WO2012085338A1

WO2012085338A1 - Paper machine belt, belt manufacturing method, and arrangement in connection with paper machine

Info

Publication number: WO2012085338A1
Application number: PCT/FI2011/051115
Authority: WO
Inventors: Rauno Enqvist; Juha METTÄLÄ; Petri M. NIEMINEN
Original assignee: Metso Fabrics Inc.
Priority date: 2010-12-22
Filing date: 2011-12-16
Publication date: 2012-06-28
Also published as: FI20106362A0; FI20106362A; FI123001B

Abstract

The invention relates to a paper machine belt, a method of manufacturing a paper machine belt, and to an arrangement in connection with a paper machine. The paper machine belt (1) is provided with at least one sensor (3). The sensor is arranged in a recess (8) provided in the structure of the belt. The recess (8) is covered by at least one separate protective layer (9), the sensor thus being under protection in a sensor space defined by the structure of the belt and the protective layer.

Description

Paper machine belt, belt manufacturing method, and arrangement in connection with paper machine

Background of the invention

[0001] The invention relates to a paper machine belt which is provided with one or more sensors attached to the fabric.

[0002] The invention further relates to a method of manufacturing a paper machine belt, and to an arrangement in connection with a paper machine.

[0003] The field of the invention is described in more detail in the preambles of the independent claims of the application.

[0004] Paper machine belts include wet wires, drying wires, press felts, shoe press belts, conveyor belts as well as other support bands which participate in processing a fibrous web in a paper machine, a cardboard manufacturing machine or a cellulose processing machinery. The purpose of paper machine belts may be to support and convey the fibrous web in the machine. In addition, they may participate in water removal. Paper machine belts may be woven from synthetic yarns on a weaving machine. Alternatively, the basic structure of paper machine belts may comprise a non-woven type of a yarn arrangement which may be wound, for instance. Further, instead of yarns, a paper machine belt may comprise another fibrous material. In this application, a paper machine belt refers to all band-like products used in paper machines, cardboard manufacturing machines and cellulose industry devices and arranged against the fibrous web as well as to cylindrical roll coverings irrespective of their detailed structure, use and manufacturing technique.

[0005] A paper machine belt may be provided with a sensor for measuring physical properties during use of the belt. However, the task of fastening the sensor to the paper machine belt has turned out to be a difficult one.

Brief description of the invention

[0006] An object of the present invention is to provide a novel paper machine belt, a method of manufacturing a paper machine belt and, further, an arrangement utilizing such a paper machine belt in connection with a paper machine.

[0007] A paper machine belt according to the invention is characterized in that the paper machine belt is provided with at least one recess; the recess is provided with at least one sensor; and the recess is covered by at least one separate protective layer on at least one side of the belt, the sensor thus being under protection in a sensor space defined by the structure of the belt and the protective layer.

[0008] A method according to the invention is characterized by providing the structure of the paper machine belt with at least one recess; arranging at least one sensor in the recess; and covering the recess by at least one separate protective layer, the sensor thus being under protection in a sensor space defined by the structure of the belt and the protective layer.

[0009] An arrangement according to the invention is characterized in that the sensor is arranged in a recess provided in the paper machine belt; and the sensor is covered by at least one separate protective layer.

[0010] The idea is that the paper machine belt is provided with at least one recess wherein at least one sensor is arranged. The recess is covered by at least one separate protective layer. The recess in the structure and the one or more protective layers define a sensor space inside the belt.

[0011] An advantage is that the sensor is arranged in the sensor space inside the structure of the belt, thus being well under protection e.g. from mechanical stress and severe paper machine conditions. The protective layer further gives additional protection to the sensor. Consequently, the solution enables durable and reliable measurement and identification in demanding operational conditions. Furthermore, owing to the protective layer, it may be possible to avoid, or completely prevent, formation of markings caused by the recess and the sensor in the fibrous web being processed. A possible advantage is also that it enables quite a simple and inexpensive manner of fastening different sensors to different paper machine belts.

[0012] The idea of an embodiment is that the recess is formed by removing material from the paper machine belt. In such a case, the basic structure of the paper machine belt may be manufactured by a manufacturing technique being used at a given time without having to take into account the sensor space, its location, size, shape or the number thereof while manufacturing the basic structure. The recess may be formed in a complete or semi- complete paper machine belt in connection with finishing phases thereof.

