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Патент USA US2408571

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oct- 1, 1946-
,
H. L.‘ MITCHELL
2,408,571
NAVIGATIONAL COMPUTING INSTRUMENT
Filed April 24, 1944
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Oct. 1, 1946.
~ H. L. MITCHELL
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2,408,571 I
NAVIéATIONAL COMPUTING INSTRUMENT
' Filed April 24, 1944
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Oct. 1, 1946.
2,468,571
H. L. MITCHELL
NAVIGATIONAL COMPUTING INS TRUMENT
. Filed Ap ril
24, 1944
5 Sheets-Sheet 3
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Patented Oct. 1, 1946
2,408,571
UNITED
STATES:
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PATENT . OFFICE? ' o
'2;40s,57;1.
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NAvIcArIoNnri ‘COMPUTING 'IN‘srRUMEN-rr
_ HuliertL. Mitchell, Houston; Tex.
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Application 'April'2'4, 1944, serial Not-532,519’
..
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1'
Figure 7 shows anedgeiview' of; the‘ trackponj
invention relates to. a‘ computing instru
whichithe leeway
is mounted to slidasl'iov'r
ing said. grid- adjusted to eccentric positionrela
ment, __d'esigned for‘ use in navigation. .
‘ The‘ invention herein described embodies cer
tain improvements over the instrument disclosed
in lny' copending application Serial‘, Number
tivelthereto.
rFigurel8 shows
’ ‘ an enlarged;_ fragmentary
" _ bot
525,297, ?led March 6, 1944. _
tomperspectivevie'w of the'leeway grid;
I
_ v,
,
,
‘ v 7
‘ Figure 9 shows'a perspectiveview of they track,‘
,An object‘ of the invention“ is, to provide an in
and.
'
strument formed with a navigational side. which
Figure 10 sh-ows'iasimple form ‘arena-gums!
supplies convenient means for, at once‘, solving
various angle problems, which replaces traverse 10 tratingthe useiofithei i'nst'rumen't'as a protractor;
tables; which ascertains the vessel’s .positionfrom
7 Referring now more particularly to thedra‘wf
two angles, by means of which the true course,
ingsi wherein like‘. numerals of‘referience designate
true heading, cruising speed, speed over bottom,
similar parts each o'f'th'e ?gures the numeral‘ I"
designates a disc having a compass‘ros'ej on" one“
leeway and force andv direction of currents may
be known; also which may be used as a conven 15 side. 7 This part I is shown ‘as a relativel'yfthin disc
tional protractor, without‘ the use of a straight
but-itmay- he of any selected sha'p'e'or thickness. "
edge.
'
'
"
'rIlhere is a current velocity; or wind'drift‘ grid,’
2- rnounted to rotate 0n the disc 1 within the corn
.
As herein used the term “current” represents
the sum of the effects of wind: current‘ and sea
current; and “leeway” represents thenumloer of
20
degrees correction’ necessary to compensate for
current.
,
_
,
passv rose. It. is provided’ with a current arrow
3-and'1amargi'na1 shift tab 4'. It also has spaced~
lines, 5. which are parallel‘ with the arrow; This
arrow and its parallel lines, when the instrument‘
isinuse; point in the.‘ direction of‘ the current.
There are also'the spaced lines 6, onv thisgrid', at
_
The instrument herein disclosed‘ is intended,
inactual'use; to be also provided-with a slide rule
side;- as shown-inthe copending' application and 25 right angles to the arrow“ and which are used to
used to‘ multiply; divide; ?nd percentage, propor
measure. the strength of the current.
;
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tions, square roots, speed-time—distance relations,
YIt. willbe noted'from, ‘aninspection of Figure
to-con-vert miles-per any given time unit to‘miles
6 that the lines 5 and" 6 are alternately heavy
per any other timeunit and to‘ convert nautical
and-v light. Intervalfrom a heavyto a light line
and’ statute - miles‘ to‘ determine fuel consumption. 30
represents current. speed-‘of one-half mile, and‘
EMore. generally speaking the instrument has‘
interval. from a heavy line to the next heavy line
b'een'jdesignedfor use in‘ water navigation as'an
aidv inmakingquick solutions of problems’ con-e
fronting‘ the‘ navigator and: in obtaining‘ the in
represents current speed of‘ one mile. For cone
formation required pertaining to the‘ movements
venience in reading, the arrow‘ and these' lines
sliould be of a bright color, preferably red.
35 , 'There is also. a ‘leeway‘grid T marked in‘ de
ofithe'vessel; the instrument is also capable of
grees. This is superimposed on; the grid 2; and
use in air navigation‘ by‘ the necessary conversion‘
should'jbe transparent so that the grid 2 willbe
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visible through it. On it is the true course ar
With-the above and otheryobjects in view this
row 8‘ which should indicate the true course; if‘
invention has particular relation to certain novel 40 known; if not after reading degree of wind cur
rent from instrument will indicate true heading.
features of construction, operation and arrange
ment of parts, an example of which is given in
On the grid 7, to the right and left of the true
of its unit-readings;
course arrow 8 are uniformly spaced leeway
lines 9 which converge to a center common to
Figure 1 shows a plan View of the navigational 45 the lines and to the line of arrow 8,‘ which cen
. ter is remote from the grid. These lines are
side of the instrument.
this speci?cation and illustrated in the accom
panying drawings, wherein:
Figure 2 shows a diagrammatic edge view illus
trating the relative positions of the instrument
parts.
