WO2012175728A1

WO2012175728A1 - Method of operation of a labelling machine and labelling machine

Info

Publication number: WO2012175728A1
Application number: PCT/EP2012/062170
Authority: WO
Inventors: Mattia Giuliani
Original assignee: Sidel S.P.A. Con Socio Unico
Priority date: 2011-06-22
Filing date: 2012-06-22
Publication date: 2012-12-27
Also published as: ITTO20110546A1

Abstract

A method of operating a labelling machine (1) for dispensing pressure-sensitive labels (2) from a backing web (3) fed towards an affixing station (6), wherein labels (2) are sequentially peeled off the web (3) and applied to articles (4) arriving at the affixing station (6),and wherein the advancement of labels (2) is adjusted by: -in a first portion of a label application cycle, gradually increasing the label velocity to a cycle maximum velocity and then gradually decreasing the label velocity to a not null reference velocity; and -in a second portion of said label application cycle, immediately subsequent to the second portion of the application cycle, gradually decreasing the label velocity from said not null reference velocity to a not null cycle minimum velocity, and then gradually increasing the label velocity back to said reference velocity, the leading edge of the label covering a label length over an overall advancement time given by the sum of the duration of said first and second portions of label application cycle, in a manner such that the sequential dispensing of every label (2) to be applied is timed with the sequential arrival the corresponding article (4) to be labelled at the affixing portion (6).

Description

"METHOD OF OPERATION OF A LABELLING MACHINE AND LABELLING MACHINE"

TECHNICAL FIELD

The present invention relates to a method of operating a labelling machine of the type dispensing pressure- sensitive labels from a backing web travelling along a feed path and applying the labels to articles - such as bottles, pots, cans, and the like - travelling along an article path. Furthermore, the invention is relative to a labelling machine implementing the method.

BACKGROUND ART

Labelling machines are used to apply labels to articles of all sorts, particularly to containers. Typically used with containers are self-stick labels, also known as pressure-sensitive labels, which commonly consist of a paper/polypropylene/adhesive laminate.

In applying pressure-sensitive labels to containers, a backing strip, or carrier web, to which labels are affixed spaced apart from one another, is unwound from a supply roll and pulled over a bar or blade, thereby causing each label to separate from the carrier web, which is then disposed of. Means are further provided for conveying the containers to an affixing station operatively coupled with said bar or blade and for transferring each label to a container .

Typically, labelling machines of the type referred to above comprise a supply reel of a web bearing the labels and a unit for drawing the web from the supply reel and feeding it to an affixing station, wherein self-stick labels are peeled off the web and stuck to containers being carried by a carousel or a conveyor belt.

The carousel supports along its periphery a plurality of container-holding plates, and it can be pivotally driven by a motor so as to be able to place each individual plate at one or more affixing stations arranged about the carousel. Further, a drive motor is associated with each plate, which can be operated to turn the plate around its axis, so that the container supported by the plate can be placed in the angular positions required for precise application of the labels. Similarly, the conveyor belt is driven by a motor so as to be able to sequentially place each individual container at an affixing station of the labelling machine.

A driving roller of the labelling machine powered by a corresponding motor draws the web off the supply reel and enables the feeding thereof to the downstream stages of application of the labels and recovery/disposal of the bare web off which the labels have been peeled.

Generally, containers conveyed to and through an affixing station by the carousel or by the conveyor belt advance in an intermittent (stop-and-go) fashion, so that each container stands at the affixing station (e.g. at the blade or bar enabling the peeling of labels off the carrier web) for an amount of time sufficient to enable sticking of each label to the surface of a corresponding container. The labelled container subsequently leaves the affixing station .

Besides, even when containers are advanced continuously along a path defined, at least in the proximity of the affixing station, either by the periphery of a carousel or by a length of conveyor belt, the areas on the respective outer surfaces of two consecutive containers to which labels are to be stuck shall however be slightly spaced apart from one another.

Accordingly, the web bearing the labels has to be fed to the affixing station in a manner accounting for this discontinuity, so that the peeling off of each label is timed with the arrival of a container to be labelled at the affixing station.

The drawing/feeding unit of the labelling machine therefore generally comprises push/pull rollers capable of causing the portion of the web approaching the affixing station to momentarily stop and then resume its motion, where the push/pull rollers are actuated in time with the progression of areas to be labelled on the containers travelling on the carousel or on the conveyor belt.

