U.S. patent application number 11/499085 was filed with the patent office on 2008-02-07 for metal/plastic containers with reinforcing ribs and drawing and ironing.
This patent application is currently assigned to Rexam Beverage Can Co.. Invention is credited to David Reimer, Thomas T. Tung.
Application Number | 20080029523 11/499085 |
Document ID | / |
Family ID | 38608956 |
Filed Date | 2008-02-07 |
United States Patent
Application |
20080029523 |
Kind Code |
A1 |
Tung; Thomas T. ; et
al. |
February 7, 2008 |
Metal/plastic containers with reinforcing ribs and drawing and
ironing
Abstract
A container is provided having a can body defining an interior
region for containing a product. The can body is of a metal/plastic
multi-layer structure construction. The can body includes a side
wall, a bottom profile comprising an annular rim defining a stand
for the can body, an outer transition portion integral with the
annular rim, and an inner transition portion connecting the annular
rim to a central dome portion. In one embodiment a plurality of
reinforcing ribs e.g., between 15 and 120, inclusive, are formed in
the metal/plastic multi-layer structure in at least one of the
outer transition portion and the inner transition portion. The ribs
are formed in a spaced apart relation around the perimeter of such
portion(s). In another embodiment a can body is made from a metal
plastic laminate which is drawn and ironed. In one embodiment, the
upper portion is die necked in a plurality of necking steps. In
another embodiment, a cone top having threads for receiving a
threaded closure is attached to the metal/plastic can body.
Inventors: |
Tung; Thomas T.;
(Barrington, IL) ; Reimer; David; (Elgin,
IL) |
Correspondence
Address: |
MCDONNELL BOEHNEN HULBERT & BERGHOFF LLP
300 S. WACKER DRIVE, 32ND FLOOR
CHICAGO
IL
60606
US
|
Assignee: |
Rexam Beverage Can Co.
Chicago
IL
|
Family ID: |
38608956 |
Appl. No.: |
11/499085 |
Filed: |
August 4, 2006 |
Current U.S.
Class: |
220/608 |
Current CPC
Class: |
B65D 1/165 20130101;
B65D 1/46 20130101 |
Class at
Publication: |
220/608 |
International
Class: |
B65D 6/28 20060101
B65D006/28 |
Claims
1. A container comprising: a can body defining an interior region
for containing a product, the can body formed from a metal plastic
multi-layer structure material; wherein the can body comprises a
side wall and a bottom profile comprising an annular rim defining a
stand for the can body, an outer transition portion integral with
the annular rim, a central dome portion and an inner transition
portion connecting the annular rim to the central dome portion;
wherein a plurality of reinforcing ribs are formed in the metal
plastic multi-layer structure in at least one of the outer
transition portion and the inner transition portion, said ribs
formed in a spaced apart relation around the perimeter of such
portion(s).
2. The container of claim 1, wherein the reinforcing ribs are
formed in both the outer transition portion and the inner
transition portion.
3. The container of claim 1, wherein reinforcing ribs are formed in
the inner transition portion, each of the reinforcing ribs projects
inwardly towards the interior of the can body and has a variable
depth with a maximum depth D, and wherein the maximum depth D of
the ribs is located substantially at the center the curve defining
the inner transition portion.
4. The container of claim 1, wherein reinforcing ribs are formed in
the outer transition portion, each of the reinforcing ribs projects
inwardly towards the interior of the can body and has a variable
depth and a maximum depth, and wherein the maximum depth D of the
rib is located substantially at the center of the curve defining
the outer transition portion
5. The container of claim 1, wherein the thickness of the metal in
the metal plastic multi-layer structure in the side wall of the can
body is between 20 and 50 percent of the thickness of the metal of
the starting gauge metal plastic multi-layer structure.
6. The container of claim 1, wherein ratio of the thickness of the
metal in the metal plastic multi-layer structure to the thickness
of the plastic in the metal plastic multi-layer structure is from
between about 0.8 to 1 to about 1 to 3.
7. The container of claim 1, wherein there are between 15 and 120,
inclusive, reinforcing ribs, in the at least one of the outer and
inner transition portions.
8. The container of claim 2, wherein there are between 15 and 120,
inclusive, reinforcing ribs in both the outer and inner transition
portions.
9. The container of claim 1, wherein the plastic in the metal
plastic multi-layer structure comprises polyethylene terepthalate
(PET).
10. The container of claim 3, wherein ribs have a variable depth
and wherein the maximum depth of the ribs is between about 0.5 and
about 7 times the thickness of starting gauge of the metal plastic
multi-layer structure.
11. The container of claim 1, wherein the container comprises a
container for a pressurized beverage.
12. The container of claim 1, wherein the plurality of reinforcing
ribs are formed in a forming step forming the bottom profile.
