Welding bar and bar-holder group for a bag sealing station of a bagging machine

Abstract

Welding bar for a bag sealing station of a bagging machine, comprising: a longitudinal front welding face 110a, which has an electrically heated longitudinal part suitable for making contact with the surface of the bag to be sealed, a longitudinal rear face 120a which is opposite during use to the heating face 110a in a transverse direction Y-Y and which is adapted for coupling with a bar-holder group 200; at least one pair of clasp structures 121 arranged spaced in the longitudinal direction X-X on the rear face 120a, each clasp structure being configured to engage with a terminal head 211 of a respective retractable transverse arm 210 of the bar-holder group 200 of the sealing station so that the head exerts a pulling force on the clasp structure 121 when the retractable arm 210 is retracted in the transverse direction Y-Y so as to cause stable coupling of the bar 100 to the bar holder 200; at least one pair of conductive contacts 130 arranged on the rear face 110a for electrical connection by means of contact with a respective conductive pin of the bar-holder group 200, each electrical contact 130 being electrically insulated from the rear face 120 and electrically connected to the welding part of the bar 100 for transmission of electric power thereto.

Description

[0001] WELDING BAR AND BAR-HOLDER GROUP FOR A BAG SEALING STATION OF A BAGGING MACHINE

[0002] DESCRIPTION

[0003] The present invention relates to a welding bar for a bag sealing station of a bagging machine, a bar-holder group for supporting and operating a welding bar in a sealing station and an associated bagging machine.

[0004] It is known in the products sector relating to the packaging of loose material that there exists the need to arrange said material inside bags which must be filled with a defined quantity of material and then sealed.

[0005] It is also known that, for this purpose, automatic bag filling machines have been developed, an example of said machines consisting of so-called forming and filling machines which are able to perform at high speed the cycle involving forming or removal of the bag, filling of the bag and final sealing of the bag mouth.

[0006] Sealing is normally performed by means of welding of the bag mouth using special pairs of welding bars which are arranged on opposite sides of the bag mouth, are electrically heated and are movable towards and away from each other with respect to the bag arranged in the sealing station, between a spaced position, where they do not interfere with the bag, and a position close together, where the bag is closed between the welding bars of the pair of bars. The closing / opening movement of the bars is performed and controlled by the control means for controlling the machine cycle.

[0007] Each bar of the pair is therefore attached to a bar-holder device of the sealing station by means of a mechanical connection and connected to a power supply of the machine by means of an electrical connection and wires, both the connections being generally performed by means of screwtype means.

[0008] Examples of welding bars according to the preamble of Claim 1 are described in US 2017 / 144788.

[0009] Although performing their function, the bar-holder groups and the known welding bars have a number of drawbacks arising from the fact, upon variation in the width of the bag to be sealed, it is necessary to change the welding bars in order to adapt precisely the weld to the actual dimensions of the bag; it is in fact known that the length of each bar must substantially correspond to the width of the bag mouth to be welded, since contact between the heated sealing parts of the two opposite bars must be avoided since it results very quickly in irreparable damage thereof due to overheating. The format-changing operation therefore involves removal of both the mechanical and electrical screw fixing systems and then the reassembly thereof for the new bars. The format-changing operations in the known bagging machines are extremely complex and time-consuming.

[0010] The format-changing operation therefore results in an exaggeratedly long machine downtime and therefore a drop in the productivity of the bagging machine as well as the need to use specialized personnel.

[0011] The technical problem which is posed is therefore that of providing bars for welding the mouths of bags for bagging machines and the associated barholder groups for attaching the bars to the sealing station of the machine which are able to allow rapid and safe format changing both mechanically and electrically as well as shorter machine downtimes and improved productivity.

[0012] A particular aim of the present invention is also to provide a sealing station with a bar-holder group which can be rapidly engaged both mechanically and electrically for the format changing of welding bars for sealing the mouths of bags in bagging machines.

[0013] In connection with this problem it is also required that these welding bars and the bar-holder group should be easy and inexpensive to produce and assemble on bagging machines.

