[0001] This invention relates to a method and apparatus for forming non-penetrative scored
lines on sheet material, e.g. paper, more particularly, but not exclusively, for use
in the manufacture of adhesive label laminates.
[0002] Adhesive label laminates usually consist of a release sheet or liner carrying a release
coating, typically a silicone coating, which supports a label sheet having on its
reverse a coating of pressure sensitive adhesive. The characteristics of the release
coating ensure that one element of the laminate can be readily peeled from the other,
and that the adhesive remains on the label sheet.
[0003] However, when a label is required for use, difficulties can arise in peeling the
release liner from the label due to the fact that no available edge of the backing
sheet is exposed to be gripped by the fingers to enable peeling to be effected.
[0004] United States Patent Specification No. 3,859,157 proposes as a solution to this problem
the provision of scored lines of weakness on the reverse of the release liner. When
the laminate is then flexed about an axis generally parallel to a scored line, the
release liner cracks along the scored line to present two edges which can be gripped
to peel the liner from the label.
[0005] The apparatus proposed in the above mentioned United States Patent Specification
for the formation of such scored lines consists of two metal rolls which form a nip,
with one of the rolls having a series of spaced parallel wires secured so as to extend
axially, helically or circumferentially across the surface thereof. Transverse, diagonal
or longitudinal scored lines are formed on the label laminate by passing the release
liner through the roll nip with the non release coated face presented for engagement
with the wires. The nip pressure is sufficient to compact the paper along the scored
lines and to render the paper locally weakened.
[0006] It has been found, however, that apparatus of the kind described cannot be relied
upon to produce scored lines of consistent depth. This may principally be due to the
lack of resilience of the surfaces of either of the metal rolls, which manifests itself
as insensitivity to variations in laminate thickness, or may be due to mechanical
inaccuracies in the rolls due to manufacturing tolerances or may be due to roll deflections
during use. As a result, for a given nip pressure between the rolls, the release liner
will unpredictably be under scored or over scored or unevenly scored. Such a liner
will either not crack along a scored line when required to do so, or a cut will be
formed through the liner and sometimes into the label sheet.
[0007] A solution to the problem of variability in scoring described above is proposed in
the United States Patent Specifications Nos. 4,678,457 and 4,698,052. Patent No. 4,678,457
teaches the replacement of the metal roll of US Patent No. 3,859,157 which carries
circumferential scoring wires with a series of spaced and independently mounted rotary
crush scoring knives extending in spaced relation across the width of the smooth metal
backing roll, and each formed with a rounded crushing edge. Patent No. 4,698,052 teaches
the replacement of the metal backing roll of US Patent No. 3,859,157 with a series
of spaced and independently mounted anvil rollers extending in staggered relation
across the width of the wire wound metal scoring roll.
[0008] The crush scoring knives of US Patent No. 4,678,457 and the anvil rollers of US Patent
No. 4,698,052 are each carried in a mounting bracket which is biased towards the co-operating
backing or scoring roller by air pressure, but which is mounted in such a manner that
movement towards or away from the co-operating roller is in an essentially friction-free
manner.
[0009] The use of friction-free moveable mounting brackets as described above enables the
crush scoring knives or anvil rollers to float with fluctuations in paper thickness,
and thus overcomes the over and under scoring problem experienced with the apparatus
of US Patent No. 3,859,157.
[0010] It is among the objects of the present invention to provide an alternative method
and apparatus for forming scored lines on sheet material, especially label laminates,
which takes account of variability in laminate thickness, and which has particular
advantages for use in the formation of scored lines at an acute angle, typically 45°
to the longitudinal axis of the sheet.
[0011] According to the invention there is provided a method of forming a scored line on
a sheet of scorable material comprising the step of passing the sheet through the
nip of a pair of contra-rotating rolls, one of which rolls has a hard surface and
the other of which rolls has a resilient surface and one or other of which rolls has
at least one scoring element extending over its surface. It has been found that by
this method the scoring element is pressed evenly into the sheet to be scored irrespective
of the normally occurring variations in thickness of the sheet as described previously.
It is assumed that during the scoring process the scoring element resiliently deforms
the resilient surface of one of the rolls to a varying extent to compensate for the
varying thickness of the sheet so that the scoring remains substantially constant.
[0012] Preferably the arrangement is such that this scoring element is disposed on the roll
having a resilient surface. Preferably the resilient surface has a Shore D hardness
in the range of about 60° to about 85° measured according to International Standard
ISO 868-1978 (British Standard BS2782:Part 3:Method 365B:1981 or Standard D2240 of
the American society for Testing Materials).
