US4343686A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for controlling etching of electrolytic capacitor foil
Assignee: Sprague Electric Co
•
Filing: 1981-02-27
•
Granted: 1982-08-10
•
Expires: 2001-02-27
Abstract
Abstract In a process for etching aluminum foil to increase its actual surface area to apparent surface area for use as an electrode in an electrolytic capacitor, a wire coil is placed adjacent the foil as it exits the etch station. The coil is energized to produce eddy currents in the foil. The voltage induced by theses eddy currents is sensed at the same coil or another coil. The foil drawing speed through the etch station is altered in response to that sensed voltage, or another process parameter is changed, to maintain at a constant value the ratio of the actual to apparent foil surface area.
Inventors
- 👤 John R. Hebert, Jr.
- 👤 Joseph H. Silveira
- 👤 Robert W. Herzig
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 08:41
CPC Classifications
H; H01; H01G; H01G9/00; H01G9/004; H01G9/04; H01G9/048; H01G9/055; C; C25; C25F; C25F3/00; C25F3/02; C25F3/04
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
143 words
A method for controlling in a foil etching process the ratio of the actual etched surface area to the apparent surface area of a valve metal foil that is intended for use in an electrolytic capacitor, comprising: drawing said foil through an etch station and etching said foil therein by a process having at least one process parameter that affects said actual etched surface area; generating an alternating magnetic field to produce eddy currents in said foil near the point of exit of said foil from said etching station; producing an electrical signal having an amplitude that is a function of the magnitude of said eddy currents; and adjusting said at least one process parameter in a direction that tends to maintain said signal amplitude at a constant predetermined value to control the ratio of said actual etched area to said apparent area.
Claim 2
Independent Claim
143 words
A method for controlling in a foil etching process the ratio of the actual etched surface area to the apparent surface area of a valve metal foil that is intended for use in an electrolytic capacitor, comprising: drawing said foil through an etch station and etching said foil therein by a process having at least one process parameter that affects said actual etched surface area; generating an alternating magnetic field to produce eddy currents in said foil near the point of exit of said foil from said etching station; producing an electrical signal having an amplitude that is a function of the magnitude of said eddy currents; and adjusting said at least one process parameter in a direction that tends to maintain said signal amplitude at a constant predetermined value to control the ratio of said actual etched area to said apparent area.
Claim 3
Dependent Claim
34 words
The method of claim 1 wherein said generating is accomplished by placing one wire coil adjacent said foil near said point of exit, and energizing said one coil from an alternating current energy source.
Claim 4
Dependent Claim
25 words
The method of claim 2 wherein said producing is accomplished whereby said electrical signal is made proportional to the electrical impedance of said one coil.
Claim 5
Dependent Claim
31 words
The method of claim 2 wherein said energizing is accomplished by applying a constant amplitude AC voltage across said one coil and the resulting alternating current therethrough is said electrical signal.
Claim 6
Dependent Claim
34 words
The method of claim 2 whereby said energizing is accomplished by applying a constant amplitude alternating current through said one coil and the resulting AC voltage across said one coil is said electrical signal.
Claim 7
Dependent Claim
35 words
The method of claim 2 wherein said producing is accomplished by placing another wire coil near said foil but opposite said one coil, the AC voltage appearing across said another coil being said electrical signal.
Claim 8
Dependent Claim
36 words
The method of claim 2 wherein said one coil is comprised of two coaxial essentially identical subcoils connected in series with a gap between them, said foil near said point of exit passing through said gap.
Claim 9
Dependent Claim
25 words
The method of claim 1 wherein said adjusting of said at least one parameter comprises adjusting the speed of said drawing through said etch station.
Claim 10
Dependent Claim
38 words
The method of claim 1 wherein said etching process includes contacting said foil in said etch station with a chemical etchant and wherein said adjusting of said at least one parameter comprises adjusting the strength of said etchant.
Claim 11
Dependent Claim
38 words
The method of claim 1 wherein said etching process includes submersing said foil in a liquid electrolyte and applying a voltage between said foil and said electrolyte, said adjusting of at least one parameter comprising adjusting said voltage.
Claim 12
Independent Claim
168 words
A method for controlling in a foil etching process the ratio of the actual etched surface area to the apparent surface area of a valve metal foil that is intended for use in electrolytic capacitor, comprising: drawing said foil through an etch station and etching said foil therein by a process having at least one process parameter that affects said actual etched surface area; electrically exciting a test coil that is adjacent said etched foil near the point of exit from said etching station to generate eddy currents in said etched foil producing an electrical signal having an amplitude that is a fixed function of the magnitude of said eddy currents; comparing said signal with a predetermined signal representing the desired actual surface area of said etched foil; and adjusting said at least one parameter, according to the result of said comparing step, in a direction that tends to reduce the difference between said compared signals to control the ratio of said actual to said apparent surface areas.
Claim 13
Independent Claim
168 words
A method for controlling in a foil etching process the ratio of the actual etched surface area to the apparent surface area of a valve metal foil that is intended for use in electrolytic capacitor, comprising: drawing said foil through an etch station and etching said foil therein by a process having at least one process parameter that affects said actual etched surface area; electrically exciting a test coil that is adjacent said etched foil near the point of exit from said etching station to generate eddy currents in said etched foil producing an electrical signal having an amplitude that is a fixed function of the magnitude of said eddy currents; comparing said signal with a predetermined signal representing the desired actual surface area of said etched foil; and adjusting said at least one parameter, according to the result of said comparing step, in a direction that tends to reduce the difference between said compared signals to control the ratio of said actual to said apparent surface areas.
Claim 14
Dependent Claim
66 words
The method of claim 11 wherein said comparing is accomplished by electrically exciting a reference coil that is essentially identical to said test coil, placing a sample etched valve-metal foil having the desired ratio of actual to apparent surface area adjacent to said reference coil, said predetermined signal being said fixed functions of the eddy currents generated in said sample foil by said excited reference coil.
References Cited (Backward Citations)
US2930741A
Cited
US2809346A
Cited
US2853445A
Cited
US3085950A
Cited
US3553052A
Cited
US3645876A
Cited
US3764897A
Cited
US3962048A
Cited
US3988215A
Cited
US4126510A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-08-09 | 1986-02-08 | 1986-08-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-08-09 | 1990-02-08 | 1990-08-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-08-09 | 1994-02-08 | 1994-08-10 | $7700.00 | Window Closed / Lapsed |