The present invention concerns an airtight sealing station for bags of loose and/or powdered materials, as well as a bagging system of loose and/or powdered materials using such a station. The present invention also concerns a method for sealing bags of loose and/or powdered materials and a process for bagging loose and/or powdered materials implementing such a method.

The bags intended to contain loose and/or powdered materials such as cement are typically made from paper and are provided with a slit-type filling opening arranged in the upper part of the bag, called valve. The valve is made so as to open following a compression of its ends towards one another and to automatically close up again once such a compression force is removed. In this way, to fill the bag, it is sufficient to apply a lateral compression of the upper part of the bag and remove it once filling is complete.

The Applicant has observed that a closure made in this way is not hermetic, consisting of a simple overlapping of layers of paper that however do not mechanically adhere to each other. For this reason, the closure of the valve does not represent a sealed closure capable of preventing the product from coming out.

The Applicant has noted that in particular in the first steps of movement of the bag, when the material contained is still very aerated, it tends to come out from the bag through the valve, causing product to be lost, pollution of the work place as well as contamination of the surfaces with which the bag itself comes into contact. This translates into substantial costs linked both to the value of the raw material that is lost, and to the maintenance and cleaning costs of the space and of the machinery that come into contact with the dispersed material.

The Applicant has noted that in industrial fields that produce materials with high or very high added value, like the fine chemical and pharmaceutical chemical industry, it is known to carry out a seal of the packages in bags with methods that vary according to the material of which the bag consists, its size and so on. In the case in which paper bags are used, the sealing operation is carried out by equipping the valve of the bag with a plastic end piece that, once filling is complete, is welded through an ultrasound device. Ultrasound welding consists of a process of mechanical vibration at ultrasound frequency that leads to local fusion of the contact area between the sonotrode and the detail to be welded.

The Applicant has found that the advantages linked with an evolved technology like ultrasound welding are numerous and include, for example, very short welding cycles and absolute constancy of results.

The Applicant has, however, observed that in baggers that carry out the filling of paper bags with loose and/or powdered products, the ultrasound sealing device is positioned directly on board the bagger and, in particular, at each loading spout with which the filling of the bags takes place. Considering that, in the cement industry, a bagger generally comprises between 6 and 16 loading spouts as a function of its bagging speed, the introduction of sealing devices in such apparatuses would involve a substantial modification intervention with costs that would exceed the value of the bagger itself.

The Applicant has also found that the installation of ultrasound sealing devices on board of baggers results in a substantial reduction in productivity of such apparatuses, equal to about 25 %, due to the time necessary to carry out the welding of the bag before evacuation. Indeed, the sealing apparatus installed at each loading spout of the bagger means carrying out the sealing directly after the filling step of the respective bag, lengthening the overall processing cycle of a bag on board the bagger and therefore reducing the productivity of such a machine.

The problem forming the basis of the present invention is therefore that of carrying out a sealing of the paper bags for bagging loose and/or powdered material that makes it possible to avoid modifications to the existing bagging apparatuses and at the same time does not determine a penalisation of the productivity of the bagging system.

In accordance with a first aspect thereof, the invention concerns an airtight sealing station for bags of loose and/or powdered materials comprising at least one inlet conveyor for moving a plurality of bags filled with loose and/or powdered material along an advancing direction towards an airtight sealing area, said bags being provided with a filling opening defined between at least two flaps adapted for being sealed airtight against one another; a plurality of airtight sealing apparatuses of the filling opening, arranged at the airtight sealing area; and at least one outlet conveyor for the evacuation of a plurality of bags with filling opening sealed airtight, along an evacuation direction; wherein the inlet conveyor is adapted for sorting the plurality of bags advancing between the plurality of airtight sealing apparatuses of the airtight sealing area, and the outlet conveyor is adapted for collecting the bags in outlet from each airtight sealing apparatus of the plurality of airtight sealing apparatuses.

The Applicant has noticed that an airtight sealing station for bags of loose and/or powdered materials in accordance with the present invention can be introduced into a corresponding bagging system without it being necessary to intervene with modifications on the further stations of the system. This results in substantial advantages in terms of system costs, since a modification of the pre-existing stations would be particularly onerous.

