Monitoring apparatus

Abstract: There is provided a monitoring apparatus for preventing paper breakage. For this monitoring apparatus, a light source 9 is disposed on the upper side of a wet paper 1, and a light emitting face thereof faces downward. An operation-side camera 5a and a drive-side camera 5b are disposed on the side opposite to the light source 9 with respect to the wet paper 1, and a lens face thereof faces upward. Light 9a of the light source 9 passes through the wet paper 1 after being reflected from a mirror 11, and is caught by the cameras 5a and 5b. Thus, the cameras 5a and 5b photograph a silhouette (image) of the light 9a of the light source 9, which has passed through the wet paper 1. This image is sent to an image processing unit 6, where the image is processed. The coordinates of a boundary line such that the wet paper 1 separates from a centre roll 2 is detected from the images photographed from two directions. This coordinate value is sent to a computer 8. The computer 8 converts the value into a movement amount in each sampling cycle to determine the change amount and frequency of a point 3 at which the paper separates from a roll and the whole shape of separation lines 3a and 3b. Thereby, a machine problem resulting in paper breakage can be predicted.

Description: The present invention relates to apparatus for monitoring a band-shaped object or ribbon of material running continuously and, more particularly, to apparatus for monitoring the flow of paper in, for example, a paper machine. For a conventional paper machine, through which paper is run by rolls, stable operation is achieved by a roving operator periodically checking the machine's conditions of operation. To detect the occurrence of paper breakage, otherwise known as paper cut, a paper cut detecting sensor is installed on the machine. The sensor may consist, for example, of an infrared source disposed on one side of a running paper and a detector disposed on the other side of the paper. A paper cut is recognised by the detection by the detector of infrared radiation from the source. With a paper cut detecting sensor of the type exemplified above, although the occurrence of paper cut may be identified, its cause may not be determined. For this reason, in recent years, paper conditions in a paper machine have been monitored by installing a camera and a light source. Also, the conditions have been recorded on a video cassette recorder or a digital memory, and the state of the paper at breakage can be assessed from playing back the recording. Thus, the operator can understand the cause for paper cut. However, recording provides only the possibility of assessing the cause of paper cut after it has occurred, but does not enable the prevention of paper cut. EP-A-0 329 889 on which the preamble of claim 1 is based describes a method and apparatus for monitoring the quality of a web being formed. The quality is monitored by measuring the variation in transmitted light across the width of the web so as to assess uniformity or otherwise of fibre density in the web. US-A-4 791 304 also measures web quality by transmitted light by the use of scanning light beam reflected from a rotating polyhedral mirror. DE-B-1 098 739 is concerned with checking sheet material which has optically detectable irregularities on the surface by scanning a light beam thereacross. WO98/27275 describes a system for monitoring the separation of a paper web from a roll by use of a laser-Doppler measuring device. WO99/60204 describes a method for determining the detaching angle of a paper web from a roll using video photography. The present invention has been made in view of the above described situation, and accordingly an object thereof is to provide apparatus for monitoring paper run through a paper machine, which diagnoses a problem with the machine and prevents paper breakage. Further, another object of the present invention is to monitor the path of a running ribbon of material to prevent abnormal running of the ribbon. To achieve the above objects, the present invention provides apparatus for monitoring paper run by rolls through a paper machine comprising means for projecting light at the paper, means for forming an image of the light which penetrates the paper, means for processing the image the apparatus being characterised in that the image processing means detects a boundary between said roll and the paper from the image of the forming means, and to obtain a point at which the paper separates from said roll and by means for diagnosing a problem with the machine if the position variation quantity exceeds a predetermined value, and using the output of the processing means to determine a position change in the point. The present invention can be used, for example, in a paper machine to monitor paper at a location where it is easily broken. That is to say, light from a light source may be caused to penetrate a running paper in the paper machine, an image may be formed of the running paper using the transmitted light, and the image may be processed, by which the amount of change in the point at which the running paper separates from a roll (the separation point) is monitored quantitatively to diagnose a problem of the paper machine. The present invention further provides apparatus for monitoring paper run by rolls through a paper machine comprising means for projecting light at the paper, means for forming an image of the light which penetrates the paper, means for processing the image and means for diagnosing a problem with the machine using the output of the processing