US2154404A - Electrode for ionic discharge devices - Google Patents

Description

April 11, 1939;. T. J. KILLIAN .ELECTRODE FOR IONIC DISCHARGE DEVICES Filed July 51, 195e f 1 l l l INVENTOR THQ/w.: J /f/Lm/v MHH....,.M.,..I..,M.,...,.H@mNNN Piuma A". n, iosa PATENT ori-ICE ELECTDODE FOR DEVI IONIC DISCHARGE CES Thoma .1. Killian, Seattle, Wash.

Application July 3l, I 5 Claims.

'Ihis invention relates to ionic discharge devices and it has reterencemore particularly to an improved form oi electrode for gaseous discharge devices of that class wherein ionic dis- 5 charge is caused to take place between electrodes in a closed vessel containing a rareiled gas or vapor. 'I'he invention is particularly useful where the ionic discharge is of such nature that the gas or vapor is rendered luminous, thereby adapting the device for use for illuminated signs, displays and for'various applications in domestic and commercial illumination.

It has been found in operating ionic discharge devices having internal electrodes that there is a considerable drop in potential between the electrodes' and the ionized gas a few centimeters from them. This requires high voltage for operating the devices and also necessitates more pow- -er for operating the same.

One of the objects of this invention is to provide an internal electrode for devices of the above stated character that makes possible a material increase in the length of the gas column; that is, an electrode that makes possible 8l a material increase in the eilective length of a gas filled tube between the opposite terminal electrodes.

It is an object of this invention also to provide an electrode which by reason of its novel form of construction, gives increased lighting eillciency in the lamp, at a lower gas pressure, and thereby provides for a decrease in the consumption of electrical energy an electrode which provides a reduction in the fall of potential between the electrodes and the gas as well as a reduction in sputtering.

More specifically stated, the present invention resides in the provision of an electrode for discharge devices of the above stated character, which maybe of metal, or carbon, or other suitable material, in the form of a hollow, cylindrical shell, closed at its outer` end and having a restricted, central opening in its inner end which is directed toward the arc path between electrodes.

Other objects of the invention reside in the details of construction oi' the electrode, in its disposition in the lamp and in its mode of operation, as will hereinafter be i'ullydescribed.

In accomplishing these and other objects oi the invention, I have provided the improved details of construction, the preferred forms of which are illustrated in the accompanying drawing, wherein- Fig. 1 is a view diagrammatically illustrating 1936, Serial No. 93,508

a lamp equipped with terminal electrodes in accordance with the present invention.

Fig. 2 is an enlarged, longitudinal, sectional view of the electrode and one `end of the lamp.

Fig. 3 is an end view on a smaller scale of a modiiled form of one of the electrodes.

Fig. 4 is a longitudinal section on a smaller scale through another modied form of the electrode.

Fig. 5 is a graph of operation of the electrode, showing the curve obtained by plotting electrode voltage dropagainst pressures, at constant current.

Fig. 6 illustrates a certain type of electrode used in a `lamp employed for making a comparative test, and showing also the curve obtained by plotting electrode voltage drop against pressure at constant current.

Fig. 'I is a similar diagrammatical illustration of another form of electrode commonly used in gaseous discharge devices, in a comparative test and showing a curve formed by plotting cathode voltage drops against pressures.

In carrying out the present invention an elongated hollow body of material is made of conducting' material such as metal or carbon, or is made of other material and coated with metal or carbon, for example, and is so shaped that the end to which a conducting Wire is connected is closed while the other eter or is partially closed, leaving an opening smaller than the end to which the conductor or wire is connected.

Referring more in detail to the drawing- I designates a sealed, transparent vessel, which may be a glass tube of the kind generally used for lamps of the present type and which is filled with a gas or vapor, or a combination of gas and vapor, which is of the proper kind to operate as the carrier for the luminous discharge". At its opposite ends the tube has enlargements 2 and 2, shaped as necessary to best accommodate the terminal electrodes of the present invention, which are enclosed therein and which in Fig. 1, are designated by the reference numerals 3 and 3*, and are electrically connected, respectively, with terminals 4 and 4*. These terminals are in the form of wires sealed through the tube ends and adapted for connection with a source of high potential current whereby a necessary potential may be impressed upon the electrodes to cause a discharge to be established and maintained between them in the gaseous column of the lamp. When this tube is to be used as a luminous tube the gas is preferably carbon end is of smaller diamdioxide and is at` a pressure of about .05 to about 0.5 mm. of mercury.

It isnot believed necessary in this specification to describe thelamp to any further extent except tov say that the tube may assume various designsV for desired ornamental eiIects or for adapting it to any particular use. or location. Also, the electrical current employedwould preierably be alternating and applied through a high reactance transformer of conventional type.

The terminal Velectrodes 3 and 3* are identical in construction and when the lamp is operated on alternating current, they will serve alternately as the cathode and anode. A

The electrodes are locate symmetrically within the enlargements formed at the ends of the tube i and each comprises a cylin cal metallic shell, closed at its outer end by a wall 3b to which wall the corresponding terminal wire 4 or 4a is connected. The opposite, or inner end of the tubular shell is provided with a wall 3c and a relatively small opening 5 is provided in the center of this wall, preferably concentric with the axis of the tube.

lAs seen best in Fig. 2, the electrode 3 is operatively supported by the connection at its outer end with the terminal wire 4 and it is formed about its inner end with an encircling iiange 6 to give additional strength thereto.

