FIELD OF THE INVENTION The present invention relates to a device and a method suitable for overlapping or interleaving a plurality of individual plastic bags suitable for the production of coreless rolls or the like items. The individual bags are preferably interleaved with the leading edges of trailing bags overlapping the trailing edges of leading bags.

BACKGROUND OF THE INVENTION

Most usually, rolls of plastic bags are wound into a coreless roll although sometimes bags on cores are desired. The type of bag most typically found on a coreless roll are bags known as trash or garbage bags, freezing bags or other types of bags for storing food. Obviously the before mentioned bags can be of a whole range of sizes and shapes. Consider, for example, bag shapes such as t-shirt shaped and wave-top shaped bags. It is known to provide an interleaving device wherein a leading end of a continuous plastic web or sheet of film with cross seals and perforations at each seal is separated into individual plastic bags and advanced within the device by a feeding section at a first speed followed by an advancing section advancing the leading end of the bag from the feeding section to a receiving section which receives the bags at a second lower speed while a deflection device deflects the trailing end of the bags. US5588644 discloses such a device wherein an air stream directed towards the lower surface of the bags front end in a timed relationship with the deflecting device for forming a loop is used in order to establish the desired overlap. DE1949901, EP869094, EP1266854, US2852256, US3178174 US6131901 and US6494452 all disclose different examples of stacking device for stacking sheets on top of each other. A known problem in the overlapping process is wrinkling of the front or leading end of the bags. This is not desirable as it complicates the commissioning of the bag and gives the consumer the impression that the roll of plastic bags is of a poor quality. BRIEF SUMMARY OF THE INVENTION

The object of the invention is to provide an improved device of the type mentioned above, which allows for high speed manufacturing of rolls and which may be configured to operate so a leading end of a portion of a web or an individual plastic bag is kept smooth while overlapping a trailing end of a downstream portion of web or plastic bag.

Disclosed herein is an interleaving device for overlapping portions of a plastic web with leading ends overlapping trailing ends, for subsequent winding up said overlapped portions as a roll comprising a feeding section comprising a set of feed rolls for advancing a web at a first speed, the feeding section further comprising a set of nip rolls for separating the web into portions, a receiving section for receiving a leading end of said portions at a second lower speed, and an advancing section for advancing the leading end of the portions from the feeding section to the receiving section, the advancing section further comprising a deflection device for deflecting the trailing end of said portions by providing a downwardly oriented force on the trailing end of said portions, wherein the advancing section comprises one or more vacuum belts each having along the length thereof one vacuum section or a plurality of spaced apart vacuum sections, said vacuum section(s) being arranged for holding the leading end of a respective portion. Using a vacuum belt for advancing and guiding the leading end of the portions across an overlapping zone i.e. from a feeding section to a receiving section holds the leading end smoothly towards a surface or parts of or at least the corners of the leading end to one or more surfaces during the overlapping. Thereby are wrinkles in the leading end of the portions avoided.

The attraction force or suction force from the vacuum belt may be sufficient to hold the leading end of the portions either by its own attraction or suction force or in corporation with a upward blowing nozzle or the like urging the leading end of the portions towards the vacuum belt.

The web may be a web of any material. The web may be a plastic web. The portions of the web may be segments of or individual plastic bags. The receiving section may further comprise a smoothening device for smoothening, i.e. reducing wrinkles, of the trailing end of the portions. The smoothening device may be a vacuum plate for attracting a trailing end of said portions. The deflection device may be air nozzles, pistons or the like, providing a downwardly oriented force on the trailing end of the portions. The deflection device may deflect the trailing end of the portions towards the vacuum plate. The vacuum plate may attract the trailing end of downstream portions while the advancing section advances or guides the leading end of the portions from the feeding section to the receiving section. Smoothening of the trailing end of the portions may alternatively be obtained through the use of controlled air blasts or static charging.

In one or more embodiments the vacuum belt is cooperating with a vacuum box extending from between said set of feed rolls and set of nip rolls to after a receive roll which is part of said receiving section. Hereby is the leading end of the continuous web held in position by the vacuum belt before the separation into portions by the set of nip rolls and the portions are not released before the leading end of the portions is in engagement with the receiving section.

The vacuum box may provide a permanent vacuum to the vacuum belt. The vacuum box may though alternatively provide vacuum periodically i.e. when the vacuum belt is in engagement with the web, preferably only the leading end of the continuous web or portions.

