CA1216617A - Metal melting and melt heat retaining furnace - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE:

A metal melting furnace comprising two horizontally interspaced furnace vessels each forming a melt-containing chamber and each having a side wall facing the side wall of the other furnace and an opening in its side wall opening from its chamber and horizontally aligned with the opening of the side wall of the other furnace. An inductor is positioned between the side walls and comprises a block of ceramic having opposite ends: abutting the outsides of the side walls and a transverse through-hole and two horizontal through-holes straddling the transverse through-hole and having ends open to said chambers so the latter intercommunicate. An inductor core provided with an energizing coil has a leg extending through said transfer hole.

Description

The present invention relates to a metal melting and melt heat retaining furnace.
Channel-type induction furnaces are used for the melting and melt heat-retaining of metals, such as aluminum and aluminum alloys, an example being shown by the Fredrickson et at Patent United stated patent 3,618,9]7, issued on November 9, 1971.
Each furnace vessel requires its own channel-type inductor, used for both melting and heat retaining when out-lo put of melt is interrupted. The inductor is conventionally positioned in the furnace bottom in the hottest environment around the furnace, and during such periods it must be continuously force-cooled, its channel containing a continuous flow of melt at such times.
According to the present invention there is provided a metal melting furnace comprising two horizontally inter-spaced furnace vessels each forming a melt-containing chamber and each having a side wall facing the side wall of the other furnace and an opening in its side wall opening from its chamber and horizontally aligned with the opening of the side wall of the other furnace, and an inductor positioned between said side walls and comprising a block of ceramic having opposite ends abutting the outsides of the side walls and a transverse through-hole and two horizontal through-holes straddling the transverse through-hole and having ends open to said chambers so the latter intercommunicate, and an inductor core provided with an energizing coil having a leg extending through said transfer hole.
The inductor between the two furnace vessels can be shut down during periods when melt heat retaining only is required, because the two furnace vessel roofs mount on their undersides heating means of low energy requirement, as compared to that required for the inductor during melting, but sufficient for melt heat retaining for an adequate time.
US During melting the single inductor provides melting for , I

both furnace vessels.
Preferably, the inductor is removable for replacement when required, its ends superably abutting the interfacing side walls of the two furnace vessels, one of the furnace vessels being horizontally movable towards and from the other and releasable means being provided for forcing and holding the two furnace vessels together with the inductor in effect sandwiched between the two furnace vessels. Separation of the furnace vessels permits removal of the inductor.
Preferred embodiments will now be described as examples without limitative manner having reference to the attached drawings, wherein:
Fig. 1 is a top plan view of one example of the new furnace.
Fig. 2 is a side elevation view as indicated by the Line II-II in Fig. 1.
Fig. 3 is a horizontal cross section taken on the Line III-III in Fig. 2.
Fig. 4 is a vertical cross section taken on the Line IV-IV in Figs. 1, 2 and 3.
Fig. 5 is a vertical section of a second example of the new furnace, the inductor being shown in side elevation.
Fig. 6 is a top plan view showing how three inductors can be used to accommodate a 3-phase current supply, for example.
Fig. 7 in elevation shows a core and coil assembly for the Fig. 6 arrangement.
Fig. 8 is a top plan view and shows how the three -~LZ~L6~

1 inductors can be superably integrated as a unit for easy 7 handling.
3 Fig. 9 is a side elevation of Fig. 8; and 4 Fig. 10 schematically shows by top views how one or a number of thy inductors can be optionally interconnected 6 into assemblies of differing powers for use between the two 7 furnace vessels.
8 In the first example shown by Figs. 1 through 4, the 9 two horizontally interspaced vessels 1 and 1' are identical except that the furnace vessel 1 has near its top a tapping 11 hole 2 for the melt, this being unnecessary for the furnace 12 vessel 1'. Each furnace vessel has a sheet steel shell, 3 and 13 3' respectively, and a refractory ceramic lining 4 and 4' 14 respectively, the linings enclosing chambers 5 and 5' respect-lively.
16 The furnace vessels have interfacing vertical side 17 walls and the furnace inductor 6 is positioned between these 18 side walls and comprises a single, integral, block 7 made of 19 a ceramic having adequate refractory properties and, in addition, high mechanical strength, particularly in compression.
21 The block 7 is substantially a parallelepipedic block having 22 two horizontal longitudinal through-holes 8 and 9. The two 23 interfacing vertical side walls, of the furnace vessels has 24 an opening 10 and 10' respectively, these openings being horizontally aligned with each other. The inductor block 7 has 26 its ends superably abutting the outsides of these vertical 27 side walls, its two through-holes 8 and 9 opening through the 28 openings 10 and 10' and placing the two chambers 5 and 5' in 29 intercommunication with each other. There is in effect, a hydraulic interconnection between the two chambers. The inductor 1 block 7 also has a vertical cylindrical thrill 15 which

