EP0450651B1

EP0450651B1 - Beverage container with improved drop resistance

Info

Publication number: EP0450651B1
Application number: EP91105432A
Authority: EP
Inventors: Gary Arthur Baldwin; John M. Ury; Gregory Edwin Robinson
Original assignee: Ball Corp
Current assignee: Ball Corp
Priority date: 1990-04-06
Filing date: 1991-04-05
Publication date: 1993-10-27
Anticipated expiration: 2011-04-05
Also published as: JP2771343B2; JPH06156467A; MX174630B; ATE96391T1; CA2038817C; DE69100550D1; CN1055333A; ES2045976T3; DE69100550T2; EP0450651A1; AU7394891A; AU644856B2; CA2038817A1

Abstract

A beverage container (10) with improved cumulative drop height resistance includes a generally cylindrical sidewall (12), an annular supporting portion (16) that is connected to the sidewall (12) by an outer connecting portion (28), a domed panel (38) that is disposed radially inwardly of said annular supporting portion (16), and an inner connecting portion (40) that connects the domed panel (38) to the annular supporting portion (16). By manufacturing the container (10) according to the method and dimensions of the present invention, an improvement in the cumulative drop height resistance is accomplished using the same material thickness, or material that is even thinner than that which was previously used. <IMAGE>

Description

Background of the Invention

Field of the Invention

The present invention relates generally to metal container bodies of the type having a seamless sidewall and a bottom formed integrally therewith. More particularly, the present invention relates to a bottom contour that provides increased cumulative drop resistance.

Description of the Related Art

There have been numerous container configurations produced by manufacturers. This has been especially true for the two-piece container manufacturer, that is, a container having a body that has an integral bottom wall at one end, and an opposite end that is configured to have a closure secured thereto. Container manufacturers package beverages of various types in these containers formed of either steel or aluminum alloys.
The most ideal type of container bottom wall would be a flat wall which would allow for maximum capacity for a given container with a minimum height. However, such a container is not economically feasible because, in order to prevent deformation, the thickness of the bottom wall would have to be of such magnitude that the cost of the container would be prohibitive.
In order to negate these costs, drawing and ironing processes have been installed and extensively used in recent years, especially for the aluminum container industry. In the production of these containers that utilize drawing and ironing, it is important that the body wall and bottom wall of the container be as thin as possible no that the container can be sold at a competitive price. Much work has been done on thinning the body wall.
Aside from seeking thin body wall structures, various bottom wall configurations have been investigated. In this regard, strength of the container has been a paramount factor in these investigations. An early attempt in seeking sufficient rigidity of the bottom wall was to form the same into a spherical dome configuration. This general configuration is shown in Dunn et al., U.S. Patent No. 3,760,751, September 25, 1973. The bottom wall is thereby provided with an inwardly concave dome or depression which includes substantially all of the bottom wall of the container. In effect, this domed configuration provides increased strength and resists deformation of the bottom wall under increased internal pressure of the container with little change in the overall geometry of the bottom wall throughout the pressure range for which the container is designed.
Various modifications of the dome configuration have been manufactured. In this regard, the dome structure itself has been integrally formed with other curvilinear or walled members, usually at different inclinations to that of the longitudinal axis of the container, in order to further strengthen the container structure. Although such modifications rendered improved rigidity and stability, it has been found that such characteristics can still be achieved, and in some aspects even improved, with a minimum of metal being required.
Although this domed configuration has allowed container manufacturers to somewhat reduce the metal thickness, container manufacturers are continuously working on techniques that will allow for further reduction in metal thickness without sacrificing container strength. An optimized configuration has not been an easy task.
The prior art that teaches domed bottoms also includes P. G. Stephan, U.S. Patent No. 3,349,956, October 31, 1967; Kneusel et al., U.S. Patent No. 3,693,828, September 26, 1972; Dunn et al., U.S. Patent No. 3,730,383, May 1, 1973; Toukmanian, U.S. Patent No. 3,904,069, September 9, 1975; Lyu et al., U.S. Patent No. 3,942,673, March 9, 1976; Miller et al., U.S. Patent No. 4,294,373, October 13, 1981; McMillin, U.S. Patent No. 4,834,256, May 30, 1989; and Pulciani et al., U.S. Patent No. 4,685,582, August 11, 1987, and No. 4,768,672, September 6, 1988.
Patents which teach apparatus for forming containers with domed bottoms and/or which teach containers having domed bottoms, include Maeder et al., U.S. Patent No. 4,289,014, September 15, 1981; Gombas, U.S. Patent No. 4,341,321, July 27, 1982; Elert et al., U.S. Patent No. 4,372,143, February 8, 1983; and Pulciano et al., U.S. Patent No. 4,620,434, November 4, 1986.
Stephan, in U.S. Patent No. 3,349,956, teaches using a reduced diameter annular supporting portion with an inwardly domed bottom disposed intermediate of the reduced diameter annular supporting portion. Stephan also teaches stacking of the reduced diameter annular supporting portion inside the double-seamed top of another container.
Kneusel et al., in U.S. Patent No. 3,693,828, teach a steel container having a bottom portion which is frustoconically shaped to provide a reduced diameter annular supporting portion, and having an internally domed bottom that is disposed radially inwardly of the annular supporting portion. Various contours of the bottom are adjusted to provide more uniform coating of the interior bottom surface, including a reduced radius of the domed bottom.
Pulciani et al., in U.S. Patent Nos. 4,685,582 and 4,768,672, instead of the frustoconical portion of Kneusel et al., teach a transition portion between the cylindrically shaped body of the container and the reduced diameter annular supporting portion that includes a first annular arcuate portion that is convex with respect to the outside diameter of the container and a second annular arcuate portion that is convex with respect to the outside diameter of the container.
McMillin, in U.S. Patent No. 4,834,256, teaches a transitional portion between the cylindrically shaped body of the container and the reduced diameter annular supporting portion that is contoured to provide stable stacking for containers having a double-seamed top which is generally the same diameter as the cylindrical body, as well as providing stable stacking for containers having a double-seamed top that is smaller than the cylindrical body. In this design, containers with reduced diameter tops stack inside the reduced diameter annular supporting portion; and containers with larger tops stack against this specially contoured transitional portion.
Various of the prior art patents, including Pulciano et al., U.S. Patent No. 4,620,434 (which is used as a basis for drafting claim 1 of the present patent), teach contours which are designed to increase the pressure at which fluid inside the container reverses the dome at the bottom of the container. This pressure is called the static dome reversal pressure. In this patent, the contour of the transitional portion is given such great emphasis that the radius of the domed panel, though generally specified within a range, is not specified for the preferred embodiment.
As mentioned earlier, one of the problems is obtaining a maximum dome reversal pressure for a given metal thickness. However, another problem is obtaining resistance to damage when a filled container is dropped onto a hard surface. More particularly, this other problem includes the resistance to structural damage as caused by the combination of dropping the container onto a hard surface, together with the internal fluid pressure in the container, the internal fluid pressure being a function of the type of beverage and of the temperature thereof.
When containers are shipped in cardboard cartons, damage to the containers may be obviated by the resilience of the carton material. However, if the material of the carton is made thinner, or if the containers are shrink wrapped in plastic film rather than being shipped in a cardboard container, the drop resistance of the containers becomes as critical, or even more critical, than the dome reversal pressure.
Present industry testing for drop resistance is called the cumulative drop height. In this test, a filled container is dropped onto a steel plate from heights beginning at three inches and increasing by three inches for each successive drop. The drop height resistance is then the sum of all the distances at which the container is dropped, including the height at which the dome is reversed, or partially reversed. That is, the drop height resistance is the cumulative height at which the bottom contour is damaged sufficiently to preclude standing firmly upright on a flat surface.
Further, in the cumulative drop height test, the internal fluid pressure of the beverage is closely controlled at an elevated pressure by controlling the temperature of the beverage. Thus, failure of the container is caused by the combination of the stresses induced by the internal fluid pressure and the impacts of repeated drop tests with the inertial force of the fluid in the container.
As is known, a large quantity of containers are manufactured annually and the producers thereof are always seeking to reduce the amount of metal utilized in making containers while still maintaining the same operating characteristics.
Because of the large quantities of containers manufactured, a small reduction in metal thickness, even of one-half of one thousandth of an inch, reduces manufacturing costs substantially.