means to determine a change in the point at which the paper separates from one of the rolls. In particular, the present invention can be applied even when there is deterioration, which will have an effect upon image forming, in the environment including the region being monitored, for example, by the occurrence of mist. In this case, as the light source of the light projecting means, a metal halide lamp is preferably used. It is preferable that the conditions upon the basis of which a problem is diagnosed (the problem diagnosis conditions) be set in advance based on the normally allowable amount of change of the separation point. When the problem diagnosis conditions are influenced by various environmental factors, it is preferable that the problem diagnosis conditions be changeable with the change in the environmental factors. For example, the conditions for diagnosing a problem in the diagnosis means may be capable of change according to the basis weight and draw amount of paper. When a machine is judged to have a problem, a configuration for automatic control for returning the machine operation to normal is most preferable. Specifically, when a problem is diagnosed, paper cut is prevented by further providing control means for controlling the draw amount in response to the diagnosis of a problem. The image forming with the image forming means is performed by a plurality of image forming devices. The specific region being monitored is divided into a plurality of portions and images are formed of each portion by one of the image forming devices. Also, the processing in the image processing means are performed with the plurality of images formed by the plurality of image forming devices. When the object or ribbon is a paper (running wet paper) in a paper machine, and the state of the paper is monitored, the most preferable configuration is such that (1) the image forming direction of the image forming means and the position of light projecting means are in an opposite positional relationship with respect to the paper, (2) in the image processing, the amount of change of the separation point is monitored quantitatively to diagnose a problem of the machine, (3) the problem diagnosis conditions are changed according to the basis weight and draw amount of paper, and (4) the draw amount is automatically controlled according to the result of problem diagnosis to prevent paper cut. The basis weight in this specification is a weight per one sheet of paper of 1m 2 . The draw amount is the degree of tension in the paper between parts of a paper machine, and is determined by the difference in speed between the driving rolls of sections of the machine. As is apparent from the above description, the present invention achieves the effects described below. In the present invention, light from a light source is caused to penetrate a band-shaped object running continuously, the object is photographed by using the transmitted light, and the image is processed, by which a change amount relating to the running path of the object is quantitatively monitored. Therefore, the change in running of the object can always be grasped, so that accurate monitoring can be performed. Also, the monitoring apparatus in accordance with the present invention comprises light emitting means for causing light to fall on a paper run by rolls in a paper machine, photographing means for photographing the light penetrating the paper from the light emitting means, image processing means for processing the image of the photographing means, and diagnosis means for diagnosing a trouble of the paper machine by quantitatively monitoring the change amount of separation point from the roll based on the processing results of the image processing means. Therefore, the change in running of the object can always be grasped, so that accurate monitoring can be performed. If a metal halide lamp is used as the light source of the light emitting means, the separation from the peripheral equipment can be made well in the image processing, so that accurate monitoring can be performed even when the photographing environment is adverse. If the trouble diagnosis conditions are made capable of being changed according to the basis weight and draw amount of paper in the diagnosis means, the diagnosis accuracy is improved, and most preferable monitoring can be performed. If controlling means is further provided to control the draw amount according to the diagnosis result when a trouble is diagnosed, paper cut can be prevented by correcting the shape of profile, and a press part etc. can be controlled. If the configuration is such that the photographing with the photographing means is performed by different cameras for regions provided by dividing the portion to be monitored, and the processing in the image processing means is performed with a plurality of images obtained by photographing the different regions, the effect of the photographing environment can further be reduced, and the change in the object or the running paper can be grasped exactly, so that more accurate monitoring can be performed. The invention also provides a method of monitoring paper run by rolls through a paper machine comprising determining the amount of change in a point at which the paper separates from one of the rolls and diagnosing a problem with the machine when the amount exceeds a predetermined level. The invention will now be described, by way of example, with reference to the following drawings, in which: FIG. 1 is a side view schematically showing a press part of a paper machine to which a monitoring