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Патент USA US2130432

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Sept. 20, 1938.
Filed Aug. 3, 1934
Patented ‘Sept. 20, 1938
Rudolf Schmook, Berlin-Siemensstadt, Germany,
assignor to Siemens & Halske, Aktiengesell
schaft, Siemensstadt, near Berlin, Germany, a
corporation of Germany
Application August 3, 1934, Serial No. 738,198
In Germany August 3, 1933
3 Claims. (Cl. 175-359)’
The present invention relates generally to cou
a cylindrical casing 8 which serves to preclude
pling systems and more particularly to air-core stray lines. It has been found that by the aid
of such a cylinder, which, of course, should sur
The object of the present invention is to devise round the coils as snugly as feasible on the out
5 an air-cored high~frequency transformer which side in order to exercise an appreciable influence 5
distinguishes itself from the forms of construc
upon the stray lines, the ?ux can be held or
tions customary in the earlier art in that it oper
crowded together, as it were, to a great extent
rates with an extremely low leakage flux so that
it insures a very high degree of coupling.
In accordance with this invention the said out
standing advantages are obtained by shielding
the spaces through which the magnetic flux
so that the maximum coupling that is attainable
will have a high value. The coupling factor, of
course, is considerably higher than when two coils 10
of the same sort are used in exactly the same
The shielding effect as here secured may be ex
position but without the outside shield. What
is essential in this connection is that the shield
ing shell should be open at its ends to permit
emergence of the flux lines. In this way the flux 15
lines have an opportunity to form a closed loop
in the outside space. If the casing were com
pletely closed the flux lines would be compelled
plained in such a way that such stray flux lines
to form closed loops inside the shielded space,
lines are to pass by means of a casing of high
electric conductivity from the emergence of alter
'l5 nating current stray ?uxes, said casing being
electrically subdivided so that it will not consti
tute a short-circuiting ring for the main flux.
20 as may escape, occasion in the conducting casing
eddy-currents which, in turn, set up counter~
active magnetic ?elds which will act in opposi~
tion to the leakage ?elds.
T_wo exempli?ed embodiments are shown in
the drawing to better explain the idea underlying
the invention. In the drawing, Figure 1 illus—
trates the invention applied to a transformer
wherein the primary and secondary windings are
?xed as regards their space relationship, and,
30 Figure 2 illustrates the application of the inven
tion to an arrangement wherein at least one of
given case; indeed, -it need not necessarily be
cylindrical. It is also possible to use prismatic
shields of other cross-section, say, four-sided ele- 25
ments. The arrangement described with refer
ence to Fig. 2 could be used also as a regulable
inductance, and not only as a transformer or as
a coupling system.
So far as the leakage between the coils and
thus also the attainable coupling and the inducthe transformer windings may be varied spacially. tance are concerned, the relationship between coil
Figure 1 shows an R. F. transformer in which
diameter and coil length is .of importance. In
the two coils I and 2 are positioned at a ?xed the light of investigations it, has been shown that
35 space relation to each other. These coils are it is a suitable plan to choose the said relationsupported by a bush 3 which possesses high elec
ship in such a way that the diameter will be
trical conductivity, and which is designed so that about from two to four times the length.
it will act upon such stray lines as may escape in '
Inasmuch as for the production of the desired
the desired manner. Inasmuch as by the aid of effect high electric conductivity of the casing is a
40 the said coil body or coil-former '3 having the prerequisite, it is primarily copper that would
action of a shield or screen, conditions are made
come into consideration for making the casing,
so that the same flux will traverse both coils, the and‘ it is also a good plan to make the casing
shape of the ?ux-lines outside the arrangement walls of adequate thickness seeing that, if the
is quite immaterial. Still, it would be possible to
45 mount a protective shell which will surround the
coils also from the outside so that the coils I
and 2 in this instance are perfectly embedded,
as it were, within a conducting case.
In the embodiment shown in Figure 2 only
50 one of the two coils, i. e., coil 4 is ?xed in space.
The coil 5 is supported by a spindle 6, and by
the aid of the latter, say, by revolving a small
wheel or knob ‘I, it is capable of being operated
to different positions with reference to the coil 4.
55 Both coils are outwardly shielded by the aid of
and this would tend to defeat the very purpose 20
that is aimed at here. The shape of the casing
may be adapted to the conditions prevailing in a
thickness of the walls were smaller, eddy-currents
would not get a chance to develop in the desired 45
manner in order to displace the stray lines.
Where the frequencies are extremely high, the
wall thickness may be very small to make condi
tions adequate.
It is preferable not to make the shield of solid ‘50
or compact material, but to subdivide or stratify
it into constituent layers, or even to use a com
pressed dust which may be molded with insula
tion material.
It is known that not only the coupling, but 55
also other properties of the high-frequency trans
former are governed to a great extent by the
leakage. However, inasmuch as the leakage
varies with the frequency, it may be said that
said properties are a function of the frequency.
However, in the case of any set of prevailing
conditions it will be feasible to ?nd a solution
which will satisfy to a large degree the require
ment of frequency dependence. The subdivision
10 of the shielding means as described constitutes
a way particularly suited inlthe said respect.
I claim:
1. An air core radio frequency transformer in
cluding a hollow‘ spool of material having high
conductivity shaped to provide a central
15 hub portion with a radially outwardly extending
?ange at each end, and primary and secondary
coils wound alongside each other and in close
proximity to each other and to the hub and
?anges of the spool, the coils and spool ?anges
being radially co-extensive.
2. An air core high frequency transformer in
cluding a hollow spool composed of compressed
?nely divided material having a high electrical
conductivity, said spool being shaped to provide
a central hub portion with a radially outwardly (a
extending ?ange at each end, and primary and
secondary coils wound alongside each other and
in close proximity to each other and to the hub
and flanges of the spool, the coils and spool
?anges being radially co-extensive.
3. An air core high frequency transformer in
cluding a hollow spool made up of laminations
of a material having high electrical conductivity,
said spool being shaped so as to provide a central
hub portion with a radially outwardly extending
?ange at each ‘end, and primary and secondary
coils wound alongside each other and in close
proximity to each other and to the hub and
?anges of the spool, the coil and spool ‘?anges .
being radially co-extensive.
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