Radiation imagery chemistry: process – composition – or product th – Stripping process or element – Forming nonplanar image
Reexamination Certificate
2001-10-04
2002-11-12
McPherson, John A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Stripping process or element
Forming nonplanar image
C430S259000, C430S945000
Reexamination Certificate
active
06479208
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
None.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not applicable.
BACKGROUND OF THE INVENTION
The present invention generally relates to product marking and identification and more specifically to the marking of hot glass, as typified by picture tube components.
There is a need to piece identify hot glass articles. Picture tube components, for example panels and funnels, start life by being solidified in one of several, say 10, molds. Each piece contains mold related dimensional defects and is uniquely stressed as it is handled, cooled, and then annealed. Of the initially molded pieces, typically more than 30% never have the dimensional accuracy and strength to make it out of the plant.
This 30% loss is tolerable only because the broken (cull) glass can be recycled (one or more times) and, in fact, contributes to a better breed of glass. However, the scrap loss becomes very costly if much processing is done prior to scrapping.
Piece tracking will permit the plant operator to test and update the database for each piece and, thereby, determine if its history supports being scrapped rather than processed.
Suppose that the plant operator knew that mold #7 (and its associated shell) currently was producing dimensionally defective pieces and that they should be scrapped at the lehr exit, where they are known to be “dead on arrival”. The downstream costs of processing these parts, through to the first gauging point, could be saved. This, of course, is a simplistic example, because the reason for known defects commonly may involve the interaction of two (or more) machines prior to annealing. The only way such interactions can be discovered quickly is through individual piece tracking.
In the mold #7 hypothetical, the average production rate is assumed to be 5 pieces/minute and that the costs associated with unnecessary post lehr processing is $4.00/piece (this figures includes labor, equipment amortization, consumables (e.g., grinding and polishing materials), maintenance, power, technical support, gauging costs, etc.). If the plant operator can scrap the 10% of production (those pieces formed by mold #7 or another currently defective mold) prior to downstream processing, the plant operator will save over $2.00/minute (approximately $500,000/year). If the post lehr processing equipment throughput is in fact limiting on plant production (especially when a machine is down), the savings can be significantly higher, because a “good” shippable piece can replace every predictably “dead” piece. An additional good piece, of course, is worth far more than $4.00. The beneficial results of piece tracking include more production throughput and a savings when the operator eliminates unnecessary processing of bad pieces.
A variety of techniques for marking hot glass (picture tube panels and funnels) as they exit the forming mold at between about 400° and 650 ° C. can be envisioned. These techniques are listed below along with the problems associated with each:
Direct laser marking
Poor contrast
See for example U.S. PAT. NO.
Possible shard/crack generation
6,227,394 (Shinoda)
Also see C. Buerhop and R.
Weismann, “Temperature development
of glass during CO
2
laser irradiation-
Part 1”, Glass Technology, Vol. 37 No.
2 (April 1996)
Glass tag (frit bonded)
Fragile edges of tag
Frit melt/temperature/cure
match is delicate
Spray background (then laser cut
Overspray
away)
Delicate balance between
See for example U.S. PAT. NO.
cut/shard
4,323,755 (Nierenberg)
Possible shock to glass
(nebulizing air)
Spray reliability
Spray background (then laser blacken)
Overspray
More liquid material & thermal
shock
Spray reliability
Pad apply laser darkenable patch
Pad transfer buildup
Multiple stamps-requires
significant time
Tape apply laser darkenable patch
May require 2 stations
(cure time)
Difficult to formulate
adhesion &
(clean/strong/black)
markability together in
one tape coating
Thus, all of the tabulated approaches lead to complicated, difficult to maintain and/or messy equipment. A new approach to labeling hot glass for identification, therefore, is needed.
BRIEF SUMMARY OF THE INVENTION
Method for marking hot glass article having a surface uses a flexible carrier ribbon bearing a laser ablatable, high temperature, diffusely reflective coating, preferably white in color. A pattern is imaged in said coating on carrier ribbon by laser ablation. The patterned carrier ribbon is pressed against the surface only for a time adequate for transferring the patterned coating to the surface. The carrier ribbon then is released from pressing against the surface. A “pattern” for present purposes includes alphanumeric characters, numbers, graphics, and bar codes (e.g., laser scanable and vision system readable bar codes).
REFERENCES:
patent: 4515867 (1985-05-01), Bleacher et al.
patent: 5698366 (1997-12-01), Tutt et al.
patent: 6165594 (2000-12-01), Moh et al.
patent: 6227394 (2001-05-01), Shinoda
Infosight Corporation
McPherson John A.
Mueller and Smith LPA
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