The present invention falls within the technical field of automatic machines for forming containers starting from a sheet of packaging material. More specifically, the present invention concerns a method for forming containers filled with a liquid and sealed, starting from a sheet of multilayer packaging material. The present invention also relates to an apparatus capable of implementing the aforementioned method for forming containers.

In particular, the present invention, preferably though non-exclusively, applies to a process for forming containers filled with a liquid and sealed, starting from a sheet of multilayer packaging material, such as a paper or paperboard-based material that is polythene-coated and laminated to be used in the packaging of liquid or viscous foodstuffs, for example, unwound from a reel along a processing path, to which reference will be made hereinafter without losing generality.

A first process for forming containers filled with a liquid and sealed, in particular containers whose seals are made on two side walls and on the bottom wall but not on the top wall, generally includes the following steps: folding a sheet of multilayer packaging material in half along a main axis parallel to a sheet advancement direction; sealing, e.g. with the aid of a heat-sealable material tape, the sheet folded in half in order to obtain a tube; filling the tube obtained with the liquid product to be packaged; performing, on the lower end of the tube, in succession and in a manner synchronised with the sheet advancement, transverse seals that generate on the tube, one after the other, individual containers filled with the liquid product and sealed; separating the individual containers from the tube by cutting; and shaping the individual containers by means of a shaping operation with the desired geometry and final appearance.

A further process for forming containers filled with a liquid and sealed, in particular containers whose seals are made on a side wall as well as on the lower and upper walls, generally includes the following steps: wrapping a sheet of multilayer packaging material in a tube-like shape around a main axis parallel to a sheet advancement direction; sealing, e.g. also in this case with the aid of a heat-sealable material tape, the sheet wrapped in a tube along this axis; filling the tube made with the liquid product to be packaged; performing, on the lower end of the tube, in succession and in a synchronised manner with the sheet advancement, transverse seals that generate on the tube, one after the other, individual containers filled with the liquid product and sealed; separating the individual containers from the tube by cutting; and shaping the individual containers by means of a shaping operation with the desired geometry and final appearance.

The steps of both the forming processes are performed in a machine by means of respective forming and filling units. In the present disclosure as well as in the accompanying claims, certain terms and expressions are deemed to have, unless otherwise expressly indicated, the meaning given in the following definitions.

In an automatic machine for forming containers starting from a sheet of packaging material advancing along a feed direction, a first station is considered to be “upstream” of a second station when such first station precedes the second station with reference to the sheet feed direction, conversely, the second station is considered to be “downstream” of the first station as it follows the first station still with reference to the sheet feed direction.

With reference to the sheet of packaging material advancing along the feed direction inside the automatic machine, “longitudinal direction” refers to a direction parallel to the feed direction, “oblique direction” refers to a direction forming with the feed direction an angle other than a multiple - even zero - of 90°, “transverse direction” refers to a direction orthogonal to the feed direction.

The term “parallel” refers to a substantial parallelism between two elements, comprising both the ideal case in which these elements are arranged in relation to each other so as to form a null angle, and more frequent cases in which the two elements are arranged in relation to each other so as to form an angle that is not null but still negligible or irrelevant for the purposes of the present solution, such as equal to 10°.

A first element is considered to be “above” a second element when, with reference to a common plane perpendicular to the direction defined by the force of gravity or deviating from the force of gravity by a maximum of 10°, the first element has a higher position than the second element and the projections of said first element and second element on the common plane overlap at least partially.

With respect to a reference direction, the term “displacement” of two elements or if two elements are said to be “displaced” means that the orthogonal projections of said two elements on a plane perpendicular to the reference direction overlap by less than 50%.

The terms “creasing line” and “folding line” refer to a line at which the material has been weakened, e.g. mechanically by impressing or by cutting, in order to facilitate and adjust subsequent folding thereof. The “creasing lines” or “folding lines” also help to improve the mechanical strength and stability of the final containers and define geometries and specific aspects thereof.

A “graphic sign” is an identifying element chosen, for example, from a geometric figure, a letter, a number, an inscription, an icon, a code (e.g. alphanumeric, bar, QR, ChArUco), and may be printed, in monochrome or polychrome, or applied, or engraved. The “rotation speed” of a rotating body refers to the average angular speed, i.e. the angle described by the rotating body in the unit of time, while the “peripheral speed” is by definition the average speed possessed by a point located on the outer surface of the same rotating body i.e. the distance covered by the point in the unit of time.

