U.S. patent application number 15/303110 was filed with the patent office on 2017-02-09 for a sheet of absorbent material, roll, log and method for manufacturing the same.
This patent application is currently assigned to SCA Tissue France. The applicant listed for this patent is SCA Tissue France. Invention is credited to Donald BARREDO, Gilles CATTACIN, Denis GENET, Pierre LAURENT, Julien MARIETTA-TONDIN, Remy RUPPEL, Rene SIGWALT.
Application Number | 20170037579 15/303110 |
Document ID | / |
Family ID | 51293104 |
Filed Date | 2017-02-09 |
United States Patent
Application |
20170037579 |
Kind Code |
A1 |
MARIETTA-TONDIN; Julien ; et
al. |
February 9, 2017 |
A SHEET OF ABSORBENT MATERIAL, ROLL, LOG AND METHOD FOR
MANUFACTURING THE SAME
Abstract
A sheet of absorbent material having opposite sheet side edges
spaced apart from one another to define an overall width of the
absorbent sheet, the sheet of absorbent material including zones of
weakness spaced along the sheet of absorbent material according to
a machine direction, each zone of weakness extending substantially
transversally to said machine direction, each zone of weakness
defining two adjacent individual absorbent sheet portions, each
zone of weakness being a tear line. The tear line comprises two
edge regions and a central region, a first edge region beginning at
one of the sheet side edges towards the central region, a second
edge region beginning at the other sheet side edges towards the
central region, the central region including alternating perforated
segments and unperforated segments. The edge regions are
unperforated so as to constitute attachment areas within the tear
line between two adjacent individual absorbent sheet portions.
Inventors: |
MARIETTA-TONDIN; Julien; (St
Ouen, FR) ; CATTACIN; Gilles; (St Ouen, FR) ;
BARREDO; Donald; (Ingersheim, FR) ; RUPPEL; Remy;
(Durrenentzen, FR) ; SIGWALT; Rene; (Kunheim,
FR) ; LAURENT; Pierre; (Turckheim, FR) ;
GENET; Denis; (Marckolsheim, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SCA Tissue France |
Saint-Ouen |
|
FR |
|
|
Assignee: |
SCA Tissue France
Saint-Ouen
FR
|
Family ID: |
51293104 |
Appl. No.: |
15/303110 |
Filed: |
April 10, 2014 |
PCT Filed: |
April 10, 2014 |
PCT NO: |
PCT/IB2014/001032 |
371 Date: |
October 10, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B65H 2301/41484
20130101; B65H 2301/515326 20130101; D21H 27/02 20130101; B65H
2301/515323 20130101; B65H 2301/5152 20130101; D21H 27/002
20130101; B65H 2701/1924 20130101; D21H 27/005 20130101; B26F 1/20
20130101; A47K 10/16 20130101; B65H 35/08 20130101 |
International
Class: |
D21H 27/00 20060101
D21H027/00; A47K 10/16 20060101 A47K010/16; B65H 35/08 20060101
B65H035/08; D21H 27/02 20060101 D21H027/02 |
Claims
1. A sheet of absorbent material having opposite sheet side edges
spaced apart from one another to define an overall width of the
sheet of absorbent material, the sheet of absorbent material
comprising zones of weakness spaced along the sheet of absorbent
material according to a machine direction, each zone of weakness
extending substantially transversally to said machine direction,
each zone of weakness defining two adjacent individual absorbent
sheet portions, each zone of weakness being a tear line, wherein:
the tear line comprises two edge regions and a central region, a
first edge region beginning at one of the sheet side edges towards
the central region, a second edge region beginning at the other
sheet side edges towards the central region, the central region
comprising alternating perforated segments and unperforated
segments, said edge regions are unperforated so as to constitute
attachment areas within the tear line between two adjacent
individual absorbent sheet portions.
2. The sheet of absorbent material of claim 1, wherein a width
ratio of the edge regions relatively to the central region ranges
from about 4% to about 20%
3. The sheet of absorbent material of claim 1, wherein an edge
region width ranges from about 3 mm to about 10 mm.
4. The sheet of absorbent material according to claim 1, wherein
the central region comprises alternating perforated segments and
unperforated segments according to a perforation pattern comprising
at least two perforated segments separated by one unperforated
segment, each segment having substantially an identical width.
5. The sheet of absorbent material according to claim 1, wherein
the central region comprises alternating perforated segments and
unperforated segments according to a perforation pattern comprising
multiple perforated segments, two adjacent perforated segments
being separated by one unperforated segment, each perforated
segment having a width increasing from one side edge towards the
opposite side edge, each unperforated segment having a constant
width.
