EP0032775B1

EP0032775B1 - Furnace, especially a ceramic or heating furnace

Info

Publication number: EP0032775B1
Application number: EP81200061A
Authority: EP
Inventors: Theodor Johann Sevink
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-01-18
Filing date: 1981-01-19
Publication date: 1985-07-24
Also published as: NL8000342A; EP0032775A1; ATE14478T1; DE3171439D1

Abstract

The problem that the constructor of an electrically heated felt furnace has to place thousands of little pins (15) for suspending the resistance elements (16) between the felt layer, is overcome by providing strips (14)having a great number of these pins or hooks. One can either put the strip itself or his pins between the felt layers.

Description

The present invention relates to a furnace, consisting of heating means and a casing, whose jacket, bottom and cap are coated with a heat-insulating material, whereby the bottom of the casing is formed by a bottom plate on which the jacket of the casing rests removably, and the cap is secured to the jacket by means of connection means.
Such a furnace is known from GB-A-590 358.
A disadvantage of the known furnace is that after the heating process has been terminated, the cap has to be left open for some time before the, then cooled products, can be taken from the furnace and the furnace can be loaded again, so that there is a loss in time and heat.
It is the object of the present invention to provide a furnace of the above mentioned type, which does not have said disadvantage.
This object is achieved in that in the furnace according to the invention: a) the bottom plate has a lower layer of concrete or a similar material, on which, while leaving the outer portions of the top surface uncovered, the insulating material is provided, whereas the lower side of the jacket of the casing rests on said outer portions under intermediary of a layer of sealing insulating material, and b) the cap is secured to the jacket by means of disengageable means.
In this way it is possible after the termination of the burning process to lift the jacket with closed cap from the bottom plate and to place it on another bottom plate, after which a next burning process can be started immediately, whereas the product on the first bottom plate can cool. If, however, the obtained products do not permit such a rather unequal cooling, then it is possible first to remove the cap and to leave the furnace open for some time, before placing the jacket with cap on another bottom plate. This procedure could also be carried out with a furnace as known from GB-A 819982.
The heat insulating material with which the bottom plate is coated, is preferably connected by means of a scalariform joint to the heat-insulating material with which the jacket is coated.
The heat-insulating material is preferably formed by layers of a felt material. In this way the jacket and cap have a considerably small weight relative to the known furnaces which are coated with ceramic material.
When using the felt material for the heat-insulating material of the bottom plate uprights are secured in the layer of concrete, which uprights extend through the felt layers, as provided on the layer of concrete, and carry at their tops a load-supporting plate of ceramic material.
When using electric resistance elements to heat the furnace the walls of the jacket are coated with a pile of horizontally deposed layers of the felt material, whereas at certain places between two of said layers a strip of ceramic material is clamped, which is provided with pins from which the electric resistance elements are suspended.
Because of what is mentioned above it is no longer necessary for a constructor of furnaces to provide numerous little pins separately. Furthermore there is practically no contact between the elements and the furnace wall, so that there is no direct heat-flow to said wall, so that the furnace is more economic and it is possible to let the burning process take place up to a higher temperature.
The above mentioned strips can be formed according to two mutually different embodiments. The first embodiment is characterized by the feature that the pins consist of inwardly, freely protruding hooks.
It is also possible, however, that the pins of the strip are provided between two layers of heat-insulating material, and that the pins are provided with a protrusion to keep the resistance elements spaced from the layers. The pins may have a lens-shape when considered in cross-section and, starting at the protrusion, they may have a T-shaped cross-section. Thereby the lowest possible heat transfer by conduction is achieved.
When using burners to heat the furnace said burners may advantageously be provided in the cap. Thus after termination of the burning process the cap with the valuable burners and pertaining protection means can be placed on another jacket which is already loaded. In this way the valuable apparatus can be used continuously and the furnace is not useless during the cooling period. If the burnt or heated products do not permit the furnace to be suddenly and completely opened, then a simple intermediate cap may be provided which remains on the furnace when the main cap and the burners are removed.
It is also possible that the burners and protection means are mounted on a displaceable frame and to remove only this frame and to place it on a successive furnace if a quick cooling action is not desired.
It is remarked that a so-called bell-furnace is known which is composed of a bell-shaped section which rests on a bottom and can be lifted as a whole from said bottom. In this type of furnace the load cannot cool equally after being burnt.
The invention is further described on the basis of the drawing, in which

Fig. 1 is a cross-section through a part of the furnace according to the invention,
Fig. 2 is a perspective view, in which the way of securing the electric resistance elements is shown;
Fig. 3 is a plane view of a second embodiment of a strip, and
Fig. 4 is a cross-section according to the line IV-IV of Fig. 3.

