Line and method for labelling articles

Abstract

A labelling line for labelling articles (2) comprises: an applicator unit (3), including a cutting device (6) for separating individual labels (E) from a web (7) of labels by cyclically cutting the web (7) according to a work cycle, and a transporting carousel (9) configured to transport the labels (E) in proximity to the articles (2); a feed unit (10) configured to feed the web (7) to the applicator unit (3); a detecting device (17) including a camera configured to capture image data representing at least one cyclic reference (T) present on the web (7); a control unit (16) connected to the camera and programmed to derive a synchronization signal representing the work cycle and to instruct the camera to capture the image data in a time window derived dependently on the synchronization signal and to process the image data and, based on the processing, to generate a control signal to synchronize the web (7) relative to the knife.

Description

[0001] DESCRIPTION

[0002] LINE AND METHOD FOR LABELLING ARTICLES

[0003] Technical field

[0004] This invention relates to a line and a method for labelling articles.

[0005] Background art

[0006] This invention can be advantageously, though not exclusively, applied to the labelling of consumer articles or packages, for example, the labelling of cylindrical containers such as bottles, jars, vials, etc.

[0007] In particular, this invention relates to a line for labelling articles and comprising a feed unit for feeding a web of labels and an applicator unit for applying the individual labels to the containers. The label applicator unit is usually provided with a cutting device to separate the individual labels from a continuous web by cyclically cutting the web (usually transversely); the web feed unit is configured to feed the web to the applicator unit and in turn comprises a web unwinding station for unwinding the web from at least one reel of labels.

[0008] The operating rate of the label applicator unit is determined by the rhythmic sequence of label cutting operations whereby the labels are applied in synchrony to the individual articles being conveyed in sequence at the production speed of the line; the web feed rate is chosen so that the web remains taut, without letting it slacken or subjecting it to jerking movements. Generally speaking, to synchronize the operating rhythm of the label applicator unit relative to that of the web feed unit, the web feed unit may comprise a buffer for temporarily accumulating the web, interposed between the unwinding station and the cutting device. An article labelling line of the kind described above is known, for example, from patent application WO2024 / 110836, in the name of the present Applicant.

[0009] Generally speaking, to synchronize the cutting operation relative to web feed, hence to cut the labels centrally with respect to a graphical design on them, the labelling unit includes a device for detecting a cyclic reference mark on the web. The detecting device is connected to the label applicator unit so as to provide a synchronization signal which controls the cutting device. In other words, the labelling line must be able to cut the web at very precise positions so that the printing on the labels is exactly centred. To be able to cut the labels correctly, the manufacturers of the label reels add a small black rectangle, called "spot" or "mark" to the printed design on the labels so that label web feed can be synchronized relative to the cutting operation. Prior art labelling lines can be provided with a detecting device, defined by a contrast sensor, which allows detecting spots and the cyclic rate (frequency and phase) at which the spots pass through the web feed unit.

[0010] In the zone around each spot, there is a reading space, known as "spot reading window" which does not have any printed text or images on it, so as to make it easier for the sensor to identify the spot without confusing it with other printed designs on the labels.

[0011] Patent document W02024170063A1 describes an example of a system for detecting the spot inside the reading space, using a fixed reference visible to a sensor. A system of this kind is not precise and may lead to errors cutting the labels.

[0012] Disclosure of the invention

[0013] This disclosure therefore has for an aim to provide a line for labelling articles which allows the labels to be cut in a precise and reliable manner. Another need of the sector is to increase the productivity of a labelling line by providing it with a reel change system configured to rapidly splice the web of the old, depleted reel to the web of a new reel, ready to take the place of the depleted reel. For this purpose, the feed unit may comprise a web splicing device which splices the web which is nearing depletion to the web supplied alternatively from a first reel or from a second reel, that is to say, from the reel which is the standby reel at that moment.

[0014] In this case, too, generally speaking, in order to synchronize the cutting operation relative to web feed so that the graphic design of each label being cut is situated centrally on the label, the labelling unit may comprise a device for detecting at least one cyclic reference present on the web. This detection device may be connected to the label applicator unit so as to provide the label applicator unit with a synchronization signal used to control the cutting device.

[0015] The reel change operation may be performed manually, automatically or semi-automatically but, whatever the case, it usually involves stopping the line. In effect, this operation requires adjusting the phase of the spots on the new web relative to the cutting device to make it the same as it was for the old web which is nearing depletion, and such adjustment is normally carried out after stopping the line.

[0016] In the prior art, as known for example from patent document EP4310038A1 , splicing is facilitated using a sensor mounted in the proximity of the splicing device.

[0017] The aim of this invention is to provide a line for labelling articles which allows the reel to be changed easily and economically without stopping the line.

[0018] A further aim of this invention is to provide a line for labelling articles which allows the reel to be changed in a precise and reliable manner.

[0019] These aims are fully achieved by the line and method for labelling articles according to this invention, as characterized in the appended claims.

[0020] In particular, the line for labelling articles comprises an applicator unit. The applicator unit is configured to transport the labels near the articles. In particular, the applicator unit may be configured to apply the labels to the articles. The labels are obtained from a web of labels.

[0021] The applicator unit includes a cutting device which is configured to separate individual labels from a web of labels. In particular, the cutting device comprises a cutting roller which rotates about a first rotation axis, and a knife which is integral with the cutting roller to separate individual labels from a web of labels by cyclically cutting the web according to a work cycle. Thus, the cutting device is configured to separate individual labels by cyclically cutting the web of labels. The periodicity of the label cutting operation is determined by the speed of the cutting roller, by the size of the cutting roller and, where applicable, by the number of knives attached to the cutting roller. If the cutting device comprises one knife attached to the cutting roller, the cutting device (the knife) cuts one label at each rotation about the first rotation axis.

[0022] The applicator unit includes a transporting carousel which is configured to transport the labels in proximity to the articles. The transporting carousel may be configured to receive the cut labels from the cutting device.

[0023] The labels may be cut in any of several different ways known in the relevant industry. For example, the labels may be cut by the cutting roller interacting with the transporting carousel; one example of this way of cutting the labels is described in patent document WO2024 / 110836, in the name of the present Applicant and incorporated herein by reference.

[0024] In an embodiment, the cutting device (in particular, the cutting roller) and the transporting carousel are one and the same. For example, the cutting device (or the transporting carousel) may include a plurality of recesses disposed along the cutting device (or along the transporting carousel); inside each recess there is a knife and cutting the label is done by cyclic suction which sucks the web operatively facing the knife into the recess.

[0025] The labelling line comprises a feed unit, configured to feed the web of labels to the applicator unit. In particular, the feed unit is configured to feed the web to the applicator unit.

[0026] In an embodiment, the feed unit includes a first reel. A first coil of web is wound around the first reel. In other words, the first reel is configured to receive a first coil of web wound around the first reel itself. The feed unit includes a second reel. A second coil of web is wound around the second reel. The feed unit includes an unwinding station configured to alternately unwind the first coil from the first reel and the second coil from the second reel.

