WO2000002777A1

WO2000002777A1 - Machine for wrapping products with an extensible film

Info

Publication number: WO2000002777A1
Application number: PCT/ES1998/000198
Authority: WO
Inventors: Josu Errasti Iriarte
Original assignee: Ulma C Y E, S. Coop.
Priority date: 1998-07-08
Filing date: 1998-07-08
Publication date: 2000-01-20
Also published as: EP1036738A1; JP2002520224A; BR9812053A; CA2303211A1

Abstract

In this machine intended to wrap products with an extensible film, the article (1), when entering the machine, passes in front of a barrier (18) which detects its dimensions and sends them to a microprocessor which controls all the movements of the machine, positioning in an appropriate manner the article (1) at the appropriate location of an elevator (3); the stroke of the traction tong (17) is controlled in order to extract and take a predetermined length of film (4), according to the size of the article (1), the stroke or displacement of the lateral tongs (19) being also controlled in order to stretch the film in the transverse direction, controlling at the same time the activation and deactivation of the supply bobbin brake and the movements of the folding blades in relation to the article to be wrapped and the film used in order to obtain a homogeneous wrapping with the optimum film quantity.

Description

PRODUCT WRAPPING MACHINE WITH EXTENSIBLE FILM

D E S C R I P C I Ó N

OBJECT OF THE INVENTION

The invention relates to an article wrapping machine with extensible film, the obvious purpose of which is to wrap an article by means of a portion of film that is finally sealed in closure, and which has means for supplying film from a reel towards the article to be wrapped, with means that make the correct positioning between the article and the film to be wrapped, as well as the folding and final sealing of the film once the article is wrapped.

The machine is of the type in which the entry and exit of the items to be wrapped is carried out on the same front, in order to be able to integrate in said wrapping machine, if necessary, weighing and labeling equipment.

The object of the invention is to provide an article wrapping machine, such as trays containing products of any kind, in which the movements of all its devices and means involved in its operation are duly controlled from a previously programmed microprocessor, of so that depending on the dimensions of the tray, it is properly placed in the elevator, providing and cutting the portion of stretch film to be used depending on the specific dimensions of the article. That is, the machine's microprocessor controls on the one hand the Placement of the article and, depending on its dimensions, also controls the portion of the film to be wrapped, as well as the tensioning of the film and the adequate synchronization of the movements of all the mechanisms and elements involved in the wrapping operation.

BACKGROUND OF THE INVENTION

Some types of wrapping machines of articles or products with extensible film are known, being able to cite among them the one described in the patent US 4501106, intended to wrap trays containing certain products, so that in said machine the tray to be wrapped accesses through a feeding car that has it in a fixed position on an elevator, regardless of the size of the tray and the dimensions of the product contained in it. This elevator then moves vertically upwards with the tray, until reaching the film sheet destined to wrap said tray, sheet that is supplied from a coil and pulled, for delivery, by means of an extraction clamp, said machine having Folders of the film to wrap the tray laterally and inferiorly and then move on to a band where the final closure takes place by hot sealing, preferably.

This machine has some drawbacks, among which the following can be mentioned:

- The portion of film that is extracted by the extraction clamp is always the same, regardless of the size of the tray and the height reached by the product contained in it. This causes that, when packing trays that present a lot of height on the opposite side of the feed reel, as the amount of film available on that side is fixed, the film must be stretched so that a very elastic and high micron film must be used to prevent it from being possible to break.

- The folder removes the long part of the film, that is, the one that will cover the base of the article, stealing directly from the reel but, while the folder pushes the stolen film under the tray, at the same time it pushes said tray against the stop thereby increasing the pressure of the film against the tray and against the articles contained therein, in such a way that it can sometimes cause damage to the tray itself and even in the articles without being sufficiently delicate. In any case, this overpressure of the film as a result of the machine's own activity and, more specifically, of the folding system, forces the use of films with an oversized weight.

- The film cutting blade acts at a fixed point in the machine cycle, regardless of the size of the article, since the movement of said blade comes from the general camshaft of the machine, so that whatever means of folding provided in this machine always steal an amount of film from the coil, this sometimes represents an unnecessary waste of film.