[0014] These results and further advantages are obtained according to the present invention by a welding bar according to the characteristic features of Claim 1 and a bar-holder group according to Claim 11 .

[0015] The welding bars are designed with clasp structures which allow rapid coupling to the bar-holder groups and which have retractable arms which can be operated so as to firmly hold or release the clasp structures and therefore the bars, improving the rapidity and the simplicity of the formatchanging operation. The innovative rapid-engagement system eliminates the need for screws or other traditional screw-type fixing means, reducing significantly the difficulty of the format-changing operation and the time required therefor.

[0016] The present invention relates furthermore to a bag sealing station of a bagging machine and a method for assembly or disassembly of welding bars in a sealing station of a bagging machine.

[0017] Further details may be obtained from the following description of a nonlimiting example of embodiment of the subject of the present invention provided with reference to the attached drawings in which:

[0018] Figure 1 : shows a perspective view, from the front side, of a welding bar and a bar-holder group according to the present invention, arranged facing each other before assembly;

[0019] Figure 2: shows a perspective view, from the rear side, of the welding bar and the bar-holder group according to Fig. 1 , in the disengaged position;

[0020] Figure 3: shows a partially transparent schematic view, from above, of the bar and the bar-holder group according to Figs. 1 -2 in the disengaged condition;

[0021] Figure 4: shows a partially transparent schematic view, from above, of the bar and the bar-holder group according to Fig. 3 in a first engaged condition following transverse translation of the bar towards the bar holder;

[0022] Figure 5; shows a partially transparent, schematic view, from above, of the bar and the bar-holder group according to Fig. 3, in a stable assembled condition following the longitudinal movement of the bar with respect to the bar holder and retraction of retractable arms of the bar holder, engaged in the clasp structures of the bar.

[0023] As shown in Figs. 1 -2 and assuming a pair of reference axes, i.e.: a longitudinal axis X-X, corresponding to the greater dimension or length of a welding bar, parallel during use to the widthwise dimension of the bag mouth to be welded and a positioning line of the said mouth for sealing in a sealing station; transverse direction Y-Y, parallel to the thickness of a bar between a welding inner face thereof, directed during use towards the bag, and a face thereof for coupling with the bar-holder group; and a vertical heightwise direction Z-Z of the bar, perpendicular to the preceding direction, a preferred example of a welding bar 100 for sealing the mouth of bags comprises:

[0024] - a longitudinal welding body 110, which has a longitudinal welding front face 110a, suitable for making contact with the surface of the bag to be sealed. The front face may have, for example, an electrically heated longitudinal strip, which is powered by a suitable circuitry (not described in detail since conventional per se);

[0025] - a longitudinal connection body 120, which supports the welding body 110 and has a longitudinal rear face 120a which is opposite during use to the heating face 110a in the transverse direction Y-Y and which is adapted for coupling with a bar-holder group 200.

[0026] At least one pair of clasp structures 121 are arranged spaced from each other in the longitudinal direction X-X on the rear face 120a.

[0027] In the example of embodiment shown, each clasp structure 121 is formed by an L-shaped plate with a transverse arm 121b projecting in the transverse direction from the rear coupling face 120a and having, extending therefrom, a twin-tooth fork 121c with two longitudinal prongs arranged parallel to and spaced from the rear face 120a for coupling to the bar holder 200.

[0028] The fork 121c defines between its prongs a laterally open longitudinal slot 121 d designed to receive a respective retractable transverse arm 210 of the bar-holder group 200 of the sealing station, while the terminal head 211 of the arm, which has a diameter greater than the vertical dimension of the slot 121 d remains engaged against the prongs of the fork 121c so as to be able to exert a pulling force thereon when the arm is retracted in the transverse direction Y-Y.

[0029] Advantageously, each clasp structure 121 provides a rapid engagement system for the head 211 of the respective arm 210 which in particular does not require fixing by means of screw / female thread means, such as screws or bolts, which have to be screwed / unscrewed in order to couple or uncouple the welding bar to / from the bar-holder group.

