Method for making electrical energy storage devices and corresponding winding machine for making such devices

Abstract

The invention concerns a method for making electrical energy storage devices of the type comprising a wound element (11) formed by winding a first electrode film (17), a second electrode film (18) between which at least one separator (19, 20) is interposed, and a corresponding winding machine. The method provides to feed at least one strip (15) provided with at least two of a first separator (19), a second separator (20), a first electrode film (17) and a second electrode film (18), to a winding core (16) at a winding station (26); rotating the core (16) to wind the at least one strip (15) around it, forming the wound element (11); cutting the at least one strip (15) when the wound element (11) has been formed around the core (16).

Description

[0001] “METHOD FOR MAKING ELECTRICAL ENERGY STORAGE DEVICES AND CORRESPONDING WINDING MACHINE FOR MAKING SUCH DEVICES” FIELD OF THE INVENTION

[0002] The present invention concerns a method for making electrical energy storage devices and a corresponding winding machine for making such devices. The storage devices can be cylindrical or substantially cylindrical shaped batteries, commonly known as jelly rolls, or oval-shaped batteries, obtained by winding around a flat mandrel.

[0003] BACKGROUND OF THE INVENTION

[0004] Batteries that have a cylindrical or oval shape and 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.

[0005] To produce these batteries, there are so-called winding machines in which the strip is made starting from four reels, each formed by a respective anode film, a cathode film and the two separators. Each of these films is then unwound from the respective reel and fed through a feeding station, in which the strip is formed by overlapping the aforementioned four films, up to a core, around which it is wound. While the strip is wound around the core, the latter remains in a fixed position. A winding machine of this type is known from document CN-B-I08063276.

[0006] In addition to the core, the four reels from which the films are fed are also motorized, and their rotation is continuously controlled. Usually, the reels are unwound continuously at a constant linear unwinding speed.

[0007] Conversely, the core’s winding speed has strong accelerations (as the winding starts) and decelerations (as the winding reaches completion) due to the variation in the diameter of the wound element during the process, and to the downtime inevitably present to cut and start the new winding. In addition, the feed of the material onto the core has to be stopped when moving from one core to another subsequent core, this stop being due to the intermittent nature of the machine’s operation. Since the unwinding of the reels never stops, it is necessary to collect, in the buffers mentioned above, the material unwound from the reels while its feed toward the core is stopped.

[0008] To compensate for the continuous unwinding of material from the reels while the feed of the same material toward the core is interrupted, bulky buffer systems are required. One problem with buffers for these types of applications is that they are large and therefore difficult to manage. Another problem encountered lies in the fact that interrupting and resuming the feed of the material represents an operation bottleneck, since it consumes cycle time and cannot be done beyond certain dynamics. Another problem with known machines concerns cutting the four strips fed to the winding core. The cutting occurs while the strips are moving toward the core, and therefore requires the knife to be accelerated together with the strips, therefore with considerable accelerations, because the cutting cannot take place in shadow time. The cutting operation is made even more difficult by the need to cut the four strips into segments of generally different lengths, and by the need to synchronize their movement in order to match them according to predefined parts. The dynamics of this operation represent a critical issue for the very management of the materials.

[0009] There is therefore the need to perfect a method for making electrical energy storage devices and a corresponding winding machine capable of making such devices, which can overcome at least the disadvantage of the state of the art disclosed above.

[0010] To do this, it is necessary to solve the technical problem of keeping the strip in constant tension while it is wound around the core, without the need to have bulky buffers, with a consequent reduction of the space occupied by the machine.

[0011] 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.

[0012] SUMMARY OF THE INVENTION 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.

[0013] In accordance with the above purpose 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 is provided for making electrical energy storage devices comprising a wound element formed by winding a first electrode film, a second electrode film and at least one separator interposed between the two electrode films.

[0014] The method comprises the steps of:

[0015] - providing a first separator, a second separator, a first electrode film and a second electrode film;

[0016] - layering and uniting the first separator, the second separator, the first electrode film and the second electrode film according to a predefined sequence, with one of the first or second electrode films interposed between the first and second separators, at a joining station that forms a multilayer strip;

[0017] - feeding the strip to a winding core in a winding station along a feeding path;

[0018] - rotating the winding core to wind the strip thereabout; and subsequently, - cutting the strip wound around the winding core to form a wound element.

[0019] In accordance with one aspect of the present invention, the method also comprises, during the rotating step, a step of varying a travel distance travelled by the strip along the feeding path between the joining station and the winding core by means of a speed compensation unit which is placed along the feeding path between the joining station and the winding station, wherein the speed compensation unit cooperates with the strip, so that a given displacement of the speed compensation unit can lengthen or shorten the strip’s travel distance, thereby differences in speed between the speed at which the strip travels along the feeding path and the speed at which the strip has been wound around the winding core can be continuously compensated.

[0020] In accordance with one aspect of the present invention, the speed compensation unit is separate from the winding station. Advantageously, the compensation unit is located upstream to the winding station, with respect to the strip’s feeding direction. The method provides to act on the strip, by means of the compensation unit, in order to temporarily modify its feeding path, in particular in order to lengthen or decrease the length of the feeding path.

