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Патент USA US2118190

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May 24, 1938.
Filed Sept. 5, 1935
2 Sheets
May 24, 1938.
2 Sheets-Sheet 2
Filed Sept. 3, 1935
Patented May 24, 1938
Frank W. Godsey, Jr., North Adams, and Robert
C. Sprague, Williamstown, Mass, assignors to
Sprague Specialties Company, North Adams,
Mass, a corporation of Massachusetts
Application September 3, 1935, Serial No. 39,020
(Ci. 175-415)
2 Claims.
responding contraction of the plates takes place.
The present invention relates to variable con
densers of the type as used for trimmer or pad- .
ding condensers, antenna condensers, etc.
Condensers of this type have to meet various
5 manufacturing and operating requirements. For
instance, they must be small and compact, in
expensive, easily adjustable, and be so designed
as to readily lend themselves to economical manu
facture in mass'production.
In addition, they
10 must be mechanically stable and return to the
same capacitive setting after being subjected to
a heat cycle. Furthermore, the adjustments must
be simple and continuously variable throughout
the rated capacity range of the condensers, and
15 any obstacle interfering with a. continuous ad
justment, suchas binding of the elements or of
the adjusting means, undue friction, and the like,
is to be avoided.v
Such condensers usually consist of at least one
?xed and at least one ?exible and adjustable
metal condenser plate, between which metal
plates is disposed a plate or layer of dielectric
material, for example of mica. To obtain a con
tinuous variation of the capacity by manual ad
25 justment, the ?exible plate is made of resilient
material having a high degree of elasticity, and
its capacitive relationship to the ?xed plateis
varied by ?exing it toward or away from the
?xed plate by means of adjusting screws, nuts or
the like.
The main di?iculty heretofore encountered with
this type of condensers, was due to a sidewise dis
placement of the ?exible plate relative to the
fixed plate, and/or a binding of the condenser
plates and dielectric plates, due to inadequacy of
the mounting and adjusting means, and especial
ly due to a lack or inadequacy of the guiding
Such a relative displacement of the condenser
40 plates or their binding was not only brought about
in prior art condensers when the adjustment oi
the condenser was changed, but also took place
with a set adjustment, due to the successive ex
pansions and contractions of the condenser
45 plates, as a result of the heat cycle which the
condensers undergo in use; this because the con
densers are used as a rule in devices, for example
in radio receiving sets, in which a considerable
heat development takes place during operation,
60 so that even if the heat development in the con
denser per se is negligible, it heats up because
of the heat developed in the radio set. Such
heating up causes an expansion of the condenser
plates, and when the radio set is placed out of
operation and the condenser cools down, a cor
To overcome some of these di?iculties construc
tions have been suggested in which the end por
tions of the ?exible condenser plates were riveted
to the base. This expedient besides considerably
increasing the size of the condenser—as much
of the total area of the plates merely serves for
their anchoring without adding to the effective
capacity of the condenser-permits the plates to
expand only in one and not in two directions, as
a result of which strains are set up during the
heating and cooling cycle, which cause the buck
ling of the plates and may also result in other
mechanical defects.
To permit the plates to have relatively free ex
pansion and contraction in both directions, con
structions were suggested which limited the free
dom of the condenser plates merely by guides
placed sidewise to the plates. Such guides as a
rule are expensive and necessitate the use of ex
cessive material.
It is the object of our invention to eliminate
the above referred to dililculties, and to provide
a condenser, which for a given capacity value, is
more compact and requires less material than 25
the prior art condensers.
Another object of the invention is to provide
for guiding means of thecondenser plates, which
provide merely the three guiding points theoret
ically required for the proper- location of one body 30
with respect to another.
Another object of the invention is to combine
two condensers into a. single unit with novel ad
justing means permitting individual adjustment
of either condenser from the same side of the
A further object of our invention is to eliminate
objectionable capacitive coupling in a multiple
condenser structure.
Further objects and advantages of our inven
tion will appear as the speci?cation progresses.
