Machine and method for making electrical energy storage devices

Abstract

The method for making electrical energy storage devices of the type comprising a wound element (11) wound around a longitudinal axis (X) thereof, provides a step of transporting a wound element (11) on a respective mobile carriage (20) along a guide (12 A) of a conveyor (12) which defines an advancement path (A) to a welding station (13, 13') provided with a welding seat (51) configured to accommodate a first end (11 A, 11B) of said wound element (11), and where a collector disc (100) has been positioned to be welded to said first end (11A, 1 IB), wherein said wound element (11) is horizontally oriented with said longitudinal axis (X) transverse with respect to said advancement path (A).

Description

[0001] “MACHINE AND METHOD FOR MAKING ELECTRICAL ENERGY STORAGE DEVICES”

[0002] FIELD OF THE INVENTION

[0003] The present invention concerns a machine for making electrical energy storage devices and a corresponding method. In particular, the machine and method are for making the type of electrical energy storage devices that comprise a wound element, known as a jelly roll or jelly roll-shaped element, with a cylindrical or substantially cylindrical or oval shape.

[0004] BACKGROUND OF THE INVENTION

[0005] Batteries with a cylindrical or oval shape which contain, as a single electrochemical cell, a strip wound around a core have long been known. The strip consists of a cathode film and an anode film between which a separator film is inserted. Usually, the strip also comprises another separator film to cover the cathode.

[0006] Two covers are provided at the ends of the wound strip, each consisting of a respective disc acting as an electric current collector, one relating to the anode and the other relating to the cathode. These discs are connected to the ends of the wound element through welding.

[0007] This operation, made delicate because of the absolute precision required when welding, is usually carried out by means of special welding machines in which the welding device is fed on one side with the wound elements in orderly succession, and on the other side with the discs, in orderly succession, to be welded to the ends of the wound elements.

[0008] An example of these welding machines is described in patent document CN 108393583.

[0009] Known machines do not fully meet the needs of the industry and are affected by several disadvantages.

[0010] For example, known machines are able to move the disc only in a same plane, so that the orientation of the wound element at the time of welding determines the orientation of the disc during its entire feed. For example, in the event the wound element is oriented horizontally at the time of welding, the disc has to be fed in a vertical plane, in particular parallel to the ends of the wound element. This limited flexibility creates problems in managing one or both of either the wound element or the disc.

[0011] Another problem with known machines lies in the complexity of checking the correct orientation of the disc while it is being fed, that is, checking that the disc is fed with the faces oriented correctly relative to the orientation they have to have at the time of welding.

[0012] Another problem concerns the alignment between the wound element and the disc at the time of welding. Known machines do not allow to achieve an optimal precision of the alignment between these two elements.

[0013] Another problem arises during welding, especially when using a laser welder. During this step, so-called weld spatter or splashes are created, which spread uncontrollably and stick almost everywhere. This leads to a considerable need for preventive scheduled maintenance, which can involve frequent cleaning of the station where the welding is performed, and / or an equally frequent replacement of the welding jig in which the disc is accommodated during welding.

[0014] In addition, replacing the welding jig is a long and challenging operation because it contains internal channels connected in a fluidic manner, through ducts, to a suction system to keep the disc fixed during welding. Each time the disc is replaced, it is therefore necessary to detach all the ducts in order to remove the jig and reattach them all after putting on the new jig. This results in different and long machine downtimes, to the detriment of plant productivity.

[0015] In addition, the jig is very complex, and consequently very expensive. The economic impact is such that, within a few months, the spare parts of the single jig become more expensive than the purchase price of the machine itself.

[0016] There is therefore the need to perfect a machine and method for making energy storage devices that can overcome at least one of the disadvantages of the state of the art.

[0017] To do this, it is necessary to resolve the technical problem of being able to optimally manage both the wound elements as well as the discs to be welded.

[0018] In particular, one purpose of the present invention is to provide a machine and perfect a method for making electrical energy storage devices that allow to orient the wound elements and the discs to be welded independently of each other while they are fed, before welding. Another purpose of the present invention is to provide a machine and perfect a method for making electrical energy storage devices that allow to check the correct orientation of the faces of the discs automatically, quickly and reliably while they are fed.

[0019] Another purpose of the present invention is to provide a machine and perfect a method for making electrical energy storage devices that, at the time of welding, offer a very high precision in the alignment of the wound element and the disc to be welded.

[0020] Another purpose of the present invention is to provide a machine and perfect a method for making electrical energy storage devices that allow to reduce or eliminate the damage to the welding jig caused by the accumulation of welding spatter.

[0021] Another purpose is to provide a machine and perfect a method for making electrical energy storage devices that allow to replace the welding jig easily and quickly.

[0022] Another purpose is to provide a machine and perfect a method for making electrical energy storage devices that are economical and allow to replace only a part of the welding jig.

[0023] The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

[0024] SUMMARY OF THE INVENTION

[0025] The present invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.

[0026] In accordance with the above purposes and to resolve the technical problem described above in a new and original way, also achieving considerable advantages compared to the state of the prior art, a method according to the present invention for making electrical energy storage devices of the type comprising a wound element, wound around a longitudinal axis thereof and formed by winding a first electrode film, a second electrode film and at least one separator interposed between the first and second electrode film, comprises a step of transporting a wound element on a respective mobile carriage operated by a drive system along a guide of a conveyor which defines an advancement path towards a welding station comprising a welding seat configured to accommodate a first end of the wound element, and where a collector disc to be welded to the first end has been positioned, wherein the wound element is oriented with the longitudinal axis horizontal and transverse, preferably perpendicular, with respect to the advancement path.

[0027] In accordance with one aspect of the present invention, when the wound element reaches the welding station, the method comprises a step of stopping the carriage at the welding seat; a step of approaching the wound element against the welding seat, wherein the wound element is pushed along its longitudinal axis so as to insert the first end into the welding seat; a step of welding the collector disc onto the first end of the wound element. In addition, after the stopping step but before the approaching step, the method comprises a decoupling step in which the carriage is decoupled from the drive system so that the carriage, during the approaching step, is capable of moving bidirectionally on the guide along the advancement path so as to allow the alignment of the wound element with the collector disc without the aid of the drive system.

[0028] Doing so achieves at least the advantage of guaranteeing that the longitudinal axis of the wound element and the central axis of the collector disc are perfectly aligned, despite the slight variations in shape that the wound element may have. Furthermore, the optimized alignment is achieved in a quick and simple manner.

