Perforating unit for web material

Abstract

A perforation unit (GP) for forming perforation lines (P) on the web material (N), where the perforation lines are formed by a predetermined number of perforations (F) spaced apart by a predetermined value and aligned along a predetermined perforation direction (CD); the perforation unit comprises an optical unit (3) capable of optically detecting the perforations (F) and configured for acquiring an image of the web material (N) corresponding to the perforation lines (P) and connected to a programmable processing unit (4) receiving an electrical signal generated by the optical unit (3), and transmit an error signal indicative of an abnormal condition related to operation of a group of perforations (GP) in accordance with a comparison of the detected number of perforations with a predetermined number of perforations.

Description

[0001] manual

[0002] The invention relates to a perforating unit for web material with a perforation control system.

[0003] In particular, but not exclusively, the system for controlling a perforating unit for a web material according to the invention may be used for controlling the perforation of a paper layer supplied to a rewinder in a paper converting process.

[0004] As is well known, in the paper processing process, a rewinder converts paper from a large diameter reel (usually called a "mother reel") into a plurality of smaller diameter rolls, which are subsequently subjected to transverse cutting to obtain rolls of predetermined lengths, such as toilet paper rolls, kitchen rolls, kitchen paper towels, etc. Upstream of the rewinder, a perforation unit is arranged to form transverse perforation lines on the web material provided by the mother reel. In this way, each roll will be formed by a series of paper webs separated by perforation lines, which facilitate the separation of the individual paper webs when necessary. Typically, the perforation unit comprises a blade holder roller on which a number of equiangularly spaced blades are mounted and a roller on which a counter blade is mounted. Typically, the blade holder roller rotates around its own axis at a predetermined angular velocity, while the counter blade is fixed. The perforation lines are generated by the periodic contact between the blade and the counter blade.

[0005] The perforations may be defective due to wear or breakage of one or more blades or counter blades, or due to improper assembly, or because the relative position of the rollers may be lost. For example, there may be fewer perforations than required.

[0006] US2014 / 121085 discloses a machine equipped with a perforating unit for producing perforation lines on a web material, the perforating unit comprising an optical unit for counting the perforation lines to count the number of pages defined by the perforation lines, thereby maintaining the perforating element after forming a given number of pages.

[0007] The main object of the present invention is to provide a system for controlling a perforating unit, which system is adapted to automatically detect the operating state of said unit by analysing the perforations performed on the web material.

[0008] According to the invention, this result is achieved by adopting the idea of ​​implementing a system having the features indicated in claim 1. Other characteristics of the invention are the subject of the dependent claims.

[0009] Thanks to the invention, the operating state of the perforating unit can be monitored by analyzing the perforations performed on the web material. The relative positions of the blade and the counter blade being used can also be automatically adjusted based on the analysis of the perforations to correct detected errors. In addition, the control system according to the invention has a relatively low cost compared to the advantages it provides and can also be implemented in existing production facilities.

[0010] These and other advantages and features of the present invention will be more fully understood by those skilled in the art thanks to the following description and accompanying drawings, which are provided by way of example only and are not to be considered limiting, in which:

[0011] ■ Figure 1-2 show a perspective view and a side view, respectively, of a perforating unit which can be used, for example, to provide transverse perforations in a web of paper material for producing paper rolls;

[0012] ■ Figure 3 yes Figure 1 and Figure 2 A schematic top view of a perforating unit of , wherein the rollers 1 and 2 are not shown, but the corresponding axes A1 and A2 are shown;

[0013] ■ Figure 4 schematic representation of the passage of a web material through a perforated unit;

[0014] ■ Figure 5 Schematic representation of a mesh material with transverse perforation lines;

[0015] ■ Figure 6 schematically represents an optical control area according to a possible embodiment;

[0016] ■ Figure 7 is a simplified block diagram relating to a possible mode of realization of a control system in a perforating unit according to the invention;

[0017] ■ Figure 8 is a schematic top view of a possible installation mode of the optical unit 3;

[0018] ■ Figures 9A-9D schematic representation of the passage of a mesh material through a control sub-region;

[0019] ■ Figures 10A-10C Schematic representation of possible defects of the perforation line produced by the perforator unit.

