Shearing head for cutting a metal strip for the production of armatures of electric motors, machine and method using said shearing head

Abstract

The invention relates to a shearing head for machines for cutting a metal strip for the production of armatures of electric motors, in particular axial-flux motors. The head comprises a support plate for a plurality of punches arranged parallel along a first z direction and configured to form an m × n matrix on a section plane perpendicular to said first z direction, with m rows arranged along a second x direction and n columns arranged along a third y direction. The punches are supported so as to be translatable in the x direction, in the y direction, and in the z direction, thereby allowing the selection of a punch Pij to be used for the shearing operation by translating the punch matrix so that said punch Pij is exposed toward the surface of the strip to be sheared and at a certain distance from said strip. The punches are constrained to move in groups in the z direction relative to the support plate so that the translation in the z direction of a punch Pij toward the strip to be sheared with respect to the support plate results in moving an entire row of punches Pi closer to the strip to be sheared. The invention also relates to a machine comprising such a head and to a related cutting method.

Description

Shearing head for cutting a metal strip for the production of armatures of electric motors, machine and method using said shearing head.DESCRIPTION

[0001] The present invention relates to the field of machines for manufacturing components of electric motors, in particular for manufacturing armatures that make up the stators or rotors of such electric motors.

[0002] These machines are designed to assemble the armatures starting from material originally stored in a warehouse where it is available in the form of a semi-finished strip; the machine operates on said semi-finished material in a semi-automatic manner, carrying out, among other things, cuts or incisions on the strip and then winding it around a mandrel to form said armatures.

[0003] Specifically, the electric motors to be produced include armatures involved in the generation of magnetic fields with axial flow. Such armatures are obtained by winding a strip of known material, to which a specific shaping has been applied, around a rotating mandrel to form a structure such as a motor core having a spiral configuration with radial grooves.

[0004] Hereinafter, unless otherwise specified, the terms "slot," "opening," "groove," and "channel" will be used interchangeably to indicate the radial openings obtained or obtainable in the rotor or stator armature of the motor.

[0005] Furthermore, a "strip" of material may also be referred to as a "band" of material, with reference to elements of substantially elongated shape that develop along a longitudinal axis, relative towhich it is also possible to define the length of the element or o f a portion thereof ; transversely to the longitudinal axis a transverse axis of the element can be identi fied, along which, among other things , its width can be measured, and said longitudinal axis defines a direction of advancement of the element ( strip / band) within the apparatus ; along the direction perpendicular to the aforementioned axes , the thickness of the element is defined .

[0006] For the purposes of this description, an electric "motor" may also be understood as an electric "generator" for the processes and components of interest herein, namely the production of armatures which are not precluded from being used either to convert electrical energy into mechanical energy or vice versa .

[0007] In its simplest form, electric motors and generators of axial- flow type essentially comprise a stator and a rotor having cylindrical shape , with the rotor positioned inside the stator . One way of producing axial rotors and / or stators includes the step of winding a strip of magnetic sheet , suitably pre- formed, around a mandrel to form a lamination stack .

[0008] The lamination stack is manufactured in such a way as to present a certain number of radial grooves or grooves having an orientation with a radial component , of known shape and dimension, for housing windings of electrical conductors . An example of such construction is disclosed in EP4340192A1 .

[0009] Compared to other types of electric motors such as radialflux motors , axial- flux motors of fer speci fic advantages not further discussed herein, but which j usti fy the need to optimi ze the manufacturing processes of such devices .

[0010] Processes and devices are known for the production of spiral armatures for axial- flux motors that carry out machining operations on a mother strip ; these operations mainly include punching of the strip and the subsequent winding of the same around a mandrel in such a manner that the wound spiral presents the desired radialgrooves .

[0011] The precision of the grooves is one of the critical aspects for achieving the best possible performance of the motor, measured according to various criteria such as thermal, magnetic, or electrical efficiency and / or effectiveness. Known machines, despite refinements made in recent years, nevertheless present limitations which the applicant aims to overcome, at least in part, with the present invention.

