GB1588014A

GB1588014A - Container end wall

Info

Publication number: GB1588014A
Application number: GB26451/76A
Authority: GB
Original assignee: Metal Box PLC
Current assignee: Crown Packaging UK Ltd
Priority date: 1976-06-25
Filing date: 1976-06-25
Publication date: 1981-04-15
Also published as: DE2728592A1; ZA773669B; IN148287B; CA1121748A

Description

(54) A CONTAINER END WALL (71) We, METAL Box LIMITED, of Queens House, Forbury Road, Reading RGl 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 follow ing statement: This invention relates to a container end wall and more particularly but not exclusively to the end wall of a can and cans having such an end wall.

Metal cylindrical pressure vessels are known which have convex end walls of semi-elliptical cross-section such that the length of the major axis of the ellipse equates to the diameter of the cylindrical body. The peripheral portion of the end wall is butt welded to the cylindrical body. In order to minimise the space occupied )by the pressure vessel it is desirable to use end walls having a ratio of major axis to minor axis greater than the preferred 2:1. However, as the ratio is increased, making the end wall shal lower, sufficient metal thickness must be pro vided to ensure stability of the end wall under load. For example, an elliptical end wall having a ratio of major axis to minor axis equal to 10:1 requires a metal thickness equal to two hundredths of the length of the minor axis.

A known end wall of a built up container for beer has two distinct portions, a peripheral portion adapted for attachment to the body of the container and a central flat closure panel surrounded and supported by the peripheral portion. However rigid the support provided for a flat central panel a point is reached, under conditions of excessive pressure, when the hoop stress, induced by outward distortion of the flat panel, causes local buckling, sometimes called peaking.

With current separate end wall configur ations, centre panel failure values are substan tially lower than that of the supporting peri pheral element. The configuration proposed utilizes more fully the potential strength of the supporting peripheral element, by pro viding a central panel which efficiently directs the loads into the peripheral element, to per mit the use of thinner sheet metal while obtain ing satisfactory strength.

This invention provides a container end wall, which comprises sheet metal deformed to provide a circular central panel of semielliptical 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. If desired the central panel is joined to the anti-peaking bead by a cylindrical portion.

In a first embodiment the annular wall portion is cylindrical and the arcuate crosssection of the anti-peaking bead is a semicircle. In a second embodiment the wall portion is frustroconical. The ratio of the major axis to minor axis of the ellipse is preferably within the range 10:1 and 25:1.

The container end wall may have a peripheral rim in the form of a cover hook adapted for engagement with a can body by means of a double seam. Alternatively the container end wall may be integral with a cylindrical can bod wall drawn from a sheet metal blank, so that the can body wall extends from the outer periphery of the peripheral rim.

Various embodiments of the invention will now be described, by way of example, and the reference to the accompanying drawings in which: Figure 1 is a sectioned side elevation of a known welded cylindrical pressure vessel, Figure 2 is a sectioned side elevation of a part of a known beam can, Figure 3 is a side elevation of a can end, according to the invention, sectioned on a diameter and Figure 4 is a similar view of an alternative embodiment.

In Figure 1 the cylindrical pressure vessel comprises a convex end portion 1 joined by a peripheral weld 2 to a body portion 3. The cross-section of the end portion 1 is a semiellipse with the major axis of the ellipse equating to, and lying diametrically across, the diameter of the body portion 3. The ratio of the major axis to the minor axis of the ellipse is approximately 3 to 2, and the convex end portion is relatively high.

In Figure 2 the beer can comprises an end portion 4 and a body portion 5 joined together by a double seam 6. The end portion 4 has been stamped from nitrogenised tinplate 0.0160 inches thick to have a flat closure panel 7 surrounded by, and integral with an anti peaking beak 8 which supports the closure panel 7 and joins it to the cylindrical countersink wall 9.

The countersink wall 9 is surrounded by the end material of the double seam 6. Such a can is able to contain pressures of the order of 45 p.s.i. However, excessive pressures within the can distort the closure panel 7 and the hoop stresses generated can cause local buckling of the closure panel 7 and initiate buckling of the anti-peaking bead 8.

