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Apnl 5, 1949.
_
_
T. M. FERRILL, JR
2,456,018
VIBRATOHY STRAND REFERENCE APPARATUS WITH
‘
'
LONGITUDINÀL COMPONENT DRIVE
Filed Aug. 2, 194s
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Tvc/9ms M. FERR/¿L , (/Q.
Patented Apr. 5, 1949
2,466,018
UNITED STATES PATENT OFFICE
2,466,018
VIBRATORY STRAND REFERENCE APPARA
TUS WITH LONGITUDINAL COMPONENT
DRIVE
Thomas M. Ferrill, Jr., Hempstead, N. Y., assignor
Sperry Corporation,
re
a corporation of
Application August 2, 1946, Serial No. 688,157
21 Claims. (Cl. 318i-489)
.
2
of vibration of a vibratory element is not directly
limited by the “Q” thereof, but may be carried
appreciably beyond the limits normally imposed
vibratory element.
ment of a vibrating
by the energy losses per cycle of vibration of the
As set forth in patent application Serial No.
556,186, ñled September 28, 1944, by the present
inventor, there has heretofore been provided a
sta‘ble reference system
fine-gauge strand of elastic material stretched 1 O
15
pacitor pick-olf elements energized by a direct
voltage source were provided in that apparatus
20
e. g., with a “Q” of the order of 50,000 to 100,000.
In accordance with a further feature of this
invention, the longitudinal drive component may
’ be supplied by magnetostrictive action which in
trande evacuated supporting structure and the
volves ma-gnetostrictlve effects
coil arranged to i
ñelds substantially along the axis
As has been set
plication Serial
35
the frequency of transverse vibration of the
strand are employed both for passage directly
through the strand land for passage through the
longitudinal excitation coils, the ratios of these
currents being
sired relative magnitudes of the longitudinal drive
component and the transverse drive component.
By the magnetostrictive action, the tension of
the strand is varied through two cycles in each
erence purposes.
ln'object of the present invention is to provide
»roved vibratory stable reference apparatus,
l more particularly, it is an object of this `in
thereof.
'I'he invention in another of its aspects relates
tion to provide vibratory stable reference ap
to novel features of the instrumentalities de~
itus wherein the long-time stability of the plane 55 scribed herein for achieving the principal objects
of the invention and to novel principles employed
2,466,018
3| and 33. The longitudinal forces thus exerted
tend to sustain transverse vibration of the strand
I3 at its natural period of vibration.
Coils 3|, 33 may be made to exert sufficiently
in those instrumentalities, whether or not these
features and principles are used for the said prin
cipal objects or in the said field.
A vfurther object of the invention is to provide
improved apparatus and instrumentalities em
bodying novel features and principles, adapted
5
strong forces on the strand I3 to provide full
compensation for energy loss accompanying
transverse vibratory movement of this strand, vas
for use in realizing the above >objects and also
due both to gas damping within the envelope II
and to the molecular friction within strand I3
adapted for use in other fields.
Further objects will become apparent and the l0 caused by the alternate elongation and contrac
above objects and features will be more fully un
tion thereof. Under such- a condition, the strand
derstood by reference. to the following descrip
I3 would be retained in transverse vibration even
if potentiometer 31 were adjusted for zero output
tion of an embodiment of the present invention,
taken in conjunction with the drawing, wherein
voltage, eliminating the current through the
Fig. 1 is a schematic representation of vibratory 15 strand I3, and accordingly, eliminating the trans
stable reference apparatus constructed in ac
verse drive component therefor. However, in
most practical applications, it is desirable that
cordance with the present invention,
is a fragmentary view representing _a modifica
some degree of control be exercised upon the
strand to regulate the direction of vibration
20 thereof. Accordingly, the longitudinal drive cur
paratus including a rigid envelope I I of dielectric
rent is adjusted to a condition of insufficiency for
material such as glass or quartz, within which is
fully sustaining the vibration of the strand I3,
suspended a slender strand I3 of elastic mate
and the potentiometer 31 is adjusted in such a
way that the deficiency of the longitudinal drive
rial such as nickel or a nickel-iron alloy, or an
alloy which may contain nickel, iron and cobalt 25 is made up by the transverse driving forces ex
or chromium, if desired. Such a material is sus
erted by the electric motor reaction of the alter
ceptible to magnetostrictive elongation and con
nating current through strand I3 with the am
tion of the structure shown in Fig. 1.