[0029] In accordance with another aspect of the present invention, there is also provided a machine for making electrical energy storage devices of the type comprising a wound element, wound around a longitudinal axis thereof and formed by winding a first electrode film, a second electrode film and at least one separator interposed between the first and second electrode film. The machine comprises a conveyor configured to transport the wound elements along an advancement path wherein the wound elements are arranged with the longitudinal axis horizontal, each one on a respective carriage so that the longitudinal axis is transverse, preferably perpendicular, to the advancement path, by means of a drive system configured to move the carriage on a guide; at least one welding station provided with a welding seat configured to accommodate a first end of the wound element to be welded to a respective collector disc, wherein the drive system is configured to stop the carriages at the at least one welding station so as to position them, one at a time, facing the welding seat; a welding device configured to weld the collector disc onto the first end of the wound element; and a pushing member configured to bring the wound element close to the welding seat.

[0030] The machine further comprises a central control unit programmed to respectively control the drive system so that, when the wound element reaches the welding station, the corresponding carriage carrying the wound element is stopped; the pushing member so as to drive it in order to bring the wound element close to the welding seat, pushing the wound element along the longitudinal axis until the first end is inserted into the welding seat; and, after stopping the carriage but before bringing the wound element close to the welding seat, a decoupling of the carriage from the drive system, so that the carriage can move bidirectionally on the guide along the advancement path while it is pushed by the pushing member, so as to allow the alignment of the wound element with the collector disc without the aid of the drive system.

[0031] DESCRIPTION OF THE DRAWINGS

[0032] These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of an embodiment, given as a non-restrictive example with reference to the attached drawings wherein:

[0033] - fig. 1 is a plan view of a machine for making electrical energy storage devices, according to the present invention;

[0034] - fig. 2 is a three-dimensional view of a wound element;

[0035] - figs. 3 A and 3B are three-dimensional views of the two surfaces of a collector disc to be welded to one end of the wound element of fig. 2;

[0036] - fig. 4 is a schematic three-dimensional view of a feeding unit of the machine of fig. 1, which also shows a laser device of the machine;

[0037] - fig. 5A is a schematic, enlarged scale lateral view of a transfer unit comprised in the feeding unit of fig. 4;

[0038] - fig. 5B is a partial, schematic top plan view of the transfer unit of fig. 5A, which also shows a flattening station comprised in the machine;

[0039] - fig. 6 is a partial and schematic three-dimensional view of a welding station of the machine of fig. 1, showing in particular a welding jig;

[0040] - figs. 7A and 7B are three-dimensional views of the two faces of a welding jig of the machine of fig. 1 ;

[0041] - figs. 8A and 8B are three-dimensional views of two components of the welding jig of figs. 7A and 7B;

[0042] - figs. 9 and 10 are three-dimensional section views of the welding station, shown from different angles, in which both an electrical energy storage device to which a collector disc is being welded, and also the welding jig of figs. 6, 7A, 7B and a portion of the laser device that is intended to be coupled to the welding jig are visible;

[0043] - figs. 11 and 12 are lateral section views of a portion of the welding jig, of the electrical energy storage device to which the collector disc is being welded, and of a portion of the laser device that is intended to be coupled to the welding jig, wherein this latter portion is shown at a waiting position and at an advanced coupling position, respectively;

[0044] - fig. 13 is a partial and schematic three-dimensional view of the laser device comprised in the machine according to the present invention;

[0045] - fig. 14 is a three-dimensional enlarged scale view of an extremal connection member of the welding device.

[0046] We must clarify that the phraseology and terminology used in the present description, as well as the figures in the attached drawings also in relation as to how described, have the sole function of better illustrating and explaining the present invention, their purpose being to provide a non-limiting example of the invention itself, since the scope of protection is defined by the claims.

[0047] To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can be conveniently combined or incorporated into other embodiments without further clarifications.

[0048] DESCRIPTION OF AN EMBODIMENT OF THE PRESENT INVENTION

[0049] With reference to fig. 1, a machine 10 for making electrical energy storage devices according to the present invention is configured to weld collector discs 100 to the ends 11A, 1 IB of wound elements 11, which collector discs 100 then act as a cathode and anode for the electrical energy storage device.

[0050] The wound elements are of a known type, in particular they are each formed by winding at least a first electrode film, a second electrode film and at least one separator interposed between the first and second electrode film.

[0051] The wound elements 11 have a substantially cylindrical shape (fig. 2) with a central axis coinciding with a longitudinal axis X, and therefore have two ends 11 A, 11B with a circular or substantially circular shape, on each of which a respective collector disc 100 is welded.

[0052] Each collector disc 100 has an internal face 100A (fig. 3 A), intended to be placed in contact with an end HA, 1 IB of the wound element 11, and an external face 100B (fig. 3B) opposite to the internal face 100A, and has a central axis Y.

[0053] The collector discs 100 are the same for both ends 11A, 1 IB, and in the example given here have three welding zones 101 angularly distributed in a homogeneous manner on which a laser beam L is incident, shown in figs. 4 and 5 A with a dashed line. Each welding zone 101 is substantially fan-shaped and protrudes slightly from the internal face 100A, so as to come into contact with the cathode or anode sheet of the wound element 11. The collector discs 100 also comprise a central protrusion 102 which also protrudes from the internal face 100A, so as to come into contact with a central zone of the ends 11 A, 1 IB of the wound element 11 (figs. 3 A and 3B).

[0054] The welding zones 101 and the central protrusion 102 create corresponding recesses in the external face 1 IB, since they protrude from the internal face 100 A.

[0055] The machine 10 comprises a conveyor 12 configured to transport the wound elements 11 along an advancement path A that passes in succession through a first welding station 13, a turnover station 14, and a second welding station 13’. The conveyor 12 offers the technical advantage of having the wound element 11 already substantially oriented at the welding position when it reaches the first and second welding station 13, 13’.

[0056] Advantageously, at each of the latter the advancement path A is rectilinear. Preferably, the welding stations 13, 13’ and the turnover station 14 are on a same rectilinear segment of the advancement path A.

[0057] The welding 13, 13’ and turnover 14 stations are located along an external side of the advancement path A, which is configured as a closed-loop path and lies in a horizontal plane. The wound elements 11 are transported thereon with their longitudinal axis X arranged horizontally and oriented transversely, in particular perpendicular, to the advancement path A (fig. 1). At the first welding station 13, a collector disc 100 is welded to the first end 11A of the wound element 11. In order to be able to weld another collector disc 100 onto the other end 1 IB of the wound element 11 at the second welding station 13 the wound element 11 is overturned by 180° in a known manner at the turnover station 14, so that it always has the longitudinal axis X arranged horizontal and oriented perpendicular to the advancement path A, but with the second end 1 IB facing outside the path, that is, facing the second welding station 13’.

