiz Carlos Silva.
Application Number | 20070029061 11/498470 |
Document ID | / |
Family ID | 36975255 |
Filed Date | 2007-02-08 |
United States Patent
Application |
20070029061 |
Kind Code |
A1 |
Scherb; Thomas ; et
al. |
February 8, 2007 |
Machine for the production of tissue paper
Abstract
This invention relates to a machine for the production of a
tissue paper web with a forming section in which the tissue paper
web is formed from a pulp suspension on a skin and with a nip which
is formed between the cylindrical surface of a drying cylinder, in
particular a Yankee drying cylinder, and a mating surface and
through which the tissue paper web can be conveyed together with
the skin. The configuration of the machine is variable such that,
depending on the quality of the tissue paper to be produced, for
example its absorbency or tear resistance, the skin is either a
three-dimensionally structured skin, a structured mesh, a
non-structured skin, or a felt, whereby the mating surface is
formed by the cylindrical surface of a press roller which includes
a suction zone and in which provision is made for bores
communicating with the suction zone.
Inventors: |
Scherb; Thomas; (Sao Paulo,
BR) ; Silva; Luiz Carlos; (Sao Paulo, BR) ;
Berardi; Rogerio; (Sao Paulo, BR) ; Oyakawa;
Danilo; (Sao Paulo, BR) |
Correspondence
Address: |
TAYLOR & AUST, P.C.
142 SOUTH MAIN STREET
P. O. BOX 560
AVILLA
IN
46710
US
|
Family ID: |
36975255 |
Appl. No.: |
11/498470 |
Filed: |
August 3, 2006 |
Current U.S.
Class: |
162/289 ;
162/303; 162/304; 162/358.1; 162/363 |
Current CPC
Class: |
D21F 3/10 20130101; D21F
3/0272 20130101; D21F 11/145 20130101; D21F 11/14 20130101; D21F
3/0209 20130101; D21F 3/0281 20130101 |
Class at
Publication: |
162/289 ;
162/303; 162/304; 162/363; 162/358.1 |
International
Class: |
D21F 9/00 20070101
D21F009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 5, 2005 |
DE |
10 2005 036 891.3 |
Claims
1. A machine for the production of a tissue paper web, comprising a
skin being one of a three-dimensionally structured skin, a
structured mesh, a non-structured skin and a felt; a drying
cylinder having a cylindrical surface; a press roller having a
mating surface that is formed by a cylindrical surface of said
press roller, said cylindrical surface having a plurality of bores
therein; and a forming section in which the tissue paper web is
formed from a pulp suspension on said skin, between said
cylindrical surface of said drying cylinder and said mating surface
a nip is formed, through said nip the tissue paper web is conveyed
together with said skin, a configuration of the machine being
variable such that depending on said quality of the tissue paper to
be produced, said quality being at least one of absorbency and tear
resistance, said skin altered between said three-dimensionally
structured skin, said structured mesh, said non-structured skin and
said felt, said mating surface being formed by said cylindrical
surface of said press roller which includes a suction zone, at
least some of said plurality of bores communicating with said
suction zone.
2. The machine of claim 1, wherein said three-dimensionally
structured skin is used for said production of tissue paper with
higher absorbency and said non-structured skin for said production
of tissue paper with lower absorbency.
3. The machine of claim 1, further comprising a dewatering
apparatus positioned between said forming section and said nip,
said dewatering apparatus being operated in relation to said nip
such that the tissue paper web is dewatered by said dewatering
apparatus to a greater extent during operation with said structured
skin and to a smaller extent during operation with said
non-structured skin than by said nip.
4. The machine of claim 3, wherein during operation with said
non-structured skin the tissue paper web is not conveyed through
said dewatering apparatus.
5. The machine of claim 1, wherein said bores are arranged and
constructed such that the tissue paper web downstream from said nip
when operating the machine with one of said structured mesh and
said felt has a dry content of 31% or more.
6. The machine of claim 1, wherein said bores have a diameter of
less than 3.8 mm.
7. A machine for said production of a tissue paper web, comprising:
a drying cylinder having a cylindrical surface; and a press roller
having a cylindrical surface that serves as a mating surface to
said drying cylinder, said cylindrical surface of said press roller
having a plurality of bores therein, a nip being defined between
said cylindrical surface of said drying cylinder and said mating
surface, the tissue paper web being conveyed through said nip
together with a permeable skin between said skin and said
cylindrical surface, said press roller having a suction zone, at
least some of said plurality of bores communicating with said
suction zone, said bores having a diameter of less than 3.8 mm.
8. The machine of claim 7, further comprising a forming section for
forming the tissue paper web from a pulp suspension and said skin
arranged such that the tissue paper web is formed in said forming
section on said skin and is conveyed through said nip.
9. The machine of claim 8, further comprising a dewatering
apparatus arranged between said nip and said forming section.
10. The machine of claim 7, wherein said bores have a diameter of
one of equal to and less than 3.5 mm.
11. The machine of claim 10, wherein said diameter of one of equal
to and less than 3.0 mm.
12. The machine of claim 11, wherein said diameter of one of equal
to and less than 2.7 mm.
13. The machine of claim 7, wherein said plurality of bores have a
total open area of between 16% and 30% of said cylindrical surface
area.
14. The machine of claim 13, wherein said total open area is
between 18% and 26%.
15. The machine of claim 14, wherein said total open area is
between 20% and 22%.
16. The machine of claim 7, wherein said bores on said cylindrical
surface of said press roller form a regular pattern in at least
some areas.
17. The machine of claim 7, wherein some of said plurality of bores
are blind bores which are non-communicating with said suction zone,
said blind bores having a diameter of one of equal to and less than
2.7 mm.
18. The machine of claim 17, wherein said diameter is one of equal
to and less than 2.4 mm.
19. The machine of claim 17, wherein said blind bores on said
cylindrical surface are arranged between said bores in at least
some areas.
20. The machine of claim 7, wherein said bores and said blind bores
on said cylindrical surface of said press roller form a regular
pattern in at least some areas.
