USRE21361E - R gunn - Google Patents

Description

"eh. 20. 1940. R GUNN Re. 21,361

APPARATUS FOR THE DETECTION OF DISPLACEMENTS 3 Sheets-Sheet 1 Original Filed Dec. 4, 1936 INVENTOR H055 (hum ATTORNEY Feb. 20, 1940. R. GUNN Re. 21,361

APPARATUS FOR THE DETECTION OF DISPLACEMENTS Original Filed Dec. 4, 1936 3 Sheets-Sheet 2 AIIIHIII III INVENTOR R055 (in/um BY 4 W A TTORNEY R. GUNN Feb. 20, 1940.

APPARATUS FOR THE DETECTION OF DISPLACEMENTS Original Filed Dec. 4, 1936 3 Sheets-Sheet I5 lOl INVENTOR Ross Gunn. W

ATTORNEY Reissued Feb. 20, 1940 UNITED STATES PATENT OFFICE Rosa Gunn, Washington, D. 0.

Original No. 2,155,419,

for reissue December 308,883

12 Claims.

(Granted dated April 25, 1939, Serial No. 114,111, December 4, 1936. Application 12, 1939, Serial No.

under the act of March 3. 1883, as

amended April 30, 1928; 370 O. G. 757) My invention relates to an apparatus tor detecting displacements and more particularly to an electrical apparatus for the remote and substantially instantaneous detection or measurement of mechanical displacements.

In carrying out my invention I employ a space discharge device which includes at least a cathode and a movable anode and provide means responsive to the displacement to be detected or measured for imparting movement to the said anode. Any movement imparted to the anode results in a change in the average internal resistance between the anode and cathode with at tendant change in the space current through the space discharge device. By connecting the space discharge device in a proper circuit and providing suitable indicating or recording means, a displacement c! any desired character or magnitude may be detected or measured. Various types of novel space discharge devices and circuits may be advantageously employed in carryin my invention into effect all of which will be pointed out more in detail hereinafter.

The apparatus of my invention is capable oi detecting or measuring high frequency periodic or non-periodic mechanical displacements. whose values closely approximate the wave length of red light and by the employment of suitable auxiliary means is readily adaptable to detecting or measuring displacements even to as great a value as a foot. Because oi. its simplicity, ruggedness, practicability and extreme sensitivity, my apparatus has a wide field at application. As illustrative or its many uses it may be employed for detecting or measuring mechanical or elastic vibrations such as occur in bridges, buildings, various machinery and other structures; for detecting or recording earthquakes, either natural or such as are produced as incidental to geo-physical exploration; for detecting or measuring elastic defamation such, tor example. as would occur in a ship's structureor a propeller shaft; for detecting or measuring angular displacements; and for detecting or measuring instantaneous liquid or gaseous pressures. Many other uses will readily occur to those skilled in the art.

With the foregoing preliminary discussion in view, it is an object of my invention to provide a simple, rugged and eflective electrical apparatus for detecting or measuring periodic or non-periodic mechanical displacements of either large or small magnitude.

It is another obiect of my invention to provide an electrical apparatus for detecting or measuring mechanical displacements wherein any change in the value of an electro-motive force incorporated in a balanced electrical circuit of the apparatus or any change in the electron emissivity of a cathode oi a space discharge device incorporated in a like circuit and iorming part of the apparatus will not aiiect any indication of the indicating means.

It is another and further object my invention to provide an electrical apparatus tor detecting or measuring angular displacements.

It is another and still further object 01 my invention to provide new and novel space discharge devices for incorporation in my detecting or measuring apparatus but which, however. are .susceptible oi. being advantageously used in other environments.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

Fig. 1 discloses one embodiment 01 my invention;

Fig. 2 discloses an alternative embodiment of my invention employing a different space discharge device and circuit arrangement;

Fig. 3 depicts a further modification of my invention differing over that of Fig. 2 principally in the employment of a grid circuit;

Fig. 4 shows another form that my invention may take and wherein a diflerential galvanometer is employed;

Fig. 5 depicts a still further embodiment of my invention which is especially designed for detecting or measuring angular displacements;

Fig. 6 is a sectional view taken on the line 8-0. Fig. 5;

Fig. 7 shows another modification 01 my appsratus employing two cathodes in the space discharge device thereof and an amplifier for amplifying any voltage diflerential of the bridge circult;

Figs. 8 and 9 represent different embodiments of my invention wherein the displacement of the movable electrode or electrodes of the space discharge device is controlled by suitable external magnetic means; and

Fig. 10 depicts a modification 01 my invention suitable tor the detection or measurement of fluid pressure.

