Metal deforming – By application of fluent medium – or energy field – Using fixed die
Reexamination Certificate
2000-05-04
2001-06-26
Jones, David (Department: 3725)
Metal deforming
By application of fluent medium, or energy field
Using fixed die
C072S056000, C029S421100
Reexamination Certificate
active
06250122
ABSTRACT:
The present invention generally relates to reshaping container bodies and, more particularly, to utilizing one or more pressurized streams for container body reshaping operations while the container is under axial load.
BACKGROUND INFORMATION
Numerous techniques have been employed for forming thin-walled work pieces, including in particular, longitudinal welding and drawing/redrawing/ironing techniques used in forming three-piece and two-piece cylindrical metal container bodies, respectively. Subsequent modifications to metal container bodies can be achieved via die necking, roll or spin necking, and other secondary processes.
With regard to further shaping operations, recently symmetric longitudinal flutes or ribs, and diamond, waffle and numerous other patterns have been imparted to cylindrical container bodies through the use of either an internal roller and an external compliant mat, or by an internal roller and a matching external rigid forming element. Expanding mandrels have also been utilized on three-piece metal container bodies to impart such patterns. Applying an axial load on the end of a cylinder as it is radially expanded is a common method of assisting in the expansion. Those of skill in the art understand “shaping” (or “reshaping”) to include not only forming or changing a general contour, outline, section, or the like, but to also include a number of other items such as, e.g., embossing (or debossing), texturizing and the like.
The noted techniques are limited as to the diametric extent and complexity of shaping that can be achieved. By way of example, die-necking cannot readily be employed for current aluminum drawn and ironed beverage containers (e.g., containers having a sidewall thickness of about 4-7 mil.) to achieve diametric changes of more than about 3% in any single operation, and does not generally allow for container diameters to be increased then decreased (or vice-versa) or for discontinuous/angled designs to be shaped along the longitudinal extent of a container body. While spin forming techniques have been found to allow for relatively high degrees of expansion (e.g., in excess of 15% for current aluminum drawn and ironed beverage containers), relative rotation between a container body and the forming roller is necessary, thereby restricting the ability to achieve non-circular cross-sections along the longitudinal extent of a container body.
Other proposed techniques also have limitations. For example, electromagnetic and hydrostatic processes have been considered which entail the use of magnetic fields and pressurized vessels, respectively, by themselves, to force a container body sidewall outward against an outer shaping die. Both processes require, however, a container body to be of sufficient ductility to withstand substantial attendant plastic deformation without failure. For current drawn and ironed aluminum beverage containers, such deformation limits are believed to be less than 3% (and generally less than 2%) before failure is realized due to the limited ductility of the aluminum alloys utilized. While annealing such container bodies may provide sufficient ductility to allow a greater degree of metal deformation, it would lower the strength of container bodies and require additional undesirable thermal processing.
INVENTION SUMMARY
In one embodiment, a container reshaping process may involve local working using a pressurized stream while placing the container under axial load such as pressing a preferably floating support against a container flange. Axial load may be accomplished using a spring assembly consisting of a spring located between a spring top cap and a lower body such as an air pressurization chamber body. In one configuration, a spring assembly rests against a floating support. The spring assembly may provide an axial load, in one condition, of between about 5 and about 100 pounds force, but preferably between about 10 and about 40 pounds of force. The axial load seals an interface between a floating seal ring and a container flange. In one embodiment, an axial load applied on a container flange results in an axial load applied to the container body sidewall, and is believed to assist in metal flow as the container is expanded outward by a can shaping operation.
The container body may be placed in tooling in a plurality of ways. For example, there can be clearance between the container body and die cavity such that the container is held (e.g. at a container flange end) by a floating second support and/or at the upper end by the die cavity, but not necessarily clamped by the die cavity on its sidewall. Furthermore, if an embodiment uses internal air pressurization of the container body, such pressurization does not necessarily hold the container against the die cavity wall until the container body has expanded to contact the die cavity. Further variations of the die cavity fit interaction include a slight interference fit between the container body wall and cavity internal diameter. For example, the container body sidewall may be clamped by the die cavity surface when the die cavity is in a closed position. Another embodiment of a die cavity fit interaction includes a large interference fit between the container body wall and the cavity internal diameter.
If both the container and cavity are continuous surfaces of revolution, there is preferably only a slight interference fit between the container and cavity or the container will be crushed by the cavity as it closes. Upon internal pressurization of the container body, the container is held in the die cavity, at least partially, by a combination of an interference fit between the die cavity/container and the radial expansion of the container body sidewall from internal pressure in the container. This inhibits the container from rotating in an undesirable manner in a die cavity.
In addition, the cavity may contain a discontinuous profile such as ribs, flutes or embossed letters that may be partially pressed into the container when the cavity closes. These high points on the cavity profile will remain in the container surface after the container is shaped and create a debossment into the container surface while the portions of the container that are expanded outward by the shaping operation will be raised out from the original container surface. In this fashion, an increased degree of local relief can be created in the container with a lower degree of absolute expansion of the container diameter (compared to previous methods). Ribs or other features will also tend to lock the container in the cavity, particularly if pressurized, and prevent the container from rotating. The effective circumferential length of the profile on the cavity should be longer than the circumferential length of the wall in the container preform to decrease the likelihood that the container will be crushed by the cavity when the cavity closes. The degree of debossment into the container wall by the tooling cavity is thus, in at least some circumstances, limited by the circumferential length of the container wall.
Another aspect of an embodiment of a present invention generally relates to container body shaping/reshaping operations utilizing two fluids. One of these fluids is for effectively exerting local reshaping forces on a container body and the other is for effectively “controlling” a container body during the application of these reshaping forces to a container body (e.g., to effectively “control” or “hold” the metal of the drawn and ironed container body while being reshaped).
The container body may be “pre-loaded” (axially loaded) either in a single fluid embodiment or in the above-noted multiple fluid aspect of an embodiment of a present invention. An axially-directed load (e.g., compressive) may be applied to the container body during the exposure of the container body to a pressurized first fluid and/or during the application of reshaping forces to a container body, e.g., by the action of a second fluid on the surface of a container body.
REFERENCES:
patent: 5794474 (1998-08-01), Willoughby
Chasteen Howard Curtis
Robinson Greg
Willoughby Otis
Ball Corporation
Jones David
Sheridan & Ross P.C.
LandOfFree
Method and apparatus for reshaping a container body does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for reshaping a container body, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for reshaping a container body will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2543626