Improvements in Apparatus for Measuring or Ascertaining Distances.
Year: 1895

page_text: Date of Application, 13th June, 1895
Complete Specification Left, 13th Mar., 1896-Accepted, 18th Apr., 1895
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Measuring or Ascertaining
Distances.
I, FRANCIS WELDON, of Erlimount, Earley, in the County of Berks, Colonel
in the Indian Staff Corps, do hereby declare the nature of this invention to be as
follows:-
The object of my invention is to effect improvements in the construction of the
range-finders, or instruments for measuring and ascertaining distances by means of
prisms cut to reflect certain required angles, for which Letters Patent were granted
to me, bearing date 24th May, 1883, No. 2589, and 17th September, 1888,
No. 13398 respectively, and my invention relates more particularly to improvements
in instruments of that class, or pattern, which consists in the combination of prisms
with a telescope, and forms the subject of the second of my said Letters Patent,
viz. No. 13398 of 1888.
In such instruments, the form of construction employed, rendered it difficult to
ensure the axis about which the prisms revolved, being always parallel with the
axis of the telescope, and when such want of parallelism occurred, errors were
thereby presented in the measurements taken by the instrument.
The principal object of my invention is to overcome the above defect.
I employ a short telescope, and in order to obtain the advantage of the focus
remaining practically constant for near and distant objects, I prefer to make the
said telescope of low magnifying power.
On the side of the telescope, I provide a long socket, or other suitable device,
adapted to hold a spindle, or axis always in fixed parallelism with the telescope
axis, while at the same time permitting rotation of the said spindle in the said
socket, or its withdrawal therefrom.
On the outer end of the said spindle, I affix a prism, cut to reflect any desired
angle, and so situated with regard to the telescope, that on looking through the
latter, an object to the right or left of the observer, (according to the way the
instrument is held) will be seen through the telescope by resection from the prism,
together with an object in front viewed by direct vision through the telescope.
By this arrangement the prism can be turned up or down, so that the image of
the reflected object can be brought either above or below the image of the object
viewed directly, as may be required, while in all positions of the prism the axis of
its rotation always remains parallel to that of the telescope.
Two, or more prisms may be attached around the telescope, in the same manner
as the single oue already described.
The distance of an object is ascertained by the instrument in the same manner
as described in the Specification of my aforesaid Letters Patent, No. 2589
of 1883.
In the case of an instrument with more than one prism, one of the said prisms
would preferably be cut to reflect an angle of 90°, while the other prisms might be
cut to such angles that they would, in combination respectively with the 90° angle
prism, give bases measuring one fiftieth, one twentieth, one quarter and so on of
the range, but I do not confine myself to the employment of any particular number
of prisms, nor to the angles or proportions of the bases.

page_text: In the case of an instrument with a single prism, the said prism would be cut to
reflect an angle of less than 90°, for as it must be used for each end of the base, an
isosceles triangle is necessarily observed to obtain the range.
The prisms with their spindles, can be immediately removed from their sockets,
for cleaning, or when the telescope is to be used for direct vision alone.
In some cases, if desired, a group of two, or more prisms may be arranged on one
spindle, though in practice I prefer to provide a separate spindle and socket for
each prism.
I provide on the telescope an arrangement by means of which, when the correct
focus is once ascertained for any one observer, the eyepiece can be locked, in the
ascertained position. The said eyepiece is formed with a long screwed portion which
screws into the end of the ordinary draw tube, and such screwed portion is provided
with a lock-nut.
In practice, the draw tube is pulled out to its full extent and then the eyepiece
screwed in or out till the correct focus is obtained.
It is then secured by the lock-uut in this position, so that for all subsequent
observations, it is only necessary to pull out the draw tube as far as it will go.
This device affords considerable saving in time, over the ordinary method of
adjusting the focus, when taking an observation.
Dated this 13th day of June 1895.
