Note: Descriptions are shown in the official language in which they were submitted.
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BUSTER-TYPE PACKAGE
BACKGROUND INFORMATION
1. Field of the Invention
The present invention relates to a blister-type package for the packaging of
loose items such as might be sold at retail rack displays.
2. Background of the Invention
In the packaging of retail products other than food, the principal functions
of a package are to contain the product (and possibly to compile many small
products in the same package), to protect the packaged items) from dust and
dirt,
and to display the products) in a way that enhances sales appeal. An
increasingly
important feature is the ability of the package to be hung because hanging
racks
have been widely adopted as the most convenient and space efficient way to
display small items.
I 5 Presently, loose items can be packaged in one of two primary forms: the
so-called blister package or the so-called skin package.
A blister package consists of a stiff, usually clear, thermoformed plastic
box, shaped to more or less fit the contours of the articles to be packaged
which is
lidded with a sheet of plastic or coated paperboard that carries the graphics
and
which can be perforated for rack-hung display. The package has an appealing
appearance, but the packaging system lacks flexibility. Whenever the shape or
the
size of the item to be packaged is changed, the thermoformed plastic box where
the item is loaded must be changed. Furthermore, the amount of plastic waste
generated is very high because the thermoformed sheet generally has a
thickness
of from about 0.1 to about 1 mm.
Like the blister package, a skin package normally uses printed paperboard
as one component. However, the other component of the package is made from a
plastic film that is drawn down by vacuum around the product to be packaged
until the film conforms so faithfully to the product contours that it becomes
like a
skin. This skin film holds the product in place on the paperboard and protects
it
from contaminants such as, for example, dust and dirt. In skin packages, the
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product typically is positioned on a printed, plastic coated card which then
moves
onto a platen that contains air passages connected to a vacuum system. Plastic
film is held in a frame above the product-carrying card. While in the frame,
the
film is heated for softening and then lowered over the product and onto the
card.
A vacuum is applied to bring the film into intimate contact with the product
and
coated card. Residual heat in the plastic film creates a heat seal with the
coated
card.
In skin and vacuum skin packaging, the skin top film is softened, optionally
stretched, and drawn down to conform to the shape of the product to be
packaged. Because the film thins during the skin packaging process, thick
films
generally are necessary to avoid package breakage.
That which has not been described previously is a blister-type package that
requires a small amount of plastic material, that can be used for the
packaging of
products) of different shapes and sizes without requiring major modifications
in
the overall packaging process, and that can be easily and efficiently recycled
after
use. Provision of such a package remains desirable.
SUMMARY OF THE INVENTION
Briefly, the present invention provides a blister-type package that includes
one or more products sandwiched between a backing and a thermoplastic film.
The film covers the products) and is sealed to the backing along a line
external to
and spaced from the product(s). The film is mono- or bi-axially oriented when
applied to the backing and, thereafter, is heat shrunk. Unlike films in skin
packages, the film used in the blister-type package of the present invention
does
not completely shrink around the product(s); instead, the film encapsulates
the
products) by forming a blister-like cavity around it/them. The film is
tensioned
over the products) and secures it/them to the backing.
In another aspect, the present invention provides a method of making a
blister-type package. The method includes loading one or more items on a
backing, sealing a mono- or bi-axially oriented thermoplastic film to the
backing
so as to form a package precursor, and heating the package precursor so as to
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shrink the thermoplastic film to at least a point where the
thermoplastic film is tensioned over the items) and holds
it/them to the backing. The thermoplastic film is sealed to
the backing along a line external to and spaced from the
item(s). Thus, the resulting package is a blister-type
package as opposed to a skin package.
According to one aspect of the present invention,
there is provided a blister-type package comprising: a) a
backing; b) at least one product disposed on said backing;
and c) a thermoplastic film covering said at least one
product and sealed to said backing along a line external to
and spaced from and around said at least one product, said
film being mono- or bi-axially oriented when applied to said
backing, being heat shrunk so as to be tensioned over said
at least one product and secure said at least one product to
said backing.
