U.S. patent application number 11/914942 was filed with the patent office on 2009-08-20 for three-piece square can and method of manufacturing the same.
This patent application is currently assigned to TOYO SEIKAN KAISHA, LTD.. Invention is credited to Munemitsu Hirotsu, Masayuki Ishii, Manabu Iwaida, Shinichi Kaneda, Hisashi Katoh, Shigeaki Mori, Kei Oohori, Shigeki Oyama, Zenrou Shirane, Hitoshi Toda, Takeshi Yamagami, Koichi Yamamoto, Norifumi Yasuda.
Application Number | 20090206096 11/914942 |
Document ID | / |
Family ID | 37431238 |
Filed Date | 2009-08-20 |
United States Patent
Application |
20090206096 |
Kind Code |
A1 |
Hirotsu; Munemitsu ; et
al. |
August 20, 2009 |
THREE-PIECE SQUARE CAN AND METHOD OF MANUFACTURING THE SAME
Abstract
The present invention provides a three-piece rectangular can
which can overcome drawbacks (joint defect) of a can body joint
portion of a three-piece can, and is of a new type which overcomes
shortage of a can body strength which a two-piece can possesses,
and exhibits excellent liquid leakage resistance, excellent can
body strength and excellent heat radiation property or the like
even when the can is used as a casing of a battery or electric
equipment. For this end, the three-piece rectangular can of the
present invention is formed such that a circular blank formed of an
aluminum plate which forms an organic film on at least one surface
thereof is formed into a bottomed circular can by deep drawing such
that the organic film forms an inner side of the can, a cylindrical
sleeve having no seam on a side surface thereof is formed by
cutting a can bottom of the bottomed circular can, a rectangular
can body portion having no seam on a side surface thereof is formed
by deforming the cylindrical sleeve into a rectangular shape, a
necking formed portion is formed by applying necking forming to
opening portions at both ends of the rectangular can body, and a
top lid and a bottom lid are mounted on the opening portions at
both ends of the rectangular can body by double seaming by way of
an organic compound.
Inventors: |
Hirotsu; Munemitsu;
(Kanagawa, JP) ; Kaneda; Shinichi; (Kanagawa,
JP) ; Shirane; Zenrou; (Kanagawa, JP) ;
Oohori; Kei; (Kanagawa, JP) ; Toda; Hitoshi;
(Kanagawa, JP) ; Ishii; Masayuki; (Kanagawa,
JP) ; Yasuda; Norifumi; (Saitama, JP) ; Katoh;
Hisashi; (Saitama, JP) ; Iwaida; Manabu;
(Saitama, JP) ; Yamamoto; Koichi; (Saitama,
JP) ; Mori; Shigeaki; (Saitama, JP) ;
Yamagami; Takeshi; (Saitama, JP) ; Oyama;
Shigeki; (Saitama, JP) |
Correspondence
Address: |
BROWDY AND NEIMARK, P.L.L.C.;624 NINTH STREET, NW
SUITE 300
WASHINGTON
DC
20001-5303
US
|
Assignee: |
TOYO SEIKAN KAISHA, LTD.
Chiyoda-ku
JP
Honda Motor Co., Ltd.
Minato-ku
JP
|
Family ID: |
37431238 |
Appl. No.: |
11/914942 |
Filed: |
May 16, 2006 |
PCT Filed: |
May 16, 2006 |
PCT NO: |
PCT/JP2006/309757 |
371 Date: |
January 21, 2009 |
Current U.S.
Class: |
220/612 ; 72/121;
72/347 |
Current CPC
Class: |
B21D 51/2646 20130101;
H01M 50/116 20210101; B65D 7/06 20130101; H01M 50/10 20210101; H01M
50/169 20210101; Y02E 60/10 20130101; H01M 10/0404 20130101; B65D
7/36 20130101; B65D 7/40 20130101; B21D 51/2638 20130101; B21D
51/2653 20130101; H01M 50/1243 20210101 |
Class at
Publication: |
220/612 ; 72/347;
72/121 |
International
Class: |
B65D 6/28 20060101
B65D006/28; B21D 22/00 20060101 B21D022/00; B21D 3/02 20060101
B21D003/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 17, 2005 |
JP |
2005-144046 |
May 17, 2005 |
JP |
2005-144407 |
May 17, 2005 |
JP |
2005-144414 |
May 17, 2005 |
JP |
2005-144490 |
Claims
1. A three-piece rectangular can in which a necking formed portion
is formed by applying necking forming to opening portions at both
ends of a rectangular can body portion having no seam on a side
surface thereof, and a top lid and a bottom lid are seamed by
double seaming to the opening portions at both ends of the
rectangular can body portion by way of an organic compound, wherein
the three-piece rectangular can is formed of an aluminum plate
having an organic film formed on at least one surface thereof, and
the organic film is formed on at least inner surfaces of the
rectangular can body, the top lid and the bottom lid.
2. A three-piece rectangular can according to claim 1, wherein the
rectangular can body portion having no seam on the side surface
thereof is formed such that a cylindrical sleeve having no seam on
a side surface thereof which is formed by cutting a bottom portion
of a bottomed circular can from a circular blank by deep drawing is
deformed into a rectangular sleeve and the rectangular sleeve has
the opening portions at both ends thereof, and the necking formed
portion is formed on the opening portions by applying necking
forming to the opening portions.
3. A three-piece rectangular can according to claim 1, wherein the
rectangular can body portion having no seam on the side surface
thereof is formed such that a cylindrical sleeve having no seam on
a side surface thereof which is formed by cutting a bottom portion
of a bottomed circular can from a circular blank by deep drawing is
deformed into a rectangular sleeve and the rectangular sleeve has
the opening portions at both ends thereof, the necking formed
portion is formed on the opening portions by applying necking
forming to the opening portions and, thereafter, a plurality of
beads is formed on the rectangular can body portion in a state that
the beads surround the rectangular can body.
4. A three-piece rectangular can according to claim 1, wherein a
through hole is formed in center portions of the top lid and the
bottom lid which are mounted on the opening portions at both ends
of the rectangular can body portion having no seam on the side
surface thereof by double seaming, and an electrode is mounted in
the through hole by way of an insulator.
5. A three-piece rectangular can according to claim 1, wherein the
top lid or the bottom lid of the three-piece rectangular can is
formed of an aluminum plate to which a non-stretched polyester film
which sets a degree of crystallization thereof within a range from
20% to 40% by preheating treatment before forming is applied.
6. A three-piece rectangular can according to claim 1, wherein the
three-piece rectangular can which is used as a battery container
and is formed of an aluminum plate which applies a biaxially
stretched polyester film to at least the inner surfaces of the
rectangular can body portion, the top lid and the bottom lid, and
the biaxially stretched polyester film possesses an X-ray
diffraction intensity ratio which satisfies
5.gtoreq.I.sub.A/I.sub.B.gtoreq.1, wherein I.sub.A is an X-ray
diffraction intensity on a diffraction plane which is parallel to a
surface of the polyester film and has a surface distance of
approximately 0.34 nm (a CuK.alpha.X-ray diffraction angle being
set to a value which falls within a range from 24.degree. to
28.degree.), and I.sub.B is an X-ray diffraction intensity on a
diffraction plane which is parallel to the surface of the polyester
film and has a surface distance of approximately 0.39 nm (a
CuK.alpha.X-ray diffraction angle being set to a value which falls
within a range from 21.5.degree. to 24.degree.).
7. A manufacturing method of a three-piece rectangular can being
characterized in that a circular blank formed of an aluminum plate
which forms an organic film on at least one surface thereof is
formed into a bottomed circular can by deep drawing such that the
organic film forms an inner side of the can, a cylindrical sleeve
having no seam on a side surface thereof is formed by cutting a
bottom portion of the bottomed circular can, a rectangular can body
portion having no seam on a side surface thereof is formed by
deforming the cylindrical sleeve into a rectangular shape, a
necking formed portion is formed by applying necking forming to
opening portions at both ends of the rectangular can body, and a
top lid and a bottom lid are mounted on the opening portions at
both ends of the rectangular can body by double seaming by way of
an organic compound.
8. A necking method of a rectangular can being characterized in
that, in performing necking forming for squeezing an opening
portion of a rectangular can body of a rectangular can, a first
core is arranged in the inside of a necking formed portion of the
rectangular can, a second split core which is expansible and
shrinkable is arranged on a lower portion of the necking formed
portion and, thereafter, the necking formed portion is formed using
a necking die.
9. A necking method of a rectangular can according to claim 8,
wherein the rectangular can body is arranged outside the second
core on a bolster, the second core is moved in an expansible manner
in a state that the second core supports a lower portion of the
necking formed portion and, thereafter, the first core mounted on a
slide is lowered toward the second core thus positioning the first
core at the necking formed portion, and the necking die is lowered
to perform the necking forming.
10. A necking method of a rectangular can according to claim 8,
wherein the expansion and the shrinking of the second core and the
insertion and the removal of the first core are performed in an
interlocking manner with lowering and elevation of the slide.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a new type of rectangular
can which can eliminate a joint defect at a joint portion of a can
body and has an excellent strength and, more particularly to a
three-piece rectangular can which is applicable to a battery casing
and various kinds of casings for electrical equipment and a
manufacturing method thereof.
BACKGROUND OF THE INVENTION
[0002] Recently, along with progress in electric technology, the
development of high performance, the miniaturization, the
realization of high energy and the improvement on portable
structure of electronic equipment, and the realization of high
performance of an electrically driven automobile (for example, a
so-called hybrid vehicle) have advanced. Accordingly, casings for
various kinds of batteries which are used as power sources for
driving the electronic apparatus and the electrically driven car,
particularly, casings for electric double-layered capacitors have
been required to exhibit an excellent can body strength, an
excellent liquid leakage resistance, an excellent air-tightness, an
excellent heat radiation property and the like.
[0003] With respect to the content leakage proof and the
air-tightness of the battery casings and the casings of various
kinds of electrical equipment, it is necessary to hold the high
air-tightness for preventing the leakage of contents from the
casings for a long period after filling a power generating element
in the casings. In many cases, the content leakage proof and the
air-tightness of the casings are influenced by a joint state of a
can body of a can, a sealed state between the can body and a can
lid or the like.
