WO2003096750A1

WO2003096750A1 - Device for stabilizing a multi-legged resistor element

Info

Publication number: WO2003096750A1
Application number: PCT/SE2003/000697
Authority: WO
Inventors: Lars Göran JOHANSSON
Original assignee: Sandvik AB
Current assignee: Sandvik AB
Priority date: 2002-05-07
Filing date: 2003-04-29
Publication date: 2003-11-20
Anticipated expiration: 2004-11-07
Also published as: SE0201382L; SE521744C2; SE0201382D0; AU2003224583A1

Abstract

A device for stabilising a vertically mounted multi-leg electric resistance element (1) of molybdenum silicide type or its correspondence, comprising at least two lower curved portions (2,3,4). The invention is characterised by a spacer (13) which is supported by the curved lower portions (2,3,4) and which spacer (13) includes parts (14,15) that physically distance each pair of adjacent curved portions.

Description

DEVICE FOR STABILIZING A MULTI-LEGGED RESISTOR ELEMENT

The present invention relates to a device for stabilising a multi-leg resistance element.

A typical type of element for heating inter alia industrial ovens or furnaces is comprised of molybdenum suicide and alloyed molybdenum suicide.

One problem encountered with industrial ovens/furnaces and corresponding applications in which conventional legged elements of this kind are used may involve the achievement of sufficient power density in a given space. Although the use of two-legged elements will often suffice in such cases, it may be necessary to use elements having four, six, eight or more legs.

Such elements are most often installed vertically in an endeavour to prevent changes in the shape of the elements when they become hot.

The plasticity of a molybdenum suicide element increases with increasing temperature.

A problem arises when using elements that have four, six or more legs. Such elements have at least one curved portion at its upper part and two curved portions at its lower part when the lead-in parts of the elements extend through a vertical outlet transit or lead through that has two through-penetrating holes. The outlet transit is placed in the oven ceiling above the element. Only the outer legs of the element are therewith held in position in the oven by means of the transit or lead through.

The above mentioned curved upper part or parts is/are are anchored by means of a hook in theoutlet transit and therewith held in position. The lower curved parts, however, hang freely. When the plasticity increases, the risk of the legs at the lower parts of the element being drawn towards one another as a result of the magnetic field generated by the element also increases. This results in short circuiting of the element, which then has to be replaced.

This problem is solved by the present invention. The present invention thus relates to a device for stabilising a vertically fitted multi-leg electric resistance element of molybdenum suicide type or its correspondence that includes at least two lower curved portions. The invention is characterised by a spacer which is supported by the curved lower portions and which includes parts that physically distance each pair of adjacent curved portions.

The invention will now be described in more detail partly with reference to an embodiment of the invention shown in the accompanying drawing, in which

Figure 1 illustrates an element provided with a device according to the invention; and

Figure 2 illustrates only said arrangement.

Figure 1 shows a device for stabilising a vertically mounted multi-leg electric resistance element 1 of molybdenum suicide type or its correspondence that includes at least two lower curved portions 2, 3. Figure 1 shows a six-leg element which consequently has three lower curved portions 2, 3, 4.

The lead-ins 5, 6 of the element 1 pass through an outlet transit or lead-through 7. The upper curved portions 8, 9 of the element are anchored by respective hooks 10, 11 in the outlet transit 7 and are thus held in position. The hooks 10, 11 are fastened to holders 12 on the upper surface of the outlet transit 7.

The outlet transit is comprised of highly refractory brick.

According to the invention there is provided a spacer 13 which is carried by at least two of the curved lower portions 2, 3, 4 of the element 1. The spacer 13 also includes parts 14, 15 that function to physically distance each pair of adjacent curved portions 2, 3, 4.

According to one preferred embodiment, the spacer is an elongate structure and is provided with a groove 16, 17, 18 or a notch for each lower curved part 2, 3, 4 of the element 1. The spacer 13 is intended to rest with its respective grooves or notches 16,17,18 facing towards respective curved portions 2, 3, 4. The spacer is preferably comprised of highly refractory brick. It is particularly preferred to produce the spacer from Al O -brick when the element is comprised of molybdenum suicide.

The spacer need not be secured to the lower curved portions of said element, but may simply rest thereon under the force of its own weight. The weight of the spacer must be less than the weight at which the type of element concerned would lengthen when heated to operating temperature.

It will thus be obvious from the aforegoing that the spacer solves the problem mentioned in the introduction and keeps the free lower portions of the element in position relative to one another so as to prevent the occurrence of a short circuit.

It will also be understood by the person skilled in this art that the spacer can be given a structural design other than that shown in the drawing. For example, the grooves or notches can be given a different form, provided that they prevent displacement of mutually adjacent lower curved portions of the element towards one another.

Consequently, the present invention shall not be considered as being limited to the above described exemplifying embodiments, since variations and modifications can be made within the scope of the accompanying claims.

Claims

1. A device for stabilising a vertically mounted multi-leg electric resistance element (1) of molybdenum suicide type or its correspondence, comprising at least two lower curved portions (2, 3, 4), c h a r a c t e r i s e d by a spacer (13) which is supported by the curved lower portions (2, 3, 4) and which spacer (13) includes parts (14, 15) that physically distance each pair of adjacent curved portions.

2. A device according to Claim 1, c h a r a c t e r i s e d in that the spacer (13) is elongate and provided wih a groove (16, 17, 18) for each lower curved portion (2, 3,

4) of the element (1); and in that the spacer rests with respective grooves (16, 17, 18) facing towards respective curved portions (2, 3, 4).

3. A device according to Claims 1, 2 or 3, characterised in that the spacer (13) is comprised of highly refractory brick.

4. A device according to Claim 4, characterised in that the spacer (13) is comprised of Al₂O₃-type brick.