In the drawings forming part of this speci
Figure 1 is a plan view of one embodiment of
our invention;
Fig. 2 is a cross-sectional elevation along lines
2-—2 of Figure 1;
Fig. 3 is a cross-sectional elevation of a twin or
dual condenser made in accordance with our in
Figs. 4 and 5 are plan views of a condenser
plate and of an insulator plate respectively, used‘
in connection with the ‘condensers shown in
Figs. l-3;
plate 3.5 register with the hole I‘ and the ribs
20-20 respectively.
Fig. ii is a side elevation at the dual condenser
of Fig. 3;
Fig. 'i is a fractional bottom view of the corn
denser of Figs. 3 and 6.
Fig. 8 is a partial vertical sectional view show
ing a variation in the adjusting means of the
condenser of Figs. 3 and d;
It will be noted from Fig. 1 that in the as-_-_
sembled condenser one of the metal plates, for
example the ?at plate 25, engages with its notch
Blithe corresponding left-hand rib 20, whereby
its left-hand edge 98, ialls at a distance L from
the left-hand wall I8 of base in; whereas the
right-hand edge 99 contacts with the right side
wall l8. Thus, when plate 25 is expanded by
heat,‘ it can freely expand in both length and
width directions, whereas at the same time it is
securely guided at the three theoretically re
Fig. 9 is a plan view of another form of coin
denser, in accordance with our invention;
Fig. 10 is a vertical section taken on the lines
l?-IO of Fig. 9;
Fig. ii is a plan view of still another i'orm of
condenser, in accordance with our invention.
quired points; two such points being provided
by its right side edge 99 hearing against side wall
i8, and the third point being aiforded by the
Fig. 12 is a vertical section on the lines Eli-l2
of Fig. ll.
Referring to Figs. 1 and 2, a molded base it
of insulating material such as arti?cial resin or
the like, having rounded corners ii, is provided
on its top with an open-ended shallow recess, be
tween the side walls l8 of which is placed a con
denser assembly A, later more fully described,
and has on. its twosides upwardly-projecting in
tegral mounting lugs iii-412 having holes l3--li'i
to receive suitable attachment bolts.
A central hole M of the base it is adapted to
receive a. slotted-end screw [15, which screw pro
,iects upwardly above the‘top face i6 of the base
it and passes through the condenser assembly
The screw l5 with a nut l1 forms the ad
30 lusting means for the condenser. inwardly from
the lugs l2—-l2 extend rounded guide'ribs 20—2il,
which are preferably integrally molded with the
base it. The ribs 20-20 serve to locate the con
denser assembly A and to guide the ?exible plate
semicircle contact between notch 30 and the left
hand rib 20. To be able to freely expand in all
directions there must be a slight clearance be
tween the end rib 20 and notch 30.
The insulating plate 35 is placed on top of plate
25 and extends substantially irom one side wall
E8 to the other side wall 58, and also extends
beyond both ends of plates 25 and 25'.
The vaulted and adjustable plate 25’ lies with 25
its left-hand edge 98’ close to the left-hand wall
l8, whereas its right-hand edge 98' is spaced from
the right side walllii, and its notch 30’ engages
the right-hand rib 2m in a manner similar to that
of plate 25.
It will be also noted that the inclined exten
sion lugs 21 and 21' extend at the'same end, but
at opposite sides of the assembly.
Onv top of the ?exible plate 25' there is pro
vided a concave spring washer 40, by which‘ a 35
uniformpressure can be exerted on the assembly
A under action of nut l1.
The adjustment of the condenser depends on
condenser assembly A and contact with parts 1
the position of nut I1, and by exerting a greater
thereof '/alon_g a semicircle of small radius.
or smaller pressure on plate 25’ this plate is ?exed 4.0
The condenser assembly A consists of two me
of the assembly.
