EP0048645B1 - Electric heating furnace with low thermal inertia - Google Patents

Electric heating furnace with low thermal inertia Download PDF

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Publication number
EP0048645B1
EP0048645B1 EP19810401335 EP81401335A EP0048645B1 EP 0048645 B1 EP0048645 B1 EP 0048645B1 EP 19810401335 EP19810401335 EP 19810401335 EP 81401335 A EP81401335 A EP 81401335A EP 0048645 B1 EP0048645 B1 EP 0048645B1
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EP
European Patent Office
Prior art keywords
furnace
plates
plate
insulating wall
bricks
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP19810401335
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German (de)
French (fr)
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EP0048645A1 (en
Inventor
Jacques Bourdeau
Jean Brunet
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Porcher SA
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Porcher SA
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Publication of EP0048645A1 publication Critical patent/EP0048645A1/en
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/62—Heating elements specially adapted for furnaces
    • H05B3/66—Supports or mountings for heaters on or in the wall or roof
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D1/00—Casings; Linings; Walls; Roofs
    • F27D1/04—Casings; Linings; Walls; Roofs characterised by the form, e.g. shape of the bricks or blocks used
    • F27D1/06—Composite bricks or blocks, e.g. panels, modules
    • F27D1/063—Individual composite bricks or blocks
    • F27D1/066—Individual composite bricks or blocks made from hollow bricks filled up with another material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D11/00—Arrangement of elements for electric heating in or on furnaces
    • F27D11/02—Ohmic resistance heating

