US2774906A

US2774906A - Voltage regulator

Info

Publication number: US2774906A
Application number: US463846A
Authority: US
Inventors: Russell R Law
Original assignee: Columbia Broadcasting System Inc
Current assignee: CBS Broadcasting Inc
Priority date: 1954-10-22
Filing date: 1954-10-22
Publication date: 1956-12-18
Anticipated expiration: 1973-12-18

Description

Dec. 18, 1956 R. R. LAW

VOLTAGE REGULATOR 3 Sheets-Sheet l Filed Oct. 22, 1954 iiulf Q INVENTOR.

Russell R. Law

By ATTORNEY Dec. 18, 1956 R. R. LAW

VOLTAGE REGULATOR 3 Sheets-Sheet 2 Filed Oct. 22. 1954 vFIG.4

INVENTOR.

' Russell R. Low

ATTORNEY Dec. 18, 1956 R. R. LAW

VOLTAGE REGULATOR Filed Oct. 22, 1954 3 Sheets-Sheet I5 INVENTOR. Russell R. Low

ATTORNEY United States Patent VOLTAGE REGULATOR Russell R. Law, Wenham, Mass., assignor to Columbia Broadcasting System, Inc., a corporation of New York, doing business under the name CBS-'Hytron, a Division of Columbia Broadcasting System, Inc., Danvers, Mass.

Application October 22, 1954, Serial No. 463,846

7 Claims. (Cl. 313-208) This invention relates in general to electronic tubes and in particular to voltage regulator tubes.

Glow-discharge type voltage regulator tubes are well known and widely used in the electronics industry. Their operation depends upon the fundamental physical phenomena that under proper conditions a glow discharge exhibits a substantially constant voltage drop over a relatively wide range of current. That is, the volt-ampere characteristics of a gaseous discharge has a region where the current is substantially independent of the voltage.

This useful characteristic of a glow discharge is well known. It is believed that the slope of the characteristic in this region depends upon the positive-ion concentration in the neighborhood of the anode. In any event, it is possible by well known structures and adjustments of gas pressure to adjust this slope as desired. The voltage drop on the other hand, is largely determined by the cathodefall or voltage between the plasma and the cathode.

In the voltage regulator tube, the voltage drop is a most important characteristic. This voltage drop depends upon many factors including the kind of gas, the pressure of the gas, the impurities in the gas, and the character of the cathode surface. The cathode surface depends not only upon the material of the cathode and the impurities on its surface, but upon the surface changes brought about by the glow discharge itself.

This dependence of the cathode surface on the discharge itself may be explained in part as follows: The discharge is maintained by positive ions from the plasma falling 'down the potential hill surrounding the cathode and releasing electrons. These electrons in turn are attracted up this same potential hill and accelerated to such a velocity that they ionize the residual gas, thereby restoring the positive ions initially lost from the plasma. The voltage drop must adjust itself to such a value that equilibrium is established. This equilibrium is:

Electrons Electrons Positive ions leaving bombarding cur rz ii a i oss I the cathode the cathode discharge However, the ratio of the number of electrons leaving the cathode to the number of positive ions bombarding the cathode depends upon the surface condition, i. e., Work function, etc. This, in turn, is altered by positive ion bombardment. The relatively massive positive ions strike the surface with suificient energy to strip off the surface layers.

In tubes of conventional design the glow-discharge is not constrained to a particular path. After the arc is started, it may alter the cathode surface in that particular zone to such an extent that the original path is not the most favorable arc path. The arc will then jump to a new more favorable path. Because of the differences in surface conditions, this shift in arc path is ordinarily accompanied by a change in voltage. This erratic, unpredictable change in voltage is a major defect in conventional glow-discharge type voltage regulator tubes.

Therefore, it is an object of the present invention to provide voltage regulator tubes having a constant voltage drop throughout their life.

It is a further object of the present invention to provide a structure for a voltage regulator tube which constrains the discharge to a predetermined path.

It is a still further object of the present invention to provide voltage regulator tubes having stable characteristics and long useful life.

In general, the present invention consists in a structure wherein the cathode and anode of a voltage regulator tube are so designed and spaced one from another that control of the discharge is maintained in a predetermined area. This is accomplished by locating the cathode of the tube in such relationship to the anode that a region of minimum spacing is provided. The configuration and orientation of the anode and the cathode are such that any movement of the arc to a path other than that predetermined is inhibited by an increase in arc length. For a better understanding of the invention, together with other and further objects, features, and advantages, reference should be made to the following description which is to be read in connection with the accompanying drawings in which:

Fig. 1 is an elevation view, partly cut away, of a voltage regulator tube incorporating the principles of the present invention;

Fig. 2 is a section taken through the tube of Fig. 1 along the line 2-2;

Fig. 3 is an elevation view, partly cut away, of another embodiment of the present invention in a voltage regulator tube;

Fig. 4 is a section taken through the tube of Fig. 3 along the line 44; and

Fig. 5 is a front elevation, partly cut away, of an operative voltage regulator tube embodying the principles of the present invention.

Referring particularly to Fig. 1, there is illustrated a tube which is of the miniature type, the glass envelope being removed for ease of understanding. As is conventional in such tubes, the mount includes a getter 13 disposed upon the electrodes adjacent the top of the bulb where it is accessible for flashing to aid evacuation of the tube after finishing. A baflle mica 14 is provided beneath getter 13 to prevent the deposition of getter material on working electrodes of the tube.

