OF A ROTATING ROLL

Related Application

[0001] The present application claims priority from U.S. Provisional Patent Application No. 61/587,361, filed January 17, 2012, the disclosure of which is hereby incorporated herein in its entirety.

Field of the Invention

[0002] The present invention relates generally to industrial rolls, and more particularly to industrial rolls with sensing systems.

Background of the Invention

[0003] In a typical papermaking process, a water slurry, or suspension, of cellulosic fibers (known as the paper "stock") is fed onto the top of the upper run of an endless belt of woven wire and/or synthetic material that travels between two or more rolls. The belt, often referred to as a "forming fabric," provides a papermaking surface on the upper surface of its upper run which operates as a filter to separate the cellulosic fibers of the paper stock from the aqueous medium, thereby forming a wet paper web. The aqueous medium drains through mesh openings of the forming fabric, known as drainage holes, by gravity or vacuum located on the lower surface of the upper run (i.e., the "machine side") of the fabric.

[0004] After leaving the forming section, the paper web is transferred to a press section of the paper machine, where it is passed through the nips of one or more presses (often roller presses) covered with another fabric, typically referred to as a "press felt." Pressure from the presses removes additional moisture from the web; the moisture removal is often enhanced by the presence of a "batt" layer of the press felt. The paper is then transferred to a dryer section for further moisture removal. After drying, the paper is ready for secondary processing and packaging.

[0005] Cylindrical rolls are typically utilized in different sections of a papermaking machine, such as the press section. Such rolls reside and operate in demanding environments in which they can be exposed to high dynamic loads and temperatures and aggressive or corrosive chemical agents. As an example, in a typical paper mill, rolls are used not only for transporting the fibrous web sheet between processing stations, but also, in the case of press section and calender rolls, for processing the web sheet itself into paper.

[0006] Typically rolls used in papermaking are constructed with the location within the papermaking machine in mind, as rolls residing in different positions within the papermaking machines are required to perform different functions. Because papermaking rolls can have many different performance demands, and because replacing an entire metallic roll can be quite expensive, many papermaking rolls include a polymeric cover that surrounds the circumferential surface of a typically metallic core. By varying the material employed in the cover, the cover designer can provide the roll with different performance characteristics as the papermaking application demands. Also, repairing, regrinding or replacing a cover over a metallic roll can be considerably less expensive than the replacement of an entire metallic roll. Exemplary polymeric materials for covers include natural rubber, synthetic rubbers such as neoprene, styrene-butadiene (SB ), nitrile rubber, chlorosulfonated polyethylene ("CSPE" - also known under the trade name HYPALON® from DuPont), EDPM (the name given to an ethylene-propylene terpolymer formed of ethylene-propylene diene monomer), polyurethane, thermoset composites, and thermoplastic composites.

[0007] In many instances, the roll cover will include at least two distinct layers: a base layer that overlies the core and provides a bond thereto; and a topstock layer that overlies and bonds to the base layer and serves the outer surface of the roll (some rolls will also include an intermediate "tie-in" layer sandwiched by the base and top stock layers). The layers for these materials are typically selected to provide the cover with a prescribed set of physical properties for operation. These can include the requisite strength, elastic modulus, and resistance to elevated temperature, water and harsh chemicals to withstand the papermaking environment. In addition, covers are typically designed to have a predetermined surface hardness that is appropriate for the process they are to perform, and they typically require that the paper sheet "release" from the cover without damage to the paper sheet. Also, in order to be economical, the cover should be abrasion- and wear-resistant.

[0008] As the paper web is conveyed through a papermaking machine, it can be very important to understand the pressure profile experienced by the paper web. Variations in pressure can impact the amount of water drained from the web, which can affect the ultimate sheet moisture content, thickness, and other properties. The magnitude of pressure applied with a roll can, therefore, impact the quality of paper produced with the paper machine.

[0009] It is known to include pressure and/or temperature sensors in the cover of an industrial roll. For example, U.S. Patent No. 5,699,729 to Moschel et al. describes a roll with a helically-disposed leads that includes a plurality of pressure sensors embedded in the polymeric cover of the roll. The sensors are helically disposed in order to provide pressure readings at different axial locations along the length of the roll. Typically the sensors are connected to two leads or an optical fiber which transmit sensor signals to a processor that processes the signals and provides pressure and position information.

[0010] Because multiple sensors are attached to the two common leads or fiber, the signals from different sensors travel along the same leads or fiber. Therefore, the processor should have some way to distinguish which sensor has produced a particular signal; otherwise, the processor does not recognize the axial position of the sensor providing the signal. One common technique is the use of a "trigger" signal that alerts the processor to each revolution of the roll. This technique, described in U.S. Patent No. 5,699,729, supra, employs a trigger signal generator that provides a signal every time a particular position on the roll passes a particular location. However, this technique can be susceptible to false readings due to noise in the signal. As such, it may be desirable to provide a technique for employing a trigger signal that addresses the signal noise inaccuracy. Summary of the Invention

[0011] As a first aspect, embodiments of the invention are directed to a method of determining the angular position of a roll, comprising the steps of: (a) detecting signals generated by an accelerometer attached to an end of a rotating roll; (b) determining whether a signal generated in step (a) has reached a pre-trigger threshold, and repeating step (a) if the signal has not reached the pre-trigger threshold; (c) if the signal is determined in step (b) to have reached the pre-trigger threshold, detecting a subsequent signal generated by the accelerometer; (d) determining whether the signal detected in step (c) has reached a trigger threshold, and repeating step (c) if the signal has not reached the trigger threshold; and (e) if the signal has reached the trigger threshold, establishing the angular position of the roll based on the signal that has reached the trigger threshold. This method can ensure that a triggering signal correctly indicates the proper position of the roll rather than being the result of noise.