[0013] The idea of an embodiment is that the recess is formed by removing yarns or parts of yarns from the basic structure of the paper machine belt over the recess. This enables the basic structure of the belt to be manufactured in a normal manner without taking the sensor space into account. The recesses for sensors may be provided in the finishing phases of the paper machine belt. The arrangement enables sensor spaces to be formed even in already existing belts.

[0014] The idea of an embodiment is that the paper machine belt comprises two, three or more machine-direction yarn systems. The recess is formed by removing, at the recess, yarns travelling in the surface of the belt. In such a case, the machine-direction yarns travelling in the surface are also cut and removed at the recess. Since the fabric according to the embodiment includes a plurality of machine-direction yarn systems, one or more intact machine-direction yarn systems are provided at the recess which are capable of receiving machine-direction stresses directed at the belt.

[0015] The idea of an embodiment is that the paper machine belt comprises two, three or more successive independent fabric layers, each layer having a machine-direction yarn system of its own. The fabric layers may be manufactured by weaving simultaneously or non-simultaneously, or the successive fabric layers may be structures formed by a non-woven technique, e.g. wound structures. The fabric layers manufactured in separate phases may be attached to one another e.g. with glue or by a thermal connection technique. One or more recesses for arranging a sensor are provided in the outermost fabric layer of at least one surface of such a paper machine fabric having two or more layers. The recess is formed by removing, at the sensor space, yarns of the outermost fabric layer. The removal of yarns does not make the paper machine belt substantially weaker or otherwise influence its properties, since the other layers of the fabric, and their machine-direction yarns in particular, remain intact at said recess.

[0016] The idea of an embodiment is that the paper machine belt is a woven double-fabric structure provided with a web-side fabric and a machine-side fabric which are interconnected by means of one or more binding yarns or the like. The fabric layers are woven simultaneously on one weaving machine.

[0017] The idea of an embodiment is that the paper machine belt has a basic structure which comprises at least machine-direction yarns. Further, at least one surface of the basic structure is provided with at least one material layer. This material layer may be made e.g. of a polymer material, batt fibre or another coating which has the desired thickness and properties. The recess is formed in this coating layer. The protective layer may be made of the same material as the coating layer or it may be made from a different material than the coating layer. The solution according to this embodiment may be relevant e.g. in shoe press belts which may be provided with a cast surface layer.

[0018] The idea of an embodiment is that the recess is formed by cutting yarns travelling in the surface of the paper machine belt and removing the yarns at the recess. The yarns may be cut mechanically with a knife or a corresponding tool. Alternatively, the yarns may be cut by a laser or another device utilizing electromagnetic radiation.

[0019] The idea of an embodiment is that the recess is formed in the surface of the paper machine belt by grinding or milling or in another manner by removing the material mechanically. This embodiment is particularly useful in situations wherein the height of the sensor being used is very small.

[0020] The idea of an embodiment is that the recess is formed in the paper machine belt by removing material therefrom by a device utilizing electromagnetic radiation, e.g. by a laser or ultrasound grinding. This embodiment enables dimensionally accurate recesses with a good surface quality and demanding shapes to be manufactured.

[0021] The idea of an embodiment is that the recess is formed in the paper machine belt by thermoforming. In thermoforming, material of the belt may be evaporated or flow off the belt or, alternatively, the material of the belt may condense and melt.

[0022] The idea of an embodiment is that the recess is formed in the paper machine belt by compressing it permanently, which results in a recess. The pressing may be carried out in a press and it may utilize moisture and heat.

[0023] The idea of an embodiment is that the recess is formed in the paper machine belt by dissolving material therefrom. While manufacturing the belt, dissoluble yarns, fibres or another material i may be arranged in its basic structure at the desired recess. The material may be soluble in water or in some other solvent. When such a material is dissolved off, a recess is formed therein.

[0024] The idea of an embodiment is that the recess for the sensor space is formed in the basic structure of the paper machine belt during its manufacture. For instance a weaving technique may be used for forming a recess in the fabric by choosing the yarns and the weave appropriately. The surface of the fabric may be provided with a wavelike section by weaving, for in- stance. A technique called tubular weaving may also be utilized in the formation of recesses. Further, one or more appropriate recesses may be formed in paper machine belts comprising cast and coated sections, such as belts, in connection with casting.

