US5944955A — Fast basis weight control for papermaking machine

Claim 1

Independent Claim 175 words

A sheetmaking system having a wet end and a dry end wherein the wet end includes a headbox through which wet stock is discharged onto a water permeable moving wire, said system comprising: a source of wet stock from which wet stock is introduced into the headbox through a first line and a second line; a first controllable stock valve that regulates flow through the first line; a second controllable stock valve that regulates flow through the second line; a first control loop including means for obtaining basis weight measurements within said dry end and means for performing coarse adjustments to the first controllable stock valve in response to said dry end basis weight measurements, said first control loop having an associated first response time; and a second control loop including means for obtaining basis weight basis weight measurements within said wet end and means for performing fine adjustments to said the second controllable stock valve in response to said wet end basis weight measurements, said second control loop having an associated second response time.

Claim 2

Dependent Claim 175 words

A sheetmaking system having a wet end and a dry end wherein the wet end includes a headbox through which wet stock is discharged onto a water permeable moving wire, said system comprising: a source of wet stock from which wet stock is introduced into the headbox through a first line and a second line; a first controllable stock valve that regulates flow through the first line; a second controllable stock valve that regulates flow through the second line; a first control loop including means for obtaining basis weight measurements within said dry end and means for performing coarse adjustments to the first controllable stock valve in response to said dry end basis weight measurements, said first control loop having an associated first response time; and a second control loop including means for obtaining basis weight basis weight measurements within said wet end and means for performing fine adjustments to said the second controllable stock valve in response to said wet end basis weight measurements, said second control loop having an associated second response time.

Claim 3

Dependent Claim 23 words

The system of claim 1 wherein the flow rate through the first line is higher than the flow rate through the second line.

Claim 4

Dependent Claim 19 words

The system of claim 1 wherein the second response time is less than that of the first response time.

Claim 5

Dependent Claim 45 words

The system of claim 1 wherein the means for obtaining the basis weight measurements within the wet end comprises a sensor that is positioned under the moving wire which generate signals that are indicative of the basis weight of the wet stock on the wire.

Claim 6

Dependent Claim 31 words

The system of claim 4 wherein the sensor comprises a plurality of individual water weight sensor cells arranged essentially in a row parallel to the direction of movement of the wire.

Claim 7

Dependent Claim 35 words

The system of claim 4 wherein the sensor includes an electrode configuration for electrically detecting property changes in the wet stock being processed in said sheetmaking system to obtain the wet end basis weight measurements.

Claim 8

Dependent Claim 39 words

The system of claim 1 wherein the means for obtaining the basis weight within the dry end comprises a scanning type sensor positioned at the dry end which generates signals that are indicative of the dry end basis weight.

Claim 9

Dependent Claim 58 words

The system of claim 1 wherein the means for obtaining the basis weight within the dry end comprise a sensor positioned underneath the sheet at the dry end and which generates signals that are indicative of the dry end basis weight, wherein the sensor includes an electrode configuration for electrically detecting property changes in the sheet being produced.

Claim 10

Independent Claim 188 words

A method for controlling a sheetmaking system having a source of wet stock that is connected to a headbox by a first line and a second line and having a wet end and a dry end, with the first line having a first controllable stock valve that regulates flow through the first line and the second line having a second controllable stock valve that regulates flow through the second line, and wherein the wet stock is discharged through the headbox discharged onto a water permeable wire, said method comprising the steps of: (a) implementing a first control loop having an associated first response time by performing at least the steps of: (i) obtaining basis weight measurements within said dry end; and (ii) performing coarse adjustments to first controllable stock valve in response to said dry end basis weight measurements; and (b) implementing a second control loop having an associated second response time by performing at least the steps of: (i) obtaining basis weight measurements within said wet end; and (ii) performing fine adjustments to the second controllable stock valve in response to said wet end basis weight measurements.

Claim 11

Independent Claim 188 words

A method for controlling a sheetmaking system having a source of wet stock that is connected to a headbox by a first line and a second line and having a wet end and a dry end, with the first line having a first controllable stock valve that regulates flow through the first line and the second line having a second controllable stock valve that regulates flow through the second line, and wherein the wet stock is discharged through the headbox discharged onto a water permeable wire, said method comprising the steps of: (a) implementing a first control loop having an associated first response time by performing at least the steps of: (i) obtaining basis weight measurements within said dry end; and (ii) performing coarse adjustments to first controllable stock valve in response to said dry end basis weight measurements; and (b) implementing a second control loop having an associated second response time by performing at least the steps of: (i) obtaining basis weight measurements within said wet end; and (ii) performing fine adjustments to the second controllable stock valve in response to said wet end basis weight measurements.

Claim 12

Dependent Claim 37 words

The method of claim 9 wherein said step of performing coarse adjustments comprises adjusting the flow through the first stock valve and said step of performing fine adjustments includes comprises adjusting flow through the second stock valve.

Claim 13

Dependent Claim 23 words

The method of claim 9 wherein the flow rate through the first line is higher than the flow rate through the second line.

