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Патент USA US2411810

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Patented Nov. 26, 1946
2,411,810
UNITED STATES PATENT OFFICE
2,411,s1o
AUDIO REAUI'QR
Morris Sander, Philadelphia, Pa, asslgnor to
Radio Corporation of America, a. corporation of
Delaware
Application September 20, 1943, Serial No. 503,054
1
7 Claims.
My present invention relates to a reactor for
use at audio frequencies, the inductance of which
it is desired to vary over a predetermined range.
In practice it has been found dif?cult to obtain
adequate inductance change in high Q, low-fre
quency inductors. In one application of the pres
ent invention, operating at about 939 cycles per
second, I have been able to obtain an inductance
variation of :l;Ll5%, the Q of the coil being be
tween 30 and 35.
(Cla I'll-“242).
2
l which are rectangular in cross-section. The
‘ three compartments are open-ended at the top
and bottom, are aligned with one another, and
disposed in parallel relation. The central com“
partnoent which is extended somewhat above and
below the two end compartments, as shown more
clearly in Fig. 4, is adapted to receive an iron
core made of compressed iron dust, the core be
ing sliclably adjustable within the compartment
Ml 5 by means to ‘be hereinafter described.
The two end compartments" 6, ‘l are each
is made adjustable and comprises a coil form oi
adapted to receive the center leg 9, Si’ of a com
insulating material having a central and two end
posite ?xed core M3 constituted by stacks of lami
compartments which are open-ended, in align
nations which may be of Numetal (a niclzel alloy)
ment and disposed in parallel relation. A coil of
or other suitable material. For convenience of
wire is wound around the coil form in a direction
assembly the ?xed laminated core it is made of
transverse to the direction of the compartments,
two similar parts it and it’ which are paired,
and a ?xed laminated iron core having an air
as shown more clearly in Fig. 3, to provide the
gap ‘is positioned within each of the end com
center leg d, 9', the portions of which are adapted
partments. There is further provided within the
to be inserted into an end compartment from op
central compartment a powdered-iron core which
posite sides and to be positioned in ?tted spaced
is capable of adjustment relative to the coil and
relation to provide an air gap iii’ between them.
air-‘gaps of the ?xed cores for the purpose of
In order to maintain the pair of laminated
varying the inductance of the reactor.
The novel features characteristic or" my inven~ 25 cores ill in ?xed parallel relation and also to
rigidly retain in position the two parts M, ii’ of
tion are set forth with particularity in the ap~
each.
core there is provided at each end a clamp“
pended claims. The invention itself, however,
ing plate 92 to which a pair of brackets l3 are
both as to its construction and mode of opera
spot welded or otherwise attached. The two
tion together with the objects and advantages
brackets of each clamping plate are properly
thereof, will best be understood by reference to
spaced and are adapted to embrace the corre
the following description taken in connection
sponding sides of the two ?xed cores it, and by
with theaccompanying drawing in which
means of four screws it the oppositely disposed
Fig. 1 is a plan view to scale of the reactor as~
In accordance with the invention, the reactor
'sern‘cly in accordance with the invention;
Fig. 2 is a front elevational view of Fig. 1;
Fig. 3 is a view in cross-section taken along the
- line 3-3 in Fig. 1, showing the two-part fixed
laminated core;
Fig. 4i is a cross-section taken along the line
il-d in Fig. 1;
.
Fig. 5 shows the complete assembly of the re
actor enclosed in a casing;
Fig. 6 is a detail view of the core adjusting
means, and
,7 represents the schematic circuit of the
reactor.
Referring to Fig. l the reactor comprises an
inductance winding or coil 5 which is wound, in
a plane parallel to the surface of the drawing,
clamping plates it‘ are held together. Each plate
is provided with a ?ange or foot portion i5 for
convenience or" attachment by means of screws,
rivets or otherwise to a base plate it (Fig. 5).
The base plate to has attached to it a pair of
terminals ll, ll’ to which the leads 3, d from the
inductance coil l are connected. A suitable rec
tangular-shaped metal can housing to is ?tted
over the entire assembly and is soldered or other
wise connected to an upturned flange it of the
base plate it. The can housing is provided at its
two shorter sides with a pair of flanges or foot
portions ill for attachment to a chassis or other
mounting, and is further provided in its upper
wall with an opening through which there is
passed a screw shaft 26 which is adapted to slid- ‘
ably adjust the iron core 8 within the center
around a centrally located spool or coil form 2.
50 compartment 5 of the coil form 2.
The coil leads are indicated at 3 and It. The
The iron dust core 8 is also square-like in cross
spool '2 may be of moulded nylon or other suit
able insulating material and is provided with
a central compartment 5, square-shaped in cross
section, and two similar end compartments 6 and
section and is provided with a centrally located
bore 22 which extends for about three-quarters
of the length of the core from the bottom. The
remaining portion of the core above the bore is
2,411,810
internally threaded and is adapted to ride on the
screw shaft. Frictionally within the bore and
positioned near the lower end thereof is a nut
plate Or retaining member 23 through which the
screw shaft_is also threaded. A compression
as a magnetic shield to con?ne the magnetic
?ux between them.
'
While I have shown and‘rdescribed a preferred
' embodiment of my invention, it will be under
spring 25 is concentrically arranged around the
shaft within the bore and extends between the
nut plate and the opposing internal rim portion
of the core in orderlto take up any play ‘or back
stood that various modi?cations and changes will '
occur to those skilled in the art without depart;
ing from the spirit and scope of this invention.
I therefore contemplate by the appended claims
to cover any such modi?cations as fall within the
10 true spirit and scope of my invention. ‘
lash between the core and the screw shaft.
