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Патент USA US2115916

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Mxipy 3, 1938.
M.v osNos
original Filed May 5, 19:52
BY /fíëmw "
Patented May 3, 1.938
Mendel Osnos, Berlin, Germany, assigner to Tele
funken Gesellschaft für Drahtlose Telegraphie
m. b. ll., Berlin, Germany, a corporation of
Application May 5, 1932, Serial No. 609,401. Re
newed July 25, 1936. In Germany July 2, 1931
3 Claims'.
(Cl. F15-41.5)
This invention relates to an improved electric such a condenser is directly proportional to the
condenser whose capacity varies very markedly variation in the temperature, indeed, it is pos
with the temperature. A condenser of this in
vention is particularly adapted to use in a cir
cuit for tuning the capacity of a vacuum tube
transmitter, especially when short-waves are em
ployed, and is to be controlled from a remote
point or else for the purposes of stabilizing fre
quency of a valve transmitter controlled by the
agency of a piezo-electric crystal.
According to the invention a. vcondenser of this
kind is created so that it active surface or its
inter-electrode distance, or else both, are adjusted
or regulated by a fluid possessing a large tem
perature coeflicient of expansion or else by a gas
sible to write with close approximation:
whereTo and Ca the temperature and capacity.
respectively when the level of the column of the
liquid> between the lateral walls is flush with the
lower edges of the tinfoil coats or slightly above
them, T a higher temperature and C'a corre
spondingly increased capacity, Vo the volume of
the liquid at temperature To, K a constant which
is a function of the nature of the liquid and of
the dimensions of the container.
bination of both, _for example, by means of elec
If the liquid consists of mercury having a co
efficient of thermal expansion of say 0.000181,
if the distance between the surfaces of the shell:
1 mm., the wall thickness 1 mm., and if a kind of
tric .heating to a more or less high degree, with
the result that the capacity of the condenser is
then with close approximation:
(say, air) or a combination thereof. It is then
feasible to heat the liquid or the gas or a com
glass is used having a dielectric constantz'l,
regulable or adjustable at will at anyv desired
A number of practical embodiments are shown
in the drawing, of which,
Fig. 1 is a vertical cross section of the improved
condenser having double walls;
Fig. 2 is a vertical cross section of a simple
modification of this condenser;
-Figl 3 is a vertical cross section of another30 modification of this condenser;
Fig.k 4iso. Wiring diagram of the heating sys
Referring to Fig. 1, I and IA denote a double
walled (jacketed) glass vessel of cylindrical form
whose space between the lateral walls is very
small (say, 1/2 to 1 mm. in radial direction) but
comparatively large between the bottom or4 end
pacitance) between the liquid and the metal plate
9 is `very low so that the capacity according to
Equation (2) comes to be close to that between.
the contacts 8 and 5.
Another simpler, though somewhat less favor
able, embodiment is shown in Fig. 2, where l is
a glass jar or bottle having a base or bottom- con
siderably larger in area than the cross-section
of the neck, and 2| a metallic electrode which
can‘ be screwedby means of a screwthread 4 on
the collar ring or flange 22 so as to be at the
correct distance above the liquid’s level (mer
cury) .
Now, if the liquid mercury ~ls heated by means
'I‘he space or cavity between> the bottoms of the of the heater windingv 'i wrapped around the body
two cylinders is filled entirely by a suitable liquid , 9 the liquid will be caused to expand, the distance
2 such as mercury, for instance.
The space be
tween the shells is not filled at all or only up to
a certain height or level h; but the entire space
between the shells is suitably exhausted. The
inner and ‘the outer shell starting at a certain
level ho is coated with a highly conducting metal
il,À and 3A say, tinfoil.
The entire vessel is supported by a coil body 9,
preferably made of metal which carries a wind
ing 1 heated by current.
between its surface and the electrode 2| de
creases, andthe capacity increases.
Equation (2) shows, since the coefficient K is
equal to 2X10-3 that a considerable volume Vo
must be provided in ord-r that, in the presence of 45
a moderate change in the temperature there may
be obtained an appreciable change in, the ca
pacity. This involves the drawback that the con
denser must be made of considerable size so that
it would occupy much space _in the metal -housing 50
When the temperature of the liquid mercury
increases its level will rise in the space between
where C in cm., Vn in cm. cu., and T in degl'. C.
For short waves the capacitive reactance (ca
of the transmitter. Another point is that a large
the lateral Walls and there is formed a capacity
volume of the vconducting liquid confined inside
the sheet-metal casing would occasion seriousl
between the liquid and the tinfoil coat.
losses where short waves are dealt with.