Before proceeding with a detailed description of the various embodiments 01 my invention it is deemed advisable at this point in the interest of clarity and in order to avoid needless repetition in the subsequent description to make certain general remarks concerning the space discharge devices and circuits employed in my apparatus. As pointed out hereinbefore, each space discharge device includes at least one cathode which serves as a source of electrons. A cursory examination of the drawings will show that all cathodes have been depicted therein as of the thermionic type, the heating thereof to insure electron emission being accomplished either directly or indirectly by a suitable source of electro-motive force. I wish to emphasize in this connection, however, that I do not desire to be restricted to this type of cathode since cathodes which emit electrons due to bombardment by rapidly moving ions, electrons, or metastable atoms and are said to be secondarily emissive, or photo-electric cathodes, or cold or non-thermionic cathodes which spontaneously emit electrons due to-treatment thereof by a radioactive substance, all will serve the purpose of my invention equally well. As for the thermionic cathode, it may be fabricated of a pure metal, be oxide-coated, be of a metal provided with an adsorbed monatomic film of one of the electro-positive metals or be of any other type known to the art. The envelopes of my space discharge devices which are fashioned from any of the materials known to the prior art and serve to enclose the electrodes may be evacuated to produce a high vacuum and thus insure a substantially pure electron discharge or may alternatively be provided with a suitable filling of a gas or vapor, gases or vapors, or mixtures of gases and vapors at a selected pressure or pressures to insure the desired operating characteristics.

Many of the circuits employed in various embodiments of my invention take the form of a Wheatstone bridge in which three electrodes oi a space discharge device are connected to form two branches thereof, the remaining two branches being formed by two variable resistances which serve to eflect a balancing of the bridge circuit prior to any detecting operation. Means responsive to the displacement to be detected or measured serve to impart movement to at least one of the said three electrodes to cause simultaneously thereamong a decrease in electrical resistance between the first and second electrodes and an increase in electrical resistance between the first and third electrodes, thus causing an unbalancing of the bridge circuit which is indicated by a suitable indicating or recording device. It is, of course, apparent that the indicating device may be suitably calibrated to indicate not only the magnitude of the displacement but also its direction.

The basic principle underlying my invention may be best appreciated by considering the embodiment disclosed in Fig. 1 of the drawings. There is shown depicted in this fi ure an envelope I of a space discharge device which includes as part thereof a flexible bellows-like metallic or glass extension 2 to the end of which is rigidly secured the anode 3 by means of the lead-in wire 4. A cathode I, which may be of a thermionic type, is heated to an electron emissive temperature by the source of electro-motive force I. The plate circuit of the space discharge device includes the source of electro-motive force I and an indicating device 8 which may be a milliammeter. The force, pressure or displacement to be detected is represented schematically by the arrow 9/ A small spring and anvil III are arranged to return the extension 2 of the space discharge device to its initial and desired position with a given plate potential the space current density varies in a non-linear manner with the electrode spacing and increases rapidly as the spacing between the anode and cathode structures is reduced. This fact was first established by Child andis known as Child's law. Thus, the

average internal resistance between the anode 3 and cathode 5 is a definite and reproducible function of the spacing between these electrodes, which spacing is controlled by displacing the end of the flexible extension 2 by a force or pressure 9. It is therefore evident that any change in spacing between the electrodes 3 and 5 will result in a. changein space current, the indicating device 8 reading more or less depending upon whether the spacing between the electrodes is decreased or increased. Hence, any departure from a predetermined and initial reading or reference point of the milliammeter serves to detect a displacement, the magnitude of which is easily ascertainable by suitable calibration of 1 the milliammeter or indicating means 8.

