APPARATUS FOR CONTROLLING THE FEED OF WEB MATERIAL TO AUTOMATIC MACHINES

Technical Field

[01] The present invention relates to an apparatus for controlling the feed of web material to automatic machines using said web material for production purposes.

Prior art

[02] Use of automatic machines that use reels of web material for manufacturing or packaging products is currently known in various technical sectors. The operation of these automatic machines requires the unwinding of the web material from one or more reels and the feeding of this web material to the machine, so as to suit the production needs of the machine.

[03] In particular, it is usually required that the web material is fed to the machine with a suitable tension and at the speed required in each operating step of the machine. In fact, it is common for the unwinding speed of the web material from the reel to be momentarily different from the speed required to feed the machine. Typically, for example, the unwinding of the web material from the reel can take place at a constant speed, while the speed of feeding the same web material to the machine can be variable depending on the production process. In this case, therefore, it is necessary to compensate for the difference between the constant unwinding speed of the web material from the reel and the discontinuous process of the machine.

[04] Therefore, apparatuses has been developed that can automatically control the feeding of the web material to automatic machines that utilize this web material. A device known for this purpose provides for forming, along the feed path of the web material, a mechanical loop having variable amplitude development in a direction substantially transverse to the line. The amplitude of the mechanical loop remains unchanged at constant speed. When, instead, the machine requires a higher speed of feeding of the web material, for example for an operational phase, the width of the loop is shortened to meet this greater demand.

[05] A known solution for making the aforementioned mechanical loop provides that the web material is wound on a control roller adapted to be operated in contrast with specific actuating means, in order to change the width of the loop itself. Said actuating means act on the control roller, via appropriate intermediate mechanical members, in order to guarantee the correct tension of the web material.

[06] For example, in the system commonly referred to as a "dancer roller", the control roller is rotatably carried at the end of a lever arm equipped with a fixed fulcrum and subject to the elastic action of a special actuator, for example of the pneumatic type. The control roller moves as a function of the greater pulling force exerted by the machine on the web material, changing the width of the loop; when this pulling force turns back to the default value, the actuator restores the initial position of the control roller.

[07] US 4,787,544 illustrates an embodiment of a "dancer roller" system in which the control roller exerts a tensile stress due to the force of gravity.

[08] A drawback complained of in the known control apparatuses consists in the fact that in order to transfer to the web material the traction force necessary to provide the correct tension, a mechanical chain formed by a plurality of moving parts, rotating or translating, is necessary. The moving masses of these mechanical members have a generally considerable inertia and this constitutes a significant limit on use in high dynamic machines, i.e. with sudden speed variations in one or both branches of the loop, such as for example the machines used for the construction of electrical energy storage devices.

[09] In this specific sector, use of electrical energy storage devices consisting of a cylindrical winding of the electrodes known as "jelly roll" is currently known. Such a cylindrical winding comprises at least an anode element and a cathode element made in the form of flexible web and separated from each other by a separator element. The winding of the electrodes is placed inside a cylindrical container, for example of metallic material.

[10] The respective electrode terminals are protruding from the anode and cathode elements at the opposite ends of the cylindrical winding.

[11] These electrode terminals are obtained from web materials that have a series of external fin-shaped terminations on at least one side, known in the specific sector as "flags".

[12] Another need that must be met when feeding the web material to automatic machines is to ensure the correct longitudinal alignment of the web material itself. This is particularly important in the aforementioned sector of machines for manufacturing electrical energy storage devices, in which it is necessary to obtain windings consisting of a plurality of web materials of different types, generally having a very thin thickness. The web materials used in the field of machines for making the anode and cathode of electrical energy storage devices generally have a thickness of a few tenths of a mm, for example 2 or 3 tenths of a mm; those used for the construction of the separating element can be reduced to an order of hundredths of a mm.

