US3205388A

US3205388A - Drill hole type cathode with cooling means

Info

Publication number: US3205388A
Application number: US79836A
Authority: US
Inventors: Lany Beatrice Pearson De; Paul L Copeland
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-12-30
Filing date: 1960-12-30
Publication date: 1965-09-07
Anticipated expiration: 1982-09-07

Description

P 7, 1965 B. P. DE LANY ETAL 3,205,388

DRILL HOLE TYPE CATHODE WITH COOLING MEANS Filed Dec. 30, 1960 2 Sheets-Sheet 1 z l 54 f 1 0/1298 A A Sbdrce l INVENTORS.

par/kw" Z far/er lf/far/feyz p 1965 a. P. DE LANY ETAL 3,205,388

DRILL HOLE TYPE GATHODE WITH COOLING MEANS Filed Dec. 30, 1960- 2 Sheets-Sheet 2 IN V EN TORE from the nearest part of the cathode.

United States Patent 3,205,388 DRILL HOLE TYPE CATHODE WITH COOLING MEANS Beatrice Pearson De Larry, 36 La Gorce Circle, Miami Beach, Fla., and Paul L. Copeland, 17 W. 80 Oak Lane,

Bensenville, Ill.

Filed Dec. 30, 196i), Ser. No. 7%,836

7 Claims. (Cl. 313-35 This invention relates to gas discharge tubes and in particular to improvements in the cathode of said tubes.

A primary purpose of the present invention is to provide a means for selectively cooling the cathode hole of a gas discharge tube to improve the operation of the discharge.

A further purpose is to provide an electric discharge tube of the gas type wherein the cathode has an elongated hole which is cooled to increase the density of the gas within it.

Another purpose is to provide a tube of the type described having increased stability of the are or glow at low-current densities.

Another purpose is to provide a means for selectively cooling the cathode in an electric discharge tube of the type described.

Another purpose is to provide an improved voltage regulator tube of the type described,

Other purposes will appear in the ensuing specification, drawings and claims.

The invention is illustrated diagrammatically in the following drawings wherein:

FIGURE 1 is a longitudinal section through a gas discharge tube of the type described showing one means for cooling the cathode,

FIGURE 2 is a section, similar to FIGURE 1, showing a further means for cooling the cathode,

FIGURE 3 is a longitudinal section showing a variant form of gas type discharge tube and yet a further means for cooling the cathode,

FIGURE 4 is a section along plane 4-4 of FIGURE 3,

FIGURE 5 is a partial section showing a further means for cooling the cathode, and

FIGURE 6 is a schematic illustration of the tube of this invention in a voltage regulator circuit.

If a drill hole with its diameter suitably related to the mean-free-path of electrons in the gas is present in the cathode of a glow discharge, the discharge at the cathode will be confined almost entirely to the interior of said hole. In the glow discharge electrons are emitted from the cathode as a result of any of several processes in the discharge.

These electrons are immediately accelerated in the cathode fall of potential. There is some chance that -an electron will ionize a molecule of the gas either near the end of the cathode fall or in the luminous gas which marks the beginning of the less rapid potential variation. If an electron in the drill hole, however, has not lost its energy in elastic impacts with gas molecules by the time it enters the cathode fall diametrically across from its point of origin, it again traverses nearly the entire cathode fall and is slowed down in the process. Its potential energy, however, has increased, and after being brought to rest for an instant, it is again accelerated away As it acquires kinetic energy, it becomes able to ionize the gas molecules. In this way it may oscillate back and forth between diametrically opposite sections of the circumference of the cathode hole until it has lost a large part of its energy in the production of ions. The concentration of electrons moving through the hole space during any period of time is thus greatly increased. The potential difference across the discharge is reduced when it operates in this Way, and the drill hole is so effective that the discharge often concentrates within it, leaving other more exposed portions of the cathode structure dark,

The effectiveness of a drill hole in the cathode of an electrical discharge device at a given pressure of gas depends upon the temperature of the walls of the drill hole. To increase the effectiveness of the cathode, the material should be cooled. In other words, the cathode should be selectively cooled, as obviously to cool the entire tube is not useful, because it merely reduces the pressure without a significant increase in the concentration of molecules within the drill hole. According to the general gas laws an increase in pressure and decrease in temperature give rise to effects in the same sense. In other words, according to the general formula PV=RT, either an increase in pressure at constant temperature or a decrease in temperature at constant pressure will increase the density of the gas. As in many applications it is not practical to increase the amount of gas in the tube, it is therefore necessary to provide a method of cooling the cathode in order to increase the density of the gas within the cathode hole. Accordingly, it is the primary purpose of this invention to provide a gas type discharge tube utilizing a cathode hole with means for cooling the cathode hole to increase the density of the gas Within the hole.

