Bottom for a package with internal overpressure

Details Bottom for a package with internal overpressure Bottom for a package with internal overpressure

1998-10-28

2001-01-16

Pollard, Steven (Department: 3727)

Receptacles

End wall structure

One-piece side and end wall

C220S612000, C220S623000

Reexamination Certificate

active

06173857

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a bottom for a three part package, preferably of polymer coated aluminum, for fill goods under pressure, including a barrel, which preferably can be frusto-conical or cylindrical, a top or a cover and a bottom.
BACKGROUND OF THE INVENTION
A typical example of a traditional three part package is a tin can, which is soldered and/or folded together of plate. The ordinary can is cylindrical and is thus manufactured of a rolled rectangular barrel, a circular cover and a circular bottom. A tin can is normally not exposed to any substantial internal overpressure, which means that the cover and the bottom can be generally planar.
A bottom design for a cylindrical package is shown in U.S. Pat. No. 4,023,700. This design enables the package to be exposed for an internal overpressure. The material in the package is thin aluminium, which at least internally is coated with polyethylene type HD, which enables a sealing. The bottom has a dome, which faces downward and whose circular outer edge is folded to a rim, which by heating can be melt connected to the cylindrical barrel of the package. For preventing the internal overpressure from creating a force for splitting up the package between the barrel and the bottom the space around the dome at its outside against the barrel is filled with thermoplastic foam. A further reinforcement can be accomplished by means of an adhesive band around the package on its outside.
It goes without saying that such a design leads to high material and manufacturing costs and adds to the weight of the package, which is an important negative factor.
THE INVENTION
The object of the invention is to accomplish a bottom of the kind described above, which does not suffer from the drawbacks mentioned above.
This is according to the invention attained in that the bottom comprises the following main parts: a central, circular dome facing inwardly in the package, outside thereof a circular portion, which is inwardly curved and extends towards the barrel, and a rim, which extends downwardly from the curved portion and is intended for sealing to the barrel.
A further drawback with the design according to U.S. Pat. No. 4,023,700 mentioned above is that the package will stand on the lower edge of the barrel, which may be uneven and have a sharp edge and for that reason can need treatment for becoming more suitable for this purpose.
This drawback can be obviated at a bottom according to the invention in that a circular bead between the dome and the curved portion is arranged at a lower level than the rim and thus the barrel after the sealing thereto, so that the package will stand on the bead.
For preventing to a certain extent splitting forces from the curved portion from reaching the rim a connection therebetween may be formed as a rounded edge, which in section is generally semi-circular.
An even better result in this respect is accomplished, if this connection is double curved, i e the generally semi-circular edge is supplemented at its inside with a curve, which for example may be press rolled.
A transition portion from the dome to the circular bead may be generally vertical, but a better result with regard to decreasing the split risk between the rim and the barrel is obtained in that this transition portion is slanted outwardly with an angle of for example 15° with the vertical.


REFERENCES:
patent: 163747 (1875-05-01), Cummings
patent: 1718322 (1929-06-01), Walker
patent: 2197437 (1940-04-01), McManus et al.
patent: 3693828 (1972-09-01), Kneusel et al.
patent: 3878963 (1975-04-01), Knize
patent: 4023700 (1977-05-01), Buquet et al.
patent: 4363404 (1982-12-01), Westphal
patent: 4448322 (1984-05-01), Kraska
patent: 4467933 (1984-08-01), Wilkinson et al.
patent: 4606472 (1986-08-01), Taube et al.
patent: 4809861 (1989-03-01), Wilkinson et al.
patent: 0337500 (1985-09-01), None
patent: 0482586 (1991-10-01), None

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