IMPROVEMENTS IN THE CONSTRUCTION OF BINOCULAR TELESCOPES AND OPERA GLASSES
Year: 1879

page_text: LETTERS PATENT to George William Frodsham, of No. 4, Change Alley,
Cornhill, in the City of London, Chronometer Maker, for the Invention of
"IMPROVEMENTS IN THE CONSTRUCTION OF BINOCULAR TELESCOPES AND OPERA
GLASSES"
Sealed the 31st October 1879, and dated the 3rd May 1879.
PROVISIONAL SPECIFICATION left by the said George William Frodsham
at the Office of the Commissioners of Patents on the 3rd May 1879.
GEORGE WILLIAM FRODSHAM, of No. 4, Change Alley, Cornhill, in the City
of London, Chronometer Maker. "IMPROVEMENTS IN THE CONSTRUCTION OF
BINOCULAR TELESCOPES AND OPERA GLASSES."
My Invention consists in connecting the cylinders which carry the object glasses
and the framework containing the eye pieces and screw adjustment, so as to enable
the user to slide the latter (framework) into the former (cylinders); and I effect
that by pivotting the open ends of the cylinders by means of screwed or rivetted
pivots on to the ends of the framework. I also employ a circular engraved scale
to surround the central pivot, so that when the instrument has been opened for use
the distances between the cylinders may be adjusted to suit the position of the
eyes of the person using the instrument."

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said George William Frodsham in the Great Seal Patent Office on the
3rd November 1879.
GEORGE WILLIAM FRODSHAM, of No. 4, Change Alley, Cornhill, in the City
of London, Chronometer Maker. "IMPROVEMENTS IN THE CONSTRUCTION OF
BINOCULAR TELESCOPES AND OPERA GLASSES."
My Invention will be understood by the following explanation and reference to
the Drawings which represent a binocular opera glass in three several states, i.e.,
closed, half open, and entirely open ready for use, as shown in Figures 1, 2, and 3.
Figure 3 shows the completely developed opera glass, the cylinders containing
the object glasses being moveable about screws which act as pivots and are screwed
into the bar carrying the screw adjustment for focus.
These cylinders contain within them at their upper ends (vide Figure 3) smaller
cylinders which have in them the holes necessary to receive the screw pivots, and
are attached to the bar thereby.
These smaller cylinders or tubes are about one third the length of those that
contain the object glasses, and are so fitted as to be capable of being slidden the
whole length within the outer or object glass cylinders, and are prevented from
being entirely drawn out of the same by suitable stops.
This arrangement permits the whole of the remaining portion of the opera glass
to be slidden into these two cylinders, first rotating the object glass cylinders
through a quarter of a circle about the screw pivots, so as to bring them into the
position shewn in Figure 2, and afterwards causing them to approach each other
until the whole presents the appearance shewn in Figure 1.
This it will be perceived is effected by the smaller tubes which have the screw
holes in them for the pivot screws being capable of being slidden in the object glass
tubes.
As, however, the remaining portion referred to above could not possibly enter the
object glass tubes even with the focussing arrangement screwed in so as to bring
the eye pieces as close as they can be brought to the object glasses on account of
the eye pieces being mounted in tubes which project considerably above the upper
bar (Figure 3), it is first necessary to close down these eye piece tubes until their
flanges project only their own thickness above the upper bar. This is effected in
the manner usual with ordinary telescope tubes, there being no additional screw
adjustment for drawing out and pushing in these small tubes which are drawn out
by the fingers to their full extent when it is desired to open this folding opera
binocular, the focus being afterwards found by using the ordinary screw focus
adjustment.
Fig. 2 shews the binocular with the eye pieces towards the viewer of the
Drawings; in this state the glass is ready to be either opened or closed.
The operation of closing the instrument having been described it remains only to
state that the instrument may be opened by reversing the several procedures above
detailed.
I do not claim any of the parts taken separately, but what I claim as my Inven-
tion is the combination and arrangement, substantially as herein before described
and as illustrated by the Drawings filed herewith.
.
In witness whereof, I, the said Georgo William Frodsham, have hereunto set
my hand and seal, this Third day of November, in the year of our Lord
One thousand eight hundred and seventy nine.