The vacuum box may comprise two vacuum chambers and a vacuum track connecting the two vacuum chambers wherein the vacuum belt runs along the vacuum track. The vacuum track may extend outside the two vacuum chambers so that the entire length of the vacuum track is not directly below the two vacuum chambers. The attraction force or suction force in the vacuum track may be decreased in any section of the vacuum track which is not directly below one of the two vacuum chambers. The suction force when handing over the web from the advancing section to the receiving section may thereby be decreased before the portions engage with the receiving section.

In one or more embodiments the vacuum belt comprises an endless belt, the endless belt comprising a vacuum section having a suction hole, wherein said vacuum section being optionally thicker than said endless belt, so that only the vacuum section of the vacuum belt is in contact with the web. The vacuum section provide an upwardly oriented force on the leading end of the portions.

The endless belt may comprise more than one vacuum section for example one to ten vacuum sections, more preferably two to three vacuum sections, or any other number of vacuum sections suitable for the handling of a particular type or size of portions. The vacuum sections may be spaced apart groups of suction holes and may be evenly distributed along the endless belt. The vacuum section may be an individual part attached to the endless belt. The individual part may be glued to the endless belt. Or the vacuum section may be a section of the endless belt i.e. where the vacuum section is not an individual part. The vacuum section or at least the surface of the vacuum section engaging with the web may be made of a material with a suitable friction for holding on to the web. The material may be a rubber material. Furthermore the vacuum section may have more than one suction hole for example one to twenty suction holes, more preferably six to ten suction holes or any other number of suction holes suitable for the handling of a particular type or size of portions. The suctions holes may be arranged in any pattern suitable for holding the front end of a web such as in a longitudinal row parallel with the length of the endless belt.

The vacuum section may also have the same thickness as the endless belt so that also different parts of the endless belt than the vacuum section are in contact with the web.

The vacuum belt may comprise more than one endless and parallel sub belts for example one to ten endless sub belts, more preferably three to five endless sub belts or any other number of endless sub belts suitable for the handling of a particular type or size of portions.

The vacuum belt may be driven at the same speed as the feeding section at least when a vacuum section of the vacuum belt is in engagement with the leading end of the continuous web or portions i.e. the first speed. The vacuum belt may run continuously with the first speed. The vacuum belt may be driven by one or more drive shafts. In one or more embodiments the vacuum belt is driven by means of an intermittently driven shaft.

The intermittently driven shaft provides the possibility of adjusting the overlapping device to handle portions with different lengths and to adjust the size i.e. the length of the overlapping area of two portions. The intermittently driven shaft may be servo driven or driven by a mechanism having a clutch device. In one or more embodiments the vacuum belt comprises a plurality of endless sub belts driven by a plurality of intermittently driven shafts wherein one or more of the plurality of intermittently driven shafts is configured to run in one speed pattern and the residual intermittently driven shafts are configured to run in a different speed pattern.

This is particular useful when overlapping or interleaving portions of a web where the edge profile of the leading end is shaped differently, i.e. not as a straight edge profile, the straight edge profile preferably being perpendicular to the length of the web, such as portions having a wave-top shaped or a t- shirt shaped edge profile.

In case of handling portions having a wave-top edge profile all portions or every second portion may have a wave-top edge profile in a leading end. Likewise may every second trailing end of the portions have a wave-top edge profile.

In one or more embodiments one or more of said plurality of endless sub belts can be connected and/or disconnected to each of said plurality intermittently driven shafts. The connection and/or disconnection of the endless sub belts to an intermittently driven shaft may be obtained by means of a clutch system. The possibility of connecting and/or disconnecting the individual endless sub belts of the vacuum belt to different and individually driven shafts configured to run in different speed patterns renders the overlapping device more flexible as the overlapping device is capable of smoothly overlapping or interleaving portions of a web with multiple different edge profiles. The leading end of the portions can thereby be hold in position and kept smooth along the edge profile independently of the shape of the edge profile.

It may be possible to disconnect one or more individual endless sub belts of the vacuum belt from all driven shafts. This may be useful if handling webs of different widths.

