Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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AIRTIGHT FOOD PACKAGING AND A METHOD,
DEVICE AND TRAY FOR THE PRODUCTION THEREOF
Description
The invention relates to a food package according to the
preamble of claim 1, as well as a method for the manufacturing of such
a package according to claim 13, a device for the implementation of
such a method according to the preamble of claim 19, a suitable semi-
finished product or tray in the form of erected or glued trays according
to claim 23, and a method for the manufacturing thereof.
Food packages are marketed in many different forms,
whereby in recent times special emphasis is being placed on restricting
the content of non-recyclable plastics in such packages to a minimum.
In this respect, food packages in the form of deep-drawn plastic trays
have gained acceptance, which normally are thermoformed of a base
material, which is comprised, for example, of PVC, polystyrene, or
polyester.
In conventional trays that are produced from PVC, polyes-
ter, or polystyrene, limitations of the production technology in so-called
"vacuum forming and filling systems" lead to the creation of very non-
uniform thickness distributions based on the available original thickness
available in the known thermoplastic forming process.
On the one hand, this requires a high initial thickness of up
to 1000 ~.m, with respect to the desired mold depth and container shape,
to obtain the required remaining wall thickness in the rounded base
sections. On the other hand, reductions in thickness of the plastic film
to be used in the forming of the plastic trays in the rounded base sec-
tions often leads to so-called "buckling fractures", which can occur in
particular during transport.
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Also, serial investigations have shown that the barrier layer
used in the manufacturing of the plastic trays, which preferably consists
of polyvinyl alcohol (PVA), provides the required oxygen barrier, and
in a previously described application of so-called rigid-film compounds
is embedded between the carrier film and the sealing layer, results in
significantly poorer molding results, i.e. lower remaining wall thickness
of this PVA layer.
Consequently it is necessary to equip the plastic carrier
material of the trays to be formed; which is necessary to ensure dimen-
sional stability, with an additional oxygen barrier layer. This oxygen
barrier layer normally consists of polyvinyl alcohol. In addition, a third
film layer is required to be able to establish the seal of the cover film.
This requires a so-called multi-layer composite film, which
consists of several components, is comparatively thick, and precludes
recycling, i.e. the reuse of unmixed materials.
EP 0169799, for example, describes such a tray. It also
discloses a method to introduce a multitude of individual, separate trays
into a filling- and sealing station. Successively, the trays are lined with
a thin plastic film, before they are filled with food and are conveyed to a
sealing station. In the sealing station, a cover film is sealed onto the
food-filled trays. This creates a tray, the carrier material of which is
mostly mechanical wood pulp or foamed plastic. An advantage of
packaging systems with such trays is to be seen in the fact that the
packaging device can possess a clear design, whereby a modular config-
uration of the device is also possible.
On the other hand, attempts have been made to reduce the
plastic content of such a food package, which must be relatively high in
v
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order to achieve the required remaining wall thickness in the rounded
base sections, by using laminated cardboard. However, hereby it was
found that it is difficult to process cardboard with laminated plastic
materials in devices that predominantly use known or existing modules.
Moreover, the maximum possible molding depth for such containers
pressed from laminated cardboard is limited to 25 to 30 mm.
Even though a lining with a barrier layer coating can render
such containers produced in a cold molding process essentially imper-
meable to oxygen, wrinkles will form as a result of the cold molding
process, due to material displacement. These wrinkles extend up to the
peripheral flange regions of the containers, making it impossible for the
cover film to provide a seal that is secure and uninterrupted, and in
particular oxygen-tight. To be able to manufacture container depths of,
for example, more than 30 mm molding depth, one uses receptacles of
laminated cardboard, which are formed of cutouts. These receptacles,
which are made from laminated cardboard on a separate unit, are
erected, folded, and glued, and are delivered to the packing system as
containers.
However, in these containers manufactured from laminated
cutouts it is not possible to achieve a truly gas- and oxygen-tight bond at
the positions being cut and glued. Problems of this nature in particular
can arise in containers that possess a peripheral flange. Using the
known lamination of cardboard cutouts one only achieves a certain level
of resistance to moisture, whereby it is not entirely possible to protect
against moisture along the open cut edges.
However, there is a need to create a food package accord-
ing to the preamble of patent claim 1, which can be manufactured on
conventional horizontal forming-, filling- and sealing- systems with little
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retooling effort, wherein the plastic content is reduced to a minimum,
while at the same time the stability of the container and the
impermeability to oxygen are maintained at a very high level.
There exists a further need to further develop a method for
the oxygen-tight packaging of foodstuff by using a food package of the
above type in such a way that conventional packaging systems can be
operated at higher work cycles, and even more economically. Finally,
one attempts to find a device for the implementation of the above
mentioned method that is characterized by the packaging equipment's
especially low susceptibility to breakdown, even at top work cycles.
To satisfy these requirements, the patent application P 196
54 230, to the content of which we explicitly refer, proposes a food
package as well as a method for the manufacturing thereof and a device
for implementing the method using a suitable semi-finished product or
tray.
