GB1567518A

GB1567518A - Integrally footed metal can

Info

Publication number: GB1567518A
Application number: GB2318377A
Authority: GB
Original assignee: Ball Corp
Current assignee: Ball Corp
Priority date: 1976-07-07
Filing date: 1977-06-01
Publication date: 1980-05-14
Also published as: CA1079659A; IT1106752B; NL7706668A; AU2573077A; DE2728511A1; JPS538287A; BE856527A; DE2728511C2; AU502822B2; FR2370645A1; FR2370645B1; JPS6050654B2; MX146867A

Description

(54) INTEGRALLY FOOTED METAL CAN (71) We, BALL CORPORATION, a corporation organised and existing under the laws of the State of Indiana, United States of America, located at 345 South High Street, Muncie, Indiana 47304, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to the manufacture of metallic 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 disk-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 formation while the bottom remains substantially the same thickness as the blank from which the can is made. (Terminology used in the industry has not always been unambiguous.

Occasionally, two-piece cans are termed "one-piece" cans or "seamless" cans, because their can bodies are all one seamless piece. For purposes of this application, two-piece can and three-piece can terminology will be utilized.) At first, three-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 manufactured 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 conceived can body and end structures to reduce the raw materials consumed in can manufacture.Since the yearly consumption of cans for beer and beverages is substantial any saving in metal consumption is readily translated into a substantial monetary savings.

For whatever reason, the bottoms of cans are presently 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 pressures. Traditionally, beer cans are designed to withstand up to 90 p.s.i.

while the actual pressure may be substantially less in application. Nevertheless, the cans do 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.

According to one aspect of the present invention there is provided 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 being discontinuous and comprising a plurality of circumferentially 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.

The container is typically a drawn and ironed beverage can body whose bottom wall is coaxially formed with 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 is completed, of all the can bottom portions the feet protrude furthest outwards to provide a stable support for the can. The bottom design disclosed herein may be used on two or three-piece beer and beverage containers, aerosol containers, and other similar pressure restraining containers. In the preferred embodiment, the bottom is initially domed inwards and a ring at the outer perimeter of the can bottom protrudes furthest outwards.

Then, after filling and closing, as the can contents are internally pressurized, e.g.

during beer pasteurization, 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.

According to another aspect of the present invention there is provided 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 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 being discontinuous and comprising a plurality of circumferentially spaced feet. the feet becoming solely effective 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 processing step, sensing, with respect to each can, whether it stands at a height that corresponds to its being supported upon said second annular contact band thereof or at a lesser height that evidences a failure to achieve sufficient internal pressurization.

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 sectional view of a conventional two-piece, flat-bottom can body, without 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 internal pressurization of a sufficient magnitude to cause the dome to revert or dome outwardly to produce a distorted rocker-shaped can bottom; Figure 6 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 internally pressurized, so that the feet remain retracted.

Figure 7 is a bottom plan view thereof; and Figure 8 is a longitudinal sectional view of the can of Figures 6 and 7, following a time when internal pressurization thereof has everted the dome and thereby extended the feet.

Some present can bodies 10 (Figure 1) have a substantially flat bottom 12, which serves adequately if the metallic material of which the can body 10 is formed has such a combination of thickness and stiffness that internal pressure, for instance resulting from gas in the canned product, after the can is filled and closed, domes the can and 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) initially have a centrally inwardly domed bottom 16, 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 contact 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 magnitude of growth upon eversion will place the center 24 axially beyond the contact band 22 (Figure 5) whereupon this can also becomes a "rocker", unable to stand stably upright.

Apparently, a smooth can bottom central region that is surrounded by an unbroken, ring-shaped structure is predisposed 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 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.

The can body 50 shown in Figure 6 is similar to the one shown in Figure 3, except that the can bottom wall 52 has been locally deformed at, for instance, five equiangularly spaced sites to provide a plurality of axially outwardly projecting individual dimples or feet 54, located intermediate the center and perimeter of the bottom 52. For instance, the feet may be of circular figure and generally 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 material, are exceeded.

Otherwise, the present invention includes various arrangements of plural dimples on can bottoms.

A can which has a bottom strength more nearly equivalent to conventional domedbottom cans can be made of thinner sheet, for instance of 13.5 thousandths inch thick 3004-H19 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 savings of $2.00 per 1,000 cans or $90 million per year for the United States beer and beverage industry.

Also, one must consider the axial compressive stress placed on cans when they are being double-seamed at the canners. A beverage can may be subjected to as much as 360 pounds axial compressive force (typically 250) during filling and doubleseaming. Especially where lighter than presently conventional gauge sheet is being used, the feet of the cans should not project outwardly from the bottom before filling since they could be flattened or crushed somewhat, causing too many rejects. With a view toward anticipating and overcoming the difficulty, for instances where the prospect of either being a problem is a worrisome factor, the present inventors developed the can shown in Figures 6 to 8.

