US3485928A - Inductor for low-frequency induction furnace - Google Patents

Description

Dec. 23. 1989 mos nc mAw ET AL 3,485,928 INDUCTQ FQR LOW-FREQUENCY INDUCTION FURNACE Filed Nov. 15., 196T 2 Sheets-Sheet 1 {I HI [I INVENTORS f/IRASI/l mum/9am RaKuRd Maw/mam yum/m aucu/ BY 7 M ATTORNEYS Dec. 23, 1969 HIROSHI ICHIKAWA ETAL 3,485,928

INDUCTOR FOR LOW-FREQUENCY INDUCTION FURNACE Filed NOV. 15, 1967 2 Sheets-Sheet 2 INVENTORS fl/IQAS/l/ mil/449M RJ/(Ukfl [Mal/Mall! yam/M nae/ll BY 0W7 71W ATTORNEYS United States Patent 3,485,928 INDUCTOR FOR LOW-FREQUENCY INDUCTION FURNACE Hiroshi Ichikawa, Rokuro Kawanishi, and Yutaka Ouchi, Tsuchiura-shi, Japan, assignors to Hitachi Cable, Ltd., Tokyo, Japan, a corporation of Japan Filed Nov. 15, 1967, Ser. No. 683,269 Claims priority, application Japan, Feb. 3, 1967, 42/6 603 Int. Cl. Hb 5/14 US. Cl. 1329 1 Claim ABSTRACT OF THE DISCLOSURE An inductor for low-frequency induction furnaces and a method of constructing such an inductor, in which the outer casing of the inductor is split into halves and the outer casing sections so split are then mechanically jointed together to facilitate accurate centering of an iron core With respect to core receiving openings. In the method, the iron core is inserted in the core receiving openings in one outer casing section packed with a refractory material or refractories and then the other outer casing section which may be preliminarily packed or may be later packed with the refractory material is coupled to the opposite outer casing section to complete the construction of the inductor.

BACKGROUND OF THE INVENTION This invention relates to inductors for low-frequency induction furnaces which are used as melting furnaces, melt reserving furnaces and the like forming part of casting apparatus for metals such as iron, copper and aluminum, and relates also to methods of constructing such inductors.

Recently, channel type low-frequency induction furnaces have been increasingly employed as melting furnaces or melt reserving furnaces for use in casting apparatus, especially in semi-continuous or fully continuous casting apparatus for steel, aluminum, copper and other metals. The channel type low-frequency induction furnace is preferred by virtue of its simple structure, satisfactorily high workability, high safety, ease of maintenance and improved casting economy by use of the same.

The channel type low-frequency induction melting furnace has a structure as, for example, illustrated in FIG. 1. The furnace comprises a body 1 which is rotatably supported on support blocks 3 by means of rollers 2, and two inductors provided on each side of the furnace body 1. A hydraulic cylinder 7 is operatively connected with the furnace body 1 to cause tilting movement of the furnace body 1 so that a molten metal 4 in the melting chamber 5 can be discharged through a gate 6 to be poured through, for example, a melt transfer trough into a melt reserving furnace (not shown). The inductor 10 priorly employed in the furnace of this kind is shown in enlarged in FIG. 2. The inductor 10 comprises an iron core 11 having two coil-receiving legs, a coil 12 Wound about each leg of the iron core 11, protective cylinders 13 surrounding the coils 12, a mass of refractory material 14 surrounding the protective cylinders 13, and an outer casing 15.

Melting channels 16 run through the mass of refractory material 14.

Generally, the inductor 10 is constructed in such a manner that the iron core 11 equipped with the coils 12, the portions of the refractory material 14 integral with the protective cylinders 13, and the portion of the refractory material 14 integral with the outer casing are separately prepared, and then the legs of the iron core 3,485,928 Patented Dec. 23, 1969 11 equipped with the coils 12 are inserted into the protective cylinders 13. In an exceptional case, the coils 12 may be prepared integrally with the protective cylinders 13. When, however, the inductor 10 has a large capacity, for example, a l,250-kva. rating with a three-phase alternating current, the prior inductor structure has been encountered with a difficulty that insertion of the legs of the iron core 11 into the protective cylinders 13 can not be smoothly attained. Centering of the legs of the iron core 11 with respect to the protective cylinders 13 is a matter of difificulty when these legs are simultaneously inserted into the corresponding protective cylinders 13 as shown in ,FIG. 2. The insertion of the legs of the iron core 11 has frequently given rise to injury of the cylinders 13 or coils 12, and in an extreme case, imparted a damage to the refractory material 14. Since the refractory material 14 is formed from, for example, a material consisting of 34.5% SiO 60.5% A1 0 and 5% water, any impact imparted thereto by the iron core 11 will induce cracks in the refractory material 14, with the result that the inductor 10 must be reconstructed, which doubles the cost of inductor construction. Further, troublesome work is required to adjust the relative positions of the coils 12 and the protective cylinders 13 to es ablish a concentric relationship therebetween after the iron core 11 has been inse tted into the protective cylinders 13, and thus improvements in the construction of the inductor have been demanded.

