Receptacles – End wall structure – Joint or seam between sidewall and end wall
Patent
1989-12-01
1991-09-10
Spruill, Robert L.
Receptacles
End wall structure
Joint or seam between sidewall and end wall
72348, 413 8, 413 56, B21D 5144, B21D 4300
Patent
active
050466372
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the production of can end shells for seaming onto the ends of can bodies to form cans capable of withstanding substantial internal pressures.
The can end shells to which the invention relates comprise an annular flange or seaming panel for seaming the shell to a can body, a frustoconical chuck wall, a flat central panel, and an annular, generally U-shaped, channel known as an anti-peaking bead connecting the chuck wall to the central panel. Apparatus for making can end shells of this type is described for example in U.S. Pat. No. 3,537,291, U.S. Pat. No. 3,957,005, U.S. Pat. No. 4,109,599, and EP 0153115. In U.S. Pat. No. 3,537,291 and U.S. Pat. No. 3,957,005, the anti-peaking bead is formed by a profiled punch acting against a fixed correspondingly profiled die. In U.S. Pat. No. 4,109,599 a preliminary shell comprising a peripheral seaming panel, a frustoconical wall and a flat central panel is formed in a first stage and, in a second stage, the central panel is moved towards the sealing panel such that a reinforcing anti-peaking bead is formed between the frustoconical wall and the central panel. The anti-peaking bead is formed largely by bending and is constituted by material from the outer periphery of the central panel of the perliminary shell. In EP 0153115 the two stages described in relation to U.S. Pat. No. 4,109,599 are carried out sequentially in a single piece of apparatus. In this case however the anti-peaking bead is formed by a reforming action which incorporates material from the frustoconical wall into the anti-peaking bead.
It is known that the resistance of a can end shell to internal pressures after seaming onto a can body is dependent upon the profile of the anti-peaking bead and thickness of the material from which the shell is made. The art of making can end shells, without tightening (reforming) of the anti-peaking bead, permitted use of aluminium sheet 0.32 mm thick for a can end of about 57 mm diameter ("206"). The combined shell drawing and reforming apparatus described in EP-0153115 permitted use of aluminium alloy sheet 0.29 mm thick with a possibility of using sheet 0.27 mm thick. In order to make can end shells from lower nominal gauge material it is desirable to make the nominal radius of the anti-peaking as small as possible whilst avoiding the creation of overworked areas in the anti-peaking bead leading to yield of material and failure under pressure.
The present invention relates to an improved method and apparatus for making can end shells from thin gauge stock material (such as aluminium alloy sheet in the range 0.245 to 0.29 mm thick) and having anti-peaking beads of small nominal radius and in which the creation of overworked regions in the anti-peaking bead are avoided.
Accordingly the present invention provides for making a preliminary shell in which a preformed anti-peaking bead in the form of a generally U-shaped channel having a relatively large nominal radius is formed in a controlled drawing action by means of corresponding profiles on a punch center, a die, and a reform pad. In a second stage, material from the frustoconical wall is reformed into the anti-peaking bead whilst being urged radially inwardly to form a final shell having an anti-peaking bead of relatively narrow nominal radius.
According to a first aspect of the present invention there is provided apparatus for forming a reinforced pressure resistant can end shell from sheet material, said apparatus comprising a cutting ring, a cutting punch shell enterable into said ring to blank out a disc of material therebetween, an annular draw ring axially aligned with said cutting punch shell to support a peripheral margin of the disc held against it by said cutting punch shell, a die center ring arranged coaxially and slidably within the draw ring and having an end face profiled to define a surface of a seaming panel of the can end shell, an ejector pressure ring arranged coaxially and slidably within the cutting punch shell and axially aligned with the die center ring so that when
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CMB Foodcan plc
Spruill Robert L.
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