DESCRIPTION OF THE INVENTION

The recommended machine has been designed to solve all this problem to full satisfaction, based on the fact that the different movements and operational phases of it are programmed, depending always of the dimensions of the article, controlling both the placement of said article to be wrapped, as well as the size of the portion of film to be used, as well as the movements of the extraction clamp, of the folding elements and of the blade itself. cut, so that all this will be based on the dimensions of the article and the film used.

More specifically, one of the characteristics of the invention is that the article will be arranged on the corresponding elevator in a position determined by the microprocessor, depending on the dimensions thereof, so that the distribution of the film in the envelope will achieve closure by superposition on its lower base.

Therefore, based on that first characteristic, the position of each article is determined at the most appropriate point for its wrapping, depending on the dimensions of the article and, specifically, its width.

As a result of being able to place the article in any position of the elevator, it will be possible to distribute the film optimally in the wrapping process.

The elevator itself, traditionally formed by a series of boluses equipped with folding heads, which aims to keep the items stable when lifting and wrapping operations are carried out, has been perfected, eliminating springs and any other mechanism until now necessary for get dejection and recovery of the heads.

Indeed, the bolus body is expected to It is made of flexible plastic material and that it is opportunely coupled to a head, also made of plastic, through a neck designed to produce the precise folding and recovery movements for the normal operation of the folding blades.

Another feature of the invention is that the film extraction clamp is provided with a variable longitudinal movement to extract a portion of film proportional to the transverse perimeter of the article to be wrapped, the necessary amount of film being extracted in each case to perform optimally, with the precise amount of film, the last folding or subsequent folding.

The extraction clamp has a variable movement in the direction of the product exit, moving below the sealing strip. This movement is very important because thanks to it it is possible to control the stretching of the film in the final folding.

In addition, the extraction clamp will make a stretch of the film that will be proportional to the degree of flexibility of the film and the necessary cutting tension.

The film extraction clamp is capable of performing a zone clamp, defining three zones, two lateral and one central, so that the clamping of the film is done in unison in the three zones, while its release is sequential, first the lateral areas to facilitate lateral folding, that is, to free the outer areas of the film and facilitate its introduction under the article, while the central part will follow held or pinched until the moment of final folding.

Another novel feature of the wrapping machine of the invention is that it includes lateral clamps that hold the film when it is fully extended and tensioned in the longitudinal direction, these clamps being laterally movable to make a stretch of the film in a transverse direction, which It will be programmable to the width of the film used and the length of the article to be wrapped. These lateral clamps have a movement of approach to the variable film, in order to be able to hold the film by its external edges, whatever the width of the film feeding reel. On the contrary, in the direction of stretching, the displacement of the lateral clamps is fixed, in order to always achieve the same degree of stretching, independent of the width of the film.

Another characteristic of novelty that the machine presents, is that the corresponding film feeding reels have a brake whose activation and deactivation occurs in a programmed way depending on the item to be wrapped. This brake remains activated until the lifting of the article causes contact with the film, at which time the brake is deactivated and the article continues its ascent by stealing an additional amount of film from the reel, the brake being connected again before the elevator race is completed, to obtain the tension in the film necessary to facilitate its subsequent cutting.

The exact moment of braking is determined by the programmer, depending on the product to be wrapped and, therefore, the specific film needs, managing to optimize the use of the least amount of film possible in each wrap, also avoiding breakage of the film by exceeding the elastic limit of the film, making the wrap with an optimal tension for the best presentation of the wrapped item.

As for the wrapping process itself, it begins with the introduction of side folding blades and a rear folding blade, so that to make the lateral folds the tension of the film will be maintained and the machine control will order the deactivation of the film clamping system at the exact moment when the side presser presses the film and starts folding.

On the other hand, the activation of the movement of the lateral clamps that hold and that have previously stretched it in that direction, can be programmed so that said clamps are introduced simultaneously with the lateral folding blades, being the deactivation point of the programmed lateral clamps depending on the length of the product to be wrapped.

The folding by the front or last folding, that is to say, of the portion located between the extracting clip and the sealing band to which the article already practically wrapped will be accessed and where the final sealing is carried out, is carried out by pushing of said article by means of an ejector system that causes the latter to advance on the film portion, for which it is necessary that the extractor clip releases the film that is still held in its central area, the movements of the ejector and the clip being synchronized by the microprocessor . Another novel feature is that the central folding machine incorporates the ejector mechanism, so that said central folder makes the last folding and after it has finished, the ejector mechanism is transferred by transferring the article to the welding band.