13. The container of claim 1, wherein the annular rim has a radius
of curvature and wherein said radius of curvature is less than
0.040 inches.
14. The container of claim 1, wherein the ribs have a length and a
width and wherein the length and width of the ribs is between about
3 and about 10 times the starting gauge thickness of the metal
plastic multi-layer structure.
15. The container of claim 14, wherein the ribs have a variable
depth and wherein the maximum depth of the ribs is between about
0.5 and about 7 times the starting gauge thickness of the metal
plastic multi-layer structure.
16. A method of making a metal plastic multi-layer structure can
body from a multi-layer structure material having an aluminum alloy
layer and a plastic layer, comprising the steps of: drawing the
multi-layer structure material into a cup; drawing and ironing the
cup to form a can body having a sidewall; forming a bottom profile
on the can body, wherein the bottom profile comprises an annular
rim defining a stand for the can body, an outer transition portion
integral with the annular rim, a central dome portion and an inner
transition portion connecting the annular rim to the central dome
portion; and wherein the forming step further comprises the step of
forming a plurality of reinforcing ribs in the aluminum alloy and
plastic multi-layer structure in at least one of the outer
transition portion and the inner transition portion, said ribs
formed in a spaced apart relation around the perimeter of such
portion(s).
17. The method of claim 16, wherein the reinforcing spaced ribs are
formed in both the outer transition portion and the inner
transition portion.
18. The method of claim 16, wherein there are between 15 and 120,
inclusive, reinforcing ribs, in the at least one of the outer and
inner transition portions.
19. The method of claim 16, wherein there are between 15 and 120,
inclusive, reinforcing ribs in both the outer and inner transition
portions.
20. The method of claim 16, wherein ribs have a variable depth and
wherein the maximum depth of the ribs is between about 0.5 and 7
times the thickness of starting gauge of the multi-layer structure
material.
21. The method of claim 16, wherein the can body comprises a
container for a pressurized beverage.
22. The method of claim 16, wherein the plurality of reinforcing
ribs are formed in a forming step forming the bottom profile.
23. The method of claim 16, wherein the annular rim has a radius of
curvature and wherein said radius of curvature is less than 0.040
inches.
24. The method of claim 16, wherein the ribs have a length and a
width and wherein the length and width of the ribs is between about
3 and about 10 times the starting gauge thickness of the metal
plastic multi-layer structure material.
25. The method of claim 24, wherein the ribs have a variable depth
and wherein the maximum depth of the ribs is between about 0.5 and
7 times the starting gauge thickness of the metal plastic
multi-layer structure material.
26. The method of claim 16, wherein the forming step comprises the
step of forming the reinforcing ribs in the inner transition
portion, each of the reinforcing ribs projecting inwardly towards
the interior of the can body and having a variable depth, and
wherein the maximum depth D of the ribs is located substantially at
the center of the curvature defining the inner transition
portion.
27. The method of claim 16, wherein the forming step comprises the
step of forming the reinforcing ribs in the outer transition
portion, each of the reinforcing ribs projecting inwardly towards
the interior of the can body and having a variable depth, and
wherein the maximum depth of the ribs is located substantially at
the center of the curvature defining the outer transition
portion.
28. The method of claim 16, wherein the drawing and ironing step
further comprises the step of reducing the thickness of the metal
in the metal plastic multi-layer structure in the side wall of the
can body to between 20 and 50 percent of the thickness of the metal
of the starting gauge metal plastic multi-layer structure.
29. A method of making a metal plastic multi-layer structure can
body from a multi-layer structure material including an aluminum
alloy layer and a plastic layer, comprising the steps of: drawing
the multi-layer structure material into a cup; drawing and ironing
the cup to form a can body having a sidewall; forming a bottom
profile on the can body, wherein the bottom profile comprises an
annular rim defining a stand for the can body, an outer transition
portion integral with the annular rim, a central dome portion and
an inner transition portion connecting the annular rim to the
central dome portion; and die necking the can body in a multitude
of die necking steps to form a tapered neck portion.
30. The method of claim 29, wherein the forming the bottom profile
step further comprises the step of forming a plurality of
reinforcing ribs in the multi-layer structure in at least one of
the outer transition portion and the inner transition portion, said
ribs formed in a spaced apart relation around the perimeter of such
portion(s).
31. The method of claim 29, wherein the drawing and ironing step
further comprises the step of reducing the thickness of the metal
in the multi-layer structure in the side wall of the can body to
between 20 and 50 percent of the thickness of the metal of the
starting gauge multi-layer structure.
32. The method of claim 29, wherein the step of forming the bottom
profile further comprises the step of forming the annular rim with
a radius of curvature less than 0.040 inches.
33. The method of claim 29, wherein the ratio of the thickness of
the plastic in the multi-layer structure to the thickness of the
metal in the multi-layer structure is in the range of between 0.8
to 1 and 3 to 1.