[0030] In particular, as shown in Figs. 3-5, each clasp structure 121 may be configured to allow engagement of the head 211 of the respective retractable arm 210 by means of a first relative translation movement M1 in the transverse direction Y-Y between the clasp structure 121 and the bar holder 200 and a subsequent relative translation movement M2 in the longitudinal direction X-X.

[0031] The rear face 120a for coupling with the bar-holder group 200 also has at least one pair of conductive contacts 130 for electrical connection by means of contact; each electrical contact 130 is electrically insulated from the connection body 120 and electrically connected to the welding body 110 for the transmission of electric power to the welding part thereof. Each electrical contact is, for example, in the form of a contact plate 131 , which is preferably coplanar with the rear face 120a. For electrical connection to the welding part, each contact 130 may for example comprise a vertical tongue 132, projecting from the connection body 120 and connected by means of a wired electrical connection 132a with a respective, vertical, conductive tongue 112 projecting from the welding body 110 of the bar 100.

[0032] Preferably, the clasp structures 121 are arranged between the two electrical contacts 130 in the longitudinal direction, with the electrical contacts arranged in the vicinity of opposite longitudinal ends of the longitudinal connection body 120.

[0033] The rear face 120a for coupling with the bar holder 200 may also have a pin 124 projecting in the transverse direction and designed to be inserted inside a longitudinal groove 224 of the opposite front face 220a for coupling of the bar holder 200, so as to guide the bar 100 during the second relative translation movement M2 of the bar with respect to the bar holder, during coupling.

[0034] With reference still to Figs. 1-5, a further aspect of the present invention relates to a bar holder for use in a sealing station of a bag filling and sealing machine, such as an FFS (filling / forming / sealing) machine.

[0035] During use, the station will comprise a pair of bar holders 200 arranged on opposite sides of a longitudinal line for positioning the bag mouth inside the sealing station. Each bar holder 200 may be fixed to devices for performing translational displacement in the transverse direction away from / towards the longitudinal positioning line of the bag, so that the bar holders 200 and the respective bars 100 supported by them will be movable towards and away from each other in the transverse direction between a separated position and a close-together position, in which the welding parts of the bars 100 will be arranged in contact with the opposite surfaces of the top edge of the bag in order to heat them and press them against each other so as to obtain the sealed welding of the mouth.

[0036] As shown in the example, each bar holder 200 has a longitudinal body, for example with a substantially parallelepiped form, which has said longitudinal front surface 220a for coupling to the rear surface 120a of the bar 100 and an opposite longitudinal rear surface directed towards the sealing station.

[0037] The front surface for coupling to the bar has a plurality of inset longitudinal seats 220 which are open on the coupling surface directed towards the respective bar 100. The number of inset longitudinal seats 220 corresponds to the number of clasp structures 121 of the bar. Each longitudinal seat 220 has a depth in the transverse direction such as to allow the insertion of the L-shaped part of a clasp structure projecting from the inner surface of the bar. Each longitudinal seat also has a longitudinal length such as to allow a longitudinal translation of said clasp structure 121 inside the seat 220.

[0038] Each seat comprises a longitudinal, inner, rear wall.

[0039] Each seat communicates with the rear surface by means of a through-duct passing from the rear surface to the inner rear wall of the seat. A retractable arm 210 is inserted through the duct, said arm having a terminal part comprising a head 211 suitable for engagement with the clasp structure 121 for pulling thereof in the transverse direction.

[0040] The retractable arm is movable in the transverse direction upon operation of a respective drive 215 between an extended position, where the head of the arm is arranged at a maximum distance from the inner rear wall of the respective seat, into a retracted position, where the head is arranged at a minimum distance from said inner rear end wall of the seat.

[0041] The retractable arm 211 may for example be the piston of a pneumatically operated cylinder / piston unit or the movable arm of an electric linear actuator, controlled by an electric drive.

[0042] The head 211 of the arm has the form of a semi-spherical cap, with a diameter greater than an end part of the arm 21 connected to the head 211 and convex surface connected to the arm and directed towards the inner rear surface of the longitudinal seat.

