Patent US3617325A successfully refreshed from Google Patents.
US3617325A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Writing
Assignee: Chem-Rite Associates
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Filing: 1969-06-17
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Granted: 1971-11-02
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Expires: 1989-06-17
Abstract
Abstract Impermanent marks, they may disappear in a day or less, are created by ''''writing,'''' with a stylus presenting an alkanolamine, on a sheet of paper coated with a material which changes to a distinctive color upon exposure to the amine. The marks disappear in a short period of time so that exercise books used at the elementary school level can be reused in the following semester or term without additional cost as would be entailed in the purchase of new books.
Inventors
- 👤 Raymond E Spokes
- 👤 John William Edwards Jr
- 👤 Daniel Ward Edwards
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 13:58
CPC Classifications
B; B44; B44F; B44F1/00; B44F1/08; B44F1/10
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
17 words
A method according to claim 1 in which the amine is a mixture of monoethanolamine and diethanolamine.
Claim 2
Dependent Claim
20 words
A method according to claim 1 in which the paper is represented by the pages of a grade school workbook.
Claim 3
Dependent Claim
20 words
A method according to claim 2, in which the paper is represented by the pages of a grade school workbook.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-11-01 | 1975-05-03 | 1975-11-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-01 | 1979-05-03 | 1979-11-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-01 | 1983-05-03 | 1983-11-02 | $7700.00 | Window Closed / Lapsed |