It will be noted that the ribs ‘ill-e20 are dis
posed on opposite ends of the shortvaxis of the
to a greater or lesser amount and thereby ac
tallic condenser plates 25 and 25' (see Fig. 4)
of identical shape except that plate 25 is flat,
whereas plate 25' is concave downward.’ The
cordingly changes its capacitive relation to the
?xed plate 25.
plate 25' is of highly resilient spring material,
Figs. 3 and 6 illustrate a twin condenser ac
cording to our invention in which two individual
45 for example phosphor bronze, whereas plate 25
may be of the same material, but may also be
of non-resilient-material.
adjustable condenser assemblies B and B’ are
mounted on a common base 50 and are inde
The plates 25 and 25' are provided with cen
tral clearance holes 26 and 26' respectively
50 which are su?lciently large to permit noncon
tacting passage oi screw l5-and also with ex
tending integral and inclined connection lugs ill
and 21’ respectively. The plates 25 and 25' fur
thermore are provided with two rounded end
pendently adjustable from the same side. The
upper portion of the base 50, ‘which receives as
sembly B, is substantially identical with the base 50
l0 shown in Fig.2; the base 50, however, extends
downwardly and is provided with an open-ended
recess having side walls |8’-—I8’, ribs 2G'-23',
and downwardly-extending mounting lugs i'W-A
55 notches 29 and 30, and 29' and 30' respectively.
I2’. The
the recesses
formedB on
The notches 30 and 30' are of a size to ?ttingly -
surround the ribs 20—20, whereas notches 29 and
29’ are larger so as not to engage the ribs 20-20
when the plates 25 and 25' are mounted on the
When assembling the condenser the plates 25
and 25’ are placed with identical faces turned
toward each other, i. e., with lugs 21 and 21' on
opposite sides and with notches 29 and 30' and
notches 29' and|30 respectively on the same side
of the assembly.
A thin plate 35 (see Fig. 5) of dielectric mate
lie], for instancemica, and having a slightly
greater length and width than metal plates 25
70 and 25', is interposed between plates 25 and 26'.
The dielectric plate 35 is provided with two iden .
and lower portion of the base 50, in the a
manner as has been described in connection with
condenser assembly A of Figs. 1 and 2.
For the individual adjustment of the two con - 60'
densers there are provided adjusting means whl sh
comprise a metallic bushing 5| having at the
lower end two preferably knurled annular ?anges
molded into the middle portion 01' the base 50. ,
The bushing 5| extends upwardly beyond the 65
base 50 and is provided with internal and external
- Against the bottom face of the condenser as
sembly B’ lies a washer 56 (see Fig. 7) of insu
lating material having a substantially elliptical 70
contour} a flat bearing face, and a conical face.
tical notches 31-»31 adapted to snugly engage ‘ The washer 56 is provided with‘ a central counter
the ribs 20'—V20, and with a central hole 36 which
is smaller than holes 26 and 26'. In the assem
is bled condenser, the hole 36 and slots 31—-31 of
bored hole I00 and with two notches 63-43
provided at the two ends of its long axis. Into
the counterbore, of hole I00 _?ts the head 51 of a 75
bolt 55, which is provided at its upper end with
a slot 65 and engages the internal threads of
bushing 5|. The notches 58-58 engage the lower
ribs 20’—20’, and thereby fixedly hold the washer
rower in width than the depressions 10 into which
it ?ts. One end of the plate 80 is provided with
an extension or terminal lug 8I, which passes
58 against rotation.
whereas the other end of the plate 80 falls short
A nut 54 engages the ex
ternal threads of bushing 5| and presses against
the spring washer 40.
of the opposite end of depressions 10.
