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Патент USA US2406405

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Aug. 27, 1946.
`
F, L, sALlsBURy ‘
2,406,405
COAXIAL coNDENsER CRYSTAL AND METHOD oF MAKING SAME
Filed May 19, 1941
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HIS
ATTORNEY .5
Patented Aug. 27, 1946
2,406,405
UNITED STATES PATENT OFFICE
2,406,405
COAXIAL CONDENSER CRYSTAL AND
METHOD OF MAKING SAME
Frederick L. Salisbury, Hempstead Gardens, N. Y.,
assignor to Sperry Gyroscope Company, Inc.,
Brooklyn, N. Y., a corporation of New York
Application May 19, 1941, Serial No. 394,239
8 Claims. (C1. Z50-31)
1
This invention relates to mountings for crystals
apparent in the following speciñcation and draw
such as are used for rectiñers or detectors, and
ing, wherein,
to a method for making these mountings.
In the Well-known “cat’s-whisker” type of
crystal mounting, the crystal is held in a conduct
ing body which forms one terminal, and the sec
ond terminal, or “cat’s-whisker” is held against
a sensitive spot on the crystal. It is not only
Fig. 1 is a section along the axis or" a complete
crystal mounting and adaptor for concentric
diiiicult to ñnd a sensitive spot on the crystal
suitable for use, but it has been exceedingly difû
cult or impossible in devices heretofore used to
keep the “cat’s-whisker” in contact with such a
l
transmission lines;
Fig. 2 is an enlarged fragmentary vieW of the
crystal engaging tip of the “cat’s-whisker”;
Fig. 3 shows the testing and assembling device
for the crystal mounting of Fig. 1; and
Figs. 4 to 6 diagrammatically show cathode ray
10
tube indications under various conditions to ex
plain the testing of the crystal in the device of
spot. Mechanical vibration, temperature varia
Fig. 3.
i
tions, change in humidity of surrounding atmos
Fig. 1 shows the completely assembled crystal
phere, oxidation of Wire, etc., all tend to impair 15 rectifier or detector. This is made of a holder I,
this contact and hence the eñìciency and eilec
of brass or any other conductive material, pro
vided With a recess 3 of suitable diameter. A
small outlet or bleeder hole 5 is provided from
tiveness of the crystal.
It is an object of the present invention to pro
vide _an improved crystal mounting which is stable
the >outside of holder I to the bottom of recess 3.
in operation and ln which the contact between 20 Apiece of crystal 'i having unidirectional con
crystal and “cat’s-whisker” is substantially not
ducting properties, such as Zincite, silicon, Car
alîected by vibration, moisture, temperature or
borundum, galeria, hertzite, molybdenum, etc., is
other iniluences to which crystal contacts have
forced into recess 3 so as to make good electrical
heretofore been subject.
and mechanical contact with the inner Walls of
It is another object of this invention to provide 25 holder I. Before placing the crystal in position
an improved crystal mounting which is sealed
it may be tested, in the manner to b-e described
from the atmosphere and is mechanically secure
beloW, to insure that a sensitive portion is placed
against vibration, thus being suitable for use
facing the opening of recess 3.l
under conditions of change in temperature, hu
The holder I and crystal 'l are then heated
midity, pressure and vibration, as, for example, 30 together by any Suitable means, as by being placed
are found on airplanes.
on the surface of an electric iron. When hot,
some thermoplastic substance 3' having good di
It is still another object to provide a crystal
mounting in which the “cat’s-Whisker” is perma
nently sealed in place by a thermoplastic dielec
electric qualities at ultra-high frequencies of the
order of 109 cycles per second, such as Various
tric material having high e?liciency at ultra high
frequencies, thereby permitting the crystal to be
satisfactorily used at such high frequencies.
types of materials known as polystyrene, is placed
It is a further object of this invention to pro
vide a, novel method of manufacturing a, mounted
properties suited to the intended use of the crys
Within the recess 3.
It should be noted here that
any thermoplastic material having electrical
tal may be used. When properly heated, the
crystal unit which makes it possible to manufac 40 thermoplastic material becomes semi-fluid and
ture such units in extremely small size and of
flows around the crystal 1. All air is forced out
high emciency, such as are necessary for use with
the bleeder hole 5 and the thermoplastic mate
ultra-high frequency circuits._,
rial thoroughly wets and surrounds the exposed
A further object is to provide a useful mounting
surface of crystal l and ñlls holder l so that,
for a crystal which is easily adapted to be con 45 after cooling, the crystal l is kept completely
nected in a concentric transmission line circuit.
separated from and independent of all atmos
Another object is to provide a useful crystal
pheric influences.
