US3508102A - Indicator tube with electrodes supported by a rigid insulating mass - Google Patents

Description

Apnl 21, 1970 r A. B. SHESSER 3,508,102

. INDICATOR TUBE WITH ELECTRODES SUPPORTED BY A RIGID INSULATING MASS Filed April 30. 1968 FIG.Z

INVE/WDR. ARTHUR B. SHESSER BY M4 aw ATTORNEY United States Patent US. Cl. 313-1095 6 Claims ABSTRACT OF THE DISCLOSURE The disclosure is of a cold cathode, gas-filled indicator tube which has an envelope of minimal diameter and length and includes a stack of cathode electrodes in the form of characters which face the side wall of the envelope. The envelope includes a flat base and a flat dome which lie close to the upper and lower ends of the cathode electrodes. Support for the upper end of the electrode assembly may be provided in diiferent ways, and, at the lower end, tube pins support the anode and cathodes. In addition, the cathode leads and the tube pins to which they are connected are embedded in a mass of insulating material which serves to shield the cathode leads and the tube pins and to provide a rigid support for the lower ends of the cathode characters. The mass of insulating material is shaped to prevent the deposition of continuous paths of sputtered cathode metal between adjacent cathode characters.

BACKGROUND OF THE INVENTION Indicator tubes of the general type described above have been manufactured successfully and have been used commercially for many years. However, there is an everpresent need to miniaturize, eliminate parts, and reduce the cost of manufacture of these tubes.

SUMMARY OF THE INVENTION Briefly, a display tube embodying the invention includes a gas-filled envelope having a base and dome including an electrode assembly which occupies substantially the entire volume of the envelope. The base of the envelope carries tube pins to which the anode and cathode mounting tabs are secured, and, in addition, the cathode mounting tabs and their tube pins are embedded in a mass of insulating material as part of the support therefor. This permits a minimum number of auxiliary support elements to be employed. The insulating material is shaped to prevent the formation of continuous conducting paths between cathodes as may be formed by sputtering of the cathode material during manufacture or operation.

DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a perspective view of a tube embodying the invention;

FIG. 2 is a front elevational view, partly in section, of the base portion of the tube of FIG. 1; and

FIG. 3 is a side elevational view of the stem portion of the tube of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An indicator tube embodying the invention includes an envelope 20 which contains a gas suitable for supporting cathode glow. Such a gas may be argon, neon, or the like, at a pressure which may be in the range of about 30 to about 100 mm. of mercury. If desired, other substances such as mercury may be added in small quantities to the gas content of the envelope.

3,508,102 Patented Apr. 21, 1970 The envelope 20 is generally elongated and its side wall 30 comprises a viewing window through which glowing cathodes may be viewed. The envelope 20 includes a base or stem 40, through Wich metal pins or leads extend, and by means of which electrical connection is made from the cathode character electrodes within the tube to external electrical circuitry. For maximum utilization of space, the pins of leads 50 are oriented in two rows parallel to a diameter of the stern as shown. However, it is clear that these leads 50 may be oriented in a single row or in a circle or in any other manner, if desired. Two or more auxiliary leads or pins are provided in the stern for connection to the tube anode, and these pins are provided with glass sleeves for shielding purposes, if this is deemed necessary. Two other pins are provided for connection to auxiliary electrodes to be described.

The upper end of the envelope remote from the stem is known as the dome of the envelope and carries a tubulation for evacuating the envelope and filling it with the desired gas atmosphere. Tubulation 110 could be at another location on the tube envelope, if desired.

The electrode assembly of tube 10 includes a stack of cathode electrodes which are in the form of numerals, letters or other characters, and a tubular anode electrode which surrounds and encloses the cathode electrodes. The anode electrode comprises a solid back plate and a front mesh screen which curve and meet each other at the sides of the cathode stack where they merely touch or are welded together. The pins 60* at the rear of the stem are welded to the anode back plate 130 to provide support and to serve as means for applying operating potential to the anode. A similar lead may also be secured to the screen 140, if desired.

The cathode electrodes 120 are of a metal such as stainless steel, and each includes a main body portion, in the shape of a character, and upper and lower mounting leads or tabs and 160, respectively. The lower tabs extend downwardly from the main body portions of their cathodes so that the come into direct alignment with leads 50, and each tab is welded to a lead. Preferably, the tabs 160 of adjacent cathodes in the stack are welded to pins in difierent rows to maximize the spacing between them.

The upper cathode tabs 150 may be supported in different ways. In one arrangement, a support post is secured between the rear plate 130 and front screen 140 by means of eyelets or by welding or the like, and the cathode tabs 150 are mounted thereon by means of suitable apertures or slots in the tabs, and they are insulated from each other by insulating washers 180. The post 170 is either made of an insulating material, or it is made of metal and coated or sleeved with glass, or the like. The upper cathode tabs may also be supported in many other ways known in the prior art. For example, a box-like member (not shown) may be secured between the anode plate and screen, and the cathode tabs may be inserted into the box through appropriate slots and held in place by an insulating cement. Alternatively, if the cathodes are sufliciently strong, they may not require an upper support.

