| 摘要 |
<p>PURPOSE:To almost uniform operation temperatures of three base metals so as to dissolve the change of tint in operation by lowering the calorific value of a heating element at the center as compared with the calorific values of the heating elements on its both sides. CONSTITUTION:The film thicknesses of heating elements 5a, 5b, 5c consisting of three films of tungstens are the same, but the ribon width of the central heating element 5b is more narrowed than those of the heating elements 5a, 5c on its both sides. The electric resistance value of the central heating element 5b becomes larger than that of the heating elements 5a, 5c on the both sides, accordingly the current which flows to the heating element 5b becomes small but the temperature of the heating element 5b rises by receiving heat radiation or heat transmission from the heating elements 5a, 5c on both sides, and the temperatures of three heating elements 5a-5c become equal. Hereby, the temperature of a base metal corresponding to each heating element is equalized, so electron radiation characteristic is stabilized extending for a long period and change of tint, etc., in working can be restrained.</p> |
