More particularly, the present invention relates to resistance elements with an insulation sleeve for heating optical fibres in the process of joining said fibres together.

Applicant manufactures several different types of resistance elements. An element comprised of molybdenum silicide (MoSi2) is an example of one such type of element in this regard. When such elements are heated electrically to high temperatures, such as to temperatures in the range of 1750°C, the plasticity of the element increases therewith reducing the self-supporting capacity of the element.

Multiple-leg molybdenum silicide elements are normally installed by fastening the element in a surrounding insulating ceramic material with the aid of MoSi2 staples.

Insulation sleeves for joining optical fibres are available. These sleeves have a through- passing cylindrical passageway. Along the passageway there is provided a slot that extends radially in relation to the passageway through the sleeve and opens to the surroundings.

The task of hanging elements in such an insulation sleeve with the aid of staples is both troublesome and difficult to achieve.

The present invention solves this problem.

Thus, the present invention relates to a heating device that includes electric resistance elements, wherein said element is located in a cavity in an insulation sleeve, wherein said sleeve includes a through-passing cylindrical passageway ; along which there is provided a slot which extends radially in relation to the passageway and the cavity through said insulation sleeve and opens to the surroundings, and wherein the heating device is characterised in that the resistance element is curved such as to include a number of legs in said cavity; in that the legs are not secured in the insulation sleeve; in that at least one or

more of the lower legs rests, or rest, on the inner wall of the cavity; and in that the element conductors face downwards when the heating device is orientated in its operating position.

The invention will now be described in more detail partly with reference to an exemplifying embodiment of the invention illustrated in the accompanying drawings, in which - Figure 1 is a perspective view of a first embodiment of an element housed in an insulation sleeve; - Figure 2a is a vertical sectioned view of a passageway in the device shown in Figure 1 ; - Figure 2b is a vertical sectioned view transversely of said passageway in the device shown in Figure 1; - Figure 2c is a view of the device shown in Figure 1 from above; - Figure 3 is a perspective view of a second embodiment of an element housed in an insulation sleeve ; - Figure 4a is a vertical section view along a passageway in the device shown in Figure 3; - Figure 4b is a vertical section view taken transversely of said passageway in the device shown in Figure 3; - Figure 4c shows the device of Figure 3 from above; - Figure 5 is a perspective view of a third embodiment showing an element housed in an insulation sleeve; - Figure 6a is a vertical sectioned view taken along a passageway in the device shown in Figure 5; - Figure 6b is a vertical sectioned view taken transversely of said passageway in the device shown in Figure 5 ; and - Figure 6c illustrates the device of Figure 5 from-above.

Figures 1,3 and 5 thus show elements in which the legs are of mutually different designs.

The invention relates to a heating device that includes an electrical resistance element 1-3, which is located in a cavity 4 in an insulation sleeve 5. The sleeve includes a through- passing cylindrical passageway 6 along which there is disposed a slot 7 that extends radially through the insulation sleeve in relation to the passageway 6 and the cavity 4 and opens into the surroundings.

According to the invention, the resistance element 1 is curved, or bent, so as to include a number of legs in the cavity. The legs are not fastened in the insulation sleeve 5 but at least the lower leg, or the lower legs 8; 9-11; 12-13, rests/rest on the inner wall of the cavity 4.

Further the element conductors 14-15; 16-17 ; 18-19 face downwards when the heating device is orientated in its operating position. The operating position of said device is the position shown in Figures 1,3 and 5.

Because the conductors face downwards and because the legs of respective elements rest against the cavity walls, the legs of said elements will not bend down to any appreciable extent as a result of softening of the element under the effect of high temperatures.

In order to safeguard against downward bending of the legs, the number of legs included will preferably not exceed five and the length of each leg will preferably not exceed about 30 millimetres. A preferred number of legs is from three to five.

It is preferred that legs extend along the full length and width of the cavity, and that the cavity has a diameter of 10 to 30 millimetres and a length of from 10 to 50 millimetres.

According to one preferred embodiment, the element is comprised of molybdenum silicide (MoSiz), although the elements may be comprised of some other material.

The insulation sleeve 5 will preferably be comprised of a ceramic material or a high temperature fibre material.

In the manufacture of the heating device, the insulation sleeve 5 is produced in two halves, which are joined together with the element situated between said halves. The dividing plane, or partition plane, between the halves is flat and extends in the plane in which the two conductors are located.

According to one highly preferred embodiment, the legs of the element are designed so as to form through the heating device a free and straight passageway 4,6 whose diameter corresponds at least to the diameter of the passageway 6 in the insulation sleeve.

According to another preferred embodiment, the legs of said element are designed so that said slot 7 will form a free path to said free and straight passageway 4,6.

This arrangement enables a fibre optic cable 20 to be inserted into the slot 7 and brought to an inner position 22 in the heating device, as indicated by the arrow 21. The intention in this respect is to insert two fibre ends into the cavity 4 and hold said ends in contact with one another in said cavity. The ends of the fibres will fuse together when the element is heated, whereafter the thus joined fibre can be removed from the heating device.

The invention thus provides a very compact heating device in which said elements need not be secured to the inner walls of the insulation sleeve.

Although the invention has been described above with reference to a number of element embodiments, it will be obvious that the legs of said elements can be designed in some other way while achieving the same technical effect as that described above.

The present invention shall not therefore be considered limited to the aforedescribed embodiments thereof, since variations can be made within the scope of the accompanying Claims.