34. The method of claim 16, wherein the ratio of the thickness of
the plastic in the multi-layer structure to the thickness of the
metal in the multi-layer structure is in the range of between 0.8
to 1 and 3 to 1.
35. The method of claim 16, further comprising the step of seaming
a cone top onto the can body.
36. The method of claim 16, further comprising the step of necking
the can body into a bottle configuration with a threaded neck.
37. The method of claim 29, wherein the necking step comprises the
step of necking the sidewall to have a bottle configuration having
a threaded top for receiving a threaded closure.
38. The method of claim 30, wherein the step of forming the bottom
profile further comprises the step of forming the annular rim with
a radius of curvature less than 0.040 inches.
39. A method of making a metal plastic multi-layer structure can
body from a multi-layer structure material including an aluminum
alloy layer and a plastic layer, comprising the steps of: drawing
the multi-layer structure mateiral into a cup; drawing and ironing
the cup to form a can body having a sidewall; forming a bottom
profile on the can body, wherein the bottom profile comprises an
annular rim defining a stand for the can body, an outer transition
portion integral with the annular rim, a central dome portion and
an inner transition portion connecting the annular rim to the
central dome portion; and attaching a cone top to the can body.
40. The method of claim 39, wherein the cone top further comprises
integral threads.
41. The method of claim 39, wherein the forming the bottom profile
step further comprises the step of forming a plurality of
reinforcing ribs in the metal/plastic multi-layer structure in at
least one of the outer transition portion and the inner transition
portion, said ribs formed in a spaced apart relation around the
perimeter of such portion(s).
42. The method of claim 39, wherein the step of forming the bottom
profile further comprises the step of forming the annular rim with
a radius of curvature less than 0.040 inches.
43. The method of claim 39, wherein the ratio of the thickness of
the plastic in the multi-layer structure to the thickness of the
metal in the multi-layer structure is in the range of between 0.8
to 1 and 3 to 1.
Description
BACKGROUND
[0001] A. Field
[0002] The invention relates to metal/plastic multi-layer structure
containers, such as containers in the form of can bodies for
containing beer or carbonated beverages wherein the container is
made from a multi-layer structure including a metal layer and
plastic layer.
[0003] B. Related art
[0004] Conventional aluminum beverage cans are made from an
aluminum alloy disc which is drawn into a cup and then subject to
further drawing and ironing into a can body. The can body has a
sidewall and an integral bottom wall. In the drawing and ironing
process, the bottom of the can is formed into a central
inwardly-directed dome configuration and a peripheral, lowermost
annular rim (sometimes referred to as a "stand" or "nose radius")
which forms the structure supporting the can when the can is placed
on a horizontal surface. The bottom portion of the can, including
the dome, annular rim, and adjacent curved wall structures is known
in the art as the "bottom profile."
[0005] Aluminum beverage cans are made in vast quantities. As such,
reducing the cost of the container, by using less raw material, is
an important consideration in the design of beverage cans. If less
raw material is used (i.e., a thinner gauge aluminum disc is used),
the sidewall and bottom wall are thinner for a can of the same
capacity or volume and external dimensions. Generally speaking,
thinner gauge and reduced sidewall and bottom wall thickness
negatively impact the strength of the can and its ability to
contain a highly pressurized product without deformation of the
bottom profile. The industry has established strength tests for
beverage cans, including a buckle test, a drop test and a dome
growth test. These tests are described in the patent and technical
literature and persons skilled in the art are familiar with them.
The specific design of the bottom profile is especially important
in designing a can body from thin gauge aluminum alloys that meet
industry standards for can performance.
[0006] The bottom profile of the current drawn and ironed cans is a
performance limitation for avoiding excess deformation of the
container bottom due to the pressure generated by carbonated
beverage contained within the container. Many different can bottom
profile geometries have been proposed to improve the bottom profile
strength while using less raw material for the can body. One
technique is to perform a reforming operation on the bottom
profile. U.S. Pat. Nos. 5,222,385 and 5,697,242, both assigned to
American National Can Co., describe a can body reforming apparatus
and methods for reforming can bodies to increase the strength of
the bottom profile.
[0007] Prior art of interest directed to bottoms of containers
includes Werth et al., U.S. Pat. No. 6,736,284 (see FIGS. 4-12);
Chang, U.S. Pat. No. 4,436,216; Silvers et al., U.S. patent
application publication 2002/0074336, Buchner et al., U.S. Pat. No.
3,430,805; Bojanowski, U.S. Pat. No. 3,070,257; and the early
patent to Hadden, U.S. Pat. No. 77,280. The following patents
relate to reinforcing concepts for a dome or lid on a container:
Diamond et al., U.S. Pat. Nos. 5,938,067 and 5,636,761 and Le Bret,
U.S. Pat. Nos. 4,784,282 and 4,697,972.
