Historical Document · 1970
The basic vacuum-fluorescent display patent, filed 19 October 1967 (Japanese priority 27 March 1967) and granted 21 April 1970: fine oxide cathode, mesh grid, phosphor-coated segment anodes viewed through the cathode, about 0.8 V on the filament and +25 V on grid and anodes.
April 21, 1970 MIKIHARU TANJI 3,508,101 ; CHARACTER INDICATING ELECTRON TUBE Filed Oct. 19, 1967 % 38 a, 37 2) ae 13 ! ! 33 4 /4. 3 45 A 20 27 <2 eee) 35 = Ph /4. #33 “iy iN? LL 7? oe 34. aa iiiie Se ee ‘7 Fig. 2 36 3 2 ang —t 22 > [44 43— 45 20 ~25 447 : l-—35 ff 47 NB SF eee ; 27 Kt so dg j Frg. Sd ~~ 3 . Fi F. Se mm Fig. 3b ed /6 F 1g. 3a INVENTOR. MUKA AR FANS! BY, 4a. NEY 7/10/2024 14:01:34 Page 1 of 4 United States Patent Office 3,508,101 Patented Apr. 21, 1970 1 3,508,101 CHARACTER INDICATING ELECTRON TUBE Mikiharu Tanji, Ise-shi, Japan, assignor to Ise Electronics Corporation, Ise-shi, Japan, a company of Japan Filed Oct. 19, 1967, Ser. No. 676,580 Claims priority, application Japan, Mar. 27, 1967, 42/19,047 Int. Cl. H01j 7/42; HO1k 1/60 US, Ci. 313—109.5 6 Claims ABSTRACT OF THE DISCLOSURE The character indicating tube in accordance with the invention includes a sectionalized anode, a grid and cath- ode and means for energizing selected anode sections to produce characters, such as the numerals 1—9 and 0, and the like. This invention relates to an improved character indicat- ing tube of the electron type which will provide an indi- cation of any one of.a group of numerals or characters and wherein all of the characters are formed in a substantially common plane. Indicating tubes or devices for visually displaying nu- merals or other characters are widely used in computers, measuring apparatus, and the like, in order to provide a visual display of information. The structure for conven- tional indicating tubes generally embodies a plurality of numerals or characters displaced in depth and sealed within a gas-filled envelope. Voltages are applied to se- lected electrodes thereby causing the selected electrode to glow and provide an indication. Normally, the glowing electrode affords relatively low illumination and inasmuch as the electrodes are placed in spaced in depth within the enclosure, there is a variation in luminescence depending on the position of the electrode within the tube. Further- more, when a plurality of such conventional indicating tubes are used for indicating a number of figures, the fig- ures are not all displayed in the same plane and in many cases the displayed number cannot be easily read. Further- more, conventional iubes require voltages as high as 170 volis in order to provide adequate Iuminescence. If the apparatus with which such tubes are utilized involves con- ventional vacuum tubes, then the provision of a high op- erating voltage does not afford any great difficulty. How- ever, in the case of transistorized or integrated circuits, the operating voltages are very low and separate power sources are required for the indicating tubes. Accordingly, one object of the invention resides in the provision of a novel and improved indicating device which overcomes the aforementioned disadvantages of known indicating tubes and provides an improved tube capable of operating at a relatively low operating voltage. Another object of the invention resides in a novel and improved character indicating tube affording a relatively high degree of luminescence. Still another object of the invention resides in the provision of a novel and improved indicating tube wherein all of the characters are disposed in substantially the samc plane. A still further object of the invention resides in the provision of a novel and improved indicating tube char- acterized by its simplicity, ease of manufacture and rela- tively long life. The above and other objects of the invention will be- come more apparent from the following description and accompanying drawings forming part of this application. In the drawings: FIGURE 1 is a prospective view in partial section of an indicating tube in accordance with the invention; 7/10/2024 14:01:34 10 15 20 25 30 35 40 45 50 55 60 65 70 2 FIGURE 2 is a vertical cross-sectional view of the tube shown in FIGURE 1; and FIGURES 3a, 3b, 3c and 3d are front elevational views of the individual elements of the tube shown in FIGURES 1 and 2. The improved tube in accordance with the invention includes a hermetically sealed vacuum envelope, at least one side of which includes transparent material, such as glass, A cathode is arranged within the container and ad- joining the transparent side thereof. The cathode is ar- ranged so that it will not interfere with the visual observa- tion of any indicated characters and may be formed of a very fine, almost invisible wire capable of providing elec- tronic emission when heated. A grid electrode formed of a plurality of very fine wires is positioned rearwardly of the cathode and controls electron emission emanating from the cathode. If desired, the next rearwardly positioned ele- ment may be a character forming electrode made of metal and having openings formed therein in a predetermined pattern to facilitate the formation of the characters. The rearwardmost element is a luminescent anode formed of a metal layer shaped in a contour corresponding to the contour of a character to be indicated on the surface and carrying a layer of fluorescent material. If the anode is to selectively indicate more than one type of character, the anode may comprise a plurality of mutually insulated anode elements, each having a fluorescent layer and form- ing a combined pattern. By selectively exciting different portions of the combined pattern, various characters can be visually displayed. Appropriate lead wires are connected to each of the elements of the luminescent anode, the grid electrode