JPS5913599Y2 - vacuum firing furnace - Google Patents

Description

[Detailed description of the invention] The present invention relates to a vacuum firing furnace, in particular a firing furnace body installed above a base, and small objects to be fired such as dentures that can be moved up and down between the body and the base. The present invention relates to an improvement in a vacuum firing furnace of the type that is equipped with a firing table for firing the fired product in the furnace and then lowering it to take out the fired product.

Conventionally, this type of vacuum firing furnace has a firing furnace main body 2 provided above a base 1, and a base 1, as schematically shown in FIG.
It mainly consists of a firing table 3 that moves up and down between the firing furnace body 2 and the firing table 3.

The firing furnace body 2 has a cylindrical shape with an open bottom, and a thermocouple 4 is attached to the side wall of the furnace.

Although not particularly shown, the firing table 3 is raised between the base 1 and the firing furnace body 2 by an elevating mechanism consisting of a rack and a pinion, and the object to be fired for dentures placed on the firing table 3 is moved up and down between the base 1 and the firing furnace body 2. 5
is stored approximately in the center of the furnace, and then the inside of the furnace is maintained in a vacuum state by a vacuum pump (not shown).

Thereafter, the inside of the furnace is maintained at around 1000° C. by a heating coil 6 such as a platinum wire disposed inside the firing furnace body 2, so that the object to be fired for dentures has properties such as predetermined hardness, color and luster. It is fired like this.

FIG. 2 schematically shows the internal structure of the furnace during firing work.

In such a conventional vacuum firing furnace, during the firing operation, the temperature inside the furnace is detected by the thermocouple 4, and the temperature of the denture to be fired 5 is detected.
The firing conditions are adjusted to provide the optimum firing conditions.

However, in reality, the inside of the furnace during the firing operation has a temperature distribution, so there is a temperature difference between the surrounding atmosphere of the denture to be fired 5 and the vicinity of the furnace side wall.

Therefore, it is extremely difficult to manage the heat inside the furnace using the thermocouple 4 so that the firing conditions are optimal for the denture to be fired 5.

The purpose of this invention is to solve the problems of the conventional technology described above, and to provide a vacuum firing furnace that can easily manage the heat inside the furnace so that the firing conditions are optimal for the objects to be fired stored in the furnace. It is about providing.

The present invention comprises a cylindrical vertical firing furnace body installed above the base, and a disc-shaped firing table that moves up and down between the body and the base and has a stand for attaching the objects to be fired. In the vacuum firing furnace, the thermocouple extends upward from the approximate center of the firing table, and the outer peripheral edge of the thermocouple is attached to a heat-resistant spacer that is removably stacked on the table. The vacuum firing furnace is characterized in that each central portion in the height direction of the object to be fired placed on the heat-resistant spacer is located approximately at the tip of the thermocouple.

Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

FIG. 3 is a longitudinal sectional view showing an example of the vacuum firing furnace of the present invention.

This vacuum firing furnace consists of a base 16, a cylindrical firing furnace main body 8 provided above the base 16 via a support 7 erected on the base 16, and a cylindrical firing furnace main body 8 between the base 16 and the firing furnace main body 8. It mainly consists of a firing table 9 that moves up and down between the two.

A heating coil IOA made of platinum wire or the like is disposed on the inner peripheral side wall of the firing furnace body 8 .

The firing table 9 consists of a disk-shaped table main body 10 and a cylindrical body 11 whose upper end is fixed to the center of the bottom surface of the table main body 10 by welding.

The disc-shaped stand main body 10 has a hole in the center, and a stainless steel cylindrical body 12 is fixed therein, and inside this cylindrical body 12 and the cylindrical body 11, a thermoelectric conductor made of platinum-platinum rhodium is installed. Built-in vs. 13.

The tip of the thermocouple 13 projects slightly upward from the upper end of the cylindrical body 12.

Further, an annular projection 14 extending upward is formed on the outer peripheral edge of the base body 10, and a rubber ring 15 is attached to the inner peripheral surface of the projection 14.

A flange portion 24 is formed at the lower end of the cylindrical body 11, a bottom plate 17 is airtightly fixed to the flange portion 24 with bolts and nuts via an O-ring, and a thermocouple 13 is fixed to the bottom plate 17 by welding.

A protrusion 23 is provided in the side of the cylindrical body 11 to fit a rubber hose connected to a vacuum pump (not shown).

In FIG. 3, 18°, 19.20 indicate heat-resistant spacers made of ceramic.

These spacers 18, 19, 20 are disk-shaped with a hole in the center, and in particular, notches are formed on the outer peripheral edge of each upper surface of the spacers 18, 19, and the spacers 18, 19, 20 are located above each of these notches. The projections formed on the outer periphery of each bottom surface of the spacers 19 and 20 engage with each other.