AMBROSE MYALL,
2 Lancaster Place, London, W.C., Agent for the Applicant.
Improvements in Apparatus for Measuring or Ascertaining
Distances.
I, FRANCIS WELDON, of Erlimount, Earley, in the County of Berks, Colonel
in the Indian Staff Corps, 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 improvements in the construction of the
range finders or instruments for measuring and ascertaining distances, by means of
prisms cut to reflect certain required angles, for which Letters Patent were granted
to me, bearing date 24th May, 1883, No. 2589, and 17th September, 1888,
No. 13398 respectively, and my invention relates more particularly to improvements
in instruments of that class or pattern, which consists in the combination of prisms
with a telescope, and forms the subject of the second of my said Letters Patent,
viz. No. 13398 of 1888.
In such instruments the form of construction employed, rendered it difficult to
ensure the axis about which the prisms revolved, being always parallel with the
axis of the telescope, and when such want of parallelism occurred, errors were
thereby presented in the measurements taken by the instrument.
The principal object of my invention is to overcome the above defect.
In the accompanying two sheets of drawings, which form part of this Specification,
and in which similar letters of reference denote similar parts throughout.
Fig. 1 is a side elevation of an instrument constructed in accordance with my
invention, drawn to full size.
Fig. 2 is a sectional elevation of the prism detached from the instrument,
Fig. 3 is an end elevation, and
Fig. 4 is a part sectional elevation of the telescopic part of the instrument.
Fig. 5 is a top plan,
Fio 6 is an under plan and

page_text: Fig. 7 is an end elevation of a modified form of the instrument, and
Figs. 8 and 9 are end elevations, shewing the prisms in different positions.
Referring first to Figs. 1 to 3, I employ a short telescope A, and in order to
obtain the advantage of the focus remaining practically constant for near and
distant objects, I prefer to make the said telescope of low magnifying power.
On the side of the telescope, I provide a long socket B, or other suitable device,
adapted to hold a spindle or axis C, always in fixed parallelism with the telescope
axis, while at the same time permitting rotation of the said spindle in the said
socket, or its withdrawal therefrom.
On the outer end of this spindle I affix a casing or frame D, containing a prism E,
cut to reflect any desired angle, and so situated with regard to the telescope A,
that on looking through the latter, an object to the right or left of the observer
(according to the way the instrument is held) will be seen through the telescope by
reflection from the prism, together with an object in front viewed by direct vision
through the telescope.
By this arrangement the prism can be turned up or down, so that the image of
the reflected object can be brought either above or below the image of the object
viewed directly, as may be required, while in all positions of the prism, the axis of
its rotation always remains parallel to the axis of the telescope.
In the end view Fig. 3, the prism E is shewn turned up to lie across the upper
part of the object glass F, so that the image reflected by the prism appears above
the image seen directly through the object glass.
The prism E with its spindle C, can be immediately removed from the socket B
for the purpose of cleaning, or when the telescope is to be used for direct vision
alone, but for the latter purpose it is sufficient to turn the prism away from the
object glass, as indicated by the dotted lines in Fig. 3. If desired, the spindle C
can be secured within the socket B by means of a nut and washer, as hereinafter
described.
Two or more prisms may be attached around the telescope, in the same manner
as the single one already described.
In Figs. 5 to 9, an instrument is shewn consisting of a telescope A, having three
prisms E, E, E³, combined therewith.
The prisms E E2 have spindles C, working in sockets B as before described,
while the prism E³, which is placed between them, works on a hinge H, in such
manner that its axis is always in the same plane as the telescope axis.
The spindles C are shewn as secured within their sockets by means of nuts C¹
and washers C2 ou their ends, but a plain spindle, as before described, may be
employed if preferred.
Normally, the prisms occupy the position shewn in Figs. 5, 6 and 7, but when
the prism E³ is turned back, clear of the object glass, either of the prisms E'
or E can be brought into use by being turned partly across the object glass, the
other being swung on one side out of the way, as shewn in Fig. 8. To use
prism E³, the others are both swung out of the way, E³ remaining in the centre
of the field, as shewn in Fig. 9.