[0012] A first limitation lies in the fact that the punching is carried out using a punch of specific dimensions selected for the required cut on the strip. Consequently, to change the cut dimension, it is necessary to change the punch, which must be done manually and therefore with the intervention of an operator, resulting in machine downtime; this entails the need to have specific punches and trained personnel to carry out the operation.

[0013] A further limitation lies in the flexibility of the machine, namely the maximum number of different shapes that can be executed without the need to modify and / or redesign new tooling. In a punch press, the need for a new format requires the design of new tooling suitable for performing the new shape.

[0014] The need to perform cuts of different dimensions also arises during the production of windings for individual components of motors having the same characteristics. By progressively varying the width of the grooves in one or more portions of the shaped strip that constitutes the armature, it is in fact possible to generate a rounding at the radially innermost and / or radially outermost edges of the armature grooves, with a predetermined radius of curvature.

[0015] It is evident that such an armature configuration would be difficult to achieve using punching machines operating with fixed- dimension punches, as it would require multiple punch changes, even during the process of manufacturing a single armature.

[0016] The object of the present invention is to provide a head thatallows for the rapid automatic change of punches in a punching machine for armatures used in the production of axial motors .

[0017] The invention achieves this obj ect with a shearing head for machines for cutting a metal strip for the production of armatures of electric motors , in particular with axial flow, said head comprising a support plate for a plurality of punches arranged parallel along a first z direction and so as to form an m x n matrix on a section plane perpendicular to said first z direction, with m rows arranged according to a second x direction and n columns arranged according to a third y direction . The punches are supported translatable in the x direction, in the y direction, and in the z direction so as to be able to select a punch Pij to be used for the shearing by translating the matrix of punches so that said punch Pij is exposed towards the surface of the strip to be sheared and at a certain distance from said strip . The punches are constrained to move in groups in the z direction with respect to the support plate so that the translation in the z direction of a punch Pij towards the strip to be sheared with respect to the support plate causes the movement of an entire row of punches Pi into a position closer to the strip to be sheared .

[0018] In an embodiment , the head advantageously comprises a first actuator, a second actuator, and at least one cam . The first actuator acts on a first slide so as to induce a translation of the matrix of punches in the x direction, whereas the second actuator acts on a second slide so as to induce a translation of the matrix of punches in the y direction . The cam is advantageously fixed with the support plate or with an element associated therewith, such that , during the translation of the matrix along the y axis , the head of a punch, or of an element fixed thereto , interferes with the cam in the manner of a tappet , thereby inducing a translation of said punch along the z axis and, consequently, of the row of punches to which said punch belongs .

[0019] The cam is preferably positioned centrally so that theselection of a row of punches results in the translation of said row in the z direction by acting in proximity to the central portion of the head.

[0020] The head may comprise a third actuator that acts on the support plate or on an element fixed thereto so as to induce a rigid translation of the plate and, consequently, of all the punches, in the z direction so as to adjust the distance of the punches relative to the strip to be sheared.

[0021] In a refinement, the punches belonging to a same row are staggered in height, i.e. they have an extension in the z direction that increases or decreases. In this manner, it is possible to ensure that punches adjacent to the working punch do not interfere with the strip during the shearing operation.

[0022] Such a head allows for automatic and fast punch changes without significant interruptions in production. This improves the overall efficiency of the manufacturing process by reducing downtime and enabling greater flexibility in adapting to production needs.

[0023] The easy automatic punch change may be advantageously used to progressively adjust the opening of the slots on the stator or rotor, enabling the creation of chamfers that improve the motor' s efficiency.

[0024] The automation of this process not only improves the precision and consistency of the chamfers, but also enables greater flexibility in optimizing the motor design based on specific requirements. This may result in more efficient and higher- performing motors while reducing production time and costs associated with manual operations.

[0025] The head according to the invention can be fastened to the ram of the press of the punching machine either directly or by means of suitable interfaces.

[0026] To this end, the invention also relates to a machine for cutting a strip comprising a support for a shearing head accordingto the invention and a press conf igured to exert a pressing force on said support in a manner synchroni zed with the advancement of the strip to be sheared . The head is advantageously mounted so that the direction of the pressing force coincides with the z direction of the punches and the strip advances in the y direction .

