EP3027404B1

EP3027404B1 - A method for the production of plastic bags by means of the non continuous advancement of a continuous plastic strip and relative machinery

Info

Publication number: EP3027404B1
Application number: EP14741670.5A
Authority: EP
Inventors: Luciano Conti
Original assignee: Amutec SRL
Current assignee: Amutec SRL
Priority date: 2013-08-01
Filing date: 2014-06-05
Publication date: 2017-05-17
Anticipated expiration: 2034-06-05
Also published as: WO2015015327A1; DK3027404T3; ITFI20130180A1; EP3027404A1; ES2629731T3

Description

Technical field

The present invention concerns the technical field relative to the machineries of the "start and stop" type, and relative method, for the production of rolls of plastic bags starting from a continuous strip.
In particular, the invention refers to an innovative machinery of the "start and stop" type, and relative method, which is able to realize the die-cutting of the bag, the welding and the subsequent removal of the die-cutting, guaranteeing a very precise subsequent winding of the strip and reducing to the minimum the risks of incidental tears.

Background art

Machineries for the production of plastic bags have long been known (cf. US 2006/045393 ).
In accordance with the known art, an unwinding section is foreseen through which a reel in plastic material is unrolled, which will form the bags. Through specific cutting sections, the continuous strip is subdivided into one or more strips, or tracks, which, each one of them, constitutes the roll of bags that wants to be produced. In that case, we speak of a multiple-track machine, track being meant as the number of strips worked. The strips pass onto a welding section which operates a closure of the strip in such a way as to close the bottom of a bag and the top of the preceding or subsequent bag. The operation of die-cutting is further foreseen, which in fact foresees the realization of an etched closed section, for example with saw-tooth and/or continuous blades, which is thus removed. In this way, following the removal of the die-cutting (also called patch in technical jargon) the handles and the mouth of the bag are formed.
Such an operation, described above in a very general manner, can be made with machineries of the "start and stop" type or with continuous machineries, or in which the strip is never stopped. The two big types of machines described above are significantly different between them structurally since they work according to two significantly different and diametrically opposed concepts. In the case of the start and stop machine, the strip is stopped when, for example, a die-cutting and/or welding work has to be made on it. The great advantage is that the working precision is high and there is no need of particular synchronization systems. Obviously, the yield of the product is generally a bit lower. On the other hand, the continuous machines, that is the machines in which the strip advances without ever being stopped, have a greater yield but are much more complex structurally since they have to include complex synchronization systems and a controller is necessary that varies, during the advancement of the strip, the tensioning following the formation of the welding (in particular the tensioning has to be lowered to avoid incidental tears on the welding line). Moreover, the apparatus that physically operate the welding and/or the die-cutting are completely different from those used in machineries of the "start and stop" type since, while in the "start/stop" machineries a translation is enough towards the underlying "still" strip, the second machineries have to be capable also of "following" the strip that translates and contextually explicate the working (welding and/or die-cutting).
A machine of the start/stop type is, for example, described in Italian patent application MI2009A000430 in the name of MOBERT S.R.L.
The application describes a machine in which there is a single section provided with a welding bar and with a die-cutting bar. The die-cutting bar is in fact a bar translating vertically towards the underlying strip and that mounts fixed blades which cut a closed area of strip which, when removed, generates the formation of the handles and the mouth of the bag. In the same way, the welding bar is a bar that translates towards the underlying strip and that mounts a head that operates the welding of the strip in such a way as to form the top of a bag and the bottom of the subsequent strip.
When the continuous strip arrives to the die-cutting and welding section, the strip is "stopped" in such a way that both the welding bar and the die-cutting bar can be lowered on the strip so as to create the patch (that is the die-cutting) and the welding that forms the bottom of a bag and the top of the subsequent or preceding one.
The stopping system of the strip foresees a carriage on which passage rolls of the strip are mounted. The concept is that of making the carriage translate in the direction opposite to the advancement of the strip and with the same speed. In this way, the absolute speed of the strip with respect to the die-cutting and to the welding machine is null, even if the strip is fed in origin in continuous.
Having said that, said patent describes the removal of the die-cutting through an aspiration bell placed exactly under the die-cutting itself. In such a manner, as soon as the die-cutting cuts-out the die-cutting area in the strip, it is right afterwards sucked up and removed by the underlying bell.
The technical problem of such a solution is that in exit from said die-cutting/welding section, the strip has to make a significant path (also several meters) before arriving to its winding section where the track/s is/are wound for the formation of the rolls, for example around winding cores. The continuous strip in exit from the welding/die-cutting section now lacks an internal area constituting the patch removed. In that sense, according to the overall tensioning of the strip, it can deform, for example get squeezed and diminish its width, risking of affecting the subsequent winding. In most cases, therefore, the winding does not take place correctly and rolls of strip are obtained that have to be discarded. Moreover, there is the risk of incidental tear along the transversal pre-cutting or tearing line precisely because the support of the patch previously removed is missing.