apparatus in accordance with one embodiment of the present invention is applied; FIG. 2 is an enlarged view of a centre roll outlet at the press part shown in FIG. 1; FIG. 3 is a system block diagram for a monitoring apparatus in accordance with one embodiment of the present invention; FIG. 4 is a configuration view of hardware shown in FIG. 3; FIG. 5 is a perspective view schematically showing a positional relationship between an operation-side camera, a drive-side camera, a centre roll, and a wet paper; FIG. 6(a) is a view showing a typical image photographed by an operation-side camera 5a, and FIG. 6(b) is a view showing an image photographed by a drive-side camera 5b in this case; and FIG. 7 is a graph obtained by the processing performed by an image processing unit and a computer, FIG. 7(a) showing a change in separation point, in which the ordinates represent the change amount from the reference and the abscissas the time (s), and FIG. 7(b) showing a separation line at a certain time, in which the ordinates represent the change amount from the reference and the abscissas the position in the width direction of a centre roll 2. An embodiment of a monitoring apparatus in accordance with the present invention will now be described with reference to the accompanying drawings. The following is a description of a case where a monitoring apparatus in accordance with one embodiment of the present invention is applied to a paper machine. In this case, the monitoring apparatus monitors the operation conditions of the paper machine. A paper machine broadly includes a stock inlet, a wire part, a press part, and a dry part. Additionally, it is usually provided with a calender part and a reel part. As one example, a papermaking process in the case of a Fourdrinier paper machine will be explained. Carefully selected pulp liquid is sprayed from the stock inlet onto an endless wire. The pulp liquid is dehydrated in a suction box, and passes through a slice and gets a fixed thickness. At the press part, a felt is turned together with press rolls to squeeze water and at the same time to smoothen the surface of paper (formation of web). Subsequently, the paper is heated to dry at the dry part. At the calender part, the paper surface is smoothened and calendered. Finally, the web is wound by the reel part. Next, the press part at which the monitoring apparatus is disposed will be explained. The press part of this embodiment shown in FIG. 1 has four-stage presses of a first press (1P) to a fourth press (4P), and is provided with a centre roll 2, press top rolls 14, press bottom rolls 15, suction rolls 16, and a paper roll 4. A wet paper 1 is conveyed in the direction of arrow A by these rolls 2, 14 to 16, and 4, and a felt 17. This wet paper 1 is a web that has been formed at the wire part and transferred to the press part. To clean the centre roll 2, a shower (not shown) is provided in the vicinity thereof. At the centre roll section of the press part, the wet paper 1 is separated from the felt 17. Further, as shown in FIG. 2, the wet paper 1 is separated from the surface of the centre roll 2 at a separation point 3 (separation), and is transferred to the next process via the paper roll 4. At this separation point 3, the wet paper 1 is not supported by the felt 17 or the like (open draw). Therefore, paper breakage (paper cut) occurs most frequently at this point. Thus, monitoring of the separation point 3 is a great need for stable operation of machine without paper breakage. The monitoring apparatus in accordance with one embodiment of the present invention monitors the change around the separation point 3. Next, elements of the monitoring apparatus will be explained with reference to FIG. 3. The monitoring apparatus comprises image forming means constituted by an operation-side camera 5a and a drive-side camera 5b, an image processing unit 6, a monitor TV 7, a computer 8, a light source 9, a motor 10, and a mirror 11. The motor 10 and the mirror 11 constitutes a scanner 12 for scanning with light 9a of the light source 9. The monitor TV 7 displays the cross sections of the centre roll 2 and the paper roll 4 and the shape of the running wet paper 1 and the separation line 3a, 3b thereof as shown in FIGS. 6(a) and 6(b), for example. The operation-side camera 5a and the drive-side camera 5b are connected to the image processing unit 6. This image processing unit 6 is connected to the monitor TV 7 and the computer 8. This computer 8 is connected to the scanner 12. The mirror 11 of this scanner 12 is mechanically connected to the motor 10 so that the direction of the surface thereof is changed by the motor 10 (see arrow B in FIG. 4). As this mirror 11, for example, a galvanometer-mirror or a polygon-mirror can be used. This galvanometer-mirror or polygon-mirror is a rotating member having a series of planar reflecting surface, and is used in a scanning system for reflecting light from a light source from a scanned object. As the light source 9, a metal halide lamp is used in this embodiment. This metal halide lamp is a high intensity discharge lamp in which light is emitted by electric discharge in a mixture of metallic vapour and dissociation product of halide, serving as a powerful light source with a flat wavelength distribution. By using this metal halide lamp, the paper can be separated well from the peripheral equipment in image processing by making the best use of a feature of the wet paper 1 being white. Next, a positional relationship between the operation-side camera 5a, the drive-side camera 5b, the centre roll 2, and the wet