[0025] The idea of an embodiment is that a recess is provided on the side of one surface of the paper machine belt. Such a recess which opens out from the basic structure only to the side of one surface of the belt is covered by one or more protective layers on the side of one surface of the paper machine.

[0026] The idea of an embodiment is that the recess resides on the side of one surface of the paper machine belt and has a bottom. The surface of the bottom is smooth, which enables the sensor to be attached firmly against the bottom of the recess. The bottom may be ground smooth.

[0027] The idea of an embodiment is that the sensor is attached to the bottom of the recess by an adhesive. The sensor may comprise a glue surface or it is possible to apply the adhesive to the sensor or to the bottom of the recess. An alternative is that the sensor is provided with an adhesive tape surface.

[0028] The idea of an embodiment is that the recess extends through the basic structure of the paper machine belt from the web-side surface to the machine-side surface. In such a case, the recess opens up in the structure of the belt to both outer surfaces thereof. Consequently, both surfaces of the belt, i.e. the web-side surface and the machine-side surface, are provided with one or more protective layers arranged to define the sensor space. The recess extending through the belt may be formed by cutting with a blade or by die cutting, or it may be formed by a laser or other electromagnetic radiation: Alternatively, such a through-hole may be formed already while manufacturing the structure.

[0029] The idea of an embodiment is that in the plane of the paper machine belt, the recess is defined by the basic structure of the belt. In such a case, the recess, so to speak, is provided with edges. In a direction transverse to the plane of the belt, the sensor space is defined by the bottom of the recess and the protective layer or, if the recess extends through the basic structure of the belt, the sensor space is in the direction transverse to the plane defined by means of the protective layers on both sides. [0030] The idea of an embodiment is that the recess is an elongated groove or slot having a restricted length or, alternatively, the elongated recess may extend continuously in the machine-direction of the belt or it may extend from edge to edge in the transverse direction of the belt. Such a groove may be formed by removing material from the basic structure, or it may be formed while manufacturing the basic structure.

[0031] The idea of an embodiment is that the web-side surface of the paper machine belt is provided with a recess which is provided with a sensor and covered by a protective layer.

[0032] The idea of an embodiment is that the machine-side surface of the paper machine belt is provided with a recess which is provided with a sensor and covered by a protective layer.

[0033] The idea of an embodiment is that the paper machine belt comprises a seam area provided with means for interconnecting the contact ends of a planar belt so as to form an endless loop. The seam area of the paper machine belt is provided with one or more sensor spaces and a sensor arranged therein. The sensor in the seam area may be configured to measure and monitor a tensile stress directed at the seam area, for instance.

[0034] The idea of an embodiment is that the paper machine belt is dimensioned to be wider in the transverse direction than the fibrous web being processed. In such a case, the paper machine belt has a middle section, i.e. a so-called track area, residing at the fibrous web being processed. The track area may be provided with one or more sensor spaces and one or more sensors arranged therein.

[0035] The idea of an embodiment is that the paper machine belt is dimensioned to be wider in the transverse direction than the web being processed, whereby in the middle thereof resides a so-called track area located at the fibrous web being processed. The edge area of the paper machine, i.e. an area outside the track area, may be provided with one or more sensor spaces and one or more sensors arranged therein. In some paper machine applications, the edges of the belt may be subject to heat, blow, pressure, moisture or another stress influencing the strength of the belt that is greater than that in the track area since the edges are not protected by the fibrous web being processed and, furthermore, control members or other actuators may be provided over the edges. Measurement data obtained from the sensor may be used for determining the service life of the belt and for controlling the process. [0036] The idea of an embodiment is that the paper machine belt is a drying wire whose one or both machine-direction edge areas are provided with one or more sensors for monitoring the temperature directed at the edge area. In drying parts that apply a blowing technique, for instance, the edges of the drying wire may be subject to heat that is clearly greater than that in the track area. Measurement data obtained from sensors arranged in the critical edge areas may be used when assessing the strength and service life of the belt and, further, for providing information for controlling the process.

[0037] The idea of an embodiment is that the depth of the recess is between 0.2 mm and 0.5 mm.

[0038] The idea of an embodiment is that the thickness of the protective layer is between 0.3 mm and 1.0 mm.

[0039] The idea of an embodiment is that the protective layer is made of a porous material, in which case it is permeable to liquid and air. Such a porous protective layer enables a discontinuity in the paper machine belt caused by the sensor space to be prevented.

