PROCEDURE AND ASSEMBLY FOR WRAPPING ONE OR MORE PACKAGES WITH STRETCH FILM FROM A ROLL

Abstract

A method for wrapping packages with stretch film from a roll, wherein said one or more packages (13) comprising one or more products are in transit through a wrapping machine comprising at least one wrapping unit (14) comprising at least one ring winder (16) that rotatably disposes of stretch film around said one or more packages (13), wherein said film (21) is provided to be unwound from a roll (20) disposed on a rotating ring (17) of said ring winder and directed to dispose around one or more packages (13) during the transit of said packages through the winding unit, wherein in the winding method (a) in a first step,said stretchable film (21) being unwound from said reel (20) passes through a pre-stretch group (22) that generates an axial deformation of said film (21) predetermining a quantity of elastic return thereof, b) in a second step in which said axially deformed stretchable film in step a) interacts with a vacuum box (30) having a known volume placed downstream of the pre-stretch group (22),which guarantees the possibility that a buffer (tank) capable in its volume compensates for the difference between the average development rate of the film during the rotation of the ring (17) with respect to the specific application rate of the film in one or more packages (13) regardless of their geometry and producing a constant auxiliary tension on the previously stretched film equal to the value of the head within the vacuum box (30) for the projection of the interface surface of the film with said vacuum box, c) in a third step in which the film is applied on said one or more packages (13) with a constant tension residue at each point of application of said previously stretched film after the addition of the constant load generated by the vacuum box (30), producing one or more fully wrapped packages with a programmed tension residue at each point of the perimeter of one or more packages (13),wherein the deposit of said film is carried out through at least one complete turn of said ring (17) around said one or more packages (13).,

Description

METHOD AND ASSEMBLY OF WINDING ONE OR MORE BUNDLES WITH STRETCH FILM FROM A REEL * * *The present invention relates to a method and assembly for wrapping one or more bundles with stretch film from reels.In the field of bundle packaging, various types of machines have been developed which pack the bundles inside stretch film. An example of a machine and a method of this type is described in patent EP 3414167.In such a stretch film packaging machine for bundles consisting of one or more products, the presence of at least one wrapping unit is envisaged which arranges the stretch film around the bundle by means of at least one ring wrapping machine. The film is conducted around the bundle and is stably arranged around it thanks to its extensibility characteristics, but does not guarantee equal tension at every point of the bundle due to the geometric inconsistencies it has with respect to the angular wrapping linearity that this method produces.It should be noted that the bundle, or the individual products that make it up, only minimally have a circular section, i.e. cylindrically shaped, but mostly have a parallelepiped or prismatic shape with more or less marked edges.The different geometry between the circumference covered by the release point of the film integral with the rotating ring and the section, different from being circular, predominantly rectangular or comparable to it, of the product to be wrapped, means that the tension of the film is not constant and well distributed on the bundle. In other words, by transferring the film onto the product due to a rotation around the center of instantaneous rotation of this system, even at a constant angular envelope velocity, we are in the presence of reactive effects on the film tension due to adjustment / laying down2195796 de 11 around the bundle that are variable. The sum of these tensioning effects, which are clearly of geometric conjugation, normally lead to a non-homogeneous tensioning on the final bundle or package, resulting in an unsuitable packaging when the product to be wrapped does not have a high structural rigidity.By unsuitable packaging we mean a deformation of the product, poor stability of the package which causes difficulty in subsequent handling or even a potential for injury to the packaged product.Furthermore, in the prior art, attempts are made to obtain a correct tensioning of the film being wound on the bundle with so-called dancer systems. In fact, attempts are made to achieve, with these systems, a deposition of the film which is a function of the geometry of the product in order to limit the undesired residual stresses responsible for the deformation effects which can be found on the products.With such systems known as a dancer, the variation of the position of the film and its tensioning are negatively influenced by the inertial conditions of the masses present in such systems, such as rollers, support structures of the same, nonconstant elastic compensation systems.The masses constituting the dancer or the compensation systems make the bundle subject to an increase in tension of the film caused, for example, by the reversal of motion of these masses during the deposition of the film, due to the effect of natural forces of inertia.The main purpose of the present invention is to deposit film on any bundle with a predetermined