and the cathode. These lead wires are, in turn, connected to pins extending through the sealed envelope to facilitate connection with external circuits. With a character indicating tube as described above, upon the application of +10 to +25 volts to the grid with respect to the cathode and then upon the application of a positive voltage of a similar magnitude to selected ele- ments of the luminescent anode, any one of a group of characters can be displayed. The luminescence can be ob- served from the exterior of the tube nothwithstanding the presence of the grid or cathode. In the event that the character forming electrode is provided the indicated char- acter will be observed through the openings in that elec- trode. When the anode comprises a plurality of anode elements, it is apparent that any one of a number of char- acters can be selected and displayed. It will be observed that the operating voltage of about 25 volts is of the ord2r of that utilized in the operation of semi-conductor and ia- tegrated circuits and, accordingly, affords a substantial ad- vantage over prior known devices. Furthermore, since a single luminescent anode is utilized, all characters are displayed in the same plane, and, therefore, the distance between the observer and the indicated character will not vary, notwithstanding the particular character being displayed. Furthermore, a relatively high luminescence is obtained and the characters can be easily observed even with high ambient light. Still an additional advantage resides in the fact that a variety of fluorescent substances may be utilized so that a wide selection of colors is afforded. Referring now to the drawings, the envelope 1 in the in- stant embodiment of the invention is formed of glass and it includes a luminescent anode 2 having a ceramic base plate 3 and a plurality of continuous ridges 4, 5, 6, ... 12, 13 dividing the surface of the plate into eleven areas 21, 22, 23, . . . 30, 31. Each of the areas 21—31 includes a conductive film 14 with such films being mutually in- sulated one from the other and coatings of fluorescent material 15 overlying each of the conductive films 14. Page 2 of 4 3,508,101 If the anode is to indicate a single character then a con- ductive film 14 would merely be applied to the ceramic base 3 in the configuration of the character and a fiuores- cent coating would be applied to the conductive film. A plurality of lead wires 16 extend through the back side of the ceramic plate 3 and contact the conductive films 14. The other ends of the leads are connecied to pins 17 extending through the envelope 1. If desired, a character forming electrode 18 is disposed in front of the luminescent anode 2. Though such elec- trode is not necessary for the operation of the tube, it does, however, afford improved appearance of the char- acters being displayed. When the character forming elec- trode is employed in a device for displaying a plurality of characters, such as the numerals 1-9 and 0, it would in- clude a plurality of openings 41-51 as may be observed more clearly in FIGURE 3b. The openings 41-51 are co- ordinated with the specific elements 21-31, previously de- scribed. Electrode 18 is secured in overlying relationship to the anode by providing appropriate attaching means at the upper and lower portions of the ceramic base plate 3. A separate lead wire is connected to the character form- ing electrode and to one of the pins 17. A very fine mesh type grid 20 is disposed in front of the character forming electrode 18 and has an area at least as large as the area of electrode 18. The grid is held in position by supports 33, 33 and is connected through a lead wire 34 to one of the pins 17. A cathode 35 formed of a single fine wire of the order of 30-50 microns is disposed in front of the grid 20. The upper end of the cathode is connected directly to one of the pins lead wire 37 to one of the pins 17 while the lower end of the cathede is connected directly to one of the pins 17. A getter ring 38 is positioned at the top of the tube in order to remove residual oxygen remaining after evacu- ation. In the indicating tube, as described above, approxi- mately 0.8 volt is applied to the cathode 35 in order to to heat it to a dark red color. A voltage of about +25 volts is applied to the grid 20 and to the character forming electrode 18. If the anode 2 is provided with a single char- acter the application of a voltage of about +25 volts is applied to illuminate the character. If the anode contains a plurality of elements, as illustrated in the drawings, then by the application of a positive voltage of the order of +25 volts to selected elements, the selected elements will be illuminated by reason of the emission from the cathode which is accelerated by the grid and passes through selected openings in the character forming electrode to illuminate corresponding elements of the anode. For in- stance, if the numeral 1 is to be displayed, the positive voltage is applied to the anode elements 24 and 28. The cathode emission then will pass through the holes 44 and 48 in the character forming electrode and excite to lumi- nescence anode elements 24 and 28. The indicating tube, of course, is viewed in the direction of the arrow as in- dicated in FIGURE 2. If a signal voltage is applied to the anode elements 22, 25, 26, 27 and 30, the numeral 2 will be viewed through the openings 42, 45, 46, 47 and 50 of the character form- ing electrode 18. Similarly, through the selective applica- tion of the signal voltage to other anode elements the numerals 3-9 and 0 can be displayed. The illustrated em- bodiment of the invention further includes an element 21 in the ‘upper left-hand corner of the anode as viewed in FIGURE 3a and is aligned with the opening 41 of the character forming element shown in FIGURE 