US1746164A - Method of exhausting vacuum tubes - Google Patents

Description

Feb. 4, 1930. o, w, PIK 1,746,164

METHOD OF EXHAUSTING VACUUM TUBES Filed Jan. 21. 1928 HEA77/V6 CURRENT- Inventor:

Otis W. Pike by MW His Attorney.

Patented Feb. 4, 1930 UNITED STATES PATENT OFFICE OTIS W. PIKE, OF SCHENECTADY, NEW YORK, ASSIGNOB TO GENERAL ELECTRIC' COMPANY, ACORPORATION OF NEW YORK 2 METHOD OF EXHAUSTING VACUUM TUBES Application filed January 21, 1928. Serial No. 248,581.

' The present invention relates to electric discharge devices and more particularly to a method forexhau'sting such devices.

While heretofore various methods have been employed to heat the electrodes of a discharge device during evacuation and thus cause removal of occluded gases, none of the former methods have provided means whereby a circulating current of appreciably greater value than that encountered in the usual or normal operation of the tube might be passed between the electrodes to heat the various parts of the tube during the evacuation process.

According to the present invention, I heat 1 the electrodes, leads and seals by a high frequency circulating current which has a wave length of the order of five meters and is substantially independent of the current due to electron emission from the cathode. At this short wave length the interelectrode capacity permits the passage of a circulating current between the electrodes which is at least twice the value of currents normally encountered in the operation of the discharge device. In this manner the electrodes and especially the leading-in wires and seals may be heated during the exhaust to temperatures far in excess of the temperatures ordinarily encoun- 80 tered in the operation of the dischargedevice and as a result an unusually high degree of vacuum may be initially secured in the discharge device and this degree of vacuum may be maintained even under severe con- 85 ditions of use, such, for instance, as are obtained when using the tube at the shorter wave lengths.

In carrying the present invention into effect, I connect the tube to be evacuated to a diffusion or other suitable exhaust pump and at the same time oscillate the tube by means of a short wave oscillatory circuit of such type and adjustment that the high frequency currents will be much larger than those normally encountered in practice.

.electrode 3 and filamentary cathode 4. A

diffusion exhaust pump 5 is connected to receptacle 1 through a glass tube 6 which passes through the usual liquid air trap 7. A short wave, oscillating, resonant circuit is associated with the discharge device and comprises grid 3, anode 2, inductances 8, 9, an ammeter 10, and alarge condenser or capacity unit 11. Radio frequency chokes 12, 13, 14 and 15 are inserted in the electrode leads. A source of comparatively low voltage alternating current is connected to a transformer 16 which supplies heating current to cathode 4, while a voltage of 500 volts or greater may be connected to the anode lead and ground. A grid leak resistor 17 connects the grid leading-in wire with the secondary winding of the transformer 16.

As thus arranged the oscillating circuit will be resonant at a frequency of about 60,- 000 kilocycles and will carry a current of very low power factor; With the pump 5 in operation, the circulating current flowing in the oscillatory circuit will vary from 5 amperes upwardly, depending on the size of the discharge device employed. The interelectrode capacity permits the use of circulating currents of the value and frequency indicated although currents of similar value and having relatively low frequencies could not be employed at voltages which would not endanger the tube.

The circulating current in the oscillatory circuit depends upon the capacity between the grid and anode and the high frequency voltage and is substantially independent of filament emission. For example, the circulating current may have a value of about 30 amperes while the electron current at the same time might not-have a value greater than one ampere. Variations in the filament emission above normal operating value will not cause any appreciable change in the circulating current in the oscillatory circuit. The use of this large'circulating current effectively removes all occluded gas from the various parts of the tube and permits the establishment of a very high degree of vacuum.

d What I claim as new and desire to secure by Letters Patent of the United States, is,- 1. The method of exhausting an electric discharge device containing a pair of electrodes, which comprises connecting said pair of electrodes in a circuit resonant at a certain frequency and supplying current of that frequency to said circuit while the discharge device is connected to an evacuating 2. The method of exhausting an electric discharge device comprising a grid, anode and a filamentary electrode adapted to be heated to incandescence, which comprises energizing the filament coupling the grid and anode together to form a high frequency oscillatory circuit and supplying current to said circuit, the value of said current being dependent upon the capacity between the grid and anode.

3. The method of exhausting an electric I discharge device comprising a grid, anode and the grid and anode, then causingan alternatin space current of high frequency to flow tween the grid and anode while the device is being evacuated thereby to heat the electrodes and remove the occluded ases, 1

have hereunto set of January, 1928. OTIS W. PIKE.

a filamentary electrode adapted to be heated to incandescence, whichcomprises rendering the filament electronically active, coupling the grid and anode together to form a high frequency oscillatorycircuit and supplying current to said circuit, the value of said current being substantially independent of the electron current in the device,

4, The method of exhausting an electric discharge device comprising a grid, anode and a filamentary electrode adapted to be heated to incandescence, which comprises causing the filament to emit electrons, coupling the grid and'anode together to form a high frequency oscillatory circuit and supplying current to said circuit, the value of said current being substantially independent of the current inthe device due to filament emission but dependent upon the capacity between the grid and anode.

5. In the art of exhausting an electric discharge device comprising a grid, anode and a filamentary electrodeadapted to be heated to incandescencefthe" method which consists in energizing the- -filament to produce electrons for reducing the impedance between I

Images