EDGE SENSING ARRANGEMENT

Abstract: The invention relates to an arrangement in connection with a wire guide roll of a paper machine. The arrangement comprises a wire guide roll (3) which is arranged to guide a wire (1), if the wire is driven to the side from its normal track of travel. The wire guide roll is turned in the direction of travel (A) of the wire by means of at least one actuator (5). The lateral (B) position of the wire is observed by means of a guide flap (2) monitoring the movement of the wire edge, from which guide flap the guidance information is transmitted to a control unit (4) which, for its part, controls said actuator. Furthermore, at least one sensor is arranged in connection with the guide flap to determine the position of the guide flap and to control the lateral exceedings of the wire.

Description: EDGE SENSING ARRANGEMENT The invention relates to an arrangement in connection with a wire guide roll of a paper machine, which arrangement comprises a wire guide roll transverse to the direction of travel of a wire, the wire guide roll being arranged to be turned in the direction of travel of the wire by means of at least one actuator, and which arrangement comprises a guide flap arranged against the wire edge and adapted to observe the lateral position of the wire, and in which arrangement the wire guide roll is arranged to turn and guide the wire on the basis of information provided by the guide flap on the lateral position of the wire and which arrangement further comprises means that are arranged to inform a control system of the paper machine of the lateral position of the wire. Various wires are used in paper machines for conveying and supporting a fibre web. In this connection, a paper machine can also be under- stood as a board machine, a pulp washing apparatus and similar paper manufacturing equipment provided with wires. When a wire is passed around and supported by different rolls in a paper machine, the wire may be driven to either edge in its direction of travel, which makes the wire edge rub against the structures of the paper machine. The wire does not naturally withstand this kind of strain, but will be damaged. The wire itself can be the reason why the wire is driven to the side, but usually this is caused by erroneous positions of rolls. Also impurities adhered to the rolls and the wire may cause the wire to move in the lateral direction. To solve the problem 'a wire guide roll', which prevents the wire from drifting in the lateral direction, is arranged in connection with wire circulation. When the wire is driven to the side, the wire guide roll is automatically turned to the required direction, and the wire is guided back to its right track of travel. The guide roll receives the guidance information from a guide flap which continuously monitors the edge of the wire. In addition to the guide flap, paper machines generally have edge flaps at both edges of the wire, which sense the lateral position of the wire and give an alarm to the control system of the paper machine, if the wire is for some reason driven too close to the edge. A prior art solution is described later in Figure 1 and in its description. A drawback of the known solution is, however, that arranging the equipment into a paper machine is laborious. It is difficult to arrange several flaps, fasteners of the flaps and cables leading to the flaps to narrow places with demanding conditions. In addition, maintenance is difficult, since the sen- sors are located on different sides of the paper machine and far away from each other. Some mass washing apparatuses apply a thin single-layer wire, and when the known solution is employed, the problem has arisen that the guide flap bends the thin wire from its edge, and as a result of the bent edge the edge flaps provide the control system of the paper machine with wrong information and the operation of the flaps is also otherwise unreliable. In addition, since the guide flap and the edge flaps are at a distance from the guide roll in the direction of travel of the wire, delays occur in the wire adjustment and control. It is also expensive to manufacture the solution, since it comprises a lot of various components. Furthermore, solutions are known, in which optical sensors or pressurized air streams are used in sensing the position of the wire. The problem of such solutions is, however, that the sensors become dirty and faulty under severe conditions and, compared to mechanically performed monitoring, the operation is also otherwise unreliable. The use of inductive sensors has also been tested, but similar problems have come up in connection with them as well. The solution further requires that a metal strip or the like, which the inductive sensor detects, is arranged to the wire edge. This kind of a wire is, however, expensive. It is an object of the invention to provide an arrangement by which prior art problems can be avoided. The arrangement of the invention is characterized in that at least one sensor is arranged in connection with the guide flap and that the information on the lateral position of the wire is adapted to be transmitted from the sensor to the control system of the paper machine. The essential idea of the invention is that the guide flap is arranged to observe the edge of the wire in continuous contact and, in case the wire is driven to the side, give guidance information to the control unit controlling the actuator, whereupon the wire guide roll is made to turn and the wire is guided back to its right lateral position. Further, means for transmitting information on the lateral overtravel of the wire to the control system or the like of the paper machine are arranged in connection with the guide flap. The guide flap is arranged after the guide roll, into its immediate proximity, in the direction of travel