JPH0150057B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present application relates to a method of manufacturing a cover glass for a box-shaped display tube.

Conventionally, cover glass for square-shaped box-shaped display tubes was manufactured by placing individual glass pieces and a glass plate in a graphite mold, and raising the temperature to heat the glass pieces together and the glass pieces and the glass plate. This is done by welding.

For example, FIG. 1 shows a lower mold, 2 an upper mold, and the individual glass pieces 3 to 3 are placed in the groove of the lower mold Q to form a square shape as shown in FIG. 2, and then the glass plate 4 is placed. The cover glass is placed on top of individual pieces of glass and heated and welded to produce a box-shaped cover glass as shown in Fig. 3.

However, with this manufacturing method, the four corners of the cover glass (P, P', P'', P in Fig. 3) tend to be insufficiently welded, which is a major drawback in ensuring vacuum tightness. is the gathering point of the three glass parts, i.e., the long side a, the short side b, and the display surface c in Fig. 3, and air lines are likely to be formed at these four corners due to fluctuations in the temperature conditions during welding. There is.

The present application improves on these conventional drawbacks, and the gist of the present application is to provide a cover that is characterized in that during heat welding, the welded areas between the individual glass pieces and the display surface are pressed from the display surface side at the four corners of the cover glass. It's in the method of manufacturing glass.

Next, an example will be explained.

FIG. 4 shows the mold of the present invention, in which projections are locally provided on the upper mold for pressing the four corners.

Figure 4 S shows this protrusion, which locally presses the four corners during heat welding, and in the finished cover glass, the four corners are more rounded than the surrounding areas other than the four corners as shown in Figure 5. The shape of this protrusion is not particularly limited, but if it is too large, the appearance of the display surface will be unsightly, so it should be covered by at least the thickness of the glass piece. As much as possible is enough;
Experiments have also shown that by making the height of the protrusion slightly higher than the areas other than the four corners, it was possible to completely eliminate air lines that tend to occur at the four corners.

In this application, the same effect can be obtained to a certain extent by heating and welding the display surface and the periphery of the individual glass pieces while pressing uniformly, but it is also possible to press the four corners deeper than the periphery while also pressing the periphery. within the scope of the claims. Pressing the periphery, especially the upper and lower parts of the display surface, which are important to the viewing angle, will distort the glass, which will affect the viewing angle, and it cannot be pressed too hard.

In the present application, the four corners, which do not affect the viewing angle and are likely to impair vacuum tightness, are welded while being pressed more strongly than the surrounding areas, thereby obtaining a reliable cover glass that does not impede the viewing angle.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional mold, FIG. 2 is a perspective view showing a combination of individual glass pieces, FIG. 3 is a perspective view of a cover glass molded with a conventional mold, and FIG. The sectional view shown and FIG. 5 are perspective views showing the cover glass according to the present application. 1...lower mold, 2...upper mold, 3...piece of glass,
4... Glass plate, P... Four corners of cover glass, Q
... Groove of the lower mold, a ... Long side of the glass piece, b ... Short side of the glass piece, c ... Display surface, R ... Traces of pressing at the four corners of the cover glass, S ... Protrusion of the mold.

Claims (1)

[Claims] 1. By placing the part corresponding to the side wall portion from the individual glass pieces and the part corresponding to the display portion from the glass plate in a mold and increasing the temperature, the individual glass pieces are separated from each other and the glass pieces are separated from the glass plate. In manufacturing box-shaped cover glass for display tubes that are heat-welded,
A method for producing a cover glass for a display tube, characterized in that during heat welding, the welded parts between the four corner pieces of glass and the display surface of the square-shaped cover glass for a box-shaped display tube are pressed from the display surface side.