The Applicant has also realised that the plurality of sealing apparatuses arranged at the relative airtight sealing area makes it possible to carry out many sealing operations simultaneously, thus offering advantages both in terms of overall productivity, and in terms of optimisation of layout of the system. In accordance with the present invention, it is indeed no longer necessary to foresee a number of airtight sealing apparatuses equal to the number of loading spouts of the filling station. The choice of the number of sealing apparatuses used in the sealing station according to the present invention is conditioned solely by the need not to penalise the productivity of the system, in any case always being less than the number of loading spouts of the filling station installed in the system.

The Applicant has also found out that, for the use of the airtight sealing station according to the present invention in a bagging system, it is possible to place it downstream of the filling station so that the latter feeds the former with filled bags to be sealed. The two stations thus operate independently from one another, therefore making it possible to keep the original productivity of the filling station unaltered.

In accordance with a second aspect thereof, the invention concerns a bagging system of loose and/or powdered materials in bags provided with a filling opening comprising at least a filling station of bags with loose and/or powdered materials comprising a plurality of loading spouts each adapted for engaging with the filling opening of a bag, for filling a plurality of bags; and a sealing station of filled bags arranged downstream of the bag filling station, wherein the sealing station is adapted for receiving a plurality of bags filled through the plurality of loading spouts of the filling station and for carrying out the sealing of the bags received.

Advantageously, the bagging system of loose and/or powdered materials according to the invention achieves the technical effects described above in relation to the airtight sealing station.

In particular, the Applicant has found that the provision of two mutually independent work stations, one arranged downstream of the other so that the filling station feeds the airtight sealing station with filled bags to be sealed, makes it possible to keep the original productivity of the filling station unaltered. An overall optimisation of the productivity of the system is thus obtained.

The Applicant has also realised that a bagging system according to the present invention can be implemented from a system that does not foresee the sealing of the bags in a quick and simple manner, requiring a minimum idle time, given that the mounting of an independent airtight sealing station can take place with the filling station in operation.

In accordance with a third aspect thereof, the invention concerns a method for sealing bags of loose and/or powdered materials coming from a filling station and provided with a filling opening defined between at least two flaps adapted for being sealed airtight against one another, comprising the steps of conveying, in succession towards a sealing area, a plurality of bags advancing from said filling station along an advancing direction; sorting the bags advancing between a plurality of sealing apparatuses arranged in the sealing area, adapted for carrying out an airtight sealing of the flaps defining the filling opening; sealing the flaps defining the filling opening of each bag transiting through a sealing apparatus of the plurality of airtight sealing apparatuses airtight against one another; evacuating the bags coming out from each sealing apparatus of the plurality of airtight sealing apparatuses.

Advantageously, the method for sealing bags of loose and/or powdered materials according to the invention achieves the technical effects described above in relation to the airtight sealing station.

In accordance with a fourth aspect thereof, the invention concerns a process for bagging loose and/or powdered materials in bags each provided with a filling opening defined between at least two flaps adapted for being sealed airtight against one another, comprising the steps of: loading at least one empty bag onto a filling station, thereby engaging the filling opening of the at least one empty bag with a filling spout of the filling station; filling the bag with loose and/or powdered material dispensed through the filling spout; unloading the bag filled in the filling station and conveying it towards an airtight sealing station arranged downstream of the filling station; sealing the flaps defining the filling opening of each bag airtight against one another.

Advantageously, the bagging process of loose and/or powdered materials according to the invention achieves the technical effects described above in relation to the bagging system of loose and/or powdered materials.

The present invention in at least one of the aforementioned aspects can have at least one of the following preferred features; they can in particular be combined with each other as desired in order to satisfy specific application requirements.

Preferably, the inlet conveyor comprises a transportation surface having an inlet portion and an outlet portion opposite the inlet portion with respect to the advancing direction, the outlet portion of the transportation surface of the inlet conveyor facing towards the sealing area and being mobile between a plurality of loading positions, wherein each loading position corresponds to an inlet of an airtight sealing apparatus of said plurality of airtight sealing apparatuses.