Typical operation parameters of the push/pull rollers of a labelling machine of the type described thus shall now be illustrated in greater detail with reference to Figures 1A and IB. In particular, Figure 1A is a position-vs . -time plot for a succession of three labels being applied to respective containers, whereas Figure IB is a velocity-vs . - time plot for the very same succession of three labels.

In the situation exemplified by said plots, 70mm labels are being applied to bottles spaced apart from one another by 100mm. For the sake of simplicity, Figures 1A and IB depict an ideal situation where all labels have exactly the same length, i.e. the 70 mm nominal length.

The conventional start-stop cycle operation of push/pull rollers results in each label being alternately advanced and then fully arrested. As clearly shown by Figure IB, in the application cycle of every single label, the label velocity is first increased from zero to a maximum value v_max and then decreased back to zero over a predetermined advancement time t_A, following which the label velocity is maintained null for a given stop time t_s.

In a corresponding manner, as illustrated in Figure 1A, the position of the leading edge of every label is made to cover a distance equivalent to the label length L over the advancement time t_A, following which the leading edge of the label stands idle over the stop time t_s.

However, while the portion of carrier web off which the label is about to be dispensed at the affixing station of the labelling machine is subjected to the dynamic start- stop action of the push/pull rollers described above, fresh carrier web bearing labels is instead continuously unwound from its supply reel through operation of a motor driving a drawing roller of the drawing/feeding unit.

As a consequence, different portions of the carrier web being driven across the drawing/feeding unit are subjected to dramatically different dynamics: while the portion of the web proximal to the affixing station is intermittently stopped and driven on, the portion of the web being unwound off the supply reel and fed into the drawing/feeding unit advances in a continuous manner, albeit generally at a variable speed.

To take these circumstances into account, the drawing/feeding unit comprises means for compensating discontinuities and non-homogeneity in the advancing speed of the carrier web, such as a chamber for accommodating a swollen length of web, or the like. Further, a plurality of idler rollers and dancer rollers are generally provided in the drawing/feeding unit in order to ensure that the carrier web is suitably tensioned at all times and under all circumstances.

However, tension exerted on the carrier web due to pull by drawing roller, especially in combination with the speed fluctuations and non-homogeneity described above, may cause undue stretching and deformation of the carrier web and labels borne by it. This is highly undesirable, especially in the case where particularly elastic, fragile and/or thin material is used, because breaks may occur very frequently .

The occurrence of a breakage results in the labelling machine having to be stopped, so that the broken portion of the web may be disposed off and the intact carrier web may be advanced into a correct working configuration again.

Therefore, it is desirable that the breakage rate be kept at a minimum and that the complexity of the gearing elements through which the web passes along its pathway across the drawing/feeding unit is reduced, so that resuming operation in case of a breakage is as little time- consuming as possible.

In fact, a reduction in the breakage rate and in the gearing complexity would also result in a much desirable reduction of both operating and production costs.

Furthermore, operation of the push/pull rollers causing the portion of the web approaching the affixing station to momentarily stop and resume its motion is complicated by possible irregularities in the labelling material fed thereto.

In fact, push/pull rollers are basically responsible for dispensing each pressure-sensitive label to a respective container, hence their operation needs to be properly timed with the movement of said container approaching and then leaving the affixing station, so that each pressure-sensitive label is properly detached from the web by which it is borne and applied to the surface of the container to be labelled in the desired ultimate position. Therefore, any fluctuation in the length of pressure- sensitive labels being fed to the affixing station can cause alterations and inaccuracies in the quality of label application, which typical push/pull rollers cannot compensate.

That is especially true in the case where variations in the length of pressure-sensitive labels being fed to the affixing station are frequent and their effect accumulates over time, thereby making the entity of the inaccuracy no longer acceptable from a production quality perspective. Furthermore, fluctuations in the pressure-sensitive label length may eventually hinder the correct operation of the push/pull rollers and their interaction with the labelling material and the blade at which the labels are detached from the support web. It is therefore also highly desirable that irregularities and possible anomalies in the labelling material fed to the affixing station not alter significantly the quality and reliability of the process of label application in all its phases, as concerns both phases of dispensing (i.e. detaching off the support web) and applying (to a relative container surface) each single label .

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a method of operation of a labelling machine which makes it possible to satisfy the needs felt in the technical field as described above, thereby overcoming the above-mentioned drawbacks in straightforward and inexpensive fashion.