[0021] Doing so achieves at least the advantage that the compensation unit decouples the feeding of the electrode films and of the separators from the strip winding operation, which allows to drive the winding core with less demanding dynamics, which would otherwise be caused by the need to necessarily take into account the amount of time between the beginning and end of a winding operation. The strategy chosen for the rotation of the core benefits from the presence of the compensation unit and can have different objectives, such as for example maintaining a constant linear feed speed and an adequate tension of the strip between the joining station and the winding core, making the core rotate at a constant or substantially constant speed at least for the majority of the winding step, or maintaining a constant winding speed. The displacement of the compensation unit allows to control the tension of the strip simply and reliably, compensating for the variability of the winding speeds which is due to the variations in the core’s diameter.

[0022] According to some embodiments, during the winding, the speed of rotation of the core and the speed of displacement of the compensation unit are such as to keep the tension of the at least one strip constant or substantially constant while it is wound on the winding core. This tension of the strip can be measured directly or indirectly through the winding torque.

[0023] In particular, the compensation unit can be either passive or actuated in position.

[0024] In the first case, the rotation of the winding core is set, and the displacement of the compensation unit is an indirect consequence of the tension balance. In the second case, it is possible to move the compensation unit according to a predefined path, controlling the rotation of the core as a consequence of the monitoring of the strip’s tension.

[0025] Monitoring the tension of the wound strip also allows to indirectly measure any variability in the thickness of the strip, since these variabilities lead to variations in diameter and therefore the need for a different number of winding turns.

[0026] In particular, it is possible to estimate the diameter of the wound element by knowing the thicknesses of the separators and electrodes, by measuring the length of the strip that is fed to the winding core and the number of turns made by the winding core to obtain the wound element. This estimate can be made both during the formation of the wound element, and also at the end of its formation.

[0027] According to another aspect of the present invention, there is provided a method for making electrical energy storage devices as defined above, wherein the method comprises the steps of:

[0028] - providing a first separator, a second separator, a first electrode film and a second electrode film;

[0029] - feeding a complete strip formed by the first separator, the second separator, the first electrode film and the second electrode film layered according to a predefined sequence, to a winding core of a winding station;

[0030] - rotating the winding core to wind the complete strip thereabout; and subsequently,

[0031] - cutting the complete strip wound around the winding core to form a wound element.

[0032] According to one aspect of the present invention, in this embodiment the method further comprises:

[0033] - layering and uniting the first separator, the second separator and the second electrode film, with the second electrode film interposed between the first and second separators, at a joining station forming a partial multilayer strip;

[0034] - feeding the partial multilayer strip, preferably at constant speed, to the winding core along a first feeding path;

[0035] - feeding the first electrode film, preferably at the same speed as the partial multilayer strip, along a second feeding path, separate from the first feeding path, until joining with the partial multilayer strip in order to form the complete strip, the first electrode film joining with the partial multilayer strip preferably at the winding core; and during the rotating step, varying a first travel distance travelled by the partial multilayer strip along the first feeding path between the joining station and the winding core by means of a first speed compensation unit which is placed along the first feeding path between the joining station and the winding station, wherein the first speed compensation unit cooperates with the partial multilayer strip, so that a given displacement of the first speed compensation unit can lengthen or shorten the first travel distance of the partial multilayer strip, thereby differences in speed between the speed at which the partial multilayer strip travels along the first feeding path and the speed at which the complete strip has been wound around the winding core can be continuously compensated.

[0036] In accordance with one aspect of the present invention, the first speed compensation unit is separate from the winding station.

[0037] In accordance with the above purpose 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 winding machine according to the present invention for making electrical energy storage devices comprising a wound element formed by winding a first electrode film, a second electrode film and at least one separator interposed between the two electrode films.

[0038] The machine comprises:

[0039] - a joining station configured to layer and couple the first and second separators, the first and second electrode films according to a predefined sequence, with one of the first or second electrode film interposed between the first and second separators, forming a multilayer strip;

[0040] - a winding station having at least one winding core configured to rotate the strip coming from the joining station; - a strip cutting member configured to cut the strip wound around the winding core to form a wound element.

[0041] In accordance with one aspect of the present invention, the winding machine comprises a speed compensation unit placed along a feeding path between the joining station and the winding station, and cooperating with the strip, the speed compensation unit being configured to be displaced in order to vary a travel distance travelled by the strip along the feeding path between the joining station and the winding core, so that a given displacement of the speed compensation unit can lengthen or shorten the strip’s travel distance, thereby differences in speed between the speed at which the strip travels along the feeding path and the speed at which the strip has been wound by the winding core can be continuously compensated.

[0042] In accordance with one aspect of the present invention, the speed compensation unit is separate from the winding station. Advantageously, the compensation unit is located upstream to the winding station, with respect to the strip’s direction of feed. The compensation unit is configured to act on the strip so as to temporarily modify its feeding path, in particular so as to lengthen or decrease the length of the feeding path.

[0043] According to another aspect of the present invention, there is provided a winding machine for making electrical energy storage devices as defined above, wherein the machine comprises a winding station having at least one winding core configured to rotate to wind a complete strip thereabout, the complete strip being formed by a first separator, a second separator, a second electrode film interposed between the first and second separator and a first electrode film; and a cutting member configured to cut the complete strip wound around the winding core to form a wound element.