SUMMARY OF THE INVENTION It is therefore the primary object of the present invention to provide a novel and improved inductor having such a structure that the legs of an iron core can be extremely easily inserted into protective cylinders embedded in a mass of refractory material.

Another object of the present invention is to provide an inductor having such a structure that the legs of the iron core when inserted into the protective cylinders can be easily centered with respect to the protective cylinders, and to provide a method of constructing such an inductor.

A further object of the present invention is to provide a novel and improved inductor having such a structure that the legs of the iron core when inserted into a refractory material may not in any way injure the protective cylinders, coils and refractory material, and to provide a method of constructing such an inductor.

Another object of the present invention is to provide to method of constructing an inductor which obviates any need for the reconstruction of the inductor.

Still another object of the present invention is to provide a method of easily, efiiciently and inexpensively constructing an inductor, and an inductor constructed thereby.

The above and other objects, advantages and features of the present invention will become apparent from the following description with reference to the accompanying drawings:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic elevational view showing an exemplified form of a low-frequency induction furnace.

FIG. 2 is an enlarged cross-sectional view showing an exemplified form of the prior inductor structure, as pointed out above, used in the low-frequency induction furnace.

FIG. 3 is a partly sectional plan view of the inductor embodying the present invention.

FIG. 4 is a schematic View showing the external appearance of an iron core equipped with coils employed in the inductor shown in FIG. 3.

3 DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with one aspect of the present invention, there is provided an inductor for a low-frequency induction furnace comprising an iron core equipped with coils wound about legs of said core, a mass of refractory material disposed to surround said coils, and an outer casing; characterized by the fact that said outer casing is split into halves along the aligned transverse center lines of insertion openings for receiving therein the legs of said iron core equipped with said coils, and means are provided to mechanically join the two sections of said outer casing.

In accordance with another aspect of the present invention, there is provided a method of constructing an inductor for a low-frequency induction furnace comprising an iron core equipped with coils wound about legs of said core, a mass of refractory material disposed to surround said coils, and an outer casing; characterized by the steps of splitting said outer casing into halves along the aligned transverse center lines of insertion openings for receiving therein the legs of said iron core equipped with said coils, providing means on the jointing portions of the half-split outer casing sections for effecting mechanical jointing therebetween in a later step, preliminarily packing the refractory material in each of the halfsplit outer casing sections in a manner to define therein slots for forming said core receiving openings, inserting and fixing the legs of said iron core equipped with said coils in the slots of one of said outer casing sections with or without interposition of protective cylinders therebetween, then bringing the other said outer casing section packed with the refractory material into jointing contact with said first-mentioned outer casing section, and firmly jointing both said outer casing sections together.

In accordance with a further aspect of the present invention, there is provided a method of constructing an inductor for a low-frequency induction furnace comprising an iron core equipped with coils wound about legs of said core, a mass of refractory material disposed to surround said coils, and an outer casing; characterized by the steps of splitting said outer casing into halves along the aligned transverse center lines of insertion openings for receiving therein the legs of said iron core equipped with said coils, providing means on the jointing portions of the half-split outer casing sections for effecting mechanical jointing therebetween in a later step, preliininarily packing the refractory material in one of the halfsplit outer casing sections in a manner to define therein slots for forming said core receiving openings, inserting and fixing the legs of said iron core equipped with said coils in the slots of said outer casing section through protective cylinders interposed therebetween, bringing the other said non-packed outer casing section into jointing contact with said first-mentioned outer casing section, firmly jointing both said outer casing sections together, and then packing the refractory material into said nonpacked outer casing section.

In the above description, the word iron core equipped with coils is used to mean the fact that coils are disposed about an iron core, and is not in any way intended to limit the manner of coil mounting on the iron core. The coils may be preliminarily mounted on the legs of the iron core or may be mounted on the legs of the iron core after the iron core has been assembled. The coils may have a capacity of, for example, 120 kva., 300 kva. or 1,000 kva., while the iron core may be of single leg type or two leg type depending on a single-phase or three-phase current.

The outer casing which is split into halves is commonly made from a plate of iron or steel which may be singly used or used in combination with fire bricks. The halfsplit outer casing sections may be mechanically jointed together by providing a tongue and a groove at the jointing portions thereof and fastening them by means of bolts, or by forming flanges at the jointing portions and fastening them by means of bolts, or by welding an iron piece to one of the outer casing sections and fastening them at the jointing portions by means of bolts. The above jointing means may be provided on any side, either the inner side or the outer side, of the outer casing sections. In this connection, it is most practical to fasten the half-split outer casing sections by bolts so as to facilitate disassembling and reassembling of the outer casing for the repacking of the refractory material resulting from termination of its service life and for the reconstruction of the inductor.