As is evident, the program of the microprocessor that incorporates the machine will allow the automatic choice of the coil to be used, depending on the length of the product to be wrapped, and its characteristics.

Obviously, in order for the programmer to control and determine the exact moment of movement of each machine element, it is necessary that the dimensions of the article be detected before entering the machine, specifically on the feeding belt to it, for which has been foreseen the incorporation of a photoelectric barrier that captures the dimensions of the article and sends them to the respective microprocessor for the control of all the aforementioned means and devices, depending on the dimensions of the article or product detected.

The machine thus constituted allows to wrap articles of any size, even articles of low consistency, using all types of films and optimizing the amount of film to be used, always with a homogeneous tension of the film throughout the wrapping, and a portion of concrete film for Each item to wrap.

Finally, to say that the machine incorporates means that allow positioning the free end of the film of the reel in the corresponding feeder device, of Fast and comfortable way.

In short, the main operations performed by the machine commanded by the microprocessor can be specified in the following:

- Choice of the film reel to use depending on the dimensions of the article.

- Transport of the article from a stable area of the feeding car to a specific position of the elevator, depending on the width of the article to be packaged.

- Disconnection of the brake of the bobbin holder to be able to extract the necessary film.

- Start of the elevator race.

- Extraction, by means of pinching and stretching, of the film from the preselected coil, extracting a variable amount of film depending on the width of the article.

- Bobbin holder brake connection for stretching the film at the end of its extraction.

- Disconnection of the brake of the bobbin holder in the last phase of the upward stroke of the elevator to steal the necessary additional film.

- Bobbin holder brake connection at the end of the elevator stroke.

- Introduction of the lateral clamps to clamp the film by its margins and then its stretched in transverse direction synchronously with the operation of the side folder.

- Cutting of the film sheet in synchronism with the central folder.

- Rear folding of the portion of film cut by the central blade.

- Expulsion of the article wrapped in the sealing and sealing area of the film supposed at the base of the article.

The controlled execution of all the movements and maneuvers referred to enables automatic wrapping of a wide variety of products or items, depending on their dimensions, shapes and properties, being able to use different types of stretch film.

The hot sealing band can be displaced and replaced instead by a tray transfer system with the product, from the exit position to a side of the machine, in order to automate the removal of trays and give the possibility of installation of an automatic heavy-labeling equipment, or an automatic label dispenser.

DESCRIPTION OF THE DRAWINGS

To complement the description that is being made and in order to help a better understanding of the features of the invention, according to a preferred example of practical realization thereof, an integral part of said description is attached, an set of drawings in which, with an illustrative and non-limiting nature, the following has been represented:

Figure 1 shows a view corresponding to a schematic side elevation of the assembly of the machine object of the invention.

Figure 2.- It shows a plan view of the film that runs between a feeding comb and a comb corresponding to the extraction clamp, a film that runs between a pair of lateral clamps through which stretching in that direction of the film.

Figure 3.- It shows a view similar to that of the previous figure, with the lateral clamps displaced outward causing the film to stretch.

Figure 4.- Shows a front view of the tray to be wrapped in an elevated position, pushing the film held on its sides by the lateral stretching tongs, and above them the lateral folding blades.

Figure 5.- Shows a view similar to that of the previous figure, with the lateral folding of the film on the article.

Figure 6.- It shows a top plan view of the side folding blades and the central or rear folder.

Figure 7.- Shows a final sequence of the application of the envelope on the tray, from which and by means of the pusher observed in said figure, the article will pass with the wrap towards the hot band where the end of the wrapping phase and the sealing of the film will take place.

Figure 8.- Schematically shows the moment in which the lateral blades fold the lateral film and collide with the bowling heads, which fold down as a result of the crash.

Figure 9.- Shows a longitudinal section of one of the bolus of the elevator.

Figure 10.- Shows the central folding blade with the ejector mechanism integrated in it, the latter being observed in the collected position and in the extraction position.

Figure 11.- Shows the extraction clamp in plan view and its two sides.