According to another aspect of the present
invention, there is provided a method of packaging one or
more items in a blister-type package comprising: a) loading
at least one item on a backing; b) along a line external to
and spaced from and around said at least one item, sealing a
mono- or bi-axially oriented thermoplastic film to said
backing so as to form a package precursor; and c) heating
said package precursor so as to shrink said thermoplastic
film to at least a point where said thermoplastic film is
tensioned over said at least one item and holds said at
least one item to said backing so as to form a blister-type
package.
Advantageously, the blister-type package of the
present invention has an appealing appearance and requires
only a small amount of plastic material. If desired, the
package of the present invention can be used in conjunction
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with standard retail hanging displays. Also, the package of
the present invention advantageously can be used for the
packaging of products) of different shapes) and sizes)
without requiring major modifications in the overall
packaging process. Furthermore, the package of the present
invention can include paperboard and plastic materials
which, beneficially, can be separated easily from each other
in a manner that allows for recycling of each.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view showing one embodiment of a
package according to the present invention.
FIG. 2 is a side view of the package shown in
FIG. 1.
FIG. 3 is a plan view showing another embodiment
of a package according to the present invention.
FIG. 4 is a bottom view of the package shown in
FIG. 3.
FIG. 5 is a side view showing still another
embodiment of a package according to the present invention.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
FIGS. 1 (plan view) and 2 (side view) show
package 10, which represents an embodiment of the package of
the present invention in which a single item 11 sits on
backing 12. Backing 12 preferably is substantially planar
(i.e., flat) and can be printed, if desired. Where rigid
paperboard is used as backing 12, the thickness thereof can
range from about 0.75 to about 3.75 mm (i.e., about 30 to
about 150
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mils), typically from about I .25 to about 3.0 mm (i.e., about 50 to about 120
mils), and preferably from 1.5 to about 2.25 mm (i.e., about 60 to about 90
mils).
Alternatively, backing 12 can be a rigid or semi-rigid sheet of
thermoplastic material. Mono- or multi-layer sheets can be used and can
include
one or more layers made from, for example, polyethylene terephthalate,
polyvinyl
chloride, polypropylene, polystyrene, and the like. Such a backing can be
printed,
trap-printed, or laminated to a paper label bearing graphics. Its thickness
typically
ranges from about 0.2 to about 1.25 mm (i.e., about 8 to about 50 mils) and
preferably from about 0.3 to about 1.0 mm (i.e., about 12 to about 40 mils).
A sheet of a foamed polymer such as, for example, foamed polystyrene,
foamed polyethylene terephthalate, or foamed polypropylene, also can be used
as
backing 12. The thickness of such a sheet can be greater than those indicated
previously; for example, thicknesses of about 2.5 mm (i.e., about 100 mils) or
even greater are possible.
Regardless of the type of material used, backing 12 can be coated with a
heat-sealable polymer. Polymers particularly suitable for this purpose include
ethylene homo- or co-polymers such as, for instance, low density polyethylene
(LDPE); homogenous or heterogeneous ethylene/a.-olefin copolymers (e.g.,
linear
low density polyethylene or "LLDPE", linear medium density polyethylene or
"LMDPE", very low density polyethylene or "VLDPE", etc. ); ethylene/vinyl
acetate copolymer (EVA); and the like.
Where a non-perforated heat-shrinkable film is used as thermoplastic film
13, backing 12 preferably contains at least one venting hole 16 that is not
blocked
by the item to be packaged. Venting hole 16 allows excess air within package
10
to escape during the shrinking step (described infra), thus avoiding
ballooning of
the package. (Where thermoplastic film 13 must shrink only minimally to be
suffciently tensioned over product 11, a venting hole is not absolutely
necessary.)
The shape of venting hole 16 is not critical. Round, elliptical, or semi-
circular
holes, and even slits, can be used. The size thereof should be sufficient to
allow
for the passage of air forced from package 10 during the heat-shrinking step.
Where venting hole 16 is large, it can be closed after heat-shrinking of
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S
thermoplastic film 13, if desired, to prevent dust and dirt from entering
package 10
and possibly contaminating product 11.
Where a perforated film is used as thermoplastic film 13, venting hole 16
need not be present in backing 12. The pattern of perforations in such a film
is not
critical provided it does not compromise the mechanical properties of the
film.
