FI78999C - Device placed in front of an image tube for shielding against radiation and static electricity - Google Patents

Description

1 78999

A device that is installed in front of a picture tube to protect against radiation and static electricity

The present invention relates to a device for providing protection against radiation and static electricity, which device is arranged in front of a picture tube and consists of an electrically conductive frame connected to a ground connection and a fine mesh net of electrically non-conductive plastic material, preferably nylon material.

When reading image surfaces, more and more readers suffer from skin problems and eye and throat irritations. Namely, the image surface develops an electric field with potentials of up to +15000 V. The reader of the image surface also becomes charged, for example, when the feet rub against the floor. The potential of the reader is from +3000 Vs to +6000 Vs. The field strength between the imaging terminal and the reader can be up to 40,000 V / m. The particles in the ambient air are electrically charged, which results in a flow of particles in the electric field between the image surface and the reader. These particles settle on the face of the reader, to which they adhere and cause the above-mentioned ailments.

U.S. Pat. No. 4,253,737 discloses a cover with a reflection shield which is directly against the picture tube. As a result of this direct contact between said reflection shield and the image tube, a substantial reduction in reflection attenuation is created and, in addition, an interfering interference image and so-called Newton rings are created. This known shield does not protect against static electric fields.

It is known from DE-1 614 020 to introduce an electrically conductive metal layer either directly on the glass surface of the picture tube or with a separate glass plate mounted in front of the picture tube. In this case, the disadvantages caused by the reflection of light on the glass surface are not avoided.

2 78999

U.S. Pat. No. 3,801,418 discloses a window which should conduct static electricity and at the same time reduce the risk of accidental explosion of explosives by applying an electrically conductive metal layer directly to one surface of the glass sheet.

DE-2 329 484 discloses a method for producing an electrically conductive fiber, but this does not provide any indication of how light reflections and the generation of a static electric field can be avoided in the vicinity of the picture tube.

The object of the invention is to provide a device which eliminates the electric field in front of the picture tube, prevents particle flows, provides a more skin- and eye-friendly environment and achieves an anti-reflex effect.

This object is achieved in that the device in the preamble of the claim is characterized by what is stated in the characterizing part.

The present invention provides a combined protection against electric field, skin contamination and reflections while achieving a pleasant and user-friendly environment without adversely affecting image quality.

The invention will be described in more detail below with reference to the accompanying figures, in which Figure 1 shows a view of a device according to the invention, Figure 2 shows a vertical cross-section through the device of Figure 1, Figure 3 shows a cross-section similar to Figure 1 through a modified device according to the invention.

The device shown in Figures 1 and 2 comprises a cover 1 which is shown as rectangular but which may have a square or other shape and has a sufficient surface area so as to substantially cover the image surface in front of which the cover 1 is intended to be placed. The cover 1 consists of a rectangular, electrically conductive frame 2, a fine-meshed nylon mesh 3 tensioned therein and electrically conductive wires 4 stretched between opposite frame parts of the frame 2 and in contact with the nylon mesh 3, as shown in Figures 1, 2. The number 5 means the connection of frame 2 to the ground potential. The number of wires 4 is adjusted according to the size of the frame 2, which in turn is adjusted according to the size of the image surface of the image surface terminal located in front of the image tube. Instead of the arrangement according to Figures 1, 2, the yarns 4 can be more or less woven or braided into a nylon net, i.e. they can run next to the yarns of the nylon net and cut these.

The described cover 1 is mounted in front of the relevant image surface, which may be in image terminals, video devices, etc. In this case, the cover 1 with nylon nets 3 supporting electrically conductive wires 4 connected to a grounded frame neutralizes the electric field between the image surface and the reader. ibova problems or irritated eyes or throat occur. Namely, the electrical properties of the nylon mesh 3 and the conductive wires 3 together with the electrically conductive, grounded frame 2 are sufficient to insulate said electric field.

The shield shown in Fig. 3 includes, like the shield 1, an electrically conductive, grounded frame to which a nylon mesh 3 is tensioned, but the conductive wires 4 present in the shield 1 have been replaced by a transparent and electrically conductive layer 7 electrically connected to the frame 2.

The cover 6 is suitably mounted so that the conductive layer 7 4 78999 will be located closest to the image surface, i.e. inverted. Even in this cover structure, the flow of particles towards the reader and especially his face is effectively prevented.

The design of the cover can be modified within the scope of the invention. For example, the frame may be formed of only two opposite frame parts, which may be mounted on holders or a readable device, and the means adapted to insulate the electric field, namely a nylon mesh and wires or a layer, may have some other suitable structure. The nylon mesh can, of course, be replaced by another mesh made of non-conductive plastic.