Summary of the Invention

According to the present invention, a drawn and ironed beverage container includes an annular supporting portion that is disposed radially inwardly from the sidewall of the container and that is disposed around and concentric to a vertical axis, a domed panel, or concave panel, that is disposed inwardly of the annular supporting portion, and an outer connecting portion that connects the annular supporting portion to the sidewall.
The outer connecting portion includes a lower concave annular arcuate portion and an upper convex annular arcuate portion that is connected to the lower concave annular supporting portion and to the sidewall.
The annular supporting portion includes inner and outer convex annular portions which preferably are arcuate and are disposed about the same center of curvature. The annular supporting portion, and the inner and outer convex annular portions thereof, provide an annular supporting surface for supporting the container on a flat and horizontal surface, for providing means for nesting the containers when they are stacked.
The container includes an inner connecting portion that connects the domed panel, or concave panel, to the annular supporting portion. The inner connecting portion includes an inner concave annular portion that extends radially outward from the domed panel and that curves downward toward the inner convex annular portion, and an inner wall that is disposed circumferentially around the vertical axis, that connects the inner concave annular portion to the inner convex annular portion, and that disposes the domed panel at a positional distance above the annular supporting surface.
It has been discovered that by careful selection of the dimensions for the various parameters, the strength of a container, as determined by the cumulative drop height test, is increased to an unexpected magnitude.
In stark contrast to the prior art in which decreasing of the radius of curvature of the domed panel was avoided because of a reduction in the static dome reversal pressure of the container, in the present invention the radius of curvature of the domed panel is reduced into a range wherein the static dome reversal pressure is degraded to the point wherein the container would not perform satisfactorily.
This radical reduction in the radius of curvature of the domed panel produces not only an entirely unacceptable reduction in the static dome reversal pressure, but also produces a dramatic, and an unexpected increase in the cumulative drop height resistance. This increase in the cumulative drop height resistance may be as much as, or even more than, six hundred percent. And this tremendous improvement in the cumulative drop height resistance is achieved with the same thickness of material.
As beneficial as this dramatically improved cumulative drop height resistance is, the benefits are of no commercial value without accompanying means for obviating most, or nearly all, of the detrimental decrease in the static dome reversal pressure that accompanies the required reduction in the radius of curvature of the domed panel.
It has been by careful selection of various other parameters of the container, such as the positional distance from the supporting surface to the domed panel and the height of the inner wall of the inner connecting portion, that all, or nearly all, of the reduction in the static dome reversal pressure can be obviated.
Moreover, if an improvement of less than a six hundred percent in cumulative drop height resistance is acceptable, by careful selection of parameters, it is even possible to increase the static dome reversal pressure of the container while obtaining an excellent improvement in the cumulative drop height resistance.
In summary, the present invention provides a container with an excellent static dome reversal pressure, an astoundingly increased cumulative drop height resistance, and makes it possible for not only permitting the use of shrink wrap and other inexpensive means in the place of cardboard for packaging containers, but also the possibility of using thinner metal stock material for the containers and achieving a reduction in material cost.
In the first three aspects of the present invention, a container includes a sidewall that is disposed around a vertical axis, an annular supporting portion that is disposed around the vertical axis, and that includes an annular supporting surface disposed around the vertical axis and orthogonal thereto, an outer connecting portion that interconnects the sidewall and the annular supporting portion, a concave panel that is disposed inwardly from the annular supporting portion, and an inner connecting portion that is connected to the annular supporting portion, that extends upwardly into the container, that is connected to the concave panel, and that disposes the concave panel at a positional distance above the supporting surface.
More particularly, in the first aspect of the present invention, the curvature of the concave panel is increased into a range wherein dome reversal pressure of the container is decreased with an increase in pressure, for increasing the cumulative drop height resistance of the container.
In the second aspect of the present invention, the positional distance from the supporting surface to the curved portion is increased to increase the dome reversal pressure of the container.
In the third aspect of the present invention, the curvature of the concave panel is reduced wherein the dome reversal pressure of the container is decreased with increases in the curvature, for increasing the cumulative drop height resistance of the container, and the positional distance from the supporting surface to the concave panel is increased to at least partially prevent the increase in the curvature of the concave panel from decreasing the dome reversal pressure of the container.
In the fourth and fifth aspects of the invention, a container includes a sidewall that is substantially cylindrical and that is disposed concentrically around a vertical axis, an annular supporting portion that includes an annular supporting surface orthogonal to the vertical axis, and that includes a convex annular portion disposed around the vertical axis curving inwardly and upwardly from the supporting surface, an outer connecting portion that interconnects the sidewall and the supporting portion, a concave panel that includes a substantially spherical contour and that is disposed radially inwardly from the convex annular portion, a concave annular portion that is disposed circumferentially around the concave panel, that is connected to the concave panel, and that curves downwardly toward the convex annular portion, a circumferential inner wall that is connected to the convex annular portion, that extends upwardly from the convex annular portion, and that is connected to the concave annular portion.
More particularly, in the fourth aspect of the present invention, the radius of curvature of the concave panel is reduced into a range wherein the dome reversal pressure of the concave panel is decreased with decreases in the radius of curvature, for increasing the cumulative drop height resistance of the container.
In the fifth aspect of the invention, the radius of curvature of the concave panel is reduced into a range wherein the dome reversal pressure of the concave panel is decreased with decreases in the radius of curvature, for increasing the cumulative drop height resistance of the container, and the height of the inner wall is increased, for increasing the dome reversal pressure of the concave panel.
In the fifth, sixth, and seventh aspects of the present invention, a method is provided for increasing the strength of a container, in which the container includes a sidewall that is disposed around a vertical axis, a supporting portion that is disposed around the vertical axis and that includes an annular supporting surface disposed around the vertical axis, an outer connecting portion that connects the sidewall to the supporting surface, and a concave panel that is disposed inwardly from the annular supporting portion, an inner connecting portion that is connected to the annular supporting portion, that extends upwardly into the container, and that disposes the concave panel at a positional distance above the supporting surface.
More particularly, in the fifth aspect of the invention, the cumulative drop resistance of the container is increased by increasing the curvature of the concave panel, and by limiting the increasing step to an allowable decrease in the dome reversal pressure.
In the sixth aspect of the invention, the dome reversal pressure of the container is increased by increasing the positional distance from the supporting surface to the concave panel.
In the seventh aspect of the invention, the dome reversal pressure and the cumulative drop strength of a container are optimized by increasing the curvature of the domed panel to a curvature in which the dome reversal pressure is reduced from that which is produced by a smaller curvature, thereby increasing the cumulative drop strength, and increasing the positional distance to at least partially compensate for the reduction in the dome reversal pressure.
In an eighth and ninth aspect of the invention, a container includes a generally cylindrical sidewall that has a first diameter and that is disposed circumferentially around a vertical axis, an annular support that is disposed circumferentially around the vertical axis, that is disposed radially inwardly from the sidewall, that includes an outer convex annular portion, and that includes an inner convex annular portion disposed radially inwardly from the outer convex annular portion and attached to the outer convex annular portion, for supporting the container, an outer connecting portion that includes an upper convex annular portion connected to the sidewall, that includes a recessed annular portion disposed radially inwardly of a line tangent to the outer convex annular portion and the upper convex annular portion, for connecting the sidewall to the outer convex annular portion of the annular supporting means, a domed panel that is generally spherically-shaped, that is disposed radially inwardly from the annular supporting means, and that curves upwardly with respect to the vertical axis, and an inner connecting portion that includes a circumferential inner wall extending generally upwardly with respect to the vertical axis for connecting the domed panel to the annular supporting means, and the domed panel has a dome radius that is smaller than the mean diameter of the container.
Finally, in the tenth aspect of the present invention, a container capable of substantially resisting dome reversal upon impact includes a structure with a seamless cylindrical sidewall and a bottom wall integrally formed with the sidewall at the lower extremity thereof, an outer connecting member that extends downwardly and inwardly from the sidewall toward the vertical axis of the container, the outer connecting member including an upper convex portion with an interior radius and a lower concave portion with an exterior radius, the radii being substantially equal, an annular bottom member that is integrally connected with and that extends downwardly from the lower concave portion to provide a supporting means for the container, a frustoconical surface that integrally connects with the annular bottom member and that extends upwardly and inwardly therefrom, said frustoconical surface forming a slight angle with respect to the vertical axis of the container, and a downwardly concave center panel that is integrally connected with the frustoconical surface and that extends upwardly and inwardly from the frustoconical surface, and the radius of curvature of the downwardly concave center panel being substantially equal to or less than the diameter of the annular supporting surface.