of the wire, and the devices that monitor and control the lateral position of the wire form an entity. Furthermore, an essential idea of a preferred embodiment of the invention is that there are limit switches or corresponding sen- sors at the guide flap arm, which determine the lateral position of the wire. This way it is also possible to register the cases where the wire exceeds the allowable predetermined operating range. The essential idea of another preferred embodiment of the invention is that there are sensors at the guide flap, which continuously observe the lateral position of the wire and transmit information on the lateral position of the wire to the control system of the paper machine. The invention provides the advantage that no separate edge flaps are required at both edges of the wire, but the wire position is only observed by means of the guide flap. Sensors observing the wire edge are arranged at the guide flap. Thus, edge flaps need not be manufactured and installed at all. The structure of the system becomes simpler and the maintenance much easier. The solution also enables the use of thin wires, which are cheaper and easier to run. In addition, since the guide flap is located near the guide roll, the wire at the guide flap is well supported by the guide roll, and therefore the thin wires no longer tend to bend because of the guide flap either. Thus, the wire edge can be observed accurately and reliably. The arrangement of the invention further allows the wire to be run looser as before, which makes the wires to last longer in use. When the guide flap is arranged in connection with the guide roll, no harmful delays occur in the control system. The invention will be described in greater detail in the attached drawings, in which Figure 1 is a top view of a prior art arrangement, Figure 2 is a schematic side view of a solution of the invention, Figure 3 schematically shows a detail of a solution of the invention, and Figure 4 schematically shows a detail of another solution of the in- vention. Figure 1 is a top view of a prior art arrangement for controlling the lateral position of a wire. A wire 1 is run in the direction A. For various reasons the wire may be driven to the side in the direction B transverse to the direction of travel of the wire. The position of the wire in the lateral direction B is sensed by means of a guide flap 2 which is arranged after a guide roll 3 in the direction of travel of the wire. The guide flap is in continuous contact with the wire edge. A guide flap, or 'a spoon', is a plate-like element, usually bent to be slightly curved, which is pushed by means of a spring, for example, against the edge of the wire. Guidance information is transmitted from the guide flap to a control unit 4 which controls an actuator 5 operating the guide roll. The actuator is typically a pneumatic bellows, and the pressure that is fed to it is regulated by means of an air control valve of the control unit. Usually the guide flap is directly arranged to mechanically use the air control valve. Based on the guidance information obtained from the guide flap, the actuator moves one end of the guide roll in the longitudinal direction C of the wire. Since the other end of the guide roll is arranged pivotally to the frame, the actuator makes the guide roll turn. On the other side of the guide roll there is another pneumatic bellows 8, to which constant pressure is fed. Thus the direction of movement of the guide roll is determined by the interrelation of the pressures to be fed to the first and the second bellows. The known arrangement further comprises edge flaps 6 and 7 which are arranged at both sides of the wire and give an alarm if the wire comes into contact with the flaps. The alarm that indicates the exceedings of the edge zone is transmitted to the control system 15 of the paper machine. Thus the edge flaps and the guide flap in connection with the wire guidance are entirely separate units from each other, and moreover, they are complicatedly arranged at a considerable distance from each other. Figure 2 shows a simplified view of an arrangement of the invention, as seen from the movable end of a wire guide roll. A wire 1 is arranged to move in the direction A via a guide roll 3 which, to make the guidance more effective, is arranged to be elevated such that the wire bends slightly at the guide roll. The end of the guide roll is supported by a bearing support 9, which is pivoted to a frame 11 by means of slide blocks 10 or rollers, for example, whereupon it can be moved in the direction C. The guide roll end is turned by means of actuators 5 and 8. The actuators are preferably pneumatic bellows as shown in the figure, but also pneumatic and hydraulic cylinders, electric motors and other devices that are suitable for this purpose can be used. Although the figure shows two different actuators arranged at opposite sides of the guide roll, the guide roll can also be used by only one actuator that can be moved in two directions, or the return motion can be performed by means of a spring element, for instance. The guide roll can also be moved from its both ends, but usually this is not necessary. According to the idea of the invention, a guide flap 2 is arranged into immediate proximity of the guide roll. The guide flap is then so close to the guide roll that the wire edges are still firm, due to the supporting effect caused by the nearby guide roll. Preferably the guide roll, control unit and guide flap form an entity, to which it is easy to install the required cables, pipes etc. and which can be serviced via one service lid, if necessary. An air-pressure duct leading to an air control valve 4 is marked with a line of dots and dashes 16 in the figure, a channel leading to the first actuator with a line of dots and dashes 17 and a channel to