[0027] The machine advantageously comprises a control unit interfaced with the actuators of the head and configured to select a working punch by translating the matrix of punches in the x and / or y directions relative to a die element configured to receive the selected punch in a cavity during the shearing operation of the strip .

[0028] The die element , commonly referred to as "die , " extends longitudinally in the y direction of advancement of the strip to be sheared and transversely in the x direction, and features movable walls to adapt the longitudinal length of the die cavity to the y- direction dimension of the selected punch .

[0029] In a refinement , the control unit is configured to adj ust the distance of the punches from the die prior to the shearing operation by actuating the head actuator configured to translate the punch matrix in the z direction, so that , given s as the stroke induced by the press on the head, x the distance of the working punch from the die , and d the height di f ference between the working punch and the adj acent shorter punch, on the same row, it results that s < d, so that said punch adj acent to the working punch does not interfere with the die , and hence with the strip, during the shearing operations .

[0030] Since the punches are typically staggered in height in the x direction, it is desirable that any punch adj acent to the working punch and having a greater height than the latter ( for example , in the case of selecting an intermediate working punch) is positioned away from the die during the shearing operation . For this reason, in a refinement , given 1 as the width of the strip and Im as thewidth of the opening to be made in the strip, the control unit is configured to present the working punch to the strip in such a way that the adj acent punch, located on the same row and facing the portion of the strip having a width 1-lm not facing the working punch, is the one with the lower height , so that said punch adj acent to the working punch does not interfere with the strip during the shearing operation .

[0031] The invention also relates to a method for shearing a metal strip for the production of armatures of electric motors , in particular axial- flow motors , comprising the following steps :- providing a shearing head equipped with a group of punches ;- placing the strip on a die matrix or on a support surface having an opening of variable dimensions configured to receive one of the punches during the shearing operation;- selecting a punch from the group so as to expose said punch toward the strip to be sheared at the opening of the support surface ;- varying the dimensions of the opening of the support surface as a function of the dimensions of the selected punch;- moving the shearing head in an alternating manner and in synchroni zation with the advancement of the strip so as to carry out sequential openings on said strip of a dimension corresponding to that of the selected punch; wherein the selection of the punch occurs by moving the group of punches so that the selected punch is positioned at the opening of the support surface and at a certain distance from said surface , the movement of the group of punches taking place in a first direction so as to select a subset of punches from the group of punches and in a second direction so as to select the desired punch from the subset , the translation in the first direction inducing, via a cam device , a translation of said subset of punches in a third direction towards the support surface .

[0032] Since the punches in the subsets selectable from the group of punches via translation in the first direction advantageously have staggered heights, in a refinement the method provides for adjusting the distance of the group of punches from the support surface prior to the shearing operation, so that, given s as the stroke of the shearing head, x the distance of the working punch from the support surface, and d the difference in height between the working punch and the adjacent lower-height punch belonging to the subset selected via translation in the first direction, it holds that s < d, so that said punch adjacent to the working punch does not interfere with the support surface, and thus with the strip, during the shearing operations.

[0033] According to a further refinement, the shearing head is equipped with a group of punches having different dimensions in the y direction among at least two of the punches in the group, and the punching of the strip to be wound to build the armature is carried out using different punches in different portions of the strip. In this way, it is possible to create radial grooves having different widths as a function of the radial coordinate of the groove itself.

[0034] One practical, non-limiting case, already described herein, is shown in Figure 4b, where two chamfers 43' and 43' ' (although further configurations are possible, such as with only one of the two chamfers) can be clearly seen in the radially outer and inner portions of the groove. This variant advantageously enables the production of armatures that are more compatible with the windings of electrical conductors that will be housed in the grooves and wound in the armature area between two consecutive grooves, thus remaining more closely adhered near the chamfered zones where the electrical conductor is bent.

[0035] An armature thus obtained also constitutes an object of the present invention.

[0036] Further features and refinements are the subject of thedependent claims .

