US3160773A - Direct viewing storage tubes having ceramic spacers between collector electrode and storage grid - Google Patents

Description

8, 1964 E. ZIEMER ETAL ,7

DIRECT VIEWING STORAGE TUBES HAVING CERAMIC SPACERS BETWEEN COLLECTOR ELECTRODE AND STORAGE GRID Filed Jan. 15, 1962 \1 M 1 42 38-92 z' m la I6 fi\ f /.r/////.'/.'/, I u 4s 7 I F|g.2. Z Z

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INVENTORS Eric Ziemer,Fronk E Whittle L 0nd Augustus Miele m ra 1 ATT ORNEY United States Patent 3,160,773 I DIRECT VEEWING STORAGE TUBES HAVINQ E= RAB EC SlACERS BETWEEN CQLLEQTOR ELE- TRGDE AN 1) STGRAGE GRID Eric Zierner, Horseheads, and Frank F. Whittle, Elmira, N.Y., and Augustus Miele, Canoga Park, ilali'b, assign= ors, to'WestinghouseElectric Qorporation, East Pittsburgh, Pa a corporation of Pennsylvania Filed Jan. 15, 1962, Ser. No. 166,047 5 Claims. (Cl. 313-68) This invention relates to cathode ray tubes and more particularly to improvements for mounting the storage surface grid and the collector electrode in direct view storage tubes.

Direct viewing storage cathode ray tubes for storing the signal image for direct viewing are well known. In addition to the usual luminescent screen and writing gun, or guns, of the conventional cathode ray tubes, such storage tubes include a storage screen, a secondary electron collimating system and a reading or viewing gun.

In general, the storage grid is a'dielectric material deposited on a fine metal mesh called the backing electrode. This backing electrode is usually mounted between the collectorelectrodeand the luminescent screen. In operation, this storage grid is charged to a uniform potential which is very near the viewing gun cathode potential. The writing gun scans the storage screen and creates a charge pattern on the surface of the storage grid by secondary emission from the dielectric material of the storage screen. Because this dielectric material is an excellent insulator, the charge pattern does not leak away, but remains for a long period of time. The secondary electrons liberated from the storage surface are attracted to the collector electrode which is a very fine metal mesh pervious to electrons from the two types of guns.

The reading or viewing gun does not scan the target system, which in this case includes the collector electrode,

the backing electrode, the storage grid and a luminescent viewing screen, but instead it produces a wide angle beam of electrons which floods the entire target system and penetrates through the holes in the collector electrode and storage grid to bombard the luminescent viewing screen.

The charge pattern written upon the storage screen con trols the electrons from the viewing gun beam in a manner similar to the control of plate current by the signal applied to the control grid of a conventional triode vacuum tube. In this way the signals applied to the writing guns are converted to patterns on the storage screen and these produce corresponding patterns of luminescence on the viewing screen. The penetration of electrons through the storage grid is proportional to the charge written upon it and accordingly the shades of gray and half tones may be faithfully reproduced. In such tubes it is desired that the display be extremely bright and accordingly, a very high potential is applied to the viewing screen, which produces a very high electron current density.

It should be readily apparent from the previous general description that the components of the target system must be held immovably with respect to each other and with respect to the collimating flood grid and the electron beams from the writing and viewing guns. At the same time the various electrodes, including the backing electrode and the collector electrode must be insulated from each other to withstand the high voltages involved.

l-leretofore in maintaining the proper spacing and'the insulation between these electrodes, glass materials were used for insulation in a type of mounting support that necessitated the use of metal parts having substantially the same'coefficient of expansion as that of the glass insulating material. All such materials which have the proper coefiicient of expansion are usually magnetic and this adversely affected the path of some of the electrons,

3,160,773 Patented Dec. 8, 1964 "Ice provide a novel and improved means for mountingthe' storage screen in the proper relation to the other components of the storage tube.

A more specific object is to providea novel and improved means for mounting the storage surface grid on the collector'electrode support, which improved mounting will be simple, rugged, inexpensive to manufacture, and will lend itself'to flexibility in varying the length'of the mounting and will be especially adaptable to mass production techniques.

The novel features that are considered characteristic of this invention are set forth with particularity in'the appended claims. The invention itself, however, both as to its organization and method of operation as' well asadditional objects and advantages will best beunderstood from the following description when read'in connection with the accompanying drawing, in which:

FIGURE 1 is a'schematic representation,partially in section, of a cathode ray storage tube in acco'rdancewith the present invention;

FIG. 2 is a partial side elevational View, partly in section, of a cathode ray tube in accordance with them vention;

FIG. 3 is an enlarged end'view of a spacer mountingfor the storage surface grid; and,

FIG. 4 is a portion of the electrode grid assemblies, showing an enlarged side view, partly in section, of one of the spacers.

