Method and apparatus for forming an insulator on a uniaxial tension focus mask of a color selection electrode

A method of making a uniaxial tension focus mask for a color cathode-ray tube having an electron gun for generating and directing three electron beams through openings in said uniaxial tension focus mask to a luminescent screen, comprising the steps of:

• a) securing a uniaxial tension mask sheet to a substantially rectangular frame having two long sides and two short sides, said mask sheet having two long sides with a plurality of transversely spaced-apart first metal strands extending therebetween, the space between adjacent first metal strands defining parallel slots, said long sides of said mask sheet being attached to the long sides of said frame, said frame applying tension to said first metal strands of said mask sheet,
• b) forming a continuous insulator layer on a first major surface of said first metal strands of said mask sheet facing said luminescent screen across an effective picture area of said screen, by positioning a charging gun having a source of a dry glass powder at a distance from said first major surface and charging and directing said dry glass powder toward said first major surface of said first metal strands of said mask sheet to provide a continuous coating of said dry glass powder thereon,
• c) providing means for preventing said dry glass powder from extending into the parallel slots between adjacent first metal strands of said mask sheet and being deposited onto any portion of said mask sheet except said first major surface of said first metal strands,
• d) heating said mask sheet with said continuous coating of said dry glass powder thereon to a temperature and for a time sufficient to sinter said continuous coating to form a first insulator layer,
• e) providing a plurality of second metal cross-strands, substantially perpendicular to said first metal strands, on said first insulator layer,
• f) repositioning said charging gun, having said source of dry glass powder, at a distance from said first major surface of said mask sheet and charging and directing said dry glass powder toward said first insulator layer to provide a continuous second coating of said dry glass powder overlying said first insulator layer,
• g) providing means for preventing said dry glass powder from extending into the parallel slots between adjacent first metal strands of said mask sheet and being deposited onto any portion of said mask sheet except onto said first insulator layer, and
• h) heating said mask sheet with said continuous second coating of said dry glass powder thereon to a temperature and for a time sufficient to sinter said second coating and said second metal strands to said first insulator layer.