IMPROVEMENTS IN NAVAL BANGE FINDERS
Year: 1884

page_text: I, THORSTEN NORDENFELT of N° 53 Parliament Street in the City of Westminster
Civil Engineer do hereby declare the nature of my invention for "IMPROVEMENTS
IN NAVAL BANGE FINDERS"-partly a communication to me from abroad by
C. G. Middelboe, a Lieutenant in the Royal Danish Navy of Copenhagen in the
Kingdom of Denmark to be as follows:-
:-
This Invention has for its object improvements in instruments for measuring
distances at sea.
I make these instruments to indicate conveniently and directly and without the
aid of calculations or tables, the distance of a ship or other object at sea.
The main principle upon which the instrument is constructed is: that for any
given height above the sea level the angle between the line from the eye to the
horizon and the perpendicular lowered from the eye to the sea level is known and
is constant and differs but slightly from a rectangle. Therefore when the angle
between the line from the eye to the horizon, and the line from the eye to the
waterline of a ship or other object can be measured then in the rectangular
triangle determined by the following three points.
1st the eye of the observer,
2nd the point to which the distance is to be measured and
3rd the base of the perpendicular lowered from the observer's eye to the sea level,
two angles and one side, are known-therefore any other element of the triangle
can be calculated.
A scale is fixed on the instrument showing the distances resulting from varying
angles between the line from the eye to the horizon and the line from the eye to
the object, when the height of the eye is known. The operator measures the last
named angle when an index directly indicates the distance on the scale.
This is done simply by what I call my Naval Range binocular or Telescope
which has the form of an ordinary Naval telescope or binocular glass. The angle
to be measured is given by the positions of two wires or webs visible through the
instrument, one or both of them being moveable by means of an ordinary fine
threaded or micrometer screw or screws turned directly by hand, or by means of
CDB31

page_text: cogged gearing, or this can be done by an eccentric connected with a barrel fixed
at the rear end of the instrument. The screw head or the rotating wheel or handle,
or the outside of the barrel is marked with the scale of distances or with several
scales if it is found desirable to use the same instrument at different heights above
the surface of the sea.
A slow motion screw can effect a change of the zero point when a line of shore
or any other object at known distance intercepting the view of the horizon is used
in lieu of the horizon.
•
In order to read more easily on the scale, the movement for very small angles,
can be enlarged by means of cog wheels or screws which multiply the movement
of the scale under the indicator.
Or in order to meet the wishes of Naval Officers who are trained to use the
sextant, I make the following modification while I gain the same object on the
same principles in what I call my Naval Range Sextant in which I make my
instrument of the form of a usual Naval Sextant, and measure the before named
angle by the two mirrors of the sextant instead of by two wires or webs.
The scale or scales will in this modification be marked on the arc of the sextant.
In this range sextant the moveable arm does not carry the moveable mirror as in
an ordinary sextant, but in order to read more easily on the scale the movement
for small angles, that movement is múltiplied by the movement of the moveable
mirror being effected by a combination of levers.
To make the divisions on the scale for long ranges more clear and legible the
arrangement of these levers may be such that the index lever moves further to
produce a given movement of the mirror at the smaller angles than at the larger.
The same convenience for reading the scale can be obtained by a system of cog-
wheels to multiply the angle-and these cogwheels can be made elliptical instead
of circular if I desire to make the divisions for long distances more legible.
In this modification a slow motion screw can also be used for changing the
position of the indicator if a shore or other object at known distances intercepts
the horizon as already previously explained.
This ech namba 1001.

page_text: "
I THORSTEN NORDENFELT of 53 Parliament Street in the City of Westminster
Civil Engineer do hereby declare the nature of my invention for "IMPROVEMENTS
IN NAVAL RANGE FINDERS (partly a communication to me from abroad by
C. G. Middelboe, a Lieutenant in the Royal Danish Navy, of Copenhagen in the
Kingdom of Denmark) and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement :—
This Invention has for its object improvements in instruments for measuring
distances at sea.
I make these instruments to indicate conveniently and directly and without the
aid of calculations or tables, the distance of a ship or other object at sea.
The main principle upon which the instruments are constructed is, that for any
given height above the sea level the angle between the line from the eye to the
horizon and the perpendicular lowered from the eye to the sea level is known (it is
constant, and differs but slightly from a rectangle) and if the angle between the
line from the eye to the horizon, and the line from the eye to the water line of a
ship or other object can be measured, then in the rectangular triangle determined
by the following three points. 1- the eye of the observer. 2. the point on the
water line the distance of which is, to be measured and 3-the base of the perpen-
dicular lowered from the observers eye, to the sea level, two angles and one side
are known—therefore any other element of the triangle can be calculated.
I provide my instruments with a scale by which the necessity for calculation is
avoided. This scale shows the distances resulting from varying angles between the
line from the eye to the horizon and the line from the eye to the object, when the
height of the eye is known. The operator measures this angle and an index
directly indicates the distance on the scale.
My naval range binocular or telescope is shown by Figure 1 of the annexed
drawings in form it resembles an ordinary naval telescope or binocular glass. It
has erecting eye pieces such as are employed in terrestrial telescopes. The angle
to be measured is given by the positions of two wires or webs properly focussed in
the eye piece and visible through the instrument, one or both of them being
moveable. The requisite movement may be imparted by means of an ordinary
fine threaded or micrometer screw or screws turned directly by hand, or by means
of cogged gearing. The screw head, or the rotating wheel or part is marked with
the scale of distances, or the scale may be on the outside of the barrel and an index
on the screw head or revolving part. Several scales may be provided if it is found
desirable to use the same instrument at different heights above the surface of
the sea.
Figures 2. 3 and 4 illustrate a convenient arrangement for operating the wires
wherein both wires are moved simultaneously in opposite directions.
Figure 2 is a disc or stop in the focus of the eye piece, it has upon it a pair of
parallel guides a, a in which the pieces b. b. are able to slide. c. c. are two horizontal