It can be proved that the change in capacity of
Now, this> drawback can be obviated by that
only part of the conducting liquid mercury is
placed inside the sheet-metal housing, while
that the change in capacity, as already pointed
out, is predicated only upon the temperature
` the major part thereof is outside.
differences of the two spaces.
'I'he difference in the temperatures of the two
spaces may be regulated, for instance, by means 5
of a bridge arrangement according to Fig. 4,
.(3) where,
as previously, 6 and I3 the heater resistors
In practice it will befound advisable to make . of the spaces 3| and |2,vwhi1e Il denotes a po
the quantity
tentiometer located at the control point whose
voltage division ls regulated by a slide contact
(4) I5. In case of diñerential heating the resist
But it Will be noted that Vo even in the limiting ances and the cooling conditions of spaces 3| and
case must be equal to 500 cu. cm. Assuming that I2 may be so chosen that the temperature of the
the liquid is mercury, the weight thereof would ambient will exercisevno influence upon the ca
be as much as 0.5><13.6=6.8 kilos. However, the. pacity so that the capacityis merely a function
of the position of contact Il ‘(Fig. 4).
volume of the conductive liquid may be apprecia
I claim:
bly reduced if for the actuation of the mobile
l. An electric condenser comprising an insulat
‘electrode recourse is had to the thermal expan
sion of a liquid or gaseous substance which, while ing cylindrical casing having a double wall, said
being non-conducting or but slightly conductive, double wall having a relatively small internal 20
possesses a high coefficient of thermal expansion. space in the radial direction but a substantially
An embodiment of this kind is shown in Fig. 3. large space between the bottom of one of said
The constituent parts of the device are as fol
walls\and the top ofthe other wall, a metallic
coating on the upper outside surface of each
What follows further-from ’Formula I(2) is that
_ 3| is a-space within the glass vessel I which
is filled either with liquid or with a gas (air)
wall, a mobile electroderwithin said walls, and an 25
external electric heating element comprising a
disk-like coil body having a heater winding and
located below said container to control the level
or with both, which though not conducting elec
tricity, possesses a high coeñj'icient of thermal ex
pansion; 2 is a conductin’g liquid mercury, 3 and of said mobile electrode.
2. An electric condenser comprising an insulat 30
3a tinfoil coats, I the cylindrical glass vessel
ing cylindrical casing having a double wall, said
with a double wall being open inside a short dis
tance above the bottom, 35 a cover being èe-' double wall having a relatively small internal
mented on the' ‘glass vessel I, 9 a heater body, space in the radial direction but a substantially
31 insulated lead-ins to the heater body, 38 large space between the bottom of one of said
terminals for the latter, 39 a seal for the lead walls and the top of the other w`all, a metallic 35
coating on the upper outside surface of each
to the liquid electrode, 30 lead to the liquid elec
-trode, 34 cementing of the cover 35, i2 space wall, a mobile electrode located within the lower
above the conducting liquid between the shells portion of said walls, the space in the upper por
of the two cylinders. 'I‘he space is» either tion of‘said walls being evacuated, and an ex
40 evacuated or contains a gas (air) of lower pres
ternal electric heating element` comprising a 40
disk-like body having a heater winding and lo
sure than the pressure inside space 3|; option
ally also a heater coil I3 for heating the space I2. cated below said container to control the level
If the heater element 6 is heated electrically, of said mobile electrode.
3. An electric condenser comprising an.inthe pressure inside space 3| will rise and thus
also the mercury in space I2, and thus alter sulating cylindrical casing having a double wall, 45
said double wall having a relatively small in
4the capacity of the condenser.
If space I2 is' small enough compared with ternal space in the radial direction but a sub
space 3l it can be proved that the capacity of stantially large space between the -bottom of one
of said walls and the top of the other wall, a
the condenser is nearly proportional to the tem
50 perature in the space 3|, if space I2 is evacuated.
metallic coating on the upper outside surface of 50
each wall, a mobile electrode of mercury within
But if the space I2 is not exhausted then the ca
pacity of the condenser is proportional to the ' the lower portion of said walls, the space in -the
temperature and pressure difference between upper portion of said walls being evacuated, and
spaces I2 and 3|.
an external electricheatlng element comprising55
Instead of the space 3| it would be possible a disk-like body having a heater winding and lo-~ 55
also to heat the space I2, and then the capacity cated below said container to control the level
decreases with increasing heating current. It of said mobile electrode.
would also be feasible to heat both spaces though
at diñerent temperature, for it will be understood
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