US3168667A - Indicator tube - Google Patents

Description

Feb. 2, 1965 G. A. KUPSKY INDICATOR TUBE Filed May 51, 1962 INVENTOR. GEOEGEAKUPSKY Magi ATTORNEY United States atent nsnrcaron TUBE Gear e A. Kn sh Plainiield NJ. assignor to Burroughs P y: a s

Corporation, Detroit, Mich, a corporation of h iiehigan Filed May 31, 1962, @er. No. 199,127

Claims. ill. 313-4995) This invention relates to gaseous cold cathode glow tubes.

Cold cathode tubes of the type to which the present invention relates generally comprise a transparent envelope which contains an anode electrode, one or more cathode glow electrodes, and a gas suitable for supporting cathode glow. When a suitable electrical potential is applied be- .tween the anode and a selected cathode electrode, the

cathodeelectrode glows and current fiows through the gas from the cathode to the anode. Generally, during this operation, the cathode is bombarded by positive gas ions which may cause erosion of the material of the cathode surface. This isknown as cathode sputtering. The sputtered metal may be deposited on the dormant cathode electrodes in the tube and on the tube envelope. Ultimately, the cathode electrodes from which metal particles cal in indicator glow tubes which include a plurality of cathode electrodes in theshapeof indicator characters arranged parallel to each other in a stack, the cathode elec trodes having a comparatively small unit surface area. In

tubes of this type, in the past, the adverse effects of sputtering have been comparatively rapid, and, as a result, the tubes have had undesirably short life. At the present time,

in cathode indicator tubes and in other types of gaseous cathode glow tubes, various precautions are taken to minimize the adverse effects of sputtering. These expedients include the provision of auxiliary shield electrodes within the tube to trap sputtered metal, or the provision of protective coatings on surfaces which may be adversely affected by sputtering. However, these preventive measures have not beenentirely satisfactory in extending tube life, "and, in addition, they represent an undesirable factor in the cost of such tubes and they may introduce technical problems in tube construction and operation.

Accordingly, the principles andobjects of the invention are directed toward the provision of an improved gaseous,

ode sputtering.

' Briefly, a gaseous, cold cathode indicator glow tube, to

which the principles of the invention are particularly applicable, includes an envelope in which is mounted a stack t of cold cathode indicator glow electrodes in the form of numerals, letters, or other characters. Each cathode indicator electrode is adapted to glow when a voltage is applied between it and an anode electrode. The envelope is filled with an ionizable, cathode glow-supporting gas such as argon or neon or a combination of these, and, in order to minimize cathode sputtering, a quantity of sputter-inhibiting agent comprising an organic polymer which is inert with respect to tube components and vaporizes during tube operation to provide large molecules in the tube atmosphere along with the ionizable glow-supporting gas.

The invention is described in greater detail with reference to the drawing wherein:

FIG. 1 is a perspectiveview of a cold cathode gaseous glow tube embodying the invention; and

cold cathode glow tube having means for preventing cath- FIG. 2 is a sectional view of a portion of a modification of the invention.

Referring to the drawing, a typical gaseous indicator glow tube 10 prepared according to the invention includes an envelope 12 which has been evacuated of air and filled with a primary gas suitable for supporting cold cathode glow. Such a gas may be argon, neon, or a combination of these at a suitable pressure which may be in the range of about 25 to about 70 mm. of Hg at room temperature. The actual gas pressure is not critical but is selected to provide desired tube operating characteristics including firing voltage, light output, current flow, etc. The envelope includes a base portion, or stem 14, through which metal base pins 16 extend and by means of which electrical connection is made to suitable external electrical circuit elements. Two diameterically opposed pins 16' are provided with extension posts 18 within the envelope and are thus adapted to receive and support the various electrode elements of the tube. The posts 18 are coated with a suitable insulating material (not shown) such as glass or the like. The envelope 12 also includes a transparent viewing window 2Q through which glowing indicator cathode electrodes 22 are viewed. A sealed-oil exhaust tubulation (not shown) is provided in the stem 14.