residual tension, mainly if not exclusively produced by the elastic return of the film due to the action of a programmed pre-stretch, since the mechanical characteristics of the stretchable film are known, in addition to2195796 de 11 the size of the latter, the desired residual film tension is easily obtainable.Another object of the present invention is that of realizing a method of winding a bundle which is capable of solving the above mentioned drawbacks of the prior art in a simple, economical and functional way.The aforesaid objects are achieved by a method implemented according to the independent claim 1 and the sub-claims which follow.The invention relates to a winding method whose sequence of process steps is characterized by the introduction of the punctual control of the axial deformation of the film so that it determines a known and constant elastic residue as well as a buffer system of the same film designed to be the compensation element between the geometric inconsistencies of the element or elements to be packaged with respect to the unwinding linearity that the film has due to the rotation around the product; in order to be effective and constant in the tensional quantity accessory to the winding process, the buffer system is assisted by a negative head system with the aim of eliminating any relevant physical mass element of certain energy perturbation during the suddenness of the compensatory movement.In particular, to guarantee the fact of being able to deposit the film or the film with any type of tension beyond that pregenerated with the pre-stretch or in any case with an additional tension but in any case determined and controllable, it was identified downstream of the pre-stretch a film deposit compensation system on the package capable of determining a constant and uniformly distributed tensioning residue along the periphery of the product.The additional tensioning control is guaranteed with a vacuum2195796 de 11 box whose effect is a tension proportional to the absolute value of the vacuum for the surface of the box interfaced with the film; the moving masses are exclusively those of the film as a reactive element of the vacuum produced. Since the mass of the film is substantially irrelevant whatever the strategy of movement of the film in the vacuum box, it will never have an appreciable relevance of energy addition other than that produced by the vacuum.The structural and functional characteristics of the present invention and its advantages over the known art will become even clearer and more evident from an examination of the following description, referred to the attached schematic drawings, which show a non-limiting embodiment of the invention itself, where:figure 1 shows a perspective view of a bundle packaging machine with the method according to the present invention;figure 2 shows a perspective view from a different direction of the machine shown in Figure 1;figure 3 shows a flow of products to be packaged entering a machine according to figures 1 and 2;figure 4 shows a second embodiment of magnetic transmission used in such machines;figure 5 shows another perspective view from a different direction of the machine shown in figure 1.In the following description, for the illustration of the figures, identical reference numerals are used to designate construction elements with the same function. Furthermore, for clarity of illustration, some reference numbers may not be repeated in all the figures.Indications such as vertical and horizontal, upper and lower (in the absence of other indications) must be read with reference to the assembly (or operating) conditions and2195796 de 11 referring to the normal terminology in use in current language, where vertical indicates a direction substantially parallel to that of the gravity force vector g and horizontal a direction perpendicular to it.With reference to the exemplifying and non-limiting figures, an embodiment of a wrapping portion of a bundle packaging machine is shown.In fact, a conveyor belt (12) is envisaged which carries a bundle (13) forward towards a positioning unit (36) which, moving in the direction perpendicular to that of advancement of the bundle (13) on the belt (12), moves the bundle on the plane support (37) in a suitable position for winding. We have indicated bundle (13) that which is intended to be wrapped and which can include both one or more bundles and one or more products.The wrapping unit (14) comprises a frame (15) which supports at least one ring wrapper (16) which operates on bundles (13) carried forward by the positioning unit (36). The wrapping unit (14) is also arranged astride the support plane (37) and the bundles (13) that advance inside it.This ring wrapper (16) comprises a ring (17) which is rotatable with respect to guide rollers (18), arranged on the frame (15). This ring (17) is arranged in a plane perpendicular to the advancement direction of the bundles (13) and is rotated by a gearmotor (11) by means of a control friction roller (10).A reel holder (19) for a reel (20) of stretch plastic film (21) is integrally mounted on the ring (17).Further downstream of the reel holder (19) with reel (20) there is a pre-streching unit (22) which allows to have a constant physical pre-stretch of the dispensed film (21).This pre-streching unit (22), in a non-limiting example thereof, comprises a plate (23) integral with the ring (17). The plate (23)2195796 de 11 supports an insertion of the stretch film (21) comprising a first driven