The short oblique edges of plate 80 (see Fig. 9)
The adjustment of the'upper condenser assem
are so proportioned as to guide the plate in the
bly B is eii'ected in a manner similar to that ex
depressions "I0 by the matching oblique sides 83
10 plained in connection with Fig. 1 by turning the
nut 54. Adjustment of the capacity of the lower
condenser assembly B’ takes place by moving the
bolt 55' along the internal threads of bushing 5I
using slot 65.
slopingly downwards through the channel ‘I8,
It will be thus noted that the capacities of the
two condenser assemblies B and B’, can be ad
justed independently, and that both adjustments
thereof. A central clearance hole 84 within plate 10
80 permits the passage of an adjusting screw 85
Plates 90, which are similar in size and shape
to the plate 80, are provided with lugs 8| passing
slopingly down through the right-hand channels
‘I3. The plates 90, which are of heavy and re
silient material, for instance phosphorusgbronze,
can be e?ected from the same side of the unit,
are concave downwards and are also provided
which is especially desirable when the condenser
with central clearance holes 92 for the passage
therethrough of the adjusting screw 85.
The thin octagonal-shaped pieces 86 of mica or
20 is mounted on a panel or in an inaccessible place.
A variation of the adjusting means shown in
Figs. 1, 3, and 6 is shown in Fig. 8, wherein a
metallic insert 60 is rigidly molded in the insu
lating base 50 of the condenser, and is provided
25 with an externally-threaded extension 6|. The
extension 8| is provided with a smooth inner bore
adapted to snugly receive a bolt 82 recessed into
the washer 58 to prevent turning, and extending
upwardly through same and beyond the top of
30 the extension 5| to receive an adjusting nut 63.
In the constructionshown in Fig. 8 adjust
ment of the lower condenser B’ is effected by
turning1the nut 83 against the upper end of ex
tension iI, whereby condenser B’ is to a greater
or lesser extent compressed. Condenser B is ad
justed by turning nut 54—adapted to ?t the ex
ternal threads of extension IiI-—whereby pressure
is transmitted through the concave washer 40 to
the condenser assembly B.
Referring to Figs. 9 and 10, a molded base I20
of a suitable vitreous insulating material and hav
ing parallel faces 68 and 88 and rounded corners
88 is provided with three mounting holes 81 lo
cated on one central axis'thereof. On either side
45 of the central axis are disposed identical con
denser assemblies C-C later to be more fully
other insulating material which separate the
plates 80 and 90, have a greater width and length
than do the plates 80 and 90 and extend longi
tudinally to the ends of the depressions ‘IO-‘I0 25
and laterally into the openings ‘II-‘II and in
dentations ‘I2—-12, whereby the plates 80 and 80
are effectually insulated from one another. The
insulating pieces 86 are. each provided with a
central hole 88, of smaller diameter than that of 30
the holes 84 and 92, whereas oblique sides closely
fit the matching oblique sides of the depressions
and are ?xed thereby.
A circular washer 85 of bakelite or other insu
lating material, and a thicker metallic washer 58 35
of similar size and shape are placed over the
upper plate 88 in the order given; the’ latter
washer bearing against the under side of the head
of the adjusting screw 85 which extends through
the holes of washers 55 and 96 and into the 40
threaded portion of the insert 14. Rotation of
screw 85 changes the capacitive adjustment of
the condenser by decreasingor increasing the
?exure of the upper metallic plate 80.
Figures 11 and 12 illustrate a form of construc
tion adapted to multiple condensers; only one unit
being shown here. In the form shown in these
?gures the base H5, which is of metal, acts as a
The face 68 is provided with two identical de
pressions ‘I0—'I0 having octagonal cross sections ' fixed plate for condenser D, and is provided with
60 arranged with their longer'axes parallel to the upturned edges II5, one of which is extended to
form'a mounting and terminal lug III.
axis of the holes 5'I—-6‘I. The depressions con
nect along their respective outer side with open
The condenser unit, later to be more fully de- '
ings ‘II_‘II and' with indentations ‘I2—‘I2 along scribed, is rectangular in shape and is guided on
three sides by the upturned edges H8, while the
their inner sides; openings 'II—‘II and indenta
tions ‘I2--'I2 extending in the same direction as fourth side is guided by two tabs I I8 pressed up
the depressions ‘III--‘I0which also connect at both wards from the bases II5, which tabs also serve
ends with molded channels 13-13 extending to guide one side of an adjacent unit (not shown).