Definitions

  • the present invention relates to the production of an oven heated by electrical resistance having a low thermal inertia.
  • Reducing the thermal inertia of an oven is particularly advantageous when it is an intermittent heating oven, so as to achieve, on the one hand, an energy saving insofar as one can maintain a quality of insulation similar to that of ovens of known types and, on the other hand, an acceleration of the operating cycles.
  • the energy saving obviously comes from the fact that the calories stored by the insulating materials which the oven contains, the calories which are lost at least partially at each operating cycle, are all the more reduced as the thermal inertia of the oven is more low.
  • the heat-insulating wall of an electrically heated oven consists of a stack of refractory bricks, which have sufficient mechanical strength to support the supports of the electrical resistances of the heating.
  • refractory bricks have a high thermal inertia and store a large amount of heat at the time of the rise in temperature of the oven so that, for intermittent ovens where we carry out successive loading and unloading of parts to be cooked , there is a fairly high heat loss which results in an unfavorable thermal efficiency; in addition, the duration of the cooking cycle is greater the greater the thermal inertia of the oven, so that ovens of this type unfortunately have a reduced operating rate.
  • Refractory heat-insulating materials which, on the one hand, have low thermal inertia and, on the other hand, constitute good thermal insulators.
  • these materials made from refractory fibers, always have a low mechanical resistance, so that, if they are used in place of refractory bricks for a conventional production of the heat-insulating walls of an oven, it is no longer possible. to hang on the walls the electric heating resistances of the oven, especially in the case where the temperatures reached in the oven are high, for example of the order of 1200 ° C, as for ceramic kilns.
  • the object of the present invention is to describe an electrically heated oven, the heat-insulating wall of which is produced by means of a material with low thermal inertia and good insulation characteristics, the invention having provided special means allowing the support of electrical heating resistances despite the low mechanical resistance of the insulating materials used.
  • the present invention therefore has for its object an oven heated by electrical resistances comprising a heat-insulating wall held by a frame, supports of electrical resistances being arranged on the face of said wall which is turned towards the interior of the oven, characterized by the fact that the heat-insulating wall consists of an assembly of modular elements made of a thermally insulating material with low mechanical resistance and low thermal inertia, the resistance supports being arranged at the level of the horizontal joint planes of the assembled modular elements and consisting of rigid refractory plates assembled side by side horizontally, each plate being supported by at least one rigid support member disposed inside a modular element of the wall, said member resting on the plate, which is located at right him at a lower level, the pads, which are at the lowest level being supported by an o carrier, which rests on the frame of the oven.
  • the modular elements are hollow bricks made of a felt of refractory fibers; the hollow bricks are filled, preferably after their placement, with a flock of loose refractory fibers; the heat-insulating wall is made up of a single thickness of modular elements, each modular element being fixed to the frame of the oven by at least one clip disposed on the face of the modular element, which faces the outside of the oven; the fasteners of the modular elements are arranged at the horizontal joint planes of said elements; in the middle zone of each element, each fastener acting simultaneously on two superimposed modular elements.
  • the plates constituting the resistance supports have a substantially rectangular shape and have two flanges substantially parallel to a plate edge, these two flanges being arranged inside the oven and delimiting between them a channel, where an electrical resistance is placed. heating, part of the wafer being arranged inside the heat-insulating wall; the plates constituting a resistance support in a horizontal plane are arranged with contiguous edges and constitute a continuous channel on the internal face of the heat-insulating wall, the seals two adjacent plates being offset from the joints of two adjacent modular elements of the same level of the wall; the joint of two adjacent plates of a resistance support is substantially perpendicular to the heat-insulating wall of the furnace and disposed in the central zone of a modular element, the length of the plates being equal to the length of the modular elements of the wall; each plate has a third flange, which is arranged in the vicinity of the middle of the thickness of the heat-insulating wall, parallel to the other two flanges and along an edge of the plate; the third edge of the plates cooperates with
  • the rigid support members are tubes of refractory material, each tube being positioned relative to each of the plates, between which it forms a spacer, by a centering surface; each plate has in relief, in its part located inside the heat-insulating wall and on either side of its horizontally arranged mean plane, at least one boss whose horizontal section corresponds, at least in part, to the section inner right of the tubes constituting the load-bearing members; the tubes constituting the bearing members have a circular section and each plate has, on either side of its horizontally arranged mean plane, a boss having a horizontal semicircular section, formed at the edge of the plate to constitute with the boss corresponding to the adjacent plate a circular boss having substantially the diameter of the inner section of the tubes; the face of each hollow brick, which is arranged towards the inside of the oven, is inserted between the tube placed inside said brick and that of the edges delimiting the channel which is the most towards the outside of the oven.
  • the structure defined above made it possible to use materials with low thermal inertia despite their low mechanical resistance and nevertheless to ensure satisfactory maintenance of the electrical resistance supports. It has also been found that the structure defined above makes it possible to considerably improve the thermal efficiency of electrically heated ovens and more particularly of intermittent ovens.
  • the invention finds, in particular, its application in furnaces for firing ceramic pieces, where it has been noted, thanks to the invention, an energy saving of 30% for an oven performing a firing at about 1200 ° C with an available interior volume of 8 m 3 and cooking a load of 1200 kg.
  • the oven according to the invention comprises an external frame designated by 1 as a whole; the frame 1 consists of an assembly of metal beams 2 between which are placed sheets 3 constituting the external covering of the furnace.
  • the chassis 1 has the general shape of a very long rectangular parallelepiped; the oven constitutes a tunnel comprising a bottom 4 and an entry door 5 capable of being opened for charging and discharging the load whose oven is intended for cooking.
  • the oven which will be described by way of example, is intended for firing a ceramic load of 1200 kg at 1230 ° C. Its useful interior volume is 8 m 3.
  • the theoretical heating power is 340 Kva.
  • the load is introduced into the tunnel, which constitutes the oven, on three wagons, which run on rails 6 arranged on the ground, on either side of the axis of the oven and parallel to this axis.
  • the wagons, designated by 7 as a whole, are clearly visible in Figures 5 and 6 of the drawing; Figure 6 shows only, due to the removal of the middle part of the section, the ends of the first and third wagons introduced into the oven.
  • the wagons 7 have a refractory plate 8, which supports an insulating layer 9 on which are placed, in refractory angles 10, electrical resistances 11.
  • the plate 8 supports vertical tubes 12, which pass through the heat-insulating layer 9 and support tables 13 of which are arranged the load to be cooked.
  • the tubes 12 and the tables 13 are made of refractory material.
  • the insulating layer 9 is produced by means of an assembly of hollow bricks made of a felt of refractory fibers; in this example, we used bricks with the trade name "FIBERCHROM” produced by the American company "Johns-Manville”. These bricks have a substantially parallelepiped shape and have on one of their small lateral faces a rounded relief 14a, which cooperates for assembly with a rounded hollow 14b of corresponding shape.
  • the insulating layer 9 is produced by assembling a single thickness of these bricks on the plate 8, the two longitudinal edges of the layer 9 having rounded reliefs 14a, the front transverse edge of the layer 9 also having a rounded relief 14a, while the rear transverse border represents a rounded hollow 14b.
  • hollow bricks 15 identical to the bricks constituting the layer 9, oriented so that facing rounded reliefs 14a , the hollow bricks 15 have a rounded hollow 14b and that opposite a rounded hollow 14b, the hollow bricks 15 have a rounded relief 14a.
  • a clearance 16 has been provided for ensuring the placement of the wagons 7 in the furnace, the thermal sealing of the oven vis-à-vis the outside being produced by metal plates 17 arranged vertically along the longitudinal edges of the wagons, said plates 17 plunging into angles 18 filled with sand 19 and arranged at the base of the longitudinal walls of the oven .
  • the bricks 15, which are arranged at the base of the side walls of the oven are supported either by supports 20 secured to the chassis or by a support 21 secured to the door 5, which is itself carried by the chassis.
  • the bricks 15 are held on the frame or on the door structure by fasteners 22 each consisting of a bolt and a retaining plate, the retaining plate being placed in the hollow brick 15; it should be noted that the fasteners 22 are thermally protected by the bricks 15 and therefore do not have to suffer from the rise in temperature inside the oven.
  • the bricks 15 are filled, at the time of their installation, with a flock of loose refractory fibers in order to improve the insulation.
  • the heat-insulating wall of the oven is thus produced, for its lower horizontal layer, by the insulating layer 9 and the bricks 15.
  • the upper horizontal part of the heat-insulating wall it is produced in the same way by an assembly of bricks hollow 23, which are supported by fasteners 24 by the beams 2, which form the roof of the oven.
  • the fasteners 24 are made up of bolts and fastening plates and are protected from the rise in temperature by the insulating layer that constitutes the bricks 23 themselves.
  • the bricks 23 have on their edges recesses 23a, 23b allowing their mechanical assembly to constitute the vault of the oven.
  • an air exhaust orifice 25 is provided, which is connected to a suction fan, to ensure rapid cooling of the oven; during the cooling phase, aeration hatches 26 open at the bottom of the oven are opened so as to allow cold air to enter and the oven to cool.
  • the side wall of the oven carries electrical resistances 27 intended to ensure the heating of the oven.
  • the resistors 11 previously described have an action complementary to that of the resistors 27.
  • the problem solved by the invention is the production of a lateral heat-insulating wall by means of hollow bricks of the same type, as those which constitute the layer insulating 9, simultaneously ensuring the support of resistors 27; the difficulty comes from the fact that the hollow bricks "FIBERCHROM", if they have a low thermal inertia, also have a low mechanical resistance so that they are not capable of carrying the weight of the supports of the resistors 27.
  • the hollow bricks 15 are traversed by tubes 28 of resistant refractory material, these tubes 28 resting by their base on the supports 20 and coming, by their high end, at the level of the first resistance support.
  • the tube 28 passes through a hollow brick 29, the front part of which is hollowed out to allow the passage of the tube 28.
  • the part of the tube 28, which projects above the corresponding brick 15, is surrounded by a sleeve 30 ensuring its thermal protection, said sleeve 30 stopping at the same level as the tube 28.
  • the sleeve 30 can be obtained by cutting a hollow brick identical to brick 29.
  • the plate 31 is arranged, which constitutes the resistance support 27 having the lowest level on the side wall of the oven.
  • a resistance support is arranged horizontally on the side wall of the furnace and is constituted by the assembly of plates 31 arranged side by side.
  • the plates 31 are made of a refractory material having good mechanical strength and have a shape which, seen in plan, is substantially rectangular (FIGS. 7 and 8).
  • the flanges 32 and 33 are formed along the two longitudinal edges of each plate 31 along the two longitudinal edges of each plate 31 .
  • a rim 34 which projects on either side of the mean plane of the wafer.
  • the flanges 32 and 34 define between them a channel 35 inside which the heating resistor 27 can be positioned.
  • the plate 31 comprises, on its transverse edge and on either side of its mean plane, a boss 36 having, seen in plan, the shape of a semicircle.
  • the channel 35 is continuous and the bosses 36 of two adjacent plates constitute circular bosses.
  • the tube 28 is disposed below a boss 36 and supports two adjacent plates 31, in the plate zone which is located beyond the rim 34 in the direction of the boss 36.
  • the tube 28 is located in the middle zone of the bricks 29 and 30 so that the joints of these bricks are offset from the joints of the plates 31; the length of the bricks 29 and 30 is the same as the length of the plates 31.
  • each brick is placed in line with the row of bricks, which is lower than it; it has on its underside a cutout 38, which allows the passage of the rim 33 of the underlying plate 31; it has, on its upper face, a cutout 39 which allows the embedding of the plate 31 disposed above the brick 37, which plate 31 rests by means of a tube 40 on the underlying plate 31 ( Figure 9 ).
  • the tube 40 is centered on a boss 36 of the underlying plate 31 and on a boss 36 of the plate 31 which it supports.
  • the tube 40 is disposed inside the hollow brick 37 and its height is equal to the distance from two superimposed plates 31.
  • the depth of the cutout 39 of the brick 37 is such that the plate 31 supported by the brick 37 is horizontal, the "plate 31 coming from its lower face at the level of the upper edge of that of the faces of the brick 37, which is placed towards the inside of the oven. It can therefore be seen that all of the superimposed plates 31 are carried, by means of the tubes 40 which act as spacers, by the tube 28 and, consequently, by the support 20 of the chassis.
  • the resistance supports do not have to be carried by the hollow bricks 37, which constitute the thermal insulation, so that it is no longer important that these bricks have their own mechanical resistance.
  • the bricks 37 are also carried by the plates 31 arranged below them and there is therefore no risk of collapse of the stack of bricks 37 produced to constitute the side wall of the furnace.
  • Each brick 37 is retained against the chassis by fasteners 41 consisting of an attachment plate and a bolt, said attachments being protected from the rise in temperature by the bricks 37 themselves.
  • the bolt of the fasteners 41 is arranged at the level of the connection plane of the external faces of the bricks 37 and provision is made, for the passage of the bolts of the fasteners 41, a recess 42 in the corresponding wall of the brick 37.
  • the fasteners 41 are arranged in the part of the bricks 37 which is located midway between the rounded reliefs 43a and the rounded recesses 43b, which allow the assembly of two bricks 37 arranged side by side in the same horizontal row; the conformations 43a, 43b are, of course, identical to the conformations 14a, 14b previously cited for the hollow bricks constituting the insulating layer 9.
  • the attachment plate of an attachment 41 acts simultaneously on two superimposed bricks 37. Like the bricks of the insulating layer 9 and the bricks 15, the bricks 29, 30 and 37 are filled at the time of their installation with a flock of loose refractory fibers to improve the insulation.
  • tubes 28 and possibly tubes 40 are also stuffed with refractory fibers in bulk.
  • the faces of the bricks 37 which are located towards the inside of the furnace, are in fact inserted between the tubes 40 and the edges 34 of the plates 31. As a result, this is already ensured in the transverse direction of the plates 31 and of the heat-insulating wall formed by the set of bricks 37.
  • the joints of two adjacent plates 31 of the same level are located approximately in the middle of the bricks 37, which support them and which overcome them.
  • the cutouts 38 and 39 of the lower and upper planes of the bricks 37 make it possible, by cooperation with the rim 33 of the plates 31, to ensure the transverse maintenance of the plates with respect to the two rows of bricks, between which the plates are placed. square.
  • the embodiment which has just been described, allows the weight of the resistance supports to be carried directly by the chassis thanks to the spacers 28 and 40 and also to support each brick of the heat-insulating wall so that can use bricks with very low mechanical strength.
  • This technique therefore makes it possible to use bricks of low weight with low thermal inertia for the production of heat-insulating walls, which constitutes a great advantage in terms of energy saving, this advantage being all the more significant. that it is an intermittent oven.
  • the time required for the cooling of the oven by ventilation is lower, since the thermal inertia of the oven is lower, and it is therefore possible to reduce the time of the cooking cycles and increase the production rates.

