Note: Descriptions are shown in the official language in which they were submitted.
This invention relates -to double-walled cup-
shaped containers comprising an outer cup-shaped paper
container and an lnner thermoplastic synthetic resin
container having a similar shape and a smaller applied
on at least the side wall thereof to the side wall of the
paper container. The inner thermoplastic synthetic resin
container is formed of a seamless continuous synthetic
film or sheet. This invention also relates to the method
for producing such double-walled containers having an
adhesive applied to the inner surface thereof which com-
prises the steps of placing a preformed paper cup in the
cavity of a shaping die set, positioning a piece of
thermoplastic synthetic resin sheet or film on the top
of the die set across the mouth of the paper cup, heating
the resin sheet or film to render the sheet plastic and
drawing the sheet or film under negative pressure into
the cavity in the paper cup to cause the sheet or film
to adhere to at least the inner surface o~ the side wall
of the paper cup.
There have been proposed and practically employed
a variety of double-walled paper cups for holding liquid
products for drinking in the past. The prior art double- ;
walled paper cup has been hithertofore produced by providing
a preformed paper cup having an adhesive applied to the
inner surface thereof, laminating a piece of synthetic
resin sheet or film onto the adhesive-applied inner surface
of the paper cup to form the inner layer of the paper cup
and curling the mouth upper peripheral rim of the paper
cup together with the laminated resin layer_ The thus
produced double-walled paper cup has the advantages that
the curled mouth upper peripheral rim gives a pleasant
appearance to the paper cup and that the curled construction
of the cup mouth upper peripheral rim provides a substantial
rigidity against deformation of the cup when gripped.
However, although the paper material of the paper cup has
the resin film laminated thereon, the liquid content tends
to leak through the seam between the cup side wall and
laminated resin film to the paper material of the cup to
make sog~y and weak the paper cup. Especially, when the
content of the paper cup is a liquid at elevated temperature,
the content leaking and paper weakening problems become
more serious.
Since the mouth upper peripheral rim of the
paper cup has been curled together with the laminated
resin film, although the external surface of the curled
mouth upper peripheral rim of the paper cup is covered
by the laminated synthetic resin sheet or film, a portion
of the external surface of the cup side wall immediately
below or contiguous to the curled mouth upper peripheral
~0 rim is exposed. Thus, when the user desires to drink the
liquid content, his lips inevitably contact the exposed
external surface portion of the cup side wall directly
and this is not agreeable from the view point of hygienics.
Although the prior art vacuum formed containers have the
advantage that they can be produced at relatively less
expense, since the container has a small thickness, the
prior art vacuum formed containers have the disadvantage
that they have a low shape holding ability insufficient to
maintain their shape against deformation when gripped.
~0 There have been also proposed paper co~tainers
... . ..
.. ~ : ~ . - . .... . .
for holding liquid products provided with a peeping window.
The paper containers of the type have a transparent plastic
film applied to the ~indow area. Thus, the paper containers
have the disadvantage that the production of the containers
require much manual efforts to the degree that the containers
are rendered not suitable for mass production system.
Thexefore, one object of the present invention is
to provide a double-walled paper container for holding liquid
products at low or high temperatures for a fairly long
period of time eliminating the problem relating to leaking
andlor becoming soggy by integrally applying a seamless
continuous piece of synthetic resin film or sheet to at
least the inner surface of the side wall and bottom of a
preformed paper container.
Another object of the present invention is
to provide a method for producing a double-walled paper
container having a peeping window in the side wall of
the container and a sin~le transparent plastic film applied
to the inner surface of the container including the portion
of the peeping window at relatively less expense The
plastic ~ilm applied to the inner surface of the paper
container has a reduced thickness in a substantial portion
except for the portion thereof covering the peeping window
in the container.
Yet still further object of the present invention
is to provide a double-walled paper aontainer which is
less expensive and which comprises an inner synthetic resin
container formed by vacuum shaping a single piece of
synthetic resin film or sheet as conventionally practiced
and an outer paper container applied to the external surface
-- 3
... ~ .. , .. ~ .. . . . .
of the inner synthetic resin container to give a high shape
holding ability to the inner resin container.