[0004] In general, a metal can which constitutes a three-piece can
is configured such that a side surface of the can body is formed by
joining such as welding, adhering, caulking or the like (side
seam), and joint portions for mounting a top lid and a bottom lid
are formed on opening portions at both ends of the can body.
[0005] The three-piece can has the side seam in the can body and
the joint portions with the lids and hence, there exists a drawback
that a leakage of contents attributed to a joint defect is liable
to occur. However, due to the top lid and the bottom lid which are
joined to both opening portions of the can body, the three-piece
can has an advantageous effect that a can body shape is reinforced
by the top lid and the bottom lid joined to both opening portions
of the can body portion so that a deformation resistance strength
of the can body can be enhanced.
[0006] Further, there has been also known a technique which forms
surface irregularities which are referred to as beads in a state
that the beads are formed on peripheries of the can body for
further enhancing the can body strength. However, the technique has
a drawback that the sealing property at the side seam of the can
body is liable to be easily decreased due to the formation of the
beads.
[0007] As another type of the metal can, there has been known a
two-piece can which is constituted of two parts. That is, the
two-piece can is constituted by mounting a top lid on an opening
portion of a circular or a rectangular bottomed can which is formed
by deep drawing a flat blanked plate or by drawing and ironing a
flat blanked plate. In the two-piece can, the top lid is mounted on
only the opening portion which is formed by drawing and hence, a
shape of a can bottom side formed by drawing is limited by
restrictions attributed to conditions such as mold designing or a
material for drawing whereby the enhancement of the rigidity of the
can bottom side is also limited.
[0008] Further, with respect to the three-piece can or the
two-piece can, as a sealing method for mounting the lid on the
opening portion, laser welding, caulking, double seaming or the
like is used in general.
[0009] Further, with respect to a battery casing used for housing a
large number of batteries connected with each other, from a
viewpoint that a rectangular-shaped battery casing can be arranged
without a gap and can enhance a volumetric efficiency compared to a
cylindrical-shaped battery casing, a profile shape of the battery
casing is formed into a rectangular shape.
[0010] As an example which uses the above-mentioned metal can as a
casing for electric equipment, Japanese Patent Laid-open
2002-343310 (patent document 1) proposes a two-piece can which
sandwiches an insulator between a casing body and a lid member, and
seals an opening portion of the can body by double seaming.
[0011] Japanese Patent 3427216 (patent document 2) also proposes a
battery casing in which a resin film such as a polypropylene film
or the like is preliminarily formed on a metal plate by coating and
the metal plate is configured to function as a gasket at the time
of sealing.
[0012] The two-piece can which is proposed in the patent document 1
and the patent document 2 is formed of a can which seals an opening
portion thereof by double seaming and hence, a liquid leakage
resistance can be enhanced. However, the properties which the
casing of the battery or the electric equipment is required to
possess are not limited to the liquid leakage resistance and the
volumetric efficiency of a can body.
[0013] Accordingly, it is an object of the present invention to
provide a can which can further enhance a can body strength which
is a property that a storage casing is required to possess and, at
the same time, it is also an object of the present invention to
provide a can which exhibits a high heat radiation property to cope
with the increase of the generation of heat which is increased
along a recent demand for high battery energy.
[0014] Further, it is another object of the present invention to
provide a three-piece rectangular can which overcomes a drawback
(joint defect) at a joint portion of a can body (side seam) while
making use of favorable properties of the three-piece can.
[0015] Further, it is still another object of the present invention
to provide a new type of three-piece rectangular can which can
overcome an insufficient can body strength attributed to the
structural limitation imposed on a bottom portion of the two-piece
can.
[0016] Further, it is a further object of the present invention to
provide a three-piece can which exhibits excellent liquid leakage
resistance, an excellent can body strength and an excellent heat
radiation property or the like also as a casing for housing various
kinds of batteries, electric equipment or the like.
[0017] Further, it is a still further object of the present
invention to provide a battery container which exhibits excellent
corrosion resistance against an electrolytic solution which
contains highly corrosive propylene carbonate salt as a main
component.
[0018] Particularly, it is an object of the present invention to
provide a battery container which exhibits excellent corrosion
resistance at four corner portions thereof.
[0019] Further, it is a further object of the present invention to
provide a necking method which can deform a rectangular can into a
stable shape by applying necking forming.
Patent Document 1: Japanese patent laid-open 2002-343310
Patent Document 2: Japanese Patent 3427216
DISCLOSURE OF THE INVENTION
[0020] A three-piece rectangular can according to claim 1 of the
present invention is directed to a three-piece rectangular can in
which a necking formed portion is formed by applying necking
forming to opening portions at both ends of a rectangular can body
having no seam on a side surface thereof, and a top lid and a
bottom lid are seamed by double seaming to the opening portions at
both ends of the rectangular can body by way of an organic
compound, wherein the three-piece rectangular can is formed of an
aluminum plate having an organic film formed on at least one
surface thereof, and the organic film is formed on at least inner
surfaces of the rectangular can body, the top lid and the bottom
lid.
[0021] As described above, since the rectangular can body, the top
lid and the bottom lid which are formed by applying the organic
film such as a polyester film to the aluminum plate are seamed by
double seaming by way of the organic compound, the three-piece
rectangular can exhibits an excellent liquid leakage resistance
and, at the same time, the three-piece rectangular can has no seams
which the conventional three-piece can has on the side surface of
the can body and hence, it is possible to prevent the generation of
corrosion caused by a defect of a resin coating film which is
liable to occur at a seam portion of the three-piece can.
[0022] The three-piece rectangular can according to claim 2 is
characterized in that, in the constitution described in claim 1,
the rectangular can body having no seam on the side surface thereof
is formed such that a cylindrical sleeve having no seam on a side
surface thereof which is formed by cutting a bottom portion of a
bottomed circular can from a circular blank by deep drawing is
deformed into a rectangular sleeve and the rectangular sleeve has
the opening portions at both ends thereof, and the necking formed
portion is formed on the opening portions by applying necking
forming to the opening portions.
[0023] The rectangular can body is formed such that a bottomless
cylindrical sleeve is formed by cutting the bottom portion of the
bottomed circular can formed by deep-drawing from the circular
blank and the bottomless cylindrical sleeve is deformed into a
rectangular shape. Accordingly, it is unnecessary to use a
complicated rectangular drawing die thus reducing the formation of
defect portions such as drawing wrinkles in the can body attributed
to defective drawing.
[0024] In general, a rectangular can is formed such that a
rectangular blank is formed into a cylindrical shape and both sides
of the cylindrical rectangular blank are joined to form a sleeve
and, thereafter, the sleeve is sequentially formed into a
rectangular shape. Alternatively, the rectangular can is formed
using a rectangular drawing mold. To the contrary, according to the
present invention, the rectangular can body having no seam on the
side surface thereof is formed such that the bottomless cylindrical
sleeve is formed by cutting the bottom portion of the bottomed
circular can formed by deep-drawing and the bottomless cylindrical
sleeve is deformed into a rectangular shape. Then, the necking
forming is applied to the opening portions at both ends of the
rectangular can body, and the top lid and the bottom lid are seamed
to opening portions at both ends by double seaming. Accordingly, it
is possible to easily manufacture a three-piece rectangular can
having free sizes in the directions of length, width and
height.
[0025] The three-piece rectangular can according to claim 3 is
characterized in that, in the constitution described in claim 1,
the rectangular can body having no seam on the side surface thereof
is formed such that the cylindrical sleeve having no seam on a side
surface thereof which is formed by cutting a bottom portion of a
bottomed circular can from a circular blank by deep drawing is
deformed into a rectangular sleeve and the rectangular sleeve has
the opening portions at both ends thereof, and the necking formed
portion is formed on the opening portions by applying necking
forming to the opening portions and, thereafter, a plurality of
beads is formed on the rectangular can body in a state that the
beads surround the rectangular can body.
[0026] The plurality of beads is formed on the rectangular can body
in a state that the beads surround the rectangular can body and
hence, the rigidity of a can wall is increased by making use of the
beads and the strength of the can body (deformation resistance
strength against inner pressure and outer pressure, fall-resistant
strength or the like). Further, when the three-piece rectangular
can is used as a battery casing, the beads can increase a surface
area of the can wall and hence, it is possible to enhance the
radiation of heat thus suppressing the shortening of battery
lifespan and the deterioration of the adhesiveness of the resin
film to the can body.
[0027] Further, when a large number of battery casings is arranged,
a non-contact gap is formed between valleys of the beads of the
neighboring battery casings. Accordingly, the convection of air is
generated thus realizing the efficient heat radiation.
[0028] The three-piece rectangular can according to claim 4 is
characterized in that, in the constitution described in any one of
claims 1 to 3, a through hole is formed in center portions of the
top lid and the bottom lid which are mounted on the opening
portions at both ends of the rectangular can body having no seam on
the side surface thereof by double seaming, and an electrode is
mounted in the through hole by way of an insulator.
[0029] In mounting the electrodes on both of the top lid and the
bottom lid which are mounted on the opening portions at both ends
of the rectangular can body by double seaming, the electrodes are
mounted in the through holes formed in the center portions of the
top lid and the bottom lid by way of the insulator and hence, it is
possible to ensure the insulation between the electrodes and the
can body.
[0030] The three-piece rectangular can according to claim 5 is
characterized in that, in the constitution described in any one of
claims 1 to 4, the top lid or the bottom lid of the three-piece
rectangular can is formed of an aluminum plate to which a
non-stretched polyester film which sets a degree of crystallization
within a range from 20% to 40% by preheating treatment before
forming is applied.
[0031] Accordingly, it is possible to prevent the generation of
wrinkles on the polyester film at the time of manufacturing the
lid.
