IMPROVEMENTS IN CHRONOMETERS
Year: 1867

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in
the County of Middlesex, for the Invention of "IMPROVEMENTS IN
CHRONOMETERS."-A communication from abroad. by Simon Vissière
Chronometer Maker, of 29, Boulevart St. Martin, Paris.
Sealed the 19th May 1868, and dated the 29th November 1867.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark
at the Office of the Commissioners of Patents, with his Petition, on the
29th November 1867.
1, ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of
Middlesex, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN CHRONOMETERS," to be as follows:-
This Invention relates to improvements in the ordinary compensating
balance of chronometers with a view to produce regularity of action whatever
may be the changes of temperature to which they are exposed. The action
of an ordinary chronometer provided with a compensating balance is sufficiently
regular at extreme temperatures (freezing point and 90 degrees), but differs
at intermediate temperatures, reaching a maximum at an average of 60
degrees.
This Invention consists in the application to compensating chronometer
balances of weights devised for the purpose of producing regularity in their
action both in extreme and intermediate temperatures.

page_text: This Invention is illustrated in the accompanying Drawing which shows
one application of the weighted bi-metallic rings to an ordinary compensating
balance.
Figure 1 shows a partial view of a compensating balance, weighted as in
ordinary, Figure 2'a partial view of a similar balance provided with a weighted
bi-metallic ring according to this Invention, and Figure 3 a vertical section of
same, taken in the line a, o, Figure 2. The same letters apply to the three
Figures.
A, ordinary compensating balance; a, slide or runner placed on the balance
provided with a screw for fixing the same; b, c, d, bi-metallic ring having an
arm e and intersected at 9: f, hollow screw for fixing the ring on the slide a;
h, weight placed on the ring near the slit g and fixed by a screw i; it is also
provided with a screw n at its centre for regulating the weight; k, balancing
screw, auxiliary weight mounted on the periphery of the balance, the
weight of which regulated by that of h serves to determine the compensating
action. The ordinary compensating balance of a chronometer, as at Figure 1,
consists of a bar A mounted at point o on the axis receiving the spiral; this
bar forms part of a bi-metallic ring, one half of which is represented at
B, C, D, composed of brass on the outside and steel inside with slits at E, E.
Adjustable weights M are placed on this ring at points determined by
experiment. The diameter and weight of the balance in relation to the
spiral serves to regulate the action of the chronometer at a given temperature.
If this temperature increases the spiral and the bar A expand and retard the
vibrations of the balance, but as the two metals of the ring B, C, D, expand
in different degrees, the brass more so than the steel, it follows that the ring
assumes the dotted position C', D', and thus brings the weights M nearer the
centre Olessening the real radius of the balance and consequently quickening
the vibrations. It will be understood that the effect may be varied by changing
the position of the weights M on the ring B, C, D, so as to obtain quicker
motion equivalent to the retardation produced by the dilatation of the spiral
and bar A so obtaining a compensating action. If the laws regulating these
two effects were the same the motion would be equal for all changes of
temperature, but being different the compensating action is obtained either at
freezing point or 90 degrees. Intermediate temperatures however produce
different motions, the maximum increase occurring on an average at about
60 degrees, whence it may be deduced that at this temperature the diameter
of the balance is relatively too small.
The weighted bi-metallic ring, Figures 2 and 3, forming the object of
the present Invention acts as a substitute for the weight M, Figure 1, the

page_text: centre of gravity of said ring being changeable according to the temperature
with a view to remedy the defect above mentioned. The bar e and the
internal ring b, c, d, are made of steel, and the exterior of brass intersected
at g. When the temperature increases the ring bends as at b, c, carrying
with it the weight h and causing it to describe an are concentric therewith
and assume the position h'. By placing the centre of the weight h on the
line x, o, of the balance passing through the centre k of the ring at a tem-
perature of 60 degrees, on a rise or fall taking place in such temperature
the ring will be bent as at b, c, or b², c², the weight h then occupying the
positions or 2, the distances from the centre o of the balance being less
than o, h; thus the balance will have a greater diameter at 60 degrees when
the weight h occupies its normal position. It has been observed that at this
temperature the balance becomes too small, and I thus obtain the desired
compensation between the two conditions with great exactness by adjusting
the mutual positions of the weights h and l, the latter acting in the same
manner as the weight M, Figure 1. It will be understood that each balance
is provided in all cases with two similar weights placed diametrically
opposite..
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Alexander Melville Clark in the Great Seal Patent Office on
the 27th May 1868.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-ninth day of November, in the year of our
Lord One thousand eight hundred and sixty-seven, in the thirty-first year
of Her reign, did, for Herself, Her heirs and successors, give and grant
unto me, the said Alexander Melville Clark, Her special licence that I, the
said Alexander Melville Clark, my executors, administrators, and assigns, or
such others as I, the said Alexander Melville Clark, my executors, adminis-
trators, 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 Mau, an In-.
vention for "IMPROVEMENTS IN CHRONOMETERS," a communication to me from

