DESCRIPTION

The subject of the invention is a roll-pack for bags made of thermoplastic film or the like, which is capable of allowing very easily the extemporaneous removal of individual bags. Packs of this type are widely used in supermarkets and other shops.

One object of the invention is to avoid the difficulties encountered when tearing the bag off from the continuous strip of bags which are generally delimited by discontinuous transverse perforations which are not always easy to tear. Another object of the invention is to provide a bag with the access mouth opening in the sense the bag is pulled to remove it, but without this mouth having a "toothed" edge, .as happens in the case of bags which are removed by tearing along the separation line with discontinuous transverse perforations. These and other objects and advantages will become clear from the text which follows.

Essentially, the invention consists of a roll-pack of plastic bags, in which the successive bags are tubular with a transverse separation weld, are separated one from another, are arranged with the opening oriented in the direction of removal (and advantageously in the sense of removal) and are circu ferentially staggered and partially mutually superposed.

The bags can be of the type having an opening formed by a linear transverse cut (open mouth bags) or of the type in which the opening has an aperture forming two strap handles (shoppers), or of any other form of bag which can be packed in a roll.

Each bag in the state of being removed is located superposed on the outside of the next bag to be

removed, which remains retained on the roll but which also unwinds partially so as to make taking hold of it easy for the next removal. Each bag is superposed on that underneath by an amount approximately equal to half its own length.

The invention also relates to an apparatus for the production of the above pack.

The drawing shows possible embodiments of the invention, and a machine for making them. In particular.

Fig. 1 shows in perspective a roll according to the invention with bags of the abovementioned "shopper" type and with the end part of the roll raised from the external surface of the roll itself; Figs 2 and 3 show in basic detail a roll in a removal device, at the start of a removal operation and after the operation has taken place;

Figs 4 and 5 show the way in which the pack according to the invention is formed, respectively with strap-handled bags, known as shoppers, and with bags in which the access mouth is obtained by transverse cutting of the tubular material used to form the bags;

Figs 6 and 7 show diagrammatically in vertical longitudinal section and in plan view an apparatus for implementing the invention;

Fig. 8 shows in isolation a roll obtained with the apparatus shown in Figs 6 and 7;

Fig. 9 shows an enlarged detail of the part indicated by the arrow IX in Fig. 6. As can be seen in Figs 1 to 3, a roll R of bags packed so that they are separate from one another is constituted by the bags SO, SI, S2 etc. which are detached and partially superposed on one another, with the opening with straps B facing the direction of removal indicated by the arrow fP in Figs 1 and 2; the bags are arranged partially mutually superposed in such a manner that, on the external surface of the roll during successive removals, each bag to be removed is located on the outside of the next bag, as can be seen

in particular by examining Fig. 1 where the external end part of the roll-pack is illustrated raised from the periphery of the roll itself for the sake of clarity. For removal, the roll R is received in a container device which is generally and as a whole indicated by D (Fig. 2), where the roll can be mounted either to rotate about its own axis, which can be fixed or mobile, or to slide with its external surface on appropriate supports which can also be of the rolling type. In the region of the removal opening A - which can be on the side or in the bottom of the containing box constituted by the device D - the roll R can, in the zone adjacent to and in front of the opening A, be subjected to a greater or lesser pressure effect by a. pressing member PR, which acts on the periphery of the roll whatever the stage of consumption - initial, intermediate or final - of the roll R from which the bags S are removed extemporaneously and individually. In the state of waiting for removal, a bag SI

(Fig. 2) can be gripped with the fingers via the part having the straps B of the opening, the bag projecting from the opening either at the side or at the bottom, according to the position in which the pressure roller PR, the opening A, the roll R and the bag SI are situated in the removal state. By grasping the end of the bag SI by the so-called straps B, and acting according to the arrow fp to remove it, the bag SI is made to reach the position SO in which it is still retained - via the rear end adjacent to the rear separation weld EP - between the roll R and the presser PR, while the next bag S2 will advance as shown in Fig. 3, drawn along by the same movement imposed according to the arrow fp by the bag SI which has been gripped and pulled out with the fingers. Immediately after reaching the position SO, the bag SI, with the continuation of the extraction according to fp, frees itself from the grip of the presser PR, since the end EP of this bag Si has passed beyond the zone of

pressure of said presser PR, while the bag S2 has also advanced as illustrated in Fig. 3 to assume essentially the position of waiting for removal previously assumed by the bag SI in the position illustrated in Fig. 2. The removal takes place simply by pulling and without the need to tear the bag grasped for removal away from the next bag.