[0058] Given the horizontal positioning of the wound elements 11 at the welding stations 13, 13’, it can be concluded that at these stations the collector discs 100 have to be at a welding position SI that lies on a vertical or substantially vertical welding plane Pl, so that their central axis Y can be aligned with the longitudinal axis X of the corresponding wound element 11.

[0059] The wound elements 11 are transported to the welding 13, 13’ and turnover 14 stations individually. For this purpose, carriages 20 (figs. 4 and 6) are provided movable along the advancement path A, slidably coupled to a guide 12A of the conveyor 12 that develops along the advancement path A. Respective urging members 131, 131 ’ are also provided in the welding stations 13, 13’, configured to approach the wound element 11 against the welding seat 51. In this way, with a single member of each welding station 13, 13’ it is possible to insert and align the wound elements 11 in the welding seat 51 , in collaboration with other members described below.

[0060] The carriages 20 are operated, along the guide 12 A, by a drive system 120. Particularly advantageously, the drive system 120 is of the linear motor type and comprises a plurality of primary windings 121, fixedly arranged in the guide 12A and functioning as the linear motor’s stators, and at least one permanent magnet 122, arranged on each carriage 20 and functioning as the linear motor’s rotor. Each primary winding 121 can be energized independently of the others to control the motion of the carriage 20. The primary windings 121 are arranged in succession, so as to cover the entire advancement path A.

[0061] The linear motor drive system 120 allows for a fast, flexible and precise movement of the individual wound elements 11 along the path, wherein each wound element 11 is loaded onto a single independent carriage 20.

[0062] Furthermore, with this configuration it is possible to decouple the carriages 20 from the drive system 120, simply by temporarily ending the energization of one or more primary windings 121, when required, for example when the carriage 20 reaches the welding stations 13, 13’. This allows, for example, to keep one or two carriages 20 stationary at one or both of the welding stations 13, 13’, and while the collector discs 100 are welded onto the corresponding wound elements 11 , move other carriages 20 along the advancement path A.

[0063] The drive system 120 is controlled by a central control unit 200 of the machine 10, which also controls the other feeding units and operating stations of the machine 10.

[0064] Each carriage 20 comprises a base 21 coupled to the guide 12A and in which the permanent magnet 122 is housed, and a support member 22 mounted on the base 21 and on which a respective wound element 11 is rested. The support member 22 is equipped with gripping means 23, specifically a pair of grippers 23 A that partly wrap around the wound element 11 externally, allowing to keep the wound element 11 at a stable position during the advance of the carriage 20 along the advancement path A. The support member 22 is slidably mounted on the base 21 of the carriage 20 in a direction perpendicular to the advancement path A, and it is connected to the carriage 20 by means of a suitable return member 24, specifically a pair of springs. The return member 24 is configured so as to automatically return the support member 22 to a rest position when the push by the urging member 131, 131 ’ ceases, and in a direction away from the welding position SI.

[0065] Corresponding feeding units 30 configured to feed the collector discs 100 individually are provided at the welding stations 13, 13’. We must clarify that the two feeding units 30 are identical to each other, and are configured to bring the collector discs 100 into a substantially horizontal withdrawal plane P2 (shown in fig. 5A).

[0066] Each feeding unit 30 comprises a storage device 31, configured to rotate about a vertical rotation axis V 1 and circumferentially housing a plurality of cartridges 110, each containing a plurality of collector discs 100. Obviously, in the cartridges 110 the collector discs 100 are stacked upon each other and arranged horizontally. Such a feeding unit 30 offers the advantage of allowing to load the collector discs 100 into cartridges 110, thus not having to continuously monitor the storage device 31. The later can advantageously comprise a loading station (not shown in the drawings) accessible to an operator in order to manually load collector disc 100 cartridges.

[0067] The collector discs 100 are picked up individually from the cartridges 110 at a first position PPI, by means of pick and place members 32, and transferred to a centering station 33 at a second position PP2, and subsequently to a transfer carousel 34 at a third position PP3 (fig. 4). The transfer carousel 34 is configured to rotate about a vertical axis V2 in order to move, along an arc of circumference C (fig. 1), singularized collector discs 100 housed in respective housing seats 34A lying on the withdrawal plane P2 towards the withdrawal position W.

[0068] The pick and place members 32 comprise, for example, two suckers 321, 322 spaced apart by a distance “d” equivalent to the distance between the first position PPI and the second position PP2, so that when a first sucker 321 is in position to pick up a collector disc 100, the second sucker 322 is at the centering station 33 to release another previously picked up collector disc 100. Similarly, the third position PP3 is positioned at the same distance d from the second position PP2, so that when the first sucker 321 is in the centering station 33, the second sucker 322 releases another collector disc 100 to the transfer carousel 34. This allows to carry out two collector disc 100 transfers while the machine is working.

[0069] In order to pick up and release the collector discs 100, the suckers 321, 322 are advantageously connected in a known manner to a suction system, controlled by the central control unit 200.

[0070] The centering station 33 comprises a centering chuck 33 A configured to move the collector disc 100 so as to bring its central axis Y into a predetermined centering position. This guarantees the correct positioning of the collector discs 100 subsequently, in particular at the welding position SI.

[0071] The transfer carousel 34 instead comprises three housing seats 34 A, angularly distributed around its vertical rotation axis V2, each containing a respective collector disc 100 (fig. 4). The housing seats 34A are of course configured and dimensioned to each accommodate a single collector disc 100. The transfer carousel 34 can contain a plurality of arms, at least two. Preferably, the transfer carousel 34 has three arms 34B that extend radially and are evenly distributed around the vertical rotation axis V2. Each arm 34B contains, substantially at its end, a respective housing seat 34A.

[0072] The housing seats 34A are preferably connected to a suction system to temporarily retain the collector discs 100 in position, the suction system being in turn controlled by the central control unit 200.

[0073] The carousel 34 is configured to transfer, in the withdrawal plane P2, the collector discs 100 from the aforementioned third position PP3 first to a control station 35 and, subsequently, to a withdrawal position W where the collector discs 100 are then fed to a transfer device 40, described below.

[0074] The third position PP3, the control station 35 and the withdrawal position W are also angularly distributed around the vertical rotation axis V2, so that they are simultaneously occupied by the three housing seats 34A of the transfer carousel 34.

[0075] The control station 35 is configured to check the relative arrangement of the internal face 100 A and / or the external face 100B of the collector disc 100 housed in the housing seat 34A of the transfer carousel 34.