[0032] The three-piece rectangular can according to claim 6 is
characterized in that, in the constitution described in any one of
claims 1 to 4, the three-piece rectangular can which is used as a
battery container and is formed of an aluminum plate which applies
a biaxially stretched polyester film to at least the inner surfaces
of the rectangular can body, the top lid and the bottom lid.
[0033] Here, the biaxially stretched polyester film possesses an
X-ray diffraction intensity ratio which satisfies
5.gtoreq.I.sub.A/I.sub.B.gtoreq.1, wherein I.sub.A is an X-ray
diffraction intensity on a diffraction plane which is parallel to a
surface of the polyester film and has a surface distance of
approximately 0.34 nm (a CuK.alpha.X-ray diffraction angle being
set to a value which falls within a range from 24.degree. to
28.degree.), and I.sub.B is an X-ray diffraction intensity on a
diffraction plane which is parallel to the surface of the polyester
film and has a surface distance of approximately 0.39 nm (a
CuK.alpha.X-ray diffraction angle being set to a value which falls
within a range from 21.5.degree. to 24.degree.).
[0034] Accordingly, the three-piece rectangular can of the present
invention can excellently prevent the deterioration of the
polyester resin film applied to an inner surface of a container by
the corrosive liquid (an electrolytic solution) thus manufacturing
an excellent battery container.
[0035] The manufacturing method of a three-piece rectangular can
according to claim 7 is characterized in that a circular blank
formed of an aluminum plate which forms an organic film on at least
one surface thereof is formed into a bottomed circular can by deep
drawing such that the organic film forms an inner side of the can,
a cylindrical sleeve having no seam on a side surface thereof is
formed by cutting a bottom portion of the bottomed circular can, a
rectangular can body having no seam on a side surface thereof is
formed by deforming the cylindrical sleeve into a rectangular
shape, a necking formed portion is formed by applying necking
forming to opening portions at both ends of the rectangular can
body, and a top lid and a bottom lid are mounted on the opening
portions at both ends of the rectangular can body by double seaming
by way of an organic compound.
[0036] Due to such a constitution, in general, a rectangular can is
formed such that a rectangular blank is formed into a cylindrical
shape and both sides of the rectangular blank are joined to form a
sleeve and, thereafter, the sleeve is sequentially formed into a
rectangular shape. Alternatively, the rectangular can is formed
using a rectangular drawing mold. To the contrary, according to the
present invention, the rectangular can body portion having no seam
on the side surface thereof is formed such that the bottomless
cylindrical sleeve is formed by cutting the bottom portion of the
bottomed circular can formed by deep-drawing and the bottomless
cylindrical sleeve is deformed into a rectangular shape. Then, the
necking forming is applied to the opening portions at both ends of
the rectangular can body, and the top lid and the bottom lid are
seamed to opening portions at both ends by double seaming.
Accordingly, it is possible to easily manufacture a three-piece
rectangular can having free sizes in the lengthwise direction, in
the widthwise direction and in the height direction.
[0037] A necking method of a rectangular can according to claim 8
is characterized in that, in performing necking forming for
squeezing an opening portion of a rectangular can body portion of a
rectangular can, a first core is arranged in the inside of a
necking formed portion of the rectangular can, a second split core
which is expansible and shrinkable is arranged on a lower portion
of the necking formed portion and, thereafter, the necking formed
portion is formed using a necking die.
[0038] Due to such a constitution, besides supporting the necking
formed portion on the first core, the lower portion of the necking
formed portion is supported on the second core and hence, it is
possible to form flat portions of the rectangular can in the same
manner as the corner portions of the rectangular can thus obtaining
a stable can shape and, at the same time, it is possible to form
the can into a desired shape by necking forming. Further, also in
applying the necking forming to the opening portions at both ends
of the rectangular can body, by shrinking the second core, it is
possible to facilitate a takeout operation of a product after
necking forming.
[0039] A necking method of a rectangular can according to claim 9
is characterized in that, in the constitution described in claim 8,
the rectangular can body portion is arranged outside the second
core on a bolster, the second core is moved in an expansible manner
in a state that the second core supports a lower portion of the
necking formed portion and, thereafter, the necking formed portion
is positioned on the second core by lowering the first core mounted
on a slide, and the necking die is lowered to perform the necking
forming.
[0040] Due to such a constitution, by lowering the slide toward the
second core and the rectangular can which are set on the bolster,
the first core can be set on the second core at a predetermined
position and, thereafter, by further lowering the slide, the
necking forming can be performed using the necking die.
Accordingly, it is possible to form the rectangular can in
accordance with steps substantially equal to steps of usual necking
forming even when the first and second cores are used.
[0041] The necking method of a rectangular can according to claim
is characterized in that, in the constitution described in claim 8
or claim 9, the expansion and the shrinking of the second core and
the insertion and the removal of the first core are performed in an
interlocking manner with lowering and elevation of the slide.
[0042] Due to such a constitution, the expansion and the shrinking
of the second core and the insertion and the removal of the first
core are performed in an interlocking manner with lowering and
elevation of the slide. Accordingly, in an interlocking manner with
the elevation and the lowering of the slide, it is possible to
bring the first and second cores into a set state in which the
first core and the second core are set or into a removal state in
which the first core and the second core are removed. Accordingly,
the necking forming can be effectively performed without increasing
the number of manufacturing steps.
BRIEF EXPLANATION OF THE DRAWINGS
[0043] FIG. 1 is a perspective view of a three-piece rectangular
can of an embodiment 1 of the present invention.
[0044] FIG. 2 is a perspective view of a three-piece rectangular
can of an embodiment 2 which mounts a top lid and a bottom lid on
both opening ends of a can body portion having no seam on a side
surface thereof on which beads are formed in a state that the beads
surround the rectangular can body portion by double seaming.
[0045] FIG. 3 is a perspective view of a three-piece rectangular
can of an embodiment 3 which is used as an electric double-layered
capacitor casing.
[0046] FIG. 4 is a cross-sectional view for explaining a material
for manufacturing the three-piece rectangular can.
[0047] FIG. 5 is a graph showing an X-ray diffraction spectrum of a
biaxially stretched polyester film which is measured using an X-ray
diffractometer.
[0048] FIG. 6 is an explanatory view of influences of preheating
treatment and crystallization on the generation of film
wrinkles.
[0049] FIG. 7 is an explanatory view showing manufacturing steps
(first step to forth step) of the three-piece rectangular can.
[0050] FIG. 8 is an explanatory view showing manufacturing steps
(fifth step to seventh step) of the three-piece rectangular
can.
[0051] FIG. 9 is an explanatory view showing a principle of the
constitution of the three-piece rectangular can in deforming a
circular can into a rectangular shape.
[0052] FIG. 10(a) is a plan view and a front view of a rectangular
can body portion before necking forming is applied, and FIG. 10(b)
is a plan view and a front view of a rectangular can after the
necking forming is applied.
[0053] FIG. 11(a) is a vertically cross-sectional view of a necking
device before and after the necking forming is applied, and FIG.
11(b) is a plan view of a second core portion of the necking device
before and after the necking forming is applied.
[0054] FIG. 12 is a view of steps of the necking forming of the
rectangular can.
[0055] FIG. 13 is an explanatory cross-sectional view of an angle
of an inclination surface of a necking die.
[0056] FIG. 14 is an explanatory view of double-seaming steps.
[0057] FIG. 15 is a schematic cross-sectional view of a rectangular
can of an embodiment 3 which is used as an electric double-layered
capacitor casing.
BEST MODE FOR CARRYING OUT THE INVENTION
[0058] Hereinafter, a three-piece rectangular can according to the
present invention is explained in detail. FIG. 1 is a perspective
view of a three-piece rectangular can of an embodiment 1 of the
present invention. FIG. 2 is a perspective view of a three-piece
rectangular can of an embodiment 2 according to the present
invention. A top lid and a bottom lid are mounted on both opening
ends of a can body portion having no seam on a side surface
thereof, and beads are formed on a rectangular can body by double
seaming in a state that the beads surround the rectangular can
body. FIG. 3 is a perspective view of a three-piece rectangular can
of an embodiment 3 according to the present invention when the
three-piece rectangular can shown in FIG. 2 is used as an electric
double-layered capacitor casing.
[0059] In the embodiments 1 to 3, the three-piece rectangular can
mounts a top lid 2 and a bottom lid 3 on both opening ends of a
rectangular can body portion 1 having no seam on a side surface
thereof by way of a top lid double seaming portion 2a and a bottom
lid double seaming portion 3a. Further, in the three-piece
rectangular can shown in FIG. 2, beads 1b are formed on the
rectangular can body portion 1 in a state that the beads 1b
surround the rectangular can body portion 1. Further, in the
three-piece rectangular can shown in FIG. 3 which constitutes an
electric double-layered capacitor casing, through holes 6 (a
through hole formed in the bottom lid 3 not shown in the drawing)
are formed in planar center portions of the top lid 2 and the
bottom lid 3, and an upper electrode 5a is mounted in the through
hole 6 by way of an insulator 4.
[0060] FIG. 4 is a cross-sectional view for explaining a material
for forming the three-piece rectangular can of the present
invention. A resin-covered aluminum plate is formed such that, as
shown in FIG. 4(a), to both surfaces of an aluminum plate 10 which
constitutes a base material, a surface treatment layer 11 is
applied for enhancing the adhesiveness between an organic film and
the aluminum plate 10 when the organic film such as a polyester
film is formed on both surfaces of the aluminum plate 10, and the
resin film (organic film) 12 described later is stacked on the
surface treatment layer 11 as shown in FIG. 4(b).
[0061] Hereinafter, the aluminum plate which constitutes the base
material, the surface treatment layer, the resin film, the film
stacking method and the like are explained in detail.
(Aluminum Plate)
[0062] As an aluminum plate which constitutes a base material of
the three-piece rectangular can of the present invention, various
kinds of aluminum materials, for example, aluminum alloys in the
order of 3000, 5000 and 6000 described in JIS4000 can be named. Out
of these aluminum alloys, the aluminum alloy in the order of 3000
has been preferably used. In forming the rectangular can body
portion 1 of the present invention, from viewpoints of a can body
strength, flange formability and the like, contents of Mn and Cu
are preferably set as follows.
