AU2001245512A1 - Refiner disk sensor and sensor refiner disk - Google Patents

Description

REFINER DISK SENSOR AND SENSOR REFINER DISK Field of the Invention

The present invention relates to a sensor, a sensor refiner disk, a system for

increasing the accuracy of a measurement made from a parameter sensed in the refining

zone, and a method of improving the accuracy of the measurement made.

Background of the Invention

Many products we use everyday are made from fibers. Examples of just a few of

these products include paper, personal hygiene products, diapers, plates, containers, and

packaging. Making products from wood fiber, fabric fiber and the like, involves breaking

solid matter into fibrous matter. This also involves processing the fibrous matter into individual fibers that become fibrillated or frayed so they more tightly mesh with each

other to form a finished fiber product that is desirably strong, tough, and resilient.

In fiber product manufacturing, refiners are used to process the fibrous matter,

such as wood chips, fabric, and other types of pulp, into fibers and to further fibrillate

existing fibers. The fibrous matter is transported in liquid stock to each refiner using a

feed screw driven by a motor.

Each refiner has at least one pair of circular ridged refiner disks that face each

other and are driven by one or more motors. During refining, fibrous matter in the stock

to be refined is introduced into a gap between the disks that usually is quite small. Relative rotation between the disks during operation fibrillates fibers in the stock as the stock passes radially outwardly between the disks. One example of a disk refiner is shown and disclosed in U.S. Patent No.

5,425,508. However, many different kinds of refiners are in use today. For example, there

are counter rotating refiners, double disk or twin refiners, and conical disk refiners.

Conical disk refiners are often referred to in the industry as CD refiners.

During operation, many refiner parameters are monitored. Examples of

parameters include the power of the drive motor that is rotating a rotor carrying at least

one refiner disk, the mass flow rate of the stock slurry being introduced into the refiner,

the force with which opposed refiner disks are being forced together, the flow rate of

dilution water being added in the refiner to the slurry, and the refiner gap.

It has always been a goal to monitor conditions in the refining zone between the

pairs of opposed refining disks. However, making such measurements have always been a

problem because the conditions in the refining zone are rather extreme, which makes it rather difficult to accurately measure parameters in the refining zone, such as temperature

and pressure.

While sensors have been proposed in the past to measure temperature and

pressure in the refining zone, they have not heretofore possessed the reliability and robustness to be commercially practicable. Depending on the application, temperature

sensors used in the past also lacked the accuracy needed to provide repeatable absolute

temperature measurement, something that is highly desirable for certain kinds of refiner

control.

Another problem grappled with in the past is how and where to mount sensors. In the past, sensors have been mounted to a bar that is received in a pocket in the refining surface. This mounting technique is undesirable because it reduces total refining surface

area and can adversely affect the flow pattern during refining, leading to less intense

refining and increased shives.

Hence, while sensors and sensing systems used in the past have proven useful,

improvements nonetheless remain desirable.

Summary of the Invention A sensor, sensor disk, sensor correction system and method used in making a

measurement of a parameter or characteristic sensed in the refining zone of a rotary disk

refiner that refines fibrous pulp in a liquid stock slurry.

The sensor disk includes at least one sensor that is embedded in a refining surface

of the sensor disk. The sensor disk preferably includes a plurality of spaced apart sensors that are each at least partially embedded in the refining surface. Each sensor preferably is

a temperature sensor or a pressure sensor but, in any case, is a sensor capable of sensing a

characteristic or parameter of conditions in the refining zone from which a measurement

can be made. In one preferred embodiment, the sensor disk has at least three sensors

which are radially spaced apart and which can be disposed in a line that extends in a

radial direction. Even if not disposed in a line, the sensors preferably are radially distributed along the refining surface.

Each sensor is disposed in its own bore in the refining surface of the sensor disk

and has a tip that is disposed no higher than the height of the axial surface of an adjacent refiner bar, such as the refiner bar that is next to the sensor. The tip of the sensor is

disposed slightly below the axial refiner bar surface to prevent the tip from being physically located in the refining zone while still accommodating bar wear. In one

preferred embodiment, the tip is located at least about 0.050 inch (1.3 mm) below the

axial bar surface. In another preferred embodiment, the tip is located at least about 0.100

inch (2.5 mm) below axial bar height.

Each sensor preferably is disposed in a bar or groove of the refining surface. Each

sensor includes a spacer that spaces a sensing element of the sensor from the surrounding

material of the sensor refiner disk. The sensing element is carried by a sensor housing that

is carried by the spacer. The sensor housing extends outwardly from the spacer and has its

tip located flush with or below the axial refiner bar surface. The sensing element or at

least one end of the sensing element can be spaced from an axial end or edge of the

spacer.

In a preferred embodiment, the spacer is disposed in a bore in the refining surface.

The spacer is tubular and configured to telescopically receive at least a portion of the

sensor housing, which can protrude outwardly from the spacer.

At least where the sensor is a temperature sensor, the sensor housing and spacer

enclose the sensing element. The housing is comprised of a thermally conductive material

and at least part of the housing is immersed in the stock during refiner operation. The

spacer is made of a thermally insulating material that thermally insulates the sensing

element from the thermal mass of the sensor refiner disk. The sensing element preferably

is disposed between the tip of the sensor housing and the spacer. The housing preferably protrudes from the insulating spacer to space the sensing element or the end of the sensing element from the spacer to minimize the impact of the insulating spacer on measurement of a temperature in the refining zone.

Where the sensor is a temperature sensor, the temperature sensor can be used to

obtain an absolute measurement of temperature in the refining zone adjacent the sensor.

Where a temperature sensor is used to obtain an absolute temperature measurement, the

sensing element preferably is of a type that is capable of being calibrated so as to provide

measurement repeatability. In one preferred embodiment, the sensing element is an RTD,

preferably a three wire platinum RTD.

In another embodiment, the sensor is embedded in a plate set in a pocket in the

refining surface of a refiner disk. The spacer is disposed in the bar and carries the sensor

or is an integral part of the sensor. The spacer spaces the sensor, including its sensing element, from the surrounding material of the bar and the surrounding material of the

refiner disk in which the bar is received. Where the sensor is a temperature sensor, the

spacer preferably insulates the sensing element from the thermal mass of the surrounding

material.

In one preferred refiner sensor disk embodiment, the sensor disk has a plurality of

spaced apart bores in its refining surface that each receives a sensor. Each bore

communicates with a wiring passage leading to the backside of the refiner disk. Each of

the sensors can be carried by a fixture that is received in a pocket in the backside of the

disk. In another embodiment, no fixture is used. In either embodiment, a bonding agent,

such as a high temperature potting compound or an epoxy, can be used to seal and anchor the fixture, the wiring, and the sensors to prevent steam and material in the refining zone from leaking from the refining zone. The sensors of a sensor refiner disk can be linked to a signal conditioner in the

vicinity of the refiner in which the disk is installed and can be mounted on the refiner.

Each sensor is ultimately linked to a processing device that processes sensor signals into

measurements. The processing device is linked to at least one module that holds

calibration data or calibration information about one or more sensors of the sensor refiner

disk. Preferably, the module holds calibration data or information about each sensor of

the sensor refiner disk in an on board memory storage device.

The calibration module is received in a connector box that is linked to the

processing device. The module has a connector that removably mates with a

complementary connector or socket on board the connector box that is connected to a

communications port. The connector box preferably has a plurality of module connectors so that calibration modules for a plurality of sensor disks can be plugged in. The

connector box enables sensor calibration data of sensors in sensor disks installed in

different refiners to be read and used.

In a method of assembly, one or more bores are formed in the refining surface of a

refiner disk or a refiner disk segment. One or more sensors are selected and calibrated before or after being installed in the finished sensor refiner disk or sensor disk segment.

The calibration data is stored on a calibration module that is packaged and shipped with

the sensor disk or segment to a fiber processing plant having a refiner where the sensor

disk or segment is to be installed.

Where one or more of the sensors are temperature sensors and the sensor output will be used to obtain an absolute temperature measurement, a pair of calibration variables preferably is stored for each such temperature sensor. Where a pair of

calibration variables is used, one variable preferably provides an offset or an adjustment

to the slope of an ideal temperature sensor for the type of sensor used and the other

variable preferably provides an intercept offset or intercept adjustment.