In FIGURE 1, a gas impervious envelope 10, which may be a glass envelope as conventional, encloses an anode 12 having a lead-in wire 14. The space Within the envelope 10 may be filled with an inert gas, for examples helium or argon, or any one of a number of suitable gases. At the end of the envelope 10 opposite the anode 12 is a cathode 16 in the form of an elongated rod or bar having a longitudinal bore or hole 18. The bore or hole faces 01' opens into the interior of the tube and may be axially aligned with the anode 12. A lead-in 20 supplies the electric connection for the cathode. The cathode 16 may have a shell consisting of copper sealed to the glass of the tube in a conventional housekeeper seal shown attached to the envelope 10 at 22, or it may have its exterior formed of one of the alloys which is chosen to have an expansion coefiicient matching that of the glass to which it is sealed. The drill hole itself may be in a slug of material which is fitted into the metallic shell completing the envelope. This slug may be of misch metal or one of its purified components such as cerium, or it may be of barium or strontium. A material of low work function is desirable for the interior surface of the drill hole, and cesium or another of the alkali metals may be used in a film coating the interior surface of the drill hole.

In the form of the invention shown in FIGURE 1, the cathode is selectively cooled by placing the body of the cathode outside of the envelope 10. In other words, the cathode body 16 will be surrounded by air at atmospheric pressure and temperatures so that the heat of the cathode will be dissipated to the surrounded volume.

In FIGURE 2, an air impervious envelope 24 encloses an anode 26 having a lead-in wire 28. In this form of the invention, the cathode includes a cathode body 30 formed similarly to the cathode body 16 of FIGURE 1 and including a drill hole or bore 32 opening into the interior of the tube 24, and again generally axially aligned with the anode 26. The envelope 24 extends toward and along the cathode 30 to define a cup-like area 34 around the cathode 30. This cup-like area 34 may hold a suitable cooling medium, for example water, ice or solid carbon dioxide. Any one of these materials is satisfactory'for dissipating the heat of the cathode. Preferably, the out side of the cathode and the bottom 36 of the cup-like area 34 is formed of copper. Again there is a conventional housekeeper seal between the copper plate and the glass tube 24.

In the structure shown in FIGURE 2 the heat genertube envelope.

ated by the cathode is dissipated through the cooling medium placed in the cup-like area 34 to accordingly cool the drill hole within the cathode 30.

FIGURE 5 shows a modification of FIGURE 2 in which a spiral coil 23 passes around the cathode 30. The coil may have an inlet 25 and an outlet 27 and, may carry any suitable coolant. A continuously circulating coolant is quite efficient in cooling the drill hole.

A further form of the invention, shown in FIGURE 4, is utilized with a tube having an identical element at each end. Such a tube may be used with alternating current and each element alternately serves as the cathode of the tube. An air impervious envelope 38, encloses two identical elements 40 each of which are composed of a central elongated body 42 having an axial or longitudinal bore or hole 44 and a plurality of radially extending fins 46. A lead-in48 is used as the electrical connection between the element within the tube and the circuit.

In this form of the invention, the radially extended fins 46 provide a means for dissipating the heat of the cathode, or in effect, cooling the cathode drill hole. FIGURE 6 shows one use of the tube described herein. When the tube 50 is positioned in parallel with a load 52 and a source 54 it provides an excellent voltage regulator.

