WO2005119727A1

WO2005119727A1 - Color picture tube having an internal magnetic shield with integral circuit connector

Info

Publication number: WO2005119727A1
Application number: PCT/US2004/016760
Authority: WO
Inventors: Louis Emmanuel Matalon; Steven William Haun; Jonathan Bradford Fowler
Original assignee: Thomson Licensing
Priority date: 2004-05-27
Filing date: 2004-05-27
Publication date: 2005-12-15

Abstract

The novel cathode-ray tube (110) has a funnel (115) sealed to a panel (112), which form an evacuated envelope (111) that contains therein a mask-frame assembly (125) supported in proximity to a screen (122), an internal magnetic shield (145) near the mask-frame assembly (125) having a main body portion (147) and at least one circuit connecting portion (160), wherein at least one integral piece of metal forms at least a part of the main body portion (147) and the at least one circuit connecting portion (160). The tube (110) further includes an electron gun (126) mounted in a neck (114) connected to the funnel (115) and an internal conductive coating (113) supported on the inside surface of the funnel (115). The coating (113) is in electrical contact with an anode button (116) on the funnel (115). The at least one circuit connecting portion (160) is in contact with the internal conductive coating (113).

Description

COLOR PICTURE TUBE HAVING AN INTERNAL MAGNETIC SHIELD WITH INTEGRAL CIRCUIT CONNECTOR

Field of the Invention

This invention relates to a cathode ray tube (CRT), and particularly to a CRT having an internal magnetic shield with an integral contact arm.

Background of the Invention

FIG. 1 shows a conventional color cathode-ray tube (CRT) 10. CRTs generally comprise a glass envelope 11 having a faceplate panel 12 connected to a funnel 15. The funnel 15, on end opposite to the panel 12, is also connected to a tubular neck 14. The CRT further includes, in its interior, a multi-aperture color selection electrode, or mask-frame assembly- frame assembly 25 supported within the panel 12, in a predetermined spaced relation to a luminescent screen 22 that is on the interior surface of a faceplate 18 of the panel 12. The funnel 15 has an internal conductive coating 13 that is in contact with, and extends from, an anode button 16 to the neck 14. The screen 22 may include a multiplicity of screen elements comprising red-emitting, green-emitting, and blue-emitting phosphor stripes R, G, and B, respectively, arranged in triads, each triad including a phosphor line of each of the three colors. The panel 12 can further comprise a peripheral flange or sidewall 20 which is the portion that seals the panel 12 to the funnel 15 by use of a glass frit 21. The CRT 10 further includes an electron gun 26 which is mounted within the neck 14, and can be designed to generate and direct three inline electron beams 28, a center and two side or outer beams, along convergent paths through a shadow mask of a mask-frame assembly 25 to the screen 22. An external magnetic deflection yoke 37 is mounted in the neighborhood of the funnel-to-neck junction and subjects the three electron beams 28 to magnetic fields that cause the electron beams 28 to scan a horizontal and vertical rectangular raster across the screen 22. Other components of the CRT 10 include the metallic internal magnetic shield (IMS) 45 which is designed to be attached to the mask-frame assembly-frame assembly 25 and has a contour that approximately parallels part of the contour of the funnel 15. The IMS 45 is used and designed to negate the affect of ambient magnetic fields and changes thereof on the electron beams 28. Without the IMS 45, in changing ambient magnetic fields, the electron beams 28 would likely otherwise deviate from their desired trajectory. In conventional CRTs, to maintain the components inside the envelope 11 at the same potential as the anode potential of the anode button 16, contact springs 50 are placed on the IMS 45 such that they extend therefrom and contact the internal conductive coating 13, thereby ensuring that at least the IMS 45 and the mask-frame assembly 25 are maintained at the potential of anode button 16.