[0044] According to one aspect of the invention, in this embodiment the machine also comprises a joining station configured to layer and couple the first and second separators and the second electrode film, with the second electrode film interposed between the first and second separators, forming a partial multilayer strip, a first speed compensation unit placed along a first feeding path between the joining station and the winding station, and cooperating with the partial multilayer strip, and an electrode feed station configured to feed the first electrode film along a second feeding path, separate from the first feeding path, until joining with the partial multilayer strip in order to form the complete strip, the first electrode film joining with the partial multilayer strip preferably at the winding core.

[0045] The first speed compensation unit is configured to be displaced to vary a first travel distance travelled by the partial multilayer strip along the first feeding path between the joining station and the winding core, so that a given displacement of the first speed compensation unit can lengthen or shorten the first travel distance of the partial multilayer strip, thereby differences in speed between the speed at which the partial multilayer strip travels along the feeding path and the speed at which the complete strip has been wound by the winding core can be continuously compensated.

[0046] According to one aspect of the invention, the first speed compensation unit is separate from the winding station.

[0047] DESCRIPTION OF THE DRAWINGS

[0048] These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein:

[0049] - fig. 1 is a schematic front view of a first embodiment of a winding machine for making electrical energy storage devices, according to the present invention; - fig. 1 A is an enlarged view of a detail of a strip formed in the winding machine of fig. 1 ;

[0050] - fig. IB is an enlarged view of a winding station of the winding machine;

[0051] - fig. 2 is a plan view of a wound element to be arranged inside an electrical energy storage device;

[0052] - figs. 3-9 are partial views of the winding machine of fig. 1 in an operating sequence of the winding machine’s operation;

[0053] - fig. 10 is a schematic front view of a second embodiment of a winding machine, according to the invention; - fig. 10A is an enlarged view of a detail of a strip formed in the winding machine of fig. 10; and

[0054] - fig. 10B is an enlarged view of a winding station of the winding machine of fig.

[0055] 10, during an operating step of its operation.

[0056] 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.

[0057] To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings, ft is understood that elements and characteristics of one embodiment can be conveniently combined or incorporated into other embodiments without further clarifications. DESCRIPTION OF SOME EMBODIMENTS OF THE PRESENT INVENTION

[0058] With reference to fig. 1, a winding machine 10 according to the present invention for making electrical energy storage devices comprising a wound element 11 , comprises an unwinding part 12 and a winding part 13, separated by a joining station 14 in which the strip is formed.

[0059] The wound element 11 is of the type obtainable in a known manner, by winding a strip 15 around a winding core 16 of the winding machine 10. In this embodiment, the strip 15 consists of a first electrode film 17, a second electrode film 18, a first separator 19 interposed between the first electrode film 17 and the second electrode film 18, and a second separator 20 placed to cover the second electrode film 18 (figs. 1A and 2). In the example shown, the first electrode film 17 is an anode film, the second electrode film 18 is a cathode film. It is however obvious that the reverse configuration, that is, in which the first electrode film is the cathode, and the second electrode film is the anode, is equally possible and falls within the scope of the present invention.

[0060] The first electrode film 17, the second electrode film 18, the first and second separator 19, 20, also in film form, are all made available individually, unwound by respective reels, indicated with reference numbers 17A, 18 A, 19A, 20A, which are located in the unwinding part 12 of the winding machine 10, in a known manner (fig- I)-

[0061] Each reel 17 A, 18A, 19A, 20 A is motorized independently of the others, so that the unwinding of the respective films 17, 18, 19, 20 is controlled. The films 17, 18, 19, 20 are then fed along respective unwinding paths 17B, 18B, 19B, 20B, in each of which there is provided a respective tensioning system 17C, 18C, 19C, 20C to keep a correct tensioning of the films 17, 18, 19, 20. The electrode films 17, 18 and the separators 19, 20 are fed along a feeding direction A to the joining station 14. At exit from the joining station 14, the strip 15 is fed along the same feeding direction A, for a first segment of a strip feeding path.

[0062] The unwinding paths 17B, 18B of the electrode films 17, 18 are equipped with respective cutting members 21, 22 and respective feed means 23, 24 arranged upstream to the joining station 14, while the unwinding paths 19B, 20B of the first and second separators 19, 20 are without cutting members. The cut to size of the separators 19, 20 will be explained in detail below.

[0063] It is therefore evident that the first 17 and second 18 electrode films are fed to the joining station 14 discontinuously, that is, in pieces. As can be seen from fig. 1 A, two consecutive pieces of the second electrode film 18 are distanced from each other by a first distance dl and two consecutive pieces of the first electrode film 17 are distanced from each other by a second distance d2.

[0064] The first distance dl and the second distance d2 are advantageously coordinated with respect to each other, are known and easily obtainable for a person of skill in the art.

[0065] The joining station 14 comprises a couple of rollers arranged with their respective axes of rotation parallel to each other, counter-rotating with respect to each other and at a close distance from each other, so that the films 17, 18, 19, 20, which are fed between the two rollers, are coupled to form, directly at exit from the joining station 14, the strip 15 to be wound around the core 16.

[0066] The winding part 13 is located downstream to the joining station 14, with respect to the feeding direction of the films and strip, in which winding part 13 there are at least two winding cores 16, placed parallel to the axes of rotation of the rollers of the joining station 14, to allow the winding cores 16 to wind the strip

[0067] 15 without any defects. In the example shown here, there are four winding cores

[0068] 16 (figs. 1 and IB).

