Metal fusion bonding – Process – With shaping
Reexamination Certificate
1998-02-28
2001-12-11
Ryan, Patrick (Department: 1725)
Metal fusion bonding
Process
With shaping
C228S184000, C228S203000, C219S064000
Reexamination Certificate
active
06328197
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a dispensing container and more particularly, to an aerosol dispensing container formed by a welded metal sheet having a corrosion-resistant protective laminate.
BACKGROUND OF THE INVENTION
Known aerosol containers are made of a metal sheet which is wrapped into a cylindrical body so that overlapping edges may be welded into a seam. Shaped caps are fitted onto the ends in a sealed manner, and one of these seals is typically provided with a dispensing valve. Such a container is useful for containing a liquid product and a pressurized propellant.
It is desirable to use tinplated steel blanks to form cans in appropriate applications because such a material is inexpensive. Tinplated steel is suitable for a container so long as the contents do not corrode the tin and steel. Unfortunately, tinplated steel has been found unsuitable for many aerosol dispensing container applications because it tends to corrode when exposed to certain corrosive compounds found in certain applications such as saline solutions, hair mousse treatments, and dimethyl ether (DME) propellants. In an attempt to avoid corrosion, aerosol cans have typically been produced from aluminum or coated with thin organic coatings, which, although they exhibit good corrosion resistance, are also relatively expensive. However, constructing the body from tinplated steel requires some means of preventing exposure of the metal to the corrosive contents.
One known aerosol container prevents the product from contacting and corroding the metal container body using a collapsible bag for housing the product. The propellant, contained within the container body, exteriorly surrounds the bag and selectively compresses the bag to dispense the product in response to a release valve. Unfortunately, the presence of the bag requires additional components and assembly steps, which also increases costs.
Another means of preventing corrosion of the container body is to laminate or coat its interior and/or exterior surface with a corrosion-resistant layer. For example, certain varnishes, paints, inks or plastic laminates are suitable to protect a metal blank such as tinplated or tin-free steel from corrosion, so long as the corrosion-resistant layer is compatible with the product contents. Corrosion-resistant layers, such as coatings or laminates, if present at the overlapping weld site, however, introduce a foreign substance that can weaken the weld or prevent an effective weld from forming. Therefore, the overlapping area must be free from the coating or laminate material. Accordingly, it is known to apply the corrosion-resistant layer partially to the metal, leaving exposed portions or strip-shaped areas. For example, a lacquer coating or laminate can be applied to the metal blank in a striped pattern to leave exposed metal strips at the area to be overlapped and welded. After welding, a supplemental corrosion-resistant layer can be applied over the seam to prevent it from corroding. The process of applying a corrosion-resistant layer to only a predetermined portion of a sheet, however, can be expensive.
It is also known to coat or laminate the entire surface of the metal sheet, then remove portions of the corrosion-resistant layer to expose areas at the sites of metal to be welded. This is conventionally done by mechanical means, such as by sanding, grinding, milling, scraping, or by burning or applying heat, such as with a laser. These conventional layer-removal means do not provide reliably clean surfaces suitable for welding, and may also create undesirably airborne dust or smoke. Moreover, these require potentially dangerous equipment.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved method for making an aerosol dispensing container.
It is another object of the present invention to provide an aerosol container that can be manufactured inexpensively. A related, more specific object of the present invention is to provide an aerosol dispensing container which can be made of an inexpensive material, such as tinplated or tin-free steel, formed by welding along a seam, yet which provides good corrosion resistance.
A further object of the invention is to provide a method for making an aerosol container in which removal of the corrosion-resistant layer and specifically a laminate-stripping step is performed in a safe and clean manner.
These objects are achieved by means of the invention, wherein a method is provided that utilizes pressurized water jets to strip an anti-corrosion layer from a metal sheet. In one embodiment of the invention, the method for making an aerosol dispensing container uses a composite sheet having a metal layer and a corrosion-resistant layer on at least one surface of the metal layer. A water jet peeler or stripper is directed and applied to the surface of the composite sheet to remove a portion of the corrosion-resistant layer to expose the sites that are to be welded together. A generally rectangular blank is then formed from the composite sheet, such as by shearing or cutting so that the exposed areas, or portions thereof, are disposed generally along two opposite edges of the blank. It will be appreciated that the blank may also be stripped after it is cut from the composite sheet. The blank is then bent or otherwise shaped using conventional means into a tube or cylinder so that the exposed areas at opposite edges overlap each other. The overlapping edges of the blank are welded together at the exposed areas. Advantageously, the exposed areas formed by the water stripping step are clean areas which facilitate a good, reliable weld.
Additionally, an embodiment of the invention covers a method wherein the composite sheet has a laminated layer on the outside, such as for a label. The water jet stripping process of the invention could be applied to remove the exterior laminate from an exterior surface of the container body for aesthetic enhancement or to provide a weldable surface.
The water jet stripping process of the invention advantageously removes the plastic laminated or coated layer from a controlled area in an efficient manner, allowing a weld to be made, increasing production speed, and minimizing expenses. This is useful for stripping overlapping edges to be welded together.
These and other features and advantages are described in, and will be apparent from, the detailed description of the preferred embodiments, the drawings, and from the claims.
REFERENCES:
patent: 3416217 (1968-12-01), Walker
patent: 5364012 (1994-11-01), Davis et al.
patent: 5433099 (1995-07-01), Katsuhiro et al.
patent: 2-30382 (1990-01-01), None
patent: WO 82/02697 A1 (1982-08-01), None
Edmondson Lynne
Polster Lieder Woodruff & Lucchesi L.C.
Ryan Patrick
United States Can Company
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