PREFERRED EMBODIMENT OF THE INVENTION

In view of the aforementioned figures, it can be seen how the machine of the invention is intended to wrap items or products (1), for example trays containing any type of product, items (1) that are fed through an endless band or conventional feeder (2), to a conveniently located elevator (3) and on which each of the items (1) will be placed to be lifted so as to be wrapped by a portion of film (4) coming from a coil (5), being able to see in figure 1 how the machine includes two reels (5), each of which will have a certain type of film, the film being selected from one or the other depending on the type of product to wrap.

The film (4), from the corresponding coil (5), passes through a feeder constituted by a comb (6) that is part of a general and tilting device (7) which in turn comprises means for positioning the free end of the film (4) on the feeder comb (6), both when a new reel (5) is put in the machine and when a film jam occurs.

In any case, the device (7) is tilting around the axis (8), being maintained in its operative position by actuating a pneumatic cylinder (9) whose piston has a support end (10) for a roller (11) belonging to the general body of the device (7), all this so that when the cylinder (9) is actuated the piston thereof is extended and therefore pushed upwards, and supporting through the end (10) of the piston, with the particularity that the positioner is constituted by a roller (12) that presses on a wheel (13), when it is in the closed position referred to above, that is, pushed up the device (7) by means of the cylinder ( 9), so that the film (4) is forced to pass between the roller (12) and wheel (13).

When it is desired to arrange the free end of the film (4) on the feeder comb (6), for the replacement of a coil, it will be necessary to deactivate the cylinder (9), retracting its plunger and therefore allowing the device to swing (7) , thus releasing the film (4) from the pressing between the roller (12) and wheel (13), which allows the corresponding handling for the film positioning.

The wheel (13) is mounted on a support (14) that at its opposite end to that of the latter is a carrier of another roller (15) that keeps the film properly positioned (4) once it has been sectioned by means of the cutting blade (16), as depicted in Figure 1.

The machine also has an extraction clamp (17) that is movable forward and backward, and is located in the area opposite to that of the coils (5), below the sealing band (27), of so that the article (1) raised by means of the elevator (3) is located under the film (4), between said extraction clamp (17) and the feeding zone referred to above.

In this way, the article (1) to be wrapped enters the machine, through the front part of the same, through the already mentioned feed belt (2), passing in front of a pick-up barrier (18), which verify the dimensions of the article (1), transmitting the data to the corresponding microprocessor, so that it carries out the appropriate orders to control the movements of all the means and devices that make up the machine.

Said article (1) is arranged on the elevator (3), in a position determined by the programmer itself, depending on the dimensions thereof.

Next, the clip (17) extracts a variable portion of the film (4) proportional to the dimensions of the article (1), also producing a pre-stretching of the same depending on its characteristics, always keeping in mind that, according to the product to be wrapped, the machine will select one or another type of film, coming from one or the other of the coils (5).

As already indicated, the extraction clamp (17) has a variable and programmable movement in the direction of the output of the product, said clamp moving below the sealing strip (22). By virtue of the programmed variation of this movement of the extraction clamp, the stretching of the film in the final folding operation can be controlled.

When the film is fully extended and tensioned, lateral tweezers (19) clamp the film (4) by its margins and produce a programmed transverse stretch based on the characteristics of the film. Said transverse stretching is always the same, whatever the width of the starting film, that is, the displacement of the tweezers (19) in the direction of stretching is always the same, while the displacement in the other direction is variable and dependent on the width of the film.

The lifting system is then activated, that is, the elevator (3), and the article (1) is raised up to the envelope area represented in figure 1, the elevator ascent (3) being controlled by a counter of impulses that informs the programmer of the position of the tray at all times. When the tray, or what is the same, the upper part of the product contained therein, contacts the film sheet (4), a brake provided in the corresponding bobbin holder is disconnected, in order to extract some film from the respective coil (5), connecting again the brake before the article (1) reaches the point of greatest elevation, so that a stretch of the film is produced that provides adequate tension for its subsequent cutting.

Once this position has been reached, folding and lateral blades (20) and a rear folding blade (21) intervene, making the lateral folding, as shown in figures 4 and 5, and the subsequent folding of the film on the article (1 ), so that at the moment when the side press brakes (20) press the film (4) and start folding, the programmer will deactivate the side clips (19) that will release the film, to allow folding of the film.

