JP4437728B2 - Cast metal melting equipment - Google Patents

Description

The present invention relates to a metal melting apparatus for casting a small product such as a dental or jewelry such as a denture, and particularly when it is determined that the metal has been melted in a state suitable for casting. The present invention relates to a cast metal melting apparatus in which casting is stopped and heating of a metal is stopped when it is determined that the melting of the metal is not properly completed.

  Conventionally, as a cast metal melting apparatus, there exists a thing as disclosed by patent document 1, for example. In the melting apparatus of this document, a metal material is accommodated in a casting container, and the container is heated by high frequency induction. When the light generated by the metal in the container is received by a light receiver and the value of the specific frequency component of the received light signal from the light receiver is equal to or higher than a predetermined reference value, the high-frequency signal being high-frequency induction heated is reduced to a low frequency. Amplitude-modulated, induction-heated by this amplitude-modulated high-frequency signal, and when the state where the value of the specific frequency component exceeds the reference value continues for a predetermined time or more, the metal is melted and cast into the mold .

JP 2001-252758 A

  However, in this apparatus, when the metal to be melted is, for example, an oxide film type metal, since the oxide film covers the metal surface, the movement of the molten metal based on the modulated high-frequency signal is small, and the specific frequency component Even if the value exceeds the reference value, it may soon fall below the reference value. In this case, high frequency induction heating is continued. Therefore, since the metal is actually melted, heating to the metal may be continued for a long time, and boiling of the metal or partial heating of the metal occurs, so it is necessary to stop the heating manually. . In this case, it is necessary to replace the material and perform heating again, and the material and the work process overlap, resulting in waste.

  An object of the present invention is to eliminate the rework and waste of materials due to melting failure.

  A casting metal melting apparatus according to the present invention includes a melting container containing a metal to be melted, for example, a metal containing a metal covered with an oxide film, and high-frequency induction heating of the metal contained in the melting container. A high-frequency induction heating means for melting; a high-frequency signal source for supplying a high-frequency signal to the high-frequency induction heating means; a low-frequency signal source for generating a low-frequency signal for low-frequency amplitude modulation of the high-frequency signal; A light receiver that receives light emitted from the metal and generates a light reception electric signal corresponding to the light; and a frequency component extraction unit that extracts a frequency component resulting from a sudden change in the light reception electric signal due to a change in the light; The extracted output signal representing the frequency component is compared with a preset reference signal, and when the output signal exceeds the reference signal, the low frequency signal source is enabled and the high frequency A comparator for generating a start signal for starting low-frequency amplitude modulation high-frequency induction heating by low-frequency amplitude modulation of the signal, and an output signal representing the frequency component for the reference signal for a predetermined period (to be described later in FIG. 3) T1) including timer means for stopping the high-frequency induction heating and generating a command signal for casting the molten metal into the mold when continuously exceeded. Further, when the output signal representing the frequency component exceeds the reference signal for a period shorter than the predetermined period, the high-frequency induction heating means has the low-frequency amplitude for a predetermined extension period (T2 described later in FIG. 3). The modulated high frequency induction heating is configured to be executed in an extended manner. If necessary, a certain period after the start of high-frequency induction heating (during T3 described later in FIG. 3) or a certain period after extraction of the frequency component (during T4 described later in FIG. 3) has elapsed. However, when the output signal is not maintained above the reference value continuously for the predetermined period (T1), the high frequency induction heating is stopped, and the metal material is replaced as necessary.

  The timer means is configured to generate a casting command signal only when the output signal of the frequency component extracting means continues for a predetermined period (the aforementioned T1) and the low frequency amplitude modulation high frequency induction heating continues. Yes. This is due to the following reason. That is, if the metal mass falls, moves, falls, or tilts for any reason during the high-frequency induction heating period before melting, the temperature of the metal in the container is still low, the received electrical signal is Exhibits a similar vibration or level spike. When this is mistakenly considered as melting of the metal and low frequency amplitude modulation high frequency induction heating (hereinafter, sometimes referred to as low frequency amplitude modulation heating) is started, particularly in the case of a metal covered with an oxide film, Casting may be performed in a state where the metal is not completely melted. Therefore, a casting command signal is generated when low-frequency amplitude-modulated high-frequency induction heating is executed for a predetermined period after the vibration or level of the light-receiving electrical signal increases rapidly.