[0076] For this purpose, the control station 35 comprises a control seat 35 A, in which there is positioned a housing seat 34A of the transfer carousel 34 with a respective collector disc 100, and a visual control device 35B oriented towards the control seat 35A and configured to check that the collector disc 100 is oriented correctly, in particular that its external face 100B is visible. The visual control device 35B is also configured to check the orientation of the collector disc 100 around its central axis Y.

[0077] In the event it is detected that the collector disc 100 is upside down, therefore with the wrong face oriented towards the visual control device 35B, it is discarded. If, on the other hand, an incorrect angular orientation is detected, this angular orientation will then be corrected before the collector disc 100 is fed to the transfer device 40.

[0078] After the control station 35, the transfer carousel 34 transfers the collector discs 100 to the withdrawal position W, at which a lifting member 36 (fig. 5 A) is placed, configured movable along a vertical development axis V3 thereof to engage a respective collector disc 100 from below, which lies on the withdrawal plane P2, and push it towards the transfer device 40 positioned above the withdrawal position W (figs. 4 and 5A). The lifting member 36, which can comprise a simple rod, is also configured rotating about its longitudinal axis in order to rotate the collector disc 100 about its central axis Y, so as to potentially correct its angular orientation if - as mentioned above - the control station 35 has detected an incorrect angular orientation, in view of its subsequent welding to the wound element 11.

[0079] We must specify that when the collector discs 100 are transferred to the transfer device 40, they are oriented in a horizontal plane, while in order to be welded to the wound element 11 they have to be in the vertical welding plane Pl . To this end, the transfer device 40 is configured to transfer the collector discs 100 from a horizontal plane to a vertical plane. In particular, at the withdrawal position W the transfer device 40 is configured to pick up, one at a time, the collector disks 100 lying on the horizontal withdrawal plane P2, therefore with their central axis Y vertical, and to transfer them, by rotation, to the welding position S 1 of the welding station 13, 13 ’ on the welding plane P 1 , which is vertical, so that the collector discs 100 are arranged with the respective central axis Y oriented horizontal.

[0080] The transfer device 40 is rotatable about a rotation axis R (figs. 4 and 5A) inclined with respect to the welding plane Pl and to the withdrawal plane P2, in particular being approximately coincident with the bisector of these two planes. That is, the rotation axis R is inclined by 45° with respect to the horizontal and vertical.

[0081] The transfer device 40 comprises at least one pick-up arm 41. The at least one pick-up arm 41 is configured to rotate about the rotation axis R. Preferably, the transfer device 40 comprises two pick-up arms 41, each lying on a lying plane P3 inclined with respect to the rotation axis R so that the lying plane P3 is, alternatively, parallel to the horizontal withdrawal plane P2 and parallel to the vertical welding plane Pl (figs. 4 and 5 A). The transition from the position parallel to the withdrawal plane P2 to the position parallel to the welding plane Pl, and vice versa, occurs through a rotation about the rotation axis R.

[0082] Each pick-up arm 41 is oriented at 45° with respect to the rotation axis R. Furthermore, the two pick-up arms 41 are orthogonal to each other and diametrically opposite with respect to the rotation axis R, so that a 180° rotation of a pick-up arm 41, starting from an orientation parallel to the welding plane Pl, results in a 90° re-orientation parallel to the withdrawal plane P2, and vice versa (fig. 5A). By doing so, while one pick-up arm 41 receives a collector disc 100 at the withdrawal position W, the other pick-up arm 41 is at the welding position SI, where a collector disc 100 is welded to a wound element 11.

[0083] The transfer device 40 comprises, at each pick-up arm 41, in particular at an external face thereof, a respective welding jig 50 configured and dimensioned to simultaneously accommodate at the welding position SI one end 11A, 1 IB of the wound element 11 and the respective collector disc 100 to be mutually welded (fig. 6). The welding jig 50 has a first side 50A (fig. 7A) and a second side 50B (fig. 7B) opposite to the first.

[0084] A welding seat 51 is defined in the welding jig 50, at which the collector discs 100 are effectively welded to the wound elements 11 (fig. 7A). The welding seat 51 also acts as a seat for accommodating the discs 100. Each welding seat 51 has a first side 51 A, facing the welding station 13, 13’ when it is located there, and in which the collector disc 100 is located, and a second side 5 IB opposite to the first. The first side 51 A of the welding seat 51 is at the first side 50A of the welding jig 50, and the second side 5 IB of the welding seat 51 is at the second side 50B of the welding jig 50.

[0085] The welding seat 51 receives the collector discs 100 on its first side 51 A, at the withdrawal position W, and retains them with suction. For this purpose, each welding jig 50 is connected to a suction system, in turn controlled by the central control unit 200.

[0086] When the pick-up arm 41 is at the corresponding welding station 13, 13’, the welding seat 51 coincides with the welding position SI. At this position, the pickup arm 41, and therefore also the welding jig 50, is located at a distance from the guide 12A of the conveyor 12, so as to allow the free passage of the carriages 20 and the free rotation of the transfer device 40. To be able to insert one end 11 A, 1 IB of the wound elements 11 into the welding seat 51, the machine 10 is equipped, at the welding station 13, 13’, with an urging member 131, 131 ’ (fig. 6) for pushing the wound element 11 perpendicularly to the advancement path A towards the external side of the conveyor 12.

[0087] The push of the wound element 11 is also allowed by the fact that each of the carriages 20 has a support member 22 slidably mounted on the base 21, as described above and as can be seen in fig. 6. As mentioned above, in the step of welding the collector disc 100 to the corresponding wound element 11 , their respective central Y and longitudinal X axis have to be aligned very precisely, in order to create the electrical connections in an optimal manner. To create a perfect alignment between the aforementioned axes, the welding jig 50 is equipped with movable alignment elements 52 (figs. 6 and 7). These are configured to approach each other until they come into contact with the end 11 A, 1 IB of the wound element 11 when the carriage 20 is idle, which allows to center and align the longitudinal axis X of the wound element 11 and the central axis Y of the collector disc 100 in an automatic and optimized manner.

[0088] Advantageously, these alignment elements consist of a pair of centering members 52 A, with a preferably curved shape mating the external shape of the wound elements 11 and movable between a distanced position, in which they accommodate the end 11 A, 1 IB of the wound element 11 between them, and an approached position, in which they align the wound element 11 with the collector disc 100 to be welded (figs. 6 and 7). This guarantees that, at the time of welding, the longitudinal axis X of the wound element 11 and the central axis Y of the collector disc 100 are perfectly aligned (fig. 6). In particular, the centering members 52A are mutually movable along a direction parallel to the advancement path A at each welding station 13, 13’. This allows to easily bring the end 11 A, 1 IB of the wound element 11 into perfect alignment with the collector disc 100.

