External magnetic shield for CRT

• US 5,235,243 A
• Filed: 05/29/1990
• Issued: 08/10/1993
• Est. Priority Date: 05/29/1990
• Status: Expired due to Fees

• Current Assignee: Zenith Electronics Corporation (LG Corporation)
• Original Assignee: Zenith Electronics Corporation (LG Corporation)
• Inventors: Tong, Hua S.
• Primary Examiner(s): Yusko, Donald J.
• Assistant Examiner(s): PATEL, NIMESHKUMAR D
• Application Number:
  US07/530,037
• Time in Patent Office: 1,169 Days
• Field of Search: 313/313, 313/479, 313/160, 313/477 R, 313/402, 315/85, 174/35 MS, 358/245
• US Class Current: 313/479
• CPC Class Codes: H01J 29/867 Means associated with the outside of the vessel for shielding, e.g. magnetic shields screens for shielding inside the vessel H01J29/06; magnetic shielding in general H05K9/00

Abstract

A cathode ray tube has an external magnetic shield adapted for tight fitting positioning upon and about the funnel portion of the CRT. The external magnetic shield includes a shell preferably of conventional plastic and a soft magnetic material having high permeability and low coercivity. The soft magnetic material may be either disposed as a layer on the surface of the shell or distributed throughout the shell in the form of small particles. The external magnetic shield is installed over the CRT funnel following CRT evacuation and frit-sealing for improved magnetic shielding in a low cost, easily assembled magnetic shielding arrangement.

Claims

1. For use with a cathode ray tube (CRT) having a funnel, a faceplate attached to a forward portion of the funnel and including a plurality of phosphor elements on an inner surface thereof, and an electron gun for directing an electron beam onto the phosphor elements for producing a video image, an magnetic shield comprising:

a non-magnetic shell configured to generally conform to the outside surface of the funnel;

a layer comprised of a soft magnetic material having high magnetic permeability and low coercivity disposed on said shell; and

extension means extending from a forward portion of said magnetic shield and disposed over forward peripheral portions of the faceplate.

2. The magnetic shield of claim 1 wherein said extension means comprises a plurality of flaps disposed on a forward portion of said magnetic shield and adapted for folded positioning over forward peripheral portions of the faceplate.

3. The magnetic shield of claim 2 further comprising magnetic shielding means disposed on an outer surface of the faceplate and engaging said flaps for preventing radiation emission from the CRT faceplate.

4. The magnetic shield of claim 3 wherein said magnetic shielding means includes a plurality of elongated, linear strips disposed on an outer surface of the faceplate adjacent to the edges thereof.

5. The magnetic shield of claim 4 further comprising a safety panel disposed on the outer surface of the CRT faceplate and attached to said elongated shielding strips.

6. A method for shielding at least one electron beam in a cathode ray tube (CRT) having a faceplate and a funnel from an external magnetic shield in ensuring that said at least one electron beam is incident on a designated location on an inner surface of the faceplate, said method comprising the steps of:

forming a non-magnetic shell in the general contour of an outer surface of the CRT funnel;

forming on an outer surface of the thus-formed shell a layer of soft magnetic material;

positioning the shell with the outer layer of soft magnetic material over the CRT funnel in tight fitting relationship;

attaching the shell to an outer surface of the CRT funnel; and

folding a forward portion of the shell over peripheral edge portions of the CRT faceplate.

7. For use with a cathode ray tube (CRT) having a funnel, a faceplate attached to a forward portion of the funnel and including a plurality of phosphor elements on an inner surface thereof, and an electron gun for directing an electron beam onto the phosphor elements for producing a video image, an magnetic shield for shielding the electron beam from external magnetic fields, said magnetic shield comprising:

a nonmagnetic shell configured to generally conform to the outside surface of the funnel;

extension means disposed on a forward portion of said shell and covering a forward peripheral portion of the faceplate; and

a layer comprised of a soft magnetic material having high magnetic permeability and low coercivity disposed on said shell and said extension means.