JPS5926875B2 - dental electric furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dental electric furnace, and more particularly to a control device for an electric furnace.

Dental electric furnaces are used to form molds for casting denture metals or alloys when forming dentures.

As materials for the mold, the main raw material called investment material is quartz or crys+palite, and the binding material is gypsum hemihydrate or silicate gel.

The investment material expands only slightly up to around 550°C, but significantly expands at 573°C due to the transition from low-temperature α-quartz to high-temperature β-quartz.

For this reason, rapid heating of the investment material causes cracks, and to prevent this, electric furnaces heat the inside of the furnace to a predetermined temperature (low temperature) (period T1), as shown in the heating characteristics in Figure 1.
Thereafter, two-step temperature control is performed: low-temperature mooring is performed for a predetermined time (T2), followed by heating to a high temperature (period T3) and high-temperature mooring for a predetermined time (T4).

Conventional electric furnaces use a manual switch to switch the energization rate to the furnace heater for low and high temperatures, so switching from low-temperature mooring to high-temperature mooring (low-temperature mooring time) and high-temperature mooring time can last several hours. Therefore, time management was troublesome and it was difficult to control time appropriately.

In some cases, there was a problem of cracks in the investment material.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a dental electric furnace that enables appropriate heating of investment materials by automating furnace temperature control and eliminates the hassle of time management. With the goal.

FIG. 2 is a circuit diagram of a control device showing one embodiment of the present invention.

When the main power switch 1 is turned on, the temperature controller power source 2 is turned on and the relay 3 is activated to connect the furnace heater 4 to the power source.

Heater 4 is two furnaces A. By switching the furnace changeover switch 5, the relay 6 switches the energization of the furnaces A and B.

At the same time, the relay 6 switches the thermocouple 7 for detecting the temperature inside the furnace.

Turning the heater 4 on and off and controlling the energization rate, that is, controlling the temperature inside the furnace, turns the triac 8 on and off at a predetermined energization rate.
This is done with off braking.

The turning on of the main switch 1 is indicated by the lighting of the power-on lamp 10 due to the energization of the transformer 9.

The delay circuit 11 enables energization control of the heater after a predetermined time delay after the power is turned on.

This delay is to ensure that the contact state is as expected after the power is turned on to the temperature controller, which will be described later, and may be unnecessary depending on the temperature controller used.

Now, automatic heating control of the furnace is performed by turning on the auto switch 12.

When the auto switch 12 is turned on, its state is indicated by the lighting of the pilot lamp 13 and the power line is switched to the start timer contact 114 side.

The start timer contact 14 is in the state shown in the figure while the timer is operating, and the lamp 15 indicates that the timer is in operation, and is switched from the state shown in the figure after the timer expires.

This start timer is for starting automatic control of the furnace a predetermined time after the auto switch 12 is turned on.If the furnace is to be automatically controlled at the same time as the auto switch 12 is turned on, the timer operation is stopped.

A phase control circuit 16 that controls the conduction rate of the triac 8 is supplied with a synchronizing signal from the power supply line, and a temperature rise setting device 17,
An ignition signal that achieves the energization rate set in 1B is output.

The temperature increase setting device 17 sets the rate at which the furnace is heated from room temperature to the low temperature range, and the temperature rise setter 18 sets the rate at which the furnace is heated from the low temperature to the high temperature range.

The selection of these temperature rise setting devices 17.18 is by relay 19.20.
It will be held in

After the auto switch 12 is turned on and the start timer expires, the power line is connected to the output contact 22 of the low temperature temperature controller through the contact of the high temperature manual setting switch 21 in the state shown in the figure, and relay 19
energize.

By energizing the relay 19, the conduction rate of the triac 8 is controlled by the set value of the temperature increase setting device 17, and the furnace is heated from room temperature to a low temperature range.

When it is heated to a predetermined low temperature, the low temperature temperature controller detects this, its contact 22 is switched, and the low temperature mooring timer 23 is activated.

When the low temperature mooring timer 23 is started, the self-holding contact 23A is activated.
The timer operation is continued even when the temperature controller contact 22 returns (due to a drop in temperature), and the lamp 24 lights up the output contact 23B, which is in the state shown in the figure, to indicate this state.

While the timer 23 is operating, when the temperature inside the furnace drops by a certain value from the low temperature range, the contact 22 of the temperature controller 22 returns to the state shown in the figure, energizing the relay 19 and turning on the triac 8 again. The temperature inside the furnace is kept at a predetermined temperature (low temperature) repeatedly.

After the low-temperature mooring period has passed, the power line is connected to the output contact 26 of the high-temperature temperature controller through the contact of the low-temperature manual setting switch 25 in the illustrated state by switching the contact 23B, and the relay 20 is energized.

By energizing the relay 20, the flow rate of the tri-rack 8 is controlled according to the set value of the temperature increase setting device 18, and the furnace is heated from a low temperature to a high temperature range.

After being heated to a predetermined high temperature, high-temperature mooring is performed by the temperature controller 26 and high-temperature mooring timer 27 in the same way as the low-temperature mooring described above, and this state is displayed by the lamp 28.

After the high temperature mooring period has passed, the buzzer 30 sounds through the setting switch 29 by switching the contact 27B.
Announce the end of mold formation.

If this notification is not required, the switch 29 is left open and the live 31 is turned off.

Note that to manually control the temperature of the furnace, switch 21.
25 switching operations, and each state is changed to a lamp 32.
33 is displayed.

Both switches 2L25 and the automatic switch 12 are of a self-holding single point selection type.

Further, a buzzer 30 is used to notify the mooring period after the mooring period is low or high.

Further, in the event of a power outage during automatic control, sequence control from low temperature control may be performed again after the power is restored, but this can be resolved by switching from automatic to switch 21 or 25 depending on the control state.

As explained above, the dental electric furnace according to the present invention automatically controls the furnace temperature suitable for casting by simply turning on the automatic switch, and the control start time can also be set by setting the start timer. This simplifies the temperature control of the furnace and reduces the chance of failures in heating control.

[Brief explanation of the drawing]

FIG. 1 is a time chart used for temperature control of a dental electric furnace, and FIG. 2 is a circuit diagram of a control device showing an embodiment of the present invention. 2...Temperature controller source, 4...Heater, 5
・・・・・・Furnace selector switch, γ・・・Thermocouple,
12...Automatic switch, 14...Start timer, 16...Phase control circuit, 17,
18... Temperature increase setting device, 21... High temperature setting switch, 22.26... Temperature controller, 23° 27... Timer, 25. ...Low temperature setting switch, 29...Buzzer switch, 30.
·····buzzer.

Claims (1)

[Claims] 1. A heater drive device capable of turning on/off driving a heater in a furnace and setting a flow rate when turned on, and a heater drive device capable of heating a furnace from room temperature to a first temperature and heating the furnace to the first temperature. A first controller that controls the heater drive device to maintain the heater at the temperature for a predetermined time after heating.
a second control circuit that controls the heater drive device to heat the furnace from the first temperature to a second temperature and to keep the furnace at the temperature for a predetermined period of time after heating the furnace to the second temperature; and an autoswitch that can automatically instruct furnace heating control by a second control circuit following the furnace heating control by the first control circuit. 2. The dental electric furnace according to claim 1, wherein the auto switch is provided with a start timer that can set the command output time.