FI113804B - Method and apparatus for measuring voltage of a continuously moving member - Google Patents

Description

113804

Method and apparatus for measuring tension in a continuous movable member

The invention relates to a method for measuring the tension of a continuous member, such as a web or tissue, traveling in a paper machine or a paper finishing machine, wherein the measurement is made at a plurality of locations across the movable member by a pressure sensitive membrane sensor located in a rotatable roller. The invention also relates to apparatus for measuring continuous tension in a paper machine or paper finishing machine, comprising a pressure sensitive membrane sensor located on a rotatable roller through which a continuous movable member is arranged to travel and a plurality of measuring points in the transverse direction of the continuous moving member. arranged to measure 15 tensions.

The paper machine or paper finishing machine shall continuously monitor the tension of the wide paper web being transported therein to adjust the drives affecting the paper web passage and to avoid web breaks. The track tension measurement data generally gives a good idea of the stability of the web flow, possibly other web properties, and can be used to anticipate problem situations.

* i * 'An on-line apparatus for measuring the tension of a paper web passing through a machine is based on measuring the pressure of an air cushion between a high speed web and a curved surface at various points *: across the web. Such apparatus is shown e.g. in U.S. Patent No. 80,522, which is assigned to U.S. Patent No. 5,502,223. The transverse transverse measuring beam of the machine has a curved surface with 30 intervals of apertures through which the corresponding pressure sensors within the beam are affected by the air cushion pressure. The apparatus has been successfully used at various sites to measure track tension from a passing web. The problem, however, is that the spacing of the current pressure sensors • · '·: · * determines how accurately the track tension can be measured. The pressure transducers are differential pressure transducers, each of which measures a local pressure: · · * through an orifice relative to the reference pressure introduced into the beam. In order to achieve good resolution over the entire width of web 113804 2, the measuring points and the bores and pressure sensors drilled into the beam, respectively, should be densely spaced across the machine, increasing the cost of manufacturing the equipment.

5 On the other hand, the paper machine or paper finishing machine has other high-speed continuous wide (transverse) planar flexible, substantially uniform thickness elements which are exported in machine direction along the path required by the manufacturing or processing process, to anticipate. Such members include, in addition to the paper web, many different fabrics, such as blankets and wires, which are located across the entire width of the machine and at least the width of the web being driven and are used to transport the paper web at least part of the journey. Today, 15 felt or wire tension is measured with weighing sensors from the roller bearing housings. Alternatively, the tension can be measured indirectly from the oil pressure of the hydraulic pistons loading pistons. The tension measurement methods described above give an idea of the total tension of the tissues, but not of the transverse tension profile.

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WO-89/10544 discloses a solution for determining the force exerted by a ribbon-like material or the position of the material on the roll. : by pressure-sensitive material. The pressure-sensitive material in Figures 5 and 6 of the disclosure is secured as separate strands around the roll. The pressure-25 sensitive material determines the clamping force applied to the peripheral surface 5 (the outer surface of the sleeve 2 - *****). The solution according to the publication is intended to measure the properties of a strip-like metal material.

WO-84/02121 discloses a method for measuring the tension of a paper web in which a plurality of pressure-sensitive elements 4, which are separate from one another, are fixed to the roll surface. On page 4 of the publication, lines 23-27 mention that the elements 4 may also be located in a straight line.

It is an object of the invention to eliminate the above drawbacks and to provide a method and apparatus for measuring a moving continuous member of a paper machine or paper finishing machine 113804 by a simple jig online. To accomplish this purpose, the method according to the invention is mainly characterized in that the pressure-sensitive membrane sensor is arranged in a spiral-like manner around a roll as a continuous strip. The pressure-5 sensitive membrane sensor can thus be arranged in the transverse direction of the machine so that the tension is measured at a sufficient number of points across the width of the paper web or fabric. The solution is simple because in practice a single sensor can measure the tension at different points in the web width direction.

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Preferably, as a pressure-sensitive membrane sensor, an electromechanical or piezoelectric membrane, in particular a so-called "electro-mechanical", can be used as a pressure / force-readable signal, e.g. An EMFi film, which is a permanently electrically charged foam film, or 15 PVDF films. However, the invention is not limited to these named membrane materials. The diaphragm is generally of the type capable of converting a pressure or force substantially perpendicular to its plane into a signal which can be conducted along a suitable conductor or to a wireless data processing unit where it can be processed by known methods of processing measurement signals.

t · «. ,: The pressure sensitive membrane sensor is placed in a rotating roll according to the movement of the movable member. • The passing paper web or fabric will apply pressure to the membrane • · 25 sensors, depending on the tension of the member at that point in the cross machine direction and the corresponding electrical signal. At various points, the signals obtained in the cross machine direction can be formed into a tension profile which can be utilized in a known manner.

