WO2003076320A1

WO2003076320A1 - Apparatus and method for winding a paper web and equipment therefor for controlling nip load

Info

Publication number: WO2003076320A1
Application number: PCT/SE2003/000363
Authority: WO
Inventors: Ulf Johan RÅGÅRD; Lars-Erik Roland ÖNNERLÖV
Original assignee: Metso Paper Karlstad Ab
Priority date: 2002-03-08
Filing date: 2003-03-05
Publication date: 2003-09-18
Also published as: CN1639037A; WO2003076320A8; AU2003214738A1; WO2003076320A9; US20050156078A1; EP1497211A1

Abstract

A winding apparatus for winding a paper web (1), comprising a reel spool (3) onto which the web is wound to form a paper roll (4), a support member (2) forming a nip (5) with the paper roll, and an actuator (24) mounted at the support member or reel spool to control the distance therebetween. According to the invention the apparatus has a measuring and controlling equipment comprising a light-emitting member (6) to illuminate the paper roll by light providing a line (7) on the cylindrical surface (8) of the paper roll, a receptive system arranged to depict the line, and a control unit (10) connected to the receptive system and arranged to analyse the depicted line in order to calculate the distance between the paper roll and the support member and send a position-correcting signal to the actuator when the distance calculated deviates from a predetermined distance. The invention also relates to such a measuring and controlling equipment and a method for controlling the distance between the paper roll and the support member.

Description

Apparatus and method for winding a paper web and equipment therefor for controlling nip load

The present invention relates to a winding apparatus for winding a paper web, comprising a rotatably mounted reel spool onto which the paper web is wound to form a roll of paper, a support member forming a nip with the roll of paper, and - an actuator mounted either at the support member or the reel spool in order to control the distance between the support member and the roll of paper.

The invention also relates to a method for winding a paper web comprising the steps of rotatably mounting a reel spool onto which the paper web is to be wound to form a roll of paper, mounting a support member forming a nip with the roll of paper, and - mounting actuators either at the support member or the reel spool in order to control the distance between the support member and the roll of paper.

The invention also relates to an equipment in a winding apparatus for winding a paper web, for measuring and controlling a distance between a roll of paper being wound and a support member, which winding apparatus comprises a rotatably mounted reel spool onto which the paper web is wound to form said roll of paper, said support member forming a nip with the roll of paper, and an actuator mounted either at the support member or the reel spool in order to control the distance between the support member and the roll of paper. In the continuous manufacture of paper in a paper machine the paper web is wound onto reel spools to form finished rolls of paper, i.e. parent rolls. To facilitate subsequent processing of the parent rolls, it is essential to ensure that each parent roll is formstable and substantially circular-cylindrical in shape. It is important also to ensure that winding. takes place in such a manner that the properties the paper web acquired during production, such as stretchability and bulk, are not lost. When winding creped soft paper with low gram age and density known as high-bulk tissue, for instance, it is desirable that the pressure between adjacent layers of paper in the parent roll is as low as possible, as well as being substantially constant through the whole parent roll. However, at the same time, sufficient pressure must be applied to prevent the parent roll from "telescoping" or becoming deformed in some other way.

In order to control the winding it is common to form a nip between the roll of paper being wound and a support member such as a surface winding drum or an endless belt. The roll of paper and the support member thus form a nip through which the paper web passes. By controlling the linear load between the roll of paper and the support member, i.e. the ratio of the force acting between the roll and the support member, and the width of the roll of paper, the pressure between adjacent layers of paper in the roll of paper is controlled.

A good control of the linear load is thus important in order to obtain rolls of paper of high quality. The linear load is usually measured using force sensing elements such as load cells or pressure transducers arranged between the carriage supporting the roll of paper and the stand of the winding device. However, this method has the drawback that the signal generated by the linear load in the force sensing element risks being drowned in signals caused by friction forces and inertia forces from the rotating roll of paper. In conventional winding devices having a primary system and a secondary system it is particularly difficult to control the linear load in the primary system and when transferring the roll of paper from the primary system to the secondary system.

US 6,036,137 describes a reel-up utilizing the fact that a given linear load between a roll of paper and a support member in the form of a surface winding drum can be correlated to the radial indentation of the roll of paper where it abuts the surface winding drum. The reel-up comprises a measuring device having a first sensor that measures the increasing diameter of the roll of paper by measuring the distance between a known position of the winding drum and the cylindrical surface of the roll of paper. The measuring device also comprises a second sensor that measures the distance between the axis of the roll of paper and a known second position relative to the axis of the surface winding drum. The measured values are supplied to a control unit in which the indentation of the roll of paper is calculated and compared with a desired indentation corresponding to an optimal linear load. If the discrepancy between measured and desired indentation is too great, the desired indentation is set by a controlled regulation of the distance between the axis of the surface winding drum and the axis of the roll of paper. Examples of suitable sensors mentioned in US 6,036,137 are laser-based sensors which measure said distance using triangulation or interferometry techniques . In order to unequivocally determine the radius and axis position of the roll of paper, therefore, two location-separated distance sensing systems must be used. This is a drawback since a common detailed calibration of the two systems is necessary in order to obtain accurate values for the radius and axis position of the roll of paper.

