Uncoiling device and uncoiling method

Abstract

To provide an uncoiling device which can inhibit coil deviation when uncoiling a coil with a pair of cradle rolls, and to provide an uncoiling method.SOLUTION: An uncoiling device for a coil having a coil crown, includes a pair of cradle rolls which uncoils a coil placed thereon. A contact angle between the pair of cradle rolls and each of the coil is set to be not smaller than 30° and not larger than 60°.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a coil unwinding device and a coil unwinding method using a pair of cradle rolls. [Background technology]

[0002] In a continuous processing line for steel strips (strip steel sheets), a coiled steel strip is discharged by a payoff reel, and the steel strip is continuously subjected to predetermined processing. In order to stably perform such continuous processing of steel strips, it is important to properly unwind the coil and discharge the steel strip. Therefore, various methods have been devised for unwinding the coil.

[0003] For example, in the coil unwinding method disclosed in Patent Document 1, an opener is used to open the tip of a coil attached to a payoff reel. At this time, a pressure roll, which is used to prevent bending of the unwound steel strip, is used to straighten the curl of the tip of the coil opened by the opener.

[0004] Also, for example, in the coil unwinding method disclosed in Patent Document 2, a pressure roll is used to straighten the curl of the tip of the coil that has been unwound by an opener, similar to the method disclosed in Patent Document 1. Furthermore, in the method disclosed in Patent Document 2, after unwrapping the tip of the coil, the opener moves away from the payoff reel in synchronization with the feed speed of the coil caused by the rotation of the payoff reel.

[0005] In addition, for example, in a steel strip unwinding device disclosed in Patent Document 3, after the outer periphery of the coil is pressed by a pressure roll, the pressure of the pressure roll is reduced to bring side guides into contact with both widthwise ends of the steel strip, and the steel strip is paid out from the pay-off reel. In such a case, the upward displacement of the steel strip is regulated by the pressure roll, and the widthwise displacement is regulated by the side guide, thereby stabilizing the running state of the steel strip paid out from the pay-off reel. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5212191 [Patent Document 2] Patent No. 5435121 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-266121 Summary of the Invention [Problem to be solved by the invention]

[0007] In a continuous processing line, the steel strip is usually paid off from the coil by a pay-off reel as described above, but when unwinding the coil, in order to shorten the handling time and improve throughput, the tip of the coil may be paid off before the coil is inserted into the pay-off reel. Specifically, the coil is loaded on a pair of rolls (hereinafter referred to as "cradle rolls"), and the cradle rolls are rotated to rotate the coil and unwind it.

[0008] In such cases, the rotation of the coil can cause a skew (a slight cross) between the coil and the cradle roll. This skew can then cause the coil to move axially due to the thrust force. If the coil moves and shifts on the cradle roll, it can become difficult to insert the coil into the payoff reel. Furthermore, the coil may fall over on the cradle roll, potentially causing damage to the equipment.

[0009] The main cause of coil misalignment is a faulty cradle roll equipment. However, due to its nature, faulty cradle roll equipment is difficult to correct. The causes of coil misalignment will be described in detail later.

[0010] Furthermore, in order to suppress coil slippage, it is sufficient to reduce the amount of coil rotation; however, depending on the arrangement of equipment in the continuous processing line, restrictions are imposed on the amount of steel strip discharged from the tip of the coil, and there are limits to controlling the amount of coil rotation. For example, when the distance between the coil and the equipment upstream of the continuous processing line is large, it is difficult to suppress the amount of coil rotation. In other words, suppressing coil slippage poses a potential problem in that it also leads to restrictions on the configuration of the continuous processing line.

[0011] It should be noted that all of the methods disclosed in Patent Documents 1 to 3 relate to methods for unwinding a coil inserted into a payoff reel, and are not methods for unwinding a coil before inserting it into a payoff reel. Therefore, Patent Documents 1 to 3 do not address the problem of coil misalignment on the cradle roll, and naturally do not mention any method for solving this problem.