The food package proposed in that application possesses as
supporting base a cardboard cutout that is lined with a thin plastic
composite film, which can be erected automatically, and the interior
area of which is glued along the cut edges. The cardboard cutting
further contains a peripheral flange with individual peripheral flange
segments, to which the cover film will be attached. Furthermore, the
outside of the peripheral flange according to this invention is shaped in
such a manner that the peripheral flange segments come into flush
contact in the sealing position. For this purpose, the individual periph-
eral flange segments possess predetermined cut lines, using which the
angle of the peripheral flange can then be set. The use of prefabricated
cardboard cutouts has the advantage of not giving rise to a reduction of
the thickness of the material during the erecting of the cardboard cut-
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outs, in contrast to the known tray. This overcomes the drawbacks
caused by the reduction in thickness of the material in the invention's
food package. The fact that the peripheral flange segments abut against
each other in the sealing position is responsible for a solid peripheral
flange surface, which can be utilized for a secure sealing of the card-
board cutout.
But, in gas- or oxygen-tight packages of this nature, special
attention must be paid to whether the tightness that is created by the
sealing flanges can be maintained over prolonged time periods. Other-
wise it would not be possible to meet the requirements related to food
processing technology. In the package proposed earlier, the quality of
the seal is determined by the precision of the cutout. In other words,
the risk that ambient air can over the medium term enter into the pack-
age via capillaries in the sealing flange can only be reduced by ex-
tremely high precision in the manufacturing of the erected trays and in
the positioning in the lining- and sealing stations. This can unduly
reduce the operating speed.
Consequently, the invention has the objective to create a
food package of the above-described type, which is characterized by the
above-described merits and additionally by the fact that it can be manu-
factured more rapidly and more reliably with lasting impermeability to
gas or oxygen. A further objective is to provide a method for the
manufacturing of such a food package, which can be implemented in an
uncomplicated process. Finally, a device for the implementation of the
manufacturing process has to be created that has an uncomplicated
structure and offers the special advantage that conventional packaging
equipment can be integrated into the device to a maximum possible
extent. Finally, a semi-finished packaging or packaging tray has to be
created that is especially suitable for the invention's packaging process,
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whereby the design should offer the advantage of allowing the produc-
tion of high piece volumes per unit of time with a precision so high, that
the quality specifications for a oxygen-tight packaging are guaranteed
even at maximum operational throughput of the packaging equipment.
This objective is attained with respect to the food package
by the features of patent claim 1. According to the invention, the
packaging is equipped with a continuous collar, which consequently
provides a continuous surface for the sealing of the package. The
continuous, i.e. uninterrupted collar proves to be of advantage, even
when tacking the plastic film that lines the inside of the package, since
this creates ideal conditions for an extended-surface connection between
the plastic film and the peripheral flange.
At the same time, it results in the additional advantage that
damage to the plastic film can be ruled out, even at higher operating
speeds of the packaging machine. But the deciding advantage becomes
apparent in the sealing of the package. Namely, the uninterrupted
surface of the peripheral flange that is covered by the lining plastic film
provides optimum conditions for a sealing of the cover film along a
surface that is as large as possible. It has been found that in this manner
the operating speed of the packaging machine can be increased signifi-
cantly without any risk of forming capillary-like radial channels between
the cover film and the lining film, which would be detrimental to the
long-term tightness.
This invention's design of the food package does require a
more complex design of the package cutout. However, it has been
found that the continuous flange can be utilized to stabilize the packag-
ing tray in an especially advantageous manner, even if the joining of the
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tray components is carried out only at selective points or sections and
not on the entire surface .
An especially advantageous development is the further
development according to patent claim 2. This design permits weight
savings in the area of the tray part, which has a positive effect on DSD
feed .
It is in principle possible to design the attached continuous
collar as a closed ring.
The development of patent claim 3 results in very little
waste product, which is of particular advantage. In other words, card-
board material can be used for the stabilization of the side walls of the
tray part in a practical and effective manner.
Fastening, preferably gluing, the tabs of the peripheral
flange to the inside of the side walls of the tray part results in the
particular advantage that the entire outer surface of the side walls can be
used for printing, i.e. as informational and advertising space.
This invention's packaging is especially suited for a semi-
finished product of cardboard.
If, according to claim 6, the plastic composite film com-
prises an oxygen barrier layer, preferably of polyvinyl alcohol, a sealing
layer, preferable of peelable polyethylene, as well as an adhesive layer,
preferably of a modified polyethylene, in particular a copolymer of
ethylene with 6 % methacrylic acid, which has been partially (50 % )
neutralized with sodium- or zinc ions (Surlyn A), then a flexible com-
1 DSD = Duales System Deutschland: German regulations requiring manufactur-
ers to pay recycling fees for their products. (The Translator)
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pound is used, the oxygen permeability of which can be set in advance
and will not change in the embedded state. Consequently, a signifi-
cantly thinner PVA layer embedded in a flexible compound can be used.
