CA1079659A

CA1079659A - Integrally footed container

Info

Publication number: CA1079659A
Application number: CA279,659A
Authority: CA
Inventors: Roger B. Cannon; Arlin L. Campbell
Original assignee: Ball Corp
Current assignee: Ball Corp
Priority date: 1976-07-07
Filing date: 1977-06-01
Publication date: 1980-06-17
Also published as: DE2728511A1; BE856527A; JPS6050654B2; NL7706668A; IT1106752B; JPS538287A; AU2573077A; MX146867A; FR2370645B1; GB1567518A; AU502822B2; DE2728511C2; FR2370645A1

Abstract

ABSTRACT
A can body whose bottom wall is coaxially formed with a ring of individually outwardly convex dimples or feet whose bottom wall is otherwise flat, centrally domed outward or inward, or otherwise formed, provided that after canning is completed, of all the can bottom portions the feet pro-trude furthest outwards to support the can. In the pre-ferred embodiment, the bottom is initially domed inwards and a ring at the outer perimeter of the can bottom pro-trudes furthest outwards. Then, after filling and closing, as the can contents are internally pressurized, e.g. during beer pasteurization, the central dome pops outwards pro-jecting the feet outwards beyond the perimetrical ring.
e body of the can actually grows during pressurization to provide a can of sufficient volume and strength. The overall result of the feet and bottom configuration is to provide a can of thinner material which meets the structural requirements previously met by a convention can manufactured of thicker material.

Description

11;)79~

The present invention relates to the manufacture of metallic containers such as cans.
A significant proportion of foods and beverages, particularly soft drinks and beer are at present packaged in metal cans.
Three-piece cans are made by fabricating a tubular side wall, securing a disk-shaped bottom at one end of the body, filling the can, and securing a di~k~shaped lid at the opposite end of the body.
` Two-piece cans are usually made by deforming a disk-shaped blank into a can body (a tubular sidewall having an integral, disk~shaped bottom at one end), filling the can and securing a disk-shaped lid at the opposite end of the body. The wall of a two-piece can is thinned during forma-tion while the bottom remains ~ubstantially the same thick-ness as the blank from which the can is made. (Terminology used in the industry has not always been unambiguous. Oc-casionally, two-piece cans are termed "one-piece" cans or "seamless" cans, because their can bodies are all one seam-less piece. For purposes of this application, two-piece can and three-piece can terminology will be utilized.) At first, th~ee-piece cans were easier to make in desired sizes and were predominant, however, the apparent attainability of the goal of making more, adequately strong cans, more efficiently encouraged the development of two-piece can technology. As one result, much of the soft drinks and beer is presently being canned in two-piece cans manu-factured by drawing and ironing or drawing and redrawing thin sheet disks of aluminum or steel. The industry is constantly motivated to devise innovative means to manufacture newly

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conceived can body and end structures to reduce the raw materials consumed in can manufacture. Since the yearly consumption of cans for beer and beveragesis substantial any saving in metal consumption is readily translated into a substantial monetary savings.
For whatever reason, the bottoms of cans are pres- ~
ently either substantially flat, or are centrally domed ;
inwards and provided with a perimetrical ring upon which the can stands when supported on a flat surface.
Can bodies are designed to withstand certain pres-sures. Traditionally, beer cans are designed to withstand up to 90 p.s.i. while the actual pressure may be substan-tially less in application. Nevertheless, the cans so fail; the primary source of failure is the bottom of the can. Failure occurs in the form of reversal, a term used to indicate that the inwardly or upwardly domed portion of the can body is distorted to bulge outwardly to cause the can bottom to be uneven.
- It is accordingly an objective of the present inven-tion to provide a stronger can bottom configuration than heretofore attainable with conventional bottom configura-tions.
The present invention provides a metallic can body with a tubular sidewall extending upwards from a bottom end wall, the bottom end wall being provided with two coaxial, radially spaced annular contact bands, the first of these being radially outermost and initially solely effective ~' for supporting the can body upright, and the second of these comprising a plurality of spaced feet, said feet becoming solely effective upon sufficient internal pres-$~ .
' .. , .. . ,. ~ :

