WINDING SYSTEM FOR USE IN PLASTIC FILMS PRODUCTION LINES, IN PARTICULAR EXTENSIBLE PLASTIC FILMS, AND METHODS FOR WINDING PLASTIC FILM REELS

Abstract

A winding system for use in plastic films production lines comprising a plurality of winders (11-13) constrained to a star-shaped winder holder (10) rotatable around its own axis, said winders (11-13) being arranged around said star-shaped winder holder (10) in such a manner that at least one first winder (11) of said plurality of winders is arranged at an operating position for winding a film (18) to form a reel (19), characterised in that associated to said at least first winder (11-13) are contact means (26-28) moveable between a first position of contact with said reel (19) to wind on said first winder (11-13) and a second position distal from said reel (19), said contact means (26-28) being further preferably rotatable around said axis of said star-shaped winder holder (10) with the aim of maintaining said first position in contact with said reel (19) when said first winder (11-13) is moved away from said winding position.

Description

The present invention refers to a winding system for use in plastic films production lines, in particular extensible plastic films, and to a method for winding plastic film reels.

The extensible plastic films, also referred to as film stretch, is a product widely used in the packaging industry, representing the most common type of packaging in Europe and in the United States.

There are several applications of such types of films and they cover most of the products used commonly, both for industrial and domestic purposes.

Plastic films differ according to their composition which allows obtaining films with different characteristics among which the toughness, elongation, tensile strength, elastic memory, resistance to perforation, and so on and so forth, thus meeting the requirements of various applications.

Plastic films can be made up of three or more layers made up for example from mixtures of linear low density polyethylene (LLDPE), low and very low density polyethylene (LDPE, VLDPE, ULDPE), metallocene-based polyolefin (mLLDPE, mPP), ethylene-vinyl-acetate in various percentages (EVA from 9% to 28%), polypropylene homopolymer, random or block copolymer, terpolymer (PP homo, PP copo, PP ter) or biodegradable materials (Mater-Bi, PLA).

Therefore, there are various formulations realised through production lines having combinations of two or more extruders with the aim of obtaining stratifications capable of meeting the requirements of the applications they are intended for.

Depending on the type and the thickness of the film known are different types of applications, most important among which are the food industries, pharmaceutical industries, paper mills, brick and ceramic industries, mechanical industry, large-scale distributors, agricultural industry and domestic use.

Such wide variety of use implies an equally wide range of type of films, both in terms of composition and thickness, generally varying from 10 μm up to more than 100 μm, and also in terms of winding, which comes in different shapes depending on the subsequent use the film is intended for, that is depending on the subsequent manual use, use in automatic machines, semi-automatic machines and so on and so forth.

For example, in case of the film stretch type of reels for industrial packaging, regardless of the characteristics of the film in terms of mechanical resistance and elongation to tear, used are particular automatic packaging machines, or “palletizers”, arranged on which are stretch reels of specifically defined size and weight.

In particular, referred to for such type of application are reels with an overall weight of 12.5 kg which are wound on cardboard cores approximately weighing 1.25 kg having an internal diameter of about 76 mm and have a band width equivalent to about 500 mm.

In the same manner, the reels for manual use, with an overall weight of about 2.5 kg and width of about 450÷500 mm, on the other hand have cores with an internal diameter equivalent to 50 mm and weight of about 0.5÷0.6 kg, thus resulting easier to handle and use without the help of machines.

Therefore, a serious concern facing the industry is that of optimising the plastic films production lines with the aim of obtaining the utmost efficiency of such lines, automating them most possible to reduce possibility of mistakes to the minimum, quickening the production and simultaneously maintaining high flexibility characteristics.

The flexibility of the lines, in particular, becomes more and more important considering the fact that in order to reduce the high storage logistics costs, transport costs and so on and so forth, there is an ever-growing tendency to produce, as a matter of fact, “just in time”. Such production strategy is possible only if the systems are capable of offering enough flexibility to produce film reels classified according to the type of film or winding, with very little waste of time in particular during the procedures of modifying the structure or material and during the start-up procedures.