When the sensor disk or segment and its calibration module arrives at the fiber

processing plant, the sensor disk or segment is installed in one of the refiners linked to the

processing device and its module is connected to the device. Where more than one sensor

disks or segments are linked to the processing device, the module can be plugged into a

socket of a connector box that is associated with the refiner in which the sensor disks or

segments have been installed. In another preferred embodiment, the module is plugged

into any free socket and it is linked by software to the proper refiner. The module can be configured with a unique digital address that is used to assign it to the proper refiner.

In a method of operation, the output is read from each sensor of the installed

refiner disk or segment. Where a signal conditioner is used, the output read by the

processing device is a signal from the signal conditioner. The processing device

calculates a measurement from the output or signal from each sensor. The measurement is

corrected through application of the calibration data or calibration information for the

sensor read. If desired, the calibration data is read upon startup of the processing device.

It may also be read each time a corrected measurement calculation is made.

Where the sensor is a temperature sensor and an absolute temperature measurement is to be obtained, the signal or output from the temperature sensor is read

and its magnitude determined. The magnitude is inputted into an equation that multiplies it by a slope value. The slope value is a corrected slope value that is the result of the slope

of an ideal temperature sensor plus or minus a slope calibration offset from the calibration

module. An intercept value is added to the result. The intercept value is a corrected

intercept value that is the result of the intercept of an ideal temperature sensor plus or

minus an intercept calibration offset from the calibration module.

When the sensor disk or segment becomes worn or spent, it is removed and

another sensor disk or segment is installed. The calibration module for the spent disk is

removed and the calibration module that was shipped with the new disk is installed.

In a broader context, one or more sensors can be carried by a removable sensor

module, such as a segment of a refiner disk, that is connected to the processing device linked to at least one calibration module containing calibration data for each sensor of the

sensor module.

Objects, features, and advantages of the present invention include at least one of

the following: a sensor that is capable of sensing a parameter or characteristic of conditions in the refining zone; that is robust as it is capable of withstanding severe

vibration, heat, pressure and chemicals; is capable of repeatable, accurate absolute

measurement of the refining zone characteristic or parameter; is simple, flexible, reliable,

and long lasting, and which is of economical manufacture and is easy to assemble, install,

and use. Other objects, features, and advantages of the present invention include at least

one of the following: a sensor disk or segment that has a plurality of sensors in its refining

zone such that refining intensity, flow, and quality are maintained; embeds sensors in the grooves and bars of the refining surface where they are protected yet advantageously

capable of accurately sensing the desired refining zone parameter or characteristic; is

formed using a minimum of machining steps, time and components; can be formed from

any disk or segment having any refiner surface pattern; is capable of being used in a

refiner with a minimum modification of the refiner; and is simple, flexible, reliable, and

robust, and which is of economical manufacture and is easy to assemble, install, and use.

Additional objects, features, and advantages of the present invention include at

least one of the following: a sensor measurement correction system and method that is

capable of correcting sensor measurements of a sensor refiner disk with calibration data

prestored on a calibration module associated with the sensors of that disk or segment;

improves measurement accuracy; improves measurement repeatability; enables an

absolute measurement to be determined; is advantageously adaptable to refiner process

control schemes; is simple, flexible, reliable, and robust, and which is of economical

manufacture and is easy to assemble, install, configure and use. Other objects, features, and advantages of the present invention will become

apparent to those skilled in the art from the detailed description and the accompanying

drawings. It should be understood, however, that the detailed description and

accompanying drawings, while indicating at least one preferred embodiment of the

present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without

departing from the spirit thereof, and the invention includes all such modifications.

Brief Description of the Drawings Preferred exemplary embodiments of the invention are illustrated in the

accompanying drawings in which like reference numerals represent like parts throughout

and in which:

FIG. 1 is a fragmentary cross sectional view of a disk refiner equipped with a

sensor refiner disk or disk segment;

FIG. 2 is a front plan view of a sensor refiner disk segment;

FIG. 3 is an exploded side view of a preferred embodiment of a sensor assembly

and sensor refiner disk segment;

FIG. 4 is an exploded side view of a second preferred embodiment of a sensor

assembly and sensor refiner disk segment;

FIG. 5 is an enlarged partial fragment cross sectional view of a sensor disposed in

a bore in the sensor refiner disk segment;

FIG. 6 is a partial fragment cross sectional view of a sensor disposed in a bore in a

refiner bar of the sensor refiner disk segment; FIG. 7 is a top plan view of the sensor and refiner bar;

FIG. 8 is a front elevation view of a refiner disk segment that has sensors mounted

in a plate;

FIG. 9 is a schematic view of a sensor measurement correction system;

FIG. 10 is a top plan view of a connector box; FIG. 11 is a top plan view of a sensor calibration module, cutaway to show a

calibration data storage device inside;

FIG. 12 is a table of calibration constants; FIG. 13 is a table of calibration constants for temperatures sensors; and

FIG. 14 is a schematic view of a refiner monitoring and control system that uses a

sensor measurement coπection system and calibration modules capable of providing

corrections to measurements from sensors in as many as, for example, four different

refiners.

Detailed Description of the Invention

FIGS. 1-3 illustrate a refiner 30 to which the invention is applicable. The refiner

30 can be a refiner of the type used in thermomechanical pulping, refiner-mechanical

pulping, chemithermomechanical pulping, or another type of pulping or fiber processing

application. The refiner 30 can be a counter rotating refiner, a double disk or twin refiner,

or a conical disk refiner known in the industry as a CD refiner. The refiner 30 has a refiner disk or refiner disk segment 32 (FIG. 2) carrying at

least one sensor for sensing a parameter in the refining zone during refiner operation. The

refiner 30 has a housing or casing 34 and an auger 36 mounted therein which urges a

stock slurry of liquid and fiber introduced through a stock inlet 38 into the refiner 30. The auger 36 is carried by a shaft 40 that rotates during refiner operation to help supply stock to an arrangement of treating structure 42 within the housing 34 and a rotor 44. An

annular flinger nut 46 is generally in line with the auger 36 and directs the stock radially

outwardly to a plurality of opposed sets of breaker bar segments, both of which are indicated by reference numeral 48.

Each set of breaker bar segments 48 preferably is in the form of sectors of an

annulus, which together form an encircling section of breaker bars. One set of breaker bar

segments 48 is fixed to the rotor 44. The other set of breaker bar segments 48 is fixed to

another portion of the refiner 30, such as a stationary mounting surface 50, e.g. a stator, of

the refiner or another rotor (not shown). The stationary mounting surface 50 can comprise

a stationary part of the refiner frame 52.

Stock flows radially outwardly from the breaker bar segments 48 to a radially

outwardly positioned set of refiner disks 54 and 56. This set of refiner disks 54 and 56

preferably is removably mounted to a mounting surface. For example, one disk 56 is

mounted to the rotor 44 and disk 54 is mounted to mounting surface 50. The refiner 30

preferably includes a second set of refiner disks 58 and 60 positioned radially outwardly

of the first set of disks 54 and 56. Disk 60 is mounted to the rotor 44, and disk 58 is mounted to a mounting surface 62 that preferably is stationary. These disks 58 and 60

preferably are also removably mounted. Each pair of disks 54, 56 and 58, 60 of each set is

spaced apart so as to define a small gap between them that typically is between about

0.005 inches (0.127 mm) and about 0.125 inches (3.175 mm). Each disk can be of unitary

construction or can be comprised of a plurality of segments.

The first set of refiner disks 54 and 56 is disposed generally parallel to a radially extending plane 64 that typically is generally perpendicular to an axis 66 of rotation of the

auger 36. The second set of refiner disks 58 and 60 can also be disposed generally parallel

to this same plane 64 in the exemplary manner shown in FIG. 1. This plane 64 passes through the refiner gap between each pair of opposed refiner disks. This plane 64 also

passes through the space between the disks that defines the refining zone between them.

Depending on the configuration and type of refiner, different sets of refiner disks can be

oriented with their refining zones in different planes.

