GB2040586A

GB2040586A - Insulation structure for a demagnetising coil

Info

Publication number: GB2040586A
Application number: GB8000267A
Authority: GB
Original assignee: Cosmofil
Current assignee: Cosmofil
Priority date: 1979-01-17
Filing date: 1980-01-04
Publication date: 1980-08-28
Also published as: GB2040586B; JPS5597783A; ES240801U; IT7928437A0; DE3000335A1; ES240801Y; IT1165415B; DE3000335C2; FR2447124A1

Abstract

A demagnetising coil (1) e.g. for a colour television receiver tube comprises insulation covering the conductors (3) which is formed by at least two sleeves (6, 5) one inside the other, each sleeve being formed by a channel-section extrusion, the ends (7b, 8b, 10b, 11b) of which are folded over each other, and sealed together by heat treatment or by an adhesive. <IMAGE>

Description

SPECIFICATION Coil This invention relates to a coil, for example for use with a colour television receiver tube for demagnetising the various steel parts close to the face of the tube.

Such demagnetising coils have to have external insulation against the high voltages experienced.

In this respect, it should be pointed out that safety standards have been set in many countries and these must be met by the demagnetising coils In certain known embodiments, the coil is insulated by means of a tape of insulating material wound around the coil in a substantially helical form, with each turn of the tape being at least partially superimposed over the adjacent turn.

The winding of this type of insulation is laborious and the result tends to be irregular. Also it is susceptible to damage during assembly and repair.

In another known embodiment, the coil winding is in a tube of insulating material which is closed longitudinally after receiving the winding. The insulation is regular, and manufacture is simple, but there is still the danger of the insulation being damaged during manufacture, or installation of the coil in the television receiver and during repair.

According to the present invention, a coil, for example, for use as a demagnetising unit for a colour television receiver tube, is covered by at least two flexible sleeves of insulating material fitted snugly one inside the other, each of said sleeves being formed as a channel section strip, the parts of the sides of the channels adjacent the free edges of the sleeves being folded over to overlap one another. This has the advantage that should one sleeve become damaged during manufacture, installation or repair, the second sleeve will still provide sufficient insulation, since it is most unlikely that they both will be damaged in the same place.

The folded-over parts can be interleaved one with another, and finally sealed together by heat sealing or an adhesive.

The coil can be easily made from two extrusions cut to length, and is very resistant to subsequent insulation damage.

The invention may be carried into practice in various ways, but one embodiment will now be described by way of example with reference to the accompanying drawings, in which: FIGURE 1 shows two coils at the back of a colour television receiver tube; FIGURE 2 is a perspective view on a larger scale and in cross section, of the channel section strips prior to folding down and sealing to form the insulating sleeves for the conductor wires; FIGURE 3 is a cross section view of the assembled coil; and FIGURE 4 is a perspective view on a different scale, of the complete coil prior to assembly with the receiver tube.

In FIGURE 1, there are illustrated two coils 1, mounted at the back of a television receiver tube 2 for demagnetising the various steel components adjacent the surfuce of the tube.

Each coil 1 comprises a bundle of conductor wires 3 with external insulation provided by a channel shaped outer strip 5 and a channel shaped inner strip 6, which are flexible and made from insulating material, such as PVC.

The channel shaped outer strip 5 is U-shaped with a base portion 5a and sides 7 and 8 longer than the base.

The base 5a is shown as being straight and the sides are normal to the base, nevertheless, other configurations, such as a curved base are possible.

In the inner surface of each side 7 or 8 is a groove 9 and between each groove 9 and the respective edge 7a or 8a the sides 7b or 8b becomes progressively thinner. Such thinning may instead be immediate.

The sides 7 and 8 are of unequal length, so that when folded at the grooves 9, the outer surface of the shorter longitudinal portion 7b is easily contained within the inner surface of the longer longitudinal portion 8b to close the insulation around the wires 3.

In turn, the inner channel shaped strip 6 has a similar configuration to the strip 5, so as to be able to fit snugly inside the latter. The strip 6 has, therefore, a base 6a similar to the base 5a and sides 10 and 11 having respective edges 1 0a and 11 a. Each of the arms is provided with a step 12 so that the outer parts 1 Ob and 1 b of the sides are thinner than the rest of the strip 6. The steps 12 enable the folded-over parts 6 to fit snugly together as shown in FIGURE 3. Said stepped portions are at the same height as the grooves 9 and may indeed be replaced by grooves similar to the grooves 9. The sides 1 Ob and 11 b may then be stepped as shown, or may taper towards their edges.The side portion 1 Ob is shorter than the side portion 11 b.

The strips are cut to length, nested together and formed into loops ready to receive the coil.

After the coil of conductor wires 3 has been placed in the bottom of the channels of the strips 5, 6, the side portions 1 or, 7b, 1 b and 8b are folded over in that order to enclose the wires in a sleeve 1 3.

The assembly is held closed conventionally, for example by heat sealing or by adhesive means.

The bundle of conductor wires itself can be used as a support against which a sealing tool can press the folded-over components. The tapering of the wall at the edge 7a makes a smooth joint.

External connections 1 4 lead from the winding out of the insulating sleeve as free wires which are attached to connectors.

The channel shaped strips 5, 6 may be produced by extrusion and can therefore, be of a length cut according to the size of the coil.

The double protection shown and described is sufficient to guarantee against such accidental defect and such insufficient insulation as would be possible with single insulation systems.

Nevertheless, it is obvious that, if necessary, the invention may be applied to triple or multiple insulation.

The double layer sleeve with a thickness of 0.4 mm in each layer can give an effective insulation resistance in excess of 8,000V, which meets the standard established in several countries, such as DVE 0860 and SEMKO 101-1966.

Claims

1. A coil for example for use as a demagnetising unit for a colour television receiver tube covered by at least two flexible sleeves of insulating material fitted snugly one inside the other, each of said sleeves being formed as a channel section strip, the parts of the sides of the channels adjacent the free edges of the strips being folded over to overlap one another.

2. A coil as claimed in Claim 1 in which one or more of the sides has a longitudinal groove defining a fold line.

3. A coil as claimed in either of the preceding claims in which one or more of the folded-over parts of the sides are thinner than the unfolded part of the side.

4. A coil as claimed in any preceding claim in which there is a folded-over part of one sleeve between the two folded-over parts of the other sleeve.

5. A coil as claimed in any preceding claim in which the folded-over side parts are sealed together.

6. A coil constructed and arranged substantially, as herein specifically described with reference to FIGURES 2 and 3 of the accompanying drawings.