In order to prevent the lower cathode tabs 1'60 and their pins 50 from glowing during tube operation and to provide a rigid mounting arrangement and support therefor, these members are embedded in a mass 200 of insulating material which extends from the top surface of the stem up to the lower edge of the character-shaped main body portion of each cathode 120. Sufiicient insulating material is used to embed the tabs and pins and to provide a solid, rigid mass which performs both the insulating function and the function of supporting the cathode electrodes by supporting their lower tabs. One suitable material for the insulating mass 200 is a mixture of chrome oxide and sodium silicate which adheres well to the metals normally used in such tubes. Other materials such as sauereisen, a mixture of aluminum oxide and potassium silicate, or various glass frits, might also be used.

Sometimes, during the processing or operation of tubes such as tube 10, metal is sputtered off by the cathode electrodes, and this metal deposits on the cathode tabs and other supporting members. If a continuous path of metal forms between two cathodes, then the cathodes are shorted and the tube is rendered useless. To prevent this from happening on the mass 200 which supports the lower cathode tabs, notches 220 are formed in the mass between adjacent cathodes. These notches are preferably deeper than they are wide to insure their performing the desired function. The formation of paths of sputtered metal at the upper ends of the cathodes is prevented by having the washers 180 on post 170 between cathodes of a special shape to provide maximum surface, as is well known in the art.

For optimum operation and long life, the tube includes in its atmosphere a small quantity of mercury vapor which serves to minimize cathode sputtering during tube operation. The mercury may be provided in any suitable fashion. For example, it may be introduced directly with the primary gas atmosphere, or it may be released by heat from a capsule 230 suitably located within the envelope.

The tube 10 also includes the auxiliary characters 90 such as decimal points or commas or the like which are located on both sides of the stack of cathodes at positions which such characters would normally occupy. Each auxiliary character arrangement includes a pin 80 provided with a glass sleeve 70, and a ceramic washer 240 seated on the upper end of the glass sleeve 70. A metal disk 250 of cathode material, which comprises a decimal point, is positioned with its lower edge resting on the washer 240 and is welded to pin 80.

What is claimed is:

1. A side-view cathode glow indicator tube comprising an elongated envelope containing a gaseous atmosphere capable of supporting cathode glow, said envelope including an elongated viewing window parallel to the principal axis of said envelope,

said envelope including a base at its lower end and a dome at its upper end having a tubulation,

an electrode assembly comprising cathode electrodes and an anode electrode mounted within said envelope facing said viewing window,

a plurality of first cathode tube pins extending through said base into said envelope for connection to said cathode electrodes and for connecting said cathode electrodes to external electrical circuits,

other tube pins extending through said base into said envelope, at least one of which is connected to said anode electrode,

said cathode electrodes comprising character-shaped electrodes assembled in a stack and arrayed in substantially parallel planes facing said viewing window,

each cathode electrode including a character-shaped portion and at least one cathode support at the lower end thereof, each said cathode support being secured to one of said first tube pins so that the lower ends of said cathodes are secured in place with respect to the base of the tube,

a rigid mass of insulating material enclosing said first tube pins and said lower cathode supports to which they are secured and extending from the surface of said base to the lower end of said character-shaped portion of said cathode electrodes whereby only the character-shaped portion of each cathode electrode is exposed to view, and

slots in said mass of insulating material between said cathode electrodes for preventing the formation of continuous paths of sputtered cathode metal between cathode electrodes.

2. The tube defined in claim 1 wherein said insulating material comprises a mixture of chrome oxide and sodium silicate.

3. The tube defined in claim 1 and including support means engaging and supporting the upper ends of said cathode electrodes.

4. The tube defined in claim 1 and including support means engaging and supporting the upper ends of said cathode electrodes, said support means comprising a post secured to said anode electrode and carrying insulating members positioned between each of said cathode electrodes to insulate them from each other.

5. The tube defined in claim 1 wherein said anode electrode comprises an anode plate positioned behind all of said cathode electrodes, and an anode screen positioned in front of all of said cathode electrodes, and including support means secured between said anode plate and anode screen and engaging and supporting the upper ends of said cathode electrodes.

6. The tube defined in claim 5 wherein said insulating material comprises a mixture of chrome oxide and sodium silicate.

References Cited UNITED STATES PATENTS 3,358,176 12/1967 Rosenberg et al 313-1095 3,437,861 4/1969 Koshizuka et al. 313109.5

RAYMOND F. HOSSFELD, Primary Examiner D. OREILLY, Assistant Examiner U.S. Cl. X.R. 3l3266

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