[0043] The longitudinal body has preferably, on its front surface for coupling to the bar 100, a longitudinal groove 224 arranged in the longitudinal direction between the two first seats 220 and designed to receive the transverse guide pin 124 which projects from the rear face 120a of the bar 100. The guide pin 124 is in this way able to be slidingly inserted inside the longitudinal groove, thus keeping the bar holder 200 and the bar 100 correctly aligned for rapid engagement between the clasp structures 121 and the head 211 of the respective retractable arm.

[0044] On the outside of a respective one of the retractable arms 210 in the longitudinal direction, preferably at the opposite longitudinal ends of the barholder group 200, there is arranged a respective conductive pin 230 of a pair of transverse conductive pins (for example made of brass) for conveying the electric power to the welding bar 100.

[0045] Each conductive pin 230 is electrically insulated from the longitudinal body of the bar holder 200 and has a conductive end tip 231 suitable for making contact with a respective electrical contact 130 of the bar 100. Each pin 230 is movable in the transverse direction and pushed by a respective elastic element, for example a spring 22, in a forwards direction towards the respective contact 130 of the bar.

[0046] The spring 232 reacts, on one side, against a rear annular surface of the tip 231 and, on the other side, against a perforated longitudinal / vertical plate 234 arranged behind the longitudinal bar-holder body and fixed thereto, for example by means of screws 234a. The pin 230 is inserted through the perforated plate 234 and is movable in a transverse direction with respect thereto.

[0047] Therefore, the tip 231 of the pin 230 is kept pressed in contact against the respective electrical contact 130 of the bar 100, ensuring a stable conductive connection.

[0048] Preferably, in the position where each pin 230 is located, the front face of the bar holder 200 has a step 226 which has a front surface at a greater distance from the respective bar 100 than the front face part which has the seats for the clasp structures 121 a and therefore than the line of contact between the rear face of the bar and the front face of the bar holder.

[0049] In this way, the tips 231 may project in the transverse direction from the front surface of the bar holder so that their terminal end for making contact with the contact 130 of the bar is situated substantially along the line of contact between the rear surface 120a of the bar 100 and front surface of the bar holder.

[0050] With this configuration and with reference to Figs. 3-5, a method of assembling a welding bar 100 on a sealing station of a bagging machine provided with a bar-holder group 200 may comprise the following steps:

[0051] - arranging the bar 100 with its rear face 120a situated opposite and spaced in the transverse direction Y-Y from the front face of the bar holder 200 so as to align each clasp structure 121 with a respective seat 220 of the bar holder 200;

[0052] - arranging each retractable arm 210 in an extended position in the transverse direction Y-Y, such that the head 211 is situated at the minimum distance from the bar 100;

[0053] - translating the bar 100 and / or the bar holder 200 with respect to each other in the transverse direction so as to insert each clasp structure 121 inside the respective seat 220 of the front face of the bar holder 200, in a lateral position with respect to the head of the retractable arm 210 inserted inside the seat 220;

[0054] - If present, the guide pin 124 is inserted at this point inside the respective groove 224 of the bar holder 200;

[0055] - translating the bar 100 in the longitudinal direction X-X so as to arrange: o each clasp structure 121 in relative engagement with the respective head 211 of the retractable arm 210 inserted inside the seat 220; In particular, the twin-tooth fork 121 b engages the arm 210 inside the slot 121d between its prongs, behind the head 211 , which is retained between the prongs and the rear face 120a of the bar; o each tip 231 of a conductive pin 230 of the bar holder 200 in vertical and longitudinal alignment with a respective contact 130 of the bar 100, preferably already in contact with the respective contact 130;

[0056] - actuating the retractable arms 210 in the transverse direction Y-Y such that they retract from the extended position, spaced from the bar-holder body 200, into the retracted position, close to the inner wall of the respective seat 220. The movement of the arms 210 causes pulling of the corresponding clasp structures engaged by the respective head 211 of the arm towards the bar-holder group 200, in particular against the inner end wall of the seat 220, which results in stable coupling between bar 100 and bar holder 200, with the rear face of the bar held stably against the front face of the bar holder, and the compression of the elastic means 232 of each conductive pin 230 which push the respective tip against the associated contact 130 of the bar 110, resulting in the stable conductive connection between tip 231 and contact 130.