6. The sheet of absorbent material according to claim 1, wherein
the central region comprises alternating perforated segments and
unperforated segments according to a perforation pattern comprising
multiple perforated segments, two adjacent perforated segments
being separated by one unperforated segment, each unperforated
segment having a width increasing from one side edge towards the
opposite side edge, each perforated segment having a constant
width.
7. A roll of sheet of absorbent material comprising a sheet of
absorbent material according to claim 1 wound onto a core or on
itself.
8. An absorbent sheet product comprising the sheet of absorbent
material according to claim 1, wherein the absorbent sheet is
chosen among the group consisting of napkins, towels, kitchen
towels, hand towels, toilet papers, wipes and facial tissues.
9. A log base sheet made of absorbent material having opposite log
side edges spaced apart from one another to define an overall width
of the log base sheet, the log base sheet comprising zones of
weakness spaced along the log base sheet according to a machine
direction of the log base sheet, each zone of weakness extending
substantially transversally to said machine direction, each zone of
weakness being a tear line, the log base sheet comprising multiple
phantom lines parallel to the machine direction representing
imaginary lines for cutting the log base sheet, wherein: the tear
line comprises multiple successions of first edge region, a central
region and a second edge region from one of the log side edge
towards the other log side edge, the central region comprising
alternating perforated segments and unperforated segments, said
edge regions are unperforated, and each phantom line is positioned
at a boundary between two adjacent edge regions so as to constitute
attachment areas within said tear line between two adjacent central
regions.
10. The log base sheet of claim 9, wherein a central region out of
two in each tear line is replaced by an unperforated region, and
wherein two consecutive tear lines are staggered according to a
cross-machine direction such that all the central region are
positioned between two adjacent phantom lines.
11. A log of sheet of absorbent material comprising a log base
sheet made of absorbent material according to claim 9 wound onto a
core or on itself.
12. A method for manufacturing a roll of sheet of absorbent
material comprising the steps of: feeding a log base sheet made of
absorbent material into a perforating unit, the log base sheet
having opposite log side edges spaced apart from one another to
define an overall width of the log base sheet; defining zones of
weakness spaced along the log base sheet according to a machine
direction of the log base sheet, each zone of weakness extending
substantially transversally to said machine direction, by pinching
each zone of weakness as a tear line; defining multiple phantom
lines in the log base sheet parallel to the machine direction
representing imaginary lines for cutting the log base sheet;
wounding the pinched log base sheet onto a core or on itself to
form a log; cutting the pinched log base sheet once a desired log
diameter is reached; cutting the log into multiple and individual
rolls of absorbent material sheet; the manufacturing method is
characterized in that it further comprises: pinching each tear line
as multiple successions of first edge region, a central region and
a second edge region from one of the log side edge towards the
other log side edge, the central region comprising alternating
perforated segments and unperforated segments; unperforating said
edge regions; and positioning each phantom line at a boundary
between two adjacent edge regions so as to constitute attachment
areas within said tear line between two adjacent central
regions.
13. The manufacturing method of claim 12, wherein a central region
out of two in a tear line is replaced by an unperforated region,
and wherein two consecutive tear lines are staggered according to a
cross-machine direction such that all the central region are
positioned between two adjacent phantom lines.
Description
TECHNICAL FIELD
[0001] An aspect relates to a sheet of absorbent material and sheet
of absorbent material wound as a roll. Another aspect relates to a
log base sheet made of absorbent material used to manufacture such
rolls. Still another aspect relates to a method for manufacturing a
roll of sheet of absorbent material. The sheet of absorbent
material may be manufactured from a web of tissue paper (obtained
by a Conventional Wet Press or Through Air Drying manufacturing
method or other manufacturing method) or a nonwoven fabric
(obtained by an air-laid manufacturing method or spun-laid
manufacturing method or other manufacturing method). Such absorbent
sheet products find a particular, though non-exclusive, use as
sanitary or domestic purposes. As an example, such absorbent sheet
products may be used as paper towel, toilet tissue, bathroom
tissue, facial tissue, wiping tissue, kitchen tissue, etc.
BACKGROUND
[0002] A tissue paper relates to an absorbent paper based on
cellulose fibers which is also called tissue paper base-sheet in
this field of technology. A typical absorbent paper has a low basis
weight, in the range from 10 to 50 g/m2.