[0008] The art has also considered forming a beverage container
from a metal and plastic laminate, or metal/plastic/metal laminate.
Prior art of interest includes the patents of McHenry et al., U.S.
Pat. Nos. 6,098,829; 5,862,939; 5,770,290 and 5,782,375 and
published PCT application of Metal Box Ltd., publication no. WO
82/000020. Further patents showing laminated vessels include
Leslie, U.S. Pat. No. 1,662,860; Rownd, U.S. Pat. No. 3,618,807;
Gerek et al., U.S. Pat. No. 3,947,617; Seaborne et al., U.S. Pat.
No. 4,874,618; Miyazawa et al., U.S. Pat. No. 5,753,328, Ohara et
al., U.S. Pat. No. 4,937,110 and Yamada et al., U.S. Pat. No.
5,769,262.
[0009] By using a metal plastic multi-layer structure as a starting
material for a beverage can body, in theory one may reduce the
overall cost of the can since the amount of metal in the
multi-layer structure is reduced as compared to the amount of metal
in an all-metal can, and the added plastic material is less costly
than the amount of metal that is saved. However, a metal plastic
multi-layer structure container suitable for commercial use in
packaging beer, carbonated beverages and other beverage products
must meet certain strength and performance requirements. One aspect
of the present disclosure provides for beverage can bodies made
from a metal plastic multi-layer structure which are expected to
meet industry strength requirements but also cost less then
conventional all-aluminum drawn and ironed can bodies.
SUMMARY
[0010] In a first aspect, a container, e.g., for a beverage product
such as juice, beer, or carbonated beverage, is provided. The
container includes a can body defining an interior region for
containing a product. The can body is made from a metal/plastic
multi-layer structure construction, e.g., a metal such as aluminum
alloy layer which has a layer of plastic material such as PET
bonded to it. The "multi-layer structures" of this disclosure
encompass structures where the layers are adhered to one another
regardless of whether it is by extrusion, co-extrusion, thermal
bonding, in addition to laminates or use of an adhesive layer to
bond a metal layer to a plastic layer.
[0011] The can body further includes a side wall, and a bottom
profile comprising an annular rim defining a stand for the can
body, an outer transition portion integral with the annular rim
portion, and an inner transition portion connecting the annular rim
to a central dome portion. Metal plastic multi-layer structure can
bodies can be made which substantially reduce the amount of metal
used in the can body. However, multi-layer structure structures
with less metal face a potential problem of not having adequate
strength to pass industry standard tests such as drop and buckle
tests for carbonated beverage containers. To overcome this
potential problem, a plurality of reinforcing ribs are formed in
the plastic/metal multi-layer structure in at least one of the
outer transition portion and the inner transition portion, the ribs
formed in a spaced apart relation around the perimeter of such
portion(s).
[0012] The rib design in the metal/plastic multi-layer structure
can body improves the strength of the container bottom, e.g., when
used to store pressurized beverages. The rib design is a very cost
effective way to improve the stiffness of a thin wall structure
because the ribs can increase the equivalent wall thickness to
provide better rigidity at those areas subject to highest
stress--namely at the inner and outer transition portions. In one
embodiment, the ribs are positioned at both the outer transition
portion and at the inner transition portion. Furthermore, in
preferred embodiments the outside perimeter of the annular rim
provides the same contour for stacking of such cans with
conventional all-aluminum beverage cans and with cans with the
plastic/metal multi-layer structure.
[0013] As noted above, the provision of metal plastic multi-layer
structure with reinforced ribs allows a can body to meet industry
standard strength tests while using less metal, allowing for
substantial costs savings per container. There are other advantages
that are obtained as well. For example, the plastic layer allows
the manufacturer to avoid providing a spray coating on the inside
of an aluminum container to form a barrier between the product and
the aluminum alloy, since the plastic in the metal plastic
multi-layer structure performs the same function as the spray
coating. However, spray coating required the stand to generally
have a radius of 0.045 inches or more in order to prevent a
shadowing effect for the spray coating in the area of the stand or
annular rim; that is, larger radii for the stand were needed to
insure that the spray coated the entire inner surface of the can
especially in the region of the stand. As the stand radius
increases, it generally weakens the bottom profile of the can. A
can with a large stand radius often required a separate reforming
step to strengthen the bottom profile. However, with the
multi-layer structure container of this disclosure, when the bottom
profile is formed, the stand diameter can have a diameter below
0.040 inches, without worrying about shadowing effects (since the
plastic layer provides the barrier between the product and the
metal), and without requiring any subsequent reforming step.