[0069] The winding cores 16 are of a known type, each consisting of two half-mandrels 16A, 16B with a semi-circular section coupled to form a single mandrel with a circular section with a radial slot passing therethrough, in which the strip 15 is inserted (figs. 1 and IB).

[0070] Each winding core 16 is rotatable mounted on at least one movement member 25, forming a winding station 26. In the example shown, there is a movement member 25 in the form of a disc or drum with an axis of rotation parallel to the longitudinal axes of the cores 16, and on which they are arranged angularly distributed along an intermediate circumference of the disc. Alternatively, multiple movement members can be provided, for example in the form of sliders, each carrying a respective core that can be moved along a curvilinear path. In fig. IB, the cores 16 are in a resting position, with a first half-mandrel 16A located external to the second half-mandrel 16B with respect to the axis of the disc 25, so that the slot between the two half-mandrels 16A, 16B is aligned with the unwinding direction of the strip 15.

[0071] Each half- mandrel 16A, 16B is slidable, independent of the other, in a longitudinal direction and with respect to the movement member 25, between an inactive, or retracted, position, in which the half-mandrels 16 A, 16B cannot interfere with the strip 15, and an active, or extended, position, in which the halfmandrels 16A, 16B can interfere with the strip 15.

[0072] The movement member 25 is configured to displace the winding cores 16 between a plurality of predefined positions within the winding station 26, which include a first winding position 26A and a second winding position 26B (figs. 1 and IB). The first winding position 26A and the second winding position 26B are distanced angularly from each other by 90°, as are the cores 16. The presence of four cores 16 on the movement member 25 determines a third position 26C and a fourth position 26D, diametrically symmetrical to the first and second winding positions 26A, 26B, respectively, with respect to the axis of rotation of the disc 25 (figs. 1 and IB). The movement member 25 is connected to an actuator 27 configured to command its movement, which is in turn connected to a controller 28 (fig. 1), programmed to control the actuator 27 so as to move the movement member 25 in a predetermined manner, that is, in this case with a counterclockwise rotation by an angle of 90°. The winding machine 10 is also equipped with a gripping and cutting member 29 configured to grip the strip 15 at the first winding position 26A (figs. IB, 8 and 9). The gripping and cutting member 29 is configured as a gripper 30 in which a blade, called knife 31, is integrated to cut the strip 15.

[0073] In particular, the gripper 30 is configured to form a seating around the winding core 16 when closed, and to exert a grip on the strip at the cut of the knife 31.

[0074] The knife 31 is positioned downstream to the winding core 16 with respect to the feeding direction of the strip 15 in the winding station 26.

[0075] According to some variants, not shown, the knife 31 is not integrated into the gripper 30. In other variants, not shown, no gripper is provided, since only the knife 31 is provided.

[0076] In an alternative embodiment, not shown here, the winding machine 10 can comprise a gripping and cutting member 29 at each of the cores 16 and integral with the disc 25.

[0077] In the winding part 13 there is also provided a unit 32 for compensating the difference between the feed speed of the strip 15 and the winding speed around the winding cores 16.

[0078] This compensation unit can be configured as an idle roller with axis of rotation oriented parallel to the axes of rotation of the cores 16 and displaceable to change the feeding path of the strip 15 downstream to the joining station 14. The compensation unit 32 is placed upstream to the winding station 26, with respect to the feeding direction of the strip 15, and remains an element separated therefrom. The compensation unit 32 is displaceable by means of a suitable actuation member 33 configured to displace it so as to change the feeding path of the strip 15 (fig. 1). In particular, the actuation member 33 is configured to displace the compensation unit 32 back and forth in a linear direction, approaching and moving away from the winding station 26 and the joining station 14, respectively. Advantageously, the approaching and away movement of the compensation unit 32, aimed at modifying the feeding path, can be imposed or derive from monitoring the tension.

[0079] To avoid any unwanted unwinding of the wound element 11 after the separators 19, 20 are cut, a pressing element 34 is provided able to press on the wound strip, until the wound element 11 is attached on itself, preventing it from unwinding. The pressing element 34, preferably a roller, is arranged at the second winding position

[0080] 26B.

[0081] Extraction means 35 configured to extract the wound element 11 from the winding core 16 when it has been completed are also provided. In fig. 9, the extraction means 35 are shown schematically as a receptacle configured to receive the wound element and displace it outside of the winding machine 10; it is however possible to provide other types of extraction means, for example mobile gripping members.

[0082] At the second winding position 26B, taping means 36 (fig. IB) are also provided able to apply an adhesive element on the wound element 11 so as to keep it in the wound configuration after its extraction from the winding machine 10.

[0083] Abutment members 37, in particular four, can also be provided on the movement member 25, each one positioned between two consecutive cores 16 and configured to act as a rest surface for an end flap of the strip 15, after it has been cut and while it ends its winding around the core 16 in the second winding position 26B, so as to prevent it from falling.

[0084] The abutment members 37 also have the function of encountering the strip 15, during the rotation of the movement member 25, before the winding core 16, as will be explained below. In this way, loads on the winding core 16 are prevented and the strip 15 is already oriented horizontally, that is, parallel to the radial slot, when the encounter occurs.

[0085] The operation of the winding machine 10, which corresponds to the method according to the present invention, comprises the following steps.