[0003] A nonwoven fabric comprising cellulosic fibers relates to an
absorbent paper which is also called nonwoven or web made of fibers
like air-laid web in this field of technology. A typical absorbent
paper has a basis weight, in the range from 30 to 250 g/m2,
preferably 40 to 200 g/m2.
[0004] FIG. 1 schematically illustrates a method for manufacturing
a roll of absorbent sheet material 4 according to the prior art.
More precisely, at the stage of FIG. 1, an absorbent base sheet 1
has already been produced according to a known papermaking process.
FIG. 1 illustrates a later stage which is a stage where a
converting process takes place. The converting process converts
large parent base sheet 1 (e.g., strip width from 1.80 m to 7 m)
into retail sized rolls 4, e.g., bathroom tissue rolls, paper
towels rolls e.g., strip width from 8 to 40 cm). More precisely,
the base sheet 1 is fed into a space of a perforating unit 10
comprising a perforator roll and a stationary anvil roll. There,
the base sheet 1 is pinched (step S1) with the desired tear lines 5
(schematically represented by dashed lines). A tear line 5 is a
line according to a cross-machine direction CD made in the
thickness of the base sheet 1 and comprising alternating perforated
segments and unperforated segments (i.e. two perforated segments
being separated by one unperforated segment or vice-versa). Each
unperforated segment forms an attachment area between two
consecutive portions (according to the machine direction MD) of the
base sheet. Each perforated segment forms a detachment area between
two consecutive portions (according to the machine direction MD) of
the base sheet. Two consecutive tear lines 5 define the individual
sheet length L in the rolls of absorbent material sheet 4, e.g.,
typically a sheet of a bathroom tissue rolls may have a length of
around 33 cm. In FIG. 1, multiple phantom lines 20-27 parallel to
the machine direction MD are also represented on the base sheet 1
for the sole purpose of illustration. The phantom lines 20-27 are
spaced apart in the cross-machine direction CD. They schematically
represent imaginary lines where the base sheet 1 will be cut into
multiple and individual rolls of absorbent material sheet 4. The
distance between two consecutive phantom lines is equal to the full
width of the individual rolls 4. After the pinching step (S1), the
perforated base sheet 1 is wound (step S2) onto a core 3 in order
to form a wound log 2 by means of a rewinding unit 11. Various
types of rewinding unit are commonly used in the tissue industry,
for example center rewinders or surface rewinders. Once the desired
log diameter (corresponding to a substantially defined number of
individual sheets wound in the log) is reached, the base sheet 1 is
cut. The produced log 2 is separated (step S3) from the base sheet
1 and subsequently a new log begins to be produced. A loose end
forming a tail of the base sheet of the produced log 2 is adhered
to the log in a known manner. The produced log 2 is then cut (step
S4) by multiple log saws 40-47 into multiple and individual rolls
of absorbent material sheet 4. The corresponding cuts in the
produced log 2 are represented by multiple phantom lines 30-37 on
the surface of the produced log 2.
[0005] In the tissue industry, the mass production throughput
constraints imply a typical speed and tension of the converting
process. For example, the speed may be set at 650 m/min. At such a
speed, the tension in the parent base sheet required to wound the
roll may exceed the tensile strength of the tear lines. This
results in base sheet blowouts, namely breaks in the base sheet
along some of the tear lines. It is known to adjust the tensile
strength of the tear lines to solve this issue. However, increasing
the tensile strength of the tear lines may result in rolls that are
not satisfactory for the user or not adapted to the dispenser.
Indeed, they would require applying an unacceptable pulling force
in order to properly detach the individual sheets from the roll
along the tear lines.
[0006] The document U.S. Pat. No. 6,010,090 relates to a method of
perforating a web. An elongated web of paper is perforated along a
plurality of transverse lines to provide bands of web areas having
relatively high tensile strength which extend generally
longitudinally along the web. The lines of perforation can be
formed by staggered perforation lines which contain groups of
perforations which are separated by unperforated areas or by
staggered perforation lines which include groups of perforations
having relatively low tensile strength which are separated by
groups of perforations having relatively high tensile strength.
[0007] Thus, there is a need to improve the method for
manufacturing a roll of absorbent sheet material and/or the way of
coupling the individual sheets together in the roll of absorbent
sheet material for an easy dispensing. Further, this should be
obtained in economical or cost effective manner.
SUMMARY
[0008] It is an object of embodiments of the invention to propose a
manufacturing method that overcomes the drawbacks of the
manufacturing method of the prior art. It is another object of
embodiments of the invention to propose a roll method that
overcomes the drawbacks of the rolls of the prior art.
