Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR PRODUCING TENSION WRAPPED UNITS OF COMPRESSIBLE
FLEXIBLE ARTICLES
Field of the invention
The invention relates to an improvement in the process of wrapping a plastic
outer packaging material under tension around an array of packs of
compressible
flexible articles to form a tension wrapped unit.
Background of the invention
It is widely known in the art to package an array of packs comprising
compressed
?0 flexible articles encased in flexible bags in corrugated paper outer cases
for ease
of handling, storage and transport. The space, however, inside these
corrugated
paper outer cases cannot be fully utilised because of the tolerances imposed
by
the variations in the pack dimensions resulting from the production processes
and the usual automatic mechanical packaging systems. The problem of
?5 utilisation of space is becoming more and more important with the
increasingly
widespread use of pallets of standard dimensions arising from the demands of
large manufacturing, distribution and sales organisations. Furthermore, due to
the deviations in the pack dimensions arising from the packing of compressible
flexible articles into flexible bags, the cardboard cases need to be over-
30 dimensioned. As a consequence of this over-dimensioning, arrays of packs on
the bottom of pallets are incapable of supporting the imposed loads when
pallets
of products are stacked or grouped three pallets high. Therefore, the
cardboard
cases must be designed to support the extra loads.
35 An array of packs of compressed flexible articles can also be wrapped in
plastic foil. The plastic foil can comprise relatively inexpensive materials
such as
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polymeric films or thermoplastic films. Such materials reduce the severity of
the
disposal problem from an environmental standpoint both with respect to the
amount of wrapping material required and the disposability/degradability of
the
particular wrapping material. In addition, plastic foil is lighter and more
flexible
than corrugated paper, which is heavy, requires space and has less flexibility
for
storage since it is rigid and in use continues to occupy the same amount of
space even when nearly empty.
Prior art developments include EP 0 294 339 A2 which discloses a machine for
packaging a plurality of articles, either loose, collected on a tray or inside
a
container, within a stretchable or a semi-stretchable type of film web. The
machine includes a stretching device, a wrapping device and a complete sealing
unit. In particular, the invention teaches a segment of stretched and
tensioned
film web that is wrapped peripherally around the articles by pushing the film
web
I S underneath the articles and by displacing the support plane of the
articles and
eventually replacing it with two roller tables associated with the wrapping
device.
The invention takes advantage of the elastic memory of the film web to tightly
enclose the packaged articles rather than using the compressibility of the
articles
with the aid of a pusher clamp and pusher plate to form a tight tension
wrapped
2o unit.
US 3,910,011 claims an apparatus for and a method of packaging stacked
articles in a shipping container. The apparatus comprises a means for
peripherally confining a bundle of articles in an open-ended sleeve of heat
25 shrinkable film while leaving the surface portions of the bundle of
articles
accessibly exposed. The cooling of the heat shrinkable film produces a
relatively
rigid package. Similarly, US 3,672,116 discloses an apparatus and a method for
wrapping a film about four sides of~ an object or stack of objects; the film
having
sufficient elasticity to stretch without bursting. Both patents focus on the
stretch
30 properties of the films in order to
guarantee unit stability and furthermore, wrapping is only around a
circumference
of the bundle/object(s).
Therefore, the prior art does not teach a wrapping process which
35 comprises tensioning in two directions using a plastic outer packaging
material;
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3
which is independent of fixed dimensioned cases: which relies on the
compressibility of the array of flexible packs of compressible flexible
articles in
combination with a pusher clamp and pusher plate to produce a stable unit:
which is independent of the stretch properties of the plastic outer packaging
material: and which utilises a curved pusher plate that is in close proximity
to
the pusher clamp.
Objectives and summary of the invention
An object of an aspect of the present invention is to wrap an array of
packs of compressed flexible articles under tension in two directions using a
plastic outer packaging material to form a tension wrapped unit. A further
object of an aspect of the invention is to prevent the distortion and
deformation of the corners of the array of packs of compressible flexible
articles when being wrapped under tension with the plastic outer packaging
material.
The invention utilises process steps that encompass modifications in
order to produce a tension wrapped unit comprising a plastic outer packaging
material, which is most suitable as a replacement for conventional corrugated
paper outer cases. The process originally was employed to wrap arrays of
individual flexible articles to form primary wrapped packs with the aid of a
pusher clamp and a pusher plate. The array of articles were tension wrapped
in one direction only and the pusher clamp simply pushed the array of articles
to a fixed point where the wrapping process was initiated. The resultant
primary wrapped packs could be easily distorted and deformed and in
addition, the compressibility of the flexible articles was not utilised to
form a
more stable pack. The present invention is directed towards the wrapping
under tension of arrays of primary wrapped packs of compressible flexible
articles to form completely enclosed units.
During the wrapping process, the inherent compressibility of the arrays
of packs of compressible flexible articles with the aid of the pusher clamp
and
pusher plate can be taken advantage of to tightly wrap the plastic outer
packaging material around the entire array in two directions. This imparts
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4
increased stability and strength to the unit. Furthermore, Key design
optimisations - the use of a pusher plate that is curved and is in close
proximity to the pusher clamp - have been incorporated into the process.