While the thermoplastic material is still plastic,
the “cat’s-Whisker” conductor 9 is placed roughly
mounting for use with a concentric transmission
line system which has a distributed by-pass ca
pacitance built into the crystal mounting.
Y Still another object is to provide a mounting
for a crystal inside a section of concentric trans
50 concentrically Within recess 3. The conductor 9
is shown in Fig. 2 as made of metal tubing, flat
tened at one end, which is formed with an oir
mission line, whereby the crystal is electrically
shielded from extraneous electric ñelds. v
Further objects and advantageswill become
.55
set sharpened tip Il. The particular shape of
the “cat’s-Whisker” 9 is convenient for appli
cant’s method of manufacture, as will be ap~
2,406,405
parent, but any type of wire or other small
ductor may be used.
The entire unit as thus far assembled is
placed in proper position on a cooling
mounting base I3 (Fig. 3). This position
con
then
and
may
be marked by any suitable means, such as by a
recess as at I5 or a holding jig may be used. The
4
capacitance whose electrodes are holder I and
body 35. The capacitance acts as a distributed
bypass condenser for the waves rectified by the
crystal 1. Furthermore, the construction is such
that all parts of the crystal circuit are fully
shielded, since everything is within body 35 which
acts as a continuation of the outer conductor 44
unit is thereby held immediately under the
of transmission line 39. 'The output transmis
roughly concentric with an adjusting member I1
sion line 39 may be replaced by an ordinary
which is adjustably held in a split clamp I9 and ' >
fastened therein by some means such as a screw
2l. Member I1 has a reduced portion 23 which
fits snugly into the hollow portion of “cat’s
Whisker” conductor 9, which is thus held by
member I1 roughly in a position coaxial 'with
recess 3. Member I1 is then manipulated as by
turning with clamp I9 loosened until `the “c'at’s
Whisker” 9 is in contact with an optimum sensi
tive spot on crystal 1, as indicated on 'the test
device to be described below. The finding of the
sensitive spot is aided by the ofi-setting >of por
tion II of conductor 9, as this permits ra large
part `of the outward facing surface of crystal 'I
to ‘be explored. After lsuch a sensitive 'spot has
been found, clamp I9 is fastened to hold member
I1 in position while »the thermoplastic material
cools and hardens. The cooling is expedited `by
running cooling water »through suitable passage
means in metal base I3, as bypipe 2-5. The “cat’s
Whisker” '9 is thereby cast rigidly i-nto the proper ;
position. If no sensitive ‘spot 4is found before the
thermoplastic -materia-l hardens, the unit is re
moved and reheated and the process is repeated.
By the above method I >.secure a fixed crystal
unit with “cat’s-whiske'r” 9 firmly and perma
nently secured in piace. 'The contact between
crystal 1 and “cat’s-whisker” 9 is >‘completely
sealed oit from the atmosphere, and good perma
nent >contact is `secured to the crystal 1. The
unit so Aobtained is found to be vextremely stable
in its characteristics `over wide 'changes of con~
'dit-ions of use. It is especially iresist-ant to vibra
tion, and is therefore very useful‘on 4‘airplane in
stallations.
After cooling, -the -base ‘of crystal ‘holder `I is
placed in an adjustably eccentric "chuck Aof »a
lathe, while conductor 9, now a fixed part of
the unit, is used to center the unit -in the lathe.
shielded cable if high frequency emciency is not
necessary for the rectiñed currents.
The above is, of course, only one way of adapt
ing the crystal holder I of the invention to a
particular use. yThe method of mounting the
crystal 1 above fdescribed may obviously be used
to mount this crystal in an opening in any metal
lic body whatsoever, and is not restricted to the
particular
type
shown.
Successful
crystal
mountings have been made in the end of a 10-32
screw, and it is possible to make a mounting by
the method `»described in an opening as -small as
.060 inch ldeep and ».1050 »inch wide.
