US1807140A - Discharge tube - Google Patents

Description

y 1931. c. J. R. H. VON wEbEL 3 DISCHARGE TUBE Filed March 7, 1928 Patented May 26, 19 31 UNITED STATES PATENT OFFIC CARL J'. R. E. VON WEDEL, OF BERLIN, GERMANY, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO ELECTRONS, INC., A CORPORATION OF DELAWARE DISCHARGE TUBE Application filed March 7, 1928. Serial M'QWHJHEISSUED The present invention relates generally to discharge tubes, and more particularly to structures and mounting arrangements for such tubes.

A particular object of the invention is to provide a discharge tube having a usefully long discharge path for desired purposes such as colored light tubes for advertising elfec ts,'ultra violet ray tubes, and thelike, and yet can be connected for operation into a single electrical socket, such as the usual lamp sockets of lighting circuits.

A further object is an arrangement permitting close physical association of necessary discharge electrodes so shielded that the desired operating discharge can be directed over a desired long path and preventedin short direct paths necessary to the particular unitary construction herein contemplated.

The invention will be further understood by reference to the figures of the accompanying drawings in which like reference numerals represent like parts in so far as possible in the several figures.

Fig. 1 shows a discharge tube adapted for alternating current operation with electrode, shield and mounting arrangements embodying features of the invention.

Fig. 2 is a side view in section of the tube portion of Fig. 1 showing in further detail the electrode and shield arrangement.

Fig. 3 shows a discharge tube having the general features of the tube of Fig. 1, but modified as to the electrode arrangement with cooperating modifications in the supply circuits.

Referring to Fig. 1 a circular or otherwise suitably shaped tube 1 of glass or other suitable material for forming a discharge path is shown to include two discharge electrodes 2 and 3 erected on a stem 5 encompassing electrode lead-in wires usual to such tubes, the two electrodes being shielded from each other by a shield 4 so as to prevent a direct discharge between them, thus confining the desired discharge to and around the long and unobstructed path embraced by the tube structure. 1

The electrodes 2 and 3 are indicated as of the type adapted to emit electrons as by heating with a current passedthrough the wire forming these electrodes, the current of suitable potential being derived from the secondary windings 6 and 7 in the alternat- 5 ticularly desirable that an electrode structure that will withstand ionic bombardment be chosen for 2 and 3. For this reason a structure comprising. a coating of electron emissive compounds, of the nature disclosed and defined in application Serial Number 196,996 filed in the U. S. Patent Office on or about 6' June 1927 by Friedrich Meyer and Hans Joachim Spanner, or layers of electron emissive compounds, of the nature disclosed and defined in application Serial Number 251,736 filed in the U. S. Patent Ofiice on or about 3 February 1928 by Hans Joachim Spanner and myself as joint inventors, as the emissive material on a suitable metal core or wire is most suitable, as such compounds have been found capable of resisting ionic bombardment most effectively.

The shield 4 may be made of non-conductive material such as mica, or non-conductive material having a metallized surface, such as mica having a deposit of getter material, as magnesium, resulting from the deposit of'such material on internal parts of a tube accompanying the usual degassing processes with getter materials; or may be a conductive material, such as nickel, molybdenum, or other suitable metals. The shield may be mounted on the glass stem 5 by means of an upright 24 inserted into the body of the glass stem and welded or otherwise suitably attached to the shield 4:.

. By reference to Fig. 2, it is seen that the shield 4 is made to fairly closely fill the crosssectional area of the lower portion of tube 1 and the upright portion of that part of the tube surrounding the stem 5, but the shield is not shown'to extend all the way to the bottom of the stem 5. It is not necessary that the shield have an absolutely tight fit at the walls of the tube or extend to the bottom of the stem portion of the tube to prevent a discharge directly between the electrodes 2 and 3 because in operation the shield, the glass walls thereabout, and the stem 5 collect on their surfaces electrical charges by reason of the electrons in the tube, which electrical charges have the effect of neutralizing ionic effects necessary to maintaining the discharge. For example, if a discharge attempts to take place between electrodes 2 and 3 by way of the path under the shield, the electrical charges accumulated on the shield, stem and glass walls of that portion of the tube surrounding the stem, have the effect of neu tralizing ions to thereby prevent the successful establishmentof a'discharge by way of such path. The conditions of operation however, determine the closeness of fitting necessary for the shield, it being obvious that under conditions of employment of high discharge potentials more difficulty is bad in preventing a discharge than under conditions of lower potentials. In the case of very high potentials, two shields paralleling each other would be more efiective than one shield, and additional protection may be had by applying to these shields suitable potentials from outside sources. For example, the shield/l is shown connected by way of upright support 24 and lead wire 25 through the stem 5 to the primary winding 8 of the transformer, as one means of applying to the shield a potential from the outside, or to control the potential of the shield in the matter of the charge collected thereon by reason of the electrons in the tube, for it may be that a charge so collected will have a potential so high as to interfere with the desired opertion of the tube as a discharge device by way of the long path, and the connection shown would permit'of leaking olf' the charge. For example, the lead wire 25 is shown connected to the mid-point of the primary winding 8, though it may be connected to other points on this winding or other sources of potential as desired, or connected through a resistance to determine the rate of leaking away of an internal charge.