Preferably, in each loading position, the outlet portion of the inlet conveyor takes up a connection configuration between the inlet portion of the inlet conveyor and the inlet of an airtight sealing apparatus.

Advantageously, a single inlet conveyor is thus able to feed many airtight sealing apparatuses, allowing simultaneous work thereof and therefore an optimisation in terms of overall productivity of the system in which the sealing station is used. Moreover, the bulk of the sealing station is kept low leading to an optimisation of system layout.

Preferably, the outlet conveyor comprises a transportation surface having an inlet portion facing towards the sealing area and an outlet portion opposite the inlet portion with respect to the evacuation direction, the inlet portion of the transportation surface of the outlet conveyor being mobile between a plurality of unloading positions, wherein each unloading position corresponds to an outlet of an airtight sealing apparatus of the plurality of airtight sealing apparatuses.

Preferably, in each unloading position, the inlet portion of the outlet conveyor takes up a connection configuration between the outlet portion of the outlet conveyor and the outlet of an airtight sealing apparatus.

In this way, similarly to the inlet conveyor, it is thus possible to take the bags coming out from many airtight sealing apparatuses through a single outlet conveyor. Advantageously, the bulk of the sealing station is kept low, obtaining an optimisation of system layout.

More preferably, the inlet portion of the inlet conveyor and/or the outlet portion of the outlet conveyor are made like a roller conveyor.

More preferably, the outlet portion of the transportation surface of the inlet conveyor and/or the inlet portion of the transportation surface of the outlet conveyor are tilting surfaces.

Advantageously, making inlet and/or outlet conveyors with a portion of the transportation surface tilting is particularly simple and can be obtained at low cost.

Even more preferably, the outlet portion of the inlet conveyor and/or the inlet portion of the outlet conveyor are made like a conveyor belt.

Alternatively, the outlet conveyor comprises at least one fixed chute positioned at an outlet of an upper sealing apparatus of the plurality of sealing apparatuses, so as to receive a bag coming out from such an upper sealing apparatus and convey it down, towards an evacuation surface arranged substantially at the same height as the outlet of a lower sealing apparatus of the plurality of sealing apparatuses.

Such an embodiment of the outlet conveyor is advantageously even simpler and more cost-effective, also not requiring any coordination between the movements of the inlet conveyor with the outlet conveyor.

Preferably, the evacuation direction of the at least one outlet conveyor coincides with the advancing direction of the at least one inlet conveyor.

Even more preferably, the sealing apparatuses of the plurality of airtight sealing apparatuses are arranged vertically adjacent and the tilting surfaces swing about a respective rotation axis which is comprised in a horizontal plane and is perpendicular to the advancing/evacuation direction of the respective conveyor.

Thanks to the juxtaposed arrangement of the sealing apparatuses, the sealing station has a low overall bulk in plan, allowing an optimisation of the system layout.

Preferably, the horizontal plane comprising the rotation axis of at least one tilting surface is the advancing plane defined by the inlet portion of the inlet conveyor and/or by the outlet portion of the outlet conveyor.

In this way, the tilting surface is hinged to the fixed portion of the transportation surface of the respective conveyor, advantageously acting as connection of such a fixed portion with the various sealing apparatuses.

Alternatively, the sealing apparatuses of the plurality of airtight sealing apparatuses are arranged horizontally adjacent and the tilting surfaces swing about a vertical rotation axis perpendicular to the advancing direction of the respective conveyor.

Preferably, each airtight sealing apparatus comprises an ultrasound sealer.

More preferably, the ultrasound sealer comprises a device for generating mechanical vibrations for transferring vibrational energy to the flaps of the filling opening.

The use of an evolved technology like ultrasound welding brings numerous advantages including very short welding cycles, absolute constancy of results and so on. Therefore, it is possible to quickly obtain reliable and repeatable results.