The protective cylinders are disposed to surround the coils because the coils must be sufficiently thermally isolated from the refractory material which is heated to high temperatures, and in order to additionally protect the coils against heat, a cooling air passage concentrical with each coil is provided between the coil and the protective cylinder. Special attention must be given so that the cooling air passage be uniform over the entire periphery of the coil because non-uniformity of the cooling air passage results in non-uniform cooling by the cooling air and may give rise to burn of the coil. The cooling air passage may, of course, be provided between the protective cylinder and the mass of refractory material. The cooling air passage may preferably have a transverse width of the order of 10 to 50 millimeters.

The coil may preferably be a winding of flat rectangular type wire of copper or a copper alloy wrapped above by a Class H insulating layer. The coil may preferably be spaced from the molten metal a distance of to millimeters when, for example, the metal to be melted is copper which is heated to about 1,200 C.

The overall size of the inductor varies depending on its capacity, and when, for example, used in combination with the iron core of two leg type, may have such a combination that the cylinders have an inner diameter of about 280 millimeters and are spaced a center-tocenter distance of about 630 millimeters, and the outer casing has a width, height and depth of 1,050 millimeters, 700 millimeters and 600 millimeters, respectively.

The coils may be easily maintained in concentrical relation with the protective cylinders by suitably adjusting the position of the legs of the iron core inserted into the protective cylinders by slightly moving the iron core in the vertical and horizontal directions. The adjustment of the position of the iron core relative to the protective cylinders may be made by means of bolts and nuts which are provided for fastening the iron core to the outer casing sections to firmly support the iron core in place. These bolts and nuts may be conventional ones commonly employed for the spacing adjustment purpose.

Referring now to FIGS. 3 and 4, a preferred embodiment of the present invention will be described in detail. In FIG. 4, there is shown an iron core 21 of two leg type which is preliminarily equipped with coils 22 and is adapted to be combined with a core segment 21B.

In FIG. 3, there is shown an inductor construction having an outer casing and a mass of refractory material suitable for accommodating therein the iron core 21 equipped with coils 22 as shown in FIG. 4. In constructing the inductor according to the invention, half-split outer casing sections 25 and 30 are first prepared. The boundary between these two outer casing sections 25 and 30 registers with the aligned transverse center lines of insertion openings 46 for receiving therein the legs of the iron core 21 equipped with the coils 22. The outer casing section 25 is substantially shaped to the form of a box and has a reinforcing rib 26 extending thereabout. At each jointing portion 29 of the outer casing section 25 to be jointed to the corresponding portion 34 of the other outer casing section 30, a piece of iron plate 27 is firmly fixed as by a weld 28. The outer casing section 30 is substantially shaped to the form of a frame and has a peripheral flange 31 and a reinforcing rib 33 extending about the body of the casing section 30.

The construction of the inductor is started with pack ing or filling of a mass of refractory material 41 in the outer casing section 25. The refractory material 41 is formed from a sillimanite refractory of clay-like nature consisting of, for example, 34.5% SiO 60.5% A1 and 5% water, and is packed in a manner to define iron core receiving slots 42 and melting channels 43 in the outer casing section 25. In each slot 42, a protective cylinder section 23 of refractory material is disposed. Then the legs of the iron core 21 equipped with the coils 22 as shown in FIG. 4 are inserted to lie in the protective cylinder sections 23, and the core segment 21B is fitted on the iron core 21. The outer casing section 30 is then placed on the outer casing section 25, and bolts 40 are used to fasten the iron pieces 27 tothe jointing portions 34 of the outer casing section 30. Thirty-eight bolts 40 having a diameter of 18 millimeters Were used-in practice for the fastening purpose. The iron core 21 equipped with the coils 22 (not shown in FIG. 3 for the sake of convenience) Whose legs are inserted in the protective cylinder sections 23 is securely fixed to the reinforcing ribs 26 and 33 of the respective outer casing sections 25 and 30 by means of adjustable bolts and nuts (not shown) so that the iron core 21 can be securely supported in proper position in the outer casing sections 25 and 30. Prior to the fixing of the iron core 21 to the reinforcing ribs 26 and 33, the remaining protective cylinder sections 24 may be provided to completely define the insertion openings 46 in order to facilitate the adjustment of the position of the iron core 21 by means of the bolts and nuts for the sake of attaining the concentric disposition of the coils 22 on the iron core 21 relative to the insertion openings 46, thereby improving the working efficiency.

