[0001] The present invention relates to forming a sheet material, particularly a fibre based
sheet material, for example paperboard, used for example in packaging.
[0002] It is known to produce packaging such as trays from extensible sheet materials, for
example extensible paperboard materials, by positioning a sheet of the material on
a female form part having a cavity and pressing the sheet into the cavity in the female
form part by means of a male part. Such a process is described for example in
EP-A-1985437.
[0003] In
EP-A-1985437, a two stage process is in fact described. In a first step, the sheet is unrestrained
around its edge and is dragged into the cavity of the female part by the male part.
This forms creases in the sheet. In a second step, the drawn sheet is restrained around
its edge and deformed into the same or a different female mould part using the same
or a different male part.
[0004] In other processes, the sheet material may simply be retained around its edges and
drawn into the female part by the male part.
[0005] In such drawing processes, however, it has been found by the Applicant that it is
extremely important that the sheet material is firmly retained around its edge. If
this does not happen, then the sheet material may slip and be dragged into the mould
(as in
EP-A-1985437). This may lead to the severe creasing in the material and poor quality forming.
[0006] The present invention seeks to overcome or at least mitigate this problem.
[0007] From a first aspect the present invention provides a method for forming an extensible
sheet material comprising:
positioning a blank of sheet material over a female forming cavity;
clamping the periphery of said sheet around the periphery of said cavity; and
pressing said sheet material into said cavity by means of a male part; wherein
said clamping is effected by means of said periphery of said sheet material being
clamped between non-planar clamping surfaces.
[0008] From a second aspect the invention provides a tool for forming an extensible sheet
material, the tool comprising:
a first, female tool part including a forming cavity;
a second tool part mountable to said first tool part for clamping a portion of said
sheet material between opposing clamping surfaces of said first and second tool parts;
and
a third, male tool part for insertion into said forming cavity; and wherein
said clamping surfaces are non-planar
[0009] Thus in accordance with the invention, rather than the extensible sheet material
being clamped between two planar surfaces as for example disclosed in
EP-A-1985437, it is clamped between non-planar surfaces. This improves the retention of the sheet
material during the drawing process.
[0010] The non-planar surfaces may take a number of forms. For example, the surfaces may
be formed with interengaging clamping formations. A series of clamping formations
may be provided one outside the other to improve the clamping effect.
[0011] In one example, the surfaces may be provided with one or more interengaging step
formations provided around the cavity.
[0012] In another arrangement, the surfaces may be provided with one or more interengaging
channel and rib formations.
[0013] Most preferably the interengaging formations deform the sheet material through at
least a 90° angle, thereby improving the retention. Thus the edges of the step or
channel may therefore be perpendicular to the surrounding surface. However, the step
or channel may be formed at an angle to the vertical, for example within 20° of the
vertical.
[0014] The clamping formation is positioned at an appropriate spacing from the mould cavity.
This can be determined empirically for each application.
[0015] Similarly the optimum dimensions of the formations can be determined empirically.
In one embodiment however, a channel may be 1 mm wide and the complementary rib 0.5
mm wide. The channel may typically be 2 mm deep.
[0016] The end surface of the male tool part which is pressed into the sheet material is
shaped to give the desired profile to the formed sheet product. It will be understood
that the shape of the formed sheet will be determined by the male tool part. The cavity
in the female part does not need to closely complement the shape of the male tool
part. However, depending on the intricacy of the shape being formed it may be desirable
to have the male tool part bottom out in the female part cavity in order to provide
the necessary definition. It is desirable that peripherally, the cavity should provide
sufficient clearance with the male tool part so that it does not interfere with the
deformation of the sheet material by the male tool part as it moves into the cavity.
[0017] In one example, where the tool is being used for producing blister packs for example,
the end surface of the tool part may be formed with a plurality of spaced apart projections
each of which will form a blister formation on the formed sheet.
[0018] The female tool part may have a plurality of forming cavities each engaged by a corresponding
male tool part. The clamping may be effected around individual cavities or around
the array of cavities, depending on the particular application.