21. The machine of claim 7, wherein said bores or said bores and
said blind bores on said cylindrical surface are arranged along a
multiplicity of mutually parallel lines.
22. The machine of claim 7, wherein said press roller is
driven.
23. The machine of claim 7, wherein said skin is a structured
mesh.
24. The machine of claim 23, wherein said structured mesh is a TAD
mesh.
25. The machine of claim 23, wherein a side of said structured mesh
facing the tissue paper web includes depressed regions and raised
regions relative to said depressed regions.
26. The machine of claim 25, wherein the tissue paper web is formed
in said depressed and raised regions of said structured mesh.
27. The machine of claim 7, wherein a linear force generated in
said nip is less than 120 kN/m.
28. The machine of claim 7, wherein said skin is a felt.
29. The machine of claim 9, wherein said dewatering apparatus
includes: a dewatering section; a pressure apparatus; and a
pressure apparatus, said skin being one of a structured skin and a
non-structured skin, the tissue paper web being conveyed along said
dewatering section between said structured skin and a further
permeable skin and that by way of said pressure apparatus pressure
is exerted on said structured skin such that the tissue paper web
is dewatered in said direction of said further permeable skin.
30. The machine of claim 29, wherein during operation of the
machine with said structured skin said dewatering apparatus
contributes to the dewatering of the tissue paper and during
operation of the machine with said non-structured skin said
dewatering apparatus does not contribute to the dewatering of the
tissue paper web.
31. The machine of claim 30, wherein said further permeable skin is
a felt.
32. The machine of claim 29, wherein said structured skin includes
depressed regions and raised regions, during pressurization in said
dewatering apparatus the tissue paper web is compressed less
intensively in said depressed regions than in said raised
regions.
33. The machine of claim 32, wherein the compressibility of said
structured skin is less than that of said further permeable
skin.
34. The machine of claim 32, wherein a dynamic rigidity (K) is a
measure for the compressibility of said structured skin, said
dynamic rigidity (K) being one of equal to and more than 3000
N/mm.
35. The machine of claim 32, wherein a dynamic rigidity (K) is a
measure for the compressibility of said further permeable skin is
one of equal to and less than 100,000 N/mm.
36. The machine of claim 35, wherein said dynamic rigidity (K) is
one of equal to and less than 90,000 N/mm.
37. The machine of claim 36, wherein said dynamic rigidity (K) is
one of equal to and less than 70,000 N/mm.
38. The machine of claim 29, wherein a G modulus is a measure for
an elasticity of said further permeable skin, said G modulus being
one of equal to and more than 2 N/mm.sup.2.
39. The machine of claim 38, wherein said G modulus is one of equal
to and more than 4 N/mm.sup.2.
40. The machine of claim 29, wherein a permeability of said further
permeable skin is one of equal to and less than 80 cfm.
41. The machine of claim 40, wherein said permeability is one of
equal to and less than 40 cfm.
42. The machine of claim 41, wherein said permeability is one of
equal to and less than 25 cfm.
43. The machine of claim 30, wherein a gas flow is generated by
said pressure apparatus such that in order to dewater the tissue
paper web first said structured skin is charged with gas, then the
tissue paper web and finally said further permeable skin.
44. The machine of claim 43, wherein said pressure apparatus
includes a tensioned press belt which is arranged such that an
arrangement of said structured skin, the tissue paper web and said
further permeable skin can be conveyed at least in some areas along
said dewatering section between said press belt and a smooth
surface, whereby said press belt acts on said structured skin and
said further permeable skin rests on said smooth surface.
45. The machine of claim 44, wherein said gas flow through the
tissue paper web amounts to approx. 150 m.sup.3 per minute and
meter length along said dewatering section.
46. The machine of claim 45, wherein said press belt is under a
tension of at least 30 kN/m.
47. The machine of claim 46, wherein said tension is at least 60
kN/m.
48. The machine of claim 47, wherein said tension is at least 80
kN/m.
49. The machine of claim 44, wherein said press belt has an open
area of at least 25% and a contact area of at least 10% of its
total area facing said further permeable skin.
50. The machine of claim 44, wherein said press belt has an open
area of between 75% and 85% and a contact area of between 15% and
25% of its total area facing said further permeable skin.
51. The machine of claim 44, wherein said press belt has an open
area of between 68% and 76% and a contact area of between 24% and
32% of its total area facing said further permeable skin.
52. The machine of claim 36, wherein said press belt has an open
area of between 51% and 62% and a contact area of between 38% and
49% of its total area facing said further permeable skin.
53. The machine of claim 44, wherein said smooth surface is formed
by said circumferential surface of a roller.
54. The machine of claim 53, wherein said pressure apparatus for
generating said gas flow includes a suction zone in said
roller.
55. The machine of claim 54, wherein said suction zone has a length
in said region of between 200 mm and 2500 mm.
56. The machine of claim 55, wherein said length is between 800 mm
and 1800 mm.
57. The machine of claim 56, wherein said length is between 1200 mm
and 1600 mm.
58. The machine of claim 54, wherein a vacuum exists in said
suction zone of between -0.2 bar and -0.8 bar.
59. The machine of claim 58, wherein said vacuum is between -0.4
bar and -0.6 bar.
60. The machine of claim 54, wherein said pressure apparatus for
generating said gas flow includes a pressure hood arranged above
said structured skin.
61. The machine of claim 29, wherein the tissue paper web leaves
said dewatering section with a dry content of more than 30%.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a paper making machine,
and, more particularly, to a machine for the production of tissue
paper.
[0003] 2. Description of the Related Art
[0004] Many different types of production processes for tissue
paper are known.