[0037] The features of the invention and the advantages deriving therefrom will become more apparent from the following detailed description of the attached figures , in which :- Fig . 1 shows an example of a plant for the production of armatures for electric motors ;- Fig . 2 shows a single ( Fig . 2a ) and double ( Fig . 2b ) cut line made on a metal strip to be processed;- Figs . 3a and 3b show the armatures obtained by winding the strips of the previous figures ;- Fig . 4 shows a top view of two shaped strips with constant and variable width openings and the corresponding profiles of the grooves of the resulting armatures ;- Fig . 5 shows an isometric view of a shearing head according to an embodiment of the invention mounted on the ram of a punching machine press ;- Fig . 6 shows a detail of the previous figure highlighting the punch matrix and support slides ;- Figs . 7 and 8 schematically show a section of the head of the previous figures in two planes orthogonal to the support plate of the head;- Figs . 9 and 10 show the sections of the previous figures in an embodiment of the invention;- Figs . 11-13 schematically show the translation of the head in the x direction for selecting one of the three punches in a row of punches ;- Fig . 14 shows an enlargement of Fig . 11 highlighting the distances involved between punches and strip to be sheared;- Fig . 15 shows two views of an embodiment in which a mechanism is present for axial translation of the shearing head to allowadjustment of the distance of the working punch from the strip before the punching operation;- Fig. 16 shows the detail of a die matrix with movable walls to receive punches of different sizes during the shearing operation;- Fig. 17 shows in isometric view the positioning of the die matrix relative to the selected punch in an embodiment of the invention .

[0038] The shearing head of the present invention can be used in any sheet metal cutting system in which a rapid punch change is required.

[0039] In the context of the production of armatures for motors or alternators, the invention finds its most significant application. In this field, it is indeed necessary to frequently replace worn punches and to carry out variable-width cuts on a ferromagnetic strip to be used for making a winding, in particular a stator winding, which features chamfers on the armatures. For this reason, the invention will primarily be described with reference to this application, without this being considered as limiting the scope of protection .

[0040] With reference to Fig. 1, a plant for producing armatures of electric motors comprises an upstream storage unit 1 loaded with a coil containing a known amount of metal strip to be processed 9 which is processed through the plant by passing through various stations until the desired armature, wound onto a collection coil 4, is obtained.

[0041] What is of interest here is the part of the plant designated for executing incisions on the strip before it is wound onto the collection coil 4.

[0042] This part, identified with reference number 2 in the figure, is a punch-based cutting machine 3 in which at least one single cut 90 (Fig. 2a) or double cut 90' and 90' ' (Fig. 2b) is executed on the strip to be processed 9 in accordance with a predefined shape, insuch a manner as to form a shaped strip band 91 or 91' .

[0043] The shaped strip band is formed in such a way that, when wound, it can constitute the armature 4 shown in Figures 3a or 3b.

[0044] Figure 4 shows two possible embodiments of a stator armature of an axial-flow motor, in a front view of portions thereof. The winding is shown on the right while on the left a portion of the strip from which said winding was obtained is shown.

[0045] As can be seen, the radial grooves 42, 42' extend in a substantially parallelepiped shape, whose cross-section corresponds to the shape of the grooves 95, 95' that the cutting punch impresses on the strip to be processed 9.

[0046] In the case of Fig. 4a, since the openings 95 have a constant width d, an armature with sharp edges 43 is obtained.

[0047] In the case of Fig. 4b, on the other hand, since the openings 95', 95' ', 95' ' ' have variable widths dl, d2, d3, an armature with rounded edges 43', 43' ' is obtained. Specifically, the width of the grooves has been increased in the portions of the strip that go on to form a certain number of radially inner and / or radially outer turns in the terminal (outer and / or inner) portion of the turns according to a known progression such as to generate a rounding at the radially inner 43 and / or radially outer 43' ' edges of the armature grooves, with a predetermined rounding radius R. For illustrative purposes, the representation of the grooves is not necessarily in proportion or to scale with possible stator realizations; in particular, the dimensions of the cuts have been enlarged and exaggerated and the distance between one cut and another has been reduced.

