US2020393A - Gas discharge tube - Google Patents

Description

Nov. 12, 1935.

E. S. WOOLRICH GAS DISCHARGE TUBE Filed June 6, 1929 INVENTOR Edwz rd S. Woo Ir-i ch ATTORNEY-5 s PATENT OFFiQE umrro STATE 2,020,393 GAS nrscmnoa 'runu Edward S. Wooirich,

assignor, by Corporation, of New York.

Cleveland Heights, Ohio, mesne assignments, to Flexlume Tonawanda, N. Y.,

a corporation Application June 6, 1929, Serial No. 368,789 9 Claims. (Cl. IVS-126) This invention relates to luminous electrical discharge tubes of the type employing an inert gas such as neon as the current conducting medium, such tubes being extensively used for illum- Where a cathode has a convex surface exposed to the electric stream, the concentration of the electric stream is increased in proximity to such surface and a very large proportion of the posiinated signs. tively electrified ions impinge on the convex sur- 5 In tubes of the character above referred to, the face. For this reason, in the case of the cupmetallic electrodes at the ends of the tube beshaped internal electrode, such as is commonly come heated by the electric bombardment to used in the luminous tube industry, the electric such an extent that the metal at certain exposed stream is largely concentrated upon the edge of 10 points on the electrode is vaporizedand deposited the cup. 10

on the walls of the glass tube. This, of course, is In the case of cup-shaped electrodes with the objectionable, not only because of the'blackening edge of the cup fused to the edge of the glass tube, of the tube and of the metal deposit, but also there is a tendency for the current of the elecbecause the deposit absorbs the gas in the tube trodes to be distorted so that a large proportion of and shortens the life of the tube. the stream of ions strikes the electrode close to 15 It is a property of the conduction of electricity the seal. that the electric current at any point in a con- In the case of the internal cup-shaped elecductor tends-to follow a path normal to an equitrode, the concentration of the stream of ions potential surface. In case of conduction through causes excessive heating of-the edge of the cup gas, this phenomena is modified by the momenand vaporization of the metal along this edge. 20 tum of the electrified bodies which tends to keep In case of ,a cup-shaped electrode sealed to the them on their course. end of the tube, the concentration of the stream In a luminous tube, the'electric stream is not of ions at the edge of the glass seal causes exevenly distributed within the tube. The districessive heating which may damage or destroy the bution is dependent among other things on the seal which is the weakest point of the structure. 25 gas pressure within the tube. Where gas exists The present invention has for its object to proin a tube, a certain number of electrons are devide means for controlling distribution of the flected from their normal course and tend to stream of ions adjacent theelectrodes of a lumistrike the walls of the tube. If, as is usually the nous discharge tube in such a manner as to precase, the walls are composed of a non=conducting vent damage to the electrode eitherby vaporiza- 30 surface such as glass, the glass receives a negative tion of metal or by destruction of the seal. charge from the few electrons that find lodg- A further object of the invention is to provide, merit thereon and this space charge tends to dein the tube adjacent the electrode, an electrically flect the stream of-electrons toward the center of conductive meanswhich does not have a direct 5 the tube, this phenomenon being greater, the electrical connection to the electrode and which greater the pressure of the filling. receives an electrical charge ofopposite sign This deflection is further influenced by the fact from that of the electrode, forming an equip'otenthat the electrons, due to their frequent collision tial surface serving to disperse portions" of the with the atoms in the tube do not have the velocstream of ions which would normally have an 40 ity which they would havein a more completely excessive heating action on portions of the elecevacuated tube. The receiving surface of the t electrode, whatever it o m. i an equipotential With the above and other objects in view, the surface In moving away m the Surface of invention may be said to comprise the electrical the electrode, further equipotential surfaces exist discharge tube as illustrated in the accompanying. which at first follow the surface of the electrode drawing hereinafter described and particularly 45 1 g i" g g deformed g f 3 2 set forth in the appended claims, together with 8 e 60 8 increases un ey a e e such variations and modifications thereof as will orm which exists in the main body of the tube t t n km (1 i m t t m h th which, owing to the charge on the glass tube, is e apparen 0 e n e at o w c e 5 convex to the stream of electrons. The passage mventmn appertams' of the stream through these convex equipot'ential Reference smuld be had to the accompanying surfaces tends to concentrate the stream of elecdrawmg in which: trons toward the longitudinal axis of the tube, i u 1 s a s ti na vi w sh wing an elecalthough this is opposed by the mutual repulsion tri al discharge tube having n i n 11pof the electrons themselves. an element in the form oi shaped electrode and the stream of ions as to prevent localized heat! these views,

a wire ring positioned adjacent the open inner end of the electrode.

Pig. 2 is a sectional view showing the same electrode with an element in the form of a tapering coil positioned adjacent the inner end of the electrode. a

Fig. 3 is a sectional view showing an element in the form of a coil'surrounding the cup-shaped electrode and projecting beyond the inner end thereof.