During operation, the rotor 44 and refiner disks 56 and 60 rotate about axis 66

causing relative rotation between the disks 56 and 60 and disks 58 and 62. Typically, the

rotor 44 is rotated between about 400 and about 3,000 revolutions per minute. During

operation, fiber in the stock slurry is fibrillated as it passes between the disks 54, 56, 58

and 60 refining the fiber. FIG. 2 depicts a sensor disk segment 32 of a refiner disk, such as disk 54, 56, 58

or 60, which has a sensor assembly 68 disposed in its refining surface. Where the refiner

disks of a particular refiner are not segmented, the sensor assembly 68 is disposed in a

portion of one of the refiner disks. The sensor disk segment 32 has a plurality of pairs of

spaced apart-upraised refiner bars 70 that define refiner grooves or channels 72 therebetween. The segment 32 preferably is made of a wear resistant machinable material,

such as a metal, an alloy, or a ceramic. The bars 70 and grooves 72 define a refining

surface 75 that generally extends from an inner diameter 77 to an outer diameter 79 of the

segment. The pattern of bars 70 and grooves 72 shown in FIG. 2 is an exemplary pattern, as any pattern of bars 70 and grooves 72 can be used. If desired, surface 74 or subsurface

dams 76 can be disposed in one or more of the grooves 72. The segment 32 can have one

or more mounting bores 73 for receiving a fastener, such as a bolt, a screw, or the like. During refining, fiber in the stock that is introduced between opposed refiner disks is refined by being ground, abraded, or mashed between opposed bars 70 of the

disks, thereby fibrillating the fibers. Stock in the grooves 72 and elsewhere in the refining

zone between the disks flows radially outwardly and can be urged in an axial direction by

dams to further encourage refining of the fiber. Depending on the construction,

arrangement, and pattern of the bars 70 and grooves 72, differences in angle between the

bars 70 of opposed disks due to relative movement between the disks can repeatedly

occur during operation. Where and when such differences in angle occur, radial outward

flow of stock between the opposed disks is accelerated, pumping the stock radially

outwardly. Where and when the bars 70 and grooves 72 of the opposed disks are

generally aligned, flow is retarded or held back.

The sensor assembly 68 includes one or more sensors and preferably includes a

plurality of spaced apart sensors 78, 80, 82, 84, 86, 88, 90, and 92. If desired, the sensor

assembly 68 can be comprised of at least three sensors, at least four sensors, at least five

sensors and can have more than eight sensors. In the preferred embodiment shown in FIG.

2, eight sensors 78, 80, 82, 84, 86, 88, 90, and 92 are disposed generally along a radial

line and are equidistantly spaced apart. For example, in one preferred embodiment each

pair of adjacent sensors is spaced apart from their centers about 7/8 of an inch

(approximately 22 millimeters).

Even if not disposed in a radial line, the sensors preferably are located at different

radiuses along the segment such that they are radially spaced apart. Having sensors

radially spaced apart provides a distribution of measurements along the length of the refining zone. Such a distribution of measurements advantageously enables an average measurement to be determined, slopes and derivatives to be calculated, and other

calculations on the measurement distribution to be performed.

Referring additionally to FIG. 3, each sensor 78, 80, 82, 84, 86, 88, 90, and 92

(shown in phantom) is respectively disposed in a bore 96, 98, 100, 102, 104, 106, 108,

and 110 in the refining surface 75 of the disk or disk segment. In the preferred

embodiment shown in FIG. 3, each bore 96, 98, 100, 102, 104, 106, 108, and 110 is a

hole of round cross section that extends completely through the segment 32. If desired,

each bore 96, 98, 100, 102, 104, 106, 108, and 110 can extend from the refining surface

75 toward the rear surface 112 of the segment 32 a sufficient depth to receive a sensor.

Where each bore 96, 98, 100, 102, 104, 106, 108, and 110 does not extend completely

through the segment 32, the bores communicate with one or more wiring passages so that

sensor wiring can be routed to the rear of the segment 32.

Still referring to FIG. 3, each sensor is received in a spacer 114. The spacer 114

spaces the sensor from the surrounding refiner disk material and can insulate the sensor to

prevent the thermal mass of the segment from interfering with sensing the desired

parameter or parameters in the refining zone. The spacer 114 preferably also dampens refiner disk vibration by helping to isolate the sensor from normal refiner vibration as

well as the kind of shock that can occur when opposed refiner disks come into contact

with each other and clash. In one preferred embodiment, the spacer 114 is affixed to the

sensor disk segment 32 by an adhesive 115 (FIG. 5), such as a high temperature potting

compound, an epoxy or the like.

Because of the types of alloys used and the construction of the bars 70 and grooves 72 of a refiner disk or segment, the bores 96, 98, 100, 102, 104, 106, 108, and

110 preferably are produced using an electric discharge machining (EDM) method or the

like. EDM machining advantageously permits forming each sensor-receiving bore in the

refining surface such that there is a minimum of loss of refining surface area. If desired,

each bore can be cast into the refining surface.

FIG. 3 also depicts a fixture 116 in the form of hollow conduit 118 that resembles

a manifold and that can have a holder 120 for each sensor. The conduit 118 preferably is

of square cross section but can have other cross sectional shapes. The fixture 116 is

received in a pocket 122 (shown in phantom) in the backside of the segment 32. The

fixture 116 has an opening 124 at one end through which sensor wiring 126 exits the

fixture 116.

Where sensor holders 120 are used, each sensor holder 120 preferably is tubular

and telescopically receives and retains at least part of a spacer 114. In another preferred

embodiment, no sensor holders 120 are used. Instead, a sensor-receiving bore is formed

in the fixture 116 in place of each holder 120. The spacer 114 of each sensor is disposed

in one of the bores in the fixture 116.

In assembly, each sensor and spacer 114 is received in the fixture 116 and the fixture 116 is inserted into the refiner backside pocket 122 with each holder 120 disposed

at least partially in one of the sensor-receiving bores. High temperature potting compound preferably is placed around the fixture 116 to help anchor it to the segment 32 and to help

prevent steam and stock from escaping from the refining zone. If desired, potting compound or another high temperature, hardenable material can be placed in the pocket 122 to seal and anchor the fixture 116 before inserting the fixture 116 into the pocket 122.

The conduit 118 preferably is also filled with a thermally protective sealing material, such

as silicone, potting compound, or the like.

FIG. 4 illustrates another preferred arrangement where no fixture is used in the

sensor disk segment 32'. In assembly, each sensor is carried by a spacer 114. Each spacer

114 is disposed in one of the bores. If desired, the backside of the sensor disk segment 32'

(or a one-piece refiner disk where the disk is not segmented) can have a wire-receiving

channel 128. Preferably, the channel 128 connects each bore 96, 98, 100, 102, 104, 106,

108 and 110. Potting compound 130 is applied to the disk or segment backside over and

preferably into each bore (from the backside). Where the segment 32' has a wire-

receiving channel 128, potting compound 130 or another high temperature material is also

placed in the channel 128 around the sensor wires 126 to hold them in place and protect them.

Each sensor disk segment 32 (or 32') is removably mounted to a stator of the

refiner 30, such as stationary mounting surface 50 or 62. The sensor wiring 126 passes

through a bore (not shown) in the mounting surface 50 or 62 and a bore (not shown) in

the refiner housing 34 or frame 52 to the exterior of the refiner 30. Where a signal

conditioner 206 is used, it is mounted to the refiner housing 34 or frame 52, such as in the

manner depicted in FIG. 1, and connected to the sensor wiring 126. Each bore through which sensor wiring 126 passes preferably is sealed, such as with a high temperature

epoxy, potting compound or another material. If desired, the wiring 126 can be received in a protective conduit. To facilitate assembly and removal, the wiring can include a connector (not shown) inside the refiner 30 adjacent the sensor disk segment 32 that

minimizes the length of wiring each sensor disk segment needs. Where the sensor disk

segment 32 (or 32') is installed on a rotor 44, the wiring 126 can be connected to a slip

ring (not shown) or telemetry can be used to transmit the sensor signals.