[0027] The feed unit includes a buffer for temporarily accumulating the web. The buffer is configured to create a temporary store of web. The buffer may include a dandy roller or a suction chamber configured to dynamically receive a loop of web of varying depth. The buffer is interposed between the unwinding station and the cutting device.

[0028] In an embodiment, the labelling line comprises a splicing device configured to splice portions of web to each other.

[0029] In particular, the splicing device is configured to make a splice between an unwound portion of web downstream of the first reel and of the second reel and, alternatively, the second coil or the first coil of the web so as to connect the unwound portion of web to the first coil or to the second coil.

[0030] Thus, the web wound around the first reel or the second reel, passes through the buffer and arrives at the applicator unit, where it is separated into individual labels.

[0031] The labelling line comprises a control unit. The control unit is configured to instruct the cutting device to cut the web into individual labels. The control unit may be programmed to generate a splicing signal to instruct the splicing device to make the splice, preferably without interrupting the feeding of the web to the applicator unit.

[0032] In an embodiment, the labelling line comprises a mark sensor, configured to detect detection data. In particular, the detection data detected by the mark sensor represent a cyclic reference present on the web. The mark sensor is located between the cutting device and the buffer.

[0033] When the mark sensor is provided, the control unit may be connected to the mark sensor and programmed to process the detection data. The control unit may be programmed to generate a cutting signal to instruct the cutting device. Thus, the cutting signal to instruct the cutting device to make the cut is generated on the basis of the detection data from the mark sensor. When the mark sensor detects a reference on the web, the control unit issues an instruction to cut the label. The control unit may instruct the cutting device to make the cut each time the mark sensor performs a detection. In an embodiment, the control unit may receive a detection from the mark sensor at the rate of every 2 or more labels, and the control unit may be programmed to control the cutting device so as to synchronize label cutting relative to the detection rate.

[0034] In an embodiment, the control unit is programmed to process the detection data detected by the mark sensor and to generate the splicing signal. Thus, the splicing signal to instruct the splicing device to make the splice is generated on the basis of the detection data from the mark sensor.

[0035] In an embodiment, the labelling line comprises a splice sensor (in addition to the mark sensor and dedicated to splicing), configured to detect detection data. In particular, the detection data represent at least one cyclic reference present on the web. The splice sensor is located between the buffer and the splicing device.

[0036] When the splice sensor is provided, the control unit may (also) be connected to the splice sensor and programmed to process the detection data. In particular, the control unit processes the detection data detected by the splice sensor to generate a splicing signal (that is, the splicing signal) and transmits it to the splicing device so as to instruct it to make the splice, preferably without interrupting the feeding of the web to the applicator unit.

[0037] Thus, there are at least two possible modes of generating the splicing signal.

[0038] In a first mode, the labelling line uses the mark sensor located between the cutting device and the buffer to control the splicing device; in particular, the control unit instructs the splicing device on the basis of the detection performed by the mark sensor. It is noted that, preferably, the detection data from the mark sensor are also used to control cutting of the individual labels; in other words, the labelling line uses the detection data to control cutting of the individual labels to instruct the splicing device to make the splice. In a second mode, the labelling line comprises a splice sensor located between the buffer and the splicing device and the control unit instructs the splicing device based on the detection performed by the splice sensor. In this case, therefore, the labelling line comprises a specific sensor, located in proximity to the splicing device, to issue the splicing command.

[0039] In a third mode, the mark sensor may also be used to provide a phase reference for the splice sensor (in this third mode, both the mark sensor and the splice sensor are present).

[0040] The control unit may be programmed to estimate a length of web included between the mark sensor and the splicing device. This estimate may be used, in the first mode, to control the splicing system based on the mark sensor (when there is no splice sensor); the same estimate may also be used in the third mode to allow the control unit to provide the splice sensor with a phase, which depends on the detection of the mark sensor.

[0041] Thus, the control unit may be programmed to instruct the splicing device to make the splice, based on the calculated length of web.

[0042] The labelling line may comprise an automatic detection system for detecting a depletion parameter representing a web reel which is nearing depletion. The detection system may comprise one or more sensors (for example, optical sensors) configured to detect the depletion signal. In a preferred example, the detection signal is configured to process the depletion parameter through an algorithm (for example, via software). The algorithm may be configured to calculate the depletion parameter based on one or more parameters, such as, for example, an unwinding speed, or a length of wound web. One example of such a system is described in patent document VR2010A000003, in the name of the present Applicant.

[0043] In an example, the feed unit comprises a feed roller, configured to feed the web to the transporting carousel. The feed unit (the feed roller) may be configured to vary a feed speed (in particular, the rotation speed of the feed roller) in the work cycle between a maximum value and a minimum value.

[0044] Preferably, the buffer comprises a suction chamber configured to dynamically receive a loop of web of varying depth. In particular, the suction chamber is configured to vary a depth of the loop, based on the speed of the feed unit (in particular, of the feed roller). When the speed is constant (for example, at the minimum value or at the maximum value), the depth of the loop remains constant. When the feed speed changes from minimum to maximum or vice versa, the depth of the loop varies to adapt to the change of speed.

[0045] Regardless of speed changes, the suction chamber may, nevertheless, have an advantageous application. In effect, the suction chamber could be preferable to a dandy roller because it does not require a dedicated web guide (necessary in dandy roller systems) to keep the web film vertically aligned. In effect, in systems provided with dandy roller, the dandy roller does not apply a vertical constraint to the web, thus making it necessary to use an additional device to ensure that the web moves along a correctly aligned path. The loop, on the other hand, allows the web to be correctly guided without the aid of additional components.

[0046] The buffer may comprise a first through-beam photocell, configured to detect a maximum depth of the loop corresponding to a maximum quantity of web accumulated in the buffer. When the depth of the loop increases to an extent such as to reach the detection range of the first photocell, the first photocell generates a detection signal. If the depth of the loop increases beyond the maximum value, the first photocell continues to detect the presence of web; if the depth of the loop decreases, the detection range of the first photocell is uncovered and the first photocell stops generating the detection signal.

[0047] Thus, the first through-beam photocell is configured to detect a maximum depth of the loop and the control unit is programmed to receive from the first photocell a value representing the maximum depth of the loop. In particular, the control unit is programmed to instruct the mark sensor to acquire the detection data and based on the value representing the maximum depth of the loop.

[0048] When the mark sensor is present, the control unit may be programmed to estimate a length of web included between the mark sensor and the splicing device. The control unit may be programmed to instruct the splicing device to make the splice, based on the calculated length of web.

[0049] In particular, the control unit may be programmed to estimate a length of web included between the mark sensor and the splicing device, responsive to a reduction in the depth of the loop inside the chamber.

[0050] If the first, through-beam photocell is present, the estimated length of web between the mark sensor and the splicing device may be calculated in response to a detection by the first, through-beam photocell (in particular when the first, through-beam photocell is uncovered; in other words, the moment the web stops covering the first, through-beam photocell). That way, since the distance between the mark sensor and the splicing device is known, it is possible to calculate the quantity of web between the mark sensor and the splicing device.

