EP0121628A1 — Cathode-ray tube having taut shadow mask

Claim 1

Independent Claim 105 words

A cathode-ray tube comprising; an electron beam source and transmitting means for transmitting electron beams from the source onto seclected areas of a display screen to produce images thereon, and a shadow mask assembly positioned between the source and the screen to restrict impingement of the beam to the designated areas of the screen, said shadow mask assembly being characterized by, a frame and a perforated thin membrane of material mounted in the frame, said membrane being fastened to the frame in a tensioned condition whereby heating of the membrane relaxes the tension without producing physical change in the size or location of the perforations.

Claim 2

Dependent Claim 105 words

A cathode-ray tube comprising; an electron beam source and transmitting means for transmitting electron beams from the source onto seclected areas of a display screen to produce images thereon, and a shadow mask assembly positioned between the source and the screen to restrict impingement of the beam to the designated areas of the screen, said shadow mask assembly being characterized by, a frame and a perforated thin membrane of material mounted in the frame, said membrane being fastened to the frame in a tensioned condition whereby heating of the membrane relaxes the tension without producing physical change in the size or location of the perforations.

Claim 3

Dependent Claim 26 words

A cathode-ray tube as defined in Claim 1 wherein the tensioned membrane is a metallic electron beam abosrbing material having a pre-determiend coefficient of thermal expansion.

Claim 4

Dependent Claim 29 words

A cathode-ray tube as defined in Claim 2 wherein the tensioned membrane is a nickel-iron alloy and is uniformly tensioned to within half to three-quarters of its stress limitation.

Claim 5

Dependent Claim 33 words

A cathode-ray tube as defined in Claim 3 wherein the tensioned membrane material has 36% nickel and a coefficient of thermal expansion in the order of 1.6 x 10- 6 per degree centigrade.

Claim 6

Dependent Claim 25 words

A cathode-ray tube as defined in Claim 4 wherein the tensioned membrane material has a thickness in the range of .0025 centimeters to .0038 centimeters.

Claim 7

Dependent Claim 35 words

A cathode-ray tube as defined in Claim 1 wherein the display screen has a flat surface on which the electron beam impinges, and the tensioned membrane is correspondingly flat in position parallel to the screen.

Claim 8

Dependent Claim 47 words

A cathode-ray tube as defined in Claim 2 wherein the heat rise within the tensioned membrane during operation of the cathode-ray tube is predetermined and the physical stretching of the tensioned membrane in a non- operational mode exceeds the expansion of the membrane within said heat rise.

Claim 9

Dependent Claim 32 words

A cathode-ray tube as defined in Claim 1 wherein the frame is precompressed so as to exert an outwardly directed force to counterbalance the inwardly directed force generated by the tensioned membrane.

Claim 10

Dependent Claim 47 words

A process for producing a shadow mask assembly for a cathode-ray tube comprised of; stretching a sheet of membrane material to a predetermined tension, holding the membrane in the tensioned condition, and securing the membrane to a frame and thereby maintaining the membrane in its tensioned condition.

Claim 11

Dependent Claim 47 words

A process for producing a shadow mask assembly for a cathode-ray tube comprised of; stretching a sheet of membrane material to a predetermined tension, holding the membrane in the tensioned condition, and securing the membrane to a frame and thereby maintaining the membrane in its tensioned condition.

Claim 12

Dependent Claim 30 words

A process for producing a shadow mask assembly for a cathode-ray tube as defined in Claim 9 which includes etching a pattern of perforations into the sheet prior to stretching.

Claim 13

Dependent Claim 48 words

A process for producing a shadow mask assembly for a cathode-ray tube as defined in Claim 9 wherein the membrane material is a metallic membrane having a predetermined stress limit and which includes stretching the membrane to within the range of half to three-quarters of its stress limit.

Claim 14

Dependent Claim 67 words

A process for producing a shadow mask assembly comprised of selecting a shadow mask membrane material, determining a temperature range within which membrane distortion is to be avoided, stretching the membrane at the low end of the temperature range to the extent that would be produced by heat expansion of the material at the top of the temperature range, and securing the stretched membrane to a frame.

Claim 15

Dependent Claim 67 words

A process for producing a shadow mask assembly comprised of selecting a shadow mask membrane material, determining a temperature range within which membrane distortion is to be avoided, stretching the membrane at the low end of the temperature range to the extent that would be produced by heat expansion of the material at the top of the temperature range, and securing the stretched membrane to a frame.

Claim 16

Dependent Claim 39 words

A process for producing a shadow mask assembly as defined in Claim 12 including spring loading the frame during securing of the membrane to generate an outwardly directed force to counterbalance the inwardly directed force of the tensioned membrane.

Cathode-ray tube having taut shadow mask

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