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Патент USA US2411870

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Dec.l3, 1946.
v '
Filed May 31, 1943
srsheeîsl-sheet 1
.l '
, D€C- 3, 1946-
I 2,411,870 -
Filed May 51', 1943
3 Sheets-Sheet 2
Dec. 3, 1946f
Filed May 31, 1943
ßsheets-Sheet 3
Patented Dec. >3, 1946
Albert L. Chauvet, Piedmont, Calif.
Application May 31, 1943, Serial No. 489,182
This invention relates to a navigational instru
ment whereby» measurement of celestial altitudes
»may be attained with speed and accuracy under
conditions of visibility that would prevent the use
of a standard nautical sextant.
The object of the present invention is generally
to improve and simplify the construction and
operation of sextants; to provide a sextant which
is termed a universal sextant as it may be used
as a standard sextant, and by release of aclamp
is instantly converted into a sextant which may
be used at night, or under conditions of visibility
that would prevent the use of a standard sextant;
to provide a sextant having a pendulum on
which is secured a telescope, said pendulum and
telescope establishing an artificial or substitute
horizon through means of a cross-wire placed
in the optical axis of the telescope, said cross-wire
ticularly Figs. 1 to 4 inclusive, A indicates in
general the frame of the sextant. This frame is
plate-like in construction and consists of three
legs indicated at 2, 3 and 4, the legs 3 and 4
connected by a base member 5 and the arms
..5 being
2 and 3 being connected by an arcuate segment
6 which is provided with a scale 'l graduated from
zero to 120 in degrees. The frame is held when
in use by the handle 8 secured to the rear side
thereof by bracket arms 9 and I0. The frame
carries a pendulum arm Il on the lower end of
which is secured a telescope l2. The frame also
carries an index arm generally indicated at I4,
and in addition thereto, the frame carries a
horizon mirror l5 and a shaded glass tube I6,
while the index arm carries an index mirror in
dicated at l1.
The pendulum is mounted to swing about a
pivot which is best shown in Fig. 7. That is, the
forming a line which coincides with the sensible
horizon and from which all vertical angles may 20 frame proper indicated at A has a bushing
secured thereto as at I8. Disposed outside the
«be measured; and further, to provide an index
bushing is an antifrictionV ball. bearing i9 and
arm pivoted about the axis of the pendulum at
mounted freely to swing on the bearing is a collar
one end, and movable over a graduated scale at
20 from which the pendulum Il is suspended,
the opposite end, said index arm being provided
with a micrometer whereby the scale may be 25 a pivotal connection 2| being, however, formed
between the collar and the pendulum arm so
accurately read in degrees and minutes or less.
that it may also swing in a direction at right
The universal sextant is shown by way of illus
angles to the frame.
tration in the accompanying drawings, in which:
The telescope tube is secured in any suitable
Fig. 1 is a side elevation of the seXtant, said
manner to the front face of the pendulum arm,
elevation showing the index and horizon mirror in
and besides that of serving as a telescope, it also
serves as the bob or weight of the pendulum.
Fig. 2 is an end view of Fig. 1;
The pendulum arm is bent at right angles at its
Fig. 3 is a side' elevation showing the rear side
lower end as indicated at 22 in Fig. 2, and ex
of the sextant;V
Fig. 4 is a perspective view of the outer end -of
» the index arm, said -view showing the micrometer
attached thereto;
Fig. 5 is a perspective view of the micrometer
showing it removed from the index arm;l
Fig. 6 is an end view of the micrometer looking
from the drum end;
Fig. 7 vis a vertical cross-sectiontaken on line
1_1 of Fig. 1‘but showing- the index. arm swung
into a vertical position;`
Fig. 8 is a front View of the index mirror;
Fig.v 9 is a plan view of a spherical washer used
in conjunction with the index mirror;
Fig. 10 is a front View of the horizon mirror;
tended upwardly at right angles as shown at
23 on the rear side of the frame, and it carries
a counter weight 24 which is adjustable longi
tudinally to compensate for any adjustment of
the telescope I2, as will hereinafter be described.
The telescope also carries a spirit level 25 (see
Fig. 1), so adjusted by the manufacturer that
when the pendulum is swinging freely, then the
optical axis of the telescope will point to the
sensible horizon. The spirit level or bubble used
is tubular. It is calibrated and should be correct
to not more than one-quarter minute of an arc,
or fifteen seconds. The telescope consists of a
tube with an ordinary object glass and a wide
angle positive eye piece to give a broad field. A
Fig. 11 is a side elevation of the same;
Fig. 12 is a side elevation partially in section of 50 horizontal cross wire, not shown, passing through
the optical axis at the focus of the eye-piece of
a shaded glass tube; and
the telescope coincides with the sensible horizon
Fig. 13 is a vertical central longitudinal section
when proper adjustments have been made. This
of the micrometer` but showing the drum and its
bracket ’inI side elevation.
Referring tothe drawings in detail, and par
cross wire is used as a line from which all Ver
tical angles may be measured,
The index arm I 4 is pivoted to revolve about the
to verify parallelism between the horizon and
index mirrors, and, when necessary, to view ob
jects directly,
same axis as the pendulum. rlí‘he arm proper is
secured to a collar ita, and this in turn is provided
with a pin lßib which extends through the bush
To one side of the horizon mirror or between
ing I3 and is rotatable therein, the pin Mb and 5 said mirror and index mirror is disposed a tube
the index arm carried- thereby being secured
l5 such as sho-wn in Figs. l and 12. This serves
against removal by a washer and screw as clearly
shown in Fig. 7. The index arm carries an index
the purpose of a sunshade. For instance, in
taking an altitude of the sun, the eye must be pro
mirror >generally indicated at i?. This mirror is
tected by reducing the intensity of the sun’s rays.
mounted on a 'plate Via and is spaced from >the 10 This is accomplishedby mountingtwîo ¿polarizing
arm Ui by pointed pins Hh, by a spherical washer
Hc, and by a ñange iid. Two screws are pro
The disc 55 is- stationary, and is secured in the
vided, one extending through the spherical wash
lower portion of tube I6, while the disc 5S is car~
discs within the tube le as indicated ate?, and 56.
er and one being disposed at a point adjacent the
rie'd by'a tube section, 15a, which telescopes with
iiange Hd. These screws adjustabiy secure the 15 relation to the tube I6, and is rotatable. Rotation
index mirror to the index arm anid'thereby'permit
of this disc increases and decreases light-ray
correction or adjustment whenever necessary.
transmission-and light intensity may be further
The index arm has an elongated reading slot
reduced by mounting a dark colored glass of the
formed in it adjacent its outer end as indicated
type Aused by welders at the point indicated at
at 23 (see Fig, l), andit is also provided with an 20 5l. The combination ¿of polarizing and colored
-ad'justablelmagnifyingglass1-2 9 whichis normally
disposedabove -the reading-slot.
ï-‘Ie‘oï'therear-iaee of the'index arm-is secured a
.discsshowninlli‘ig V121s, of course, Aonly;intended
:fcrxiay1ight-> usev and-particularly; iorobservations
_on :the sun, but it;:must,-_.of course, ¿beg substituted
micrometer“ generallysindicated atB V(seellî‘igs.
:by v'a E tube containing :clear .feiass s when :observa
This micrometer consists of a N) Ul tions are taken at-'night,;for instance,gongthe moon
f4, l5 and ¿13).
»kJ-shaped bracket having two arms s3@ and Si
¿and stars. '.Ordinarily,¿whengsubstituting clear
Yconnectedfby a base section
-Avthird bracket
-glass Ífor the .colored ,glass :shownin iFig. i2,
¿arm ‘is-»disposed >at
and this isvseeured to the
>changingoi` theifocus .of thetelescope'would be
>base '32 by'an arm-'1%. inthe arms 3a and 32
necessary, but :as the;` plain; glasszused inrthis in
~are- disposedY pointed screws ¿i5- between whichA is 30 strument is .designatedxto,haveïthesame; rev-irac
journalled a rod-E5 havinga threaded portion 3l.
' tive „effect
the .lightrayyreducing ~medium or
On theïthreaded-portion betweenvthe arms .Se
' discs .shown in‘- Fig. `12,1. the.~ telescope maygremain
andfälïis disposed a
»andsecured ona rod
constant focus both‘ioridayfand night- obser
Ibetween the armsßl and 33 is a drum 3Q which is
vations. This is iinportantgasY _the telescope, forms
graduated'ircm zero to sixty inminutes. The
the ,bob or »weight of'the;pendulum,and anyv ad
v'upper ends of thearmsäii and Si' are drilled and
'justmenttof thetelescope; Nifgthis- were. necessary,
tapped to receive screws ¿i0 whereby the-'microm
`‘wouldithrowLthe,pendulumpbr rather the spirit
' level, out of' adjustment,¿butgasrbothf-sets; of glass,
-index arm. Two-«other screws pass through the
Vwhether clear :glass or the type; shown inA
>index armlas indicated at‘ff'èi, and these secure a 40 >havethe same refractive, effect,Y adjustment; ofthe
‘ eteras a wholeïissecured to the rear side of the
Vplate 42 fromwhich extend two `spring arms d3
A'which iric'tionally engage the` rear surface of the
varcuate member »6 Ato> iri'ctionally’- secure the .index
arm against free movement. The index arm also
carries-‘asmall bracket ¿M (see-Figli) v-in which
'fisï-jo-urnalled» a' slowmotion tangent friction roller
‘"¿iâfwhich is Irotated-by meansof a knobláiü. V»The
tangent friction roller e5 engages the Outer
telescope becomes unnecessary; andL as_previously
'stated,§.may remain _,ñxed. jAgcounterweight-Zfi
-disposedi enz-fthe“ rear;` side „ofz the ¿pendulum arm
íisprovided to ¿obtainthe necessary adjustment ci
:the pendulumand the; spirit level. ¿This weight is
longitudinaily movable on its support as the screw
'124e securing .itgoperatesfinç anI elongated slot ilélb
(see-Figs. 1'.L andA 2) . ,'.Thisf weigl’laf> when properly
>knurledI peripheral edge of the arcuate finember
radjustedgginsures correct-.positioning of the bubble
carrying’ftheedegree scale?, and when knobJi-ä 50 tin# 4the;spirit-level. vandas ,the telescope; .tube re
quires no further adjustment thereafter, the
is grasped and’rotated, it swings vthe index arm
optical systemiofv the telescope-may; remainynxed.
lupY or 'down thetscale. 'The nut ì3S previously
'referred Vto carries an index'iinger-»fi‘l (see Figs.
Ii it were >notmiîxed- itrwould be necessary to
>'5 and 6). lri’his index ringer is made of a trans
parent material'such-as Celluloid or one of the
i transparent plastics. It overlies'the scale 71 which
adjust the weight 24 from timepto'time,V which
>»would be time consumingV and anuisance.
.- 4Itr was previously statedrthat the lsextant- might
Vis divided into degrees, and as it is transparent,
be employed as a standard nautical ,sextant To
‘ permit .this a clampíhgscrew-.ßß is’providedl (see
lit mairesr it possible to read this scale through the
Figs. land-2). ‘This passes-,through a slot 6ta
magnifying‘glass and the slot-28. The index
ñn‘ger ril has two visible lines iorrnedthereon as 60 formed in the lower 'end of- thel «pendulum»v arm,
shownat^ê8~inFig~~ 5. These lines are placed
and when it is clamped, it `clamps .the-pendulum
closely together but must be spaced a suiiicient
_armi and the telescope \.to-.-the-«frame:-VA. - Con
Vvdistance apart to permit a degree line to be seen
versel'ypby releasing »theuscrews-S’ß;the pendu
lum becomes free to swingfbothfin--a direction
"between them` with a slight-margin on each side.
The function of the lines ¿i8 will-hereinafterbe (i Ul parallel to the face Yof thesextant framerfand in
' described.
:_The horizon mirror'indicated at liti -is’provided
with a- plate bent atright angles thereto as shown
- at' 50. ìThis plate has foot" lugsformed >thereon
as shown at '51,l and a screw passing-through the
-' ,plate5 >as at 52, 'and'i'nto the Írameîforms a- means
>of securing-the Amirror to the frame,l and italso
` >forms a pivotïabout which the vhorizon mirrorV may
@be swung'when it »isiadju'stedll Theïhorizon‘mirror
additionzftl'iereto'has a limitedfswinging move
ment about ‘the pivot> 2l` in a- directionßat right
angles .to :the face ofI the iframe. y; Both _of these
movements ,areï essentialetof; permit the freest
possible.` movement' of- theypendulurn; furthermore
the ends of the slot ßßarservefas stops ,-te; limit the
.. movement ¿or > swing ¿of :ther-pendulum.
.`.~Befo1‘e 4taking an'cobservation; çtghe; instrument
should be checked for accuracy. vî.'I‘ihe¿instrmnent
has a non-silver'ed» slotl53'~iormedï as 75 „is held by the yhandleinzthe ‘righthand >so'that
f e
'the f pendulumY swings freely-¿the bubble should
be at" its central position and in adjustment.
The~pendulum-is then held against the frame
by the fingers and thumb of the righthand with
must be illuminated at
night by~ a small. electricf
fbulb lin order' to be seen. In the present instru
‘m'ent, the cross-wire and the object being ob-'
served Yare the only things which can be seen inÀ
the. optical system. The bubble is not viewed,I
líthe telescope as far forward as it-will `swing with
hence no illumination'is required during night
Ythe pendulum against the frame stop or bumper.
‘With the telescope thus clamped a distant object
The lsextant shown in this application is rie=or starV is viewed through the telescope, and its
for low cost production. It requires a.
‘direct image is viewed through the slot in the
'horizon glass, and its image reñected through the 10 minimum of material and as actually designed
weighs about one pound. Practically all parts are.
iindex glass should coincide. Held thus, the zero
stamped or cut from sheet metal as they are flat,I
mark on the drum should be at its index point.
and the only other parts employed are of rod or'
'The zero line of the arc should be exactly midway
' observations.
l between the double lines on the micrometer index
tubular form.
- .
Such a structure permits a com-
finger. With these conditions verified the instru 15 pact simple assembly, low cost, light weight, as-I
aluminum alloys, stainless steel and like metals'y
ment is ready for observation. On a star, for
may be employed.v Also the optical parts are of
-example, with the index arm pushed upward, the
the simplest nature and inexpensive even thought
star is located by sighting over the top of the
producing excellent results.
telescope and along the plane of the instrument.
Having thus described my invention, what II
Holding the instrument Very steadily with the tel 20
claim and desire to secure by Letters Patent is:
escope swinging freely, almost touching the
i. A sextant comprising a frame, a pendulum.
iframe, and at the same time barely bumping
pivotally mounted on said frame, a telescope car»
:against the stop, the object is brought into view
ried^` by the pendulum to view an object observedi,I
in the'?ield of the telescope by means of the
said telescope having cross-hairs to maintain a.
tangent roller knob and lowered until its image
substitute horizon, a horizon mirror carried by theI
comes inv contact with the horizon cross wire.
frame and disposed in front of the telescope, an>
The Valtitude is measured by noting the next low
index arm pivotally mounted on the frame, a scale
est degree on the arc scale just below the double
for the index arm to indicate the angle of eleva~
index lines. The tangent knob is then turned
until this lowest degree line bisects the space 30 tion of the observed object above the horizontal;
and an index mirror carried by the index arm.
between the double index lines. The altitude
to reflect an object being observed to the horizon
then is the degree reading plus the drum read
mirror and the telescope.
ing in minutes, an operation >requiring butv a
2. A sextant comprising a frame, a pendulum
few seconds of time.
