US1565855A - Vacuum tube - Google Patents

Description

Dec. 15,1925. ,565,855

J. B. JOHNSON VACUUM TUBE Filed Nov. 26. 1920 2 Sheets-Sheet l Patented Dec. l5, 1925.

UNITED STATES PATENT OFFICE.

JOHN s. JOHNSON, or Ennuas'r. New

YORK, ASSIGNOR T0 WESTERN ELECTRIC OOHPANY, INOORPORATED, OF NEW YORK, N. Y., A CORPORATION 0F NEW YORK.

vacuum TUBE.

Application med November 26, 1920. Serial No. 426,505.

To all whom 'it may concern.'

Be it known that I, JOHN B. JOHNSON, a citizen of the United States, residing at Elmhurst, in the county of Queens, State of New York, have invented certain new and useful Improvements in Vacuum Tubes, of which the following is a full, clear, concise, and exact description. l

This invention relates toY vacuum tubes preferably has, as a source of cathode rays,

an electron emitting electrode which may be a filament heated by a battery or other suitable source. A narrow pencil of cathode rays is obtained by having a small aperture in the anode of the tube so that only a narrow beam of the rays passes beyond the anode to a receiving screen which comprises, for example, a coating of calcium tungstate or other fluorescent material, deposited directly on the end of the glass tube. As is well known iii the art, this beam of catlii'ode rays may be deflected electromagnctically or electrostatically in accordance with the wave forms to be studied. The above described electrode arrangement is old in the art and is particularly ada ted to be used in tubes containing a sma amount of gas as described and claimed in an application filed in behalf of Van der Bijl and later identified.

In accordance with this invention, in order to prevent possible areing between the anode and the cathode, the cathode is preferably surrounded by a lass tubular member, one end of which is completely closed and the other end of which is sealed to the anode in such a manner that rays from the cathode can pass through the main part of the evacuated vessel only through the aperture in the anode.

Another phase of this invention relates to the concentration of the cathode rays into a more narrow beam than has been hitherto obtained. To this end the anode comprises a metallic tube having a small diameter compared to the diameter of the containing vessel. 'lhe cathode rays are focused on the end of the tubular anode by means of an apertured plate located between the cathode and anode. This apertured plate Vmay be maintained at any desired potential with respect to the cathode, although in general it maybe found preferable to maintain it at a slightly negative potential to the cathode.

Any suitable means may be employed for dellecting the beam of cathode rays either electromagnetically or eleetrostatically in accordance with the Wave forms to be studied. In one embodiment of this invention hereinafter described, the delecting means comprises plenary members comprising either plates or grids mounted on the stem of the evacuated vessel.

This invention will be better understood by reference to the following detailed description taken in connection with the ac` companying drawings in which Fig. 1 -represents an embodiment of this invention 1n which the cathode ray-beam is deflected electiostatically in one plane and olcctromagnetically in another plane. Fig. 2 is an enlarged view of the electrode structure of the tube illustrated in Fig 1. Fig. 3 illustrates the preferred circuit connections for the tube of Fig. 1. Fig. 4 illustrates a form of grid which may be employed for controlling eleetrostatically the cathode ra beam. Fig. 5 illustrates a modified form o the electrode structure of Fig. 1, and Fig. 6 shows the preferred manner of Obtaining the electrical pnnections for the electrodes of the tube of Referring to Fig. 1, the cathode ray or Braun tube illustrated therein, comprises an elongated evacuated vessel 10 containing a hot cathode 11, a perforated plate electrode 12 and a tubular anode 13. As is well known in the art, a narrow beam ofcathode rays will pass through anode 13 when a suficient source of voltage is connected between the hot cathode and the anode. A beam of cathode rays passing through the tubular anode 13 produces a luminous ot on the coating 14 on the opposite end o the vessel, which coating may be of a suitable fluorescent material such as calcium tungstate deposited directly on the glass and held in place by sodium silicate.

The electrostatic deflection of the cathode ray beam in accordance with the Wave form to be studied, may be produced by impressing the potentials to be studied on the grid shaped structures 15 and 1G for which external connections 17 and 18 are provided. If it is desired to deflect the cathode rayy beam electromagnetically, this may be done by a plurality of coils carrying the current to be studied such as coils 2() and 2l which are preferably located adjacent a constricted portion of the tube. It is to be understood, of course, that any desired number of deflecting grids or coils may be employed.

