Machine and method for producing bobbins of stretch film

Abstract

A winding machine (10) is disclosed comprising at least one reel holder (12) mounted on a supporting frame (11) and rotatable around its own axis (13), and a plurality of reels (1-4) mounted on the holder (12) and integrally rotatable therewith so that at least one first reel (1) is in at least one operative winding position of a bobbin (5). It is further described a respective method for the in-line winding of bobbins (5) of stretch film (6), comprising the steps of rotating a core (7) on a reel (1) in an operative winding position to wind the film (6) onto the core (7), positioning a contact roll (15a) in at least one proximal contacting position in which it contacts the winding bobbin (5) for facilitating the peripheral winding of the stretch film (6) on the core (7), bringing the reel (1) from the operative winding position of the bobbin (5) to an operative unloading position of the bobbin, positioning an accompanying roll (15b) in at least one proximal contacting position in which it contacts the bobbin (5) for facilitating the peripheral winding of the stretch film (6) on the bobbin (7), transversally cutting the stretch film (6) and unloading the bobbin (5). The movement of the contact roll (15a) and the accompanying roll (15b) is carried out by means of electric actuators (18a, 18b).

Claims

1. A winding machine (10) to wind bobbins (5) of stretch film (6) comprising: a supporting frame (11), at least one reel holder (12), mounted on said supporting frame (11) and rotatable around its own axis (13), a plurality of reels (1-4) mounted on said at least one holder (12) and integrally rotatable therewith so that at least one first reel (1) is in at least one operative winding position of a bobbin (5), at least one contact roll (15a) adapted to cooperate with said at least one first reel (1) in said operative winding position of a bobbin (5), wherein said contact roll (15a) is movable between at least one proximal contacting position in which it contacts the bobbin (5) being wound, in order to facilitate the peripheral winding of the stretch film (6) on said bobbin (5), and at least one distal position from said bobbin (5), at least one accompanying roll (15b) movable between at least one distal position from the bobbin (5) being wound and at least one proximal contacting position in which it contacts the winding bobbin (5) in order to facilitate the peripheral winding of the stretch film (6) on said bobbin (5) during rotation of said at least one reel holder (12) so that said reel (1) can switch from said operative winding position of the bobbin (5) to an operative unloading position of the bobbin (5), further comprising means (24) for determining the position of said rolls (15a, 15b) with respect to said bobbin (5) being wound said contact roll (15a) and said accompanying roll (15b) being respectively coupled with at least one first operating arm (16a) and at least one second operating arm (16b) which are rotatable around respective rotation axes (17a, 17b) parallel to the rotation axis of the bobbin, and further comprising electric actuators (18a, 18b) for rotating said operating arms (16a, 16b).

2. The winding machine (10) according to claim 1, further comprising at least one electric power circuit (21) for supplying said electric actuators (18a, 18b) and a logic control unit (22) adapted to control the current output from said at least one electric power circuit (21) to said electric actuators (18a, 18b).

3. The winding machine (10) according to claim 1, wherein said means (24) for determining the position of said rolls (15a, 15b) with respect to said bobbin (5) being wound comprise at least one encoder (24a, 24b) of the absolute type.

4. The winding machine (10) according claim 1, further comprising means (23) for detecting the current absorbed by said electric actuators (18a, 18b).

5. The winding machine (10) according to claim 4, wherein said logic control unit (22) adjusts the current output from said at least one power circuit (21) to said electric actuators (18a, 18b) depending on the current absorbed by said electric actuators (18a, 18b).

6. The winding machine (10) according to claim 1, wherein said electric actuators (18a, 18b) are of linear type.

7. The winding machine (10) according to claim 1, further comprising a threading-up electric motor adapted to be magnetically coupled with a second reel (2) having a core (7) loaded thereon, for rotating said reel (2).

8. The winding machine (10) according to claim 1, further comprising an electromagnetic brake arranged at said operative position for unloading a finished bobbin (5).