[0051] In particular, the detection performed by the first, through-beam (maximum accumulation) photocell, that is, the instant the photocell is uncovered, activates a procedure whereby the control unit, which is programmed to instruct the mark sensor to acquire the detection data, starts a counter (to derive the length of web film entering the buffer) starting from the moment the first mark (the first after the photocell is uncovered) is detected. In other words, the control unit is programmed to instruct the mark sensor to acquire the detection data and to process the data based on the value representing the maximum depth of the loop. Thus, responsive to the detection performed by the first, through-beam photocell (that is, the moment the photocell is uncovered by the web), the control unit is programmed to instruct the mark sensor to acquire the detection data and to estimate a distance between the mark sensor and the splicing device, thereby instructing the splicing device to make the splice.

[0052] In particular, the labelling line is configured to adopt an average production speed during the work cycle. In an embodiment, the control unit is programmed to set a production speed of the line to a reduced value which is lower than the average production speed.

[0053] The control unit may be programmed to wait a settling time for the depth of the loop to reach a constant value. The control unit may be programmed to receive a value representing a maximum depth of the loop via the first photocell and to set a reel unwinding speed cozfor unwinding the first reel or the second reel, that is

[0054] COz= Vr / Ro — COz% where Ro is the radius of the first reel or of the second reel with the web wound thereon and coz% is a predetermined speed value, so as to reduce the depth of the loop inside the chamber.

[0055] The control unit may be programmed to estimate a length of web included between the mark sensor and the splicing device, responsive to a reduction in the depth of the loop inside the chamber, and to instruct the splicing system to make the splice based on the estimated length of web.

[0056] In an embodiment, the buffer may comprise a second through-beam photocell, configured to detect a minimum depth of the loop corresponding to a minimum quantity of web accumulated in the buffer. The depth of the loop is configured to vary between around a maximum depth and around a minimum depth. The control unit is programmed to receive a value representing the minimum depth of the loop via the second photocell. In particular, the control unit may be programmed to generate an alarm signal, based on the value received from the second, through-beam photocell.

[0057] In an embodiment, the labelling line comprises, in addition to the mark sensor, a splice sensor (that is, the splice sensor) configured to detect detection data representing the at least one cyclic reference present on the web. The splice sensor is positioned between the buffer and the splicing device. The splice sensor is connected to the control unit. When both the splice sensor and the mark sensor are present, the control unit is programmed to instruct the splice sensor to detect the detection data, based on the detection performed by the mark sensor.

[0058] In particular, the control unit is programmed to instruct the splicing device responsive to the detection data detected by the splice sensor, preferably without interrupting the feeding of the web to the applicator unit.

[0059] Thus, when the splice sensor and the mark sensor are present, detection by the mark sensor triggers detection by the splice sensor. In particular, the mark sensor may be configured to detect detection data in each work cycle; the splice sensor may be configured to detect detection data responsive to a detection by the splice sensor. Thus, the detection by the splice sensor may be activated selectively based on the detection performed by the mark sensor.

[0060] In an example, the control unit is programmed to instruct the splice sensor to acquire the detection data in a time window. In particular, the control unit is programmed to derive a synchronization signal representing the work cycle so as to instruct the splice sensor to acquire the detection data in a time window (or time instant) derived dependently on the synchronization signal.

[0061] Thus, the splice sensor is instructed to acquire the detection data based on the synchronization signal. The synchronization signal, being representative of the work cycle, may be derived from any component which operates according to the work cycle, such as, for example, a rotation of the cutting roller, the cyclic cutting of the label by the knife, and others.

[0062] In an embodiment, in addition to the splice sensor, the line comprises a mark sensor (that is, the mark sensor) located between the cutting device and the buffer and configured to detect detection data representing at least one cyclic reference present on the web. In such a case, the control unit may be programmed to derive the synchronization signal based on the detection data detected by the mark sensor.

[0063] In an embodiment, the control unit may be programmed to process the detection data detected by the mark sensor and, based on the processing, to generate a cutting signal to instruct the cutting device to cut the web into individual labels; the control unit may also generate the splicing signal dependently on the detection data detected by the mark sensor.

[0064] The control unit may be programmed to estimate a length of web included between the mark sensor and the splice sensor and to derive the synchronization signal dependently on the estimated length between the mark sensor and the splice sensor.

[0065] In an embodiment, the control unit is programmed to estimate a length of web included between the mark sensor and the splice sensor and to generate the splicing signal responsive to detection of the cyclic reference by the splice sensor. That way, the control unit is programmed to control splicing regardless of whether or not the mark sensor is used to control the splice.

[0066] If the mark sensor and the splice sensor are present, the control unit may be programmed to calculate a length of web included between the mark sensor and the splice sensor, responsive to a reduction in the depth of the loop inside the chamber, and to instruct the splicing system to make the splice based on the estimated length of web.

[0067] Preferably, the mark sensor is a contrast sensor. The splice sensor may comprise a camera; in addition or alternatively, the splice sensor may comprise a contrast sensor. If the splice sensor comprises a contrast sensor, the splice sensor (the contrast sensor) may be configured to detect the detection data representing at least one cyclic reference present on the web with periodicity related to the length of the label.

[0068] In particular, when both the mark sensor and the splice sensor are present, preferably the mark sensor is a contrast sensor and the splice sensor is a camera. The contrast sensor has the advantage of being more economical, while the camera has the advantage of being more accurate, although more expensive than a contrast sensor.

[0069] Thus, it is particularly advantageous that the mark sensor be a contrast sensor, since it has to detect the cyclic reference with a periodicity given by the work cycle, and that the detection by the splice sensor using a camera be controlled by the control unit, so as to detect the mark only when necessary.

[0070] In an embodiment, the line for labelling articles comprises a detection device. The detection device may include a camera (in particular, a mark sensor, that is, the mark sensor). The camera is located between the feed unit and the cutting device. The camera is configured to capture image data representing at least one cyclic reference present on the web.

[0071] The labelling line may comprise a fixed reference for the camera. The term "fixed reference" is used to mean an element which constitutes a reference for the camera. This reference may be physical and / or virtual.

[0072] The control unit may be connected to the camera. The control unit may be programmed to derive a synchronization signal representing the work cycle.

[0073] The control unit may be programmed to instruct the camera to capture the image data in a time window derived dependently on the synchronization signal. The control unit may be programmed to process the image data and, based on the processing, to generate a control signal to synchronize the web relative to the knife.

[0074] In particular, the control unit may be programmed to derive a reference position for the cutting device, so that, with the cutting device at the reference position, the cyclic reference is aligned with the fixed reference, preferably according to an estimate based on a length of the web included between the fixed reference and a point where the labels are separated, based on the synchronization signal.

[0075] The control unit may be programmed to generate a control signal for the camera to instruct it to capture the image data. The control signal is generated preferably based on the reference position. In particular, the control unit instructs the camera to capture the image data in a time window, where the time window may be derived dependently on the synchronization signal.

[0076] The control unit may be programmed to receive the image data from the camera and to calculate a first difference from the image data. In particular, the first difference is defined by a distance between the cyclic reference on the web and the fixed reference. The control unit may be programmed to generate a control signal to synchronize the web relative to the knife. In particular, the control unit may be programmed to apply a correction to the control signal, based on the first difference.