Generally, a few holes of up to 500 p,m of average diameter are sufficient to
allow
excess air to escape during the shrinking step without negatively af~'ecting
the film
properties. Perforations in a film can be created by any method which provides
holes of the desired average diameter. Laser and electric discharge can be
employed to microperforate with holes of an average diameter up to about I 50
pm. Flame or needle perforation can be used conveniently where holes of a
larger
average diameter are desired. Such techniques can be employed at any time
prior
to the shrinking step. If desired, such perforations can later be closed by,
for
example, application of an adhesive label.
In package 10, backing 12 has perforations 15 that create a pattern of
weakness in backing 12. When the portion of backing 12 defined by perforations
15 is removed, product 1 I can be accessed more easily. Although not shown in
FIGs. 1 and 2, the venting hole can be located in the line of perforations and
be of
a size that allows the ingress of a fingertip to grip the portion of the back
delimited
by the perforations. By tearing along the perforations, the defined portion
can be
removed and the package opened more easily.
Backing 12 also can include shaped hole 17 which allows package 10 to be
hung in conjunction with standard retail displays. In package 10,
thermoplastic
film 13 advantageously is sealed to backing 12 only in the portion thereof
that
does not include shaped hole 17.
Perforations 15, venting hole 16, and shaped hole 17 can be produced
according to conventional means known in the art, the choice of which depends
primarily on the material selected for backing 12.
Thermoplastic film 13 is sealed to backing 12 along seal line 14 which is
on the same side of backing 12 as product I 1. Thermoplastic film 13 can be
joined to backing 12 by means of a hot melt or spreadable pressure sensitive
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adhesive distributed on backing 12 in an uninterrupted manner along seal line
14
by any conventional means. Use of an adhesive allows for the use of uncoated
paperboard as backing 12 and for the easy separation thereof from
thermoplastic
film 13 (once the blister-type package is opened). This allows for the
separate
recycling of the two materials when the packaging material components of
package 10 are to be discarded.
After application of the adhesive, thermoplastic film 13 is lowered over the
product/paperboard and joined to the backing by pressing the two materials
against each other along seal line 14, which is external to and spaced from
the
items to be packaged. A suitable pressing frame can be employed for this
purpose.
Where paperboard coated with a heat-sealable polymer is used as backing
12, thermoplastic film 13 can be sealed thereto by any conventional technique
such
as, for example, impulse sealing, hot bar sealing, RF-sealing, ultrasonic
sealing,
I 5 etc., useful with the particular type of thermoplastic materials) used.
One
preferred technique is impulse sealing. The advantage of the impulse sealing
is
that it can be used for almost any type of thermoplastic material. In this
type of
sealing, a sealing wire on a sealing frame of the desired shape receives an
electric
impulse of a suitable intensity and duration that heats it to the selected
sealing
temperature while the sealing frame is lowered on the conveyor pressing the
surface of the front blister film to that of the backing along a closed line
external
to the items to be packaged. The sealing frame then is cooled and raised.
The shape of the sealing frame is not critical provided it encompasses the
items) to be packaged. However, use of a sealing frame with a shape that
essentially corresponds to that of the backing (or at least to the portion
that does
not contain shaped hole 17) can prove beneficial. As shown in FIG. 1, when
such
a frame is used, thermoplastic film 13 can be sealed near the edges of backing
12
or the portion thereof that does not contain shaped hole 17. Such a sealing
frame
can be used for packaging items of widely differing shapes and sizes.
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Excess film, if any, can be cut either simultaneous to the sealing step or in
a later step. Such cutting can be accomplished by any of a variety of suitable
blades and/or knives.
Once thermoplastic film 13 has been sealed to backing 12 and any excess
film has been removed, package 10 can be submitted to heat treatment while
still
being held horizontally. Heat treatment allows thermoplastic film 13 to shrink
and
affords the desired blister-type package. (A further description of the
shrinking
process is provided infra.)