While the apparatus of Fig. l is an entirely operative and useful structure it does, nevertheless, possess certain inherent disadvantages. If. for example, the emissivity of the cathode 5 is in any manner impaired or the value of the electromotive force of either sources 5 or I changes, this will be evidenced by first order changes in the plate current indicated by the milliammeter 8. If, then, the indicating means has been previously calibrated for a fixed electron emissivity and fixed values of electro-motive forces, it is evident that the indicating means 8 will now give inaccurate and false readings because of a changed reference point. In order to minimize any such difllculty as might be encountered in using the apparatus of Fig. 1, I provide different tube structures and circuit arrangements as will be pointed out hereinafter.

In Fig. 2 oi the drawings there is shown a space discharge device and circuit arrangement which minimize the difliculties that may be encountered with the apparatus of Fig. 1. In this figure ll denotes the envelope of the space discharge device which like that of Fig. 1 has at one end thereof a flexible metallic or glass bellowslike extension I! to which are secured and insulated from each other the two anodes l3 and I4 supported by their respective lead-in wires I 5, I B. The cathode I? which may be of a thermionic type is heated to an electron emissive temperature by the battery iii. The insulated lead-in wires II and it are connected in a bridge circuit which includes the two balancing resistances l9 and ill. It is thus seen that the bridge circuit includes four arms or branches, two of which are constituted by the resistances between the anode II, cathode l1, and anode ll, cathode II with the resistances i9 and 20 heretofore mentioned forming the remaining two branches. The indicating device II which may be a milliammeter is placed across one diagonal of the bridge and the plate potential or source of electro-motive force 22 connected across the remaining diagonal. A small spring and anvil 23 again serve to return the extension or projection I! of the space discharge device to its initial and desired position of rest upon the removal of any actuating force. I! now the end of the extension of projection I2 is displaced in any manner, such as for example by the indicated micrometer 24, the anode 12 will move toward the cathode l1 while simultaneously the anode M will move away from the cathode. this movement of the electrodes occurring due to the fact that the anodes l3 and I4 are rigidly secured to the end of the projection or extension l2 by means of the lead-in wires 15 and 16. The former electrode movement tends to decrease the internal resistance between the anode l3 and cathode l1 and the latter has a tendency to increase the resistance between the anode l4 and cathode I1. It, then, the bridge be balanced by a suitable adjustment of the variable resistances I9 and 2|) prior to the application of a force by the micrometer 24, the bridge will now be unbalanced in both its arms by the displacement of the micrometer. It is at once evident that any unbalanclng of the bridge circuit will be indicated by the milliammeter 2| and that the direction of the indication of the mlliiammeter 2| will indicate the direction of the displacement. The apparatus of Fig. 2 possesses important advantages over that disclosed in Fig. 1. For example, if the emission of the cathode I1 is in any manner impaired or if the values 01' the electro-motive forces IB and 22 change, these changes or variations in emissivity and voltage will aflect the plate circuits in the bridge equally and to the first order at least. These variations or changes, however, will not be indicated by the milliammeter 2| provided the bridge is balanced as indicated in Fig. 2 01 the drawings. Hence, the electrical balance or zero reference point will remain fixed under varying conditions of plate voltage and emissivity. This is a distinct advantage and improvement over the apparatus of Fig. 1 in that any correction to the meter reading can now be easily made when based upon a fixed reference point; whereas corrections to the meter in the apparatus of Fig. 1 are extremely diflicult because of its uncertain reierence point occasioned by any change in emissivity or voltage. It is thus clear that the apparatus of Fig. 2 provides a very rugged and practicable structure for indicating or measuring displacements.