The press brake (21) will fold the film portion (4) located between the article (1) and the cutting blade (16), the cutting control being carried out according to the dimensions of the article (1) of the type of film

After cutting, the folding blade (21) continues its advance stroke by transporting the article (1) to the sealing band (22), where the sealing of the film completely wrapped on the article (1) occurs, as a consequence that said band (22) is provided with heating means to produce the corresponding seal.

The thrust of the article (1) towards the sealing strip (22) is carried out by an ejector (23), mounted on the central blade itself (21), whose ejector is actuated by a cylinder (24), as schematically represented in figure 7. As indicated above, the central ejector folder is intended for the folding of the part of the film between the inner end of the article and the cutting blade and the transfer of the article to the welding band (22) while it is being carried out. the last folding or final folding.

The central ejector folder (23) consists of a support body (38) which has two cylindrical extensions (39), on its sides, for the accommodation of two bushes to facilitate the movement of the assembly on the respective axes. The central folding blade (21) and the ejector mechanism are integral to that support body (38). The ejector mechanism is composed of a cylinder (24) and a scissor mechanism (35) and (36) finished off in a bidder (37), all as shown in Figure 11.

The activation of the cylinder (24) of the pusher element (23) is carried out when the folding blade (21) reaches the limit of its stroke and the extraction clamp (17) releases the portion of film located between it and the article (1) , with the opening of such a clamp (17) being programmed according to the article and the characteristics of the film.

The final folding of the film portion (4) located between the clamp (6) and the sealing band (22), is carried out by the aforementioned thrust of the element or pusher (23), leaving the film portion (4) located between the bottom of such article (1) and the sealing band itself (22), so that once the latter is wrapped and located above the band (22), welding of the folds of the film itself will occur. (4), being that band (22) assisted by suitable heating means. As it may have been verified, the clamp (17) for extracting the portion of the film (4) is provided with a variable longitudinal movement, depending on the product or article (1) to be wrapped, removing that clamp (17) a length of film proportional to the previously detected perimeter of the article (1) by means of the collection barrier (18).

The extractor clamp (17), when removing the film from the coil, is divided into three parts that operate in unison or sequentially. In order to extract the film from the coil, the clamp (17) holds the film in its entire width. However, at the time of releasing it, it does so in parts, so that the lateral ends of the clamp are first opened to release the film of the lateral wings and thereby facilitate the folding maneuver of such laterals, while the part The central part of the film, held by the central part of the clamp, is still retained or pinched until the final fold is made.

To enable the aforementioned, the clamping device (17) is mounted on a body (40) that has two cylindrical extensions (41) at its ends for the location of two bushes that facilitate their movement on respective axes. On said support body (40) a plate (42) is mounted and on it the clamping mechanism consisting of three parts of which the two outer ones can move simultaneously when the actuator (43) is activated, while the central part moves through the activator (44). The activator (44) drives the part (17 '), which acts in the center, while the actuator (43), by means of the appropriate transmission, drives the clamp parts (17''), located at the ends. For the extraction of the film the three clamping parts of which the clamp consists simultaneously. However, the outer clamping parts release the film before and, in particular, when lateral folding begins, precisely to facilitate it. The central pincer part, as indicated above, opens just at the moment the final folding begins.

The machine's microprocessor will be programmed to carry out the necessary calculation so that the article (1) is placed in a defined position on the elevator (3), depending on the width of it, so that the placement in a defined and programmed position It is necessary for the correct distribution of the film in the wrapping of different products, all with the particularity that the previously programmed control will allow the introduction of an article in the machine depending on the position of the elevator (3), to avoid the introduction of a new article when said elevator is not located in its lower position.

The elevator (3), in turn, is composed of a base from which a plurality of boluses emerge, its object being to keep the items in a stable position when lifting and wrapping operations are performed.

Bowling consists of a flexible body (31) and a head (32). The head is made of injected polyester or similar material, with the rounded configuration being the part on which the articles rest, so that contact with them continues to exist when the head is tilted or ablated by the corresponding folding blade during The wrapping process.

Said head (32) is hollow in order to avoid maximum possible noise due to the collision with each other or with the folding blades.

The flexible body (31) is fixed by tongue and groove or any other shape to the head (32). The body (31) is made of a polyurethane polyurethane and has a throttle like a throat that facilitates its despondency and vertical recovery.