Brief Description of the Drawings

FIGURE 1 is a front elevation of beverage containers that are bundled by shrink wrapping with plastic film;
FIGURE 2 is a top view of the bundled beverage containers of FIGURE 1 taken substantially as shown by view line 2-2 of FIGURE 1;
FIGURE 3 is a cross sectional elevation of the lower portion of one of the beverage containers of FIGURES 1 and 2, showing details that are generally common to two prior art designs;
FIGURE 4 is a cross sectional elevation of the lower portion of a beverage container, showing details that are generally common to the preferred embodiments of the present invention;
FIGURE 5 is a cross sectional elevation, showing, at an enlarged scale, details that are generally common to both FIGURES 3 and 4;
FIGURE 6 is a graph of cumulative drop heights vs. both the radius of curvature of the domed panel, and the ratio of the radius of curvature divided by the mean diameter of the annular supporting portion, with the distance from the supporting surface to the domed panel being constant;
FIGURE 7 is a graph of cumulative drop heights vs. both the radius of curvature of the domed panel, and the ratio of the radius of curvature divided by the mean diameter of the annular supporting portion, and is different from the graph of FIGURE 6 in that parameters, such as the inner wall height have been selected to provide a constant static dome reversal pressure;
FIGURE 8 is a graph of static dome reversal pressures vs. both the radius of curvature, and the ratio of the radius of curvature divided by the mean diameter of the annular supporting portion, with the dome height, that is, the distance from the supporting surface to the domed panel, being constant; and
FIGURE 9 is a graph of static dome reversal pressure vs. both the radius of curvature of the domed panel, and the ratio of the radius of curvature divided by the mean diameter of the annular supporting portion.