rubber roller (24) followed at a distance by a second motorized rubber roller (25). To allow the correct adhesion of the film on the rollers (24) and (25), the pre-stretching system (23) is equipped with the rollers (24') and (25') in radial contact and interfering with the rollers (24) and (25) to guarantee the correct amount of friction necessary for the film to be homokinetic with the rollers (24) and (25).The roller (24) and the roller (25) are connected by a mechanical transmission (26) which determines a rotational ratio proportional to the programmed stretching amount.At the outlet downstream from the pre-streching unit (22) there is a vacuum box (30) which performs the function of a buffer, consequently representing a film tank. This vacuum box (30) is arranged so as to be capable in its volume of compensating the difference between the average envelope speed of the film (21) during the rotation of the ring (17) with respect to the punctual deposition speed of the film (21 ) on a bundle (13).Furthermore, the vacuum box (30) is capable of simultaneously depositing the film on the bundle with a tension obtained by regulating the depressive capacity of the system generating the vacuum. The final tension on one or more wrapped bundles will be the result of the deposition tension and that due to the elastic return of the film as a consequence of the pre-stretch imposed by the pre-streching unit (22). The provision of the vacuum box (30), in which the film moves within its volume, substantially maintains a constant tension equal to the amount of vacuum that we are going to regulate inside the vacuum box for the surface of the section of box interface to the film.Inside the volume of the vacuum box (30) there is a sensor system, for example an ultrasound sensor (50) which detects the presence and position of the film so as to maintain a2195796 de 11 substantially constant tension on the film (21) and an adequate amount of film.The film (21) coming out of the vacuum box (30) is arranged and directed by means of a pair of rollers (31), (32) which direct it towards one or more bundles (13).It is also envisaged that a magnetic track (40) is arranged associated with the ring (17), which magnetic track (40) rotates and causes a wheel or disc with a magnetic track (41) to rotate, the shaft (42) of which is supported by the plate (23) of the prestretching unit (22).The wheel with magnetic track (41) thus drives the second rubber roller (25), arranged integral with the shaft (42).The wheel with magnetic track (41) is a satellite disc which receives the drive through the magnetic track (40) according to speed strategies consistent with the correct amount of development necessary for the finished packaging envelope.Therefore, the pre-streching unit (22) and therefore the unwinding of the film (21) are performed by motorizing the rubber roller (25) of the pre-streching unit with a magnetic track system.In fact, as mentioned, the magnetic track (40), rotating at a suitable speed, rotates the wheel with magnetic track (41) keyed onto the same shaft (42) of the rubberized pre-streching roller (25) at the desired speed. The rotation speed of the magnetic track (40) is a function of the rotation speed of the ring (17) of the reel holder, of the average unwinding speed and of any compensations regulated by the analysis of the quantity of film present in the vacuum box which can oscillate between two thresholds from a completely full position to an exhaustion position.The magnetic transmission described above in a non-limiting manner, in a second embodiment, could be structured as in fig.2195796 de 11 with the extension of the shaft (42) and the equipping of a second magnetic disk (41') with the purpose of not causing axial loads of the magnetic transmission disk (40) and to guarantee a possible more homogeneous control of the magnetic transmission of couple.The vacuum box (30) has the task of depositing the film on the bundle (13) with tension determined by a pneumatic suction system and equipped with a suction partialization specula in the atmosphere necessary to finely and minimally determine the quantity of residual negative pressure inside the vacuum box. Substantially the vacuum box (30) performs the same task currently performed by the so-called ''dancers'' or ''dancing-roll'' with the advantage, however, of not having inertial masses which, due to the suddenness of the law of motion of the winding of the film cause, due to the inertia of their components, uncontrolled extra tensions in the packaging of the wrapped bundle.The vacuum case (30) in fact has the weight of the film (21) as its only inertial mass, which is decidedly negligible.Such a system or machine described or in an alternative form allows to implement a winding method according to the present invention.The method of wrapping bundles with stretch film from reels provides that one or more bundles (13), made up of one or more products, is or are in transit in a packaging machine.The machine, which as mentioned provides at least one wrapping unit (14) consisting of at least one ring wrapper (16) which, by rotating, arranges the stretch film around one or more bundles (13), further provides that the film (21) unwinds from a reel (20) arranged on a rotating ring (17) of the ring wrapping machine and is made to arrange itself around one or more bundles (13), during the transit of the latter in the wrapping unit.2195796 de 11In particular, the winding method of the present invention provides