9. A method for the in-line winding of bobbins (5) of stretch film (6) in a machine (10) comprising at least one reel holder (12) mounted on a supporting frame (11) and rotatable around its own axis (13), and a plurality of reels (1-4) mounted on said at least one holder (12) and integrally rotatable therewith so that at least one first reel (1) is in at least one operative winding position of a bobbin (5), the method comprising the steps of: a) rotating a core (7) on a reel (1) in an operative winding position to wind the film (6) on said core (7); b) positioning at least one contact roll (15a) in at least one proximal contacting position where it contacts the bobbin (5) being wound to facilitate the peripheral winding of the stretch film (6) on said core (7); c) bringing said reel (1) from said operative winding position of the bobbin (5) to an operative unloading position of the bobbin; d) positioning at least one accompanying roll (15b) in at least one proximal contacting position in which it contacts said bobbin (5) for facilitating the peripheral winding of the stretch film (6) on said bobbin (7) during said step c); e) transversally cutting the stretch film (6); f) unloading said bobbin (5), wherein the movement of said contact roll (15a) and said accompanying roll (15b) is carried out by electric actuators (18a, 18b), and wherein positions of said contact roll (15a) and said accompanying roll (15b) with respect to said winding bobbin (5) are determined.

10. The method according to claim 9, wherein said accompanying roll (15b) is positioned at a specific distance (D) from said bobbin (5) being wound during said step c).

11. The method according to claim 9, wherein current absorbed by said electric actuators (18a, 18b) is detected at least during said steps b) and d).

12. The method according to claim 11, wherein said contact roll (15a) and said accompanying roll (15b) are moved between a first proximal contacting position and at least one second proximal contacting position depending on the current absorbed by said electric actuators (18a, 18b) for applying to the bobbin (5) a predetermined pressure.

13. The method according to claim 9 further comprising a second reel (2) having a core (7) loaded thereon rotated by means of a threading-up electric motor magnetically coupled with said second reel (2).

14. The method according to claim 9, wherein the rotation of said at least one first reel (1) having a finished bobbin loaded thereon is stopped in said operative unloading position by means of an electromagnetic brake.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further aspects and advantages of the present invention will become more evident from the following description, made for illustration purposes and without limitation, with reference to the accompanying schematic drawings, in which:

(2) FIG. 1 is a sectional view of an embodiment of the winding machine according to the present invention;

(3) FIGS. 2-6 are sectional views of the winding machine of FIG. 1, taken from the opposite side of the sectional plane, during some operation steps according to a possible implementation of the winding method of the present invention.

(4) FIG. 7 is a sectional view of an embodiment of the winding machine according to the present invention.

(5) FIG. 8 is a lateral view of the threading-up electric motor 50.

(6) FIG. 9 is a lateral view of the electromagnetic brake 60.

METHODS FOR IMPLEMENTING THE INVENTION

(7) FIG. 1 shows a winding machine 10 comprising a supporting frame 11 and at least one reel holder 12 mounted on the supporting frame 11 and rotatable around its own axis 13. In the embodiment shown in FIGS. 1-6 a single reel holder 12 is shown for greater simplicity in explanation. It is however contemplated that in further embodiments the winding machine 10 can comprise a plurality of reel holders 12 mounted on the supporting frame 11 for winding bobbins of stretch film, which are for example produced in line by an upstream extruder. In the latter case, a film web produced by the upstream extruder is cut into bands of smaller width, each being led at the inlet of a respective reel holder 12 to be independently wound each in different bobbins.

(8) Each reel holder 12 is provided with four reels 1-4 preferably arranged 90 from each other. Reels 1-4 are integrally rotatable with the holder 12 so that at least one first reel 1 is in at least one operative winding position of a bobbin 5. In particular, the holder 12 comprises two flanges 14 (each figure showing only one of the two flanges) and each reel 1-4 is supported between the two flanges 14 of the holder 12. By rotating the holder 12, the reels 1-4 move among different operative positions described in more detail hereinafter in the present description.

(9) The winding machine 10 further comprises a contact roll 15a adapted to cooperate with a first reel 1 at an operative winding position, and an accompanying roll 15b adapted to cooperate with the above said reel, during rotation of the reel holder in order to bring the reel 1 from the operative winding position to an unloading operative position (position taken by the reel 1 shown in FIG. 1 as a result of a counterclockwise 90 rotation of the reel holder 12).

(10) The contact roll 15a and the accompanying roll 15b are respectively coupled with a first operating arm 16a and a second operating arm 16b both rotatable around respective rotation axes 17a, 17b parallel to the rotation axis of the bobbin. Preferably, the rotation axes 17a, 17b of the operating arms 16a, 16b and the rotation axis of the bobbin 5 are parallel to the rotation axis 13 of the reel holder 12. The operating arm 16a, 16b are rotated by means of electric actuators 18a, 18b.