Fig. 2 is an enlarged view of the electrode structure of tube 10 and shows the cathode 11 in close proximity to the apertured disc 12, the aperture in which is in alignment with the axis of the tubular anode 13. Cathode 11 is preferably surrounded by a glass housing 23 in order to prevent possible arcing between the anode and cathode. lt has-been found in the olwration of cathode ray tubes, wherein the anode is in such close proximity lo the cathode that the distance between the two electrodes is less than the mean free path of an electron, that positive ionization and consequently an arcing effect between the two electrodes may still be produced by electrons which take such a circuitous route between thetWo electrodesv that the distance traveled exceeds the mean free path. rl`he glass housing 23 therefore prevents stray electrons from cathode 11 taking a eireuitous route to the anode 13 and therefore insures that all electrons arriving at the anode travel along agpath considerably less than the mean free path of the electron. As shown in Fig. 2 the glass housing 23 Yis completely closed-at the lower end which is fastened to the stem 25 of evacuated vessel 10. The otherend of the glass housing 23 is sealed to the walls of the tubular anode 13. The cathode ray beam to the fluorescent screen 14 must, therefore, pass through the aperture in anode 13 and cannot arrive at screen 1-1- by any other route.

For a pressure of mercury vapor of one or two microns the mean free path of an electron is about ten inches.

The actual distance between the cathode 11 and anode 13 will depend, to a considerable degree,'upon the pressure Within the evacuated vessel. As described and claimed in a co ending U. S. ap lication to Van der Bijl, gerial No. 402,52?, filed August 10, 1.920, the pressure in this type of cathode u ray tube is preferably of the order vof from one to two microns of mercury and the gas creating this pressure should be preferably entirely mercury or some other inert gas which will not attack the filament. With tip ofthe cathode.

such a pressure it has been foundpreferable to locate the anode .O7

inches away from the Although the size of the o ening of the tubular anode may be varied cepending upon the size of the cathode ray beamdesired, best results' have been obtained with a tube having an aperture .020 inches in diameter. The aperture in the disc 12, in this embodiment of the invention, is shown as being of ap roximately the same size as -the external diameter of the anode. lVith such an arrangement the spot of light on the receiving screen can be adjusted to a diameter of .03 inches or less.

.'lhe preferred circuit arrangement for the tube ot' Fig. 1, is shown in Fig. 3, in which a battery 2Gis provided for heating the lilainent, battery 27 for maintaining disc 12 at a positive potential with respect to cathode ll, and a high voltage battery 28 for producing the desired potential difference bctween` the' anode and cathode. The potentials to be sl udied may be impressed on grids 15 and l0 by means of lead-in wires 20 and 30 if electrostatic deflection is desired, while 4the currents to be studied may be impressed on the coils 20 and 2]. by wires 3l and 3:2 providing electromagnetic deflection of the beam is desired. In the operation of tube 10 'it has been found pref rable to connect one ofthe grids 16 directly to anode 13 while connecting the other grid to anode 13 through a path containing a high resistance 3-1 which may be of the order of magnitude of 500,000 ohms. This manner o't conneciing the two grids to the anode 13 is for the purpose of preventing an accumulation of static charges on the grids, byallowing the charges to leak oil' through the connections to the anode. Resistance 34.- should be/o'f such a value that the connections to the anode do not materially short circuit the source of potential connected to the grids through leads 29 and 3 Y i The deflecting plates l5 and 10 are preferably of grid-like structure as shown in Fig. el, in oider that the eddy currents produced therein will be negligible, particular- `1y in the case Where magnetic coils are einployed outside the tube.

Although it is stated above that the preferable gas pressure in tube 10 was of the order of'one ortwo microns of mercury, it is to be understood that the amount of gas pressure preferable in any particular case will depend to a certain extent upon the ten'iperature of the hot cathode 11 and upon the potential difference applied between the anode and cathode. The pressure of one or two microns of mercury has been found quite satisfactory when a filament consisting of platinum Wire coated with earth oxides was employed with the heating battery ot two volts producing a heating current of 1.3 amperes, While the voltage applied between the anode and cathode varied from 200 to 1000 volts or even higher.

All the electrons flowing from the cathode through the anode to the i'luorescent screen must ultimately return to the anode. In the absence of any special means the electrons simply drift back from the screen through the gas to the grids`15 and 16 and then to the anode or to the anode directly. This return to the anode may be facilitated by employing an electrode 37 adjacent the screen and having the electrode by a suitable external connection 38 connected to the anode. The electrons flowing to the screen 14 will then return to the anode 13 via electrode 37 instead of drifting back through the gas. This arrangement therefore reduces the s ace charge of the tube and consequently aids in the production of a narrow beam of rays through the anode to the screen. Electrode 37 may take a variety of iorms a1- tliough, as shawn, a single turn of wire` 1nside the tube will generally to found quite satisfactory.

