US 2558357 A
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Description (OCR text may contain errors)
I Summer. Albert C. l'l'mm omeg A. C. GRIMM LEAD FOR ELECTRON DISCHARGE DEVICES Filed Sept 20, 1946 June 26, 1951 Patented June 26, 1951 LEAD FOR ELECTRON DISCHARGE DEVICES Albert C. Grimm, Lancaster, Pa., assignor to Radio Corporation of America, a corporation of Delaware Application September 20, 1946, Serial No. 698,359
The present invention relates to leads for electron discharge devices and more particularly to leads sealed through the glass portionof the envelope of such devices.
In certain types of tubes leads are taken from the base of the tube as well as from the end remote from the base. The lead entering the envelope of the tube at the end thereof remote from the base is usually required to serve as a the envelope and the lead to preserve desired pressure or vacuum conditions within the envelope. Such seals are sensitive to excessive temperatures and are likely to fail due to thermal the high frequency source.
shock produced by sudden or rapid temperature changes, or sudden or rapid application of excessive temperatures. During the outgassing operation the electrode supported by the lead in ques-, tion is subjected to relatively high temperatures to drive occluded gases therefrom. The heat of such an electrode during the outga ssing step is more rapidly conducted to the glass to-metal seal where the lead is a wire of relatively large diameter, than would be the case if the lead were of smaller diameter. It is, therefore, apparent that while large diameter leads are desirable for support purposes, small diameter leads are necessary to reduce heat transfer to the glass-to-metal seal..
It is an object of the present invention to reconcile these opposed structural considerations of the lead.
It is a further object of my invention to provide a lead for an electron discharge device which will possess the required strength for accomplishing a rugged support of an electrode of the device and yet be characterized by low heat transfer properties.
One method of heating electrodes to outgas the same is to apply high frequency electric fields thereto to cause high frequency current to flow in the electrodes. The utilization of this method of heating is accompanied by the danger that the lead itself will become coupled to the high frequency source and as a consequence be heated by currents induced thereby. In this situation the seal will be exposed to two sources of heat, namely the heat conducted to it from the It is, therefore, an additional object of my invention to provide a lead which will be rugged in structure, have relatively low heat transfer properties, and possess means for preventing the flow of induced currents therein.
A further object of my invention is a lead structure for an electron discharge device which will ruggedly support an electrode thereon and be in turn supported by a glass-to-metal seal, without danger of causing failure of the seal during out-gassing of the electrode by high frequency means.
A still further object is to provide a lead structure which will accomplish the dual purpose of decreasing thermal conductance thereby and inhibiting the flow of induced-high frequency current therein.
According to one embodiment of my invention a lead of tubular form is sealed through the glass portion of the envelope of an electron discharge device to form a vacuum-tight glass-tometal seal. An electrode within the envelope is supported at one end of the lead and the other end extends exteriorly of the envelope to provide an external connection. The use of a tubular form instead of a solid lead reduces the cross sectional area of the lead and thereby decreases the thermal conductance without materially reducing its mechanical strength.
The portion of the lead which extends into the envelope is provided with apertures or windows communicating with its interior. These apertures or windows serve the dual purpose of further decreasing the thermal conductance of the lead as well as preventing the flow of induced currents around the lead by effectively reducing the coupling between the lead and the high frequency source.
This structure of the lead of my invention, therefore, provides a rugged support for an electrode while at the same time guarding the glassto-metal seal against excessive heat such as is produced during the outgassing of the electrode. It will be noted that this protective action of the lead is directed both to conduction and gen eration of harmful heat.
While the scope of my invention is set forth with particularity in the appended claims, my invention itself will best be understood from a detailed consideration of an embodiment thereof taken in connection with the accompanying drawing in which Figure 1 shows a perspective view of an electron discharge device incorporatassess:
ing the novel lead of my invention and Figure 2 shows in cross section a portion of the device shown, surrounded by the side wall of the base It and is connected to suitable external contact pins I. The anode I2 is supported at the end of the envelope remote from the base III by a leadin conductor l5.
According to my invention, as indicated more clearly in Figure 2, conductor or lead i is tubular in shape and enters envelope ll through the glass-to-metal seal I6 which engages a periphery thereof. It will be noted that a portion of conductor I 5 extends within envelope I I and another portion extends exteriorly of the envelope. As a further feature of my invention the portion of the conductor extending within the envelope is provided with apertures or windows H. The portion extending exteriorly of the envelope is provided with an air-tight'cap I 8.
The tubular structure of conductor l5 imparts to it sufllcient rigidity to adapt it to serve as a support for anode i2. The tubular construction provides this desired rigidity with a smaller cross sectional area than would be required for a solid conductor of similar rigidity. The tubular shape of the conductor, therefore, is characterized by less thermal conductance than a solid conductor of equal ruggedness. The provision of apertures ll further reduces the cross sectional area of conductor I5 and contributes to a further reduction in the heat transfer property thereof. In addition, apertures I! serve to block the path of any currents that may be induced in conductor l5 during the outgassing operation when high frequency heating means are employed to drive occluded gases from anode l2. These apertures, therefore, prevent the generation of heat in conductor by blocking heat producing currents therein during the outgassing step.
The structure of conductor l5, therefore, effectively reduces its heat conducting characteristic as well as the generation of heat therein in response to high frequency heating means. These features of conductor ii are important in preserving intact the glass-to-metal seal l6.
It will be noted that seal it serves both to support the conductor l5, which in turn supports the anode l2, as well as to preserve desired pressure or vacuum conditions within the envelope ll. Any weakening of this seal will. disturb the in ternal spacing between cathode l3 and anode II, as well as the desired pressure or vacuum conditions within the envelope.