[0057] For disassembly of the bar 100, for example in the case of a format change which requires a welding bar with welding part which has a different longitudinal extension, the steps are performed in reverse:

[0058] - actuating the retractable arms 210 in the transverse direction Y-Y such that they extend from the retracted position, into the extended position, spaced from the inner wall of the respective seat 220; the movement of the arms 210 causes the partial disengagement of the respective clasp structures 121 engaged by the respective head 211 of the arm, freeing them for longitudinal translation inside the respective seat 220;

[0059] - translating the bar 100 in the longitudinal direction, in the opposite direction to the direction of assembly, so as to move the clasp structures 121 inside the respective seats 220, releasing the forks 121c of the clasp structures from the respective retractable arm 210;

[0060] - transverse translation Y-Y of the bar away from the bar holder 200, with extraction of the clasp structures 121 from the respective seats 220 and interruption of the electrical contact between the tips 231 and the contact plates 130;

[0061] - the bar 100 is at this point free and may be removed and replaced with a different bar 100.

[0062] Advantageously, it is possible to provide a kit of bars 100 which have a substantially identical connection body 120, at least in the relative positioning of clasp structures 121 and conductive contacts 130, so that they may be mounted on a same bar-holder group 200, but with different welding bodies 110 having a longitudinal length of the welding part adapted to the different width of the bag mouth.

[0063] In order to prevent the possibility of errors in the selection of the bar in relation to the format of the bag to be processed, each bar 100 may be provided with a tag, such as an RFID tag, which contains information about a format, or plurality of formats, so that the bar is suitable for welding. For example, the tag may contain information identifying a bar, a measurement of the welding part of the bar, information identifying a format or a plurality of bag formats which can be used with the bar, information identifying one or more working programs which are compatible with the bar, or a combination of such information.

[0064] The sealing station may be provided with a tag detection and reading device able to read the information and transmit it to a control unit of the bagging machine. If, on the basis of the working program being executed, the tag indicates that the welding bar is not compatible with the format of the bag being processed, the control unit of the machine will implement a safety measure, such as preventing the start of the processing cycle and / or the emission of an alarm signal since the bar mounted is of the wrong size.

[0065] It is therefore clear how, with the welding bar and the bar holder according to the present invention, it is possible to perform simple and quick replacement of the welding bars of a sealing station in order to change the format of a bagging machine. The assembly and disassembly operations do not require screw and female thread means, nor action on the part of specialized personnel, and do not require the application of particular force, the pulling force for stable fixing of the bar in position being performed by the retractable arms which are operated by the sealing station.

[0066] It will be clear that other embodiments are possible for achieving rapid engagement between the clasp structure and the head of the retractable arm. For example, the inset seats could be arranged on the rear surface of the bar with, inside them, the clasp structures which can be engaged in a manner similar to that described by heads of the retractable arms projecting from the front surface of the bar holder.

[0067] The tips and the electrical contacts may also be made in other ways known in the sector in order to provide stable, frontal, electrical contact.

[0068] Although described in connection with a number of embodiments and a number of preferred examples of implementation of the invention, it is understood that the scope of protection of the present patent is determined solely by the claims below.