[0005] The expensive TAD method or the method described in
PCT/EP2005/050203, for example, are used for the production of a
particularly high-quality and fleecy tissue paper with a higher
absorbency and high water absorption capacity coupled with high
tear resistance. With the method described in PCT/EP2005/050203 the
tissue paper web is formed in the forming section on a structured
mesh and then dewatered in several dewatering steps under the
action of pressure. For example, the tissue paper web is conveyed
throughout the dewatering on the structured mesh on which it was
formed. In this way a tissue paper with voluminous, less compressed
areas, and with compressed solid areas, is formed. With the method
described in PCT/EP2005/050203 an elongated nip is formed between
the Yankee drying cylinder and a mating surface constructed as a
shoe press unit. Thanks to the elongated nip a good transfer from
the structured mesh to the Yankee drying cylinder is assured. Here
the function performed by the elongated nip is solely to transfer
the tissue paper web from the structured mesh to the Yankee drying
cylinder. Therefore it would be desirable for the expensive shoe
press unit to be replaced by a cheaper press roller. In tests,
however, rollers with a solid circumferential surface display poor
transfer properties of the tissue paper web from the mesh to the
Yankee drying cylinder because a vacuum is generated in the opening
nip and leads to the tissue paper web adhering to the mesh. A
satisfactory transfer performance is obtained by way of bores in
the cylindrical surface of the roller, but the roller casings,
known from the prior art with their relatively large bores of more
than 3.8 mm, leave unacceptable shadow marks on high-quality tissue
paper.
[0006] A low production capacity is usually achieved with the above
mentioned methods than with methods in which less high-quality,
meaning less fleecy and less absorbent tissue papers are produced.
Such a method is realized, for example, by way of a paper machine
with a crescent arrangement in which the tissue paper web is formed
in the forming section on a felt and is conveyed thereon up to the
Yankee drying cylinder via an elongated nip formed between the
Yankee drying cylinder and a shoe press unit. With this method the
drying of the tissue paper web takes place, to an essential extent,
in the elongated nip. With this method, too, there is a need, due
to pressure from costs, to replace the expensive shoe press unit
with a cheaper press roller. However, tests in this connection have
shown that rollers with a solid circumferential surface and rollers
with blind bores are not suitable for replacing the shoe press unit
due to too low a dewatering performance.
[0007] Furthermore, manufacturers of tissue paper face changing
requirements with regard to the quality and quantity of the tissue
paper to be produced. For example, tissue paper manufacturers have
to provide their customers periodically with high-quality fleecy
tissue paper in small quantities and periodically with less
high-quality tissue paper often in large quantities.
[0008] The provision of production machines for both methods is
costly for the tissue paper manufacturer as this means on the one
hand that both types of production machines have to be purchased
and on the other hand that depending on the current market demands
the one or other machine cannot be used for production.
SUMMARY OF THE INVENTION
[0009] It is the object of the present invention to propose a
machine which is suitable both for the production of high-quality
tissue paper and for the production of less high-quality tissue
paper.
[0010] The known machine for the production of a tissue paper web
has a forming section in which the tissue paper web is formed from
a pulp suspension on a skin. Furthermore, the machine has a nip
formed between the cylindrical surface of a drying cylinder, in
particular a Yankee drying cylinder, and a mating surface, through
which the tissue paper web can be conveyed together with the
skin.
[0011] On the machine according to an embodiment of the present
invention provision is made for the configuration of the machine to
be variable depending on the quality of the tissue paper to be
produced. For example, the variability includes absorbency or tear
resistance, the skin is either a three-dimensionally structured
skin, in particular a structured mesh, or a non-structured skin, in
particular a felt, whereby the mating surface is formed by the
cylindrical surface of a press roller having a suction zone and
whereby provision is made for bores arranged in the cylindrical
surface communicating with the suction zone.
[0012] Thanks to the present invention a machine is provided with
which it is possible, depending on the skin selected, to produce
either high-quality voluminous tissue paper or less high-quality
and less voluminous tissue paper. When using the 3-dimensionally
structured and permeable skin, in particular the structured mesh,
the tissue paper web is formed and dewatered on the structured
mesh, as the result of which the tissue paper web acquires in some
areas a voluminous structure with a high gsm substance. Thanks to
the use of a press roller with bores for the nip formed with the
drying cylinder, in particular a Yankee cylinder, a good transfer
of the tissue paper web from the structured mesh to the drying
cylinder is assured.
[0013] The high-quality and voluminous tissue paper has,
preferably, a bulk value of 10 or more cm.sup.3/g, preferably 10-16
cm.sup.3/g, and a water retention capacity of 10 g water per g
fibers, preferably 10-16 g water per g fibers.
[0014] When using the non-structured permeable skin, in particular
the felt, the tissue paper web is formed and dewatered on the skin.
As the result of which the tissue paper web acquires a less
voluminous structure than when using the structured mesh. In
return, such a tissue paper web can be produced with greater
productivity (in tons of tissue per unit of time) on account of the
higher machine speed. Thanks to the use of a press roller with
bores for the nip formed with the drying cylinder, in particular a
Yankee cylinder, a good transfer of the tissue paper web from the
non-structured skin to the drying cylinder is assured. Furthermore,
when the tissue paper machine is operated with the non-structured
permeable skin, for example the felt, the press roller is
evacuated, thus ensuring a sufficient dewatering performance by the
nip.
[0015] The less high-quality and less voluminous tissue paper has a
bulk value of less than 10 cm.sup.3/g, preferably 6-9 cm.sup.3/g,
and a water retention capacity of less than 10 g water per g
fibers, preferably 6-9 g water per g fibers.
[0016] In practice it has turned out that the three-dimensionally
structured and permeable skin, in particular the structured mesh,
is used advantageously for the production of tissue paper with
higher absorbency, and the non-structured skin, in particular the
felt, advantageously for the production of tissue paper with lower
absorbency. Tests have shown that the dry content of the tissue
paper web during operation with the 3-dimensionally structured and
permeable skin cannot be increased through evacuation of the press
roller, which is why the press roller can be operated without
evacuation in this case.
[0017] Also, tests have shown that the transfer performance of the
tissue paper web to the drying cylinder can be increased during
operation with the 3-dimensionally structured and permeable skin
when the press roller has a blowing zone. The lifting of the tissue
paper web from the press roller is facilitated by the gas flow
generated by the blowing zone.