According to the above, the machine's operating cycle is composed of the following phases or operations, all of them commanded by the microprocessor:

- The article is placed in a defined position of the elevator (3). The microprocessor program chooses the coil to be used depending on the length of the article captured by the photoelectric barrier (18). Depending on the measurement of the width of the article, the microprocessor program calculates the length of the film necessary for the wrap in the transverse direction of the article. With this data, the clamping system (17) takes the film from the corresponding reel and extracts a portion previously selected by the program.

The machine control system allows you to program the activation and deactivation of a brake located on each bobbin holder (5), which will be activated before the caliper removes the total length of the selected film, keeping the brake activated until the lift place the article in contact with the film.

When the film is fully extended and tensioned, side clips (19) hold the film and They perform a transverse stretch. The position of these lateral clamps varies depending on the reel selected in order to hold the film always by the outermost area and achieve optimum stretching of the film depending on the width and elastic characteristics of the film.

Once the aforementioned operations have been carried out, the article wrapping process begins. The control system activates the lifting system by which the article is transported from the position defined in the feeding belt to the wrapping area. In the elevator ascent race with the article, a pulse contactor located in the elevator motor informs the control system of the position of the article at all times. With this information the control of the previously programmed system, according to the dimensions of the article, orders the following movements:

- Disconnection of the brake bobbin holder at the point of the elevator stroke in which the article contacts the previously stretched film.

- The connection of the brake bobbin holder at a programmable point of the upward stroke of the lift before the point of maximum elevation.

- The introduction of the lateral clamps that have previously stretched the film, when the article exceeds the level in which the film is.

- The movement in the opposite direction to the extraction of the film from the extractor clamp (17) of the film. These movements controlled by the microprocessor and programmable depending on the dimensions of the article to be wrapped, previously defined when the article crosses the measuring barrier (18) located in the feeding carriage (2), allows the control of the tension of the film for get to optimize the amount of film to be used in each wrap and avoid breakage.

The wrapping process continues with the introduction of the folding blades (20) which make the lateral folding and the previous folding. To make the lateral folds while maintaining the tension of the film, the machine control will order the deactivation of the film clamping system at the exact moment when the lateral press brake presses the film and the folding begins. The activation of the movement of the lateral clamps (19) that hold the film and have previously stretched it can be programmed so that said clamps are introduced simultaneously with the lateral folding blades (20). The deactivation point of the side clamps (19) has been previously programmed according to the length of the article.

After cutting, the portion of the film between the blade and the coil is fixed in the introducer system which includes a pressure mechanism that makes it possible to remove the film in the direction of the inside of the machine but prevents movement of the film in the opposite direction.

After the rear folding blade (21) has folded the part of the film between the article and the blade, said blade continues its advance by transporting the article in the direction of the sealing band. In order for this transport to be possible, an ejector system (23-24) is integrated into said blade, which is activated after the final folding.

At the moment when the rear folding blade (21), which includes the ejector system (23-24) reaches the limit of its stroke and the ejector system is activated, the film extraction clamp, which has been holding the film for The wrapping cycle releases the portion of film located between said clip and the article.

The final folding of the portion of the film between the extractor and the sealing strip is carried out by the same ejector system by means of its advance, placing the portion of the film between the article and the sealing strip when the subsequent press brake has made its stroke of breakthrough and the film has been released from the extractor.

The article already wrapped is placed on top of the hot sealing strip (22), where the folded film folds are welded against the bottom base of the article.

Claims

R E I V I N D I C A C I O N E S

the.- Product wrapping machine with stretch film, which is intended to wrap items (1), which access the inside of the machine through a feeding band (2) that deposits each item (1) in an elevator (3 ) whose ascent carries with it the provision of such article (1) under a portion of stretched and tensioned film (4), between a feeder comb disposed next to a reel (5) of film and an extraction clamp (17) located in the opposite side, counting the machine with lateral folding blades (20) and a front folding blade (21), movable to achieve the adaptation of the film on the sides and back of the article (1), which is finally dragged to a band of sealing (22) where the end of the wrapping of such product (1) with the film (4) and the sealing thereof by heating on the bottom is produced, is characterized in that the article (1) can occupy a variable position in the elevated r (3) position that is defined by the microprocessor according to the width of the article, the extraction of the film being carried out by means of an extractor clamp (17) provided with a displacement in the variable longitudinal direction, whose stroke, or what is the same, the extraction of more or less film is a function of the transverse perimeter of the article to be wrapped, the extracting clip (17) being positioned below the sealing band (22), followed by a longitudinal stretching of the film and the extraction of the amount of additional film required by sequentially activating and deactivating the brake of the bobbin holder (5) to then carry out the transverse stretching of the film by means of calipers (20) of variable displacement, which catch the film just by its edges whatever its width and fixed displacement in the direction of tensioning, tweezers that release the film just when the folding blades (20) come into operation, a central folding presser (21-23-24) having the last folding being provided and the expulsion of the wrapped item.