Disclosure of invention

It is therefore the aim of the present invention to provide a machinery of the start/stop type, and relative method, for the production of plastic bag rolls, which solves at least in part said technical inconveniences.
In particular, it is the aim of the present invention to provide a machinery, and relative method, in which the removal of the die-cutting is such as not to cause subsequent winding problems of the strip or incidental tears along the pre-cutting line, thus reducing significantly also the waste of product.
These and other aims are therefore reached with the present machinery, and relative method, for the working of a continuous strip (500) in plastic for the formation of bag rolls, in accordance with claim 1.
The machinery (250, 260) comprises:

A die-cutting station (251), forming a passage for the feeding of the continuous strip, and comprising at least a bar (251), mobile towards the passage of the strip (500) and provided with one or more blades configured to create a die-cutting area (102) on the strip;
A welding station (252) forming a passage for the feeding of the continuous strip and comprising at least a welding bar (252), mobile towards the passage of the strip and configured to operate a welding on the strip;
Means (300) to stop the feeding of the strip at least in correspondence of the die-cutting station and at least in correspondence of the welding station.

In accordance with the invention, the blades are configured in such a way that the die-cutting area (102) that can be obtained on the strip results delimited, at least in part, with lines (105, 105', 107) constituted by segments of continuous material with the strip at intervals with segments with no material, in such a way that the die-cutting realized remains united to the strip in exit by said stations.
In this way, during the advancement of the strip towards the subsequent winding section, the risks of deformation of the material and of incidental tears are reduced to the minimum since, in fact, the strip is still complete.
It is therefore foreseen a subsequent section (260) of removal of the die-cutting (102) which, in accordance with the invention, is placed downstream of said die-cutting station (251) and of the welding station (252).
In this way, the strip can be kept complete until, almost arriving at the winding station, the removal of the patch is foreseen.
Advantageously, the blades of the die-cutting station (251) can be dented in such a way that all the lines (105, 105', 107) delimiting the die-cutting area result constituted by segments of material coherent with the strip at intervals with segments with no material.
Advantageously, the welding station (252) and the die-cutting station (251) can be arranged on a same welding/die-cutting section (250).
Advantageously, both the welding bar (252) of the welding station and the die-cutting bar (251) of the die-cutting station are translatable vertically towards the feeding path of the strip.
Advantageously, the welding bar (252) of the welding station and the die-cutting bar (251) of the die-cutting station are controlled in such a way as to translate contemporaneously.
Advantageously, the distance between the welding station and the die-cutting station is adjustable at different distances.
This allows to work different formats easily.
Advantageously, the section (260) of removal of the die-cutting (102) comprises at least two rolls (264, 265) that are counter-rotating and cooperating with a plurality of fingers (262) reciprocable towards said rolls in such a way as to push the die-cutting area (102) between the two counter-rotating rolls.
In this way, the two rolls grasp the patch and tear it away.
Advantageously, a pulling device (700) is further foreseen placed downstream of the section (260) of removal of the die-cutting and in entry to a winding section.
Advantageously, a controller is further foreseen, programmed in such a way that in the segment of strip comprised between said pulling device (700) and said section (260) of removal of the die-cutting a single pre-cutting line or no pre-cutting line is present.
This solution has the advantage of reducing to the minimum the risks of incidental tear, even having a pulling that facilitates the advancement of the strip into the winding section with the correct tensioning value.
It is also here described a method for working a continuous strip (500) in plastic for the formation of rolls of bags and comprising the operations of:

Feeding of the strip towards a die-cutting station (251) and a welding station (252) and realization of an area (102) of die-cutting and of a welding (104) on the strip, said die-cutting and welding phase being made with the strip which results stopped at least with respect to the welding station and to the die-cutting station.

In accordance with the invention, the operation of formation of the die-cutting is such that the die-cutting area (102) obtained on the strip results delimited, at least in part, with continuous lines (105, 105', 107) of material at intervals with segments with no material, in such a way that the die-cutting remains united to the strip. Moreover, a subsequent phase of removal of the die-cutting in a section (260) of removal of the die-cutting (102) is foreseen, which is placed downstream of said station of formation of the die-cutting and of the welding station.

Brief description of drawings

Further features and advantages of the present machine, and relative method, according to the invention, will result clearer with the description that follows of some of its embodiments, made to illustrate but not to limit, with reference to the annexed drawings, wherein:

Figure 1 shows a portion of strip and the workings made on it. In particular, the following are shown in succession: the formation of the die-cutting 102 in phase a), the subsequent welding positioned between the transversal tearing line 103 of the strip in phase b) and, last, the removal of the die-cutting 102 in phase c). It is noted that in phase b the die-cutting is upstream of the pre-cutting line 103 with respect to the direction of advancement A of the strip;
Figure 1_Bis introduces a further working solution in which the die-cutting takes place in phase a). The subsequent phase b) realizes the welding that, contrary to figure 1, will be positioned downstream of the tearing line 103, always according to the direction of advancement A of the strip. In this way, unlike the solution of figure 1, the final roll obtained will unroll, in use, starting from the bottom of the bag and not from the handle as per figure 1. This working solution is easily obtainable by adjusting appropriately the distances between the welding bar and the die-cutting one;
Figure 1_A_Bis shows the same strip of figure 1 which is worked by inverting physically the position of the die-cutting station with that of welding. In particular, the figure shows phase a) of formation of the two welding lines upstream and downstream of the tearing or pre-cutting line 103, the formation of the die-cutting in phase b) and, last, the removal of the die-cutting in phase c;
Figure 2 is an overall lateral view of the production line;
Figure 3 shows a detail of the single die-cutting and welding section;
Figure 4 shows an example of a portion of strip worked in accordance with the section of figure 4;
Figures 5 and 6 show schematically an example a system used to annul the sliding speed of the strip with respect to the welding/die-cutting section at the moment in which it is necessary to operate said workings;
Figure 7 extrapolates in a frontal view the die-cutting and the welding station;
Figure 8 shows an axonometric view of the welding/die-cutting section and highlights the welding and the die-cutting station;
Figure 9 and figure 10 show two axonometric views of the subsequent section used for the removal of the patch;
Figure 11 shows a view in section always relative to the section of removal of the patch and highlights a subsequent pull 700 placed at the entry of a winding section of the strip.