[0018] Between the forming section and the nip the machine has a
dewatering apparatus, which can be operated in relation to the nip
such that the tissue paper web is dewatered by the dewatering
apparatus to a greater extent during operation with the structured
and permeable skin and to a smaller extent during operation with
the non-structured and permeable skin than by the nip. Tests with
the structured mesh have revealed that in this case the dry content
of the tissue paper web upstream from the nip is essentially equal
to the dry content of the tissue paper web downstream from the
nip.
[0019] To increase production further during operation of the
machine with the non-structured skin, for example the felt, it can
make sense for the tissue paper web to bypass the dewatering
apparatus, meaning it is not to be dewatered at all by the
dewatering apparatus.
[0020] On the one hand the voluminous and more absorbent tissue
paper is produced, meaning formed, on the structured mesh and
dewatered as it travels to the nip, formed by the cylindrical
surface of the drying cylinder and the cylindrical surface of the
suction press roller, and is dewatered thereby more by the
dewatering apparatus than by the nip. In this case the dewatering
takes place less by way of the nip. The latter essentially has the
job of transferring the tissue paper from the mesh to the
cylindrical surface of the drying cylinder. As tests have shown, a
good transfer is provided when the linear force generated in the
nip is less than 120 kN/m, in particular 60-90 kN/m.
[0021] On the other hand the less voluminous and less absorbent
tissue paper is formed on the felt and dewatered by the nip formed
by the cylindrical surface of the drying cylinder and the
cylindrical surface of the suction press roller. The tissue paper
is dewatered more by the nip than by the dewatering apparatus. As
the dewatering takes place more by way of the nip than by way of
the dewatering apparatus, the nip essentially has the job of
dewatering the tissue paper and transferring the tissue paper from
the mesh to the cylindrical surface of the drying cylinder.
[0022] The bores are preferably arranged and constructed such that
the tissue paper web, downstream from the nip, in both operating
modes of the machine, meaning with the structured and with the
non-structured skin, has a dry content of 31% or more. A dry
content of 31-36% is obtained downstream from the nip during
operation with the structured skin and a dry content of 37-41% is
obtained downstream from the nip during operation with the
non-structured skin. In order to reduce, or even prevent, the
marking of this tissue paper, particularly during the production of
the voluminous tissue paper, and at the same time to provide a
sufficient dewatering performance, it makes sense for the bores to
have a diameter of less than 3.8 mm, in particular less than 3.5
mm.
[0023] It is also an object of the present invention to propose a
machine for the production of tissue paper with a nip formed by a
drying cylinder and a mating surface, with which it is possible,
without the use of a shoe press unit in the nip, to produce both
high-quality voluminous and less high-quality and less voluminous
tissue paper, and to do so without marking, with good transfer
performance and with sufficient dry content.
[0024] The machine for the production of a tissue paper web has, a
nip formed between the cylindrical surface of a drying cylinder, in
particular a Yankee drying cylinder, and a mating surface, through
which the tissue paper web can be conveyed together with a
permeable skin, namely between the skin and the cylindrical
surface.
[0025] In one embodiment of a machine according to the present
invention provision is made in addition for the mating surface to
be formed by the cylindrical surface of a press roller, whereby the
press roller has a suction zone and provision is made in the
cylindrical surface for bores communicating with the suction zone.
The bores have a diameter of less than 3.8 mm.
[0026] Through the provision of an evacuated press roller, which
forms a nip with the cylindrical surface of a drying cylinder, in
particular a Yankee drying cylinder, a press configuration is
proposed which makes do without a shoe press unit. The press
configured is capable of providing a good transfer from the skin to
the cylindrical surface of the drying cylinder both for voluminous
and less voluminous tissue paper, as the formation of a vacuum in
the opening nip is counteracted by the provision of bores. As the
result of the bores being evacuated, a sufficient dewatering
performance is provided, in particular for the production of less
voluminous tissue paper, as rewetting at the opening nip is at
least greatly reduced. Surprisingly, the sufficient dewatering
performance can also be provided when the bores have a diameter of
less than 3.8 mm, without this resulting in any marking of in
particular the soft and voluminous tissue paper.
[0027] The bore diameters according to the present invention are so
small that a soft and voluminous tissue paper web cannot be pressed
into the holes on account of the tensioned mesh, in particular the
structured mesh. A result of which is that it is not only possible
to obtain a uniform crepe profile but also possible to improve the
transfer of the voluminous and soft tissue paper web to the drying
cylinder.
[0028] Provision is made for the machine to have a forming section
for forming the tissue paper web from a pulp suspension and a skin
arranged, such that the tissue paper web is formed in the forming
section on the skin, which is conveyed through the nip formed
between the cylindrical surface of the drying cylinder and the
cylindrical surface of the press roller. As such, the tissue paper
web can be conveyed on the same skin from its formation to beyond
the nip, thus ruling out transfer problems. It makes sense,
particularly in order to increase the dry content during production
of the voluminous tissue paper, for a dewatering apparatus to be
provided between the forming section and the nip.
[0029] For the production of voluminous tissue paper the skin is a
structured mesh, in particular a TAD mesh. On the side facing the
tissue paper web the structured mesh includes depressed regions
and, relative to the depressed areas, raised regions, whereby the
tissue paper web is formed in the depressed and raised regions of
the structured mesh. In this case, the formed tissue paper web has
voluminous pillow areas in the depressed regions of the structured
mesh and, in between, less voluminous areas formed in the raised
regions of the structured mesh, whereby the voluminous areas have a
higher gsm substance than the less voluminous areas. Due to the
depressed regions, the areas of the tissue paper web formed in the
depressed regions remain protected therein during the subsequent
dewatering--this is because the tissue paper web remains on the
structured mesh after the tissue paper web is formed. This results
in the tissue paper web being pressed only slightly under the
action of pressure, which is why its voluminous structure is
preserved during the dewatering through the application of
pressure. As such, typically only 25-35% of the tissue paper web is
pressed when pressure is applied.
