Cathode-ray tube with a coil-shaped high resistance body

Abstract: A high resistance body for supplying the high voltage of an anode terminal to the electrodes of an electron gun is coil-shaped. The anode terminal is mounted on the funnel portion of a glass bulb, and overlapped by a first conducting layer. The anode terminal is electrically connected to the electrodes of the electron gun comprising the coil-shaped high resistance body, second conducting layer and metal strip. The equivalent circuit comprises a resistance and condenser connected in parallel, at least an inductance generated by the coil-shaped high resistance body connected in series to the resistance, and the electrodes of the electron gun.

Description: Technical Background The present invention concerns a cathode-ray tube comprising a high voltage supplying means a cathode-ray tube comprising: a high voltage supplying means for supplying a high voltage to an electrode of an electron gun, said high voltage supplying means consisting of an internal conducting layer and discharging current buffering means for absorbing the discharging current, said discharging current buffering means comprising a coil-shaped structure and being electrically connected to th anode terminal. A device of this kind is known from JP-A-57/040839. This document shows an arrangement already suitable for damping the discharge current. Conventionally, as can be seen from Fig. 1 of the drawings, the glass bulb 1 of a cathode-ray tube comprises a funnel portion 2, anode terminal 3 mounted on the funnel portion, and conducting layer 4 deposited on the inside of the funnel portion 2. The anode terminal 3 is overlapped by the conducting layer 4, and electrically connected to the electrode 12 of an electron gun 8 having conducting layers 5 and 6 and conducting metal 7, as shown in Fig. 1. To the inside of the panel 9 of the glass bulb 1 is attached a fluorescent film 10 and metal back 16 electrically connected to the anode terminal 3. The metal back 16 comprises a conducting panel 15, spring 17 for holding a mask, mask frame 13, conducting metal strip 14, and the conducting layer 4. The equivalent circuit of the conventional cathode-ray tube is shown in Fig. 3A. A high voltage from the anode terminal 3 is applied through a high resistance body 5 (resistance R in Fig. 3A) to the electrodes 12 of an electron gun 8. In this case, there occurs frequently an electric discharge between the electrodes due to possible foreign matters such as dust, so that a discharging current of a high peak value as shown in Fig. 4A or 48 may flow to damage the circuit elements connected to the electrodes of the electron gun 8. OBJECT OF THE PRESENT INVENTION The object of the present invention is to provide an improved means for buffering or absorbing the discharging current so as to prevent the damaging of the circuit elements in the cathode-ray tube of a TV receiving system. SUMMARY OF THE INVENTION According to the present invention, there is provided a cathode-ray tube comprising a high voltage supplying means for supplying a high voltage to the electrodes of an electron gun, and a discharging current buffering means consisting of a high resistance coil-shaped body located in the funnel section of the bulb. The present invention will now be described with reference to the drawings attached only by way of example. BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS Fig. 1 is a schematic cross-sectional view of a conventional cathode-ray tube; Fig. 2A is a schematic cross-sectional view of a cathode ray tube according to the present invention; Fig. 2B is a cross-sectional view taken along line A-A' of Fig. 2A; Fig. 3A is an equivalent circuit of the conventional cathode-ray tube; Fig. 3B is an equivalent circuit of the inventive cathode-ray tube; and Fig. 4 illustrates the characteristic curves of the discharging current (Is) generated by the electrodes of electron guns, wherein A represents the case of using a low resistance body, B high resistance body, and C coil-shaped high resistance body. DETAILED DESCRIPTION OF A CERTAIN PREFERRED EMBODIMENT Referring to Figs. 2A and 2B, an anode terminal 3 is attached to the funnel portion 2 of a glass bulb 1, and overlapped by a first conducting layer 4. An electron gun 8 comprises a coil-shaped high resistance body 5a, a second conducting layer 6 and a first metal strip 7. The anode terminal 3 is electrically connected to the electrode 12 of the electron gun 8. To the inside of the panel 9 of the glass bulb are attached a fluorescent film 10 and metal back 16, which comprises a conducting panel pin 15, spring 17 for holding a mask, mask frame 13, second metal strip 14 and the first conducting layer 4. These are electrically connected to the anode terminal 3. Referring to Fig. 3B, the equivalent circuit of the inventive cathode-ray tube using the coil-shaped high resistance body 5a comprises a resistance R1 and capacitance C1 connected in parallel, at least an inductance L1 connected in series to the resistance R1, and the electrodes 12 of the electron gun 8. The inductances are produced by the coil-shaped high resistance body 5a. Hereinafter described is the operational effect of the inventive cathode-ray tube with reference to Fig. 4. When a high voltage from the anode terminal is applied to the electrodes 12 of the electron gun 8, a possible foreign matter present in the tube causes the electrodes to generate a discharging current of a high peak value. This discharging current is buffered by the inductance L1 of the coil-shaped high resistance body 5a, considerably decreased as shown by the waveform C in Fig. 4. Thus, the transistors and IC elements of the TV receiving system are effectively protected. As stated above, the inventive cathode-ray tube uses the coil-shaped high resistance body in order to buffer the discharging current of a high peak value caused by a possible foreign matter present in the tube, thus preventing the damaging of the circuit elements.

Claims: Cathode-ray tube comprising: a high voltage supplying means for supplying a high voltage to an electrode (12) of an electron gun (8), said high voltage supplying means consisting of an internal conducting layer (4) and discharging current buffering means for absorbing the discharging current, said discharging current buffering means comprising a coil-shaped structure (5a) and being electrically connected to the anode terminal (3) and to said electrode (12), characterised in that the discharging current buffering means consists of a high resistance coil-shaped body (5a) located in the funnel portion of the glass bulb.

Inventors: LEE KYUNG SANG DONG, LEE, KYUNG SANG, LEE, KYUNG SANG, 505, 318 DONG
Applicants: GOLD STAR CO, GOLDSTAR CO. LTD.
Application year: 1991
Main classification: H01J29
IPC codes: H01J29