[0014] In another aspect, a method of making a metal plastic
multi-layer structure can body from a multi-layer structure
material comprising an aluminum alloy layer and a plastic layer is
disclosed, comprising the steps of: drawing the multi-layer
structure material into a cup; drawing and ironing the cup to form
a can body having a sidewall; forming a bottom profile on the can
body, wherein the bottom profile comprises an annular rim defining
a stand for the can body, an outer transition portion connecting
the side wall to the annular rim, a central dome portion and an
inner transition portion connecting the annular rim to the central
dome portion; and wherein the forming step further comprises the
step of forming a plurality of reinforcing ribs in the multi-layer
structure in at least one of the outer transition portion and the
inner transition portion, the ribs formed in a spaced apart
relation around the perimeter of such portion(s).
[0015] In yet another aspect of this disclosure, a method is
disclosed of making a metal plastic can body from a multi-layer
structure material comprising an aluminum alloy layer and a plastic
layer, comprising the steps of: drawing the multi-layer structure
material into a cup; drawing and ironing the cup to form a can body
having a sidewall; forming a bottom profile on the can body,
wherein the bottom profile comprises an annular rim defining a
stand for the can body, an outer transition portion connecting the
side wall to the annular rim, a central dome portion and an inner
transition portion connecting the annular rim to the central dome
portion; and die necking the can body in a multitude of die necking
steps to form a tapered neck portion. The tapered neck portion may
have a substantially reduced diameter in a bottle configuration or
a slightly reduced diameter neck configuration and a flange for
attaching an end to the can body in conventional fashion. In an
alternative embodiment, instead of necking the can body, a cone top
is attached to the can body.
[0016] In one embodiment, the forming step involves forming a
plurality of reinforcing ribs in the metal/plastic multi-layer
structure in at least one of the outer transition portion and the
inner transition portion. The ribs are formed in a spaced apart
relation around the perimeter of such portion(s). In one embodiment
the ribs have a variable depth and wherein the maximum depth of the
ribs is between 0.5 and 7 times the starting gauge thickness of the
metal plastic laminate.
[0017] In one embodiment, the drawing and ironing step further
comprises the step of reducing the thickness of the metal in the
metal plastic multi-layer structure in the side wall of the can
body to between 20 and 50 percent of the thickness of the metal of
the starting gauge metal plastic multi-layer structure. In another
embodiment, the step of forming the bottom profile further
comprises the step of forming the annular rim with a radius of
curvature less than 0.040 inches.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a perspective view of a metal/plastic laminate can
body with a bottom profile having reinforcing ribs in one
embodiment of the invention;
[0019] FIG. 2 is a side elevational view of the embodiment of FIG.
1;
[0020] FIG. 3 is a cross-sectional view of the embodiment of FIGS.
1 and 2 along the lines 3-3 of FIG. 2;
[0021] FIG. 4 is a more detailed view of a bottom profile for a
container showing the inner and outer transition portions, which
are preferred locations for the reinforcing ribs;
[0022] FIG. 5 is an outline of the shape of a rib;
[0023] FIG. 6 is a perspective, partial cross-section of the
container of FIGS. 1-3 showing the ribs in greater detail;
[0024] FIG. 7 is a further detailed illustration of the stand
portion of the bottom profile of FIG. 4 of a metal plastic laminate
container, showing the stand radius R.sub.s which may be reduced
below 0.040 inches; in FIG. 7 the reinforcing ribs are omitted.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0025] Containers With Reinforcing Ribs
[0026] FIGS. 1-3 illustrate a can body 10 for a beverage container.
The can body 10 defines an interior region for containing a product
such as juice, beer, carbonated beverages, and the like. The can
body is formed from a metal plastic multi-layer structure, as shown
best in FIG. 3. The multi-layer structure comprises a plastic layer
24 such as polyethylene terepthalate (PET) which is adhered to a
sheet of aluminum alloy 22. The plastic layer 24 is on the interior
surface of the can body 10 and the metal layer 22 forms the
exterior surface of the can body 10. The "multi-layer structure"
would encompasses structures where the layers 22 and 24 are adhered
to one another regardless of whether it is by extrusion,
co-extrusion, thermal bonding, in addition to a laminate of layers
22 and 24 or use of an adhesive layer to bond a plastic layer 24 to
the metal layer 22.
[0027] The can body 10 comprises a side wall 12 and a bottom
profile generally designated at 14. The bottom profile 14 includes
an annular rim 18 defining a stand for the can body. A shown in
FIG. 4, the bottom profile 14 includes chime portion 26, heel
portion 28 and an outer transition portion or zone 30 integral with
the annular rim connecting the heel portion 28 to the annular rim
or stand 18. The bottom profile further includes a central dome
portion 20 and an inner transition portion or zone 32 connecting
the annular rim 18 to the central dome portion 20.