The apparatus shown in Fig. 3 is a variation of that shown in Fig. 2. In this figure the envelope 25 of the space discharge device is provided at one end thereof with a flexible metal seal 26 sealed to it in any manner known to the prior art, the said seal 28 having secured thereto the tubular metallic member 21 supporting the anode leads 28 and 29. The anode lead 28, as shown, supports the anode 30 and is hermetically sealed to and insulated from the tubular member 21 by means of the insulating plug 3|. The metallic tubular member 21 besides serving to impart movement to the anodes 20 and 22 serves also as a current conductor. The cathode 23, which may be of a thermionic type, is heated to an electron emissive temperature by the battery 34 and is surrounded by a grid which is connected to a suitable source of biasing voltage 38. The space discharge device 25 as in the preceding figure is connected in a bridge circuit to form two branches thereof, the remaining two branches being constituted by the variable resistances 31 and 38. Any convenient source of electro-motive force 29 serves to supply the current for energizing the bridge circuit. The tubular member 21 with the anodes 30 and 32 rigidly secured thereto is moved by any means such as the indicated micrometer 40. An osclllographic element 4! is shown in the bridge circuit to emphasize the fact that periodic or rapid displacements of the small projecting tube may be indicated and recorded by photographic or other methods. The essential difference 01 the apparatus of Fig. 3 over that of Fig. 2 resides in the employment of a grid structure 35 and a biasing battery 36. This arrangement can be made somewhat more sensitive than that of Fig. 2 and balancing of the bridge is somewhat more convenient. The apparatus of Fig. 3, however, also employs the fundamental principle of a change in plate resistance attending the simultaneous movement of the anodes 30 and 32 as a result of the application of a pressure or force to the tubular member 21.

Fig. 4 shows another modification of my apparatus wherein 42 denotes the envelope enclosing the anodes 43, 44 and the thermionic cathode 45 which is heated to an electron emissive temperature by the battery 48. A tubular member 41 supports the anodes 43 and 44 for movement within the envelope and is identical in construction and mounting with that shown in Fig. 3 of the drawings. It is to be clearly understood that the space discharge device of Fig. 4 is identical in construction and operation with that of Fig. 3 except that the grid has been omitted. A diflerential galvanometer 48 with an appropriate balancing resistance 49 is connected in the plate or bridge circuit of the space discharge device, a source of electro-motive force 50 serving to energize the circuit. The windings 5| and 52 of the differential galvanometer are, 01' course, connected so that they annul each other and if the current increases in one coil and decreases in the other, the deflection will be increased due to both causes. The balancing resistance 49 connected across the coil 5| permits the employment of the differential galvanometer as a null instrument. Again, a spring and anvil are schematically represented at 53 to return the tubular member 41 to its initial and desired position of rest upon the removal of any actuating force. Anvils I4 and and a test object 56 suggest one use of the apparatus which is applicable to the modifications previously described and to be described hereinafter. Thus, for example, if the test object 56 is a standard test piece and is introduced between the anvils 54 and 55 as shown the bridge may be balanced so that the galvanometer 48 will read some predetermined value. Then as object 56 is removed and comparison objects are introduced in place thereof, the galvanometer or indicator 48 will read more or less than the value established for the standard test piece, thus showing that the object under test is greater or less in diameter than the standard. The galvanometer 48 is readily calibrated and standardized with the result that the exact amount of departure of any test piece from that of the standard can be easily and quickly determined.