Figures 6 to 8 bear comparison with Figures 3 to 5, which depict the corresponding conventional can.

In the can 50 of Figures 6 to 8, the body is formed as described above with respect to Figure 3, except that the bottom 52 is provided with a plurality of feet 54 arranged in a circle to provide a discontinuous annular contact band. The radius of the imaginary coaxial circle on which the feet 54 are provided, compared to the magnitude of initial outward concavity of the bottom 52 (Figure 6) and the like center depths of the individual feet 54 is such that, initially, the can bottom 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.Accordingly, the can bottom formed as disclosed herein may be used on conventional filling lines without special modifications. Note from Figure 6 that the feet 54 do not extend down to the flat support surface S. It also means that when the can is 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 50 have been closed and are subjected to internal pressurization, for instance during a conventional canned beer pasteurization step, the initially concave inward (Figure 6) can bottom 52 everts and becomes convex outwards (Figure 8). That excursion which may typically occur at 18-20 p.s.i., causes the feet 54 to extend axially outward further than the band 56, so that the internally pressurized can 50 stably stands via its several feet 54 upon the flat surface S. In one embodiment, the feet may be, 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 transforming from its Figure 6 shape to its Figure 8 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.A 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 2-11116 inch, 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 3004-1119 aluminum alloy can stock, will withstand being internally pressurized up to at least 100 p.s.i., without becoming unstable due to over-doming. The feet may be 60 to 125 thousands of an inch deep and one half inch in width.

It should be apparent that the construction of the metallic can body will apply equally well no matter what contents 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. Likewise, 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 inherent advantage of the present invention is not dependent upon the material of which the can is manufactured.

A metallic can body 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. Alternatively, the feet may be formed in the cup prior to its receipt by the body-maker or as a separate step at the conclusion 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 predetermined internal pressures have been achieved. The pressures may indicate that the contents of the can has gone through certain predetermined heat or pressure ranges to thus indicate pasteurization, pressure utilization or processing 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.

Pressurization of the container also results after the container is 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 provide 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 depend upon customer desire of 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. Inherent in meeting this objective is the novel structure disclosed 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 the present invention should be understood as encompassng all such modifications as are within the scope of the following claims.

WHAT WE CLAIM IS: 1. 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 being discontinuous and comprising a plurality of circumferentially 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 compressive force, while supported upon the individual feet instead of upon the first annular contact band, the individual feet would be crushed.

3. The metallic can body of claim 1 or 2, 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

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. withstand being internally pressurized up to at least 100 p.s.i., without becoming unstable due to over-doming. The feet may be 60 to 125 thousands of an inch deep and one half inch in width. It should be apparent that the construction of the metallic can body will apply equally well no matter what contents 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. Likewise, 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 inherent advantage of the present invention is not dependent upon the material of which the can is manufactured. A metallic can body 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. Alternatively, the feet may be formed in the cup prior to its receipt by the body-maker or as a separate step at the conclusion 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 predetermined internal pressures have been achieved. The pressures may indicate that the contents of the can has gone through certain predetermined heat or pressure ranges to thus indicate pasteurization, pressure utilization or processing 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. Pressurization of the container also results after the container is 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 provide 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 depend upon customer desire of 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. Inherent in meeting this objective is the novel structure disclosed 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 the present invention should be understood as encompassng all such modifications as are within the scope of the following claims. WHAT WE CLAIM IS:

1. 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 being discontinuous and comprising a plurality of circumferentially 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.

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 downwards to a greater extent than when the first annular contact band is solely effective.

5. The metallic can body of any one of the preceding claims, 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 any one of the preceding claims wherein: the aluminum alloy is 3()()4-1119.

7. The metallic can body of any one of the preceding claims wherein the feet are each from 6() to 125 thousandths of an inch deep and one-half inch in width.

8. A caniling operation in which can bodies are being filled with a beverage or the like, closed, ind subjected to a further processing step such as pasturization in which pressure within the cans is raised to within a preselccied 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 being discontinuous and comprising a plurality of circumferentially spaced feet. the feet becoming solely effec tlve 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 processing step, sensing, with respect to each can, whether it stands at a height that corresponds to its being supported upon said second annular contact band thereof or at a lesser height that evidences a failure to achieve sufficient internal pressurization.

9. A method for projecting retracted integral individual can feet on the bottom end wall of a can according to claim 1, comprising the steps of filling said metal can body with a carbonated beverage capable of internally pressurizing the can to at least 18 p.s.i. after the can has been closed; securely closing the open end of the filled can body: and heating the beverage can sufficiently to internally pressurize the can to at least 20 p.s.i., whereby said end wall everts and the feet are projected axially outwards.

10. A metallic can body according to claim 1 constructed and adapted to to operate substantially as herein described with reference to the accompanying drawings.

11. A canning operation according to claim 8 and substantially as herein described with reference to the accompanying drawings.

12. A method for projecting retracted integral individual can feet according to claim 9 and substantially as herein described with reference to the accompanying drawings.