[0063] Mn can enhance a recrystallization temperature of aluminum
alloy and, at the same time, can enhance the corrosion resistance
of the can by changing a crystallization state of Mn in a form of
Fe compound in the aluminum alloy and hence, it is preferable to
add a quantity of Mn within a range from 1.0 to 1.5% (symbol %
being % based on weight, the symbol % being used in the same manner
hereinafter) to the aluminum plate. Cu can enhance the strength of
the can and hence, it is preferable to add Cu within a range from
0.05 to 0.20% to the aluminum plate.
[0064] Here, it is possible to add other elements within
predetermined ranges to the aluminum plate from the viewpoints of
enhancing strength, formability, corrosion resistance and the like
of the can.
[0065] In general, a plate thickness of the aluminum plate after
the aluminum plate is formed into a rectangular can body portion 1
may preferably be set to a value which falls within a range from
0.1 to 1.0 mm from viewpoints of a can body strength, flange
formability and the like. However, a plate thickness of a side wall
of the rectangular can body portion (the smallest value of the
plate thickness of the aluminum plate except for the resin film)
may preferably be set to 0.3 mm or more by taking a withstand
pressure of the can into consideration.
(Surface Treatment)
[0066] It is preferable to form the surface treatment layer 11 on a
surface of the aluminum plate 10 which constitutes the base
material for enhancing the forming adhesiveness between the
aluminum plate 10 and the resin film 12 which covers the aluminum
plate 10. The above-mentioned surface treatment layer 11 may be
formed by applying cold-rolling treatment to the aluminum plate 10
and, thereafter, by applying a surface treatment of organic or
inorganic system including a chromic-phosphoric treatment to the
aluminum plate 10 by immersing or spraying. Further, it is also
possible to form the surface treatment layer on the aluminum plate
10 by coating. In forming the treatment film on the aluminum plate
10 by chromic-phosphoric treatment, from a viewpoint of ensuring
the forming adhesiveness of the resin film which covers the
aluminum plate 10, a total quantity of chromium may preferably be
set to a value which falls within a range from 5 to 40 mg/m.sup.2,
and may more preferably be set to a value which falls within a
range from 15 to 30 mg/m.sup.2.
(Resin Film)
[0067] At least on an inner surface side of the three-piece
rectangular can, the resin film 12 is stacked on the surface of the
aluminum plate 10 on which the surface treatment layer 11 is
formed. As the resin film 12, a thermoplastic resin film having the
excellent heat resistance, for example, a polyester film, a nylon
film, a polypropylene film, a polycarbonate film or the like which
has a thickness of 2 to 50 .mu.m can be named.
[0068] Further, as the polyester film, a non-stretched film which
contains ethylene terephthalate, ethylene butyrate, and ethylene
isophthalate as main components can be preferably used. Such a
resin film is formed by using a T-die method or an inflation
film-forming method.
[0069] Here, the non-stretched polyester film is preferably used
when an emphasis is placed on measures or means to cope with
defective sealing (leaking) by seaming attributed to wrinkles of
the film covering the lid material after forming the lid. In this
case, for enhancing the sealing property when the aluminum plate is
used as the top lid member and the bottom lid member, the
non-stretched polyester film is adhered to the aluminum plate and,
thereafter, a degree of film crystallinity is increased to a value
which falls within a range from 20 to 40% by preheating.
[0070] In using the polyester film as the thermoplastic resin film,
other components may be also copolymerized. For example, as a
dicarboxylic acid component which is copolymerized with the
polyester film, a naphthalene dicarboxylic acid, a diphenyl
dicarboxylic acid, a diphenyl sulphon dicarboxylic acid, a
diphenoxy ethane dicarboxylic acid, a 5-sodium sulfo isophthalic
acid, an aromatic dicarboxylic acid such as a phthalic acid, an
aliphatic dicarboxylic acid such as an oxalic acid, a succinic
acid, an adipic acid, a sebacic acid, a dimer acid, a maleic acid
and a fumaric acid, an alicyclic dicarboxylic acid such as a
cyclohexane dicarboxylic acid, and an oxycarboxylic acid such as a
p-oxine benzoic acid or the like can be named.
[0071] Further, as a glycol component which is copolymerized with
the polyester film, an aliphatic glycol such as propanediol,
butanediol, pentanediol and neopentylglycol, an alicyclicglycol
such as cyclohexane dimethanol, an aromatic glycol such as
bisphenol A and bisphenol S, and a polyoxyethylene glycol such as a
diethylene glycol and a polyethylene glycol and the like can be
named. With respect to the above-mentioned dicarboxylic acid
component and the glycol component, two or more kinds of components
may be used in combination with each other.
(Polyethylene Terephthalate Film)
[0072] Further, when a polyethylene terephthalate film is used as
the polyester film, it is preferable that 70 mol % or more of
dibasic acid component in the copolymerized polyester and,
particularly, 75 mol % or more of the dibasic acid component is
formed of the terephthalic component, 70 mol % or more of the diol
component and, particularly, 75 mol 6 or more of the diol component
is formed of ethylene grycol, and 1 to 30 mol % of the dibasic acid
component and/or the diol component and, particularly, 5 to 25 mol
% of the dibasic acid component and/or the diol component are
formed of a dibasic acid component except for the terephthalic acid
and/or the diol component except for the ethylene grycol.
[0073] As the dibasic acid except for the terephthalic acid, one
kind of or a combination of two or more kinds of an aromatic
dicarboxylic acid such as an isophthalic acid, a phthalic acid and
a naphthalene dicarboxylic acid; an alicyclic dicarboxylic acid
such as a cyclohexane dicarboxylic acid; and an aliphatic
dicarboxylic acid such as a succinic acid, an adipic acid, a
sebacic acid and a dodecanedioic acid can be named. Further, as the
diol component except for the ethylene grycol, one kind of or two
kinds of a propylene glycol, 1,4-butanediol, diethylene grycol,
1,6-hexylene grycol, cyclohexane dimethanol, and ethylene oxide
adduct of the bisphenol A can be named.
[0074] The combination of these co-monomers is required to have a
melting point of the copolymerized polyester which falls within the
above-mentioned ranges.
[0075] Copolyester to be used is required to have a sufficient
molecular weight for forming a film. To this end, it is desirable
to set intrinsic viscosity (I.V.) to a value which falls within a
range of 0.55 to 1.9 dl/g, and more particularly to a value which
falls within a range from 0.65 to 1.4 dl/g.
[0076] It is important that the copolyester film is stretched
biaxially. The degree of biaxial stretching can be confirmed by a
polarization fluorescence method, a birefringence method, a density
gradient pipe method or the like.
[0077] When a nylon film is used as the thermoplastic resin film, a
condensation polymerization product made of diamine and
dicarboxylic acid such as nylon 66, nylon 610 or nylon 612, or a
split polymerization product of lactam such as nylon 6, nylon 11 or
nylon 12 can be used.
[0078] Such a thermoplastic resin film can be manufactured using a
known method. For example, anon-stretched film is manufactured by a
T-die method or an inflation film forming method and, thereafter, a
stretching treatment such as a uniaxial treatment, or a biaxial
treatment is further applied to the non-stretched film. A known
plasma treatment, flame treatment or the like may also be applied
to a surface of the resin film to enhance the adhesiveness of the
resin film to a surface of the aluminum plate.
[0079] Here, in place of the above-mentioned method for stacking
the resin film, coating of organic resin paint or the like may be
applied to the aluminum plate to which the surface treatment is
applied by a known means to form an organic film.
[0080] That is, the biaxially stretched polyester film which is
used in the present invention preferably possesses an X-ray
diffraction intensity ratio I.sub.A/I.sub.B which satisfies
5.gtoreq.I.sub.A/I.sub.B.gtoreq.1.
[0081] Here, I.sub.A is an X-ray diffraction intensity on a
diffraction plane which is parallel to a surface of the polyester
film and has a surface distance of approximately 0.34 nm (a
CuK.alpha.X-ray diffraction angle being set to a value which falls
within a range from 24.degree. to 28.degree.), and I.sub.B is an
X-ray diffraction intensity on a diffraction plane which is
parallel to the surface of the polyester film and has a surface
distance of approximately 0.39 nm (a CuK.alpha.X-ray diffraction
angle being set to a value which falls within a range from
21.5.degree. to 24.degree.)
(Measurement of X-ray Diffraction Intensity Ratio
I.sub.A/I.sub.B)
[0082] The X-ray diffraction intensity ratio I.sub.A/I.sub.B is
measured as follows using an X-ray diffractometer. As measuring
conditions, an X-ray tube (target) made of copper (wavelength
.lamda.=0.1542 nm) is used, and a tube voltage and a tube current
are respectively approximately 30 kV and 100 mA, and a light
receiving slit with a slit width corresponding to an angle of 0.10
or less which can separate a diffraction peak having a surface
distance which is approximately 0.39 nm (20 being about
22.5.degree.) and a diffraction peak having a surface distance
which is approximately 0.34 nm (2.theta. being about 26.degree.) is
selected. A sample is mounted such that an incident angle and a
reflection angle of the X ray is set to .theta. respectively with
respect to a diffraction angle 2.theta., and an incident X ray and
a diffraction X ray become symmetrical with respect to a normal
line of a film surface. An X-ray diffraction spectrum is measured
by scanning with the diffraction angle 2.theta. set within 20 to
30.degree. while always maintaining an incident angle .theta. and a
reflection angle .theta. at the same value.
[0083] FIG. 5 shows the X-ray diffraction spectrum measured in the
above-described manner. Here, I.sub.A is an X-ray diffraction
intensity (peak value) on a diffraction plane which is parallel to
a surface of the polyester film and has a surface distance of
approximately 0.34 nm (a CuK.alpha.X-ray diffraction angle 2.theta.
being set to a value which falls within a range from 24.degree. to
28.degree.), and I.sub.B is an X-ray diffraction intensity (peak
value) on a diffraction plane which is parallel to the surface of
the polyester film and has a surface distance of approximately 0.39
nm (a CuK.alpha.X-ray diffraction angle 2.theta. being set to a
value which falls within a range from 21.5.degree. to 24.degree.).
