| 摘要 |
<p>A heating element, esp. for use in indirectly heated cathodes of electron tubes comprises a straight wire, representing a core, around which a wire is wound in a helix. Core and helix can be made of the same metal, or they can have different resistivities, heat conductivities and dias. In an example, a spiral wire of half the dia. of the core wire and a pitch of 11/2-times the core wire dia., both made of W or W-Re, produced an element with a 14% lower resistance than the core wire alone. the surface area increased 300-400% and the difference between element and emission layer temp. was reduced by 35%, resulting in a much longer life. This new heating element has an enhanced mechanical stability. It is a simple operation to provide an insulating coating (alumina) for it and it has a greatly increased heat radiating surface area.</p> |
