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Патент USA US2115934

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May 3, 1938.
Filed Dec. 51, 1936
V %C
Patented May 3, 1938
Newell R. Smith, Bloom?eld, N. J., assignor, by
mesne assignments, to Radio Corporation of
America, a corporation of Delaware
Application December 31, 1936, Serial No. 118,523
5 Claims. (Cl. 7250-27-5)
My invention relates to electron discharge de
vices, particularly to electrode constructions and
their mount assemblies.
Minimum spacing of ‘electrodes of a mount in
I a tube with the usual tensioned ?lamentary cath
ode is limited by the room required for the cath
ode which, because of its ?exibility, is free inter
mediate its ends to vibrate and to move consid
erable distances. In power recti?ers, for exam
10 ple, it is important that the anode cathode spac
ing be as small as possible to minimize the space
impedance and permit greater anode current for
a given anode operating temperature. Mounts
employing the usual ?lament supporting means
15 are dif?cult to-assemble, particular pains being
necessary to obtain a ?xed and uniform spacing
between the ?lament and surrounding electrodes.
An object of my invention is to provide a mount
with a ?lamentary cathode and cooperating elec
so trodes that may be easily‘assembled.
A further object of my invention is to provide
a mount with an anode and rigid self-sustaining
?lamentary cathode that may be closely mounted
in cooperating relation.
‘A further and more specific object 01' my in
vention is to so form a?lamentary cathode with
‘ a'cross sectional con?guration that may lend
sufficient rigidity to the cathode to prevent its
vibration or movement between its points of sup
30 port.
According to my invention, a ?lamentary cath
ode and cooperating electrodes are so made that
they may be mounted in close spaced relation
ship, the ?lamentary cathode being stiffened to
35 make it self-sustaining in its supports, and the
anode being so formed about the cathode to in
crease the tube perviance. Ribbon-like strips of
cathode material maybe longitudinally grooved
by rolling or pressing, and the channelled ?la
Figure 1 is a sectioned perspective view of one
electrode assembly embodying my invention,
Figure 2 is a detailed view showing the cross
sectional con?guration of one form of channelled
?lament constructed according to my invention,
Figure 3 shows another electrode assembly em
bodying the characteristic features of my inven
The electron discharge device shown by way of
example in Figure ‘1 and embodying the charac
teristic features of my invention comprises an
envelope I with a re-entrant stem 2, and press
3 insulatingly supporting the usual lead-in con
ductors. The tube, chosen for illustration is
shown with a glass envelope, although a metal
envelope may be used, and with the electrodes
of a full wave recti?er comprising anodes 4 se
cured at their ends to insulating spacers 5 such
as mica discs, the entire assembly being supported
by the conductors embedded in the press.
Each anode, according to my invention, com
prises a single sheet of metal folded as shown with
two longitudinal slots or folds 6 extending to
wards the center of the tube to form indentations
facing outwardly, the portions of the anode 1 ad
jacent the folds being pressed in a cylindrical
plane to present to the wall of the envelope a heat
radiating surface of considerable area. The
walls of the indentations may be accurately
formed on a standard punch press machine to
uniformly and closely space the sides of the in
A ribbon-like ?lamentary cathode constructed
according to my invention may conveniently be
mounted in the slots with a minimum yet accu
rately ?xed-spacing between the walls of the slot
and the ?at sides of the cathode. Within each
. slot is mounted a portion of ?lamentary cathode
ment so constructed out to the proper length 8 shown in detailed section in Figure 2. The ?la
and mounted in an electrode assembly. I have, ments, preferably strips of refractory metal such
according to one embodiment of my invention, as molybdenum or nickel-iron-cobalt alloy, com
bent the channelled strip at its center to form a mercially known as “16 metal”, are longitudinally
5 “V”, and welded the ends of the legs of the “V" grooved or channelled along the center of the
to supporting lead-in wires in the press at the‘ ribbon or strip by-rolling or pressing to form the
lower end of the tube so that the bight or apex strip with any desired cross sectional con?gura
of the ?lament lightly engages at its edges, the tion. While the rectangular channel 9 shown
edges of a narrow slot in the upper insulating in Figure 2 has been found to stiffen the strip
sufficiently, the strip may be formed with any
50 spacer.
The characteristic features of this invention
are de?ned with particularity in the appended
claims and preferred embodiments are described
in the following speci?cation and attached draw
55 ing in which;
other desired cross sectional contour such for
example as a semi-circle. In the particular em
bodiment illustrated in Figure 1 each channelled
?lament is coated with an electron emitting coat
ing such as barium-strontium-carbonate, is bent
‘to form an inverted “U”, the legs of the ?lament
8, 1 1 6,984
inserted in openings or notches in the upper insu
lating spacer, and their lower ends attached by
welding to current supply conductors with the
transverse section at the top of the "U" bearing
against the upper insulating spacer S to trans
versally support it.