The use, operation and function of the invention are as follows:

This invention relates to electrical discharge in gases, and it provides a means of stabilizing the glow. An elongated cathode member having a so-called drill hole extending longitudinally or axially of the cathode may be used. The use of such a cathode hole initially stabilizes the glow within it even at low currents. It has been observed, however, that after operating a tube of this type for some time, particularly at high currents, the discharge may go out entirely when the current is reduced; or, due to the heating of the cathode, the concentration within the drill hole may be eliminated and the form of the discharge may be so radically altered that the device does not have characteristics suitable for the application attempted. A primary purpose of the present invention is to stabilize the form of the discharge between the cathode and the anode and to produce steady operation.

The particular tubes shown and described herein have an extremely wide range of application. They may be .used as sources of light and are especially suitable if a concentrated source is desired. They may also be used for achieving particular spectral characteristics of the light. 'Circuit applications of these tubes may also be made. A particular application of this tube has been found in volt- ..age regulator circuits. .the type described can supply excellent voltage regula- It has been found that a tube of metal is however preferred for the cathode although cesium or any one of the rare earth or alkali earth metals are also satisfactory. A number of different elements may be used in the cathode formation and it is not intended to restrict the invention to any single material. The same is true of the'particular gas placed within the Helium is satisfactory as is nitrogen or any one of the noble gases, as the only requirement is that the gas be inert chemically.

The pressures 'of the gas within the tube may vary Widely and in general it may be said that the pressures are lower than those conventionally used in electric discharge tubes. With drill holes of nearly an inch in diameter we have used inert gas pressures on the, order of 100 microns of mercury. The pressures as previously noted depend on the diameter of the drill hole and for "wire size" drill holes, Five microns of mercury proved a satisfactory pressure. The size of the hole will vary according to the particular size of the tube, however hole diameters in the range of of an inch to of an inch are satisfactory. As an example, if the hole has a inch diameter, it should be approximately 11 inches long, as although the exact dimensions are not critical, the relative dimensions are. For example, the ratio of hole diameter to hole length should never be less than 1:10. The hole must be long in order to provide the increased stability and range of current variation required.

The advantage of the cathode hole lies in the fact that the restricted area of the hole provides for a concentration of gas molecules within an area which is crisscrossed by heavy electron movement, thus substantially increasing the possibility of ionizing the gas molecules. In other words, the radial distance traversed by an electron as it moves from one wall of the drill hole to another is small so that the electrons rapidly move back and forth until they have an inelastic impact with a gas molecule, thus producing ionization. It has been discovered that ionization can be further increased by increasing the density of the gas or the number of molecules per cubic centimeter within the cathode hole. Accordingly, to increase the number of molecules within the cathode hole it is necessary either to selectively decrease the temperature of the hole or to increase the pressure. In most applications, it is impractical to increase the pressure by adding more gas, therefore it is necessary to decrease the temperature of the drill hole itself. The only way to decrease the temperature is to cool the cathode body. Accordingly, shown and described herein are four different methods of cooling the cathode.

In FIGURE 1, the body of the cathode is positioned outside of the tube envelope, although effectively within the tube, so that the heat of the cathode may be transferred by conduction to the surrounding atmosphere. In FIGURE 2, the cathode is not enclosed within the envelope, and has a cold storage cup-like volume around the cathode. The cup-like volume may contain any one of a number of satisfactory cooling substances. In FIG- URE 3, the cathode is cooled through the use of radially extending fins which will dissipate the heat of the cathode'to other portions of the tube. In FIGURE 5, a coolant coil passes around the cathode.

The increased ionization and hence increased stability of the discharge at low-current densities, as stated above, is caused by cooling the cathode hole. Cooling the cathode relative to the other parts of the enclosed volume increases the concentration of molecules withinthe cathode hole and also prevents the loss of ions by diffusion. Both results lead to increased efficiency of the tube. In addition, cooling the cathode will keep the cathode from disintegrating. As the cathode heats up and reaches high temperatures during operation, it is likely to partially disintegrate. Accordingly, cooling the cathode reduces the cathode disintegration and thus increases the life of the tube.

Whereas the preferred form of the invention has been shown and described herein, it should be realized that there are many modifications, substitutions and alterations thereto within the scope of the following claims.

