FIELD OF THE INVENTION

[001] The invention relates to control of a reeling machine, and particularly to control of a process of feeding a web of paper, cardboard or the like, in a reeling machine.

BACKGROUND OF THE INVENTION

[002] In a reeling machine such as that used for production of paper, cardboard, plastic etc., there are a plurality of cylinders that are used in various activities such as drying, separating, pressing and so forth. Such cylinders work in a speed mode, i.e. where the speed is maintained at a constant value; or in a torque mode, i.e. where the torque is maintained at a constant value. There may be certain situations that lead to a change in the speed / torque during operation. For example, there may be a rupture in a web of paper, which causes a drive operating a pope (bearing) reel, to rotate the pope reel at the maximum speed in order to maintain the required torque.

[003] There are certain solutions available for detecting such unfavourable situations. In one solution, a load loss is detected by simply comparing the load and / or current with a threshold for a certain duration. If it is detected that the load, or the current, is less / more-than a certain level for that duration, then it could be interpreted as a fault, and the corresponding action can be taken. There are. other solutions that make use of sensors for detecting rupture of paper. Such solutions have some limitations. In the first solution mentioned above, even if the drive is running at a minimum load, there could still be a fault due to load loss. For example, the speed may be higher than prescribed, because the load has not fallen below a threshold. In case of sensors, there could be issues like generation of false signals due to gas / vapours being present. Due to such problems, there is a significant downtime (in several minutes depending on the type of error), which leads to unwanted production losses.

[004] In view of the above, there is a need of an improved method for feeding a web of paper, cardboard or the like, in a reeling machine.

SUMMARY OF THE INVENTION

[005] An aspect of the invention relates to a method for feeding a web in a reeling machine. The reeling machine may be used for production of one or more of, but not limited to, paper, cardboard, and plastic. Accordingly, the web can be one of paper, cardboard, plastic and so forth.

[006] The reeling machine comprises a plurality of cylinders, at least one winding core, and optionally one or more sensors. Each of the plurality of cylinders is for at least one of supporting, reeling, and pressing the web. For example, there could be one or more cylinders that are used in a drying / separation stage, while one or more cylinders may be used for pressing / rolling, and so forth. The at least one winding core is for winding at least one roll of the web. For example, there could be a reel spool (also referred as winding tube or core) that could be used for preparing a roll of paper,. cardboard etc. The one or more sensors may be for sensing one of the speed and the torque of at least one cylinder of the plurality of cylinders, wherein the at least one • cylinder operates in one of a torque mode and a speed mode. For example, a pope (bearing) reel (also referred as a support drum, a reeling drum, or a pressing roll), can operate in a torque mode. In such a case, the torque is maintained by a corresponding drive or controller at a constant value, and the speed may vary. Accordingly, a sensor ' may be utilized for sensing the speed.

[007] In accordance, with the aspect, the method comprises monitoring one of the speed and the torque of the at least one cylinder. The monitoring is performed based on the mode of operation of the at least one cylinder. Taking the above example, the method can monitor the speed of the pope reel. Alternately, if a cylinder or roll is operating in a speed mode, then the torque may be monitored. Taking another case . where monitoring of both speed and torque is desired, both the speed and torque may be monitored using the one or more sensors (e.g. one, two or multiple).

[008] The method further comprises detecting a change in one of the speed and the * torque based on said monitoring. For example, there may be a change in speed of the pope reel due to a fault or a potential fault. Such change in speed may be detected by

comparing the monitored speed with a reference value. Reference values for comparison may be stored in the system beforehand by a user (e.g. an operator). The comparison may be performed periodically.
[009] Thereafter, the method comprises estimating a rate of change of one of the speed and the torque based on said detection. For example, in case of speed mode, the change in torque over a period of time may give the rate of change. The rate of change is compared with a threshold to determine an error condition, wherein the error condition the at least one cylinder operates at one of a speed and a torque that is one of higher and lower than one of a predetermined speed and a predetermined torque. For example, if the rate of change of speed is over a certain amount, the cylinder / roll may start spinning at a rate that is beyond control. Taking another example, if the rate of change of torque is higher than a certain amount, the cylinder / roll may come to a halt, leading to a jam. This determination can be performed very fast at a drive as compared to any external controller. In one implementation, the determination of the error condition is performed in about 2 to 5 seconds (e.g. in 2.5 seconds).