[0028] Referring again to FIGS. 1-3, a plurality of reinforcing
ribs 16 are formed in the metal plastic multi-layer structure in at
least one of the outer transition portion 30 and the inner
transition portion 32. The ribs are formed in a spaced apart
relation around the perimeter of such portion(s). In the embodiment
of FIGS. 1 and 3, the reinforcing ribs are formed in both the outer
transition portion 30 and the inner transition portion 32. The ribs
16 project inwardly towards the interior of the can body and are
formed in the can body in the same forming operation which forms
the bottom profile.
[0029] As perhaps shown best in FIG. 6, in one possible embodiment,
the reinforcing ribs 16 are formed in the inner transition portion
32, such that each of the reinforcing ribs 16 projects inwardly
towards the interior of the can body 10, and has a variable depth
with a maximum depth D. The maximum depth D of the ribs is
preferably located at a point which is substantially at the center
of the curvature defining the inner transition portion 32. This
point where the maximum depth of the rib is located is shown as
point 16A in FIG. 4. This design increases the stiffness of the
bottom profile in the area where the stress is high (the center of
the transition) and where the need for increasing strength is
important.
[0030] In another possible embodiment also illustrated in FIG. 6,
reinforcing ribs 16 are formed in the outer transition portion 30,
each of the reinforcing ribs 16 projects inwardly towards the
interior of the can body and has a variable depth and a maximum
depth, and wherein the maximum depth D of the ribs is located
substantially at the center of the curvature defining the outer
transition portion 30. This point where the maximum depth of the
rib 16 is located is shown as point 16B in FIG. 4. The ribs achieve
a maximum depth of preferably between about 0.5 and about 7 times
the thickness of starting gauge of the metal plastic multi-layer
structure.
[0031] In the illustrated embodiment, reinforcing ribs are shown in
the both the inner and outer transition zones 32 and 30. However,
in one possible embodiment the ribs are formed in just one of the
inner and outer transition zones. The number of ribs in each of the
inner transition zone or outer transition zone is variable, and may
be between 15 and 120, inclusive. The number will vary depending on
such factors as the size of the container, the depth and size of
the ribs, and the thickness of the metal in the metal plastic
multi-layer structure.
[0032] In one embodiment, as shown in FIG. 5, the ribs have a
length L and a width W (defined as the direction extending
circumferentially around the transition zone), and wherein the
length and width of the ribs is between about 3 and about 10 times
the starting gauge thickness of the metal plastic multi-layer
structure.
[0033] The geometry of the ribs is not believed to be particular
critical. Generally, oval or elliptical shaped ribs (in a plane
where the ribs intersect the bottom profile), such as shown in FIG.
5, are believed suitable. The ribs need not be perfectly
symmetrical. Preferably, the ribs are oriented such that the length
of the ribs extends along a direction in a plane that contains the
longitudinal axis of the can body (i.e., the ribs follow the
contour of the transition zone). However, the ribs could be
oriented such that they are not aligned substantially in this
plane, such as in alternating arrangement with pairs of adjacent
ribs oriented in a V configuration, all the ribs tilted one way or
the other, or groups of ribs tilted one way and an adjacent group
of ribs tilted in the other direction.
[0034] Because the metal plastic multi-layer structure container
does not include or require a spray coating on the inside of the
container to form a barrier between the metal and the product, the
radius of curvature of the stand portion 18 may be reduced from
what it has been heretofore, since the requirement of avoiding
spray shadowing (leading to larger radii) is not present. In
particular, the embodiments disclosed herein may have a stand
radius R.sub.s (FIG. 7) which is less than 0.040 inches, such as
between 0.035 and 0.039 inches. The tighter radius R.sub.s produces
a stiffer, stronger can in the region of the stand.
[0035] Metal plastic multi-layer structure containers as described
herein may have sidewall 12 (FIG. 1) in which the metal thickness
in the sidewall is substantially thinner than the starting gauge
thickness of the metal in the metal plastic multi-layer structure.
Such reduction in thickness allows the use of less metal in the
container. The sidewall thickness is reduced by drawing and
ironing, using conventional drawing and ironing tooling, as
explained in the sections below. In one embodiment, the thickness
of the metal in the metal plastic multi-layer structure in the side
wall 12 of the can body is between 20 and 50 percent of the
thickness of the metal of the starting gauge metal plastic
multi-layer structure. For example, if the starting gauge thickness
of the metal in the metal plastic multi-layer structure is 10
units, the sidewall may be reduced to between 2 and 5 units of
thickness.
[0036] The starting gauge metal plastic multi-layer structure will
preferably have a ratio of the thickness of the metal to the
thickness of the plastic from between about 0.8 to 1 to about 1 to
3 (in other words, the thickness or width of the plastic in the
multi-layer structure is between about 0.8 and three times the
thickness of the aluminum alloy).