[0089] To allow the aforementioned alignment, the central control unit 200 is configured to control the decoupling of the carriages 20 from the drive system, at the welding stations 13, 13’. In this way, the carriages 20, when decoupled from the drive system 120, are free to move bidirectionally on the guide 12A of the conveyor 12 along the advancement path A, typically for small displacements, while the wound element 11 they carry is pushed by the urging member 131, 131 ’ and is aligned with the collector disc 100 by the alignment elements 52.

[0090] Particularly advantageously, each welding jig 50 consists of a first part 501 and a second part 502, removably connectable to each other (figs. 7 A, 7B, 8 A, 8B). More precisely, the first part 501 is fixedly connected to the corresponding pickup arm 41 of the transfer device 40, while the second part 502 is removably connected to the first part 501. The first part 501 has a first side 511, where the welding seat 51 is located, and a second connection side 512, opposite to the first side 511. The second side 512 is configured to couple to the second part 502, in particular on the second side 5 IB of the welding seat 51 (fig. 7B). Furthermore, the first fixed part 501 is configured to retain the collector disc 100, in particular at the welding position SI. It is also configured to accommodate overlapping a collector disc 100 and one end 11 A, 1 IB of the wound element 11. The second removable part 502 is configured to be interposed between the first fixed part 501 and an extremal connection member 61 of the welding device 60, so as to at least partly shield the first fixed part 501 from the degrading effects caused by the laser beam L during the mutual welding of the disc 100 and the first end 11 A, 1 IB of the wound element 11.

[0091] It can be concluded that the second part 502 is configured to be replaced with a new second removable part 502 at the end of its useful life, without having to replace the first fixed part 501 of the welding jig 50, protected by the second removable part 502.

[0092] The second part 502 comprises at least one welding channel 53 configured to direct a shielding gas towards the disc 100 and / or the end 11 A, 1 IB at the welding position SI . The at least one welding channel is also configured to allow a laser beam L of the welding device 60, 60’ to be directly incident on the welding seat that accommodates the collector disc 100 and the end 11A, 11B of the wound element 11 at the welding points.

[0093] Preferably, the second removable part 502 is substantially symmetrical with respect to a central axis. In the example shown, the second part 502 is substantially configured as a ring from which three attachment portions 502 A extend perpendicularly, with a substantially truncated-cone shaped section, angularly distributed around a central axis of the second part 502 (fig. 8A). A through welding channel 53 is made in each attachment portion 502 A, configured to let a welding beam pass. Please note that in the example shown in figs. 7A and 7B, the welding channels 53 are aligned with the welding zones 101 of the collector disc 100, so as to direct the laser beam directly onto the points to be welded.

[0094] The first part 501 and the second part 502 are made of metal materials. They can be made of the same material; however, it is more advantageous for them to be made of different materials. For example, the second part 502 can be made of anodized aluminum, which is particularly hard and therefore suitable to increase the useful life of the second part, thus reducing the frequency of its replacements and therefore having lower maintenance costs. The first part 501 can instead be made of stainless steel.

[0095] The second part 502 is a sacrificial element, since it is directly subjected to the welding’s effects, that is, the spatter (splashes of molten metal) caused by the instability that characterizes the laser welding of the materials involved (copper, aluminum). The use of anodized aluminum is particularly advantageous since it has longer spatter antisticking properties than other materials. Moreover, it is much less expensive than the stainless steel of the first part 501 of the jig 50.

[0096] More precisely, the surface of the second removable part 502 has been subjected to an anodizing surface treatment in order to give the second part 502 antisticking properties, so that it is able to at least partly repel the spatter caused by welding towards or away from the welding jig 50, increasing its useful life and, consequently, increasing the availability of the welding station 13, 13’ in which it is applied.

[0097] The second part 502 also comprises three ducts 54 for delivering a shielding gas, each leading obliquely into a respective welding channel 53. The supply ducts

[0098] 54 each have an inlet aperture 54A made at the annular surface of the second part 502 (figs. 7B and 8A).

[0099] Similarly, the first part 501 comprises three attachment counter-portions 501 A with a truncated cone conformation and angularly distributed, so as to be complementary to the attachment portions 502 A of the second part 502 (fig. 8B).

[0100] There is a corresponding connection duct 55 in each attachment counter-portion 501 A to connect the welding seat 51 to suction means (fig. 9) in a fluidic manner, thus allowing to keep the collector disc 100 in the welding seat 51 through suction. It can therefore be concluded that the welding jig 50 comprises connection ducts

[0101] 55 distributed circumferentially around the welding seat 51, which leads to the advantage of maintaining their orientation during the rotation of the arm 41 of the transfer device 40 about the rotation axis R. Preferably, the connection ducts 55 are connected to suction means in a fluidic manner, in order to keep the collector disc 100 in position. Preferably, the first fixed part 501 will be equipped with the connection ducts 55 that lead into the welding seat 51.

[0102] The connection ducts 55 provide an inclined part 55 A whose end 55B is at the external surface of the corresponding attachment counter-portion 501 A.

[0103] The machine 10 also comprises a welding device 60, 60’ in each welding station 13, 13’ (fig. 1). The two welding devices 60, 60’, preferably of the laser type, are advantageously identical to each other. In particular, each one comprises a laser source 60A (fig. 13) configured to emit the laser beam L in a welding direction X’.

[0104] Each of the welding stations 13, 13’ comprises a fixed frame 64 and a sliding frame 65 (fig. 13). The sliding frame 65 is slidably mounted on the fixed frame 64, which is attached to the base. The welding device 60, 60’ of the respective welding station 13, 13’ is stably fixed to the sliding frame 65.

[0105] According to a preferred embodiment, the fixed frame 64 comprises at least one guide 66, more preferably two guides 66, parallel to each other and oriented so that a sliding direction X” of the sliding frame 65 with respect to the fixed frame 64 is parallel to the welding direction X’ and to the longitudinal axis X of the wound element 11 when it is arranged at the welding position. The sliding frame 65 can comprise at least one carriage 67, preferably a pair of carriages 67 for each guide 66 of the fixed frame 64, so that the welding device 60, 60’ attached to the sliding frame 65 can move close to, and away from, the welding seat 51 in the sliding direction X”. The fixed frame 64 further comprises a linear actuator 68 to operate the sliding movement of the sliding frame 65 along the sliding direction X”.

