JPS58104591A - Interference magnetic field reducing method for cathode ray tube - Google Patents

Abstract

PURPOSE:To prevent picture distortion of a cathode ray tube, by reducing the effect of induced magnetic field from distribution lines and electric machines, through the provision of a single closed circuit coil not requiring any power supply at the outside of the cathode ray tube. CONSTITUTION:Closed circuit coils 2a-2d are placed at the circumference of a cathode ray tube 1. If a magnetic field interlinked with the coils 2a-2d exists, a coil interlinked with the magnetic field induces a current which cancels the interlinked magnetic field. Then, the interlinked magnetic field can be reduced. Thus, the picture distortion of the cathode ray tube 1 can be prevented to the utmost.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is designed to reduce the influence of induced magnetic fields from power distribution lines, electrical equipment, etc. on cathode ray tubes for televisions, oscilloscopes, etc., and to prevent image distortion in cathode ray tubes. Relating to a magnetic field reduction method.

When a cathode ray tube used in televisions, oscilloscope radars, etc. is under the influence of magnetic fields generated from IE wiring or electrical equipment, the electrons emitted from electron gun a are affected by the alternating magnetic field, as shown in Figure 1. As a result, the traveling path becomes distorted, and as a result, the image on the screen C becomes blurred.

Therefore, the cathode ray tube d is surrounded by a metal plate e with high magnetic permeability, such as iron or permalloy, to weaken the magnetic field reaching the cathode ray tube d.

However, in order to obtain such an effect, the metal plate e is required to have a considerable thickness, which inevitably increases the weight of the device.

Therefore, due to its weight, attachment to the cathode ray tube d becomes troublesome and time-consuming.

Moreover, if a slit exists between adjacent metal plates e% 0, the magnetic resistance will increase, and the effect of reducing the disturbing magnetic field will be halved.

For this reason, the joints between the metal plates ES have to be welded, which is extremely troublesome to manufacture.

In order to deal with this problem, it has already been proposed to attach a loop-shaped coil to the cathode ray tube, and to run a current through the coil to generate a magnetic field in the opposite direction to the interfering magnetic field, thereby blocking magnetic interference. .

However, in such a known example, an external power source is required to pass current through the fill, and accordingly, current adjustment of the external power source, phase adjustment, and adjustment due to movement of the cathode ray tube are required, so the device is It is complicated and difficult to handle.

The present invention aims to solve the above problems by using a simple closed circuit coil that does not require a power source, etc. This will be explained with reference to an embodiment shown in the drawings. As shown in FIG. John, cathode ray tubes used in oscillography radar, etc. (closed circuit coil (21a)
, +21b.

Set up +21c and 121d.

In the same figure, closed circuit coils +21 a and +21 b
.

(21c, t2J d are installed directly on the circumferential surface of the cathode ray tube 11), but the invention is not limited to this.
) may be attached to a cabinet (not shown) around the coil.

Same coil 12) a, +21 b, [21c
, +21 d, as shown in FIG. 3, it is preferable to use etching of the printed circuit board (3) in view of ease of manufacture.

In Fig. 4, a fill is produced by etching the printed circuit board (3) in the same manner as above, but in this figure, the coil is formed in a spiral shape, and the terminal (41a
, (by connecting 41b with lead wire (5),
It is configured as a closed circuit.

Closed circuit coil (21a s +21 b 1 (21c
As can be seen from the drawing, the shape of the tube 1121d is trapezoidal, but it may also be made into a square so as to surround the entire surface of the cathode ray tube (1).

Also, in Figure 2, there is a closed circuit coil on the entire circumference of the cathode ray tube (tl)! 21 a, (21b, +21 c
, +21 d is installed, but depending on the magnitude and direction of the external magnetic field φ, it may not be necessary to provide it on the entire circumferential surface, but only on the - side.〇 As described above, in the present invention, a closed circuit filter is installed on the outside of the cathode ray tube. was installed to reduce the external magnetic field, so if there is a magnetic field interlinking to the closed circuit coil, a current is induced in the coil that attempts to cancel the magnetic field, and the current interlinking to the closed circuit coil is induced. The resulting magnetic field will be reduced, and image distortion will therefore be prevented as much as possible.

Moreover, since it is a mere fill, it is lightweight, and therefore not only can it be easily attached to a cathode ray tube, but it is also easy to manufacture.

Furthermore, once installed, no further adjustment is required and the system is simple in handling and construction.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a conventional example, FIG. 2 is a perspective view showing a closed circuit installation state used in the method according to the present invention, and FIGS. 3 and 4 are plan views of the same coil. ill... Braun tube +21a, (21b, +21c, 121d...
...Closed circuit coil φ...Disturbing magnetic field agent Patent attorney Makoto Ifuji Figure 1, Figure 2, 11 Figure 3, Figure 4

Claims (2)

[Claims] (1) In a method of reducing external interference magnetic fields for cathode ray tubes used in televisions, oscillographic radars, etc., a closed circuit coil is installed outside the cathode ray tube to reduce external interference magnetic fields. Features a method for reducing disturbing magnetic fields in cathode ray tubes. (2) A method for reducing interference magnetic fields in a cathode ray tube according to claim 1, characterized in that a closed circuit coil manufactured by etching a printed circuit board is provided outside the cathode ray tube.