Improvements in Apparatus for Measuring the Range and Height of Distant Objects.
Year: 1894

page_text: Date of Application, 12th May, 1894-Accepted, 19th Jan., 1895
[Communicated from abroad by THE AMERICAN RANGE FINDER COMPANY, a
corporation organised and existing under the laws of the State of West.
Virginia, and having its principal place of business at corner of Greenwich
and Thames Streets, New York, United States of America.]
Improvements in Apparatus for Measuring the Range and Height of
Distant Objects.
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent.
Agents, 45 Southampton Buildings, in the County of Middlesex, do hereby
declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement :-
The invention is an apparatus for finding the range of distant objects.
In the accompanying drawings,
Fig. 1 is a diagram illustrating the principle.
Fig. 2 is an edge view of the instrument.
Fig. 3 is a face view.
Fig. 4 is a rear view.
Fig. 5 is a detailed view of the sliding bearing and index-adjusting screw in.
horizontal section.
Similar letters of reference indicate like parts.
1 represents the index bar pivoted to frame. 2 and carrying mirror 3. 4 is a
fixed mirror upon the frame 2. The mirror 4 is silvered only on the right-hand
side, 5, of the dotted line. The left-hand half, 6, is a translucent or clear glass..
At BC, Fig. 1, is represented any distant object, as, for example, a vessel, the
water line of which is at B and the mast-head at C. The distance B C will
therefore be one side of a right-angle triangle, of which the dotted lines A C
and A B are the other sides. When the index bar 1 is in the position A E,
indicated by dotted lines, the mirrors 3 and 4 will be parallel. When it is moved.
to the position A D, so that when the point B, seen directly, and the point C, seen
by double reflection in the mirrors 3 and 4, coincide, then, according to the known
theory of the sextant, the angle C A B will be equal to twice the angle DA E.;.
or CAB=2 D A E (1). Since these angles are always very small in practice there is
BC 2 FG
no appreciable error in writing sin C A B = 2 sin DAE (2) whence
ACAF (3)
A F
=
or AC BC ×
=
2FG (4). We.c
c. can therefore determine any distance AC if we
know the length BC, and measure on the instrument the lengths F G and A Fat
the time when the direct image of B coincides with the reflected image of C. If.
the index bar 1 be so graduated that the length AF represents the distance AC,
the length F G will be a function of the distance BC, and can tlierefore be
graduated in terms of BC; because, from the fourth formula, we get, by
F
transposition, FGBC (AC) (5); or, conversely, if we so graduate the index
bar 1 that the length A represents the distance BC, the length F G will then
represent the distance AC, and hence can be graduated in terms of AC. To:
illustrate, if index bar 1 be so graduated that a distance of 2000 yards (6000 feet)
is represented, by five inches on said index bar, then a mast-head height,
[Price 8d.]