These features have subsequently led to several benefits namely, units that
are more stable and that are capable of sustaining higher load carrying
capacities; better unit shapes; improved unit appearances and improved and
optimised pallet fit during handling, storage and transport operations
results.
In accordance with the objects of aspects of the Invention, a unit
comprising an array of at least one substantially parallelepipedal pack
comprising compressed flexible articles is provided. The unit has a top and a
bottom panel, a front panel and a back panel and two side panels and
comprises a plastic outer packaging material. The pusher clamp pushes the
array towards the plastic outer packaging material consisting of two sheets
sealed at the centre. The plastic outer packaging material has a width
dimension that extends beyond the transverse limits of the array and it is
disposed adjacent to the front, top and bottom panels of the array. The array
is maintained in a fixed position by the action of a pusher plate and by
resting
on a base plate. The pusher clamp then retreats and guide rollers ensure that
the plastic outer packaging material is disposed adjacent to the back panel.
It
can then be gathered, sealed and cut. The array is compressed in a direction
of compression C by means of the pusher clamp and is pushed in a direction
perpendicular to the direction of compression C' by the pusher plate. The
plastic outer packaging material extending beyond the transverse limits of the
array is disposed adjacent to the remaining side panels of the array and then
gathered, folded, sealed and cut. The unit may comprise a least one
unobstructed opening feature in the plastic outer packaging material.
The pusher plate is curved at the edges and comprises a radius
ranging from 5 to 30 millimetres and an angle A ranging from 30 to 90
degrees. The distance H from the top of the pusher clamp to the bottom of
the pusher plate ranges from 0 to 50 millimetres.
According to the present invention, the objects of aspects of the
invention are achieved by a pusher plate having the characteristics specified
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in the claims.
In accordance with one embodiment of the present invention, a
process for producing a tension wrapped unit comprising an array of at least
one substantially parallelepipedal pack wherein a pusher clamp is disposed
adjacent side panels and back panel of said array, said pusher clamp pushes
said array towards a plastic outer packaging material comprising two sheets
of film sealed at the centre wherein width dimension of said plastic outer
packaging material extends beyond transverse limits of said array, said
plastic
outer packaging material is disposed adjacent front panel, top panel and
bottom panel of said array, said array is subsequently maintained in a fixed
position by the action of a pusher plate and by resting on a base plate, said
pusher clamp retreats and guide rollers ensure said plastic outer packaging
material is disposed adjacent said back panel, and wherein said array is
compressed in a first direction of compression by means of said pusher clamp
and is compressed in a direction perpendicular to said first direction of
compression by said pusher plate, and wherein said plastic outer packaging
material extending beyond transverse limits of said array is disposed adjacent
said remaining side panels of said array.
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Brief description of the drawings
The invention will be described hereinafter with reference to the following
drawings:
Figure 1 is a perspective view of an array of flexible packs being compressed
by
a pusher clamp in the direction of compression C;
Figure 2 shows a front elevation of the partially wrapped array of packs
supported on a base plate and being held in tension by a curved pusher plate:
Figure 3 shows a front elevation of an array.of packs after the pusher clamp
has
retreated and at the point when the plastic outer packaging material is being
gathered together;
Figure 4 shows the front elevation of the curved pusher plate.
Detailed description of the invention
Figure 1 shows an array 11 comprising at least 1 substantially
parallelepipedal
pack 12. In particular, figure 1 details two substantially parallelipedal
packs 12.
Each pack 12 is enclosed in a flexible bag and comprises compressed flexible
articles. The array 11 is compressed by means of a pusher clamp 13 in the
direction of compression C. The compressed flexible articles may comprise
disposable absorbent diapers, sanitary articles, incontinent pads or briefs,
bandages and the like. The flexible articles are compressed to between 20 and
?5 70 percent of their uncompressed volume. Each flexible pack 12 comprises
between eight to fifty disposable absorbent diapers and a flexible plastic bag
with
a thickness ranging from 30 to 120 micrometres. A method for the compression
packing of disposable absorbent diapers into flexible bags has been described
in
detail in the following patents US 4,934,535, US 4,966,286, US 5,022,216, US
5,050,742 and US 5,150,561.
According to figure 1, the array 91 of packs 12 of compressed flexible
articles comprises a top panel 14, a bottom panel 15, a front panel 16, a back
panel 17 and two side panels 18, 19. The pusher clamp 13 is disposed adjacent
to the side panels 18, 19 and to the back panel 17 of the array 11. The pusher
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6
clamp 13 pushes the array 11 towards the plastic outer packaging material 20.
The plastic outer packaging material 20 comprises two sheets of film, fed from
two infeed rollers 21, which are sealed at the centre. The width dimension of
the
plastic outer packaging material 20 extends beyond the transverse limits of
the
array 11 to be wrapped. The preferred material for the plastic outer packaging
material 20 is a polyethylene film, which can either be of a low, medium or
high
density. More specifcally, the film has a thickness ranging from 30-100
micrometres; 50 micrometres being preferred. The film can either be
transparent
or white and thus, various combinations for the array 11 of packs 12 are
possible.
