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Патент USA US2121761

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June 21, 1938.
2,121,761
E. F. LowRY
HOT CATHODE TUBE WITH METAL ENVELOPE
Filed Jan. 4, 193e
WITNESSES:
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BY
A'TTOÈNE
2,121,763.
Patented .lime 21. 1938
UNITED STATES PATENT OFFICE
2,121,761
HOT CATHODE TUBE WITH METAL
ENVELOPE
Erwin F. Lowry, Forest Hills, Pa., assigner to
Westinghouse Electric & Manufacturing Corn
pany, -East Pittsburgh, Pa., a corporation of
Pennsylvania
Application January 4, 1936, Serial No. 57,537
9 Claims. (Cl. Z50-27.5)
This invention relates to gas-filled discharge the alloy selected be unaffected by the vapor in
tubes and particularly to such tubes having a the tube.' especially when hot.
Between the rings 3 and 4 a glass iiange 5
metallic envelope.
integral with a sleeve 6 of the same material is
It is an object of this invention to provide an
interposed. The sleeve 6 forms a skirt within the 5
tube depending from the seal and making a long
leakage path separating the parts I and 2. The
flange 5 is sealed to the rings 3 and 4. If pre
ferred, the sleeve 6 and its ñange 5 may be of
refractory ceramic material and a body I0 of
glass of the kind just described may be inserted
in contact with the outer end of the flange 5.
Outside of it, but with its inner part between the
use of a directly heated cathode structure, hav
rings 3 and 4, a body II of refractory ceramic
ing an electrostatic guard to produce delayed ac
15
tion, and to support such structure by a metal material may be placed in contact with the rings
plate through which the cathode is electrically 3 and 4 and with the glass I0. The outer part
of the body II is extended over the outside sur
united with a portion of the envelope.
faces of flanges upon the rings, thereby affording
It is a further object of this invention to utilize
a cathode structure which extends substantially a long leakage path on the outside of the tube 20
between portions I and 2 of the envelope.
20 across the whole diameter of the tube and elec
An alternative structure may be chosen in
trically to unite such structure with the envelope. which
the part I0 is refractory ceramic material
It is a further object of this invention to pro
and the parts 5 and II are glass. With either
vide a seal made of several parts of different in
the sealing may be accomplished by
sulating material and to prolong the innermost structure,
placing the completed tube in an oven and heat
5
part into a skirt within the tube, thereby aiïord
ing it to the point at which the glass softens
25 ing a long creepage path within the tube between
or partially fuses, causing the glass portion to
the two main electrodes.
wet not only the rings but also the adjacent
It is a further object of this invention to pro
vide a seal including several insulating materials, ceramic refractory parts making the whole seal
gas-tight structure.
at least one of which makes a sealing union with a For
this method of sealing, it is preferable that
3 the metal of the envelope.
the central portion I0 be the glass portion. The
It is a further object of this invention to pro
ceramic parts 5 and Il then act as Stoppers conm
vide a duct for pumping the tube which also fming the glass while it is liquid or soft and also
5 arrangement of the tube electrodes in which the
two principal electrodes are electrically sepa
rated Írom one another by the seal which joins
the two main parts of the envelope.
It is a further object of this invention to s0
10 arrange the electrode that spacings may be closer
and the structure more rigid than heretofore.
It is a further object of this invention to make
serves as a conductor to one of the electrodes.
Other objects of the invention and details of
b5 Cil thc structure will be apparent from the following
description and the drawing in which:
Figure 1 is a vertical section through one form
of my device; ï
Fig. 2 is a similar section through a modifica
tion; and
Fig. 3 is a similar section showing another
application of the device.
In Fig. l, a part i of the envelope constitutes
the
anode and the cathode is electrically united
45
to another part 2 of the envelope. Between the
parts I and 2 are two rings 3 and 4, the ring 3
being welded to the part I and the ring 4 to
the part 2. Each ring comprises a portion con
tacting the edge of the adjacent part, I or 2,
of the envelope and a flange contacting the out
er surface of that part adjacent the edge. At
either or both places the contacting surfaces may
be welded together. The parts I and 2 may be
55 of any convenient metal, preferably steel, and
the rings 3 and 4 are of an alloy which can be
60
wetted by molten or softened glass, and which
will have substantially the same coefficient of
expansion as the glass.~ It is also desirable that
maintain the spatial separation between rings 3 35
and 4 while the glass is safe.
It is also possible to omit the parts Il] and II,
in which case the part 5 must be of glass.