2 is straddled by the two horizontal holes 8 and 9, the hole 13

3 therefore extending transversely with respect to the two

4 horizontal holes. A transformer or inductor core 12 has a leg 11 extending vertically through the vertical hole 15 of the 6 block, and this leg is surrounded by the primary winding or 7 coil 13. The balance of the core 12 extends around the out-8 side of one side of the block 7, as shown by Fig. 4, and it 9 as well as all outside surfaces of the inductor block 7 are encased by refractory thermal insulation 14. This retards 11 the escape of heat from the inductor block and inductor core.
12 During melt heat retaining periods, when the inductor is 13 unpowered or shut down, this thermal insulation assists in 14 maintaining molten the melt in the inductor's channels. As described below the furnace is provided with other relatively 16 low-powered heating means for retaining the melt molten in the 17 two furnace vessels during such periods.
18 The weight of the inductor 6 is supported by brackets 19 16 extending from the outsides of the two furnace vessels so that the inductors weight need not be carried solely by 21 frictional engagement between the inductor's ends and the 22 outsides of the two vertical walls of the furnace vessels. The 23 furnace vessel 1' can be carried on a horizontally running 24 carriage, so that it is movable towards and away from the other furnace vessel. Means are provided for releasable 26 forcing and holding the two furnace vessels together so that 27 the inductor block can be tightly sandwiched between the 28 furnace vessels, this means being illustrated as comprising 29 upper and lower tie bolts or tension rods 17 and 18 having their ends inserted in lugs 17 attached to the outsides of the l furnace vessels 1 and 1' respectively, and provided with nuts 2 20. When the inductor is in position, supported by the 3 brackets 16, the nuts 20 are screwed-up so the two furnace 4 vessels are pulled together with the ends of the inductor block forceable pressed against the vertical side walls of 6 the two furnace vessels with adequate force to form a seal 7 preventing escape of melt from the inductor blokes horizontal 8 thrills 8 and 9.
9 The furnace vessel 1 is provided with a normally I closed drain hole in its bottom, which can be opened to empty if the entire furnace free from a melt when the furnace is to 12 be put out of service for removal of the inductor 7. For this 13 the nuts 20 are loosened so that the furnace vessel l' can be 14 run away from the other furnace vessel enough to free the inductor 6. Then the inductor can be lifted away by a crane 16 for possible replacement by a new or reconditioned corresponding 17 inductor. When loosened the inductor will not fall because of 18 its support by the brackets 16.
19 During normal operations of the new furnace the furnace vessel l' it charged with solid metal and tapped from 21 the furnace vessel l via its tap hole 2. An interruption in 22 the charging or tapping for any reason requires holding of 23 the melt in the furnace vessels and the inductor channels 8 24 and 9. The furnace must then function only as a heat retaining furnace. In prior art furnaces this has been done by using 26 the channel-type inductor but the inductor, normally connected 27 to the bottom of the furnace in prior art furnaces, is 28 subjected to excessive heating, the hottest part of the melt 29 being in the inductor's channels. This has required the inductor to be force-cooled as by water cooling or the like.