Even more preferably, the device for generating mechanical vibrations is made like a pincer, comprising two half-parts able to be brought together so as to sandwich the flaps to be sealed between them and compress them.

Such an embodiment of the ultrasound sealer makes it possible to easily arrange it in line, at the same time acting as welder and as contrast surface thereof.

More preferably, each airtight sealing apparatus also comprises a welder conveyor adapted to convey a bag entering into the sealing apparatus towards a centring area, the centring area comprising at least one window at which the ultrasound sealer acts.

Even more preferably, stop and alignment elements act at the centring area, said elements being adapted for positioning an incoming bag so that the flaps of the bag defining the filling opening project from the window, thereby being located at the field of action of the ultrasound sealer.

A repeatable and always exact centring of the bag is thus obtained in a simple manner, which ensures correct positioning of the flaps of the filling opening at the field of action of the ultrasound sealer.

In a further preferred manner, the stop and alignment elements comprise at least one alignment edge adapted to adjust the orientation and the positioning of an incoming bag, and at least one stop edge adapted for preventing the bag from advancing along the sliding direction of the welder conveyor.

Preferably, the alignment edge is made like a thruster adapted for exerting a pressure on the bag against a fixed wall of the sealing apparatus.

Preferably, the stop edge is of the swinging type.

The particular embodiment of the stop and alignment elements makes it possible to achieve optimal and precise results whilst still providing a solution that is simple to implement.

Preferably, the sealing station of bags used in the bagging system of loose and/or powdered materials according to the present invention is made in accordance with what is outlined above.

The advantageous results associated with single aspects highlighted above are thus achieved. Preferably, the step of sorting advancing bags comprises cyclically transporting, in succession, towards each sealing apparatus of the plurality of airtight sealing apparatuses, a bag of the plurality of advancing bags.

Advantageously, many sealing apparatuses can work simultaneously inside a sealing station, thus obtaining an optimisation in terms of overall productivity of the system in which the sealing method is implemented.

More preferably, the step of transporting the advancing bags towards each sealing apparatus comprises modifying the inclination of a portion of a transportation surface for entry of the bags along the advancing direction.

Even more preferably, the inclination of the portion of transportation surface of the bags is modified by making such a surface portion swing about a rotation axis perpendicular to the advancing direction of the bags.

Advantageously, it is thus possible to feed many sealing apparatuses through a single transportation surface, obtaining advantages both in terms of bulk of the conveyor, and in terms of costs.

In a further preferred manner, the portion of transportation surface is made to swing about a rotation axis comprised in a horizontal plane.

In this way it is advantageously possible to feed juxtaposed sealing apparatuses obtaining a further optimisation of the overall bulk in plan.

Preferably, the step of airtight sealing the flaps defining the filling opening comprises generating mechanical vibrations for transferring vibrational energy to the flaps of the filling opening.

This makes it possible to obtain the advantageous effects outlined above relative to the use of ultrasound welding technology.

Preferably, the step of evacuating the bags coming out from each sealing apparatus comprises cyclically picking up, in succession, from each sealing apparatus of the plurality of airtight sealing apparatuses, a bag of the plurality of bags coming out from the sealing apparatuses.

More preferably, the step of cyclically picking up from each sealing apparatus comprises modifying the inclination of a portion of a transportation surface coming out from the bags along an evacuation direction.

Even more preferably, the inclination of the portion of transportation surface coming out from the bags is modified by making such a surface portion swing about a rotation axis perpendicular to the evacuation direction of the bags.

Preferably, in the bagging process of loose and/or powdered materials, the sealing step is carried out according to a method for sealing bags of loose and/or powdered materials in accordance with what has been outlined above.

The advantageous results associated with single aspects outlined above are thus obtained.

Further features and advantages of the present invention will become clearer from the following detailed description of some preferred embodiments thereof, made with reference to the attached drawings.

The different features in the single configurations can be combined together as desired according to the previous description, if it were necessary to have the advantages resulting specifically from a particular combination.

