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Патент USA US3021456

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Feb. 13, 1962
Filed May 16, 1955
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United States Patent
Gyshert Jacob Ekkers, Wettingen, and Aldo Patriarea,
Laufohr, near Brugg, Switzerland, assignors to Patel
hold Patentverwertuugs- 82 Elektro-Holding A.G.,
Giarus, Switzerland
Filed May 16, 15155, Ser. No. 503,343
Claims priority, application Switzerland May 15, 1954
4 Claims. (Cl. 313—204)
The present invention relates to gaseous electric dis
charge tubes and particularly those of the grid-controlled
Patented Feb. 13, 1952
well. Sinterable corundum can be easily applied to grid
13 by soaking or spraying, and subsequently it can be sin
tered to a hard, well adhesive coating through thermal
processing. The coating material 14 also covers the lead
in support conductors 15 completely down to the point
where these seal to the tube wall.
It has been proven in practice ‘that the invention,
namely the coated control ‘grid, makes it possible to re
duce the disturbing grid emission in the tube down to about
one-thousandth of its former current magnitude. Thus
the grid emission for gaseous discharge tubes ?lled with a
vapor of an alkali metal can be brought down to that level
usum‘ly found in gaseous discharge tubes ?lled with mer
cury vapor or with an inert gas.
It has been known to be advantageous to fill the interior
In the modi?ed embodiment illustrated in FIG. 2 the
of such tubes with a vapor of an alkali metal. However, 15
construction is substantially the same as in H6. 1 except
when this has been done it has been found most ditlicult
that the inner peripheral surface 16a of the annular con
to control primary emission from the grid element. Dur
trol grid 16 is left uncovered by the non-conductive layer
17. 'It has been found in practice that even with the inner
sorbs a metal layer, e.g. cesium, which very strongly di
minishes the work function for electrons. At control grid 20 peripheral surface portion 16a of the control grid 16 ex
posed to the alkali metal vapor there is no appreciable in
temperatures of about 300° C. the grid emission is already
crease in grid emission over that which obtains with the
so large that the grid either loses entirely its ability to
FIG. 1 embodiment.
control the discharge instant of the tube or the required
In conclusion it will be understood that various changes
grid control force becomes unbearably high. Forced
cooling of the grids is a possibility to overcome these dii? 25 in the speci?c constructions illustrated may be made with
out however departing from the spirit and scope of the
culties but is not economically feasible, because of the
invention as de?ned in the appended claims. The control
high costs involved, in low-priced tubes of relatively low
grid itself may be of different con?guration and the lead—
in supports for the grid will have to be protected by the
In ‘accordance with the present invention, primary
emission from the control grid is controlled and prac 30 electrically insulative coating only in those instances where
made from a material which heats appreciably.
tically fully suppressed by the novel expedient of covering
We claim:
the surface of the control grid either completely, or for
1. In an electric discharge tube having cathode, anode
the most part with an insulating i.e. electrically non-con
control grid elements and ?lled with an alkali metal
ductive material.
In the drawings which illustrate a typical embodiment 35 vapor, the improvement wherein the surface of said con
trol grid element is covered at least for the most part with
of the invention;
a non-conductive material.
FIG. 1 is a view in central vertical section of the elec
2. An electric discharge tube as de?ned in claim 1
tric discharge device with the non-conductive, insulating
wherein said non-conductive material is sintered corun
coating on the control grid; and
ing operation of the discharge tube, the control grid ab
FIG. 2 is also a view in central vertical section illustrat
ing a modi?ed construction for the improved discharge
3. An electric discharge tube as de?ned in claim 1
wherein said control grid is constituted by an annular plate
completely covered by said non-conductive material}
With reference now to FIG. 1 the gaseous discharge
4. An electric discharge tube as de?ned in claim 1
tube 10 is seen to be made of glass and is norm?ly cir
cular in transverse cross-section. Tube 19 is ?lled with 45 wherein said control grid is constituted by an annular
a vapor of an alkli metal such as cesium and encloses a
cathode 11, an anode 12 and a control grid 13 of annular
plate, said plate being covered by said non-conductive
material except for the inner peripheral surface portion
con?guration. The entire surface of grid 13 is covered
by a layer 14 of non-conductive material. One suitable
References Cited in the ?le of this patent
material for the coating layer 14 is corundum (A1203) 50
since it is not attacked by the cesium metal vapor, and it
has a very slight vapor tension and also vpossesses a high
melting point. However, other clays, i.e. zirconia or
Smith _______________ __ Nov. 29, 1938
Lake ________________ ._.. Oct. 18, 1949
beryllium oxide or their mixtures can be used equally as
Smith ________________ .._ Apr. 18, 1950
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