US1486237A - Thermionic device - Google Patents

Description

March 11 1924,

J. A. FLEMING THERMIONIC DEVICE Filed Nov. e, 1919 2 Sheets-Sheet 1 Mmh 11, 1924 I 1,486,237

J. A. FLEMING THERMIONIC DEVICE Filed Nov. 6, 1919 2 Sheets-Sheet 2 Patented lllar. ll, acre.

entree stares than PAFE

3cm: AMQROSE FLEMING, OF LONDON, ENGLAND, ASSIGNOB TO THE RADIO CORPORA- TION OF MERICA, OF NEW YORK, N. A CORPORATION OF DELAWARE- THEBMIGNEC DEVICE.-

Appllcation filed November 6, 1919. Serial Flo. 836,029.

To all whom it, may concern:

Be it known that I, JOHN AMBROSE FLEM- ING, a subject of the King of Great Britain, residing at University College, Gower e Street, London, England, have invented a new and useful'lmprovement in T hermionic Devices, of which the following is a specification.

My invention relates to improvements in m the construction of thermionic devices such as are frequently used as detectors of electric oscillations, and to the mode of using the same.

The invention is illustrated by the accom- 1e panying drawings, Figure 1 of which is a diagram showing in its simplest form a thermionic device constructed in accordance with myinvention, Figure 2 shows a preferred form of construction, Figure 3 1s a section'through the filament and adjacent parts, Figure 4 is a section of an alternative construction, Figure 5 is a diagram showing the-arrangement when my device or valve is used as a receiver of wireless waves, Figure as 6 is a diagram of a modified arrangement and Figure 7 is a diagram showing two valves connected in parallel. In Figure 1, A represents a vacuous bulb; in this bulb are a filament B, a plate ac G and two other plates D. The filament B may be of tungsten or tantalum or other suitable metal, or else of carbon, and its ends are connected to a battery E by which it can be rendered incandescent. Seeing as that the plate C may be considered as collecting the electrons emitted from the fila-' ment, 1 will call it a collecting plate. 'lo

drawthe electrons thereto it is connected to the positive end of the filament through a to current responsive device F which may be an indicating instrument such as a galvanometer, or may be a relay adapted to close a circuit or perform some other useful function.

When the filament is rendered. incandes-\ cent negative electricity escapes from the filament and passes across the vacuous space into the plate C and then returns by the external circuit passing through the instrument F to the positive terminal of the filament. This current is called the thermionic current. a

If new the plates D, which I will call potential plates, are connected to some source of h gh or low frequency alternating or even direct potential this variation of potential will cause a sudden and marked diminution in the thermionic current, which can be observed in the instrument F or can be utilized to actuate a relay.

Figure 2 shows a preferred form of valve constructed in accordance with this invention. A is a glass bulb which is hi hly exhausted of its air by processes we] known and used by all incandescent lamp and thermionic valve manufacturers. Into the neck of the bulb is sealed a glass tube G closed at its inner end through which are sealed six (platinum wires to which are'connected insi e the bulb six nickel wires between two of which is stretched a straight filament B of tungsten, tantalum, carbon, or other suitable material, while the other four serve as supports to a pair of collecting plates C and a second pairof plates D. lhese plates are in the form of segments of cylinders and have their convex sides towards the filament. It is desirablethat the plates should be placed close to the filament with their nearest surfaces about 2 to 3 millimetres or so and all at approximately equal distances. The plates are made of sheet metal preferably nickel or platinoid or any other not too fusible metal not easily oxidized.

Since the filament tends to expand then incandescent means, such as a spring H, should be provided for keeping it from becoming so slack or bent as to touch any of the plates.

It is not necessary to have a single straight filament for the incandescent electrode. lt may bein the usual loop form but in any case it must be so held and retained that in no case does it touch the curved metal anodes or come nearer to any one of them.

The ends of the latinum leading-in wires are connected insi e the tube G to copper wires which are insulated by having slipped over them thin glass tubes I.

