Receptacles – End wall structure – One-piece side and end wall
Patent
1995-01-10
1997-01-14
Moy, Joseph
Receptacles
End wall structure
One-piece side and end wall
220609, B65D 742
Patent
active
055930638
DESCRIPTION:
BRIEF SUMMARY
This invention relates to metal containers and more particularly but not exclusively to the bottom wall of a container drawn from a circular blank to comprise a bottom wall and a side wall upstanding from the periphery of the bottom wall.
A widely used container for petfoods, typically 73 mm diameter by 56 mm tall comprises a substantially flat center panel surrounded by a flexible annulus which is joined to a channel portion, or stand bead, having an inner wall joining the flexible annulus and an outer wall joining the side wall of the container. The containers are usually drawn from a laquered steel such as electrochrome coated steel or tinplate in temper DR8 of thickness 0.17 mm (about 0.007"). The side wall of this can is vulnerable to damage at point of sale. When the containers are filled, the closing machine applies a top pressure to a can end while a double seam is rollformed to join the can end to the side wall, so the side wall has to be strong enough to support this top load. When the closed containers are thermally processed the contents of the can expand so pressure develops in the container and the side wall is protected from undue distortion because the flexible annulus permits the bottom wall to bulge outwardly to increase the container volume. As the container cools, the pressure in the can abates. If the product is hot filled, a partial vacuum may develop in the container when cooled to room temperature so putting the side wall at risk of collapse unless the flexible annulus returns towards original shape.
Can ends which provide the desired expansion and contraction in container volume by simple flexure are described in U.S. Pat. Nos. 3,105,765 (Creegan) and 3,409,167 (Blanchard), and in British Patents Publications 2107273 and 2119743 (of American Can Company) but in all these patents the change of volume available in a filled and closed can is limited to that available from flexure, not permanent change of shape.
These volume change requirements are made more stringent if tall cans having a wall ironed side wall are used because the side wall may be between 0.075 mm (0.004") and 0.0125 mm (0.005").
A first objective of this invention is to provide a container having an end wall which will provide an increased volume during thermal treatment to reduce the pressures generated within the can during thermal processing. A second objective is to provide some flexibility to compensate for a residual partial vacuum in a filled and closed can. The end wall may be integral with the side wall of a drawn can body or alternatively the end wall may be a can end or lid.
Accordingly, this invention provides a container end wall comprising a peripheral channel portion, or cover hook an inner wall of which supports a center panel, wherein a deformable annulus extends both radially and axially inwards away from the inner wall to support a dependent annulus which connects the center panel to the deformable annulus, characterised in that when subjected to pressure inside a container, after closure, the central panel is temporarily deflected axially outwards and the deformable annulus is permanently deflected from its initial stable position to its second stable position to increase the volume of the container.
In one embodiment, the deformable annulus comprises a substantially flat annular portion which extends radially inwards from the inner wall of the channel portion or cover hook and surrounds an annular bead of arcuate cross-section which extends away from the inner wall before turning to join a dependent substantially cylindrical wall portion which connects the center panel and ring to the deformable annulus.
An outer wall of the channel portion may have a peripheral cover hook for attachment to the flange of the side wall of a container body; or alternatively the outer wall of the channel portion may connect with the side wall of a can body drawn from a blank.
In another embodiment the deformable annulus is frutoconical and may, if desired, be provided with a plurality of stiffening beads which exten
REFERENCES:
patent: 3693828 (1972-09-01), Kneusel et al.
patent: 3905507 (1975-09-01), Lyu
patent: 4010867 (1977-03-01), Jones
patent: 4048934 (1977-09-01), Wallace
patent: 4249666 (1981-02-01), Hubert et al.
Claydon Paul C.
McMahon Neil D.
CarnaudMetalbox plc
Moy Joseph
LandOfFree
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