[0086] Initially, the rollers of the joining station 14 are commanded, then the motors of the reels 17 A, 18 A, 19A, 20A are commanded so as to unwind the electrode films 17, 18 and the separators 19, 20 and to feed them toward the joining station 14, where the electrode films 17, 18 and separators 19, 20 are reciprocally joined to form the strip 15. During the production of the wound element 11, the electrode films 17, 18 are cut by the respective cutting members 21, 22 present on the respective unwinding paths 17B, 18B, while the separators 19, 20 are unwound continuously to guarantee the presence of segments of strip consisting solely of separators. These will be cut downstream to the joining by the gripping and cutting means 29, as described below. At exit from the joining station 14, the strip 15 extends along the feeding direction A up to the compensation unit 32 to be put into contact with its surface, and is then connected to the winding core 16 by insertion into the radial slot. The strip 15 then forms an elbow at the compensation unit 32.

[0087] Between the joining station 14 and the winding core 16, the portions of the first electrode film 17 are kept joined to the rest of the strip 15 by means of suitable mobile gripping means, not shown here.

[0088] The winding core 16 involved is in the first winding position 26 A, the gripper 30 is closed and exerts a pressure on the portion of strip 15 immediately downstream to the core 16, helping to keep the strip 15 in tension and thus facilitate its winding around the winding core 16.

[0089] The winding core 16 is then rotated to begin winding the strip 15. In this initial winding step, the wound strip 15 consists only of the two separators 19, 20. In coordination with the beginning of the rotation of the core 16, the gripper 30 is opened (fig. 3). Subsequently, after a few more turns, the electrode films 17, 18 become part of the strip 15, so as to begin the winding at generally different moments, which depend on the distances dl and d2. At this point, a portion of strip 15 consisting of the two separators 19, 20 and the electrode films 17, 18 is wound. In a first step of the winding, the speed of rotation of the core 16 is not sufficient to collect all the strip 15 at exit from the joining station 14. To compensate for this speed difference, the compensation unit 32 is displaced away from the joining station 14 and the winding station 26, that is, in this case to the right (fig. 3), while the speed of rotation of the core 16 increases progressively.

[0090] When the speed of rotation of the core 16 and the radius of the wound element 11 are such that the amount of strip 15 being fed can be received, the compensation unit stops. Then the speed of rotation of the core and the volume of the wound element 11 increase and become such that they wind more strip 15 than is being fed. Therefore, the compensation unit 32 is displaced again, but this time approaching the joining station 14 and the winding station 26, that is, in this case toward the left (fig. 4), until the winding is completed.

[0091] While the strip 15 is wound around the core 16, it is possible to set the displacement of the compensation unit 32 along its displacement path, and to control the rotation of the core 16 so as to make it vary according to the variations in the tension of the strip 15. In order to have an indirect measurement of the tension of the strip 15, the winding torque of the core 16 can be measured continuously. By doing so, it is possible to modify the speed of rotation of the core 16, so as to pull the strip 15 with a pulling force able to keep the tension of the strip 15 substantially constant while it is being wound. At the end of the winding step, the rotation of the winding core 16 slows down and stops and, in a synchronized manner, the approaching displacement of the compensation unit 32 is stopped, and its displacement away from the joining station 14 and the winding station 26 is started again (fig. 5).

[0092] The counterclockwise rotation of the rotation member 25 by an angle of 90° is then driven, in order to displace the winding cores 16 from their winding position to the next one (figs. 5 and 6).

[0093] The core 16, so far in the fourth winding position 26D, has the external halfmandrel 16A retracted and the other half-mandrel 16B extended (fig. 5 A). During the rotation of the movement member 25, the abutment member 37, between the wound element 11 and the core 16, progressively comes into contact with the strip 15 (fig. 6), so that when the core 16 arrives at the first winding station 26A the strip 15 is already in position above the extended half-mandrel 16B, and it is sufficient to again extend the half- mandrel 16A in order to determine the grip of the strip 15 in the radial slot of the core 16 (figs. 7 and 7A). Subsequently, the gripper 30 is closed and the knife 31 is driven (fig. 8) to cut the strip 15. The winding core 16 carrying the wound element 11 continues to rotate, in order to complete the winding of the end flap of strip 15 that has just been cut. This end flap slides along the abutment member 37 until the wound element 11 is obtained (fig. 8).

[0094] The core 16, now in the first winding position 26A, is in a situation analogous to that shown in fig. 1 and IB, and it is ready to start winding a subsequent portion of strip 15, as described above. At the second winding position 26B, the wound element is temporarily kept wound by means of the pressing element 34 and an adhesive tape is applied to prevent the wound element 11 from unwinding (fig. 9).

[0095] The wound element 11 is then extracted from the core 16, for example by retracting the two half-mandrels 16 A, 16B, to make the wound element 11 fall, possibly into an extraction member 35 as explained above (fig. 9), or directly into a subsequent operating station below.

[0096] The winding machine 10 comprises a tensioning element 39, which is configured for example as a motorized roller. The tensioning element 39 is adjacent to the compensation unit 32 and allows to keep the cut electrode film located between the separators 19, 20 adequately tensioned after passing through the compensation unit.

[0097] Figs. 10, 10A and 10B show a second embodiment of the winding machine, indicated in this case by the reference number 10’, which differs from the first embodiment for the fact that the unwinding path 17B of the first electrode film 17 does not pass through the joining station 14’, from which a partial multilayer strip 15’ emerges. The first electrode film 17 is fed directly to the first winding position 26 A, more precisely it is fed over the partial multilayer strip 15’, just before the winding core 16 (fig. 10B).