  The cast metal melting apparatus of the present invention is provided with a timer that starts operation in response to the output signal of the comparator, and the timer keeps counting while the comparator continues to generate the output signal, and a certain period (T1) has elapsed. Sometimes a command signal is generated to stop the low frequency amplitude modulation heating. It is also possible to provide a second timer, and the second timer is a fixed period from the start of the high frequency induction heating (period T3 described later with reference to FIG. 3), or the output signal of the comparator. When a certain period of time (period T4 which will be described later with reference to FIG. 3) elapses from the generation of the above, a stop signal for stopping all the high frequency induction heating including the low frequency amplitude modulation heating is generated.

  The extent to which the low frequency amplitude modulation heating is continued after the output signal of the frequency component extraction means, that is, the output signal of the above-mentioned comparator, is proficient based on the type of cast metal, the weight, the thickness of the oxide film, etc. Determined by the experience of the person or by prior experimentation.

  If necessary, set a period, called mooring time, to ensure that the temperature and viscosity of the melted and liquefied metal reach the same overall condition after the end of low frequency amplitude modulation heating. During this time, the molten metal can be stabilized, and the casting can be performed after the molten metal is made stationary.

  In the cast metal melting apparatus of the present invention, low frequency amplitude modulation heating is performed when the output signal of the frequency component extraction means becomes equal to or higher than the reference value due to a sudden change in the received light electric signal. Even if a thick oxide film is vibrated, the oxide film is broken and melting is accelerated, and even if the output signal does not last for a predetermined period, a certain extension period (described later with reference to FIG. 3). During the period of T2, the output signal of the frequency component extraction means rises more than the reference value again, and this makes it possible to surely melt even an oxide film type metal and stabilize a homogeneous cast product. Can be manufactured. Also, if it is determined that the metal could not be completely melted within the time limit for some reason, stop heating, continue heating involuntarily, prevent the metal from overheating and boiling, It is possible to prevent damage to the apparatus and the mold.

  FIG. 1 is a view schematically showing an embodiment of a cast metal melting apparatus according to the present invention. In the figure, a chamber 2 in which a metal melting vessel, for example, a crucible 4 and a mold 6 is disposed, is constituted by an upper chamber 3, a lower chamber 5, and a cylinder 7 coupled to the lower chamber 5 in a piston form. ing. In a state where the crucible 4 and the mold 6 are set, the lower chamber 5 is pushed up by the inert gas pressure injected into the cylinder 7 to come into contact with the upper chamber 3 at the contact portion 9 and is provided at the contact portion 9. The upper and lower chambers are kept airtight by the O-ring 11. A high frequency induction heating coil 10 is arranged on the outer periphery of the crucible 4 provided in the upper chamber 3. A metal 8 to be melted is accommodated in the crucible 4, is brought into an oxygen-free state in which an inert gas is supplied in the airtight state, and is induction-heated by the induction heating coil 10. The molten metal is poured into the lower mold 6 by the crucible 4 being opened in the vertical direction and divided into two. Since the structure of the crucible 4 and the opening / closing mechanism are known, a detailed description thereof will be omitted.

  A high frequency induction heating coil 10 for heating the crucible 4 is connected in parallel with the resonance capacitor 12 to constitute a tank circuit 13. The tank circuit 13 is connected to the secondary side of the matching transformer 14. The primary side of the matching transformer 14 is connected to the output side of an inverter 16 for high frequency induction heating including semiconductor switching elements such as a thyristor, IGBT, power FET, power bipolar transistor and the like. The high frequency signal supplied to the high frequency induction heating coil 10 is determined by the type, weight, etc. of the metal accommodated in the crucible 4, but is generally set to a frequency of 50 to 100 kHz or more.

  The input side of the inverter 16 is connected to the output side of a DC output voltage control type rectifier circuit 18 including semiconductor switching elements such as a thyristor, IGBT, power FET, and power bipolar transistor. The input side of the rectifier circuit 18 is connected to a commercial AC power supply 20.

  A control signal is supplied from the rectifier circuit control circuit 22 to the rectifier circuit 18. The control circuit 22 has a constant voltage control reference signal, detects the output voltage of the inverter 16, and the rectifier circuit 18 has a constant voltage corresponding to the constant voltage control reference voltage. The semiconductor switching element is feedback controlled.

  Reference numeral 26 denotes an inverter control circuit, which detects the phase of the output voltage and output current of the inverter 16 and adjusts the switching element of the inverter 16 so that the output frequency of the inverter 16 matches the resonance frequency of the tank circuit 13. Tracking control of switching frequency.