Pig. 4 is'a sectional view showing two elements, one surrounding and the other positioned beyond the inner end of the cup-shaped electrode.

Fig. 5 is a sectional view showing a luminous discharge tube which is provided with a cupshaped electrode sealing the end of the glass tube and provided with an element in the form of a tapering cofl within the glass tube at the end thereof.

Fig. 6 is a sectional view showing a luminous discharge tube having.an electrode such as shown in Fig. 1 and an element in the form of a wire ring which is coupled capacitatively with the electrode.

Fig. 7 shows a luminous discharge tube having the same. electrode as in Fig. 5, but with a ring shaped element coupled-to the electrode through an impedance.

Referring to the accompanying drawing, Figs.

- 1 to '4 and Fig. 6 of the drawing illustrate the invention as applied to a luminous discharge. tube having an internal cup-shaped electrode and in the glass tube isdesignated by the I and-the electrode by the The cup-shaped electrode the tube with its open end reference numeral reference numeral 2. 2 is supported within presented inwardly and is coupled to a suitable source of current by means of a leadin wire 8 extending through and sealed in a thickened portion 4 at the end of the glass tube, the lead in wire being welded, soldered or otherwise rigidly secured to the closed end of the electrode and serving to support the The electrode above described is old and well known, the present invention comprising means in the vicinity of the electrode for so controlling ing of the electrode.

As shown in Fig. 1 of the drawing, the con-. trolling means consists of an element in the form of a wire ring I supported adjacent to but out of contact with the edge of the cup-shaped electrode 2. The ring I may be supported independently of the electrode in any desired manner. As shown in Fig. 1, the wire forming the ring has one end 6 extending along the outside of the cup out of contact therewith and embedded in the thickened portion 4 of the glass tube.

The ring 6 forms an annular equipotential surface adjacent the open end of the cup-shaped electrode which acts to concentrate the stream the axis of the tube adjacent the open end of the stream of ions is dispersed over the interior surface of the cup and concentration of the stream on .the edge of the cup is prevented.

In Fig. 2 of the drawing, the element is in the form of a wire coil 1 of tapering form supported electrode in the tube.-

cup so that the major portion tact with the electrode by an end portion 8 of the coil extending along the wall of the tube I outside the electrode 2 and embedded in the. thickened portion [of the glass tube. As in the case of the ring shaped element, the wire coil forms a an equipotential surface adjacent the electrode concentrating the stream of ions adjacent the free edge of the cup shaped electrode and causing the same to be dispersed over the interior surface of the electrode; '1

In the modification shown in Fig. 3 of, the drawing, theelement is in the form of a coil I surrounding the electrode 2 and projecting beyond the open inner end thereof, the wire at one end of the coil extending along the wall of the glass tube to form a supporting extension II which is embedded in the glass at the end of the tube. As in the modifications previously described, the coil 9 is supported out of electrical contact with the electrode and serves to drive the stream of ions away from the edge of the cupshaped electrode 2.

In the modification shown in Fig. 4 of the drawing, two elements which are adapted to receive charges differing in potential are employed, one of the elements being a tapering coil beyond the inner end of the electrode similar to the coil 1 shown in Fig. 2 and the other being a, coil i2 surrounding the electrode. The two coils ii and II are supportedput of electrical contact with each other and out of electrical contact with the electrode by means of extensions l3 and H of the wire coils which are embedded in the glass of the tube.

It is essential that the element which is composed of metal or other electrically conductive 7 material receive a charge differening in potential from that of the electrode and, in the modifications above described, the elements are shown entirely disconnectedifrom the electrode. The said element, therefore, in these embodiments is not connected to power and hence no lead in wire is employed in connection with it. It is to be understood, however, that anyof the elements herein disclosed may be coupled to the electrode either capacitatively, as illustrated in Fig. 6 or through an impedance as illustrated in Fig. 7.

In Figs. 5 and 7, the invention is illustrated as applied to a luminous discharge tube in which the glass tube It has anzopen end sealed by a cup-shaped electrode II, the open end of which is sealed to the end of the glass tube l5.

In Fig. 5 of the drawing, the element is in the form of a tapering wire coil [1 having its small end adjacent the end of the tube, which is sealed within the endof the cup-shaped electrode i5 and is supported by an extension ll of the wire at the upper end of the coil, which is embedded in the glass wall of the tube. The coil l1 serves to concentrate the major portion of the stream of ions to such an extent that it will be carried past the seal and distributed over the interior surface of the electrode, thus preventing overheating of the electrode along the edge of the seal. In Fig. 6 of the drawing, there is shown an element in the form of a wire ring ll which may be embedded in the glass wall of the tube a short distance inwardly of the edge of the electrode. The wire ring llacts upon the electron stream in a manner similar to the ring I in Fig. 1 and may, if desired, be coupled capacitatively with the electrode I through a suitable condenser II.