The fact that the plastic film is peelable results in a very high environ-
s mental friendliness. As has surprisingly been discovered, even an
extremely thin plastic film can provide stability to the tray, even to a
tray consisting of simple cardboard, so that it is possible to manufacture
even packages of a comparatively high depth with sufficient stability.
If the invention's food package according to claim 9 is
equipped with a cardboard cutout that consists of a recyclable and
preferably two-ply cardboard then a food package is created that is
suitable to carry imprints of an especially high advertising appeal on the
exterior layer of the cardboard cutout. In this manner it becomes
possible to provide special optical emphasis to the invention's food
package .
The design according to patent claim 10 has the particular
advantage that the tray's surface structure is adapted to specific require-
ments. In the process of lining the tray it is of advantage if the plastic
film, which has been heated in the forming process, forms an intimate
bond with the surface of the tray part within a short time period. In
contrast, important features of the outside of the tray part are an attrac-
tive exterior and favorable conditions for the printing that will generally
take place. It was found that the second, i.e. interior layer can easily
consist of recycled cardboard, which saves costs and creates special
advantages with respect to environmental compatibility.
The invention's choice of lined cardboard cutouts creates a
container that, when entering the vacuum- or sealing station, is oxygen-
tight on all sides except one, the top side. Moreover, since the plastic
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lined cardboard cutout possesses especially high dimensional stability in
the area of this invention's peripheral flanges, this peripheral flange can
be accommodated securely between the gaskets of the closed sealing
tool, so that according to this invention only the hollow interior of the
formed carrier tray has to be evacuated.
This reduces the power consumption of the packaging
equipment required for the evacuation, which makes it possible to
substantially increase the number of work cycles of the packaging
equipment.
It was found that the invention's peripheral flanges provide
a high stability, and no uncontrolled ruptures can occur, even when the
tray is being filled with foodstuff. Moreover, the operational reliability
of the device can be further increased by supporting the peripheral
flanges, which are executed as sealing ridges and are positioned between
the interior spaces of the substrate trays, from below by means of guide-
and sliding rails which are oriented in parallel to the transport direction.
It is also practical to support the containers in the filling path from
below by means of a support belt that is synchronized with the transport
means.
Arranging the erected cardboard cutouts in a series inside
the forming station, in accordance to claim 15, allows the formation of a
wider sealing area on the peripheral flanges between adjacent cardboard
cutouts. This provides for a reliable sealing. A further result is that
several cardboard cutouts can be manufactured simultaneously and that
the sealing is simplified through the wider sealing area that is due to the
peripheral flanges being arranged adjacently.
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In particular, these developments provide advantages due to
a simplification of the packaging equipment, since this process no longer
requires any separate deep-drawing die stations or special preheating
systems. However, the processing path that is normally required for
this, can according to the invention be used to accommodate the filling
station, and can thus aid in creating a space-saving design of such a
packaging system.
Either the construction of the entire system can be kept
significantly shorter, or, if required, the utilization of the filling path
can be improved considerably, which simplifies the filling process.
Using the invention's food package can reduce the content
of non-recyclable plastics to a minimum, whereby the invention's choice
of cardboard cutouts as raw material provides added advantages in
respect to biodegradability.
Finally, the power consumption of the packaging system is
significantly reduced, in particular in the area of the forming station,
since the time required for a thorough heating of a conventional rigid
film of approximately 500 to 1000 wm thickness (PVC, polystyrene, or
polyester) can be significantly reduced. The required inherent stability
of the containers is achieved by the invention through the use of the
described cardboard cutout, in particular once the cover film has been
attached to the plastic film that lines the cardboard cutout.
The invention's food package has high dimensional stability
compared to other food packages using cardboard cutouts, and possesses
a high degree of torsional rigidity.
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Patent claim 15 presents a favorable further development of
the manufacturing process. By tacking the plastic film to the peripheral
flanges of the trays, the trays can be transferred into the packaging
system reliably and in a very synchronized manner.
This creates the further advantage that the packaging
system's module containing the filling system can be retained in unmod-
ified form, and an upstream module for feeding the trays can be incor-
porated into the system in a particularly space-saving manner, namely
with an overlap of one work cycle's advancing distance.
The development of the process according to claim 17 does
not only lead to an extremely high throughput rate, in combination with
the invention's design of the tray part it also offers the advantage that
the negative air pressure can be utilized most efficiently to pull the film
of the lining into the interior of the tray part within a very short time
period. Namely, the invention's uninterrupted collar that forms the
peripheral flange makes it possible to design the cutout of the tray part
in a way so that the side walls are separated by a slit in the erected
condition of the tray part.
Advantageous developments of the device for the imple-
mentation of the process are the subject of the dependent claims 19 to
25. The tray that is part of the invention's food package is the subject
of claims 23 to 29. The tray can be of nearly any desired shape,
whereby the special advantages can be realized if the depth of the tray
part exceeds a certain minimum depth. Preferably the base has a
polygonal shape.