  The inverter control circuit 26 is supplied with a low frequency modulation signal i obtained by amplifying the output signal of the low frequency oscillation circuit 24 with the amplifier 25. The frequency of the low frequency modulation signal i varies depending on the type and weight of the metal 8 to be melted, but is generally set in the range of 5 to 30 Hz, and is usually set to about 10 Hz. As this low frequency modulation signal, signals having various waveforms such as a sine wave, a rectangular wave, or a synthesized wave thereof can be used. If the low-frequency modulation signal has a very high frequency due to the mechanical characteristics of the metal 8, vibration due to a change in the shape of the molten metal, which will be described later, decreases, and it becomes difficult to detect melting. It is desirable that the waveform, size, frequency, etc. of the low frequency modulation signal be set to an optimum state corresponding to various conditions such as the type, weight and shape of the metal 8 and the shape and size of the crucible 4. Therefore, it is necessary to select such that it is effective for a wide range of metals. Accordingly, the frequency of the 10 Hz low frequency modulation signal is merely an example.

  The inverter control circuit 26 detects the phase difference between the output voltage and output current of the inverter 16 and matches the output frequency of the inverter 16 with the resonance frequency of the tank circuit 13 so that the resonance current of the tank circuit 13 is always maximized. It is set as follows. Here, a slight phase difference is forcibly generated between the output voltage and the current by the low frequency modulation signal. If there is a phase difference, the resonance frequency of the tank circuit 13 and the output frequency of the inverter 16 are slightly mismatched, and the resonance current of the tank circuit 13 is reduced. Since this mismatching and matching state are periodically created by the low frequency modulation signal, the magnitude of the resonance current of the tank circuit 13 is amplitude-modulated by the modulation signal.

  Note that the constant voltage control of the rectifier circuit control circuit 22 is compared with the period of the modulation signal so that the fluctuation of the output voltage of the inverter 16 due to the low frequency amplitude modulation does not affect the constant voltage control of the rectifier circuit control circuit 22. Response time is sufficiently delayed. The coil 10, the capacitor 12, the transformer 14, the inverter 16, the rectifier circuit 18, the rectifier circuit control circuit 22, the inverter control circuit 16, the amplifier 25, and the low-frequency oscillation circuit 24 constitute high-frequency induction heating means for the metal 8.

  A window 28 that transmits light generated by melting the metal 8 in the crucible 4 is provided in the upper portion of the chamber 2. The light generated by the molten metal in the crucible 4 passes through the window 28 and is received by the light receiver 30. As the light receiver 30, for example, an infrared photodiode or a pyroelectric sensor is used.

  By the high frequency induction heating by the high frequency induction heating coil 10, the temperature of the metal 8 rises as the metal 8 in the crucible 4 is heated, and the amount of light emitted from the metal 8 increases substantially in proportion to this temperature rise. The light receiver 30 receives the amount of emitted light and generates a received light signal a. The voltage representing the electric signal a generated between both ends of the load resistor 32 is input to frequency component extraction means, for example, filter means, more specifically, a low-pass cutoff (high pass) filter 34. The low-frequency cutoff filter 34 is configured to pass a frequency component equal to or higher than the frequency of the low-frequency signal generated by the low-frequency oscillation circuit 24 and cut off a frequency component lower than this. In addition, to prevent malfunction due to noise. A band pass filter that passes only the frequency of the low frequency signal of the low frequency oscillation circuit 24 may be used.

  FIG. 2A shows the level change of the received light signal a of the light receiver 30 from the start of melting of the metal 8. In the heating period t1 by high frequency induction, the temperature rise of the metal 8 is small immediately after the start of heating, and the received light signal a hardly changes. As the heating proceeds, the temperature of the metal 8 rises rapidly and begins to glow red. When the metal 8 enters a period t2 immediately before melting, the temperature rise gradually becomes gentle and the light reception electric signal a rises gradually. As the heating further proceeds, the temperature rise becomes more gradual and the melting period t3 is entered. In the melting period t3, melting and liquefaction of the metal 8 are started, and the metal starts to be liquefied from its periphery. Since there is almost no temperature increase during this period, the received light signal a does not change. After the entire metal is liquefied, when it is further heated, boiling starts, and the received light signal a rapidly increases as shown by the dotted line in FIG.