A seal may be made at the center of the part I
and 'through it a conductor I5 extends to the grid
I6. The seal for the lead I5 is in the center of a
ring I1 of metal which will form a good seal
with the glass. 'I‘his ring is welded to the ad
jacent portions of the part I. It comprises a
sleeve extending into the interior of the tube and
a flange overlapping the outside of the part l.
The seal comprises a portion I8 of glass form
ing a sealing contact both with the conductor i5
and with the inwardly extending sleeve of the
ring I1. Inside of the tube the portion i8 _is
expanded, forming a skirt I9 which extends near
ly into proximity with the grid I6. The skirt
makes a long creepage path between the part I
and the conductor I5.
The glass extends beyond the outer surface of 55
the ring I1 but not very far because it must not'
be exposed to the danger of being hit and broken.
The distance vto which the glass extends above
the ring depends on the necessary leakage path
to properly insulate the grid I6 from the anode I.
2
2,121,761
The metal sleeve, extending well along the glass
inside the tube, adds to the rigidity of the struc
ture and can extend so far because the skirt I9
affords sufficient insulation in the comparatively
short distance.
The grid I6 is spaced slightly from the end of
the skirt, whereby the inner and outer surfaces
of the skirt are both included in the leakage
path. The opening between skirt and grid is
narrow and at right angles to the boiling move
ment of mercury droplets. Mercury is, there
fore, unlikely to enter the inside of the skirt and
form a conductive coating on the inner glass sur
face.
The conductor I5 is hollow and its lower end is
flanged to afford a good connection to the grid
I6. This connection is preferably welded. The
conductor |5 thus forms a duct through which
the tube may be exhausted. After the tube is
20 pumped, the duct may be closed by welding or
if the tube is to be continually pumped during
operation the duct may be kept open to the pump.
The cathode of this tube comprises a directly
heated portion 20 which is connected by a lead
25 2| to the exterior of the tube. The portion 20
may be, as shown, a ribbon thick enough to sup
port itself even when hot or it may be supported
by a central refractory body as further described
in connection with Fig. 2. In either case, it is
30 coated with emissive material. The lead 2| passes
through a body 22 of glass which can seal to
the metal sleeve 23 extending from the bottom 24
of the tube. The bottom 24 is welded to the part
2 and its sleeve 23 may be made of the alloy de
scribed and welded to it. If desired, the bottom
24 may be made of steel and the sleeve 23 alone of
the alloy.
The upper end of the directly heated portion
20 is welded to a cap 25 which, in its turn, is
welded to a guard 26 and this, in its turn, is
welded to inwardly extending projections on a
shield 21, which surrounds the guard and the
directly heated portion. A surface of the guard
is coated with emissive material.
Surrounding the shield 21 is a second shield
28 which is welded to the shield 21 by inwardly
off-set. portions at the top. At the bottom simi
lar off-set portions of the shield 23 contact shield
21 but are not welded thereto. The bottom of the
shield 28 has outwardly extending tabs or feet
29 by which it is secured, preferably by welding,
to the plate 24. The plate 24 and the part 2
are welded together, a ñange being provided on
the bottom of the part 2 for securing an in
creased welding surface, as shown at 30.
The bottom of thc space enclosed by the guard
26 is closed by a disc 3| of refractory ceramic
material which has a flange 32 extending into
contact with the interior of the shield 21. The
disc 3| has a radial slot 33 which accommo
dates a tap 34 extending from the lower end of
the part 20 through the disc 3| where it is welded
to the conductor 2|. This cathode structure as a
65 whole, is supported from the plate 24.
The function of the structure is to delay the
beginning of current from the anode | to the
cathode until the guard has had time to become
sufficiently heated to emit electrons from its coat
70 ed surface, as explained in greater detail ln my
application Serial No. 57,536, filed January 4, 1936.
'I'he tubular conductor I5 and the lead 2| are
coaxial with each other and with the envelope.
Consequently'no attention need be paid when in
75 serting the device into its connection, to the ro
tational position of the device with respect
this axis.
In the form of my device shown in Fig. 2, the
part 20, the guard 26, the shield 21 and the shield
28 function as the corresponding parts of Fig.
1. The tab 34 is, however, at the upper end of
the part 20 and the disc 3| of refractory ceramic
material is at the top of the cathode structure.
The off-set portions and welds described in con
nection with Fig. 1 are similar in Fig. 2.