In Figure 3 a can end approximately 5 inches in diameter has been stamped from tinplate 0.0116 inches thick to have a peripheral portion 10 and a central closure panel 11 of semi-elliptical cross-section. The peripheral portion 10 comprises an annular cover hook 12, a cylindrical countersink wall 13 dependent therefrom and an anti-peaking bead 14 of semi-circular cross-section which joins the countersink wall 13 to the convex closure panel 11. The closure panel 11 spans the area within the inner periphery of the anti peaking bead and has the cross-sectional shape of a semi-ellipse. The ratio of the major axis to minor axis of the ellipse is 21:1, when on the tool block, so that the convex panel surface lies within the height of the countersink wall and therefore does not protrude beyond the cover hook.It will be appreciated that the convex surface may spring back on removal from the tool to a shallower ellipse having a ratio of the order of 25:1.

Therefore, when the can end of Figure 3 is joined to a can body by means of a double seam the convex surface is below the top of the double seam and so protected by it when filled cans are stacked to stand one upon another, in like manner to the prior art can of Figure 2.

This stacking requirement for filled cans places a constraint on the acceptable convex height of the semi elliptical closure panel 11.

We have found, for acceptable end thicknesses, that a range of ratios of major axis to minor axis between 10:land 21.6:1 is permissible for the tool block because the metal springs back a little after stamping. A ratio of 21:1 is preferred for 5flinch diameter can end. Such a closure panel is of adequate stability to utilise the strength of the peripheral anti-peaking bead which supports it. The bead 14 has an internal radius, denoted R in Figure 3, of about 0.040" to lead from the periphery of the elliptical closure panel 11 into the cylindrical counter sink wall 13. A short cylindrical portion may optionally be used to join the bead 14 to the closure panel 11 as indicated at "C".

In the alternative embodiment of Figure 4, the can end comprises a modified peripheral portion 20 and a modified closure panel 21 of semi-elliptical cross-section. The peripheral portion 20 comprises an annular cover hook 22, a frustroconical countersink wall 23 dependent from the inside therefrom and an antipeaking bead 24 which joins the countersink wall 23 to the closure panel 21.

The frustroconical countersink wall 23, extending downwardly and radially inwards in conjunction with a bead arcuate cross-section of radiusR as in Figure 3, permits the use of a closure panel of smaller diameter. Therefore the ratio of major axis to minor axis of the semi-elliptical cross-section of the closure panel may be reduced, if desired. It will be understood that the can end according to Figure 4 requires less metal than the can end of Figure 3.

Also, when the can ends of Figure 4 are stacked in the feed chute of the seaming machines used to seam the ends to can bodies, each can end nests with the next in nonwedging contact, so saving space and facilitating feeding.

Although the can ends described above are made from tinplate, the same principles may be used for can ends made of other metals, such as aluminium. Furthermore, the combination of a closure panel of semi-elliptical cross-section and a supporting peripheral portion may be incorporated into containers drawn from sheet metal. The cylindrical side wall of such drawn containers would extend from the outer periphery of the cover hook portion of Figures 3 and 4 so that the cover hook portion acts as a peripheral rim upon which the can may stand.