(11) Preferably, the electric actuators 18a, 18b are of the linear type and comprise preferably brushless electric motors 19a, 19b and each comprises a linear element, for example operating bars 20a, 20b coupled with the respective electric motors 19a, 19b by a coupling that converts the rotary motion of the electric motor into a linear motion, for example by a screw/nut thread coupling. The rotation of the electric motors 19a, 19b in one way or the other causes the operating bars 20a, 20b to be moved forward or backward. The first operating arm 16a and the second operating arm 16b are coupled with a first electric actuator 18a and a second electric actuator 18b, respectively. In particular, each operating bar 20a, 20b of the respective electric actuator 18a, 18b is constrained to a respective operating arm 16a, 16b.

(12) By means of the electric actuators it is therefore possible to move the rolls 15a, 15b between at least one proximal contacting position wherein it contacts the bobbin being wound and at least one distal position from the bobbin.

(13) In particular, the winding machine 10 comprises a circuit providing the power supply 21 to the electric actuators 18a, 18b and a logic control unit 22 adapted to adjust the current output from the electric power circuit 21 to the electric actuators 18a, 18b. The logic control unit 22 selectively drives the electric actuators 18a, 18b by adjusting the supply power provided by the power circuit 22 to each electric actuator 18a, 18b. The current can be adjusted in several ways known per se in the art, for example by means of PWM regulators or similar.

(14) The winding machine 10 further comprises means 23 for detecting the current absorbed by the electric actuators 18a, 18b. The means 23 for detecting the absorbed current can comprise for example two amperometers 23a, 23b (for example connected to the electric power circuit 21) used by the logic control unit 22 to determine the current absorbed by the respective electric actuators 18a, 18b.

(15) In this way, the logic control unit 22 can adjust the current output from the electric power circuit 21 depending on the current absorbed by the electric actuators. In particular, the logic control unit 22 adjusts the supply current provided to the electric actuators 18a, 18b in order to generate a specific torque adapted to move the operating arms 16a, 16b and, therefore, the rolls 15a, 15b depending on the detected current absorption. In this way the logic control unit 22 adjusts the supply current provided to the electric actuators 18a 18b so that at least the contact roll 15a applies a predetermined pressure to the bobbin 5 being wound. The current absorption detected by means of the amperometers 23a, 23b is a measure indicating the pressure applied by the corresponding contact roll 15a to the bobbin 5 being wound. Therefore, the present solution allows the supply current provided to the electric actuators 18a, 18b to be feedback controlled so that the rolls 15a, 15b apply to the bobbin 5 a predetermined pressure, for example a constant pressure, during the film winding through the whole winding step, thereby preventing the formation of air bubbles among the layers of wound film.

(16) The winding machine 10 further comprises means 24 for detecting the position of the rolls 15a, 15b with respect to the bobbin 5 being wound. In the embodiment shown in FIGS. 1-6, the electric actuators 18a, 18b are provided with absolute encoders 24a, 24b allowing the logic control unit 22 to detect the number of revolutions made by the respective electric motor 19a, 19b and to determine the position of the rolls 15a, 15b with respect to the bobbin 5.

(17) However, in additional embodiments position sensors can also be provided, for example optic sensors allowing the logic control unit 22 to determine the position of the rolls 15a, 15b with respect to the bobbin 5.

(18) The logic control unit 22 adjusts the current output from the power circuit 21 to the electric actuators 18a, 18b based on the position detected by means of the absolute encoders 24a, 24b (or generally by the means 24 for detecting the position of the rolls) in order to bring the rolls 15a, 15b to specific predetermined positions depending on the kind of bobbin to be produced.

(19) FIG. 2 shows the winding machine 10 while operating, when a first reel 1 is in a first operative winding position. In this state, the contact roll 15a is in a first proximal contacting position wherein it contacts the bobbin 5 being wound. The contact roll 15a is rotated by an electric motor 25a coupled with the contact roll 15a by means of drive belts. The logic control unit 22 adjusts the current output from the power circuit 21 to the first electric actuator 18a depending on the current absorbed which is detected by the ammeter 23a, in order to apply a given pressure to the film 6 being wound on the bobbin 5.

(20) The contact roll 15a is moved between a first proximal contacting position and at least one second proximal contacting position; as the diameter of the bobbin 5 increases, the roll 15a is moved away from the bobbin 5 always keeping it in contact with the latter. The logic control unit 22 determines the position of the contact roll 15a with respect to the bobbin 5 being wound by means of the absolute encoder 24a of the first electric actuator 18a. For example, the position of the contact roll 15a can be evaluated in order to determine the diameter reached by the bobbin 5 being wound.