[0020] exist Figure 1-3 The perforating unit GP shown by way of example in FIG. 1 comprises a first blade holder roller 1 and a second roller 2 mounted with a plurality of counter blades.

[0021] A plurality of blades 10A-10F are evenly distributed and mounted on the outer surface of the blade holder roller 1 .

[0022] The blade roller 1 rotates about its own longitudinal axis A1 at a predetermined angular speed and is connected to a corresponding motor M1 which acts on one of the pins 11.

[0023] For example, the number of blades 10A-10F is six, but it should be understood that their number can be determined according to the web material to be processed and the distance between the perforation lines that wish to be produced on the web material. Usually, for example, the number of blades can be between one and twelve.

[0024] In this example, the second roller 2 is stationary during the perforation of the web material. Preferably, a plurality of counter blades 20 are mounted on the roller 2, forming a kind of magazine that avoids having to dismantle the roller 2 when a counter blade needs to be replaced: by the configuration of the counter roller 2, a worn or broken counter blade 20 can be replaced by a good counter blade 20 simply by rotating the counter roller 2. Preferably, the counter blade 20 is rectilinear, mounted on the side surface of the roller 2 and parallel to the longitudinal axis of the roller 2.

[0025] Preferably, the blades 10A-10F have a helical shape and the counter blade 20 is stationary so that, in use, the contact between the blades 10A-10F and the counter blade 20 is substantially point-like and continuous over time to avoid stresses that may cause premature breakage of the blades 10A-10F.

[0026] The relative positions of the rollers 1 and 2 are adjustable. For example, the first roller 1 can be mounted on a corresponding fixed support 12 via a corresponding pin 11, and the second roller 2 can be mounted on a corresponding mobile support 22 via a corresponding pin 21, and the mobile support 22 allows the distance between it and the first roller 1 to be adjusted. Figure 1 and Figure 2 In FIG. 1 , the supports 12, 22 are shown only on the side opposite to the motor M1. The supports 22 of the roller 2 are connected to corresponding actuators 23. For example, the actuators 23 can move the supports 22 so that the roller 2 moves parallel to itself toward the first roller 1 or away from the first roller 1, or they can move the supports 22 in a different way so as to change the axial orientation of the roller 2 relative to the roller 1. Figure 3 In FIG. 2 , arrows H, K indicate possible movements of the support 22 controlled by the actuator 23. Such a structure is known per se.

[0027] The perforation unit GP produces perforation lines P transversely on the web material N passing between the blade and the counter blade. In other words, the perforation lines P are oriented along a predetermined direction CD, which is generally orthogonal to the direction MN in which the web material N is transported between the rollers 1, 2. The perforation lines P are spaced apart from each other by a predetermined value, depending on the rotation speed of the first roller 1 and the advance speed of the web material N. The perforation lines P are each formed by a predetermined number of cuts or perforations F, which are oriented transversely to the web material N and which are spaced apart from each other by a predetermined value. The mechanism for moving the web material N is known per se and is therefore not described in detail. Usually, the movement of the web material N is determined by the traction applied to it by specially provided components in the machine using the material. For example, in a rewinding machine for paper processing, the movement of the web material N is determined by the traction applied to it by the winding roller of the rewinding machine, or if the web material is subjected to embossing before being converted into a paper roll by means of the rewinding machine, it is also determined by the traction applied to it by the embossing roller.

