US1272374A - Method of preparing vacuum-tubes. - Google Patents

Description

0. E. BUCKLEY.

METHOD OF PREPARING VACUUM- TUBES.

APPLICATION FILED DEC. 30, m5.

1 72,374, Patented July 16, 1918.

UNITED STATES Paras orrron.

OLIVER ELLSWORTH BUCKLEY, OF EAST ORANGE, NEW JERSEY ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. C, A CORPORATION OF NEW YORK.

METHOD OF PREPARING VACUUM-TUBES.

To all whom it may concern:

Beit known that I, OLIVER ELLSWORTH BUCKLEY, a citizen of the United States, re-- siding at East Orange,in the county of Essex and State of New Jersey, have 111- vented certain new and useful Improvements in the Methods of Preparing Vacuum- Tubes, of which the followingis a full,

clear, concise and exact description.

Thisinvention relates to the preparation of vacuum tubes, in particular to thermionic devices having a heated cathode, an anode and an auxiliary electrode.

Its object is to provide for heating the anode by vigorous bombardment of electrons without endangering the. cathode, such bombardment being desirable in order to that treatment is to disintegrate the cathode drive out gases'occluded inthe anode.

This object is accomplished by limiting the current in the tubeby applying a nega-- tive charge to the auxiliary electrode, and

by then applying a large voltage between anode and cathode by which the energy of the striking electrons is increased to a value larger than normal.

In the construction of vacuum tubes in which it is desired to maintain a high vacuum, it has been found that unless the electrodes and walls of the vessel have been subjected to a vigorous preliminary treatment, the gases occluded by them will slowly leak out with the resultthat the vacuum is soon decreased'and ionization by collision can then take place. This preliminary treatment is usually carried out by heating the walls of the vessel externally and by direct- 3 ing a stream of electrons toward the anode.

The present invention insures that the electrons striking the anode shall do so under the influence of a large voltage and consequently with large kinetic energy, while at Specification of Letters Patent. Patented J uly 16, 1918, Application filed December 30, 1915. Serial No. 69,418.

the same time this large voltage is not able to draw more than normalcurrent from the cathode.

In a thermionic device of the type described, if the potential of the auxiliary electrode is made negative with respect to the cathode, a larger voltage between anode and cathode is necessary to produce the same current from the cathode as would appear in the absence of such a voltage applied to the auxiliary electrode. But the kinetic energy of the electrons striking the anode increases with" the increased voltage, and it is therefore possible, by applying a negative potential to the auxiliary electrode,

to increase the vpltage effective in driving electrons to the anode very much above the normal value, Whlle maintaining the current at 1ts normal value. By th1s process the vigorous bombardment of the anode is may be heated externally. The glass tubing 3 serves to connect the tube with a molecular pump 4 or other suitable means for exhausting it. The liquid air-trap 10 is included in this line of tubing for the usual purpose. The filament 5 is heated by means of alternating current furnished to it through the medium of the transformer 8,

whose primary winding is energized by means of the source of alternatlng current,

not shown in the drawing. The voltage between anode and cathode is supplied by means of the direct current generator 9, while the electromotive force required to maintain the auxiliary electrode negative with respect to the cathode is obtained from the battery 11, whose negative pole is connected to the auxiliary electrode.

During the. processv of evacuation the pump is operated,-the filament heated and a discharge started between anode and bardment of the anode at the increased voltage is contmued until no evidence of gaseous ionization in the tube canbe detected.

' release of gas from the anode. In the later As an example of the voltages employed in one type of tube, it has been found that in the early part of the process a maximum of about 200 volts'can be maintained between the cathode and the anode. By applying 110 volts between the cathode and the auxiliary electrode, making the latter nega-. tive, a maximum of 500 volts or more may be obtained with consequent more rapid stagesof exhaust a potential difference of 750 volts or more may be maintained by the use of the negative auxiliary electrode, while if that electrode were disconnected it would not be more than 550 volts. A further advantage of this method is that during the process of bombardment the negative auxiliary'electrode attracts to itself the greater part of the positive ions released by the electron discharge, and thereby prevents the bombardment of the cathode by these ions, which bombardment, as is well known, tends to disintegrate the cathode.

ode, an anode and an auxiliary electrode,

which method consists in evacuating said tube and before said evacuation is completed in performing the following steps, 2'. e. in maintaining an electron discharge between said cathode and anode and in applying between said auxiliary electrode and said cathode a voltage which shall limit the current to a given value while permitting a large voltage between anode and cathode whereby the energy of the electrons striking the anode shall be large.

2. The method of preliminary treatn'lent of a vacuum tube containing a heated cathode, an anode and an auxiliary electrode,

which method consists in evacuating said tube and before said evacuation is completed in performing the following steps, 2'. e. in maintaining the auxiliary electrode at a negative potential with respect to the oathode and in applying between anode and cathode a voltage sufficient to maintain a desired current in the tube.

lrl witness whereof, I hereunto subscribe my name this 28th day of December, A. D.-, 1915.

OLIVER ELLSWORTH BUGKLEY

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