Description of the Preferred Embodiments

Referring now to FIGURES 3, 4, and 5, these configurations are generally common to Pulciani et al. in U.S. Patents 4,685,582 and 4,768,672 and 4,620,434, to a design manufactured by the assignee of the present invention, and to embodiments of the present invention. More particularly, FIGURE 3 is common to the aforesaid prior art, FIGURE 4 is common to two embodiments of the prior art, and FIGURE 5 shows some details of FIGURES 3 and 4 in an enlarged scale.
Since the present invention differs from the prior art primarily by selection of some of the parameters shown in FIGURES 3-5, the forthcoming description refers to all of these drawings, except as stated otherwise; and some dimensions pertaining to FIGURES 3 and 4 are placed only on FIGURE 5 in order to avoid crowding.
Continuing to refer to FIGURES 3-5, a drawn and ironed beverage container 10 includes a generally cylindrical sidewall 12 that includes a first diameter D₁, and that is disposed circumferentially around a vertical axis 14; and an annular supporting portion, or annular supporting means, 16 that is disposed circumferentially around the vertical axis 14, that is disposed radially inwardly from the sidewall 12, and that provides an annular supporting surface 18 that coincides with a base line 19.
The annular supporting portion 16 includes an outer convex annular portion 20 that preferably is arcuate, and an inner convex annular portion 22 that preferably is arcuate, that is disposed radially inwardly from the outer convex annular portion 20, and that is connected to the outer convex annular portion 20. The outer and inner convex annular portions, 20 and 22, have radii R₁ and R₂ whose centers of curvature are common. More particularly, the radii R₁ and R₂ both have centers of curvature of a point 24, and of a circle of revolution 26 of the point 24. The circle of revolution 26 has a second diameter D₂.
An outer connecting portion, or outer connecting means, 28 includes an upper convex annular portion 30 that is preferably arcuate, that includes a radius of R₃, and that is connected to the sidewall 12. The outer connecting portion 28 also includes a recessed annular portion 32 that is disposed radially inwardly of a line 34, or a frustoconical surface of revolution 36, that is tangent to the outer convex annular portion 20 and the upper convex annular portion 30. Thus, the outer connecting means 28 connects the sidewall 12 to the outer convex annular portion 20.
A domed panel, or concave panel, 38 is preferably spherically-shaped, but may be of any suitable curved shape, has a radius of curvature, or dome radius, R₄, is disposed radially inwardly from the annular supporting portion 16, and curves upwardly into the container 10. That is, the domed panel 38 curves upwardly proximal to the vertical axis 14 when the container 10 is in an upright position.
The container 10 further includes an inner connecting portion, or inner connecting means, 40 having a circumferential inner wall, or cylindrical inner wall, 42 with a height L₁ that extends upwardly with respect to the vertical axis 14 that may be cylindrical, or that may be frustoconical and slope inwardly toward said vertical axis 14 at an angle α₁. The inner connecting portion 40 also includes an inner concave annular portion 44 that has a radius R₅, and that interconnects the inner wall 42 and the domed panel 38. Thus, the inner connecting portion 40 connects the domed panel 38 to the annular supporting portion 16.
The inner connecting portion 40 positions a periphery 45 of the domed panel 38 at a positional distance L₂ above the base line 19. As can be seen by inspection of FIGURE 5, the positional distance L₂ is approximately equal to, but is somewhat less than, the sum of the height L₁ of the inner wall 42, the radius of curvature R₅ of the inner concave annular portion 44, the radius R₂ of the inner convex annular portion 22, and the thickness of the material at the inner convex annular portion 22.
As seen by inspection and as can be calculated by trigonometry, the positional distance L₂ is less than the aforementioned sum by a function of the angle α₁, and as a function of an angle α₃ at which the periphery 45 of the domed panel 38 is connected to the inner concave annular portion 44.
For example, if the radius R₅ of the inner concave annular portion 44 is 1,27 mm (0.050 inches), if the radius R₂ of the inner convex annular portion 22 is 1,016 mm (0.040 inches), and if the thickness of the material at the inner convex annular portion 22 is about 0,305 mm (0.012 inches), then the positional distance L₂ is about, but somewhat less than 2,591 mm (0.102 inches) more than the height L₁ of the inner wall 42.
Thus, with radii and metal thickness as noted above, when the height L₁ of the inner wall 42 is 1.524 mm (0.060 inches), the positional distance L₂ is about, but a little less than, 4,115 mm (0.162 inches).
The annular supporting portion 16 has an arithmetical mean diameter D₃ that occurs at the junction of the outer convex annular portion 20 and the inner convex annular portion 22. Thus, the mean diameter D₃ and the diameter D₂ of the circle 26 are the same diameter. The dome radius R₄ is on the vertical axis 14.
The recessed annular portion 32 includes a circumferential outer wall 46 that extends upwardly from the outer convex annular portion 20 and outwardly 5 away from said vertical axis by an angle α₂, and includes a lower concave annular portion 48 with a radius R₆. Further, the recessed annular portion 32 may, according to the selected magnitudes of the angle α₂, the radius R₃, and the radius R₆, include a lower part of the upper convex annular portion 30.
Finally, the container 10 includes a dome height, or panel height, H₁ as measured from the supporting surface 18 to the domed panel 38, and a post diameter, or smaller diameter, D₄, of the inner wall 42. The upper convex annular portion 30 is tangent to the sidewall 12, and has a center 50. The center 50 is at a height H₂ above the supporting surface 18. A center 52 of the lower concave annular portion 48 is on a diameter D₅. The center 52 is below the supporting surface 18. More specifically, the supporting surface 18 is at a distance H₃ above the center 52.
Referring now to FIGURES 3 and 5, in the prior art embodiment of the three aforesaid patents, the following dimensions were used: D₁ = 2.597 inches; D₂, D₃ = 50,8 mm (2.000 inches); D₅ = 60,071 mm (2.365 inches); R₁, R₂ = 1,016 mm (0.040 inches); R₃ = 5,08 mm (0.200 inches); R₄ = 60,325 mm (2.375 inches); R₅ = 1,27 mm (0.050 inches); R₆ = 2,54 mm (0.100 inches); and α₁ = less than 5°. It should be noted that although R₄ is 60,325 mm (2.375 inches), the actual radius therefor was 53,848 mm (2.12 inches).
Referring again to FIGURES 3 and 5, in the prior art embodiment of the assignee to the present invention, the following dimensions were used : D₁ = 65,989 mm (2.598 inches); D₂, D₃ = 50,8 mm (2.000 inches); D₄ = 47,803 mm (1.882 inches); D₅ = 63,723 mm (2.509 inches); R₁, R₂ = 1,016 mm (0.040 inches); R₃ = 5,08 mm (0.200 inches); R₄ = 60,325 mm (2.375 inches); R₅ = 1,27 mm (0.050 inches); R₆ = 5,08 mm (0.200 inches); H₁ = 9,779 mm (0.385 inches); H₂ = 9,398 mm (0.370 inches); H₃ = 0,203 mm (0.008 inches); α₁ = 5° 9'; and α₂ = 30°. It should be noted that although R₄ is 60,325 mm (2.375 inches), the actual tooling radius therefor was 53,848 mm (2.12 inches).
Referring now to FIGURES 4 and 5, in tests run in conjunction with the present invention, the following dimensions were used: D₁ = 65,989 mm (2.598 inches); D₂, D₃ = 50,8 mm (2.000 inches); D₅ = 63,723 mm (2.509 inches); R₁, R₂ = 1,016 mm (0.040 inches); R₃ = 5,08 mm (0.200 inches); R₅ = 1,27 mm (0.050 inches); R₆ = 5,08 mm (0.200 inches); H₂ = 9,398 mm (0.370 inches); H₃ = 0,203 mm 0.008 inches; and α₂ = 30°.