surization of the can body as to lower the second annularcontact band below the first.
The present invention further provides a canning operation in which can bodies are being filled with a beverage or the like, closed, and subjected to a further processing step such as pasturization in which pressure within the cans is raised to within a preselected range and each can is tested to determine whether each can has become sufficiently internally pressurized during said further processing step, further comprising the steps of: .
(a) selecting a metallic can body with a tubular sidewall extending upwards from a bottom end wall, the bottom end wall being provided with two coaxial, radially spaced annular contact bands, the first of these being radially outermost and initially solely effective for supporting the can body upright, and the second of these con~prising a plurality of spaced feet, the feet becoming solely effec-tive upon sufficient internal pressurization of the can body as to lower the second annular contact band below the first; and (b) upon conclusion of said further pro-cessing step, sensing, with respect to each can, whether it stands at a height that corresponds to its being sup-ported upon said second annular contact band thereof or at a lesser height that evidences a failure to achieve suffi-cient internal pressurization.
The container is typically a drawn and ironedbeverage can body whose bottom wall is coaxially formed with 3a 10t79659 a ring of individual outwardly convex dimples or feet.
Otherwise, the can bottom wall may be flat, centrally domed outward or inward, provided that after canning i8 completed, of all the can bottom portions the feet protrude furthest outwards to provide a stable support for the can. The bot-tom design disclosed herein may be used on two or three-piece beer and beverage containers, aerosol container~, and other similar pressure restraining containers. ~n the preferred embodiment, the bottom is intially domed inwards and a ring at the outer perimeter of the can ~ottom protrudes furthest outwards. Then, after filling and closing, as the can con-tents are internally pressurized, e.g. during beer pasteuri-zation, the central dome pops outwards projecting the feet outwards beyond the perimetrical ring. The can bottom with feet thereon produces a stronger can if the usual thickness of can stock is used, and can be acceptably strong yet stable if, instead, a thinner can stock is used.
The principles of the invention will be further discussed with reference to the drawing wherein preferred embodiments are shown. The specifics illustrated in the drawing are intended to exemplify, rather than limit, aspects of the invention as defined in the claims.
Figure 1 is a fragmentary longitudinal sestional view of a conventional two-piece, flat-bottom can body, with-out internal pressurization;
Figure 2 is a fragmentary longitudinal sectional view of the conventional can of Figure 1, after internal pressurization of a sufficient magnitude to cause the can bottom to centrally dome outward, creating a rocker;
Figure 3 is a fragmentary longitudinal sectional view of a conventional two-piece, inwardly domed bottom can body, without internal pressurization;
Figure 4 is a bottom plan view thereof;
Figure 5 is a fragmentary longitudinal sectional view of the conventional can of Figures 3 and 4, after inter-nal pressurization of a sufficient magnitude to cause the dome to revert or dome outwardly to produce a distorted rocker-shaped can bottom;
Figures 6and 7 are fragmentary longitudinal sec-tional views of a first embodiment of the can of the inven-tion respectively before and after internal pressurization.
~he remainder of the can above the view may be conventional in structure and appearance~
Figures 8 and 9 are fragmentary longitudinal ~ec-tional views of a second embodiment of the can of the inven-tion respecitvely before and after internal pressurization.
The remainder of the can above the view may be conventional in structure and appearance.
Figure 10 is a longitudinal sectional view of a third and presently preferred embodiment of a can of the present invention, shown filled and closed, but not internal- ~-ly pressurized, so that the feet remain retracted.
Figure 11 is a bottom plan view thereof; and Figure 12 is a longitudinal sectional view of the -can of Figures 10 and 11, following a time when internal pressurization thereof has everted the dome and thereby ex-tended the feet.
Some present can bodies 10 (Figure 1) have a sub-stantially flat bottom 12, which serves adequately if the metallic material of which the can body 10 is formed has 1~7~6S9 such a combination of thickness and stiffness that internal pressure, for instance resul~ing from gas in the canned pro-duct, after the can is filled and closed, domes the can end 12 outwards (Figure 2). Such a distension of the can bottom gives the can an unstable base; it becomes a "rocker" which will not stand stably upright on a flat surface S.
Other present can bodies 14 (Figures 3 and 4) in-itially have a centrally inwardly domed bo'_tom 1~, surrounded by a perimetrically continuous, axially outwardly convex ring 18 where the bottom 16 joins the can sidewall 20. Normally, the ring 18 provides an extensively distributed annular con-tact band in a flat, radiating plane, so that the can will stand stably upright. However, if the metallic material of which the can body 14 is formed has an insufficient strength, or if the internal pressure in the can, once it is filled and closed, becomes too great, the can bottom 16 will evert and the can bottom will become misshapened to thus produce an unstable can. If the eversion does not place the center 24 of the dome axially further out than the contact band 22, the can will continue to have the capability of standing stably upright on a flat surface S. Clearly, a certain mag-nitude of growth upon eversion will place the center 24 axi-ally beyond the contact band 22 (Figure 5) whereupon this can also becomes a "rocker", unable to stand stably upr-ght.
Apparently, a smooth can bottom central region that is surrounded by an unbroken, ring-shaped structure is predispsoed to evert or dome outwards. We have found that this propensity is substantially reduced if the smoothness of the border of the central region of the can bottom is broken-up impressing a plurality of localized dimples or 10~96~