[0028] Advantageously, a control system according to the invention comprises an optical unit 3 adapted to optically detect perforations F in a predetermined control zone ZC of a path followed by the web material N downstream of the perforating unit GP, while the web material N moves along said path. The optical unit 3 is configured to acquire images of the web material N corresponding to the perforation lines P. For example, the optical unit 3 may be a camera. The optical unit 3 is connected to a programmable processing unit 4 which receives the electrical signals generated by the optical unit 3 and processes them according to programmed processing criteria, which comprise a comparison between a predetermined number of perforations F of at least one perforation line P and the number of perforations detected by the optical unit 3 on the same perforation line. Depending on the comparison carried out in this way, the processing unit 4 may emit an error signal which may be used to signal an abnormal condition related to the operation of the perforating unit GP. For example, as further described below, if on a perforation line P that should have twenty perforations F (NPP=preset number of perforations), the optical unit 3 detects only ten perforations (NPR=detected number of perforations), the error signal is emitted. Or, for example, if on a perforation line P that should have twenty perforations F (NPP), the optical unit detects sixteen perforations (NPR) and the four missing perforations F are consecutive along this perforation line, the error signal is emitted. More generally, according to the invention, the perforations F and their positions are detected for each perforation line P in order to count the number of missing perforations relative to the number of perforations that the perforation line P should have when the perforation unit is operating normally, and to check whether the missing perforations on this perforation line are consecutive. A possible criterion for signaling an incorrect operating condition of the perforation unit is that an error signal is emitted if NPR<=a*NPP, where "a" is a control parameter that can assume a predetermined value less than 1 according to the quality level considered acceptable for the finished product. For example, "a" may be a value comprised between 0.50 and 0.95. Likewise, a possible criterion for signaling a condition of incorrect operation of the perforation unit is that an error signal is emitted if the optical unit detects a number of missing consecutive perforations (NPC) (missing perforations corresponding to adjacent positions along the inspected perforation line) greater than a pre-established threshold value (NPS). These criteria may be assigned different priority levels, so that one of them may assume the role of a primary control criterion, while the others may assume the role of a secondary control criterion. For example, a criterion based on perforation count may be a primary control criterion, and a criterion based on the position of the detected missing perforations may be a secondary control criterion, it being understood that these roles may be reversed. Furthermore, the above control criteria may be combined, i.e. an error signal may be emitted if both the conditions NPR<=a*NPP and NPC>=NPS are satisfied.

[0029] The illuminator 30 is preferably associated with the optical unit 3. Depending on the desired configuration, the illuminator 30 can be arranged on the same side or on the opposite side relative to the web material N as the optical unit 3, as further described below. Experimental tests carried out by the applicant have shown that the optical unit 3 detects the perforations F more accurately if the web material N is unfolded in the detection position. To this end, the optical unit 3 is preferably arranged at a point of the path followed by the web material N, at which the web material N is guided on a guide roller 5 determining its curvature (whose radius is equal to the radius of the guide roller 5), so that a local traction of the web material after its passage over the guide roller 5 causes a slight extension of the perforations F and, therefore, causes a clearer contrast between the color of the web material N and the color of the guide roller below. More generally, the optical unit 3 is preferably arranged at a point of the path followed by the web material N, at which the web material N passes over a convex surface, wherein the convex surface faces the optical unit 3. In this configuration, the illuminator 30 is placed on the same side relative to the web material N as the optical unit 3. This configuration is Figure 6 It is shown by way of example in the diagram of FIG.

[0030] In a possible alternative mode of implementation of the invention, the illuminator 30 is placed on the opposite side of the optical unit 3 relative to the web material N.

[0031] In another alternative embodiment of the present invention, the illuminator 30 may be placed inside the guide roller 5 or the convex surface mentioned above, in which case the guide roller 5 or the convex surface is provided with an opening or surface through which light is transmitted.

[0032] Preferably, the error signal is used to activate an automatic program for identifying one or more components (one or more blades 10A-10F or counter blade 20) of the perforating unit, the state of which may have caused the emission of the error signal. For example, one or more blades 10A-10F or counter blade 20 may be broken or excessively worn. Or, for example, the relative position of blade 10A-10F and counter blade 20 may be incorrect, meaning that the distance between blade 10A-10F and counter blade 20 may be too large.

