Patent Description:
Nipped rolls are used in a vast number of continuous process industries including, for example, papermaking, steel making, plastics calendaring and printing. In the process of papermaking, many stages are required to transform headbox stock into paper. The initial stage is the deposition of the headbox stock, commonly referred to as "white water," onto a paper machine forming fabric, commonly referred to as a "wire. " Upon deposition, a portion of the white water flows through the interstices of the forming fabric wire leaving a mixture of liquid and fiber thereon. This mixture, referred to in the industry as a "web," can be treated by equipment which further reduce the amount of moisture content of the finished product. The fabric wire continuously supports the fibrous web and transfers it to another fabric called a felt which advances it through the various dewatering equipment that effectively removes the desired amount of liquid from the web. Water from the web is pressed into the wet felt and then can be removed as the wet felt passes a suction box. Dry felts can also be used to support the fibrous web through steam dryers.

One of the stages of dewatering is effected by passing the web through a pair or more of rotating rolls which form a nip press or series thereof, during which liquid is expelled from the web via the pressure being applied by the rotating rolls. The rolls, in exerting force on the web and felt, will cause some liquid to be pressed from the fibrous web into the felt. The web can then be advanced to other presses or dry equipment which further reduce the amount of moisture in the web. The "nip region" is the contact region between two adjacent rolls through which the paper web passes.

The condition of the various wires and felts can cause variations in the amount of liquid and other materials that are removed from the web which can, in turn, alter an amount of nip pressure applied to the web in a nip region. Other components in the papermaking process such as size application stations, coating stations, doctor blades, and oscillating showers can also affect the characteristics of the web. Even nip pressure axially along the roll is beneficial in papermaking and contributes to moisture content, caliper, sheet strength and surface appearance. For example, a lack of uniformity in the nip pressure can often result in paper of poor quality. Thus, there remains a need to monitor various components of the papermaking process and account for their potential effect on nip pressure at one or more nip regions.

<CIT> discloses a system associated with a sensing roll for collecting roll data comprising:a plurality of sensors located at axially spaced-apart locations of the sensing roll, wherein each sensor enters a region of a first nip between the sensing roll and a rotating component during each rotation of the sensing roll;an application station, comprising a rotatable applicator rod forming a second nip with the sensing roll, wherein each sensor enters a region of the second nip between the sensing roll and the applicator rod during each rotation of the sensing roll;each sensor generates a respective sensor signal upon entering a region of the second nip.

In accordance with one aspect of the present invention a system according to claim <NUM> is disclosed. The system also includes an application station, comprising a rotating applicator rod with an axis of rotation substantially parallel to that of the sensing roll and forming a second nip with the sensing roll, wherein each sensor enters a region of the second nip between the sensing roll and the applicator rod during each rotation of the sensing roll Further, each sensor generates a respective sensor signal upon entering a region of the second nip and the system includes structure for generating a periodically occurring starting reference associated with each rotation of the applicator rod. A processor receives the periodically occurring starting reference and the respective sensor signal generated by each sensor as it moves through the second nip and, upon receiving the respective sensor signal, the processor operates to a) determine a particular one of the plurality of sensors which generated the respective sensor signal, b) based upon a value occurring between when the respective sensor signal was generated and a most recent starting reference, identify one of a plurality of tracking segments, wherein each of the plurality of tracking segments is, respectively, associated with a different value, and c) store the respective sensor signal to associate the respective sensor signal with the identified one tracking segment.

The purpose of the applicator rod is to provide an even coating in the cross direction to an applicator roll, which may comprise the sensing roll, for transfer to a web when pressed in the first nip. Both grooved and smooth rods are at times used depending upon the viscosity of the coating and the end product. Grooved rods have alternating ridges and valleys in which an outer surface of each ridge comes in contact with the applicator roll in order to meter the correct amount of coating through open areas, or valleys, between the applicator roll and the applicator rod. The pressure of a grooved rod therefore may be directly measured by the sensing roll, when defining the applicator roll, from this contact In some instance there may be a thin film, or coating, that is present between one or more of the ridges and the applicator roll; however the sensed pressure may be considered as a directly measured pressure of the applicator rod. The smooth rod may also have a pressure applied in a direction toward the sensing roll; however, there should always be a layer of coating between a smooth rod and the applicator roll. Hence, the sensing roll can only detect the hydraulic force transmitting through the coating from the smooth rod. The rods are held along their cross-direction (CD) axis by a number of holders which are adjusted to keep pressure across the CD for both the grooved rods and the smooth rods.

Typically grooved rods are used with starch applications and the equipment is referred to as a Size Press, or press rod. Smooth rods are commonly used for coating and the equipment is referred to as a rod coater or coating rod. Both types of rods may rotate with a surface velocity different than that of the applicator roll.

In accordance with one aspect of the present invention the rotating component comprises a mating roll, a web of material travels through the first nip from an upstream direction to a downstream direction, and each sensor generates a respective sensor signal upon entering a region of the first nip. In accordance with a different aspect, each sensor generates a respective sensor signal upon entering a region of the second nip.

In accordance with related aspects of the invention each of the respective sensor signals comprises a pressure value. In accordance with other aspects of the invention the applicator rod comprises a size press rod or a coating rod.

In a related aspect of the present invention the processor receives the respective sensor signal for each of the plurality of sensors during each rotation of the sensing roll, and a plurality of the respective sensor signals occur during a plurality of rotations of the sensing roll. For each one of the plurality of the respective sensor signals, the processor identifies an associated applicator rod axial segment and its determined one tracking segment.

In yet another related aspect, the applicator rod comprises n axial segments, having respective index values: <NUM>, <NUM>,. , n; the applicator rod period comprises m tracking segments, having respective index values: <NUM>, <NUM>,. , m, such that there are (n times m) unique permutations that are identifiable by a two-element set comprising a respective axial segment index value and a respective tracking segment index value. A respective average pressure value can be associated with each of the (n times m) unique permutations, each of the respective average pressure values based on previously collected pressure readings related to the second nip.

In another related aspect of the present invention, the plurality of tracking segments associated with the applicator rod comprise one of a) a plurality of circumferential segments on the applicator rod or b) a plurality of time segments of a period of the applicator rod.

In accordance with another aspect of the invention, a method according to claim <NUM> is disclosed. The method associated with a sensing
roll for collecting roll data. includes providing a plurality of sensors located at axially spaced-apart locations of the sensing roll, wherein each sensor enters a region of a first nip between the sensing roll and a rotating component during each rotation of the sensing roll. The method also includes providing an application station, having a rotating applicator rod with an axis of rotation substantially parallel to that of the sensing roll and forming a second nip with the sensing roll such that each sensor enters a region of the second nip during each rotation of the sensing roll; wherein each sensor generates a respective sensor signal upon entering a region of the second nip. The method also includes generating a periodically occurring starting reference associated with each rotation of the applicator rod; and receiving the periodically occurring starting reference and the respective sensor signal generated by each sensor. Upon receiving the respective sensor signal: a) a particular one of the plurality of sensors which generated the respective sensor signal is determined, b) based upon a value occurring between when the respective sensor signal was generated and a most recent starting reference, one of a plurality of tracking segments is identified, wherein each of the plurality of tracking segments is, respectively, associated with a different value, and c) the respective sensor signal is stored to associate the respective sensor signal with the identified one tracking segment.

While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the present invention will be better understood from the following description in conjunction with the accompanying Drawing Figures, in which like reference numerals identify like elements.

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, and not by way of limitation, specific preferred embodiments in which the invention may be practiced.