The object of the present invention is to provide a winding apparatus which remedies the above-mentioned drawback and enables simple, accurate and" reliable calculation of the radius and axis position of a roll of paper being wound, thereby enabling simple, accurate and reliable control of the distance between the roll of paper and the support member.

The winding apparatus in accordance with the invention is characterized in that the winding apparatus further comprises a measuring and controlling equipment comprising a light-emitting member arranged to illuminate the roll of paper by light providing a line on the cylindrical surface of the roll of paper, - a receptive system arranged to depict the line, and a control unit connected to the receptive system and arranged to analyse the depicted line in order to calculate the distance between the roll of paper and the support member and send a position-correcting signal to said actuator when the distance calculated deviates from a predetermined distance.

The method in accordance with the invention is characterized by the further steps of - illuminating the roll of paper by light from a light-emitting member and providing a line on its cylindrical surface; depicting the line by a receptive system; analysing the line by a control unit connected to the receptive system; calculating by the control unit, upon analysis, a distance between the roll of paper and the support member; and sending a position-correcting signal to said actuator when the calculated distance deviates from a predetermined distance.

The equipment in accordance with the invention is characterized in that it comprises a light-emitting member arranged to illuminate the roll of paper by light providing a line on the cylindrical surface of the roll of paper, a receptive system arranged to depict the line, and a control unit connected to the receptive system and arranged to analyse the depicted line in order to calculate the distance between the roll of paper and the support member and send a position-correcting signal to said actuator when the distance calculated deviates from a predetermined distance.

According to the invention the fact is exploited that the equation for said line contains explicit information concerning the radius and axis position of the roll of paper. Placing and aligning the light-emitting member and the camera so that the projection of the line in the camera forms a curve allows the equation of the line to be calculated, given that the positions of the camera and the light-emitting member are known. The radius and axis position of the roll of paper can then be calculated from the equation of the line.

The radius and axis position of the roll of paper is preferably calculated continuously during winding, and the information is used for positioning the roll of paper at a desired distance from the support member. The linear load between the roll of paper and the support member can thus be continuously controlled. The ₍light-emitting device preferably emits luminous laser light. The light-emitting member may comprise a laser-prism arrangement that emits a curtain of light forming a coherent light track as a visible line.

Alternatively the light-emitting member may comprise a plurality of lasers that emit laser beams illuminating the line -pointwise.

Said analysis comprises preferably the steps of digitalizing the depicted line, identifying a plurality of points on the depicted line, calculating the equation of the line on the basis of the mutual positions of these points and calculating the radius and axis position of the roll of paper from the equation of the line. For accuracy of the calculation it is preferable for the line to have as large an extension as possible in the circumferential direction of the roll of paper.

The invention will be described in the following in more detail with reference to the drawings.

Figure 1 shows schematically parts of a reel-up and a measuring and controlling equipment according to a first embodiment of the invention.

Figure 2 shows schematically parts of a reel-up and a measuring and controlling equipment according to a second embodiment of the invention.

Figure 3 is a side view of a reel-up and a measuring and controlling equipment according to a third embodiment of the invention.

Figure 4 shows schematically parts of a different reel-up and a measuring and controlling equipment according to Figure 3. Figure 5 shows feasible placing of the measuring and controlling equipment according to Figure 1.

Figure 6 shows an alternative placing of the measuring and. controlling equipment according to Figure 1.

Figure 7 shows a further alternative placing of the measuring and controlling equipment according to Figure 1.

Figure 8 shows yet another alternative placing of the measuring and controlling equipment according to Figure 1.

The principle of the invention will be described in more detail in the following with reference to Figures 1 and 2 showing schematically parts of a winding apparatus in the form of a reel-up for winding a paper web 1. The reel-up comprises a support member in the form of a surface winding drum 2 rotatably mounted in the reel-up with its axis of rotation in the cross direction (CD) of the reel-up. The surface winding drum 2 is driven by a drive unit (not shown) . The reel-up also comprises a reel spool 3 disposed parallelly with the surface winding drum 2 , onto which the paper web 1 is wound to form a roll 4 of paper. The reel spool 3 may be driven by a drive unit (not shown) or caused to rotate by friction from the surface winding drum 2. During the main part of the winding process the growing roll 4 of paper rests against the surface winding drum 2 so that the growing roll 4 of paper acquires a radial indentation. The surface winding drum 2 and the growing roll 4 of paper thus form a nip 5 through which the paper web 1 passes before being wound up on the reel spool 3. To control the linear load in the nip 5 and thus also the indentation of the growing roll 4 of paper, the reel-up comprises actuators 23 that control the axis distance between the surface winding drum 2 and the growing roll 4 of paper.

The reel-up includes a measuring and controlling equipment which comprises a light-emitting member 6 in the form of a laser, that emits a. focused laser beam, and a prism that spreads the laser beam to a flat light curtain. This laser-prism arrangement, in the following called "linear laser" is arranged above the surface winding drum 2 and the roll 4 of paper and emits said light curtain in one plane, in the following called "illumination plane". Where the illumination plane encounters the roll 4 of paper the linear laser 6 illuminates the roll 4 of paper creating a visible line 7 on the cylindrical surface 8 of the roll 4 of paper. In other words the linear laser emits a line-shaped light pattern onto the roll 4 of paper.

