US2104555A

US2104555A - Electrical furnace

Info

Publication number: US2104555A
Application number: US58890A
Authority: US
Inventors: Cousteix Blaise
Original assignee: Compagnie de Saint Gobain SA
Current assignee: Compagnie de Saint Gobain SA
Priority date: 1935-01-16
Filing date: 1936-01-13
Publication date: 1938-01-04
Anticipated expiration: 1955-01-04

Description

Jan. 4, 1938. B. cousTExx ELECTRICAL FURNACE Filed Jan. 13, 1936 3 Sheets-Sheet l INVENTOR. Coz/5T /X ATTORNEYS www ma a Jan. 4, 1938. B, QU5TE|X 2,104,555

ELECTRICAL FURNACE Filed Jan. 13, 1936 3 Sheets-Sheet 2 INVENTOR.

ATTORNEYJl Jan. 4, 1938.

B. COUSTEIX ELECTRICAL FRNACE Filed Jan. 13, 1936 3 Sheets-Sheet 3 INVENTOR. BL m55 Cous *f5/X ATTORNEYS Patented Jan. 4, 1.938 T l UNITED STATES PATENT OFFICE ELECTRICAL FUBNACE Blaise Cousteix, Boulogne sur Seine, France, as-

signor to Societe Anonyme des Manufactures des Glaces a Produits Chimiques de Saint- Gobain, Chauny & Cirey, Paris, France Application January 13, 1936, Serial No. 58,890

In France January 16, 1935 d Claims. (Cl. 13-21) This invention refers to electrical furnaces for which ordinarily forms the external covering of heating, melting and/or casting various subthe furnace. The metallic casing may consist of stances, such as quartz or metals, having a high perforated or non-perforated sheets of metal or melting point. The invention relates more parof a net of interconnected metallic rods or strips.

ticularly to singlephase furnaces employing one `According to a modification of the inventive 5 or more electrical resistances which radiate heat idea, the outer steel covering of the furnace may upon the substance to he treated. be eliminated altogether and may loe substituted In furnaces of this type the heating element by a casing consisting of a non-magnetic metal. has usually the form of one or more rods extend- In rotary furnaces of comparatively large dimening throughout' the length ofthe .furnace and sions the metallic sheets which may be reinforced 10 connected to a source of electrical energy by conor corrugated can be maintained in place by rings ducting elements situated at two opposite ends supporting the rotary furnace and causing it to of the furnace. rotate around a central longitudinal axis.

Practical experience has shown that the elec- The invention will appear more clearly from trical current flowing through the heating elethe following detailed description when taken in ment causes the formation of a magnetic field connection with the accompanying drawings,

creating eddy currents in certain parts of the showing by way of example, preferred embodifurnace which absorb a considerable portion of ments of the inventive idea.

the electrical energy and thus diminish the out-. In the drawings:- put of the furnace. Figure 1 isa longitudinal section through an 20 Another drawback of prior art furnaces conelectrical furnace constructed in accordance with sists in the loss of energy caused by inductance the principles of the present invention; resulting from the form and arrangement of the Figure 2 is a section along the line 2-2 of Figconducting elements supplying the electrical enure i; ergy to the heating element situated -within the Figure 3 is an end elevation of the furnace 25 furnace. illustrated in Figures 1 and 2; v

An object of the present invention is the provi- Figure 4 is a section along the line I-l of Figsion of an electrical furnace of such construction ure 1; that the energy losses caused by inductance and Figure 5 is a longitudinal section through a eddy currents are reduced to a minimum or elimifurnace of a somewhat different construction; 30

nated entirely. Figure 6 is a section along the line 8-6 of Fig- Another object is the provision of an electrical ure 5; y furnace of greater efficiency than furnaces known Figure '7 is a section along the line 1--1 of heretofore. Figure 5;

A further object is the provision of an electri- Figures 8 and 9 illustrate further modifications 35 cal furnace comprising `simple and effective of the inventive idea. means for eliminating eddy currents and induc- The electrical rotary furnace illustrated in tance and for preventing their formation. Figures 1 to 4 of the drawings comprises an inner The above and other objects of the present inresistance or heating element Ill having the form 40 vention may be realized by causing the return of a rod which is situated within the furnace and flow of the heating current through the furnace the longitudinal axis of which substantially coitself. for instance, by providing 'an Outer furmoldes with the axis of rotation of the furnace.

