US1983638A - Glow discharge tube - Google Patents

Description

Dec. 11, 1934. M. PONTE 1,983,638

GLOW DISCHARGE TUBE Filed May 20, 1955 INVENTOR MVW ATTORNEY Patented Dec. 11,

The present invention is concerned with gasin which the variations in eous discharge tubes PATENT OFFICE GLOW DISCHARGE TUBE Maurice Ponte, Paris,

pagnie 'Generale De France, 'assignor to Com- Telegraphie Sans Fil, a

corporation of France Application May 20, 1933, Serial 'No. 672,033

In France June 7,

10 Claims.

length of a luminous column as a function of the current flowing through 5 purpose of insuring v nous tubes such as for modulation (modulation meters the tube are used for the arious applications of lumirecording, indicators of etc.

Especially in this latterinstance it is often desirable to be ableto utilize tubes of large size I designed to respond to Assurance of sufilciently great the following conditions:

brightness without'the tube being traversed by large currents,

these being conditions imposed by applications and uses of these tubeswhere they are called upon to operate with tubes or copious disintegration o avoided therein generators-of low output,

r spattering having to be so as to prevent undue blacking of the bulb. At the same-time, the law of variation intensity. should further sible.

luminous discharge de comparative character utilizing the cathode shown of the length of the column as a function of the more be as linear as poswhich forms part 1 shows one form of a vice. Fig. 2' represents istic 1 curves of "devices in Figs. 1 and 3. Fig.

3 showsa cathode construction according to the present invention. Fig.

. teristic curve o 4-represents the characf a device utilizing the cathode shown in Fig. 3, but with the cathode'wire consisting of nichrome wire,

and Fig. 5 shows the complete luminous discharge device according to the invention. I

As has been known for a long time, tubes of this kind consist of a cathode of tubular or filamentary shapemounted in the axis of atubular bulb which do mprises and contains an anode.

The variations observed are those of the length of the negative glow as intensity.

Fig. 1 shows a unction of the current tube constructed in this manner where 1 denotes the anode and 2 the cathode extending alongside which will be observed the luminous sheath or cloak, the-assembly being mounted inside of a suitable pressure. uction of tubes of great a bulb 3 which has conprinciple is attended with following diificultie'sz In the length of the cathode rod grows sufiicient diameter so as to the current required for the tube grows so that .be fed from a low-power generator such as a small multi-electrodetube.. Since at the same time the power dissipated in-v side the tube becomes relatively large (say, 10 watts and over) the cathode becomes subject to fast pulverization or distintegration, with the result that the tube is rendered unserviceable' even after a few hours of use. Finally, the characteristic curve of the tube which represents the variations in length of the column as a function of the current flowing through the tube pre-' 10 sents a state of saturation that is extremely marked whenever the column reaches a length near its maximum. Curve 2a,by way of example,

represents the characteristic graph of a tube whose cathode, has a gas is at a pressure of 2.5 mm. (diameter of cathode rod being 3.5 mm). The. abscissa in terms of milliamperes indicate the values of the current flowing, hrough the tube, while the ordinates give the length of the negative glow in 20 millimeters. After a certain length, the negative column is found to grow but very little as the current increases, an action that is often troublesome because the useful length of the tube is reduced. vTubes of reduced dimensions more: over present similar. saturation phenomena. It is impossible to remedy these difiiculties by reducing the pressure prevailing inside the tube seeing that the dark space would grow at the same time, and the tube would become impaired in brightness orluminosity.

The present invention obviates these difiiculties as hereinbefore described in that it discloses ways and means of constructing tubes of great length, of adequate brightness, low consumption and linear characteristic, this latter advantage being realizable also in tubesof smaller dimensions.

With this end in View, a first object of the invention consists in using as the cathode an insu- 0 lating tube or rod or stick having the desired diameter upon which is applied a conductor whose effective surface or area is only a fraction of that of the insulating tube. A preferable mode of carrying this latter idea into practice is to form the conductor of a helix made up of a fine conductor wire wrapped around the rod at a pitch to be chosen according to practical requirements. Fig. 3 represents a cathode thus constituted, 1 being the insulating rod, and 2 the conductor wire, the end portion 3 being shown in section. Compared with a tube containing a solid cathode of similar dimensions, this scheme insures reduced consumption, at the same gas pressure. In Fig. 2 the curves 2a and 21) represent the comparative charlength of 320 mm. and whose 15* acteristics of two similar tubes operated under similar conditions except for the cathode construction, the tube Whose characteristic is represented'by curve 2b being provided with the improved cathode shown in Fig; 3, while the tube whose characteristic is represented by curve 264 is provided with a cathode of the type shown in Fig. 1, which does not have a helical conductor wound about the cathode rod. '7

It will be noted that the characteristic of this tube, while improved from the viewpoint of energy consumption always involves the property of saturation. According to the-second object and part of this invention, the shape or trend of the characteristic can be modified and rendered linear by using for the conductor to be wrapped about the insulator rod an element sufficiently resistant in order that the current of the tube may set up a potential difference along the cathode. Indeed, it'

is evident that the saturation phenomenon will be less pronounced if, instead of leaving or allowing the surface of the cathode to become equipotential in nature, a fall of potential is created thereon which grows in proportion as the cathode glow approaches the end of the cathode located opposite to or facing the anode. The most convenient way to that end consists in employing for the wire wrapped round the insulator rod a fine and resistant wire. This method is rather elastic, as it were, for, in order to modify the characteristic, it is possible to act on or change the diameter of the wire, its nature, and the winding pitch. Indeed, these factors may be chosen in a way so that the charcteristic will turn out linear and assume a shape such as indicated for example in Fig. 4'. This graph has been plotted for a tube similar to that for which the characteristics shown by curve 2b in Fig. 2 has been plotted, but whose cathode wire consists of a nichrome wire of 33/1000 wound with a pitch of 0.3 mm. upon a glass rod of 3.5 mm. diameter. itbeing understood that these figures are merely given by way of example. The resistance of the tubes obviously will be raised, but this is no inconvenience because they can be excited by tubes of high internal resistance, such as those which are known in the art as screen grid tubes.