  In the heating period t1 and the period t2 just before melting in FIG. 2A, since the metal 8 has not yet sufficiently melted, the change in the received light signal a is sufficiently lower than the cutoff frequency of the low-frequency cutoff filter 34, The output signal b of the low-frequency cutoff filter 34 is substantially 0 (zero) as shown in FIG.

  When the state of the metal 8 gradually changes during the melting period t3 and almost the entire liquid is liquefied, the metal 8 is subjected to a sudden increase in vibration due to electromagnetic stirring, destruction of the surface oxide film, a sudden increase in the amount of emitted light, and the like. The light reception electrical signal a changes abruptly, and the high frequency component of the light reception electrical signal a appears in the light reception electrical signal a. Therefore, a vibration waveform as shown in FIG. 2B is generated in the output signal b of the low-frequency cutoff filter 34. This output signal b is full-wave rectified by a full-wave rectifier circuit 36 to generate an output signal c. The waveform of this output signal c is shown in FIG. The output signal c is input to and smoothed by a high frequency cutoff filter 38, for example, a smoothing circuit 38, and input to the voltage comparator 40 as an output signal d. A half-wave rectifier circuit may be used instead of the full-wave rectifier circuit 36 described above.

  The received light signal a is supplied to a differential value peak detection circuit 35 and a sample hold circuit 42 which constitute the reference signal generating means. The differential value peak detection circuit 35 obtains the differential value of the received light signal a shown in FIG. 2 (a), and the differential value waveform in the differential value peak detection circuit 35 is shown in FIG. 2 (e1). When the first peak value is generated in the differential value waveform (e1), the differential value peak detection circuit 35 detects the maximum value peak of the differential value and generates the timing signal e shown in FIG. 2 (e2) as the output. To do. The timing signal e is applied to the sample hold circuit 42 and used as a sample hold timing signal. The sample and hold circuit 42 samples and holds the level of the received light signal a when the timing signal e is input, and supplies the level signal to the voltage comparator 40 as the reference signal f shown in FIG. Is done. This reference signal f represents the received light signal level when the rate of temperature increase of the metal 8 during the heating period in the heating period t1 is maximized.

  In this embodiment, the differential value peak detection circuit 35 detects the timing of the differential value peak. However, when the differential value in the differential value in FIG. A signal indicating the timing immediately before the melting and liquefaction of the metal 8 may be output as a sample hold timing signal.

  The voltage comparator 40 compares the output signal d of the high-frequency cutoff filter 38 with the reference signal f of the sample and hold circuit 42, and during the period when the output signal d exceeds the level of the reference signal f, FIG. A comparison output signal g as shown in FIG. This output signal g acts as a start signal for starting low frequency amplitude modulation high frequency induction heating described later.

  The comparator output signal g is supplied to the amplifier 25 as an operation start signal for low frequency amplitude modulation. The amplifier 25 stops operating before the comparator output signal g is supplied, and the low frequency signal i is not supplied to the inverter control circuit 26. When the comparator output signal g is supplied to the amplifier 25, the amplifier 25 starts operation, and the inverter control circuit 26 is supplied with the low frequency signal i of the low frequency oscillation circuit 24, and the high frequency signal for induction heating is amplified. Modulate. After melting the metal, the low-frequency amplitude modulation heating is performed for a predetermined time, whereby the molten metal is further stirred, and in particular has an effect of accelerating the melting of the oxide film type metal.

  The comparator output signal g is also supplied to the timer 43. The timer 43 generates a timer output signal h when the comparator output signal g continues for a preset period (period T1 described later with reference to FIG. 3), and this output signal h is supplied to the amplifier 25. To stop its operation. Further, the output signal h is supplied to the inverter 16 or the rectifier circuit 18 to stop the supply of the induction heating high frequency signal to the high frequency induction heating coil 10. Further, the output signal h is supplied to the crucible operating mechanism 44 as a casting command signal. The crucible operating mechanism 44 operates the crucible 4 immediately in response to the casting command signal or, if necessary, for a certain period of time called mooring, and flows molten metal into the mold 6.

  Note that a variable gain amplifier is used as the amplifier 25. When the comparator output signal g is supplied to the amplifier 25, the low frequency signal i at a level for effectively performing the modulation is supplied to the inverter control circuit 26 to output the comparator output. Even when the signal g is supplied and after the timer output signal h is supplied, the gain may be lowered so that the level of the low-frequency signal i supplied to the inverter control circuit 26 is substantially 0 (zero). Good. The operation of the low frequency oscillator 24 or the inverter control circuit 26 may be controlled by the comparator output signal g and the timer output signal h.

