Improvements in Telescopes for Gun-sighting and other purposes.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
Improvements in Telescopes for Gun-sighting and other purposes.
I, ANDREW AINSLIE COMMON, of 63, Eaton Rise, Ealing, in the County of
Middlesex, Gentleman, do hereby declare the nature of this invention to be as
follows:-
The object of this invention is to obtain exact collimation in telescopes used
for sighting purposes on guns and measuring instruments, and the invention
consists in so mounting the object glass, that the collimation may be readily
obtained.
In carrying out this invention the object glass is mounted in a cell in the
ordinary manner, but the outside of the cell is excentric to the side. The cell
thus made is fitted into another cell or ring, the outside of which is similarly
excentric to the inside. The object glass cell and outer ring are secured in an
outer cell or fitting attached to the telescope tube. A screwed cap secures the
whole together, when the adjustment has been made. This adjustment is obtained
by the rotation of the object glass with its excentric cell, or the excentric ring,
as the case requires.
The rings may be marked so that the value of a certain amount of turning
may represent a certain amount of shift in the centre of the object glass.
The object glass may also be fixed in a circular cell, the two enclosing rings
being excentric.
When the adjustment is made, the screw cap, secures the object glass per-
manently in position, as before explained. The rings may be either parallel or
slightly taper, so as to tighten themselves when the cap is screwed down.
Dated this 22nd day of November 1899.
NEWTON & SON,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Telescopes for Gun-sighting and other purposes.
I, ANDREW AINSLIE COMMON, of 63, Eaton Rise, Ealing, in the County of
Middlesex, Gentleman, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement:-
:-
The object of the present invention is to provide ready means for obtaining
exact collimation in telescopes used for gun-sighting and other purposes.
In carrying out my invention, I mount the object glass in a cell having an
external perimeter excentric to the optical axis of the lens, and this cell is, in

page_text: its turn, mounted in a ring which is 'internally excentric. This outer ring is
fitted in the telescope tube in the usual manner. By turning these rings or cells
one upon the other, the optical centre of the object glass can be moved into
different positions, so that a ready means of obtaining collimation is thus pro-
vided.
In the accompanying drawing,
Figs. 1 and 2 are sectional and side elevations shewing my invention 'adapted
to a telescope.
Fig. 3 is a front view.
Figs. 4 to 8 are diagrams, shewing the collimating rings or cells in different
positions.
a is the object glass mounted in the cell b, which is excentric on the outside.
This cell fits snugly in the ring e, which is excentric on the inside, and the
whole is mounted in the tubular extension of the telescope tube c.
For turning round the cells b and c, holes * and * are provided in their
perimeters, which holes are accessible to a tommy through slots, and in
the extension d. f is a short tube for covering up the slots and d², and
y is a flanged ring screwing into the extension d'holding the cells band e
in place, and preventing the removal of the tube f. is the ordinary dew cap.
To remove the ring y, a special tool will be required, so that tampering
with the adjustment, after collimation has been effected, will be prevented.
Referring now to the diagrams,
Fig. 4 shews the object glass so adjusted that its optical centre is in the
axis of the telescope tube. The rotation of the inner excentric cell a quarter
turn in the direction of the arrow, while the outer excentric ring remains fixed,
will cause the optical centre to travel in an are away from its former position,
as indicated in Fig. 4.
Figs. 5, 6, and 7, shew the completion of a circular path travelled by the
optical centre during one half, three quarters, and a complete rotation, respec-
tively, of the cell b, while the ring e remains stationary.
It will be observed that in these examples the circle described by the travel
of the optical centre is below the position from which it started. By rotating
the ring e, however, for example, as shewn in Fig. 8, to the extent of one quarter
rotation in the direction of the arrow, the path of the curve is shifted to a
new position. It will be seen; therefore, that a combination of the movements
of the cell and ring e, will give within an ample range, to the optical centre
of object glass, any position necessary to ensure to the instrument correct
collimation.
•
It will be understood that the telescope is provided with an eye piece which
carries, at a suitable point in its length, the cross wires, as is usual in this class
of instrument,
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
The means described for moving the object glass so that the optical axis
(as defined by the centre of the object glass and the intersection of the cross
wires in the focus) may be made coincident with, or parallel to, the mechanical
axis of the telescope, whereby collimation is effected substantially as set forth.
Dated this 17th day of July 1900