Improvements in Range-finders.
Year: 1890

page_text: Date of Application, 6th Mar., 1890
Complete Specification Left, 6th Jan., 1891-Accepted, 14th Feb., 1891
PROVISIONAL SPECIFICATION.
Improvements in Range-finders.
I, NEVILLE LLOYD WALFORD, of 11 Brechin Place, S.W., in the County of
Middlesex, a Lieutenant-Colonel in the Royal Artillery, do hereby declare the
nature of this invention to be as follows:-
:―
The object of my invention is to effect certain improvements in the construction
of the range-finder for which Letters Patent were granted to me, bearing date
9th July 1886 and No. 8973.
On referring to the Specification of my aforesaid Letters Patent No. 8973
of 1886, it will be seen that the instrument therein described consisted of a main
telescope, provided at the focus of the eye-piece, with a vertical line engraved or
otherwise fixed on glass, and capable of being moved horizontally in guides at right
angles to the axis of the telescope.
A smaller telescope was mounted upon the main telescope, at about right angles
thereto, and was a fixture in such position. When the main telescope was directed
upon the object, of which it was required to ascertain the range or distance, the
small telescope gave the line of the base, so that in all ranges taken with this
instrument the angle between the base and the line drawn from the instrument to
the object was a constant angle, the relative position of the two telescopes being
a fixture, and this consequently necessitated a fresh base being taken for each
range observation.
According to the improvements effected in the instrument by my present invention,
I am enabled, having taken a range and fixed a base line, to take any number of
ranges in various directions from the same base line. I effect this by mounting the
small telescope upon a vertical pivot on the main telescope, so that it is capable of
being placed at any angle with regard to such main telescope.
Means are provided for clamping the small telescope at any required angle, as
also a tangent screw, or other suitable device for fine adjustment. In the original
and also in the improved form of the instrument, the graduations, on the head of
the screw operating the aforesaid vertical line in the focus of the eye-piece of the
main telescope, are so arranged than when the instrument is on the second tripod,
and the vertical line is brought to bear again upon the distant object, the reading
on the said head will give the cotangent of the angle subtended by the base from
the said object and thus the range in terms of the base. In the original instrument
the base was always approximately at right angles to the line from the instrument
to the object, but in the improved instrument, as the base may be at any angle to
this line, a horizontal graduated disc is affixed to and turns with the small telescope,
and the said graduations are so arranged that they give the ratio between the length
of the actual base and an imaginary right-angled base, i.e., the ratio between the
hypotenuse and base of a right-angled triangle, of which the hypotenuse is the
actual base of the observation, and the base is the aforesaid imaginary right-angled
base.
To measure a range, the instrument is placed on a tripod and the main telescope
turned upon the distant object, till the vertical line in the eye-piece (which is at
the extreme right or left-hand position) coincides with such object.
A staff with a clear vertical line marked on the side, is fixed in the ground at a
short distance, and the small telescope turned till a central vertical wire in the
eye-piece coincides with the line on the staff. The small telescope is then clamped
in this position and the instrument removed from the tripod and placed on another
tripod, at a distance averaging, say from ten to one hundred yards, according to the
length of the range to be measured and the nature of the ground. The device

page_text: consisting of a circle or ring with two diagonals, as described in my aforesaid Letters
Patent No. 8973 of 1886, is then placed upon the first tripod and the second tripod
adjusted until the wire in the small telescope, the intersection of the diagonals and
the line on the staff, all coincide. The line in the main telescope is then moved
until it again coincides with the distant object.
The distance between the tripods constitutes the base line, and is measured as
described in my previous Specification. The reading on the graduated disc of the
small telescope gives the ratio between the actual measured base and the right-
angled base as above described. By means of a slide-rule the length of the latter
can be instantly obtained, and such length being multiplied by the reading on the
graduated head on the main telescope, gives the range. This multiplication may
also conveniently be performed on the slide rule.
To take the range of another object in any direction, it is only necessary to
return the instrument to the first tripod, turn the main telescope on this new object,
and then turn the small telescope to the line on the staff and repeat the operation.
By this means, the base having once being set out, the range of all objects within
view can be observed without disturbing the staff or either of the tripods.
In a modified form of the instrument, I may arrange the small telescope
underneath the main telescope, in this case the small telescope would first be turned
to the staff to fix the base line, and the main telescope then turned on the required
object, the subsequent operations being the same as above.
Dated this 6th day of March 1890.
AMBROSE MYALL,
21, Cockspur Street, S.W., Agent for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Range-finders.
I, NEVILLE LLOYD WALFORD, of 11 Brechin Place, S. W., in the County of
Middlesex, a Lieutenant-Colonel in the Royal Artillery, 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 object of my invention is to effect certain improvements in the construction
of the range finder for which Letters Patent were granted to me, bearing date
9th July 1886 and No. 8973.
On referring to the Specification of my aforesaid Letters Patent No. 8973 of
1886, it will be seen that the instrument therein described consisted of a main tele-
scope, provided at the focus of the eye piece with a vertical line engraved or otherwise
fixed on glass and capable of being moved horizontally in guides at right angles to
the axis of the telescope.
A smaller telescope was mounted upon the main telescope at about right angles
thereto, and was a fixture in such position. When the main telescope was directed
upon the object of which it was required to ascertain the range or distance, the
small telescope gave the line of the base, so that in all ranges taken with this
instrument the angle between the base and the line drawn from the instrument to
the object was a constant angle, the relative position of the two telescopes being a
fixture, and this consequently necessitated a fresh base being taken for each range
observation.
According to the improvements effected in the instrument by my present inven-
tion, I am enabled after having fixed a base line to take any number of ranges in
various directions from the same base line. I effect this by mounting the small
telescope upon a vertical pivot on the main telescope, so that it is capable of being
placed at any angle with regard to such main telescope. Means are provided for
clamping the small telescope at any required angle, as also a tangent screw or other
suitable device for fine adjustment. In the original, and also in the improved form
of the instrument, the graduations on the head of the screw operating the aforesaid