Description

La présente invention a trait à la réalisation d'un four chauffé par résistance électrique ayant une faible inertie thermique.The present invention relates to the production of an oven heated by electrical resistance having a low thermal inertia.

La réduction de l'inertie thermique d'un four est particulièrement intéressante lorsqu'il s'agit d'un four à chauffage intermittent, de façon à réaliser, d'une part, une économie d'énergie dans la mesure où l'on peut maintenir une qualité d'isolation analogue à celle des fours de types connus et, d'autre part, une accélération des cycles de fonctionnement. L'économie d'énergie provient évidemment du fait que les calories emmagasinées par ies matériaux isolants que comporte le four calories qui sont perdues au moins partiellement à chaque cycle de fonctionnement, sont d'autant plus réduites que l'inertie thermique du four est plus faible.Reducing the thermal inertia of an oven is particularly advantageous when it is an intermittent heating oven, so as to achieve, on the one hand, an energy saving insofar as one can maintain a quality of insulation similar to that of ovens of known types and, on the other hand, an acceleration of the operating cycles. The energy saving obviously comes from the fact that the calories stored by the insulating materials which the oven contains, the calories which are lost at least partially at each operating cycle, are all the more reduced as the thermal inertia of the oven is more low.

Dans l'état de la technique, la paroi calorifuge d'un four à chauffage électrique est constituée d'un empilement de briques réfractaires, qui ont une résistance mécanique suffisante pour supporter les supports des résistances électriques du chauffage. Malheureusement, de telles briques réfractaires ont une inertie thermique importante et emmagasinent une grande quantité de chaleur au moment de la montée en température du four de sorte que, pour les fours intermittents où l'on effectue des chargements et des déchargements successifs de pièces à cuire, il se produit une assez forte perte calorifique ce qui entraîne un rendement thermique défavorable; de plus, la durée de cycle de cuisson est d'autant plus forte que l'inertie thermique du four est plus grande, de sorte que les fours de ce type ont malheureusement une cadence de fonctionnement réduite.In the state of the art, the heat-insulating wall of an electrically heated oven consists of a stack of refractory bricks, which have sufficient mechanical strength to support the supports of the electrical resistances of the heating. Unfortunately, such refractory bricks have a high thermal inertia and store a large amount of heat at the time of the rise in temperature of the oven so that, for intermittent ovens where we carry out successive loading and unloading of parts to be cooked , there is a fairly high heat loss which results in an unfavorable thermal efficiency; in addition, the duration of the cooking cycle is greater the greater the thermal inertia of the oven, so that ovens of this type unfortunately have a reduced operating rate.

On connaît des matériaux calorifuges réfractaires, qui, d'une part, ont une faible inertie thermique et, d'autre part, constituent de bons isolants thermiques. Malheureusement, ces matériaux constitués à base de fibres réfractaires, ont toujours une faible résistance mécanique, de sorte que, si on les utilise à la place des briques réfractaires pour une réalisation classique des parois calorifuges d'un four, il n'est plus possible d'accrocher aux parois les résistances électriques de chauffage du four, surtout dans le cas où les températures atteintes dans le four sont élevées, par exemple de l'ordre de 1200°C, comme pour les fours de cuisson de céramique.Refractory heat-insulating materials are known which, on the one hand, have low thermal inertia and, on the other hand, constitute good thermal insulators. Unfortunately, these materials, made from refractory fibers, always have a low mechanical resistance, so that, if they are used in place of refractory bricks for a conventional production of the heat-insulating walls of an oven, it is no longer possible. to hang on the walls the electric heating resistances of the oven, especially in the case where the temperatures reached in the oven are high, for example of the order of 1200 ° C, as for ceramic kilns.

La présente invention a pour but de décrire un four à chauffage électrique, dont la paroi calorifuge est réalisée au moyen d'un matériau à faible inertie thermique et à bonnes caractéristiques d'isolation, l'invention ayant prévu des moyens particuliers permettant le soutien des résistances électriques de chauffage malgré la faible résistance mécanique des matériaux isolants mise en oeuvre. Dans une réalisation préférentielle mais non limitative, on prévoit selon l'invention de réaliser la paroi calorifuge du four, au moyen de briques creuses constituées d'un feutre de fibres réfractaires, lesdites briques étant remplies d'une bourre de fibres réfractaires en vrac; des briques creuses de ce type sont disponibles sur le marché sous le nom »FIBERCHROM« et sont fabriquées par la Société américaine dite »Johns-Manville«: ce matériau résiste à des températures de l'ordre de 1200 à 1300°C et permet de réaliser des parois calorifuges ayant, au mètre carré, des poids de l'ordre de 20 kg environ.The object of the present invention is to describe an electrically heated oven, the heat-insulating wall of which is produced by means of a material with low thermal inertia and good insulation characteristics, the invention having provided special means allowing the support of electrical heating resistances despite the low mechanical resistance of the insulating materials used. In a preferred but non-limiting embodiment, provision is made according to the invention to produce the heat-insulating wall of the oven, by means of hollow bricks made of a felt of refractory fibers, said bricks being filled with a flock of loose refractory fibers; hollow bricks of this type are available on the market under the name "FIBERCHROM" and are manufactured by the American company known as "Johns-Manville": this material withstands temperatures of the order of 1200 to 1300 ° C and allows produce heat-insulating walls having, per square meter, weights of around 20 kg.

La présente invention a, en conséquence, pour objet un four chauffé par résistances électriques comportant une paroi calorifuge maintenue par un châssis, des supports de résistances électriques étant disposés sur la face de ladite paroi qui est tournée vers l'intérieur du four, caractérisée par le fait que la paroi calorifuge est constituée d'un assemblage d'éléments modulaires réalisés en un matériau thermiquement isolant à faible résistance mécanique et à faible inertie thermique, les supports de résistance étant disposés au niveau des plans de joints horizontaux des éléments modulaires assemblés et étant constitués de plaquettes réfractaires rigides assemblées côte à côte horizontalement, chaque plaquette étant soutenue par au moins un organe porteur rigide disposé à l'intérieur d'un élément modulaire de la paroi, ledit organe reposant sur la plaquette, qui se trouve au droit de lui à un niveau inférieur, les plaquettes, qui se trouvent au niveau le plus bas étant soutenues par un organe porteur, qui repose sur le châssis du four.The present invention therefore has for its object an oven heated by electrical resistances comprising a heat-insulating wall held by a frame, supports of electrical resistances being arranged on the face of said wall which is turned towards the interior of the oven, characterized by the fact that the heat-insulating wall consists of an assembly of modular elements made of a thermally insulating material with low mechanical resistance and low thermal inertia, the resistance supports being arranged at the level of the horizontal joint planes of the assembled modular elements and consisting of rigid refractory plates assembled side by side horizontally, each plate being supported by at least one rigid support member disposed inside a modular element of the wall, said member resting on the plate, which is located at right him at a lower level, the pads, which are at the lowest level being supported by an o carrier, which rests on the frame of the oven.

