US1845310A

US1845310A - Thermionic tube

Info

Publication number: US1845310A
Application number: US157022A
Authority: US
Inventors: Frederick S Mccullough
Original assignee: Individual
Current assignee: Individual
Priority date: 1926-12-27
Filing date: 1926-12-27
Publication date: 1932-02-16
Anticipated expiration: 1949-02-16

Description

Feb. 16, 1932.

F. S. M CULLOUGH THERMIONIC TUBE Filed Dec. 27, 1926 INVENTOR Patented Feb. 16, 1932 UNITED STATES FREDERICK 8. MCGULLOUGH, F EDGEWOOD, PENNSYLVANIA THE'BMIONIG TUBE Application filed December 27, 1926. seriaim. 157,022.

8 According to the present invention, there emitting cathode is provided a tube wherein the anodes are entirely enclosed in a metal shell which forms part of the cathode structure, and wherein there is provided inside the shell an adapted to be maintained at a temperature relatively higher than the temperature of the shell. The invention is particularly applicable to tubes used as rectifier's for alternating current.

The invention may be readily understood by referring to the accompanying drawings in which Figure 1 is a somewhat diagrammatic view illustrating a section through a thermionic tube embodying one form of my invention,

Figure 2 is a somewhat diagrammatic section illustratin another form of the invention and showlng only the electrode structure of the tube,

Fi ure 3 is a view similar to Figure 2, showing still another form of the invention,

Figure 4 is a horizontal section in the plane of line IV-IV of Figure 3,'

Figure 5 is a View somewhat similar to Figure 3 showing another modification,

Figure 6 is a view similar to Figure 2 of still another construction, and Figure 7 is a diagrammatic view showing a circuit wherein a tube embodying the present invention is used.

In the drawings, 2' designates the envelope of a tube having a stem portion 3 at the bottom thereof. Inside the tube is an inverted cup shaped metal cathode 4, whose bottom is closed by a plate 5, and which is supported on wires 6' secured in the stem of the tube. One of the wires 6 is connected to a lead wire 7. Inside the shell or cylinder 4: is a heating element 8 having one end secured to the shell at 9 and having its other end passed through an insulating bushin 10 in the plate 5. The lower end of this filament or heating element 8 is connected to a lead Wire 11 which passes through the stem of the tube.

Inside the shell 4 are two anodes which may be of any suitable shape. They are represented as comprising plates 12 supported on wires. 13 passing through insulated bushmgs 14; in the bottom plate 5. Each of the wires 13 is connected with a lead wire 15 passing through the stem of the tube.

In operation, a relatively low voltage current is connected across the wires 7 and 11 for heating the element 8 to a temperature sufiicient to maintain electron emission. A relatively high potential is applied across the wires 7 and 15. The current applied to the wires 7 and 15 may be the current to be rectified.

There is preferably maintained inside the vessel 2 a residuum of inert gas, preferably helium.

In the operation of the tube the wire 8 is maintained relatively hot while the remainder of the cathode structure, comprising the shell 1 and the plate 5, are relatively cold. Rectification is accomplished in the usual manner, but the efficiency of the tube is very considerably increased over the efliciency of the usual hot cathode tube by reason of the surrounding shell 4, which, being charged similarly to the hot cathode 8 and which constitutes part of the cathode structure, tends to direct the entire electron flow toward the anodes 12.

In the arrangement shown inFi re 2, the structure is generally similar to t at shown in Figure 1, but in this modification the heater wire is enclosed in .an electron emitting cylinder. In this construction, 16 designates the metal shell, 17 the bottom plate, 18 the heater wire and 19 the anodes. Lead wires 20 are provided for the anodes and these wires pass through insulating bushings 21 in 99 the plate 5. Surrounding the filament or heating wire 18 is a heat resisting insulating sleeve 22. Surrounding the sleeve 22, and in intimate contact therewith is an electron emitting cylinder 23. This cylinder may be 5 provided with a coating of any suitable material, such as barium or strontium oxide, for giving high emissitivity.

In the operation of the tube a source of heating current is connected across a wire 24 leadin to the cathode structure, and a wire 25 lea in to one end of the heater 18. The other cm of the heater is connected to the cathode structure, as shown. The current to be rectified is a plied to the anodes 19 and to the wire 24. T e energization of the heator 18 causes the temperature of the cathode 23 to be raised to a point where electron emission is sustained, and rectification 1s effected as in the structure described in connection with Figure 1. The particular advantage of this structure resides in the fact that a relatively large emission surface 1s provided in the tube.

In the construction shown in F1gure 3 the general arrangement is again somewhat similar to that described in connection w1th F gure 1, but in this construction the he ater wire is not in series with the shell'as 1t

1s 1n F1gures

1 and 2. In this figure, 26 designates the metal shell of the cathode structure, 27 the bottom plate and 28 is a metal sleeve centrally located in the shell 26. Th s shell 1s preferably coated on its exterior wlth a substance adapted to secure high electron emission.

Inside this sleeve is a rod of porcelain, quartz, or other refractory 29. Passing through or embedded in'the rod 29 is a looped w1re 30 through which a heating current is adapted to be assed.

Lead wires

31 and 32 are connected to the o posite ends of the heater wire 30, and one of these wires is also connected to the cathode structure at 33.