The other dimensions such as R₄, D₄, H₁, α₁, L₁ and the thickness of material which were used in the tests, are as specified in the tables which are included herein, together with the test results thereof.
In each of the tables, the static dome reversal pressure (S.D.R) is in pounds per square inch one pound per square inch being 0,0068947 N/mm², the cumulative drop height (C.D.H.) is in inches one inch being 25,4 mm, and the internal pressure (I.P.) at which the cumulative drop height tests were run is in pounds per square inch one pound per square inch being 0,0068947 N/mm².
Referring now to Tables 1-10, the radius of curvature R₄ of the domed panel 38, as specified in the tables, is the actual radius of curvature of the container, as measured, not the radius of curvature of the domer tooling. For instance, a radius of curvature R₄ of 60,325mm (2.375 inches), is made with a tool that has a radius of 53,848 mm (2.120 inches). This difference in radius of curvature for the actual container and the tooling is true for both the three aforementioned patents and the prior art embodiments of the assignee of the subject invention.
More particularly, in Tables 1-10 the following Table A comparison between tooling radius and the actual dome radius R4 of the containers.
Therefore, in the tables, a radius of curvature R₄ of 60,325 mm (2.375 inches) compares to the prior art of FIGURES 3 and 4, in which the radius of the domer tooling was 53,848 mm (2.120 inches); and the improvements of the present invention, at other radii of curvature, can be seen as a comparison to an R₄ of 60,325 mm (2.375 inches).
The tests of Tables 1-10 were run with two thickness of metal, as specified. The 0,2997 mm (0.0118 inch) thickness is the standard gauge for use in the United States; and the 0,3226 mm (0.0127 inch) thickness is used for special orders, particularly for use outside the United States. All of the test material was aluminum alloy which is designated as 3104 H19, and the test material was taken from production stock.
The cumulative drop heights in the tables represent the average of eighteen tests, and the static dome reversal pressures represent the average of ten tests. The internal fluid pressures in each container prior to dropping is shown in the table for each drop test.
The purpose for the cumulative drop height is to determine the cumulative drop height at which a filled can exhibits partial or total reversal of the domed panel.
The procedure is as follows: 1) warm the product in the containers to 32,22 ± 1,11 degrees Celsius (90 degrees, plus or minus 2 degrees, Fahrenheit); 2) position the tube of the drop height tester to 5 degrees from vertical to achieve consistent container drops; 3) insert the container from the top of the tube, lower it to the 76,2 mm (3 inch) position, and support the container with a finger; 4) allow the container to free-fall and strike the steel base; 4) repeat the test at heights that successively increase by 76,2 mm (3 inch) increments; 5) feel the domed panel to check for any bulging or "reversal" of the domed panel before testing at the next height; 6) record the height at which dome reversal occurs; 7) calculate the cumulative drop height, that is, add each height at which a given container has been dropped, including the height at which dome reversal occurs; and 8) average the results from 10 containers.
One beverage producer has proposed that containers supplied to that company have a minimum cumulative drop height resistance of 1524 mm (60 inches). Heretofore, container manufacturers have been unable to achieve this cumulative drop height resistance. Therefore, it is unknown whether an industry standard of 1524 mm (60 inches), 762 mm (30 inches), or merely 508 mm (20 inches), will be adopted. Further, it is not certain that any industry standard will be adopted.
However, the present invention provides a container with a cumulative drop height resistance that greatly exceeds that of prior art containers; and containers manufactured according to the present invention are able to meet a cumulative drop height requirement of 508, 762, 1016 or even 1524 mm (20, 30, 40, or even 60 inches) without any increase in the gauge of the material, and without any increase in cost.
Referring now to Table 1, it will be noticed that the numbers in columns three and four correspond exactly to the numbers in columns one and two. The reason for this is that the object in the tests for columns three and four was to vary the dome depths to match the static dome reversal of the prior art of FIGURE 4. Since the parameters of Table 1 are the same as that of the prior art of FIGURE 4, the numbers in columns three and four are identical to those in columns one and two.
Continuing to refer to Table 1, and test results for the prior art configuration of FIGURE 4, the cumulative drop heights were 127 mm (5.0 inches) and 444,5 mm (17.5 inches), for metal thicknesses of 0,2997 mm (0.0118 inches) and 0,3226 mm (0.0127 inches), respectively, and with internal pressures of 0,43023 N/mm² (62.4 pounds per square inch) and 0,42058 N/mm² (61.0 pounds per square inch), respectively. Notice that the static dome reversal pressures were 0,66051 and 0,76462 N/mm² (95.8 and 110.9 pounds per square inch) for the two metal thicknesses.
It is important to remember that the radius of curvature of the domed panel for Table 1, as listed, is 60,325 mm (2.375 inches), and that this is the actual radius of curvature for prior art in which the domer tooling radius is 53,848 mm 2.120 inches.
Referring now to Table 10, in stark contrast to test results on the prior art embodiment of Table 1, with a dome radius R₄ of 44,45 mm (1.750 inches) of the container, and with a post diameter D₄ of 47,93 mm (1.887 inches) for the same two metal thicknesses, 0,2997 mm (0.0118 inches) and 0,3226 mm (.0127 inches), and for internal pressures of 0,4385 N/mm² (63.6 psi) and 0,41644 N/mm² (60.4 psi), respectively, the cumulative drop heights of the present invention were 1867 mm (73.5 inches) and 3497,6 mm (137.7 inches), respectively, as shown in columns one and two. Notice that the static dome reversal pressures were 0,57433 N/mm² (83.3 psi) and 0,67982 N/mm² (98.6 psi), respectively.
That is, the present invention increased the cumulative drop height by more than fourteen times, from 127 mm (5.0 inches) to 1867 mm (73.5 inches) for the thinner stock, and by nearly eight times, from 444,5 mm (17.5 inches) to 3497,6 mm (137.7 inches) for the thicker stock.
However, referring to Tables 1 and 10, this dramatic increase in the cumulative drop height was accompanied by an undesirably large decrease in the static dome reversal pressures. The dome reversal pressures reduced from 0,66051 N/mm² (95.8 psi) and 0,76462 N/mm² (110.9 psi), respectively, for the thinner and the thicker stock in Table 1, to 0,57433 N/mm² (83.3 psi) and 0,67982 N/mm² (98.6 psi), respectively, for the thinner and the thicker stock of Table 10.
The present invention provides means for obviating, or at least ameliorating, this decrease in the static dome reversal pressure that accompanies the dramatic increase in the cumulative drop height.
Referring now to Table 1 and to columns three and four of Table 10, the present invention increased the cumulative drop height from 127 mm (5.0 inches) and 444,5 mm (17.5 inches), respectively, to 1778 mm (70.0 inches) and 3454,4 mm (136.0 inches), respectively for the thinner and the thicker stock. Therefore, the present invention increased the cumulative drop height by fourteen times for the thinner stock and by almost eight times for the thicker stock.