The tube 1 is shown mounted in a base casing 11 to which is attached the usual electric lamp screw plug 12 employed in connection with the usual lighting socket. The base casing is shown to include an alternating current transformer having a primary 8 and secondaries 6 and 7, which secondaries determine the potential of the heating currents of electrodes2 and 3. The iron core required by such a transformer can well be shaped to fit into a circular arrangement of base,-or other suitable form, and carry thereon the necessary primary and secondary windings. The only energy that the transformer need handle is that required for heating the electrodes, and a few watts suffice for this purpose, so that the transformer and windings can be simple affairs of very fine wire.

The resistances 9 and 10 are inserted in series with a supply circuit leading to the electrodes 2 and 3, so that when a discharge takes place between these electrodes these resistances are in series with the discharge path, and by selecting these resistances of suitable values they determine the amount of current involved in the discharge. These resistances may be inserted inside the casing 11 wound in suitable form and on suitable structures to bring within the casing a sufficient length of resistance wire to obtain the needed amount of resistance. However, there is necessarily some heat generated in these resistances which must be satisfactorily dissipated. One satisfactory wayv of accomplishing the result would be to make the casing 11 of a double wall having sufiicient spacing between the walls to permit of winding the resistance wire exteriorly of the innerwall and interiorly of the outer wall, which arrangement is shown-more in detail in Fig. 3. As a further means of dissipating heat the outer wall may be provided with corrugations or cooling ribs in manner and of construction well known in the general practice of heat dissipation effects, also shown more in detail in Fig. 3.

Lead-in wires for energizing the primary winding 8 and energizing the electrodes 2 and 3 by way of resistances 9 and 10 connected to center points in windings 6 and 7 are indicated as suitably connected at points 13 and 14 of the screw plug arrangement 12 in a manner already well known in electric lamp practice.

The arrangement shown can be inserted into the usual light socket, so that closing the switch or pressing the wall button usually associated with lighting systems will, in the one operation, permit of heating the electr0de wires 2 and 3, and at the same time apply a difference of potential between these electron emitting electrodes, and since the discharge cannot take place in the short in terval of separation because of the shield 4:, a discharge is set up between these electrodes by way of the long path around the tube, resulting in the desired light or other effects sought from such a discharge.

The electron-emitting electrodes have the effect of substantially eliminating the usualcathode drop present in such tubes, leaving the resistance of the discharge path and the anode drop as the resistances to be overcome in creating the desired discharge, and since theseresistances are reasonably low in tubes having-gas pressures giving the desired col- 'ored light and other effects wanted in such tubes, a reasonably long discharge can be obtained with the electrical potentials available from usual commercial circuits.

Since the two electrodes2 and 3 are elec tron emitting, the arrangementoperates most readily with alternating current, the electrodes acting alternately as cathodes and anodes, and also permit the starting of the new discharge at each half cycle of alternating current early inthe building-up of the potential of each half cycle, a feature most desirable in eliminating flicker effects common to usual tubes operated by an alternating current source.

The arrangement in Fig. 3 is similar .to that in Fig. 1 in the features permitting employing the tube in connection with a single socket. The arrangement diifers from that of Fig. 1 inproviding for electrodes 17 and 18 which are normally cold, but are-heated for starting-operation and'in part duringoperation by an ionic bombardment between the main electrode 17 and auxiliary electrode 19 and main electrode 18 and corresponding auxiliary electrode (not shown).

As in the case of Fig. 1, resistances 9 and 10 are connected in series with the main discharge path to limit the operating value of the discharge current to a desired degree. a part of the total resistance being shown as resistance winding 9 in series with resistance 9 wound between the inner and outer walls of the casing 11, and resistance windinglO in series with resistance 10 also wound between the inner and outer casings. Of course all of the resistancev in each'circuit may be wound either within the casing or within the space between the walls, and the same'may be done with resistances 15 and 16.