[0040] The idea of an embodiment is that the protective layer is perforated, in which case it is permeable to liquid and air. The protective layer may be provided with a large number of small apertures e.g. mechanically, by a laser or in some other manner.

[0041] The idea of an embodiment is that the protective layer is made of fabric:

[0042] The idea of an embodiment is that the protective layer is woven on top of the recess.

[0043] The idea of an embodiment is that the protective layer is a fabric which is separate from the basic structure. A fabric permeable to steam but impermeable to particles larger than that may be used as such a protective fabric. The fabric mayibe e.g. fabric marketed under the trade name Coretex.

[0044] The idea of an embodiment is that the protective layer is made of a paste, a polymer paste or a silicone paste, for instance. Such a paste is easy to apply to the fabric, and it adheres firmly thereto with no separate means or agents of adherence. The paste may also protect the sensor from moisture and thus improve the durability of the sensor. The paste to be used is chosen such that it does not significantly interfere with propagation of measurement signals. Further, the paste enables the sensor to be supported firmly in place. In addition, an elastic paste is capable of receiving mechanical impacts, thus being able to protect the sensor.

[0045] The idea of an embodiment is that the protective layer only covers the recess and does not extend beyond it. This makes the discontinuity in the belt as small as possible.

[0046] The idea of an embodiment is that the protective layer covers the recess and also extends slightly beyond the edges of the recess. This embodiment is relevant e.g. in situations wherein the adherence of the protective layer is problematic, or when the protective layer is to support the basic structure of the belt around the recess. The protective layer may be fastened at sections which extend beyond the recess.

[0047] The idea of an embodiment is that the protective layer receives forces directed at the paper machine belt. This enables the protective layer to be used for compensating for the reduced strength of the basic structure, which may be caused by yarns having been removed at the recess or by yarns having become thinner due to the influence of grinding, for instance.

[0048] The idea of an embodiment is that once fastened, the protective layer is finished. The outer surface of the protective layer may be made smooth e.g. by grinding, polishing, calendering, pressing or in some other manner. The aim is that the protective layer causes markings and discontinuity as little as possible.

[0049] The idea of an embodiment is that the paper machine belt comprises yarns made of a polymer material.

[0050] The idea of an embodiment is that the paper machine belt is mainly made of metal.

[0051] The idea of an embodiment is that the paper machine belt comprises metallic yarns. The structure of the belt may be made e.g. by weaving from metallic yarns.

[0052] The idea of an embodiment is that the paper machine belt is made of a metal band. The metal band may be provided with recesses e.g. by milling.

[0053] The idea of an embodiment is that the paper machine belt is made of a metal band coated with an appropriate coating once the sensor has been arranged in the sensor space. In such a case, the coating may serve as a protective layer or a part thereof. Brief description of the figures

[0054] Some embodiments will be explained in closer detail in the accompanying drawings, in which

Figure 1 schematically shows a paper machine belt provided with remote-readable sensors,

Figure 2a is a schematic top view showing a part of a paper machine belt according to the invention whose basic structure is provided with a sensor space,

Figure 2b schematically and in cross-section along A - A shows a detail of the paper machine belt of Figure 2a wherein a recess is formed by removing yarns of a surface layer,

Figure 3 schematically shows a detail of a paper machine belt provided with a recess on a side of its one surface,

Figure 4 schematically shows a detail of a paper machine belt wherein a recess extends through the structure,

Figure 5 schematically shows a detail of a paper machine belt wherein a recess is formed by removing material from a surface of the belt e.g. by grinding,

Figure 6 schematically shows a detail of a paper machine belt wherein a recess is provided with a thread-like sensor and wherein the sensor is arranged to be surrounded by a paste,

Figures 7a to 7c schematically and as seen from a machine direction show some solutions for arranging recesses and sensors in a paper machine belt,

Figure 8 schematically shows a paper machine belt which is a double-fabric structure and provided with a sensor space and a sensor,

■ ' ' Figure 9 schematically shows a part of a paper machine and paper machine belts used therein, the figure further illustrating utilization of sensors provided in the belts,

Figure 10 schematically shows a seam area of a paper machine belt with a seam, the seam area being provided with a sensor, and

Figure 11 is a simple diagram showing features and ideas disclosed in this application.