[0037] Table 1 is a table listing the thicknesses of various
portions of the drawn and ironed can body, with "base" being
measured in the region of the dome 20 (this dimension is not
thinned from drawing and ironing, and is equivalent to starting
gauge thickness of the metal plastic multi-layer structure),
"mid-wall" being the portion of the sidewall above the bottom
profile and below the top of the can, generally in the middle 2/3
of the can side wall, and "top-wall" being defined as that portion
of the side wall at the top of the sidewall in the area where
necking occurs.
TABLE-US-00001 TABLE 1 Total thickness PET Aluminum PET to Aluminum
Thickness mils mils mils thickness ratio Base 18 11 7 1.6 Mid-wall
4.5 2.7 1.8 1.5 Top-wall 7.4 4.5 2.9 1.6
In general, the ratio of dome thickness to mid-wall thickness
ranges from about 2 to 1 to 5 to 1. The ratio of PET thickness to
aluminum thickness ranges from about 0.8 to 1 to about 3 to 1.
[0038] Oblong or elliptical-shaped reinforce ribs 16 may be located
on either or both transition sections 30 and 32. Such transition
sections define the area where the bottom dome 20 or the sidewall
chime 26 meets the stand 18 at the base of the can. The reinforcing
rib 16 has shallower deformation at its perimeter and with greatest
deformation and maximum depth toward the middle of the rib but not
necessarily at its geometric center. In one embodiment, the rib
only has one intersection through the total wall thickness section
with a line parallel to the axis of the container at a given
azimuthal and radial position.
[0039] The following numbers are typical preferred rib dimensions
for the rib geometries. The dimensions of ribs length and width
range from 3 to 10 times of total base wall thickness and the depth
at its greatest deformation range from 0.5 to 7 times of total base
total thickness. The measurements are from its perimeter or
mid-plane of the ribs with both inward and outward sections. For an
18 mils thick dome, the ribs dimension length and width range from
54 mils to 180 mils, and the greatest deformations range from 9
mils to 126 mils. The total number of ribs in a given container may
range from 15 to 120 for the above example. Equivalently, the ribs
are spread about the periphery of the transition zone with one rib
every 3 degrees to every 24 degrees. Depending on the size of the
container, the number of ribs range from 2 to 22 per inch along the
direction of the circumference of the transition portion 30 or
32.
[0040] Methods for Making Metal Plastic Multi-Layer Structure
Containers With Reinforcing Ribs
[0041] Methods of making a metal plastic multi-layer structure can
body from a multi-layer structure having a metal layer such as an
aluminum alloy layer and a plastic layer are described herein. The
metal plastic multi-layer structure is obtained from a supplier in
the form of a web or coil, for example as a metal plastic laminate,
with a plastic layer such as PET adhered to a layer of aluminum
alloy. The ratio of the thickness of the plastic to the thickness
of the metal can vary, but in one possible embodiment is in the
range of between about 0.8 to 1 and 3 to 1. The methods of making
such a metal plastic multi-layer structure material is known in the
art and described in the patent literature, hence a detailed
description is omitted from this document for the sake of
brevity.
[0042] Disks are then cut from the web of multi-layer structure
material. The disk is then drawn into a cup using a conventional
cup forming machine known in the beverage can art. The cup is then
drawn and ironed in a can body maker to form a can body having a
sidewall, again using conventional drawing and ironing tooling
known in the beverage can art. No special modification to the cup
forming or drawing and ironing tooling is presently believed
required to accommodate the multi-layer structure material, except
perhaps for change in the surface finish to the tooling on the
plastic side of the multi-layer structure.
[0043] The drawing and ironing tooling includes a forming tool for
forming a bottom profile in the can body. The bottom profile
comprises an annular rim defining a stand for the can body, an
outer transition portion connecting the side wall to the annular
rim, a central dome portion and an inner transition portion 32
connecting the annular rim 18 to the central dome portion 20, and
the bottom profile 14 may have the form generally shown in FIGS. 3
and 4, although the specifics of the bottom profile are not
considered critical. The forming step further comprises the step of
forming a plurality of reinforcing ribs 16 in the aluminum alloy
and plastic multi-layer structure in at least one of the outer
transition portion 30 and the inner transition portion 32, the ribs
formed in a spaced-apart relation around the perimeter of such
portion(s). The forming step is provided by including rib
protrusion features in the bottom profile forming die which produce
inwardly-directed ribs in the bottom profile as shown in FIGS. 3
and 6. The forming of the bottom profile and the ribs thus occurs
at the same time in the same tooling.
[0044] As noted above and shown in FIG. 6, in one embodiment the
reinforcing ribs 16 are formed in both the outer transition portion
and the inner transition portion. The number of ribs in the inner
transition portion 32 or the outer transition portion 30 is
generally variable but may be between 15 and 120, inclusive,
depending on factors such as the size of the ribs, the size of the
containers, the base metal thickness and other factors. The ribs 16
may have the geometrical considerations as explained above.
