Coating apparatus – Solid applicator contacting work – With work-handling or work-supporting
Utility Patent
1998-10-23
2001-01-02
Weldon, Kevin (Department: 1734)
Coating apparatus
Solid applicator contacting work
With work-handling or work-supporting
C118S261000
Utility Patent
active
06168661
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable.
BACKGROUND OF THE INVENTION
The field of invention is electrochemical batteries, more particularly, a method and apparatus for applying an electrochemically active material onto an ultra-thin metal film for use in electrochemical batteries.
Developments in the field of electrochemical batteries have produced batteries having electrochemical cells that have both excellent charge and discharge characteristics. These cells require ultra-thin films of a metal such as lead, nickel or metal alloys having a thickness of 2-5 mils coated with extremely thin layers of an electrochemically active material, having a thickness of approximately 1-5 mils.
A typical electrochemical cell, as shown in
FIGS. 2 and 3
, includes an ultra-thin strip
2
of lead alloy of approximately 2 inches in width and 2-5 mils thick. The electrochemically active material
3
is a compound that includes lead monoxide, sodium sulfate and other inactive materials. The compound
3
is applied to the top and bottom surfaces of the metal strip
2
, coating the entire width of the strip
2
except for an uncoated strip edge
4
approximately 0.2 inches wide on both surfaces of the strip to provide an uncoated electrical connection surface.
Methods have been developed to produce lead and other suitable metals and alloys in the form of an ultra-thin film that is suitable for use in these electrochemical cells. The use of these ultra-thin strips is disclosed in U.S. Pat. No. 5,677,078.
The electrochemically active material can be applied to the metal strip in a fluid form and then dried to produce a solid coating. Various means and methods to coat the ultra-thin metal films have proved less than satisfactory. One particular method sprays the aqueous solution onto the sides of the metal films. Due to environmental hazards that exist with spraying a solution containing metals such as lead, this method is unacceptable for use.
Other methods coat a side of the thin film using a roller apparatus that applies the fluid solution to a film that is supported by a backing roller to prevent the ultra-thin film from breaking. The use of a backing roller only allows coating a single side of the film at a time with an intermediate drying step, thus lengthening the time necessary to manufacture the electrochemical cell. The use of a coating roller also does not typically provide a clean edge that is suitable for an electrical connection without masking the edge at the point of application or a subsequent step of wiping.
A method used to coat both sides of a thin film simultaneously is to dip the entire film in the aqueous solution. This particular method does not provide an uncoated edge without a subsequent step of wiping or other method to remove some of the coated material. Additionally, this particular method requires that the same coating material is applied to both sides of the film, which is unacceptable for certain applications, such as in use with bi-polar batteries.
Providing a clean edge for an electrical connection is important to ensure the performance of the assembled battery. The steps described above such as wiping and masking have proven unacceptable for various reasons. Wiping does not always completely remove the coated material leaving a residue that affects the battery performance. Additionally, the thin film has a low tensile strength that is subject to tearing during the wiping process.
Masking is a process of covering the area that is not to be coated during the coating process. Typically, a roller covers the edge as the remaining portion of the strip is coated. This roller tends to become fouled, that is coating material can be splattered on the masking roller which is then transferred to the edge that should be left clean, thus reducing the battery performance.
BRIEF SUMMARY OF THE INVENTION
In one of its aspects, the invention relates to a method and apparatus for coating both sides of a thin metal strip with electrochemically active material by the use of coating rod mechanism acting on a single side of the metal strip. The method is preferably carried out by applying the coating to one face of the strip drawn from the supply roll, reversing the direction of travel of the strip coating the opposite side of the strip and drying the coated sides. The dried and coated strip may be wound up on a take up reel.
In the preferred embodiment, the strip from the feed roll first passes a web guide which reverses the direction of travel of the strip before the first side is coated. The strip then passes around a second web guide which again reverses the strip direction of travel before the second side of the strip is coated and the coated strip is dried. The web guides, supply reel, and take-up reel controls the speed and tension in the strip so that back up rolls are not needed at the coating mechanisms.
The invention also resides in a coating mechanism that includes a reservoir, a mixing rod relating through fluid coating material in the reservoir, and a coating rod receiving coating material from the mixing rod and applying the coating material to the strip. The mixing rod is longitudinally grooved and the coating rod is circumferentially grooved.
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Shinjiro Murakami et al., “Kawasaki Steel's Multipurpose Coating Line”,Iron And Steel Engineer, pp. 36-41, vol. 70, No. 7, Jul. 1, 1994.
George L. Booth, “Coating Rods, Equipment, Processes And Applications”,Coating Equipment And Processes, Lockwood 1970.
Donald M. MacLeod, “An Introduction to Wire-Wound Rod Coating”, Industry Tech.
Johnson Controls Technology Company
Quarles & Brady LLP
Weldon Kevin
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