In obtaining an diffraction intensity ratio between the X-ray
diffraction intensity I.sub.A and the X-ray diffraction intensity
I.sub.B, as shown in FIG. 4, respective intensity regions of
I.sub.A with 2.theta. ranging from 24.degree. to 28.degree. and
I.sub.B with 2.theta. ranging from 21.5.degree. to 24.degree. are
connected by linear lines (Ua, Ub) to form backgrounds, and a ratio
between lengths in the direction perpendicular to the backgrounds
is set as a value of the diffraction intensity ratio
I.sub.A/I.sub.B.
[0084] The finding that the X-ray diffraction intensity ratio
I.sub.A/I.sub.B is closely relevant to the corrosion resistance is
acquired as a result of trials and errors made through a large
number of experiments carried out by inventors of the present
invention. That is, it is considered that when the X-ray
diffraction intensity ratio I.sub.A/I.sub.B is increased exceeding
a fixed reference value, splitting is liable to occur due to a kind
of fibrillation of polyester and the corrosion resistance of a
surface of the container or the lid after forming is deteriorated.
Further, it is also considered that when the X-ray diffraction
intensity ratio I.sub.A/I.sub.B is decreased below a fixed
reference value, the thermal stability of the orientation crystals
of the polyester film is lowered and hence, cracks occur in the
polyester film of an inner surface of the container or the lid
during bulging forming or bending forming after heating thus
deteriorating the corrosion resistance.
[0085] Accordingly, the battery-use container which constitutes the
three-piece rectangular can is configured such that, to enhance the
corrosion resistance of the container, the X-ray diffraction
intensity ratio I.sub.A/I.sub.B is set to the value which falls
within the fixed reference.
[0086] The X-ray diffraction intensity ratio I.sub.A/I.sub.B can be
controlled based on the resin composition and a melting point of
the polyester film and a lamination temperature at the time of
laminating the polyester film to the aluminum plate. For example,
the X-ray diffraction intensity ratio I.sub.A/I.sub.B can be
increased by elevating the melting point of the polyester film,
while the X-ray diffraction intensity ratio I.sub.A/I.sub.B can be
decreased by elevating the lamination temperature at the time of
laminating the polyester film to the aluminum plate. Further, with
the use of a copolymer polyethylene terephthalate biaxially
stretched film, it is possible to further decrease the X-ray
diffraction intensity ratio I.sub.A/I.sub.B.
[0087] Here, in stretching the polyester film, it may be possible
to select an area extension magnification ratio within a range from
2.5 to 16.0, particularly within a range from 4.0 to 14.0, at a
temperature of 80 to 110.degree. C. such that diffraction intensity
ratio which satisfies 5.gtoreq.I.sub.A/I.sub.B.gtoreq.1 in view of
the relationship between the area extension magnification ratio and
other conditions including the resin composition of polyester.
[0088] Further, in thermally fixing the film, it may be possible to
select a thermal fixing temperature within a range from 130.degree.
C. to 240.degree. C., particularly within a range from 150 to
230.degree. C. such that the diffraction intensity ratio which
satisfies 5.gtoreq.I.sub.A/I.sub.B.gtoreq.1 in view of the
relationship between the thermal fixing temperature and other
conditions in the same manner as the area extension magnification
ratio.
(Thickness of Resin Film)
[0089] It is desirable to set the thickness of the resin film to a
value which falls within a range from 2 to 50 .mu.m, particularly
to a value which falls within a range from 12 to 40 .mu.m by taking
the relationship among barrier property against corrosive
components, formability and opening property into
consideration.
[0090] The resin film may be blended with film blending agents
known per se, for example, an anti-blocking agent such as amorphous
silica, pigment such as carbon black (black), various charging
prevention agent, a lubricant or the like in accordance with a
known process.
(Adhesive Primer)
[0091] An adhesive primer may be interposed between the resin film
and the aluminum plate. It is desirable to use the adhesive primer
which exhibits excellent adhesiveness to both of the aluminum plate
and the resin film. As the typical adhesive primer which exhibits
the excellent close adhesiveness and the corrosion resistance, a
phenol-epoxy primer which is formed of a resol-type phenol-aldehyde
resin derived from various phenols and formaldehyde and a
bisphenol-type epoxy resin is named. Particularly, the primer which
contains phenol resin and epoxy resin at a weight ratio of 50:50 to
5:95, particularly at a weight ratio of 40:60 to 10:90 is named. In
general, the adhesive primer layer may have a thickness of 0.3 to 5
.mu.m.
(Covering of Resin Film on Aluminum Plate by Coating)
[0092] As a method for covering aluminum plate with the resin film
by coating, a method which covers a surface of the aluminum plate
with a non-stretched film by pressing the non-stretched film to the
heated aluminum plate using a roll so as to melt an interface is
preferably adopted. The non-stretched film formed by heating and
melting resin pellets by an extruder at a temperature 20 to
40.degree. C. higher than a melting temperature of resin and by
extruding the resin in a film shape from a slit of a T-die, and by
cooling the resin with a surface of a casting roller.
[0093] Further, in another film forming method, a film-shaped resin
extruded from a slit of the T-die is directly and continuously fed
to a surface of a moving heated aluminum plate to cover the
aluminum plate by coating and is cooled.
[0094] In covering the aluminum plate with the resin film by
coating, a time during which the resin film to be coated passes
through a crystallization temperature region is set as short as
possible. It is preferable that the resin film passes through the
crystallization temperature region within 10 seconds, particularly
within 5 seconds. Accordingly, in covering the aluminum plate by
coating, it is preferable that only the aluminum plate is heated,
and immediately after the aluminum plate is covered with the resin
film by coating, the resin-coated aluminum plate is forcibly
cooled.
[0095] In cooling the resin-coated aluminum plate, a direct contact
of the aluminum plate with cold air or cold water or a pressure
contact of the aluminum plate with a cooling roller which is
forcibly cooled is used. In covering the aluminum plate with the
resin film by coating, by heating the resin film to a temperature
close to a melting point and quenching the resin film after
coating, it is possible to alleviate the degree of crystalline
orientation.
(Preheating Treatment of Aluminum Plate Coated with Non-Stretched
Film)
[0096] In using the non-stretched-film-coated aluminum plate as a
material of the top lid or the bottom lid of the three-piece
rectangular can, a preheating treatment may be preliminarily
applied to the aluminum plate before forming the can lids.
[0097] In general, in forming a metal plate which is covered with a
various kinds of resin films into can lids or the like using a
press, the strong adhesiveness is required between the metal plate
and the resin film to prevent cracks in the coated resin film per
se or peeling of the resin film from the background metal plate.
Since the non-stretched film is not stretched in the longitudinal
and lateral directions in plane at the time of film forming, the
non-stretched film is in a non-oriented state. Accordingly, the
non-stretched film is considered to exhibit no deviation in
physical properties in the planner direction of the film, thus
allowing the non-stretched film to follow the relatively flexible
and strict forming. In this manner, with respect to the
non-stretched film, the film per se possesses the favorable
workability and hence, the non-stretched film is used in many
applications such as press-formed products by being laminated to a
surface of a metal plate.
[0098] Also in the rectangular can lid, there exists a demand for
decreasing a radius of four corner portions of a chuck wall portion
of the can lid. Since the strict workability is necessary, the
non-stretched film which exhibits excellent workability is
applicable to the formation of the rectangular can lid. However,
even when the non-stretched film which is considered to possess the
favorable workability compared with the biaxially stretched film is
used, in the strict forming which requires the radius of four
corner portions of the chuck wall portion of the rectangular can
lid to assume 10 mm or less as in the case of the rectangular can
lid, there exists a possibility of generating wrinkles on the film
or peeling of the film.
[0099] To prevent the occurrence of the above-mentioned film
wrinkles on the front and back surfaces of the corner portions of
the can lid, with respect to the aluminum plate which is covered
with the non-stretched film, by adjusting the degree of
crystallization of the resin film which is preliminarily subject to
the heat treatment before forming and covers the aluminum plate, it
is possible to prevent the occurrence of wrinkles at the time of
such forming.
[0100] FIG. 6 shows a result of the adjustment. As can be
understood from FIG. 6, the degree of crystallization under a
condition 1 in which the preliminary heat treatment of the resin
film is not performed before forming is 5% and the wrinkles occur
in the corner portion. Conditions 2 to 4 are set by changing a
heating time at the same temperature of 190.degree. C., wherein the
heating times under the respective conditions 2 to 4 are set to 10
minutes (condition 2), 30 minutes (condition 3) and 40 minutes
(condition 4). When the heat treatment under the condition 2 is
performed, the degree of crystallization becomes 19%. However, the
wrinkles occur in the corner portion. When the heat treatment under
the condition 3 is performed, the degree of crystallization becomes
30% and no wrinkles occur in the corner portion. The condition 4 is
a condition in which the heating treatment time is further
prolonged. When the heat treatment is performed under the condition
4, the degree of crystallization is increased to 45% and no
wrinkles occur in the corner portion.
[0101] Further, to investigate the conditions for the preheating
treatment, a heating temperature is elevated to 200.degree. C.
Conditions 5 to 7 are set by changing a heating time at the same
temperature of 200.degree. C., wherein the heating times under the
respective conditions 5 to 7 are set to 2 minutes (condition 5), 10
minutes (condition 6) and 20 minutes (condition 7). When the heat
treatment under the condition 5 is performed, the degree of
crystallization becomes 10%. However, the wrinkles occur in the
corner portion. When the heat treatment under the condition 6 is
performed, the degree of crystallization becomes 20% and no
wrinkles occur in the corner portion. The condition 7 is a
condition in which the heating treatment time is further prolonged.
When the heat treatment is performed under the condition 7, the
degree of crystallization is increased to 39% and no wrinkles occur
in the corner portion.