[0012] As a second aspect, embodiments of the invention are directed to an industrial roll assembly, comprising: a cylindrical roll having a plurality of sensors mounted thereto and an accelerometer mounted to an end thereof; and a controller operatively associated with the accelerometer. The controller is configured to: (a) detect signals generated by the accelerometer; (b) determine whether a signal generated in (a) has reached a pre-trigger threshold, and repeating (a) if the signal has not reached the pre-trigger threshold; (c) if the signal is determined in (b) to have reached the pre-trigger threshold, detect a subsequent signal generated by the accelerometer; (d) determine whether the signal detected in (c) has reached a trigger threshold, and repeating (c) if the signal has not reached the trigger threshold; and (e) if the signal has reached the trigger threshold, establish the angular position of the roll based on the signal that has reached the trigger threshold.

[0013] As a third aspect, embodiments of the invention are directed to a computer program product for determining the angular position of a roll, the computer program product comprising a computer readable storage medium having computer readable program code embodied therein, the computer readable program code configured to: (a) detect signals generated by the accelerometer; (b) determine whether a signal generated in (a) has reached a pre-trigger threshold, and repeat (a) if the signal has not reached the pre-trigger threshold; (c) if the signal is determined in (b) to have reached the pre-trigger threshold, detect a subsequent signal generated by the accelerometer; (d) determine whether the signal detected in (c) has reached a trigger threshold, and repeat (c) if the signal has not reached the trigger threshold; and (e) if the signal has reached the trigger threshold, establish the angular position of the roll based on the signal that has reached the trigger threshold.

Brief Description of the Figures

[0014] Figure 1 is a front view of an industrial roll according to embodiments of the invention.

[0015] Figure 2 is an enlarged end view of the roll of Figure 1 showing an

accelerometer and vectors created thereby during rotation of the roll.

[0016] Figure 3 is a schematic diagram of an electronics subassembly of the roll of Figure 1.

[0017] Figure 4 is a graph plotting the accelerometer vector as a function of roll angle, which shows that the curve created by this plot is sinusoidal.

[0018] Figure 5 is a flow chart illustrating operations of the roll of Figure 1 according to embodiments of the invention.

Detailed Description of Embodiments of the Invention

[0019] The present invention will be described more particularly hereinafter with reference to the accompanying drawings. The invention is not intended to be limited to the illustrated embodiments; rather, these embodiments are intended to fully and completely disclose the invention to those skilled in this art. In the drawings, like numbers refer to like elements throughout. Thicknesses and dimensions of some components may be exaggerated for clarity.

[0020] Well-known functions or constructions may not be described in detail for brevity and/or clarity.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. Where used, the terms "attached," "connected," "interconnected," "contacting," "coupled," "mounted," "overlying" and the like can mean either direct or indirect attachment or contact between elements, unless stated otherwise.

[0022] Some embodiments may be embodied in hardware (including analog circuitry and/or digital circuitry) and/or in software (including firmware, resident software, micro-code, etc.). Consequently, as used herein, the term "signal" may take the form of a continuous waveform and/or discrete value(s), such as digital value(s) in a memory or register. Furthermore, various embodiments may take the form of a computer program product on a computer-usable or computer-readable storage medium having computer-usable or computer-readable program code embodied in the medium for use by or in connection with an instruction execution system.

Accordingly, as used herein, the terms "circuit" and "controller" may take the form of digital circuitry, such as a logic gate array and/or computer-readable program code executed by an instruction processing device(s) (e.g., general purpose microprocessor and/or digital signal processor), and/or analog circuitry. Although some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows.

[0023] An industrial roll, such as a roll used in papermaking, is shown in Figure 1 and is designated broadly therein at 20. The roll 20 includes a core (not shown) and a polymeric cover 24; the polymeric cover 24 typically includes a base layer and a topstock layer. Exemplary materials and construction of the core and cover 24 are described in U.S. Patent Publication No. 2007/01 1 1871 and U.S. Patent Publication No. 2005/0261 1 15, the disclosures of which are hereby incorporated herein.

[0024] Figure 1 also illustrates a sensing system 29 comprising a plurality of sensors 30 that are disposed along the length of the roll 20 in a single helical configuration. The sensors 30 are mounted on leads 28a, 28b, which are connected to a microprocessor/transmitter 31. Signals as sent from the microprocessor/transmitter 31 wirelessly (via wireless link 26) to a remote processor/display 32. Various exemplary configurations of the sensing system are described in detail in, for example, U.S. Patent Nos. 5,562,027; 699,729; 6,981,935;7,572,214; and 8,236,141, and U.S Patent Publication Nos. 2005/0261115 and 2011/0301003, each of which is incorporated by reference herein.