The normal direction of the illumination plane forms substantially a right angle to the machine direction (MD) of the reel-up and an angle of approximately 90° to the axial direction of the roll 4 of paper, i.e. the normal direction of the illumination plane substantially coincides with the cross direction (CD) . The line 7 thus describes a circle arc that has a radius of curvature from which the radius of the growing roll 4 of paper can be calculated, and a centre of curvature corresponding to the position of the axis of the roll 4 of paper. The line 7 thus contains information as to the radius and axis position of the roll 4 of paper, from which information the indentation of the roll 4 of paper can be calculated, provided that the radius and axis position of the surface winding drum 2 are known.

The measuring and controlling equipment comprises a receptive system or light detection device. In the embodiments shown the receptive system is in the form of a reproducing optical system, that includes a camera 9. The measuring and controlling equipment also comprises a control unit 10 connected to the camera 9 and comprising an image analyzer. The camera 9 is placed at a distance from the linear laser 6 and aligned so that its optical axis forms an angle in the interval of 15 to 45° to the illumination plane. The camera 9 thus depicts the line 7 as a curve. Provided that the position and alignment of the camera 9 are known, the image analyzer calculates the radius and axis position of the roll 4 of paper on the basis of the depicted line 7. Provided that the radius and axis position of the surface winding drum 2 are known, the control unit 10 then calculates the distance between the roll 4 of paper and the surface winding drum 2, which gives the indentation of the roll 4 of paper. The control unit 10 compares the calculated distance between the roll 4 of paper and the surface winding drum 2 with a predetermined, desired distance between the roll 4 of paper and the surface winding drum

2, which corresponds to a desired indentation of the roll 4 of paper. If the calculated distance deviates from the desired distance, the control unit 10 sends a distance-correcting signal to said actuator which then moves the reel spool 3 closer to or further away from the surface winding drum 2 so that the desired indentation is obtained.

During the winding process the radius of the roll 4 of paper is constantly growing. In order for the measuring and controlling equipment to maintain the desired indentation the axis of the paper roll 4 need to move away from the surface winding drum 2 in a controlled manner. The speed of this movement of the axis of the roll 4 of paper away from the surface winding drum 2 needs to be relatively higher at an early stage of the winding process due to a relatively small radius of the roll 4 of paper at this early stage. However, at a later stage of the winding process the speed of the movement needs to be relatively lower due to a relatively large radius of the roll 4 of paper.

The control unit 10 preferably also calculates the peripheral speed of the growing roll 4 of paper by. multiplying the radius calculated by the image analyzer, by the speed of rotation of the roll 4 of paper that is obtained from the drive unit of the reel spool 3 or drive unit of the reel spool 3 (not shown) . If the calculated peripheral speed deviates from a desired peripheral speed, the control unit 10 sends a signal correcting the rotational speed to the drive unit which then adjusts the speed of rotation so that the desired peripheral speed is obtained.

The linear laser 6 preferably illuminates the growing roll 4 of paper throughout the winding process so that the indentation and peripheral speed of the roll 4 of paper can be continuously controlled.

The depicted line 7 is preferably digitalized at an early stage in the image analyzer of the control unit 10, or alternatively already in the camera 9, and the continued processing in the image analyzer then takes place in digital form. The image analyzer preferably comprises a microprocessor for this processing. The algorithm that calculates the equation of the line 7 preferably comprises the steps of identifying a plurality of evenly distributed points along the line 7, after which the radius of curvature and centre of curvature of the line 7 are calculated in known manner on the basis of the relative positions of the points. It will be recognized that, from the point of view of accuracy, the line 7 should be as long as possible. The linear laser 6 enables illumination of half the circumference of the roll 4 of paper and, in general, the extension of the line 7 in circumferential direction of the roll 4 of paper should be as great as possible. Since the line 7 describes an arc, at least three points must be used in the algorithm in order to unambiguously define the radius of curvature and centre of curvature. However, more points are preferably used for increased accuracy. Other known algorithms to determine the radius of curvature and centre of curvature of a curve with the aid of an image analyzer may alternatively be used.

In an alternative process, the light curtain also illuminates the surface winding drum 2 creating a second visible line 11 on the cylindrical surface 12 of the surface winding drum 2. In other words the linear laser also emits a line-shaped light pattern onto the surface winding drum 2. In this case the camera 9 is aligned to depict the first line 7 as well as the second line 11. The radii of curvature and centres of curvature of the lines 7, 11 are calculated in the image analyzer in the same manner as described above. The control unit 10 then calculates the distance between the surface winding drum 2 and the roll 4 of paper, after which the indentation of the roll 4 of paper is calculated. In this process the indentation of the roll 4 of paper is thus obtained directly without the need for previous knowledge of the radius or axis position of the surface winding drum 2.