Description of a preferred embodiment

Figure 1 describes a strip 100 for the formation of plastic bag rolls.
The figure highlights an arrow A that is indicative of a possible direction of segment or feeding of said strip in a machinery described below, during its working phase. In this way, with reference to the strip represented, it is possible to highlight a working phase a) in which the formation of the die-cutting 102 takes place. Subsequently, the die-cutting 102 formed, through the sliding of the strip, passes onto the welding station that forms the transversal tearing line 103 and the two welding lines 104, upstream and downstream of the tearing line 103 (phase b). Subsequently, in the last phase c, the strip passes onto a specific removal section of the die-cutting 102 and that, as highlighted always in figure 1, determines the formation of the handles 110 and creates the mouth 115 of the bag.
The die-cutting is formed by an area delimited by lines. It is clear that the die-cutting can have any form. For example, in a non-limiting way, the die-cutting of figure 1 is formed by two longitudinal lines 107 and by two transversal lines 105 and 105'.
The transversal line 105' further coincides with the tearing line 103.
The lines delimiting the die-cutting are, in accordance with the present invention, tearing lines formed not by a continuous cut but rather, as always shown in figure 1, by continuous lines coherent with the strip and alternated at cut-out segments. As clarified below, the die-cutting thus described is therefore obtainable with a dented blade that reproduces the form of the die-cutting (that is more or less a square-shaped closed blade in the case of figure 1 or other forms) and which is lowered on the strip in order to etch it. The teeth penetrate in the strip, holing it in points to which continuous segments of material follow. The teeth obviously penetrate through the entire thickness of the strip. Alternatively, the blade can also be smooth and interrupted by transversal cuts.
As clarified below, the realization of a die-cutting, entirely delimited by lines constituted of continuous material with the strip and interrupted by segments with no material, has the advantage of keeping the patch united to the rest of the strip and allowing the removal thereof in a subsequent section placed downstream of the stations that operate the welding and the die-cutting. In particular, said removal section of the die-cutting is upstream of a winding station and above all placed as near as possible to the same winding station of the strip. In this way, during the course that goes from the section of formation of the patch to the winding station, the deformations of the strip are reduced to the minimum and a better winding is therefore guaranteed. This is because such a segment is in fact crossed with the strip still entire, that is not lacking the patch as in the known art described. Also the risk of incidental tear along the pre-cutting lines 103 is now very reduced.
Although the preferred embodiment of the invention describes a die-cutting (or patch) limited by "dented" sides (that is in which the continuous material alternates with holes or segments lacking material), it would also be possible a solution in which at least two opposed sides, or anyway at least a part of the entire die-cutting (for example, in the case of circular die-cutting) are "dented" and the remaining ones are instead constituted by a net cut. In this way, the patch continuous to remain united to the strip even if its contribution to balance the tensioning acting on the strip, and therefore its deformation, is reduced with respect to the preceding case.
Having said that, figure 2, in a non-limiting manner, shows an overall view of a production line.
In particular, an unwinding station 200 is highlighted, through which a reel 210 of plastic strip is unwound along the production line.
The strip is fed through the other sections placed in succession and through which the strip is subdivided into one or more tracks, each one forming the bag rolls.
In particular, the sections 220, 230 and 240 are highlighted, which are respectively the cutting and welding group that forms the tracks starting from the initial reel, the bellows group and an additional pull for controlling the tension of the strip. Such sections are obviously well known in the state of the art and for that purpose will not be further described here.
Figure 3 highlights the section 250, object of the invention, which is afterwards described in detail and in which the two working phases a) and b) represented in figure 1 and 1_Bis take place.
As said, for obtaining the working as per figure 1_A_Bis it is instead necessary to invert the positions of the welding and die-cutting station.
Such a section, shown in an expanded way in figure 3, foresees a die-cutting station 251 and a welding station 252. The figure shows for clarity purposes also the direction A of advancement of the strip for coherence with figure 1 and 1_Bis.
The strip that passes, and that is described in figure 1 and 1 Bis, is therefore stopped in the station 250 so that the die-cutting and the welding can be made on it in the segment comprised between the die-cutting and welding stations, obtaining a working as that of figure 4 (the case of figure 1 and of figure 1_Bis). The formation of the welding and die-cutting takes place through the lowering of the two welding and die-cutting bars when the strip is stopped under said stations. After the formation of the welding and the die-cutting the strip starts again, advancing of a pre-defined quantity, in such a way as to stop again and repeat cyclically the operation described.