There
are, however, some differences; the off-set p0r
tions at the top of shields 21 and 28 are not weld
ed and no, or at most, very little heating cur
rent flows through the shields or guard. At the
bottom of the cathode structure a metal plate 3l
is provided to which each of the several cylin 15
ders of the cathode structure are welded. From
the tab 34, a hollow conductor 39 extends through
a bore in the center of a. refractory insulator 40
to the exterior of the tube. The insulator 44 is '
provided with staggered teeth 4| which support
the individual whorls of the part 2U. The top
of the insulator 40 is fitted into a recess in the
disc 3| which prevents relative movement be
tween it and the other members of the cathode
structure. Its bottom rests upon the top of a 25
flanged ceramic member 42.
The flange of member 42 extends from a sleeve
which fits a tube 43 which extends from the cen
ter of the plate 38 to the exterior of the tube.
Within the tube 43 there is also fitted a glass 30
portion 44 and a second portion 45 of ceramic in
sulation. The tube 43 is made of alloy which
can form a sealed Joint with the glass 44. The
plate 38 may be made of the same alloy and it
and the sleeve 43 may be homogeneous, or if 35
desired, the plate may be made of any selected
metal, such as nickel, and the tube 43 welded
thereto.
The envelope of the tube shown in Fig. 2 com
prises. an anode 4B, which is essentially the shape 40
of a bell jar and has a flange at the bottom shown
at 41, by which it is welded to the bottom 4l.
This bottom 4B has a 'central sleeve 49, integral
therewith, or welded thereto, which is of the alloy
aforementioned, capable of forming a seal with 45
the glass. Within the tube 49 is fitted a body 5|
of ceramic refractory material having at its
upper end, which extends beyond the tube 49
into the interior of the tube, a flange or skirt 52.
The flange 52 at the top of the body 5| makes a
long creepage path between the cathode, which
is electrically united with the sleeve 43 and the
anode, which is electrically united with the
sleeve 49.
Contacting with the bottom of the body 5| is 55
a body 53 of glass, capable of forming a seal with
the aforesaid alloy, which fits the interior of the
tube 49, and contacting with the bottom of the
body 53 is a thimble-like member 54 of ceramic
material, the outer surface of which flts the tube 60
49. The top of the member 54 is formed into an
inwardly extending flange fitted to the exterior
of the sleeve 43.
'I'he several insulating bodies 42, 44 and 45
have an aligned central bore through which the 65
metallic tube 39 extends and the bodies of insu
lation 5|, 53 and 54 have a bore to accommodate
the tube 53. The two bores, the tubes 43 and
49 and all the insulating bodies are coaxial, the
common axis being the center of the tube 39.
The exterior terminals of the anode, the cath
ode and the cathode heating circuit are thus
three coaxial cylindrical metallic tubes.
'I'he inner one 39 is welded shut when the
2,181,761
pumping of the device is finished and when so
welded forms a peg 55 which can be the inner
terminal coaxial .with the exterior surface I9 and
the intermediate surface 43. Nothing depends
on the position rotationally of the tube, but the
correct contact may be made even though the
tube is rotated, about its conductor 39 as an axis.
to any extent whatever. This device is a rectifier
and has no control electrode like the grid i6 in
10
3
The skirt 18 acts to increase the leakage path
from thimble 58 to conductor 11. The extension
of the bottom of the thimble along the glass 18
adds to the stiiïness of the structure. The re
cess in the thimble accommodates the external
part of the glass and also protects it from acci
dental injury. The externally extended glass also
adds to the leakage path between the anode and
the igniter.
When the mercury in the pool 12 is heated,
Fig. i.
'
mercury vapor rises into the interior of the anode
The tube in Fig. 3 has an anode 5i which is portion 8i of the envelope and is condensed lthere
separated from the cathode part 62 of the en
to a greater extent than it is condensed in the
velope by a seal 53. Rings of appropriate seal
lower space because the part 62 of the envelope
ing metal Gli and 55 are welded to the envelope is a good thermal conductor in contact with the 15
15 portions 8| and 62 at the edges where the en
pool 12. The condensed mercury, descending,
velope joins the seal. The seal 63 consists of forms droplets on the adjacent surfaces of anode
an outer portion of refractory material and an
51. The other or outer surface of the skirt
inner portion 66 of glass. This portion forms a skirt
61 does not receive mercury droplets and so ai.’
flange on the sleeve 61. This sleeve constitutes fords good leakage protection between the two 20
20 a skirt from the seal 53 adding to the length of the portions of the envelopes 6i and 62. The interior
leakage path on the inside of the envelope be
of the skirt 19 is well protected from droplets
tween the anode portion 6i and the cathode por»
by the skirt itself and because the skirt is
tion 62. The outside of the seal is extended, both
located in a hot region. It thus affords an eiîec
overlapping the rings 6G and 65,- and thus in
25
tive prevention against leakage.