The upper plate I05 is rectangular in shape and
through the base I20. '
The base I20 is also provided with two similar has a narrow downwardly-bent terminal lug I05;
internally-threaded metallic inserts ‘I4 (only one the base H5 and one side H6 being cut away in 60
oi.’ which is shown), having hexagonal heads ‘I5 Fig. 12'at .I III to more clearly show this.
As shown in Fig. 12, the upper plate I05 is com
recessed in corresponding indentations ‘I6 in the
face 58 and having their upper ends crimped, as pletely compressed, but in its free condition this
indicated at 11 upon cushioning washers “I8 cen
,05 trally located in recesses ‘I9 in the bottom of the
plate is concave downwards in the direction of its
long axis. A thin rectangular-shaped separator 65
ydepressions ‘I0. The washers ‘I8 may be omitted
I0‘I of mica or other insulating material (as seen
ii the base I20 is made of bakelite or similar type
of molded plastics, but are used when the base
is of vitreous material, for example, porcelain or
in place in Fig. 12), separates the base H5 and
the plate I05, and overlaps all edges of the
the like.
An upper insulating plate III of the same size 70
and shape as the separator I01, but of greater
thickness, is placed over the plate I05 and trans
mits the pressure of the adjusting screw III to
The condenser assemblies C—C (only one of
which is shown in section in Fig. 10) comprise a
_ lower metal plate 80 and an upper metal plate
88 separated by a thin insulator 88. _ The plate 80
75 is substantially octagonal in shape and is nar
plate I05.
the flexed plate I05; plates I05, I01 and III being
each provided with central clearance holes, per 75
aria, 1%
mltting the noncontacting passage of the screw
H2 therethrough and onto cooperating threads
in the lease lid.
The plate ill is oi such length that it substan
tially ?lls the space between the upturned edges
iii, and is provided on its shorter sides with slots
ll! adapted to receive upturned extensions tilt
of the plate £105, which extensions terminate he
low the top suriace of plate ill when assembled,
iii and whereby the plate M5 is effectively guided.
We have iound that in past constructions in
which two condenser assemblies were mounted
What we claim is:
l. ‘in an adjustable condenser, a base of insu
lating material provided with a lateral recess
open at the ends, each side-wall of said recess be
ing provided with an inwardly-projecting rib, a
condenser plate provided on one side edge with a
small notch and on its opposite edge with a
larger notch, said plate being disposed in said
recess with the larger notch clearing one of said’
ribs and with the corresponding edge in contact 10
with the side wall, the opposite edge of the
on a common loose, a capacitive intercoupling
occurred between the two condensers due to the
plate losing spacedly located vfrom the opposite
side wall with the small notch ?ttingly engaging
the corresponding rib.
16 metallic parts or the adjusting means.
This drawback is eliminated in our construction
by making the bolt 55 (see Fig. 3) ct insulating
material, or by so dimensioning the metallic parts
of the adjusting means that the capacitive eilfect
on one side edge with a small notch and on its
of the third condenser so formed remains below
objectionable values. .As a rule it is sumclent it
the capacity of this third condenser does not ex
ceed 2% of the capacity oi the condensers oi
assemblies B and B’.
While we have described our invention on hand
or specific examples and in speci?c applications,
we do not wish to he limited thereto, but desire
the appended claims to he construed as broadly
as permisoihle in View at the prior
2. in an adjustable condenser, a base of insu
lating material provided with a recess having two
opposite side walls each provided with an in
wardly-projecting rib, a condenser plate provided
opposite edge with a larger notch, said plate be
ing disposed in said recess with the larger notch
clearing one of the said ribs and with the corre
sponding edge contacting the side wall, the oppo
site edge oi’ the plate being spaced from the oppo
site side wall with the small notch ?ttingly en- .
gaging the corresponding rib.
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