[0025] When sensors, such as pressure or temperature sensors 30, are mounted onto a rotating roll such as the roll 20, it may become necessary to trigger data gathering or some other activity at a specific point in each rotation, i.e., at a particular angular position. The following describes a technique that can be used to trigger data gathering at the same point of rotation.

[0026] The system comprises a device 40 (Figure 1) that mounts on the end of the roll 20 and contains an accelerometer 42 of conventional construction that is mounted to detect acceleration in a direction perpendicular to the axis of the roll. As shown in Figure 2, a typical mounting location is near the circumference of the roll 20. With the accelerometer 42 mounted tangentially to the roll 20, as the roll 20 turns an accelerometer vector caused by the acceleration of gravity rotates also. Referring to the roll 20 in Figure 2, which is shown to rotate clockwise, when the accelerometer 42 is at the "3 o'clock" position the vector points down and has a magnitude of 1G. When the accelerometer 42 is at the "6 o'clock" position (i.e., its lowest point), it reads a magnitude of zero since the gravity vector is orthogonal to the accelerometer vector. When the accelerometer 42 is at the "9 o'clock" position the accelerometer 42 reads -1G, and at "12 o'clock" it reads zero (again, because the gravity vector is orthogonal to the accelerometer vector). Since the accelerometer 42 is mounted tangentially the centrifugal forces generated by the rotation are substantially constant and therefore are not a factor.

[0027] Figure 3 is an electronics diagram that illustrates an arrangement that can be used to monitor the accelerometer signal. An analog-to-digital converter 50 can be used to convert the signal transmitted by the accelerometer 50 from a voltage to a digital data stream, which is then fed to the microprocessor 31. Because the roll 20 is rotating about its axis, the accelerometer data follows the rotating gravity vector and, therefore, is generally sinusoidal in shape when plotted as a function of angular position. A graph of an exemplary theoretical sinusoidal function is shown in Figure 4. [0028] A method for establishing a trigger point is shown in Figure S, with certain terms illustrated in Figure 4. A data sample from the accelerometer is taken (block 100). This reading is compared to a predetermined "pre-trigger" threshold (decision 102). Assuming that it is not, another sample is taken (block 100) and the same comparison is made. At some point the value of the accelerometer data sample goes below the pre-trigger threshold, at which point the angular position of that sample is noted (block 104 - see also Figure 4). Following the flow chart of Figure 5, additional accelerometer data samples are taken (block 106) as the data levels pass through the "pre-trigger box" and advance toward a pre-determined "trigger point" level. These samples are compared to the trigger point level (decision 108), with sampling continuing until the level of the signal passes above the trigger level. At this point a trigger has occurred (block 110 - see also Figure 4), and now can begin sampling of sensor data can begin, as the angular position of the roll is known.

[0029] The flowchart of Figure 5 illustrates the architecture, functionality, and operations of embodiments of hardware and/or software according to various embodiments of the present invention. It will be understood that each block of the flowcharts, and combinations of blocks in the flowcharts, may be implemented by computer program instructions and/or hardware operations. In this regard, each block represents a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s).

[0030] It should be noted that, in other implementations, the function(s) noted in the blocks may occur out of the order noted in Figure 5. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending on the functionality involved.

[0031] The computer program instructions may be provided to a processor of a general purpose computer, a special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowcharts.

[0032] The computer program instructions may also be stored in a computer usable or computer-readable memory that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer usable or computer-readable memory produce an article of manufacture including instructions that implement the function specified in the flowcharts.

[0033] The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowcharts.

[0034] By using the accelerometer data to generate a trigger the position of the roll can be found almost exactly. The roll will trigger at the same point in the cycle repeatedly, and thus can be used to identify sensors strung around the roll. The use of both a low pre-trigger level and a higher trigger level can ensure that the accelerometer is at the bottom of the rotation for the example shown in Figure 4. Because the method ensures that a pre-trigger level signal has been received prior to looking for a trigger level signal, a false positive due to signal noise can be avoided. The precise location of the trigger signal can be especially important in a sensor configuration reading multiple events per rotation, such as a roll having multiple sets of sensors.

[0035] Notably, the technique described above may, in some embodiments, be performed such that the pre-trigger threshold is located near an extremum (i.e., a maximum or minimum) of the sinusoidal curve of the accelerometer function, and/or the trigger threshold may be near the midpoint of the sinusoidal curve. The data points near the midpoint tend to define a higher slope than those near an extremum; thus, locating the trigger threshold near the midpoint can reduce the chance that an incorrect, "noisy" signal could set off the trigger. In some embodiments, the trigger threshold is separated from the extremum by between about 70 and 110 degrees. In other embodiments, the trigger threshold is separated from the pre-trigger threshold by between about 90 and 130 degrees.

[0036] The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.