It will be noted that in the arrangement of this invention the length of the column is directly controlled or determined by the modulated current, and that it is the variations of the current of the tube which serve to create the auxiliary differences of potential that are used to improve its characteristic. Hence, the basic principle of the invention diifers from that of certain tubes used in recording work wherein use is made of an electrode on which is created a potential difference by means of an auxiliary battery with a modulation potential being superposed thereon. The two electrodes (or the single equivalent electrode) are in that case parallel and the length of the discharge is determined by the point where the voltage falls below the ignition or flash potential. The situation is wholly different in the present case and tube where the properties of the negative glows are used and where, no matter at what point the tube may be working, the voltage will never fall below the flash potential.

Fig. 5 finally represents a tube constituted in accordance with the present invention as an example of an industrial product without any limitations being imposed as regards its character. 1' denotes an insulating tube made from glass which supports the resistor wire 2 which represents the cathode conductor and which is brought out at 4'. The anode 3 serves also to support the rod 1, the assembly being mounted inside a bulb 5' in the interior of which is the filling gas atmosphere. 6' is the anode lead-in conductor. The dimensions of the elements of the tube, for instance, may be the same as hereinbefore suggested, though itwill be understood that there is no objection to use, for instance, a different pitch so as to alter the shape of or the law governing the negative glow in the case of certain practical applications.

What is claimed is:

1. A discharge device comprising a gas filled envelope and a pair of coaxially disposed electrodes between which a discharge may be passed located therein, one of said electrodes comprising a support extending linearly in said envelope and a resistance wire wound about said electrode. *2. A discharge device comprising a long tubular gas filled vessel, an anode. and a cathode, the latter comprising along insulating rod extending axially of said tubular vessel, and a high resistance wire helically wound about said insulating rod for a substantial distance thereof, the anode being coaxially disposed with respectto the cathode insulating rod.

3. A discharge device comprising a'tubular gas filled vessel, an anode at one end of said vessel, a substantially lengthy insulating rod extending axially of said tubular vesseland coaxially with respectQto the anode, and a nichrome wire helically wound about said insulating rod for a substantial distance thereof.

4. A glow discharge device comprising a tubular gas filled vessel, a substantially lengthy glass rod extending axially bf said tubular vessel, a disc-shaped anode located at one end of said vessel and having a central opening through which one end of said glass rod is inserted for supporting the same, and a fine resistance wire helically wound about said glass rod for a substantial distance thereof.

5. A glow discharge device comprising a tubular gas filled vessel, a substantially lengthy glass rod extending axially of said tubular vessel, a disc-shaped anode located at one end of said vessel and having a central opening through which one end of said glass rod is inserted for supporting the same, and a fine nichrome wire helically wound about said glass rod for a substantial distance thereof.

6. A luminous discharge device comprising a gas filled vessel, a helically wound cathode and an anode coaxially aligned within the vessel and between which a discharge may be passed, and means for creating a potential difference along the cathode comprising a source of potential connected between the anode and one end only of the cathode.

'7. A current indicating device comprising a gas filled tubular vessel, a pair of coaxially aligned electrodes therein between which a discharge may be passed, one of said electrodes comprising a substantially lengthy insulating rod and a fine wire resistance coil wrapped about the surface of said rod, and means for applying a suitable potential between the anode and one extremity of said coil, the other extremity thereof being open, whereby a potential difference is created along the surface of said rod of such value that length of the discharge is linearly proportional to the current intensity through the device.

8. A current indicating device comprising a gas filled tubular vessel, a pair of coaxially aligned electrodes therein between which a discharge may be passed, one of said electrodes comprising being small as compared with the support sura substantially lengthy insulating rod, and means face, and means for applying a potential differfor applying a suitable potential between the ence to said electrodes. anode and one extremity of said wire, the other 10. A discharge device for indicating currents extremity thereof being open, and a fine niohrome conducted therethrough by the length of a glow wire wrapped about the surface of said rod luminous column, comprising a gas-filled tubular whereby a potential difference is created along vessel, a pair of electrodes axially aligned therethe surface of said rod of such value that length in, one of said electrodes comprising a substanof the discharge is linearly proportional to the tially lengthy insulating support and a resistant current intensity through the device. conductor disposed thereupon, the surface of the 1 9. A discharge device for indicating currents conductor being small as compared with the supconducted therethrough by the length of a glow port surface, and the resistance of the former luminous column, comprising a gas-filled tubular being so selected that the discharge luminous vessel, a pair of electrodes axially aligned therein, length is proportional to the discharge current, one of said electrodes comprising a substantially and means for applying a potential difference to 15 lengthy insulating support and a conductor dissaid electrodes. posed thereupon, the surface of the conductor MAURICE PONTE.

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