[0055] For the sake of clarity, the figures show some embodiments of the invention in a simplified manner. In the figures, like reference numerals identify like elements. Detailed description of some embodiments

[0056] Figure 1 shows a paper machine belt 1 which is an elongated, band-like piece having a length in a machine direction MD of a paper machine and a width in a cross machine direction CMD of the paper machine. The paper machine belt 1 is run in the machine direction MD of the paper machine. The paper machine belt 1 may be arranged in the manner shown in Figure 1 as a continuous loop to be run on the paper machine. The paper machine belt 1 may be directly made into such a continuous loop, or it may be made into a planar structure with cross-machine-direction CMD connection ends that may be interconnected at a seam point 2 so as to form a continuous structure. Paper machine applications and positions therein also exist wherein the paper machine belts used are not continuous structures.

[0057] The transverse width of the paper machine belt 1 may be equal to that of a fibrous web being processed. In such a case, the entire width of the paper machine belt is a so-called track area K which, during a run, is covered by the fibrous web. Typically, however, the fibrous web is slightly narrower than the paper machine belt 1 , in which case the edges of the belt 1 are provided with narrow machine-direction MD edge areas R. Between the edge areas R resides a middle area, i.e. the track area K. Figure 1 further shows that the paper machine belt 1 has a web-side surface P against which the fibrous web being processed lies during the run, as well as an opposite machine-side surface T residing against rollers or corresponding control surfaces of the paper machine. As already mentioned above, in this application a paper machine belt 1 is construed broadly. Thus, the paper machine belt may be e.g. a wet wire, a drying wire, a press felt, a shoe press belt, a conveyor belt or another support belt participating in processing and refining a fibrous web in a paper machine, cardboard manufacturing machine; cellulose processing machine or the like

[0058] The paper machine belt 1 is provided with one or more sensors 3 arranged in recesses 4 provided in the belt 1 , as shown below in Figures 2a to 8. The sensors 3 may be arranged on a side of the web-side surface P or on a side of the machine-side surface T of the belt 1 or in the middle of the structure of the belt 1 , over a section between the outer surfaces. Measurement data obtained from the sensors 3 may be communicated to one or more control units 4 wherein the measurement data may be processed, stored, and forwarded. The control unit 4 may be arranged in connection with the paper machine, or it may be a mobile terminal device.

[0059] Figure 2a is a top view showing a part of a paper machine belt 1 which may comprise machine-direction MD yarns 5 and cross-machine- direction CMD yarns 6. The belt 1 may be a woven double-layer structure whose layer 7a on the side of the web-side surface P contains machine- direction yarns 5 and cross-machine-direction yarns 6 criss-crossing with one another. Alternatively, the belt 1 may be e.g. a yarn arrangement containing yarns 5 and 6. A layer 7b on the side of the machine-side surface T may be similar to or different from the layer 7a. The surface layer 7a is provided with a recess 8 for a sensor 3 by cutting some yarns 5 and 6 of the surface layer 7a by means of a blade, for instance. Figure 2b shows that the machine-direction yarns 5 of the bottom layer 7b are intact at the recess 8, thereby receiving machine-direction MD stresses directed at the fabric 1. The recess 8 forms a sensor space in which the sensor 3 is arranged and which is protected by one or more protective layers 9. The protective layer 9 may be made of an appropriate paste with which the sensor space is easy to cover. The sensor 3 may comprise a measurement part 3a for measuring one or more physical properties from the fabric. The sensor 3 may further comprise a data communications part 3b which forwards measurement data from the sensor 3 to the control unit. Examples of and more detailed information about the sensor technique will be discussed below in this application.

[0060] In Figure 3, the recess 8 is formed in the surface layer 7a on the side of the web-side surface P of the belt by removing yarns travelling at the recess. The recess 8 is covered by a protection layer 9 which extends beyond the edges of the recess. The protection layer 9 may be e.g. a piece of fabric or another sheet-like piece adhered e.g. by means of stitches, glue, melting, welding or in another appropriate manner to the fabric 1 at adherence points 10 extending beyond the recess 8. The adherence and the protective layer 9 itself may be dimensioned such that the protective layer 9 is capable of receiving forces directed at the belt 1 , enabling the decrease in support for the surface layer 7a caused by the recess 8 to be compensated for.