FIGS. 3 (plan view) and 4 (bottom view) show package 20 in which single
item 21 sits on backing 22. Backing 22 includes perforations 25 and shaped
hole
27; however, backing 22 does not include a separate venting hole (as did
package
10 from FIGs. 1 and 2). In package 20, shaped hole 27 acts to vent air from
the
package during the heat shrinking process.
Thermoplastic film 23 extends over the entire top surface of backing 22
and is sealed on the bottom surface thereof (shown in FIG. 4). Thermoplastic
film
23 is sealed near the edges of backing 22, resulting in some excess film
beyond
seal line 24.
The same materials mentioned previously in conjunction with package 10
can be used in the manufacture of thermoplastic film 23 and backing 22 of
package 20. Additionally, thermoplastic film 23 can be sealed to backing 22
using
the same techniques described previously.
FIG. 5 shows a side view of package 30 in which single item 31 sits on
backing 32. Thermoplastic film 33 extends over the entire tap surface
ofbacking
32 and is sealed thereto along seal line 34 which corresponds to the side
edges of
backing 32. The materials used and sealing methods employed are the same as
those described previously
Regardless of where the thermoplastic film is sealed to the backing, the
sealing technique employed preferably provides a seal with a seal strength of
at
least about 1500 g/25 mm, preferably at least about 2000 g/25 mm.
The thermoplastic film is mono- or bi-axially oriented and heat shrinkable.
As used herein the term "mono- or bi-axially oriented, heat-shrinkable film"
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identifies a film that has been mono- or bi-axially oriented by stretching at
a
temperature higher than the highest glass transition temperature (TQ) of the
resins
which make up the film and lower than the highest melting point of at least
one
polymer of the film, i.e., at a temperature where at least some of the resins
from
S which the film is made are not in the molten state.
Mono- or bi-axially oriented heat-shrinkable films are made by
(co)extruding polymeric resins from a melt into a thick film, followed by
quickly
quenching (to prevent or delay crystallization) and then orienting the thick
film by
stretching it, either monoaxially or biaxially, under temperature conditions
where
molecular orientation occurs yet the film does not tear. Upon subsequent re-
heating at a temperature close to the orientation temperature, an oriented
heat-
shrinkable film tends to shrink in seeking to recover its original dimensional
state.
When a bi-axially oriented heat-shrinkable film is desired, it can be obtained
by
(co)extruding the polymer resins) through a round die, yielding a thick,
tubular
film that is immediately and quickly quenched, typically to about room
temperature, by means of a water bath or cascade. This tubular film then is
heated
to the orientation temperature (which generally depends on the type of polymer
resins employed and is, in any case, lower than the melting temperature of at
least
one polymer used) and stretched biaxially by, for example, the so-called
"trapped
bubble" technique where internal gas pressure expands the tube to form a large
bubble and the expanded tube is advanced at a rate which is greater than the
extrusion rate so as to obtain orientation in both the transverse direction
(TD) and
the longitudinal direction (LD). Typically, the stretch achieved by such a
technique is at least about 3 x in each direction. The film then is cooled so
as to
retain the property of heat shrinkability.
Alternatively, mono- or bi-axially oriented heat-shrinkable films can be
obtained by extruding the polymer resins) through a flat die in the form of a
sheet
and, after a quenching step, heating the sheet to its orientation temperature
and
stretching it. Orientation in the LD typically is obtained by running the
sheet over
at least two series of pull rolls wherein the second set runs at a higher
speed than
the first one. Orientation in the TD typically is accomplished by means of a
tenter
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frame where the edges of the sheet are grasped by clips carried by two
continuous
chains running on two tracks that move progressively wider apart. (Where
biaxial
orientation is desired, stretching can be done in both directions
simultaneously as
opposed to sequentially, i.e., either longitudinally and then transversely or
vice-
s versa.. The oriented film then is cooled and processed in the normal
fashion. The
stretch achieved by this type of technique typically is at least about 3 x in
each
direction as well, although higher ratios are not uncommon.
As used herein, the term "heat-shrinkable" is used to describe those films
which exhibit a percent free shrink of at least 15% in at least one direction
when
heated and unrestrained at a temperature of 120°C for 4 seconds in
accordance to
ASTM D 2732, as set forth in the 1990 Annual Book of ASTM Standards, vol.
