Method and apparatus for joining ends of webs of weldable film, for the formation of bags and the like

Abstract: For the continuous formation of bags for containing bulk materials - in the form of granules, powders and the like - the end of the web (EN), from a new bobbin (BA) in readiness, is laid, with the surface to be welded on the outside, around a welding bar (18) carried by a movable element (12), and said bar (18) is positioned opposite a counterbar (20), along which the web (N) being exhausted from the previous bobbin (B) runs; bar and counterbar are brought close to one another to carry out transverse welding and cutting, in such a manner that a superimposed and welded edge (BS) emerges transversely from the continuous web thus joined, from the surface opposite that of welding.

Description: The invention relates to a method and an apparatus for making a join between ends of webs made of weldable material, intended for the formation of bags for containing bulk material in general, and in particular (but not exclusively) food products in grains or small pieces or in the form of powder; the webs in such cases are expediently to be welded by means of corresponding surfaces, that is to say the two surfaces intended generally to be internal or the two surfaces intended to be external in the finished bag; in any case, in the two bobbins - that being exhausted and the new one - such surfaces are oriented in the same direction. DE-A-3727339 discloses a method for joining ends of webs of weldable film and an apparatus making a join between ends of webs made of film of weldable material intended for the formation of bags for containing bulk material, which comprises a combination of: a work position for a first, unwinding bobbin, and a position of readiness for a second bobbin arranged for replacement, guide means for a first web fed from said first bobbin unwinding with a trajectory not far from said second bobbin. Starting from this known apparatus, the object of the invention is to provide a method and an apparatus for rapidly cutting and welding in the correct mutual position, the ends of two webs of weldable material. This and other objects and advantages will become clear from the following specification. The invention firstly refers to a method for joining a first web of weldable film material from a first bobbin to the front end of a second web from a second bobbin in rediness position, is laid around a bar of a transverse welding group including said bar, a counterbar and a cutting blade, with the surface to be welded facing away from said bar, wherein said bar, with said front end laid around it, is brought in a position essentially contraposed to said counterbar, the web from said first bobbin being fed between said bar and said conterbar, wherein said counterbar is brught in contact with the surface opposite that to be welded of the web being exhansted from the first bobbin, and wherein said bar and counterbar are moved one towards the other to bring the surfaces to be welded together in order to carry out the transverse welding and cutting of the webs upstream of the transverse weld, in such a manner that a superimposed and welded edge, emerges transversely from the continuous web thus joined, from the surface opposite that of welding. For carrying out this method, the invention provides an apparatus of the above mentioned type including: a movable element with a transverse welding bar constituting a first of the two components of a transverse welding group, said element having a first position adjacent to said second bobbin in which the end of a second web from the second bobbin is laid around said transverse welding bar with the weldable surface facing away from said transverse welding bar and turned towards the weldable surface of the first web unwinding along said trajectory; a counterbar constituting the second component of said transverse welding group, and including a transverse cutting blade, said counterbar being arranged on the side opposite said transverse welding bar, in relation to the trajectory of the unwinding web; and means for bringing together said transverse welding bar and said counterbar in order to weld and to cut transversely the double thickness of web material situated between them. Said movable element can be developed in the form of a portal with arms articulated about an axis parallel to the axes of the bobbins and connected by said bar; the bar, in a position removed from that of welding, positions itself to receive the end of the second bobbin in the position of readiness with the weldable surface on the outside. The counterbar also can be movable towards and away from the trajectory of the web, synchronously with the bar. The apparatus can comprise guide means between the two positions of readiness and of work, for the transfer of a bobbin to the work position, after lowering of the bar element in the space between said guide means. The invention will be understood more clearly by following the description and the attached drawing, which shows a exemplary embodiment of the invention itself and in which: Figs 1, 2, 3 and 4 show diagrammatically a vertical longitudinal cross-section of the machine in four successive stages of a cycle of operation for replacement of the bobbin and joining the webs, and Fig. 5 shows a detail of the bar and the counterbar for welding. According to what is illustrated in the attached drawing, a structure 1 forms a seat 3 for a position of readiness and a seat 5 for a work position, the latter at least being defined by rotary rollers 5A, on which the hub M of a bobbin in the work position can rotate for the distribution of the web N towards the utilization, in particular towards a packaging machine for the formation of bags which - immediately after formation - are filled with bulk material (such as food