[0010] In addition, the method comprises generating a signal based on said determination. The signal is generated for controlling the operation of the at least one cylinder according to the error condition. For example, if the speed is high, then a warning / alarm may be sent to an operator, who can manually adjust the speed. Taking another example, the signal may be sent to a control system, which automatically . adjusts the speed/torque of the cylinder.

[0011] In one embodiment, the at least one cylinder is a pope reel. Here, controlling the operation of the pope reel comprises altering the speed of the pope reel.. This is because the pope reel works in a torque mode, and this control helps in avoiding overspeed / underspeed related issues.

[0012] The steps of detecting, estimating, comparing and generating, may be performed at one of a drive and a controller of the reeling machine.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The subject matter of the invention will be explained in more detail in the following text with reference to exemplary embodiments which are illustrated in the attached drawings, in which:

[0014] Fig; 1 illustrates a simplified diagram of a reeling machine, in accordance with an embodiment of the invention; -

[0015] Fig. 2 illustrates a graph of a cylinder of the reeling machine operating in a speed mode;

[0016] Fig. 3 illustrates a graph of a cylinder of the reeling machine operating in a speed mode, in accordance with an embodiment of the invention; and

[0017] Fig. 4 illustrates a graph of a cylinder of the reeling machine operating in a . torque mode, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

[0018] Referring to Fig. 1, which illustrates a simplified diagram of a reeling machine 100. As illustrated, reeling machine 100 may include a plurality of cylinders such as, but not limited to, cylinders 102a, 102b, 102c and 102d. Each of the plurality of cylinders may be used for one of, but not limited to, supporting, drying, rolling, and pressing. For example, cylinder 102a may be used for drying a web, while cylinders 102b and 102c may be used as guide rolls, and 102d may be a pope reel.

[0019] Reeling machine 100 also has one or more winding cores such as, but not limited to, a winding core 104, which acts as a reel spool. In addition, reeling machine 100 has one or more drives and / or one or more controllers (not illustrated in figures) that control the plurality of cylinders. Reeling machine 100 also has one or more sensors (not illustrated in figures) for detecting one of speed and torque of one or more cylinders . of the plurality of cylinders.

[0020] One or more of the plurality of cylinders may work in one of a speed mode, and a torque mode.. For example, cylinder 102d, which is a pope reel, works in a torque mode. Depending on the mode of the cylinder, the speed or torque may be monitored.

[0021] Fig. 2 illustrates a graph of a cylinder operating in a speed mode in accordance with prior art methods. As illustrated, in the speed mode, the speed reaches a specific ; value and remains constant, while the torque may vary. Here, a deviation in the torque level over a duration may indicate an over-load or under-load condition, as shown in the graph. For example, when t2 - tl is greater than a threshold number of seconds, and the torque is higher / lower than a specific value throughout the duration, it is assumed that it is an over-load / under-load.

[0022] The invention enables faster detection of such over-load or under-load conditions, as shown in Fig. 3 (for speed mode) and Fig. 4 (for torque mode). With reference to Fig. 3, the detection may be enabled as soon as the speed reaches the speed reference, which may be fixed based on previous data.

[0023] Here, a rate of change of torque may be determined upon sensing a change in torque levels, to detect abnormal operating conditions such as jamming, load loss and so forth, In one embodiment, the rate of change of torque is compared with threshold values to determine if:

dT/dt>Xl (l);or
dT/dt