[0106] Each of the welding devices 60 comprises an extremal connection member 61 configured movable to couple to the welding jig 50, in particular to the second removable part 502, preferably to the second side 5 IB of the welding seat 51. In particular, the extremal connection member 61 has an annular shape configured to connect to the second side 5 IB of the welding seat 51 (figs. 9 and 10).

[0107] The extremal connection member 61 of the welding device 60 comprises a central aperture 610 delimited by a first circular edge 611, the latter having a front surface 612 in turn delimited externally by a second circular edge 613 (figs. 9 and 10).

[0108] The extremal connection member 61 of the welding device 60 also contains connection means 62 configured to put at least one supply duct 54 of a welding channel 53 in connection with a source of the shielding gas, when the extremal connection member 61 is coupled to the welding jig 50. The shielding gas delivered by the source reaches the supply duct 54 after having passed through one or more flexible ducts 69 (fig. 13).

[0109] The connection means 62 comprise respective ducts 620 created inside the extremal connection member 61. The ducts 620 comprise respective apertures 621 on the front surface 612 (fig. 14), which are aligned with the ends 54A of the shielding gas supply ducts 54 of the second parts 502 of the welding jig 50, in order to put them in fluidic communication with the shielding gas source, when the extremal connection member 61 is at the coupling position PA2.

[0110] The extremal connection member 61, in particular its front surface 612, faces the welding seat 51 , that is, the welding position S 1.

[0111] Thanks to the cooperation between fixed frame 64 and sliding frame 65 described above, the welding device 60, 60’ moves back and forth parallel to the sliding direction X”. This movement allows to move the extremal connection member 61 between a waiting position PAI, in which it is far removed from the welding position SI (fig. 11), and an advanced coupling position PA2, in which it rests on the second side 5 IB of the welding seat 51 (fig. 12). In the backward waiting position PAI it allows to have the necessary space to position a new collector disc 100 to be welded to a wound element 11 at the welding position S 1. At the coupling position PA2, the connection means 62 connect to the supply ducts 54 of the second part 502 of the welding jig 50, so as to create a hermetic passage of the shielding gas that reaches the welding seat 51 through the welding channels

[0112] 53, where the welding occurs.

[0113] It can be concluded that the welding channels 53, preferably their supply ducts

[0114] 54, are dimensioned so as to couple to the connection means 62 when the welding jig 50 is arranged at the welding position SI and the extremal connection member 61 has reached the coupling position PA2, so as to allow the passage of the shielding gas coming from the source and incident on the collector disc 100. In particular, the coupling of the welding channels 53 to the connection means 62 is such as to achieve a hermetic seal of the shielding gas coming from the respective source and incident on the collector disc 100.

[0115] In accordance with one variant, the machine 10 comprises, upstream of at least one of the welding stations 13, 13’ (preferably both), a station 15, 15’ for flattening the ends 11A, 1 IB of the wound elements 11 (fig. 5B). This flattening station 15, 15’ is configured to flatten the first or second electrode film constituting the wound element 11, in order to facilitate the welding of the collector disc 100.

[0116] In particular, the flattening station 15, 15’ comprises a further pushing member

[0117] 151, 151 ’ configured to push the wound elements 11 against a flattening surface

[0118] 152, 152’. The latter is vertical and oriented transversely with respect to the longitudinal axis X of the wound elements 11 , that is, parallel to the linear segment of the advancement path A.

[0119] Advantageously, the two flattening stations 15, 15’ are identical to each other and the further pushing members 151, 151 ’ are in turn identical to the urging members 131, 131 ’ of the welding stations 13, 13’. In this way, the configuration of the carriage 20, in particular of the support member 22 slidably mounted on the base 21 in a direction transverse to the advancement path, is exploited to flatten the first electrode sheet at a first end 11 A and, in the second flattening station 15’, the second electrode sheet at the second end 11B of the wound element 11, just before welding a corresponding collector disc 100 thereto. This allows to have, in an effective manner, the flattening stations 15, 15’ in the same machine 10 for welding the collector discs 100, immediately before the welding stations 13, 13’.

[0120] The operation of the machine 10 for making electrical energy storage devices described heretofore comprises the following steps.

[0121] The wound elements 11 are fed one by one on respective carriages 20, which are then made to advance along the advancement path A of the conveyor 12, through the central control unit 200 which controls the drive system 120.

[0122] Each wound element 11 is transported to the first flattening station 15, in which it is pushed against the flattening surface 152 by the pushing member 151 , in order to align the end edge of one of either the first electrode sheet or the second electrode sheet. The wound element 11 is then transported to the first welding station 13, where it is stopped.

[0123] We must clarify that during the transport steps, the wound element 11 is kept in position on the carriage 20 by means of the gripping means 23.

[0124] Meanwhile, a corresponding collector disc 100 is fed to the same welding station 13. As mentioned above, the collector disc 100 is fed by the feeding unit 30 in a horizontal, or substantially horizontal, withdrawal plane P2, while at the welding station 13 it is transported in a vertical, or substantially vertical, welding plane Pl. The collector disc 100 is picked up at the first position PPI of the pick and place member 32 and transferred thereby at the second position PP2, in the centering station 33, where its position is centered with precision. This transfer is performed with the first sucker 321.

[0125] After the centering, the pick and place member 32 is operated again so as to pick up the collector disc 100 from the centering station 33 and transfer it to the third position PP3, in a housing seat 34A of the transfer carousel 34. This second transfer is performed by means of the second sucker 322. Meanwhile, a subsequent collector disc 100 is picked up from the first position PPI with the first sucker 321 and transferred to the centering station 33, at the second position PP2.

[0126] Once a collector disc 100 has been transferred to the transfer carousel 34, the latter rotates by approximately 120° clockwise so as to position the collector disc 100 at the control station 35, where it is checked that the collector disc 100 is oriented correctly. In particular, the angular orientation of the collector disc 100 is checked, so that its welding zones 101 are in a position that will then overlap with the welding channels 53 of the welding jig 50. Furthermore, it is also checked that the collector disc 100 is oriented with the correct face (in this case with the external face 100B) facing upwards.

[0127] If it is detected that it is the internal face 100A of the collector disc 100 that is arranged upwards, the collector disc 100 is discarded, while if it is detected that the angular position is not correct, this can be corrected at the next withdrawal position W, where the collector disc 100 is transferred once the check is finished, again by the transfer carousel 34.

[0128] At the withdrawal position W, the collector disc 100 is engaged from below by the lifting member 36, which is rotatable about its axis in order to be able to correct the angular orientation of the collector disc 100, if necessary. For this correction, the angular orientation of the collector disc 100 is checked by a corresponding visual control device.