[0030] With regard to the structure of the structured mesh and with
regard to the formation of the tissue paper web on the structured
mesh, reference is made to PCT/EP2005/050203, which herewith is
included in full in this application.
[0031] For the production of less voluminous and less high-quality
tissue paper the skin used is a felt.
[0032] As tests have shown, a sufficient dewatering, and the nearly
complete reduction of markings on the tissue paper web, can be
provided simultaneously when the bores have a diameter of 3.5 mm or
less, preferably 3.0 mm or less, and in particular preferably 2.7
mm or less.
[0033] Furthermore it has been found that the dewatering
performance, but not the marking behavior, is influenced by the
open area in the cylindrical surface of the press roller. With the
above mentioned bore diameters the best results, with regard to
dewatering performance, are achieved when an open area of 16% to
30%, preferably 18% to 26%, in particular preferably 20% to 22% of
the total area of the cylindrical surface, is formed by the bores.
Furthermore it has been found that a good dewatering performance
can be provided when the bores on the cylindrical surface of the
press roller form a regular pattern in at least some areas.
[0034] To improve the transfer properties of the tissue paper web
from the skin onto the cylindrical surface of the drying cylinder
the cylindrical surface includes blind bores which are
non-communicating with the vacuum zone and have a diameter of 2.7
mm or less, in particular 2.4 mm or less, whereby the blind bores
on the cylindrical surface can be arranged, at least in some areas,
between the bores.
[0035] Together, the bores and the blind bores form an open area of
16% to 30%, preferably 18% to 26%, in particular preferably 20% to
22% of the total area of the cylindrical surface. For the further
improvement of the dewatering performance the bores and the blind
bores on the cylindrical surface of the press roller form together
a regular pattern, at least in some areas. The bores or the bores
and the blind bores on the cylindrical surface can be arranged
along a multiplicity of mutually parallel lines, for example.
[0036] Also, tests have shown that the transfer of the tissue paper
web from the skin to the cylindrical surface of the drying cylinder
can be improved when the press roller is driven.
[0037] The dewatering apparatus includes a dewatering section and a
pressure apparatus. The dewatering apparatus is constructed such
that the tissue paper web can be conveyed along the dewatering
section between the structured skin, in particular the structured
mesh, and a further permeable skin, and that by way of the pressure
apparatus pressure can be exerted on the structured mesh, the
tissue paper web and the further permeable skin such that the
tissue paper web is dewatered in the direction of the further
permeable skin. The further permeable skin is preferably a felt
having a sufficiently high water absorption capacity for the water,
which is pressed out of the tissue paper web. With regard to the
structure of the lower skin, reference is made to
PCT/EP2005/050198, which herewith is included in full in this
application.
[0038] The compressibility (change of thickness in mm upon
application of force in N) of the structured mesh is preferably
smaller than the compressibility of the further permeable skin. The
voluminous structure of the tissue paper web upon the application
of pressure is thus retained. Tests have shown that a particularly
good and gentle dewatering is possible when the dynamic rigidity
(K), as a measure for the compressibility of the structured mesh,
is 3000 N/mm or more.
[0039] Given a hard or excessively hard further permeable skin, the
voluminous pillow areas of the tissue paper web would not be
compressed at all. Due to the compressible structure of the further
permeable skin the voluminous pillow areas of the tissue paper are
slightly pressed and hence gently dewatered. Tests in this
connection have shown that the dynamic rigidity (K), as a measure
for the compressibility of the further permeable skin, is 100,000
N/mm or less, preferably 90,000 N/mm, in particular preferably
70,000 N/mm or less. Similarly it is an advantage for the G
modulus, as a measure for the elasticity of the further permeable
skin, to be 2 N/mm.sup.2 or more, and preferably 4 N/mm.sup.2 or
more.
[0040] Also, tests have shown that the water stored in the further
permeable skin, for example felt, can be expelled more easily with
a gas flow when the permeability of the further permeable skin is
not too high. It proves to be an advantage when the permeability of
the further permeable skin is 80 cfm or less, preferably 40 cfm or
less, and in particular preferably 25 cfm or less. In the above
mentioned ranges the rewetting of the tissue paper web by the
further permeable skin is largely prevented.
[0041] The pressure exerted here on the arrangement of a structured
mesh, tissue paper web and further permeable skin can be generated
by a gas flow. In addition or alternatively to this, the pressure
exerted can be generated by a mechanical pressing force. Preferably
a gas flow can be generated by the pressure apparatus such that in
order to dewater the tissue paper web, first the structured mesh is
charged with gas, then the tissue paper web and finally the further
permeable skin. The dewatering of the paper web takes place in this
case in the direction of the further permeable skin.
[0042] In addition or optionally to gas charging of the above
mentioned arrangement provision can be made for the pressure
apparatus to include a tensioned press belt, which is arranged such
that the arrangement of structured mesh, tissue paper web and
further permeable skin can be conveyed, at least in some areas
along the dewatering section, between the press belt and a smooth
surface. The press belt acts on the structured mesh and the further
permeable skin rests on the smooth surface. In this case, too, the
dewatering of the paper web takes place in the direction of the
further permeable skin.
[0043] The arrangement of structured mesh, tissue paper web and
further permeable skin is preferably charged with the gas flow, at
least in some areas in the region of the dewatering section, so
that the dewatering takes place simultaneously by the pressing
force of the press belt and the through-flow of gas. Tests have
shown that the gas flow through the tissue paper web amounts to
approx. 150 m.sup.3 per minute along the dewatering section.
[0044] The pressing force can be increased by a high tension of the
press belt. Tests have shown that sufficient dewatering,
particularly of the non-voluminous areas of the tissue paper, is
obtained when the press belt is under a tension of at least 30
kN/m, preferably at least 60 kN/m or 80 kN/m. Here the press belt
can have a spiralized structure and be constructed as a so-called
spiral link fabric, for example. Furthermore, it is possible for
the press belt to have a woven structure.