In the embodiment shown in Figure 2 the light-emitting member has the form of a set of lasers 13. The lasers 13 are arranged in a line and directed so that their laser beams define an illumination plane that coincides with the previously mentioned illumination plane. Consequently a first group of lasers 13a illuminates the roll 4 of paper pointwise along the line 7, and a second group of lasers 13b illuminates the surface winding drum 2 pointwise along the line 11. In other words, the first group of lasers 13a emits a first light pattern onto the roll 4 of paper and the second group of lasers 13b emits a second light pattern onto the surface winding drum 2, said first and second light patterns having the shape of luminous points following the line 7 and 11, respectively. The illuminated points 14, 15 on the lines 7, 11 are depicted by the camera 9. The image analyzer of the control unit 10 calculates the radii of curvature and centres of curvature in known manner, on the basis of the relative positions of the points 14, 15, after which the indentation and peripheral speed of the roll 4 of paper are calculated to constitute a basis for any control signals to said actuator and drive unit, respectively. The advantage of this embodiment is that a set of lasers is normally cheaper than the technically more complicated laser-prism arrangement.

To be able to calculate the indentation and peripheral speed of the roll 4 of paper as described above it is required that the camera 9 is positioned and directed so that it depicts the lines 7, 11 as curves. In other words, the position of the camera 9 must be separate from the illumination plane. If the camera 9 were to be arranged in the illumination plane the projections of the lines 7, 11 in the camera 9 would be straight and the image analyzer would be unable to calculate said radii of curvature or centres of curvature.

In principle the measuring method is independent of the alignment of the illumination plane and the camera, provided the reproducing requirements as to curvature of the depicted lines are fulfilled. However, it is preferred that the light-emitting member be aligned so that the normal direction of the illumination plane substantially forms a right angle to the machine direction in order to avoid that the geometry of the depicted lines and calculation of the radii and centres of curvature becomes unnecessarily complicated. The normal direction of the illumination plane may thus be permitted to form an angle in the interval of 0-90° to the cross direction, and the optical axis of the camera may be permitted to form an angle to the illumination plane which is also in the interval of 0-90°': An alternative to the alignments of the light-emitting member and the camera as described in Figures 1 and 2, for instance, is for the light-emitting member to be aligned so that the illumination plane forms an angle of 45° to the cross direction, and for the camera to be aligned so that its optical axis coincides with the normal direction of the illumination plane.

If the light-emitting member comprises a set of lasers the lasers need not be arranged so that their laser beams define a single plane, i.e. a flat surface. Theoretically it is possible to determine the radius and centre of curvature of the roll of paper also in the case when the laser beams define some form of curving surface. In this case, however, the calculations would be relatively complicated.

Figure 3 is a side view of a reel-up for winding a paper web 1 with the aid of a surface winding drum 2. The reel-up comprises a primary system and a secondary system. The primary system comprises a lowering arm 33 arranged to collect a reel spool 3 from a stock 22 of reel spools 3. The primary system also comprises a primary arm 21 arranged to receive the reel spool 3' from the lowering arm 33, in which primary arm 21 the reel spool 3' is accelerated to the same peripheral speed as the surface winding drum 2 and is moved towards the surface winding drum 2 so that the paper web 1 is wrapped around the reel spool 3'. The secondary system comprises a second carriage 23, which is displaceable in the machine direction (MD) along a rail 25 by an actuator 24. After the wrapping, the reel spool 3' is transferred from the primary arm 21 to the secondary carriage 23 where a drive unit (not shown) drives the reel spool 3" so that a roll 4 of paper is formed. The reel-up comprises an equipment similar to the type described above in conjunction with Figure 2, i.e. an equipment wherein the light-emitting,member comprises a set of lasers 27. As far as possible the lasers 27 are combined,to one and the same position, i.e. they are placed so that, to all intents and purposes, they can be deemed to emit their laser beams from one and the same position. Each laser beam forms an angle of 45° to the axial direction of the roll 4 of paper. The laser beams thus define an illumination plane whose normal direction forms an angle of 45° to the axial direction of the roll 4 of paper and right angle to the machine direction (MD) . The laser beams illuminate the roll 4 of paper and the surface winding drum 2 pointwise along lines on the cylindrical surfaces 8, 12 of the roll 4 of paper and the surface winding drum 2, respectively. In other words the lasers 27 emit a first light pattern onto the cylindrical surface 8 of the roll 4 of paper and a second light pattern onto the cylindrical surface 12 of the surface winding drum 2 , The angular area covered by the laser beams is sufficient for them to be able to illuminate the roll 4 of paper when this is on the secondary carriage 23 as well as when it is on the primary arm 21. The equipment also comprises a camera 9, the optical axis of which coincides with the normal direction of the illumination plane, and a control unit

(not shown) which depicts and analyses the lines in the manner described above. The control unit is connected to the actuator 24 in order to maintain the desired radial indentation of the roll 4 of paper or, which is equivalent, the desired linear load between the roll 4 of paper and the surface winding drum 2. The control unit is also connected to the drive unit of the secondary carriage 23 in order to maintain a desired speed of rotation of the roll 4 of paper.

The method in accordance with the invention is also suitable for use with reel-ups where the support member . is a member other than a surface .winding drum. Figure.4 illustrates such a reel-up in which -the. support member is an endless belt 28 with an unsupported section 29 running between two rolls 30, 31. When the paper web is being wound, the roll 4 of paper and the unsupported section 29 form a nip 5 through which the paper web passes. A measuring system, similar to that in Figure 3 is arranged to calculate the radius and position of the roll 4 of paper. The positions of the rolls 30, 31 being known, the control unit then calculates the indentation of the unsupported section 29 of the belt 28 by the roll 4 of paper in order to control the indentation.

