US4597048A — Digital flow regulation of liquid-level control f…

Claim 1

Independent Claim 198 words

In a continuous casting apparatus of the type wherein liquid metal is supplied from a liquid reservoir to a mold through a valve mechanism, said valve mechanism having a movable valve member the position of which determines the rate at which said liquid is supplied to said mold, detection means for detecting the level of liquid in said mold, comparison means for comparing the detected liquid level with a desired level to generate an error signal, control signal generating means for generating a control signal in response to said error signal and control means for moving said valve member in response to said control signal, said control signal generating means comprising: first means responsive to said error signal for generating a first signal corresponding to a desired change in the position of said valve member, said first means comprising means for receiving a sequence of said error signals and for calculating a value FO according to: FO=KG[(E1-E2)+KI(E1)+KD(E1-2E2+E3)] where E1, E2 and E3 are consecutive error signals and KG, KI and KD are predetermined constants; and second means responsive to the value of said first signal for generating said control signal having a duration corresponding to said first signal.

Claim 2

Dependent Claim 198 words

In a continuous casting apparatus of the type wherein liquid metal is supplied from a liquid reservoir to a mold through a valve mechanism, said valve mechanism having a movable valve member the position of which determines the rate at which said liquid is supplied to said mold, detection means for detecting the level of liquid in said mold, comparison means for comparing the detected liquid level with a desired level to generate an error signal, control signal generating means for generating a control signal in response to said error signal and control means for moving said valve member in response to said control signal, said control signal generating means comprising: first means responsive to said error signal for generating a first signal corresponding to a desired change in the position of said valve member, said first means comprising means for receiving a sequence of said error signals and for calculating a value FO according to: FO=KG[(E1-E2)+KI(E1)+KD(E1-2E2+E3)] where E1, E2 and E3 are consecutive error signals and KG, KI and KD are predetermined constants; and second means responsive to the value of said first signal for generating said control signal having a duration corresponding to said first signal.

Claim 3

Dependent Claim 44 words

A continuous casting apparatus as defined in claim 1, wherein said control means moves said valve member at a predetermined rate during the presence of said control signal, whereby the movable valve member moves a distance proportional to the duration of said control signal.

Claim 4

Dependent Claim 120 words

A continuous casting apparatus as defined in claim 1, wherein said first means further comprises means for calculating a pulse duration signal PD corresponding to said first signal, said pulse duration signal PD being calculated substantially as follows: PD=(FO+PT+FP)×T.sub.cm where PT is a compensation factor for compensating for a delay time between the commencement of said control signal and movement of said valve member, FP is a compensation factor for compensating for free play or the like encountered during a change in direction of movement of said valve member, and T cm is a calibrated movement time of said control means, i.e. the amount of time required by said control means to move said valve member through a predetermined distance.

Claim 5

Dependent Claim 76 words

A continuous casting apparatus as defined in claim 1, wherein a cast strand is withdrawn from said mold at a casting speed, said apparatus further comprising: limit detection means for comparing said error signal to at least one limit value and for providing an output signal when said error signal exceeds said at least one limit value; and speed control means responsive to said output signal from said limit detection means for adjusting said casting speed.

Claim 6

Dependent Claim 56 words

A continuous casting apparatus as defined in claim 1, further comprising reservoir level detection means for detecting changes in the level of liquid in said reservoir and for generating a signal DHD corresponding to the present value and direction of change of the reservoir level, and means for calculating a sum (FO+DHD) as said first signal.

Claim 7

Dependent Claim 178 words

In a device of the type wherein a liquid is supplied from a liquid supply to a liquid container through a valve mechanism having a movable valve member the position of which determines the rate at which said liquid is supplied to said container, a method of controlling the level of liquid in said container, said method comprising the steps of: detecting the level of said liquid in said container; generating an error signal corresponding to the difference between the detected liquid level and a reference level; calculating a first signal corresponding to a desired change in the position of said valve member, including the step of calculating a value FO according to the following equation: FO=KG[(E1-E2)+KI(E1)+KD(E1-2E2+E3)] where E1, E2 and E3 are consecutive error signals corresponding to the difference between the detected liquid level and said reference level and KG, KI and KD are predetermined constants; generating a control signal having a duration corresponding to the value of said first signal; and moving said valve member by an amount proportional to the duration of said control signal.

Claim 8

Dependent Claim 178 words

In a device of the type wherein a liquid is supplied from a liquid supply to a liquid container through a valve mechanism having a movable valve member the position of which determines the rate at which said liquid is supplied to said container, a method of controlling the level of liquid in said container, said method comprising the steps of: detecting the level of said liquid in said container; generating an error signal corresponding to the difference between the detected liquid level and a reference level; calculating a first signal corresponding to a desired change in the position of said valve member, including the step of calculating a value FO according to the following equation: FO=KG[(E1-E2)+KI(E1)+KD(E1-2E2+E3)] where E1, E2 and E3 are consecutive error signals corresponding to the difference between the detected liquid level and said reference level and KG, KI and KD are predetermined constants; generating a control signal having a duration corresponding to the value of said first signal; and moving said valve member by an amount proportional to the duration of said control signal.

Claim 9

Dependent Claim 118 words

A method as defined in claim 6, wherein said calculating step further comprises calculating a pulse duration signal PD corresponding to said first signal, said pulse duration signal PD being calculated according to the following equation: PD=(FO+PT+FP)×T.sub.cm where PT is a compensation factor for compensating for a delay time between the commencement of said control signal and movement of said valve member, FP is a compensation factor for compensating for free play or the like encountered during a change in direction of movement of said valve member, and T cm is a calibrated movement time of said control means, i.e. the amount of time required by said control means to move said valve member through a predetermined distance.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1989-06-23	1989-12-23	1990-06-24	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1993-06-23	1993-12-23	1994-06-24	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1997-06-23	1997-12-23	1998-06-24	$7700.00	Window Closed / Lapsed

Digital flow regulation of liquid-level control for a continuous casting mold

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