page_text: 100
5
120
or BC, of 100 feet will be represented on FG by one-half an inch; for, by
formula 5, FG =
x 5 = of a foot equal one-half inch, and a height
2 x 6000
of 50 feet will be represented by one-quarter inch. Or, if the index bar be so
graduated that the mast-head height of 100 feet is there represented by five inches,
then, by the same formula, a distance of 6000 feet will be represented on F G by
one-half inch, and a distance of 12,000 feet will be represented by one-quarter
inch so that upon the instrument we may graduate the index bar 1 in terms of
distance, and the length F G on the frame of the instrument for mast-head heights.
Or, we may graduate the index bar for mast-head heights, and the length FG for
distances; and therefore, by the use of the instrument, if we know either the
mast-head height B C or the distance A C, the corresponding distance or mast-head
height may be read at once when the direct and reflected image of the points B
and C are made to coincide.
Referring now to the other figures of the drawing, the frame 2 carries the
telescope 25 disposed opposite the mirror 4, as in the ordinary sextant, so that the
line of sight of the telescope may pass directly through the unsilvered portion of
the mirror 4 to the object. The relation of the mirror 3, mirror 4 and telescope 25
is also as in the ordinary sextant. The frame is also provided with a suitable
handle, 26, on its rear side, and with legs, 7. A spring, 8, bears against a screw, 9
and moves the index bar 1 in the opposite direction to that in which it is moved by
its adjusting screw 10. This screw passes through a sliding piece, 11, and has a
conical end which is received in a. reinforce, 12, upou the edge of the index bar.
The force of the spring 8 may be adjusted by means of the screw 9. The sliding
piece 11 is disposed in, a long slot, 13, in the frame, and also has a guidé rib, 14,
which is received in a groove, 15, also in the frame and parallel to the slot 13.
Arranged in the long slot 13 in the frame is a long screw, 16. By turning the
head 17 and so rotating the screw 16, the sliding piece 11 may be caused to move
along the slot 13. The index bar 1 carries a scale, which is preferably graduated
for mast-head heights, and the sliding piece 11 carries. an index plate, 18, provided.
with a central mark which is used for reading from said scale; hence, when the
head' 17 is turned, the index plate 18 travels along the scale on index bar 1.. The
scale ou index bar 1 therefore represents A F on Fig. 1.
I place the axis of the screw 10 along the line F G and arrange the graduations
on the cylinder 19, which is carried upon the screw 10, to represent distances A. C.
Upon the sliding piece 11 is carried au index arm, 20, by means of which the
indications of the latter may be read. As the screw 10 is turned inwards,
successive circles on the cylinder 19 will be brought up to the index 20. At the
end of the index bar 1 is a pointer, 21, which moves over graduations on the
frame 2 each graduated interval representing the movement of the index bar 1
due to one revolution of the cylinder 19. Hence, by noting the number of intervals
passed over by the pointer 21 to the left, it can be seen at once how many
revolutions of the cylinder 19 have been made, and hence from what circle
the scale on said cylinder is to be read. There will always be a ratio between the
reading of the scale on the index bar 1 and the reading of the scale on the
cylinder 19.
I will now explain how I use this instrument practically. The mast-head
heights of most of the warships, for example, of the world are known and tabulated.
When such a vessel is sighted, and has been recognized, this instrument may be at
once used for finding her distance or range from the point of observation. This is
done by turning the milled head 17 until the mark on the scale plate 18 is adjusted
opposite to the scale mark on index bar 1 corresponding to said known mast-head
height. Then the vessel is looked at through the telescope 25, the instrument
being held by its handle 26 in the right hand of the observer, who, with his left.
hand, turns the cylinder 19 in one direction or the other, thereby moving the index
bar 1 on its pivot, and so adjusting the mirror 3 until the image of the mast-head,
reflected' first from mirror 3 and then again from the silvered portion of mirror 4,

page_text: comes into coincidence with her water-line as seen directly through the unsilvered
portion of mirror 4. Or, in other words, the point C of Fig. 1 is brought into
coincidence with the point B. When this happens, the observer first notes the
number of intervals passed over by the pointer 21, and then reads the indication on
the proper circle of the cylinder 19. As shown in Fig. 2, where the index plate 18
is set at 90, representing a mast-head height of 90 feet, the pointer 20 shows the
distance 1000 yards on cylinder 19. Now if the vessel observed moves, or if
the point of observation moves, thus changing the distance A C and so throwing the
points B and C out of coincidence, all that the observer has to do is to move them
into coincidence again, which can be done by a slight turn of the head 17, and
again read the range or distance from the cylinder 19; and this he can keep doing
constantly, thus getting the range of the distant vessel as often as is desired.
Similarly, the instrument can be used for measuring the unknown heights of
objects which are at known distances from the observer. The cylinder 19 is set so
that the bar 20 indicates the known distance, and the milled head 17 turned, so
moving the plate 18 over the scale on index bar 1 until the points B and C of the
distant object coincide as before. The height or interval between B and C is then
read directly from the scale on index bar 1; so that, if in Fig. 2 the cylinder 19 is
set to show 1000 yards, previously known, and the milled head 17 turned to bring
the images into coincidence, the height of the object is read as 90 feet from the
scale.
This instrument may also be used to recognize the varying distances between
two ships, after an initial distance between them has been measured by another
form of range finder. The cylinder 19 is immediately set to indicate the distance
so found. The instrument is then directed upon the approaching vessel, and the
milled head 17 is manipulated in the manner already described until the mast-head
of that vessel, seen through the telescope 25, appears to coincide with her water-line.
As soon as that is done, the height of the mast-head is read off on the scale on the
index bar 1. The instrument is now set, and for all future determinations of
distance, it is unnecessary to move the scale plate 18. All that the observer then
does, in order to determine the range of the vessel at any moment, is to rotate the
cylinder 19 so as to keep the two chosen points in coincidence through the
telescope; therefore, for the ship that is looked at, the instrument efficiently
supplements the regular ship range finder by which the distance is at the outset
originally determined.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondents I declare that what I claim is
The construction and arrangement of the instrument for measuring the distance
or the height of a distant object; comprising mirrors and a supporting frame, a
pivoted index bar and a scale showing the extent of angular movement thereof, an
adjusting device for operating said bar, the said adjusting device being itself
movable longitudinally on said index bar and a scale on said bar showing the
extent of movement of said adjusting device: the said scales being constructed in
definite ratio one to the other and the whole operating in the manner and as and
for the purposes hereinbefore set forth.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.