[0012] The present invention has been made in consideration of these points, and aims to provide a coil unwinding device and a coil unwinding method that can suppress coil misalignment when unwinding a coil using a pair of cradle rolls. [Means for solving the problem]

[0013] As mentioned above, the mechanism by which coil misalignment occurs on the cradle roll is that the coil moves due to the thrust force caused by the skew between the coil and the cradle roll. However, the inventors further investigated the causes of coil misalignment and found that the influence of coil crown is significant. The presence of coil crown causes the coil and cradle roll to come into near-point contact (almost the same as one-point contact, but with a contact area that is slightly larger than the one-point contact point), reducing the contact area. This weakens the constraint on the coil by the cradle roll, causing the coil to rotate around its vertical axis (horizontal rotation), increasing the coil skew and accelerating coil misalignment.

[0014] Therefore, the present inventors have come to the knowledge that controlling the contact angle between the coil and the cradle roll is effective in suppressing the rotation of the coil about the vertical axis, which can cause the coil to slip.

[0015] The present invention is a coil unwinding device having a coil crown, which is provided with a pair of cradle rolls that load the coil and unwind the coil, and is characterized in that the contact angle between the pair of cradle rolls and the coil is 30° to 60°.

[0016] The coil unwinding device may have a function of reducing the contact angle when a coil misalignment is detected after unwinding of the coil has started, and fixing the contact angle when the coil misalignment becomes smaller.

[0017] The present invention also provides a method for unwinding a coil having a coil crown, comprising the steps of loading the coil onto a pair of cradle rolls and rotating the pair of cradle rolls to unwind the coil, wherein the contact angle between the pair of cradle rolls and the coil during the step of loading the coil and the step of unwinding the coil is set to 30° to 60°.

[0018] In the step of unwinding the coil, the contact angle may be reduced when a coil misalignment is detected, and the contact angle may be fixed when the coil misalignment becomes smaller. [Effects of the Invention]

[0019] According to the present invention, by controlling the contact angle between the pair of cradle rolls and the coil to be within a predetermined range, it is possible to strengthen the restraining force of the pair of cradle rolls on the coil and geometrically restrain the coil, which in turn makes it possible to suppress the thrust force due to the skew between the coil and the cradle rolls and to suppress the displacement of the coil on the cradle rolls. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is an explanatory diagram showing an outline of the configuration of a continuous processing line. [Figure 2] FIG. 1 is a perspective view showing an outline of a partial configuration of a coil unwinding device (coil positioner). [Figure 3] FIG. 10 is a graph showing the relationship between the coil crown amount and the coil misalignment amount. [Figure 4] FIG. 10 is a diagram illustrating parallelism misalignment of the cradle roll. [Figure 5] FIG. 10 is a diagram illustrating horizontal misalignment of a cradle roll. [Figure 6] FIG. 10 is a diagram illustrating the contact angle between a cradle roll and a coil. [Figure 7] FIG. 10 is a graph showing the relationship between the amount of coil misalignment and the contact angle. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0022] <Configuration of continuous processing line> First, the configuration of a continuous processing line in which a coil unwinding device according to this embodiment is implemented will be described with reference to Figure 1. In this embodiment, a case will be described in which the continuous processing line 1 is a cold rolling line, as an example. In the continuous processing line 1, a coil C produced in a hot rolling process is unwound, and a steel strip S is delivered, and predetermined processes such as welding and rolling are continuously performed on the steel strip S.

[0023] Fig. 1 is an explanatory diagram showing the outline of the configuration of a continuous processing line 1. As shown in Fig. 1, the continuous processing line 1 is equipped with a coil unwinding device 10, deflector rolls 11, pinch rolls 12, a leveler 13, and a welding machine 14. Note that the continuous processing line 1 is further equipped with devices such as a rolling mill downstream of the welding machine 14 in the conveying direction, but for the sake of explanation, Fig. 1 does not show the entire continuous processing line 1, but shows the configuration from the coil unwinding device 10 to the welding machine 14.

[0024] The coil unwinding device 10 unwinds the coil C and delivers the steel strip S toward the welding machine 14. The deflector roll 11 changes the direction of the steel strip S so that the steel strip S delivered from the coil C is transported to the welding machine 14. The pinch rolls 12 are provided as a pair, one above the other, and sandwich the steel strip S between them to transport it to the welding machine 14. The leveler 13 has a plurality of work rolls arranged in a staggered pattern above and below along the transport direction of the steel strip S, and corrects the shape of the steel strip S. The welding machine 14 welds the rear end of the preceding steel strip S to the front end of the following steel strip S.

[0025] <Basic configuration of coil unwinding device> Next, the basic configuration of the coil unwinding device 10 will be described with reference to Figures 1 and 2. Figure 2 is a perspective view showing an outline of a partial configuration of the coil unwinding device 10 (coil positioner 20).

