US3897614A

US3897614A - Method for manufacturing a segmented raised anode fluorescent symbol display tube

Info

Publication number: US3897614A
Application number: US353156A
Authority: US
Inventors: James B Armstrong
Original assignee: Sperry Rand Corp
Current assignee: Sperry Corp
Priority date: 1971-06-23
Filing date: 1973-04-20
Publication date: 1975-08-05
Anticipated expiration: 1992-08-05

Abstract

A method for securing display anodes to related support pins in a segmented planar raised anode fluorescent symbol display tube employing a weld and deweld procedure.

Description

United States Patent Armstrong *Aug. 5, 1975 [5 METHOD FOR MANUFACTURING A 156] References Cited SEGMENTED RAISED ANODE UNITED STATES PATENTS FLUORESCENT SYMBOL DISPLAY TUBE 3.666.91 1 5/1972 Armstrong 219/1 17 [75] Inventor: James B. Armstrong, Phoenix, Ariz. 1 47 8/1972 Ruago 313/1 8 R 3.7l6.899 2/1973 Kersletter et ul 1. 29/2514 [73] Assignee: Sperry Rand Corporation, New

York Primary Examiner-Roy Lake Notice; The porticm of the t f thi Assistant Examiner-James W. Davie patent subsequent to May 30, 1989, Attorney Agent, or F1'rmS. C. Yeaton; Howard P. has been disclaimed Terry [22] Filed: Apr. 20, 1973 [57] ABSTRACT [21] Appl' NOJ 353l56 A method for securing display anodes to related sup- Related US. Application Data port pins in a segmented planar raised unode fluores- [63] Continuation of Ser. No. 155956, June 25' 1971. cent Symbol p y tube employing a weld and abandonedt weld procedure.

[52] US. Cl 29/25.l6; 3l3/496 511 1111.01. HOlj 9/36 [58] Field 01 Search 29/2513, 25.14. 25.15, 2 C'amm 6 Drawmg Flgures 29/2516; 3l3/lO8 R, 109.5, 496

PATENTED 5l975 3,897, 614

.I/VVEIVTORS JAMES B. ARMSTRONG F|G.l.

A TTOR/VE) PATENTEDAUB 5197s 3. 8 97, 614 SHEET L l l y l INVENTORS JAMES E. ARMSTRONG METHOD FOR MANUFACTURING A SEGMENTED RAISED ANODE FLUORESCENT SYMBOL DISPLAY TUBE This is a continuation of application Ser. No. 155,956 filed June 23, I971 abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to a method of manufacturing a fluorescent symbol display tube and more particularly to a method for mounting the tube display anodes on respective support pins.

2. Description of the Prior Art Known fluorescent tubes comprise a sealed and evacuated envelope housing a supporting member containing anodes of luminescent material, and an electron emitter. The luminescent material, such as phosphor, is deposited on the supporting member in the desired anode configuration. Where a plurality of anodes are used, each is physically separated from the others by a minimum distance so as to simulate a continuity between adjacent excited anodes to provide a visually acceptable display. In compact small-sized tubes, the physical separation between the anodes is small resulting in a design which is susceptible to electrical leakage due to deposition of electrically conducting particles between adjacent anodes. In some fluorescent tube designs, a mask is used to determine the configuration of each of the anodes, rather than shaping the anodes themselves in the desired configuration. Such a design necessarily precludes continuity between the adjacent excited anodes and may limit the viewing angle of the display.

SUMMARY OF THE INVENTION The invention teaches a unique construction ofa planar fluorescent indicator. The external envelope includes a substrate and a transparent portion or viewing window. A spacer, which may be an integral part of the substrate or the transparent portion, is disposed therebetween to define the envelope to be hermetically sealed. The substrate includes a plurality of electrical conductors, or pins, extending therethrough. Each of a plurality of ribbonlike segments of metal having at least one surface coated with luminescent material is at tached to the ends of a first set of pins extending into the envelope and each forms an anode of the display. The resulting raised anodes cooperatively provide the desired indicia, which may be of a segmented numeric type. An electron emitter, such as a wire connected to a second set of pins, is disposed within the envelope to provide the electron source necessary to excite the luminescent material. The manner of selectively exciting the anodes causing them to luminesce may be by any of the well known electronic driving and switching means whereby the output of said means or circuitry is attached to the pins extending from the envelope and selectively energizes one or more of the leads for the desired indicium, as well as energizing the electron emitter.