Briefly, the present invention resides in the novel and improved means for mounting the fine wire mesh, which is called the backing electrode and carries the storage surface, in the form of a novel ceramic-tab sub-assembly constituting an eflicient insulator andmounting support for mounting the backing electrode, on the collector electrode assembly. The storage surface grid is a dielectric material deposited on the backing electrode in the form of a dielectric grid. The tabs on the ceramic-tab sub assembly provide convenient means by which the subassembly can be secured to the collector electrode assembly and the backing electrode. The subassembly reduces the number of assembly operations on the main assembly line since these subassembly units can be made as a separate assembly operation devoted entirely to this subassembly. This subassembly unit then becomes one of the components which is added on the main line. One of the tabs is first welded to the collector electrode after which the other tab is welded to the backing electrode to provide a very rugged and accurately dimensioned mount, ing support. 7

In the embodiment of the invention illustrated in the drawings, a direct-viewing storage tube in accordance with the present invention comprises an evacuated'em velope =14) having a neck portion, disposed asshown in FIG. 1, housing two electron writing electron guns 12 each having a cathode 14, a signalinput grid 16, a first anode 18, a second anode 22, a focusing grid 24 and defiection plates 26. These writing guns are similar to those in electrostatically focused and deflected oscilloscope tubes. They are capable of forming a well defined beam having high current density for providing high resolution and fast writing speed. The deflecting systems for these guns is energized by appropriate beam deflecting control signals in conventional manner to cause the electron beams to trace rasters on the collector electrode 28. The elec: trode '28 is pervious to the electron beams and is disposed between the cathodes of the guns and the viewing screen 32. The backing electrode 34 is interposed between the collector electrode 28 and the viewing screen 32.

stitutes the backing electrode 34. The backing electrode 34 and the storage surface griddfi are also pervious to the electron beams. Initially, this storage surface grid 48 is charged to a uniform potential approximately that of the potential of the viewing or flooding gun cathode -38. The storage surface grid 43 especially cooperates with both of the writing guns l2 and the viewing gun 36in 'a special manner; the writing guns scan the storagesurface grid and create a charge pattern by a secondary emission from the storage surface and the electron emission from the viewing gun transfers this charge pattern to the viewing screen 32 in the form of a video image. 7

Since this dielectric storage surface grid 48 is an excellent insulator, the charge patterns do not leak away read- 14, and that potentialis approximately the same as'the potential of the storage surface grid 48, and since the potential of the viewing screen 32 is of the order of 10,000 volts, it is necessary to have means for providing the necessary mechanical support and the electrical insulation between the collector electrode 23 and the backing electrode 3.4. The present invention provides such a non- 'magnetic mounting support which has also very high electrical insulating qualities in the form of the ceramic-tab ily, but remain there for some time. The secondary electrons liberated from the storage surface grid 43 are attracted to the collector electrode 28. As previously mentioned, the viewing gun 36 does not scan the viewing screen 32'as do the writing guns, but on the other hand produces a wide angle beam of electrons which floods? the entire area of the storage surface grid 4%. The electrons penetrate through the holes in the meshes of the collector electrode 28 and the backing electrode 3410 bombard the luminescent layer of the viewing screen 32. The charge pattern written upon the storage surface grid 43 by the writing guns 12, acting either jointly or individually, controls the electrons from the viewing gun cathode 38 in a manner similar to the control of plate current by the signal applied to the controlgrid of an ordinary triode vacuum tube. In this way the signals supplied to the two writing guns 12 through the signal input grids 16 are converted to charge patterns on the storage surface 48 and these produce corresponding video images on the viewing screen 32. The number of electrons which pass through the storage surface grid 4d is proportional to the charge written upon it by the writing guns 12 and accordingly the variations in the incremental area charges of the charge pattern are faithfully reproduced as a video image on the viewing screen 32.

One of the exacting requirements of the system neces- I sary to provide a sharp and crisp video image on screen 32 is that all of the electrons from the viewing gun 36 strikes the storage surface grid 48 at right angles thereto.

This is necessary so that the electrons will have energy components in paths normal to the storage surface grid.