To produce a pack of bags which are detached from one another and partially superposed, that is to say in the state also shown in Fig. 4, the advance of the strip N of tubular thermoplastic film material with the longitudinal inward folds Nl typically used in the formation of bags with straps B is brought about; the strip N is subjected as usual to the punching T which is made in a U shape, with the two longitudinal- branches of the U shape corresponding to the part of the tubular material N with four thicknesses; the welding and separation cutting along the welding and separation lines EP and SS are then carried out; the welding EP serves to close the bottom of the bag; the welding SS completes the strap B. The zone indicated by P, and defined by both the line of welding and of cutting EP and SS and by the punching line T, is then removed to obtain the strap conformation B. Each bag is then made to advance at a speed greater than the average speed of advance in order to obtain the superposition of the successive bag on the preceding bag, as can be seen clearly in the intermediate zone NC in said Fig. 4, and the winding and thus the formation of the roll R are then carried out, - with the winding according to the arrow fA. The temporary retention of the bags in the state of partial superposition can be brought about in an appropriate manner, for example with recourse to electrostatic charges generated temporarily during this operation of winding. These operations are performed using an apparatus which will be defined in greater detail below.

Fig. 5 illustrates, in a similar manner to Fig. 4, the formation of a roll of bags in which the

mouth BO is transverse and made by cutting along the weld for closing the bottom indicated by SF which also serves the purpose of defining the cut for the mouth BO. In this case also, there is the partial superposition of the bags before winding but without the formation of the straps B.

The partial superposition can be of any amount but generally a partial superposition which does not exceed half the length of the successive bag is sufficient.

The rolling of the bags which are partially superposed and joined temporarily in a manner such as that indicated above, can be brought- about easily and using means which are known per se. Figs 6 to 9 show a solution for an apparatus for implementing the process described above.

The strip N, which is provided with the U- shaped cuts T, is fed in an intermittent manner according to the arrow ± as shown in Fig. 4, on the left looking at the drawing; in this state, the material is fed to a welding and cutting assembly which is indicated as a whole by 11 and carries out the welds EP and SS and the transverse cutting, in a position which corresponds to the ends of each U-shaped cut indicated by T in Fig. 4. The assembly 11 is not shown in Fig. 7 and is of a type which is conventional per se.

Following the cutting assembly 11 is a first advance assembly 13 with annular belts 13A which are driven by two cylinders 13B, 13C and by a third driving cylinder 13E along the trajectory travelled by the cut bags; the cylinder 13E is advantageously perforated to allow suction in order to tear off and detach the parts P delimited by the cuts T and by the cut formed along and between the welds EP and SS. Along the section between the cylinder 13B and the cylinder 13E (that is to say along the trajectory of advance of the bags) and/or along the section between the cylinders 13E and 13C, it is also possible to provide a suction effect by

96/15039 PC 1

- 6 - means of suction boxes 13F and perforations on the belts 13A, so that the parts P can be pulled away. A mechanism 13G can be provided to carry out the punching and the retention of the piece P so as to ensure the detachment of this piece from the advancing bag. The transport belts 13 and other external transport belts 16 also driven by the cylinder 13B, as well as internal belts 18 which are driven by a driving cylinder 18A and by an additional driving cylinder 20, together constitute a transporter 22 of the advancing material, said transporter having a speed which is lower than the average feed speed according to the arrow f^, with a speed of advance V which is approximately half the feed speed according to the arrow f _j . The belts 16 - and if appropriate the belts 18 also - can be perforated and- suction boxes 24, which ensure the adhesion of the individual bag advancing according to the arrow V and transported by the belts 16 and by the internal belts 18, expediently perforated, can be associated therewith. The belts all have the same speed, essentially equal to half the feed speed according to fτ_. After cutting and welding, the assembly 11 pushes (that is to say throws) the bag according to fj and the partial superposition of each bag on top of the bag in front is thus obtained, in an arrangement which may be that shown in Fig. 4 or with a superposition different to that shown in Fig. 4.