Fig. 1 illustrates vibratory stable reference ap
traction, and is selected primarily for this prop
bient magnetic field component.
erty. The strand I3 may be attached at its ends
In order to facilitate the ideal proportioning
to ferrules I5 and I1 sealed to the ends of the
of the settings of potentiometers 31 and 41 for
30 a desired degree of transverse control over the
envelope II.
An arrangement is provided for maintaining
plane of vibration of strand I3, and to facilitate
the strand I3 in transverse planar vibration.- This
arrangement includes a capacitor pick-off element
I9 energized by a source 2l through a resistor 23,
the adjustment of these potentiometers to a con
dition- in which the total driving forces acting
35 upon the strand I3 are just sufficient to maintain
the vibration thereof at a desired constant ampli-tude, amplifier 21 may include an amplitude limit
ing stage or an automatic gain control circuit
arr-anged to suppress changes of output voltage
40 of the amplifier. Such circuits are not absolutely
essential, however, as amplifiers are inherently
limited by the characteristics of the vacuum tubes
and coupled through a capacitor 25 to the input
circuit of an ampliñer 21. Amplifier 21 has its
output circuit coupled through a transformer 29
both to the strand I3 and to a magnetostrictive
driving system including coils 3i and 33. The
transformer 29 includes one secondary winding 35
connected to a potentiometer 31, the movable tap
39 of the potentiometer and a. grounded terminal
4I thereof being connected respectively to the
upper ferrule I5 and the grounded lower ferrule 45
I1, for application of alternating driving voltage
directly to strand I3 and hence, for passage of
alternating current therethrough. This alter
nating current through the strand I3 reacts with
the component of an ambient magnetic field per 50
pendicular to the strand I3 for inducing the strand
I3 to vibrate in a plane through strand I3 per
pendicular to the ambient magnetic field com
and supply circuits ordinarily provided.
For convenience in utilization of the stable ref
erence propensities afforded by the vibration oi
strand I3, -a second capacitor pick-off plate 5I may
be supported in proximity to the strand I3, anc'
may be arranged to supply an alternating signa
upon angular departure about the axis of stran:
I3 from a predetermined angular relation between
the plane of vibration of strand I3 and the en
velope II. Capacitor pick-ofi element 5I may b
energized by a voltage source 55 through a re
sistor 53, and may be coupled through a capacite
A further secondary winding 43 of the trans 55 51 to the input circuit of an amplifier 59 arrange
to supply an amplified alternating voltage to th
former 29 is connected to the input circuit of a
phase shifter 45, and the output circuit of the
input circuit of a phase sensitive amplifier 5
phase shifter is connected through a potentiom
Unit GI is supplied with a phase reference voltar
eter 41 to the magnetostrictive driving coils 3|
by an auxiliary secondary winding 53 of tran:
and 33. Coils 3I, 33 are arranged in the envelope 00 former 29, and this amplifier 5I supplies a dire
II in substantially coaxial positional arrangement
output voltagev of magnitude and polarity varyir
with the strand I3, so that they produce magnetic
according to the amplitude of the voltage supplia
fields extending along the strand. Through the
from amplifier 59 and the phase of this voltal
phase shifter 45 and the potentiometer 41, these
relative to the phase of the voltage from seconda
coils are energized with alternating current at 65 winding 63.
the frequency of the current through'the strand
The output voltage from phase sensitive amp‘
I3; and accordingly, they produce alternating
iler 6I may be supplied to control terminals
magnetic fields along the strand I3 of this fre
such as field winding terminals of a reversil
quency. The magnetostrictive drive is non
motor $1, which may have a principal pair
polarized, however, so that the strand I3 responds 70 power input terminals such as armature t1
ponent.