[0009] According to one aspect, there is provided a sheet of
absorbent material having opposite sheet side edges spaced apart
from one another to define an overall width of the sheet of
absorbent material, the sheet of absorbent material comprising
zones of weakness spaced along the sheet of absorbent material
according to a machine direction, each zone of weakness extending
substantially transversally to said machine direction, each zone of
weakness defining two adjacent individual absorbent sheet portions,
each zone of weakness being a tear line, [0010] wherein [0011] the
tear line comprises two edge regions and a central region, a first
edge region beginning at one of the sheet side edges towards the
central region, a second edge region beginning at the other sheet
side edges towards the central region, the central region
comprising alternating perforated segments and unperforated
segments, [0012] said edge regions are unperforated so as to
constitute attachment areas within the tear line between two
adjacent individual absorbent sheet portions.
[0013] A width ratio of the edge regions relatively to the central
region may range from about 4% to about 20%.
[0014] An edge region width may range from about 3 mm to about 10
mm.
[0015] The central region may comprise alternating perforated
segments and unperforated segments according to a perforation
pattern comprising at least two perforated segments separated by
one unperforated segment, each segment having substantially an
identical width.
[0016] The central region may comprise alternating perforated
segments and unperforated segments according to a perforation
pattern comprising multiple perforated segments, two adjacent
perforated segments being separated by one unperforated segment,
each perforated segment having a width increasing from one side
edge towards the opposite side edge, each unperforated segment
having a constant width.
[0017] The central region may comprise alternating perforated
segments and unperforated segments according to a perforation
pattern comprising multiple perforated segments, two adjacent
perforated segments being separated by one unperforated segment,
each unperforated segment having a width increasing from one side
edge towards the opposite side edge, each perforated segment having
a constant width.
[0018] According to another aspect, there is provided a roll of
absorbent material sheet comprising a sheet of absorbent material
according to an embodiment of the invention wound onto a core or on
itself.
[0019] According to still another aspect, there is provided a use
of the sheet of absorbent material according to an embodiment of
the invention for manufacturing absorbent sheet products chosen
among the group comprising napkins, towels, kitchen towels, hand
towels, toilet papers, wipes and facial tissues.
[0020] According to still a further aspect, there is provided a log
base sheet made of absorbent material having opposite log side
edges spaced apart from one another to define an overall width of
the log base sheet, the log base sheet comprising zones of weakness
spaced along the log base sheet according to a machine direction MD
of the log base sheet, each zone of weakness extending
substantially transversally to said machine direction, each zone of
weakness being a tear line, the log base sheet comprising multiple
phantom lines parallel to the machine direction representing
imaginary lines for cutting the log base sheet, [0021] wherein:
[0022] the tear line comprises multiple successions of first edge
region, a central region and a second edge region from one of the
log side edge towards the other log side edge, the central region
comprising alternating perforated segments and unperforated
segments, [0023] said edge regions are unperforated, and [0024]
each phantom line is positioned at a boundary between two adjacent
edge regions so as to constitute attachment areas within said tear
line between two adjacent central regions.
[0025] A central region out of two in each tear line may be
replaced by an unperforated region, and wherein two consecutive
tear lines are staggered according to a cross-machine direction CD
such that all the central region are positioned between two
adjacent phantom lines.
[0026] According to still another aspect, there is provided a log
of absorbent material sheet comprising a log base sheet made of
absorbent material according to an embodiment of the invention
wound onto a core or on itself.
[0027] According to still a further aspect, there is provided a
method for manufacturing a roll of sheet of absorbent material
comprising the steps of: [0028] feeding a log base sheet made of
absorbent material into a perforating unit, the log base sheet
having opposite log side edges spaced apart from one another to
define an overall width of the log base sheet; [0029] defining
zones of weakness spaced along the log base sheet according to a
machine direction MD of the log base sheet, each zone of weakness
extending substantially transversally to said machine direction MD,
by pinching each zone of weakness as a tear line; [0030] defining
multiple phantom lines (20-27) in the log base sheet parallel to
the machine direction MD representing imaginary lines for cutting
the log base sheet; [0031] wounding the pinched log base sheet onto
a core or on itself to form a log; [0032] cutting the pinched log
base sheet once a desired log diameter is reached; [0033] cutting
the log into multiple and individual rolls of absorbent material
sheet; [0034] pinching each tear line as multiple successions of
first edge region, a central region and a second edge region from
one of the log side edge towards the other log side edge, the
central region comprising alternating perforated segments and
unperforated segments; [0035] unperforating said edge regions; and
[0036] positioning each phantom line at a boundary between two
adjacent edge regions so as to constitute attachment areas within
said tear line between two adjacent central regions.