An object advances or is led “with interference” between a pair of rollers spaced-out from each other and with their respective axes parallel when, in a direction transverse to the advancement direction and to the axes of the rollers, the distance between these rollers is lower, even slightly, than the size of the object being led, so that the two rollers exert a pressure on the object and are able to drag it.

The sheet of packaging material is generally printed with a repeated pattern including images and lettering, e.g. to record useful information for the consumer or advertising information on the final container and to give it a distinctive and attractive appearance for the consumer. In addition, to facilitate the step of shaping the packaging material into final containers, the packaging material sheet itself is provided with appropriate weakening lines at preset positions depending on the printing pattern, which are called creasing lines or folding lines.

The creasing lines, when not present on the reel of the packaging material, are suitably made by a creasing group during a machine creasing process, pressing the sheet material between two plates or between pairs of rollers provided with respective creasing elements. The sheet is generally led through the creasing group by a pair of braking rollers and a pair of feed rollers.

One of the two plates or one of the two rollers of the creasing group, which is referred to as the “male”, is provided with protruding elements defining a raised creasing pattern, while the other plate or the other roller of the creasing group, which is referred to as the “female”, is provided with recesses intended to cooperate with the aforementioned protruding elements and defining an engraved creasing pattern, in particular complementary to the raised creasing pattern.

The Applicant first noted that the process of machine creasing the printed sheet may represent a critical element in forming containers filled with liquid and sealed. In fact, the creasing lines may potentially be made in positions other than the preset ones, resulting in a final container that is different from the desired one, for example with partial or displaced images and lettering, suggesting the idea of a product of poor quality and unattractive to the consumer. This critical element becomes more frequent as the production speed increases and particularly in highly automated production lines.

The Applicant therefore felt the need to control the machine creasing process according to the pattern printed on the sheet of packaging material being fed through the machine at an advancement speed. The Applicant realised that aligning, in the initiating step, the creasing group with the pattern printed on the packaging material sheet and setting an operating speed of the creasing group equal to the advancement speed of the sheet in the machine would not be sufficient for this purpose, either because the print on the sheet often has imperfections that compromise the periodicity of the repeated pattern, or because the sheet advancing in the machine may undergo short and sudden decelerations or accelerations and thus have a non-constant advancement speed.

The Applicant therefore realised that adjusting the drive speed of the creasing group according to the repeated pattern actually printed on the sheet would allow for printing imperfections to be taken into account.

In addition, the Applicant verified that the short decelerations or accelerations which the sheet is suddenly submitted to are mainly due to braking rollers, which can, for example, wear out and turn at peripheral speeds other than the desired ones or lose their grip on the sheet. The Applicant therefore also realised that adjusting the operation of the braking rollers would facilitate the advancement of the sheet at a substantially constant speed during the creasing process.

The Applicant therefore found, on the one hand, that identifying preset positions on the sheet of packaging material and controlling the drive speed of the creasing group in order to impress the creasing lines at such preset positions, and on the other hand, that controlling at least one of the drive speed and torque of one of the braking rollers in order to stretch the sheet with a certain tension and impart a constant speed thereto during the creasing process, would make it possible to manufacture containers with properly positioned images and lettering, i.e. with an aesthetically distinctive and attractive appearance for the consumer.

Therefore, the present invention, in a first aspect thereof, relates to a method for manufacturing containers filled with a liquid and sealed starting from a sheet of packaging material, preferably moved in a feed direction.

Preferably, the method comprises the step of rotating a first braking roller of a braking group.

Preferably, the method comprises the step of rotating a first creasing roller of a creasing group, preferably located downstream of said braking group.

Preferably, the method comprises the step of rotating a first feed roller of a feed group, preferably located downstream of said creasing group.

Preferably the method comprises the step of leading said sheet with interference between said first feed roller and a second feed roller of said feed group, in particular to move said sheet in said feed direction. Preferably said sheet is moved at a speed equal to said peripheral speed of said first feed roller.

Preferably, the method comprises the step of leading said sheet with interference between said first braking roller and a second breaking roller of said breaking group, in particular to stretch said sheet between said braking group and feed group.

Preferably, the method comprises the step of controlling at least one of the rotation speed and torque of said first braking roller in order to stretch said sheet between said braking group and feed group with a certain tension.

Preferably, the method comprises the step of leading said sheet with interference between said first creasing roller and a second creasing roller of said creasing group, in particular in order to impress a plurality of creasing lines on said sheet and to obtain a creased sheet. Preferably said first creasing roller and second creasing roller are provided with respective creasing elements.