  The second timer 58 counts the elapsed time in response to the comparator output signal g or counts the elapsed time with the start of the high frequency induction heating. The second timer 58 will be described later with reference to FIG. As described below, when the first limit period T4 (for example, 10 to 20 seconds) has elapsed from the generation of the comparator output signal g, or for the second limit period T3 (for example, 2 minutes) from the start of the high-frequency induction heating. When the time has elapsed, an output signal for stopping the high frequency induction heating is generated. In order to stop the high-frequency induction heating, the operation of the inverter 16, the rectifier circuit 18, or the commercial AC power supply 20 may be stopped as described above.

  Next, the low frequency amplitude modulation heating operation after the generation of the comparator output signal g will be described with reference to FIG. 3A to 3E, the hatched heating period indicates that low-frequency amplitude modulation heating is performed, and the non-modulated high-frequency induction heating is performed in the heating period not hatched. It represents.

  FIG. 3A shows a normal melting operation. First, unmodulated high-frequency induction heating is performed, and when the frequency component due to a sudden change in the received electrical signal a exceeds a reference value, a comparator output signal g is generated. Then, the amplifier 25 is operated to start the heating with the low frequency amplitude modulation indicated by the hatched portion, that is, the low frequency amplitude modulation high frequency induction heating (low frequency amplitude modulation heating). When the comparator output signal g continues for T1 (for example, 2 seconds), the timer 43 generates a command signal h, stops high frequency induction heating including low frequency amplitude modulation heating, and further operates the crucible operating mechanism 44 to operate the crucible. Command to cast 4 molten metal into mold 6.

  FIG. 3b shows the operation in the first case in which the state does not continue for the period T1 even if the above-described frequency component becomes equal to or higher than the reference value. The low-frequency amplitude modulation heating indicated by the shaded area is started by the comparator output signal g, but the comparator output signal g is reset once without continuing for the period of T1, the timer 43 is similarly reset, and then 1 Continue low frequency amplitude modulated heating for an extension time T2 of ~ 2 seconds. During the extension period T2, the frequency component becomes equal to or higher than the reference value and the comparator output signal g is generated again. When this continues for the set time T1 of the timer 43, the low frequency amplitude modulation is performed by the command signal h of the timer 43. High frequency induction heating including heating is stopped, and molten metal is cast into the mold 6.

  FIG. 3c shows the operation in the second case in which the state does not continue for the period T1 even if the frequency component becomes equal to or higher than the reference value. In the case of FIG. 3C, the low frequency amplitude modulation heating indicated by the hatched portion is started by the comparator output signal g, but after the extinction of the comparator output signal g, the frequency component is within the extension time T2. Does not return above the reference value. In this case, the operation of the amplifier 25 is stopped, the low frequency amplitude modulation heating is temporarily stopped, the first unmodulated high frequency induction heating is performed, and this unmodulated high frequency induction heating is continued until the frequency component becomes equal to or higher than the reference value again. to continue. Thereafter, when the frequency component becomes equal to or higher than the reference value, the comparator output signal g is generated again, and the low frequency amplitude modulation heating indicated by the hatched portion is continued for T1. When T1 has elapsed, high frequency induction heating including low frequency amplitude modulation heating is stopped by a command signal h of the timer 43, and molten metal is cast into the mold 6. In order to perform this operation, the amplifier 25 is configured to automatically stop the operation unless the comparator output signal g is supplied again within the time T2 after the extinction of the comparator output signal g. ing. As described above, operations other than the amplifier 25 such as the low-frequency oscillator 24 or the inverter control circuit 26 may be controlled by the comparator output signal g and the timer output signal h.

  In FIG. 3d, even when the frequency component becomes equal to or higher than the reference value and the low frequency amplitude modulation heating indicated by the hatched portion is started, the state does not continue for T1, and the heating is started for a time limit T3 (for example, 2 minutes). ) Represents a case where the frequency component does not maintain the reference value for the period of T1 or more. For example, the second timer 58 that starts timing by turning on the power stops high-frequency induction heating when T3 has elapsed. As a method of stopping the high frequency induction heating, the operation of the inverter 16, the rectifier circuit 18 and the like is stopped.

  In FIG. 3e, even if the frequency component becomes equal to or higher than the reference value and the low frequency amplitude modulation heating indicated by the hatched portion is started, the state does not continue for T1, and the time limit from the first generation of the comparator output signal g is reached. The period of T4 (for example, 10 to 20 seconds) represents a case where the frequency component does not continue to exceed the reference value for the period of T1, and in this case, high-frequency induction heating is performed in the same manner as in FIG. Stop.

