Appeal No. 1998-1869
Application 08/688,423
The disclosed invention pertains to a scandate
dispenser cathode for use in an electric discharge tube. The
invention is particularly related to a coating having an
emissive surface on the cathode body. The coating is a three
layer coating with each of the layers having a specific
composition.
Representative claim 1 is reproduced as follows:
1. An electric discharge tube having a scandate
dispenser cathode, which is composed of a cathode body and a
coating having an emissive surface, said cathode body
comprising a matrix material of at least one refractory metal
or at least one refractory alloy and a barium compound which
is in contact with the matrix material to supply barium to the
emissive surface by means of a chemical reaction with said
matrix material, said coating containing a multilayer which
includes a bottom layer of tungsten or a tungsten alloy, an
intermediate layer of rhenium or a rhenium alloy and a top
layer of scandium oxide, a mixture of scandium oxide and rare-
earth metal oxides, a scandate or a scandium alloy.
The examiner relies on the following reference:
Watanabe et al. (Watanabe) 4,855,637 Aug. 8, 1989
Claims 1 and 2 stand rejected under 35 U.S.C. § 102(b)
as being anticipated by the disclosure of Watanabe. Claim 4
stands rejected under 35 U.S.C. § 103 as being unpatentable
over the teachings of Watanabe.
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