US4263108A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Control system for the electrolytic recovery of silver from photographic fixing solution
Assignee: Foresight Enterprises Inc
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Filing: 1980-03-27
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Granted: 1981-04-21
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Expires: 2000-03-27
Abstract
Abstract Plating current in a silver-recovery process is controlled as a function of the cell voltage of the system taken in the absence of plating current, and held as a control determinant. The control is modified to produce certain characteristics at low silver concentration to further reduce sulfiding.
Inventors
- 👤 Bernard J. Berg
- 👤 Darrell T. Thompson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 11:59
CPC Classifications
C; C25; C25C; C25C1/00; C25C1/20; C25C7/00; C25C7/06
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
87 words
A method fo controlling the plating current of an electrolytic silver-recovery process including placing cathode and anode elements in a solution containing silver ions, and applying a current through said solution via said elements as a function of the concentration of silver ions in said solution, wherein the improvement comprises: repeatedly sampling the residual cell voltage in said solution at periods when the exterior applied voltage is substantially zero, and obtaining a voltage pulse under this condition; and controlling said current as a function of said pulses.
Claim 2
Independent Claim
87 words
A method fo controlling the plating current of an electrolytic silver-recovery process including placing cathode and anode elements in a solution containing silver ions, and applying a current through said solution via said elements as a function of the concentration of silver ions in said solution, wherein the improvement comprises: repeatedly sampling the residual cell voltage in said solution at periods when the exterior applied voltage is substantially zero, and obtaining a voltage pulse under this condition; and controlling said current as a function of said pulses.
Claim 3
Dependent Claim
29 words
A method as defined in claim 1, including the combination of said pulses with a feedback signal related directly to the voltage applied across said anode and cathode elements.
Claim 4
Dependent Claim
26 words
A method as defined in claim 2, wherein said pulses and feedback signal are additionally combined with a reference voltage modified as a function of temperature.
Claim 5
Dependent Claim
41 words
A method as defined in claim 1, wherein the control of said current as a function of said pulses is modified at low pulse intensity to decrease the applied current to produce a substantially constant relationship between current and silver concentration.
Claim 6
Dependent Claim
20 words
A method as defined in claim 1, wherein said residual cell voltage is taken via said cathode and anode elements.
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) | 1984-04-20 | 1984-10-20 | 1985-04-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-04-20 | 1988-10-20 | 1989-04-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-04-20 | 1992-10-20 | 1993-04-21 | $7700.00 | Window Closed / Lapsed |