US3067355A

US3067355A - Indicator tube

Info

Publication number: US3067355A
Application number: US15475A
Authority: US
Inventors: John H Mccauley
Original assignee: Burroughs Corp
Current assignee: Unisys Corp
Priority date: 1960-03-16
Filing date: 1960-03-16
Publication date: 1962-12-04
Anticipated expiration: 1979-12-04

Description

Dec. 4, 1962 J. H. MOCAU LEY 3,067,355

INDICATOR TUBE Filed March 16, 1960 IN VEN TOR.

JOHN H. Mc CHULEY ATTORNEY United States Patent Ofiiice 3,%7,355 Patented Dec. 4, 1962 3,067,355 INDICATOR TUBE John H. McCauley, Elizabeth, N.J., assignor to Burroughs Corporation, Detroit, Mich, a corporation of Michigan Filed Mar. 16, 1960, Ser. No. 15,475 8 Claims. (Cl. 3132l0) This invention relates to cold cathode gaseous indicator tubes and particularly to tubes of this type which may be constructed and operated to provide light output of diiferent colors.

Cold cathode gaseous indicator tubes generally include a plurality of cathode electrodes in the form of indicator characters mounted in a suitable envelope filled with an ionizable gas such as neon, argon, or the like. Such tubes provide cathode glow having a characteristic color which is determined by the gas filling in the envelope. Presently available commercial devices of this type produce cathode glow which is generally pink, orange, or red. There are many applications in which, for example, blue light is desirable. However, at the present time, a cold cathode indicator or readout glow tube providing blue or other light output cannot be made simply and inexpensively and in commercial quantities. Accordingly, the principles and objects of the present invention are concerned with the provision of an improved cold cathode gaseous indicator glow tube which may be adapted to provide different colors of light output.

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 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 gas such as neon and a small quantity of mercury which, together, provide cathode glow which is light orange or light pink in color.

According to the invention, the characteristic light orange or pink cathode glow may be changed to an effective white light by raising the tube operating temperature above the typical normal level. With the tube thus operated to provide white light output, any desired color of glow may be obtained by means of a suitable light filter coupled to the tube.

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

FIG. 1 is a perspective view, partly in section, of a cold cathode gaseous glow tube embodying the invention; and

FIG. 2 is a sectional, elevational view of a modification of a portion of the apparatus of FIG. 1.

Referring to the drawings, a typical gaseous indicator glow tube 10 useful in practicing the invention includes an envelope 12 which has been evacuated of air and filled with a gas suitable for supporting cold cathode glow. Such a gas may be argon, neon, or the like at a suitable pressure which may be in the range of about 30 to about 100 mm. of Hg. 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 diametrically opposed pins 16' are provided with insulated extension posts 18 within the envelope and are thus adapted to receive and support the various electrode elements of the tube. The envelope 12 also includes a transparent viewing window 20 through which glowing indicator cathode electrodes 22 are viewed.

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 10 wherein the glow cathode indicator elements are numbers, ten of such elements are provided, including the numbers 0 to 9. Fewer than ten glow cathodes are shown in FIG. 1 for purposes of simplifying the 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'. The cathode elements 22 are stacked on the posts 18 one 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 elements 22 are mounted with suitable insulating spacers 24 between them, the spacers having sufficient surface area to cover and insulate the cathode tabs to prevent them from glowingduring operation of the tube. The stack of electrodes is locked on posts 18 by mica rings 26 or the like.

Each cathode indicator element is provided with a fine wire connecting lead 28 which is welded or otherwise secured at its free end to one of the pins 16 within the envelope 12. The leads 28 may be of the same material as the numbers, or they may be of any other suitable material.

The tube 10 includes an anode which is preferably 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 lead wires 28 extend to the pins 16. The stack of cathode electrodes is, in effect, contained within the cup, with the cathode leads 28 and tube pins 16 lying outside the cup. The cup 36 rests on, but is insulated from, the pins 16 by an insulating disk 38 of mica or the like. The anode cup is also electrically connected to one of the pins 16 by a suitable lead (not shown).