A container in accordance with the present
invention includes a double-walled paper container comprising
a paper container including the bottom and the side wall having
a single seamless continuous synthetic resin sheet adhered
to the inner surfaces of said bottom and side wall of the
paper container, in which said side wall of the paper container
is provided with a peeping window portion and said synthetic
resin sheet applied to the inner surface of the side wall
is applied to said window portion. The portion of the
synthetic resin sheet applied to the peeping window portion
has a greater thickness than that of the sheet portion
applied to the inner surface of the side wall.
The above and other objects and attendant advan-
tages of the présent invention will be more readily apparent
to those skilled in the art from a reading of the following
detailed description in conjunction with the accompanying
~rawings which show preferred embocliments of the invention
for illustra-tion purpose only, but not for limiting the
scope o~ the same in any way.
Fig. 1 is an elevational view of a preformed
paper container to be lined with a plastic
film according to one embodiment of the
present invention showing one half portion
thereof in vertical section,
Fig. 2 is a fragmentary vertically sectional view
on an enlarged scale of said preformed
container showing how to form the curled
mouth upper peripheral rim in said paper
cup as shown in Fig. l;
-- 4 --
. .
: . ' '
Fig. 3 is a fra~mentary schematic plan view of
one embodiment of apparatus suitably
employed in carrying out the method
for producing a double-walled paper cup
in accordance with the present invention,
Fig. 4 is a fragmentary vertically sectional
view on an enlarged scale of the shaping
die set of said apparatus as shown in
~ig. 3, :
Fig. 5 is a fragmentary vertically sectional
view of one embodiment of the shaping
: die set employed in said apparatus as
shown in Fig. 3,
Fig. 6 is similar to Fig. 5, but shows the upper
frame and assist plug in their lowered
positions,
Fig. 7 is a vertically sectional view of one half
portion of one type of double-walled paper
container or product produced by the method
~20 in accordance with the present invention,
Fig. 8 is a vertically sectional view o~ another~
type of double-walled paper container of
product produced by the method in accordance
with the present invention, ::
igs. 9, 10 and 11 are vertically sectional views
showing another type of shaping die set :~
employed in an apparatus for producing ~
the product as shown in Fig. 8 in accordance ~:
with the present invention, :.
Fi~. 12 is a vertically sectional view of one
: _ 5 -
:
::` :
: . .,, ,, -
6~
half portion of another type of double~
walled paper container or product
produced by the method in accordance
with the present invention,
Fig. 13 is a vertically sectional view of
another type of shaping die set
employed in the apparatus for producing
the double-walled paper container of
product as shown in Fig. 12;
Fig. 14 is a fragmentary vertically sectional
view of another type of shaping die
set for producing the double-walled
paper container or product as shown
in Fig. 8,
Figs. 15 and 16 are explanative views showing
the operation of said shaping die
set as shown in Fig. 14,
Fig. 17 is a plan view of the blank of which
a cup having a peeping window therein
is -formed,
Fig. 18 is a schemative elevational view of
another type of shaping die set for
produciny a double-walled paper
container' and
Figs, 19 and 20 are fragmentary views of
another type of shaping die set for
producing a double-walled container
having the bottom which is formed of
plastic only.
~5~
Referring now to the accompanying drawings and
more particularly, to Fig. 1 thereof in which a preformed
container 10 having the cross section configuration as shown
suitable for mass production system is shown in a partial
vertically section. The curled upper peripheral rim 11
of the mouth of the container 10 is pinched between the
cavity forming die member 21 and the reciprocally movable
upper frame 121l of a die set 21 to be flattened in at
least the upper portion of the curl as shown in Fig. ~ and
thereafter, a suitable adhesive is applied to the external
surface of the curled and flattened upper peripheral rim 11
of the mouth and the inner surfaces of the side wall 12 and
bottom 13 of the container 10, respectively by means of
spray coating and the like, for example. A plurality of
preformed con-tainers 10 having the adhesive coating applied
to the parts thereof referred to hereinabove are in succession
conveyed on a conveyor system 22, 22' through the shaping
apparatus as shown in Fig. 3. As the containers 10 are
conve~ed on the conveyor system, the containers are aligned
in rows on movable aligning plates 23, 23~ respectively ~ ,~
provided along the conveyor system 22, 22~ and then placed
in shaping die sets 31, 31l. As more clearly shown in
Fig. 3, the first die set 31 and second die sets 31~, both
are connected at the respective ends to make one body for
movement together leftwards or rightwards as seen in
Fig. 3. While the containers 10 are being placed in the
first die set 31 by means of an assist plug 24, for example,
the second die set 31' in which the preformed containers 10
have been previously placed is positioned within the shaping
~pparatus 30 in which the containers 10 are to be applied
- 7 ~
.. . . . ~ , .