Claims

CLAIMS1. Welding bar for a bag sealing station of a bagging machine, comprising: a longitudinal front welding face (110a), which has an electrically heated longitudinal part for making contact with the surface of a bag to be sealed; a longitudinal rear face (120a), which during use is opposite to the heating face (110a) in a transverse direction (Y-Y) and which is adapted for coupling with a bar-holder group (200); characterized in that it comprises: at least one pair of clasp structures (121) arranged spaced in the longitudinal direction (X-X) on the rear face (120a), each clasp structure being configured to engage with a terminal head (211 ) of a respective retractable transverse arm (210) of the bar-holder group (200) of the sealing station such that the head exerts a pulling force on the clasp structure (121) when the retractable arm (210) is retracted in the transverse direction (Y-Y) so as to cause stable coupling of the bar (100) to the bar holder (200); at least one pair of conductive contacts (130) arranged on the rear face (110a) for electrical connection by means of contact with a respective conductive pin of the bar-holder group (200), each electrical contact (130) being electrically insulated from the rear face (120) and electrically connected to the welding part of the bar (100) for transmission of electric power thereto.

2. Welding bar according to Claim 1 , wherein each clasp structure (121 ) is configured to engage with the head (211) of the respective retractable arm (210) by means of a first relative translation movement (M1 ) in the transverse direction (Y-Y) between the clasp structure (121) and the bar holder (200) and a subsequent relative translation movement (M2) in the longitudinal direction (X-X).

3. Welding bar according to one of the preceding claims, wherein each clasp structure (121) comprises an L-shaped plate with a transverse arm (121b) projecting in the transverse direction from the rear face (120a) of the bar (100) and a twin-tooth fork (121c) extending from the transverse arm and comprising two longitudinal prongs arranged parallel to and spaced from the rear face (120a) for coupling to the bar holder (200).

4. Bar according to the preceding claim, wherein the fork (121c) defines between its prongs a laterally open longitudinal slot (121d) designed to receive the respective retractable transverse arm (210) of the bar-holder group (200) of the sealing station, while the terminal head (211 ) of the arm, which has a diameter greater than a vertical dimension of the slot (121d) remains engaged against the prongs of the fork (121c) so as to be able to exert a pulling force thereon when the arm is retracted in the transverse direction (Y-Y).

5. Bar according to one of the preceding claims, wherein each clasp structure (121) provides a rapid engagement system for the head (211) of the respective arm (210) which does not require fixing by means of screw / female thread means which require screwing / unscrewing in order to couple or uncouple the welding bar to / from the bar-holder group.

6. Bar according to one of the preceding claims, wherein the at least two clasp structures (121 ) are arranged between the two electrical contacts (130) in the longitudinal direction.

7. Bar according to one of the preceding claims, further comprising a pin (124) projecting in a transverse direction from the rear face (120a) and designed to be inserted inside a longitudinal groove (224) in the opposite front face (220a) of the bar holder (200) so as to guide the bar (100) during a relative translational movement of the bar with respect to the bar holder for engagement between the clasp structures and the arms (210) of the bar holder (200).

8. Welding bar according to one of the preceding claims, comprising a longitudinal welding body (110) which has said longitudinal front face (110a) and a longitudinal connection body (120) which supports the welding body (110) and has the longitudinal rear face (120a), wherein the electrical contacts are electrically insulated from the connection body.

9. Welding bar according to one of the preceding claims, wherein each of said electrical contacts (130) includes a contact plate (131 ), preferably having a contact surface coplanar with the rear face (120a).

10. Welding bar according to one of the preceding claims, wherein each of said electrical contacts (130) has a vertical tongue (132) projecting vertically from the rear surface (120a) and connected by means of a wiredelectrical connection (132a) to a respective, vertical, conductive tongue (112) projecting from a welding body (110) of the bar (100).

11. Welding bar according to one of the preceding claims, further comprising a tag, such as an RFID tag, which contains information about a working program or format, or a plurality of working programs or formats, for which the welding bar is suitable for welding.

