Патент USA US2400582

May 21, 1946. `
F. wEs’T, JR
. 2,400,582
NORTHERLY-TURNING ERROR COMPENSATING MEANS
Filed Feb. 28 , 1942
FIG.
F|G.2
-
v
m,
INVENTOR
FRANCIS WEST, JR.
2,400,582
Patented May 21, 1946
UNITED STATES PATENT OFFICEv
NoR'rHERLY TURNING ERROR
coMPENsA'rING MEANS
.
Francis West, Jr., Roslyn, N. Y., assignor to
Sperry Gyroscope Company, Inc., Brooklyn,
N. Y., a corporation of New York
Application February 28, 1942, Serial No. 432,740
8 Claims. (Cl. 33-225)
This invention relates to means for compen
the employment of shielding means for the mag
sating a magnetic compass against movement
netic compensating element which renders -the
due to the so-called northerly turning error and f
same ineifective with respect to the compass‘un
less actuated by the turn responsive device.. As
more particularly to a magnetic linking element
for exerting a corrective torque on the compass
which is controlled by a gyroscopic turn indicator
or other turn responsive device.
a consequence, an undesired corrective or com
pensating torque is notV exerted by the element
when the sameA is subject to forces resulting in
inclination of the card as the-vehicle changes
An object of the invention is, therefore, to
attitude in bank, climb, or glide,l during straight
obviate the error in the indication of a magnetic
,
»s
f
compass Ainstrument due to turning of the craft 10 line movement.
A still further feature `of- the invention resides
from a straight course.
y
in the provision of a mounting structure for the
The main error in the magnetic compass due
error compensating' element for 'the compass
to this cause being a maximum for turns about
which provides a damping means for the rate
a northerly course is usually termed the north
erly turning error, the same resulting largely 15 of turn measuring gyro instrument. ' 1 "1
Other objects, features and structural'details
by reason of the pendulosity of the card of the
of the invention >will be apparent from the fol
compass instrument which renders it subject to
lowing description when read in connection with
centrifugal forces during turns or changes in
the accompanying drawing, wherein
.
velocity rduring straight line movement of the
craft. The forces affecting the instrument at 20 Fig. 1 is a side elevation view, partly in sec
such a time cause the compass card to swing out
tion, showing the combined magnetic compass
and turn responsive gyro instruments and one
of its normal horizontal plane, tilting the same
form of the turning error compensating means
so it is subject to a magnetic torque caused by
employed therewith, the instruments being shownthe difference in direction between the N-S axis
of the card and the projection of the earth’s field 25 in spaced vertical relation and arranged on an
instrument mounting panel.
’ ‘
in the plane of the tilted card. Such error af
Fig. 2 vis a cross-section view taken on line .
fecting torque normally tends to rotate the com
2--2 in Fig. 1.
.
pass card in the direction of turn of the craft
Figs. 3 and 4 are schematic vviews illustrat
when turning out of northerly courses.
Any course having a northerly component will 30 ing the operation of an error compensated mag
netic compass constructed in accordance with
exhibit such northerly turning error in the com
pass instrument upon turn of the craft, the er- l
the teaching of the present invention.
' ' »
Fig. 5 is a detail front elevation view showing
ror being at a maximum when the turn is made
a modified form of the invention for controlling
from a North heading. The error diminishes
from this maximum to a negligible amount for 35 the error compensatingmeans from the gyro in
strument. .
turns of the craft made from an East or West
Fig. 6 isa side elevation view of the detail
heading. On courses having southerly compo
modification shown in Fig. 5. `
Y
i Y
nents, the error is not as serious because a turn
Fig. 7 is an enlargeddetail side elevation view
in the proper direction is always shown by the
card of the compass instrument, the amount of 40 illustrating a further modiñcation of the inven
tion in which the compensating element isÁ di
the turn, however, being exaggerated in this in
rectly moved by the gyro Yinstrument and the
stance. All such errors are however'generally
elementforms a part of a mounting structure
termed the northerly turning error. At the mag
with which it also provides a damping means
netic equator there is >no northerly` turning er
ror inasmuch as there is no vertical component 45 for the rate of turn measuring gyro instrument.