be led to the second actuator, intended for transmitting constant pressure, with a line 18. A conductor leading to the control unit of the paper machine is marked with a broken line 19. Figure 3 shows a detail of an arrangement of the invention. A guide flap 2 is arranged to the free end of an arm 12, whereby the lateral movement of a wire 1 turns the arm in respect to the pivot point of the arm. The arm is combined with the air control valve of a control unit 4 such that the movement of the arm opens and closes the connection from a compressed air source to a pneumatic bellows 5 according to the lateral position of the wire. The allowable transversal range of movement of the wire is marked with a reference L in the figure. The exceeding of the allowable range of movement is controlled for example by means of edge sensors 13 and 14 arranged to give an alarm to a control system 15 of the paper machine. The edge sensors can be limit switches, inductive sensors or the like which are arranged to be activated when the arm 12 moves to a certain extent. The relative position of the edge sensors can be adjusted, and thus the size of the allowable operating range can be changed. In addition, one or more sensors 20 measuring the position of the guide flap can be used, and the measuring result is transmitted to the control system 15 of the paper machine. In this case the lateral position of the wire can be continuously measured during the operation of the paper machine. Such an application is shown in Figure 4. Values corresponding to the allowable range of movement can be programmed in the control system/automation system of the paper machine. The information on the exceedings of the allow- able range of operation L and the position of the wire can be utilized in the maintenance, when the conditions of the wire and wire guide roll are evaluated and further when the operating parameters of the paper machine are adjusted. It can also be seen from Figure 4 that the guide flap can also be arranged to be moved linearly in the direction B by means of a suitable slide mechanism, for instance. In this application, a control system of a paper machine is understood as various automation systems, a user interface and, in its simplest, a control panel of a paper machine. A control unit, for its part, can in its simplest be an air distributor with a mechanically or electrically operated control valve for controlling the pneumatic actuator. The control unit may also be a programmable logic controlling the electric motor, for instance, or some other suitable controller between the actuator and the guide flap. The drawings and the related description are only intended to illustrated the idea of the invention. The details of the invention may vary within the scope of the claims. Consequently, besides a plate-like flap, the guide flap refers to other elements which can be applied to the monitoring of the position of the wire edge and arranged into physical contact with the wire edge.

Claims: CLAIMS 1. An arrangement in connection with a wire guide roll of a paper machine, which arrangement comprises a wire guide roll (3) transverse to the direction of travel (A) of a wire (1), the wire guide roll being arranged to be turned in the direction of travel of the wire by means of at least one actuator (5), and which arrangement comprises a guide flap (2) arranged against the wire edge and adapted to observe the lateral position of the wire, and in which arrangement the wire guide roll (3) is arranged to turn and guide the wire (1) on the basis of information provided by the guide flap on the lateral position of the wire and which arrangement further comprises means that are arranged to inform a control system (15) of the paper machine of the lateral position of the wire, characterized in that at least one sensor is arranged in connection with the guide flap (2) and that the information on the lateral position of the wire is adapted to be transmitted from the sensor to the control system (15) of the paper machine. 2. An arrangement as claimed in claim 1, characterized in that the guide flap is arranged to the free end of an arm that is arranged piv- otally, that the arm is arranged to pivot according to the lateral (B) position of the wire and that the arrangement comprises at least one sensor (13, 14) ar- ranged in connection with the arm (12), whereby the lateral movement of the guide flap (2) and thereby that of the wire are arranged to be determined by means of said sensor. 3. An arrangement as claimed in claim 2, characterized in that a first and a second sensor are arranged in the direction of movement of the arm (12) to different sides of the arm at a distance from each other, this distance being arranged to determine the allowable lateral operating range (L) of the wire. 4. An arrangement as claimed in claim 3, characterized in that the relative position of the sensors is adjustable, whereby the size of the allowable operating range (L) is also adjustable. 5. An arrangement as claimed in any one of the preceding claims, characterized in that the sensors are limit switches. 6. An arrangement as claimed in claim 1, characterized in that the sensor is arranged to measure the position of the guide flap and thereby transmit the measuring information on the lateral position of the wire to the control system (15) of the paper machine. 7. An arrangement as claimed in any one of the preceding claims, characterized in that the guide flap is arranged in connection with the guide roll, into its immediate proximity, so that due to the nearby guide roll the wire edges are still firm at the guide flap.

Inventors: JUUTINEN VESA, JUUTINEN, VESA
Applicants: JUUTINEN VESA, METSO PAPER INC, JUUTINEN, VESA, METSO PAPER INC.
Application year: 2000
Main classification: D21F1
IPC codes: B65H23, D21F1, D21F7