Figs. 5 and 6 illustrate a still further modification of my apparatus which is especially designed for indicating or measuring angular displacements. In this embodiment E1 designates the grid structure surrounding the cathode 58 and as shown consists of a. plurality of conductors i! which are arranged more or less parallel to the electron emissive cathode. The anode or plate structures 50 and BI are also each made of plurality oi conductors which are parallel to those u of the grid and substantially parallel to the oathode and are so arranged that when the conductors of the anode 99 (see Fig. 6) are behind the grid conductors and thus substantially fully shielded from the cathode, the conductors of the anode 9| are substantially fully exposed to the cathode. The envelope of the space discharge device includes an insulating portion 92 to which is sealed a metallic portion 63 having a part thereof terminating at 64 which is flexible and to which twisting or torsional movements may be imparted. Rigidly secured to the part or extension 64 is a tubular metallic member 95 in which the lead-in wires of the anodes 69 and BI are insulatingly supported and hermetically sealed by the insulating plug 69. It is evident that any angular movement of the extension 64 will result in rotary or angular movement of the anodes 99 and BI. A suitable source of electro-motive force 91 serves to bias the grid while the remaining electrodes of the space discharge device are connected in a bridge circuit which includes the variable resistances 68 and 69 and the voltage source I9 for energizing the same. As in the previous embodiments of my invention a suitable indicating device II is provided for detecting any differential voltage in the bridge circuit. The manner of operation of the apparatus in Fig. 5 is believed to be clear. Thus if any torsional movement is imparted to the flexible extension 64 by any means whatsoever rotary movement of the anodes 69 and GI will result. Assuming that the initial positions of the anodes 99 and BI are shown in Fig. 6 if the movement is in the direction indicated by the arrow the conductors of the anode 69 will be exposed more to the cath ode 58 while simultaneously the conductors of the anode BI will be moved progressively from their exposed positions to the cathode to positions where they are shielded by the grid conductors. If the bridge be balanced prior to the initiation of any movement it is clear that the angular displacement of the anode 69 will result in an increased current flow thereto while the current to the anode BI is decreased. Since movement of the anodes causes a variation in the tube resistances with attendant variation of currents in the bridge circuit it is evident that the bridge is now unbalanced and any differential voltage thus caused is indicated by the indicating device II. In this manner it is possible to indicate or meas-- ure angular displacements.

In the modification of Fig. 7, 12 indicates the envelope of the space discharge device to which is sealed the flexible metallic cap I3 for movably mounting the anode 14. The anode as shown is interposed between two cathodes I5 and 16 of the indirectly heated type which are heated to an electron emissive temperature by the resistance units 11 and I8 energized by the battery 19. A small spring and anvil 99 serve to return the anode to its initial and desired position of rest, movement being imparted to the anode, for example, by the test piece 9| which is shown interposed between the anvil 92 and micrometer 93. The space discharge device of Fig. 7 has certain advantages over those previously described in that it is not necessary to insulate two moving lead-in wires for the anodes and as in the previous embodiments is connected in a bridge circuit which includes the variable resistances 94 and 95 and a suitable source of electro-motive force 95. The apparatus depicted in Fig. 7, however, difiers over those previously described in that any differential voltage produced in one diagonal of the bridge circuit is amplified, this being accomplished by connecting parts of the bridge circuit as shown to grid 89 and an indirectly heatedcathode 91 of an amplifier tube 89. This amplifier tube in turn forms one branch of a second or auxiliary bridge circuit, the remaining three branches of which are constituted by the variable resistances 89, 99 and 9| and energized by a suitable source of electro-motive force 92. This scheme insures amplification of any differential voltage in one diagonal of the first bridge circuit which is indicated or recorded by any proper indicating means such as, for example, an oscillograph 93. It is to be emphasized that this arrangement for amplifying any difierential voltage may be employed in any other modification of my invention and that any convenient number of stages may be employed.

A further modification of my invention is shown in Fig. 8 in which the anodes 94 and 95 aremade of a magnetic material which can be magnetized by induction or may be permanent magnets with poles as indicated. The anodes are secured to relatively flexible lead-in wires 99 and 91, a cathode 99, which may be of a thermionic type, being interposed between the said anodes. The electrodes of the space discharge device are connected in a bridge circuit to form two branches thereof, the remaining two branches being formed by the variable resistances 99 and I99 and energized by a suitable source of electromotlve force I9I. As in the previous modifications an indicating device I92 serves to indicate or measure any displacement of the anodes 94 and 95 with respect to the cathode 99. The position or the anodes within the space discharge device is controlled by any suitable external magnetic means such as, for example, a permanent magnet I93. The position or the magnet I93 is controlled by the displacement which it is desired to detect or measure, it being apparent that the magnet may be moved in a desired manner. Thus, Ior example, rotation of the magnet I93 about its axis of symmetry will produce a displacement of the magnetic anodes within the tube in such a way that angular displacements may be readily indicated on the milllammeter or indicating device I92.

