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Патент USA US2397532

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April 2, 1946.‘
E. W. CHAFEE
' 2,397,532
RANGE FINDER
Original Filed June 3. 1938
LINE OF SlGHT
COMPUTING
MECHANISM
INVENTOR
E. W. C HAF E E
‘2,391,532
Patented Apr. 2, 1946
UNITED STATES£397,532PATENT‘ orsics
RANGE FINDER
Earl W. Choice, New York, N. Y., assignor to Sper
ry Gyroscope Company, Inc., Brooklyn, N. Y.,
. a corporation of New York
Original application June 3, 1938, Serial No.
211,550. Divided and this application April 2,
1943, Serial No. 481,636
8 Claims.‘ (CI. 88-22)
shaped prisms the line of sight passes through a
This invention relates to range ?nders of the
rotatable erecting prism 20. telescope tube 2|
type ordinarily employed in inter-aircraft ?re
and angularly tiltable prisms 22, whence the
control systems, although the invention may have
line of sight emerges laterally toward‘the target.
general application wherever it is desired to ‘de
The line of sight is represented as rotatableyin
> termine the distance to an object having a known
azimuth from shaft 23, illustrated in this case
lateral dimension. This application constitutes.
as‘ emerging from the computing mechanism ll.
a division of copending application Serial No.
Shaft 23 turns the assembly on which prism 22
211,550. entitled “Fire control system for air
is mounted through pinion 24 and gear 25. The
craft guns," ?led June 3, 1938, in the name of
line oi‘ sight is tiltable in elevation by means of
10 a rod 26 pivoted to datum at 21, 21' through par
Earl W. Chafee.
In such ?re control systems the- line of sight
allel links 26' and movable up and down from
de?ned by the optical system- and the range
segmental gear 28 through line 29. Said gear in
?nder is oriented toward the target in elevation
turn is rocked in elevation from shaft 8|! which
and azimuth either from a manually operated
emerges from computing mechanism ii. The
control or from a suitable computing mecha 15 motion of rod 26 is communicated to prism 22
nism. Having been thus oriented, and having
through an arcuately grooved guide I05 carried
received data corresponding to an assumed target
by said rod and a hall ended arm extension. IN
dimension, the range ?nder then computes data
movable in said guide, whereby the up and down
indicative of the slant range to the target and
movement of rod 26 rocks the prism 22 about a
introduces this data. into the computing mecha 20 transverse axis 22’ ‘to give the line of sight the
nism for further calculations.
proper elevation movement for all positions of the
It is the primary purpose of this invention to
prism in azimuth (see Fig. 2).
provide improved and more accurate range ?nder
The wedge prisms i5 and I6 are used in ?nding
means for accomplishing this result. Other ob
the slant range of the target. They are circular
jects and advantages will become apparent from 25 glass discs which may have their inward iaces
the speci?cation taken in connection with the
parallel and their outer races inclined thereto at
. accompanying drawing wherein the invention is
embodiedin concrete form.
Iin the drawing:
_
Fig. l is a schematic representation of the im
proved range ?nder of the present invention.
Fig. 2 is a detail of the mechanism for rotating
in elevation the line of sight de?ned by the range
a small angle and which can be rotated in oppo
site directions by the above-described gearing
30 i6’, H’, II and knob i9. This arrangement
makes the two wedges optically act as one single
‘ wedge with the wedge angle variable from zero to
a maximum, the resultant wedge angle being pro
portional to the sine of the angle A through which
?nder.
35 the wedges are turned.
Figs. 3A and 3B are diagrams illustrating the
Fig. 3A shows the wedges with their inclined
passage of light rays through a portion of the
outer faces parallel. In this position» the bending
of a light my by one wedge is neutralized by the
optical system of the range ?nder.
' '
Fig. 4 is a diagram showing the principles of
bending in the opposite direction by the other
operation or the invention, and
40 wedge so that the'emerging and entering paths
Fig. 5 is a detail of the range computing mech
anism.