Preferably, the method comprises the step of identifying said preset positions on said sheet.

Preferably the method comprises the step of controlling a rotation speed of at least one of said first creasing roller and second creasing roller, in particular in order to impress said plurality of creasing lines at said preset positions on said sheet;

Preferably, the method comprises the step of feeding a forming and filling unit of said apparatus with said creased sheet.

The present invention, in a second aspect thereof, concerns an apparatus for manufacturing containers filled with a liquid and sealed starting from a sheet of packaging material.

Preferably the apparatus comprises a forming and filling unit.

Preferably the apparatus comprises a creasing unit, preferably located upstream of said forming and filling unit.

Preferably said creasing unit comprises a braking group. Preferably said braking group includes a first braking roller and a second braking roller, preferably parallel to each other, preferably spaced- out for leading with interference said sheet of packaging material.

Preferably said creasing unit comprises a creasing group, preferably located downstream of said braking group. Preferably said creasing group includes a first creasing roller and a second creasing roller, preferably parallel to each other, preferably spaced-out for leading with interference said sheet of packaging material, in particular to impress a plurality of creasing lines on said sheet and have a creased sheet. Preferably said first creasing roller and second creasing roller are provided with respective creasing elements.

Preferably said creasing unit comprises a feed group, preferably located downstream of said creasing group. Preferably said feed group includes a first feed roller and a second feed roller, preferably parallel one another, preferably spaced-out for leading with interference said sheet of packaging material.

Preferably said creasing unit comprises a drive unit. Preferably said drive unit is connected to said braking group, in particular to drive said first braking roller in rotation. Preferably said drive unit is connected to said creasing group, in particular to drive said first creasing roller in rotation. Preferably said drive unit is connected to said feed group, in particular to drive said first feed roller in rotation.

Preferably said creasing unit comprises a first detecting unit, preferably connected to said braking group, preferably intended for detecting at least one of rotation speed and torque of said first braking roller.

Preferably said creasing unit comprises a second detecting unit connected to said creasing group. Preferably said second detecting unit is intended to detect said preset positions on said sheet. Preferably said second detecting unit is intended to detect a displacement between said plurality of creasing elements and said preset positions on said sheet.

Preferably said creasing unit comprises a control unit. Preferably said control unit is connected to said drive unit, preferably to control at least one of a rotation speed and torque of said first breaking roller, preferably, to control a rotation speed of at least one of said first creasing roller and second creasing roller as a function of said detected displacement. Preferably said control unit is connected to said first detecting unit. Preferably said control unit is connected to said second detecting unit. By controlling the rotation and/or torque speed of the first braking roller, possible decelerations or accelerations to which the sheet is suddenly submitted may be promptly detected and counteracted, so that the sheet is kept properly stretched between the braking group and the feed group and is advanced at a basically constant, known or detectable, speed during the creasing process. In addition, the identification of preset positions on the sheet of packaging material and the control of the drive speed of the creasing group together allow the rotation of the creasing rollers to be synchronised to the repeated pattern actually printed on the sheet, and allow to take into account possible imperfections in the print, facilitating the impression of the creasing lines in the preset positions.

The combined and simultaneous control action of the rotation and/or torque speed of the first braking roller and of the control of the drive speed of the creasing group thus makes it possible to produce containers with properly positioned images and lettering, with the desired aesthetic appearance and actually distinctive and attractive to the consumer.

In at least one of the aforesaid aspects, the present invention may also have at least one of the preferred characteristics hereinafter described.

Preferably said plurality of creasing lines includes creasing lines parallel to said feed direction. Preferably said plurality of creasing lines includes creasing lines transverse to said feed direction. Preferably said plurality of creasing lines includes creasing lines both parallel as well as transverse to said feed direction.

Preferably said plurality of creasing lines includes curved creasing lines.

Preferably, the creasing elements comprise longitudinal creasing elements, which are intended to produce on the sheet creasing lines parallel to a longitudinal direction. Preferably, the creasing elements comprise transverse creasing elements, which are intended to produce creasing lines on the sheet parallel to a transverse direction. Preferably, the creasing elements comprise oblique creasing elements, which are intended to produce creasing lines on the sheet parallel to an oblique direction. In one or more embodiments, the creasing elements have curved sections.