[13] In this case, a precise longitudinal alignment of the web materials to be superimposed is obviously necessary. It is known, however, that the web material often has internal tensions deriving from the production process such that it has the tendency, in operation, to deform and deviate from the correct direction of travel. It is therefore necessary to introduce in line special alignment systems for web materials that significantly increase production costs.

[14] A further problem that arises in the field of machinery for manufacturing of electrical energy storage devices is linked to the fact that web materials are often used that have, on at least one side, a series of fins or flags that can easily bend or be damaged. These fins can be extended for a more or less long section and have different steps or alternate with empty sections. Under normal conditions, the fins should remain coplanar with the web; vice versa, sometimes they can be lifted when passing at the roller that defines the loop. This can obviously be the cause of an inadmissible amount of waste during the production phase.

[15] Figures 6, 7 and 8 show, by way of example only, different types of web material commonly used in the aforementioned apparatus, and more specifically: web material 2 without fins or flags; web material equipped along one side with fins or flags 21 obtained by notches 22 and interspersed with portions 23 of removed material; web material equipped with fins or flags 21 along both sides. More specifically, the notches 22 are substantially orthogonal to the longitudinal direction of the web material 2 and can be made with constant pitch, i.e. equidistant from each other, or with variable pitch, i.e. not equidistant from each other, along the longitudinal direction of the web material. Furthermore, the portion 23 of web comprised between two successive notches can be removed, thus forming a notched profile of the longitudinal edge of the web material.

[16] Another drawback frequently complained of in the field of machinery for manufacturing electrical energy storage devices is the fact that, in operation, the anode and cathode forming web materials can emit particles of different sizes capable of contaminating the feed process to the machine, with very serious effects on the final products. For example, contamination may occur between anode and cathode or particles large enough to damage the separator element may be released. A need exists in the art for a high degree of cleanliness of the apparatus during all the phases of feeding the web material.

[17] Ultimately, the current development of increasingly high-performance automatic machinery, capable of reaching very high production speed, makes it urgent to control the feeding of the web material in order to meet the demands of the machines.

Disclosure

[18] The purpose of the present invention is to solve the aforementioned problems, by devising an apparatus that allows optimum control of the feeding of web material to automatic machines using this web material for manufacturing or packaging products.

[19] Within this task, it is a further object of the invention to provide an apparatus that allows to control the tension and the longitudinal alignment of the web material fed to the machine.

[20] Another object of the invention is to provide an apparatus for controlling the feeding of web material to automatic machines that is able to compensate for the difference between the unwinding speed of the web material from the reel and the feed speed required in feeding the machine.

[21 ] Another object of the invention is to provide an apparatus for controlling the feeding of web material to automatic machines that allows the achievement of a high production speed.

[22] Another object of the invention is to provide an apparatus for controlling the feeding of web material to automatic machines that ensures a high degree of cleanliness of the web material fed to the machine.

[23] Still another object of the invention is to provide an apparatus for controlling the feeding of web material to automatic machines capable of preserving the integrity of such web material.

[24] Even further object of the invention is to provide an apparatus for controlling the feeding of web material to automatic machines of simple constructive and functional design, which is reliable in operation, versatile in use, as well as relatively inexpensive.

[25] The aforementioned objects are achieved, according to the present invention, by the apparatus and method for controlling the feeding of web material to automatic machines according to claims 1 and 9.

[26] The apparatus for controlling the feeding of web material to automatic machine comprises a container adapted to receive said unwinding web material from a respective reel and having a front end that is open and a rear end closed by a bottom wall.

[27] Preferably said container is elongated.

[28] Said container comprises at least a first and a second longitudinal wall that are opposite and parallel to each other.

[29] Preferably, said opposite and parallel longitudinal walls respectively constitute an upper wall and a lower wall of the container.

[30] Guide means for guiding said web material respectively into and out of said container are arranged at said open front end of the container, said web material developing inside the same container so as to form a loop between an inlet branch and an outlet branch of the same web material.

