Field of the Invention The present invention refers, in general, to a stack of mutually affixed metallic laminations and, more particularly, to a stack of metallic laminations for the formation of the stator or rotor of an electric motor, said laminations being affixed to each other by metallic beading.

The invention further relates to a metallic lamination and to a method for packing a plurality of metallic laminations.

Prior Art The overlapping of rotor and stator laminations with their mutual fixation being effected through saliences and recesses, which fit onto each other by interference, has been previously proposed.

The progressive tool cuts the plate in several stages, until all the desirable details for the lamination of a stator or rotor have been obtained. In the final stage, a lamination unit of the stator or rotor is cut from the rest of the plate, at each strike of the press, which lamination will be deposited in a slot, with interference, known as lamination brake. In the next strike, the tool cuts another lamination, which is placed over the previous one. The previous lamination experiments the friction force of the lamination brake, and the lamination that. has been cut is pushed by a device provided at the upper part of the tool, and thus these forces make the salience of the cut lamination to enter with interference in the recess of the previous lamination.

This description is basic, since other inventors in different countries patented other details. The basic features that are common to these solutions are the

salience, the recess, and the interference between the salience and the recess upon the cutting operation thereof in one of the stages of the tool. This is one of the major differences between the present invention and the solutions already pertaining to the state of the art.

One of the problems concerning the interference between the salience and the recess is related to the mechanical characteristics of the material that forms the plate to be stamped. The salience is usually smashed and deformed due to the interference and to the mechanical characteristics of the plate. Thereby, the salience cannot enter into the recess to secure the lamination, because the latter is pushed upwardly.

Objective of the Invention It is an object of the present invention to provide a metallic lamination and a stack of metallic laminations, particularly a stack of metallic laminations to form the stator or the rotor of an electric motor, which requires a reduced force to affix one lamination to the other, while increasing the joining force between the laminations and mainly reducing the effects of the mechanical characteristics of the plate upon packing the laminations.

It is a further object of the invention to provide a metallic lamination and a stack of metallic laminations, as mentioned above, which can be obtained with lower tolerances for the packing tool, increasing the useful life of the latter.

It is still a further object of the invention to provide a stack of metallic laminations such as defined above, which can be repeatedly obtained within the desired pattern, even when using lots of different materials.

It is still a further object to provide a method to

produce the lamination stack, which reduces the difference of the mechanical characteristics (one of the present problems) and which allows joining laminations consisting of different materials.

There are few visual differences between the present method and the state of the art. In the method of the invention there is only a small throughbore of any geometry in the center of any traditional salience.

The difference in the tolerance is considerable. The traditional technique does not allow a gap to exist between the salience and the recess. In the method of the present invention, said gap can exceed 0.02 mm.

The traditional technique uses the principle of fine cutting tools (a punch, whose cut is equal to or smaller than the die). The method of the invention uses the principle of a cutting tool with forging (a punch, whose cut is larger than the die).

Another difference is how the salience of a lamination is set in the recess (throughbore 11) of the adjacent lamination. In the traditional technique, the salience is fitted into the recess of the other lamination with no gap therebetween, being thus affixed in said recess. In the method of the present invention, the salience is easily fitted in the recess of another adjacent lamination, and then, through a forming punch, the salience is pressed against the lateral wall of the recess, being thus affixed in said recess.

Summary of the Invention The present invention is equal to the related prior art solutions only in the requirement of having the salience and the recess. The fixation method is completely distinct.

The salience and the recess can have any geometry (square, circular, hexagonal, rectangular, triangular, etc. ) and any profile (half-round, cylindrical, etc.)

and there is always a throughbore provided in the center of the salience and made in one of the stages prior to the production of the salience and recess.

There is no interference between the salience and the recess, but a centesimal gap exists therebetween, which is obtained by providing the cross section of the cutting punch, which forms the recess, with a contour that is similar to and slightly larger than the contour of the cross section of the die that forms the salience. Thus, there is not a gap between the cutting punch and the die, and so the cutting punch cannot, under no circumstances, penetrate into the die. Moreover, the punch has a centesimal rugosity in the longitudinal direction of the punch so that, during stamping, this rugosity is formed on the lateral surface area of the salience, which rugosity is generally defined by longitudinal linear fillets.

After providing the throughbore in the center of the area where the salience will be formed, the salience and the recess are produced in their respective stages in the tool, and the plate, after receiving all the other details, reaches the final stage, where the lamination unit is separated. The lamination is deposited in the lamination brake, and the next lamination will have no difficulty to fit its salience in the recess of the previously placed lamination, since there is no interference between the salience and the recess.

The fixation of the salience in the recess will be achieved by a forming punch, which is provided at the upper part of the tool and presents an end portion or a tapered end, and a pressing surface to redirect the deformations of the salience. The end portion of the forming punch enters into the throughbore of the salience and forces the material of the salience

against the lateral walls of the recess, and the pressing surface redirects the possible deformations that can occur on the upper surface of the salience.

The rugosity that is formed in the recess serves to absorb the force by deformation of the linear fillets of the rugosity, and thus it prevents the occurrence of material eruptions around the lamination.

Brief Description of the Drawings The invention will be described below, with reference to the enclosed drawings, in which: Fig. 1 is a schematic sectional view of a plate, which is previously and adequately provided with a throughbore for each projection to be formed and seated on a die and under a cutting punch positioned to stamp the plate, in order to form the salience and the recess of each lamination to be obtained; Fig. 2 is a similar view to that of fig. 1, but illustrating the cutting punch in an operative position for forming the salience and the recess on the plate; Fig. 3 is a sectional view of a lamination already formed with a salience and a respective recess with its lateral walls provided with the rugosity formed by linear fillets; Fig. 4 is a top plan view of a lamination containing only one salience and formed according to the invention; Fig. 5 is a cross sectional view of three overlapped laminations prior to the final stage of obtaining the fixation of one lamination to the other, further showing a forming punch in an inoperative exploded position; Fig. 6 is a cross sectional view of the insertion of a salience into a recess, with rotation of the lamination stack at each strike of the tool;

Fig. 7 is a sectional view of a lamination, presenting the projection and the recess in the shape of a channel with a trapezoidal profile; and Fig. 8 is a top plan view of the lamination illustrated in fig. 7.

