US3065372A

US3065372A - Grid controlled gaseous discharge tube

Info

Publication number: US3065372A
Application number: US111874A
Authority: US
Inventors: Paul W Stutsman
Original assignee: Raytheon Co
Current assignee: Raytheon Co
Priority date: 1949-08-23
Filing date: 1949-08-23
Publication date: 1962-11-20
Anticipated expiration: 1979-11-20

Description

Nov. 20, 1962 P. w. STUTSMAN 3,065,3 72

GRID CONTROLLED GASEOUS DISCHARGE TUBE Filed Aug. 23, 1949 3 Sheets-Sheet 1 SIGNAL INPUT P. W. STUTSMAN GRID CONTROLLED GASEOUS DISCHARGE TUBE Nov. 20, 1962 3 Sheets-Sheet 2 Filed Aug. 23, 1949 PELHY COIL d w d M w M M L 6 a 2 w w a PM P 0/ a 1 Q H Q; W J m 6 T 6 mnl 4 flu 52g v. R 1 I II I III 1 1/ 1 I I 2% 5 5525 5 5 a M 3 mum INVENTOR 5'7UT5'MAN ATTORNEY Nov. 20, 1962 P. w. STUTSMAN 3,065,372

GRID CONTROLLED GASEOUS DISCHARGE TUBE Filed Aug. 23, 1949 5 Sheets-Sheet 3 H it 59 *72 73 50 v 1- I? 239 l INVE/V 70/? P1901. W STUTSMfl/V United States Patent ice 3,065,372 GRID CDNTRQLLED GASEOUS DISCHARGE TUBE Paul W. Stutsinan, Needlram, Mass, assignor to Raytheon Company, Lexington, Mass, a corporation of Delaware Filed Aug. 23, 1949, Ser. No. 111,874 12 Claims. (Cl. 313197) This application rel-ates to gaseous discharge devices and more particularly to gaseous discharge devices of the grid control type capable of passing high peak currents.

Prior gas discharge devices, capable of passing relatively large peak currents such as, for example, the OA4G and the 1021, have a useful life that is relatively short due to depletion of electron emissive material from the cathode surface. In order to lengthen the useful life of gas tubes of this general class applicant has provided a cathode comprising a hollow cylinder coated with electron emissive material on its inner surface whereby emissive material sputtered off from the inner wall of the cathode cylinder will usually remain inside the cylinder and redeposit on another part of the wall. The use of this type cathode creates the problem of utilizing this type cathode in a cold cathode gas discharge device which may be triggered by relatively low grid input signals. In applicants device a keep-alive discharge of, for example, 1 milliampere is maintained between the cathode and a keep-alive electrode positioned between the cathode and the anode. Electrons may then be drawn from this keep-alive discharge by a relatively low positive potential on the control grid, the electrons passing through the control grid being accelerated to the anode to initiate firing of the device. For example, a peak grid voltage of 20 volts is suflicient to reliably fire the tube. In addition, by adequately shielding the anode from the cathode a relatively forward large voltage may be applied between the anode and cathode, for example, several hundred volts without firing the tube in the absence of an input signal to the control grid.

In a species of the invention illustrated herein applicant provides means whereby the voltage required to initiate keep-alive discharge is materially lowered. To accomplish this a starter electrode is made in the form of a U-shaped wire which is inserted into the hollow interior of the cathode thus bringing the starter electrode in close proximity with the electron emissive surface of the cathode. Due to the close proximity of the starter electrode to the emissive surface of the cathode a relatively low voltage, for example, 110 volts will initiate a discharge, this discharge being then transferred to the keepalive electrode.

Applicant further provides circuits particularly adapted to utilize the various species of the tubes illustrated herein. Particularly, applicant provides a circuit wherein relaxation oscillations take place in the starter electrode discharge circuit whereby there occurs a resultant diffusion of ions away from the plasma, some toward the keepalive electrode. In this manner the discharge extends to the keep alive electrode whence the keep-alive current increases and more electrons become available upon which the control grid may act to fire the tube.

Thus it may be seen that applicant has provided herein a discharge device having extremely long life due to the sputter conservation construction of the cathode, a relatively low grid firing volt-age due to a keep-alive discharge, said device being incorporated in a subminiature tube which is more sensitive, versatile and rugged, and capable of handling larger peak currents than prior discharge devices of this type.