-5-1 Contrasting with the above with this new furnace 2 the inductor is completely shut-down, or unpowered, when heat 3 retaining only is required.
4 for heat retaining each one of the furnace vessels 1 and 1' is provided with a removable roof 22 and 22'

6 respectively made of sheet metal with a lining of heat-

7 insulating refractory. The underside or bottoms of the roofs

8 have electric resistors 23 and 23', respectively, connected

9 to them and which can optionally be electrically powered.
They are powered during any heat retaining period.
11 Each of the two electric resistors may have a maximum 12 power substantially less than that of the inductor 6, preferably 13 less than 5% thereof, and a 15~ value can be considered as a 14 maximum. The heat output provided by the two resistors 23 and 23' should be adequate, with the inductor 6 unpowered, to 16 keep the melt in the two furnace vessels in a molten state for 17 at least several hours and preferably for several days, during 18 which time the inductor is idle and free from excessive 19 heating. The inductor's two horizontal through-holes or channels are straight and hydraulically interconnect the two 21 melts in the furnace vessels, so the melt in these channels 22 is not apt to solidify. The heat is largely retained by the 23 thermal insulation 14 surrounding the inductor.
24 Excepting for a complete shut down of the furnace, the melt level in the furnace should always be high enough 26 so that the inductor's two straight through-holes or channels 27 8 and 9 are kept filled with melt, the secondary circuit then 28 being formed in the melt as a loop extending through the two 29 straight channels and looping at their ends in the melts in the two furnace vessels. Both covers 22 and 22' can be swung up 1 and out of the way by any suitable mechanism, the mechanisms 2 illustrated by Fits. 1 and 2 therefore requiring no specific 3 description.
4 Charging of the new furnace with solid metal is normally done by removing tune roof of the furnace vessel 1' and 6 charging directly in its chamber 5'. When the melt reaches up 7 to the tapping hole opening 2 in the vessel, additional charging 8 results in molten metal running out of the tapping hole 2.
g The tapped molten metal may be used directly or can be fed to a special heat retaining furnace designed only to retain the 11 heat of the melt, and from which the melt is drawn as needed.
12 This special furnace is not shown.
13 When such a special heat retaining furnace is not 14 available for storage of the melt, the new furnace may be designed as shown by Fig.5.In this case a furnace vessel 25 is 16 used, having a substantially larger capacity than the furnace 17 vessel 1 of Figs. 1 and 2. This furnace vessel 25 also has a 18 heat-insulating cover 26 on the bottom side of which an 19 electric heat resistant element 21 is connected, for use as described before. Because of the larger size of this furnace 21 vessel 25 it is designed to provide a furnace chamber 28, 22 defined in the upper direction by the cover 26. By means of 23 a vertical partition wall 30', this chamber 28 is divided into 24 two compartments 29 and 30 arranged adjacent to each other.
The only way in which a melt in the compartment 29 can 26 communicate with the compartment 30 is by flowing over an 27 overflow edge 32 of the partition 30'.
28 With the melting operation substantially as described 29 before the melting proceeds so that eventually the surface level 34 in the compartment 29 is flush with the level 35 in the 1 chamber 25. When the charging continues molten metal flows 2 over the overflow edge 32 and is collected in the compartment 3 30, its surface level 33 then rising. In this way the furnace 4 design provides for a replacement of the conventional metal heat retaining furnace, the furnace compartment 30 functioning 6 both as a replacement for the furnace vessel 1 of Figs. 1 and 2 7 while functioning as a special heat retaining furnace such as 8 is normally separate from the melting furnace. The compartment 9 30 can accommodate at least twice as much and preferably three times as much melt as the compartment 29. The vertical 11 distance between the overflow edge 32 and the furnace vessel 12 cover 26 is preferably smaller than 40~ of the average height 13 of the compartment 28. The compartment 30 containing the melt 14 is provided with a controllable tapping hole 36 at its bottom.
The compartment 30 can accommodate at least twice as much, 16 preferably three times as much molten metal as the compartment 17 29 and which is functioning like the furnace vessel 1 of 18 Fig. 2. This compartment 29 communicates via the inductors 19 longitudinal or horizontal channels with an opening 31 in the I furnace vessel 25 and of course with the opening 10' in the 21 furnace vessel 1'.
22 In general the height of the petition 30 and therefore 23 the level of its overflow edge 32 should be such that the 24 compartment chamber 29 has an adequate volume so that when 2j containing a melt it cooperates with the furnace vessel 1', 26 in the manner previously described.
27 This special vessel is also provided with a roof 26 28 to the bottom of which the heat retaining electric resistance 29 heating means is connected as shown at 21, for use during heat-I retaining when the inductor is not operating.