feet therein. By "localized", it is meant that, while the feet may be arranged in a coaxial ring on the can bottom, the feet are a plurality of individuals which are spaced-apart from one another angularly of the can longitudinal axis.
One version of the new can bottom is shown in Figures 6 and 7, a second version is shown in Figures 8 and 9, and a third, presently preferred version, is shown in Figures 10-12.
The can body 30 shown in Figure 6 is just like the one shown in Figure 1, except that the can flat bottom wall 32 has been locally deformed at, for instance, five equi-angularly spaced sites to provide a plurality of axially outwardly projecting individual dimples or feet 34, located intermediate the center 36 and perimeter 38 of the bottom 32.
For instance, the feet may be of circular figure and gener-ally part-spherical profile. Other shapes, such as ovals, tear drops, toroids and generally triangular, rounded-apex star points could be used.
It has been discovered that the exact dimensions, locations, or numbers of the dimples may be critical in that fracture or rupture may occur if certain depth to diameter ratios of the dimples or the ultimate strength of the mate-rial, are exceeded. Otherwise, the present invention in-cludes various arrangements of plural dimples on can bottoms.
Example I
Fourteen drawn and ironed two-piece beverage can bodies 30 manufactured ~rom 16.5 thousandths of an inch thick 3004-Hl9 aluminum alloy to meet United States Brewers Association, Inc. standards for a 211 by 413 can body were ., ~; ., ; :, each impressed with five feet 34, using an internal die with five one-half inch diameter part-spherical foot-formers pro-jecting axially outwards approximately 0.125 inch at their respective centers. A range of pressing forces used among the several cans caused feet of a progression of magnitudes of center depths to be formed. Externally, each can bottom was backed with a die having formed reliefs which matched the internal foot-formers. Five of the fourteen test cans were not tested. On the nine tested, foot-forming die pres-sure ranged between 3500 pounds and 6000 pounds, with an average of 4000 pounds. Individual foot center depths ranged from 0.102 inch on one relatively lightly impressed can, to 0.110 on several cans impressed using at least 4000 pounds.
Each of the nine cans was internally pressurized to 160 pounds per square inch with no indications of metal failures or leaks.
(Usually, beverage cans are not called upon to contain an internal pressure of more than about 100 p.s.i., e.g. when used to contain carbonated soft drinks.) In addition, the nine cans were tested for support stability by standing each upon a flat surface S (Figure 7) and increasing the internal pressure therein until the can bottom centrally domed outwards enough to cause the center ; 36 t~ touch the surface S. That condition was reached at an internal pressurization of from 140 to 155 p.s.i., in proportion to foot depth, at an average of 148 p.s.i. Again, this is a substantially greater internal pressurization than normally present in carbonated beverage cans.
It has been determined, that the cans of this ex-ample, when internally pressurized in the ranges tested ;.