[0019] The distance the male tool part is inserted into the female tool part will depend
on the particular material being formed and the desired final shape of the sheet.
The skilled person will be able empirically to determine how far the male tool part
can be inserted without causing rupture or unacceptable thinning of the sheet material.
[0020] The male tool part and the periphery of the female forming cavity should preferably
have no sharp edges which might cause tearing of the sheet material during its deformation.
Thus the forming edges in the tool parts are preferably curved.
[0021] The material used in the invention is an extensible sheet material. Preferably the
material is an extensible fibre based sheet material for example a paperboard material
such as a FibreForm board material produced by Billerud.
[0022] The material should preferably have an extensibility of at least 0.1 and more preferably
at least 0.13. By extensibility is meant the strain at breakage of the material (as
determined by IS01924-3:2005 (E) divided by 100. The extensibility may also be expressed
as a percentage, namely the extensibility multiplied by 100. Thus the material preferably
has an extensibility of at least 10%, more preferably at least 13%.
[0023] As stated above, the invention is preferably used in packaging. It allows shapes
of package to be produced which previously could only have been produced by a plastics
moulding technique. From a further aspect, therefore, the invention provides a container
having a product containing pocket formed in a sheet material formed in accordance
with the invention.
[0024] From a further aspect the invention provides a blister pack comprising a capsule
receiving body having a plurality of capsule receiving pockets formed therein and
formed from a stretched paper based board material and a film sealed over the pockets.
[0025] Some preferred embodiment of the invention will now be described by way of example
with reference to the accompanying drawings in which:
Figure 1 shows an exemplary first tool part;
Figure 2 shows an exemplary second tool parts;
Figure 3 shows an exemplary third tool part; and
Figure 4 shows a schematic vertical cross section through the assembled tool parts.
[0026] With reference to Figure 1, a first, female tool part 2 of a tool in accordance with
the invention for producing blister packs is shown. The first toll part 2 comprises
a body 4 having an upper surface 6. The upper surface 6 is formed with a channel 8
which surrounds an array of cavities 10. The channel 8 and upper surface 6 together
form a first non-planar clamping surface.
[0027] In this embodiment, the first tool part 2 is of a moulded plastics material and the
channel 8 may be formed by being moulded into the upper surface 6 or by being machined,
e.g. milled or laser cut, into the upper surface 6 after moulding
[0028] The channel 8 is about 2 mm deep and 2 mm wide in this embodiment, but other sizes
of channel 8 are contemplated within the scope of the invention. The dimensions of
the channel will be determined by, amongst other things, the thickness of the sheet
material being formed.
[0029] Each cavity 10 is generally racetrack shaped in this embodiment and has an upper
edge 12 which is rounded or chamfered. This is to avoid tearing or damaging of the
sheet material as it is deformed around this edge 12.
[0030] The inner wall 14 of each cavity tapers slightly inwardly, for example at an angle
of 2 to 5° to the vertical.
[0031] The upper surface 6 is also formed with a number of locating apertures 16.
[0032] Figure 2 shows a second tool part 20. This second tool part 20 has a lower surface
22 (shown uppermost in Figure 2 for clarity purposes). A central cavity 24 extends
through the second tool part 20. Arranged around the central cavity 24 is an upstanding
rib 26. The rib 26 and lower surface 22 together constitute a second non-planar clamping
surface.
[0033] The rib 26 may for example be about 1.5 mm high and 1.0 mm wide and project at 90°
to the lower surface 22 such that it may be received in the channel 8 of the first
tool part 2 with a sheet of material arranged between them. Again the dimensions of
the rib 26 are determined taking into account the thickness of the sheet material
being formed.
[0034] In this embodiment the rib 26 is formed integrally with the second tool part 20,
which is preferably moulded but it could for example be formed as a separate element
mounted thereto.
[0035] The surface 22 is also provided with a number of locating members 28 for location
in the locating apertures 16 of the first tool part 2.