The parts B, C, l), G, H and L are as.- sembledtogether and the tube G is then sealed intothe bulb which is then exhausted of its air! in the usual manner for makinf har valves.- I desire it to be understoo however, that this particular mode of holdthe plates and cut on a stem does not to a necessary part oiimy invention but that any other convenient method may he adopted. For instance, the four curyed plates may he carried on platinum w res sealed through the sides of a cylindrical bulb, and the filament to be rendered mcandescent y pass down the axis of the bulb as shown in 4. r

5 shows diagrammatically one of my valves connected up for use in the detection of wireless waves incident upon an aerial K coupled to an oscillatory circuit L which is connected tothe plates D. The incidence of the waves on the aerial will produce a difl'erence of potential between the two plates 11) and this will cause the therminected to a relay ll/l adapted to close the cironto current through the device]? to dilhis device F may he a galvanometer, but preferably employ a telephone magneto receiver of which the coil is connected directly between the collecting plates G and the positive and of the filament, as illustrated, or in any other suitable manner, such as by means of a coupling transformer. The sudden decrease in the thermionic current due to the incidence of the waves will cause a sound to he heard in the telephone. If the waves used are damped trains then as long as they fall on the aerial a continuous sound will he heard in the telephone and this sound can he cut up into Morse code signals by a key in the distant transmitter circuit. The device l? may also a he. a relay adapted .to close a local circuit when a difference of potential is impressed upon the plates l). relay may Work a Morse inker or other telegraphic recorder or ring an electric hell, light an electric lamp or start an electric motor so as to move some mechanism.

In the modified arrangement shown in Figure 6 the collecting plates C, C, are concuit of a battery N and an instrument G such as a call bell, lamp or motor. The

plates l), l), are connected to opposite ends, of a high resistance Q, inserted with a high.

roltae battery R in the circuit of the plate S t filament T ofa three-electrode valve U the grid V and filament T of which are connected in the well known manner which needs no description here to an oscillatory circuit L coupled to an aerial K. A small current from the battery it normally flows through resistance Q and from plate S through the vacuum to filament 'l and this creates between the plates D, D a difierence of potential sufficiently great to reduce the thermionic current from the filament B to the collecting plates G, C. 'Wnen, however,

wares fall on the aerial K they give rise to a negative charge on the grid V and this means? the plates D, l), is therefore reduced and the thermionic current through relay M 15 increased suficiently to close the local circuit through the instrument 0. In cases in which the available variation of potential or current is very small the necessary dit ference between the plates D511), can he purposes, for example, to steer a boat or acroplaneelectrically by wireless waves sent from a distance.

l have found that the above described thermionic instrument responds not only to high it'requency alternating but also to direct or unidirectional potential difl'erences applied tot-he potential plates D, l), and that such low fi'equency potential differences also efiect a reduction in the thermionic current passing to the collecting plates G, C, from. the filament. Hence there is-a variety of uses of such a detector in alternating current measurements. For example, I can utilize the device as a detector in an alternating current titheatstone bridge either by direct connection across the arms of the bridge or by coupling to a diagonal coil,

connected across the arms of the bridge.

It is clear also that a number of these detectors can be operated in parel, the

thermionic currents ofa number of bulbs passing through one and the same current detecting instrument and the potential plates of all bulbs being influenced simultaneously by the same source of alternating potential as shown in Figure 7.

When using 'the above described thermionic instrument as a detector in wireless telegraphy, with an air core transformer'in the receiv" circuit by using a suitably wound trans ormer I can increase the potential difierence applied to these plates in a well-lmown manner.

lin the same way when employing low fi'equency potential difierences I can step them up by interposing a suitably wound low frequency transformer with its high tension terminals connected to the potential plates.

I. A thermionic device comprising a.

vacuous bulb, a filament, a pair sf collecting plates and a pair of potential plates, the four plates heingfarranged substantially symmetrical to and closely surrounding the filament. a 1

- 2. .d. thermionicdevice comprising. a

access? arranged. symmetrically around the filament and in close proximity thereto, a current responsive device connected to one pair of opposite plates and to the filament and means for appl ing a difference of potential with said circuit.

to the plates 0 the other pair.

4. The combination of a thermionic device comprising avacuous bulb, a filament, a pair of collecting plates and a pair of potential plates, the four plates bemg arranged substantially symmetrical around andin close proximltyto thefilament with a receiving'circuit connected to the potential plates, a relay connected to the collecting plates and to the filament and a calling device cooperating with said relay.

