Improvements in Telemeters.
Year: 1897

page_text: Date of Application, 23rd Mar., 1897-Accepted, 29th May, 1897
Improvements in Telemeters.
:
I, FREDERICK JOAQUIM BARBOSA CORDEIRO, Surgeon of the United States Navy,
Newport, Rhode Island, 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 telemeters or optical instruments for measuring distances,
and the object is to provide an instrument of this character in which there are very
few parts compactly arranged, and with which a single observation, by a single
observer, will ascertain the distance, and in which the manipulation of the instrument
may be easily acquired.
I will describe an instrument embodying my invention, and then point out the novel
features in the appended claims.
Reference is to be had to the accompanying drawings, forming a part of this
specification, in which similar characters of reference indicate corresponding parts
in both the figures.
Figure 1 is a plan view of an instrument embodying my invention, and
Figure 2 is a side elevation thereof.
The telemeter comprises an arm 1, supported by and extended at right angles to a
vision-instrument or telescope 2. This arm may conveniently be about three feet
long, so that the instrument may be easily handled by one observer. The end of the
arm 1, adjacent the telescope 2, is provided with a graduation-scale 3 for either angles
or distances. Rigidly mounted on the arm 1, and coincident with the lower half of
the field of the telescope 2, is a horizon-glass 4, which is here shown as a totally-
reflecting right-angle prism, but I do not wish to confine my invention to said prism
form, as it is obvious that other forms of reflectors may be employed-such, for
instance, as half-silvered glass.
A lever 5 has one end pivoted to the outer end of the arm 1, as at 6, and the
opposite end is provided with a vernier 7, coacting with the graduation 3. This
vernier may be adjusted by means of a screw 8, extended through a tapped hole in
a lug on the arm 1, and engaging at its end with the lever 5.
Rigidly connected to the pivoted end of the lever 5, and having its reflecting-
surface at an angle of forty-five degrees to the axis of the lever, is an index-glass 9,
which is here shown as a right-angle prism, but other forms of index or reflecting
surfaces may be employed, such as a mirror or burnished metal.
The arm 1 may be provided with a handle 10, placed in such position that the two
ends of the instrument may be equally balanced therefrom.
In use, the instrument is so placed that the line of collimation through the telescope
and horizon-glass 4 will be in the direct line of the object the distance of which is
to be measured, and then the lever 5 will be manipulated to cause the glass 9 to
receive the image and reflect it to the horizon-glass at a point coincident with the
line of collimation.
The angle, by means of the vernier, may be known, and as the length of base-line
is known, the distance of the object may be readily ascertained by computation or
from prepared tables, or, better, the scale is marked empirically for distances, so that
distances are read at once.

page_text: 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 :-
1. A telemeter, comprising a telescope, an arm arranged at right angles thereto and
having a scale at its end near the telescope, a right-angled prism supported on the
arm in the line of vision of the telescope, a lever having pivotal connection with said
arm at its end opposite that containing the scale, a vernier on said lever coacting with
the scale, and an index-glass on said pivoted lever at its pivotal point, the said index-
glass consisting of a right-angled prism and having one of its right-angled sides
-extended toward one of the right-angled sides of the first-named prism, substantially
as specified.
2. A telemeter, comprising a telescope, an arm arranged at right angles thereto,
the said arm serving as a base-line and also as a radius for measuring angles, a sight
or horizon glass supported on said arm in the line of vision of the telescope, a lever
having its end pivoted to the end of the arm, an index-glass mounted on said lever at
its pivotal point, and a vernier on the opposite end of said lever coacting with a scale
-on the arm, substantially as specified.
Dated this 9th day of March 1897
WHEATLEY & MACKENZIE,
40 Chancery Lane, London, W.C., Agents.