[0098] For this purpose, it is advantageous to provide a suitable guide 38 in proximity to the first winding position 26A to guarantee the correct feed of the first electrode film 17 (fig. 10B). Advantageously, the guide 38 can be mobile, so that the strip 15 can be accompanied from the cutting members 21 up to the winding core 16.

[0099] In this embodiment, the strip 15 is made up successively of the two separators 19, 20, and then the two separators 19, 20 with the second electrode film 18 between them (fig. 10A), but it does not contain the first electrode film 17 before reaching the winding core 16.

[0100] The unwinding path 17B develops from a station 14” for feeding the first electrode film 17 up to a last segment, indicated by reference 17D, whose beginning is located upstream to the winding station 26, at the top and to the right in the case shown, so that the first electrode film 17 is fed in the same direction as the partial multilayer strip 15’ at the first winding position 26A.

[0101] The cutting member 21 and the feed means 23 are provided in this last segment 17D, the cutting member 21 being located downstream to the feed means 23 with respect to the feed of the partial multilayer strip 15’. The task of the feed means 23 is to slow down the feed of the first electrode film 17 after the cutting member 21 has made the cut, and to resume the feed in order to create the distance d2.

[0102] The example shown in fig. 10 provides that the first electrode film 17 is fed to an additional compensation unit 40, distinct from the compensation unit 32, and then toward the winding core 16, passing through the feed means 23 and the cutting member 21, as shown in fig. 10.

[0103] In particular, the additional compensation unit 40 is also called second compensation unit and it is separate from the aforementioned compensation unit 32, also called first compensation unit 32, and it can move synchronously with it, for example being integral therewith. By way of example, the two compensation units 32, 40 can be mounted on two sliders 41 ’, 41” driven by a respective actuator 33 (fig. 10). Alternatively, the two compensation units 32, 40 can be mounted on a same slider, or the two sliders 41 ’, 41” can be integral. In order to achieve the same compensation of the first part 15 ’ of strip and of the second part 15” of strip (in the example first electrode film 17), as is desirable, it is possible to provide, upstream or downstream to the respective compensation units 32, 40, idler rollers that keep the paths of the partial multilayer strip 15” and of the second part of strip 15” (that is, of the first electrode film 17) parallel to each other upstream to the respective compensation units 32, 40.

[0104] The operation of the second embodiment is substantially identical to the operation of the first embodiment, with the difference that the first electrode film 17 is fed to the winding core 16, at the winding station 26, through the second compensation unit 40 but without passing through the joining station 14’. It is clear that modifications and / or additions of parts may be made to the winding 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. 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 a method for making electrical energy storage devices and of a corresponding winding machine for making such devices, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

[0105] 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) formed by winding a first electrode film (17), a second electrode film (18) between which a first separator (19) is interposed, and a second separator (20), said method comprising the steps of:- providing a first separator (19), a second separator (20), a first electrode film (17) and a second electrode film (18);- layering and uniting said first (19) and second (20) separators, said first (17) and second (18) electrode films according to a predefined sequence, with one of said first (17) and second (18) electrode films interposed between the first (19) and second (20) separators, at a joining station (14) forming a multilayer strip (15);- feeding said strip (15) to a winding core (16) in a winding station (26) along a feeding path;- rotating said winding core (16) to wind said strip (15) thereabout; and subsequently,- cutting the strip (15) wound around the winding core (16) to form a wound element (11); said method being characterized by further comprising, during said rotating step, a step of varying a travel distance travelled by the strip (15) along the feeding path between the joining station (14) and the winding core (16) by means of a speed compensation unit (32) which is placed along said feeding path between the joining station (14) and the winding station (26), wherein said speed compensation unit (32) cooperates with the strip (15), so that a given displacement of the speed compensation unit (32) can lengthen or shorten said travel distance of the strip (15), thereby differences in speed between the speed at which said strip (15) travels along the feeding path and the speed at which said strip (15) has been wound around said winding core (16) can be continuously compensated, and in that said speed compensation unit (32) is separate from said winding station (26).

2. Method as in claim 1, characterized in that said strip (15) is slidingly coupled to said speed compensation unit (32).

3. Method as in claim 1 or 2, characterized in that during said rotating step, said speed compensation unit (32) has been displaced back and forth along a linear direction.

4. Method as in any one of the preceding claims, characterized in that said winding core (16) rotates about an axis of rotation which remains substantially in a fixed position during the rotating step.

5. Method as in any one of the preceding claims, characterized in that said speed compensation unit (32) comprises at least one roller on which said strip (15) can slide around.

6. Method as in any one of the preceding claims, characterized in that during said layering and uniting step, said first (19) and second (20) separators, said first(17) and second (18) electrode films run between a couple of counterrotating rollers of said joining station (14), said couple of counterrotating rollers forming said strip (15).

7. Method as in any one of the preceding claims, characterized by further comprising, upstream to said joining station (14), cutting said first (17) and second(18) electrode films forming a sequence pieces of film of predefined length, distanced from each other at a respective predefined pitch, so that the strip (15) is formed at said joining station (14) with said pieces of film of said first (17) and second (18) electrode films layered with said first (19) and second (20) separators which have been left in a continuous form.