Disclosed herein is furthermore a method of overlapping portions of a plastic web with leading ends overlapping trailing ends, for subsequent winding up said overlapped portions as a roll, comprising the steps of advancing a web by means of a feeding section comprising a set of feed rolls, separating the web into portions by means of a set of nip rolls, advancing a front end of a portion from said feeding section to a receiving section by means of an advancing section, overlapping said portion with a downstream portion, and deflecting a trailing end of said portion by means of a deflection device by providing a downwardly oriented force on the trailing end of said portion, wherein the advancing section comprises one or more vacuum belts each having along the length thereof one vacuum section or a plurality of spaced apart vacuum sections, said vacuum section(s) being arranged for holding the leading end of a respective portion and sucking said leading end to said vacuum belt.

The deflecting of a trailing end of said portions by means of the deflection device may be towards a smoothening device such as a vacuum plate attracting the deflected trailing end. In one or more embodiments said portion have at said leading end a front part and a rear part, wherein the method further comprises overlapping said rear part with said front part by the advancing section engaging with said rear part.

In one or more embodiments the method as described above is performed by means of the device also described above.

Disclosed herein is furthermore a machine for processing plastic web comprising the aforementioned interleaving device and an apparatus for winding up a roll of said portions having leading ends overlapping trailing ends.

The interleaving device as described above may also be used in a machine for winding rolls of a continuous web or a sequence of a continuous web comprising non-separated portions, wherein the continuous web may have cross seals and perforations at each cross seal formed in the web defining the portions. The set of nip rolls may then be used for separating one continuous web or a sequence of the continuous web with a suitable length to be wound into one roll from the infeed continuous web.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, as follows;

Fig. 1 schematically shows a cross-sectional view of a machine for interleaving portions of a web and winding the portions into rolls. Fig. 2 schematically shows a perspective view of an interleaving device for overlapping portions of a web. Fig. 3 schematically shows a perspective view of a vacuum section of a vacuum belt.

Fig. 4 schematically shows a cross-sectional view of an alternative structure of an interleaving device for overlapping or interleaving portions of a web and a closer view of a vacuum chamber.

Figs. 5 A-C schematically show the process of separating portions from a continuous web followed by overlapping or interleaving a portion with a downstream portion.

Figs. 6 and 7 schematically show the displacement of vacuum sections, when overlapping portions with a wave-top edge profile. Figs. 8 A and B schematically show the overlapping of portions with a wave- top edge profile without displacement of vacuum sections.

Description of preferred embodiments

Fig. 1 shows a cross-sectional view of a machine 1 for processing a web of a plastic foil (not shown) and including an interleaving device referenced generally by numeral 100 for separating the continuous plastic web into portions followed by an overlapping or interleaving of the portions, and an apparatus referenced generally by numeral 20 for making rolls 5 of portions of the web, in particular rolls 5 of overlapped or interleaved bags, in a winding-up procedure. Referring to Fig. 1 , the initial processing of the web, including such steps as the separating of the web into portions and interleaving those portions, takes place in an interleaving device 100 according to the present invention in the left side half of the machine 1 while the apparatus 20 for making the rolls 5 is incorporated in the right side half of the machine 1 . In this arrangement, the left side half of the machine 1 has the web infeed section for one or two streams of the web while the right side half has a section 30 for discharge of completed rolls 5.

The machine 1 includes a frame 8 and a housing 10 having an end wall 1 1 delimiting the right side half of the machine, as well as two opposite longitudinal sides 12 extending parallel with the aforementioned streams.

Fig. 2 schematically shows an interleaving device 100 for overlapping or interleaving the portions 102 according to the invention (Fig. 5 A-C). The interleaving device 100 comprises a feeding section 1 10 for advancing a leading end of a continuous web 101 and portions 102 thereof with a first speed, a receiving section 130 operating at a second speed for slowing the advancing leading end and forming a loop between opposite ends of each incoming portion and an advancing section 150 between the feeding and receiving section for advancing and guiding the leading end 102a of the successive incoming portions 102 at the first speed to the receiving section and overlapping a portion with the trailing end 102b of a downstream portion. The second speed may be 60% to 90% of the first speed or more preferably 70% to 80% of the first speed.