[0129] The lifting member 36 is then operated to push the collector disc 100 upwards until it reaches the welding seat 51 created in one of the pick-up arms 41, located above waiting. The collector disc 100 is then held in the welding seat 51 by suction, by the suction system operating be means of the connection ducts 55.

[0130] The collector disc 100 is subsequently transferred, performed individually by means of the pick-up arm 41 of the transfer device 40 lying on a lying plane P3 inclined with respect to the rotation axis R, from a position in which the lying plane P3 is parallel to the withdrawal plane P2 and in which the collector disc 100 is picked up from the withdrawal position W, to the welding position S 1 , in which the lying plane P3 is parallel to the vertical welding plane P 1.

[0131] The transfer device 40 is then operated so as to make it rotate by 180° about the rotation axis R inclined at 45°, this allows to move the collector disc 100 from the horizontal withdrawal plane P2 to the vertical welding plane Pl, at the welding station 13. By doing so, the welding seat 51 is positioned at the welding position SI, together with the collector disc 100.

[0132] The carriage 20 carrying the wound element 11 has been stopped in the welding station 13, in a point such that the wound element 11 is aligned with the welding seat 51, that is, also with the collector disc 100. We must point out that, in the context of the present application, by alignment of the wound element 11 and the collector disc 100, we mean the alignment of the longitudinal axis X of the wound element 11 and of the central axis Y of the collector disc 100.

[0133] Despite the high precision of the carriage 20 in stopping at the desired point, the wound element 11 may not be perfectly circular, but tends to have a certain ovalization. This means that it is not possible to known exactly where the longitudinal axis X is located for each wound element 11. To guarantee that these axes are perfectly aligned, the drive system 120 of the conveyor 12 is controlled by means of the central control unit 200 to temporarily cease the energization of the primary windings 121 of the carriage 20 at the welding station 13, so as to decouple the carriage 20 from the drive system 120. The carriage 20 is then free to move forward or backward along the advancement path A, without the aid of the drive system 120.

[0134] It is evident that if the drive system 120 is different from the linear motor described above, it is sufficient that the system provides for the possibility of releasing the carriage 20 from the guide 12A at the welding station 13.

[0135] The wound element 11 is then approached against the welding seat 51, pushing it along the longitudinal axis X so as to insert the end 11A into the welding seat 5 1. This push is performed by means of the urging member 131 on the second end 1 IB of the wound element 11 (fig. 4). The welding seat 51 is configured so that, during the approach, it displaces the carriage 20 along the guide 12A, until a coincidence between the longitudinal axis X of the wound element 11 and the central axis Y of the collector disc 100 is achieved. This displacement is carried out by means of the alignment elements 52, consisting of the pair of movable opposite centering members 52A, which are operated to move from their distanced position, in which they accommodate the end 11 A to be welded between them, to the approached position, in which they align the wound element 11 with the collector disc 100 to be welded.

[0136] The alignment is achieved when the centering members 52A approach the wound element 11 and clamp the end HA between them. This clamping determines the coincidence between the longitudinal axis X of the wound element 11 and the central axis Y of the collector disc 100. Since the carriage 20 is decoupled from the guide system 120, it is moved with play along the advancement path A due to the clamping between the pair of centering members 52 A, so as to allow the aforementioned coincidence between the longitudinal axis X and the central axis Y.

[0137] It can therefore be concluded that the approach of the wound element 11 against the welding seat 51 provides a first axial displacement sub-step in which the first end HA is introduced into the welding seat 51, and a second transverse displacement sub-step in which the end 11 A is aligned with the collector disc 100, by moving the wound element 11 along the guide 12A. The aforementioned steps are controlled by the central control unit 200. This guarantees, first and foremost, the entry of the end HA, 1 IB of the wound element 11 into the welding seat 51 and, by means of a small displacement of the pair of centering members 52A, the further alignment, during the same pushing step, in which the carriage 20 is idle.

[0138] Subsequently, the collector disc 100 is welded to the end HA of the wound element 11.

[0139] This welding step provides to move the extremal connection member 61 from the waiting position PAI, where it has been until this moment, closer to the advanced coupling position PA2, so that the extremal connection member 61 rests on the second side of the welding jig 50, in particular on the second side 5 IB of the welding seat 51. We must point out that, in the present application, the extremal connection member 61 is part of the welding device 60, which is therefore also moved closer to the welding position S 1.

[0140] Subsequently, a laser beam L is emitted in a welding direction X’. The laser beam L, emitted by the welding device 60, passes through a welding channel 53 of the welding jig 50 and is incident on the collector disc 100, in particular on a welding zone 101 thereof aligned with the corresponding welding channel 53, and the end 11 A, in order to mutually weld them.

[0141] Advantageously, the approach of the extremal connection member 61 consists in the linear displacement thereof along a direction substantially parallel to the welding direction X’ of the laser beam L.

[0142] The welding provides a step of delivering a shielding gas that flows from its source to the connection means 62 of the extremal connection member 61 up to the welding channel 53, through which the laser beam L is directed. More precisely, the shielding gas reaches the welding channel 53 through the corresponding supply duct 54.

[0143] Once the step of welding the collector disc 100 to the end 11A of the wound element 11 is completed, the extremal connection member 61 is far removed from the welding jig 50. For example, similarly to what has been said for the approach, the distancing can consist of a linear displacement along the sliding direction X” to once again bring the extremal connection member 61 to the backward waiting position PAI.

[0144] The urging member 131 is then controlled to return to its initial position, backwards with respect to the guide 12 A, so that its push on the wound element 11 ceases. Due to the return members 24 between the support member 22 and the base 21 of the carriage 20, the backward movement of the urging member 131 causes the support member 22, and with it the wound element 11, to be automatically taken back to the rest position, far removed from the welding seat 51.

[0145] Subsequently, the carriage 20 is re-coupled to the drive system 120 of the conveyor 12, again controlling the energization of the primary windings 121, so as to make it advance to the turnover station 14, where the wound element 11 is overturned so as to have the second end 11B towards the outside of the advancement path A.

[0146] The carriage 20 is then made to advance through the second flattening station 15’, in order to also flatten the second end 11B, and through the second welding station 13’, where another collector disc 100 is welded to the second end 11B of the wound element 11. The second flattening and the second welding are performed in the same manner as described for the flattening and welding on the first end 11 A. It is clear that modifications and / or additions of parts may be made to the machine 10 and to the method as described heretofore, without thereby departing from the field and scope of the present invention, as defined by the claims.

[0147] It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art will be able to achieve other equivalent forms of machine and method for making electrical energy storage devices, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

[0148] In the following claims, the sole purpose of the references in brackets is to facilitate their reading and they must not be considered as restrictive factors with regard to the field of protection defined by the claims.