[0061] In Figure 4, the recess 8 extends from the web-side surface P of the belt 1 to the machine-side surface T thereof. The sensor space thus extends through the belt 1. On both sides, the recess 8 is covered by the protective layers 9. No machine-direction yarns 5 are provided at the recess 8, in which case the protective layers 9 may be arranged such that they participate in transmission of forces in the belt, when necessary.

[0062] In Figure 5, the recess 8 is formed by removing material from one surface of the belt, in this case from the web-side surface P. The material may be removed by grinding, for instance. This is applicable to situations wherein the sensor 3 has a flat structure. When the recess 8 is shallow, the machine-direction yarns 5 remain intact, which is advantageous to the strength and stability of the belt.

[0063] It is to be noted that the solutions shown in Figures 2a, 3, and 5 may, of course, also be applied to situations wherein the recess 8 resides on the machine-side T of the belt. Further, the belt may be provided with a plurality of recesses equipped with sensors, and they may be placed both on the web-side and on the machine-side of the belt.

[0064] Figure 6 shows an embodiment of a solution similar to that of Figure 4. Now the sensor 3 is a thread-like piece arranged in an elongated recess 8 which, in this case, is cross-machine-direction CMD but may alternatively be machine-direction MD. The elongated recess 8 has a predetermined length. The sensor space, defined in plane by the edges of the recess 8 and in a thickness direction by the protective layers 9, may be filled with an appropriate paste 11 , whereby the sensor 3 is well protected inside the belt 1.

[0065] Figure 7a shows a paper machine belt 1 having a recess 8 provided with a sensor 3. The surface of the belt 1 is coated, in which case the coating may form a protective layer 9 or it may be part of a protective layer. The belt 1 may be e.g. a metal band wherein one or more recesses 8 are made e.g. by a chip removal technique.

[0066] Figure 7b shows a structure comprising at least three successive layers 7a to 7c. The outermost layers may be provided with recesses 8 and sensors 3. The sensor spaces may be placed on top of one another, i.e. they are aligned in the thickness direction of the belt 1. The middle layer 7c may be an insulating layer between the sensor spaces, which may be advantageous if the sensors 3 are temperature sensors and the purpose is to measure the temperature of the opposite surfaces of the belt 1. The middle layer 7c may also participate in receiving loads.

[0067] In Figure 7c, both surfaces of the belt 1 are provided with sensor spaces. The sensor spaces may be placed such that they have a distance parallel to the surface of the belt 1 , i.e. they are located at different points in the lateral direction. In such a case, the recesses 8 in the opposite surfaces do not make the structure weaker and yet the sensors in the opposite surfaces, when viewed in the direction of the surface, may be located close to one another.

[0068] The sensor spaces shown in Figures 7b and 7c may reside in the edge area of the belt 1.

[0069] Figure 8 shows a structure of a drying wire, which comprises two fabric layers 7a, 7b. The fabric layers 7a, 7b may be independent woven structures comprising yarn systems of their own. The fabric layers may be woven simultaneously on one weaving machine, and the layers may be interconnected by binding yarns. Transverse filling yarns 6c may be provided between the fabric layers. The recess 8 may be formed in one surface of the fabric 1 , in which case the other fabric layer remains intact. By way of example it may be mentioned that yarns whose cross-section has the shape of a rectangular and whose dimensions are 0.30 ^* 0.80 mm may be used as machine-direction yarns 5a, 5b in such a drying wire. Further, the thickness of the fabric may be 1.5 mm, the depth of the recess 8 may be 0.5 mm, the thickness of the sensor 3 may be 0.2 mm, and the thickness of the protective layer 9 may be 0.3 mm. As the protective layer 9, a dense silicone paste which provides the sensor with a good moisture protection may be used.

[0070] As discussed above, in respect of the basic structure of the paper machine belt, the protective layer 9 is a separate layer or piece which may be attached to the basic structure after arranging the sensor.

[0071] Figure 9 shows a part of a paper machine 12. The paper machine 12 may have several different positions 13a to 13d wherein different paper machine belts 1 may be used for supporting and conveying a fibrous web 14 being processed and for influencing the properties thereof. During use, the sensors 3 arranged in the paper machine belts 1 measure information on r the belt or the process, and measurement data may be read by reading devic- .^'. es 15 which may be fixedly arranged in each position or which may be mobile. The reading devices 15 may forward the measurement data wirelessly or wiredly to one or more control units 4 wherein the measurement data may be processed. Further, the control unit 4 may forward monitoring results to a process control unit 16 and a belt monitoring unit 17.