25 creasing the exterior leakage path between the
The terminal stud 13 and the conductor 11 are
anode portion of the envelope and the cathode in line with each other and are central of the
portion thereof.
envelope. Consequently the device can be put
In the middle of the anode portion 5i a thimn into working relation with the external connec
ble 58 is provided having a iiange which contacts tions in any postiion around this axis. It is not 30
36 with the exterior of the portion 5i and may be necessary to rotate the device about this axis into
welded thereto. The inwardly extending portion
any particular position.
of the cup-shaped part of the thimble 58 is screw
In the operation of the grid glow tube shown
threaded on its outer side which is inside of the in Fig. l, the element 2l! is a source of electrons
envelope, and thus forms a threaded stud pro
which are confined to thevinterior of the guard 35
35 jecting into the interior of the tube. A graphite 26 until the guard has acquired suiîicient tem.
member 10 is screwed upon this stud and it is perature to cause the oxide coating thereon to
expanded into a skirt 1i which is electrically in
electrons. The guard is heated by heat from
tegral with the anode portion 6i of the envelope emit
the member 20 and this heat is supplied by cur
and projects nearly to the cathode. The cath
rent which enters the lead 2i and departs main
40 ode is formed by a pool 12 of mercury, which ly through the outer shield 28. To some extent
rests upon the bottom of the tube and is, there
shield 21 may conduct the current in parallel
fore, electrically continuous with the portion 62 with
shield 25 but not much because the junction
of the envelope. At the middle of the bottom of
at
the
bottom is not welded. Thence the cur
the envelope a terminal 13 is provided integral
rent in through the feet 29 to the bottom 24 of 45
with
the
envelope
portion
62.
45
An igniter, having a tip 15 of silicon carbide or the tube, the exterior of which constitutes at 23,
cathode terminal. The anode Í is connected
boron carbide, is supported in contact with the the
pool 'l2 of`mercury, occupies the central position by any'suitableexterior device to the positive
in the tube. The tip 15 is supported by a screw potential. When the guard 26 has reached the 50
proper temperature, the guard and the structure
50 1G formed on the end of a conductor 11. The in its interior become a source of electrons which
conductor is surrounded by a glass seal 18 similar
to the seal i8 in Fig. l, and ending in a skirt 19 pass to the anode. The grid i6 is controlled
similar to the skirt i9 in said figure.v Because through the conductor I5 and when »it has a. suf~
the igniter structure is straight from the top of ñciently negative' potential, prevents the anode 55
current from starting.
55 the device to the mercury pool, it is shorter and
In the rectifier shown in Fig.Y 2, the cathode
the structure is more rigid than it would other
structure
acts like that described in Fig. 1, be
wise be and because it is central there is good pro
tection against shorting. The skirts 19 and 61 coming a source of electrons as soon as the guard
26 has acquired suiiicient temperature to emit
add'to this protection. This position of the ig
60
'60 niter vgives a structure permitting closer spacing electrons from its coated surface. Current from
of the electrodes >and skirt. An exhaust 86 is the anode 46 through the gas in the tube to the
connected, preferably by welding, by a flange 8i to cathode structure is possible after this tempera
the anode part 6i of the envelope which is per
ture is acquired, butin the opposite direction,
forated at 82 for cooperation with the exhaust. such current is not possible. This tube. there
fore, acts as a rectiñer of alternating current.
65 The pipe 80 may be permanently connected to
a pump, or when the tube has been sufficiently The connection, both to the heating circuit and
exhausted, may be sealed off.
to the circuit in which the current is to be recti
If it be desired to exhaust the tube of Fig. 3 iled are made by inserting the device in its
through a conductor as the tubes of Figs. 1 and 2
socket, no special positioning being needed as
70 are exhausted the conductor 11 may be hollow would be with the usual plurality of connecting
and an opening may be made in the side thereof pins. The direct heating oí the cathode mem
in the part within the skirt 19. When this is ber 20 in this tube is by current which enters at
done the pipe 8U will be omitted and no hole 82 the exterior end of tube 39 and departs from the
provided. When the pumping is iinished the sleeve I3. The current to be rectiñed has the
75 tube 11 may be closed by welding or otherwise.
4
2,121,761
sleeve 49 for one terminal and the sleeve 43 for
the other terminal.
'
In the controlled arc device in Fig. 3, the cur
rent controlling the igniter 15 is introduced at
the terminal 'Il and departs through the mercury
‘I2 and the cathode terminal 13. The current to
be conducted by the mercury arc is between the
terminal ‘I3 and any desirable connection to the
10 exterior of the anode 6|.
