GB1588765A - Iron cores for electrical chokes or transformers - Google Patents

Description

(54) IRON CORES FOR ELECTRICAL CHOKES OR TRANSFORMERS (71) We, Ov HELVAR, a joint stock company organised under the laws of Finland, of Purotie 1-3, 00380, Helsinki, Fin- land, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to iron cores for electrical chokes or transformers.

An object of the present invention is to provide an iron core with the lowest possible consumption of material, virtually without loss.

This object is achieved, according to the invention, by an iron core in an electrical choke or transformer comprising two stacks of oppositely directed L-shaped plates arranged so that the vertical limbs of each stack provide an outer leg of the core and the horizontal limbs of two stacks cooperating to provide a lower yoke of the core, and a stack of T-shaped plates arranged between the two stacks of Lshaped plates so that the vertical limb of the stack provides a central leg of the core and the horizontal limb provides an upper yoke entering between the two outer legs, the upper ends of the vertical limbs of L-shaped plates being chamfered to provide each of the outer legs with an outwardly-directed upper corner face and the horizontal limbs of the L-shaped plates being chamfered to provide faces inclined downwards away from the centre of the lower yoke.

It is possible by a method according to the invention to produce the L plates virtually without any losses by punching the L plates from a sheet iron strip in such manner that the 90-degree angle of the Lplates lies in the central area of the punched strip and the ends of the L legs are on the margins of the strip.

An additional advantage of the iron core of the invention is a good filling factor, achieved by the fact that the L pieces can be brought from the sides of the coil and pressed tightly against the coil. In order to guide the tips of the L plates and to form an air gap it has been understood in the invention to join the T plates together to form a sheet package, using a bar running in a groove in the lower end face of the vertical leg.

The invention will now be described with 'preference to the accompanying -drawings, in which: Figure 1 is a cross-section of an iron core of a choke according to the invention.

Figure 2 illustrates how "L" plates are punched from a sheet iron strip, and Figure 3 illustrates how "T" plates are punched from a sheet iron strip.

The choke coil iron core illustrated in the drawing comprises a stack of "T" shaped plates 1 and two stacks composed of "L" shaped plates 2. The iron core is encircled by a sheet metal casing 3. The winding which resides in the winding windows 4 is not illustrated.

Chamfers 5 are provided on both ends of the "L" plates 2. The chamfers 5 are obtained by punching the L-shaped plates from a sheet iron strip in the manner shown in Figure 2, whereby the chamfered ends of the L legs will arise from the straight edges of the sheet iron strip. In practice, a number of L-shaped plates are punched across the width of the strip, and the chamfers 5 may be angular or curved. In that case, the ends of the L plates in adjacent strips are interpolated, whereby the strip of material remaining between punching strips is minimized.

In the assembly of the plate stacks 1 and 2, the L plate stacks are brought up from the side and pressed tightly against the winding, whereby a good filling factor is obtained. The T plates 1 are joined to form a plate stack, by means of a bar 6 running in a groove in the lower end surface of the vertical leg of the T, this bar acting at the same time as a spacer for the L plates so that a suitable air gap is formed between these and the vertical leg. Other procedures known in themselves may be employed for the final adjustment of the air gap.

In an iron core manufactured by the procedure of the invention the height of the winding window is completely freely select able by choosing appropriate widths of the punching strips.

WHAT WE CLAIM IS: 1. An iron core in an electrical choke or transformer comprising two stacks of oppositely directed L-shaped plates arranged so that the vertical limbs of each stack provide an outer leg of the core and the longitudinal limbs of two stacks co-operating to provide a lower yoke of the core, and a stack of T-shaped plates arranged between the two stacks of L-shaped plates so that the vertical limb of the stack provides a central leg of the core and the longitudinal limb provides an upper yoke entering between the two outer legs, the upper ends of the vertical limbs of L-shaped plates being chamfered to provide each of the outer legs with an outwardly-directed upper corner face and the longitudinal limbs of the L-shaped plates being chamfered to provide faces inclined downwards away from the centre of the lower yoke.

2. An iron core according to Claim 1, wherein the stack of T-shaped plates has a groove running in the lower surface of the vertical leg, and a bar is located in the groove to act as a spacer for the stacks Lshaped plates so that an air gap is formed.

3. An electrical choke or transformer substantially as described with reference to the accompanying drawings.

4. A method of manufacturing the iron core of a choke or transformer according to Claim 1, wherein the L plates are punched from a sheet iron strip in such manner that the 90-degree angle of the L plates lies in the central area of the punching strip and the ends of the L legs lie on the edges of the strip.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. able by choosing appropriate widths of the punching strips. WHAT WE CLAIM IS:

1. An iron core in an electrical choke or transformer comprising two stacks of oppositely directed L-shaped plates arranged so that the vertical limbs of each stack provide an outer leg of the core and the longitudinal limbs of two stacks co-operating to provide a lower yoke of the core, and a stack of T-shaped plates arranged between the two stacks of L-shaped plates so that the vertical limb of the stack provides a central leg of the core and the longitudinal limb provides an upper yoke entering between the two outer legs, the upper ends of the vertical limbs of L-shaped plates being chamfered to provide each of the outer legs with an outwardly-directed upper corner face and the longitudinal limbs of the L-shaped plates being chamfered to provide faces inclined downwards away from the centre of the lower yoke.

2. An iron core according to Claim 1, wherein the stack of T-shaped plates has a groove running in the lower surface of the vertical leg, and a bar is located in the groove to act as a spacer for the stacks Lshaped plates so that an air gap is formed.

3. An electrical choke or transformer substantially as described with reference to the accompanying drawings.

4. A method of manufacturing the iron core of a choke or transformer according to Claim 1, wherein the L plates are punched from a sheet iron strip in such manner that the 90-degree angle of the L plates lies in the central area of the punching strip and the ends of the L legs lie on the edges of the strip.