[0037] Optionally, A central region out of two in a tear line may
be replaced by an unperforated region, and wherein two consecutive
tear lines are staggered according to a cross-machine direction CD
such that all the central region are positioned between two
adjacent phantom lines.
[0038] With certain embodiments of the invention, it is possible to
improve the method for manufacturing a roll of absorbent material
sheet and/or the way of coupling the individual sheets together in
the roll for an easy dispensing.
[0039] Other advantages will become apparent from the hereinafter
description of embodiments of the invention.
[0040] BRIEF DESCRIPTION OF THE DRAWINGS
[0041] Embodiments of the present invention are illustrated by way
of examples and not limited to the accompanying drawings, in which
like references indicate similar elements:
[0042] FIG. 1 schematically illustrates a method for manufacturing
a roll of sheet of absorbent material according to the prior
art;
[0043] FIG. 2 schematically and partially illustrates a method for
manufacturing a log of sheet of absorbent material according to a
first exemplary embodiment of the invention;
[0044] FIG. 3 schematically and partially illustrates a method for
manufacturing a log of sheet of absorbent material according to a
second exemplary embodiment of the invention;
[0045] FIG. 4 is a perspective view schematically illustrating a
roll of sheet of absorbent material manufactured according to the
first or second embodiment;
[0046] FIGS. 5 and 6 are perspective views schematically
illustrating a perforating unit for the first and second exemplary
embodiment, respectively; and
[0047] FIGS. 7 to 11 schematically illustrate various perforating
patterns (top part) and corresponding knife (bottom part) for the
perforating unit illustrated in FIGS. 5 and 6.
DETAILED DESCRIPTION
[0048] FIG. 2 schematically and partially illustrates the method
for manufacturing a log of sheet of absorbent material according to
a first exemplary embodiment of the invention. More precisely, FIG.
2 schematically and partially shows a converting operation taking
place after a base sheet 1 has been produced by a paper making
machine. At this stage, the base sheet 1 is fed into a converting
line.
[0049] In FIG. 2, multiple phantom lines 20-27 parallel to the
machine direction MD are also represented on the base sheet 1 for
the sole purpose of illustration. The phantom lines 20-27 are
spaced apart in the cross-machine direction CD. Each phantom line
schematically represents an imaginary line where the base sheet 1
will be cut at the end of the converting process in order to form a
plurality of individual rolls of sheet of absorbent material. Thus,
two adjacent phantom lines define the future edges of the
individual roll. The distance between two consecutive phantom lines
is equal to the full width of the individual roll.
[0050] The base sheet 1 is fed into the space of the perforating
unit 10, namely between a perforator roll 11 and an anvil roll 12
of the perforating unit 10. The perforating unit 10 will be
described in details in relation with FIGS. 5 and 6. The base sheet
1 is pinched (step S1) with the tear lines 50 (schematically
represented by dotted lines). The tear line 50 is a line according
to a cross-machine direction CD (i.e. transversally to the machine
direction MD) made in the thickness of the base sheet 1 that
constitutes a zone of weakness. According to an embodiment of the
invention, the tear line 50 comprises two edge regions 56 and a
central region 55. A first edge region begins at one of the sheet
side edges towards the central region 55. A second edge region
begins at the other sheet side edges towards the central region 55.
The central region 55 comprises alternating perforated segments and
unperforated segments. The two edge regions 56 are short
unperforated segments. The central region 55 comprises alternating
perforation segments having a particular perforating pattern. The
perforating pattern of the perforation segments 55 will be
described in details in relation with FIGS. 7 to 11. The short
unperforated segments of the two edge regions 56 are crossed
substantially in the middle by a corresponding phantom line 20-27
or, in other word, each phantom line 20-27 is positioned at a
boundary between two adjacent edge regions 56. Each perforation
segment 55 is positioned in the middle of the full width defined by
two adjacent phantom lines (e.g., 21 and 22), more precisely at a
distance a from both phantom lines that defines the future edges of
the individual roll. Thus, the length of the short unperforated
segments 56 in the cross direction CD is noted 2.alpha.. The length
of the perforation segments 55 in the cross direction CD is noted
.beta.. Two consecutive tear lines 50 define the individual sheet
length L in the rolls 4 (e.g., a length around 33 cm).