[0026] The coil unwinding device 10 is provided with a coil positioner 20 that loads the coil C and moves it to a predetermined position, and a payoff reel 21 that pays off the steel strip S from the coil C.

[0027] The coil positioner 20 is configured to be able to move the coil C horizontally and vertically, and moves the coil C sequentially to a coil receiving position P1, a leading edge feeding position P2, and a payoff reel insertion position P3. The coil positioner 20 includes cradle rolls 30a, 30b, stands 31a, 31b, motors 32a, 32b, and a moving frame 33.

[0028] Each cradle roll 30a, 30b extends in the Z direction and is arranged side by side in the X direction. That is, the pair of cradle rolls 30a, 30b is arranged substantially parallel. Each cradle roll 30a, 30b is arranged horizontally. Each cradle roll 30a, 30b is configured to be able to load a coil C so that the axial direction of the coil C faces the Z direction. Each cradle roll 30a, 30b is configured to be rotatable, and the coil C is rotated to unwind. In the example shown in FIG. 2, the cradle rolls 30a, 30b are rotated counterclockwise, and the coil C is rotated clockwise.

[0029] In the following description, the cradle roll 30a on the upstream side (entry side) of the rotation direction of the coil C (unwinding direction of the coil C) is referred to as the upstream cradle roll 30a, and the cradle roll 30b on the downstream side (exit side) of the rotation direction of the coil C is referred to as the downstream cradle roll 30b. In the example shown in Fig. 2, the rotation direction of the coil C is clockwise, the upstream cradle roll 30a is disposed on the positive side of the X direction, and the downstream cradle roll 30b is disposed on the negative side of the X direction.

[0030] The base 31a supports the upstream cradle roll 30a. The base 31a may have any configuration. For example, the base 31a supports both ends of the central axis 34a of the upstream cradle roll 30a in the X direction, is disposed below the upstream cradle roll 30a with a gap therebetween, and extends in the Z direction. The base 31b has a similar configuration to the base 31a, and supports the central shaft 34b of the downstream cradle roll 30b.

[0031] The motor 32a is provided below the upstream cradle roll 30a and on the negative Z-direction side of the stand 31a. The motor 32a rotates the upstream cradle roll 30a via a gear (not shown). The motor 32b has a configuration similar to that of the motor 32a, and is provided below the downstream cradle roll 30b and on the negative Z-direction side of the base 31b. The motor 32b rotates the downstream cradle roll 30b.

[0032] The moving frame 33 supports the mounts 31a and 31b. The moving frame 33 is configured to be movable in the horizontal and vertical directions by a moving mechanism (not shown).

[0033] In the coil positioner 20 having the above configuration, the positive Z direction side is the work side (WS), and the negative Z direction side is the drive side (DS).

[0034] <Continuous processing method> In the continuous processing line 1 having the above-described configuration, first, at the coil receiving position P1, the coil C is delivered to the coil positioner 20 and loaded onto the pair of cradle rolls 30a, 30b.

[0035] Next, the coil positioner 20 is moved to the leading end feed position P2. At the leading end feed position P2, the pair of cradle rolls 30a, 30b are rotated to rotate the coil C. As a result, the coil C is unwound and the leading end of the steel strip S is paid out.

[0036] The steel strip S unwound from the coil C passes through a deflector roll 11, a pinch roll 12, and a leveler 13, and is transported to a welding machine 14. In the welding machine 14, the leading end of the steel strip S is welded to the trailing end of the preceding steel strip S.

[0037] In the welding machine 14, while the rear end of the preceding steel strip S is being welded to the front end of the following steel strip S (the paid-out steel strip S), the coil positioner 20 is moved to the pay-off reel insertion position P3. At the pay-off reel insertion position P3, the pay-off reel 21 is inserted into the coil C by a moving mechanism (not shown). Thereafter, the steel strip S is paid out from the coil C inserted into the pay-off reel 21.

[0038] <Mechanism of coil misalignment> In the coil unwinding device 10 of the continuous processing line 1, from the time when unwinding of the coil C begins at the leading end feed position P2 until the payoff reel 21 is inserted into the coil C at the payoff reel insertion position P3, the coil C loaded on the pair of cradle rolls 30a, 30b moves approximately in the Z direction, which may cause coil misalignment on the cradle rolls 30a, 30b. The mechanism of coil misalignment will be explained below.