08.02, pp. 368-71. Thermoplastic films used in the package of the present
invention preferably exhibit a free shrink of at least 25%, more preferably at
least
35%, in at least one direction.
The thermoplastic film used in the package of the present invention is
mono- or bi-axially oriented and heat-shrinkable. When subjected to heat
treatment, the film shrinks. The heat releases a force (so-called "shrink
force"
and, when referring to the sample cross-section, "shrink tension") that is
useful to
overcome the frictional forces between the packaged items) and the
thermoplastic
film and to tension the film, thereby avoiding wrinkles and creases on the
package
and at the same time keeping the items tightly in place on the backing even
when
the package is hung.
Films with a shrink tension of from about 2 to about 50 kg/cmz can be
employed beneficially in the package of the present invention; preferred films
are
those with a shrink tension of from about 5 to about 40 kg/cmz, and most
preferred are those with a shrink tension of from about 8 to about 3 5 kg/cm2.
(Low shrink tension, for the purposes of the present invention, refers to a
shrink
tension below about 15 kg/cm2.) In monoaxially oriented films, shrink tension
develops only in the direction of the orientation. In biaxially oriented
films, shrink
tension develops, upon heating, in both the LD and TD.
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The thermoplastic film used in the package of the present invention can
have a low, medium, or high shrink tension depending on the type of product to
be
packaged and the type of backing used. For example, where a rigid and thick
backing is used for packaging a non-deformable product, a medium-high shrink
tension film preferably is employed. Alternatively, where a semi-rigid,
deformabie
backing is used to package a soft product, a low shrink tension film
preferably is
used so as to avoid bending of the backing or deformation of the packaged
product.
As indicated previously, shrink tension is the shrink force referred to the
sample cross-section and is calculated by simply dividing the shrink force by
the
thickness of the film. Presently, no test method for measuring shrink force is
recognized as a standard. The method used herein to measure this attribute
involves cutting a specimen of a test film (2.54 cm x 14.0 cm); clamping the
specimen between two jaws, one of which is connected to a load cell, so as to
keep the specimen in the center of a channel into which an impeller blows
heated
air which increases the temperature therein at a rate of 2°C/sec;
measuring the
temperature of the channel (with, for example, three thermocouples) as well as
the
signal supplied by the load cell (in g); supplying the signals of the
temperature and
load signals to a recorder; and recording the temperature signal n the X axis
and
the load signal on the Y axis. As the temperature increases, the X/Y recorder
displays the profile of shrink force versus temperature in the form of a curve
that
shows a gradual increase of the shrink force with temperature passing through
a
maximum at a temperature close to the orientation temperature. By dividing the
specimen width (in cm) into the values thus recorded (multiplied by 10'3),
shrink
force values (in kg/cm) are obtained; by further dividing the shrink force
values by
the specimen thickness (in cm), shrink tension data (in kg/cm2) are obtained.
As
used herein "shrink tension" refers to the maximum value thus obtained over
the
entire temperature range tested.
The thickness of the thermoplastic film used in the package of the present
invention can depend on the shape, weight, and/or rigidity of the items) to be
packaged. Mechanical properties of oriented, heat shrinkable films generally
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increase with increasing thickness. Therefore, a thicker film is preferred for
packaging items with protruding edges or irregular shapes. Thicker films also
can
prove beneficial in the packaging of heavy and/or thick items, particularly
where
the package is to be hung. For relatively light and regularly shaped items,
such as
most stationery articles currently sold in blister packages, films from about
8 to
about 3 S p.m thick can satisfactorily be employed; in more demanding
applications, films as thick as 50 p.m or even more can be usec. In general,
however, films of from 8 to 15 p.m suitably can be employed for light products
with a regular shape, while films from 15 to 35 ~m are satisfactory for heavy
and/or irregularly shaped products. (Unlike skin packaging, in the packaging
process according to the present invention, the thermoplastic film does not
reduce
its thickness but, on the contrary, can become slightly thicker depending on
the
amount of shrink. ) The ordinarily skilled artisan can determine without undue
burden the optimum thickness range for a given thermoplastic film and a given
article to be packaged.