. - , :
a synthetic resin film and to form a double-walled paper
container shaped in -the manner as will be described
hereinafter in connection with various embodiments of the
invention. In this way, the firs-t and second die sets 31,
31' alternately receive the containers 10 therein and move the
received containers to and into the shaping apparatus 30 and
this operation is repeated for the succeeding containers to
be conveyed.
As more clearly shown in Fig. 4, the die set 31
has a frame member 32 on the top thereof and when the curled
upper peripheral rims 11 of the mouths of the preformed
containers 10 are seated on the frame member, the containers
10 are suspended in the correspondin~J cavities 34 formed in
a cavity forming die member 33 by means of the upper peripheral
rlms 11 seatin~ on the frame member 32 with the undersurfaces
of the rims 11 in contact with the upper surface of the
frame member 32. With the containers 10 being suspended in
the~corresponding cavity 34 in this way, there is provided
a clearance between the undersurface o~ -the container bottom
wall 13 and the inner bottom surface 35 of the cavity forming
die mem~er 33. The bottom of the cavity forrning member 33
is provided with an exhaust conduit 39 which communicates
at one or the inner end with the cavities 34 and at the
other or outer end with a vacuum pump (not shown).
Ater the preformed containers 10 have been received
in the corresponding cavities 34 in the die set 31 in the
manner mentioned hereinabove (only one container 10 and its
associated cavity 34 are shown in Figs. 5 and 6), a piece
of heated synthetic resin film 61 is positioned above the
die set 31 which is now positioned within the shaping
- 8 -
~2~~
apparatus 30 to extent across the mouth of the preformed
container 10, the vertically reciprocal upper frame
member 51 is lowered down towards the die set 31 until
the pressure application portion 54 of the upper frame
51 presses the edge of the film 61 against the frame
member 32 associated with the particular cavity 34 in
which the paper container 10 is now suspended therein
and then, an assist plug 53 which is slidably received
in the upper frame 51 is driven downwardly into the
cavity 34 to draw the film 61 deep in~o the cavity 34 which
in turn stretches the film as shown by reference numeral
63 in Fi~. 6. Thereafter, negative pressure is applied
to the exhaust conduit 39 by the actuation of the vacuum
pump (not shown) so as to apply negative pressure to
the cavity 34 whereupon the undersurface of the upper
peripheral rim 11 of the container mouth is caused to
closely contact the frame member 32 and the negative
pressure within the cavity 34 incr.ea.ses. As the result,
the clearance 14 defined by the bottom 13 and side wall
12 of -the paper container 10 is maintained at negative ; -
pressure and the cavity 15 in the paper container 10 is
also maintained at ne~ative pressure by virtue of the
permeability of the material of the bottom and side wall
of the paper contalner whereby the stretchesl film 63 is
caused to closely contact the entire inner surface of the
side wall 12 and bottom 13 of the container 10 and positively
secured to the paper container 10 by means of the adhesive
applied to the inner surface of the paper container as
an integral component of the container. In order to
positively secure the film 61 to the external surace of
~
the mouth upper peripheral rim l:L, it is an effective
means to pass the die set 31 through and over in which
the film is subjected to contraction action.
Thus, as more clearly shown in Fig. 7, a single
syn-thetic resin film 64 is applied to the extern~l surface
of the mouth upper peripheral rim 11 and the inner surfaces
of the side wall 12 and bottom 13 of the container 10
as an integral component thereof. Thereafter, the upper
frame 51 is further lowered into the cavity 34 until the
cutting edge 55 on the upper frame 51 shears or trims the
synthetic resin film 61 (Fig. 6). Thereafter, the upper
frame 51 is raised up and air at positive pressure is
pumped through the e~haust conduit 3~ into the cavity
34 in the cavity forming die memher 33 whereby the paper
container 20 which has now the synthetic resin film
integrally applied to the inner surface thereof rises
upwardly out of the cavit~ formi~g d.ie me~mber 31 onto
the conveyor 26 (Fig. 3).