We claim:

1. An electric discharge tube including an air impervious envelope filled with an inert gas at a pressure between microns and 5 microns of mercury, an anode positioned within said envelope and a lead-in for said anode, an elongated solid metallic cathode positioned opposite and away from said anode and arranged to provide an electric discharge therebetween, a lead-in for said cathode, a longitudinal elongated hole in said cathode generally in alignment with said anode, and means for selectively cooling said cathode to stabilize the discharge between the cathode and anode and to increase the gas density within the hole.

2. The structure of claim 1 further characterized in that the means for selectively cooling said cathode in clude a plurality of outwardly extending fins positioned upon and around the periphery of said cathode and within said envelope.

3. The structure of claim 1 further characterized in that the body of said cathode is outside of said envelope with the hole opening into the interior of said envelope.

4. The structure of claim 1 further characterized in that the body of said cathode is outside of said envelope with the hole opening into the interior of said envelope, and means for maintaining a cooling medium around the body of said cathode.

5. An electric discharge tube including an air impervious envelope filled with an inert gas, an anode positioned within said envelope and a lead-in for said anode, an elongated solid metallic cathode positioned opposite and away from said anode and arranged to provide an electric discharge therebetween, a lead-in for said cathode, a longitudinal elongated hole in said cathode generally in alignment with said anode, the ratio of length to width of said cathode hole being at least :1 and the hole being round in cross section.

6. An electric discharge tube including an air impervious envelope filled with an inert gas, an anode positioned within said envelope and a lead-in for said anode, an elongated solid metallic cathode positioned opposite and away from said anode and arranged to provide an electric discharge therebetween, a lead-in for said cathode, a longitudinal elongated hole in said cathode generally in alignment with said anode, the body of said cathode being outside of said envelope with the hole opening into the interior of said envelope, and means for maintaining a cooling medium around the body of said cathode to stabilize the discharge between the cathode and anode and to increase the gas density within the hole, including an extension of said air impervious envelope forming a cup-like volume around said cathode, with the cathode being generally in the center of said cup-like volume.

7. An electric discharge tube including an air impervious envelope filled with an inert gas, an anode positioned within said envelope and a lead-in for said anode, an elongated solid metallic cathode positioned opposite and away from said anode and arranged to provide an electric discharge therebetween, a lead-in for said cathode, a longitudinal elongated hole in said cathode generally in alignment with said anode, the body of said cathode being outside of said envelope with the hole opening into the interior of said envelope, and means for maintaining a cooling medium around the body of said cathode, to stabilize the discharge between the cathode anl anode and to increase the gas density within the hole, including a cooling coil passing around said cathode.

References (Zited by the Examiner UNITED STATES PATENTS 1,912,097 5/33 Rinia 313-209 1,914,762 6/33 Thomas 313-213 X 1,932,025 10/33 Thomas 313-211 X 1,954,958 4/34 Smythe 313-209 X 2,029,013 1 36 Blackburn 313-40 2,087,735 7/37 Pirani 313-42 2,401,059 5/46 Eitel et a1. 313-40 X 2,887,603 5/59 Haidinger 313-217 X 2,966,601 12/60 Peek 313-161 X GEORGE N. WESTBY, Primary Examiner.

RALPH G. NILSON, DAVID GALVIN, Examiners.

Claims

1. AN ELECTRIC DISCHARGE TUBE INCLUDING AN AIR IMPERVIOUS ENVELOPE FILLED WITH AN INERT GAS AT A PRESSURE BETWEEN 100 MICRONS AND 5 MICRONS OF MERCURY, AN ANODE POSITIONED WITHIN SAID ENVELOPE AND A LEAD-IN FOR SAID ANODE, AN ELONGATED SOLID METALLIC CATHODE POSITIONED OPPOSITE AND AWAY FROM SAID ANODE AND ARRANGED TO PROVIDE AN ELECTRIC DISCHARGE THEREBETWEEN, A LEAD-IN FOR SAID CATHODE, A LONGITUDINAL ELONGATED HOLE IN SAID CATHODE GENERALLY IN ALIGNMENT WITH SAID ANODE, AND MEANS FOR SELECTIVELY COOLING SAID CATHODE TO STABILIZE THE DISCHARGE BETWEEN THE CATHODE AND ANODE AND TO INCREASE THE GAS DENSITY WITHIN THE HOLE.