A primary object of the invention is to provide a thin planar fluorescent indicator.

Another object of the invention is to provide an increased surface electrical path between adjacent fluorescent anodes.

Another object of the invention is to provide an effective heat sink for the fluorescent anodes to dissipate the heat and thereby extend the life of the indicator.

Another object of the invention is to provide a fluorescent indicator with a large viewing angle.

Another object of the invention is to provide fluorescent anodes having directly attached header pins.

Another object of the invention is to provide a simple inexpensive fluorescent tube structure which can be assembled by mass production techniques.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates the basic elements of a fluorescent display indicator;

FIG. 2 illustrates a cross-sectional view of the raised anode;

FIGS. 3a and 3b are schematic diagrams representative of the electrical circuits;

FIG. 4 illustrates a modification of the electron emitter, and

FIG. 5 illustrates the tabs connecting each segment to a sheet; the figure is substantially identical to FIG. I from U.S. Pat. No. 3,666,911 incorporated by reference infra.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 there is shown an exploded view of the basic elements of the fluorescent tube 14 comprising the invention, including a substrate 1, a plurality of anodes in the form of segments 2, an electron emitter 3, a spacer 4, and a transparent faceplate 5 for viewing the desired displayed indicium. The combination of substrate 1, spacer 4, and faceplate 5 form the enve lope of the indicator. It is to be understood that either the substrate 1 or the faceplate 5 may incorporate spacer 4 if desired. The substrate 1 contains a plurality of conducting members 6, which may be metallic pins, that extend beyond the surface on either side of the substrate. The ends of the pins 6 extending beyond the outside of the envelope are connected to driving circuitry (not shown) whereby voltage may be selectively applied to each of the anodes. The ends of the pins 6 extending into the envelope have attached thereto me tallic ribbonlike segments 2, generally having greater width than thickness. This ratio may of course be modi fied depending on the type of indicium that is to be displayed. Each of the pins 6 extends into the envelope a uniform distance and each of the attached segments 2 are located in the same general plane.

The means for attaching the segments 2 to the pins 6 may be by the process as described in a pending patent application entitled Method for Manufacturing Planar Raised Cathode Gas Tubes," Ser. No. 5,436, filed Jan. 23, 1970 and issued May 20, 1972, as US. Pat. No. 3,666,9II, assigned to the instant assignee. Briefly, in that process each of the segments are formed in a metallic sheet and retained within the sheet by minute connecting tabs. The sheet is juxtaposed with the pins of the substrate such that the pins are aligned with the segments. Each segment is welded to its respective pin by connecting the pin and the segment to a current source. After all welds are completed, current is applied to each pin and the metallic sheet itself, whereby the current passing through the tabs will cause them to melt and free the segments from the retaining sheet. As each segment is severed, the current path becomes open-circuited and the cessation of current flow provides a clear indication that the welding process has been completed.

The height of the segments 2 above the substrate 1 may be determined in any of several ways. The pins 6 may be formed as an integral part of the substrate 1 itself with one end flush with the surface of the substrate and the other end extending therefrom. The flush side is then etched to preferentially remove a portion of the substrate leaving the pins 6 extending above the substrate 1. Another method may be that of inserting the pins 6 into a plurality of holes in the substrate 1 and extending a predetermined distance from either side and sealing them thereto.

The segment side of each anode which faces toward the viewer is coated with a luminescent material, which may be a phosphor material (see FIG. 2). The phosphor coating 7 may be of any of many known compositions and is selectable on the basis of its characteristics of persistence, color, brightness, efficiency, and its excitation voltage requirements. The phosphor coating 7 may be applied to the sheet itself before or after the segments are identified, as manufacturing requirements dictate, or it may be applied to the segments 2 after they are attached to their respective pins 6. Dip coating or screen coating techniques are considered to be two feasible and satisfactory techniques for applying the phosphor coating. Scalable fill tube 8 is attached to the substrate 1 and is used to evacuate the envelope.