What I claim is:
In order that the adjustable core may be ac
1..A reactor comprising a coil form of insulat
curately centered within its compartment there
ing material having a, central and two end com
is utilized a block member or plug 25 formed with
partments, said compartments being open-ended,
an aperture 28 within which the lower end of
the screw shaft is adapted to be seated. The 15
centering block is suitably attached by screws,
rivets, or the like, to the cover plate i8, is simi
larly shaped in cross-section as the center com-i
in alignment and disposed in parallel relation, a
coil of wire wound around the coil form in a direc
tion transverse to the direction of the compart
ments, a ?xed laminated iron core extending into
each of the end compartments, and an adjustable
partment, and is of su?icient length to extend
powdered-iron core extending into the central,
into said compartment at the lower end and to 20 compartment.
be snugly ?tted therein.
‘2. A variable reactor for audio frequencies com=
In order that the. core may be adjustably set
from the outside of the can housing, the latter
prising a coil form of insulating material having
a central and two end compartments which are
disposed in parallel relation, a coil wound around
is provided in its top'wall with an aperture it’
through which there extends an externally 25 the coil form in a direction transverse to the
threaded bushing 21!, the intermediate portion of
direction of the compartments, a ?xed iron core
which is provided with a ?rst disc member 36 and
extending into each of the end compartments,
a second‘ larger disc member 30’. The two disc
members may form an integral part of the bush
' said fixed cores each having an air gap located
in the field of the coil, and a powdered-iron core
or otherwise mounted thereon, as by means 30 adjustably movable within the central compart
of a forced ?t. The larger disc 3%’ is concentri
ment for varying the inductance of the reactor.
cally arranged with respect to the housing aper
3. A variable reactor for audio frequencies com
ture it’ and is soldered to the top wall of the \ prising a coil form of insulating material having
housing. By means of a washer 28 and a locknut ‘
a central and two end compartments, said com
. ing,
29, the bushing and its associated parts are
clamped in position. The bushing is adapted to
receive within its bore the upper unthreaded end
of the screw shaft 25 which is retained therein
and confined only to rotary motion by means of
partments being open-ended, in alignment and
disposed in parallel relation, a coil of wire wound
around the coil form in a direction transverse to
the direction of the compartments, a ?xed lami
nated iron core provided with an air gap extend
a C washer 3i engaging a circumferential groove 40 ing into each of the end compartments, and an
32 in the shaft. A washer 33 and a spring washer
adjustable powdered-iron core ‘movable within
3d are interposed between the C washer and the
the central compartment capable of varying the
bushing in order to lock the shaft against verti
inductance of the reactor.
cal movement. For effecting the desired adjust
4. A variable reactor in accordance with the
ment of the core, rotation of the screw shaft by
invention de?ned in claim 3 wherein the reactor
means of a suitable tool, such as a screw /driver,
is housed within a container provided with an
will cause the core to ride up or down depending
aperture which is aligned with the central com
upon the direction of shaft rotation. An inter
partment and through which there is adapted to
nally tapped cap 35 may be provided to ?t over the 59 extend the means for adjusting the powdered
exposed end of the bushing on which the screw
iron core.
head is seated to prevent tampering after an
5. A reactor comprising a coil form of insulat
adjustment has been made.
ing material having a central and two end com
In one embodiment of the invention the coil
partments said compartments being open-ended,
consisted of 1,000. turns of wire, the air gap in 55 in alignment and disposed in parallel relation, a
each ?xed core was 311", and the adjustable core
coil of wire wound around the coil form in a di
was 1" ‘in length and .594" square. With the
rection transverse to the direction of the com
adjustable core 8 all the way in (Fig. 5) and a
partments, a pair of three-limbed laminated iron
source of voltage at the input terminals of the
cores having their respective central limbs ex
reactor of 1 volt and a frequency of 1,000 cycles, 60 tending into one of the end-compartments and
the inductance was approximately 0.47 henry,
their outer limbs positioned externally of the
whereas with the core all the way out, the in
ductance was approximately.0.36 henry, an in
vcoil, and an adjustable powdered-‘iron core ex
tending into the central compartment.
ductance change of approximately 30%,' or
6. A variable reactor for audio frequencies com
115% from a mean core adjustment giving 0.415 ” prising a coil form of insulating material having
a central and two end compartments which are
henry. The inductance change is due to the fact
that the powdered iron dust core varies the in
ductance not only by acting on the turns of the
coil but also by short circuiting the air gaps‘o'f
the ?xed core stacks.
‘
In contradistinction to the usual reactor ‘as
semblies employed in radio apparatus, the in
. ductance and the Q of the reactor of the present
disposed in parallel relation, a coil wound around
the coil form in a direction transverse to the di
rection of the.compartments, a pair of three
limbed iron cores having their respective central
limbs extending into one of the end compart
ments and their outer limbs positioned exter
nally of the coil, each of said cores constituting
a closed magnetic circuit except for an air gap
invention are not affected by the can housing for 75 in the central limb located in the ?eld of the coil,
the reason that. the ?xed laminated cores act‘
2,411,810
and‘ a powdered-iron core adjustably movable .
within the central compartment relatively to the
coil and air gaps for varying the inductance of the
‘ reactor.
‘
7. A variable reactor for audio frequencies com
prising a coil form of insulating material having
a central and two end compartments, said corn
partments being open-ended, in alignment and
disposed in parallel relation, a. coil of wire wound
around the coil form in a‘ direction transverse to 10
the direction of the compartments, a pair of lami
nated iron cores disposed in parallel planes, each
provided with a central limb located in one of
the end compartments, each of said cores consti~
tuting a closed magnetic circuit except for an air
gap in each core, and an‘ adjustable powdered
iron core movable within the central compart
ment relatively to the coil and air gaps for vary
ing the inductance of the reactor.
MORRIS SANDER.
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