More importantly, in the area where the body passes the membrane sensor, it passes free without contact with other parts, whereby its tension is interrupted. as strong as possible on the surface of the membrane sensor without interfering factors. On the other hand, it is possible to take a measurement at a point where 't' over the first continuous member (such as a wire or felt) is second:. '* I 35 continuous member (such as paper web) and detect any sudden changes , which can cause interference such as track breakage.

113804 4

The invention will now be described in more detail with reference to the accompanying drawings, in which: Fig. 1 shows a measuring apparatus in a perpendicular section to the machine, Fig. 2 shows a top view of the apparatus of Fig. 1, Fig. 3 is a perspective view of a possible embodiment of Fig. 3 , and Fig. 5 is a side elevational view of the same in cross-machine direction.

Figure 1 is a side elevation view of a web tension measuring apparatus for a paper machine or paper finishing machine (off-line calender, off-line coating machine, winder or intermediate roller) arranged to measure the tension of the web passing past the web at various points; -: in the direction, ie, the track tension profile. The apparatus includes a beam 1 extending across the web, with a curved surface toward the passing web W. In this application, the paper machine also refers to other machines for making fibrous web-like continuous material, such as tissue and board machines, and a paper finishing machine. the aforesaid web-based '····' post-processing machines. Similarly, the term paper web W is also not limited to a specific basis weight range, and may be used; ..; i '30 also includes a tissue paper or cardboard web.

: V. The pressure-sensitive membrane sensor 2 is placed on a curved surface used in a known type of beam 1, curved in the direction of travel of the web, e.g., over a beam '*; · *. There are several membrane sensors of the same type, • as separate sensors across the machine. In the case shown in Fig. 2: * ·: the sensors 2 are in strips of a certain width, e.g.

10 mm wide strips. The curved surface creates an air gap between the film ribs 113 and the paper web W, and the pressurized air pressure on the film at the tight points of the paper causes a greater pressure / force on the film surface than the loose points, resulting in a paper profile tension profile. The sensitivity of the membrane sensor 2 5 can be adjusted by placing several membranes on top of each other. The diaphragm can register even small changes in compressed air pressure. The sensor film can be protected from mechanical wear either by a metal plate or by a protective film 4 without compromising the measurement accuracy of the film. The thickness of the shielding material is selected taking into account the quality of the material and the sensitivity of the diaphragm sensor below, so that sufficient measurement sensitivity is maintained. Figure 2 shows the bar 1 from above, showing how the diaphragm sensors are at a given pitch in the cross machine direction.

The solution of Fig. 1 also has the advantage of reducing the space requirement outside the measuring beam 1 15, since in the membrane application the amplifier cards 3 from which the signals are output are located inside the beam 1. The beam thus directly outputs the measured values as electrical signals along a line L through which the signals pass to a data processing unit (not shown) where the signals are processed and functions performed to obtain a tension profile. The data processing unit is a part of process automation, and through this, tension information can be utilized in process control and monitoring.

Figure 3 is a perspective view of another embodiment of the apparatus 25 in which pressure-sensitive membrane sensors 2 of the same type are disposed on a rotating roll 5 having a jacket contacting a continuous member passing through the roll in a particular sector such as paper web or fabric F (e.g., wire or felt). The sensors 2 can be arranged separately, e.g., on a band which is attached to the roll shell in the axial direction of the roll. The diaphragm 30 sensors 2 operate in the same manner as in Figures 1 and 2, i.e. they convert the pressure (mechanical: v. Input) of a passing continuous body into a suitable wired or wireless communication line • · conductive, pressure or force-proportional output - *; · 'to a large, e.g. electronic signal. As the roll rotates, signals proportional to the rotation values must be received by the off-roll data - *: · *: processing system on your wireless device. The electronics required for transmitting the signals are housed in a small transmitter box 6 at the end of a line of membrane sensors 2 113804 6 at the end of the roll shell. Near the end of the roll is a receiver unit 7, opposite which the transmitter box 6 comes once during each roll of the roll. Figures 4 and 5 illustrate how there may be two receiver units 7, the first one in the circumferential loading area of the roll and the second in the unloaded area opposite the end of the sheath, for example as shown in diameters on opposite sides of the roll. Thus, with a row of sensors 2 or a similar grouping unloaded, with the transmitter box 6 at the second receiver unit 7, reference values 10 corresponding to zero load are obtained for the same sensors. From the receiver unit 7, the measurement signal can be applied along a fixed communication line L to a data processing unit.

Again, in this roller-driven option, the sensors can be protected by a topsheet, such as 15 plastic or metal, and the thickness of the protective material is selected taking into account the nature of the material and the sensitivity of the membrane sensor below.

The tension profile of the wire or felt on the roller 5 can also be measured at the point where the paper web is over the wire or felt, since the effect of web tension is usually so small that it does not interfere with the measurement. On the other hand: a sudden change in the tension value can be used to identify a situation where:. : The web is no longer on the wire or felt, so a web break can be detected.