The process for the manufacturing of trays according to
claim 30 makes it possible to join the two components of the tray in a
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minimum time period and with the greatest possible accuracy, wherein
one realizes the advantage that the manufacturing of the trays remains
independent of the operating speed of the packaging equipment.
Preferably, the trays are placed into a storage magazine in
nested configuration, and from there are individually supplied onto a
transport belt of the transfer module of the packaging machine.
Further advantageous embodiments are the subjects of the
dependent claims. In the following, an embodiment example of the
invention is illustrated in more detail with the help of schematic draw-
ings.
Fig. 1 shows a schematic side view of a first embodiment
of the packaging equipment according to the invention.
Fig. 2 shows an exploded view of a first embodiment of a
cardboard tray to be used in the manufacturing of the package according
to the invention.
Fig. 3 shows a top view of a cardboard cutout for the collar
of the package according to Fig. 2.
Fig. 4 shows a top view of the cutout according to Fig. 3,
including ready-to-assemble folded tabs.
Fig. 5 shows a top view of the associated cardboard cutout
for the tray part.
Fig. 6 shows a top view of the cutout of Fig. 5 in its
erected state.
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Fig. 7 shows a perspective view of a row of erected card-
board cutouts.
Fig. 8 shows an enlarged side view of the forming station
of the packaging equipment.
Fig. 9 is a front view of the forming station shown in Fig.
8, showing the loaded cardboard cutouts arranged in contiguous rows
and the plastic composite film that is being supplied for the lining.
Fig. 10 is a perspective view of cardboard cutouts arranged
in a side-by-side series that already have been lined with plastic compos-
ite film, whereby the slightly enlarged view of Fig. l0A is a section
along the line indicated by an arrow in the cardboard cutouts arranged
in rows and shows the heat-laminated peripheral flange area.
Fig. 11 is a front view of the vacuum- and sealing station
with inserted cardboard cutouts, which already have been lined with
plastic composite film and thereby have been combined to a row.
Fig. 12 is a perspective view of the linked cardboard
cutouts with plastic composite film and sealed cover film, whereby Fig.
12A illustrates at a larger scale in more detail the cardboard cutout and
the adhering layers.
Fig. 13 is a perspective view of a ready-to-use or ready-to-
consume package according to the invention.
Fig. 14 is a perspective view of the invention's tray with
the cover film partially peeled off.
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Fig. 15 is a perspective view of the invention's tray with
partially peeled-off cover film and partially peeled-out inner film.
Fig. 16 is a schematic illustration of a detail of the equip-
ment used in the manufacturing of the cardboard trays.
Fig. 17 is an exploded view analogous to Fig. 2 of a
variation of the tray.
Fig. 18 is a view, similar to that of Fig. 1, of the packaging
machine in which trays according to Fig. 17 are processed.
Fig. 1 shows a side view of the packaging system compris-
ing on the whole five main processing stations, namely a tacking station
HS for tacking a lining film 134 for pre-manufactured trays, a forming
station (FS), wherein the plastic film is molded into the trays, a filling
path (BS), a sealing and vacuum station (VS), and a preferably two-
stage separating unit 181, 182, whereby the latter can also be of a
single-stage design.
Preferably, the cardboard cutouts or erected trays 110,
which are arranged fittingly in a row, are transported to the individual
stations by a conveyor chain 148, or if a so-called tray-sealer is used, by
a specially configured conveyor belt with receiving spaces for the side
by-side cardboard cutouts.
To reduce the load on the conveyor chain 148 in sections,
support belts, which are not shown in detail, can be provided under-
neath the conveyor chain 148.
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Upstream of the module labeled 'I' of the actual packaging
machine, which predominantly is configured as a standard commercially
available machine and only might have to be reconfigured in certain
sections, an additional module II is positioned, in which the trays 110,
which were taken in in a magazine or dispenser 112, are separated and
then transferred to module I.
The prefabricated cardboard cutouts 110 - preferably side-
by-side in rows of 2 to 5 trays - are in fixed-cycle operation placed
onto a partitioned belt 112 with the aid of a separating device VV9 that
preferably is operated pneumatically. Still in fixed-cycle operation, the
partitioned belt 112 transports the at least one cardboard cutout to a
transfer station LJS. There, by means of a lifting station and a special
transport die 113, the at least one tray 110 in fixed-cycle operation is
lifted vertically upward into the plane EKF of the plastic foil 134 and
into the area of the tacking station HS, where by means of heated dies
118 the lining film is tacked, preferably at individual spots, to the
leading and/or trailing area of the peripheral flange of the trays. In a
tray-sealer system, the cardboard cutouts are inserted into the corre-
sponding receptacle spaces of the conveyor chain 148.
Using this configuration it is possible to arrange the module
II in a very space-saving manner and to avoid the overlapping region UB
along the transport direction.
Starting from this tacking station, in which the pre-manu-
factured trays are arranged close to each other in rows in contact with
the plastic film, and from where the trays are fed into the forming
station FS, begins the actual forming- or lining process of the trays 110
by means of the plastic film, preferably plastic composite film 134. In
the forming station the interior surface of the cardboard trays 110,
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which are arranged in rows, is lined with an oxygen-sealing plastic
composite film 134.