A continuous plastic web 101 or sheet of film enters the machine 1 at the infeed end thereof, i.e. at the feeding section 1 10. This web would typically have cross seals and perforations at each cross seal formed in the web upstream of the interleaving device 100. The web could have been folded longitudinally to make several layers of film prior to entering the machine 1 (Fig. 1 ), or the web could have been folded prior to forming cross seals for manufacturing star bottom bags or T-shirt bags. This would be the usual situation for bags. In more detail, the feeding section 1 10 generally includes a set of feed rolls 1 1 1 a and 1 1 1 b, a set of nip rolls 1 12a and 1 12b for separating the web into portions and a first upper and lower conveyor belt 1 13a and 1 13b. The continuous plastic web 101 is drawn into the feed rolls 1 1 1 a and 1 1 1 b which are driven by a motor (not shown), which may be a servomotor, through a drive belt (not shown), which may be a timing belt. The drive belt may be in direct engagement with either the upper or lower feed roll. The feed rolls 1 1 1 a and 1 1 1 b are speed matched with the output feed rolls on an upstream bag machine (not shown). The web will proceed downstream carried between the first upper conveyor belt 1 13a and the first lower conveyor belt 1 13b generally passing the set of nip rolls 1 12a and 1 12b. The nip rolls 1 12a and 1 12b may be driven by a different motor (not shown), which may be a servomotor, through a different drive belt (not shown), which may be a timing belt. The drive belt may be in direct engagement with the lower or upper nip roll. The lower and upper nip roll is connected by another drive belt so that both nip rolls is driven by the motor. The first upper and lower conveyor belt 1 13a and 1 13b can be sub belts made up of a plurality of individual rope like round elements or belt like flat elements received in peripheral grooves formed within the feed and nip rolls and which grooves at least partially corresponds to the contour of the sub belt. The sub belts may be of a material such as polyurethane.

When a perforation in the continuous plastic web 101 is positioned between the feed rolls 1 1 1 a and 1 1 1 b and the nip rolls 1 12a and 1 12b the speed of the nip rolls accelerates for a short period of time, to a speed greater than the surface speed on the feed rolls and to a speed capable of pulling off a portion of the continuous web 101 . The speed of the nip rolls returns to the first speed before the new trailing end of the continuous web 101 passes the nip rolls. The feeding sections 1 10 may additionally comprise a set of front rolls 1 15a, 1 15b for guiding the web towards the feed rolls.

The advancing section 150 engage with the leading end 101 a of the continuous web 101 before the web is separated into portions 102 (Fig. 5 A- C). The advancing section 150 generally includes a vacuum belt 151 cooperating with a vacuum box 152 and comprising a number of endless sub belts 153, in the presently illustrated embodiment five endless sub belts, driven by at least one driven shaft 154 and 155, and a deflection device (not shown), for making a loop between the leading and trailing end 102a, 102b of the portions 102 in order to urge the trailing end 102b of the portions 102 towards a smoothening device 131 on the receiving section 130. In the presently illustrated embodiment the deflection device is a row of air nozzles as shown in Fig. 4. and the smoothening device 131 is a vacuum plate 131 . The driven shafts 154 and 155 may be intermittently driven by two servo motors (not shown). The vacuum belt or sub belts are capable of establishing a local attraction force on the web where local apparatus in the vacuum section become aligned with the vacuum box. When there is no such alignment the belts close off the vacuum box and provide no attraction force on the web. As shown in more detail, Fig. 3 shows the vacuum belt 151 or sub belt 153 having a vacuum section 157 with a group of suction holes 158, in the presently illustrated embodiment a row of eight suction holes 158 placed parallel with the length of the vacuum belt and approximately in the middle of the width of the vacuum belt. The vacuum section 157 extends along a portion of the length of the vacuum belt. The suction holes draw air flow into them and urge the portions to be held closely to the engagement surface 163 of the vacuum section 157. In the presently illustrated embodiment the vacuum section 155 is an individual part attached to the endless sub belt 153 and the vacuum section has a pattern 159 of recesses for enhancing the holding ability of the engagement surface 163 of the vacuum section.

Returning to Fig. 2 the advancing section 150 leads and hands over the portions to the receiving section 130. The receiving section generally includes a second lower conveyer belt 104 whereon the portions (not shown) are arranged in a stream of interleaved portions, a receive roll 132 in engagement with a second upper conveyer belt 133 and a vacuum plate 131 for smoothening, i.e. reducing wrinkles, of the trailing end of the portions when overlapping the trailing end with an upstream portion. The second upper conveyer belt 133 can be sub belts made up of a plurality of individual rope like round elements or belt like flat elements received in peripheral grooves formed within the receive roll and which grooves at least partially corresponds to the contour of the sub belt. The sub belts may be made of a material such as polyurethane.