The light-emitting member and the depicting optical system may be placed in various ways in relation to the roll of paper. Figure 5 shows possible placing of the light-emitting member, in this case a linear laser 6, and the camera 9. The linear laser 6 and camera 9 are placed side by side along a line in the transverse direction of the reel-up in a stand (not shown) above the roll 4 of paper and the surface winding drum 2. Figure 6 shows an alternative placing in which the linear laser 6 and camera 9 are placed on one side of the reel-up in a stand (not shown) above the roll 4 of paper and the surface winding drum 2. The measuring and controlling equipment may have a separate stand. Alternatively the linear laser and camera may be placed in a stand carrying the various parts of the reel-up. Figures 7 and 8 illustrate examples of this, where the linear laser 6 and camera 9 are placed on one of the beams 32 carrying the stock 22 of reel spools of the The light-emitting member and camera may thus be placed in a number of different ways. However, the condition is, as mentioned above, that the light-emitting member and camera are positioned and aligned so that the light-emitting member illuminates the roll of paper . and possibly also. the surface winding cylinder along lines ^• on their cylindrical surfaces, and that the lines depicted by the -camera are curves. Provided these requirements are fulfilled the light-emitting member and camera may be placed inside the width of the paper web, as shown in Figures 5-8. Alternatively the light-emitting member and camera may be placed outside the width of the reel-up where there is less dust to disturb the measuring and controlling equipment, or even on the ceiling of the building where the reel-up is located.

It is recognized that the invention can be combined with conventional technology. The radius of the roll of paper may be calculated in accordance with the invention, for instance, while the axis position of the roll of paper may be measured with a conventional position transducer, preferably one connected to the control unit .

The measuring and controlling equipment should preferably operate with visible light, preferably visible laser light. However, it will be recognized that the invention is not only limited to light-emitting members and receptive or reproducing optical systems that operate in the visible range of wave lengths, i.e. 390-770 nanometer. Measuring systems operating in the ultraviolet, infrared or other ranges of wave lengths may also be used. A condition is, however, that the electro-magnetic waves have such physical properties that the detection of a distinct line on the cylindrical surface of the roll of paper is possible. Consequently the concepts "light" and "optical" shall not be interpreted here to be associated only with visible electro-magnetic waves.

The invention has been described. above in connection with a reel-up, however, it should be understood that the invention also is applicable to all types of winding apparatus wherein a nip load is to be controlled during a web winding process, for instance a rewinding machine.

Claims

C L A I M S

1. A winding apparatus for winding a paper web (1) , comprising - a rotatably mounted reel spool (3) onto which the paper web (1) is wound to form a roll (4) of paper, -, a support member (2, 28 ) forming a nip (5) with, the roll. (4) of paper, and ■ - an actuator (24) mounted either at the support member (2, 28) or the reel spool (3) in order to control the distance between the support member (2, 28) and the roll (4) of paper, characterized in that the winding apparatus further comprises a measuring and controlling equipment comprising a light-emitting member (6, 13, 27) arranged to illuminate the roll (4) of paper by light providing a line (7) on the cylindrical surface (8) of the roll (4) of paper, - a receptive system arranged to depict the line (7) , and a control unit (10) connected to the receptive system and arranged to analyse the depicted line (7) in order to calculate the distance between the roll (4) of paper and the support member (2, 28) and send a position-correcting signal to said actuator (24) when the distance calculated deviates from a predetermined distance .

2. An apparatus according to claim 1, characterized in that the receptive system comprises a camera (9) positioned and aligned to depict the line (7) as a curve .

3. An apparatus according to any of claims 1 and 2, characterized in that upon said analysis of the depicted line (7) the control unit (10) is arranged to calculate the radius and the axis of position of the growing roll (4) of paper.

4. An apparatus according to claim 3, characterized in that the. support member (2, 28) is. arranged at a known- position in the reel-up, and in that the control unit .

(10) is arranged to calculate, the distance between, the roll (4) of paper and the support member (2, 28). on the basis of the calculated radius and axis position of. the roll (4) of paper and of the known position of the support member (2, 28) .

5. An apparatus according to any of claims 2 and 3 , characterized in that the support member is a surface winding drum (2) and that the light-emitting member (6, 13, 27) is arranged to illuminate the surface winding drum (2) with light also providing a second line (11) on the cylindrical surface (12) of the surface winding drum (2) , that the camera (9) is positioned and aligned to depict the second line (11) as a curve, that the control unit (10) is arranged to analyse the depicted second line (11) in order to calculate the radius and axis position of the surface winding drum (2) , and that the control unit (10) is arranged to calculate the distance between the growing roll (4) of paper and the surface winding drum (2) on the basis of the calculated radii and axis positions of the roll (4) of paper and the surface winding drum (2) .

6. An apparatus according to any one of claims 3-5, characterized in that the control unit (10) is arranged to calculate the peripheral speed of the roll (4) of paper by multiplying the radius of the growing roll (4) of paper by the speed of rotation of the roll (4) of paper, comparing the calculated peripheral speed with a desired peripheral speed and sending a signal correcting the rotational speed to the drive unit of the reel spool (3) when the calculated peripheral speed deviates from the desired one; • . .

