Metal deforming – Process – Deforming sheet metal
Reexamination Certificate
1996-03-20
2001-09-11
Larson, Lowell A. (Department: 3725)
Metal deforming
Process
Deforming sheet metal
Reexamination Certificate
active
06286357
ABSTRACT:
The present invention relates to a method for manufacturing a shaped metal can of the beverage can type and more particularly a shaped metal can comprising, on one hand, a bottom and a peripheral wall or skirt having a succession of regions of different diameters and, on the other hand, a lid crimped or seamed on the peripheral wall.
It is known to make shaped metal cans consisting of a peripheral wall having a succession of regions of different diameters, a bottom crimped or seamed on an end of the peripheral wall, and a lid crimped or seamed on the other end of said peripheral wall. This lid is provided for example with an easily opened device opened by rupture of a line of reduced strength or with a tapped neck for receiving a screwed stopper.
The peripheral wall of this type of metal can comprises a cylindrical sleeve which is welded longitudinally and expanded so as to form a succession of regions of different diameters.
Usually the peripheral wall is produced from a metal blank of soft steel having a low carbon content and a yield strength of about 250 MPa.
Such a steel permits producing without much difficulty an expansion of the welded sleeve with an expansion ratio calculated from the following formula:
Final
D
-
Initial
D
Initial
D
×
100
which may be as much as 20%, the initial D being the initial diameter of the welded sleeve and the final D being the diameter of the welded sleeve after expansion.
To make this type of can, the welded sleeve is produced, said sleeve is expanded to obtain a peripheral wall having a succession of regions of different diameters, and a bottom and a lid are respectively crimped or seamed on each end of the sleeve.
The sleeve is usually expanded by means of a forming method employing air or nitrogen under pressure or a forming method employing an incompressible fluid.
It is also known to make a metal can of the beverage can type comprising, on one hand, a bottom and a peripheral wall in one piece with the bottom and, on the other hand, a lid crimped or seamed on the peripheral wall.
The bottom and the peripheral wall in one piece with the bottom are produced in particular by drawing and ironing a cup cut from a metal blank or strip.
For this purpose, the cup is first of all subjected to a drawing operation with a relatively large reduction on a press comprising in the conventional manner, on one hand, a fixed punch and a support constituting a peripheral blank holder which is slidable around said punch and on which the cup rests and, on the other hand, a die adapted to be applied against the cup with a force transmitted vertically by an upper slide.
The cup comprising a bottom and a flange formed by the drawing operation is then either calibrated by a light drawing operation without the use of a blank holder, or redrawn with a blank holder, and is then subjected to an ironing operation which comprises drawing the flange by means of a draw die with successive reductions so as to progressively form the peripheral wall of the can.
Thereafter, the bottom is formed on a draw die so as to impart a given geometry thereto and the neck of the peripheral wall is formed in accordance with a die-necking method with the use of a die, or in accordance with a spin-necking method employing a forming roller.
The necking method employing a die comprises in forcing the neck into a die having a conical inlet profile and a cylindrical outlet profile. A cylindrical element guides the formed wall as it leaves the die.
The force required to deform the metal is derived from the thrust applied to the bottom of the can and transmitted axially through the peripheral wall.
The spin-necking method employing a forming roller comprises driving in rotation the can which is held between a pusher and a centering ring. The profile of the neck is produced by simultaneous displacements of the rollers, the centering ring and the pusher.
This type of can is usually produced from a blank of steel having a very low carbon content.
After the drawing of the flanges of the peripheral wall, the metal is highly work hardened so that the yield strength of the peripheral wall is about 700 MPa and sometimes even exceeds this value, so that it has a practically zero expansion capability.
The possible overall expansion ratio of the peripheral wall is less than 1% and even less than 0.5% for very thin walls.
On the other hand, the advantage of such a can is that is permits obtaining very small thicknesses since the metal of the wall is a very stiff metal having high mechanical characteristics, which results in light weight and low material expenditure.
Further, such a can is produced in two parts, the bottom and the peripheral wall being in one piece, which is an advantage from the aesthetic point of view.
An object of the invention is to provide a process for manufacturing a shaped metal can, of the beverage can type, obtained for example by drawing and ironing, comprising a bottom and a peripheral wall in one piece with the bottom whereby it is possible to achieve an expansion ratio higher than 2% in the region of the peripheral wall.
The invention therefore provides a process for manufacturing a shaped metal can comprising, on one hand, a bottom and a peripheral wall including a succession of regions of different diameters and, on the other hand, a lid crimped or seamed on the peripheral wall, characterized in that it comprises:
producing from a metal blank a cylindrical preliminary can comprising a bottom and a peripheral wall of a diameter equal to a given diameter of a region of the peripheral wall;
effecting a necking operation on a part of the peripheral wall of the preliminary can situated above said region of said given diameter of the peripheral wall of the formed can to bring it to a diameter which is smaller than said given diameter ;
and effecting at least one expanding operation on a part of the peripheral wall situated above said region of said given diameter for producing the succession of regions of different diameters of said peripheral wall.
According to other features of the invention:
the process comprises, after having effected the necking operation on the part of the peripheral wall of the preliminary can situated above said region of said given diameter, effecting a single expanding operation for producing the succession of regions of different diameters of said peripheral wall.
the diameter of the part of the peripheral wall of the preliminary can situated above said region of said given diameter is equal to the diameter of the region of the peripheral wall of the smallest diameter.
the process comprises, after having effected the necking operation on the part of the peripheral wall of the preliminary can situated above said region of said given diameter, effecting a succession of expanding and necking operations on the whole of the part of the peripheral wall of the preliminary can situated above the previously necked or expanded region.
the process comprises producing the preliminary can by drawing and ironing a metal blank of steel, aluminium or aluminium alloy.
the process comprises producing the preliminary can by drawing and redrawing a metal blank of steel, aluminium or aluminium alloy.
REFERENCES:
patent: 1645971 (1927-10-01), Riegel
patent: 517913 (1931-01-01), None
patent: 1 900 597 (1970-02-01), None
patent: 31 06 245 (1982-07-01), None
patent: 0 543 695 A1 (1993-05-01), None
patent: WO 94/16842 (1994-08-01), None
D'Amore Michel
Erhard Patrick
Muia François
Larson Lowell A.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Sollac
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