Dans un mode préféré de réalisation, les éléments modulaires sont des briques creuses constituées d'un feutre de fibres réfractaires; les briques creuses sont remplies, de préférence après leur mise en place, d'une bourre de fibres réfractaires en vrac; la paroi calorifuge est constituée d'une seule épaisseur d'éléments modulaires, chaque élément modulaire étant fixé sur châssis du four par au moins une attache disposée sur la face de l'élément modulaire, qui est tournée vers l'extérieur du four; les attaches des éléments modulaires sont disposées au niveau des plans de joint horizontaux desdits éléments; dans la zone médiane de chaque élément, chaque attache agissant simultanément sur deux éléments modulaires superposés.In a preferred embodiment, the modular elements are hollow bricks made of a felt of refractory fibers; the hollow bricks are filled, preferably after their placement, with a flock of loose refractory fibers; the heat-insulating wall is made up of a single thickness of modular elements, each modular element being fixed to the frame of the oven by at least one clip disposed on the face of the modular element, which faces the outside of the oven; the fasteners of the modular elements are arranged at the horizontal joint planes of said elements; in the middle zone of each element, each fastener acting simultaneously on two superimposed modular elements.

Avantageusement, les plaquettes constituant les supports de résistance ont une forme sensiblement rectangulaire et comportent deux rebords sensiblement parallèles à une bordure de plaquette, ces deux rebords étant disposés à l'intérieur du four et délimitant entre eux une rigole, où est placée une résistance électrique de chauffage, une partie de la plaquette étant disposée à l'intérieur de la paroi calorifuge; les plaquettes constituant un support de résistance dans un plan horizontal sont disposées à bords jointifs et constituent une rigole continue sur la face intérieure de la paroi calorifuge, les joints de deux plaquettes adjacentes étant décalés par rapport aux joints de deux éléments modulaires adjacents d'un même niveau de la paroi; le joint de deux plaquettes adjacentes d'un support de résistance est sensiblement perpendiculaire à la paroi calorifuge du four et disposé dans la zone centrale d'un élément modulaire, la longueur des plaquettes étant égale à la longueur des éléments modulaires de la paroi; chaque plaquette comporte un troisième rebord, qui est disposé au voisinage du milieu de l'épaisseur de la paroi calorifuge, parallèlement aux deux autres rebords et le long d'une bordure de la plaquette; le troisième rebord des plaquettes coopère avec une découpe appropriée des plans de joint horizontaux des éléments modulaires pour assurer un maintien des plaquettes perpendiculairement à la paroi calorifuge.Advantageously, the plates constituting the resistance supports have a substantially rectangular shape and have two flanges substantially parallel to a plate edge, these two flanges being arranged inside the oven and delimiting between them a channel, where an electrical resistance is placed. heating, part of the wafer being arranged inside the heat-insulating wall; the plates constituting a resistance support in a horizontal plane are arranged with contiguous edges and constitute a continuous channel on the internal face of the heat-insulating wall, the seals two adjacent plates being offset from the joints of two adjacent modular elements of the same level of the wall; the joint of two adjacent plates of a resistance support is substantially perpendicular to the heat-insulating wall of the furnace and disposed in the central zone of a modular element, the length of the plates being equal to the length of the modular elements of the wall; each plate has a third flange, which is arranged in the vicinity of the middle of the thickness of the heat-insulating wall, parallel to the other two flanges and along an edge of the plate; the third edge of the plates cooperates with an appropriate cutting of the horizontal joint planes of the modular elements to ensure that the plates are held perpendicular to the heat-insulating wall.

De préférence, les organes porteurs rigides sont des tubes en matériau réfractaire, chaque tube étant positionné par rapport à chacune des plaquettes, entre lesquelles il forme une entretoise, par une portée de centrage; chaque plaquette comporte en relief, dans sa partie située à l'intérieur de la paroi calorifuge et de part et d'autre de son plan moyen disposé horizontalement, au moins un bossage dont la section horizontale correspond, au moins en partie, à la section droite intérieure des tubes constituant les organes porteurs; les tubes constituant les organes porteurs ont une section circulaire et chaque plaquette comporte, de part et d'autre de son plan moyen disposé horizontalement, un bossage ayant une section horizontale en demi-cercle, ménagé en bordure de la plaquette pour constituer avec le bossage correspondant de la plaquette adjacente un bossage circulaire ayant sensiblement le diamètre de la section intérieure des tubes; la face de chaque brique creuse, qui est disposée vers l'intérieur du four, est insérée entre le tube disposé à l'intérieur de ladite brique et celui des rebords délimitant la rigole qui est le plus vers l'extérieur du four.Preferably, the rigid support members are tubes of refractory material, each tube being positioned relative to each of the plates, between which it forms a spacer, by a centering surface; each plate has in relief, in its part located inside the heat-insulating wall and on either side of its horizontally arranged mean plane, at least one boss whose horizontal section corresponds, at least in part, to the section inner right of the tubes constituting the load-bearing members; the tubes constituting the bearing members have a circular section and each plate has, on either side of its horizontally arranged mean plane, a boss having a horizontal semicircular section, formed at the edge of the plate to constitute with the boss corresponding to the adjacent plate a circular boss having substantially the diameter of the inner section of the tubes; the face of each hollow brick, which is arranged towards the inside of the oven, is inserted between the tube placed inside said brick and that of the edges delimiting the channel which is the most towards the outside of the oven.

On a constaté que la structure ci-dessus définie permettait d'utiliser des matériaux à faible inertie thermique malgré leur faible résistance mécanique et d'assurer néanmoins un maintien satisfaisant des supports de résistance électrique. On a constaté, en outre, que la structure ci-dessus définie permettait d'améliorer considérablement le rendement thermique des fours à chauffage électrique et plus particulièrement des fours intermittents. L'invention trouve, en particulier, son application dans les fours de cuisson de pièces céramiques, où l'on a pu noter, grâce à l'invention, une économie d'énergie de 30% pour un four réalisant une cuisson à environ 1200°C ayant un volume intérieur disponible de 8 m3 et réalisant la cuisson d'une charge de 1200 kg.It was found that the structure defined above made it possible to use materials with low thermal inertia despite their low mechanical resistance and nevertheless to ensure satisfactory maintenance of the electrical resistance supports. It has also been found that the structure defined above makes it possible to considerably improve the thermal efficiency of electrically heated ovens and more particularly of intermittent ovens. The invention finds, in particular, its application in furnaces for firing ceramic pieces, where it has been noted, thanks to the invention, an energy saving of 30% for an oven performing a firing at about 1200 ° C with an available interior volume of 8 m 3 and cooking a load of 1200 kg.

Pour mieux faire comprendre l'objet de 1 invention, on va en décrire maintenant, à titre d'exemple purement illustratif et non limitatif, un mode de réalisation représenté sur le dessin annexé.To better understand the object of the invention, we will now describe, by way of purely illustrative and non-limiting example, an embodiment shown in the accompanying drawing.