[0048] By varying the size of the shearing punches 3, it is also possible to create differentiated configurations between groove and groove of the same armature and / or differentiated profiles that can be easily used for the production of different types of armatures, for example of different size or with a different number of grooves,limiting, i f not eliminating, the setup operations in the machine .

[0049] Here are the details of the cutting machine and its operation .

[0050] This is essentially a press with a ram having vertical movement along the z direction ( Figures 5 and following) , equipped with a shearing head 10 with punch 3 . The strip 9 moves in a y direction lying in a plane transverse to the z direction such that the punch 3 , in its reciprocating up / down stroke , meets the strip 9 in the vicinity of an underlying die 5 , commonly referred to as matrix . The die 5 features a support surface 50 for the strip in which an opening is provided suitable to receive the punch 3 at the end of the stroke . The characteristics of this component will be detailed further on .

[0051] Since there is a need to perform a rapid change of the shearing punch, embodiments of the invention provide that the head 10 is equipped with a plurality o f punches 3 that can be selected to perform shearing operations having desired shapes and si zes .

[0052] One solution could be the use o f a pneumatic system that individually controls each punch of the plurality so as to expose the working punch in the z direction of shearing . This would make the system very complex and expensive , as for example described in document EP0658383A1 . For this reason, the inventors turned to solutions without actuators capable of controlling the individual punch .

[0053] Document EP0658383A1 discloses a system based on a modular punch matrix integrated in a high-frequency press processing plant . Each module is equipped with a series of punches housed in a structure composed of a mobile head, an intermediate guide , and a base plate , all constrained by guide columns . The punches are selected and brought into the operating position by sliding slides or rotating cams which, under CNC control , activate only the tools required for each pressing cycle . The modules can be moved laterally with respect to the material feed direction by means of electricmotors , hydraulic actuators , or ball screws , and their position is updated between one cycle of the press and the next .

[0054] Such a known system presents high mechanical and control complexity, due to the large number of actuators and moving components , and relative slownes s in reconfiguration, especially when the tool-module combinations need to be changed . The system also provides for the activation, i . e . the shearing movement , of a plurality of punches simultaneously, as a consequence of the independent control of each punch . In contrast to the invention described herein, the activation of multiple punches in EP0658383A1 is a deliberately chosen operating mode , whereas in the present invention the choice to move multiple punches simultaneously by grouping them in rows is the way in which a simpli fied structure and rapid change from one punch to another is achieved . In fact , as seen, in some embodiments staggered punches are provided and a die matrix is adj ustable in such a way that only one punch strikes the strip .

[0055] According to the invention, one solution provides for the use of a group of punches arranged side by side along the z punching direction so as to form a matrix o f m rows and n columns on a plane transverse to the z direction . The rows and columns are not necessarily orthogonal , but may nevertheless be inclined with respect to each other . In one embodiment , the columns are parallel to the y direction of strip advancement , while the rows are perpendicular thereto in the x direction, so that the x, y, z triad represents a Cartesian reference system . Other configurations are possible depending on the reference system used and the orientations of the individual elements .

[0056] With reference to Fig . 5 , the shearing head 10 according to one embodiment of the invention comprises a support plate 11 adapted to be fixed to the ram 100 of the press of the punching machine either directly or by means of suitable interfaces .

[0057] As best seen in Fig. 6, the punches, which in this example are 9, organized in a 3x3 matrix, have a cylindrical base with a parallelepiped-shaped head and are mounted to slide axially like pistons in a support plate 12 provided with corresponding holes. The support plate 12 is fixed to a first slide 13 capable of translating in the y direction with respect to a second slide 14 in turn capable of translating in the x direction with respect to the support plate 100.

[0058] The translation of the two slides is handled by a pair of actuators which, in the specific example shown in Fig. 5, are represented by two electric motors with shafts coupled to worm screws .

[0059] The two motors position the set of punches along x and y in the predefined position for the shearing of the strip. In this embodiment, the movement occurs via recirculating screw and dovetail guides to ensure the highest possible compactness and precision. This is not to be considered limiting for other possible equivalent implementations .

[0060] Figures 7 and 8 respectively show the translation of the punch matrix along the x direction and along the y direction.