The cathode glow indicator electrodes 22 of the tube 10 may take substantially any desired shape; for example, they may be numbers, letters, or the like, and they may be as few in number as desired, or as many as is practical for the size of the tube. In one form of the tube lltlwherein the glow cathode indicator elements are numbers, tenof such elements provided, including the numbers 0 to 9. Fewer than ten glow cathodes are shown inFIG. 1 for purposes of simplification-ofthe drawing. The cathode indicator elements 22 are made of any suitable metal, for example, stainless steel, aluminum, nichrome, molybdenum, or the like, and they may be made in any suitable fashion, for example, by etching, stamping, or the like.

The cathode elements are provided with diametrically opposed apertured end tabs'(not shown) by means of which they are mounted and supported on the extension posts 18 of the pins 16'. stacked on the posts lbone above the other with their surfaces oriented parallel to each other and transverse to the vertical axis of the tube and facing the viewing window 20 of the envelope 12. The cathode elemeritsZZ are mounted with suitable insulating spacers 24 between them,

' the spacers having sufiicient surface area to cover and insulate the cathode tabs to prevent them from glowing during operation" of the tube. The stack of electrodes is 1 locked on posts 18 by mica rings 26.

Each cathode indicator element is provided with a fine l wire connecting lead28 which is welded or otherwise secured at its-tree endto one of the pins 16 within the en velope 12. The leads 28 may be of the same material as thenumbers, or they may be of any other suitable material.

The tube 10 includes an anode which is in the form of a cup 36'having a pair of diametrically opposed longitudinal slots 37 aligned with the support posts 18 and through which the cathode leadfwires 28 extend to the pins 16. The stack of cathode electrodes is, in efiect', contained within the cup, and the cup rests on, but is in sulated from, the pins 16 by an insulating disk 35 of mica or the like. The anode cup is also electrically connected to one of the pins 16 by a suitable lead (not shown),

According to the invention, sputtering of the metal of the cathodes 22 during operation of the tube is inhibited by the inclusion of a vaporizable sputter-inhibiting agent within the envelope. The ettectiveness of thefsputter-inhibiting agent depends ina general way on the weight or mass of its molecules which vaporize and are apt to collide with atoms'of the tubesinert gas filling. Generally, the

The 'cathode elements 22'are .3 heavier the molecule, the more efiective is its sputter-inhibiting action. The selected sputter-inhibiting agent is an organic polymer which is inert with respect to the tube contents and which can vaporize under the normal conditions of tube operation. A wide variety of such materials are known.

Among the many organic substances which are suitable for the purposes of the invention are synthetic resins known as epoxy resins. Such resins which are used ordinarily as components in adhesives are suitable. Typical substances include resinous ethylene oxide derivatives, sulfonamide-epoxides, the epoxy compositions made from polyhydric phenols and epichlorhydrin, and the like.

In one method of introducing the selected anti-sputtering agent into the enevelope, the resin is held immobilized within the tube envelope while the tube is assembled.

' After the tube is assembled, it is aged, and at a selected time either before or during the aging process, the resin is freed and admitted to the envelope. In one arrangement for carrying out this process, a small ball of resin 38 is placed in an evacuated frangible capsule 4% of glass or the like, through which a heating wire 42 extends. The capsule is sealed in the tube envelope, and at the desired time in the manufacturing process, heating current is passed through the wire, and the resin is heated and caused to vaporize and crack the glass capsule. When the capsule cracks, the resin escapes and readily enters the primary tube atmosphere.

Duringtube operation, the heat generated by the tube maintains a quantity of the resin vaporized, and the molecules of the resin which are thus present in the tube atmosphere collide with ions of the primary gas thereof and absorb energy from these gas ions. The gas ions thus do not have sufiicient energy to bombard the glow cath odes and cause any significant sputtering.

In another form of the invention illustrated in FIG. 2,

the antisputtering material is introduced in a different tion that the principles disclosed may be employed with any type of electron tube having the problem of electrode sputtering due to ion bombardment. It is also clear that the organic-sputtering agent is not particularly critical and is not selected because of its chemical nature and that any organic polymer which is inert with respect to the tube components and which provides some vapor during the tube operation issatisfactory.