Thanks to the possibility of including longitudinal, transverse and oblique creasing elements, possibly with curved sections, the creasing rollers can produce various types of creasing patterns on the sheet, making it possible to form containers having also complex shapes that are particularly attractive to the consumer.

Preferably, each creasing roller includes at least one respective adjustment surface. Preferably, said adjustment surface is comprised between two successive transverse creasing elements. Preferably, said adjustment surface is free of transverse creasing elements and oblique creasing elements. Preferably, said adjustment surface is free of creasing elements with curved lines.

Preferably, the method comprises controlling a rotation speed of at least one of said first creasing roller and said second creasing roller according to preset transverse positions of said preset positions identified on said sheet, in particular so as to impress a plurality of transverse creasing lines at said preset transverse positions identified on said sheet.

Preferably, said rotation speed of at least one of said first creasing roller and second creasing roller is controlled when respective adjustment surfaces of the first creasing roller and second creasing roller operate simultaneously on the sheet led with interference between them.

The presence of adjustment surfaces on the first creasing roller and the second creasing roller makes it possible to advantageously control the rotation speed of the creasing group without having to stop the sheet processing, i.e. without reducing the throughput. It should be noted that, in case of displacement between the transverse creasing elements of the creasing group and the predefined transverse positions identified on the sheet, the control includes a possible change in the rotation speed (acceleration or deceleration) of the first creasing roller and/or second creasing roller, which inevitably leads to the creasing rollers slipping on the sheet. In view of the above, an adjustment surface is a portion of the side surface of a creasing roller that is either devoid of any creasing elements or comprising only longitudinal, in particular straight, creasing elements. The friction exerted on the sheet by such an adjustment surface is lower than the friction exerted on the same sheet by oblique and transverse creasing elements, with or without curved sections. By commanding an acceleration or deceleration of the first creasing roller and/or the second creasing roller when the respective adjustment surfaces are facing each other and operate simultaneously on the sheet led with interference between them, i.e. when the creasing rollers exert as little friction as possible on the sheet, the risk of the sheet being ruined during the processing, e.g. scratched or tom by the creasing elements, particularly due to the slipping of the creasing elements of the male cylinder on the sheet, is advantageously reduced.

In one or more embodiments, said first braking roller has a lower peripheral speed than a peripheral speed of said first feed roller. In one or more embodiments, said first braking roller has a peripheral speed substantially equal to a peripheral speed of said first feed roller.

In one or more embodiments, said first creasing roller has a peripheral speed substantially equal to said peripheral speed of said first feed roller.

In one or more embodiments, the method comprises controlling a torque of said first braking roller. The wear of the rollers of the braking group corresponds to a wear of the side surface of these rollers and determines an increase in the distance between them, i.e. a reduction in the interference on the sheet led by the braking rollers. As a result, the force with which the braking rollers act on the sheet of packaging material, which, under the action of the feed rollers, is led to accelerate in the advancement direction, is lower. The specific control on the torque of the first braking roller makes it possible to indirectly control the force with which both braking rollers are acting on the sheet and thus to promptly detect a loss of force, i.e. of the grip of the braking rollers on the sheet. In one or more embodiments, the method comprises detecting a torque of said first braking roller. Preferably, the method comprises comparing said detected torque with a reference torque.

Providing a reference torque, which helps to identify the ideal operation of the creasing group, makes it possible to advantageous verify, by a simple comparison, whether the creasing rollers are working under ideal or substantially ideal conditions, or whether they are subject to faults or malfunctions.

Preferably, the method comprises determining a torque difference between said detected torque and reference torque. Preferably the method comprises, when said torque difference is other than zero, mutually moving said first braking roller and second braking roller, in particular to adjust a braking power of said braking group on said sheet.

Preferably, the method comprises moving said first braking roller and second braking roller towards each other by an approach distance when said measured torque is lower than said reference torque, in particular to increase a braking power of said braking group on said sheet.

Preferably the method comprises moving said first braking roller and second braking roller away from each other when said measured torque is greater than said reference torque, in particular to reduce a braking power of said braking group on said sheet.

The movement of the braking rollers closer to and/or away from each other, determines a reduction or increase in the distance between them, i.e. a greater or lower interference on the sheet led by the braking rollers. Moving the braking rollers closer to each other makes it possible to increase the action, i.e. the braking power of the braking group on the sheet, when said braking power is not sufficient and the sheet may be subject to acceleration due to the drive of the feed group. On the contrary, moving the braking rollers away from each other allows to reduce the braking power of the braking group on said sheet, when such braking power is excessive and the sheet could suffer deceleration or stop advancing, or even be subjected to excessive tension and tear.