As illustrated in <FIG>, a sensing roll <NUM> and a mating roll <NUM> define a nip <NUM> receiving a fibrous web <NUM>, such as a paper web, to apply pressure to the web <NUM>. It is contemplated that, in some cases, a continuous band felt may support the web such that the felt and the web enter the nip <NUM>. The sensing roll <NUM> comprises an inner base roll <NUM> and an outer roll cover <NUM>. As shown in <FIG>, a set <NUM> of sensors <NUM> is disposed at least partially in the roll cover <NUM>. The set <NUM> of sensors <NUM> may be disposed along a line that spirals around the entire length of the roll <NUM> in a single revolution to define a helical pattern, which is a common sensor geometry arrangement for roll covers. However, the helical pattern is merely an example and any arrangement is contemplated in which at least one sensor is placed at each axial position, anywhere along the circumference, at which data is to be collected. Each sensor <NUM> can, for example, measure the pressure that is being exerted on the sensor when it enters a region of the nip <NUM> between the rolls <NUM> and <NUM>. In particular, the set <NUM> of sensors <NUM> may be positioned in the sensing roll <NUM>, for example, at different axial locations or segments along the sensing roll <NUM>, wherein the axial segments are preferably equally sized. In the illustrated embodiment, there are fourteen axial segments, labelled <NUM>-<NUM> in <FIG>, each having one sensor <NUM> located therein. It is also contemplated that the set <NUM> of sensors <NUM> may be linearly arranged so as to define a line of sensors, i.e., all sensors reside at the same circumferential location. One of ordinary skill will readily recognize that more than fourteen, or less than fourteen, axial segments may be provided as well along with a corresponding equal number of axially-spaced sensors located on the sensing roll. Also, in the description below, each sensor <NUM> may be referred to as a pressure sensor, for example, but other types of sensors can also be contemplated such as, for example, temperature sensors.

Because having even nip pressure is beneficial during paper manufacturing, correctly calculating and displaying the nip pressure profile are also beneficial since any corrections or adjustments to be made to the rotating rolls based on an inaccurate calculated nip pressure profile could certainly exacerbate any operational problems. There are three primary measurements of variability. The nip pressure profile has variability that can be termed cross-directional variability as it is the variability of average pressure per cross-direction position across the nip. Another type of variability represents the variability of the high speed measurements at each position in the single line of sensors. This variability represents the variability of other equipment in the paper making process including the rotational variability of the mating roll, i.e., the roll nipped to the sensing roll. The third variability in the nip profile includes the variability of multiple sensors, discussed below, at each cross-directional position of the roll. This variability represents the "rotational variability" of the sensing roll as it rotates through its plurality of sensing positions and cannot be detected unless a plurality of sensor are used per position.

One benefit of embedding a single set of sensors in covered rolls is to measure the real-time pressure profile and adjust loading pressures and roll crowns or roll curvature (using, for example, internal hydraulic cylinders) to achieve a flat pressure profile. As an alternative to a single set of sensors, two pluralities or arrays of sensors can be included on a sensing roll as described more fully in <CIT>, <CIT>. The sensing roll can, for example, be separated into <NUM> axial segments. First and second pluralities of sensors, respectfully, are disposed at least partially in the roll cover. Each of the first plurality of sensors is located in one of the <NUM> axial segments of the sensing roll. Likewise, each of the second plurality of sensors is located in one of the <NUM> axial segments of the sensing roll. Each sensor of the first plurality has a corresponding sensor from the second plurality located in a same axial segment of the sensing roll. The first plurality of sensors can be disposed along a line that spirals around the entire length of the roll in a single revolution to define a helical pattern. In a similar manner, the second plurality of sensors can be disposed along a line that spirals around the entire length of the roll in a single revolution to define a helical pattern. The first and second pluralities of sensors can be separated from one another by <NUM> degrees. Each sensor measures the pressure that is being exerted on the sensor when it enters a region of a nip. It is contemplated that the first and second pluralities of sensors may be linearly arranged so as to define first and second lines of sensors, which are spaced approximately <NUM> degrees apart. Various alternative configurations of a plurality of sensors are also contemplated. For example, a plurality of sensors could be helically arranged in a line that spirals, in two revolutions, around the entire length of roll.

Typically, the sensing roll <NUM> and the mating roll <NUM> are sized differently, i.e., they have a different size radially and circumferentially. Each roll may have variations in its size circumferentially across the axial dimension. Further, as the roll rotates, the distance from the central axis (radial dimension) to the outer surface may vary for each axial position at the same angle of rotation even were the circumferential dimensions to be the same for each axial position.

For example, rolls are periodically ground which results is small arbitrary changes in diameter from the manufacture's specification. There may also be slippage with one or more of the rolls resulting in the sensing roll surface traveling at a speed that is different than the mating roll surface. Consequently, it is rare that two rolls would have exactly the same period of rotation or have periods that are exact harmonics.

Thus, as the sensing roll <NUM> and mating roll <NUM> travel through multiple rotations relative to one another, a particular sensor <NUM> may not always enter the region of the nip <NUM> with the same circumferential portion of the mating roll <NUM> as it did in a previous rotation. This behavior can be utilized to create data maps corresponding to the surface of the mating roll <NUM>. Different average pressure matrices, each collected and built during different periods of time can be compared with one another to investigate how they vary from one another. Variability between the different data maps can indicate possible problems with the mating roll <NUM>, such as roll surface irregularities, bearing wear, and roll flexing. Variability analysis of the sensor data may also indicate possible problems with upstream or downstream processing equipment, e.g., upstream rolls, an upstream forming wire, an upstream felt, an upstream coating station or downstream rolls.

The sensing and mating rolls <NUM> and <NUM> may be each separated into <NUM> axial segments. All of the axial segments on the sensing roll <NUM> may or may not be of the same length, and all of the axial segments on the mating roll <NUM> also may or may not be of the same length. In the illustrated embodiment, it is presumed that all of the axial segments on the sensing roll <NUM> are of the same length and all of the axial segments on the mating roll <NUM> are of the same length. The axial segments on the sensing roll <NUM> may be aligned with the axial segments on the mating roll <NUM>. Furthermore, the mating roll <NUM> may be separated into individual circumferential segments such as, for example, <NUM> circumferential segments, all of substantially the same dimension.

<FIG> illustrates how rotation of the sensing roll <NUM> and the mating roll <NUM> can change a circumferential segment of the mating roll <NUM> that enters a nip region coincidentally with a sensor on each rotation of the sensing roll <NUM>. <FIG> is presented as series of position snapshots from <NUM> to <NUM> of the sensing roll <NUM> which also correspond to <NUM> rotations of the sensing roll <NUM> and <NUM> rotations of the mating roll <NUM>. The left-most portion of <FIG> shows a starting position (i.e., where a first sensor reading is collected) and the right-most portion represents a position of the two rolls <NUM> and <NUM> after <NUM> rotations of the sensing roll <NUM> after the first sensor reading was collected. At the starting position, circumferential segment #<NUM> of the mating roll <NUM> is positioned in the region of the nip <NUM> along with the sensor 26A. The mating roll <NUM>, in this example, is rotating slightly faster than the sensing roll <NUM> such that at a second position snapshot following a complete rotation from the starting position, the sensor 26A is once again positioned in the region of the nip <NUM> but the mating roll <NUM> has rotated so that circumferential segment #<NUM> is in the region of the nip <NUM>. The values of <FIG> are selected just as examples to illustrate with concrete numbers operating principles of the present invention. In accordance with the example values of <FIG>, when the sensing roll had completed <NUM> rotations, the mating roll <NUM> has completed <NUM> rotations. Thus, after <NUM> rotations from the starting position (i.e., position #<NUM> in <FIG>), the sensor 26A of the sensing roll <NUM> has been able to collect <NUM> sensor readings, presuming it collected a reading at the starting position and has "seen" all portions of the circumference of the mating roll. Therefore, <NUM> circumferential segments can be selected as an example number of circumferential segments. One of ordinary skill will recognize that the mating roll <NUM> could be broken into more circumferential segments but that it would take more than <NUM> rotations of the sensing roll <NUM> to collect data from sensor 26A that corresponds to each of the different circumferential segments.

It would be rare that the period of the mating roll would be an integer ratio of the period of the sensing roll. Hence, it is very unlikely a stationary pattern would be maintained between these rolls and this would tend to even out the sampling of the tracking segments.

Because the one sensor 26A enters the region of the nip <NUM> concurrently with different circumferential segments of the mating roll <NUM> in the illustrated embodiment, the nip pressure measured by the one sensor 26A may vary during sequential roll rotations due to the change in pressure caused by the mating roll <NUM>. Aspects of the present invention contemplate mapping readings, or signals, from each sensor <NUM> of the set <NUM> over time to see how the pressure readings, or signals, vary for each sensor due to each sensor entering the region of the nip <NUM> concurrently with different circumferential segments of the mating roll <NUM>. As noted above, the mapped data may be used to determine possible problems with the mating roll <NUM> and, as more fully described below, data collection can be performed involving possible problems related to upstream or downstream processing equipment other than the sensing roll <NUM> and the mating roll <NUM>.

