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US4298569A
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Steam-formaldehyde sterilization indicator
Assignee: 3M Co
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Filing: 1980-01-28
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Granted: 1981-11-03
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Expires: 2000-01-28
Abstract
Abstract Indicators for the steam-formaldehyde sterilization process are provided which undergo a color change when placed in a steam-formaldehyde environment.
Inventors
- 👤 David M. Read
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 22:33
CPC Classifications
G; G01; G01N; G01N31/00; G01N31/22; G01N31/226; A; A61; A61L; A61L2/00; A61L2/26; A61L2/28
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
125 words
A method for indicating that an article has undergone steam-formaldehyde sterilization which comprises attaching an indicator to an article, said indicator comprising a substrate carrying a dye which will undergo an irreversible color change when exposed to formaldehyde vapor in the presence of low temperature steam and wherein a buffering agent is mixed with said dye and said buffer has a pH of from 4 to 6, and then inserting said article with indicator into an environment wherein the article and indicator are exposed to steam and formaldehyde so that the article is sterilized wherein said steam is between 60° and 80° C. and where said indicator will not change color when exposed to 134° C. steam in the absence of formaldehyde for 31/2 minutes.
Claim 2
Independent Claim
125 words
A method for indicating that an article has undergone steam-formaldehyde sterilization which comprises attaching an indicator to an article, said indicator comprising a substrate carrying a dye which will undergo an irreversible color change when exposed to formaldehyde vapor in the presence of low temperature steam and wherein a buffering agent is mixed with said dye and said buffer has a pH of from 4 to 6, and then inserting said article with indicator into an environment wherein the article and indicator are exposed to steam and formaldehyde so that the article is sterilized wherein said steam is between 60° and 80° C. and where said indicator will not change color when exposed to 134° C. steam in the absence of formaldehyde for 31/2 minutes.
Claim 3
Dependent Claim
16 words
The method of claim 1 wherein said dye and buffering agent are mixed in a binder.
Claim 4
Dependent Claim
14 words
The method of claim 1 or 2 wherein said dye comprises 3,3'-[4,4'-bisphenylylene-(azo)] bis [4-amino-1-naphthalene].
Claim 5
Dependent Claim
13 words
The method of claim 1 or 2 wherein said dye comprises Congo Red.
Claim 6
Dependent Claim
36 words
A method for indicating that an article has undergone steam-formaldehyde sterilization which comprises attaching the indicator of claim 1 to an article which requires sterilization and inserting said article with indicator into a steam-formaldehyde sterilization chamber.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-11-02 | 1985-05-04 | 1985-11-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-11-02 | 1989-05-04 | 1989-11-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-11-02 | 1993-05-04 | 1993-11-03 | $7700.00 | Window Closed / Lapsed |