In the embodiment described hereinabove,
although the preformed paper container 10 is applied
the adhesive to the external surface of the mouth upper
peripheral rim 11 and the inner surfaces of the side
wall 12 and bottom 13 of the container, the present
invention is not limited to the employment of the adhesive
application step. Instead, it is also contemplated that
an adhesive is applied to one side of the blank for the
paper container at the areas constituting the side wall
and bottom when the blank is formed into the preformed
container and the blank is shaped into the container so as
3Q to dispose the adhesi~e-appli.ed side inside and then place~
-- 10 --
in the cavity forming die member 3L in which the paper is
subjected to the above-mentioned shaping step to obtain
the complete double-walled paper container 20 having the
plastic film integrally applied thereto~ Alternatively,
when low density polyethylene or the like which exhibits
a good adhesion for the paper material of the container
is employed as the adhesive synthetic resin film, the
adhesive application step may be eliminated.
And it is also contemplated that a fine through
hole or holes are formed in the side wall and/or bottom
of the preformed container 10 to accelerate the application
of negative pressure through the cavity 34 in the cavity
~orming die member 31 to the cavity 35 in the paper
container to thereby reduce the shaping cycle time resulting
in improvement of container p~oduction efficiency. In such
case, the fine through hole or holes formed in the side
wall and/or ~ottom of the preformed paper container should
have a small size sufficient enough to be ~locked by the
synthetic resin film applied to the container.
And as described hereinabove in connection ~;
with Fig. 2, after the mouth upper peripheral rim 11 has
been flattened by being pinched between the components
; of the die set 21, when the paper container 20 is filled
with a desired liquid content and covered by a suitable
cover, the contairer has the advantage that a positive seal
is easily formed in the container.
However, a container 20 having a synthetic
resin film applied to the inner surface thereof can be
produced without flattening the mouth upper peripheral rim
11 of the preformed so as to seal the mouth and accordingly
~ ' ,
the -flattening step described in connection with Fig. 2
may be eliminated in the present invention if desired.
Although the container 20 having the synthetic
resin film 64 laminated on the inner surface thereof is
capable of receiving a liquid and hygienic, such container
has the disadvantage that when a user desires to drink the
liquid content, his lips tend to directly contact the
external paper layer of a preformed container 10 immediately
below or contiguous the mouth upper periphera]. rim 11 of the
container 20. Thus, in order to eliminate this disadvantage,
a container 20 in which the synthetic resin film 64 extends
to the external surface of the portion of the side wall
12 of the preformed container 10 immediately below or
conti~uous to the mouth upper peripheral rim 11 of the
container and the extension of the resin film is shown
by reference numeral 66 in Fig. ~. The method Eor producing
such a container will be now describedl
The preformed ~o~ta.iner 10 which has been
produced by the conventional methocl as described in con-
neccion with Fi~. 1 is placed in the shaping die set 31 asshown in Fig. 9. In this case. the depth or height d of
the cavity 34 formed in the die set 31 is smaller than
the height h of the preformed container 10 so that the
mouth upper peripheral rim 11 and a portion 16 of the
side wall 12 immediately below or contiguous to the rim
of the container protrude upwardly of the top frame member
32 of the die set 31 when the container 10 is placed in
the die set 31 (see Fig. 9). After the preformed container
10 has been placed in the die set 31 in the manner as
mentioned hereinabove, a synthetic resin film 61 is positioned
above the die set 31 across the mouth of the preformed
container 10 and the upper frame 51 having a pressure
application portion 54 extending downwardly therefrom
is lowered towards the die set 31 to press the peripheral
edge of opposite ends of the film against the frame
member 32 as shown in Eig. 9. Thereafter, heated air
is pumped from an external source (not shown) through
the exhaust conduit 39 formed in the die set to the
cavity 3~ in the die set to heat the film 61 to thereby
stre-tch the film 61 into the cavity 52 in the vertically
reciprocal upper frame 51 as shown by reference numeral ~ -
63 in Fig. 9. Thereafter, an assist plug 53 which is
slidably received in the upper frame 51 is lowered into
the cavity 15 in the preformed container 10. Thereafter,
negative pressure from an external vacuum source (not shown)
is applied through the exhaust conduit 39 to the cavity
34 in the die set whereby the Eilm portion 65 disposed
between the mouth curled upper peripheral rim 11 and
the upper frame member 32 is drawn against the external
~0 surface of the preformed container 10 positioned immediately
below or contiguous to the curled mouth upper peripheral
rim 11 to -form the laminar G6 on the external surface of
the side wall portion 12 (See Fig. 8) and at the same time,
the negative pressure is also a~plied through the side wall
12 and bottom 13 of the container to the cavity 15 in the
container so as to cause the film 63 to stretch into the
paper cavity 15 by the assist plug 53 to closely contact
the inner surfaces of the side wall 12 and bottom 13 of
the container. Thereafter, the upper frame 51 is further
lowered until the cuttin~ ed~e 55 on the upper frame 51
- 13 -
shears off the film 61 adjacent and inwardly of the outer
peripheral edge thereof and thereafter, the upper frame
51 is raised away from the die set and at the same time,
positive pressure is applied through the exhaust conduit
39 to the shaping die set 31 to discharge the complete
double-walled container 20 having the film applied to
desired areas thereof as shown in Fig. 8 out of the die
set 31.