Regarding contact springs 50, they are typically stainless steel and contain two contact points that contact the internal conductive coating 13. The contact springs 50 are typically manually snapped into the IMS 45. Some manufacturers have welded the contact springs 50 to the IMS 45 or the mask-frame assembly 25. The disadvantage of these springs 50 is that these add more cost to the CRT and waste resources, with regards to labor and equipment. This cost is further compounded by (1) the system redundancy needed to insure electrical continuity between the IMS 45 and the internal conductive coating 13 and (2) product yield losses due to error in the attachment. As such, a need exists for a CRT having an improved means of electrically connecting the IMS 45 to the internal conductive coating 13.

Summary of the Invention

The invention is a cathode-ray tube having a funnel sealed at one end to a panel with a viewing faceplate containing a screen on an interior surface thereof, the funnel and the panel form an evacuated envelope, a mask-frame assembly supported within the envelope and in proximity to the screen, an electron gun mounted in a neck connected to another end of the funnel, comprising an internal conductive coating supported on an inside surface of the funnel, the funnel having an anode button in electrical contact with the internal conductive coating and an internal magnetic shield supported in the envelop and having a main body portion and at least one circuit connecting portion. The main body portion has a funnel shape and is adjacent to the mask-frame assembly and has a large electron beam clearance aperture at one end facing the screen and a smaller electron beam clearance aperture facing the electron gun. At least one integral piece of metal forms at least a part of the main body portion and the at least one circuit connecting portion, wherein the at least one circuit connecting portion contacts the internal conductive coating.

Brief Description of the Drawings

The invention will now be described by way of example with reference to the accompanying figures.

FIG. 1 is a cross sectional view of a prior art cathode ray tube.

FIG. 2 is a cross sectional view of a portion of a cathode ray tube according to the invention.

FIG. 3 represents an integral internal magnetic shield in FIG. 2 having a main body portion and circuit connector portions, which are in the form of an arched bridge spring.

FIG. 4 represents an alternative internal magnetic shield according to the invention, wherein the circuit connector portions are in the form of a bow spring. FIG. 5 represents an alternative internal magnetic shield according to the invention, wherein the circuit connector portions are in the form of a contoured plate.

FIG. 6 represents an alternative internal magnetic shield according to the invention, wherein the circuit connector portions are in the form of a rigid contact beam.

FIG. 7 represents an alternative internal magnetic shield according to the invention, wherein the circuit connector portions are a multitude of the flaps in a starburst pattern.

Detailed Description of the Invention Figure 2 shows a cathode ray tube (CRT) 110 according to the invention. The CRT

110 comprises an evacuated glass envelope 111 having a rectangular faceplate panel 112 sealed to a funnel 115 by a frit 121. The panel includes a viewing faceplate 118 and sidewalls 120. The viewing faceplate 118 has on its interior a luminescent screen 122. The screen 122 can be a tri-color screen. The tube further includes a color selection electrode or a mask-frame assembly 125 which is supported within the envelope 111 in proximity to the luminescent screen 122. Typically, the mask-frame assembly 125 can be supported in the panel 112 by springs attached to the mask-frame assembly 125 that engage studs (not shown), which can be embedded in the sidewalls 120. The CRT 110 further includes an internal magnetic shield 145 adjacent to the mask-frame assembly 125 that has a main body portion 147 and circuit connecting portions 160. Fig. 2 also shows an electron gun 126 mounted within the neck 114, which is attached to the funnel 115 on the end opposite the screen 122. The electron gun 126 generates and directs electron beams 128 toward the mask-frame assembly 125. An external magnetic deflection yoke 137 is mounted in the neighborhood of the funnel-to-neck junction and subjects the electron beams 128 to magnetic fields that cause the electron beams 128 to scan a horizontal and vertical rectangular raster across the screen 122. Fig. 2 further shows that the interior of the funnel 115 contains an internal conductive coating 113 electrically in contact with the anode button 116 on the funnel 115. The circuit connecting portions 160 of the IMS 145 contacts the internal conductive coating 113 and thereby permits the IMS 145 to be maintained at the same potential as the anode button 116. More particularly, the IMS 145 of the preferred embodiment of the invention is comprised of a single integral piece of metal, wherein the main body portion 147 is funnel- shaped and is contoured to approximate the interior surface of the funnel 115. Further, the circuit connector portions 160 of the IMS 145 extends from the end of the IMS 145 having the smaller electron beam clearance aperture 149. The IMS 145 can be secured to the mask-frame assembly 125 by fastening the end of the IMS having the large electron beam clearance aperture 151 thereto.