Fig. 8 i's a front elevation view of the modi
of the earth’s magnetic field at the same.
ñed form of the invention shown in Fig. ’7, and
One of the features of the invention resides
Fig. 9 is an enlarged longitudinal cross-sec
in the utilization, with a magnetic compass in
tion taken through the‘fixed cylinder and pis
strument and turn responsive gyro instrument,
of a normally ineffective magnetic means con 50 ton damping structure shown in Figs. 7 and 8.
With reference particularly to Figs. 1 and 2,
trolled by the gyro instrument and cooperating
the compensating means of the present invention
with the magnetic element of the compass in
strument for compensating the compass against
is used in combination with a well known direc
tion indicating instrument and an equally fa-l
movement due to northerlyturning error. ~
miliar turn responsive instrument. One of the
Another feature of the invention consists in
2,400,582V
instruments is a magnetic compass embodying '
ployed for ¿this purpose by directing air upon the Y
the usual features which include a iiuid >contain
bucket containing periphery of the rotor. The air
supplied thecasing 3i by way of the jet directing '
ing enclosed case 2e that is suitably mounted on
an instrument panel 2l Vin the vehicle with which
it Vis employed. The >front part of the case 29
nozzle 33 either under'pressure or by vacuum is
suitably withdrawn. therefrom through the port
has a window opening therein through which the
39.
indications contained on the periphery of a com
Y
‘
Y`
When the vehicle on which the instrument is ~
mounted turns ,to the right, the casing 3l moves
correspondingly about awertical axis, the frame
pass card 22 maybeobserved,‘with'reference to.
a `given lubber "line, bythe pilot or observer of ‘
The compass card or sensitive 10V and disc 31, Fig, 2, precessing in a counter-clock
the instrument.
element of the instrument Ais supported 0n a yield-- Í
ably mounted jewel post 23 situated on'a-¿bracketl ,
forming piece 2li iixed in position withinjtheiinf ~`
terior of `the enclosing casing 2c. The circular Y
Awise direction against the action of spring 36.
j_l‘he'extentof. this movement is dependent upon
'the rate oiturn oi the vehicle, the samebeing
compass card has diametrically positioned»arms>
'- the opposite direction causes the disc .t0 process Y
prmiortionallyA related.
A turn of the vehicle in
in_a similanrnanner'in a clockwise direction as
at the center of which is the usual pivotal mount
ingV pin for the same which rests on the slightly
viewed inïFig. 2. The direction and extent of such _' Y
` concave top surface provided at the top Vof theïì.. ` movement-fis indicated by means of `a pointer si Y '
which is >driven from disc 3'! by Way of aV reversing
. jewel forming post 23. Two direction determin-Y
_ing members' or magnets 25 are preferably ern--v :20 motion mechanism which includes a pin 42 that
ployed to position the card 22 in azimuth, the
same beingrarranged in parallel relation and be
engages a slotted member d3 which controls the
ing. suspended from the` cross arms of the instru
to rotate with shaft @tithe same beingffurthen
situated to the~ rear of a'windo-w opening in the
ment on suitable straps.