In the embodiments of the method for producing
paper containers according to the present invention as
shown in Figs. 9 and 10, although the shaping die set 31
is shown as having a height smaller than that of the
preformed paper container 10, the present invention is
not limited to the use of such a shaping die set.
Thus, as shown in Fig. 11, for example, when the inner
diameter of the annular frame member 32 is reduced by a
small amount, the container 10 is s~ripped in a position
between the upper and lower ends thereof of the side wall
12 by the frame member 32 of the shaping die set 31 in
a suspension state in the cavity 34 or alternatively, a
rest having a suitable height may be placed on the bottom
of the die cavity 3~. Such alternative embodiments are
also within the scope of the present invention.
The complete double-walled paper container 20 as
shown in Fig. 7 or 8 has the synthetic resin film covering
the mouth upper peripheral rim 11 is hygienic and presents
a pleasant appearance. ~owever, since the mouth upper
peripheral rim 11 where the container or cup xeceives its
holdiny or gripping force and holcls the mouth against de-
formation has only the synthetic resin film laminated on
- 14 -
, ' , ' -
the external suxface of the paper material of the rim,
the cup holding force provided by the rim is insufficient.
Therefore, according to the present invention, as shown
in Fig. 12, the paper material of the mouth upper peripheral
rim 11 is sandwiched in between synthetic resin film layers
64, 67 to form a laminar construction and the paper
material and film layers are rolled together radially
and outwardly to give the reinforced mouth upper peripheral
rim 11 to the complete double-walled container 20. Such
a container 20 is produced by the arrangement as shown
in Fig. 13.
Referring now to Fig. 13, another embodiment of
the present invention is exemplified. A paper container
lOb has the side wall 12 and bottom 13 integrally formed
and the mouth upper peripheral rim which has not been
curled and the container lOa is placed in the cavity 34a
formed in the shaping die set 31a with an upper portion 17a
of the side wall 12a where the rim is formed extending
upwardly of the annular frame member 32a. Thereafter, a
synthetic resin film 61a is po~itioned on the ~rame
member 32a across the mouth o~ the container and the upper
frame 51a having the pressure application portion 54
thereon is lowered towards the shaping die set 31a until
~he outer peripheral edge of the film 61a is pinched
between the pressure application portion 54a and frame
member 32a. In this embodirnent, prior to and/or after
the pinching of the film, the film is heated by a suitable
heating means and stretched into the cavity 15a in the
paper container lOa by the descending assist plug 53a.
Thereafter, prior to or after t,he lowering of the
-- 15 ~
~%~
shearing cu-tti~g edge 55a to remove excess material from
the film 61a, negative pressure from an external vacuum
source (not shown~ is applied through the exhaust conduit
39a to the shaping die cavity 34a to thereby firmly
apply the film layers 67a and 64a to the external surface
of the side wall upper extension 16a and the inner surface
of the side wall 12a of the container lOa, respectively
and then, the container is taken out of the shaping die set
31a .
