An Improvement in Sextants and other similar Instruments used for Solar, Lunar, and Astronomical Observations.
Year: 1891

page_text: Date of Application, 22nd Jan., 1891
Complete Specification Left, 21st Oct., 1891-Accepted, 21st Nov., 1891
PROVISIONAL SPECIFICATION.
An Improvement in Sextants and other similar Instruments used
for Solar, Lunar, and Astronomical Observations.
I, LEWIS KNOX BELL, of The Junior Army and Navy Club, St. James's
Street, Westminster, in the County of Middlesex, Lieutenant in Her Majesty's
Navy, do hereby declare the nature of this invention to be as follows:-
The object of my invention is to combine with sextants, and other similar instru-
ments used for solar, lunar and astronomical observations, a device whereby the
lightest shade (preferably) of the index glass or moveable mirror, may be put into
position or out of position, for shading the reflected image of the sun &c. by a
motion of the hand or finger of the observer whilst he is holding the instrument in
the necessary position for taking an observation, thereby enabling a rapid change
to be effected in the degree of shading required to suit the eye of the observer, to
correspond to the varying brightness of the sun &c., caused by drifting clouds of
ununiform density, or intervening smoke or steam from ships funnels &c. or other
causes.
My invention consists for this purpose in applying to the sextant &c. a trigger
or equivalent device in connection with the said shade, whereby it may be thrown
into or out of shading position by a comparatively small or quick motion of the
hand or finger, preferably of the fore finger of the hand holding the instrument.
The means employed for this purpose may he greatly varied, and may depend
on the form of the framework of the instrument. Thus the trigger may be con-
nected by a rod to a very short arm attached to the shade, so that a small move-
ment of such arm by the trigger will effect the required motion of the shade; or
the motion in one direction may be effected by a spring, so that after moving the
shade into the other position by the trigger, it will spring back 'on releasing the
pull on the trigger. Or instead of effecting the connection between the parts by
a rod, it may be effected by toothed gearing, or by a crank motion. Or again the
shade may be connected to a spring device so arranged that on giving the shade a
slight motion by the trigger in one direction or the other, it will complete its motion
automatically.
'Or again the shade may be made to raise or lower in a plane perpendicular to
the plane of the instrument in a slot, and be actuated in its motion by a similar
motion of the finger &c.
Or again' the shade'may be made to rise or fall like a
and be actuated by a similar motion.
Dated this 22nd day of Tra 1001
66
flap" on the instrument
ABEL & IMRAY,
Agents for the Applicant.
COMPLETE SPECIFICATION.
An Improvement in Sextants and other similar Instruments used
for Solar, Lunar, and Astronomical Observations.
I, LEWIS KNOX BELL, of The Junior Army and Navy Club, St. James's
Street, Westminster, in the County of Middlesex, Lieutenant in Her Majesty's
Navy, 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 combine with sextants, and other similar instru-
ments used for solar, lunar, and astronomical observations, a device whereby-the
[Price l