Similar characters of reference are used in all
are parallel. B represents such a ray, the slight
oiiset which occurs in passage through the double
wedge not being shown. The position of the
wedges indicated in Fig. 3A is referred to as their
of the above ?gures to indicate corresponding
parts. Arrows are employed to indicate the direc 45 neutral position. When the two wedges are ro
tated 90° in opposite directions, producing a rela
tion of ?ow of information or control in?uence.
tive rotation of 180", they are positioned as shown
Referring now to Fig. l, the line of sight enters
in Fig. 3B. A ray B’ is then bent in the same
the eye piece l3 and passes horizontally through
direction by the two wedges making a maximum
pentaprism I4 and thence vertically through the
lens Ill and a pair of reversely rotated wedge 50 angle of deviation from its original path. Inter
mediate positions of the two wedges will obviously
shaped prisms l5 and I6. Said wedge prisms are
cause an intermediate amount of bending of
oppositely turned by being mounted in annular
ray B’.
gears l6’ rotated from shaft ll. pinion l1’ and
reversing gearing l8, shaft i1 being turned from
,the knob is. Alter passing through the wedge
The wedges both have a round hole i2 in their
center so that about one-halt‘ 01' all the light
2
2,897,582
rays entering the wedge area will go through
the hole I! without de?ection, as illustrated by
In my sight I prefer to solve Equation 5 in its
logarithm form which may be written:
(6) log R=log K+log cos Az-log (0 sin A)
Log K is set in by turning knob 3| until the
'index 48' reads the correct value for the wing
raycinli'lgs. 8Aand3l3. Thebalanceofthe
rays pass through the wedge proper and are de
?ected as described above. A person looking
through the eye piece will hence see two images
of the target, one direct image a and one de
spread K on the logarithmic dial 32. As shown
flected image b, as shown in Fig. 4. Image b will
more clearly in Fig. 5, turning knob 3| also ro
be shifted to one side or the direct image a in
all cases except where the two wedges are in 10 tates a cylinder 3|’ which then rotates a cam
pinion “which is threaded through a rack bar
their exact neutral position, that is, oppositely
It and also spring pressed against a cam 35.
positioned, and the angular distance through
which the images are shifted depends on the
rotary position or angle A that the two wedges
make with respect to each other. In the said
neutral position which is reached by turning 15
Cylinder 3|’ is slotted to permit axial translation
of cam pin 34 with respect to it. The position of
bar 33 is therefore the algebraic sum of the lift
of pin 34 and the rotation of knob 3 l. Log cos As
is the lift of said cam pin 34 governed from the
the wedge adjusting knob I I until both images
cam 35 which cam is rotated in accordance with
merge into one, this angle is zero. In operation
the azimuth angle Az from shaft 23. Therefore,
by a suitable adjustment of knob It the de?ected
the total motion of rack bar 33 represents
image of the target is brought into a position
log K-Hog cos Az.
where its wing tip just touches that of the direct
Log C sin A is represented by the lift value of
‘image, as shown at b’.
>
the
cam 36 which is rotated in accordance with
In the triangle thus set up, it is obvious that
the angle A between the wedges from knob l9.
Cam pin 38 carries rack teeth ‘which rotate
(1)
tan B=IT§
25 through pinion 38 one arm of a subtracting dif
ferential It. The second arm is rotated from
in which ,6 is the angle between the direct and
rack 38 through pinion 4| and shaft 4|’. The
refracted lines of sight (3' and C of Fig. 3B).
third arm of said differential therefore rotates
R is the slant image. and K is the actual wing
through gears 42 a-logarithmic range dial'li by
spread of the target. since for the condition
an amount proportional to log it in accordance
illustrated in Fig. 4 with the target ?ying in
with the aforesaid Equation 6.
the direction or the line of sight, the distance be
The range may therefore be set into the com
tween the centers of the two images will be
puting mechanism II as a proportional rotation
proportional to the wing spread. Since K is
of shaft 44' either through a power follow-up’
known from the type of bomber being attacked,
mechanism or from a handle 44 which turns the
and since 5 may be determined from the setting
dial 45 to match the reading of a ?xed index 43'.
of the wedges, the slant range can thus be ob
If desired, an extra dial ‘6 together with knob
tained, being
41 may be provided, operating in conjunction with
the dial 32, for compensating for changes in the
=L
tan B
or, for the very small values of ,0 here encoun
40
tered,
by turning knob 41, thereby shifting the reference
K
(2 )
R= B
The angle 5 is moreover proportional to the
sine of the angle A through which the wedges are
turned or,
B=C sin A
where C is a constant. Hence, we may write
' (3)
muzzle velocity of the gun. Variations in muzzle
velocity (A M. V.) may then be taken care of by
introducing a corresponding correction in range
45
index 46' for dial 32.