[0102] As can be estimated from the result of the experiment shown
in FIG. 6, the higher the heating temperature or the longer the
treatment time, the higher the degree of crystallization of the
resin film becomes in general. Further, there exists the close
relationship between the occurrence of wrinkles at the time of
forming and the degree of crystallization of the coated resin film.
That is, the minimum degree of crystallization which can prevent
the occurrence of wrinkles of the corner portion is 20%, and even
when the degree of crystallization is increased (up to 45%), no
wrinkles occur.
[0103] That is, in forming the rectangular can lid, as the
pretreatment which prevents the occurrence of wrinkles in the
can-lid corner portion, it is necessary to set the degree of
crystallization of the resin film to 20% or more by preheating the
resin coated aluminum plate before forming. Here, provided that the
degree of crystallization is 20% or more, no wrinkles occur in the
can-lid corner portion. However, it is preferable to suppress the
heating treatment energy which brings about the increase of a total
energy cost of the manufacture of the can lid as small as possible
and hence, from an economical viewpoint, an upper limit value of
the degree of crystallization which can prevent the occurrence of
wrinkles is set to 40%.
[0104] In accordance with the above-mentioned results, even when a
radius of the corner portion of the rectangular can lid is
decreased, it is possible to increase leaking liquid resistance in
double seaming without the occurrence of film wrinkles.
(Measurement of Degree of Crystallization)
[0105] The measurement of the degree of crystallization of the
coated film is as follows. A front surface layer of the resin film
coated on the aluminum plate is shaved and, thereafter, heat
treatment of the resin film is performed at the temperature of
185.degree. C. for 10 minutes and retort treatment of the resin
film is performed at the temperature of 110.degree. C. for 60
minutes. Thereafter, the measurement of the degree of
crystallization of the film is performed using a differential
scanning calorimeter (DSC). The measurement is performed at a
temperature elevation rate of 10.degree. C./min using DSC7-RS made
by PERKIN ELMER Ltd. The degree of crystallization is calculated
using a following formula based on a value of a melting peak
.DELTA.H acquired by the measurement.
[0106] The degree of crystallization
(%)=(.DELTA.H(PET)-|.DELTA.Hc|)/.DELTA.H(PET).times.100.DELTA.H(PET)=122.-
25 J/g
(Manufacture of Can Body)
[0107] Next, a manufacturing method of a three-piece rectangular
can according to the present invention is explained.
[0108] First of all, in FIG. 7 and FIG. 8, steps for forming the
above-mentioned resin-coated aluminum plate into a rectangular can
are explained. In respective flow charts shown in FIG. 7 and FIG.
8, an upper side is a plan view and the lower side is a
longitudinal cross-sectional view.
[0109] The first step is a step for deep-drawing a circular blank
in which a bottomed circular can K having a can bottom 1a and a can
body D1 is formed. On an upper-end opening portion of the bottomed
circular can K, an outer periphery of the circular blank remains as
a periphery 1c of the opening portion. The deep drawing in this
step may adopt not only a method which draws the blank one time but
also a method which continuously performs drawing such as a
drawing-re-drawing method.
[0110] The second step is a trimming step in which the periphery 1c
of the opening portion formed on an upper end of the bottomed
circular can K and the can bottom 1a are cut from each other thus
separating the periphery 1c from the can body D1 by cutting. The
can body D1 forms a cylindrical sleeve D2 which has both ends
thereof completely opened and has no seam on a side surface
thereof.
[0111] The third step is a reforming step in which the cylindrical
sleeve D2 having no seam on the side surface thereof is deformed
into a rectangular cross-section from a circular cross-section. A
principle of a mechanism which reforms the circular cross-section
into the rectangular cross-section is shown in FIG. 9. In FIG.
9(a), four reforming rods 20 having a circular cross-section are
arranged around an inner surface of the cylindrical sleeve D2
equidistantly such that the reforming rods 20 are brought into
contact with the cylindrical sleeve D2. By moving the reforming
rods 20 in an enlarging manner in the diagonal directions (four
directions indicated by an arrow A) as shown in FIG. 9(b), the
cylindrical sleeve D2 having no seam on the side surface thereof is
reformed into the rectangular can body portion 1 having a
rectangular shape.
[0112] Here, FIG. 9a and FIG. 9b show one example in which the
reform mechanism is constituted of four rods having a circular
cross-section and being moved in an enlarging manner. However, as
other method, the reforming mechanism may be configured to arrange
a split mold in the inside of the cylindrical sleeve D2 and to
expand the cylindrical sleeve D2. The present invention is not
limited to such a method.
[0113] The fourth step is a necking step in which molds are pushed
to outer portions of both ends of the rectangular can body portion
1 for narrowing peripheries of the upper and lower opening portions
thus forming necking formed portions in which are deformed toward
the inside of the rectangular can body portion 1.
[0114] A necking device for forming the necking formed portions 1n
in the rectangular can body portion 1 (hereinafter, simply referred
to as a necking device) 30 performs, as shown in FIG. 10(a), for
example, necking forming which narrows the upper and lower opening
portions of the rectangular can body portion 1 thus enabling the
acquisition of a rectangular can 24 having a quadrangular
cross-sectional shape which includes necking formed portions 24c as
shown in FIG. 10(b). Necking forming is uniformly performed on flat
portions 24a and corner portions 24b.
[0115] As shown in FIG. 11, such a necking device 30 is, in the
same manner as a related art, constituted of a first core 31 which
is positioned inside the necking formed portions 24c and supports
the necking formed portions 24c, and a necking die 32 which
constitutes an outer mold. The necking device 30 further includes a
second core 33 which supports lower portions of the necking formed
portions 24c and is constituted of an expansible and shrinkable
split mold.
[0116] In such a necking device 30, the first core 31 is supported
on a slide 35 of a press mechanism 34 and is configured to be
integrally elevated and lowered with the slide 35. Further, to
allow the relative elevation and lowering of only the first core
31, the first core 31 is suspended from the slide 35 by way of
slidable suspension bolts 36 and springs 37 which bias the first
core 31 downwardly. The first core 31 has a profile thereof formed
in a quadrangular ring shape and forms support portions 31a having
a quadrangular profile corresponding to a profile of the necking
formed portions 24c and forms a penetration hole 31b in a center
portion of the support portion 31a.
[0117] Further, the necking die 32 which constitutes an outer mold
includes a portion 32a which is mounted on the slide 35 of the
press mechanism 34 using bolts, is arranged outside the first core
31, and has an inner side of a lower end portion thereof positioned
outside the rectangular can body portion 1, and a squeezing forming
portion 32b for performing necking forming above the portion
32a.
[0118] Due to such a constitution, when the slide 35 of the press
mechanism 34 descends, the first core 31 and the necking die 32
descend in an interlocking manner. Accordingly, the first core 31
is set as described later and, thereafter, the necking forming is
performed by the necking die 32.
[0119] On the other hand, the second core 33 which supports the
lower portion of the necking formed portions 24c of the rectangular
can body portion 1 is mounted on a bolster 38 of the press
mechanism 34 and is constituted of the expansible and shrinkable
four split molds.
[0120] The second core 33 is constituted by combining four split
molds 39 which are divided at the center of a rectangular planar
portion and respectively have an angle of 90 degrees with respect
to respective corner portions. Each split mold 39 includes a core
portion 39a which projects toward the inside of the rectangular can
body portion 1 and a horizontal portion 39b which is positioned
above the bolster 38, wherein an upper portion of the core portion
39a is positioned below the necking formed portions 24c. The second
core 33 which is formed of the four split molds 39 is configured to
be expansible and shrinkable in a state that the split molds 39
respectively move in the radial direction with respect to the
corner portions which are arranged in the diagonal directions of
the rectangular shape. Key grooves formed in the respective split
molds 39 are guided along keys 40 mounted on the bolster 38 and, at
the same time, a ring-shaped pressing member 41 is provided to
cover outer portions of segment-like horizontal portions 39b which
form a disc-like shape when four split molds 39 are combined. In
the inside of the pressing member 41, the respective split molds 39
are movable in an expansible and shrinkable manner.
[0121] Further, as a movement unit 42 which performs the expansible
and shrinkable movement of the respective split molds 39 of the
second core 33, a piston rod 43 is arranged at a center portion of
the second core 33, a conical surface 43a is formed on a side
surface of a column in a recessed manner. Further, with respect to
the second core 33, quarter partial conical surfaces 39c are formed
on a piston-rod-43 side of the respective split molds 39 in a
projecting manner. Due to such a constitution, by pushing the
piston rod 43 in a state that these conical surfaces 43a, 39c are
brought into contact with each other, it is possible to bring about
an expanded state in which the respective split molds 39 are moved
to open toward the outside and hence, the side surface of the
column of the piston rod 43 and the cylindrical-portion inner
surfaces of the respective split molds 39 are brought into contact
with each other thus maintaining the expanded state. On the other
hand, to bring the respective split molds 39 into a shrunken state
by moving the split molds 39 of the second core 33 in a closing
direction, for example, grooves (two grooves in the illustrated
example) are formed in a lower portion of a mold portion 39a, and
coil springs 44 are mounted in the inside of the grooves in a state
that the coil springs 44 surround four split molds 39 thus biasing
four split molds 39 in the shrinking direction. Here, in place of
the grooves and the coil springs 44, springs may be interposed
between an outer peripheral portion of a horizontal portion 39b and
the pressing member 41 so as to bias four split molds 39 in the
shrinking direction.
[0122] A necking method of a rectangular can is explained in
conjunction with a flowchart shown in FIG. 12 together with an
operation of the necking device 30 for a rectangular can having the
above-mentioned constitution.
[0123] First of all, by bringing the second core 33 on the bolster
38 of the press mechanism 34 into a state in which the piston rod
43 of the movement mechanism 42 is pulled up, a closed shrunken
state is established, and the rectangular can body portion 1 is set
on the outside of the second core 33 (see FIG. 12(a)).
[0124] Then, by allowing the slide 35 of the press mechanism 34 to
descend, an upper end surface of the piston rod 43 which
constitutes the movement unit 42 of the second core 33 which passes
through a penetrating portion 11b of the first core 31 is brought
into contact with the slide 35 (see FIG. 12(b)).
