US4660586A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Liquid level control
Assignee: Alcoa Corp
•
Filing: 1984-12-21
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Granted: 1987-04-28
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Expires: 2004-12-21
Abstract
Abstract An apparatus for controlling liquid level, comprising containment means for containing and dispensing liquid, flow varying means operable for varying flow of liquid into the containment means, stepper motor means for operating the flow varying means, sensor means for sensing level of liquid in the containment means, and PDD controller means connected between the sensor means and the stepper motor means for controlling liquid level.
Inventors
- 👤 David J. Knapp
- 👤 Marion D. Waltz
- 👤 David W. Clarke
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 08:21
CPC Classifications
G; G05; G05D; G05D9/00; G05D9/12; Y; Y10; Y10T; Y10T137/00; Y10T137/0318; Y10T137/0324; Y10T137/7287; Y10T137/7306
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
65 words
An apparatus for controlling liquid level, comprising containment means for containing and dispensing liquid, flow varying means operable for varying flow of liquid into the containment means, stepper motor means for operating the flow varying means, sensor means for sensing level of liquid in the containment means, and PDD controller means connected between the sensor means and the stepper motor means for controlling liquid level.
Claim 2
Independent Claim
65 words
An apparatus for controlling liquid level, comprising containment means for containing and dispensing liquid, flow varying means operable for varying flow of liquid into the containment means, stepper motor means for operating the flow varying means, sensor means for sensing level of liquid in the containment means, and PDD controller means connected between the sensor means and the stepper motor means for controlling liquid level.
Claim 3
Dependent Claim
19 words
An apparatus as claimed in claim 1, the PDD controller means functioning according to Y(t)=(RK1*X(t))+(RK2*X(t-1))+(RK3*X(t-2)) where RK1=C1*(C2+(1.0+C2*C3)/TD+C3/TD**2) RK2=(-C1/TD)*(1.0+C2*C3+2.0*C3/TD) RK3=C1*C3/TD**2.
Claim 4
Dependent Claim
23 words
An apparatus as claimed in claim 2, wherein fractional motor steps are accumulated and steps are executed upon attainment of a whole step.
Claim 5
Independent Claim
81 words
A method for controlling level of a liquid being dispensed from a containment comprising sensing the liquid level, comparing the sensed level to a setpoint for determining error, and varying flow of replenishment liquid into the containment by a stepper motor, the steps of stepper motor movement being the sum of a term proportional to the error itself, a term proportional to the first time derivative of the error and a term proportional to the second time derivative of the error.
Claim 6
Independent Claim
81 words
A method for controlling level of a liquid being dispensed from a containment comprising sensing the liquid level, comparing the sensed level to a setpoint for determining error, and varying flow of replenishment liquid into the containment by a stepper motor, the steps of stepper motor movement being the sum of a term proportional to the error itself, a term proportional to the first time derivative of the error and a term proportional to the second time derivative of the error.
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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) | 1990-04-27 | 1990-10-27 | 1991-04-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-04-27 | 1994-10-27 | 1995-04-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-04-27 | 1998-10-27 | 1999-04-28 | $7700.00 | Window Closed / Lapsed |