New-York tribune., 1922-08-27
Huge Tube MAY
Throw Voice
Across Sea
Most Powerful Vacuum Tube
in World, Developed by
Bell Laboratories, Will
Deliver 100 Kilowatss
Can Supplant Machines
Mystery Surrounds Purpose
of New Tube; Engineers
Refuse TO Discuss Plans

produced in the Bell Laboratories with
an output of 100 kilowatts. This re-
markable instrument, which is the
elimination of an extended period of
research work, is expected TO COM
pletely revolutionize long-distance
wireless telegraph communication and
may also make transatlantic radio te-
lephony possible within very short
time
There is not the slightest doubt but
that it places this country in the most
strategic position in the race to be the
first TO throw the voice across the broad
expanse of the Atlantic.
Although the new tube can be con-
venientiy held IN one hand it will pro-
duce sufficient power to bridge the ocean
for telegraphic purposes, and will in
time completely replace the cumber-
some and ponderous machinery which
is now necessary for that purpose.
Moreover, the cost of maintaining
trans Atlantic service with such tubes
will be almost infinitesimal as COM
pared with the machinery.
Trans Atlantic Telephony
The engineers who have developed
these tubes will not discuss the pur-
pose to which they will be applied, but
it is my belief that two such tubes
carry the voice across the ocean, while
four of them will unquestionably do
80 under%practicall all conditions that
may exist, so that reliable uninter-
rupted service could be maintained be-
tween New York and London.
Back Of the development of these big
tubes there lies a story of steady
progress in overcoming physical OBJ
stacies, and as consequence the tube
e A.. ..-.41 e
all existing types. The success attained
with it is due to two outstanding fea-
tures-frst, the system Of water cool
ing, and, second, the process whereby
large pieces of metal have been sealed
into glass in such a manner that the
vacuum can be maintained under wide
ranges of temperature.
The tube differs from the standard
form in that the plate is on the out
side of the tube, so that it can be
placed in a socket where water is cir
culating, and thus take care of the
cooling of the tube during the period
of operation.
The original work on the develop
ment of the high power tubes in the
Bell Laboratories at the Western Elec.
trio Company was undertaken by Dr..
L. r. Stoekle and DIR. O. e. Buckley,
and the water cooling system was de-
vised by the former.
Ten-Kilowatt Tube Built
At the conclusion of the war steps
were taken to continue the work by
construction of a 10kilowatt tube. The
story of this early work is told by Dr..
W. Wilson, who is in direct charge Of
vacuum tube design in the Bell Labora-
tories, in the following words:
mir. W. G. Housekeeper and DR.. Nj.
IL S.l- l1,S f,r,- h
provement of the water-coofed tube,
the former assuming the task of de-
veloping the mechanical structure, ana
the latter that of determining the
electrical design and the process Of
tube exhaust
'Mr. Housekeeper adopted into the
construction of the tube a remarkable
type of vacuum seal which he had
previously developed, These seals are
made between glass and metal and can
be made in any desired size. They are
capable of withstanding repeated heat
ing and cooling over wide ranges of
temperature, from that of liquid air to
$50 degrees C, without cracking and
without impairment of their vacuum
holding properties.
1T is no exaggeration to say that
the invention of these seals has made
possible the construction of vacuum
tubes capable of handling in single
units powers of any magnitude which
may be called for in wireless telegraph
and telephone transmission.
Seal Withstands Stress
THE underlying principle connected
\ with the making of this seal consists
n in obtaining an intimate connection
- between the glass and metal, either
by chemical combination or by mere
,..,~ -. L
glass and metal portions of the seal
that the stresses produced when the
seal is heated or cooled will not be
great enough to rupture either the
= glass or the junction between the glass
and metal.
The three principal types of seals
developed by Mn. Housekeeper are
known as the ribbon seal, the disk seal
and the tube seal
IF copper ribbon is directly sealed
through glass it is found that the
glass and copper adhere along the fiat
faces of the seal, but that ruptures
to the fact that as the seal eools after
being made the glass in contact with
metal is capable of resisting the shear
ing and tensile stresses that occur
along the faces, while the glass wrap
ping around the edges of the ribbon
is called upon to withstand much
greater tensile stresses and gives
way. II the edges of the ribbon are
sharpcned tight seal results, the
reason being that the forces of adj
hesion between the glass and copper
acting along the fiat contact faces are
sufficient to stretch the thin copper at
the edge and prevent it's drawing away
when cooled. There is definite re-
lation between the elastic properties of
the metal and glass and the angle OF
edge that can be used for q successful
seal.
"Rv proper shaping of the metal
eTppon seals have been successfully
made up to very large sizes. Some of
these are about one inch in width and
capable OF successfully conducting a
current OF $50 to 200 amperes.
Getting Vacuum Difficult
One of the greatest difficulties in
constructing The I0-kilowatt tube was
the problem of exnausting the tube
This was due to the large amount OF
oeciuded gas contained by the metal
parts Of the internal assembly. This
extended the period of pumping and
IL first caused dangerous warping
of the internal structure because Of
the fact that during the period of
pumping the tube elements were main
tanned at much higher temperature
than they were ever called upon to
sustain during normal operation.