7. An apparatus according to any one of: claims.1-6,' characterized in- that upon said analysis of the depicted line (7) on the cylindrical surface (8) of the roll (4) of paper the control unit (10) is arranged to digitalize the depicted line (7) , identify a plurality of points on the line (7) , calculate the equation of the line (7) on the basis of the relative positions of the points, and calculate the radius and axis position of the roll (4) of paper on the basis of the equation of the line (7) .

8. An apparatus according to any one of claims 1-7, characterized in that the light-emitting member (6, 13) is aligned to emit light in one plane.

9. An apparatus according to claim 8, characterized in that the light-emitting member (6, 13) is aligned so that the normal direction of said plane forms substantially a right angle to the machine direction of the apparatus.

10. An apparatus according to claim 9, characterized in that the light-emitting member (6, 13) is aligned so that the normal direction of said plane forms an angle in the interval of 15 to 45° to the axial direction of the roll (4) of paper.

11. An apparatus according to any one of claims 1-10, characterized in that the light-emitting member (6) comprises a laser and a prism which are arranged to emit a coherent curtain of light that illuminates the line (7) on the cylindrical surface (8) of the roll (4) of paper.

12. An apparatus according to any one of claims 1-10, characterized in that the light-emitting member comprises a set of lasers (13, 27) which are arranged to emit laser beams that pointwise illuminate the line (7) on the cylindrical surface (8) of the roll (4) of paper.

13. An apparatus according to any one of claims 1-12, characterized in that the light-emitting member (6, 13, 27) and the camera (9) are arranged within the width of the paper web (1) .

14. An apparatus according to any one of claims 1-12, characterized in that the light-emitting member and the camera are arranged outside the width of the paper web (1) .

15. A method for winding a paper web (1) comprising the steps of rotatably mounting a reel spool (3) onto which the paper web (1) is to be wound to form a roll (4) of paper, - mounting a support member (2, 28) forming a nip (5) with the roll (4) of paper, and mounting actuators (24) either at the support member (2, 28) or the reel spool (3) in order to control the distance between the support member (2, 28) and the roll (4) of paper, characterized by the further steps of illuminating the roll (4) of paper by light from a light-emitting member (6, 13, 27) and providing a line (7) on its cylindrical surface (8) ; - depicting the line (7) by a receptive system; analysing the line (7) by a control unit (10) connected to the receptive system; calculating by the control unit (10) , upon analysis, a distance between the roll (4) of paper and the support member (2, 28); and sending a position-correcting signal to said actuator (24). when the calculated distance deviates from a predetermined distance .

16. A method according to claim 15, characterized by depicting the line (7) as a curve by means of a camera (9) .

17. A method according to any of claims 15 and 16, characterized by calculating the radius and the position of axis of the roll (4) of paper upon said analysis by the control unit (10) .

18. A method according to claim 17, characterized by, when the position of the support member (2, 28) is known, defining the distance between the roll (4) of paper and the support member (2, 28) by the control unit (10) on the basis of the calculated position of the roll (4) of paper and the known position of the support member (2, 28) .

19. A method according to any one of claims 16 and 17, characterized by the steps of, when the support member is a surface winding drum (2) , illuminating the support member in the form of a surface winding drum (2) to provide a second line (11) on its cylindrical surface (12) , by light from the light-emitting member (6, 13, 27); depicting the second line (11) as a curve by the camera (9) ; analysing the second line (11) by the control unit (10) which, upon analysis, calculates the radius and axis position of the surface winding drum (2) ; and defining the distance between the roll (4) of paper and the surface winding drum (2) by the control unit (10) on the basis of the calculated radii and axis positions of the roll (4) of paper and the surface winding drum (2) .

20. ^■A method according to any, one of claims 17-19, characterized by calculating the peripheral speed of the- roll (4). of paper by multiplying the calculated radius of the roll (4) of paper by the speed of rotation of the roll (4) of paper; comparing the calculated peripheral speed of the roll

(4) of paper with a desired peripheral speed; and - sending a signal correcting the rotational speed to the drive unit of the reel spool (3) when the calculated peripheral speed deviates from the desired peripheral speed.

21. A method according to any one of claims 16-20, characterized by analysing the line (7) on the cylindrical surface (8) of the roll (4) of paper by the steps of digitalizing the depicted line (7) , - identifying a plurality of points on the line (7) , calculating the equation of the line (7) on the basis of the relative positions of the points, and calculating the radius of curvature and the centre of curvature of the roll (4) of paper on the basis of the equation of the line (7) .

22. An equipment in a winding apparatus for winding a paper web (1) , for measuring and controlling a distance between a roll (4) of paper being wound and a support member (2, 28), which winding apparatus comprises a rotatably mounted reel spool (3) onto which the paper web (1) is wound to form said roll (4) of paper, said support member (2, 28) forming a nip (5) with the roll (4) of paper, and an actuator (24) mounted either at the support member (2, 28) or the reel spool (3) in order to control the distance between the support member (2, 28) and the . roll (4) of paper, characterized in that the equipment comprises a light-emitting member (6, 13, 27) arranged to illuminate the roll (4) of paper by light providing a line (7) on the cylindrical surface (8) of the roll (4) of paper, - a receptive system arranged to depict the line (7) , and a control unit (10) connected to the receptive system and arranged to analyse the depicted line (7) in order to calculate the distance between the roll (4) of paper and the support member (2, 28) and send a position-correcting signal to said actuator (24) when the distance calculated deviates from a predetermined distance.