FIG. 5 illustrates a single sensor, sensor 78 for example, embedded at least

partially in a sensor disk segment 32. The tip of the sensor 78 preferably is located

between an axial outer surface 132 of an adjacent refiner bar 70 and a floor 134 of the

segment 32. In FIG. 3, the floor 134 is the bottom surface 136 of an adjacent groove 72,

e.g. the groove next to the sensor 78 or in which it is disposed. If desired, such as where it

is desirable to minimize turbulence or other phenomena from affecting sensor operation,

the floor around the sensor 78 can be a well, such as a countersink, a counterbore, or the

like, that is set below the surface 136 of the adjacent groove 72. For example, such a floor

134 can be a machined or cast depression or the like. When located in a groove 72, the

sensor 78 and spacer 114 advantageously collectively functions as a surface or subsurface

dam to urge radially flowing stock up and over the sensor 78 to help encourage refining.

The tip 138 of the sensor 78 is located flush with or below the axial outer surface

132 of an adjacent bar 70 to prevent the sensor 78 from being damaged during refiner

operation. For example, by locating the tip of the sensor 78 below surface 132 of adjacent

bar 70, it helps prevent matter in the stock slurry from forcefully impinging against and damaging the sensor 78. Additionally, it prevents refiner disk clashing from damaging the

sensor 78.

In the preferred embodiment shown in FIG. 5, the tip 138 of the sensor 78 preferably is offset a distance, a, below the axial outer bar surface 132 of an adjacent bar

70 so that it does not end up protruding into the refining zone when the axial height of the

bar 70 decreases as a result of wear. Depending on the type of refiner, the type of refining

being performed, the refiner disk alloy or alloys used, and other factors, the magnitude of

the offset, a, selected can vary. Preferably, the offset, a, is at least 0.050 inch (1.27 mm)

below the axial bar surface 132 when the segment 32 is new, e.g., the tip 138 of the

sensor 78 is located at least 0.050 inch below the axial bar surface 132 when the segment

32 is in a new or unused condition. In another preferred embodiment, the offset, a, is

0.100 inch (2.54 mm) or greater.

The sensor 78 preferably includes a tubular housing 140 that is carried by the

spacer 114. A sensing element 142, shown in phantom in FIG. 3, is carried by the housing

140. The housing 140 preferably protects the sensing element 142. The housing 140

protrudes from the spacer 114 to space the end of the sensing element 142 (adjacent tip

138) from the spacer 114 such that the spacer 114 does not shield the sensing element 142

too much and interfere with its operation.

As is shown in FIG. 5, a second offset between the tip 138 of the housing 140 and

the end 144 of the spacer 114 is indicated by reference character b. In one preferred

embodiment, the tip 138 of the housing 140 has an offset, b, of at least 1/16 inch (1.6

mm) such that the axial end of the sensing element 142 adjacent the tip 138 is spaced at least about 1/32 inch (0.8 mm) from the end 144 of the spacer 114. In another preferred

embodiment, the tip 138 of the housing 140 has an offset, b, of at least 1/8 inch (3.2 mm)

such that the end of the sensing element 142 is spaced at least about 1/16 inch (1.6 mm) from the end 144 of the spacer 114.

In the latter case, as is shown in FIG. 5, the entire sensing element 142 is spaced

from the end 144 of the spacer 114. Where the housing 140 has a rounded or a rounded

and enclosed end, the tip of the housing 140 can be spaced from the end 144 of the spacer

114 a distance at least as great as the radius of curvature of the rounded end to help

ensure that the entire sensing element 142 or enough of the sensing element 142 is not

shielded by the spacer 114.

The sensing element 142 preferably is a temperature-sensing element, such as an

RTD, a thermocouple or a thermistor. Where it is desired to measure the absolute

temperature of the stock slurry in the refining zone, one preferred sensing element 142 is an RTD that preferably is a platinum RTD. Where greater temperature measurement

accuracy is desired, an RTD sensing element 142 also is prefeπed. This is because an

RTD sensing element is a relatively accurate device, advantageously can be accurately

calibrated, and can be used with rather compact signal conditioning devices that can

transmit conditioned temperature measurement signals relatively long distances, typically

in excess of 4000 feet (1219 m), to a remotely located processing device.

As is shown in FIG. 5, the temperature sensing element 142 is disposed inside the

housing and is affixed to an interior wall of the housing 140 using an adhesive 146

(shown in phantom), such as a high temperature epoxy, a potting compound, or the like. In the preferred embodiment depicted in FIG. 5, the sensing element 142 has at least one wire 126 and preferably has a pair of wires 126 and 148. Where an RTD sensing element

is used, the sensing element 142 can have a third wire 150 to prevent the electrical resistance of the wires 126 and 148 from impacting temperature measurement. If desired,

a four wire RTD temperature sensing element can also be used.

The housing 140 functions to protect the temperature-sensing element 142 but yet

permit heat to be conducted to the element 142. In a preferred embodiment, the housing

140 is made of a stainless steel that has a thickness of about one millimeter for providing

a response time at least as fast as 0.5 seconds where an RTD temperature-sensing element

142 is used. For example, a platinum RTD temperature-sensing element 142 has a

response time of about 0.3 seconds when a one millimeter thick stainless steel housing

140 is used.

As is shown in FIG. 5, at least part of the housing 140 is telescopically received in

the spacer 114 and preferably is affixed to it by an adhesive, such as a high temperature

epoxy, a potting compound, or the like. The spacer 114 is telescopically received in a

bore 96 and affixed to the interior sidewall of the bore 96 by an adhesive 115, such as a

high temperature epoxy, a potting compound, or the like. FIGS. 6 and 7 depict a sensor 78 embedded in a refiner bar 70. Depending on the

width of the bar 70, the entire sensor 78 can be embedded in the bar 70 or only a part of

the sensor 78 can be embedded. FIG. 7 more clearly shows the spacer 114 encircling the

sensor housing 140.

The wall thickness, c, of the spacer 114 preferably is at least about 1/64 inch (about 0.4 mm). In one preferred embodiment, the spacer 114 has a wall thickness of

about 1/16 inch (about 1.6 mm). The spacer 114 preferably is of tubular or elongate and generally cylindrical construction. As a result of using a spacer and sensor that is small, preferably no wider than

about 3/8 inch (9.5 mm), the width or diameter of each sensor-receiving bore in the

segment 32 also preferably is no greater than about 7/16 inch (11.1 mm). As a result, the

percentage of surface area of all of the bore openings is very small. By locating the array

of sensors 78, 80, 82, 84, 86, 88, 90, and 92 within the pattern of refiner bars 70 and

grooves 72 and by keeping each sensor small relative to the total area of the refining

surface, pulp quality is not affected by use of the sensors. Because the sensors are located

in the refiner bars and groove, shives and other objects cannot follow sensors and bypass

being refined because each sensor is surrounded about its periphery by refining surface. In

one preferred embodiment, each spacer and sensor is no wider than about 1/4 inch (6.4

mm) and the width or diameter of the bore in the segment 32 is no greater than about 5/16

inch (7.9 mm).

In a preferred embodiment, the spacer 114 also is an insulator that insulates the

sensing element 142 from the thermal mass of the surrounding refiner disk. An insulating spacer 114 also helps insulate the sensing element 142 from thermal transients caused by

refiner disks clashing during operation. Preferably, at least where the sensing element 142

is a temperature sensing element, the insulating spacer 114 spaces the sensor from the

sensor disk segment 32 at least about 1/32 inch (about 0.8 mm). Preferably, the insulating

spacer 114 is made of a material and has a thickness that provides an R-value of at least about 5.51 * 10^"3 h*ft*°F/Btu to ensure that the sensing element 142 is sufficiently

insulated from the thermal mass of the surrounding material.

An example of a suitable insulating spacer is a generally cylindrical tube made of a ceramic material, such as alumina or mullite. Other examples of suitable insulating

materials include an aramid fiber, such as KEVLAR, or a tough thermoplastic capable of

withstanding temperatures at least as great as 428° F (220° C) and the severe environment

found inside the refining zone. For example, a suitable insulating spacer material should

be capable withstanding refiner disk vibration and thermal cycling, be chemically inert,

be able to withstand moisture, and be abrasion resistant.

