Note: Descriptions are shown in the official language in which they were submitted.
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CONTAINER BODY
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The present invention relates to a container body,
and more particularly to a cup-shaped container body having
high gas-barrier property which is light-weight and not
susceptible to significant deformations such as collapse.
A cup-shaped container body formed by drawing
a relatively thin laminate blank including a metal foil
and a thermoplastic film is advantageous in that it is
light-weight, inexpensive and has high gas-barrier property.
However, a hermetically sealed container formed by sealing
the container body with a lid after filling a product tends
to deform if it is opened or during transit or the like.
Particularly when it collapses when opened, the product
flows out of the container and pollutes fingers, tables
or the like.
There are cases where it is desired to form
concave patterns having a predeterm~ned shape on the
sidewall and/or the bottom wall of the aforementioned
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container body so as to enhance design effect or indicate
the name of a manufacturing plant thereof and the like.
However, in order to form the concave pattern when drawing,
a die and a punch having a convex portion and a concave
portion, respectively, corresponding to the concave pattern
must be prepared, and a lot of labor is needed for making
the punch and the die and adjusting them prior to the
drawing. Further, some types of the concave pattern such
as a circumferential ring pattern are not applicable to
a drawn article.
In case when the aforementioned cup-shaped
container body is made by thermoforming such as vacuum
forming at a temperature above the softening temperature
of the plastic concerned, the concave pattern is readily
formed. However, since thermoforming is accompanied by
large expansion of the wall of a formed article, the metal
foil in the laminate is broken discontinuously, whereby
the container body thus formed will have poor gas-barrier
property.
A general object of the invention is to provide
a cup-shaped container body having high gas barrier property
which is light weight and not susceptible to significant
deformations such as collapse.
A specific object of the invention is to provide
a cup-shaped container body which can be formed concave
patterns onto the wall portion thereof by retort sterilization
under pressure or the like.
The invention provides a cup-shaped unitary container body
comprising:
(a) a laminated, flexible, outer hollow article, impervious
to gas and light, comprising a metal foil layer less than lOO~m
in thickness and an inner layer of a thermoplastic film material
less than 200 ~m in thickness, said outer hollow article being
shaped by drawing in a die, and having a flange portion at an
open end thereof, a sidewall portion and a bottom wall portion;
and
(b) a reinforcing, inner hollow article thermoformed from a
blank of a thermoplastic material of at least 0.3mm in thickness,
so as to substantially eliminate residual stress, said article
having a flange portion at an open end thereof, a sidewall portion
and a bottom wall portion, and having a configuration correspond-
ing to said outer hollow article;
said inner hollow article being positioned within said
outer hollow article with said flange portions superimposed and
said sidewall portions and said bottom wall portions in close con-
tact with each other, and
said outer hollow article and said inner hollow article
being hermetically joined by heat sealing of said flange portions.
The invention also provides a method of producing a cup-
shaped unitary container body comprising the steps of:
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(a) forming a laminated, flexible, outer hollow article, im-
pervious to gas and light, comprising a metal foil layer less than
100 ~m in thickness and an inner layer of a thermoplastic film mat-
erial less than 200 ~m in thickness, said outer hollow article being
shaped by drawing in a die, and having a flange portion at an open
end thereof, a sidewall portion and a bottom wall portion,
(b) forming a reinforcing, inner hollow article by thermoform-
ing a blank of a thermoplastic material of at least 0.3 mm in thlck-
ness, so as to substantially eliminate residual stress, said article
having a flange portion at an open end thereof, a sidewall portion
and a bottom wall portion, and having a configuration corresponding
to said outer hollow article,
(c) inserting said inner hollow article into said outer hollow
article such that said flange portions are overlapped upon each
other, and said sidewall portions and said bottom wall portions are
in close contact with each other, respectively, and
(d) hermetically joining said outer hollow article and said
inner hollow article by heat sealing said flange portions.
The inner hollow article may be formed with a concave
portion having a predetermined shape on the wall portion thereof,
and the outer surface of the inner article may be in substantial
contact with the inner surface of the outer hollow article except
the concave portion. The outer article may be formed with a con-
cave pattern by exerting a fluid pressure to the container body.
These and other advantages inherent in and encompassed by
the invention will become more apparent from the specification and
the accompanying
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drawings wherein like parts are designated by like numerals
throughout the various figures.