[0033] Furthermore, preferably, the error signal is used to activate an automatic procedure for correcting the position of components of the perforating unit, such as the position of a counter blade in use. An example of an automatic correction procedure is described below.

[0034] According to a possible embodiment of the present invention, the processing unit 4 passes through the encoder 40 (only Figure 7) is connected to the first roller 1. Thus, the processing unit 4 captures the position of the blades 10-10F and thereby the position of the perforation lines P on the web material N when the perforation lines are formed. The same processing unit 4 controls the activation of the optical unit 3 via the controller 300 of the unit 3 and synchronously controls the activation of the illuminator 30 to perform the aforementioned detection of the perforation lines P at the point where the optical unit 30 is arranged. For this purpose, the processing unit 4 has an output 41 connected to an input of the controller 300, the controller 300 being driven in this way by the processing unit 4. The output 32 of the optical unit 3 is connected to a corresponding input 42 of the processing unit 4, which receives in this way the image captured by means of the optical unit 3. The output of the controller 300 is connected to the input 31 of the optical unit 3. In Figure 7 In the diagram of FIG. 4 , the controller 300 is connected to the output 41 of the processing unit 4, and the processing program is indicated by the reference numeral EP. The program can be stored in the internal memory part of the processing unit 4, or can also be stored in an external unit connected to the processing unit 4.

[0035] Preferably, the illuminator 30 is a pulsed linear illuminator.

[0036] For the experimental test, an Omron STC-MBS 163POE matrix camera with an Omron FH2050 controller was used, with a shutter speed of one microsecond, and the camera was located 30 cm from the web material N (composed of white tissue paper used in the production of toilet paper rolls). The illuminator 30 used for the experimental test was a Genesi GEVX 34-6K-UD-200-M12S illuminator. At the image acquisition point, the web material N passed over a black support roller.

[0037] By performing the above optical detection at a point in the path followed by the web material N (at which point the web material is stretched, e.g., as previously described, at which point the web material follows a convex surface profile), the aperture of the camera can be fully opened so that more light can enter the camera despite the short exposure time. Furthermore, the stretching of the web material results in greater visibility of the underlying surface, and therefore greater visibility of the perforations F.

[0038] It goes without saying that using a surface of a different colour than the web material N placed behind the material itself facilitates a more correct optical detection of the perforations F on each perforation line P.

[0039] A particularly advantageous solution from an economic point of view consists in providing an optical unit capable of framing a portion (for example one third) of the width of the web material, i.e. a portion (for example one third) of each perforation line P, and mounting this optical unit on a carriage CM movable orthogonally to the direction MD followed by the web material N in the control zone ZC. The carriage CM can be mounted on corresponding guides GC oriented perpendicularly to said direction MD in the control zone ZC. The carriage CM can be operated by a corresponding actuator AC controlled by a processing unit 4 appropriately connected to it. Reference Figures 10A-10C , the carriage CM positions the optical unit 3 in control positions C1, C2 and C3, i.e. corresponding to the lateral parts C1, C2 and the central part C3 of the path followed by the web material N. In this way, the optical unit 3 can frame the lateral part and the central part of each perforation line. Figures 9A-9D In the diagram of FIG. 1 , the perforation lines are indicated by reference numerals P1, P2, P3, P4, P5, P6, assuming that six blades 10A-10F are mounted on the blade holder roller 1, so that each perforation line P1-P6 is produced by the interaction of the corresponding blade 10A-10F with the counter blade 20. However, it should be understood that the control positions can be different numbers (for example, two, or four, or five) depending on the width of the web material and the shooting field CR of the optical unit 3. In a possible control cycle according to the invention, initially the carriage CM is positioned at the control point C1, and at six different times t1-t6, the optical unit 3 driven by the processing unit 4 captures the image of the corresponding transverse portion of each perforation line P1-P6 while the web material N moves along the direction MD. This process can be repeated up to a predetermined number of times (for example ten times) to reduce the risk of emitting a false signal not due to the absence of perforations but due to, for example, the temporary presence of dust at the control point C1. If the image acquired by the optical unit at the transverse control point Cl shows that all perforations are always absent on all perforation lines P1-P6, the processing unit 4 emits an error signal, which can be used to activate a warning program assigned to the operator of the machine and / or an automatic calibration procedure, which consists of adjusting the deflection of roller 2 or moving roller 2 parallel to itself towards roller 1, acting on the corresponding mobile support 22 to restore the correct operation of the perforation unit. If the error still exists despite the activation of the calibration procedure, the operator will stop the machine to manually intervene in the perforation unit, assuming that the counter blade is damaged or excessively worn. On the other hand, if the processing unit 4 does not emit an error signal, the carriage CM is moved to the other side control point C2 and the previously described procedures are repeated. Finally, the carriage CM is moved to the central control point C3 and the previously described procedures are repeated. In each of the above-mentioned procedures, an error signal can be emitted by the processing unit 4 even if, for example, the optical unit 3 detects the absence of a predetermined part of the perforations on the perforation lines P1-P6 at the control point.

