CATHODE SUPPORTING PLATE FOR FLUORESCENT DISPLAY TUBE

PURPOSE: To make a cathode supporting plate be a common member in a fluorescent display tube. CONSTITUTION: Cathode supporting plates 1 are installed respectively in both end parts in the inside of a box like outer casing 11 of a fluorescent display tube to support both end parts of a filament-like cathode. Based on the number of lead terminals of the fluorescent display tube, the pitch of the lead terminals, and the length of the outer casing 11, the gap (the size a) between round rods 14 to be connected with the cathode supporting plates 1 and the end parts of the outer casing 11 is determined. Based on respective design conditions, the size a is calculated for a plurality of types of fluorescent display tubes for which the cathode supporting plates 1 are to be employed as a common member and the maximum value and the minimum value of the size are computed. The width (w) of the cathode supporting plates 1 is determined so as to cope with the maximum value and the minimum value of the size a. The round rod 14 of the cathode supporting plates 1 is installed at proper positions of the cathode supporting plates 1 corresponding to the conditions of a fluorescent display tube for which the cathode supporting plates are to be employed. Even in the case the cathode supporting plates 1 are employed for any type of a fluorescent display tube, the round rod 14 can be installed in the cathode supporting plates 1 at positions proper for the pitch of lead terminals of the fluorescent display tube.