.
spaced apart to indicate. two degrees between
them. There are also arc lines It], on grid 1, in
tersecting true course arrow, having a common
Figure 3 shows the compass rose.
50 center with the leeway lines 9, and spaced uni
formly apart to represent cruising speed as well
Figure 4 shows a plan view of the leeway grid.
Figure 5 shows a cross sectional view thereof,
as speed over bottom. When the true course ar
row 8 actually indicates the true course, the
taken on the line 5—5 of Figure 4.
strength of. the current is measured from the
Figure 6 shows a plan view of the velocity cur
55 center in the reverse direction from that indi
rent, or winddrift, grid.
.
2,408,571
3
4
cated by the arrow 3. When the true course ar
of the current arrow is set at 45 degrees on the
compass rose since current is from the northeast.
From the center of the instrument two small
intervals should be counted to the ?rst heavy red
line along current arrow 3 and toward the feather
thereof. This interval should be counted since
the current, of the problem in question, has a
strength of one knot. The leeway grid 1 is now
moved radially to a position where the 6 knot arc
will intersect this point.
row indicates true heading, the strength of the
current is measured from the center in the di
rection indicated by the arrow 3.
In traverse, leeway error, vertical angle, bear
ing angle and sun’s altitude problems, intervals
on both grids 3 and ‘I become units of proportion.
The leeway grid ‘I is of considerable thickness
and for convenience may be three ply, as shown
in Figure 5, with the ply securely glued, or
otherwise fastened, together. This grid has a
It will then be noted on leeway grid that there
is an 8 degree correction shown at that point,
the cruising speed being 6 knots. Between the
long dovetailed diametrical groove la, co-axial
with the true course arrow 8 and the centerpf
the grid. The leeway grid is mounted to slide
last noted point and the true course arrow ascer
on a track 1b and the upper face of the track 15 tain the number of degrees which in the present
instance will be 8 degrees, to ?nd leeway.
is provided with the end lugs 10, 1c arranged to
interengage with cooperating lugs 1d, ‘Id locat
ed within, and arranged adjacent the ends of, the
Since‘ the current is from the left side of the
true course arrow, in the present problem, sub
tract 8 degrees (leeway) from 99 degrees (true
groove la so as to allow freedom of movement of
the leeway grid in any direition but to prevent 20 course) to ?nd true heading of 91 degrees; then
add 15 degrees .(westerly variation), to 91 degrees
'
merit from the trac .
v
_
true heading and this will give the magnetic
ltsTdI‘l3:a§'lI:lmera1 ll designates a disc which is
designed to carry the index scale of the slide rule \ . course of 106 degrees. This becomes the compass
hereinabove referred to.
The disc assembly is
_ "i
course if deviation error is eliminated from the
held together by a grommet as It! whose head 15 25 boat’s compass.
attached to the track ‘lb, as shown in Figure '7
On the true course arrow, at center of the in
and this grommet passes centrally through the
strument, note the speed over bottom, which will
winddrift grid 2, the compass rose disc I and
be 5.4 knots.
the disc H so that these discs may rotate, rela
tive to each other, about a common center. Alc
30
cordingly, the leeway grid may be rotated relative
to the Winddrift grid 2 or compass rose, or shifted
in any desired radial direction relative to them.
As hereinbefore indicated, the instrument may
What I claim is:
1. An instrument of the character described
comprising a compass rose, a current grid thereon
having a diametrical course pointer, a track
mounted to rotate on substantially a common
axis with the current grid and compass rose, a
be used for various purposes.
For example,
it .
_
may be used for charting a course. Assuming a
leeway grid mounted to slide on said track radi
vessel is to sail from a given point l2 on the
chart, as shown on Figure 10 to another point
as Is shown on said ?gure, with cruising speed
at 6 knots, against northeast current averaging 1
across the current grid and compass rose.
knot, variation being 15 degrees west. The prob
lem is to ?nd the compass course and the speed
over the bottom.
A line is drawn on the chart
from the point of departure to the point of
ally with respect to and substantially entirely
2. An instrument of the character described
comprising a compass rose, a current grid thereon,
a track extended entirely across the compass rose
and mounted to rotate on substantially a com
mon axis with the current grid and compass
rose, a leeway grid mounted to slide substantially
, from end to end of said track and means for pre
destination. The instrument is then placed 011
the chart so that its center coincides with the
intersection of the line drawn as above stated
with a meridian of longitude nearest midpoint
venting detachment of the leeway grid from the.
track.
3. An instrument of the character described
between the'point of departure and the point of
destination. In the present illustration the '70 '
section, and mounted to rotate on substantially
degrees 20 minutes meridian is used. The com
pass rose is now turned until N and S lie on
the meridian. The true course is shown from
the compass rose on the side nearest point of
destination that is on the right hand side as
being 99 degrees, the true bearing. The true
course arrow of the leeway grid 1 is now turned to
99 degrees on the compass rose and the feather
comprising a compass rose, a current grid mount
ed to rotate thereon, a track, dovetailed in cross
a common axis with the current grid and com
pass rose, a leeway grid of approximately the
same transverse diameter as the compass rose
7 and having a transverse dovetailed groove which
receives said track, said leeway grid being slid
able on the track substantially entirely across
the current grid and compass rose.
HUBERT L. MITCHELL.
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