The control grid 42, the accelerating grid' z and the collimating grid 46, which is a conductive coating applied to the inside of the envelope wall, as well as the collecting electrode 28 cooperate to orient the electrons from the viewing gun '36 so thatthey strike the storage surface grid 48 normal thereto. The electrons from the cathode 38 of theviewing gun are highly divergent as they emerge from the aperture of the. grid 44, but by properadjus ment of the potential on the collimating grid 46, the col lector electrode mesh 28 and the backing electrode 34, the electron stream is collimated to provide a uniform normal flooding of the backing electrode 34. Only under operating conditions when the paths of the electrons are normal to the backing electrode 34 and the storage surface grid 48 will equal charges at various points on the storage surface grid 48 have equal control of the flood beam. From the above, it will be' seen that it is highly desirable that there not be any magnetic material in the vicinity of the collector electrode mesh, storage surface grid ed, the backing electrode and the viewing screen'32 to interfere with the flow of electrons.

Also, since the writing gun cathode 38 is approximately minus 2400 volts'with respect to the viewing gun cathodes subassemblies shown in detail in FIGS. 3 and 4.

The collector electrode and the storage surface grid I assembly 54 comprises an annular sleeve 56 having resilient centering tabs 58. These tabs are suitably secured toflthe outer surface of the sleeve 56 and extend outwardly, having outer portions substantially concentric with the sleeve which are adapted to engage the inside surface of the glass envelope in an area beyond the col limating grid 46. Only one centering tab 58 is shown in FIG. 2, but it should be understood that additional the pairs of tabs is welded to an annular metal ring 72 which forms the support for the backing electrode 34. The radial depth of the metal ring 72 is about the same as the combined thickness of the flange 62 on the sleeve 56 plus the radial depth of the flange 62, which is sub stantially the same as the width of the tabs 66 shown in FIG. 3. The collectorelectrode 28, the backing electrode $4 with the storage surface grid 48 and the viewing screen 32 may be considered to be the'ta'rget assembly for the storage tube. As clearly shown in the drawings the collector electrode23is nearest the electron guns of the tube and the backing electrode-34, with the storage grid, is interposed between the collector electrode and the viewing screen 32.

The ceramic-tab assemblies 52 constitute the means for supporting the backing electrode 34 and the storage surface grid 48 on the sleeve 56 at the same time providing efiicient high potential electrical insulation between the storage surface grid 48 and the collector electrode 28.

The ceramic-tab assemblies 52'include ceramic blocks, preferably cylindrical in shape, the ends of which are provided with a metallic coating 68 a few thousandths of an inch thick of molybdenum manganese. The coat ing 68 is applied by'paintingthe surface of the ceramic blocks. The ceramic blocks are porous so that the coating 68 penetrates the block to provide a roughened surface which is'interlocked with the interstices of the block. To these coatings 63 on the opposite end of the blocks is brazed the tabs 66 of a'copper-silvereutectic alloy. lnorder to avoid damage to the pervious electrodes from weiding'or brazing splatter, a nickel slurry is applied to the parts being joined before the brazing operation to reduce the brazing temperature required. These tabs 68 constitute convenient attaching members which can be conveniently attached by brazing or welding to the attaching members, such as the metal rings 64 and 72. The ceramic-tab assemblies 52 greatly facilitate the assembly operationfor assemblingthe collector electrode 28, thebacking electrode 34 and the storage surface grid 58 in a predeterminedrelation to very close tolerances.

any desired length, which feature lends itself to the inexpensive manufacture of devices such as electronic storage tubes. The subassembly units can be made on a separate assembly line and then assembled with the other components of the storage tube on the main assembly line with a minimum amount of interference with the operations on the main assembly line, thus minimizing the down time of the main assembly line. Since the units 52 can be made up as a separate operation apart from the main assembly line they can then be Welded to the collector electrode assembly and then during the final assembly operations the backing electrode support ring can be welded to the ceramic-tab subassembly units.

It will be apparent from the above description that the present invention provides a novel and improved method and means for application to a storage tube by which the backing electrode and storage grid can be mounted directly on the collector electrode assembly in a predetermined spaced relation to very close tolerances. The tabs on the novel support units made of eutectic alloy make it possible to conveniently attach the tabs on one side of the support units to the collector electrode assembly by brazing or welding and then bringing the backing electrode and storage grid assembly into the proper spaced relation determined by the length of the support units after which the tabs on the other side of the supporting units are welded or brazed to the backing electrode assembly.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit and scope of the invention.