rotation of a shafted. The pointer ¿l is mounted ~
The jewel supported
sensitive element ofthecompass is slightly pendu- ' 25 front of the casing 3! and to the front of a mask '
lous so that the card and magnets arersituated Y 7 @t5 on which is contained a left, central and right
in*V a horizontal plane during normal straight line
indication against whichthe pointer may Ibe com
nightor travel of the vehicle or craft on-which "
pared by the observer of the instrument; The
extent oimovement ofthe pointer Vfrom a cen-Y
the instrument ismounted.; Applicant'does not - '
1
¿F tral position eitherto the right or left isa meas- 1
claim thecompass instrument, pern se, the same
being of_ conllentional construction and being
ure of the rate of turn of the vehicle-as Well asian
shown purposely asan integral unitfwhich, is con
indication ofthe direrction’íof theÈ turn. Y"This in
strumentis of conventional constructie-hand is
employed in connection with the .compass instru
Y trollableinaccordance> with the. teachings of the
present inventionl without the necessity otem
j ment in assisting the operator to navigatethe ve~
bodying or incorporating> thesamexin a rede-signedinstrument case. Thus by completely
shielding thegdescribed instrument from its con-.v
Lhicle on whichboth ofthe same are mounted.
In accordance with lthe teaching of the present ` v
invention theY two< described instruments are
grouped togetherso thatr error compensating
netic compass instrument;A Itis apparent, how
ever, that the compassmay be contained within 40 .y control of` the> compass may be effected. In Figs.v
trolling means, .the-same provides the usual mag,- l '
`" 1 and 2, `the magnetic element or meansfor exert
the same; case as Vthe instrument.l to be- hereinafter.
described.
ing an error corrective torque onthe compassis '
.
The second of >the"conventional instrunir-:ntslî
employed in Connection with the-presentimen
directly- controlled Yby vthe n turn responsive gyro
instrument. This-element
extending masnetsälland
consists of two5l Curved
which , '
tion isV a turn; indicator. ., `This Well Yknown iii-„ 45. 4longitudinally
strument is mounted on Vthe instrumentA panel 2in;
are ñxed in arcuate‘sleeve 52 that-in turn is di
rectly mounted on .disc V`3l byvrneansef extendingl
in spaced vertical relation tothe compass instru.
ment, the same, in this instance shown,;being
arm 53.
placed directly;` below . the compass. ~ `A' -curved
posed so that the south poles of each ofthe same,
The polarities ofthe magnetsïare o'p-` I
glass> tube asindicated in section at Sil in Fig. il.
in this_instance, are atthe extremitiesthereof.
provides the lbanli indicating >portionpof this in.- .§50 The element moves withmovement of the disc
strument, the tubecontaining a suitable. damping
in response tothe operation of .the Ígyro instru-M_
ment. Due to its centralized position,the means
fluid and a ball indicator.- therein. Theturnfin'Í-`
Y for magnetically linking the magnet-,_V pieces to the
cally controlled. The ¿moving'parts of the instrueîï 55 vcompa/ss instrumentis normally 'ineiîective inas- 1 >
' ment are housedv within’ a casingr 3i which pro».
muchas Ythe same would exert-,equal >and «opposite
vides Ía support for trunnions 32 and Lili.L l.The
turning torqueson thecompass. To insurefthe` „
' dicaítor portion oi.the"instrument is'gyroscopii- I
rotor bearing frame .filioflthe provided' gyroscope _
existence of this; normally ineffective. condition . .«
of the elementduring suchoccasions 'aswvariable' Y `
is mounted to precess-about the axis.. deñnedby
the trunnions 32 vand' 33.L The gyro rotor 35. has a
speed straight line.mover‘nentfofA the vehieleéor>
normal .horizontal spin axis, the same being
situatedïon asuitable shaft having ends whiz-:hare
when theV vehicle is> inclined'` to 'thef horizontal, .