[0061] A mechanical or hydraulic mechanism is advantageously present, for example a cam, which is capable of bringing only one set of three punches closer to the strip while the other two remain distant from the strip. This occurs by changing the position of the slide along the y axis as shown in Figs. 8 and 10.

[0062] In particular, the cam 131 (only partially shown) causes a set of punches 3', 3' ', 3' ' ' grouped along a row R and oriented in the x direction transverse to the y direction of strip advancement to rise. This causes the sliding of bars 132 into the seat of slide 13. The bars 132, when the punches are not in contact with the cam, are kept spaced apart by return elements acting between a stationary surface of plate 12 and a surface of the mobile structure withinwhich the punches of row R are grouped, said elements being, for example, springs 133. In this way, activation of the cam causes a translation in the z direction approaching the strip of an entire row of punches 3', 3' ', 3' ' ', while deactivation of the cam causes a translation of the same in the opposite direction, moving away from the strip, as a result of the action of the return springs 133.

[0063] The movement of the matrix in the y direction therefore allows the selection of one of the rows of punches, positioning it in the shearing area.

[0064] The choice among the punches in the row is made by translating the punch matrix in the other x direction such that the punch of interest is aligned with the strip in correspondence with the die 5, as shown in Figs. 11-13.

[0065] The choice to bring the punch of interest closer to the strip using a double translation movement, combined with a mechanism such as a cam, allows avoiding the use of complex pneumatic systems that act on the punches individually. Moreover, the sole movement of one component (for example, the punch row R along the x direction) is sufficient to switch from one punch to another.

[0066] Since the strip may have a transverse dimension greater than the distance between two punches in the same row, it is possible to avoid the adjacent punch interfering with the strip by staggering the punch heights in the x direction. As can be seen from Figures 11-13, the punches 3', 3' ', 3' ' ' have different heights. If, in this specific example, the translation in the x direction occurs from right to left, only the lower adjacent punch (3' ' in Fig. 11, 3' in Fig. 12) with respect to the working punch is exposed towards the strip .

[0067] In a refinement, it is possible to adjust the distance of the punches in the z direction so as to avoid any undesired contact between the non-shearing punches and the sheet during the operation of the shearing punch.

[0068] Figure 14 helps to understand this aspect. If the punch set can also translate in the z direction, it is possible to adjust the distance of the group of punches from the support plate 11 before starting the shearing operation in such a way that, s being the stroke of the shearing head, x the distance of the working punch from the support surface, and d the height difference between the working punch and the adjacent lower-height punch belonging to the subset of punches selected by the translation in the y direction, it results s < d so that said punch adjacent to the working punch does not interfere with the support surface, and hence with the strip, during the shearing operations.

[0069] If the adjustment along the z axis is available, the sequence of working phases for a set of three punches arranged along a row R of the matrix can be summarized as follows, using Figures 11 to 13 already discussed as reference:Phase 1: Punch 3' ' ' shears the sheet for a certain number of strokes (Fig. 11) .Phase 2: The x axis positions punch 3' ' in working position and the z axis brings it closer to the strip to the working distance; Punch 3' ' shears the sheet for a certain number of strokes (Fig. 12) .Phase 3: The x axis positions punch 3' in working position and the z axis brings it closer to the strip to the working distance; Punch 3' shears the sheet for a certain number of strokes (Fig. 13) .

[0070] Usually, punching machines have an adjustable punch stroke depending on the sharpening state of the punch and the thickness of the sheet; this is, in the vast majority of cases, done remotely by the operator acting on the control system (rarely does the operator manually intervene on the machine to adjust the stroke via linkages or other systems) .

[0071] In variable-stroke punching machines, theoretically, to ensure movement along the z axis, the already existing stroke adjustment system can be used and no additional axis is required.In this case , therefore , the quick-change matrix can be directly constrained to the ram of the punching machine by implementing a software function that adj usts the stroke amplitude as required by the application, acting at the programming level in the existing machine .

[0072] In all other cases , where there is no stroke adj ustment mechanism or the stroke change is too complicated / slow, it is possible to implement an additional electric axis as shown in Fig . 15 .