1~79659 'igrow" from about 80 to about 100 thousandths of an inch taller, as a result of centrally outward doming of the can bottom. While that magnitucle of growth, and an attendant increase in can volume is deemed acceptable for a significant segment of the can market, there are some instances where it would be undesirable and that has led to the development of the embodiment shown in Figures 8 and 9.
The can 40 shown in Figures 8 and 9 is identical to the can 30 of Figures 6 and 7, except that in the second embodiment 40, the can bottom wall is even initially gener-ally spherically domed slightly outwards over its full radial exten by, for instance, sixty to seventy thousandths of an inch or so. Accordingly, when the can 40 is filled, closed and internally pressurized to about lO0 p.s.i., it will }5 "grow" only about 20 to 30 thousandths of an inch taller.
That is because the initial doming partially "pre-grows" the can. The can 40 can be made of the same thickness of metal sheet as is presently used to make beverage cans which are similar but for lacking feet, e.g. 16.5 thousandths inch thick sheet. In that case, the can 40 will be st~ronger, and, for instance, able to contain about 148 pounds per square inch internal pressure yet remain stably supported on its feet 44 without its center 46 engaging the support surface S. That compares with about 90-lO0 p.s.i. internal pressure for over-doming protrusion or eversion of an otherwise sim-ilar, conventional domed-bottom but non-footed can.
A can 40 which has a bottom strength more nearly equivalent to conventional domed-bottom cans can be made of thinner sheet, for instance of 13.5 thousandths inch thick 3004-Hl9 aluminum alloy can stock. That results in a saving of from about 11 percent up to a maximum of 18 percent in -can body metal weight. Such a saving in metal weight is estimated to result in a sa~tings of $2.00 per l,G00 cans or $90 million per year for the United States beer and beverage industry.
Note that even before the can 30 of Figures 6 and 7 or can 40 of Figures 8 and 9 is internally pressurized, the feet protrude axially outwards further than the peri-metrically extending ridge where the can body bottom meets the body sidewall. Although there are ma~y instanceq where that will cause no problem, some can makers and canners who would be natural customers for the present invention may have a reason for concern that the protruding feet would cause jamming or erratic conveying on the particular designs of conveyors those can makers or canners have in use at their existing plants.
Also, one must consider the axial compressive stres4 placed on cans when they are being double-seamed at the can-ners. A beverage can may be subjected to as much as 360 pounds axial compressi~e force (typically 250) during filling and double-seaming. Especially where lighter than presently ;
conventional gauge sheet is being used, the feet of the cans of Figures 6-9 could be flattened or crushed somewhat, caus-ing too many rejects.
With a view toward anticipating and overcoming the difficulties set forth in the two foregoing paragraphs, for ~ ances where the prospect of either being a problem is a wQ~risom~ ~dtcr~, ~he present inventors developed their third embodiment, the ane shown in Figures 10-12.
Figures 10-12 bear comparison with Figu~2æ 3-5, : . .. ;: ;;;.. . . .

1~79659 which depict the corresponding conventional can.
In the embodiment 50 of Figures 10-12, the body i8 formed as described above with respect to Figure 3, except that the bottom 52 is provided with a plurality of feet 54 as described above with respect to Figure 6. The radius of the imaginary coaxial circle on which the feet 54 are pro-vided, compared to the magnitude of initial outward concavity of the bottom 52 (Figure 10) and the like center depths of the individual feet 54 is such that, initially, the can bot tom 50 rests on the annular perimetrical rim or band 56 where the bottom 52 joins the sidewall 58. This is important. It means that while such a can is being conveyed at the can making plant, and at the brewers or other cannery, its feet are retracted and not available to foul in conveyors. Ac-cordingly, the can bottom formed as disclosed herein may be used on conventional filling lines without special modifica-tions. Note from Figure 10 that the feet 54 do not extend down to the flat support surface S. It also means that when the can i8 being filled, e.g. with carbonated beverage 60 and being provided with a lid 62, perimetrically seamed thereto at 64 at the opposite end of the can body, the can will have widely distributed, extensive support at 56, which is much like the way and place that conventional cans are supported. See Figure 3.
However, after the cans S0 have been closed and are subjected to internal pressurization, for instance during a conventional canned beer pasteurization step, the initially concave inward (Figure 10) can bottom 52 everts and becomes convex outwards (Figure 12). That excursion which may typi-cally occur at 18-20 p.s.i., causes the feet 54 to extend :
: : .~ .:

10796~9 axially outward further than the band 56, so that the in-ternally pressurized can 50 stably stands via its several feet 54 upon the flat surface S. In this embodiment, the feet may be axially shorter, for instance 80-85 thousandths of an inch in depth, and the can may "grow" as much as about 160 to about 180 thousandths of an inch in height when trans~
forming from its Figure 10 shape to its Figure 12 shape.
Such a gain in height is accompanied by a change in volume that also depends upon the length to diameter ratio of the can. ~ typical increase in contained volume for a can 50 drawn and ironed using equipment normally used to make a 12-ounce, 211 beverage can, i.e., a can having a diameter of 2-11/16 i!~lch, is from about 13.8 ounces to about 14.35 ounces.
These footed cans 50, when made from 13.5 thousandths of an inch thick 3004-Hl9 aluminum alloy can stock, will withstand being internally pressurized up to at least 100 p.s.i., without becoming unstable due to over-doming.
It should be apparent that the principles of the invention will apply equally well no matter what contents 2~ internally pressurize the can. The invention is thus not limited to beer, soft-drink or beverage cans and may find application for aerosol cans as well as other pressurized containers. hikewise, the present invention may be employed in the formation of a three-piece can body to provide similar results.
While a particular alloy in widespread use has been cited in the examples, it is not limiting. The present invention may find equal acceptance in the manufacture of tin-plated steel cans as well as aluminum cans. The inher-ent advantage of the present invention is not dependent upon 10796~i~