This object is achieved by providing a method of operating a labelling machine as claimed in claim 1.

Furthermore, the invention also provides a labelling machine as claimed in claim 5.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, a preferred, non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which :

Figures 1A and IB show respective diagrams wherein the position and velocity of a succession of pressure-sensitive labels being dispensed and applied, by means of a conventional labelling machine, to respective containers are plotted vs. time (prior art) ;

Figure 2 shows a schematic perspective view of a labelling machine according to the invention;

Figure 3 shows a schematic view of the driving control system of the labelling machine of Figure 2 ;

Figure 4 shows a flow-chart depicting phases of a method of operation of a labelling machine according to the invention; and

Figures 5A and 5B show respective diagrams wherein the position and speed of successive pressure-sensitive labels being dispensed and applied, by means of a labelling machine according to the invention, to respective containers are plotted vs. time.

BEST MODE FOR CARRYING OUT THE INVENTION

Number 1 in Figure 2 indicates as a whole a labelling machine for dispensing pressure-sensitive labels 2 from a backing web 3 travelling along a feed path FP and applying the labels 2 to each of a plurality of articles 4 travelling along an article path AP .

Labelling machine 1 comprises a supply reel 5 off which a backing web 3 bearing pressure-sensitive labels 2, preferably spaced apart from one another, is unwound and fed along a feed path towards an affixing station 6 of the labelling machine.

In the case illustrated in the Figures, supply reel 5 is rotatably mounted on a support shaft 7 secured to a main support frame 8 of labelling machine 1.

Labelling machine 1 further comprises means 9 for unwinding backing web 3 off supply reel 5. In particular, unwinding means 9 comprise a driving roller 10, which is positioned, with reference to a main travelling direction of backing web 3 along the feed path, downstream of supply reel 5, and which is operatively coupled with a shaft of a variable speed motor 11. The linear velocity imparted to the backing web by motor 11 may be advantageously controlled .

At affixing station 6 the labels are sequentially peeled off backing web 3 and applied to corresponding articles 4 sequentially arriving at the affixing station.

To this purpose, labelling machine 1 further comprises means 12 for adjusting the advancement along the feed path of the labels borne by backing web 3 in accordance with the advancement along article path AP of articles 4.

Adjusting means 12 are positioned downstream of unwinding means 9 and preferably comprise driving means 13 the operation of which may controlled, as shall be described in the following, so as to adequate the movement of backing web 3 to the movement of articles 4 at affixing station 6.

In the embodiment illustrated in Figure 1, driving means 13 comprise a pair of rollers 14a and 14b mounted on respective shafts operatively coupled, for example by means of a timing belt transmission, with a variable speed brushless motor 15 which may be actuated to rotate both rollers 14a and 14b in an anti-clockwise direction for advancing the length of backing web 3 bearing the next label 2 to be applied towards a dispensing device 16 of affixing station 6.

To this purpose, adjusting means 12 further comprise a driving control system 40 for adjusting the speed of driving means 13 in response to a signal which is a function of at least one of: the position along the feed path of the next label 2 to be applied, the length L of the next label to be applied; and the speed at which the next container 3 to be labelled advances along article path AP .

In particular, driving control system 40 is configured to properly time the sequential dispensing of every label 2 to be applied with the sequential arrival and advancement of the corresponding article 4 to be labelled at the affixing portion 6, in accordance with a method which shall described in greater detail in the following.

As illustrated in Figure 3, the driving control system 40 of adjusting means 12 comprises a driving control unit 41 which is operatively connected to driving means 13 and to a plurality of sensing means configured to detect specific process variables.

In particular, the driving control unit 41 is operatively connected to a unit 42 for measuring the length L of a label 2 to be applied to a relative article 4, the measuring unit 42 being in turn operatively coupled to one or more sensors (not shown) capable of detecting one or more identification marks on said label 2 or on the backing web 3 bearing the label. Based on the information acquired by these sensors, the measuring unit 42 identifies the leading and trailing edges of the label and computes the actual label length accordingly.

Thus, oscillations in the length of labels 2 being fed to the affixing station 6 may conveniently be accounted for during operation of the labelling machine 1, as shall become apparent from the method description in the following .

