Cathode ray display tube having external magnetic shield
First Claim
1. A cathode ray tube comprising an envelope containing means for generating an electron beam and a phosphor screen and having a transparent faceplate through which the display produced by the screen is visible, a magnetic shield comprising a mesh of high permeability magnetic material positioned over the outside of the faceplate, the mesh comprising an apertured sheet of the magnetic material having an array of regularly spaced apertures, characterized in that the apertures of the array are polygonal and defined by interconnected straight edged bars of the magnetic material.
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Accused Products
Abstract
A cathode ray display tube has a magnetic shield comprising a mesh (60) of high permeability magnetic material such as mumetal covering the outer surface of its transparent faceplate (14) through which a display from a screen (16) is visible and which together with a magnetic shielding box (70) surrounding the remainder of the tube'"'"'s envelope (10) inhibits extraneous magnetic fields entering the envelope and affecting the electron beam undesirably. The shielding arrangement is particularly useful with a flat tube having a relatively large area faceplate and using a low-energy scanning electron beam (32). The mesh (60) may be supported by one or more transparent members (66), and may be treated to enhance contrast of the display and also to act as a electromagnetic radiation shield.
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Citations
14 Claims
- 1. A cathode ray tube comprising an envelope containing means for generating an electron beam and a phosphor screen and having a transparent faceplate through which the display produced by the screen is visible, a magnetic shield comprising a mesh of high permeability magnetic material positioned over the outside of the faceplate, the mesh comprising an apertured sheet of the magnetic material having an array of regularly spaced apertures, characterized in that the apertures of the array are polygonal and defined by interconnected straight edged bars of the magnetic material.
Specification