[0051] The short unperforated segments 56 of length 2.alpha. form
attachment areas within the tear line 50 according to the
cross-machine direction CD of the base sheet. The short
unperforated segments form a plurality of attachment areas between
two consecutive portions according to the machine direction MD of
the base sheet. With an appropriately chosen length 2.alpha., the
resulting tensile strength of the tear lines 50 is significantly
improved. This avoids, at least considerably reduces, the blowouts
in the base sheet during production. Indeed, breaks in the base
sheet cannot propagate, at least with difficulty, along the tear
line 50. As a non-limitative example, the length 2.alpha. may be
chosen around or superior to 8 mm (i.e. .alpha..gtoreq.4 mm).
[0052] After the pinching step (S1), the perforated base sheet 1 is
wound (step S2) onto a core 3 (or alternatively on itself for
coreless log) in order to form a wound log 2 by means of the
rewinding unit 11. Then, though not represented and similarly to
the method for manufacturing a roll of sheet of absorbent material
represented in FIG. 1, once the desired log diameter is reached:
[0053] the base sheet 1 is cut; [0054] the produced log 2 is
separated from the base sheet 1 and subsequently a new log begins
to be produced; [0055] a loose end forming a tail of the base sheet
of the produced log 2 is adhered to the log; and [0056] the
produced log 2 is cut into multiple and individual rolls 4.
[0057] Considering the size of the individual roll, a width ratio
of the edge regions relatively to the central region may range from
about 4% (i.e. 2.alpha.=2.times.4 mm for a sheet width of the
individual roll of 200 mm) to about 20% (i.e. 2.alpha.=2.times.10
mm for a sheet width of the individual roll of 100 mm).
[0058] FIG. 3 schematically and partially illustrates the method
for manufacturing a log of sheet of absorbent material according to
a second exemplary embodiment of the invention. The second
exemplary embodiment differs from the first exemplary embodiment in
that the base sheet 1 is pinched (step S1) with staggered tear
lines 51 and 52 (schematically represented by dotted lines). One
central region out of two in each tear line is replaced by an
unperforated region, and two consecutive tear lines are staggered
according to a cross-machine direction CD such that all the central
region are positioned between two adjacent phantom lines. More
precisely, two identical adjacent tear lines 50 in the first
exemplary embodiment are replaced by a first tear line 51 adjacent
to a second tear line 52, the first tear line 51 being staggered or
offset according to the CD direction relatively to the second tear
line 52. Further, the tear line 51 or 52 comprises alternating
perforation segments 55 having a particular perforating pattern and
long unperforated segments 56 (corresponding to two edge regions
and one unperforated central region). The perforating pattern of
the perforation segments 55 will be described in details in
relation with FIGS. 7 to 11. The perforated segments 55 are
positioned in the middle of the full width defined by two adjacent
phantom lines (e.g., 20 and 21 for the first tear line 51), more
precisely at a distance a from both phantom lines that defines the
future edges of the individual roll. Still, the length of the
perforation segments 55 in the cross direction CD is noted .beta..
Compared to the first exemplary embodiment, in the second exemplary
embodiment each long unperforated segment 56 has the length
2.alpha. increased from the length of a roll width, or a length
2.alpha.+.beta.+2.alpha.=4.alpha.+.beta.. Two consecutive tear
lines 51 or 52 define the individual sheet length L in the rolls of
sheet of absorbent material 4 (e.g., a length around 33 cm). Two
adjacent tear lines 51 and 52 are separated by a distance 6 in the
machine direction MD.
[0059] The long unperforated segments 56 of length 4.alpha.+.beta.
form attachment areas within the tear line 51, 52 according to the
cross-machine direction CD of the base sheet. The long unperforated
segments form a plurality of attachment areas between two
consecutive portions according to the machine direction MD of the
base sheet. Thus, the resulting tensile strength of the tear lines
51, 52 is significantly improved. This avoids, at least
considerably reduces, the blowouts in the base sheet during
production. The breaks in the base sheet cannot propagate, at least
with difficulty, along the tear line 51 or 52. As a non-limitative
example, the length 2.alpha. may be chosen around or superior to 8
mm (i.e. .alpha..gtoreq.4 mm).