ln previous fluorescent tubes, the phosphor coating was deposited directly on a base member located within an envelope. Any temperature rise of one of the excited anodes resulted in transfer of heat to the base member in addition to the heat absorbed from other thermal sources within the envelope, specifically, the electron-emitting heated filament. Over a prolonged period, such a temperature rise has a detrimental effect on the base member and its phosphor coatings and reduced the effective life of the tube. The instant invention circumvents this deleterious effect as heat build-up in the phosphor bearing members is prevented by dissi pating the heat through the pins 6 to the electrical terminals of the peripheral equipment. The attachment of segments 2 directly onto external connecting pins 6 provides a heat sink very much superior to conventional practice where the thermal path is degraded by an intermediate connecting wire and two welds. The additional length and generally smaller diameter of this connecting wire provides a poor thermal path for dissipating heat into external attachments to the leads. The technique of heat sinking in the subject invention per mits higher currents, and therefore increased brightness without reducing the life of the tube.

Additional conducting members extend through the substrate and into the envelope. These may also be pins 9 and form both thesupporting and energizing means for the electron emitter 3. As with the pins 6 for the anodes 2, they are connected to appropriate driving cir cuitry to establish a potential gradient between the electron emitter 3 and the anodes 2. In the simplest form, the electron emitter 3 is a wire extending across a portion of the substrate 1 and on the same side of the segments 2 as the phosphor coating 7. its exact length and location in respect to the anodes 2 is dependent on the electrical and optical requirements of the indicator itself (principally uniformity) and may be determined empirically.

LII

As illustrated in FIG. 1 and described above, a fluorescent tube built according to the teaching of the instant invention requires only simple and straightforward assembly techniques. As such, the tube assembly process is well suited to presently existing mass production techniques.

FIG. 2 illustrates a cross-sectional view of two adjacent anodes 2. The pins 6 extend into and out of the envelope as described. The anodes 2 attached to the pins 6 are raised above the substrate 1 as shown. The effect of raising the segments 2 substantially increases the surface path between the segments 2 to a substantially greater value than the actual least separation between segments. The increase in surface distance between the segments 2 tends to inhibit the formation of a continuous surface electrical path from segment to segment and thereby reduces the probability of the anodes 2 shorting out.

In previous fluorescent displays, the base member supporting the anodes was housed within an envelope, usually of a cylindrical shape. Such an envelope dictated that the front to back tube dimension be no less than the width of the base member. When mounted in a display panel, the display character in such a configuration is substantially recessed from the plane of the front of the panel, which severely limits the effective viewing angle. in the instant invention, the substrate 1 supporting the anodes 2 also forms a part of the envelope and thus eliminates the need for a separate anode supporting member. With a reduction in the number of required internal structural components, the volumetric and manufacturing efficiency is increased. As the faceplate 5, or window, is planar and parallel to the displayed character, it may be positioned parallel and very close to the anodes. Thus, the front to back distance of the instant invention may be reduced to that of the thickness of the substrate 1, the faceplate 2, and the evacuated chamber containing the anodes 2. The close proximity of the displayed character to the faceplate outer surface results in a substantial increase of the viewing angle over prior art devices.

A screen 10 shown in FIG. 1 may be placed between the electron emitter 3 and the anodes 2 and energized through further conducting means, such as pins 13. The potential of the screen 10 must be positive with respect to the electron emitter 3, and may be less than or equal to the potential of the anodes 2, in order that is will attract and accelerate the emitted electrons toward the anodes 2. The addition of the screen 10 may aid in dispersing the emitted electrons to more evenly distribute the electron shower upon the anodes 2. As the phosphor coating 7 on the anodes 2 is luminescently responsive to the amount of excitation, an even or near uniform electron shower will provide an essentially uni form visible response from all of the phosphor coated anodes 2.

FIG. 3a illustrates a schematic diagram for electrically connecting the electron emitter 3 and the anodes 2, absent a screen 10. As shown, one power supply 11 operates to heat the electron emitter 3 while the other power supply 12 establishes a potential gradient between the electron emitter 3 and anode 2 to direct the electrons toward the anodes 2. FIG. 3b illustrates the modification necessary if a screen 10 is utilized. If the screen 10 is at the potential of the anodes 2, the electrons which do not strike the screen 10, will continue on their trajectory and strike the anodes 2, causing excitation of the phosphor coating 7. It is anticipated that there may be modifications of the circuits shown in FIGS. 3a and 3b to incorporate any one of known techniques to obtain a uniform density of emitted electrons at the anodes 2.