page_text: abroad by Simon Vissière, Chronometer Maker, of 29, Boulevart St.
Martin, Paris, upon the condition (amongst others) that I, the said
Alexander Melville Clark, my executors or administrators, by an instrument
in writing under my, or their, or one of their hands and seals, should par-
ticularly 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.
NOW KNOW YE, that I, the said Alexander Melville Clark, do hereby
declare the nature of the 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 Sheet of Drawings hereunto
annexed, and to the letters and figures marked thereon (that is to say) :-
This Invention relates to improvements in the ordinary compensating
balance of chronometers with a view to produce regularity of action whatever
may be the changes of temperature to which they are exposed. The action
of an ordinary chronometer provided with a compensating balance is sufficiently
regular at extreme temperatures (freezing point and ninety degrees) but
differs at intermediate temperatures, the maximum deviation taking place
at an average of sixty degrees.
This Invention consists in the application to compensating chronometer
balances of weights devised for the purpose of producing regularity in their
action, both in extreme and intermediate temperatures.
This Invention is illustrated in the accompanying Drawing which shows
one application of the weighted bi-metallic ring to an ordinary compensating
balance.
Figure 1 shows a partial view of a compensating balance, weighted as in
ordinary; Figure 2 a partial view of a similar balance provided with a weighted
bi-metallic ring according to this Invention; and Figure 3 a vertical section of
same, taken on the line a, o, Figure 2. The same letters apply to the three
Figures.
A, ordinary compensating balance; a, slide or runner placed on the balance
provided with a screw for fixing the same; b, c, d, bi-metallic ring having an
arin e and intersected at 9; f, hollow screw for fixing the ring on the slide a;
h, weight placed on the ring near the slit g and fixed by a screw i, it is also
provided with a screw n at its centre for regulating the weight; balancing
screw; 1, auxiliary weight mounted on the periphery of the balance, the
weight of which, in connection with h, serves to determine the compensating
action. The ordinary compensating balance of a chronometer, as at Figure 1,

page_text: consists of a bar A mounted at point o on the axis of the spiral; this bar
forms part of a bi-metallic ring, one half of which is represented at B, C, D,
composed of brass on the outside and steel inside intersected at E, E.
Adjustable weights M are placed on this ring at points determined by
experiment. The diameter and weight of the balance in relation to the spiral
serve to regulate the action of the chronometer with a given temperature.
If this temperature increases the spiral and the bar A expand and retard the
vibrations of the balance, but as the two metals of the ring B, C, D, expand
in different degrees, the brass more so than the steel, the ring assumes the
dotted position B, C, D', and thus brings the weights M nearer the centre O,
lessening the real radius of the balance and consequently quickening the
vibrations. It will be understood that the effect may be varied by changing
the position of the weights M on the ring B, C, D, so as to obtain quicker
motion equivalent to the retardation produced by the dilatation of the spiral and
bar A, so obtaining a compensating action. If the laws regulating these two
effects were the same the motion would be equal for all changes of temperature,
but being different the compensating action is obtained either at freezing
point or ninety degrees. Intermediate temperatures however produce different
speeds, the maximum increase occurring on an average at about sixty degrees,
whence it may be deduced that at this temperature the diameter of the
balance is relatively too small.
The weighted bi-metallic ring, Figures 2 and 3, forming the object of the
present Invention acts as a substitute for the weight M, Figure 1, the centre
of gravity of said ring being changeable according to the temperature with a
view to remedy the defect above mentioned. The bar e and the internal
ring b, c, d, is made of steel and the exterior of brass intersected at y. When
the temperature increases the ring bends, as at c, carrying with it the
weight hand causing it to describe an are concentric therewith, and assume
the position. By placing the centre of the weight h on the line c, o, of the
balance passing through the centre of the ring at a temperature of
sixty degrees, on a rise or fall taking place in such temperature the ring will
be bent as at c or c; the weight h then occupying the positions h¹ or ², the
distances of which from the centre o of the balance are less than o, h; thus
the balance will have a greater diameter at sixty degrees when the weight h
occupies its normal position. It has been observed that at this temperature
the balance ordinarily becomes too small, and I thus obtain the desired com-
pensating effect between the two extremes with great exactness by adjusting
the mutual positions of the weights
manner as the weight M, Figure 1.
and 1, the latter acting in the same
It will be understood that each balance

page_text: is provided in all cases with two similar weights placed diametrically
opposite.
Having described the nature of this Invention, and the manner of performing
the same, I declare that what I claim as the Juvention to be protected by the
berein-before in part recited Letters Patent is, the application of a bi-metallic
ring to the ordinary compensating balance of a chronometer for producing
regularity of action under all changes of temperature, the whole arranged in
the manner herein-before described, and as represented in the accompanying
Drawings.
In witness whereof, I, the said Alexander Melville Clark, bave here-
unto set my hand and seal, this Twenty-seventh day of May, in the
year of our Lord One thousand eight hundred and sixty-eight.
A. M. CLARK. (L.S.)