Claim 14

Dependent Claim 17 words

The method of claim 9 wherein the second response time is less than the first response time.

Claim 15

Dependent Claim 41 words

The method of claim 9 wherein said step of performing said coarse adjustments comprises controlling a first stock valve using a Dahlin controller and said step of performing said fine adjustments comprises controlling a second stock valve using a PID controller.

Claim 16

Dependent Claim 34 words

The method of claim 9 wherein the step (b)(i) comprises positioning a sensor under the moving wire which generate signals that are indicative of the basis weights of the wet stock on the wire.

Claim 17

Dependent Claim 29 words

The method of claim 14 wherein the sensor comprises a plurality of individual sensor cells arranged essentially in a row parallel to the direction of movement of the wire.

Claim 18

Dependent Claim 33 words

The method of claim 14 wherein the sensor includes an electrode configuration for electrically detecting property changes of wet stock processed in said sheetmaking system to obtain the wet end basis weight measurements.

Claim 19

Dependent Claim 31 words

The method of claim 9 wherein the step (a)(i) comprises positioning a scanning type sensor at the dry end which generates signals that are indicative of the dry end basis weight.

Claim 20

Dependent Claim 55 words

The method of claim 9 wherein the step (b)(i) comprises positioning a sensor at the dry end and underneath the sheet and which generates signals that are indicative of the dry end basis weight wherein the sensor includes an electrode configuration for electrically detecting property changes of the sheet being produced in said sheetmaking system.

Claim 21

Dependent Claim 224 words

In a sheetmaking system that forms a sheet of wet stock on a moving water permeable wire and having a wet end and a dry end wherein a sheet of wet stock that forms on a moving water permeable wire of a de-watering device that has a source of wet stock that is connected to a headbox through a first line having a first control valve that regulates flow through the first line and that has means for measuring the basis weight within the dry end, said system comprising: means for measuring the basis weight within the dry end and generating first signals indicative of the dry end basis weight; means for diverting a portion of wet stock flow from the source of wet stock through a second line having a second control valve that regulates flow through the second line and into the headbox; a sensor positioned underneath and adjacent to the wire for measuring the basis weight of the wet stock and which generates second signals indicative of the wet end basis weight, said sensor being positioned upstream from a dry line which develops during operation of the system; means for adjusting the flow rate through the first line in response to the first signals; and means for adjusting the flow rate through the second line in response to the second signals.

Claim 22

Dependent Claim 224 words

In a sheetmaking system that forms a sheet of wet stock on a moving water permeable wire and having a wet end and a dry end wherein a sheet of wet stock that forms on a moving water permeable wire of a de-watering device that has a source of wet stock that is connected to a headbox through a first line having a first control valve that regulates flow through the first line and that has means for measuring the basis weight within the dry end, said system comprising: means for measuring the basis weight within the dry end and generating first signals indicative of the dry end basis weight; means for diverting a portion of wet stock flow from the source of wet stock through a second line having a second control valve that regulates flow through the second line and into the headbox; a sensor positioned underneath and adjacent to the wire for measuring the basis weight of the wet stock and which generates second signals indicative of the wet end basis weight, said sensor being positioned upstream from a dry line which develops during operation of the system; means for adjusting the flow rate through the first line in response to the first signals; and means for adjusting the flow rate through the second line in response to the second signals.

Claim 23

Dependent Claim 29 words

The system of claim 19 wherein the sensor comprises a plurality of individual sensor cells that are positioned at different locations in the direction of movement of the wire.

Claim 24

Dependent Claim 42 words

The system of claim 19 wherein the means for diverting a portion of the of the wet stock creates a flow rate through the second line that is less than about 25% by weight of the flow rate through the first line.

Claim 25

Dependent Claim 81 words

The system of claim 19 wherein the sensor includes a first electrode and a second electrode which is spaced-apart and adjacent to said first electrode, said wet stock being between and in close proximity to said first and said second electrodes, said sensor is coupled in series with an impedance element between an input signal and a reference potential; and wherein fluctuations in at least one of said properties of said wet stock causes changes in voltage measured across said sensor.

Claim 26

Dependent Claim 25 words

The system of claim 22 wherein said first electrode is coupled to said impedance element and said second electrode is coupled to said reference potential.

Claim 27

Dependent Claim 25 words

The system of claim 22 wherein said first electrode is coupled to said input signal and said second electrode is coupled to said impedance element.

Claim 28

Independent Claim 50 words

The system of claims 23 further including a third electrode coupled to said reference potential, said first electrode being spaced-apart and residing between said second and said third electrodes, wherein another portion of said sheet of material is between and in close proximity to said first and said third electrodes.

Claim 29

Dependent Claim 42 words

The system of claim 22 further comprising means for providing a feedback signal to adjust said input signal such that said fluctuations in at least one of said properties are due to fluctuations in a single physical characteristic of said wet stock.