nace casing which consists of a non-magnetic The end portion II of the heating rod III is pro metal COndllCtVely inflected with the heating vided with screw threads, While the opposite end element situated within the furnace, sothat the i2 of the rod has the shape of a cone. The end 45 electrical current supplied by a source of electrltl of the rod i0 is screwed into a suitable opencal energy flows consecutively through the heating i3 of a support I4, the opening I3 being proing element and the metallic casina; the conduct-S vided with inner screw threads corresponding to ing 'elements which connect said source with said the outer screw threads of the end portion Il.

5@ element and said metallic casing being situated The support ill which is made of a conducting 50 next to each other at the same end of the furmaterial comprises a main substantially cylint nace. drical portion and a conical end portion I5 which The metallic casing may consist either totally is supported by a conducting sleeve or block I8. or in part of copper or other non-magnetic metal As shown in Figure 1, the block Ii has a central and may be situated within the steel cylinder conical opening I1. The end portion I5 of the 55 support i6.

While the end il of the heating rod I8 is rmly screwed into the support I4, the opposite end I2 of the rod i6 is free and is supported merely by surface contact. The end I2 of the rod I Il fits into a conical opening I8 which is formed in one end of a second support I 9.

rlhe support I9 is situated opposite the support I4 at the other end of the furnace and is provided with a conical portion 20 fitting into a conical central opening 2| formed in a sleeve or block 22. As indicated in Figure l of the drawings, the block 22 is situated further away from the rod IIJ than the support I4, so that the support I9 is somewhat longer than the support I4. On the other hand, in the example illustrated, the block 22 is smaller than the block I6. The support I9 and the block 22 are both made of a conducting material.

The block IG is surrounded by a casing 23 which is made of a non-magnetic metal, such as copper, and is provided with an annular fiange 24. The casing 23 is held in place upon the block I6 by a metallic sleeve or casing 25, which may be made of steel. A disk 26 which is used as a closure for this end of the furnace is connected with the casing 25.

The block 22 situated at the opposite end of the furnace is surrounded by a casing 21 made of a non-magnetic metal such as copper. The casing 21 is surrounded and held-in place by a metallic casing 28, which may be made of steel or the like.

The main body of the furnace comprises a furnace lining 29 consisting of refractory material surrounded by suitable heat-insulating layers. As shown in Figure 1, the lining 29 comprises a central cylindrical portion surrounding the interior of the furnace and two end portions forming a continuation of the central portion and surrounding at least a part of the supports I4 and I9, respectively.

The lining 29 is supported and enclosed by two concentric casings. The first casing 3U consists the opening of the block of a non-magnetic metal, such as copper, and

comprises a central cylindrical portion 3|, a conicel end portion 32, a cylindrical end portion 33 and a flange 34 which is situated opposite the above-described flange 24 and connected by bolts I4I. The opposite end of the casing 38 has the form of a flange 35.

A separate casing 36 which is also made of a non-magnetic metal comprises a conical portion 31, a cylindrical end portion 39 and a ange 40.

Another casing 38 surrounds the casing 30 and is concentric therewith. The casing 38 is made of an ordinary magnetic metal, such as steel, and is similar in form to the casing 30. Similarly, the casing 36 is surrounded by a casing 4I which is made of a magnetic metal, and which is concentric in relation to the casing 36. The casing 4I is substantially similar in form to the casing 36.

Bolts 58 connect the casings 36 and 4I with the casings 3D and 38.

In the example illustrated, the casing 38 is directly in contact with the casing 30, while the casing 4I is directly in contact with the casing 36. Due to this arrangement, the casings consisting of a non-magnetic metal, and the casings consisting of a magnetic metal are both serving as conductors for the return flow of the electrical current.

attacca Rings 42 and 43 are carried by the casing 38 and are situated upon the outer periphery of said casing. However, these rings are insulated in relation to the casing 38. The rotatable elements of the electrical furnace are supported by

rollers

44 and 45 which are in engagement with the

rings

42 and 43, respectively. The furnace is also provided with an insulated toothed ring 46 engaging a gear wheel 41, which is driven through the medium of a suitable transmission gear by an electro-motor 48. Due to this arrangement, the furnace may be oscillated about its longitudinal axis which, in the example illustrated, coincides substantially with the longitudinal axis of the heating rod I0.

