Improvements in and relating to Theodolites and similar Measuring Instruments.
Year: 1899

page_text: Date of Application, 1st Nov., 1899-Accepted, 1st Nov., 1900
[Communicated from abroad by REINHARD REEH, of Wetzlar, in the German
Empire, Surveyor.]
Improvements in and relating to Theodolites and similar Measuring
Instruments.
I, WILLIAM PINILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for Foreign
Patent Solicitors, 322, High Holborn, in the County of Middlesex, 6, Lord Street,
Liverpool, and 6, Bank Street, Manchester, both in the County of Lancaster, and
Lower Temple Street, Birmingham, in the County of Warwick, Civil Engineer,
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 an improved reading-off apparatus for directly denoting
angles, for use with surveyors' telescopes, theodolites, tacheometers and the
like.
In order to obviate the numerous defects and deficiencies which occur in reading
off angles by means of verniers, for instance the inaccessibility of the verniers
when the instruments are set up in unfavourable positions such as mines, the
difficulty of fixing the coincidence owing to parallax, or the glass casings of the
verniers becoming dim owing to humidity of atmosphere or splashes of water and
so forth; an apparatus is described below which transfers images of the azimuth
and altitude scales in such a way into the plane of vision of the telescope that
the images can be observed at the same time as the object aimed at.
The apparatus consists of microscopes with micrometric scales, the images of
said scales being brought into the plane of vision through the horizontal axis
of the trunnions of the telescope, by means of glass prisms and convex lenses to
the eye tube, where they are clearly visible at any position of the eye-piece.
Referring to the accompanying drawings:
Figures 1 and 2 shew views of the scales as seen through the apparatus in the
two positions of an observation.
Figure 3 shews a general sectional elevation of the apparatus in a small mine
theodolite, the telescope pointing downwards.
Figure 4 shews a cross-section of the eye-piece on the line A-B of Figure 3.
Referring now to Figure 3 of the accompanying drawing, I provide a telescope 1
having a hollow horizontal axis or trunnion 2 and turning on suitable Ys 3,
said Ys carrying the altutude scale 4 and the azimuth microscope tube 5 by
means of suitable supports G.
The telescope 1 has the usual movable eye-piece 7 in which is fixed a lens 8
bisected on the diameter and the halves fixed vertically on each side of the
visual axis of the telescope; said halves of lens 8 are a short distance apart in
order that the image of the object viewed through the telescope is not obstructed
(see Figure 4).
In one side of the horizontal axis 2 is placed a prism 9 and a lens 10: and in
the microscope tube 5 is placed a prism 11 and a lens 12; said prism 11 being
placed at the end of the microscope tube 5 furthest away from the azimuth
scale 13. The microscope tube 5 is so arranged that the image of the azimuth
017

page_text: scale is reflected from prism 11 through lens 10 to prism 9, and from prism 9
through lens 8 to the plane of vision. In the other side of horizontal axis 2
are placed prisms 14 and 16 and lens 15; prism 16 being so placed in the
horizontal axis 2, that said prism is also at the end of the altitude microscope
tube 17. The microscope tube 17 is fixed in the trunnion of the telescope and
rotates with the telescope; said tube has a lens 18. The image of the altitude
scale 4 is reflected through lens 18 to prism 16, and from prism 16 through lens 15
to prism 14, and from prism 14 through lens 8 to the plane of vision. The
azimuth scale 18 is supported on any suitable table 19.
The arrangement above set forth is capable of universal application wherever
optical reading-off devices with divided circles or scales are employed, for trans-
ferring scales in planes at right angles of vision into the plane of vision of the
telescope.
This arrangement is of special importance for tachcometer theodolites because
it is possible, with the telescope in any position, to obtain a result with one
single reading-off on the horizontal or azimuth and vertical or altitude circles,
as one side of the device can be used for the observation of the horizontal or
azimuth circle and the other side for the observation of the vertical or altitude
circle. In this way the observer is enabled practically at the same time and
with a single glance to observe the surveying staff and the two circles.
The divisions in the vertical or altitude circle are preferably placed upon the
inner side of the ring, and the microscope tubes are preferably arranged at right
angles to the horizontal axis of the telescope.
Having now particularly described and ascertained the nature of my
invention and in what manner the same is to be performed, I declare that what
I claim is: :-
1. The improvements in apparatus for measuring angles such as theodolites,
'tacheometers and the like, having optical arrangements for simultaneous reading-
off and observing, consisting of mirrors or prisms 11 and 9 and 14 and 16 placed
in the axis of rotation of the reading-off device, of which prisms 11 and 16 are
secured to the upper ends of microscope tubes placed vertically over the divisions
of the scales and prisms 9 and 14 are connected with the observing mechanism,
in combination with lenses 10, 15 and 8 for the transmission of the pictures or
images of the divided scales either directly or indirectly with the observing
mechanism such as a telescope or the like, into the plane of vision in such a
manner that these pictures appear within a reading-off scale simultaneously and
equally clearly with the object viewed, substantially as described.
2. The improved apparatus for simultaneous viewing of a distant object and
measuring of the angles thereof, constructed and operating substantially as
described with reference to the accompanying drawings.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C.,
Patent Agents for the Applicant.