thata) in a first step, said stretch film (21) which is being unwound from said reel (20) passes through a pre-stretching group (22) which generates an axial deformation of said film (21) predetermining an elastic return quantity thereof,b) in a second step wherein said stretch film axially deformed in step a) is caused to interface with a vacuum box (30) having a known volume positioned downstream of the prestretching group (22), which guarantees the possibility of a buffer (tank) capable in its volume of compensating for the difference between the average development rate of the film during the rotation of the ring (17) with respect to the specific deposition rate of the film on one or more bundles (13) regardless of its / their geometry and producing a constant auxiliary tensional stress on the pre-stretched film equal to the value of the head inside the vacuum box (30) for the projection of the interface surface of the film with said vacuum box, c) in a third step wherein the film is deposited on said one or more bundles (13) with a constant stress residue at each point of application of said pre-stretched film after the addition of the constant load generated by the vacuum box (30), producing one or more bundles completely wrapped with a programmed stress residue in each point of the perimeter of the one or more bundles (13), wherein the depositing of said film is effected through at least one complete revolution of said ring (17) around said one or more bundles (13).According to the present invention, therefore, a system or a machine has been created which implements a winding method which solves the problems of the prior art.2195796 de 11The main advantages are:- Produce a bundle wrapped in stretch film with punctual and constant control of the wrapping tension, using a magnetic transmission system from the outside to the inside without contacts, with torque limitation, without the need for particularly refined geometric coherence, consequently to the advantage of low-cost structures.- The activity of these magnetic transmission structures governs a pre-streching unit which allows for constant physical deformation and a programmed and homogeneous elastic resultant of the film.- The vacuum box downstream of the pre-streching system allows for the possibility of a buffer (tank) capable in its volume of compensating the difference between the average speed of development of the film during the rotation of the ring with respect to the punctual speed of deposit of the film on a bundle regardless of its geometry. The function of the vacuum box, in which the film moves within its volume, is to maintain a constant tension equal to the amount of vacuum that we are going to regulate inside the vacuum box for the interface surface with the film.Consequently, the film around the bundle, regardless of any type of geometry, will have a residual degree of tension given by the sum of the amount of vacuum per interface surface that exists in the vacuum tank with the film plus the tension due to the return elastic of the film as a result of the pre-stretch performed.The aim mentioned in the preamble of the description is thus achieved.The scope of protection of the present invention is defined by the attached claims.2195796 de 11BERTI, LAURA MARGARITA - 27051983098Digitally signed by PORTALTRAMITES - INPIDate: 2023.03.15 15:36:50 -03:00Reason: Firmado Digitalmente por el INPILocation: Buenos Aires, Argentina2195796

Claims

1. A method for wrapping packages with stretch film from a roll, wherein one or more packages (13), composed of one or more products, are in transit in a packaging machine having at least one wrapping unit (14) comprising at least one ring wrapping machine (16) which, by rotating, arranges the stretch film around one or more packages (13), wherein said film (21) is unwound from a roll (20) arranged on a rotating ring (17) of said ring wrapping machine and is arranged around one or more packages (13) during their transit in the wrapping unit, wherein in the wrapping method (a), in a first step, said stretch film (21) being unwound from said roll (20) passes through a pre-stretching group (22) which generates an axial deformation of said film (21) predetermining a quantity of elastic return thereof,b) in a second step in which said axially deformed extensible film in step a) interacts with a vacuum box (30) having a known volume placed downstream of the pre-stretching group (22), ensuring the possibility of a buffer (tank) capable in its volume of compensating for the difference between the average development rate of the film during the rotation of the ring (17) with respect to the specific application rate of the film in one or more packages (13) regardless of their geometry and producing a constant auxiliary tension on the pre-stretched film equal to the value of the head within the vacuum box (30) for the projection of the interface surface of the film with said vacuum box,c) in a third step in which the film is deposited onto said one or more packages (13) with a constant residual tension at each point of application of said film previously stretched after the addition of the constant load generated by the vacuum box (30), producing one or more fully wrapped packages with a programmed residual tension at each point of the perimeter of one or more packages (13), wherein the application of said film is effected by means of at least one complete turn of said ring (17) around said one or more packages (13). Seven claims follow.