Claims

CLAIMS1. Method for making electrical energy storage devices comprising a wound element (11) extending along a longitudinal axis (X) and obtained by winding a first electrode film, a second electrode film and at least one separator interposed in between, said method comprising a step of transporting a wound element (11) on a respective mobile carriage (20) operated by a drive system (120) along a guide (12A) of a conveyor (12) which defines an advancement path (A) towards a welding station (13, 13’), said welding station (13, 13’) comprising a welding seat (51) configured to accommodate a first end (11A, 1 IB) of said wound element (11), where a collector disc (100) has been positioned to be welded to said first end (11 A, 11B), wherein said wound element (11) is horizontally oriented with said longitudinal axis (X) transverse, preferably perpendicular, with respect to said advancement path (A) wherein when said wound element (11) reaches said welding station (13, 13’), the method includes the steps of:- stopping said carriage (20) at said welding seat (51);- approaching said wound element (11) against said welding seat (51), wherein the wound element (11) is pushed along said longitudinal axis (X) so as to insert said first end (11A, 1 IB) into said welding seat (51);- welding together said collector disc (100) and said first end (11A, 1 IB); characterized in that after the stopping step and before the approaching step, said method comprises a decoupling step in which said carriage (20) is decoupled from said drive system (120), so that said carriage (20), during the approaching step, is capable of moving bidirectionally on said guide (12A) along said advancement path (A) so as to allow the alignment of said wound element (11) with said collector disc (100) without the aid of said drive system (120).

2. Method as in claim 1, characterized in that the welding seat (51) is provided with alignment elements (52) movable along a direction parallel to said advancement path (A) to move, during the approaching step, said carriage (20) along said guide (12A) until a coincidence is obtained between said longitudinal axis (X) of said wound element (11) and a central axis (Y) of said collector disc (100).

3. Method as in claim 2, characterized in that said alignment elements (52) comprise a pair of centering members (52A), opposite to each other, and movablebetween a position of mutual distance, wherein they accommodate said first end (11 A, 1 IB) to be welded therebetween, and a position of mutual approach, wherein they align said wound element (11) with the collector disc (100) to be welded.

4. Method as in any of the previous claims, characterized in that said approaching step comprises a first axial displacement sub-step wherein said first end (11A, 1 IB) is introduced into said welding seat (51) and a second sub-step of transverse movement wherein said first end (11A, 1 IB) is aligned with said collector disc (100) by moving the wound element (11) along said guide (12A).

5. Method as in claim 4 when it depends on 3, characterized in that during said second movement sub-step, the centering members (52A) are moved to said mutual approach position, so as to affect the movement of said carriage (20) along said advancement path (A).

6. Method as in any of the previous claims, characterized in that said drive system (120) of the conveyor (12) is a linear motor and comprises a plurality of primary windings (121) fixedly arranged in said guide (12A) functioning as stators of the linear motor, and at least one permanent magnet (122) arranged on a respective carriage (20) functioning as the rotor of said linear motor, wherein each primary winding (121) can be energized independently to control the motion of the carriage (20).

7. Method as in the previous claim, characterized in that in said decoupling step the energization of the primary windings (121), and therefore of the permanent magnet (122), is temporarily ceased, at said welding seat (51).

8. Method as in any of the previous claims, characterized in that in said transporting step, said wound element (11) is kept by means of gripping means (23) provided on said carriage (20).

9. Method as in any of the previous claims, characterized in that said approaching step is carried out by means of an urging member (131, 131 ’) which pushes on a second end (1 IB, 11 A) of said wound element (11) opposite to said first end (11A, 1 IB).

10. Machine (10) for making electrical energy storage devices comprising a wound element (11) extending along a longitudinal axis (X) and obtained by winding a first electrode film, a second electrode film and at least one separator interposed in between, said machine comprising:- a conveyor (12) configured to transport said wound elements (11), horizontally arranged, along an advancement path (A), each wound element (11) being carried on a respective carriage (20) with said longitudinal axis (X) transverse, preferably perpendicular, to said advancement path (A);- a drive system (120) configured to move said carriage (20) on a guide (12A);- at least one welding station (13, 13’) provided with a welding seat (51) configured to accommodate a first end (11 A, 1 IB) of said wound element (11) to be welded together a respective collector disc (100), wherein said drive system (120) is configured to stop each of said carriages (20) at said at least one welding station (13, 13’) positioning them, one at a time, facing said welding seat (51);- a welding device (60) configured to weld said collector disc (100) on said first end (11 A, 1 IB) of said wound element (11);- an urging member (131, 131 ’) configured to bring said wound element (11) close to said welding seat (51); characterized by further comprising a central control unit (200) programmed to respectively control:- said drive system (120) to stop the carriage (20) which carries said wound element (11) when it reaches said welding station (13, 13’);- said urging member (131, 131 ’) to bring the wound element (11) on the stopped carriage (20) close to said welding seat (51), pushing the wound element (11) along said longitudinal axis (X), until said first end (11 A, 1 IB) is inserted into said welding seat (51); and- after stopping the carriage (20) and before bringing the wound element (11) close to the welding seat (51), a decoupling of said carriage (20) from said drive system (120), so that said carriage (20) can move bidirectionally on said guide (12A) along said advancement path (A) while it is pushed by said urging member (131, 131 ’), so as to allow the alignment of said wound element (11) with the collector disc (100).

11. Machine (10) as in claim 10, characterized in that said at least one welding station (13, 13’) comprises alignment elements (52) movable along a direction parallel to said advancement path (A), in order to align said wound element (11) with the collector disc (100) to be welded.

12. Machine (10) as in claim 11, characterized in that said alignment elements(52) comprise a pair of mutually opposite centering members (52A) movable between a position of mutual distancing, wherein they accommodate said first end (11 A, 1 IB) therebetween, and a position of mutual approach, wherein they align said wound element (11) with the collector disc (100) to be welded.

13. Machine (10) as in any of the claims 10 to 12, characterized in that said drive system (120) of the conveyor (12) is a linear motor and includes a plurality of primary windings (121) arranged fixed in said guide (12A) and functioning as stators of the linear motor, and at least one permanent magnet (122) arranged on a respective carriage (20) and functioning as a rotor of said linear motor, wherein each primary winding (121) can be independently energized to control the motion of the carriage (20).

14. Machine (10) as in claim 13, characterized in that said central control unit (200) controls the decoupling between said drive system (120) and the carriage (20) by temporarily ceasing the energization of the primary winding (121), and therefore of said magnet (122), at said welding seat (51).

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