23. An equipment according to claim 22, characterized in that the receptive system comprises a camera (9) positioned and aligned to depict the line (7) as a curve .

24. An equipment according to any of claims 22 and 23, characterized in that upon said analysis of the depicted line (7) the control unit (10) is arranged to calculate the radius and the axis of position of the roll (4) of paper.

25. An equipment according to claim 24, characterized in that the support member (2, 28) is arranged at a known position in the reel-up, and in that the control unit (10) is arranged to calculate the distance between the roll (4) of paper and the support member (2, 28) on the basis of the calculated radius and axis position of the roll (4) of paper and of the known position of the support member. (2, 28) .

26. An equipment according to any of claims 23 and' 24, characterized in that, when the support member is a surface winding drum (2) , the light-emitting member (6, 13, 27) is arranged to illuminate the surface winding drum (2) with light providing also a second line (11) on the cylindrical surface (12) of the surface winding drum (2) , - the camera (9) is positioned and aligned to depict the second line (11) as a curve, the control unit (10) is arranged to analyse the depicted second line (11) in order to calculate the radius and axis position of the surface winding drum (2) , and the control unit (10) is arranged to calculate the distance between the growing roll (4) of paper and the surface winding drum (2) on the basis of the calculated radii and axis positions of the roll (4) of paper and the surface winding drum (2) .

27. An equipment according to any one of claims 24-26, characterized in that the control unit (10) is arranged to calculate the peripheral speed of the roll (4) of paper by multiplying the radius of the growing roll (4) of paper by the speed of rotation of the roll (4) of paper, comparing the calculated peripheral speed with a desired peripheral speed and sending a signal correcting the rotational speed to the drive unit of the reel spool (3) when the calculated peripheral speed deviates from the desired one.

28. An equipment according to any one of claims 22-27 , characterized in that upon said analysis of the depicted line (7) on the cylindrical surface (8) of the roll (4) of paper the control unit (10) is arranged to digitalize the depicted line (7), identify a plurality of points on the line (7) , calculate the equation of the line (7) on the basis of the relative positions of the points, and " calculate the radius and axis position of the roll (4) . of paper on the basis of the equation of the line (7) .

29. An equipment according to any one of claims 22-28, characterized in that the light-emitting member (6, 13) is aligned to emit light in one plane.

30. An equipment according to claim 29, characterized in that the light-emitting member (6, 13) is aligned so that the normal direction of said plane forms substantially a right angle to the machine direction of the apparatus .

31. An equipment according to claim 30, characterized in that the light-emitting member (6, 13) is aligned so that the normal direction of said plane forms an angle in the interval of 15 to 45° to the axial direction of the roll (4) of paper.

32. An equipment according to any one of claims 22-31, characterized in that the light-emitting member (6) comprises a laser and a prism which are arranged to emit a coherent curtain of light that illuminates the line (7) on the cylindrical surface (8) of the roll (4) of paper.

33. An equipment according to any one of claims 22-31, characterized in that the light-emitting member comprises a set of lasers (13, 27) which are arranged to emit laser beams that pointwise illuminate the line (7) on the cylindrical surface (8) of the roll (4) of paper.

34. An equipment according to any one of claims 22-33, characterized in that the light-emitting member

(6, 13, 27) and the camera (9) are arranged within the width of the paper web (1) .

35.. An equipment according to any one of claims 22-33, characterized in that the light-emitting member and the camera are arranged outside the width of the paper web (1) .

36. A winding apparatus for a paper web, the apparatus comprising: a rotatable reel spool configured to receive the web thereon to form a paper roll; a support member adjacent to the growing paper roll, the support member and the growing paper roll defining a nip therebetween; an actuator configured to control a nip load between the growing paper roll and the support member; a light emitting member configured to emit a light pattern onto a portion of the growing paper roll; - a light detection device configured to receive a reflection of the light pattern from the growing paper roll; and a control unit in communication with the light detection device and configured to determine a value representative of the nip load between the growing paper roll and the support member based on the reflection of the light pattern from the growing paper roll , wherein the control unit is configured to communicate with the actuator to provide a desired nip load between the growing paper roll and the support member by moving the actuator.

37. An apparatus according to claim 36 wherein the control unit is configured to calculate a radius of the growing paper roll and a position of a rotational, axis of the growing paper roll based on the reflection of the light pattern received from the growing paper roll.

38. An apparatus according to claim 36 wherein the value representative of the nip load between the growing paper roll and the support member is an indentation of the support member into the growing paper roll.

39. An apparatus according to claim 36 wherein the support member is positioned at a predetermined position in the apparatus and the control unit is configured to determine the value representative of the nip load according to a calculated radius and axial position of the growing paper roll relative to the predetermined position of the support member based on the reflection of the light pattern received from the growing paper roll.