The plastic films production lines comprise extrusion, cooling and winding systems made up of a variable number of extruders, depending on the characteristics intended to be imparted to the product, arranged downstream of which are the winding systems which receive the extruded and cooled film and wind it into reels.

The extrusion and cooling part is not particularly difficult in terms of flexibility, given that it is based on technologies already consolidated over the years.

However, considering the high costs of such part, there arises the need to have high production volumes, considering the fact that the final products have a very low added value, thus implying the necessity to rely on large scale production in order to attain sufficient operating margins.

In order to attain such goal there arises the need to produce plastic films at extremely high actual speeds, close to, if not exceeding, 500 m/min, also due to the fact that use of materials such as linear polyethylene allows reaching such speeds from an extrusion point of view.

The winding systems downstream of the extrusion and cooling systems, must thus have a sufficient winding capacity in such a manner to provide for the amount of film produced over time.

Furthermore, the necessity to produce at high speeds requires—in case of line production of reels of small diameter for manual use, that is short in terms of measurement—very frequent replacements ejecting the full reel and inserting a new core within very few seconds of time.

This requirement forcedly limits the production speed, in that it conditions the entire extrusion process due to the physical and mechanical constraints caused by the movements adapted to perform the replacement cycle. Therefore, in order to enhance the winding capacity in line, the so called “jumbo” reels—that is reels with a band equivalent to 500 mm but with an external diameter up to 500 mm and above—have thus resulted easier to wind, hence allowing overcoming the abovementioned limits allowing a considerable elongation of the times required to replace a reel.

However, the winding of the film at high speeds, implies the physiological presence of air trapped between the turns, thus complicating the subsequent use of the film itself and in any case representing a waste of space during transport.

The low added value of such products leads to the cost of transport having a highly considerable impact on the production costs, thus also for such reason, alongside the aforementioned practical reasons of usability of the films, they require “hard” e and compact reels, that is without air trapped between the turns.

In particular in case of a film stretch, the aspect of the film itself, very sticky, implies contact winding, that is “squeezing out” the reel against a motorized cylinder which facilitates the ejection of the air inevitably drawn by the film itself during its winding motion around the reel core, which would otherwise remain trapped between the wound turns.

However, the currently known systems performing contact winding still do not offer satisfactory results when it comes to the quality of the reels if wound at an excessively high speed. Given that transport of air, essentially due to the centripetal force of the rotating rollers, is proportional to the speed squared, such problem represents the greatest obstacle to obtaining a good winding in case of very fast systems like the ones used for producing film stretch.

Furthermore, in such systems, during the replacement step upon completing winding a reel, the cylinder which facilitates the ejection of the drawn air is not capable of acting on the reel, in such a manner that during the winding of the end part of the film there is an absorption of air which reduces the overall quality of the reel.

A general object of the present invention is that of overcoming the abovementioned drawbacks of the prior art in an extremely simple, inexpensive and particularly functional manner.

Another object of the present invention is that of providing a winding system for use in plastic films production lines capable of guaranteeing an ideal quality of the wound reels though operating at high production speeds.

A further object is that of providing a winding system for use in plastic films production lines requiring less amount of time for the steps of ejecting the full reel and inserting a new core.

Last but not least, an object of the present invention is that of conceiving a method for winding plastic film reels capable of guaranteeing an ideal quality of the wound reels though operating at extremely rapid cycles.

Regarding the abovementioned objects, according to the present invention, conceived was a winding system for use in plastic films production lines and a method for winding plastic film reels having the characteristics outlined in the attached claims.

The structural and functional characteristics of the present invention and its advantages with respect to the known techniques shall be clearer and more evident from an observation of the following description, referring to the attached drawings, which show a winding system for use in plastic films production lines made according to the innovative principles of the invention itself.

In the drawings:

FIG. 1 shows a side view of a winding system according to the present invention;

FIG. 2 shows a sectional schematic view of the winding system of FIG. 1;

FIGS. 3 to 7 show the various steps of the cycle for winding and replacing the plastic film reels according to the present invention.

Referring to the drawings, the winding system in question is indicated in its entirety by 100.

The winding system 100 for use in plastic films production lines comprises a star-shaped winder holder 10 constrained against which is a plurality of winders 11-13 arranged around the same 10, each provided with a reel core 16 wound around which is a reel 19 of plastic film 18.

