Can manufacture
AssigneeCrown Packaging Technology, Inc.
InventorsAlain Presset, Keith Alan Vincent, Stuart Alexander Monro
Life of this patent
Estimating the term…
Abstract
A method for manufacture of a metal can body is described in which two or more stretching operations are used so as to reduce the thickness of the central part of a cup base, prior to drawing the cup sidewall and forming a can body. By using two or more stretching operations, it has been found possible to control the thickness of the base without significantly reducing pressure performance of the finished can. Alternative embodiments of apparatus comprising tooling for carrying out this method are also described.
Claims12
An apparatus for manufacture of a metal can body from a cup formed of metal sheet, in which the cup has a sidewall and an integral base, the apparatus comprising:
- i) a cup holder on which a cup is mountable;
- ii) a first clamp ring which is adapted to clamp a first annular region on the base by contacting a top portion of the annular region with a first annular projection and contacting a bottom portion of the annular region with a second annular projection to define a first enclosed portion which includes a central part of the base;
- iii) a first stretch punch which is adapted to deform and stretch at least some of the central part of the base to thereby increase its surface area and reduce the thickness of the base;
- iv) a second clamp ring which is adapted to clamp a second annular region on the base and defines a second enclosed portion having a larger area from that of the first enclosed portion and including the central part;
- in which the first clamp ring and the second claim ring are adapted to restrict metal flow from radially outside respective clamped regions into the first enclosed portion and the second enclosed portion, respectively, during stretching;
- v) a second stretch punch which is adapted to deform and stretch at least some of the second enclosed portion to reduce the thickness of the base further, and
- vi) drawing tooling for drawing the cup into a can body by pulling and transferring outwardly material of the stretched and thinned base.
A method for manufacture of a metal can body, the method comprising the following stages:
- i) a first stretching stage comprising:
- on a cup having a sidewall and an integral base, the cup being formed of metal sheet, clamping an annular region on the base to define a first enclosed portion which includes a central part of the base, the clamping including contacting a top portion of the annular region with a first annular projection and contacting a bottom portion of the annular region with a second annular projection, and
- deforming and stretching at least some of the first enclosed portion to thereby increase the surface area and reduce the thickness of the base;
- ii) a second stretching stage comprising:
- stretching a second enclosed portion of the base, the second enclosed portion having a larger area than the first enclosed portion, the second area including the central part of the base;
- in which the step of clamping the annular region of the base is adapted to restrict metal flow from radially outside the annular region into the first enclosed portion during stretching;
- and
- iii) a drawing operation comprising drawing the cup into a can body by pulling and transferring material outwardly from the thinned base.
Dependencies are inferred from the claim text.