[0077] The synchronization signal, being representative of the work cycle, may be derived from any component of the line which operates according to the work cycle, such as, for example, a rotation of the cutting roller, the cyclic cutting of the label by the knife, and others.

[0078] In particular, the synchronization signal is derived from a cutting position signal or a signal of another axis synchronized relative to the cutting roller (blade) (for example, the transfer carousel). The cutting position signal may be representative of a position of the cutting device around the first rotation axis. For example, the cutting position signal may relate to the rotation of the cutting roller around the first rotation axis and / or to the position of the knife around the first rotation axis. Alternatively, the synchronization signal may be derived from a sensor located in a suction chamber (for example, a sensor, such as a through-beam photocell, used to regulate the quantity of web in the loop of the suction chamber); in another alternative, the synchronization signal may be derived from a signal representing a rotation of the cutting roller, detected, for example, by an encoder. The synchronization signal may be derived from a signal representing a rotation of the transporting carousel (for example, in the case where the label web is cut when the portion of web operatively facing a recess containing a knife is sucked into that recess).

[0079] Thus, the cutting device acts as a master for cutting the web, that is to say, for synchronizing the web relative to the knife.

[0080] Preferably, the labelling line comprises a rotary encoder. The encoder may be located on the cutting roller. The rotary encoder is configured to detect the cutting position signal.

[0081] In an embodiment, the rotary encoder is an incremental encoder. The rotary encoder is configured to generate a signal A (or track A) and a signal B (or track B). The signals A and B are called "squaring signals". The rotary encoder is configured to generate an index signal Z (or index Z). The control unit may be programmed to derive a cutting position signal based on the index signal Z (in an example embodiment, the encoder has a processor of its own which is programmed to generate, through the index signal Z, the trigger signal which is sent directly to the camera; in practice, such an encoder processor forms part of the generic concept of control unit). In addition or alternatively, the control unit may be programmed to derive the position signal based on the signal A and signal B. For example, the control unit may be programmed to count a predetermined number of pulses of signal A and / or B and to derive the synchronization signal based on the count.

[0082] In an embodiment, the control unit is programmed to receive a position signal. The position signal may be representative of a position around the first rotation axis of the cutting device, preferably at the moment the image data are captured. The control unit may be programmed to calculate a second difference defined by a distance between the effective position of the cutting device and the reference position of the cutting device. The control unit may be programmed to apply a further correction to the control signal, based on the second difference.

[0083] In an embodiment, the fixed reference may be a virtual reference. The camera may define a field of vision and the fixed reference is a virtual point defined by a reference point in the field of vision. For example, the field of vision of the camera may include a dot matrix in two-dimensional space and the reference point may be a point with coordinates (x, y) in the two-dimensional space. For example, the reference point may be the point with coordinates (x, y)=(0, 0). The reference point may be a point with coordinate x. For example, the reference point may be the point with coordinate x=0.

[0084] In an example, the fixed reference point is printed or engraved on a fixed support, where the web is configured to slide on the support, between the camera and the support.

[0085] Thus, in both cases, the web slides in front of the field of vision of the camera and the camera is configured to see the fixed reference. In the first case, the fixed reference is virtual and it is not necessary to have a fixed support on which the web is made to slide, whereas in the second case, the fixed reference is physical and needs the support.

[0086] In an embodiment, the control unit is programmed to instruct the camera to capture the image data every two or more labels.

[0087] In an example, the feed unit comprises a first reel, around which a first coil of the web is wound, and a second reel, around which a second coil of the web is wound; an unwinding station configured to alternately unwind the first coil from the first reel and the second coil from the second reel and a splicing device configured to make a splice alternately between the first coil and the second coil so as to connect the first coil to the second coil or vice versa.

[0088] The line may be configured to adopt an average production speed during the work cycle.

[0089] In an embodiment, responsive to a splice made by the splicing device, the control unit is programmed to set a production speed of the line to a reduced value which is lower than the average production speed, to instruct the camera to capture a plurality of image data elements in sequence and to generate a further control signal to synchronize the web relative to the knife.

[0090] The feed unit may include a feed roller, preferably provided with a motor of its own. The control unit may be programmed to drive the motor of the feed roller based on the control signal.

[0091] This disclosure also provides a method for labelling articles.

[0092] In an example, the method comprises a step of providing an applicator unit including a cutting device having a cutting roller which rotates about a first rotation axis, and a knife which is integral with the cutting roller to separate individual labels from a web of labels, and a transporting carousel for transporting the labels in proximity to the articles. The method comprises a step of providing a feed unit, including a first reel, around which a first coil of the web is wound, and a second reel, around which a second coil of the web is wound, an unwinding station, a buffer for temporarily accumulating the web, interposed between the unwinding station and the cutting device, and a splicing device. The method comprises a step, via the unwinding station, of unwinding the first coil from the first reel and the second coil from the second reel, alternately; a step of temporarily accumulating the web via the buffer; a step, via the splicing device, of making a splice between an unwound portion of web downstream of the first reel and of the second reel and, alternatively, the second coil or the first coil of the web so as to connect the unwound portion of web to the first coil or to the second coil; a step, via a feed unit, of feeding the web to the applicator unit; a step, via a knife of the cutting device, of separating the web into individual labels by cyclically cutting the web during a work cycle.

[0093] The method may comprise a step, via a mark sensor, located preferably between the cutting device and the buffer, of detecting detection data representing at least one cyclic reference present on the web. The method may comprise the following steps, via the control unit: processing the detection data and generating a cutting signal to instruct the cutting device to cut the web into individual labels; generating a splicing signal to instruct the splicing device to make the splice, in particular without interrupting the feeding of the web to the applicator unit.

[0094] In an embodiment, the method comprises a step, via the control unit, of estimating a length of web included between the mark sensor and the splicing device, so as to instruct the splicing device to make the splice based on the length of web estimated.

[0095] In particular, the feed unit comprises a feed roller for feeding the web to the transporting carousel. In particular, the buffer comprises a suction chamber for dynamically receiving a loop of web of varying depth. The web may vary the depth of its loop inside the suction chamber based on a speed of the feed unit. The method may comprise a step of varying a rotation speed of the feed roller, during the work cycle, between a maximum value and a minimum value.

[0096] In an embodiment, the buffer comprises a first through-beam photocell, configured to detect a maximum depth of the loop corresponding to a maximum quantity of web accumulated in the buffer, where the depth of the loop varies around the maximum depth. The method may comprise the following steps, via the control unit: setting a production speed of the line to a reduced value which is lower than an average production speed; waiting a settling time for the depth of the loop to reach a constant value; receiving a value representing a maximum depth of the loop via the first photocell and setting a reel unwinding speed cozfor unwinding the first reel or the second reel, that is

[0097] COz= Vr / Ro — COz% where Ro is the radius of the first reel or of the second reel with the web wound thereon and coz% is a predetermined speed value, so as to reduce the depth of the loop inside the chamber. The method may comprise a step of estimating a length of web included between the mark sensor and the splicing device, responsive to a reduction in the depth of the loop inside the chamber, and a step of instructing the splicing system to make the splice based on the estimated length of web.