Furthermore, the driving control unit 41 is operatively connected to first article-side sensing means 43 (e.g. an encoder) for detecting the instant speed (e.g. the speed of the carousel carrying the containers) at which the next article 4 to be labelled advances along article path AP towards affixing station 6, and to second article- side sensing means 44 for detecting the transit of said article 4 to be labelled at a given position along article path AP, i.e. at a predetermined distance along article path AP from a label dispensing position - the identification of which shall be better defined in the following.

Thus, any variation in the carousel speed or anomalies in the transition of containers being advanced along article path AP towards affixing station 6 (e.g. a container in the succession is missing) may conveniently be accounted for during operation of labelling machine 1, as shall become apparent from the method description given below .

In the embodiment depicted in Figure 1, labelling machine 1 is furthermore provided with an expansion chamber 21 through which backing web 3 travels along a portion of feed path FP comprised between unwinding means 9 and adjusting means 12. More particularly, expansion chamber 21 is designed so as to allow backing web 3 to swell as a result of the speed differential which may occur, during operation of the labelling machine, between unwinding means 9 and adjusting means 12.

In other words, since the advancement of backing web 3 is alternately accelerated and decelerated at affixing station 6, yet means 9 for unwinding backing web 3 off supply reel 5 are intended to be continuously actuated at a constant speed, a portion of backing web 3 upstream of adjusting means 12 shall keep advancing along feed path FP at a given feeding speed whilst a portion of backing web 3 downstream of adjusting means 12 is slowed down to a second operating speed which may be lower than said feeding speed. This may cause for a length of backing web 3 to accumulate and swell upstream of adjusting means 12, thereby compensating for the speed differential described above.

Advantageously, expansion chamber 21 is designed so as to accommodate the accumulating and swelling length of web thereby preventing any interaction thereof with other moving parts of the machine. Between the inlet to and the outlet from expansion chamber 21, the accumulating length of backing web 3 may be advantageously exposed to a flow of air by providing a fan F within the expansion chamber.

Advantageously, the driving control system 40 is programmed to manage operation of adjusting means 12 - more particularly of driving means 13 - in the manner that shall be described hereafter.

In particular, driving control system 40 is advantageously programmed to actuate adjusting means 12 so that, in the application cycle of every single label 2 (see Figure 5B, continuous line profiles) :

- in a first portion of the application cycle, having duration ti, the label velocity is first gradually increased to a cycle maximum velocity v_max and then gradually decreased to a not null reference velocity v_ref; and

- in a second portion of the application cycle, immediately subsequent to the first portion of the application cycle and having duration t₂, the label velocity is gradually decreased from the not null reference velocity v_ref to a not null cycle minimum velocity v_min and then gradually increased back to the reference velocity v_ref.

In a corresponding manner, as illustrated in Figure 5A (see the continuous line profile) , the position of the leading edge of every label is made to cover a distance equivalent to the nominal label length L over an overall advancement time t_OVER_ALL which is given by the sum of ti and t₂.

Over each application cycle, accordingly, a length of backing web 3 bearing the next label 2 to be applied is pulled over a peeler blade of dispensing device 16, so as to accurately and reliably place said label 2 onto the surface of container 4.

Preferably, over each application cycle the difference between the cycle maximum velocity v_max and the reference velocity v_ref is greater than the difference between the reference velocity v_ref and the cycle minimum velocity v min .

First and second portion of the application cycle may have the same duration, i.e. it may be that ti = t₂. Alternatively, the ti/t₂ ratio may be greater or lesser than 1. In the embodiment illustrated by Figures 5A and 5B,

Typically, the leading edge of the label 2 contacts, and is pasted upon, the relative article surface early during the first portion of the application cycle and therefore continues to move driven by said article moving along article path AP, the article being in turn driven by the carousel.

On the other hand, at least part of the rest of the label 2 continues to advance with backing web 3 for a fraction of the application cycle, until the label 2 is wholly detached off backing web 3 and adhering to the article surface. As a matter of fact, there can typically exist a slight speed difference between the part of label 2 already adhering to its relative article and the part of the label 2 still adhering to backing web 3.

Driving control system 40 is advantageously programmed to actuate adjusting means 12 so that the speed difference mentioned above can be conveniently compensate.

In particular, driving control system 40 is advantageously programmed to calculate an optimal ti/t₂ ratio as a function of the label length L and the pitch by which consecutive articles to be labelled are separated along article path AP .

