Profiled bottom wall for containers

Abstract

A profiled bottom wall for a drawn and ironed container having a cylindrical side wall and integral bottom wall is disclosed herein. The bottom wall and side wall merge with each other along an annular outwardly directed bead and the bottom wall has an annular inwardly directed bead located within the outwardly directed bead. The adjacent ends of the two beads are interconnected by an arcuate portion that produces a convex surface within the container and the portion of the container bottom wall within the inwardly directed bead is generally flat and merges with the adjacent end of the inwardly directed bead along a further arcuate portion that defines a concave surface within the container.

Description

BACKGROUND OF THE INVENTION

For many years container manufacturers have been striving to produce what is referred to in the industry as a two-piece container at a competitive price. The two-piece container consists of a body that has an integral botom wall at one end and the opposite end is configured to have a closure secured thereto. An early example of such type of container is disclosed in U.S. Pat. No. 2,142,743.

In more recent years, many foods and beverages, particularly carbonated beverages, have commonly been packaged in metal containers formed of either aluminum or steel.

In the manufacture of drawn and ironed containers for packaging carbonated beverages, it is essential to maintain the body wall and bottom wall of the container as thin as possible so that the container can be marketed at a competitive price. The cost of the container is extremely important since, for many products, the cost of the container approaches or exceeds the cost of the product being packaged therein. As such, any reduction in cost is extremely desirable.

Furthermore, because of the large market for metal containers, particularly those formed of aluminum, a very small savings in the cost of the material for a single can will produce a substantial difference in price in considering a normal order from a packager, which may include hundreds of thousands of containers. Thus, if the container manufacturer can reduce the thickness of the metal utilized in forming the container by even one-thousandth of an inch, the savings in cost can be substantial.

To meet the competitive market price and manufacture of the most economical drawn and ironed container, one of the most difficult requirements to attain is the buckle resistance of the bottom wall when the container is used for packaging carbonated beer or other beverages while still utilizing a material that is most workable and is the thinnest possible to reduce the cost.

When a carbonated beverage is packaged in a relatively thin drawn and ironed container, the bottom wall of the container tends to buckle outwardly when exposed to normal pressures that are developed within the containers during normal summer temperatures and during the past pasteurizing process.

Quite recently, container manufacturers have been striving to produce a competitively priced container that has sufficient resistance to buckling that may result from the high pressures developed within the container. Examples of these containers are shown in U.S. Pat. No. 3,690,507 and U.S. Pat. No. 3,760,751. Both of these patents disclose drawn and ironed containers that have specifically designed bottom walls which have improved resistance to outward bulging that may result from high pressures in the container.

SUMMARY OF THE INVENTION

According to the present invention, a cylindrical container having a circular side wall and an integral bottom wall is formed to be capable of withstanding pressures on the order of 90 p.s.i. minimum without having the bottom wall buckle. This is accomplished by a particularly profiled bottom wall that will allow the container wall thickness to be reduced by more than 10 percent of the thickness of present day commercially competitive containers for the same product.

The profiled container bottom wall is joined to the side wall by an outwardly directed bead so that the peripheral edge of the bottom wall is less in diameter than the outside diameter of the container. The bottom wall consists of a flat circular panel at the center of the container which has an annular spherical portion around the periphery thereof that defines a concave surface inside the container. The annular spherical surface is connected to the outwardly directed bead through an arcuate portion having compounded radii. This connecting portion consists of an upwardly directed bead having one end connected to the outer end of the spherical annular section and the opposite end connected to the adjacent end of the bead through an arcuate portion that define a convex surface within the container.

With the configuration for the bottom wall as described, at least some of the forces that are developed on the container bottom wall by pressure from the product within the container counteract each other so that the actual forces which would tend to bulge the bottom wall outwardly are substantially reduced. Furthermore, the particular configuration of the bottom wall and its connection to the side wall reduces the overall diameter for the bottom wall. The arcuate portion defining the convex surfaces also adds stiffness or rigidity to the container bottom wall to thereby improve the buckling resistance as compared to conventional dome profiles.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF DRAWINGS

FIG. 1 shows a fragmentary side elevation view, partly in section, showing the bottom portion of a drawn and ironed container; and

FIG. 2 is an enlarged fragmentary sectional view of the outer periphery of the container bottom wall and a small portion of the side wall.

DETAILED DESCRIPTION

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail a preferred embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

Generally speaking, the container of the present invention, designated by the reference numeral 10, has a cylindrical side wall 12 and a bottom wall 14 which are joined with each other by an annular outwardly directed bead 16. The container bottom wall 14 has an inverted flat dome profile at the center thereof which is connected to outwardly directed bead or punch nose portion 16 through a portion 20 which has a double curvature between bead 16 and inverted flat dome 18.

The configuration of the bottom wall of the container provides improved buckling resistance to withstand the internal pressures of processing and warehousing while still allowing for considerable latitude for dome-depth control and design of containers particularly adapted for packaging carbonated beverages.