Claim 30

Dependent Claim 42 words

The system of claim 26 wherein said physical properties include dielectric constant, conductivity, and proximity of said portion of said wet stock to said sensor and said single physical characteristic of said wet stock comprises one of weight, chemical composition, and temperature.

Claim 31

Dependent Claim 61 words

The system of claim 22 wherein said impedance element is one of an inductive element and capacitive element each having an associated impedance and said input signal has an associated frequency and wherein said associated impedance of said one of said inductive and capacitive element may be set to a particular magnitude by adjusting said associated frequency to a given magnitude.

Claim 32

Dependent Claim 40 words

The system of claim 28 wherein said sensor has an associated impedance and said associated frequency is adjusted such that said sensor impedance and said impedance of said one of said capacitive element and said inductive element are approximately equal.

Claim 33

Independent Claim 207 words

A method of controlling the formation of a sheet of wet stock that forms on a moving water permeable wire of a de-watering machine, having a wet end and a dry end, that has a source of wet stock that is connected to a headbox through a first line having a first control valve that regulates flow through the first line and that has means for measuring the basis weight within the dry end, said method comprising the steps of: (a) diverting a portion of wet stock flow from the source of wet stock through a second line having a second control valve that regulates flow through the second line; (b) placing a sensor underneath and adjacent to the wire and upstream from a dry line which develops during operation of the machine; (c) operating the machine and measuring the basis weight within the dry end and generating first signals indicative of the dry end basis weight and measuring the basis weight with the sensor and generating second signals indicative of the wet end basis weight; (d) adjusting the flow rate through the first line in response to the first signals; and (e) adjusting the flow rate through the second line in response to the second signals.

Claim 34

Independent Claim 207 words

A method of controlling the formation of a sheet of wet stock that forms on a moving water permeable wire of a de-watering machine, having a wet end and a dry end, that has a source of wet stock that is connected to a headbox through a first line having a first control valve that regulates flow through the first line and that has means for measuring the basis weight within the dry end, said method comprising the steps of: (a) diverting a portion of wet stock flow from the source of wet stock through a second line having a second control valve that regulates flow through the second line; (b) placing a sensor underneath and adjacent to the wire and upstream from a dry line which develops during operation of the machine; (c) operating the machine and measuring the basis weight within the dry end and generating first signals indicative of the dry end basis weight and measuring the basis weight with the sensor and generating second signals indicative of the wet end basis weight; (d) adjusting the flow rate through the first line in response to the first signals; and (e) adjusting the flow rate through the second line in response to the second signals.

Claim 35

Dependent Claim 25 words

The method of claim 30 wherein step (b) comprises placing a plurality of sensors at different locations in the direction of movement of the wire.

Claim 36

Dependent Claim 29 words

The method of claim 30 wherein the flow rate through the first line is at least about 70% of the combined flow rate through the first and second lines.

Claim 37

Dependent Claim 85 words

The method of claim 30 wherein each of said sensors includes a first electrode and a second electrode which is spaced-apart and adjacent to said first electrode, said wet stock being between and in close proximity to said first and said second electrodes, said each sensor is coupled in series with an impedance element between an input signal and a reference potential; and wherein fluctuations in at least one of said properties of said wet stock causes changes in voltage measured across said each sensor.

Claim 38

Dependent Claim 25 words

The method of claim 33 wherein said first electrode is coupled to said impedance element and said second electrode is coupled to said reference potential.

Claim 39

Dependent Claim 25 words

The method of claim 33 wherein said first electrode is coupled to said input signal and said second electrode is coupled to said impedance element.

Claim 40

Dependent Claim 50 words

The method of claim 34 further including a third electrode coupled to said reference potential, said first electrode being spaced-apart and residing between said second and said third electrodes, wherein another portion of said sheet of material is between and in close proximity to said first and said third electrodes.

Claim 41

Dependent Claim 42 words

The method of claim 33 further comprising means for providing a feedback signal to adjust said input signal such that said fluctuations in at least one of said properties are due to fluctuations in a single physical characteristic of said wet stock.

Claim 42

Dependent Claim 43 words

The method of claim 37 wherein said physical properties include dielectric constant, conductivity, and proximity of said portion of said wet stock to said each sensor and said single physical characteristic of said wet stock comprises one of weight, chemical composition, and temperature.

Claim 43

Dependent Claim 61 words

The method of claim 33 wherein said impedance element is one of an inductive element and capacitive element each having an associated impedance and said input signal has an associated frequency and wherein said associated impedance of said one of said inductive and capacitive element may be set to a particular magnitude by adjusting said associated frequency to a given magnitude.

Claim 44

Dependent Claim 42 words

The method of claim 39 wherein said each sensor has an associated impedance and said associated frequency is adjusted such that said each sensor's impedance and said impedance of said one of said capacitive element and said inductive element are approximately equal.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2002-08-30	2003-03-01	2003-08-31	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2006-08-30	2007-03-01	2007-08-31	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2010-08-30	2011-03-01	2011-08-31	$7700.00	Window Closed / Lapsed

Fast basis weight control for papermaking machine

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