Fig. 1 is a vertical sectional view showing a
container body of a first embodiment according to the
invention;
Fig. 2 is an enlarged sectional view of the
portion A in Fig. 1;
Fig. 3 is a plan view of a hermetically sealed
container formed by heat sealing a lid to the container
body of Fig. 1;
Fig. 4 is a vertical sectional view taken along
line IV-IV of Fig. 3;
Fig. 5 is a vertical sectional view illustrating
a state where the sealed container of Fig. 3 is being
opened;
Fig. 6 is a front view showing a container body
of a second embodiment according to the invention;
Fig. 7 is a horizontal sectional view taken along
line VII-VII of Fig. 6;
Fig. 8 is a vertical sectional view taken along
line VIII-VIII of Fig. 7;
Fig. 9 is a front view of a hermetically sealed
container having the container body of Fig. 6 showing a
state after retort sterilization under pressure;
Fig. 10 is a horizontal sectional view taken along
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line X-X of Fig. 9;
Fig. 11 is a vertical sectional view taken along
line XI-XI of Fig. 10;
Fig. 12 is a fragmental horizontal sectional view
of the sidewall portion of a container body of a third
embodiment according to the invention;
Fig. 13 is a fragmental horizontal sectional view
of the sidewall portion of Fig. 12 showing a state after
the container body of Fig. 12 has been placed under fluid
pressure;
Fig. 14 is a front view of a eontainer body of
a fourth embodiment according to the invention after placed
under fluid pressure;
Fig. 15 is a vertical sectional view of a
container body of a fifth embodiment according to the
invention;
Fig. 16 is an enlarged sectional view of the
portion B in Fig. 15.
Referring to Figs. 1 and 2 a container body 1
eonsists of a eup-shaped outer hollow artiele 2 formed by
drawing a flexible laminate blank and then eurling the open
edge of the drawn artiele, and a reinforcing cup-shaped
inner hollow article 3 formed by thermoforming a
thermoplastic blank and received in the outer hollow artiele
2. The outer hollow artiele 2 and the inner hollow artiele
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3 have flange portions 4 and S, respectively, and shapes
corresponding to each other except in a curl portion 6 of
the outer hollow article 2 such that the latter can be
substantially fitted into the former.
Herein drawing or draw forming means a method
of making a cup-shaped hollow article using a punch, a die
having a cavity and a blank-holder, wherein a blank is
introduced into the cavity by the punch to form the article
while the portion of the blank on the upper surface of the
die is pushed by the blank-holder against the upper surface,
so as to prevent wrinkles from developing, and drawn into
the cavity sliding between the upper surface and the
blank-holder. The thickness of the sidewall portion of
the drawn article is substantially same as that of the
blank. Drawing is usually carried out at normal room
temperature.
As best shown in Fig. 2, the flange portion 5
of the inner hollow article 3 is thermally adhered to the
flange portion 4 of the outer hollow article 2 through an
inner layer 2a of the flange portion 4 to form a heat sealed
portion 7 such that the two are hermetically jointed to
prevent the inner hollow article 3 from separating from
the outer hollow article and hinder steam and air from
entering between both the hollow articles during retort
sterilization or the like.
It is preferable that the sidewall portion 2x
of the outer hollow article 2 and the sidewall portion 3a
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of the inner hollow article 3 as well as the bottom wall
portion 2y of the outer hollow article 2 and the bottom
wall portion 3c of the inner hollow article 3 are in close
contact with each other, so as to prevent dents from
generating when pushed with fingers and so on, and enhance
heat transfer during retort sterilization. The close
contact can be facilitated by inserting the inner hollow
article 3 into the outer hollow article 2 in the presence
of vacuum.
As shown in Fig. 2, the outer hollow article 2
consists essentially of the inner layer 2a made of a
thermoplastic film, an intermediate layer 2b made of a metal
foil such as aluminum foil, steel foil, electrolytic iron
foil and an outer layer 2c made of a thermoplastic foil,
each layers being jointed via an adhesive layer (not shown)
made of an urethane adhesive, a carboxylic acid modified
polyolefin adhesive and so on.