In one or more embodiments, the method comprises calculating said approach distance of said first braking roller and second braking roller as a function of a comparison of said detected torque and reference torque. Preferably the method comprises comparing this approach distance with a maximum approach value. Preferably, the method comprises triggering an alarm procedure when said approach distance is greater than said maximum approach value.

Preferably, the method comprises updating said maximum approach value as a function of said approach distance. Preferably, the method comprises updating the maximum approach value by subtracting said approach distance from said maximum approach value.

The maximum approach value identifies the maximum stroke that the rollers may cover moving closer to each other from the initial position. Advantageously, the maximum approach value is updated as the rollers are moved by an approach distance, i.e. they have already completed part of the maximum stroke. When the approach distance is greater than the residual stroke the rollers may perform, an alarm procedure is triggered to signal to the operator that the apparatus needs to be serviced, for example because one of the braking rollers is excessively worn and is no longer able to operate properly, so it must be replaced.

In one or more embodiments, the method comprises triggering an alarm procedure when said torque difference is equal to or greater than a threshold differential value.

In one or more embodiments, the method comprises keeping track of a time trend of said torque difference.

Providing a threshold differential value helps to identify situations in which the detected torque is excessively different from the reference torque and a simple movement of the brake rollers closer to or away from each other would not be sufficient to bring the relative torque back to the reference torque values, so an operator intervention on the equipment is required.

In one or more embodiments, the method comprises triggering an alarm procedure when said detected torque is greater than a maximum threshold value. The maximum threshold value corresponds, in particular, to the maximum braking power that the braking rollers can apply to the sheet without damaging it and beyond which the operator must be alerted.

In one or more embodiments, the method comprises triggering an alarm procedure when said detected torque is below a minimum threshold value.

The minimum threshold value corresponds, in particular, to the minimum braking power that the braking rollers can apply to the sheet without losing grip thereon and below which the operator must be alerted.

Preferably said alarm procedure comprises stopping the operation of the apparatus. Stopping the machine operation when the torque values of the braking group deviate too far from the ideal values or are too high/low makes it possible for an operator to intervene on the machine before the sheet or machine is damaged.

In one or more embodiments, the method comprises bringing at least one of said first creasing roller and second creasing roller against a matching element. In one or more embodiments, said matching element comprises a main element and a plurality of laminar elements. In one or more embodiments, said matching element comprises a calibrated thickness.

In one or more embodiments, the method comprises varying a thickness of said matching element to vary a distance between said first creasing roller and second creasing roller.

In one or more embodiments, said varying a thickness of said matching element comprises varying the number of said laminar elements.

Preferably, said matching element is located between said first creasing roller and second creasing roller. The creasing rollers thereby operate on the sheet of packaging material with such a force that they overcome the normal resistance of the paper to being creased, which would cause the creasing rollers, particularly the male creasing roller, to move away from the surface of the sheet on which it operates.

Equally preferably, said matching element is located between one of said first creasing roller and second creasing roller and a machine frame. In one or more embodiments, the method comprises detecting a force exerted by at least one of said first creasing roller and second creasing roller on said matching element.

In one or more embodiments, the method comprises adjusting a distance between said first creasing roller and second creasing roller according to said detected force. In one or more embodiments, the method comprises reducing said distance between said first creasing roller and second creasing roller when said detected force is lower than a working force.

The distance adjustment allows the creasing rollers to be properly configured so that they operate on the sheet with an effective force, i.e. with a force that allows to obtain creasing lines of a suitable depth for subsequent sheet forming. In particular, detecting the force exerted by the creasing group on said matching element makes it possible to verify that the pneumatic cylinders push the male cylinder towards the female cylinder with such a force as to ensure contact against the matching element. This contact identifies a constant geometric penetration of the creasing elements of the male cylinder into the creasing elements of the female cylinder, thus a constant creasing of the sheet.

In one or more embodiments, the method comprises triggering an alarm procedure when said detected force is greater than a maximum force value.

The maximum force value corresponds, in particular, to the maximum limit force that the creasing rollers can apply to the sheet without damaging it and beyond which the operator must be alerted. In one or more embodiments, the method comprises triggering an alarm procedure when said detected force is lower than a minimum force value.

Said minimum force value corresponds to the minimum force that guarantees the contact of the creasing group on the matching element, i.e. the geometric configuration that impresses the correct creasing on the paper. If the detected force falls below said minimum force value, it means that the sheet may not be properly creased, e.g. because it is pushing the male roller away.