Hence, the present invention contemplates using sensors <NUM> to measure for rotational variability that is generated by the high speed rotation of the mating roll <NUM> when pressure signals, or readings, from the sensors <NUM> are time synchronized to the mating roll position. In order to measure for rotational variability, the mating roll <NUM> must have some impact on the pressure in the nip <NUM> to be measured. The dominant impact on the sensed nip pressure will likely be that of the mating roll <NUM> which directly presses against the sensing roll <NUM>. However, it may be possible to synchronize sensor measurements with upstream rolls which form another nip and impact the water content and thickness of the web which affect the nip pressure seen by the sensing roll <NUM>. Furthermore, as rolls (not shown) in a downstream nip may pull the web and cause changes in web tension, it may be possible to also synchronize sensor measurements with these rolls. The sensing and mating rolls <NUM> and <NUM> will be used to illustrate the principles of this invention; however all principles are applicable to upstream and downstream processing equipment, such as upstream and downstream rolls, an upstream coating station, an upstream forming wire or an upstream felt. Continuing the example of <FIG>, the mating roll <NUM> may have rotational characteristics that generate, for example, a smusoidal pressure pattern which is about <NUM> kPa (<NUM> pounds per square inch, psi) peak-to-peak. In the illustrated example of <FIG> and <FIG>, to start, the pressure pattern is "<NUM>" when circumferential segment #<NUM> is in the region of the nip <NUM>. <FIG> and <FIG> are a table of how collecting <NUM> sensor readings from sensor 26A would be associated with the different circumferential segments of the mating roll <NUM>. The left column <NUM> is the sequential number assigned to the sensor reading and the middle column <NUM> represents a pressure reading value from sensor 26A according to the sinusoidal pattern described above. Each pressure reading value is time-synchronized with the period of rotation of the mating roll <NUM> by associating that value with one of the circumferential segments of the mating roll <NUM> that was in the region of the nip <NUM> when the pressure reading was sensed.

One convenient way to characterize the difference in periodicity is using units-of-measure that measure that difference in terms of time segments, e.g., <NUM> time segments in the illustrated embodiment. The length of each time segment is the mating roll period divided by the number of predefined time segments. As discussed below, the predefined number of time segments may correspond to a predefined number of mating roll circumferential segments. A period of the sensing roll <NUM> can be described as being x time segments smaller/larger than a period of the mating roll <NUM>. For example, according to <FIG>, the sensing roll <NUM> may have a period that is <NUM> mating roll time segment more than the period of the mating roll <NUM> (equivalently, the mating roll <NUM> can have a period that is <NUM> mating roll time segment smaller than the period of the sensing roll). In such an example, as the sensing roll <NUM> makes one complete revolution, the mating roll <NUM> will make more than a complete revolution by an amount equal to <NUM> mating roll time segment due to it having a smaller period than the sensing roll <NUM>.

As noted above, the <NUM> time segments of the mating roll period can correspond to <NUM> circumferential segments around the mating roll <NUM>. Thus, even though, at a conceptual level, it is the period of the mating roll <NUM> that is being separated into a plurality of time segments, that concept can correspond to a physical circumference of the mating roll <NUM>, wherein each individual time segment of the mating roll period also corresponds to a circumferential segment around the mating roll <NUM>. Accordingly, differences in rotational periods between the sensing roll <NUM> and the mating roll <NUM> measured in units of "time segments" can just as easily be considered in units of "circumferential segments. " In the description of at least some embodiments of the present invention below, reference to "circumferential segments" is provided as an aid in understanding aspects of an example embodiment of the present invention. However, one of ordinary skill will recognize that "time segments" and mating roll periodicity could be utilized as well without departing from the scope of the present invention. The "circumferential segments" and "time segments" can also be referred to generically as "tracking segments"; this latter term encompassing both types of segments associated with the mating roll <NUM> and other periodic components as described below.

As mentioned above, data similar to that of <FIG> and <FIG> is captured for each sensor <NUM> of the set <NUM>. Thus, as each sensor <NUM> arrives at the region of the nip <NUM> and senses a pressure reading, a particular mating roll outer surface portion at an axial location corresponding to that sensor and at one of the <NUM> circumferential segments of the mating roll <NUM> will also be in the nip <NUM>. Determining the mating roll segment that is in the nip <NUM> can be accomplished in a variety of different ways. One way involves indexing a particular one of the <NUM> mating roll segments with a trigger signal that is fired each time the mating roll <NUM> completes one revolution; a time period since the last trigger signal can be used to determine which of the <NUM> segments (measured relative to the indexed segment) is in the nip <NUM>. For example, if the time between each firing of the trigger signal is <NUM>, then each time segment is <NUM>, which corresponds to one of the <NUM> mating roll circumferential segments. A pressure signal generated by a sensor <NUM> in the nip region occurring at <NUM> after the trigger signal would be assigned to time segment <NUM> as three <NUM> segments will have passed, e.g., the nip region, from when the trigger signal is made to when the pressure signal is generated.

In <FIG>, a processor <NUM> can be present that can generate a real-time nip profile. In addition, the processor <NUM> can also receive a trigger signal <NUM> related to the rotation of the mating roll <NUM>. As just described, some circumferential segment or position <NUM> of the mating roll <NUM> can be indexed or encoded such that a signal generator <NUM> detects the encoded segment <NUM> and generates the trigger signal <NUM> each time the signal generator <NUM> determines that the segment <NUM> of the mating roll <NUM> completes another full rotation. When the mating roll <NUM> is rotated such that the circumferential position or segment <NUM> is aligned with a detector portion of the signal generator <NUM>, then the one of the <NUM> circumferential segments that happens to be positioned in the nip region can arbitrarily be labeled as the first circumferential segment such that the other circumferential segments can be numbered relative to this first segment. This particular rotational position of the mating roll <NUM> can be considered a reference position. As the mating roll <NUM> rotates, its rotational position will vary relative to that reference position and the amount of this variance determines which of the <NUM> circumferential segments will be positioned in the nip region. Accordingly, based on the rotational position of the mating roll <NUM> relative to that reference position a determination can be made as to which of the <NUM> circumferential segments is in the nip region when a particular sensor <NUM> generates a pressure signal. <FIG> illustrates the overall architecture of one particular system for monitoring paper production product quality. The system of <FIG> includes the processor <NUM>, noted above, which defines a measurement and control system that evaluates and analyzes operation of the roll <NUM>. The processor <NUM> comprises any device which receives input data, processes that data through computer instructions, and generates output data. Such a processor can be a hand-held device, laptop or notebook computer, desktop computer, microcomputer, digital signal processor (DSP), mainframe, server, other programmable computer devices, or any combination thereof. The processor <NUM> may also be implemented using programmable logic devices such as field programmable gate arrays (FPGAs) or, alternatively, realized as application specific integrated circuits (ASICs) or similar devices. The processor <NUM> may calculate and display the real-time average pressure profile calculated at the end of the prior collection session. For example, the pressure measurements from the sensors <NUM> can be sent to a wireless receiver <NUM> from transmitter(s) <NUM> located on the sensing roll <NUM>. The signals can then be communicated to the processor <NUM>. It is contemplated that the processor <NUM>, in addition to calculating a real-time average pressure profile, may use the real-time average pressure profile to automatically adjust crown and loading mechanisms to achieve a flat pressure profile. Crown and loading mechanisms may also be adjusted manually by an operator using information provided by the real-time average pressure profile.

There are other ways to determine the position of the mating roll <NUM>. One way is to use a high precision tachometer that divides the rotation of the roll <NUM> into a number of divisions, perhaps <NUM>. In this example, each time segment would be <NUM> positions on the high precision tachometer. All methods of determining the position of the mating roll are included in this invention.

