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Патент USA US2134267

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Oct. 25, 1938.
Filed June 29, 1935
Patented Oct. 25, 1938
2,134,267‘ ,
Erich Schwartz, Berlin-Zchlcn?orf, .Germany, as—'
signor to the ?rm‘0f Fernseh Aktiengesell
schaft, Zehlendorf, near Berlin, Germany
Application June 29, 1935, SerîalNo. 29,136
Germany June»3, 1934
. .
,~ ..
v 1 Claim. (01. 250—,27.5)
This invention relates to Braun tubes, and are arranged as in a horseshoebathode, vvhere
particularly to the construction of the hot cathode as, according to Fig. 2, they are crossed to reduce
in cathode ray tubes for television or oscille
the effect of the ?eld produced by the leads upon
graphic purposes, and to a method of producing the cathode ray. In Fig. 3, the leads are dis- '
5 such cathodes.
posedparallel and closely side by side to elimi- 5
One object of the invention is to provide a hot mate disturbing ?elds as much as possible. The
cathode Whose emitting surface has coinciding spherical portion I may be covered wholly or
axes of symmetry and rotation.
partly with the emitting substance Il).
A further object of the invention is to form
In Figure 3 the emitting substance Il] is shown
10 the cathode and arrange it relative to an elec- covering only the upper portion of the sphere l. 10
trode, such as a Wehnelt cylinder, so as to proIn Fig. 4, the spherical part I rests on a pin
vide, as much as possible, for linear dependence
or bar4 surrounded by' a tube 5 of insulating ma
of the anode current upon the potential of the
Wehnelt cylinder.
winding is arranged, preferably in bi?lar turns,
On the outside of the tube 5 a heatîng
Another object of the invention isto produce
a cathode which produces a bundle of electrons
and traversed by the current, the spherical part 15
l'being connected toa suitable potential by th
that converges from the very beginning instead
pin 4.
of a considerably diverging one as produced by
the cathodes hitherto in use.
Here only_ that portion of sphere l which is
superior to tube5 is covered by emitting mate
Still another object of the invention is a cathode which can be produced in a particularly
rial l0.
‘ The hot cathodes are preferably produced ac
simple manner and which has a favorable heat- cording to the invention by twisting together
ing power.
the points of two wires or by bending one wire
According to the invention, the cathode sur- to form a horseshoe cathode and melting the
25 face has the shape of a sphere or a sector thereof point of this cathode, for instance by a blower 25
and the preferred method of producing a cathode ?anie, until the tip thereof has the shape of a
comprises the steps of ?rst constructing a horse- spherical drop. Melting is continued or inter
shoe type-cathode, then imparting to the point rupted in time'so as to impart the desired size
thereof drop shape by melting and ?nally apply-. to the diameter of the spherical part. In the
30 ing thereto the emitting substance.
construction the hitherto employed cathode ma- 30
A cathode according to the invention has a
terial, such as platinum or platinum—nickel may
relatively long life and aiÏords numerous othér
be used.
advantages which will be pointed out below With
‘ A hot cathode made in the manner described
_ V
reference to the accompanying drawing which,
is distinguished by high ?lament power, since,*
35 by way of example, illustrates the invention and ' owing to the melting process the current sup- 35
in which
plying wire and the emitting surface form a unit L
Figures 1, 2 and 3 show, on an enlarged scale,
a cathode according to the invention, and indi-
cate an emissive coating thereon;
Fig. 4 is a view of an indirectly heated cathode;
Fig. 5, a view of a cathode and adjacent control electrode; and
Figs. 6, 7a and 7b show cathodes of the hitherto usual type in comparison With which the mer45 its of the new construction are indicated.
Referring to the drawing, the cathodes shown
' in Figs. 1, 2 and 3 have each a spherical part I
provided With an emitting substance I!) and two
leads 2 and 3 connected to the spherical part I
50 and serving also as carriers and current supplies
for the latter.
The emitting substance Il] is shown as covering the entire sphere 1, except the junctures With
legs 2 and 3, in Figures 1 and 2.
In the construction shown in Fig. 1 the leads
whereby harmful heat transition resistances are
It Will be round-in operation that the cathode
constitutes an advantage0us construction with 40
respect to heating and the course of the heating
current, because the current ?bws chie?y through
the lower part of the sphere, so that, owing to the
distance of the ‘emitting surface from ‘the part
traversed by the current, the group of electronic 45
rays is not disturbed by the magnetic ?eld of
the heating wire.
A further advantage during operation of the
cathode is that a converging pencil of rays hav
ing coinciding axes of symmetry and rotation is 50
formed. Fig. 5 shows part of a Wehnelt cylinder
1 and the course of the potential if the Wehnelt
cylinder is negative relative to- the cathode. The
potential ‘surface 0 always starts vertically to r
the cathode surface. The effective emitting part 55
of the cathode is the calotte located on the posi
tive side of the potential surface 0. The indi
that frequently two separate electronic rays are
formed. The spherical cathode according to the
cated course of the potential shows that the
invention, on the other hand, affords as stated
pencil of rays designated by broken lines and
coming from the cathode is convergent.
Figs. 6, 701 and '71) illustrate cathode types of
the usual kind to bring out the di?erence be
tween the art and the invention. At the pointof
the cathode 8 in Fig. 6 the potential surface 0
the advantage of insuring the production of a
convergent pencil of rays, in which the axes of
10 forms so that the extreme end of the cathode
emits and a considerably diverging group of rays
is produced, so that it is necessary to shield con
symmetry and rotation coïncide.
I claim:
‘A Braùn tube Cathode comprising a spherical
portion, an electron emissive coating covering a
substantial part of said spherical portion, sup 10
ïporting means formed integrally therewith ex
tending from the nonemissive part thereof, an
siderable portions of the cathode ray wherebÿ 'insulating supporting member surrounding and
the current yield of the tube isreduced. The contacting said supporting means and engaging
horseshoe cathode 9, of whichFigs. 7a and 7b are, the noneiniÿssive part of said spherical portion in 15
respectively, front and side views, generates’ in‘ direct heat transfer?ng relationshïp thereto, and
one direction, 1. e., in the plane of Fig. 7b;;aÿ_ . means disposed about said insulating member
strongly diverging pencil of rays, Whereas in the for;heating said insulating member and causing a
plane of Fig. 7a the pencil is convergent. The conductive heat transfer to said supporting
20 distribution of intensity in the electronic 'ray i5’ ‘means and said spherical portion.
thereîore correspondingly ~unsymmetrical, s0
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