At the same time, by increasing the height L₁ of the inner wall 42, from 0,889 mm (0.035 inches) to 2,032 mm (0.080 inches) for the thinner stock and 1,905 mm (0.075 inches) for the thicker stock, the containers had a static dome reversal pressure of 0,63018 N/mm² (91.4 psi) and 0,73704 N/mm² (106.9 psi) respectively.
Therefore, increasing the height L₁ of the inner wall 42 limited the reduction in the static dome reversal pressure to less than 5 percent for the thinner stock, and by 4 percent for the thicker stock, while achieving increases in the cumulative drop height by about eight to fourteen times, depending upon the metal thickness.
Referring now to FIGURE 9, cumulative drop heights and static dome reversal pressures are shown for various radii of curvature R₄ of the domed panel 38, and for various ratios of radii of curvature R₄ to the mean diameter D₃ of the annular supporting portion 16.
Notice that in FIGURE 9, with increased heights L₁ of the inner wall 42, it is possible to obtain phenomenal, but not maximum, increases in the cumulative drop heights without decreasing the static dome reversal pressure below that which was achieved by the prior art.
Or, refering now to Tables 1 and 8, notice that the prior art static dome reversal pressures of 95.8 and 110.9 (0,66051 N/mm² (95.8 psi) and 0,76462 N/mm² (110.9 psi)) of Table 1, are exceeded by the static dome reversal pressures of 96.0 and 111.0 (0,66189 N/mm² (96.0 psi) and 0,76531 N/mm² (111.0 psi)) of Table 1, and that increases in cumulative drop height from 127 mm (5.0 inches) to 1122,7 mm (44.2 inches), and from 444,5 mm (17.5 inches) to 2263,1 mm (89.1 inches), respectively, are achieved.
Therefore, in the present invention, highly significant increases in the cumulative drop heights can be achieved without any reduction in static dome reversal pressures.
Furthermore, it is believed that further improvement is possible by varying such parameters as the angle α₁ of the inner wall 42, and the height L₁ of the inner wall; because the test results submitted herein indicate that increasing the height L₁ increases the static dome reversal pressure, and decreasing the angle α₁ of the inner wall 42 increases the static dome reversal pressures.
Referring now to FIGURE 6 and Table 11, the test data of Tables 1-10 has been rearranged in Table 11 to show variations in test results when the dome height H₁ is kept constant; and in FIGURE 6, the data of Table 11 is plotted to show the cumulative drop heights vs. the radius of curvature R₄ for tests wherein the dome height H₁ is kept constant at 9,779 mm (0.385 inches).
It should be noted that in Tables 11 and 12, the designation B6A denotes a container made in accordance with the dimensions presently given for the prior art container of the assignee of the subject invention. the other container designations (e.g., X0133) refer to experimental drawing numbers of various experimental tools.
In like manner, referring now to FIGURE 7 and Table 12, the test data of Tables 1-10 has been rearranged in Table 12 to show variations in test results when the dome height H₁ is varied to maintain a constant, or nearly constant, static dome reversal pressure of 0,66189 N/mm² (96 psi) for the 0,2997 mm (0.0118 inches) stock thickness and 0,76531 N/mm² (111 psi) for the 0,3226 mm (0.0127 inches) stock thickness. In FIGURE 7, the data of Table 12 is plotted to show the cumulative drop heights vs. the radius of curvature R₄ for tests wherein the static dome reversal pressure is kept constant, or nearly constant, as noted for Table 12.
Referring now to FIGURE 8, the static dome reversal pressures are plotted for various radii of curvature R₄ of the domed panel 38, and for various ratios of radii of curvature R₄ to the mean diameter D₃ of the annular supporting portion 16. In the curves of FIGURE 8, the dome height H₁, that is, the distance from the supporting surface 18 to the domed panel 38 along the axis 14, is kept constant at 9,779 mm (0.385 inches).
In summary, the present invention yields unexpected results. It is believed that one skilled in the art would not have anticipated that a decrease in the dome radius R₄ would achieve such a remarkable increase in cumulative drop strengths. Moreover, it is believed that there is no hint in the prior art that any increase in cumulative drop strength can be achieved by a reduction in the dome radius R₄ as disclosed and claimed herein.
In addition, being able to reduce, or to obviate, the reduction in static dome reversal pressures that accompanies this phenomenal increase in cumulative drop heights, or even being able to increase the static dome reversal pressure, by increasing the height L₁ of the inner wall 42 constitutes unexpected results.
In order to better understand the claims, it should be recognized that increasing the height L₁ of the inner wall 42, for a given radius of curvature R₄ of the domed panel 38, increases the dome height H₁.
Therefore, reciting an increase in the dome height H₁, or a limit thereof, is one way of reciting an increase in, or a limit of, the height L₁ of the inner wall 42.
Further, it should be recognized that increasing the height L₁ of the inner wall 42 increases the positional distance L₂.
Therefore, reciting an increase in the positional distance L₂, or a limit thereof, is one way of reciting an increase in, or a limit of, the height L₁ of the inner wall 42.
Further, it should be understood that reciting the positional distance L₂ distinctly defines dimensions, or limits, of the present invention without regard to the size or shape of the inner convex annular portion 22, the size or shape of the inner concave annular portion 44, the shape or inclination of the inner wall 42, or the thickness of the metal.
Finally, the present invention provides these remarkable and unexpected improvements by means and method as recited in the aspects of the invention which are included herein.
Although aluminum containers have been investigated, it is believed that the same principles, namely decreasing the dome radius R₄, increasing the height L₁ of the inner wall 42, increasing the dome height H₁, increasing the positional distance L₂ from the supporting surface 18 to the domed panel 38, and selecting, and/or minimizing the angle α₁ of the inner wall 42, would be effective to increase the strength of containers made from other materials, including ferrous and nonferrous metals, plastic and other nonmetallic materials.
Referring finally to FIGURES 1 and 2, upper ones of the containers 10 stack onto lower ones of the containers 10 with the outer connecting portions 28 of the upper ones of the containers 10 nested inside double-seamed tops 56 of lower ones of the containers 10; and both adjacently disposed and vertically stacked containers 10 are bundled into a package 58 by the use of a shrink-wrap plastic 60.
While this method of packaging is more economical than the previous method of boxing, possible damage due to rough handling becomes a problem, so that the requirements for cumulative drop resistances of the containers 10 is more stringent. It is this problem that the present invention addresses and solves.
While specific methods and apparatus have been disclosed in the preceding description, it should be understood that these specifics have been given for the purpose of disclosing the principles of the present invention and that many variations thereof will become apparent to those who are versed in the art. Therefore, the scope of the present invention is to be determined by the appended claims.