[0013] Preferably the method comprises the step of applying pressure to the rolls to control
the nip. The nip pressure of the rolls will preferably lie in the range 70 to 160
lb (32 to 73 kgs) per wire when scoring sheets of paper.
[0014] Preferably the method comprises the preliminary step of adjusting the pair of rolls
so that the axis of one of them is disposed either upstream or downstream with respect
to the axis of the other roll to a small extent e.g. by an amount of around 1 mm.
[0015] The method may comprise the preliminary step of arranging the hard roll to form a
nip only with its central portion so as to leave marginal portions of the sheet unscored.
[0016] The method may comprise the preliminary step of skewing the axes of the pair of rolls
relative to one another to a small extent or for example one or two degrees.
[0017] The method may comprise the preliminary step of wrapping a scoring element helically
round the resilient roll and tensioning the scoring element.
[0018] From another aspect the invention provides a method of making a laminate for use
in making a label or the like from a paper fibrous material layer, comprising the
steps of applying a liquid release coating to one surface of the paper layer and drying
it thereon, thereafter forming a plurality of weakened reduced thickness score lines
in the other surface of the paper layer by passing the paper layer through the nip
of a pair of contra-rotating rolls, one of which rolls has a hard surface and the
other of which rolls has a resilient surface and one or other of which rolls has at
least one scoring element extending over its surface, and laminating a layer of adhesive
and a face sheet to said paper layer with said adhesive layer being intermediate the
paper layer and the sheet and being bonded to the said one surface of the paper layer.
[0019] From yet another aspect the invention is a sheet of scorable material scored by the
method described above.
[0020] A sheet of scorable material scored by the method described above can be distinguished
from a sheet secured by previously known processes in that the method of the present
invention provides an exceptionally even score. Usually the even score is such as
to be readily distinguishable by eye from scores made in paper and the like by known
scoring processes.
[0021] From another aspect the invention is a flexible laminate for use as a label or the
like, comprising a face sheet, a layer of pressure sensitive adhesive secured to the
back surface of said face sheet, and a fibre paper backing layer removably secured
to said adhesive layer, the paper backing layer having a release coating on its surface
engaging the adhesive layer and having a reduced thickness potential tear line formed
therein, the fibres of the paper backing layer being compacted at the potential tear
line by passing the backing layer through the nip of a pair of contra-rotating rolls,
one of which rolls has a hard surface and the other of which rolls has a resilient
surface and one or other of which rolls has at least one scoring element extending
over its surface.
[0022] From another aspect the invention provides a rotatably mounted and substantially
rigid scoring roll, for use in co-operation with a substantially rigid and rotatably
mounted anvil roll having a hard surface, to form a nip through which scorable material,
such as paper, can be passed for the formation of scored lines thereon, said scoring
roll having one or more linear scoring elements extending over a resilient surface
layer formed on said scoring roll, said surface layer having Shore D hardness in the
range of about 60° to about 85° measured according to International Standard ISO 868-1978
(British Standard BS2782:Part 3:Method 365B:1981 or Standard D2240 of the American
Society for Testing Materials).
[0023] In another aspect, the invention provides apparatus for forming scored lines of a
required depth on a sheet of scorable material, comprising a rotatably mounted and
substantially rigid scoring roll having one or more linear scoring elements extending
across the surface thereof, a substantially rigid anvil roll having a hard surface
and rotatably mounted in substantially parallel relation to said scoring roll to define
a nip therewith, and means for generating pressure between said rolls at said nip
to form scored lines of the required depth on said scorable material during passage
thereof through said nip, with one of said rolls having a resilient surface layer
formed thereon having a Shore D hardness in the range of about 60° to about 85° measured
according to International Standard ISO 868-1987 (British Standard BS2782:Part 3:Method
365B:1981 or Standard D2240 of the American Society for Testing Materials).
[0024] In a further aspect, the invention provides apparatus for forming scored lines of
a required depth on a sheet of scorable material, comprising a steel scoring roll
having a plurality of tensioned wires between about 1.1 mm and 1.4 mm in diameter,
extending helically, and in substantially parallel relationship across a resilient
surface layer formed on said roll and having a Shore D hardness in the range of about
60° to about 85° measured according to International Standard ISO 868-1978 (British
Standard BS2782:Part 3:Method 365B:1981 and Standard D2240 of the American Society
for Testing Materials), a steel anvil roll, means for mounting said scoring and anvil
rolls for rotation about substantially parallel horizontal axes, means for moving
at least one of said rolls towards the other roll to form and generate pressure at
a nip, so that contra-rotation of said rolls to draw a sheet of scorable material
through said nip will generate on said material a series of parallel scored lines
of the required depth extending at an acute angle to the direction of movement of
said material.