An endless reel 133, which is mounted on a bracket above
the packaging system, pulls the plastic composite film 134 via deflection
rolls, which are not shown, over the trays 110, which are arranged in
rows in the molds, essentially in a direction parallel to the conveyor
chain 148.
When a tray sealer is used, the conveyor chain 148 in
synchronized manner carries the trays 110, which rest in rows in the
accommodating spaces of the conveyor chain, underneath a forming
station FS, the operating principle of which in the lining of the interior
of the trays 110 with plastic composite film corresponds to the Iso-Pack-
system of the firm MULTIVAC as employed in a forming-, filling-, and
sealing system.
Subsequently, the trays 110 are carried by means of the
conveyor chain 148 into the region of a filling path BS, which is also
configured to allow a synchronized in-line filling.
To reduce the load on the conveyor chain 148, the trays
110, which are now linked by the plastic composite film 134, can be
supported by a support belt, which is synchronized to the conveyor
chain.
From the filling path BS, the filled trays enter into a
vacuum- and sealing station VS, whereby simultaneously a cover film
120, which is supplied by the endless reel 122 via a deflection roller
system, is carried into the vacuum- and sealing station VS, essentially
parallel to the transport path. The operating method of the vacuum-
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and sealing station VS corresponds to that of conventional systems, e.g.
systems by the firm Multivac, and is described in detail in Fig. 12.
After the filled packaging containers have been sealed, they
are carried to the separating stations 181, 182 by means of the conveyor
chain, whereby it is again possible for a conveyor belt 150 in synchro-
nized operation to provide support for the trays 110 that are linked in
rows.
As shown in Fig. 1, the transport path of the conveyor
chain 148 and the support belt 150 extends from the dispenser to di-
rectly downstream of the two-stage separating station 181, 182, to that
the entire system can be operated in synchronicity.
A characteristic feature of the packaging device is that on
one hand it employs a tray 110 of a special design, and on the other
hand this tray 110 is manufactured in a special manner and is supplied
to the packaging system as semi-finished product.
Contrary to conventional implementations of such packag-
ing systems, the dispenser 112 supplies a tray 10, which is already
preformed, has been stabilized, e.g. by gluing, and comprises an upper
peripheral flange 52. The semi-finished products or trays 10 supplied
to the packaging device - as shown in the exploded view of Fig. 2 -
according to the invention possess specially designed peripheral flanges
52, which are formed by a continuous collar that is placed onto a tray
part 40.
Fig. 2 shows the two components of the tray 10 in their
preformed state, immediately before the components are assembled and
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connected, preferably glued. Figs. 3 to 5 show these components in
detail in a top view.
Both parts are executed as cardboard cutouts, preferably
employing cardboard of two or more layers, so that the tray's exterior
can possess different properties than the interior. The design of the
collar that forms the peripheral flange 52 contains incisions - as shown
in Fig. 3 - for the purpose of forming trapezoidal tabs 51, which are
attached to the peripheral flange along predetermined folds.
The tray part 40 has a design according to Figs. 5 and 6.
The side wall sections 43 are attached to the base component 41 along
folds 42. In their erected state (Figs. 6 and 2), the side wall sections 43
come into contact with each other.
Since the folded tabs 51 are connected, preferably glued, to
the side walls 43 once they are mounted on the tray part 40, the side
walls gain stability from the peripheral flange 52, so that a high tor-
sional stability of the tray can be achieved even with the use of small
quantities of material - low cardboard weight.
Preferably, the gluing is executed along spots or lines, as
indicated by the hatched areas 47 in Fig. 2.
The tabs 51 are mounted to the inside of the side walls 43,
so that the outsides of the side walls remain free, which is favorable for
printing.
The height H43 of the walls 43 is greater than the height
H51 of the tabs 51, i.e. the tabs cover only part of the area of the side
walls, which saves weight and DSD fees.
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Fig. 7 shows a perspective view of erected cardboard
cutouts 10 in a row formation, showing a recessed grip GM, which may
be included on an edge segment of the peripheral flange 52.
The side view of Fig. 8 shows the manner in which the half
molds 116 and 118 of the forming station FS interact with the lined-up
trays and line the insides or surface areas of the lined-up trays 10 with
the plastic composite film 134 by means of heating means 172.
The tool of the forming station FS, which operates using
the so-called Skin process, consists of an upper mold 118 and a lower
mold 116, which open and close synchronously according to the arrow
shown in Fig. 8. Hereby, the lower mold 116 preferably has a profile
section suited for the form-fitting receiving of the cardboard cutouts 10,
so that the peripheral flanges 52 of the cardboard cutouts 10 can be
supported in a sealed manner. In addition, the upper mold 118 is
configured so that it can contain heating means 172. The labels 173 and
173A refer to recesses in the upper and lower mold 116, 118, respec-
tively, which are developed appropriate for the recessed handles GM.