Industrial Applicability

The present invention is applicable to containers made of aluminum and various other materials. More particularly, the present invention is applicable to beverage containers of the type having a seamless, drawn and ironed, cylindrically-shaped body, and an integral bottom with an annular supporting portion.
The invention may be summarized as follows:
A container having increased cumulative drop height resistance, which container comprises:
a sidewall being disposed around a vertical axis;
an annular supporting portion being disposed around said vertical axis and having an annular supporting surface;
an outer connecting portion interconnecting said sidewall and said annular supporting portion;
a concave panel being disposed inwardly from said annular supporting portion; and
an inner connecting portion being connected to said annular supporting portion, extending upwardly and toward said vertical axis, being connected to said concave panel, said concave panel being disposed a positional distance above said supporting surface;
said concave panel having a preselected curvature wherein the static dome reversal pressure of said container is decreased.
A container in which said supporting surface includes an arithmetical mean diameter;
said preselected curvature includes at least a portion that is substantially spherical about a radius of curvature; and
said radius of curvature of said spherical portion is less than about 105 percent of said mean diameter.
A container in which said supporting surface includes an arithmetical mean diameter; and
said decrease in said dome reversal pressure is at least partially obviated by said positional distance being more than about 8 percent of said arithmetical mean diameter.
A container in which said supporting surface includes an arithmetical mean diameter;
said container includes a panel height as measured along said axis from said supporting surface to said concave panel; and
said decrease in said static dome reversal pressure is at least partially obviated by said panel height being more than about 20 percent of said mean diameter.
A container in which said sidewall is substantially cylindrical;
said preselected curvature includes at least a portion that is substantially spherical about a radius of curvature; and
said radius of curvature is less than about 80 percent of the diameter of said sidewall.
A container in which said sidewall is substantially cylindrical; and
said decrease in said static dome reversal pressure is at least partially obviated by said positional distance being more than about 6.2 percent of the diameter of said sidewall.
A container in which said sidewall is substantially cylindrical;
said container includes a panel height as measured along said axis from said supporting surface to said concave panel; and
said decrease in said static dome reversal pressure is at least partially obviated by said panel height being more than about 15.0 percent of the diameter of said sidewall.
A container in which said supporting surface includes an arithmetical mean diameter;
said container includes a panel height as measured along said axis from said supporting surface to said concave panel;
said preselected curvature includes at least a portion that is substantially spherical about a radius of curvature;
said radius of curvature of said spherical portion is less than about 105 percent of said mean diameter; and
said decrease in said static dome reversal pressure is at least partially obviated by said panel height being more than about 20 percent of said mean diameter.
A container in which said sidewall is substantially cylindrical;
said container includes a panel height as measured along said axis from said supporting surface to said concave panel;
said preselected curvature includes at least a portion that is substantially spherical about a radius of curvature;
said preselected curvature comprises said radius of curvature being less than about 80 percent of the diameter of said sidewall; and
said decrease in said static dome reversal pressure is at least partially obviated by said panel height being more than about 16.0 percent of said sidewall diameter.
A container having increased cumulative drop height resistance, which container comprises:
a sidewall being disposed around a vertical axis;
an annular supporting portion being disposed around said vertical axis, and having an annular supporting surface that is disposed around said vertical axis and that is orthogonal thereto;
an outer connecting portion interconnecting said sidewall and said annular supporting portion;
a concave panel being disposed inwardly from said annular supporting portion;
an inner connecting portion being connected to said annular supporting portion, extending upwardly into said container, being connected to said concave panel, and disposing said concave panel a positional distance above said supporting surface; and
said concave panel having a preselected curvature wherein the static dome reversal pressure of said container is decreased.
A container in which said annular supporting surface includes an arithmetical mean diameter; and
said positional distance is more than about 8 percent of said mean diameter.
A container in which said sidewall is substantially cylindrical; and
said positional distance is more than about 6.2 percent of the diameter of said sidewall.
A container in which said annular supporting surface includes an arithmetical mean diameter;
said container includes a panel height as measured from said supporting surface along said axis to said concave panel; and
said positional distance comprises said panel height being more than about 20 percent of said mean diameter.
A container in which said container includes a panel height as measured from said supporting surface along said axis to said concave panel; and
said positional distance comprises said panel height being more than about 15 percent of the diameter of said sidewall.
A container in which said annular supporting surface includes an arithmetical mean diameter;
said container includes a panel height as measured from said supporting surface along said axis to said concave panel; and
said positional distance is more than about 8 percent of said mean diameter and said panel height is more than about 20 percent of said mean diameter.
A container in which said sidewall is substantially cylindrical;
said container includes a panel height as measured from said supporting surface along said axis to said concave panel;
said positional distance is more than about 6.2 percent of the diameter of said sidewall; and
said positional distance comprises said panel height being more than about 15 percent of said diameter of said sidewall.
A container having increased drop height resistance, which container comprises:
a sidewall being disposed around a vertical axis;
an annular supporting portion being disposed around said vertical axis and having an annular supporting surface;
an outer connecting portion interconnecting said sidewall and said annular supporting portion;
a concave panel being disposed inwardly from said annular supporting portion;
an inner connecting portion being connected to said annular supporting portion, extending upwardly into said container, being connected to said concave panel, said concave panel being disposed a positional distance above said supporting surface;
said concave panel having a preselected curvature wherein the static dome reversal pressure of said container is decreased; and
means, comprising said positional distance, for at least partially preventing said preselected curvature of said concave panel from decreasing said static dome reversal pressure of said container.
A container in which said supporting surface includes an arithmetical mean diameter;
said preselected curvature includes at least a portion that is substantially spherical about a radius of curvature; and
said radius of curvature is less than about 105 percent of said mean diameter.
A container in which said supporting surface includes an arithmetical mean diameter; and
said positional distance is more than about 8.1 percent of said arithmetical mean diameter.
A container in which said sidewall is substantially cylindrical;
said preselected curvature includes at least a portion that is substantially spherical about a radius of curvature; and
said radius of curvature is less than about 80 percent of the diameter of said sidewall.
A container in which said sidewall is substantially cylindrical; and
said positional distance is more than about 6.2 percent of the diameter of said sidewall.
A container in which said supporting surface includes an arithmetical mean diameter;
said container includes a panel height as measured along said axis from said supporting surface to said concave panel; and
said positional distance comprises said panel height being more than about 20 percent of said mean diameter.
A container in which said sidewall is substantially cylindrical;
said container includes a panel height as measured along said axis from said supporting surface to said concave panel; and
said positional distance comprises said panel height being more than about 15 percent of the diameter of said sidewall.
A container having increased cumulative drop height resistance, which container comprises:
a sidewall being substantially cylindrical, and being disposed concentrically around a vertical axis;
an annular supporting portion comprising an annular supporting surface that is orthogonal to said vertical axis, and comprising a convex annular portion that is disposed around said vertical axis and that curves inwardly and upwardly from said supporting surface;
an outer connecting portion interconnecting said sidewall and said annular supporting portion;
a concave panel having a substantially spherical contour and being disposed radially inwardly from said convex annular portion;
a concave annular portion being disposed circumferentially around said concave panel, being connected to said concave panel, and curving downwardly toward said convex annular portion;
a circumferential inner wall being connected to said convex annular portion, extending upwardly therefrom, and being connected to said concave annular portion; and
said concave panel having a preselected radius of curvature in the range wherein the static dome reversal pressure of said concave panel is decreased with decreases in said radius of curvature.
A container in which said preselected radius of curvature of said spherical contour is less than about 2.1 inches.
A container in which said decrease in said static dome reversal pressure is at least partially obviated by said inner wall being more than about 0.08 inches.
A container in which said container includes a panel height as measured along said axis from said supporting surface to said concave panel;
said decrease in said static dome reversal pressure is at least partially obviated by a selected height of said inner wall; and
said selected height of said inner wall comprises said panel height being more than about 0.39 inches.
A container in which said container includes a panel height as measured along said axis from said supporting surface to said concave panel;
said decrease in said static dome reversal pressure is at least partially obviated by said inner wall having a selected height of more than about 0.08 inches; and
said selected height of said inner wall comprises said panel height being more than about 0.39 inches.
A container in which said preselected radius of curvature of said spherical contour is less than about 2.1 inches; and
said static dome reversal pressure is at least partially obviated by said inner wall being more than about 0.08 inches.
A container in which said preselected radius of curvature of said spherical contour is less than about 2.1 inches;
said container includes a panel height as measured along said axis from said supporting surface to said concave panel;
said decrease in said static dome reversal pressure is at least partially obviated by a selected height of said inner wall; and
said selected height of said inner wall comprises said panel height being more than about 0.39 inches.
A container in which the radius of curvature of said spherical portion is less than about 2.1 inches;
said container includes a panel height as measured along said axis from said supporting surface to said concave panel;
said decrease in said static dome reversal pressure is at least partially obviated by said inner wall having a selected height of more than about 0.08 inches; and
said selected height of said inner wall comprises said panel height being more than about 0.39 inches.
A container in which said inner wall is substantially frustoconical and comprises a smaller diameter that is distal from said supporting surface; and
said frustoconical inner wall slopes inwardly toward said axis by an angle of between about 0 and 5 degrees.
A container in which said container includes a panel height as measured along said axis from said supporting surface to said concave panel of between about 0.38 and 0.44 inches.
A container in which said inner wall has a height that is between about 0.06 and 0.1 inches.
A container in which said inner wall has a height that is between about 0.06 and 0.1 inches; and
said container includes a panel height as measured along said axis from said supporting surface to said concave panel of between about 0.38 and .44 inches.
A container with increased cumulative drop height resistance, which container comprises:
a sidewall being substantially cylindrical, and being disposed concentrically around a vertical axis;
an annular supporting portion comprising an annular supporting surface that is orthogonal to said vertical axis, and comprising a convex annular portion that is disposed around said vertical axis and that curves inwardly and upwardly from said supporting surface;
an outer connecting portion interconnecting said sidewall and said annular supporting portion;
a concave panel having a substantially spherical contour and being disposed radially inwardly from said convex annular portion;
a concave annular portion being disposed circumferentially around said concave panel, being connected to said concave panel, and curving downwardly toward said convex annular portion; and
a circumferential inner wall being connected to said convex annular portion, extending upwardly therefrom, and being connected to said concave annular portion;
said concave panel having a preselected radius of curvature in the range wherein static dome reversal pressure of said concave panel is decreased with decreases in said radius of curvature; and
said inner wall having a selected height for increasing the dome reversal pressure of said concave panel.
A container in which said supporting surface includes an arithmetical mean diameter; and
said spherical contour includes a radius of curvature that is between about 85 and 105 percent of said mean diameter.
A container in which said supporting surface includes an arithmetical mean diameter; and
said selected height of said inner wall is between about 4 and 5 percent of said arithmetical mean diameter.
A container in which said sidewall is substantially cylindrical; and
said spherical contour includes a radius of curvature that is between 6 and 8 percent of the diameter of said sidewall.
A container in which said sidewall is substantially cylindrical; and
said selected height of said inner wall is between about 3 and 3.7 percent of the diameter of said sidewall.
A container in which said supporting surface includes an arithmetical mean diameter;
said container includes a panel height as measured along said axis from said supporting surface to said concave panel; and
said selected height of said inner wall comprises said panel height being between about 19 and 22 percent of said mean diameter.
A container in which said sidewall is substantially cylindrical; and
said container includes a panel height as measured along said axis from said supporting surface to said concave panel between about 14 and 16.3 percent of the diameter of said sidewall.
A method for increasing the cumulative drop height resistance of a container, in which said container includes a sidewall being disposed around a vertical axis, an annular supporting portion being disposed around said vertical axis and having an annular supporting surface that is disposed around said vertical axis, an outer connecting portion connecting said sidewall to said supporting surface, and a concave panel being disposed inwardly from said annular supporting portion, an inner connecting portion being connected to said annular supporting portion, extending upwardly into said container, and disposing said concave panel at a positioned distance above said supporting surface, and in which said method comprises:
increasing the curvature of said concave panel to increase said cumulative drop height resistance of said container; and
limiting said increasing step to an allowable decrease in static dome reversal pressure.
A method which comprises forming said supporting surface with an arithmetical mean diameter, and forming said concave panel with at least a portion thereof that is substantially spherical and that has a radius of curvature; and
said increasing step comprises decreasing said radius of curvature to less than about 105 percent of said mean diameter.
A method which comprises forming said sidewall substantially cylindrical, and forming said concave panel with at least a portion thereof that is substantially spherical and that has a radius of curvature; and
said increasing step comprises decreasing said radius of curvature to less than about 78 percent of the diameter of said sidewall.