During the advance according to the arrow and at the speed V, the material of the partially superposed bags can pass through the interspace between two electrodes 26 and 28, between which an electric field is established by means of the continuous potential difference between said electrodes 26 and 28. It follows from this that the material of the partially superposed bags is charged electrostatically; the electrostatic charges thus establish a stable - but temporary - connection between the successive bags, as a result of which the flow of bags which are partially superposed according to the strip-shaped structure NC

shown in Fig. 4 can advance as a single strip thereby allowing winding in the form of a roll R at the end of the trajectory of advance. The electrodes 26 and 28 can extend over the entire transverse front of the tubular strip-shaped material of the superposed bags and over a longitudinal distance in the direction of advance which is expediently fixed and can also, if appropriate, be variable. It is moreover possible for the electrostatic field established between the electrodes 26 and 28 to be discontinuous both in the longitudinal direction and in the transverse direction, so as to be able, if necessary, to modify the magnitude of the electric charges and/or obtain partialization of the zones in which the electric field is applied, modifying the electrostatic attraction between the various advancing partially superposed manufactured articles. Moreover, it is also possible to have a speed of advance V other than one which is 50% of the average feed speed according to the arrow f _] _, so as to obtain a more or less marked superposition between the successive bags, again for the purpose of expediently proportioning the strength of the connection produced by the electrostatic charges.

Provided at the end of the system of transport 22 by means of the belts 16 and, if appropriate, 18 is a delivery assembly 30 (see also Fig. 9) for the delivery of the strip-shaped structure NC to a winding assembly 32 which comprises a mandrel 34 illustrated diagrammatically in the drawing, on which the strip-shaped structure NC formed by the partially superposed bags is wound. The assembly 30 comprises the driving cylinder 20 for the belts, a further lower driving cylinder 36 and a pair of upper cylinders 38 and 40. Extending between the cylinders 20 and 36 and between the cylinders 38 and 40 are continuous belts 42 and 44, expediently guided in corresponding grooves of the cylinders of the two respective pairs to ensure with suitable means, for example comb means, that the regular detachment of the

strip-shaped structure NC from the transport system to the winding assembly 32 takes place.

To ensure the initial winding, the cylinder 38 can initially rest on the cylinder 20 underneath to ensure the holding of at least two bags during winding. It is moreover possible to provide a suitable guide system between the pair of end cylinders 36, 40 and the winding mandrel 34 which is at a suitable distance from these. This guide system can be obtained for example by a series of detachment prongs (not illustrated) and by nozzles borne by a manifold 46, which nozzles, blowing upwards, make possible the movement of the initial end of a structure NC towards the mandrel 34 to ensure that this initial end reaches the mandrel in the correct direction of rotation for winding. The initial end of the strip-shaped structure NC can be made to adhere directly to the rotating mandrel which has a number of holes, through which a pneumatic suction is applied which draws and grips the initial end of the strip- shaped structure NC; alternatively, it is possible for the mandrel 34 to be equipped with a tubular core which is engaged on it and can be slipped off it and which is equipped on the outside with an adhesive zone which is sufficient to ensure the gripping of the initial end of said strip-shaped structure NC to begin winding. To ensure that the winding is sufficiently compact compatibly with the adhesion between the successive and staggered bags - it is possible to provide a suitable pressure which is exerted on the strip-shaped structure IIC between the cylinders 20 and 38 advantageously, or also between the cylinders 36 and 40.

When production according to Fig. 5 is being carried out, it is only necessary to exclude the components of the assembly 13 from active functioning.