Electrical conduction means for use in tension mask color cathode ray tubes

A color cathode ray tube is disclosed having an envelope including a faceplate with an electrically conductive screen, and a funnel having an electrically conductive film on its inner surface charged to a high electrical potential. An electrically insulative glass shadow mask support assembly is sealed between the faceplate and the funnel has a shelf extending into the envelope for mounting a metallic foil shadow mask in tension adjacent to the screen. The shelf has at least one hole therethrough for receiving electrical conduction means according to the invention. The electrical conduction means includes a center member for insertion into the hole, and contacting means at both extremities for contacting the electrically conductive coating on the funnel, the shadow mask, and the metallic film on the screen. As a result, and according to the invention, the high electrical potential on the conductive film of the funnel is electrically conducted through the electrically insulative glass shadow mask support assembly to the shadow mask and the screen to establish the components at a common high potential.

CROSS-REFERENCE TO RELATED APPLICATIONS AND PATENTS 
This application is related to but in no way dependent upon copending 
applications Ser. No. 572,088 filed Jan. 18, 1984, now U.S. Pat. No. 
4,547,696; Ser. No. 572,089 filed Jan. 18, 1984, now U.S. Pat. No. 
4,595,857; Ser. No. 735,887 filed Aug. 8, 1984, now U.S. Pat. No. 
4,656,388; Ser. No. 729,020 filed Apr. 30, 1985, now U.S. Pat. No. 
4,652,791; Ser. No. 727,486 filed Apr. 26, 1985, now U.S. Pat. No. 
4,695,523; and Ser. No. 743,184 filed June 10, 1986, now U.S. Pat. No. 
4,678,447, all of common ownership herewith. 
BACKGROUND OF THE INVENTION 
This specification includes an account of the background of the invention, 
a description of the the best mode presently contemplated for carrying out 
the invention, and appended claims. 
FIELD OF THE INVENTION 
This invention relates to color cathode ray picture tubes, and is addressed 
specifically to improved electrical conduction means for use in a color 
cathode ray tube having a tensed foil shadow mask. The invention can find 
application in color tubes of various types, including those used in home 
entertainment television receivers, and in medium-resolution and 
high-resolution tubes intended for color monitors. 
The use of the tensioned foil mask and flat faceplate provides many 
benefits in comparison to the conventional domed shadow mask and 
correlatively curved faceplate. Chief among these is a greater 
power-handling capability which makes possible as much as a three-fold 
increase in brightness. The conventional curved shadow mask, which is not 
under tension, tends to "dome" in picture areas of high brightness where 
the intensity of the electron beam bombardment is greatest. Color 
impurities result as the mask moves closer to the faceplate. As it is 
under high tension, the tensioned foil mask will dome, but negligibly in 
comparison with the curved mask. Its relative immunity to doming provides 
for greater brightness potential while maintaining color purity. 
The tensioned foil shadow mask is a part of the cathode ray tube front 
assembly, and is located in close adjacency to the faceplate. The front 
assembly comprises the faceplate with its screen consisting of deposits of 
discrete light-emitting phosphor elements, a shadow mask, and support 
means for the mask. 
The area enclosed by the funnel and the front assembly of a color cathode 
ray picture tube is typically established as a field-free region for the 
excursion of the electron beams that selectively excite the phosphor 
elements. The field-free region is established by charging the inner 
surfaces of the funnel and faceplate and the adjacent components to a high 
potential, typically in the range of 20-30 kilovolts. The surfaces so 
charged include the conductive coating deposited on the inner surface of 
the funnel, and an electrically conductive film, usually aluminum, 
disposed on the back of the picture imaging screen. The shadow mask must 
also be charged to the same high potential. The electrically conductive 
coating on the inner surface of the funnel receives a high potential from 
a metallic "anode button" that protrudes through the wall of the funnel, 
and which in turn is connected to a conductor leading to an high voltage 
power supply. It is essential that an electrical path be established 
between the inner conductive coating, the screen, the shadow mask, and any 
component linked thereto to establish the field-free region. 
A typical anode contact spring for use in the conventional curved 
mask/curved faceplate cathode ray tube is disclosed in U.S. Pat. No. 