Sur ce dessin:

  • la figure 1 représente, en perspective, une vue extérieure d'un four intermittant à chauffage électrique selon l'invention;
  • la figure 2 représente, en élévation, le four de la figure 1;
  • la figure 3 représente une vue en plan du four de la figure 2, selon III-I de la figure 2;
  • la figure 4 représente une vue en bout du four des figures 1 à 3, selon IV-IV de la figure 3;
  • la figure 5 représente une coupe transversale selon V-V de la figure 2, ladite coupe ayant été supprimée dans sa zone médiane pour une question d'encombrement;
  • la figure 6 représente une coupe longitudinale selon VI-VI de la figure 3, les parties médianes de la coupe ayant été supprimées pour une question d'encombrement;
  • la figure 7 représente, en perspective, une plaquette réfractaire constitutive d'un support de résistance;
  • la figure 8 représente, vu en plan, l'assemblage de plusieurs plaquettes réfractaires successives constituant un support de résistance et le positionnement de ces plaquettes par rapport aux briques creuses constituant la paroi calorifuge du four;
  • la figure 9 représente, en perspective, une brique creuse constitutive de la paroi calorifuge du four comportant les antailles, qui assurent le maintien des plaquettes par rapport aux briques.
On this drawing:
  • FIG. 1 represents, in perspective, an external view of an intermittent oven with electric heating according to the invention;
  • Figure 2 shows, in elevation, the oven of Figure 1;
  • 3 shows a plan view of the oven of Figure 2, along III-I of Figure 2;
  • 4 shows an end view of the oven of Figures 1 to 3, according to IV-IV of Figure 3;
  • 5 shows a cross section along VV of Figure 2, said section having been removed in its middle area for a question of space;
  • 6 shows a longitudinal section along VI-VI of Figure 3, the middle parts of the section having been removed for a question of space;
  • FIG. 7 represents, in perspective, a refractory plate constituting a resistance support;
  • FIG. 8 represents, seen in plan, the assembly of several successive refractory plates constituting a resistance support and the positioning of these plates relative to the hollow bricks constituting the heat-insulating wall of the furnace;
  • FIG. 9 represents, in perspective, a hollow brick constituting the heat-insulating wall of the oven comprising the tabs, which ensure the maintenance of the plates relative to the bricks.

En se référant au dessin, on voit que le four selon l'invention comporte un châssis extérieur désigné par 1 dans son ensemble; le châssis 1 est constitué d'un assemblage de poutrelles métalliques 2 entre lesquelles sont disposées des tôles 3 constituant le recouvrement externe du four. Le châssis 1 a la forme générale d'un parallélépipède rectangle de grande longueur; le four constitue un tunnel comportant un fond 4 et une porte d'entrée 5 susceptible d'être ouverte pour l'enfournement et le défournement de la charge dont le four est destiné à assurer la cuisson. Le four, qui va être décrit à titre d'exemple, est destiné à la cuisson d'une charge de céramique de 1200 kg à 1230°C. Son volume intérieur utile est de 8 m3. La puissance théorique de chauffage est de 340 Kva.Referring to the drawing, it can be seen that the oven according to the invention comprises an external frame designated by 1 as a whole; the frame 1 consists of an assembly of metal beams 2 between which are placed sheets 3 constituting the external covering of the furnace. The chassis 1 has the general shape of a very long rectangular parallelepiped; the oven constitutes a tunnel comprising a bottom 4 and an entry door 5 capable of being opened for charging and discharging the load whose oven is intended for cooking. The oven, which will be described by way of example, is intended for firing a ceramic load of 1200 kg at 1230 ° C. Its useful interior volume is 8 m 3. The theoretical heating power is 340 Kva.

La charge est introduite dans le tunnel, que constitue le four, sur trois wagonnets, qui roulent sur des rails 6 disposés au sol, de part et d'autre de l'axe du four et parallèlement à cet axe. Les wagonnets, désignés par 7 dans leur ensemble, sont bien visibles sur les figures 5 et 6 du dessin; la figure 6 représente seulement, en raison de la suppression de la partie médiane de la coupe, les extrémités des premier et troisième wagonnets introduits dans le four. Les wagonnets 7 comportent un plateau réfractaire 8, qui supporte une couche isolante 9 sur laquelle sont placées, dans des cornières réfractaires 10, des résistances électriques 11. Le plateau 8 supporte des tubes verticaux 12, qui traversent la couche calorifuge 9 et supportent des tables 13 sur lesquelles est disposée la charge à cuire. Les tubes 12 et les tables 13 sont réalisés en matériau réfractaire. La couche d'isolation 9 est réalisée au moyen d'un assemblage de briques creuses constituées d'un feutre de fibres réfractaires; on a utilisé, dans cet exemple, des briques répondant à la dénomination commerciale »FIBERCHROM« produites par la Société américaine »Johns-Manville«. Ces briques ont une forme sensiblement parallélépipédique et comportent sur l'une de leurs petites faces latérales un relief arrondi 14a, qui coopère pour l'assemblage avec un creux arrondi 14b de forme correspondante. La couche isolante 9 est réalisée par l'assemblage d'une seule épaisseur de ces briques sur le plateau 8, les deux bordures longitudinales de la couche 9 présentant des reliefs arrondis 14a, la bordure transversale avant de la couche 9 présentant également un relief arrondi 14a, alors que la bordure transversale arrière représente un creux arrondi 14b.The load is introduced into the tunnel, which constitutes the oven, on three wagons, which run on rails 6 arranged on the ground, on either side of the axis of the oven and parallel to this axis. The wagons, designated by 7 as a whole, are clearly visible in Figures 5 and 6 of the drawing; Figure 6 shows only, due to the removal of the middle part of the section, the ends of the first and third wagons introduced into the oven. The wagons 7 have a refractory plate 8, which supports an insulating layer 9 on which are placed, in refractory angles 10, electrical resistances 11. The plate 8 supports vertical tubes 12, which pass through the heat-insulating layer 9 and support tables 13 of which are arranged the load to be cooked. The tubes 12 and the tables 13 are made of refractory material. The insulating layer 9 is produced by means of an assembly of hollow bricks made of a felt of refractory fibers; in this example, we used bricks with the trade name "FIBERCHROM" produced by the American company "Johns-Manville". These bricks have a substantially parallelepiped shape and have on one of their small lateral faces a rounded relief 14a, which cooperates for assembly with a rounded hollow 14b of corresponding shape. The insulating layer 9 is produced by assembling a single thickness of these bricks on the plate 8, the two longitudinal edges of the layer 9 having rounded reliefs 14a, the front transverse edge of the layer 9 also having a rounded relief 14a, while the rear transverse border represents a rounded hollow 14b.

Au niveau de la couche isolante 9, on a disposé dans la paroi, qui délimite le four, et dans la porte 5, des briques creuses 15 identiques aux briques constitutives de la couche 9, orientées de façon qu'en regard des reliefs arrondis 14a, les briques creuses 15 présentent un creux arrondi 14b et qu'en regard d'un creux arrondi 14b, les briques creuses 15 présentent un relief arrondi 14a. Entre les briques 15, qui sont à la base des parois du four, et les briques constitutives de la couche isolante 9, on a ménagé un jeu 16 permettant d'assurer la mise en place des wagonnets 7 dans le four, l'étanchéité thermique du four vis-à-vis de l'extérieur étant réalisée par des plaques métalliques 17 disposées verticalement le long des bordures longitudinales des wagonnets, lesdites plaques 17 plongeant dans des cornières 18 remplies de sable 19 et disposées à la base des parois longitudinales du four. Les briques 15, qui sont disposées à la base des parois latérales du four sont soutennes soit par des supports 20 solidaires du châssis soit par un support 21 solidaire de la porte 5, laquelle est ellemême portée par le châssis. Les briques 15 sont maintenues sur le châssis ou sur la structure de porte par des attaches 22 constituées chacune d'un boulon et d'une plaque de retenue, la plaque de retenue étant mise en place dans la brique creuse 15; il convient de remarquer que les attaches 22 sont thermiquement protégées par les briques 15 et n'ont donc pas à souffrir de l'élévation de température à l'intérieur du four. Les briques 15 sont remplies, au moment de leur mise en place, d'une bourre de fibres réfractaires en vrac afin d'améliorer l'isolation.At the insulating layer 9, there are disposed in the wall, which delimits the oven, and in the door 5, hollow bricks 15 identical to the bricks constituting the layer 9, oriented so that facing rounded reliefs 14a , the hollow bricks 15 have a rounded hollow 14b and that opposite a rounded hollow 14b, the hollow bricks 15 have a rounded relief 14a. Between the bricks 15, which are at the base of the walls of the furnace, and the bricks constituting the insulating layer 9, a clearance 16 has been provided for ensuring the placement of the wagons 7 in the furnace, the thermal sealing of the oven vis-à-vis the outside being produced by metal plates 17 arranged vertically along the longitudinal edges of the wagons, said plates 17 plunging into angles 18 filled with sand 19 and arranged at the base of the longitudinal walls of the oven . The bricks 15, which are arranged at the base of the side walls of the oven are supported either by supports 20 secured to the chassis or by a support 21 secured to the door 5, which is itself carried by the chassis. The bricks 15 are held on the frame or on the door structure by fasteners 22 each consisting of a bolt and a retaining plate, the retaining plate being placed in the hollow brick 15; it should be noted that the fasteners 22 are thermally protected by the bricks 15 and therefore do not have to suffer from the rise in temperature inside the oven. The bricks 15 are filled, at the time of their installation, with a flock of loose refractory fibers in order to improve the insulation.