In the electrode structure shown in Fig. 5, the arrangement of the cathode 40, anode 41 and disc 42 is similar to the arrangement of Fig. l, except that the aperture in disc 42 has been slightly enlarged and anode 41 has its lower end slightly projecting into the aperture of the disc 42. This relation of anode 41 and disc 42 is preferable if disc 42 is to be maintained at a slightly negativeV potential with respect tn the cathode.

The arrangement of Fig. 5, also differs from that of Fig. l, in that two sets of planary members are provided for defiecting the cathode ray beam in two planes at right angles to each other. The parallel grid members 43 and 44 may be employed for deecting the beam in one plane while the parallel plates 45 and 46 may be employed for defleeting the beam in a plane at right angles to the first plane. As shown in the drawing, the two grids and the two plates are supported by an extension of the lass housing 48 which in turn is supported rom the stem 49 of the vessel.

The lower end of the evacuated vessel 50 is shown supported by a base 51 of the type employed quite generally for aiidions. The four terminal lugs 52, 53, 54 and 55 project below the base 51 and are adapted to coopcrate with a suitable socket for making electrical connections. Lugs 52 and 54 are connected by the internal lead wires 57 and 58 to the two terminals of cathode 40. Lug 53 by lead-in wire 59 is connected by wire 70 to anode 41 and plate 46 and by wire 71 to grid 43. Lug 55 by lead-in wire 61 s connected'to the apertured dise 42. Grid 44 by lead wire 63 is connected to a suitable external connection G4 set in the ring 66 of insulating material, such as hard rubber, which rests on thetop of base 51. A second external connection 65 set in the ring 66 by lead wire 68 is connected to the late 45. The defieetion of the lcathode ray cam by grids y43 and 44 may therefore be made by connecting the source of voltage between lug 5 3 and the external connection 64. Deflection by plates 45 and 46 may be roduced by connecting the source of voltageictween lug 53 and the external connection 65. Although one set of deflecting members is shown as comprising two grids 43 and 44, and the other set is shown as comprising two plates 45 and 46, it is obvious that two sets of .plates may be employed or two sets of grids, in case such an arrangement would be desirable.

Fig. 6 illustrates the preferred manner of making .the electrical connections for vthe tube of Fig. 5. A battery 70 is connected for heating the cathode 40, the battery 71 is connected for applying negative potential to the disc electrode 42 and the battery 72 is connected for applying the proper voltage between the anode 41 and the cathode. It is to be noted that battery 71 is so poled that the disc electrode 42 is maintained at a constant negative potential with respect to the cathode. This negative potential on the disc electrode is desirable especially in cases where the anode projects slightly into the aperture of the disc. A resistance element 73 is included in series with battery 72 for the purposes of preventing the short-circuiting of battery 72 in case areing should occur between the anode and the cathode. This resistance 73, in one'case, had a value of the order of 10,000 ohms. Deiecting plate 45 is connected through a high resistance 74 to the anode and delecting grid 44 is connected to the anode through a similar high resistance 75. The purpose of these high resistances has already been described in connection:

with Fig. 3.

It is to be understood that this invention, in certain aspects, is not limited in its use to vacuum tubes of the Braun type. It is also to be understood that the particular electrode structure above described may be variously employed without departing, in any wise, from the spirit of this invention as defined in the appended claims.

What is claimed is:

1. In an electric system, a vacuum tube comprising an enclosing vvessel` containing a cathode, an anode having an aperture, means for establishing an electron stream between said cathode and anode, fluorescent means within said vessel activated by electrons passing through the aperture in said anode, and means to intercept electrons projected from said cathode in paths exterior of the direct path between said cathode and anode.-

2. In an electric system, a vacuum tube comprising an evacuated vessel, a cathode,'

- a tube of insulating material surrounding said cathode, said anode being sealed in one end thereof, whereby electrons projected in paths exterior of the direct path between said cathode and anode are intercepted by said tube.

3. In an electric system, a vacuum tube comprising an evacuated vessel, a cathode, an anode, said anode being located from sald cathode a distance less than the mean free path of an electron, and means for preventing any electrons arriving at said anode from traveling over a path from Dsaid cathode greater than the mean free path of an electron.

4. A vacuum tube comprising an enclosing vessel having a stem, a cathode supported from said stem, a tube of insulating material surrounding` said cathode, a tubular anode sealed in one end of said tubular member, and a fluorescent screen adapted to be activated by electrons projected from said cathode through said anode.

5. A vacuum tube comprising an evacuated vessel, a cathode, an anode, a press, and a tubular member of insulating material mounted upon said press and supporting said anode, said cathode being located within said tubular member. y

6. A vacuum tube comprising an evacuated vessel containing a press, an anode, a cathode. and a hollow member of insulating material closed at one end and supported from said press, said anode being supported in an aperture in the opposite end ,of said member.