products), then to be closed, in particular welded. Between the position 3 and the position 5, the structure 1 forms guide means 7 which can be sliding means - with chain drive - for the projecting ends of the hub M of the bobbin B. 9A, 9B, 9C indicate some of the guide means for the web N which is fed from the bobbin B and made to run along a trajectory T towards the packaging machine or other utilization. A second bobbin BA, which is to replace the first bobbin B after the latter has been exhausted, can be positioned in the position of readiness 3. The final end of the web of the first bobbin B and the beginning of the web of the second bobbin BA, which is in the position of readiness, are to be welded to one another. Webs of film, which are especially intended for the packaging of food products or the like, generally have an internal surface which is weldable and an external surface which generally is not, or is not easily, weldable. The apparatus forming the subject of the invention makes possible welding between the weldable surfaces of the web which are generally the internal surfaces of a bag and which in any case are the surfaces of the web which are turned towards the bobbin and for example, therefore, the lower surfaces of the web N unwinding from the bobbin B in Fig. 1 and, correspondingly, the surface which faces the bobbin of the end EN of the second bobbin BA in the position of readiness (see Fig. 2). In order to carry out welding with rapid operation between the end of the web of the bobbin B being exhausted (see Fig. 2) in the position 5 and the front end EN of the second bobbin BA in the position of readiness 3, the apparatus described below is provided. This apparatus comprises an element 12 which is movable angularly about an articulation 14 with an axis parallel to the axis of the bobbins B and BA; the movable element 12 is developed in the form of a portal with arms 16 articulated at 14 and a bar 18 which connects the movable ends of the portal structure of the element 12 and which constitutes one of the two components of the welding group. The element 12 is capable of being displaced from a lowered position 18X below the guides 7 to a raised welding position, passing between the two guides 7 which support the hub M of the bobbin during the transfer between the two positions. The other component of the welding group comprises a counterbar 20 which is carried by arms 22 articulated at 24 about an axis which is also parallel to the axes of the bobbins installed in the positions; the whole 20, 22 is controllable by means of an actuator, for example 25. In relation to the trajectory T of the unwinding web, which is defined by the guide means 9A, 9B, 9C or equivalents, the two components of the welding group (12, 16, 18 and 20, 22, 24 respectively) are situated on opposite sides and can be displaced into the active position of approach of the bar 18 to the counterbar 20 as shown in Fig. 3, reaching beforehand the almost contraposed position shown in Fig. 2. In the state indicated in Fig. 1, the first bobbin B in the work position 5 unwinds the web which is drawn expediently along the trajectory T; the position of readiness 3 is available to receive a second bobbin BA to be arranged to continue the distribution essentially continuously. The front end EN of the bobbin BA located in the position of readiness 3 is wound around the bar 18 which is situated in the lowered position 18X of readiness as shown by way of indication in Fig. 2 and as shown in Fig. 1; the arrangement of the end EN on the bar 18 can also be carried out after raising from the position 18X to the position shown. When the first bobbin B is being exhausted as shown in Fig. 2, the element 12 is raised from the position in Fig. 1 to the position in Fig. 2 so as to bring the welding bar 18 from the position 18X to the position shown in Fig. 2 which is essentially contraposed to the counterbar 20; the end EN wound on the bar 18 has its welding surface facing the welding surface of the web N coming from the bobbin B. By bringing the counterbar 20 close to the bar 18, and possibly with a corresponding displacement of the guide means 9A and 9B, the welding and the cutting is brought about of the double thickness of material which remains between bar and counterbar. As can be seen in particular in Fig. 5, the active welding portion of the bar 18 is that indicated by 18S, while 20S indicates the corresponding active welding part of the counterbar 20; the latter also comprises a cutting blade 20L which at the right time brings about the cutting of the two thicknesses upstream of the weld carried out by the portions 20S, 18S, in relation to the direction of displacement of the web. As a result, the double thickness of the edges welded to one another, which are adjacent to the cut effected by the blade 20L, is capable of ensuring the continuity of the final end of the web coming from the bobbin B and the beginning of the web coming from the bobbin BA; from the welding condition indicated by Fig. 3, distribution is thus brought about from the bobbin BA, the front end EN of which is welded by means of the double welding edge BS to the end of the web previously unwound from the bobbin B, the residue of which is discarded. From the state in Fig. 4, the state in Fig. 1 is reached, having brought about the disposal of the empty bobbin from the work position 5 and the displacement of the bobbin BA from the position 3 of readiness to the work position 5 by sliding or rolling along the guide means 7; the state in Fig. 1 is thus reached once again with a replaced bobbin. It is clear that it is possible by means of this arrangement to bring about essential continuity in the distribution of the web upon replacement of an exhausted bobbin by a new bobbin. This apparatus is particularly suitable for the uses mentioned above.