Where the sensing element 142 is a temperature-sensing element, the spacer 114

is an insulating spacer. One preferred insulating spacer 114 is an OMEGATITE 200

model ORM cylindrical thermocouple insulator commercially available from Omega

Engineering, Inc., One Omega Drive, Stamford, Connecticut. This insulating spacer 114

is comprised of about 80% mullite and the remainder glass. One preferred insulating

spacer 114 is a model ORM-1814 thermocouple insulator. This insulating spacer 114 has

an outer diameter of ^lA inch (about 6.4 mm), an inner diameter of 1/8 inch (about 3.2

mm), and a wall thickness of about 1/16 inch (about 1.6 mm). Such an insulating spacer

114 accommodates a sensor 78 having housing that is about 1/8 inch (3.2 mm) in

diameter or smaller.

Where the sensing element 142 is a temperature-sensing element, the end or tip of

the housing 140 preferably completely encloses the sensing element 142 to protect it. For

another type of sensing element, such as a pressure-sensing element, the end or tip of the housing 140 can be open to permit stock from the refining zone to directly contact the

sensing element.

The combination of a platinum RTD temperature sensor 78 and insulating spacer 114 provides a robust sensor assembly that is advantageously capable of withstanding the

rather extreme conditions in the refining zone for at least the life of the sensor disk

segment 32, if not longer. For example, the combination of a one millimeter thick

stainless steel housing 140, platinum RTD sensing element 142, and ceramic insulating

spacer 114 produces a temperature sensor 78 embedded in a refiner disk segment and

exposed to the refining zone that can withstand a pressure in the refining zone that can lie

anywhere within a range of about 20 psi (1.4 bar) to about 120 psi (8.3 bar), a temperature

in the refining zone that can lie anywhere between 284° F (140° C) and 428° F (220° C),

and last at least the life of a typical refiner disk segment, which is at least 800 hours and

which typically ranges between 800 hours and 1500 hours.

If desired, one or more sensors 78, 80, 82, 84, 86, 88, 90 and 92 of a sensor refiner

disk segment 32 can be a pressure sensor. If desired, each of the sensors 78, 80, 82, 84,

86, 88, 90 and 92 of a sensor refiner disk segment 32 can be a pressure sensor. If desired,

a combination of pressure and temperature sensors can be used in a single segment 32. Where one or more pressure sensors are used to sense pressure in the refining zone, a

ruggedized pressure transducer, such as one of piezoresistive or diaphragm construction,

can be used. An example of a commercially available pressure transducer that can be used

is a Kulite XCE-062 series pressure transducer marketed by Kulite Semiconductor Products, Inc. of One Willow Tree Road, Leonia, New Jersey.

FIG. 8 illustrates a plurality of the aforementioned sensors 78, 80, 82, 84, 86, 88,

90 and 92 that are each mounted in a plate 156 that is disposed in a refiner disk segment 152. The plate 156 is disposed in a radial channel or pocket machined or cast into the refining surface 75 of the segment 152. The bar or plate 156 can be anchored to the

segment 152 by an adhesive, such as a potting compound or an epoxy. If desired, one or

more fasteners can be used to anchor the plate 156.

FIGS. 9-14 illustrate a calibration module 160 and a sensor correction system 162

for using calibration data stored on the module 160 to obtain more accurate

measurements from the data from one or more of the sensors 78, 80, 82, 84, 88, 90, and

92 of a sensor refiner disk or disk segment. Calibration data for each sensor 78, 80, 82,

84, 88, 90, and 92 is stored on the module 160. By storing sensor calibration data on a module 160 for each sensor, the sensors are precalibrated, the calibration data stored on

the module, the sensors assembled to a sensor refiner disk or disk segment, and the sensor

refiner disk or segment shipped together with its module 160 to a fiber processing plant

for installation into a refiner. The module 160 associated with that particular sensor refiner disk or disk segment is plugged into a socket or port linked to a processing device

164 that is linked to the refiner 32 into which the sensor refiner disk or sensor disk

segment is installed.

FIG. 9 is a schematic depiction of a sensor correction system 162 that has four

calibration modules 160a, 160b, 160d and 160e connected by links 166, 168, 170 and 172

to a port 174 of the processing device 164. Each of the links 166, 168, 170 and 172

preferably comprise one or more digital data lines that can be connected through the port 174 to a bus of the processing device 164. The processing device 164 has an on-board

processor, such as a microcomputer or microprocessor, and preferably comprises a

computer, such as a personal computer, a programmable controller, or another type of computer. The processing device 164 maybe a dedicated processing device or a computer

that also controls some aspect(s) of operation of the refiner 32. An example of such a

processing device 164 is a distributed control system computer (DCS) of the type

typically found in fiber processing plants, such as paper mills and the like.

FIG. 10 illustrates a module connector box 176 that can be a multiplexing data

switch or the like. The module connector box 176 has four sockets or connectors 178,

180, 182, and 184, each for receiving one of the modules 160a, 160b, 160c and 160d. The

box 176 also has an output socket or connector 186 that preferably accepts a cable 188

that links the modules 160a, 160b, 160c, and 160d to the processing device 164 (not

shown in FIG. 10). The cable 188 has a connector 190 at one end that is complementary

to and mates with connector 186. The cable 188 has a connector 192 at its opposite end that mates with a complementary connector (not shown) of the processing device 164. If

desired, the connector box 176 can comprise a card, such as a PCI card, that is inserted

into a socket inside the processing device and that has a plurality of ports each linked to

one of the modules 160a, 160b, 160c and 160d.

Where a cable 188 is used, the cable 188 preferably is a computer cable

containing a plurality of wires each capable of separately carrying digital signals. In one preferred embodiment, the cable 188 is a parallel printer cable having one 25-pin

connector and a second connector that can have either 25 pins or 36 pins. Such a cable preferably is attached to a parallel port 174 of the processing device 164, such as a printer

port that can be bi-directional. The cable 188 can also be configured to attach to other types of ports including, for example, an RS232 port, an USB port, a serial port, an Ethernet port, or another type of port. Other types of connectors can also be used. The

same is true for the connectors 178, 180, 182 and 184 on board the connector box 176.

FIG. 11 illustrates one preferred embodiment of the calibration module 160. The

module 160 has an on board storage device 194 in which the calibration data is stored.

The on board storage device 194 is received inside a protective housing 196 of the

module 160. The embodiment depicted in FIG. 11 has one multiple pin female connector

198 and one multiple pin male connector 200 permitting pass through of digital signals.

This feature advantageously permits other devices to piggyback on or chain to the module

160. The module 160 also has a pair of fasteners 202 to secure the module 160 to one of

the connectors 178, 180, 182 or 184 of the connector box 176.

The on board storage device 194 preferably is an application specific integrated circuit (ASIC) chip with on board programmable memory storage. Other suitable onboard storage devices that can be used include an erasable programmable read only

memory (EPROM), an electronically erasable programmable read only memory

(EEPROM), a programmable read only memory (PROM), a read only memory (ROM), a

flash memory, a flash disk, a non-volatile random access memory (NVRAM), or another

type of integrated circuit storage device that preferably retains its contents when electrical power is turned off. If desired, a static random access memory (SRAM) chip can be

connected to an on board battery to retain the calibration data when electrical power is turned off.

In its preferred embodiment, the plug-in module 160 is small, not more than 2.5 inches by 2.5 inches (63.5 mm by 63.5 mm) in size, and is lightweight, weighing not more than two ounces (0.06 kg). Such a small and lightweight module 160

advantageously makes it easy and inexpensive to ship with the sensor refiner disk

segment with which the module is configured to operate. In one preferred embodiment,

the module 160 is a HARDLOCK E-Y-E key that is a dongle with two parallel

connectors and is commercially available from Aladdin Knowledge Systems of 1094

Johnson Drive, Buffalo, Grove, Illinois. Another suitable module 160 is a HARDLOCK

USB that is also commercially available from Aladdin Knowledge Systems.

FIG. 12 illustrates a lookup table of calibration constants for the sensors 78, 80,

82, 84, 86, 88, 90 and 92 that are stored in the calibration module 160 for a particular

sensor refiner disk. Each sensor has at least one calibration constant that is applied to its

output by the processing device 160 to make sensor measurements more accurate. It can

be applied through addition, subtraction, multiplication or another mathematical operation.

