US1969646A - Discharge tube electrode - Google Patents

Description

7, 1934. F. HOTCHNER DISCHARGE TUBE ELECTRODE Filed May 25, 1929 INVENTOR Patented Aug. 7, 1934 UNITED STATES PATENT OFFICE Claims.

This invention relates to a discharge tube electrode for vacuous or ionization conductor electric devices or the like. While in the specification it is illustrated as applied to an ionization 5 conductor illuminating tube, it is applicable in many other ways in the art. One of the objects of the invention is to provide an electrode in which the ratio of emission capacity to volume of electrode material is greatly increased as com pared with prior devices in order to reduce the amount of occluded gases to be disposed of in the pumping process. A further object is to reduce the amount of electrode material for a given current capacity in order to reduce the probability of contamination of the tube by residual gases in the electrode.

A further object is to provide an electrode that is small and compact and that does not require the enlarged electrode terminals now commonly used on illuminating tubes when so applied.

In my Patent No. 1,789,901 and several previously-filed co-pending applications I have disclosed several types of discharge tube electrodes in which the detrimental eifects of positive ion bombardment are overcome. A theory is. advanced to enable those skilled in the art to make and use the devices. However it is to be understood that the theory is given in the way of explanation, and as the disclosures are in each case complete enough, without depending upon the theoretical explanation, to enable those skilled in the art to make the devices, the present invention is not to be understood as being limited by such explanation or by any further theory set forth herein. I also desire to have it understood that inasmuch as the present invention is applicable in many different ways in the art other than in the particular forms and applications herein described, it is not to be limited thereby, but only by the prior art and the appended claims.

In previous disclosures I have shown that if two emission surfaces are positioned close to each other and the discharge confined to the surfaces, properly protecting the edges and corners thereof, under the right conditions of pressure and gaseous content and assuming further that the dimensions are properly selected, the effects of positive ion bombardment are absent. My theory is that the ions are acted upon by opposing forces that reduce their velocity to a very low value. The important discovery has been made and disclosed, that an aperture with an extremely small opening positioned near the emission surfaces passes current-freely'in both directions and also seems to increase the emission power of a pair of surfaces so positioned. Thus I have produced an electrode suitable for an ionization conductor tube, such as an illuminating tube, that can be operated on alternating current and in which the plating out of the electrode material is not a source of trouble. The total area of emission surface necessary for efiicient operation with electrodes of the types disclosed is far below what has heretofore been described as the critical area of vaporization below which electrode of the prior art having emission surfaces freely exposed to positive ion bombardment would plate out" in short order.

The present invention utilizes a. further discovery. I have found that when the opposing surfaces are positioned very close together that the part of the surfaces closest to the aperture apparently are more emcient in electron emission. I believe this to be due to the fact that the electrons moving from the more distant parts of the surfacesset up a secondary action. Therefore I have provided a construction in which the dimension of the emission surfaces is increased enormously parallel to the aperture and reduced to a very low value at right angles to the aperture.

Construction features are provided to make an electrode in which a considerable extent of emis sion units are contained in a very small space.

In the drawing Figure 1 is a sectional view of an electrode made according to this invention.

Figure 2 is a cross section of the electrode shown in Figure 1 taken on the line 2--2.

Figure 3 is a sectional view of an electrode in which a very large amount of emission surface is required.

Figure 4 is an enlarged section of the active element shown in Figure 3.

Numeral 1, Figure 1 indicates the end of the positive column portion of an illuminating tube; 2, indicates a reentrant stem; and 4, a lead-in conductor. The conductor is spot welded onto the end of a channel shaped electrode 5 which is covered by the glass shield 6. The shield and the end '7 of the stem 2 are fused together thus protecting the lead-in wire. The shield is so formed as to leave a very constricted orifice 8 running the length of the channel and directing the discharge into the open end 9 thereof. The orifice opens into the atmosphere of the tube through the gradually opening channel 10.

As indicated by numeral 11, Figure 2, the edges and ends of the metal of the channel are protected by the material of the shield which is melted down over them.

In Figure 3, an electrode of high emission power is shown. The emission elements are assembled in a stack 15 which is built onto the end 16 of the reentrant stem 17, the whole being enclosed in the enlarged electrode bulb 18 opening into the discharge tube proper 19. The stack is composed of the ring shaped emission elements 20, 21, 22, 23, 24 and 25; the ring shaped aperture elements of dielectric material 26, 27, 28, 29, 80, 31 and 32; and the thimble of glass or other suitable material 33. The lead-in conductor 34 is sealed through the stem and passes through the thimble at 35, joining a conductor 36 which contacts with all of the emission elements. Each of the emission elements is channel shaped in cross section, the channel opening into a ring shaped aperture extending around the opening of the channel. As shown in Figure 4, the dielectrio aperture elements are so formed as to shield the edges and ends of the emission elements and direct the discharge into the inside of the channel. Preferably the apertures are made very constricted.

This electrode is suitable for use under conditions that make the use of prior devices difficult. The fact that a minimum of electrode material is used simplifies the processes of pumping, purifying and charging the tubes. The small size of the electrode permits its installation on apparatus in connections decidedly unfavorable to the use of the electrodes of the prior art.

Numerous applications of the invention will be apparent to those skilled in the art. The disclosure of this invention to investigators and designers offers solutions for numerous perplexing problems in the development of discharge tube devices.

This invention is distinguished from the electrode described in my application filed May 30, 1929, Serial No. 351,196, in that the present invention pertains to electrodes of the general type described in which the depth of the chamber formed by the opposing emission surfaces with respect to the orifice is very small as compared with the length of the emission surfaces with respect to the length of the orifice thereby providferred to as evaporation or sputtering of the material of the electrode by positive ion bombardment.

Having thus described my invention, what I claim is:

1. In a bi-dircctional, positive column, gaseous conduction discharge tube, a pair of electrodes, each of said electrodes having an active element with an emission surface in the form of a groove of length at least ten times the width or depth thereof.

2. In a bi-direction, positive column, gaseous conduction discharge tube, a pair of electrodes, each of said electrodes having an active element with an emission surface in the form of a groove of length at least ten times the width or depth thereof, and means to confine the main discharge to the emission surfaces within said grooves.

3. In a bi-direction, positive column, gaseous conduction discharge tube, a pair of electrodes, each of said electrodes having an active element with an emission surface in the form of a groove of length at least ten times the width or depth thereof, and shielding means preventing the discharge from attacking the edges and corners of said active elementand confining the discharge to the inside of said groove.

4. In a bi-directional, positive column, gaseous conduction discharge tube, a pair of electrodes, each of said electrodes having an active element with an emission surface in the form of a groove of length at least ten times the width or depth thereof, and a shield over the opening of said groove having a constricted orifice extending substantially the length of said opening for the passage of the discharge from the emission surface of said electrode to the main chamber of said tube.

5. In a bi-directional, positive column, gaseous conduction discharge tube, a pair of electrodes, each of said electrodes having an active element in the form of a channelled member with a groove therein of length at least ten times the width or depth thereof, and a shielding member of dielectric material extending around said channelled member and having an opening corresponding to the opening of said groove and protecting the edges and corners of said active element from the discharge.

FRED HOTCHNER.

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