[0025] It will be understood that the required depth of score will vary depending upon the
material being scored and the purpose for which the score is being applied. Furthermore,
for any particular material being scored, variations in the depth of score within
certain limits are in practice acceptable. The term "required depth" is understood
as being any depth of score within such acceptable limitations.
[0026] Preferably the scoring and anvil rolls are made of steel and the resilient material
with which one or other of the rolls is coated is preferably polyurethane. Preferably,
the resilient material has a Shore D hardness of about 70° to about 80° measured as
specified above and optimally the hardness is about 75°.
[0027] Use of a resilient surface layer having a hardness of less than about 60° results
in uncontrollable variability in the scored lines, and generally to underscoring.
If the hardness is greater than about 85°, the roll system is insufficiently sensitive
to variations in laminate thickness and over or under scoring results.
[0028] The rolls may be disposed with their axes extending horizontally and with the anvil
roll positioned substantially vertically above the scoring roll.
[0029] The axis of the anvil roll may be offset slightly upstream or downstream on the axis
of the scoring roll in the direction of sheet movement, for example by an amount of
1 mm. Such an offset has been found to afford increased stability of operation.
[0030] Advantageously, the anvil roll is also formed with a central land which forms the
nip with the scoring roll so that scoring is not effected across the full width of
the scored web. This has been found to give more reliable operation, in that the full
tensile strength of the web is present at the web edge, so reducing the chance of
the web breaking. Furthermore, the axis of the anvil or scoring roll may be skewed
very slightly, for example by 1° or 2° with respect to the axis of the other roll,
the amount of skew depending on the length of the rolls. Such skewing can sometimes
improve the pressure distribution across the nip, depending on the length, diameter
and degree of flexibility, perpendicular to their axes, of the scoring and anvil rolls.
[0031] The linear scoring elements preferably present a radiused edge, having a diameter
of about 1.2 mm. The use of wire, such as 18 gauge piano wire, having a diameter of
1.15 mm, has been found to be satisfactory and that simple tensioning of such wire
across the surface of the roll affords adequate stability. The use of linear scoring
elements which have too small a diameter, for example 0.5 mm or the use of linear
scoring elements of too great a diameter, for example 2.0 mm will require different
and excessive nip pressures in order to achieve scoring. Also the performance of the
final product may not be as acceptable.
[0032] The linear scoring elements are preferably straight and extend in parallel relation
across the surface of the scoring roll. However, the use of divergent or convergent
elements is not excluded, provided that they do not intersect. The linear scoring
elements may also have other configurations, for example a sinusoidal configuration.
[0033] The use of axially aligned linear scoring elements is undesirable since their use
might lead to excessive repetitive shocks on the roller bearings as the scoring elements
enter the nip, especially during high speed operation. In addition very high nip pressures
would be required to achieve scoring since adequate pressure would need to be applied
to the entire length of each scoring element as it passes through the nip.
[0034] Circumferentially extending linear scoring elements may be used for the formation
of longitudinal score lines in the sheet, provided that they extend across a resilient
surface formed on the roll in accordance with the invention. If the wires are applied
circumferentially to a metal surfaced roll, wire movement may otherwise take place
as a result of slackening caused by localised stretching produced when the wire is
subjected to nip pressure.
[0035] The invention will now be further described with reference to the accompanying drawings
in which:-
Figure 1 is a semi-diagrammatic front elevation, partly in section of a scoring apparatus
according to the invention;
Figure 2 is an end elevation on the line II-II of Figure 1, and
Figure 3 is an isometric view of the apparatus of Figure 1 in use for scoring the
reverse of the release sheet of an adhesive laminate.
Referring first to Figures 1 and 2 of the drawings, the apparatus 1 shown comprises
a pair of vertical side frames 2 each formed with a vertical slideway 3 at the upper
end and a horizontal slideway 4 at the lower end.
[0036] A roll 5 comprises a cylindrical steel shell 6 extending between end plates 7, the
end plates 7 being carried on stub shafts 8. The stub shafts 8 are journalled for
rotation in bearing blocks 9 having horizontal slideways grooves 10 co-operable with
the horizontal slideways 4. The bearing blocks 9 are secured in the required position
in the slideways 4 by conventional jacking bolts (not shown) whereby the axis of rotation
of the roll 5 can be shifted in a horizontal plane.