[0098] In an example, the method comprises a step, via a splice sensor located between the buffer and the splicing device, of detecting detection data representing the at least one cyclic reference present on the web, and a step, via the control unit, of instructing the splice sensor to detect the detection data based on the detection performed by the mark sensor.

[0099] In an embodiment, the method comprises a step, via a splice sensor, located between the buffer and the cutting device, of detecting detection data representing at least one cyclic reference present on the web. The method may comprise a step of deriving a synchronization signal representing the work cycle so as to instruct the splice sensor to acquire the detection data in a time window derived dependently on the synchronization signal. The method may comprise a step, via the control unit, of generating a splicing signal to instruct the splicing device to make the splice without interrupting the feeding of the web to the applicator unit.

[0100] In an example, the method comprises a step, via a mark sensor located between the cutting device and the buffer, of detecting detection data representing at least one cyclic reference present on the web, where the step of deriving the synchronization signal is carried out on the basis of the detection data detected by the mark sensor.

[0101] The method may comprise the following steps, via the control unit: processing the detection data detected by the mark sensor and, based on the processing, generating a cutting signal to instruct the cutting device to cut the web into individual labels; estimating a length of web included between the mark sensor and the splice sensor, where the step of deriving the synchronization signal is carried out also on the basis of the length of web included between the mark sensor and the splice sensor; estimating a length of web included between the splice sensor and the splicing system; generating the splicing signal responsive to detection of the cyclic reference by the splice sensor.

[0102] In particular, the buffer comprises a suction chamber configured to dynamically receive a loop of web of varying depth, where the suction chamber varies a depth of the loop based on the speed of the feed unit; the method may comprise the following steps: via a first through-beam photocell of the buffer, detecting a maximum depth of the loop, corresponding to a maximum quantity of web accumulated in the buffer, the depth of the loop varying around the maximum depth; via the control unit, a step of receiving from the first photocell a value representing the maximum depth of the loop, and instructing the mark sensor to acquire the detection data based on the value representing the maximum depth of the loop.

[0103] The method may comprise the following steps, via the control unit: setting a production speed of the line to a reduced value which is lower than an average production speed; waiting a settling time for the depth of the loop to reach a constant value; receiving a value representing a maximum depth of the loop via the first photocell and setting a reel unwinding speed coz for unwinding the first reel or the second reel, that is coz= Vr / Ro - coz%, where Ro is the radius of the first reel or of the second reel with the web wound thereon and coz% is a predetermined speed value, so as to reduce the depth of the loop inside the chamber; calculating a length of web included between the mark sensor and the splicing device, responsive to the reduction of the depth of the loop inside the chamber; instructing the splicing system to make the splice based on the length of web estimated.

[0104] In an example embodiment, the method comprises a step of capturing image data representing at least one cyclic reference present on the web, via a camera (in particular, via a mark sensor and, more specifically, via the mark sensor) of a detection device located between the feed unit and the cutting device. The method may comprise a step, via a control unit, of deriving a synchronization signal representing the work cycle and, based on the synchronization signal, deriving a reference position for the cutting device, so that, with the cutting device at the reference position, the cyclic reference is aligned with the fixed reference according to an estimate based on a length of the web included between the fixed reference and a point where the labels are separated. The method may comprise a step, via the control unit, of generating a command signal for the camera, based on the reference position, to instruct the camera to capture the image data in a time window derived dependently on the synchronization signal. The method may comprise a step, via the control unit, of receiving the image data from the camera and calculating a first difference from the image data, the first difference being defined by a distance between the cyclic reference on the web and a fixed reference; a step, based on the processing, of generating a control signal to synchronize the web relative to the knife, and applying a correction to the control signal, based on the first difference.

[0105] In an embodiment, the method comprises a step, via a rotary encoder located on the cutting roller, of detecting a position signal of the cutting roller, representing a position of the cutting device around the first rotation axis. The synchronization signal may be derived from the cutting position signal.

[0106] In an example, the encoder is an incremental encoder and the method comprises the following steps: via the encoder, generating a signal A, a signal B and, in particular, an index signal Z; via the control unit, deriving the position signal based on the index signal Z, or deriving the position signal based on the signal A and the signal B.

[0107] The method may comprise the following steps, performed by the control unit: receiving a position signal representing a position around the first rotation axis of the cutting device at the moment the image data are captured; calculating a second difference defined by a distance between the effective position of the cutting device and the reference position of the cutting device; applying a further correction to the control signal, based on the second difference.

[0108] Brief description of the drawings

[0109] These and other features of the invention will become more apparent from the following description of a preferred embodiment of it, illustrated purely by way of non-limiting example in the accompanying drawings, in which:

[0110] - Figure 1 schematically illustrates a line for labelling articles made according to one or more aspects of this invention; - Figure 2 schematically illustrates a labelling line made according to one or more aspects of this invention;

[0111] - Figure 3 illustrates a portion of a labelling line according to one or more aspects of this invention;

[0112] - Figure 4 illustrates a portion of web 7;

[0113] - Figures 5 and 6 schematically illustrate a labelling line made according to one or more aspects of this invention.

[0114] Detailed description of preferred embodiments of the invention

[0115] The numeral 1 in the accompanying drawings denotes in its entirety a line for labelling articles 2.

[0116] In the case where the articles 2 are in the form of bottles or other cylindrical containers, these may be labelled by the line 1 using methods similar to those described in patent application WO2024 / 110836, in the name of the present Applicant and incorporated herein by reference.

[0117] The line 1 comprises an applicator unit 3 for applying labels E to the articles 2, which are conveyed in succession by a carousel 4 which rotates about a vertical rotation axis 5 and which also forms part of the labelling line 1 .

[0118] The applicator unit 3, associated with the carousel 4, is provided with a cutting device 6 to separate the labels E from a continuous web 7 by cyclically cutting the web 7 transversely. In particular, the cutting device 6 comprises a cutting roller which rotates about a rotation axis and which is motor-driven, and a knife which is integral with the cutting roller to cut the labels E from the web 7.

[0119] Upstream of the cutting device 6, with reference to the conveying direction V of the web 7 inside the applicator unit 3, the applicator device 3 is provided with a gluing device 8 to apply glue to the web 7 at each label E, on the face which is intended to be placed on the respective article 2.

[0120] The cutting device 6 and the gluing device 8 cooperate with the outer periphery of a transporting carousel 9 of the applicator unit 3. The transporting carousel 9 is configured to rotate about a vertical axis.

[0121] The applicator unit 3 comprises a pulling roller 18, located at an inlet of the applicator unit 3. The transporting carousel 9 is configured to receive the web 7 from the pulling roller 18.

[0122] The knife of the cutting device 6 is configured to cooperate with the outer periphery of the transporting carousel 9.

[0123] The transporting carousel 9 may be provided, on its outer periphery, with a succession of suction seats (of known type). The suction seats may be equispaced from each other to hold the labels E cut by the cutting device 6 and to transfer them in synchrony with the respective articles 2 conveyed by the carousel 4.

[0124] The labelling line 1 comprises a feed unit 10 configured to feed the web 7 to the applicator unit 3 which applies the labels E.