La paroi calorifuge du four est ainsi réalisée, pour sa couche horizontale inférieure, par la couche isolante 9 et les briques 15. En ce qui concerne la partie horizontale supérieure de la paroi calorifuge, elle est réalisée de la même façon par un assemblage de briques creuses 23, qui sont supportées grâce à des attaches 24 par les poutrelles 2, qui forment le toit du four. Les attaches 24 sont constituées de boulons et de plaques d'attache et sont protégées de l'élévation de température par la couche isolante que constituent les briques 23 elles-mêmes. Les briques 23 présentent sur leurs bordures des décrochements 23a, 23b permettant leur assemblage mécanique pour constituer la voute du four. Dans la zone centrale de la voute du four, on a prévu un orifice d'évacuation d'air 25, qui est relié à un ventilateur d'aspiration, pour assurer le refroidissement rapide du four; pendant la phase de refroidissement, on ouvre des trappes d'aération 26 disposées à la partie basse du four de façon à permettre l'entrée d'air froid et le refroidissement du four.The heat-insulating wall of the oven is thus produced, for its lower horizontal layer, by the insulating layer 9 and the bricks 15. With regard to the upper horizontal part of the heat-insulating wall, it is produced in the same way by an assembly of bricks hollow 23, which are supported by fasteners 24 by the beams 2, which form the roof of the oven. The fasteners 24 are made up of bolts and fastening plates and are protected from the rise in temperature by the insulating layer that constitutes the bricks 23 themselves. The bricks 23 have on their edges recesses 23a, 23b allowing their mechanical assembly to constitute the vault of the oven. In the central zone of the vault of the oven, an air exhaust orifice 25 is provided, which is connected to a suction fan, to ensure rapid cooling of the oven; during the cooling phase, aeration hatches 26 open at the bottom of the oven are opened so as to allow cold air to enter and the oven to cool.

La paroi latérale du four porte des résistances électriques 27 destinées à assurer le chauffage du four. Bien entendu, les résistances 11 précédemment décrites, ont une action complémentaire à celle des résistance 27. Le problème résolu par l'invention est la réalisation d'une paroi calorifuge latérale au moyen de briques creuses du même type, que celles qui constituent la couche isolante 9, en assurant simultanément le soutien des résistances 27; la difficulté provient du fait que les briques creuses »FIBERCHROM«, si elles ont une faible inertie thermique, ont également une faible résistance mécanique de sorte qu'elles ne sont pas capables de porter le poids des supports des résistances 27. Selon l'invention, les briques creuses 15 sont traversées par des tubes 28 de matière réfractaire résistante, ces tubes 28 reposant par leur base sur les supports 20 et venant, par leur extrémité haute, au niveau du premier support de résistance. Le tube 28 traverse une brique creuse 29, dont la partie avant est évidée pour permettre le passage du tube 28. Par ailleurs, la partie du tube 28, qui fait saillie au-dessus de la brique 15 correspondante, est entourée par un manchon 30 assurant sa protection thermique, ledit manchon 30 s'arrêtant au même niveau que le tube 28. Le manchon 30 peut être obtenu par découpe d'une brique creuse identique à la brique 29. Sur l'ensemble constitué par les tubes 28 et les manchons 30, on vient disposer la plaquette 31 qui constitue le support de résistance 27 ayant le plus bas niveau sur la paroi latérale du four.The side wall of the oven carries electrical resistances 27 intended to ensure the heating of the oven. Of course, the resistors 11 previously described, have an action complementary to that of the resistors 27. The problem solved by the invention is the production of a lateral heat-insulating wall by means of hollow bricks of the same type, as those which constitute the layer insulating 9, simultaneously ensuring the support of resistors 27; the difficulty comes from the fact that the hollow bricks "FIBERCHROM", if they have a low thermal inertia, also have a low mechanical resistance so that they are not capable of carrying the weight of the supports of the resistors 27. According to the invention , the hollow bricks 15 are traversed by tubes 28 of resistant refractory material, these tubes 28 resting by their base on the supports 20 and coming, by their high end, at the level of the first resistance support. The tube 28 passes through a hollow brick 29, the front part of which is hollowed out to allow the passage of the tube 28. Furthermore, the part of the tube 28, which projects above the corresponding brick 15, is surrounded by a sleeve 30 ensuring its thermal protection, said sleeve 30 stopping at the same level as the tube 28. The sleeve 30 can be obtained by cutting a hollow brick identical to brick 29. On the assembly formed by the tubes 28 and the sleeves 30, the plate 31 is arranged, which constitutes the resistance support 27 having the lowest level on the side wall of the oven.

Un support de résistance est disposé horizontalement sur la paroi latérale du four et est constitué par l'assamblage de plaquettes 31 disposées côte à côte. Les plaquettes 31 sont réalisées en un matériau réfractaire ayant une bonne résistance mécanique et ont une forme qui, vue en plan, est sensiblement rectangulaire (figures 7 et 8). Le long des deux bordures longitudinales de chaque plaquette 31 se trouvent deux rebords 32 et 33, qui font saillie d'un côté du plan moyen de la plaquette. A proximité du rebord 32 se trouve un rebord 34, qui fait saillie de part et d'autre du plan moyen de la plaquette. Les rebords 32 et 34 définissent entre eux une rigole 35 à l'intérieur de laquelle peut venir se positionner la résistance de chauffage 27. Dans la zone comprise entre les rebords 33 et 34, la plaquette 31 comprend, sur sa bordure transversale et de part et d'autre de son plan moyen, un bossage 36 ayant, vu en plan, la forme d'un demi-cercle. Lorsque les plaquettes 31 sont assemblées côte à côte, la rigole 35 est continue et les bossages 36 de deux plaquettes adjacentes constituent des bossages circulaires.A resistance support is arranged horizontally on the side wall of the furnace and is constituted by the assembly of plates 31 arranged side by side. The plates 31 are made of a refractory material having good mechanical strength and have a shape which, seen in plan, is substantially rectangular (FIGS. 7 and 8). Along the two longitudinal edges of each plate 31 are two flanges 32 and 33, which project from one side of the mean plane of the plate. Near the rim 32 is a rim 34, which projects on either side of the mean plane of the wafer. The flanges 32 and 34 define between them a channel 35 inside which the heating resistor 27 can be positioned. In the zone between the edges 33 and 34, the plate 31 comprises, on its transverse edge and on either side of its mean plane, a boss 36 having, seen in plan, the shape of a semicircle. When the plates 31 are assembled side by side, the channel 35 is continuous and the bosses 36 of two adjacent plates constitute circular bosses.

Le tube 28 est disposé au-dessous d'un bossage 36 et supporte deux plaquettes 31 adjacentes, dans la zone de plaquette qui est située au-delà du rebord 34 en direction du bossage 36. Le tube 28 se trouve dans la zone médiane des briques 29 et 30 de sorte que les joints de ces briques sont décalés par rapport aux joints des plaquettes 31; la longueur des briques 29 et 30 est la même que la longueur des plaquettes 31.The tube 28 is disposed below a boss 36 and supports two adjacent plates 31, in the plate zone which is located beyond the rim 34 in the direction of the boss 36. The tube 28 is located in the middle zone of the bricks 29 and 30 so that the joints of these bricks are offset from the joints of the plates 31; the length of the bricks 29 and 30 is the same as the length of the plates 31.