Inside the shell 26 are two anodes 34 having lead wires 35 connected thereto, these lead wires passing through insulating bushings 36 in the bottom plate 27. In this construction the cathode structure is shown as being .provided with two supporting wires 37,

neither of which constitute lead wires to the electrode. This structure, like that shown in Figures 1 and 2, can be mounted in a vessel having a standard four prong base. In the operation of the tube, heating @urrent is applied to the

wires

31 and 32. One side of the rectifier circuit is connected to the wire 32 and the other sides of the high voltage circuit connect to the anodes 34 through wires 35 d Rectification is effected in the usual manner, and the shell 26 functions to increase the efficiency of the tube, as explained in connection with the structure shown in Figure 1.

The arrangement shown in Fi re 5 is general similar to that shown inT i re 3, but in this construction the heater or the cathode is reversed so that the leads for the heater wire can be entered in the top of the tube instead of through the standard base. In this figure, 40 designates theshell of the cathode structure, is a sleeve centrally located in the shell and having a porcelain or other refractory rod 43 entered therein from the top of the shell. Embedded in the rod 43 is a heater wire 44 to the opposite ends of which areattached lead 41 is the bottom plate, 42 7

wires

45 and 46. These lead wires can ass through the top of the tube. Inside the s ell 40 at opposite sides of the sleeve 42 are anodes 47 having lead wires 48 connected thereto, which pass throu h insulating bushings 48' in the plate 41. The base for a tube having a cathode structure of this nature would nee only three pron s. A wire .49 is connected to the sleeve 42 or connecting the cathode in the rectifier circuit.

In the arran ement shown in Figure 6 the shell of the cat ode-is designated 50, and 51 isthe plate for closing the lower end thereof. Mounted on a post 52 on the plate member 51, so as to be connected to the plate member 51, is a thin metal sleeve 53 whose surface is coated with an electron emitting substance adapted to give a relatively high emission at comparatively low temperatures. A post 54 is secured to the top of the sleeve 53 and the end of this post is connected to the upper end of a small coil spring 55 adapted to yieldably support the element 53. The anodes 56 are arranged in the manner hereinbefore described in connection with the other constructions, and have lead wires 57 attached thereto which pass through insulating bushings 58 in the plate 51.

The construction shown in Figure 6 difiers from all of the other embodiments herein disclosed in that there is provided no resistance heated cathode. The cathode shown in this arrangement is capable of sustaining electron emission when gaseous ionization occurs in the tube upon the application of a high potential across the electrodes.

The tube is used the same as any ordinary rectifier tube. A rectifier circuit, such as is commonly employed in the so called B battery eliminators for radio purposes, is shown in Figure 7. In this figure, 6O designates the envelope of the tube, having

anodes

61 and 62, a metal shell cathode 63, corresponding,

for instance, to the shell 26 of the structure shown in Figure 3, and an indirectly heated cathode element,64 having a resistance heater 65 therein. The diagram in Figure 7 shows iagrammatically the type of tube more fully illustrated in Figure 3. The cathode 64 is connected to one side of a rectifier circuit 66 in which are included choke coils 67 for eliminating the A. G. ripple in the output circuit. The

anodes

61 and 62 are connected to the opposite ends of the secondary winding of a transformer, this secondary winding being designated 68.. The midpoint of the winding 68 is tapped, as indicated at 69, and a wire 70 leads from this tap and provides the other side of the rectifier circuit. Condensers 1 are connected across the

wires

66 and 70 for the purpose of minimizing the A. C. ripple. The primary for the transformer has not been shown, but such primary would be of the usual construction, and would be inbe rectified. A small secondary winding 72 is illustrated for applying a heating current to the heating element 65. y

In all of the embodiments herein illustrated, the tube is provided with a cathode structure comprising a relatively large shell and having a relatively small 'hot or electron emitting cathode entirely contained therein. In each-case the hot cathode or electron emitting cathode is directl connected to the shell so that the shell an the emitting element are always of the same potential, In each of the embodiments, the anodes are contained inside the shell so that a maximum of efii- 15 ciency is obtained. Due to the fact that a 7 hot cathode is em 10 ed and there is a rarified gas in the tube, t e rop across the electrodes is relatively low as compared with some types of rectifier tubes. Furthermore, by causing go the hot cathode and the anodes in the outer cold cathode or shell, the active gas is confined in a small space and flickering between the hot cathode and the anode is prevented. The tube is therefore capable of giving a rela- 25 ti'vely heavy current in the output of the rectifier circuit.

While I have illustrated and described certain specific embodiments of my invention, it will be understood that these are merely an, illustrative of the invention, and that various modifications may be made in the construction and arrangement of parts within the contemplation of my invention and under the scope of'the following claim SI I claim A thermionic tube havin an inverted cup shaped cathode, a' late closmg the lowerend of the cup shape cathode, a central sleeve in the cup shaped cathode adapted to form 40' an electron emitting element, said sleeve being connected to the shell, means projecting into the sleeve from the top of the cathode for heating the sleeve, anodes enclosed within the cathode, said anodes being provided with lead wires which pass through said plate, said lead wires being insulated from the plate. In testimony whereof I have hereunto set my hand. FREDERICK S. MOCULLOUGH.