IE51834B1

IE51834B1 - A laminated magnetic circuit with fixed air gap and procedure for adjustment thereof

Info

Publication number: IE51834B1
Application number: IE1423/81A
Authority: IE
Inventors: Gilles Desombre; Marc Dujardin; Gerard Haroux
Original assignee: Clarel Sa
Priority date: 1980-06-30
Filing date: 1981-06-26
Publication date: 1987-04-15
Also published as: ES272474U; ES272474Y; IE811423L; GR74360B; FI75446B; PT73282A; FI812017L; DK244581A; EP0042898A1; ATE9749T1; DE3069353D1; FI75446C; NO812219L; PT73282B; EP0042898B1

Abstract

1. Laminated magnetic circuit with air gap, comprising and E-shaped part and an I-shaped part (4), and wherein the lenght of the end bars (2) of the E part determines the depth of the air gap opposite the central bar (3) of this E part, characterized in that the side of the I part (4) which rests on the end bars (2) of the E part forms an obtuse angle (alpha) wiht the sides at the end of the part I part (4), and in that the two end bars (2) of the E part each have a prolongation (5) and these are arranged at a distance from one another corresponding to the lenght of the I part (4), so as to fit the shape of the said obtuse angle (alpha) in engaging about the I part (4).

Description

The present invention concerns a laminated magnetic circuit with fixed air gap, composed of an E-shaped part and an I-shaped part in which the length of the outer limbs of the E-part determines the width of the air gap at the face of the middle limb of this E-part.

The object of the invention is to provide such a laminated circuit suitable, for example, as a ballast for fluorescent lamps having high reliability to maintain its reactance value during its life and permitting easy adjustment of the reactance value at the time of manufacture.

According to the present invention there is provided a laminated circuit having a fixed air-gap comprising an E-shaped part and an Ishaped part in which the length of the outer limbs of the E-part determines the width of the air gap from the face of the middle limb of this E-part wherein the side of the I-part resting on the outer limbs of the E-part forms an obtuse angle with the sides of the ends of the I-part, and the two outer limbs of the E-part are each formed with an extension spaced apart the length of the I-part for enclosing the I-part and conforming to the shape of the said obtuse angle.

The invention is hereinafter described with reference to the accompanying drawings showing an embodiment thereof by way of example.

Figure 1 of the drawings is a sectional view of a magnetic circuit according to the invention, taken between two laminae of the E-part and I-part.

Figure 2 is an elevation of a stamped-out sheet.

In a casing 1,1', which is known, for example, by published Patent Specification No. 1,638,339, comprising two outer limbs 2 and a very short middle limb 3, the width of the inter-space is bridged over by a part 4 of the I-part. The side of the part 4 resting on the limbs 2 forms with the sides at the end of the part 4 an obtuse angle a. The two limbs 2 each have an extension 5. The two extensions 5 are arranged apart a distance equal to the length of the part 4 so as to hold the part 4 between them, making a contact angle of a therewith. By this arrangement the part 4 is retained correctly centered with respect to the E-part. The dimensions are chosen in such a manner that a bearing is assured between the extremities of the part 4 of the E-part and the parts of the limbs 2 parallel to the extremities of the middle limb and that a light wedging may be assured between the part 4 and the inclined parts of the extensions 5 in such a way that the principal flux finds a sufficient path and that the dispersion of the flux at the place of contact between the part 4 and the limbs 2 may be reduced to a very weak value. Moreover the lines of force of the dispersed flux do not then traverse the casing 1 and do not produce sounds. The obtuse anqle a is for example from 91° to 120°. It is chosen relatively near to a right-angle in order to avoid the part 4 from becoming detached from the E-part.

As the part 4 is maintained centrally with respect to the E-part it is easy to adjust the mean value of the air gap or what amounts to the value of the reactance as it affects the magnetic circuit of a ballast induction coil, for example. In order to do this it is sufficient to deform one or more laminae of the part 4 of the E-part at one or more places by a limited number of punctiform depressions where it is near to the limb 3.

The procedure involving punctiform depressions, equidistant apart or not, does not permit the introduction of a plastically deformable distancing material into the clearance space, as for example aluminium, as would be the case for example if the whole of the I-part was made the subject of a depression To facilitate the punctiform depressions the section of the laminae of the part 4 of the I-part facing the limb 3 may be weakened, especially by punching out apertures 6. It may be noted here that these apurtures 6 need not be used in assembling the laminations of the part 4. If it is desired to use the apertures 6 in the assembling of the laminations of the part 4, the diameter of the apertures 6 may be sensibly greater than the diameter of a pin which passes through them to enable the puncti15 form depressions of certain of the laminae to be accurately positioned. 4s the depressions do not have to be made on all the laminae, the air gap may be a little irregular. The inconvenience of these irregularities may be avoided by choosing, for example, a series of equidistant places where the depressions are disposed.

When the magnetic circuit described is used in a ballast according to Trench Patent No. 1,291,362, the impregnation ducts are left not only along the clearance space and the coil, but also the perforations 6 which provide an impregnation duct at a particularly critical place which could be the source of sounds, because they are opposite to the air gap. The other impregnation ducts are arranged between the ends of the limbs 2 and the casing where all pressure in the direction of the part 4 is avoided so as not to affect the principal contact between the E and I parts.

The invention enables very great accuracy in the air gap from the start.

In fact, as shown by the view of stamped-out lamination 8, Figure 2, the faces defining the air gap are cut by being punched out (cross-hatched surface 9) much more precisely than by shearing with reference to the line 10.

Claims

1. A laminated magnetic circuit having a fixed air-gap comprising an E-shaped part and an I-shaped part in which the length of the outer limbs of the E-part determines the width of the air gap from the 5 face of the middle limb of this E-part wherein the side of the I-part resting on the outer limbs of the E-part forms an obtuse angle with the sides of the ends of the I-part, and the two outer limbs of the E-part are each formed with an extension spaced apart the length of the I-part for enclosing the I-part and conforming to the shape of the said obtuse 10 angle.

2. A magnetic circuit according to claim 1 wherein the I-part comprises a weakening in its cross-section, preferably an aperture opposite the middle limb of the E-part.

3. A method of adjusting the air gap of a magnetic circuit according 15 to Claim 1 or 2, wherein one or more of the laminae of the I-part is deformed by a limited number of punctiform depressions at one or more places in proximity to the middle limb of the E-part.

4. A laminated magnetic circuit constructed substantially as described herein with reference to the accompanying drawings.