Lorsque la mise en place des premières plaquettes 31 a été ainsi effectuée, on monte l'ensemble de la paroi latérale du four en utilisant des briques du type »FIBERCHROM« découpées comme indiqué sur la figure 9 et en mettant en place, entre deux rangées de briques superposées, une rangée de plaquettes 31. Les briques creuses constituant ainsi la paroi calorifuge ont été désignées par 37 dans leur ensemble; chaque brique est disposée au droit de la rangée de briques, qui lui est inférieure; elle comporte sur sa face inférieure une découpe 38, qui permet le passage du rebord 33 de la plaquette 31 sousjacente; elle comporte, sur sa face supérieure, une découpe 39 qui permet l'encastrement de la plaquette 31 disposée au-dessus de la brique 37, laquelle plaquette 31 repose par l'intermédiaire d'un tube 40 sur la plaquette 31 sousjacente (figure 9). Le tube 40 est centré sur un bossage 36 de la plaquette 31 sousjacente et sur un bossage 36 de la plaquette 31 qu'il supporte. Le tube 40 est disposé à l'intérieur de la brique creuse 37 et sa hauteur est égale à la distance de deux plaquettes 31 superposées. La profondeur de la découpe 39 de la brique 37 est telle que la plaquette 31 supportée par la brique 37 est horizontale, la" plaquette 31 venant par sa face inférieure au niveau de la bordure supérieure de celle des faces de la brique 37, qui est disposée vers l'intérieur du four. On constate donc que toutes les plaquettes 31 superposées sont portées, par l'intermédiaire des tubes 40 qui jouent le rôle d'entretoises, par le tube 28 et, par conséquent, par le support 20 du châssis du four. Il en résulte que les supports de résistance n'ont pas à être portés par les briques creuses 37, qui constituent l'isolation thermique, de sorte qu'il n'est plus important que ces briques aient une résistance mécanique propre. Les briques 37 sont également portées par les plaquettes 31 disposées au-dessous d'elles et il n'y a donc aucun risque d'affaissement de l'empilement de briques 37 réalisé pour constituer la paroi latérale du four. Chaque brique 37 est retenue contre le châssis par des attaches 41 constituées d'une plaque d'attache et d'un boulon, lesdites attaches étant protégées de l'élévation de température par les briques 37 elles-mêmes. Le boulon des attaches 41 est disposé au niveau du plan de raccordement des faces externes des briques 37 et l'on prévoit, pour le passage des boulons des attaches 41, un évidement 42 dans la paroi correspondante de la brique 37. Les attaches 41 sont disposées dans la partie des briques 37 qui est située à mi-distance entre les reliefs arrondis 43a et les creux arrondis 43b, qui permettent l'assemblage de deux briques 37 disposées côte à côte dans une même rangée horizontale; les conformations 43a, 43b sont, bien entendu, identiques aux conformations 14a, 14b précédemment citées pour les briques creuses constitutives de la couche isolante 9. La plaque d'attache d'une attache 41 agit simultanément sur deux briques 37 superposées. De même que les briques de la couche isolante 9 et les briques 15, les briques 29, 30 et 37 sont remplies au moment de leur mise en place, d'une bourre de fibres réfractaires en vrac pour améliorer l'isolation. De plus on bourre également de fibres réfractaires en vrac les tubes 28 et éventuellement les tubes 40.When the positioning of the first plates 31 has been carried out in this way, the entire side wall of the furnace is mounted using bricks of the "FIBERCHROM" type cut out as indicated in FIG. 9 and by placing between two rows of stacked bricks, a row of plates 31. The hollow bricks thus constituting the heat-insulating wall have been designated by 37 as a whole; each brick is placed in line with the row of bricks, which is lower than it; it has on its underside a cutout 38, which allows the passage of the rim 33 of the underlying plate 31; it has, on its upper face, a cutout 39 which allows the embedding of the plate 31 disposed above the brick 37, which plate 31 rests by means of a tube 40 on the underlying plate 31 (Figure 9 ). The tube 40 is centered on a boss 36 of the underlying plate 31 and on a boss 36 of the plate 31 which it supports. The tube 40 is disposed inside the hollow brick 37 and its height is equal to the distance from two superimposed plates 31. The depth of the cutout 39 of the brick 37 is such that the plate 31 supported by the brick 37 is horizontal, the "plate 31 coming from its lower face at the level of the upper edge of that of the faces of the brick 37, which is placed towards the inside of the oven. It can therefore be seen that all of the superimposed plates 31 are carried, by means of the tubes 40 which act as spacers, by the tube 28 and, consequently, by the support 20 of the chassis. As a result, the resistance supports do not have to be carried by the hollow bricks 37, which constitute the thermal insulation, so that it is no longer important that these bricks have their own mechanical resistance. The bricks 37 are also carried by the plates 31 arranged below them and there is therefore no risk of collapse of the stack of bricks 37 produced to constitute the side wall of the furnace. Each brick 37 is retained against the chassis by fasteners 41 consisting of an attachment plate and a bolt, said attachments being protected from the rise in temperature by the bricks 37 themselves. The bolt of the fasteners 41 is arranged at the level of the connection plane of the external faces of the bricks 37 and provision is made, for the passage of the bolts of the fasteners 41, a recess 42 in the corresponding wall of the brick 37. The fasteners 41 are arranged in the part of the bricks 37 which is located midway between the rounded reliefs 43a and the rounded recesses 43b, which allow the assembly of two bricks 37 arranged side by side in the same horizontal row; the conformations 43a, 43b are, of course, identical to the conformations 14a, 14b previously cited for the hollow bricks constituting the insulating layer 9. The attachment plate of an attachment 41 acts simultaneously on two superimposed bricks 37. Like the bricks of the insulating layer 9 and the bricks 15, the bricks 29, 30 and 37 are filled at the time of their installation with a flock of loose refractory fibers to improve the insulation. In addition, tubes 28 and possibly tubes 40 are also stuffed with refractory fibers in bulk.

Il convient de préciser que les faces des briques 37, qui se trouvent vers l'intérieur du four, sont en fait insérées entre les tubes 40 et les rebords 34 des plaquettes 31. Il en résulte que l'on assure déjà ainsi la solidarisation dans le sens transversal des plaquettes 31 et de la paroi calorifuge constituée par l'ensemble des briques 37. Les joints de deux plaquettes 31 adjacentes d'un même niveau se trouvent approximativement au milieu des briques 37, qui les supportent et qui les surmontent. En outre les découpes 38 et 39 des plans inférieur et supérieur des briques 37 permettent, par coopération avec le rebord 33 des plaquettes 31, d'assurer le maintien transversal des plaquettes par rapport aux deux rangées de briques, entre lesquelles les plaquettes sont mises en place.It should be noted that the faces of the bricks 37, which are located towards the inside of the furnace, are in fact inserted between the tubes 40 and the edges 34 of the plates 31. As a result, this is already ensured in the transverse direction of the plates 31 and of the heat-insulating wall formed by the set of bricks 37. The joints of two adjacent plates 31 of the same level are located approximately in the middle of the bricks 37, which support them and which overcome them. In addition, the cutouts 38 and 39 of the lower and upper planes of the bricks 37 make it possible, by cooperation with the rim 33 of the plates 31, to ensure the transverse maintenance of the plates with respect to the two rows of bricks, between which the plates are placed. square.