In practice, driving control system 40 is programmed to actuate adjusting means 12 so that their cyclic motion mimics the motion which they would be subjected to if driven by a cam profile system. In other words, the driving control unit 41 is programmed to compute a so-called "virtual cam profile" to be supplied, as an actuation signal, to the adjusting means.

In this context, a "virtual cam profile" is meant to include information regarding the operation parameters defining the application cycle, such as v_max, v_ref, v_min, ti and t₂. Preferably, also data relative to the velocity increase and decrease gradient at all times during the application cycle of a label may form part of the "cirtual cam profile".

Advantageously, the driving control unit 41 is programmed to compute, for every label to be applied, a so- called "updated virtual cam profile", based on real-time data received from any of label length measurement unit 42, first and second article-side sensing means 43 and 44 - i.e. data relative to the position along feed path FP of the next label 2 to be applied, the length L of the next label to be applied; and the speed S at which the next container 4 to be labelled advances along article path AP .

Thus, the "updated virtual cam profile" is conveniently corrected, with respect to the reference cam profile computed based on the nominal label length L, to account for labels having actual length L' greater than nominal length L, or labels having actual length L' ' lesser than nominal label length L.

Accordingly, the "updated virtual cam profile" shall include the updated value of at least one of the cycle maximum velocity v_max, the reference velocity v_ref and cycle minimum velocity v_min.

In more general terms, the "updated virtual cam profile" may preferably include updated (yet possibly unchanged) values for the main operation parameters, e.g. updated values for v_max, v_ref, v_min, ti and t₂, but preferably also data relative to the velocity increase and decrease gradient at all times during the application cycle of the label.

It should be noted that, accordingly, for each application cyle, the cycle maximum velocity v_max may be slightly greater/lesser than the cycle maximum v_max velocity reached during the immediately previous application cycle. Similarly, for each application cycle, the cycle minimum velocity v_min may be slightly greater/lesser than the minimum cycle velocity v_min reached during the immediately previous application cycle.

This is also illustrated in Figure 5B (see dotted line profile) . By way of example, Figure 5B illustrates the case of a succession of three labels having length differing from the nominal label length, namely a first label of actual length L' slightly greater than the nominal length L, followed by two consecutive labels of actual length L' ' slightly lesser than nominal label length L.

Each label is advantageously dispensed over the overall advancement time t_OVER_ALL which is the sum of ti and t₂, yet the velocity profile followed by the label during the first and second portion of the respective application cycle is adjusted, with respect to the theoretical profile corresponding to the nominal label length L, to account for label length oscillation.

The flow-chart of Figure 4 illustrates in greater detail the logic operation of driving control unit 41, in use .

It should be noted that, when the labelling machine 1 is first activated, the driving control unit is supplied with data relative to the nominal label length (block 100) and (blocks 101-103) the actual length of the first label is measured by having the first label stop to this purpose. Said first label is actually not used for labelling, i.e. it is discarded and the labelling procedure matter-of- factly begins when the next label 2 on backing web 3 is fed further on.

It should be noted that, first of all, stopping the first label makes it possible to achieve proper label- article alignment.

Secondly, stopping and measuring the first label on the backing web enables prevention of a number of glitches which may occur upon re-activation of a labelling machine.

For instance, the labelling machine currently being activated could have previously been used with labels having a different length, or, in spite of a change in label geometry, the operator might have forgotten to update the nominal length data. As a result, driving control unit might not be properly configured to manage the label format currently being supplied. On the contrary, by stopping and measuring the actual length of the first label on the backing web, correct and up-to-date label information may be directly acquired by driving control unit 41.

Since the very first label 2 on the backing web is stopped and matter-of-factly excluded from application on a relative article, the application cycle of the very first label to actually be applied (i.e. the next label 2 on backing web 3) differs slightly from the following application cycles in that the label velocity is increased to the cycle maximum velocity from a null velocity value, and not from the reference velocity v_ref (see Figure 5B) .

For each label 2 fed towards affixing station 6 and approaching adjusting means 12, the actual label length is measured (block 104) by means of label length measurement unit 42.

Subsequently, based on the actual label length value just acquired, the driving control unit 41 assesses (block

105) whether a correction of the "virtual cam profile" is required, by comparing said value with the nominal label length.

At the same time, the driving control unit 41 receives real-time information relative to the carousel speed (block

106) and the approach of the next container to be labelled towards affixing station 6 (block 107) .