4,333,033 to Cordingly et al, of common ownership herewith. The spring 
provides for an electrical path from the electrically conductive coating 
to the skirt of the shadow mask to energize the mask with high voltage. 
The novelty of the spring lies in its means of attachment to the skirt of 
the mask, wherein the spring can be clipped onto the skirt with an 
anti-twistoff locking feature. 
In U.S. Pat. No. 4,450,379, Kikuchi et al discloses an anode contactor for 
use in a cathode ray tube having a flat faceplate. The contactor consists 
essentially of a flat plate that extends substantially along the inner 
surface of the funnel and into the faceplate area. One end of the plate is 
in contact with the anode button, with attachment to the button made by 
what appears to be a rivet. The other end of the plate is in contact with 
the screen. The configuration of the tube makes possible the use of a 
contactor of relatively straightforward design as there appear to be no 
barrier to the direct conduction of high voltage from the anode button to 
the screen. Other representative electrical conductive means are disclosed 
in U.S. Pat. Nos. 3,898,510 to Davis et al, and 3,432,803 to Nice. 
OBJECTS OF THE INVENTION 
It is an object of the invention to provide improved means for conducting 
high voltage to the screen and shadow mask in cathode ray tubes having a 
tensed foil shadow mask and a substantially flat faceplate; 
It is another object of the invention to provide means for the high-voltage 
energizing of internal components of a cathode ray tube having a tensed 
foil shadow mask mounted on a component that serves as a barrier to 
electrical conduction.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 1 and 2 depict a novel high-resolution cathode ray tube 12 having an 
envelope that includes a glass faceplate 16 with an electrically 
conductive phosphor screen 18 made electrically conductive by virtue of a 
deposit of metallic film thereon which typically comprises aluminum. The 
envelope of tube 12 includes a funnel 20 having an electrically conductive 
film 22 on its inner surface; film 22 is charged to a high electrical 
potential typically in the range of 20 to 30 kilovolts. The high voltage 
potential is indicated as being supplied through an anode button 24 
connected in turn to a high-voltage power supply (not indicated) as is 
well known in the art. Funnel 20 is shown as tapering down to a narrow 
neck 26 depicted as enclosing an electron gun 28. Gun 28 is represented as 
projecting three electron beams 30, 32 and 34 onto the screen 18 of 
faceplate 16. The screen 18 on the inner surface of faceplate 16 comprises 
deposits of phosphor elements (not indicated) which comprise triads of 
red-light-emitting, green-light-emitting, and blue-light-emitting 
phosphors which emit light when excited by respective ones of the electron 
beams 30, 32 and 34. 
As indicated by FIG. 1, and in greater detail by FIG. 2, an electrically 
insulative glass shadow mask support assembly 36 is depicted as being 
sealed between the sealing surfaces of faceplate 16 and funnel 20. Mask 
support assembly 36 is represented as having first and second 
plano-parallel spaced apart sealing surfaces 38 and 40, with sealing being 
accomplished by layers 42 and 44 of devitrifying frit cement. As a result, 
the color electrode assembly 36 is sealed between faceplate 16 and the 
funnel 20 so as to become an integral part of the envelope. 
Shadow mask support assembly 36 is depicted as having a shelf 46 extending 
into the tube envelope for mounting a metallic foil shadow mask 48 in 
tension adjacent to screen 18. The mask 48 as mounted will be noted as 
being flat and parallel with the screen 18. Shelf 46 is indicated as 
comprising a peripherally continuous recessed support surface, attachment 
of the mask 48 to shelf 46 is indicated as being by means of a layer of 
cement 50. Shadow mask 48 is indicated as having a first field 52 of 
apertures therein which provide for color selection in the finished tube, 
and a second field 54 of apertures peripheral to the first field 52. The 
second field 54 of peripheral apertures comprise cement-passing apertures 
sized to pass cement in its viscous state, indicated as comprising layer 
of cement 56. A layer of conductive frit 55 may underlie the second field 
54 of apertures of shadow mask 48 to ensure positive electrical contact. 
