JPS633431B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention makes it possible to detect melting of a water-cooled induction heating coil due to leakage of hot water from a furnace body, thereby preventing an explosion accident in a water passage section. This invention relates to a hot water leak detection device for an induction furnace.

[Prior art and its problems]

A conventional example of a hot water leak detection device for an induction furnace will be explained based on FIG. This figure shows a crucible-shaped induction furnace, in which a water-cooled induction heating coil 4 made of a hollow electric conductor is wound around the outer periphery of a furnace body 3 consisting of a crucible 1 and a refractory lining 2 surrounding it. A molten metal 5 melted by the induction heating action of the coil 4 is housed inside. In the current distribution of the coil 4, the current density i is larger toward the inner circumference, and as the distance x (m) from the inner circumference increases, the current density i _x rapidly decreases as shown in FIG. 2. A hollow hole 4a through which cooling water passes is provided on the outer peripheral side of the coil 4 where the current density i is low. A leak detection electrode 6 made of a high melting point metal such as stainless steel is buried in the bottom of the furnace body 3 with its tip in contact with the molten metal 5. Further, a plurality of electrodes 7 made of metal such as stainless steel are inserted between the furnace body 3 and the coil 4. The electrodes 6 and 7 are connected to a power source 8 via a current detector 9, and when the detector 9 detects a current, a display 10 such as a lamp or a buzzer is used to warn of the occurrence of hot water leakage.

When the induction furnace is used for a long period of time, the furnace body 3 becomes molten metal 5.
If this condition is left unattended, the molten metal 5 will eventually leak and burn out the coil 4. Therefore, a detection device consisting of the electrodes 6, 7, etc. is used to detect the leakage of the molten metal. This was to prevent the coil 4 from burning out.

In such a structure, if a crack occurs at an intermediate position between the plurality of electrodes 7 inserted between the furnace body 3 and the coil 4, the coil 4 in that part will be melted without activating the hot water leak detection device, and this melting will occur. There was a drawback that an explosion could occur if the cooling water reached the hollow hole 4a through which it passed.

[Purpose of the invention]

In order to eliminate the above-mentioned drawbacks, the present invention provides a hot water leak detection device for an induction furnace that is capable of detecting melting of a water-cooled heating coil due to hot water leakage and preventing an explosion accident in a water passage section. The purpose is to

[Key points of the invention]

In order to achieve the above object, the present invention attempts to prevent an explosion accident by detecting the melting of the water-cooled heating coil before it reaches the water passage section.

[Embodiments of the invention]

FIG. 3 shows an embodiment of the present invention, in which a hollow hole 34a through which cooling water passes is provided on the outer circumferential side of a water-cooled heating coil 34, and a V-shaped cross section is formed on the conductor surface on the inner circumferential side of the hollow hole 34a. Groove 34b is coil 3
It is located concentrically with 4. The hollow hole 34a
The groove 34b is formed by drawing together with the coil 34, and the groove 34b may be provided only on one surface, and the cross-sectional shape may be U-shaped or square.
Inside this groove 34b is an optical fiber 3 with a small outer diameter.
5 is embedded, and both ends of the optical fiber 35 are connected to a light emitting section 36 and a light receiving section 37, respectively, as shown in FIG. The optical fiber 35 is fused when the coil 34 melts down to the groove 34b due to hot water leakage, and the light receiving portion 3 is fused due to the fused optical fiber 35.
When the coil 7 becomes unable to receive light, a lamp, a buzzer, etc. are used to warn that the coil 34 has melted.

According to the embodiment, the optical fiber 35 is made of an electrically insulating material such as glass, so the insulating performance is not impaired, and the optical fiber 35 is buried in the groove 34b, which facilitates positioning and saves extra space. It is not necessary and does not interfere with coil insulation. Furthermore, if the groove 34b is brought closer to the inner circumferential side of the hollow hole 34a, the loss in conductor cross-sectional area is small because the current density i is low. By pulling out the tap from the optical fiber 35, it is possible to easily identify the melted portion of the coil 34.

〔Effect of the invention〕

According to this invention, in a hot water leakage detection device for an induction furnace, an optical fiber is buried concentrically with the conductor surface of the water-cooled heating coil on the inner circumferential side of the water passage hole to prevent melting of the coil due to hot water leakage. Since the optical fiber is fused before reaching the water portion, it is possible to detect the melting of the coil by the fusion of the optical fiber, thereby preventing an explosion accident in the water passage portion. Furthermore, even if there is no leakage of hot water and the detection electrode does not operate in the case of a layered layer due to thermal deterioration of the coil insulation, the layered layer can be detected if the optical fiber is fused by the layered layer.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the configuration of a conventional hot water leak detection device for an induction furnace, FIG. 2 is a curve diagram showing the current density in the coil of FIG. 1, and FIG. 3 is a longitudinal cross-sectional view of an embodiment of the present invention. FIG. 4 is a connection diagram of an embodiment of the present invention. 3... Furnace body, 34... Coil, 34a... Hollow hole, 34b... Groove, 35... Optical fiber, 36
... Light emitting section, 37 ... Light receiving section.

Claims (1)

[Claims] 1. A water-cooled induction heating coil made of a hollow electric conductor is wound around the outer circumference of the furnace body of an induction furnace, and a groove is provided concentrically with the coil on the conductor surface on the inner circumferential side of the hollow hole of the coil, and an optical fiber is buried. A hot water leak detection device for an induction furnace is characterized in that a light emitting part and a light receiving part are connected to the optical fiber.