JPH022818B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an airtight window in which a transparent glass is hermetically sealed in a hole in a metal plate.

2. Description of the Related Art An airtight window as shown in FIGS. 1 and 2 is used in a peephole for observing the flow of refrigerant gas in a cooler or the like, or an oil level gauge in a tank or the like. In the figure, 1 is an annular metal plate, in the center of which a through hole 2 for glass sealing is formed, and on its outer periphery an annular groove 3 into which an O-ring made of an elastic material such as rubber is inserted is formed. A mounting hole 4 is formed on the outside. 5 is a transparent glass hermetically sealed inside the through hole 2.
Then, an O-ring is fitted into the groove 3 so as to partially protrude, and the airtight window is attached to the wall of an airtight container such as a cooler using the mounting hole 4. As shown in FIG. 3, another type of airtight window is one in which a transparent glass 9 is hermetically sealed in a through hole 8 of a metal plate 6 having a sloped portion 7 on the upper periphery. This airtight window is installed by projection welding with the sloped portion 7 of the metal plate 6 in line contact with the periphery of a window mounting hole of a closed container such as a cooler.

Regardless of the structure described above, it is desirable that the transparency of the transparent glasses 5 and 9 be as high as possible.
However, conventional airtight windows have a problem of low transparency, and those with high transparency are expensive due to high processing costs.

That is, as shown in FIG. 4, this type of airtight window is generally made by placing a metal plate 1 on a sealing jig 10 made of graphite and having a protrusion 11 in a part with the groove 3 facing downward. The protrusion 11 is placed so as to partially fit into the through hole 4, and assembled with the transparent glass disk 50 placed in the through hole 2 of the metal plate 1, and the whole is placed in a neutral or weakly reducing atmosphere. It is manufactured by heating the transparent glass disk 50 to approximately 1000° C. in the interior, melting the transparent glass disk 50, and welding it to the metal plate 1.

However, the upper surface 11a of the protrusion 11 of the sealing jig 10 has a surface roughness of 20μ or more due to the cutting process, and therefore, the airtight window manufactured as described above is As shown in the figure, the sealing jig contact surface 5a of the transparent glass 5 becomes an uneven surface,
Since light is diffusely reflected by this uneven surface, the transparency of the transparent glass 5 is deteriorated.

Therefore, in order to increase the transparency of the transparent glass 5, the airtight window shown in FIG. Then, it is reheated at a temperature higher than the softening point of the transparent glass 5 and lower than the sealing temperature to melt and lower the convex portion of the sealing jig contact surface 5a, forming a relatively smooth surface 5b and improving the transparency. It is also considered that the airtight window manufactured as shown in FIG.
It is also considered that the transparency can be increased by reheating under the same heating conditions. However, both of these methods require two heating steps;
This is not only complicated but also increases processing time.
The disadvantage was that the processing costs were high and the airtight windows were expensive.

Therefore, the main object of this invention is to provide a highly transparent airtight window with a single heating process.

In summary, the present invention is characterized in that the surface roughness of the surface of the sealing jig that comes into contact with glass is set within a range of 7 to 15 microns.

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.

FIG. 7 is an exploded sectional view before glass sealing for explaining the manufacturing method of the present invention. In the figure,
The same parts as in FIG. 4 are given the same reference numerals. The difference from FIG. 4 is in the sealing jig 20. This sealing jig 20 is entirely made of graphite as shown in FIG. The surface roughness of 21a is set within the range of 7 to 15μ. Such surface roughness can be formed, for example, by polishing the upper surface 21a of the protrusion 21 with sandpaper of about 320 to 400 grit. The metal plate 1 is placed on the sealing jig 20 with the groove 3 facing downward so that the protrusion 21 fits into the through hole 2 of the metal plate 1, and then Hole 2
A transparent glass disk 50 is placed inside and heated to about 1000° C. in a neutral or weakly reducing atmosphere. Then, the transparent glass disk 50 is melted and welded to the metal plate 1, so that when cooled, an airtight window as shown in FIG. 8 is obtained. In this airtight window, the jig contacting surface 5c of the transparent glass 5 is a smooth surface, and the transparency of the transparent glass 5 is extremely high.

Note that if the surface roughness of the upper surface 21a of the protrusion 21 exceeds 16μ, the jig contact surface 5 of the transparent glass 5
c becomes an uneven surface, and the transparency is not much different from that of the conventional one.On the other hand, when the surface roughness becomes less than 7μ, the molten glass tends to adhere to the upper surface 21a of the protrusion 21, and the transparent glass 5 per jig. A thin film of graphite is formed on the surface 5c, and the jig contacting surface 5c of the transparent glass 5 becomes opaque as if covered with a white curtain. Therefore, the surface roughness of the upper surface 21a of the protrusion 21 of the sealing jig 10 is set within the range of 7 to 15 microns.

The airtight window manufactured by the method of this invention was able to secure the same transparency as the conventional two-time heating process (a 4 mm □ character can be read with a separation of 30 mm) through a single heat sealing process. .

The above embodiment describes the case of manufacturing an airtight window having the structure shown in FIGS. 1 and 2.
The same method can be used to manufacture an airtight window having the structure shown in the figure. However, when manufacturing the airtight window shown in FIG. 3, it goes without saying that the protrusion 21a is unnecessary.

Further, in the above embodiment, the case where the transparent glass disk 50 is used has been described, but the metal plate 1 is placed on the sealing jig 20, and the through holes 2 of the metal plate 1 are
It can also be applied to the case where transparent glass is formed by supplying molten glass into the interior.

As described above, the present invention provides a method for manufacturing an airtight window in which a metal plate having a through hole is placed on a sealing jig made of graphite, and glass is welded into the through hole. Since the surface roughness of the surface in contact with the glass is set within the range of 7 to 15 microns, the jig contacting surface of the transparent glass becomes a smooth surface, resulting in an airtight window with high transparency of the transparent glass. Moreover, since the desired transparency can be obtained in a single heating step, an airtight window with high transparency can be obtained at low cost.

[Brief explanation of drawings]

Figure 1 is a plan view of an example of an airtight window, and Figure 2 is a top view of an example of an airtight window.
3 is a sectional view of another example of the airtight window, FIG. 4 is an exploded sectional view for explaining the conventional manufacturing method of the airtight window shown in FIG. 1, and FIG. is a cross-sectional view of an airtight window manufactured by a conventional method, FIG. 6 is a cross-sectional view for explaining another conventional method for improving the transparency of transparent glass, and FIG.
An exploded sectional view for explaining the case where the airtight window shown in the figure is manufactured by the manufacturing method of the present invention, No. 8
The figure is a sectional view of an airtight window manufactured according to the present invention. DESCRIPTION OF SYMBOLS 1, 6... Metal plate, 2, 8... Through hole, 5, 9... Transparent glass, 20... Sealing jig, 21a... Surface (top surface) in contact with glass.

Claims (1)

[Scope of Claims] 1. A method for manufacturing an airtight window, in which a metal plate having a through hole is placed on a sealing jig made of graphite, and the upper surface of the glass is welded in a free state into the through hole, comprising: A method for manufacturing an airtight window, characterized in that the surface roughness of the surface of the jig to be welded to the glass is set within the range of 7 to 15μ.