Upon completion of the above adjustment step, another mass of refractory material 44 is packed or filled in the space in the outer casing section 30. The refractory material 44 is packed in a manner to define therein melting channels 47 which communicate with the aforementioned melting channels 43. Because of the fact that the protective cylinder sections 24 have already been disposed, the refractory material 44 can be packed to define iron core receiving slots 45 without in any way affecting the coils 22 lying in the openings 46. Bolt holes 32 are bored through the flange 31 so that bolts may be passed therethrough for securely fixing the inductor to the furnace body 1.

The embodiment described above has referred to a case in which the jointing iron pieces 27 are provided in the outer casing section 25, but it will be understood that the construction sequence is not limited to that described above and may be suitably varied without departing from the spirit of the invention. Such change in the construction sequence is allowable if it can improve the efiiciency of constructing the inductor.

It should be further noted that the boundary between the mass of refractory material 41 and the mass of refractory material 44 in FIG. 3 is provided merely for the sake of explanation, and in the packing or filling stage of the refractory material 44, these masses are brought into completely intimate contact with each other and there is actually no gap therebetween:

According to another embodiment of the invention, externally extending flanges may be formed at the jointing portions 29 and 34 in lieu of the iron piece 27 shown in FIG. 3 and may be fastened together by volts at the outside of the outer casing sections 25 and 30. According to this manner of construction, the refractory material 44 may be preliminarily filled in the outer casing section 30 instead of the final filling since the fastening by the bolts 40 can be made in the last stage of construction. This embodiment is convenient in that the protective cylinder sections 23 and 24 may be provided in a later stage of construction. In other words, the manner of construction may be such that the masses of refractory materials 41 and 44 are preliminary filled in the respective outer casing sections 25 and 30, the legs of the iron core 21 equipped with the coils 22 are inserted in the insertion openings 46, then the outer casing sections 25 and 30 are jointed together, and the position of the iron core is suitably adjusted to maintain the coils 22 in concentrical relation with the insertion openings 46.

As will be apparent from the above embodiments, the structure of the inductor according to the present invention and the method of constructing the same are advantageous in that the legs of the iron core can be remarkably easily inserted into the protective cylinders embedded in the mass of refractory material and the centering of the iron core legs with respect to the insertion openings after insertion of the former can be simply carried out. The invention is further advantageous in that there is utterly no possibility of injuring the refractory material or damaging the coils or protective cylinders during insertion of the legs of the iron core into the insertion openings formed in the mass of refractory material, and the inductor is free from any necessity for the reconstruction thereof resulting from the damage on those elements. Thus, the present invention as a whole provides a method of easily, efficiently and economically constructing an inductor.

According to the prior inductor structure and the method of constructing the same, damage to the protective cylinders, coils or refractory material has inevitably taken place in the stage of insertion of the legs of the iron core into the protective cylinders embedded in the mass of refractory material. In contrast to the above, the results of tests made by the inventors on a practical inductor constructed according to the present invention have proved that no damage whatsoever occurs during the construction and assembling of the inductor, and the time required for the construction can be reduced to one-half of the time priorly required. The construction time according to the invention can be reduced to about one-third of the priorly required construction time when the time required for the reconstruction of the inductor due to the damage of the nature as described above is taken into account. Thus, the invention makes possible about 40% reduction of the cost in an economical aspect.

Indirect effects derivable from the present invention include remarkable extension of the service life of the refractory material as well as the coils. The former effect is considered to be derived from the fact that no crack would develop during the construction of the inductor, while the latter effect is considered to be derived from the fact that the coils can be uniformly cooled by virtue of the accurate centering of the coils with respect to the insertion openings. The latter effect is also considered to be derived from the fact that wear of the coils proceeds uniformly according to the invention, whereas such wear of the coils in the prior structure is quite localized.

From the foregoing description, it will be appreciated that the present invention elucidates all the technical problems involved in inductors for low-frequency induction furnaces and discloses novel and improved technical means which effectively solves such technical problems to thereby yield a novel technical effect which cannot be attained by the prior inductor structure.

What is claimed is:

1. An inductor for a low-frequency induction furnace comprising an iron core having at least one leg with coils wound thereabout; an outer casing split into halves along a plane defined by a transverse center plane passing through at least one insertion opening formed therein for receiving a corresponding leg of the iron core equipped with coils; means for rigidly fixing the casing halves into an integral outer casing; a mass of refractory material packed into each half of the split casing in such a manner so as to define a melting channel and at least one 7 half-split iron core receiving slot aligned with a corresponding insertion opening; a half of a split protective cylinder embedded in each half-split iron core receiving slot between the slot and the wound coils of the corresponding leg of the iron core and having cooling air passages; wherein both split casing halves packed with the refractory material can be assembled into an integral conductor having a continuous melting channel of archshaped cross section at least over a portion of its length permitting efiicient construction with accurate centering of 10 the iron core.

References Cited UNITED STATES PATENTS JOSEPH V. TR-UHE, Primary Examiner L. H. BENDER, Assistant Examiner US. Cl. X.R.

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