  As a method of stopping the low frequency amplitude modulation heating described above, instead of stopping the operation of the amplifier 25 or the low frequency oscillation circuit 24, switch means for cutting off the low frequency modulation signal i between the amplifier 25 and the inverter control circuit 26. Can also be provided.

  In order to stop the high-frequency induction heating, any one of the matching transformer 14 and the inverter 16, the inverter 16 and the rectifier circuit 18, or the rectifier circuit 18 and the AC power supply 20 is cut off by a switch. You can also

It is a schematic block diagram for demonstrating the structure and operation | movement of one Embodiment of the cast metal melting apparatus by this invention. It is a figure which shows the signal waveform of each part explaining operation | movement of the cast metal melting apparatus of FIG. In the cast metal melting apparatus of FIG. 1, it is a figure which shows the various heating state when melting the metal in a crucible by high frequency induction heating.

Explanation of symbols

2 chamber 4 crucible (melting container)
10 High frequency induction heating coil (heating means)
13 Tank circuit (heating means)
16 Inverter (heating means)
19 Switch (heating stop means)
24 Low frequency oscillation circuit (low frequency amplitude modulation means)
25 Amplifier (low frequency amplitude modulation means)
26 Inverter control means (heating means)
30 Receiver 34 Low-frequency cutoff filter (frequency component extraction means)
40 Voltage comparator 43 Timer (heat stop and casting command signal generator)
58 Timer (Overheat stop signal generator)

Claims (3)

A melting container containing the metal to be melted;
High frequency induction heating means for melting the metal contained in the melting container by high frequency induction heating;
A high-frequency signal source for supplying a high-frequency signal to the high-frequency induction heating means;
A low frequency signal source for generating a low frequency signal for low frequency amplitude modulating the high frequency signal;
A light receiver that receives light emitted by the metal during heating of the metal and generates a light-receiving electrical signal corresponding to the light;
A frequency component extracting means for extracting a frequency component resulting from a sudden change in the received light signal accompanying a change in the light;
The extracted output signal representing the frequency component is compared with a preset reference signal, and when the output signal exceeds the reference signal, the low frequency signal source is enabled and the high frequency signal is converted to a low frequency amplitude. A comparator that generates a start signal to modulate and initiate low frequency amplitude modulated high frequency induction heating;
Timer means for stopping the high-frequency induction heating and generating a command signal for casting molten metal into a mold when an output signal representing the frequency component continuously exceeds the reference signal for a predetermined period (T1). ,
Including
The high frequency induction heating means extends the low frequency amplitude modulation high frequency induction heating for a predetermined extension period (T2) when the output signal representing the frequency component exceeds the reference signal for a period shorter than the predetermined period. Configured to run ,
The high frequency induction heating means includes
When the output signal representing the frequency component exceeds the reference signal for a period shorter than the predetermined period, the low frequency amplitude modulation high frequency induction heating is extended and executed for the predetermined extension period (T2). If the output signal representing the frequency component again exceeds the reference signal within (T2), the low frequency amplitude modulation high frequency induction heating is continued for the predetermined period (T1), and the command signal of the timer means Stop high frequency induction heating and cast molten metal,
If the output signal representing the frequency component does not exceed the reference signal within the extension period (T2), high-frequency induction heating without low-frequency amplitude modulation is performed, and then the output signal representing the frequency component is When the reference signal is exceeded, the low frequency amplitude modulation high frequency induction heating is continued for the predetermined period (T1), the high frequency induction heating is stopped by a command signal of the timer, and molten metal is cast.
A casting metal melting device configured as follows . The cast metal melting apparatus according to claim 1 , wherein the high-frequency induction heating unit includes:
When the output signal representing the frequency component does not continuously exceed the reference signal within the predetermined period (T1) within a predetermined time limit (T3 or T4), the high frequency induction heating is stopped. Casting metal melting equipment. 3. The cast metal melting apparatus according to claim 2 , wherein as the means for setting the predetermined time limit, an elapsed time (T3) from the start of high-frequency induction heating of the metal or an output signal representing the frequency component is first set as a reference. There is provided a second timer that counts both or one of the elapsed time (T4) from when the signal is exceeded and generates a stop signal when at least one of the two elapsed times is reached. , Casting metal melting equipment.

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