US2950414A

US2950414A - Storage tube

Info

Publication number: US2950414A
Application number: US803415A
Authority: US
Inventors: Richard D Ketchpel
Original assignee: Hughes Aircraft Co
Current assignee: Raytheon Co
Priority date: 1959-04-01
Filing date: 1959-04-01
Publication date: 1960-08-23
Anticipated expiration: 1977-08-23

Description

A 1960 R.'D. KETCHPEL I 2,950,414.; I

STORAGE TUBE Filed April 1, 1959 lkwwm hie 2,95%, il i Patented Aug. 23, 1960 STORAGE TUBE Richard D. Ketchpel, Los Angeles, Calif., assignor to Filed Apr. 1, 1959, Ser. No. 803,415 2 Claims. 01. 315- 1) This invention relates to a method and apparatus for providing a voltage lead-in for a cathode-ray type tube, which lead-in does not require any holes or materials wll'ch place a strain on the glass envelope of the tube.

According to present day techniques, voltage lead-ins are presently provided by employing Kovar pins which are fritted into the side of the glass face panel of the tube envelope. This fritting operation necessitated the drilling of one or more holes through the side of the face panel, glass-beading a Kovar lead, fitting the glass beaded Kovar lead to the hole and fritting the lead to the face panel.

In the above operation, drilling holes through the glass envelope in the side of the face panel is very time consuming and, in addition, introduces strains into the face panel which may later cause cracking in the face panel through the voltage lead-ins. Also, leaks often develop around the lead-ins during final bake-out of the tube.

It is therefore an object of the present invention to provide an improved voltage lead-in through the envelope of an electron discharge device.

Another object of the invention is to provide a lead-in for cathode-ray type tubes which are easily installed and which do not introduce any strains in the glass envelope.

Still another object of the present invention is to provide a process for installing a glass lead-in through the envelope to the face panel of a cathode-ray type tube.

The voltage lead-in of the present invention is preferably installed through the glass envelope of cathoderay type tubes at the time when the face panel is sealed to the main body of the tube envelope. In accordance with the invention, at each desired lead-in point a patcof a conducting mixture composed of silver flake and glass frit is painted from the inside of the tube around the edge to be sealed and onto the outside of the tube. Electrical contact is made to the various elements of the tube by either extending the portion of the patch of the silver flake and glass frit painted on the inside of the tube envelope to a particular element with conductive paint or making electrical contact to the patch of silver flake and glass frit by means of leaf-springs and connecting the spring to the element. In the event that the leadins have been extended to the desired tube element by means of a conductive coating, the conductive areas may be glazed so that the voltages applied to the lead-ins do not produce electrostatic fields which may disturb the operation of the tube. The edges to be sealed are then coated with a plain frit mixture and placed together and heated to a temperature at which the frit melts thereby to produce a seal.

The above-mentioned and other features and objects of this invention and the manner of obtaining them will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, wherein:

Figs. 1-3 illustrate steps in the process of fabricating the lead-in of the present invention; and

- Fig. 4 shows a cross-sectional view of the voltage leadin of the present invention.

Referring now to the drawings, Figs. 1 to 3 illustrate the process of installing the lead-ins in accordance with the present invention concurrently with the sealing of a face panel 10 to a funnel portion 12 (only partially shown), both of which are constituted of a glass having characteristics identified as Corning 9019. A conductive frit mixture, which is compounded in container 14- in a manner hereinafter explained is painted with a paintbrush 15 over the seal-edge 16 of the face panel 10 for a distance of approximately one-half inch /2) therealong and extended perpendicular to the seal-edge 16 on both the inside and outside of the face panel 10 for a distance which may also be of the order of one-half inch' /2). In the face panel 10 illustrated in Fig. 1, three conductive patches 18, 19 and 20 are painted over the seal-edge 16 at points therealong where it is desired to install voltage lead-ins in accordance with the present invention. There is nothing critical with regards to the width of the conductive strips 18, 19 and 24 They can be as wide as is consistent with adequate separation for insulative purposes between adjacent patches and, on the other hand, may be made as narrow as is compatible with the minimum conductivity which may be tolerated. The thickness of the conductive patches 18, 19 and 2% however, is made of the order of one-sixteenth of an inch 0/16)- The conductive frit mixture compounded in container 14- is composed of frit and silver flake with nitro-cellulose used as a vehicle or base and amyl acetate as a thinner. The particular frit employed which has been found to be satisfactory is made from glass known commercially as Corning 7572. The size of the granules constituting the frit are such that they can pass through a screen having of the order of 325 meshes per inch. This frit is then ball-milled for approximately 24 hours prior to being used. In mixing the conductive frit mixture, one part by weight of vehicle or base, such as nitro-cellulose, is

