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Патент USA US2137005

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NOV. 15, 1938. _
A original Filed May 28, 1937
Patented Nov. 15, 1938
Carl F. Miller, Emporium, Pa., assigner to Hy
grade Sylvania Corporation, Salem, Mass., a
corporation of Massachusetts
Original application May 28, 1937, Serial No.
145,198. Divided and this application Novem
ber 17, 1937, Serial No. 174,981
2 Claims.
This invention relates to electron discharge
devices and more especially to radio tubes of the
high frequency amplification type.
An object of the invention is to provide an irn
5 proved form of enclosing envelope for a radio
tube of the top-cap contact type.
A feature of the invention relates to a radio
tube of the top-cap contact type having an outer
metal envelope with a reentrant top to shield the
top-cap contact electrostatically.
Another feature relates to a radio tube of the
top-cap contact type having an outer enclosing
metal envelope which is shaped so as to protect
the top-cap contact of the tube electrostatically
and mechanically.
A further feature relates to an improved struc
ture of a radio tube of the shield-grid type.
A further feature relates to a novel structure
of metal envelope radio tube of the shield-grid
20 type.
A still further feature relates to the novel or
ganization, arrangement and disposition of parts
which constitute an eflicient radio tube of the
shield-grid type.
Other features and advantages not specifically
enumerated will be apparent after a considera
tion of the following detailed descriptions and
the appended claims. While the invention will
be disclosed in connection with specific types of
30 tubes, it will be understood that this is done
merely for purposes of explanation and not by
way of limitation. Accordingly, in the drawing,
Fig. 1 shows the invention embodied in a radio
tube of the glass-bulb type.
Fig. 2 shows the invention embodied in a radio
tube of the metal-bulb type.
Fig, 3 is a modification of Fig. 1.
In certain types of radio tubes, for example
those employing a plurality of grids especially
40 tubes of the so-called screen or shield-grid type,
it is the usual practice to bring the connection
to the control grid out through the top of the
tube envelope, and to provide a top-cap for
making the external circuit connection thereto.
45 Because of the relatively large surface area of
such top-caps, it becomes important in some sys
tems of circuit connections, to reduce the elec
trostatic pick-up to the top-cap to as low a value
as possible. Furthermore, it is desirable to pro
tect the top-cap against blows or jars which
would tend to loosen the cap. I have found that
by providing a metal enclosing envelope having a
reentrant top within which the top-cap of the
tube is located, the above and other advantages
55 are achieved.
(.Cl. Z50-«275)
One manner of’ accomplishing these results is
shown in Fig. l. In this figure, the tube proper
comprises a glass-enclosing envelope or bulb I
which is provided with a suitable base carrying
the Contact prongs 2. Suitably mounted within
the bulb I is an electrode mount or assembly des
ignated generally by the numeral 3. When this
assembly is of the so-called shield or screen-grid
type, it is the usual practice to make connection
to the control grid through a top-cap 4 which is 10
cemented or otherwise fastened on the top of the
bulb I. The lead-in wire 5 is sealed through the
wall of the bulb I and connects the control-grid
of the electrode assembly with the cap 4. Be
cause of the relatively large surface area of the
metal cap 4, it is susceptible to an appreciable
electrostatic pick-up.
In accordance with the
present invention, the glass-bulb I is provided
with a metal sheath 6 which preferably closely
its the bulb I and is fastened at its lower end to
the base of the tube in any convenient manner.
For example, the glass-bulb I may be provided
at its lower end with a metal cup-shaped member
such as described and disclosed in detail in ap
plication Serial No. 145,198 and the lower end of 25
sheath 5 may be welded or otherwise fastened to
the cylindrical wall of this cup-shaped member.
As shown in Fig. 1, the sheath B extends up
wardly beyond the cap 4 for an appreciable dis
tance and is formed with a reentrant portion 'I 30
having a central opening 8 materially larger
than the diameter of cap 4, so as to avoid short
circuiting thereto. If desired an insulator wash
er or grommet may be provided between the
cap 4 and the edge of opening 8 as shown in Fig.
3, although when the sheath 6 is rigidly fastened
to the base of the tube as above mentioned, and
when it ñts the bulb I snugly, such insulating
washer may not be necessary. By reason of the
upwardly extending reentrant portion of sheath 40
6, the top-cap 4 is eifectively shielded electro
statically. It will be understood of course that
the sheath 6 is connected to ground or some other
suitable steady base potential when the tube is
connected in circuit so as to effect the necessary
electrostatic shielding of the top-cap 4. Because
of the reentrant portion l, the top-cap 4 is also
to a certain extent protected against blows or
jars since it is entirely surrounded by the said
reentrant portion l.
Fig. 2 shows the invention embodied in a tube
of the metal-bulb type. This tube may be of the
conventional metal-tube construction compris
ing an inverted cup-shaped metal header 9 carry
ing a plurality of metal eyelets IU within which
are sealed the glass beads II, and sealed through
the latter are the various lead-in and support
Wires for the electrode mount I2. Also fitted and
held Within the member 9, is an insulator disc I3
carrying the contact prongs I4. Welded to the
header 9 is an evacuated metal-bulb I5 which in
accordance with the invention, extends upwardly
beyond the mount for an appreciable distance.
The lead-in Wire I6 leading for example to the
10 control grid of the mount, is sealed into a glass
bead I‘I which in turn is sealed into a metal eye
let I8, a metal contact cap I9 connected to the
Wire I6 and is fastened in any suitable manner
on the glass-bead I‘I.
The upper end of the metal-bulb I5 is formed
with a reentrant portion 20 having an opening
at its base into which is sealed, as by welding or
brazing, the metal eyelet I8. It will be under»
stood that the particular method of insulating
20 the lead Wire I6 from the eyelet I8 and the par
ticular manner. of-attaching the cap I9 so that
it also is-insulated fromthe said eyelet I8 is mere
ly typical. In this embodiment, When the tube is
connected in to circuit, the metal-bulb I5 may be
25 connected to ground thus electrostatically shield
ing the mount I2 at the same time that it serves
as the enclosing envelope for the mount. By
reason of the reentrant portion 20, the top-cap I9
is both electrostatically and mechanically pro
tected at all times. While certain specific shapes
of tubes have been illustrated herein, it will be
understood that various changes and modifica
tions may be made therein without departing Ul
from the spirit and scope of the invention.
This application is a division of application
Serial No. 145,198, filed May 28, 1937.
What I claim is:
1. In combination, a radio tube mount, an 10
enclosing envelope for said mount, a top-cap con
tact carried by the envelope, and reentrant metal
means extending beyond the mount and through
which said Contact insulatingly passes, said re
entrant means extending upwardly beyond the
upper end of said top Contact.
2. In combination, a tube mount, a glass en
closing envelope for said mount, said envelope
carrying contact prongs at the lower end, a metal
contact cap carried by the upper end of said en
velope, and a tubular metal sheath fastened at its
lower end to said base and closely fitting said en
velope, said sheath having a downwardly reen
trant dish-shaped portion through the bottom of
which said Contact cap insulatingly passes, said
sheath extending upwardly beyond said cap to
protect it electrostatically and mechanically.
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