[0039] The main causes of the coil misalignment include (1) the coil crown of the coil C, (2) misalignment in parallelism of the cradle rolls 30a and 30b, and (3) misalignment in horizontality of the cradle rolls 30a and 30b.

[0040] (1) Coil crown of coil C The coil C transported to the continuous processing line 1, which is a cold rolling line, was previously produced in a hot rolling process. In the hot rolling process, when a steel plate is rolled with a rolling roll, the rolling roll undergoes elastic deformation, causing the thickness of the steel plate to increase in the center of the width direction and decrease at both ends. When the steel plate rolled in this way is wound into a coil, the plate crown of the steel plate overlaps, giving the coil C an outer shape like a barrel, with the coil diameter increasing in the center of the width direction and decreasing at both ends. The difference between the coil radius of this coil C at the center and the coil radius at the ends is the coil crown.

[0041] If the coil C has a coil crown, the coil C and the upstream cradle roll 30a will be in approximately point contact, reducing the contact area, and the coil C and the downstream cradle roll 30b will be in approximately point contact, reducing the contact area. This weakens the restraint of the coil C by the cradle rolls 30a and 30b. Furthermore, depending on the parallelism and horizontality of the cradle rolls 30a and 30b (described later) and the method of loading the coil C onto the cradle rolls 30a and 30b, the axial direction of the coil C may be tilted relative to the axial direction of each cradle roll 30a and 30b (hereinafter referred to as "coil tilt"). This coil tilt creates a difference in peripheral speed between the coil C and the upstream cradle roll 30a and also between the coil C and the downstream cradle roll 30b. In other words, relative slip occurs due to the difference in diameter between the contact surfaces caused by the coil crown, generating a rotational moment around the Y-axis in the coil C. Furthermore, because the restraint of the coil C by the cradle rolls 30a and 30b is weak, the coil C becomes more rotatable.

[0042] When the rotation moment is generated, the coil C moves, resulting in a skew (slight cross) between the coil C and each of the cradle rolls 30a and 30b. Then, the thrust force caused by this skew moves the coil C in the axial direction (approximately the Z direction).

[0043] The present inventors conducted an FEM analysis to verify the influence of coil misalignment due to coil crown. In this analysis, the parallelism (described below) of the cradle rolls 30a and 30b (described below) was set to 4 mm and the horizontality (described below) was set to 0 (zero) mm, as equipment-related disturbances that could cause coil misalignment. Figure 3 shows the results of this analysis, showing the relationship between the amount of coil crown (horizontal axis) and the amount of coil misalignment (vertical axis). Referring to Figure 3, when there was no coil crown, almost no coil misalignment occurred. In contrast, as the amount of coil crown increased, the amount of coil misalignment increased. It is presumed that the reason for the increased coil misalignment when there was coil crown is the geometric constraint of the coil C by the cradle rolls 30a and 30b, as described above. As described above, it was verified that coil misalignment occurs due to coil crown.

[0044] (2) Parallelism misalignment of the cradle rolls 30a and 30b Typically, the cradle rolls 30a and 30b are arranged parallel to one another. However, due to equipment design issues, there is a certain degree of error, and the cradle rolls 30a and 30b are not arranged perfectly parallel to one another. That is, as shown in FIG. 4, the distance Lws between the cradle rolls 30a and 30b in the X direction on the positive Z-direction side (WS side) is different from the distance Lds between the cradle rolls 30a and 30b in the X direction on the negative Z-direction side (DS side). In the example of FIG. 4, the distance Lws is greater than the distance Lds, and the cradle rolls 30a and 30b are arranged in a V-shape in plan view. In the following description, the absolute value of the difference between the distance Lws between the cradle rolls 30a and 30b on the WS side and the distance Lds between the cradle rolls 30a and 30b on the DW side is referred to as parallelism (=|Lws - Lds|). The state in which the cradle rolls 30a, 30b are parallel to each other and are not parallel to each other is called parallelism misalignment.

[0045] If there is misalignment in the parallelism of the cradle rolls 30a, 30b, skew occurs between the coil C and the cradle rolls 30a, 30b, and the thrust force caused by this skew generates a rotational moment about the Y axis in the coil C. When this rotational moment occurs, the skew between the coil C and the cradle rolls 30a, 30b is further accelerated, and the thrust force also increases. Then, the thrust force caused by this skew causes the coil C to move in the axial direction (approximately the Z direction).