Thermoplastic forming the inner layer 2a
preferably may be heatsealable plastic having a relatively
low melting point, such as polyethylene, polypropylene,
a copolymer or blend thereof, nylon 11 or 12, linear
polyester copolymer, polyester-ether or the like. The
thickness of the inner layer 2a preferably may be about
10 ~ 200 ~m, more preferably about 30 to 100 ~m. Thickness
thinner than about 10 ~m will fail to form the heat sealed
portion 7 having a satisfactory jointing strength, while
thickness layer than about 200 ~m will cause large residual
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stress during draw forming, which will result in large
spring-back after draw forming and thermal deformation
during retort sterilization. It is desirable that the inner
layer 2a is as thin as possible from the viewpoint of low
material cost, in the range that shape-retainable property
and satisfactory heat sealing strength can be assured.
The thickness of the metal foil forming the
intermediate layer 2b preferably may be about 7 to 100 ~m,
more preferably about 7 to 60 ~m. Thickness thinner than
about 7 ~m will cause pores in the foil, thus reducing gas
barrier against oxygen, carbonic acid gas, steam and so
on, while thickness larger than about 100 ~m will fail to
realize low material cost and low weight. When the
thickness is about 7 to 60 ~m, a satisfactory product
can not be formed by a conventional drawing method using
a blank holder, since remarkable wrinkles will develop at
the flange portion 4 and the sidewall portion 2x, and
rupture will occur when large blank-holding force is applied
so as to eliminate the wrinkle.
However, in case where drawing is carried out
while elastic force is being exerted to the blank along
the radiused corner portion of a die according to the method
described in British Laid-open Patent Publication GB
2001893A proposed by the present inventors, a satisfactory
product can be obtained without generating wrinkles.
Thermoplastic forming the outer layer 2c may be
nylon 6, nylon 6, 6, nylon 6, 10, drawn or non-drawn
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polyethylene terephthalate, polyethylene, polypropylene,
and a copolymer or a blend thereof and so on. It is
desirable from the viewpoint of low material cost that the
thickness of the outer layer 2c is as thin as possible in
the range that laminating operation is possible, and
shape-retainable property and anti-corrosion of the metal
foil can be assured, and usually may be less than about
50 ~m. Printed container bodies may be obtained by
photogravuring the back surface of the film forming the
outer layer 2c.
In case where the intermediate layer 2b is
relatively thick, the metal foil may be directly applied
an anti-corrosion lacquer coating as the outer layer 2c
without applying the thermoplastic film.
The inner hollow article 3 is formed by
thermoforming from a blank of thermoplastic which is
heatsealable with the inner layer 2a, that is, preferably
same or of same type as the thermoplastic forming the inner
layer 2a, wherein e.g. low density polyethylene is of same
type as medium density polyethylene.
Herein thermoforming means a method of molding
a cup-shaped hollow article at a softened or melt state
of the plastic concerned, such as vacuum forming, pressure
air forming and injection forming wherein residual stress
in the formed article is substantially zero or slight, and
thus thermal shrinkage due to retort sterilization is
substantially zero or slight.
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The thickness of the inner hollow article 3
preferably may be about 0.3 to 2.0 mm, more preferably about
0.5 to 1.0 mm. The wall portions thinner than about 0.3 mm
will be flexible and fail to reinforce the flexible outer
hollow article 2, while thickness larger than about 2.0 mm
will make the heat sealing of the flange portion 5
difficult, and incur high material cost and increased
weight. The heat sealing of the flange portion may be
carried out by any suitable method such as a high-frequency
induction heating method, an ultrasonic method and an
impulse method or the like.
Figs. 3 and 4 illustrate a hermetically sealed
container 15 formed by filling a product 14 in the container
body 1 and then heat sealing a lid 8 thereto. The lid 8
includes a metal sheet such as an aluminum alloy sheet or
tinplate and a thermoplastic film (not shown) which is
heatsealable with the thermoplastic forming the inner hollow
article 3 and laminated to the inner surface of the metal
sheet. The peripheral portion 8a is heat sealed to the
flange portion 5 of the inner hollow article 3 to form a
heat seal portion 19. The lid 8 is an easy opening end
of so-called full-open type formed with a circular score
17 defining the opening portion and having a ring pull-tab
16 adhered to the lid 8 at the fixing portion 16a.
