The invention relates to a suspension device for loop- shaped resistor elements in furnaces, particularly in furnac insulated with ceramic fibre materials. Such fibre materials render essential advantages, such as effective insulation, low heat capacity and lower total costs than e.g. bricks.

However, the ceramic fibre materials also have certain dis¬ advantages, such as high porosity, low strength and a tenden to crumble.

Various arrangements have previously been suggested on h to mount electrical resistor elements in furnaces insulated with ceramic fibre materials. Thus, US-A-4 272 638 discloses a device for the suspension of meander-shaped element loops horizontal ceramic rod elements being fixed to the furnace wall, which consists of fibre material blocks, by means of fasteners holding the rod element against the furnace wall.

Along its length, the rod element is provided with grooves o recesses in which the upper end portions of the meander loop are secured. However, the assembly and dismounting of the ro elements is rather complicated. The object of the invention is to achieve an improved su pension device permitting a high heating power per unit are of the furnace wall and enabling a simple installation and dismountning of the resistor elements, e.g. in connection wi repairs of the furnace lining. Another object is to permit the use of standard parts to a great extent.

These objects are achieved, according to the invention, in that the supporting means for the substantially horizonta rod element consist of consoles adapted to support the rod element at a distance from the furnace walls and that the resistor element loops form dense winding coils hanging free from the rod element substantially in a flattened helical co figuration. Hereby, one may easily and advantageously use helically wound or bent resistor elements, particularly of a metallic material, and preferably of Fe-Cr-Al alloys (e.g. of the type sold under the registered trade mark KANTHAL) , which are resistant in most atmospheres even at temperatures as high as up to about 1300°C. Owing to the fact that the resistor element loops are supported at the top by the rod

element and hang freely therefrom at a distance from the furnace wall, the entire resistor element can easily be dis¬ mounted by mere lifting of the rod element with the resisto element supported thereby, e.g. should the furnace walls nee to be repaired or partly exchanged. It is hereby a great advantage that the element loops are hanging freely at a distance from the furnace wall, since the resistance materia may become rather brittle after a long period of operation and, thus, does not stand much mechanical strain or load. Further features and advantages of the invention will appear from the detailed description below of some preferred embodiments, reference being made to the appended drawings.

Fig. 1 shows schematically in elevational view a suspens device according to a first embodiment with consoles arrange adjacent to the terminal portion of the resistor element;

Fig. 2 shows the device according to Fig. 1 from one end thereof;

Fig. 3 shows in a perspective view one of the consoles of the device according to Fig. 1; Figs. 4 and 5 show schematically in elevational views th joint between the terminal portion and the resistor element for flat elements bent edgeways and round resistor elements, respectively;

Fig. 6 shows a cross section of a console according to a second embodiment;

Fig. 7 shows the console according to Fig._ 6 in a perspe tive view;

Figs. 8 and 9 show two modifications of the console according to Figs. 6 and 7; Figs. 10 and 11 show in perspective views two additional embodiments of the rod element; and

Fig. 12 shows in cross section a third embodiment of a console.

In Fig. 1 a furnace wall 1 is schematically shown, said wall being assumed to consist essentially of an insulating, ceramic fibre material, wherein consoles 2 and 3 are mounted at the furnace wall 1 and support a substantially horisonta oriented rod element 4 in the form of a ceramic tube (compar Fig. 2) . On the rod element 4 a loop-shaped resistor element 5 is suspended. The resistor element consists of a metallic

material, namely a Fe-Cr-Al alloy of the type sold under the trade mark KANTHAL, having the shape of a flat band being wound into a helix and thereafter suspended in a flattened configuration from the rod element 4, so that each winding coil hangs freely from the rod element, preferably at a distance downwards corresponding to at least five times the diameter of the rod element, so that the resistor element lo together rather densely cover a relatively large surface are somewhat inside the furnace wall 1. In practice, the hanging loops can reach downwards approx. 200 to 1000 mm. However, when the operational temperature of the resistor elements is high, e.g. 1100-1300°C, the downward extension should not exceed approx..500 mm (due to the self-dilatation under the influence of gravity). As indicated by dashed lines, a ^' guidin rod 6 could possibly be arranged to guid the lower portions of winding coils. If so desired, the guiding rod could be provided with recesses or means to maintain the winding coil at a uniform distance from each other.