FIG. 13 illustrates a second lookup table of exemplary calibration constants that

preferably are used when the sensing element 142 is a temperature-sensing element, such

as an RTD. Each temperature-sensing element 142 provides an output that is substantially linear relative to temperature and can thus be approximated as a line with a slope and

intercept:

T * M*MC + 1 (Equation I)

where T is the temperature, M is the slope, MC is the measured characteristic, and I is the

intercept. For example, for an RTD sensor the measured characteristic is the resistance of the sensing element that the sensing element outputs during operation. The measured resistance varies generally linearly with temperature. For a thermocouple, the measured

characteristic that gets outputted is voltage.

Each temperature sensor can be approximated by an equation of a line that

represents a perfectly accurate sensor of the particular sensor type:

T « Mi*MC + Ii (Equation U)

where Mj is the slope of the ideal line and I; is the intercept of the ideal line.

However, each temperature sensor typically deviates somewhat in slope and

intercept from an ideal line. To estimate this deviation, each sensor is calibrated by

subjecting it to known temperature references, such as ice or ice water and boiling water,

and its output at those reference temperatures is read. Other temperature references, such

as specific temperatures from a calibration oven or the like can be used to calibrate

sensors in their expected operating temperature range.

The equation of a line is then determined from the output data and compared to

the ideal line of the perfectly accurate ideal sensor. The difference in slopes provides a

first calibration constant, Ci , for the particular sensor that will later, during actual sensor

operation, be applied to the ideal line equation as a slope offset. The method used to

determine the slope offset, Ci, is set forth below:

C] = Mj-M (Equation ITl)

The difference in intercepts provides a second calibration, C , constant for the particular sensor that will later, during actual sensor operation, be applied to the ideal line equation as an intercept offset. The method used to determine the intercept offset, C₂, is set forth below:

C₂ = Ii-I (Equation IY)

Therefore, to obtain a more accurate temperature reading from the particular

sensor, Equation TJ above is modified below as follows:

T_COTT = (Mj+Ci)*MC + ( +C₂) (Equation V)

where T_corr is the corrected temperature reading obtained by applying calibration

constants C_\ and C₂ to the measured characteristic outputted by the sensor.

By storing slope and intercept offset calibration constants on a calibration module

160, the temperature actually measured by each sensor 78, 80, 82, 84, 86, 88, 90 and 92

of a particular sensor refiner disk segment can be corrected to provide an absolute

temperature value that is accurate to at least within about ± 2.5° F (± 1.5° C). Where the

temperature sensing element is an RTD, preferably a platinum RTD, and calibration is

done with ice or ice water and boiling water, the temperature measured by each sensor 78,

80, 82, 84, 86, 88, 90 and 92 can be corrected using such calibration constants to

advantageously provide an absolute temperature that is highly repeatable and accurate to

at least within about ± 0.5° F (± 0.3°C). Where the temperature sensing element is an

RTD, preferably a platinum RTD, and calibration is done using a calibration oven over a

temperature range anywhere in between about 212° F (100° C) to about 392° F (200° C),

the temperature measured by each sensor 78, 80, 82, 84, 86, 88, 90 and 92 can be corrected using such calibration constants to advantageously provide an absolute

temperature that is highly repeatable and accurate to at least within about ± 0.18° F (±

0.1° C). As a result of using multiple temperature sensors that sense temperature in the refining zone generally along the radius of the disk or disk segment, a profile of the

temperature throughout the refining zone can advantageously be obtained and graphically

be depicted on a computer display in real time.

FIG. 14 depicts a refiner monitoring and control system 204. The system 204

includes a pair of sensor refiner disk segments 32 (bars and grooves not shown in FIG. 14

for clarity) each installed in a separate refiner 30a and 30b. Each segment 32 has a

plurality of sensors 78, 80, 82, 84, 86, 88, 90 and 92 embedded in its refining surface. The

sensors 78, 80, 82, 84, 86, 88, 90 and 92 are each connected by wiring 126 to a signal

conditioner 206. The signal conditioner 206, in turn, is connected by a link 208 that can

be a wire, such as is depicted, but can also be a wireless link, such as can be achieved

using telemetry or the like.

As is shown in FIG. 1, the signal conditioner 206 preferably is mounted to the

housing 34 of the refiner 30 and can be a commercially available signal conditioner that

outputs an electrical current signal for each sensor that varies between four and twenty milliamps, depending on the magnitude of the measured characteristic outputted by the

sensor. Where one or more sensors on board the sensor refiner disk segment 32 is a

platinum RTD temperature, a signal conditioner 206 is used. Depending on the

construction of the signal conditioner 206, more than one sensor can be connected to it.

In assembly, sensor-receiving bores 96, 98, 100, 102, 104, 106, 108 and 110 are formed in a refiner disk segment. Where the segment is an already formed conventional refiner disk segment, the bores 96, 98, 100, 102, 104, 106, 108 and 110 are formed using

a metal removal process, preferably an EDM machining process, that converts the conventional disk segment into a sensor refiner disk 32.

Sensors 78, 80, 82, 84, 86, 88, 90 and 92 for the sensor disk segment 32 are then

selected. Where it is needed to assemble sensors before inserting them into the bores 96,

98, 100, 102, 104, 106, 108 and 110 of the segment 32, preassembly of the sensors is

performed. At least where temperature sensors are used, the sensing element 142 of each

sensor is disposed inside a housing 140 and attached to the housing 140, preferably using

an adhesive. Each sensor or housing 140 of each sensor is inserted at least partially into

and attached to a spacer 114, such as by using an adhesive. Where a manifold-like fixture

is used, such as fixture 116, the sensors and spacers can be assembled to the fixture

before calibrating the sensors.

The selected sensors 78, 80, 82, 84, 86, 88, 90 and 92 are each calibrated to obtain

at least one calibration constant for each sensor. Where one or more of the sensors 78, 80,

82, 84, 86, 88, 90 and 92 comprise temperature sensors, a slope offset calibration

constant, C_\, and an intercept offset calibration constant, C , preferably are determined by

calibration and stored for each such sensor. While each of the sensors 78, 80, 82, 84, 86,

88, 90 and 92 can be calibrated after being assembled to the sensor disk segment 32, each

sensor 78, 80, 82, 84, 86, 88, 90 and 92 preferably is calibrated before being assembled to

the disk segment 32. The calibration constants for the selected group of sensors 78, 80,

82, 84, 86, 88, 90 and 92 are stored on a calibration module 160. At least one calibration constant preferably is stored for each sensor.

The calibration module 160 and the assembled sensor refiner disk segment 32 are

preferably put in the same package, such as a box (not shown), and shipped together to a fiber processing plant equipped with a sensor coπection system 162. The sensor refiner

disk segment 32 is removed from its package, assembled to a refiner 32, and the sensor

wiring 126 is connected to a signal conditioner 206, if one is used. The module 160 is

removed from the same package and plugged into a port, such as port 180, of a connector

box 176 or the processing device 164.

The port 180 preferably is the port associated with the particular refiner 30 into

which the sensor disk segment 32 has been installed. In this manner, it is assured that the

right calibration data for the sensors 78, 80, 82, 84, 86, 88, 90 and 92 of a particular

sensor disk segment 32 is read from the right calibration module 160. In another method

of making sure that the proper calibration data is applied to the sensors 78, 80, 82, 84, 86,

88, 90 and 92 of a particular sensor disk segment 32, any port into which the module 160

is plugged can be assigned to a particular sensor disk segment 32 of a particular refiner

30. For example, each calibration module 160 preferably can be configured with its own

unique memory address that can be selected using software, such as control software or another type software that processes sensor measurements, to read the calibration data

from a specific module 160.

When the sensor disk segment 32 becomes worn or is scheduled for replacement,

it is removed from the refiner 30, and its associated calibration module 160 is also unplugged and removed. Thereafter, a new sensor disk segment 32 is installed along with the calibration module 160 that was shipped with it. If desired, the sensors 78, 80, 82, 84,

86, 88, 90 and 92 of the spent segment 32 can be removed and reused along with its

associated calibration module 160. In operation, the sensors 78, 80, 82, 84, 86, 88, 90 and 92 of the sensor disk

segment 32 of each refiner 30a and 30b sense a particular parameter in their respective

refining zone during refiner operation. Referring to sensor disk segment 32 of refiner 30a,

each sensor 78, 80, 82, 84, 86, 88, 90 and 92 is read by processing device 164 and the

calibration constants for each sensor 78, 80, 82, 84, 86, 88, 90 and 92 from the module

160a is applied to the data read from the respective sensor. Likewise, each sensor 78, 80,

82, 84, 86, 88, 90 and 92 of the sensor disk segment 32 of refiner 30a is read by

processing device 164 and the calibration constants for each sensor 78, 80, 82, 84, 86, 88,

90 and 92 from the module 160b is applied to the data read from the respective sensor.