Preferably, the winders 11-13 are at least three so as to be able to simultaneously perform the operations of winding the reel, ejecting the full reels and inserting the cores on which the new reels are to be wound.

In the case of the illustrated embodiment comprising three winders 11-13, the arrangement around the star-shaped winder holder 10 can be for example with pitches respectively of 120°.

The winders 11-13 are preferably controlled by means of alternating motors, for example controlled by an inverter, and installed coaxially.

Furthermore, provided for at one end of the winders 11-13 is a star-shaped flange 14 which holds the tailstocks 15 which support the reel cores 16 of the winders 11-13, which are preferably expansible.

The passage of compressed air for the pneumatic expansion of the reel cores 16 is ensured by a rotating seal installed in the support of the shaft of the same 16.

The tailstocks 15 are preferably provided with pneumatic movement.

The star-shaped flange 14 is shaped in such a manner to facilitate the passage of a core 17 wound around which shall be a film 18 upon the subsequent replacement and a fully wound reel 19 of a film 18 respectively.

For such purpose, the flange 14 has a plurality of cavities substantially of the same size as the section of a reel core 16 and/or substantially of the same size as the section of a full reel 19.

At a determined so-called angular winding position, which in the illustrated embodiment corresponds to the position in FIG. 3 in which the first winder 11 is found, provided for is a suitable motorization adapted to control the winding of the film 18 at a determined winding speed around the winder 11 which is at such angular position.

Further provided at the angular winding position is a drawing and pressure device 36 adapted to regulate the tensioning of the film 18 during winding.

Such drawing and pressing device 36 comprises at least one cylinder 20 which during the winding of the film 18 on the winder 11-13 is in contact with the respective winder 11-13 and provides, along with a rubber roller 21, a device for drawing the film 18 itself. Such cylinder 20 is connected to a pair of levers controlled in movement through pneumatic pistons, preferably provided with hydraulic breaking, and constrained to rotate around a torsion axis 22.

During the step of winding and replacing the reel, the abovementioned device 36 has a rotational movement around the axis 22 controlled by pneumatic pistons 23 with the aim of always maintaining the contact pressure constant on the reel.

Furthermore, provided for at the winding position, is a blade 24 for cutting the film 18 upon termination of the step of winding an entire reel 19 of film.

The removal and reinsertion of the transverse cutting blade 24 is controlled by a pair of pneumatic cylinders 25.

According to the present invention, associated to at least the winder 11 arranged at the winding position are special contact means 26 which maintain the contact with the reel being wound constant, also during the replacement step.

In such case, the contact means 26, during the replacement step, follow the winder bearing the full reel and, once the winding is definitely completed, return to the winding position again.

In the illustrated preferred embodiment, each winder 11-13 is provided with special contact means 26-28 which follow the rotation movement of the related winder 11-13 during the entire cycle, thus not constantly requiring returning to the winding position again. In such manner, it is not necessary to provide a special synchronisation between the movement of the contact means 26-28 and the movement of the winders 11-13.

According to a non-restrictive embodiment, the contact means 26-28 are made up of an anodized and motorized steel cylinder.

The constant contact with the reel is advantageously provided for by means of a pneumatically controlled lever mechanism with adjustable pressure.

In such manner, provided for is also a guide for the last meters of the film, which otherwise, during the replacement step in which the star-shaped winder holder 10 is rotated from the position in FIG. 3 to the position in FIG. 4, would be without contact and thus would cause the absorption of air.

Furthermore, the presence of a double opposite contact on the same winder made by means of a contact cylinder 20 and the contact means 26-28 actually eliminates the flexure phenomena to which the winder 11-13 would be subjected in case of contact with a single cylinder.

Such cylinders of the contact means 26-28 are preferably controlled, through a belt drive, by an alternating motor controlled by an inverter. The final drive occurs by means of a telescopic cardanic joint.

The abovementioned parts, just like the motorizations of the winders 11-13, reel cores 16 and tailstocks 15, are installed on the star-shaped winder holder 10 which rotates in a unidirectional manner. The rotation of the star-shaped winder holder 10 is preferably controlled by a gear motor 29 controlled by an inverter and connected by means of a driving belt.

