Mass rate control system for paper stock refiners

Claim 2

In combination with a refiner for processing fluid paper stock which includes a pair of relatively rotatable and axially movable refining elements, a drive motor for relatively rotating said elements and a control motor for axially shifting one of said elements with respect to the other, a control system comprising a power control loop responsive to the actual power consumed by said drive motor to operate said control motor in accordance with any difference between a signal representative of the actual power consumed by said drive motor and a power set point signal, and an energy-per-unit-mass control loop responsive to rate of flow and consistency data derived from the fluid stock passing through said refiner to provide a calculated energy per unit mass signal which is compared with a set point signal indicative of a desired energy per unit mass so as to provide said power set point signal in accordance with any difference therebetween, whereby the power required by said drive motor is relatively uniform.

Claim 3

The combination of claim 1 in which said energy-per-unit-mass control loop includes first calculating means responsive to said rate of flow and consistency data for providing a signal representative of tons per hour of stock flowing through said refiner, second calculating means for providing a signal that is the ratio of the difference between the no-load power value required by said refiner for the particular flow condition and a power value with respect to the value of said tons-per-hour signal, and means for comparing the value of said ratio signal with said set point signal that is indicative of the desired energy per unit mass to provide said power set point signal.

Claim 4

The combination of claim 2 in which the value of said power set point signal constitutes the power value, the no-load power value being subtracted from the value of said power set point signal by said second calculating means to provide said difference.

Claim 5

The combination of claim 2 in which the value of the actual power consumed by said drive motor constitutes the power value, the no-Load power value being subtracted from the value of the actual power by said second calculating means to provide said difference.

Claim 6

The combination of claim 1 including a stock property loop responsive to the value of a given stock property for modifying the amount of actual power supplied to said drive motor in accordance with the difference between the measured value of said given stock property and the value of a desired value of said given stock property.

Claim 7

In combination with a refiner for processing fluid paper stock which includes a pair of relatively rotatable and axially movable refining elements, a drive motor for relatively rotating said elements and a control motor for axially positioning one of said elements with respect to the other, a control system comprising a power control loop including a power transmitter for providing a signal which is a measure of the actual power being consumed by said drive motor, comparator means for comparing said actual power signal with a power set point signal to provide an error signal representative of any difference therebetween, means responsive to said error signal for operating said control motor in accordance with the value of said error signal so as to position said one refining element axially witH respect to said other refining element, means providing a signal which is a measure of the flow rate of fluid stock through said refiner, means providing a signal which is a measure of the consistency of said fluid stock, first calculating means for computing a mass stock rate signal from said flow and consistency signals, second calculating means for computing a signal representative of energy per unit mass, said energy-per-unit-mass signal being derived from a ratio of the difference between first and second signals with respect to said mass stock rate signal wherein said second signal is representative of the power required by said refiner under no-load conditions, comparator means for comparing said energy per unit mass signal with a set point signal indicative of a desired energy per unit mass to provide an error signal in accordance with any difference therebetween, and means responsive to said last-mentioned error signal for providing said power set point signal.

Claim 8

In combination with a refiner for processing fluid paper stock which includes a pair of relatively rotatable and axially movable refining elements, a drive motor for relatively rotating said elements and a control motor for axially positioning one of said elements with respect to the other, a control system comprising a power control loop including a power transmitter for providing a signal which is a measure of the actual power being consumed by said drive motor, comparator means for comparing said actual power signal with a power set point signal to provide an error signal representative of any difference therebetween, means responsive to said error signal for operating said control motor in accordance with the value of said error signal so as to position said one refining element axially witH respect to said other refining element, means providing a signal which is a measure of the flow rate of fluid stock through said refiner, means providing a signal which is a measure of the consistency of said fluid stock, first calculating means for computing a mass stock rate signal from said flow and consistency signals, second calculating means for computing a signal representative of energy per unit mass, said energy-per-unit-mass signal being derived from a ratio of the difference between first and second signals with respect to said mass stock rate signal wherein said second signal is representative of the power required by said refiner under no-load conditions, comparator means for comparing said energy per unit mass signal with a set point signal indicative of a desired energy per unit mass to provide an error signal in accordance with any difference therebetween, and means responsive to said last-mentioned error signal for providing said power set point signal.

Claim 9

The combination of claim 6 in which said first signal corresponds to said power set point signal.