12. Bar-holder group (200) for use in a sealing station of a bag filling and sealing machine, comprising a longitudinal body which has a longitudinal front face (220a) for coupling to a rear face (120a) of a welding bar (100) and a rear longitudinal face, opposite to the front face in a transverse direction; characterized in that the front face for coupling to the bar communicates with the rear surface by means of a plurality of transverse through-ducts, wherein each duct receives, inserted through it, a respective retractable arm (210), movable in the transverse direction upon operation of a drive (215) between an extended position, where the head of the arm is arranged at a maximum distance from the rear face of the bar holder (200), and a retracted position, in which the head is at a minimum distance from said rear face; and in that each retractable arm comprises a terminal head (211) adapted for engagement with a respective clasp structure (121 ) of the welding bar (100) for pulling thereof in the transverse direction when the arm is retracted from the extended position into the retracted position; wherein the bar holder (200) also has at least one pair of transverse conductive pins electrically insulated from the longitudinal body of the bar holder (200), each designed to convey an electric power supply to a respective electrical contact of the welding bar (100), each conductive pin (230) having a conductive end tip (231) arranged and configured to establish a stable electrical contact with the respective electrical contact (130) of the bar (100) when the bar (100) is stably coupled to the bar holder (200) by means of pulling by the retractable arms (210) engaged with the respective clasp structures (121).

13. Bar-holder group according to the preceding claim, wherein the front face for coupling to the bar has a plurality of inset longitudinal seats (220), which are open on the front face, each seat (220) having a longitudinal, inner, rear wall communicating with the rear surface by means of arespective one of said transverse ducts, passing from the rear face (220) to the inner rear wall of the seat, wherein each duct is crossed by a respective retractable arm comprising a terminal head (211) suitable for engagement with a respective clasp structure (121 ) of the bar (100) for pulling thereof in the transverse direction, wherein each retractable arm (210) is inserted inside the respective duct and is movable in the transverse direction between the extended position, where the head of the arm is arranged at a maximum distance from the inner rear wall of the respective seat, into a retracted position, where the head is arranged inside the seat, at a minimum distance from said inner rear end wall of the seat.

14. Bar-holder group according to Claim 12 or 13, wherein each conductive pin (230) is arranged on the outside of a respective one of the retractable arms (210) in the longitudinal direction.

15. Bar-holder group according to one of Claims 12-14, wherein each conductive pin (230) is movable transversely with respect to the longitudinal body of the bar-holder group (200) and pushed by a respective elastic element (232) in a forward direction towards the respective contact (130) of the bar.

16. Bar-holder group (200) according to the preceding claim, wherein the elastic element is a spring (232) which reacts on one side against the tip (231) and on the other side against a perforated longitudinal plate (234), arranged behind the longitudinal body of the bar holder and fixed thereto, wherein the pin (231 ) is inserted through the perforated plate (234) and is movable in a transverse direction with respect thereto.

17. Bar-holder group according to one of Claims 12-16, wherein each longitudinal seat (220) has a depth in the transverse direction such as to allow insertion of a clasp structure of the bar (100), projecting from the rear surface of the bar, each longitudinal seat (220) also having a longitudinal length such as to allow a longitudinal translation (M2) of said clasp structure (121) inside the seat (220).

18. Bar-holder group according to one of Claims 12-17, wherein, between each pin (230) and an adjacent retractable arm (210), the front face of the bar holder (200) has a step (226) which positions the front surface of the front face at a greater transverse distance from the respective bar (100)than the front face part which has the arms for engagement with the clasp structures (121) and therefore than the contact line between the rear face of the bar and the front face of the bar holder.

19. Bar-holder group according to the preceding claim, wherein the tips (231) project in the transverse direction from the front surface of the bar holder and are pushed by the elastic element in the transverse direction towards a position such that a terminal end thereof for making contact with the contact (130) of the bar is situated substantially along the line of contact between the rear surface (120a) of the bar (100) and front surface of the bar holder.

20. Bar holder group according to one of Claims 12-19, wherein each retractable arm (211) is a piston of a pneumatically operated cylinder / piston unit or a movable arm of an electric linear actuator.

21. Bar-holder group according to one of Claims 12-20, wherein the head (211) of the arm has the form of a semi-spherical cap, with a diameter greater than an end part of the arm (210) connected to the head (211) and a convex surface connected to the arm and directed towards the inner rear surface of the inset longitudinal seat (220).