[0125] When the slide 35 further descends from such a state, the
piston rod 43 is pushed down and hence, the conical surface 43a and
the partial conical surfaces 39c of the respective split mold 39 of
the second core 33 are brought into contact with each other whereby
the respective split molds 39 are moved to the outside in an
opening manner thus bringing the second core 33 into an expanded
state so as to support the lower portion of the necking formed
portion 24c. Further, on an upper end surface of the second core 33
which is expanded along with the descending of the slide 35, the
first core 31 which is suspended from the slide 35 using suspension
bolds 36 and springs 37 is placed, and the necking formed portion
24c is supported on a support portion 31a of the first core 31 (see
FIG. 12(c)).
[0126] From the above-mentioned state in which the necking formed
portion 24c is supported on the first core 31 and the lower portion
of the necking formed portion 24c is supported on the second core
33, by allowing the further descending of the slide 35 of the press
mechanism 34, necking forming of the rectangular can body portion 1
is started by the necking die 32. The rectangular can 24 which is
subject to the necking forming is formed such that the flat
portions 24a is formed into a predetermined shape in the same
manner as the corner portions 24b thus allowing both of the flat
portions 24a and the corner portions 24b to acquire uniform and
stable shapes. Here, during a period in which the necking die
descends, the first core 31 is stopped above the second core 33,
and performs the relative movement with respect to the slide at a
suspending-bolt-36 portion (see FIG. 12(d)).
[0127] When the slide 35 is elevated after forming, the necking die
32 which constitutes the outer mold is elevated in an interlocking
manner with the elevation of the slide 35 and, at the same time,
the first core 31 is elevated so that the first core 31 is
automatically removed from the inside of the rectangular can 24.
Accordingly, it is possible to effectively perform the necking
forming without requiring mounting and removing of the first core
31 by a manual operation.
[0128] Further, by pushing up the piston rod 43 which constitutes
the movement unit of the second core 33, the piston rod 43 is moved
to close four split molds 39 which are biased in the shrinking
direction with the coil spring 44 to bring the split molds 39 into
a shrunken state. Accordingly, even when the lower-end opening
portion of the rectangular can 24 is already subject to necking
forming, it is possible to take out the rectangular can 24.
[0129] Further, in the above-mentioned necking method and device,
the lower portion of the necking formed portion 24c of the
rectangular can body portion 1 is supported by expanding and
shrinking the second core 33 and hence, the flat portions 24a can
be formed into a uniform and stable shape in the same manner as the
corner portions 24b. Further, even when the lower-end opening
portion of the rectangular can 24 is already subject to necking
forming, by mounting such a rectangular can 24, it is possible to
easily perform the necking forming of the upper-end opening portion
of the rectangular can 24 and the removal of the rectangular can 24
after forming.
[0130] Further, the expanding and shrinking movement of the second
core 33 can be performed in an interlocking manner with the
elevation/descending of the slide 35 of the press mechanism 34 and
hence, there is no increase of steps attributed to necking forming,
and necking forming can be also performed without requiring a
manipulation to be performed along with the expanding and shrinking
movement.
[0131] In the necking die 32 which constitutes the outer mold used
in such a necking device 30, an angle .THETA. of an inclined
surface of the necking die 32, that is, as shown in FIG. 13, using
a vertical line which extends upwardly from a portion which faces
the second core 33 as a reference, a tilting angle .THETA. of the
inclined surface in the direction toward the center of the can body
is set to a value which falls within a range of 25 to 35 degrees,
preferably 30 degrees with respect to the reference.
[0132] When the tilting angle is increased by laying the inclined
surface of the necking die 32, an axial load which a portion of the
inclined surface of the rectangular can body portion 1 to which
necking forming is applied is brought into contact with the necking
die 32 firstly is increased and hence, a portion of the lower-end
opening portion of the rectangular can body portion 1 which is
already subject to necking forming is liable to buckle. That is,
due to the axial load applied in the second necking forming, a
buckling phenomenon is not generated in the necking formed portion
per se but is generated in the portion which is already subject to
necking forming. In an experiment in which the tilting angle
.THETA. is set to 45 degrees, the buckling occurs.
[0133] On the other hand, when the angle .THETA. of the inclined
surface of the necking die 32 is made small by raising the inclined
surface of the necking die 32, a shape effect (shrinking effect)
due to necking forming is not clearly observed. Further, there
exists a possibility of causing a drawback that the wrinkles or the
like are generated.
[0134] Further, when an experiment is carried out by setting the
angle .THETA. of the inclined surface of the necking die 32 to 30
degrees, compared to a case in which the angle .THETA. is set to 45
degrees, the axial load applied to the rectangular can 24 can be
decreased and, at the same time, a buckling strength of the portion
which is already subject to necking forming can be also increased
and hence, all of the above-mentioned drawbacks can be overcome,
the upper and lower opening portions of the rectangular can 24 can
be formed into required shapes by necking forming, and neither
buckling nor the generation of wrinkles is observed.
[0135] The above-mentioned narrowing of the opening portions of the
rectangular can body portion 1 is performed for setting outer sizes
of double seaming portions of the rectangular can body portion 1
when the top lid and the bottom lid are formed by double seaming in
a final step to a value equal to or slightly smaller than an outer
size of a rectangular can body portion 1. By setting the outer
sizes of the double seaming portions to the value equal to or
slightly smaller than the outer size of the rectangular can body
portion 1, when a large number of rectangular cans are arranged in
parallel, it is unnecessary to form a wasteful gap between the
neighboring rectangular cans and hence, a volumetric efficiency in
the arrangement of the rectangular cans can be enhanced.
[0136] Next, the fifth step shown in FIG. 8 is a flanging step. In
this step, the necking formed portions in at both ends of the
rectangular can body portion 1 which are formed by squeezing in the
necking step are expanded outwardly over the whole circumference of
the opening portions thus forming flanges 1f. These flanges 1f form
end-portion seam margins of the rectangular can body portion 1 in
double seaming for mounting the top lid and the bottom lid.
[0137] The sixth step is a bead forming step which is performed
when necessary. In this step, beads 1b having concave and convex
portions which surround the rectangular can body portion 1 are
formed. The beads 1b have a function of remarkably increasing a
deformation resistance strength of the rectangular can body portion
1 and, at the same time, a function of increasing an outer front
surface of the body portion. That is, the beads 1b have a function
of easily dissipating or radiating heat generated in the inside of
an electric double-layered capacitor casing or a battery casing to
the outside. Further, when a large number of rectangular cans are
arranged in parallel in the horizontal direction as the
electric-double-layered capacitor casings or battery casings, a gap
is formed between the neighboring cans due to the concave and
convex portions of the beads 1b and hence, the convection of air is
generated thus enhancing the radiation of heat.
[0138] With respect to the electric double-layered capacitors and
the batteries which are used for the regeneration/acceleration
assist driving of clean energy vehicles, the increase of power (the
increase of an electric current) is in progress, and a demand for
the increase of heat radiation of casings used in such applications
is increased. The elevation of temperature of a can body promotes
softening and deterioration of adhesiveness of the resin film
stacked on the aluminum plate. Accordingly, such enhancement of the
heat radiation efficiency satisfies demands required by various
electronic appliance casings without being limited to casings for
the electric double-layered capacitor and batteries.
[0139] The seventh step shown in FIG. 8 is a step for mounting the
top lid and the bottom lid on the can body.
[0140] In this seventh step, when the rectangular can is used as a
casing for an electric double-layered capacitor casing or the like,
the bottom lid is mounted on the rectangular can body portion 1 by
double seaming, an electric generating element is filled in the
rectangular can body portion 1 and, thereafter, the top lid is
mounted on the rectangular can body portion 1 by double seaming to
seal the opening. FIG. 14 shows the cross-sectional structure of a
double seaming portion before and after double seaming in an
enlarged manner. First of all, as shown in FIG. 14(a), a curling
portion 2c of the top lid 2 is arranged to align with the
opening-portion flange 1f of the rectangular can body portion 1.
Here, an organic compound 2b is applied by coating to the whole
circumference of an inner surface of the curling portion 2c for
ensuring the sealing property and the insulation property of the
sealing opening portion.
[0141] In the double seaming step shown in FIG. 14(b), in a state
that the rectangular can body portion 1 is covered with the top lid
2, a pressure is applied to the opening-portion flange 1f and the
curling portion 2c by a seaming roller 60b from an outer periphery
of the curling portion 2c while rotating the can body with a rotary
roller 60a thus forming double seaming portions 2a, 3a by seaming
the top-lid curling portion 2c and the flange 1f in an overlapped
state inwardly.
[0142] The organic compound 2b is an insulating material having
resiliency such as rubber. Conventionally, as such an organic
compound 2b, a known material which is used for enhancing sealing
property of the double seaming portion or the like is used, for
example, one of styrene-butadiene rubber, ethylene propylene
rubber, polyisoprene rubber, a polyamide-based resin and a
polyolefin resin or a mixed material which is produced by mixing a
desired dilution agent or a curing agent into the above-mentioned
material may be used.
[0143] FIG. 15 is a schematic cross-sectional view of the
three-piece rectangular can which is formed in the above-mentioned
manner when the three-piece rectangular can is used as an electric
double-layered capacitor casing. Lead lines (50a, 50b) are
respectively led to upper and lower electrodes 5a, 5b formed on the
top lid and the bottom lid from upper and lower portions of an
electricity generating element 50 filled in the inside of the
rectangular can. The upper and lower electrodes 5a, 5b are mounted
on the top lid 2 and the bottom lid 3 such that through holes are
formed in center portions of the top lid 2 and the bottom lid 3,
and the top lid 2 and the bottom lid 3 are mounted in the through
holes by way of annular insulators 4 which are fitted in the
through holes for establishing the electric insulation between the
can body and the electrodes 5a, 5b.
[0144] Here, as indicated by wave line shown in FIG. 15, to allow
the connection of the electric double-layered capacitor casings in
series in the longitudinal direction, a profile of the upper
electrode 5a is formed in a female shape and a profile of the lower
electrode 5b is formed in a male shape.