Claims

A container (10) having increased cumulative drop height resistance and a desired static dome reversal pressure, which container (10) comprises:
a sidewall (12) being disposed around a central axis (14);
an annular supporting portion (16) being disposed around said central axis (14) and having an annular supporting surface (18) with an arithmetical mean diameter (D₃);
an outer connecting portion (28) interconnecting said sidewall (12) and said annular supporting portion (16);
a concave panel (38) being disposed inwardly from said annular supporting portion (16) and having a radius of curvature (R₄) and panel height (H₁) as measured along said central axis (14) from said supporting surface (18) to said concave panel (38); and
an inner connecting portion (40) interconnecting said annular supporting portion (16) and said concave panel (38) said inner connecting portion (40) extending upwardly and toward said central axis (14) at an angle (α₁); characterised by
said angle (α₁), panel height (H₁), radius of curvature (R₄) and arithmetical mean diameter (D₃) being jointly selected to provide said cumulative drop height resistance and said desired static dome reversal pressure, whereby the ratio of said selected radius of curvature (R₄) to said selected arithmetical mean diameter (D₃) is less than 1.05, the ratio of said selected panel height (H₁) to said selected arithmetical mean diameter (D₃) is greater than 0.2, and said selected angle (α₁) is less than 5° from vertical.
A container (10) as claimed in Claim 1, wherein at least a portion (32) of said outer connecting portion (28) is concave.
A container (10) as claimed in Claim 1, wherein said outer connecting portion (28) comprises first and second ends (30, 20) adjacent said sidewall (12) and said annular supporting portion (16), respectively, at least a portion (32) of said outer connecting portion (28) between said first and second ends (30, 20) being inwardly displaced, relative to said central axis (14), from a plane (34) extending through said first and second ends (30, 20).
A container (10) as claimed in Claim 1, wherein the ratio of said selected radius of curvature (R₄) to said selected arithmetical mean diameter (D₃) is less than 1.019.
A container (10) as claimed in Claim 1, wherein the ratio of said selected radius of curvature (R₄) to said selected arithmetical mean diameter (D₃) is within the range of 0.875 to 1.019.
A container (10) as claimed in Claim 1, wherein said selected angle (α₁) is between 1.25° and 3.5°.
A container (10) as claimed in one of the preceding claims, wherein
said outer connecting member (28) comprises an upper convex portion (30) having an interior radius (R₃) and a lower concave portion having an exterior radius (R₆), said radii being substantially equal.
A container (10) as claimed in one of the preceding claims, wherein said container is made of an aluminium alloy.