[0040] In this way, quality control of the perforations is divided over a strip of web material having a pre-established lateral width.

[0041] exist Fig. 10A , Fig. 10B and Fig. 10C In the exemplary illustration of FIG. 1 , the perforated line shows that the right side band ( Fig. 10A ), left side belt ( Fig. 10B ) and the central zone ( Fig. 10C ) does not have any perforations.

[0042] Preferably, the optical unit 3 first captures the image of the perforation line at the lateral control points C1, C2, and then captures the image of the perforation line at the central control point C3. This is because experience shows that the loss of perforations occurs more frequently on the side bands of the web material.

[0043] However, it is possible to use an optical unit 3 whose photographing range extends to the entire control zone ZC, even though this solution may be more expensive since in this case the optical unit 3 must be equipped with more expensive optical and electronic components since they are able to provide a clear image of a larger area.

[0044] If the defect detected by the optical unit 3 always concerns the same perforation line, for example perforation line P4, the error signal can be used to control an automatic adjustment of the perforation unit, for example by moving the support 22 to bring the roller 2 closer to the roller 1. If the error persists, it can be assumed that the corresponding blade 10D is damaged, and in this case it can be replaced.

[0045] It will be appreciated that the specific procedure for emitting an error signal and / or the specific automatic calibration procedure activated by the emission of the error signal may differ from those described above by way of example. Typically, in fact, both the total number of missing perforations on the same perforation line and the number of consecutive missing perforations on the same perforation line may be predefined, depending on the pre-established quality of the finished product.

[0046] For example, the web material N may be a paper web formed from one or more superimposed layers, or a film or nonwoven fabric of a plastic or bioplastic material.

[0047] As is apparent from the foregoing description, a perforating device according to the present invention comprises: at least one blade 10A-10F and a counter blade 20, the blades 10A-10F and the counter blade 20 being configured to form perforated lines P on a web material N moving along a predetermined path, wherein each of the perforated lines is composed of a predetermined number of perforations F, which are spaced apart by a predetermined value from each other and aligned along a predetermined perforating direction CD; and an optical unit 3, the optical unit 3 being configured to form a perforated line P on a web material N moving along a path in a control zone ZC arranged downstream of the perforating unit GP along the path when the web material N moves along the path. The optical unit 3 is adapted to capture an image of the web material N corresponding to the perforation line P, the optical unit 3 being connected to a programmable processing unit 4, which receives the electrical signal generated by the optical unit 3 and processes the electrical signal according to programmed processing criteria, the programmed processing criteria comprising a comparison between the predetermined number of perforations F of the perforation line P and the number of perforations detected by the optical unit 3 on each perforation line, and, depending on the comparison thus performed, the processing unit 4 is able to emit an error signal indicative of an abnormal condition associated with the operation of the perforation unit GP.