[0125] In particular, the feed unit 10 is configured to feed the web 7 to the pulling roller 18 located at the inlet of the applicator unit 3.

[0126] The feed unit 10 comprises an unwinding station 11 , configured to unwind the web 7 from a first reel B1 or from a second reel B2, which also form part of the feed unit 10 and which can be used alternately to feed the web 7. A first coil of web 7 is wound around the first reel B1 and a second coil of web 7 is wound around the second reel B2.

[0127] More precisely, during operation of the labelling line 1 , one of the two reels B1 or B2 is in use, while the other constitutes a standby reel, ready to take the place of the reel being used when the latter is nearly depleted.

[0128] The feed unit 10 for feeding the web 7 comprises a buffer 12 for temporarily accumulating the web 7 and which is located between the unwinding station 11 and the cutting device 6 of the applicator unit 3 which applies the labels E.

[0129] More in detail, the buffer 12 is located upstream of the pulling roller 18 of the applicator unit 3, and thus, in particular, the buffer 12 is located between the unwinding station 11 and the pulling roller 18.

[0130] The buffer 12 is preferably a pneumatic buffer, that is to say, it is provided with a suction chamber 13 capable of receiving a loop 14 of web 7 of varying depth hence of dynamically accumulating a quantity of web 7 of varying length; the purpose of the suction chamber 13 is to coordinate the operating rate of the applicator unit 3, which applies the labels E, with that of the feed unit. The operating rate of the applicator unit 3 is determined by the rhythmic sequence of operations of cutting the labels E to be applied in synchrony to the individual articles 2 being conveyed in sequence by the carousel 4 at the production speed of the line 1 ; this avoids subjecting the web to a succession of jerking movements.

[0131] The pneumatic buffer 12 is preferable to a buffer provided with dandy rollers because it is not subject to the mechanical inertia typical of dandy rollers and thus, at high production speeds, it is more suitable to dynamically compensate the rapid fluctuations in the feeding of the web 7 to the applicator unit 3.

[0132] In an example, the feed unit 10 comprises a feed roller, configured to feed the web to the transporting carousel 9 and to vary a rotation speed, in the work cycle, between a maximum value Vamax and a minimum value Vamin. In such a case, the buffer 12 adapts the depth of the loop based on the speed of the feed roller.

[0133] The feed unit 10 also comprises a splicing device 15 for splicing the web 7 from the reel (B1 or B2) which is nearly depleted to the alternative web 7 provided by the new reel (B2 or B1 ), that is, by the reel (B2 or B1 ) which is on standby. In other words, the splicing device 15 is configured to make a splice between an unwound portion of web 7 downstream of the first reel B1 and of the second reel B2 and, alternatively, the second coil or the first coil of the web 7 so as to connect the unwound portion of web 7 to the first coil or to the second coil.

[0134] The unwinding station 11 may comprise two power-driven shafts driven by respective motors M1 , M2 to unwind the respective reels B1 , B2 present in the unwinding station 11 itself.

[0135] The function of the splicing device 15 is, therefore, to join the web 7 being unwound from the reel which is nearly depleted to the leading end of the web wound around the new reel which is the standby reel at that moment.

[0136] The splicing device 15 is of known type and is not therefore described in detail here. The splice may be carried out by applying an adhesive strip to an end-to-end splicing zone between the trailing end of the web which is nearing depletion and the leading end of the new web, after a cutting operation needed to join the webs uninterruptedly to maintain the same cyclic rhythm of the graphic designs printed on the web 7 and corresponding to the respective labels. The cutting operation is performed by a cutting element 22, forming part of, or associated with, the splicing device 15.

[0137] The labelling line 1 also comprises a control unit 16.

[0138] The control unit may control the splicing device 15, and in particular, the cutting element 22 thereof.

[0139] In an embodiment, the line 1 comprises a mark sensor 17 located between the cutting device 6 and the buffer 12 and configured to detect detection data representing at least one cyclic reference T present on the web 7. In particular, the mark sensor 17 is located downstream of the buffer 12 at a proximal position, that is to say, just upstream of the pulling roller 18 with reference to the feed direction V. Alternatively, the mark sensor 17 is located at a position proximal to the cutting roller of the cutting device 6, upstream of the cutting roller 6 (more specifically, between the cutting device 6 and the pulling roller 18).

[0140] The control unit 16 is connected to the mark sensor to receive the detection data and to process them, so as to generate a signal to instruct the cutting device 6 to cut the web 7 into individual labels E. The control unit 16 may process the detection data so as to generate a splicing signal to instruct the splicing device 15 to make the splice.

[0141] In particular, the cutting element 22 of the splicing device 15 is configured to cut the web 7 responsive to the splicing signal, without interrupting the feeding of the web 7 to the applicator unit 3.

[0142] The mark sensor 17 is configured to detect the detection data representing the mark T with a cyclic rate given by the marks T present on the web 7, hence at each label E. In effect, the cutting operation must be synchronized relative to the feeding of the web 7 so the labels E are cut so that the graphic design on them is centred.

[0143] The above-mentioned cyclic reference present on the web 7 is preferably a dark (preferably black) rectangle on a light (preferably white) background, called spot or mark T in the jargon of the trade, placed in the printed design of the web 7. In the zone around each spot (or mark) T, there is a reading space, known as "spot reading window" which does not have any printed text or images on it, so as to make it easier for the mark sensor 17 to identify the mark T without confusing it with other printed designs on the web 7.

[0144] Preferably, the mark sensor 17 is a contrast sensor. At a limited cost, it allows effectively detecting the marks T and the cyclic rate (frequency and phase) at which the marks pass through the applicator unit 3 which applies the labels E.

[0145] Thus, the mark sensor 17 provides the control unit 16 with a signal which is synchronized relative to the cyclic rate of the labels E. Since it is a signal which is synchronized (and phased) relative to the work cycle, the splicing cut can be made very precisely at the correct point. The signal of the mark sensor 17 allows the new web being fed to remain in synchrony with the cyclic operating rate of the cutting device 6, just like the old web which is nearing depletion.

[0146] The buffer 12 is provided with a first through-beam photocell 19, configured to detect a loop of web 7 corresponding to a maximum quantity of web 7 accumulated in the buffer 12.

[0147] Following hereunder is a description of the operation of the labelling line 1 . The labelling line 1 is configured to adopt an average production speed Vpduring the work cycle. In particular, the average production speed Vpis the average speed of the web 7 downstream of the buffer 12.

[0148] At this stage, preferably, a rotation speed co of the motor M1 , M2 for unwinding the reel B1 or B2 in use is controlled at a constant value so that the quantity of web 7 accumulated in the loop of the buffer 12 remains around the maximum value.

[0149] The motor M1 , M2 may be controlled by the aforementioned control unit 16 or by a main control unit (not illustrated) of the labelling line 1 , of which the control unit 16 may form a section of a more complex hardware architecture.

