US3780326A

US3780326A - Symbol display tube with auxiliary electrode

Info

Publication number: US3780326A
Application number: US00174666A
Authority: US
Inventors: R Raago
Original assignee: Wagner Electric Corp
Current assignee: Cooper Industries LLC
Priority date: 1971-08-25
Filing date: 1971-08-25
Publication date: 1973-12-18
Anticipated expiration: 1990-12-18
Also published as: FR2150295A2; IT952496B; DE2218234A1; CA999633A; JPS4831051A; FR2150295B2; GB1385973A

Abstract

An evacuated envelope having a transparent display face contains a plurality of selectively energizable, phosphor-coated anode display elements for presenting a symbol display, with an auxiliary electrode disposed either behind or coplanar with said display elements and electrically insulated therefrom. A cathode comprising one or more filaments is situated in front of said display elements, i.e., between the display elements and the display face of the envelope, to provide a direct electron beam to the phosphor-coated surfaces of the display elements.

Description

0 United States Patent 1191 1111 3,780,326 Raago Dec. 18, 1973 SYMBOL DISPLAY TUBE WITH 3,619,694 11/1971 Tanji 313/1095 AUXILIARY ELECTRODE 3,584,252 6/1971 Du Bois, Jr. 313/1095 317,633 5/1885 Edison 313/278 x Inventor: Rein Raago, Morristown, NJ.

Wagner Electric Corporation, Newark, NJ.

Filed: Aug. 25, 1971 Appl. No.: 174,666

Assignee:

References Cited UNITED STATES PATENTS 6/1972 Shimada 313/108 R X 12/1968 Frouws et a1. 313/1095 Primary Examiner-Palmer C. Demeo Attorney-William D. Lucas [5 7] ABSTRACT An evacuated envelope having a transparent display face contains a plurality of selectively energizable, phosphor-coated anode display elements for presenting a symbol display, with an auxiliary electrode disposed either behind or coplanar with said display elements and electrically insulated therefrom. A cathode comprising one or more filaments is situated in front of said display elements, i.e., between the display elements and the display face of the envelope, to provide a direct electron beam to the phosphor-coated surfaces of the display elements.

8 Claims, 2 Drawing Figures PAIENTEDntc 18 ms INVENTOR FEW 64/1 0 W ATTO. NEYS /1/VODE- Tmqb- P04 55 E/VEEA roe SYMBOL DISPLAY TUBE WITH AUXILIARY ELECTRODE CROSS-REFERENCES TO RELATED APPLICATIONS The present application relates to an improved embodiment of the symbol display tube disclosed in copending application Ser. No. 66,403 filed Aug. 24, 1970 in the name of Rein Raago, which issued as U. S. Pat. No. 3,688,147 on Aug. 29, 1972.

BACKGROUND OF THE INVENTION l. Field of the Invention The present invention is properly classifiable in class 313, subclass 109.5 (Electrical Lamp Discharge Devices with Indicia or Scale).

2. Description of the Prior Art Various circuits have been devised to strobe a multitube array comprising tubes of the type disclosed in the related applications cited above. Specifically, U.S. Pat. No. 3,555,544 issued on Jan; 12, 1971 upon an application filed in the name of Carl E. Atkins and US. Pat. No. 3,553,525 issued on Jan. 5, 1971 upon an application filed in the name of Francis A. MCGUIIk, Jr. each discloses circuitry for strobing the symbol display tube disclosed in the related applications by turning the cathode-energizing voltage on and off. This strobing technique requires more complex circuitry than is necessary with applicants symbol display tube. Such simplified control circuitry as is disclosed herein affords the economies of fewer components and reduced consumption of electrical power.

US. Pat. No. 3,584,252 issued on June 8, 1971 upon an application filed in the name of Richard DuBois, Jr. discloses a symbol display tube in which an electrically conductive layer is disposed about the display elements on a surface of the transparent envelope. This device is described as being operative in cooperation with related circuitry to perform a blanking function by placing the shielding layer at a negative potential with respect to the cathode. However, because of the variable and relatively large distances between the display elements and the surface of the conductive layer, this prior art device is unable to perform with the speed and uniform effectiveness of applicants device.

SUMMARY OF THE INVENTION Applicants invention is embodied in and carried out by a symbol display tube having a plurality of selectively energizable display elements coated with phosphorescent material to enable the formation of a predetermined group of symbols, with a strobbing or auxiliary electrode disposed either behind or coplanar with said display elements and electrically insulated therefrom to enable high speed, time-sharing operation of the complete display formed by a plurality of such symbol display tubes with relatively simple external circuitry having low power requirements.

BRIEF DESCRIPTION OF THE DRAWING A more complete understanding of the present invention may be obtained by referring to the accompanying drawing, of which:

FIG. 1 is an isometric view of a display tube constructed in accordance with the present invention, partly broken away to illustrate the spatial relationships and cross-sections of tube elements; and

FIG. 2 is a block diagram of a circuit incorporating a plurality of display tubes constructed in accordance with the present invention.