Claim 10

The combination of claim 6 in which said first signal corresponds to said signal which is a measure of the actual power being consumed by said drive motor.

Claim 11

The combination of claim 6 including the means responsive to a measured stock property for modifying the value of said first-mentioned error signal in accordance with any difference between said measured stock property and the set point representing a desired stock property.

Claim 12

In combination with a refiner for processing fluid paper stock which includes a pair of relatively rotatable and axially movable refining elements, an electric drive motor for relatively rotating said elements and an electric control motor for axially positioning one of said elements with respect to the other, a control system comprising a power control loop including a power transmitter for providing a signal which is a measure of the actual power being consumed by said drive motor, first comparator means for comparing said actual power signal with a power set point signal to provide a first error signal representative of any difference therebetween, a deadbanded pulse duration power controller responsive to said error signal for furnishing pulses to said control motor having a duration proportional to the value of any such error signal so as to position said one refining element with respect to said other refining element in accordance with the length of pulses supplied by said controller, means providing a signal which is a measure of the flow rate of fluid stock through said refiner, means providing a signal which is a measure of the consistency of said fluid stock, first calculating means for computing a signal representative of tons per hour of stock flowing through said refiner, second calculator means having first, second and third input lines, said first input line being connected to said first calculating means, said second input line introducing into said second calculating means a given kilowatt signal and said third input line introducing into said second calculating means a signal representative of the kilowatts required by said refiner under no-load conditions, said second calculating means ratioing the difference between said signals introduced via said second and third input lines with respect to the signal introduced via said first input line to provide an output signal representative of calculated kilowatt hour per ton, second comparator means for comparing said calculated kilowatt-hours-per-ton signal with a set point signal representative of a desired number of kilowatt hours per ton to provide a second error signal in accordance with any difference therebetween, and a kilowatt-hours-per-ton controller responsive to said last-mentioned error signal for providing said power set point signal.

Claim 13

In combination with a refiner for processing fluid paper stock which includes a pair of relatively rotatable and axially movable refining elements, an electric drive motor for relatively rotating said elements and an electric control motor for axially positioning one of said elements with respect to the other, a control system comprising a power control loop including a power transmitter for providing a signal which is a measure of the actual power being consumed by said drive motor, first comparator means for comparing said actual power signal with a power set point signal to provide a first error signal representative of any difference therebetween, a deadbanded pulse duration power controller responsive to said error signal for furnishing pulses to said control motor having a duration proportional to the value of any such error signal so as to position said one refining element with respect to said other refining element in accordance with the length of pulses supplied by said controller, means providing a signal which is a measure of the flow rate of fluid stock through said refiner, means providing a signal which is a measure of the consistency of said fluid stock, first calculating means for computing a signal representative of tons per hour of stock flowing through said refiner, second calculator means having first, second and third input lines, said first input line being connected to said first calculating means, said second input line introducing into said second calculating means a given kilowatt signal and said third input line introducing into said second calculating means a signal representative of the kilowatts required by said refiner under no-load conditions, said second calculating means ratioing the difference between said signals introduced via said second and third input lines with respect to the signal introduced via said first input line to provide an output signal representative of calculated kilowatt hour per ton, second comparator means for comparing said calculated kilowatt-hours-per-ton signal with a set point signal representative of a desired number of kilowatt hours per ton to provide a second error signal in accordance with any difference therebetween, and a kilowatt-hours-per-ton controller responsive to said last-mentioned error signal for providing said power set point signal.

Claim 14

The combination of claim 10 in which said power set point signal constitutes said given kilowatt signal introduced via said second input line to said secoNd calculating means.

Claim 15

The combination of claim 10 in which said actual power signal constitutes said given kilowatt signal introduced into said second calculating means via said second input line.

Claim 16

The combination of claim 10 including a third comparator means disposed between said first comparator means and said deadbanded pulse duration power controller for comparing said first error signal with a stock property signal having a value representative of any change that said stock property signal has deviated from a desired value so as to provide a third error signal in accordance with the difference between said stock property signal and said first error signal, said third error signal controlling said deadbanded pulse duration power controller in accordance with the value thereof.

Claim 17

The combination of claim 13 including a stock property transmitter for providing a signal which is the measure of the stock property of stock flowing through said refiner, and a fourth comparator means for comparing said measured stock property signal with a set point signal representative of the stock property that is desired so as to produce said third error signal.