The IMS 145 according to the invention is an advantage over that in the prior for several reasons. First, the IMS 145 eliminates the need to carry an inventory of contact springs 50. Also, yield loss due to error in the attachment contacts springs 50 would be reduced and yield loss due to the particle generation from welding or inserting contact springs into LMSs would be reduced. Additionally, the use of the IMSs 145 in the novel CRT allows for more automation in the CRT manufacturing plants. There is also an advantage from an ecological perspective in that the use of this type of LMS 145 promotes less waste of material resources. The reason is a greater percentage of the starting flat sheet metal is incorporated into the finished IMS 145, as opposed prior art IMS 45. Both IMS types are made with progressive cutting and forming operations (i.e., stamping), producing waste material. When the prior art IMS 45 is stamped from the starting flat sheet metal, the entire central portion of the sheet metal, which corresponds to the smaller electron beam clearance aperture, is stamped out and discarded. However, when the IMS 145 according to the invention is stamped from the starting flat sheet metal, only part of the central portion of the sheet metal is stamped out and discarded; as such, the central portion of the sheet metal not stamped out is efficiently and conveniently used for the circuit connector portions 160.

During conception of the invention, a concern was whether it was possible to maintain the necessary contact pressure of the circuit connecting portions 160 of the IMS 145 on the internal conductive coating 113. The concern was based on the premise that the standard IMS metals are very ductile (because they are typically made from thin sheet metal material) and, as such, one would expect inadequate pressure and possibly the potential for partial plastic deformation during installation and during the standard manufacturing thermal cycles (i.e. the cycles for curing the frit 121 and evacuating the envelope 111). Typically the IMS material is

0.004 to 0.006 in. in thickness. Several preferred geometries have been derived which addressed these concerns and make the applicability of the invention a reality.

In one embodiment, the connector portions 160 can be an arched bridge spring 161 as shown in Fig. 3 or an arched bow spring 261 as shown in Fig. 4. In both cases the connector portions protrude from the main body portion 147 near the smaller electron beam clearance aperture 149. The connector portions can include protruding funnel contacts 155, which would contact the internal conductive coating 113. These methods are primarily systems that rely on the material elasticity in a two-dimensional structure to provide sufficient contact force. The bridge spring 161 has a free end 171 which serves as sliding contact point on the main body portion 147. On the other hand, the IMS using the arched bow spring 261 has one attachment location 270, which is a formed slot for the free end 171 of the arched spring 160 to affix thereto.

In another embodiment, the connector portions 160 which are also integrally part of the IMS 145 are contoured plates 361 having funnel contacts 155 as shown in Fig. 5. In this case, large deformation in a direction somewhat normal to the plates can be achieved with relatively low stress distributed throughout the plates 361, allowing the deformation to be elastic for the required travel. This method is particularly useful for thin material. In this embodiment, having the concave side of the plates 361 facing away from the internal conductive coating is preferred. However, the contour direction can functionally be in the opposite direction. Other embodiments include the connector portions 160 being a rigid contact beam 461 as shown in Fig. 6 or a starburst configuration 561 as shown in Fig. 7. The rigid beam 461 is contoured to have at least one strength enforcing grooved ridge 462 that runs parallel with the longer dimension of the connector portion 160 as shown in FIG. 6. The rigid beams 461 can also include protruding funnel contacts 155. The starburst configuration provides a multitude of at least 4 separate connector portions 160 in the form of flaps 562. The multitude of the flaps 562 provides added certainty of the electrical connection between the IMS 145 and the internal conductive coating 113. FIG. 7 A shows the configuration of the flaps immediately after stamping and FIG. 7B show the IMS 145 with the flaps oriented for insertion into a CRT 110.