In such drawings, figure 1 is a schematic top side view of an exemplary embodiment of the airtight sealing station of bags of loose and/or powdered materials according to the present invention; figure 2 is a schematic partial plan view of an exemplary embodiment of a bagging system of loose and/or powdered materials according to the present invention; figure 3 is a partial perspective view of the airtight sealing station of figure 1 ; figure 4 is an enlarged detail of figure 3; figure 5 is a perspective view of the detail of figure 4 seen from another angle of view.

In the following description, for illustration of the figures identical reference numerals are used to indicate constructive elements with the same function. Moreover, for clarity of illustration, some reference numerals are not repeated in all of the figures.

With reference to the figures, an airtight sealing station for bags of loose and/or powdered materials is shown, wholly indicated with 10.

As shown in figure 1, the airtight sealing station 10 comprises an inlet conveyor 11 for moving a plurality of bags 30 filled with loose and/or powdered material along an advancing direction A towards an airtight sealing area 12.

The bags 30 are generally made from paper material and are provided on the upper side with a filling opening (not illustrated), also called valve, which is defined between at least two flaps (not illustrated) of the bag adapted for being sealed airtight against one another. Specifically, each flap of the bag is coupled inside a covering film made of plastic material that, by melting, determines the welding of the two flaps against one another and therefore the sealing of the opening.

A plurality of airtight sealing apparatuses 12a, 12b, 12c is arranged in the airtight sealing area 12. In the embodiment illustrated by way of example, there are advantageously three sealing apparatuses 12a, 12b, 12c. However, according to the present invention, in the sealing area there can also be a number of apparatuses different from three, for example one, two, four, five and so on.

Each sealing apparatus 12a,12b,12c preferably comprises a sonotrode 21, i.e. a device capable of generating mechanical vibrations at ultrasound frequency for transferring vibrational energy to the flaps of the bag defining the filling opening. Such a vibrational energy determines a local melting of the covering film of the flaps and therefore the sealing of the opening. In the details of the illustrated embodiment, the sonotrode 21 is made in the form of a pincer, comprising two half-parts 21a,21b able to be brought together so as to sandwich the flaps to be sealed between them and compress them.

As shown in figure 3, each sealing apparatus 12a,12b,12c also preferably comprises a welder conveyor 22 adapted for conveying an incoming bag 30 to the sealing apparatus 12a, 12b, 12c towards a centring area 23. The centring area 23 comprises at least one window 24, shown in detail in figures 4 and 5, at which the pincer sonotrode 21 acts.

At least one alignment edge 25 acts at the centring area 23 to adjust the orientation and positioning of an incoming bag 30, so that the two flaps of the bag defining the filling opening project from the window 24, being located at the field of action of the sonotrode 21, i.e. at the field of contact between the two half-parts 21a,21b of the pincer. The alignment edge 25 is for example made in the form of a thruster adapted for exerting a pressure on the bag 30 in contact with a fixed wall 27 of the sealing apparatus 12a, 12b, 12c, preferably parallel to the sliding direction of the welder conveyor 22.

The centring area 23 is also delimited by a stop edge 26 that prevents the advancing of the bag along the sliding direction of the welder conveyor 22 as long as the sonotrode 21 acts on the flaps. Once the flaps are sealed, the stop edge 26 is moved, preferably swung, to be brought into open position, allowing the bag 30 to advance transported by the welder conveyor 22.

The inlet conveyor 11 comprises a flat transportation surface with a fixed inlet portion 1 la and a mobile outlet portion 1 lb. The outlet portion 1 lb is mobile so as to be able to take up a plurality of connection configurations between the fixed inlet portion 11a and the inlet of a sealing apparatus 12a, 12b, 12c.

In the illustrated embodiment, the mobile outlet portion l ib swings about an axis B perpendicular to the advancing direction A of the bags and, specifically, comprised in the horizontal plane defined by the fixed inlet portion 11a of the inlet conveyor 11. In this way, the mobile outlet portion 1 lb swings between a configuration tilted upwards, a flat configuration and a configuration tilted downwards, thus connecting the fixed inlet portion 11a alternatively to the inlet of an upper sealing apparatus 12a, an intermediate sealing apparatus 12b and a lower sealing apparatus 12c.