(Manufacture of Lids)
[0145] Here, the above-mentioned top lid and bottom lid are
manufactured as follows, for example. First of all, a resin coated
aluminum plate is blanked into rectangular plates and these
rectangular plates are formed into desired lid shapes by a press.
Further, using a mold, recessed portions and through holes are
formed in center portions of these lid-shaped plates thus forming
the top lid and the bottom lid.
[0146] Hereinafter, the biaxially stretched polyester film used in
the present invention is explained in further detail.
Embodiment 1
[0147] A substrate is formed by applying a chromic phosphoric
treatment with an amount of chromium of 20 mg/m.sup.2 in metal
chromium conversion to a surface of an aluminum plate (3003-H14)
having a plate thickness of 0.5 mm and having the composition
consisting of 1.1 weight % of Mn, 0.19 weight % of Cu, 0.30 weight
% of Si, 0.43 weight % of Fe and a balance of Al.
[0148] To one surface of the substrate, a biaxially stretched film
(thickness: 30 .mu.m) formed of a polyethylene terephthalate/iso
phthalate (PET/I) for copolymer resin containing 10 molecular % of
isophthalic acid as a copolymer content is laminated at a
temperature of 245.degree. C. thus manufacturing a resin-coated
aluminum plate. This film has a melting point of 240.degree. C. and
exhibits an X-ray diffraction intensity ratio I.sub.A/I.sub.B of
5.0.
[0149] The resin coated aluminum plate obtained by the
above-mentioned manner is blanked into a circular blank and,
thereafter, drawing forming is applied to the circular blank. After
trimming lug portion and a bottom of the opening end, an expander
is inserted into the inside of the circular blank to perform
expanding forming to enlarge a diameter of the circular blank. Bead
forming and necking/flanging forming are applied to a side wall of
a can to deform the can into a rectangular can body portion. A top
lid and a bottom lid are mounted on both-end opening portions by
double seaming, and a resin is applied to an inner surface of a
container thus manufacturing a rectangular can.
Embodiment 2
[0150] This embodiment 2 is substantially equal to the embodiment 1
except for that a biaxially stretched film (thickness: 30 .mu.m)
which has a melting point different from the melting point of the
biaxially stretched film used in the embodiment 1 is laminated to
the surface of the substrate used in the embodiment 1 at a
temperature of 230.degree. C. A film formed by this embodiment 2
has a melting point of 230.degree. C. and an X-ray diffraction
intensity ratio of I.sub.A/I.sub.B is 4.0.
Embodiment 3
[0151] This embodiment 3 is substantially equal to the embodiment 1
except for that a biaxially stretched film (thickness: 30 .mu.m)
which has a melting point different from the melting point of the
biaxially stretched film used in the embodiment 1 is laminated to
the surface of the substrate used in the embodiment 1 at a
temperature of 235.degree. C. A film formed by this embodiment 3
has a melting point of 230.degree. C. and an X-ray diffraction
intensity ratio of I.sub.A/I.sub.B is 3.5.
Embodiment 4
[0152] This embodiment 4 is substantially equal to the embodiment 1
except for that a biaxially stretched film (thickness: 30 .mu.m)
which has a melting point different from the melting point of the
biaxially stretched film used in the embodiment 1 is laminated to
the surface of the substrate used in the embodiment 1 at a
temperature of 240.degree. C. A film formed by this embodiment 4
has a melting point of 230.degree. C. and an X-ray diffraction
intensity ratio of I.sub.A/I.sub.B is 2.0.
Embodiment 5
[0153] This embodiment 5 is substantially equal to the embodiment 1
except for that a biaxially stretched film (thickness: 30 .mu.m)
which has a melting point different from the melting point of the
biaxially stretched film used in the embodiment 1 is laminated to
the surface of the substrate used in the embodiment 1 at a
temperature of 250.degree. C. A film formed by this embodiment 5
has a melting point of 230.degree. C. and an X-ray diffraction
intensity ratio of I.sub.A/I.sub.B is 1.0.
Comparison Example 1
[0154] To one surface of the substrate which is substantially equal
to the substrate used in the embodiment 1, a non-oriented film
(thickness: 30 .mu.m) formed of a polyethylene terephthalate/iso
phthalate (PET/I) for copolymer resin containing 10 molecular % of
isophthalic acid as a copolymer content is laminated at a
temperature of 210.degree. C. thus manufacturing a resin-coated
aluminum plate. This film has a melting point of 210.degree. C. and
no peaks are detected with respect to the X-ray diffraction
intensities I.sub.A and I.sub.B.
[0155] The resin-coated aluminum plate obtained in the
above-mentioned manner is subject to the forming in the same manner
as the resin-coated aluminum plate in the embodiment 1 thus
manufacturing the rectangular can substantially equal to the
rectangular can manufactured in the embodiment 1.
Comparison Example 2
[0156] This comparison example 2 is substantially equal to the
comparison example 1 except for that a biaxially stretched film
(thickness: 30 .mu.m) which has a melting point different from the
melting point of the biaxially stretched film used in the
comparison example 1 is laminated to the surface of the substrate
used in the comparison example 1 at a temperature of 240.degree. C.
A film formed by the comparison example 2 has a melting point of
240.degree. C. and an X-ray diffraction intensity ratio of
I.sub.A/I.sub.B is 6.0.
Comparison Example 3
[0157] This comparison example 3 is substantially equal to the
comparison example 1 except for that a biaxially stretched film
(thickness: 30 .mu.m) of polyethylene terephthalate (PET) is
laminated to the surface of the substrate used in this comparison
example 1 at a temperature of 260.degree. C. A film formed by this
comparison example 3 has a melting point of 255.degree. C. and an
X-ray diffraction intensity ratio of I.sub.A/I.sub.B is 10.0.
Comparison Example 4
[0158] This comparison example 4 is substantially equal to the
comparison example 1 except for that a biaxially stretched film
(thickness: 30 .mu.m) which has a melting point different from the
melting point of the biaxially stretched film used in the
comparison example 1 is laminated to the surface of the substrate
used in the comparison example 1 at a temperature of 260.degree. C.
A film formed by this comparison example 4 has a melting point of
230.degree. C. and an X-ray diffraction intensity ratio of
I.sub.A/I.sub.B is 0.5.
(Evaluation Method)
[0159] A corrosive electrolytic solution containing a propylene
carbonate salt as a main component is filled in the inside of
rectangular cans (battery containers) of embodiments and comparison
examples manufactured in the above-mentioned manner, and these
samples are left at a temperature of 80.degree. C. for 30 days to
evaluate the corrosion resistance (an accelerated test
corresponding to a product long-period preservation test). Here,
the battery containers for evaluation are sealed without forming
through holes in the top lid and the bottom lid. The evaluation is
performed on 10 pieces of battery containers for each of these
embodiments and comparison examples.
(Evaluation Result)
[0160] According to a result of the evaluation, with respect to the
battery containers of the embodiments 1 to 5, by setting the X-ray
diffraction intensity ratio I.sub.A/I.sub.B to values which fall
within a range from 1.0 to 5.0, neither discoloring nor floating of
film is found on an inner surface of the container even the
container is preserved for a long period thus achieving the
excellent evaluation on corrosion resistance. Further, also at the
time of forming the container, neither floating of film (peeling)
nor whitening is found thus also exhibiting excellent
formability.
[0161] On the other hand, with respect to the containers which use
the non-oriented resin film in the comparison example 1, floating
of film is found on an inner surface of the container and it is
estimated that an inner-surface film is peeled with lapse of time.
Further, also with respect to the containers of the comparison
examples 2 to 4, at the time of forming the containers, floating of
film and whitening are found thus exhibiting poor corrosion
resistance.
[0162] Although the evaluations on discoloring and floating of film
are performed by observing with naked eyes the inner surfaces of
the containers by discharging the electrolytic solution after
performing the product long-period reservation test. A result of
the test is shown in Table 1.
TABLE-US-00001 TABLE 1 heat treatment temperature corrosion
resistance polyester film lamination formability (80.degree. C./30
days) resin melting point temperature drawing expansion bead flange
floating composition (.degree. C.) (.degree. C.) I.sub.A/I.sub.B
forming forming forming forming discolored of film Embodiment PET/I
240 245 5.0 G G G G G G 1 Embodiment PET/I 230 230 4.0 G G G G G G
2 Embodiment PET/I 230 235 3.5 G G G G G G 3 Embodiment PET/I 230
240 2.0 G G G G G G 4 Embodiment PET/I 230 250 1.0 G G G G G G
Comparison PET/I 210 210 no G G G G G B Example 1 (non-oriented)
peak Comparison PET/I 240 240 6.0 G film-floating: film-floating: G
G F Example 2 trivial trivial Comparison PET 255 260 10.0 film B
not not not not Example 3 floated evaluated evaluated evaluated
evaluated Comparison PET/I 230 260 0.5 film crack: film film G G F
Example 4 trivial whitening: whitening; trivial trivial PET:
polyethylene terephthalate PET/I: polyethylene
terephthalate/isophthalate copolyester G: good F: fair B: bad
INDUSTRIAL APPLICABILITY
[0163] As has been explained heretofore, although a conventional
three-piece rectangular can having a top lid and a bottom lid forms
a seam by joining on a can body portion, a three-piece rectangular
can of the present invention having a rectangular can body portion,
a top lid and a bottom lid has no seam by joining on the can body
portion and hence, there is no possibility of the generation of
cracks attributed to a defect of a joint portion which is liable to
be generated at the time of performing bead forming or the like.
Further, when the three-piece rectangular can of the present
invention is applied to a casing of an electric double-layered
capacitor or the like, a surface area of the casing is increased
and hence, the heat dissipation is increased whereby the
deterioration of the battery performance and the can body can be
prevented. Accordingly, the three-piece rectangular can of the
present invention can cope with the high performance which is
required by various casings for electric equipment and batteries of
nowadays. Further, the present invention can provide the battery
containers which exhibit high corrosion resistant at a low
cost.
* * * * *