paper 1 will be explained with reference to FIGS. 4 and 5. As shown in FIG. 5, the operation-side camera 5a and the drive-side camera 5b are arranged in parallel. The operation-side camera 5a is disposed on the operation side of the centre roll 2, and the drive-side camera 5b is disposed on the drive side of the centre roll 2. The operation-side camera 5a and the drive-side camera 5b photograph a change in separation point. Specifically, a separation line 3a (indicated by the broken line in FIG. 5) on the operation side from the centre in the axial direction of the centre roll 2 is photographed by the operation-side camera 5a, and a separation line 3b (indicated by the solid line in FIG. 5) at the remaining half portion is photographed by the drive-side camera 5b. In FIG. 5, the separation line 3a is indicated by the broken line. However, this broken line does not mean a hidden line, and is used to distinguish it from the separation line 3b in this figure. The separation point 3 in this embodiment is defined as a point where the paper edge of the wet paper 1 separates from the centre roll 2, and the separation line 3a, 3b in this embodiment is defined as a line connecting positions where the wet paper 1 separates from the centre roll 2 at an arbitrary position along the axial direction of the centre roll 2 at a certain point of time. As shown in FIG. 4, the light source 9 is disposed on the side opposite to the operation-side camera 5a and the drive-side camera 5b with respect to the wet paper 1. The operation-side camera 5a and the drive-side camera 5b are arranged on the lower side of the centre roll 2, and the lens faces thereof face upward obliquely. The light 9a of the light source 9 passes through the wet paper 1 after being reflected from the mirror 11, and is caught by the operation-side camera 5a and the drive-side camera 5b. In other words, the operation-side camera 5a and the drive-side camera 5b photograph a silhouette (image) of the light 9a of the light source 9, which has passed through the wet paper 1. This configuration can provide a clearer image. The reason for this is as follows: At the press part, a mist is easily produced by the aforesaid shower. Although light is generally irradiated from the same place as the camera, in such a place having an influence of mist, the separation point 3 and the separation lines 3a and 3b cannot be observed by the installation of ordinary cameras only, conjointly with a reason of less space. Also, at such a place, an image obtained by causing the light 9a to pass through the wet paper 1 is clearer than an image obtained by reflecting the light 9a from the wet paper 1. Also, the photographing by using two cameras can increase the accuracy of change amount. The reason for this is as follows: If photographing is performed from only one direction, for example, on the operation side, the image cannot be photographed enlargedly, so that a high detection accuracy of separation line cannot be obtained over the whole width. Specifically, because the photographing region differs between the nearby part and the distant part, although the accuracy is high at the nearby part, the accuracy at the distant part is poor. When photographing is performed from both of the operation side and the drive side to obtain images up to a position near the centre of the centre roll 2, the separation line can be photographed enlargedly, and a detection accuracy that is double the accuracy provided by the photographing on one side only can be obtained. Further, because the influence of mist can be reduced, the detection accuracy can be increased further, so that a clear image can be obtained. Additionally, if the number of cameras for photographing from one side is increased (for example, two, three, and so on) to perform photographing dividedly, the accuracy increases further including a reason of a reduction in the influence of mist. Thus, the portion to be monitored is divided into many regions, and each divided region is photographed by a different camera. The number of cameras is equal to the number of divisions. The following is a description of the processing of image thus obtained. Outlining with reference to FIGS. 3 and 4, the images photographed by the operation-side camera 5a and the drive-side camera 5b are inputted to the image processing unit 6 (see signal 13A in FIG. 4), where the images are processed, and the change amount of separation point is quantified. FIG. 6 shows examples of the images photographed by the operation-side camera 5a and the drive-side camera 5b. In FIG. 6(a), the separation line 3a on the operation side is given, and in FIG. 6(b), the separation line 3b on the drive side is given. The image processing unit 6, which uses an image processing method such as a spatial filter, detects the boundary line between the centre roll 2 and the wet paper 1 with an image plane co-ordinate system (a two-dimensional plane co-ordinate in which the upper left point of image is taken as (0, 0)) from the images photographed from two directions in such a way (see FIGS. 6(a) and 6(b)). The detected co-ordinate values are sent to the computer 8 according to the sampling cycle (see signal 13B in FIG. 4). Specifically, the separation point of the wet paper 1 from the roll, which is shown as a boundary line of light and shade by using transillumination, can be extracted by a method such as a spatial filter for detecting an edge, which has generally been used in image processing. The co-ordinates on the image plane of the extracted separation lines 3a and 3b are sent to the computer 8. The