Generally, the thermoplastic film need not possess oxygen barrier
properties. Suitable films include mono- or mufti-layer polyolefin films that
include one or more of ethylene homo-, co-, or ter-polymers and propylene homo-
co-, or ter-polymers. Examples of such polymers include, but are not limited
to,
polyethylene, ethylene/a.-olefin co- and ter-polymers, ethylene/vinyi acetate
copolymers, ethylene/alkyl (meth)acrylate copolymers, ethylene/(meth)acrylic
acid
copolymers, ionomers, polypropylene, propylene/ethylene copolymers,
propylene/ethylene/butene terpolymers, anhydride grafted polyethylene,
anhydride
grafted ethylene/a-olefin co-and ter-polymers, anhydride grafted
ethylene/vinyl
acetate copolymers, and the like.
Regardless of the foregoing, blister-type packages with oxygen barrier
properties can be usefial in packaging food or other items which are sensitive
to
oxygen. When oxygen barrier properties are desired, the thermoplastic film can
include one or more layers that include oxygen barrier resins such as, for
example,
vinylidene chloride copolymers; ethylene/vinyl alcohol copolymers; polyvinyl
alcohol; or, where moderate oxygen barrier properties are sufficient,
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(co)poiyamides. Where a film with oxygen barrier properties is employed as the
thermoplastic film, the backing also preferably is coated with an oxygen
barrier
layer (e.g., aluminum foil, an oxygen barrier film, or the like). In such a
case, the
venting holes) can be closed with, for example, oxygen barrier adhesive labels
immediately after the shrinking step.
In the manufacture of a package according to the present invention, the
backing typically is prepared in its finished form (including holes/slits,
printing,
coating, etc.) and placed horizontally on a conveyor. The items) to be
packaged
then are positioned over the backing. (When the thermoplastic film is not
perforated, closing all potential venting holes in the backing (for example,
by
covering them with the items) to be packaged) is not preferred.) An oriented
film
then is placed over the items) and sealed to the backing along a closed line
external to the item(s). Sealing can be accomplished by any of the methods
discussed previously or by other methods that are substantially equivalent.
Once
sealed, the package is heat treated to shrink the thermoplastic film. The heat
treatment can occur either during or subsequent to the sealing cycle. Heat
treatment can be accomplished by, for example, passing the package through a
hot
air shrink tunnel. Upon heating, the thermoplastic film shrinks until it is
restrained
from further shrinking by~the packaged product. Therefore, the thermoplastic
film
is tensioned over the product. Excess film, if any, then can be trimmed from
the
package.
Objects and advantages of this invention are fizrther illustrated by the
following examples. The particular materials and amounts thereof, as well as
other conditions and details, recited in these examples should not be used to
unduly limit this invention.
EXAMPLE
A brush (200 mm long, 60 mm wide, and 20 mm thick) weighing 200 g
was positioned on a polyethylene-coated paperboard (2 mm thick, 300 mm long
and 100 mm wide). A 3-layer irradiated film (15 p,m thick) with a core layer
of
LLDPE and two outer layers made from a blend of LLDPE, LMDPE, and EVA
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was prepared as described in Embodiment II ofU.S. Patent No. 4,551,380 and
had the following shrink properties:
free shrink (at shrink tension (kg/cm
120C) )
LD 65% 26
TD 64% 3 5
The film was sealed to the backing by means of an impulse system (0.5 sec
sealing time, 3 x 105 Pa sealing pressure, 12 mA impulse power) using a
rectangular sealing frame (with an outer perimeter of 300 mm x 100 mm wide).
Excess film was cut by a series of knives contouring the sealing frame was
removed.
The sealed package was passed through a hot air tunnel set at
140°C. The
final package had a very nice appearance and could be hung from a standard
display rack. The amount of thermoplastic material used in the film used was
nearly one-tenth of the amount of plastic material used for a conventional
thermoformed front blister.
Various modifications and alterations that do not depart from the scope
and spirit of this invention will become apparent to those skilled in the art.
This
invention is not to be unduly limited to the illustrative embodiments set
forth
herein.
