US1827292A - Electrode - Google Patents

Description

- Oct. 13, 1931. I 1.. W. LAUB E Y ,8 7, 9

ELECTRODE Original Filed June 6, 1929 INVENTOR Louis Wilbur Liubc.

ATTORNEY .5 v

Patented Oct. 13, 1931 UNITED STATES PATENT OFFICE LOUIS WILBUR LAUBE, OI EAS'ILCLEVELAND, OHIO, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO FLEXLUME CORPORATION, OF TONAWAND'A, NEW YORK, A CORPORA- 'IION or new YORK\\ ELECTRODE Application filed June 6, 1929, Serial No. 368,813. Renewed March 3, 1931.

This invention relates to electrodes for 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 illuminated signs. The present invention relates particularly to cup-shaped electrodes which have their open ends sealed to the open endsof a glass tube and form closures for the ends of the tube.

The interior surface of the glass tube receives a negative charge by reason of the fact that some of the electrons find lodgment thereon. It is a property of the conduction of electricity that the electric current at one point along the conductor tends to follow a path normal to an equipotential surface. In an electrical discharge tube, the receiving surface of the electrode, whatever its form, is equipotential. In moving away from the surface of the electrode, further equipotential surfaces exist which at first follow the surface of the electrode very closely, but are deformed as the distance from the electrode increases until they take the form which exists in the main body of the tube which, owing to the charge on the glass tube, is convex to the stream of ions. Passage of the stream through the convex equipotential surfaces tends to concentrate the stream of ions toward the longitudinal axis of the tube although this is opposed by the mutual repulsion of the electrons. Inside the cup-shaped electrode, however, the curvature of the equipotential surfaces is reversed so that the stream of ions tends to spread outwardly to the wall of the electrode.

In the case of cup-shaped electrodes with the edge of the cup fused to the edge of glass tube, there is a tendency for the stream of ions to spread as it passes into the electrode so that a large proportion of the stream strikes the electrode close to the seal, the concentration of the electron stream at the edge of the glass seal causing excessive heating at this point which is objectionable since the seal is the weakest point of the structure.

The present invention has for its object to provide a cup-shaped electrode which is of such form that concentration of the stream of ions adjacent the seal connecting the open end of the electrode to the open end of the glass tube is prevented.

With the above and other objects in view, the invention may be said to comprise the electrode as illustrated in the accompanying drawings hereinafter described and particularly set forth in the appended claims, togetherwith such variations and modifications thereof as will be apparent to one skilled in the art to which the invention appertains.

Reference should be had to the accompanyr. ing drawings in which:

Figure 1 is a sectional view showing a portion of the glass tube with the electrode of the present invention attached thereto.

Fig. 2 is a diagrammatic view illustrating the effect of the electrode on the electronic stream.

The glass tube which may form a part of an illuminated sign of the neon tube type is indicated by the reference numerall and the cup-shaped electrode is indicated generally by the reference numeral 2. The electrode is preferably formed of copper and may be made from a piece of copper tubing, the outer end portion of the electrode being formed by swaging the tubing to a small diameter to provide a stem 3, and enlarging the tubing above the stem to provide an enlarged portion 4 of the globular form of greater diameter than the glass tube 1.

A series of heat radiating fins 5.may be attached in a suitable manner to the stem. In its inner end, the electrode has a cylindrical edge portion 6 which is of a diameter-to fit upon the exterior of the glass tube which is sealed to the edge of the electrode by fusion, as well understood in the art. The portion of the electrode above the stem 3 is cup-shaped and the side wall is bulged outwardly immediately below the end of the glass tube. The portion of the side wall of the electrode immediately below the end of the glass tube is thus curved outwardly so that the exposed interior surface flares outwardly from the end of the glass tube.

As above explained, the equipotential surfaces adjacent the surface of the electrode conform closely to the surface of the electrode and gradually decrease in curvature as in I the glass tube flares away from the tube, the

deflection of the stream of ions at the mouth of the electrode is considerably decreased with the result that a large proportion of the stream passes into the electrode past the seal and is distributed quite uniformly over the interior surface of the electrode without any objectionable concentration of the stream along the edge of the seal.

By reason of the fact that, during its passage through the glass: tube, the stream of ions is concentrated centrally of the tube, a considerable portion of the stream would normally be concentrated upon the central portion of the bottom of the electrode. In order to disperse this portion of the stream of ions over a greater area of electrode surface, a recess 7 of small diameter extending into the stem may be provided at the bottom of the cup-shaped portion of the electrode.- Ions adjacent the axis of the electrode passing into the recess 7 are deflected laterally toward the sidewall of the recess and are thus distributed over a greater area of electrode surface.

In Fig. 2 of the drawings, lines of travel of the ions are indicated by the dotted lines a and successive equipotential surfaces within the tube and electrode are indicated by the dotted lines 6.

As shown in this figure, the equipotential surfaces 7) within the glass tube are convex to the stream of ions and within the electrode concave thereto.

By reason of the outward flare of the in terior surface of the electrode immediately adjacent the end of the glass tube, the change in equipotential surfaces from the convex to concave with respect to the stream of ions is less abrupt than with the cup-shaped electrode of uniform diameter so that the speading of the stream entering the electrode is lessened and a greater proportion of the ions strike the interior surface of the electrode well below the seal. Also, as the central portion of the stream of ions approaches the flaring mouth of the recess 7, there is a spreading of this portion of the stream which is thus distributed over a considerably greater surface. area than it would be if the bottom of tfihe electrode cavity were flat or substantially It will thus be apparent that the electrode of the present invention is of such form that the stream of ions will be distributed quite uniformly over the interior surface and local heating effects are thereby eliminated.

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:

1. An electrode for luminous discharge tubes adapted to seal the end of a glass tube and having an open end of a diameter to fit over the end of the glass tube, said electrode being enlarged outwardly of the open end thereof to provide an interior surface flaring outwardly from the end of the glass tube.

2. An electrode for luminous discharge tubes adapted to seal the end of a glass tube and having an open end of a diameter to fit over the end of the glass tube, said electrode being cup-shaped, of greater diameter than the glass tube and of substantially globular form.

3. An electrode for luminous discharge tubes adapted to seal the end of a glass tube and having an open end of a diameter to fit over the end of the glass tube, said electrode being cup-shaped, of greater diameter than the glass tube and of substantially globular form, said electrode having a recess of relatively small diameter in the bottom thereof substantially in axial alinement with the end of the glass tube to which the electrode is attached.

In testimony whereof I affix my signature.

LOUIS WILBUR LAUBE.

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