During the development oi this invention, certain tests were made to determine the operating characteristics of luminous tube lamps in `which this invention was embodied. In Fig. 5, I have illustrated graphically the relationship of voltage and gas pressure. In plotting voltages versus gas pressures at a constant current using an electrode of aluminum in a lamp lled with carbon dioxide gas, the curve :l: was obtained. This shows an operation differing from" that generally observed with reference to electrodes of the conventional design in that it shows a drop in voltage with a decrease in gas pressure, whereas with electrodes of the usual sort there will be an increase in volt.- age with a decrease in gas pressure. Without limiting myself to any theory of the present unusual or unexpected result disclosed in the graph of Fig. 3, I may `say that radiation in the form of soft X-rays or metastabie atoms may be responsible to a more or less degree. There is also a change in the electric eld and electric potential distribution due to the enclosure which4 seems to cause the density of electrons and positive ions to increase. It may be this increased density which causes the voltage drop to decrease. Certain comparative tests which involved the ploti ting of voltages versus pressures to ascertain the characteristics, rst using in this same lamp an electrode in the form of a at disk, as indicated at d in Fig. 6; then making a like test using an electrode in the form of a cylindrical s hell e, as designated in Fig. '1, which is similar to that of the present form except that its inner end is entirely open, have led tothe conclusion mentioned above.

The curve resulting from plotting the charac- .teristic of the rst type of electrode is designated at f, in Fig. 6. It shows a steady and pronounced increase in voltage required for constant current with the decrease'in gas pressure. 4The curve g obtained in the test of the second type, as illustrated in Fig. 7, shows a drop in voltage with a decrease in the gas pressure up to a certain point, then a very abrupt rise in voltage, as shown by the portion h.

I have found that by reducing the size of the opening l in the end of the electrode 3, lower voltage drops with constant gas pressure and current would result, but when the openings were too small dimculty in establishing the discharge at lower pressures was experienced. The practical limit in diameter of this opening was determined to be about onquarter oigan inch, when using an electrode two inches long and two inches in diameter. Furthermore, decreasing the diameter of the electrode appeared to cause a decrease in the voltage required in the operating region. The lengths of these electrodes may vary greatly in proportion to their transverse dimensions and the size oi the openings 5 may also vary considerably in proportion to the size of the ends 3. So far the most satisfactory results have been obtained by having cylindrically shaped aluminum electrodes 2 inches long and 1 inch in diameter with the openings 5 about 145 of an inch in diameter, the walls of theelectrodes being only about ,Blf of a inch-thick; f/

The electrodes 3 may also vary in shape and instead of being cylindrical they may be of polygonal or other shaped cross section. In Fig. 3 an end view of an electrode is shown that is hexagonal in shape with an hexagonal end 3c' having an hexagonal opening 5. 'I'he corners of the hexagons of the tube itself and the'opening 5 may be on radial lines or otherwise disposed.

It is also not necessary to have the electrodes of uniform diameter from end to end. For example, the electrodes may be tapered, as illustrated in Fig. 4, in which the electrode 3" has one end closed, as shown at 3b" and tapering toward the other end leaving an opening 5".

' It has been found by using electrodes of the sort described above, that there is an appreciable reduction in the electrode drop or -potential difference between the electrode and the ionized gas in the tube l a few centimeters from the electrode, thus reducing the necessary power required to operate the tube. Furthermore, it has been found that this potential drop decreases in such a tube when the gas pressure in the tube decreases, instead of increasing as is the case with ordinary electrodes in such a tube. This enhances the stability of operation of the tube and enables the same to be operated with less attention. It has also been foundthat in electrodes oi this sort the current can be increasedV to the .point where the tube operates satisfactorily and then the current can be increased without further appreciable rise in voltage drop at the electrodes.

The use of a lamp equipped with electrodes of the kind above illustrated and described has denitely proven that a lamp of greater eiiiciency is obtained, that greater lighting value is possible at lower voltages and that the lamp will operate with a lower consumption of electrical energy. The fact that lower gas pressure may be utilized in the tubes permits the same voltage to be used for tubes of considerably greater length than those heretofore used.

Although the electrodes may be made of different sorts of metal and may also be made of other materials coated with metal, the most satisfactory results have been obtained when the electrodes were made of aluminum.

Having thus described my invention, what I claim as new therein and desire to secure by Letters Patent is: l

1. An internal electrode for a low pressure ionic f lessthanaboutincheeondadiameteroinot lessthanaboutiincmciooedotoneendond having in the other end an opening about* of an inch in diameter.

2. Aninternal electrode for a low pressure ionic discharge device comprising a hollow electrically conductive body closed at one' end. the ratio ot the length to the diameter thereof being not greater than about2, the other end thereof being closed except for an opening about A ot an inch in diameter. I 3.y An internal electrode for a low pressure imiic discharge device comprising a hollow body of aluminum about 2 inches long and not less than 1 inch in diameter. closed at one end and lrinovided st the other end with an opening of about oi an inch in diameter.

4. An internal electrode for a low pressure ionic conductive body closed at one end and partially closed at the other end,l the ratio of the length to the diameter oi' the electrode and the size of the opening in one end thereof being such as to give to the electrode a falling voltage drop char acteristic with a decrease in pressure within the range of pressure of from .05 to .5 millimeter of mercury.

v 5. An internalvelectrode for a low pressure carbon dioxide discharge device comprising a. hollow 10V electrically conductive body closed at one end and partially closed at the other end, the ratio oi' the length to the diameter of the electrode and the size of the opening in one en d thereof being such as to give to the electrode a falling voltage 15 drop characteristic with a decrease in pressurewithin the range oi pressure of from .05 to millimeter of mercury.

` THOMAS J. KILLIAN.

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