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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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;

FIG. 2 is a side elevational view of the embodiment of FIG. 1;

FIG. 3 is a cross-sectional view of the embodiment of FIGS. 1 and 2 along the lines 3-3 of FIG. 2;

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;

FIG. 5 is an outline of the shape of a rib;

FIG. 6 is a perspective, partial cross-section of the container of FIGS. 1-3 showing the ribs in greater detail;

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_s which may be reduced below 0.040 inches; in FIG. 7 the reinforcing ribs are omitted.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Containers With Reinforcing Ribs

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.

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.

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.

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.

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.

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.

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.

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.

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_s (FIG. 7) which is less than 0.040 inches, such as between 0.035 and 0.039 inches. The tighter radius R_s produces a stiffer, stronger can in the region of the stand.

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.

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).

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 ⅔ 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 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.

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.

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.

Methods for Making Metal Plastic Multi-Layer Structure Containers With Reinforcing Ribs

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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

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.

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.

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.

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; anddie 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; andattaching 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.