Fig. 4 shows a front view of the forming station FS. It can
be seen that the lower mold 116 contains ridge-like inserts 166, the
shape of which is matched to the cross section of the lined-up trays 10.
Hereby, the peripheral flanges of neighboring trays are in close proxim-
ity and rest fittingly on this ridge-like inserts, so that in the closed state
of the half molds 116 and 118 the individual trays are additionally
positively supported by the provided mold inserts 158, the surface
contours of which correspond fittingly to the shape of the trays.
The following is a brief description of the operating princi-
ple of the forming station FS, and in particular of the Skin process:
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Once a series of erected cardboard cutouts, the peripheral
flanges of which are in close proximity and form a saddle-shaped
support, is carried into the forming station FS by the tacked plastic film
134 (tacking spots), the lower mold 116, which previously had been
lowered, moves upward in the direction indicated by the arrows. When
the lower mold 116 is brought into contact with the upper mold 118, one
applies a nearly perfect vacuum to the upper mold 118. Due to this, the
entire surface of the plastic composite film 134, which is lying over the
cardboard cutouts 10 that are arranged in a tight row, is brought into
contact with the heated plate 172 and thus thoroughly heated.
After the specified heating time has elapsed, air is supplied
into the top mold 118, while at the same time the bottom mold 116 is
evacuated. This transition creates a differential pressure of approxi-
mately 1 bar, which effects the full-surface heat-laminating of the plastic
composite film and the tray interiors (see dotted line 134A) . Due to the
design of the tray part 40, there remain slit-shaped openings between the
side wall sections 43, which promotes the drawing-in of the film.
At the same time, the continuous peripheral flanges 52 are
heat-laminated over their entire surface.
Now that the interiors of the closely spaced cardboard
cutouts have been lined with the plastic composite film, the forming
station FS is opened in a synchronized manner, which releases the trays,
which are now linked by the plastic composite film and are transported
towards the filling using the conveyor chain 148.
Fig. 10 shows the linked row of trays, which is formed by
closely spaced trays 10 and is lined on its inside with plastic composite
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film 134, as it leaves the forming station FS. It can also be seen that the
plastic composite film 134 also covers the recessed handle GM in the
peripheral flange.
Fig. l0A (sectional view along the peripheral flange 52 of a
tray 10 with attached composite film 134) shows the individual layers
making up the composite film. The plastic composite film 134 com-
prises an oxygen-blocking layer 136, preferably made of polyvinyl
alcohol (PVA), a sealing layer 138, preferably of a peelable polyethyl-
ene, as well as an adhesive layer 137, preferably of a modified polyeth-
ylene. It has been shown that the interior lining of the carrier material
forming the food package can be executed extremely thinly. Preferably,
the film thickness in the area of the remaining wall thickness in the
rounded base sections is between 25 and 30 gym.
The interlocking of the film 134 with the cardboard can be
optimized by choosing a suitable surface structure of the cardboard on
the inside of the tray 10.
Moreover, the plastic composite film 134 can possess a
structure and adjusted characteristics, so that after the package has been
used it can be peeled from the cardboard carrier, so that unmixed
components are available for disposal or recycling. According to the
invention, the recessed handle GM also serves this purpose.
After leaving the forming station FS, the linked trays 10
pass the filling station along the filling path BS, during which time they
are filled with the foodstuff to be packaged. The transport of the linked
trays 10 through the common system takes place in fixed-cycle opera-
tion. From the filling path BS, the filled trays 10 enter into the vacuum-
and sealing station VS, where they are fittingly accepted into the lower
CA 02353684 2000-12-22
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part 116 by appropriately shaped inserts (see Fig. 11). Such a vacuum-
and sealing station of a conventional design consists of a lower part 216
and an upper part 218, which are opened and closed in fixed-cycle
operation. Preferably, the lower mold 216 is of a shape that can com-
pletely accommodate the tray 10 of the design according to this inven-
tion in such a way that the peripheral flanges of the trays can be sup-
ported in a sealed manner. The upper part is designed so that it can
accommodate a heater plate 274 that possesses a line pattern and is
movable in the vertical direction.
The line pattern is designed so that it defines planar areas in
which the peripheral flange of the cardboard cutout is to be sealed to the
cover film 120.
Fig. 12 shows the operation of such a vacuum- and sealing
tool in operation in accordance to this invention. In this process it is
also possible to employ well-known and proven conventional systems
with minor modifications.
Fig. 12 shows the lower mold 216 with the ridge-like
inserts 266, the shape of which is adapted to the cross section of a
saddle strip being formed between two neighboring peripheral flanges of
the trays 10, so that in the closed position of the half molds 216 and 218
the linked trays 10 are positively supported by the provided shaped
inserts 258, the shape contour of which corresponds to the shape of the
tray resting thereon. The label 270 indicates gaskets, with which the
peripheral flanges or saddle ridges of the linked trays 10 come into
contact in the closed position of the mold 216 and 218, so that the
individual cardboard cutouts, which at this point already contain food,
can be evacuated.