Fig. 4 shows a cross-sectional view of an alternative structure of an interleaving device 100 for overlapping or interleaving portions according to the invention. The cross-sectional view shows the following parts of the feeding section; the set of feed rolls 1 1 1 a and 1 1 1 b and the set of nip rolls 1 12a and 1 12b, the following parts of the advancing section; the vacuum belt 151 comprising endless sub belts 153 and vacuum sections 157, the vacuum box 152 and the deflection device 156, and the following parts of the receiving section; the second lower conveyer belt 104 and the receive roll 132.

In more details is shown a vacuum box 152 according to the invention. The vacuum box is divided into a series of vacuum sub boxes 152, one for each endless sub belt 153. Each vacuum sub box includes two vacuum chambers 160 and a vacuum track 161 wherein both vacuum chambers is in engagement with the vacuum track so that the vacuum chambers is connected through and aligned by the vacuum track. Along each vacuum track 161 runs an endless sub belt 153 having three vacuum sections 157. The vacuum track 161 in the presently illustrated embodiment extends outside the two vacuum chambers 160 so that the entire length of the vacuum track is not directly below the two vacuum chambers. The suction force in the vacuum track 161 when handing over the web from the advancing section 150 to the receiving section 130 is thereby decrease before the portions engages with the receiving section. Furthermore the deflection device 156 in the presently illustrated embodiment is a number of air nozzles blowing in a downward direction on each side of or between the endless sub belts 153. The deflection devise may as well be a mechanical device such as a mechanical arm, piston or the like.

The vacuum sections, i.e. the three vacuum sections 157 in the presently illustrated embodiment, are spaced apart groups of suction holes 158 distributed along the endless sub belt 153. The vacuum sections 157 are arranged to provide an upwardly oriented force on the leading end 102a of the portions 102.

The receive roll 132, the second upper conveyer belt 133 and the second lower conveyer belt 104 runs at a lower speed than the feed rolls 1 12a and 12b in the feeding section and the vacuum belt 151 in the advancing section.

Turning now to Figs. 5 A-C the overlap forming and interleaving operation will be described by discussing the progressive figures from Fig. 5 A to Fig. 5 C.

As can be seen in Fig. 5 A the leading edge on the leading end 101 a of a continuous web 101 is being driven downstream by the feed rolls 1 1 1 a and 1 1 1 b between driven first upper and lower conveyer belts 1 13a and 1 13b. The vacuum belt 151 engages with the leading end 101 a between the set of feed rolls and the set of nip rolls 1 12a and 1 12b. As a first portion 102 of web is nipped of at nip rolls 1 12a and 1 12b the vacuum belt 151 leads the portion 102 towards an into engagement with the receive roll 132 together with the second upper conveyer belt 133 and the second lower conveyer belt 104. The leading end 102a of the portion 102 is released or disengaged from the vacuum belt 151 just after the engagement with the receive roll 132. As shown in Fig. 5 B receive roll 132 and second upper and lower conveyer belts 104 and 133 are driven at a speed slower than feed rolls 1 1 1 a and 1 1 1 b so a loop will form in the web 102 in a loop forming or overlap forming zone between the feeding section and receiving section. To assist in forming the loop a discharge of air emanates from the deflection device (not shown) comprising a number of air nozzles (not shown) with an air flow delivered in a downward direction.

The trailing end 102b of each bag or portions 102 of web, shown as 102b has been perforated upstream of an upstream bag machine (not shown) as stated above. When this perforation passes the set of feed rolls 1 1 1 a and 1 1 1 b and reaches a preselected location the set of nip rolls 1 12a and 1 12b will accelerate and create a nip that drives the web faster than the normal web speed of the set of feed rolls 1 1 1 a and 1 1 1 b. The faster web speed of the nip rolls 1 12a and 1 12b relative to the feed rolls 1 1 1 a and 1 1 1 b see Fig. 5 C, will increase the tension in the web between these two sets of rolls and separate the web into portions or bag segments 102 at the perforation. A gap such as 103 will form between the portions102 . The set of nip rolls 1 12a and 1 12b then will decelerate to obtain the same speed for the web as the speed of the web at the feed rolls before the leading end 101 a of the continuous web 101 reaches to the set of nip rolls 1 12a and 1 12b. This action thus separates each trailing end 102b of the leading bag segment or portion from the leading end 102a of the successive bag segment or portion on the continuous perforated web 101 .