In an example environment in which there are <NUM> axially arranged sensors <NUM>, each of which can be uniquely referred to using an axial segment index value that ranges from "<NUM>" to "<NUM>", and there are <NUM> circumferential segments on the mating roll <NUM> (or time segments), each of which can be uniquely referred to using a tracking segment index value ranging from "<NUM>" to "<NUM>", there are <NUM> (i.e., <NUM> x <NUM> = <NUM>) unique permutations of pairs consisting of a sensor number and a circumferential segment number (or time segment number), wherein each permutation is identifiable by a two-element set comprising a respective axial segment index value and a respective tracking segment index value. In the illustrated embodiment, the sensor numbers also correspond to the mating roll axial segments. Therefore the data collected can be considered a <NUM> x <NUM> matrix as depicted in <FIG>. Each row of <FIG> represents one of the <NUM> mating roll circumferential segments (or time segments) and each column represents one of the <NUM> axially arranged sensors <NUM> and, thus, each cell represents one of the possible <NUM> permutations. Each column also corresponds to a mating roll outer surface portion at an axial location aligned with and corresponding to the sensor <NUM> assigned that column. Each cell represents a combination of a sensor number (or axial segment number) and a particular mating roll circumferential segment (or time segment). For example, cell <NUM> represents a value that will relate to a pressure reading that occurred when sensor number <NUM> (number <NUM> of the <NUM>-<NUM> sensors defining the set <NUM>) entered the region of the nip <NUM> concurrently with a mating roll outer surface portion at an axial location corresponding to sensor number <NUM> and mating roll circumferential segment number <NUM> (or time segment number <NUM>). Thus, each cell of the matrix represents a unique permutation from among all the possible permutations of different axial segment numbers (e.g., <NUM>-<NUM>) and circumferential segment numbers (e.g., <NUM>-<NUM>) (or time segments <NUM>-<NUM>). A value stored in a particular matrix element is thereby associated with one particular permutation of possible axial segment numbers and circumferential segment numbers (or time segments).

The matrix of <FIG> can, for example, be a "counts" matrix wherein each cell represents the number of times a particular sensor and a particular mating roll outer surface portion at an axial location corresponding to that sensor and a particular mating roll circumferential segment were concurrently in the region of the nip <NUM> to acquire a pressure reading value. <FIG> illustrates a similarly sized matrix (i.e., <NUM> x <NUM>) but the values within the matrix cells are different from those of <FIG>. The cell <NUM> still represents a value that is related to sensor number <NUM> (or axial segment <NUM>, out of <NUM>-<NUM> axial segments, of the mating roll <NUM>) and circumferentia <NUM> segment <NUM> but, in this example, the value is a cumulative total of pressure readings, e.g. in kPa (1kPa = <NUM>,<NUM> pounds per square inch; psi), acquired by the sensor for that circumferential segment during plurality of rotations of the sensing roll <NUM>. Thus, each time sensor number <NUM> happens to enter the region of the nip <NUM> along with the mating roll circumferential segment number <NUM>, the acquired pressure reading value is summed with the contents already in the cell <NUM> Each of the <NUM> cells in this matrix of <FIG> is calculated in an analogous manner for their respective, associated sensors and segments.

From the matrices of <FIG> and <FIG>, an average pressure matrix depicted in <FIG> can be calculated. For example, cell <NUM> includes the number of pressure readings associated with sensor number <NUM> (or axial segment <NUM> of the mating roll <NUM>) and circumferential segment number <NUM> while cell <NUM> includes the total or summation of all those pressure readings. Thus, dividing cell <NUM> by cell <NUM> provides an average pressure value for that particular permutation of sensor number and mating roll circumferential segment number which entered the region of the nip <NUM> concurrently.

As a result, the matrix of <FIG> represents an average pressure value that is sensed for each particular sensor number and mating roll circumferential segment number. The length of time such data is collected determines how many different pressure readings are used in such calculations.

The data set out in <FIG> and <FIG> is simulated data.

The raw pressure readings, or pressure signals, from the sensors <NUM> can be affected by a variety of components in the system that move the web of material. In particular, the average values in the average pressure matrix of <FIG> are related to variability synchronized to the mating roll <NUM>. However, there may be other variability components that are not synchronized with the mating roll <NUM> such as variability in a cross direction (CD), shown in <FIG>. One measure of this CD variability is captured by calculating an average for each column of the average pressure matrix. Thus, the average pressure matrix of <FIG> can also include a row <NUM> that represents a column average value. Each of the <NUM> columns may have <NUM> cells that can be averaged together to calculate an average value for that column. For example, cell <NUM> would be the average value in the <NUM> cells of the second column of the average pressure matrix.

Individual collection sessions of pressure readings to fill the matrices of <FIG>, <FIG>, and <FIG> may be too short to build robust and complete matrices due to data buffer and battery life limitations of data acquisition systems in communication with the sensing roll <NUM>. In such cases, consecutive collection sessions can be combined by not zeroing the matrices (i.e., counts and summation matrices) upon starting a new collection session or combining the separate matrices collected in a post hoc fashion. Consequently, collections may be stopped and restarted without loss of data fidelity as long as the synchronization of the mating roll is maintained. In particular, combining multiple collection sessions that are separated by gaps in time can be beneficial to help populate the matrices. For example, if the period difference between the two rolls were closer to <NUM> instead of <NUM> time or circumferential segments, the collection would have a tendency to collect only evenly numbered time/circumferential segments in the short term (i.e., evenly numbered segments are those that are offset an even number of segments from a starting segment) until sufficient time has passed to move the collection into the odd numbered time/circumferential segments. Combining collection sessions separated by a long time delay may help to shift the collection so that data is more uniformly captured for all the different time/circumferential segments because there is no expectation that the period of the mating roll will be related to arbitrary time gaps between collection sessions.

The press of <FIG> can be located at a number of different positions within the chain or serial sequence of different components that are part of a modem paper processing operation. <FIG> illustrates an exemplary process and system configuration in accordance with the principles of the present invention in which each of the various circles represents a rotating component (e.g. a roll) that helps propel a web of material <NUM> through the process/system. The process starts at a headbox <NUM> where a fiber slurry is distributed over a wire mesh <NUM> which allows liquid to readily drain from the slurry. From the wire mesh <NUM>, the web of material <NUM> travels to a first wet felt station <NUM> having a felt <NUM> that helps dry the web of material <NUM>. The felt <NUM> is a continuous band arranged to travel in a loop pattern around a plurality of rolls <NUM>. In the example of <FIG>, there are four rolls <NUM>. The felt <NUM> enters a press area <NUM> between one of the rolls <NUM> and a sensing roll <NUM>. The sensing roll <NUM> may operate similar to the sensing roll <NUM> of <FIG>. Downstream from the wet felt station <NUM> is another wet felt station <NUM> having its own felt <NUM> traveling in a loop pattern around another set of four rolls <NUM>. There is also a second press region <NUM> having a press roll <NUM>, which, in the illustrated embodiment, is not a sensing roll. The last wet felt station <NUM> has a felt <NUM> traveling in a loop pattern around another set of four rolls <NUM>. The felt <NUM> is pressed by one of the rolls <NUM> and a second sensing roll <NUM> in a third press region <NUM>. The felts <NUM>, <NUM>, <NUM> are pressed into the web of material in their respective press regions <NUM>, <NUM>, <NUM> to absorb liquid from the web of material <NUM>. In this manner, the web of material <NUM> is drier after passing through the wet felt stations <NUM>, <NUM>, <NUM>. By "drier" it is meant that the fibers in the web of material <NUM> have a higher percentage by weight of fibers after the wet felt stations than before. Additional drying can be performed, however, by separate dryers <NUM> before the web of material <NUM> progresses further downstream in the process of <FIG>.

The process or system of <FIG> includes an application or coating station <NUM> where application material can be applied to one or both sides of the web of material <NUM>. In the illustrated example of <FIG>, the application station <NUM> affects both sides of the web of material <NUM>. On the left side, a first applicator roll <NUM> travels through a trough <NUM> which holds a first application material that adheres to a cover of the applicator roll <NUM>. The first applicator roll <NUM> and a first applicator rod <NUM> form a nip <NUM> that changes a thickness of the first application material that is on the cover of the applicator roll <NUM>. The first applicator roll <NUM> defines a nip <NUM> with a second applicator roll <NUM>. On the right side, the second applicator roll <NUM> travels through a trough <NUM> which holds a second application material (which may or may not be different than the first material in the trough <NUM>) that adheres to a cover of the second applicator roll <NUM>. The second roll <NUM> and a second applicator rod <NUM> form a nip <NUM> that changes a thickness of the second application material that is on the cover of the roll <NUM>. When the first and second application materials on the first and second rolls <NUM> and <NUM> enter the nip <NUM>, the first and second applicator rolls <NUM> and <NUM> press the first and second application materials into the web of material <NUM>. The first and second application materials may comprise a conventional liquid paper surface sizing composition. Also, one or both of the first and second application materials can comprise conventional coating compositions. Example application materials are disclosed in <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>.