In one or more embodiments, said preset positions on said sheet are identified by detecting, by means of a detecting system, at least one marker on said sheet.

In one or more embodiments, said marker is a graphic sign. Preferably said detecting system is of the optical type. Preferably said optical detecting system operates in visible frequencies. Equally preferably, said optical detecting system operates in the non-visible frequencies, in particular, in the infra-red or ultraviolet frequencies.

In one or more embodiments, said marker includes magnetic particles and said detection system is of the magnetic type.

In one or more embodiments, the method comprises detecting a position of said creasing elements, in particular of said transverse creasing elements, by means of a position transducer. Preferably said position transducer is an encoder. Preferably, the method comprises detecting a position of said longitudinal creasing elements by means of an optical acquisition device.

In one or more embodiments, the method comprises comparing said detected position with a predefined position as a function of said marker.

In one or more embodiments, when a position of said transverse creasing elements is detected, the method comprises varying a rotation speed of said first creasing roller as a function of a difference in position between said detected position and a predefined transverse position of said preset positions identified on said sheet. Preferably the method comprises increasing or reducing said rotation speed of said first creasing roller when said position difference is positive or negative respectively. Preferably the method comprises reducing or increasing said rotation speed of said first creasing roller when said position difference is positive or negative respectively.

Preferably, the method comprises a preliminary and an operating step. Preferably, said preliminary step is carried out before the operating step. Preferably said preliminary step includes setting the operating parameters of at least one of said braking group, feed group and creasing group. Preferably said preliminary step is carried out when the sheet is led with interference between said first creasing roller and second creasing roller. Preferably, said preliminary step is carried out when said sheet is led with interference between said first braking roller and second braking roller. Preferably said preliminary step is carried out when said sheet is led with interference between said first feed roller and second feed roller.

In one or more embodiments, the method comprises adjusting a transverse position of at least one of said first creasing roller and second creasing roller with respect to said feed direction, particularly during said preliminary step. In one or more embodiments, when a position of said longitudinal creasing elements is detected, said transverse position is adjusted as a function of the difference in position between said detected position and a preset longitudinal position of said preset positions identified on said sheet.

In one or more embodiments, at least one of said first braking roller and second braking roller is movable closer to or away from the other of said first braking roller and second braking roller.

In one or more embodiments, at least one of said first creasing roller and second creasing roller is movable closer to or away from to the other of said first creasing roller and second creasing roller. In one or more embodiments, said second detecting unit comprises a position transducer.

In one or more embodiments, said second detecting unit comprises an optical or magnetic detecting system to detect said preset positions on said sheet.

In one or more embodiments, said apparatus comprises a pneumatic cylinder. In one or more embodiments, one of said first creasing roller and second creasing roller is a roller located above the other of said first creasing roller and second creasing roller. Preferably said pneumatic cylinder is connected to said roller located above. In some embodiments, said pneumatic cylinder is intended for keeping said roller located above against said matching element. In other embodiments, said pneumatic cylinder is intended for exerting a constant pressure on said roller located above, in particular for keeping said roller located above at a given distance from the other roller.

The method may comprise the step of detecting a pressure exerted by said pneumatic cylinder on said machine frame.

In one or more embodiments, said apparatus comprises a load cell.

In some embodiments, said load cell is connected to a predetermined roller of said first and second creasing rollers, in particular to detect a force exerted by the latter on said matching element, preferably when said matching element is interposed between said first creasing roller and said second creasing roller.

In one or more embodiments, when the load cell is connected to said predetermined roller, the method comprises adjusting said force exerted by said predetermined roller on said matching element. In one or more embodiments, the method comprises increasing said force exerted by said predetermined roller on said matching element when said detected force is lower than a working force.

Adjusting the force exerted on the matching element by the predetermined roller between said first and second creasing rollers allows the creasing rollers to be properly configured so that they operate on the sheet with an effective force, i.e. with a force that makes it possible to obtain creasing lines of a suitable depth for subsequent sheet forming. In particular, detecting the force exerted by the creasing group on said matching element makes it possible to check whether the creasing group is operating with a decreasing force, close to the limit of said minimum force required to keep said first creasing roller in contact with said matching element interposed between the first and second creasing rollers (and therefore at a predefined distance from the second creasing roller) so as to obtain creasing lines of a suitable depth.