After the container 20a has been taken out of the
shaping die set 31a, the mouth upper peripheral rim of
the container is curled by a conventional curling machine
to thereby obtain a double-walled paper container 20a
having the mouth upper peripheral rim lla comprising the
paper layer having the synthetic resin film applied to
the opposite sides thereof (see Fig. 12). Since the mouth
upper peripheral rim lla of the double-walled container
has the film layers 64a, 67a laminated on the both sides
thereof and rolled together, the thus formed mouth upper
peri.pheral rim lla not only presents a pleasant appearance
and a good fee~ing to the userls lips, but also has a
sufficient strength. And since the container is ~ree of
deformation when gripped with a normal gripping force,
the container 20a holds its shape suitable for drin~ing.
In addition, since the film 64a on the inner surface of
the container is formed of a seamless single film piece,
even when the container is filled with hot water, the
container has the advantage that the hot water will not
permeate into the paper layer through the inner film.
The method and apparatus for easily producing
- 16 -
36~L
the double-walled paper container having the synthetic
resin film 66 applied to the external surfaces of the
mouth upper peripheral rim 11 and adjacent portion 16
of the side wall 12 immediately below and contiguous
to the rim will be described hereinbelow.
Referring to Fig. 14, further embodiment of the
present invention is exemplified. The preformed paper
container lOb produced by the conventional mass production
system and having the bottom 13, side wall 12 and mouth
upper peripheral rim 11 formed therewith is placed in
the cavity forming die member 33b of the shaping die set
31b as shown in Fig. 14. In the shaping apparatus of
Fig. 14, the depth or height d of the cavity 3~b in the
cavity formin~ die member 33b of the shaping die set 31b
is smaller than the height h of the container lOb so that
the mouth upper peripheral rim llb and its contiguous side
wall portion 16 of the preformed container lOb will protrude
upwardly of the cavity forming die member 33b of the shaping
die set 31b. After the placement of the paper container 10
~0 in the shaping die set 31 in this ~ay, a plastic film 61
i5 posikioned on the die set 31b across the mouth of the
containèr and then, the upper frame 51b is lowered until
the lower end of the upper frame Slb pinches the peripheral
edge of the film 61b in cooperation with the upper end of
the die set 31b to hold the film under tension. ~hereafter.
the film 61b is heated by any suitable heating means and
the assist plug 53b is lowered into the paper container cavity
15b to stretch the film. Following the stretching step
of the film, negati~e pressure from any external vacuum
source is applied through the exhaust conduit 39b to the
cavity 3~b in -the cavity forming die 33b of -the shaping
die set 31b an~ to the annular outer cavity 36b defined
between the cavity forming die member 33b and shaping
die set 31b whereby the negative pressure is also applied
to the cavity 15b in the cup or container lOb. The
application of negative pressure to the container cavity
15b draws the film 61b which has ~een stretched by the
assist plug 53b against the inner surfaces of the container
side wall 12b and bottom 13 and stretches the film portion
65b present between the mouth upper peripheral rim llb
and upper frame 32 to cause the film to adhere to the
e~ternal surface of the side wall upper portion 16 as shown
by reference numeral 66b (see Fig. 15).
Thereafter, the cavity forming die member 33b
having the preformed paper container lOb received therein
is raised. As the cavity forming die member 33b and the
preformed paper container lOb rise up wlthin the shaping
die set 31b, the tapered upper end 37b of the cavity
forming die member 33b shears the film portion 68~
extendin~ along the inner surface of the shaping die set
31b off the film 61b as excess film material ~see Fig. 16)
and also trims the lower e~d of the film portion 66b
adhering to the external surface of the side wall portion 12.
In the past, it has been proposed that a paper
container having the synthetic resin film 6~ applied to
the inner surface of the side wall 12 is provided with a
peeping window 17 so that the color and shape of the
content within the container can be clearly observed, but
the prior art container of the type has the disadvantages
that the production of the container requires many manual
- 18 -
~ ~2,~
operations and that an excessive amount of synthetic resin
ma-terial is consumed to the degree that the container can
not be economically produced. However, according to the
present invention, the container provided with the peeping
window can be produced at relatively less expense.