[0046] (3) Horizontal misalignment of the cradle rolls 30a and 30b Typically, the cradle rolls 30a, 30b are arranged horizontally. However, due to equipment design issues, there is a certain degree of error, and the arrangement of the cradle rolls 30a, 30b is not completely horizontal. That is, as shown in FIG. 5 , with a horizontal axis passing through the center of the width of the upstream cradle roll 30a as a reference, there is a vertical distance Hws in the Y direction from the horizontal on the positive Z-direction side (WS side) of the upstream cradle roll 30a, and there is also a vertical distance Hds in the Y direction from the horizontal on the negative Z-direction side (DS side) of the upstream cradle roll 30a. In the following description, the absolute value of the difference between the vertical distance Hws on the WS side of the upstream cradle roll 30a and the vertical distance Hds on the DW side is referred to as the horizontality (=|Hws-Hds|). Similarly, for the downstream cradle roll 30b, the absolute value of the difference between the vertical distance Hws on the WS side and the vertical distance Hds on the DW side is referred to as the horizontality. Furthermore, the state in which the cradle rolls 30a and 30b are not horizontal is called horizontal misalignment.

[0047] If there is misalignment in the horizontality of each of the cradle rolls 30a, 30b, the thrust force due to gravity will cause the coil C to move in the axial direction (approximately in the Z direction).

[0048] As described above, the main causes of coil misalignment include (1) the coil crown of the coil C, (2) misalignment in parallelism of the cradle rolls 30a and 30b, and (3) misalignment in horizontality of the cradle rolls 30a and 30b. Analysis by the present inventors has revealed that the amount of coil misalignment caused by (3) misalignment in horizontality of the cradle rolls 30a and 30b is extremely small compared to the amount of coil misalignment caused by (1) the coil crown of the coil C and (2) misalignment in parallelism of the cradle rolls 30a and 30b.

[0049] Therefore, in the present invention, the following factors are considered to cause coil misalignment: (1) the coil crown of the coil C and (2) the parallelism misalignment of the cradle rolls 30a, 30b. Note that (1) the coil crown of the coil C inevitably occurs in the pre-treatment hot rolling process. Furthermore, errors in the equipment design of the cradle rolls 30a, 30b cannot be avoided, and (2) the parallelism misalignment of the cradle rolls 30a, 30b also inevitably occurs. Moreover, since the parallelism of the cradle rolls 30a, 30b increases during operation due to wear and tear on the equipment, it is difficult to control in terms of productivity and work efficiency.

[0050] <Method for preventing coil misalignment> In the present invention, (1) we focus on the coil misalignment caused by the coil crown of the coil C and suppress the coil misalignment. As described above, the presence of the coil crown reduces the contact area between the coil C and each of the cradle rolls 30a, 30b. This weakens the constraint on the coil by the cradle rolls 30a, 30b, causing the coil C to rotate around the Y axis, increasing the skew of the coil C and accelerating the coil misalignment.

[0051] Therefore, the present inventors have studied methods for strengthening the restraining force of the coil by the cradle rolls 30a, 30b, and have come up with the idea of ​​controlling the contact angle between the pair of cradle rolls 30a, 30b and the coil C.

[0052] [Definition of contact angle] First, the definition of the contact angle between the pair of cradle rolls 30a, 30b and the coil C, which will be focused on below, will be described with reference to Fig. 6. Fig. 6 is a diagram for explaining the contact angle between the cradle roll and the coil.

[0053] In this embodiment, when defining the contact angle between the pair of cradle rolls 30a, 30b and the coil C, attention is focused on the positional relationship between the pair of cradle rolls 30a, 30b and the coil C at the center position in the plate width direction (Z-axis direction in FIG. 6) of the coil C. FIG. 6 is assumed to schematically show the positional relationship between the pair of cradle rolls 30a, 30b and the coil C at the center position in the plate width direction of the coil C.

[0054] Here, consider a line segment connecting the central axis of one of the cradle rolls and the central axis C1 of the coil C. The angle between the horizontal line (a line parallel to the X-axis direction in FIG. 6) at the contact position between the cradle roll of interest and the coil C and the above line segment is defined as the contact angle θ (0°<θ<90°) between the cradle roll of interest and the coil C.

