An Improved Instrument for Measuring Distances.
Year: 1890

page_text: Date of Application, 6th Sept., 1890-Accepted, 8th Nov., 1890
COMPLETE SPECIFICATION.
[Communicated from abroad by GUSTAV ADOLF KREISEL, of Pomnitz, near Kösen, in
the Empire of Germany, Shoemaker.]
An Improved Instrument for Measuring Distances.
I, HUGH DONALD FITZPATRICK of 70 Wellington Street, Glasgow, Lanarkshire,
Registered Patent Agent, 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:-
This invention relates to a distance measurer or telemeter, which is characterised by
a double sighting arrangement and is founded on the formation of a right-angled
triangle, in which the length of one of the sides of the right angle is known and
stands in a fixed proportion to the length of the other side, which forms the distance
of the point to be ascertained.
And in order that my said invention may be properly understood I have hereunto
appended an explanatory sheet of drawings, whereon-
Figs. 1, 1, 1 show the new distance measurer or telemeter as adapted to the
measurement of the distance of a point from the observer and as adapted to the calcu-
lation of the distance between two points.
Figs. 2, 3, 4 are cross sections on the lines I-I, II—II, III—III in Fig. 1.
On the pillar A the bar B carrying the scale b is arranged so that it not only turns
on its own longitudinal axis, but can also be inclined at pleasure to the axis of the
pillar. The bar B carries at its lower end, and at right angles to it, a fixed sight C
and besides a second sliding sight D which slides on the scale b at a fixed angle to
the bar B.
If now, for example, the distance of the point ✗ from the observer is to be ascer-
tained, the lower sight is directed upon X, the micrometer screw a on the pillar A
enabling an exact adjustment of the line of vision in a vertical plane.
By adjusting the sight C in a vertical plane, the bar B is, of course, inclined more
or less out of the perpendicular; but, as the angle which the sight D forms to the
pillar B is, as already mentioned, constant, the displacement of the latter makes no
change in the angle.
After the sight C is directed exactly on X the bar B is fixed by a pinching screw h
or the like; and the sight D is now slid on the scale b until the point X lies exactly
in the new line of vision.
As, then, the length of the side of the right angle is given on the scale, and this
side, as already mentioned, stands in a fixed proportion to the other side or base of
the right angle, the length of the latter, that is, the distance of the point X from the
observer, is determined. As the scale is divided correspondingly to this proportion,
the required distance can, after completing the adjustment of the sight D be
read off.
If, for instance, one millimetre of the scale corresponds to one centimetre on the
vision line of C, the inclination of the sight D being known, every further graduation
which the sight D is displaced on the bar B indicates a further distance on the vision
line of one centimetre.
In the measurement represented in Fig. 1, the sight D is pushed up 30 mm. and
the point must therefore be 30 cun. distant, as the side of the right angle on the
scale stands in the proportion of 1 to 10 to that ended by the point X.
If the inclination of the sight D is such that the proportion of length of the side of
the right angle to the base line is 1 to 100, the indicator of the sight D would in the
same way show the point X to be 3 metres distant from the observer.
It is therefore clear that after proper positioning of both sights C and D on one

page_text: and the same point, the distance of this point from the observer can be immediately
road off.
In order now to measure also the distance between two unknown points X
and a sliding bracket G is fixed to the pillar A which carries a small tele-
scopically working pillar e, capable of sliding in itself and on the bracket. G, in
the upper end of which a measuring-bar E, which can be pulled out, is fixed
horizontally.
If the distance between the points X and Y is to be measured, the distance of
the point is first ascertained in the manner just described and the measuring-
bar E is then pushed along the bracket G until its index point (Fig. 1) rests
at a graduation which is marked off on the bar ((the har being graduated similarly
to the scale 6) representing exactly the same distance as between the sights (and Ď
on the scale b
Then after fixing the measuring-bar E, sight with the point X. The sight
thus sets against the scale of the measuring-far E and indicates in its and position
on the line A-X, by e f the distance of the two points.
In this operation it is assume that X and Y are equidistant from the observer.
If this he not the case, or not known to be so, it is necessary to sight with Cthe
point and to ascertain this distance also exactly with the help of sight D; then
turn the measuring-bir E, the index point of which was, as formerly, placed at the
distance (read on the scale 6) of the point Y, so far that it strikes the mark-point .' on
the sight towards X and hereby, in the length (Fig. 1) the distance between
the points X and Y is ascertained.
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―
An instrument for measuring the distance of a point from the observer
characterised by the arrangement of two sights (U, D),), one above the other, on a
movable bar (B) provided with a scale (b) of which the lower sight (C) is immovably
fixed to this bar at right angles, while the other sight (D) is arranged at a fixed
angle to slide on the scale; and also, for measuring the distance betweon two points,
by a third measure-bar (E) which is so arranged that when placed at the ascertained
mark-points, it indicates the required distance, substantially as hereinbefore described
and illustrated on the drawings annexed.
Dated this 5th day of September 1890.