[0060] FIG. 4 is a perspective view schematically illustrating the
individual roll of sheet of absorbent material 4 manufactured
according to the first embodiment of FIG. 2 or the second
embodiment of FIG. 3. The roll 4 may be a roll of paper, for
example a roll of toilet paper or a roll of kitchen towels. The
roll may comprise a core or may be coreless. The roll has evenly
spaced-apart transverse tear lines 50, 51, 52 which extend across
the width of individual sheet of absorbent material 59 (e.g., a
paper web). The tear lines 50, 51, 52 enable tearing off and
separation of individual sheets of paper 19 of a predetermined
length L when the roll is unwound in the direction of the arrow.
The two attachment areas between two consecutive individual sheets
19 (according to the machine direction MD of the sheet) resulting
from the short unperforated segments of length a on each edge of
the individual roll do not impair the separation of each individual
sheet 19 from the roll 4 when the dimension .alpha. is
appropriately chosen.
[0061] FIG. 5 is a perspective view schematically illustrating a
perforating unit 10 used for pinching the base sheet 1 according to
the manufacturing method of the first exemplary embodiment.
[0062] The perforating unit 10 comprises the perforator roll 11 and
the anvil roll 12. The space 18 is defined therebetween. The
perforator roll 11 carries at least one knife, for example two
knifes 14, 15. In this non limitative example, the first knife 14
is positioned at 180 degrees relatively to the second knife 15.
More knifes and different positioning angle are possible. The anvil
roll 12 carries a spiral blade 13. The perforator roll 11 and the
anvil roll 12 are both rotating so that when the base sheet 1 is
fed into the space 18, it is pinched according to a scissors like
movement between one of the knife 14 or 15 and the spiral blade
13.
[0063] In the embodiment of FIG. 5, each knife 14, 15 extends all
along the width of the perforator roll 11. This width corresponds
at least to the width of the base sheet 1 or the width of the log
2. Each knife is used to cut the tear line 50 (see FIG. 2) in the
base sheet 1. Each knife 14, 15 comprises multiple zones 16, each
zone corresponding to a perforation segment 55 having a defined
perforating pattern that may be chosen among the represented
perforating pattern of FIGS. 7 to 11. Each zone 16 is separated
from an adjacent zone by the distance 2..alpha..
[0064] FIG. 6 is a perspective view schematically illustrating
another perforating unit 10 used for pinching the base sheet 1
according to the manufacturing method of the second exemplary
embodiment. The embodiment of FIG. 6 differs from the embodiment of
FIG. 5 in that both knifes 14 and 15 comprises segmented zones 16.
Similarly, each segmented zone 16 corresponds to a perforation
segment 55 having a defined perforating pattern that may be chosen
among the represented perforating pattern of FIGS. 7 to 11. The
first knife 14 is used to cut the first tear line 51 (see FIG. 3)
in the absorbent base sheet 1.The second knife 15 is used to cut
the second tear line 52 (see FIG. 3) in the absorbent base sheet 1.
A zone 16 of the first knife 14 is shifted relatively to a zone 16
of the second knife 15 by the distance 2..alpha. (corresponding to
the two adjacent unperforated edge regions) so as to pinch the base
sheet 1 according to staggered tear lines 51 and 52.
[0065] FIG. 7 schematically illustrates a first exemplary
perforating pattern of a perforation segment 55A (top part) and the
corresponding zone 16A of the knife 14, 15 (bottom part). The
perforation segment 55A comprises two perforated segments 60
separated by one unperforated segment 61. The unperforated segment
61 forms an attachment area between two consecutive portions
(according to the machine direction MD) of the base sheet. Each
perforated segment 60 forms a detachment area between two
consecutive portions (according to the machine direction MD) of the
base sheet. The zone 16A of the knife 14, 15 comprises a succession
of blade elements and notch corresponding to the first exemplary
perforating pattern.
[0066] FIG. 8 schematically illustrates a second exemplary
perforating pattern of a perforation segment 55B (top part) and the
corresponding zone 16B of the knife 14, 15 (bottom part). The
perforation segment 55B comprises four perforated segments 62, two
adjacent perforated segments 62 being separated by an unperforated
segment 63. The zone 16B of the knife 14, 15 comprises a succession
of blade elements and notches corresponding to the second exemplary
perforating pattern.
[0067] FIG. 9 schematically illustrates a third exemplary
perforating pattern of a perforation segment 55C (top part) and the
corresponding zone 16C of the knife 14, 15 (bottom part). The
perforation segment 55C comprises eighteen perforated segments 64,
two adjacent perforated segments 64 being separated by an
unperforated segment 65. The zone 16C of the knife 14, 15 comprises
a succession of blade elements and notches corresponding to the
second exemplary perforating pattern.