The method of testing the -c‘rysta‘ïl for to Adeter
mine when the “catfs-whisker” -S -is in «contact
with a suitable sensitive spot will vnow be ex
plained. Referring to Fig. 3, it will be seen ¿that
clamp i9 is insulated from base ~I3 and bracket
45 ‘as by an insulating block 41. Conductor 9
which is one termina-i fof crystal '1, «is connected
as through members I1 Aand clamp II9 and by
mea-ns of a conductor 59, -`to a »resistor '49 which
is connected in turn to one terminal of the sec
ondary winding -of stepdown `trans-former ~5I en
ergized from Lan A. (C. supply »line 53. The ïholder
I, which «acts as the other terminal of y'the ~cry’s‘
tal 1, is connected, for example, through base
I3 and bracket 45 and by means fofconduotor 6I
to the other side of the secondary winding -of
transformer 5I, 'which fis 4designed to .have `suit
able seccndary -voltage chosen so as 'to Yprevent
any damage fto the crystal 1. Resistor 49 pre
vents excessive current from flowing in <the crys
tal circuit. A standard~oscillograph155 is ener
gized from the same supply line 53 through' -its
usual power supply >¿51. AOne pair 'of »deflecting
plates of oscillograph 35:5, such Aas 'the 4horizontal
deflectin'g plates, is connected across "resistor 49.
The fot-‘her pair, such »as 'the vertical defle'cting
The “outside of Vholder lI is no'w turned Jdown lon
pla-tes, is »connected across conductors -59 ¿and ïGI ,
the ‘lathe to roughly Acylindrical Vshape but having
which lare connected tothe crystal A1,1s'o îthat'this
pair` is energized by the voltage across crystal 1.
lThe usual amplifiers may be used »for-amplifying
`a'slight ltaper l23, and it is ‘made concentric with
member 9. vIf conductor 9 vdid vnot lharden ‘into
~place exactly -coaXia-l with recess ‘3, the walls 'of
the voltages applied to ‘the fdeiiecting plates, lf
desired. Ii conductors 59 and ïEI ~were ‘open
rcircuited, the ‘voltage across resistor >49 would be
Zero and that across conductors 59, 6I would be
maximum. ~Accordinglly, fa trace ‘163 such as -that
shown in Fig. 4 would be obtained. If `conductors
V59 and :6I were short-circuit‘ed, 'their potential
conductor ‘9. An insulating tape having 'good 60 diiîerence would be '-Zero, while vvthe voltageßacross
resistor 49 ‘would be maximum so that ïthe trace
Adielectric properties at the operating frequencies
-65 `'shown in Fig. 5 would »be obtained. It thus
is now wound Aon the tapered portion, `as at `33,
will be seen that'the cathode «ray osciîlïlo‘g-raph
and the wound unit 4is then forced into ‘a `mating
holder I will `not be of uniform thickness, but
this is immaterial. The ‘unit is Vnow placed in ‘a
tapered 'chuck which ñts the taper formed on
the unit, and a tip 3| is formed by turning down
the end of the unit. This tip 3‘I is `also formed
concentric with 'the outside of the 'unit a'nd'with
trace indicates, byïitsf's'lo'pe, the :impedance of ¿the
taper in body 35 which has `standard >clamp
adaptors 31 at ‘each end whereby the 'completed 65 circuit connected to v'conductors ì59, 31. 'A verti
cal ‘trace 63, having 'infinite slope, indicates 'in
unit may be connected to concentric transmis»
Afinite impedance 'Kopen-circuit). A 'horizontal
sion lines such as 38, 39. With Asuoli connection,
trace 65, having 'zero slope, indicates zero im
=conductor ‘9 'may slide over `the 'inner vconductor
pedance (short-circuit). Since Ahorizontal :de
"40 of transmission line v38, as `at 4l, and tip 3l
may slide into the inner ‘conductor 42 of the 70 iiection is proportioned 'to current through ~the
'crystal 1, and vertical deflection >is proportional
other transmission Aline 39,'asat 43. It is obvious
to voltage across crystal 1, ‘the slope «o'f >the trace,
that either or both conductor 9 'and tip 3`I could
which is therefore vproportional "to voltage -`di“
slide over or lunder its corresponding connecting
vided by current, >will Valways v"indicate the true
member.
The tape 33 forms'the dielectric of a'distributed 75 impedance of the crystal `‘|. A‘theoreticallyfper
2,406,405
6
fect crystal should be a perfect short-circuit for
half-cycles of applied A. C. of one polarity, and
a perfect open-circuit for half -cycles of the other
polarity, giving a trace 61 as shown in dotted
lines in Fig. 6. Such a perfect trace 61 is rarely
obtained. A good trace 69 often realized is shown
in full lines in Fig. 6. Hence, in exploring th‘e
said tubular member form output terminals, and
iier or detector having the desirable qualities set ’
a conducting member serving as a terminal for
said body and tubular member form a by-pass
condenser.