The casing 28 is provided with several rollers 5I which roll upon guides 52. The guides 52 are insulated by pieces of insulation material E3 from an outer casing 54 which consists of a non-magnetic metal such as copper and which comprises a main cylindrical portion and flanges 55 and 56, the flange 55 being situated opposite the flange 48 of the casing 36 and connected to it by bolts |42. T'his end of the furnace is closed by a disk or cover 51 having a central opening 58 and attached to the flange 56 of the casing 54 by the bolts 68. Insulation pieces 6I are situated between the cover 51 and the flange 56 of the casing 54.

One end of a conducting cable 62 is connected to a source of electrical energy not shown in the drawings. The opposite free end of the cable 62 is attached to the cylindrical portion of the. casing 54, as shown in Figure 1.

Another cable 63 connected to the same4 source of electrical energy is attached to one end of 'the conducting rod or plate 64 extending through the opening 58 formed in the cover 51. The opposite end of the rod 64 is provided with arms 65 which are in contact with the casing 21 made of a nonmagnetic metal.

Due to the described arrangement, the heating rod I0 can expand freely while it is being heated.

While the end I I of the heating rod I 0 is firmly attached to the support I4, the opposite end I2 of the rod I8 is free. so that it can expand in the direction of the arrow 66 shown in Figure 1. Such expansion will cause a movement of the support I9 in the direction of the arrow 66 along with the block 22, the casing 21 and the sleeve 28. The sleeve 28 will roll upon the rollers 5I along the guides 52 in the direction of the arrow 66, as soon as the heating rod begins to expand.

In order tu prevent the heating rod I0 from losing contact with the support I9 during contraction of the rod I0, the rod 64 carries a suitable pin 61 which is in engagement with a lever 68. One end of the lever 68 is pivotally mounted at 10 upon a support 1I carried by the cover 51. 'Ihe opposite end of the lever 68 is provided with an opening through which extends a bolt 12 carried by the cover 51. The free threaded end of the bolt 12 carries a winged nut 13. A coiled spring 14 is situated between the nut 1,3 and the lever 68 and surrounds the bolt 1i.

'Ihe pin 61 moves along with the rod 64 and the arms 65, when the non-magnetic metallic casing 21 is moved in the direction of the arrow 66 by the expansion of the heating rod I8, thereby swinging the lever 68 and compressing the spring 14. When the heating rod I0 begins to contract, the spring 14 will press upon the lever 68 which in its turn will move the pin 61 and the rod 64 carrying this pin in a direction opposite to the direction of the arrow 66. Then the rod 64 p of a non-magnetic metal, such will cause the casing 28 to roll backwards upon the guides 52. Therefore, as the heating rod l0 contracts, the support |9 will move in a direction toward the rod |0, so that the surfaces of the opening |8 will always remain in contact iwith the conical surfaces of the end portion |2 of the rod |0.

The electrical current sent bythe source of energy not shown in the 'drawings will flow through the cable 63 and the rod 64 and will be transmitted by the arms 65 to the casing 21 consisting of a non-magnetic metal. Thence the current will flow through the block 22 and the support I9 toward the resistance |0. The current leaving the resistance I0 will flow through the support I4 and the block I6 to the casing 23 consisting of a non-magnetic metal. The current will be transmitted through the flanges 24 of the casing 23 andthe flanges 34 of the casing 30 to the last-mentioned Acasing and will flow through the same, as well as through the casing 36. The current will pass through the flange 40 of the casing 36 and the flange 55 of the casing 54 and will leave the furnace through the cable 62 attached to the casing 54. Metal, quartz, or any other material which is to be treated in the furnace is introduced into its interior through a suitable door 11. Then the current is switched on and the furnace is caused to oscillate by the motor 48. The treated material is removed through the same door, by taking the furnace apart, or by any other suitable means.