It is known that excessive heat at the seal will affect its stability. It will be appreciated, therefore, that the novel conductor l5 of my invention in limiting the conduction of heat to the seal l6 and in preventing the generation of heat by induction from the high frequency heatin means effectively prevents impairment of seal l6 and contributes to the fabrication of a reliable tube.
It willbe obviou to persons skilled in the art that my invention is not limited to the embodiment chosen for illustrative purposes. Thus my novel lead-in conductor is not only advantageous during the outgassing operation referred to but may be relied upon to protect a; glass-tometal seal from excessive temperatures during normal operation of a tube using it when the electrode served by my conductor is normally subjected to heat in operation which might otherwise afiect the seal harmfully. Furthermore, while my conductor has been shown to be cylindrical it may have any desired cross-sectional configuration without appreciable impairment of its effectiveness to awomplish the purposes specified. In addition, the apertures or windows H are not to be regarded as limited to the exact shape shown. For instance, they may be rectangular instead of oval, or of any other shape and still retain their beneficial effects on the conductor. I, therefore, desire to include these and other modifications within the scope of the appended claims.
What I claim is:
1. An electron discharge device having an envelope, electrodes within said envelope, and a lead-in for one of said electrodes, said lead-in comprising a thin walled hollow structure extending through a wall of said envelope and sealed directly to said wall, said structure having a portion extending within said device and directly supporting said one of said electrodes and having apertures in the side wall thereof between said seal and said electrode for impeding heat generation therein and heat transfer therethrough, and another portion extending exteriorly of said device and having a cap sealing its exterior end.
2. An electron discharge device including an envelope, a cathode and an anode within said envelope, a support for said anode, said support comprising a lead-in conductor, said lead-in conductor having a portion extending within said envelope and directly connected to and supporting said anode, and another portion extendin exenvelope, an electrode within said envelope, and a lead-in conductor connected to and supporting said electrode, said lead-in conductor comprising an elongated tubular body closed at one end and extending through and directly joined in a seal at a periphery intermediate its ends to said envelope whereby a portion of said tubular body extends into said envelope and another portion thereof extends exteriorly of said envelope, said first-named portion having aperture in the wall thereof, whereby heat transfer from said electrode to said periphery is reduced and the generation of heat in said tubular body within said envelope is substantially prevented, whereby said Zeal at said periphery is preserved from harmful eat.
4. An electron discharge device including a glass envelope, an anode and a cathode within said envelope, a hollow elongated conductor extending through a wall of said envelope and supporting said anode, a glass-to-metal seal directly between said envelope and said conductor, said seal being disposed intermediate the ends of said conductor whereby said conductor includes a portion extending outside of said envelope and another portion extending within said envelope, the free end of said first-named end portion being closed, the side walls of said second-named portion having apertures therein providing discontinuities in the periphery thereof, whereby heat transfer from said anode to said seal is impeded and induced electrical currents along a periphery of said conductor are substantially prevented for protecting said seal from harmful heat.
5. An electron discharge device including a glass envelope, an anode and a cathode electrode, a lead-in conductor extending from said envelope and supporting one of said electrodes, a glass-to-metal seal directly between said envelope and said conductor, said conductor being hollow in cross-section for reducing heat transferred from one of said electrodes to said seal, and means for arresting the generation of heat in said conductor, said means comprising a portion of said conductor having apertures therein whereby protection is ailorded said seal against failure due to excessive temperatures.
6. An electron discharge device including a glass envelope, electrodes within said envelope, a tubular lead-in conductor directly sealed through said envelope and supporting one of said electrodes, whereby said tubular structure has a longitudinal portion extending within said envelope and another portion extending exteriorly of said envelope, said first-mentioned portion having apertures therein providing discontinuities in one cross section thereof whereby conduction of heat through said cross section is reduced and the generation of induced currents therein is prevented.
7. An electron discharge device having a glass envelope, a lead-in conductor extending through said envelope, a glass-to-metal seal directly between said envelope and said conductor, an electrode supported on said conductor within said envelope, said conductor being of tubular form for reducing thermal conductance from said electrode to said seal, said tubular conductor having apertures for reducing response of the portion of said conductor located within the envelope to high frequency heating means.
8. An electron discharge device including a glass envelope, an anode of elongated tubular form closed at one end, and a lead-in for said anode comprising an elongated tubular form having a closed end and an open end, said open end being directl connected to said anode at said closed end thereof for providing a rugged support for and good electrical connection to said anode, a peripheral portion of said lead-in intermediate its ends being directly sealed to said envelope in a glass-to-metal seal, and means between said anode and said seal for preventing generation and transfer of heat to said seal, said means comprising a portion of said lead-in intermediate said anode and said seal having apertures therein for interrupting electrical paths therein normal to the axis of said lead-in and for interrupting the paths of heat conduction from said anode to said seal whereby said seal is preserved against excessive heat.
9. An electron discharge device including an envelope, a lead-in conductor comprising an elongated tubular structure closed at one end and open at the other, said tubular structure extending through said envelope and directly sealed thereto in a seal at a peripheral portion intermediate its ends with said closed end extending outside of said envelope and said open end extending into said envelope for directly supporting an electrode therein, said tubular structure having apertures in the portion thereof extending into said envelope for impeding heat conduction from its said open end to said peripheral portion and for preventing heat generation by induced electrical currents in paths normal to the longitudinal axis of said structure, whereby said seal is protected from excessive heat.
ALBERT C. GRIMM.
REFERENCES CITED The following references are of record in the