[0068] FIG. 10 schematically illustrates a fourth exemplary
perforating pattern of a perforation segment 55D (top part) and the
corresponding zone 16D of the knife 14, 15 (bottom part). The
perforation segment 55D comprises multiple perforated segments 66,
two adjacent perforated segments 66 being separated by an
unperforated segment 67. The width of the perforated segments 66
increases along the perforation segment 55D, as depicted from the
left to the right (or conversely). The width of the unperforated
segment 67 is constant along the perforation segment 55D. The zone
16D of the knife 14, 15 comprises a succession of blade elements
and notches corresponding to the second exemplary perforating
pattern. The width of the blade elements increases along the zone
16D of the knife while the width of the notch is constant.
[0069] FIG. 11 schematically illustrates a fifth exemplary
perforating pattern of a perforation segment 55E (top part) and the
corresponding zone 16E of the knife 14, 15 (bottom part). The
perforation segment 55E comprises multiple perforated segments 68,
two adjacent perforated segments 68 being separated by an
unperforated segment 69. The width of the perforated segments 68 is
constant along the perforation segment 55E. The width of the
unperforated segment 69 increases along the perforation segment
55D, as depicted from the left to the right (or conversely). The
zone 16E of the knife 14, 15 comprises a succession of blade
elements and notches corresponding to the second exemplary
perforating pattern. The width of the blade elements is constant
along the zone 16D of the knife while the width of the notch
increases.
[0070] In the represented perforating pattern of FIGS. 7 to 11, the
numbers of perforated segments and unperforated segments are given
as non-limitative examples, other numbers would also be
satisfactory in the context of embodiments of the present
invention.
[0071] The roll of sheet of absorbent product of an embodiment of
the invention can be dispensed in various dispensers, for example
in center-feed dispensers for dispensing sheets from the center of
the roll or in tangential dispensers for tangentially dispensing
sheets from the roll.
[0072] Tensile strength measurements according to the standard CEN
12625-4 (determination of tensile strength, stretch at break and
tensile energy absorption of tissue paper and tissue products) have
been performed on sheets according to the prior art and according
to an embodiment of the invention. The characteristics of the
central region comprising alternating perforated segments 60, 62,
64, 66, 68 of dimension and unperforated segments 61, 63, 65, 67,
69 of dimension US around 4 mm PS around 1 mm gives an unperforated
ratio or bond ratio of 20% (1 mm over 5.degree. mm). The
perforating pattern is the one of FIG. 9.
Tensile Strength Measurements:
TABLE-US-00001 [0073] Prior Art Invention Invention Invention US =
1 mm .alpha. = 0 mm .alpha. = 3 mm .alpha. = 5.5 mm .alpha. = 8 mm
PS = 4 mm N/m N/m N/m N/m Single ply 64 56 63 71 Two plies 132 124
132 142
The log base sheet according to an embodiment of the invention can
be converted at speeds typical in the industry, e.g., up to
650.degree. m/min without the occurrence of sheet blowouts. This
shows an improved tensile strength of each zone of weakness (tear
line) of the log base sheet when runs into the converting machine.
Further, the tensile strength of the sheet (e.g., wound as an
individual roll) is similar, even less, to the one of the prior
art, thus showing an easy dispensing. In particular, an edge region
having a width (.alpha.) ranging from about 3 mm to about 5 mm
gives excellent results in term of tensile strength, thus allowing
easy dispensing. This is a surprising results because whatever the
size of the edge zone (within said range) and at equivalent
unperforated ratio, the tensile strength of the tear line of the
sheet is identical or at least quite similar, while one could have
expected an increased tensile strength resulting in poor
dispensing.
[0074] The drawings and their descriptions hereinbefore illustrate
rather than limit the embodiments of the invention.
[0075] In the description and the drawings, each zone of weakness
(being a tear line) have been described and/or shown as extending
substantially transversally to the machine direction. This should
be interpreted in a broad sense, meaning that the zone of weakness
may be inclined relatively the cross-machine direction CD, as an
example according to angle in a range of .+-.10.degree..
[0076] The application of the absorbent sheet product is broad and
encompasses numerous away-from-home, domestic or sanitary
applications, e.g., towels, kitchen towels, hand towels, toilet
papers, wipes, facial tissues, bath tissues, napkins etc.
[0077] Any reference sign in a claim should not be construed as
limiting the claim. The word "comprising" does not exclude the
presence of other elements than those listed in a claim. The word
"a" or "an" or "at least one" preceding an element does not exclude
the presence of a plurality of such element.
* * * * *