PRODUCED BY MEANS OF A BLOW FORMING PROCESS

The present invention relates to an innovative apparatus for cutting and opening films obtained by means of a blow forming process during the production thereof, with particular, but not exclusive, reference to films for agriculture.

The present invention is totally innovative, since, to date, no similar ones have existed, and it is also inventive, as it has been devised to definitively solve the issues directly and indirectly related to the current need for optimizing the step of cutting blown films, so as to limit the need for large diameter extruders while obtaining great width films.

Currently, blown films are produced by cutting the film that comes out of the blown bubble into two separate parts, whose width is equal to half of the overall circumference of the film coming out of the extruder. Two cuttings are usually preformed: one on each side of the film which was flattened immediately after having been sufficiently cooled down. If, for example, the average circumference of the blown bubble is two meters, two film coils may be obtained whose width is one meter each. It is therefore evident that, in order to have a two-meters wide open film coil, it is necessary to have, with said cutting technology, an extruder which creates a blown bubble with a four- meters circumference, while to have a three-meters one, the circumference produced by the extruder must be six meters wide, and so on. As it is well understood, the fundamental disadvantage of the technique known to date is related to the cutting procedure based on the width of the elastomeric film which must be obtained, or better is linked to the impossibility of minimizing the size of the extruder based on the circumference of the blown bubble which must be obtained with the current cutting procedures .

It is the object of the present invention to overcome all the disadvantages of the background art by providing a device which performs only one longitudinal cutting - instead of two - on the blown bubble exiting the extruder and which automatically opens the cut film with specific stretching means, thus making the width of the film, which is wound already completely open on the collecting coil, correspond to the overall circumference of the film produced by blowing, allowing the drastic reduction of the bulk of the extruder, as well as, advantageously, the size of the plants for the production of blown films, with respect to the width of the films which are usually produced.

Such objects have been achieved by providing a new apparatus for cutting and opening blown films during the production thereof, as better specified in the claims attached to the present description.

These objects and the consequent advantages, as well as the features of the device according to the present invention, will become more apparent from the following detailed description of a preferred solution, given by way of explanation, but not by way of limitation, with reference to the accompanying drawings, in which:

Figure 1 shows a bidimensional diagrammatic view of the currently known production process N of the blown film 2, in which two cuttings are performed along the side edges;

Figure 2 shows a bidimensional diagrammatic view of the new production process P of the blown film 2 of the present invention;

- Figure 3 shows a diagrammatic view of the device for cutting and opening 1 the blown film 2 during the production thereof, according to the present invention; in which the arrows indicated therein show the spreading stress actions on the blown film 2 during the opening process thereof;

Figure 4 is a diagrammatic sectional view of the blown film 2 upon reaching the size, in section, with a final radius R, where it is clear that a single cutting line T of the blown film 2 itself is provided;

- Figure 5 is a diagrammatic view of the open elastomeric sheet 13 following the cutting of the blown film 2, where it is clear how, with a single cutting T, it is possible to produce a sheet with a length of about 6.28 R, i.e. equal to the entire circumference of the blown film;

Figures 6 to 9 diagrammatically show a variant of the film opening and stretching means, given as an alternative to those shown in the preceding Figures.

In the accompanying Figures, the simplicity of the inventive idea is clear, consisting in that the present process P for forming the blown films 2 and the related new procedure for the single cutting T and opening of the blown films 2 during the production thereof have been devised to be easily applicable also to known processes N for the production of blown films 2, thus providing an innovative production process P (Figure 2) and an inventive device for cutting and automatically opening 1 the blown film 2 (shown in a preferred, but not limitative, solution, in Figures 2 and 3, accompanying the present description), together with the related methods for cutting T and opening the blown film 2 (as shown in a solution with a final radius R in Figures 4 and 5).

The present process P for forming blown films is characterized in that it includes the use of a special automatic device for cutting and opening 1 the blown film 2 during the production thereof (Figures 2 and 3), completely innovative and inventive with respect to what has been known to date, since it achieves, with a single knife 18, a single cutting T on the blown bubble 2, proceeding then to stretch and open it to the maximum extension of the plane film 13 (substantially equal to 6.28 times the final radius R obtained from the forming head 10), i.e., to bring it on a single plane (Figures 3, 4, 5), to then be capable of winding it by means of a single winder 4 on a single coil 11 (contrarily to what occurs in the background art, where the winders 4 are at least two and, therefore, two are the collecting coils 4 of the sheet obtained from the double cutting of the blown film 2, by means of the double knife 5 of Figure 1). Said single cutting T and the related opening, cause the width of the film 2 obtained to coincide with the entire circumference of the blown bubble with a final radius R, as it is easily understood by observing Figures 4 and 5.

