GB2026778A

GB2026778A - Core laminations for transformers chokes and the like

Info

Publication number: GB2026778A
Application number: GB7919331A
Authority: GB
Original assignee: Blum Eisen & Metallind
Current assignee: Blum Eisen & Metallind
Priority date: 1978-06-02
Filing date: 1979-06-04
Publication date: 1980-02-06
Also published as: FR2427669A1; FR2427669B1; GB2026778B; BE876741A; DE2824207A1

Abstract

A one-part electromagnetic core lamination has one or more openings or windows 2, 3 each connected to the outer periphery of the lamination by a cut or division 9, 10 forming a narrow air gap. To provide a sufficient width for the air gaps to avoid jamming during assembly, without the need for an extra cutting operation, dents 15 are formed in portions of the lamination remote from the air gaps, so that the limbs 6, 7 swing outwardly in the direction of the arrows 17 to space the air gap edges 9a, 9b and 10a, 10b respectively. Air gaps of stepped shape as well as different positions for the dents are also disclosed (Figs. 2 and 3, not shown). Wedge-shaped airgaps are also envisaged. <IMAGE>

Description

SPECIFICATION Core laminations for transformers chokes and the like The invention relates to a one-part core lamination with at least one window for transformers, chokes, voltage stabilizers or the like, wherein for the purpose of introducing the lamination into a coil by means of a portion of the lamination, for example a limb, there is a division present starting from the window and extending up to the outer contour of the lamination and an air gap is present between the dividing edges disposed opposite one another.

In core laminations with one window the division is carried out as a rule in the region of the yoke, so that the limb can be introduced into the coil former. In core laminations with two windows the centre limb is passed through one of the yokes with the aid of dividing slits and is connected to the other yoke and, when the lamination is inserted into the coil, that is on stacking or batching, it is introduced into the coil by means of its centre limb. In order to ensure easy and secure stacking or batching, there must be an interval between the dividing slits, since otherwise catching together or lamming of the lamination portions adjacent the dividing slits occurs. On the other hand, however, the interval must not be too large, since a large air gap considerably impairs the electromagnetic properties.The production of such laminations takes place in so-called followon or sequence tools and, in fact, as a rule, the punching of the windows takes place first, in another sequence the limb is divided from the yoke and in a following sequence the air gap is completed by after-punching or after-shaving and the core lamination is thereafter cut off from the sheet-metal strip. There are economic and technical limits to the production of the smallest possible air gaps in the punching process, for example because of the necessary expenditure for the accuracy of the tools, the requirement of frequent resharpening and the risk of breakage (in the case of thin punchings, in particular, it may happen that they remain behind in the tool and thus are not removed satisfactorily, as a result of which the breaking of punches cannot then be avoided).The width of the air gap therefore represents a compromise between the width which is still acceptable from the electromagnetic aspect and an economic cost.

The problem underlying the present invention is to ensure as small an air gap as possible in core laminations of the kind mentioned at the beginning, so as to improve the electromagnetic properties, and nevertheless ensure more economics, simpler and cheaper production.

According to the invention, this is achieved in that in such core laminations the air gap or gaps is or are formed by partial introduction of permanent deformations, that is partial deformations going beyond the elastic limit, in zones of the core lamination remote from the gap or gaps.

This may be effected by widening a defined interstice or gap between the dividing or separating edges by deformation of the material, it being merely necessary to effect division and the air gap no longer having to be subject to a shaving process. One station can therefore be saved in the tool in this case. The widening of the interstice by deforming the material can be achieved by producing the deformation of the material in a cross-sectional zone of the core lamination which is adjacent a particular window by expansion, that is a so-called compression expansion.

A smallest possible defined air gap may also be formed, however, by first punching a relatively large gap between the dividing edges and thereafter narrowing this gap to the specific size by a deformation of the material of the core lamination. The dividing edges which are initially disposed relatively far apart are therefore brought closer to one another, which may be effected, for example, by deforming the material in a crosssectional zone of the core lamination which is adjacent the outer contour. One station can also be saved in the tool in this case compared with the methods of production known heretofore.