-
in the same way to a positive half-cycle of the
minals 69 supplied by a separate source, e. g.
alternating current through the coils 3|, 33 as it
does to the negative half-cycle of the current.
Accordingly, two cycles of contractive and ex
pansive forces are produced in the strand I3 by 5
each cycle of alternating current through coils 7
battery 1I. The motor 61 is coupled througi
gear train 13 to a large gear element 15 c(
nected to the vibratory unit II, I5, I1 and 1
ranged to rotate the supporting structure of '
5
ß
strand Il, and accordingly, the strand 'Il itself,
in such a way as to suppress the alternating
Il.
voltage developed in capacitor pick-off elementv
,
,
tive forces directly within a magnetostrictively
susceptible strand I3, such transverse disturb
ance is minimized or substantially eliminated.
envelope Il _may be pivotally suspended in a craft
larly, for providing a stable reference about a
such as anfaircrai't for rotation about a vertical
vertical axis in predetermined relation to the di<
axis. In such a use of the invention, the motor
rection of the horizontal component of the
Il is fixed to the aircraft and employed for re- i0 earth's magnetic field, it will be readily apparent
taining gear element .1I and the elements asthat the longitudinal drive features of the' pres
« sociated therewith fixed in space about the ver-
ent invention are readily usable in` other ar
tical axis, by reference to the plane oi vibration
rangements. as for example, where the ambient
>of the strand I3. This system then serves as a
magnetic field for sustaining vibration is pro
stabilized magnetic compass, if the earth’sma'p 15 vided by a local vmagnetic system, whether the
netic field is employed as the ambient neld for
strand is normally aligned vertically or hort
reaction with the current through' the strand I3.
zontally, or in a direction oi' intermediate in
Where the earth's magnetic neld is thus permitclination.
ted to act directly on the strand. the strand I3
While the features of the present invention
vibrates in the vertical east-west plane, i. e., 20 relieve" to some extent the dependency upon ob»n
in the vertical plane perpendicular to the horizontal component of the earth's magnetic neld.
Accordingly, element 1l may be engraved with
taining very high " ” of the vibratory system
for enhancement of stability thereof, and make
possible the provision or a moderately long-time
compass rose directional designations, the east»
stability where the “ ” or the mechanical citi
west designations being aligned parallel with the 25 ciency or the vibratory system is relatively low,
eifective surface of capacitor element il.
it may none-the-less be desirable to provide rela»
With this arrangement, so long as element 'Il
tively high "Q” in order that extremely high
remains properly oriented in space relative to
stability be achieved. For this reason, it is con
fore. motor l1 is inactive. Upon rotation of the
ated, so that a desired set oi’ performance char
craft about'the vertical axis, however, as when
acteristics may be obtained according to the ex»
a turn of the craft is commenced, there is a tend»
tent to which this structure is evacuated.
ency to turn gear element ‘ll from its predeSince many changes could be made in the
termined orientation relative to the earth's field, 40. above construction and many apparently widely
and as it commences to revolve with the craft,
diifercnt embodiments o1' this invention could
an alternating voltage is supplied ‘to the input
be made without departing from the scope therem
circuit of amplifier Il as the face oi' pick-off
of, it is intended that all matter contained in the
element Il becomes non-parallel with the‘plane
above description or shown in the accompanying
of vibration of the strand I3. Under these con- 45 drawings shall >be interpreted as illustrative and
ditions, the phase sensitive amplifier Il supplies
not in a limiting sense.
to motor 61 a /voltage oi.' the polarity required to
What is claimed is:
urge element 1l in the direction to restore the
i. Stable reference apparatus _comprising a
» .
