Method and assembly of winding one or more bundles with stretch film from a reel

Abstract

A method of wrapping bundles is with stretch film from a reel. Bundles include products in transit through a wrapping machine including a wrapping unit having a ring winder which rotatably arranges stretch film around the bundles. During transit through the winding unit, the stretch film is unwound from the reel and passes through a pre-stretching group which generates axial deformation of the film predetermining an elastic return quantity. The axially deformed film interfaces with a vacuum having a vacuum box producing a constant auxiliary tensional stress on the pre-stretched film equal to the head inside the vacuum box. The film is then deposited on the bundles with a constant stress residue at each point of application of the pre-stretched film after adding the constant load generated by the vacuum box, producing bundles completely wrapped with a programmed stress residue.

Claims

1. A method for wrapping bundles with stretch film from a reel, wherein one or more bundles, composed of one or more products, is/are in transit in a packaging machine that has at least one wrapping unit comprising at least one ring wrapping machine which, on rotating, arranges the stretch film around one or more bundles, wherein said film is unwound from a reel arranged on a rotating ring of said ring wrapping machine and is caused to be arranged around one or more bundles, during the transiting of the bundles in the wrapping unit, the wrapping method comprising: a) a first step, in which said stretch film which is being unwound from said reel passes through a pre-stretching group which generates an axial deformation of said film predetermining an elastic return quantity, b) a second step wherein said stretch film axially deformed in step a) is caused to interface with a vacuum box having a known volume positioned downstream of the pre-stretching group, which provides a buffer having a volume compensating for a difference between an average development rate of the film during rotation of the ring with respect to a deposition rate of the film on one or more bundles regardless of geometry of the one or more bundles and producing a constant auxiliary tensional stress on the pre-stretched film equal to a value of a head inside the vacuum box for projection of an interface surface of the film with said vacuum box, c) a third step wherein the film is deposited on said one or more bundles with a constant stress residue at each point of application of said pre-stretched film after addition of the constant load generated by the vacuum box, producing one or more bundles completely wrapped with a programmed stress residue in each point of a perimeter of the one or more bundles, wherein the depositing of said film is effected through at least one complete revolution of said ring around said one or more bundles.

2. The method according to claim 1, wherein said pre-stretching group is powered by a magnetic track system, wherein said magnetic track system is associated with said rotating ring and rotates and causes a wheel or disc with a magnetic track to rotate, wherein a magnetic track shaft is supported in said pre-stretching group to cause traction action for unwinding the stretch film.

3. The method according to claim 1, wherein the film inside the volume of the vacuum box maintains a substantially constant tension of the stretch film equal to the value of the head inside the vacuum box for the projection of the interface surface of the film with said vacuum box regardless of a quantity of film occupying the volume of said vacuum box.

4. The method according to claim 1, wherein said predetermined tensioning on the stretch film in said pre-stretching group of the stretch film is generated by a first driven rubberized roller followed, at a distance, by a second motorized rubberized roller which are connected by a mechanical transmission which creates a rotational ratio proportional to a stretching quantity programmed, wherein complementary rollers are provided in radial contact and interfering with the first and second roller guaranteeing the correct amount of friction necessary for the film to be homokinetic with said rollers.

5. An assembly for wrapping bundles with stretch film from a reel in a packaging machine of one or more bundles comprising one or more products, wherein said packaging machine comprises at least one wrapping unit comprising at least one ring wrapping machine which, on rotating, arranges stretch film around one or more bundles, wherein said film is unwound from a reel arranged on a rotating ring of said ring wrapping machine and is caused to be arranged around one or more bundles, during transiting of the one or more bundles in the wrapping unit, wherein the assembly comprises: a pre-stretching group of the stretch film which generates an axial deformation of said stretch film which is being unwound from said reel and is passed through said pre-stretching group, a vacuum box which continuously receives said stretch film provided with said axial deformation generated in the pre-stretching group, wherein said vacuum box is provided with a volume in an interior within which the film moves and keeps axial deformation of the film generated in said pre-stretching group substantially constant as the film passes forward in the interior, wherein said vacuum box is arranged downstream of said pre-stretching group and both said vacuum box and said pre-stretching group are arranged on said rotating ring around said one or more bundles, and wherein said assembly provides a supporting plane which receives said one or more bundles moved by a positioning unit into a position for being wrapped within said rotating ring of said ring wrapping machine.

6. The assembly according to claim 5, wherein a magnetic track is associated with said rotating ring and rotates and causes a wheel or disc with a magnetic track to rotate, wherein a shaft of the magnetic track is supported in said pre-stretching group and drives a rubberized roller on which said film passes.

7. The assembly according to claim 5, wherein a system of sensors, which detects presence and position of the film, is arranged inside the volume of the vacuum box.

8. The assembly according to claim 5, wherein said pre-stretching group of the stretch film comprises a first driven rubberized roller followed at a distance by a second motorized rubberized roller which are connected by a mechanical transmission which creates a rotational ratio proportional to a predetermined amount of stretching, wherein complementary rollers are provided in radial contact and interfering with the first and second rollers guaranteeing a correct amount of friction for the film to be homokinetic with said rollers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a perspective view of a bundle packaging machine with the method according to the present invention;

(2) FIG. 2 shows a perspective view from a different direction of the machine shown in FIG. 1;

(3) FIG. 3 shows a flow of products to be packaged entering a machine according to FIGS. 1 and 2;

(4) FIG. 4 shows a second embodiment of magnetic transmission used in such machines;

(5) FIG. 5 shows another perspective view from a different direction of the machine shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

(6) 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.

(7) 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 and 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.

(8) With reference to the exemplifying and non-limiting figures, an embodiment of a wrapping portion of a bundle packaging machine is shown.

(9) 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.

(10) 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.

(11) 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).

(12) A reel holder (19) for a reel (20) of stretch plastic film (21) is integrally mounted on the ring (17).

(13) 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).

(14) This pre-stretching unit (22), in a non-limiting example thereof, comprises a plate (23) integral with the ring (17). The plate (23) 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).

(15) 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.

(16) 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.

(17) 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 a substantially constant tension on the film (21) and an adequate amount of film.

(18) 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).

(19) 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 pre-stretching unit (22).

(20) The wheel with magnetic track (41) thus drives the second rubber roller (25), arranged integral with the shaft (42).

(21) 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.

(22) 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.

(23) 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.

(24) The magnetic transmission described above in a non-limiting manner, in a second embodiment, could be structured as in FIG. 4 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.

(25) 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.

(26) 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.

(27) The vacuum case (30) in fact has the weight of the film (21) as its only inertial mass, which is decidedly negligible.

(28) Such a system or machine described or in an alternative form allows to implement a winding method according to the present invention.

(29) 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.

(30) 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.

(31) In particular, the winding method of the present invention provides that a) 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 pre-stretching 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).

(32) 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.

(33) The main advantages are:

(34) 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.

(35) 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.

(36) 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.

(37) 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.

(38) The aim mentioned in the preamble of the description is thus achieved.