What is claimed is:

1. A gaseous cold cathode glow tube including an envelope having a viewing window, a plurality of cathode electrodes in the form of characters and an anode electrode spaced apart Within said envelope, each said cathode electrode being adapted to glowwhen a voltage is applied between it and said anode, and a filling in said envelope of an ionizable gas selected from the group consisting of argon and neon, said filling being at a pressure capable of sustaining cathode glow along the surface of said cathode electrodes, and including a substance for inhibiting sputtering from said cathode electrodes, said substance comprising an organic polymer which is inert with respect to the components or" the tube and provides some vapor at tube operating temperatures, said vapor operating to re duce cathode sputtering by absorbing energy from the ions of said gas.

2. A gaseous cold cathode glow tube including an envelope having a viewing window, a plurality of cathode glow electrodes in the shape of indicator characters arranged in close proximity to one another in a stack Within said envelope, an anode electrode, said cathode electrodes facing said viewing window and being adapted to glow when a voltage is applied between any one or" them and said anode, and a filling of an ionizable gas at a pressure capable of sustaining cathode glow along the surface of said cathode electrodes and a synthetic resin which is vaporizable directly in said envelope with said cathode electrodes and adapted to inhibit sputtering of said cathode electrodes due to bombardment by ions of said gas filling.

3. The tube defined in claim 2 wherein said tube in cludes an envelope and a stem and said synthetic resin is provided as a sealing layer between said envelope and said stem and is readily accessible to the atmosphere within said envelope.

4. The tube defined in claim 2 wherein said synthetic resin comprises an epoxy resin.

5. A gaseous cold cathode glow tube for the selective display of a variety of luminous indicia in a substantially common field including an envelope having a viewing window, an anode electrode within said envelope, a plurality of closely spaced substantially planar cathode electrodes each including a metallic filament portion in the form of one of the indicator characters, said cathode electrodes being arranged in said envelope in closely spaced electrical insulatively stacked relationship, the space between the filament portions of successive ones thereof being free of intervening insulation material or light obstrucing or reflecting material, each cathode electrode being adapted to glow when a voltage is applied between it and said anode and each such electrode having at least one thin metallic mounting tab integral with its character portion and extending laterally in a direction away from the area generally defined thereby, mounting means in fixed relationship in said envelope but located outside of the area defined by the character portions of the cathode electrodes, said mounting means engaging the tabs of successive cathode electrodes in substantial alignment and serving to mount said cathode electrodes in said stacked relationship in the envelope, and a filling in said envelope of a gas including neon and an organic polymer which does not react with tube components and provides some vapor at tube operating temperature in an amount sufficient to inhibit sputtering from said cathode electrodes,

'said filling being at a pressure capable of sustaining oathode glow along the surface of said cathode electrodes.

References (liter! in the file of this patent UNITED STATES PATENTS 2,103,038 Moers Dec. 21, 1937 2,949,562 Stanney et al Aug. 16, 1960 2,991,387 McCauley July 4, .1961

Claims (1)

1. A GASEOUS COLD CATHODE GLOW TUBE INCLUDING AN ENVELOPE HAVING A VIEWING WINDOW, A PLURALITY OF CATHODE ELECTRODES IN THE FORM OF CHARACTERS AND AN ANODE ELECTRODE SPACED APART WITHIN SAID ENVELOPE, EACH SAID CATHODE ELECTRODE BEING ADAPTED TO GLOW WHEN A VOLTAGE IS APPLIED BETWEEN IT AND SAID ANODE, AND A FILLING IN SAID ENVELOPE OF AN IONIZABLE GAS SELECTED FROM THE GROUP CONSISTING OF ARGON AND NEON, SAID FILLING BEING AT A PRESSURE CAPABLE OF SUSTAINING CATHODE GLOW ALONG THE SURFACE OF SAID CATHODE ELECTRODES, AND INCLUDING A SUBSTANCE FOR INHIBITING SPUTTERING FROM SAID CATHODE ELECTRODES, SAID SUBSTANCE COMPRISING AN ORGANIC POLYMER WHICH IS INERT WITH RESPECT TO THE COMPONENTS OF THE TUBE AND PROVIDES SOME VAPOR AT TUBE OPERATING TEMPERATURES, SAID VAPOR OPERATING TO REDUCE CATHODE SPUTTERING BY ABSORBING ENERGY FROM THE IONS OF SAID GAS.

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