[31] Preferably said guide means comprise a first and a second roller arranged freely rotatable with parallel rotation axes, transverse to the longitudinal axis of said container, said web material to be fed to the machine, unwinding from a relative reel, being guided to the inlet inside the container by said first roller and out of said second roller.

[32] According to the present invention, the apparatus comprises a vacuum pump connected to said container in proximity to said bottom wall and adapted to create, inside the container itself at said rear end, a controlled negative pressure that is external to said loop formed by the web material, to draw taut the web material.

[33] Said web material unwinding inside said container is kept in connection, at the inside of said loop, with the ambient pressure, so as to create a pressure difference with the area outside the loop, which is put under vacuum by said vacuum pump.

[34] According to another aspect of the invention, the apparatus comprises an auxiliary roller arranged floating inside said web material unwinding inside said container, at said pneumatic loop.

[35] Said container has side walls adapted to contain said auxiliary roller. [36] Said auxiliary roller on which said loop of web material is wound is free to move along said container following the movement imparted on said pneumatic loop.

[37] Preferably said auxiliary roller is made of lightweight material such as carbon fiber and the like.

[38] Preferably said auxiliary roller comprises a thin cylindrical element, connected to an axial hub by means of a plurality of radial elements.

[39] Preferably, said cylindrical element of the auxiliary roller extends for a length close to the width of said container, so as to be substantially very close at the opposite ends to said side walls of the same container.

[40] Preferably, a stem having a length equal to that of the auxiliary roller itself is associated with said hub of the auxiliary roller.

[41] Preferably said stem ends at opposite ends with spherical cap-shaped end portions which, in operation, are protruding from the same auxiliary roller to come into contact with the side walls of said container.

[42] This allows to limit the contact between said stem and said side walls of the container to a substantially point zone.

[43] The present invention also relates to a method for controlling the feeding of web material to automatic machines using said web material for production purposes, comprising the steps of a. feeding said unwinding web material from a relative reel inside an elongated container having an open front end and a rear end closed by a bottom wall; b. guiding said web material fed into said container so as to form a loop between an input branch and an output branch of the same web material from the container; c. arranging a floating auxiliary roller inside said web material unwinding within said container, at said loop; d. creating, by means of a vacuum pump connected to said container near said bottom wall, inside the container itself, a controlled negative pressure external to said loop formed by the web material and wound on said auxiliary roller; e. keeping said web material unwinding inside said container in connection, at the inside of said loop, with the ambient pressure, in order to create a controlled pressure difference with the area outside the loop, put under vacuum by said vacuum pump; f. due to said pressure difference acting on said loop of the web material (2), drawing taut said web material unwinding inside said container.

[44] Suitably, said controlled negative pressure affects an area inside said container arranged at said rear end and between the outer surface of the web material creating said loop and said bottom wall of the container.

[45] Suitably, the method provides for drawing any particles released in operation by said unwinding web material inside said container by means of said vacuum pump.

Description of drawings

[46] The details of the invention will be more apparent from the detailed description of a preferred embodiment of the apparatus for controlling the feeding of web material to automatic machines, illustrated by way of example in the attached drawings, in which:

Figure 1 is a longitudinal sectional view of the apparatus for controlling the feeding of web material to automatic machines according to the present invention;

Figure 2 is a longitudinal sectional view of a different embodiment of the apparatus for controlling the feeding of web material according to the present invention;

Figures 3 and 4 are respective cross-sectional views of the apparatus of Figure 2;

Figure 5 is an axial section view of a detail of the apparatus of Figure 2

Figures 6, 7 and 8 are a plan view of different types of web material suitable for use in the subject apparatus.

Description of embodiments of the invention

[47] With particular reference to these figures, 1 indicates as a whole the apparatus for controlling the feeding of web material 2 to automatic machines that use this web material for production purposes.