The objects of the invention are accomplished by causing the tube 10 to generate substantially white light and coupling a selected filter to the tube to provide the desired color of light. The desired white light is obtained, according to the invention, by a combination of features in both tube construction and tube operation. Thus, a small quantity of mercury is added to the gas in the envelope, say neon, so that, under typical normal operating conditions, the cathode glow is light orange or light pink in color. The mercury may be added to the neon filling in any suitable manner during tube preparation which may follow well-known procedures. In one arrangement for carrying out this process, referring to FIG. 2, a small ball of mercury 38 is placed in an evacuated frangible capsule 40, 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 mercury is heated and caused to vaporize and crack the glass capsule. When the capsule cracks, the mercury escapes and condenses on the tube envelope. Alternatively (FIG. 2), a coil 42' of heating wire surrounding the capsule may be used to crack the capsule and free the mercury.

According to the invention, the typical and normal light pink color of cathode glow of the tube 10 is con verted to substantially white glow by operating the tube at an elevated temperature. The desired elevated temperature may be achieved by operating the tube at higherthan-normal cathode currents. Thus, with about volts applied between the anode and the cathodes, a

cathode current of about eight milliamperes provides sufficient heat to cause substantially white cathode glow. Alternatively, elevated temperature may be achieved by passing heating current through the heating coil 42'. The heat generated by current in the coil 42 heats the gases in the tube 1!) to the required temperature to provide white light cathode glow. With the latter method of operation, a normal cathode current level of about two milliarnperes is maintained.

With the tube thus adapted to provide substantially white light, light of any desired color may be obtained by combinin a suitable optical filter with the tube 14 Thus, for example, a sheet 44 of light filtering material is positioned in front of the viewing Window 26 of the tube. Any suitable support means for the filter may be provided. For example, a hollow tube 46 may be secured to the tube envelope l2 and the filter sheet 4-4 may be suitably mounted in the tube.

What is claimed is:

l. A cold cathode gaseous indicator tube assembly comprising an envelope containing an anode and an indicator glow cathode adapted to exhibit cathode glow when an appropriate operating potential is applied between it and said anode, said cathode glow being provided by a glowing sheath of gas surrounding said cathode, said envelope containing a filling of an ionizable gas and a smal quantity of mercury suitable for providing substantially white cathode glow when said tube is operated at an elevated temperature, and an optical filter in operative relation with said cathode.

2. The assembly defined in claim 1 and including circuit means for raising the temperature of the tube in operation.

3. The assembly defined in claim 1 and including auxiliary heating means inside the tube envelope for raising the temperature of the tube during its operation.

4. The assembly defined in claim 1 and including an auxiliary heating wire disposed within the tube envelope for raising the temperature of the tube during operation.

5. A cold cathode gaseous indicator tube assembly comprising an envelope having a viewing window and containing an anode and a stack of indicator glow cathodes facing said viewing window, each of said cathodes being adapted to exhibit cathode glow when an appropriate operating potential is applied between it and said anode, the cathode glow being provided by a glowing sheath of gas surrounding the cathode, said envelope containing a filling of an ionizable gas and a small quantity of mercury suitable for providing substantially white cathode glow when said tube is operated at an elevated temperature, and an optical filter coupled to said envelope in front of said viewing window, said optical filter being selected to provide a predetermined color of light output from said tube.

6. The assembly defined in claim 5 and including auxiliary heating means inside the tube envelope for raising the temperature of the tube during its operation.

7. The method of operating a cold cathode gaseous glow tube to provide light output of a selected color, said glow tube including a glow cathode and an anode and a gas filling of an ionizable gas and mercury, the method comprising the steps of applying an operating voltage between the cathode and the anode and thereby causing the cathode to glow with its characteristic color, ieating said tube so that the cathode glow is substantially White, and optically filtering the desired color from the cathode glow.

8. The method of operating a cold cathode gaseous glow tube to provide light output of a selected color, said glow tube including a glow cathode and an anode and a gas filling of an ionizable gas and mercury, the method comprising the steps of applying an operating voltage between the cathode and anode to provide a level of current flow therebetween at which the cathode glows with its characteristic color, increasing the current flow to a higher level at which the temperature of the tube is elevated and the cathode glow is substantially white, and optically filtering a selected color from the cathode glow.

References (Iited in the file of this patent UNITED STATES PATENTS 666,602 Couch Jan. 22, 1901 2,068,287 Gabor Jan. 19, 1937 2,479,164 Inman Aug. 16, 1949