Il est clair que la réalisation, qui vient d'être décrite, permet de faire porter le poids des supports de résistance directement par le châssis grâce aux entretoises 28 et 40 et de supporter également chaque brique de la paroi calorifuge de sorte que l'on peut utiliser des briques dont la résistance mécanique est très faible. Cette technique permet donc de mettre en oeuvre pour la réalisation des parois calorifuges des briques de faible poids ayant une faible inertie thermique, ce qui constitue un grand avantage sur le plan de l'économie d'énergie, cet avantage étant d'autant plus sensible qu'il s'agit d'un four à fonctionnement intermittent. De plus, le temps nécessaire au refroidissement du four par ventilation est plus faible, puisque l'inertie thermique du four est plus faible, et l'on peut, en conséquence, réduire le temps des cycles de cuisson et augmenter les cadences de production.It is clear that the embodiment, which has just been described, allows the weight of the resistance supports to be carried directly by the chassis thanks to the spacers 28 and 40 and also to support each brick of the heat-insulating wall so that can use bricks with very low mechanical strength. This technique therefore makes it possible to use bricks of low weight with low thermal inertia for the production of heat-insulating walls, which constitutes a great advantage in terms of energy saving, this advantage being all the more significant. that it is an intermittent oven. In addition, the time required for the cooling of the oven by ventilation is lower, since the thermal inertia of the oven is lower, and it is therefore possible to reduce the time of the cooking cycles and increase the production rates.

Il est bien entendu que le mode de réalisation ci-dessus décrit n'est aucunement limitatif et pourra donner lieu à toutes modifications désirables, sans sortir pour cela du cadre de l'invention.It is understood that the embodiment described above is in no way limiting and may give rise to any modifications desirable, without departing from the scope of the invention.

Claims (14)

1. A furnace heated by electric resistors, comprising an insulating wall retained by a frame, electric resistor supports being disposed on the face of the said wall, which face is directed towards the interior of the furnace, characterized in that the insulating wall is formed by an assembly of modular elements (37) made from a heat-insulating material having low mechanical resistance and low thermal inertia, the resistor supports (27) being arranged at the level of the horizontal joint faces of the assembled modular elements (37) and being constituted by rigid refractory plates (31) assembled adjacent one another and horizontally, each plate (31) being supported by at least one rigid bearing member (28, 40) arranged inside a modular element (29, 37) of the wall, the said member resting on the plate (31) which is at right angles with the latter at a lower level, the plates (31), which are at the lowest level, being supported by a bearing member (28) which rests on the frame (1) of the furnace.
2. A furnace as claimed in claim 1, characterized in that the modular elements (29, 37) are hollow bricks constituted by a felt of refractory fibres.
3. A furnace as claimed in claim 2, characterized in that the hollow bricks (29, 37) are filled with a wad of loosely packed refractory fibres, preferably after they have been positioned.
4. A furnace as claimed in one of claims 1 to 3, characterized in that the insulating wall is constituted by a single thickness of modular elements, each modular element (29, 37) being fixed on the frame (1) of the furnace by at least one connection piece (41) arranged on the face of the modular element, which face is directed towards the exterior of the furnace.
5. A furnace as claimed in claim 4, characterized in that the connection pieces (41) of the modular elements (29, 37) are arranged at the level of the horizontal joint faces of the said elements, in the median zone of each element, each connection piece acting simultaneously on two superposed modular elements.
6. A furnace as claimed in one of claims 1 to 5, characterized in that the plates (31) forming the resistor supports (27) have a substantially rectangular shape and comprise two raised edges (32, 34) which are substantially parallel to a plate edge, these two raised edges being arranged inside the furnace and defining between themselves a channel (35) in which an electric heating resistor is placed, one part of the plate (31) being arranged inside the insulating wall.
7. A furnace as claimed in claim 6, characterized in that the plates (31) constituting a resistor support in a horizontal plane are arranged at contiguous edges and form a continuous channel (35) on the inner face of the insulating wall, the joins of two adjacent plates being staggered with respect to the joins of the two adjacent modular elements (29, 37) of one level of the wall.
8. A furnace as claimed in claim 7, characterized in that the join of two adjacent plates (31) of a resistor support is substantially perpendicular to the insulating wall of the furnace and is arranged in the central zone of a modular element (29, 37), the length of the plates (31) being equal to the length of the modular elements (29, 37) of the wall.
9. A furnace as claimed in one of claims 6 to 8, characterized in that each plate (31) comprises a third raised edge (33) which is arranged in the vicinity of the centre of the thickness of the insulating wall, parallel to the two other raised edges (32, 34) and along one edge of the plate (31).
10. A furnace as claimed in claim 9, characterized in that the third raised edge (33) of the plates (31) cooperates with a corresponding slit in the horizontal joint faces of the modular elements (29, 37), so as to ensure that the plates (31) are retained perpendicular to the insulating wall.
11. A furnace as claimed in one of claims 1 to 10, characterized in that the rigid bearing members (40) are tubes made of refractory material, each tube being positioned with respect to each of the plates (31), between which it forms a cross-piece by means of a centring bearing (36).
12. A furnace as claimed in claim 11, characterized in that each plate (31) comprises in relief, in its part located inside the insulating wall and on both sides of its horizontally disposed median plane, at least one boss (36), the horizontal section of which corresponds at least partially to the inner cross-section of the tubes (40) constituting the bearing members.
13. A furnace as claimed in claim 12, characterized in that the tubes (40) forming the bearing members have a circular section and in that each plate (31) comprises, on both sides of its horizontally disposed median plane, a boss (36) which has a semi-circular horizontal section and is provided in the edge of the plate to form, with the corresponding boss (36) of the adjacent plate (31), a circular boss substantially having the diameter of the internal section of the tubes (40).
14. A furnace as claimed in claims 2 and 13 taken together, characterized in that the face of each hollow brick (37), which face is disposed towards the interior of the furnace, is inserted between the tube (40) disposed inside the said brick and that one (34) of the raised edges defining the channel (35) which is nearest the exterior of the furnace.
EP19810401335 1980-09-19 1981-08-24 Electric heating furnace with low thermal inertia Expired EP0048645B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8020269A FR2490797A1 (en) 1980-09-19 1980-09-19 ELECTRICALLY HEATED OVEN WITH LOW THERMAL INERTIA
FR8020269 1980-09-19

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EP0048645A1 EP0048645A1 (en) 1982-03-31
EP0048645B1 true EP0048645B1 (en) 1984-04-04

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EP19810401335 Expired EP0048645B1 (en) 1980-09-19 1981-08-24 Electric heating furnace with low thermal inertia

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EP (1) EP0048645B1 (en)
DE (1) DE3162977D1 (en)
FR (1) FR2490797A1 (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1986004478A1 (en) * 1985-01-25 1986-07-31 Ludwig Riedhammer Gmbh Electrically-heated industrial oven
FR2642512B1 (en) * 1989-02-02 1991-09-20 Commissariat Energie Atomique CONTINUOUS SINTERING OVEN
GB9420443D0 (en) * 1994-10-11 1994-11-23 Groom Bryan Ltd Heat insulating apparatus
DE19529190A1 (en) * 1995-08-09 1997-02-13 Abb Patent Gmbh Deglorofen
FR2818366A1 (en) * 2000-12-18 2002-06-21 P A Technologies Anchor, for holding refractory linings on furnace walls, has tetrahedral head with strap holding it at set spacing from furnace wall

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1794310A (en) * 1929-07-31 1931-02-24 Herbert J Mccauley Electric furnace and electric resistance element therefor
US2688685A (en) * 1951-10-29 1954-09-07 Paul H Goodell Sheath-resistance heater and panel supporting structures therefor which are built into heating devices
US4088825A (en) * 1976-08-04 1978-05-09 General Electric Company Electric furnace wall construction
FR2394774A1 (en) * 1977-06-17 1979-01-12 Produits Refractaires REFRACTORY TRIM ELEMENT FOR OVEN OR ANALOGUE

Also Published As

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FR2490797B1 (en) 1983-12-16
DE3162977D1 (en) 1984-05-10
FR2490797A1 (en) 1982-03-26
EP0048645A1 (en) 1982-03-31

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