4. A device as claimed in claim 3 further com
prising adapting means for connecting said in
put terminals to a concentric transmission line,
and for connecting said output terminals to a
crystal 'l with the “cat’s-Whisker” 9, the latter
shielded line.
is manipulated until a trace at least as good as
5. A shielded crystal mounting comprising a
69 is obtained, and the “cat’s Whisker” 9 is then 10 conducting body having a recess therein, an uni
held in position until the thermoplastic material
directionally conducting crystal seated within
sets, thereby yielding a permanent crystal recti
the recess in electrical contact with said body,
forth above.
said crystal, and insulating material holding said
Although the invention has been illustrated by 15 conductor in electrical contact with said crystal,
one embodiment, it is evident that many different
a tubular member placed outside said conducting
embodiments of the invention could be made
body and means electrically insulating said mem
without departing from the scope thereof. It is
ber from said bodyÍ whereby said conducting
therefore intended that the above description
member and said tubular member form input ter
shall be interpreted as illustrative only, and not 20 minals to said crystal, said conducting body and
in a limiting sense.
said tubular member form output terminals, and
Having described my invention, what I claim
said body and said tubular member form a by
and desire to secure by Letters Patent is:
pass condenser.
'
l. A concentric transmission line mounting for
6. In a mounting for a unidirectional conduct
a crystal comprising a shielding outer conductor, 25 ing crystal, a body of electrically conducting ma
an inner conducting body insulated from said
terial formed with a recess in which said crystal
outer conductor and having a cavity therein, a
is seated in intimate contact with said body, a
crystal ñtting snugly into the cavity so as to
conductor extending into said recess into Contact
make intimate contact with' the Walls thereof,
with a sensitive area of said crystal, solidiiied in
a Wire serving as a terminal for said crystal, and 30 sulating means contained within said recess `for
insulating material holding said wire in electri
retaining said crystal therein and surrounding
cal contact with said crystal.
and retaining said conductor in contact with said
2. The method of making a mounted crystal
crystal within said recess, and substantiallyrax
which comprises the steps of forming a recess in
ially aligned connector terminals for said body
a body of electrically conductive material, form 35 and said conductor respectively projecting 'from
ing a bleeder hole at the bottom of said recess,
opposite ends of said body.
forcing a unidirectionally conducting crystal into
7. In a mounting for a unidirectional conduct
said recess to make intimate contact with the
ing crystal, a member of electrically conducting
Walls of said recess, placing a thermoplastic sub
material formed rwith a recess in which said crys
stance in said recess, heating said body and sub 40 tal is seated in intimate contact with said mem
stance above the temperature at which' said sub
ber, a conductor extending into said recess into
stance becomes plastic, whereby said substance
contact With a sensitive area of said crystal,
Will iiow around said crystal and make intimate
solidiñed insulating means retaining said crys
contact therewith, inserting a conductor into said
tal in said recess and retaining said conductor`
plastic substance to make contact with said crys
in contact with said crystal, a second member of
tal, exploring the surface of said crystal until said
conducting material extending about said ñrst
conductor is in a position making contact with
member, and electrical insulation between said
a sensitive spot of said crystal, holding said con
members.
ductor in said position and simultaneously cool
8. A mounting for a unidirectional conducting
ing said thermoplastic material to below its plas- f crystal comprising a body of electrically conduct
tic temperature, whereby it solidiiies and holds
ing material formed with a recess in which said
said conductor permanently in said position.
crystal is disposed in intimate contact with said
3. A shielded crystal mounting comprising a
body, a conductor in contact with a sensitive area
roughly cylindrical body having a recess substan
of said crystal, insulating means securing said
tially concentric thereof, a unidirectionally con
crystal to the walls of said recess and retaining
ducting crystal pressed into said recess, a wire
said conductor in contact with said crystal, and
held in contact with said crystal roughly concen
substantially axially aligned connector terminals
tric of said body and a tubular member placed
for said body and said conductor respectively
outside said body and insulated therefrom,
projecting from opposite ends of said body.
whereby said wire and said ltubular member form
input terminals to said crystal, said body and
FREDERICK L. SALISBURY.
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