The control of the position of the star-shaped winder holder 10 is ensured by an absolute encoder mounted in axis with the gear motor 29, while the maintenance of the position is provided for by a disk brake operated pneumatically (not represented in the figure).

A distinctive characteristic of the winding system 100 according to the present invention consists in the fact that the control and command part of all the parts installed in the star-shaped winder holder 10 is ensured by the apparatus installed on a rotating plate coaxial to the star-element 10 itself.

Fixed on such plate are processing means such as for example a PLC (programmable logic controller), motor inverters and the required power parts, as well as the regulation and control valves of the pneumatic cycle.

A collector with three phase rings, one of which is of the mercury type for connecting with the processing means of the line and one of the pneumatic power supply, provide for supplying the star-shaped winder holder 10.

Lastly, the removal of the full reels 19 is performed by a mechanical arm 30 which slides on a linear guide 31 controlled by a gear motor 32.

Analogously, insertion of the cores 17 occurs by means of a ring 33 which slides on a second linear guide 34, also controlled by a gear motor 35.

The operation of the winding system 100 is as follows. During the normal winding, the film 18 is wound on the winder 11 which is arranged at the winding position, that is in contact with the drawing and pressure device 36 (FIG. 3).

At the end of said first step, that is when the film reel 19 is completed (FIG. 4), the so-called replacement step is performed, wherein a second winder 12 is initially started up at a peripheral speed slightly higher with respect to the winding one.

Subsequently, the star-shaped winder holder 10 rotates for a predetermined angular portion, for example 120° clockwise with reference to the implementation, moving the second winder 12 to the winding position (FIG. 5).

As observable in the figures, during the entire operation the contact means 26 corresponding to the first winder 11 never lose contact with the winder itself, thus constantly guaranteeing the “squeezing out” of the air between the turns.

The rotation speed of the star-shaped winder holder 10, summed with the peripheral speed of the winder 11, leads to further tensioning of the film 18.

Such rotation further moves the film 18 to the cutting position where the blade 24 (FIG. 6) intervenes, without the risk of the film 18 being lost during the passage from the first winder 11 to the second 12.

For such purpose, the film 18 is also precharged by means of an electrostatic discharge thus being attracted towards the core 17 of the reel core 16 of the winder 12 without requiring glues or adhesives.

In order to avoid the dragging of the film 18 against the contact means 27 relative to the second winder 12, the same means 27 are provided with a housing or anti-adherent cover (not shown) which allows the film 18 to slide without hindrance.

Upon termination of the cutting step, the contact means relative to the second winder 12 are arranged in contact with the corresponding reel core 16, and where they remain up to the subsequent replacement cycle.

On the other hand, in case the contact means 26-28 are single and common to all the winders 11-13, upon termination of the step of winding the end of the cut film 18, the contact means 26-28 oscillate backwards thus returning to the winding position and in contact with the reel being wound on the second winder 12 shortly after the start of such step.

Once terminated the winding of the cut end, the star-shaped flange 14 removes the tailstocks 15 that support the reel cores 16 relative to the winders 13 and 11, in such a manner to be able to insert a new core 17 on the third winder 13 and simultaneously eject the reels 19 wound on the first winder 11 (FIG. 7).

The operations of ejecting the full reel 19 and inserting the new core 17 occur simultaneously by means of special mechanical actuators 30 and 33 which operate at high speeds.

Thus, the winding system 100 according to the present invention is capable of considerably reducing the replacement times and thus obtain production speeds when winding reels for manual use similar to the production speeds for “jumbo” reels.

Due to the optimisation of the above-mentioned operations, the operating cycle generally lasts for about 15 seconds.

The entire process herein described is performed within very short periods of times and thus it is required that the control occurs by means of a particularly sensitive control and management device.

According to the points outlined above with reference to the figures, it is clear how a winding system for use in plastic films production lines according to the points outlined above is particularly useful and advantageous.

Thus, with the winding system described it is possible to produce ideal quality plastic film reels in a rapid manner

It is thus possible to produce reels extremely short in size also due to the short periods of time required for the operations of ejecting the full reels and inserting the new cores which, in the described system, may occur simultaneously.