2a.- Product wrapping machine with stretch film, according to claim 1 ^§ , characterized in that the extraction clamp (17) has a variable movement in the direction of the output of the product, moving below the sealing band, movement that allows control the stretching of the film in the final folding.

3 §.- Product wrapping machine with stretch film, according to previous claims, characterized in that the bobbin holder (5) includes a brake whose activation and deactivation is controlled by the microprocessor, so that a first deactivation of the brake occurs so that the caliper extractor (17) take the amount of film ordered by the microprocessor, then activate until in its elevation the article (1) comes into contact with the film (4) that extends over it, deactivating at that time to obtain the amount of film required programmed, activating again before the elevator completes its career, so that the film remains with the optimum tension that allows its cutting.

4§.- Product wrapping machine with stretch film, according to previous claims, characterized in that the extractor clip (17) has three pinching areas that operate simultaneously to clamp and sequentially to release the film, the two outer areas being the first ones to release the film just when the blades (20) start the lateral folds, while the central area of clamping releases the film just at the moment when the final folding begins.

5a.- Product wrapping machine with stretch film, according to previous claims, characterized in that the extractor clip (17) is constituted from a support (40) with tubular extensions (41) for movement on corresponding guide axes, in whose plate actuators (43) and (44) are mounted, one of which drives the extreme clamping zones (17 '') while the other drives the central clamping zone (17 ').

6§.- Product wrapping machine with stretch film, according to claim 13, characterized in that the ejector central folder (21-23-24) consists of a support body (38) provided with tubular extensions (39) for movement on corresponding axes guide, of whose body the blade itself (21) and a scissor ejector mechanism (35-36), finished off in a pusher (37), ejector mechanism that is actuated by a pneumatic cylinder (24).

7§.- product wrapping machine stretch film according to claim 1 ^§, characterized in that the elevator is provided with a plurality of pins formed by a body of flexible material (31), such as polyurethane polymer, and a head (32) , hollow, with rounded geometry and also constructed of plastic material, such as injected polyester, the body and the head being joined through a throttling of the body as a neck, which facilitates its folding in any direction and subsequent recovery.

83.- Product wrapping machine with stretch film, according to claim 1, characterized in that the film feeder (4) from the respective reel (5) is associated with a free end positioning device of said film (4), a device that includes a tilting support (7) provided with a roller (12) and a wheel (13) between which the film (4) is passed to the respective comb (6) of the feeder, the support device (7) being kept in operative position in which the film (4) is pressed between the roller (12) and wheel (13), by means of a cylinder (9) whose rod has an end on which a roller belonging to the support device (7) rests, allowing the deactivation of such a cylinder (9) the tilting of said device (7) for positioning the free end of the film on the feeder.

93.- Product wrapping machine with stretch film, according to claim 1 ^§ , characterized in that the operating sequences of the machine, all of them commanded by the microprocessor, are the following: a) Positioning of the article at a specific point of the elevator. b) Disconnecting the brake from the bobbin holder to remove the film. c) Start of the elevator run. d) Bobbin holder brake connection for film stretching at the end of extraction. e) Disconnection of the brake of the bobbin holder in the elevator stroke. f) Bobbin holder brake connection at the end of the elevator stroke. g) Introduction and control of the side clamps depending on the width of the film. h) Transverse stretch of the film. i) Movement of the lateral clamps that stretch the film accompanying the lateral press brake to the point of release of the film, j) Cutting of the film k) Movement of accompaniment of the film extractor when the article is raised. 1) Final fold and ejection of the article to the sealing band.