While certain embodiments of the invention have been disclosed, the spirit of the invention is not limited to CRTs 110 only having these specific IMS embodiments. The invention is intended to include those CRTs having IMSs 145 which have both ledge portions 162 that surround the smaller electron beam clearance aperture 149 or the LMSs which do not have such ledge portions. Further, while some of the embodiments include protruding funnel contacts 155, the invention is not limited to CRTs 110 have such contacts 155, but rather other parts of the connector portions 160 can contact the internal conductive coating 113. Additionally, the scope of the invention is meant to include CRTs having IMSs 145, wherein at least one integral piece of metal forms at least a part of the main body portion and at least one circuit connecting portion 160 such that the circuit connecting portion 160 contacts the internal conductive coating 113.

Claims

What is claimed is:

1. A cathode-ray tube having a funnel sealed at one end to a panel with a viewing faceplate containing a screen on an interior surface thereof, said funnel and said panel form an evacuated envelope, a mask-frame assembly supported within said envelope and in proximity to said screen, an electron gun mounted in a neck connected to another end of said funnel, comprising: an internal conductive coating on an inside surface of said funnel, said funnel having an anode button in electrical contact with said internal conductive coating, an internal magnetic shield secured to said mask-frame assembly and having an exterior surface extending along at least a portion of said funnel and being spaced therefrom, and an integral circuit connection member extending from said magnetic shield for contacting said internal conductive coating.

2. The cathode-ray tube according to claim 1, wherein at least one said circuit connecting member is an arched bow spring that protrude from said magnetic shield and contacts said internal conductive coating.

3. The cathode-ray tube according to claim 2, wherein said arched bow spring has a free end that slidably affixes into a formed slot on said exterior surface of said internal magnetic shield.

4. The cathode-ray tube according to claim 1, wherein at least one said circuit connecting member is a contoured plate having funnel contacts protruding therefrom that contact said internal conductive coating.

5. The cathode-ray tube according to claim 1, wherein at least one said circuit connecting member is a rigid beam, said rigid beam is contoured to have at least one strength enforcing grooved ridge that runs parallel to a long dimension of said rigid beam, and said rigid beam includes funnel contacts protruding therefrom that contact said internal conductive coating.

6. The cathode-ray tube according to claim 1, wherein at least one said circuit connecting portion comprises a plurality of flaps is a rigid beam and said plurality of flaps contact said internal conductive coating.

7. A cathode-ray tube having a funnel sealed at one end to a panel with a viewing faceplate containing a screen on an interior surface thereof, said funnel and said panel form an evacuated envelope, a mask-frame assembly supported within said envelope and in proximity to said screen, an electron gun mounted in a neck connected to another end of said funnel, comprising: an internal conductive coating supported on an inside surface of said funnel, said funnel having an anode button in electrical contact with said internal conductive coating and an internal magnetic shield supported in said envelop and having a main body portion and at least one circuit connecting portion, wherein said main body portion has a funnel shape and is adjacent to said mask-frame assembly, said main body portion having a large electron beam clearance aperture at one end facing said screen and a smaller electron beam clearance aperture facing said electron gun, and at least one integral piece of metal forms at least a part of said main body portion and said at least one circuit connecting portion, said at least one circuit connecting portion contacting said internal conductive coating.

8. The cathode-ray tube according to claim 7, wherein said at least one circuit connecting portion is an arched bow spring that protrude from said main body portion and contacts said internal conductive coating.

9. The cathode-ray tube according to claim 8, wherein said arched bow spring has a free end that slidably affixes into a formed slot on said main body portion.

10. The cathode-ray tube according to claim 7, wherein said at least one circuit connecting portion is a contoured plate having funnel contacts protruding therefrom that contact said internal conductive coating.

11. The cathode-ray tube according to claim 7, wherein said at least one circuit connecting portion is a rigid beam, said rigid beam is contoured to have at least one strength enforcing grooved ridge that runs parallel to a long dimension of said rigid beam, and said rigid beam includes funnel contacts protruding therefrom that contact said internal conductive coating.

12. The cathode-ray tube according to claim 7, wherein said at least one circuit connecting portion comprises a plurality of flaps is a rigid beam and said plurality of flaps contact said internal conductive coating.