The process is also characterized by the use of an innovative device 1 for cutting and automatically opening the blown film 2 in line, before winding it on the already completely open collecting coil, the device having been specially devised for such a purpose and being characterized by the following constructive features (Figures 2, 3, 4 and 5):

> at least one pair of stretching elements 14 positioned obliquely on the inside of the blown film 2 after the forming thereof, in which said means 14 are preferably, but not exclusively, provided with a plurality of small holes or micro-holes for expelling compressed air which facilitates the sliding of the film, reducing the sliding friction of the film itself on the stretcher;

> at least one pair of support means 15 positioned horizontally, and preferably coaxial, so that, by penetrating into each other, by means of the activation of a pair of cranks 17, they may allow varying the stretching width "L" of the blown film 2, on the basis of specific needs;

> means for guiding and conveying 16 the open film, which may be obtained by means of a plane metal profile or with rotatable conveying cylinders or rollers (not shown).

Said means 14-15 for stretching the film are respectively positioned obliquely and horizontally, so as to provide a shape of the automatic device 1 for opening and cutting the blown film 2 approximately in the form of a trapezium.

Said trapezium shape of the device 1 may be adjustable in width or kept in a fixed position, preferably by transforming said trapezium shape in the form of a triangle, coaxially closing said horizontally positioned stretching means 15.

Said stretching means arranged obliquely 14 may preliminarily be subjected to a non-stick surface treatment, such as, for example, a Teflon coating treatment .

It should be noted that it is not indispensable that said obliquely positioned stretching means 14 emit compressed air, since they may also be equipped with one or more sleeves coaxial to the tubes themselves, which idly rotate to allow the free sliding of the film which is opened following the longitudinal cutting, or they may simply be smooth.

It should be noted that the provision of said means for transporting and projecting compressed air 14-15 as well as said rotatable external sleeves 17 is exclusively required for the purpose of increasing the production speed of the plane sheet 13 to be wound on coil 11.

The apparatus for cutting and automatically opening 1 the blown film 2 has been designed to be simply and easily manufactured on an industrial level, being now essentially provided with a single knife 18, necessary for performing the cutting T of the blown film 2, as well as to achieve the innovative and inventive complete opening of the blown film 2 itself in a sheet 13, said sheet 13 thus being completely open, easily woundable on a coil 11, by means of a conventional winder 4.

Therefore, the innovative apparatus for cutting and automatically opening 1 the blown film 2 (shown in the dashed box of Figure 2 and enlarged in Figure 3) is characterized in that it performs a single cutting T of said film 2 and automatically and simultaneously spaces apart the cut edges from each other, allowing the complete opening of the film 13 itself to be obtained in the direction of the width L thereof, based, as already said, on the radius R of the annular-shape extrusion or forming head 10.

The apparatus for cutting and automatically opening 1 the blown film 2 implements a process for obtaining a completely open film 13 to be wound on the coil 11, which in a preferred, but not limitative, solution includes the following steps:

> positioning of a single cutting blade 18 in a position where the cooling down and the forming of the blown film 2 have already completely occurred;

> cutting of the blown film 2 along a single cutting line T;

> complete automatic and continuous opening of the film 13 thus obtained, along the entire width "L" thereof, equal to the circumference of the blown film 2;

> conveying of the film 13, completely open by means of spreading 19, towards a single winder 4 on the collecting coil 11. It is worth observing that said plane film 13, completely open and thus produced, is not perfectly smooth in the winding thereof on the collecting coil 11, since it has slight enlargements, corresponding to the folding areas of the two side edges of the cooled film 6, upon passing between the top rollers 6 before being cut and stretched until the complete opening thereof by means of the stretching device 1 described up to now.

The fundamental advantage of the present invention with respect to the background art is inherent in that, following said single cutting of the blown film and the complete automatic opening thereof, the latter is already completely open on the winding coil, contrarily to the coils produced up to date, which provide for the sheet to be wound and closed, i.e., folded up on itself, with the disadvantage that the latter may be opened - manually - only when it is unrolled from the coil, requiring a significant increase in work by the operator for opening and laying it to protect the various crops.

Therefore, the undoubted advantage of the present invention is inherent in that the blown film is cut and opened (stretched) in an automated manner before being sent to the collecting coil, so that on such a coil the film is already available in the entire width thereof and may be directly unrolled and used, even with mechanized unrolling systems.

A further advantage of the present invention consists in that the sheet thus produced is not perfectly smooth but has two longitudinal reinforcing cords at the folding areas of the two side edges of the film caused by the passage between the top dragging rolls 6 before being cut and stretched.