The calibration constants are read from each module before being used to correct

sensor data. If desired, the calibration constants can be read at the startup of the

processing device 164.

Where a temperature sensor is read and it is desired to obtain an absolute temperature measurement, at least one calibration constant is applied to the data read.

Where more precise absolute temperature measurement is desired, two calibration

constants are applied to the data read, preferably using Equation V above. If desired,

multiple temperatures obtained from more than one temperature sensor of a single sensor

disk segment 32 can be averaged to obtain an average temperature measurement in the refining zone. Preferably, the sensors 78, 80, 82, 84, 88, 90 and 92 of each sensor disk segment 32 are read in sequence by the processing device 164.

The sensor data read preferably is used to monitor and control operation of each

refiner connected to processing device 164 or another processing device that communicates with processing device 164. For example, temperature sensed in the

refining zone can be used to control one or more aspects of refiner operation, such as the

mass flow rate of stock entering the refiner 30. Pressure sensed in the refining zone can

also be used to control one or more aspects of refiner operation, such as the mass flow

rate of stock entering the refiner 30, the plate pressure, refiner gap, or another parameter.

It is also to be understood that, although the foregoing description and drawings

describe and illustrate in detail one or more preferred embodiments of the present

invention, to those skilled in the art to which the present invention relates, the present

disclosure will suggest many modifications and constructions as well as widely differing

embodiments and applications without thereby departing from the spirit and scope of the

invention. The present invention, therefore, is intended to be limited only by the scope of

the appended claims.

Claims (58)

CLAIMSWhat is claimed is:

1. A rotary disk refiner for refining fibrous pulp in a liquid stock comprising:

a housing having a stock inlet;

a rotor within the housing that rotates about an axis of rotation during operation;

a refiner disk mounting surface within the housing that opposes the rotor;

a first refiner disk carried by the rotor, the first refiner disk comprised of a

plurality of pairs of upraised bars that define grooves therebetween that collectively

form a first refining surface; a second refiner disk carried by the refiner disk mounting surface, the second

refiner disk comprised of a plurality of pairs of upraised refiner bars that define refiner

grooves therebetween that collectively form a second refining surface, wherein the second refiner disk opposes and is spaced from the first refiner disk, and wherein a

refining zone is defined between the opposed refining surfaces of the first and second

refiner disks; and

a sensor disposed in the refining surface of one of the first and second refiner

disks that is exposed to the refining zone and that senses a characteristic of conditions in the refining zone.

2. The rotary disk refiner of claim 1 further comprising a spacer disposed between

the sensor and the refiner disk in which the sensor is disposed.

3. The rotary disk refiner of claim 2 wherein the sensor comprises a pressure

sensor.

4. The rotary disk refiner of claim 2 wherein the spacer has a tubular shape and is

comprised of a thermally insulating material that thermally insulates the sensor from the

thermal mass of the refiner disk in which the sensor is disposed.

5. The rotary disk refiner of claim 4 wherein the spacer is comprised of a ceramic

insulating material having a sidewall thickness of at least 1/32 of an inch (0.8 mm) to sufficiently thermally isolate the sensor from the thermal mass of the refiner disk in

which the sensor is disposed to prevent the thermal mass of the refiner disk from

interfering with sensing of the characteristic of conditions in the refining zone.

6. The rotary disk refiner of claim 5 wherein the sensor comprises a temperature

sensor.

7. The rotary disk refiner of claim 2 wherein the sensor has a sensing element that

is disposed between the spacer and the refining zone.

8. The rotary disk refiner of claim 7 wherein the spacer is disposed in a bore in the refining surface.

9. The rotary disk refiner of claim 8 further comprising two pairs of the sensors

and spacers with one of the spacers carrying one of the sensors and disposed in a first

bore in the refiner disk refining surface and the other of the spacers carrying the other

of the sensors and disposed in a second bore in the refiner disk refining surface.

10. The rotary disk refiner of claim 8 further comprising at least three pairs of the

sensors and spacers with a first one of the spacers carrying a first one of the sensors and disposed in a first bore in the refiner disk refining surface, a second one of the

spacers carrying a second one of the sensors and disposed in a second bore in the

refiner disk refining surface, and a third one of the spacers carrying a third one of the

sensors and disposed in a third bore in the refiner disk refining surface, wherein the first bore, the second bore, and the third bore are radially spaced apart.

11. The rotary disk refiner of claim 10 wherein the first bore, the second bore and

the third bore are disposed along a generally radially extending line.

12. The rotary disk refiner of claim 7 wherein the spacer is tubular and disposed in

a bore in the refiner disk refining surface and the sensor comprises a sensor housing that is partially telescopically received in the spacer.

13. The rotary disk refiner of claim 12 wherein the spacer is attached to the refiner

disk by a first bond and the sensor housing is attached to the spacer by a second bond.

14. The rotary disk refiner of claim 12 wherein the sensor housing encloses the

sensing element, the sensing element is attached to the sensor housing by a bond, and

the sensor housing is in contact with the liquid stock during refining.

15. The rotary disk refiner of claim 7 wherein (a) each refiner groove has a bottom

axial surface and each refiner bar has an axial outer refining surface that is located a

height above the bottom surface of an adjacent refiner groove, and (b) the sensor has an outer tip that is disposed between the axial outer refining surface of an adjacent one of

refiner bars and the bottom axial surface of an adjacent one of the refiner grooves.

16. The rotary disk refiner of claim 15 wherein the spacer carries the sensor and is

at least partially embedded in one of the refiner bars.

17. The rotary disk refiner of claim 16 wherein the spacer is completely embedded

in the one of the refiner bars.

18. The rotary disk refiner of claim 15 wherein the spacer carries the sensor and

both the spacer and sensor are disposed in one of the refiner grooves.

19. The rotary disk refiner of claim 18 wherein the spacer and sensor form a dam in

the one of the refiner grooves that obstructs the radial outward flow of stock in the one

of the refiner grooves.

20. The rotary disk refiner of claim 1 wherein there are a plurality of the sensors

that are spaced apart and each of the sensors is embedded in the refining surface of the refiner disk in which it is disposed.

21. The rotary disk refiner of claim 20 wherein each refiner groove has a bottom

surface, each refiner bar has an axial outer surface, each of the sensors has a tip and the tip of each of the sensors is disposed flush with or below the axial outer surface of an

adjacent one of the refiner bars.

22. The rotary disk refiner of claim 21 wherein the tip of each of the sensors is disposed between the axial outer surface of an adjacent one of the refiner bars and the bottom surface of an adjacent one of the refiner grooves.

23. The rotary disk refiner of claim 22 wherein the sensor comprises a sensor

housing having the tip and a sensing element located inside the sensor housing that is

disposed between the tip and the spacer.

24. The rotary disk refiner of claim 23 wherein the sensor housing contacts stock

from the refining zone during operation of the rotary disk refiner.

25. The rotary disk refiner of claim 23 wherein (a) the spacer has an axial end

disposed between the axial outer surface of the adjacent one of the refiner bars and the

bottom surface of the adjacent one of the refiner grooves, (b) the sensing element has

an axial end disposed between the axial outer surface of the adjacent one of the refiner

bars and the bottom surface of the adjacent one of the refiner grooves, and (c) the axial

end of the sensing element is disposed between the axial end of the spacer and the axial outer surface of the adjacent one of the refiner bars.

26. The rotary disk refiner of claim 1 wherein the first and second refiner disks are

each comprised of a plurality of disk segments, wherein the sensor is disposed in one of

the segments of the refiner disk in which the sensor is disposed, and further comprising a tubular spacer disposed in a bore in the refining surface of the disk segment in which

the sensor is disposed, and wherein the spacer telescopingly receives the sensor with

part of the sensor protruding from the spacer.

