JPS644075Y2 - - Google Patents

Description

[Detailed description of the invention] Generally, when metal materials with good wettability such as copper or aluminum are melted in a low-frequency or high-frequency induction furnace, a graphite crucible is often used as the melting chamber.

Such a graphite crucible induction furnace has conventionally been constructed as shown in FIG.

A graphite crucible 2 forming a melting chamber 1 is surrounded by back sand 3, and an induction coil 5 is spirally wound around the outer periphery of this crucible with a coil cement 4 interposed therebetween. 6
is a return path iron core provided outside the induction coil 5 along its axial direction, and is surrounded by the furnace frame 7.

A first antenna 8 is attached to the bottom surface 2a of the graphite crucible 2 in contact therewith, and this first antenna 8 penetrates through the back sand 3 and the bottom refractory material 9 and is connected to the lower furnace frame 7a. There is. As shown in FIG. 2, the first antenna 8 has a contact portion 11 formed by spirally winding a nichrome wire 10, and the center portion of the contact portion 11 extends downward.

Reference numeral 12 denotes a leak detection net wound around the inner periphery of the coil cement 4, and a second antenna 13 is attached to the lower part of the net. is connected to constitute a hot water leak detection mechanism.

In the graphite crucible induction furnace configured as described above, a metal material is put into the melting chamber 1, power is supplied from the power source to the induction coil 5 to generate alternating magnetic flux, and this alternating magnetic flux is transferred to the graphite crucible 2 and the melting chamber 1. The eddy current is induced by acting on the metal material, and the generated Joule heat heats and melts it. In addition, when the graphite crucible 2 cracks and leaks, and this reaches the leak detection network 12, the first antenna 8 and the second antenna 13 become electrically connected and the detector operates to detect the leak. The system detects the occurrence and stops the power supply.

However, in the conventional structure described above, as the graphite crucible 2 expands and contracts during melting, the first antenna 8 may gradually separate from the bottom surface 2a of the graphite crucible 2, making it impossible to detect a leak.

This is because the contact part 11 of the first antenna 8 has a configuration in which the nichrome wire 10 is spirally wound and is supported on the upper surface of the back sand 3. This is because the back sand 3 enters through the gap between the wires 10 and is gradually embedded in the back sand 3, making it impossible to establish electrical contact. Furthermore, since the first antenna 8 is made of a thin nichrome wire 10 wound spirally, it has a large surface area, and has the disadvantage of being susceptible to embrittlement due to thermal oxidation, resulting in poor reliability.

The present invention eliminates the above-mentioned drawbacks, and provides a graphite crucible type induction furnace that ensures the contact of the first antenna with the graphite crucible, reduces embrittlement due to thermal oxidation, and improves the reliability of leak detection. The purpose is to obtain.

An embodiment of the present invention will now be described in detail with reference to Figs.

A graphite crucible 2 forming a melting chamber 1 is surrounded by back sand 3, and an induction coil 5 is spirally wound around the outer periphery of this crucible with a coil cement 4 in between. A first antenna 8 is attached to the bottom surface 2a of the graphite crucible 2 in contact with the bottom surface 2a.

As shown in an enlarged view in FIG. 4, the first antenna 8 includes two plates 14, 14 made of a non-magnetic and heat-resistant metal such as stainless steel or a nickel-chromium alloy, a fulcrum shaft 15, and a connecting member. It is constructed by combining a bolt 16 and a nichrome wire 10.

The plate materials 14, 14 have an inverted L-shape consisting of contact pieces 14a and 14b, and a locking piece 14c is provided at the end of the bent piece 14b.
4b and 14b are arranged to face each other on the inside and to provide a space between them. Double-folded piece 14b, 1
A round bar-shaped fulcrum shaft 15 is interposed between the fulcrum shafts 4b, and the lower part of the fulcrum shaft 15 is held from both sides by locking pieces 14c to prevent it from falling. Bent portion 1 of plate materials 14, 14 located above fulcrum shaft 15
Bolts 16 are attached to 4d and 14d, and the two plates 14 and 14 are tightened and connected while maintaining the distance between the two bent portions 14d and 14d, and the contact pieces 14a and 1
4a is biased inward. The first antenna 8 is connected to the contact pieces 14a, 14
A is spread out, its upper surface is made flat, and it is supported on the upper surface of the back sand 3 so as to be in close contact with the bottom surface 2a of the graphite crucible 2, and set as shown in FIG. A nichrome wire 10 is connected to the bolt 16 of the first antenna 8, and its lower part passes through the back sand 3 and the furnace bottom refractory material 9 and is connected to the lower furnace frame 7a.

Therefore, in the graphite crucible induction furnace according to the present invention, the first antenna 8 is formed by two plates 1 having an inverted L shape.
4 and 14 are connected via the fulcrum shaft 15, and the contact piece 1
4a, 14a are always urged inward with the fulcrum shaft 15 as a rotational fulcrum, so even when the graphite crucible 2 expands and contracts, the contact pieces 14a, 14a remain on the bottom surface 2a. Reliably remains in contact. Further, since the contact pieces 14a, 14a are in the form of a flat plate, the back sand 3 does not enter through the gap unlike in the conventional spiral shape, and is not embedded, so that a reliable conductive state can be maintained.

Furthermore, since the inverted L-shaped plates 14, 14 have a smaller surface area relative to mass than conventional spiral structures, embrittlement due to thermal oxidation is less likely to progress, resulting in excellent reliability.

In the above embodiment, the bolt 16 is used as a means for connecting the two plate materials 14, 14, but the present invention is not limited to this, and the connection may be made by winding the nichrome wire 10, and the fulcrum shaft 15 The support is not limited to the structure in which the support is locked from both sides by the locking pieces 14c, 14c, but the nichrome wire 10
A structure may also be used in which the bolt 16 is wound around the bolt 16 and connected to the bolt 16.

As explained above, according to the present invention, the graphite crucible-shaped induction wire ensures the contact of the first antenna with the graphite crucible, reduces embrittlement due to thermal oxidation, and improves the reliability of leak detection. You can get a furnace.

[Brief explanation of the drawing]

FIG. 1 is a vertical front view showing a conventional graphite crucible induction furnace, FIG. 2 is a perspective view showing the first antenna of FIG. 1, and FIG. 3 is a graphite crucible induction furnace according to an embodiment of the present invention. FIG. 4 is a front view showing the first antenna of FIG. 3. FIG. 1... Melting chamber, 2... Graphite crucible, 3... Back sand, 5... Induction coil, 7... Furnace frame, 8...
...First antenna, 10... Nichrome wire, 11...
... Contact portion, 12 ... Hot water leak detection net, 13 ... Second antenna, 14 ... Plate material, 14a ... Contact piece, 1
4b...Bending piece, 14c...Locking piece, 14d...
Bent part, 15... Fulcrum shaft, 16... Bolt.

Claims (1)

[Scope of utility model registration request] A graphite crucible forming a melting chamber, an induction coil wound around the outer periphery of the graphite crucible, a furnace frame housing these, and a first antenna attached in contact with the bottom of the graphite crucible. In a graphite crucible type induction furnace comprising a second antenna connected to a leak detection net wound around the outer periphery of a graphite crucible back sand, the first antenna has an upper surface in contact with the bottom surface of the graphite crucible and is bent. It consists of two plates forming an inverted L shape with the pieces facing each other at a distance, a fulcrum shaft interposed between the two bent pieces, and a connecting member connecting the two bent parts. A graphite crucible induction furnace characterized by comprising: