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v Septvlo, 1946.:
Filed April io, _1942
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2 sheets-¿Sheet i
Sept V10» 1946-
Filed April l0, 1942
Sheets-Sheet 2
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Patented Sept. 10, 1946
Hall Langstroth, Hempstead, and Fred C. Wallace,
Flushing, N. Y., assignors to Sperry Gyroscope
Company, Inc., Brooklyn, N. Y., a corporation
of New York
Application April 10, 1942, Serial No. 438,398
9 Claims.
(Cl. Z50-11)
The present invention relates to scanning de
vices for scanning highly directive radiant energy
radiation or receptivity patterns over apredeter
mined conical solid angle.
In many types of devices, such as object de
Further objects and advantages of the present
’invention will be apparent from the following
specification and drawings.
Fig. 1 shows an elevation view partly in sec
tion of one embodiment of the present invention.
tectors, it is necessary to project or receive a
Fig. 2 shows an enlarged detailed vertical sec
sharply directional radiant energy radiation or
tion view of a portion of Fig. 1.
receptivity pattern and to scan this pattern over
Fig. 3 is a section view of the device of Fig. 1
a definite portion of a sphere, especially for the
taken along they line 3-3 thereof.
purpose of obtaining radiant energy reflections 10
Fig. 4 is a View similar to Fig. 1 showing a modi
from anyl object which may be in the field of this
fication of a .portion of the device of Fig. 1.
radiation and for using such reflected radiation
Fig. 5 shows a, detail side elevation of Fig. 4
to indicate the presence and/or position of the
viewed along the line 5-5.
reñecting object. It is also desirable to inter
Fig. 6 is an elevation view partly in section
rupt this scanning motion when an object has
showing a modiûed construction for the device
been detected and to produce a conical motion
of Figs. 1 and 4.
having a very small apex angle, such as of the
Fig. 7 is a View similar to Fig. 5 showing a modi
order of four degrees, for the purpose of giving
ñed construction suitable for use in Figs. 4,/ 5, or 6.
a finer and more accurate indication of the posi
Fig. 8 is an elevation view partly in section
tion of the reflecting object.
20 showing a further modification of the invention.
In the present invention a beam of radiant
Fig. 9 is a detail view similar to Fig. 8 showing
energy,v such as a high frequency radio beam,_is v still another modiñcation.
projected from a suitable highly directional radi
Referring to Fig. 1 a suitable directional radi
ating or receiving arrangement for radiant en
ator which is caused to oscillate slowly or “nod”
about an axis substantially perpendicular to the
ergy, such as a metallic reñector I preferably of
direction of the beam. At the same time, this
paraboloidal form and containing a suitable an
“nod” axis itself is rotated at a fairly high speed
tenna arrangement, is supported for rotation
about a “spin” axis normal to the “nod” axis so
about an axis 3 as by means of suitable brackets
that the beam in effect sweeps out a spiral pat
5 fixed to reflector I and pivotally mounted in a
tern caused by the widening of the circles pro 30 yoke l, which is integrally formed with or fas
duced by the fast spin motion in response to the
tened to .a sleeve 9 whose axis II is perpendicular
slow nod motion. Accordingly, the present de
to axis 3. Axis 3 is termed the “nod” axis, and
vice is enabled to scan in a spiral fashion a sub
axis II the “spin” axis. Any suitable type of
stantially conical portion of the sphere whose
motive means, such as an electric motor, is con
extent is determined by the angular limits of the 35 nected to drive an input shaft I3, which has
nod oscillation. In addition, means are provided
bearings mounted in a ñxed casing I5. Fastened
for substantially instantly changing this spiral
to shaft I3 are two gears I1 and I9 which are
thereby rotated at a fixed speed. Gear I‘I en
gages a gear 2I fixed to or integrally formed on
position and retaining only the spinning motion. 40 sleeve 9, and thereby :causes the reflector I to
The apex angle of this conical scanning is ob
continuously rotate at a predetermined speed
scanning motion of the beam into a small conical
scan by interrupting the nod motion near its zero
tained by ofi-setting the orientation of the beam
from the axis of spin.
about spin axis I I. Engaging with gear I9, which
is also continuously rotated from shaft I3, is a
further gear 23 to which is connected a second
Accordingly, it is an object of the present in
vention to provide an improved apparatus >for 45 sleeve 25 mounted rotatably and concentrically
scanning a predetermined portiony of the sphere
within sleevevS. Fastened to the end of sleeve 25
by a directional radiation or receptivity pattern.
is a suitable cam 2l formed as a ñat disc con
It is another object of the present invention
taining a groove 29 eccentric to spin axis II and
to provide improved devices for scanning a highly
of a, .predetermined shape, chosen, as will 'be de
directional radiation or receptivity pattern in a 50 scribed, to provide a suitable type of nod motion
for reii‘ector I.
It is still another object of the present inven
Engaged in groove 29 of cam 21 is a suitable
tion to provide improved devices for effecting
follower 3l. It is to be understood that follower
spiral scanning and for «converting such spiral
3l is actually located in a plane passing through
scanning into ñxed conical scanning,
spin axis H and Vertical to the plane of the draw
move back and forth in a straight line perpen
its nod cycle.
ing of Fig. l, but is shown as in Fig. 1 for pur
poses of clarity. Cam follower 3| is restricted in
its motion to translation only and hence, by the
motion of cam 21 relative to yoke 1, is caused to
One method of performing this
operation is shown in Figs. 1 to 3.
Mounted on the nod axis 3 and fìXed with
respect to reflector | is a suitably shaped cam or
dicular to the plane of the figure.
Fastenedto :cam follower 3| is a rack 33 which
engages with a pinion 35 fixed to a- cross shaft
31 as by a key 39. Key 39 and shaft 31 are
locking piece 59 which has its smallest radius,
as at point 9|, at the position corresponding to
zero nodof reflector l; that is, at the position
where the axis of symmetry of reflector | is most
nearly coincident with the spin axis ||, differ
adapted to move axially with respect to gear 35 10 ing therefrom only by the apex angle defined
above. From this point 3| the radius of cam
but any rotational movement of gear 35 produces
increases smoothly in both directions to a
a corresponding rotational movement of shaft 31.V
maximum radius at its tips, as at 63.y
Also fixed for rotational motion with shaft 31 as
by key 39 is a gear 4|, which engages a gear sec
tor 43 fixed to reflector | by a suitable bracket 45.
Cooperating with cam 59 is a roller detent B5
mounted on a suitable rod 31 which is normally
held away from engagement with cam 59 against
the force of a spring 99 by means of a latching
As described above, yoke 1 and reflector Al are
continuously spinning about spin axis l! at a
arrangement comprising a latching member 1|
predetermined speed. Cam follower 3| and rack
and a projection 13 on the end of shaft 31 serv
33 are also thereby spinning at this spin rate.
The gear ratio between gears |9 and 23 is chosen 20 ing as a detent. As described above, shaft 31 is
axially translatable.
to be slightly different from that between gears
1n the position shown in Fig. 1, roller 55 is held
l1 and 2l, whereby cam 21 is driven at a rate
away from cam 59. However, upon translating
slightly different from lthe rate of rotation of
shaft 31 to the left, its enlarged portion or detent
yoke 1 in spin. Th'is difference is the rate of
13 will move away from latch 1|, permitting the
nod, and produces translation of cam follower
smaller diameter section 15 of shaft 31 to move
3| and rack 33 with respect to yoke 1, and there
within a slot 11 of latch 1l and thereby permit
by, through gears 35 and 39 and gear sector 43,
ting spring 33 to urge roller 35 into engagement
produces the nodding motion of reflector | about
with cam 59. Spring 99 is chosen of such strength
nod axis 3. Since the rate of nod is much slower
than the rate of spin it will be clear that the 30 that if reflector | is free to turn roller 65 en
gaging cam 59 will cause reflector | to rotate
axis of symmetry of reñector | is caused to sweep
until roller 35 engages the smallest radius por
out a series of widening or narrowing circles, the
tion Si of cam 59, and will thereafter hold reflec
circles being generated by spinning about spin
tor i centralized in this position. Reflector |
axis Il and the widening or narrowing being
is made free to rotate in response to the action of
caused by nodding about nod axis 3. This in
cam 59 and roller E5 by motion of key 39 out of
effect produces a spiral scanning of the axis of
engagement with gear 35 upon axial motion of
reflector | over a predetermined solid angle.
shaft 31. When this occurs, gear 35 is left free
If the system is to act as a radiator, the radiant
to rotate upon shaft 31 and can produce no mo
energy to be radiated from reflector | is intro
tion of shaft 31, gear 4| and gear sector 43 at
duced through a suitable wave guide 41. In view
tached to reflector |.
of the fact that the radiating arrangement is
Such axial motion of shaft 31 is provided by
spinning rapidly about spin axis || it is neces~
the energization of a suitable solenoid 11 fas
sary to provide a suitable rotating joint 49 for
tened to the base or housing l5. Upon energiza
coupling the stationary portion 41 of the wave
guide to the rotating portion 5| carried by yoke 45 tion of solenoid 11 its »magnetic armature plunger
19 is drawn upward against the tension of a
1. Suitable types of rotating joint are shown in
spring 8|, thereby rotating arm 83 about a pivot
copending application Serial No. 429,494, for Di
rective antenna structure, filed February 4, 1942,
in the names of R. J. Marshall, W. L. Barrow,
and W. W. Mieher. Rotating wave guide 5| is
thenbent around in arcs of suitable radius to
extend coaxial with nod axis 3, as at 53. Here
again, since the reflector | oscillates about nod
axis 3 with respect to mounting yoke 1, a further
rotating joint indicated at 55 is provided be- .r
tween the section 53 carried by the yoke and
section 51 of the wave guide carried by the re
flector i.
35 fixed to base l5. The far end of arm 83
carries a roller 81 which normally rolls within
a, pair of guides 89 formed on a third sleeve 9|
located co-ncentrically and slidably within sleeves
25 and 9. Thereby, energization of solenoid 11
will produce a downward motion of sleeve 9|,
which spins at the same rate as yoke 1.
Pivoted to the upper end of sleeve 9| is a link
arrangement 93 which, upon a downward mo
tion of sleeve 9|, produces a leftward motion of
shaft 31, as by means of an arm 95 engaging the
end 91 of shaft 31. Shaft 31 is thereby moved
Wave guide 51 terminates within reflector | in
to the left upon energization of solenoid 11, and
any suitable well known type of termination, 60 acts bo-th to disengage the nod driving mechanism
such as shown in copending application Serial
of reflector | and to disengage latch 1|, whereby
No. 429,494. Preferably this termination is so
the centralizing cam and roller arrangement
adjusted that the orientation of the maximum
59-55 is actuated to centralize the reflector |
directivity of the radiation pattern of reflector í
and maintain it with its axis of symmetry at
is at a slight angle to the axis of spin || even in
a fixed scanning angle with respect t0 spin axis
the position of Zero nod.
This angle is chosen
to be the apex angle of the conical scanning to
be described below. ‘The angle may be formed
Thereafter, so long as solenoid 11 is ener
gized, reflector | will be rotating only about’its
spin axis | l, and the directional beam of radiant
by selecting the proper zero nod condition, or 70 energy, which as described above, is off-set from
by off-setting the antenna within reflector |.
When conical scanning is desired in the ar
rangement already set forth it is merely neces
sary to interrupt the nodding motion and to fix
th'e reflector | at a predetermined position in 75
` the spin axis | l, will generate a cone. Preferably
the off-set angle is chosen substantially equal to
the angular width of the directional radiation
pattern, so that an accurate determination of the
orientation of a distant object may be made.
-Upon deenergi'zation of solenoid 11, spring 8|
causes plunger 19 to withdraw from soleonoid 11,
thereby moving >sleeve r9| upward and releasing
arm 95 from the end of shaft 31. A spring 99,
having one end ñXed to the spinning mount IUI
and the other end rotatably engaging a collar |03
fixed to shaft 31, urges shaft 31 toward the right.
In so doing, and before detent 13 on shaft 31 can
enter its mating opening 14 in latch 1|, key 39
once more connects gear 35 to gear sector 43
through gear 4|, and starts the reflector nodding
about nod axis 3. In so doing cam 59 now drives
roller 65 and its rod 61 downward.
As rod 61
vantage of greater simplicity over that of Fig.
1, since the use of cam 59 and its follower and
the translation shaft 31 is eliminated. However,
it has the disadvantage that the system must wait
until the reflector I has reached its centralized
position in its normal course of operation before
reflector I may be centralized to perform conical
scanning, whereas, in the system of Fig. 1, no
matter what the position of reflector I is at the
moment solenoid 'I1 Vis energized, the reflector |
is immediately disengaged from the nod drive and
returned to its centralized position.
Fig. 6 shows a modified form of construction
reaches its lowest position, projection 'I3 of shaft
which may replace the cam_21 and the nod-actu
31 slips into its mating opening 14 and thereafter 15 ating apparatus in Figs 1 and 4. Here yoke 1
holds roller 65 away from engagement from cam
59 and the system resumes its spiral scanning as
described above.
As an alternative construction, shaft 31 need ~
not bemade to rotate. Thus, gears 35 and 4| may
be coupled by key 39, which thereby rotates with
respect to shaft 31. Key 39 is adapted to be dis»
is actuated by sleeve 9 in the same manner as in
Figs. l and 4.
Sleeve 25 actuates a cylindrical cam I2|, which
replaces flat cam 21 in Figs. 1 and ll. Cam I2I
is provided with a continuous groove |23 whose
disposition on the cylindrical surface of cani |2|
is so chosen as to provide a desired type of trans
lational motion for its follower |25. Since cam
I2I rotates relative to yoke 1, being driven at a
engaged from gear 35 by actionof a shoulder on
shaft 31, when shaft 31 is shifted axially in re~
Sponse to actuation of solenoid 11, as already de 25 different speed therefrom, follower |25 is trans
_lationally oscillated in a direction parallel to spin
It will be clear that by the apparatus just de
axis II. Accordingly, to provide nod motion it is
scribed the transition to conical scanning is made
merely necessary to couple cam follower |25 to
with the greatest accuracy, ksince the position of
the reflector I, as by a suitable arm |21 and a
the reflector I during conical scanning is de
pivotally connected link |29.
termined directly with respect to yoke 1, avoid
The mechanism for interrupting the nod mo
ing any inaccuracies arising from backlash, etc.,
tion to provide conical scanning in Fig, 6 is il»
which would appear yif reflector I were held at
lustrated as being the same as in Fig. 4.
any other point of i-ts drive.
Fig. '1 shows a modification of a portion of Figs.
Suitable counterweights may be provided about
e, 5, and 6. Thus, in place of member I 95 having
both axes 3 and || to provide both static and
a notch |91 and cooperating with projection |99
dynamic equilibrium during scanning.
in sleeve 9| as shown in Figs. 4, 5, and 6, member
Figs. 4 and 5 show a modiñed arrangement for A
converting from spiral scanning to conical scan
§95 may be provided in the form of a cam |95’
similar in contour to cam 5-9 shown in Fig. 3, and
ning. Here vcam 59, its roller 95, spring 69, latch 40 projection |99 of sleeve 9| may terminate in a
1| and detent 13 on shaft 31 are omitted. In their
suitable roller I lû similar to roller 65 in Fig. 3.
place a suitable member |95 having a notch | e1 is
‘ rl‘he operation of this modification clearly com
fastened to reflector |, notch |91 corresponding
bines the desirable features of Figs. 1 and 4. Thus
to the zero nod position of reflector I in' which its
the complicated latch and detent mechanism of
axis of symmetry most nearly coincides with spin .Y Fig. l is eleminated, while retaining the advan
axis | I. Formed upon the end of sleeve 9|, which
tage of returning the parabola I to its zero nod
is now arranged to be drawn upward upon energi
position substantially instantaneously.
zation of solenoid 11', is a projection |99 prefer
Fig. 8 shows a Vfurther modification of' the in
ably rounded and adapted to cooperate with a
vention including a modified type of nod--pron
preferably V-shaped notch |91 in member I 95. 50 ducing and nod~interrupting mechanism. Thus,
Therefore, upon energization of solenoid 11',
driving shaft f3 rotates gear I9 which engages
sleeve '9| moves upward urging projection |09
a further gear »23 connected as by a suitable pin
against member |05. Projection |99 therefore
slips into notch |91 when reflector | reaches the
or key to sleeve 25. Sleeve 25, however, instead
of rotating a cam as in Figs. l, 4, and 6, rotates
proper position and serves to hold reflector I yin
a carrier member I3I carrying floating pinions
this position for conical scanning. At the same
|33 illustrated in the figure as being two in num
time, as projection |99 slips into notch |91, a key
ber, but which may comprise any desired num
| I I which serves to couple gear 23 to sleeve 25
ber. The pivots I 35 of pinions |33 are mounted
during spiral scanning, is slid upward into a suit
equidistant from and parallel to the axis of ron
able, preferably annular, recess I I3 in sleeve 9 and 60 tation of carrier I 3| , which is chosen as spin axis
disengages sleeve 25 from gear 23 whereby the
II. At the same time, gear 23 rotates a gear |31
motion of cam 21 and hence of the power drive for
suitably fixed thereto. Gear |31 is illustrated as
reflector | in nod is removed. Thereafter reflector
being an elliptical gear of the well known type
| is maintained centralized and conical scanning
and engages with a second elliptical gear |39.
is performed. If desired, recess IIS could be a 65
As is well known, two elliptical gears pivoted
simple» notch matched to key |I| when projec
at respective focal points spaced the proper dis
tion |99 falls into notch |01.
tance apart will continuously mesh with one an
Key | || is shown formed integrally with or
other and one will provide a varying speed output
fixed to the lower part l9|’ of sleeve 9|, which
when the other is driven at a constant speed,
therefore rotatesat the same rate as sleeve 25 70 which output speed cscillates between two limits
and cam 21. Since the upper part 9|” of sleeve
respectively above and below the driving speed.
9| must rotate at the same rate as yoke 1, a suit
Accordingly, the output speed of shaft | 4| car
able rotatable joint 92 is inserted between the two
rying elliptical gear |39 will be alternately slower
parts of sleeve 9|.
and faster than the speed of shaft 25 and carrier
The system shown in Figs. 4 and 5 has the ad 75 |3I, Also attached to shaft I4| is a pinion |43
actuates a further gear |82 Aalso fixed to sleeve
|41. Gear |82 operates through a suitable train
at whose upper end is mounted an internal gear
of gears |83 and |84 to actuate member |53 which
|49 meshing with pinions |33.
is similar in function to member |53 shown in
Floatingly mounted and concentric with sleeves
Fig. 8.
25 and |41 is a spur gear |5| engaging pinions
Member |53 carries bevel gear teeth which en
|33. It will be clear that internal gear |59, car
gage with bevel gear sector |55 fixed to the pa
rier |3| and its pinions |33, and gear l5 |, provide
rabola | as in Fig. 8. The gear ratios involved
one well known type of differential gear and ac
are so selected that bevel gear |53, which is
cordingly, the rotation of gear |5| will be pro
portional to the difference in speeds of internal 10 driven at a varying rate of speed, has an aver
age speed equal to that of spinning yoke 1. Ac
gear |f|| and carrier |3|.
with respect to yoke 1, gear |53 alter
As stated above, carrier |3| is rotated at con
up and slows down, and therefore
stant speed while internal gear |159 is rotated atreverses its direction of motion. In this manner
a continually varyingspeed. As a result', the out
the nod oscillation is produced.
put gear |5| will also be rotated at a continually
varying speed which oscillates between two fixed
scanning may be produced in any of the man
limits. 'I'he various gear ratios are so chosen
ners described with respect to the previous fig
that the average speed of gear |5| will be the
ures. Thus, if desired, a member |6| carrying a
same as the speed of yoke 1, which is driven from
, projection |55, similar to the arrangement of Fig.
shaft I3 by way of gear |1, gear 3|, and sleeve
8 may be provided to halt the nod motion at a
9, as in the other iigures. In this way gear |5|
particular point of the nod cycle as discussed
alternately speeds up and slows down with re
with respect to Fig. 8. At the same time, the
spect to yoke "I and accordingly, it periodically
nod drive may be interrupted either in the man
reverses its direction of rotation with respect to
engaging a further gear |45 fixed to a sleeve |41
yoke 1.
25 ner shown in Fig. 8, or by an immobilizing mem
Fastened to gear |5| is a beveled gear |53 which'
engages with a beveled gear sector |55 suitably
fastened to the parabola |. lin this way, parabola
| is oscillated back and forth as the yoke 1 ro
tates, and there is thus produced the required nod »
motion and spin motion. Itis to be understood
that the values of the gear ratios are chosen to
provide a suitable rate of non-oscillation.
To provide a nod interruption, sleeve 9| is
ber |15 of differential |13. This may be done
in any suitable manner, as by disengaging rack
|16 from gear |11, or by declutching the drive
shaft |19 of this oscillating motion from its source
of power.
Alternatively, gear |53 may be simultaneously
disengaged from bevel gear |55, as by the re
ciprocation of member -|6| and sleeve 9| iixed
thereto. It will be clear that many other de
again provided controlled in a manner similar
vices for producing this result may be readily
to that of Fig. 1 by a solenoid 11. The upper end
evolved from the above description.
of sleeve 9| carries a projecting collar |51 so that
upon energization of solenoid 11 sleeve 5| moves
downward and disengages gear |53 from gear
As many changes could be made in the above
for the nod motion.
At the same time, a projection |59 on a flange
|5| fastened to the end of sleeve 9| bears down
on beveled sector |55 and is adapted to fall into
a notch in sector |55 when the proper orienta
tion of parabola | is obtained. These members are
so arranged that the nod drive continues until
intended that all matter contained in the above
description or shown in the accompanying draw
ings shall be interpreted as illustrative and not
construction and many apparently widely differ
ent embodiments of this invention could be made
sector |55, thereby interrupting the power drive 40 without departing from the scope thereof, it is
in a limiting sense.
l What is claimed is:
l. A scanning device comprising a directive
antenna mounted for rotation and oscillation
about independent axes, drive means, means
driven by said drive means for rotating said
ing the power drive and stopping nod. In this 50 antenna including a first sleeve mounted to ro
tate about its longitudinal aXis, means driven
way, parabola | is locked into the proper posi
by said drive means for oscillating said antenna
tion for conical scanning, as discussed above.
including a second sleeve concentric with said
If desired, a suitable cam and roller arrange
ñrst sleeve and rotatably movable with respect
ment similar to those of Fig. 3 or Fig. ’1 may be
thereto, normally ineffective means for holding
provided to centraline the parabola I instan
said antenna in a fixed position with reference
taneously upon energization of solenoid “i1 and
to its axis-of oscillation including a third sleeve
interruption of the nod power drive.
concentric with said ñrst and second sleeves and
Fig. 9 shows a further modiñcation similar in
reciprocatively movable with respect thereto,
many respects to that of Fig. 8. Thus, drive shaft
I3 spins yoke 1 by means of gear |1, gear 2|, and 60 means for disabling said oscillating means, means
for rendering said holding means effective, and
sleeve 9. Gear |9, also driven from drive shaft
means for effecting simultaneous operation of
I3, actuates a gear 23 floatingly mounted about
both said disabling and rendering means.
axis || which thereby drives one member |1| of
projection |59 falls into its corresponding notch
in sector |55, thereby simultaneously interrupt
2. A Vscanning device as claimed in claim l,
a suitable differential gear |13 of any well known
type. A second member |15 of differential |13 is 65 in which the reciprocatively movable part of said
holding means is a detent and the part that
adapted to be oscillated as by means of a rack
cooperates with the same is a locking piece
|15` engaging therewith and oscillated as by
mounted to move with movement of the antenna
means of a crank drive arrangement |18 whose
about its axis of oscillation.
actuating shaft |15 is suitably driven.
3. A scanning device as claimed in claim 1,
As a result, the third member |8| of differen
in which said holding means is a detent and
tial |13 is driven at a varying speed due to the
the part that cooperates with the same is a lock
combined rates of motion of constantly driven
ing piece mounted directly on the antenna in a
member |1| and oscillated member |15. Output
position to move with movement of the same
member |5| of differential |13 is coupled to a
suitable gear |45 fixed to a sleeve |41 and thereby 75 about its axis of oscillation.
4. A scanning device as claimed in claim 1,
in which the axis of rotation of the antenna is
vertical and the axis of oscillation of the antenna
is horizontal.
5. A scanning device as claimed in claim 1,
in which said oscillating means includes a rotat
ing cam plate having a translatably mounted
follower therefor.
input element of the diñerential at a variable
speed, disengageable means for controlling the
motion of the antenna about its axis of oscilla~
tion from the output element of the differential,
normally ineffective means for interrupting mo
tion of the antenna about its axis of oscillation,
and means for simultaneously rendering said in
terrupting means effective and disengaging said
6. A scanning device comprising a directive an
disengageable means.
tenna mounted for rotation and oscillation about
8. A scanning device comprising a directive an
independent axes, a differential having two input
tenna mounted to spin about one axis and nod
elements and a single output element, means for
about another axis, mechanism operable to spin
driving one of the input elements at a constant
said antenna including a ñrst sleeve, mechanism
speed, means for driving the other input element
operable to nod said antenna including a second
of the diiîerential ata variable speed, and means 15 sleeve concentric to said first sleeve, and mech
for controlling the motion of the antenna about
anism operable to interrupt the nodding motion
its axis of oscillation from the output element of
of said antenna including a third sleeve concen
the diñerential.
tric to said first and second sleeves.
'7. A scanning device comprising a directive
9. A scanning device of the character claimed
antenna mounted for rotation and oscillation 20 in claim 8, in which said nodding mechanism in
about independent axes, a differential having tWo
cludes a rotating cam plate and a reciprocating
input elements and a single output element,
means for driving one of the input elements at
a constant speed, means for driving the other
cam follower.
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