EP3088339B1

EP3088339B1 - Device and method for the winding of a plurality of rolls of pre-cut bags on a single axis

Info

Publication number: EP3088339B1
Application number: EP16166485.9A
Authority: EP
Inventors: Roberto Trezzi; Maurizio Toniato
Original assignee: Mobert Srl
Current assignee: Mobert Srl
Priority date: 2015-04-30
Filing date: 2016-04-21
Publication date: 2019-06-05
Anticipated expiration: 2036-04-21
Also published as: DK3088339T3; EP3088339A1; ES2741743T3

Description

The object of the present invention is a device and a method of winding on a single axis of a plurality of rolls of pre-cut bags wound on a core.
In the present description "pre-cut bags" refers to plastic film bags both with open mouth, of the refuse collection type, and so-called "shopper" bags, with punched handles, used in particular in the fruit and vegetable sections of supermarkets or any other type of bag in a material also not plastic.
These bags are produced, in a manner in itself known, from flattened tubular films, whereon operations of sealing, optional punching and pre-cutting are performed, in successive phases, in order to facilitate the separation of the bags from the roll during use.
In order to produce several rolls of bags simultaneously, machines with several tracks with several independent winding assemblies, one for each track, are currently used.
This solution of using separate and independent winding assemblies is too costly, due to the fact that the members necessary for the functioning of the machine are multiplied by the number of the tracks, starting from the motor drives of the various assemblies.
Moreover independent winding assemblies do not allow adaptation in a simple manner of the machine to the winding of strips of pre-cut bags of different width.
It is therefore preferable to have a machine with several tracks with a single axis of winding of the various strips of pre-cut bags.
However the different strips of bags being wound on the same axis can be of different thickness or have folds, thus determining different tensions in the different strips of bags in that, on a par with the number of turns of the winding axis, the peripheral speed of winding (and therefore the linear speed of the strip of bags) varies as a function of the diameter of the roll, or rolls of bags are created with different diameter on a par with the number of bags wound.
This entails slackenings of one or more tracks which, winding on the drive rollers, tear due to the lack of any tensioning, making machining impossible if not by using coils of film with extremely narrow thickness tolerances.
Moreover, if after winding the pre-cuts of the bags are not aligned at the end of the roll, it is not possible to detach simultaneously all the bags of the different tracks being machined, thus creating machine stops and manual work in order to match up the tracks. The tracks are not aligned if the diameters of the rolls being wound are different.
This is the reason why few machines with several tracks on a single winding axis have been proposed to date on the international market.
The same Applicant had produced such a machine with several tracks with a single winding axis, without however succeeding in matching up the tracks optimally, i.e. obtaining rolls of the same diameter and with the same number of pre-cut bags, without damaging the product.
Subsequently the Applicant proposed a solution forming the object of the European patent application EP 2759503 , whereby the correction of the tension of each strip of bags is performed by means of the motorisation of a contrast roller resting on the respective roll which, in the case of slackening of the respective strip, is made to rotate at a higher angular speed compared to that of the other rolls, in order to recover this slackening.
It has been noted, however, that this system created folds and slippages of the film during the phase of angular acceleration of the roller and this entailed the production of rolls not properly aligned on the edges and therefore not of good quality.
US 3 934 833 A , which belongs to the technological background of the present invention, discloses a plurality of hysteresis clutch means which are arranged in spaced array to simultaneously transmit torque from a driving mandrel to a plurality of film winding bobbins where the bobbins are of varying widths.
The object of the invention is that of eliminating the disadvantages of the prior art described above, allowing the winding on a single axis of a plurality of rolls of pre-cut bags, compensating automatically and in real time possible differences in diameter between the various rolls, without the risk of damaging the material of the bags being wound.
A further object of the invention is that of allowing this result to be obtained simply and economically.
These objects are achieved by the device and by the method according to the invention which have the features of the appended independent claims 1 and 9.
Advantageous embodiments of the invention are disclosed by the dependent claims.
Substantially, the device for winding on a single axis (A) of a plurality of rolls (R) of pre-cut bags fed in parallel strips or tracks (S) according to the invention, wherein said axis (A) comprises a spindle (60) on which sleeves (62), suitable for receiving the core (80) of the rolls (R) being wound, are mounted by means of free-wheel mechanisms (70), said free-wheel mechanisms (70) being such as to allow the coupling of the spindle (60) with the sleeves (62) in the winding direction only, said device comprising, for each strip (S) of bags, means (40) suitable for detecting the tension of said strip of bags (S) and means (50) apt, when needed, co-operating with the axis (A), to accelerate the winding of the strip (S), said means (50) being controlled by the detecting means (40), when a slackening in the corresponding strip of bags (S) is detected, wherein said means (50) comprise a motorised element (51) placed to the side of the corresponding roll (R), which can be brought into contact with a respective sleeve (62), for making said sleeve (62) and the corresponding roll (R) rotate at an angular speed greater than that of the other rolls on the same axis (A).
Further features of the invention will be made clearer by the following detailed description, referred to a purely non-limiting example thereof, illustrated in the accompanying drawings in which:

Figure 1 is a schematic side view of a device of winding on a single axis of a plurality of rolls of pre-cut bags according to the invention;
Figure 2 is a schematic cross section of the device of Figure 1;
Figure 3 is a schematic view of the axis of winding of the rolls;
Figures 4 and 5 are enlarged views respectively of the left part (shown for convenience in different proportions) and of the central part of the axis of winding of Figure 3;
Figure 6 is an enlarged schematic view of the means suitable for compensating the slackening of a strip of bags.

The device shown in the accompanying Figures 1 and 2 shows the final station of a machine for the production of rolls of bags which, in a manner in itself known, is fed by tubular films of plastic material which, in successive stations placed upstream of the winding station, perform the sealing, the pre-cutting and the optional punching of the tubular films in order to obtain strips of bags to be wound into rolls.
The machine as a whole is to be considered known and therefore will not be described further.
In the case in question the machine is with several tracks, in particular three (see Figure 2), wherein the strips of bags, denoted by S1, S2, S3 in Figure 2 and generically by S in Figure 1, are wound into rolls R on a single winding axis A, whose structure will be described here below. Naturally the number of strips of bags can be different from that indicated.
In the following description the strips of bags S, for the sake of convenience, will also be referred to as tracks or films, given that they are made up of tubular films.
The axis of winding A is carried by the opposite side panels 11, 12 of a carousel 10 rotating around a central axis 13 and supported by intermediate supports mobile along the axis 13 in order to adapt their distance to the width of the roll R to be formed.
In the drawings 21 and 22 instead denote the side panels of the machine.
During the functioning of the machine the carousel 10 is rotated sequentially through 120° in order to bring the winding axis A from a position of winding start P0 to a working position P1 where the roll R is formed and an unloading position P2 where the roll of bags formed is unloaded (Figure 1).
The same layout can be applied also on carousels provided with a different number of stations (2, 4 and over).
Figure 1 shows a roll R in the phase of winding in the position or station P1 and a roll ready to be unloaded in the position P2. When the roll R has reached the diameter set in the work station P1 the strip of bags S is separated in the zone of pre-cutting between P0 and P1 and starts the winding in the position P0, after which the carousel 10 is rotated through 120° so that the roll continues to wind in the work station P1, while the roll formed goes to the unloading station P2.
The above is in any case to be considered known and therefore will not be described in detail.
As described previously, the problem which arises in the winding of several separate strips of bags S on a single winding axis A is that when the latter, made up of tubular films, are rolled, during the overlapping of the various turns different diameters of rolls can be created, due to the different thickness of the material and/or of folds which can be formed on some of the strips of bags S.
Since the peripheral linear speed varies as a function of the diameter of the roll, if the rolls R1, R2, R3 being wound have different diameters, different tensions are determined on the various strips of bags S, with misalignment of the pre-cuts. In fact the axis of winding, being only one, rotates at a single speed, making it impossible to match the linear speeds for the tracks which are found to have a different diameter of the roll.
In order to solve this problem the winding device according to the invention comprises, for each strip of bags S, means 40 suitable for detecting the tension of said strip of bags S and means 50 suitable, if necessary, co-operating with the axis A, for accelerating the winding of the film, bringing the relative rotation speed of the roll to an appropriate value and such that the linear speed of the track itself is in the end equal to that of the others, thus cancelling out the different tension of the tracks.
In the embodiment illustrated in Figure 1, the means of detecting the tension of the strip of bags S are made up of a rocker arm 41 which rests, with a feeler 42, on the strip of bags S, and a sensor 43 which determines the tension of the strip of bags S by detecting the angular position of the rocker arm 41. In the drawing the rocker arm 41 is shown with dotted lines in condition of normal functioning, i.e. with the film S which advances at the right tension, while with continuous lines in a condition of slackening, due to a lesser winding of film on the roll R, therefore with a smaller diameter.
An idle contrast roller 91 carried by a pair of arms 92 pivoted in 93 and held by a piston 94 in contact or abutting with a respective roll being wound R compresses the roll, releasing the air which is formed between the layers of the tubular film S.
The means 50, apt to accelerate the winding of the film, will be described here below.
The axis A, illustrated in Figures 3-5, comprises a spindle 60 which in the example shown is divided into two parts 60', 60" which join centrally at the head by means of two conical ferrules 61. The provision of the spindle in two parts is useful because it facilitates the unloading of the rolls formed, with withdrawal of the two parts from the two side panels of the machine. It is however evident that the spindle can be formed in a single piece and here below in this description, for the sake of convenience, reference will be made to the spindle 60 without further specifying that it is formed in several parts.
Rigid sleeves 62 are mounted on the spindle 60 by means of free-wheel mechanisms 70 in a number equal to the number of the rolls R to be wound, three in this case. It is however clear that the number of sleeves 62 can be varied as a function of the number of rolls R. The free-wheel mechanism is a device in itself known in the art and therefore will not be described further. In practice it allows the coupling of the spindle with the sleeves only in one direction of rotation (that of winding) so that the sleeves, driven to rotate by the spindle, can rotate only in the direction of the winding, if necessary at a speed higher but not lower than that of the spindle. Externally to each free wheel 70, placed at a respective end of a corresponding sleeve 62 between the latter and the spindle 60, an airtight seal 71 is placed.
A respective expandable membrane 63 is placed on each sleeve 62, held in position by means of two locking rings 64 attached to the sleeve by means of screws 65. An airtight OR ring 66 is placed between each ring 64 and the sleeve 62.
An axial channel 67 for feeding compressed air is provided in the spindle 60, wherefrom at least one radial channel 68 branches off at each sleeve 62, wherein at least one hole 69 is provided for the passage of the air which will go to inflate the respective expandable membrane 63 which locks a respective core (80), normally in cardboard, fitted on the sleeve and whereon a respective strip of bags S is wound to form a respective roll R. The aforesaid seals 66 and 71 prevent the release of the air and allow the expandable membrane 63 to be kept inflated during the winding.
The sleeves 62, driven by the respective free-wheel mechanisms 70, all rotate at the same speed as the spindle 60 during the normal winding and are held axially in position by spacers 73 interposed between successive sleeves.
The means 50, apt to accelerate the winding of the film, comprise a motorised element 51 placed to the side of each roller R and can be brought into contact directly or indirectly with the respective sleeve 62.
The element 51 can be a small wheel, or any tangential contact system, such as a friction wheel, a belt, a gear or a contactless magnetic system, or other.
Each motorised element 51 takes the motion from a single motorisation drive motor axis RM driven by a special motor M, which is actuated in the manner to be stated here below. Naturally the motorised elements 51 can be actuated by independent motors.
The motorised element 51 is carried by an arm 52 oscillating around a fulcrum 53 on the axis RM under the action of an actuator 55 in order to be carried from a position detached from the sleeve 62 to a position of contact, direct or indirect, with the sleeve 62.
More particularly, in the illustration shown in the drawings, the actuator 55 comprises a pair of opposite pistons 56 acting in series, so as to arrange the element 51 in three different fixed positions:

A) a position of distancing of the motorised element 51 from the sleeve 62 during the phase of rotation of the rotating carousel, when the pistons 56 have both exited;
B) a position in proximity of the sleeve 62 but not in contact during the phase of normal winding, when a piston 56 has exited and the other is in retracted position;
C) a position of correction in contact with the sleeve 62, when both the pistons are in retracted position.

Naturally the arrangement with three fixed positions is only an example and offers the advantage of having a fast passage from position B to C when a correction is required.
In the case of use, as motorised element 51, of a friction wheel or belt covered with friction material (e.g. cork), on the sleeve 62 in the zone of contact of the motorised element a rubber ring 57 is added with the aim of increasing the coefficient of friction with the motorised element 51.
When the means 40 detect a slackening of the corresponding strip S, i.e. when the rocker arm 41 is placed for example in the continuous line position illustrated in Figure 1, which, as mentioned, is caused by a reduction in the diameter of the roll of the corresponding track with respect to those of the others, the sensor 43 pilots the motor M which rotates the axis RM and therefore all the motorised rollers 51 at a higher peripheral speed than that of the corresponding film or strip of bags S. Bringing tangentially to the corresponding sleeve 62 the motorised element 51 of the strip of bags which has slackened, there will be an acceleration and therefore an increase in the relative speed of the sleeve 62, which will rotate faster with respect to the spindle 60. In this way the excess film due to the slackening of the corresponding track is recovered by winding it on the roll by means of a higher speed of rotation of the same roll, consequently matching up the tracks.
When the rocker arm 41 returns into the position indicated with dotted lines in Figure 1, indicating that the corresponding strip of bags S has reached the correct degree of tensioning, the distancing of the motorised element 51 from the sleeve 62 and the stop of the motor M are actuated.
Whenever one or more tracks were to present an incorrect tensioning (indicated by the respective detection means 40), the respective correction means 50 will be brought into contact with the respective sleeve 62, producing the recovery of the slackened track.
Considering in fact that: $V = ω \emptyset / 2$