[48] The apparatus 1 comprises a box-shaped elongated container 10, having for example a rectangular cross section. In particular, the container 10 has a first and a second longitudinal wall 11 , 12 that are opposed to each other and parallel, hereinafter for simplicity also referred to as the upper wall and the lower wall.

[49] The container 10 has an open front end and a rear end closed by a bottom wall 13. An opening 14 for connection to a vacuum pump, not shown, is obtained near the bottom wall 13, on a side wall of the container 10, to create an appropriate negative pressure inside the container 10 itself. The container 10 is also closed on the sides by side walls 15.

[50] At the open front end of the container 10, a first and a second roller 3, 4 having parallel axes of rotation, transverse to the longitudinal axis of the container 10, are arranged freely rotatable. The web material 2 to be fed to the machine, unwinding from a relative reel, is guided to the entry inside the container 10 by the first roller 3 and to the exit by the second roller 4. The web material 2 develops inside the container 10 by forming a loop 20 between an input branch that runs close to the upper wall 11 and an output branch that runs close to the lower wall 12.

[51] In operation, inside the container 10 a pressure difference is created between the area inside the loop 20 formed by the web material 2, open to ambient pressure, and the area outside the same loop 20, put in vacuum. This pressure difference determines a tension on the web material 2, which substantially undergoes tensile stress in the direction of the bottom of the container 10. [52] By adjusting this pressure difference, it is possible to adjust the tension of the web material 2 according to the production needs imposed by the machine.

[53] It should be noted that the pneumatic loop 20 so formed is also adapted to act as a temporary accumulation device or buffer to compensate for a different speed of the web material upstream and downstream of the same apparatus.

[54] The operation of the apparatus for controlling the feeding of web material to automatic machines is easily understandable from the following description.

[55] The web material 2 unwinding from the relative reel is fed into the elongated container 10, where it forms a loop 20 between an input branch and an output branch from the open front end of the same container 10. The web material 2 is guided into the container 10 by the first roller 3 and out by the second roller 4.

[56] In particular, the web material 2 fed into the container 10 develops so as to form a loop 20 between an input branch and an output branch of the same web material 2 of the container 10. The input branch and the output branch of the web material 2 run close to the upper longitudinal wall 11 and the lower longitudinal wall 12, opposite and parallel to each other, of the container 10, respectively.

[57] According to the present invention, by means of a vacuum pump 14 connected to the container 10 near the bottom wall 13, a controlled negative pressure is created inside the container 10 itself outside said loop formed by the web material 2.

[58] Essentially, the negative pressure affects an area inside the container 10 at said rear end and between the outer surface of the web material 2 creating the loop 20 and the bottom wall of the container 10 itself.

[59] The web material 2 unwinding inside the container 10 is kept in connection, at the inside of said loop 20, with the ambient pressure, so as to create a controlled pressure difference with the area outside the loop 20, put under vacuum by the vacuum pump 14.

[60] As a result of the pressure difference acting on the loop of the web material 2, the web material 2 unwinding inside the container 10 is drawn taut. This tension of the web material 2 is suitably adjustable by adjusting the negative pressure external to the loop 20 produced by the vacuum pump 14.

[61 ] According to another aspect of the invention, as shown in Figure 2, the apparatus comprises an auxiliary roller 5 arranged floating inside the web material 2 unwinding inside the container 10, at the pneumatic loop 20.

[62] A feature of such a solution is the fact that the auxiliary roller 5 is not constrained to the side walls 15 of the container 10, but is free to move along said container 10 as well as to vary its inclination with respect to said side walls 15.

[63] In practice, the position of the auxiliary roller 5 with respect to the container 10 can be changed by varying the negative pressure external to the loop 20 produced by the vacuum pump 14.

