GB1602309A

GB1602309A - Containers

Info

Publication number: GB1602309A
Application number: GB24464/78A
Authority: GB
Original assignee: Metal Box PLC
Current assignee: Crown Packaging UK Ltd
Priority date: 1978-05-30
Filing date: 1978-05-30
Publication date: 1981-11-11
Also published as: GR64865B; PT69681A; ZA792470B

Description

(54) CONTAINERS (71) We, METAL BOX LIMITED, of Queens House, Forbury Road, Reading RG1 3JH, Berkshire, England a British Company, 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: This invention relates to an end wall for a container and more particularly but not exclusively to a can end having a central panel and a peripheral portion adapted to permit attachment to a can body by means of a double seam.

Our co-pending British Patent Application No. 26451/76 Serial No 1588014 claims: 1. A container end wall, which comprises sheet metal deformed to provide a circular central panel of semi-elliptical cross-section, an anti-peaking bead of arcuate cross-section the inner periphery of which is joined to the periphery of the central panel, an annular wall portion extending from the outer periphery of the anti-peaking bead, and a peripheral rim the inner periphery of which is joined to the anti-peaking bead by the wall portion, the central panel and peripheral rim being concave and the anti-peaking bead convex to the interior side of the container end wall which when in use is subject to the container contents, the peripheral rim being externally proud of the central panel.

2. A container end wall according to claim 1 wherein the central panel is joined to the anti-peaking bead by a cylindrical portion.

3. A container end wall according to claim 1 or claim 2 wherein the annular wall portion is cylindrical and the arcuate cross-section of the anti-peaking bead is a semi-circle.

4. A container end wall according to claim 1 or claim 2 wherein the annular wall portion is frustoconical.

5. A container end wall according to any preceding claim wherein the ratio of the major axis to minor axis of the ellipse is within the range 10:1 and 25:1.

The semi-ellipses described in our co-pending British Patent Application No. 26451/76 Serial No. 1588014 are very shallow and we have found that greater resistance to internal pressures within a can, may be obtained by use of such can ends having deeper ellipses, other governing parameters being equal.

Various embodiments of the invention will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 is a side elevation of a round can end sectioned upon - a diameter; and Figure 2 is a diagrammatic representation of an ellipse.

In Figure 1 the can end 1 has been drawn from a sheet of metal such as tinplate or aluminium to have a peripheral portion generally denoted 2 and a convex central panel 3 of semi-elliptical cross-section. The peripheral portion 2 comprises an annular cover hook 4, a substantially cylindrical countersink wall 5 dependent from the inside of the cover hook 4, and an annular anti-peaking bead 6 in the form of a channel which joins the peripheral portion to the periphery of the central panel 3.

The dashed line denoted A' shows where the periphery of the central panel 3 joins the anti-peaking bead 6; and the line A' in Figure 1 is substantially equal in length to the length of the major axis, marked A in Figure 2.

In Figure 2 the minor axis of the ellipse is marked B and the ratio of the major axis A to the minor axis B is about 5:1. The curvature of the central panel 3 in Figure 1 is represented by the upper half of the ellipse shown in Figure 2.

The load which the can end of Figure 1 has to support when attached to a can body containing a product under pressure, is proportional to the pressure within the container and the area of the can end presented to the product. Known ways of designing cans include making the can body small in diameter; using thicker sheet metal for the can end; and improving the contours of the can end to distribute the load on to the double seam which joins the can end on to the body. In our co-pending application we teach the use of convex central panels having a semi-elliptical cross-section which delivers the load to the anti-peaking bead efficiently. In this specification we teach a preferred range of ratios for the elliptical cross-section.

It will be understood by those practiced in the art that after sheet metal is pressed to a shape between a pair of tools the metal tends to spring back somewhat from the exact shape imposed by the tools.

In the table of results which follows, the ratio of the major axis to minor axis of the male tool is tabulated and it will be understood that the results of pressure tests tabulated relate to ends made on such tools when removed from the tools and seamed on to a can body.

The "failure pressure" tabulated refers to the pressure at which the ends failed to contain the internal pressure and locally buckled under the influence of hoop stresses arising as the central panel 3 bulged.

In the following table the results of tests on can ends of two diameters are shown, first a 502 diameter can end and second a 603 diameter can end. In each case the can end having a semi-elliptical profile for the central panel is compared with a can end of like diameter having a flat panel.

502 Diameter can ends made from tinplate: ELLIPSE RATIO END THICKNESS FAILURE PRESSURE (MIN) Flat Panel 0.0116 inches 25 p.s.i.

Flat Panel 0.0160 inches 40 p.s.i.

Ellipse 9.34:1 0.0116 inches 40 p.s.i.

Ellipse 9.34:1 0.0160 inches 70 p.s.i.

Ellipse 9.34:1 0.0169 inches 75 p.s.i.

Ellipse 9.1:1 0.0160 inches 75 p.s.i.

603 Diameter can ends made from tin plate: ELLIPSE RATIO END THICKNESS FAII,URE PRESSURE (MIN) Flat Panel 0.0160 inches 30 p.s.i Ellipse 7.88:1 0.0160 inches 55 p.s.i.

The foregoing table shows that in all cases the elliptical profiled can ends are stronger than the prior art flat panelled can ends of like thickness, the performance of which is tabulated for comparison.