With: V= linear speed of the film (e.g. mm/sec)
ω = speed of rotation of the axis (rad/sec)
Ø= diameter of the roll (mm)

EXAMPLE:

Ø track 1= 50 mm
Ø track 2= 49 mm
Ø track 3= 50 mm
1 axis turn= 2 π radians
10 tums/sec= 10 x 2 π = 62.8 rad/sec
V1= 62.8 x 50/2 = 1570 mm/sec
V2= 62.8 x 49/2 = 1558.6 mm/sec
V3= 62.8 x 50/2 = 1570 mm/sec
As can be noted from the example, the central track 2 finds itself having a roll diameter slightly different from the other two (for the reasons explained previously). This difference with respect to the other two tracks (of a single mm) causes a difference in speed of 31.4 mm/sec (1570-1538.6), i.e. every second the central track loses approximately 32 mm of material with respect to the other two. After a few seconds the central track will have loosened to the point of preventing the functioning of the machine.
From what is described the advantages appear clear of the invention which allows a plurality of rolls of pre-cut bags to be wound on a single axis, maintaining the single strips of bags perfectly matched up.
Naturally the invention is not limited to the particular embodiment previously described and illustrated in the accompanying drawings, but numerous detailed changes may be made thereto, within the reach of the person skilled in the art, without thereby departing from the scope of the invention itself as defined by the appended claims.

Claims

Device for winding on a single axis (A) a plurality of rolls (R) of pre-cut bags fed in parallel tracks or strips (S), wherein said axis (A) comprises a spindle (60) on which sleeves (62), apt to receive the core (80) of the rolls (R) being wound, are mounted by means of free-wheel mechanisms (70), said free-wheel mechanisms (70) being such as to allow the coupling of the spindle (60) with the sleeves (62) in the winding direction only,
said device comprising, for each strip (S) of bags, means (40) suitable for detecting the tension of said strip of bags (S) and means (50) apt to co-operate, when needed, with the axis (A) to accelerate the winding of the strip (S), said means (50) being controlled by the detecting means (40) when a slackening in the corresponding strip of bags (S) is detected,
characterised in that said means (50) comprise a motorised element (51) placed to the side of the corresponding roll (R), which can be brought into contact with the relevant sleeve (62), for making said sleeve (62) and the corresponding roll (R) rotate at an angular speed greater than that of the other rolls on the same axis (A).
Device according to claim 1, characterised in that said motorised element (51) is a small wheel, a friction wheel, a belt, a gear, or the like, or a contactless magnetic system, carried by an arm (52) oscillating around a fulcrum (53) to be brought in tangential contact with said sleeve (62).
Device according to claim 2, characterised in that said fulcrums (53) are located on a single motor drive axis (RM) driven by a motor (M).
Device according to claim 2, characterised in that said motorised elements are driven by independent motors.
Device according to any one of claims 2 to 4, characterised in that said motorised element (51) is driven by an actuator (55) comprising a pair of opposed pistons (56) acting in series, so as to be arranged in three different fixed positions: away from the sleeve (62), in proximity of the sleeve (62) and in contact with the sleeve (62).
Device according to any one of the preceding claims, characterised in that a contrast idle roller (91) is provided in contact with or in abutment with each winding roll (R), said contrast idle roller (91) compressing the roll so as to let out the air formed between the layers of the strip of bags (S).
Device according to any one of the preceding claims, wherein said detecting means (40) comprise a rocker arm (41) with feeler (42) resting on said strip of bags (S) and a sensor (43) which detects the tension of the strip of bags (S) by detecting the angular position of the rocker arm (41).
Device according to any one of the preceding claims, characterised in that said single winding axis (A) is carried by a rotating carousel (10) with at least two stations in order to be moved sequentially from a working position (P1) wherein the rolls (R) are formed, to a position (P2) of unloading of the finished rolls.
Method of winding on a sole axis (A) of a plurality of rolls (R) of pre-cut bags fed in parallel tracks or strips (S), characterised in that it provides the detection of the tension of each strip of bags (S) and, in the case of slackening of a strip (S), the actuation of a motorised element (51) placed to the side of the corresponding roll (R) being formed in proximity of a sleeve (62) carrying the roll (R), to rotate said sleeve (62) and the corresponding roll (R) at an angular speed higher than that of the other rolls on the same axis (A).
Method according to claim 9, characterised in that said motorised elements (51) are actuated by a single motor drive axis (RM) driven by a motor (M).
Method according to claim 9, characterised in that said motorised elements (51) are actuated by independent motors.