. which would render the 'element _eiïective when»
journaled'inoppositely disposedï’arms of the' bear- l
ing frarneßâ. As is usual in a turn responsive
undesired Vbecause of tilt-¿ofthe compass card ’
with relation to ¿the samefaïshield memberit is
gyro of-this- character, the frame Sli’is normally 65 also provided having a curvedslotïthrough¿which ~
centralized by meansY of a Aspring 3S, one end-of
the arm 53 extends. ¿'Iihejshieldï@meinber'is in
whichis ñXedf to the casing 3l »andthe other end ^
of'vvhich is connectedïto a pin Vwhich extends
from a disc member 3l located at the left-hand
side 'of- the frameßßi; asviewed in Fig; 1. The spin '
axis of the> rotor 35 is perpendicular` to the trun
nion deñned axis of theframeläci. lAny suitable
means-may beemployed to spin-the _gyro rotor-'35. '
Y In this instance, the rotor _is'spun--pneurnaticallg
a nozzle piece 38 located incasing 3i being em-
the shapel of av` curved concentric sleeve_which.` .y
normally »covers theèmagnet 4elements >`541- 'and' 5l; Í
the ends of theelements*V 56V andßlbeing'sub: '
70 ïstantiallyjflush withjthe "ends, [email protected] the shielding .Y
sleeve. ` Shield 54, is iixed inf position _by means
the interior. ,top- v
f Yof Ya connecting arm äß’securedto
portion of thecasinghäi." L ' " ,
Y V111„describingtheoperaban Ofiheiiòrpií. . -eté
«ing torque-applying means of the present‘inven`-
3
2,400,582
tion reference isv first made to Fig. 3 in which,
fromV the observer’s pointy of view, the. compass
instrument indicates a North heading of the ve
hicle. A turn to the right as indicated by arrow
6B, for example, is now taken by the vehicle.
The ease 20 of the compass moves correspond
ingly in the direction indicated at 6|. The mag
neticv torque of the northerly turning error, as
indicated by the arrow 62 tends to` move the
sleeve retaining structure. The compensating
element in this event is ñxed and the shield ormeans for rendering the element normally in
effective is moved by the turn responsive gyro
instrument. Because of the difference in relative
movement of the associated parts in this form of
the invention, it is also necessary to alter the re
lation of the magnets 5B and 5l so that the north
poles are situated at the respective ends of the'
compass card in the same direction as vthe case. 10 longitudinally arranged combined magnets, as
Where the rate of turn is rapid the movement
of the card clue to the northerly turning error
may exceed the movement of the case so that an
apparent turn lto the left is indicated by the in
strument. Upon turn of the vehicle in the di
rection selected the gyro rotor frame precesses
and disc 31 moves in the counter-clockwise direc
tion as viewed in Fig. 2 to an extent which is4
proportional to the rate of turn of the vehicle.
A corresponding movement of the compensating 20
element ’dil-«5i` is effected, the element moving
out of its shield 541, as shown in both Figs. 2 and
3, to an effective position under control of the
turn response gyro instrument. The extending
south pole of the magnet 50 exerts a compensat
ing torque whose direction is indicated at 63
which is immediately effective to resist movement
of the card due to northerly turning error. By
adjusting the strength of the magnets Eil-5! and
shown.
With reference to Figs. 7 to 9, inclusive, a-fur
ther modiiication is kshown in which the com
pensating element is situated within a mounting
structure therefor which provides a damping
means for the gyro instrument. In this form of
the invention the compensating element com
prises magnets 50 and 5I which are situated in
longitudinal relation in an axial position within
a piston formingmember 1i! which reciprocates
within a ñxed cylinder 1l.
Shield 513 nts over
the cylinder 1|, which in the form shown is closed
at one end only, both of these parts being mounted
in a ñxed position within the casing 3| by means
of a bracket holding piece 12. An arm 15 is ñxed
to the wall of the piston 1B and extends through
adjacent horizontal slots in both the cylinder
and shield. A roller 13 at the end ofthe arm 15
engages a radial slot 14 in the disc 31 controlled
banked turn” is one in which the resultant of the
vectors of centrifugal and gravitational forces
»by the turn responsive gyro instrument. Conse
quently the rotary movement of the disc 31 is
converted by this construction into a transla
tional movement of the compensating element
with respect to its shield. The dash pot action
of the piston within cylinder 1l also simultane
ously provides for the damping of the oscillations
lies in the normally vertical axis of. the aircraft,
of the gyro instrument.