5. The combination of a vacuous vessel, an electron emitting filament therein, a battery having its two poles connected to the two ends of the filament, a pair of potential plates within the vessel, means for applying a variable potential to these plates,

an electron collecting plate also within the vessel, a circuit connected between the collecting plate and one end of the filament and a current responsive device cooperating with said circuit. 7

6. The combination of a vacuous vessel, an electron emitting filament therein a battery having its two poles connected to the two ends of the filament, a pair of potential plates within the vessel, means for applying a variable potential to. these plates, an electron collecting'plate also within the vessel, a circuit connected between the collecting plate and the positive end of the filament and a current responsive device cooperating 7. The combination of a vacuous vessel, an electron emitting filament therein, a battery having its two'poles connected to the two ends of the filament, a pair of potential plates within the vessel, means for applying a variable potential to these plates, a pair ct electron collecting plates also within the vessel, a circuit connected between the collecting plates and one end of the filament and a current responsive device cooperating with said circuit. I

8. The combination of a vacuous vessel, an electron emitting filament therein, a battery having its two poles connected tothe two ends of the filament, a pair of potential plates within the vessel, means for applying a variable potential to these plates, a pair of electron collecting plates also within the vessel, a circuit connected between the collecting plates and the positive end of the filament and a current responsive device cooperating with said circuit.

9. The combination of a vacuous vessel, an electron emitting filament therein, a bat; tery havin its two poles connected to the two ends 0 the filament, a pair of potential plates arranged within the vessel opposite one another on either side of the filament, a pair of electron collecting plates arranged w1tl1in the vessel 0 osite one another on either side of they. ament, a circuit connected between the collecting plates and the positive end of the filament and a current responsive device cooperating with said circuit.

10. The combination of a vacuous vessel, an electron emitting filament therein, a battery havm its two poles connected to the two ends 0 the filament, a pair of potential an electron emitting filament therein, a battery havin its two poles connected to the two ends 0 the filament, an electron collecting plate within the vessel, a current respon- 'sive device connected between the collecting plate and the positive end of the filament, a pair of potential plates within the vessel, one on either side of the filament, an aerial, an oscillatory circuit coupled to the aerial and connections between the circuit and the potential plates.

12. Thecombination of a vacuous vessel, an electron emitting filament therein, a battery having its two poles connected to the two ends of the filament, .an electron pair of collectingv plates, one on each side of the sive device connected between the collecting plates and the positive end of the filament, a pair of potential plates one on each side of the filament withln the vessel, an aerial, an oscillatory circuit coupled to the aerial and connections between the circuit and the potential plates.

13. The combination of a vacuous vessel, a filament therein, a battery having its two poles ponnected to the two ends of thefilament, a collecting plate within the vessel, a relay connected between the collecting late and the positive end of the filament, a coal circuit adapted to be actuated by the relay, a pair of potential lates within the; vessel, one on either side 0 the filament, an aerial, an oscillatory circuit cou'led to the-aerial and connections between t e circuit and the potential plates.

filament within the vessel, a current vrespon-r M. The combination of a vacuous vessel, a filament therein, a hattery having its two poles connected to the two ends oi the filawent, a pair of collecting plates, one on either side of the filament Within the vessel, a'cnr ent' responsive device cdnnected hetween the collecting plates and the positive end of the-filament, a pair of potential plates, one on either side of the filament Within the vessel, an aerial, an oscillatory circuit'coupled to the aerial and an amplitying device connected to the potential plates and to the circuit.

- 15. The combination of a vacnoas vessel,-

a filament therein, a battery having its two poles connected to the two ends of the filament, a pair of collecting plates, one on either side of the filament within the vessel,

lay, a pair of potential plates, one on each side of the filament wit the vessel, a re sistance havin one end connected to each of thepotentia plates, an aerial, an oscillatory circuit coupled to the aerial, a threeelectrode valve having its grid and filament.

connected to the circuit and its anode connected to one end of the resistance and a hattery connected hetaveen the filament of the three-electrode valve and the other end of the resistance.

as my invention l have signed my name this 15th day of Uctoher, 1919.

JQHN AMJRQS E FLEMING.

In testimony that l claim the foregoing V

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