3b. This element of the electrode may be used to indicate an apos- trophe or for any other similar purpose. The element 31 on the anode is used to provide a decimal point and would be observed through the opening 51 in the character forming electrode 18. As described above, the numerals can be readily ob- served from the front of the tube, notwithstanding the 7/10/2024 14:01:34 10 20 25 40 45 50 55 60 65 70 4 presence of the cathode 25 or the grid 20 since they are both made of very fine wire. Further, although a voltage of about 25 volts is normally applied to the grid 20 of the character indicating tube, if the grid voltage is lowered to a potential equal to or lower than the voltage of the cathode, the cathode emission cannot reach the anode and thus luminescence of the anode is prevented. Thus, the grid 20 functions to diffuse the emissions from the cathode and also accelerate and decclerate emission from the cathode. In the illustrated embodiment of the invention, the char- acter forming electrode 18 is utilized and since it is polar- ized at a voltage of +25 volts, any particles evaporated from the cathode 35 will be generally absorbed by the character forming electrode. This minimizes deterioration of the fluorescent material on the anode and accordingly affords long tube life. Advantages of the character indicating tube as described above are as follows: (1) AJL characters and marks are indicated in the same plane which greatly facilitates reading of the characters being displayed and overcomes the disadvantage of con- ventional tubes having a plurality of electrodes displaced in depth. (2) The tube can be operated at voitages of the order of 25 volts and is, therefore, readily adapted for use with low voltage circuits such as transistorized and integrated circuits. (3) The indicated characters are bright and clear be- cause each character is indicated by luminescence of flu- orescent material on the anode surface and the outline of the character can be precisely defined by a character forming electrode. (4) The structure of the tube is relatively simple and can be manufactured easily and inexpensively. (5) The tube has relatively long life as compared with conventional character indicating tubes. Hi desired, the character forming electrode may. be coated with an insulating material, such as alumina (Al,03), magnesium oxide (MgO), chromic oxide (Cr203), etc. These coatings increase the cathode emis- sion reaching the anode and thus cause the fluorescent layers to luminesce more strongly. Further, the lumines- cent anode may be formed of beryllia ceramic or alumina porcelain and then coated with a conductive film and a fluorescent layer. Thereafter, grooves may be formed in the anode to provide a plurality of anode elements as pre- viously described. Furthermore, although the cathode was described as one providing electron emission, it is un- derstood that photoelectric cathodes and other cathodes which emit electrons into space may also be utilized. While only certain embodiments of the invention have been illustrated and described, it is apparent that altera- tions, modifications and changes may be made without de- parting from the true scope or spirit of the invention as defined by the appended claims. What I claimed is: 4. A character indicating tube comprising a hermeti- cally sealed evacuated envelope having at least one trans- parent side portion, an elongated heated cathode adjoin- ing the transparent side of said envelope, a conductive luminescent anode in substantially parallel spaced rela- tionship to said cathode and facing said cathode and trans- parent envelope portion, said luminescent anode includ- ing a conductive portion and a layer of fluorescent mate- rial on said conductive portion, said fluorescent material facing said cathode, an accelerating grid interposed be- tween said anode and cathode, said cathode and grid be- ing formed to permit substantially unobstructed observa- tion of said luminescent anode. 2. A character indicating tube according to claim 1 wherein said luminescent anode is formed with a plural- ity of mutually insulated conductive anode elements ar- ranged in a selected pattern, a fluorescent layer overlying Page 3 of 4 3,508,101 said conductive portions and means for selectively energ- izing said conductive portions. 3. A character indicating tube according to claim 1 wherein said cathode is a fine wire and said tube further includes means for heating said wire to effect electron emission therefrom. 4, A character indicating tube according to claim 1 including a character forming electrode positioned be- tween said grid and said anode, said character forming electrode having a plurality of openings therein corre- sponding to the configuration of the fluorescent layer formed on the surface of said anode. 5. A character indicating tube according to claim 1 including means for applying potentials to said grid and said anode which are substantially equal and positive with respect to said cathode. 6. A character indicating tube according to claim 4 in- cluding means for energizing said grid, character form- ing electrode and anode positively with reference to said cathode. 7/10/2024 14:01:34 10 15 6 References Cited UNITED STATES PATENTS 1,928,407 9/1933 Batchelor ....-___ 313—108 X 3,406,288 10/1968 Du Bois et al. ____ 313—109.5 X 3,008,065 1241/1961 Chamberlin _____ 313—109.5 XK 3,082,341 3/1963 Balaskovic ____._____ 313—70 3,133,221 5/1964 Knochel et al. _______ 313—108 3,201,634 8/1965 Weidel et al. ______ 313—109.5 3,281,619 10/1966 Greene _________ 313—109.5 X FOREIGN PATENTS 11,265 5/1964 Japan. OTHER REFERENCES “What's Up Front Counts,” May 29, 1968 Electronics, vol, 40, pp. 212-213. JAMES W. LAWRENCE, Primary Examiner 20 D. O’REILLY, Assistant Examiner US. Cl. X.R. 313—108 Page 4 of 4