Referring now to Fig. 17, there is shown a
container blank 18 for the side wall 12 of a preformed
container lOc having a desired size and provided with
a through hol~ 17 by punching. The preformed container
lOc having the blank 18 is placed in the cavity formed
in the cavity forming die member 33 of the shaping die
set 31 together with a bottom panel blank 13 for preformed
the container lOc as shown in Fig. 18. A plastic ~ilm
61c is positioned on the top of the shaping die set 31c
across the mouth of the container and thereafter, the
upper frame 51c is lowered towards the die set 31c to pinch
the peripheral edge of the film 61c in cooperation with
the upper end of the die set 31c. Thereafter, the vertically
reciprocal assist plug 53c slidably received in the upper
frame 51c is lowered into the cavity 15c in the container
lOc to stretch the film 61c to a suitable shape and
size as shown by reference numeral 63c. At this time, the
plastic film 61c extending across the mouth of the container
and ~ assist plug 53c are heated to a suitable and desired
temperature to thereby assist the stretc~ing of the film 61c.
As more clearly shown in Fig. 18, a cooling die 56c having
a cooling end face is movably mounted on the upper frame 51c
in a position adjacent the through hole 17c in the prerormed
container lOc and as the plastic film 61c is stretched by
the assist plug, when the film has stretched to a desired
thicXness, the cooling die 56c is lowered to abut against
the ~ilm 61c at the area
-- 19 --
~2~
surrounding the through hole 17c to cool and set the
area of the film surrounding the through hole. The
cooling end face of the cooling die 56c is maintained
at a low temperature by circulating water 57c through
the cooling die. Thereafter negative pressure from an
external vacuum source (not shown) is applied through
a pipe 39c in the shaping die set 31c to the cavity
34c in the cavity forming die member 33c whereby the
plastic film 61c stretches and expands to closely contact
the inner surfaces of the bottom and side wall o~ the
paper container by virtue of the permeability of the
bottom and side wall of the container lOc and adheres
to the inner ~urface of the container by the temperature
maintained in the film. ;
However, the portion 69c of the plastic film 61
facing the window forming through hole 17 o the pre~ormed
paper container lOc is prevented from ~urther stretching
and accordingly, decreasing in thickness after the plastic
has reached to a desired thickness because the film portion ~ ;
69c has been cooled by the cooling die 56c and maintained
at a low temperature and the plastic portion 69c maintains
the thickness obtained at the time when the cooling die
56c abutted against the film portion and adheres to the
portion of the container side wall surrounding the through
hole 17c to thereby form tha peeping window.
The double-walled paper container produced in
the manner mentioned just above has the side wall 12c
provided with the peeping window 17 and since the container
is a double-walled paper container 20c provided a peeping
window and having one piece o~ transparent plastic ~ilm
- 20 -
;6~3~
applied to the inner surface thereof, the container can
be easily produced, and since a substantial portion of
the plastic f~lm is smaller in thickness as compared
with the peeping window portion, the container has the
advantages that a relatively small amount of plastic
material is required, that the container has a water-
resistance property and that the container can be produced
at less expense requiring a small number of manual operations.
As mentioned just above, accordin~ to the present
invention, it is contemplated that the plastic film 61c
i.s positioned on the top of the shaping die set across
the mouth of the preformed container lOc, the film is
heated to a desired temperature, the assist plug S3c is
lowered in two discrete stages to stretch and expand into
the container and as the film is s~retched and expanded,
when the film portion 69c corresponding to the peeping
window 17c has reached a desired thickness, the cooling
die 56c abu-ts against the film portion to cool and set
the film portion. However, the configuration of the lower
end face of the assist plug 53c, the descending timing of
the assist plug, the configuration of the cooling face o~
the cooling die 56c and the abutting timing o~ the cooling
die end face against the film can be selectively varied
depending upon the size and tapered con~iguration of the
preformed cup-shaped container lOc and the position and
size o~ the peeping window as desired and necessary.
In any of the embodiments described hereinabove,
the container is a double-walled construction comprising
the preformed paper container having the side wall and
bottom and the thin synthetic resin container having the
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side wall and bottom similar in shape to and smaller in
size than the corresponding components of the paper container.
The double-walled construction has in combination the ad-
vantageous perfect water-tight property inherent in the
synthetic resin container and the less expensive and rigid
properties inherent in the paper container. However, the
rigidity of the container is required to maintain the shape
of the container ~hen gripped and thus, only the side wall
is required to be rigid sufficient to bear the container
gripping force and the bottom is not required to have high
rigidity.