The applicator rods <NUM>, <NUM> may be either size press rods or coating rods. A size press rod typically has spaced apart grooves with ridges between the grooves that touch the cover of the applicator roll into which the size press rod is pressed, with possibly a thin lubricating film between the ridges and the applicator roll. The grooves help distribute the application material (e.g., sizing composition) in a uniform manner across the cover of the roll. A coating rod typically will not contact the cover of the roll against which it is opposed; rather, the coating rod indirectly presses into the opposing roll by pressing onto the coating of application material that is on the cover of the roll. The coating rod helps to create a coating of application material on the roll that is of uniform thickness. As an example, a sizing composition can be applied to reduce the rate at which liquid will penetrate the ultimately produced paper product, see previously noted <CIT>. A coating, for example, can include material that will produce a change in the texture and/or color of a product on the side to which it is applied. One of ordinary skill will recognize that various sizing and coating materials can be applied to one or both sides of the web of material <NUM> without departing from the scope of the present invention. Furthermore, one of ordinary skill will recognize that there are a variety of different specific ways to adhere a sizing composition or a coating material to a cover of a roll before being metered by a press rod or coating rod. Embodiments of the present invention contemplate utilizing any of these techniques without departing from the scope of the present invention.

<FIG> illustrates details of an application station in accordance with the principles of the present invention. The left-side first applicator roll <NUM> is described by way of example but the same features can be attributed to the right-side second applicator roll <NUM> as well. In the discussion below of many of the various aspects of the present invention, only a single side of the application station <NUM> may be described but it is intended that the description be applicable to both sides of the station <NUM>.

The roll <NUM> rotates in a clockwise direction through a trough <NUM> of a first application material <NUM> that becomes a portion of first application material <NUM> that adheres to the first applicator roll <NUM> before encountering the first applicator rod <NUM>. The first applicator rod <NUM> (e.g., coating rod or sizing rod) in this example rotates in a clockwise direction and forms the nip <NUM> with the first applicator roll <NUM>. The first applicator rod <NUM> could also be configured to rotate in a counter-clockwise direction as well. As mentioned earlier, if the first applicator rod <NUM> is a size press rod, then it will have a grooved outer surface and have ridges that typically contact the outer surface of the first applicator roll <NUM>. If the first applicator rod <NUM> is a coating rod with a smooth surface, then it is typically rides on top of the coating material <NUM> a small distance from the outside surface of the first applicator roll <NUM> such that it does not directly contact the outside surface of the first applicator roll <NUM>. In the embodiment illustrated in <FIG>, the first applicator rod <NUM> is a coating rod. In this embodiment, the first applicator rod <NUM> helps to evenly distribute the material <NUM> in an axial direction and define with the first applicator roll <NUM> the nip <NUM> such that the first application material <NUM>, after passing through the nip <NUM>, has a substantially uniform thickness. The first applicator roll <NUM> continues to rotate so that the relatively uniform application material <NUM> enters the nip <NUM> defined between the first and second rolls <NUM> and <NUM>. The rolls <NUM> and <NUM> are configured as a press station such that the material <NUM> that enters the nip <NUM> is pressed into the web of material <NUM>. In <FIG>, the example application station <NUM> also includes a second applicator roll <NUM> that forms a nip <NUM> with a second applicator rod <NUM>. Thus, a portion <NUM> of a second application material <NUM> can adhere to the second applicator roll <NUM> and be uniformly distributed by the second applicator rod <NUM> into a uniform coating <NUM> of the second application material that enters a region of the nip <NUM> to be pressed into the web of material <NUM>.

The first applicator roll <NUM> can be a sensing roll similar to the sensing roll <NUM> described above. The applicator roll <NUM>, see <FIG>, may have <NUM> axially-spaced sensors 26B, for example, which correspond to <NUM> different axial segments <NUM> of the first applicator rod <NUM>. As such, a plurality of sensors 26B can be arranged around the outside surface of the sensing roll <NUM> as shown in <FIG> and <FIG> illustrate details about the application station <NUM> of <FIG>. In particular, <FIG> depicts the rolls <NUM> and <NUM> along with the first applicator rod <NUM> from an overhead perspective. A hypothetical cross-sectional view of the nip <NUM> is also included in <FIG> to show the presence of the first application material <NUM>, the web of material <NUM>, and the second application material <NUM>. In <FIG> and <FIG>, the first applicator rod <NUM> is, by way of example, illustrated as a coating rod because it has a smooth, continuous outer surface <NUM> and defines with the first applicator roll <NUM> the nip <NUM> extending along or substantially along the entire length of the sensing roll <NUM>. Because of the angle of view in <FIG>, it appears that the first applicator rod <NUM> and the first applicator roll <NUM> are in contact at the nip <NUM>, however, as is shown in <FIG>, there is a layer of first application material <NUM> between the rod <NUM> and roll <NUM>. In operation, pressure is applied (e.g., by a rod holder (not shown)) substantially uniformly along the length of the first applicator rod <NUM>. If the first applicator rod <NUM> were, for example, a size press rod, or metering rod, then the ridges of that press rod would be substantially in contact with the sensing roll <NUM> along the entire length of the nip <NUM> and each of the grooves would define a distance between the press rod and the sensing roll <NUM>. In either case, a surface of the first applicator rod <NUM> is beneficially a uniform distance from the outer surface of the first applicator (or sensing) roll <NUM> at the nip <NUM>. In the illustrated embodiment, the first applicator roll <NUM> may comprise <NUM> sensors 26B spaced an equal distance apart axially.

In the earlier description of the mating roll <NUM>, it was segmented into <NUM> axial segments to correspond to each of the sensors 26A of the sensing roll <NUM>. Similarly, as mentioned above, the first applicator rod <NUM> can be segmented into <NUM> axial segments <NUM> that each correspond to one of the sensors 26B on the first applicator roll <NUM>.

The first applicator rod <NUM>, which, in an illustrated embodiment, may have a diameter <NUM> of about <NUM> (<NUM>/<NUM> inches) as compared to a diameter of about <NUM> (<NUM> inches) for the applicator roll <NUM>. is typically driven by a first drive motor <NUM> on one end and a second drive motor <NUM> on another end that are synchronized to cause the first applicator rod <NUM> to uniformly rotate about its central axis and at a constant rotational speed. An application roll may typically rotate at about <NUM> rotations per second while an application rod may typically rotate at between about <NUM>-<NUM> rotations per minute. However, it is believed that unequal rotational forces imparted on the first applicator rod <NUM> by the drive motors may cause flexing and torsional responses that cause the distance from the surface of the first applicator rod <NUM>( e.g., the valleys, or grooves, of a press rod, or an outer surface ofa coating rod) to be non-uniform along the length of the nip <NUM>. Additionally, as sections of the first applicator rod <NUM> wear, some circumferential segments of the first applicator rod <NUM> can have different radial dimensions, as measured from the rod's central axis, when compared to other circumferential segments. As a result of these occurrences, the uniformity of the coating of material <NUM> may be imperfect and cause different amounts of material to be pressed into the web of material <NUM> thereby affecting the uniformity and quality of the ultimately produced paper product. Detecting operating conditions that may indicate that non-uniformity of the coating of material <NUM> is occurring may be beneficial in improving the operation of application stations such as station <NUM>.