FIG. 4 illustrates an end view of a modification in positioning the electron emitter 3. ln applications where the height, that is, substrate 1 to faceplate 5 distance, must be minimized, the electron emitter 3 may be placed adjacent the substrate 1 and below the raised anodes 2. Where there is a danger of the heated electron emitter 3 cracking the substrate 1, it may be raised above the substrate 1 as shown. In operation, there may be an unequal degree of excitation of one portion of the phosphor coating 7 on one anode 2, or one or more anodes may be more highly excited than other anodes, causing varying degrees of luminescence. To overcome this variation, two or more physically separated electron emitters 3 may be used to establish a more uniform electron circuit across the phosphor coating 7 of each anode 2 and from anode to anode. It is understood, of course, that a plurality of electron emitters may be utilized in the viewing side of the anodes 2 as well.

While the invention has been described in its preferred embodiment, it is to be understood that the words which have been used are words of description rather than limitation and that changes within the purview of the appended claims may be made without departing from the true scope and spirit of the invention in its broader aspects.

I claim:

1. A method for fabricating an anode array and base assembly of a display tube comprising the steps of providing a substantially planar non-conductive tube base having electrically conductive anode support pins passing in hermetically sealed relation through the base and extending upward from at least one surface thereof,

providing an electrically conductive sheet having anode segments formed therein in a predetermined pattern and retained within the sheet by tabs connecting each segment to the sheet,

juxtaposing the conductive sheet with the tube base so that each anode segment is positioned adjacent an extending end of a mating anode support pin,

bonding each anode segment to a mating support pin to establish a mechanically rigid electrical connection therebetween such that the anode segments will remain substantially in a common plane upon being disconnected from the electrically conductive sheet,

melting the tabs to sever the anode segments from the remaining portion of the conductive sheet. and

applying a luminescent coating to the side of the anode segments viewed in normal use of the tube after severing the anode segments from the remaining portion of the conductive sheet.

2. A method for fabricating an anode array and base assembly of a display tube comprising the steps of providing a substantially planar non-conductive tube base having electrically conductive anode support pins passing in hermetically sealed relation through the base and extending upward from at least one surface thereof,

bonding each anode segment to a mating support pin to establish a mechanically rigid electrical connec tion therebetween such that the anode segments will remain substantially in a common plane upon being disconnected from the electrically conductive sheet,

melting the tabs to sever the anode segments from the remaining portion of the conductive sheet, and

applying a luminescent coating to the conductive sheet prior to juxtaposing the sheet with the tube base so that the luminescent coating on each anode segment is viewable during normal use of the tube.

Claims

1. A method for fabricating an anode array and base assembly of a display tube comprising the steps of providing a substantially planar non-conductive tube base having electrically conductive anode support pins passing in hermetically sealed relation through the base and exteNding upward from at least one surface thereof, providing an electrically conductive sheet having anode segments formed therein in a predetermined pattern and retained within the sheet by tabs connecting each segment to the sheet, juxtaposing the conductive sheet with the tube base so that each anode segment is positioned adjacent an extending end of a mating anode support pin, bonding each anode segment to a mating support pin to establish a mechanically rigid electrical connection therebetween such that the anode segments will remain substantially in a common plane upon being disconnected from the electrically conductive sheet, melting the tabs to sever the anode segments from the remaining portion of the conductive sheet, and applying a luminescent coating to the side of the anode segments viewed in normal use of the tube after severing the anode segments from the remaining portion of the conductive sheet.

2. A method for fabricating an anode array and base assembly of a display tube comprising the steps of providing a substantially planar non-conductive tube base having electrically conductive anode support pins passing in hermetically sealed relation through the base and extending upward from at least one surface thereof, providing an electrically conductive sheet having anode segments formed therein in a predetermined pattern and retained within the sheet by tabs connecting each segment to the sheet, juxtaposing the conductive sheet with the tube base so that each anode segment is positioned adjacent an extending end of a mating anode support pin, bonding each anode segment to a mating support pin to establish a mechanically rigid electrical connection therebetween such that the anode segments will remain substantially in a common plane upon being disconnected from the electrically conductive sheet, melting the tabs to sever the anode segments from the remaining portion of the conductive sheet, and applying a luminescent coating to the conductive sheet prior to juxtaposing the sheet with the tube base so that the luminescent coating on each anode segment is viewable during normal use of the tube.