Thus, it is also one object of the present in~
vention to provide a double-walled paper container lined
with a seamless continous and water~tight piece of synthetic
resin which can be produced at relatively less e~pense,
which can eliminate any paper layer on the bottom where
sufficient ri~idity is not required while ret~ining a
required shape holdin~ stren~th against gripping force
and the method for producing the paper container.
The embodiment of the present invention as shown
in Fi~. 19 and Fig. 20 is directed to a so-called "no-bottom
container" comprising only the mouth upper peripheral rim
lld and side wall 12d with the bottom eliminated therefrom.
In the production of the no-bottom container a paper
container having only the side wall 12d provided with the
curled mouth upper peripheral rim lld at the upper end
thereof is preformed, the preformed paper container lOd
is placed in the cavity 34d in the shaping die set 31d,
a piece of synthetic resin films 61d is positioned on the
frame mëmber 32d of the die set across the mouth upper
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~Z~i613~L
peripheral rim lld of the container, the upper frame 51d
is lowered towards the die set 31d to pinch the film
between the lower end of the upper frame 51d and the top
of the frame member 32d of the die set 31d.
Thereafter, the assist plug 53d having the flat
surface portion 54d maintained at a low temperature with
the water 58d circulating the water conduit 57d is lowered
into the cavity in the upper frame 51d to abut against the
film 61d, hot air is pumped from an external source (not
shown) through the exhaust conduit 39d formed in the die
set 31d to stretch the film 61d by reference numeral 62 and
the assist plug 53d is lowered into the cavity in the side
wall 12d to a predetermined position whereupon the portion
of the film where the flat surface portion 54d of the
assist plug 53d contacts is cooled and depressed down
without stretching and maintaining its thickness obtained
at the time o contact by the assist plug 53d to form the
relatively thick bottom 70d for the complete paper container.
On the other hand, the remaining portion of the film 61d
where the flat sur~ace portion 54d of the assist plug 53d
did not contact is stretched downwardly as the assist
plug 53d descends to form the thin resin side wall 71d
(see Fig. 20). Thereafter, negative pressure is applied
from an external vacuum source (not shown~ through the
exhaust conduit 39d formed in the die set 31d to the
cavity 34d in the shaping die 31d and at the same time,
more or less positive pressure is applied against the ex-
ternal surface of the assist plug 53d within the cavity
52d in the upper frame Sld to there~y produce differential
pressure on the upper and lower surfaces of the film 61d
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so as -to draw the resin container side wall 71d against the
inner surface of the paper container side wall 12d to cause
the side wall to firmly adhere to the resin container side
wall. In such case, if a heat seal agent has been previously
applied to the inner surface of the paper container side
wall 12d, a more positive joint is established between the
resin container side wa]l 71d and paper container side wall
12d.
The container 20d produced in the manrler mentioned
10 hereinabove comprises the inner resin container including
the relati~ely thin resin side wall 71d and relatively
thic~ resin bottom 70d and the outer paper container in-
cluding the paper side wall 12d disposed outside of the
corresponding side wall 71d and integrally secured to the
latter. Thus the amount of synthetic resin employed is
a relatively small amount and the container can be produced
at less expense. Although the resin container side wall
71d has a thin thickness, since the side wall is integrally
joined to the outer paper container side wall 12d, the resin
20 container side wall has a sufficient shape holding ability
and is free of deformation when gripped.
And according to the present invention, after
the synthetic resin container bottom 70d has been formed
by the assist plug 53d having the cooled lower flat portion
54d negative pressure is lied from the external vacuum
source through the exhaust conduit 39d to the cavity 34d
in the shaping die set 31d and at the same time, hot air
under pressure is applied to the external surface of the
assist plug 53d to firmly contact the thin synthetic resin
30 to the paper container mouth upper peripheral rim and side
-- 24 --
:. , ~: ,.
wall 12d, the upper frame 51d is then lowered in two
discrete stages to shear excessive film off the film
61d by the cuttiny edge 55d on the upper frame 51d, the
upper frame 51d is raised and the cavity in the shaping
die set supplied with air under pressure through the
exhaust conduit 39d to remove the complete double-walled
container from the die set.
While preferable embodiments of the invention have
been shown and described in detail, it will be understood
that the same are for illustration purpose only and not
to be taken as a definition of the invention, reference
being had for this purpose to the appended claims.
This application is a division of application
Serial ~o. 299,489, filed March 22, 1978.
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