The particular manner whereby the aforementioned spirally wrapped around anode rod 26. Anode rod 26; is then joined, for example, by welding to a lead-in wire- 3,065,372 Patented Nov. 20, 1962 advantages are accomplished will now be described in detail reference being had to the drawings wherein:

FIG. 1 illustrates a longitudinal cross-sectional view of one species of the discharge device taken along line 11 of FIG. 2;

FIG. 2 illustrates a transverse cross-sectional view of, the species shown in FIG. 1 taken along line 2-2 of FIG. 1;

FIG. 3 illustrates a circuit adapted to utilize the discharge device of FIGS. 1 and 2;

FIG. 4 illustrates a longitudinal cross-sectional view of another species of the discharge device taken along line 4-4 of FIG. 5;

FIG. 5 illustrates a transverse cross-sectional view of the species shown in FIG. 4 taken along line 5-5 of FIG. 4;

FIG. 6 illustrates a circuit adapted to utilize the dis-' the species shown in FIG. 7 taken along line 8-8 of FIG.

7; and

FIG. 9 illustrates a circuit adapted to utilize the discharge device of FIGS. 7 and 8.

Referring now to FIG. 1, there is shown a glass envelope 20 consisting of a tube, one end of which is pressed together as at 21 and through which extenda plurality of lead-in wires. The other end of the glass tube 20 is curved together and contains at its center a mass of glass 22 which is used to seal the envelope aft-er filling of the envelope with the correct gaseous medium. Extending upward from the glass press 21 inside envelope 20 are three

glass tubes

23, 24 and 25 whose axes are all parallel and lying in the same plane and spaced an equal distance apart. The center glass tube '24 extends approximately.

one-third the length of envelope 20. Inside the glass.

tube 24 which is hollow, is an anode rod 26 which ex,

tends from the open end of the glass rod 24 toward the; glass press 21 through a spacer 27 consisting of a wire;

28 which extends through the glass press 21.

The end of the tube 24 which is open, is covered by a cup-shaped grid 29 of wire mesh which may be made of 60 x 60 strands per inch screening using .005 inch nickel wire. The diameter of the cup-shaped grid 29 is slightly larger than the diameter of the glass tube 24 and extends for somewhat more than one diameter of the glass tube over the end of said rod. The bottom of said cupshaped grid 29 is in close proximity but not touching the end of the tube 24 and the anode element 26. Cup

shaped grid 29 is supported by being attached as by welding to a strap 30 at the lip of said cup-shaped grid. The strap 30 extends around the tubes 23- and 25 thereby rigidly supporting the grid 29. The

tubes

23 and 25 are somewhat longer than the tube 24 and extend further into the envelope 20 past the end of tube 24 and the grid 29. A lead-in wire 31 is attached to the strap 30 as by Welding and extends along the side of envelope 20 through the glass press 21.

Surrounding the grid 29 is a second cup-shaped grid 32 which is similar in shape to grid 29 but somewhat larger in diameter. The second grid 32 is supported by a strap 33 placed around the

rods

23 and 25 similar to that supporting grid 29. A lead-in member 34 attached along the

rods

23 and 25 with the result that the grid 32 3 is insulated from the grid 29. The

glass rods

23 and 25 extend slightly beyond the bottom of cup-shaped grid 32.

Extending the length of

rods

23 and 25 which are hollow, are a pair of support rods 35 which are butt welded to lead-in members 36 extending through the glass press 21. The rods 35 have spacers 37 thereon similar to the spacer 27 on anode rod 26. The rods 35 extend out of the open ends of the

glass rods

23 and 25 for a distance equal to approximately the diameter of envelope 20, said rods passing through a mica plate 38. The mica plate 38 is flat and has a shape conforming to the inside contour of the envelope 20 at a section taken at the right angles to the rods 35. The mica support member 38 has a hole therein approximately equal in diameter to and concentric with the inside diameter of the glass anode shielding tube 24. A second mica member 40 similar in shape to the mica member 38 and having a hole therein similar to the hole in mica member 38 and concentric therewith, is positioned parallel with the member 38 and spaced slightly therefrom on the opposite side of member 33 from the grid 32. Between

mica members

38 and 40 is positioned a flat, mesh grid 41 completely covering the holes in

mica members

38 and 40, said grid being attached to a lead-in member 39 which passes down through envelope 20 and press 2 1.