27. The rotary disk refiner of claim 1 wherein (a) each refiner groove has a bottom

axial surface and each refiner bar has an axial outer refining surface that is located a

height above the bottom surface of an adjacent refiner groove, (b) the sensor has a tip

that is disposed between the axial outer refining surface of an adjacent one of refiner

bars and the bottom axial surface of an adjacent one of the refiner grooves, and (c) the

tip of the sensor is disposed at least 0.050 inch (1.27 mm) below the axial outer surface

of the adjacent refiner groove so that the tip of the sensor remains flush with or below

the axial surface of the adjacent one of the refiner bars when the adjacent one of refiner

bars wears as a result of refiner operation.

28. The rotary disk refiner of claim 27 wherein the sensor further comprises a spacer, a sensor housing that extends outwardly from the spacer, and a sensing element

carried by the sensor housing, wherein the spacer is embedded in the refiner disk and

disposed between the sensing element and the refiner disk.

29. A rotary disk refiner for refining fibrous pulp in a liquid stock comprising:

a housing having a stock inlet; a rotor within the housing that rotates about an axis of rotation during operation;

a refiner disk mounting surface within the housing that opposes the rotor; a first refiner disk carried by the rotor, the first refiner disk comprised of a plurality of refiner disk segments that each have plurality of pairs of upraised refiner

bars that define refiner grooves therebetween that collectively form a first refining

surface;

a second refiner disk carried by the refiner disk mounting surface, the second

refiner disk comprised of a plurality of refiner disk segment that each have a plurality

of pairs of upraised refiner bars that define refiner grooves therebetween that

collectively form a second refining surface, wherein the second refiner disk opposes

and is spaced from the first refiner disk, and wherein a refining zone is defined between

the opposed refining surfaces of the first and second refining disks, wherein an elongate pocket is in the refining surface of one of the refiner disk segments of one of the first

and second refiner disks;

a plate disposed in the elongate pocket; and a sensor and a spacer embedded in the plate with the sensor being carried by the

spacer and spaced from bar by the spacer.

30. The rotary disk refiner of claim 29 wherein the sensor comprises a sensor

housing that extends from the spacer and a sensing element carried by the sensor

housing.

31. The rotary disk refiner of claim 30 wherein (a) the sensing element is a temperature sensing element, (b) the sensor housing and spacer completely encloses the temperature sensing element and prevents stock in the refining zone from directly

contacting the temperature sensing element, (c) the spacer comprises an insulating

spacer that thermally insulates the temperature sensing element from the thermal mass

of the refiner disk segment in which the plate is disposed, and (d) the sensor housing

contacts the stock during refiner operation.

32. A rotary disk refiner for refining fibrous pulp in a liquid stock comprising:

a housing having a stock inlet;

a rotor within the housing that rotates about an axis of rotation during operation;

a refiner disk mounting surface within the housing that opposes the rotor; a first refiner disk carried by the rotor, the first refiner disk comprised of a

plurality of refiner disk segments that each have plurality of pairs of upraised refiner

bars that define refiner grooves therebetween that collectively form a first refining

surface;

a second refiner disk carried by the refiner disk mounting surface, the second

refiner disk comprised of a plurality of refiner disk segment that each have a plurality

of pairs of upraised refiner bars that define refiner grooves therebetween that

collectively form a second refining surface, wherein the second refiner disk opposes and is spaced from the first refiner disk, and wherein a refining zone is defined between

the opposed refining surfaces of the first and second refining disks; and a sensor embedded in the refining surface of one of the refiner disk segments of one of the first and second refining disks, the sensor being exposed to the refining zone

such that the sensor comes into contact with stock during operation, and the sensor

sensing a characteristic of conditions in the refining zone.

33. The rotary disk refiner of claim 32 wherein the sensor further comprises an

insulating spacer embedded in the refining surface of the one of the refiner disk

segments, a sensor housing extending outwardly from the insulating spacer, and a

sensing element that is carried by the sensor housing.

34. The rotary disk refiner of claim 33 wherein (a) the sensing element comprises a

temperature sensor, (b) the characteristic sensed is temperature in the refining zone

adjacent the sensor, and (c) the housing and insulating spacer completely enclose the

sensing element such that it does not come into contact with the stock during disk refiner operation.

35. A rotary disk refiner for refining fibrous pulp in a liquid stock comprising:

a housing having a stock inlet; a rotor within the housing that rotates about an axis of rotation during operation;

a refiner disk mounting surface within the housing that opposes the rotor;

a first refiner disk carried by the rotor, the first refiner disk comprised of a

plurality of refiner disk segments that each have plurality of pairs of upraised refiner bars that define refiner grooves therebetween that collectively form a first refining surface;

a second refiner disk carried by the refiner disk mounting surface, the second

refiner disk comprised of a plurality of refiner disk segment that each have a plurality

of pairs of upraised refiner bars that define refiner grooves therebetween that

collectively form a second refining surface, wherein the second refiner disk opposes

and is spaced from the first refiner disk, and wherein a refining zone is defined between

the opposed refining surfaces of the first and second refiner disks;

a thermally insulating spacer embedded in the refining surface of one of the

refiner disk segments of one the first and second refining disks; a sensor housing extending from the thermally insulating spacer; a temperature-sensing element carried by the sensor housing;

wherein the sensor housing contacts stock during refiner operation and the

thermally insulating spacer thermally insulates the sensing element from the thermal

mass of the refiner disk segment in which the insulating spacer is embedded.

36. The rotary disk refiner of claim 35 wherein (a) the sensor housing is comprised

of a thermally conductive material, (b) the temperature sensing element is disposed inside the sensor housing, and (c) the sensor housing and the thermally insulating spacer enclose the temperature sensing element.

37. A refiner disk for a rotary disk refiner comprising a refining surface comprised

of a plurality of spaced apart and upraised refiner bars that define therebetween refiner

grooves and a sensor disposed in the refining surface.

38. The refiner disk of claim 37 wherein the sensor is at least partially disposed in

one of the refiner bars.

39. The refiner disk of claim 37 wherein the sensor is disposed in one of the refiner

grooves.

40. The refiner disk of claim 37 wherein the refining surface surrounds the entire

periphery of the sensor.

41. The refiner disk of claim 40 further comprising a spacer disposed between the

refiner disk and the sensor.

42. The refiner disk of claim 41 wherein the spacer is disposed in a bore in the

refining surface.

43. The refiner disk of claim 42 wherein the spacer is tubular and the sensor is

partially telescopically received in the spacer.

44. The refiner disk of claim 43 wherein the sensor comprises a temperature sensor

and the spacer comprises an insulating spacer.

45. The refiner disk of claim 37 wherein the sensor has a tip that does not extend

above any of the refiner bars.

46. The refiner disk of claim 45 wherein the sensor is imbedded in the refining

surface.

47. The refiner disk of claim 46 comprising a plurality of the sensors that are

radially spaced apart and each carried by a spacer that is disposed between the refiner

disk and the sensor.

48. A refiner disk segment for a rotary disk refiner comprising a refining surface

comprised of a plurality of spaced apart and upraised refiner bars that define

therebetween refiner grooves and a sensor disposed in the refining surface.

49. The refiner disk segment of claim 48 wherein the sensor is at least partially disposed in one of the refiner bars.

50. The refiner disk segment of claim 48 wherein the sensor is disposed in one of

the refiner grooves.

51. The refiner disk of claim 48 wherein the refining surface surrounds the entire

periphery of the sensor.

52. The refiner disk of claim 51 further comprising a spacer disposed between the

refiner disk and the sensor.

53. The refiner disk of claim 51 wherein the spacer is disposed in a bore in the

refining surface.

54. The refiner disk of claim 53 wherein the spacer is tubular and the sensor is

partially telescopically received in the spacer.

55. The refiner disk of claim 54 wherein the sensor comprises a temperature sensor

and the spacer comprises an insulating spacer.

56. The refiner disk of claim 48 wherein the sensor has a tip that does not extend

above any of the refiner bars.

57. The refmer disk of claim 56 wherein the sensor is imbedded in the refining

surface.

58. The refmer disk of claim 57 comprising a plurality of the sensors that are

radially spaced apart and each carried by a spacer that is disposed between the refiner

disk and the sensor.