The deepening of the ellipse from 9.34:1 to 9.1:1 increased the failure pressure of a 502 can end made from 0.0160" tinplate from 70 p.s.i. to 75 p.s.i.

Increasing the thickness of tinplate used increased the failure pressure of the 502 diameter can ends.

The results tabulated for the 603 diameter can ends show firstly the influence of can diameter on the failure pressure; for example the flat panelled 502 end made from 0.0160" tinplate failing at 40 p.s.i. can be compared with the 603 can end made from like material and failing at 30 p.s.i. The use of a semi-elliptical profile on the 603 diameter can end raised the failure pressure to 55 p.s.i., an improvement of 25 p.s.i. This improvement is similar in magnitude to that obtained by providing the 502 diameter can ends with a semi-elliptical profile for the central panel.

Whilst the results tabulated relate to can ends made from tinplate the invention is not limited to tinplate can ends. Ends according to the invention may be made from other sheet metals such as aluminium and aluminium alloys. The 502 and 603 diameter can ends described are used in large beer cans, the beer being of a kind which generates lower pressures within the can than is common with the beer packed in smaller cans. However the invention may be applied to the can ends for can bodies of 211 diameter which are used for beer and carbonated beverages. In which case, the end may, if desired, include one of the easy opening features commonly used in the trade.

WHAT WE CLAIM IS: 1. A modification of the container end wall claimed in claim 5 of our British Patent Application No. 26451/76 serial no. 1588014 in which the ratio of major axis to minor axis of the ellipse is greater than 5:1 and less than 10:1.

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

Claims

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

containing a product under pressure, is proportional to the pressure within the container and the area of the can end presented to the product. Known ways of designing cans include making the can body small in diameter; using thicker sheet metal for the can end; and improving the contours of the can end to distribute the load on to the double seam which joins the can end on to the body. In our co-pending application we teach the use of convex central panels having a semi-elliptical cross-section which delivers the load to the anti-peaking bead efficiently. In this specification we teach a preferred range of ratios for the elliptical cross-section.

It will be understood by those practiced in the art that after sheet metal is pressed to a shape between a pair of tools the metal tends to spring back somewhat from the exact shape imposed by the tools.

In the table of results which follows, the ratio of the major axis to minor axis of the male tool is tabulated and it will be understood that the results of pressure tests tabulated relate to ends made on such tools when removed from the tools and seamed on to a can body.

The "failure pressure" tabulated refers to the pressure at which the ends failed to contain the internal pressure and locally buckled under the influence of hoop stresses arising as the central panel 3 bulged.

In the following table the results of tests on can ends of two diameters are shown, first a 502 diameter can end and second a 603 diameter can end. In each case the can end having a semi-elliptical profile for the central panel is compared with a can end of like diameter having a flat panel.

502 Diameter can ends made from tinplate: ELLIPSE RATIO END THICKNESS FAILURE PRESSURE (MIN) Flat Panel 0.0116 inches 25 p.s.i.

Flat Panel 0.0160 inches 40 p.s.i.

Ellipse 9.34:1 0.0116 inches 40 p.s.i.

Ellipse 9.34:1 0.0160 inches 70 p.s.i.

Ellipse 9.34:1 0.0169 inches 75 p.s.i.

Ellipse 9.1:1 0.0160 inches 75 p.s.i.

603 Diameter can ends made from tin plate: ELLIPSE RATIO END THICKNESS FAII,URE PRESSURE (MIN) Flat Panel 0.0160 inches 30 p.s.i Ellipse 7.88:1 0.0160 inches 55 p.s.i.

The foregoing table shows that in all cases the elliptical profiled can ends are stronger than the prior art flat panelled can ends of like thickness, the performance of which is tabulated for comparison.

The deepening of the ellipse from 9.34:1 to 9.1:1 increased the failure pressure of a 502 can end made from 0.0160" tinplate from 70 p.s.i. to 75 p.s.i.

Increasing the thickness of tinplate used increased the failure pressure of the 502 diameter can ends.

The results tabulated for the 603 diameter can ends show firstly the influence of can diameter on the failure pressure; for example the flat panelled 502 end made from 0.0160" tinplate failing at 40 p.s.i. can be compared with the 603 can end made from like material and failing at 30 p.s.i. The use of a semi-elliptical profile on the 603 diameter can end raised the failure pressure to 55 p.s.i., an improvement of 25 p.s.i. This improvement is similar in magnitude to that obtained by providing the 502 diameter can ends with a semi-elliptical profile for the central panel.

Whilst the results tabulated relate to can ends made from tinplate the invention is not limited to tinplate can ends. Ends according to the invention may be made from other sheet metals such as aluminium and aluminium alloys. The 502 and 603 diameter can ends described are used in large beer cans, the beer being of a kind which generates lower pressures within the can than is common with the beer packed in smaller cans. However the invention may be applied to the can ends for can bodies of 211 diameter which are used for beer and carbonated beverages. In which case, the end may, if desired, include one of the easy opening features commonly used in the trade.

WHAT WE CLAIM IS: 1. A modification of the container end wall claimed in claim 5 of our British Patent Application No. 26451/76 serial no. 1588014 in which the ratio of major axis to minor axis of the ellipse is greater than 5:1 and less than 10:1.
2. A container end wall according to claim 1 substantially as hereinbefore described

with reference to the accompanying drawings.
3. A container end wall according to claim 1 substantially as hereinbefore described with reference to the table of results.