JPS6313244Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an overheating prevention device for a direct current heating type salt bath furnace used for heat treatment of industrial machine parts.

(Background Art) Conventional direct current heating type salt bath furnaces use radiation thermometers or thermocouples to measure temperature for temperature control. According to this, in the case of a radiation thermometer, it is necessary to clean the lens of the radiation temperature detector, check the measurement field of view, and check the cooling water and blown air, etc., and in the case of a thermocouple, since it is installed inside the furnace, it is necessary to It is necessary to check the wear and tear. In particular, in the case of temperature control methods that use thermocouples that are prone to wear and tear, there is a risk that the thermocouples will suddenly deteriorate or become disconnected or short-circuited, making normal temperature control impossible. There was a risk that the salt in the furnace would expand and boil and leak out, leading to a dangerous overheating accident.

SUMMARY OF THE DEVICE The object of the present invention is to provide a reliable and durable overheating prevention device for a direct electric heating type salt bath furnace.

(Disclosure of the invention) As shown in Figure 3, the present invention focuses on the fact that in the salt bath furnace, if the power supply voltage is constant, the rise in the temperature of the furnace and the increase in the heating power are correlated, and directly A meter relay ammeter that outputs a conduction signal depending on the magnitude of the measured current is connected to the power supply of the current-heating salt bath furnace via a current transformer, and a relay is connected to the output signal of the meter relay ammeter. This is an overheat prevention device for a direct current heating type salt bath furnace, which is characterized by being connected to an alarm and a power switch. With this configuration, when the temperature of the salt bath furnace exceeds the preset current value of the meter relay type ammeter, the power switching device is cut off to turn off the power, and at the same time an alarm device is sounded. As a result, it has become a reliable and reliable method to prevent overheating of the furnace. Therefore, even if an abnormality occurs in the radiation temperature detector or thermocouple for temperature control and normal temperature control becomes impossible, dangerous overheating accidents will no longer occur.

(Explanation of Embodiment) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows that the measured current is A meter relay type ammeter 7 that outputs a conduction signal depending on the size is connected, and the continuity contact of the meter relay type ammeter 7 is connected.
CH, connected to alarm B14 and holding relay R13.

To explain its operation according to the circuit diagram shown in FIG. 2, if the temperature of the direct current heating type salt bath furnace 1 rises abnormally for some reason, the current also abnormally increases, so the control output of the meter relay type ammeter 7 contact
CH conducts. This activates the alarm B14, and at the same time, the holding relay R13 activates the actual self-holding contact Ra.
It stays in place. Therefore, holding relay R1
Contact Rb of No. 3 opens, and power switch M.S4 suddenly disconnects. Therefore, since the power to the furnace is immediately cut off at the same time as the alarm is issued, overheating accidents of the furnace can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is an electric circuit diagram showing the operation of Fig. 1, and Fig. 3 shows the relationship between temperature and current of a direct current heating type salt bath furnace for each workpiece. This is the graph shown. 1...Direct heat current heating type salt bath furnace, 4...Power switchgear, 5...Power supply, 6...Current transformer, 7...Meter relay type ammeter, 13...Relay, 14...Alarm .

Claims (1)

[Scope of utility model registration request] A meter relay type ammeter that outputs a conduction signal according to the magnitude of the measured current is connected to the power supply of the direct current heating type salt bath furnace via a current transformer, and a relay is connected to the output signal of this meter relay type ammeter. , an overheating prevention device for a salt bath furnace of direct current heating type, characterized in that an alarm and a power supply switch are connected.