For example, in axial locations of the nip <NUM> where the first applicator rod <NUM> may "lift" away from the first applicator roll <NUM>, resulting in more application material being present at corresponding axial locations or regions of the nip <NUM> than at other locations of the nip <NUM>, a lower pressure reading may result at those axial locations where the rod lifted away than if no "lifting" had occurred. Conversely, in axial locations of the nip <NUM> where more application material is present than at other nip locations, the extra material will result in a higher pressure reading than if no extra material had been present. If the presence of application material at an axial location of the nip <NUM> is considered to be indicative of the moisture content of the web of material at a corresponding region or portion of the web of material having a corresponding axial location, then a pressure reading sensed at the axial location of the nip <NUM> is correlated with the moisture content of the corresponding web of material portion having a corresponding axial and circumferential location. In other words, portions of the web of material <NUM> that have a higher moisture content will cause a higher pressure reading. However, with respect to pressure readings sensed at different locations of the nip <NUM>, pressure readings and the presence of more application material are inversely correlated such that lower pressure readings occur at an axial location where more application material is present.

This variation in pressure readings can be used to identify that a problem may exist with the interaction of the first applicator rod <NUM> and the first applicator roll <NUM>. As a result, an operator may replace the first applicator rod <NUM> with a larger size rod or may change the rotational speed of the first applicator rod <NUM>. Other possible corrective actions could include analyzing the synchronization between the drive motors <NUM>, <NUM> or adjusting the holder (not shown) which presses the first applicator rod <NUM> against the first applicator roll <NUM>.

As will be discussed further below, pressure readings taken at the region of the nip <NUM> at which the coating of material <NUM> is applied to the first applicator roll <NUM> or in the region of the nip <NUM> defined by the first and second applicator rolls <NUM> and <NUM> through which the coating of material <NUM> is applied to a web of material <NUM>, for example, may be used to determine the uniformity of the coating of material <NUM> on the surface of the roll <NUM>. The coating of material <NUM> is pressed into the web of material <NUM> at an area <NUM> of the nip <NUM>, see <FIG>.

It is also noted that pressure readings taken by pressure sensors associated with the second applicator roll <NUM> taken at the region of the nip <NUM> defined by the second roll <NUM> and the second applicator rod <NUM> can be used to determine the uniformity of the second coating material <NUM> on the surface of the second roll <NUM>.

<FIG> illustrates the first applicator rod <NUM> and the first applicator/sensing roll <NUM> arranged in alignment similar to the sensing roll <NUM> and the mating roll <NUM> of <FIG>. The sensing roll <NUM> and the first applicator rod <NUM> form the nip <NUM> and each of the sensors 26B, <NUM> in the illustrated embodiment, at a corresponding axial section of the sensing roll <NUM> passes through a region of the nip <NUM> once each rotation of the sensing roll <NUM>. On the first applicator rod <NUM>, an indexed or encoded location <NUM> is positioned such that each time it is adjacent a signal generator 900A it produces a time reference signal that is communicated to a processor 903A. Accordingly, upon each rotation of the first applicator rod <NUM>, a new time reference signal will be generated. Also, a wireless transceiver 40A can be included on the first applicator/sensing roll <NUM> to communicate sensor reading information to the processor 903A. The first applicator rod <NUM> has a circumference that can be broken into <NUM> circumferential segments 1002A - 1002AX (in <FIG> only <NUM> such segments are explicitly labeled 1002A, 1002V, 1002Y, 1002AX).

Thus, as shown in <FIG>, the processor 903A can be present that can generate a real-time nip profile. In addition, the processor 903A can also receive a trigger signal defined by the time reference signal related to the rotation of the first applicator rod <NUM>. As just described, some circumferential segment or position <NUM> of the first applicator rod <NUM> can be indexed or encoded such that the signal generator 900A detects the encoded segment <NUM> and generates the trigger or time reference signal each time the signal generator 900A determines that the segment <NUM> of the first applicator rod <NUM> completes another full rotation. When the first applicator rod <NUM> is rotated such that the circumferential position or segment <NUM> is aligned with a detector portion of the signal generator 900A, then the one of the <NUM> circumferential segments 1002A-1002AX that happens to be positioned in the region of the nip <NUM> can arbitrarily be labeled as the first circumferential segment such that the other circumferential segments can be numbered relative to this first segment. This particular rotational position of the first applicator rod <NUM> can be considered a reference position. As the first applicator rod <NUM> rotates, its rotational position will vary relative to that reference position and the amount of this variance determines which of the <NUM> circumferential segments 1002A - 1002AX will be positioned in the nip region. Accordingly, based on the rotational position of the first applicator rod <NUM> relative to that reference position a determination can be made as to which of the <NUM> circumferential segments 1002A - 1002AX is in the nip region when a particular sensor 26B generates a pressure signal.

As described with respect to the mating roll <NUM> and sensing roll <NUM>, each sensor reading value from each of the sensors 26B on the first applicator/sensing roll <NUM> as it is in the region of the nip <NUM> can be associated with one of the plurality of circumferential segments 1002A - 1002AX that is also concurrently in the region of the nip <NUM>. These pressure reading values for all sensors at all of the axial segments of the first applicator/sensing roll <NUM> can be collected over a period of time to build a nip profile for the nip <NUM>.

In an example environment in which there are <NUM> axially arranged sensors 26B on the first applicator/sensing roll <NUM>, each of which can be uniquely referred to using an axial segment index value that ranges from "<NUM>" to "<NUM>", and there are <NUM> circumferential segments on the first applicator rod <NUM> (or time segments), each of which can be uniquely referred to using a tracking segment index value ranging from "<NUM>" to "<NUM>", there are <NUM>,<NUM> (i.e., <NUM> x <NUM> = <NUM>,<NUM>) unique permutations of pairs consisting of a sensor number and a circumferential segment number (or time segment number), wherein each permutation is identifiable by a two-element set comprising a respective axial segment index value and a respective tracking segment index value. In the illustrated embodiment, the sensor numbers also correspond to the press rod axial segments <NUM>. Therefore, the data collected can be considered a <NUM> x <NUM> matrix similar to that depicted in <FIG>, Each row of the <NUM> x <NUM> matrix represents one of the <NUM> applicator rod circumferential segments (or time segments) and each column represents one of the <NUM> axially arranged sensors 26B and, thus, each cell represents one of the possible <NUM>,<NUM> permutations. Since the sensor numbers correspond to the applicator rod axial segments <NUM>, each column also corresponds to an applicator rod axial segment, i.e., an outer surface portion of the applicator rod at an axial location aligned with and corresponding to the sensor 26B assigned that column. Each cell represents a combination of a sensor number (or axial segment number) and a particular applicator rod circumferential segment (or time segment). Thus, each cell of a matrix similar to that of <FIG> represents a unique permutation from among all the possible permutations of different axial segment numbers (e.g., <NUM>-<NUM>) and circumferential segment numbers (e.g., <NUM>-<NUM>) (or time segments <NUM>-<NUM>). A value stored in a particular matrix element is thereby associated with one particular permutation of possible axial segment numbers and circumferential segment numbers (or time segments). The matrix similar to the one of <FIG> can, for example, be a "counts" matrix wherein each cell represents the number of times a particular sensor and a particular applicator rod outer surface portion at an axial location corresponding to that sensor and a particular rod circumferential segment were concurrently in the region of the nip <NUM> to acquire a pressure reading value.

Thus, similar to how a "sums" matrix of <FIG> and an "average" matrix of <FIG> were calculated, similar matrices could be calculated using the data collected from the first applicator/sensing roll <NUM> and the applicator rod <NUM> regarding the nip <NUM>. The "average" matrix provides data that could reveal a periodically occurring pressure increase or decrease at one or more of the rod tracking segments for a rod axial segment as compared to other axial segments or as compared to other rod tracking segments for that particular rod axial segment. The occurrence of such a pressure variance could be indicative of an operational issue with the first applicator rod <NUM>.

Similarly, a "counts" matrix, "sums" matrix and "average" matrix could be calculated using data collected from the first applicator/sensing roll <NUM> and the second applicator roll <NUM> regarding the nip <NUM>, with such data being time synchronized to a period of rotation of the first applicator rod <NUM>. Again, this "average" matrix also provides data that could reveal a periodically occurring pressure increase or decrease at one or more of the rod tracking segments for a rod axial segment as compared to other rod axial segments or as compared to other rod tracking segments for that particular rod axial segment. The occurrence of such a pressure variance could be indicative of an operational issue with the first applicator rod <NUM>.