the distance of the same from the compass mag- '
nets 25, the compensating torque on the compass
is made approximately proportional to the north
erly turning error of the compass for any prop
erly banked turn of the aircraft. A “properly
\
In the previously described adjustment of the
strength
or position of magnets Eil-5l, in order
maintained in its central position. Once having
been adjusted for any particular properly'banked 40 to produce a correcting torque which is approxi
mately equal to that of the- northerly turning
turn, magnets äû-EI will be of approximately
or one in which the ball bank indicator is always
the correct strength and position for any other
degree of bank providing the aforesaid conditions
error, it was assumed that the angle of dip of
the earth’s magnetic field was a constant. If,
however, the vehicle should change its latitude,
are maintained. When the vehicle turns toward
the lei‘t from this heading, directionally reversed 45 it would encounter a change in the aforesaid
angle of dip, which would result in an over or
conditions to those previously described affect
under-correction or" the northerly turning error,
the compass card and the same result is obtained.
according to the direction in which the change
With reference to Fig. 4, movement of the vehicle
occurred. If the vehicle crosses the magnetic
in a South heading is shown and a turn is taken
to the right, as indicated by arrow E0 out of this 50 i equator, it is necessary to reverse the polarities`l
of magnets Eil-5 I . Within the same hemisphere,
heading. In this event, the northerly turning
error movement of the card, whose direction is
indicated at 62, exaggerates the turn of the ve
it is necessary to amplify the correcting torque
as the latitude is increased (in a direction towards
the magnetic pole) and diminish as the latitude
hicle. The effective position of the compensating
is decreased (towards the magnetic equator).
element is similar to that described in connection 55 To accomplish this correction for latitude a
with Fig. 3, the torque resulting therefrom, how
shielding plate, located -between the compass and
ever, being exerted in the direction shown at 63
' therate of turn gyro, is adjusted until the proper
which is in opposed relation to that of the north
amount of correcting torque is obtained. The
erly turning error. The normally ineiîective
shielding
plate employed for this purpose is shown
60
compensating means which is rendered effective
as formed by two relatively movable soft iron
under the control of and in response to move
parts 80 and 8| which are situated on top of the
ment of the rate of turn measuring gyro instru
turn indicator casing 3l in the present instance.
ment is magnetically linked to the compass in
The
flux gap between the parts 80 and 8| is de
strument of the combination. `The compass in
strument is consequently compensated against 65 termined by means of screw shaft connection 82
for the parts in which there are right and left
movement due to northerly turning error.
hand threaded portions. Manual means for posi
l'n the form of the invention illustrated in Figs.
tioning the shaft 82 is provided by the scaled
5 and 6, the shield 54 of the compensating ele
knob 83.
ment is moved by the disc 31 on the rotor frame`
As many changes could be made in the above
of the gyro instrument. The curved sleeve form
construction and many apparently widely differ
ing shield is provided with a slot in the upper
ent embodiments of this invention could be made
portion of the same through which an arm 65
without departing from the scope thereof, it is"
extends from a ñXed location within the casing
intended that all matter contained` in the above
3l to support the magnets >5l) and 5| in their 75 description or shown in the accompanying draw
4
' 2,400,582.:
ing shall be interpreted asillustrative and not vin
' mentV of said compass, means for movably sup-`
porting saidmagneaa magnetic shield ñxed With
a limiting sense.
What is claimed is:
1, VThe combination of, a magnetic. compass, a .
turn responsive gyro instrument, and a movablyY
mounted, normally ineffectively positioned, mag'
netic element movable by and in response to turn
responsive movement of said gyrro, instrument 'to
5 ,
respect to said magnet and arranged to Lcontrol l
the'linkage ofi thef flux of the permanent magnet
iîeldlwitn said compass element, and an instru
ment responsive to turningmovement of the craft '
operatively connected to said magnet for eifect
ing movement thereof relative to Asaid shield.
an eiïective position in which the same is mag-f
5. The combination'with a magnetic compass vof
netically linked to said compass, the extent of . 10, meansfor compensating for the northerly turn
such movement providing a compensating torque
ior said compass which 'is approximately propor
tional to and opposed to the torque tending to
cause northerly turning error of the compass for
a particular turn thereof'.