Above mica member 40 is a cathode 42 comprising a metallic cylinder 43 which may be, for example, of nickel whose diameter is somewhat smaller than the diameter of envelope 20 and whose length is somewhat greater than its diameter. The lower end of the cylinder 43 rests on the mica member 40 and has attached thereto an end plate 44 which may be of nickel and which has a hole 45 therein, concentric with the holes in

mica members

38 and 40, and whose diameter is somewhat less than the inside diameter of the rod '24. The upper end of the cylinder 43 is sealed by a second end plate 46. The upper end of the cylinder 40 rests against a mica member 47 similar to member 40 but having no hole therein. Inside the cylinder 43 is wound a wire 48 which contains electron emissive material said wire completely covering the inside of cylinder 43. The lower end of the cathode 42 is supported by the rods 35 which extend through the bottom plate 44 of the cathode 42 just inside the cylinder 43 and wire winding 48 for approximately half the length of the cylinder 43 and are rigidly attached to the end plate 44 and the wire 48.

Referring now to FIG. 3 there is shown a circuit diagram utilizing the species of the device shown in FIGS. 1 and 2. The cathode 42 is connected to ground. The anode is connected to a positive voltage source through load 49. Grid 29 adjacent the anode 26 is connected to B+ through three

series resistors

52, 53 and 54 which may be 3 megohms, 1 megohm, and 100 kilohms respectively. Grid 29 is also connected to source of signals through a DC. blocking condenser 50. The grid 32 is connected to the junction between

resistors

53 and 54. The grid 41 which acts as the keep-alive grid, is connected to the junction between the

resistors

52 and 53.

In the absence of a signal on grid 29 keep-alive current flows from the cathode to the keep-alive grid in the form of a glow discharge. The application of a signal to grid 29 draws electrons from the keep-alive stream of electrons through shielding grid 32 whereupon they are drawn to the anode 26 creating positive ions by collision with gas molecules. These positive ions bombard cathode 42 creating a suflicient supply of electrons for an arc discharge of the tube through the load 49 which may be, for example, a relay coil.

' Referring now to FIGS. 4 and 5, there is shown a modification of the device of 'FIGS. 1 and 2, like elements of the species having like reference numerals. This device issimilar to the species of FIGS. 1 and 2 except that another electrode 55 has been added which acts as a starter electrode. This electrode 55 comprises a piece of wire bent in a U-shape, said U-shape section extending into the cathode through the hole 45 for a distance approximately equal to the diameter of said hole. The legs of the U extend downward through the hole and their ends are bent at right angles outwardly. These bent ends rest on and are firmly attached to a metallic ring 56 surrounding the hole in the mica spacer 49. Lying on top of said metallic ring 56 firmly pushing the ring 56 and the bent ends of the U-shaped member 55 against the mica spacer 40 is another mica spacer 57 similar to the mica spacer 40. The mica spacer 57 is spaced from the cathode 42 by two heads 58 surrounding the rods 35 and positioned between the bottom of the cathode 42 and the mica spacer 57.

The U-shaped member 55 has one of its ends connected to a lead-in member 59 which extends along the side of envelope 2% through the glass press 21 at the bottom of the tube. The U-shaped member 55 does not touch the cathode 42 as it passes through the hole in base member 44. Attached to the top of cathode 42 is a getter support 44 containing getter material in detents therein.

By applying a suitable potential between the member 55 and the cathode 42 a glow discharge current is caused to flow between the cathode 42 and the member 55. Since the U-shaped member 55 extends into the cathode cylinder 43 it is possible to initiate this keep-alive discharge between the cathode 42 and the grid 55, with a relatively low voltage. The discharge between grid 55 and cathode 42 may then be extended to the keep-alive grid 41 thereby creating the keep-alive discharge on which the control grid may act.