computer 8 converts the received plane co-ordinates into movement amount in each sampling cycle. In other words, the computer 8 determines the change amount and frequency of the separation point 3 of the paper edge and the whole shape of the separation line 3a, 3b from the received co-ordinate by computation. Specifically, if the installation position of camera is determined, the roll edge face and the roll intermediate portion of the three-dimensional orthogonal co-ordinate system are made have correspondence to a position on a planar image in advance, and a position on the plane co-ordinates can be converted into a position on the three-dimensional orthogonal co-ordinate system. For example, conversion is made into an orthogonal co-ordinate system in which the roll cross section is the XZ plane and the roll width direction is the Y axis. The computation results are sent to the image processing unit 6 (see signal 13C in FIG. 4), and are outputted to the monitor TV 7 (see signal 13D in FIG. 4). The computer 8 outputs a control signal to the motor 10 (see signal 13E in FIG. 4). The computer 8 carries out control to synchronise the operation-side camera 5a, the drive-side camera 5b, the image processing unit 6, and the scanner 12. Although basically, the camera system cannot accommodate a frequency higher than 60 Hz, the change frequency of separation point is lower than 60 Hz, so that there is actually no problem. Next, graphs obtained by the above-described processing will be explained with reference to FIG. 7. FIG. 7 (a) shows a change in separation point, in which the ordinates represent the change amount from the reference and the abscissas the time (s), and FIG. 7(b) shows a separation line at a certain time, in which the ordinates represent the change amount from the reference and the abscissas the position in the width direction of a centre roll 2. With the apparatus of this embodiment, since a mechanism in which photographing is performed while scanning with the light 9a of the light source 9, the separation line at the same time as that of FIG. 7(b) cannot strictly be obtained. However, since the scanning speed is high, the shift of time of one scan is neglected. The separation point 3 at the paper edge on the operation side changes as shown in FIG. 7(a). The state of change can be understood by this graph. Therefore, the allowable values (trouble or problem diagnosis conditions) of the change amount and frequency of the separation point 3 can be set in the computer 8. In setting these trouble diagnosis conditions, the conditions can be changed appropriately according to the basis weight and draw amount of paper. Although the computer 8 has a function of quantitatively monitoring the change amount of separation point and diagnosing a trouble or problem of the paper machine (diagnosis means) in this embodiment, diagnosis means may be provided separately from the computer 8. Also, if the movement amounts at positions in the paper width direction of wet paper 1 (the width direction of the centre roll 2) are connected, the shape of separation line 3a, 3b can be determined. That is to say, unlike FIG. 7(a) showing one point, the change in the width direction can be found. If the shape of separation line at the normal time has been determined in advance, the change amount can be determined. Therefore, the trouble diagnosis conditions can be set as the change amount with respect to the shape of the separation line 3a, 3b at the normal time. For example, when the change amount of at least one point of separation points exceeds a predetermined value, the machine can be judged to have a trouble. However, needless to say, the method is not limited to this. In this case as well, the conditions can be changed appropriately according to the basis weight and draw amount of paper. Thus a machine trouble resulting in paper breakage can be predicted. Also if such trouble occurs, for example, an alarm can be given to tell the operator the occurrence of trouble. Therefore, the draw amount can be changed before paper breakage occurs. That is to say, by changing the draw amount, the press part can be controlled so as to correct the shape of profile. The change amount of separation point and the shape of separation line are important in predicting paper breakage, and paper breakage can be prevented before it happens. The configuration may be such that the draw amount can be controlled automatically by control means (not shown) connected to the computer 8. In addition, by the shape of separation line and the magnitude of change amount of separation point, the change time of a tool such as the felt can be identified. Immediately after the change of felt, if the draw is constant, the dehydration state is poor, and the separation point changes. By changing the draw, the separation point is controlled to a fixed separation position. In two or three days, the felt adjusts itself to the machine, so that the dehydration state is improved. Therefore, by changing the draw, the separation position is set at a predetermined position. If the machine is operated in this state, the dehydration state becomes poor after a certain period of time, and the separation point changes, so that the tool must be changed at an earlier time. Therefore, the dirt and surface condition of the changed felt are analyzed quantitatively and are used as a data base together with the draw amount and the change amount of separation point, by which a proper change time considering both of the paper quality and the economical condition of tool cost etc. can be identified.