[0037] The surface of the cylindrical shell 6 carries a resilient sheath 11, 12 mm thick,
of polyurethane resin. The cured resin has Shore D hardness of around 75° measured
according to International Standard ISO 868-1978 (British Standard BS2782:Part 3:Method
365B:1981 or Standard D2240 of the American Society for Testing Materials).
[0038] At one end of the roll 5, the stub shaft 8 has a flanged boss 12 secured thereon,
with the flange 13 thereof having a diameter slightly larger than that of the cylindrical
shell 6. A series of regularly spaced small axially extending apertures (not shown)
are formed in the flange 13 near the periphery thereof, with each hole being intersected
by a threaded radial hole (not shown) in which a grub screw (not shown) is engaged.
[0039] At the other end of the roll 5 a further boss 14 is secured on the other stub shaft
8. The boss 14 carries two flanges, 15 and 16. The flange 15 has secured in the periphery
thereof a series of radially extending and regularly spaced steel pins (not shown)
formed with apertures extending parallel to the axis of the roll 5. The flange 16
is formed with axially extending and regularly spaced threaded radial holes (not shown)
each fitted with a grub screw essentially as described with reference to the flanged
boss 12.
[0040] A series of 18 gauge wires (1.2 mm in diameter) are passed through the axial holes
in the flange 13 and the wire ends secured therein by tightening the grub screws.
The wires are laid helically and in parallel relation across the surface of the polyurethane
coating 11 and at an angle of 45° to the axis of the roll 5. At the other end of the
roll 5, the wires are passed around the radially extending pins located in the flange
15 and then through the axially extending apertures in the flange 16, where, after
tensioning, they are secured by tightening the grub screws. The wires could alternatively
be tensioned with springs as shown in the prior art.
[0041] Mounted immediately above the roll 5 is a hardened steel roll 20 having reduced diameter
ends so as to leave a central land 21. The roll 20 is carried on stub shafts 22 rotatably
mounted in vertically slidable bearing blocks 23. The bearing blocks 23 are formed
with slideway grooves 26 and are mounted for vertical sliding movement in the slideways
3 of the frames 2, and are connected by piston rods 24 to pneumatic piston and cylinder
units 25. The piston and cylinder units 25 are of a conventional kind. Appropriate
control of air pressure facilitates raising or lowering of the roll 20 and generation
of nip pressure when a nip is formed between the rolls 5 and 20.
[0042] Turning now to Figure 3, this shows the essential features of the apparatus of Figures
1 and 2 when in use to form diagonal scored lines on the reverse of a release sheet
30. The sheet 30 is fed through a nip formed between the rotating rolls 20 and 5 at
which nip pressure is generated by the pneumatic piston and cylinder units 25. As
a result, the wires 17 generate diagonal scored lines 31 on the release sheet 30,
the scored lines extending across a width corresponding to the width of the land 21.
Due to the resilience of the layer 11, continuous scored lines of the required depth
are formed.
[0043] The scoring process can be fine tuned by adjusting the position of the roll 5 with
respect to the roll 20 either upstream or downstream to a small extent, e.g. by 1
mm, and/or by skewing the axis of the roll 5 slightly, e.g. by 1 or 2 degrees, relative
to the axis of the roll 20. This adjustment is carried out by moving the positions
of the bearing blocks 9 in the slideways 4.
[0044] It will be apparent that modifications to the embodiment shown may be adopted without
departing from the invention. Thus, for example, the wires 17 may be laid down directly
on the cylindrical steel shell 6 of the roll 5, with the resilient coating 11 being
applied to the land 21 of the roll 20. This will produce scored lines marginally less
sharp than those produced by the embodiment above described, but they will generally
be of acceptable quality. It is sufficient for the accomplishment of the invention
that a single resilient layer of the specified hardness should be present as one of
the roll surfaces at the nip.
1. A method of forming a scored line (31) on a sheet (30) of scorable material comprising
the step of passing the sheet (30) through the nip of a pair of contra-rotating rolls
(5, 20), characterised in that one of the rolls (5, 20) has a hard surface and the
other of the rolls (5, 20) has a resilient surface (11) and in that one of the rolls
(5, 20) has at least one scoring element (17) extending over its surface.
2. A method according to claim 1, characterised in that the scoring element (17) is
disposed on the roll (5) having a resilient surface (11).
