| 摘要 |
<p>708,135. Cathode-ray tubes. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Aug. 27, 1951 [April 23, 1951], No. 20140/51. Class 39(1) [Also in Group XXXV] A magnetic structure used for focusing in an electron discharge tube comprises high permeability parts 2, 3 in which is arranged a thin permanent magnet insert 1 magnetized across its thickness and having a coercivity of at least 750 Oersteds and a low remanence (e.g. less than 5000 Gauss), the surface area of the poles of the high permeability parts being at most two thirds and preferably not more than one half as large as the surface area of the magnet pole faces. The structure shown forms a solid of revolution about an axis lying centrally of the channel through which the electrons pass, and in which flux is generated by the structure. The invention may be applied to chokes and loudspeaker and other permanent magnets (see Group XXXV) and measuring instruments. Suitable materials are those forming the subject of Specification 708,127, [Group XXXV]. Specifications 708,132, 708,133 and 708,134 also are referred to.</p> |
