IMPROVEMENTS IN THE CONSTRUCTION OF MARINE CHRONOMETER BOXES
Year: 1868

page_text: LETTERS PATENT to John Hammersley, of Spencer Street, Clerkenwell,
in the County of Middlesex, Chronometer and Watch Manufacturer,
for the Invention of "IMPROVEMENTS IN THE CONSTRUCTION OF MARINE
CHRONOMETER BOXES."
Sealed the 5th September 1868, and dated the 5th March 1868.
PROVISIONAL SPECIFICATION left by the said John Hammersley at
the Office of the Commissioners of Patents, with his Petition, on
the 5th March 1868.
I, JOHN HAMMERSLEY, of Spencer Street, Clerkenwell, in the County
of Middlesex, Chronometer and Watch Manufacturer, do hereby declare
the nature of the said Invention for "IMPROVEMENTS IN THE CONSTRUCTION
OF MARINE CHRONOMETER BOXES," to be as follows:-
This Invention consists in the construction of the brass boxes of
marine chronometers with a flexible diaphragm or diaphragms whereby
the external air is prevented from entering the box.
To carry out this Invention I make an opening in the side or bottom of
the box, or if more than one diaphragm be used in both, in or over which
I fix a thin flexible diaphragm of thin corrugated metal, oiled silk, gold

page_text: beater's skin, or other suitable flexible material. This diaphragm is pro-
tected by a suitable cover perforated with one or more holes. If desired,
this diaphragm can be placed inside the box, in which case the bottom
or side of the box would form sufficient protection without the cover.
These arrangements allow for the condensation or expansion of the
air in the box, and prevent a vacuum being formed therein as the
diaphragm is forced in by the external pressure as the air in the box
condenses, thereby making the pressure equal inside and out. These
improvements are applicable to chronometer boxes at present in use.
SPECIFICATION in pursuance of the conditions of the Letters Patent
filed by the said John Hammersley in the Great Seal Patent Office
on the 5th September 1868.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HAMMERSLEY, of Spencer Street, Clerkenwell, in the County of Mid-
dlesex, Chronometer and Watch Manufacturer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fifth day of March, in the year of
our Lord One thousand eight hundred and sixty-eight, in the thirty-
first year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said John Hammersley, Her special licence
that I, the said John Hammersley, my executors, administrators, and
assigns, or such others as I, the said John Hammersley, my executors,
administrators, and assigns, should at any time agree with, and no
others, from time to time and at all times thereafter during the term
therein expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
THE CONSTRUCTION OF MARINE CHRONOMETER BOXES," upon the condition
(amongst others) that I, the said John Hammersley, my executors or
administrators, by an instrument in writing under my, or their, or one
of their hands and seals, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be
performed, and cause the same to be filed in the Great Seal Patent
Office within six calendar months next and immediately after the date
of the said Letters Patent.

page_text: NOW KNOW YE, that I, the said John Hammersley, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement, reference being had to the Drawing hereto annexed,
and to the figures and letters marked thereon, that is to say:-
This Invention consists in the construction of the brass boxes of
marine chronometers with a flexible diaphragm or diaphragms whereby
the external air is prevented from entering the box.
To carry out the Invention I make an opening in the side or
bottom of the box, or if more than one diaphragm be used in both,
in or over which I fix a thin flexible diaphragm of corrugated metal,
oiled silk, gold beater's skin, or other suitable flexible material. The
diaphragm is protected by a suitable cover perforated with one or
more holes. If desired the diaphragm can be placed inside the box,
in which case the side or bottom of the box would form sufficient
protection without the cover. These arrangements allow for the con-
densation and expansion of the air in the box, and prevent a vacuum
Being formed therein as the diaphragm is forced in by the external
pressure as the air in the box condenses, thereby making the pressure
equal inside and out. These improvements are applicable to chrono-
meter boxes at present in use.
To make my Invention better understood I will now proceed to
describe the best means I am acquainted with for carrying the same
into effect by reference to the accompanying Drawing in which
Figure 1 is a plan (seen from below) of a chronometer box with my
improvements applied thereto, and Figure 2 section of same on line A, B,
of Figure 1.
a, a, is the brass chronometer box, in the bottom of which I form
the hole b, as shewn; over this hole is applied the diaphragm c made
of a suitable flexible air-tight material, the diaphragm is fixed in its
place by the cap d, which cap is fixed to the box by screws e, e, as shewn,
or by other suitable means; fis a hole in the cap for the admission of
the external air. By this arrangement it will be seen that in the event
of the air in the box condensing the pressure of the external air will
force inwards the diaphragm c and thus prevent a vacuum being formed
in the box; on the air expanding again the diaphragm will be forced
into its normal position. The wind-up hole g, the bezzle, and other
joints are made air-tight by ordinary known means.

page_text: Having thus described the nature of my said Invention, and the
manner of performing the same, I wish it to be understood that I do
not confine myself to the precise details herein laid down and shewn
in the accompanying Drawing; but what I claim is, the construction
of marine chronometer boxes with a flexible air-tight diaphragm
substantially in the manner and for the purpose herein-before described
and represented in the accompanying Drawing.
In witness whereof, I, the said John Hammersley, have hereunto
set my hand and seal, this Fifth day of September, in the year
of our Lord One thousand eight hundred and sixty-eight.
J. HAMMERSLEY. (L.S.)