We claim as our invention:

1. A direct-viewing electronic storage tube, a collector electrode having a supporting metal ring, a storage surface grid and a viewing screen, said collector electrode and said storage surface grid being pervious to electrons, said storage surface grid comprising a coating of dielectric material on a metal wire mesh backing electrode also pervious to electrons and having a supporting metal ring, said storage surface grid being disposed between said collector electrode and said viewing screen, said collector electrode being mechanically supported on a 2. A direct-viewing electronic storage tube com-prising an evacuated glass envelope, a source of electrons, a target assembly including a collector electrode, a storage surface grid, a backing electrode and a viewing screen, said collector electrode being pervious to electrons, said storage grid surface being pervious to electrons and comprising a coating of dielectric material deposited on said backing electrode, said storage grid surface and said-backing electrode being disposed between said collector electrode and said viewing screen, said collector electrode including a metal ring supported on a metal cylinder mounted in the end of said envelope adjacent said viewing screen, said backing electrode including a metal ring, said backing electrode being mechanically supported on said sleeve and electrically insulated therefrom by a plurality of ceramic-tab supporting units comprising: ce-

ramic blocks, a pair of metal coatings having one of their respective surfaces attached to said blocks by engagement with the interstices of the surface of the block, metal tabs brazed to each of said coatings, one of said tabs being welded to the ring of said collector electrode and the other of said tabs being welded to the ring of said backing electrode.

3. A target assembly for an electronic storage tube having an outer glass envelope, said assembly comprising, a metal cylindrical sleeve having an inwardly extending flange, said sleeve adapted to be supported on resilient tabs atfixed to the outer surface of said sleeve and engaging the inner surface of said glass envelope, a collector electrode including a fine metal mesh pervious to electrons and having an annular metal ring welded to said flange of said sleeve, a storage surface grid pervious to electrons and comprising a dielectric material deposited on a metal mesh and having an outer annular metal ring, said second metal mesh being mounted upon and insulated from said cylindrical sleeve by a plurality of units comprising electrical insulation blocks having a porous surface, a pair of metal coatings on said blocks having a roughened surface interlocked with the interstices of the surface of said insulation blocks, a pair of metal tabs brazed respectively to said coatings on said blocks and having only portions thereof fixed to said coatings, one of said tabs of said pair being welded to said first ring and the other tab of said pair being welded to said second ring.

4. A target assembly for an electronic storage tube having an outer glass envelope comprising, a cylindrical sleeve having an inwardly extending flange, said sleeve adapted to be supported on resilient tabs aifixed to the outer surface of said sleeve and engaging the inner surface of said glass envelope, an electron pervious collector electrode having an annular metal ring welded to said flange, a storage surface grid comprising dielectric material deposited on a metal mesh having an outer annular ring, said second ring being mounted upon and insulated from said first ring by a plurality of units comprising porous ceramic insulation blocks having a porous surface, metal coatings on said individual blocks, said metal coatings being a eutectic all'oy comprising copperand silver and having a roughened surface interlocked with the interstices of the porous surface of said insulation blocks and the other surface being coated with a nickel slurry, first and second metal tabs having portions brazed to the respective coatings on said blocks said first tab being Welded to said first ring and said second tab being welded to said second ring."

5. A direct viewing electronic storage tube comprising a collector electrode in the form of "a mesh andhaving a supporting metal ring, a storage surface grid, said storage surface grid comprising a mesh andhaving a supporting metal ring,"said collector electrode being spaced from said storage grid by a plurality of ceramic tab support members, each of said ceramic tab members comprising a ceramicblock member, a pair of metal tabs brazed to said'ceramic block members, one of said pair of tabs welded to the supporting ring for said collector electrode and the other of said pair of tabs welded to the supporting ring of said storage electrode.

References Cited in the file of this patent UNITED STATES PATENTS 7 Hunter Mar. 1, 1960

Claims (1)

1. 5. A DIRECT VIEWING ELECTRONIC STORAGE TUBE COMPRISING A COLLECTOR ELECTRODE IN THE FORM OF A MESH AND HAVING A SUPPORTING METAL RING, A STORAGE SURFACE GRID, SAID STORAGE SURFACE GRID COMPRISING A MESH AND HAVING A SUPPORTING METAL RING, SAID COLLECTOR ELECTRODE BEING SPACED FROM SAID STORAGE GRID BY A PLURALITY OF CERAMIC TAB SUPPORT MEMBERS, EACH OF SAID CERAMIC TAB MEMBERS COMPRISING A CERAMIC BLOCK MEMBER, A PAIR OF METAL TABS BRAZED TO SAID CERAMIC BLOCK MEMBERS, ONE OF SAID PAIR OF TABS WELDED TO THE SUPPORTING RING FOR SAID COLLECTOR ELECTRODE AND THE OTHER OF SAID PAIR OF TABS WELDED TO THE SUPPORTING RING OF SAID STORAGE ELECTRODE.

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