Fig. 5 denotes a state where the container 15
is opened by pulling up the pull-tab 16 with a finger 18
and rupturing the score 17. In this case the container
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body 1 is gripped relatively strongly by a hand against
the force needed to rupture the score 17, but the container
body 1 will not collapse by virtue of the reinforcing
function of the inner hollow article 3, and thus the
S contents 14 will not flow out from the container body 1,
preventing the hand and so on from polluting.
Referring to Figs. 6, 7 and 8, a container body
11 is different from the container body 1 in that the
sidewall portion 13a of an inner hollow article 13 is formed
with a plurality of (eight in the drawing) elongated concave
portions 13b extending straightly and substantially axially
during thermoforming. The outer hollow article 2 is not
formed with such a concave portion, and thus the outer
surface of the sidewall portion 13a of the inner hollow
article and the inner surface of the sidewall portion 2x
of the outer hollow article 2 as well as the outer surface
of the bottom wall portion 13c of the inner hollow article
13 and the inner surface of the bottom wall portion 2y of
the outer hollow article 2 are substantially in contact
with each other except along the concave portions 13b.
Figs. 9, 10 and 11 denote a hermetically sealed
container 15' formed by filling a product 14, heat sealing
a lid 8 and then subjected to retort sterilization under
pressure (e.g. 120C x 30 minutes at 2 kg/cm2). The
portions of the sidewall portion of the flexible outer
hollow article 2 corresponding to the concave portions 13b,
as shown in Figs. 10 and 11, are depressed into the concave
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portion 13b radially inwardly under pressure during retort
sterilization to form concave patterns 12 having a
configuration corresponding to the concave portion 13b.
The inner hollow article 3 formed by thermoforming
is usually subjected to no or slight thermal shrinkage,
e.g. less than of about 1.0 to 1.5% in diameter, by heating
during retort treatment, while the outer hollow article
2 including the metal foil will not thermally shrink since
it is restrainted by the metal foil. Accordingly, and due
to the hermetically heat sealed portion 7, in case where
the concave portions 13b are not formed such as in case
of the container 15, a slight vacant space will develop
between the outer and inner hollow articles. Since the
vacant space is under negative pressure, it tends to cause
irregular, uneven patterns in the sidewall portion of the
flexible outer hollow article 2 and reduce commercial value
of the container.
In case where the concave portions 13b are formed
such as in case of the container 15', however, when the
concave patterns 12 are formed, the portions 2xl except
the concave portions 12 of the sidewall portion 2x of the
outer hollow article 2 are pulled circumferentially and
brought into close contact with the inner hollow article
3, as best shown in Fig. 10, and thus the aforementioned
irregular, uneven patterns will not develop.
The regular concave patterns 12 will enhance
aesthetic appearance of the container 15'. Furthermore,
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it is possible to judge whether any container having the
container body 11 was subjected to retort sterilization
or not, based on the presence or the absence of the concave
patterns 12.
In case of hermetically sealed containers which
are generally not subjected to retort sterilization under
pressure such as hot-packed containers which are usually
filled liquid products such as juices of about 85 to 95C,
or sealed containers containing dry foods, the container
body 11 preparatory to filling a product may be placed in
a pressure chamber having a fluid pressure such as air
pressure or liquid pressure higher than 1 kg/cm2, preferably
2 kg/cm2 to form the concave patterns 12, preferably after
heated or while heating to or at a temperature higher than
60C and lower than the melting point of the plastic
concerned, e.g. a temperature of 120C.
The shapes of the concave portion for forming
the concave pattern can be determined suitably according
to the design desired. Referring to Fig. 12, a container
body 21 has an inner hollow article 23 received in the outer
hollow article 2, the inner article 23 being formed with
a multitude of elongated concave portions 23b extending
linearly and substantially axially to form a corrugated
sidewall portion. In this case also, as shown in Fig. 13,
there can be formed corrugated patterns 22 having a shape
corresponding to the concave portions 23b, by a pressure
treatment such as retort sterilization under pressure.
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Fig 14 illustrates a container body 31 having
the outer hollow article 2 whose sidewall portion is formed
with a circumferential, circular concave pattern 32a, a
circumferential, wavy pattern 32b, an A-shaped dent pattern
32c and a C-shaped dent pattern 32d. These concave patterns
usually can not be formed by only drawing a flexible
laminate blank.