The deformation of the material may be created, for example, by a dent, that is an impression, in suitable zones. Moreover, it may be advantageous for the impression to be made in a wedge shape.

It is particularly advantageous for the deformation of the material to be provided in zones of low density of lines of force, so that no impairment or only a negligibly small impairment of the magnetic flux occurs.

To produce such core laminations, a method may be advantageous wherein the introduction of a partial permanent deformation of the material is effected prior to the formation of the dividing edges and the detachment of the core lamination from the strip of material and there is thereby imposed on the material a tension which, after detachment of the lamination on the side on which the division or cutting is performed, causes the material to project and the exactly defined air gap to be formed in this way.It is also possible, however, to employ a working method wherein the introduction of the partial permanent deformation of the material is effected in the tool after the formation of the dividing edges and prior to the detachment of the core lamination from the strip of material and a tension is thereby imposed on the material, so that after the detachment of the lamination from the strip of material on the side of the lamination facing or adjacent the division or cut the defined gap is produced in that the dividing edges are then able to move away from one another.

Another method of producing such core laminations may consist in that a relatively wide gap in the form of a slit is first produced in the tool at the division locations and a tension is thereafter imposed on the material by introducing a partial permanent deformation thereof in a zone of the core lamination which is adjacent the outer contour, so that after the detachment of the lamination from the strip the gap narrows.

Both in the case of the gap produced by widening and in that of the gap produced by narrowing, it may be advantageous for the permanent deformation of the material to be introduced after the window has been punched out. In some cases, however, it may also be advantageous for the permanent deformation of the material and the imparting of a corresponding tension or stress thereto to be effected prior to the punching out of the window.

irrespective thereof, it has proved to be particularly advantageous for the introduction of the partial permanent deformation of the material to take place on the sinking of cutting punches into the die of the tool, be they cutting punches for producing the fixing holes, for punching out the windows or for forming the slit or gap.

Particularly suitable for carrying the method for producing such laminations into effect is a tool wherein the reciprocating part, as a rule, therefore, the upper part of the tool, has a chisel-like stamping portion for introducing the partial permanent deformation. Moreover, it is advantageous for the chisel-like stamping portion to be arranged to be movable - as seen in the axial direction -- in the upper part of the tool and to be loaded towards the workpiece by a spring bias, so that when a cutting punch or cutting punches sinks or sink into the die the chisel-like stamping portion strikes the corresponding place on the core lamination to be formed with a certain force or energy and the deformation of the material or change of structure and the production of a corresponding tension are thereby produced.

The invention will be described in detail for shell core laminations with two windows with reference to embodiments shown in detail in Figures 1 to 5.

Figures 1 to 3 show various shell core laminations, while Figure 4 illustrates the working sequence in a tool and Figure 5 illustrates the design of a tool.

In Figures 1 to 3, the one-part core lamination 1 has in each case two windows 2, 3 and also two yokes 4, 5 and two limbs 6, 7. A tongue 8 extends from one yoke 4 towards the other yoke 5 and is separated from the opposite yoke 5 by air gaps 9, 10 and 11, 12 and 13, 14, respectively, extending from the windows 2, 3 up to the outer contours of the yokes 5.

The air gaps in Figures 1 and 3 have a rectilinear course, while the air gaps in Figure 2 have a step-like course.

The air gaps 9, 10 and 11, 12 according to Figures 1 and 2 are formed by the dividing edges 9a and 96, 10a and 10b and 11a and 1 16 and 1 2a and 1 2b respectively, formed in the tool being merely produced by dividing or cutting the yoke 5.

