JPS59108246A - Inspection method for projection type cathode ray tube - Google Patents

Abstract

PURPOSE:To reject defective cathode ray tube prior to operation by heating the raster section of face plate through a heating member having approximately same shape with raster to be formed by electron beam from cathode ray tube thereby producing tension in the circumference of face plate. CONSTITUTION:A heating member 22 having approximately same shape with raster is placed on a supporting table 21 while a positioning zig 23 is provided on said table 21 such that the raster section of explosion-proof cathode ray tube will come onto said heating member 22. A projection type cathode ray tube comprising face plate, funnel 3, stem 4 and explosion-proof band 5 is mounted on such inspection table while facing the face plate downward then the heating member 22 is left at same temperature with that of raster section under operation for predetermined time. Consequently tensile distortion is produced in the side wall section of face plate and if there is a defect in this section it will shrink explosively to enable rejection of defective Braun tube. The maximum temperature of heating member 22 is operating temperature plus 100 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for inspecting a projection cathode ray tube.

[Technical background of the invention and its problems]

A projection type cathode ray tube is designed to draw a high-brightness image on a fluorescent surface on the inner surface of a face plate, and enlarge this image onto a screen using an optical system such as a lens and a reflector.

In order to draw this high-brightness image, K sends an electron beam current that strikes the fluorescent surface from a normal cathode ray (1), funnel (2), neck (3), stem (4), and explosion-proof band (5). Of the projection type cathode ray tube, in particular, the raster part (6) corresponding to the raster shape formed by the electron beam shown by diagonal lines on the face plate (1) is heated and thermally expanded. On the other hand, the periphery of the face plate 1/-, for example, points A and B, are hardly heated.

The group of curves in Figure 3 shows the temperature rise at point A, point B, and the zero point at the center of the rask part (6), and curve a (7)
indicates 0 point, curve (8) indicates point B, and curve (9) indicates 0 point.

As a result, as shown in Fig. 4, the tension strain at point A has a value as shown by the curve Q11, and the tension strain at point B has a value as shown in curve Q11.As shown in Fig. 5, the tension strain at point A and B It will occur in the direction of the arrow circle and arrow α with the center at .

On the other hand, several dozen steps are required to complete a projection cathode ray tube, and during this process, scratches (IQ) may be formed on the periphery of the face plate (1), for example near point A.Especially on the face plate (1). Since a metal band (5) is attached to the outer periphery of the ring, it is easily damaged.

If this flaw θ9 is located on the periphery of the face plate (1), a rack circle will be formed as shown in FIG. 6 due to tension strain applied in the direction of arrow Oa Q3 during operation.

However, this type of rack (I4) is extremely dangerous as it occurs during operation of the projection cathode ray tube, but it is difficult to detect the scratches that will become crank I during the manufacturing process. An effective testing method is desired.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned needs, and it generates tension distortion around the face plate without operating the projection cathode ray tube, and removes scratches from the projection cathode ray tube before operation due to this tension distortion. It is an object of the present invention to provide a method for inspecting a projection type cathode ray tube, which can be used to remove the defects.

[Summary of the invention]

That is, the present invention is a projection type cathode ray tube inspection method in which a part of the raster of the face plate is heated by a heating element having approximately the same raster shape as the raster shape formed by the electron beam of the projection type cathode ray tube. The same temperature as the temperature of part of the face plate during operation or +10 to this temperature
It is characterized by a temperature range including 0°C.

[Embodiments of the invention]

Next, an embodiment of the present invention will be described with reference to FIGS. 7' and 8. In the figures, the same reference numerals as in the conventional example indicate the same parts, and no particular explanation will be given.

That is, on the support stand (21) there is placed a heating element (2) having a shape almost the same as the raster shape, and on the support stand (2+), a part of the rask of the explosion-proof cathode ray tube is placed on the heating element 02B. A projection type cathode ray tube consisting of a face plate, a funnel (3), a stem (4) and an explosion-proof band (5) which cannot be seen in the figure is placed on such an inspection table. If the plate is placed with the plate facing down and the heating element (2) is kept at the same temperature as the raster part during operation for a predetermined period of time, a tension strain similar to that shown in Figure 4 will occur on the side wall of the face plate. Therefore, if there is a scratch in this part, it will implode and the defective projection type cathode ray tube can be removed.

The time for placing the heating element (221) may be about 90 minutes, as can be seen from the curve in FIG.

Note that the higher the temperature of the heating element (221), the more likely it is that tension strain will occur, but considering the phosphor formed on the inner surface of the face plate and the structure of the projection cathode ray tube,
The maximum temperature is around 100°C, and care must be taken as increasing the temperature higher than this may result in a destructive test.

The simplest heating element is one in which a heater is embedded in a metal or an insulating material with relatively good thermal conductivity.

〔Effect of the invention〕

As mentioned above, according to the present invention, it is possible to detect damage to the projection cathode ray tube during operation, and it is possible to ship products of extremely high quality, so the industrial value thereof is extremely large. It is.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of a projection cathode ray tube, FIG. 2 is a perspective view showing a temperature measurement point at the center of the side wall of the face plate and a part of the raster with the metal band removed;
Figure 3 is a graph showing the temperature progression at the temperature measurement point, Figure 4 is a graph showing changes in tension strain on the side wall of the face plate, and Figure 5 is a graph showing the direction of tension strain and scratches on the side wall of the face plate. Perspective view, No. 6
The figure is a perspective view showing a state of cracks due to scratches, FIGS. 7 and 8 are views showing one embodiment of the present invention, FIG. 7 is a perspective view showing an inspection table, and FIG. 8 is a projection on the inspection table. FIG. 2 is a perspective view showing a state in which a type cathode ray tube is placed. 1... Face plate 5... Metal hunt 6.
... Raster part 13 ... Scratch 14 ... Crack 22 ... Heating body representative patent attorney Inoue - Male

Claims (2)

[Claims] (1) A method for inspecting a projection cathode ray tube, which comprises heating a part of the rask of the face plate with a heating element having approximately the same shape as the raster formed by the electron beam of the projection cathode ray tube. (2) Projection according to claim 1, characterized in that the temperature of the heating element is within the same temperature range as the temperature of a part of the raster of the face plate during operation to +100° C. above this temperature. Inspection method for model cathode ray tubes.