[0036] The central cavity 24 of the second tool part 20 slidably receives a third, male
tool part 30 shown in Figure 3. The male tool part 30 has outer wall 32 which is complementary
in shape to the shape of the central cavity 24 and a lower end surface 34 (shown uppermost
in Figure 3 for clarity).
[0037] The lower end surface 34 of the male tool part 30 is formed with a plurality of spaced
apart projections 36. As shown in Figure 4, these projections 36 are to be received
in the cavities 10 of the female tool part 2 and as such are arranged in a complementary
array to that of the cavities 10. The shape of the lower surface 34 corresponds to
the desired shape of the sheet product to be formed by the tool.
[0038] Each projection 36 has a flat lower surface 38 and an inclined side wall 40. The
edge 42 formed between the lower surface 38 and the side wall 40 is rounded or chamfered
to avoid tearing of the sheet material as it is deformed about this edge 42.
[0039] The horizontal cross section of the projections 36 is generally complementary to
that of the cavities 10, but the projections 36 are preferably dimensioned such that
the side walls 40 of the projections 36 do not come into contact with the internal
walls 14 of the cavities 10 or do not trap sheet material being formed between them.
Thus typically the angle of inclination of the side walls 40 is greater than that
of the internal walls 14, for example by 2° or more.
[0040] In use, a piece of extensible fibre based sheet material 50 preferably of a paper
based material for example a paperboard material is positioned on the upper surface
6 of the tool part 2 so as to project outwardly of the channel 8. The sheet material
should preferably have an extensibility of at least 0.10 (10%) and preferably at least
0.13 (13%). Such paper based materials are available from, for example, Billerud AS.
[0041] The second tool part 20 is then placed over the first tool part 2 with the locating
members 26 locating in the locating apertures 16. This properly aligns the first and
second tool parts 2, 20 so that the rib 26 of the second tool part is located over
the channel 8 of the first tool part 2.
[0042] The first and second tool parts 2, 20 are then clamped together by suitable clamping
means. For example, an external clamp such as a toggle clamp 52 illustrated schematically
in Figure 4 may be provided between the mould parts. In another arrangement, fasteners
may extend through the tool parts to clamp them together. Alternatively, external
pressure may simply be applied one or both of the tool parts. Any form of clamping
is contemplated within the scope of the invention
[0043] The clamping will cause the rib 26 to push the sheet material 50 into the channel
8 thereby not only clamping the sheet material 50 between the opposed clamping surfaces
6, 22 but between the rib 26 and the channel 8 to provide additional clamping.
[0044] Once the sheet material 50 has been clamped in place, the male tool part 30 may be
pressed onto the sheet material 50 such that the projections 36 enter the cavities
10. As the periphery of the sheet material 50 is firmly retained by the clamping mechanism
described above, the sheet material 50 will not be dragged into the cavities 10. Rather
it will be stretched and drawn into the cavities 10 by the projections 36. The rounding
of the edges 12, 42 on the cavities 10 and the projections 36 will avoid tearing of
the material at these points. Moreover the clearance between the walls 14, 40 of the
cavities and projections will allow the sheet material to be drawn smoothly into the
cavities 10 by the male tool part 30.
[0045] The sheet material 50 will therefore assume the shape of the end surface 34 the male
tool part 30 and will not be crimped or otherwise deformed due to slippage of the
sheet material 50 in the tool.
[0046] After forming, the tool parts 2, 14 may be separated and the formed sheet removed.
The sheet may then be trimmed to remove excess material which may or may not include
the deformed clamped part. In the present embodiment, the sheet 50 will be preferably
be trimmed to leave a peripheral flange of an appropriate size surrounding a plurality
of blister-like formed pockets. The pockets may then be filled with product and a
film then sealed around the flange to close the pack.
[0047] It will be understood that the desired shape of the sheet material will depend on
its final application. As discussed above, the formed sheet is advantageously used
in packaging, for example in the production of blister packs. However, other packages
are easily made using the described method.
[0048] In a simple embodiment, the formed sheet may simply assume a tray-like shape after
forming. In this case, a single cavity and projection of the appropriate shape may
be formed on the respective female and male tool parts.