In accordance with a preferred embodiment of functioning of such a section, the operations of welding and die-cutting take place contextually, that is in a single phase. In particular, as clarified below, the strip is stopped in correspondence of said section 250 and contextually the lowering of the welding and of the die-cutting bar takes place that mounts the blade that forms the die-cutting, realizing in a single phase both workings, as indicated in figure 4. In fact, phases a) and b) take place contextually.
In this way, there is the advantage of speeding up the operation of formation of the welding and of the die-cutting in a machine that operates with the start/stop modality.
Obviously, both the welding bar and the die-cutting bar are controlled with independent engines and controlled and managed through a specific software. In that sense, nothing would impede to operate at different times the welding bar and the die-cutting bar, for example first the die-cutting and then the welding or vice-versa.
It is also noted that, in the case of contextual lowering of the welding bar and of the die-cutting bar, actually the lowering of the welding bar anticipates of some fraction of a second the lowering of the die-cutting. This is because the welding bar needs some instants of contact with the underlying strip for realizing the welding, unlike the blade that immediately etches the strip. In that sense, in the present patent application, in the term contextual lowering of welding bar and of die-cutting bar is obviously included also the case in which said lowerings do not start exactly in the same instant but are somehow shifted between them of some thousandth of a second.
As already said, the welding and die-cutting section operates in "start and stop" conditions in the sense that the strip is stopped when in entry to the section 250. The system that allows the stop of the strip is arranged under the die-cutting 251 and welding 252 stations in the section 250 that foresees them.
The system, even if long known, is described in detail in figure 5 and in figure 6.
Figure 5 and figure 6 extrapolate the carriage 300 on which two rolls 310 of strip passage 500 are mounted. The carriage 300, comprising said rolls 310, is therefore rigidly translatable horizontally with respect to the frame of the section 250 where it is mounted. For example, figure 3 shows with number 255 guiding rolls inserted into loops obtained in the frame and that serve to allow the carriage 300 to translate forward and backward on guides controlled by belts. Figure 5 and figure 6 are simplified schematizations since they schematize a single welding station 251 but, obviously, it is the same in the case of the presence also of the die-cutting station or vice-versa, as indicated in figure 3.
In accordance with the invention, when it is necessary to operate the welding and the die-cutting, the carriage 300 translates in the opposite direction with respect to the advancement direction of the strip 500 and at the same speed in module. The result will be that of the absolute speed of the strip, with respect to the overlying welding and die-cutting station, being null. In such a way, in fact, the strip is kept still, although the feeding is upstream continuous, during the operation of lowering of the welding bar and die-cutting bar. That allows to obtain a precise welding and die-cutting. At the end of the operation the carriage translates in the opposite direction, going back to the initial configuration of figure 5 and allowing the strip to recover the lost segment. The strip can now advance again normally until the next block. The operation is repeated cyclically at each die-cutting/welding to be operated.
The contextual lowering of the welding and die-cutting bar has therefore also the advantage of avoiding the need to operate the carriage 300 twice consecutively, that is one for operating the welding and subsequently for operating the die-cutting or vice-versa.
Continuing with the structural description of the invention, figure 7 and figure 8 describe in detail the die-cutting section and that of welding.
The die-cutting station comprises a bar 251 translatable vertically towards the strip (see direction of arrow in figure 7) and that mounts a blade, preferably a single blade, conformed according to the profile of the patch 102 to be realized. The blade is dented or continuous and is applicable to the bar in a removable way with well-known fixing systems, such as fixing screws. The blade can be composed also of more than one piece of separate blades.
The welding station 252 is instead formed by a welding bar, also translatable vertically towards the bottom and synchronized with the lowering of the die-cutting bar through independent engines.
The welding bar is also adjustable in distance with respect to the die-cutting bar, and vice-versa, in such a way as to adjust different measures of format of the bag and/or different workings (see figure 1 and figure 1_bis). To that aim, a sliding binary is foreseen on which the welding bar and/or the die-cutting bar is made to slide to then fix the selected position, for example with blocking vices, screws and the like.
The same welding and die-cutting bars can be disassembled and re-assembled in the inverted position (that is one in the place of the other one) in such a way as to obtain a working as that of figure 1_A_Bis.