Claims: Apparatus for monitoring paper (1) run by rolls (2,4,14,15,16) through a paper machine comprising means (9) for projecting light at a part where the paper (1) separates from a roll, means (5) for forming an image of the light which penetrates the paper (1), means (6) for processing the image to detect a boundary between said roll and the paper (1) from the image produced by the image forming means (5) and to obtain a point (3) at which the paper (1) separates from said roll, means (8) for diagnosing a problem with the machine if the position variation quantity of the point of separation (3) exceeds a predetermined value, and using the output of the processing means (6) to determine a position change in the point (3) the apparatus being characterised in that the paper (1) is divided into a plurality of portions in the width direction and the image forming means comprise a corresponding plurality of image forming devices (5) each forming an image of one portion, and the image processing means (6) processes the plurality of images formed by the plurality of image forming devices (5). Apparatus according to claim 1 wherein a metal halide lamp (9) is used as a light source in the light projecting means. Apparatus according to either claim 1 or claim 2 wherein the conditions upon the basis of which the diagnosing means (8) diagnoses a problem are changeable according to the basis weight and draw amount of paper (1). Apparatus according to claim 3, further comprising control means for controlling the draw amount in response to the diagnosis of a problem. A method of monitoring paper (1) run by rolls (2, 4, 14, 15, 16) through a paper machine, the method including the steps of: providing means (9) for projecting light at a part where the paper (1) separates from a roll; providing means (5) for forming an image of the light which penetrates the paper (1); providing means (6) for processing the image to detect a boundary between said roll and the paper (1) from the image forming means (5) and obtaining a point (3) at which the paper separates from said roll, providing means (8) for diagnosing a problem with the machine if the degree of position variation of the point of separation (3) exceeds a predetermined value, and using the output of the processing means (6) to determine a position change in the point (3) the method being characterised by dividing the paper into a plurality of portions in the width direction and by providing a corresponding plurality of image forming devices (5) each forming an image of one portion and the image processing means (6) processing the plurality of images formed by the plurality of image forming means. A method according to claim 5 further including the step of controlling the draw amount in response to diagnosis of a problem by the problem diagnosing means.

Inventors: IWATA HIROSHI, KAKU MASATOSHI, KODAKA ISAO, OGAWA MASAYUKI, SUZUKI SETSUO, TOKUDOME TOSHIRO, USOGOE HISAO, YAMASHITA HIROSHI, IWATA, HIROSHI, KAKU, MASATOSHI, KODAKA, ISAO, OGAWA, MASAYUKI, SUZUKI, SETSUO, TOKUDOME, TOSHIRO, USOGOE, HISAO, YAMASHITA, HIROSHI, Iwata, Hiroshi, Hiroshima R &amp; D Center, Suzuki, Setsuo, Mihara Michinery Works, Yamashita, Hiroshi, Hiroshima R &amp; D Center
Applicants: MITSUBISHI HEAVY IND LTD, OJI PAPER CO, MITSUBISHI HEAVY INDUSTRIES, LTD., OJI PAPER CO., LTD.
Application year: 1999
Main classification: B65H26
IPC codes: D21F7, B65H26