JPS5924746B2 - How to manufacture surveillance windows - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a monitoring window in which transparent glass is hermetically sealed within a metal outer ring.

A monitoring window for internal monitoring is sometimes provided in various cases, tanks, etc., and this type of monitoring window is, for example, as shown in Figs. 1 and 2, inside the metal outer ring 1 made of iron or low carbon steel. It has a structure in which transparent glass 2 made of soda lime glass is hermetically fused and sealed.

By the way, as shown in FIG. 3, this type of monitoring window is constructed by placing a metal outer ring 1 on a graphite sealing jig 3, and placing a transparent glass disc 2' inside this metal outer ring 1. The transparent glass disk 2' is heated to about 1000° C. in a neutral or weakly reducing atmosphere to melt the transparent glass disk 2' and hermetically seal it to the metal outer ring 1. . For this reason, the upper surface of the transparent glass 2 during sealing is a smooth free surface 2a, but the lower surface is a jig contact surface and is a rough surface 2b with fine irregularities. . Therefore,
When this monitoring window is installed on the tank mentioned above, the rough surface 2
Because of b, the transparent galanus 2 becomes ground glass-like and has low transparency, resulting in a problem that its function as a monitoring window is poor. Therefore, the main object of the present invention is to provide a highly transparent monitoring window in which the jig-contacting surface of transparent glass is not rough. In summary, the present invention is characterized in that after transparent glass is sealed to a metal outer ring in the same manner as in the conventional method, it is cooled down and then reheated again at a temperature equal to or higher than the melting point of the transparent glass.

The above objects and other objects and features of the present invention will become more apparent from the following detailed description with reference to the drawings.

In this invention, first, as shown in FIG. 4, a metal outer ring 1 is placed on a graphite sealing jig 3,
A transparent glass disc 2' is placed inside the metal outer ring 1, and heated at a temperature of 950 to 1020°C in a neutral or weakly reducing atmosphere to melt the transparent glass disc 2' and remove the metal. ring 1
After fusion, the whole is taken out of the furnace and cooled.

Then, as shown in FIG. 5, a monitoring window 4a is obtained in which the transparent glass 2 is hermetically sealed within the metal outer ring 1. In this monitoring window 4a, the upper surface of the transparent glass 2 is a free surface 2a as in FIG. 2, and the lower surface is a rough surface 2b because it is a jig contact surface. Firstly, as it is, the rough surface 2b
As mentioned above, the transparency of the transparent glass 2 is low because of this. In this invention, the whole body is heated to 950 to 1
Reheat at a temperature of 0.020°C. And when it cools down again,
As shown in FIG. 6, the rough surface 2b becomes a smooth surface 2c, and a monitoring window 4b with high transparency of the transparent galanus 2 is obtained. As mentioned above, the reason why the rough surface 2b becomes the smooth surface 2c by reheating is not clear, but it is thought to be as follows.
That is, since the sealing jig 3 is made by cutting relatively fragile graphite, as shown in FIG.
It has a large number of unevenness 3a, and a large number of graphite fine powders 3b are attached thereto. Therefore, in the first sealing process, the fine powder 3b is rolled into the transparent glass 2 as shown in FIG. However, although the transparent glass 2 is remelted in the reheating process, since the fine powder 3b has already adhered to the contact surface of the transparent glass 2 with the sealing jig 3 from the first sealing process, no further melting is possible. Since the fine powder 3b did not adhere and was in contact with the sealing jig 3 during the first sealing process,
The surface layer of the contact surface with the sealing jig 3 is changed in material, and the surface tension of the molten galanus is increased. For this reason, as shown in FIG. 8, the fine powder 3b that was caught in the transparent glass 2 during the first sealing process is expelled from the glass by remelting, and the lower surface of the transparent glass 2 is removed from the sealing process. Since the molten glass solidifies while being supported in point contact by the unevenness 3a of the tool 3 and the fine powder 3b, the flatness becomes much higher than after the first sealing. Thereafter, when the fine powder 3b adhering to the surface layer of the transparent glass 2 is removed by washing, a highly transparent monitoring window 4b with a smooth lower surface 2c of the transparent glass 2 is obtained. Next, the effects of this invention will be specifically explained. Outer diameter is 16mTf
Lφ, inner diameter 10m71Lφ, thickness 5mmφ iron metal outer ring 1, transparent galanu made of soda lime galanu 2
By using a monitoring window 4a similar to the conventional product, which is only sealed with the above, and a monitoring window 4b, which is made by remelting the transparent glass 2 according to the present invention, type No. 1, type No. 3, type No. 5, type 7, etc. When I read the ``Kyo'' in print, the distances from which it could be read from the print surface were as follows. From this result, it will be understood that the effects of this invention are extremely large.

In addition, in this invention, it is important to perform the first sealing process as in the conventional method, cool it once, and then reheat it to a temperature higher than the melting point of the transparent glass. The result will not be affected whether or not the contact surface with the attachment jig 3 is changed between the initial sealing process and the reheating process.

Therefore, it is desirable to use the sealing jig 3 used in the first sealing process in the reheating process in order to reduce the number of steps.
In addition, the temperature of the reheating process is 250°C, which is higher than the softening point of transparent galanu 2 (700°C for soda lime glass).
It is desirable that the value be higher than that.

Therefore, it is convenient to use the same heating furnace as the same temperature as in the first sealing process. As described above, this invention seals a transparent glass inside a metal outer ring in the same way as in the past, cools it once, and remelts the transparent glass to form a rough surface of the transparent glass per jig. This has the effect that a monitoring window with extremely high transparency can be manufactured using transparent galanu.

[Brief explanation of drawings]

Fig. 1 is a plan view of a conventional example of a monitoring window, Fig. 2 is a sectional view taken along the line in Fig. 1, and Fig. 3 is a seal for explaining the conventional manufacturing method of the monitoring window shown in Fig. 1. 4 to 6 are sectional views before the process, and sectional views at different steps for explaining the manufacturing method of the monitoring window according to the present invention. FIGS. FIG. 3 is an enlarged sectional view of a main part for explaining the reason why transparency becomes high. 1...Metal outer ring, 2...Transparent glass, 3...Sealing jig.

Claims (1)

[Claims] 1 Place the metal outer ring on the graphite sealing jig,
A process of placing a transparent glass plate inside this metal outer ring, heating and melting the glass plate to airtightly seal it to the metal outer ring, a process of once cooling the whole, and a process of sealing the above-mentioned sealed body with a graphite cure. and reheating the glass at a temperature higher than the melting point of the glass on the glass.