In accordance with the invention, the rod element 4 is supported at a distance from the furnace wall 1 by means of the consoles 2 and 3. In this case, the consoles are located adjacent to the terminal portions 1 , 7' of the element 5. In Fig. 2 it is shown how the terminal portion 7 extends inside a lead-through means in the form of a ceramic tube 30 throug the furnace wall 1 and into the furnace through the console For this purpose, the latter is constituted by two bent plat members 8,9, preferably also of a Fe-Cr-Al alloy, each such member having a leg 8a and 9a, respectively, abutting flat against the furnace wall 1, and a leg 8b and 9b, respectivel extending perpendicularly thereto. Each leg 8b, 9b is provide with a substantially semi-cylindrically bent portion 8c and 9 respectively, which are connected to each other, e.g. through welding, while enclosing the terminal portion 7', within the complementary portions -8c, 9c. Hereby, the entire console 2 will be supported by the terminal portion 7' and no separate fasteners between the respective console 2, 3 and the furnace wall 1 are therefore needed. Adjacent to the outer, free end portions of the legs 8b and 9b, respectively, a recess 10 is made at the upper edge. The recess 10 has an upward V-shape and is dimensioned to form a bearing surface for the tubular _.

rod element 4, so that the latter rests in a well defined position at a distance from the furnace wall 1. This distanc should correspond to at least one tube diameter (for the tub 4) , so that the loop portions of the element 5 located close to the furnace wall hang freely inside the furnace wall 1. W dismounting the resistor element 5, the consoles 2,3 are pul straight out from the inside of the furnace wall 1 (upon disconne ting the terminal portions at the outside of the furnace wal 1), so that both the terminal portions 7,7', the rod element as well as the resistor element 5 supported thereby will fol along as one unit. In this way, damages on the element loops are avoided and the element can be used again, e.g. after re construction or repair of the furnace lining.

In temperature regions, where the plate material gets de formed, e.g. above 1000 C, it may be suitable instead, en¬ tirely or partly, to make the consoles 2,3 of a ceramic material, e.g. Sillimanit or Mullit.

The embodiment according to Figs. 1-3 with consoles rest on the terminal portions of the resistor element is also ver advantageous in existing furnaces with linings of brick material. Then, only through holes need to be made, and specific fasteners are not needed.

In Figs. 1-3 the resistor element 5 is made from a flat-woun band. As possible alternatives hereto. Figs. 4 and 5 show a part of a likewise flat band 5' (Fig. 4) wound or bent edge¬ ways and a wire 5" of circular cross section (Fig. 5) , respe tively, wherein in both cases only the connection to the terminal portion 7 is shown.

Figs. 6 and 7 show an alternative embodiment of the con- soles supporting the rod element 4, here generally denoted by the numeral.11. The consoles 11 are hereby separately arranged in relation to the terminal portions 7, the lead- through tube 30 (compare Fig. 2) and each console 11 thus being located at some distance from each other in the longi- tudinal direction of the rod element. The console 11 consist of a ceramic body having a substantially circular base porti 12 and an outer portion 13 shaped as a hook, said portion 13 forming a hook opening 14 for supporting the rod element 4 (compare Fig. 1) . Even in this case, the hook opening 14 is located at a distance of at least one tube diameter (4.)--~f-r©_ι