Referring now to FIG. 6, there is shown a circuit utilizing this species of the device. The anode circuit is similar to that of FIG. 3, and the cathode 42 is grounded. The starter electrode 55 is connected to B+ through a resistor 63 of, for example, 1 megohm which is bypassed by a condenser 61 of, for example, .002 microfarad thereby maintaining a substantially constant keep-alive voltage between the cathode 42 and grid 55 during firing of the tube. Grid 41 is connected to B-lthrough resistor 62 of, for example, 2 megohms which is bypassed by a condenser 63 of, for example, .002 microfarad to maintain the voltage on the keep-alive grid constant during tube discharge. The grid 32 is connected to B+ through a resistor 64 which may be, for example, .5 megohm by-passed by a 5 micro-microfarad condenser 65. Grid 29 is connected to grid 32 through a grid load resistor 66 of, for example, 3 megohms and to a source of signals through a DC. blocking condenser 50.

The electron emissive wire 43 has been omitted from the inside of the cathode cylinder 43 and electron emissive material is coated directly on the inside of the cylinder 43.

Due to relaxation oscillations in the plasma between the starter electrode and the cathode, which are not damped by the external circuit, ions are diffused from this discharge, some moving toward the keep-alive grid 41 thus these ions by bombardment of gas molecules create electrons which are attracted to the grid 41 thus extending the discharge thereto. A signal applied to grid 29 attracts electrons from the glow discharge between grid 41 and cathode 42 through the grid 32 to the anode 26 thus firing the tube by the action previously described.

Referring now to FIGS. 7 and 8, there is shown a modification of the species described in FIGS. 4 and 5 wherein cup-shaped

grids

29 and 32 have been replaced by fiat grids. In this device the cathode 42,

grids

55 and 41, and

mica spacers

38, 43 and 57 and the supports therefor are similar to those shown in FIGS. 4 and 5.

Below spacer 38 is a grid 67 similar to grid 41 which is attached to lead-in 34 extending through the glass press 21. Below grid 67 is a mica spacer 68 similar to spacer 38. Beneath mica spacer 68 is another grid 69 similar to

grids

41 and 67 and attached to the lead-in member 31. Beneath grid 69 is a mica spacer 70 similar to the mica spacer-

s

33 and 68 but having a somewhat larger hole therein. Beneath the mica spacer 70 is a metallic plate 71 slightly larger in diameter than the hole in spacer 7t) and covering the bottom of said hole. This metallic plate 71 which constitutes the anode, is attached to the anode rod 26 which extends slightly beyond the end of the anode sleeve 24. Beneath the plate 71 is a mica spacer 72 surrounding the anode rod 26 and resting against the end of anode insulating sleeve 24 thus holding the various layers of the aforementioned grid and mica spacer assembly firmly pressed together. Resting on the ends of the

glass tubes

23 and 25 is a mica spacer 73 similar to spacer 72 whose purpose is to maintain the relative position of the various lead-in wires.

By using flat grids rather than basket-shaped grids, the anode and cathode may be spaced somewhat closer together thus decreasing the anode drop during discharge and in addition simplifying the fabrication of the grids.

Referring now to FIG. 9, there is shown a circuit diagram which may be used in conjunction with the species shown in FIGS. 7 and 8. In this circuit the cathode 42 is connected to ground, and the anode circuit is similar to those previously described. The starter electrode 55 is connected to 13+ through a 2 megohm resistor 74, and to ground through a condenser 78 of, for example, .005 microfarad. Grid 41 is connected to grid 69 and to B+ through a resistor 75 of .066 megohm and to ground through a tapped resistor 7 6 which may be, for example, 2 /2 megohms. Grid '67 is connected to the tap on resistor '76 through a grid load resistor 77 of 3 megohms and to a signal input through a DC. blocking condenser 50.

This completes the description of the specific embodimerits illustrated herein. However, modifications will be apparent to persons skilled in the art, for example, the discharge between anode and cathode may be in the form of a glow discharge, rather than an arc discharge, and the relay coil could be put between cathode and ground rather than in the anode circuit. Therefore, applicant does not wish to be limited to the particular details of the modifications described herein except as defined by the appended claims.

What is claimed is:

1. An electron discharge device comprising an envelope containing a gaseous medium, a hollow cathode, an anode positioned outside said cathode and a starter electrode extending inside said cathode, said starter electrode being substantially surrounded by the electron-emissive surface of said cathode.