In Fig. 7 of the drawing, there is shown a wire ring element 22 similar to the element shown in Fig. 6 but coupled with the electrode l6 through an impedance coil 23.

In all of the modifications above described, the concentration of the stream of ions on certain exposed portions of the electrodes, which in the operation of the tubes act alternately as anodes and cathodes, is prevented by providing an equipotential surface so disposed with respect to the portions of force the major portion of the stream away from the portions of the electrode which it isdesired to protect whereby a more even distribution of the stream of ions over the surface of the electrode is obtained and localized heating of the electrode is avoided. The means by which the stream of ,ions is controlled in the vicinity of the electrodesabsorbs a considerable part of the heat generating energy of the stream and hence reduces to a considerable extent the heating action of the stream upon the electrodes. be apparent, therefore, that inasmuch as the said means is also utilized to control the direction of the concentrated stream that the practice of the invention enables the use of electrodes. having relatively small active surfaces. The concentration of the stream of ions in the manner described 7 does not affect the voltage drop across the electrodes. Hence the invention may be employed with various forms or sizes of electrodes while preserving this desirable characteristic.. It will also be apparent that the distribution and control of the stream of ions in the manner described have the advantage that the electrodes may be composed of metals which while desirable because of their low drop have not heretofore been capable of withstanding the bombarding action to which they have been subjected where the stream of ions has not been controlled. For example, electrodes of magnesium, or principally of magnesium are desirable because of their low drop. The present invention, therefore, enables the use of electrodes of such a metal. v

Furthermore, it is to be understood that the particular form of apparatus shown and described, and the particular procedure set forth,

are presented for purposes of explanation and illustration and that various modifications of said apparatus and procedure can be made without departing from my invention as defined in the appended claims.

What I claim is: i

1. A luminous electrical discharge tube having a cup-shaped electrode mounted with its open end facing inwardly, and an element in the form of a wire coil supported coaxially with the electrode, and out of contact therewith adjacent the open end thereof.

2. In a luminous electrical discharge tube, the combination with an elongated glass tube containing a gas which acts as a current conducting medium and having electrodes at the ends thereof, of meansfor controlling the stream of ions in the vicinity ofthe electrodes comprising an element of'electrically conductive material in the,

tube adjacent each electrode, each element being coupled capacitatively with its respective electrode.

. 3. A luminous electrical discharge tube having a cup-shaped electrode, and an annular element of electrically conductive material within the tube adjacent the edge of the cup-shaped electrode,

the electrode to be protected as to It will .medium and having rection of the body of the tube and tapering from the said element emerges therefrom in a concen- Opening in the direction of the body of the tube taining a gas which acts as a current conducting medium and having electrodes at the ends thereof, of means for controlling the stream of ions in the vicinity of the electrodes comprising an element of electrically conductive material within the tube adjacent the inner end of each electrode 10 and adapted to receive an electrical charge of a potential different from that of the electrode, each element being electrically coupled with its electrode and an impedance interposed between,

the element andelectrode. v

5. A luminous electrical discharge tube having a cup-shaped electrode, and an annular element of electrically conductive material within the tube adjacent the edge of the cup-shaped electrode, said element being electrically coupled with its electrode and an impedance interposed bethe element and electrode.

6. A luminous electrical discharge tube having a cup-shaped electrode mounted with its open end facing inwardly, and an element in the form of a wire coil supported coaxially 'with'the electrode, and out of contact therewith adjacent the open end thereof, said coil being of tapered form and having its small end adjacent the open end of the electrode.

'7. A luminous electrical discharge tube, the combination with an elongated glass tube containing a gas which acts as a current conducting an electrode at an end of the tube. of means for controlling the stream of ions in the vicinity of the electrode comprising an element of electrically conductive materialwithin the tube adjacent the inner end of the electrode and spaced inwardly from said end, said element being insulated from said electrode and 40 having no lead in wire.

8. In a luminous electrical discharge tube, the combination with an elongated glass tube containing a gas which acts as a current conducting medium and having electrodes at the ends thereof, 4 of means for controlling the stream of ions in the vicinity of the electrodes comprising an element of electrically conductive material in the tube adjacent each electrode, said element being formed with a relatively large opening in the disaid opening in the direction of the electrode with which it is associated to a relatively smaller opening whereby the stream of ions passing through trated condition.

9. In a luminouselectrical discharge tube, the combination with an elongated glass tube containing a gas which acts as a current conducting medium and having hollow open ended electrodes at the ends thereof, of means for controlling the stream of ions in the vicinity of the electrodes comprising an element of electrically conductive material in the tube adjacent each electrode, said element being formed with a relatively large 6;

andtapering from said opening in the direction of the electrode with which it is associated whereby the stream of ions as it passes through the said element is concentrated and directed into the interior of the electrode.

' EDWARD S. WOOLRICH.

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