Thus, there is no air gap, but, on the contrary, a spreading or expansion of the material occurs when the dividing operation is carried out, so that when stacking is effected, that is when the core lamination is introduced into a coil by means of the tongue 8, the dividing edges would become caught together. For this reason, the air gaps 9 to 1 2 have heretofore been formed firstly by cutting and then by a subsequent after-shaving operation, the efficiency being all the greater the smaller the gap that is produced. Nevertheless, it is not possible to go below a certain size of air gap for technical and economic reasons.

According to the invention, in the core laminations according to Figures 1 and 2, the air gaps 9, 10 and 11, 12 are formed in that permanent deformations in the form of dents 1 5 (in Figure 1) and 1 6 (in Figure 2) are introduced in the zones remote from the dividing edges, as a result of which the limbs swing out in the direction of the arrows 1 7, 18 and the dividing edges 9a, 9b to 12a,12b move away from one another.

Through suitable pressure or energy by which the permanent deformation is introduced at 1 5 and 16, respectively, the air gaps 9, 10 and 11, 12, respectively, widen and can be kept small to an extent such as cannot be achieved by normal punching or shaving.

The deformations of the material at 1 5 and 16 are suitably provided in zones in which there is a low density of the lines of force 1 9, so that the electromagnetic properties are not impaired.

In the embodiment according to Figure 3,the initial basis for the air gaps 13, 14 is a relatively wide slit 1 3a-1 3b and 1 4a-1 4b, respectively, which is made smaller by introducing a deformation of the material in the form of a dent 20. As a result of the introduction of the dents 20, the limbs 6 and 7 swing in the direction of the arrows 21 towards the previously formed edges 13a,14b separating the tongue 8, it being possible to achieve the desired defined small size of the air gaps 13, 14 by suitable choice of the shape and length of the impressions 20 and the energy and depth of formation thereof. The deformation 20 is also provided in this case in a zone which is not touched,or is only insignificantly touched, by the magnetic lines of force 22.The air gap can then extend in a wedge shape, so that the smallest magnetic resistance prevails in the zone of the greatest length of the lines of force and conversely.

A possible method of producing a core lamination according to Figure 1 will be described with reference to Figure 4 by means of an example of a working sequence in a multistage tool.

The fixing holes 24 and the windows 2, 3 are punched out in a sheet-metal strip 23 at a first station I. In the second sequence, the notches 25 are formed and the tongue 8 is separated from the yoke 5 by means of the dividing edges 9a, 9b 9b (sic), 106. The dents 1 5 can be formed at the same station II in the zones adjacent the windows 2, 3. The detachment of the core lamination 1, which is now finished, takes place at the third station III by means of a separating cut 26. Due to the dents introduced at 15, the limbs 6, 7 can spring open, so that the gaps 9, 10 and a core lamination 1 according to Figure 1 are formed.

Figure 5 shows a portion of a tool from the illustrated station II and in accordance with a section on the line V-V in Figure 4.

The sheet metal strip 23 can be seen, the strip being passed through between a die 27 and the movable part 28 of the tool. Moreover, the still connected yoke portions 4, 5 can be seen.

Furthermore, the hold-down element 29, the guide 30, the retaining plate 31 and the upper part 32 and also the hold-down springs 33 can be seen. An insert 34 is held in the retaining plate so that it is axially fixed in one direction, but is axially movable upwardly and held under bias by a spring assembly 35. The insert 34 is moreover guided to be axially movable in the guide 30 and the holddown element 29 and has a wedge-like or chisellike profile 36 on its end facing the sheet-metal strip 23.

The tool is so designed that first the hold-down element applies itself to the sheet-metal strip 23 while one of the punches - in a working sequence according to Figure 4 the cutting punch for forming the dividing edges 9a, 9b, 1 Oa and 1 Ob -- is advanced with respect to the chisel-like or wedge-like profile 36 and, in fact, in such manner that this punch has already reached the position 37, that is plunges out of the material and into the die, while the chisel-like portion 36 begins to penetrate into the cross-section of the yoke 4 and form the deformation 1 5.