In other embodiments, said load cell is connected to said pneumatic cylinder, in particular to detect a pressure exerted by the latter on said machine frame.

In one or more embodiments, when the load cell is connected to said pneumatic cylinder, the method comprises adjusting a distance between said first creasing roller and second creasing roller as a function of said detected pressure. Preferably the method comprises reducing said distance between said first creasing roller and second creasing roller when said detected pressure is lower than a working pressure.

In one or more embodiments, the method comprises triggering an alarm procedure when said detected pressure is below a minimum pressure value.

Said minimum pressure value corresponds to the minimum pressure that the pneumatic cylinder must exert in order to ensure contact of the creasing group on the sheet, i.e. the geometric configuration that impresses the correct creasing on the paper. If the detected pressure falls below said minimum pressure value, it means that the sheet may not be properly creased, e.g. because it is pushing the male roller away. The characteristics and advantages of the invention will become clearer from the detailed description of a preferred embodiment thereof, shown, by way of non-limiting example, with reference to the appended drawings wherein:

- Figure 1 globally shows an apparatus according to the present invention in an operating cycle, with some parts omitted for the sake of simplicity;

- Figure 2 is a side view of a creasing group according to the present invention;

- Figure 3 is a schematic representation of the creasing group of Figure 3 acting on a sheet of packaging material.

- Figure 4 is a section view of a portion of the creasing group of Figure 3.

Figure 1 illustrates, very schematically, an apparatus for manufacturing containers P filled with a liquid and sealed starting from a sheet S of packaging material, in particular printed with a repeated pattern not visible in the figure, e.g. unwound from a reel R and led into the apparatus along a feed direction F. Certain parts of the apparatus have been omitted for ease of discussion, as they are not directly involved in the understanding of the present invention.

The apparatus comprises a forming and filling unit 200 for forming, sealing, filling and separating individual containers P, and a creasing unit 100 located upstream of the forming and filling unit 200.

The creasing unit 100 comprises a braking group 10, a creasing group 20 located downstream of braking group 10, and a feed group 30 located downstream of the creasing group 20.

The braking group 10 includes a first braking roller 11 and a second braking roller 12, which are arranged so as to be parallel to each other, spaced-out for leading with interference the sheet S of packaging material, and movable closer to or away from each other. The creasing group includes a first creasing roller 21 and a second creasing roller 22, arranged so as to be parallel to each other, for example the first creasing roller 21 being placed above the second creasing roller 22, spaced- out for leading with interference the sheet S, and also movable closer to or away from each other. The feed group 30 includes a first feed roller 31 and a second feed roller 32, arranged so that they are also parallel to each other and spaced-out for leading with interference the sheet S.

In particular, first and second braking rollers 11, 12, first and second creasing rollers 21, 22, first and second feed rollers 31, 32 have respective rotation axes parallel to the sheet S and perpendicular to the feed direction F of the latter.

The first creasing roller 21 and the second creasing roller 22 are provided with respective creasing elements 23, for example the first creasing roller 21 is a male creasing roller provided with creasing elements 23 protruding from the side surface of the first creasing roller 21, and the second creasing roller 22 is a female roller equipped with creasing elements 23 which are engraved on the side surface of the second creasing roller 22 and cooperate with the protruding creasing elements 23 of the first creasing roller 21, to impress a plurality of creasing lines 26 on the sheet S led along the feed direction F and have a creased sheet S. In particular, the creasing elements 23 extend either radially along the circumference of the respective creasing roller 21, 22 thus constituting longitudinal creasing elements, or from one end to the other of the same creasing roller 21, 22 thus constituting transverse creasing elements, and may possibly have curved segments and/or oriented along an oblique direction thus constituting oblique creasing elements. The creased sheet S will thus have creasing lines parallel to the feed direction F and creasing lines transverse to the feed direction F, and creasing lines oblique to the feed direction F. In an embodiment not shown, the creasing elements may possibly have curved lines.

Along the circumference of each creasing roller 21, 22, between two successive transverse creasing elements there is a respective adjustment surface (not visible in the figure) with no further transverse creasing elements and no oblique creasing elements, in particular a portion of the side surface of the respective creasing roller 21, 22 with only longitudinal creasing elements.