page_text: lightest shade (preferably) of the index glass or moveable mirror, may be put into
position or out of position, for shading the reflected image of the sun &c., by a
motion of the hand or finger of the observer whilst he is holding the instrument in
the necessary position for taking an observation, thereby enabling a rapid change
to be effected in the degree of shading required to suit the eye of the observer, to
correspond to the varying brightness of the sun &c., caused by drifting clouds of
ununiform density, or intervening smoke or steam from ships funnels &c. or other
causes.
My invention consists for this purpose in applying to the sextant &c. a trigger
or equivalent device in connection with the said shade, whereby it may be thrown
into or out of shading position by a comparatively small or quick motion of the
hand or finger, preferably of the fore finger of the hand holding the instrument.
The means employed for this purpose may be greatly varied, and may depend on
the form of the framework of the instrument.
Thus the trigger may be connected by a rod to a very short arm attached to
the shade, so that a small movement of such arm by the trigger will effect the
required motion of the shade; or the motion in one direction may be effected by a
spring, so that after moving the shade into the other position by the trigger, it
will spring back on releasing the pull on the trigger. Or instead of effecting the
connection between the parts by a rod, it may be effected by toothed gearing, or
by a crank motion. Or again the shade may be connected to a spring device 50
arranged that on giving the shade a slight motion by the trigger in one direction
or the other, it will complete its motion automatically.
Or again, the shade may be made to raise or lower in a plane perpendicular to
the plane of the instrument in a slot, and be actuated in its motion by a similar
motion of the finger &c.
66
Or again, the shade may be made to rise or fall like a flap" on the instrument
and be actuated by a similar motion.
Fig. 1 of the accompanying drawings shews a part plan of a sextant with one
arrangement of my above described invention,
Fig. 2 shews a sectional elevation.
A is one of the pivotted shades between the index glass B and horizon
glass C. Its boss is formed with a toothed segment D, with which gears a toothed
sector E of larger radius pivotted to a bracket F and having a lever or trigger G
fixed or formed thereon so that by moving this lever in one direction or the other
by means of a finger H of the hand that holds the handle I of the sextant, the
shade A can be rapidly moved either in front of the index glass, as shewn in full
lines or away from it, as in dotted lines.
Instead of working the trigger in both directions by the finger, it may be acted
upon by a spring K in one direction as at Fig. 3, so that the finger only requires
to press the trigger upward for bringing the shade in front of the index glass, and
to release the trigger for allowing the spring to remove the glass.
Fig. 4 shews a construction in which the boss of the shade A. is formed with two
flat faces at an angle to each other, of which the one or other bears upon a
spring I, so that on moving the shade by the lever G attached thereto until the
apex M of the boss has just passed the vertical line in compressing the spring, the
latter, in acting with an upward pressure against the other flat face of the boss,
will effect the rapid completion of the shade's motion.
In the arrangement shewn at Fig. 5, the boss of the shade is formed with a deep
uotch into which takes a finger N on the sliding trigger N, which may either be
urged in one direction by a spring O, or which may be moved in both directions by
the finger inserted in the loop N².
Fig. 6 shews a side view and Fig. 7 a front view of an arrangement in which the
shade A is made to turn up and down in a plane at a right angle or other angle to
the index glass. The boss is formed with a notch as in the preceding case into
which takes a finger P¹ on an axis P carried on the underside of the frame and
turned in one direction or the other by the trigger Q.

page_text: Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is :--
1. The use in combination with the index glass or moveable mirror of a sextant
or other instrument used for observations, of a shade actuated by a trigger or
equivalent device controlled by the hand of the observer, such trigger or other
device being so arranged that the shade can be rapidly moved in front of and away
from the index glass or mirror by the hand that holds the instrument, substantially
as described.
2. In a combined shade and trigger such as is referred to in the preceding claim,
constructing the trigger as a double ended lever pivotted to the framing of the
instrument carrying the shade and having on its one arm a toothed sector gearing
with teeth on the boss of the shade, motion being imparted to the trigger either
in both directions by the finger of the operator, or only in one direction by the
finger and in the other direction by a spring, substantially as described with
reference to Figs. 1, 2 and 3 of the drawings.
3. In a combined shade and trigger such as is referred to in the first claim, con-
structing the boss of the shade with two flat faces at right angles to each other,
against either of which bears a blade spring, so that when a slight motion is-
imparted to the shade on its pivot by a trigger or lever, the spring will automatically
effect the completion of such motion in passing from the one flat face of the boss to
the other, substantially as described with reference to Fig. 4 of the drawings.
4. In a combined shade and trigger such as is referred to in the first claim,
arranging the trigger to act with a sliding motion as described with reference to
Fig. 5 of the drawings.
5. In a combined shade and trigger such as is referred to in the first claim,
arranging the shade to turn in a plane at a right or other angle to the index glass,
substantially as described with reference to Figs. 6 and 7 of the drawings.
Deted this 20th day of October 1891
ABEL & IMRAY,
Agents for the Applicant.