A cathode 15 is provided and has the shape of a cylinder. The actual active surface of the cathode is the inner wall of the cylinder. Since the current handling capacity of tubes such as that of the present invention is determined in large part by the cathode area, normal electrode structures are reversed, the cathode, as noted, being a relatively large cylindrical structure. An anode 16, is provided Within cylindrical cathode 15 and takes the shape of a rod. A disc 17 is placed within cathode 15 and is welded or otherwise maintained in good physical and electrical contact therewith. A stem 18, of conventional design has suitable leads sealed therethrough and connected to cathode 15 and anode 16. These leads, of course, provide both support and electrical connection to the electrode of the tube.

Referring now to Fig. 2, more detail on disc 17 is shown. Anode 16 and cathode 15 are concentrically disposed. The structure of disc 17 is such, however, that an opening of circular shape is formed therein. This opening is not concentric with anode 16 or cathode 15 and, therefore, is disposed relative to anode 16 such that an area of minimum spacing is provided. In an actual embodiment of the present invention as built into an operative regulator tube this spacing was .018".

Referring now to Fig. 3, a second embodiment incorporating the present invention is disclosed. In this figure, getter 13, baflle 14, cathode 15 and anode 16 are all identical to those disclosed in Fig. 1. Also, the stem 18 with its leads is identical to that of Fig. 1. For convenience, the envelope has been removed in this view as well. However, the disc 27 replaces the disc 17 shown in Fig. 1. Disc 27 has a cylindrical portion thereof which is welded to the inner surface of the cathode, cylinder 15 and a conical section beneath the cylindrical section which tapers to an opening surrounding anode 16. As may be seen in Fig. 3 and also in Fig. 4, the lower opening in conical section 27 is eccentric in respect to anode 16 and cylinder 15. In some instances, the conical shape of disc 27 is preferred over that disclosed in Fig. 1 as a means to better control the region in which the arc strikes when the tube is being used.

In operation, it has been demonstrated that the arc prefers to strike across the region of minimum spacing because of the greater gradient in that region. Moreover, the arc continues across that path with the result that the objections of erratic, unpredictable voltage change as found in conventional glow-discharge voltage regulator tubes are overcome. This situation obtains for the life of the tube, despite the fact that ion bombardment alters the cathode surface to some extent. Stable operating characteristics can be postulated with the structure of the invention and are not subject to objectionable change.

Referring now to Fig. 5, one embodiment of the present invention may be seen incorporated in an operative tube. In this figure, the electrode structure is the same as that shown in Figs. 1 and 3. That is, the tube 12 has a cylindrical cathode 1S and a rod-like anode 16 concentrically mounted therein, a getter 13, a baflie mica 14 and a stem 18 having leads sealed therethrough. A disc 17 is shown sealed within the cathode 15 although it should be noted that a conical section such as the section 27 in Fig. 3 could be utilized in place of disc 17.

After assembly of the heretofore described parts in the envelope 10, the envelope may be exhausted, filled with one of the numerous gases useful in glow discharge tubes, such as argon, and then sealed. The pressure of the gas is predetermined to adjust the striking voltage of the tube as desired. In addition, the inner surface of the cathode 15 may be coated with a rare earth metal such as cesium to change the characteristics of the tube 12. However the characteristics of the tube 12 are changed to provide different operating ranges, it will be found that, if either the flat disc 17 or the conical section 27 is incorporated in the tube 12, much closer control of the characteristics is obtained without any special precautions being taken as to the alignment of such a disc or conical section.

Although preferred embodiments have been shown and described, this invention should not be limted to the details disclosed. The concept of establishing and maintain ing an arc in a predetermined region is believed to be novel in its application to glow-discharge voltage regulator tubes, and the appended claims to structure embodying this concept are believed to define the invention comrnensurately.

What is claimed is:

1. In a glow-discharge voltage regulator tube, an anode, a cathode surrounding said anode, and a circular insert connected to and within said cathode, said insert having a portion thereof spaced more closely to said anode than the remainder thereof.

2. A glow-discharge voltage regulator tube comprising, an envelope containing ionizable gas, a cylindrical cathode having a circular opening therethrough, a cylindrical anode disposed within said opening, the axes of said cylindrical cathode and said cylindrical anode being common but displaced from the axis of said circular opening.

3. A glow-discharge voltage regulator tube comprising, an envelope containing ionizable gas, a cylindrical cathode having an opening therethrough, a circular insert within and connected to said cathode, said insert having a substantially circular opening therethrough disposed eccentrically of said cathode, and an anode concentric with said cathode passing through said opening.

4. A glow-discharge voltage regulator tube comprising, an envelope containing an ionizable gas, a cylindrical cathode having an axial opening therethrough, a circular insert within and connected to said cathode, said insert having a substantially circular opening therethrough disposed eccentrically of said cathode, and an anode of smaller outside diameter than the diameter of said opening in said circular insert, said anode being concentric with said cathode.

5. A glow-discharge voltage regulator tube comprising, an envelope containing ionizable gas, an anode disposed centrally of said envelope, a cathode concentric with and surrounding said anode, a substantially conical insert within and connected at its large end to said cathode, said conical insert having an eccentric opening in the small end thereof, said anode passing through said opening.

6. A glow discharge tube including an envelope containing an ionizable gas, a tubular electrode having a longitudinal axis, an insert connected internally of said tubular electrode and containing. an opening having an axis parallel to the axis of said tubular electrode, and

a rod electrode having a longitudinal axis passing through said opening, at least one of said axes being displaced from another of said axes.

7. A glow discharge tube including an envelope containing an ionizable gas, a tubular electrode, an insert arranged transversely of said tubular electrode and having an opening therein, and a rod electrode arranged within said tubular electrode and within said opening with a single point on the edge of said opening nearer to said rod electrode than any other point on said edge.

References Cited in the file of this patent UNITED STATES PATENTS 1,760,524 Rentschler May 27, 1930 2,194,432 Pomfrett Mar. 19, 1940 2,401,911 Corson June 11, 1946