Fig. 9 illustrates another form which my apparatus may take. In this embodiment two thermionic cathodes are employed, one of which is designated in general by the numeral I94 and made in two portions I94 and I94", the remaining cathode I95 being similarly constructed and consisting of the parts I95 and I95". The cathodes I94 and I95 are heated to an electron emissive temperature by the respective sources of electro-motlve force I96 and I91. The anode is shown at I99 as a magnetized body and is interposed and mounted for rotation between the cathodes, The space discharge device as in the previous embodiments is connected in a bridge circuit to form two branches thereof, the

remaining two branches of which are constituted by the variable resistances I99 and H9 which are energized by the source of electromotive force III. Any differential voltage in a diagonal of the bridge is indicated by a suitable indicating device H2. As in the modification of Fig. 8 the position of the anode I99 is controlled by any suitable external magnetic means such as, for example, the magnet H9, the position of the said anode with respect to a selected initial position being indicated by the indicating device H2.

One important application of my apparatus is to the measurement of instantaneous fluid pressures such, for example, as the changes in pressure in the cylinders of a Diesel engine when it is in operation. Fluid pressures of any character may be conveniently indicated or measured by the apparatus shown in Fig. 10 of the drawings. In this embodiment Ill designates a vessel of any suitable insulating material apertured at points H and II 6 and transversely of which there extend two flexible partitions III, I I8 which may be of metal to thus provide upper and lower chambers I I9, I20 and an intermediate hermetically sealed chamber I2I. Anodes I22 and I28 are electrically connected to and supported by the respective diaphragms or partitions H1, H8, a thermionic cathode I24 being interposed between the anodes for cooperation therewith. As in many of the preceding em.- bodiments the electrodes within the hermetically sealed chamber I2I are connected to form two branches of a bridge circuit of which the remaining two branches are constituted by the variable resistances I25 and I26. Any suitable indicating device I21 serves to indicate any dilierential voltage in the bridge circuit which is energized by the source of electro-motive i'orce I28. The chambers H9 and I20 serve as receptacles for the fluid, the pressure of which is to control the displacements of the diaphragms I I1 and 8. It is evident that any pressure applied to the diaphragm IlI will cause a displacement thereof thus decreasing the spacing between the anode I22 and the cathode I24 with attendant unbalancing of the bridge circuit as evidenced by an indication of the indicating means I21. The indication of the indicating means I21 will of course be proportional to the displacement of the diaphragm Ill. The diaphragm II! .which is electrically connected in the bridge circuits and to the anode I23 is introduced for two reasons. It serves as a means for balancing out irregularities in emission of the cathode or any voltage variation in the sources of electro-motive force under balanced circuit conditions but is primarily intended to correct for any changes in barometric pressure. As pointed out hereinbefore, it the diaphragm II I is subjected to fluid pressure the displacement of the diaphragm will be proportional to the pressure exerted upon it. It, for example, the apparatus is employed as a fuel gauge in aircraft, operations at high altitudes will reduce the displacement oi. the diaphragm Ill and in order for the indicating device I21 to read the proper pressure-head the anode I23 must be displaced a distance equal to the distance displaced by the anode I22 due to the increased altitude. To insure a displacement of the anode I23 and hence a correct and accurate reading of the indicating device I21 the diaphragm H8 is provided. It is clear that the apparatus of Fig. may be used to indicate differential pressure.

All the novel features of my space discharge devices are claimed in this application, the teatures of novelty of my system or apparatus as a whole, however, being claimed in application Serial Number l14,1l2 filed concurrently herewith.

The invention herein described and claimed may be used and/or manufactured by or for the Government of the United States oi America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. A space discharge device comprising an envelope enclosing at least three electrodes, said electrodes including two independent and immovably mounted cathodes and one movably mounted anode, the said three electrodes being mounted for simultaneous cooperation and being disposed to cause an increase in one anode cathode resistance simultaneously with a decrease in a like resistance, and means operable to impart movement to said anode to cause a change in spacing between said anode and cathodes.