DESCRIPTION OFTHE PREFERRED EMBODIMENTS Referring now specifically to FIG. 1, the display tube 10 may be seen to comprise a composite envelope having a flat, transparent display face 12 and a dished, substantially rectangular support member 14 which is preferably opaque. Seven

anode display elements

16A, 16B, 16C, 16D, 16E, 16F, and 166 in a figure-8 array are each formed by a stick-shaped conductive layer deposited on the floor (major inner surface) of support member 14 with an overlying, coextensive phosphor coating. Optionally, a period or decimal point may be formed in the display by another SLllCh anode display element 16H. A strobing or auxiliary electrode 17 is also disposed on the floor of support member 14, and surrounds each of the anode display elements l6A-H while being insulatedly spaced therefrom. When the electrode 17 is placed at a positive potential with respect to the cathode 18, it will act as an accelerator of electrons, resulting in a brighter display. Thus, the electrode 17 can be used as a means to control display intensity. Also, when thus operated, electrode l7 acts as a means for producing uniform current density over a relatively large area, especially when the electrons are emitted from a one-or two-line source. When placed at negative potential, electrode 17 will prevent the flow of electrons to the anode display elements l6A-H. Thus, the electrode 17 may also serve to perform a strobing function. A cathode 18 comprising a substantially parallel pair of

filaments

18A and 18B is disposed between the display face 12 and the display elements l6A-H to provide an even distribution of high-velocity electrons to each of the display elements. The

cathode filaments

18A, 18B lie in a plane which is substantially parallel to the plane in which the display elements lie. A plurality of connecting

pins

20A, 20B, 20C, 20D, 20E, 20F, 20G and 20H are connected to the conductive portions of

display elements

16A, 16B, 16C, 16D, 16E, 16F, 16G and 16H, respectively, and extend through the insulating support member 14 to enable electrical connection of the display elements to an external control circuit. The connecting

pins

22, 24 and 26 are attached to the terminals of cathode l8 and extend through the support member 14 for connection to the source of electrical power. As shown, the strobing or auxiliary electrode 17 is insulatedly spaced away from the

pins

22, 24 and 26. The upper ends of

filaments

18A, 18B are connected to the ends of filament spring 23, which in turn is connected perpendicularly to the upper connecting pin 22. The lower ends of

filaments

18A, 18B are connected to the lower connecting

pins

24, 26, respectively. This arrangement makes it possible to energize the cathode filaments as either parallel-connected resistances or series-connected resistances. With one terminal of a source of electromotive force (EMF) connected to pin 22, and the other terminal connected to

pins

24, 26, the

filaments

18A, 18B are energized as parallel-connected resistances. With one terminal of a source of EMF connected to pin 24 and the other terminal to pin 26, pin 22 being left floating or unconnected, the

filaments

18A, 18B are energized as seriesconnected resistances. Connecting pin 28 is connected to electrode 17, and extends through the support member 14 to enable electrical connection to external control circuitry. An exhaust tube 30 may be either integrally formed with the support member 14 from the same material, or formed from a different material and then joined with support member 14 in the region of aperture 32 extending through the thickness of support member 14.

Referring now specifically to FlG. 2, the circuit shown therein includes three symbol display tubes l1, l0-2 and -3 constructed in accordance with the foregoing description of the tube shown in FIG. 1. Each of these tubes has its anode display elements 16 connected to the anode-cathode power supply and switching circuit 34. The corresponding anodes in each of the three tubes are connected in parallel with one another and to a terminal of the power supply and switching circuit 34. The cathodes of the three tubes are also connected in parallel and energized by power supply and switching circuit 34. Pulse generator 36 draws its power and receives synchronizing signals from power supply and switching circuit 34, and normally maintains the strobing or auxiliary electrodes 17 in the three tubes at a voltage which is sufficiently negative to prevent the flow of emitted electrons from the cathodes 18 to any energized anodes 16. In operation, a first group of anode display elements 16 is placed at a positive potential with respect to the cathode 18 for a first time interval A 1. During this time period A 1 t, the pulse generator 36 places only the electrode 17 of tube 10-1 at either ground or positive potential. Thus, the accelerated flow of electrons from the cathode 18 to the energized anode display elements 16 in tube 10-1 is unimpeded, and a first symbol will be displayed by this first tube. However, even though the corresponding parallel-connected anode display elements in tubes 10-2 and 10-3 are also placed at a positive potential with respect to their associated cathodes, these tubes are blanked because their electrodes 17 remain at their normal negative potential to prevent the flow of electrons from the cathodes to the energized anode display elements. During a second time interval A 1, a second group of anode display elements in each of the three tubes is energized, and only the electrode 17 of tube 10-2 is placed at either ground or positive potential by the pulse generator 36. Thus, a second symbol will be displayed by the tube 10-2 as a result of the accelerated flow of electrons from its cathode to its energized anodes. Tubes 10-1 and 10-3 will be blanked during the interval A because their electrodes 17 are at their normal negative potential. Finally, during a third time interval A a third group of anode display elements 16 in each of the three tubes is energized and only the electrode 17 of tube 10-3 is placed at either ground or positive potential by pulse generator 36. Thus, a third symbol will be shown by tube 10-3, while tubes 10-1 and 10-2 are blanked by the negative potential placed on their respective electrodes 17. This sequence is repeated at a sufficiently high rate to give the appearance that the tubes 10-1, 10-2 and 10-3 are each constantly energized.