It is obvious that due to this arrangement the magnetic field and the eddy currents are elimu inated entirely in the steel casings of the furnace. Furthermore, due to the provision of the described means for supplying the current to the furnace, no losses through inductanee can occur.

The electrical rotary furnace illustrated in Figures 5 to '7 of the drawings has no steel casing. This furnace comprises a central heating rod or resistance 80, one end of which is screwed in to a support 8|. The opposite end of the resistance is carried by a support 82 and is situated within a suitable opening formed in the support. The support 8| comprises a conical portion surrounded by a sleeve or a block 83. The supports 8| and 82 and the sleeve 83 are made of a conducting material.

The sleeve 83 is surrounded by a casing 84 made as copper. An outer sleeve or casing 85 surrounds the casing 84 and is provided with an annular chamber 86 used for the circulation of a cooling medium such as water. The chamber 86 is connected with any suitable means for introducing the water and for removing the same.

The support 82 situated at the opposite end of the furnace comprises a conical end portion surrounded by a conducting sleeve or block 81. A casing 88 surrounds the block 81 and is provided with a flange portion 89 covering the outer side surface of the block 81. The casing 88 is made of a non-magnetic metal, such as copper. A sleeve or casing 90 madeof steel or the like surrounds the casing 88 and is provided with an annular chamber 9| used for the circulation of the cooling water. The casing 90 is supported by rollers 92 whichy are movable along guides 93 carried by insulation pieces 94.

The resistance 80 is surrounded by a layer of refractory material 95 which constitutes the lining of the furnace. The lining 95 surrounds the inner heating chamber of the electrical furnace and also surrounds the major portions of the supports 8| and" 82. Two

layers

96 and 91 consisting of a heat-resisting and heat-insulating material surround the lining 95. The lining 95 and the

layers

96 and 91 are enclosed by a casing made of a non-magnetic metal such as copper, and comprising a central cylindrical portion 98 and two covers 99 and |00.

The cover |00 is attached by bolts |06 to the flange |01 of the casing 98.

A separate 'casing |08 which is made of a nonmagnetic conducting metal is situated close to the cover |00 and comprises a disk |09 closing this end of the furnace and a flange ||0 which is situated opposite the flange of the cover |00. The opposite end of the casing |08 is open and is provided with a flange ||2 which is separated by insulation ||3 from the flange I|4 of a a casing l5.

The casing ||5 is also made of a non-magnetic metal and it supports the insulation pieces 94 which carry the guides 93. The casing I|5 is provided with an outer flange ||6 which carries a disk ||1 constituting a closure for this end of the casing.

The electrical current is supplied from a source of energy not shown in the drawings through a cable ||9 which is attached of the casing ||5. Another cable ||8 causing the return flow of the electrical current to the source of electrical energy is attached to an outerl surface of the casing |08.

A conducting cable |20 has an end which is attached to an inner surface of the casing ||5 adjacent the cable ||9. The cable |20 is situated Within the casing ||5 and the opposite end of the cable |20 is attached to a sleeve |2| made of a non-magnetic metal and mounted upon a flange |22. The annular flange |22 is carried by the bent portion 89 of the casing 88 and constitutes a part of this casing.

A coiled spring |23 is situated within the casing ||5. One end of the spring |23 presses against a supporting piece l|24 which is in contact with the adjacent end of the support 82. The supporting piece |24 is surrounded by the flange |22 and is in contact with the edges of the flange 89.

The closure disk ||1 comprises a central annular opening which is surrounded by a tubular portion |25. A hollow bolt |26 is screwed into the ange |25 and is provided with a suitable handle |21. o

One end of the coiled spring |23 is in engagement with the supporting member |24, while the opposite end of the spring is in contact with the bolt |26.

Cooling water is supplied to thechamber 9| of the casing 9 0 through two tubes |28 and |29 situated concentrically one within the other. The interior of these tubes is connected by suitable passages with the chamber 9|. The cooling water may be supplied through the annular interior of the tube |28 and removed through the interior of the tube |29, or vice versa.