and the plane oi’ vibration of the strand I3. Units 60 stretched between two points in said supporting`
hence, to hold the directionally calibrated ele- u tional pick-off means for producing an output
ment 15 in correct orientation in azimuth relasignal varying according to the direction of the
tive to the earth's magnetic neld.
transverse plane of vibration o‘i‘ said strand, and
In Fig. 1, the magnetostrictive driving coils
means responsive to said signal for controlling the
Il. 33 are illustrated as supported within en-
direction of said pick-oil' means to maintain a
velope -I| for concentration of their magnetic go predetermined directional relation -between said
coil I2. SUI'I‘OUndiIls the envelope Il. While Dart 65 tibie material stretched between two points in
or all of the magnetostrictive drive could be ex-
said supporting member, means for producing an
ercised upon the ferrules Il and l1, ii' desired,
alternating magnetic field along said strand for
I l, in view ofthe dimculty of providing such pre- 7o pick-oil’ means coupled to the strand for produc
9,460,018
7
tational stability transverse said field, said means
being so constructed and arranged that the vi
bration sustaining power supplied through said
3. In combination, a supporting member, a
strand of elastic and magnetostrictively 'suscep
tible material stretched between two points in
longitudinal forces exceeds the power supplied
said supporting member, electromagnetic coil 5 through said transverse forces, whereby the
means aligned with said strand for producing' a
transverse directional influence of said field is
magnetic field extending therealong, and means
rendered relatively slight.
l
responsive to vlbratory movement of said strand
9i In combination, a supporting member, a
for supplying to said coil means energizing al
strand of elastic and magnetostrictively suscep
ternating current of frequency and phase deter l0 tible material stretched between two points in
mined by the movement of said strand for sus
said supporting member, and means for passing
alternating current through said strand for pro
taining vibration of said strand.
\
4. In combination, a supporting member, a
ducing transverse force reactions with an ambi
strand of elastic material stretched between two
ent magneticl field and for providing an alter
points in said supporting member, alternating 15 nating magnetic field component , along said
strand for exerting alternating "longitudinal
current means for varying the tension in said
strand at a frequency double the frequency of
the current, and means responsive to transverse
forces thereon, whereby said strand is vibrated
transversely of said ambient magnetic field and '
vibration of said strand for supplying to said last
thereby endowed with orientations! stability, and
named means alternating current of the fre 20 the burden of sustaining the vibration of said
quency of transverse vibration of said strand.
strand is partially borne by the maßnetostrictive
whereby the tension> of said strand is varied at
drive in such a way as to limit the directional
the frequency of the elongation and contraction
coercion on the direction of vibration of said
strand due to the force reactions in said ambient
5. In combination, a supporting member, a 25 magnetic ileld.
strand of elastic material stretched between two
l0. In combination, a supporting member, a
points in said supporting member, alternating
strand of elastic material stretched between two
current responsive magnetostrictlve means for
points in said supporting member, and means for
exerting longitudinal forces on said strand at a;
exerting both alternating longitudinal forces and
frequency double the frequency of an applied 35 alternating transverse forces on said strand, said
current to cause transverse vibration of said
alternating longitudinal forces including a com
strand, and means responsive to transverse' vi
ponent at twice the frequency of the alternating
bration of said strand for supplying to said last
transverse forces, whereby said strand is trans
named means alternating current of the fre
versely vibrated for'endowment of orientational
quency of transverse vibration of said strand, 35 stability and such a part of the burden of sus
whereby the tension of said strand is varied at
taining the vibration of said strand is borne by
the frequency of the elongation and contraction
the longitudinal drive forces as to limit the trans
verse directional coercion on said strand for long
thereof.
_
thereof.