More specifically, the bottom wall consists of an arcuate portion 22 that merges at a juncture J1 (FIG. 2) with one end of outwardly directed bead 16, the opposite end of which is connected to side wall 12 through a connecting portion 24. Arcuate portion 22 is joined at its opposite end at a juncture J2 to an inwardly directed bead 26 and the opposite end of bead 26 is integrally joined with a second arcuate portion 28 which defines an annular spherical portion around a central flat portion 30.

Considering now the dimensional aspects of the present invention, it will be noted that an outwardly directed annular bead has a radius R1 which has its center located inside the container while inwardly directed bead 26 has a radius R2 which has its center located outside the container. Also, arcuate portion 22 has a radius R3 which is located outside the container so that a convex surface 29 is formed inside the container. The second arcuate portion 28 has a radius R4 which is located inside the container and therefore defines a concave surface 32 that integrally joins flat panel 30 with the adjacent end of inwardly directed annular bead 26.

Container side wall 12 has an outside diameter D1 which is tapered inwardly slightly along arcuate portion 24 and is joined to arcuate portion 22 by bead 16 having radius R1. This results in having the lowermost edge of bead 16 define a diameter D2 which is smaller than the diameter D1. The uppermost edge of inwardly directed bead 26 defines a diameter D3 while the peripheral edge of flat panel 30 defines a diameter D4.

The particular configuration and radii of the various arcuate sections between container side wall 12 and flat panel 30 result in a vertical dimension H1 between flat panel 30 and the lowermost edge of outwardly directed annular bead 16 and an overall height of bottom wall 14, designated by the reference H2, which is the vertical dimension between the uppermost edge of the inwardly directed annular bead and the lowermost edge of outwardly directed bead 16. The particular dimensions all play some role in determining the rigidity of the container bottom wall which in turn determines the effective resistance to pressure applied to the inside surface of container 10.

The most important aspects of the configuration of the bottom of the container are the fact that (1) the lowermost edge of outwardly directed annular bead 16 (D2) is connected to the uppermost edge of inwardly directed annular bead 26 (D3) by a compound curve which will be described in more detail later, and (2) the flat panel 30 is displaced below the uppermost edge of inwardly directed annular bead 26 by a predetermined dimension. The result is that pressure applied to the portion of the bottom wall which is located above flat panel 30 (the area generally between the difference of H2 and H1) will produce forces which have horizontal components that will act against each other and thereby result in a zero resultant force on the container bottom wall. More specifically, the horizontal components of the forces developed on concave surface 32 and the portion of bead 26 located inside diameter D3 will be counteracted by forces developed in the upper portion of convex surface 29 and the portion of bead 26 which is located outside diameter D3.

Also, the effective diameter of the container bottom wall will be defined by the lowermost edge of the annular bead 16 which is less than the diameter of the container and this acts as an anchor point for bottom wall 18. The result is that the overall area of the container bottom wall 18, defined by diameter D2, is less than the diameter of the container.

This arrangement has a distinct advantage over containers of the type shown in U.S. Pat. No. 3,690,507. A container designed according to the teachings of this patent will have a tendency to expand at the juncture between the side wall and bottom wall. The result is that the side wall will tend to bulge outwardly or "grow" at the lower end which will effectively increase the diameter of the bottom wall. The net result is that the bottom wall will bulge or buckle at a lower pressure.

The rigidity of the container bottom wall is further increased by the convex surface 29 located adjacent the outer peripheral diameter of bottom wall 18. The compound curvature of the section 20 between diameters D2 and D3 is particularly important in producing an extremely rigid bottom wall with metal of minimum thickness.

An inspection of FIG. 2 shows that a line L1 drawn tangent to the juncture J1 between arcuate surface 22 and outwardly directed annular bead 16 defines an angle A with respect to the outer adjacent surface of the container side wall 12, which is represented by the plane P drawn through the center of radius R1. A second tangent line L2 at the juncture between the arcuate portion 22 and inwardly directed annular bead 26 defines an angle B with respect to plane P. It has been determined that the proper relationship of these angles plays an extremely important role in preventing outward deformation of the connecting portion 20 between diameters D2 and D3. Also, the particular radii and diameters as well as the height H1 and H2 can be directly correlated to the outside diameter of container side wall 12 and the thickness (T1) of bottom wall 18. These dimensions have been determined to be within the following ranges: Dimensions Ranges ______________________________________ A 0.degree. to 15.degree. B 20.degree. to 35.degree. T1 = Thickness of Metal at Bottom D1 = Outside Diameter of Container D2 0.85 to 0.95 D1 D3 0.75 to 0.95 D2 D4 0.65 to 0.85 D3 R1 3.0 to 5.0 T1 R2 4.0 to 6.0 T1 R3 0.5 to 3.0 D1 R4 0.5 to 2.0 D1 H1 8.0 to 15 T1 H2 15 to 25 T1 ______________________________________

While not limiting to any specific direct relationship to the various dimensions listed above, a typical example of an acceptable container could have the following dimensions:

A = 7.degree. B = 25.degree. D2 = 0.9 D1 D3 = 0.85 D2 D4 = 0.75 D3 R1 = 3.5 T1 R2 = 5 T1 R3 = 1.5 D1 R4 = 1.0 D1 H1 = 10 T1 H2 = 18 T1

Summarizing the present invention, the side wall 12 of the drawn and ironed cylindrical container body, which may be formed of either aluminum or steel, is joined to bottom 18 at a reduced diameter portion D2 and bottom wall has a compound curvature between the lowermost edge and the uppermost edge with a partial spherical annular surface inside the uppermost edge which is ultimately connected to an inverted flat panel portion that defines the center of the bottom wall 18.