In addition, the film may comprise graphical indicia, which can also be
coloured.
The plastic outer packaging material 20 is disposed adjacent to the front
panel
16, the top panel 14 and the bottom panel 15 of the array 11 and maintained in
tension by the pusher clamp 13. The pusher clamp 13 compresses the array 11
in the direction of compression C and ideally, the circumference of the array
11 is
reduced by a figure in the range from 2-20 percent; 5 percent being preferred.
Figure 2 shows the plastic outer packaging material 20 wrapped tightly against
the front panel 16, the top panel 14 and the bottom panel 15 of the array 11.
The array 11 is subsequently maintained in a fixed position by resting on a
base
plate 22 and by the action of a curved pusher plate 23. The curved pusher
plate
23 is disposed adjacent to the top panel of the array 11 and compresses the
array 11 from above in the direction of compression C'. The circumference of
the
array 11 around the side panels 18, 19 is reduced by approximately 2-8
percent;
preferably by 5 percent. The array 11, which is partially wrapped, is still
being
subjected to a side compression from the pusher clamp 13.
In figure 3, the pusher clamp 13 retreats and the guide rollers 24 ensure that
the
plastic outer packaging material 20 is pulled under tension and disposed
adjacent to the back panel 15 of the array 11. The plastic outer packaging
material 20 is subsequently gathered, sealed and cut. The seal may comprise a
straight seal. In order to gather the plastic outer packaging material 20 to
form
the tight seal, some of the compression of the array 11 may be lost, but this
is
minimal and is about 2-4 percent. Upon cutting, the outer plastic packaging
material 20 is released from the array 11 and is available for wrapping around
the
next array 11 of packs 12. The plastic outer packaging material 20 extending
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7
beyond the transverse limits of the array 11 is pulled around and disposed
adjacent to the remaining side panels 18, 19 of the array 11. The plastic
outer
packaging material 20 is then gathered, folded, sealed and cut. The side seal
may either be folded or comprise a straight seal. As before, the cutting step
is
not essential. The end product is a tension wrapped unit 10.
Figure 4 shows the front elevation of the pusher plate 23. The pusher plate is
typically characterised by a flat surface and its dimensions are usually
smaller
than the array of packs to be wrapped. The new design is based on a curved
surface and is designed to frt the dimensions of the array 11. This
modification
results in a much higher level of compressed matter being retained within the
array 11 since the uppermost corners ~ of the array 11 are contained.
Furthermore, the pusher plate is placed in close. proximity to the pusher
clamp 13
in order to provide for a much tighter tensioned wrapped unit 10. By placing
the
pusher clamp 13 close to the pusher plate 23, a reduced level of excess
compressed matter can escape when gathering and sealing the panels 17, 18,
19. Usually, the excess compressed material held in compression by the flat
surfaced pusher plate could be easily squeezed out through the free space
located at the corners of the primary wrapped packs.
The radius R of the pusher plate can range from 5 to 30 millimetres though
20 millimetres is the preferred radius. The angle A ranges from 30 to 90
degrees
with 60 degrees being the preferred angle. The distance H from the top of the
pusher clamp 13 to the bottom of the pusher plate 23 can vary from 0 to 50
millimetres with 5 millimetres being the preferred distance.
In relation to all the figures, the plastic outer packaging material 20 may
comprise
an unobstructed opening feature 25, which is readily located and which can be
easily and reliably opened in order to gain easy access to the packs 12 within
the
array 11 of the unit 10. The unobstructed opening feature 25 is included in
order
to provide a more controlled release of the compressive forces acting on the
compressed flexible packs 12. The plastic outer packaging material 20
comprises at least one unobstructed opening feature 25, which may comprise a
predetermined tear portion in the form of a line of weakness. Lines of
weakness
can be formed by many means well known in the art and typically comprise, for
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example, perforations. The lines of weakness may be produced on-line or they
may be already present in the plastic outer packaging material 20 as provided
by
the suppliers. Thus, the unobstructed opening feature 25 comprises a line of
weakness, which may traverse the circumference of the entire unit 10 in either
the horizontal or vertical plane or which either may traverse the top panel 14
or
the bottom panel 15 of the unit 10 or which either may traverse the top panel
14
and part of the side panels 18, 19 or the bottom panel 15 and part of the side
panels 18, 19. In addition, graphical indicia may be provided on the plastic
outer
packaging material 20 to highlight the location of the unobstructed opening
feature 25.
For the purposes of transport and storage, ~ a number of units 10. each unit
10
preferably comprising two to twelve packs 12, can be stacked or grouped in a
plurality of configurations on a pallet such that a load is applied to an
upper panel
or to a side panel of the pallet configuration with the direction of the load
being
perpendicular to the direction of-compression, which is around the
circumference
of the pallet configuration. The units 10 are less compressible in directions
perpendicular to the direction of compression.
Glossary
10 unit
11 array
12
pack
13 pusher clamp
14 top panel
15 bottom panel
16 front panel
back panel
18, 19 side panels
20 plastic outer packaging material
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21 infeed rollers
22 base plate
23 pusher plate
24 guide rollers
25 unobstructed opening feature