2. A space discharge device comprising an envelope enclosing at least three electrodes, said electrodes including at least one immovably mounted cathode and at least one movably mounted anode, the said three electrodes being mounted for simultaneous cooperation and being disposed to cause an increase in one anode cathode resistance simultaneously with a decrease in a like resistance, and means operable to impart rotational movement to at least one 01. said three electrodes to cause simultaneously thereamong a decrease in electrical resistance between the first and second electrode and an increase in electrical resistance between the first and third electrode.

3. A space discharge device comprising an envelope enclosing at least three electrodes, the said three electrodes being mounted for simultaneous cooperation and being disposed to cause an increase in resistance between two electrodes simultaneously with a decrease in a like resistance, and means operable to impart rotational movement to at least one of said three electrodes to cause simultaneously thereamong a decrease in electrical resistance between the first and second electrodes and an increase in electrical resistance between the first and third electrodes.

4. A space discharge device comprising an envelope enclosing a cathode, grid and two anodes, the said electrodes being mounted for simultaneous cooperation and being disposed to cause an increase in one anode cathode resistance simultaneously with a decrease in a like resistance, and

'means operable to impart rotational movement to said anodes.

5. A space discharge device comprising an envelope enclosing a cathode, grid and two anodes, the said grid and anodes each being formed of a plurality of longitudinally extending conductors with the grid surrounding the cathode, the said electrodes being mounted for simultaneous cooperation and being disposed to cause an increase in one anode cathode resistance simultaneously with a decrease in a like resistance, and means operable to impart rotational movement to said anodes.

6. A space discharge device comprising an envelope enclosing a cathode, grid and two anodes, the said grid and anodes each being formed of a plurality of longitudinally extending conductors which are arranged such that when the conductors of one anode are substantially fully shielded by the grid conductors from the cathode the conductors of the other anode are substantially fully exposed to the cathode, and means operable to impart rotational movement to said anodes to thereby vary the positions of the anode conductors with respect to the grid conductors.

7. A space discharge device comprising an envelope enclosing two independent spaced electron emlssive cathodes and an anode interposed therebetween, the said three electrodes bing mounted for simultaneous cooperation and being disposed to cause an increase in one anode cathode resistance simultaneously with a decrease in a like resistance, and means operable o mpart movemeat to said anode to cause simultaneously a decrease in spacing between the said anode and first cathode and an increase in spacing between the said anode and the second cathode.

8. A space discharge device comprising an envelope including at each end a flexible metallic diaphragm, an anode electrically connected to and supported by each diaphragm and a cathode interposed between said anodes.

9. A space discharge device controllable by fluid pressure, comprising a vessel, a. plurality of flexible partitions extending across said vessel to form therewith end chambers and an intermediate chamber, an anode supported by each of said flexible partitions for movement within said intermediate chamber and a cathode interposed between said anodes, the said end chambers constituting receptacles tor the fluid medium, the pressure 01' which is to control the characteristics of the space discharge device.

10. A space discharge device controllable by fluid pressure, comprising a vessel, a plurality oi flexible partitions extending across said vessel to form therewith a plurality of chambers, an anode supported by each of said flexible partitions for movement within one of said chambers, and a cathode interposed between said anodes, the remaining chamber constituting a receptacle for the fluid medium, the pressure 0! which is to control the characteristics of the space discharge device.

11. A space discharge device controllable by fluid pressure, comprising a vessel, a plurality of partitions extending across said vessel and torming therewith a plurality of chambers one oi. which is hermetically sealed, one of said partitions being flexible, an anode supported by said flexible partition for movement within said hermetically sealed chamber and a cathode cooperating therewith, the remaining chamber constituting a receptacle for the fluid medium, the pressure of which is to control the characteristics oi the space discharge device.

12. A space discharge device controllable by fluid pressure, comprising a vessel, a plurality of partitions extending across said vessel and forming therewith a plurality of chambers, one of which is hermetically sealed, one of said partitions being flexible, an anode and cathode electrode mounted. for cooperation within said hermetically sealed chamber, one of said electrodes being supported by the aforesaid flexible partition, the remaining chamber of said device constituting a receptacle for the fluid medium, the pressure of which is to control the characteristics oi the space discharge device.

ROSS GUNN.

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