[0073] In this case , the support plate 11 of the punch matrix is not connected directly to the ram 100 , but is mounted to be slidable and brought to an appropriate distance from the strip to be sheared by means of an electric axis 110 . The electric axis 110 , connected directly to the ram 100 , by moving the support 11 closer to or farther from the strip, thus the punch matrix, performs the movement along the z axis that ensures the correct spacing between the punch and the strip .

[0074] To avoid interference , in a refinement the die or matrix 5 is adapted to the width of the punch by means of a system for adj usting the opening of the lateral walls 51 , 52 consisting of a recirculating screw paired with a motor 53 and two right-hand / lef t- hand threaded nuts as shown in Fig . 16 .

[0075] Figure 17 shows the positioning of punch 3 ' selected in correspondence with the matrix 5 with axially adj ustable walls 51 , 52 so as to form a cavity capable of receiving the selected punch along its entire extension .

[0076] A control unit (not shown in the figures ) underlies the operation of the plant in general , and the punching machine in particular, setting the translations necessary to perform the selection of the working punch . The control unit comprises at least one electronic control board, input / output interfaces , and a memory in which at least one software is loaded which, when executed,controls the machine and allows, among other things, execution of the steps of the control method.

Claims

CLAIMS1. Shearing head (10) for machines for cutting a metal strip for the production of armatures of electric motors, in particular with axial flow, characterized in that it comprises a support plate (11) of a plurality of punches (3) arranged parallel to a first z direction and so as to form an m x n matrix on a section plane perpendicular to said first z direction, with m rows arranged according to a second x direction and n columns arranged according to a third y direction, wherein the punches (3) are supported translatable in the x direction, in the y direction and in the z direction so as to be able to select a punch Pij to be used for the shearing by translating the matrix of punches so that said punch Pij is exposed towards the surface of the strip (9) to be sheared and at a certain distance from said strip, the punches (3) being constrained to move in groups in said first z direction with respect to the support plate (11) so that the translation in the z direction of a punch Pij towards the strip to be sheared (9) during the shearing operation with respect to the support plate involves moving an entire row (R) of punches Pi into a position closer to the strip to be sheared.2 Shearing head according to claim 1, further comprising a first actuator (15) , a second actuator (16) , and at least one cam (131) , said first actuator (15) acting on a first slide (14) so as to induce a translation of the punch matrix in the x direction, said second actuator (16) acting on a second slide (13) so as to induce a translation of the punch matrix along the y direction, the cam (131) being integral with the support plate (11) so that, during the translation along the y axis of the matrix, the head of a punch, or of an element integral therewith, interferes with the cam acting as a tappet (131) , inducing a translation along the z axis of said punch (3) and,consequently, of the row of punches (R) to which said punch belongs .

3. Shearing head according to claim 2, wherein the cam (131) is arranged in a median position so that the selection of a row of punches (R) involves the translation of said row in the z direction acting in proximity to the central part of the head.4 Shearing head according to one or more of the preceding claims, wherein the punches belonging to the same row (R) are scaled in height, i.e., have an increasing or decreasing extension in the z direction.5 Shearing head according to one or more of the preceding claims, comprising a third actuator (110) which acts on the support plate (11) or on an element integral therewith so as to induce a rigid translation of the plate (11) and, therefore, of all the punches, in the z direction so as to adjust the distance of the punches with respect to the strip to be sheared (9)6 Machine for cutting a strip comprising:- a shearing head (10) according to one or more of the preceding claims;- a support for said shearing head;- a press suitable for imparting a pressure force on said support in a manner synchronized with the advancement of the strip (9) to be sheared;- a die element (5) capable of receiving the selected punch in a cavity during the shearing operation of the strip; the shearing head (10) being mounted so that the direction of the pressure force coincides with the z direction of the punches and the strip moves in the y direction.7 Machine according to claim 6, comprising a control unit interfaced with the actuators of the shearing head (10) and configured to select a working punch Pij by translating thematrix of punches in the x and / or y directions with respect to the die element (5) .