Based at least on said information, the driving control unit 41 computes (108) the cam profile to be supplied to the driving means 13, at once accounting for any possible oscillation in the label length and properly timing the dispensing of the next label 2 with the arrival of the next container 4 to be labelled at affixing station 6. In response to the control activity of driving control unit 41, driving means 13 are conveniently actuated to dispense (block 110) the label 2 onto the surface of container 4.

Along the whole of feed path FP, backing web 3 bearing the pressure-sensitive labels 2 is unwound off supply reel 5 to pass around a first idler roller 25 and to extend toward driving roller 10. Backing web 3 is thereby pulled and fed into expansion chamber 20.

Subsequently, backing web 3 bends whilst travelling across expansion room 20 and out of it, then passes around a second idler roller 26.

Continuing downstream, backing web 3 is pulled by roller 14a, and fed on around another two consecutive idler rollers 27a and 27b and then off to the peeling blade of dispensing device 16.

Once past the peeling blade, the bare web off which labels have been peeled continues along feed path FP around yet another idler roller 27c and to roller 14b, which is also provided with a counter-roller.

Downstream of roller 14b, the bare web passes around another group 28 of idler rollers, optionally in conjunction with a dancer arm, and finally fed to a waste means 29 for accumulating the bare web for subsequent disposal.

During operation of labelling machine 1, articles to be labelled are advanced, by a carousel or conveyor belt, towards affixing station 6.

Unwinding means 9 are continuously operated, at a variable speed which may be controlled as a function of the web swelling state in expansion room 20, to pull backing web 3 off supply reel 5.

Driving means 13 are alternately accelerated and decelerated so as to bring each next label 2 to be applied at the label stop position adjacent to the peeling edge of dispensing device 16 in time with the sequential arrival thereat of the next article 4 to be labelled.

The label 2 is thereby peeled off the backing web 3 and applied to the corresponding article 4, which then advances along article path AP away from affixing station 6.

The bare backing web 3 off which the label 2 has been peeled off is advanced along feed path FP towards the waste means 29.

Throughout operation of labelling machine 1, driving control system 40 actuates adjusting means 12 in order to time the dispensing of each label 2 with the arrival of each container 4 to be labelled at affixing station 6.

The advantages of the method of operation of a labelling machine and of a labelling machine according to the present invention will be clear from the above description .

First of all, by virtue of the method of the invention, the occurrence of a breakage resulting in the labelling machine having to be stopped is greatly reduced, because speed oscillations and non-homogeneity of speed along the backing web 3 along its feeding path FP are, for the most part, eliminated. In particular, according to the method of the invention, all portions of the backing web 3 are constantly advancing along FP at a not null speed, therefore the unduly stretching of the labelling material caused by the start-stop action of conventional labelling machines and methods is dramatically reduced with respect to solutions based on a start-stop motion of the web.

Furthermore, fluctuations in the carousel speed or anomalies in the transition of containers being advanced along article path AP towards affixing station 6, as well as fluctuations in the label length are conveniently accounted and substantially compensate for during operation of the labelling machine, which results in a more efficient management of the whole labelling process. In particular, a better precision of application can be achieved.

Also, the production and maintenance costs are conveniently reduced because the driving components are simplified, and productivity may be increased.

Clearly, changes may be made to the method for operating a labelling machine and to the labelling machine described and illustrated herein without, however, departing from the scope of protection as defined in the accompanying claims.

Claims

1) A method of operating a labelling machine (1) for dispensing pressure-sensitive labels (2) from a backing web

(3) travelling along a feed path and applying the labels (2) to articles (4) travelling along an article path (AP) , comprising :

- unwinding a backing web (3) carrying a plurality of pressure-sensitive labels (2) off a supply reel (5) and feeding the web (3) along the feed path towards an affixing station (6) of the labelling machine;

- sequentially peeling the labels (2) off the backing web (3) at the affixing station (6) and applying the labels (2) to the articles (4) sequentially arriving thereat; and

- adjusting the advancement along the feed path of the labels (2) borne by the backing web (3) in accordance with the advancement along the article path (AP) of the articles

(4) to which the labels (2) are to be applied;

characterised in that the step of adjusting the advancement of labels (2) borne by the backing web (3) comprises:

- in a first portion of a label application cycle of duration tl, gradually increasing the label velocity to a cycle maximum velocity v_max and then gradually decreasing the label velocity to a not null reference velocity v_ref; and - in a second portion of said label application cycle, immediately subsequent to the first portion of the application cycle and having duration (t2), gradually decreasing the label velocity from said not null reference velocity (v_ref) to a not null cycle minimum velocity (v_min) , and then gradually increasing the label velocity back to said reference velocity (v_ref) , the position of the leading edge of the label being made to cover a distance equivalent to its length over an overall advancement time (tOVERALL) given by the sum of the duration of said first and second portions of label application cycle (tl, t2);

in a manner such that the sequential dispensing of every label (2) to be applied is timed with the sequential arrival the corresponding article (4) to be labelled at the affixing portion (6) .

