1. Field of the Invention
The present invention relates to an arrangement for mounting an electric heating element in a furnace.
2. Description of the Related Art
Electrically heated furnaces or ovens that include a process tube in which objects are heated are known to the art. Furnace insulation comprised of high grade brick, such as aluminum oxide brick, is provided externally of the process tube and in spaced relationship therewith. Such a furnace, or oven, will normally have a generally circular cross-section and will typically operate at a temperature of around 1700° C.
The heating elements used are placed equidistantly around the furnace, and heating zones are positioned in the space defined between the outer surface of the process tube and the inner surface of the brick insulation. The contacts of the elements are placed outside the brick insulation, i.e., externally of the furnace. The electrical conductors of the elements extend through holes in the brick insulation.
The aforesaid space has a narrow dimension in the radial direction of the furnace and, hence, the heating zone of the elements is disposed parallel with the outer surface of the process tube. The length of the heating zone is significantly greater than the width of said space.
A serious problem with this solution is that the elements cannot be replaced from outside the furnace. It is therefore necessary to first cool down the furnace and then remove the process tube, in order to be able to reach and to exchange the elements. The elements are therewith removed by withdrawing them inwardly into the furnace. It will be obvious from this that the exchange of the elements is both laborious and complicated.
This problem is solved by the present invention, which provides an arrangement by means of which the elements can be replaced from outside the furnace and without removing the process tube.
Accordingly, the present invention relates to an arrangement for mounting electric heating elements in a furnace in which objects are to be heated, wherein the furnace wall furnace insulation comprised of high grade brick. The heating zones of respective electric heating elements are placed vertically and parallel with the inner surface of the furnace wall in operation. The electrical leads or conductors of each heating element are mounted in a cassette and extend in channels provided therein, and the heating zone of respective heating elements project out and define an angle with the longitudinal axis of the cassette. The furnace insulation includes for each cassette a hole which is larger at its outer end than at its inner end, therewith enabling the cassette to be rotated in a vertical plane as the heating zone of the element is inserted through the hole and into said operating position parallel with the furnace wall. A wedge-like body is provided whose shape corresponds to the shape of the empty space created by the shape of the hole and is located between the hole and the cassette when the cassette is placed in operating position in the hole. The body is placed in the empty space during operation.
The invention will now be described in more detail partly with reference to an exemplifying embodiment thereof illustrated in the accompanying drawings, in which:
Although the invention is described below with reference to a furnace that includes a process tube, it will be understood that the invention can be applied equally as well to a furnace without a process tube.
Located externally of the process tube 3 and in spaced relationship therewith is furnace insulation 4 comprised of high grade brick. The process tube 3 and the furnace insulation 4 are normally cylindrical and have their longitudinal axes placed vertically.
As will be seen from
The aforesaid space is only slightly wider than said heating zones.
According to the invention, the electric leads, or conductors, 7, 8 of each heating element 2 are mounted in a cassette 9 and extend in channels 10, 11 therein, as shown in
The channels may have the form of cylindrical holes or may be upwardly open, as in
The elements are of a suitable kind and are supplied by the Applicants of this Patent.
As shown in
The arrangement also includes a wedge-like body 13 whose shape corresponds to the shape of the empty space created by the shape of the hole 12 and located between the hole 12 and the cassette 9 when the cassette is placed in its operating position in said hole. As will be best seen from
An element is removed by first removing the wedge-shaped body and then the cassette. In this case, the cassette has the design shown in
A new element can then be fitted in the reverse order of the above steps.
Thus, it is possible to remove and to fit elements as the furnace is in operation, which affords a significant advantage over known techniques.
According to one preferred embodiment of the invention, the element is at an angle of between 30 and 60 degrees, although said angle may, of course, be adapted to the design of the hole and to the width of the space 5 between the process tube and the insulation 4, so that the element can be inserted and withdrawn in the aforesaid manner.
According to one preferred embodiment, each cassette 9 is elongate and has a generally rectangular cross-section.
It is preferred that the furnace insulation 4 and the cassettes 9 are made from high grade brick, such as from aluminum oxide brick.
It is also preferred that the body 13 is made from high grade brick, such as aluminum oxide brick.
The aforesaid hole will preferably have a generally rectangular cross-section.
It is also preferred that the hole 12 has a horizontal undersurface, parallel vertical side edges and an upper side that defines an angle with the horizontal plane.
In case of such a design of the hole, it is preferred that the cassette 9 will abut the upper side of the hole 12 when in its operating position.
Assuming that the cassette 9 has the same width as the hole 12 and that the cassette 9 abuts the upper side of said hole when fitted, a wedge shaped open space will be formed beneath the cassette 9, as shown in
It will be obvious that the present invention solves the problem mentioned in the introduction.
It will also be obvious that the invention can be varied with regard to the design of the cassettes, the configuration of the holes and said body without departing from the function of achieving a seal essentially against the leakage of heat at said elements.
The present invention shall not therefore be considered as restricted to the embodiments indicated above, since variations and modifications can be made within the scope of the accompanying claims.
Number | Date | Country | Kind |
---|---|---|---|
0104453 | Dec 2001 | SE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/SE02/02375 | 12/18/2002 | WO | 00 | 1/24/2005 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO03/056877 | 7/10/2003 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
1839613 | Swoboda et al. | Jan 1932 | A |
4394566 | Magnusson | Jul 1983 | A |
Number | Date | Country |
---|---|---|
1393081 | Feb 1965 | FR |
Number | Date | Country | |
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20050129085 A1 | Jun 2005 | US |