40. An apparatus according to claim 36 wherein the support member is a winding drum, the light emitting member is configured to emit a second light pattern on a surface of the winding drum, the light detection device is configured to receive a reflection of the second light pattern from the winding drum, and the control unit is configured to determine the value representative of the nip load according to a calculated radius and axial position of the growing paper roll based on the reflection of the light pattern received from the growing paper roll relative to a calculated radius and axial position of the winding drum.

41. An apparatus according to claim 36 wherein the control unit is configured to calculate a peripheral speed of the growing paper roll according to a calculated radius of the growing paper roll based on the reflection of the light pattern received from the growing paper roll and a rotational speed of the growing paper roll, compare the peripheral speed to a desired peripheral . speed, and control the peripheral speed of the growing paper roll according to a deviation of the peripheral speed from the desired peripheral speed.

42. An apparatus according to claim 36 wherein the control unit is configured to identify a plurality of points in said light pattern and determine a radius and center of curvature of the growing paper roll according to the plurality of points.

43. An apparatus according to claim 36 wherein the light emitting member is configured to emit light substantially in one illumination plane.

44. An apparatus according to claim 43 wherein the light emitting member is configured such that a normal direction of the illumination plane is substantially perpendicular to a machine direction of the apparatus, the machine direction being perpendicular to the longitudinal direction of the growing paper roll .

45. An apparatus according to claim 44 wherein the light emitting member is configured such that the normal direction of the illumination plane forms an angle of- between about 15 and 45 degrees with the longitudinal direction of the growing paper roll.

46. An apparatus according to claim 36 wherein the light emitting member is a laser prism having a laser configured to direct a laser beam toward a prism, and wherein the prism is configured to spread the beam to form a coherent light curtain directed toward the growing paper roll and illuminate a line on a generally cylindrical surface of the growing paper roll to form said light pattern.

47. An apparatus according to claim 36 wherein the light emitting member is a plurality of lasers, each laser configured to direct a beam of light toward a surface of the growing paper roll .

48. An apparatus according to claim 36 wherein the light emitting member and the light detection device are positioned inside a width of the paper web.

49. An apparatus according to claim 36 wherein the light emitting member and the light detection device are positioned outside a width of the paper web.

50. An apparatus according to claim 36 wherein the light emitting member is configured to direct light in an illumination plane substantially perpendicular to a longitudinal direction of the growing paper roll and an optical axis of the light detection device is configured at an angle relative to the illumination plane such that the light detection device receives light reflected from the growing paper roll at an angle relative to the illumination plane.

51. An apparatus according to claim 36 wherein the light emitting member is configured to direct light in an illumination plane obtuse to the longitudinal direction of the growing paper roll and an optical axis of the light detection device is configured substantially perpendicular to the longitudinal direction of the growing paper roll such that the light detection device receives light reflected from the growing paper roll at an angle relative to the illumination plane.

52. A method of controlling a nip load between a growing roll of paper and a support member, the method comprising: rotating a reel spool to receive a web of paper thereon to form the growing paper roll, the growing paper roll defining a nip with the support member; emitting a light pattern onto a surface of the growing paper roll; receiving a reflection of the light pattern from the growing paper roll; determining a value representative of a nip load between the growing paper roll and the support member according to the reflection of the light pattern; and adjusting the relative distance between the growing paper roll and the support member to control the nip load.

53. A method according to claim 52 further comprising calculating a radius of the growing paper roll and a position of an axis of the growing paper roll based on the reflection of the light pattern received from the growing paper roll .

54. A method according to claim 53 further comprising: - emitting a second light pattern onto the support member; receiving a reflection of the second light pattern from the support member; and determining a position of the support member according to the reflection of the second light pattern, wherein the value representative of the nip load is calculated according to the position of the support member and the radius and axial position of the growing paper roll .

55. A method according to claim 52 further comprising: calculating a peripheral speed of the growing paper roll according to a calculated radius of the growing paper roll based on the reflection of the light pattern received from the growing paper roll and a rotational speed of the growing paper roll; comparing the peripheral speed to. a. desired peripheral speed; and adjusting the peripheral speed of the growing paper roll according to a deviation of the peripheral speed from the desired peripheral speed.

56. A method according to claim 52 wherein said determining step comprises identifying a plurality of points in said light pattern and determining a radius and center of curvature of the growing paper roll according to the plurality of points.

57. A method according to claim 52 wherein the emitting step comprises emitting light substantially in one illumination plane.

58. A method according to claim 52 wherein the emitting step comprises emitting the light in the illumination plane such that a normal direction of the illumination plane is substantially perpendicular to a machine direction of the apparatus, the machine direction being perpendicular to the longitudinal direction of the growing paper roll .

59. A method according to claim 52 wherein the emitting step comprises emitting the light in the illumination plane such that the normal direction of the illumination plane forms an angle of between about 15 and 45 degrees with the longitudinal direction of the growing paper roll.

60. A method according to claim 52 wherein the emitting step comprises emitting light in the illumination plane substantially perpendicular to a longitudinal direction of. the growing paper roll and the receiving step comprises receiving light reflected from the growing paper roll at an angle relative to -the illumination plane .

61. A method according to claim 52 wherein the emitting step comprises emitting light in the illumination plane obtuse to a longitudinal direction of the growing paper roll and the receiving step comprises receiving light reflected from the growing paper roll in a plane substantially perpendicular to the longitudinal direction of the growing paper roll.