3. A method according to claim 1 or claim 2, characterised in that the resilient surface
has a Shore D hardness in the range of 60° to 85°.
4. A method according to any preceding claim, characterised by the step of applying
pressure to the rolls (5, 20) to control the nip.
5. A method according to claim 4, characterised in that the nip pressure of the rolls
(5, 20) lies in the range 32 to 73 kgs per scoring element (17).
6. A method according to any preceding claim, characterised by the step of adjusting
the pair of rolls (5, 20) so that the axis of one of them is offset with respect to
the axis of the other roll.
7. A method according to any preceding claim, characterised by the step of arranging
the hard roll (20) to form a nip only with its central portion (21) so as to leave
marginal portions of the sheet (30) unscored.
8. A method according to any preceding claim, characterised by the step of skewing
the axes of the pair of rolls (5, 20) relative to one another.
9. A method according to any preceding claim, characterised by the step of wrapping
a scoring element (17) helically round the resilient roll (5) and tensioning the scoring
element.
10. A method of making a laminate for use in making a label or the like from a paper
sheet, comprising the steps of applying a liquid release coating to one surface of
the paper sheet (30) and drying it thereon, thereafter forming a plurality of weakened
reduced thickness score lines (31) in the other surface of the paper sheet by passing
the paper sheet through the nip of a pair of contra-rotating rolls (5, 20), characterised
in that one of the rolls (5, 20) has a hard surface and the other of the rolls (5,
20) has a resilient surface (11) and in that one of the rolls (5, 20) has at least
one scoring element (17) extending over its surface, and characterised by laminating
a layer of adhesive and a face sheet to said paper sheet (30) with said adhesive layer
being intermediate the paper sheet and the face sheet and being bonded to the said
one surface of the paper sheet.
11. A sheet of scorable material scored by the method of any preceding claim.
12. A flexible laminate for use as a label or the like, comprising a face sheet, a
layer of pressure sensitive adhesive secured to the back surface of said face sheet,
and a fibre paper backing layer removably secured to said adhesive layer, the paper
backing layer having a release coating on its surface engaging the adhesive layer
and having a reduced thickness potential tear line formed therein, the fibres of the
paper backing layer being compacted at the potential tear line by passing the backing
layer through the nip of a pair of contra-rotating rolls (5, 20), characterised in
that one of the rolls (5, 20) has a hard surface and the other of the rolls (5, 20)
has a resilient surface (11) and in that one of the rolls (5, 20) has at least one
scoring element (17) extending over its surface.
13. Apparatus for scoring sheet material comprising a rotatably mounted scoring roll
(5), a co-operating rotatably mounted anvil roll (20) having a hard surface, the rolls
(5, 20) forming a nip through which scorable material (30) can be passed for the formation
of scored lines (31) thereon, characterised by a resilient surface layer (11) on the
scoring roll (5), at least one linear scoring element (17) extending over the resilient
surface layer (11) on said scoring roll (5), said surface layer having Shore D hardness
in the range 60° to 85°.
14. Apparatus according to claim 13, characterised in that the linear scoring elements
(17) comprise a plurality of tensioned wires in the range 1.1 mm to 1.4 mm in diameter,
extending helically, and in substantially parallel relationship across the resilient
surface layer (11).
15. Apparatus according to claim 13 or claim 14, characterised in that the material
forming the resilient surface layer (11) is polyurethane.
16. Apparatus according to claims 15, characterised in that the resilient material
has a Shore D hardness in the range 70° to 80°.
17. Apparatus according to claim 16, characterised in that the resilient material
has a Shore D hardness of about 75°.
18. Apparatus according to any one of claims 13 to 17, characterised in that the rolls
(5, 20) are disposed with their axes extending horizontally and with the anvil roll
(20) positioned substantially vertically above the scoring roll (5).
19. Apparatus according to any one of claims 13 to 18, characterised in that the axis
of the anvil roll (20) is offset from the axis of the scoring roll (5).
20. Apparatus according to any one of claims 13 to 19, characterised in that the anvil
roll (20) is formed with a central land (21)which forms the nip with the scoring roll
(5) so that scoring is not effected across the full width of the scored web (30).
21. Apparatus according to any one of claims 13 to 20, characterised in that the axis
of one roll (5, 20) is skewed with respect to the axis of the other roll (5, 20).
22. Apparatus according to any one of claims 13 to 21, characterised in that the linear
scoring elements (17) present a radiused edge.