[0072] Figure 10 shows a paper machine belt 1 comprising a seam area 2. The belt 1 is a two-layered structure comprising a surface layer 7a and a bottom layer 7b. The machine-direction yarns of the bottom layer 7b form a seam loop channel 18 into which a seam yarn 19 is arranged to connect connection ends 20a and 20b. The surface layer 7a may be a woven structure or it may be another structure. The sensor 3 may be arranged in the surface layer 7a, within the seam area 2, in which case the sensor 3 may be arranged to measure e.g. the strain of the machine-direction yarns forming seam loops or another property critical for the strength of the seam. The seam may also be formed by employing another alternative seam technique, e.g. by using a separate seam spiral or a corresponding connection member.

[0073] In Figure 11 , features disclosed in this application that may be applied and combined in many different ways are collected into a diagram.

[0074] The sensor technique will be discussed next. The sensor is configured to measure or monitor physical phenomena the belt is subject to. The sensor may also be configured to measure and monitor physical phenomena for controlling and monitoring the process. The phenomena to be measured include e.g. pressure, acceleration (vibration), temperature, moisture, speed, force (compression, strain), etc. The sensor may transmit measurement data to a control unit and a data acquisition system capable of processing and storing data. The sensor may comprise a transmitter or a transceiver for communicating the measurement data wirelessly to a reading device or directly to the control unit. The sensor may be remote-read untouchably by means of electromagnetic radiation. According to the teachings of physics, electromagnetic radiation is the wave motion of an electromagnetic field. Depending on the wavelength, the electromagnetic radiation used in the identification may be one of the following: radiowaves, microwaves, infrared radiation, light, ultraviolet radiation, X-ray radiation, and gamma radiation.

[0075] The sensor may also comprise identification information, which may be a code, an ID number or the like. In addition to the identification information,, the sensor may comprise at least one other piece of information, which may be e.g. a belt type number, manufacturer information, orderer information, date, order number or another piece of necessary information which may be utilized e.g. in installation, during use, for maintenance, in manufacture or quality control of the belt or for ordering new belts. The sensor may comprise at least one memory wherein, in addition to the identification information, at least one piece of information may be stored. The information stored in the memory may be changed during the process, during repair or washing of the belt as well as during storage thereof.

[0076] The monitoring data obtained from the sensor may be utilized in controlling the process, choosing an appropriate belt, clearing failures as well as in choosing parameters. The enhanced data acquisition system may thus significantly improve the efficiency of the process. Data may be forwarded from the data acquisition system for managing storage of the belts.

[0077] The sensor may comprise a tag responding to radio- frequency electromagnetic radiation. Identification distances and wave trans- mittivity, for instance, may be influenced by using different radio frequencies. The data acquisition system may further utilize tags responding to different frequencies in different elements.

[0078] The sensor may comprise a tag, a transponder containing an antenna for receiving radio-frequency electromagnetic radiation as well as a microchip wherein the identification information is stored.

[0079] The sensor may comprise a so-called Radio Frequency Identification (RFID) tag. The tag may be extremely small, which makes it easier to arrange in the paper machine belt. In addition, the tag is inexpensive, reliable and highly available.

[0080] The sensor may be a passive RFID tag which comprises no power source of its own but the extremely low electric current required by its operation is induced by radio-frequency scanning received by the antenna contained therein and transmitted by the reading device. By means of this induced current, the tag is able to transmit a response to an inquiry sent by the reading device. In other words, the reading device searches through (scans) the environment for a tag, and the tag transmits the ID code stored in the microchip (response) after the scanning has induced thereto the electric current necessary for the transmission. The RFID tag may be read at a radio frequency without visual communication and it may be read even through obstacles. In addition, an RFID reader may read a plurality of RFID tags simultaneously.

[0081] The system may comprise one or more portable electronic terminal devices serving as a reading device. The portable terminal device may be a data acquisition device, portable computer, palmtop computer, mobile telephone or another electronic device provided with the necessary means for remote-reading a tag. The terminal device may comprise a control unit included in the monitoring system. [0082] In some cases, the features disclosed in this application may be used as such, irrespective of other features. On the other hand, when necessary, the features disclosed in this application may be combined to provide different combinations.

[0083] The drawings and the related description are only intended to illustrate the idea of the invention. The details of the invention may vary within the scope of the claims.