This current is con
trolled by the igniter 'l5 in a way familiar to
those skilled in the art. It may be actuated by a
dozen volts while the igniter requires some fifty
to one hundred and fifty volts.
15
Many modifications beside those speciñcally il
lustrated and described will occur to those skilled
in the art, and I do not desire to be limited by the
specific illustration and description oi the modi
ñcation shown.
20
25
30
I claim as my invention:
1. A discharge device comprising a cathode
structure having a directly heated source of elec
trons, a lead lor the heating current, a plurality
of radiation shields therearound and `an elec
trostatic guard surrounding said directly heated
a seal separating said lead from said portion,
another portion of the envelope being electrically
continuous with the anode and another seal sep
arating said portions.
2. A discharge tube comprising a metallic en
velope having two portions, one of which is elec
35 trically continuous with a cathode structure hav
the tube, a control electrode in said tube and a
lead to said control electrode extending to the
exterior of th envelope and a4 seal distinct from
the first-named seal through which the lead ex
tends.
5. A discharge device comprising a metal enve
lope having two portions, one of which is elec
trically continuous with the cathode structure,
said structure comprising a source of electrons, a
cylindrical guard around the source, and at least
one radiation shield around said guard, said
guard being electrically connected to said source
of electrons at one end only, said guard being
also electrically connected to one said portion of
the envelope, the other said portion of the en
velope being electrically continuous with the
anode, and a body of insulation separating said
portions of the envelope, said body of insulation
having glass and ceramic materials, at least one
of which forms a seal with the metal of the enve
lope.
6. A discharge device comprising a metallic
envelope having two portions, one of which is
electrically continuous with the anode structure
and the other with the cathode structure, a body
of insulation between said portions, said body
including a part of material forming a sealing
junction with the metal envelope and a part pro
jecting from the gap between said two portions
into the space within the device to form a skirt 30
materially adding to the length of the interior
leakage path between the cathode and anode.
7. A discharge tube comprising a metallic enve
lope having two portions, one oi' which is electri
ing a heated source of electrons and associated
metallic parts, a support for said structure ex
cally continuous with a cathode structure having '
a heated source of electrons and associated me
tending approximately the diameter o1' the tube,
tallic parts, a support for said structure extend
lng approximately the diameter of the tube the
other said portion of the envelope being electri
cally continuous with the anode, a seal separat
lng said portions and having a skirt projecting
from the gap between said two portions into the
interior of the tube, a lead i'or the heating cir
cuit, a return for the heating circuit including
the other said portion of the envelope being
40 electrically continuous with the anode, a seal
separating said portions and having a skirt ex
tending into the interior of the tube, a lead for
the heating circuit, a return for the heating cir
cuit including said support, and a seal concen
tric with and adjacent said first-named seal be
tween said lead and said return, whereby all ex
ternal terminals of cathode and anode have the
same relative position independent of the rota
tional position of the tube.
3. A discharge device comprising a metallic
40
said support, and a seal between said lead and
said return.
8. A discharge tube comprising a metallic enve
lope having two portions, one of which is electri
cally continuous with a cathode structure having
a heated source of electrons and associated me
tallic parts, a support for said structure extend 50
ing approximately the diameter of the tube the
other said portion of the envelope being electri
i cally continuous
55
velope, said seal having a skirt extending into
the interior of the tube and providing a long
leakage path on the inside of the tube between
anode and cathode, and an insulating extension
on the outside of the seal affording a long leak
age path between anode and cathode on the
outside of the tube.
4. A discharge device comprising a metallic en
velope having two portions, one cf which is elec
trically continuous with the anode, the other
said portion being electrically continuous with the
cathode, an insulating seal separating said- por
tions and constituting a portion of the envelope,
said seal having a skirt extending into the in
70 terior of the tube and providing a long leakage
path on the inside of the tube between anode and
cathode, and an insulating extension on the out
side oJ the seal aii'ording a long leakage path
betwetsA anode and cathode on the outside of
with the anode, a seal separat
ing said portions and having a skirt projecting
from the gap between said two portions into the
interior of the tube, a lead for the heating circuit,
a return for the heating circuit including said
support, and a seal concentric with said first
named seal, between said lead and said return.
A discharge device comprising a metallic (il)
`envelope having two portions, one of which is
electrically continuous with the anode structure
and the other with the cathode structure, bodies
of insulation between said portions, at least one
body being of a glassy material, at least one body
being of ceramic material, one of said bodies
forming a sealing Junction with the metal enve
lope and one of said bodies having a part extend
ing within the device to form a skirt materially
adding to the length of the interior leakage path 70
between the cathode and anode.
ERWIN F. LOWRY.
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