The novelty lies in the fact that the pitch of 35 pivotally mounted on said frame, a telescope car
ried by the pendulum to View an object observed,
screw corresponding to one revolution of the drum
said telescope having cross-hairs to maintain a
must be greater than the corresponding space to
substitute horizon, a horizon mirror carried by
be measured on the scale so that one revolution
the frame and disposed in front of the telescope,
of the drum advances the double line along the
scale a distance greater than that between two 40 an index arm pivotally mounted on the frame,
a scale for the index arm to indicate the angle of
lines of the scale. Therefore, if at zero of the
elevation of the observed object above the hori
drum a line of the scale bisects the space between
zontal, an index mirror carried by the index arm
the double lines, then the next line of scale will
to reflect an object being observed to the horizon
again bisect the space between the double lines
mirror and the telescope, and means carried by
before the drum can make one complete revolu
the frame for controlling the intensity of light
tion. The advantage of this is that any screw die
entering the telescope.
can be used to cut the thread as long as its pitch
3. A sextant comprising a frame, a pendulum
is greater than the spaces between the arc lines.
pivotally mounted on said frame, a telescope car
All the micrometer has to do is to measure a dis
tance with less than one turn of the drum. 50 ried by the pendulum to view an object observed, ,
said telescope having cross-hairs to maintain a
Therefore, the drum can be accurately divided
substitute horizon, a horizon mirror carried by
f without difñculty to read any degree of precision.
the frame and disposed in front of the telescope,
' The reading is almost instantaneous and' the
an index arm pivotally mounted on the frame, a
„ micrometer is inexpensive to make.
The use of a spirit level or bubble to establish 55 scale for the index arm to indicate the angle of
elevation of the observed object above the hori
:an artificial or substitute horizon is not new,
zontal, an index mirror carried by the index arm
1 as a number of bubble sextants are in use. Bubble
._sextants are diiiicult to use as it is practically '
¿impossible to hold the spirit level in the hands
to reflect an object being observed to the horizon
mirror and the telescope, and means interposed
1. and maintain the bubble in its central position for 60 between the index and horizon mirror for control
ling intensity of light reflected into the tele
: more than an instant. In other words, the bubble
; sextants in use are not provided with means for
1i. A sextant comprising a frame, a pendulum
, stabilizing the bubble. By providing a pendulum
pivotally mounted on said frame, a telescope se
1 and mounting the spirit level thereon, as in the
vpresent structure, the bubble is stabilized and is 65 cured to the pendulum to view an object observed,
said telescope having cross-hairs to maintain a..
.readily maintained at rest in a central position
:thereby insuring that the telescope which forms
‘the bob of the pendulum will point precisely to
:the sensible horizon.
In bubble sextants now in use, the bubble is
'visible in the optical axis of the telescopes, hence,
- the object being observed together with the bubble
must be viewed at the same time. Furthermore,
a source of electric current must be provided in
substitute horizon a spirit level carried by the
telescope and having a bubble to indicate when
the telescope points to the sensible horizon, a
horizon mirror secured to the frame in front of
the telescope, an index arm rotatable about the
same pivot as the pendulum, a scale for the index
arm to indicate the angle of elevation of the ob
served object above the horizontal, and an index
the form of dry batteries or the like as the bubble 75 mirror` carried by the index arm to reflect the
object being observed to the horizon mirror and
'- 5". telescopen
‘A seXtant comprising
'i Y a,î frame, a, F'î:pendulum
pivotally? mountedr'on Said framegla'telescope' *se
cured to the pendulum to-'view an object'observed,
said telescope having cross-hairs ïto lmaintain a
substitute horizon ‘a ¿spiriti level lcarried by-«the
telescope and having a bubble to indic'ateäwhen
the ftele‘scopeî point'sàto ïthefsensible^horizo1i a
horizon mi?ronseéured to the/frame ini froninolîY l0
the telescope, an index yarm rotatable about the
same' pivot-'as the pendulumiea-'scale- for the index
arm to -indicate'fthe çangl‘efofr. elevation ofithekm ob
served object `:ibovetlue horizontal; an- index‘mir
ror ‘carried-` by “ehe-index ,fa-rmïto yreflect; theobject
being observed to thehorizon mirrorand `thetele
scope, land AamV adjustable counterweight-'carried
by the pendulum;
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