[0049] Two formed sheet members may be joined together around their edges for example, to
form a package. An example of this type of packaging would be a clam-shell type package.
[0050] In another example, a living hinge may be formed in the sheet during the forming
process and the formed sheet then folded about the hinge to form a package.
[0051] These are just examples of possible packages using a formed sheet material and other
possible constructions will be apparent to the skilled person.
[0052] Also, the invention is not limited to package production and the formed sheet may
be used in any desired application.
[0053] It will be appreciated that the described tool is merely exemplary and that other
tool constructions will fall within the scope of the invention.
[0054] For example the described rib/channel arrangement could be replaced by a step/step
arrangement. i.e. with respective steps formed in the surfaces 6, 22. Also, the rib/channel
could possibly be of other shapes e.g. V-shaped or U-shaped. Moreover, more than one
set of interengaging formations may be provided. Thus there could be a series of two
or more formations formed one outside the other. Also, the rib and channel may be
formed on either of the first and second tool parts. The rib may be integrally formed
in the respective tool part or a separate member attached to it. It is also possible
that the channel could be formed as a separate member inlaid into the respective tool
part.
[0055] Also, locating features such as those described may or may not be necessary and may
be omitted in certain embodiments.
1. A method for forming an extensible sheet material comprising:
positioning a blank of sheet material over a female forming cavity;
clamping the periphery of said sheet around the periphery of said cavity; and
pressing said sheet material into said cavity by means of a male part; wherein
said clamping is effected by means of said periphery of said sheet material being
clamped between non-planar clamping surfaces.
2. A tool for forming an extensible sheet material, the tool comprising:
a first, female tool part including a forming cavity;
a second tool part mountable to said first tool part for clamping a portion of said
sheet material between opposing clamping surfaces of said first and second tool parts;
and
a third, male tool part for insertion into said forming cavity; and wherein
said clamping surfaces are non-planar
3. A method or tool as claimed in claim 1 or 2 wherein the material is an extensible
fibre based sheet material, for example an extensibility of at least Q.1 I and more
preferably at least 0.13.
4. A method or tool as claimed in any preceding claim wherein the clamping surfaces are
formed with interengaging clamping formations, for example a series of clamping formations
provided one outside the other.
5. A method or tool as claimed in claim 4 wherein the clamping surfaces are provided
with one or more interengaging step formations provided around the cavity.
6. A method or tool as claimed in claim 4 or 5 wherein the clamping surfaces are provided
with one or more interengaging channel and rib formations.
7. A method or tool as claimed in any of claims 4 to 6 wherein the interengaging formations
deform the sheet material through at least a 90° angle, for example wherein the edges
of the step or channel are perpendicular to the surrounding surface.
8. A method or tool as claimed in claim 4, 5 or 6 wherein the step or channel is formed
at an angle to the vertical, for example within 20° of the vertical.
9. A method or tool as claimed in any preceding claim wherein the end surface of the
male tool part which is pressed into the sheet material is shaped to give the desired
profile to the formed sheet product.
10. A method or tool as claimed in any preceding claim wherein the male tool part bottoms
out in the female part cavity.
11. A method or tool as claimed in any preceding claim wherein the cavity provides clearance
with the male tool part so that it does not interfere with the deformation of the
sheet material by the male tool part as it moves into the cavity.
12. A method or tool as claimed in any preceding claim wherein the end surface of the
male tool part is formed with a plurality of spaced apart projections for forming
a blister formation on the formed sheet.
13. A method or tool as claimed in claim 12 wherein the female tool part comprises a plurality
of forming cavities each engaged by a corresponding male tool part, and wherein optionally
clamping is effected around individual cavities or around an array of cavities.
14. A method or tool as claimed in any preceding claim wherein the forming edges in the
tool parts are curved.
15. A blister pack comprising a capsule receiving body having a plurality of capsule receiving
pockets formed therein and formed from a stretched paper based board material and
a film sealed over the pockets.