As a result, one matrix can be generated that represents an average pressure value, at the nip <NUM>, that is sensed for each particular sensor number and press rod circumferential segment number or press rod time-based tracking segment. Alternatively, or in addition, a second matrix can be generated that represents an average pressure value, at the nip <NUM>, that is sensed for each particular sensor number and tracking segment number of the press rod. The length of time such data is collected determines how many different pressure readings are used in such calculations.

Thus, pressure readings at the nip <NUM> can be time synchronized with one or more of the second applicator/sensing roll <NUM>, the first applicator rod <NUM>, or the second applicator rod <NUM>. Pressure readings at the nip <NUM> can be time synchronized with the first applicator rod <NUM> and pressure readings at the nip <NUM> can be time synchronized with the second applicator rod <NUM>. For example, the embodiment described with respect to <FIG> happens to have the first applicator/sensing roll <NUM> and the first applicator rod <NUM> define the nip <NUM>. However, referring back to <FIG>, there is also a second applicator rod <NUM> which does not form a nip with the first applicator/sensing roll <NUM>. Instead, the second applicator rod <NUM> forms a nip <NUM> with the second applicator roll <NUM>. This second applicator roll <NUM> may also be a sensing roll or it may be a mating roll instead without pressure sensors. Pressure readings at various axial regions of the nip <NUM> are still influenced by the second applicator rod <NUM> that is involved with applying the second application material portion <NUM> to the second applicator roll <NUM>. Thus, even though the second applicator rod <NUM> and the first applicator/sensing roll <NUM> do not form a nip with one another, pressure readings at the nip <NUM> sensed by the first applicator/sensing roll <NUM> can still be time-synchronized with a rotational period of the second applicator rod <NUM> using the techniques described above. Hence, variations in pressure readings taken at the nip <NUM> by the sensors of the first sensing roll <NUM> can be used to identify a problem that may exist with the interaction of the second applicator rod <NUM> and the second applicator roll <NUM>.

<FIG> illustrate a simulated data set representing collecting and averaging pressure readings at the nips <NUM>, <NUM> at a plurality of distinct axial locations in a manner that is time-synchronized with a period of rotation of the first applicator rod <NUM>. Continuing with the example embodiments described above, the first applicator rod <NUM> can have its period of rotation segmented into <NUM> tracking segments (see <FIG>, 1002A - 1002AX). These tracking segments could be either physical circumferential segments of the first applicator rod <NUM>, as noted above, or correspond to time-based segments of a period of rotation of the first applicator rod <NUM>. Additionally, the first applicator/sensing roll <NUM> can include <NUM> axially spaced-apart sensors 26B (as shown in <FIG>) that correspond to <NUM> axial segments of the first applicator rod <NUM>. Each of the <NUM> axial segments <NUM> of the first applicator rod <NUM> also corresponds to a respective axial segment of the first applicator/sensing roll <NUM>.

Accordingly, a <NUM>,<NUM> cell matrix can be constructed that has a cell for each permutation of a tracking segment number (e.g., <NUM> - <NUM>) and an axial segment number (e.g., <NUM>- <NUM>). Pressure reading values are sensed by each of the <NUM> sensors 26B in a region of the nip <NUM>. For each pressure reading, one of the <NUM> tracking segments is identified based on the reference signal from signal generator 900A and the pressure reading value is associated with an appropriate cell of the <NUM>,<NUM> cell matrix. As explained above, data is collected for a period of time to capture a number of pressure readings for each cell so that an average pressure reading can be calculated for each cell.

As described above, these tracking segments could be either physical circumferential segments of the first applicator rod <NUM> or correspond to time-based segments of a period of rotation of the first applicator rod <NUM>. When using time-based segments, some circumferential segment or position <NUM> of the first applicator rod <NUM> can be indexed or encoded such that a signal generator 900A detects the encoded segment <NUM> and generates a starting reference signal each time the signal generator 900A determines that the segment <NUM> of the first applicator rod <NUM> completes another full rotation. When the first applicator rod <NUM> is rotated such that the circumferential position or segment <NUM> is aligned with a detector portion of the signal generator 900A, the starting reference signal can be generated from which to measure, or index, the <NUM> sequentially occurring time segments into which the period of rotation of the first applicator rod <NUM> has been segmented. Thus, a first time segment starting concurrently with the generation of the starting reference signal can be considered a reference time-segment. As the first applicator rod <NUM> rotates, the number of time segments that have transpired since the occurrence of the reference time segment will depend on the amount of time that has transpired since generation of the reference starting signal. Accordingly, based on the number of time segments that have occurred between a pressure reading being sensed at a region of the nip <NUM> and the most recent starting reference signal, a determination can be made as to which of the <NUM> time-based tracking segment is to be associated with that pressure reading.

<FIG> depict a simulated matrix of average pressure values for each cell of the <NUM>,<NUM> cell matrix collected at the nip <NUM> and time synchronized with the rotation of the first applicator rod <NUM>. Each row <NUM> corresponds to one of the tracking segments of the first applicator rod <NUM> and each column <NUM> corresponds to one of the <NUM> sensors 26B (or equivalently, one of the <NUM> axial segments <NUM>). Thus, each cell <NUM> corresponds to a unique permutation of axial segment number and tracking segment number with the value of that cell providing an average pressure reading value at the nip <NUM> for that particular permutation of numbers. In <FIG>, the cell values happen to be measured in kPa (<NUM> kPa = <NUM>,<NUM> pounds per square inch; psi) and for brevity, only the first <NUM> and last <NUM> of the <NUM> sensor locations are depicted.

The sensors 26B also rotate through the nip <NUM> and, thus, pressure readings can be collected that represent a pressure profile at the nip <NUM>. These pressure readings are collected in a substantially similar manner as just described but are sensed at the nip <NUM> instead of (or in addition to) the nip <NUM>.

Accordingly, an alternative, or additional, <NUM>,<NUM> cell matrix can be constructed that has a cell for each permutation of a tracking segment number (e.g., <NUM> - <NUM>) and an axial segment number (e.g., <NUM>- <NUM>). Pressure reading values are sensed by each of the <NUM> sensors 26B in a region of the nip <NUM>. For each pressure reading, one of the <NUM> tracking segments is identified based on the reference signal from signal generator 900A and the pressure reading value is associated with an appropriate cell of the additional <NUM>,<NUM> cell matrix. As explained above, data is collected for a period of time to capture a number of pressure readings for each cell so that an average pressure reading can be calculated for each cell.

Unlike the behavior described above with respect to the mating roll and sensing roll of <FIG>, the various pressures sensed at regions of the nip <NUM> are being collected such that they are synchronized with a rotating element that does not form or define the nip <NUM>. In other words, the sensed pressure readings for each axial segment are synchronized with the period of rotation of the first applicator rod <NUM> which does not define the nip <NUM>. More specifically, the period of rotation of the first applicator rod <NUM> can be segmented into a number of sequentially-occurring time segments that, for example, can be indexed based on generation of a reference signal such that the "first" time segment corresponds to when the reference signal is generated and the sequentially indexed time segments correspond to sequentially occurring time segments from when the reference signal was generated. Thus, at an axial location, as each particular pressure reading is sensed as a sensor at that axial segment enters a region of a nip, that pressure reading can be associated with one of the indexed time segments and, more particularly, the pressure reading can be associated with the specific time segment that is indexed by an amount region of the nip.

As a result, at an axial segment, there may be one particular circumferential segment of the first applicator rod <NUM> that is in a region of the nip <NUM> when a sensor, on the first applicator roll <NUM>, at that same axial segment enters a region of the nip <NUM> and senses a pressure reading. Thus, when the sensor reading at a region of the nip <NUM> is sensed there happens to be a first portion of the first application material that is in the region of the nip <NUM> that affects the pressure reading and there also happens to be a second portion of the first application material <NUM> that is in contact with some physical circumferential segment of the first applicator rod <NUM>. Even though the sensor reading at the region of the nip <NUM> will be associated with a particular one of the tracking segments that is a fraction of the period of rotation of the first applicator rod <NUM>, that does not mean that the pressure reading is associated with the physical circumferential segment of the first applicator rod <NUM> that was previously in the region of the nip <NUM> and previously in contact with the first portion of the first application material <NUM>.