‘
Since many changes could be made in the above
construction and many apparently widely differ
ent embodiments of this invention could be made
without departing from the scope thereof, it is
intended that all matter contained in the above
50 description or shown in the accompanying draw
ing shall be interpreted as illustrative and not in _
(4)
a limiting sense.
12:5 sf A
What is claimed is:
' .
This condition of course only holds true where
1. A range ?nder adapted to be used in con
the target is directly ahead and the attacking 65 nection wlth‘a computing mechanismfor ?re con
craft is ?ying a parallel course. In case it is
trol comprising compensating means for approxi
not directly ahead, the wing spread will be fore
mately correcting for a ioreshortened view of a
shortened which may be taken into account by
introducing the azimuth angle Az which the
target controlled by the orientation in azimuth
is strictly true only when the attacking plane
the target.
of the range ?nder when tracking a target, an
line of sight makes with the fore and aft axis 60 optical system in said range ?nder including a
of the attacking craft, so that the equation may
member adjustable to determine an angle at said
be written
range ?nder equivalent to that subtended by a
known dimension of the target and means jointly
__K 00s A:
(5)
“*m
65 controlled by the ?rst mentioned means and said
member for registering the approximate range of
The above introduction of the azimuth angle As
-
.
2. A range ?nder adapted to be used in con
files a course parallel to the target. However,
nection with a computing mechanism for ?re
since the departure from parallel course, when
it occurs, is normally small, and the correspond 70 control comprising’ means for approximately cor
rooting for a foreshortened view of the target so
ing variation of cos A: is still smaller, this small
coupled with the range ?nder as to be displaced
error in range, which e?’ects only a correction
therewith as the target is being tracked in azi
\ factor, is neglected in view of the more compll- V
muth, an optical system in said range finder in
cated mechanism required for an exact solution
under all conditions.
75
cluding a member adjustable to measure the an
gle atf'said ?nder subtended by a. known lumen
b
3
2,897,532
sion of the target, a differential mechanism hav
ing one input operated by the ?rst mentioned
means, a second input connected to said mem
ber so as to be moved in proportion to the ad
said openings and the other through the prisms,
and wherein said member is adapted when moved
to cause the relative rotation of said prisms
thereby varying the relative position of said im
justment of said member whereby the output of
said differential is displaced in proportion to the
approximate range oi the target.
ages.
muth, an optical system in said range ?nder in
seen through said prisms, said image being dis
7. A range finder according to claim 1 in which
the optical system comprises a pair of rotatable
complementary prisms having coaxialiy disposed
3. A range ?nder adapted to be used in con
aligned holes therethrough, and in which said
nection with a computing mechanism for ‘fire
control comprising means for approximately cor 10 member is coupled to said prisms so as to cause
when adjusted the relative rotation thereof, the
recting for a ioreshortened view of the target so
target as viewed through said holes forming a
coupled with the range ?nder as to be displaced
?xed reference {or a movable image of the target
therewith as the target is being tracked in azi
cluding a member adjustable to measure the an 15 placed with respect to the ?xed reference to an
extent governed by the relative position ‘of the
gle at said ?nder subtended by a target, means
prisms.
in said range ?nder adapted to be set according
8. A range ?nder adapted to be used in con
to a known dimension of the target, a differential
nection with a computing mechanism for ?re
having one input adapted to be moved jointly
by the ?rst and last mentioned means and an 20 control comprising means for approximately cor
recting for a foreshortened view of the target so
other input connected to said member so as to be
coupled with the range ?nder as to be displaced
moved in proportion to the adjustment of said
therewith as the target is being tracked in azi
‘member whereby the output of the diil’erential
muth, an optical system in said range ?nder in
registers a range component of the target.
4. A range ?nder according to claim 1 in which 25 cluding a member adjustable to measure the an
gie at said ?nder subtended by a target, a di?er
the optical system comprises a pair oi’ prisms
and in which said member is adapted when ad
justed to produce relative movement of the
Prisms.
5. A range ?nder according to claim 1 in which
the optical system comprises a pair of rotatable
complementary prisms and in which said mem
ber is adapted when adjusted to cause the rela
tive rotation of the prisms.