Claims

What is claimed is:

1. A metal container having a cylindrical side wall and an effectively rigid bottom wall integral therewith at the bottom end thereof, said bottom wall and side wall merging along one end of an annular outwardly directed bead, said bead having an end opposite to said one end spaced diametrically inwardly thereof, said bottom wall having an annular inwardly directed bead located within said outwardly directed bead, said inwardly directed bead having opposite ends one of which is adjacent said opposite end of said outwardly directed bead, and an arcuate portion interconnecting the two adjacent ends of the respective beads, said arcuate portion producing a convex surface within said container between said beads, said arcuate portion and said beads providing resistance to outward deformation of said bottom wall when pressure is applied inside said container, said bottom wall further including a generally flat central portion within said inwardly directed bead, said generally flat portion being spaced vertically above the lower end of said outwardly directed bead and vertically below the upper end of said inwardly directed bead, said generally flat portion merging with an adjacent end of said inwardly directed bead along a second arcuate portion defining a concave surface inside said container.

2. A container as defined in claim 1, in which said arcuate portion has a radius in the range of 0.5 to 3.0 times the outside diameter of said side wall.

3. A container as defined in claim 1, in which a lowermost edge of said outwardly directed bead defines a first diameter which is less than the outside diameter of said side wall and in which said inwardly directed bead has an uppermost edge which defines a second diameter that is in the range of 0.75 to 0.95 times said first diameter.

4. A container as defined in claim 3, in which said first diameter is in the range of 0.85 to 0.95 times the outside diameter of said side wall.

5. A container as defined in claim 2, in which said outwardly directed bead has a second radius which is in the range of 3.0 to 5.0 times the thickness of said bottom wall and said inwardly directed bead has a third radius which is in the range of 4.0 to 6.0 times the thickness of said bottom wall.

6. A container as defined in claim 5, in which said bottom wall has a generally flat portion inside said inwardly directed bead, said flat portion merging with said inwardly directed bead along a second arcuate portion defining a concave surface inside said container, said concave surface having a fourth radius in the range of 0.5 to 2.0 times the outside diameter of said side wall.

7. A container as defined in claim 1, in which a line tangent to the juncture between said outwardly directed bead and said arcuate portion defines a first angle less than 15.degree. with respect to the adjacent side wall and a line tangent to the juncture between said inwardly directed bead and said arcuate portion defines an angle of less than 35.degree. with respect to the adjacent side wall of the container.

8. A container as defined in claim 1, in which the vertical dimension between the lowermost edge of said container and said flat portion is in the range of 8.0 to 15.0 times the thickness of said bottom wall.

9. A container as defined in claim 8, in which the vertical dimension between the lowermost edge of said container and the uppermost edge of said inwardly directed bead is in the range of 15 to 25 times the thickness of said bottom wall.

10. A metal container having a cylindrical side wall and an integral effectively rigid bottom wall, said bottom wall and side wall merging along an annular outwardly directed bead having one end joined to said side wall and an opposite end spaced diametrically inwardly thereof, said bottom wall having an annular inwardly directed bead located within said outwardly directed bead, said inwardly directed bead having opposite ends one of which is adjacent said opposite end of said outwardly directed bead, said bottom wall having an arcuate portion between adjacent ends of said beads, said portion having a first juncture with said opposite end of said outwardly directed bead and a second juncture with an adjacent end of said inwardly directed bead, a line tangent to said first juncture defining an angle of less than 15.degree. with said side wall and a line tangent to said second juncture defining an angle greater than 20.degree. with said side wall, said arcuate portion producing a convex surface within said container between said beads, said arcuate portion and said beads providing resistance to outward deformation of said bottom wall when pressure is applied inside said container, said bottom wall further including a generally flat portion within said inwardly directed bead, said generally flat portion being spaced vertically about the lower end of said outwardly directed bead and vertically below the upper end of said inwardly directed bead, said generally flat portion merging with said inwardly directed bead along an arcuate portion defining a concave surface inside said container.

11. A container as defined in claim 10, in which said flat portion is vertically positioned to be approximately equally spaced from the uppermost edge of said inwardly directed bead and the lowermost edge of said outwardly directed bead.

12. A container as defined in claim 11, in which said outside diameter of said side wall defines a first diameter and said lowermost edge of said outwardly directed bead defines a second diameter which is in the range of 0.85 to 0.95 times the first diameter, and in which said uppermost edge of said inwardly directed bead defines a third diameter in the range of 0.75 to 0.95 times the second diameter, and said flat portion has a fourth diameter in the range of 0.65 to 0.85 times the third diameter.

13. A container as defined in claim 12, in which said portion between adjacent ends of said beads is arcuate and defines a convex surface inside said container, said convex surface having a radius in the range of 0.5 to 3.0 times said first diameter.