In the embodiment shown, a matching element 71 is located between the first creasing roller 21 and the second creasing roller 22. The first creasing roller 21 is kept against the matching element 71 by a pneumatic cylinder 70. A load cell 80 is connected to the first creasing roller 21 to detect a force exerted by the latter on the matching element 71. The force exerted by the creasing group 20 on the sheet S is linked to the force exerted by creasing group 20 on the matching element 71 by the pneumatic cylinder 70, irrespective of the resistance of the sheet S to being creased. In addition, detecting the force exerted by the creasing group 20 on the matching element 71 also allows to monitor and control the force exerted by the same creasing group 20 on the sheet S, detecting situations wherein the creasing group 20 is operating on the sheet S with insufficient and ineffective force.

The apparatus comprises a drive unit 40 connected to the braking group 10, creasing group 20 and feed group 30. For example, the drive unit 40 comprises a first motor connected to the braking group 10 to rotate the first braking roller 11, a second motor connected to the creasing group 20 to rotate the first creasing roller 21, and a third motor connected to the feed group 30 to rotate the first feed roller 31. The first motor, second motor and third motor are not shown in the figure.

The apparatus comprises a first detecting unit 50 connected to the braking group 10 and intended for detecting, for example, a torque of said braking group 10, and a second detecting unit 60 connected to the creasing group 20 and intended for detecting the preset positions on the sheet S of packaging material to detect any displacement between the creasing elements 23 and the preset positions on the sheet S. The second detecting unit 60 comprises, for example, an encoder 61 for detecting a position of the first creasing roller 21 i.e. of the creasing elements 23, and an optical detecting system 62 pointed at the sheet S advancing along the feed direction F. In particular, the optical detecting system 62 captures a plurality of images of the sheet S, which are subsequently processed to detect the presence of a marker, with respect to which preset positions may be identified on the sheet S.

A control unit 90 of the apparatus is connected to the drive unit 40, the first detecting unit 50 and the second detecting unit 60, to control the torque of the first braking roller 11 according to the torque value detected by the first detecting unit 50, and to control the rotation speed of the first creasing roller 21 as a function of the displacement value detected by the second detecting unit 60. When the apparatus is operated to manufacture the containers P starting from the sheet S of packaging material unwound from the reel R, the control unit 90 rotates the first braking roller 11, the first creasing roller 21 and the first feed roller 31, in particular so that the first braking roller 11 and the first creasing roller 21 have a peripheral speed substantially equal to the peripheral speed of the first feed roller 31. For example, the first creasing roller 21 and the first feed roller 31 are driven with a peripheral speed of 100 mm/s.

The control unit 90 drives the first braking roller 11 in rotation in a direction opposite to the rotation direction of the first creasing roller 21 and the first feed roller 31.

The sheet S is then led with interference between the feed group 30, the creasing group 20 and the braking group 10, in the feed direction F. In view of the friction generated by the led sheet S, the first braking roller 11 is forced to rotate in the same direction as the first creasing roller 21 and the first feed roller 31, overcoming the force with which the control unit 90 actuated the first braking roller 11. Due to the braking action exerted by the braking group 10 in relation to the feed group 30, the sheet is therefore stretched between said braking group 10 and feed group 30.

The creasing group 20, the first creasing roller 21 of which is kept against the matching element 71 by the pneumatic cylinder 70 with a constant force, impresses the creasing lines 26 on the sheet S to have a creased sheet S.

The first detecting unit 50 controls the torque of the first braking roller 11 and compares it with a reference torque. If the detected torque is lower than the reference torque, the first braking roller

11 and the second braking roller 12 are moved closer to each other; conversely, if the measured torque is greater than the reference torque, the first braking roller 11 and the second braking roller

12 are moved away from each other. The braking power of the braking group 10 on the sheet S is thereby properly adjusted in order to stretch the latter with the right tension and move it at a substantially constant speed between the braking group 10 and the feed group 30.

At the same time, the encoder 61 detects the position of the first rotating creasing roller 21, i.e. of the creasing elements 23, and transmits it to the control unit 90, while the optical detecting system 62 captures images of the sheet S and transmits them to the control unit 90 so that the latter can detect the presence of the marker and identify the preset positions. In the event that a displacement is detected between the creasing elements 23 and the preset positions on the sheet S, in particular between the transverse creasing elements and the preset transverse positions of the preset positions detected on the sheet, the control unit 90 increases or reduces the rotation speed of the first creasing roller 21 in order to solve the displacement.

The creased sheet S thereby has creasing lines 26 at the preset positions.

The forming and filling unit 200 is finally fed with the creased sheet S and outputs containers P with properly positioned images and lettering, with an actually distinctive and attractive appearance for the consumer.