The embodiment of the shadow mask 48 as shown and the means of mounting is 
not the subject of the present application, but is described and claimed 
in referent copending application Ser. No. 729,020. 
The layers of frit cement 42, 44 and 50 may comprise a devitrifying glass 
frit such as that supplied by Corning Glass Works of Corning, N.Y. under 
the designation Glass 7595. A devitrifying frit is compounded as a viscous 
glass which crystallizes and hardens when heated to a predetermined 
temperature, and which does not remelt upon reheating to that temperature, 
so that a permanent bond is made that is unaffected by the heat of final 
assembly. 
Tube 12 is indicated as having internal indexing means 57 for the 
registration of faceplate 16 and the shadow mask support assembly 36. The 
sets of indexing means, typically three in number, are internally spaced 
at preselected locations about the periphery of the faceplate 16; one of 
the sets is indicated in FIGS. 1 and 2 by reference number 57. Indexing 
means 56 in this prior art embodiment is depicted as comprising a ball 
which rides in mating grooves in the sealing surfaces of the faceplate and 
mask support assembly 36. The indexing means shown and variations thereof 
are not the subject of the present application but are described and fully 
claimed in various ones of the referent copending applications Ser. Nos. 
572,088 and 572,089; Ser. No. 735,887; and Ser. No. 727,486. 
Shelf 46 has at least one hole therethrough for receiving electrical 
conduction means according to the invention, as shown by hole 58 in FIGS. 
2 and 3. Electrical conduction means 60 includes a central member 62 for 
insertion into hole 58. Electrical conduction means 60 according to the 
invention also includes contacting means at both extremities for 
contacting the electrically conductive coating 22 on funnel 20, the shadow 
mask 48, and the metallic film on screen 18. The contacting means for the 
embodiment of the invention depicted in FIGS. 2 and 3 are indicated as 
being resilient spring means 64 on one extremity of electrical conduction 
means 60 for contacting conductive coating 22 on funnel 20 and on the 
other extremity, resilient spring means 66 shown as contacting shadow mask 
48, and resilient spring means 68 depicted as contacting screen 18. As a 
result, and according to the invention, the high electrical potential on 
conductive film 22 on funnel 20 is conducted through the electrically 
insulative glass shadow mask support assembly to the shadow mask 48 and 
the screen 18 to establish the components at a common high potential. 
The center member 62 of electrical conduction means 60 is depicted as being 
a rod-like member having its extremities the resilient spring means 
described. Center member 62 is according to the invention, a mechanically 
expansible member for insertion into hole 58 and locking into hole 58 in 
shelf 46. The mechanical expansion according to the invention may be 
accomplished by the compressive effect of rivet means 70 upon rod-like 
member, which may be comprised of a material which expands under the 
compression of the rivet means 70. The heads of the rivet are indicated as 
retaining the springs means at the extremities. Alternately, rod-like 
center member 62 may comprise a tube with a number of lateral slits 
therethrough which will result in the expansion of the tubing under the 
compression of the rivet means 70. The electrical conduction means is 
hence permanently locked into the hole after its insertion. Alternatives 
to the rivet means of assembly may comprise compression bolts, locking 
screws, or studs, by way of example. 
Another configuration of an electrical conduction means according to the 
invention is depicted in FIG. 4. In this embodiment, the center member 72 
of electrical conduction means 74 comprises a multiform spring means 
depicted as having a spread, but contractible, center 76 which provides 
for press-fitting of the electrical conduction means into hole 78 of shelf 
80. Electrical conduction means 74 according to the invention will be 
noted as having resilient contacting means at both extremities for 
contacting the electrically conductive coating 84 on funnel 86, the shadow 
mask 88, and the metallic film on screen 90. A benefit of this embodiment 
lies in the fact that the electrical conduction means may be installed 
easily, and just as easily removed in tube reclamation. 
While a particular embodiment of the invention has been shown and 
described, it will be obvious to those skilled in the art that changes and 
modifications may be made in the inventive means without departing from 
the invention in its broader aspects, and therefore, the aim of the 
appended claims is to cover all such changes and modifications as fall 
within the true spirit and scope of the invention.