7. A vacuum tube comprising an evacuated vessel. a cathode, a press, a tubular mem` ber of insulating material mounted on said press and surrounding said cathode, and a disc electrode cooperating with said cathode and surrounded by said tubular-member.

8. A vacuum tube comprising an anode, a cathode, a control electrode on the opposite side of said anode from said cathode, and an internal electrical connection between said control electrode and said anode.

9. A vacuum tube comprising an anode, a cathode, a plurality of control electrodes, and an internal electrical connection between said control electrodes and said anode.

10. A vacuum tube comprising an anode, a cathode, a control electrode located beyond said anode with respect to said cathode and a connection of high impedance-between said control electrode and said anode.

11. A vacuum tube comprising an anode, 'a cathode, a control electrode located beyond said anode with respect to said cathode, and aconnection of high resistance between said control electrode and said lanode.

a thermiomc cathode,

aperture, and an electrical connection be i tween sa1d controlelectrode and one of said other electrodes.

13. A vacuum tube comprising a cathode,

a tubular anode, an a ertured electrode be` tween said anode an cathode, one end of said tubular anode being almost in contact with said apertured electrode, and means for maintaining said a ertured electrode at a different potential t an said anode with respect of said cathode.

14. A vacuum tube comprising a cathode, an apertured anode, an apertured late between said anode and cathode, sald anode being almost but not quite in contact with said plate, and means for maintaining said plate at a different potential than said anode with respect to said cathode.

15. A vacuum tube comprising an anode, a cathode, means for producing a stream of cathode rays from said cathode, fluorescent means within said tube to be activated by said cathode rays, an apertured electrode between said anode and said cathode, and means for maintaining said apertured electrode at a diierent potential than said anode with respect to said cathode.

16. A vacuum tube com rising an anode, a cathode, means for deecting a narrow beam of cathode rays from said cathode, means within said tube for rendering said deection visible, an apertured electrode located between said anode and said cathode, and means for maintaining said apertured electrode at a different potential than said anode with respect to said cathode.

17. A vacuum tube comprising an evacuated vessel containing a tubular member of insulating material, said tubular member being of small diameter as compared to the diameter of said evacuated vessel, a cathode enclosed in said tube, an vanode fastened at one end of-said tube, and an apertured elec.- trode between(s said anode and cathode.

18. A vacuum tube comprising an evacuated vessel having a stern, a tubular member of insulating material supported thereby, a cathode enclosed in said member, a tubular anode fastened at one end of said member, said anode having an internal diameter approximately the size of the cathode ray beam desired from said cathode.

19. A vacuum tube comprising an evacuated vessel containing a cathodea tubular anode, means for producing a stream yot cathode rays from said cathode, and means for deilecting said stream, said tubular anode having an internal diameter throughout its length approximately the size of the cathode ray beam desired.

20. A vacuum tube comprising an'evaeuated vessel containing a cathode, a tubular anode, a screen for receiving rays from said cathode passing through said tubular anode,

said tubular anode having an internal diameter throughout its length of approximately the samesizeas the size o the cathode ray beam directed toward said screen.

21. A vacuum tube comprising an evacuated vessel containing a stem, a cathode, an anode supported by said stem, and a lurality of parallel plates supported by sai stem.

22. A Vacuum tube comprising an evacuated vessel containing a stem, a cathode, an anode, a plurality of planary members supported by said stem, said members being located on that side of said anode remote from said cathode, and means or impressing a difference of potential between said planary members.

23. A vacuum tube comprisin a stem, an anode, a cathode, and a contro electrode sup orted by said stem, 'said control electro e being located beyond said anode with respect to said cathode, and having a face directed parallel to a line passing between the central portions of said anode and said cathode.

24. A vacuum tube comprising an anode, a cathode, a plurality of control electrodes located beyond said anode WithA respect to said cathode, a common support for said anode, cathode and control electrode, and

means for -variable potentials 'y a screen for intercepting' a beam of ra sfrom said cathode, means for deflecting said beam, and an additional electrode remote from said means and adjacent said screen.

27. A Braun tube comprising a cathode, an anode, a screen for intercepting. a beam of 'rays from said cathode, means for deiecting said beam, and meansfor preventing the electrons comprising said beam after striking said screen from drifting back to said anode or deflecting means through the gas in said tube.A

28. A vacuum tube comprisin a cathode, an anode, a screen for interceptlng a beam of rays from said cathode, means for deecting said beam, and means comprising an electrode remote from said first means and adjacent said screen for reducing the space charge in said tube.

In witness whereof, I hereunto subscribe by name this 19th day of November A. D.,

JOHN B. JOHNSON.

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