Lo 1 The motor 37 of an air-cooling fan as shown in Fig. 5 2 for the purpose of cooling the inductor 6 should this be 3 required.
4 Because the inductor hock is externally parallelepepdic it adapts itself to combinations with other corresponding 6 inductors having such inductor blocks.
7 For example, Fig. 6 shows how three of the inductors 8 6 with their straight channels 38 and 39, 40 and 41, and 42 and 9 43 respectively, can be held together as an integrated unit in side-by-side arrangement, using transverse tension rods or, 11 tie-bolts 44 as shown in Figs. 8 and 9 which also illustrate 12 this modification. A layer of ceramic felt (not shown) can 13 be positioned between the inductor block. The straight 14 inductor channels are shown at 38 to 43 in Figs. 6 and 9. With the three inductors integrated they can be positioned between 16 furnace chambers comparable to those shown at 1 and 1' in Figs.
17 1 and 2, with appropriate vertical side wall openings.
18 Fig. 7 serves to show how using this multiplicity 19 Of inductors the cores and windings can be made as a unit insertable into all three of the vertical or transverse holes 21 of the inductor blocks, the yoke 12 shown at the bottom of 22 Fig. 9 being then integrated with this core assembly.
23 Fig. 10 shows how using this integrating or module 24 concept -the new inductors of the present invention can be used singly or in multiples to provide for differing power inputs 26 ranging from 130 ow to 750 ow. In all cases the inductors are 27 individually the same, thus reducing manufacturing costs and 28 replacement costs. This versatility follows from the unique 29 shape of the inductors.

1 In the case of the first example the furnace and all 2 its parts is symmetrical about a vertical plane IV-IV indicated 3 in Figs. 1 and 2. The furnace operation therefore is uniform 4 as to both furnace vessels. This plane cuts through the center of the inductor.
6 In all examples the side wall openings for the 7 inductors horizontal through holes are near or at the bottoms 8 of the furnace vessel chambers.

lo I

Claims (9)

WHAT IS CLAIMED IS:

1. A metal melting furnace comprising two horizontally interspaced furnace vessels each forming a melt-containing chamber and each having a side wall facing the side wall of the other furnace and an opening in its side wall opening from its chamber and horizontally aligned with the opening of the side wall of the other furnace, and an inductor positioned between said side walls and comprising a block of ceramic having opposite ends abutting the outsides of the side walls and a transverse through-hole and two horizontal through-holes straddling the transverse through-hole and having ends open to said chambers so the latter intercommunicate, and an inductor core provided with an energizing coil having a leg extending through said transfer hole.

2. The furnace of claim 1 in which the opposite ends of the inductor's said block seperably abutt the outsides of said side walls, one of said furnace vessels is horizontally movable towards and from the other furnace vessel so that the inductor is removable, and the furnace has means for releasably forcing and holding the furnace vessels together with the inductor between the side walls.

3. The furnace of claim 1 in which one of said furnace vessels has a removable cover for charging the furnace vessel and has heat retaining heating means for a melt in the furnace vessel, and the other furnace vessel has a cover and heat retaining means for a melt therein, said inductor hydraulically interconnecting the two furnace vessels so that the melt levels in the two furnaces remains the same, and said other furnace vessel has a tapping hole near its top.

4. The furnace of claim 1 in which at least one of said furnace vessels has a cover provided on its bottom with a heating means adapted to retain the heat of a melt in that furnace vessel for a period of time when said inductor is unpowered.

5. The furnace of claim 1 in which said furnace vessels and inductor are symmetrically arranged.

6. The furnace of claim 1 in which at least one of said furnace vessels has a tapping hole positioned near its top.

7. The furnace of claim 1 in which one of said furnace vessels is substantially larger than the other furnace vessel and forms a larger melt-containing chamber divided into two compartments by a vertical wall extending horizontally across the chamber and forming on one side a small compartment to which the said opening in the furnace vessel's said wall opens, the wall extending vertically to an overflow ledge at a level near the top of the furnace vessel over which a melt from the other furnace vessel can flow during progressive melting in the other furnace, said wall forming on its other side a large compartment for receiving the melt from the small compartment, at least the large compartment having heat means for retaining the heat from a melt therein.

8. The furnace of claim 1 in which a plurality of said inductors are positioned between said furnace vessels.

9. The furnace vessel of claim 1, 2 or 7, in which said inductors are integrated into a unit by transversely extending tension tie bolts.