`
ing error effect ofthe vertical component ofthe
earth’s ' field` -on >the magnetic, iield-sensitive ele
ment of said compasswhen turning rof the craft
occurs on which said compass is mounted, saidA Y
IESv means comprising'a permanent magnet arranged .
2. The combination with a magnetic compass
Within influencing distance- of the magnetic ele- `
of means for compensating for the northerly
ment of said compass, a magnetick shield, means»
turning error effect of the vertical. component
for movably supporting said shield to move rela
of the earth’s field on the magnetic, ñeld-sensi'
tive to said magnet’whereby-to control the linkage
tive element of said compass when turning of 27o of the flux of the permanentmagnet ñeld' with
the craft occurs on which said compass is mount
said compass, andaninstrument responsive to
ed, said means comprising a permanent magnet
turning movement 'ofthe' craft operatively con
arranged Within influencing distance of the mag
nected to' said shield for eîecting movement
netic element of said compass, shielding means
for said magnet, said magnet and shielding means 25
6. ~The combination with a magnetic compass of .
being relatively movablefto vary the linkage of
means for compensating for the northerly’turn
the flux of the permanent magnet ñeld with saidV
ing error effect ofthe Vvertic'al'component of the
compass element, an instrument responsive to
earth’s field on the magnetic, field-sensitive ele
turning movement of the craft, and means actu
ment of said~compass when turning of the craft
ated by said instrument fori effecting relative 30 occurs on-Which said compass is mounted', said
movement of said magnet and shielding means.Y
means comprisinga` pair of'permanent magnets
3. The combination with a magnetic compass
arranged with their‘magnetic axes in substantial
of means for compensating `for the northerly
alignment and withÍ like poles adjacent each other,
thereof.
turning error effectV of the Vertical component of
~
'
`
"
‘
~
shielding means "for said magnets,~ said magnets
vand shielding means being relatively'movable to
the'earth’s iield on the magnetic, ñeld~sensitive
element of said compass when turning of the craft ~
occurs on which said compass is mounted, said
~
vary the linkage of theñux ofthe ñeld ofsaid
- magnets with vsaid compass element, a rate of turn
` means comprising a permanent magnetarranged
gyro,_and means responsive to said rate of turn
gyror for relatively moving said magnets and
ment of said compass, shielding means for said 40 shieldingmeans an amount dependent upon the
magnet, said magnet and shielding means being
rate Vof turn of said craft.
relatively movable to vary the linkage of the ilux
7. The combination of elements recited in claim "
of the permanent magnetñeld with said compass _
3, together With dampi-ng means'comprising a cyl
element, a rate of turnfgyro, and means responsive
inder element .and pistonV element> therein, said
to said rate of'turn gyro for effecting relative 45 permanent magnet being incorporated at least
movement of 'said magnet and shielding means.
as a part of one of' said damping elements.
Within influencing distance of the magnetic ele
Y 4. The combination with a magnetic compass of
means for compensating for the northerly turn
ing error eiîect of the vertical component of the
earth’s iield on the magnetic, field-sensitive eleu 50
8. The combination of velements claimed in `
claim 2, including a second shieldingV means hav
ing parts defining an yadjustable air gap'situate'd
`between the permanent `magnet and themag- . Y
ment of said compass when turning of the craft
netic element of the compass, and means for
occurs on which said compass is mounted, said
setting the’lparts 'of vthe second shielding meansV
means comprising a permanent magnet arranged
Within influencing distance of the magnetic ele-y
_ in accordance with Ythe latitude 0f the craft. .
FRANCIS W'EST, JR.>
.A