With the open sided slots in the anode and the
stiff ?lamentary cathode of my invention, the
electrodes may be automatically assembled by
10 machines, eliminating the usual hand operations.
A chuck, for example, may be inserted through
the open side of the slot to guide the ?lament
into place where it is welded, at its lower end,
to current supply conductors. It has been found
ll that a ?lament constructed and mounted as
shown in Figures 1 and 2 is self-sustaining, re
quires no sprlng tensiouing means, commonly ac
cepted as being indispensable for ?lamentary
cathodes, and is rigidly held in place by the two
welds at the lead-in wires. The parallel faces
of the ribbon-like ?lament and walls of the slots
minimize the anode-cathode impedance of the
tube and with the plane of the ?lament normal to
the wall of the envelope electrostatic in?uences
on the cathode. such as "grid efl'ec ” noticeable
particularly in tubes with metal envelopes, is
materially reduced. This construction is strik
ingly simple when compared with the usual
mount of this type, is easy to assemble, and in
30 expensive to manufacture.
My ?lament has been successfully employed in
a commercial tube known as the "80" when the
ribbon ?lament is bent at its center to form a
“V", as shown in Figure 3, the ends of its legs
36 welded to lead-in conductors l0 and its apex slid
ably held at the edges of the strip in opening it
constructed, the apex of the ?lament above the
spacer may be ?attened to rest upon the bridge.
Such a bridge would serve to prevent the apex of
the ?lament from slipping through the opening
and disengaging the spacer.
Since many modi?cations may be made in this
invention without departing from the spirit
thereof, it is desired that this invention be limited
only by the prior art and the appended claims.
I claim:
1. Anelectron discharge device comprising an
envelope, an anode in said envelope with a cylin
drical surface concentric with the wall of the
envelope and two elongated indentations extend
ing lengthwise of said anode with the sides of said 16
indentations opening in the cylindrical surface of
the anode facing said envelope, and a U-shaped
?lament of ribbon-like refractory metal, the legs
of said ?lament being insulatingly supported in
the indentations with the plane of the ribbon 20
like ?lament parallel to the walls of the slots.
2. An electron discharge device comprising an
anode and a ?lamentary cathode, an insulating
spacer, the anode and cathode insulatingly held in
cooperating spaced relation, and the cathode com 26
prising a strip of refractory metal stiffened
throughout its length with a longitudinal channel,
the lower end of the stiffened cathode strip be
mg ?xed and the other end of the strip being free
to move longitudinally and slidably guided by 80
said insulating spacer.
3. An electron discharge device comprising an
envelope, an anode in said envelope comprising a
metal sheet, said sheet being folded to form an
elongated indentation, the sides of said indenta 35
tion opening upon the wall of said envelope, an.
in the insulating spacer. Any desired arrange
ment of grids could. of course, be placed between
insulating spacer, a ribbon-like cathode of re
the anode and cathode.
the cathode, secured in and spaced from the sides
of said indentation, one end of the cathode ribbon (0
The upper end of the
?lament is free to slide through the opening when
the ?lament changes in length due to heating,
the edge-to-edge contact between the ?lament
strip and mica spacer offering minimum frictional
resistance to the movement of the ?lament.
With the ends of the legs of the V-type ?lament
anchored, its apex is free to move only in the
plane of the ?lament legs and the edge-to-edge
contact between the ?lament and spacer o?ers
maximum resistance to the ?ow of heat from the
?lament to the spacer. In manufacture it may
be found desirable to stamp out the upper insu
lating spacer 5 with a transverse portion or bridge
across the center of openings II to underlie that
portion of the ?lament extending above the sur
face of the upper insulaton, With the spacer so
fractory metal, longitudinally grooved to sti?en
being ?xed and the other end of the ribbon being
slidably guided by said insulating spacer.
4. An electron discharge device comprising an
anode and a ?lamentary cathode, an insulating
spacer, the anode and cathode being insulatingly
held in co-operating spaced relation said cathode
comprising a ribbon of refractory metal sti?ened
throughout its length with a longitudinal channel,
the width of the channel in said ribbon being sub
stantially less than the width of said ribbon.
5. A cathode for an electron discharge device
comprising a straight flat ribbon, a longitudinal
channel in said ribbon to stiffen the ribbon, and
electron emissive material in said channel.
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