Returning to Fig. 5 B just after the trailing end 102b of the portion leaves the nip rolls 1 12a and 1 12b a blast of high pressure air emanates from the deflection device, i.e. air nozzles (not shown). This high pressure blast of air will push the trailing end 102b of the portion 102 of web into the overlap forming zone so that it is directed (by gravity assist or otherwise) into contact with the vacuum plate 131 . The vacuum plate is a structure having a front face provided with a plurality of perforations there through that draws air flow into them and urges the portion of segment 102 to be held closely to the front face of the vacuum plate 131 .

The trailing end 102b of the portion 102 will continue to travel toward the roll- making or wind-up apparatus 20 at a slower rate than the leading end 102a of the next portion as it is being driven through the feed rolls 1 1 1 a and 1 1 1 b. The leading end 102a of the incoming portion will be guided onto the top of the trailing end 102b of the previous portion 102 as is shown in Fig. 5 C and once its leading end 102a is trapped between the previous portion 102 and the second upper conveyer belt 133 it will be drawn through the system as was the first portion 102 described above.

It is expected that for some applications the second bag or portion 102 will easily become mated with the trailing end 102a of the first bag or portion 102 as the portions 102 are overlapped and drawn into the receive roll 132 and second lower conveyer belt 104, however for some portions or bag elements it may be desirable to create a light or temporary adhesion between the trailing end 102b of one portion 102 and the leading end 102a of a second portion 102 either in the overlap area and/or along the second lower conveyer belt 104. The inventors contemplate that this could be done in various ways. For instance, a static charge may be applied to the web from a static charge inducer. The static charge may be applied either to the top side or under the full length of the portions 102, on the top side of the trailing end 102b or under the leading end 102a of incoming portions 102.

Once the overlap has been formed, the stream of portions or bag segments, is supported on the second lower conveyer belt 104 to the roll-making or wind-up apparatus 20 where a roll of interleaved or overlapped portions or bag segments are rolled up. Turning now to Figs. 6 and 7 showing the displacement of vacuum sections 157 of the endless sub belts 153 when running portions of webs 102 with a wave-top edge profile 105. In the presently illustrated embodiment, one of three active endless sub belts 153"' is driven by one intermittently driven shaft, for example driven shaft 154, as the two remaining active endless sub belts 153' and 153" is driven by another intermittently driven shaft, for example driven shaft 155. The driven shafts 154 and 155 is configured to run with two different speed patterns so that the vacuum section 157 of the endless sub belt 153"' engages with the leading end of the portion before the vacuum section 157 of the endless sub belts 153' and 153". This is though usually only the case every second time a vacuum section 157 engages with the web as the edge profile of the leading end in turns will be either wave-top shaped 105 or straight 106. The straight edge profile preferably being perpendicular to the length of the web as it is shown in Fig. 7.

Figs. 8 A and B show an alternative way of overlapping or interleaving portions 102 and 102' with a wave-top edge profile 105 and 105'. Instead of displacing the vacuum sections 157 the vacuum sections are kept in line as shown in Fig. 8 A. The vacuum sections 157 engage the portion 102', not along the edge of the leading end but in a rear part 107' of the leading end 102a', preferably a part of the portion where the portion has its full width and/or is uninterrupted in the full width. On a portion having a wave-top edge profile, this rear part 107' may preferably be the part of the portion just before the wave-top edge profile starts, i.e. the wave-top edge profile being in a front part of said leading end. As shown on Fig. 8 A the leading end 102a' of the portion comprising the wave-top edge profile 105' is folded towards the underside of the portion 102', i.e. overlapping the rear part 107' with the front part of the leading end, prior to overlapping the portion with the downstream portion 102. In this way the portion 102' obtains a straight edge profile 106' in the leading end 102a'. Fig. 8 B shows a trailing end 102b of the portion 102 overlapped or interleaved with a leading end 102a' of the portion 102'.

Usually the leading end of every second portion will be folded as described above. The driven shaft (not shown) driving the vacuum belt or endless sub belts (not shown) may therefor run with a speed pattern alternating between two different speeds, as the portions will be of two different lengths (Fig. 8 A).

The concept of engaging the portions 102' in a predetermined rear part 107' of the leading end may also be used with portions having a straight edge profile preferably perpendicular to the length of the web or any other desired edge profile.

This way of overlapping or interleaving is suitable for portions of a web or particular bag segments 102 comprising more than one film sheet layer and with a wave-top edge profile, a t-shirt shaped profile, a straight edge profile or any other desired edge-profile. The advantage is that it becomes easier to take a roll of the interleaved portions into use, i.e. pull of a portion or bag segment from the roll, without the film layers begin to unfold.