Claims

1. One-part core lamination with at least one window for transformers, chokes, voltage stabilizers or the like, wherein for the purpose of introducing a portion thereof into a coil a division starting from the window and extending up to the outer contour of the lamination is provided and an air gap is present between the dividing edges disposed opposite one another, characterised in that the air gap 10, 1 1, 12, 13, is formed by partial introduction of a permanent deformation (15, 16, 20) in a zone remote from the gap.

2. Core lamination according to claim 1, characterised in that the air gap (9, 10, 11, 12) between the dividing edges (9a, 9b; 10a, Ob; 11a, 1 1h; 12a, 12h) is widened by means of an introduced deformation (1 5, 1 6) of the material.

3. Core lamination according to claim 1 or 2, characterised in that the air gap (13, 14) is produced by a narrowing of a gap provided between the dividing edges (13a, 136, 14a, 146) by means of an introduced deformation (20) of the material.

4. Core lamination according to claim 2, characterised in that the deformation (15, 26 (sic)) of the material is provided in a zone of the lamination (1) which is adjacent the window (2, 3).

5. Core lamination according to claim 3, characterised in that the deformation (20) of the material is provided in a zone of the lamination (1) which is remote from the window (2, 3).

6. Core lamination according to any one of claims 1 to 5, characterised in that the deformation is formed by a dent (1 5, 16, 20).

7. Core lamination according to claim 6, characterised in that the deformation (15, 16,20), as seen in cross-section, has a cross-section narrowing in the direction of impression.

8. Core lamination according to claim 7, characterised in that the dent (1 5, 16, 20) has a wedge-like cross-section.

9. Core lamination according to any one of claims 1 to 8, characterised in that the deformation (15, 16,20) of the material is provided in zones of low density of the lines of force (19, 20 (sic)).

10. Method of producing a core lamination in a tool according to at least one of claims 1 to 9, characterised in that the introduction of a partial permanent deformation (15, 16) of the material is effected prior to the formation of the dividing edges(9a,9h; 10a, lOb; 11a, 11h; 12a, 12h)and the detachment of the core lamination (1) from the strip of material (23) and a tension is thereby imposed on the material, so that after detachment (at 26) a widening gap (9, 10, 11, 12) is produced between the dividing edges.

11. Method of producing a core lamination according to any one of claims 1 to 9, characterised in that the introduction of a partial permanent deformation (15, 16) of the material is effected after the formation of the dividing edges (9a, 9h; 1-Oa,10b; 1 la, 11b; 12a, 12h) and prior to the detachment (at 26) of the core lamination (1) from the strip of material (23) and a tension is thereby imposed on the material, so that after detachment (at 26) a widening gap (9,10,11,12) is produced between the dividing edges.

12. Method of producing a core lamination according to any one of claims 1, 3 and 5 to 9, characterised in that the division is created in the form of a relatively wide slit (1 3h-1 3a; 1 4h-1 4a) and a tension is imposed on the material by introducing a partial permanent deformation (20) thereof in a zone of the core lamination (1) which is adjacent the outer contour, so that after detachment the gap (13,14) becomes smaller.

13. Method of producing a core lamination according to at least one of claims 1 to 9 and 10 to 12, characterised in that the introduction of the partial permanent deformation (1 5, 1 6, 20) of the material takes place on the sinking of cutting punches into the die (27) of the tool.

14. Tool for carrying into effect the method according to any one of claims 10-13 for producing a core lamination according to any one of claims 1 to 9, characterised in that the reciprocating part (28) of the tool has a chisel-like stamping portion (36) for introducing the partial permanent deformation (1 5, 16, 20).

1 5. Tool according to claim 14, characterised in that the chisel-like portion (36) is arranged to be movable, as seen in the axial direction, in the movable part (28) of the tool and has a spring bias towards the workpiece (23).