Cooling flanges or ribs on the, outer wall-of the casing 11 indicate one aidto dissipating heat generated in the resistances and other elements within the casing."

There are also included resistances 15 and 16 in series with each of the auxiliary discharge paths between the main electrodes. 17 and 18 and the corresponding auxiliary electrodes. These resistances 15 and 16, in .usual construction, will be much larger in resistance values than resistances 9 and 10, both because of the proximity of the auxiliary electrodes to the main electrodes and because normal operation will not require as large an auxiliary discharge for starting and heating purposes as is required in the main discharge. Again, the starting discharge may require a fairly large current, but which is not needed once starting has taken place and the main discharge is operating to provide the electrode heating. The arrangement shown so connects the resistances 15 and 16 with relation to the main discharge circuit and the resistances 9 and 10 therein that oncev the main discharge has'taken place, the current in the auxiliary discharge paths is limited,

all as more fully explained in my copending application, Serial No. 254,921, filed February 17, 1928. V

In Figs. 1 and 3 the inlead wires to the main and auxiliary electrodes are indicated with both alternating and direct current. If

operated with direct current obviously one of the main electrodes permanently acts as a cathode and the other as an anode. The use of resistances only in the arrangement'of Fig. 3 simplifies the matter of including all of the required control elementswithin a single simply constructed base.

I claim 1'. A discharge tube having a single stem portion, a stem in said portion, a pair of electrodes erected on said stem, a hollow toroidal envelope mounted upon said s'tem portion-and forming a continuous elongated discharge path extending in two directions from said stem portion, and a "discharge preventing shield between said electrodes whereby discharges therebetween are confined to said elongated path. 1

2. A discharge tube including a ringshaped portion, a stem portion opening into said ring-shaped portion, a stem within said ioe stem portion, a pair of electrodes erected on v said stem so as to project into said ringshaped'port'ion', and a discharge preventing shield erected on said stem between said electrodes and their supports, whereby discharges between said electrodes are. confined to the long path around the-ring-shaped portion of said tube.

' 3. A discharge tube including a tubular portion closed upon itself, a stem portion opening therein, a stem within said portion, a pair of electrodes erected'on said stem so as to project into said tubular portion, and a discharge preventing shield for ionic isolation of said electrodes except by way of the long path around said tubular portion.

4. A discharge tube including a tubular portion closed upon itself, .a stem portion opening into said tubular portion, a pair of electrodes projecting from said stemportion into said tubular portion, and a discharge preventing shield for ionic isolation of said electrodes exce' t by way of the long path around said tu ular portion.

, 5. The combination of a discharge tube having an elongated discharge path portion toroidal in shape, a single stem portion opening into said elongated portion, a. pair f discharge electrodes extending into said d1scharge portion from said stem portion, a discharge preventing shield between said' electrodes, connections to said electrodes leading externally of said tube by way of saidstem 10 portion, a base and circuit connecting portion aflixed to said stem portion, and current controlling elements within said base in extension of said connections to said electrodes.

6. The combination of a discharge tube including a tubular portion closed upon itself, a' stem portion opening into said tubular portion, a plurality of electrodes extending into said tubular portion'from said stem portion, connections to said electrodes leading ex ternally of said tube by way of said stem portion, a base afiixed to said stem portion, current controlling elements within said base in extension of said connections to said electrodes, and means aflixed to said base for connecting said current controlling elements to an electrical circuit outlet.

7. The combination of a discharge tube including a plurality of electrodes, connections to said electrodes leading externally of said tube, a base afiixed to said tube and havin a plurality of spaced walls, the outer of whlch carries heat radiating fins, current control ling elements in circuit with said electrodes byway of said external connections including resistance arranged within the space between said double walls of said base, and means affixed to said base for connecting said current controlling elements to an electrical circuit outlet. 1 V

40. 8. A discharge tube including a tubular portion closed u on itself, a stem portion openin into sai tubular portion, a pair of electro es projecting from said stem portion into said tubular portion, aj discharge pre- 45. venting shield between'said electrodes, and v a potential determining connection to said. shield leading externallyof'saidtube.

9. In a glow discharge device, a transparout envelope consisting of a transparent tubular memberof relatively small cross-section,

said tubular member being bent'and the ends thereof sealed to each other, a stem portion opening into. said tubular member, a stem within said portion, a air of electrodes erected on said stem an extending said tubular member and an electrostatic shield mounted on said stem and substantially preventing any straight line discharge between the electrodes. CARL J. R. ,H. VON WEDEL.

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