[0055] For example, when focusing on the cradle roller 30a, consider a line segment La connecting the central axis 34a of the cradle roller 30a and the central axis C1 of the coil C, and the angle θ formed by this line segment La and the horizontal line at the contact position between the cradle roller 30a and the coil C is the contact angle θ between the cradle roller 30a and the coil C. Similarly, when focusing on the cradle roller 30b, consider a line segment Lb connecting the central axis 34b of the cradle roller 30b and the central axis C1 of the coil C, and the angle θ formed by this line segment Lb and the horizontal line at the contact position between the cradle roller 30b and the coil C is the contact angle θ between the cradle roller 30b and the coil C.

[0056] [Relationship between contact angle θ and coil displacement] As described above, in the present invention, the contact angle between the pair of cradle rolls 30a, 30b and the coil C is controlled in order to strengthen the restraining force of the cradle rolls 30a, 30b on the coil.

[0057] The inventors conducted an FEM analysis to verify the relationship between the contact angle θ defined above and coil misalignment. In this analysis, the parallelism of the cradle rolls 30a and 30b as described above was set to 4 mm, and the horizontality was set to 0 (zero) mm, as equipment-related disturbances that could cause coil misalignment. The coil diameter at the center of the coil C in the sheet width direction was set to 1531 mm, and the diameter of the cradle roll was set to 350 mm. The distance between the axes of the pair of cradle rolls on the WS side was set to 830 mm. The contact angle θ was varied within a range of 30° to 60°, and the values ​​of the coil misalignment were verified.

[0058] Figure 7 shows the results of this analysis, illustrating the relationship between the contact angle θ (horizontal axis) and the amount of coil slippage (vertical axis). Referring to Figure 7, it is clear that the overall trend is that the amount of coil slippage increases as the contact angle θ increases. Furthermore, when the slope of the line shown in Figure 7 is considered, it is estimated that the increase in the amount of coil slippage approaches asymptotically when the contact angle θ is 60° or greater, and beyond that, there is almost no effect in suppressing the amount of coil slippage. It is presumed that this suppression of the amount of coil slippage occurs because the restraining force of the coil C by the cradle rolls 30a and 30b is strengthened as the contact angle θ decreases.

[0059] Furthermore, as a result of verification by the present inventors, the relationship between the contact angle θ and the amount of coil displacement showed results similar to those shown in FIG. 7, even when the coil diameter was changed.

[0060] From the above results, it was verified that coil slippage on the cradle roll can be suppressed by setting the contact angle θ between the cradle rolls 30a, 30b and the coil C within the range of 30° to 60°, and further that the amount of coil slippage decreases as the contact angle θ becomes smaller.

[0061] (Coil unwinding device) Based on the findings described above, in the coil unwinding device according to this embodiment, the contact angle θ between the pair of cradle rolls 30a, 30b and the coil C is set to 30° to 60°. This strengthens the constraint of the coil C by the cradle rolls 30a, 30b. This suppresses rotation of the coil C about the Y axis, and reduces the thrust force caused by the skew between the coil C and the cradle rolls 30a, 30b. As a result, axial movement of the coil C can be suppressed, and coil misalignment can be suppressed.

[0062] 6, even if the diameter of the cradle rolls 30a, 30b is constant, the value of the contact angle θ varies depending on the diameter of the loaded coil C. Therefore, in the coil unwinding device according to this embodiment, the value of the contact angle θ is controlled depending on the diameter of the loaded coil C.

[0063] A contact angle of more than 60° is undesirable because the restraining force of the coil C by the cradle rolls 30a, 30b is reduced, resulting in insufficient suppression of coil slippage. On the other hand, a smaller contact angle is preferable because it reduces the amount of coil slippage. However, a smaller contact angle increases the amount of coil dropping below the cradle rolls, causing interference with the moving frame 33 and the stands 31a, 31b, and increasing the risk of the coil falling between the cradle rolls due to elastic deformation of the coil. Therefore, a contact angle of 30° or more is preferable. Therefore, in the coil unwinding device according to this embodiment, the contact angle θ is set within a range of 30° to 60°, and more preferably within a range of 30° to 55°. The value of the contact angle θ is even more preferably 35° to 50°.