WHAT WE CLAIM IS: 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 and inner periphery of which is joined to the antipeaking 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 antipeaking 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 containing Claim 1 or Claim 2 wherein the annular wall portion is frustroconical.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. is approximately 3 to 2, and the convex end portion is relatively high. In Figure 2 the beer can comprises an end portion 4 and a body portion 5 joined together by a double seam 6. The end portion 4 has been stamped from nitrogenised tinplate 0.0160 inches thick to have a flat closure panel 7 surrounded by, and integral with an anti peaking beak 8 which supports the closure panel 7 and joins it to the cylindrical countersink wall 9. The countersink wall 9 is surrounded by the end material of the double seam 6. Such a can is able to contain pressures of the order of 45 p.s.i. However, excessive pressures within the can distort the closure panel 7 and the hoop stresses generated can cause local buckling of the closure panel 7 and initiate buckling of the anti-peaking bead 8. In Figure 3 a can end approximately 5 inches in diameter has been stamped from tinplate 0.0116 inches thick to have a peripheral portion 10 and a central closure panel 11 of semi-elliptical cross-section. The peripheral portion 10 comprises an annular cover hook 12, a cylindrical countersink wall 13 dependent therefrom and an anti-peaking bead 14 of semi-circular cross-section which joins the countersink wall 13 to the convex closure panel 11. The closure panel 11 spans the area within the inner periphery of the anti peaking bead and has the cross-sectional shape of a semi-ellipse. The ratio of the major axis to minor axis of the ellipse is 21:1, when on the tool block, so that the convex panel surface lies within the height of the countersink wall and therefore does not protrude beyond the cover hook.It will be appreciated that the convex surface may spring back on removal from the tool to a shallower ellipse having a ratio of the order of 25:1. Therefore, when the can end of Figure 3 is joined to a can body by means of a double seam the convex surface is below the top of the double seam and so protected by it when filled cans are stacked to stand one upon another, in like manner to the prior art can of Figure 2. This stacking requirement for filled cans places a constraint on the acceptable convex height of the semi elliptical closure panel 11. We have found, for acceptable end thicknesses, that a range of ratios of major axis to minor axis between 10:land 21.6:1 is permissible for the tool block because the metal springs back a little after stamping. A ratio of 21:1 is preferred for 5flinch diameter can end. Such a closure panel is of adequate stability to utilise the strength of the peripheral anti-peaking bead which supports it. The bead 14 has an internal radius, denoted R in Figure 3, of about 0.040" to lead from the periphery of the elliptical closure panel 11 into the cylindrical counter sink wall 13. A short cylindrical portion may optionally be used to join the bead 14 to the closure panel 11 as indicated at "C". In the alternative embodiment of Figure 4, the can end comprises a modified peripheral portion 20 and a modified closure panel 21 of semi-elliptical cross-section. The peripheral portion 20 comprises an annular cover hook 22, a frustroconical countersink wall 23 dependent from the inside therefrom and an antipeaking bead 24 which joins the countersink wall 23 to the closure panel 21. The frustroconical countersink wall 23, extending downwardly and radially inwards in conjunction with a bead arcuate cross-section of radiusR as in Figure 3, permits the use of a closure panel of smaller diameter. Therefore the ratio of major axis to minor axis of the semi-elliptical cross-section of the closure panel may be reduced, if desired. It will be understood that the can end according to Figure 4 requires less metal than the can end of Figure 3. Also, when the can ends of Figure 4 are stacked in the feed chute of the seaming machines used to seam the ends to can bodies, each can end nests with the next in nonwedging contact, so saving space and facilitating feeding. Although the can ends described above are made from tinplate, the same principles may be used for can ends made of other metals, such as aluminium. Furthermore, the combination of a closure panel of semi-elliptical cross-section and a supporting peripheral portion may be incorporated into containers drawn from sheet metal. The cylindrical side wall of such drawn containers would extend from the outer periphery of the cover hook portion of Figures 3 and 4 so that the cover hook portion acts as a peripheral rim upon which the can may stand. WHAT WE CLAIM IS:

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 and inner periphery of which is joined to the antipeaking 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.

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.

6. A container end wall according to any preceding claim wherein the peripheral rim is in the form of a cover hook adapted for engagement with a can body by means of a double seam.

7. A container end according to Claim 6 when attached to a can body by means of a double seam.

8. A container end wall according to any of Claims 1 to 5 when integral with a cylindrical can body wall extending from the outer periphery of the peripheral rim.

9. A can end substantially as herein described with reference to and shown in Figure 3 of the accompanying drawings.

10. A can end substantially as hereinbefore described with reference to and shown in Figure 4 of the accompanying drawings.