Electron gun having concave coined grid and annular rib

Claim 1

A cathode ray tube electron gun having a cathode and a plurality of sequential electrodes formed and spaced therein to provide the source, acceleration and control of an electron beam, said gun having an axis and comprising in combination: a first grid electrode spacedly positioned relative to said cathode, said first grid having a functional portion with an axis therethrough, said portion being formed in a concave manner having a defined depth with the concavity thereof facing away from said cathode, a beam control aperture formed as a substantially axial bore through said functional portion, said material thickness immediately surrounding said aperture being of reduced thickness provided by concave coining of the material relative to the outer surface of said concavity; an axially oriented annular rib formed in said functional portion in a manner to protrude within said concavity adjacent said coined aperture therein, said protruding rim being of a height not exceeding the depth of the concavity of said functional portion; and a second grid electrode having an axis and a functional portion protruding outwardly toward the concavity of said first grid electrode, said functional portion having a diameter less than that of said annular rib.