22. Bar-holder group according to one of Claims 12-21 wherein, on its front surface for coupling to the bar (100), the longitudinal body has a longitudinal groove (224), arranged in the longitudinal direction between two inset longitudinal seats (220) and designed to receive a transverse guide pin (124) which projects from the rear face (120a) of the bar (100).

23. Sealing station of a bagging machine for filling and sealing bags, comprising a pair of bar holders (200) arranged on opposite sides of a longitudinal line for positioning the mouth of a bag in the sealing station, each bar holder (200) being able to be displaced in a transverse direction from / towards the longitudinal line for positioning of the bag, so that the bar holders (200) and the respective bars (100) supported by them are movable towards and away from each other in a transverse direction between a position spaced from each other and a position close together, where welding parts of the bars (100) are arranged in contact with the opposite surfaces of the top edge of the bag in order to heat them and press them against each other so as to obtain sealed welding of the mouth, wherein each bar-holder group (200) is in accordance with one of Claims 12-22and / or has a bar in accordance with one of Claims 1-11 stably mounted thereon.

24. Station according to the preceding claim, further comprising means for detecting and reading a tag, such as an RFID tag, mounted on the bar (100) and containing information about a working program or format, or a plurality of working programs or formats, for which the bar is suitable for welding, the station being configured for transmission of the read information to the control unit of the bagging machine.

25. Method of assembling a welding bar (100) according to one of Claims 1 -11 on a sealing station of a bagging machine provided with a bar-holder group (200) according to one of Claims 12-22, comprising the following steps:- arranging the bar (100) with its rear face (120a) situated opposite and spaced in the transverse direction (Y-Y) from the front face of the bar holder (200) so as to align each clasp structure (121) with a respective seat (220) of the bar holder (200);- arranging each retractable arm (210) in an extended position in the transverse direction (Y-Y), positioning the head (211) at a minimum distance from the bar (100);- translating the bar (100) and / or the bar holder (200) with respect to each other in the transverse direction so as to insert each clasp structure (121) inside the respective seat (220) of the front face of the bar holder (200), in a lateral position with respect to the head of the retractable arm (210) inserted inside the seat (220);- translating the bar (100) in the longitudinal direction (X-X) so as to arrange: o each clasp structure (121) in relative engagement with the respective head (211) of the retractable arm (210) inserted inside the seat (220); o each tip (231) of a conductive pin (230) of the bar holder (200) in vertical and longitudinal alignment with a respective contact (130) of the bar (100), preferably already in contact with the respective contact (130);- actuating the retractable arms (210) in the transverse direction (Y-Y) such that they retract from the extended position, spaced from the bar holder body (200), into the retracted position, close to the inner wall of the respectiveseat (220), so that the movement of the arms (210) causes pulling of the respective clasp structures engaged by the respective head (211) of the arm towards the bar holder group (200), in particular against the inner end wall of the seat (220) which results in stable coupling together of the bar (100) and bar holder (200), with the rear face of the bar held stably against the front face of the bar holder and the stable conductive connection between tip (231) and contact (130).

26. Method of disassembling a bar (100) according to one of Claims 1 -11 mounted on a bar holder group (200) according to one of Claims 12-22 of a sealing station of a bagging machine, comprising the following steps:- actuating the retractable arms (210) in the transverse direction (Y-Y) such that they extend from the retracted position into the extended position, spaced from the inner wall of the respective seat (220), so as to cause partial disengagement of the respective clasp structures (121) engaged by the respective head (211) of the arm, freeing them for longitudinal translation inside the respective seat (220);- translating the bar (100) in the longitudinal direction so as to move the clasp structures (121 ) inside the respective seats (220), releasing them from the respective retractable arm (210);- transverse translation (Y-Y) of the bar away from the bar holder (200), with extraction of the clasp structures (121) from the respective seats (220) and interruption of the electrical contact between the tips (231) and the contact plates (130);- removal of the bar (100) from the sealing station.

27. Kit comprising a plurality of bars according to one of Claims 1-11 , each suitable for assembly on a same bar-holder group according to one of Claims 12-22, at least some of said plurality of bars having a welding part with a longitudinal length different from that of another bar (100).

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