* · • * · y. '.' The above-mentioned piezoelectric membranes, such as a thin (usually less than 1 mm) EMF film having a cellular structure and a permanent electrical charge due to a change in the electrical output signal, can be used as membrane sensors, which is most pronounced as a change in the thickness of the empty cells' 30 as. This is a change based on the microstructure of the film. Such a membrane sensor acts as a type of capacitor in the measurement. I can. Another relevant film sensor is a piezoelectric film based on the properties of the film material, for example PVDF (polyvinylidene fluoride film). This membrane is also capable of transforming the mechanical inlet quantity (pressure or force) into an electrical output: ·: · which can be processed by measurement techniques. Another type of sensor is the so-called sensor. A PLL sensor (piezo-pyroluminescent sensor) which, under the influence of a pressure applied to a membrane sensor, is capable of generating an optical signal whose intensity is directly proportional to the pressure. The output quantity is then optical instead of electronic, and can also be processed by a measuring technique, and such a signal can be converted at a suitable stage into a second proportional amount, e.g. an electronic signal, for further processing of the data.

Because the EMF membrane is particularly capable of measuring dynamic changes, it is advantageous to use it in the above-described alternative 10 using roll 5 where it is momentarily subjected to the pressure of the paper web or fabric as it moves to an area where the web or fabric covers the roll outside this sector it is free of load. However, the EMF film may also be used in a transverse beam measuring 15 webs. The suitability of the diaphragm for measuring dynamic changes can then be used, for example, by lowering the measuring bar from the web at intervals of a few minutes and performing a reset in this state. The beam may then be raised again to the measuring position for the next measuring cycle 20. Similarly, a membrane sensor that measures well static pressure, such as a PVDF sensor or a PLL sensor, is preferably suitable for use in measuring equipment where it is continuously under pressure from the web or tissue, as is the case with the sensors in the static measuring bar 1. However, the PVDF sensor and the PLL sensor 25 may also be used in a rotating roll 5.

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Embodiments not included in the invention are described above with respect to sensor placement. The positioning of the sensors may also be different from that described above. In the case of the rotating roller 5, the sensors may be arranged side by side in an axial row, as shown in Fig. 3, but the group formed by them may also be arranged in angular direction. to be inclined with respect to the axial direction of the roll, i.e. the axis of rotation. In this case, only a part of the sensors can in turn become pressurized, i.e. located in the sector where the web W or the web F covers the surface of the roll shell 35, i.e., measurement at different points is done at different times of roll rotation: · *! at intervals depending on the speed. In an embodiment of the invention, the membrane sensor 2 is in a roll as a continuous strip which is helically wound around the roll. If such a tape rotates, for example, 360 ° around the roll, there is always a certain proportion thereof under the pressure exerted by the web or fabric, and this arrangement also provides information on the tension profile during one spin of the roll, though not as good resolution as separate placed sensors.

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Claims (9)

A method of measuring the voltage of a continuous means running in a paper machine or a finishing machine for paper, such as a web (W) or a tissue, the measurement being carried out at several different places in the transverse direction of the moving member with a pressure sensitive film sensor. (2) located in a roller (5) which is stored rotatingly and through which the continuous moving member moves, characterized in that the pressure-sensitive film sensor (2) is positioned as a continuous band in a spiral-like manner around the roller ( 5). 2. A method according to claim 1, characterized in that the continuous moving member whose tension is measured is a paper web (W). 15 Method according to claim 1, characterized in that the continuous moving means whose tension is measured is a tissue (F) of a paper machine or a paper finishing machine. 20 4. A method according to any of the preceding claims, characterized in that the film transducer (2) converts the force or pressure which · · · · affects the same to a proportionally measured measuring signal which is controlled: along a wired or wireless data transmission line, possibly by convert it in between, to a data processing unit. 25 5. A method according to claim 4, characterized in that the film transducer (2) converts the force or pressure acting on it into a proportional electrical or optical measuring signal. 30 Method according to claim 5, characterized in that the film encoder (2) is an EMFI film or a PVDF film or a piezo and pyro: v, lyminescent (PLL) encoder. • · »· 7. A method according to any of the preceding claims, characterized in that, with the measurement of the voltage, the voltage ·: · 1: profile is determined by a continuous member, such as a web (W) or a tissue (F). · 113804 Apparatus for measuring the tension of a continuously moving member, such as a web or tissue of a paper machine or a paper after-processing machine, comprising a pressure sensitive film transducer 5 (2) located in a roller (5) which is stored rotating ooh through which the continuous movable member is arranged to move, and in the transverse direction of the movable member several measuring points in which the pressure-sensitive film sensor (2) is arranged to measure the voltage, characterized in that the pressure-sensitive film sensor (2) ) is positioned as a continuous belt in a spiral-like manner around the roller (5). 9. Device according to claim 8, characterized in that the film encoder (2) is of such a type that can convert the force and pressure acting on it to a proportionate electrical or optical measuring signal, such as an EMFI film or a PVDF. film or a piezo and pyrolyminescent transducer (PLL transducer). 1 · • · Mill