Claims

1. A paper machine belt

which is an elongated band-like piece having a machine-direction (MD) length and a cross-machine-direction (CMD) width, as well as a web-side surface (P) on a side of a fibrous web being processed and a machine-side surface (T) on a side of a paper machine; and

which comprises at least one sensor (3) attached to the belt (1); characterized in that

the paper machine belt (1) is provided with at least one recess (8); the recess (8) is provided with at least one sensor (3); and the recess (8) is covered by at least one separate protective layer (9) on at least one side of the belt (1), the sensor (3) thus being under protection in a sensor space defined by the structure of the belt and the protective layer (9).

2. A paper machine belt as claimed in claim 1, characterized in that

the recess (8) is formed by removing material from the paper machine belt (1).

3. A paper machine belt as claimed in claim 1 , c h a r a c t e r i z e d in that

the recess (8) is formed in the structure of the paper machine belt (1) during manufacture thereof.

4. A paper machine belt as claimed in any one of the preceding claims, characterized in that

the recess (8) is provided on a side of one surface of the paper machine belt (1); and

the protective layer (9) covers the recess (8) on the side of one surface of the paper machine belt (1).

5. A paper machine belt as claimed in any one of the preceding claims, c h a r a c t e r i z e d in that

the paper machine belt (1) comprises machine-direction yarns (5) in at least two successive layers (7a, 7b); and

at the recess (8), the machine-direction yarns (5) of at least one layer (7a, 7b) travel intact, receiving machine-direction (MD) stresses.

6. A paper machine belt as claimed in claim 5, characterized in that the paper machine belt (1) is a drying wire woven from a plurality of machine-direction (MD) yarns and a plurality of cross-machine-direction (CMD) yarns;

the paper machine belt (1) is a double-fabric structure provided with two successive independent fabric layers which comprise machine-direction yarns of their own and cross-machine-direction yarns of their own; and

the fabric layers are woven simultaneously on one weaving machine and fastened to one another by a plurality of binding yarns.

7. A paper machine belt as claimed in any one of preceding claims 1 to 3, c h a r a c t e r i z e d in that

the recess (8) extends through the structure of the paper machine belt (1), from the web-side surface (P) to the machine-side surface (T) thereof; and

the protective layers (9) are arranged to cover the recess (8) in the web-side surface (P) and the machine-side surface (T).

8. A paper machine belt as claimed in any one of the preceding claims, c h a r a c t e r i z e d in that

at least one protective layer (9) extends, in the plane of the paper machine belt (1), to an area beyond the recess (8);

the protective layer (9) is attached to the paper machine belt (1) at least in sections extending beyond the recess (8); and

the protective layer (9) is dimensioned to participate in receiving forces directed at the paper machine belt (1) and parallel to the plane thereof.

9. A paper machine belt as claimed in any one of the preceding claims, c h a r a c t e r i z e d in that

the protective layer (9) is made of a moisture-insulating paste.

10. A method of manufacturing a paper machine belt, the method comprising:

forming a paper machine belt (1); and

providing the paper machine belt (1) with at least one sensor (3) configured to monitor at least one physical property and communicate measurement data wirelessly to at least one control unit (4) external to the paper machine belt (1);

c h a r a c t e r i z e d by

providing the structure of the paper machine belt (1) with at least one recess (8); arranging at least one sensor (3) in the recess (8); and

covering the recess (8) by at least one separate protective layer (9), the sensor (3) thus being under protection in a sensor space defined by the structure of the belt and the protective layer (9).

11. A method as claimed in claim 10, c h a r a c t e r i z e d by forming a paper machine belt (1) having machine-direction yarns (5) in at least two successive layers (7a, 7b); and

forming the recess by cutting and removing yarns from one layer (7a, 7b) of the fabric.

12. An arrangement in connection with a paper machine, the arrangement comprising:

a paper machine (12) having a plurality of positions wherein a fibrous web (14) being processed lies against a paper machine belt (1);

a paper machine belt (1) provided with at least one sensor (3) configured to monitor at least one physical property; and

at least one control unit (4); as well as

a wireless data transmission connection for communicating measurement data from the sensor (3) to the control unit (4);

c h a r a c t e r i z e d in that

the sensor (3) is arranged in a recess (8) provided in the paper machine belt (1); and

the sensor (3) is covered by at least one separate protective layer.