6. A range ?nder according to claim 1 in which
the optical system comprises a pair of rotatable
complementary'prisms having coaxially disposed
V entiai having one input operated by the ?rst men
tioned means, a second input connected to said
member so as to be moved thereby in proportion
to the adjustment thereof, means for adjusting
one of said inputs according to a ballistic com
ponent, means in said range ?nder adapted to be
set according to a known dimension oi the tar
get, means coupling the last mentioned means
to one oi’ the inputs of said di?’erential, whereby
the output of the differential is adjusted in pro
portion to the range of the target.
aligned holes therethrough whereby two images
EARLW. CHAFEE.
of the target may be seen, one directly through
Certi?cate of Correction
April 2, 1946.
Patent No._ 2,397,532.
EARL W. CHAFEE
It is hereby certi?ed that errors appear in the Frinted s eci?cation of the above
age 1,
t column, line 29, for
_
"Iin” read In; page 2, ?rst column line 29, for “image” read range; and that the said
Letters Patent should be read with these corrections therein that the same may
numbered patent requiring correction as follows:
conform to the record of the case in the Patent O?ce.
Signed and sealed this 3rd day of September, A. D. 1946.
[ml
LESLIE FRAZER,
First Accident Uommlnioner of Pm.
3
2,897,532
sion of the target, a differential mechanism hav
ing one input operated by the ?rst mentioned
means, a second input connected to said mem
ber so as to be moved in proportion to the ad
said openings and the other through the prisms,
and wherein said member is adapted when moved
to cause the relative rotation of said prisms
thereby varying the relative position of said im
justment of said member whereby the output of
said differential is displaced in proportion to the
approximate range oi the target.
ages.
muth, an optical system in said range ?nder in
seen through said prisms, said image being dis
7. A range finder according to claim 1 in which
the optical system comprises a pair of rotatable
complementary prisms having coaxialiy disposed
3. A range ?nder adapted to be used in con
aligned holes therethrough, and in which said
nection with a computing mechanism for ‘fire
control comprising means for approximately cor 10 member is coupled to said prisms so as to cause
when adjusted the relative rotation thereof, the
recting for a ioreshortened view of the target so
target as viewed through said holes forming a
coupled with the range ?nder as to be displaced
?xed reference {or a movable image of the target
therewith as the target is being tracked in azi
cluding a member adjustable to measure the an 15 placed with respect to the ?xed reference to an
extent governed by the relative position ‘of the
gle at said ?nder subtended by a target, means
prisms.
in said range ?nder adapted to be set according
8. A range ?nder adapted to be used in con
to a known dimension of the target, a differential
nection with a computing mechanism for ?re
having one input adapted to be moved jointly
by the ?rst and last mentioned means and an 20 control comprising means for approximately cor
recting for a foreshortened view of the target so
other input connected to said member so as to be
coupled with the range ?nder as to be displaced
moved in proportion to the adjustment of said
therewith as the target is being tracked in azi
‘member whereby the output of the diil’erential
muth, an optical system in said range ?nder in
registers a range component of the target.
4. A range ?nder according to claim 1 in which 25 cluding a member adjustable to measure the an
gie at said ?nder subtended by a target, a di?er
the optical system comprises a pair oi’ prisms
and in which said member is adapted when ad
justed to produce relative movement of the
Prisms.
5. A range ?nder according to claim 1 in which
the optical system comprises a pair of rotatable
complementary prisms and in which said mem
ber is adapted when adjusted to cause the rela
tive rotation of the prisms.
6. A range ?nder according to claim 1 in which
the optical system comprises a pair of rotatable
complementary'prisms having coaxially disposed
V entiai having one input operated by the ?rst men
tioned means, a second input connected to said
member so as to be moved thereby in proportion
to the adjustment thereof, means for adjusting
one of said inputs according to a ballistic com
ponent, means in said range ?nder adapted to be
set according to a known dimension oi the tar
get, means coupling the last mentioned means
to one oi’ the inputs of said di?’erential, whereby
the output of the differential is adjusted in pro
portion to the range of the target.
aligned holes therethrough whereby two images
EARLW. CHAFEE.
of the target may be seen, one directly through
Certi?cate of Correction
April 2, 1946.
Patent No._ 2,397,532.
EARL W. CHAFEE
It is hereby certi?ed that errors appear in the Frinted s eci?cation of the above
age 1,
t column, line 29, for
_
"Iin” read In; page 2, ?rst column line 29, for “image” read range; and that the said
Letters Patent should be read with these corrections therein that the same may
numbered patent requiring correction as follows:
conform to the record of the case in the Patent O?ce.
Signed and sealed this 3rd day of September, A. D. 1946.
[ml
LESLIE FRAZER,
First Accident Uommlnioner of Pm.
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