[0045] To be able to obtain a good dewatering of the tissue paper
web by the mechanical tensioning of the press belt and as the
result of the gas flow through the press belt the press belt has an
open area of at least 25% and a contact area of at least 10% of its
total area facing the upper skin. A uniform mechanical pressure is
exerted on the arrangement of the structured upper skin and lower
skin by increasing the contact area of the press belt.
[0046] Satisfactory results are obtained with all the values,
stipulated below, for the contact area and open area of the press
belt. Provision is made accordingly for the press belt to have an
open area of between 75% and 85% and a contact area of between 15%
and 25% of its total area facing the upper skin. Also, provision is
made for the press belt to have an open area of between 68% and 76%
and a contact area of between 24% and 32% of its total area facing
the upper skin. Very good results with regard to dry content and
voluminosity of the tissue paper are obtained when the press belt
has an open area of between 51% and 62% and a contact area of
between 38% and 49% of its total area facing the upper skin. In
particular through the construction of the press belt, with a woven
structure, it is possible for the press belt to have an open area
of 50% or more and a contact area of 50% or less of its total area
facing the upper skin. As such it is possible to provide for a good
gas flow through the press belt as well as a homogeneous pressing
force by way of the press belt.
[0047] The smooth surface is formed by the circumferential surface
of a roller. Here the gas flow can be generated by a suction zone
in a roller. In this case the suction zone has a length in the
range between 200 mm and 2500 mm, preferably between 800 mm and
1800 mm, in particular preferably between 1200 mm and 1600 mm. The
vacuum in the suction zone amounts to between -0.2 bar and -0.8
bar, preferably between -0.4 bar and -0.6 bar. Optionally or in
addition to this, the gas flow can also be generated by an excess
pressure hood arranged above the top skin.
[0048] The temperature of the gas flow is between 50.degree. C. and
180.degree. C., preferably between 120.degree. C. and 150.degree.
C., and the excess pressure amounts to less than 0.2 bar,
preferably less than 0.1 bar and in particular preferably less than
0.05 bar. The gas can be hot air or steam.
[0049] Through the above described dewatering operation it is
possible for the tissue paper web to leave the dewatering section
with a dry content of more than 30%.
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] The above-mentioned and other features and advantages of
this invention, and the manner of attaining them, will become more
apparent and the invention will be better understood by reference
to the following description of embodiments of the invention taken
in conjunction with the accompanying drawings, wherein:
[0051] FIG. 1 shows a machine according to one embodiment of the
present invention in the configuration for the production of
high-quality tissue paper;
[0052] FIG. 2 shows the machine from FIG. 1 in the configuration
for the production of less high-quality tissue paper;
[0053] FIGS. 3-6 show a method for the production of tissue paper
with the configuration for the machine of FIG. 1;
[0054] FIG. 7 shows the cylindrical surface of a suction press
roller with small bores according to the present invention and the
transverse profile of a tissue paper web produced therewith;
[0055] FIG. 8 shows the cylindrical surface of a suction press
roller with large bores known from the prior art and the transverse
profile of a tissue paper web produced therewith; and
[0056] FIGS. 9-11 show the method for the production of tissue
paper with the configuration of the machine from FIG. 2.
[0057] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrate one preferred embodiment of the invention, in one
form, and such exemplifications are not to be construed as limiting
the scope of the invention in any manner.
DETAILED DESCRIPTION OF THE INVENTION
[0058] Referring now to the drawings, and more particularly to FIG.
1 there is shown a tissue paper machine 1 with a forming section 2
in which a tissue paper web 3 is formed from a pulp suspension 4 on
a skin 5 (or 11 of FIG. 2) and with a nip 10 that is formed between
cylindrical surface 6 of a Yankee drying cylinder 7 and cylindrical
surface 8 of a press roller 9 and through which tissue paper web 3
can be conveyed together with skin 5 or 11. According to the
present invention the configuration of machine 1 is variable, such
that depending on the quality of tissue paper 3 to be produced, for
example its absorbency or tear resistance, either a structured mesh
5 or a felt 11 (this configuration is shown in FIG. 2) is used.
Press roller 9 includes a suction zone 12 and bores 30
communicating with suction zone 12 which are provided in the
cylindrical surface 8 of the press roller 9.
[0059] In the configurations presented in the FIGS. 1 and 2
structured mesh 5 is used for the production of tissue paper 3 with
higher absorbency and felt 11 is used for the production of tissue
paper 3' with lower absorbency.
[0060] In the configuration of FIG. 1 tissue paper web 3 is
conveyed through a dewatering apparatus 34 arranged between forming
section 2 and nip 10 and dewatered by the apparatus. By contrast,
in the configuration of machine 1 shown in FIG. 2 tissue paper web
3 is not conveyed through dewatering apparatus 34 arranged between
forming section 2 and nip 10 and hence is not dewatered by
apparatus 34.
[0061] The method for the production of high-quality voluminous and
absorbent tissue paper 3 with the configuration of machine 1
according to FIG. 1 will be explained with reference to the FIGS.
3-6. Pulp suspension 4 emerges from a headbox 13 such that
suspension 4 is injected into the ingoing nip between a forming
mesh 14 and the structured, in particular 3-dimensionally
structured mesh 5, as the result of which a tissue paper web 3 is
formed.
[0062] Forming mesh 14 has a side 15 facing tissue paper web 3,
which relative to side 16 of structured mesh 5 facing tissue paper
web 3 is smooth. Here side 16 of structured mesh 5 facing tissue
paper web 3 has depressed regions 17 and, relative to depressed
areas 17, raised regions 18 such that tissue paper web 3 is formed
in depressed regions 17 and raised regions 18 of structured mesh 5.
The difference in height between depressed regions 17 and raised
regions 18 amounts to preferably 0.07 mm and 0.6 mm. The area
formed by raised regions 17 amounts to preferably 10% or more, in
particular preferably 20% or more and in particular preferably 25%
to 30% of side 16 facing tissue paper web 3. In the embodiment
presented in FIG. 3 structured mesh 5 is constructed as a TAD mesh
5.