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The label 274 indicates heater means, which are housed in
the upper mold half 218 in a pattern that is aligned with the peripheral
ridges, so that in the closed position of the half molds 216 and 218 the
cover film 120 is sealed to the corresponding peripheral flanges of the
individual containers in such a way as to create a continuous circumfer-
ential sealing area.
Due to the special design of the continuous peripheral
flange 52, the seal remains free of capillary channels, through which a
gas exchange with the environment could take place.
At this point it must be emphasized that a standard commer-
cial vacuum station can be employed, in which the standard gas mixture
N2/COZ in a 70:30 ratio can be charged after the evacuation process.
The heater plate 274 located in the upper part of the mold 218 is prefer-
ably equipped with raised sealing ridges, whereby through heat- and
pressure action the cover film is sealed to the seal coating of the cir-
cumferential peripheral flange and the saddle ridges of the linked trays.
Fig. 12 shows the sealed, linked trays 10, now filled with
food, after they have left the vacuum- and sealing station.
As indicated by hatching, the entire plastic composite film
134 is heat-bonded to the cover film 120 along the intended sealing
areas. Only in the area of the recessed grip, designated GM, in the
rear peripheral flange region (as seen in running direction), a special
design of the sealing tool prevents the plastic composite film 134 from
sealing to the cover film 120. Using the recessed grip GM punched in
the rear peripheral flange and the fact that the cover film 120 is not
sealed to the plastic composite film 134 at this location, allows a future
CA 02353684 2000-12-22
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peeling-off of the film cover or the peeling of the plastic composite film
out of the tray 10.
After leaving the vacuum- and sealing station VS, the filled
trays, which are still linked by the cover film and the plastic composite
film 134, are carried to a separating system that preferably is of a two-
stage design.
It is also possible to employ combination punching and
separating of the individual food package. In combination punching, the
second stage of the separating will be omitted. Fig. 13 shows the
individual trays after leaving the separating station.
With the above food package it becomes possible, depend-
ing on the desired design, to save on average approximately 20 g of
non-recoverable plastic per food package, i.e. approximately 70 % of
the quantity that is created in conventional packaging of this type.
The working width of the device is of course not limited.
But it has been found that the width should be at least approximately 420
mm, to maintain the economic efficiency of the device at a very high
level.
Preferably the cover film 120 is also manufactured of a
plastic composite film 134 that contains an oxygen barrier layer, that is
covered by a peelable plastic film, preferably of a modified polyethyl-
ene, on the side that faces the cardboard cutout. This film, together
with the plastic composite film 134, then forms the sealed seams over
the sealing ridges of the peripheral flanges.
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The film layer that faces the heater- or sealing element 272
preferably consists of a film grade with an especially high melting point
or a heat-blocking layer, which preferably contains polyethylene and
lies above the oxygen barrier layer, so it can provide sufficient dimen-
sional stability with the lower mold part during the sealing process.
Since the sealing layers of both the cardboard cutouts and the cover film
are preferably matched to each other in their "peeling characteristics", a
solid bond is formed in the sealing of these two sealing layers, which
can be peeled by hand, essentially without damaging the cardboard
cutout layer 34 (See Fig. 14).
It goes without saying that embodiment examples are
possible that differ from those described above, without breaking with
the fundamental idea of the invention. For example, the number of
supplied lined-up trays per row or work cycle can be varied in any way
desired.
It is also conceivable to de-germ or sterilize the rows of
trays in a special device after they have left the forming station FS.
Advantageously, this would be a so-called hydrogen-peroxide shower.
Due to the employed process according to the invention in
both the oxygen-blocking plastic composite film and the oxygen-block-
ing cover film 120, one can employ a compound combination of films of
the polyolefm group. This compound combination can be recycled as a
single-component film. It has been found that this re-granulate can be
used as filler in the field of high-density PE film manufacturing.
The stability of the tray is significantly improved by the
invention's design of the peripheral flanges, due to the lining of the
interior with plastic composite film. After solidifying, the plastic
CA 02353684 2000-12-22
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composite film 134 significantly loses flexibility and reinforces the
entire tray over the peripheral flanges.
The subsequent sealing using the cover film over the
circumferential peripheral flanges provides additional torsional rigidity
and dimensional stability to the cardboard cutout.
The invention provides for a very reliable sealing of the
tray lined with barrier layer composite film by means of the barrier
layer cover film. This is achieved due to the circumferential peripheral
flanges forming closely spaced, so-called saddle ridges with a sealing
surface, which is increased to twice what it is in conventional peripheral
flanges.
Since the entire available sealing surface, which is heat
laminated with the sealing side of the barrier layer plastic composite
film 134, is available as sealing surface with the cover film 120, the fact
that the packages are only separated after the sealing always ensures a
sufficiently wide surface area for the formation of a secure sealing
seam.