[64] Suitably the auxiliary roller 5 is made of lightweight material, preferably carbon fibre or the like. In the context of the present invention, lightweight material means that the auxiliary roller 5 has a mass that is in relation to the accelerations imparted in operation on the web material 2 by the user machine. In other words, knowing the accelerations imparted on the web material by the machine, depending on the different types of use, it is possible to predict the mass of the auxiliary roller by acting appropriately on the dimensions and material of the auxiliary roller itself. In the case of highly dynamic machines, i.e. with sudden variations in the speed, such as those used for the construction of electrical energy storage devices, the mass of the auxiliary roller must be proportionally reduced.

[65] More precisely, as visible in figure 5, the auxiliary roller 5 is made up of a thin cylindrical element 50, for example in the order of 1 mm, connected to an axial hub 51 via a plurality of radial elements 52.

[66] The cylindrical element 50 of the auxiliary roller 5 extends along its axis for a length close to the width of the container 10, so as to be substantially close to the opposite ends the side walls 15 of the same container 10.

[67] Advantageously, the axial hub 51 of the auxiliary roller 5 is associated with a stem 53 whose length is equal to that of the auxiliary roller 5. The stem 53 ends at the opposite ends with end portions in the shape of a spherical cap which, in operation, protrude from the same auxiliary roller 5 to come into contact with the side walls 15 of the container 10. In this way, even when the inclination of the axis of the auxiliary roller 5 with respect to the aforementioned lateral walls 15 varies, the contact always occurs on a substantially pointlike area, minimizing friction phenomena. Essentially, the reciprocal movement between the auxiliary roller 5 and the side walls 15 of the container 10 occurs by sliding at substantially point-like contact areas, defined by the spherical cap-shaped end portions of the stem 53.

[68] An advantageous aspect of this solution is the fact that web materials 2 having different widths can be wound on the auxiliary roller 5, forming the pneumatic loop 20. It is therefore not necessary, in this case, to provide for the adjustment of the width of the container 10, i.e. the mutual distance between the side walls 15.

[69] The apparatus according to the present invention achieves the aim of optimally controlling the feeding of web material in machines that use this web material for the production or packaging of products.

[70] In particular, the apparatus for controlling the feeding of web material according to the present invention allows accurate control of the tension and longitudinal alignment of the web material fed to the machine.

[71] This is made possible thanks to the inventive idea of creating a pneumatic loop of the web material inside an elongated casing having an open front end and a rear end closed by a bottom wall and of putting under tension said loop of the web material via a controlled negative pressure created at the rear end of the container, outside of said loop.

[72] A feature of the present invention is the fact that an auxiliary roller is arranged floating inside said web material being unrolled inside said container. The floating roller wraps around said pneumatic loop and is free to move along said container following the movement imparted on the pneumatic loop.

[73] It is worth highlighting in particular the fact that the apparatus and the method in question allow the feeding of the web material to automatic machines to be carried out in an optimal manner, using said web material for production purposes, in particular for manufacturing electrical energy storage devices, providing a solution to specific problems linked both to the characteristics of these materials and to the characteristics of the machines themselves, such as high dynamics, i.e. the occurrence of sudden variations in the speed in operation.

[74] Thanks to the inventive idea of tensioning the web to be fed to the machine by creating a pneumatic loop, the masses of the moving mechanical parts are drastically reduced, allowing operation without imbalances even in the presence of sudden variations in the speed.

[75] The pneumatic loop so formed is suitable to also act as a temporary accumulation device or buffer to compensate for a different speed of the web material upstream and downstream of the same apparatus.

[76] Furthermore, the apparatus permits to draw in, via the vacuum pump, any impurities or particles released by the web materials during the unwinding, in order to ensure a high degree of cleanliness of the web material fed to the machine.

[77] The apparatus described by way of example is susceptible to numerous modifications and variations according to different needs.

[78] In the practical embodiment of the invention, the materials used, as well as the shape and the dimensions, may be modified depending on needs.

[79] Should the technical features mentioned in any claim be followed by reference signs, such reference signs were included strictly with the aim of enhancing the understanding of the claims and hence they shall not be deemed restrictive in any manner whatsoever on the scope of each element identified for exemplifying purposes by such reference signs.