2. An electron discharge device comprising an envelope containing a gaseous medium, a hollow cathode, an anode positioned outside said cathode coaxial with said cathode and spaced therefrom longitudinally along the axis thereof, and a starter electrode extending inside said cathode, said starter electrode comprising a U-shaped wire and being substantially surrounded by the electronemissive surface of said cathode.

3. An electron discharge device comprising an envelope containing a gaseous medium, a cathode comprising a hollow cylinder having its inner surface substantially entirely coated with electron emissive material, an anode positioned outside said cathode, and a starter electrode extending inside said cathode, said starter electrode comprising a U-shaped wire substantially entirely surrounded by the electron-emissive surface of said cathode.

4. An electron discharge device comprising an envelope containing a gaseous medium, a cathode comprising a cylinder having its inner surface coated with electron emissive material, an anode positioned outside said cathode and surrounded by a sleeve of insulating material, a grid substantially covering the exposed end of said insulating sleeve and shielding said anode, and a keep-alive grid positioned adjacent said cathode.

5. An electron discharge device comprising an envelope containing a gaseous medium, a cathode comprising a cylinder having its inner surface coated with electron emissive material, an anode positioned outside said cathode and surrounded by a sleeve of insulating material, a grid substantially covering the exposed end of said insulating sleeve and shielding said anode, and a starter electrode extending inside said cathode, said starter electrode comprising a U-shaped wire.

6. An electron discharge device comprising an envelope containing a gaseous medium, a hollow cathode, an anode surrounded by a sleeve of insulating material, a first grid substantially covering the end of said insulating sleeve and shielding said anode, a starter electrode extending inside said cathode, and a second grid interposed between said starter electrode and said first grid.

7. An electron discharge device comprising an envelope containing a gaseous medium, a hollow cathode, an anode surrounded by a sleeve of insulating material, a first grid substantially covering the end of said insulating sleeve and shielding said anode, a starter electrode extending inside said cathode, said starter electrode comprising a U shaped Wire, and a second grid interposed between said starter electrode and said first grid.

8. An electron discharge device comprising an envelope containing a gaseous medium, a hollow cathode, an anode surrounded by a sleeve of insulating material, a cup-shaped grid surrounding said insulating sleeve and said anode, a starter electrode extending inside said cathode, said starter electrode comprising a U-shaped wire, and a cup-shaped grid between said starter electrode and said first-mentioned cup-shaped grid.

9. An electron discharge device comprising an envelope containing a gaseous medium, a hollow cathode, an anode surrounded by a sleeve of insulating material, a cup-shaped grid surrounding said insulating sleeve and said anode, a starter electrode extending inside said cathode, said starter electrode comprising a U-shaped wire, and a planar grid between said starter electrode and said cup-shaped grid.

10. An electron discharge device comprising an envelope containing a gaseous medium, a hollow cathode, an anode, a first grid substantially shielding said anode from said cathode, a control grid positioned between said first grid and said anode, and a grid positioned adjacent said cathode and adapted to maintain a keep-alive discharge therewith.

11. A gaseous discharge device comprising a large area main cathode, an electrode adjacent said. main cathode, means biasing said electrode and cathode to maintain a keep alive discharge therebetween, a small area anode opposite said cathode and defining a gap therewith, means biasing said anode relative to said cathode at a potential above the sustaining potential of said gap but insufficient in itself to eifect breakdown of the gap, a control electrode adjacent said anode in said gap, and means biasing said control electrode for effecting the controlled injection of electric carriers from said discharge into said gap.

12. A gaseous discharge device comprising a large area cold cathode, a small area main anode opposite said cathode and defining a main gap therewith, an auxiliary anode in said gap adjacent said cathode and defining a keep alive gap therewith, and a large area control electrode in said main gap adjacent said main anode.

References Cited in the file of this patent UNITED STATES PATENTS 1,877,607 Skellett Sept. 13, 1932 1,939,063 Knowles Dec. 12, 1933 1,986,397 Hund Jan. 1, 1935 2,015,498 Schroter et a1. Sept. 24, 1935 2,435,246 Stutsman Feb. 3, 1948 2,479,274 Simons Aug. 16, 1949 2,481,365 Stutsman Sept. 6, 1949 2,491,425 Stutsman Dec. 13, 1949 2,541,335 Oarne Feb. 13, 1951