the material of which the can is manufactured.
A can bottom according to the present invention may be formed in a separate pressing step, or by appropriate bodymaker tooling modificaitons to include foot-formers to form the feet simultaneously with the can body bottom. Al-ternatively, the feet may be formed in the cup prior to its receipt by the body-maker or as a separate step at the con-clusion of the body-maker stroke. Other means or methods for manufacture of the present invention will occur to those skilled in the art.
One embodiment of the present invention may be utilized to advantage in monitoring or indicating that pre-determined internal pressures have been achieved. The pres-sures may indicate that the contents of the can has gone through certain predetermined heat or pressure ranges to thus indicate pasteurization, pressure utilization or pro-cessing in the form of cooking, blanching or sterilizing.
In a traditional canning operation of carbonated drinks, the can is supplied with a predetermined amount of liquid, the liquid and any resulting foam is permitted to settle and then the can is closed. The head space above the liquid is occupied, traditionally, by carbon dioxide prior to closure. In most beer canning processes, the beer is pastuerized after it is enclosed in the container, Pres-surization of the container^also results after the containeris closed.
In the embodiment of the present invention where the bottom is concave inwardly prior to pressurization, the volume of the container after pressurization is greater than the volume of the container prior to pressurization. Thus, .. . .

the actual head space provided at the mouth of the can body could possibly be reduced knowing that the volume of the can would actually increase after closure. Such reduction in head space may in reality depend upon improved methods of transporting the container after filling and prior to closure or other modifications or improvements of the canning process.
Nevertheless, to further reduce the amount of metal used to manufacture a can and to optimize one use of the present invention, the dimensions of the can body may be modified to selectively provid.e the desired can volume after closure and pressurization.
Modification of can body dimensions could occur in various ways. For example, the length of the body could be varied. Alternatively, the diameter of the body could be decreased or a combination of changes in length and diameter could be selected. The particular change envisioned may de-pend upon customer desire or the desire of the filler not to modify certain structural components of his filling line.
The ultimate result in any case would be a further reduction in metal needed to provide a can of a desired volume. In-herent in meeting this objective is the novel structure dis-closed herein providing a can body which actually "grows"
after closure due to internal pressurization.
Because the integrally footed container can be modified to some extent without departing from the principles of the invention as they have been outlined and explained in this specification, the present invention should be under-stood as encompassing all such modifications as are within the spirit and scope of the following claims.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A metal can body integrally formed from a single piece of metal with a tubular sidewall extending upwards from a bottom end wall, the bottom end wall being provided with two coaxial, radially spaced annular contact bands, the first of these being radially outermost and initially solely effective for supporting the can body upright, and the second of these comprising a plurality of spaced feet, said feet becoming solely effective upon sufficient internal pressurization of the can body as to lower the second annular contact band below the first.

2. The metallic can body of claim 1 in which: the metal of the can body bottom wall is so thin that were the can body lidded, with application of axial compres-sive force, while supported upon the individual feet instead of upon the first annular contact band, the indi-vidual feet would be crushed.

3. The metallic can body of claim 1, wherein: when the first annular contact band is solely effective, the bottom end wall is domed concavely downwards to a greater extent than when the second annular contact band is solely effective.

4. The metallic can body of claim 1, 2 or 3, wherein: when the second annular contact band is solely effective, the bottom end wall is domed convexly down-wards to a greater extent than when the first annular contact band is solely effective.

5. The metallic can body of claim 1, 2 or 3, of aluminum alloy can stock in the can stock thickness range of 16.5-13.5 thousandths of an inch thick.

6. The metallic can body of claim 1, 2 or 3 wherein:
the aluminum alloy is 3004-H19.

7. The metallic can body of claim 1, 2 or 3 wherein the feet are each from about 60 to about 125 thousandths of an inch deep and about one-half inch in width.