The electrical current supplied by the source of electrical energy flows through the cable H9, the casing ||5 and the cable |20 to the sleeve |2|. Since the sleeve |2| is conductively connected with the flange |22, the electrical current will flow through the ilange |22, the casing 80, the block 0l, the support 82 and the heating rod 8G. The current leaving'the heating rod 80 will iiow through the support 8|, the block 83, the casing 80, the sleeve |05, the flange |04, the cover 99, and the casing 98. 'I'he current will leave the furnace through the cover |00, the casing |08 and the cable HS.

As shown more clearly in Figure 6 of the drawings, the casing 32 consists of corrugated metallic sheets held in place by rings |30 and |3| which are insulated in relation to the casing 98. These rings are supported by several rollers |32 and |33 which carry the central portion of the furnace. The furnace is oscillated by an annular toothed ring i3d which is insulated in relation to the casing 0i? and which is driven by an electromotor 35 through the medium oi a suitable transmission gear.

The casing QS is also surrounded by rings |35 and i3?. Transverse beams |38 and |39 interconnect the rings |36 and |31 and serve as a framework for a door |40 which is used for inserting the material to be treated into the interior of the furnace and for removing such material after it has been treated.

Figure 8 illustrates a furnace having an outer casing |50 which consists of a magnetic metal such as steel. The lining |5| of the furnace consists of the usual refractory material and is surrounded by a casing |52 which consists of a nonmagnetic metal such as copper. The copper casing |52 and the outer steel casing |50 are separated from each other by an insulating layer |53. This construction is similar in all other respects to the one illustrated in Figs. l to 4 of the drawings. Due to the provision of the insulating layer |53, the electrical current ow- 40 ing through the casing |52 will not be transmitted to the outer casing |50, which is entirely insulated from the inner casing.

In the furnace illustrated in Figure 9 of the drawings, the non-magnetic metallic casing consists of a series of conductors, such as conducting rods or strips |60 which are connected in parallel with each other by rings |6|, one of which is shown in the drawings. The conductors |60 and the rings |6| are all made of copper or other non-magnetic metal and are covered by a casing |62 consisting of steel or the like.

In the hereinabove described examples for the realization of furnaces according to the present invention, the displacement of the furnace around its axis is an oscillation. This displacement is possible due to the flexibility and the sufcient length of the cables, but it is obvious that the displacement around the axis of the furnace may be also a complete rotating motion. Convenient known means such as brushes or sliding contacts may be used for this purpose.

What is claimed is:

l. An electrical furnace, comprising a heating resistance, a casing for the material to be treated, said casing surrounding said resistance and comprising an envelope consisting of a nonmagnetic conducting metal, another metallic envelope surrounding the first-mentioned casing and conductively connected therewith, and means rmly interconnecting the two envelopes, means conductively connecting one end of said resistance to a source of electrical energy, means conductively connecting the opposite end of said resistance with the adjacent end of the casing,

and means conductively connecting the other end of the casing with said source of electrical energy, whereby the casing is connected in series with said resistance and constitutes a part of the electrical circuit which includes said source of electrical energy and said resistance.

2. An electrical furnace, comprising a heating resistance, a casing for the material to be treated, said casing surrounding said resistance and comprising an envelope consisting oi a non-magnetic conducting metal, another metallic envelope surrounding the Erst-mentioned envelope, an insulating layer separating the rst mentioned envelope from the second-mentioned envelope, and means firmly interconnecting the two envelopes, means conductively connecting one end of said resistance to a source of electrical energy, means conductively connecting the opposite end of said resistance with the adjacent end of the first-mentioned envelope, and means conductively connecting the other end oi' the rst-mentioned envelope with said source of electrical energy, whereby the first-mentioned envelope is connected in series with said resistance and constitutes a part of the electrical circuit which includes said source of electrical energy and said resistance.

3. An electrical furnace, comprising a heating resistance, a casing for the material to be treated, said casing surrounding said resistance and comprising an envelope consisting of a plurality of interconnected rods of a non-magnetic conducting metal, another metallic envelope surrounding the first mentioned envelope, and means firmly interconnecting the two envelopes, means conductively connecting one end of said resistance to a source of electrical energy, means conductively connecting the opposite end of said resistance with the adjacent end of the iirstmentioned envelope, and means conductively connecting the other end of the first-mentioned envelope with said source of electrical energy, whereby the first-mentioned envelope is oonnected in series with said resistance and constitutes a part of the electrical circuit which includes said source of electrical energy and said resistance.