Clearly it is also possible to devise alternative embodiments, in which the sealing apparatuses 12a, 12b, 12c are arranged horizontally adjacent and the swinging axis B of the mobile outlet portion 1 lb is vertical.

Downstream of the sealing area 12 with respect to the advancing direction A there is an outlet conveyor 13, shown in figure 1, for the evacuation of the bags coming out from the sealing apparatuses 12a, 12b, 12c along an evacuation direction A' that, in the illustrated embodiment coincides with the advancing direction A.

The outlet conveyor 13 comprises a flat transportation surface with a mobile inlet portion 13a and a fixed outlet portion 13b. The inlet portion 13a is mobile so as to be able to take up a plurality of connection configurations between the fixed outlet portion 13b and the outlet of the sealing apparatuses 12a,12b,12c.

In the embodiment illustrated in figure 1, the mobile inlet portion 13a swings about an axis B' perpendicular to the advancing direction Α,Α' of the bags and, specifically, comprised in the horizontal plane defined by the fixed outlet portion 13b of the outlet conveyor 13. In this way, the mobile inlet portion 13a swings between a configuration tilted upwards, a flat configuration and a configuration tilted downwards, thus connecting the fixed outlet portion 13b alternatively to the outlet of the upper sealing apparatus 12a, of the intermediate sealing apparatus 12b and of the lower sealing apparatus 12c.

Similarly to what has been outlined in relation to the inlet conveyor 11, in the case of sealing apparatuses 12a, 12b, 12c arranged horizontally adjacent, the swinging axis B' of the mobile inlet portion 13a is vertical.

In the embodiment illustrated in figure 1, the fixed portions 11 a, 13b of the transportation surfaces of the inlet and outlet conveyors 11, 13 are made in the form of a roller conveyor, whereas the mobile portions l ib, 13a are made in the form of a conveyor belt. However, it is possible to devise different embodiments and/or combinations of embodiments of such portions of the transportation surfaces of the inlet and/or outlet conveyors, in practice through any element capable of defining a flat transportation or advancing surface.

The conveyor belts of the mobile portions l ib, 13a of the embodiment of figure 1 are controlled in movement through respective motorisation groups 15,15', preferably of the electric type.

The mobile portions l ib, 13a are preferably constrained to respective lifting groups 14,14' each comprising an arm 14a, 14a' hinged to the corresponding mobile portion l ib, 13a and controlled in rotation through an actuation device 14b, 14b', preferably an electric motor, in order to control the rotation of the respective mobile portion l ib, 13a about the relative rotation axes Β,Β'.

The rotation imparted by the lifting group 14,14' on the respective arm 14a, 14a' imparts on the relative mobile portion l ib, 13a a linear force along the vertical, determining a lifting or a lowering of the free end of such a mobile portion 1 lb, 13a.

Preferably, at the free end of the mobile portions 1 lb, 13a there are presence sensors (not illustrated), like for example photocells, adapted for detecting the passage of a bag 30 at such free ends. It is thus advantageously possible to drive the rotation of the mobile portions 1 lb, 13a in a synchronised manner with respect to the passage of the bags 30 on the conveyors. Alternatively, according to an embodiment that is not illustrated, the outlet conveyor 13 comprises a plurality of fixed chutes positioned at the outlets of the sealing apparatuses 12a, 12b, 12c so as to convey downwards, towards an advancing surface in the advancing direction Α,Α', for example a conveyor belt, arranged substantially at the same height as the outlet of the lower sealing apparatus 12c.

In a bagging system of loose and/or powdered materials 100, like the one shown in figure 2, the airtight sealing station 10 is arranged downstream of a filling station 50. The filling station 50 can be of any type.

In the embodiment illustrated in figure 2 as an example, the filling station 50 comprises a plurality of loading spouts 51 each adapted for engaging with the filling opening of a bag. The filling spouts 51 are preferably mounted on a carousel that transports each spout 51 in rotation between a loading position in which the spout 51 receives an empty bag, and an unloading position in which the filled bag is unloaded from the filling station 50. The filling of the bag takes place during the rotation of the spout 51 between the two loading and unloading positions.