[0045] The drawing and ironing process reduces the thickness of the
metal in the side wall portion of the container 10 such that the
thickness in the sidewall is preferably between twenty percent and
fifty percent of the starting gauge thickness of the metal plastic
multi-layer structure disk.
[0046] After forming the ribs 16 and the bottom profile 14, the
container is removed from the drawing and ironing tooling and sent
to a trimming station and then to a washing station, and then to a
conventional die necking station, where a can body is subject to a
plurality of necking operations (e.g., 10 or more) to form a
tapered neck portion. Such die necking is also well known in the
art and will not be described here for sake of brevity. After die
necking, a flange is formed on the upper edge of the container for
seaming an end onto the top of the container, also
conventional.
[0047] In one variation, the neck of the container is die necked
into a tapered bottle shape, with a relatively narrow neck or
chimney at the top having threads (possibly of lug type) for
receiving a threaded closure. In one further variation, the can
body is not necked. A flange is formed at the top of the can body
and a cone top is seamed onto the top of the flange, as disclosed
in U.S. Pat. Nos. 6,010,028 and 6,010,026, the contents of which
are incorporated by reference herein. The cone top, which includes
a neck feature, may optionally include a sleeve, having threads or
lugs, that fits over the neck, or the threads may be formed
integrally in the neck of the cone top.
Methods for Making Drawn and Ironed Metal Plastic Multi-Layer
Structure Containers
[0048] In a further aspect of this disclosure, a method of making a
metal plastic multi-layer structure can body from a multi-layer
structure material including an aluminum alloy layer and a plastic
layer is disclosed. The metal plastic multi-layer structure is
obtained from a supplier in the form of a web or coil of metal
plastic multi-layer structure material with a plastic layer such as
PET adhered to a layer of aluminum alloy. The ratio of the
thickness of the plastic to the thickness of the metal is
preferably in the range of between about 0.8 to 1 and 3 to 1.
[0049] A disk is cut from the web. The method includes the steps of
drawing the multi-layer structure material (disk) into a cup;
drawing and ironing the cup in a can body maker (known in the art)
to form a can body 10 having a sidewall 12; and forming an integral
bottom profile 14 on the can body, wherein the bottom profile
comprises an annular rim 18 defining a stand for the can body, an
outer transition portion 30, a central dome portion 20 and an inner
transition portion 32 connecting the annular rim 18 to the central
dome portion. The bottom profile is formed in the can body in the
can body maker as is conventional in the art.
[0050] In one embodiment, a cone top is secured such as by seaming
onto the can body. The cone top can have integral threads for
receiving a threaded closure cap or may incorporate a plastic
sleeve which has threads.
[0051] In one alternative embodiment, the can body is die neck in a
plurality of die necking steps to form a tapered neck portion, such
as 10 or 20 necking steps. In one possible configuration, the
tapered neck portion may be like that shown in FIG. 3 (receiving a
conventional end), and the process may include a flange forming
operation which forms an outwardly directed conventional flange for
seaming the end onto the can body. In another possible
configuration, the die necking may taper the can body to a bottle
configuration which has a relatively narrow chimney or neck with
threads for receiving a conventional threaded closure cap.
[0052] In one possible embodiment, depending on the strength
requirements of the container and factors such as the thickness of
the multi-layer structure, the step of forming the bottom profile
optionally comprises the step of forming a plurality of reinforcing
ribs in the metal/plastic multi-layer structure in at least one of
the outer transition portion and the inner transition portion, the
ribs formed in a spaced apart relation around the perimeter of such
portion(s). The ribs may have the features disclosed above, such as
for example a variable depth and wherein the maximum depth of the
ribs is between 0.5 and 7 times the starting 5 gauge thickness of
the metal plastic multi-layer structure
[0053] In one preferred embodiment, the drawing and ironing step
further comprises the step of reducing the thickness of the metal
in the metal plastic multi-layer structure in the side wall of the
can body to between twenty and fifty percent of the thickness of
the metal of the starting gauge metal plastic multi-layer
structure.
[0054] In another embodiment, the step of forming the bottom
profile further comprises the step of forming the annular rim with
a radius of curvature less than 0.040 inches.
[0055] While presently preferred and alternative embodiments have
been described, variation from the illustrated embodiments is
possible without departure from the scope of the invention. The
scope is to be determined by reference to the appended claims. As
used herein, the term metal/plastic multi-layer structure is
intended to encompass both two layer multi-layer structure
constructions (one layer metal, the other plastic) as well as
metal/plastic multi-layer structures which have an additional metal
layer, the plastic sandwiched between opposed metal layers.
* * * * *