8. Method for making electrical energy storage devices comprising a wound element (11) formed by winding a first electrode film ( 17), a second electrode film(18) between which a first separator (19) is interposed, and a second separator (20), said method comprising the steps of:- providing a first separator (19), a second separator (20), a first electrode film (17) and a second electrode film (18); - feeding a complete strip (15) formed by said first (19) and second (20) separators, said first (17) and second (18) electrode films layered according to a predefined sequence, to a winding core (16) of a winding station (26);- rotating said winding core (16) to wind said complete strip (15) thereabout; and subsequently, - cutting the complete strip (15) wound around the winding core (16) to form a wound element (11); said method being characterized by further comprising:- layering and uniting said first (19) and second (20) separators and said second(18) electrode film with said second (18) electrode film interposed between the first (19) and second (20) separators, at a joining station (14’) forming a partial multilayer strip (15’);- feeding said partial multilayer strip (15’), preferably at constant speed, to a winding core (16) along a first feeding path;- feeding said first electrode film (17), preferably at the same speed as the partial multilayer strip (15’), along a second feeding path, separate from said first feeding path, until joining with said partial multilayer strip (15’) in order to form said complete strip (15), said first electrode film (17) joining with the partial multilayer strip (15’) preferably at said winding core (16); and- during said rotating step, varying a first travel distance travelled by the partial multilayer strip (15’) along said first feeding path between the joining station (14’) and the winding core (16) by means of a first speed compensation unit (32) which is placed along said first feeding path between the joining station (14’) and the winding station (26), wherein said first speed compensation unit (32) cooperates with the partial multilayer strip (15 ’), so that a given displacement of the first speed compensation unit (32) can lengthen or shorten said first travel distance of the partial multilayer strip (15’), thereby differences in speed between the speed at which said partial multilayer strip (15’) travels along the first feeding path and the speed at which said complete strip (15) has been wound around said winding core (16) can be continuously compensated, and in that said first speed compensation unit (32) is separate from said winding station (26).

9. Method as in the claim 8, characterized in that said partial multilayer strip (15’) is slidingly coupled to said first speed compensation unit (32).

10. Method as in claim 8 or 9, characterized in that during said rotating step, said first speed compensation unit (32) has been displaced back and forth along a linear direction.

11. Method as in any one of the claims 8-10, characterized in that said first speed compensation unit (32) comprises at least one roller on which said partial multilayer strip (15’) can slide around.

12. Method as in any one of the claims 8-11, characterized in that during said layering and uniting step, said first (19) and second (20) separators, and said second (18) electrode film run between a couple of counterrotating rollers of saidjoining station (14’), said couple of counterrotating rollers forming said partial multilayer strip (15’).

13. Method as in any one of the claims 8-12, characterized by further comprising, during said rotating step, controlling a winding torque of the winding core (16) by controlling a speed of rotation of the winding core (16) and / or a speed of movement of said first speed compensation unit (32), in order to keep said partial multilayer strip (15’) at a tension substantially constant.

14. Method as in any one of the claims 8-13, characterized by further comprising, before said layering and uniting step, cutting said second electrode film (18) forming a sequence of pieces of said second electrode film (18) of predefined length, distanced from each other at a predefined pitch, so that the partial multilayer strip (15’) is formed at said joining station (14) with said pieces of said second electrode film (18) layered with said first (19) and second (20) separators which have been left in a continuous form.

15. Method as in any one of the claims 8-14, characterized by further comprising cutting said first electrode film (17) forming a sequence of pieces of said first electrode film (17) of predefined length, distanced from each other at a predefined pitch, so that one piece at a time of said pieces of said first electrode film (17) has been fed to the winding core (16) for each wound element (11).

16. Method as in any one of the claims 8-15, characterized by further comprising during said rotating step, varying a second travel distance travelled by the first electrode film (17) along said second feeding path by means of a second speed compensation unit (40) which is placed along said second feeding path, wherein said second speed compensation unit (40) cooperates with the first electrode film (17), so that a displacement of the second speed compensation unit (40) can lengthen or shorten said second travel distance of the first electrode film (17), thereby differences in speed between the speed at which said first electrode film (17) travels along the second feeding path and the speed at which said complete strip (15) has been wound by said winding core (16) can be continuously compensated, and in that said second speed compensation unit (40) is separate from said winding station (26).

17. Method as in the claim 16, characterized in that said first (32) and second (40) speed compensation units are displaced together concurrently.

18. Winding machine (10) for making electrical energy storage devices comprising a wound element formed by winding a first electrode film (17), a second electrode film (18) between which a first separator (19) is interposed, and a second separator (20), said machine comprising: a joining station (14) configured to layer and couple said first (19) and second (20) separators, said first (17) and second (18) electrode films according to a predefined sequence, with one of said first (17) and second (18) electrode film interposed between the first (19) and second (20) separators, forming a multilayer strip (15); a winding station (26) having at least one winding core (16) configured to rotate to wind the strip (15) coming from the joining station (14); a strip cutting member (31) configured to cut the strip (15) wound around the winding core (16) to form a wound element (11), characterized by further comprising a speed compensation unit (32) placed along a feeding path between the joining station (14) and the winding station (26), and cooperating with the strip (15), said speed compensation unit (32) being configured to be displaced to vary a travel distance travelled by the strip (15) along the feeding path between the joining station (14) and the winding core (16), so that a given displacement of the speed compensation unit (32) can lengthen or shorten said travel distance of the strip (15), thereby differences in speed between the speed at which said strip (15) travels along the feeding path and the speed at which said strip (15) has been wound by said winding core (16) can be continuously compensated, and in that said speed compensation unit (32) is separate from said winding station (26).