page_text: vertical line in the focus of the eye-piece of the main telescope, are so arranged that
when the instrument is on the second tripod, and the vertical line is brought to bear
again upon the distant object, the reading on the said head will give the cotangent
of the angle subtended by the base from the said object, and thus the range in terms
of the base. In the original instrument the base was always approximately at right
angles to the line from the instrument to the object, but in the improved instrument,
as the base may be at any angle to this line, it is necessary to provide an apparatus by
which the ratio between the length of the actual base and an imaginary right-angled
base is automatically given; this is done by means of a horizontal graduated disc,
which is affixed to and turns with the small telescope, and the said graduations are
so arranged that they give the ratio between the hypotenuse and base of a right-
angled triangle, of which the hypotenuse is the actual base of the observation, and
the base is the aforesaid imaginary right-angled base.
In the accompanying three sheets of drawings,
Fig. 1 is a side elevation and Fig. 2 a plan of my improved instrument.
Fig. 3 is a plan of the graduated disc attached to the small telescope, and
Figs. 4, 5, and 6 are diagrams, shewing the method of using the instrument.
Similar letters of reference denote similar parts throughout the drawings.
Referring to Figs. 1, 2, and 3, B is the main telescope, provided at the focus of
the eye-piece C with a vertical line engraved or otherwise fixed upon glass, and
capable of being moved horizontally in guides at right angles to the axis of the
telescope by a screw operated by the divided head J. N is the small telescope,
mounted by means of a vertical pivot O on the main telescope B, so that it can be
turned to any angle with relation thereto. P is a horizontal disc affixed to the
telescope N, and turning with it on the pivot O. This disc is graduated as before
described, and as shewn clearly in Fig. 3, the graduations being read against a fixed
pointer, or index Q. R is a clamping device operating on the disc P for fixing the
telescope N at any required angle. S is a screw giving a fine angular adjustment to
the telescope, after being fixed by the clamping device R. If preferred the
disc P may be fixed to the telescope B, and a pointer, connected to the telescope N,
travel round it.
To measure the range of any object o from the station a (see diagrams Figs. 4,
5 and 6) the instrument is placed upon a tripod or other suitable support at a and
the telescope B turned upon the object o till the vertical line in the eye-piece
(which has been placed in the zero position) coincides with such object. A staff
with a clear vertical line marked on the side, is fixed in the ground at a short
distance in any convenient position b, and the small telescope N turned till a
central vertical wire in the eye-piece coincides with the said line on the staff.
By means of the clamping device R the telescope is secured in this position, and
the final adjustment, if necessary, given by the screw S. The instrument is now
removed from the tripod and placed on another tripod at c, at a distance from a
averaging from, say ten to one hundred yards, according to the length of the range
to be measured and the nature of the ground. The device consisting of a circle or
ring with two diagonals, as described in the Specification of my aforesaid Letters.
Patent No. 8973 of 1886, is then placed upon the tripod at a and the tripod at c
adjusted until the vertical wire in the telescope N, the intersection of the diagonals
and the line on the staff 6 all coincide. (This operation may be conducted from
either end of the base, the staff being placed at when the first station of the
instrument is at c.) The vertical line in the main telescope B will now appear
at o¹ on the right of the object o, but by means of the head J it is moved until
coincidence is again obtained and the reading on the head is taken.
When the angle o ac is a right angle (see Fig. 4) the actual base a c is multiplied
(preferably by means of a slide rule) by the reading on J. Where the angle o a c
is not a right angle (see Figs. 5 and 6) the imaginary right angled base dc (the
length of which has been obtained by means of the disc P as before described) is
multiplied by this reading. In the second and third cases the product gives the
range o d which is practically equal to o c. In the first case, where the angle o a c

page_text: is a right angle, the imaginary base de coincides with the actual base a c and the
correct range is therefore o a, which also practically coincides with o c. In
practice, especially for artillery purposes, it is unimportant from which end of the
base the range is measured.
The base a c being once fixed and measured, any number of ranges in various
directions on either side of this base may readily be observed in the manner
above described.
No range can be observed from the base a c where the object lies in the line of
the said base, or forms only a very small angle with it. In practice I find it convenient
to limit the space within which ranges shall be observed to within about 60° on
each side of the normal to the base, and where a number of ranges are to be taken
from the same place the direction of the base line should be selected as far as
possible with the object in view.
In a modified form of the instrument, I may arrange the small telescope N
underneath the main telescope B. In this case the telescope N would first be
turned to the staff at b to fix the base line, and the telescope B then turned on the
required object, the subsequent operations being the same as before described.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
:―
In a range finder, the combination with a main telescope B, having a line capable
of motion within the focus of the eye-piece, of a small telescope N, pivoted thereto
so that the telescopes can be placed with their axes at any angle to each other,
and a disc P, so graduated, as automatically to give the ratio between the
measured base and the imaginary base used in the calculation of the range,
substantially as herein set forth.
Dated the 6th January 1891
AMBROSE MYALL,
21, Cockspur Street, London, S.W., Agent for the Applicant.