From the accompanying Figures, even a person who is not skilled in the art may immediately understand the advantageous manufacturing simplicity of the present system, diagrammatically shown in a preferred, but not limitative, solution in the characterizing parts thereof, in the accompanying Figures 2, 3, 4 and 5.

The further advantages of the present process and of the related procedure derive from the relative ease of manufacture and industrial implementation.

It is a further feature of the present invention that the position of the longitudinal cutting blade of the film may be adjusted manually or by means of electromechanical actuators, which may be remotely operated and controlled by an operator by means of a camera configured to locate the center of the film on which the longitudinal cutting is to be performed.

It is also evident that the embodiment described above, given by way of explanation and not by way of limitation, may be subject to numerous revisions, adaptations, additions, variations and substitutions of elements with other functionally equivalent ones, without however departing from the scope of protection of the following claims.

For example, a variant of the invention, shown in Figures 6 to 9, provides that said film stretching means consist of two rows of rotary shaped rollers, arranged in sequence in the motion direction of the film and transversely thereto, configured to allow the film itself to freely slide, for opening and stretching it, respectively.

In particular, said first row of film opening rollers consists of two side rollers 15', having a substantially ogive or spherical shape, and at least one cylindrical central roller 16', while said second row of stretching rollers consists of two cylindrical side rollers 14', with the external end being rounded in the form of a hemisphere, and at least one cylindrical central roller 16'.

According to a special feature of the invention, the rollers of said two rows are mounted rotatably idle on the respective axes thereof, so that the film may slide in contact therewith without rubbing, which may damage or tear the film during the processing.

A further peculiarity of the invention consists in that the rotation axis of said side rollers 15' and 14' may also be directed/inclined with respect to the axis of the central cylinder, according to processing needs to modify the tension applied to the film.

Finally, said two rows of rollers are also movable in the relative position with respect to each other and with respect to the film.

All the movements described up to now may be operated manually and/or motorized, in this second case, the automated management of the motorized movements being also provided.

REFERENCE CHARACTERS

1. DEVICE FOR AUTOMATICALLY CUTTING AND OPENING THE BLOWN FILM DURING THE PRODUCTION THEREOF 2. BLOWN FILM

3. FILM FOLDED INTO TWO FOLLOWING THE COOLING DOWN STEP

4. COIL WINDER

5. DOUBLE KNIFE FOR CUTTING THE BLOWN FILM 2 IN THE KNOWN SYSTEM

6. ROLLERS OR CYLINDERS FOR SPREADING THE FILM 3

7. FREEZING LINE

8. CYLINDERS FOR CONVEYING THE BLOWN FILM 2

9. AXIS FOR SPREADING THE BLOWN BUBBLE 2

10. ANNULAR-SHAPE EXTRUSION/FORMING HEAD

11. FILM COLLECTING COIL

12. COOLING GRIDS

13. FILM IN A PLANE CONFIGURATION, COMPLETELY OPEN/STRETCHED AFTER THE SINGLE CUTTING OF THE

BLOWN FILM 2

14. STRETCHING MEANS POSITIONED OBLIQUELY, PREFERABLY, BUT NOT EXCLUSIVELY, PROVIDED WITH MICRO-HOLES FOR THE EMISSION OF COMPRESSED AIR 15. STRETCHING MEANS POSITIONED HORIZONTALLY, PREFERABLY, BUT NOT EXCLUSIVELY, PROVIDED WITH MICRO-HOLES FOR THE EMISSION OF COMPRESSED AIR 16. MEANS FOR GUIDING AND CONVEYING THE FILM IN THE PLANE CONFIGURATION 13, PRESENT IN THE DEVICE 1 17. CRANKS FOR ADJUSTING THE WIDTH "L" OF THE FILM 13 BY MEANS OF THE COAXIAL SLIDING OF SAID MEANS 15

18. SINGLE CUTTING KNIFE

19. PULLING OF THE COMPLETELY OPEN FILM READY FOR THE FOLLOWING STEP OF WINDING ON THE COLLECTING COIL

14', 15', 16'. ROTARY SHAPED ROLLERS L VARIABLE WIDTH OF THE FILM 13 BASED ON THE RADIUS

OF THE EXTRUSION/FORMING HEAD 10

N KNOWN PROCESS FOR FORMING BLOWN FILM 2

P NEW PROCESS FOR PRODUCING BLOWN FILM 2 AND AUTOMATED CUTTING AND OPENING THEREOF, BEFORE

WINDING ONTO THE COLLECTING COIL R FINAL RADIUS OF THE BLOWN FILM 2

T SINGLE CUTTING LINE OF THE BLOWN FILM