The advantages of the present invention will be apparent to those skilled in the art, as well as changes which could be made in the foregoing embodiments without departing from the spirit and scope of the invention. For example, the anode display elements may be coplanar with or on either side of the strobing or auxiliary electrode. Also, instead of utilizing two or more discrete parallel cathode filaments, a single, a continuous filament having two or more portions thereof similarly arrayed could be advantageously utilized. Also, instead of arranging either the discrete cathode filaments or sections of a continuous cathode filament in parallel spatial relationship, a V-shaped (two filaments or filament segments) or N-shaped (three filaments or filament segments) array could be advantageously employed. With such arrays, the mutual repelling forces would be greater in the region where the filaments or filament segments are in close proximity and weaker in the region where they are farther apart, thus effecting spreading of the electron streams to the degree required by the spacing at any particular level of the display. It will be readily apparent that, in an embodiment employing a continuous, series-energized cathode filament, a break in that filament will completely disable the source of the electrons. In many applications, it is far more hazardous to have an erroneous readout, which might occur if one of several discrete cathode filaments failed, than it would be to have no readout at all. In the latter situation, an observer will at least know that the display tube is not functioning, whereas with an erroneous readout, an observer might have no reason to believe that there is a display tube malfunction.

Therefore, it should be understood that the present invention is not to be limited to the foregoing description of the specific embodiments thereof, but is to be determined by the spirit and scope of the accompanying claims.

What is claimed is:

l. A display tube comprising:

1. an evacuated envelope including a transparent display face and a support member;

2. a plurality of anode display elements each of which is coated with a phosphor, all disposed in a first plane within said envelope so as to form any of a desired group of symbols by selectively energizing said anode display elements;

3. an electrode, disposed in a second plane within said envelope, surrounding each of said anode display elements and being electrically insulated therefrom;

4. an electron-emissive cathode disposed between said transparent display surface and said plurality of anode display elements; and

5. a plurality of connector means extending through said support member and operative to enable electrical connection of said anode display elements, said electrode and said cathode to external control circuitry.

2. The display tube according to claim 1 wherein said first plane in which said anode display elements are disposed is coincident with said second plane in which said electrode is disposed.

3. The display tube according to claim 1 wherein said support member is substantially rectangular and dished to form a floor therein, and said transparent display face is flat.

4. The display tube according to claim 3 wherein said electrode is disposed on said floor of said support member.

5. The display tube according to claim 3 wherein said anode display elements are disposed on said floor of said support member.

6. The display tube according to claim 1 wherein said is mounted, and extending through said support electron emissive cathode comprises at least first and member; and second filaments spaced apart in a third plane substan- 3. second and third connecting pins extending tially parallel to said first plane in which said anode disthrough said support member and having the secplay elements are disposed. 5 0nd adjacent ends of said first and second fila- 7. The display tube according to claim 6 wherein said ments, respectively, connected thereto. plurality of connector means includes: 8. The display tube according to claim 1 wherein l. a filament spring disposed within said envelope seven anode display elements are arranged in a figureand having the first adjacent ends of said first and eight pattern for forming the digits from 0 to 9, inclusecond filaments connected thereto; 10 sive.

2. a first connecting pin on which said filament spring

Claims

1. A display tube comprising: 1. an evacuated envelope including a transparent display face and a support member; 2. a plurality of anode display elements each of which is coated with a phosphor, all disposed in a first plane within said envelope so as to form any of a desired group of symbols by selectively energizing said anode display elements; 3. an electrode, disposed in a second plane within said envelope, surrounding each of said anode display elements and being electrically insulated therefrom; 4. an electron-emissive cathode disposed between said transparent display surface and said plurality of anode display elements; and 5. a plurality of connector means extending through said support member and operative to enable electrical connection of said anode display elements, said electrode and said cathode to external control circuitry.

2. a first connecting pin on which said filament spring is mounted, and extending through said support member; and

3. second and third connecting pins extending through said support member and having the second adjacent ends of said first and second filaments, respectively, connected thereto.

6. The display tube according to claim 1 wherein said electron-emissive cathode comprises at least first and second filaments spaced apart in a third plane substantially parallel to said first plane in which said anode display elements are disposed.

7. The display tube according to claim 6 wherein said plurality of connector means includes:

8. The display tube according to claim 1 wherein seven anode display elements are arranged in a figure-eight pattern for forming the digits from 0 to 9, inclusive.