Such winding system can be prepared both for winding reels with an internal core equivalent to 50 mm, that is reels for manual use, and for winding reels on cores of 76 mm, that is reels for use in automatic machines, thus offering a high degree of flexibility.

The winding system can also be used on production lines having a multiple finished band measuring 1 metre according to a chequered disposition of the winding devices, which thus also allows the simultaneous production of reels on 50 mm reel cores and reels on 76 mm reel cores, further increasing the flexibility of the production lines, due to the possibility of differentiating the final result of the work without adjusting any parameter of the line.

Obviously, the winding system for use in plastic films production lines according to the invention can be implemented differently with respect to the implementation described and illustrated strictly for exemplifying and non-limiting purposes.

Therefore, the scope of protection of the present invention is delimited by the attached claims.

Claims

1. Winding system for use in plastic films production lines comprising a plurality of winders (11-13) constrained to a star-shaped winder holder (10) rotatable around its own axis, said winders (11-13) being arranged around said star-shaped winder holder(10) in such a manner that at least one first winder(11) of said plurality of winders is at an operating position for winding a film (18) to forth a reel (19), associated to at least said first winder (11-13) being provided contact means (26-28) moveable between a first position in contact with said reel (19) winding on said first winder (11-13) and a second position distal from said reel (19), said contact means (26-28) being further preferably rotatable around said axis of said star-shaped winder holder (10) with the aim maintaining said first position at contact with said reel (19) when said first winder (11-13) is moved away from said winding position, characterised in that said winders (11-13) are at least three and each comprises a reel core (16) supported by a tailstock (15) and/or substantially of the same size as the section of a reel core (16) and/or substantially of the same size as the section of a full reel(19), said winding system further comprising a mechanical arm (30) sliding in a linear manner adapted to eject a full reel (19) and a ring (33) sliding in a linear manner for inserting a core (17).

2. Winding system for use in plastic films production lines according to claim 1, characterised in that associated to each winder (11-13) are respective contact means (26-28).

3. Winding system for use in plastic films production lines according to claim 1, characterised in that said contact means (26-28) comprise a controlled motorized roller between said first and second position through a lever mechanism.

4. Winding system for use in plastic films production lines according to claim 1, characterised in that, provided for at said winding operating position, is a drawing and pressure device (36) adapted to adjust the tensioning of the film (18) during winding.

5. Winding system for use in plastic films production lines according to claim 4, characterised in that said drawing and pressure device (36) comprises at least one cylinder (20) connected to a pair of levers constrained to rotate around a torsion axis (22) to move said cylinder (20) to a position of contact with a reel being wound.

6. Winding system for use in plastic films production lines according to claim 1, characterised in that provided for at said winding position, is a blade (24) for cutting the film (18) following the termination of the step of winding a full reel (19).

7. Winding system for use in plastic films production lines according to claim 1, characterised in that provided for at said winding position, is a motorization adapted to drive the winding of the film (18) around a first winder (11) arranged in such position.

8. (canceled)

9. (canceled)

10. Winding system for use in plastic films production lines according to claim 1, characterised in that said reel cores (16) are expansible.

11. (canceled)

12. (canceled)

13. Method for winding plastic film reels comprising the steps consisting in:

moving the first winder (11) inserted with a core (17) to a winding position and starting winding a film (18) around said core (17) at a winding speed, to form a reel (19);

moving said contact means (26-28) in contact with said reel (19) being wound;

when said reel (19) is substantially full, moving said first winder (11) to a distal position from said winding position maintaining said contact means (26-28) in contact with said reel (19);

cutting said film (18);

winding the cut end part of said film (18);

moving said contact means (26-28) to a distal position from said reel (19) further comprising the steps consisting in:

starting a second winder (12) inserted with a core (17) at a peripheral speed higher with respect to the winding speed;

precharging the film (18) to be wound on said second winder (12) through an electrostatic discharge;

moving said second winder (12) to a winding position.

14. (canceled)

15. Method for winding plastic film reels according to claim 13 further comprising the steps consisting in:

ejecting said reel (19) from said first winder (11);

inserting a new core (17) onto a third winder (13).