In individually supplied trays that do not possess the inven-
tion's special peripheral flange design, such a sealing area of uniform
width and thus sufficient reliability can not be achieved, due to toler-
ances during the fixing of the tray in the process's operation or produc-
tion related variations in the production of the cardboard cutouts. A
further essential aspect of the invention is the separating of the oxygen-
tight interior film component from the actual stability-providing card-
board cutout (see also Fig. 14). The plastic composite film lining the
interior of the trays is heat laminated with the fibers of the interior walls
and of the base of the cardboard cutout.
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Using well known processes, for example the Multivac
Skin system, the heated, and thus plasticized, plastic composite film
with the specially formed laminating layer, which preferably contains a
Surlyn mixture by Dupont or a mixture (PE type) with an especially
high (preferably above 20 % ) ethylene vinyl acetate content, is pressed
by an appropriate pressure difference against the tray's interior surfaces,
and can penetrate into the fibers of this interior surface.
Following the evacuating or supply of gas, the cover film
120 is in a sealing station firmly joined to the base of the package, along
the circumferential peripheral flanges and the saddle ridges of the series-
linked trays, which are coated with a sealing layer as described.
The provided semi-oval punch-out (GM) of the, in transport
direction rear, peripheral flange and the design of the corresponding
area of the sealing tool make it possible, using a so-called grip strap
which is formed of cover film that at this location is not sealed by lining
film, to peel the entire composite system at the provided recessed grip
from the cardboard cutout, which is then pure and can be composted as
unmixed material.
Part of the range of application of the food package is
opening of the packaging by peeling the cover film off the sealing ridges
to be able to remove the content of the packaging easily and without any
tools. This can be accomplished by a special design of the sealing tool in
the sealing station, without extensive retooling effort.
The consumer peels the cover film from the sealing areas
until he can easily remove the contents (see Fig. 15). The plastic
composite film together with the not completely detached cover film are
then removed from the actual cardboard cutout using the grip strap at
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the provided recessed grip. This provides for the separation into un-
mixed materials, and the individual materials can now be supplied to
further processing.
Fig. 16 shows a schematic view of a tool for the manufac-
turing of the trays 10. The cardboard cutout 40 is erected in a lower
mold 316 and is fittingly stabilized by means of an air-evacuating device
319. The upper mold 318, which carries the erected collar with periph-
eral flange 52, is aligned above the lower mold .
After a cold adhesive or a hot-setting adhesive have been
applied to one of the surfaces of the side walls and/or tabs that will be
overlapping, the forms 316 and 318 are closed. If a hot-setting adhesive
is used, the setting time can be controlled more precisely, and thus it is
possible to reduce the cycle times of the manufacturing even further.
Fig. 16 indicates the areas onto which the adhesive has been applied by
different shapes, which is meant to emphasize that it is possible to vary
the design, depending on where the tray is subjected to stresses.
Naturally, variations of the shown variants are possible
without being untrue to the basic concept of the invention. Fig. 17
shows a slightly modified tray design. The collar 452 is executed
without tabs, and is positioned exactly over the angled peripheral flange
segments 444 of the side walls 443 of the tray part 440 and is solidly
connected thereto, preferably glued. The label 'x' indicates those areas
where adjacent wall segments 443 are joined by overlapping tabs 443A.
In combination with this kind of tray it can be practical to
modify the packaging system according to Fig. 18. Erected or pre-
manufactured trays 510 are removed from a magazine 512 and set in
rows and are transferred to a synchronized conveyor belt 511. Subse-
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quently, the trays 510 are transported underneath a plug device with a
plug 517, which folds the peripheral flange formed by the segments 444
before the collar 452 is attached in the gluing station 452. This occurs
by forming a surface that is as planar as possible for positioning the
collar and for an optimum alignment of the sections 444. The plug 517
is designed so that the peripheral flange is folded into an angle for the
sealing positions that are permitted depending on the miter cuts at the
ends of the peripheral flange segments 444. The transfer station IJS
follows downstream of the gluing station (see Fig. 1 ) .
If a process with a tray-sealer is employed, then the con-
veyor chain 148 in fixed-cycle operation transports the closely spaced
trays 10 into the forming station FS. The forming station FS can also
be configured as, for example, a station of a forming-, filling-, and
sealing system operating according to the Skin-system, according to
Multivac CD6000.
Thus, the invention creates a food package in the form of a
dimensionally stable cardboard cutout with a circumferential top periph-
eral flange, which according to the invention is continuous and is placed
onto the tray part. In this manner, the seal area along the flange is of
high quality, ensuring permanent tightness.
The substrate tray consists of cardboard and, along the
inside area of the flaps, executed as peripheral flanges, carries an
oxygen-barrier plastic film that can be sealed by the cover film.
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Also described is a process, a device for the manufacturing
of an oxygen-tight food package, whereby pre-formed and
dimensionally stable trays are supplied by a dispenser system, or, if a
so-called tray-sealer is employed, are directly placed into the receiving
molds of the conveyor chain of the tray-sealer by the dispenser. In a
forming station the trays are lined with a plastic composite film, which
preferably contains an oxygen barrier layer.