<FIG> depict a simulated matrix of average pressure values for each cell of the additional <NUM>,<NUM> cell matrix collected at the nip <NUM> and time synchronized with the rotation of the first applicator rod <NUM>. Each row <NUM> corresponds to one of the tracking segments of the first applicator rod <NUM> and each column <NUM> corresponds to one of the <NUM> sensors 26B ( or equivalently, one of the <NUM> axial segments <NUM> ). Thus, each cell <NUM> corresponds to a unique permutation of an axia <NUM> segment number and tracking segment number with the value of that cell providing an average pressure reading value at the nip <NUM> for that particular permutation of numbers. In <FIG>, the cell values happen to be measured in kPa (<NUM> kPa = <NUM>,<NUM> pounds per square inch; psi) and for brevity, only the first <NUM> and last <NUM> of the <NUM> sensor locations are depicted.

<FIG> depicts a portion of the simulated data of the matrix of <FIG> but in a graphical manner. Similarly, <FIG> depicts a portion of the simulated data of the matrix of <FIG> but also in a graphical manner.

In <FIG>, <NUM> different average pressure values for three different axial segments are depicted. Graph <NUM> represents the <NUM> different values (i. e, the rows of <FIG>) for the <NUM>th axial segment associated with the first applicator rod <NUM> (i.e., the <NUM>th column of <FIG>). Graph <NUM> represents the <NUM> different values (i.e., the rows of <FIG>) for the <NUM>th axial segment associated with the first applicator rod <NUM> (not shown in <FIG>). Graph <NUM> represents the <NUM> different values (i.e., the rows of <FIG>) for the <NUM>th axial segment associated with the first applicator rod <NUM> (i.e., the <NUM>th column of <FIG>). For example, the graph <NUM> reveals that at axial segment <NUM> the pressure readings for the <NUM> different tracking segment tend to be between <NUM> kPa and <NUM> kPa (<NUM> PSI and <NUM> PSI) but that around tracking segment <NUM>, the pressure reading dips below <NUM> kPa and <NUM> kPa (<NUM> PSI and <NUM> PSI). Such a dip may indicate that the first applicator rod <NUM> is periodically lifting away from the first applicator roll <NUM> in a region of the nip <NUM> corresponding to axial segment <NUM>.

In <FIG>, <NUM> different average pressure values for three different axial segments are depicted. Graph <NUM> represents the <NUM> different values (i.e., the rows of <FIG>) for the <NUM>th axial segment associated with the first applicator rod <NUM> (i.e., the <NUM>th column of <FIG>). Graph <NUM> represents the <NUM> different values (i.e., the rows of <FIG>) for the <NUM>th axial segment associated with the first applicator rod <NUM> (not shown in <FIG>), Graph <NUM> represents the <NUM> different values (i.e., the rows of <FIG>) for the <NUM>th axial segment associated with the first applicator rod <NUM> (i.e., the <NUM>th column of <FIG>). The relative magnitude of the pressure kPa( PSI) readings in <FIG> as compared to <FIG> show that a pressure sensed in regions of the nip <NUM> can be around <NUM> times greater than the pressure readings sensed at regions of the nip <NUM>. Also, as one example, the graph <NUM> reveals that at axial segment <NUM> the pressure readings for the <NUM> tracking segments tend to be in a range of about <NUM> to <NUM> kPa ( <NUM><NUM> to <NUM> psi). However, around tracking segment <NUM> or <NUM>, the average pressure value extends upwards to about <NUM> kPa ( <NUM> psi). A higher pressure such as this can indicate that periodically, more application material <NUM> is passing through the nip <NUM> as a result of some periodic phenomena occurring between the first applicator rod <NUM> and the first applicator roll <NUM> along the region of the nip <NUM> corresponding to axial segment <NUM>.

<FIG> is a flowchart of an exemplary method of time-synchronizing data in accordance with the principles of the present invention. The method begins in step <NUM> by generating a respective sensor signal from each of a plurality of sensors located at axially spaced-apart locations of a sensing roll. More particularly, each respective sensor signal is generated when each sensor enters a region of a first nip between the sensing roll and a press rod or a region of a second nip between the sensing roll and a mating roll during each rotation of the sensing roll. For the sensing roll and mating roll, they are located relative to one another to create the second nip therebetween through which a web of material passes that travels through the second nip from an upstream direction to a downstream direction. For the sensing roll and the press rod, they form the first nip therebetween and are part of an application station that applies either a sizing composition or coating to the cover of the sensing roll so that it is eventually pressed into the web of material. The method continues in step <NUM> by generating a periodically occurring time reference associated with each rotation of the press rod. Next, in accordance with the method, the respective sensor signal generated by each sensor is received in step <NUM> whether that sensor signal occurs based on the sensor being in the region of one of the first or the second nips. In step <NUM>, upon receiving the respective sensor signal, the method involves three different actions: a) determining a particular one of the plurality of sensors which generated the respective sensor signal, b) identifying one of a plurality of tracking segments associated with the press rod based upon an amount of time that elapsed between when the respective sensor signal was generated and a most recent time reference, and c) storing the respective sensor signal to associate the respective sensor signal with the identified one tracking segment. Of particular note, each of the plurality of tracking segments is, respectively, associated with a different amount of elapsed time. In accordance with the method of <FIG>, the press rod can comprise either a size press rod or a coating rod.

In addition to the time-based techniques described above for identifying different tracking segments associated with an applicator rod, alternative techniques are contemplated as well. For example, an applicator rod could include multiple, evenly-spaced marks that could be detected (e.g., optically) and counted as each such mark passes a location of a sensor or detector. A reference mark could be provided and would be distinctive from all the other marks such that when the sensor detects the reference mark, the counter circuitry resets and starts counting from an initial value (e.g., "<NUM>" or "<NUM>"). As an example, each evenly-spaced mark could be a single tick mark, a tick mark of a particular width, or a mark of a particular color. The reference mark could be a double-tick mark, a thicker (or thinner) tick mark, or a mark of a unique color. The marks would function so as to separate the applicator rod into different segments and a counter, or similar circuitry, would increment a count each time a mark was detected so that any collected data could be associated with one of the segments of the applicator rod. Accordingly, there may be structure for generating a starting reference that includes a detector proximate to the surface of the applicator rod for detecting each of the plurality of marks traveling by the detector; and a signal generator in communication with the detector for generating the starting reference each time the distinctive reference mark is detected. Furthermore there may also be a counter in communication with the detector for counting a number of the plurality of marks that have been detected since the most recent starting reference, wherein a value related to an amount the applicator rod has rotated is equal to the number of the plurality of marks that have been detected since the most recent starting reference. Also, as an example, the generating of the starting reference can be accomplished by resetting the counter to an initial value (e.g., "<NUM>" or "<NUM>" as mentioned above). If the techniques of segmenting the applicator rod just described were utilized, then it would be unnecessary to explicitly measure an elapsed time since the most recent generation of a reference timing signal that is generated each revolution of the applicator rod; instead, detection and counting of tick marks could be used to define a plurality of count-based tracking segments.

Claim 1:
A system associated with a sensing roll (<NUM>) for collecting sensor signals, the system comprising:
a plurality of sensors (26B) located at axially spaced-apart locations of the sensing roll, wherein each sensor enters a region of a first nip (<NUM>) between the sensing roll and a mating roll (<NUM>) during each rotation of the sensing roll;
an application station (<NUM>), comprising a rotatable applicator rod (<NUM>) forming a second nip (<NUM>) with the sensing roll, wherein each sensor enters a region of the second nip between the sensing roll and the applicator rod during each rotation of the sensing roll, and wherein each sensor generates a respective sensor signal upon entering a region of the second nip; a structure for generating a periodically occurring starting reference associated with each rotation of the applicator rod; and
a processor (903A) to receive the periodically occurring starting reference and the respective sensor signal generated by each sensor as it moves through the second nip and, after receiving the respective sensor signal, the processor operates to:
determine a particular one of the plurality of sensors which generated the respective sensor signal,
based upon a value occurring between when the respective sensor signal was generated and a most recent starting reference, identify one of a plurality of tracking segments of the applicator rod, wherein each of the plurality of tracking segments is, respectively, associated with a different value, and
store the respective sensor signal to associate the respective sensor signal with the identified one tracking segment.