In FIG. 3, reference numeral 21 indicates an object to be fired for dentures, and 22 is a sample stand for fixing the object to be fired for dentures, and is made of ceramic.

In the vacuum firing furnace of the present invention configured as described above,
When performing firing work, spacers 1B and 19 are attached to the cylindrical body 12.
．． 20 are fitted one after another in a stepped manner, and a sample stage 22 in which a denture to be fired 21 is fitted is placed on the surface of the spacer 20.

At this time, the height of each center of the object to be fired 21 is
It is adjusted so that it is located at the tip of the

Next, the firing table 9 is raised to the firing furnace main body 8 side by a lifting mechanism (for example, a rack and pinion) (not shown), and the firing furnace main body 8 and the disc-shaped stand main body 10 are moved by a heat-resistant rubber ring 1.
Sealed by 5.

Thereafter, the inside of the furnace is maintained in a vacuum state using a vacuum pump, and the heating coil 10A is energized so as to maintain the inside of the furnace at a predetermined firing temperature condition, for example, about 1000°C.

At this time, the tip of the thermocouple 13 is located at the center of the furnace, and the storage position of the object to be fired 21 within the furnace is also approximately at the center of the furnace where there is little temperature gradient.

Therefore, the temperature measured by the thermocouple 13 is the temperature near the object to be fired 21, so the thermocouple 13 can always maintain the atmosphere near the object to be fired 21 at the predetermined firing conditions, and the temperature inside the furnace Management becomes easier.

After the baking process has been completed, the baking table 9 is lowered and the processed material is taken out of the machine together with the sample table 22.

In the present invention, the tip of the thermocouple is designed in advance so that it is located approximately at the center of the furnace when the firing table 9 is raised toward the firing furnace main body 8 and the furnace is in a vacuum state for firing. There is.

Therefore, the size of the spacer or the number of stacked spacers is selected depending on the size of the object to be fired 21, and
The height of each central part of the object to be fired 21 fixed to the thermocouple 2 can be adjusted so that it is located at the tip of the thermocouple 13.

In order to simplify the adjustment of the height of the spacer part, a hole A is formed in the center of the disk-shaped body, and the circular tube body is radially extended from this hole A, as shown in Fig. 4. It is desirable to use a spacer 25 having a notch B large enough to allow the spacer 12 to be inserted therethrough.

According to this spacer 25, the height can be adjusted to a predetermined value by simply inserting and removing the spacer 25 from the side of the cylindrical body 12.

Note that the temperature distribution within the cylindrical vertical firing furnace body occurs in the vertical direction within the furnace, and hardly occurs in the horizontal direction.

Therefore, the heating temperature of many workpieces installed horizontally without temperature distribution is almost constant, and since the thermocouple is located at a position corresponding to the center of many workpieces, The heating temperature can be determined simultaneously and accurately.

It goes without saying that the objects to be fired in the vacuum firing furnace of the present invention are not limited to those for dentures, but can be applied to all relatively small objects to be fired.

Further, as the thermocouple 13, thermocouples formed from various metals can be selected and used depending on the firing temperature conditions depending on the object to be fired.

As described above, according to the present invention, (1) during the firing operation, the thermocouple and the object to be fired can always be placed at a close distance, so even if the inside of the furnace has a constant temperature distribution, The temperature near the fired product can be measured, making heat management easy.

(2) Since the thermocouple and the object to be fired move simultaneously when the firing table is moved up and down, the temperature near the object to be fired can be constantly measured.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the structure of a conventional vacuum firing furnace;
Figure 2 is a schematic configuration diagram showing the structure of the vacuum firing furnace shown in Figure 1 during firing operation, Figure 3 is a longitudinal sectional view showing an example of the present invention, and Figure 4 is a spacer used in the present invention. It is a perspective view showing an example. 1.16... Base, 2,8... Firing furnace body, 3,9... Firing table, 4.13...
・Thermocouple, 5, 21... Item to be fired (denture), 6
゜10A...Heating coil, 12...Cylindrical body (made of stainless steel), 15...Rubber ring,
18,19.20...Spacer (made of ceramic).

Claims (1)

[Scope of utility model registration request] Vacuum firing equipped with a cylindrical vertical firing furnace body installed above the base, and a disc-shaped firing table that moves up and down between the body and the base and has a stand for attaching objects to be fired. In the furnace, the thermocouple extends upward from approximately the center of the firing table, and the attachment of the thermocouple to the outer periphery includes providing a heat-resistant spacer that is removably stacked on the table, and A vacuum firing furnace characterized in that each central part in the height direction of the object to be fired placed on the heat-resistant spacer is located approximately at the tip of the thermoelectric lamp.