(21) Once the bobbin 5 reaches a predetermined diameter (for example depending on the kind of bobbin to be produced), the reel holder 12 is rotated counterclockwise, for example by about 30, so as to bring the first reel 1 from the first operative winding position shown in FIG. 2 to a second operative winding position shown in FIG. 3. During the rotation of the reel holder 12, the contact roll 15a is kept in contact with the bobbin 5, while the accompanying roll 15b is moved by means of the second electrical actuator 18b and brought to a given distance D from the bobbin 5 being wound (preferably at a distance D of less than one millimeter, more preferably about half a millimeter from the bobbin 5).

(22) FIGS. 2A and 2B show schematically the accompanying roll 15b and the bobbin 5 having two different final diameters. In particular, the bobbin 5 shown in FIG. 2A is of the type having a final diameter minor than the final diameter of the bobbin 5 shown in FIG. 2B.

(23) In both cases, the distance D between the bobbin 5 being wound and the accompanying roll 15b is the same. In other words, the second electric actuator 18b allows to set the distance D independently from the kind of bobbin to be produced. In this way, the positioning of the accompanying roll 15b in contact with the bobbin is carried out in the same way independently from the diameter achieved by the bobbin 5.

(24) The logic control unit 22 determines the position of the second roll 15b by means of the second absolute encoder 24b and adjusts the supply current to the second electric actuator 18b by means of a feedback control so that the accompanying roll 15b reaches a given position detected by means of the encoder 24b, at a specific distance D from the bobbin 5.

(25) The accompanying roll 15b is moved by the electric actuator 18b depending on the position the contact roll 15a has taken, detected by the encoder 24a. The logic control unit 22 can use the position of the contact roll 15a (indicating the size of the diameter of the bobbin 5, for example when the reel 1 is in the second winding position) for obtaining the position to be reached by the accompanying roll 15b so that the latter is positioned at a given distance D from the bobbin 5.

(26) Then, the accompanying roll 15b is brought into contact with the bobbin 5 and at the same time the contact roll 15a is brought to a distal position from the bobbin 5. The rolls 15a, 15b simultaneously contact the bobbin 5 being wound for a split second (typically of the order of a millisecond).

(27) The logic control unit 22 adjusts the supply current to be provided to the second electric actuator 18b based on the current absorption detected by the ammeter 23b so that the accompanying roll 15b keeps applying a predetermined pressure on the bobbin (for example the same pressure previously applied by the contact roll 15a). Also the accompanying roll 15b is rotated by a similar electric motor 25b coupled to the roll 15b by means of a drive belt. In this way the first reel 1 keeps winding at the same rotation speed of the contact roll 15a.

(28) Subsequently, the reel holder 12 rotates more 60 counterclockwise to bring the first reel 1 to an operative unloading position (as shown in FIG. 4). During the rotation of the reel holder 12, the accompanying roll 15b is kept in contact with the bobbin 5 so as to apply a similar pressure value on the film 6 being wound around the bobbin 5.

(29) At the same time, a second reel 2 having a new core 7 previously loaded thereon is rotated by a threading-up electric motor (not shown in figures) arranged behind the flange 14 and coupled with the second reel 2 by means of a magnetic coupling.

(30) Preferably, the threading-up operation is carried out during the rotation of the holder 12 to bring the second reel 2 to the operative winding position (while the first reel 1 is brought to the unloading position). In particular, the threading-up electric motor is provided with an electromagnet for coaxially coupling with the second reel 2. During rotation of the holder 12 the threading-up electric motor is integrally moved with the holder 12 so that the electromagnet is still coaxial to the second reel 2. The electromagnet transmits the rotary motion of the threading-up electric motor to the second reel 2, without any contact among the parts, so as to cause the second reel 2 to have a rotation speed close to that of the contact roll 15a.

(31) Once the second reel 2 reaches the operative winding position (as shown in FIG. 4), the contact roll 15a is moved by means of the first electric actuator 18a and brought in contact with the film 6 so that the film 6 is pressed against the core 7 loaded on the second reel 2. Then, the threading-up motor is moved in the opposite way to be brought back to the starting position (i.e. the diametrically opposite position with respect to the unloading position of the bobbin).