Claims: A method for joining a first web (N) of weldable film material from a first bobbin (B) to the front end (N) of a second web from a second bobbin (BA) in a rediness position, in a continuous formation of bags for containing bulk materials, e.g. granules, powders and the like, wherein: said front end (EN) of the said second web is laid around a bar (18) of a transverse welding group including said bar (18), a counterbar (20) and a cutting blade (202), with the surface to be welded facing away from said bar (18); said bar (18), with said front end (EN) laid around it, is brought in a position essentially contraposed to said counterbar (20), the web (N) from said first bobbin (B) being fed between said bar and said counterbar (20); said counterbar (20) is brought in contact with the surface opposite that to be welded of the first web (N) being exhausted from the first bobbin (B); and said bar (18) and counterbar (20) are moved one towards the other to bring the surfaces to be welded together in order to carry out the transverse welding and cutting of the webs upstream of the transverse weld, in such a manner that a superimposed and welded edge (BS) emerges transversely from the continuous web thus joined, from the surface opposite that of welding. Apparatus making a join between ends of webs made of film of weldable material intended for the formation of bags for containing bulk material, which comprises a combination of: a work position (5) for a first, unwinding bobbin (B), and a position (3) of readiness for a second bobbin (BA) arranged for replacement, guide means (9) for a first web (N) fed from said first bobbin (B) unwinding with a trajectory (T) not far from said second bobbin (BA), characterized in that it includes: a movable element (12) with a transverse welding bar (18) constituting a first of the two components (18, 20) of a transverse welding group, said element (12) having a first position adjacent to said second bobbin (BA) in which the end (EN) of a second web from the second bobbin (BA) is laid around said transverse welding bar (18) with the weldable surface facing away from said transverse welding bar (18) and turned towards the weldable surface of the first web (N) unwinding along said trajectory (T); a counterbar (20) constituting the second component of said transverse welding group, and including a transverse cutting blade (202), said counterbar (20) being arranged on the side opposite said transverse welding bar (18), in relation to the trajectory (T) of the unwinding web (N); and means (25) for bringing together said transverse welding bar (18) and said counterbar (20) in order to weld and to cut transversely the double thickness of web material situated between them. The apparatus as claimed in claim 2, wherein said movable element (12) is developed in the form of a portal with arms (16) articulated and oscillating about an axis parallel to the axes of the bobbins (B;BA) and connected by said transverse welding bar (18); the transverse welding bar (18), in a position removed, that is to say lowered, from that of welding, positioning itself to allow the transfer of the second bobbin (BA) from the position of rediness (3) to the work position (5), and possibly to receive the end (EN) of the second web from the second bobbin (BA) in the position of readiness (3). The apparatus as claimed in claim 2 or 3, wherein the counterbar (20) is movable towards and away from the trajectory (T) of the web, to a greater or lesser extent synchronously with or preferably after the raising of the transverse welding bar (18). The apparatus as claimed in claims 2 and 3, which comprises guide means (7) between the two positions of readiness (3) and of work (5), for the transfer of the second bobbin to the work position, after lowering of the transverse welding bar (18) in the space between said guide means.

Inventors: CARDINI GIUSEPPE, CHITI UGO, CARDINI, GIUSEPPE, CHITI,UGO
Applicants: RICCIARELLI GARIBALDO SRL, GARIBALDO RICCIARELLI S.R.L.
Application year: 1991
Main classification: B65H19
IPC codes: B65H19, B29C65, B29L22