[0064] Furthermore, the coil unwinding device according to this embodiment preferably has a function of decreasing the contact angle when coil misalignment is detected after unwinding of the coil has begun, and fixing the contact angle when the coil misalignment becomes small. As shown in an example in Figure 7, the amount of coil misalignment can be reduced by setting the contact angle θ to a smaller value. Therefore, by implementing the above-described function in the coil unwinding device according to this embodiment, even if coil misalignment occurs, the contact angle θ can be changed so that the amount of coil misalignment is suppressed, thereby eliminating the coil misalignment.

[0065] For example, after the start of unwinding the coil, when it is determined that the amount of coil misalignment exceeds a predetermined threshold and falls outside the allowable operational range, the geometric positional relationship may be controlled so that the contact angle θ becomes smaller, and when the coil misalignment becomes smaller and falls below the predetermined threshold, the contact angle θ may be fixed. Furthermore, such a threshold for the amount of coil misalignment may be set appropriately depending on the operational conditions, etc.

[0066] In addition, in the coil unwinding device of this embodiment, whether or not a coil misalignment has occurred during unwinding can be easily determined, for example, by placing a detection device such as a position sensor on at least one of the WS or DS ends of the coil C and referring to the output from such detection device.

[0067] Furthermore, in the coil unwinding device according to this embodiment, the contact angle θ can be changed by changing the geometrical positional relationship between the coil C and the cradle rolls 30a, 30b. There are no particular restrictions on the method for changing the geometrical positional relationship, and various methods may be employed as appropriate. For example, by providing a movement mechanism such as a hydraulic actuator on the stands 31a, 31b on which the cradle rolls 30a, 30b are mounted, and then changing the distance between the axes of the pair of cradle rolls, the contact angle θ can be easily changed.

[0068] (How to unwind the coil) As shown in FIG. 1, in the coil unwinding device 10, first, at the coil receiving position P1, the coil C is delivered to the coil positioner 20 and loaded onto a pair of cradle rolls 30a, 30b.

[0069] Next, the coil positioner 20 is moved to the leading end feed position P2. At the leading end feed position P2, the pair of cradle rolls 30a, 30b are rotated to rotate the coil C. As a result, the coil C is unwound and the leading end of the steel strip S is paid out.

[0070] In the coil unwinding method according to this embodiment, when the coil is loaded and when the coil is unwound as described above, the contact angle θ between the pair of cradle rolls 30a, 30b and the coil C is set to a range of 30° to 60°. This strengthens the constraint of the coil C by each of the cradle rolls 30a, 30b. This suppresses rotation of the coil C about the Y-axis and reduces the thrust force caused by the skew between the coil C and each of the cradle rolls 30a, 30b. As a result, axial movement of the coil C can be suppressed, and coil misalignment can be suppressed.

[0071] Next, the coil positioner 20 is moved to the payoff reel insertion position P3. At the payoff reel insertion position P3, the payoff reel 21 is inserted into the coil C by a moving mechanism (not shown). Thereafter, the steel strip S is paid out from the coil C inserted into the payoff reel 21.

[0072] Furthermore, in the coil unwinding method according to this embodiment, when the coil is unwound, it is preferable to perform control so that if coil misalignment is detected, the contact angle θ is reduced, and if the coil misalignment becomes smaller, the contact angle θ is fixed. In this way, even if coil misalignment occurs, the contact angle θ can be changed so that the amount of coil misalignment is suppressed, thereby eliminating the coil misalignment that has occurred.

[0073] <Action and effect> According to the above embodiment, even if there is a misalignment in the parallelism of the cradle rolls 30a, 30b when unwinding the coil C, the contact angle between the coil C and each cradle roll 30a, 30b can be controlled according to the coil diameter, thereby suppressing the rotation and skew of the coil C around the Y-axis caused by the coil crown of the coil C, and suppressing the coil misalignment.

[0074] While one embodiment of the present invention has been described above, the present invention is not limited to the illustrated embodiment. It is clear that a person skilled in the art can conceive of various modifications and alterations within the scope of the ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

[0075] Furthermore, the effects described herein are merely descriptive or exemplary and are not limiting. In other words, the technology according to the present disclosure may achieve other effects that would be apparent to a person skilled in the art from the description of this specification, in addition to or in place of the above-described effects. [Example]

[0076] An experiment was conducted to verify the coil misalignment suppression effect of the present invention. This verification was carried out using a coil loaded on a pair of cradle rolls, similar to the coil positioner shown in Figure 2.