(32) FIG. 5 shows the cutting step of the film 6 by means of a blade 8 coupled with a respective operating arm 9 rotatable around a rotation axis 30 parallel to the rotation axis 13 of the holder 12. As a result of the cut the portion of the film upstream of the cut, with respect to the sliding direction of the film 6, begins to wind around the core 7 loaded on the second reel 2 and the contact roll 15a is moved by means of the first electric actuator 18a between a first proximal contacting position and at least one second proximal contacting position for applying a predetermined pressure on the film 6 being wound, in a manner similar to that previously described for the first reel 1 in the winding position shown in FIG. 2.

(33) The portion of the film downstream of the cut, with respect to the sliding direction of the film 6, keeps on winding around the bobbin 5 loaded on the first reel 1 in an operative unloading position with the accompanying roll 15b being kept in a contact position wherein it contacts the bobbin until the latter is finished.

(34) Once the film portion downstream of the cut is completely wound around the bobbin 5, the accompanying roll 15b is brought by means of the second electric actuator 18b to a distal position from the bobbin 5 to allow the finished bobbin 5 to be unloaded from the first reel 1 in an unloading position.

(35) After detaching the accompanying roll 15b from the finished bobbin 5, the bobbin 5 keeps on rotating by inertia. In order to speed up the unloading of the bobbin 5, the winding machine 10 further comprises a brake, for example of the electromagnetic type, to brake the rotation of the first reel 1 in the unloading position. Preferably, the magnetic brake (not shown in figures) is positioned behind the flange 14 at the unloading position of the bobbin. The electromagnetic brake comprises an electromagnet which, when activated, brakes until stopping the first reel 1 having the finished bobbin loaded thereon, thereby generating parasitic currents by electromagnetic induction, as known per se in the art.

(36) Once the reel 1 carrying the finished bobbin has been stopped, then the unloading step of the bobbin follows (shown in FIG. 6). The bobbin 5 is pulled out of the reel 1 by means of a mechanical arm 31 which is slid along the reel 1. In particular, the bobbin 5 is passed through a hollow (not illustrated) in one of the two flanges 14 and then unloaded onto a platform positioned at a certain height from the bobbin 5, preferably flush with the finished bobbin 5, so as to prevent the bobbin 5 from being bumped while unloaded from the reel 1. The height at which the platform is positioned is calculated depending on the kind of produced bobbin, i.e. depending on the diameter reached by the bobbin at the end of the winding, positioning it so as to allow the reel and bobbin to be mutually extracted from one another. Therefore, the bobbins can be removed from the winding machine through a belt or roll conveyor that takes away the finished bobbins.

(37) At the same time of the unloading step of the finished bobbin, a new core 7 is loaded onto a third reel 3 positioned 90 from the unloading position (in a position diametrically opposite to the operative winding position). By means of an additional mechanical arm 32, the new core 7 is fitted around the third reel 3 in a way similar to the unloading step of the finished bobbin 5 from the first reel 1. In particular, the new core 7 is fitted on the third reel 3 by passing it through a further hollow (not shown) in one of the two flanges 14.

(38) The fourth reel 4, arranged in the position diametrically opposite to the unloading position, carries a core 7 which was loaded during the step of unloading the finished bobbin and loading a new core of the previous cycle.

(39) At the end of the step of unloading the finished bobbin and loading a new core, the arrangement shown in FIG. 2 is back again and the steps of the method are repeated to implement a new cycle.

(40) Although not specifically shown in figures, the reels 1-4 can be of the expandable type, for example mechanically driven, so as to be able to accommodate cores having different diameters. Moreover, although a single core 7 has been referred to for the sake of simplicity, it is also possible that two or more cores are loaded at the same time on the same reel depending on the size of the bobbins to be simultaneously wound.

(41) FIG. 7 is a view similar to that of FIG. 1, but taken from the opposite side. The threading-up electric motor is indicated by the reference number 50 and the electromagnetic brake is indicated by the reference number 60; a piston 55 moves the threading-up electric motor 50 from a resting position (that shown in new FIG. 7) to an operative position in which the axis of the threading-up electric motor 50 is aligned with the second reel 2 and can be magnetically coupled to the same.

(42) FIG. 8 shows the threading-up electric motor 50 having a motor 51 and an electromagnet 53 to perform the magnetic coupling with the second reel 2;

(43) FIG. 9 shows a lateral view of the electromagnetic brake 60 consisting of an electric motor 61 and an electromagnetic 62. The electromagnetic brake 60 is slidingly mounted on a rail system 63 and moved back and forth by means of a piston 64.