8. Machine according to claim 6 or 7, wherein the die element (5) extends longitudinally in the y direction of sliding of the strip to be sheared and transversely in the x direction and has movable walls (51, 52) to adapt the longitudinal length of the die cavity to the dimension in the y direction of the selected punch .9 Machine according to claim 6 or 7 or 8, wherein the control unit is configured to adjust the distance of the punches from the die element (5) before the shearing operation by driving the third actuator (110) of the shearing head (10) suitable for translating the matrix of punches in the z direction so that, s being the stroke induced by the press to the shearing head, x the distance of the working punch from the die element, and d the height difference between the working punch and the adjacent punch of smaller length, on the same row, to the working punch it results s<d so that said punch adjacent to the working one does not interfere with the die element (5) , and therefore with the strip (9) , during the shearing operations.10 Machine according to claim 9, wherein 1 is the width of the strip (9) and Im the width of the opening to be made on the strip, the control unit being configured to face the working punch to the strip so that the adjacent punch, arranged on the same row (R) and facing the portion of strip of width 1-lm not facing the working punch, is of lower height so that said punch adjacent to the working punch does not interfere with the strip during the shearing operation.11 Method of shearing a metal strip for the production of armatures of electric motors, in particular with axial flow, which method comprises : a) providing a shearing head (10) according to one or more ofthe preceding claims 1-5; b) positioning the strip on a die matrix (5) , that is, a support surface (50) equipped with an opening of variable dimensions suitable for receiving one of the punches (3) during the shearing operation; c) selecting a punch from the group so as to expose said punch (3) towards the strip to be processed (9) in correspondence with the opening of the support surface; d) varying the dimensions of the opening of the support surface according to the dimensions of the selected punch; e) moving the shearing head (10) alternately and synchronized with the movement of the strip (9) along a y direction of sliding of said strip so as to create sequential cutouts on said strip of a size corresponding to the dimension of the selected punch measured along said y direction; wherein the selection of the punch takes place by moving the group of punches so that the selected punch is positioned in correspondence with the opening of the support surface (50) and at a certain distance from said surface, the movement of the group of punches taking place in a first direction, coinciding with the y direction of advancement of the strip (9) , so as to select a subgroup of punches arranged along a row (R) from the group of punches and in a second x direction, transverse to said y direction, so as to select the desired punch from the subgroup of punches, the translation in the first direction inducing by means of a cam device (131) a translation of said subgroup of punches in a third z direction, orthogonal to said x and y directions, of approach to the support surface (50) .

12. Method according to claim 11, wherein the punches of the subgroups of punches (r) selectable from the group of punches by the translation in the first x direction are scaled in height, the method providing to adjust the distance of the groupof punches from the support surface ( 50 ) before starting the shearing operation so that , s being the stroke of the shearing head, D the distance of the working punch from the support surface , and d the height di f ference between the working punch and the adj acent punch of lower height belonging to the subgroup of punches selected by the translation in the first direction, it results s<d so that said punch adj acent to the working one does not interfere with the support surface , and therefore with the strip, during the shearing operations .13 . Method according to claim 11 or 12 , wherein :- in step a ) a shearing head is provided equipped with a group of punches having a mutually di f ferent dimension in the y direction between at least two of the punches of said group of punches ;- steps c ) , d) , e ) are repeated using two or more punches of the group of punches chosen according to a known and predefined order, selecting punches of mutually di f ferent dimensions measured along a direction parallel or coinciding with the y direction of advancement of the strip ( 9 ) .14 . Armature of electric motor produced by winding around a winding element a longitudinal portion of a strip sheared according to claim 13 .15 . Armature of electric motor according to the preceding claim, comprising a plurality of radial grooves ( 42 ' ) with rounded edges in the radially outermost part ( 43 ' ) and / or radially innermost part ( 43 ’ ’ ) with a predefined radius of curvature R, said armature being obtained by winding a longitudinal portion of a sheared strip so as to provide width of the cutouts in the portions of strip forming a given number of turns radially more internal and / or radially more external in the terminal part , outer and / or inner, of the turns according to a known progression .

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