[0048] Therefore, according to the invention, the comparison is performed based on the detection of the number of perforations of each perforation line using an optical unit 3 that detects the perforations of each perforation line and a processing unit that performs said comparison.

[0049] In practice, with respect to the various elements described and illustrated, the execution details may in any case vary in an equivalent manner without thereby abandoning the idea of ​​the solution adopted and thus remaining within the scope of protection conferred by this patent according to the following claims.

Claims

1. A perforation unit (GP), comprising: At least one blade (10A-10F) and a counter blade (20), the at least one blade (10A-10F) and the counter blade (20) being configured to form perforation lines (P) on a web material (N) moving along a predefined path, wherein each of the perforation lines is formed by a predetermined number of perforations (F), the perforations (F) being spaced apart from each other by a predetermined value and aligned along a predetermined perforation direction (CD), characterized in that the perforation unit (GP) comprises an optical unit (3), the optical unit (3) being adapted to optically detect each perforation (F) of each perforation line (P) in a control zone (ZC) arranged downstream of the perforation unit (GP) along the path when the web material (N) moves along the path. F), the optical unit (3) being configured for capturing an image of the web material (N) corresponding to the perforation line (P), the optical unit (3) being connected to a programmable processing unit (4), the programmable processing unit (4) receiving the electrical signal generated by the optical unit (3) and processing the electrical signal according to programmed processing criteria, the programmed processing criteria comprising a comparison between the predetermined number of perforations (F) of the perforation line (P) and the number of perforations detected by the optical unit (3) on each perforation line, and, depending on the comparison thus performed, the processing unit (4) being susceptible to emitting an error signal indicating an abnormal condition relating to the operation of the perforation unit (GP).

2. The perforating unit according to claim 1, characterized in that: The processing unit (4) is programmed to emit the error signal if the total number of perforations (F) detected by the optical unit (3) on one or more perforation lines (P) in the control zone (ZC) is less than a predetermined percentage of the predetermined number of perforations.

3. The perforating unit according to claim 1, characterized in that: The processing unit (4) is programmed to emit the error signal if the number of consecutive perforations (F) detected by the optical unit (3) on one or more perforation lines (P) in the control zone (ZC) is less than a predetermined value.

4. Perforating unit according to one or more of the preceding claims, characterized in that: The control zone (ZC) is divided into a plurality of control sub-zones (Cl, C2, C3), which are aligned transversely with respect to the moving direction (MD) of the web material (N) in the control zone, and the optical unit (3) is cyclically moved between the control sub-zones (Cl, C2, C3) by means of corresponding handling units (CM, AC).

5. The perforating unit according to claim 4, characterized in that: The control sub-zone includes two lateral control sub-zones (Cl, C2), and wherein the handling unit (CM, AC) first positions the optical unit (3) at a position corresponding to the lateral control sub-zone (Cl, C2), and then positions it at a position corresponding to any other control sub-zone included between the lateral control sub-zones (Cl, C2).

6. Perforating unit according to one or more of the preceding claims, characterized in that: The processing unit (4) controls the activation of the optical unit (3).

7. Perforating unit according to one or more of the preceding claims, characterized in that: The path comprises a convex surface on which the control zone (ZC) is arranged.

8. Perforating unit according to one or more of the preceding claims, characterized in that: The at least one blade (1A-10F) and the counter blade (20) are mounted on respective supports, the mutual position of the supports being adjustable, characterized in that the error signal controls the mutual positioning of the supports.

9. Perforating unit according to one or more of the preceding claims, characterized in that: An illuminator (30) activated by the processing unit (4) is associated with the optical unit (3).

10. Perforating unit according to one or more of the preceding claims, characterized in that: The processing unit (4) is programmed to emit the error signal if the abnormal condition detected by the optical unit (3) occurs a preset number of times.

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