[0077] In this verification, the maximum coil misalignment amount was measured when 20 m of each of ten coils with outer diameters of 1.2 m to 2.0 m and widths of 1.0 m to 1.6 m was unwound. The diameter of each cradle roll was 350 mm, and the roll width (body length) was 1 m. In this case, the coil misalignment amount was measured as the absolute value of the amount of axial movement of the coil from the position of the coil when it was loaded on the pair of cradle rolls. The coil crown of a 1.5 m wide coil was measured to be 3 mm.

[0078] In this test, the distance between the axes of the WS side of the pair of cradle rolls was varied within a range of 600 to 1300 mm depending on the coil diameter, with a standard value of 830 mm. In this test, a smaller contact angle θ is preferable because, as mentioned above, the amount of coil misalignment is reduced. However, the smaller the contact angle θ, the greater the downward projection of the coil, increasing the possibility of contact with the equipment located below the cradle roll. Therefore, in this test, the contact angle θ was adjusted within a range of 45° or more, taking into account the geometric arrangement with the equipment.

[0079] Regardless of the movement of the cradle rolls, the distance between the axes of the WS end of the pair of cradle rolls was 4 mm larger than the distance between the axes of the DS end of the pair of cradle rolls. In other words, the pair of cradle rolls were arranged non-parallel (in a V-shape), causing parallelism misalignment.

[0080] As the condition for the contact angle θ, at least one of the following condition A and condition B was set. Condition A: Before loading the coil, adjust the distance between the cradle roll axes so that the contact angle θ is 45°. Condition B: When unwinding the coil, the distance between the cradle roll axes is adjusted according to the amount of coil misalignment so that the contact angle θ falls within the range of 30° to 60°.

[0081] The conditions for each example and comparative example and the verification results obtained are summarized in Table 1 below.

[0082] [Table 1]

[0083] As shown in Table 1 above, in the comparative example in which the contact angle θ was not controlled, the maximum coil deviation was 300 mm, whereas in Examples 1 and 2 in which the contact angle θ was controlled, the maximum coil deviation was 100 mm and 110 mm, respectively, thereby successfully suppressing coil deviation.

[0084] Furthermore, in Example 3, in which the contact angle was adjusted when the coil was loaded and also adjusted when the coil was unwound, the maximum coil misalignment amount was 80 mm, and the coil misalignment could be significantly suppressed.

[0085] From the above results, it was confirmed that the amount of coil misalignment can be suppressed by controlling the contact angle between the pair of cradle rolls and the coil. It was also confirmed that the amount of coil misalignment can be further suppressed by adjusting the contact angle when loading the coil and also by adjusting the contact angle when unwinding the coil. [Industrial Applicability]

[0086] The present invention is useful when unwinding a coil using a pair of cradle rolls. [Explanation of symbols]

[0087] 1 Continuous processing line 10 Coil unwinding device 11 Deflector roll 12 Pinch Roll 13 Leveller 14 Welding machine 20 Coil Positioner 21 Payoff Reel 30a Upstream cradle roll 30b Downstream cradle roll 31a, 31b Mounting stand 32a, 32b motor 33 Moving Frame 34a, 34b center axis 40 recess C coil P1 Coil receiving position P2 Lead edge feed position P3 Payoff reel insertion position S steel strip

Claims

1. 1. An unwinding device for a coil having a coil crown, comprising: a pair of cradle rolls for loading the coil and unwinding the coil; A coil unwinding device characterized in that the contact angle between the pair of cradle rolls and the coil is 30° to 60°.

2. 2. The coil unwinding device according to claim 1, further comprising a function of reducing the contact angle when a coil misalignment is detected after the start of unwinding the coil, and fixing the contact angle when the coil misalignment becomes smaller.

3. 1. A method for unwinding a coil having a coil crown, comprising: loading the coil onto a pair of cradle rolls; and rotating the pair of cradle rolls to unwind the coil. A coil unwinding method, characterized in that in the coil loading step and the coil unwinding step, a contact angle between the pair of cradle rolls and the coil is set to 30° to 60°.

4. 4. The coil unwinding method according to claim 3, wherein in the step of unwinding the coil, the contact angle is reduced when a coil misalignment is detected, and the contact angle is fixed when the coil misalignment becomes smaller.

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