An empty bag is preferably loaded onto a filling spout 51 through special suction means (not illustrated) set in action when such a filling spout 51 is at an empty bags dispensing store (not illustrated).

A filled bag 30 is preferably unloaded onto a further conveyor (not illustrated) preferably coinciding with or connected to the inlet conveyor 11 of the airtight sealing station 10.

The operation of the bagging system of loose and/or powdered materials 100 foresees to load at least one empty bag onto the filling station 50, thereby engaging the filling openings of a plurality of empty bags each respectively with a loading spout 51 of the filling station 50.

The filling station 50 takes care of filling the bag, dispensing loose and/or powdered material through the loading spout 51 and then unloading the filled bag 30 to convey it towards the sealing station 10 arranged downstream.

In the detail of the illustrated embodiment, the filling station 50 is able to fill the bags with a flow equal to 4200 bags/h. By setting a speed of the conveyors equal to 1200 mm/sec, the distance between two successive bags is equal to about 600 mm. The tilting inlet and outlet surfaces l ib, 13a are always in operation and are positioned at a sealing apparatus 12a,12b,12c of the plurality of airtight sealing apparatuses.

In this way, a first filled bag 30 entering the sealing station 10 is conveyed towards a first sealing apparatus 12a, 12b, 12c, where the sealing of the flaps of the filling opening takes place.

For this purpose, the bag 30 passes from an engagement with the tilting surface 1 lb of the inlet conveyor 11 to an engagement with the welder conveyor 22 that conveys it towards the centring area 23 of the sealing apparatus 12a, 12b, 12c. At the centring area 23, the advancing of the bag 30 is stopped by the stop edge 26 that is in closed configuration. At this point, the alignment edge 25 acts, pushing the bag towards a fixed wall 27 of the sealing apparatus 12a, 12b, 12c, in which the window 24 is made which looks onto the field of action of the pincer sonotrode 21. In this way, the flaps of the filling opening of the bag 30 are at the field of action of the sonotrode 21, projecting through the window 24.

Therefore, the airtight sealing of the flaps defining the filling opening of each bag takes place by pressing them against one another. For this purpose, the two half-parts 21a,21b of the pincer sonotrode 21 are closed against one another, sandwiching the two flaps between them and applying a pressure to them, whereas the sonotrode 21 generates mechanical vibrations at ultrasound frequency, in such a way transferring vibrational energy to the flaps, the parts of which made from plastic material consequently melt.

Once sealing is complete, the two half -parts 21a,21b of the sonotrode 21 are opened again. The stop edge 26 is swung and brought into open configuration, so that the sealed bag can advance towards the outlet conveyor 13.

The presence sensors respectively detect the passage of the bag 30 on the tilting surface l ib of the inlet conveyor 11 and/or, respectively, on the tilting surface 13a of the outlet conveyor 13. As soon as the transit of a bag 30 on the tilting surfaces l ib, 13a of the inlet and/or outlet conveyors 11, 13 has ended, the movement of the relative tilting surfaces l ib, 13a is enabled so as to position them at the subsequent sealing apparatus 12a,12b,12c.

The tilting surfaces l ib, 13a of the inlet conveyor 11 and of the outlet conveyor 13 are moved cyclically and in a respectively corresponding manner between the single sealing apparatuses 12a, 12b, 12c. From the description that has been made the features of the station and of the method for airtight sealing bags of loose and/or powdered materials as well as the relative bagging system and process object of the present invention are clear, as are the relative advantages.

Further variants of the embodiments described above are possible, without departing from the teaching of the invention.

Finally, it is clear that an airtight sealing station and a bagging system of loose and/or powdered materials thus conceived can undergo numerous modifications and variants, all of which are covered by the invention; moreover, all of the details can be replaced by technically equivalent elements. In practice, the materials used, as well as the sizes, can be whatever according to the technical requirements.

Bird & Bird