the inside of the furnace wall 1, so that the loops of the resistor element 5 hang freely downwards from the rod elemen The hook body 11 is detachably coupled by means of bayonet coupling members 15, 16, to a holder 17, in the form of a bo or a pot, anchored to the furnace wall 1, the bottom of the holder being secured by a metallic pin 18 having a metal washer 19 and the edge portion thereof being formed as a circumferential flange 20. This flange 20 abuts and holds a ceramic disc 21 located at the inside of the furnace wall 1. The pin 18 extends through a hole in the bottom of the pot, and the disc 19,being screwed thereon as a nut or secured by welding, anchors the pot 17, the ceramic disc 21 and the hoo body 13, the other end of the pin 18 being fixed to the oute plate mantle 22 of the furnace wall 1 in a suitable manner. Between said outer plate mantle 22 and the inner ceramic dis 21 as well as inside the pot 17, a ceramic fibre material is disposed for heat insulation of the furnace wall. The hook body 11, the pot 17 and the ceramic disc 21 may consist of a suitable refractory material, e.g. Sillimanit or Mullit. The hook body 11 also serves as a lid to the pot 17 and contributes to the temperature reduction of the metallic anchoring means 18,19. The hook body can easily be detached from the holder pot 17 by rotation of e.g. 90 , so that the bayonet coupling members 15,16 ^l are freed. Hereby, it is especially suitable to turn the pot 17, whereas the hook body can maintain its position and support the rod element 4.

Instead of a hook body, the modification shown in Fig. 8 is provided with an eye body 11' with a through-hole 14' for the rod element. In this case, it is necessary that the eye body maintains its position when dismounting, e.g. by turning the pot 17 in the manner mentioned above. As appears from Fig. 9, the eye body 11' can also be divided into two halves 11'a and 11'b, whereby the mounting is further facilitated. When the eye body is divided, it can be provided with recesse for the terminal portions of the resistor elements, which terminal portions then can be combined with the anchoring pin 18 (Fig. 6) .

Figs. 10 and 11 show modified embodiments of the rod ele¬ ment 4 in the form of a reversed U-profile (Fig. 10) and a T-profile (Fig. 11) , respectively, of a ceramic ater a_ ^he

supporting means of the consoles (not shown) are of course adjusted to each profile, respectively, so that the rod ele¬ ment is fixed at a desired distance from the furnace wall.

The profile member 4* according to Fig. 10 is in the cent web portion provided with transversal slots 23 in the region of each element loop, which in this case consists of a flat band 5' bent edgeways (compare Fig. 4). Upon introducing the upper portions of the loops from underneath through the slots 23 (the width of which only slightly exceeds the band thick- ness) , the band loops are bent somewhat sideways, as shown at 24, so that the bent out band portions 24 rest on the top side of the profile member 4* adjacent each respective slot 2 In Fig. 11, the T-shaped profile member 4" is provided wi recesses 25 on the longitudinal edges of the horizontal profi leg for securing each resistor element loop 5". In this case the resistor element consists of a helically wound wire havin a circular cross section (compare Fig. 5) .

Fig. 12, finally, shows an example of a fixedly arranged console 26 consisting of a ceramic body, which is mounted already when manufacturing the furnace wall blocks by vacuum forming of a ceramic fibre material. For additional anchorage and positioning of each console 26, a tube 27 is inserted through a hole 28 in the inner end portion of the console and is embedded into the wall insulation as well as, if necessary, also connected to one or several additional con¬ soles 26. At its free end portion located inside the furnace wall 1, the console 26 has a hook opening 29 facing obliquely inwards/upwards towards the interior of the furnace, into which opening 29 a rod element 4 can be inserted and suspende together with a corresponding resistor element 5. In this case as well, the terminal portions 7 (compare Fig. 2) are le through separate openings (not shown) in the furnace wall.

The rod element as.well as the consoles and the other par can be modified in different ways within the scope of the in ventive idea. For example, the consoles can be adapted to be secured to the ceiling of the furnace. The essential idea is to provide for substantially horizontal suspension of the ro element 4 in the consoles, so that the resistor element loops hang freely at a distance from the furnace wall substantially in a flattened helical configuration.