While certain embodiments of the invention have
been described for purposes of illustration, it is to be
understood that there may be various embodiments and
modifications within the general scope of the invention.
For example, concave portions for forming concave patterns
may be formed onto the outer surface of the bottom wall
portion of the inner hollow article. The outer and inner
hollow articles may be of any configurations such as a
cup-shape of round-cornered square in a horizontal section,
in the scope of the spirit of the invention. The lid may
be of the type which is not provided with the score and
the pull-tab and is adapted to be opened by peeling off
the heat sealed portion.
A practical example will be described hereinbelow:
Practical Example
An outer hollow article 2 having a configuration
shown in Figs. 6 to 8 was formed by cold drawing a laminate
blank by means of a punch having an elastic rubber sleeve
of the type described in British Laid-open Patent
Publication GB 2001893A and then curling the open edge of
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the drawn article, the laminate including an inner layer
2a made of a polypropylene film of 70 ~m thick, an
intermediate layer 2b made of a soft aluminum foil of 50 ~m
thick and an outer layer 2c made of a non-drawn nylon 6
film of 40 ~m thick whose back surface is photogravured,
each layers being jointed to each other with an urethane
adhesive.
The height up to the upper surface of the flange
portion 4 of the hollow article 2, the width of the flange
portion, the diameter of the inner edge of the flange
portion 4 were 30 mm, 3 mm and 65 mm, respectively, and
the capacity thereof was 75 c.c.
An inner hollow article 3 having concave portions
13b of the type shown in Figs. 6 to 8 and having a
configuration wherein the inner hollow article 3 is
insertable into the outer hollow article 2 so as to be in
close contact with the outer article 2 except along the
concave portions 13b, was formed from a polypropylene blank
of 0.8 mm thick by vacuum forming at 190C, the thickness
of the sidewall portion 13a being about 0.5 mm. Thereafter,
the inner article 13 was inserted into the outer article
2 under vacuum, and the flange portions 4 and 5 were heat
adhered to each other by high-frequency induction heating.
A lid 8 having a ring pull-tab 16 was formed from
a laminate blank, the laminate having an inner layer made
of polypropylene of 50 ~m thick, an intermediate adhesive
layer of maleic anhydride modified polypropylene of 10 ~m
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thick, and an outer layer of aluminum foil of 100 ,um thick
whose outer surface is applied with epoxy-phenolic lacquer
coating.
The container body 1 thus made was filled with
5 70 grams of potato salad containing 1 weight % of salt,
and then heat sealed with the lid 8 along the flange portion
S by means of a heating bar for 1 second at 230C to form
the hermetically sealed container 15'.
The container 15' was subjected to retort
sterilization for 30 minutes at 120C under air pressure
of 2 kg/cm, and concave patterns 12 such as shown in Figs.
9 and 10 were formed without developing irregular, uneven
deformations in the sidewall portion. The container 15'
as sterilized was opened by pulling up the ring pull-tab
15 16 as shown in Fig. 5 without causing significant
deformations such as collapse in the container body 11.
Figs. 15 and 16 illustrate a container body 41
comprising a cup-shaped reinforcing plastic hollow article
43 which corresponds to the inner hollow article 3 and a
20 cup-shaped flexible laminate hollow article 42 which
corresponds to the outer hollow article 2 and is received
in the plastic article 43.
Thermoplastic film forming the outer layer 42c
of the laminate article 42 is substantially same in its
25 kind and thickness as the thermoplastic film forming the
inner layer 2a in Fig. 2 such that the laminate article
42 and the plastic article 43 can be heat sealed along the
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flange portions 44 and 45 to form a heat sealed portion
47. Except the outer layer 42c, the material structures
of the laminate article 42 and the plastic article 43 are
substantially same as those of the outer article 2 and the
inner article 3, respectively. For example, the inner layer
42a and the intermediate layer 42b are made of substantially
same material as the inner layer 2a and the intermediate
layer 2b of the outer article 2, respectively. A lid (not
shown) is heat sealed to the portion of the inner layer
42 corresponding to the flange portion 44.
The container body 41 has an appearance of a
plastic container and high gas-barrier property, and is
not susceptible to significant deformations such as
collapse.
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