[0063] In the embodiment of the present invention presented in FIG.
3 the arrangement of TAD mesh 5, tissue paper web 3 and forming
mesh 14 is directed around a forming roller 19 and tissue paper web
3 is dewatered essentially by forming mesh 14 before forming mesh
14 is taken off tissue paper web 3 and tissue paper web 3 is
transported further on TAD mesh 5.
[0064] Evident in FIG. 4 is the structure of tissue paper web 14
formed between flat forming mesh 14 and TAD mesh 5. Voluminous
pillow areas C' of tissue paper web 3 formed in depressed regions
16 of TAD mesh 5 have a higher volume and a higher gsm substance
than areas A' of tissue paper web 3 formed in raised regions 18 of
TAD mesh 5.
[0065] Accordingly, tissue paper web 3 already has a 3-dimensional
structure as the result of its forming on structured mesh 5.
[0066] In the configuration presented in FIG. 1 tissue paper web 3
is conveyed between structured mesh 5, which is arranged above, and
a further permeable skin 20, which is constructed as felt 20,
whereby during the dewatering step along a dewatering section 21
pressure is exerted on structured mesh 5, tissue paper web 3 and
felt 20 such that tissue paper web 3 is dewatered in the direction
of felt 20, as indicated by arrows 22 in FIG. 5. Here the fibers of
tissue paper web 3 are pressed against felt 20, as the result of
which, the side of tissue paper web 3 brought into contact with
felt 20 becomes nearly flat.
[0067] As the result of tissue paper web 3 being dewatered during
this dewatering step in the direction of felt 20 and as the result
of tissue paper web 3 being dewatered on structured mesh 5 on which
it was previously formed, voluminous areas C' are less intensively
compressed than areas A', thus resulting in the voluminous
structure of areas C' being preserved.
[0068] The pressure for dewatering tissue paper web 3 is generated
during the dewatering step, at least in some areas, simultaneously
by a gas flow and a mechanical pressing force.
[0069] Here the gas flow passes first through structured mesh 5,
then tissue paper web 3, and finally the further skin constructed
as felt 20. The gas flow through tissue paper web 3 amounts to
around 150 m.sup.3 per minute and meter web length. The gas flow is
generated by a suction zone 23 in a roller 24, suction zone 23
having a length in the region of between 200 mm and 2500 mm,
preferably between 800 mm and 1800 mm, and in particular preferably
between 1200 mm and 1600 mm. The vacuum in suction zone 23 amounts
to between -0.2 bar and -0.8 bar, preferably between -0.4 bar and
-0.6 bar.
[0070] With regard to performing the dewatering step by mechanical
pressing force and, optionally, or in addition, with a gas flow,
and with regard to the various configurations of apparatus for
performing such a dewatering step, PCT/EP2005/050198 is included in
full in the disclosure content of this current application.
[0071] The mechanical pressing force is generated during the
dewatering step by conveying the arrangement of structured mesh 5,
tissue paper web 3 and felt 20 to a dewatering section 21 between a
tensioned press belt 25 and a smooth surface 26, in which case
press belt 25 acts on structured mesh 5 and felt 20 rests on smooth
surface 26. Smooth surface 26 is formed by circumferential surface
26 of roller 24.
[0072] Dewatering section 21 is defined essentially by the wrap
zone of press belt 25 around circumferential surface 26 of roller
24, whereby the wrap zone is defined by the distance between the
two deflector rollers 27 and 28.
[0073] Press belt 25 is under a tension of at least 30 kN/m,
preferably at least 60 kN/m or 80 kN/m, and has an open area of at
least 25% and a contact area of at least 10% of its total area
facing the upper skin. In this specific case, press belt 25 is
constructed as a spiral link fabric and has an open area of between
51% and 62% and a contact area of between 38% and 49% of its total
area facing the upper skin.
[0074] With regard to the structure of the press belt,
PCT/EP2005/050198 is hereby included in full in the disclosure
content of this present application.
[0075] Tissue paper web 3 leaves dewatering section 21 with a dry
content of 30% or more. After the dewatering step tissue paper web
3 can be subjected to an additional drying step performed by
implied apparatus 29.
[0076] Before tissue paper web 3 runs through nip 10, tissue paper
web 3 is conveyed together with structured mesh 5 around an
evacuated deflector roller 32, whereby structured mesh 5 is
arranged between tissue paper web 3 and evacuated deflector roller
32. Moisture can thus be drawn out of structured mesh 5.
[0077] After the dewatering step performed by dewatering apparatus
19 tissue paper web 3 is conveyed together with structured mesh 5
through nip 10, whereby tissue paper web 3 in nip 10 is arranged
between structured mesh 5 and smooth roller surface 6 of a Yankee
drying cylinder 7 (see FIG. 6). Here nip 10 is formed by Yankee
drying cylinder 7 and a shoe press roller 9.
[0078] On the side, which was formed on flat forming mesh 15 and in
whose direction tissue paper web 3 was dewatered in dewatering
apparatus 34, tissue paper web 3 rests with a relatively large area
amounting to 90% or more of the total area of this side on Yankee
drying cylinder 7, while on the other side, tissue paper web 3
rests on structured mesh 5.
[0079] The linear force generated in nip 10 amounts to 60-90 kN/m,
so that essentially only a transfer of tissue paper web 3 from
structured mesh 5 to Yankee drying cylinder 7 is effected by nip
10.
[0080] As press roller 9 has bores 30 and 31, as shown in FIG. 7,
in its cylindrical surface 8, a good transfer of tissue paper web 3
is assured. Furthermore, press roller 9 is driven, whereby the
transfer of tissue paper web 3 from structured mesh 5 to Yankee
drying cylinder 7 is improved further.