[0150] Under these conditions, when the reel in use unwinds less web than that which is "pulled" by the roller 18 downstream, the photocell 19 is uncovered. Vice versa, when the reel in use unwinds more web than that which is "pulled" by the roller 18 downstream, the photocell 19 is covered. When the conditions for changing the reel are reached (radius of reel in use is less than a certain threshold or a manual reel change command is given), the speed of the labelling line 1 is reduced and switches to an average web feed speed Vrwhich is reduced in a predetermined way compared to the production speed Vp(e.g. 30 m / min). For this purpose, the control unit 16 is programmed to set a production speed of the line 1 to a reduced value Vrwhich is lower than the average production speed Vp.

[0151] The speed co of the motor M1 , M2 for unwinding the reel in use is reduced accordingly and the system waits for the end of a transient step to restore the steady conditions for accumulating the web 7 in the buffer 12, as described above. Thus, the control unit 16 waits a settling time for the depth of the loop 14 to reach a constant value.

[0152] The control unit 16 receives via the first photocell 19 a value representing a maximum depth of the loop 14 and sets a reel unwinding speed coz. Then, after a transient stage, where To is the instant in which the photocell 19 is covered (thus when the control unit 16 receives from the first photocell 19 the value representing the maximum depth), the control unit 16 sets an unwnding speed coz, being the speed of the motor M1 , M2 for unwinding the reel in use at a constant rate, whose value is given by:

[0153] COz= Vr / Ro - COz% where Ro is the radius of the reel in use (measured or calculated) at the instant To and coz% is a percentage correction, that is to say, a predetermined speed value such as to reduce the depth of the loop 14 inside the chamber. In particular, coz% is a value such that the photocell 19 is uncovered very slowly starting from the instant To.

[0154] Under these conditions, once the mark sensor 17 has detected the first mark T at an instant Ti after the instant To (and considering the fluctuation in the length of the web 7 in the buffer 12 to be negligible), it is possible to estimate the length of web 7 included between the mark sensor 17 and the splicing device 15. In other words, it is possible to estimate a position of the mark T which is as close as possible to the splicing device 15, hence to derive the offset of the mark T relative to the position necessary for the operation of the splicing device 15.

[0155] Based on the fixed speed cozand considering the reel radius value Ro to be fixed in the range AT= Ti- To, it is possible to calculate the time needed to unwnd the reel in use in order to zero the aforementioned offset and to trigger splicing in synchrony. The time can be calculated from the above- mentioned parameters, which we know, from the geometry of the labelling line 1 , such as the size and structure of the buffer 12, the position of the first photocell 19 and the general layout of the components which convey the web 7, and also from the operating conditions of the labelling line 1 itself, such as the suction rate of the chamber 13 inside the buffer 12 and the material the web 7 is made of, which together contribute to creating a sail effect to a varying degree inside the buffer 12.

[0156] The logic described above itself allows obtaining a satisfactory degree of precision for the splicing operation (in the order of + / - 5 mm) compared to a perfect synchronization of the marks T (between nearly depleted web and new web) which will then be used for the step of cutting the labels E. Advantageously, this method allows the mark detecting sensor 17, which is in any case necessary to synchronize the cutting of the labels E, to be used also to synchronize the webs to be spliced during the reel change operation, in particular, the cutting operation which is performed by the cutting element 22 and which has a considerably reduced cyclic rate compared to that needed for cutting the labels E.

[0157] The electronic control circuitry of the labelling line 1 can thus be considerably simplified, which in turn means the overall costs of the line are reduced.

[0158] In other words, the mark sensor 17 is used not only to synchronize the cutting of the labels E but also to synchronize the webs to be spliced during the reel change operation without having to provide the splicing device 15 with a specific detecting device.

[0159] In a variant, the synchronization of the webs to be spliced during reel change, may be controlled individually, that is to say, independently, responsive to a specific detecting device used especially for that purpose.

[0160] In such a case, the labelling line 1 is provided with a splice sensor 21 . The splice sensor 21 is configured to detect detection data representing at least one cyclic reference T present on the web 7. The splice sensor 21 is located between the buffer 12 and the splicing device 15, in particular proximal to the splicing device 15.

[0161] The splice sensor 21 may be of a type identical or similar to the mark sensor 17.

[0162] The splice sensor 21 may be a contrast sensor which, at a limited cost, allows effectively detecting the marks T and the cyclic rate (frequency and phase) at which the marks pass through the feed unit 10.

[0163] In another variant, the webs to be spliced during the feel change operation may be synchronized responsive both to a detection by the mark sensor 17 and to a detection by the splice sensor 21 .

[0164] The control unit 16 is connected to the splice sensor 21 and is programmed to derive a synchronization signal representing the work cycle. The control unit 16 may instruct the splice sensor 21 to detect the detection data in a time window (or instant) derived dependently on the synchronization signal.

[0165] Based on the detection by the splice sensor 21 , the control unit generates a splicing signal and drives the splicing device 15, in particular without stopping the feeding of the web 7 to the applicator unit 3.

[0166] In particular, when the splice sensor 21 detects a mark T, a second offset with which to correct the splicing operation may be calculated. Since the splice sensor 21 is proximal to the splicing device 15, the error is more limited than the first offset, making it possible to further increase the precision (resulting in an error in the order of + / - 1 .5 mm).

[0167] In the variant comprising both the splice sensor 21 and the mark sensor 17, the synchronization signal is derived from the detection data detected by the mark sensor 17. This configuration is particularly advantageous in that it allows the mark sensor 17, which is in any case necessary to synchronize the cutting of the labels E, to be used also to help synchronize the webs to be spliced during the reel change operation, thereby making the control logic simpler.

[0168] Thus, the combined and coordinated use of the two sensors 17, 21 allows increasing the precision compared to the situation where only the mark sensor 17 or only the splice sensor 21 is used. Reliability is also increased.

[0169] In effect, the splicing device 21 is advantageously "guided" by the detecting device 17 in finding the marks T in pre-identified regions, thus reducing possible false readings by the splice sensor 21 .

[0170] In an embodiment, the mark sensor 17 is a camera.

[0171] Although the camera is more expensive than a contrast sensor, it advantageously allows the marks T to be distinguished more reliably from other features, text or images present on the web 7 and having a colour which is identical or similar to that of the marks T.

[0172] The labelling line 1 comprises a fixed reference Trfor the camera.

[0173] The control unit 16 is connected to the camera (in this case, the control unit 16 may be a PLC). The control unit 16 can generate a control signal (or trigger) for the camera, instructing it to capture image data. The camera preferably has a processing time of less than 40 ms.

[0174] Generally speaking, the control unit 16 receives as input a position of the cutting device 6 to then generate a control signal for the camera.

[0175] The control unit 16 derives a synchronization signal representing the work cycle and, based on that, derives a reference position Prif for the cutting device 6. In particular, when the cutting device 6 is at the reference position Prif, the cyclic reference T on the web 7 is expected to be aligned with the fixed reference Tr. This expectation is based on an estimate of a length of the web 7 included between the reference Tr and a point where the labels E are separated.

[0176] Based on the reference position Prif, the control unit 16 generates a control signal for the camera to instruct it to capture the image data in a time window derived dependently on the synchronization signal.