4. An electrical furnace, comprising in combnation a heating resistance, a casing comprising a cylindrical furnace lining adapted to contain the material to be treated and surrounding said resistance, an envelope of a non-magnetic conducting metal containing said furnace lining, and another metallic envelope surrounding the .first-mentioned envelope and conductively connected therewith; means conductively connecting one end of said resistance to a source of electrical energy, means conductively connecting the opposite end of said resistance with the adjacent end of the casing, and means conductively connecting the other end of the casing with said source of electrical energy, whereby the casing is connected in series with said resistance and constitutes a part of the electrical circuit which includes said source of electrical energy and said resistance.

5. An electrical furnace, comprising in combination a heating resistance, a casing comprising a cylindrical furnace lining adapted to contain the material to be treated and surrounding said resistance, an envelope of a. non-magnetic conducting metal containing said furnace lining, another metallic envelope surrounding the iirstmentioned envelope, an insulating layer separating the first-mentioned envelope from the sec- Cil ond-mentioned envelope, and means rmly interconnecting the two envelopes and the lining, means conductively connecting one end of said resistance to'a source of electrical energy, means conductively connecting the opposite end of said resistance with the adjacent end of the rstmentioned envelopeI and means conductively connecting the other end of the first-mentioned envelope with said source of electrical energy, whereby the .first-mentioned envelope is connected in series with said' resistance and constitutes a part of the electrical circuit which includes saidy source of electrical energy and said resistance.

6. An electrical furnace, comprising a heating resistance having thef'orm of an elongated rod a conducting support ilrmly holding one end of said rod, another conducting support carrying the opposite end of said rod, conducting means connected with the second-mentioned support for permitting a movement of the`secondmen tioned support in a predetermined direction when said rod is expanded, conducting means connected with the first-mentioned means for moving the second-mentioned support on the opposite direction when said rod is contracted, means conductively connecting the second-mentioned means with a source of electrical energy a casing surrounding said rod and comprising an envelope consisting of a non-magnetic conducting metal, another envelope surrounding the first-mentioned envelope and consisting of a magnetic metal, means conductively connecting the mst-mentioned support with the first-mentioned enevelope, another casing supporting the rst mentioned means and insulated therefrom, the second-mentioned casing being conductively connected with the first-mentioned envelope, means conductively connecting the second-mentioned casing with said source of electrical ener'gy, and means connected with the second-mentioned envelope for turning the first-mentioned casing about the axis of said rod.

7. An electrical furnace, comprising a heating resistance having the form of an elongated rod,

a conducting support firmly holding one end of said rod, another conducting support carrying the opposite end of said rod, conducting means connected with the second-mentioned support for permitting a movement of the second-mentioned support in a predetermined direction when said rod is expanded, conducting means engaging the second-mentioned support for moving the same in the opposite direction when said rod is contracted, a casing surrounding said rod and comprising an envelope consisting of a non-magnetic conducting metal, and another envelope consisting of a non-magnetic conducting metal and conductively connected with the first-mentioned envelope, another casing supporting the first-mentioned means and conductively connected therewith, means conductively connecting the first-mentioned casing with the rstmentioned support, means conductively connecting a source of electrical energy with the second-mentioned envelope, means conductively connecting the second-mentioned casing with said source of electrical energy, and means connected with the first-mentioned envelope for turning the rst-mentioned casing about the axis of said rod.

8. A rotary electrical furnace, comprising a substantially horizontal heating resistance, a

substantially horizontal casing for the material to be treated, saidcasing surrounding said resistance and comprising an envelope consisting of a non-magnetic conducting metal, another metallic envelope surrounding the first-mentioned envelope and conductively connected therewith, and means interconnecting the two envelopes; means conductively connecting one end of 'said resistance to a source of electrical energy, means conductively connecting the opposite end of said resistance with the adjacent end ofthe casing, means conductively connecting the other end of the casing with said source of electrical energy, and insulated means engaging said casing for rotating it around said resistance.

BLAISE COUSTE'IX.