The distance of an object is ascertained by the instrument, in the same manner
as described in the Specification of my aforesaid Letters Patent No. 2589
of 1883.
In the case of an instrument with a single prism, as shewn in Figs. 1 to 3, the
said prism would be cut to reflect an angle of less than 90°, for as it must be
used for each end of the base, an isosceles triangle is necessarily observed to
obtain the range.
In the case of an instrument with more than one prism, one of the said prisms
would probably be cut to reflect an angle of 90°, while the other prisms might be
cut to such angles that they would in combination respectively with the 90° angle
prism, give bases measuring one fiftieth, one twentieth, one quarter and so on of
the range, but I do not confine myself to the employment of any particular
number of prisms, nor to the angles reflected, nor the proportions of the bases.

page_text: In some cases, if desired, a group of two or more prisms may be arranged on
one spindle, though in practice I prefer to provide a separate spindle and socket
for each prism.
I provide on the telescope, an arrangement, by means of which, when the correct
focus is once ascertained for any one observer, the eye piece can be locked in
the ascertained position. The said arrangement is shewn most clearly in Fig. 4.
The eye piece J is formed with a long screwed portion K, which screws into the
internally threaded end of the ordinary draw tube L, and M is an interually
threaded ring with a milled edge, screwing on the portion K and acting as a
.lock nut.
In practice the draw tube L is pulled out to the full extent permitted by its
stop, and then the eye piece J screwed in or out until the correct focus is
obtained. The ring M is then rotated till it bears tightly against the edge of
the draw tube, as shewn in Figs. 1 and 5, thus locking the eye-piece in the
required position, so that for all subsequent observations by the same person, it is
-only necessary to pull out the draw tube as far as it will go.
This device affords considerable saving in time over the ordinary method of
adjusting the focus, whenever an observation is taken.
The apparatus forming the subject of my invention constitutes a very convenient,
and compact instrument, occupying little or no space, and yet affording the means
of rapidly taking observations of considerable accuracy.
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. In a range finder, or instrument for measuring and ascertaining distances, in
-combination, a telescope and one or more prisms cut to reflect certain required
angles, and capable of rotation about an axis or axes in fixed parallelism to the
axis of the telescope, substantially as and for the purpose herein set forth.
2. In a range finder, or instrument for measuring and ascertaining distances, in
combination, a telescope and one or more prisms cut to reflect certain required
angles, and provided with axes capable of rotation in sockets in parallelism to the
axis of the telescope and capable of removal from and replacement in said sockets,
without disturbance of the said parallelism, substantially as and for the purpose
.herein set forth.
3. In the telescope of a range finder, or instrument for measuring and ascertaining
distances, an eye piece J having a screwed portion K, an internally threaded draw
tube L to receive said portion K, and a locking ring M to fix said eye piece therein
at any ascertained focus, substantially as herein set forth.
4. A range finder, or instrument for measuring and ascertaining distances,
-consisting of a telescope A with a focus locking device, as set forth in the preceding
claim and a prism E rotatable about an axis C in fixed parallelism to the telescope
.axis, substantially as herein described and shewn, with reference to Figs. 1, 2, 3
and 4 of the accompanying drawings.
5. A range finder, or instrument for measuring and ascertaining distances,
⚫consisting of a telescope A with a focus locking device, as set forth in Claim 3,
prisms E E rotatable about axes C C in fixed parallelism to the telescope axis,
and a prism E³ movable about a hinge H, substantially as herein described and
shewn with reference to Figs. 4, 5, 6, 7, 8 and 9 of the accompanying drawings.
Dash: 19th 1 CM
1000
AMBROSE MYALL,
2 Lancaster Place, London, W.C., Agent for the Applicant.