Y
-
6. In combination, a supporting member, a
time stability thereof.
strand of elastic material stretched between two 40 1l. In combination. a supporting member, a
points in said supporting member, means for
strand of elastic material stretched between two
exerting both relatively great alternating longi
points in said supporting member, means respon»
tudinal forces and relatively slight alternating
sive to vibration of said strand for producing an ~
transverse forces on said strand, and means re
alternating current at the frequency of vibration
sponsive to transverse vibration of said strand 45 of said strand, and means utilizing said alternat
for controlling the frequency of said force exert»
ing current for exerting alternating transverse
ing means whereby said strand is transversely
forces on said strand at the frequency of said
current and for exerting alternating longitudi
vibrated for endowment with orlentational sta
nal forces on said strand at a frequency twice
bility and the transverse directional influence is
rendered relatively slight accordingly as the vi' 50 the frequency of said current whereby said strand
is transversely vibrated at its natural frequency
bration sustaining power is principally supplied
for endowment lwith orientational stability and a
by the longitudinal forces.
'
predetermined part of the burden of sustaining
7. In combination, a supporting member, a
the vibration of said strand is made noncoercive
strand of elastic and magnetostrictive material
stretched between two points in said supporting 55 as to the direction of transverse vibration there
of for enhancement of the long-time stability of
member, and means for magnetostrictively exert
ing alternating longitudinal forces on said strand
the direction of vibration of the strand.
12. Stable reference apparatus comprising a
tubular envelope, a strand of elastic material
transverse forces on said strand >whereby said
strand is transversely vibrated for endowment 50 stretched between two points axially displaced
along said envelope, said envelope being substan
with orientational stability in a plane deter
tially evacuated to
ize damping of vibra
mined by the time integral of the directions of
tion of said strand. and electromagnetic coil
transverse drive over a period rendered -relatively
means fixed to said envelope in substantially co
long accordingly as the vibration sustaining
power for said strand is principally supplied by es axial relation with said strand and adapted to
be energized by alternating current for periodi-l
the longitudinal magnetostrictive force exerted
cally varying the tension in said strand to pro
thereon.
vide transverse plane of vibration of said strand 3
8. In combination. a supporting member, al
and to endow it with vibration directional
strand of elastic material stretched between two
points in said supporting member, and means for 70 stability.
13. In combination. a tubular envelope, a
passing alternating current through said strand
strand of elastic and magnetostrictively suscep
to provide transverse force reaction with an am
bient magnetic field and for exerting alternating
tible material stretched between two points axial-v
ly displaced in said envelope. said envelope being
longitudinal forces on said strand, whereby said
to minimize gaseous
strand is maintained in vibration transverse said 75 substantially -e
and for electromagnetically exerting alternating
ambient magnetic field and endowed with orien
2,466,018
damping of vibration of said strand, and means
including an electromagnetic coil fixed to said
envelope in a position of substantially coaxial
with said strand for producing an al
coupled to said
an output
signal varying according to its direction
of vi~
bration.
Y
20. A stable reference element driven longi~
dow said strand with vibratory stability.
14. The combination defined in vclaim 13,
wherein said coil is iixed within said envelope
and surrounding said strand.
`
10
15. The combination defined in claim 13,
wherein said coil surrounds said envelope.
16.' The combination defined in claim 13,
wherein a plurality of coils are provided axially
displaced along said strand.
tudinally -by magnetostriction and synchronously
driven transversely, and means including a vibra
tion pick~off coupled to said element and an am
transverse drive of said element.
21. Stable reference apparatus
supporting member, a, strand of
17. Stable reference apparatus comprising a vi
bratory member, magnetostrietive means for ex
erting alternating longitudinal forces on said
20
25
said axis to restore said predetermined align~
ment.
18. Stable reference apparatus
claim 17, wherein said predetermined axis is ver
THOMAS M FERRILL. Jig.
REFERENCES onen
30
The following references are of record in the
ñie of this patent:
UNITED STATES PATENTS
action with the earth’s magnetic ñeld.
35 Number
1,616,416
2,120,985
Fessenden ________ -_ Feb. 1, 1927
Melhose _________ -_ June 21, 1938
2,223,537
Sykes ..---_...---.---- Dec. 3, 1940
Name
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