[0177] The control unit 16 also processes a first difference, defined by a distance between the cyclic reference T present on the web 7 and the fixed reference Tr. The distance is positive if the mark T is before the fixed reference Tr (considering the unwnding direction) and negative if vice versa.

[0178] Since the distance between the cyclic reference T present on the web 7 and the fixed reference Tr may be affected by an error due to the system delay, the control unit 16 may also calculate a second difference between a distance between the position Prif and an effective position Pact of the cutting device. For this purpose, the control unit 16 processes a current position Pact from a position signal representing a position of the cutting device 6 around the axis the moment the image data are captured.

[0179] Next, it generates a control signal to synchronize the cutting of the web 7 by the knife, applying a correction to the control signal, based on the first difference and, if necessary based also on the second difference.

[0180] In an embodiment, the camera defines a field of vision and the fixed reference Tris a virtual point defined by a reference point in the field of vision. Alternatively, the fixed reference Tr is engraved on a support 23 on which the web 7 slides.

Claims

CLAIMS1. A labelling line (1 ) for labelling articles (2), comprising:- an applicator unit (3), including a cutting device (6) having a cutting roller which rotates about a first rotation axis, and a knife which is integral with the cutting roller to separate individual labels (E) from a web of labels (7) by cyclically cutting the web (7) according to a work cycle, and a transporting carousel (9) configured to transport the labels (E) in proximity to the articles (2);- a feed unit (10) configured to feed the web (7) to the applicator unit (3),- a detecting device (17) including a camera, located between the feed unit (10) and the cutting device (6) and configured to capture image data representing at least one cyclic reference (T) present on the web (7);- a fixed reference (Tr) for the camera;- a control unit (16) connected to the camera and programmed to derive a synchronization signal representing the work cycle and, based on the synchronization signal, to derive a reference position (Prif) for the cutting device (6), so that, with the cutting device at the reference position (Prif), the cyclic reference (T) is aligned with the fixed reference (Tr) according to an estimate based on a length of the web (7) included between the fixed reference (Tr) and a point where the labels (E) are separated; based on the reference position (Prif), generate a command signal for the camera (17) to instruct it to capture the image data in a time window derived dependently on the synchronization signal; receive the image data from the camera and calculate a first difference from the image data, the first difference being defined by a distance between the cyclic reference (T) on the web and the fixed reference (Tr), generate a control signal to synchronize the web (7) relative to theknife, and apply a correction to the control signal, based on the first difference.

2. The labelling line according to claim 1 , wherein the synchronization signal is derived from a cutting position signal, representing a position of the cutting device (6) around the first rotation axis.

3. The labelling line according to claim 2, comprising a rotary encoder, located on the cutting roller (6) and configured to detect the cutting position signal.

4. The labelling line according to claim 3, wherein the rotary encoder is an incremental encoder configured to generate a signal A, a signal B and an index signal Z and the control unit:- is programmed to derive the position signal based on the index signal Z, or- is programmed to derive the position signal based on the signal A and the signal B.

5. The labelling line according to any one of the preceding claims, wherein the control unit is programmed to:- receive a position signal representing a position around the first rotation axis of the cutting device (6) at the moment the image data are captured;- calculate a second difference defined by a distance between the effective position (Pact) of the cutting device (6) and the reference position (Prif) of the cutting device (6), and- apply a further correction to the control signal, based on the second difference.

6. The labelling line according to any one of the preceding claims, wherein the camera defines a field of vision and the fixed reference (Tr) is a virtual point defined by a reference point in the field of vision.

7. The labelling line according to any one of the preceding claims, wherein the control unit is programmed to instruct the camera to capture the image data every two or more labels (E) cut.

8. The labelling line according to any one of the preceding claims, whereinthe feed unit (10) comprises:- a first reel (B1 ), around which a first coil of the web (7) is wound, and a second reel (B2), around which a second coil of the web (7) is wound;- an unwinding station (11 ) configured to alternately unwind the first coil from the first reel (B1 ) and the second coil from the second reel (B2);- a splicing device (15) configured to make a splice alternately between the first coil and the second coil so as to connect the first coil to the second coil or vice versa.

9. The labelling line according to claim 8, configured to adopt an average production speed (Vp) during the work cycle, wherein, responsive to a splice made by the splicing device, the control unit is programmed to:- set a production speed of the line (1 ) to a reduced value (Vr) which is lower than the average production speed (Vp);- instruct the camera to capture a plurality of image datasets in sequence;- generate a further control signal to synchronize the web (7) relative to the knife.

10. The labelling line according to any one of the preceding claims, wherein the feed unit (10) includes a feed roller provided with a motor of its own, the control unit being programmed to drive the motor of the feed roller based on the control signal.

11. A labelling method for labelling articles (2), comprising the following steps:- providing an applicator unit (3) including a cutting device (6) having a cutting roller which rotates about a first rotation axis, and a knife which is integral with the cutting roller to separate individual labels (E) from a web of labels (7), and a transporting carousel for transporting the labels (E) in proximity to the articles (2);- via a feed unit (10), feeding the web (7) to the applicator unit (3);- via a knife of the cutting device (6), separating the web (7) into individual labels (E) by cyclically cutting the web (7) during a work cycle;- via a camera of a detecting device (17), located between the feed unit(10) and the cutting device (6), capturing image data representing at least one cyclic reference (T) present on the web (7);- via a control unit: deriving a synchronization signal representing the work cycle and, based on the synchronization signal, deriving a reference position (Prif) for the cutting device (6), so that, with the cutting device at the reference position (Prif), the cyclic reference (T) is aligned with the fixed reference (Tr) according to an estimate based on a length of the web (7) included between the fixed reference (Tr) and a point where the labels (E) are separated; based on the reference position (Prif), generating a command signal for the camera (17) to instruct it to capture the image data in a time window derived dependently on the synchronization signal; receiving the image data from the camera and calculating a first difference from the image data, the first difference being defined by a distance between the cyclic reference (T) on the web and a fixed reference (Tr); based on the processing, generating a control signal to synchronize the web (7) relative to the knife, and applying a correction to the control signal, based on the first difference.

12. The method according to claim 11 , comprising the following steps:- via a rotary encoder located on the cutting roller (6), detecting a position signal of the cutting roller (6), representing a position of the cutting device (6) around the first rotation axis, wherein the synchronization signal is derived from the cutting position signal.

13. The method according to claim 12, wherein the encoder is an incremental encoder and the method comprises the following steps:- via the encoder, generating a signal A, a signal B and an index signal Z;- via the control unit, deriving the position signal based on the index signal Z, orderiving the position signal based on the signal A and the signal B.

14. The labelling method according to any one of claims 11 to 13, comprising the following steps, performed by the control unit:- receiving a position signal representing a position around the first rotation axis of the cutting device (6) at the moment the image data are captured;- calculating a second difference defined by a distance between the effective position (Pact) of the cutting device (6) and the reference position (Prit) of the cutting device (6);- applying a further correction to the control signal, based on the second difference.

15. The labelling method according to any one of claims 11 to 14, wherein the camera defines a field of vision and the fixed reference (Tr) is a virtual point defined by a reference point in the field of vision.

Images