19. Winding machine (10) as in the claim 18, characterized in that said speed compensation unit (32) comprises a roller on which said strip (15) can slide around, said roller being rotatable mounted on a displaceable member (41 ’) configured to be displaceable back and forth along a linear direction by an actuator (33).

20. Winding machine (10) as in the claim 18 or 19, characterized in that said joining station (14) comprises a couple of counterrotating rollers.

21. Winding machine (10) as in any one of the claims 18-20, characterized by further comprising, upstream to said joining station (14), first (21) and second (22) film cutting members configured to cut said first (17) and second (18) electrode films respectively, forming a sequence of pieces of film of predefined length,distanced from each other at a respective predefined pitch, so that the strip (15) formed at said joining station (14) comprises said pieces of film of said first (17) and second (18) electrode films layered with said first (19) and second (20) separators left in a continuous form.

22. Winding machine (10’) for making electrical energy storage devices comprising a wound element formed by winding a first electrode film (17), a second electrode film (18) between which a first separator (19) is interposed, and a second separator (20), said machine (10’) comprising a winding station (26) having at least one winding core (16) configured to rotate to wind a complete strip (15) thereabout, said complete strip (15) being formed by a first separator (19), a second separator (20), a second electrode film (18) interposed between said first (19) and second (20) separator and a first electrode film (17); and a cutting member (31) configured to cut said complete strip (15) wound around the winding core (16) to form a wound element (11), characterized by further comprising a j oining station (14’) configured to layer and couple the first ( 19) and second (20) separators and the second electrode film (18), with the second (18) electrode film interposed between the first (19) and second (20) separators, forming a partial multilayer strip (15’), a first speed compensation unit (32) placed along a first feeding path between the joining station (14’) and the winding station (26), and cooperating with the partial multilayer strip (15’), and an electrode feed station (14”) configured to feed said first electrode film (17) along a second feeding path, separate from said first feeding path, until joining with said partial multilayer strip (15’) in order to form said complete strip (15), said first electrode film (17) joining with the partial multilayer strip (15’) preferably at said winding core (16), wherein said first speed compensation unit (32) is configured to be displaced to vary a first travel distance travelled by the partial multilayer strip (15’) along the first feeding path between the joining station (14’) and the winding core (16), so that a given displacement of the first speed compensation unit (32) can lengthen or shorten said first travel distance of the partial multilayer strip (15’), thereby differences in speed between the speed at which the partial multilayer strip (15’) travels along the first feeding path and the speed at which said complete strip (15)has been wound by said winding core (16) can be continuously compensated, and in that said first speed compensation unit (32) is separate from said winding station (26).

23. Winding machine (10’) as in the claim 22, characterized in that said speed compensation unit (32) comprises a roller on which the partial multilayer strip(15’) can slide around, said roller being rotatable mounted on a displaceable member (41’) configured to be displaceable back and forth along a linear direction by an actuator (33).

24. Winding machine (10’) as in the claim 22 or 23, characterized in that said joining station (14’) comprises a couple of counterrotating rollers.

25. Winding machine (10’) as in any one of the claims 22-24, characterized by further comprising a first film cutting member (21) configured to cut said first electrode film (17) forming a sequence of pieces of said first electrode film (17) of predefined length, distanced from each other at a predefined pitch, so that one piece at a time of said pieces of said first electrode film (17) has been fed to the winding core (16) for each wound element (11).

26. Winding machine (10’) as in any one of the claims 22 - 25, characterized by further comprising, upstream to said joining station (14’), a second film cutting member (22) configured to cut said second electrode film (18), forming a sequence of pieces of said second electrode film (18) of predefined length, distanced from each other at a respective predefined pitch, so that the partial multilayer strip (15’) formed at said joining station (14’) comprises said pieces of said second electrode film (18) layered with said first (19) and second (20) separators left in a continuous form.

27. Winding machine (10’) as in any one of the claims 22-26, characterized by further comprising a controller (28) configured to control a speed of rotation of the winding core (16) and / or a speed of displacement of said first speed compensation unit (32), in order to keep said partial multilayer strip (15’) at a tension substantially constant during the formation of the wound element (11).

28. Winding machine (10’) as in any one of the claims 22-27, characterized by further comprising a second speed compensation unit (40) placed along said second feeding path between the electrode feed station (14”) and the winding station (26), and cooperating with the first electrode film (17), said second speedcompensation unit (40) being configured to be displaced to vary a second travel distance travelled by the first electrode film (17) along the second feeding path between the electrode feed station (14”) and the winding core (16), so that a given displacement of the second speed compensation unit (40) can lengthen or shorten the second travel distance of the first electrode film (17), thereby differences in speed between the speed at which the first electrode film (17) travels along the second feeding path and the speed at which said complete strip (15) has been wound by said winding core (16) can be continuously compensated, and in that said second speed compensation unit (40) is separate from said winding station (26).

29. Winding machine (10’) as in the claim 28, characterized in that said first (32) and second (40) speed compensation units are configured to be displaced together concurrently.

Images