[0081] Downstream from nip 10 tissue paper web 3 is conveyed over
heated cylindrical surface 6 of Yankee drying cylinder 7 and then
taken off of cylinder 7 with a crepe doctor (not illustrated). To
increase the drying performance, a drying hood 33 can be arranged
in addition, above Yankee drying cylinder 7 such that tissue paper
web 3 is conveyed between drying hood 33 and cylindrical surface 6
of Yankee drying cylinder 7.
[0082] FIG. 7a shows a plane view of a detail of cylindrical
surface 8 of evacuated press roller 9. Cylindrical surface 8 has
bores 30 and 31. Bores 30 communicate with suction zone 12 of press
roller 9, meaning they are in fluidic connection with suction zone
12 of press roller 9. Bores 30 have a diameter of 2.9 mm, which
prevents marking of tissue paper 3 while passing through nip 10.
Furthermore, blind bores 31, with a smaller diameter than that of
bores 30, are arranged on cylindrical surface 8 between bores 30.
In the embodiment under consideration blind bores 31 have a
diameter of 2.4 mm. Due to blind bores 31 the marking of tissue
paper 3 is reduced further. An open area of 22% of the total area
of cylindrical surface 8 is formed by bores 30 and blind bores 31
together, whereby bores 30 and blind bores 31 together form a
regular pattern on cylindrical surface 8 of press roller 9.
[0083] In this specific case, bores 30 and blind bores 31 on
cylindrical surface 8 are arranged along a multiplicity of mutually
parallel lines (implied by the dashed lines). FIG. 7b shows the
transverse profile of the produced tissue paper web 3 as it exists
after creping following the rotation around Yankee drying cylinder
7. As the result of bores 30 and blind bores 31 having a small
diameter, no marking of tissue paper 3 in nip 10 occurs, meaning
that the profile of tissue paper web 3 is uniform.
[0084] For comparison, FIG. 8b shows a transverse profile of a
tissue paper web as it exists after creping following the rotation
around Yankee drying cylinder 7. The tissue paper web, shown in
FIG. 8b, was produced under the same conditions as tissue paper web
3, the sole difference being that cylindrical surface 8' of press
roller 9' used in nip 10 has bores with a diameter of 3.8 mm or
more. As can be seen, the profile has elevations which correlate
with bores 30' (FIG. 8a).
[0085] The method for the production of less high-quality and less
voluminous and absorbent tissue paper 3' with the configuration of
the machine according to FIG. 2 will now be explained with
reference to FIGS. 9-11.
[0086] Pulp suspension 4 emerges from headbox 13 such that
suspension 4 is injected into the ingoing nip between a forming
mesh 14 and the non-structured skin constructed as felt 11, as the
result of which a tissue paper web 3' is formed.
[0087] Forming mesh 14 has a side 15 facing tissue paper web 3',
which is approximately equally as smooth as side 34 of felt 11
facing tissue paper web 3'.
[0088] In an embodiment of the present invention as presented in
FIG. 9 the arrangement of felt 11, tissue paper web 3' and forming
mesh 14 is directed around forming roller 19 and tissue paper web
3' being dewatered essentially by forming mesh 14 before forming
mesh 14 is taken off tissue paper web 3' and tissue paper web 3' is
transported further on felt 11.
[0089] Evident in FIG. 10 is the two-sided smooth structure of
tissue paper web 3' formed between flat forming mesh 14 and felt
11. Here tissue paper web 3' is conveyed through dewatering
apparatus 34 arranged between forming section 2 and nip 10 and
dewatered accordingly by apparatus 34. Tissue paper web 3' can be
dewatered by a drying step performed by implied apparatus 29.
[0090] Before tissue paper web 3' runs through nip 10, tissue paper
web 3' is conveyed together with felt 11 around the evacuated
deflector roller 32, whereby felt 11 is arranged between tissue
paper web 3' and the evacuated deflector roller 32. In this way, so
much moisture can be drawn from felt 11 as to enable it to pick up
sufficient moisture pressed from tissue paper web 3' in the
subsequent dewatering step in nip 10.
[0091] After this, tissue paper web 3' together with felt 11 is
conveyed in a dewatering step through nip 10, whereby tissue paper
web 3' in nip 10 is arranged between felt 11 and smooth roller
surface 6 of Yankee drying cylinder 7. Here nip 10 is formed by
Yankee drying cylinder 7 and a shoe press roller 9. The linear
force generated in nip 10 amounts to 120 kN/m, so that a dewatering
of tissue paper web 3' and a subsequent transfer of tissue paper
web 3' from felt 11 to Yankee drying cylinder 7 is effected by nip
10. FIG. 11 shows tissue paper web 3' while passing through nip
10.
[0092] In its cylindrical surface 8 press roller 9 has bores 30
which communicate with the suction zone 12 of press roller 9, hence
rewetting in the opening nip is prevented, as the result of which,
the dry content of tissue paper web 3' is increased. Also, due to
the bores a good transfer of tissue paper web 3' to Yankee drying
cylinder 7 is assured. Furthermore, press roller 9 is driven,
whereby the transfer of tissue paper web 3' from felt 11 to Yankee
drying cylinder 7 is improved further.
[0093] Downstream from nip 10 tissue paper web 3' is conveyed over
the heated cylindrical surface 6 of Yankee drying cylinder 7 and
then taken off cylinder 7 with a crepe doctor, not illustrated. To
increase the drying performance a drying hood 33 can be arranged
above Yankee drying cylinder 7 such that tissue paper web 3' is
conveyed between drying hood 33 and cylindrical surface 6 of Yankee
drying cylinder 7.
[0094] As tissue paper web 3' has an essentially more compact
structure than tissue paper web 3 formed with the configuration of
FIG. 1, there is no risk with tissue paper web 3' of it being
marked in nip 10 on account of bores 30 and 31.
[0095] While this invention has been described as having a
preferred design, the present invention can be further modified
within the spirit and scope of this disclosure. This application is
therefore intended to cover any variations, uses, or adaptations of
the invention using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains and which fall within the limits of
the appended claims.
* * * * *