Said blades that form the die-cutting and the transversal tearing line 103 can be mounted entirely in the die-cutting section, or in part in the die-cutting section and in part in the welding section. For example, the transversal segments of blade that serve to complete the cut 103 of figure 1, that is the segment that goes from the ends of the cut 105' to the end of the strip, are for example applicable to the welding bar. However, the solution with all the blades in the die-cutting section is preferable since it is much more precise because the strip, when it arrives at the welding station, could have moved either laterally or longitudinally, therefore affecting the real position of the final pre-cutting.
As shown in figure 3 the section 250 comprises contextually both the station of formation of the die-cutting 251 and the station of welding 252. This solution simplifies significantly the structure of the machine and its compactness and allows, with a single system 300, to block the strip under said stations to make welding and die-cutting in a single phase.
Going on with the structural description of the invention, figure 9 shows the subsequent station 260 of removal of the die-cutting.
Such a station foresees a bar 261 on which a plurality of fingers 262 is mounted. The bar is hinged from its two ends 263 (figure 9 displays only one of these two ends) to the frame of the section 260. The hinging is such that the bar can rotate of a certain angulation around its axis in one direction and in the opposite one. To that aim, a specific engine is foreseen (not shown in the figure for simplicity purposes) that controls such a rotation or oscillation around the axis. In such a way, said fingers 262 are pulled in rotation with respect to the axis of the bar 261 on which they are fixed, therefore lifting and lowering their ends. The fingers are formed in such a way as to insert at least their ends into two counter-rotating rolls, that is the rolls 264 and 265, better highlighted in figure 10. In particular, the roll 264 foresees specific grooves that allow the insertion of the finger without physical contact between the rotating roll and the finger itself.
As highlighted in figure 11, the strip passes under the fingers 262 which are controlled in such a way as to lower in correspondence of the reaching of position of the patch below the fingers and allow the removal thereof through the two counter-rotating rolls. The rolls thus grasp a portion of the patch pushed by the fingers and remove it, pulling it away along the pre-cutting lines.
The fingers are synchronized with the passage of the patches obtained in the strip during the sliding of the strip.
Below said counter-rotating rolls a collection bell 600 is foreseen through which the patches removed are sucked up (through a suction pump) and addressed with specific conduit towards a collection area.
Always as shown in figure 11, downstream of said section of removal of the die-cutting, and upstream of the winding section, a pulling device 700 is present comprising two counter-rotating rolls (701, 702) and that facilitate the pull of the strip passing between them.
The roll 702 of such a pull is the motorized one, while the other one 701 is the pulled one, and both facilitate the pull until the subsequent winding station.
During the working described, the overall tensioning state in the line, in particular in the welding and die-cutting section, is a low tension value. This has the advantage of reducing the risks of incidental tear and deformation with consequent weakening of the welding.
The motorization that controls one of the two counter-rotating rolls (264, 265) of removal of the patch is such that the rotation speed of such a roll is greater with respect to the pulling roll 702 of the strip. This is because it is possible in this way to make a fast and sudden tear of the patch along its pre-cutting lines.
It is to be noted that the present machine further foresees a controller programmed with a specific software in such a way that the operation of the fingers starts when the patch is below the fingers. Complex mechanical systems of individuation of the position of the patch (for example, photocells or sparks systems) are therefore not implemented, but the software makes a calculation based on the advancement speed of the strip (V) and on the format worked, in particular the length of each bag and therefore the distance between two subsequent transversal lines 103. In this way, the software is able to calculate the moment in which, during the feeding of the strip, it is necessary to fare reciprocate the finger to remove the patch.
Advantageously, although the "useful instants" to remove the patch would be different (that is the interval of time necessary for the patch, which has a certain length, to complete its passage under the finger), the software selects that instant (T) in which no transversal line 103 results inside the segment of path between the rolls (264, 265) of tearing and the pulling section 700, if the format of figure 1_Bis is worked. In the case of the format of figure 1, the software selects that time of operation of the finger in which only a pre-cutting line 103 is present inside between the pull and the tear, that is the tearing line coinciding with a line of the patch to remove. This has the advantage of reducing to the minimum the risks of incidental tear of the strip along the transversal line 103 during the removal of the patch.
In the present description, with the term "start and stop" it is intended, in a general way, a block of the advancement of the strip which can take place contextually in the entire production line or only in a specific section of the line.

