TRUVIDIONAL DILUIFICATION
Year: 1888

page_text: Date of Application, 16th Aug., 1888
Complete Specification Lett 17th June 1889-Accented. 10th Aug.. 1889
TRUVIDIONAL DILUIFICATION
A Range Finder.
I WILLIAM FARQUHARSON of the City of Montreal District of Montreal, Province
of Quebec Canada late Sergeant of Her Majestys Regiment 78th Highlanders,
Merchant Taylor, do hereby declare the nature of this invention to be as follows:-
My invention relates to the construction of a range finder wherein an optical square,
of well known construction is combined with a table having a graduated scale and an
index arranged and operating as described in the specification to my patent 8748 of
1885, in such manner that on first sighting by means of the optical square the object
at the distance to be measured, and an object at right angles thereto at a given distance
from the observing station and then on taking such last named distant point as the
station, on turning the index round upon the scale until the distant point is observed
through a sighthole and a foresight which are brought into coincidence with the
object, the distance of such object will be read in yards upon the said scale.
For this purpose the index is connected to the moveable part carrying the sighthole
and foresight by multiple gearing so that a comparitively large movement of the
index will produce a comparatively small movement of the sight hole as described in
my aforesaid specification.
If it is desired to combine a telescope with the range finder, a spindle carried by
the moveable part with the sight hole is made to pass up through a tubular spindle
carrying the index and is made to carry a telescope above the latter so that the
telescope moves with the sight hole.
Dated this 16th day of August 1888.
ABEL & IMRAY,
Agents for the Applicant.
COMPLETE SPECIFICATION.
A Range Finder.
I, WILLIAM FARQUHARSON, of the City of Montreal, District of Montreal, Province
of Quebec, Canada, late Sergeant of Her Majesty's Regiment 78th Highlanders,
Merchant Taylor, 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 :-
My invention relates to the construction of a range finder wherein an optical square
of any well known construction is combined with a table having a graduated scale and
an index arranged and operating in a similar manner to that described in the
Specification to my Patent 8748 of 1886, in such manner that on first sighting by
means of the optical square, the object at the distance to be measured, and an object
at right angles thereto at a given distance, and then on taking such last named distant
point as the station, on turning the index round upon the scale until the distant point
is observed through a sight hole and a fore sight which are brought into coincidence
with the object, the distance of such object will be read in yards upon the said scale.
For this purpose, according to one arrangement, the index is connected to a
movable part carrying the sight hole and foresight by multiple gearing so that a
comparatively large movement of the index will produce a comparatively small move-
ment of the sight hole as described in my aforesaid specification. According to
another arrangement the index instead of actuating the sight hole and fore sight,
which are in this case stationary, is made to actuate one of the mirrors of the optical
square as I will proceed to describe with reference to the accompanying drawing.
Fig. 1 shews a plan of the instrument, Fig. 2 a sectional plan and Fig. 3 a cross
section. The casing A which is adapted to be screwed on to a stand at A¹, has
fixed to it a plate B which carries firstly, a mirror C that is mounted on a centre

page_text: which coincides with the line X X passing through the sight hole D and foresight E,
fixed to the plate B, the mirror being held in position by an adjusting screw F
so that by turning this screw by means of a key, the angle which it forms with
the sighting line X X can be adjusted. The plate B carries also a second mirror G
mounted on an arm H that can revolve through a certain angle on the pivot H¹,
and that is provided with a toothed sector H2 gearing with a pinion I on a spindle
arried by the plate B and by a bracket J. On this spindle is also fixed a toothed
wheel K gearing with which is a pinion L on an axis M coinciding with the centre
of the casing and carrying above the disiancing table N fixed to the casing, the
index O which can revolve over the divisions on the table N.
From this construction it will be seen that on turning the index O through a
certain angle (for which purpose it is provided with the pivotted handle O¹) it will
effect the turning of the mirror G on its axis H' through an angle which will be a
fraction of the angle of the index, determined by the ratio of the gearing H I K L.
When the mirror G is in the position indicated at Fig. 2, it will reflect on to the
mirror C and thence to the sight hole D a distant object in the line Y parallel with
the axial line X X, and this is the one extreme, or the ". zero position of the
mirror in this position it is made to bear against the stop P. If now, by rotating
the index O a corresponding number of times, the arm H be turned into the other
extreme position, indicated by dotted lines, in which it bears against a second
stop P1, the mirror G will have been brought into such a position relatively to C
as to reflect upon the mirror C and thence to the sight hole D any object situated
along the line Z, which is at right angles to the line X X, and consequently when
the mirrors are in this relative position they will constitute an optical square."
The index. O will then be in a position with its edge 02 coinciding with the line
on the table N marked 90°.
"
Assuming now that it be desired to ascertain the distance of an object Q Fig. 4
from a point R, then the operator, having bis instrument set as last described so
as to constitute an optical square, first places himself at R and determines a point S
at a given distance (which is regulated by the scale on the table N) at right angles
to the line R Q. He then places himself at S and, after sighting the point R direct
through the sights D, E, and transparent part of the mirror C, he turns the index
until by bringing the mirror G to a certain intermediate position between zero
and 90°, he brings the reflected image of Q in line with the directly sighted image R,
whereupon the index O will point to a division on the scale, the number on which
will give the distance of the object Q from R in yards or any other desired unit.
The scalo as marked is intended to indicate distances between four hundred and
1800 yards. For setting out this scale in the first instance, the total length of
1800 yards is set off on a line R Q and this is divided into any desired number of
units, say 25 yards. the points being marked; a distance of 25 yards is then measured
at right angles to R, Q, say to S, and the operator placing himself at S and sighting R
then turns his index O so as to bring the mirror successively in positions for reflecting
the several points of said division in line with the line of sight R S., and when each
division has been sighted, he marks the position of the index upon the scale and
numbers it to correspond with the distance of the division.
In order to prevent all looseness in the gearing of the wheels, the sector H2 and
the wheel K are by preference both provided with two sets of teeth, one of which can
slide relatively to the other and is acted upon by a spring T and U, so as to bear upon
the side of the pinion's teeth that are in gear with them opposite that on which the
other set of teeth bear.
The part A2 of the casing is made to turn upon A so as to close the openings
thereof when not in use.
Having now particularly described and ascertained the nature of this 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 of an optical square with a table having a

page_text: graduated circular scale and a rotatable index, the axis of which is connected by a train
of wheels to a moveable part of the optical square so that by turning the index through
a certain angle the moveable part of the optical square will be shifted through a
certain fraction of the said angle, the distance of the object sighted when the said
part is so shifted being indicated by the position of the index upon the scale,
substantially as herein described.
2. Constructing a range finder such as is referred to in the preceding claim, in the
manner herein described with reference to the accompanying drawings.
Dated this 17th day of June 1889.
ABEL & IMRAY,
Agents for the Applicant.