As shown in Fig. 1 the furnace comprises a jacket 1, which rests disengageable on a bottom plate construction 2, whereas the jacket is closed at its top by means of a cap 3 which is removably secured on the jacket by means of latches 4.
The bottom plate construction 2 comprises a frame which is formed by angle-irons 5 in which the steel plate 6 is placed. On the plate 6 a layer of concrete 7 is provided, in which the uprights 8 are received. On the plate of concrete 7 layers 9 of felt material are provided, whereas on the uprights 8 a plate 10 rests, which is made of ceramic material and which supports the load. The outer sections of the layer of concrete 7 are coated by a layer 11 of a sealing, insulating material on which the jacket 1 rests.
The jacket 1 comprises an envelope 12 of plate steel, in which the layers of felt material 13 are provided, and in which the lower layers 13 are connected to the felt layers 9 of the bottom plate by means of a scalariform joint.
At certain places between two felt layers 13 the strips 14 of ceramic material are clamped, which are provided with the inwardly, freely projecting hooks 15, from which the electric resistance elements 16 are suspended.
At the top of the envelope 12 a layer of sealingly insulating material 17 is provided, on which the cap p 3 rests.
The cap 3 comprises an envelope 18 of plate sheet, in which the felt layers 19 are bonded.
The complete furnace rests on a foot 20.
A support eye 21 is welded to the envelope, and with the aid of said eye either the cap 3 and jacket 1 can be lifted as a whole from the bottom plate construction 2 when the latches 4 are closed, or when the latches 4 are opened, only the cap 3 can be lifted from the jacket 1.
In Fig. 2 the electric resistance elements 16 are drawn in the configuration of filaments, but mostly this will not be so. A normal capacity of a furnace is 4 kW and this can be produced by four folded belts 22 of 5 x 0.6 mm Kanthal steel. A part of one of such belts is shown in Fig. 3 and 4. In said figure the ceramic strip 14 is just outside the felt layer 13, whereas the pins 15 project into the felt layer now.
Protrusions 23 are provided on said pins, which protrusions serve as spacers. The cross-section of the pins is preferably lens-shaped, which can simply be achieved by means of spacing plaster blocks, with the aid of which the casting mould for the strips are made, when making holes in the separation surface.
The pins may also be a different cross-section at the location of the filter layer, as indicated in Fig. 4 by dotted lines, namely a T-shaped cross-section which is beneficial for correctly securing them and at the same time provides the lowest possible heat transfer by conduction.

Claims

1. A furnace, consisting of heating means and a casing, whose jacket (1), bottom and cap (3) are coated with a heat-insulating material, whereby the bottom of the casing is formed by a bottom plate (2) on which the jacket (1) of the casing rests removably, and the cap (3) is secured to the jacket by means of connection means (4), characterized in that a) the bottom plate (2) has a lower layer (7) of concrete or a similar material, on which, while leaving the outer portions of the top surface uncovered, the insulating material (9) is provided, whereas the lower side of the jacket (1) of the casing rests on said outer portions under intermediary of a layer (11) of sealing insulating material, and b) the cap is secured to the jacket (2) by means of disengageable means (4).

2. A furnace according to claim 1, characterized in that the heat insulating material (9) with which the bottom plate (2) is coated is connected by means of a scalariform joint to the heat-insulating material (13) with which the jacket (1) is coated.

3. A furnace according to claim 1 or 2, characterized in that the heat-insulating material (9, 12) is formed by layers of a felt material.

4. A furnace according to claim 1-3, characterized in that in the layer of concrete uprights (8) are secured, which extend through the felt layers, as provided on the layer of concrete, and that they carry at their tops a load-supporting plate (10) of ceramic material.

5. A furnace according to claims 3 and 4, wherein the heating means are formed by electric resistance elements (16), characterized in that the walls of the jacket are coated with a pile of horizontally deposed layers of the felt material, whereas at certain places between two of said layers a strip (14) of ceramic material is clamped, which is provided with pins (15) from which the electrical resistance elements (16) are suspended.

6. A furnace according to claim 5, characterized in that the pins (15) consist of inwardly, freely protruding hooks.

7. A furnace according to claim 5, characterized in that the pins (15) of the strip (14) are provided between two layers (13) of heat-insulating material, and that the pins are provided with a protrusion (23) to keep the resistance elements (16) spaced from the layers.

8. A furnace according to claim 7, characterized in that in cross-section the pins have a lens-shape.

9. A furnace according to claim 7 or 8, characterized in that, starting at the protrusion (23), the pins have a T-shaped cross-section.

10. A furnace according to claims 1-9, wherein the heating means are formed by burners, characterized in that the burners are provided in the cap.

11. A furnace according to claim 10, characterized in that the burners are mounted on a removable frame.