Detailed Description of the Invention According to the drawings, each lamination 10 stamped from a plate 1 comprises: at least one salience 12 projecting orthogonal from one of the sides of the lamination 10 by a distance"d"that is inferior to the thickness"e"of said lamination 10. In the illustrated embodiment, each salience 12 presents a substantially cylindrical shape, but it should be understood that the salience 12 could present different cross section geometries.

Each lamination 10 is also provided with a recess 13 opened to the other side of the lamination 10, and presenting a similar cross section, which is slightly larger and coaxial in relation to a corresponding cross section of a respective salience 12. The recess 13 presents a depth"f"that is inferior to the thickness"e"of the lamination 10, and substantially equal to the projecting distance"d"of the salience 12 in relation to the adjacent side of the lamination 10.

Before stamping the plate 1 for the formation of each lamination 10, the plate 1 is provided with a throughbore 11 located in the center of the area in which each salience 12-recess 13 assembly will be formed.

The throughbore 11 having a cross section of any contour is defined in the plate 1 in a stage of the progressive tool prior to the stage of forming the salience 12 and the recess 13. Figures 1 and 2 show how the salience and the recess are obtained.

Linear fillets are provided in a cutting punch 3, in the form of a rugosity having a centesimal millimeter dimensioning, which is made longitudinally to the cutting punch through abrasives, electro-erosion by wire or electro-erosion with penetration. In these figures, it can be noted that the cross section of the cutting tool 3 is larger than that of a die 5 on which is positioned the portion of the plate 1 to be stamped. With this dimensioning, the cutting punch 3- die 5 assembly produces a salience 12 smaller than the recess 13 of figure 3, eliminating the interference therebetween when one lamination 10 is fitted into the other.

Figures 3 and 4 present a lamination 10 already provided with the salience 12, the recess 13, the throughbore 11 and with a rugosity 13a, which is generally defined by linear fillets formed in the surrounding lateral wall of the recess 13, by action of the linear fillets of the cutting punch 3. When the plate 1 reaches the final stamping stage, one lamination 10 is cut at each strike and deposited in a brake means, not illustrated. When the next lamination 10 is cut, its salience 12 will fit with no difficulty in the recess 13 of the previous lamination 10, remaining loosely and entirely housed therein, since there is no interference between the salience and the recess of the two laminations, as shown in figure 5.

With the progressive displacement of the upper part of the tool, a forming punch 4 of the final stage, as shown in figure 5, enters with its tapered end portion 4a in the throughbore 11, radially expanding the latter and pushing the material of the salience 12 against the surrounding lateral wall of the recess 13 of the lamination 10 immediately below. Undesirable deformations will occur on the upper and lower parts

of the salience 12 being punched, as well as undesirable deformations on the upper and lower parts of the lamination 10 around the recess 13 of the lamination 10 immediately below. These deformations occur because the material that is pushed flows in the direction where there is less force against its movement. The deformations around the recess 13 of the lamination immediately below the one receiving the forming punch 4 are reduced with the linear fillets, as better illustrated in figure 4, which absorb the fixation forces by their own deformation, filling the empty spaces between one linear fillet and the other.

Important factors for the successful fixation are: the penetration height of the forming punch 4, the tapering angle of the end portion 4a of the forming punch 4; and the diameter of the forming punch in relation to the throughbore 11 of said lamination 10, whose salience 12 receives the forming punch 4. The deformations of the salience 12 that receives the forming punch 4 are reduced at the upper part by the pressing annular surface 4b, of the forming punch 4, which surrounds the base of the tapered end portion 4a and redirects the deformations and, on the lower part, in case deformations are present, by the recess 13 of the lamination immediately below exerting force against the deformation. All these aspects contribute to direct the deformations of the salience 12 that is being affixed against the lateral walls of the recess 13 of the lamination 10 immediately below.

Figures 7 and 8 illustrate a construction in which the salience 12 and the recess 13 present the profile of a trapezoidal channel. One of the main problems of this embodiment is the perfect fit of the parts, which fit should be made without interference. Thus, it is necessary to rotate the lamination stack at each

strike and, upon stamping the lamination 10, to always make the number of saliences 12 equal to the number of recesses 13.

In some situations, such as for example that mentioned in the previous paragraph and illustrated in Fig. 6, each lamination 10 placed over the first lower lamination of a lamination stack comprises at least one assembly formed by a salience 12 and a respective recess 13, and also by a through-recess 13 that is opened to both sides of the lamination 10, the fixation of each of said laminations 10 with those immediately adjacent being achieved according to alternate alignments coinciding with the salience 12- recess 13 assemblies and with the through-recesses 13.

Usually, at the beginning of the formation of each stack, the first lamination 10 is provided with a through-recess 13, which is opened to both sides of the lamination 10 in order to lodge and affix, against its surrounding lateral wall, a respective salience 12 of the lamination 10 immediately above, as illustrated in figures 5 and 6. This is necessary to provide a separation between one stack and the other in the brake device, as well as for aesthetic purposes.

This new fixation method is not only intended for the fixation of laminations 10, made of the same material, to form the rotor and stator of electric motors, or intercalating laminations made of different materials, but it may also be used for the fixation of mutually overlapped plates for other applications.