page_text: and parallel wires or webs carried by the pieces b. b. so that the movement of these
pieces varies the distance between the wires or webs. d. d. are springs bearing on
pins fixed to the pieces band tending to separate them. On the other side of the
pieces bare other pins e. e, indicated by dotted lines in Figure 2 and also seen in
section in Figure 3.
In Figure 3 ff. is a ring capable of rotating about the axis of the eye piece it
carries the eccentric or cam surfaces g. g. The springs & hold the pins e in contact
with the surfaces g and so when the ring f is turned the distance between the wires
is slowly altered.
The ring f receives upon it a graduated ring as seen at h in Figures 4.
Two or more such rings are provided corresponding to different elevations of the
eye of the observer above the sea level and one or other of these rings is employed
as the case requires.
i is a frame in which the ring & turns and on this frame is the index mark by
which the graduations on the ring are read. The frame i has a circle of worm teeth
upon it and by turning the frame a short distance by the aid of the worm ka
change in the position of the zero point is brought about. This adjustment is
required when a line of shore or other object at a known distance intercepting the
view of the horizon is used in lieu of the horizon. The graduation on the rings h
correspond to distances of the object from the observer. Any convenient unit may
be selected-for example one degree of the scale may correspond to one thousand
feet and the cam surfaces g g may be so formed that the length of a degree or
division of the scale corresponding to the selected unit of distance is the same or
nearly so in every part of the scale.
I also according to my invention make a range finder in the form of a sextant
and operating in accordance with the principles already explained. This instrument
which is specially adapted to measure the vertical angle between the horizon and
the water line of a floating body I call my naval range sextant.
The scale or scales will in this modification be marked on the arc of the sextant.
In this range sextant-the moveable arm does not carry the moveable mirror as in
an ordinary sextant, but in order to read more easily on the scale the movement
for small ang'es, that movement is multiplied by the movement of the moveable
mirror being effected by a combination of levers.
In this modification a slow motion screw can also be used for changing the
position of the indicator if a shore or other object at known distances intercepts the
horizon as already previously explained.
The instrument is shown by Figure 5 of the annexed drawings. is the frame,
it carries upon it a graduated scale m as in an ordinary sextant except that the
graduation is different and by preference the scale can be easily removed and
replaced by another. n is the horizon glass fixed upon the frame / one half of
this glass is silvered and the other half transparent as in an ordinary sextant. o is
the radius arm it turns about a centre upon the frame at o¹.
The radius arm carries an index and this index can be shifted by turning a
button os. The instrument is thus adjusted for use when a shore line at a known
distance obstructs the view of the horizon as already explained. p is the moveable
mirror, it is mounted on a lever capable of turning upon the frame. The tail of
this lever is curved and a spring (not seen in the drawing) causes it to bear
constantly against a pin o* on the radius arm o.
The movement of the radius arm causes a small variation in the position of the
plane of the mirror p relatively to that of the mirror n but in this instrument the
two glasses are never far from parallel. q is the observing telescope fixed to
the frame l. Looking through this telescope and through the transparent part of
the glass n the object may be seen whilst at the same time the horizon is visible
by double reflection at the mirrors n and q. Then by suitably placing the radius
arm o the water line of the object is brought to correspond with the horizon and
the reading of the scale gives the distance of the object from the observer.

page_text: If the tail of the lever p be suitably formed the divisions of the scale each
representing an unit of distance may be of the same size in every part of the scale.
The tail of the lever may be however straight but in this case an unevenly
graduated scale is required.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
(1.) A binocular or other telescopic Range finder with parallel wires or lines in
the eye piece and adjusting mechanism for varying the distance between such wires
or lines and so graduated that when one wire or line is made to coincide with the
horizon and the other wire or line with the water line of a floating body the
distance of the said floating body from the observer can be read off.
(2.) A sextant Range finder in which one of the mirrors is moved through a
small angle by a radius arm or equivalent part moving through a larger angle and
in which in connection with the radius arm or equivalent part there is a scale and
an index the former so graduated that when the water line of a floating body
and the horizon as seen through the instrument have been brought to coincide the
distance of the said floating body from the observer can be read off.
(3.) A Range finder by which the vertical angle between the horizon and the
water line of a floating body may be measured and which then indicates upon a
scale graduated to any unit of length the distance of the said floating body from
the observer.