2) A method as claimed in Claim 1, wherein, over each label application cycle, the difference between the cycle maximum velocity v_max and the reference velocity v_ref is greater than the difference between the reference velocity v_ref and the cycle minimum velocity v_min.

3) A method as claimed in Claim 1 or 2, wherein said step of adjusting the advancement of labels (2) borne by the backing web (3) comprises a step of calculating an optimal ratio of the duration of said first portion of application cycle (tl) to the duration of said second portion of application cycle (t2) as a function of the label length (L) and the pitch by which consecutive articles to be labelled are separated along said article path (AP) .

4) A method as claimed in any one of Claims 1 to 3, wherein said step of adjusting the advancement of labels (2) borne by the backing web (3) comprises:

- detecting at least one variable selected from the group consisting of: the position along the feed path of the next label (2) to be applied, the actual length of the next label (2) to be applied; and the speed at which the next container (4) to be labelled advances along article the path (AP) ; and

- adjusting at least one of said cycle maximum velocity (v_max) , reference velocity (v_ref) and cycle minimum velocity (v_min) in response to a signal which is a function of said at least one variable.

5) A labelling machine (1) for dispensing pressure- sensitive labels (2) from a backing web (3) travelling along a feed path and applying the labels (2) to articles (4) travelling along an article path (AP) , said labelling machine (1) comprising:

a supply reel (5) of a backing web (3) carrying a plurality of pressure-sensitive labels (2); - means (9) for unwinding the web (3) off the supply reel (5) and for feeding the web (3) along the feed path towards an affixing station (6) of the labelling machine (1), at which the labels (2) are sequentially peeled off the backing web (3) and applied to the articles (4) sequentially arriving thereat; and

- driving means (12) for controlling the advancement along the feed path of the labels (2) borne by the backing web (3) in accordance with the advancement along the article path (AP) of the articles (4) to which the labels (2) are to be applied;

characterised in that it further comprises a driving control system (40) programmed to control operation of the adjusting means (12) in accordance with a method as claimed in any one of Claims 1 to 4.

6) A labelling machine as claimed in Claim 5, wherein said driving control system (40) comprises a driving control unit (41) operatively connected to said adjusting means (12) and to a plurality of sensing means configured to:

- detect at least one variable of: the position along the feed path of the next label (2) to be applied, the actual length of the next label (2) to be applied and the speed at which the next container (4) to be labelled advances along article the path (AP) ; and supply said adjusting means (12) with a corresponding actuation signal which is a function of said at least one detected variable.

7) A labelling machine as claimed in Claim 6, wherein said driving control unit (41) is operatively connected to a unit (42) for measuring the actual length a label (2) to be applied to a relative article (4), said measuring unit (42) being in turn operatively coupled to one or more sensors capable of detecting one or more identification indicia on said label (2) or on the backing web (3) bearing said label and computing the actual label length.

8) A labelling machine as claimed in Claim 6 or 7, wherein said driving control unit (41) is operatively connected to first article-side sensing means (43) for detecting the instant speed at which the next article (4) to be labelled advances along the article path (AP) and to second article-side sensing means (44) for detecting the transit of said next article (4) to be labelled at a predetermined position along the article path (AP) .

9) A labelling machine as claimed in any one of Claims

5 to 8, wherein said adjusting means (12) comprise driving means (13, 14a, 14b, 15) adapted to alternately accelerate and decelerate the backing web (3) advancing towards the affixing station (6) .

10) A labelling machine as claimed in any one of Claims 5 to 9, characterised by further comprising an expansion chamber (21) arranged between said unwinding means (9) and said adjusting means (12), said expansion

(21) chamber being adapted to accommodate a length of web (3) swelling to compensate for a differential between the backing web linear velocity at the unwinding means (9) and the backing web linear velocity at the adjusting means

(12) .