Claims

A machinery (250, 260) for working a continuous strip (500) in plastic for the formation of rolls of bags and comprising:
- A die-cutting station (251), forming a passage for the feeding of the continuous strip, and comprising at least a bar (251), mobile towards the passage of the strip (500) and provided with one or more blades configured to create a die-cutting area (102) on the strip;

- A welding station (252) forming a passage for the feeding of the continuous strip and comprising at least a welding bar (252), mobile towards the passage of the strip and configured to operate a welding on the strip;

- Means (300) to stop the feeding of the strip at least in correspondence of the die-cutting station and at least in correspondence of the welding station;
Characterized in that said blades are configured in such a way that the die-cutting area (102) that can be obtained on the strip results delimited, at least in part, with lines (105, 105', 107) constituted by sections of continuous material with the strip at intervals with sections with no material, in such a way that the die-cutting realized remains united to the strip, and wherein a subsequent section (260) of removal of the die-cutting (102) is foreseen, which is placed downstream of said die-cutting station (251) and of the welding station (252).
A machinery, as per claim 1, wherein said blades of the die-cutting station (251) are dented in such a way that all the lines (105, 105', 107) delimiting the die-cutting area result constituted by sections of material coherent with the strip at intervals with sections with no material.
A machinery, as per claim 1 or 2, wherein the welding station (252) and the die-cutting station (251) are arranged on a same welding/die-cutting section (250).
A machinery, as per one or more of the preceding claims, wherein both the welding bar (252) of the welding station and the die-cutting bar (251) of the die-cutting station are translatable vertically towards the feeding path of the strip.
A machinery, as per one or more of the preceding claims, wherein the welding bar (252) of the welding station and the die-cutting bar (251) of the die-cutting station are controlled in such a way as to translate contemporaneously.
A machinery, as per one or more of the preceding claims, wherein the distance between the welding station and the die-cutting station is adjustable at different distances.
A machinery, as per one or more of the preceding claims, wherein the section (260) of removal of the die-cutting (102) comprises at least two rolls (264, 265) counter-rotating and cooperating with a plurality of fingers (262) reciprocable towards said rolls in such a way as to push the area (102) of die-cutting between the two counter-rotating rolls.
A machinery, as per claim 7, wherein a pulling device (700) is further foreseen placed downstream of the section (260) of removal of the die-cutting and in entry to a winding section.
A machinery, as per one or more of the preceding claims, wherein a controller is further foreseen, programmed in such a way that in the segment of strip comprised between said pulling device (700) and said section (260) of removal of the die-cutting a single pre-cutting line or no pre-cutting line is present.
A method for working a continuous strip (500) in plastic for the formation of rolls of bags and comprising the operations of:
- Feeding of the strip towards a die-cutting station (251) and a welding station (252) and realization of an area (102) of die-cutting and of a welding (104) on the strip, said die-cutting and welding phase being made with the strip which results stopped at least with respect to the welding station and to the die-cutting station;
Characterized in that said operation of formation of the die-cutting is such that the die-cutting area (102) obtained on the strip results delimited, at least in part, with continuous lines (105, 105', 107) of material at intervals with segments with no material, in such a way that the die-cutting remains united to the strip, and in which a subsequent phase of removal of the die-cutting in a section (260) of removal of the die-cutting (102) is foreseen, which is placed downstream of said station of formation of the die-cutting and of the welding station.