mixed with 10 parts by weight of frit. Silver flake is then added in a ratio of one part silver flake by weight to the 10 parts of frit. The silver flake employed may be obtained commercially from Handy and Harmon Corps. under the commercial designation of SI-1M Flake. Amyl acetate is then mixed with the resulting mixture to make it sufiiciently thin so that the conductive frit mixture may be applied to the face panel 10 around the seal-edge 16 with the paintbrush 15 in the manner hereinbefore described.

Next, frit, which may be of the same type as described above, is mixed with a nitro-cellulose base in a container 22 of Fig. 2 to form a non-conductive frit mixture that has a heavy consistency. A pipette 24 is partially filled with this mixture from container 22 and applied to both the remaining exposed portions of the seal-edge 16 of face panel 10 and to the seal-edge 26 of the funnel portion 12 of the cathode ray tube being fabricated. The sealedge 16 of face panel 10 is then juxtaposed to the sealedge 26 of funnel portion 12 and the portions of the face panel 10 and funnel portion 12 adjoining the seal-edges 16, 26 are heated to a temperature of the order of 440 C. by means of a circular burner 28 thereby to vitrify the frit and thus form a vacuum seal. It is, of course, evident that other means of virtrifying the frit may be employed such as, for example, placing the entire face panel 1% in funnel portion 12 together in the desired manner and placing them in an oven which is heated to the desired temperature, i.e. 440 C. If is not deemed necessary to evacuate the envelope during this sealing operation.

Referring to Fig. 4, there is shown a partial crosssectional view of the conductivefrit seal made in accordanb'e' with'thepfsent invention. This"'cross'-sectional view is taken, for example, through the conductive patch a 18 disposed around the sealedge16 of the, face panel of both the non-conductive and conductive .frit mixtures intcr-mediatethe seal-edges 16 2 6 of face panellfi and funnel portion 12, respectively. Contact to the portion ofthe conductive patch" 18 of the outside of face panel i may be made by means of a leafspring 32 held in contact therewith by means of a circular harness 33 which extends about the'periphery of the tube. A lead 35 from the leaf-spring 32 may then be connected to any appropriate voltage'source. i

of the larger extremity of said tunnel section being juxtaposed to the 'edge'of said face panel sectiong'a layer of vitrified conductive fi'it mixture containing metallic flake and glass fi'it interposed between said funnel section and said face panel section of said cathode ray tube along at least a portion of the juxtaposed edges thereof; means for providing a seal between" said funnel section and said face panel section along the remaining portion of On'the inside of the tube it is often desirable to have a fluorescent screen 36covered over with a thin 'film of aluminum 3 7. This thin film of aluminum may be connected to the' conductive patch 18 by, means of a conductive coating 38: which is painted therebetween and made to overlap both the aluminumrfilm 37 and conductive patch 18 by amounts 'sufficient to establish electrical contact therewith. The inner portion of the seal 30 and conductive patch .18, together with the conductive strip38, may thenfbe covered with a layer 40 composed of anon-conductive frit mixture of the type mixed in 7 container 22 101? Fig. 2 and subsequently vitrified by appropriate heating. There is thus provided a lead-in from the deaf-spring 32 to the viewing screen 35 which re-. quires that no holes be drilled through the side of the face panel 1%} to efiect its installation and which is completely insulated :by the layer 40 of vitrified frit, thereby e a viewing screen 35 disposed on" the inner surface of the r face panel 10. viewing screen 35 generally includes said juxtaposed edgestfirst and second patches of said vitrified conductive fiit mixture disposed on the inside and outside of said envelope'respectively, said first and second patches being in electrical contact with said layer; and meansfor making electrical contact to said first and second patchesthe'reby' to provide an electrical lead-in throughsaid envelope.

2. The'cathode ray tube as defined in claim 1 which additionally includes an element within said envelope adapted to be maintained at a predetermined potential level, at least a portion of saidelement being supported by said envelope, a conductive coating disposed on the inside surface of said enyelope extending between and in electrical contact with said first patch and said elementtmeans for maintaining said second patch at said predetermined potential level, and a vitrified layer of hit disposed over said first patch and said conductive coating thereby to insulate said first patch and'said conductive coating from the inner regions of said envelope. 7

References Cited in the file of this patent 7 UNITED STATES PATENTS